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Biomedical subjects

A Brown

Publications and source records attributed to A Brown.

At least 613 records · Page 34Linked to original sources
PubMed1979

Adoptive transfer of cross-protection among alphaviruses in mice requires allogeneic stimulation.

Cell-mediated (T-effector cell) immunity is proposed as playing the major role in cross-protection between Sindbis and Semliki Forest viruses, which are alphaviruses that do not elicit cross-neutralizing antibodies. In adoptive transfer experiments, T-cells from spleens of Sindbis virus-immunized mice were found to confer specific cross-protection to Semliki Forest virus upon recipient mice. This cross-protection was observed in the outbred ICR strain of mice and when transfers were made between several combinations of inbred and hybrid strains. Cross-protection was substantially reduced if syngeneic rather than allogeneic cell transfers of one spleen equivalent per mouse were made. The results suggest that allogeneic stimulation (mixed lymphocyte reaction in vivo) is necessary to increase the number of effector cells (donor) in the recipient. This was supported by the observation that blastogenic stimulation of donor cells in vitro by concanavalin A induces cross-protection in syngeneic animals. Conversion of recipient cells to specific effector cells also appears to play a role in protecting mice against Semliki Forest virus. This was concluded from the experiments described above, a time course study, and the results of experiments that involved serial passages of transferred cells across histocompatibility barriers. Thus, we propose that both donor and recipient cells are active in protecting recipient mice against challenge with Semliki Forest virus after adoptive transfer.

Animals↗
PubMed1979

Effect of local radioactivity on trachael mucous velocity of sheep.

The effects of local isotope radiation and x-ray radiation on mucociliary transport of sheep were investigated. X-ray radiation from fluoroscopy equivalent to that used to determine tracheal mucous velocity in intact animals (approximately 3 min) did not alter transport of teflon discs in an isolated sheep trachael preparation. In conscious sheep, 2 ml of a solution containing 8 mCi of macroaggregates of albumin labeled with technetium-99m (99mTc) and 99mTc-pyrophosphate were instilled under direct vision into the trachea via a fiberoptic bronchoscope, providing an actual deposition on the tracheal epithelium of 1.8 to 2 mCi. Physiologic saline and unlabeled macroaggregates of albumin were instilled as control solutions. Tracheal mucous velocity measured by movement of teflon discs increased by 93.2 per cent with 99mTc-labeled macroaggregated albumin and 86.7 per cent with 99mTc-pyrophosphate (P less than 0.01), but no significant increase occurred after saline or unlabeled macroaggregates of albumin. Discrepancies in the values of trachael mucous velocity determined using inert particles and radioactive tracer solution or aerosols might be related in part to the local effects of the tracer radiation.

Animals↗
PubMed1979

The quantitative histochemistry of ribonucleic acid using gallocyanin.

A method for the cytophotometric estimation of ribonucleic acid in tissue sections using gallocyanin-chrome alum is described. The dye obeys Beer's law in gelatin sections. The effect of deoxyribonuclease on the staining of ribonucleic acid is also investigated. The results indicate that this method is of value in the quantitation of ribonucleic acid.

Alum Compounds↗
PubMed1979

In vitro heterologous cytotoxicity by T effector cells from mice immunized with Sindbis virus.

An in vitro correlate of cell-mediated cross-protection among alpha-viruses was demonstrated by cytotoxicity of Sindbis-immune spleen cells from mice to both Sindbis and Semliki Forest virus (SFV)-infected target cells. This cytotoxicity was shown to be mediated by the T cell population of the spleen and was independent of the presence of macrophages or B cells. The time when the level of the lymphocyte-mediated cytotoxicity (LMC) to SFV-infected cells was maximal coincides with the time when immunity to SFV is maximal in vivo, as reported previously, and when adoptive immunity to SFV can be transferred. After one i.p. injection of Sindbis virus, the level of homologous LMC was higher than the level of heterologous LMC. However, following a second injection of Sindbis virus as immunogen, at a time when the mice are cross-protected to SFV, the heterologous LMC was considerably higher than homologous LMC. We propose that there is suppression of the effector T cells specific for Sindbis-infected cells after the second immunizing injection, probably by homologous antibody. In contrast, there appears to be an anamnestic cell-mediated response to SFV.

Animals↗
PubMed1978

Biosynthesis of low molecular weight RNA in mouse myeloma cells.

The low molecular weight RNAs in the nucleus and cytoplasm of mouse myeloma cells have been characterized. There are major nuclear species (other than 5-S and tRNA), four of which contain 'capped' 5' termini. There are three major small cytoplasmic RNAs none of which contain 'caps'. The biosynthesis of the nuclear species when studied using [3H]adenosine as an RNA precursor is characterized by a rapid, transient appearance in the cytoplasm, followed by fixation in the nucleus. Within 15 min, the amount in the cytoplasm has reached a steady-state level maintained for 60 min, while the accumulation in nuclei is linear after a short lag (less than 5 min). When biosynthesis is studied using [Me-3H]methionine as a precursor, much less labeled RNA is present in the cytoplasm, suggesting that methylation may immediately precede fixation into the nucleus.

Adenosine↗
PubMed1978

Lipofuscin and transsynaptic degeneration.

The periodic acid Schiff reaction was applied to neurones in the Lateral Geniculate Body (L.G.B.) of a series of normal and blind patients over a wide age range. The quantity of the reaction product was determined as a measure of lipofuscin which was found to increase linearly with age in the L.G.B. neurones. The amount in the neurones of the blind patients was found to be less than that in the controls, and a further group of four patients with apparently normal vision and central nervous system disease had an intermediate amount of lipofuscin. It is suggested that the component of lipofuscin measured by this technique represents an index of both metabolic activity and functional activity of the neurone. The reduced amounts in the patients with C.N.S. disease may reflect reduced visual function in association with non-visual pathway disease.

Adolescent↗
PubMed1978

Effect of ammonia on the glutamate dehydrogenase catalyzed oxidative deamination of L-glutamate: production of an ammonia-containing intermediate in the "burst" phase.

We have studied the effects of ammonium acetate on the transient "burst" phase of the oxidation of L-glutamate by glutamate dehydrogenase. Two measurable changes are observed in the "burst" phase as ammonium acetate concentration is increased: (i) an increase in the apparent first-order rate constant, kapp, and (ii) a decrease in the amplitude of the absorbance change measured at 320 nm. The increase in kapp shows a hyperbolic dependence on ammonium acetate concentration and is independent of glutamate concentration. The results demonstrate the existence of an intermediate immediately following hydrogen transfer. The intermediate contains enzyme, reduced coenzyme, ammonia, and alpha-ketoglutarate moieties and is in equilibrium with the known complex consisting of enzyme, reduced coenzyme, and alpha-ketoglutarate. At high concentrations of ammonium acetate, the equilibrium favors the ammonia containing complex.

Ammonia↗
PubMed1978

Transfection of Fv-1 permissive and restrictive mouse cells with integrated DNA of murine leukemia viruses.

Whole-cell DNA preparations isolated from SC-1 cells chronically infected with N- or B-tropic murine leukemia viruses (MuLV) were tested for infectious activity in an Fv-1n (NIH-3T3) and two Fv-Ib (C57BL/6 and SV-A31) cell cultures. Efficiency of transfection for all DNAs was better in the NIH-3T3 cells than in C57BL/6 or SV-A31 cells; and an [N-tropic MuLV]SC-1 cell DNA preparation was slightly more infectious than a [B-tropic MuLV]SC-1 cell DNA preparation in all three cell cultures, regardless of their Fv-1 genotypes. Progeny viruses from the transfection showed N- or B-tropism corresponding to that of the parent viruses produced by the infected SC-1 cells that were used for the DNA preparation. DNA dose-response studies in NIH-3T3 cells revealed a one-hit mechanism for both the [B-tropic MuLV]SC-1 cell DNA and the [N-tropic MuLV]SC-1 cell DNA preparation. These results demonstrate that, in contrast to virion infection, transfection of N- and B-tropic MuLV with DNA preparations from chronically infected cells is not affected by the Fv-1 gene.

Cell Line↗
PubMed1978

Effect of the Fv-1 locus in vivo: host range pseudotypes of murine sarcoma virus.

Fv-1-specific host-range pseudotypes of murine sarcoma virus (MuSV) were developed by rescue from nonproducer cells with N- or B-tropic leukemia viruses. The MuSV(B) and MuSV(N) pseudotype viruses were tested in vitro and were restricted specifically by the Fv-1 gene locus. When the pseudo-type viruses were tested in vivo in mice of specific Fv-1 geno-types, tumor induction was completely restricted in nonpermissive animals, including athymic nude mice, whereas tumors grew progressively in permissive animals. All tumors regressed in adult heterozygous mice, but not in adult athymic nude mice.

Animals↗
PubMed1978

The identification of the tRNA substrates for the supK tRNA methylase.

Purified preparations of the tRNA methylase deficient in supK strains of Salmonella typhimurium transfer methyl groups from S-adenosylmethionine (SAM) to at least two tRNA species, an alanine tRNA and a serine tRNA. The identity of the tRNA substrates for this enzyme was determined by a change in the elution position of the methyl-labeled tRNA from BND-cellulose columns before and after aminoacylation with a specific amino acid followed by derivatization of the free primary amino group with phenoxy- or naphthoxyacetate. The radioactive methyl group enzymatically added to these tRNAs is both acid and base labile and can be hydrolyzed to a volatile product at pHs above 7.5 and also at pH 1. The methylated 3'-nucleotide isolated from digested tRNA is a pyrimidine derivative and chromatographs like a modified uridylic acid. Its identity has not been established, but it is likely that it corresponds to the methyl ester of V, uridin-5-oxyacetic acid.

Alanine↗
PubMed1978

The dependence of some strains of Mycobacterium avium on mycobactin for initial and subsequent growth.

This paper demonstrates that various degrees of mycobactin dependence exist within the M. avium group of mycobacteria and that this characteristic is not confined to M. paratuberculosis. The strains employed came from a wide range of animal species and all were virulent for chickens. Mycobactin dependence was observed in the M. avium serotypes 1, 2 and 3. The importance of employing a medium containing mycobactin for primary isolations observation may be of interest in relation to the primary isolation of other species of mycobacteria.

Animals↗
PubMed1978

Transfer of Fv-1 locus-specific resistance to murine N-tropic and B-tropic retroviruses by cytoplasmic RNA.

A standardized bioassay for transfer of Fv-1 gene-specific resistance to N-tropic and B-tropic murine retroviruses was developed using X plaque reduction in SC-1 (Fv-1-) cells inoculated with virus. Testing of subcellular fractions of restrictive cells showed that the resistance transfer activity was present in the cytoplasmic (microsomal and cytosol) fractions. The activity of the cytoplasmic extract was destroyed by treatment with ribonuclease, but not with deoxyribonuclease or proteases. RNA prepared by phenol-chloroform extraction of mouse tissues, including embryos and livers of weanling mice, transferred Fv-1 locus-specific resistance into DEAE-dextran-treated SC-1 cells. The activity of isolated RNA preparations against virus of the appropriate host-range type has been demonstrated to correspond to the Fv-1 genotypes of the cell sources. The specific transfer of resistance with cellular RNA was effective within a 5- to 6-h period from 2 h before to 4 to 5 after virus infection. Sucrose gradient centrifugation of the RNA showed that the activity sedimented as a broad peak, with an apparent maximum in the 22S region. Affinity chromatography of whole-cell RNA on polyuridylic acid-Sepharose tended to separate more activity into the polyadenylic acid RNA fraction than the non-polyadenylic acid RNA fraction. Except for the reciprocal inhibitory activity for the two host-range virus types, the RNAs of Fv-1n and Fv-1b specificities showed similar properties in all aspects studied.

Animals↗