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Biomedical subjects

N Schor

Publications and source records attributed to N Schor.

At least 73 records · Page 4Linked to original sources
PubMed1992

Renal sodium conservation during starvation in rats.

The natriuresis of fasting has been well characterized in man and rabbits but not in rats. The daily effects of fasting on glomerular filtration rate (GFR) and urinary sodium and potassium excretion were evaluated in Munich-Wistar rats (260-310 g) submitted to prolonged starvation (2-8 days). Rats do not present the natriuresis of fasting. Sodium excretion was reduced since the first few hours (0-4 h) of starvation. Antinatriuresis was abrupt during the early periods (1st and 2nd days) and stabilized at very low levels. During the early phase (4 days), sodium retention occurred due to both reduced glomerular filtration and increased tubular reabsorption. However, during the late phase (after the 4th day), antinatriuresis was mainly induced by the elevation in tubular reabsorption, since a normalization of GFR was observed. Thus, these homeostatic mechanisms permit adequate renal sodium conservation during starvation in rats.

Animals↗
PubMed1991

Metabolic disturbance as a cause of recurrent hematuria in children.

Metabolic disturbance as a cause of recurrent hematuria in children. To evaluate metabolic disturbance as a cause of hematuria, 250 children, aged eight months to fourteen years, with recurrent hematuria were studied. In the present series, metabolic disturbance was mainly due to idiopathic hypercalciuria (IH), the most common etiology of hematuria without proteinuria in childhood. Sixty-seven (27%) of the children had IH, ten children (4%) had hyperuricosuria, and 27 (11%) had nephrolithiasis. To better characterize the IH into renal (RH) or absorptive hypercalciuria (AH) subtypes, 45 of the 67 children (ranging age from six to twelve years) were further submitted to an oral calcium load test. Eighteen patients (40%) had AH, 7 (15.5%) RH and 20 (44.4%) could not be classified as having AH or RH [indeterminant (ID) idiopathic hypercalciuria group]. Intravenous pyelography or ultrasound were normal in all children. The oral calcium load test may be useful in characterizing the subtype of IH in some children; however, a great number of the IH children were characterized as indeterminant. Also hyperuricosuria, recently described as another metabolic disturbance associated with hematuria, may be an important cause of recurrent hematuria in children.

Adolescent↗
PubMed1991

Nephrotoxicity of cyclosporine: the role of platelet-activating factor and thromboxane.

Cyclosporine (CsA), an immunosuppressive agent, is potentially nephrotoxic. We had previously observed that acute administration of CsA to Munich-Wistar rats induced a decrease in single nephron glomerular filtration rate, due to a decline in glomerular plasma flow, and in the glomerular ultrafiltration coefficient. Moreover, these alterations were prevented when an antagonist of platelet-activating factor (PAF) was administered. In the present study we examined whether the protective effect of the PAF blocker in CsA nephrotoxicity could have been mediated by thromboxane (TxA2). Our data show that the PAF effects were not mediated by TxA2, since administration of dazmegrel, a thromboxane synthetase inhibitor, did not ameliorate the acute renal failure caused by CsA. Thus, PAF appears to be a direct mediator of acute CsA nephrotoxicity, while TxA2 is not significantly involved in this process.

Animals↗
PubMed1991

Effect of platelet-activating factor antagonist BN 52063 on the nephrotoxicity of cisplatin.

Cisplatin (DDP) is an effective anticancer agent that has been successfully applied against various solid tumors. However, DDP commonly causes nephrotoxicity. We observed that DDP led to significant alterations in renal microcirculation when administered to Munich-Wistar rats, with a concomitant decrease in single nephron glomerular filtration rate due to reduction in glomerular plasma flow and transcapillary hydraulic pressure difference. BN 52063, a platelet-activating factor antagonist, caused a striking change in acute renal failure induced by DDP leading toward normalization of all parameters of renal function. The results suggest that BN 52063 could be used as a novel drug to control DDP nephrotoxicity.

Animals↗
PubMed1991

Role of platelet activating factor in gentamicin and cisplatin nephrotoxicity.

The present study was undertaken to evaluate the effects of platelet activating factor (PAF) antagonists on nephrotoxicity induced by gentamicin (GENTA) and cisplatin (DDP) in rats. PAF infusion provoked a 56% decline in single nephron (SN) GFR due to a decrease in glomerular plasma flow (QA, 55%), glomerular transcapillary hydraulic pressure (delta P, 13%), and glomerular ultrafiltration coefficient (Kf, 37%). Four days after a single dose of DDP (6 mg/kg, i.p.) we observed non-oliguric acute renal failure (ARF) with reduced SNGFR (45%), QA (46%) and delta P (10%) and unchanged Kf. GENTA administration for 10 days (40 mg/kg, i.p. daily) induced a decline in SNGFR (40%), QA (41%) and Kf (41%). Chronic treatment with a GENTA + PAF antagonist (BN 52021) partially prevented the decline in SNGFR (22%) by an amelioration in QA (25%) and Kf (13%). However, simultaneous treatment with DDP and BN 52063 completely prevented the ARF induced by DDP, normalizing all parameters of renal function. Thus, PAF may be a potential mediator involved in the nephrotoxicity induced by GENTA and DDP.

Acute Kidney Injury↗
PubMed1991

Evaluation of acute administration of natural products with potential diuretic effects, in humans.

In order to evaluate the potential diuretic effect of two natural products, Elephantopus scaber and Alpinia speciosa, a trial administration was carried out in ten healthy volunteers and the effects compared to the those of a placebo. The substances were given on different days, with a seven day interval between doses. The amount of substance administered to the subjects was five times the usual dose i.e. 7.5 g/100 ml and 0.8 g/100 ml respectively. The following parameters were measured: urinary and plasma sodium, potassium, uric acid, calcium, phosphate, urea, creatinine. The subjects were also examined clinically and total urinary volume was assessed. The only significant findings (p < 0.05) was a slight diuresis with Alpinia speciosa, which also lowered the diastolic (p < 0.05) and systolic (p < 0.01) blood pressures. No effect on electrolytes or renal function parameters was observed, and this probably excludes any renal tubular or glomerular effect from these substances.

Adult↗
PubMed1991

Metabolic factors for urolithiasis in acromegalic patients.

1. Acromegaly is associated with metabolic disturbances of calcium and phosphorus which can also contribute to renal lithogenesis. 2. In order to characterize these disturbances more precisely, an oral calcium load test was performed on 14 active acromegalic patients. Serum and urinary levels of calcium, phosphorus, uric acid, creatinine and urinary cyclic AMP were determined. 3. Of the 14 patients, 5 (36%) presented hypercalciuria, 5 (36%) presented intestinal calcium hyperabsorption, and 6 (43%) had uric acid hyperexcretion. Two patients (14%) presented nephrolithiasis. 4. The medical records of 32 additional acromegalic patients with or without active disease were reviewed for a history of previous stones, which was observed in three cases (9.5%). 5. The present data suggest that nephrolithiasis occurs more frequently among acromegalic patients because of the underlying metabolic disturbances of calcium presented by this population.

Acromegaly↗
PubMed1990

Effects of systemic hypertension, antidiuretic hormone, and prostaglandins on remnant nephrons.

Renal function was evaluated in normal and after 30 days of 5/6 renal mass reduction (CRF) in Munich-Wistar (MW) rats, spontaneously hypertensive rats with superficial glomeruli (EPM), and in Brattleboro rats with congenital diabetes insipidus (DI). Mean arterial pressure was higher in EPM-Control and EPM-CRF rats as compared with MW and DI rats. MW and EPM rats with CRF showed increases of 120% and 196%, respectively, in single nephron glomerular filtration rate as compared with their controls. However, DI rats with CRF did not show any increase in single nephron glomerular filtration rate as compared with the control group. Therefore, the data suggest that the presence of hypertension enhances the adaptive mechanisms on remnant kidney's function. Conversely, in the absence of antidiuretic hormone, adaptive mechanisms of remnant nephrons did not occur. In addition, it was observed that rats with CRF submitted to prostaglandin blockade with indomethacin showed for MW rats a 55% and 20% reduction in ultrafiltration coefficient and in single nephron glomerular filtration rate, respectively. Decreases of 60% and 30% in ultrafiltration coefficient and single nephron glomerular filtration rate, respectively, were observed for EPM rats. In contrast, DI rats did not show any alteration on renal function after indomethacin. It seems, therefore, that prostaglandins play a role in remnant nephron function of MW and EPM rats, but in the absence of antidiuretic hormone, prostaglandins do not affect remnant glomerular hemodynamics.

Animals↗
PubMed1990

[The occurrence of abortion in inpatients at urban center hospitals of the state of São Paulo, Brazil].

Certain characteristics--biological, demographical, social and institutional--based on data collected from the recorded case histories of 2,588 women suffering complications after abortion, attended in a hospital of Santo André, an industrial urban area of Greater S. Paulo, State of S. Paulo, Brazil, in the period from January 1978 to December 1982, are identified Data show a two-fold increase in the number of women with complications after abortion over the period studied, rising progressively from 302 in 1978, to 672 in 1982. However, the number of births attended at the same hospital underwent an increase of only 14% in the same period, resulting in an average abortion/birth ratio of 1:3.6 and 1:1.8 in 1978 and 1982, respectively. The majority of the population under study (60%) professed non-skilled occupations. Age presented a statistically significant relationship with martial status, colour, profession and gestational results. A significant relationship was also observed between age at first menstruation, age at first sexual relationship and age at first pregnancy among those women belonging to the primigesta group.

Abortion, Induced↗
PubMed1990

[Adolescence and contraception: 1. A study knowledge and use among women hospitalized for childbirth or abortion].

A study of the knowledge and utilization of contraceptive methods by adolescent is presented. An analysis was carried out based on data collected from interviews with and recorded case histories of 78 puerperal adolescents (childbirth or abortion), assisted by an obstetric service in the county of Cotia, SP, Brazil, between May 1 and July 31, 1986. Of all the adolescents studied, 61.5% had some knowledge of contraceptive methods; the findings showed that such knowledge was influenced by factors such as: age, school background, parity and marital status. The main sources of information on contraception were: friends, relatives and partners, in this order; those least sought for in this regard were health professionals. Only one in each ten adolescents made use of some contraceptive measure, the most prevalent methods being the contraceptive pill, the Ogino-Knauss method, condoms and coitus interruptus. In all of the cases of the utilization of these methods the same had been "recommended" by persons belonging to the adolescents' social group, and had been acquired in shops, without any health control.

Adolescent↗
PubMed1989

Renal function and glomerular hemodynamics in male endotoxemic rats.

The renal effects of a single intravenous dose of two different E. coli lipopolysaccharides (LPS 0111:B4 and LPS 0127:B8), at the same dose of 100 micrograms/kg, were evaluated in euvolemic Munich-Wistar (MW) rats by whole kidney clearance techniques and micropuncture studies. Following LPS infusion, a significant decrease (8%) in mean BP was observed only in the LPS 0127:B8 treated group. Inulin clearance fell 57% (LPS 0111:B4), P less than 0.01, and 38% (LPS 0127:B8), P less than 0.01. Para-aminohippuric (PAH) clearance decreased 31% (P less than 0.01) and total effective renal vascular resistance rose 70% (P less than 0.03) in response to LPS 0111:B4. No significant change in PAH clearance was noted in the LPS 0127:B8 group. Superficial single nephron glomerular filtration rate (SNGFR) was reduced 69% (LPS 0111:B4), P less than 0.03, and 33% (LPS 0127:B8), P less than 0.02. Superficial glomerular plasma flow fell 48% (LPS 0111:B4), P less than 0.03, and 24% (LPS 0127:B8), P less than 0.03. Both lipopolysaccharides were associated with an increase in afferent arteriolar resistance (RA) which accounted for a reduction in the glomerular capillary hydraulic pressure (PGC). There was no change in the proximal tubular pressure in either group and, therefore, the net transcapillary hydraulic pressures were reduced. No measurable change in the ultrafiltration coefficient. Kf, was observed in either group. In a second set of protocols, the effect of prior administration of indomethacin or captopril on LPS 0111:B4 action was investigated. A significant decrease in BP occurred when animals were pretreated with captopril. Both indomethacin and captopril prevented the renal effects of LPS 0111:B4.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1989

Urinary excretion of glycosaminoglycans in normal and stone forming subjects.

There is evidence suggesting that glycosaminoglycans (GAG) are potent inhibitors of growth and aggregation of calcium oxalate crystals in vitro. This finding raises the possibility that the urinary GAG could play an inhibitory role in the urolithiasis. To investigate this hypothesis, a study on the urinary excretion of GAG in normal and stone forming adults and children was undertaken. Different methods were compared, and the best results were obtained when the GAG were measured by densitometry after agarose gel electrophoresis. Although the GAG concentration was increased in the morning urine compared to the 24-hour urine samples, and in males compared to females, the GAG/creatinine ratio was independent of period of urine collection and of sex. So, it was advantageous to express the amounts of urinary GAG as mg/g of creatinine. Children excreted more GAG than adults, with a higher proportion of chondroitin sulfate. We have shown that the stone forming subjects, both adults and children, excreted lower levels of urinary GAG as compared to normal subjects, independently of the metabolic disorder. The proportions between chondroitin sulfate and heparan sulfate and the structures of these GAG were unaltered in the stone formers. These results indicate that there is a definite difference in terms of levels of GAG between normal and stone forming urines, and suggest a correlation between the urinary GAG concentration and urolithiasis.

Adult↗
PubMed1989

Effect of platelet-activating factor antagonist on cyclosporine nephrotoxicity. Glomerular hemodynamics evaluation.

In order to evaluate the effect of platelet-activating factor (PAF) antagonist BN 52021 (5 mg/kg i.v.) on cyclosporine (50 mg/kg i.v.) nephrotoxicity, euvolemic Munich-Wistar rats were submitted to micropuncture studies. BN 52021 alone did not change the total (1.08 +/- 0.07 vs. 1.04 +/- 0.06 ml/min) or single nephron (SN) (29.1 +/- 50 vs. 31.3 +/- 4.0 nl/min) and glomerular filtration rate. The CsA administration caused a decline on GFR (0.47 +/- 0.07 vs. 0.96 +/- 0.04 ml/min, P less than 0.05) and on SNGFR (14.0 +/- 3.5 vs. 27.9 +/- 3.4 ml/min, P less than 0.05). An increase in afferent (RA) and efferent (RE) arteriolar resistances, 180% and 360%, respectively, that caused a decrease on glomerular plasma flow rate (QA) from 100.99 +/- 17.09 to 44.37 +/- 13.37 nl/min (P less than 0.05) was observed. Moreover, the glomerular ultrafiltration coefficient (Kf) declined by 70% (0.096 +/- 0.003 to 0.031 +/- 0.10 ml/sec mmHg, P less than 0.05). The previous BN 52021 administration on rats treated with CsA blunted its effects on superficial nephrons. The SNGFR (22.3 +/- 3.0 vs. 28.0 +/- 25 nl/min), QA (72.2 +/- 5.9 vs. 91.7 +/- 12.1 nl/min) and KF (0.038 +/- 0.009 vs. 0.048 +/- 0.005 nl/s mmHg) remained unaltered. By contrast, the total renal function was not prevented by BN 52021 treatment: GFR 0.45 +/- 0.12 vs. 0.94 +/- 0.05 ml/min (P less than 0.05). Thus, this study suggests that PAF may participate in CsA nephrotoxicity. Furthermore, the protective effect of BN 52021 on superficial nephrons may indicate that BN 52021 is a drug that can minimize the impairment of renal function induced by CsA.

Animals↗
PubMed1989

Effect of cisplatin on glomerular hemodynamics.

1. The effects of cisplatin on renal microcirculation were evaluated in euvolemic Munich-Wistar rats submitted to micropuncture. Nine rats received a single dose of cisplatin (6 mg/kg, ip), and 6 control rats received the same volume (0.3 ml) of 150 mM NaCl 4 days before the measurements. 2. Cisplatin administration induced non-oliguric acute renal failure by decreasing glomerular filtration rate (GFR) from 0.96 +/- 0.05 to 0.33 +/- 0.04 ml/min (P less than 0.05) and by increasing urinary volume from 3.3 +/- 0.3 to 12.4 +/- 2.2 microliters/min (P less than 0.05). 3. Cisplatin administration decreased single nephron GFR from 34.2 +/- 2.1 to 20.1 +/- 2.3 nl/min (P less than 0.05) due to a reduction in both glomerular plasma flow from 106 +/- 9 to 61 +/- 6 nl/min (P less than 0.05) and transcapillary hydraulic pressure difference from 31 +/- 1 to 27 +/- 1 mmHg (P less than 0.05). An increase in arteriolar resistances, mainly afferent arteriolar resistance from 2.5 +/- 0.2 to 4.7 +/- 0.5 x 10(10) dyn.s.cm-5 (P less than 0.05), was observed. The glomerular ultrafiltration coefficient was unchanged.

Animals↗
PubMed1989

[Pregnancy in adolescents: a comparative study].

A population of 349 women who gave birth, in an Obstetric Clinic in Greater S. Paulo, Brazil, during the period from 01/05/86 to 31/07/86 were studied. The results show that the group of pregnant adolescents (22.2%) received inadequate prenatal assistance, as the large majority of them (70.6%) started consultations during the second trimester of their pregnancy, and had an average of two consultations. During pregnancy this group presented a lower incidence of pathological disorders leading to out-patient and hospital treatment (39.3% and 7.9%, respectively) than did the adult pregnant women (44.4% and 14.7%, respectively). With regard to the type of delivery, the adolescents underwent a larger proportion of surgical deliveries, 25.7% of forceps births and 22.9% of cesarean sections, as compared with 14.7% and 19.7%, respectively, for the adult pregnant women. A larger proportion of intra-parturition intercurrencies was registered for the pregnant adolescents (12.9%, as against 8.2% for the adult pregnant women), hemorrhage and toxemia being the most important. During the puerperium there were complications in 15.7% of the pregnant adolescents and 11.8% of the adults post partum anemia, toxemia and puerperal infection being the commonest disorders.

Adolescent↗
PubMed1987

Glomerular hemodynamics and hormonal participation on cyclosporine nephrotoxicity.

The mechanism of cyclosporine A (CyA) nephrotoxicity is unclear. In order to evaluate renal microcirculation seven euvolemic Munich-Wistar (MW) rats were studied after acute CyA treatment (50 mg/kg, i.v.). Both total glomerular filtration rate (GFR, 0.96 +/- 0.04 vs. 0.47 +/- 0.07 ml/min) and single nephron GFR (27.90 +/- 3.39 vs. 14.02 +/- 3.49 nl/min) declined significantly (P less than 0.001). It was observed an increase in afferent (RA, increases 188%) and efferent (RE, increases 360%) arteriolar resistances that caused a decrease on glomerular plasma flow rate (QA) from 100.99 +/- 17.09 to 44.37 +/- 13.37 nl/min (P less than 0.001). Mean glomerular capillary hydraulic pressure (PGC) increased from 45 +/- 1 to 55 +/- 4 mm Hg (P less than 0.05) and the glomerular ultrafiltration coefficient (Kf) decreased by 70% (0.096 +/- 0.030 to 0.031 +/- 0.010 nl/sec X mm Hg, P less than 0.05). Additionally, in order to study hormonal participation in this nephrotoxicity, other three groups of MW rats were previously treated with captopril (2 mg/kg, i.v.), verapamil (20 micrograms/kg/min, i.v.) or indomethacin (2 mg/kg, i.v.). Both captopril and verapamil minimized the renal effects of CyA, with a decline of approximately 25% instead of approximately 50% on GFR and RPF. Moreover, two groups of Brattleboro rats were studied. Acute CyA administration in homozygote Brattleboro rats produced a decline of only approximately 22% and approximately 31%, respectively, in GFR and renal plasma flow (RPF), when compared with MW rats (P less than 0.05). Similar results were observed in heterozygote Brattleboro rats when compared with MW rats, disclosing differences due to a different strain of rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Effects of cyclosporin on renal microcirculation.

To evaluate renal microcirculation during acute cyclosporin (CsA) administration (50 mg/kg, i.v.), seven euvolaemic Munich-Wistar rats were studied. CsA infusion caused a significant decrease in total glomerular filtration rate (GFR) (0.96 +/- 0.04 vs 0.47 +/- 0.07 ml/min) and in single-nephron GFR (SNGFR) (27.90 +/- 3.4 vs 14.02 +/- 3.5 nl/min). The efferent arteriolar resistance increased substantially (P less than 0.05) while the afferent resistance rose moderately. Consequently, there was an increase (P less than 0.05) in mean glomerular capillary hydraulic pressure (PGC), from 45 +/- 1 to 55 +/- 4 mmHg, together with an important decrease in mean glomerular plasma flow rate (QA), from 100 +/- 17 to 44 +/- 13 nl/min. Since tubular hydraulic pressure was maintained unaltered, an elevated transglomerular hydraulic pressure difference was observed (P less than 0.05). The lower values of SNGFR were accounted for by both the decrease in QA and in the glomerular ultrafiltration coefficient (Kf). The latter was reduced from 0.096 +/- 0.03 to 0.031 +/- 0.010 nl/sec per mmHg (P less than 0.05) by CsA. Additionally, three groups of Munich-Wistar rats were previously treated with captopril (2 mg/kg per h, i.v.), verapamil (20 micrograms/kg per min, i.v.) or indomethacin (2 mg/kg, i.v.). Both captopril and verapamil minimised the renal effects of CsA, with a decline of approximately 25% instead of approximately 50% on GFR and RPF. Thus CsA infusion caused a decline on SNGFR due to an important reduction in QA and Kf with an impressive increase on arteriolar resistance, a mark of angiotensin II stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗