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Biomedical subjects

R D Ward

Publications and source records attributed to R D Ward.

At least 91 records · Page 5Linked to original sources
PubMed1992

Public health issues.

In a recent MSMS survey, MSMS members ranked public health as one the top five issues of major concern to Michigan physicians. Tobacco use, chronic illness, and HIV-infected health care workers comprise some of the major public health issues facing physicians and patients in Michigan. Following is a brief examination of each of these issues. Also included is a brief discussion of medical doctors as public health directors. Should all public health directors be medical doctors? This question is addressed in this cover story.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Localization of wheat germ agglutinin and antibody binding sites on the plasma membranes of sea urchin sperm heads as revealed by label-fracture and fracture-flip.

Freeze-fracture electron microscopy reveals that intramembrane particles are concentrated in a band encircling the posterior portion of the acrosome of Strongylocentrotus purpuratus sperm. Two colloidal gold labeling methods, label-fracture and replica-staining fracture-flip, were employed to show that the plant lectin wheat germ agglutinin, which recognizes a 210 kDa sperm surface glycoprotein, binds to this localized band of intramembrane particles. Monoclonal antibody J18/2, which also recognizes the 210 kDa surface glycoprotein, shows this localized binding in approximately 20% of the sperm observed in this study. The majority of sperm displayed a uniform distribution of receptor sites for monoclonal antibody J18/2. Since wheat germ agglutinin and monoclonal antibody J18/2 are known to agglutinate Strongylocentrotus purpuratus sperm but not sperm of another sea urchin, Lytechinus pictus, similar determinations were made for the latter species. Lytechinus pictus sperm are not labeled with wheat germ agglutinin and are only sparsely labeled with monoclonal antibody J18/2. The acrosomal localizations of wheat germ agglutinin and monoclonal antibody J18/2 receptors in Strongylocentrotus purpuratus sperm are consistent with the involvement of the 210 kDa surface glycoprotein in an egg jelly-induced sperm acrosome reaction. Low-temperature post-embed labeling of thin sections with wheat germ agglutinin and monoclonal antibody J18/2 show concentrations of label within the acrosomal vesicle of Strongylocentrotus purpuratus sperm, suggesting the presence of an intracellular storage site for the 210 kDa glycoprotein.

Animals↗
PubMed1991

Response of the sandfly Lutzomyia longipalpis to an oviposition pheromone associated with conspecific eggs.

Response of female Lutzomyia longipalpis Lutz & Neiva (Diptera: Psychodidae) to an oviposition attractant and/or stimulant associated with conspecific eggs was investigated in the laboratory. Females of two populations laid significantly higher mean number of eggs on sites with 160 eggs already present than on bare control sites. This response was lost when eggs placed on test sites were previously washed in organic solvents and distilled water. Age of eggs placed on test sites, 1-6 days after being laid, did not seem to affect the oviposition response of the females. Comparing effects of different numbers of eggs, positive responses were obtained when 80, 160 or 320 eggs were placed on test sites. No significant differences between mean egg numbers laid on test sites and controls were detected when batches of only 20 or 40 eggs were used.

Animals↗
PubMed1991

Methods of reducing Ascogregarina chagasi parasitaemia in laboratory colonies of Lutzomyia longipalpis.

Ascogregarina chagasi is an aseptate gregarine parasite found naturally in populations of Lutzomyia longipalpis. Under intensive rearing conditions in the laboratory, the parasite is known to reduce longevity and egg production, therefore, it is thought to be a major contributing factor to the phenomenon of colony crashes. A study is described to test egg cleansing techniques, with a view to controlling this parasite in laboratory colonies. Methods used include washing eggs with formol, benzalkonium chloride and irradiating with ultraviolet light. It was concluded that cleansing with 0.1% formol solution was the most efficient method of controlling A. chagasi.

Animals↗
PubMed1991

Chemical factors controlling oviposition of Lutzomyia longipalpis (Diptera: Psychodidae).

In choice chambers, Lutzomyia longipalpis females were attracted and/or stimulated to lay eggs on sites containing hexane extracts of conspecific eggs, a result which supported previous findings on the presence of an oviposition pheromone on the eggs. Gas Chromatography analysis of hexane extracts of the eggs demonstrated the presence of several compounds, of which cholesterol and squalene were identified. Cholesterol and squalene did not, however, induce an oviposition attraction and/or stimulation response by the females, indicating that other compounds were responsible for the observed behaviour.

Animals↗
PubMed1991

Gas-chromatographic analysis of Lutzomyia longipalpis tergal pheromone gland extract.

Lutzomyia longipalpis is the vector of visceral leishmaniasis (VL) in South America. Previous gas-chromatographic (GC) analyses of tergal gland extracts of Lu. longipalpis have demonstrated two distinct pheromone types. These have been classified as a farnesene/homofarnesene type compound and a diterpene type compound. GC analysis of tergal gland extracts of Lu. longipalpis from other areas of South America demonstrates that there may be other different pheromone producing forms of this sandfly. Gland extracts are more complex than has previously been indicated, and they have been shown to differ in the chemicals present and in the ratio of these compounds to each other.

Animals↗
PubMed1991

Molecular approaches applied to the analysis of sympatric sandfly populations in endemic areas of western Venezuela.

To understand the epidemiology of cutaneous and mucocutaneous leishmaniasis in three distinct endemic foci of Tachira state, Western Venezuela, we aim to improve vector identification methods by developing species-specific sandfly DNA probes. These probes will be able to distinguish between sympatric sandfly populations thereby providing epidemiological data for determining the significance of individual sandfly groups related to their vectorial capacity.

Animals↗
PubMed1991

Pheromones in mate choice and sexual isolation between siblings of Lutzomyia longipalpis (Diptera:Psychodidae).

Pheromone-disc contact experiments are described in which different populations of the sandfly Lutzomyia longipalpis from Brazil were exposed to each others male pheromone extracts. The Jacobina population reacted only to the conspecific pheromone. The Sobral 2S population, however, would respond to the pheromone of Jacobina males, but if given a choice showed a preference for conspecific extract. Mate choice experiments are also described using sandflies of two pheromone types from Sobral. One population preferentially selected conspecific sexual partners, but the other showed poor mating propensity.

Animals↗
PubMed1991

Osseointegrated implants with an intramobile element in the treatment of edentulous jaws.

Edentulous patients have demonstrated impaired masticatory ability with conventional dentures. The masticatory deficiency is due, in part, to the instability of the mandibular denture and the lack of proprioception of conventional dentures. The Interpore IMZ implant offers an intramobile element in the design that may enhance proprioception of screw-retained dentures. The following case reports evaluated the stability and patient response of 10 edentulous patients who received a screw-retained denture with the intramobile element. The results indicated that the IMZ system can be successfully incorporated in this design.

Dental Implantation, Endosseous↗
PubMed1990

Localization of bindin expression during sea urchin spermatogenesis.

Expression of the bindin gene was examined in testicular cells of the sea urchin Strongylocentrotus purpuratus. In situ hybridization studies, using an 35S-labeled antisense RNA probe transcribed from a bindin cDNA, reveal that bindin mRNAs are localized in spermatogenic cells displaced towards the lumens of maturing testicular acini. Little or no hybridization is observed in spermatogenic cells displaced towards the perivisceral epithelium or in somatic cells of the testis. A similar localization of the bindin protein itself is observed using a rhodamine-conjugated polyclonal antibody against bindin, which shows a punctate immunofluorescence pattern in late spermatogenic cells. Immunogold labeling of ultrathin sections and electron microscopy reveal that this punctate immunofluorescence is an apparent result of localized deposits of bindin in intracellular vesicles. Through the terminal stages of spermatogenesis, these bindin-containing vesicles apparently fuse to form the single acrosomal vesicle of the mature spermatozoon. These results indicate 1) that bindin mRNAs are transcribed relatively late in spermatogenesis, 2) that bindin is translated soon after production of its mRNA, 3) that bindin quickly associates with intracellular vesicles during or soon after its synthesis, and 4) that these vesicles fuse to form the single acrosomal vesicle during the terminal stage of spermatogenesis.

Animals↗