Biomedical subjects

S Kasparian

Publications and source records attributed to S Kasparian.

4 recordsLinked to original sources

PubMed1994

Cell death and neuronal recruitment in the high vocal center of adult male canaries are temporally related to changes in song.

Adult male canaries modify their song every year. Most of these changes occur during late summer and early fall, after the end of the breeding season, and in late winter, immediately before the onset of the next breeding season. The high vocal center (HVC) is an important nucleus in the brain pathway that controls this learned behavior. New neurons continue to be added to the HVC of adult male canaries, where they replace older neurons that have died. The present report describes the monthly incidence of cell death and neuronal addition in the HVC of such birds. Different groups of 1- to 2-year-old male canaries were treated with [3H]thymidine, a marker of cell birth, during each month of the year and killed 27 days later. The ratio of 3H-labeled neurons to all neurons in the HVC showed seasonal peaks and troughs. This ratio was highest in October and March. Peaks in the ratio of pycnotic (dying) HVC cells to all neurons in HVC preceded the peaks in the ratio of 3H-labeled neurons. We suggest that seasonal peaks in cell loss and neuronal recruitment in HVC are related to endocrine changes and that all three play a role in the seasonality of song modification.

Animals↗

PubMed1991

Differential staphylococcal protein A-induced enhancement of natural killer cell activity of lymphocytes from HIV-seropositive individuals.

A decrease in Natural Killer (NK) cell activity is a common feature of the immune dysfunction found in patients with HIV-induced acquired immune deficiency syndrome (AIDS). We and others have shown earlier that staphylococcal protein A (SpA) preparations enhance NK cell activity against tumor targets. The present study was aimed at exploring whether the decreased NK activity of lymphocytes from HIV seropositive subjects could be modulated or restored in vitro by SpA. Two types of HIV-seropositive subjects were studied: hemophiliac and non-hemophiliac; matched controls were chosen among hospital staff and HIV-seronegative hemophiliac volunteers. In vitro proliferation and interleukin-2(IL-2)/interferon gamma (IFN gamma) release in response to mitogens were also studied. NK cell responses of peripheral blood lymphocytes (PBL) of HIV-seropositives were lower than those of seronegatives. However, exposure of PBL from HIV-seropositive individuals to SpA boosted their NK cell responses against NK-resistant target cells of tumor origin. The decrease in NK activity could not be attributed to the low number of NK cells, since no significant difference in NK cell number was observed between HIV-seropositive individuals and controls. Mitogen-induced blastogenic responses were present in all four groups, as was the mitogen-induced IFN gamma release. We conclude that impaired NK activity and its boosting against NK-resistant targets after SpA induction is an important characteristic of lymphocytes of HIV-seropositive individuals regardless of the disease state and that this NK defect may not be irreversible.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

Epstein-Barr virus receptor expression on human CD8+ (cytotoxic/suppressor) T lymphocytes.

In 1977 we showed that cells of a human lymphocytic leukaemia-derived T line (Molt-4) have receptors for Epstein-Barr virus (EBV). More recently, EBV-positive human T cell lymphomas have been recognized and human T cell lines containing the EBV genome have been established in vitro. To understand better the interaction of EBV with T cells, we decided to determine first whether human peripheral blood T lymphocytes express receptors for EBV. Using flow cytometry we examined the binding of both lymphocyte-transforming (B95-8) and non-transforming (P3HR-1) strains of EBV to T lymphocyte subpopulations, using a double labelling technique with T cell-specific phycoerythrinated monoclonal antibodies (Leu 2a) and fluoresceinated viral preparation. Our results suggest that, in general, about 50% of the CD8+ (or suppressor/cytotoxic) T cell subpopulation from both EBV-seropositive and -seronegative individuals can bind EBV. EBV receptor expression on these T cells was about 10 and 51 times less than that on Molt-4 and Raji (an EBV receptor-positive B cell line) cells, respectively. The specificity of this binding was demonstrated by the inhibition of attachment of viral preparations preincubated with a monoclonal antibody directed against the viral ligand (gp240/350), and by preincubating these target T cells with unlabelled virus. We were unable to detect EBV-induced antigens in infected T cells, suggesting that, as in Molt-4 cells, virus internalization may not occur in fresh T cells and/or that the virus receptor may not be completely functional. We were also unable to detect C3d (or CR2) receptors on these T cells, or to inhibit virus attachment by treating the targets with an anti-CR2 monoclonal antibody (OKB7), suggesting that the EBV receptor on CD8+ peripheral blood lymphocytes is different from that on B cells.

Cell Line↗

PubMed1981

Brain space for a learned task.

Forty-six adult male and female canaries were sacrificed, their brains were weighed and the volume of several brain nuclei reconstructed from the cresyl violet-stained material. Two forebrain vocal control nuclei, hyperstriatum ventrale, pars caudale (HVc) and nucleus robustus archistriatalis (RA), were approximately 4 and 3 times larger, respectively, in males than in females, confirming previous findings. There was no consistent right-left asymmetry in the volume of these nuclei in males and females. Twenty-five male birds in this study had their song repertoire recorded during the peak of the singing season. They were sacrificed 3 to 4 months later. The size of the song repertoire, measured as number of different syllable types, showed a positive and significant correlation with the size of HVc and RA. There was no significant correlation between size of the syllable repertoire and age, brain weight or the volume of two brain nuclei not involved in song control. This is the first time that the amount of brain allotted to a specific learned skill has been shown to correlate positively with the amount of that skill that is learned. Interestingly, too, there was a positive and significant correlation between testis weight at the end of the breeding season and the volume of RA at that time, suggesting a hormone-mediated seasonal modulation of part of the brain space occupied by song control pathways. This material seems well suited for studying the relation between space and learning, and the manner in which this relation is influenced by gonadal hormones.

Animals↗