Reduced mononuclear leukocyte ascorbic acid content in adults with insulin-dependent diabetes mellitus consuming adequate dietary vitamin C.

Several recent studies suggest that vitamin C (ascorbic acid [AA]) status may be altered in insulin-dependent diabetes mellitus (IDDM). We measured the AA content of mononuclear leukocytes (MN-AA) as an indicator of tissue vitamin C status in adults with IDDM and nondiabetic adults matched for age and sex. Dietary vitamin C intake and plasma AA were analyzed to ensure that vitamin C availability was adequate. Dietary vitamin C intakes were above recommendations and were not different between the groups. MN-AA was reduced by 33% on average (P less than .05) in adults with IDDM (1.75 microgram/mg total protein [TP]) when compared with nondiabetics (2.60 micrograms/mg TP). When MN-AA is indexed to the dietary vitamin C intake (MN-AA/100 mg diet C), the storage deficit in adults with IDDM averages 50% (P less than .05). This observation suggests an impaired tissue AA storage in adults with IDDM and supports the theory that intracellular scurvy contributes to the chronic degenerative complications of the disease.

A demonstration of a strain related restriction effect in the formation of experimental metastases.

In view of the role of histocompatibility proteins in mediating many types of cell interaction it was decided to investigate their role in the formation of experimental metastatic deposits using the B16 mouse melanoma cell line. The expression of both major histocompatibility complex (MHC) Class I and Class II proteins was studied in vitro. Expression of both MHC Class I and Class II proteins was greater in the highly metastatic F10 cell line as compared with the poorly metastatic F1 line. Intravenous injection of cells into syngeneic and semi-allogeneic animals revealed a strain related restriction effect on tumour growth following intravenous injection. However, this was mediated by a locus other than H-2. No restriction of lung trapping of radiolabelled cells or local growth following intraperitoneal injection was found. It is suggested that non-H-2 Class I proteins may mediate some of the stages of metastatic tumour growth independent of the immune system.