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4.  Release of mitogenic factors by cultured preadipocytes from massively obese human subjects. 
Journal of Clinical Investigation  1987;79(2):632-636.
In this study, possible paracrine factors in adipose tissue from lean and obese subjects were sought. Conditioned media were prepared by incubation in alpha minimum essential medium of adipocyte precursors derived from lean and massively obese subjects. Adipocyte-precursor-derived conditioned media from the obese stimulated replication of cultured rat perirenal adipocyte precursors by about fourfold over control. The effect of media conditioned by precursors derived from lean subjects was much less evident. The mitogenicity of conditioned media was abolished by trypsin, indicating the protein nature of the mitogenic factor(s). Sephacryl S-200 chromatography of adipocyte-precursor-derived conditioned media from obese subjects revealed one major active fraction with molecular masses in the range of 25,000-40,000. Our results demonstrate that adipocyte precursors derived from massively obese subjects release factors mitogenic on cultured rat adipocyte precursors. These principles may act as paracrine factors contributing to the development of the adipocyte hyperplasia characteristic of massive obesity.
PMCID: PMC424150  PMID: 3805285
7.  The Canadian general internist: education and future role. 
Available manpower data indicate that for the forseeable future there will be a continuing requirement in Canada for specialists in general internal medicine. While these specialists will be located predominantly in community hospitals, they will also be needed in university medical centres. The major roles of the general internist will be (a) to provide consultative service to primary care physicians and to other specialists, (b) to provide continuing care to patients with complex serious illness and (c) to participate in intensive care, particularly in community hospitals. Therefore training programs in this specialty must provide adequate experience in consultative medicine in both university and community hospitals, an opportunity to follow up patients with chronic serious illness over long periods, and experience in a variety of intensive care settings including surgical intensive care units. In some university departments the organization and supervision of training programs in this discipline have been carried out by a division of internal medicine that has equal status with other specialty divisions within the department. This seems to have been a salutory development.
PMCID: PMC1817967  PMID: 630500
13.  Ontario cholesterol controversy. 
PMCID: PMC1451873  PMID: 2311029
14.  Varying capacities for replication of rat adipocyte precursor clones and adipose tissue growth. 
Journal of Clinical Investigation  1989;83(5):1741-1746.
Rat adipocyte precursor populations contain clones varying in capacity for replication. In this study we explored factors controlling the frequency of clones of varying replicative capacities (clonal composition). We also explored the relationship between this frequency and fat depot growth. In perirenal and epididymal depots clonal composition was identical bilaterally; perirenal depots contained more extensively replicating clones. Although there were large interanimal differences in clonal composition, variation between animals was always in the same direction for both depots. Clonal composition was unaffected by undernutrition while with animal growth the frequency of the most extensively replicating clones was reduced. Differentiation of precursors occurred in all clones, while differentiation did not occur in skin fibroblasts cloned under identical conditions. Clonal composition and mature fat cell number were related in that fat cell numbers were identical bilaterally in both depots and increased more extensively with growth in perirenal than epididymal tissue. We conclude (a) that clonal composition of adipocyte precursor populations is regulated genetically and by age, (b) that this composition determines, at least in part, the capacity for adipose depot growth.
PMCID: PMC303884  PMID: 2708530
16.  Regulation of DNA synthesis in fat cells and stromal elements from rat adipose tissue 
Journal of Clinical Investigation  1968;47(11):2485-2498.
The incorporation of tritiated thymidine into the deoxyribonucleic acid (DNA) of adipose fat and stromal cells was followed under a variety of conditions. After in vitro incubation of adipose slices or up to 2 days after in vivo injection of the isotope, all DNA radioactivity was in the stromal cell fraction. From 2 to 15 days after thymidine injection total tissue DNA radioactivity was constant, while between 2 and 5 days after injection label in fat cell DNA increased markedly. Thus new labeled fat cells, initially collected in the stromal pool, required 2-5 days after completion of DNA synthesis to accumulate sufficient lipid to be harvested in the fat cell fraction. Fasting before thymidine injection practically abolished DNA synthesis in primordial fat cells and reduced less drastically formation of stromal elements. However fasting sufficient to deplete lipid stores by 50% neither destroyed mature fat cells nor impaired their capacity to reaccumulate fat with refeeding. Other studies evaluated the role of new fat cell formation in the process of lipid accretion accompanying refeeding. These experiments indicated that at least during the early phase of rapid weight gain, accumulation of fat was due to deposition of triglyceride in existing cells rather than to accelerated formation of new fat cells. Studies with hypophysectomized rats demonstrated that pituitary ablation variably affected stromal DNA synthesis and nearly abolished the formation and (or) maturation of primordial fat cells. In these animals growth hormone markedly enhanced thymidine incorporation into stromal DNA but had no effect on fat cell precursors. In intact animals the predominant effect of growth hormone was also on the stromal fraction, although an action of the hormone of lesser magnitude on fat cell precursors was also evident.
PMCID: PMC297413  PMID: 4304653
17.  Polycystic Ovaries Associated with Congenital Adrenal Hyperplasia 
Polycystic ovaries were found in a 16-year-old female with congenital absence of vagina, male-like external genitalia, and congenital adrenal hyperplasia. Masculinization was sufficiently severe to cause the patient to be reared as a male. Biochemical studies of ovarian tissue revealed hyperactivity and an imbalance of enzyme systems concerned with steroid-hormone biosynthesis, which led to production of large amounts of androgens. The pathway towards estrogens was preserved but less efficient than normal. Urinary steroid metabolites before and after hysterectomy and bilateral salpingo-oophorectomy revealed an absence of Porter-Silber chromogens and tetrahydrocortisone. Excretion of aldosterone was normal and that of corticosterone slightly higher than normal. The patterns of urinary 17-ketosteroids, pregnanediol, pregnanetriol and pregnanetriolone were similar to those commonly seen in congenital adrenal hyperplasia with steroid 21-hydroxylase deficiency. Urinary estrogens after panhysterectomy were low, being in the post-menopausal range. The pathogenesis of polycystic ovaries and their possible contribution to masculinization are discussed.
PMCID: PMC1935165  PMID: 5901591
18.  The effect of health care reform on academic medicine in Canada. Editorial Committee of the Canadian Institute for Academic Medicine. 
Although Canadian health care reform has constrained costs and improved efficiency, it has had a profound and mixed effect on Canadian academic medicine. Teaching hospitals have been reduced in number and size, and in patient programs have shifted to ambulatory and community settings. Specialized care programs are now multi-institutional and multidisciplinary. Furthermore, the influence of regional planning bodies has grown markedly. Although these changes have likely improved clinical service, their impact on the quality of clinical education is uncertain. Within the academic clinical department, recruitment of young faculty has been greatly complicated by constraints on licensing, billing numbers, fee-for-service income and research funding. The departmental practice plan based on university funds and fee-for-service income is being replaced by less favourable funding arrangements. However, emphasis on multidisciplinary programs has rendered these departments more flexible in structure. The future of Canadian academic medicine depends on an effective alliance with government. Academia and government must agree, particularly on human-resource requirements, research objectives and the delivery of clinical and academic programs in regional and community settings. The establishment of focal points for academic health sciences planning within academic health sciences centres and within governments would assist in these developments. Finally, government and the academic health sciences sector must work together to remove the current impediments to the recruitment of highly qualified young faculty.
PMCID: PMC1487837  PMID: 8624998
19.  Influence of anatomic site and age on the replication and differentiation of rat adipocyte precursors in culture. 
Journal of Clinical Investigation  1983;72(4):1200-1208.
Using a propagating cell culture system of adipocyte precursors from 70-400-g rats, we explored the possibility that regional variations in properties of adipose tissue may reflect site-specific characteristics intrinsic to the cells, rather than extracellular influences. Initially, studies were made of the nature of the fibroblastlike cells from perirenal adipose tissue stroma. Using colony-forming techniques, it was shown that these cells were adipocyte precursors; each confluent colony that was derived from a single cell displayed differentiated adipocytes. This characteristic was evident in cells from rats of all ages and persisted during secondary culture. At all ages of rats studied, perirenal cells replicated more rapidly than epididymal precursors, e.g., for 179-g rats the population-doubling times were 19.3 +/- 0.7 vs. 25.5 +/- 1.2 h (means +/- SEM, P less than 0.03). With aging of the rats, the replication rate of their perirenal cells decreased progressively. Under clonal conditions, the colony size distribution of both perirenal and epididymal precursors revealed heterogeneity in their capacity for replication, perirenal cells showing greater proliferation. These also differentiated more extensively by morphologic and enzymatic criteria. Age and site had effects that persisted through many cell generations; however, high-fat feeding had no perpetuating influence. The dissimilar properties of perirenal as compared with epididymal precursors may reflect differences in regulation of gene expression. The data are also compatible with a later development in embryological life of perirenal tissue. We suggest that the composition of the adipocyte precursor pool is an important determinant of the growth of adipose tissue that occurs in response to a nutrient load. Interregional or interindividual variation in composition may explain regional and individual differences in fat accumulation.
PMCID: PMC370403  PMID: 6630508

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