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Biomedical subjects

M Howell

Publications and source records attributed to M Howell.

At least 19 recordsLinked to original sources
PubMed1992

Cloning a replication function from the streptomycete bacteriophage FP43.

Streptomyces griseofuscus cells carrying a 4.4-kb SphI DNA fragment from bacteriophage FP43 inhibited plaque formation (Pin) by FP43, and the Pin function was localized to a 0.96-kb SacII fragment. The same 4.4-kb SphI fragment was able to replicate freely in several streptomycetes, including S. griseofuscus, and the replication (Rep) function was localized to a 1.2-kb SphI-FspI fragment. Plasmids with FP43 Rep function are unstable and are present at about 20-50 copies per chromosome. Plasmids with FP43 Rep function are compatible with SCP2* plasmids.

Bacteriophages↗
PubMed1992

Self-reactivity and the expression of memory markers vary independently in MRL-Mp+/+ and MRL-Mp-lpr/lpr mice.

MRL-Mp-lpr/lpr mice contain phenotypically abnormal populations of T cells, and exhibit an SLE-like autoimmune disease in which autoantibodies are a prominent feature. We analyzed the phenotype and T-cell receptor V beta expression pattern in CD4+ T cells of this mutant mouse strain to detect abnormalities that could explain the autoimmunity. The CD4+ T cells contain two distinct abnormal populations. One of these expresses B220 and HSA, and in these and other respects closely resembles the accumulating CD4-CD8- population. The other expresses a high level of CD44 (Pgp-1), and a high level of the 16A epitope of CD45, and so resembles post-activation T cells. Both of these cell types are exclusive to MRL-Mp-lpr/lpr. We also identified V beta 5- and V beta 11-positive CD4+ T cells, in both MRL-Mp-lpr/lpr and MRL-Mp-+/+ mice. We conclude that autoimmune T cells can be detected in these mice, but that they are not the cause of the accumulation of abnormal CD4+ and CD4-CD8- cells.

Animals↗
PubMed1991

Structure and expression of subunit A from the bovine chromaffin cell vacuolar ATPase.

Subunit A of the vacuolar H(+)-ATPase class is thought to be responsible for the ATP hydrolysis which drives proton-pumping. We report here the cloning and sequence determination of the first mammalian cDNA encoding a bovine vacuolar ATPase subunit A from an adrenal medulla cDNA library. Northern blots of bovine adrenal medulla RNA reveal a message of approximately 3.8 kb. The predicted peptide sequence, consisting of 618 amino acids with a calculated molecular weight of 68397 daltons, is similar to the sequences of the three known subunit A proteins. beta-Galactosidase-subunit A fusion proteins were immuno-decorated by an antiserum raised to the subunit A protein from corn coleoptile vacuoles.

Adenosine Triphosphatases↗
PubMed1991

Effect of a bulk-forming cathartic on diarrhea in tube-fed patients.

Diarrhea is a significant complication for the patient being tube-fed. The purpose of this study was to observe whether giving a bulk-forming cathartic to patients receiving enteral nutrition via nasogastric or nasoduodenal tube would result in firmer stools for these patients. Forty-nine patients in a large medical center were randomly assigned to either a control or an experimental group. During the 6-day study period 1 teaspoon (5 ml) of psyllium preparation was administered through the feeding tube three times a day. Data were analyzed by using the Mann-Whitney U test for nonparametric data. The hypothesis that giving a bulk-forming cathartic would lead to firmer stools was supported at an alpha level of less than 0.01. The results of this study suggest that use of a bulk-forming cathartic in tube-fed patients will significantly reduce the diarrhea associated with this type of feeding.

Administration, Oral↗
PubMed1988

CD3+ CD8+ T cell lymphocytosis masking B cell leukaemia.

A patient with CD3, CD8 positive lymphocytosis presented with features consistent with T cell chronic lymphocytic leukaemia/proliferations of large granular lymphocytes. The marrow and blood lymphoid populations (19.4 x 10(9)/l) contained more than 80% CD3 and CD8 positive cells with no evidence of a monotypic B cell population. A biopsy specimen of a vasculitic rash showed a diffuse infiltrate of CD3, CD8 positive cells into the upper dermis, consistent with T cell lymphocytic disease. After follow up for two years without treatment the blood lymphocyte count was 53 x 10(9)/l and was composed of cytologically small lymphocytes. A monoclonal SIg M D k lymphoid population (more than 90%) was demonstrable in sample blood and marrow aspirate. Gene rearrangement studies carried out on DNA extracted from peripheral blood lymphocytes at presentation and at two year follow up exhibited JH and Ck immunoglobulin gene rearrangement but no rearrangement of T cell receptor TcR gamma and beta genes. It is thought that this is the first well documented case of an aggressive CD8 positive lymphocytosis preceding, or in response to, an underlying B cell neoplasm.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1986

The non-ionic dimers: a new class of contrast agents.

Non-ionic dimers are a new class of iodinated radiological contrast agents. Some physico-chemical and pharmacological properties of three representative compounds are presented. Non-ionic dimers are iso-osmolar with plasma at all iodine concentrations unless diluted with saline and in terms of chemotoxicity they appear to be closely comparable with the established non-ionic monomeric agents. It is shown that the data lend support to the theory that it is the degree of steric hindrance of the hydrophobic iodine atoms by side-chains which determines this chemotoxicity. Areas in which agents of this type may find applications are indicated.

Chemical Phenomena↗
PubMedDate not supplied

Autonomic and cardiovascular responses of preschool children to television programs.

This exploratory study examined the heart rates (HR) and skin temperatures (ST) of 18 preschool children while they viewed two clips of everyday children's television (TV) programming. The measurements were made in a day care setting, in a naturalistic environment designed to mimic the real world of children's TV viewing. The purpose of the study was to determine whether cardiovascular and autonomic arousal to TV programming might occur in some children. Since a large body of psychosocial literature addresses the affects of TV violence on children, HR and ST were examined during exposure to scenes from Mr. Roger's Neighborhood and G.I. Joe cartoons. The Mr. Roger's clip was slow, rhythmic, prosocial, and nonviolent, while the G.I. Joe clip was fast-paced, staccato, colorful, and full of verbal and action violence. The study found a significant effect of exposure to the cartoon violence on HR, with HR increasing. ST decreased, but not significantly, and there was a significant effect of time on the ST, due possibly to habituation. This finding has relevance to nursing assessment, intervention, and education of parents and children, since TV viewing is a pervasive cultural phenomenon. The possibility of excessive or inappropriate autonomic and cardiovascular responsiveness in some children to TV must be considered.

Body Temperature↗