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Biomedical subjects

R Menzel

Publications and source records attributed to R Menzel.

At least 37 records · Page 2Linked to original sources
PubMed1985

Serum magnesium in insulin-dependent diabetics and healthy subjects in relation to insulin secretion and glycemia during glucose-glucagon test.

UNLABELLED: In order to investigate the influence of insulin secretion on serum magnesium concentrations 33 insulin-dependent diabetics and 10 control subjects were studied. The residual insulin secretion (RIS) was investigated by measurement of human C-peptide (HCP) before and after stimulation during on OGTT (1.75 mg/kg)-glucagon (i.v. 0.1 mg glucagon/kg)-test. RESULTS: Certain RIS existed in 11 insulin-dependent diabetics, 12 were without any RIS (uncertain RIS in 10 patients). Glucose tolerance and daily glycemia differed significantly among the two groups. However, all diabetics were far from euglycemia, (3.3-9.3 mmol/l): Fasting plasma glucose 12.0 +/- 0.9 (certain RIS), 15.0 +/- 0.8 (no RIS), 13.9 +/- 1.8 (uncertain RIS). Serum magnesium was significantly lower in all diabetics, both before and during the test. There was no change during the OGTT-glucagon-test and no difference among the three groups of insulin-dependent diabetics. So, we conclude that a small RIS in our longterm insulin-dependent diabetics has no influence on the behaviour of serum magnesium. But, magnesium depletion can influence coronary blood flow, blood clotting, and atherogenesis. Therefore, it should be necessary to pay more attention to the hypomagnesemia in insulin-dependent diabetics.

Adult↗
PubMed1979

Behavioural access to short-term memory in bees.

Memory formation proceeds in temporal phases which differ in their effectiveness in controlling subsequent behavior and in their susceptibility to amnestic treatment. The initial phase of memory formation, frequently termed short-term memory, is generally considered a necessary precursor to long-term memory. However, the course of short-term memory differs widely between animal species and is dependent on experimental procedure. Information may even bypass the short-term phase en route to the long-term one. Experiments reported here using honey bees in a behavioural learning situation suggest that the greatest significance of short-term memory is its function as a mode of memory storage which may be altered effectively by new and contradictory information. Freely flying honey bees were presented two colour alternatives and rewarded on first one and then the other in a reversal learning paradigm. Subsequent colour preference was dependent on the interval between the two trials. Several new features of short-term memory are described. It is concluded that a single mechanisms of short- to long-term memory transfer cannot account for the observed bimodal interval dependent behaviour. Two mechanisms are proposed.

Animals↗
PubMed1976

Insect UV-, and green-photoreceptor membranes studied by the freeze-fracture technique.

The membranes of the microvilli of UV- and green-photoreceptors of the ant Myrmecia gulosa have been studied with the freeze-fracture technique. Both inner fracture faces, the cytoplasmic P-face and the extracellular E-face, are covered by globular particles. The P-face particles appear to be randomly distributed, occasionally forming clusters. Their density is about 7,000/mum2, and their mean diameter is 8.5 nm. The E-face particles, however, are arranged in an ordered square pattern with a center-to-center spacing of 9 nm. The density and distribution of P- and E-face particles are the same in both the UV- and the green-photoreceptor membranes. No differences were found in the ultrastructural organization of photoreceptor membranes after dark or light adaptation. It is suggested that the P-face particles represent rhodopsin molecules.

Animals↗
PubMed1976

Enhancement of glucose-stimulated insulin secretion from isolated rat pancreatic islets by human insulin antibodies.

Isolated pancreatic rat islets incubated in vitro were used as a bioassay system for investigating the influence of human insulin antibodies on insulin secretion. Serum samples with different titres of insulin antibodies were obtained from juvenile diabetics after various periods of insulin therapy. The insulin secretion of isolated islets is enhanced by insulin antibodies and positively correlated to the measured antibody titres in serum.

Adult↗
PubMed1976

Treatment of diabetic coma with low-dose injections of insulin.

Twenty-one patients in severe diabetic coma were treated with small doses of insulin at a rate of 4.1 units per hour (total dose about 100 units per 24 hours). Using single doses of 4 to 10 units by the intravenous or intramuscular routes the fall of blood glucose was steady in all cases. In the treatment of diabetic coma this regimen of insulin administration has proved simple, safe and effective since 1946. Main dangers during recompensation of diabetic coma are: hypovolaemia with oliguria -- anuria, dysequilibrium syndrome with cerebral edema and hypokalaemia. Therefore early intensive and adequate intravenous fluid and electrolyte replacement is the most important part of treatment. Most of the cases in this study were undiagnosed diabetics (14) and elderly patients (9). Three patients older than 65 years and a 56-year old diabetic died. In this context the most important aspects of treatment to avoid death are: prevention of diabetic coma and adequate fluid and electrolyte replacement especially in geriatric patients.

Adolescent↗
PubMed1975

Determination of total insulin (TIRI) in plasma of insulin-treated diabetics and newborn infants of insulin-treated diabetic mothers.

Plasma of insulin-treated diabetics and of newborn infants of insulin-treated diabetic mothers contains insulin antibodies which invalidates the radioimmunoassay of insulin. Therefore, the endogenous insulin antibody complex must be splitted at a pH lower than 5 and the total IRI (TIRI) is separated by ethanol extraction. It was investigated the recovery rate in dependence upon plasma volume used for extraction. By reduction of used plasma volume from 500 to 200 mul per extraction the recovery rate was increased from 65.1 +/- 8.4 to 88.3 +/- 4.2% (mean +/- SEM). The low plasma volume of 200 mul for TIRI extraction made it possible to determine TIRI during glucose loads of newborn infants. To eliminate different conditions of incubation for standard and unknown plasma samples the TIRI levels were computed by means of so-called "extracted" standard curve, obtained with extracted insulin from standard insulin dilution in insulin-free pooled human plasma. Using the described method a temporary regeneration of insulin secretion of a newly diagnosed juvenile diabetic after insulin treatment could be shown. In contrast to newborn infants of healthy mothers a biphasic/insulin release was found during the intravenous glucose loads in newborn infants of insulin-treated diabetic mothers.

Adult↗