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Biomedical subjects

J Nestor

Publications and source records attributed to J Nestor.

10 recordsLinked to original sources
PubMed1991

Distinct mechanisms of regulation of protein kinase C epsilon by hormones and phorbol diesters.

In this study, we examined the effects of T cell activators on the regulation of protein kinase C (PKC) isozymes present in thymocytes. Using affinity-purified anti-PKC antisera, we determined that the major PKC isoforms in murine thymocytes are PKC beta and PKC epsilon. The CD4+/CD8+ thymocyte subset expressed high levels of both PKC beta and PKC epsilon, whereas the CD4-/CD8- subset expressed much less of both. PKC beta was down-regulated following treatment of thymocytes with phorbol 12-myristate acetate (PMA) (2 x 10(-8) M) or ionomycin (0.4 microM). In contrast, PMA did not induce the down-regulation of PKC epsilon. Ionomycin alone, however, induced PKC epsilon down-regulation, similar to its effect on PKC beta. Similar observations were made on a promonocytic cell line, U937, which expresses PKC alpha, PKC beta (Strulovici, B., Daniel-Issakani, S., Oto, E., Nestor, J., Jr., Chan, H., and Tsou, A.-P. (1989) Biochemistry 28, 3569-3576), and PKC epsilon. To facilitate the study of PKC beta and PKC epsilon, we established a Chinese hamster ovary cell line which expresses murine PKC epsilon in addition to endogenous PKC alpha and PKC beta. Both PKC isoforms (beta and epsilon) were mostly in particulate form. PMA treatment left the majority of immunoreactive PKC epsilon intact. By contrast, thrombin treatment caused the disappearance of particulate and cytosolic PKC epsilon (60% by 10 min and 80% by 1 h). PMA and thrombin promoted the down-regulation of PKC beta with similar kinetics (100% down-regulation by 3 h). These results indicate that: 1) thymocytes express PKC epsilon; and 2) this isozyme exhibits a novel form of regulation distinct from the other PKC isozymes.

Amino Acid Sequence↗
PubMed1989

Activation of distinct protein kinase C isozymes by phorbol esters: correlation with induction of interleukin 1 beta gene expression.

Treatment of human promyelocytic leukemia cells U937 with phorbol 12-myristate 13-acetate (TPA) induces them to differentiate into monocytic cells [Harris, P., & Ralph, P. (1985) J. Leukocyte Biol. 37, 407-422]. Here we investigated the effects of TPA on interleukin 1 gene expression and the possible role of protein kinase C (PKC) in this process. Addition of TPA to serum-starved U937 cells induced the expression of the interleukin 1 beta (IL-1 beta) gene. This effect was apparent as early as 2 h and peaked at 24 h in the presence of 5 X 10(-8) M TPA. Higher concentrations of TPA, which partially or totally depleted protein kinase C levels in the cells (10(-9)-2 X 10(-5) M), had an inhibitory effect on IL-1 beta mRNA expression. Cell-permeable 1,2-dioctanoyl-sn-glycerol (diC8), a diacylglycerol that activates PKC in intact cells and cell-free systems, did not mimic the effect of TPA on the IL-1 beta mRNA induction. To determine the protein kinase C isozymes present in the control and TPA- (5 X 10(-8) M) treated U937 cells, we prepared antipeptide antibodies that specifically recognize the alpha, beta, and gamma isoforms of protein kinase C in rat brain cytosol and U937 cell extracts. In "control" U937 cells, 30% of PKC alpha was particulate, and PKC beta was cytosolic, while there was no detectable PKC gamma.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibody Specificity↗
PubMed1988

Human perioral directional sensitivity.

The capacity of 41 neurologically healthy young adults to distinguish opposing directions of brush motion across the skin innervated by the mental nerve was determined. The velocity and orientation and the length and width of skin traversed by the moving tactile stimuli were carefully controlled. Directional sensitivity, d', was found to vary curvilinearly with velocity over the range 0.5 to 32 cm/s. Because the data from most subjects were well described by a generalized gamma function, it was possible to characterize this velocity dependency quantitatively. Specifically, indices derived from these functions were found to describe the subject's peak (i.e., maximal) sensitivity, the velocity which resulted in peak sensitivity (i.e., the optimal velocity), and the degree to which stimulus velocity influenced the ability to recognize direction of motion (i.e., the velocity-tuning of d'). Peak sensitivity, optimal velocity, and the degree of global velocity-tuning were found to differ between males and females. Confidence limits (the lower and upper 2.5% points) for the normative data were determined to enable detection and characterization of deficits in orofacial tactile motion sensitivity in individuals with damaged mandibular nerves.

Adult↗
PubMed1986

[Public health impact of adsorption of enteroviruses on ocean and river sediments].

Fixation of enteroviruses in sands, ocean sediments, and river mud constitutes a very real public health risk. The authors review the physicochemical and biological mechanisms of virus attachment to particles. Rates of adherence frequently reach 90 to 100%, especially in montmorillonites and sands. Studies devoted to microorganism adherence are mentioned. Attachment of enteroviruses to particles in suspension, to bacteria and other microorganisms--all becoming vectors--is described. Also reviewed is the manner in which these pathogenic substances are disseminated in the environment, especially at beaches, recreational areas and shellfish breeding areas. Greater vigilance to the dangers is advocated on the part of public health authorities, those responsible for environmental salubrity and for shellfish grounds.

Disease Reservoirs↗
PubMed1983

In vitro synthesis of the tryptophan operon leader peptides of Escherichia coli, Serratia marcescens, and Salmonella typhimurium.

We used an in vitro DNA-dependent protein-synthesizing system to demonstrate de novo synthesis of the leader peptide specified by the tryptophan (trp) operons of several bacterial species. Peptide synthesis was directed by self-ligated short restriction fragments containing the trp promoter and leader regions. Synthesis of leader peptides was established by demonstrating that they were labeled in vitro only by those amino acids predicted to be present in the peptides. Leader peptide synthesis was abolished by the addition of the Escherichia coli trp repressor. The E. coli trp leader peptide was found to be extremely labile in vitro; it had a half-life of 3-4 min. In a highly purified DNA-dependent peptide-synthesizing system, synthesis of the di- and tripeptides predicted from the Salmonella typhimurium trp operon leader sequence, fMet-Ala and fMet-Ala-Ala, also was observed. Using this dipeptide synthesis system, we demonstrated that translation initiation at the ribosome binding site used for trp leader peptide synthesis was reduced 10-fold when the transcript contained a segment complementary to the ribosome binding site.

Bacterial Proteins↗
PubMed1976

Coherent anti-Stokes Raman scattering (CARS) spectra, with resonance enhancement, of cytochrome c and vitamin B12 in dilute aqueous solution.

Coherent anti-Stokes Raman scattering (CARS) spectra have been obtained for ferrocytochrome c and cyano cobalamin in aqueous solution at millimolar concentrations, using a pair of tunable dye lasers pumped by a pulsed nitrogen laser. Resonance enhancement was obtained by tuning the omega1 laser to the visible absorption bands of the samples. The spectral features correspond to those observed in the conventional resonance Raman spectra. It appears that CARS spectroscopy, with its advantageous fluorescence rejection, can be usefully applied to biological samples by exploiting resonance enhancement. While the background scattering from water is 10 times higher than that of benzene and other aromatic solvents, it is actually at the low end of the scale for most liquids. The anomalously low background of aromatic liquids is thought to result from competition by the unusually efficient stimulated Raman scattering which they display. Off-resonance spectra for both cobalamin and cytochrome c contain negative peaks, i.e., absorption bands in the background. These are interpreted as inverse Raman processes induced by the omega1 photons in the presence of the continuum provided by the background scattering. While both CARS and the inverse Raman effect are subject to resonance enhancement, the wavelength dependence of CARS is evidently steeper.

Cytochrome c Group↗