bluuebunny/crossref_metadata_2025 huggingface dataset:
GABAergic and nitrergic mechanisms in the paraventricular nucleus of hypothalamus (PVN) are involved in the basal autonomic regulation but not in the cardiovascular responses to chemoreflex activation in awake rats
Authors: Cruz Josiane C. , Machado Benedito H.
Published: June 2021

There is evidence of PVN involvement in the autonomic responses to chemoreflex activation in awake and in anesthetized rats. In the present study we evaluated the role of GABAergic and nitrergic mechanisms in the PVN of awake rats on the cardiovascular responses to chemoreflex activation. Guide‐cannulas were bilaterally implanted in the PVN of male Wistar rats. Femoral artery and vein were catheterized one day before of the experiments. Chemoreflex was activated with KCN (40 μg, iv) before and after the microinjections into the PVN. Microinjection of bicuculline, a GABAA receptor antagonist, into the PVN (n=10) produced an increase in baseline MAP (99±1 vs 114±4 mmHg) and HR (344±6 vs 444±13 bpm), but had no effect on the pressor (48±5 vs 40±5 mmHg) or bradicardic (−204±17 vs −277±34 bpm) responses to chemoreflex activation. Microinjection of L‐NAME, a non‐selective inhibitor of nitric oxide‐synthase, into the PVN (n=6) produced an increased in the baseline MAP (93±2 vs 111±3 mmHg) and HR (344±8 vs 454±27 bpm), but had no effect on the pressor (55±6 vs 46±8 mmHg) or bradicardic (−246±15 vs −326±31 bpm) response to chemoreflex activation. We conclude that GABAA receptors and nitric oxide in the PVN are involved in maintenance of the baseline autonomic activity to the cardiovascular system but not in the modulation of the cardiovascular responses to chemoreflex activation. Supported by FAPESP, CNPq and CAPES.
Chronic intermittent hypoxia (CIH) enhances spontaneous synaptic transmission in the nucleus tractus solitarii (NTS) neurons of juvenile rats
Authors: Almado Carlos Eduardo L. , Accorsi‐Mendonça Daniela , Machado Benedito H. , Leão Ricardo M.X.
Published: June 2021

CIH induces several changes in the cardiovascular system including hypertension. Previous experiments from our laboratory showed that juvenile rats exposed to CIH presented hypertension and an increased sympathoexcitatory response to chemoreflex activation. In the present study we evaluated possible changes in synaptic transmission in NTS neurons of juvenile rats submitted to CIH. 21‐day‐old rats were exposed to 10 days of CIH, and after this period electrophysiological experiments were performed in brainstem slices containing NTS. After CIH, spontaneous synaptic transmission in NTS neurons was enhanced. The frequency of total spontaneous post‐synaptic currents (sPSCs) was significantly increased in NTS neurons of CIH rats (n=21) when compared to NTS neurons of control rats (n=27), (1.84 ± 0.30 Hz vs 1.19 ± 0.17Hz, p<0.05). In addition, amplitude (39.2 ± 4.7 vs 27.0 ± 2.6 pA, p<0.05) and half‐width (3.18 ± 0.30 vs 2.20 ± 0.20 ms, p<0.01) of those spontaneous events were also augmented in NTS neurons of CIH rats. Moreover, half‐width of glutamatergic spontaneous current was increased after CIH (2.49 ± 0.16 vs 1.86 ± 0.14 ms, p<0.01). These data indicate that CIH enhances spontaneous synaptic transmission in NTS neurons, which may explain, at least in part, the autonomic dysfunction and hypertension observed on this experimental model. Supported by FAPESP and CNPq.
The differential effects of imidazoline‐like drugs on the components of baroreflex function in the nucleus of the solitary tract in anesthetized rats
Authors: Wang Wei‐Zhong , Wang Li‐Gang , Yuan Wen‐Jun , Wang Wei
Published: June 2021

Imidazoline‐like drugs (clonidine and moxonidine), agonists of I1‐imidazoline receptor (I1R) and/or α2‐adrenoceptors (α2AR), has been suggested to produce the cardiovascular inhibition in the central nervous system, which is associated with baroreflex modulation. The nucleus of the solitary tract (NTS) is a crucial region involved in cardiovascular and baroreflex regulation. This study was to comparatively detect the effects of clonidine and moxonidine on the baroreflex control of heart rate (HR) or renal sympathetic nerve activity (RSNA) in normotensive rats. In urethane and α‐chloralose anesthetized rats, bilateral microinjection of clonidine (2 nmol), a mixed agonist of I1R and α2AR, into the NTS increased the baroreflex control of HR (1.13 ± 0.1 vs. 1.79 ± 0.2 bpm/mmHg, P<0.05) and RSNA (1.19 ± 0.2 vs. 1.73 ± 0.3 %/mmHg, P<0.05). Bilateral NTS injection of the selective I1R agonist moxonidine (4 nmol) increased the baroreflex control of RSNA (1.22 ± 0.2 vs. 1.79 ± 0.3 %/mmHg, P<0.05) without affecting the baroreflex control of HR (1.15 ± 0.1 vs. 1.18 ± 0.2 bpm/mmHg, P>0.05). In conclusion, the present results demonstrate that the imidazoline‐like drug clonidine and moxonidine in the NTS differentially modulate the baroreflex components, which probably is dependent on acting receptors. (Supported by the National Natural Science Foundation of China, No. 30470636 and 30670759)
Activation of 5‐hydroxytryptamine type 3 receptor‐expressing C‐fiber vagal afferents inhibits retrotrapezoid nucleus chemoreceptors in rats
Authors: Moreira Thiago S , Takakura Ana C , Guyenet Patrice G
Published: June 2021

Retrotrapezoid nucleus (RTN) chemoreceptors are regulated by inputs from the carotid bodies (CB) and from pulmonary mechanoreceptors. Here we tested whether RTN neurons are influenced by 5‐hydroxytryptamine type 3 receptor‐expressing C‐fiber vagal afferents. In urethane‐anesthetized rats, selective activation of vagal C‐fiber afferents by phenylbiguanide (PBG) eliminated the phrenic nerve discharge (PND) and inhibited RTN neurons (n = 24). PBG had no inhibitory effect in vagotomized rats. Muscimol injection into the solitary tract nucleus, commissural part, reduced inhibition of PND and RTN by PBG (73%), blocked activation of PND and RTN by CB stimulation (cyanide) but had no effect on inhibition of PND and RTN by lung inflation. Bilateral injections of muscimol into interstitial NTS reduced the inhibition of PND and RTN by PBG (53%), blocked the inhibitory effects of lung inflation but did not change the activation of PND and RTN neurons by CB stimulation. PBG and lung inflation activated post‐inspiratory neurons located within the rostral ventral respiratory group (rVRG) and inhibited inspiratory and expiratory neurons. Bilateral injections of muscimol into rVRG eliminated PND and partially decreased RTN neuron inhibition by PBG (32%). In conclusion, activation of cardiopulmonary C‐fiber afferents inhibits the activity of RTN chemoreceptors. The pathway relays within a broad medial region of the NTS and involves the rVRG to a limited degree. The apnea triggered by activation of cardiopulmonary C‐fiber afferents may be due in part to a reduction of the activity of RTN chemoreceptors.

Supported by: HL 74011 (PGG) & Capes‐BEX 4402/05‐7 (ACT).
A lack of potentiating effect of increasing temperature on the responses to chemical activators in vagal sensory neurons isolated from TRPV1‐null mice
Authors: Ni Dan , Lee Lu‐Yuan
Published: June 2021

A recent study demonstrated that the responses of rat pulmonary sensory neurons to TRPV1 activators were enhanced by increasing temperature (Ni and Lee, FASEB J., 2007), but the role of the TPRV1 channel in the potentiating effect could not be determined. In the present study, we used whole cell perforated patch‐clamp technique to study the effect of increasing temperature on the response of isolated nodose/jugular sensory neurons to non‐selective TRPV1 channel activators in TRPV1‐null (TRPV1−/−) and wild type (WT) mice. Our results showed that, in voltage‐clamp mode, the inward current evoked by 2‐aminoethoxydiphenyl borate (2‐APB), a common activator of TRPV1‐3 channels, was greatly potentiated by increasing temperature from 36 to 40.5°C in WT neurons (n = 9; P < 0.01), but was not affected in TRPV1−/− neurons (n = 9; P = 0.54). Similarly, the inward current evoked by acid (pH 5.5), an activator of both TRPV1 channel and the acid sensing ion channel, was enhanced by increasing temperature (n = 7; P < 0.05), and this effect was not observed in TRPV1−/ − neurons (n = 13; P = 0.11). These results demonstrated that disruption of the TRPV1 channel eliminates the potentiating effect of increasing temperature on the response of nodose/jugular neurons to non‐selective TRPV1 channel activators, suggested a possible interaction between these chemical activators and increasing temperature at the TRPV1 channel.
The role of antioxidant & oxidative status in the protection against altitude‐associated reductions in uterine artery (UA) blood flow & fetal growth afforded by Andean ancestry
Authors: Julian Colleen Glyde , Vargas Enrique , McCord Joe M , Hageman Jennifer L , Davila Rita Daniela , Yamashiro Henry , Wilson Megan J , Rodriguez Carmelo , Rodriguez Armando , Browne Vaughn A , Moore Lorna G
Published: June 2021

Objective: To determine the role of antioxidant & oxidative status in the protection of uterine artery blood flow (UAVF) & fetal growth at high altitude in Andean populations. Methods: Erythrocyte catalase (CAT) & superoxide dismutase (SOD), plasma isoprostanes (8‐ISO‐PGF‐2α) & UA VF were measured at 20 & 36w of pregnancy & and in the non‐pregnant state in Andean (AND) & European (EUR) women at low (LA, 416m) or high (HA, 3600m) altitude. CAT, SOD & 8‐iso‐PGF‐2α were assessed by spectrometry, UA VF by Doppler ultrasound & birth weight (BW) by medical records review. Data was analyzed by t‐tests, 1‐ & 2‐way ANOVA. Results: At LA, ancestry had no effect on CAT or SOD. AND had higher CAT (20 & 36w p<0.05) & SOD activity (36w p<0.05) than EUR at HA. At HA, UA diameter and UA VF were greater in AND than EUR. Altitude decreased BW in AND (p<0.05) and EUR (p<0.01), and at HA EUR ancestry reduced BW (β= − 0.238 p<0.05). Small‐for‐gestational age (SGA) infants occurred 2‐times more frequently at HA than LA in EUR. SOD was lower at 20w in SGA at both altitues, or HA alone (all p<0.05). In EUR, CAT tended to be lower at 20w in SGA. 8‐ISO‐PGF2α reduced UA diam (p<0.05) & UA VF (p<0.01) in all women. Conclusion: Elevated endogenous antioxidant activity may contribute to the protection against altitude‐associated reductions in UA blood flow & fetal growth afforded by Andean ancestry. NIH HL079647,AHA 0610129Z & NSF BCS‐064719.
Effect of prior heavy exercise on O2 uptake kinetics in the upper regions of the moderate‐intensity domain
Authors: Kowalchuk John Michael , Rossiter Harry B. , Chin Lisa M.K. , Paterson Donald H. , Whipp Brian J.
Published: June 2021

That pulmonary O2 uptake (VO2) kinetics in the upper region of the moderate‐intensity exercise domain are slow relative to the lower region is thought to reflect an intrinsic characteristic of the recruited muscles (Brittain et al., EJAP 86:125, 2001). Because prior heavy exercise speeds moderate‐intensity VO2 kinetics when they are slow, we wished to determine whether prior heavy exercise would similarly speed VO2 kinetics in the upper moderate‐intensity domain. Ten males performed 4–6 repeats of two double‐step (S) cycle ergometer protocols: 1) S1‐S2: 20 W to 80% of the estimated lactate threshold made in two equal increments, and 2) HS1‐HS2: as protocol 1, but with S2 preceded by heavy exercise (Δ50%); each step lasted 6 min. VO2 was measured breath‐by‐breath using a turbine and mass spectrometer. The fundamental VO2 time constant (τ) was greater (p<0.05) in S2 (41 ± 15 s) than S1 (21 ± 4 s). After heavy exercise, τVO2 was lower (p<0.05) in HS2 (31 ± 10 s) than S2, but remained greater (p<0.05) than HS1 (22 ± 5 s). Thus VO2 kinetics in the upper moderate‐intensity domain are not immutable, becoming faster after heavy exercise. However, this effect (presumably due to activation of intramuscular enzymes, improved oxidative substrate provision and/or improved O2 transport kinetics) did not entirely overcome the intrinsically‐slow kinetics in this region. Supported by NSERC, Canada; Wellcome Trust, UK
Molecular impact of divalent metal‐ion transporter (DMT1) mutations (V114del and G212V) found in a compound heterozygote with microcytic anemia and hepatic iron overload
Authors: Shawki Ali , Illing Anthony C , Mackenzie Bryan
Published: June 2021

DMT1 is a H+‐coupled divalent metal‐ion transporter critical for intestinal iron (Fe) absorption and erythroid Fe utilization. Beaumont et al (Blood 107, 4168 [2006]) described a patient compound heterozygous for two new DMT1 mutations (V114 deletion and G212V) associated with hypochromic‐microcytic anemia and hepatic Fe overload. The proband's sibling and parents each possess one mutated allele but were asymptomatic. We expressed mutant and wildtype (wt) DMT1 in Xenopus oocytes and used voltage‐clamp and radiotracer assays to examine the molecular impact of these novel mutations. The V114 deletion abolished 55Fe2+ transport activity whereas 55Fe2+ transport mediated by G212V‐DMT1 did not differ from wtDMT1. G212V had no effect on the pH dependence of 55Fe2+ transport, presteady‐state kinetics, or the affinity for Fe2+ (K0.5 = 1.7 ± 1.1 μM c.f. 1.3 ± 0.5 μM in wtDMT1). To our surprise, however, G212V‐DMT1 mediated much smaller Fe2+‐evoked currents than did wtDMT1. From simultaneous measurement of currents and 55Fe2+ fluxes, we arrived at a wildtype H+/Fe2+ ratio of 17 ± 1 which greatly exceeds that expected for strict stoichiometric transport, i.e. most of the wtDMT1‐mediated current arises from H+ slippage. Such slippage is normally thought of in terms of the energetic penalty to the cell; however, indications that H+ slippage, but not Fe2+ transport, is disrupted in the G212V mutant associated with disease raise the possibility that H+ slippage serve a physiological role.
Manipulation of the sympathetic nervous system (SNS) with repetitive trans‐spinal magnetic stimulation in healthy adult humans
Authors: Paxton Roger John , Malcolm Matthew P. , Newsom Sean A. , Rynn Grant M. , Maddox Hal W. , Strevey Daniel , Little Suzanne K. , Richards Jennifer C. , Supon Ryan J. , Heulin Kara R. , Bell Christopher
Published: June 2021

Trans‐cranial magnetic stimulation (TCMS) is a non‐invasive, pain‐free technique used to stimulate and study the human brain and is able to elicit brief (< 5 s) changes in SNS activity. Use of TCMS to elicit longer‐term changes in SNS activity is problematic because magnetic stimulation of the cortex does not directly activate SNS control centers, and prolonged magnetic brain stimulation increases the risk of seizure. Repetitive trans‐spinal magnetic stimulation (rTSMS) represents a novel application of the same technology that avoids the risks associated with TCMS. We have examined the utility of rTSMS for modulation of SNS in adult humans. 32 adults (age: 18–47 yr) were randomly assigned to receive either rTSMS (1 Hz; n = 6, 10 Hz; n = 10, or 20 Hz; n = 8 at 50% intensity of stimulator output) or sham stimulation (SS; n = 8). Skeletal muscle SNS activity (MSNA; microneurography), R‐to‐R interval (RRint; ECG) and standard deviation of RRint (SDRRint; a marker of heart rate variability) were measured prior to, during, and post rTSMS or SS with the magnetic coil aligned with the spinous processes of the 6th and 7th cervical vertebrae. Compared with SS, rTSMS at any frequency did not affect any of the dependent variables: condition/time interaction ‐ MSNA: P = 0.89, RRint: P = 0.15, or SDRRint: P = 0.87. These preliminary data suggest that rTSMS does not influence SNS in adults.

Support: NIA AG022053, CSU College of Applied Human Sciences
In vivo subcutaneous injection of Alcian blue at acupuncture points to trace a circulatory path from skin to organs
Authors: Han Hyun‐Jung , Sung Baeckkyoung , Ogay Vyacheslav , Soh Kwang‐Sup
Published: June 2021

Acupuncture has been thought to be a therapeutic treatment to regulate the function of internal organs by stimulating singular points at skin. This study was designed to trace a path from acupoints to corresponding organs by subcutaneous injection of Alcian blue (Ab) at certain acupoints. As the injection points, two acupoints BL23 and GB25 in rats, the control points of kidney, were selected and 200 μℓ of Ab was injected. After 2–7 hours from administration, internal organs were observed with a stereomicroscope. Ab‐stained corpuscles (Bong‐Han corpuscles) and spots along flow paths were observed from the injection points toward cranial direction in the dorsal skin. Furthermore, Ab‐stained spots were detected in the outer medulla region of the kidney, which showed that the Ab flowed from BL23 and GB25 in skin to kidney. In conclusion, the Ab injection at acupoints demonstrated a circulatory path from specific acupuncture points in skin to their corresponding internal organs. This can be utilized as a new effective drug delivery path.
The effects of growth factors on hIK1 protein expression levels in transfected HEK293 cells
Authors: O’Rourke Kellie Leatha , Mague Alissa Renee , Jones Heather Marie
Published: June 2021

The calcium (Ca2+)‐activated potassium (K+) channel, hIK1, is a human intermediate conductance channel expressed in numerous epithelia linings including the placenta, lungs and gastrointestinal tract. The functional roles for hIK1 underline processes such as ion transport, volume regulation, cell growth and proliferation. To investigate hIK1's role in cell growth, we examined the effects of the growth factors: epidermal growth factor (EGF), fibroblast growth factor (FGF), and tumor necrosis growth factor alpha (TNF‐α) on hIK1 protein expression. The protein levels were measured by treating human embryonic kidney (HEK) cells transfected with hIK1. The growth factors were administered 24 hours prior to analysis. Cells were lysed, total protein was collected and equal quantities were run on SDS‐page gel. Antibodies were used to detect hIK1 expression. From the total isolated protein the relative thickness of the treated cell bands on the western blot were compared to the untreated hIK1‐HEK cell bands to determine if total hIK1 protein expression was increased or decreased. It was found that EGF‐treatment increased total hIK1 protein expression and TNF‐α treatment decreased hIK1 protein levels. These results suggest that growth factor interactions with hIK1 are mediating the channel's role in cell growth and proliferation.
Evidence for cAMP‐mediated transepithelial ion flux in porcine vocal fold epithelia
Authors: Sivasankar Mahalakshmi , Nofziger Charity , Blazer‐Yost Bonnie
Published: June 2021

Vocal fold epithelia are exposed to osmotic challenge and inflammatory perturbations at the glottal interface. Emerging data on transepithelial vectorial ion fluxes and associated passive water movement suggest potential mechanisms by which vocal folds may defend against osmotic and chemical challenge. However, the ion transport mechanisms underlying vocal fold defense to inflammatory perturbations are not understood. In vocal folds from an Ossabaw swine model, we used electrophysiological techniques to confirm the presence of the epithelial Na+channel, ENaC, and the Cl−channel CFTR. As cAMP plays an important role in signal transduction and may serve as a second messenger for a variety of inflammatory mediators and cytokines, we examined whether porcine vocal fold epithelia are sensitive to the cAMP activator, forskolin. 30 minutes of exposure to forskolin (5mM) significantly increased ion transport, the characteristics of which are consistent with Cl− secretion as compared to sham controls (N = 10, p < 0.05) and concurrently significantly increased intracellular cAMP (N = 4, p < 0.05). These findings provide evidence for the presence of cAMP mediated ion flux in porcine vocal fold epithelia. Vocal fold inflammation is a leading cause of laryngeal disease and understanding the mechanisms involved in the inflammatory process will lead to improved treatment options for this common communication disorder.
Identification of the multivalent PDZ domain protein PDZK1 as a binding partner of sodium‐coupled monocarboxylate cotransporter 2 (SMCT2) by yeast two‐hybrid assay
Authors: Srivastava Sunena , Anzai Naohiko , Yamanishi Ai , Ganapathy Vadivel , Endou Hitoshi
Published: June 2021

Sodium‐coupled monocarboxylate transporter SMCT2 (SLC5A12), mediates the transport of pyruvate, nicotinate and lactate (Gopal et al., BBA. 2007). Since URAT1 transports urate in exchange for intracellular organic anions such as lactate and nicotinate, SMCT2, as well as SMCT1, seems important for the transport function of URAT1 (Anzai et al. Curr Opin Rheumatol, 2007). In addition, SMCT2 C‐terminal domain is in the cytoplasm and contains PDZ motif, suggesting that it interacts with PDZ proteins. In the present study, we used the yeast two‐hybrid screening to investigate the putative SMCT2‐associated proteins in the kidney. Using the SMCT2 C‐terminus (SMCT2‐CT) as bait, we performed a yeast two‐hybrid screen of a human adult kidney cDNA library. From a total of 1.2 [~ 107 independent colonies screened, 34 positive clones were obtained. Of these, 8 yielded an identical sequence encoding the gene for the multivalent PDZ protein PDZK1. Deletion of C‐terminal PDZ motif abolished the interaction with PDZK1 in the yeast two‐hybrid system. In addition, the first, second and fourth PDZ domains of PDZK1 associate with SMCT2‐CT. The elucidation of these interactions may lead to the further understanding of functional regulation of urate transport via monocarboxylate handling in human kidney.
Intracellular Ca2+‐store depletion triggers a Na+ influx via SOCs in guinea pig tracheal smooth muscle
Authors: Romero‐Mendez Ana Catalina , Algara‐Suarez Paola , Sanchez‐Armass Sergio , Mandeville Peter B , Meza Ulises , Espinosa‐Tanguma Ricardo
Published: June 2021

Guinea pig epithelial‐free tracheal rings were incubated with an EGTA‐buffered Ca2+‐free solution and the SR‐Ca2+‐ATPase blocker thapsigargin (Tg) 1 uM in order to deplete the intracellular Ca2+ stores and induce a contraction upon Ca2+ readmission. The contraction was inhibited (in %) by (mean +/− se; n= 4): SKF‐96365 (100 uM) 66.3 +/− 4.4, TRIM (100 uμM) 41.3 +/− 5.2 (inhibitors of SOC); nifedipine (1 uM) 86.2 +/− 3.4, verapamil (10 uM) 76.9 +/− 5.9 (inhibitors of CaV1.2 channels) and niflumic acid (20 uM) 41.1 +/− 9.8 (inhibitor of the CaCC). Moreover, in Na+‐free conditions (Na+ substituted by NMDG) the contraction evoked by Ca2+ readmission was significantly inhibited. The resulting contraction under these conditions was, in turn, importantly reduced by nifedipine and niflumic acid when Na+ was replaced by NMDG+ and eliminated by nifedipine but resistant to niflumic acid when Na+ was replaced by Li+. These findings support the idea that SOCs are non‐selective cation channels that permit Na+ entry leading to an increase in cytosolic [Na+] and cell depolarization. Depolarization and the increase of intracellular Na+ levels are key events that induce the Na+‐Ca2+ exchanger to switch to its reverse mode, promoting a Ca2+ influx that, in turn, activates CaCC increasing the depolarization phenomena and therefore the opening Cav1.2 channels. Supported by CONACYT 62220 to RET, UM and SSA and UASLP C05‐FAI‐10‐3.24 to SSA.
Modeling the hemodynamic response due to vasodilatory signals conducted upstream along the arteriolar tree
Authors: MacKie S.J. Meaghan , Milkovich Stephanie , Ellis Christopher G. , Goldman Daniel
Published: June 2021

To study local regulation of convective O2 delivery, in vivo experiments were conducted using a gas chamber to oscillate the O2 environment at one surface of rat skeletal muscle. Intravital video microscopy enabled quantification of the hemodynamic (RBC velocity, V, and hematocrit, H) and O2 saturation responses in capillaries. To assess how changes in arteriolar diameters lead to the observed blood flow response, a model of the lower three levels of the arteriolar tree was constructed based on published data. Sinusoidal changes in vessel diameter were imposed at the distal end of one terminal arteriole, and the upstream conduction of these diameter changes was simulated. A quasi‐steady model of two‐phase (RBCs and plasma) blood flow was used to calculate time‐dependent hemodynamics in the network. For a range of forcing frequencies, conduction velocities (Vcond), and attenuation lengths, the ability of the system to control RBC supply in a terminal arteriole was studied. Attenuation lengths within the physiological range (2mm to 2cm) did not affect the flow response. Decreases in frequency and increases in Vcond increased the amplitude of the flow response. For a frequency of 0.025 Hz, varying Vcond from 10 μm/sec to 50 μm/sec increased the RBC supply response by 35%. Predicted changes in H and V showed qualitative agreement with experimental results. Supported by NIH HL‐089125, CIHR to CGE and DG, and NSERC to SJMM.
Dose‐dependent effects of DOCA treatment on cardiovascular function and brain sodium content in the rat
Authors: Abrams Joanna M , Dubinsky Janet M , Guzman Pilar Ariza , Osborn John W
Published: June 2021

Rats were uninephrectomized, implanted with transmitters for the measurement of arterial pressure (AP), and given either water or 0.9% NaCl to drink. Fluid ingestion (FI) and Na balance were calculated daily. Rats were implanted with a silicone pellet containing 0, 50, or 100 mg DOCA, resulting in 4 groups: control (n=6)

saline: 0 mg DOCA + 0.9% NaCl (n=8)

50 mg: 50 mg DOCA + 0.9% NaCl (n=9)

100 mg: 100 mg DOCA + 0.9% NaCl (n=9)

DOCA treatment increased AP, FI, and Na balance (p<0.05). Although 50 mg and 100 mg rats had identical increase in AP, 100 mg rats consumed 2‐fold more saline. Positive Na balance was observed in both DOCA groups, but not in control animals; however, only 100 mg rats showed a significant increase in Na balance as compared to saline rats.

We analyzed Na content of several brain regions, including hypothalamus, brainstem, cortex, and, as a measure of overall brain Na content, homogenized half‐brain. Na content was constant across all regions with the exception of the hypothalamus. DOCA treatment increased Na content in the hypothalamus in a dose‐dependent manner.

Our results indicate that while increasing DOCA dose from 50 mg to 100 mg has no effect on AP, other variables showed dose‐sensitive modulation. In particular, brain handling of increasing sodium load may be region‐dependent, and the hypothalamus may play a unique role in driving responses to DOCA‐salt treatment. HL064178.
Failure Mode Effects Analysis (FMEA) of Cryospray Ablation in the Airways of Swine
Authors: Krimsky William , Sarkar Saiyad , McKenzie Karen , Petras Robert , Cartledge Jennifer , Askew Timothy
Published: June 2021

Background: Cryospray Ablation (CSA) evokes tissue necrosis, allowing the regeneration of healthy tissue. In order to determine feasibility and safety of CSA for human lung disease, we tested FMEA in swine.

Methods: Three swine were tested to cardiopulmonary collapse defined as the absence of tissue perfusion and oxygenation. Physiologic measurements were continuously assessed, including pulmonary artery pressure, end tidal (EtCO2), pulse oximetry, EKG, BP, and fluoroscopy of the chest. The cryospray catheter was placed into the airway via the bronchoscope and a closed system was maintained. Cryospray was delivered into the airway until cardiopulmonary collapse (CPC).

Results: The appearance of barotrauma on fluoroscopy defined as a visible pneumothorax did not result in substantive change of hemodynamic or gas exchange parameters. However, progressive increases in intrathoracic pressure from the continued delivery of the cryospray resulted in CPC secondary to right heart failure. The heralding event of collapse in all animals was the eventration of the right ventricle on fluoroscopy followed rapidly by the development of a non‐perfusing rhythm, the loss of a waveform on the pulmonary artery catheter (PAC), and the loss of EtCO2 and pulse oximetry data. Using pulmonary artery systolic pressure (PASP) as a surrogate for intrathoracic pressure, PAC data suggested it was necessary to raise PASP to greater than 70mmHG (baseline values ∼20mmHG) to achieve the above result. Cardiac function could be restored to normal upon the retardation of cryospray. There was no evidence of airway disruption.

Conclusion: FMEA of the CSA system in the airway suggests the potential to safely use this modality for the treatment of human lung diseases.
Reductions in adipose tissue mitochondrial content in high fat diet‐induced obesity and lean models of insulin resistance
Authors: Sutherland Lindsey Nicole , Capozzi Lauren C , Taylor Donna J , Dunichand‐Hoedl Abha R , Bell Rhonda C , Wright David C
Published: June 2021

Insulin resistance is associated with reductions in adipose tissue mitochondrial content. It is not known how rapidly these changes occur and how they relate to changes in glucose homeostasis. In order to establish the temporal relationship between diet‐induced adipose tissue insulin resistance and mitochondrial content, rats were fed a high fat (HF) diet for 2, 4, or 6 weeks. We found that 6 weeks of HF feeding was necessary for reductions in mitochondrial content in epididymal adipose tissue to occur, as demonstrated by decreases in the protein content of cytochrome C and COXIV, reduced Mitotracker staining, and reductions in mitochondrial size as estimated by electron microscopy. Similar results were seen in dexamethasone treated rats, a model of lean insulin resistance. Intraperitoneal Glucose Tolerance Tests (IPGTT) were completed at 4 and 6 weeks to determine whole‐body insulin action. At 4 weeks and 6 weeks, the integrated AUC for glucose and insulin was higher in the HF fed rats versus control. Although reductions in mitochondrial content did not appear to precede changes in whole‐body insulin action, it did appear to be associated with a worsening of insulin sensitivity, a phenomenon that can occur in both lean and obese models of insulin resistance.

Funding: Alberta Heritage Foundation for Medical Research, Natural Sciences and Engineering Research Council, Alberta Diabetes Institute
Comparison of Physical Fitness in Type 1 Diabetic and Healthy Children Matched by Age, Gender, and BMI
Authors: Lee Jane Soyoun , Oliver Stacy R. , Rosa Jaime S. , Pontello Andria M. , Graf Scott C. , Galassetti Pietro R.
Published: June 2021

Physical activity is important in the growth and development of children and long‐term prevention of cardiovascular disease (CVD). Children with chronic diseases, such as diabetes, with increased risk for CVD, may display altered exercise adaptations requiring individually tailored exercise regimens. While assessment of physical fitness is a crucial component in the design of exercise strategies, conflicting conclusions exist concerning fitness in type 1 diabetic (T1DM) children (with both normal and reduced levels reported), possibly due to difficulty in recruiting closely‐matched controls. Our study aimed to compare fitness in 40 T1DM (19 F, ages 11–15) children and 40 healthy controls rigorously selected as one‐on‐one matches for gender, age (0.13 years mean difference) and BMI (1.5 mean difference). Maximal aerobic capacity (VO2peak) was determined through a standard incremental exercise test on a cycle ergometer. VO2peak was comparable across groups (38 ± 1 vs. 37 ± 1 ml/min/kg, NS), even when subdivided by gender (T1DM vs. control: girls 34 ± 2 vs. 35 ± 2; boys 44 ± 2 vs. 40 ± 2 ml/min/kg). Physical fitness was similar between T1DM and rigorously‐matched healthy children, suggesting that T1DM does not intrinsically limit a child's ability to fully derive the physiological health benefits associated with exercise.

Support: NIH grants M01‐RR00827–28; K‐23 RR018661–01; & JDRF #11–2003–332
Altered reactivity to α2‐adenergic stimulation in the vasculature of the Obese Zucker rat
Authors: Mintz James , DeLima Philip D. , Elms Shawn C. , Lehn R. Andrew , Price Eric W. , Stepp David W.
Published: June 2021

Obesity is associated with marked changes in adrenergic vasoconstriction of the resistance circulation. Stimulation of α1 receptors with phenylephrine promotes increased hindlimb vascular resistance (HVR) and decreased mesenteric resistance (MVR) in obese Zucker rats (OZR). Effects of obesity on constrictor reactivity to α2 receptor stimulation are unknown. Anesthetized lean Zucker rats (LZR) and OZR were instrumented with arterial catheters and flow probes around the mesenteric and renal arteries and distal aorta to measure MVR, renal vascular resistance (RVR) and HVR. I.v. injections of clonidine caused drops in blood pressure consistent with the central actions of clonidine that were similar in LZR and OZR. To rule out central effects reactivity was evaluated after 2 mg/kg mecamylamine. Clonidine (0.05–5 μg) caused increases in HVR that were similar in OZR and LZR. However, increases in MVR were greater in OZR vs. LZR (62±5 vs. 49±6 % of basal) as were increases in RVR (10±2 vs. 25±7%). To determine if NO deficit explains increased constriction, experiments were repeated with 500 μg/kg L‐NAME. Increases in MVR (72±4 vs 73±6%) and RVR (11±2 vs. 25±8%) persisted suggesting a difference in reactivity to α2‐receptor stimulation rather than loss of buffering NO. Together, these data indicate that loss of α1 vasoreactivity in the splanchnic and renal beds may be offset by increases in α2 vasoreactivity. (HL076533‐03)
Phrenic long‐term facilitation is induced by acute intermittent hypoxia despite systemic ATP receptor antagonist attenuation of hypoxic phrenic response in rats
Authors: Sibigtroth Christine Marie , Mitchell Gordon S.
Published: June 2021

Phrenic long‐term facilitation (pLTF) is a form of respiratory plasticity induced by acute intermittent hypoxia (AIH; Mitchell et al., 2001). Although pLTF is elicited in carotid denervated rats, its magnitude is reduced in proportion to the reduction of the hypoxic phrenic response (~35% normal; Bavis and Mitchell, 2002). Thus, the role of residual chemosensory afferent activity and hypoxic phrenic responses in pLTF induction remains unclear. Since ATP is necessary for hypoxic stimulation of carotid chemoafferent activity and the hypoxic ventilatory response (Rong et al., 2003), we tested the hypothesis that systemic P2X receptor antagonism would block both the hypoxic phrenic response and pLTF following AIH in anesthetized rats. Pyridoxal‐phosphate‐6‐azophenyl‐2',4'‐disulfonic acid (PPADS; 100 mg/kg IV), a non‐selective P2X receptor antagonist, was administered to anesthetized, vagotomized, paralyzed and ventilated male Sprague‐Dawley rats prior to AIH (3, 5‐min episodes of 10% O2; 5 min intervals). Although PPADS strongly attenuated the hypoxic phrenic amplitude response (3 ± 5% baseline), significant pLTF was observed in phrenic burst amplitude 60 min post‐AIH (34±8% baseline, n=4; p < 0.05). Thus, AIH initiates mechanisms of pLTF independently from the hypoxic phrenic response and, presumably, chemoafferent neuron activation.

Supported by: NIH HL80209 and T32RR17503
Episodic Spinal 5‐HT7 Receptor Activation Induces Phrenic Motor Facilitation
Authors: Hoffman Michael S. , Mitchell Gordon S.
Published: June 2021

Spinal activation of Gs protein‐coupled adenosine A2A receptors trans‐activates the high affinity BDNF receptor tyrosine kinase, TrkB, inducing a long‐lasting phrenic motor facilitation (PMF). We hypothesized that other Gs protein‐coupled receptors also elicit PMF. Since serotonin receptors underlie multiple forms of spinal respiratory plasticity, and Gs protein‐coupled 5‐HT7 serotonin receptors are expressed in phrenic motor neurons, we hypothesized that cervical spinal 5‐HT7 receptor activation would induce PMF in anesthetized, vagotomized and ventilated male Sprague Dawley rats. Intrathecal (C4) injections of 5‐HT7 receptor agonist, AS‐19 (4μl, 3×5min; 9μg*kg−1), increased phrenic nerve burst amplitude at 60, 90 and 120 minutes post‐injection (44%, 50%, 86±8% baseline, respectively; n=4, p<0.001). Pretreatment with a 5‐HT7 receptor antagonist (SB 269970; 16μg*kg−1) prevented AS‐19‐induced PMF (−4%, 0% and 4±9%, respectively; n=3, p<0.05). Thus, spinal 5‐HT7 receptor activation induces a long‐lasting facilitation of phrenic motor output, possibly via TrkB receptor trans‐activation. Although mechanistic details of PMF remain uncertain, molecules that induce respiratory motor facilitation may be useful for treatment of ventilatory control disorders and/or respiratory insufficiency following spinal injury or neurodegenerative disease (NIH HL80209 and HL07654).
Ventilatory efficiency during pregnancy: the influence of obesity
Authors: Steinback Craig Douglas , Davenport Margie H , Mottola Michelle F
Published: June 2021

We examined the effect of pregnancy and obesity on ventilatory efficiency at rest and during exercise in women of child‐bearing age. We hypothesized that obesity would have a detrimental effect on ventilatory efficiency compared to the normal weight pregnant and non‐pregnant populations.

Forty pregnant women (20 normal weight, PG; and 20 obese, PGOB) between 16 and 20 weeks of gestation and 14 non‐pregnant controls (NP) performed a progressive treadmill test to volitional fatigue. Oxygen consumption (VO2), minute ventilation (VE) and an index of ventilatory efficiency (VE/VCO2 ratio) were compared at rest and at peak exercise (PKE).

PGOB exhibited a hyperventilation at rest (VE = 14.5±2.5 L/min) compared to PG (12.7±2.7 L/min, P<0.001) and NP (11.5±1.6 L/min, P<0.001) despite a lower VO2 (P<0.05). Ventilatory efficiency was reduced (higher VE/VCO2 ratio) in obese subjects at rest (4.1±0.7) and at PKE (3.0±0.4) compared to NP (2.3±0.3 and 1.8±0.2 respectively; P<0.001) and PG (2.7±0.3 and 2.1±0.2 respectively; P<0.001). Further, BMI was inversely related to efficiency across all subjects at rest (r2=0.83, P<0.001) and at PKE (r2=0.72, P<0.001).

These data indicate that obesity results in a hyperventilation and decreased ventilatory efficiency that is unrelated to pregnancy. This may have implications for exercise capacity and fetal health during pregnancy.

Funded by HSFO, OGS and CIHR.
Exercise training increases extracellular superoxide dismutase protein content in soleus muscle feed arteries of aged rats.
Authors: Trott Daniel Wayne , Woodman Christopher R
Published: June 2021

Exercise training attenuates or reverses age‐induced endothelial dysfunction in skeletal muscle vascular beds. The purpose of this study was to test the hypothesis that exercise training improves endothelium‐dependent dilation through alterations in vascular antioxidant enzyme protein content and phosphorylation of endothelial nitric oxide synthase (eNOS) on ser1177 (Ser 1177 phospho‐eNOS). Young (2 mo) and Old (22 mo) male Fischer 344 rats were exercise trained (Ex) or remained sedentary (Sed) for 10–12 weeks resulting in four groups of rats: Young Sed (4 mo; n = 7), Young Ex (4 mo; n = 8), Old Sed (24 mo; n = 8), Old Ex (24mo; n = 8). At the end of the exercise training program, immunoblotting was performed on soleus muscle feed arteries (SFA) to assess eNOS, Ser 1177 phospho‐eNOS, Cu/Zn cytosolic superoxide dismutase (Cu/ZnSOD) and extracelluar superoxide dismutase (ecSOD) protein content. Results indicate that eNOS and Ser 1177 phospho‐eNOS content was greater in Old rats compared to Young regardless of training status. Exercise training induced increases in ecSOD protein content in both Young and Old rats. There were no differences in Cu/ZnSOD protein content between groups. These data suggest that exercise training improves endothelium‐dependent dilation in senescent SFA in part due to increases in ecSOD protein content, resulting in an improvement in vascular antioxidant capacity. Supported by NIH AG‐00988, AHA Texas Affiliate Grant 0765043Y and an ACSM Foundation Research Grant (FRG)
Differential susceptibility of lung endothelial and epithelial cells to ceramides‐induced apoptosis
Authors: Petrusca Daniela Nicoleta , Rush Natalia , Hubbard Walter C. , Shuherk Shaeffer Jennifer R. , Smith Patricia , Petrache Irina
Published: June 2021

Ceramide upregulation may induce paracellular ceramides and alveolar cell apoptosis in both alveolar endothelial and epithelial cells, but their susceptibility to ceramide‐mediated apoptosis are unknown. We hypothesized cell‐type specificity in apoptotic responses to ceramide. Human lung microvascular endothelial (EN)‐, small airway epithelial (SEP)‐, and bronchial epithelial (BEP) cells were treated with ceramides (6:0 or 16:0) or dihydroceramide. Apoptosis and endogenous ceramides were quantified by caspase activation, annexin, mitotracker, cytochrome c, and mass spectrometry, respectively. Alveolar EN manifested susceptibility to both ceramides, which induced caspase‐9 activity 12‐fold. In contrast, SEP exhibited mitochondrial‐mediated apoptosis in response to short‐chain ceramide (30% apoptosis, 6h), whereas BEP were least sensitive to ceramide‐induced apoptosis. All cells upregulated endogenous intra‐ and paracellular ceramides after treatment with ceramides, but only epithelial cells released paracellular ceramides in response to dihydroceramides. Paracellular ceramides had marked pro‐apoptotic effects in EN, blocked by neutralizing ceramide antibodies. Our data suggest alveolar and airway epithelial cells have differential susceptibility to ceramide‐induced apoptosis, characteristic which could be exploited in specific interventions in emphysema. NIH HL077328.
DEVELOPMENT OF MUSCLE DIVING PHYSIOLOGY IN MARINE MAMMALS
Authors: Noren Shawn Ranee , Noren Dawn Page
Published: June 2021

Pinniped muscle development tracks life history such that species with short maternal dependency periods attain greater proportions of adult myoglobin levels earlier in life than species with protracted dependency periods. To determine if a similar pattern exists for mammals that develop at sea, the development of muscle myoglobin and acid buffering capacity due to non‐bicarbonate buffers was measured in the longissimus dorsi of harbor porpoise (Phocoena phocoena) and compared to data from bottlenose dolphins (Tursiops truncatus). The life history patterns of these species differ, with weaning occurring at 1 and 2.5–5 year(s) postpartum for porpoise and dolphins, respectively. Similar to dolphins, porpoise calves (n = 3) had significantly lower myoglobin content (0.8 ± 0.1 g myoglobin/100 g wet muscle mass) and acid buffering capacity (52.5 ± 0.1 slykes) than adult (n = 4) conspecifics (myoglobin: t = 4.9, P = 0.005; acid buffering capacity: t = 3.8, P = 0.013). However, the level of muscle maturity in porpoise and dolphin calves that were proportionally the same relative to adult length (50%) varied. Porpoise calves had 33% and 72% of mature myoglobin content and acid buffering capacity, respectively compared to only 10% and 65%, respectively for dolphin calves. Like pinnipeds, interspecific differences in muscle maturation in cetaceans track maternal dependency periods. Funded by NOAA NWFSC.
Effects of benzocaine on vascular smooth muscle contractility of the sea lamprey dorsal aorta
Authors: Bilyk Olenka , Olson Kenneth , Dombkowski Ryan
Published: June 2021

Benzocaine is a common fish anesthetic. This experiment was undertaken in order to determine the action of benzocaine and the mechanisms of action of calcium in the vascular smooth muscle from the dorsal aorta (LDA) of sea lamprey (Petromyzon marinus). Benzocaine contracted otherwise unstimulated vessels and vessels precontracted with either norepinephrine (NE) or KCl in a dose dependent manner. The vehicle, ethanol, also effected contraction in a dose dependent manner. LDA contracted significantly more when exposed to benzocaine in ethanol than to an equal volume of ethanol alone. LDA stimulated with NE were significantly more sensitive to benzocaine than were either unstimulated LDA or in LDA precontracted with KCl. LDA stimulated with KCl contracted significantly less in the absence of extracellular (EC) Ca2+ but the contractions doubled when EC Ca2+ was added back. Ethanol contractions were insignificant in the absence of EC Ca2+. Benzocaine‐induced contractions of LDA treated with thapsigargin and caffeine were significantly reduced in both the presence and absence of EC Ca2+. Therefore, KCl− and ethanol‐induced contractions were found to be dependent upon EC Ca2+ entry, while benzocaine was dependent upon intracellular Ca2+, most likely from the sarcoplasmic reticulum. These are important considerations to take into account when anesthetizing fish, particularly cyclostomes.
Selenium and iodine supplementation in older New Zealanders
Authors: Thomson Christine Dumont , Campbell Jennifer M , Skeaff Sheila A , Miller Jody C , Livingstone Vicki
Published: June 2021

Selenium (Se) and iodine are essential for optimal thyroid hormone metabolism. Suboptimal Se and iodine status reported in New Zealanders is likely to be exacerbated in older adults. The aim was to assess effects of Se, iodine, Se plus iodine supplementation on thyroid hormones. A randomized, double blind trial was conducted with 97 subjects (73±4.8 years) with 100μg Se as selenomethionine (+Se), 80μg iodine (+I), 100μg Se and 80μg iodine (Se+I), or placebo daily for 12 weeks. Thyroid hormone status (TSH, free T3, free T4, thyroglobulin), Se status (plasma Se, whole blood glutathione peroxidase (WBGPx)) and median urinary iodine concentration (MUIC) were determined at baseline, weeks 2, 4, 8, 12. The three treatments were compared with placebo. Baseline MUIC baseline was 48μg/l (IQR, 33,72), and increased by 34μg/l in +I group (P<0.001) and 13 μg/l in Se+I group. Mean baseline plasma Se was 1.20 (0.33)μmol/l and increased by 0.99 and 0.96μmol/l in +Se and Se+I groups, respectively (P<0.0001). WBGPx increased by 9% in Se groups (P<0.001). Tg concentration decreased by 27% (P<0.001) and 18% in +I and Se+I groups. No significant time by treatment effects were observed for TSH, free T3, free T4. Older New Zealand adults are moderately iodine deficient. Their Se status is insufficient for optimal GPx activity, but appears to be sufficient for optimal thyroid hormone function. Otago Medical Research Fund.
Selenium status in healthy adults in a longitudinal study using both traditional biochemical and molecular biology‐based biomarkers
Authors: Sunde Roger A , Paterson Elaine , Barnes Kimberly M , Evenson Jacqueline K , Lovegrove Julie A , Gordon Michael A
Published: June 2021

Human Se requirements are currently based on biochemical markers of Se status. Gpx1 mRNA levels can also be used to determine rat Se requirements. We found that Gpx1 mRNA levels decrease in rat blood and that Selh and Sepw1 mRNAs are also highly down‐regulated (<40%). Thus we collaborated with a Reading UK study, which examined effects of vegetable‐fruit‐based juices (with negligible Se <1 μg/d) in 39 subjects (24 female, 15 male, age 45 ± 11, BMI 24.5 ± 3.2). Diet records (5 d) and blood were obtained at 2, 8, 17 and 23 wk. There was no effect of juice on any Se marker, and there was no significant longitudinal effect on Se markers, so time‐point values were averaged. Se intake was 46 ± 9 μg/d for females and 45 ± 11 μg/d for males. Plasma Se values were 1.13 ± 0.04 μmol/L. Plasma Se v Se intake (Se/kcal) were significantly correlated, but neither Gpx3 activity v Se intake nor Gpx3 activity v plasma Se were correlated. Collectively, this indicates that these subjects were on the response curve plateaus. Similarly, blood mRNA levels for Gpx1, Selh, and Sepw1 (highly regulated by Se in rodents) as well as Sepp1, Gpx3 and Gpx4 were also not significantly correlated with plasma Se. Thus selenoprotein mRNAs are readily quantitated in human blood. These molecular markers, however, as well as biochemical and chemical markers, do not suggest that this population is marginal in Se status. (Supported in part by NIH DK74184)