Increase In Frequency Of Contractions Research Articles

Increased contractile activity and dilation of popliteal lymphatic vessels in the TNF-α-overexpressing TNFΔARE/+ arthritic mouse

AimsTNF-α acute treatment has been found to disrupt lymphatic drainage in the setting of arthritis through the NF-kB-iNOS- signaling pathway. We examined whether popliteal lymphatic vessels (pLVs) contractile activity was altered in 12- and 24- week-old females of an arthritic mouse model overexpressing TNF-α (TNFΔARE/+). Main methodspLVs were prepared for intravital imaging to measure lymph flow speed, and ex vivo functional responses to a stepwise increase in transmural pressure in the absence or presence of the non-selective NOS inhibitor (L-NNA) or the selective iNOS inhibitor (1400W) were compared between TNFΔARE/+ and WT mice. Total eNOS (t-eNOS) and eNOS phosphorylated at ser1177 (p-eNOS) were evaluated by western blotting. Key findingsIn vivo imaging revealed a significantly increase in lymph flow speed in TNFΔARE/+ mice in comparison to WT at both ages. Pressure myography showed an increase in contraction frequency, diameters and fractional pump flow at both ages, whereas amplitude and ejection fraction were significantly decreased in older TNFΔARE/+ mice. Additionally, contraction frequency was increased in the presence of 1400W, and systolic diameter was abolished with L-NNA in TNFΔARE/+ mice compared to WT. Significant increases in p-eNOS expression and neutrophil recruitment (MPO activity) were observed in TNFΔARE/+ mice compared to WT. SignificanceOur data reveal functional changes in pLVs, especially in advanced stage of arthritis. These alterations may be related to eNOS and iNOS response, which can affect drainage of the inflammatory content from the joints.

The pro-inflammatory signature of lipopolysaccharide in spontaneous contracting embryoid bodies differentiated from mouse embryonic stem cells.

Embryonic stem (ES) cells differentiate towards all three germ layers, including cardiac cells and leukocytes, and may be therefore suitable to model inflammatory reactions in vitro. In the present study, embryoid bodies differentiated from mouse ES cells were treated with increasing doses of lipopolysaccharide (LPS) to mimic infection with gram-negative bacteria. LPS treatment dose-dependent increased contraction frequency of cardiac cell areas and calcium spikes and increased protein expression of α-actinin. LPS treatment increased the expression of the macrophage marker CD68 and CD69, which is upregulated after activation on T cells, B cells and NK cells. LPS dose-dependent increased protein expression of toll-like receptor 4 (TLR4). Moreover, upregulation of NLR family pyrin domain containing 3 (NLRP3), IL-1ß and cleaved caspase 1 was observed, indicating activation of inflammasome. In parallel, generation of reactive oxygen species (ROS), nitric oxide (NO), and expression of NOX1, NOX2, NOX4 and eNOS occurred. ROS generation, NOX2 expression and NO generation were downregulated by the TLR4 receptor antagonist TAK-242 which abolished the LPS-induced positive chronotropic effect of LPS. In conclusion, our data demonstrate that LPS induced a pro-inflammatory cellular immune response in tissues derived from ES cells, recommending the in vitro model of embryoid bodies for inflammation research.

The enhancing effect of 5-HT on phasic contractions of human isolated distal ureter and the mechanisms mediating these effects

5-Hydroxytryptamine (5-HT) can enhance human ureteral contractions. However, the mediating receptors have not been clarified. This study sought to further characterize the mediating receptors using several selective antagonists and agonists. Human distal ureters were obtained from 96 patients undergoing cystectomy. The mRNA expression levels of 5-HT receptors were examined using RT-qPCR experiments. The phasic contractions of ureter strips, either spontaneous or evoked with neurokinin, were recorded in an organ bath. Among the 13 5-HT receptors, 5-HT2A and 5-HT2C receptors showed the highest mRNA expression levels. 5-HT (10-7–10-4 M) increased the frequency and baseline tension of phasic contractions in a concentration-dependent manner. However, a desensitization effect was observed. The 5-HT2C receptor selective antagonist, SB242084 (10,30,100 nM), shifted the 5-HT concentration-response curves (frequency and baseline tension) rightward with a pA2 value of 8.05 and 7.75, respectively. 5-HT2C receptor selective agonist, vabicaserin, increased contraction frequency with an Emax of 35% of 5-HT. 5-HT2A receptor selective antagonist, volinanserin (1,10,100 nM), only reduced baseline tension with a pA2 of 8.18. The selective antagonists of 5-HT1A, 1B, 1D, 2B, 3, 4, 5, 6, and 7 had no antagonism. Blockade of voltage-gated sodium channels, α1-adrenergic receptors, adrenergic neurotransmission, and neurokinin-2 receptors using tetrodotoxin, tamsulosin, guanethidine, and Men10376, respectively, and desensitization of sensory afferents using capsaicin (100 μM), significantly reduced 5-HT effects. We conclude that 5-HT enhanced ureteral phasic contractions mainly by activating 5-HT2C and 5-HT2A receptors. Sympathetic nerve and sensory afferents partly contributed to 5-HT effects. 5-HT2C and 5-HT2A receptors could be promising targets for ureteral stone expulsion.

The impact of maternal obesity on in vivo uterine contractile activity during parturition in the rat.

Maternal obesity is associated with increased risk of prolonged and dysfunctional labor and emergency caesarean section. To elucidate the mechanisms behind the associated uterine dystocia, a translational animal model is required. Our previous work identified that exposure to a high-fat, high-cholesterol (HFHC) diet to induce obesity down-regulates uterine contractile associated protein expression and causes asynchronous contractions ex vivo. This study aims to investigate the impact of maternal obesity on uterine contractile function in vivo using intrauterine telemetry surgery. Virgin female Wistar rats were fed either a control (CON, n=6) or HFHC (n=6) diet for 6 weeks prior to conception, and throughout pregnancy. On Day 9 of gestation, a pressure-sensitive catheter was surgically implanted aseptically within the gravid uterus. Following 5 days recovery, intrauterine pressure (IUP) was recorded continuously until delivery of the 5th pup (Day 22). HFHC induced obesity led to a significant 1.5-fold increase in IUP (p=0.026) and fivefold increase in frequency of contractions (p=0.013) relative to CON. Determination of the time of labor onset identified that HFHC rats IUP (p=0.046) increased significantly 8h prior to 5th pup delivery, which contrasts to CON with no significant increase. Myometrial contractile frequency in HFHC rats significantly increased 12 h prior to delivery of the 5th pup (p=0.023) compared to only 3h in CON, providing evidence that labor in HFHC rats was prolonged by 9h. In conclusion, we have established a translational rat model that will allow us to unravel the mechanism behind uterine dystocia associated with maternal obesity.

In Vitro Irradiation of Lymphatic Vessels Enhances Lymphatic Pump Function

Active lymphatic pumping is critical for propulsion of lymph against a pressure gradient as well as transport of lipids and immune cells to the central venous circulation. When lymphatic pumping is impaired, diminished lymph flow leads to interstitial edema, immune cell accumulation and sustained inflammation. However, a majority of radiation biology research has primarily focused on the effects of ionizing radiation (IR) on blood vessels. These studies reported that IR induces imbalance between vaso‐dilatory and ‐constrictive pathways and impairs vascular tone. Only a handful of the studies have investigated the acute effects of IR on lymphatic vessels. Furthermore, the studies evaluating IR‐induced changes in lymphatic tone and pumping in vivo are limited because, in addition to the intrinsic contractility of the lymphatic muscle, lymphatic tone and pumping in vivo is modulated by a variety of substances present in the luminal lymph and the surrounding interstitial fluid. Therefore, the goal of the present study was to characterize the effects of IR on lymphatic tone and pumping independent of the confounding effects of IR on the other tissues.Mesenteric lymphatic vessels (MLVs), isolated from male Sprague Dawley rats, were randomly divided into SHAM and IR groups and were placed in chilled APSS. MLVs from the IR group were then irradiated with X‐rays at 10 Gray Dose. Immediately after irradiation, MLVs from both groups were placed in chilled APSS until further use. MLVs were then cannulated and perfused with warm APSS. Lymphatic pumping was assessed in spontaneously contracting vessels. Role of nitric oxide (NO) and cyclooxygenase (COX) pathways was evaluated by assessing pump function in separate MLVs before and after incubation in N(ω)‐nitro‐L‐arginine methyl ester (L‐NAME; 100 µM) and Indomethacin (INDO; 10 µM).Evaluation of the lymphatic pumping in response to changes in transmural pressure revealed significantly increased contraction frequency and calculated active lymph flow in IR MLVs compared to those in SHAM MLVs. However, stroke volume normalized to passive volume and diastolic tone were not significantly different between the IR and SHAM MLVs. The increase in contraction frequency in IR MLVs was partially restored by the blockade of COX pathways with INDO. Blockade of NOS with L‐NAME, however, led to further increase in contraction frequency of IR MLVs, which was significantly higher than that in SHAM MLVs.Early studies investigating the IR effects on lymphatic endothelial cells reported that lymphatic endothelium is resistant to IR. Conflicting findings of the in vivo lymphatic studies have further confounded the insights into the lymphatic responses to IR. It has been widely believed that lymphatic vessels are unaffected by IR, and therefore, the role of the lymphatic system‐ the other half of the circulatory system, in radiation injury has been mostly ignored. However, it is evident from the findings of the present study that lymphatic vessels are indeed affected by IR. Furthermore, IR‐induced increase in contraction frequency observed in the present study suggests that lymphatic acute responses to IR differ from the blood vessel responses.

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.

Transcriptomic Analysis of Cardiomyocyte Extracellular Vesicles in Hypertrophic Cardiomyopathy Reveals Differential snoRNA Cargo.

Hypertrophic cardiomyopathy (HCM) is characterized by increased left ventricular wall thickness that can lead to devastating conditions such as heart failure and sudden cardiac death. Despite extensive study, the mechanisms mediating many of the associated clinical manifestations remain unknown and human models are required. To address this, human-induced pluripotent stem cell (hiPSC) lines were generated from patients with a HCM-associated mutation (c.ACTC1G301A) and isogenic controls created by correcting the mutation using CRISPR/Cas9 gene editing technology. Cardiomyocytes (hiPSC-CMs) were differentiated from these hiPSCs and analyzed at baseline, and at increased contractile workload (2 Hz electrical stimulation). Released extracellular vesicles (EVs) were isolated and characterized after a 24-h culture period and transcriptomic analysis performed on both hiPSC-CMs and released EVs. Transcriptomic analysis of cellular mRNA showed the HCM mutation caused differential splicing within known HCM pathways, and disrupted metabolic pathways. Analysis at increasing contraction frequency showed further disruption of metabolic gene expression, with an additive effect in the HCM background. Intriguingly, we observed differences in snoRNA cargo within HCM released EVs that specifically altered when HCM hiPSC-CMs were subjected to increased workload. These snoRNAs were predicted to have roles in post-translational modifications and alternative splicing, processes differentially regulated in HCM. As such, the snoRNAs identified in this study may unveil mechanistic insight into unexplained HCM phenotypes and offer potential future use as HCM biomarkers or as targets in future RNA-targeting therapies.

PSX-B-10 Effect of undigested neutral detergent fiber concentration and forage inclusion rate on ruminal pH, reticular motility, and total tract permeability for finishing beef heifers

Abstract This study evaluated the effects of undigested neutral detergent fiber (uNDF) concentration and forage inclusion (FI) rate on dry matter (DM) intake, ruminal pH, reticular contractions, and gastrointestinal permeability for finishing beef cattle. Five ruminally cannulated Hereford′Simmental heifers (699±69.1 kg) were used in an incomplete 6×6 Latin square (26-d periods) with a 2×3 factorial treatment arrangement. Barley grain-based diets were formulated using barley silage or wheat straw to provide low or high uNDF (7.1 vs. 8.5% DM) with forage proportions of 5, 10, or 15% of dietary DM. Dry matter intake (P ≥ 0.10) and eating time (P ≥ 0.13) were not affected by uNDF, FI, or uNDF′FI. With low uNDF diets, increasing FI numerically (P = 0.02) increased rumination time (min/d); while, with high uNDF diets, rumination time increased with 5 to 10% FI, but not thereafter (P = 0.03). Mean ruminal pH was not affected by uNDF (6.17 vs. 6.19; P = 0.08), but increased with increasing FI (6.04b, 6.23a, and 6.28a; P = 0.02). Duration of ruminal pH &amp;lt; 5.5 was not affected by uNDF but tended (P = 0.07) to be reduced with increasing FI. High uNDF diet tended to increase the frequency of reticular contractions (1.43 vs. 1.51 contractions/min; P = 0.07) but decreased the contraction duration (13.2 vs. 14.1 sec; P = 0.04). Increasing FI increased contraction frequency (1.39b, 1.50a, and 1.53a contractions/min; P = 0.03) and tended to reduce contraction duration as forage increased from 5 to 10 and 15% (14.3, 13.1, and 13.6 sec; P = 0.07). Feeding high uNDF decreased (P = 0.05) permeability of the gastrointestinal tract based on the appearance of Cr-EDTA in urine following an intra-ruminal dose. Increasing FI tended to reduce gastrointestinal tract permeability (P = 0.06). Limited interactions indicate that uNDF and FI act independently suggesting that increasing dietary uNDF, without increasing FI rate, can stimulate frequency of reticulo-ruminal contractions and reduce gastrointestinal permeability for finishing cattle.

Functional lymphatic reserve capacity is depressed in patients with a Fontan circulation.

BackgroundLymphatic abnormalities play a role in effusions in individuals with a Fontan circulation. Recent results using near‐infrared fluorescence imaging disclosed an increased contraction frequency of lymphatic vessels in Fontan patients compared to healthy controls. It is proposed that the elevated lymphatic pumping seen in the Fontan patients is necessary to maintain habitual interstitial fluid balance. Hyperthermia has previously been used as a tool for lymphatic stress test. By increasing fluid filtration in the capillary bed, the lymphatic workload and contraction frequency are increased accordingly. Using near‐infrared fluorescence imaging, the lymphatic functional reserve capacity in Fontan patients were explored with a lymphatic stress test.MethodsFontan patients (n = 33) were compared to a group of 15 healthy individuals of equal age, weight, and gender. The function of the superficial lymphatic vessels in the lower leg during rest and after inducing hyperthermia was investigated, using near‐infrared fluorescence imaging.ResultsBaseline values in the Fontan patients showed a 57% higher contraction frequency compared to the healthy controls (0.4 ± 0.3 min−1 vs. 0.3 ± 0.2 min−1, p = 0.0445). After inducing stress on the lymphatic vessels with hyperthermia the ability to increase contraction frequency was decreased in the Fontan patients compared to the controls (0.6 ± 0.5 min−1 vs. 1.2 ± 0.8 min−1, p = 0.0102).ConclusionsFontan patients had a higher lymphatic contraction frequency during normal circumstances. In the Fontan patients, the hyperthermia response is dampened indicating that the functional lymphatic reserve capacity is depressed. This diminished reserve capacity could be part of the explanation as to why some Fontan patients develop late‐onset lymphatic complications.

Oxygen uptake, heart rate and activities of locomotor muscles during a critical swimming speed protocol in the gilthead sea bream Sparus aurata.

Oxygen uptake, heart rate and contraction frequencies of slow oxidative (SO) and fast glycolytic (FG) muscle were measured simultaneously in gilthead seabream Sparus aurata submitted to stepwise increases in current speed in a swimming respirometer. Variation in oxygen uptake was closely related to variation in heart rate, over initial steps these rose in concert with an increase in contraction frequency of SO muscle. There was an asymptote in oxygen uptake and heart rate at high speeds that reflected a transition from exclusive use of aerobic SO muscle to a combination of SO and anaerobic FG muscle, and which preceded fatigue.

Effects of Elevated Downstream Pressure and the Role of Smooth Muscle Cell Coupling through Connexin45 on Lymphatic Pacemaking.

Lymphatic vessels rely on spontaneous lymphatic muscle cell (LMC) contractions and one-way intraluminal valves to efficiently pump lymph and return it into the bloodstream. Intraluminal pressure is known to regulate the contractile function of lymphatics, with pressure elevation leading to increased contraction frequency and decreased amplitude. Contractions are normally initiated by a dominant pacemaker and are highly entrained among strongly coupled LMCs. Previously, we found that connexin45 is the major connexin isoform mediating LMC-LMC electrical coupling. Lymphatics from mice lacking smooth muscle connexin45 display uncoordinated, impaired contractions. Here, we utilized this connexin45-deficient model, pressure myography, and recently developed, novel analytical tools to assess the effects of elevated downstream pressure on the number, location, and frequency of lymphatic pacemakers. Our results show that, in vessels from healthy controls, an increase in downstream pressure resulted in the recruitment/development of new pacemakers and increased contractile frequency while a dominant pacemaker continued to be observed. In contrast, vessels from connexin45-deficient mice displayed significantly more pacemakers, but none were dominant; this worsened with elevated downstream pressure. These results suggest a potential protective mechanism through which the lymphatic vasculature adapts to transient increases in downstream pressure, but which may not be sustained in scenarios with chronic elevated downstream pressure.

Assessing Peristalsis at the Endometrial–Myometrial Junctional Zone: A Reproducible Ultrasound Technique?

Background: Uterine peristalsis occurs in the endometrial–myometrial junctional zone. It is involved in sperm transport and embryo implantation in spontaneous and in vitro fertilization (IVF) cycles. We investigated the reproducibility of transvaginal assessment of peristalsis and endometrial combined thickness (ECT) as a surrogate marker for contraction frequency and directionality. Methods: We studied 74 women undergoing IVF between 2015 and 2018. On day 9 of stimulation, participants had a transvaginal ultrasound to assess follicular development and ECT. Women proceeding to fresh embryo transfer had an ultrasound preprocedure. A videoclip was analyzed for frequency (total contractions per minute) and directionality of contractions (cervical to fundal [CF] and fundal to cervical [FC]). Anonymized images were reviewed on three separate occasions by a single observer. Intraclass correlation (ICC with 95% CI) and Bland–Altman plots were constructed to assess intraobserver agreement. Secondary analysis was performed to assess peristalsis with ECT and pregnancy rates. Results: Between the first and second observations, there was suboptimal correlation between visual assessment of contraction frequency and directionality (ICC–total 0.67 (0.43–0.80) p &lt; 0.001, ICC–CF 0.62 (0.35–0.78), p &lt; 0.001, ICC–FC 0.74 (0.55–0.85), p &lt; 0.001. Correlation for both frequency and directionality significantly improved between second and third viewing (ICC–total 0.97 (0.95–0.98), p &lt; 0.001, ICC–CF 0.84 (0.73–0.91), p &lt; 0.001, ICC–FC 0.89 (0.81–0.94), p &lt; 0.001). Good agreement was seen on Bland–Altman plots with narrower limits of agreement on second and third viewing. Median ECT was 10 mm (interquartile range [IQR] 8–12 mm). Women with ECT [Formula: see text] 10 mm versus &lt;10 mm demonstrated more contractions per minute (2.2 ± 0.7 vs. 1.7 ± 0.6, p = 0.02). The clinical and ongoing pregnancy rates were 33% (20/60) and 22% (13/60), respectively. There was no association between pregnancy and peristalsis frequency or directionality. Conclusion: Uterine peristalsis is a reproducible observation displaying a learning curve to achieve excellent agreement. Endometrial thickness [Formula: see text]10 mm was associated with increased contraction frequency. There was no association between contraction frequency and/or directionality and clinical pregnancy rates.

What Is the Mechanism Underlying Pressure‐induced Chronotropy in Collecting Lymphatic Vessels?

The rhythmic contractions of lymphatic smooth muscle (LSM) cells enable lymph propulsion against adverse pressure gradients. These contractions are initiated by LSM action potentials (APs), generated by an ionic pacemaker, whose rate is sensitive to the transmural pressure difference. We recently showed that SM‐specific deletion of the Ca2+‐activated Cl− channel, anoctamin1 (Ano1), reduced the basal AP firing rate of mouse inguinal‐axillary lymphatic (IALs) vessels to ~25% of normal and abrogated pressure‐induced chronotopy. However, IALs are efferent vessels that show only a modest (2‐fold) increase in contraction frequency over the presumed physiological pressure range 0.5 – 8 cmH2O. In contrast, popliteal afferent lymphatics (PLs) exhibit an 8‐fold increase in chronotropy from 0.5 – 5 cmH2O and SM‐specific deletion of Ano1 attenuates but does not abolish their pressure‐induced chronotropy. Here we asked: 1) what other ionic mechanisms participate in pressure‐induced chronotropy of PLs? 2) what accounts for the residual, pressure‐independent pacemaking in IALs and PLs after Ano1 deletion?To address these questions we measured the frequency‐pressure relationship (F‐P) of cannulated, pressurized PLs from control mice and mice deficient in key mechanosensitive and second‐messenger‐gated ion channels implicated in arterial pressure sensing. SM‐specific deletion of the mechanosensitive cation channel Piezo1 had no significant effect on F‐P. Global deletion of the osmosensitive cation channel TRPV4, or the DAG‐gated cation channels TRPC3 or TRPC6, or both, had no significant effect on F‐P. TRPM4−/− mice were not available, but the selective TRPM4 inhibitors, CBA and NBA, had minimal effects on F‐P. SM‐specific deletion of the cation channel TRPP1 (Pkd2) had no significant effect on F‐P. Deletion of T‐type Ca2+ channels Cav3.1 and/or Cav3.2 (previously implicated in lymphatic pacemaking), had no significant effect on F‐P. However, SM‐specific deletion of IP3R1, the only IP3R isoform expressed in mouse LSM, produced a phenotype similar to Ano1 deletion: a reduction in basal frequency and blunting of the F‐P relationship, suggesting a pressure‐induced IP3 generation downstream from mechanosensitive G‐protein(s). We then tested the prominent arterial SM mechanosensitive GPCR, AT1R. The inverse agonist losartan had no effect on F‐P nor did global knock out of AT1bR, the only isoform expressed in mouse LSM. In conclusion, our results point to a GPCR mechanosensing mechanism, independent of AT1R, that generates IP3 in a pressure‐sensitive manner to activate Ano1 and regulate the cycling rate of the ionic pacemaker in lymphatic smooth muscle.Support or Funding InformationNIH‐HL‐122578

Evidence of functional ryanodine receptors in rat mesenteric collecting lymphatic vessels.

In the current study, the potential contributions of ryanodine receptors (RyRs) to intrinsic pumping and responsiveness to substance P (SP) were investigated in isolated rat mesenteric collecting lymphatic vessels. Responses to SP were characterized in lymphatic vessels in the absence or presence of pretreatment with nifedipine to block L-type Ca2+ channels, caffeine to block normal release and uptake of Ca2+ from the sarcoplasmic reticulum, ryanodine to block all RyR isoforms, or dantrolene to more selectively block RyR1 and RyR3. RyR expression and localization in lymphatics was also assessed by quantitative PCR and immunofluorescence confocal microscopy. The results show that SP normally elicits a significant increase in contraction frequency and a decrease in end-diastolic diameter. In the presence of nifedipine, phasic contractions stop, yet subsequent SP treatment still elicits a strong tonic contraction. Caffeine treatment gradually relaxes lymphatics, causing a loss of phasic contractions, and prevents subsequent SP-induced tonic contraction. Ryanodine also gradually diminishes phasic contractions but without causing vessel relaxation and significantly inhibits the SP-induced tonic contraction. Dantrolene treatment did not significantly impair lymphatic contractions nor the response to SP. The mRNA for all RyR isoforms is detectable in isolated lymphatics. RyR2 and RyR3 proteins are found predominantly in the collecting lymphatic smooth muscle layer. Collectively, the data suggest that SP-induced tonic contraction requires both extracellular Ca2+ plus Ca2+ release from internal stores and that RyRs play a role in the normal contractions and responsiveness to SP of rat mesenteric collecting lymphatics.NEW & NOTEWORTHY The mechanisms that govern contractions of lymphatic vessels remain unclear. Tonic contraction of lymphatic vessels caused by substance P was blocked by caffeine, which prevents normal uptake and release of Ca2+ from internal stores, but not nifedipine, which blocks L-type channel-mediated Ca2+ entry. Ryanodine, which also disrupts normal sarcoplasmic reticulum Ca2+ release and reuptake, significantly inhibited substance P-induced tonic contraction. Ryanodine receptors 2 and 3 were detected within the smooth muscle layer of collecting lymphatic vessels.

Contraction frequency after administration of misoprostol in obese versus nonobese women

Objective: To examine impact of obesity on contraction frequency following misoprostol. Our hypothesis is that an increased volume of distribution reduces the bioavailability of misoprostol and may be an explanation for reduced efficacy. We examined the contraction frequency as a surrogate marker for bioavailability of misoprostol.Study design: We compared the rate of contractions at five time intervals in 313 subjects: prior to administration, and at four intervals post administration. We compared number of contractions in obese versus nonobese. As a planned secondary analysis, we then compared the rate of change in contractions per hour at four time intervals: a repeated measures analysis to compare the rate of change in contractions per hour over the 5-hour window controlling for race (White versus non-White) and parity (primiparous versus multiparous). General linear model and repeated measures analysis were conducted to report the parameter estimates, least square means, difference of least square means, and p values.Results: Nonobese women presented with more contractions at baseline, 7 ± 5 versus 4 ± 5 c/h, p < .001. At all four time intervals after misoprostol administration obese women had fewer contractions per hour. The rate of change in contraction frequency after administration found obese women had a lower rate of increase in contraction frequency over the course of all four hours. We found a least squares means estimate (c/h): first hour (−0.87), p = .08, second hour (−2.43), p = .01, third hour (−1.80), p = .96, and fourth hour (−2.98), p = .007.Conclusions: Obese women have a lower rate of contractions per hour at baseline and at four intervals after misoprostol administration. In addition, the rate of change in the increase in contractions/hour also was reduced in obese women versus nonobese women. This suggests a lower bioavailability of misoprostol in women with a larger volume of distribution which would likely impact the efficacy of misoprostol in obese women when given the same dose of misoprostol. It is unknown if higher misoprostol dosing would increase efficacy of misoprostol in obese women.

A Validation Study of Near-Infrared Fluorescence Imaging of Lymphatic Vessels in Humans

Near-infrared fluorescence (NIRF) imaging is a new imaging technique that is used to visualize lymphatic vessels in humans. It has a high spatial and temporal resolution, allowing real-time visualization of lymphatic flow. The current study investigated the intra- and inter-individual variability of the technique, and how local hypo- and hyperthermia (20°C, 40°C), as well as exercise affect lymph transport. In this study, 10 healthy volunteers were studied twice, with 2 weeks between. NIRF imaging was conducted by using intradermal Indocyanine green injections and a custom-built camera setup. All data were blinded before analysis and presented as mean ± standard deviation. Mean contraction frequency and lymph propulsion velocity were 0.59 ± 0.13 minutes-1 and 1.51 ± 0.24 cm/s, respectively, with no significant difference during each 4 hours examination or between the two visits. The maximal pressure that the lymphatic flow in the vessels could overcome on test day 1 and 2 was 56 ± 9 mmHg and 57 ± 9 mmHg, respectively (p = 0.496). Local hyperthermia increased contraction frequency from 0.62 ± 0.4 minutes to 1.46 ± 0.5 minutes-1 (p < 0.05). Hypothermia caused no significant changes. Immediately after exercise (exercising at a simulated distance of 1.4 km on a cycle ergometer), an increase in lymph propulsion velocity from 1.5 ± 0.49 to 2.2 ± 0.63 cm/s was observed (p < 0.05); whereas contraction frequency was unaltered. A decrease in contraction frequency from 0.68 ± 0.25 minutes to 0.35 ± 0.19 minutes-1 was observed 10 minutes after exercise, without a change in velocity. NIRF imaging can be conducted for 4 hours without a change in lymphatic activity. Furthermore, it has the sensitivity to detect changes in lymphatic activity by local hyperthermia and exercise. No changes were seen after local hypothermia. Pumping pressure shows good repeatability, whereas the other parameters show poor repeatability.

Home uterine monitoring for detecting preterm labour.

To reduce the morbidity and mortality associated with preterm birth, home uterine activity monitoring aims for early detection of increased contraction frequency, and early intervention with tocolytic drugs to inhibit labour and prolong pregnancy. However, the effectiveness of such monitoring is disputed. To determine whether home uterine activity monitoring is effective in improving the outcomes for women and their infants considered to be at high risk of preterm birth, when compared with care that does not include home uterine activity monitoring. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 June 2016), CENTRAL (Cochrane Library 2016, Issue 5), MEDLINE (1966 to 28 June 2016), Embase (1974 to 28 June 2016), CINAHL (1982 to 28 June 2016), and scanned reference lists of retrieved studies. Randomised control trials of home uterine activity monitoring, with or without patient education programmes, for women at risk of preterm birth, compared with care that does not include home uterine activity monitoring. Two review authors independently assessed trials for inclusion and risks of bias, extracted data and checked them for accuracy. We did not attempt to contact authors to resolve queries. We assessed the evidence using the GRADE approach. There were 15 included studies (6008 enrolled participants); 13 studies contributed data. Women using home uterine monitoring were less likely to experience preterm birth at less than 34 weeks (risk ratio (RR) 0.78, 95% confidence interval (CI) 0.62 to 0.99; three studies, 1596 women; fixed-effect analysis) (GRADE high). This difference was not evident when we carried out a sensitivity analysis, restricting the analysis to studies at low risk of bias based on study quality (RR 0.75, 95% CI 0.57 to 1.00; one study, 1292 women). There was no difference in the rate of perinatal mortality (RR 1.22, 95% CI 0.86 to 1.72; two studies, 2589 babies) (GRADE low).There was no difference in the number of preterm births at less than 37 weeks (average RR 0.85, CI 0.72 to 1.01; eight studies, 4834 women; random-effects, Tau2 = 0.03, I2 = 68%) (GRADE very low). Infants born to women using home uterine monitoring were less likely to be admitted to neonatal intensive care unit (average RR 0.77, 95% CI 0.62 to 0.96; five studies, 2367 babies; random-effects, Tau2 = 0.02, I2 = 32%) (GRADE moderate). This difference was not maintained when we restricted the analysis to studies at low risk of bias (RR 0.86, 95% CI 0.74 to 1.01; one study, 1292 babies). Women using home uterine monitoring made more unscheduled antenatal visits (mean difference (MD) 0.48, 95% CI 0.31 to 0.64; two studies, 1994 women) (GRADE moderate). Women using home uterine monitoring were also more likely to have prophylactic tocolytic drug therapy (average RR 1.21, 95% CI 1.01 to 1.45; seven studies, 4316 women; random-effects, Tau2 = 0.03, I2 = 62%), but this difference was no longer evident when we restricted the analysis to studies at low risk of bias (average RR 1.22, 95% CI 0.90 to 1.65; three studies, 3749 women; random-effects, Tau2 = 0.05, I2 = 76%) (GRADE low). The number of antenatal hospital admissions did not differ between home groups (RR 0.91, 95% CI 0.74 to 1.11; three studies, 1494 women (GRADE low)). We found no data on maternal anxiety or acceptability. Home uterine monitoring may result in fewer admissions to a neonatal intensive care unit but in more unscheduled antenatal visits and tocolytic treatment; the level of evidence is generally low to moderate. Important group differences were not evident when we undertook sensitivity analysis using only trials at low risk of bias. There is no impact on maternal and perinatal outcomes such as perinatal mortality or incidence of preterm birth.

Role of endothelin-1 for the regulation of renal pelvic function.

Endothelin-1 (ET-1) stimulates contractions in isolated rat renal pelves. The signal transduction mechanisms that mediate ET-1-induced renal pelvic contractions and the role of ET-1 for the in vivo regulation of renal pelvic function are not well characterized. We tested if ET-1 stimulates contractions in murine and human renal pelves, if ET-1 activates the renal pelvic RhoA/ROCK pathway, and if low renal ET-1 formation or ET receptor blockade reduce renal pelvic contractile activity. ET-1 increased contraction frequency and force in murine renal pelves. The majority of human renal pelvic tissue samples showed tonic contractions in response to ET-1. Seven out of 20 human tissue samples showed phasic contractions. In four samples, they were elicited by ET-1 at 10-33nmol/l. ET-1 increased renal pelvic RhoA-GTP content and myosin phosphatase target subunit 1 phosphorylation in isolated rat renal pelves. Renal pelvic contraction frequency (29 ± 2 vs. 29 ± 3min(-1)) and renal pelvic pressure (7.1 ± 0.9 vs. 5.9 ± 1.7mmHg) were similar in collecting duct-specific ET-1 knockout mice and in ET-1 floxed controls in vivo. ET-1 sensitivity of isolated renal pelves was similar in both groups. ET receptor blockade did not significantly affect pelvic contraction frequency and pressure in rats. We conclude that ET-1 stimulates phasic contractions in murine, rat, and, to a lesser extent, in human renal pelves. ET-1 activates the RhoA/ROCK pathway in the renal pelvic wall. Endogenous, kidney-derived ET-1 does not play a major role for the regulation of renal pelvic contractions in vivo.

Involvement of TRPM4 in Stretch‐Induced Modulation of Lymphatic Pumping

Rhythmic and phasic contractions of collecting lymphatic vessels are critically involved in tissue fluid homeostasis and immune response. This contractile activity, or lymphatic pumping, is exquisitely regulated by luminal fluid pressure. However, the molecular contributors of stretch‐induced lymphatic pumping are not known. Some members of the TRP channel family, in particular TRPM4,have been shown to respond to stretch or pressure and to contribute to myogenic vasoconstriction and vascular response to stretch.Using pressure myography, electrophysiology, pharmacology and quantitative real‐time PCR, we tested the hypothesis that TRPM4 is also a major contributor of the lymphatic vessel response to stretch.We demonstrated the expression of TRPM4 mRNA in rat mesenteric lymphatic vessels and showed that the contraction frequency of the vessels pressurized at 3 mmHg was inhibited in a concentration‐dependent manner by the TRPM4 blocker 9‐phenanthrol (IC50=1.2 µM). The blocker (10 µM) also inhibited the pressure‐induce increase in contraction frequency in an endothelium‐independent manner and caused a hyperpolarization of the lymphatic muscle. These findings suggest an important role for TRPM4 in the ability of lymphatic vessels to adapt their contractile activity to changes in intraluminal lymph pressure.

Home uterine monitoring for detecting preterm labour.

To reduce the morbidity and mortality associated with preterm birth, home uterine activity monitoring aims for early detection of increased contraction frequency, and early intervention with tocolytic drugs to inhibit labour and prolong pregnancy. However, the effectiveness of such monitoring is disputed. To determine whether home uterine activity monitoring is effective in improving the outcomes for women and their infants considered to be at high risk of preterm birth, when compared with conventional or other care packages that do not include home uterine monitoring. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 October 2014), CENTRAL (The Cochrane Library 2014, Issue 8), MEDLINE (1966 to 31 August 2014), EMBASE (1974 to 31 August 2014), CINAHL (1982 to 31 August 2014) and scanned reference lists of retrieved studies. Randomised control trials of home uterine activity monitoring, with or without patient education programmes, for women at risk for preterm birth, in comparison to the same care package without home uterine activity monitoring. Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We did not attempt to contact authors to resolve queries. There were 15 included studies (total number of enrolled participants 6008); 13 studies contributed data. Women using home uterine monitoring were less likely to experience preterm birth at less than 34 weeks (risk ratio (RR) 0.78; 95% confidence interval (CI) 0.62 to 0.99; three studies, n = 1596; fixed-effect analysis) (GRADE high). The significant difference was not evident when we carried out a sensitivity analysis, restricting the analysis to studies at low risk of bias based on study quality (RR 0.75; 95% CI 0.57 to 1.00, one study, 1292 women). There was no significant difference in the rate of perinatal mortality (RR 1.22; 95% CI 0.86 to 1.72; two studies, n = 2589) (GRADE low)There was no significant difference in the number of preterm births at less than 37 weeks (average RR 0.85; CI 0.72 to 1.01; eight studies, n = 4834; random-effects, T² = 0.03, I² = 68%) (GRADE very low). Infants born to women using home uterine monitoring were less likely to be admitted to neonatal intensive care unit (average RR 0.77; 95% CI 0.62 to 0.96; five studies, n = 2367; random-effects, T² = 0.02, I² = 32%) (GRADE moderate). The difference was not statistically significant when only high quality studies were included (RR 0.86; 95% CI 0.74 to 1.01; one study, n = 1292). Women using home uterine monitoring made more unscheduled antenatal visits (mean difference (MD) 0.49; 95% CI 0.39 to 0.62; two studies, n = 3707) (GRADE moderate). Women using home uterine monitoring were also more likely to have prophylactic tocolytic drug therapy (average RR 1.21; 95% CI 1.01 to 1.45; seven studies, n = 4316; random-effects. T² = 0.03, I² = 62%) but this difference was no longer significant when the analysis was restricted to higher quality studies (average RR 1.22; 95% CI 0.90 to 1.65, three studies, n = 3749,random-effects, T² = 0.05, I² = 76%) (GRADE low). One small study reported that the home uterine monitoring group spent fewer days in hospital antenatally. No data on maternal anxiety or acceptability were found. Home uterine monitoring may result in fewer admissions to a neonatal intensive care unit but more unscheduled antenatal visits and tocolytic treatment, but the level of evidence is generally low to moderate. Important group differences were not evident when sensitivity analysis was undertaken using only high quality trials. There is no impact on maternal and perinatal outcomes such as perinatal mortality or incidence of preterm birth.