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Biomedical subjects

E Ritz

Publications and source records attributed to E Ritz.

At least 793 records · Page 44Linked to original sources
PubMed1983

Effect of 1,25-dihydroxycholecalciferol on sarcoplasmic reticulum calcium transport in strontium-fed chicks.

Feeding of chicks with strontium, an inhibitor of 1,25-dihydroxycholecalciferol synthesis in kidney, during 7 days, significantly depressed the initial rate of calcium uptake and calcium storing capacity of sarcoplasmic reticulum membranes from skeletal muscle. Oral administration of 1,25(OH)2D3 to strontium-fed animals returned calcium transport values to normal. The changes observed could not be related to differences in the relative proportions of transport ATPase and calcium binding proteins. The results are consistent with a role of 1,25(OH)2D3 in muscle function.

Animals↗
PubMed1983

Reversal of decreased phosphorylation of sarcoplasmic reticulum calcium transport ATPase by 1,25-dihydroxycholecalciferol in experimental uremia.

When compared to that from sham-operated controls, sarcoplasmic reticulum isolated from skeletal muscle of uremic rabbits had a lower rate of calcium uptake and storing capacity. In vivo administration of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] restored the values in uremic animals toward normal. To obtain information about the mechanisms responsible for these differences, phosphorylation of the calcium transport ATPase was studied. The steady-state levels of phosphoprotein in uremic membranes were lower and returned to normal when the secosteroid was administered. Electrophoresis of the membranes phosphorylated with 32P-inosine triphosphate (32P-ITP) showed that the differences were related to a 100,000 dalton protein. The rate of phosphoprotein formation, determined with 32P-ITP and at 0 degrees C, was considerably lower in uremic than in control animals. Pretreatment with 1,25(OH)2D3 prevented this change. The hypothesis is advanced that the vitamin D metabolite affects the steady-state concentration and rate constant of formation of active sites in the Ca-ATPase. These results may partly explain the altered Ca transport function of the sarcoplasmic reticulum in experimental uremia.

Animals↗
PubMed1983

Does low urinary sIgA predispose to urinary tract infection?

Median urinary secretory IgA (sIgA) (ELISA technique in unprocessed urine) was 1.36 mg/liter (range, 0.29 to 2.31) in healthy female controls at various times of the menstrual cycle. It was significantly lower in women with urinary tract infection (UTI) without antibody-coated bacteria. Such decrease was found both in women with acute UTI episodes (median, 0.16; range, 0.06 to 1.71) and in asymptomatic nonbacteriuric women with a history of UTI (median, 0.52; range, 0.05 to 2.13). In the latter women, sIgA in nasal secretions tended to be low, but salivary sIgA was unchanged. Urinary sIgA was elevated significantly in individuals with nephrostomy and antibody-coated bacteria (14.4 mg/liter, range, 3.6 to 20). The study showed that locally synthesized sIgA immunoglobulins were low in the urine of individuals with recurrent UTI independent of the presence or absence of bacteriuria at the time of the study. UTI per se did not interfere with sIgA secretion as shown by high sIgA in patients with upper UTI. Low urinary sIgA may represent one factor predisposing to recurrent UTI.

Adolescent↗
PubMed1983

Glycogen metabolism in phosphorus-depleted rats.

Glycogen content as well as the enzymes of glycogenolysis and glycogen synthesis were examined in myocardium, skeletal muscle, liver and kidneys of rats with dietary phosphorus deprivation. Myocardial glycogen content was decreased and this was accompanied by activation of the enzymes of glycogenolysis and inhibition of the enzymes of glycogen synthesis. Beta blockade (nadolol) abolished the effect of phosphorus depletion (PD) on myocardial glycogen metabolism, documenting that the effect of PD is mediated, at least in part, by increased sympathetic activity. Furthermore, administration of insulin caused a marked increase of glycogen content in the heart of both control and phosphorus-depleted (PD) animals. There was no change of glycogen content or the activities of enzymes of glycogen metabolism in skeletal muscle or kidney, but a decrease of glycogen content of the liver was observed in PD animals.

Adrenergic beta-Antagonists↗
PubMed1983

Altered beta-receptor responsiveness in uraemic rats.

Beta-receptor responsiveness was evaluated in 24-hour nephrectomised rats. Heart rate responses following intravenous isoproterenol injections into conscious uraemic (n = 9) and sham operated controls (n = 7) were measured. These preliminary results indicate that heart rate at rest and after blockade of the autonomic nervous system was slower in uraemic rats. Blood pressure before and after autonomic blockade was not different between groups, Maximal heart rate increase following intravenous isoproterenol was significantly less pronounced in uraemic than 0.05). The blood pressure decreasing effect of intravenous isoproterenol was enhanced in the nephrectomised group (p less than 0.01).

Animals↗
PubMed1983

Non-A, non-B hepatitis in hemodialysis.

Episodes of presumable non-A, non-B hepatitis were determined among hemodialysis patients during a two year period as well as possible secondary infections in household contacts. We determined hepatitis A and B markers by commercial RIA kits, and IgM-anti-CMV and IgM-anti-EBV by ELISA techniques. 154 dialysis patients, 118 relatives of patients, and 42 members of the staff were included in the study. 71% of the center dialysis patients, 63% of the home dialysis patients, 50% of the staff, and 19% of the relatives were HBV marker positive. Spouses of patients more often had HBV markers than other relatives. Anti-HAV was highly prevalent both in center patients (98.8%) and in home dialysis patients (83.3%). The incidence of IgM-anti-CMV was marked in home dialysis patients (15.5%). During a two year period, 9% of all dialysis patients had an episode of presumable non-A, non-B hepatitis. As compared to previous data in the same dialysis centers, there is a change in the epidemiology of hepatitis.

Adult↗
PubMed1983

New beta-lactam antibiotics and hemorrhagic diathesis: comparison of moxalactam and cefotaxime.

Two new beta-lactam antibiotics, moxalactam and cefotaxime, were administered to two groups of patients with clinical indications for cephalosporin therapy and bacteriologically confirmed infection. The ten patients receiving moxalactam included five patients with impaired renal function; the ten receiving cefotaxime included seven with impaired renal function (serum creatinine greater than 1.3 mg/dl). Antibiotics were administered for seven days in dosages adjusted to the level of renal function. Serum trough levels, measured by microbiological assay, were within the therapeutic range: moxalactam median, 3 micrograms/ml (range, 0.6-20 micrograms/ml) and cefotaxime median, 2.9 micrograms/ml (range, 0.5-16 micrograms/ml).

Adolescent↗
PubMed1983

Clinical and serological features of mesangial IgA glomerulonephritis.

IgA-glomerulonephritis (IgA-GN) accounts for approximately 20 per cent of all glomerulonephritis in our unit. Seventeen out of 50 patients with IgA-GN developed renal failure, which appeared in 11 out of 17 over the course of a mean follow-up of 68 months. Haemodialysis was required in three patients. Twenty-two out of 50 patients had hypertension, five with malignant hypertension. Perivascular IgA deposits were found in skin biopsies of 29 per cent of patients with IgA-GN and also in 19 per cent of patients with other GN, but not in healthy controls. Mucosal (salivary and nasal) secretory IgA concentrations were normal. In cutaneous and glomerular IgA/IgM deposits, IgA1 was demonstrated using monoclonal antibodies. No excess of HLA-A, B or DR antigens and no relation of clinical course and HLA-Bw35 were found.

Adolescent↗
PubMed1983

Skeletal growth in experimental uremia.

Although in recent years experimental work on growth in uremia has clarified many issues, many key questions cannot be answered with available experimental data. In our own studies on subtotally nephrectomized rats, uremic animals consumed less food and grew less. However, although low energy intake diminishes growth, it has not been established that high protein energy intake will normalize growth. We showed that uremia reduced growth (and net protein synthesis) even under conditions of controlled food intake. In renal failure the optimal dietary protein level for growth or for efficiency of utilization has not been established, particularly since protein intake has an independent injurious effect on long-term renal function. Calcium and vitamin D supplements improved growth in uremic rats, but the data cannot easily be extrapolated to humans. The growth-promoting action of 1,25(OH)2D3 was not superior to that of equipotent doses of vitamin D3. Correction of anemia and physical exercise did not improve growth. Diminished stimulation of growth cartilage cyclic AMP with PTH and augmented stimulation with calcitonin was noted in uremic animals. Growth hormone in supraphysiological doses improved growth and raised IGF carrier protein in uremic animals. Spermine, a potential uremic toxin, inhibited growth cartilage 3H-thymidine incorporation, but only in concentrations higher than that encountered in uremia.

Animals↗
PubMed1983

Cardiac function in experimental uremia.

In acutely uremic animals, the contractile force of the heart is consistently increased; such an increase can be dissociated from changes of afterload or catecholaminergic drive. It is associated with diminished sarcolemmal Na,K-ATPase activity in the heart which, in turn, may be related to increased levels of endogenous digitalis-like substances (endigens) that have been postulated to represent a natriuretic factor. In patients with chronic uremia, myocardial contractility is usually normal, but occasionally there may be heart failure unrelated to pre-existing hypertension, coronary heart disease, anemia, fluid overload, or other recognizable factors. So far, the experimental basis for this clinical observation is uncertain. Possible causes for the clinical syndrome include an excess of parathyroid hormone or cardiodepressor substances. There is experimental evidence of impaired cardiac response to beta adrenergic agonists, e.g., decreased isoproterenol-dependent calcium uptake, diminished inotropic and chronotropic responses. In acutely uremic rats, cardiac cyclic AMP levels are high but can be reversed by beta blockers. Heart calcium content is variable and heart weight is constantly increased in acutely uremic rats, despite decreased skeletal muscle mass. The change in heart weight is not related to anemia, to an excess of parathyroid hormone, or to sympathetic activity; its cause remains unknown. Experimental studies to date have shown a variety of abnormalities, but do not provide a uniform concept of the mechanisms or an explanation for the cardiac dysfunction so often observed in patients with uremia.

Animals↗
PubMed1983

Effect of vaccination schedule and dialysis on hepatitis B vaccination response in uraemic patients.

Antibody response to vaccination with hepatitis B vaccine (HB-Vax) was evaluated in 43 staff, 81 dialysis patients and 12 non-dialysed uraemic patients. We confirmed less frequent seroconversion and lower concentration of antibody to hepatitis B surface antigen (anti-HBs) in dialysis patients despite a higher dose (40 micrograms vaccine). However, more frequent vaccination (5 times vs 3) increased anti-HBs concentration to almost normal. Concomitant administration of hepatitis B immunoglobulin (HBIG) and hepatitis B vaccine (passive/active) did not interfere with vaccination success. Antibody response was equally poor in dialysed non-dialysed uraemic patients.

Adult↗
PubMed1983

Different effects of oral glycine and methionine on urinary lithogenic substances.

Nine male healthy volunteers were examined during a control period, during an oral glycine load (45 g/day, 600 mmol) and oral methionine (6 g/day, 40 mmol). Glycine caused a significant increase of urinary oxalate above baseline (from 644 to 797 mumol/day) without change in calciuria (4.74 vs 4.84 mmol/day). In contrast methionine caused no change of oxaluria, but a significant increase in calciuria (from 4.74 to 6.9 mmol/day). Alterations of lithogenic ions in urine after protein ingestion are mediated by different amino acids. The particular lithogenic risk of animal protein may be related to its high methionine/cystine and glycine content.

Adult↗