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S De Guise

Publications and source records attributed to S De Guise.

25 records · Page 2Linked to original sources
PubMed1994

The anatomy of the male genital system of the beluga whale, Delphinapterus leucas, with special reference to the penis.

The genital organs of four male adult beluga whales and one newborn animal were dissected and the main characteristics are described. As in other species of cetaceans, the testes and the greatest part of the penis are located inside the abdominal cavity. The penis has a sigmoid flexure and belongs to the fibroelastic type with a thick tunica albuginea and a small amount of vascular spaces in the erectile tissue. The prostate gland, found in other cetaceans, was not seen macroscopically, but only small prostate rudiments could be identified histologically. The os penis and the other accessory glands are absent as in other whales.

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PubMed1994

Tumors in St. Lawrence beluga whales (Delphinapterus leucas)

A population of 450-500 belugas (Delphinapterus leucas) resides in the polluted estuary of the St. Lawrence River. Stranded carcasses of this endangered population were recovered and necropsied. High concentrations of organochlorines, heavy metals, and benzo-a-pyrene exposure were demonstrated in tissues of these whales. Between 1988 and 1990, 21 tumors were found in 12 out of 24 carcasses. Among these tumors, six were malignant and 15 were benign. The animals were between 1.5 and > 29 years of age, and the ages of animals with and without tumors did not differ when two juvenile animals (1.5 and 3.5 years of age) were excluded. Seven other neoplasms had been reported previously in six out of 21 well-preserved carcasses examined in the same laboratory between 1982 and 1987. Overall, 28 of the 75 confirmed tumors reported so far in cetaceans (37%) were from this small population of beluga whales in the St. Lawrence Estuary. Such a high prevalence of tumors would suggest an influence of contaminants through a direct carcinogenic effect and/or a decreased resistance to the development of tumors in this population.

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PubMed1994

True hermaphroditism in a St. Lawrence beluga whale (Delphinapterus leucas).

A hermaphrodite beluga whale (Delphinapterus leucas) was found in the St. Lawrence Estuary, Québec, Canada. This animal had two testicles, two separate ovaries, and the complete ducts of each sex; cervix, vagina and vulva were absent. Mature spermatozoa were found in the lumen of seminiferous tubules in the testicles, and numerous involuted corpora lutea were recognized in the ovaries. This represents the first case of true hermaphroditism in a cetacean, and is the fourth hermaphrodite mammal with two testicles and two separate ovaries.

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PubMedDate not supplied

Phenotyping of beluga whale blood lymphocytes using monoclonal antibodies.

Widespread efforts are currently made to classify morphologically indistinguishable lymphocyte subpopulations in several species. In order to increase the knowledge in cetacean immunology, cross-reactivity of antibodies against bovine, human, ovine and mouse cell surface proteins was tested on beluga whale (Delphinapterus leucas) peripheral blood lymphocytes using flow cytometry. Anti-MHC class I and II as well as anti-CD2 reacted with virtually all peripheral blood lymphocytes. Anti-TCR gamma delta and anti-CD4 reacted with respectively 31% and 30% of peripheral blood lymphocytes. B lymphocytes were identified by an anti-surface IgM which was present on 6% of blood lymphocytes. Specificity of these antibodies was demonstrated by immunoprecipitation of beluga proteins with similar molecular weight to that of other species. These results could be useful for further immunotoxicological evaluation of highly versus mildly contaminated populations of belugas.

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PubMedDate not supplied

Purification of functional T lymphocytes from splenocytes of the beluga whales (Delphinapterus leucas).

In an effort to gain knowledge on immune functions in beluga whales, Delphinapterus leucas, we have used two physical methods for the purification of T lymphocytes of spleen cells. Isolation by sheep red blood cells (SRBC) rosetting and by adherence on nylon wool columns were tested. SRBC-rosetting gave unreliable results in obtaining purified T cells. Therefore, the purification of T cells was done using nylon wool columns. Less than 3% of the IgM(+) B cells remained in effluent populations. In the later population, 45% gave positive staining with mouse anti-human CD4 allowing us to verify functionality of the cells. The study of calcium mobilization and tyrosine kinase activation, mediated by CD4 cross-linking permitted verification of the functionality of cells. We also showed that upon activation with mitogens, beluga T cells upregulate the density of MHC class II molecules on their surfaces. CD4 cross-linking with a specific antibody inhibited the proliferation response. Overall, the activation of beluga whales lymphocytes did not differ markedly from what is known in other species. This study can help in the groundwork for functional investigation of the beluga whale's immune system.

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