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M H Brown

Publications and source records attributed to M H Brown.

At least 91 records · Page 5Linked to original sources
PubMed1989

Vasopressin-deficient rats show a reduced amplitude of the circadian sleep rhythm.

The hypothalamic suprachiasmatic nuclei are responsible for the generation of many circadian rhythms, including the rhythm of arginine vasopressin (AVP) in the cerebrospinal fluid (CSF). We used cortical EEG recordings taken from AVP-deficient (Brattleboro strain) rats to investigate the possible role of AVP in the generation of circadian sleep/arousal rhythms. When housed either in a light-dark cycle or in constant light, Brattleboro rats showed circadian rhythms of arousal, slow-wave sleep, and paradoxical sleep. However, the amplitudes of the slow-wave and paradoxical sleep (but not arousal) rhythms in these animals were significantly lower than in controls. The results indicate that hypothalamic synthesis of AVP is not necessary for the generation of circadian sleep rhythms, but the amplitude of the rhythms may be modulated by the circadian release of AVP into CSF.

Animals↗
PubMed1989

Computer-assisted semen analysis: results vary across technicians who prepare videotapes.

Automated semen analyses revealed differences of 21% to 30% in concentration-related parameters and 5% to 11% in motion-related parameters between means of groups of replicate specimens. Disparities among videotapes produced by two laboratory technicians accounted for the divergence in concentration-related parameters. This resulted partially from differences between the two technicians in propensity to dilute concentrated specimens. The causes of the greater portion of disparities between videotaping technicians, however, have not been identified. Differences in motion-related parameters could not be ascribed to technicians, but the basis for these differences is also unknown. The results suggest that values obtained from the CellSoft image analysis system may not be comparable between technicians or laboratories, despite use of identical computer parameter settings. Until effective quality control measures have been implemented, such comparisons must be made with caution.

Diagnosis, Computer-Assisted↗
PubMed1989

Unit-based research forums: a model for the clinical nurse specialist to promote clinical research.

Although nurse researchers have generated research findings, practitioners in clinical practice have not consistently utilized them. Evaluation and modification of clinical practice through research is a key component of the role of the clinical nurse specialist (CNS). In this paper, an innovative model is described in which the Clinical Nurse Specialist coordinates specialty-based clinical research through the use of unit-based research forums, an outgrowth of unit-based quality assurance. Such a model allows staff at the unit level to engage in problem-solving dialogues, resulting in increased use of research findings and generation of original research.

Clinical Nursing Research↗
PubMed1988

Murine CD2 gene expression during fetal thymus ontogeny.

The expression of the murine CD2 gene and the interleukin 2 receptor IL2R has been investigated during fetal thymus ontogeny. CD2 mRNA was undetectable at embryonic day 14 but was readily detectable at day 15 of gestation. Surface IL2R expression was maximal at day 14 and was clearly detectable at day 13. These results indicate that IL2R expression precedes that of CD2 by at least 2 days.

Animals↗
PubMed1988

Species conservation of the T cell lymphocyte CD2 cell surface antigen.

A rabbit polyclonal antiserum was raised against a synthetic peptide, termed CD2-300, comprizing 18 amino acid resides which are conserved among the cytoplasmic domains of the human, rat and mouse CD2 antigens. Cross-depletion experiments showed that the CD2 monoclonal antibody OKT11 and purified CD2-300 antibodies (Ab) precipitated the same molecules from the surface of human T lymphoblasts. The results of immunoprecipitation analyses indicated that the purified CD2-300 Ab were specific for human and mouse CD2, and that the CD2-300 peptide competitively and specifically inhibited precipitation by CD2-300 Ab in both species. When employed to stain murine tissues, the CD2-300 Ab gave the anticipated pattern of distribution for the CD2 antigen, although there was some nonspecific labeling of non-T cells.

Animals↗
PubMed1988

Unusual expression of CD2 in sheep: implications for T cell interactions.

The CD2 adhesion/activation molecule on the surface of mammalian T lymphocytes binds to a ubiquitous receptor, LFA-3. We show that CD2 in sheep differs significantly in its expression from CD2 in humans, and this most likely relates to the high level of expression of the sheep LFA-3 molecule. In sheep, in contrast to man, CD2 was weakly expressed on peripheral T cells and thymocytes. Moreover, a large subset of T cells identified by the monoclonal antibody T19 and considered to be gamma/delta receptor-bearing T cells completely lacked the CD2 molecule. T19+ cells constituted up to 50% of peripheral blood T cells in lambs, and 20-30% of T cells in older sheep, whereas the CD4+ and CD8+ subsets, which are both CD2+, constituted relatively small subsets in peripheral blood. Only those T cells which did express CD2 adhered as "rosettes" to dendritic cells, and the localization of CD2 to the membrane junction indicated that CD2 was critical for this adhesion. However, CD2 adhesion was not necessary for CTL-mediated killing of allogeneic target cells, since T19+ cells generated in bulk mixed lymphocyte culture were extremely efficient at killing appropriate target cells. Some of the behavioral differences between T19+ and CD4+/CD8+ subsets might be explained by the presence or absence of CD2. The results also indicate that the expression of CD2 (and LFA-3) may differ markedly between species.

Animals↗
PubMed1988

The structure of the human CD2 gene and its expression in transgenic mice.

We report the genomic organization of the human CD2 gene and its expression in transgenic mice. A 28.5 kb segment of DNA consisting of 4.5 kb 5' flanking sequences, 15 kb containing the gene's five exons and 9 kb of 3' flanking sequences can direct the expression of the CD2 gene only on thymocytes, circulating T cells and megakaryocytes of the transgenic mice. The expression of each copy of the human CD2 transgene appears to be as high as the endogenous mouse CD2 gene and as high as the expression on the surface of human T lymphocytes, independent of the site of integration and dependent on the copy number of genes that have integrated.

Amino Acid Sequence↗
PubMed1988

The human LFA-3 gene is located at the same chromosome band as the gene for its receptor CD2.

Lymphocyte function-associated antigen 3 (LFA-3) is a widely distributed cell surface glycoprotein that has been assigned a role in cell-cell adhesion on the basis of its capacity to bind to the T-lymphocyte CD2 antigen. The amino acid sequences of the extracellular domains of these two antigens, predicted from their cDNA sequences, show significant similarities, and both are members of the immunoglobulin supergene family. In this communication, a probe prepared from LFA-3 cDNA has been used in Southern blot analyses of somatic cell hybrids and in in situ hybridization to assign the LFA-3 gene to the human chromosome band 1p13. This is the same location previously assigned to CD2. Thus the LFA-3 and CD2 genes have probably arisen by duplication of a common evolutionary precursor. These genes therefore represent a further instance in which related members of the immunoglobulin superfamily are located in adjacent regions of the genome.

Animals↗
PubMed1988

Axon-sparing lesions of the hypothalamic paraventricular nucleus abolish gonadal responses to photoperiod in male Syrian hamsters.

Intrahypothalamic injections of the excitotoxin N-methyl-D,L-aspartic acid (NMA) that destroyed the parvocellular regions of the paraventricular nucleus (PVN) prevented gonadal regression in male hamsters (Mesocricetus auratus) kept in short days (LD 6:18). After 17 weeks in short days, these NMA-injected animals had large, functional gonads and displayed all components of male sexual behavior. These findings confirm that neurons of the PVN are part of the pathway that mediates photoperiodism in hamsters.

Animals↗
PubMed1988

The monoclonal antibody, UCHL1, recognizes a 180,000 MW component of the human leucocyte-common antigen, CD45.

The leucocyte-common antigen (L-CA or CD45) is a family of high molecular weight glycoproteins, ranging from 180,000 to 220,000 MW that are expressed only on cells of lymphoid and myeloid origin. CD45 monoclonal antibodies (mAbs) recognize epitopes present on all polypeptides of the family, while other mAbs, termed CD45R, recognize determinants found only on the 220,000 MW and 200,000 MW polypeptides. In contrast the mAb UCHL1 recognizes a 180,000 MW antigen. UCHL1-coupled Sepharose beads were used to absorb antigen from lysates of cell lines. CD45 mAbs bound to this immobilized antigen. Antigen immobilized with CD45 mAb-coupled Sepharose beads bound UCHL1. Antigen purified by absorption and elution from the MOLT-4 cell line with CD45 mAb-coupled beads yielded molecules of 180,000 and 190,000 MW. Reprecipitation of the eluted antigen with UCHL1 resulted in a 180,000 MW band only. In a reciprocal experiment, CD45 mAb reprecipitated a 180,000 MW molecule from purified UCHL1 antigen. UCHL1 and the CD45R mAb 2H4 showed a mutually exclusive pattern of reactivity with human T- and B-cell lines, but co-expression of the antigens was seen on two myeloid and one erythroleukaemic cell line. In contrast, epitopes recognized by other putative CD45R mAbs were co-expressed with UCHL1 both on myeloid, erythroid and many T- and B-cell lines. We conclude that UCHL1 recognizes an epitope present only on the 180,000 MW polypeptide of CD45. Expression of this antigen is essentially reciprocal to the epitope detected by the CD45R mAb 2H4.

Antibodies, Monoclonal↗
PubMed1988

Deterioration of semen quality during summer in New Orleans.

A retrospective investigation of semen quality was undertaken at a fertility clinic in New Orleans. Semen specimens obtained during the summer had significantly lower sperm concentration, total sperm per ejaculate, percent motile sperm, and motile sperm concentration than samples provided at other times of year. Substantial summer deterioration in semen quality was likely to occur only among men whose work places were probably not air-conditioned. These findings suggest that the deleterious effects of summer heat on spermatogenic cells or on epididymal spermatozoa may reduce male fertility and account, at least partially, for the deficit of spring births in warm climates throughout the world.

Analysis of Variance↗
PubMed1987

Evidence that neurons of the paraventricular nucleus of the hypothalamus with projections to the spinal cord are sensitive to the toxic effects of N-methyl aspartic acid.

Controversy exists concerning the sensitivity of neurons of the paraventricular nucleus (PVN) of the hypothalamus to the toxic effects of N-methyl aspartic acid (NMA). To further investigate this problem, male golden hamsters (Mesocricetus auratus) received unilateral intrahypothalamic injections of NMA, coupled with injections of horseradish peroxidase into the area of the spinal cord which receives projections from the PVN. Histological evaluation of the brains showed that the NMA injections destroyed PVN neurons that project to the spinal cord. These results are discussed in reference to previous reports on the effects of NMA injections on photoperiod-dependent seasonal cycles in hamsters.

Animals↗
PubMed1987

Purification and N-terminal amino acid sequence of the human T lymphocyte CD2 (T11) surface antigen.

CD2 (the sheep erythrocyte receptor) is a surface antigen of human T lymphocytes. A role for CD2 in T cell function has been implicated from the observation that antibodies against CD2 are capable of transmitting both positive and negative signals for cell growth. Biochemically, the molecule has been identified as a broad band on sodium dodecyl sulfate (SDS)-polyacrylamide gels of about 50-58 kDa. This communication demonstrates that CD2 contains N-linked carbohydrate as endo-beta-N-acetylglucosaminidase F digestion reduced its apparent mol. mass to a compact band of 40 kDa. CD2 was purified from the T leukemia cell line J6 by immunoaffinity chromatography and preparative SDS-polyacrylamide gel electrophoresis (PAGE). Four bands of 52, 54, 56 and 58 kDa could be distinguished in the immunoaffinity-purified protein which formed a broad zone on SDS-PAGE extending from about 45 to 58 kDa. Preparative SDS-PAGE yielded a product suitable for determining the N-terminal amino acid sequence. Assignments were made for the first 26 (excluding the 23rd) residues and the sequence identified a novel polypeptide.

Amino Acid Sequence↗
PubMed1987

The murine homologue of the T lymphocyte CD2 antigen: molecular cloning, chromosome assignment and cell surface expression.

The human T lymphocyte antigen CD2 (T11, sheep erythrocyte receptor) is expressed on all peripheral T cells and all but the most immature thymocytes. Experiments with monoclonal antibodies against CD2 suggest that CD2 is the cell surface receptor for a natural ligand involved in T cell proliferation. Clarification of the functional role of CD2 would be facilitated by the identification of CD2 in the mouse. However, antibodies that recognize the murine homologue have not been described. An alternative approach to the identification of the murine homologue was to use cross-species DNA hybridization, employing human CD2 cDNA as a probe. Clones encoding the murine homologue were isolated from a murine T helper cell cDNA library. The murine cDNA sequence encoded a predicted mature polypeptide of 322 amino acids that showed 54% identity with the predicted human sequence. As with the human polypeptide, the cytoplasmic domain was large, and rich in proline and basic residues. CD2 mRNA was expressed in murine thymus and spleen, and in the T cell line EL4. The murine CD2 gene was assigned to chromosome 3 by Southern blot analysis of mouse-hamster somatic cell hybrids. A rabbit antiserum raised against purified human CD2, precipitated from surface-labeled mouse thymocytes a glycoprotein of Mr 55,000-66,000 which decreased to Mr 35,000 on digestion with endo-beta-acetylglucosaminidase F. These sizes are consistent with those predicted for the murine CD2 antigen from the cDNA sequence.

Amino Acid Sequence↗
PubMed1987

The gene coding for the human T-lymphocyte CD2 antigen is located on chromosome 1p.

A cDNA clone encoding the human T lymphocyte sheep erythrocyte receptor [the CD2 (T11) antigen] was used as a probe to define the chromosomal location of the gene. The signal, revealed by hybridisation to Southern blots of genomic DNA from somatic cell hybrids, showed a high degree of concordance for human chromosome 1. In particular, the hybrid F4Sc13C19 which contained the short arm only of human chromosome 1 was positive. The location of the CD2 gene to 1p13 was confirmed by in situ hybridisation.

Animals↗