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Biomedical subjects

C Dobson

Publications and source records attributed to C Dobson.

At least 91 records · Page 5Linked to original sources
PubMed1982

The biology of Angiostrongylus cantonensis larvae in immune rats.

Rats acquired protective immunity to Angiostrongylus cantonensis after a single infection with 50 infective larvae. Immunity was stronger after subsequent infections. Fewer worms were recovered which were shorter and produced fewer progeny after secondary and tertiary infections. However, the growth of A. cantonensis during the early developmental stages in the brain and the ability of the young adult parasites to migrate to the lungs was not affected in the immune host.

Angiostrongylus↗
PubMed1981

Immunodiagnosis of parasitic zoonoses: sensitivity and specificity of in vitro lymphocyte proliferative responsiveness using nematode antigens purified by affinity chromatography.

The sensitivity of in vitro lymphocyte proliferative responsiveness using antigens purified by affinity chromatography, was greater than that of three serological tests and allowed the specific identification of Dirofilaria immitis, Toxocara canis, Angiostrongylus cantonensis and Ascaris lumbricoides in animals sensitized with parasite antigens, and the diagnosis of natural (D. immitis, T. canis and Angiostrongylus cantonensis) and zoonotic nematode infections. Lymphocytes remained viable in whole blood suspensions in RPM 1640 in a polystyrene insulation box at air temperature for at least 12 hours and reacted in the cell-mediated immunity test (CMIT) without loss of response. The CMIT proved useful in the early immunodiagnosis of nematode infections and showed that parasite antigens purified by affinity chromatography retained a high degree of specificity and sensitivity in both the CMIT and serological tests.

Animals↗
PubMed1981

Genetic control of liability to infection with Nematospiroides dubius in mice: selection of refractory and liable populations of mice.

Quackenbush strain and wild Mus musculus were assayed for their liability to primary infection with 100 L3 Nematospiroides dubius using an experimentally derived selection index. Refractory and liable colonies of mice were established over 5 generations. Liability to N. dubius infection was found likely to be controlled by several genes; the heritability (h2) of this trait was estimated at 0.45. Positive linear correlation was found between the number of parasite eggs voided and the number of adult N. dubius recovered, negative correlation between the pre-patent period of infection in days and the number of parasite eggs voided and positive correlation in 2 of 5 generations between live mouse body weight and the number of adult N. dubius recovered. Further, positive correlation was found between the liability of female mice to N. dubius and their progeny litter size number. The genetic mechanisms controlling the liability trait and the possible evolutionary significance of these results are discussed.

Animals↗
PubMed1981

Evidence that changes in luteinizing hormone secretion regulate the growth of the preovulatory follicle in the ewe.

The aim of the present study was to gain evidence that the level of LH secretion preceding the preovulatory LH surge is an important determinant of follicular maturation and corpus luteum function in the ewe. In addition it was hoped to establish whether the pattern of LH delivery to the ovary (pulsatile v. constant) is a critical factor in the maturation of a preovulatory follicle. To accomplish this, progesterone-primed anoestrous ewes were repeatedly injected i.v. with LH or luteinizing hormone-releasing hormone (LH-RH), or given an i.v. infusion of LH, over a 72 h period. These animals, together with the appropriate controls, were exposed to a sexually active ram so that oestrous activity could be recorded. All ewes were subjected to intensive blood sampling regimes so that the plasma levels of LH and progesterone could be determined and compared to those which occurred in the same breed of sheep during the oestrous cycle. Collectively the data suggest that the plasma levels of LH preceding the preovulatory LH surge are an important determinant of follicular maturation as judged by subsequent corpus luteum function. Moreover, they show that follicular maturation can be achieved with widely differing patterns of LH delivery to the ovary during the preovulatory period and that a strict pulsatile delivery of LH may not be an absolute requirement.

Anestrus↗
PubMed1981

Accumulation of luteinizing hormone, oestradiol and androstenedione by sheep ovarian follicles in vivo.

The temporal relationship between the levels of LH in peripheral plasma and in follicular fluid of ovarian follicles in anaesthetized sheep were investigated for a 10-h period after a single i.m. injection of LH releasing hormone (LH-RH; 100 microgram). The ovarian secretion rates of oestradiol and androstenedione and the levels of these steroids accumulating in different sized follicles at varying time-intervals after the LH-RH injection were also compared. The data show that the rates at which pituitary LH enters and leaves the intrafollicular fluid-filled spaces are substantially slower than those of peripheral blood. Two hours after LH-RH injection the levels of LH in plasma had increased from 1 to 200 ng/ml, whereas in the follicle the levels remained at approximately 2ng/ml. Ten hours after the LH-RH injection, the levels of LH in plasma had returned to basal values (approximately 1.4 ng/ml) but in both small and large follicles the levels of LH (approximately 20 ng/ml) were comparable to those present in similar sized follicles 4h earlier. The data also indicate that more than 90% of the oestradiol produced by a large antral follicle (greater than or equal to 5 mm diameter) probably enters the bloodstream without first accumulating within the follicular antrum. Finally it is concluded that the clearance of the small amount of oestradiol which does accumulate in the follicular antrum is negligible compared with the clearance of this hormone from peripheral plasma.

Androstenedione↗
PubMed1980

Immunodiagnosis and seroepidemiology of Angiostrongylus cantonensis zoonoses in man.

The development of serum and cellular assays to measure responses to Angiostrongylus cantonensis antigen, purified by affinity chromatography, formed the basis of this study. The specificity and sensitivity of these techniques were established in immunized rabbits and in naturally and laboratory-infected rats. The assays were then used to determine levels of immunological responsiveness to A. cantonensis in four Australian populations. There was a direct correlation between the prevalence of the parasite in rodents and the proportion of human reactors to A. cantonensis antigen in each population studied. Five patients with similar clinical histories and presenting symptoms suggesting eosinophilic meningitis were investigated; three were admitted to hospital. Haematological examination demonstrated hypereosinophilia in all five while three had, in addition, a cerebrospinal fluid eosinophilia. Serological tests and assays of cell-mediated responses to A. cantonensis antigen showed elevated immunological reactivity during the acute phase of illness with a subsequent decrease in reactivity corresponding with the progressive recovery of the patient.

Adult↗
PubMed1979

Anomia, self-esteem, and life satisfaction: interrelationships among three scales of well-being.

The extent to which anomia, self-esteem, and life satisfaction are conceptually distinct was studied by using factor analysis of the items from Srole's anomia scale, Rosenberg's scale of self-esteem, and the LSI-Z. The data came from interviews held with 1,332 older men living in nonmetropolitan areas of Iowa. The analysis demonstrated that, while the concepts of anomia and self-esteem are distinct, the domain of life satisfaction overlaps those of anomia and self-esteem. The representation of the five components of life satisfaction by the items of the LSI-Z is questioned, and caution in using the six-items version of Rosenberg's measure of self-esteem with older adults is suggested.

Aged↗
PubMed1978

Immunodiagnosis of parasitic zoonoses: comparative efficacy of three immunofluorescence tests using antigens purified by affinity chromatography.

Three immunofluorescent antibody assays were developed during this study: the direct (DFAT) and indirect (IFAT) fluorescent antibody tests using frozen worm sections, and the cyanogen bromide indirect fluorescent antibody test (CNBr-IFAT) using helminth antigens purified by affinity chromatography bound on to commercially prepared CNBr-Sepharose 4B beads. Purified antigens used in the CNBr-IFAT gave greater specificity and sensitivity than either the DFAT or IFAT. Dirofilaria immitis, Toxocara canis, Angiostrongylus cantonensis and Ascaris lumbricoides infections were studied in natural and zoonotic hosts and in rabbits immunized with antigens prepared from these parasites. In addition, a serological survey of Aboriginal Australians from Queensland was made.

Animals↗