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H E Duncan

Publications and source records attributed to H E Duncan.

5 recordsLinked to original sources
PubMed1996

Molecular lesions associated with alleles of decapentaplegic identify residues necessary for TGF-beta/BMP cell signaling in Drosophila melanogaster.

We have identified the molecular lesions associated with six point mutations in the Drosophila TGF-beta homologue decapentaplegic (dpp). The sites of these mutations define residues within both the pro and ligand regions that are essential for dpp function in vivo. While all of these mutations affect residues that are highly conserved among TGF-beta superfamily members, the phenotypic consequences of the different alleles are quite distinct. Through an analysis of these mutant phenotypes, both in cuticle preparations and with molecular probes, we have assessed the functional significance of specific residues that are conserved among the different members of the superfamily. In addition, we have tested for conditional genetic interactions between the different alleles. We show that two of the alleles are temperature sensitive for the embryonic functions of dpp, such that these alleles are not only embryonic viable as homozygotes but also partially complement other dpp hypomorphs at low temperatures. Our results are discussed with regard to in vitro mutagenesis data on other TGF-beta-like molecules, as well as with regard to the regulation of dpp cell signaling in Drosophila.

Alleles↗
PubMed1995

Host-microbe interaction in the gastrointestinal tract.

In order for an infection to occur, the target organ must come in contact with sufficient microbes, the microbe must possess specific virulence factors, these virulence factors must be expressed, and the defenses of the organ system must be overcome. This dynamic process, which is ongoing in all living entities, can be described by the following relationship: [formula: see text] The establishment of infection first occurs in a particular organ. This phenomenon is known as tissue trophism and the association of microbes with organ systems governs the practice of clinical microbiology and infectious disease. With some microbes (e.g., Giardia, Cryptosporidium) the interaction with the particular organ is so specific that infections are almost always confined to one site; with others (e.g., Salmonella, enterovirus) the microbe has the potential to become systemic. When attempting to establish health risk assessment from microbes by contact with food and drinking water, one must therefore consider that the gastrointestinal tract is a complex organ system with a variety of specific host defense mechanisms. It is only when the microbe has particular virulence factors for sites in gastrointestinal tract, and the specific host defense mechanisms in the gastrointestinal tract are breached, that infection of this organ system occurs. Therefore, the general terms "immunosuppression" or "immunocompromise" are meaningless unless the specific immune defect is known. A description of the microbial virulence factors active against the gastrointestinal tract and the defense mechanisms of this organ system are reviewed to provide a biological basis health risk assessment and future food and drinking water regulations.

Antibody Formation↗
PubMed1990

Evaluation of alveolar bone in relation to nutritional status during pregnancy.

Demand for nutrients necessary for the formation of mineralized tissues increases dramatically during pregnancy to meet fetal requirements. The purpose of this clinical study was to identify short-term effects of pregnancy and dietary intakes of calcium, phosphorus, protein, and vitamin C on radiographic density and alveolar crest morphology of the mandible. Seventy-six subjects between ten and 20 weeks' gestational age were recruited from the Jefferson County, Alabama, Department of Health maternity clinic. Initially, an evaluation of their diet was done, and a single periapical radiograph was taken in the canine-premolar region of the mandible. A final evaluation of the diet and a periapical radiograph of the same teeth were obtained at a time as close to the expected date of delivery as possible. Dietary evaluation consisted of a 24-hour recall history and a food-frequency history at the two visits. Radiographs were made with a bite-block film-holding system with occlusal registration in acrylic for reproduction of projection geometry at the two visits. An aluminum stepwedge was incorporated for densitometric standardization. Measurements of plaque, and bleeding and pocket-depth probing were recorded for control of local effects on alveolar change. Standard statistical procedures of regression determined correlation of 12 nutrients and periodontal variables with bone density change and with alveolar crest morphology change. Vitamin C intakes (24-hour recall) showed a positive correlation (p = 0.033) with bone density change, and calcium intakes (24-hour recall) showed a negative, but not significant, correlation (p = 0.058) with bone density change, contributed particularly by subjects with the highest calcium intakes. The strongest relation with alveolar crest morphology change was the interproximal pocket-depth change (p = 0.086).

Adult↗
PubMedDate not supplied

Assessment of dilation methods in achalasia: large diameter mercury bougienage followed by pneumatic dilation as needed.

In a retrospective study, 33 achalasia patients were treated with dilation therapy using large diameter mercury bougienage (mean, 56 French) and/or pneumatic balloon dilation. Mean follow-up time was 35 months. Mercury bougienage, performed in 20 patients, was successful in 10 (50%) with no complications. Pneumatic dilation was performed as initial therapy or in those having failed previous pharmacologic therapy and/or bougienage. A successful response was achieved in 19 of 23 patients (83%), with a 3.2% complication rate. In addition, in four patients with eventual recurrence of symptoms after initial pneumatic dilation, bougienage was used as a successful alternative to repeat pneumatic treatment. The combined efficacy of both forms of dilation was 88% with a complication rate of 1.4%. These data indicate that mercury bougienage should be considered initial therapy for achalasia in view of its simplicity, safety, and acceptable efficacy, followed by pneumatic dilation if bougienage is unsuccessful. Bougienage also may be considered if eventual recurrent symptoms develop after initially successful pneumatic dilation. Surgery should be utilized only if dilation therapy fails to achieve a satisfactory response.

Catheterization↗