Higher Contraction Frequency Research Articles

The role of pannexin/purinergic signaling in intervascular communication from capillaries during skeletal muscle contraction in male Golden hamsters.

We sought to determine the physiological relevance of pannexin/purinergic-dependent signaling in mediating conducted vasodilation elicited by capillary stimulation through skeletal muscle contraction. Using hamster cremaster muscle and intravital microscopy we stimulated capillaries through local muscle contraction while observing the associated upstream arteriole. Capillaries were stimulated with muscle contraction at low and high contraction (6 and 60CPM) and stimulus frequencies (4 and 40 Hz) in the absence and presence of pannexin blocker mefloquine (MEF; 10-5 M), purinergic receptor antagonist suramin (SUR 10-5 M) and gap-junction uncoupler halothane (HALO, 0.07%) applied between the capillary stimulation site and the upstream arteriolar observation site. Conducted vasodilations elicited at 6CPM were inhibited by HALO while vasodilations at 60CPM were inhibited by MEF and SUR. The conducted response elicited at 4 Hz was inhibited by MEF while the vasodilation at 40 Hz was unaffected by any blocker. Therefore, upstream vasodilations resulting from capillary stimulation via muscle contraction are dependent upon a pannexin/purinergic-dependent pathway that appears to be stimulation parameter-dependent. Our data highlight a physiological importance of the pannexin/purinergic pathway in facilitating communication between capillaries and upstream arteriolar microvasculature and, consequently, indicating that this pathway may play a crucial role in regulating blood flow in response to skeletal muscle contraction.

P-342 Uterine contractile patterns in adenomyosis patients normalize under hormonal contraception use: the WAVES study

Abstract Study question Comparison of uterine contractility (UC) in adenomyosis patients (AP) with and without hormonal contraception (HC) compared to controls with HC, measured by transvaginal ultrasound (TVUS). Summary answer AP with HC show better contraction coordination compared to untreated AP. AP with HC show comparable UC compared to controls with HC. What is known already Adenomyosis is a disease of the uterus that can cause dysmenorrhoea, menorrhagia, dyspareunia and subfertility. These symptoms could be explained by the different contraction patterns in women with adenomyosis compared to healthy controls. Therapeutic use of hormonal contraception reduces the symptoms experienced by women with adenomyosis. This could be explained by the normalization of contraction patterns, which has not yet been objectively quantified due to the absence of a suitable measurement tool. A novel speckle-tracking and strain analysis by 2D TVUS recordings has recently been used to assess differences in contraction coordination, contraction frequency, velocity and direction in healthy women. Study design, size, duration This study is part of an ongoing multi-centre prospective observational cohort study investigating UC on TVUS. Our study includes the TVUS recordings of 23 women with adenomyosis without hormonal contraception treatment, 15 women with adenomyosis undergoing hormonal contraception treatment, and 17 women with healthy uteri undergoing hormonal contraception treatment. Patients were included in 3 centres from 2017 to 2023 (Catharina Hospital Eindhoven, Fertility Clinic Thessaloniki and University Federico Napels). Participants/materials, setting, methods 23 women with sonographic suspicion of adenomyosis without HC, 15 women with adenomyosis undergoing HC treatment and 17 women with healthy uteri with HC were included. HC included oral combined HC, progesterone only pill and hormonal IUD. UC frequency, amplitude, velocity and coordination were assessed by applying a dedicated speckle-tracking and strain analysis to 2-4-minute TVUS recordings in midsagittal section. AP with HC were compared to AP without contraception and to healthy controls with HC. Main results and the role of chance Age, BMI, parity and uterus volume were significantly higher in the women with adenomyosis compared to the healthy controls (p < 0.05). The adenomyosis group with contraception showed more contraction coordination compared to the adenomyosis group without hormonal contraception treatment (0.23 ±0.10 vs. 0.29 ±0.11, p = 0.041). There was a tendency towards higher contraction frequency (1.53 ±0.21 vs. 1.42, p = 0.153) and lower amplitude (0.56 ±0.04 vs. 0.65 ±0.04, p = 0.159) in the adenomyosis group with hormonal contraception treatment compared to the adenomyosis group without hormonal contraception treatment. There were no significant differences in uterine contractility between the adenomyosis group with hormonal contraception treatment compared to the healthy group with hormonal contraception treatment. Limitations, reasons for caution No sub-analysis was done to assess effects of additional adenomyosis and contraception characteristics due to this being an ongoing study. Women with extensive adenomyosis were not included due to impossibility to perform analysis of ultrasound recordings. AP were older, had higher BMI and larger uterus volumes than healthy controls. Wider implications of the findings The normalization of UC under therapeutic use of HC compared to untreated AP and the lack of differences in UC between AP and healthy controls with HC, confirms the therapeutic effect on adenomyotic symptoms. This presents a new therapeutic efficacy marker for adenomyosis. Trial registration number NL52466.100.15 Study funding Yes Funding source Funding by commercial/corporate company(ies)

P-342 Uterine contractile patterns in adenomyosis patients normalize under hormonal contraception use: the WAVES study

Abstract Study question Comparison of uterine contractility (UC) in adenomyosis patients (AP) with and without hormonal contraception (HC) compared to controls with HC, measured by transvaginal ultrasound (TVUS). Summary answer AP with HC show better contraction coordination compared to untreated AP. AP with HC show comparable UC compared to controls with HC. What is known already Adenomyosis is a disease of the uterus that can cause dysmenorrhoea, menorrhagia, dyspareunia and subfertility. These symptoms could be explained by the different contraction patterns in women with adenomyosis compared to healthy controls. Therapeutic use of hormonal contraception reduces the symptoms experienced by women with adenomyosis. This could be explained by the normalization of contraction patterns, which has not yet been objectively quantified due to the absence of a suitable measurement tool. A novel speckle-tracking and strain analysis by 2D TVUS recordings has recently been used to assess differences in contraction coordination, contraction frequency, velocity and direction in healthy women. Study design, size, duration This study is part of an ongoing multi-centre prospective observational cohort study investigating UC on TVUS. Our study includes the TVUS recordings of 23 women with adenomyosis without hormonal contraception treatment, 15 women with adenomyosis undergoing hormonal contraception treatment, and 17 women with healthy uteri undergoing hormonal contraception treatment. Patients were included in 3 centres from 2017 to 2023 (Catharina Hospital Eindhoven, Fertility Clinic Thessaloniki and University Federico Napels). Participants/materials, setting, methods 23 women with sonographic suspicion of adenomyosis without HC, 15 women with adenomyosis undergoing HC treatment and 17 women with healthy uteri with HC were included. HC included oral combined HC, progesterone only pill and hormonal IUD. UC frequency, amplitude, velocity and coordination were assessed by applying a dedicated speckle-tracking and strain analysis to 2-4-minute TVUS recordings in midsagittal section. AP with HC were compared to AP without contraception and to healthy controls with HC. Main results and the role of chance Age, BMI, parity and uterus volume were significantly higher in the women with adenomyosis compared to the healthy controls (p < 0.05). The adenomyosis group with contraception showed more contraction coordination compared to the adenomyosis group without hormonal contraception treatment (0.23 ± 0.10 vs. 0.29 ± 0.11, p = 0.041). There was a tendency towards higher contraction frequency (1.53 ± 0.21 vs. 1.42, p = 0.153) and lower amplitude (0.56 ± 0.04 vs. 0.65 ± 0.04, p = 0.159) in the adenomyosis group with hormonal contraception treatment compared to the adenomyosis group without hormonal contraception treatment. There were no significant differences in uterine contractility between the adenomyosis group with hormonal contraception treatment compared to the healthy group with hormonal contraception treatment. Limitations, reasons for caution No sub-analysis was done to assess effects of additional adenomyosis and contraception characteristics due to this being an ongoing study. Women with extensive adenomyosis were not included due to impossibility to perform analysis of ultrasound recordings. AP were older, had higher BMI and larger uterus volumes than healthy controls. Wider implications of the findings The normalization of UC under therapeutic use of HC compared to untreated AP and the lack of differences in UC between AP and healthy controls with HC, confirms the therapeutic effect on adenomyotic symptoms. This presents a new therapeutic efficacy marker for adenomyosis. Trial registration number NL52466.100.15

The Effect of Uterine Contractions on Fertility Outcomes in Frozen Embryo Transfer Cycles: A Cohort Study.

The relationship between uterine peristalsis before embryo transfer and the success of assisted reproductive techniques (ARTs) has not been properly investigated. In this study, the effect of uterine contractions on embryo implantation in frozen embryo transfer (FET) cycles was investigated to determine whether the frequency of uterine contractions can be used as a quantitative marker to assess endometrial receptivity. In this cohort study of 68 eligible FET candidates, one hour before embryo transfer (ET), frequency of uterine contractions was assessed with transvaginal ultrasonography. Patients were followed up for 20 weeks. The association between FET outcomes including clinical pregnancy, abortion, and ectopic pregnancy with uterine contractions was evaluated. Binary logistic regression was conducted to test the association between clinical pregnancy outcomes in different groups. The p<0.05 were considered statistically significant. Of 68 patients, 25 (36.8%) experienced clinical pregnancy. Multiple logistic regression for omitted confounders (age, BMI, duration, type and cause of infertility) revealed that patients with uterine peristaltic wave frequency less than 2≤ wave/min had higher chance of successful pregnancy compared to those with ≥4 wave/min (odds ratio: 10.8; 95% confidence interval: 1.5-79.4, p=0.019). The Pearson's correlation showed a statistically significant relationship between the frequency of uterine contraction and endometrial thickness (r= 0.42, p=0.002). Patients with uterine peristalsis of <4.0 wave/min before embryo transfer had a higher chance of successful implantation and pregnancy compared with those with higher contraction frequencies. It seems that measuring uterine contraction frequency before embryo transfer might help to predict pregnancy outcomes.

Quantitative Ultrasound Measurement of Endometrial Waves in Adenomyosis Versus Women with Normal Uteri - the Waves Study

<h3>Study Objective</h3> Measurement and analysis of uterine contractions by quantitative 2D transvaginal ultrasound measurements in women with abnormal uteri due to adenomyosis versus women with normal uteri. <h3>Design</h3> Multi-centre prospective observational cohort study. <h3>Setting</h3> Outpatient gynaecology department of participating centres. <h3>Patients or Participants</h3> 29 women with adenomyosis with a natural menstrual cycle were compared to 70 women with normal uteri and regular menstrual cycles. Patients were included from September 2014 up to January 2022. <h3>Interventions</h3> Patients underwent a 4-minute 2D transvaginal ultrasound of the uterus in mid-sagittal section. Uterine motion analysis was implemented by a dedicated speckle tracking and strain analysis algorithm; with frequency, amplitude, coordination and velocity -related features extracted from the derived signals to characterise the uterine contractions. Measurements were carried out at different points of the menstrual cycle (menstrual, early follicular, periovulatory and early and late luteal phases. <h3>Measurements and Main Results</h3> Results differed most significantly between groups in the periovulatory phase, with women with adenomyosis showing lower frequency (1.44 vs. 1.79 contractions/minute, p=0.025), higher amplitude (0.09 vs. 0.04, p=0.000) and lower velocity of uterine contractions (0.62 vs. 0.83 mm/sec, p=0.0008). In the menstrual phase, women with adenomyosis showed a trend toward higher contraction frequency (1.37 vs, 1.33 contractions/minute, p=0.592), amplitude (0.05 vs. 0.04, p=0.259) and velocity (0.72 vs. 0.67, p=0.456). Across all phases, women with adenomyosis showed a trend towards reduced contraction coordination (0.23-0.34 vs. 0.15-0.26). This being statistically significant in the late luteal phase (p=0.018). <h3>Conclusion</h3> Our results confirm differences in uterine movement in abnormal versus healthy uteri. This could add to the aetiological understanding of clinical symptoms of these conditions (i.e. dysmenorrhoea or infertility). The notable difference between groups regarding coordination identifies this feature as a potential prognostic or therapeutic marker. Further research in women with (other) benign uterine disorders will hopefully lead to a better understanding of the clinical implications of abnormal uterine contractility.

THE EFFECTIVENESS OF ADDITIONAL INTRAMUSCULAR LUTEAL PROGESTERONE SUPPORT IN WOMEN WITH ENDOMETRIAL CONTRACTILITY ON ULTRASOUND THE DAY PRIOR TO PROGRAMMED FROZEN EMBRYO TRANSFER

Increased contractility at the time of embryo transfer (ET) adversely affects embryo implantation and pregnancy rates in IVF (1). It has been postulated that the high uterine contraction frequency seen on the day of ET resulted from an insufficient response to the uterorelaxing properties of progesterone (2). Therefore, we decided to investigate the effectiveness of increasing luteal progesterone support based on endometrial contractility (EC) prior to programmed frozen embryo transfer (FET).

The association between uterine contraction frequency and fetal scalp pH in women with suspicious or pathological fetal heart rate tracings: A retrospective study

ObjectiveCurrent guidelines provide little supporting literature for the definition of uterine tachysystole during labour and no distinction is made for optimal contraction frequency depending on the clinical situation. We hypothesize that fetal hypoxia is frequently caused by uterine tachysystole and that high uterine contraction frequencies are especially harmful when fetal heart rate (FHR) abnormalities are present. We studied the association between contraction frequency and fetal scalp pH values in women with an indication for fetal blood sampling (FBS) based on FHR abnormalities. Study designA retrospective study including 762 women was performed in a tertiary teaching hospital in the Netherlands from January 2015 until January 2020. Women with a singleton pregnancy with a gestational age ≥ 34+0 weeks were included when FBS was performed because of suspicious or pathological FHR tracings. Exclusion criteria were maternal age < 18 years, failed fetal scalp pH values, lack of thirty minute registration by tocodynamometry prior to FBS, poor quality of uterine monitoring, intrauterine resuscitation in the thirty minutes prior to FBS, maternal body mass index ≥ 30 kg/m2 and neonatal birth weight < 10th percentile.Uterine contractions in the thirty minutes prior to FBS were manually annotated by a researcher who was blinded to FBS values, FHR and other obstetrical data. Linear and logistic analysis were used to explore the association between uterine contraction frequency and FBS results. ResultsLow fetal scalp pH values were significantly associated with contraction frequency prior to FBS. Fetuses of women with four to five contractions per ten minutes prior to FBS were 2.4 times more likely to have hypoxia as compared to fetuses of women with two to three contractions per ten minutes (aOR 2.4, 95% CI 1.1–5.4). With increasing contraction frequency, the risk of fetal hypoxia further increased. ConclusionsContraction frequency above four per ten minutes prior to FBS is significantly associated with fetal hypoxia in women with FHR abnormalities. We suggest to aim for a maximum contraction frequency of four per ten minutes in these women.

Variations in knee range of motion during repeat knee extension with an amputated lower leg at different contraction rhythms over 8 consecutive days in a patient with severe diabetic neuropathy: A clinical study

Background: This clinical study sought to understand the knee range of motion (KROM) in an amputated stump during repeat voluntary knee extension with or without a 0.5 kg weight in the acute/early phase after amputation can vary between different target knee extension rhythm frequency (KER) levels in the amputated lower leg of a patient with severe diabetic sensory disorder and leg ischemia. Case Presentation: A 51-year-old male patient with severe diabetic neuropathy had a right lower leg amputation due to necrosis and ulcer lesion following a burn injury to the first toes and severe ischemic peripheral vascular disease. In a sitting position with the base of the foot of the non-amputated left leg on the ground, he performed repeat knee extension of the resected stump (knee active extension and passive flexion without a target KROM) for 1 min with both self-controlled free KER and different target KERs (30, 40, 50, 60, and 80 contractions per minute [cpm] using a metronome), with or without a 0.5 kg weight placed on the resected stump over 8 consecutive days. The KROM was measured using a goniometer placed between the resected stump and the thigh muscle with a continuous data acquisition system. The mean values achieved for KER, KROM, and angle rate during a 1 min session was determined during each daily session, and consecutively average values over sessions on 8 consecutive days was also evaluated. The achieved mean KER at all target KERs corresponded closely with the target KER. The average KROM was approximately 60 degrees over a range of targets between 30 and 60 cpm, but the value was lower at approximately 50 degrees at 80 cpm. The angle rate increased consistently with the increase from a target of 30 to 60 cpm, but it was reduced at 80 cpm. The mean KROM was inversely related (r=-0.390, P&lt;0.01, n=40) to the mean KER without the weight, but not significantly (r=-0.256, P=ns, n=40) with the 0.5 kg weight. The achieved KER in the self-controlled free trial with or without the 0.5 kg weight might increase with an increase in sessions over 8 days with a range between approximately 30 and 60 cpm. Conclusion: The present case study showed that a higher contraction frequency may limit KROM determined below 60 cpm because of the reduced angle rate in an amputated lower leg. A low and moderate KER below 60 cpm may be appropriate to maintain KROM with a stable angle rate. Furthermore, voluntary KER with free self-controlled rhythm may increase over the course of multiple sessions as familiarity improves with kicking the amputated limb and generating a potential improvement in performance/ability effect with consecutive leg exercise with no use of a prothesis such as in the early/acute phase post-amputation using audible biofeedback.

Progressive Collecting Liver Lymphatic Vessels Dysfunction over the Course of Extrahepatic Cholestasis

Liver produces a large fraction of total lymph flow (25–50%). Transport function of lymphatics is altered during inflammation, which impacts the pathogenesis of numerous diseases. Despite their importance in liver function, the functional characteristics of liver lymphatic vessels (LLVs) have been never evaluated in health and disease. We evaluated liver lymphatic vessel (LLV) function in normal and cholestatic rats following extrahepatic bile duct ligation (BDL). LLV contractility/pumping characteristics were determined in LLVs isolated from Sprague‐Dawley rats in control, 1, 3 and 7 days after BDL (BDL1, BDL3, and BDL7) and sham groups. LLV pumping/contractility was analyzed in all groups. Control LLVs had outer diameters of ~500 um, typical lymphatic tone (~7%), moderate contraction amplitude (15–35%), high contraction frequency (12–21 contractions/min) and strong active pumping (5–7.5 vol/min). Over the course of its duration, the BDL significantly altered LLV contractile/pump function, inducing an enlargement of LLVs; their decreased tone; lowering of phasic contractions frequency responses to increases in stretch. Cumulatively, BDL induced progressive decline in minute pumping of LLVs with complete cessation of phasic lymphatic contractions after seven days of BDL. In addition, BDL even after one day completely ablated the light imposed flow‐dependent relaxatory/inhibitory reactions of LLVs observed in control. Progressive dysfunction of LLVs correlates with cholestasis‐induced alterations in liver and bile ducts. We believe that observed BDL‐induced changes in LLVs are likely the result of the liver inflammation and will further promote the inflammatory edema known to occur in the liver during BDL. Thus, LLV dysfunction may play important roles in the ensuing pathogenesis of cholestasis and merit further study.Support or Funding InformationNIH/NIDDK R01 DK110035; NIH/NHLBI 1U01HL123420; funds from TAMU HSC COM and Dept. of Medical Physiology.

Progressive dysfunction of collecting liver lymphatics during the development of extrahepatic cholestasis

Lymphatics are necessary anatomical structures of body systems to maintain tissue fluid and molecular homeostasis and are tightly involved in immune reactions of the body. Transport function of lymphatics is altered during inflammation, which impacts the pathogenesis of many diseases. Despite their importance in liver function, the functional characteristics of liver lymphatic vessels (LLVs) have not been evaluated. In this study we, for the first time, measured the function of LLVs in normal and cholestatic rats following extrahepatic bile duct ligation (BDL). In this study parameters of lymphatic contractility/pumping of isolated, cannulated and pressurized segments of LLVs were determined in male 5 moth old Sprague‐Dawley rats. The following animal groups were used: control, 1, 3 and 7 days, after BDL (BDL1, BDL3 and BDL7) and sham control 3 days after surgery. Segments of LLVs located in close proximity to the liver were dissected for the study. Lymphatic contractility parameters were measured and analyzed in isolated, cannulated and pressurized LLV segments under standard transmural pressures and imposed flow ranges in all groups. Healthy LLVs with outer diameter of ~500±50 μm have significant lymphatic tone (7–9%), moderate contraction amplitude (10–25%), high contraction frequency (14–25 contractions/min) demonstrating therefore strong pumping (4–7 volumes/min). Contractility of LLVs from sham and control group were not significantly different. BDL induced specific changes in tone and phasic contractions of LLVs. BDL caused an increase in vessel size (up to 900±100 μm of outer diameter in BDL7 group), progressive lowering of lymphatic tone over period of time after BDL (up to ~2–3‐fold lower lymphatic tone in BDL7 group). Effects of BDL on lymphatic contraction amplitude were as follows: BDL1‐LLVs contraction amplitude was ~2–2.5 times higher than control, BDL3– back to control values, BDL7– amplitude was 0 (a complete cessation of phasic contractions). At the same time contraction frequency in BDL1 and BDL3 LLVs was ~2–2.2 fold lower than control with no contractions in BDL7 group. Cumulatively, we observed a progressive decline in LLVs' pumping in BDL1 and BDL3 groups with complete lymphatic pump failure in BDL7 group. Additionally, LLVs possess comparatively light flow‐dependent responses, which were ablated by BDL. The data indicate that over the time course of cholestasis, the transport capabilities of LLVs are progressively diminished introducing severe, harmful disturbances in fluid/macromolecular homeostasis of the cholestatic liver, which could alter proper trafficking of immune cells and promote liver inflammation. Further research on underlying mechanisms of liver lymphatic dysfunction will shed light on the pathogenesis of cholestatic liver disease and may reveal novel therapeutic approaches.Support or Funding Information1U01HL123420 (DZ, AG); DK110035 (SG, GA)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Morphology and Function of the Lymphatic Vasculature in Patients With a Fontan Circulation.

The Fontan procedure has revolutionized the treatment of univentricular hearts. However, it is associated with severe complications such as protein-losing enteropathy, plastic bronchitis, and peripheral edema that may involve the lymphatic circulation. We aimed to assess lymphatic function and morphology in patients with a univentricular circulation. The functional state of lymphatic vessels in the lower extremities of patients with a Fontan circulation (n=10) was investigated using the novel technique near-infrared fluorescence imaging and compared with an age-, sex-, and weight-matched control group of healthy volunteers (n=10). The lymphatic morphology was described using T2-weighted magnetic resonance imaging, and microvascular permeability was estimated by strain gauge plethysmography. The Fontan patients had 17% lower lymphatic pumping pressure (50±3.1 mm Hg) compared with controls (60±2.8 mm Hg; P=0.0341) and a 62% higher contraction frequency (0.8±0.1 min-1) compared with the healthy controls (0.5±0.1 min-1; P=0.0432). Velocity by which the lymph is moved and refill time after manual emptying of the lymphatic vessels showed no differences between the 2 groups. The thoracic duct was elongated 10% ( P=0.0409) and with an abnormal course in the Fontan patients compared with normal. No difference in microvascular permeability was found between the 2 groups. Patients with a Fontan circulation have an impaired lymphatic pumping capacity and morphologically changed thoracic duct. Our results indicate a challenged lymphatic vasculature in the Fontan circulation and may play a role in the pathogenesis of the complications that are seen in Fontan patients. URL: https://www.clinicaltrials.gov . Unique identifier: NCT03379805.

Stress-strain analysis of duodenal contractility in response to flow and ramp distension in rabbits fed low-fiber diet.

Previously we demonstrated that low-fiber diet in rabbits affects the passive mechanomorphological properties in the small intestine, resulting in reduced intestinal wall thickness and collagen content, as well as intestinal wall softening. The aim of the present study was to evaluate the contractility in rabbits on long-term low-fiber diet and specifically to compare the contraction threshold, the frequency, and the amplitude of flow-induced and distension-induced contractions in the duodenum between rabbits on normal diet and on long-term low-fiber diet. Ten rabbits were fed a low-fiber diet for 5months (Intervention group), and five rabbits were fed normal diet (Control group). The duodenal segments were used for determination of mechanical parameters for analyses of contractility. The duodenal experiments were carried out in organ baths containing physiological Krebs solution. Pressure and diameter changes induced by contractions in response to flow and ramp distension were measured. The frequencies and amplitude of contractions were analyzed. Distension-induced contraction thresholds and maximum contraction amplitude of flow-induced contractions were calculated in terms of mechanical stress and strain. Multiple linear regression analyses were applied to study dependencies between contractility parameters and wall thickness, wall area, and muscle layer thickness. During distension, the pressure, stress, and strain thresholds for induction of phasic contraction were biggest in the Intervention Group (P<0.05). In addition, the contraction frequencies during flow-induced contraction were highest in the Intervention Group (P<0.05), whereas the maximum contraction amplitudes in terms of pressure, diameter, stress, and strain were lowest in the Intervention Group (P<0.05). The contraction thresholds and contraction frequencies were negatively associated with the wall thickness, wall area, and muscle layer thickness, whereas maximum contraction amplitudes were positively associated with the wall thickness, wall area, and muscle layer thickness. Duodenal contractility in rabbits fed with long-term low-fiber diet exhibited low contraction amplitudes and high contraction thresholds and frequencies. The changes were associated with the low-fiber diet-induced histomorphological remodeling. Studies on detailed structural and functional diet-induced changes in smooth muscle and intestinal nerves are needed for better understanding the remodeling mechanisms.

How often does the embryo implant at the location to which it was transferred?

To determine how often the embryo implants exactly at the site of transfer and what additional factors may affect the eventual site of implantation in assisted reproductive technology (ART) cycles. This was a prospective observational study of women undergoing ART treatment in a tertiary university unit. Several factors inherent to the embryo transfer (ET), such as the location of the air bubbles and uterine contractility at 1 and at 60 min after ET were assessed with two-dimensional and three-dimensional (3D) ultrasound. In women in whom there was a resulting pregnancy, the position of the gestational sac (i.e. right, left, center or low) was subsequently assessed using 3D ultrasound, and predictors of its location were evaluated. Of 239 recruited women with visualization of air bubbles at ET, 71 singleton gestational sacs were subsequently observed on 3D ultrasound. Overall, 40.8% (29/71) of embryos implanted at the location where the air bubbles were visualized at 1 min after ET, and 50.7% (36/71) implanted where the air bubbles were visualized at 60 min after ET (Cohen's kappa coefficients 0.21 and 0.37, respectively; comparison of agreement values: P = 0.28). Specifically, at 1 min the correspondence between the location of the air bubble and embryo implantation was 37.5% (6/16), 57.1% (8/14), 36.8% (7/19) and 36.4% (8/22) for right, left, central and lower uterus, respectively (4 × 4 contingency table, P < 0.01); at 60 min, the correspondence was 72.2% (13/18), 50.0% (9/18), 33.3% (8/24) and 85.7% (6/7), respectively (5 × 4 contingency table, P < 0.001). In addition, higher vs lower frequency of uterine contractions at 60 min was associated with different sites of implantation (5.6% (1/18), 11.1% (2/18), 27.8% (5/18) and 55.6% (10/18) vs 34.0% (18/53), 24.5% (13/53), 13.2% (7/53) and 28.3% (15/53) for right, left, central and lower uterus, respectively, P < 0.05). In particular, a high uterine contraction frequency following ET was associated with a twofold increased chance of the pregnancy implanting in the lower part of the uterine cavity (relative risk, 1.96 (95% CI, 1.08-3.56), P < 0.05). The position of the air bubbles within the first 60 min of ET appears to predict the site of implantation in approximately half of cases, denoting an overall poor agreement. This implies significant embryo migration, and has important clinical implications, as it demonstrates that other factors such as uterine contractility may dictate where the embryo will eventually implant following transfer. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Capillary Response to Skeletal Muscle Contraction: Implications for Redundancy in Microvascular Blood Flow Control

Redundancy, during active hyperaemia (AH), describes a regulatory control paradigm in which the vasoactive effect of a dilator can be amplified to compensate for the loss of another vasodilator's effect. This paradigm necessitates that some dilators exert an inhibitory influence on the dilatory ability of others. Thus, the compromised release of one dilator would remove its inhibition on another dilator thereby amplifying its effect to compensate for its loss. We have previously shown redundant signalling between dilators in arterioles of skeletal muscle microcirculation (Lamb &amp; Murrant, 2015). However, given the importance of capillaries in the coordination of blood flow to active skeletal muscle we sought to determine whether redundancy is important at this vascular level. Using intravital microscopy of the hamster cremaster we stimulated capillaries via micropipette application of metabolic dilators and assessed changes in diameter of the upstream terminal arteriole, associated with the stimulated capillary. Alone, potassium (K+, 10mM), nitric oxide (NO) donor S‐Nitroso‐N‐acetylpenicillamine (10−6M) and adenosine (ADO, 10−6M) caused a conducted response (CR) up the vascular tree. However, the magnitude of NO and ADO's CR was significantly blunted when added in the presence of KCl, demonstrating that dilators relevant to contraction can exert inhibitory influences on other dilators at the capillary level. We then aimed to determine the physiological relevance of redundant interactions during muscle contraction. CRs were elicited by contracting skeletal muscle fibres underlying capillary modules (via a microelectrode) for 2 minutes at 6,15, 24 and 60 contractions per minute (cpm). We found that inhibition of NO, via NO synthase inhibitor L‐NG‐Nitroarginine methyl ester (L‐NAME, 10−6M), significantly blunted the CR elicited by 6, 15 and 24cpm by ~102%, ~92%, and ~46%, respectively, but the CR elicited by 60cpm was unaffected. Presumably NO would be present during all contraction frequencies but we have shown it was not effective in mediating the CR at 60cpm. Based on the data from the micropipette protocol we hypothesized that K+ may be inhibiting NO's effectiveness. To determine whether K+ was exerting an inhibitory influence on NO at high contraction frequencies we antagonized K+ release, via inhibition of voltage‐gated K+ channels using 3,4‐Diaminopyridine (DAP, 3×10−4M), in addition to L‐NAME during contraction. In the presence of L‐NAME and DAP the CR elicited by 60cpm was significantly blunted by ~79%, showing that in the absence of K+ NO plays a significant role in mediating the CR elicited by 60cpm. Given that interstitial K+ concentration ([K+]i) is correlated with muscle contraction we postulated that at low contraction frequencies [K+]i may not be sufficient in attenuating NO's dilatory ability, but as contraction frequency increases the associated increase in [K+]i may be sufficient in exerting an inhibitory effect on NO. Together our data demonstrate that inhibitory effects between vasodilators exist at the level of the capillary. Further, we have shown that these interactions are important during muscle contraction, demonstrating the physiological relevance of redundancy. This fundamentally shifts our understanding of blood flow regulation during skeletal muscle activity, as these data provide evidence that AH is governed by a complex redundant interplay between dilators.Support or Funding InformationNSERC Canada.

Taurine depresses cardiac contractility and enhances systemic heart glucose utilization in the cuttlefish, Sepia officinalis

Taurine is the most abundant amino acid in the blood of the cuttlefish, Sepia officinalis, where levels can exceed 200 mmol L(-1). In mammals, intracellular taurine modulates cardiac Ca(2+) handling and carbohydrate metabolism at much lower concentrations but it is not clear if it exerts similar actions in cephalopods. Blood Ca(2+) levels are high in cephalopods and we hypothesized that taurine would depress cardiac Ca(2+) flux and modulate contractility in systemic and branchial hearts of cuttlefish. Heart performance was assessed with an in situ perfused systemic heart preparation and contractility was evaluated using isometrically contracting systemic and branchial heart muscle rings. Stroke volume, cardiac output, and Ca(2+) sensitivity were significantly lower in systemic hearts perfused with supplemental taurine (100 mmol L(-1)) than in controls. In muscle ring preparations, taurine impaired relaxation at high contraction frequencies, an effect abolished by supra-physiological Ca(2+) levels. Taurine did not affect oxygen consumption in non-contracting systemic heart muscle, but extracellular glucose utilization was twice that of control preparations. Collectively, our results suggest that extracellular taurine depresses cardiac Ca(2+) flux and potentiates glucose utilization in cuttlefish. Variations in taurine levels may represent an important mechanism for regulating cardiovascular function and metabolism in cephalopods.

Effects of renal denervation on renal pelvic contractions and connexin expression in rats.

The renal pelvis shows spontaneous rhythmic contractile activity. We assessed to what extent this activity depends on renal innervation and studied the role of connexins in pelvic contractions. Rats underwent unilateral renal denervation or renal transplantation. Renal pelvic pressure and diuresis were measured invivo. Spontaneous and agonist-induced contractions of isolated renal pelves were investigated by wire myography. Rat and human renal pelvic connexin mRNA abundances and connexin localization were studied by real-time PCR and immunofluorescence respectively. Renal denervation or transplantation increased renal pelvic pressure invivo by about 60 and 150%, respectively, but did not significantly affect pelvic contraction frequency. Under invitro conditions, isolated pelvic preparations from innervated or denervated kidneys showed spontaneous contractions. Pelves from denervated kidneys showed about 50% higher contraction frequencies than pelves from innervated kidneys, whereas contraction force was similar in pelves from denervated and innervated kidneys. There was no denervation-induced supersensitivity to noradrenaline or endothelin-1. Renal denervation did not increase pelvic connexin37, 40, 43 or 45 mRNA abundances. Gap junction blockade had no effect on spontaneous pelvic contractile activity. The denervation-induced effect on pelvic pressure may be the consequence of the enhanced diuresis. The mechanisms underlying the denervation-induced effects on pelvic contraction frequency remain unknown. Our data rule out a major role for two important candidates, by showing that renal denervation neither induced supersensitivity to contractile agonists nor increased connexin mRNA abundance in the pelvic wall.

Prostaglandins induce vasodilatation of the microvasculature during muscle contraction and induce vasodilatation independent of adenosine

Blood flow data from contracting muscle in humans indicates that adenosine (ADO) stimulates the production of nitric oxide (NO) and vasodilating prostaglandins (PG) to produce arteriolar vasodilatation in a redundant fashion such that when one is inhibited the other can compensate. We sought to determine whether these redundant mechanisms are employed at the microvascular level. First, we determined whether PGs were involved in active hyperaemia at the microvascular level. We stimulated four to five skeletal muscle fibres in the anaesthetized hamster cremaster preparation in situ and measured the change in diameter of 2A arterioles (maximum diameter 40 μm, third arteriolar level up from the capillaries) at a site of overlap with the stimulated muscle fibres before and after 2 min of contraction [stimulus frequencies: 4, 20 and 60 Hz at 15 contractions per minute (CPM) or contraction frequencies of 6, 15 or 60 CPM at 20 Hz; 250 ms train duration]. Muscle fibres were stimulated in the absence and presence of the phospholipase A2 inhibitor quinacrine. Further, we applied a range of concentrations of ADO (10(-7)-10(-5) M) extraluminally, (to mimic muscle contraction) in the absence and presence of L-NAME (NO synthase inhibitor), indomethacin (INDO, cyclooxygenase inhibitor) and L-NAME + INDO and observed the response of 2A arterioles. We repeated the latter experiment on a different level of the cremaster microvasculature (1A arterioles) and on the microvasculature of a different skeletal muscle (gluteus maximus, 2A arterioles). We observed that quinacrine inhibited vasodilatation during muscle contraction at intermediate and high contraction frequencies (15 and 60 CPM). L-NAME, INDO and L-NAME + INDO were not effective at inhibiting vasodilatation induced by any concentration of ADO tested in 2A and 1A arterioles in the cremaster muscle or 2A arterioles in the gluteus maximus muscle. Our data show that PGs are involved in the vasodilatation of the microvasculature in response to muscle contraction but did not obtain evidence that extraluminal ADO causes vasodilatation through NO or PG or both. Thus, we propose that PG-induced microvascular vasodilation during exercise is independent of ADO.

Very low force-generating ability and unusually high temperature-dependency in hummingbird flight muscle fibers

Hummingbird flight muscle is estimated to have among the highest mass-specific power output among vertebrates, based on aerodynamic models. However, little is known about the fundamental contractile properties of their remarkable flight muscles. We hypothesized that hummingbird pectoralis fibers generate relatively low force when activated in a tradeoff for high shortening speeds associated with the characteristic high wingbeat frequencies that are required for sustained hovering. Our objective was to measure maximal force-generating ability (maximal force/cross-sectional area, Po/CSA) in single, skinned fibers from the pectoralis and supracoracoideus muscles, which power the wing downstroke and upstroke, respectively, in hummingbirds (Calypte anna) and in another similarly sized species, zebra finch (Taeniopygia guttata), which also has a very high wingbeat frequency during flight but does not perform a sustained hover. Mean Po/CSA in hummingbird pectoralis fibers was very low - 1.6, 6.1 and 12.2 kN m(-2), at 10, 15 and 20°C, respectively. Po/CSA in finch pectoralis fibers was also very low (for both species, ~5% of the reported Po/CSA of chicken pectoralis fast fibers at 15°C). Q10-force (force generated at 20°C/force generated at 10°C) was very high for hummingbird and finch pectoralis fibers (mean=15.3 and 11.5, respectively) compared with rat slow and fast fibers (1.8 and 1.9, respectively). Po/CSA in hummingbird leg fibers was much higher than in pectoralis fibers at each temperature, and the mean Q10-force was much lower. Thus, hummingbird and finch pectoralis fibers have an extremely low force-generating ability compared with other bird and mammalian limb fibers, and an extremely high temperature dependence of force generation. However, the extrapolated maximum force-generating ability of hummingbird pectoralis fibers in vivo (~48 kN m(-2)) is substantially higher than the estimated requirements for hovering flight of C. anna. The unusually low Po/CSA of hummingbird and zebra finch pectoralis fibers may reflect a constraint imposed by a need for extremely high contraction frequencies, especially during hummingbird hovering.

Protein kinase D increases maximal Ca2+-activated tension of cardiomyocyte contraction by phosphorylation of cMyBP-C-Ser315

Cardiac myosin-binding protein C (cMyBP-C) is involved in the regulation of cardiac myofilament contraction. Recent evidence showed that protein kinase D (PKD) is one of the kinases that phosphorylate cMyBP-C. However, the mechanism by which PKD-induced cMyBP-C phosphorylation affects cardiac contractile responses is not known. Using immunoprecipitation, we showed that, in contracting cardiomyocytes, PKD binds to cMyBP-C and phosphorylates it at Ser(315). The effect of PKD-mediated phosphorylation of cMyBP-C on cardiac myofilament function was investigated in permeabilized ventricular myocytes, isolated from wild-type (WT) and from cMyBP-C knockout (KO) mice, incubated in the presence of full-length active PKD. In WT myocytes, PKD increased both myofilament Ca(2+) sensitivity (pCa(50)) and maximal Ca(2+)-activated tension of contraction (T(max)). In cMyBP-C KO skinned myocytes, PKD increased pCa(50) but did not alter T(max). This suggests that cMyBP-C is not involved in PKD-mediated sensitization of myofilaments to Ca(2+) but is essential for PKD-induced increase in T(max). Furthermore, the phosphorylation of both PKD-Ser(916) and cMyBP-C-Ser(315) was contraction frequency-dependent, suggesting that PKD-mediated cMyBP-C phosphorylation is operational primarily during periods of increased contractile activity. Thus, during high contraction frequency, PKD facilitates contraction of cardiomyocytes by increasing Ca(2+) sensitivity and by an increased T(max) through phosphorylation of cMyBP-C.

Tachyduodenia in mitochondrial neurogastrointestinal encephalomyopathy

In a 38-year-old male patient diagnosed with mitochondrial neurogastrointestinal encephalomyopathy an abnormally high duodenal contraction frequency of 20 per minute was found to be present. It is speculated that this tachyduodenia is caused by a metabolic effect on Cajal cells.