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Biomedical subjects

D L Williamson

Publications and source records attributed to D L Williamson.

At least 55 records · Page 3Linked to original sources
PubMed1987

New spiroplasmas from insects and flowers: isolation, ecology, and host association.

Eight spiroplasma strains from insects and one from spring flowers failed to react with antisera specific for any of the 11 described spiroplasma groups, with sera directed against spiroplasma Group I subgroups, or with sera directed against two unnumbered groups previously reported to occur in tabanid flies. Strains, all from Maryland, were isolated from the hemolymph of the spotted cucumber beetle Diabrotica undecimpunctata and the lampyrid beetle Ellychnia corrusca, and the guts of the cantharid beetles Cantharis bilineatus and C. carolinus. Other strains were obtained from a tabanid fly, Tabanus gladiator and from the firefly Photuris pennsylvanica in Maryland and from the mosquito Culex tritaeniorhynchus in Taiwan. An isolate from pooled Cicadulina bipunctella leafhoppers in Syria apparently represented a unique group. A single isolate from spring flowers in Oklahoma also appeared to be unrelated to existing groups or subgroups. One-way deformation tests using sera prepared against known beetle and tabanid spiroplasmas showed each of the above strains to be unique. Although these results strongly indicate that the nine strains studied are representatives of unique new spiroplasma groups, the formal designation of new groups awaits fulfillment of recently proposed criteria.

Animals↗
PubMed1987

Cell-assisted culture of fastidious spiroplasmas: initial analysis of growth factors.

Half of the spiroplasmas observed microscopically in insects cannot be cultivated and are thus inaccessible to study. Media mixed with cultured insect cells have now been used to isolate two of these spiroplasmas--the sex-ratio organism (SRO) of Drosophila and the Colorado potato beetle spiroplasma (CPBS). Studies described herein indicate that at least one of the cell-supplied factors is involved in redox maintenance. A wide variety of insect cell culture systems were suitable for primary isolation of the CPBS. The SRO and CPBS were found to attach to insect cells in vitro.

Anaerobiosis↗
PubMed1987

SpV3 viruses of Drosophila spiroplasmas.

The presence of spiroplasmas in the hemolymph of four Drosophila willistoni group species has been shown to cause elimination of males from the progeny of infected females. These spiroplasmas, known as sex-ratio organisms (SROs), are found in D. equinoxialis (ESRO), D. nebulosa (NSRO), D. paulistorum (PSRO), and D. willistoni (WSRO). In addition, a nonmale-lethal spiroplasma (HIS) has been found in the hemolymph of D. hydei. Only the WSRO has been cultivated. Each of the Drosophila spiroplasmas sheds at least one endogenous virus into the hemolymph by a budding process. These viruses are short-tailed polyhedrons resembling the SpV3 virus of Spiroplasma citri, and all have been shown to lyse at least one other strain of SRO. The Drosophila spiroplasma viruses have been extracted from infected flies and purified by metrizamide gradient centrifugation. The viruses, thus purified, maintained infectivity and lysed indicator strains of SROs. Electrophoresis of viral DNA produced bands indicating genomes of three different sizes: 17, 21.8, and greater than 30 kbp. Some SRO strains have more than one SpV3 virus. Restriction endonuclease digestion of DNA of the spiroplasma viruses HSV and NSV (both 21.8 kbp) produce patterns on agarose gels that indicate linear, circularly permuted genomes. The fragments generated by cleavage of NSV with EcoRI have been cloned into pBR325 and amplified in Escherichia coli. Restriction endonuclease digestion of NSV DNA hybridized with these clones indicates that there are two different 21.8-kbp SpV3 viruses in NSRO.

Animals↗
PubMed1984

Tsetse fly feeding preference as determined by vehicular trapping in Tanzania.

In eastern Tanzania an electric grid trap carried in the back of a moving pick-up truck was used to capture engorged Glossina morsitans morsitans and G. pallidipes for an analysis of their food sources. Although 12 000 head of domestic cattle represented c. 75% of the animal biomass in the survey area, they provided only 5.6% of the total blood meals, while 74.8% were from warthogs and bushpigs. The percentage of females among the captured flies was 12 and 47 for G. m. morsitans and G. pallidipes, respectively. The incidence of engorged flies captured by this method ranged from 15 to 20% in males and 26 to 42% in females.

Animals↗
PubMed1984

Spiroplasma fibrils.

A fundamental question in biology concerns the morphology of spiroplasmas: How does a wall-less microorganism maintain its characteristic morphology as a helical filament? An answer to this question began to form when it was discovered that spiroplasmas treated with any of a number of detergents (sodium deoxycholate, Triton X-100, Nonidet P-40) release their cytoplasmic contents. If this procedure is performed on a formvar-coated electron microscope grid and the resultant preparation negatively stained and observed by transmission electron microscopy, numerous striated microfibrils can be seen where spiroplasmas once were. The fibrils are of varying lengths, 4 nm in width, and show a striation repeat at 9 nm along their length. It is not possible to discern from the pattern of the released fibrils just how they are organized within the intact spiroplasma; nor is it yet possible to identify a fibrillar substructure in thin sections or in freeze-fractured organisms. Townsend and his colleagues at the John Innes Institute in Norwich, UK, purified fibrils by density gradient centrifugation. SDS-PAGE showed the fibrils to consist of a 55,000-dalton protein recognizable in the four serogroups tested by protein blotting with an antiserum made against the PAGE-separated protein. The presence of fibrils is a feature common to all spiroplasma, regardless of whether they are helical or nonhelical, as in the Ixodes tick-derived spiroplasma or Townsend's ASP-1 strain of Spiroplasma citri. We have employed gentle demembranation treatments that preserve filamentous substructure in an effort to elucidate the organization of the fibrils within the spiroplasma cell.

Bacterial Proteins↗
PubMed1981

Helical mycoplasmas (spiroplasmas) from Ixodes ticks.

A new spiroplasma isolated from Ixodes pacificus collected in Oregon was serologically and morphologically distinct from known spiroplasmas. The new spiroplasma could also be isolated in tick cell cultures. Discovery of a new fastidious mycoplasma in ticks offers opportunities to explore the possible role of these agents in human and animal diseases.

Animals↗
PubMed1979

How big is the normal liver?

Ultrasonographic determinations of the craniocaudal dimension of the liver in the right midcalvicular line were performed on 96 healthy subjects. These values were compared to those obtained in the same individuals by two techniques of percussion, as well as the values for hepatic dullness predicted for those individuals using a popular nomogram. It was found that the traditional nomogram values, and both techniques of percussion, tended to underestimate this dimension of the liver as determined by ultrasound.

Female↗
PubMed1977

Pathogenic mycoplasmas: cultivation and vertebrate pathogenicity of a new spiroplasma.

A spiroplasma recovered from allantoic fluids of chick embryos infected with the tick-derived suckling mouse cataract agent was grown in continuous passage on a new artificial culture medium. The cultured organisms induced typical ocular and other disease symptoms in susceptible animals, and were reisolated from involved host tissues. Although spiroplasmas have been previously recognized as plant and insect pathogens, this is the first spiroplasma shown to multiply at 37 degrees C and to be pathogenic for vertebrates.

Animals↗
PubMed1971

Induction of sterility in Drosophila paulistorum: effect of cytoplasmic factors.

Male hybrids from Mesitas and Santa Marta (Colombia) strains of Drosophila paulistorum are sterile. Homogenates of males belonging to these strains and from the hybrids were injected into Mesitas or Santa Marta females, which were crossed to males of their own strains, so that their progenies were genetically nonhybrid. Nevertheless, some of the males from these progenies were sterile. Male progenies of females that were injected with homogenates from males that disagreed in the source of cytoplasm with the recipients were sterile. No sterility was induced if the donors and the recipients had similar cytoplasm.

Animals↗
PubMed1968

Unusual filamentous structures in the paragonia of male Drosophila.

Drosophila paulistorum is a complex of five incipient species which when crossed produce sterile hybrid males and fertile females. Sterility of the male progeny can sometimes be induced by injecting females of one strain (Mesitas) with a homogenate of males of another strain (Santa Marta) or of hybrids between these strains, and then crossing the recipient females to Mesitas males. Filamentous structures have been found in cytoplasmic vacuoles in paragonial cells in males of these and other similar strains and their hybrids. These structures, which contain RNA, possess a helical substructure and resemble certain viruses. Large filamentous structures found in the lumen of the paragonia are also described.

Animals↗