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Biomedical subjects

C H Hollenberg

Publications and source records attributed to C H Hollenberg.

At least 37 records · Page 2Linked to original sources
PubMed1983

Medullary carcinoma of the thyroid.

Medullary cancer of the thyroid is rare but of unusual biologic interest. It originates in the thyroid parafollicular or C cells that are of neural crest origin and that secrete calcitonin. Calcitonin measurements, particularly after pentagastrim administration, are useful in detecting the tumor and following its progression. Ninety percent of medullary cancers are sporadic and 10% are familial; the latter may be associated with pheochromocytoma and parathyroid hyperplasia-adenoma. Initial symptoms of both the sporadic and familial varieties include thyroid mass, diarrhea, and less often, flushing. Uninvolved members of kindreds with the disease should be followed up by repeated measurements of calcitonin after pentagastrim and calcium infusion and should be treated when a positive test result is obtained. Therapy involves total thyroidectomy plus node dissection if indicated. In addition, postoperative radiation may reduce the recurrence rate.

Calcitonin↗
PubMed1983

Influence of anatomic site and age on the replication and differentiation of rat adipocyte precursors in culture.

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.

Adipose Tissue↗
PubMed1980

Very low density lipoprotein binding to adipocytes.

Human very low density lipoprotein (VLDL) has been found to interact with both isolated adipocytes and adipocyte membranes in a manner which is saturable, reversible and dependent on time and temperature. Except for a difference in maximum binding capacity, a similar pattern is seen with both rat epididymal adipocytes and human omental adipocytes. The capacity of rat cells is 0.04 micrograms VLDL per 2 x 10(5) cells. For human cells the capacity is 0.321 micrograms VLDL per 2 x 10(5) cells. Scatchard plots of the competition data are linear. This, and dissociation studies conducted in the presence or absence of unlabelled VLDL suggest that there is no cooperative interaction between the binding sites. Unlabelled VLDL and HDL each compete equally with 125I-labelled VLDL for binding sites. LDL is 25 times weaker as a competitor. Intralipid and unrelated peptides have no effect. These data suggest that the ligand is not apolipoprotein B and not apolipoprotein A. The competitive effect of HDL is not dependent on its apolipoprotein E content. A preparation of C apolipoproteins (75% C-11) is as potent as unlabelled VLDL in competing with 125I-labelled VLDL for binding sites. These data indicate that VLDL can bind to adipocytes. The receptor can interact with other lipoproteins. If differs from the LDL receptor as it does not interact with apolipoprotein B or apolipoprotein E, but binds to a C apolipoprotein.

Adipose Tissue↗
PubMed1978

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.

Canada↗
PubMed1978

Effect of calcium on [125I]insulin binding to rat adipocytes.

The specific binding of [125I]insulin to rat adipocytes was reduced in the absence of extracellular calcium. The addition of calcium to the calcium-free medium during incubation restored [125I]insulin binding towards normal. The specific binding of insulin was significantly increased with calcium concentrations as low as 0.5 mM and maximal binding occurred with 5 mM calcium. Scatchard analysis of the data suggests two major binding sites, one a high-affinity low-capacity site (Kd, 1.5 X 10(10) M-1) and the other a lower-affinity high-capacity site (Kd, 4.7 X 10(9) M-1). There was a 50% decrease in the number of high-affinity sites in absence of extracellular calcium. The dissociation curve of receptor-bound insulin was nonlinear both in the absence and presence of extracellular calcium suggesting receptor heterogeneity. The dissociation rate of receptor-bound insulin was greater when insulin was bound in the absence of extracellular calcium than in its presence. These results indicate that extracellular calcium, by increasing the number of high-affinity receptor sites, can alter the the ratio of high-affinity to low-affinity receptors for insulin in adipocytes.

Adipose Tissue↗