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N Schechter

Publications and source records attributed to N Schechter.

85 records · Page 5Linked to original sources
PubMed1979

Activity of choline acetyltransferase and acetylcholinesterase in the goldfish optic tectum after disconnection.

Activities of choline acetyltransferase (CAT) and acetylcholinesterase (AChE) were investigated in the goldfish optic tectum after disconnection of the optic afferents. Permanent disconnection was achieved by eye removal, and optic nerve crush produced a temporary disconnection until regeneration. There was a rapid loss in total activity per tectum for both enzymes under the two disconnection conditions. At longer intervals after optic nerve crush the levels of total activity for both enzymes returned toward control levels, as regeneration of the nerve proceeded. Total activity for both enzymes remained depressed after eye removal, however. Variable results were obtained in specific activity data, expressed per unit protein, although there was a 10% loss in specific activity of CAT at early intervals after eye removal. The data are interpreted as consistent with the possibility that at least a fraction of the axons in the retinotectal pathway of goldfish are cholinergic, and parallel our previous observations showing similar rapid losses of nicotinic-cholinergic receptor activity in this system.

Acetylcholinesterase↗
PubMed1976

Conformational changes of 30S ribosomes measured by intrinsic and extrinsic fluorescence.

The intrinsic tryptophan fluorescence and the fluorescence of N-(3-pyrene)maleimide, a covalently bound sulfhydryl-specific extrinsic probe, have been used to study the conformation of the 30S ribosomal subunit of Escherichia coli. (a) The tryptophan fluorescenct spectrum of the free ribosomal proteins is shifted to shorter wavelengths than that of free tryptophan. When the proteins are incorporated into the organized structure of the ribosome, there is a small additional blue shift and the emission band becomes narrower. In 6 M urea, the spectrum of the proteins, whether free or in the ribosome, becomes identical with that of the amino acid, reflecting exposure of previously shielded tryptophan residues. (b) When magnesium-depleted ribosomes are unfolded at low ionic strength, the tryptophan fluorescence spectrum changes, although circular dichroism shows no change in alpha-helix content of the proteins. (c) Intrinsic and extrinsic fluorescence were both found to be sensitive to a limited and fully reversible transition that takes place when ribosomes are incubated under conditions that increase their activity in vitro. This suggests that both probes may be of use in monitoring conformational changes that occur under conditions consistent with activity. The kinetics of the concurrent changes in extrinsic fluorescence and aminoacyl-tRNA binding activity were compared. (d) Conditions are described for labeling ribosomes with N-(3-pyrene)maleimide without impairing their activity.

Circular Dichroism↗
PubMed1969

Cell-free amino acid-incorporating systems from Bacillus licheniformis and Bacillus stearothermophilus 10.

Cell-free amino acid-incorporating systems were prepared from log-phase cells of Bacillus licheniformis and B. stearothermophilus 10. No differences were observed between the two systems with respect to the types and relative amounts of the ribosomes, the time dependence of incorporation, and the optimal magnesium ion concentration (4 mm). The B. licheniformis system showed greater dependence on added transfer ribonucleic acid (tRNA) and was less stimulated by polyuridylic acid (poly U) than the B. stearothermophilus 10 system. Neither system was saturated at a level of 450 mug of poly U per incubation mixture. The S-100 fraction and the isolated tRNA inhibited incorporation in the B. stearothermophilus 10 system at 55 C but not at 37 C. No such inhibition was observed in the B. licheniformis system at either temperature. The tRNA prepared from B. subtilis, B. licheniformis, or B. stearothermophilus 10 could be used interchangeably in the two cell-free systems.

Bacillus↗
PubMedDate not supplied

Participation of the central cholinergic system in blood pressure regulation in the Dahl rat model of essential hypertension.

Participation of the cholinergic system in the regulation of blood pressure (BP) in the Dahl salt-sensitive (DS) and salt-resistant (DR) rat model of essential hypertension was investigated. It was found that systemic administration of 0.25 or 0.50 mg/kg physostigmine (PSTG) to unanesthetized, normotensive DS and DR rats caused a significant elevation in BP but did not affect heart rate. At both dose levels, the pressor response was markedly greater and significantly longer in DS rats than in DR rats. The response in both DS and DR rats was blocked by pretreatment with atropine sulfate but not with atropine methylnitrate. These results suggest that the pressor effects of PSTG are mediated by central cholinergic mechanisms, and enhanced central cholinergic activity may participate in the pathogenesis of hypertension in the DS rat.

Animals↗
PubMedDate not supplied

Induction of donor-specific immune modulation and successful renal transplantation with a simplified method of donor-specific blood transfusion.

We developed a new method of donor-specific blood transfusion (DST) for prospective kidney transplant recipients from a living related donor. Forty-four patients were transfused with 100 ml of one-haplotype matched kidney donor's whole blood at 1, 8, and 15 days after its storage. Ten of these patients received azathioprine (1.5 mg/kg per day) in addition to DST. After DST, three patients (6.8%) developed donor-specific lymphocytotoxic antibodies. The incidence of sensitization was not different between azathioprine-treated and untreated patients. Following DST, donor-specific mixed lymphocyte culture (MLC) was significantly suppressed without any accelerated (secondary type) response in early MLC. Subsequently, 24 patients received a kidney transplant from the donor. Graft survival rates were 96% and 90% at 12 and 24 months, respectively. Nine additional patients, seven from a two-haplotype matched sibling and two from a no-haplotype matched sibling also received DST. None of these patients became sensitized following DST, and all have functioning grafts for 6 to 18 months. This study indicates that 100 ml of stored whole blood DST three times at weekly intervals is a practical, less immunizing, and effective approach to enhance graft survival in recipients of a living related donor graft, DST produces donor-specific adaptive responses that might be conductive to successful graft outcome, and this protocol could be used in sibling donor-recipient pairs who do not share a haplotype.

Adult↗