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Biomedical subjects

D M Baker

Publications and source records attributed to D M Baker.

At least 55 records · Page 3Linked to original sources
PubMed1993

Magnetic resonance imaging of the thoracic aorta.

Magnetic resonance imaging (MRI) is steadily becoming recognized as a premier imaging modality for evaluating the thoracic aorta. Its noninvasive, nonimaging approach and refined resolution capabilities effectively combine the advantages of echocardiography, angiography, and computed tomography (CT) under the auspices of a single imaging device. On static spin-echo MRI, blood flow appears dark, allowing superb depiction of both intra- and extra vascular anatomy. With dynamic MR studies, gradient echo (cine) and phase velocity mapping techniques have proven effective in assessing the physiological consequences of anatomic vascular abnormalities in a qualitative and quantitative manner, respectively. Magnetic resonance angiography (MRA) is fast becoming a prominent vascular imaging method. Although still evolving, MRA bolsters the vascular imaging capabilities of MRI by enhancing the imaging resolution of the major branch vessels and collateral vessels. With continued advances in this area, MRI may adopt the role as the primary imaging method for assessing the thoracic aorta.

Aorta, Thoracic↗
PubMed1993

Protective efficacy of BCG vaccine against leprosy in southern Malaŵi.

This paper describes a matched case-control study to determine the efficacy of BCG vaccine in preventing the occurrence of leprosy in southern Malaŵi, a previously unstudied area. The BCG immunization rate amongst 145 individuals with leprosy was 44.8%, compared to 62.5% in 290 matched controls. The protective efficacy of BCG vaccine against leprosy in this region was estimated to be 63.6%; smallpox immunization had no effect. These findings support the view that BCG vaccine should be considered as a control measure in areas where leprosy is endemic.

Adolescent↗
PubMed1993

Assessment and management of impairments in swallowing.

Assessment of related factors and defining characteristics can assist the nurse to identify and refer patients with potential or actual impaired swallowing. Once the nature of the patient's swallowing difficulties has been confirmed, nurses can intervene to decrease the risk of aspiration, maintain food and fluid intake, and teach patients and families.

Combined Modality Therapy↗
PubMed1993

Outcome of surgical management of the thoracic outlet compression syndrome in a district general hospital.

The 5-year experience of one surgeon in treating 50 consecutive patients (57 limbs) with the thoracic outlet compression syndrome (TOCS) is described. A predominance of neurological symptoms presented; each was treated in a similar fashion with extensive resection of the first rib and excision of fibrous bands and cervical ribs. Results of surgery (84% complete resolution or improvement of symptoms) compare favourably with others. This series demonstrates that although the technicality of the surgery demands a surgeon very familiar with the operation, this need not be undertaken in a regional centre.

Adolescent↗
PubMed1992

Identification of the promoter of the myelomonocytic leukocyte integrin CD11b.

The CD11b (or macrophage-1 antigen; MAC-1) subunit of the leukocyte integrin family forms a noncovalently associated heterodimeric structure with the CD18 (beta) subunit on the surface of human granulocytes and monocyte/macrophages, where it enables these myeloid cells to participate in a variety of adherence-related activities. Expression of the CD11b subunit is restricted to cells of the myelomonocytic lineage and depends upon the stage of differentiation with the most mature myeloid cells expressing the highest levels of CD11b. To study the regulation of CD11b expression, a genomic clone corresponding to the 5' region of the CD11b gene was isolated from a human chromosome 16 library. Primer extension and RNase protection assays identified two major transcriptional start sites, located 90 base pairs and 54 base pairs upstream from the initiation methionine. DNA sequence analysis of 1.7 kilobases of the 5' flanking sequence of the CD11b gene indicated the absence of a "CAAT" or "TATA" box; however, potential binding sites for the transcription activators Sp1, PU.1, ets, and AP-2 are present, as well as retinoic acid response elements. The 1.7-kilobase CD11b promoter sequence displayed functional activity in transient transfection assays in the monocytic cell line THP-1 and the myeloid cell line HL-60. In contrast, this 1.7-kilobase promoter sequence did not display functional activity in the Jurkat T-lymphoid cell line. Detailed characterization of the CD11b promoter sequence should provide insight into the molecular events regulating the tissue-specific and developmental stage-specific expression of the CD11b molecule in myelomonocytic cells.

Amino Acid Sequence↗
PubMed1990

Development of a quantitative histochemical method for determination of succinate dehydrogenase activity in autonomic neurons and its application to the study of aging in the autonomic nervous system.

An accurately validated method was developed for quantitative determination of succinate dehydrogenase (EC 1.3.99.1; SDH) activity in individual sympathetic neuron perikarya by microdensitometric measurement of an SDH-nitroblue tetrazolium-derived formazan final reaction product. Optimal incubation medium and reaction conditions were determined for measurement of reaction product in cryostat sections of rat superior cervical and celiac-superior mesenteric ganglia. The Beer-Lambert laws were verified for the ganglion tissue, and microdensitometric measurements (expressed as mean cell density readings; MCDR/min-1), characteristic of the Michaelis-Menten equation, enabled the results to be used for enzyme kinetic determinations of SDH activity. Km and Vmax values were obtained following Hans linear transformation of the readings. Between the ages of 6-24 months no significant variations in Km values were recorded, indicating an unchanged structure for SDH (overall mean Km = 0.083 +/- 0.055 mM). However, in both ganglia there were significant decreases (ranging from 43-54%) in Vmax values for SDH at 24 months. The overall mean Vmax value at 6 months was 4.01 +/- 0.61 (MCDR) and at 24 months was 2.07 +/- 0.76 (MCDR). This suggests that an overall decrease in metabolic activity takes place with age in sympathetic neurons of the rat superior cervical and celiac-superior mesenteric ganglia.

Aging↗
PubMed1990

Isobestic wavelength determination for succinic dehydrogenase-nitroblue tetrazolium-derived formazans in autonomic neurons.

Two methods have been used to determine the isobestic (equiconcentration) wavelength of formazans derived from nitroblue tetrazolium-succinate dehydrogenase (EC 1.3.99.1) activity in cryostat sections of the rat superior cervical ganglion prior to microdensitometric measurements. Both methods indicate that maximal absorbance of the final reaction product is at a wavelength of 540-550 nm. This wavelength differs by 35-45 nm from that used to measure the same reaction product in sections of other rat tissues such as liver and implies that it may be unwise to adopt a "standard" wavelength for a particular reaction product when making microdensitometric measurements in relation to quantitative enzyme histochemistry.

Animals↗
PubMed1989

Expression of surface antigen and mRNA for the CD11c (alpha X, p150) subunit of the human leukocyte adherence receptor family in hematopoietic cells.

We characterized the surface antigen and mRNA expression for the CD11c (alpha X, p150) subunit of the human leukocyte adherence receptor family during hematopoietic cell differentiation. The CD11c subunit antigen and mRNA are constitutively expressed in undifferentiated HL-60 promyelocytic leukemia cells, and levels increase markedly with differentiation along the monocyte/macrophage pathway using phorbol myristate acetate. Human monocyte-derived macrophages and human alveolar macrophages express elevated levels of the CD11c subunit antigen and mRNA, indicating that the changes observed in vitro are present in vivo. Dot blot analysis of immature and mature lymphoid and myeloid cells and cell lines demonstrate equivalent levels of CD11c mRNA expression. We conclude that CD11c gene expression is selectively increased during hematopoietic cell differentiation along the monocyte/macrophage pathway.

Antigens, Differentiation↗
PubMed1989

Morphometric studies on the microvasculature of pre- and paravertebral sympathetic ganglia in the adult and aged rat by light and electron microscopy.

Morphometric measurements have been made by light and electron microscopy on sections of perfused sympathetic ganglia from rats of 6-24 months of age with special reference to the microvascular bed. Capillaries, postcapillary venules and small venules comprised the majority of the vessels studied but small arterioles were, in addition, included in the light microscopical part of the study. Light microscopical measurements using image analysis showed that there was a decrease in the density of the microvascular bed (number of vascular profiles/area) and in the total vascular luminal area with age in both ganglia. The ratio of neurons to microvessels remained constant in the superior cervical ganglion (SCG) but decreased with age in the coeliac-superior mesenteric ganglion (CSMG). However, the distribution of microvessels in relation to individual neurons remained unchanged throughout life in both ganglia. Ultrastructural studies revealed fenestrations in 12% of SCG microvessel profiles and in 38% of CSMG microvessels at 6 months, but the percentage of fenestrated profiles in the CSMG had declined by 24 months. There were no significant differences in the number of fenestrations per fenestrated profile. The basal lamina surrounding the microvessels increased significantly (almost doubling) in thickness with age. The range and distribution of microvessel wall thicknesses, expressed as harmonic mean wall thickness, were comparable in both ganglia at both ages and increased linearly according to the amount of pericyte covering present. No consistently significant relationships could be discerned between the microvessel wall thickness and luminal diameter or between the wall thickness and the area available to a given volume of blood for exchange of metabolites (luminal perimeter/luminal area). We conclude that the ganglionic capillary bed is similar in both ganglia and, in old age, accommodates structural changes that occur in the ganglion by maintaining its structure and relationship to individual neurons.

Age Factors↗
PubMed1989

Image analysis of the sympathetic innervation of the myenteric plexus in the small intestine of mammalian species.

1. The arrangement of the sympathetic innervation of the myenteric plexus varies between mammalian species. 2. In larger mammals the density of sympathetic innervation of the myenteric plexus is significantly less than in small (less then 1 kg) species. 3. The number of varicosities on the terminal parts of sympathetic neurons innervating the gut is significantly less in larger mammals.

Animals↗
PubMed1989

cDNA sequence for the alpha M subunit of the human neutrophil adherence receptor indicates homology to integrin alpha subunits.

The receptor on human neutrophils (polymorphonuclear leukocytes) that mediates cellular adherence consists of two noncovalently associated subunits, designated alpha M (Mac-1 alpha, Mol alpha, or CD11b; Mr, 170,000) and beta (Mac-1 beta, Mol beta, or CD18; Mr, 100,000). We isolated a cDNA clone for the human neutrophil alpha M subunit by screening a lambda gt 11 cDNA library made from chronic myelogenous leukemia neutrophils by using an affinity-purified rabbit polyclonal antibody directed against the alpha M subunit. We used this cDNA clone to obtain additional clones from cDNA libraries made from differentiated HL-60 promyelocytic leukemia cells. Together these cDNAs constitute the complete 1137-amino acid sequence for the mature human alpha M subunit protein. The deduced amino acid sequence indicates the presence of an extensive extracellular domain with three putative metal-binding regions, (i) an amino acid region that is homologous to the A domain of von Willebrand factor, (ii) a 26-amino acid hydrophobic sequence that is a potential transmembrane domain, and (iii) a 19-amino acid cytoplasmic region. The amino acid sequence for the human neutrophil alpha M subunit contains regions that are closely related to amino acid sequences of adhesion receptors belonging to the integrin family.

Amino Acid Sequence↗