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Biomedical subjects

R C Thompson

Publications and source records attributed to R C Thompson.

At least 361 records · Page 20Linked to original sources
PubMed1983

Proliferation and metastases formation of larval Echinococcus multilocularis. I. Animal model, macroscopical and histological findings.

Using surgical techniques, 70 Meriones unguiculatus were infected by implantation of 0.15-0.20 g of larval Echinococcus multilocularis tissue into the subcutis of the neck region. In 64 of 65 animals necropsied, the transplants had increased in size and weight and reached an average weight of 4.1 g at the end of the experiment 12 weeks post infection (p.i.). Metastatic Echinococcus lesions developed in the regional lymph nodes and in the lungs; in 18 animals the parasite proliferated into the thoracic cavity. Of 41 animals examined 10 and 12 weeks p.i., 88% had multiple or single metastatic lung lesions, the first being observed 6 weeks p.i. Typical cysts and protrusions ("buds") of the germinal layer were detected in samples of parasite tissue before and after transplantation to experimental animals, as well as in lymph nodes and lungs in which metastases had developed. Similar structures were found in liver sections of two patients with alveolar echinococcosis. It is concluded that the spread of the parasite from the subcutis of the neck region to the draining lymph nodes and the lungs had taken place via the lymph and blood system. The possible role of the "buds" in metastases formation is discussed.

Animals↗
PubMed1983

Proliferation and metastases formation of larval Echinococcus multilocularis. II. Ultrastructural investigations.

The larval stage (metacestode) of Echinococcus multilocularis was studied by means of electron microscopy (SEM, TEM) before and after subcutaneous transplantation to jirds (Meriones unguiculatus) and in their lymph nodes and lungs with parasite metastases. It was found that the metacestode consists of a network of solid, cellular protrusions (buds) of the germinal layer which transform to tube-like and cystic structures devoid or with a laminated layer. Proliferation of the metacestode apparently occurs by protruding filamentous solid cell columns (buds) from the germinal layer. Their tips have diameters of only one cell: they are covered with a smooth syncytial tegument without microtriches and are filled with undifferentiated cells which contain a nucleus with a large nucleolus. The tegument is constantly enlarged by fusion with the underlying undifferentiated cells that divide repeatedly. At some distance from the tip a cavity develops inside the protrusion, thus finally giving rise to a tube-like structure which may transform to a cystic expansion. Simultaneously, the surface of the protrusion changes by the formation of microtriches and the occurrence of an amorphous laminated layer. The latter is concentrically covered by connective tissue cells and large amounts of collagen. Within cyst-brood capsules, finally protoscoleces are formed from accumulations of undifferentiated cells beneath the tegument. The study has unequivocally proven the cestode nature of the cellular protrusions, and it is assumed that detachment of cells from these structures and their subsequent distribution via the circulation may play a role in the formation of metastases. The origin of the laminated layer is discussed.

Animals↗
PubMed1983

Observations on Echinococcus multilocularis in the definitive host.

Six dogs were found to be susceptible to experimental infections with a European isolate of Echinococcus multilocularis from southern Germany. Two cats were only poorly susceptible. Adult worms were not evenly distributed throughout the small intestine and the majority of parasites were found in the posterior region. The mode of attachment of E. multilocularis in the dog was similar to that for E. granulosus with the adult worm extending its rostellum deep within a crypt of Lieberkühn. In cats only few worms were found to have penetrated deeply between the villi. E. multilocularis was found to possess a modified group of rostellar tegumental cells, morphologically and functionally identical to those described in E. granulosus and previously referred to as the "rostellar gland". By studying development in vivo and in vitro, the time required for the production of shelled eggs was demonstrated to be only 28 days. Concurrent experimental infections in dogs with E. multilocularis and E. granulosus revealed that both species will develop together in the same host. Their development was not retarded in any way by the presence of the other and both species were able to coexist in the same area of the intestine.

Animals↗
PubMed1983

The effects of selective immunosuppression on resistance to Mesocestoides corti in strains of mice showing high and low initial susceptibility.

Previous work has shown that C57BL/6 mice had the lowest initial susceptibility to Mesocestoides corti of six strains of mice examined. Parasite burdens in this strain and in CBA/H mice, a strain showing a higher initial susceptibility to M. corti, were compared following selective immunosuppressive treatments. Irradiation, splenectomy and the administration of cyclophosphamide and methyl prednisolone all resulted in higher parasite burdens in C57BL/6 mice. In contrast these treatments had a minimal effect on parasite burdens in CBA/H mice. In the light of these results the role of antibody in controlling parasite proliferation is discussed.

Adrenal Cortex Hormones↗
PubMed1983

Effect of ppGpp on the accuracy of protein biosynthesis.

The maintenance of accuracy in protein biosynthesis in amino acid-starved rel+ strains of Escherichia coli has been attributed to an effect of ppGpp on the accuracy of aa-tRNA selection by the ribosome. It has been determined that concentrations of ppGpp characteristic of those found in amino acid-starved cells have no effect on the rate of reaction of poly(U)-programmed ribosomes with either the cognate (Phe) or the near-cognate (Leu2) ternary complexes. Neither the rate of GTP hydrolysis, which signals selection of the ternary complex, nor the rate of peptide formation, which signals the acceptance of the aa-tRNA after proofreading, is affected by the nucleotide. The results indicate that the effect of ppGpp in maintaining the accuracy of protein biosynthesis in cells starved for an amino acid is not due to a direct effect on the rate constants for substrate selection by the ribosome.

Escherichia coli↗
PubMed1983

Factors influencing the establishment of Mesocestoides corti in mice following oral inoculation of tetrathyridia.

Factors which influence the establishment of tetrathyridia of Mesocestoides corti in mice following inoculation per os were examined. Only a proportion of the tetrathyridia penetrate the gut wall and gain access to the peritoneal cavity and liver, and most of these penetrate through the wall of the small intestine. It appears that tetrathyridia must attach to the intestinal mucosa and commence penetration immediately or they pass into the large intestine and are voided. Establishment was not influenced by strain, sex or age of host. However, the temperature at which tetrathyridia were maintained before inoculation influence their ability to penetrate the intestinal wall. Additionally it appears that tetrathyridia have to undergo a morphological change before or during, this penetration phase.

Animals↗
PubMed1983

The susceptibility of the European red fox (Vulpes vulpes) to infection with Echinococcus granulosus of Australian sheep origin.

A detailed comparative study was made of the development of Echinococcus granulosus of Australia sheep origin in European red foxes (Vulpes vulpes) and dogs. No significant differences in growth, segmentation or maturation of the parasite between dogs or foxes was found, although worm burdens were slightly lower in foxes than in dogs. It is concluded that although the role of foxes in the epidemiology of hydatidosis in Australia may not be significant, foxes should nevertheless be regarded as potential definitive hosts of the Australian strains of E. granulosus.

Animals↗
PubMed1983

1976 Hanford americium exposure incident: overview and perspective.

Salient features of the 1976 Hanford americium exposure incident are discussed. Comparisons are made with previous human and animal exposure data, and conclusions drawn relative to the injured workman, to health physics practices, and to the adequacy of current exposure limits.

Accidents, Occupational↗
PubMed1983

The effects of indirect blunt trauma on adult canine articular cartilage.

UNLABELLED: In order to determine the effect of subfracture loads on articular cartilage, we impacted twelve adult canine patellofemoral joints utilizing a drop-tower with two different force-levels. The joints were examined with light and electron microscopy at two, four, and six weeks after impaction. In ten additional animals a single knee was impacted and they were analyzed biochemically at similar time-periods, using the contralateral joint as a control. In all impacted specimens changes were observed in the zone of calcified cartilage, represented by an increase in cellular clones, vascular invasion, and proteoglycan content of the matrix. Ultrastructural evaluation of the superficial and deep radial zones of the articular cartilage revealed loss of the cellular processes and territorial matrices of chondrocytes in both layers. Ruthenium-red staining of impacted samples revealed a 40 per cent decrease in proteoglycan associated with collagen fibers in the extraterritorial matrix. An increase in collagen-fiber width was observed in the four and six-week groups. The earliest changes in articular cartilage included activation of the zone of calcified cartilage as well as ultrastructural alterations in the superficial and radial zones. Biochemical analysis revealed an increase in water content and hexuronic acid at two weeks. These changes occurred at a subfracture level in the absence of surface disruption. CLINICAL RELEVANCE: These animal experiments indicate that adult articular cartilage may show significant alterations in its histological, biochemical, and ultrastructural characteristics without disruption of the articular surface. This model of articular cartilage "contusion" may represent a corollary to the joint damage that is observed following direct blunt trauma transmitted across articular surfaces without radiographic evidence of fracture. The possibility that this form of injury may be the precursor of chondromalacic changes in patellar or femoral cartilage merits further study.

Animals↗
PubMed1982

A review of the taxonomy and speciation of the genus Echinococcus Rudolphi 1801.

The taxonomy of Echinococcus is reviewed and consideration given to speciation within the genus. The morphological and other biological characteristics of all species and subspecies so far described are given, and evidence for the existence of other intraspecific variants is presented. A total of 16 species have been described but only four have well-defined characteristics and are generally accepted as being taxonomically valid; E. granulosus, E. multilocularis, E. oligarthrus and E. vogeli. The taxonomic status of intraspecific variants is uncertain. Some authorities consider that the majority of described subspecies are invalid taxonomically. However, concern is expressed that previous taxonomic considerations of Echinococcus have not taken into account the nature of its reproductive mechanism which, like that of most cestodes, defies the application of traditional taxonomic concepts and definitions derived from dioecious cross-fertilising organisms. At the present time intraspecific variants of Echinococcus are referred to as strains. The existence of such strains, particularly of E. granulosus, in different parts of the world is firmly established. Their importance in the epidemiology of hydatidosis has high-lighted the needed to establish criteria for their differentiation and characterisation. The limitations of morphology as a sole differential criterion are emphasised. Attention is given to recent studies on strain variation which have demonstrated the value of applying several different criteria in which the developmental, physiological and biochemical characteristics of different strains are compared in conjunction with morphological investigations.

Animals↗
PubMed1982

The production of eggs by Echinococcus multilocularis in the laboratory following in vivo and in vitro development.

Adult worms of Echinococcus multilocularis produced eggs in vitro following partial development in the definitive host for 20-21 days and maturation for 8 days in a monophasic or diphasic medium. The technique was shown to be reproducible with morphologically normal eggs produced in two separate experiments. The onset of egg production in vitro was identical to that in vivo although the number of eggs produced by each worm was less in vitro.

Animals↗
PubMed1982

Aspergillus osteomyelitis. Report of four cases and review of the literature.

Four cases of Aspergillus osteomyelitis are presented and the world literature is reviewed, for a total of 19 cases. Aspergillus osteomyelitis is largely a disease of immunosuppressed hosts, although wound and other infections in "normal" hosts are seen. In children, contiguous spread from an adjacent pulmonary infection is most common, whereas in adults hematogenous spread is the rule. The survival rate in immunocompromised patients is poor, whereas the cure rate is uniform in "normal" hosts. A combined medical-surgical therapeutic approach has been used most often and seems appropriate.

Acetabulum↗