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Biomedical subjects

R Hahn

Publications and source records attributed to R Hahn.

At least 109 records · Page 6Linked to original sources
PubMed1983

Analysis of cardiovascular risk factors in chronic hemodialysis patients with special attention to the hyperlipoproteinemias.

A group of 252 chronic hemodialysis patients was examined for various risk factors. Special emphasis was placed upon the comparison of patients who had marked cardiovascular alterations with the remainder of the group. The seriousness of the risk factors was determine by hypertension and hyperlipoproteinemia, 78% of the patients received antihypertensive medication or had changes in the fundus of the eye or both. In 74% of the patients there were pathological changes in the plasma lipids or lipoproteins or both. Hypertriglyceridemia (49%) and a HDL cholesterol decrease (61%) were the most striking findings. The average VLDL cholesterol value was significantly higher and the HDL cholesterol significantly lower in the coronary heart disease group than in the remaining group. These results show that hyperlipoproteinemia and a decrease in HDL, together with other risk factors such as hypertension and anemia, play an important role in the accelerated development of atherosclerosis in a hemodialysis group.

Age Factors↗
PubMed1983

Does atherosclerosis caused by dialysis limit this treatment?

A retrospective study of 332 dialysis patients (observation period up to 17 years) demonstrated that cardiovascular and cerebrovascular death rates due to atherosclerosis did not increase with length of time on dialysis. Data analysis showed that cardiovascular and cerebrovascular morbidity and mortality during dialysis is primarily caused by high blood pressure existing prior to commencement of dialysis and an unfavourable very low-density lipoprotein/high-density lipoprotein (VLDL/HDL) cholesterol quotient at the beginning of dialysis treatment. The treatment of the patient before acceptance onto dialysis seems therefore to be the determining factor in the prognosis on dialysis.

Adult↗
PubMed1982

Combination chemotherapy for advanced endometrial cancer. An evaluation of three regimens.

In patients with advanced uterine corpus carcinoma treated with the combination chemotherapy of megestrol, cyclophosphamide, and doxorubicin (MCA) or with this combination and 5-fluorouracil (MCAF), the overall response rate was 22%. There was no significant difference in response rates between the two regimens. There is some indication that survival was longer in ambulatory patients who were treated with MCA, but this combination produced more hematologic toxicity than MCAF. Patients unsuitable for treatment with doxorubicin received megestrol, 1-phenylalanine mustard, and 5-fluorouracil (MLF), which produced objective responses in 2 of 12 patients.

Antineoplastic Agents↗
PubMed1981

[Increased cardiovascular arteriosclerosis risk in patients with analgesic nephropathy (author's transl)].

The retrospective investigation of 54 patients with analgesic nephropathy showed the relatively early occurrence of coronary sclerosis and an increased frequency of arteriosclerotic renal artery stenosis. Angina pectoris was found in 14 patients with a mean age of 48 1/2 years. Summation of risk factors is the probable cause of the tendency for arteriosclerosis: hypercholesterolaemia and hypertriglyceridaemia was found in 29 patients, arterial hypertension in 42 patients, which was so severe in half of the patients that combined treatment with two or more drugs was necessary. The causes of lipid metabolism disturbances as well as the pathogenesis of arterial hypertension are not known. Arteriosclerotic renal artery stenoses observed in 8 patients are not likely to be the cause of hypertension.

Adult↗
PubMed1980

Sequential CT scan as a parameter in the management of CNS lesions.

The value of sequential CT scans as a management determinant in various types of CNS lesions is described. Case reports are cited in support of such a contention. The prediction is that in the not too distant future, intraoperative CT scans will be as commonly done as the plain radiographs currently employed.

Adolescent↗
PubMed1979

Activation of glutaminase by phosphoribosyl-pyrophosphate and its interference with the assay of phosphoribosylpyrophosphate amidotransferase.

Phosphate-dependent glutaminase (L-glutamine amidohydrolase, EC 3.5.1.2) from rat liver was found to be strongly activated by phosphoribosylpyrophosphate (P-rib-PP), the substrate of amidophosphoribosyltransferase (EC 2.4.2.14). Since the assay of the latter is based on the P-rib-PP-dependent conversion of glutamine to glutamate, the amidotransferase activities determined in crude tissue preparations were found to be too high. The interference of glutaminase, however, could be completely eliminated by its inactivation at 50 degrees C. Amidotransferase was not affected by the heat treatment. Because of the increased rate of the glutamate formation at this temperature, the incubation time of the assay could be significantly reduced.

Amidophosphoribosyltransferase↗
PubMed1978

The fate of extracellular glutathione in the rat.

When intravenously administered to rats, [U-14C]glycine-labelled GSSG, GSH and its analogue ophthalmic acid were rapidly removed from the blood. In perfusion studies with isolated liver, however, the compounds did not enter the liver tissue. Thus, uptake by this tissue is obviously not responsible for the removal of gamma-glutamyl tripeptides from the blood. Instead, rapid hydrolysis of the tripeptides was observed. The undegraded tripeptides were only detected in the blood immediately after administration. Within tissue the degradation product glycine accounted for all the radioactivity. After intravenous injection of the labelled tripeptides the radioactivity accumulated first in the kidney, as shown by autoradiographic studies and chemical analysis of different tissues. The hydrolysis of the gamma-glutamyl tripeptides decreased markedly after the renal arteries were clamped. These observations strongly suggest that renal tissue is the principal site of the degradation of the tripeptides. Inhibition studies and experiments with isolated renal tubules revealed that gamma-glutamyl transpeptidase catalyses the fast hydrolysis of the extracellular peptides. The results indicate that, when entering the extracellular space, glutathione and its analogues are completely hydrolysed and must be resynthesized after reuptake of the constituent amino acids. It is concluded that the degradation occurs mainly on the luminal surface of the renal brush-border membrane and that gamma-glutamyl transpeptidase is a glutathionase acting on extracellular glutathione.

Animals↗
PubMed1978

Relation between myelin sheath thickness and axon size in spinal cord white matter of some vertebrate species.

The relation between number of myelin lamellae and axon size in the CNS was examined by electron microscopy of spinal cord white matter fibres in different vertebrate species (cat, rabbit, guinea pig, rat, mouse, frog and perch). The results show that the number of myelin lamellae increases with increasing axon size in a non-linear fashion. Below an axon size of 4--5 micron the relation follows a fairly straight line but above this size rectilinearity is lost. The mouse and the frog differ from the pattern shared by the other animals. In the mouse the lamellar number increases more slowly with axon size and the relation is close to linear. In the frog the number of lamellae increases very slowly with axon size and the relation is markedly curvilinear. Measurements of the myelin repeating period show that in the mammals and the frog the average period of thick sheaths is about 85% of that in thin sheaths, in accordance with previous findings in the cat. In the perch a clearcut difference in this respect between thick and thin sheaths is not found. Calculations of the g-ratio on the basis of the findings indicate that it increases with increasing fibre size. This is most pronounced in the perch and the frog in which the g-ratio for the largest fibres far exceeds the functionally optimal value defined in theoretical analyses on impulse propagation.

Animals↗
PubMed1976

On the role of gamma-glutamyltransferase in renal tubular amino acid reabsorption.

The degradation of glutathione in the kidney of the rat was investigated in vivo and in vitro. When radioactive glutathione or its analogue ophthalmic acid was administered intravenously to mice or rats, the tripeptides were rapidly and completely degraded. Within the organs, no radioactive glutathione, but only labelled glycine was found. The main part of the degrading activity was localized in the kidney. Kidney homogenate degraded glutathione at a rate of 46.5 nmoles/min per mg of protein. This could be inhibited by the gamma-glutamyltransferase inhibitor serine-borate. Isolated renal tubules degraded the tripeptide at a rate of 18 nmoles/min/mg; this reaction was also inhibited by serine-borate. The whole activity was found in the particulate fraction (100000 xg). Glycine and gamma-glutamylglycine were identified as the radio-active products. The results indicate that gamma-glutamyltransferase is able to split glutathione extracellularly in the lumen of the tubule at a very high rate. It is concluded that the enzyme faces the luminal side of the brush border membrane with respect to its substrate gluthathione. This seems to be incompatible with a basic topological prerequisite for the in vivo function of the gamma-glutamyl cycle in renal tubular amino acid reabsorption.

Animals↗