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Biomedical subjects

M D Smith

Publications and source records attributed to M D Smith.

At least 199 records · Page 11Linked to original sources
PubMed1997

Granuloma annulare.

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Granuloma Annulare↗
PubMed1997

A nonradioactive method of in situ hybridization that uses riboprobes and paraffin-embedded tissue and its combination with immunohistochemistry.

Current research into cytokine production in tissue sections relies on the detection of cytokine proteins using a variety of immunohistochemical methods. The disadvantages of this technique are that precise localization to a particular cell is difficult and it is uncertain whether the cells detected by this method are the origin or target of the cytokine or rather have nonspecifically absorbed the secreted cytokine. This question can be clarified using in situ hybridization, but current techniques are insensitive, poorly localizing, or time consuming. Biotin-labeled riboprobes were generated from cDNA fragments sandwiched between two RNA polymerase promoters (SP6 and T7 RNA polymerases) using a commercial riboprobe generation kit containing biotin-labeled UTP. The in situ hybridization technique was used to demonstrate cytokine mRNA in a range of tissues containing an inflammatory infiltrate and with a range of cytokine probes. This technique of in situ hybridization was combined with immunohistochemistry using an immunoalkaline phosphatase technique to show the powerful combination of these two techniques. The biotin-labeled riboprobes were sensitive enough to detect a range of cytokine mRNAs in a variety of tissue sections. The technique can be completed over a 24-h period and produces a stable color product that can be stored for long periods and can be quantitated using image analysis techniques. This technique was performed on paraffin-embedded tissue as well as cryosections and allowed for the detection of mRNA in archival tissue. It was also successfully combined with immunohistochemical techniques to determine simultaneously the localization of a cytokine product in particular cell lineages. A nonradioactive method for in situ hybridization using biotin-labeled riboprobes is described; it is capable of detecting mRNA products from a range of genes in a variety of tissue samples. An amplification step in the method enhances the sensitivity to a level that approaches that of radioactive methods, while maintaining the speed, safety, and simplicity of an immunoperoxidase detection system. The ability to use paraffin-embedded tissue with this method allows for improved tissue architecture and examination of archival tissue. These features should ensure greater use of in situ hybridization techniques in future research studies.

Arthritis, Rheumatoid↗
PubMed1997

Ribotype differences between clinical and environmental isolates of Burkholderia pseudomallei.

Burkholderia pseudomallei is isolated frequently from the soil in regions where the disease melioidosis occurs. However, recent surveys in Thailand have shown that the frequency of isolation of the organism from soil samples is not directly related to the incidence of melioidosis in an area. To determine whether strain populations of B. pseudomallei prevalent in soil are gentypically related to strains causing clinical disease, rRNA BamHI restriction fragment length polymorphisms (RFLP) of 139 soil environmental isolates and 228 human isolates were compared. Two groups of ribotype patterns were found. Group I comprised 37 different ribotype patterns which were characterised by five to eight hybridisation bands of 2.8- > 23 kb. All of these ribotypes were identified among the clinical isolates, and 18 of them were also found in 59 environmental isolates. Group II was represented by 12 ribotypes found only in environmental strains. These ribotype patterns comprised one to five bands in the size range 9- > 23 kb. All but one of the 73 isolates in this group grew on a minimal medium supplemented with L-arabinose. In contrast, only 3% of the 66 isolates from the environment with group I ribotype patterns could utilise this sugar as their sole energy source. These findings suggest that B. pseudomallei strains that utilise arabinose constitute a population that is genetically distinct from other environmental and clinical strains.

Arabinose↗
PubMed1997

Arabinose assimilation defines a nonvirulent biotype of Burkholderia pseudomallei.

Two distinct types of Burkholderia pseudomallei, differentiated by the ability to assimilate L-arabinose but with similar morphologies and antigenicities, can be isolated from soil in Thailand. Approximately 25% of soil isolates from northeast Thailand were arabinose assimilators (Ara+), but in 1,200 sequentially studied patients, only arabinose "nonassimilators" (Ara-) caused melioidosis (P < 0.0001). In a murine model, there was a striking difference in virulence between Ara- and Ara+ B. pseudomallei. The mean (standard deviation) 50% lethal dose (LD[50]) inoculum for Ara- isolates was 182 (111) CFU/mouse compared with approximately 10(9) CFU/mouse for Ara+ soil isolates. There was no significant difference between the LD(50)s for clinical and soil Ara- isolates. All attempts to convert the biochemical phenotype by selective culture failed, which suggests that the biotype is stable.

Animals↗
PubMed1997

Specificity and functional activity of anti-Burkholderia pseudomallei polysaccharide antibodies.

The lipopolysaccharide (LPS) of Burkholderia pseudomallei, the causative agent of melioidosis, consists of two O-antigenic polysaccharides designated O-PS I and O-PS II. In this study, the O-PS specificity and functional activity of a protective polyclonal antiserum and an immunoglobulin M (IgM) monoclonal antibody were determined. The polyclonal antiserum recognized both O-PS I and O-PS II, while the monoclonal antibody was O-PS II specific. Both mediated phagocytic killing of B. pseudomallei by polymorphonuclear leukocytes. Patients acutely infected with B. pseudomallei also produced antibodies to the two O-PSs, but these antibodies were not produced by asymptomatic individuals from an area of endemicity who were seropositive by an indirect hemagglutination test using sonicated heat-killed whole organisms as antigen. IgM antibodies were detected only in patients with localized infection. IgG antibodies were detected in all acutely infected patients, but there was no significant difference in antibody levels among patients with localized infection, patients who survived septicemic illness, and patients who died from septicemic illness. Further analysis of the IgG response revealed production of IgG1 and IgG2 antibodies by all patient groups, while an IgG3 response was seen only in survivors of septicemic infection. IgG4 was not detectable even when a fivefold-lower serum dilution was used. Patient sera also mediated phagocytic killing by polymorphonuclear leukocytes, and the killing effect was enhanced by complement. These results suggest that antibodies to the LPS O-polysaccharides of B. pseudomallei are protective by promoting phagocytic killing. The antibodies develop during human infection and may facilitate clearance of the organisms, as seen in a diabetic rat model of B. pseudomallei infection.

Antibodies, Bacterial↗
PubMed1997

The Brn-3a transcription factor induces neuronal process outgrowth and the coordinate expression of genes encoding synaptic proteins.

The Brn-3a POU family transcription factor is expressed only in posmitotic neurons in the central nervous system and identifies the first differentiated neurons to appear in the midbrain, hindbrain, and spinal cord during development. This factor is also induced when undifferentiated proliferating ND7 cells cease dividing and differentiate to a mature neuronal-like phenotype bearing numerous neurite processes. We show that overexpression of Brn-3a in undifferentiated ND7 cells induces a mature neuronal phenotype characterized by process outgrowth and the induction of genes encoding synaptic proteins, although the cells continue to proliferate. In contrast, the closely related factors Brn-3b and Brn-3c do not have this effect. Although the N-terminal activation domain of Brn-3a is required for maximum induction of neurite outgrowth and gene expression, these effects are primarily dependent on the DNA binding POU domain, which also acts as an activation domain. Overexpression of the isolated POU domain of Brn-3a is sufficient to induce neurite outgrowth, while the ability of full-length Brn-3a to do so is abolished by mutating a single amino acid in the Brn-3a POU homeodomain to its equivalent in Brn-3b. Thus, Brn-3a appears to play a critical role in the specification of the mature neuronal phenotype, acting by stimulating the expression of genes whose products are required for process outgrowth and synapse formation.

Animals↗
PubMed1997

Differential effects of polycationic protein on Cl- secretory and Na+ absorptive airways.

Effects of cationic proteins on electrolyte transport depend on the specific channels and electrochemical driving forces expressed by epithelia. The bioelectric responses of canine tracheal and bronchial epithelia (CTE and CBE, respectively) to a polycationic protein, protamine, were therefore compared. CTE exhibited a brief transient inhibition of shortcircuit current (I(SC)) followed by a prolonged increase of 18 microA/cm2. The apical membrane transiently hyperpolarized and then depolarized by 11 mV. The increase in I(SC) was inhibited by bumetanide. Adenosine 3',5'-cyclic monophosphate, ionomycin, and thapsigargin attenuated the response whereas indomethacin or hypotonic solution had no effect, indicating that latent cystic fibrosis transmembrane regulator Cl- channels were activated. CBE preparations exhibited a 4-microA/cm2 decrease in I(SC), 2 mV hyperpolarization of the apical membrane, and an increase in fractional resistance of the apical membrane on exposure to protamine. These results were consistent with inhibition of the Na+ conductance in the apical membrane of CBE and confirmed that polycationic proteins exert differential effects on Cl- secretory and Na+ absorptive airways.

Absorption↗
PubMed1997

Hormone replacement therapy: a review of the risk versus benefit--Part II.

As the large ¿baby-boom¿ cohort of women enters the period of menopause, much attention is being focused on the potential public health benefits of hormone replacement therapy (HRT) and its relative safety. Increasingly, economic models derived from these studies define populations of women most likely to benefit from this treatment. This paper will review the clinical efficacy and safety of HRT and examine published pharmacoeconomic studies evaluating the use of HRT for post-menopausal women. Ultimately, the cost effectiveness of HRT is dependent on the extent of the cardioprotective effect of estrogen and estrogen-progestin combination therapy. Part II of this article describes the pharmacologic evidence that serves as a basis for evaluating HRT.

Aged↗