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A Simard

Publications and source records attributed to A Simard.

At least 55 records · Page 3Linked to original sources
PubMed1977

Specific inhibition of the incorporation of tritiated thymidine in regenerating rat liver by a rat hepatocytes supernatant.

Studies on endogenous inhibitors obtained from supernatant fluids of rat hepatocytes indicated that the supernatant arrests the normal cell cycle at two points, namely, before the beginning of the S phase and at the onset of metaphase when assayed in regenerating liver cells in situ. The specificity of this (these) inhibitory substance(s) was evidenced by the finding that no inhibition of cell division was observed in situ in tongue, intestine, or kidneys of animals injected with concentrations of the hepatocyte supernatant that inhibited cell division in regenerating liver. When higher concentrations of the inhibitor-containing supernatant were used, only the tongue epithelial cells were affected in addition to the regenerating liver cells.

Albumins↗
PubMed1975

[Biochemical study of cultured hepatocytes obtained from normal adult rats].

A method has been developed for the preparation of hepatocytes that contained 98.6% of that cell type with a yield of 50%. No change was detected in the DNA content per nucleus but losses were noted in RNA and proteins in freshly isolated hepatocytes. The hepatocytes have been kept alive for long periods in suspension or static cultures without any mitoses being observed. However DNA content doubled over a period of two weeks. This level was maintained during the third week. Tritiated thymidine incorportation similarly increased for a period of two weeks and then remained constant. RNA content went down rapidly to one fourth of the original level and remained unchanged thereafter. The protein content did not vary significantly. Incorporation of labelled leucine into proteins has also been measured at various periods of time following isolation of the cells. Even after 62 days in suspension culture, the hepatocytes continued to incorporate leucine into proteins. The incorporation of leucine proceeded through the normal pathway since the presence of t-RNA-bond-leucine was observed. The results reported here suggest that the hepatocytes are arrested in the G2 phase of the cell cycle.

Animals↗
PubMed1974

Inhibition of cell proliferation in the livers of hepatectomized rats by a rabbit hepatic chalone.

A purified chalone isolated from rabbit liver was tested in vitro on regenerating rat liver slices incubated with tritiated thymidine to determine more precisely the phase of the normal cell cycle that was blocked by that substance. Biochemical and radioautographic studies showed that the inhibition of tritiated thymidine incorporation during chromosomal DNA replication resulted chiefly from a block in the G(1)-S transition in the normal cell cycle. Under these conditions the chalone had little inhibitory effect on hepatocytes that were in the S phase of the cell cycle. The inhibitory effects of the liver chalone appeared to be specific for hepatocytes and no significant inhibition of cell division was observed when that compound was tested against intestinal villi or tongue epithelial cells of the rat. When, on the other hand, the purified chalone was injected into rats following partial hepatectomy, not only was an inhibition observed during the G(1)-S transition but an increase in the ratio of metaphases to anaphases was found, suggesting that a block also occurs at metaphase as a result of the action of the purified liver chalone used in this study. The injection of a crude supernatant fluid obtained from rabbit liver homogenates into partially hepatectomized rats resulted not only in a more pronounced block at the G(1)-S transition than was observed when the purified chalone was used, but the supernatant liquid also affected significantly DNA synthesis during the S phase of the cell cycle. These inhibitory effects were observed not only in hepatocytes but in intestinal epithelium and tongue epithelial cells of the rat as well. The rabbit liver supernatant fluid thus appears to contain, in addition to the liver chalone, one or more nonspecific inhibitors of DNA synthesis.

Animals↗
PubMedDate not supplied

Cancer of the pancreas in two brothers and one sister.

Over the past decades, pancreatic cancer has emerged as one of the most important malignancies in humans. This disease assumes a position of growing importance in view of its rising incidence and poor prognosis. Some familial pancreatic cancer has been reported with suggestions of hereditary, nutritional, home and familial environmental risk factors, and the possible role of genes in the development of this cancer among the members of one family. In an on-going case-control study of diet and cancer of the pancreas in Montreal, so far we were able to identify several familial cases of cancer of the pancreas. The most interesting case is the occurrence of this disease in two brothers and one sister all in their seventh decade of life. There was no history of pancreatitis among the cases or their relatives. Data from this study suggest that a familial predisposition to pancreatic cancer may occur in later decades of life. The role of genetic and environmental factors such as home remedies, familial food habits, etc., in the etiology of this cancer among these blood relatives, all in the same generation of one family, are unknown.

Adenocarcinoma↗
PubMedDate not supplied

Reported family aggregation of pancreatic cancer within a population-based case-control study in the Francophone community in Montreal, Canada.

As part of the SEARCH Collaborating Study Group of the International Agency for Research on Cancer (IARC), a population-based case-control study of cancer of the pancreas was conducted in Montreal, interviewing 179 patients and 179 controls matched for age, sex, and language (French) and selected by a modified random-digit dialing method. Results showed a positive and strong association between cigaret smoking and pancreatic cancer. Total fat, particularly saturated fat, and cholesterol consumption and excess energy derived from fat were associated with positive risk; dietary fiber intake, retinol equivalent, beta-carotene, vitamin C, and calcium showed inverse association with risk. History of such medical conditions as constipation, gallbladder problems, and diabetes was also found to be associated with risk. More important, 7.8% of the pancreatic cancer patients reported a positive family history of the same disease, as compared with 0.6% among controls, a 13-fold difference between cases and controls. Within the original case-control study a further study of patients with instances of familial pancreatic cancer was conducted, based on 14 cases and 56 matched controls. The results support the finding of the main study, and there were no apparent differences in environmental-risk-factor profile in familial and nonfamilial cases. This unusual aggregation of familial pancreatic cancer among French Canadians cannot be explained by environmental factors alone. Some familial predisposition (hereditary factors) may play an important role in the etiology of this cancer, at least in this study region. The findings suggest the potential importance of conducting genetic studies of pancreatic cancer.

Canada↗