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Biomedical subjects

S Roth

Publications and source records attributed to S Roth.

At least 361 records · Page 20Linked to original sources
PubMed1978

Properties of a double gradient model for retinotectal specificity.

The properties of a double gradient model for retinotectal specificity are discussed. The model utilizes only two complementary molecules, each located on both retina and tectum, to determine position along the dorsoventral axis. Two possible modes of interaction between these molecules are assumed. One of these allows all possible bonds between a retinal cell and tectal loci to be formed. This results in a rigid retinotectal projection in which the adhesion of each retinal cell to its normal tectal locus is maximal. The other assumes stochastic interactions between the molecules, and results in retinotectal specificity only if additional constraints are imposed on the system. Either of these modes of interaction predicts adhesive preferences for retinal cells to tectal halves similar to those observed experimentally.

Animals↗
PubMed1978

In vitro studies on neural specificity.

The migration of the retinal ganglionic axons through the optic nerve, over the tectal surface, and into the tectum to synapse correctly with brain neurons has been one of the most studied paradigms of neural specificity. Through the use of dissected tecta from the developing chick embryo, dissociated retinal cells can make the same choices in vitro that the ganglion cell termini make in vivo. That is, cells from the dorsal retina prefer to adhere to ventral tectum fragments and vice versa, in accord with the final map of the retina on the tectum. This assay has been used to analyze the biochemical components on the cell and tectal surfaces that might account for the recognition observed. Also, the assay has made it clear that virtually all the retinal cells can distinguish between dorsal and ventral tectal fragments, even though the cells of the retina that normally synapse with the tectum make up not more than 5% of the total population of the retina. One reason for this may be that, although only the retinal ganglion cells send their processes into the brain, these processes use all of the retina initially to get to the fundus of the retina, where the optic nerve begins. The vast majority of the retinal cells may possess surface recognition molecules not for finding the tectum but for serving as substrates for the few retinal cells whose axons must first leave the retina before finding the correct tectal locus.

Animals↗
PubMed1977

Nanosecond time-dependent fluorescence depolarization of diphenylhexatriene in dimyristoyllecithin vesicles and the determination of "microviscosity".

The nanosecond time dependence of the fluorescence depolarization of 1,6-diphenyl-1,3,5-hexatriene in L-alpha-dimyristoyllecithin vesicles was determined at temperatures above and below the midpoint of the gel-liquid crystalline transition. In neither case could the decay of the total fluorescent emission or the decay of the emission anisotropy be described adequately in terms of single exponential decay laws. At the lower temperature, the emission anisotropy did not approach zero in the time window available for measurement, a finding which may indicate that the range over which rotation of the probe can freely occur is restricted. The results are discussed in relation to the concept of microviscosity of bilayer membranes.

Benzene Derivatives↗
PubMed1977

Transformation of chicken chondrocytes by Rous sarcoma virus.

Chicken chondrocytes isolated from 11-day-old chicken vertebrate cartilage were transformed by Rous sarcoma virus ts LA24 of the Prague strain as well as by the wild-type Prague strain of Rous sarcoma virus. The morphology of chondrocytes transformed by Rous sarcoma virus ts LA 24 was dependent on the temperature, and the change was reversible. A similar but irreversible change in morphology was observed with chondrocytes transformed by wild-type virus. Hyaluronic acid production and deoxyglucose transport were markedly increased in the transformed chondrocytes. A marked increase of labeled acetate incorporation was observed with the transformed chondrocytes. In contrast to the normal chondrocytes, the labeled hyaluronic acid synthesized by the transformed chondrocytes was mostly released into the culture medium.

Animals↗
PubMed1977

Biochemical investigations of retinotectal specificity.

An in vitro assay for retinotectal specificity has been described. The results show that, in the chick embryo, cells dissociated from the dorsal retina preferentially adhered to ventral tectal surfaces while cells from the ventral retina preferentially adhered to dorsal tectal surfaces. These adhesive preferences thus mimic the retinotectal specificity observed in vivo. The assay has been extended for use with plasma membrane preparations from retinal cells. Experiments in which retinal cells or tectal surfaces were treated with purified proteases and glycosidases have partially characterized the moieties responsible for the observed specificities. These results are consistent with a double gradient in the dorsal-ventral axis of complementary proteins and carbohydrates. The carbohydrate moiety would be expected to terminate in an acetylated hexosamine and to be more concentrated dorsally in both retina and tectum. A protein that is complementary to the hexosamine terminus would be localized in the ventral part of retina and tectum.

Animals↗
PubMed1976

[Alpha-chain disease presenting as malabsorption syndrome with exudative enteropathy (author's transl)].

A 30-year-old Turk was admitted with signs of exudative enteropathy together with malabsorption. There was no improvement on a gluten-free diet. Immunological investigations demonstrated atypical IgA-immunoglobulin in the serum which did not precipitate with antisera against L-chains. Peroral ileal biopsy and surgical biopsy material showed a diffuse proliferation of plasma cells in an altered ileal mucosa and in the mesenteric lymph nodes. Skeletal X-rays showed no osteolysis and the bone marrow showed no evidence for multiple myeloma. Treatment with melphalan and steroids resulted in a three year remission. In the terminal stage an intra-abdominal malignant lymphoma developed.

Adrenal Cortex Hormones↗
PubMed1976

Pharmacokinetics of sisomicin in patients with normal and impaired renal function; its efficacy in urinary tract infection.

Serum concentration, biological half-life, distribution space and serum clearance of sisomicin, a new aminoglycoside antibiotic, have been studied in twenty-three patients in comparison with the pharmacokinetics of 125I-labelled iothalamate, a compound only filtered by the kidney. 10 patients had normal or borderline abnormal serum creatinine (less than 1,5 mg/100 ml), 8 had various degrees of renal insufficiency (serum creatinine 1.7-9.6 mg/100 ml) and 6 were being treated by intermittent haemodialysis. After intravenous injection of sisomicin 1 mg/kg body weight in patients with normal or borderline renal function its half-life was 3.5 h, very similar to that of iothalamate, 3.2 h. The mean distribution space was 20.1% per cent of body weight; iothalamate, 23.7%. In patients with renal insufficiency there was a positive correlation between serum creatinine level and the half-life of sisomicin, and an even stronger correlation between the clearances of iothalamate and sisomicin. In patients dependent on haemodialysis, the mean serum half-life between dialysis was 40 h, compared to approximately 100 hours for iothalamate, which implies additional extrarenal clearance or tubular secretion of sisomicin. The results of pharmacokinetic studies indicated that a regime of sisomicin 1 mg/kg every 8 to 12 hours in patients with normal renal function would result in serum and urine levels sufficiently high to treat most urinary tract infections. In patients with impaired renal function the dosage interval should be increased according to the serum creatinine level, and in patients dependent on haemodialysis one standard dose at the end of each dialysis period should suffice. 9 patients with a chronic urinary tract infection severely complicated by an underlying disease were treated according to this dosage regimen with a satisfactory bacteriological and clinical result. No adverse reactions or signs of accumulation were observed.

Adult↗