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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Local blood flow in the cortex and thalamus was measured by the hydrogen clearance method in spontaneously hypertensive rats (SHR) and normotensive rats (NTR) before and after bilateral carotid occlusion. There were no differences in the resting blood flow values between SHR and NTR. Following carotid occlusion cortical blood flow in SHR was markedly reduced to 17% of the resting level at 1 h and, further, to less than 10% at 3--5 h period, while in NTR it decreased only to 36--38% during 5 h occlusion. Thalamic blood flow in SHR was decreased to 39% at 1 hr and to below 20% at 3--5 h, while in NTR it remained approximately 40% of the resting level during 5 h occlusion. The blood flow reduction in either cortex or thalamus after carotid occlusion was much greater in SHR than in NTR. This difference was highly significant. The increased cerebral vascular resistance caused by persistent hypertension may play an important role in a greater reduction of blood flow in SHR after carotid occlusion. Relation of the blood flow reduction to the brain metabolism is discussed.
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PMID:Changes in local cerebral blood flow following bilateral carotid occlusion in spontaneously hypertensive and normotensive rats. 730 79

Twenty persons living at an altitude of 2,240 meters were studied in order to examine the relative roles of passive and active factors in the genesis of pulmonary arterial hypertension in obesity (overweight, 75 +/- 39 percent). Pulmonary arterial hypertension was present in 80 percent (16) of the patients (mean pulmonary arterial systolic pressure, 45 +/- 17 mm Hg). In 95 percent (19) of the 20 patients, resistance to pulmonary flow at the end of diastole was increased (estimated mean pulmonary arteriolar resistance, 210 +/- 144 dynes.sec.cm-5; mean pulmonary arterial diastolic-pulmonary wedge pressure gradient 7.86 +/- 1.40 mm Hg). The mean arterial oxygen pressure was 50 +/- 9 mm Hg, the arterial carbon dioxide tension was 37 +/- 6 mm Hg and the arterial pH was 7.42 +/- 0.08. Since the pulmonary arterial systolic pressure has been reasonably predicted (r = 0.91; P < 0.001), it would appear that the compliance of the elastic pulmonary arteries in obese patients follows a normal pattern. The behavior of the right ventricular end-diastolic pressure at rest (mean change, 4.6 mm Hg; P < 0.001) and of the pulmonary wedge pressure (mean change, 4.7 mm Hg; P < 0.001) during passive lifting of the legs was indirect evidence of the increase in pulmonary blood volume. The presence of an abnormal resistance to pulmonary blood flow at the end of diastole is suggestive of a decrease in the distention of the pulmonary microcirculation. The pulmonary arterial diastolic-pulmonary wedge pressure gradient and the pulmonary arterial diastolic pressure were related to arterial oxygen unsaturation (r = 0.70; P < 0.05) but not to the concentration of hydrogen ions; thus hypercapnic acidemia appears as a secondary factor in the genesis of pulmonary arterial hypertension at high atitudes. The explanation could be the relative hyperventilation of high altitudes, with a compensatory metabolic alkalosis. The increased pulmonary blood volume and the alveolar hypoxia are the main causes in the pathogenesis of pulmonary arterial hypertension in the grossly obese patient at this altitude.
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PMID:Behavior of the pulmonary circulation in the grossly obese patient. Pathogenesis of pulmonary arterial hypertension at an altitude of 2,240 meters. 741 79

Recent advances in magnetic resonance imaging (MRI) technology have had a great impact on the delectability of minute, asymptomatic lesions of the central nervous system. The clinical significance and treatment modes of these lesions, such as white matter hyperintensity (WMH) lesions detected by T2 MRI, remain controversial. To address these problems, we retrospectively evaluated WMH lesions in relation to clinical parameters for 240 neurologically asymptomatic persons who had visited a hospital for a medical check-up of the brain. Proton and T2-weighted MRI were obtained using a 0.5 T superconducting MR imager using the spin echo technique with a repetition time (TR) of 2800 msec. An echo delay times (TE) of 40 msec was used for the proton MRI, and a TE of 100 msec was used for the T2-weighted MRI. The images were visually analyzed according to a four-point grading system. The MRI findings were correlated with clinical parameters including age, gender, presenting symptoms, and hypertension. The overall frequency of WMH increased with age. Grades 2 and 3 of WMH were more frequent in aged persons, whereas the occurrence of grade 1 WMH remained relatively constant across age groups. Based on multiple regression analysis, age was the most significant variable influencing the frequency of WMH, followed by hypertension. These results imply that WMH lesions may simply be a phenomenon of aging, or may be an indicator of prepathologic state in an ischemic brain.
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PMID:White matter hyperintensity in neurologically asymptomatic subjects. 748 64

Platelet-activating factor (PAF) causes pulmonary hypertension and lung edema in animals and isolated perfused lungs by poorly understood mechanisms. Because oxidative mechanisms have been implicated in PAF-mediated cellular injury, we tested the hypothesis that superoxide anion (O2-.) contributes to PAF-induced lung injury by determining whether superoxide dismutase (SOD) could prevent the lung injury. Isolated rabbit lungs were perfused with PAF (100 nM) at a dose that caused transient hypertension and mild edema. Lungs pretreated with Cu,Zn SOD (100 U/ml) for 10 min developed persistent pulmonary hypertension and more lung edema formation in response to PAF. Enhanced responses to PAF also were observed in lungs perfused with 200 U/ml Cu,Zn SOD, but not with 10 or 40 U/ml Cu,Zn SOD. The higher doses of SOD also decreased thromboxane B2 levels in the perfusate. Potentiation of the PAF effect by Cu,Zn SOD was eliminated if the enzyme was inactivated or if the lung was treated with an anion channel blocker. The augmented PAF response in the presence of SOD was not altered by catalase (200 U/ml) or by nitric oxide synthase inhibitor. The data suggest that excessive Cu,Zn SOD enzyme activity potentiates PAF-induced injury in perfused rabbit lung presumably by overscavenging extracellular O2.- generated from intercellular sources. The augmented responses to PAF are not directly attributable to increased hydrogen peroxide, nitric oxide-related products, or thromboxane A2 production. These results suggest the new hypothesis that a balance between O2-. production and its metabolism determines vascular and endothelial responses to PAF.
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PMID:Superoxide dismutase potentiates platelet-activating factor-induced injury in perfused lung. 751 30

The aspartic proteinases are an important family of enzymes associated with several pathological conditions such as hypertension (renin), gastric ulcers (pepsin), neoplastic disease (cathepsins D and E), and AIDS (HIV proteinase). Studies of inhibitor binding are therefore of great importance for design of novel inhibitors for potential therapeutic applications. Numerous X-ray analyses have shown that transition-state isostere inhibitors of aspartic proteinases bind in similar extended conformations in the active-site cleft of the target enzyme. Upon comparison of 21 endothiapepsin inhibitor complexes, the hydrogen bond lengths were found to be shortest where the isostere (P1-P'1) interacts with the enzyme's catalytic aspartate pair. Hydrogen bonds with good geometry also occur at P'2, and more so at P3, where a conserved water molecule is involved in the interactions. Weaker interactions also occur at P2, where the side-chain conformations of the inhibitors appear to be more variable than at the more tightly held positions. At P2 and, to a lesser extent, P3, the side-chain conformations depend intriguingly on interactions with spatially adjacent side chains, namely P'1 and P1, respectively. The tight binding at P1-P'1, P3, and P'2 is also reflected in the larger number of van der Waals contacts and the large decreases in solvent-accessible area at these positions, as well as their low temperature factors. Our analysis substantiates earlier proposals for the locations of protons in the transition-state complex. Aspartate 32 is probably ionized in the complexes, its charge being stabilized by 1, or sometimes 2, hydrogen bonds from the transition-state analogues at P1. The detailed comparison also indicates that the P1 and P2 residues of substrate in the ES complex may be strained by the extensive binding interactions at P3, P'1, and P'2 in a manner that would facilitate hydrolysis of the scissile peptide bond.
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PMID:A structural comparison of 21 inhibitor complexes of the aspartic proteinase from Endothia parasitica. 770 59

We investigated the possible relationship between endothelin-1 injection into the dorsolateral periaqueductal gray area and the glutamatergic system in the control of cardiovascular function. Endothelin-1 was injected into the dorsolateral periaqueductal gray area of freely moving rats at doses ranging from 0.1 to 10 pmol. Endothelin-1 increased arterial blood pressure (from 7.0 +/- 1.6 to 55.0 +/- 4.1 mm Hg, mean +/- SEM) in a dose-dependent manner and induced characteristic behavioral changes such as longitudinal rolling of the body (barrel-rolling). DL-2-Amino-5-phosphonovaleric acid and (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[D-alpha] cyclohepten-5,10-imine hydrogen maleate, both selective N-methyl-D-aspartate excitatory amino acid receptor antagonists, but not 6-cyano-7-nitroquinoxaline-2,3-dione, a non-N-methyl-D-aspartate excitatory amino acid receptor antagonist, significantly decreased endothelin-1-induced cardiovascular and behavioral changes (P < .01). Prazosin and propranolol, adrenergic blocking agents, and reserpine, a depletor of catecholamine stores, also prevented these effects. We propose that the glutamatergic system may exert, via N-methyl-D-aspartate receptors, a significant influence on endothelin-1-induced cardiovascular and behavioral effects after its injection into the periaqueductal area.
Hypertension 1995 Apr
PMID:Endothelin-1 in rat periaqueductal gray area induces hypertension via glutamatergic receptors. 772 91

Microalbuminuria (urinary albumin excretion between 20 and 200 micrograms/min) and abnormalities of red blood cell sodium-hydrogen exchange coexist in essential hypertensive patients. To evaluate how the two phenomena relate, we recruited 10 untreated microalbuminuric male essential hypertensive patients without diabetes to be compared with an equal number of matched essential hypertensive patients excreting albumin in normal amounts as well as 10 healthy control subjects. Sodium-hydrogen exchange values were increased to a comparable extent in microalbuminuric and normoalbuminuric hypertensive patients. Systolic and mean blood pressures were higher in microalbuminuric patients. Fasting insulin was greater and high-density lipoprotein cholesterol lower in patients than control subjects. Urinary albumin excretion correlated positively with both mean blood pressure and left ventricular mass values in the absence of a relationship with circulating lipid and insulin levels. In contrast with microalbuminuria, sodium-hydrogen exchange covaried only with high-density lipoprotein cholesterol and insulin levels. Thus, microalbuminuria and an abnormal sodium-hydrogen exchange are unrelated phenomena in essential hypertensive patients. Microalbuminuria appears to be a hemodynamically driven biological variable, while an accelerated sodium-hydrogen exchange seems primarily conditioned by the metabolic abnormalities of hypertension, possibly in the context of an insulin-resistant syndrome.
Hypertension 1995 May
PMID:Microalbuminuria and erythrocyte sodium-hydrogen exchange in essential hypertension. 773 37

The in vivo effects of adenosine triphosphate (ATP) have not been investigated in cerebrovascular diseases. The use of the long-acting cobalt-ATP complex (Co-ATP) permits us to observe the effects of ATP without the influence of its metabolites. This study was designed to compare the effects of intravenous Co-ATP on the cerebral blood flow (CBF), polarographically detected oxygen currents (O2a), mean arterial blood pressure (MABP), heart rate, respiration rate, cerebral electrical activity, arterial blood gases, pH, and glucose in 13 normotensive (NT) rabbits to those in 14 stroke-prone spontaneously hypertensive (HT) animals. CBF was measured by the hydrogen and heat clearance methods. In response to Co-ATP, MABP decreased and CBF increased significantly in both groups. The decrease in MABP was more marked in HT rabbits, while CBF response was 25% smaller than in NT animals. The ratio of O2a to CBF diminished moderately and simultaneously with the CBF increase in NT rabbits. In HT rabbits, the decrease in O2a/CBF was larger and began when CBF response reached its maximum. We suggest that despite the restricted CBF response, long-acting ATP should still be taken into consideration as a supplementary treatment of hypertensive encephalopathy because of its beneficial effects on cerebral metabolism and hypertension.
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PMID:Beneficial vascular and metabolic effects of cobalt-ATP in spontaneously hypertensive rabbits with diffuse chronic cerebral ischaemia. 779 24

Nifedipine, (1,4-dihydro-2,6,dimethyl-4-(2-nitrophenyl)-3, 5-pyridinedicarboxylic acid dimethyl ester) a calcium channel blocker widely used in treatment of hypertension, is strongly photolabile. This may represent a problem in patients taking nifedipine and in handling of nifedipine samples. Reactive radical intermediates were determined and characterized in the process of nifedipine illumination using EPR spectroscopy. On illumination of nifedipine by daylight or by a mercury lamp, a nitroxide radical, RIIL-NIFNO.X was observed (in the first step), in various solvents like benzene, cyclohexane, methanol, acetonitrile, dimethylsulphoxide, or aqueous suspensions of liposomes. RIIL-NIF represents the nifedipine skeleton centered with phenyl group, and X is an EPR silent substituent. The generation of RIIL-NIFNO.X is coupled with the formation of nitroso compound, RIIL-NIFNO, as characterized by UV-visible spectroscopy. In a further step, RIIL-NIFNO abstracts hydrogen from nifedipine skeleton under the formation of RIIL-NIFNO.H radical. In addition to this, in system containing RIIL-NIFNO and unsaturated lipids, nitroxide radicals RIIL-NIFNO.RLIPIDS are formed probably via a pseudo Diels-Alder mechanism (RLIPIDS represents lipidic skeleton). The unusually easy photochemical activation of nifedipine is probably stimulated by photosensitization of its nitro group interacting with suitably positioned hydrogen or carboxylic methyl ester group from the pyridinyl ring.
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PMID:Reactive radical intermediates formed from illuminated nifedipine. 786 71

To determine the effects of intravenous administration of dopamine hydrochloride (DA) on tumor blood flow (TBF), we measured the blood flow of normal subcutaneous tissue and subcutaneous tumor (LY-80, a variant of Yoshida sarcoma) in enflurane-anesthetized male Donryu rats using a hydrogen clearance method. Measurements were made before and during intravenous infusion of DA at a rate of 5 micrograms/kg/min, while recording the mean arterial blood pressure of the rats. Under mild hypertension induced by DA, the blood flow of normal subcutis decreased and TBF increased significantly. SCH-23390, an antagonist of the DA1 receptor, inhibited the enhancement of TBF by DA; while domperidone, an antagonist of the DA2 receptor, did not modify the effects of DA. In experimental chemotherapy against the tumor using adriamycin (ADM) 5 mg/kg i.v., only the combination of DA and ADM significantly inhibited the tumor growth. Moreover, DA reduced the weight loss caused by ADM. These results indicate that DA could have a role in increasing TBF and possibly enhance drug delivery to tumors. Moreover, it appears that the DA1 receptor contributes, at least in part, to the enhanced blood flow in rat subcutaneous tumor following DA administration.
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PMID:Effects of intravenous infusion of dopamine on tumor blood flow in rat subcutis. 801 14


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