UMLS:C0020538 - FACTA Search

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Query: UMLS:C0020538 (hypertension)
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Forty hypertensive patients were studied to examine the assumption that the angiotensin pressor dose reflects endogenous renin activity. Peripheral renin activity was assayed by the method of Boucher et al.(4) Sensitivity to the infusion of synthetic angiotensin II was determined as suggested by Kaplan and Silah.(1)Sixteen patients with essential hypertension with normal renal angiography required 3.8 ng. angiotensin/kg./min. to raise the diastolic pressure 20 mm. Hg. All but one were sensitive to angiotensin infusion of less than 5 ng./kg./min. Renin activity was normal in all except in one sensitive subject. Angiotensin infusion response and mean renin activity in 13 patients with essential hypertension with abnormal renal angiography were similar to that of the first group. The pressor dose in 11 renovascular hypertensives was 9.8 ng./kg./min. All but three had elevated plasma renin activity.OUR RESULTS SUGGEST THAT: (1) the angiotensin infusion test is suitable for differentiating patients with true renovascular hypertension from those with essential hypertension with or without associated renal artery disease; (2) the angiotensin pressor dose correlates with the level of peripheral venous renin activity (p < 0.01).
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PMID:The angiotensin infusion test and peripheral venous renin activity. 429 Aug 36

THE AUTHORS OF THIS PAPER SUMMARIZED the major themes that emerged from a 2-day workshop entitled Epidemiology of Hypertension in Hispanic Americans, Native Americans, and Asian/Pacific Islander Americans, sponsored by the National Heart, Lung, and Blood Institute (NHLBI) in Washington, DC. Data from the papers were synthesized using seven points: similarities, variability within and between groups, lost prevention opportunities, emergence of explanatory variables, differences in types of data collected, missing or inconsistently reported data, and socioeconomic characteristics. Virtually all of the population groups demonstrated rises in blood pressure with age. These rises appear to be largely attributable to potentially modifiable risk factors, for example, high body mass index (BMI). Despite high levels of awareness, the levels of control of high blood pressure were poor in each population studied. Based on the themes that emerged from the data, we presented several recommendations to the workshop. One was that data be collected on these population groups repeatedly and in a standardized fashion. Another called for increased efforts aimed at control of high blood pressure in these groups. A third recommended major nationwide programmatic efforts aimed at the prevention and control of high blood pressure.
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PMID:Putting it all together: summary of the NHLBI Workshop on the Epidemiology of Hypertension in Hispanic American, Native American, and Asian/Pacific Islander American Populations. 889 84

HYPERTENSION-ASSOCIATED ABNORMALITIES THAT PROMOTE CORONARY DISEASE: Although antihypertensive treatment has been effective in reducing premature cardiovascular mortality, the effect on various organ-specific morbid events has been unequal; the effect is much more impressive on stroke reduction than on reduction of coronary events. A student of pathophysiology would have anticipated such an outcome since blood pressure elevation is only one of multiple abnormalities in hypertension. Even in its mildest form hypertension is associated with the metabolic syndrome of dyslipidemia/insulin resistance which is conducive to early atherosclerosis. A large proportion of patients also have increased sympathetic and decreased parasympathetic tone, a constellation conducive to arrhythmias and, ultimately, to sudden death. An elevated hematocrit is also found in a substantial proportion of male patients and excessive platelet aggregability has also been described in hypertension. These hematologic abnormalities are conducive to coronary thrombosis. Angiotensin II and norepinephrine, two of the most potent trophic hormones, are frequently elevated in hypertension. The effect of these hormones on the cardiac and vascular structure further increases the predilection for negative outcomes. Left ventricular hypertrophy is a potent risk factor of coronary mortality, congestive heart failure and sudden death. Vascular hypertrophy reduces the coronary reserve and at the level of skeletal muscles contributes to the evolution of the metabolic syndrome. ORGAN-SPECIFIC HYPERTENSION TREATMENT: Because of these abnormalities we are entering a new era of treatment in hypertension. Whereas an effective fall in blood pressure remains the main goal of treatment, differential effects of various antihypertensive agents on organ-specific morbidity are being actively explored. If this research proves that certain drugs have a specific advantage in defined subgroups of patients, clinical practice will change. It is reasonable to expect that in the next century we will witness a further improvement in the impact of antihypertensive treatment on public health.
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PMID:Coronary disease in hypertension: a new mosaic. 921 91

Over the past few years, a substantial body of evidence has accumulated that indicates hyperhomocysteinemia as a significant risk factor for cardiovascular disease. Hyperhomocysteinemia arises from a lack of key enzymes or vitamins such as methylenetetrahydrofolate reductase, vitamin B6, and folate which are involved in homocysteine metabolism. Heavy coffee consumption is also known to elevate homocysteine levels. The adverse effects associated with hyperhomocysteinemia are extensive. It increases risk of myocardial infarction, cardiovascular-related morbidity and mortality, peripheral vascular disease, atherosclerosis, coronary heart disease, and cerebrovascular disease. Its seriousness as a risk factor has been equated to hypercholesterolemia and smoking, two leading causes for cardiovascular disease. It also has been shown to produce a multiplicative effect with these and other risk factors such as hypertension. Two major hypotheses have been proposed to explain how homocysteine induces its harmful effects. It can damage endothelial cells lining the vasculature, allowing plaque formation. Simultaneously, it interferes with the vasodilatory effect of endothelial derived nitric oxide. Also, homocysteine has been found to promote vascular smooth muscle cells hypertrophy. Both of these processes induce vessel occlusion. Maintaining a normal plasma level of homocysteine as a means to prevent cardiovascular disease appears promising. This is achieved through increased intake of folate and vitamin B6 through diet or supplementation. Despite the overwhelming evidence suggesting homocysteine as a significant risk factor, no long-term prospective studies have been completed to demonstrate that folate and vitamin B6 can prevent cardiovascular disease related morbidity and mortality in patients with hyperhomocysteinemia. Homocysteine is a key metabolite in amino acid synthesis. During the process of methylation, S-adenosylmethionine (Ado Met), derived from methionine, is converted to S-Adenosylhomocysteine (Figure 1). This product is quickly hydrolyzed to form homocysteine and adenosine. Homocysteine can undergo 1 of 3 reactions depending on the status of the organism. If cysteine levels are inadequate, homocysteine utilizes the coenzyme pyridoxal phosphate (vitamin B6) to condense with serine, forming the intermediate cystathionine. Subsequent reactions with cystathionine lead to the formation of cysteine. When methionine levels are low, homocysteine is remethylated in a reaction involving the coenzyme N5-methyltetrahydrofolate or betaine. Finally, when both amino acids are in adequate supply, homocysteine is cleaved by the enzyme homocysteine desulthydrase (cystathionase) to form a-ketobutyrate, ammonia, and H2S. Thus, homocysteine's physiological role is to assist in maintaining sulfur-amino acid homeostasis. Beyond these metabolic processes, homocysteine is beginning to be recognized as a significant risk factor for cardiovascular disease including atherosclerosis, coronary artery disease, cerebrovascular disease, and myocardial infarction.
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PMID:Hyperhomocysteinemia: an additional cardiovascular risk factor. 1063 97

Hydrogen sulfide (H2S) is recently found to be a new gaseous messenger playing an important role in many physiological and pathophysiological processes. The aim of this study was to explore the changes in endogenous H2S pathway and examine the effects of H2S on the development of spontaneous hypertensive rats (SHR). A controlled study on SHR and WKY rats at the age of 4 weeks showed that after 5 weeks of experiment, the blood pressure of SHR was markedly increased as compared with WKY rats (183.57 +/- 11.80 mm Hg vs 107.5 +/- 22.68 mm Hg, P < 0.05) and the ratio of left heart weight to whole heart weight of SHR was also increased as compared with WKY rats (0.85 +/- 0.02 vs 0.83 +/- 0.02, P < 0.05). While, the aortic H2S producing rate and H2S plasma level were decreased in SHR compared with WKY rats (15.63 +/- 2.89 nmol.min-1.g-1 vs 25.31 +/- 5.99 nmol.min-1.g-1, 20.35 +/- 9.20 mumol.L-1 vs 48.40 +/- 13.36 mumol.L-1, P < 0.05). NaHS, however, attenuated the high blood pressure and the ratio of left heart weight to whole heart weight of SHR (158.13 +/- 12.52 mm Hg vs 183.57 +/- 11.80 mm Hg and 0.83 +/- 0.03 vs 0.85 +/- 0.02), respectively. The above findings suggested that the reduced production of endogenous H2S was important in the development of spontaneous hypertension. The authors also observed that 5 weeks after the experiment the relaxing rate of aortic rings in response to acetylcholine in SHR was higher than that of WKY rats and NaHS enhanced the relaxing-response of aortic rings to acetylcholine in SHR significantly(P < 0.05). The aortic relaxing activities in both SHR and WKY rats displayed a dose-dependent response to different doses of NaHS. In conclusion, the reduced production of endogenous H2S in aorta is involved in the pathogenesis of spontaneous hypertension and is of great biological importance in modulating vasorelaxation.
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PMID:[Endogenous H2S is involved in the development of spontaneous hypertension]. 1292 Aug 21

Recent studies suggest that apart from nitric oxide (NO) and carbon monoxide (CO), hydrogen sulfide (H2S) is another inorganic gaseous mediator in the cardiovascular system. H2S is synthesized from L-cysteine by either cystathionine beta-synthase (CBS) or cystathionin gamma--lyase (CSE), both using pyridoxal 5'-phosphate (vitamin B6) as a cofactor. CBS is the main H2S-producing enzyme in the brain and CSE is involved in H2S formation in the cardiovascular system. H2S induces hypotension in vivo and vasodilation vitro by opening KATP channels in vascular smooth muscle cells. Chronic administration of CSE inhibitor induces arterial hypertension in the rat. In addition, decreased H2S generation has been demonstrated in the vasculature of spontaneously hypertensive rat, in experimental hypertension induced by NO synthase blockade, and in hypoxia-induced pulmonary hypertension, and administration of exogenous H2S donor has significant therapeutic effects in these models. Deficiency of H2S may contribute to atherogenesis in some patients with hyperhomocysteinemia, in whom the metabolism of homocysteine to cysteine and H2S is compromised by vitamin B6 deficiency. Reduced H2S production in the brain was observed in patients with Alzheimer's disease. On the other hand, excess of H2S may lead to mental retardation in patients with Down's syndrome and may be involved in the pathogenesis of hypotension associated with septic shock.
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PMID:[Hydrogen sulfide as a biologically active mediator in the cardiovascular system]. 1528 Jul 98

Sulfur emission through fuel combustion is a global problem because it is a major cause of acid rain. Crud oil contains many heterocyclic organic sulfur compounds, among which dibenzothiophene (DBT) and DBTs bearing alkyl substitutions usually are representative compounds. A strain was isolated from refinery sludge and identified as Corynebacterium ZD-1. The behavior of DBT degradation by ZD-1 in aqueous phase was investigated. Corynebacterium ZD-1 could metabolize DBT to 2-hydroxybiphenyl(2-HBP) as the dead-end metabolite through a sulfur-specific pathway. In shake flask culture, ZD-1 had its maximal desulfurization activity in the late exponential growth phase and the specific production rate of 2-HBP was about 0.14 (mmol x kg dry cell(-1) x min(-1), mmol x KDC(-1) x min(-1)). Active resting cells for desulfurization should be prepared only in this period. 2-HBP inhibited the growth of strain ZD-1, the production of DBT degradation enzymes, and the activity of enzymes. Sulfate inhibited the production of dibenzothiophene (DBT) degradation enzymes but had no effect on the enzymes' activity. The production rates of 2-HBP at lower cell densities were higher and the maximum amount conversion of DBT to 2-HBP (0.067 mmol/L) after 8 h was gained at 9.2 g dry cell/L rather higher cell density. The results indicated that this newly isolated strain could be a promising biocatalyst for DBT desulfurization.
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PMID:Desulfurization of dibenzothiophene by a newly isolated Corynebacterium sp. ZD-1 in aqueous phase. 1590 Jul 40

The discovery of nitric oxide (NO) initiated a novel research field, gaseous signal molecules. Other two gaseous signal molecules, carbon monoxide (CO) and hydrogen sulfide (H2S), have been approved subsequently. All of these three gaseous signal molecules are generated endogenously and exert extensive biological effects. This article reviews the significance of gaseous signal molecules in the pathogenesis of cardiovascular diseases. In the cardiovascular system, the endogenous NO, CO and H2S form three specific and relevant pathways with their corresponding enzymes including nitric oxide synthase (NOS), heme oxygenase (HO), and cystathionine-gamma-lyase (CSE). The gaseous signal molecules not only participate in the maintenance of physiological function and structure of the cardiovascular system, but also exert important pathophysiological effects in the pathogenesis of cardiovascular diseases, such as hypertension, pulmonary hypertension, septic shock and atherosclerosis. Further studies on gaseous signal molecules will remarkably promote the basic research in the cardiovascular fields, and provide a novel direction for the clinical research as well.
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PMID:[Significance of gaseous signal molecule in the pathogenesis of cardiovascular diseases]. 1617 52

The gaseous mediators hydrogen sulphide (H2S) and nitric oxide (*NO) are synthesised in the body from L-cysteine and L-arginine, respectively. In the cardiovascular system, *NO is an important regulator of vascular tone and its over- or under-production has been linked to a variety of diseases. The physiological significance of H2S is not yet clear but, like *NO, it exhibits vasodilator activity and may play a part in septic and haemorrhagic shock, hypertension, regulation of cardiac contractility, and in inflammation. To date, there have been no reports of a chemical interaction between H2S and *NO. Here we show that incubation of the H2S donor, sodium hydrosulphide, with a range of *NO donors and *NO gas in vitro leads to the formation of a nitrosothiol molecule as determined by a combination of techniques; electron paramagnetic resonance, amperometry, and measurement of nitrite. We further show that this nitrosothiol did not induce cGMP accumulation in cultured RAW264.7 cells unless *NO was released with Cu2+. Finally, using liver homogenates from LPS treated rats we present evidence for the endogenous formation of this nitrosothiol. These findings provide the first evidence for the formation of a novel nitrosothiol generated by reaction between H2S and *NO. We propose that generation of this nitrosothiol in the body may regulate the physiological effects of both *NO and H2S.
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PMID:Evidence for the formation of a novel nitrosothiol from the gaseous mediators nitric oxide and hydrogen sulphide. 1654 95

Hydrogen sulfide (H2S), which is well known traditionally as a toxic gas, has been proven to be produced endogenously by 3 enzymes in mammalian tissues and plays important roles in physiological and pathophysiological conditions. In the central nervous system, H2S functions as not only a neuromodulator, but also a neuroprotectant against oxidative stress. In the cardiovascular system, H2S relaxes vascular smooth muscles by the activation of KATP channels and inhibits smooth muscle cell proliferation via the mitogen-activated protein kinase signaling pathway. These effects are important for maintaining blood pressure and preventing vessel structural remodeling, and identifies H2S as an important factor in the development of some vascular diseases, such as hypertension. H2S also shows cardioprotective effects in ischemic myocardium and septic and endotoxin shock. Recent studies have demonstrated a new mechanism to explain the motor effect of H2S on the rat detrusor muscle, which is through the activation of the capsaicin-sensitive primary neuron. This review focuses on the recent research achievements on H2S and discloses the great potential of H2S as the third gaseous transmitter in cardiac protection.
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PMID:Hydrogen sulfide: third gaseous transmitter, but with great pharmacological potential. 1795 20

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