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Biomedical subjects

M C Riddle

Publications and source records attributed to M C Riddle.

10 recordsLinked to original sources
PubMed1992

Combining insulin and sulfonylurea. A therapeutic option for type II diabetes.

Non-insulin-dependent (type II) diabetes mellitus is a progressive disease that requires sequential therapy to achieve optimal control. When diet and sulfonylurea fail to maintain glycemic control, the addition of a single daily injection of insulin may be indicated. The best candidates for this combined therapy are patients with typical adult-onset disease that has been present less than 10 to 15 years.

Diabetes Mellitus, Type 2↗
PubMed1992

A model for the apparent decrease in optical transmittance of the diabetic eye.

This paper compares observed changes of ocular transmittance at short and long wavelengths in diabetic patients with values predicted by a model based on the Rayleigh light scattering properties of albumin. Selective chromatic adaptation was used to obtain critical flicker fusion (CFF) frequency thresholds from 21 subjects and 18 patients with insulin-dependent diabetes. The Ferry-Porter characteristic of each color-sensitive mechanism of each patient was compared to age-specific control values. For those eyes without an indication of neural injury, changes in optical density associated with the red- and blue-sensitive mechanisms were calculated and adjusted to reflect accelerated yellowing of the lens produced by increased duration of diabetes. The range of concentration of glycosylated albumin required to fit the model to the adjusted short-wavelength changes in optical density was determined and used to calculate the theoretical long-wavelength changes in optical density. The experimentally derived long-wavelength changes in optical density fell within the 95% confidence level of the values described by the model. These results support the premise that the apparent decrease in optical transmittance observed in patients with diabetes mellitus is caused by light scattering produced by dilute increase of plasma proteins within the retina.

Adaptation, Ocular↗
PubMed1990

The mental efficiency of the elderly person with type II diabetes mellitus.

Cognitive function is often impaired in type I diabetes mellitus, especially when onset is in early childhood. Limited evidence suggests similar impairment in the much larger population of older persons with type II diabetes. We report here the results of 13 measures of mental efficiency in persons between 65 and 77 years of age without gross mental impairment. Nineteen persons with type II diabetes were compared with 19 controls with normal glycosylated hemoglobin values and to seven persons not previously known to have diabetes but who had elevated glycosylated hemoglobin. Significant differences (P less than .05) between the nondiabetic control and diabetic groups were noted on eight of the 13 tests. The group of subjects with elevated glycosylated hemoglobins showed levels of cognitive performance intermediate between the normal and known diabetic groups on the majority of tests. These findings confirm that mental efficiency is frequently impaired in older persons with diabetes. Given the high prevalence of diabetes in the aging population we suggest that diabetes may be another important factor contributing to premature loss of cognitive abilities in older people.

Aged↗
PubMed1990

Evening insulin strategy.

A series of regimens based on intermediate-acting insulin given in the evening have been proposed as an alternative to conventional insulin therapy for non-insulin-dependent diabetes mellitus (NIDDM). This concept dates back to the earliest use of sustained-action insulin and has a rationale strengthened by recent physiological insights. Specifically, the predominance of fasting over postprandial hypoglycemia and occurrence of the dawn phenomenon in NIDDM argue for carefully timed overnight delivery of insulin. High nocturnal concentrations of free fatty acids in NIDDM may contribute to hepatic insensitivity to insulin and fasting hyperglycemia and can be suppressed by evening insulin. Although several clinical studies suggest that evening insulin regimens are safe and effective, their role in clinical practice is not yet established. Further study of this approach may clarify not only its proper use but also the best use of conventional strategies.

Blood Glucose↗
PubMed1990

Diabetic neuropathies in the elderly: management update.

Diabetic neuropathy is a common, varied, and disabling disease that is potentially responsive to therapy. While its pathogenesis is as yet unclear, its clinical presentations and natural history are well known. Present information suggests glycemic control can prevent neuropathy and in some cases cause established neuropathy to regress. Drug therapy is useful only for painful neuropathy. Avoidance of alcohol and behavioral and surgical relief of nerve entrapment are helpful in certain cases.

Aged↗
PubMed1989

Efficacy of bedtime NPH insulin with daytime sulfonylurea for subpopulation of type II diabetic subjects.

Although insulin and sulfonylureas often have additive clinical effects when used in combination for type II (non-insulin-dependent) diabetes, these results are variable and a clinical role for this approach is not yet established. This study tests the efficacy of a specific combined regimen for a subpopulation of patients with a randomized double-masked placebo-controlled crossover design and under conditions similar to those of clinical practice. Twenty subjects with limited duration (less than 15 yr) type II diabetes who were moderately obese (less than 160% ideal wt) and proved imperfectly controlled on 10 mg glyburide twice daily completed two 4-mo crossover protocols, comparing a single injection of NPH insulin in the evening plus 10 mg glyburide in the morning with insulin plus placebo. Insulin dose was adjusted by experienced endocrinologists seeking the best glycemic control consistent with safety. All subjects had glycosylated hemoglobin values less than or equal to 150% of the control mean on combined therapy, and combined therapy was superior to insulin alone (fasting plasma glucose 8.0 +/- 0.3 vs. 11.1 +/- 0.6 mM, P less than .01; glycosylated hemoglobin 9.8 +/- 0.1 vs. 10.6 +/- 0.2%, P less than .01). Despite greater weight gain on combined therapy, blood pressure and plasma lipid concentrations were the same on the two regimens. These results suggest this simple regimen offers another option, besides multiple injections of insulin, for patients of this kind who are unsuccessful with a sulfonylurea or a single injection of insulin alone.

Adult↗
PubMed1977

Two cholesterol ester hydrolases. Distribution in rat tissues and in cultured human fibroblasts and monkey arterial smooth muscle cells.

Hydrolytic activity against acetone-dispersed [4-14C]cholesterol oleate has been assayed as a function of pH in seven parenchymal tissues, blood cells, and plasma of the rat, as well as in cultured human fibroblasts and monkey (Macaca nemestrina) arterial smooth muscle cells. Both acid and neutral hydrolytic activities were present in all of these except rat plasma. The pH optima were in all cases close to pH 4.5 and pH 6.8. Acid activity was quite constant from tissue to tissue, while neutral activity varied greatly, being greatest in adrenal, testis, and adipose tissue. Subcellular fractionation of human fibroblasts allowed demonstration that activities at pH 4.5 and pH 6.8 were concentrated in different fractions, apparently lysosomal and polysomal, respectively. It appears most cell types, including fibroblasts and smooth muscle cells, contain two separate enzymes capable of hydrolyzing cholesterol esters. The neutral pH polysomal enzyme, which is especially prominent in certain tissues, may have a function related to the specialized roles of these tissues.

Animals↗
PubMed1975

Cholesteryl ester hydrolytic acitivity of rat liver plasma membrane.

Cholesteryl ester hydrolyzing activity of rat liver plasma membranes was studied using acetone-dispersed [4-14-C] cholesteryl oleate as substrate. In contrast to whole liver homogenates which displayed ample activity at both acid (4.5) and neutral (6.2-7.4) pH, purified plasma membrane fractions contained little activity at neutral pH as compared to acid pH. Moreover, rate-zonal sucrose density-gradient centrifugation patterns of plasma membrane rich fractions suggested a specific association with plasma membrane only in the case of the acid activity. These findings suggest that in vivo hepatic cell surface membranes contain little or no cholesteryl ester hydrolytic activity at extracellular pH. They support the possibility that plasma lipoprotein cholesteryl esters enter hepatic parenchymal cells prior to hydrolysis.

Animals↗