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Biomedical subjects

A Iaina

Publications and source records attributed to A Iaina.

At least 73 records · Page 4Linked to original sources
PubMed1995

Is obstructive sleep apnea a common cause of essential hypertension?

Obstructive sleep apnea (OSA) occurs in about 10% of the middle-aged population but in about 30% of the hypertensive population of the same age. About 20% of the middle-aged population has hypertension but about 50% of patients with OSA have hypertension. Despite this close relationship between these two entities, previous attempts to determine whether the respiratory abnormalities in OSA were responsible for the hypertension were inconclusive, particularly because of the confounding effect of obesity which is common to both conditions. Data from recent observational and intervention studies, however, have succeeded in avoiding many of the pitfalls of earlier studies and it is now becoming evident that OSA may be a major cause of hypertension--responsible for about 30% of all cases. Successful treatment of OSA by any means has been shown in most studies to cause significant reductions in blood pressure throughout the 24 h period, while at the same time alleviating the vast array of symptoms and clinical abnormalities associated with this common and serious condition. Despite the encouraging results of these recent data, more studies are urgently required which should include larger numbers of patients and controls in order to clarify further the relationship between OSA and hypertension.

Airway Obstruction↗
PubMed1994

Role of nitric oxide (EDRF) in radiocontrast acute renal failure in rats.

This study was undertaken to examine the possible role of endothelium-derived relaxing factor (EDRF), identified as nitric oxide (NO), in the pathogenesis of radiocontrast-induced acute renal failure in rats. Normal and salt-depleted rats were monitored for 60 min or 24 h after radiocontrast administration. The administration of L-arginine to normal rats abolished the immediate decrease in p-aminohippurate clearance (CPAH) and attenuated the decrease in inulin clearance (CIn). The administration of NO synthase inhibitor to the salt-depleted animals resulted in a significantly more pronounced decrease in CPAH compared with both the control and the L-arginine-treated animals. The recovery of CIn 24 h after radiocontrast administration to the salt-depleted rats was significantly better in the L-arginine-treated rats than in either the control or inhibitor-treated groups. The administration of radiocontrast material resulted in a significant decrease in urinary guanosine 3',5'-cyclic monophosphate as well as NO2 + NO3 excretion. This decrease was significantly attenuated by L-arginine. Our results 1) suggest that NO plays a major role in the pathogenesis of radiocontrast-induced acute renal failure and 2) suggest a novel therapeutic approach, i.e., the use of L-arginine in this form of acute renal failure.

Acute Kidney Injury↗
PubMed1994

Pharmacokinetic profile of nifedipine GITS in hypertensive patients with chronic renal impairment.

25 hypertensive patients with normal or impaired renal function underwent pharmacokinetic and safety studies after single and multiple dose administration of nifedipine GITS (Gastro-Intestinal Therapeutic System) 60mg tablets. Complete pharmacokinetic data were obtained from 23 of these patients. Blood pressure and heart rate changes were compatible with the known properties of the drug. Impaired renal function did not affect the maximum plasma concentrations or bioavailability of nifedipine after single or multiple dose administration of nifedipine GITS, nor was there any evidence of excessive drug accumulation in the presence of renal impairment.

Administration, Oral↗
PubMed1994

Effect of chronic cholesterol loading in the development of acute ischemic renal failure in rats.

The effect of chronic cholesterol loading and lovastatin administration in renal artery clamping acute renal failure in rats is not known. Acute renal failure was induced by 60-min left renal artery clamping immediately after right nephrectomy. The changes in renal function after renal artery clamping in the hyperlipidemic rats were unexpected. The acute renal failure in the cholesterol-loaded groups was less severe than in the nonhyperlipidemic rats. The lovastatin administration had some favorable effect on renal function after ischemia; however, this effect was not additive to the high dietary cholesterol administration. Our results seems to favor the concept that in this special form of experimental renal ischemic acute renal failure, serum cholesterol levels, elevated through diet, may have protective effects with respect to renal tubular lesions during or following the acute ischemic insult.

Acute Kidney Injury↗
PubMed1994

Role of nitric oxide in glycerol-induced acute renal failure in rats.

EDRF results from the metabolism of L-arginine. N-omega-nitro-L-arginine is a nitric oxide synthase inhibitor (L-arginine competitive inhibitor). Acute renal failure was induced by i.m glycerol (50%) 5 ml/kg bw. L-arginine: 3 mg/kg bw/min for 60 min before and 60 min after glycerol administration. L-arginine inhibitor (150 micrograms/kg bw/min for 120 min). Cin, Cpah and FENa% were measured immediately or 24 h after glycerol (mean of three periods of 20 min). A second series of similar experiments was done in dehydrated (16 h) rats with a high dose of glycerol (50% solution, 10 ml/kg bw). L-arginine ameliorates the severity of ARF immediately after glycerol administration and enhances the recovery of glycerol-induced ARF. The L-arginine inhibitor resulted in a more severe ARF. Urinary cGMP decreased significantly after glycerol administration. It is concluded that nitric oxide has an important pathogenetic role in the glycerol induced ARF.

Acute Kidney Injury↗
PubMed1994

Continuous intravenous heparin administration in humans causes a decrease in serum lipolytic activity and accumulation of chylomicrons in circulation.

Heparin is a well-known, widely used anticoagulant drug. In addition to its anticoagulant properties, however, it also has a marked influence on fat metabolism. Postprandial lipoproteins may contribute significantly to the development of coronary heart disease. Therefore, it is important to evaluate the effects of heparin on these lipoproteins. The effect of continuous heparin administration on postprandial lipoprotein metabolism was studied in 11 patients with thromboembolic disease. Results were compared with those in a group of six patients given no heparin. Two vitamin A-fat loading tests were done: the first, 5 days before heparin was started and the second, on the fourth day of continuous heparin drip of 1000 U/h, maintaining PTT levels at twice the baseline. To study the effect of acute heparin, an additional fat loading test was done in five patients on the first day of heparin treatment. Vitamin A, specifically labels intestinally derived lipoproteins with retinyl palmitate (RP). The concentrations of chylomicron (Sf > 1000)- and nonchylomicron (Sf < 100)-retinyl palmitate were measured for 10 h postprandially. Four days of continuous intravenous heparin administration increased the area below the chylomicron RP curve from 11091 +/- 4393 to 17684 +/- 5949 micrograms/l.h (P < 0.003). When measured on the first day of heparin treatment in five patients, the area of the chylomicron fraction was reduced from 16678 +/- 6895 to 10474 +/- 3893 micrograms/l.h (P < 0.05). Postheparin lipoprotein lipase activity was significantly lower on the fourth day of heparin, administration than before treatment: 1.8 +/- 1.1 vs. 4.1 +/- 1.3 mumol/FFA per ml per h, respectively (P < 0.0005). In the six control patients with thromboembolic disease in whom heparin therapy was not indicated, no changes in postprandial lipoprotein levels or in lipolytic activity during hospitalization were found. The study demonstrates that 4 days of heparin administration causes an accumulation of chylomicrons in the circulation, most probably as a result of a marked decrease in serum lipolytic activity.

Adult↗
PubMed1993

Experimental uremia in male rats: effect on the reproductive tract and fertility.

Chronic renal failure was induced in 3-month-old male rats by 5/6 nephrectomy. Potency and fertility studies were performed after 3 months of chronic uremia. The mean serum testosterone at the end of the experiments was significantly lower: 0.96 +/- 0.14 ng/mL compared to a control group of sham-operated male rats, 2.86 +/- 0.59 ng/mL, p < .001. All the uremic male rats had normal accessory gland weights at the end of the study. Fertility and, in most animals, sexual behavior and mating were not different from the normal control group. It is concluded that in 5/6-nephrectomized uremic male rats, in spite of low testosterone level, fertility and reproductive system are maintained similar to normal control male rats.

Animals↗
PubMed1993

Effect of verapamil on disposition of intravenous potassium in diabetic anephric uremic rats.

Calcium channel blockers decrease the plasma potassium concentration in acutely nephrectomized rats exposed to an acute potassium load. We examined the effect of verapamil on the plasma potassium concentration during an acute potassium load in anephric-uremic diabetic and non-diabetic rats. The plasma potassium concentration was measured at 15-min intervals during 60 min of continuous KCl infusion, with and without verapamil. The baseline potassium concentrations were higher in diabetic rats vs. nondiabetic controls. Verapamil blunted the increase in plasma potassium in diabetic and nondiabetic rats compared with the respective controls. The pH and hematocrit were similar in all groups. We conclude that the effect of verapamil on extrarenal potassium disposal are independent of insulin and the renin angiotensin system in the uremic state.

Animals↗
PubMed1992

Severe defect in clearing postprandial chylomicron remnants in dialysis patients.

Lipid abnormalities have been suggested as a major cause of the accelerated atherosclerosis and the high incidence of coronary heart disease in chronic renal failure patients. In the present work the postprandial lipoprotein metabolism was studied in chronic dialysis patients with or without fasting hypertriglyceridemia using the vitamin A loading test. This method investigates specifically postprandial lipoprotein metabolism. The determination of vitamin A ester level retinyl palmitate (RP) differentiates the circulating plasma chylomicron and chylomicron remnant fractions from the endogenous VLDL and IDL. Subjects with normal renal function with or without fasting hypertriglyceridemia served as control groups. Dialysis patients have significantly higher level of chylomicron remnants for a more prolonged period of time than controls, irrespective of their fasting triglyceride levels. The area below retinyl palmitate chylomicron remnants curve was 26308 +/- 12422 micrograms/liter.hr in the normolipidemic dialysis patients, significantly higher than (6393 +/- 2098 micrograms/liter.hr; P < 0.0001) in the normolipidemic controls. The retinyl palmitate chylomicron remnants curve of the hypertriglyceridemic dialysis patients was 21021 +/- 4560 micrograms/liter.hr, which was higher than 12969 +/- 2215 micrograms/liter.hr (P < 0.0001) in the hypertriglyceridemic controls. Moreover, the hypertriglyceridemic dialysis patients had an additional defect in the lipolysis metabolic step, that is, accumulation of chylomicrons in circulation. These findings show a severe defect in postprandial lipoprotein metabolism in chronic renal failure patients. The prolonged exposure of the vascular wall to high chylomicron remnant concentrations might be an important pathogenetic factor in the accelerated atherosclerosis seen in chronic dialysis patients.

Adult↗
PubMed1992

Early diagnosis of gram-negative peritonitis in continuous ambulatory peritoneal dialysis patients with the Lymulus amebocyte lysate assay.

The treatment of peritonitis in continuous ambulatory peritoneal dialysis patients is empiric until the bacteriological results are available. The Lymulus amebocyte lysate assay (LAL) is a very sensitive method for the detection of endotoxin, a structural component of gram-negative bacteria. We performed the LAL assay in a prospective study in 36 consecutive episodes of peritonitis. The LAL assay was positive in all 10 episodes of gram-negative peritonitis (100% specificity). Treatment directed specifically against gram-negative or -positive infection was started based on the LAL assay result. In 26 episodes with LAL-negative test, a gram-positive bacterium was cultured in 23 episodes, in 1 there was fungal infection and 2 were sterile. In summary: the LAL assay is a rapid (1 h) and sensitive method for the differentiation of gram-positive or -negative peritonitis and enables starting an immediate and more appropriate antibiotic therapy.

Endotoxins↗
PubMed1992

Normal renin-aldosterone-insulin and potassium interrelationship in FMF patients and amyloid nephropathy.

The renin-aldosterone system and plasma insulin were studied in 19 patients with familial Mediterranean fever (FMF). Their relationships to serum potassium level at rest and before and after oral glucose loading are described. An interesting finding is the occurrence of hyperkalemia in the absence of oliguria, in the advanced stages of renal failure. No differences were found in the activity of the renin-angiotensin-aldosterone system to explain these variations in serum potassium found in some of the patients. The response of the renin-aldosterone system to glucose loading showed no abnormality, and the regular relationship between serum potassium, plasma renin activity (PRA), aldosterone, insulin, and plasma pH is maintained. Levels of insulin, potassium, and bicarbonate in serum or plasma pH were found similar in FMF patients with normal renal function with and without proteinuria. Further decrease in renal function due to the progression of the underlying disease is manifested by an increase in FENa+ and FEK+ and a hyperchloremic metabolic acidosis, as is the case in other patients with chronic renal failure.

Adult↗
PubMed1990

Oxygen free radical scavenger system intermediates in essential hypertensive patients before and immediately after sublingual captopril administration.

Oxygen-free radical intermediates/scavengers were measured in 43 patients with essential hypertension who, although under antihypertensive therapy (without angiotensin-converting enzyme inhibitors), still had high blood pressure values. Measurements were taken before and 30, 60 and 120 min after sublingual administration of 25 mg captopril. Both systolic and diastolic blood pressures were reduced significantly. Twenty normotensive healthy volunteers were used as controls. The hypertensive patients had lower glutathione peroxide activity (GSHPx), higher superoxide dismutase (SOD) and serum glutathione reductase activity (GSHRx) compared with the controls. After captopril (30, 60 min) the glutathione and GSHPx increased compared with the pretreatment values. SOD and GSHRx remained high compared with the controls, while whole blood glucose-6-phosphate dehydrogenase remained low. Another group of 19 essential hypertensive patients, free of any antihypertensive medication (for at least 3 weeks), had lower GSHPx, SOD and higher GSHRx than the normal control group. Our results show significant differences in the oxygen free radical scavenger system of hypertensives compared with the normal subjects. It may be that captopril has a concomitant scavenging action together with its antihypertensive effect. Our study raises the question whether cell/organ damage will occur in hypertensive patients exposed to oxidative stress during periods of low antioxidative capacity.

Adult↗
PubMed1988

Proton MR properties of lyophilized urine samples from normal and stone former individuals.

Proton MR measurements were performed in lyophilized urine samples collected from 5 normals (N) and 5 idiopathic hypercalciuric recurrent stone formers (SF). T1 and T2 relaxation times were measured with a Bruker PC Multispec at 20 MHz and 37 degrees C in the lyophilized samples and in samples gradually rehydrated. Significantly (p less than 0.01) prolonged T1 and T2 relaxation times were measured after addition of water to the lyophilized samples. The relaxation time prolongation patterns were significantly different (p less than 0.01) for the two groups; the rehydration curves of the lyophilized urine samples from the SF group had relatively shorter lag than that of N group. In calculations of water compartmentalization for similar water content, significant (p less than 0.01) differences in the fraction of bound water (FB) were found between the two groups. These results may reflect differences in the macromolecular properties, contents, in the amount of water binding sites and/or in the water multilayer thickness between the two groups. These differences, expressed as changes of the relaxation times values may provide new diagnostic possibilities of different renal pathologies.

Female↗
PubMed1988

Hydration properties of urinary compounds obtained from normal and stone former individuals. An NMR study.

Proton magnetic resonance measurements were performed on lyophilized urine samples collected from 10 recurrent calcium oxalate stone former (SF) patients, 10 thiazide treated (TSF) patients and 14 normal (N) individuals. T1 and T2 relaxation times were measured with a Bruker PC Multispec at 20 MHz and 37C on the lyophilized sample and thereafter during gradual controlled rehydration. The prolongation of the relaxation times was found to be significantly different (p less than 0.001) for the SF and N groups, while it was similar for the SF and TSF groups. Water compartmentalization was then calculated according to the Fast Proton Infusion model. After the addition of similar amounts of water, significantly (p less than 0.01) different hydration fraction (HF) and fraction bound (FB) values were calculated for the N and SF groups, while similar values were obtained for the SF and TSF groups. The results reflect differences in the urinary contents and/or properties of N and SF groups. It seems that there are more hydrophilic compounds in the urine of N individuals than in that of SFs. It can be speculated that the urinary macromolecules of SFs differ from those of Ns in the amount of water binding sites and in the water multilayer thickness surrounding them. The present results point to possible pathogenic differences between SF and N individuals.

Adult↗