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Biomedical subjects

A Stock

Publications and source records attributed to A Stock.

54 records · Page 3Linked to original sources
PubMed1987

S-adenosylmethionine may not be essential for signal transduction during bacterial chemotaxis.

We previously showed that a mutant strain of Salmonella typhimurium completely deficient in both the chemoreceptor methylating (CheR) and demethylating (CheB) enzymes can still exhibit chemotaxis to aspartate and other attractants (J. Stock, A. Borczuk, F. Chiou, and J. E. B. Burchenal, Proc. Natl. Acad. Sci. USA 82:8364-8368, 1985). We used this cheR cheB mutant to examine the possibility of an additional requirement for S-adenosylmethionine in chemotaxis besides its role in chemoreceptor methylation. A metE mutation was transduced into a cheR cheB double mutant, and the cells were starved for methionine. Despite the fact that intracellular S-adenosylmethionine dropped from approximately 100 microM to less than 0.2 microM, chemotaxis was largely unaffected. In contrast, a corresponding cheR+ cheB+ metE mutant completely lost its chemotaxis ability after being starved for methionine. We conclude from this observation that the primary requirement for S-adenosylmethionine during bacterial chemotaxis is in the methylation of receptor proteins.

Bacterial Proteins↗
PubMed1985

Homologies between the Salmonella typhimurium CheY protein and proteins involved in the regulation of chemotaxis, membrane protein synthesis, and sporulation.

Chemotactic receptors at the bacterial cell surface communicate with flagellar basal structures to elicit appropriate motor behavior in response to extracellular stimuli. Genetic and physiological studies indicate that the product of the cheY gene interacts directly with components of the flagellar motor to control swimming behavior. We have purified and characterized the Salmonella typhimurium CheY protein and have determined the nucleotide sequence of the cheY gene. Amino acid sequence comparisons showed CheY to be homologous over its entire length (129 residues) to the N-terminal regulatory domain of another protein involved in chemotaxis, the CheB methyl esterase. The entire CheY protein and the regulatory domain of CheB also homologous to the N-terminal portions of the Escherichia coli OmpR and Dye proteins and the Bacillus subtilis Spo0A protein. These homologies suggest an evolutionary and functional relationship between the chemotaxis system and systems that are thought to regulate gene expression in response to changing environmental conditions.

Amino Acid Sequence↗
PubMed1983

[The rat as a training model for microvascular surgery. Methods and results].

Before the clinical application of microvascular surgery the experimental training is necessary. The techniques of end-to-end anastomosis of femoral artery and vein and groin flap autotransplantation are described in detail on the rat model and results are presented. These techniques seems to be suitable for persons still learning without much experience.

Animals↗
PubMed1976

Assessment of urinary tract obstruction using a perfusion technique.

A perfusion technique is described which enables differentiation in a dilated upper urinary tract between one which is obstructed and one which is not. It has been found invaluable in the assessment of patients prior to surgical intervention and has saved many patients from an operation.

Adult↗
PubMed1975

Special diets in hospitals: discrepancy between what is prescribed and what is eaten.

An assessment has been made in four hospitals of the food eaten by 40 patients on special diets restricted in energy, carbohydrate, fat, protein, or sodium. The diets eaten by most patients were significantly different from those prescribed, partly because of patients' unrestricted access to food they possessed or could buy in the ward, but mainly because of the extra or alternative foods provided by ward staff. Not only may the patients, progress be prevented or hindered by excessive consumption but also the lack of progress may be interpreted as indicating that the dietary treatment has failed rather than that it has not been followed.

Attitude of Health Personnel↗
PubMedDate not supplied

Thyroid hormone receptors bind to an element in the connexin43 promoter.

Thyroid hormones stimulate gap junctional communication in rat liver WB-F344 epithelial cells, elevating connexin43 mRNA and protein levels. In the present work we analysed connexin43 expression in liver and heart samples from thyroid hormone-treated Wistar rats. Connexin43 mRNA was elevated 2.1-fold in rat liver samples as compared to controls, while there was no change in heart. Thyroid hormone response elements in the rat connexin43 promoter region were examined; a candidate sequence, including a binding site for ligand-dependent transcription factors, was identified at position -480 to -464. This putative regulatory element, rCx-480, contains a direct repeat structure separated by three base pairs (DR3-type element). In electrophoretic mobility shift assays using in vitro translated proteins, the rCx-480 element formed stronger complexes with thyroid hormone receptor alpha/retinoid X receptor alpha heterodimers than with vitamin D receptor/retinoid X receptor alpha heterodimers. In transfected Cos-7 cells, promoter activation was observed via this element after treatment with 3,3',5-triiodo-L-thyronine. Loss of binding was seen when the 3' half-site or the spacer region of the rCx-480 element were experimentally mutated, while a stronger binding was observed with mutations introduced in the 5' half-site.

Animals↗