Murine colon adenocarcinoma: syngeneic orthotopic transplantation and subsequent hepatic metastases

Syngeneic murine colon adenocarcinoma (MCA-38) cells were transplanted in the submucosa of distal colon, proximal colon, cecum, ileum, jejunum, and duodenum of male C57BL/6 mice, with local lymphoid follicles used as points of entry. The tumor grew best at the cecum and led to liver and mesenteric lymph node metastases in 8 and 9 weeks, respectively, after transplantation. Histologically, a local inflammatory reaction involving polymorphonuclear leukocytes was observed within 48-72 hours following transplantation; after this time, the microscopic tumor foci began to grow progressively. Mononuclear lymphoid cells of the gut-associated lymphoid tissue did not infiltrate the progressively growing tumor; however, polymorphonuclear leukocytes were constantly observed at the tumor periphery in the lamina propria. The studies indicated that orthotopic transplantation as a model system can provide a means of examining the role of the local immune response as a focus of host resistance and as a factor in metastatic tumor spread. The findings also suggested the usefulness of this model in immunotherapeutic and chemotherapeutic studies of secondary hepatic disease.

The effects of long-term therapy with oral hypoglycemic agents on the oral glucose tolerance test dynamics in male chemical diabetics

The effect of fixed doses of oral hypoglycemic agents and placebo (diet alone) on the blood glucose, serum insulin, triglyceride, and cholesterol responses during oral glucose tolerance tests done annually for up to four years' follow-up was studied, in a double-blind manner, in five groups of mild male chemical diabetics. The drugs used were chlorpropamide (100 mg. O.D.), tolbutamide (500 mg. b.i.d.), phenformin (50 mg. O.D.), acetohexamide (250 mg. O.D.), and placebo. Each subject was given an individualized diet aimed at attaining and maintaining ideal weight. Comparison by chi-square analysis between the placebo group and each of the drug groups showed (a) no significant differences with regard to the number of subjects with normal glucose tolerance in each of the tests and (b) no change in the insulin secretion dynamics. Comparison between the initial test and each of the subsequent tests within each group showed (a) a greater number of subjects with normal glucose tolerance in the first follow-up test in the chlorpropamide group only, (b) no change in the insulin secretion dynamics except in the chlorpropamide group, where there was an increased insulin/glucose ratio in the first follow-up test, and (c) no change in the fasting serum triglyceride and cholesterol levels.

The significance of lipoprotein lipase in rat skeletal muscles

Lipoprotein lipase was assayed in extracts of acetone-ether powders of rat skeletal muscles. Enzyme activity in soleus had typical characteristics of lipoprotein lipase in other tissues: inhibition by molar NaCl and protamine sulfate and activation by the human apolipoprotein, R-glutamic acid. Activity in muscles with predominantly red fibers (soleus, diaphragm, lateral head of gastrocnemius and anterior band of semitendinosus) was higher than in those with predominantly white fibers (body of gastrocnemius and posterior band of semitendinosus). No effect of a 24 hour fast upon enzyme activity was observed in ten skeletal muscles, but activity decreased substantially in four adipose tissue depots and increased slightly in heart muscle with fasting. Four minutes after intravenous injection of labeled lymph chylomicrons, skeletal muscles with predominantly red fibers incorporated several times more chylomicron triglyceride fatty acids than thos with predominantly white fibers. Estimated lipoprotein lipase activity in total skeletal muscle was about two-thirds that in total adipose tissue of rats fed ad libitum. After a 24 hour fast, total activity in skeletal muscle was about twice that in adipose tissue. These data suggest that a substantial fraction of lipoprotein lipase is in skeletal muscle of rats and that this tissue, especially its red fibers, is an important site of removal of triglycerides from the blood.

Serum insulin response to slow-rise glucose infusion in "genetic prediabetics" (offspring of two diabetic parents)

The insulin response to a programed slow-rise glucose infusion designed to mimic the postprandial rise in glucose was studied in five offspring of two diabetic parents (ODP) and seven normal subjects. The ODP had higher mean blood glucose levels towards the end of the infusion and during the postinfusion period. The rates of glucose disappearance calculate during the postinfusion period were comparable in the two groups. Despite the apparent similarity of serum insulin levels of ODP and normal subjects, the amount of insulin secreted per unit of glycemic stimulus was lower in the ODP group. When the glucose infusion test was preceded by an acute load of glucose, similar findings in the insulin secretory dynamics were found in the ODP group. These data suggest that an impairment in insulin secretion exists in ODP when they are challenged by the slow rise of blood glucose achieved by this type of an intravenous glucose infusion.

Murine colon adenocarcinomas: methods for selective culture in vitro

Two murine colon adenocarcinoma cell lines were established from primary cultures. The MCA-38 cell line was begun by treatment of the primary culture with trypsin to remove the fibroblastoid elements. The MCA-36 epithelial cells were sensitive to trypsin; therefore, the growth medium of MCA-36 primary cultures was augmented with collagenase to release the tumor-cell elements from the fibroblast network. These tumor elements were dissociated with trypsin and placed in tissue culture. Each cell line was cultured for at least 10 passages in vitro and gave rise to tumors when reimplanted in vivo.

Amino acid levels across normal forearm muscle and splanchnic bed after a protein meal

To characterize further the role of blood cells in amino acid transport, four normal volunteers were asked to ingest 200 g of broiled ground sirloin within a 10-min period. Blood samples from a radial artery, a deep vein draining forearm muscle bed, and a tributary of the hepatic vein were obtained prior to and for 4 hr after the meal and analyzed for various hormones and substrates. At rest, analysis of arterio-deep venous differences across the forearm revealed the blood cell and plasma amino acid compartmentmental contents to be relatively constant except for alanine and glutamine. Whole blood arterio-hepatic venous (A-HV) amino acid differences were not significantly different from zero; however, blood cell A-HV difference analysis revealed a significant release of threonine from the splanchnic bed while plasma A-HV difference analysis revealed modest but significant releases of glutamate and ornithine and uptakes of phenylalanine and histidine. After the ingestion of the meat meal, plasma and blood cell levels of almost all of the measured amino acids increased significantly. Notable exceptions included glycine and alanine, levels of which did not change significantly and glutamine. The arterial blood cell content of the latter amino acid paradoxically decreased while arterial plasma levels increased significantly. Most importantly, large quantities of branched chain amino acids were released from the splanchnic bed and removed by forearm muscle. These data suggest that the blood cells of normal man do actively participate in amino acid transport, and that the magnitude and direction of change induced by the ingestion of a proteins meal varies with the individual amino acid.

Serum insulin and growth hormone response patterns in monozygotic twin siblings of patients with juvenile-onset diabetes

To detect abnormalities in the secretion of insulin and growth hormone in monozygotic twin siblings of patients with juvenile-onset diabetes, their responses during oral, cortisone-primed oral, and intravenous, glucose tolerance tests and intravenous tolbutamide tests were compared to those of matched controls. The twins had higher mean serum insulin levels during all tests, but differences reached statistical significance (P less than 0.02) only in the cortisone-primed test. Growth hormone levels were higher in the twins (P less than 0.04) in the intravenous tolbutamide tolerance test. The frequency of abnormal oral glucose tolerance tests among controls, diabetic monozygotic twins and the offspring of two diabetic parents was also compared. Twins and controls had nearly the same frequency of normal tests; however, the diabetic offspring had a significantly higher (P less than 0.001) prevalence of abnormal tests. These data suggest that magnitudes of environmental and genetic factors operating in monozygotic "pre-diabetic" children of diabetic parents.

Studies of glucagon secretion in pancreatectomized patients

Intravenous arginine infusions were performed in two totally pancreatectomized patients and two age/sex-matched normal subjects. Plasma glucagon concentrations did not increase in the pancreatectomized patients, whereas a four- to sixfold rise of the glucagon levels following arginine administration was seen in the control subjects. Measurements of plasma glucagon-like im-munoreactivity revealed no difference between normal and pancreatectomized subjects. The data suggest the absence of a significant number of normally functioning alpha cells in extrapancreatic sites.