Biomedical subjects

D R Lock

Publications and source records attributed to D R Lock.

8 recordsLinked to original sources

PubMed1988

Glycemic indices of various foods given to pregnant diabetic subjects.

The applicability of the glycemic index concept in pregnancy has not been established. The postprandial glucose curves were measured for nine foods (glucose, bread, raisins, dates, sweet corn, bananas, oranges, spaghetti, and green peas) in 28 gestational diabetic subjects. Uniform glycemic indices were observed for each food, similar to those reported by others in nonpregnant subjects. Postprandial glucose levels reached their peak later after glucose and bread ingestion than after the remaining seven foods. These results demonstrate that despite known changes in gastrointestinal function in pregnancy, glycemic indices are uniform after the ingestion of foods. Pregnancy does not appear to alter the glycemic indices of the foods tested.

Adult↗

PubMed1985

Distribution of apolipoproteins A-I and B among intestinal lipoproteins.

Chylomicrons and very low density lipoproteins (VLDL) are produced by the intestine and these nascent particles are thought to be similar to their counterparts in intestinal lymph. To study the relationship between these lipoproteins within the cell and those secreted into the lamina propria and lymph, we have isolated enterocytes, lamina propria, and mesenteric lymph from rats while fasted and after corn oil feeding. Apolipoprotein A-I and B content were measured by radioimmunoassay in cell, lamina propria, and lymph fractions separated by Sepharose 6B and 10% agarose chromatography, and by KBr isopycnic density centrifugation. ApoA-I in the cell and the underlying lamina propria was found partly in those fractions in which chylomicron and very low density lipoproteins (chylo-VLDL) and high density lipoproteins (HDL) elute, but more abundantly where unassociated 125I-labeled apoA-I was eluted. In the lymph, however, 74% of apoA-I eluted in the HDL region and no peak of free apoA-I was found. ApoB and apoC-III within the enterocyte were found distributed in the position of particles eluting not only with chylomicrons and VLDL, but also in the regions corresponding to LDL and HDL. In the lamina propria and lymph, on the other hand, most of the apoB was found in the region of VLDL and chylomicrons. These results indicate that the patterns in lymph lipoproteins and the lamina propria do not exactly mirror the distribution of apoA-I and B among lipoproteins inside the cell. This may be because intracellular apoproteins may be unassociated with lipoproteins, or they could be associated with lipoproteins in various stages of assembly of protein with lipids. Furthermore, the apoprotein composition of intestinal lipoproteins is altered after secretion from the enterocyte. Finally, not all apoproteins seem to be secreted in association with identifiable lipoprotein particles from the enterocyte.

Animals↗

PubMed1983

Apolipoprotein B subspecies in chylomicrons isolated from a patient with chyluria.

The diagnosis and the clinical course of a 17-year-old white male with chyluria are reported. Cloudy, milky urine appeared spontaneously, in the absence of edema or any signs or symptoms of parasitic infection. Pedal lymphangiography demonstrated the presence of a lymphatic renal fistula, and digital subtraction angiography showed aneurysmal dilatation of the aorta at the level of the renal arteries. This case provided an opportunity to ascertain which of the forms of apolipoprotein B were present in lymph chylomicrons. Apolipoprotein B is needed for chylomicron secretion. It exists in several forms--B-100, B-74, B-48, and B-26. After a meal consisting of fat, chylomicrons in which apolipoprotein B-48 was virtually the only apolipoprotein B present appeared in the urine, while apolipoprotein B-100 was the only apolipoprotein B present in the plasma very low-density lipoproteins. Chyluria disappeared two weeks after institution of a low-fat diet. This case illustrates an interesting, rare cause of chyluria. Because of the presence of chyluria, it was also demonstrated that chylomicrons in which apolipoprotein B-48 is virtually the only apolipoprotein B present are a physiologically normal product of the intestine.

Adolescent↗

PubMed1983

Effect of probucol on the composition of lipoproteins and on VLDL apoprotein B turnover.

We studied the effect of probucol on lipoprotein composition and VLDL apo B turnover. In 7 hypercholesterolemic subjects, probucol therapy lowered mean total cholesterol, HDL cholesterol and HDL triglycerides, raised LDL triglycerides and did not change LDL cholesterol. LDL cholesterol:LDL triglycerides mass ratios fell. In all 6 subjects studied by rate-zonal ultracentrifugation, the flotation rate of LDL decreased. The isolated LDL were depleted of cholesteryl esters relative to protein. Thus, there were changes in the physical and chemical properties of LDL. All 6 subjects had reductions in HDL2, with variable changes in HDL3 on zonal ultracentrifugation. Probucol did not cause significant alterations in VLDL apo B turnover in 4 patients. The results suggest that the alterations in HDL probably are not related to changes in the flux of VLDL plasma, but rather may be due to direct effects of the drug on HDL production or catabolism.

Adult↗

PubMed1983

ApoA-I/ApoA-II ratios in plasmas of vegetarians.

Diets low in fat and cholesterol and high in P/S ratio are accompanied by low HDL-cholesterol levels. Short-term experimental feeding of such diets demonstrates that the HDL2 fraction is reduced preferentially. In order to ascertain whether the HDL2 lowering effects persist over the long-term, apolipoprotein A-I/A-II ratios, which are indices of the HDL2 relative to HDL3 in plasma, were measured in three groups of vegetarians (n = 35) who had been eating vegetarian diets for 1 to more than 5 years varying in cholesterol contents from less than 10 to 300 mg/d, fat between 30% to 50% of calories, and P/S ratio between 0.7-2.5. Concentrations of apoA-I were lower in those eating the least cholesterol and the highest P/S ratio, ie, apoA-I correlated positively with dietary cholesterol (r = 0.38, P less than 0.05), and both apoA-I and the A-I and the A-I/A-II ratio correlated negatively with the ratio of polyunsaturated-to-saturated (P/S) fatty acids (r = -0.39, P less than 0.05, and r = -0.41, P less than 0.02, respectively). There was no significant correlation between apoA-I, apoA-II, the A-I/A-II ratio or the high-density lipoprotein cholesterol/apoA-I ratio and consumption of total calories, fat, protein, or carbohydrate. Since the A-I/A-II ratio is much higher in HDL2 than in HDL3, these data suggest that cholesterol intake and the P/S ratio are important long-term dietary determinants of plasma HDL2 levels. Thus, in vegetarians, despite a reduced risk of coronary heart disease, the high-density lipoprotein cholesterol (HDL-C) and especially HDL2 concentrations were low. More work is needed to elucidate this interesting paradox.

Adult↗

PubMed1982

Apolipoprotein E levels in vegetarians.

Vegetarians are known to have low lipoprotein lipid and apolipoprotein Al and B levels. Since dietary cholesterol has recently been shown to have important effects on apolipoprotein E (apo E) metabolism, we measured plasma apo E levels in three groups of vegetarians. Group I (n = 36) consumed less than 10 mg cholesterol daily and 42% of calories as fat (P:S ratio 2.6). Group II (n = 10) and Group III (n = 18) consumed 97 and 179 mg cholesterol daily, and 35% of calories as fat (P:S ratios 0.7 and 0.9) respectively. Compared to control values, vegetarian plasma cholesterol and triglyceride levels were decreased by 10%-30% and 30%-55%. Plasma apo E levels were decreased equally in all groups by 35% (2.4 +/- 0.1 mg/dl versus 3.6 +/0 0.1 mg/kl, P less than .001). Plasma apo E levels were increased in parallel with lipid levels in pregnant vegetarians but were not different from non-lactating vegetarians in postpartum lactating women. Decreased apo E levels did not correlate with relative body weight, P:S ratio or intake of fat, carbohydrates or protein. Since all vegetarian diets studied were low cholesterol diets, decreased cholesterol intake may contribute to the low apo E levels. The apparent modification of apo E metabolism by vegetarian diets may be important in mediating effects of lipid lowering diets on atherogenesis.

Apolipoproteins↗

PubMedDate not supplied

Hypoglycemic coma associated with subcutaneous insulin infusion by portable pump.

The incidence of hypoglycemia in insulin-dependent diabetic patients managed by continuous subcutaneous insulin infusion (CSII) has been reported to be very low. We report a case of hypoglycemia coma occurring in a highly compliant and intelligent patient while on CSII by a portable pump. Factors contributing to this episode included high risk off hypoglycemia due to tight control, failure to recognize early hypoglycemic symptoms, and maintenance of hypoglycemia for over 2 h by the open-loop device. Hypoglycemia is a complication of CSII by portable pump. We join others in recommending its use solely by experienced physicians. Constant supervision of patients while on CSII is important to eliminate this potentially lethal complication.

Adult↗

PubMedDate not supplied

Levodopa pharmacokinetics. Alterations after benserazide, a decarboxylase inhibitor.

Plasma levodopa decay curves appeared to be triexponential up to 6 hr after single intravenous injections of levodopa in rats, rabbits, and dogs. After pretreatment of each of these three species with benserazide (Ro-4-4602), a decarboxylase inhibitor, plasma levodopa concentrations declined biexponentially. Administration of benserazide decreased both total plasma clearance and apparent volume of distribution of levodopa, but did not change the rate constant of the terminal phase of the plasma levodopa decay curve. Thus, decarboxylase inhibition failed to alter the plasma half-life of levodopa.

Animals↗