Search PubMed⌕ Search

Biomedical subjects

S F Hayes

Publications and source records attributed to S F Hayes.

60 records · Page 4Linked to original sources
PubMed1980

Sexual transmission of spotted fever group rickettsiae by infected male ticks: detection of rickettsiae in immature spermatozoa of Ixodes ricinus.

Electron microscopic evidence is provided showing that the newly described "Swiss agent," a spotted fever group rickettsia, is incorporated into the reproductive cells of its male tick vector, Ixodes ricinus. Rickettsiae were found in spermatogonia, spermatocytes, and maturing spermatids. The potential significance of these observations is briefly discussed in relation to published data on sexual transmission of rickettsiae by ticks.

Animals↗
PubMed1979

Ultrastructure of Rickettsia rhipicephali, a new member of the spotted fever group rickettsiae in tissues of the host vector Rhipicephalus sanguineus.

Rickettsia rhipicephali is similar in ultrastructure to R. rickettsii while differing from other rickettsiae of the typhus group and of Q fever and others by its lack of a prominently reticulated cytoplasmic matrix and in the thickness of the inner osmophilic layer of the cell wall. In tissues of the tick vector Rhipicephalus sanguineus, R. rhipicephali had a mean length and width of 1.2 and 0.46 micrometer, respectively. It possessed a trilaminar cell wall with an adhering capsule-like layer. The trilaminar cell wall was approximately 12 to 18 nm thick; its inner osmophilic layer was thicker than that previously reported for other rickettsiae. The capsule-like layer varied from 7 to 18 nm thick. The plasma membrane was similar in structure, measurement, and appearance to that of other reported rickettsiae. The cytoplasm appeared to be composed of a finely granular, amorphous, ground substance and randomly dispersed ribosomes and lacked a reticular matrix or nuclear fibrils. In massively infected salivary glands and ovarial tissues of its tick vector, R. rhipicephali produced a low degree of histopathology which does not appear to affect the engorgement and egg-laying process of the ticks.

Animals↗
PubMed1979

Ixodes ricinus: vector of a hitherto undescribed spotted fever group agent in Switzerland.

A tick/rickettsial survey in various parts of Switzerland revealed the presence of a new, hitherto undescribed spotted fever group rickettsia ("Swiss agent") in up to 11.7% of I. ricinus collected off vegetation. Infection in ticks was found to be generalized with rickettsiae developing intracellularly and occasionally also intranuclearly. As a result of massive growth in ovarial tissues, including the germinative cells, the rate of transovarial and filial infection was 100%. The "Swiss agent" appears to be nonpathogenic for guinea pigs, domestic rabbits, and Swiss mice, but in male meadow voles (Microtus pennsylvanicus) it produces a microscopically detectable infection in the tunica vaginalis. The rickettsia grows well in tissue culture systems including chick embryo fibroblast, Vero, and vole tissue cells, when inoculated via yolk sac into 5-day-old hens' eggs, it kills 100% of the embryos after 5 to 7 days. Antigenic relatedness of the "Swiss agent" to rickettsiae of the spotted fever group was indicated by indirect and direct fluorescent antibody staining. Preliminary serologic typing by microimmunofluorescence and by microagglutination indicated that the "Swiss agent" differs from all prototype strains of spotted fever group rickettsiae studied so far.

Animals↗
PubMedDate not supplied

Pathophysiology of the Lyme disease spirochete, Borrelia burgdorferi, in ixodid ticks.

The pathophysiology of Borrelia burgdorferi, the Lyme disease spirochete, is unique in tick/vector relationships, differing substantially from that of other spirochetes, e.g., Borrelia duttonii, the agent of tick-borne relapsing fever, and Borrelia recurrentis, the agent of louse-borne relapsing fever, in their respective vectors. Following ingestion by a tick, B. burgdorferi lodges in the midgut diverticula, in some instances penetrating the gut wall and invading various tissues. Certain investigators suggest that transmission of the spirochete occurs via infectious saliva, although, in light of the fact that only 5% of adult ticks are systemically infected, this mechanism is open to question. Alternatively, transmission may occur via periodic regurgitation of gut fluids during the feeding process. While ticks of the genus Ixodes were once thought to be the only vectors, it now appears that other genera, and possibly other hematophagous arthropods, may also be involved.

Animals↗
PubMedDate not supplied

A molecular strategy for the study of bacterial invasion.

Bacterial populations are often clonal, and even within a bacterial species, the frequency of gene exchange and recombination is quite low. Consequently, mobile genetic elements--plasmids, bacteriophages, and transposons--have been the central factors in the evolution of pathogenic traits. One central feature of pathogenicity, the capacity to enter epithelial cells, is encoded by the bacterial chromosome of Yersinia pseudotuberculosis but by plasmid genes in enteroinvasive Escherichia coli. A single Yersinia gene, inv, which encodes a single 107,000-dalton protein, can be cloned in E. coli K12, and its presence is sufficient to permit the bacteria to enter cultured human cells. In contrast, fully 70 kilobases of a virulence plasmid from enteroinvasive E. coli must be transferred to E. coli K12 to achieve the same result. While researchers are at the early stages of understanding microbial entry into host cells, they can now investigate the molecular basis of this event in greater detail than has previously been possible.

Animals↗