bluuebunny/crossref_metadata_2025 huggingface dataset:
Age‐related impairment in endothelium‐dependent dilation is related to diminished sirT deacetlylase expression and increased eNOS acetylation
Authors: Magerko Katherine Ann , Seals Douglas R , Durrant Jessica R , Lawson Brooke R , Lesniewski Lisa A , Donato Anthony J
Published: June 2021

Aging impairs vascular endothelial function through diminished nitric oxide (NO) availability. The cellular deacetylases family, sirT, modulates endothelium‐dependent dilation (EDD) and NO availability via regulation of endothelial NO synthase (eNOS) acetylation/activation. Acetylcholine (Ach)‐induced peak EDD was lower in isolated femoral arteries of old (O: 30 mo, n = 12) vs. young (Y: 6 mo, n = 14) B6D2F1 mice (O: 85 ± 1%, Y: 95 ± 1%, P < 0.001) and was mediated by reduced NO availability related to lower aortic protein expression of sirT 1 & 3 (O: 0.6 ± 0.1, Y: 1.0 ± 0.1 sirT 1/GAPDH, P < 0.05; O: 0.5 ± 0.1, Y: 1.0 ± 0.3 sirT 3/GAPDH, P = 0.05). Aortic eNOS expression did not differ with age (O: 1.17 ± 0.11, Y: 1.00 ± 0.06, eNOS/GAPDH, P = 0.2), but acetylated eNOS was higher in old (O: 6.40 ± 4.64, Y: 1.00 ± 0.30 I.P. acetylated eNOS, P < 0.05). Incubation with SIRTINOL, a sirT inhibitor, reduced peak EDD and abolished age differences (O: 41 ± 8%, Y: 38 ± 4%, P = 0.4). Reductions in peak EDD with SIRTINOL + L‐NAME, an eNOS inhibitor, did not differ (O: 2 ± 5%, Y: 7 ± 3%, P = 0.5). Endothelium‐independent dilation (EID; sodium nitroprusside) was not altered with age (P = 0.8). In older (64 ± 1 yrs, n = 18) vs. young (25 ± 1 yrs, n = 14) healthy humans, Ach‐induced forearm EDD was impaired (P = 0.01) and associated with reduced sirT 1 protein expression in brachial artery endothelial cells (immunofluorescence; O: 0.37 ± 0.03, Y: 0.50 ± 0.05, sirT 1/HUVEC, P < 0.05), whereas EID did not differ (P = 0.9). Changes in sirT may play an important role in vascular endothelial dysfunction with aging.

NIH AG029337, AG033755, AG013038
Total arterial compliance estimated from the time constant of aortic pressure decay: the influence of downstream pressure
Authors: Chemla Denis , Nitenberg Alain
Published: June 2021

The influence of downstream pressure (Po) on total arterial compliance (C) was studied in 16 adults (14 M, 2F; aged 44±16 yrs) undergoing left heart high fidelity pressure catheterization. A two‐element RC model of the circulation was assumed, where R is the vascular resistance. The time constant (Tau = RC) of the monoexponential fit of diastolic aortic pressure decay was calculated by using either the standard, semilogarithmic method with zero pressure asymptote, or two methods with variable pressure asymptote, namely the best‐fit method and the derivative method. Cardiac output was measured by the thermodilution technique. Diastolic aortic pressure was 82±10 mmHg. The best‐fit method and the derivative method led to similar value of Po (71±12 vs 75±12 mmHg), Tau, R and C. As compared with the semilogarithmic method, the best‐fit method led to 74% lower Tau (353±106 vs 1372±106 msec; P<0.05). When substituting Po for central venous pressure, the R was 72% less (0.42±0.17 vs 1.51±0.61 mmHg.sec.mL−1; P<0.05). This resulted in C that was 18% less (0.83±0.38 vs 1.02±0.40 mL.mmHg−1; P<0.05). The high Po value documented here was consistent with recent experimental and clinical findings suggesting that a Starling resistor mechanism could be present in vivo at the arteriolar precapillary level of the various systemic vascular beds. This may significantly impact on the clinical estimation of arterial load.

Source of research support: University.
Understanding US children's patterns of and cumulative exposure to food insecurity
Authors: Burke Michael Patrick , Jones Sonya , Frongillo Edward
Published: June 2021

To eliminate child hunger in the United States, a richer understanding of how children experience food insecurity is needed. Little is known about the cumulative exposure of children to food insecurity during the critical years of social, emotional, and physical development. Understanding children's cumulative exposure will provide insights into the prevention of child hunger and the role of food insecurity in children's developmental outcomes. Using US national longitudinal data of households with children, we characterized food insecurity patterns at four grades (kindergarten, third, fifth, and eighth). Twenty‐eight percent of households were food insecure during at least one grade. Food insecurity status was categorized into two main patterns: nonpersistent (once or intermittent) and persistent (two or more consecutive time points). Thirty‐eight percent of households were classified as persistently food insecure. Households that reported low or very low food security were more likely to be persistently food insecure than households that experienced marginal food insecurity. To eliminate food insecurity, policies that reach children in persistent food insecurity should be a high priority, followed by strategies that improve the effectiveness of existing programs for families that experience intermittent food insecurity. Funded by the University of South Carolina.
Angiotensin‐(1‐7) stimulates high atrial pacing‐induced ANP secretion
Authors: Shah Amin , Gul Rukhsana , Yuan Kuichang , Shan Gao , Oh Young‐bin , Kim Uh‐Hyun , Kim Suhn Hee
Published: June 2021

Angiotensin‐(1‐7) [Ang‐(1‐7)] has many beneficial roles in cardiovascular physiology, counterbalancing Angiotensin II functions. It is considered as one of the theurapeutic agent for cardiovascular diseases in the future. The aim of the present study is to elucidate the modulatory role of Ang‐(1‐7) in atrial natriuretic peptide (ANP) secretion using isolated perfused beating rat atria and cardiac hypertrophied rat model. Ang‐(1‐7) (10−8, 10−7, and 10−6M) increased the ANP secretion and ANP concentration in a dose‐dependent manner at high atrial pacing (6.0 Hz) with an increased cGMP amount. However, Ang‐(1‐7) did not cause any changes in atrial parameters at low atrial pacing (1.2 Hz). An antagonist of Mas receptor or inhibitors of phosphoinositide 3‐kinase (PI3K), protein kinase B (Akt), or nitric oxide synthase pretreatment blocked the increase of high atrial pacing‐induced ANP secretion by Ang‐(1‐7). The inhibition of Na+/H+ exchanger‐1 (NHE‐1) and calcium/calmodulin‐dependent kinase II (CaMKII) showed the similar result. Ang‐(1‐7) did not show any changes in intracellular calcium concentration in quiescent atrial myocytes. However, Ang‐(1‐7) attenuated an increase of intracellular calcium concentration induced by angiotensin II. Intravenous infusion of Ang‐(1‐7) increased the plasma concentration of ANP by 2‐fold without changes in blood pressure and heart rate in isoproterenol‐treated rats but not in control rats. Ang‐(1‐7) attenuated cardiac hypertrophy induced by isoproterenol. These results suggest that Ang‐(1‐7) increased the ANP secretion at high atrial pacing via Mas/PI3K/Akt pathway and the activation of NHE‐1 and CaMKII.

Supported by the KOSEF (R13‐2008‐005‐00000‐0).
Prenatal steroid exposure attenuates the nitric oxide (NO) ‐ cyclic guanosine monophosphate (cGMP) to Ang‐(1‐7) in mature male sheep
Authors: Tang Lijun , Valego Nancy , Sun Xiurong , Bi Jianli , Carey Luke , Chappell Mark , Rose James C
Published: June 2021

Prenatal steroid administration reduces the natriuretic response to combined NaCl load and Ang‐(1‐7) infusions in adult sheep. Data also suggest that NO release and cGMP generation are involved in the natriuretic effect of Ang1‐7. Therefore, we wished to determine if prenatal steroid exposure reduced the ability of Ang‐(1‐7) to stimulate nitrite/nitrate (NOx) and cGMP excretion in adult animals. Sixteen rams prenatally exposed either to a clinically relevant dose of Beta or to vehicle at 80–81 days of gestation were studied at 18 months. Glomerular filtration rate (GFR), Na, NOx and cGMP excretion rates were measured before and during the infusion. Data were analyzed by ANOVA. Ang‐(1‐7) infusion at 10 pm.kg−1.min−1, in conjunction with a Na load (0.0275 mEq/kg BW/min), increased NOx excretion from 45.6 ± 7.0 to 60.2 ± 9.0 nmol/h/kg BW (p=0.02) and cGMP excretion from 4.2 ± 0.7 to 5.6 ± 0.8 nmol/h/kg BW (p=0.03) in vehicle animals. No significant increase in excretion rates were found in Beta animals. Sodium excretion showed positive correlations with NOx (p<0.01) and cGMP (p<0.001) excretion. There were no significant changes in GFR or plasma Na, NOx and cGMP levels in either group. These data suggest that the attenuated NOx‐cGMP responses to Ang‐(1‐7) may explain, in part, the reduced natriuretic effect of the peptide in the mature males prenatally exposed to steroid. (Supported by HD47584, HD17644)
ESTROGEN RECEPTOR CONTRIBUTES TO SEX DIFFERENCES IN ACUTE KIDNEY INJURY
Authors: Ruiz Arnaldo Lopez , Juncos Ramiro , Chandrashekar Kiran , Liu Ruisheng , Reckelhoff Jane F. , Juncos Luis A.
Published: June 2021

Gender may influence the susceptibility and severity of various renal diseases. We evaluated sex difference, and the role of the estrogen receptor, in the hemodynamic and inflammatory responses to renal ischemia‐reperfusion induced‐acute kidney injury (I/R‐AKI). Adult Sprague‐Dawley rats were randomized into 4 groups (n=6–7/group), 1) Male Sham (M‐SHAM), 2) Female Sham (F‐SHAM), 3) Male‐ I/R‐AKI (M‐I/R‐AKI), 4) Female I/R‐AKI (F‐I/R‐AKI). I/R‐AKI was induced by bilateral clamping of the renal pedicles for 40min. Measurements were obtained 72 hrs after I/R‐AKI.

Cortical‐RBF (TPU)
OM‐RBF (TPU)
CrCl (ml/min/g)
NGAL (UI/ml)
IL‐10 (pg/mg)
HO Activity (pM Bilir./mg)

M‐SHAM (6)
34.7±4.5
16.9±3.0
1.00±0.03
700±181
1.9±0.1
52±8

F‐SHAM (7)
32.9±1.4
22.6±1.0
1.02±0.10
1400±240#
3.1±0.3#
90±5#

M‐I/R‐AKI (6)
13.2±2.6
11.4±1.3
0.16±0.01
3400±138
0.9±0.05
213±10

F‐I/R‐AKI (7)
15.3±2.8
17.6±1.5*
0.47±0.03*
4087±47*
2.1±0.1*
553±37*

(n). Data are Mean±SEM.

p<0.05 vs M‐I/R‐AKI.

p<0.05 vs M‐SHAM

CrCl = Creatinine Clearance; OM‐RBF = Outer Medullary‐RBF

In addition, estrogen receptor blockade in females decreased IL‐10 and HO activity, and worsened the parameters of renal function. Our data suggest that females, via estrogen receptors, have enhanced tissue protective factors (IL‐10 and HO), which may contribute to less severe impairment of hemodynamic and functional abnormalities after I/R‐AKI.
Orchidectomy Reduced Abdominal Aorta Relaxation Response to Androgens in Sprague Dawley Rats Fed a High Salt Diet
Authors: Oloyo Ahmed Kolade , Sofola Olusoga A , Nair Renuka , Harikrishnan Vijayakumar S , Fernandez Adelaide C
Published: June 2021

The role of gonadal status on direct effect of androgens on isolated abdominal aorta from rats fed a high salt diet was assessed in this study. Twenty four weanling male rats were randomly divided into 4 groups (n = 6 each) that were either intact or orchidectomised and/or placed on normal (0.3%) or high (8%) NaCl diet. 3mm Aortic rings were suspended in organ baths containing Hepes buffer bubbled with 100% oxygen. Relaxation responses to testosterone propionate and dehydroepiandrosterone (DHEA) were studied in noradrenalin (0.1μM) pre‐contracted rings. MABP was determined before and weekly throughout the experimental period using non‐invasive tail cuff method. The results indicate a significant increase (P < 0.05) in the mean arterial blood pressure of rats placed on high salt diet, compared to controls while orchidectomy elicited a reduction in MABP (p < 0.05). There was a significant decrease (p < 0.05) in the relaxation response of rats placed on high salt diet to testosterone when compared with controls, while orchidectomy almost abolished relaxation response to testosterone (P < 0.001). Orchidectomy but not high salt diet significantly reduced (P < 0.001) relaxation response to DHEA. Thus orchidectomy reduces vascular relaxation response to androgens, and these effects were aggravated by high salt diet in male Sprague Dawley rat.
Sex hormones negatively modulate STIM‐1/Orai‐1 activity during hypertension: focus on calcium regulation
Authors: Giachini Fernanda , Lima Victor V , Carneiro Fernando S , Webb R. Clinton , Tostes Rita C
Published: June 2021

We recently showed that augmented vascular activation of STIM1/Orai1 pathway in male hypertensive rats contributes to the sex‐related impairment in intracellular Ca2+handling. We hypothesized that sex hormones contribute to the vascular protection in female hypertensive rats, via a decrease in STIM1/Orai1 activation. Endothelium‐denuded aortic rings from ovariectomized (OVX, for 15 weeks) or intact (SHAM) female stroke prone spontaneously hypertensive (SHRSP) and Wistar‐Kyoto (WKY) rats, were used to functionally evaluate Ca2+ influx‐induced contractions [upon depletion and reloading of intracellular Ca2+ (Ca2+loading period)]. Sarcoplasmic reticulum Ca+2 ATPase was inhibited with thapsigargin (10μM). During the Ca2+loading period, force development was augmented in aortas from SHRSP OVX vs. other groups and increased contraction was normalized with gadolinium (100μM, CRAC channel inhibitor), as well as blockade of STIM1 and Orai1 with neutralizing antibodies. Intracellular Ca2+ store release was increased in aortas from SHRSP vs. WKY, but no differences were observed between SHAM and OVX. Orai1 and STIM1 expression were increased in aortas from SHRSP OVX vs. the other groups. We conclude that sex hormones negatively modulate the expression and activity of STIM1/Orai1, contributing to the sex‐related differences in intracellular Ca2+ handling.

Financial support: American Heart Association (AHA 09GRNT2250383)
Synchrony is altered in the respiratory pattern generator following acute hypoxic challenge
Authors: Baekey David M , Galan Roberto F , Cardenas‐Leroy German , Dick Thomas E
Published: June 2021

Arthur B. Otis stated in 1954 that the work of breathing accounts for a small fraction of basal metabolism and that inspiration, not expiration, consumes energy. In line with Otis’ findings, our hypothesis is that the respiratory control network uses synchrony, in addition to recruitment and firing rate changes, to generate an efficient respiratory pattern. We hypothesize that synchrony may have unique roles in respiration and that this property is malleable, adapting to maintain homeostasis. To test our hypotheses, we used the perfused in situ preparation of rat (SD/Harlan) and recorded (n=7) from the left phrenic nerve and ensembles of respiratory neurons (n=53) in the Bötzinger/pre‐Bötzinger region using a multielectrode array. Preparations were exposed to acute bouts (20–45s) of hypoxia and spike synchronization between neuronal pairs (n=240) was quantified during baseline and post‐hypoxic epochs (80s/epoch). Neuron pairs from populations which appeared homogenous with respect to firing pattern demonstrated consistent changes in coordinated firing after hypoxia with the exception of a subpopulation of expiratory neurons which showed both increasing and decreasing synchrony. We conclude that synchronization is malleable within populations of the respiratory pattern generator and may contribute to patterning changes during post hypoxic frequency decline. Funded by AHA SDG 0735037N and NIH HL090554
Anoxia‐mediated decrease in whole‐cell conductance and identification of putative background K+‐like currents in anoxia‐tolerant turtle liver
Authors: Hogg David William , Buck Leslie Thomas
Published: June 2021

To survive months of anoxia painted turtles (Chrysemys picta bellii) suppress ATP utilizing pathways, enabling metabolic demands to be met through anaerobic ATP production. Ion pumping is a major ATP utilizing pathway and a decrease in membrane permeability to ions or ion channel arrest (CA) is thought to reduce ATP demand. Evidence supporting CA in anoxic turtle brain includes a 50% decrease in both major excitatory glutamatergic receptor/channels ‐ AMPA and NMDA. Recently we have shown that a 25% increase in whole‐cell conductance (Gw) occurs and this is due to an increase in GABA‐A receptor currents that clamp resting membrane potential (MP) at a hyperpolarized state preventing action potential generation. In non‐excitable anoxic liver MP is maintained while Na+/K+ ATPase activity decreases by 75%, indirectly providing evidence for CA.

Using a liver slice model, we investigated anoxia‐mediated CA directly using whole‐cell and single‐channel electrophysiological techniques. We found anoxia induces a 16% depolarization of MP, 25 ± 5 mV to 21 ± 0.2mV and a 20 ± 3% decrease in Gw. We also identified a 3–5 pA potassium current that was active at normoxic MP and upon anoxia activity decreased by 40%. We conclude that 1) in liver Gw decreases with anoxia to reduce the ATP cost of maintaining concentration gradients, 2) anoxia modulates potassium currents with characteristics similar to background potassium channels.
Relating muscle phenotype to in vivo mitochondrial function
Authors: Schmitz Joep P , van Riel Natal A , Nicolay Klaas , Hilbers Peter A , Jeneson Jeroen A
Published: June 2021

A decreased mitochondrial function has been observed during aging and type II diabetes. Understanding of the mechanisms underlying this decrease is complicated by the vast amount of proteins potentially involved. We aim on developing a computational model to estimate the contribution of a change in individual protein concentrations to in vivo mitochondrial function. A computational model of skeletal muscle energy metabolism was developed and validated with 31P MRS data recorded in human quadriceps muscle. The multi cellular model contains three distinct cell types: I, IIA and IIX, respectively. Each cell incorporates detailed descriptions of mitochondrial and glycogenolytic ATP synthetic pathways, ATP buffers and ATP consumption.

The model was then applied to analyze how phenotype changes reported in literature affected mitochondrial function. ANT concentration, mitochondrial volume content and muscle fiber type composition influences mitochondrial function the most significantly, whereas, the influence of concentrations of TCA cycle proteins, oxidative phosphorylation complexes and proton leak was relative small.

It was concluded that this computational approach provides unique opportunities for investigating the relation between muscle phenotype and in vivo mitochondrial function and as such may contribute to an improved understanding of aging and type II diabetes.
Elevated fatty acid availability after exercise increases intramyocellular triglyceride content by enhancing capacity for fatty acid flux into skeletal muscle
Authors: Newsom Sean Alec , Schenk Simon , Li Minghua , Everett Allison Clare , Horowitz Jeffrey F
Published: June 2021

We previously reported a single exercise session protects against fatty acid (FA)‐induced insulin resistance, perhaps via augmented intramyocellular triglyceride (IMTG) synthesis. The aim of this study was to examine the effect of elevated FA availability after exercise on the regulation of IMTG metabolism. After exercise (90min at 65% VO2peak) 7 healthy women (BMI: 23±1 kg/m2) were infused overnight (16h) with either a lipid and heparin solution (LIP; 0.11 g fat/kg/h) or saline (SAL), and we obtained a skeletal muscle sample the next morning. Despite a 4‐fold increase in overnight plasma [FA] during LIP, whole‐body FA oxidation was not elevated (P=0.35). Conversely, IMTG increased by ~30% during LIP vs SAL (49±3 vs 38±3 umol/g dw; P=0.04), accompanied by ~25% greater localization of the FA transporter, CD36 to the muscle membrane (P<0.01) and ~8% increase in the activity of the IMTG synthetic enzyme glycerol‐3‐phosphate acyltransferase (GPAT; P=0.01). We found no difference in GPAT and diacylglycerol acyltransferase (DGAT) protein abundance, or DGAT activity between treatments. Our findings suggest augmented capacity for FA flux into muscle (i.e., via membrane‐bound CD36), perhaps together with a slight, yet significant increase in activity of a key IMTG synthetic enzyme (GPAT) may enhance IMTG storage when FA availability is high after exercise.

Supported by NIH Grant #R01 DK071955
Skeletal muscle atrophy in critical illness myopathy is associated with muscle fiber type specific apoptotic responses
Authors: Barnes Benjamin Thomas , Rich Mark M , Ferry Amy Lynn , Dupont‐Versteegden Esther Elizabeth
Published: June 2021

Critical illness myopathy (CIM) is associated with severe loss of skeletal muscle mass. The purpose of this study was to evaluate the role of apoptosis in soleus and tibialis anterior (TA) muscles using a rat model. CIM was induced by sciatic nerve transection and dexamethasone treatment (5 mg/kg/day, 7–10 days) and resulted in 65% and 54% decrease in TA and soleus muscle mass, resp. Apoptosis was increased in CIM by 320% and 417% assessed by ELISA, and 898% and 667% measured by TUNEL, in soleus and TA, resp. Caspase‐3 and ‐8 activities were elevated 2.6‐ and 2.8‐fold, resp., in TA of CIM rats, while no changes were observed in caspase‐9 and ‐12. Also, no changes in caspase activities were observed with CIM in soleus. Abundance of heat shock protein (HSP)‐27 and HSP70 was 8.6 and 4.9‐fold higher in soleus compared to TA, while no treatment effect was observed. In addition, IP assays showed that HSP70 and uncleaved caspase‐3 interact in both soleus and TA. Caspase‐independent inducers of apoptosis, EndoG and AIF, did not exhibit differences in abundance in the nuclear fraction of soleus or TA, implying that they are not involved in apoptosis with CIM. We conclude that apoptosis contributes to muscle atrophy in CIM, and that TA and soleus utilize different apoptotic pathways, possibly due to elevated HSP expression in soleus. Supported by APS UGSRF (BB) and NS040826 (MR).
Neuregulin reduces protein degradation in skeletal muscle in a PI3 kinase/Akt and MAP kinase dependent manner
Authors: Hellyer Nathan J. , Mantilla Carlos B. , Sieck Gary C.
Published: June 2021

Skeletal muscle growth is achieved by a net increase in muscle protein synthesis, decreased protein degradation or both. The Akt and mTOR signaling transduction pathways regulate both protein synthesis and degradation. We previously reported that the nerve‐derived growth factor neuregulin (NRG) increases muscle protein synthesis (~20%) in a PI3 kinase (PI3K)/Akt‐dependent manner. In the present study, we report that basal protein degradation in the diaphragm muscle is also significantly reduced by NRG treatment (23%). The NRG‐induced reduction of basal protein degradation is abrogated by pretreatment with inhibitors of PI3K (LY294002, 50 μM), mTOR (rapamycin, 100 nM) or MEK (PD98059, 50 μM). In fact, inhibition of any of these pathways alone is sufficient to increase basal protein degradation by greater than 30%. Importantly, NRG treatment nullifies the increase in protein degradation induced by PI3K or MEK inhibition, but not that induced by mTOR inhibition. Thus, unlike NRG effects on protein synthesis, the NRG‐induced decrease in protein degradation is abrogated not only by inhibition of the PI3K/Akt pathway, but also by inhibition of the MAP kinase. Based on these results, we suggest that both the PI3K/Akt and MAP kinase pathways are important for NRG effects on protein degradation, and that mTOR is a critical regulator of NRG effects on protein balance in skeletal muscle. Supported by NIH grant AR51173.
Isoflurane Enhances Mitochondrial Free Ca2+ in Response to Ca 2+ but not ADP: Possible Role of Isoflurane in Activating Mitochondrial Ca 2+ Uniporter
Authors: Agarwal Bhawana , Boelens Age , Camara Amadou , Stowe David , Bosnjak Zeljko , Beard Daniel , Dash Ranjan
Published: June 2021

Increased mitochondrial free Ca2+ ([Ca2+]m) is known to initiate a cascade of protective kinases as a possible mechanism of preconditioning against cardiac I/R injury. This study assessed the direct effects of the volatile anesthetic isoflurane (0.5 MAC) on transients of [Ca2+]m, ΔΨm, NADHm, respiration, and matrix volume after adding CaCl2 (0.25–1 mM) followed by ADP (250 μM) to rat heart mitochondria (energized with pyruvic and malic acids) suspended in Na+, Mg2+, and Ca2+ free buffer with 1 mM EGTA. Modulation of [Ca2+]m and bioenergetics in the presence of a K+ ionophore (valinomycin, 10 nM) and inhibitors of Ca2+ uniporter (RR, 25 μM), F1F0‐ATPase (OMN, 100 μM), and ATP/ADP antiporter (CATR, 1.3 μM) were also assessed. The data showed (a) dose‐dependent increases in [Ca2+]m to added CaCl2, (b) further increases in [Ca2+]m to added ADP with ΔΨm depolarization, decreased NADHm, increased respiration, and matrix contraction, all of which returned to pre‐ADP levels after ADP was consumed, and (c) isoflurane‐induced additional increases in [Ca2+]m to added CaCl2, but proportional changes in [Ca2+]m and bioenergetics to added ADP, with no significant effect of isoflurane. These data suggest (a) a possible role of isoflurane in enhancing mitochondrial Ca2+ uptake by activating Ca2+ uniporter, and (b) matrix contraction as a contributing factor to the ADP‐induced transient increases in [Ca2+]m during ATP synthesis.
Diverse Changes in Sympathetic Nerve Activity during REM Sleep in Rats
Authors: Miki Kenju , Yoshimoto Misa
Published: June 2021

This study aimed to investigate whether REM sleep evoked diverse changes in sympathetic outflows and, if so, the potential role of the diverse changes in sympathetic nerve activity in regulating systemic arterial pressure during REM sleep. Male Wistar rats were chronically instrumented with electrodes to measure renal (RSNA) and lumbar sympathetic nerve activity (LSNA), electroencephalogram, electromyogram and electrocardiogram and catheters to measure systemic arterial and central venous pressure. REM sleep resulted in diverse changes in sympathetic outflows; there was a step reduction in RNSA by 36.1 ± 2.7% (P<0,05) which was associated with a step increase in LSNA by 15.3 ± 2% (P<0.05). Systemic arterial pressure increased gradually (P<0.05) during REM sleep while heart rate decreased in a step manner (P<0.05) during REM sleep. In contrast, RSNA, LSNA, systemic arterial pressure and heart rate increased in an unidirectional manner associated with increases in physical activity levels in the order from NREM sleep, quiet awake, moving, and grooming state. It is suggested that the diverse changes in sympathetic outflows during REM sleep may be a unique way to increase systemic arterial pressure by balancing vascular resistances between muscles and vegetative organs without depending on the heart. JSPS Grant.
Intrathecal Administration of a V1a Antagonist has No Effect on Arterial Pressure in Conscious Rats under Acute or Chronic Osmotic Stress
Authors: Veitenheimer Rupp Britta J , Osborn John
Published: June 2021

Previous studies suggest a role for spinal vasopressin in the regulation of arterial pressure (AP) in conscious rats. However, the evidence that spinal V1a receptors regulate AP under physiological or pathophysiological conditions in conscious animals is limited. We tested the hypothesis that acute and chronic osmotic stimuli increase AP, in part, via activation of spinal V1a receptors. In all studies, rats were chronically instrumented with an indwelling catheter, for intrathecal (i.t.) administration of a V1a antagonist, and a radiotelemeter to measure AP. Acute intravenous hypertonic saline (n = 7; 1.4ml/kg at 3M) increased AP (ΔAP=20±3mmHg), and the response was unaffected by pretreatment with i.t. V1a antagonist (ΔAP=22±4; 100ng). 48‐hour water deprivation elevated AP 9±4 mmHg (n = 4) and i.t. V1a antagonist caused no change in AP (ΔAP=5±2; 100ng). Finally, the AP response to i.t. V1a antagonist was investigated in rats with chronic osmotic stress induced by 4 weeks of DOCA‐salt treatment (n =4). Although basal AP was elevated in DOCA‐salt rats (140±6), acute i.t. V1a antagonist had no effect on AP (ΔAP=3±5; 100ng). Taken together, these data do not support the hypothesis that spinal V1a receptors are responsible for the regulation of AP under conditions of acute or chronic osmotic stress. Supported by NIH Grant HL064178.
Hypertensive background modifies central nervous system stress responses in male rats
Authors: Hall Mara V , Gosselink Kristin L
Published: June 2021

Hypertension is a risk factor for stroke, and has been correlated with HPA axis sensitization and the initiation of immune/inflammatory processes during chronic stress. Our study examined whether hypertension affects the stress‐induced activation of brain regions involved in the generation of stress responses and cardiovascular control. Spontaneously hypertensive (SHR) and normotensive Wistar‐Kyoto (WKY) male rats were acutely (30min x 1d) or repeatedly (30min x 14d) restrained or were not stressed. Perfused brain sections were immunohistochemically stained for Fos, which was quantified in the paraventricular (PVH) and dorsomedial (DMH) nuclei and the central (CeA) and medial (MeA) amygdala. Acute stress increased Fos in the PVH and DMH of WKY rats, compared to controls, and this response habituated with repeated stress exposure. Similar results were seen in control and acute SHRs, but the habituation of Fos induction was not seen in the PVH and only partially occurred in the DMH of these animals after repeated stress. MeA and CeA responses varied by stress treatment but were largely similar in the two strains. The data suggest that hypertension leads to enhanced responses to chronic stress at the level of neuronal activation. Understanding stress‐hypertension interactions in the central nervous system will aid the development of treatments for these and related conditions. Support: NIH 5G12 RR008124
Cardiorenal Sympathetic Denervation and Baroreflex Failure in Parkinson Disease with Orthostatic Hypotension
Authors: Goldstein David S , Sewell LaToya , Holmes Courtney S
Published: June 2021

Background

About 40% of Parkinson disease (PD) patients have orthostatic hypotension (OH). We tested whether cardiac and renal sympathetic denervation and baroreflex failure characterize PD+OH.

Methods

PD patients were stratified into two groups based on presence or absence of OH. Interventricular septum and renal cortex 6‐[18F]fluorodopamine‐derived radioactivity by positron emission tomography were expressed as ratios of liver radioactivity. Baroreflex‐cardiovagal function was assessed by interbeat interval‐systolic pressure relationships during the Valsalva maneuver and baroreflex‐sympathoneural function by fractional orthostatic increments in plasma norepinephrine (NE).

Results

The PD+OH group had low mean septum:liver and renal cortex:liver ratios (p<0.0001, p=0.02), low baroreflex‐cardiovagal gain (p<0.0001), and small orthostatic increments in plasma NE (p<0.0001). Baroreflex‐cardiovagal gain and the fractional increment in plasma NE were closely related to septum:liver ratios (p<0.0001; p=0.009) and weakly related to cortex:liver ratios (p=0.05; p=0.09). Septum:liver and renal cortex:liver ratios were positively correlated (p=0.0001).

Conclusions

In PD, renal and cardiac noradrenergic denervation and baroreflex failure are associated with OH.

Source of research support: Intramural Research Program, NINDS, NIH
Skeletal muscle: Missing link between exercise and NF‐kappaB pathway regulation in Alzheimer's Disease?
Authors: Lloyd Jesse William , Kelleher Andrew , Heckstall Ebony , Holohan John , Keslacy Stefan
Published: June 2021

Introduction

Alzheimer's Disease (AD) is associated with muscle wasting and low‐grade chronic inflammation. Exercise upregulates anti‐inflammatory gene expression in skeletal muscle. NF‐κB is a key transcription factor of the inflammatory process. Hypothesis: We hypothesize that exercise, in the AD physiological milieu, will induce an NF‐κB‐depend anti‐inflammatory gene expression in skeletal muscle. APP/PS1 mice, that develop Amyloid β‐containing plaques, were exposed to running wheels for 4 weeks (EX) or were sedentary (SED). NF‐κB‐dependent gene expression was quantified using a gene array via qRT‐PCR.

Results

EX demonstrated high level of exercise, 10000 rpd. Total protein concentrations in Soleus (SOL), Gastrocnemius (GM) and Extensor Digitorum Longus (EDL) were similar between EX and SED. NF‐κB/P65 expression decreased in EDL and GM of EX. IκB follows the pattern of P65 inhibition and increased in SOL, EDL and GM of EX. Downregulation of several NF‐κB‐dependent inflammatory genes occurred in SOL of EX (Casp1, Smad3, and Tlr1/7). Genes associated with NF‐κB and involved in immune response (Crebbp, Irf1, Myd88, Slc20a1, Stat1 and TbK1) and cell growth (Akt1, Ccl2, Atf2) were upregulated in SOL of EX.

Conclusion

The beneficial effects of exercise in AD may be due to a regulation of inflammation and immune system‐related genes expression originated from skeletal muscle.
Organization of external urethral sphincter recruitment during micturition in the female rat.
Authors: D'Amico Stephen C , Collins William F
Published: June 2021

The goal of this study was to examine the activation patterns of individual external urethral sphincter (EUS) motor units (MUs) during micturition in rats. To this end, bladder intravesical pressure (BP) and EUS EMG activity were recorded in urethane anesthetized adult female Sprague Dawley rats during continuous infusion of saline into the bladder. Individual EUS MU activity was recorded using a tungsten microelectrode (1 MΩ) inserted in the EUS or by placing an L6 ventral root filament, dissected in continuity, on platinum electrodes. Four different EUS MU recruitment patterns were observed. (1) Low threshold/sustained MUs were recruited prior to bladder contraction and exhibited sustained firing. (2) Medium threshold/not sustained MUs were recruited at the beginning of bladder contraction and stopped firing at the end of bladder contraction. (3) Medium threshold/sustained MUs were recruited at the beginning of bladder contraction and exhibited sustained firing. (4) High threshold/burst only MUs were recruited shortly before EUS bursting and stopped firing shortly after EUS bursting. Every EUS MU exhibited EUS bursting at the peak of bladder contraction. Among medium threshold MUs, derecruitment varied inversely with conduction velocity with slowly conducting units exhibiting longer sustained activity. This project is supported by the New York State Spinal Cord Injury Research Board.
Physiological implications of natural versus induced arousal from torpor
Authors: Utz Jenifer , van Breukelen Frank
Published: June 2021

Hibernation is a dynamic physiological process wherein animals cycle between periods of torpor and periods of interbout arousal. Periodically, animals spontaneously exit torpor and rewarm to euthermic Tb; this rewarming process is called arousal. Arousal from torpor is a rapid event. During arousal increases in oxygen consumption, Tb, and the restoration of blood flow occur asynchronously i.e. at different times and at different rates. In addition to natural arousals, animals can also be induced to arouse prematurely in response to mild disturbances. Historically, natural and induced arousals have been regarded as synonymous events. We question the verity of this assumption. To address this question, we have examined plasma metabolites and respiratory rate during natural and induced arousals. We are also examining markers of oxidative damage. Analysis of plasma metabolites has revealed a significant (p<0.05) increase in lactate concentration during induced arousal whereas plasma glucose and free fatty acids levels are unchanged (p>0.05). Preliminary respirometry measurements indicate that the first 30 minutes of induced arousal may be differentially fueled or involve changes in acid/base regulation. Brain, heart, liver, and kidney samples collected from arousing animals at body temperatures of 10°, 20°, and 30°C are being assayed for indications of oxidative damage to proteins, lipids, and DNA.
Rapid Cold Hardening in Drosophila requires MAPK signaling
Authors: Kelty Jonathan , Ancevski Aleksandar
Published: June 2021

Increasing evidence supports the hypothesis that rapid cold hardening (RCH) protects insects in nature. However, the cellular/biochemical mechanisms of RCH remain unclear. In Sarcophaga crassipalpis RCH involves accumulation of glycerol and Mitogen Activated Protein Kinase (MAPK) signaling pathways. For Drosophila melanogaster RCH correlates with changes in membrane lipid composition, but does not appear to involve the production of low‐molecular weight cryoprotectants. The present study utilized a pharmacological approach to determine whether RCH in D. melanogaster involves MAPK signaling. Rearing D. melanogaster on yeast paste containing the MAPK inhibitor SB203580 for 2 days following eclosion impaired their ability to rapidly cold harden (evaluated as resistance to mortality caused by cold shock injury), in a dose dependent manner. These data suggest that MAPK signaling is important to RCH in D. melanogaster.
Classification and quantitative description of human embryonic stem cell‐derived cardiomyocyte action potentials during post‐differentiation maturation
Authors: Carlson Brian E , Wilson Gisela F , Zhang Jianhua , Kamp Timothy J , Beard Daniel A
Published: June 2021

Human embryonic stem cell‐derived cardiomyocytes (hESCMs) can be a powerful cellular model for understanding cardiomyocyte development and response to therapeutic drugs. However hESCMs show a wide variation in phenotype even when differentiated under consistent experimental protocols. To understand the heterogeneities inherent in this cellular model, classification and quantification of functions defining these phenotypes must be made. The best available measurement of function in hESCMs is a recording of their membrane action potential (AP). In this study, we used an informatic‐based method to determine the AP classes of developing hESCMs recorded from spontaneously contracting embryoid body (EB) outgrowths after 10–16 days and 60 days of differentiation and then we estimated the ionic channel conductances using a theoretical model. When compared to the hESCM AP classes at 10–16 days, two 60 day hESCMs AP classes show an increased phase 0 depolarization rate and maximal diastolic potential, approaching that expected in a human adult ventricular cardiomyocyte (hAVCM). Estimation of underlying channel conductances shows only a slow delayed rectifier K conductance similar to that of a hAVCM at 60 days. Combined classification and conductance estimation suggest that hESCM electrophysiological function at 60 days approaches but does not reach that of the canonical hAVCM
Mesenchymal stem cells isolated from a novel equine tissue exhibit embryonic molecular markers and adipogenic differentiation potential
Authors: Isquith Jane Marie , Shaw Kelly , Shaw Karen , Peterson Daniel , Burd Matthew
Published: June 2021

Mesenchymal stem cells (MSC) have been isolated from equine tissues, most notably adipose and bone marrow. On the basis of ability for self‐renewal, molecular marker expression and differentiation potential, we characterized MSCs isolated from a tissue not yet explored in the equine. After isolation, MSCs were maintained in culture for 25 passages before senescence was observed. Reverse transcription‐PCR revealed embryonic transcription factor Oct4 mRNA, as well as mRNA for fucosyltransferase 4 and ST3 B‐galactoside α 2,3 sialyltransferase 2, two enzymes responsible for synthesis of embryonic surface markers SSEA1 and SSEA4, respectively. Treatment with insulin, dexamethasone, indomethacin and isobutylmethylxanthine led to increased oil red O staining (P<0.05) indicating successful adipogenic differentiation. These data indicate the stem‐like nature of these cells and their successful isolation from this tissue source. However, further characterization is needed to determine their full potential.

Partially funded by College of Agriculture, Food and Environmental Science, Cal Poly San Luis Obispo
Role of AT1 receptors over the oxidative stress in chronic renal failure (CRF)
Authors: Dugaich Adriana Poli Castilho , Mantovan Nubia Fardin , Boim Mirian Aparecida , Ribeiro Daniel Araki , Campos Ruy Ribeiro , Bergamaschi Cassia Toledo
Published: June 2021

CRF is a progressive condition marked by deteriorating kidney function over time. Elevated blood pressure, renin‐angiotensin system and the imbalance of antioxidant defenses are involved in the progression of renal diseases. The aim of this study was to evaluate the effects of chronic treatment with angiotensin AT1 receptor blockade (Candesartan) in the oxidative stress and evolution of CRF. Wistar rats were divided in 3 groups: control (C, n=6), CRF (n=6) and CRF + Cand (n=6). CRF was induced by the 5/6 nephrectomy model. Treatment with Cand, 25 mg/Kg VO (2 weeks, daily) started 6 weeks after surgery. Creatinine clearance (CrCl) and TBARS (indicative of oxidative stress) were evaluated. Animals of CRF presented a reduction in CrCl and Cand treatment improves this effect (C 2,1±0,2 x CRF 0,9 ±0,1 x CRF + Cand 1,5±0,2 ml/min). Plasmatic levels of TBARS are raised in CRF and Cand treatment normalized this values (C 2,0±0,2 x CRF 3,6 ±0,06 x CRF +Cand 1,0 ± 0,3 nmoles/ml). These results suggest that blockade of AT1 receptor reduces oxidative stress and improve renal function in CRF rats. The reduction of oxidative stress can be an important factor against progression of renal disease.

Supported by: CNPq
Neither hemodilution changes nor autoregulatory or non‐autoregulatory renal medullary blood flow changes explain the amplification of RIHP during saline volume expansion in the rat
Authors: Morales‐Loredo Juan Humberto , Brito‐Orta María Dolores , López‐Rodríguez Juan Francisco , Rodríguez‐Martínez Manuel
Published: June 2021

To assess the determinants of Renal Interstitial Hydrostatic Pressure (RIHP) amplification during saline volume expansion (E), [Pr]p, Ht, renal perfusion pressure (RPP), renal medullary blood flow (RMBF) and RIHP were measured in two groups of anesthetized, left renal denervated, hormonally clamped and RPP controlled rats, with or without medullary interstitial infusion of L‐NAME (LNA group or VHC group, respectively ) during both hydropenia (H) and E (0.58 ml/min, i.v., 2.5% of bw). RMBF was measured by laser‐Doppler flowmetry and RIHP by sub‐capsular catheter. Under RPP control (100 mmHg), LNA group showed a decrease in %ΔRMBF (−24.7 ± 7 %) vs VHC group (−8 ± 4%, p=0.05) during H, however, during E both group rose similarly their %ΔRMBF (49.8 ± 13% LNA group vs 33.7 ± 5% VHC group). Delta (Δ= E ‐ H) of [Pr]p was of −1.7 ± 0.08 g/dl in LNA group vs −1.6 ± 0.07 g/dl in VHC group (ns). ΔHt was of −10.3 ± 0.6% in LNA group vs −8.0 ± 0.7% in VHC group (p=0.03). ΔRIHP was of 4.2 ± 0.7 mmHg in LNA group vs 3.6 ± 0.4 mmHg in VHC group (ns). Both groups showed a similar upper shift of %ΔRMBF/RPP relationship from H to E, however, whereas LNA group showed autoregulation of %ΔRMBF during E, VHC group did not. Both groups showed similar flat ΔRIHP/RPP relationships during H, which were amplified similarly during E. Conclusion: Data modeling indicated that RIHP amplification during E in the rat is independent of hemodilution and autoregulatory and non‐autoregulatory changes in RMBF. Supported by: C07‐FAI‐11‐14.50.
Rac1 mediates NaCl‐induced superoxide production by the thick ascending limb
Authors: Silva Guillermo B. , Garvin Jeffrey L.
Published: June 2021

NADPH oxidase‐derived superoxide (O2−) regulates Na absorption and renal hemodynamics. Increasing NaCl in the thick ascending limb stimulates O2− generation. NaCl activates the NADPH oxidase regulatory subunit Rac1 in other cells. However, it is unknown whether physiological changes in luminal NaCl augment O2−, nor the mediators involved in the thick ascending limb. We hypothesized that increasing luminal NaCl activates Rac1 and thereby stimulates O2− production in this segment. To test our hypothesis we increased NaCl from 10 to 57 mM in medullary thick ascending limb suspensions and measured O2− using lucigenin and Rac1 activity by translocation. Increasing NaCl stimulated O2− from 1.41±0.16 to 2.71±0.30 nmol O2−/min/mg protein (p<0.05). This was blocked by the Na/K/2Cl cotransporter inhibitor furosemide and the NADPH oxidase inhibitor apocynin. NaCl increased Rac1 in the particulate fraction from 6.8±0.8 to 11.7±2.4%, indicating Rac1 activation (p<0.05). Increasing intracellular Na with Nystatin increased Rac1 in the particulate fraction by 481±110% (p<0.01). In the presence of the Rac1 inhibitor, NaCl did not increase O2− (0.49±0.16 vs. 0.55±0.25 nmol O2−/min/mg protein). Dominant‐negative Rac1 decreased NaCl‐induced O2− from 0.81±0.17 to 0.33±0.04nmol O2−/min/mg protein (p<0.05), a 60% inhibition. We conclude that NaCl stimulates thick ascending limb O2− generation by activating Rac1.
Renal function evaluation in an integrative cardio‐renal pharmacology model using Culex Empis® automated drug infusion system and radio telemetry
Authors: Chen Yafei , Brott David , Bently Patricia , Kamendi Harriet , Campbell Pamela , Kinter Lewis , Bialecki Russell A
Published: June 2021

Recently we showed utility of a novel integrative pharmacology system (CUlex TElemetry: CUTE) that allows simultaneous evaluation of CNS/CV/Renal functions with automated blood sampling in the same rat. To evaluate potential risk of drug‐induced renal and cardiac dysfunction, or their bidirectional effects, a new procedure was developed for simultaneous estimation of heart and global renal function. Briefly, inulin‐FITC (2.5 mg/mL) and p‐aminohippuric acid (PAH; 40 mg/mL) were continuously co‐administered (i.v., 0.5 mL/hour) in conscious, unrestrained Han Wistar rats using Empis® automated drug infusion system combined with CUTE. Steady state was reached after 60 min, and 11 blood samples were collected over the next 3 days. Plasma clearance of inulin and PAH were determined using Fick's principle (renal clearance = infusion rate/plasma level). There were no significant differences in estimated glomerular filtration rate (eGFR) between plasma clearance (0.95 ± 0.05) vs. reference urinary clearance method (1.07 ± 0.14 mL/min/100g BW). Mean blood pressure (102.6 ± 3.54 mmHg) and heart rate (422.9 ± 8.26 bpm) were not altered by infusion of markers for 3 days. This new approach allows simple, rapid and reproducible evaluation of renal function with respect to traditional procedures, making it a useful model for preclinical cardio‐renal safety assessment.
DDAH 2 maintains blood pressure and kidney function in response to ADMA administration in both control and diabetic rats
Authors: Palm Fredrik , Lou Zaiming , Welch William J , Wilcox Christopher S
Published: June 2021

Asymmetric dimethylarginine (ADMA) inhibits nitric oxide synthases and is increased in diabetes. Dimethylarginine dimethylaminohydrolase (DDAH) 2 metabolizes ADMA and is expressed at different intrarenal sites, including the vasculature. We hypothesize that DDAH 2 prevents vasoconstriction and maintains kidney function in response to elevated ADMA levels. Control and diabetic rats (n=8–9/group) were injected with either vehicle or siRNA against DDAH‐2. Mean arterial blood pressure (MAP) and kidney function in response to exogenous ADMA administration were measured 48h later. siRNA reduced DDAH‐2 protein expression by −60% in both groups. MAP was only elevated in diabetic rats receiving siRNA (+10 mmHg). ADMA increased MAP in all groups compared to vehicle injected controls (+13 to 17 mmHg). Both diabetic groups had increased glomerular filtration rates (2.6±0.1 and 3.0±0.2 vs 1.6±0.2 and 1.5±0.3 ml/min/kidney; P<0.05) and ADMA reduced GFR in only the siRNA treated groups (diabetics −23% and controls −43%). Baseline renal blood flow (RBF) was decreased in both siRNA groups compared to vehicles (control 9.9±0.7 vs 7.5±0.7 and diabetes 9.8±0.9 vs 8.7±0.5 ml/min/kidney) ADMA reduced RBF in siRNA controls (−11%), vehicle diabetics (−11%) and in siRNA diabetics (−20%).

DDAH‐2 protects the renal vasculature from vasoconstriction and subsequently increased MAP and reduced GFR in response to elevated ADMA levels in both control and diabetic rats. These results provide further evidence that DDAH 2 and ADMA may influence kidney function. Funding: NIH/NIDDK DK077858.