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Biomedical subjects

J Todd

Publications and source records attributed to J Todd.

At least 181 records · Page 10Linked to original sources
PubMed1974

In vitro synthesis and secretion of lysozyme by mononuclear phagocytes.

Pure cultures of three types of mononuclear phagocytes-mouse peritoneal macrophages, unstimulated or after thioglycollate stimulation, and human monocytes-synthesize and secrete large amounts of lysozyme in vitro. The macrophage lysozyme is indistinguishable from authentic lysozyme in its ability to lyse M. lysodeikticus, inhibition by specific antisera, a similar size of 14,000 and cationic charge. Lysozyme secretion in culture is characterized by a large net increase in total lysozyme, 4-20-fold in 3 h, 75-95% of which is in the medium, and its continued extracellular accumulation over at least 2 wk in culture. Lysozyme is the major (14)C-labeled protein secreted into the medium by both unstimulated and thioglycollate-stimulated macrophages and the 0.75-1 microg produced per 1 x 10(6) cells/day represents 0.5-2.5% of the total cell protein. Lysozyme is a cell-specific marker for mononuclear phagocytes and the PMN, which contains preformed enzyme, since it is absent in lymphoid cells and a variety of fibroblast and epithelioid cell lines. Lysozyme production is also a useful measure of mononuclear phagocyte cell number. The rate of lysozyme production and secretion is remarkably constant for all cell types under a variety of culture conditions. Production by the mouse macrophage increases threefold on the 2nd day in culture and then remains linear with time. Production is optimal at a relatively low serum concentration, but can be maintained, in the absence of serum, in lactalbumin hydrolysate or, at a reduced level in basal media. The production and secretion of lysozyme are independent of the production of macrophage acid hydrolases. Net increase and secretion of lysozyme occur under conditions where acid hydrolases like N-acetyl beta-glucosaminidase, beta-glucuronidase, beta-galactosidase, and cathepsin D are neither accumulated nor secreted. Massive phagocytosis of latex particles has no effect on lysozyme production and secretion. Lysozyme production can be rapidly inhibited by treatment with cycloheximide (0.4 microg/ml) whereas inhibition of its production by colchicine (10(-6) M) occurs only after a lag period of more than 8 h, and is probably due to a secondary effect. These results show that mouse macrophages provide a simple in vitro system to measure lysozyme secretion and its control. These studies also indicate the possible importance of mononuclear phagocytes in the secretion of a variety of biologically active products and in the modification of their environment.

Amino Acids↗
PubMed1970

Glucose tolerance and serum insulin in identical twins of diabetics.

Glucose tolerance with serum insulin assay has been carried out in 24 apparently unaffected identical twins of diabetics. Glucose values were significantly higher and insulin values significantly lower than in control subjects, but there was considerable individual variation and in half the cases glucose tolerance was normal. There was no case of increased insulin response. In these twins glucose tolerance and insulin response were not correlated with weight, family history of diabetes, age at diagnosis of diabetes in the affected twin, time since that diagnosis, nor with age at testing the unaffected twin. On retesting 12 of the twins after two years no significant differences were found from the first testing.We conclude that not all these twins are likely to develop diabetes, that the assumption that identical twins of diabetics are necessarily "prediabetic" is probably erroneous, and that factors other than genetic ones are important in the aetiology of diabetes.

Adolescent↗