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Biomedical subjects

J Roth

Publications and source records attributed to J Roth.

At least 703 records · Page 39Linked to original sources
PubMed1978

[Studies on the sensitivity of ionization chambers (author's transl)].

In spite of small geometrical dimensions of the ionization chambers, the sensitivity distribution throughout the entire chamber must be considered if conditions are extreme (small size of field, short distances). Various types of chambers were studied with regard to their response threshold along their axis. Taking the different wall thicknesses into consideration, different ionization chambers show good agreement with regard to the accumulation effect of Co-60 gamma radiation.

Gamma Rays↗
PubMed1978

[Definition of limits of bronchial reactivity with aid of bodyplethysmography (author's transl)].

Investigations for dose-effect relationship of acetylcholine-ultrasonic-aerosols (apparatus "TUR" USI3, duration of inhalation three minutes, control of the ventilation parameters five minutes after termination of inhalation) led to the result that the delimination of the bronchial hyperreactivity is already possible by application of a 0.01% test-concentration. In this way the ultrasonic-aerosol-method also leads to results which are comparable with the nozzle-aerosol-method used in GDR (0.5% test-concentration, duration of inhalation one minute). As a limiting criteria for the evaluation of a bronchial hyperreactivity analogous to the decrease in the FEV1 of greater than or equal to 15% in comparison with the starting position for the bodyplethysmography yield an increase of the resistance totalis of greater than or equal to 3.0 cm H2O/1/s.

Acetylcholine↗
PubMed1978

[Dose distribution of photons and neutrons outside of the irradiation field of a 8-mev linear accelerator (author's transl)].

During the irradiation with a continuous radiation of 8 MeV by the linear accelerator LINAC SL 75/10, the dose distribution of photons and neutrons was measured outside of the irradiation field. The dose distribution of photons was mostly determined by thermoluminescence dose meters. There was a significant maximum of leak radiation on the back of the emitter head which showed a dose rate amounting to 7,5% of the dose rate of the central ray. Whereas the leak radiation on the patients' table was less than 0,1% of the dose of the central ray, the dose of scattered radiation emitted by the patient still amounts to 2% of the central ray dose in a distance of 15 cm from the field edge. The isodoses measured in the room demonstrate above all the importance of the lock for a sufficient radioprotection.--The dose rate of the neutrons formed in the shielding material by photonuclear reactions were measured mostly with uranium fission-track dosimeters. The highest equivalent dose rate was found on the back of the emitter head; it is about 17 rem/h. The maximum value of the equivalent dose rate of neutrons on the patient's table amounts to 1,4 rem/h and is almost independent of the size of the diaphragm. The isodoses in the room depend largely on the shape of the irradiation room; they confirm the existence of a sufficient radioprotection.

Elementary Particles↗
PubMed1977

Induction of midtrimester abortion with intra-amniotic urea and intravenous oxytocin.

Midtrimester abortions were induced in 295 patients with a combination of intra-amniotic urea and intravenous oxytocin. The mean injection-abortion interval was 26.4 hours. Abortion occurred spontaneously within 50 hours of amnioinfusion in 257 patients. The macerating effect of the hypertonic urea on fetal tissues allowed easy termination of the remaining 38 pregnancies by suction curettage at 50 hours after injection. Decreased urinary output occurred during the oxytocin infusions, but water intoxication was prevented by close monitoring of urinary output and serum electrolytes, and by the use of a concentrated solution of oxytocin in normal saline, allowing the administration of small volumes.

Abortion, Induced↗
PubMed1977

Redistribution and internalisation of anti-AH1e (anti-AHP)- and Concanavalin A-binding sites.

The redistribution and internalisation of two different lectin-binding sites on the same cell was investigated electron microscopically on unfixed rat liver cell cultures. For these purposes an electron microscopic double labeling technique was used for visualisation of the anti-AHel-binding sites by the gold-labeled lectin and for the demonstration of the Concanavalin A-binding sites by the Concanavalin A-peroxidase technique. From the experiments it was evident that the ligand-induced redistribution of the antiAHel-binding sites effects a rearrangement of the Concanavalin A-binding sites. Both markers were found in a clustered distribution on the cell surface. Following the redistribution an internalisation of both lectin-binding sites could be observed on central and peripheral cell parts. In the lateral cell parts an accumulation of the both markers occurred on the plasma membrane.

Binding Sites↗
PubMed1977

Autoantibodies to the insulin receptor. Effect on the insulin-receptor interaction in IM-9 lymphocytes.

The serum of some patients with insulin-resistant "diabetes" contains antibodies that bind to and block the cell membrane receptors for insulin. In this report, we have characterized the effects of the antireceptor antibodies on the interaction of (125)I-insulin with its receptor on the human lymphoblastoid cell line IM-9. Up to 95% of specific insulin binding can be inhibited by pretreatment of the cells with these immunoglobulins. The onset of the inhibitory effect is time- and temperature-dependent, and the effect is reversed extremely slowly if the cells are suspended in a large excess of antibody-free buffer. These features of antibody binding can be easily distinguished from those for insulin binding to its receptor. The inhibitory effect of the antibodies can be reversed by exposure of the cells to conditions known to elute surface immunoglobulins. The three antireceptor sera studied appear to alter the insulin-receptor interaction in different ways. Two antisera markedly reduce receptor affinity through combined effects on the insulin association and dissociation rates, and, additionally, have smaller effects on available receptor number. A third antiserum primarily affects available receptor number and has little effect on receptor affinity. All three antisera inhibit the capacity of insulin to promote negatively cooperative site-site interactions among insulin receptors. The data suggest that these autoantibodies to the insulin receptor bind to different determinants on the receptor and may therefore be useful as unique probes of insulin receptor structure and function.

Allosteric Regulation↗
PubMed1977

Peroxidase and gold complexes of lectins for double labeling of surface-binding sites by electron microscopy.

Double labeling experiments were performed for visualization of the binding sites of Concanavalin A and anti-AHel (the lectin from Helix pomatia). The anti-AHel was labeled with the colloidal gold whereas the membrane bound Concanavalin A was demonstrated by an affinity technique using horseradish peroxidase. The two markers used could be clearly distinguished electron microscopically. The specificity of the cell surface double labeling was demonstrated in the control experiments. A topological distinct localization of the both lectin-binding sites is evident.

Animals↗
PubMed1977

The insulin receptor of the turkey erythrocyte: similarity to mammalian insulin receptors.

Avian erythrocytes possess insulin receptors which have binding properties that are virtually identical to those of the well studied mammalian insulin receptors. The affinity for porcine insulin was identical for the turkey and mammalian receptors over the entire range of insulin concentrations, as was the affinity of each of four insulin analogues which differed 300-fold in biological potency. Insulin induced acceleration of dissociation (i.e., the negatively cooperativite site-site interaction) was indistinguishable over a 10(6) range of insulin concentrations. Sharp pH dependence of binding was identical for turkey and mammalian receptors. The effects of temperature on association, dissociation and steady state binding were also identical. Thus, although birds and mammals have evolved separately for 300 million years there has been little change in the properties of the insulin receptor over this time period.

Allosteric Regulation↗
PubMed1977

Reactivity of non-primate growth hormones and prolactins with human growth hormone receptors on cultured human lymphocytes.

Ovine placental lactogen is as reactive as human growth hormone with the human growth hormone receptor of cultured human (IM-9) lymphocytes, which confirms the findings of Carr and Friesen with receptors of human liver. We now also show that bovine and ovine growth hormones and ovine prolactin have reactivity for the human growth hormone receptor on IM-9 lymphocytes that is of the same order of magnitude (0.03%) as that previously reported for human placental lactogen. The binding studies predict that these non-primate hormones will have biological effects on skeletal growth in primates, either as agonists or antagonists. Previous studies have shown that when IM-9 lymphocytes are exposed to human growth hormone for 18 h at 37 C, there is a time and concentration dependent loss of human growth hormone receptors, and the magnitude of the loss of receptors after preincubation for 18 h at 37 C is greater than the average occupancy of receptors under steady state conditions for 90 min at 30 C. In the present study we show that human and ovine placental lactogens, ovine prolactin, and bovine and ovine growth hormones also produce this effect on the human growth hormone receptor. Since the cellular process by which a hormone induces loss of its own receptors appears to require binding of the hormone to its receptor as well as one or more subsequent steps in hormone action, it is likely that all of the preparations that induce receptor loss will be shown to have some agonist activity of human growth hormone in promoting skeletal growth in primates. Further, these studies extend the interrelationships between primate and non-primate pituitary and placental hormones from what has been suggested previously from biological and structural studies.

Animals↗
PubMed1977

Change in affinity of insulin receptors following oral glucose in normal adults.

125I-insulin binding to circulating monocytes has been studied in 4 normal volunteers in the basal state as well as at 2 and 5 hours after ingestion of 100 g of glucose. In each study five hours after glucose ingestion, the competition-inhibition curve was shifted to the left and was steeper than that in the basal study; the amount of insulin that caused a 50% decrease in specific binding of 125I-insulin in the basal study was 3-11 fold higher than at 5 hours after glucose. These changes in binding after glucose ingestion were largely due to major alterations of receptor affinity. We conclude that acute changes in receptor affinity occur normally as part of the physiologic regulation of target cell sensitivity to hormonal stimulation.

Adult↗
PubMed1977

Insulin receptors in patients with insulinomas: changes in receptor affinity and concentration.

We have measured the specific binding of 125I-insulin to insulin receptors on circulating monocytes from 5 patients with insulinomas. In all patients the concentration of insulin receptors was inversely related to the basal, circulating level of insulin (corrected for proinsulin content). In the four patients with chronically elevated concentrations of plasma insulin, receptor concentrations were decreased. In three of these patients there were also marked alterations in receptor affinity. With insulinomas, correlations with the clinical state appear to be clearer when receptor concentration and especially receptor affinity are considered in addition to circulating insulin and proinsulin levels.

Adenoma, Islet Cell↗
PubMed1977

Insulin receptor status in disease states of man.

When insulin or any peptide hormone binds to its receptor on the surface of a target cell, it initiates a series of biochemical steps that ultimately lead to the characteristic action of the hormone. The strength of the signal generated by the hormone depends equally on the hormone concentration, the receptor concentration, and the receptor affinity. Not only do hormone concentrations change rapidly and widely in vivo but so do receptor concentration and affinity. In hormone resistant states, any step in the biochemical pathway of hormone action at the target cell may be involved. Studies of insulin receptors in people indicate that the insulin receptor is altered in many common disorders such as obesity and diabetes, as well as in rare disorders such as extreme insulin resistance due to circulating antibodies directed at the insulin receptor itself. By responding to both intracellular and extracellular events, the insulin receptor is, therefore, a major site for the regulation of target cell responsiveness in vivo.

Acanthosis Nigricans↗