bluuebunny/crossref_metadata_2025 huggingface dataset:
LPS‐mediated Inflammation Alters Neonatal Central Respiratory Control
Authors: Balan Kannan V , Kc Prabha , Mayer Catherine A , Wilson Christopher G , Miller Martha J , Martin Richard J
Published: June 2021

Perinatal inflammation is implicated in precipitating lung and brain injury in preterm infants, both of which are associated with impaired respiratory control (IRC). The mechanisms that link peripheral inflammation to central respiratory control have not been well studied. We hypothesized that an endotoxin‐induced inflammatory response in the immature lung triggers cytokine upregulation in the brainstem resulting in IRC. Lipopolysaccharide (LPS, 0.1μg/g) or saline was administered intratracheally into anesthetized vagal‐intact or denervated 10–13 day old F344 rat pups. In experiment 1, 2h post LPS, pups were sacrificed and the brainstem was assessed for mRNA expression of proinflammatory cytokines by RT‐PCR. In experiment 2, the effect of LPS exposure on ventilatory responses (VR) in carotid sinus nerve (CSN) intact and denervated rat pups was quantified using unrestrained whole body plethysmography (WBP). Rat pups exposed to LPS exhibited increased IL‐1β and IL‐6 mRNA and vagotomy decreased IL‐1β mRNA. WBP showed an attenuated VR to hypoxia but not hypercapnia in LPS exposed rat pups. LPS‐instilled CSN denervated pups also showed blunting of the hypoxic response. Our data suggest that pulmonary inflammation during early development and the resulting brainstem cytokine responses are associated with impaired hypoxic VR, which cannot be attributed to altered sensory trafficking from the carotid body.

Supported by: HL50527, HL056470
Ventilatory effect following 10 days concomitant exposure to neonatal intermittent hypoxia (NIH) and neonatal caffeine treatment (NCT) in 12‐days old rats
Authors: Julien Cecile , Joseph Vincent , Bairam Aida
Published: June 2021

Caffeine is regularly used to alleviate apneas in newborn infants. Its efficiency is thought to be related to increased respiratory response to hypoxia. However, we still lack knowledge on interactions between chronic NCT and NIH. Rat pups were exposed to NIH (nadir 5%O2, 6 cycles/h followed by 1h normoxia, 24h/day from P3‐12) and daily gavaged with caffeine (15 mg/kg; NIH+NCT) or water (NIH+NWT). Two other groups exposed to normoxia but gavaged with caffeine (NCT) or water (NWT) were used. At end of exposure, ventilation (VE ml/100g/min) was measured under baseline and in hypoxia (12% O2, 20 min) by plethysmography. Apnea frequency was assessed under baseline (>2 missed breaths). Baseline VE was: 194±18; 223±11*, 234±22* and 192±14 for NWT, NCT, NIH+NCT and NIH+NWT, respectively; *p0.05 vs NWT. Apnea frequency was significantly higher in NIH+NWT pups and lower in both NCT and NIH+NCT. The increase in VE was correlated with the decrease in apnea frequency (p=0.04). In response to hypoxia, the % increase from baseline was +2% for NCT; −10% for NIH+NWT; and +18% for NIH+NCT (p=ns). In conclusion: Chronic exposure to NCT in presence of NIH enhances baseline ventilation but not the hypoxic response. This suggests that caffeine by improving baseline VE acts to decrease apnea frequency. (CIHR, FRMI)
Multiphoton calcium imaging of methylxanthine‐reversal of opioid depression of inspiratory‐related pre‐Bötzinger complex rhythm in newborn rat brainstem slices
Authors: Ruangkittisakul Araya , Panaitescu Bogdan , Ballanyi Klaus
Published: June 2021

Breathing depression by opioids is reversed by methylxanthines (e.g. theophylline). Opioids block Ca2+ channels while methylxanthines cause Ca2+ release from cellular stores at high doses. We studied in newborn rat brainstem slices with 2photon imaging whether opioid block of inspiratory center pre‐Bötzinger Complex (preBötC) and its recovery by theophylline involved cytosolic Ca2+ change.

DAMGO blocked bursting and related Ca2+ rises in most preBötC neurons. Ca2+ baseline fell by ~10% in these cells, but not in presumed astrocytes. Theophylline and phosphodiesterase‐4 (PDE4) blocker Rolipram restored rhythm with no effect on Ca2+ baseline. Ca2+ store blocker cyclopiazonic acid did not raise the baseline in preBötC neurons, but in astrocytes. Ca2+ rises became irregular upon block of L‐type Ca2+ channels with nifedipine or Ni2+(0.1mM) without effect on Ca2+ baseline or rhythm. At 2.5mM, Ni2+ blocked rhythm and Ca2+ baseline fell by 10%.

Opioid depression is associated with a Ca2+ fall in preBötC cells that is not due to block of L‐type Ca2+ channels whereas actions of methylxanthines or PDE4 blockers do not involve a major change in Ca2+.

Supported by CIHR, AHFMR, CFI‐ISRIP, MFN Health
Localization of the amphibian respiratory rhythm generator using a multilayer PDMS microfluidic chamber
Authors: Hedrick Michael S. , Klingler Michael J. , Blake Alexander J. , Williams Justin C. , Johnson Stephen M.
Published: June 2021

This study used an in vitro brainstem preparation from North American bullfrog (Lithobates catesbeianus) tadpoles placed in a multilayer polydimethylsiloxane (PDMS) microfluidic chamber to localize the site(s) for respiratory rhythm generation. Brainstems from pre‐metamorphic tadpoles were placed in the microfluidic chamber and superfused with oxygenated artificial CSF (aCSF; 20–22 °C). Spontaneous respiratory motor output was measured by a suction electrode attached to cranial nerve (CN) V or XII. A synaptic blockade cocktail (SBC) solution (50 μM Bicuculline, 50 μM Strychnine, 25 μM CNQX, 25 μM APV) was introduced into the microfluidic chamber as a laminar flow stream to create a virtual ‘slice’ that reversibly blocked synaptic activity in specific brainstem regions. Introduction of the SBC solution blocked or reduced respiratory motor output when the solution reached the level of CN X (vagus n.). This occurred whether the solution was introduced from either the rostral or caudal direction. The disruption of respiratory motor output by the SBC solution was completely reversible upon superfusion with control aCSF. These results support the hypothesis that respiratory rhythm generation in the pre‐metamorphic tadpole brainstem requires intact synaptic activity in a small region of the brainstem that coincides with the level of the vagus nerve. Supported by NIH SO6 GM48135 & NIH NS051580.
Breathing Efficiency in Systolic Heart Failure: Impact of Hyperventilation and Dead Space
Authors: Woods Paul Robert , Olson Thomas P , Frantz Robert P , O'Malley Kathy A , Hulsebus Minelle L , Johnson Bruce David
Published: June 2021

Background

Patients with heart failure (HF) often develop pulmonary system abnormalities. Specifically, an abnormal ventilation relative to metabolic demand (VE/VCO2, ventilatory efficiency) during exercise has been shown to be an important marker of disease severity and prognosis. The purpose of this investigation was to focus on the factors that underlie the abnormal breathing efficiency in this population.

Methods

14 controls (10 male) and 40 (36 male) mod‐severe HF patients, age 52±12 and 56±8 yrs, respectively, performed graded exercise on a cycle ergometer. Gas exchange and blood gas measurements were made during submaximal exercise (~65% peak VO2) and used to quantify the influence of hyperventilation (PaCO2) and dead space ventilation (VD) on VE/VCO2.

Results

The VE/VCO2 ratio was lower in controls (30±4) than in HF (45±9, p<0.001) due to a lower PaCO2 and higher VD/VT that contributed an estimated 29% and 71%, respectively, to the increased VE/VCO2 (p<0.05). The elevated VD/VT in HF was in turn the result of a tachypneic breathing pattern (lower VT, 877±306 vs 2003±504ml, p<0.01) in the presence of a relatively normal VD (9.6±3.8 vs 11.9±5.7 L/min, p=0.094).

Conclusion

The abnormal ventilation in relation to metabolic demand in HF during exercise is predominantly due to alterations in breathing pattern, rather than hyperventilation or changes in ventilation/perfusion relationships. HL71478
Regulation of arterial H+ during exercise in man
Authors: Wasserman Karlman , Sun Xing‐Guo , Stringer William W. , Beaver William L
Published: June 2021

Despite a relatively high H+ production compared to total body H+, arterial H+ concentration ([H+]a) is well regulated during exercise. This is achieved by ΔVE of exercise. The study objective was to quantify [H+]a regulation below and above the lactic acidosis threshold (LAT) during exercise.

Methods

Two progressively increasing cycle exercise protocols were performed.

Results

In the first, we related VE to [H+]a and PaCO2. All subjects developed an acidosis with exercise, respiratory below and metabolic above LAT. ΔVE correlated with Δ[H+]a up to the LAT, (ΔVE/Δ[H+]a ¡Ö15L/nM). The increase in [H+]a (2–3 nM) was attributable to PaCO2 increase. ΔVE correlated with ΔPaCO2 only up to the LAT. Above LAT, VE increased less with increasing [H+]a. The 2nd protocol compared a 4‐fold difference in work rate increase to determine the effect of time on the VE response. Below LAT, VE tracked VCO2 with equal sensitivity for the two rates. Above the LAT, VE was steeper for the more slowly increasing work rate.

Conclusion

[H+]a is regulated by sensitive ventilatory control mechanisms. ΔVE/Δ[H+]a below the LAT is of CO2 origin, rapid and steep, not‐detectibly affected by time. In contrast, ΔVE/Δ[H+]a above LAT is less and steeper with time. The difference between the ΔVE responses to the 2 H+ species is likely due to differences in chemoreceptor permeability of lipophilic and lipophobic forms of H+.
Effect of antigravity muscle activity on learning capacity and hippocampal protein expression in juvenile rats
Authors: Oke Yoshihiko , Kawano Fuminori , Nomura Sachiko , Ohira Takashi , Fujita Ryo , Nakai Naoya , Ohira Yoshinobu
Published: June 2021

Effects of inhibition of antigravity muscle activity on brain function were investigated in juvenile male Wistar Hannover rats. Rats (3‐wk old) were hindlimb‐suspended (HS) for 14 days in order to remove gravitational loading in hindlimb muscles. Learning capacity was evaluated by water maze tests immediately after the termination of HS. The maze had 3‐branch points and 3 areas including starting point, platform, or blind end. In HS rats, swim path length from starting point to platform were not improved during 4 trials. Furthermore, the expression level of triosephosphate isomerase 1 (TPI1) in the hippocampus of HS rats were lower than that of cage‐control rats. TPI1 is the only glycolytic enzyme in which functional deficiency is associated to neurodegeneration. Therefore, antigravity muscle activity in growing rats might play an essential role in the learning capacity by keeping normal protein expression. This study was supported by Grant‐in‐Aid for Scientific Research S (19100009) from Japan Society for the Promotion of Sciences and Grant‐in‐Aid for Young Scientists B (21700655) from the Ministry of Education, Culture, Sports, Science and Technology.
Leptin and ghrelin levels in humans to physical inactivity induced by simulated microgravity
Authors: Kanikowska Dominika , Sato Maki , Iwase Satoshi , Nishimura Naoki , Shimizu Yuuki , Inukai Yoko , Sugenoya Junichi
Published: June 2021

The aim of this study was to investigate the consequences of 20 days of physical inactivity induced by simulated microgravity using head‐down bed rest (HDBR) at −6° on leptin, ghrelin and counterregulatory hormone response. Eight male volunteers were subjected to HDBR for 20 days. Variables measured before, during and after HDBR included plasma cortisol, insulin, glucose, leptin, ghrelin, thyroid stimulating hormone (TSH), free thyroxine (fT4) free triiodothyronine (fT3). No changes in the ghrelin and leptin concentrations were observed during HDBR. The glucose concentration decreased significantly at the 20th day of HDBR compared to pre‐ value (day 0) of HDBR (87.6 ± 2.0 vs. 93 ± 1.6 mg/dl). Significant correlation was observed between glucose and leptin concentration. The results provide the first evidence that 20 days of HDBR is not associated with alteration in ghrelin concentration. Leptin, insulin, cortisol, concentration was not different during 20 days of HDBR.
Simulated Microgravity‐induced changes in skeletal bones as measured by X‐ray using 20 keV Electron beam
Authors: Mehta Rahul , Watson Alec M , Ali Nawab , Soulsby Michael , Chowdhury Parimal
Published: June 2021

Hind‐limb suspension (HLS) of rats is a NASA validated model of simulated weightlessness. This study examines the effects of microgravity on the skeletal system of rats to assess whether or not exposure of rats to HLS for one to two weeks will induce alteration of structural features in selected bones. Four groups of rats were used: two unsuspended controls and two suspended groups. X‐rays were measured by a liquid nitrogen cooled Si(Li) detector on a Scanning Electron Microscope that provided a 20 keV beam of electrons. The x‐ray data were collected from square cross sections ranging between 1 × 1 μm2 and 400 × 400 μm2. The bones were measured for elemental levels of calcium, phosphorus, oxygen and carbon from both control and HLS rats. A correlation among HLS and control samples in terms of the distribution of the primary elements was found in the bone tissue when analyzed as a function of position along the leg and within the cross sections as well as differences in these types of patterns. In the skull tissue samples, the distribution of elements varied with respect to the suture location. This work has physiological implications in terms of understanding the mechanism of changes in hard tissues due to microgravity.
20 wk resistance training (RT) in 70 y olds improves glucose handling and leg blood flow (LBF) responsiveness to feeding and exercise‐plus‐feeding without reversing age‐related declines in protein kinase B (PKB) responses or increasing endothelial markers
Authors: Phillips Bethan , Hildebrandt Wulf , Williams John , Atherton Philip , Rankin Debbie , Smith Kenneth , Macdonald Ian , Greenhaff Paul , Rennie Michael
Published: June 2021

Ageing blunts glucose tolerance and the LBF responses to exercise and feeding. We hypothesized that 20 wk RT would improve these and tested this in studies of healthy, normal weight (BMI 23–28 kg·m−2) young (Y) (n=12, 25±3 y, means±SE), middle‐aged (M) (n=12, 50±3 y,) and old (O) (n=8, 70±4 y) men and women (≈50:50). LBF was measured (Doppler) and muscle biopsies taken in post‐absorptive (PA) conditions and 150 min after beginning intermittent feeding (Fortisip: 16% protein, 49% carbohydrate, 35% fat; ≈6.5 kJ−1·kg−1·30 min−1), with one leg rested and the other recovering from exercise (6×8 reps, 75% 1RM). In O, plasma [glucose] before RT was greater (P≤0.05) than in Y in both PA (5.86±0.15 vs. 5.02±0.19 mM) and peak fed (8.82±0.70 vs. 7.94±0.42 mM) conditions and this was associated with blunted PKB kinase responses to feeding in O (+63% vs. +363%; P≤0.01). However, after RT, post‐feed glucose AUC fell in all (Y, −41±3; M, −34±3; O, −22±1 mM·min) without improvements in PKB responsiveness. After RT, LBF responses to exercise+feeding in M and O were enhanced (M: 147±32% vs. 101±16%; O: 115±47% vs. 59±15%, both P≤0.01) without changing whole‐muscle abundance of CD31, eNOS or α1/β2‐adrenoceptor proteins. Thus, RT rejuvenates glucose handling and LBF responsiveness in older people without resensitization of PKB or increases in endothelial markers.

Support: UK BBSRC, EC EXEGENESIS
A prior bout of contractions speeds oxygen uptake and blood flow on‐kinetics and reduces the slow component of oxygen uptake in highly‐oxidative skeletal muscle
Authors: Hernández Andrés , McDonald James R. , Lai Nicola , Gladden L. Bruce
Published: June 2021

It was the purpose of this study to examine the prior contractions effect in highly‐oxidative skeletal muscle. With arterial [O2] maintained constant, a step change in metabolic rate was elicited by stimulating canine gastrocnemii (n=12) via their sciatic nerves (6–8 V, 0.2 ms duration, 50 Hz, 200 ms train) at a rate of 2 contractions · 3 s−1 for two, 2‐min bouts separated by 2 min of recovery. Blood flow was recorded with an ultrasonic flowmeter and muscle oxygenation was monitored via near infrared spectroscopy. In comparison to the first bout, the VO2 primary τ (9.4±2.3 vs. 12.0±3.9 s), TD (1.9±1.3 vs. 4.9±1.4 s), and slow component amplitude (5.9±6.3 vs. 12.1±9.0 mlO2·kg−1ww·min−1) were significantly reduced (p<0.05) during the second bout. Blood flow on‐kinetics were significantly speeded during the second bout (7.7±2.6 vs. 14.8±5.8 s). Kinetics of muscle deoxygenation were significantly slower at the onset of the second bout (7.2±2.2 vs. 4.4±1.2 s) while relative [O2Hb] was elevated throughout the second bout. These results argue in favor of enhanced O2 delivery and/or microvascular O2 availability as underlying mechanisms for the prior contractions effect in highly‐oxidative skeletal muscle at a high contraction intensity. Additionally, altered motor unit recruitment at the onset of a second bout is not a prerequisite for reductions in the VO2 slow component amplitude after a priming contractile bout.
Impact of chronic intermittent forearm compressions on blood flow capacity in humans
Authors: Roseguini Bruno Tesini , Sheldon Ryan , Stroup Abigail , Bell Jeffrey W. , Skarbek Ian , Maurer David , Laughlin M. H. , Newcomer Sean C.
Published: June 2021

Exercise training is known to enhance muscle blood flow capacity (BFC), but the mechanisms that mediate this adaptation are poorly understood. We tested the hypothesis that long‐term application of intermittent pneumatic compressions (IPC) in the forearm increases BFC. Twelve healthy subjects were randomly assigned to three compression groups: 50, 100, and 150mmHg and underwent a program of IPC in the non‐dominant forearm (1h/day, 5d/week) for 4 weeks. IPC were achieved by cyclically inflating/deflating (2s on/3s off) two cuffs wrapped around the forearm using a cuff inflator unit. Peak forearm blood flow (PFBF, ml(100ml) −1min−1) and peak forearm vascular conductance (PFVC, ml.min−1mmHg−1) were measured with Doppler ultrasound following 10 min of forearm ischemia pre, mid and post IPC intervention. In the 150mmHg group, PFBF in the non‐dominant forearm increased from 21±1 at pre‐intervention to 27±1 and 30±2 (p<0.05) at mid and post intervention, respectively, while no changes were observed in the control forearm. Likewise, PFVC showed a trend for increase following IPC (p=0.1) only in the experimental forearm (0.28±0.02, 0.32±0.01, 0.35±0.02 at pre, mid and post intervention, respectively). No significant changes were detected in the 50 and 100mmHg groups. In conclusion, this study demonstrates that daily IPC of 150 mmHg independently enhances forearm BFC in humans. (NIH HL‐36088 and ACSM Foundation).
Endurance exercise training increases medullary and extramedullary hematopoiesis
Authors: Baker Jeff , De Lisio Michael , Parise Gianni
Published: June 2021

Increases in hematocrit are a well known adaptation to exercise training. It is not known if exercise training induces changes in hematopoietic tissues that facilitate increases in hematocrit. The colony forming unit GEMM assay was used to assess the effects of ten weeks of progressive treadmill training on the hematopoietic progenitor content in several tissues of four week old C57Bl/6 mice. Red blood cell progenitors increased by 3.1, 4.7, 2.8, and 1.3 fold (p<0.008 for all) in bone marrow, spleen, blood, and liver, respectively. White blood cell progenitors increased by 1.3 and 3.2 fold (p<0.026 for both) in bone marrow and blood, respectively. Finally, multipotent white and red blood cell progenitors increased by 3.4, 4, and 9.7 fold (p<0.007 for all) in bone marrow, spleen, and blood, respectively. This data indicates that endurance exercise training can increase the hematopoietic progenitor content of bone marrow, blood, spleen, and liver. Increased hematopoiesis in these tissues may help facilitate endurance training associated increases in hematocrit.
Are international guidelines for physical activity sufficient to improve health status?
Authors: Foulds Heather J A , Bredin Shannon S D , Charlesworth Sarah A , Ivey Adam C , Warburton Darren E R
Published: June 2021

PURPOSES

1) To determine whether international physical activity guidelines are adequate to change health status in inactive adults. 2) To examine directly the dose‐response relationship between exercise volume and indicators of health status.

METHOD

Participants (N=65; age=44±12 yr) were assigned randomly to one of five 13 week exercise training programs: 1) 10 min brisk walking 1x/week (n=11), 2) 10 min brisk walking 3x/week (n=10), 3) 30 min brisk walking 3x/week (n=16), 4) 60 min brisk walking 3x/week (n=11), and 5) 30 min running 3x/week (n=17). Health indicators were recorded before and after training including anthropometry, fasting glucose, total cholesterol (TC), high density lipoproteins (HDL) and blood pressure.

RESULTS

One 10 min weekly bout of exercise was sufficient to cause significant changes in select measures of health status. There were similar changes in fasting glucose, TC/HDL ratio, and diastolic blood pressure to that seen with higher volumes of activity. However, higher volumes of exercise (30 min or more of brisk walking per week) were required to change body mass significantly.

CONCLUSIONS

Exercise volumes as low as 10 min of brisk walking per week can lead to improved indicators of health status. However, higher volumes of exercise appear to lead to additional health benefits.

Research Support Source: Michael Smith Foundation for Health Research, CIHR, NSERC Canada.
Maternal Heart Rate and Heart Rate Variability During Pregnancy and Exercise Training
Authors: Paynter Christopher , Meacham Crystal , Ramar Cassandra , Gustafson Kathleen M , Suminski Richard R , May Linda E
Published: June 2021

Exercise in non‐pregnant women increases parasympathetic control resulting in lower resting heart rates (HR) and increased heart rate variability (HRV). This is important given the relationships between pregnancy complications (hypertension, pre‐eclampsia and gestational diabetes) and altered autonomic control. This study tested the hypothesis that maternal exercise throughout gestation alters maternal cardiac autonomic control as indicated by changes in HR and HRV. We used magnetocardiography to record maternal HR between 28 and 32 wks GA from 20 women who exercised regularly (>30 min aerobic activity, 3 times per week) and 19 women who did not exercise during pregnancy. R‐R intervals were used to determine HR and HRV. HR (82.9 + 9.1 vs 90.4 + 9.9 bpm; F=6.2(1,37);p<0.05) was lower, pNN50 was greater (16.3 + 19.4 vs. 6.1 + 6.0; F= 4.7(1,37);p<0.05), and there was a trend of higher SDNN (p=0.05) indicating increased parasympathetic control in the exercise relative to the non‐exercise group. LF/HF, an index of sympathovagal balance, was lower (0.55 + 0.36 vs. 0.82 + 0.53; F=4.3(1,37), p<0.05) in the exercise group. Indices of parasympathetic control are altered in women who exercise regularly throughout their pregnancy. Therefore, exercise can be used as an intervention to decrease the risk of pregnancy complications associated with increased sympathetic input.

Research supported by: KCUMB and Hoglund Brain Imaging Center funds
Effect of exercise‐training on EDHF‐mediated relaxation after chronic coronary occlusion
Authors: Boyle Rachel R , Smith Mallory D , Heaps Cristine L
Published: June 2021

Endothelium‐derived hyperpolarizing factors (EDHF) play an important role in maintaining vasodilatory capacity when nitric oxide bioavailability is impaired such as in coronary artery disease. We hypothesized that exercise training would increase the contribution of EDHF to endothelium‐dependent relaxation in coronary arteries from a model of ischemic heart disease. Ameroid constrictors were surgically placed around the proximal left circumflex coronary artery (LCX) of adult female Yucatan miniswine. Coronary rings (~1 mm luminal diameter) were isolated from the collateral‐dependent (LCX) and control (nonoccluded left anterior descending, LAD) arteries of sedentary (SED, pen confined) and exercise trained (EX, treadmill run; 5 days/wk for 14 wks) pigs. NOS inhibition (L‐NAME) attenuated bradykinin‐mediated relaxation to a greater extent in SED compared with EX of both LAD and LCX. Combined inhibition of NOS and prostanoids (indomethacin) partially corrected the EX‐enhanced relaxation observed after NOS inhibition alone, while concurrent inhibition of large‐conductance potassium (BKca) channels (iberiotoxin) ablated the differences. Thus the contribution of endothelium‐derived vasodilators is altered by EX in the underlying setting of ischemic heart disease, with an increased contribution of an EDHF acting via BKca channel, however, the specific EDHF remains undetermined. NIH:HL064931
The influence of the intensity of a single bout of aerobic exercise on endothelial function in obese post‐menopausal women
Authors: Cheek Dennis Jefferson , Boyd Kara , Mitchell Joel
Published: June 2021

Endothelial dysfunction increases the risk of cardiovascular disease, and regular exercise has been shown to increase endothelial function (EF); however, single bouts of exercise may also produce beneficial effects lasting at least 24 h.

Purpose

The purpose of this study was to observe the effects of two intensities of a single bout of aerobic exercise on endothelial function (EF) in obese, post‐menopausal women.

Methods

Eleven obese (% fat = 37.23 ± 2.75; BMI = 30.57 ± 2.14) women between the ages of 54 and 70 yrs completed two, one‐hour sessions of treadmill exercise at 50 and 70% of HRmax, and a resting control trial. EF was assessed via flow‐mediated dilation (FMD) of the brachial artery and via blood levels of nitrate/nitrite (N/N) before and after exercise and at two, 24, 48, and 72 hours post exercise. FMD was measured by ultrasound images of the brachial artery before and for 5 min after 5 min of occlusion. A 3 × 6 repeated measures ANOVA was used to examine differences between condition and time for FMD and blood measures.

Results

Data at 24 h post exercise are shown below (mean ± SD).

Condition
FMD Max (mm)
Δ Dilation (%)
AUC
N/N (μM)

Control
3.75±0.58
0.14±4.87
8.09±5.68
9.09±4.13

50 % HRmax
3.82±0.62
5.64±9.18
10.28±5.89
7.01±2.99

70% HRmax
3.91±0.70
4.28±10.40
8.86±5.89
7.57±4.75

None of the responses were significantly different from each other; however, there was a tendency for a greater Δ dilation in the 50% condition (p=0.075).

Conclusion

In elderly, obese females, one hour of exercise did not impact subsequent FMD responses, nor the blood markers of EF at any time points, regardless of the exercise intensity.
Short‐term AMPK activation improves vascular endothelial function in old mice by a different mechanism than habitual aerobic exercise
Authors: Lawson Brooke R , Seals Douglas R , Magerko Katherine A , Durrant Jessica R , Zigler Melanie L , Donato Anthony J , Lesniewski Lisa A
Published: June 2021

Habitual exercise improves endothelium‐dependent dilation (EDD) in old rodents by increasing nitric oxide (NO) bioavailability. Acute exercise activates adenosine monophosphate protein kinase (AMPK), activating endothelial NO synthase and increasing NO production. We determined if pharmacological AMPK activation by aminoimidazole carboxamide ribonucleotide (AICAR, 0.25 mg/kg/day for 14 days, sq) mimics habitual exercise‐induced improvements in EDD and NO bioavailability. Acetylcholine‐mediated EDD was assessed in carotid arteries of young (Y: 4–6 mo), old (O: 29–31 mo), O voluntary wheel running (O‐VR, 10–14 weeks) and O AICAR treated B6D2F1 mice. AMPK phosphorylation was lower in O vs. Y (0.2±0.1 vs. 1.0±0.2 AUs, P=0.01) and was increased after VR (1.4±0.4 AUs, P<0.05) and AICAR treatment (0.5±0.1 AUs, P<0.05) in old mice. Age‐associated decreases in maximal EDD (Y: 97±1 vs. O: 63±11%, P<0.05) and NO bioavailability (Y: 52±6 vs. O: 27±6%, P<0.005) were restored by VR (Max EDD: 96±2%, P<0.05; NO: 48±8%, P<0.05). Short‐term treatment with AICAR improved EDD (91±4%, P<0.05), but not NO bioavailability (28±4%, P=0.47). Sensitivity (IC50) to the NO donor sodium nitroprusside was not significantly different among Y, O and O‐VR groups (SNP; Y: 5.8E‐9±2.4E‐9; O: 5.3E‐9±2.0E‐9; OVR: 8.9E‐9±2.4E‐9 log M, all P>0.05), but AICAR treatment markedly increased sensitivity to SNP (5.6E‐10±1.5E‐10 log M, P<0.05) in old mice. Unlike habitual exercise, short‐term pharmacological activation of AMPK by AICAR improves EDD in old mice by increasing smooth muscle sensitivity to NO.

NIH AG013038, AG033755, AG029337
Epicardial cell transformation
Authors: Munoz‐Chapuli Ramon
Published: June 2021

The embryonic epicardium, which invests all the heart surface by midgestation, derives from an extracardiac progenitor tissue called the proepicardium. The embryonic epicardium gives rise to a population of mesenchymal cells called the epicardially‐derived cells (EPDCs) that populate the space between the myocardium and the epicardium and later invade the ventricular myocardium. EPDCs contribute to the connective and vascular tissue of the heart. The transformation of epicardial cells into EPDCs is a critical step of the cardiac development, and it can be regarded as an epithelial‐mesenchymal transition (EMT), the same cellular process that accounts for the origin of the neural crest cells or the valvuloseptal tissue of the heart. We have just started to know how epicardial EMT is controlled at the molecular level, as well as the differences between the epicardial transformation and other embryonic EMTs. The Wilms' tumor suppressor gene Wt1 is probably a main element regulating epicardial EMT, since it is able to repress E‐cadherin and to activate Snail expression, regulating in this way the switch between epithelial and mesenchymal states in EPDCs. Wt1 also directly activates Raldh2 expression in the epicardium, thus controlling the retinoic acid synthesis in this tissue. We think that epicardial EMT should be regarded as a two‐step process, with a triggering signal in the proepicardium and the acquisition of an invasive behaviour when the primitive epicardium spreads over the heart surface. Later, a process of mesenchymal‐epithelial transformation in the most external epicardial cell layer gives rise to the definitive epicardial mesothelium.
Signaling and the Progression of Coronary Vessel Formation
Authors: Tomanek Robert
Published: June 2021

Formation of the coronary vasculature requires the transformation and differentiation of cells that originate in the proepicardium and form the epicardium. The latter provides the cells that comprise the coronary vessels: endothelial, smooth muscle and pericytes. The first primitive (non‐perfused) vasculature consists of endothelial tubes that develop via vasculogenesis. They branch and also fuse with adjacent tubes to form larger channels. The regulation of these events involves many regulating molecules, e.g., GATA, Wilm's Tumor 1, and VEGF and FGF family members. Recent studies document the interdependency of growth factors in this process and indicate that that at least 6 FGFs (1, 2, 4, 8, 9, 18) promote endothelial cell proliferation and tube formation primarily, but not exclusively via FGFR1 signaling. FGF is a key player in the activation of hedgehog which stimulates VEGF signaling. Moreover, stimulation of tubulogenesis requires the availability of both FGF and VEGF. Although VEGF‐A and VEGFR‐2 are important for vasculogenesis and angiogenesis, VEGF‐B and its receptor, VEGFR‐1 as well as VEGF–C each contributes to coronary vessel development. Formation of the coronary ostia and main coronary arteries requires VEGF signaling at the precise sites on the aorta where the capillary plexus penetrates the wall of the artery to establish perfusion of the coronary vasculature. Smooth muscle recruitment to the vascular channels is facilitated by FGFs, VEGFs, TGF‐β. These signaling events are temporally and spatially regulated and are also influenced by other factors, e.g., neural crest cells, and tissue O2 levels.
Specification and Differentiation of Coronary Smooth Muscle
Authors: Majesky Mark , Dong Xiu Rong , Maguire Colin , Rodgers Laurel
Published: June 2021

Lineage mapping studies have shown that progenitors for coronary smooth muscle enter the heart following epithelial to mesenchymal transition (EMT) of epicardial cells. Primary explant culture experiments show that loss of epicardial cell‐cell adhesion is a prerequisite for transcriptional activation of coronary smooth muscle cell (CoSMC) differentiation marker genes. Thus a majority of epicardial cells are specified for a CoSMC fate, but do not express that fate while resident within the intact epicardium. Our studies suggest that epicardial cell‐cell contacts activate Notch‐dependent pathways that oppose receptor tyrosine kinase (PDGFBB, FGF2)‐mediated signals for EMT and thereby maintain the CoSMC progenitor phenotype in the intact epicardium. Later steps in coronary development produce three distinct layers of artery wall. The outer layer is known as the adventitia and is composed of epicardium‐derived cells. We observed that formation of adventitia is accompanied by local activation of sonic hedgehog (Shh) signaling that is restricted to the adventitial layer. Moreover, we found a population of stem cell antigen 1‐positive cells (AdvSca1) resident within this novel domain of Shh signaling with intrinsic potential to differentiate to pericytes and CoSMCs. The role of AdvSca1 progenitors in coronary artery maturation, remodeling and disease will be discussed. Support: HL19242, HL93594.
Endothelin‐1 induces Serine 910 phosphorylation of focal adhesion kinase via PKCdelta‐and Src‐dependent signaling pathways
Authors: Chu Miensheng , Iyengar Rekha , Koshman Yevgeniya , Kim Taehoon , Samarel Allen M
Published: June 2021

Tyrosine phosphorylation of focal adhesion kinase (FAK) is well‐studied in cardiomyocytes, but little is known about FAK phosphorylation at serine residues. Stimulation of cultured neonatal rat ventricular myocytes (NRVM) with endothelin‐1 (ET‐1, 1–100nM, 2–30min) induced time‐ and dose‐dependent FAK S910 phosphorylation. Direct activation of protein kinase C (PKC) isoenzymes with phorbol 12‐myristate 13‐acetate (PMA, 200nM) significantly increased FAK S910 phosphorylation, whereas the PKC inhibitors GF102903X (10μM) and rottlerin (20μM), but not Gö6983 (10μM) prevented ET‐1‐induced FAK S910 phosphorylation. To distinguish the roles of individual PKC isoenzymes, constitutively active (CA) and dominant‐negative (DN) PKCα, PKCδ and PKCε were introduced into NRVM by adenovirus‐mediated gene transfer. ET‐1 induced FAK S910 phosphorylation was prevented by overexpression of DN‐PKCδ but not DN‐PKCα or DN‐PKCε. In contrast, only CA‐PKCδ induced FAK S910 phosphorylation. Treatment with MEK1 inhibitors U0126 (10μM) or PD98059 (25μM) and the Src inhibitor PP2 (10–20μM) also inhibited ET‐1 induced FAK S910 phosphorylation. We conclude that ET‐1 stimulates FAK S910 phosphorylation in NRVM via PKCδ‐MEK1‐ERK1/2 and Src‐MEK1‐ERK1/2 pathways. Supported PO1 HL62426 and the Falk Medical Research Trust.
NF449 is a novel inhibitor of fibroblast growth factor receptor 3 (FGFR3) signaling active in chondrocytes and multiple myeloma cells
Authors: Chlebova Katarina , Krejci Pavel
Published: June 2021

FGFR3 receptor tyrosine kinase represents an attractive target for therapy due to its candidate role in several human disorders including skeletal dysplasia, multiple myeloma, and cervical and bladder carcinomas. By using molecular library screening, we identified a compound named NF449 based on its inhibitory activity towards FGFR3 signaling in cells. In cultured chondrocytes or murine limb explants, NF449 rescued FGFR3‐mediated extracellular matrix loss and/or growth inhibition, which represent the two major cellular phenotypes of aberrant FGFR3 signaling in cartilage. Similarly, NF449 antagonized FGFR3 action in the multiple myeloma cell lines OPM2 and KMS11, as evidenced by NF449‐mediated reversal of ERK MAP kinase activation and transcript accumulation of CCL3 and CCL4 chemokines, both of which are induced by FGFR3 activation. In a cell‐free kinase assays, NF449 inhibited kinase activity of both wild‐type and disease‐associated FGFR3 mutant (K650E), in a fashion that appeared non‐competitive with ATP. Our data identify NF449 as a novel antagonist of FGFR3 signaling, applicable for FGFR3 inhibition alone or in combination with inhibitors that target the ATP binding site.
Mitochondrial uncouplers trigger ventricular fibrillation in isolated rat hearts
Authors: Clements‐Jewery Hugh
Published: June 2021

Sudden cardiac death due to ventricular fibrillation (VF) is a major cause of mortality in the US. The purpose of this study was to investigate the role of mitochondrial depolarization on development of VF during myocardial ischemia. Rat hearts (n=8 per group) were perfused with a modified Krebs solution. After 5 minutes, the perfusion solution was switched to one containing drug vehicle (0.01% DMSO v/v), 0.3μM CCCP, 100μM 2,4‐dinitrophenol, 0.2μM cyclosporine A or 100μM 5‐hydroxydecanoate. After a further 10 minutes, the left main coronary artery was occluded. CCCP and 2,4 dinitrophenol triggered VF in 100% of hearts prior to induction of ischemia, whereas no control heart developed VF in this period (p<0.05). In all cases VF was preceded by QT shortening (e.g. from 49±2 ms 1 min before switch to CCCP to 34±3 ms 5 min after switch to CCCP; p<0.05). During ischemia, neither cyclosporine A (88% VF) nor 5‐hydroxydecanoate (100% VF) reduced the incidence of VF compared to control (100% VF; p>0.05). In addition, neither drug affected the time to onset or the total duration of VF. In conclusion, mitochondrial depolarization is a powerful trigger for VF, and may underlie the mechanism by which VF is triggered during ischemia. Activation of the mitochondrial KATP channel or permeability transition pore is unlikely to underlie mitochondrial depolarization or VF during myocardial ischemia. Supported by a WVSOM intramural grant.
Impact of dietary fish oil on the atrial endothelin system and inositol triphosphate signaling: relevance to post‐operative atrial fibrillation
Authors: Mayyas Fadia , Sakurai Seiichiro , Niebauer Mark , Chung Mina K , Van Wagoner David R
Published: June 2021

Background

Endothelin‐1 (ET‐1) modulates inositol triphosphate (IP3) signaling and may be involved in the etiology of atrial fibrillation (AF). We hypothesized that ET‐1 is also involved in post‐operative AF (POAF), and that ET‐1 signaling may be modulated by fish oil, FO. In a cardiac surgery model we studied the impact of dietary fish oil (FO) on inducibility of POAF and atrial ET system/IP3 receptors.

Methods

Adult dogs received control chow (n=10), or chow supplemented with FO (EPA/DHA, 0.6g/Kg/day, n=9) for 3 weeks. Surgery was performed to excise left atrial appendage (LAA, internal CTL). Atrial burst pacing (30s) was used daily to assess AF inducibility. Left and right atria (LA, RA) and pulmonary veins (PV) were obtained on terminal postoperative day (POD) 2 or 4.

Results

POAF was induced in 4/6 CTL but none of FO treated dogs. Plasma ET‐1 did not change after surgery, but was reduced by FO prior to surgery and at POD 1–4. Relative to baseline LAA, LA ET‐1 level was increased after surgery in both groups. ET‐1 content in the PV and RA was 2× higher than LA and was lowered by FO on the PV and LAA. After surgery, ETBR and ETAR expression was decreased in CTL LA, while IP3R‐I,II was increased. In FO group, ETAR expression was unchanged (POD2) or increased (POD4), but IP3R‐II was unchanged.

Conclusions

Our study links the atrial ET system and IP3Rs with POAF. Peri‐operative FO may in part suppress POAF by modulating IP3 signaling.
Effects Of Isoflurane Anesthesia On Murine Glucose Metabolism
Authors: Constantinides Christakis , Mean Richard , Janssen Ben JA , Hedlund Laurence W
Published: June 2021

Maintaining optimal blood glucose (Glu) and insulin (Ins) levels is essential for physiological studies in anesthetized mice. This study examined the temporal effects of varying levels of isoflurane (ISO) anesthesia on blood Glu and Ins levels in mice for 90 min. post‐induction. Male C57BL/6 mice were allowed to breath freely ISO at 1 (n=5), 1.5 (n=7), and 2.0% (n=8) in 100% O2 while body temperature was maintained at 37.1±0.4°C. ECG and respiratory flowrate were monitored. A 0.6μl tail vein blood aliquot was extracted at 5 min. intervals for Glu measurements. Ins was measured from 1ml arterial blood at 1 and 2% ISO in 20 mice euthanized at t=0, 20, 40, 60 and 80 min. Mean heart rates (±SD) were 532±39, 488±39, and 449±23 bpm at 1, 1.5, and 2% ISO respectively (p<0.0001). Glu concentrations (mg/dl) ranged between 155±28–196±76 [1% ISO], 162±43–239±38 [1.5% ISO], and 159±52–205±49 [2.0% ISO]. Ins values ranged between 3.5±0.3–4.2±0.6ng/dl [2% ISO], and 3.4±0.5–4.2±0.9ng/dl at 1% ISO. Glu values were significantly higher in the ISO=1.5 and 2% groups compared to the 1% group (p<0.0001). No significant temporal change was noted in Glu values at the 3 ISO doses. Ins concentrations did not differ significantly between groups. The results confirm that ISO levels ≥1.5% produce a mild hyperglycemic effect, prominent at later time periods post‐induction.

Research supported by the Hellenic Bank and the Research Promotion Foundation.
The central oxytocin system mediates the actions of nesfatin‐1
Authors: Yosten Gina L. C. , Samson Willis K.
Published: June 2021

Nesfatin‐1, a recently discovered neuropeptide, significantly reduces food intake and weight gain when injected intracerebroventricularly (i.c.v.) into male rats. In previous studies, we showed that i.c.v. nesfatin‐1 was also capable of increasing mean arterial pressure (MAP) in conscious rats, and that this effect, like the effect on feeding, was blocked by pretreatment with the melanocortin ¾ receptor antagonist, SHU9119. Because oxytocin (OT) has been shown to signal dendritically to influence both appetite and cardiovascular function, and may be involved in the central melanocortin circuit, we sought to determine if the actions of nesfatin‐1 were dependent on functional central OT receptors. Stainless steel cannulae were implanted into the lateral cerebroventricle of adult male rats. For feeding studies, rats were injected with either the OT receptor antagonist, [D‐(CH2)5,Tyr(me)2,Orn8]‐vasotocin (OVT) and nesfatin‐1, or nesfatin‐1 alone. Food intake was recorded every 30 minutes. For cardiovascular studies, an additional cannula was implanted into the carotid artery to measure MAP. Rats were pretreated with OVT or saline i.c.v., and then treated with either a pressor dose of nesfatin‐1 or saline i.c.v.. We found that pretreatment with OVT abrogated the effect of nesfatin‐1 on both food intake and MAP, indicating that the actions of nesfatin‐1 are likely dependent on the central oxytocin system.
Functional brainstem expression of T‐type calcium channel subunit alpha1H but not alpha1G maintaining sympathetic tone generation in neonatal B6 mice
Authors: Su Chun‐Kuei , Fan Yu‐Pei , Chen Chien‐Chang
Published: June 2021

T‐type calcium channel (T‐channel) is a low‐voltage‐activated channel allowing calcium influx in the voltage range near resting membrane potentials. Functional expression of T‐channel currents only requires alpha1 subunits, including alpha1G, alpha1H, and alpha1I. We investigated whether T‐channel subunits differentially regulate sympathetic tone generation. Wild type B6 mice and the mice of T‐channel subunit alpha1G or alpha1H knock out were used to prepare the brainstem‐spinal cord‐splanchnic nerve that could spontaneously generate sympathetic nerve discharge (SND) under optimal in vitro conditions. Amounts of SND generated from each mouse group were normalized to the ambient current noise and expressed in units of signal/noise ratio for comparisons across experiments. Comparable amounts of SND were generated in the intact preparations of wild type and alpha1G knock out mice. However, significantly less amounts of SND (~40% of the amount of wild type or alpha1G) were generated in the intact preparations of alpha1H knock out. After removal of the synaptic drives originated in the brainstem by cervical cord transections, the amounts of spinally originated SND were largely comparable across mice with different genetic backgrounds. These findings suggest that a functional expression of alpha1H T‐channel subunits in the brainstem is essential for the maintenance of SND genesis in neonatal B6 mice.
PANCREATIC PREGANGLIONIC NEURONS: DIFFERENTIAL RESPONSES TO CCK1 AND 5‐HT3 RECEPTOR STIMULATION
Authors: Verberne Anthony JM , Mussa Bashair M , Sartor Daniela M
Published: June 2021

The dorsal motor nucleus of the vagus (DMV) is the main source of vagal input to the pancreas. In vitro studies have shown that the DMV contains a mixed population of pancreatic preganglionic neurons (PPNs) but little is known about their responses to pancreatic secretagogues such as cholecystokinin (CCK) and serotonin (5‐HT) in vivo. The aims of this study were (i) to identify DMV PPNs in vivo and (ii) to characterize their responses to CCK and 5‐HT3 receptor activation. Male Sprague‐Dawley rats anesthetised with isoflurane (1.7–2.0%) were used in all experiments. PPNs were recorded extracellularly and their locations were marked using pontamine sky blue. Only PPNs that had an axon in the pancreatic vagus (collision test positive) were studied. Forty‐four PPNs were identified within the rostral, medial and caudal DMV and thirty eight were tested for responses to CCK‐8 and phenylbiguanide (PBG; 5‐HT3 receptor agonist). Their axonal conduction velocities were in the C‐fibre range (< 1 m/s). CCK and PBG (0.1–10 μg/kg, i.v.) produced three types of response: (i) PPNs in the intermediate DMV were inhibited by CCK (n = 18) and PBG (n = 10), (ii) PPNs in the caudal DMV were activated by CCK (n = 5) and PBG (n = 2) and (iii) rostral DMV neurons were not affected significantly by CCK (n = 9) or PBG (n = 7). Pancreatic secretagogues have complex actions on PPNs that may be related to their effects on pancreatic exocrine and endocrine secretion.
An initial transient is followed by steady‐state regulation of blood pressure during hibernation bouts in the Syrian hamster
Authors: Song Christine E , Pham Hai , Hamilton Jock S , Horowitz John M , Horwitz Barbara A , Chen Chao‐Yin
Published: June 2021

Hamster blood pressure and heart rate decrease during hibernation to conserve energy, but it is unclear how blood pressure changes over the course of a hibernation bout. We tested the hypothesis that blood pressure falls and then slightly recovers to a stable, regulated state during a hibernation bout. A blood pressure telemetry transmitter was implanted in a Syrian hamster (Mesocricetus auratus) for continuous recordings. Each hamster was placed in a 14:10 Light:Dark cycle at 23°C for 3 weeks and then transferred to a 8:16 Light:Dark cycle at 6°C. While euthermic, the hamster maintained mean arterial pressure at 87 ± 3 mmHg and heart rate at 352 ± 16 bpm at ambient temperatures of 23°C as well as at 6°C. Each hamster displayed multiple 3–5 day hibernation bouts. Each bout showed a two stage pattern: an initial, labile period (< 1 day) where mean pressure transiently decreased (for some bouts as low as 20 mmHg) and a steady period (2–4 days) where mean pressure was maintained at 46 ± 4 mmHg. Spontaneous baroreflex sensitivity, normalized to baseline heart rate, was −2.7 ± 1.5 and −6.7 ± 2.5 (during euthermia and hibernation, respectively). Data support the hypothesis that following a transient, mean arterial pressure is stable during a bout of hibernation. (Support: R01 HL091763)