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Biomedical subjects

R D Ward

Publications and source records attributed to R D Ward.

At least 19 recordsLinked to original sources
PubMed1998

Sugar feeding and fluid destination control in the phlebotomine sandfly Lutzomyia longipalpis (Diptera: Psychodidae).

Sandfly feeding behaviour and destination of coloured sugar meals in the gut of Lutzomyia longipalpis were investigated with particular attention to the role of the crop. Sandflies were able to ingest sugar from liquid drops, microcapillaries, a slice of pear and even sugar powder. In most cases the flies adopted a 'sugar feeding mode' with raised palps. As the fruit dried, flies of both sexes fed by piercing the tissue with the proboscis. All sugar-fed flies had a full crop plus a small amount of sugary fluid in the thoracic mid-gut, i.e. past the stomodaeal valve. Dissections of flies interrupted during feeding showed that the very first trace of sugar passed through the stomodaeal valve, but that the rest of the meal was diverted into the crop. This suggests that closure of the stomodaeal valve is initiated only after a small volume of sugar solution has passed through it.

Animals↗
PubMed1998

Stomodaeal valve ultrastructure in the sandfly Lutzomyia longipalpis (Diptera: Psychodidae).

The stomodaeal valve and adjacent cardia region of the alimentary canal of the phlebotomine sandfly Lutzomyia longipalpis have been studied using electron microscopy. With the scanning electron microscope (SEM), numerous pit-like structures of different sizes were found in the surface of the valve of male and female flies. Under the transmission electron microscope (TEM), the cells adjacent to the pores were shown to have numerous mitochondria and to lack neural innervation. It is suggested that the pit-like structures are probably secretory. A typical basiconic sensilla was found on the inner side of the oesophagus at the junction with the stomodaeal valve, with at least one dendrite which extended to the tip, indicating a chemosensory role. It is likely that this type of sensilla may control the movement of the stomodaeal valve after contact with fluids entering the mid-gut and may be responsible for diverting the sugar meal to the crop by closure of the valve.

Animals↗
PubMed1997

Phlebotomine sandflies in a focus of visceral leishmaniasis in a border area of eastern Sudan.

A field study was carried out in eastern Sudan, near the Ethiopian border, to investigate the abundance, seasonality, man-biting behaviour and resting sites of sandflies in two areas where visceral leishmaniasis (kala-azar) is endemic: Umsalala village, Galabat Province; and the adjacent Dinder National Park (DNP), Dinder Province. Abundance of the different species was determined from collections made, using light and sticky-paper traps, in various habitats between November 1993 and February 1995. Man-biting sandflies were collected as they landed on human bait. The habitats investigated for day-resting sandflies were thatched huts, chicken coops, tree-holes, termite mounds and soil cracks. Animal burrows were not investigated. The species found were Phlebotomus (Larroussius) orientalis, P. (Phlebotomus) papatasi, P. (Paraphlebotomus) saevus, P. (Anaphlebotomus) rodhaini, Sergentomyia (Sintonius) clydei, S. (Sergentomyia) antennata, S. (Sergentomyia) sckwetzi, S. (Parrotomyia) africana and S. (Grassomyia) squamipleuris. Phlebotomus orientalis was the only man-biting sandfly species found in the DNP whereas P. papatasi, P. orientalis and P. saevus were all found in Umsalala. Abundance of each species varied with the habitat. In Umsalala and a camp for game wardens in the DNP, Sergentomyia spp. predominated over Phlebotomus. In the DNP, the most abundant sandfly in a thicket dominated by Acacia seyal trees was P. orientalis, followed by Sergentomyia spp. Significant habitat 'preferences' were observed for most sandfly species in the area. In attempts to find resting flies, P. orientalis was only found resting in the mounds made by the termite Macrotermes herus and P. papatasi was only found inside huts; no resting sites were detected for other Phlebotomus spp. but Sergentomyia spp. were observed in all the sites investigated. The P. orientalis in the DNP showed a clear seasonal variation in abundance, which was closely correlated with the mean monthly temperature and relative humidity of the area. A remarkable increase in the abundance of this vector occurred at the beginning of the rainy season.

Animals↗
PubMed1997

The sandfly Lutzomyia longipalpis shows specific humoral responses to bacterial challenge.

The presence of immune molecules induced by microorganisms in the haemolymph of Lutzomyia longipalpis sandflies has been investigated. Injections of Escherichia coli and Micrococcus luteus into female sandflies induced anti-bacterial activity in the haemolymph. Inhibition zone assays showed that haemolymph from E. coli and M.luteus injected sandflies differentially inhibited M.luteus growth. This differential effect was specific to M.luteus infection since anti-E.coli activity was similar in haemolymph from both E.coli or M.luteus injected sandflies. Haemolymph following injection of either bacteria showed the induction of a 4 kDa peptide. Haemolymph from M.luteus injected sandflies also contained a 33 kDa polypeptide which was absent in haemolymph from E.coli and control uninfected insects. Sandflies, in common with other insects, were shown to possess general and specific humoral immune responses to the presence of microorganisms.

Animals↗
PubMed1997

IMGs set goals for AMA section.

International medical graduates have become an important part of the American health care structure in recent decades, but too often they remain second-class citizens within the medical community. Increasingly, voices within medicine have called for formal recognition of the unique needs of IMG physicians.

American Medical Association↗
PubMed1996

Comparison of the sex-pheromone components of Lutzomyia longipalpis (Diptera:Psychodidae) from areas of visceral and atypical cutaneous leishmaniasis in Honduras and Cost Rica.

The terpene components of extracts prepared from male Lutzomyia longipalpis (Diptera: Psychodidae) collected from four sites in Honduras and one in Costa Rica were analysed by high-performance liquid chromatography, gas chromatography and coupled gas chromatography--mass spectrometry. The terpene components of Lu. longipalpis from other regions of South America have previously been shown to be sex pheromones. The flies from the four areas of Honduras, where Leishmania chagasi infection may lead to visceral or atypical cutaneous leishmaniasis, were found to be homogenous, all producing 9-methylgermacrene-B. Three types of terpene (9-methylgermacrene-B, a novel homosesquiterpene and a small amount of diterpene) were detected in pools of flies from Liberia, Costa Rica, where only atypical cutaneous leishmaniasis has been found. These results indicate that there are probably at least two and possibly three distinct populations of Lu. longipalpis in this region. The clinical manifestation of Leishmania chagasi infection does not appear to be dependent on which population of Lu. longipalpis transmitted the parasite.

Animals↗
PubMed1996

James P. Gallagher, MD. Scrappy former boxer fights to maintain physicians' voices.

It's been an adventurous life for James Gallagher, MD, from medical school in Ireland where he was a scrappy welterweight student boxer to one of the state's foremost cardiologists, and current president of the Wayne County Medical Society. Born in County Tyrone, Northern Ireland in 1932, the fifth in an ultimate full house of nine children, Doctor Gallagher attended medical school at the National University of Dublin.

Boxing↗
PubMed1995

A mutation in glyceraldehyde 3-phosphate dehydrogenase alters endocytosis in CHO cells.

The CHO cell mutant FD 1.3.25 exhibits both increased accumulation and altered distribution of endocytosed fluid phase tracers. Neither the rate of tracer internalization nor the kinetics of recycling from early endosomes was affected, but exocytosis from late endocytic compartments appeared to be decreased in the mutant. Endocytosed tracer moved more rapidly to the cell poles in FD1.3.25 than in wild type cells. An abundant 36-kD polypeptide was found associated with taxol-polymerized microtubules in preparations from wild type and mutant; in the former but not the latter this polypeptide could be dissociated by incubation of the microtubules in ATP or high salt. The 36-kD polypeptide co-electrophoresed in two dimensions with the monomer of the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Analysis of cDNA clones showed that the mutant is heterozygous for this enzyme, with approximately 25% of the GAPDH RNA containing a single nucleotide change resulting in substitution of Ser for Pro234, a residue that is conserved throughout evolution. Stable transfectants of wild type cells expressing the mutant monomer at approximately 15% of the total enzyme exhibited the various changes in endocytosis observed in FD1.3.25.

Animals↗
PubMed1995

Sugar meal sources for the phlebotomine sandfly Lutzomyia longipalpis in Ceará State, Brazil.

In the Brazilian village of Boqueirão do Renato Parente, Ceará State, where visceral leishmaniasis is endemic, significant variation in the abundance of phlebotomine sandflies between different types of vegetation was demonstrated by castor oil sticky trap collections. Population densities of Lutzomyia longipalpis (Lutz & Neiva) sandflies were higher in beans and maize crops than in the surrounding open and tree scrub. Significant relationships were detected between the abundances of sandflies and aphids, suggesting aphid honeydew as a potential food source. Sugar meal analysis, using high-performance anion exchange (HPAE) chromatography with pulsed amperometric detection (PAD) and the cold anthrone test, was used to demonstrate that significantly more sandflies fed on bean plants contaminated with aphids and honeydew than on uncontaminated beans. Furthermore, higher concentrations of sugars were detected in flies which fed on aphid/honeydew-contaminated beans, suggesting that sugar was more easily available and/or that honeydew/aphids act as phagostimulants for sandflies. Amongst wild sandflies collected from a bean field, significantly more female sandflies were 'sugar-positive' than males, though the sugar concentrations in positive sandflies were similar for both sexes. The concentrations of di- and trisaccharides in sandfly homogenates, honeydew extracts and phloem exudates were very low.

Animals↗