Maximum Constriction Research Articles

The effect of shear stress, potassium, adenosine, and acidosis on alpha‐1 adrenergic vasoconstriction of rat soleus feed arteries (1170.14)

Arteries and arterioles constrict less to sympathetic stimulation in contracting compared to resting skeletal muscle (sympatholysis). There is some uncertainty regarding the specific agents causing sympatholysis. We hypothesized that increased levels of arterial wall shear stress, potassium, adenosine, or acidosis contribute to sympatholysis, thereby reducing sympathetic vasoconstriction. Soleus feed arteries (n = 12 per group) were isolated from male Sprague‐Dawley rats and cannulated on two glass micropipettes for in vitro videomicroscopy. We measured the constriction response to the α‐1 agonist phenylephrine (PE; 10‐9 M to 10‐4 M, 0.5 log increments) in the presence of varying levels of shear stress (0 dy/cm2, 25 dy/cm2, and 135 dy/cm2), potassium (5 mM, 7.5 mM, and 10 mM), adenosine (0 μM, 0.8 μM, and 1.6 μM) and acidosis (pH = 7.4, 7.1, 6.8, and 6.5). There was no significant difference in PE induced constriction between levels of shear stress (maximum constriction 67.6 % vs. 68.1 % and 67.6 %), potassium (maximum constriction 63.1 % vs. 56.5 % and 65.0 %), or adenosine (maximum constriction 56.2 % vs. 54.3 % and 54.2 %). However, acidosis reduced constriction to PE (maximum constriction 77.6% vs. 72.0%, 66.6%, and 66.3%). We conclude that acidity, but not shear stress, potassium, or adenosine, is sympatholytic in feed arteries from the predominantly slow twitch soleus muscle.Grant Funding Source: Supported by NSF #DBI‐1062721 and the Seaver Research Council

Resistance arteries from normally‐reared and maternal separation rats display similar vascular reactivity (1087.3)

We previously reported that MatSep (3 hours/day from days 2‐14) induces exaggerated angiotensin II (AngII)‐induced vasoreactivity with decreased nitric oxide (NO) buffering capacity in aortae of adult rats compared to control rats (normally‐reared littermates). Also, chronic AngII infusion produced exaggerated hypertension in MatSep rats. The aim of this study was to investigate whether MatSep male and female rats display exaggerated vascular reactivity of resistance arteries. Third‐order mesenteric arteries from adult rats (n=5‐6 per group) were isolated and mounted on wire myographs. Concentration‐response curves were generated for phenylephrine or endothelin and normalized to maximal potassium chloride‐induced constriction. Additionally, we tested acetylcholine and sodium nitroprusside‐induced relaxation. No differences in EC50 or %maximum constriction/dilation were observed between MatSep and control rats. Curves in the presence of L‐NAME revealed similar NO buffering capacity in MatSep and control rats. No sex differences were observed across the study. These data suggest that the abnormal vascular phenotype due to MatSep involves large conduit arteries, sparing smaller resistance arteries. However, resistance arteries are known to play an important role in blood pressure control, and thus, further investigation of these arteries in response to chronic AngII infusion is warranted.Grant Funding Source: Supported by NIH Grants: P01 HL69999, K99 HL111354

Modulation of Blood Flow, Hypoxia, and Vascular Function in Orthotopic Prostate Tumors During Exercise

Previous studies have hypothesized that tumor blood flow may be elevated or reduced during exercise, which could impact the tumor microenvironment. However, to date technical limitations have precluded the measurement of tumor blood flow during exercise. Using an orthotopic preclinical model of prostate cancer, we tested the hypotheses that during exercise tumors would experience 1) diminished vascular resistance, 2) augmented blood flow, 3) increased numbers of perfused vessels, and 4) decreased tissue hypoxia and, furthermore, that the increased perfusion would be associated with diminished vasoconstriction in prostate tumor arterioles. Dunning R-3327 MatLyLu tumor cells were injected into the ventral prostate of male Copenhagen rats aged 4 to 6 months randomly assigned to tumor-bearing (n = 42) or vehicle control (n = 14) groups. Prostate tumor blood flow, vascular resistance, patent vessel number, and hypoxia were measured in vivo in conscious rats at rest and during treadmill exercise, and vasoconstrictor responsiveness of resistance arterioles was investigated in vitro. During exercise there was a statistically significant increase in tumor blood flow (approximately 200%) and number of patent vessels (rest mean ± standard deviation [SD] = 12.7±1.3; exercise mean ± SD = 14.3±0.6 vessels/field; Student t test two-sided P = .02) and decreased hypoxia compared with measurements made at rest. In tumor arterioles, the maximal constriction elicited by norepinephrine was blunted by approximately 95% vs control prostate vessels. During exercise there is enhanced tumor perfusion and diminished tumor hypoxia due, in part, to a diminished vasoconstriction. The clinical relevance of these findings are that exercise may enhance the delivery of tumor-targeting drugs as well as attenuate the hypoxic microenvironment within a tumor and lead to a less aggressive phenotype.

Elderly bioheat modeling: changes in physiology, thermoregulation, and blood flow circulation

A bioheat model for the elderly was developed focusing on blood flow circulatory changes that influence their thermal response in warm and cold environments to predict skin and core temperatures for different segments of the body especially the fingers. The young adult model of Karaki et al. (Int J Therm Sci 67:41-51, 2013) was modified by incorporation of the physiological thermoregulatory and vasomotor changes based on literature observations of physiological changes in the elderly compared to young adults such as lower metabolism and vasoconstriction diminished ability, skin blood flow and its minimum and maximum values, the sweating values, skin fat thickness, as well as the change in threshold parameter related to core or skin temperatures which triggers thermoregulatory action for sweating, maximum dilatation, and maximum constriction. The developed model was validated with published experimental data for elderly exposure to transient and steady hot and cold environments. Predicted finger skin temperature, mean skin temperature, and core temperature were in agreement with published experimental data at a maximum error less than 0.5°C in the mean skin temperature. The elderly bioheat model showed an increase in finger skin temperature and a decrease in core temperature in cold exposure while it showed a decrease in finger skin temperature and an increase in core temperature in hot exposure.

Quantitative analysis of 3D hydrodynamic focusing of microparticles by digital holographic microscopy

In the field of life sciences, the monitoring of biological samples has become a great concern to control the ecosystem evolution. However, their characterization is often time-consuming because the typical size of the organisms/particles of interest is several orders of magni- tude smaller than the size of the sample under observation. Optical visualization systems require, then, high magnifi- cations that severely limit the depth of focus and conse- quently decrease the sampling rate. To tackle this issue, the most straightforward technique consists in focusing the samples to fit the observation field of view by means of so- called ''sheath flows''. This expedient allows for increasing the overall flow rate, inversely related to the sampling time. In this article, a cost-effective 3D hydro-focusing device is presented. Several flow rates have been tested for both sample and sheath flows, and a thorough investigation of the shape of the focused streamlines conducted in order to validate the prototype design. The 3D position of the sampled micro-objects has been located by digital holo- graphic microscopy and their distribution in cross-sections downstream the injection nozzle compared to numerical simulations. A maximum constriction—ratio between the part of the cross-sections where particles are present with and without focusing sheath flow—of 4.4 % has been observed confirming the potentiality of the technique. Also, a successful match between experiment and numerical simulation has been noted.

Event Sequence Variability in Healthy Swallowing: Building on Previous Findings

This study builds on previous work by Kendall, Leonard, and McKenzie, which investigated event sequence variability for 12 paired events during swallowing by healthy volunteers. They identified four event pairs that always occurred in a stereotyped order and a most common occurring overall order of events during swallowing. In the current study, we investigated overall event sequencing and the same four paired events in a sample of swallows by healthy young (under 45years old) volunteers. Data were collected during a 16-swallow lateral videofluoroscopy protocol, which included manipulations of bolus volume, barium density, bolus viscosity, and swallow cueing. Our results agreed with previous findings that variable event sequencing is found in healthy swallowing, and, in regard to obligatory sequencing of two paired events, movement of the arytenoids toward the base of the epiglottis begins prior to upper esophageal sphincter (UES) opening and maximum hyolaryngeal approximation occurs after UES opening. However, our data failed to replicate the previous findings that there is obligatory sequencing of maximum pharyngeal constriction after maximal UES distension and the UES opens before bolus arrival at the UES. The most common observed overall event sequence reported by Kendall et al. was observed in only 4/293 swallows in our dataset. Manipulations of bolus volume, bolus viscosity, barium concentration, swallow cueing, and swallow repetitions could not completely account for the differences observed between the two studies.

Quantifying Compressibility and Slip in Multiparticle Collision (MPC) Flow Through a Local Constriction

The flow of a compressible fluid with slip through a cylinder with an asymmetric local constriction has been considered both numerically, as well as analytically. For the numerical work, a particle-based method whose dynamics is governed by the multiparticle collision (MPC) rule has been used together with a generalized boundary condition that allows for slip at the wall. Since it is well known that an MPC system corresponds to an ideal gas and behaves like a compressible, viscous flow on average, an approximate analytical solution has been derived from the compressible Navier–Stokes equations of motion coupled to an ideal gas equation of state using the Karman–Pohlhausen method. The constriction is assumed to have a polynomial form, and the location of maximum constriction is varied throughout the constricted portion of the cylinder. Results for centerline densities and centerline velocities have been compared for various Reynolds numbers, Mach numbers, wall slip values and flow geometries.

Vasodilator response to <i>Psidium guajave</i> leaves of mesenteric bed vessels from diabetic and non-diabetic rats

Mortality from cardiovascular abnormalities is almost three times more prevalent in the diabetic population than that in the general population. Psidium guajave has been used traditionally for a long time as a medicinal herb to cure diabetes. Endothelial dependent vasorelaxation effect of Psidium guajave extract on normal aortic rings was observed. This study was designed to investigate the endothelium and nitric oxide roles inPGE-induced vasorelaxation in diabetic rat vessel. Diabetes was induced by a single intraperitoneal injection of streptozotocin. Eight weeks later, superior mesenteric arteries of non-diabetic and diabetic groups were isolated and perfused according to the McGregor method. Prepared vascular beds were constricted with phenylephrine to induce 70% - 75% of maximal constriction. Psidium guajave extract at concentrations of 0.1 to 4 mg/100ml added to the medium and perfusion pressure was recorded. Baseline perfusion pressure of diabetic group was significantly higher than non-diabetic rats in both intact and denuded endothelium. Psidium guajave extract caused a significantly dose depended decrease in perfusion pressure in non-diabetic and diabetic groups in both intact and denuded endothelium. In the presence of N (ω)-nitro-L-arginine methyl ester, Psidium guajave ex-tractinduced relaxation in intact mesenteric beds of non-diabetic and diabetic animals was not suppressed. From the results of this study, it may be concluded that vasorelaxatory effect of Psidium guajave extract is not mediated by endothelium and nitric oxide in both diabetic and non-diabetic vessel and supports the use of the plant’s leaves as a natural, adjunct phytomedicine in the management of diabetes vessel complications.

Combination of Sildenafil and Bosentan for Pulmonary Hypertension in a Human Ex Vivo Model

Both sildenafil and bosentan have been used clinically to treat pulmonary arterial hypertension. As these substances target different pathways to modulate vasoconstriction, we investigated the combined effects of both drug classes in isolated human pulmonary vessels. Segments of pulmonary arteries (PA) and veins (PV) were harvested from 51 patients undergoing lobectomy. Contractile force was determined isometrically in an organ bath. Vessels were constricted with norepinephrine (NE) to determine effects of sildenafil. They were constricted with ET-1 to assess effects of bosentan, and with NE and ET-1 to evaluate the combination of both substances. Sildenafil (1E-5 M) significantly reduced maximum constriction by NE of both PA (13.0 ± 11.1 vs. 34.9 ± 7.6% relative to KCl induced constriction; n = 6; p < 0.001) and PV (81.2 ± 34.2 vs 121.6 ± 20.8%; n = 6; p < 0.01) but did not affect basal tones. Bosentan (1E-5 M) significantly reduced maximum constriction of PV (56.6 ± 21.5 vs. 172.1 ± 30.0%; n = 6; p < 0.01) by ET-1 and led to a small but insignificant decrease of basal tone (p = 0.07). Bosentan almost completely abolished constriction of PA (1.0 ± 0.9 vs. 74.7 ± 25.7 %; n = 6; p < 0.001) by ET-1, but did not affect basal tone. Bosentan (1E-7 M) significantly attenuated combined ET-1/NE dose-response curves in PA (93.1 ± 47.4 vs. 125.3 ± 41.0%; n = 12; p < 0.001) whereas the effect of sildenafil (1E-5 M) was less pronounced (103.6 ± 20.2%; p < 0.05). Simultaneous administration of both substances showed a significantly greater reduction of maximum constriction in PA compared to individual administration (64.6 ± 26.3 %; p < 0.001). Sildenafil only at its highest concentration was effective in suppressing NE induced pulmonary vessel contraction. Bosentan was able to completely suppress ET-1 induced contraction of PA and strongly attenuated contraction of PV. The present data suggest a benefit of sildenafil/bosentan combination therapy as they affect different pathways and may allow lower dosages.

Electropalatography examination of groove width in Russian

Previous studies have indicated a difference between voiced and voiceless pairs of consonants with respect pre-constriction vocal tract volume. This article utilizes electropalatography (EPG) to examine the anterior and posterior groove width of palatalized and non-palatalized fricative pairs in Russians in order to observe different degrees of pre-constriction vocal tract volume. Measurements were taken at the point of maximum constriction using Articulate Assistant software. Higher degrees of contact with the palate were taken to indicate smaller pre-constriction vocal tract volume. The results (based on a single speaker), indicate a significant difference in the degree of contact with the palate between the voiced and voiceless pairs of non-palatalized fricatives. However, the palatalized consonants indicated no significant difference in the degree of contact with the palate. The findings suggest that the smaller vocal cavity created by the secondary articulatory gesture for palatalization is sufficient to facilitate voicing and frication; in the case of the voiced fricatives, the sub-glottal pressure is adjusted to permit vibration of the vocal cords. The findings further suggest that speakers adhere to the principle of minimal articulatory effort when producing speech.

Novel mathematical algorithm for pupillometric data analysis

Pupillometry is used clinically to evaluate retinal and optic nerve function by measuring pupillary response to light stimuli. We have developed a mathematical algorithm to automate and expedite the analysis of non-filtered, non-calculated pupillometric data obtained from mouse pupillary light reflex recordings, obtained from dynamic pupillary diameter recordings following exposure of varying light intensities. The non-filtered, non-calculated pupillometric data is filtered through a low pass finite impulse response (FIR) filter. Thresholding is used to remove data caused by eye blinking, loss of pupil tracking, and/or head movement. Twelve physiologically relevant parameters were extracted from the collected data: (1) baseline diameter, (2) minimum diameter, (3) response amplitude, (4) re-dilation amplitude, (5) percent of baseline diameter, (6) response time, (7) re-dilation time, (8) average constriction velocity, (9) average re-dilation velocity, (10) maximum constriction velocity, (11) maximum re-dilation velocity, and (12) onset latency. No significant differences were noted between parameters derived from algorithm calculated values and manually derived results (p≥0.05). This mathematical algorithm will expedite endpoint data derivation and eliminate human error in the manual calculation of pupillometric parameters from non-filtered, non-calculated pupillometric values. Subsequently, these values can be used as reference metrics for characterizing the natural history of retinal disease. Furthermore, it will be instrumental in the assessment of functional visual recovery in humans and pre-clinical models of retinal degeneration and optic nerve disease following pharmacological or gene-based therapies.

Effects of NO on the expression and function of bradykinin type 2 receptors. Role for angioedema?

Purpose: The pathophysiology of angioedema induced by angiotensin-converting enzyme inhibitors (ACEi) is not well understood. While activation of bradykinin (BK) type 2 receptors (B2) has been established, the triggering events remain obscure. In this study we investigated effect of NO as one product of B2 stimulation. Methods: Brain (bEND3), human umbilical vein (HUVEC) and porcine aortic endothelial cells (PAEC) were incubated with the NO-donors DEA/NO (10μM), DETA/NO (100μM) and SNAP (1-100μM) for 3, 6 and 12 h. B2 expression was assessed by RT-PCR and westernblot using monoclonal B2 antibodies staining either glycosylated or unglycosylated B2. Function of B2 was determined by monitoring iCa2+ upon activation with BK. Likewise, B2 protein levels were evaluated in aorta, heart and lung of (1) two different eNOS-/- strains, (2) mice with endothelial-specific overexpression of eNOS (eNOS-tg), (3) in C57Bl/6 mice treated with NOS inhibitor L-nitroarginine (L-NA). Here, B2 function was evaluated in aortic rings. Results: After 3h incubation with DEA/NO of bEND3, B2-mRNA was unchanged (160±32%, n=6, P>0.05). Likewise, B2 protein levels remained stable (98±13.6%, n=8, P>0.05). Similar results were obtained in PAECs and HUVECs and after extended incubation time and increased concentration. There was also a similar rise of iCa2+ in response to 0.01-100 μM BK in bEND3 treated with DEA/NO or vehicle as demonstrated by almost identical flourescence signals. These results obtained in cell lines and primary cultured PAEC were confirmed using transgenic mice with different levels of vascular NO-bioavailability. In aorta, neither the complete lack of endothelial NO in eNOS-/- (93±26%, n=5, P>0.05), nor overexpression in eNOS-tg (112±13.7%, n=10, P>0.05) changed B2 protein expression and a similar observation was made in C56Bl/6 treated with L-NA (110±19.4%, n=5, P>0.05). Aortic constrictor responses to 10 μM BK (related to maximal constriction to KCl) were identical in C57Bl/6 (24.3±2.7%, n=7) and eNOS-tg (30±11.8%, n=4, P>0.05). However, B2 signaling involved generation of NO as constrictor responses were significantly increased following L-NA in both C57BL/6 (64±18.3%, n=4) and eNOS-tg (67±3.6%, n=4) and a similar constriction was observed in eNOS-/- without (61±10.9%, n=7) and with L-NA (61±14.6%, n=6). None of these responses differed significantly. Conclusion: These data demonstrate that NO does not regulate vascular B2 gene expression and function suggesting that changes of B2 expression by this product of B2 activation are unlikely involved in triggering ACEi-induced angioedema.

Dynamic pupillometry as an autonomic testing tool

To determine normal values for pupillometry indices in healthy control subjects and to examine these indices in patients with autonomic dysfunction and healthy controls. Infrared video pupillometry was used to investigate the pupil response to a brief light flash in 79 healthy controls, 28 patients with normal autonomic function (composite autonomic severity score, CASS<2), and 26 patients with moderate to severe autonomic failure (CASS>4) seen in our autonomic laboratory from January 2008 to June 2011. In six subjects, we examined the effects of varying light stimulus intensity and light stimulus duration. Descriptive analysis, correlation, and ANCOVA adjusted for age were performed. We determined eight indices corresponding to parasympathetic and sympathetic pupil function. Baseline pupil diameter (BPD), maximum constriction velocity (MCV), absolute constriction amplitude (ACA), and maximum dilation velocity (MDV) negatively correlated with age (p<0.01) among controls. MCV and ACA increased with increasing intensity of light stimulus from 3.5 to 112μW. Indices of parasympathetic pupil innervation (MCV and ACA) were lower in the high CASS group compared to others (p<0.0001). Indices of sympathetic pupil function, time to reach 75% of initial resting diameter during pupillary dilation (T¾), and dilation velocity at T¾ (DV¾) did not differ significantly in the three study groups. However, T¾ corrected for the magnitude of pupillary constriction (T¾:ACA) was higher in the high CASS group suggesting sympathetic dysfunction in that group (p=0.0003). Indices of pupillomotor function significantly differ between patients with moderate to severe autonomic failure and healthy controls.

203 MUTATING THE IGF-1 ON THE VASCULAR ENDOTHELIUM: DIVERGENT EFFECTS ON WHOLE BODY AND ENDOTHELIAL INSULIN RESISTANCE

IntroductionEndothelial dysfunction is associated with the onset of atherosclerosis and cardiovascular disease. Whole body and endothelial cell insulin resistance can result in reduced nitric oxide (NO) bioavailability; this is a...

Effects of Low Serum Vitamin A Level on Pupillary Light Reflex in Japanese Black Cattle

Four parameters of pupillary light reflex were investigated from May to December in 2011 to study the effects of low serum vitamin A level on pupillary light reflex in Japanese black cattle during their vitamin A controlled stage. A 2CCD camera was used to acquire the pupillary light reflex images. Constriction amplitude in 1 second, maximum constriction velocity, maximum velocity time and initial pupil roundness were used for pupillary light reflex analysis. Cattle in low vitamin A level period had larger constriction amplitude in 1 second ( p =0.001), higher maximum constriction velocity ( p =0.016) and thinner resting pupil ( p =0.003). This result showed pupillary light reflex analysis can be used as indicators for cattle management during vitamin A controlled stage.

Pupillary Light Reflex as an Objective Biomarker for Early Identification of Blast-Induced mTBI

Purpose: There is an increase in mild traumatic brain injury (mTBI) in US Warfighters resulting from exposure to explosive devices. However, there is a lack of objective biomarkers to accurately identify mTBI in order to make a return-to-duty (RTD) determination in the battlefield. The present study examined pupillary light reflex (PLR) as a potential objective biomarker for early identification of mTBI. Methods: The PLR-200™ monocular infrared pupillometer was used to quantify PLR under mesopic conditions in 20 U.S. military personnel with blast induced-mTBI and 20 age-matched non-TBI military personnel. Eight PLR parameters were assessed: maximum diameter; minimum diameter; percent of constriction; constriction latency; average constriction velocity; maximum constriction velocity; 75% recovery time; average dilation velocity. Results: Four of the eight PLR parameters were statistically different between the groups: constriction latency, average constriction velocity, dilation velocity, and 75% recovery time. Conclusions: This study demonstrates the potential application of PLR as an objective index of autonomic nervous system activity and the value of using PLR, in conjunction with other biomarkers, to optimize the diagnosis of mTBI in the battlefield and to facilitate the RTD decisions by deployed healthcare providers.

Three‐dimensional pharyngeal airway changes in orthodontic patients treated with and without extractions

To evaluate and compare three-dimensional pharyngeal airway changes in orthodontic patients treated with and without extractions. Pharyngeal airway was analyzed for 31 subjects (15 males, 16 females) treated with extractions of four first premolars and 31 age- and gender-matched controls (15 males, 16 females) treated without extractions. The mean age of subjects was 12.97 ± 1.15 years at the beginning and 15.69 ± 1.28 years at the end of treatment. The mean age of controls was 12.86 ± 0.74 years at the beginning and 15.18 ± 0.86 years at the end of treatment. Nasopharyngeal (NP) and oropharyngeal (OP) volumes, area of maximum pharyngeal constriction (AMPC), and upper arch perimeter were measured on T0 and T1 cone beam computed tomography (CBCT) scans. Paired samples t-test was used for analyzing statistical significance of changes (p ≤ 0.05). There were no statistically significant differences in the pharyngeal airway values between the extraction and non-extraction groups at neither T0 nor T1. The extraction group showed a statistically significant increase for NP and OP volumes and AMPC values. Such increase was also noted in the non-extraction group, without statistical significance for AMPC values. The findings suggest that an extraction or non-extraction choice for orthodontic treatment would not affect the pharyngeal airway.

Analyse de la douleur lors de 1457 consultations de médecine au travail

The ability of three different intravascular stents (Gianturco-Roubin, Palmaz-Schatz, and CV Rad), and two different metals (stainless steel and tantalum) to resist vasoconstriction was evaluated in an intact artery ex vivo model.Stents were deployed in 21 rabbit thoracic aortae and five dog carotid arteries, which were constricted with phenylephrine and serotonin, respectively. Vasoconstriction was measured with the use of high-frequency ultrasonic imaging.The maximal vasoconstriction of the control segment was 37.7% ± 2.6 with rabbit aortae and 36.3% ± 4.1 with dog carotid arteries, while the average maximal constriction for all segments in which stents were placed was 5.7% ± 1.1 (P < .01). The maximal constriction of the Gianturco-Roubin stainless steel stent was 9.4% ± 2.7 versus 7.9% ± 1.6 with the tantalum version (P = .65). Both designs showed somewhat greater constriction compared with either the Palmaz-Schatz (3.3% ± 0.9) or the CV Rad (1.4% ± 1.1) stents.Although all of the stents tested substantially resist arterial vasoconstrictive forces, the Palmaz-Schatz and CV Rad stents resist vasoconstriction to a greater degree than the Gianturco-Roubin stents. Tantalum and stainless steel stents of the same design (Gianturco-Roubin) appear similar in their ability to resist vasoconstrictive forces.

Effects of spaceflight and ground recovery on mesenteric artery and vein constrictor properties in mice

Following exposure to microgravity, there is a reduced ability of astronauts to augment peripheral vascular resistance, often resulting in orthostatic hypotension. The purpose of this study was to test the hypothesis that mesenteric arteries and veins will exhibit diminished vasoconstrictor responses after spaceflight. Mesenteric arteries and veins from female mice flown on the Space Transportation System (STS)-131 (n=11), STS-133 (n=6), and STS-135 (n=3) shuttle missions and respective ground-based control mice (n=30) were isolated for in vitro experimentation. Vasoconstrictor responses were evoked in arteries via norepinephrine (NE), potassium chloride (KCl), and caffeine, and in veins through NE across a range of intraluminal pressures (2-12 cmH(2)O). Vasoconstriction to NE was also determined in mesenteric arteries at 1, 5, and 7 d postlanding. In arteries, maximal constriction to NE, KCl, and caffeine were reduced immediately following spaceflight and 1 d postflight. Spaceflight also reduced arterial ryanodine receptor-3 mRNA levels. In mesenteric veins, there was diminished constriction to NE after flight. The results indicate that the impaired vasoconstriction following spaceflight occurs through the ryanodine receptor-mediated intracellular Ca(2+) release mechanism. Such vascular changes in astronauts could compromise the maintenance of arterial pressure during orthostatic stress.

Stimulus-Specific Pupil Dynamics Measured in Birds (Gallus gallus domesticus) In Vivo with Ultrahigh Resolution Optical Coherence Tomography

To demonstrate the ability of high speed, ultrahigh-resolution optical coherence tomography (UHR-OCT) to measure and characterize in vivo visual stimulus-specific pupil dynamics in birds. Ten two-week old White Leghorn (Gallus gallus domesticus) chickens were imaged in this study. The chickens were dark-adapted for 1 hour and anesthetized with 2% isoflurane prior to the imaging procedure. Blue, green, and red single flash visual stimuli of 7 ms duration were used to evoke pupillary responses. UHR-OCT cross-sectional images of the pupil were acquired prior, during, and for several seconds after the visual stimuli onset. Images were processed with a novel custom automatic algorithm, designed to determine the pupil diameter changes over time. Results from this study show that the pupillary constriction begins with the onset of the visual stimuli; however, maximum pupil constriction occurs ∼150 ms later. No statistically significant variation in the timing of the maximum pupillary constriction was observed for stimuli of different colors. However, significant variation was observed in the maximum pupil constriction amplitudes, between red-green and red-blue stimuli, but not between blue-green stimuli. Furthermore, the magnitude of the maximum pupil constriction decreased monotonically with time under isoflurane anesthesia. We demonstrated, for the first time, measurements of visually evoked pupillary dynamics in animals using high speed UHR-OCT. The results suggest dependence of the pupillary dynamics on the color of the visual stimulus, and adverse effects of isoflurane anesthesia on the visually evoked pupillary responses in chickens.