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Biomedical subjects

C F Howard

Publications and source records attributed to C F Howard.

At least 55 records · Page 3Linked to original sources
PubMed1979

Effects of quantity and unsaturation of dietary fat on serum components in normal and diabetic Macaca nigra.

Dietary fat affects serum lipids independently of dietary cholesterol. Normal and diabetic monkeys (Macaca nigra) were fed cereal-based, specially formulated diets with either a low fat (LF = 2.5%) or a higher fat (13.2%) content; the latter had varying concentrations of safflower and coconut oil to attain greater polyunsaturation (SFO) or saturation (CCO) in the diets. Dietary cholesterol was less than 0.01%. Serum triglyceride concentrations were greatest when monkeys consumed the LF (higher carbohydrate) diet and lowest when they consumed the SFO diet. Concentrations were greater in diabetic than in normal monkeys fed the LF and SFO diets, but both groups had similar concentrations when fed the CCO diet. Cholesterol levels in diabetic monkeys were only slightly higher than in normals regardless of diet; in both groups, levels were lowest when the LF diet was fed and highest when the CCO diet was fed. The quantity of fat had a greater effect on serum cholesterol than did the degree of polyunsaturation. In both groups, triglyceride concentrations correlated significantly with VLDL protein, and cholesterol levels correlated with LDL protein. Thus the responses of Macaca nigra to dietary fat manipulation depend upon both the diet fat content and composition as well as the normal or diabetic metabolic state of each monkey.

Animals↗
PubMed1978

Insular amyloidosis and diabetes mellitus in Macaca nigra.

Amyloid in the islets of Langerhans increases with increasing severity of diabetes mellitus in Macaca nigra. The amount of insular amyloid was quantified, and diabetic monkeys averaged eight times more islet amyloid than did normal monkeys. The quantity of insular amyloid correlated significantly with glucose clearance in intravenous glucose tolerance tests and with serum glucose, triglycerides, immunoreactive insulin, and prebetallipoprotein measured after an overnight fast. As with human beings, insular amyloid appeared to be more prevalent in aging monkeys. The results support the hypothesis that the interrelated islet pathologic and metabolic events, which result in the appearance of insular amyloid concomitant with islet cell necrosis, may contribute more to maturity-onset diabetes in aging individuals than has been heretofore realized.

Amyloidosis↗
PubMed1976

An improved apparatus for mounting retinal vasculature.

An apparatus for mounting retinal vasculature substantially reduced the time required to mount the capillary bed, minimized trauma to the vessels, and consistently resulted in preparations that allowed maximal viewing of retinal capillaries.

Histological Techniques↗
PubMed1975

Basement membrane thickness in muscle capillaries of normal and spontaneously diabetic Macaca nigra.

The thickness of the capillary basement membrane of femoral muscle was examined in normal and spontaneously diabetic Macaca nigra. Thickness correlated significangly with the degree and severity of diabetes; greater thickness was associated with decreased glucose tolerance, decreased serum insulin, and increased glucose and triglyceride. In normal monkeys, the average basement membrane thickness was 696 A and in diabetic monkeys, 837 A, The minimum basement membrane thickness was 524 A in normal monkeys and 634 A in diabetics. Normals differed significantly from diabetic monkeys.

Animals↗
PubMed1975

Spontaneous diabetes mellitus in Macaca cyclopis and Mandrillus leucophaeus: case reports.

Spontaneous diabetes mellitus was reported in a Mandrillus leucophaeus (drill baboon) and a Mpacaca cyclopis (Formosan rock macaque). Each had hyperglycemia, impaired clearance of glucose during tolerance test, and reduced concentrations of immunoreactive insulin; the M cyclopis also had increased triglyceride and prebetalipoprotein concentrations. Both monkeys had extensive amyloid infiltration into the islets of Langerhans and loss of beta cells. Beta cell obliteration can account for the appearance of the diabetic syndrome in these and other nonhuman primate species.

Amyloidosis↗
PubMed1971

Lipogenesis from glucose-2- 14 C and acetate-1- 14 C in aorta.

Lipogenesis was measured with glucose-2-(14)C and acetate-1-(14)C in the everted aortas of normal and atherosclerotic rabbits. More glucose-2-(14)C than acetate-1-(14)C was incorporated into lipids in both the normal and the atherosclerotic aorta. Radiocarbon from glucose-2-(14)C appeared mainly in triglycerides and phospholipids with a small amount in cholesteryl esters. Incorporation increased almost threefold with atherosclerosis, most of the radioactivity being in the glycerol moiety; radioactivity was predominantly in carbon 2 of glycerol. About 70% of the acetate-1-(14)C incorporated into phospholipids and triglycerides was in the fatty acids, and the remainder was in glyceride-glycerol; 98% of the radioactivity in cholesteryl esters was in the fatty acid moiety. Incorporation into cholesteryl esters was increased most during the development of atherosclerosis. Fatty acid synthesis was similar from both acetate-1-(14)C and the 2 carbon unit derived from glucose-2-(14)C, viz., predominantly de novo synthesis of fatty acids with 14 and 16 carbon atoms, and elongation for those of 18 carbons and longer.

Acetates↗
PubMed1968

De novo synthesis and elongation of fatty acids by subcellar fractions of monkey aorta.

Subcellular fractions of aorta of squirrel monkey (Saimiri sciureus) were examined for their ability to synthesize and elongate fatty acids. High-speed supernate (HSS) incorporated substantial quantities of malonyl CoA into fatty acids while acetyl CoA was much less effectively utilized. Acetyl-CoA carboxylase activity exceeded the amount of acetyl CoA incorporated into fatty acids and thus does not account for the low incorporation of this substrate. Microsomes used malonyl CoA and acetyl CoA equally well; mitochondria incorporated either acetyl CoA or acetate. The amounts of substrate incorporated into fatty acids (m micro moles/mg of protein per hr) were 2.3 for HSS, 1.2 for microsomes, and 0.9 for mitochondria. The synthesized fatty acids were separated by gas-liquid chromatography, radioassayed, extracted from the scintillation fluid, and decarboxylated. HSS completely synthesized palmitic and stearic acids from malonyl CoA. Microsomes and mitochondria utilized acetyl CoA to elongate endogenous fatty acids and gave mainly palmitic, stearic, and C(18) and C(20) monoenoic acids, with lesser amounts of other saturated and unsaturated fatty acids. A significant quantity of malonyl CoA was utilized by microsomes to yield a fatty acid tentatively identified as docosapentaenoic. Radioactive fatty acids are incorporated into various lipid classes by the particulate preparations. These studies demonstrate that aortic tissue in a nonhuman primate is able to carry out several processes of fatty acid metabolism and that the aortic synthesis and elongation of fatty acids may play an important role in providing fatty acids for incorporation into aortic lipids.

Animals↗