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Biomedical subjects

A Z Gyory

Publications and source records attributed to A Z Gyory.

At least 19 recordsLinked to original sources
PubMed1998

Recognition and management of IgA nephropathy.

IgA (immunoglobulin A) nephropathy is the most common form of primary glomerulonephritis worldwide. It generally has a good prognosis, with 15-year rates of kidney survival from the apparent onset of disease usually well in excess of 70%. Progression, when it occurs, is usually a slow, indolent process, and spontaneous remission of disease activity occurs in 7% of patients. It is possible to predict, from the initial presenting features and laboratory findings, renal biopsy and clinical course during follow-up, which patients are likely to have progressive renal disease. Identification of the factors likely to be associated with progression is of importance in helping to establish which patients will benefit from specific therapeutic intervention. For all patients, attention should be directed toward general health issues in an endeavour to reverse factors that are likely to have an adverse impact on renal function. This should include early detection and tight control of hypertension (present in 50% of all patients with IgA nephropathy during the course of their disease), along with utilisation of antihypertensive agents that have specific renoprotective effects, namely ACE inhibitors or calcium antagonists. Such therapy should also be considered in normotensive patients with heavy proteinuria, as a reduction of proteinuria is often achieved by this means. Other aims should include maintenance of desirable bodyweight, correction of hyperlipidaemia, cessation of smoking, participation in an active exercise programme, avoidance of exposure to nephrotoxins and maintenance of a high fluid intake. A low protein/low phosphate diet together with phosphate binder therapy should be commenced early in the course of renal impairment. Corticosteroid and/or cytotoxic drug therapy should be considered in the small percentage of patients with heavy proteinuria or a rapid decline in renal function. Such therapeutic endeavours are likely to delay the onset of renal failure in patients with progressive IgA nephropathy.

Antihypertensive Agents↗
PubMed1996

Transferable circulating factors and epithelial sodium transport after unilateral nephrectomy in the rat.

1. In order to investigate the role of circulating serum factors in the altered renal haemodynamics and enhanced renal tubular transport observed in renal growth, micropuncture experiments were performed on normal animals infused with 20% plasma derived from animals in whom unilateral nephrectomy had been performed 3 days previously. 2. When animals infused with plasma from uninephrectomized animals (NxP) were compared with those infused with control plasma, the former had a higher tubular fluid flow rate measured at both the late proximal (LP; 26.7 +/- 1.6 vs. 18.4 +/- 1.4 nl min-1; P < 0.001) and early distal (ED; 14.9 +/- 1.0 vs. 7.8 +/- 1.0 nl min-1; P < 0.0001) sites, which was reflected in the final urine flow rate (16.1 +/- 3.4 vs. 5.1 +/- 0.8 microliter min-1; P < 0.005). 3. The single nephron glomerular filtration rate (SNGFR) was higher in animals infused with NxP as determined from samples taken at the LP (45.8 +/- 2.8 vs. 35.7 +/- 2.3 nl min-1; P < 0.01) and at the ED (34.5 +/- 2.5 vs. 28.1 +/- 1.8 nl min-1; P = 0.05) sites. However, this increase was not reflected in the whole kidney GFR (1.04 +/- 0.06 vs. 0.89 +/- 0.06; P = 0.07), suggestive of a preferential increase in filtration in the outer cortical nephrons. 4. Tubular Na+ transport was higher in the animals infused with NxP as evidenced by a decrease in the fractional delivery of Na+ at the ED site (4.5 +/- 0.4 vs. 6.5 +/- 0.6% of the filtered load; P < 0.05). However, in the final urine there was a significant increase in the urinary sodium excretion in animals infused with NxP (0.67 +/- 0.14 vs. 0.29 +/- 0.09%; P < 0.05) indicating that natriuresis and probably diuresis was a result of inhibition of Na+ and water transport in the late distal tubule and collecting duct. 5. In conclusion, these experiments demonstrate that circulating factors induced by a reduction in renal mass significantly alter glomerular filtration and tubular Na+ transport.

Angiotensin II↗
PubMed1995

Neonatal outcome in a randomized, controlled trial of low-dose aspirin in high-risk pregnancies.

OBJECTIVE: To determine the value of low-dose aspirin in high-risk pregnancies, and assess its impact on fetal growth, as well as on perinatal mortality and morbidity. METHODOLOGY: One hundred and eight women with singleton pregnancies were enrolled in a randomized, double-blind, placebo-controlled trial of 100 mg/day aspirin from 17 to 19 week gestation. Enrolment criteria included pre-existing chronic essential hypertension or renal disease, or a history of previous early, severe pre-eclampsia. RESULTS: There were four stillbirths (all aspirin) and two neonatal deaths (both placebo), to yield respective perinatal mortality rates of 69/1000 and 40/1000 (P = 0.499). Liveborn infants in the aspirin group were significantly more mature (P = 0.017) and of heavier birthweight (P = 0.034) but had similar length (P = 0.091) and head circumference (P = 0.257). Fewer infants in the aspirin group were liveborn prematurely (5/54 vs 14/50; P = 0.016) or were of low birthweight (3/54 vs 9/50; P = 0.052). There were no significant between-group differences for standard deviation (Z) scores for weight, length or head circumference, or for skinfold thickness measurements. There was no significant difference in occurrence of low Apgar scores or in neonatal intensive care unit use between the groups. CONCLUSIONS: Low-dose aspirin does not appear to have a significant effect on perinatal morbidity. The increase in weight at birth associated with low-dose aspirin therapy is due to prolongation of pregnancy rather than prevention of intra-uterine growth retardation.

Aspirin↗
PubMed1995

Comparison of simultaneous renal clearances of true endogenous creatinine and subcutaneously administered iothalamate in man.

125I-iothalamate and true endogenous creatinine clearances, measured over two short collections periods of 1 and 2 h, were compared simultaneously in 70 patients with a variety of renal diseases and a wide range of renal function. Reproducibility of the iothalamate clearance was 18.5% and that of the creatinine clearance 12.2%. The slope of the regression was not significantly different from 1 (95% confidence interval, CI, 0.964-1.155) for the whole group, nor in any subgroup chosen. The intercept at 12.6 ml/min (CI = 5.0-20.2) indicates that there is some creatinine secretion, but this was constant at all levels of GFR. It is concluded that although the clearance of true creatinine obtained during short collection periods consistently overestimates GFR by a constant proportion, it is a reproducible and accurate measure of GFR suitable for use in the clinical setting.

Adult↗
PubMed1994

Arginine vasopressin and osmolality in the elderly.

OBJECTIVES: To evaluate the influence of age on plasma arginine vasopressin (AVP) concentrations and the relationship between plasma AVP and serum osmolality in younger and older subjects, and in the elderly, to assess the effect of gender on plasma AVP concentration and to determine the impact of prostaglandin blockade on renal responsiveness to AVP. DESIGN: Cross-sectional study; randomized, double-blind, crossover, placebo-controlled study. SETTING: The Renal Laboratory, Royal North Shore Hospital (younger adults) and Clinical Room, St Vincents Hospital (elderly subjects). PARTICIPANTS: 45 younger adults (35 +/- 9 years), and 41 elderly subjects (29 males, 12 females; 78 +/- 3 years). All subjects were healthy and non-institutionalized. The elderly subjects were screened to exclude significant pathology (clinical assessment, multiple investigations). INTERVENTION: Blood samples were drawn from all younger and elderly subjects. The elderly subjects were randomly allocated indomethacin or placebo for 1 month. Following a 1 to 2-week washout, the alternative was administered for a further 1 month. MAIN OUTCOME MEASURES: Plasma AVP and serum osmolality and plasma AVP, serum, and urine osmolality at baseline were measured on indomethacin and placebo. RESULTS: In the elderly subjects, baseline plasma AVP concentration was significantly higher than in the younger subjects studied (4.7 +/- 0.7 vs 2.1 +/- 0.2 pg/mL respectively; P = 0.0003). Plasma AVP was strongly correlated with serum osmolality in the younger subjects (r = 0.76, P = 0.0001) but not in the elderly cohort (r = -0.18, P = 0.26). No difference was found between the sexes in plasma AVP (P = 0.89), and indomethacin treatment did not alter the plasma AVP/urine osmolality ratio (P = 0.85) in the elderly subjects. In addition, changes in plasma AVP with indomethacin therapy did not correlate with changes in serum osmolality (r = 0.16, P = 0.09). CONCLUSIONS: Aging is accompanied by an increase in plasma AVP concentrations. In healthy, elderly subjects, plasma AVP is not dependent on serum osmolality and is not influenced by gender. Indomethacin has no effect on the renal responsiveness to plasma AVP.

Adult↗
PubMed1992

Renal function in unilateral nephrectomy subjects.

Renal function in 32 subjects who had undergone unilateral nephrectomy (17 transplant donors and 15 subjects with unilateral renal disease) was compared with that of 22 normal subjects. The age-adjusted glomerular filtration rate was lower in transplant donors (79 +/- 15% of normal) than in those whose nephrectomy was performed for unilateral renal disease (90 +/- 12% of normal). The donors were also significantly older at nephrectomy (48 +/- 10 years versus 24 +/- 13 years, p less than 0.001). This finding may represent less capacity for compensatory hypertrophy. Proximal tubular and medullary function as assessed by 15-minute phenolsulfonphthalein excretion, maximum urinary concentration in response to water deprivation plus exogenous vasopressin, and urinary acidification in response to an oral acid load were all within normal limits for glomerular filtration rate. Overall renal function was well preserved after nephrectomy. A small number of patients did have increased cast excretion, which may signify the presence of mild renal disease in these subjects.

Adult↗
PubMed1991

Proximal tubular cell sodium concentration in early diabetic nephropathy assessed by electron microprobe analysis.

Electron microprobe X-ray analysis techniques were employed in order to assess the changes that occur in proximal tubular cell sodium concentration during the hyperfiltration phase of early diabetes mellitus induced by streptozotocin in Sprague Dawley rats. Intracellular rubidium accumulation following intravenous infusion of rubidium chloride was used as a marker of basolateral Na/K-ATPase activity. The diabetic animals studied had a significantly higher glomerular filtration rate compared with controls [1.44 +/- 0.07 vs. 1.00 +/- 0.07 ml min-1 (100 g body weight)-1; mean +/- SEM, P less than 0.001]. Intracellular Na concentration was significantly higher in diabetic animals (19.5 +/- 0.6 vs. 17.8 +/- 0.4 mmol/kg wet weight; P less than 0.01). Concurrent measurement of Rb demonstrated significantly higher intracellular accumulation in the proximal tubules of diabetic animals compared with control (7.9 +/- 0.5 vs. 5.5 +/- 0.5 mmol/kg wet weight; P less than 0.001). These results indicate that proximal tubular Na/K-ATPase activity is enhanced in the hyperfiltration phase of diabetes mellitus. Since, however, intracellular Na concentration is increased under these conditions, it may be inferred that apical Na entry into proximal tubular cells is stimulated beyond the rate of basal exit during the initial development of hyperfiltration. The reasons for these alterations in cellular Na transport are unclear but similar changes have been implicated in the pathogenesis of cell growth.

Animals↗
PubMed1991

Postnatal changes in proximal and distal tubular sodium reabsorption in healthy very-low-birth-weight infants.

We studied 7 healthy very-low-birth-weight male infants with a mean birth weight of 1,195 g and a gestational age of 29.0 weeks, from birth to 6 weeks. The filtered Na load increased fivefold but urine Na excretion decreased from 3.4 to 0.1% of the filtered Na load. The efficiency of Na reabsorption increased 8% in the proximal tubule compared with 66% in the distal tubule. Because greater than 90% of Na reabsorption always occurred proximally, the smaller percentage increase in efficiency of the proximal tubule contributed as much as the larger percentage increase in efficiency of the distal tubule to the postnatal improvement in renal Na conservation.

Absorption↗
PubMed1990

Hypertension due to renal artery stenosis in pregnancy--the use of angioplasty.

The use of transluminal percutaneous renal angioplasty for severe hypertension in the second trimester of pregnancy has not previously been reported. We describe its use in a 19-year-old female. The procedure resulted in a significant improvement in blood pressure control and allowed the pregnancy to proceed to term, resulting in the delivery of a normal female baby on the 90th percentile for weight. No morbidity to mother or fetus was observed as a result of diagnostic or therapeutic procedures. We conclude that pregnancy should not preclude making the diagnosis of renovascular hypertension as angioplasty may be a useful therapeutic option.

Adult↗
PubMed1988

Energy-dispersive X-ray microanalysis of air-dried microdroplets containing a macromolecular solute.

In the preparation of microdroplets of biological fluids for X-ray microanalysis, we have found that incorporation of a macromolecular solute, dextran, to a final concentration of 1.5-2.5% retards crystal formation and produces sufficiently uniform deposits on thin films to allow droplets to be analysed without prior freeze-drying. Analyses have been carried out at 20 kV in a scanning electron microscope, using energy-dispersive spectrometry. Absorption of Na X-rays by the added solute can be significant but its effect is minimized by preparing droplets as thin as possible, and by using standards of similar composition. The minimum detectable concentrations are increased because of the extra background contribution, and for a single determination are about 6 mM for Na and 2 mM for Cl and K. These concentrations can be further reduced by measuring replicates. The reproducibility of analysis is significantly improved (to less than 5% for Na and K) over the use of calibration curves by calculating the element concentrations from a known element in the sample, chlorine. Under our analytical conditions loss of Cl did not occur. This method requires that the Cl is measured separately by microcoulometry, but eliminates the need for a range of standard droplets on the grid, and determination of the unknowns is then independent of droplet volume, beam current, counting time and magnification. We have compared, with biological samples, the results from using Cl as an internal standard with those obtained using an added standard element, cobalt. The reproducibility using Cl was approximately two-times better than that obtained with Co, probably because of unavoidable volumetric errors when the Co is pipetted separately.

Calcium↗
PubMed1987

The effects of high Na and Cl concentrations on rat proximal volume and Na fluxes at zero tubular flow.

1. In vivo micropuncture techniques, with and without peritubular capillary perfusion, were used to study the effects of high extracellular Na and Cl concentrations on transepithelial volume (Jv) and sodium (JNa) fluxes in rat proximal tubules. 2. In a double blind manner, the shrinking drop technique of Gertz was used to measure Jv; JNa was calculated from this and the tubular fluid Na concentration. 3. At both 184 and 279 mmol/l pericellular Na concentrations (both inside and outside the tubular epithelium), net Jv decreased significantly by 15 and 64%, respectively. Net JNa remained constant at 184 but decreased by 29% at 279 mmol/l Na concentration. 4. Thus, at both Na concentrations, when translated to free flow conditions, fractional Na reabsorption must have decreased. These findings, also supported by previous results at these Na concentrations, indicate that active Na transport was inhibited by high pericellular Na concentrations. 5. When intratubular Cl concentration was varied between 108 and 138 mmol/l while peritubular Cl was maintained constant (blood perfusing the capillaries), neither Jv nor JNa changed. Thus, at zero tubular flow, differential Cl/HCO3 concentrations do not provide significant driving forces for net Jv or JNa. 6. When only intratubular but not peritubular Na was elevated to 279 mmol/l, Jv and JNa increased markedly by 50 and 187%, providing evidence that a true solvent drag (solute drag) effect does exist in rat proximal tubules. 7. These findings offer a mechanism to explain why Na reabsorption is not increased when the filtered load of Na is increased with an elevation of plasma Na.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Antihypertensive treatment in pregnancy: analysis of different responses to oxprenolol and methyldopa.

One hundred and eighty three hypertensive pregnant women were randomly assigned to antihypertensive treatment with oxprenolol (96 women) or methyldopa (87 women). Control of hypertension was equivalent in both treatment groups, and in 64 (35%) cases hydralazine had to be added to the treatment to achieve the therapeutic goal (diastolic blood pressure below 85 mm Hg). Five perinatal deaths occurred, one in the oxprenolol group and four in the methyldopa group. Detailed analysis confirmed a previous report of greater fetal growth in the group treated with oxprenolol; this trend was present regardless of severity of hypertension and parity. With increasing duration of treatment the differences between the two groups diminished, and there was no difference after 10 weeks of treatment, a finding that may explain some of the reported discrepancies among therapeutic studies. As hypertension in pregnancy may pursue an accelerated course, necessitating urgent delivery, and there is no satisfactory method of predicting the duration of treatment in individual patients fetal benefit is most likely to be achieved by treatment with oxprenolol, provided that there is no maternal contraindication to treatment with beta blockers.

Adult↗