bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence supporting the Nucleotide Axis Hypothesis: ATP release and metabolism by coronary endothelium
Authors: Buxton Iain L. O. , Kaiser Robert A. , Oxhorn Brian C. , Cheek Dennis J.
Published: December 2017

The Nucleotide Axis Hypothesis, defined and supported herein, proposes that ATP stimulates the release of vasoactive mediators from endothelium, including ATP itself. Here, we show rapid endothelium-dependent, agonist-stimulated ATP elaboration in coronary vessels of guinea pigs. Measurement of extracellular ADP metabolism in intact vessels results in the time- and substrate-dependent formation of ATP in the coronary perfusate in amounts greater than can be accounted for by release from endothelium alone. ATP formation by endothelial cells is saturable ( KM= 38.5 μmol/l, where KMis substrate concentration at which rate is half-maximal.) and trypsin-sensitive, membranes from [γ-32P]ATP-labeled cells support ADP-dependent transphosphorylation by a 20-kDa protein, Western blots reveal the presence of a nucleoside diphosphate kinase (NDPK) of ∼20 kDa in endothelial membranes, and analysis of NDPK antibody binding by flow cytometry is consistent with the presence of an ecto-NDPK on cardiac endothelial cells. Sequencing of the endothelial cell ecto-NDPK reveals a predicted amino acid sequence with 85% identity to human Nm23-H1 and consistent with a protein whose properties may confer membrane association as well as sites of regulation of activity. Our data underscore the potential importance of a nucleotide axis in cardiac blood vessels.
Altered K+ channel gene expression in diabetic rat ventricle: isoform switching between Kv4.2 and Kv1.4
Authors: Nishiyama Atsushi , Ishii Douglas N. , Backx Peter H. , Pulford Bruce E. , Birks Barbara R. , Tamkun Michael M.
Published: December 2017

Expression of voltage-gated K+ channels encoding the K+independent transient outward current in the streptozocin-induced diabetic (DM) rat ventricle was studied to determine the basis for slowed cardiac repolarization in diabetes mellitus. Although hypertrophy was not detected in diabetic rats at 12 wk after streptozocin treatment, ventricular Kv4.2 mRNA levels decreased 41% relative to nondiabetic controls. Kv1.4 mRNA levels increased 179% relative to controls, whereas Kv4.3 mRNA levels were unaffected. Immunohistochemistry and Western blot analysis of the diabetic heart showed that the density of the Kv4.2 protein decreased, whereas Kv1.4 protein increased. Thus isoform switching from Kv4.2 to Kv1.4 is most likely the mechanism underlying the slower kinetics of transient outward K+ current observed in the diabetic ventricle. Brain Kv1.4, Kv4.2, or Kv4.3 mRNA levels were unaffected by diabetes. Myosin heavy chain (MHC) gene expression was altered with a 32% decrease in α-MHC mRNA and a 259% increase in β-MHC mRNA levels in diabetic ventricle. Low-dose insulin-like growth factor-II (IGF-II) treatment during the last 6 of the 12 wk of diabetes (DM + IGF) protected against these changes in MHC mRNAs despite continued hyperglycemia and body weight loss. IGF-II treatment did not change K+ channel mRNA levels in DM or control rat ventricles. Thus IGF treatment may prevent some, but not all, biochemical abnormalities in the diabetic heart.
Annexin V staining during reperfusion detects cardiomyocytes with unique properties
Authors: Narayan Prakash , Mentzer Robert M. , Lasley Robert D.
Published: December 2017

With the use of markers of sarcolemmal membrane permeability, cardiomyocyte models of ischemic injury have primarily addressed necrotic death during ischemia. In the present study, we used annexin V-propidium iodide staining to examine apoptosis and necrosis after simulated ischemia and simulated reperfusion in rat ventricular myocytes. Annexin V binds phosphatidylserine, a phosphoaminolipid thought to be externalized during apoptosis or programmed cell death. Propidium iodide is a marker of cell necrosis. Under baseline conditions, <1% of cardiomyocytes stained positive for annexin V. After 20 or 60 min of simulated ischemia, there was no increase in annexin V staining, although 60-min simulated ischemia resulted in significant propidium iodide staining. Twenty minutes of simulated ischemia, followed by 20 or 60 min of simulated reperfusion, resulted in 8–10% of myocytes staining positive for annexin V. Annexin V-positive cells retained both rod-shaped morphology and contractile function but exhibited the decreased cell width indicative of cell shrinkage. Baseline mitochondrial free Ca2+(111 ± 14 nM) was elevated in reperfused annexin V-negative cells (214 ± 22 nM), and further elevated in annexin V-positive myocytes (382 ± 9 nM). After 60 min of simulated reperfusion, caspase-3-like activity was observed in ∼3% of myocytes, which had a rounded appearance and membrane blebs. These results suggest that the use of annexin V after simulated ischemia-reperfusion uncovers a population of cardiomyocytes whose characteristics appear to be consistent with cells undergoing apoptosis.
Ventricular hypertrophy amplifies transmural repolarization dispersion and induces early afterdepolarization
Authors: Yan Gan-Xin , Rials Seth J. , Wu Ying , Liu Tengxian , Xu Xiaoping , Marinchak Roger A. , Kowey Peter R.
Published: December 2017

The effects of left ventricular hypertrophy (LVH) on the generation of phase 2 early afterdepolarization (EAD) and transmural dispersion of repolarization (TDR) were assessed using arterially perfused rabbit ventricular wedge preparations. Transmembrane action potentials from epicardium, subendocardium, and endocardium were simultaneously recorded together with a transmural ECG. Transmural action potential duration (APD) was also mapped. LVH (renovascular hypertension model) produced significant prolongation in ventricular APD and QT interval. Preferential APD prolongation in subendocardium and endocardium was associated with a marked increase in TDR. Phase 2 EADs were generated from subendocardium or endocardium in all LVH rabbits (15 of 15) in the absence of APD prolonging agents at basic cycle lengths of 2,000–4,000 ms. Phase 2 EAD could produce “R on T” extrasystoles, initiating polymorphic ventricular tachycardia (VT). This study provides the first direct evidence from intracellular recordings that phase 2 EAD could be generated from rabbit intact hypertrophied LV wall in the absence of APD prolonging agents, resulting in R on T extrasystoles capable of initiating polymorphic VT under enhanced TDR.
Inhibitory effects of calcium channel blockers on thyroid hormone uptake in neonatal rat cardiomyocytes
Authors: Verhoeven Frank A. , Moerings Ellis P. C. M. , Lamers Jos M. J. , Hennemann Georg , Visser Theo J. , Everts Maria E.
Published: December 2017

The effects of the Ca2+channel blockers verapamil, nifedipine, and diltiazem on triiodothyronine (T3) and thyroxine (T4) uptake were tested in cultured cardiomyocytes from 2-day-old rats. Experiments were performed at 37°C in medium with 0.5% BSA for [125I]T3(100 pM) or 0.1% BSA for [125I]T4(350 pM). The 15-min uptake of [125I]T3was 0.124 ± 0.013 fmol/pM free T3( n = 6); [125I]T4uptake was 0.032 ± 0.003 fmol/pM free T4( n = 12). Neither T3nor T4uptake was affected by 1% DMSO (diluent for nifedipine and verapamil). Uptake of [125I]T3but not of [125I]T4was dose dependently reduced by incubation with 1–100 μM verapamil (49–87%, P < 0.05) or nifedipine (53–81%, P < 0.05). The relative decline in [125I]T3uptake after 4 h of incubation with 10 μM verapamil or nifedipine was less than after 15 min or 1 h, indicating that the major inhibitory effect of the Ca2+channel blockers occurred at the level of the plasma membrane. The reduction of nuclear [125I]T3binding by 10 μM verapamil or nifedipine was proportional to the reduction of cellular [125I]T3uptake. Diltiazem (1–100 μM) had no dose-dependent effect on [125I]T3uptake but reduced [125I]T4uptake by 45% ( P < 0.05) at each concentration tested. Neither the presence of 20 mM K+nor the presence of low Ca2+in the medium affected [125I]T3uptake. In conclusion, the inhibitory effects of Ca2+channel blockers on T3uptake in cardiomyocytes are not secondary to their effects on Ca2+influx but, rather, reflect interference with the putative T3carrier in the plasma membrane.
Comparison of neuronal and endothelial isoforms of nitric oxide synthase in stably transfected HEK 293 cells
Authors: Schmidt Kurt , Andrew Penelope , Schrammel Astrid , Groschner Klaus , Schmitz Verena , Kojda Georg , Mayer Bernd
Published: December 2017

The neuronal and endothelial isoforms of nitric oxide (NO) synthase (nNOS and eNOS, respectively) both catalyze the production of NO but are regulated differently. Stably transfected HEK 293 cell lines containing nNOS, eNOS, and a soluble mutant of eNOS were therefore established to compare their activity in a common cellular environment. NOS activity was determined by measuring l-[3H]citrulline production in homogenates and intact cells, the conversion of oxyhemoglobin to methemoglobin, and the production of cGMP. The results indicate that nNOS is more active than eNOS, both in unstimulated as well as calcium-stimulated cells. Under basal conditions, the soluble mutant of eNOS appeared to be slightly more active than wild-type eNOS in terms of NO and cGMP formation, suggesting that membrane association may be crucial for inhibition of basal NO release but is not required for stimulation by Ca2+-mobilizing agents. The maximal activity of soluble guanylate cyclase was significantly reduced by transfection with wild-type eNOS due to downregulation of mRNA expression. These results demonstrate that nNOS and eNOS behave differently even in an identical cellular environment.
The CYP450 hydroxylase pathway contributes to P2X receptor-mediated afferent arteriolar vasoconstriction
Authors: Zhao Xueying , Inscho Edward W. , Bondlela Muralidhar , Falck John R. , Imig John D.
Published: December 2017

This study was conducted to test the hypothesis that the cytochrome P-450 (CYP450) metabolite 20-hydroxyeicosatetraenoic acid (20-HETE) contributes to the afferent arteriolar response to P2 receptor activation. Afferent arteriolar responses to ATP, the P2X agonist, α,β-methylene ATP and the P2Y agonist UTP were determined before and after treatment with the selective CYP450 hydroxylase inhibitor, N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS) or the 20-HETE antagonist, 20-hydroxyeicosa-6( Z),15( Z)-dienoic acid (20-HEDE). Stimulation with 1.0 and 10 μM ATP elicited an initial preglomerular vasoconstriction of 12 ± 1% and 45 ± 4% and a sustained vasoconstriction of 11 ± 1% and 11 ± 2%, respectively. DDMS or 20-HEDE significantly attenuated the sustained afferent arteriolar constrictor response to ATP. α,β-Methylene ATP (1 μM) induced a rapid initial afferent vasoconstriction of 64 ± 3%, which partially recovered to a stable diameter 10 ± 1% smaller than control. Both DDMS and 20-HEDE significantly attenuated the initial vasoconstriction and abolished the sustained vasoconstrictor response to α,β-methylene ATP. UTP decreased afferent diameter by 50 ± 5% and 20-HEDE did not change this response. In addition, the ATP-induced increase in the intracellular Ca2+concentration in preglomerular microvascular smooth muscle cells was significantly attenuated by 20-HEDE. Taken together, these results are consistent with the hypothesis that the CYP450 metabolite 20-HETE participates in the afferent arteriolar response to activation of P2X receptors.
Differential inhibition by botulinum neurotoxin A of cotransmitters released from autonomic vasodilator neurons
Authors: Morris Judy L. , Jobling Phillip , Gibbins Ian L.
Published: December 2017

The role of the soluble NSF attachment protein receptor (SNARE) protein complex in release of multiple cotransmitters from autonomic vasodilator neurons was examined in isolated segments of guinea pig uterine arteries treated with botulinum neurotoxin A (BoNTA; 50 nM). Western blotting of protein extracts from uterine arteries demonstrated partial cleavage of synaptosomal-associated protein of 25 kDa (SNAP-25) to a NH2-terminal fragment of ∼24 kDa by BoNTA. BoNTA reduced the amplitude (by 70–80%) of isometric contractions of arteries in response to repeated electrical stimulation of sympathetic axons at 1 or 10 Hz. The amplitude of neurogenic relaxations mediated by neuronal nitric oxide (NO) was not affected by BoNTA, whereas the duration of peptide-mediated neurogenic relaxations to stimulation at 10 Hz was reduced (67% reduction in integrated responses). In contrast, presynaptic cholinergic inhibition of neurogenic relaxations was abolished by BoNTA. These results demonstrate that the SNARE complex has differential involvement in release of cotransmitters from the same autonomic neurons: NO release is not dependant on synaptic vesicle exocytosis, acetylcholine release from small vesicles is highly dependant on the SNARE complex, and neuropeptide release from large vesicles involves SNARE proteins that may interact differently with regulatory factors such as calcium.
Chronic estradiol treatment attenuates stiffening, glycoxidation, and permeability in rat carotid arteries
Authors: Mullick Adam E. , Walsh Barbara A. , Reiser Karen M. , Rutledge John C.
Published: December 2017

Aging-related changes in vascular stiffening and permeability are associated with cardiovascular disease. We examined the interaction of estradiol on the aging process in vascular tissue from rats by assessing the changes in endothelial layer permeability, arterial compliance, and glycoxidative damage levels. We isolated carotid arteries from ovariectomized (OVX) rats that underwent 1 yr of estrogen treatment with subcutaneous pellets and a subsequent 1 mo of cessation of treatment. Endothelial layer permeability and arterial compliance were determined using quantitative fluorescence microscopy. Endothelial layer permeability was reduced with estradiol treatment (estrogen groups, 2.58 ± 0.21 ng dextran · min−1· cm−2vs. nonestrogen groups, 4.01 ± 0.30 ng dextran · min−1· cm−2; P < 0.05). Additionally, arteries from animals treated with estradiol had an increased compliance index (estrogen groups, 82.9 ± 3.8 mm2· Torr vs. nonestrogen groups, 69.3 ± 3.2 mm2· Torr; P < 0.05). Estradiol treatment also reduced levels of pentosidine, which is a specific marker of glycoxidative damage (estrogen groups, 0.11 ± 0.03 pmol pentosidine/nmol collagen vs. nonestrogen groups, 0.20 ± 0.03 pmol pentosidine/nmol collagen; P < 0.05). These results indicate that estradiol has multiple chronic vasculoprotective effects on the artery wall to maintain normal vascular wall function.
Peripheral vagal control of heart rate is impaired in neuronal NOS knockout mice
Authors: Choate J. K. , Danson E. J. F. , Morris J. F. , Paterson D. J.
Published: December 2017

The role of nitric oxide (NO) in the vagal control of heart rate (HR) is controversial. We investigated the cholinergic regulation of HR in isolated atrial preparations with an intact right vagus nerve from wild-type (nNOS+/+, n = 81) and neuronal NO synthase (nNOS) knockout (nNOS−/−, n = 43) mice. nNOS was immunofluorescently colocalized within choline-acetyltransferase-positive neurons in nNOS+/+ atria. The rate of decline in HR during vagal nerve stimulation (VNS, 3 and 5 Hz) was slower in nNOS−/− compared with nNOS+/+ atria in vitro ( P < 0.01). There was no difference between the HR responses to carbamylcholine in nNOS+/+ and nNOS−/− atria. Selective nNOS inhibitors, vinyl-l-niohydrochloride or 1–2-trifluoromethylphenyl imidazole, or the guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one significantly ( P < 0.05) attenuated the decrease in HR with VNS at 3 Hz in nNOS+/+ atria. NOS inhibition had no effect in nNOS−/− atria during VNS. In all atria, the NO donor sodium nitroprusside significantly enhanced the magnitude of the vagal-induced bradycardia, showing the downstream intracellular pathways activated by NO were intact. These results suggest that neuronal NO facilitates vagally induced bradycardia via a presynaptic modulation of neurotransmission.
NMDA-mediated increase in renal sympathetic nerve discharge within the PVN: role of nitric oxide
Authors: Li Yi-Fan , Mayhan William G. , Patel Kaushik P.
Published: December 2017

The paraventricular nucleus (PVN) of the hypothalamus is an important site of integration in the central nervous system for sympathetic outflow. Both glutamate and nitric oxide (NO) play an important role in the regulation of sympathetic nerve activity. The purpose of the present study was to examine the interaction of NO and glutamate within the PVN in the regulation of renal sympathetic nerve activity in rats. Renal sympathetic nerve discharge (RSND), arterial blood pressure (BP), and heart rate (HR) were measured in response to administration of N-methyl-d-aspartic acid (NMDA) and N G-monomethyl-l-arginine (l-NMMA) into the PVN. We found that microinjection of NMDA (25, 50, and 100 pmol) into the PVN increased RSND, BP, and HR in a dose-dependent manner, reaching 53 ± 9%, 19 ± 3 mmHg, and 32 ± 12 beats/min, respectively, at the highest dose. These responses were significantly enhanced by prior microinjection ofl-NMMA. On the other hand, inhibition of NO within the PVN by microinjection of l-NMMA also induced increases in RSND, BP, and HR in a dose-dependent manner, reaching 48 ± 6.5%, 11 ± 4 mmHg, and 55 ± 16 beats/min, respectively, at the highest dose. This sympathoexcitatory response was eliminated by prior microinjection of dl-2-amino-5-phosphonovaleric acid, an antagonist of the NMDA receptor. Furthermore, with the use of the push-pull technique, perfusion of glutamate (0.5 μmol) or NMDA (0.1 nmol) into the PVN induced an increase in NO release. In conclusion, our data indicate that NMDA receptors within the PVN mediate an excitatory effect on renal sympathetic nerve activity, arterial BP, and HR. NO in the PVN, which is released by activation of the NMDA receptor, also inhibits NMDA-mediated increases in sympathetic nerve activity. This negative feedback of NO on the glutamate system within the PVN may play an important role in maintaining the overall balance and tone of sympathetic outflow in normal and pathophysiological conditions known to have increased sympathetic tone.
Ventricular interaction and external constraint account for decreased stroke work during volume loading in CHF
Authors: Moore Thomas D. , Frenneaux Michael P. , Sas Rozsa , Atherton J. J. , Morris-Thurgood Jayne A. , Smith Eldon R. , Tyberg John V. , Belenkie Israel
Published: December 2017

The slope of the stroke work (SW)-pulmonary capillary wedge pressure (PCWP) relation may be negative in congestive heart failure (CHF), implying decreased contractility based on the premise that PCWP is simply related to left ventricular (LV) end-diastolic volume. We hypothesized that the negative slope is explained by decreased transmural LV end-diastolic pressure (LVEDP), despite the increased LVEDP, and that contractility remains unchanged. Rapid pacing produced CHF in six dogs. Hemodynamic and dimension changes were then measured under anesthesia during volume manipulation. Volume loading increased pericardial pressure and LVEDP but decreased transmural LVEDP and SW. Right ventricular diameter increased and septum-to-LV free wall diameter decreased. Although the slopes of the SW-LVEDP relations were negative, the SW-transmural LVEDP relations remained positive, indicating unchanged contractility. Similarly, the SW-segment length relations suggested unchanged contractility. Pressure surrounding the LV must be subtracted from LVEDP to calculate transmural LVEDP accurately. When this was done in this model, the apparent decrease in contractility was no longer evident. Despite the increased LVEDP during volume loading, transmural LVEDP and therefore SW decreased and contractility remained unchanged.
Myocardial distribution and regulation of GRK and β-arrestin isoforms in congestive heart failure in rats
Authors: Vinge Leif Erik , Øie Erik , Andersson Yvonne , Grøgaard Haakon K. , Andersen Geir Ø. , Attramadal Håvard
Published: December 2017

Myocardial G protein-coupled receptor kinase 2 (GRK2) has been shown to be involved in the pathophysiology of congestive heart failure (CHF). However, the cellular distribution of this isoform, as well as the other isoforms of the GRK-arrestin system, has not been studied in myocardial tissue. Thus myocardial expression and cellular distribution of the different GRK and arrestin isoforms were investigated in a rat model of CHF. Rats subjected to ligation of the left coronary artery or sham operation were euthanized 2, 7, or 42 days after the surgical procedure. Myocardial GRK2, GRK5, β-arrestin-1, and β-arrestin-2 mRNA levels, but not that of GRK3, were induced in the failing hearts. Consistently, Western blot analysis of tissue extracts from the nonischemic region of the left ventricle revealed 3.0-, 2.6-, and 1.5-fold elevations of GRK2, GRK5, and β-arrestin-1, respectively, 7 days after induction of myocardial infarction compared with the sham-operated rats ( P < 0.05). Immunohistochemical analysis of myocardial tissue sections and Western blot analysis of isolated cells revealed localization of GRK2 and β-arrestin-1 predominantly in endothelial cells. Conversely, GRK3 was confined to cardiac myocytes. GRK5 immunostaining appeared to be homogeneously distributed in the cellular elements of the myocardium. In conclusion, myocardial mRNA and protein levels of GRK2, GRK5, and β-arrestin-1 are induced in postinfarction failure in rats. The immunohistochemical analysis suggests that GRK2 and β-arrestin-1 may act as primary regulators of endothelial function. Conversely, the cellular distribution of GRK3 and GRK5 implicates these isoforms as putative regulators of cardiac myocyte function.
SAP97 interacts with Kv1.5 in heterologous expression systems
Authors: Murata Mitsunobu , Buckett Peter D. , Zhou Jun , Brunner Michael , Folco Eduardo , Koren Gideon
Published: December 2017

PDZ domain-containing proteins such as SAP97 and ZO-1 have been implicated in the targeting and clustering of ion channels. We have explored the interactions of these polypeptides with a cardiac voltage-gated potassium channel. Immunocytochemistry in cardiac myocytes revealed colocalization of SAP97 and Kv1.5, both at the intercalated disks and the lateral membranes. Transient transfection experiments in COS-7 cells revealed that SAP97 and Kv1.5 polypeptides formed perinuclear clustered complexes that could be coimmunoprecipitated. Mutation of the three COOH-terminal amino acid residues of Kv1.5 (T-D-L to A-A-A) abolished these interactions. Whereas in most COS-7 cells the SAP97-Kv1.5 complexes were retained in the ER, functional analyses in Xenopus oocytes showed that Kv1.5-encoded outward potassium currents were augmented by coexpression with SAP97. By contrast, cotransfected ZO-1 and Kv1.5 polypeptides in COS-7 cells could not be coprecipitated nor did the coinjection of ZO-1 augment the Kv1.5-encoded currents in oocytes. Collectively, our results suggest that SAP97 may play an important role in the modulation of Kv1.5 channel function in cardiac myocytes.
Postischemic mechanoenergetic inefficiency is related to contractile dysfunction and not altered metabolism
Authors: Korvald Christian , Elvenes Odd Petter , Aghajani Ebrahim , Myhre Eivind S. P. , Myrmel Truls
Published: December 2017

Mechanoenergetic inefficiency in postischemic nonnecrotic myocardium may partly be explained by an increased fatty acid (FA) oxidation rate. In the present study, left ventricular (LV) postischemic energy transfer was characterized in 10 intact anesthetized pigs. The LV was stunned by 11 brief left main coronary artery occlusions/reperfusions (20-min accumulated ischemia). Seven pigs served as time controls. The relationship between myocardial oxygen consumption (MV˙o2) and LV pressure-volume area (PVA) was assessed. [14C]glucose and [3H]oleate markers were used to discriminate between glucose and FA consumption. In stunned hearts, severe postischemic dysfunction was observed, and contractile efficiency was reduced (increased MV˙o2-PVA slope, P = 0.001). Unloaded (nonmechanical) MV˙o2was not affected by ischemia. We observed only a small transient increase in FA preference and conclude that the contribution from increased FA utilization to postischemic mechanoenergetic inefficiency is insignificant. Disrupted postischemic chemical-to-mechanical energy transfer in vivo is, therefore, related to inefficient energy utilization in the contractile apparatus.
A human cardiopulmonary system model applied to the analysis of the Valsalva maneuver
Authors: Lu K. , Clark J. W. , Ghorbel F. H. , Ware D. L. , Bidani A.
Published: December 2017

Previous models combining the human cardiovascular and pulmonary systems have not addressed their strong dynamic interaction. They are primarily cardiovascular or pulmonary in their orientation and do not permit a full exploration of how the combined cardiopulmonary system responds to large amplitude forcing (e.g., by the Valsalva maneuver). To address this issue, we developed a new model that represents the important components of the cardiopulmonary system and their coupled interaction. Included in the model are descriptions of atrial and ventricular mechanics, hemodynamics of the systemic and pulmonic circulations, baroreflex control of arterial pressure, airway and lung mechanics, and gas transport at the alveolar-capillary membrane. Parameters of this combined model were adjusted to fit nominal data, yielding accurate and realistic pressure, volume, and flow waveforms. With the same set of parameters, the nominal model predicted the hemodynamic responses to the markedly increased intrathoracic (pleural) pressures during the Valsalva maneuver. In summary, this model accurately represents the cardiopulmonary system and can explain how the heart, lung, and autonomic tone interact during the Valsalva maneuver. It is likely that with further refinement it could describe various physiological states and help investigators to better understand the biophysics of cardiopulmonary disease.
Effects of CPAP therapy on cardiovascular variability in obstructive sleep apnea: a closed-loop analysis
Authors: Belozeroff Vasily , Berry Richard B. , Sassoon Catherine S. H. , Khoo Michael C. K.
Published: December 2017

To determine the long-term effects of continuous positive airway pressure (CPAP) therapy on cardiovascular variability, we measured R-R interval (RR), systolic blood pressure (SBP) and respiration (Δ V) in 13 awake, supine patients with moderate-to-severe obstructive sleep apnea (OSA), before and after ∼6 mo of treatment. Using these data, we estimated the dynamics of the following components of a closed-loop circulatory control model: 1) the baroreflex component, 2) the neural coupling of ΔV to RR or respiratory sinus arrhythmia (RSA), 3) the mechanical effects of respiration (MER) on SBP, and 4) the circulatory dynamics (CID) component, which is responsible for the feedforward effect of RR fluctuations on SBP. Baroreflex and RSA gains increased whereas MER and CID gains decreased in compliant subjects whose average CPAP use was >3 h/night. In contrast, baroreflex, RSA, and MER gains remained unchanged and CID gain increased in noncompliant subjects. Other summary measures were unchanged in both groups, except for mean RR, which increased in compliant patients. Closed-loop analysis provides a simple but sensitive means for quantitatively assessing cardiovascular control in OSA by using data collected from a single, nonintrusive test procedure.
Glucose uptake and glycogen levels are increased in pig heart after repetitive ischemia
Authors: McFalls Edward O. , Murad Bilal , Liow Jeih-San , Gannon Mary C. , Haspel Howard C. , Lange Alex , Marx David , Sikora Joseph , Ward Herbert B.
Published: December 2017

Repetitive myocardial ischemia increases glucose uptake, but the effect on glycogen is unclear. Thirteen swine instrumented with a hydraulic occluder on the circumflex (Cx) artery underwent 10-min occlusions twice per day for 4 days. After 24 h postfinal ischemia and in the fasted state, echocardiogram and positron emission tomography imaging for blood flow ([13N]-ammonia) and 2-[18F]fluoro-2-deoxy-d-glucose (FDG) uptake were obtained. Tissue was then collected for ATP, creatine phosphate (CP), glycogen, and glucose transporter-4 content, and hexokinase activity. After reperfusion, regional function and CP-to-ATP ratios in the Cx and remote regions were similar. Despite the absence of stunning, the Cx region demonstrated higher glycogen levels (33 ± 11 vs. 24 ± 11 μmol/g; P < 0.05), and this increase correlated well with the increase in FDG uptake ( r2= 0.78; P < 0.01). Hexokinase activity was also increased relative to remote regions (0.62 ± 0.29 vs. 0.37 ± 0.19 IU/g; P < 0.05), with no difference in GLUT-4 content. In summary, 24 h after repetitive ischemia, glucose uptake and glycogen levels are increased at a time that functional and bioenergetic markers of stunning have recovered. The significant correlation between glycogen content and FDG accumulation in the postischemic region suggests that increased rates of glucose transport and/or phosphorylation are linked to increased glycogen levels in hearts subjected to repetitive bouts of ischemia.
Geldanamycin attenuates NO-mediated dilation in human skin
Authors: Shastry Shubha , Joyner Michael J.
Published: December 2017

The binding of heat shock protein 90 (HSP90) to endothelial nitric oxide (NO) synthase (eNOS) can enhance eNOS activation. Studies have shown that the HSP90-specific inhibitor geldanamycin (GA) can cause attenuation of NO-mediated processes. Twenty subjects participated in one of two protocols. In each protocol, one forearm of each subject was instrumented with two intradermal microdialysis probes for drug delivery. Laser Doppler flowmeters were used to measure cutaneous blood flow. Skin sites were either treated with the endothelial agonist acetylcholine or locally heated to 42°C, a maneuver that evokes NO-mediated dilation. Interventions were performed with and without GA. In the presence of GA, maximal cutaneous vascular conductance (CVC) to ACh was 20 ± 3% lower than with ACh alone ( P < 0.001). During local heating, maximal CVC in the presence of GA was 22 ± 6% lower than during heating alone ( P < 0.01). The results show that GA can attenuate NO-mediated dilation in human skin, suggesting a potential role for HSP90 in activation of eNOS in the microcirculation.
ERK MAP kinases regulate smooth muscle contraction in ovine uterine artery: effect of pregnancy
Authors: Xiao Daliao , Zhang Lubo
Published: December 2017

The present study investigated the potential role of extracellular signal-regulated kinase (ERK) in uterine artery contraction and tested the hypothesis that pregnancy upregulated ERK-mediated function in the uterine artery. Isometric tension in response to phenylephrine (PE), serotonin (5-HT), phorbol 12,13-dibutyrate (PDBu), and KCl was measured in the ring preparation of uterine arteries obtained from nonpregnant and near-term (140 days gestation) pregnant sheep. Inhibiting ERK activation with PD-98059 did not change the KCl-evoked contraction but significantly inhibited the contraction to 5-HT in both nonpregnant and pregnant uterine arteries. PD-98059 did not affect PE-induced contraction in the uterine arteries of nonpregnant sheep but significantly decreased it in the uterine arteries of pregnant sheep. In accordance, PE stimulated activation of ERK in uterine arteries of pregnant sheep, which was blocked by PD-98059. PD-98059-mediated inhibition of the PE-induced contraction was associated with a decrease in both intracellular Ca2+concentration and Ca2+sensitivity of contractile proteins in the uterine arteries of pregnant sheep. PDBu-mediated contraction was significantly less in pregnant than in nonpregnant uterine arteries. PD-98059 had no effect on PDBu-induced contraction in nonpregnant but significantly increased it in pregnant uterine arteries. In addition, PD-98059 significantly enhanced PDBu-stimulated protein kinase C activity. The results indicate that ERK plays an important role in the regulation of uterine artery contractility, and its effect is agonist dependent. More importantly, pregnancy selectively enhances the role of ERK in α1-adrenoceptor-mediated contractions and its effect in suppressing protein kinase C-mediated contraction in the uterine artery.
Effect of sympathetic stimulation on gastric secretion of pepsinogen
Authors: Altamirano M. , Chiang L. , Bravo I.
Published: December 2017

In dogs the stimulation of the sympathetic fibers innervating a segment of resting gastric mucosa of the corpus did not augment the basal secretion of pepsinogen when the frequency of stimulation varied between 1 and 10/sec. At rates of 15/sec. or higher the pepsinogen output was markedly increased. Secretion of hydrochloric acid was not elicited by sympathetic stimulation alone. The output of pepsinogen was increased transiently by histamine; however, the concomitant use of histamine and sympathetic stimulation even at low frequency (less than 10/sec.) resulted in a high output of pepsinogen for a long period of time. These findings are considered to be evidence that the pepsinogen-secreting glands are stimulated by histamine. Intravenous Dibenzyline antagonized the effect of the sympathetic stimulation. The transitory effect of histamine on pepsinogen secretion and the role of the sympathetic thereon are discussed.
Analysis of repetitive transient response of lobster motor axons
Authors: Adelman W. J. , Pautler E. , Epstein S.
Published: December 2017

An analysis was made to determine the relation between spike timing and the intensity of a constant current evoking a repetitive discharge in the single lobster motor axon. Accurate measurements of repetition intervals during the transient phase showed that an intensity increase of about 10–3 rheobase units produces a significantly different change in spike interval timing at the 0.005 probability level. Applications of excitation theory to the latency-intensity data have produced an equation which predicts the latency to the nth spike in a repetitive sequence as a function of stimulus intensity. The equation implies that the excitation process producing the nth spike is similar to the process producing the first spike in the repetitive sequence. Influences of supernormality and refractoriness were incorporated into the analysis. Also repeated stimulation at a fixed intensity indicated an inherent variability in the timing of the repetitive response which was shown to be a function of the magnitude of the latency. To explain this result a fixed uncertainty in the level of the initiating excitatory state was postulated.
Exchange of iodine-131-labeled chylomicron protein in vitro
Authors: Hofmann Alan F.
Published: December 2017

Chylomicrons isolated from rat chyle were iodinated with iodine131 and the protein specific activity determined before and after incubation with normal rat serum. A marked decrease in chylomicron protein specific activity occurred during incubation because of adsorption of nonradioactive soluble serum protein as well as exchange of part of the labeled chylomicron protein with lipoprotein protein. Ultracentrifugal fractionation of serum after such incubation revealed significant radioactivity in all of the lipoprotein fractions, but with low specific activity reflecting dilution by larger protein pools. Serum proteins with density greater than 1.21 contained much less radioactivity.
Urinary excretion of radium in dogs
Authors: Hursh J. B. , Lovaas A. , Piccirilli A. , Putnam T. E.
Published: December 2017

Three female adult dogs were injected intravenously with single doses of radium-226 chloride ranging from 20 to 40 µc. Periodic sampling of blood with added heparin and of urine using a bladder catheter were performed for total elapsed times of from 1 week to 21 weeks. Analyses were made of radium in the plasma, the plasma ultrafiltrate and in the urine. Creatinine was determined in plasma and urine. Radium clearance (average = 1.6 ml/min.), creatinine clearance (average = 46 ml/min.), percentage of the plasma radium which is ultrafilterable (average = 70%), and percentage of the ultra-filtrate which is resorbed (average = 95.3%) have been calculated on a basis of the data obtained. Comparing these values for radium with other comparable published values for strontium and calcium it is inferred that the differences in urinary excretion of these materials is principally caused by differences in resorption in the kidney tubules.
Action potentials of accessory respiratory muscles in dogs
Authors: Ogawa T. , Jefferson N. C. , Toman J. E. , Chiles T. , Zambetoglou A. , Necheles H.
Published: December 2017

Among 30 so-called accessory respiratory and other muscles tested, the presence of rhythmic respiratory impulses was found in 12. Both expiratory and inspiratory impulses were detected in certain muscles, in others only in- or expiratory ones. The muscles with most frequent inspiratory impulses were the intercartilaginous intercostal muscles, the intrinsic muscle of the larynx and the nostril; those with expiratory impulses were abdominis, external and internal oblique, transversus abdominis, scalenus anterior, and lower interosseous intercostal muscles.
Hypothalamus and endocrine function in persistent estrous rats at low environmental temperature
Authors: D'Angelo Savino A.
Published: December 2017

Persistent vaginal estrus with uterine and pituitary hypertrophy were found in adult female rats 4–10 months after placement of preoptic and anterior hypothalamic lesions. Serum TSH, I131 release rate and histology of the thyroid and ascorbic acid concentration of adenohypophysis, ovary and adrenal were normal. Exposure of lesioned rats to cold (5°C, 36–55 days) profoundly altered pituitary-target gland functions. Ovarian atrophy and uterine involution resulted; vaginal cornification ceased. Pituitary hypertrophy was inhibited but ascorbic acid concentration was maintained. Serum and pituitary TSH levels decreased and acceleration of thyroidal radioiodine release was prevented. Apparent dichotomy in adrenal responses developed. Despite enlarged adrenals, plasma corticosterone level in cold stressed, operated rats averaged less than one-third that of intact controls. Adrenal ascorbic acid concentration remained normal. The results underscore the basic role of central nervous mechanisms in endocrine function under chronic cold stress. Hypothalamic lesions which permit adequate trophic hormone secretion at normal temperatures drastically curtail thyroidal and ovarian function and selectively limit adrenal responses in the cold.
Variability of carotid occlusion response as affected by vagotomy and open pneumothorax
Authors: Bevan John A. , Verity Anthony
Published: December 2017

The carotid occlusion response has been measured in the anesthetized, intact cat at different durations of occlusion. It is difficult to use this reflex for quantitative studies as variations of response to a constant duration of occlusion is considerable and the relationship between response and duration of occlusion is complex. A cat with a bilateral vagotomy and open pneumothorax has been shown to have distinct advantages over other preparations studied, which included bilateral vagotomy alone, open pneumothorax alone and the intact preparation. The response is increased in height, the variation in response to a constant occlusion is reduced at durations of occlusion greater than 7.5 seconds, the relationship between the duration of occlusion and the magnitude of the response is simple, and the median effective duration shows very little variation between animals. The increase in amplitude of the response and the change from a complex to a simple relationship between duration and magnitude is most likely due to the removal of the active baroreceptor buffering mechanism on vagotomy. The variation in response is probably reduced because this procedure removes some of the factors that contribute to the total variation in the intact animal.
Effect of blood platelets on heparin-induced clearing reaction
Authors: Hollett Charlotte , Nestel P. J.
Published: December 2017

The relationship between the fall in optical density and the rise in glycerol concentration which occur during heparin-induced clearing was studied in platelet-rich and in platelet-poor post-heparin plasmas. This relationship as determined by the significance of the regression coefficients was highly significant with both plasmas. The effect of platelets on clearing was studied in three system containing either fasting plasma or post-heparin plasma or a mixture of both plasmas. In each system platelets inhibited clearing as measured by fall in optical density but did not inhibit lipolysis as measured by production of glycerol. Addition of platelet-poor fasting plasma to platelet-poor post-heparin plasma inhibited lipolysis but did not inhibit clearing. It is concluded that there may be at least two inhibitors against clearing, one associated with platelets and one present in plasma, which inhibit optical clearing and lipolysis, respectively. When fasting plasmas were incubated with substrate endogenous clearing occurred frequently, but sometimes a rise in optical density and a decrease in glycerol concentration were found, suggesting reversal of enzymatic processes.
Absorption of serum from the peritoneal cavity
Authors: Raybuck Harry E. , Allen Lane , Harms W. S.
Published: December 2017

The subserous lymphatic plexus on the peritoneal surface of the diaphragm was obliterated to study the removal of protein from the peritoneal cavity in the absence of lymphatic drainage. Cats weighing between 2 and 3 kg were used for this study. Homologous and heterologous serum was injected into the peritoneal cavity of lightly anesthetized animals. In control animals the absorption of 50 ml of homologous serum was complete in 9 hours, and absorption of 50 ml of heterologous serum required 24–36 hours. Cats in which lymphatic peritoneal drainage had been experimentally obstructed showed an increase in time interval for absorption of injection serums. Under this condition 144 hours was required for absorption of heterologous serum and 72 hours for homologous serum.
Respiration of epithelial component of mammary gland slices
Authors: Rees E. Douglas
Published: December 2017

The respiration of slices from rat mammary gland was accounted for by the independent contributions of each of the three major components of mammary tissue: adipose, epithelial and connective. The contribution of each component was the amount of the component times its characteristic qo2. In the virgin mammary gland the adipose and connective tissue components accounted for the bulk of the observed respiration; but the qo2 increased directly and linearly with epithelial proliferation induced by various means—pregnancy, lactation, or administration of progesterone or estradiol-17ß. An equation containing only biological parameters and relating qo2 to hydroxyproline content of mammary gland was derived. A qo2 value of 14.2 ± 1.8 for the mammary epithelial cell component was obtained.
Reactive hyperemia characteristics of the myocardium
Authors: Coffman Jay D. , Gregg Donald E.
Published: December 2017

Blood flow before and after occlusion of cannulated left circumflex coronary arteries of anesthetized open-chest dogs was studied using a continuously recording rotameter. Five- to one hundred and eighty-second occlusion periods were performed. Flow in excess of control flow (reactive hyperemia), peak flow, and duration of reactive hyperemia increased in magnitude following occlusions up to approximately 2 minutes. Flow debts estimated from control flows before occlusion were almost always overpaid. Series of 30-second occlusions showed that the reactive hyperemic blood flow responses were uniform in the same dog. In 15 dogs, the effect of drugs on myocardial reactive hyperemia was variable, isoproterenol, levarterenol and epinephrine usually did not alter or increased, while Pitressin decreased, reactive hyperemic blood flow. It is concluded that the myocardial response to anoxia is a reproducible phenomenon, increases with lengthening periods of anoxia, is variably affected by drugs and that the estimated flow debt for myocardial anoxia is overpaid.
Oxygen shunting in renal cortical and medullary capillaries
Authors: Levy Matthew N. , Imperial Elias S.
Published: December 2017

The existence of shunting of oxygen from arterial to venous segments of the renal capillary bed was ascertained from densitometer tracings of renal venous blood after the injection into the renal artery of blood of high oxygen tension and containing optically labeled erythrocytes. The outer region of the renal cortex was functionally separated from the medulla plus inner cortex by means of regional hypothermia. There was observed no consistent exaggeration or attenuation of the diphasic character of the renal densitometer tracing characteristic of oxygen shunting by cooling either the superficial or deeper zones of the kidney. It is concluded that shunting of oxygen occurs in both the renal cortex and medulla, but the degree to which it occurs in each zone cannot be quantified from the present data.
Renal excretory transport of organic acids: inhibition by oxypyrimidines
Authors: Despopoulos Agamemnon
Published: December 2017

Oxypyrimidines related to barbituric acid depress active accumulation of p-aminohippurate by surviving slices of rabbit kidney cortex without depressing oxygen utilization. Selectivity of inhibition is suggested by absence of effect on transport of tetraethylammonium ion. No correlation between potency and acidic strength is indicated. Correlations between molecular structure and inhibitory potency are similar to those demonstrated for oxypurines: a three-point interaction between three oxygen atoms of the inhibitor and appropriate reactive loci on a cellular receptor molecule is postulated; sulfur may replace one of the oxygen atoms and enhances potency; absence of any one oxygen atom eliminates potency; N-methylation enhances potency, possibly by enhancing hydrogen bonding.
Irreversible hemorrhagic shock in rats: method and critical bleeding volume
Authors: Strawitz J. G. , Hift H. , Temple R. L. , Ehrhardt A. , Rozansky N.
Published: December 2017

A procedure consisting of a combination of tail bleeding and heart puncture has allowed the controlled withdrawal of predetermined amounts of blood from rats. Within a narrow bleeding range of 3.9–4.0 vol. % body weight the mortality rate has been found to rise sharply from 20–70%. Survival or death do not seem to be associated with any significant changes in the fluid contents of the small intestine despite the marked hemorrhagic discoloration seen at autopsy. The removal of 4.1 (or more) vol. % body weight of blood results in a mortality rate of 80–85% with no deaths occurring beyond 4 hours. Observations made before and after death suggest that the rats die from irreversible hemorrhagic shock. The method is applicable to experiments involving 10–20 animals at a time.
Use of coenzymes I and II in interconversion of testosterone and androstenedione
Authors: Kochakian Charles D. , Raut V. S. , Kinson Gordon
Published: December 2017

Adult male guinea pig liver and kidney homogenates were able to utilize triphosphopyridine nucleotide as well as diphosphopyridine nucleotide in the conversion of testosterone and androstenedione and the reduced coenzymes in the reverse reaction. The oxidative process was much more effective than the reductive. The only other metabolite recognized was androsterone found in trace amounts during the reductive reaction.