bluuebunny/crossref_metadata_2025 huggingface dataset:
Cholesterol Feedback: A Tale of Two Membrane Proteins and Two Sterol Sensors.
Authors: Brown Michael S. , Goldstein Joseph L.
Published: June 2021

Cholesterol is an essential component of animal cell membranes, and its concentration is tightly controlled by a feedback system that operates primarily at the transcriptional level. The feedback system consists of a pair of membrane‐bound proteins, Scap and Insig, that directly bind sterols and sense their concentrations in the membranes of the endoplasmic reticulum (ER). When sterol levels are low, Scap exists in a conformation that allows it to transport membrane‐bound SREBPs from the ER to the Golgi. In the Golgi, sequential proteolysis of SREBP by two membrane‐bound proteases releases the N‐terminal half of the SREBP, allowing its entry into the nucleus where it functions as a transcription factor, activating the genes encoding proteins involved in the synthesis and uptake of cholesterol. When excess sterols build up in ER membranes, Scap binds cholesterol and Insig binds oxysterols. As a result of these binding events, both Scap and Insig undergo conformation changes that result in a series of molecular events that block Scap's ability to transport SREBPs to the Golgi, thus terminating cholesterol synthesis and uptake.
Genetic Variations in Atherosclerosis: "Humans to Mice" and "Mice to Humans"
Authors: Maeda Nobuyo
Published: June 2021

The risk of atherosclerosis in humans increases progressively in association with the three common alleles of APOE in the order APOE*2 < APOE*3 < APOE4. To investigate the mechanism behind this association, we have generated mice expressing human apoE2, apoE3 or apoE4 in place of mouse apoE. We find that apoE4 mice, but not apoE2 or apoE3 mice, develop hypercholesterolemia and atherosclerosis, when they also genetically express high levels human LDLR. In contrast, apoE2 mice, but not apoE3 and apoE4 mice, develop atherosclerosis when the expression of LDLR is genetically low. These mice with humanized apoE have uncovered an important interplay between the apoE isoforms and LDLR levels in a manner previously not suspected. We further observe that, in response to consumption of a Western type high fat diet, the mice expressing apoE4 gain body weight less than those expressing apoE3. Mice expressing apoE2 gain weight most. These findings mirror the observations in human populations that body mass index is associated with APOE genotype in the order of APOE*2 > APOE*3 > APOE4. Interestingly, although epidydimal fat tissues in the apoE4 mice are smaller, they are composed of larger adipocytes than those in apoE3 mice. Reduced expression of PPARγ and adiponectin in the fat tissues of the apoE4 mice also suggests an impaired adipocyte differentiation. Indeed, the apoE4 mice are less efficient in handling glucose overload than the apoE3 mice. Together, these data indicate that the role of apoE is not limited to lipoprotein metabolism, and that apoE is likely to be an important player in the total energy homeostasis of the body and contributes to the development of metabolic syndrome in an isoform‐dependent fashion.
Inverse relationship between arterial tone and vasodilator sensitivity
Authors: Colton Ilsley Benjamin , Osol George
Published: June 2021

Most small arteries in vivo operate in a state of partial constriction, or tone, which also subjects the endothelium to biaxial deformation. This study tested the hypothesis that the preexisting level of tone is an important determinant of vasodilator sensitivity. Rat uterine resistance arteries (n=12) were cannulated and pressurized to 50 mmHg. Following equilibration, vessels were preconstricted with phenylephrine to reduce initial diameter by 20‐40% (low tone) or 60‐80% (high tone) prior to the addition of SNP (NO donor that acts directly on smooth muscle) or ACh (direct stimulant of endothelial NO release). EC50 values were used as an index of vasodilator sensitivity. Arteries with high levels of tone were significantly less sensitive to both vasodilators than those with low tone, such that the ratio of EC50 values (high vs. low tone) were 17:1 for SNP, but only 6.2:1 for ACh. There was also strong inverse correlation between wall tension and EC50 values, with r2 values of 0.5 and 0.7 for SNP and ACh, respectively. These results highlight the importance of wall tension in modulating arterial vasodilatory responses as a function of tone, and suggest that cellular deformation secondary to vasoconstriction may augment endothelial dilator release, as proportionately less stimulus was required to produce an equivalent amount of vascular smooth muscle relaxation in response to ACh vs. SNP.
Air pollution potentiates diabetes‐induced cardiomyocyte dysfunction
Authors: MacMillan Andrew C , Youtz Dane J , Xue Jianjing , Wold Loren E
Published: June 2021

Exposure to air pollution is a major cause of acute cardiovascular complications, with sudden cardiac death strongly linked to exposure to particulate matter (PM) from ambient air. It is well known that susceptible populations, such as diabetics, are particularly prone to sudden cardiac events on days of high pollution, potentially due to cytokine release from the myocardium. Our aim in this project was to determine whether ultrafine PM exposure exacerbates diabetes‐induced cardiomyocyte dysfunction through cytokine release. Rats were anesthetized and a cardiectomy was performed. Left ventricular myocytes were isolated from normal rats by retrograde perfusion with a collagenase‐containing buffer. Myocytes were then placed in a high glucose medium to mimic the diabetic environment in vitro. Functional analyses of these cardiomyocytes was performed using the IonOptix video‐based edge detection system. Myocyte mechanics (twitches) and intracellular Ca2+ transients were assessed. Function of myocytes cultured in a high glucose medium was more negatively affected than control myocytes cultured in a normal glucose medium, suggesting that diabetics are more prone to the effects of air pollution. Our data suggest that exposure to ultrafine PM induces cardiomyocyte dysfunction, which is exacerbated in diabetic animals. APS Undergraduate Summer Research Fellowship (ACM)
The effects of Di (2‐ethylhexyl) phthalate (DEHP) on the electrical and mechanical properties of a cardiomyocyte network
Authors: Gillum Nikki , Karabekian Zara , Sarvazyan Narine
Published: June 2021

Di(2‐ethylhexyl) phthalate (DEHP) is a widely used plasticizer that is found in a variety of polyvinyl chloride (PVC) medical products. DEHP leaches from PVC tubing and has been linked to cancerogenic and adverse reproductive effects. Currently, little is known of the impact of phthalates on the heart. The effects of DEHP were examined by conducting in vitro experiments using confluent layers of neonatal cardiomyocytes. Exposure to 50ug/mL DEHP for 72‐hours led to a decrease in conduction velocity and asynchronous contractions. These effects were caused by a decrease in the presence of gap junctional connexin‐43 expression. DEHP treatment also affected the mechanical properties of the myocyte network, leading to an unusual type of cell motion. These findings were not attributed to modifications in cell‐cell adhesion, as changes in adherens junction and focal adhesion proteins were not significantly altered by DEHP treatment. Instead, the modified motion and was linked to changes within the underlying fibroblasts. The latter expressed significantly less triton‐insoluble vimentin, compared to control samples. Applicability of these findings to human patients remains to be established. Financial support by the American Heart Association, MidAtlantic Affiliate (0715335U) and the NIH (HL076722, HL087529) is gratefully acknowledged.
Decrease in oxidative phosphorylation with aging correlates with the aging phenotype
Authors: Lemieux Hélène L , Vazquez Edwin J , Hoppel Charles L
Published: June 2021

The goal of the present study was to evaluate the implication of mitochondrial function in the age associated decrease in cardiac contractile function. Mitochondrial respiratory capacity was measured in permeabilized fibers from left ventricles of young and old rats from 3 different stains, presenting or not the aging phenotype. The Fisher 344 rats show severe age related pathology compare to the brown Norway rats. In contrast, hybrids Fisher 344 X Brown Norway showed a longer life expectancy and significantly fewer pathological lesions related to aging compared to the two other strains. A dramatic decrease of around 45% in coupled oxidative phosphorylation (OXPHOS) was observed in the old (24‐26 months) compared to the young (6 months) Fisher 344. The effect of aging on respiration was similar for complexes I, II, and IV, supporting either a decrease in mitochondrial content, an oxidative defect, or both with aging. The same trend, but without significant differences, was observed in cardiac fibers from the brown Norway, with a 15‐20% decrease in OXHPOS in the aged rats. The hybrids rats, which show better resistance to aging, do not have any loss of mitochondrial function. The severity of the age‐related pathology in the different strains correlates strongly with the presence of mitochondrial dysfunction. Our results suggest the importance mitochondrial defect in the deterioration of cardiac function during aging.
Lean Mass Gain with Resistance Training Is Independent of Gender
Authors: Chen Vincnet , Lee Chang Wook , Lee Teak , Chikani Gentle , Riechman Steven
Published: June 2021

Many people assume that resistance training has different effects on males and females with regard to muscle mass gain. The difference in serum testosterone is often cited as an explanation. However, studies examining relative muscle gain with resistance training have not been well established. The purpose of this study is to examine the relative muscle mass gain with resistance training between men and women. We examined lean mass gain in 201 men and women in three different studies. Subjects in these studies performed a standard progressive resistance training program for 10 or 12 weeks. Lean mass was measured before and after training. Both men and women in these 3 studies showed significant increases in muscle mass after resistance training. In the 18‐30 year old, 10 week study, men gained 2.9±0.4% (N=74) while women gained 2.6±0.5% (N=43, P=0.72). In the 60‐69 year old, 12 week study, men gained 1.9±0.6% (N=18) while women gained 1.9±0.5% (N=31, P=0.95). In the 50‐69 year old, 12 week study, men gained 3.6±0.8% (N=14) while women gained 4.0±0.6% (N=21, P=0.74). Across all studies percent change of lean mass did not show a significant difference between genders. These results suggest that lean mass gain with resistance training is more dependent of starting lean mass than gender.
Moderate Exercise training improves cardiovascular, metabolic and emotional parameters of diabetic‐hypertensive patients
Authors: Cunha Tatiana S , Martinez Elaine Cristina Teodoro , Miranda Vania Cristina Reis
Published: June 2021

It is well known that the practice of regular physical exercise is a non pharmacological tool for prevention and treatment of DM2. The aim of this study was to evaluate the effect of moderate exercise on cardiovascular and metabolic parameters and on the level of anxiety and depression in patients with DM2 and hypertension. Blood pressure, heart rate, blood biochemical parameters and level of anxiety and depression were evaluated in diabetic‐hypertensive patients (n=15), before and after an exercise program (walking, 50‐70% maximum heart rate, 12 wks, 3x/wk, 1 hour/day). At the end of the experimental period, there was a reduction on systolic (123±2.9 vs. 140±5.0 mmHg) and diastolic (75±2.1 vs. 84±2.8 mmHg) blood pressure, with no change on heart rate (76±2.2 vs. 82±3.4 bpm). Exercise reduced blood glucose (121±9.9 vs. 161±16.2 mg/dl), tryglicerides (134±13.4 vs. 236±38.9 mg/dL) e total cholesterol (177±6.2 vs. 222±22.0 mg/dl), with no changes on HDL (43±10.4 vs. 36±4.6 mg/dL), LDL (125±14.9 vs. 146±30.2 mg/dL), VLDL (28±7.8 vs. 42±11.6 mg/dL) and glycated hemoglobin (7.3±0,6 vs. 8.3±1.1 %). It was also observed a reduction on the level of anxiety (3.8±0.7 vs. 7.7±1.4 points) and depression (4.4±0.9 vs. 8.8±1.6 points). Results show that the practice of moderate exercise improves cardiovascular, metabolic and emotional parameters of diabetic‐hypertensive patients. It is important to highlight that the association between physical exercise and diet must also be considered on the treatment of patients with DM2, a strategy that can improve parameters that were not changed in this study.
Inhibition of neuronal nitric oxide synthase (nNOS) reduces cardiovascular responses elicited by microinjection of cholinergic agonists in the Nucleus of the Solitary Tract (NTS) in non‐anesthetized rats
Authors: da Silva Liana Gouveia , Dias Ana Carolina Rodrigues , Colombari Eduardo
Published: June 2021

Microinjection of ACh into the NTS of non‐anesthetized rats induces hypotension and bradycardia. We investigated if nNOS inhibitor (TRIM) changes the responses elicited by nicotinic and muscarinic receptors stimulation in the NTS. Five days before the experiments, rats were anesthetized with Ketamin and Xylazin and guide cannulas aiming at the NTS were implanted bilaterally. One day before the experiments, femoral artery was cannulated to record arterial pressure (AP). Unilateral NTS microinjection of nicotine (NIC 0.01 ‐ 10 pmol/100 nl) elicited dose‐dependent hypotension and bradycardia (0.5 pmol δMAP: ‐41±2 mmHg; δHR: ‐141±10 bpm; n=8, p< .05). Responses to 0.5 pmol NIC were reduced to ‐11±2 mmHg and ‐45±12 bpm (n=9, p< .05), 10 min after injection of TRIM (13.3 nmol/100 nl) into the NTS. Unilateral microinjection of pilocarpine (PIL 0.01 ‐ 10 nmol/100 nl) elicited hypotension and bradycardia (0.5 nmol: ‐32±2 mmHg and ‐147±11 bpm; n=9, p< .05). With doses of PIL higher than 0.5 nmol, the hypotension was followed by a significant increase in MAP. Ten min after unilateral injection of TRIM in the NTS, responses to 0.5 nmol PIL were reduced to ‐8±3 mmHg and ‐32±16 bpm; n=4, p< .05. Responses to NIC and PIL returned to control 60 min after TRIM microinjection. We suggest that both nicotinic and muscarinic receptors participate in ACh transmission in the NTS, and NO may modulate their responses. Supported by Fapesp, CNPq.
Gene transfer of angiotensin converting enzyme 2 to the paraventricular nucleus improves attenuated nitric oxide mechanism in rats with chronic heart failure
Authors: Zheng Hong , Liu Xuefei , Moser Joe‐Ann S , Patel Kaushik
Published: June 2021

In the present study, we investigated the effects of angiotensin converting enzyme 2 (ACE2) gene transfer on nitric oxide (NO) mechanism contributed to the elevated sympathoexcitation in the rats with coronary ligation model of chronic heart failure (CHF). Adenovirus vectors encoding either ACE2 (AdACE2) or EGFP (AdEGFP) were transfered into the paraventricular nucleus (PVN) in vivo. 3 days after application of AdACE2, the expression of ACE2 in the PVN was confirmed by immunohistochemistry. In alpha‐chloralose and urethane anesthetized rats, AdACE2 significantly improved the attenuated renal sympathetic nerve activity (RSNA), blood pressure (BP) and heart rate (HR) responses to neuronal NO synthase (nNOS) inhibitor L‐NMMA in the rats with CHF (RSNA: 29±5% vs 10±1%, P<0.05) compared to CHF‐AdEGFP group. AdACE2 transfection significantly normalized the decreased nNOS protein levels (Δ30±4%) in the PVN in CHF rats. Furthermore, neuronal NG‐108 cells were stimulated with AdACE2 or AdEGFP in a dose‐dependent manner. nNOS protein expression increased in a dose‐dependent manner after AdACE2 transfection. The highest dose showed an approximately 50% increase in nNOS protein expression compared to the control dose. We conclude that the up‐regulation of ACE2 by gene transfer significantly stimulates nNOS production and the effects of ACE2 on the NO mechanism in the PVN may play an important role in the altered balance and tone of sympathetic outflow in the CHF condition.
Increased oxidative stress in cardiovascular center of brain stem causes sympatho‐excitation in dietary‐induced obesity rat
Authors: Konno Satomi , Hirooka Yoshitaka , Kishi Takuya , Ito Koji , Araki Shuuichiro
Published: June 2021

Background

Activation of the sympathetic nerve activity (SNA) induced by leptin acting on the pituitary‐hypothalamic pathway plays a central role of hypertension in metabolic syndrome (MetS). However, the role of the cardiovascular center in the brain stem (rostral ventrolateral medulla; RVLM) in SNA and the mechanism involved in MetS are not understood. The aim of this study was to determine if oxidative stress in the RVLM in MetS is increased thereby causing hypertension.

Methods and Results

Male Sprague‐Dawley rats were fed on a moderately high‐fat diet and segregated into obesity‐prone (OP, n=5) and obesity‐resistant (OR, n=5) groups based on their body weight (BW) after 13 weeks. Adiponectin in blood sample and visceral fatty mass were measured as an indicator of MetS. Blood pressure (BP), hearts rate (HR), urinary norepinephrine excretion (UNE), body weight, and amount of visceral fat mass were significantly higher and adiponectin was significantly lower in OP than in OR. Thiobarbituric acid‐reactive substances (TBARS) levels in the RVLM were significantly higher in OP than in OR. (7.2±0.8μmol/g wet wt vs 2.2±1.9μmol/g wet wt, n=3 for each, p<0.05).

Conclusion

Oxidative stress in the RVLM of OP was increased associated with BP, HR, and UNE elevation and the changes in MetS markers. Increased oxidative stress in the RVLM may increase SNA thereby leading to hypertension in MetS.
Excess Dietary Salt Intake Selectively Enhances the Excitability of Sympathetic Neurons in the Rostral Ventrolateral Medulla
Authors: Stocker Sean D , Madden Christopher J
Published: June 2021

Compelling evidence indicates that excess dietary salt enhances sympathetic nerve activity (SNA) and arterial blood pressure (ABP) responses evoked from the rostral ventrolateral medulla (RVLM). The present study investigated whether excess dietary salt selectively enhances the excitability of RVLM neurons vs all sympathetic‐regulatory networks. Male Sprague‐Dawley rats were given access to water or 0.9% NaCl for 15‐18 days. Rats drinking 0.9% NaCl (n=5) vs water (n=6) had significantly greater increases in renal SNA (62±7 vs 40±6%, P<0.05) and mean ABP (27±4 vs 12±3mmHg, P<0.01) during electrical stimulation of sciatic afferents (500 μA, 2Hz). In marked contrast, injection of L‐glutamate (5nmol/100nL) into the medullo‐cervical pressor area produced similar increases in renal SNA (110±20% vs 133±21%) and mean ABP (25±4 vs 25±4mmHg) of rats drinking 0.9% NaCl vs water. Inhibition of the RVLM with muscimol (500 pmol/side, n=3) eliminated the increased renal SNA (45±8 vs 0±0%) and mean ABP (13±2 vs 1±1mmHg; P<0.01) to sciatic nerve stimulation, but did not affect renal SNA (95±9 vs 88±10%) or mean ABP (18±4 vs 19±5mmHg) to glutamatergic stimulation of the medullo‐cervical pressor area. The potentiated increases in renal SNA and ABP to only RVLM‐dependent responses suggest that excess dietary salt selectively enhances the excitability of RVLM sympathetic neurons. Supported by NIH HL090826, AHA 0630202N
Nucleus tractus solitarii (NTS) blood flow and oxygenation are compromised in spontaneously hypertensive rats (SHR)
Authors: Potts Jeffrey T , Yang Shaohua , Paton Julian FR
Published: June 2021

A reduction in brain blood flow, and thus oxygen delivery, may contribute to the development and maintenance of hypertension. We tested the novel hypothesis that blood flow to the NTS, a brainstem region critical to blood pressure regulation, is reduced in the SHR. The hydrogen (H2) clearance method, where H2 clearance is proportional to regional blood flow (RBF), was employed in adult Wistar‐Kyoto rats (WKY, n=5) and SHR (n=4). MAP was elevated in SHR compared to WKY (114±3 vs 88±5 mmHg, P<0.05). Although basal RBF was not different in NTS between rat strains (SHR 37±5 vs WKY 44±7 ml/100g/min, P=0.06), its ability to increase in response to neuronal activation following vagal nerve stimulation was blunted severely in the SHR (ΔRBF: SHR 8±1 vs WKY 32±7 ml/100g/min, P<0.05). Further, calculation of the relative increase in regional vascular conductance (RVC=ΔRBF/ΔMAP) was also substantially blunted in SHR (18±3 vs 99±22%, P<0.05). Whilst the oxygen tension of NTS was similar between rat strains (18 vs 18 mmHg), lowering MAP in SHR to levels seen in WKY rats produced severe hypoxia (6 mmHg). These findings support the hypothesis that vascular resistance in NTS of SHR is higher than WKY rats and that neuro‐vascular coupling which mediates the increase in blood flow in response to neuronal activation is severely impaired in the NTS of SHR. Supported by NIH HL059167 (JTP), NS054651 & 054687 (SY), British Heart Foundation (JFRP)
Role of GABAergic receptors within the nucleus of the solitary tract in spontaneously hypertensive rats
Authors: Moreira Thiago S , Colombari Eduardo
Published: June 2021

Inhibitory neurotransmission plays a crucial role in the processing of sensory afferent signals in the nucleus of the solitary tract (NTS). Gamma‐aminobutyric acid (GABA) neurons are scattered throughout NTS. Previous studies demonstrated that alterations in GABA mediated neural transmission in the NTS contribute to the attenuation of the baroreceptor reflex observed in SHR. Here, we test the hypothesis that enhanced stimulation of GABA‐A and B receptors in the NTS in SHR are responsible for the attenuation of the sympathetic baroreflex, but not the chemoreflex. Under urethane/chloralose anesthesia, baseline arterial pressure (AP) in SHR was higher than the Wistar Kyoto (WKY) rats (SHR: 146 ± 5, vs. WKY: 112 ± 6 mmHg). The effects of baroreflex and chemoreflex on AP, splanchnic sympathetic nerve discharge (sSND) and phrenic nerve discharge (PND) were test before and after bilateral injection of the GABA‐A antagonist (bicuculline) or the GABA‐B antagonist (CGP 35348) within the NTS. The baroreflex range and gain were increased after bicuculline and CGP 35348 injection into the NTS, but had no effect on sympathoexcitatory and increase PND produced by chemoreflex activation. Bilateral injection of bicuculline and GCP 35348 within the NTS in SHR produced a pronounced decrease in AP compared with WKY (Δ = ‐15 ± 4 and ‐33 ± 6 mmHg, respectively vs. WKY: Δ = ‐5 ± 4 mmHg), but did not change PND. These results suggest that alterations in GABA‐mediated neural transmission in the NTS contribute to the attenuation of the baroreceptor reflex observed in SHR.
Blockade of neuronal gap junctions modifies slow and fast oscillatory rhythms in phrenic nerve discharge in arterially‐perfused adult rat
Authors: CHUN Hyun Hye , Solomon Irene C
Published: June 2021

We have previously demonstrated that pharmacological blockade of gap junctions alters respiratory rhythm, phrenic burst pattern, and inspiratory‐phase synchronization. The pharmacological agents used to block functional gap junction coupling, however, were not specific to gap junctions composed of a specific connexin (Cx) isoform, and therefore may have exerted their effects on both neuronal and astrocytic gap junctions. To further delineate the role of neuronal gap junctions in central respiratory control, we examined the effects of mefloquine (MEQ; 0.5‐1.0 μM), which blocks neuron‐specific Cx36‐containing gap junctions, on phrenic nerve discharge in 5 arterially‐perfused adult rat preparations. We found that perfusion with MEQ increased phrenic burst frequency by 35±4% (P<0.001) due to decreases in both TI (P=0.001) and TE (P<0.001). No significant changes in burst amplitude were observed; however, time‐to‐peak activity (Tpeak/TI) was shifted from 85±2 to 72±5% (P<0.01). Perfusion with MEQ also produced a small increase in HFO spectral power (P=0.07), shifted HFO onset to an earlier time point in the phrenic burst (from 62±3 to 36±7% TI; P<0.01), and prolonged the duration of significant HFO activity. No changes in MFO activity were seen. These data suggest that neuronal gap junctions participate in both the slow and fast oscillatory rhythms underlying phrenic nerve discharge. Supported by NS045321
Purinergic modulation of rhythmic preBötzinger Complex (preBötC) activity; isolating the glial compartment
Authors: Zwicker Jennifer D , Hahn Leanne B , Huxtable Adrianne G , Fang Sheena , Baker Glen B , Posse de Chaves Elena , Funk Greg D
Published: June 2021

Analyses of rhythmic medullary slices from neonatal SD rats suggest that glial cells contribute to the P2Y1 receptor (R) excitation of preBötCinspiratory networks (Huxtable et al. this session), in part through activation of glial P2Rs. In this study we established primary cultures of glial cells from the ventral respiratory column (VRC) to directly test their ATP sensitivity, and assess whether this sensitivity might modulate neuronal activity through the subsequent release of gliotransmitters. Cultures were produced from the ventral half of 300 µm transverse preBötC sections or preBötC punches that were grown in sorbitol‐based media, and characterized as glial by presence of mRNA and immunostaining for GFAP, S100β, but not NSE (mRNA) or NF160 (immuno). Fluo‐4 Ca2+ imaging revealed that ATP (0.01 mM, n=20) or the P2Y1R agonist MRS 2365 (0.001 mM, n=20) caused 3.5‐5 fold increases in fluorescence that were reversibly reduced to 80 and 60% of control, respectively, by the P2Y1R antagonist, MRS 2279 (0.5 mM). HPLC data suggested that compared to saline, ATP (50 µM) increased the release of glutamate (30%), aspartate (50%) and taurine (100%).

These data confirm that glial cells from the VRC are sensitive to ATP and P2Y1R activation, and that ATP‐evoked release of amino acid gliotransmitters may contribute to the modulatory effects of ATP on inspiratory rhythm. Supported by CIHR, NSERC, CIHR‐MFN, AHFMR, CFI, ASRA.
P2Y1 receptor‐mediated potentiation of XII motoneuron (MN) inspiratory motor output in neonatal rat
Authors: Alvares Tucaaue , Huxtable Adrianne G , Ireland Matthew F , Lorier Amanda R , Funk Gregory D
Published: June 2021

Inspiratory rhythm generating networks in the preBötzinger Complex (preBötC) are ~100‐fold more sensitive to ATP than XII MNs that control airway patency. This is believed to reflect in part that the effects of ATP in the preBötC are primarily mediated by P2Y1Rs while P2XRs receptors dominate the actions of ATP in XII MNs. However, the effects of P2Y1R signaling on XII motor output and MN properties have not been examined. To address this deficit, we applied nerve and whole‐cell recording techniques to rhythmic medullary slices of neonatal rat.

Local application of MRS2365 (P2Y1R agonist) to the XII nucleus of rhythmic slices increased tonic discharge and evoked 22±2 (0.1 mM) and 33±4% (1 mM, n=16) increases in inspiratory burst amplitude. MRS2365 also increased the frequency and amplitude of spontaneous PSCs in non‐inspiratory and inspiratory MNs alike. In inspiratory MNs, it also increased the charge transferred per inspiratory cycle (12±6%, n=5). The increase in synaptic activity was superimposed on a small, slow, inward current that was similar in all XII MNs, averaging 27±7 pA (1 mM, n=10). Following block action potentials with TTX, MRS2365 had no effect on membrane current or resistance.

These data suggest that P2Y1Rs do not directly affect XII MN membrane properties, but potentiate inspiratory XII nerve output by specifically modulating synaptic function.

Supported by CIHR, NSERC, CIHR‐MFN, AHFMR, CFI, ASRA.
Conditional expression of central respiratory rhythm in developing fat‐tailed dunnarts (Marsupialia: Sminthopsis crassicaudata)
Authors: Fong Angelina Yin , Frappell Peter B , Milsom William K
Published: June 2021

Marsupials offer unparalleled opportunities for developmental studies as the young are born small and immature, with most development occurring in the pouch where the young are readily accessible. The fat‐tailed dunnart gives birth to one of the smallest newborns of any mammal (~4mm long, weighing 13‐15mg). Newborn dunnarts do not typically breathe until 3‐4 days postnatal (P), achieving gas exchange largely across the skin (Mortola et al., Nature, 1999). Currently, little is known about the development of respiratory rhythmogenesis in this species. We examined central respiratory rhythm in neonatal dunnarts from the day of birth up to 3 weeks of age (206‐261mg) using the in vitro brainstem‐spinal cord preparation. Under normocapnic conditions (5% CO2/95% O2, pH 7.4), fictive breathing was present at P0 and frequency increased with development until about P12. In P0 preparations, under normocapnia, fictive respiratory bursts occurred in episodes but became regular with increased drive (8% CO2, pH 7.2). In P5 and older preparations, under normocapnia, breathing was regular and fictive respiratory frequency correlated with the level of drive at all ages. These data indicate that dunnarts on the day of birth are capable of generating central respiratory rhythm even though expression of the rhythm does not occur for several days. (Supported by NSERC of Canada).
The progesterone receptor antagonist mifepristone abolishes carotid sinus nerve response to hypoxia in rat pups.
Authors: Joseph Vincent , Niane Lalah , Bairam Aida
Published: June 2021

We tested the hypothesis that endogenous progesterone enhances peripheral chemoreceptors function in rat pups. Newborn rats have been treated with the progesterone receptor antagonist mifepristone (Mif) between postnatal days 3‐12 (70μg/g/day) and compared to control (Cont). We used the in‐vitro carotid body/carotid sinus nerve (CSN) preparation to record CSN activity (impulses/sec) in 12‐day‐old rats under normoxia (perfusion medium bubbled with 21%O2‐5%CO2), in response to hypoxia (5%O2‐5%CO2), or nicotine (mediator between carotid body type I cells and CSN terminals, 100μM) supefusion for 3‐4 minutes each. Baseline CSN firing frequency was similar between groups, at 2.7±0.3 in Cont and 2.6±0.3 Hz in Mif pups. At steady state hypoxic CSN activity increased to 7.5±0.9 Hz in Cont, but was left unchanged in Mif pups (3.0±0.5 Hz, p<0.0002 between groups). In response to nicotine superfusion, CSN firing activity increased to 10.8±1.9 Hz in Cont and to 6.1±3.3 Hz in Mif (p<0.04 between groups). We conclude that endogenous progesterone plays an important role in carotid body during postnatal development in rats. Founded by SickKids Foundation (XG07‐006)
Effect of neonatal maternal separation on inspiratory response to hypercapnia in male rats: implication of central and peripheral chemodetections
Authors: Dumont Frederic , Kinkead Richard
Published: June 2021

Neonatal maternal separation (NMS) is a clinically relevant stress model which disrupts respiratory control development. NMS reduces the ventilatory response to CO2 in rats but the underlying mechanisms are unknown. The present study aimed to determine whether attenuation of this hypercapnic response occurs at the central or peripheral level. Pups subjected to NMS were separated from their mother 3h/day from post natal days 3 to 12. Fictive ventilation was measured during normocapnia and hypercapnia (PaCO2: 10Torr above baseline) using 2 approaches on anaesthetized (urethane 1g/kg + isoflurane 0.5%) adult male rats. First, to test the central chemosensibility, we recorded phrenic nerve activity in vagotomized, paralyzed and ventilated (FiO2: 0.5) rats. No differences were observed between groups. We then tested the implication of peripheral chemodetection in non‐vagotomized and spontaneously breathing rats using bilateral chemodenervation. Recording of diaphragmatic EMG showed a decreased of baseline breathing frequency by 35% in control rats only. During hypercapnia, breathing frequency decreased by 31% in controls but increased by 15% in NMS. This opposite response eliminates the difference between groups in minute activity responses. These results show that disruption of carotid body function (and/or central integration) contributes to the phenotype observed in NMS rats. Supported by CIHR.
Alpha‐1A adrenergic receptor modulates anxiety and depression in mice
Authors: Luger Elizabeth Joan , Fettig Megan , Darsie Belle , Wald Jenna , Berntson Sarah , Boese Sarah , Haselton James , Handel Evelyn , Talbot Jeffery , Rorabaugh Boyd , Doze Van
Published: June 2021

Norepinephrine (NE), an endogenous neurotransmitter, is involved in cognition as well as anxiety and depression. NE mediates its actions through the activation of adrenergic receptors (ARs). This study explored the effects of increased α1AAR activation on anxiety and depression in mice. Different sets of mice with varying degrees of α1AAR expression and activation were used in behavioral tests for anxiety and depression. The mice sets included transgenic mice with increased α1AAR expression, transgenic mice with a knockout of the α1AAR, mice treated with the α1AAR agonist cirazoline, and groups of normal control mice. The tail suspension and forced swim tests were used as models of depression and the light/dark, marble burying and elevated plus‐maze tests were used as measurements of anxiety. In addition, the open field test was used to determine the mobility of these animals. It was found that mice with increased α1AAR activation, in comparison to normal mice, demonstrated anxiolytic and antidepressant‐like behavior in several of these models. The mobility of these animals was similar. These results suggest that activation of the α1AAR reduces anxiety and depression in mice without affecting their mobility. This study was supported by NSF CAREER 0347259, NSF REU Site 0639227, NIH P20 RR016741, UND REFUNDU Program, American Physiological Society, and the Bower, Bennet & Bennet Endowed Research Award from ONU.
Absence of cocaine sensitization in OVX female rats is not due to cocaine dosage
Authors: Torres‐Diaz Yvonne Marie , Arroyo Yaria , Segarra Annabell C
Published: June 2021

Female rats show higher locomotor activity in response to cocaine than males. Estradiol is partly responsible for this enhanced cocaine‐induced hyperactivity. The present study was designed to determine the dose and/or length of exposure to cocaine necessary to induce behavioral sensitization in ovariectomized female rats. Rats were ovariectomized, half received a Silastic implant filled with estradiol benzoate (OVX‐EB); the other half received an empty implant (OVX). For 5 consecutive days rats received a daily cocaine injection (10, 15 or 30 mg/kg). On days 1, 5, and 13 animals were tested for their locomotor response to cocaine. Another group of animals received a repeated cocaine exposure of 10 days. Their locomotor response to cocaine was recorded on days 1, 5, 10, and 18. Manipulations of dose and length of exposure to cocaine did not induce behavioral sensitization in OVX rats. These results show that estradiol is necessary for female rats to develop behavioral sensitization to cocaine.

Support contributed by: NIH grants: U54NS39405 (SNRP); SO6‐GM08224 (MBRS/SCORE); and R25GM61838 (MBRS/SCORE)
Caffeine reduces motor performance and antioxidant enzyme capacity in the brain of female G93A mice, an animal model of amyotrophic lateral sclerosis (ALS)
Authors: Seevaratnam Rajini , Raha Sandeep , Tarnopolsky Mark A , Hamadeh Mazen J
Published: June 2021

Oxidative stress is associated with several neurodegenerative diseases including Parkinson's (PD), Alzheimer's (AD) and ALS. Caffeine (CAF) consumption is protective in PD and AD, however findings from our lab suggest that CAF in G93A mice may not be protective, since CAF supplementation shortened life span in females by 6 days (4.4%) vs. control (CON) mice. We therefore investigated the effect of CAF on food intake (FI), body weight (BW), body condition (BC), motor performance (MP), ability to move (AM), clinical score (CS), and antioxidant enzyme protein content (MnSOD; catalase, CAT; glutathione reductase, GR) using Western blotting techniques in the brain of sixteen 108‐d old female G93A mice. Starting at age 40 d, mice were equally divided into CON or CAF. CAF was added to the food, equivalent to amounts found in 5 ‐ 10 cups of coffee/day (mg/g body weight). FI increased over time (P < 0.001); CAF consumed 29% more vs. CON (P = 0.001). BW increased over time (P < 0.001); CAF were 5% heavier vs. CON (P = 0.032). MP was non‐significantly lower in CAF vs. CON over time (NS), with a very strong trend at age 107 d (47%, P = 0.053). CAF reduced GR by 35% (P = 0.008), CAT by 32% (P = 0.022), and MnSOD by 18% (P = 0.062) vs. CON. BC, AM, and CS were not significant between groups. We conclude that although CAF increases FI and BW, motor performance is hindered and antioxidant enzyme capacity is reduced. (Supported by HHSF, NSERC, York U‐Health).
Adenosine monophosphate kinase (AMPK) and cell‐cell adhesion: a role for AMPK in pulmonary microvascular endothelial barrier function
Authors: Creighton Judy , Sayner Sarah , Alexeyev Misha , Insel Paul
Published: June 2021

In the lung, efficient gas exchange relies on the dynamic interaction of cell‐cell tethering mechanisms to maintain capillary barrier integrity. AMPK is a molecular sensor for detecting and mediating cellular adaptation to barrier disruptive stimuli. However, the importance of AMPK activity in mediating pulmonary microvascular endothelial barrier function is not well understood. Initial studies reveal that pulmonary microvascular endothelial cells (PMVECs) selectively express the alpha 1 and not the alpha 2 isoform of the AMPK catalytic subunit. AMPK inhibition blocked PMVEC growth on matrigel. In scratch wound assays inhibition of AMPK by compound C or shRNA to AMPK alpha 1 attenuated PMVEC monolayer resealing. Transendothelial resistance studies revealed that shRNA‐induced knockdown of AMPK alpha 1 expression decreased resistance in confluent monolayers by 35%. Immunochemical staining and co‐immunoprecipitation indicated that AMPK alpha 1 co‐localizes with the cell‐cell adhesion molecule N‐cadherin. Moreover, fractionation studies revealed that membrane associated AMPK alpha 1 and N‐cadherin are restricted to lipid raft membranes with caveolin 1. Collectively, these data suggest that AMPK alpha 1 interaction with N‐cadherin contributes to cell‐cell contact important in barrier repair . Supported by research and training grants from NIH.
Adenosine stimulates mitochondrial biogenesis in microvascular endothelial cells
Authors: Kalogeris Theodore J. , Korthuis Ronald J.
Published: June 2021

Modulation of mitochondrial biogenesis may contribute to the vasculo‐protective effects of preconditioning. We tested whether adenosine (Ado), a mediator of ethanol preconditioning in vivo, could influence mitochondrial biogenesis in human microvascular endothelial cells (HMEC‐1). Cells were treated daily with or without Ado (1 µM) for 1‐8 days. At each time point, whole‐cell protein was probed for expression of several markers and mediators of mitochondrial biogenesis. Compared with control cells, Ado elicited time‐dependent increases in PGC‐1α, NRF‐2, porin, and cytochrome c oxidase (COX‐IV, subunit II), but had no effect on expression of either GAPDH or β‐actin; PGC‐1α and NRF‐2 were significantly increased by 1.5‐2‐fold after 2 days of Ado treatment and peaked at levels 3‐4‐fold higher than control by day 5. Porin showed a biphasic response, peaking on days 2‐3 (3‐fold higher than control) and rising to levels 4‐5‐fold higher than control by day 8. COX‐IV was unresponsive until day 6; by day 8, COX‐IV expression was 3‐4‐fold higher than control. In other studies, cells treated with Ado for 8 days showed a significant (42%) increase in oxidation of MTT to MTT‐formazan compared with control cells. These results are consistent with an Ado‐triggered program of mitochondrial biogenesis in endothelial cells which may contribute to vasculo‐protective effects of preconditioning. Supported by AA14945.
Endothelial phenotype is not the same among conduit arteries and veins in the systemic circulation
Authors: Laughlin Maurice Harold , Newcomer Sean , Bender Shawn B. , Arce Arturo , McAllister Richard M.
Published: June 2021

Endothelium (EC) of rat conduit arteries (A) express similar levels of endothelial nitric oxide synthase (eNOS) and superoxide dismutase (SOD) protein (J Appl Physiol 98:753, 2005). Our hypothesis was that EC of porcine conduit A's and veins (V) express similar levels of eNOS and SOD. Aorta and vena cava (thoracic and abdominal portions), brachial, femoral, and renal A's and V's, carotid A and jugular V were isolated EC was scraped from each A & V providing 12 EC samples/pig. Samples were processed for immunblot analysis with gels loaded with all 12 samples from each pig for analysis of expression levels of eNOS, and SOD‐1‐3. Results reveal that protein expression varied among ECs from the different A's and V's. The lowest eNOS content was observed in EC of brachial A's while carotid artery EC and ECs from aorta samples had 4‐5 times as much eNOS protein. EC from all of the V's exhibited 2 to 3 times greater eNOS protein content than EC of brachial A. The expression of SOD‐1, and ‐2 were similar among the 12 types of EC, ranging from 0.5 to 1.5 times the brachial A values. Thoracic aorta ECs exhibited nearly 3 times the ecSOD (SOD‐3) of brachial A ECs and all V ECs expressed less (about 50 %) ecSOD than did EC of brachial A. We conclude that ECs of conduit As and Vs express differing amounts of eNOS or SOD‐3. Of interest, brachial A exhibited lower eNOS content than any other A or V. (Supported by NIH grants HL36088 and HL52490)
Oxytocin in the CeA on OT and AVP mRNA expression and hormonal responses induced by BVE
Authors: Margatho Lisandra Oliveira , Elias Carol F , Antunes‐Rodrigues Jose
Published: June 2021

We investigated the effects of oxytocin (OT) and the oxytocinergic antagonist vasotocin (OVT) injection in the central amygdala (CeA) in the regulation of vasopressin (VP) and OT mRNA expression in the hypothalamus. We also assessed VP and OT plasma levels in response to isotonic volume expansion (BVE). Male Wistar rats with cannulas unilaterally in the CeA were subjected to BVE (2 ml/100 g bw). OT (1μg), OVT (1μg) or vehicle was injected into the CeA 20 min before the BVE. 5 min after BVE rats were decapitated and the blood was collected for OT and VP plasma determination. Another group was submitted to the same protocol and perfused 40 min after BVE. Brain sections of the paraventricular (Pa) and the supraoptic (SON) nuclei were processed for in situ hybridization using a 35S‐labeled VP or OT probe. In rats treated with vehicle in the CeA, BVE increased plasma OT levels. OT injection in the CeA reduced VP mRNA expression in the SON, but did not alter plasma VP. Also, OT in the CeA enhanced the effects of BVE on plasma OT while OVT reduced this effect. OVT in the CeA enhanced the effects of BVE on plasma VP but did not change VP mRNA expression. Our data suggest that OT in the CeA inhibits the central neural network that controls the VP mRNA expression in the SON neurons. In parallel, OT in the CeA may modulate the physiological mechanisms involved in plasma OT release but does not affect OT gene expression in the Pa and SON following isotonic BVE.
Renal and cardiovascular features of a new model of Polycystic Ovarian Syndrome
Authors: Yanes Licy L , Sartori‐Valinotti Julio C , Iliescu Radu , Romero Damian G , Zhang Huimin , Davis Deborah D , Reckelhoff Jane F
Published: June 2021

Polycystic ovary syndrome (PCOS) affects 15 % of women of reproductive age. PCOS is characterized by hyperandrogenism, polycystic ovaries and amenorrhea. Cardiovascular disease risk is higher in PCOS patients than age‐matched controls. In order to elucidate the cardiovascular consequences of hyperandrogenism in PCOS, 3 week‐old female SD rats were given dihydrotestosterone (DHT) (pellets, 7.5mg/90days) or placebo. After 12 weeks, plasma DHT was increased 5‐fold and plasma estradiol was unchanged compared to untreated females. DHT‐rats were not estrous cycling and had increased number of ovarian atresic follicles while nodular hypertricosis was decreased. DHT increased mean arterial pressure (radiotelemetry) (96±2 vs 108±2 mmHg; p<0.05), glomerular sclerosis (0% vs. 3.5±0.5 p<0.05) and albuminuria (5.09±2.22 vs 19.66±6.60 mg/24 h, p<0.05); plasma renin activity and aldosterone were decreased, and adrenal glands were atrophic. In summary, androgen supplements in young female rats induce physiological characteristics found in women with PCOS, and increase cardiovascular‐renal disease. These data suggest that treatment with anti‐androgens is crucial in the management of women with PCOS; and this is a new model in which to study the mechanisms responsible for cardiovascular‐renal disease in women with PCOS. This work was supported by NIH HL51971.
Endothelial dysfunction after hypertensive pregnancy in the rat
Authors: Colson Drew , Verzwyvelt Joseph D , Arany Marietta , Ojeda Norma , Gilbert Jeffrey S
Published: June 2021

Recent evidence indicates formerly preeclamptic women have endothelial dysfunction and increased risk for cardiovascular and renal disease in later life. Despite these observations it remains unclear if these sequelae are due to persistent effects of placental ischemia or are related to underlying genetic or environmental factors associated with preeclampsia. To this end, we employed our model of hypertension associated with reduced uterine perfusion pressure (RUPP) to determine if placental ischemia is associated with persistent changes in vascular function independent of other risk factors. We hypothesized that formerly hypertensive rats with placental ischemia during pregnancy would have endothelial dysfunction four months post‐partum (RUPP‐PP) when compared to normal pregnant post‐partum dams (NP‐PP). Arterial pressure (115 ± 6 vs. 113 ± 5 mmHg) and body weight (272 ± 7 vs. 270 ± 5 g) were not different between NP‐PP and RUPP‐PP groups. Wire myography revealed that endothelial dependent relaxation to ACh was impaired in the RUPP‐PP vs. NP‐PP as evidenced by a rightward shift in the concentration response curve (‐log EC50 ‐6.0 ± 0.3 vs. ‐6.8 ± 0.2; P<0.05). Smooth muscle dependent relaxation to sodium nitroprusside was unchanged between groups. The present data indicate that vascular endothelial dysfunction is a persistent effect of placental ischemia independent of other cardiovascular risk factors.
Temporal Changes in Cardio‐Renal impairment in Type II Diabetic Rats.
Authors: Baynes John , McClarty Jennifer , Murray David B
Published: June 2021

The potential reciprocal association of pathologic changes in renal and cardiac function as comorbidities has not been well studied. This study examined renal morphology/function as well as left ventricular (LV) systolic/diastolic parameters at two separate time points (e.g. 16 and 36 weeks of age). We hypothesize that the obese ZDF animal of type II diabetes will display systolic/diastolic dysfunction at the earlier time point which will not be associated with renal impairment, however, there will be significant loss of ventricular function at 36 weeks of age which corresponds to the severity of renal pathology. Lean Control (LC) and Zucker Diabetic Fatty (ZDF) rats were assessed for: 1) proteinuria, 2) hydronephrosis, and 3) LV structural/functional parameters at 16 and 36 weeks of age. Evidence of increased urinary albumin and decreased urinary creatinine was paralleled by a marked progression in the severity of hydronephrosis in the 36 week of age ZDF group compared to LC. Relative to LC, end diastolic volume for ZDF animals was significantly increased at 16 and 36 weeks of age without hypertrophy suggestive of LV dilatation. Our results indicate that at 16 weeks of age significant changes in ventricular structure/function already exist without renal insufficiency. At 36 weeks of age there is a strong association between decreased renal function and significant ventricular dysfunction.