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Biomedical subjects

D S Lewis

Publications and source records attributed to D S Lewis.

52 records · Page 3Linked to original sources
PubMed1982

Laboratory evaluation and assistance efforts: mailed, on-site and blind proficiency testing surveys conducted by the Centers for Disease Control.

During the last three years, the Centers for Disease Control (CDC) has conducted: 1) on-site surveys in which trained personnel visited laboratories that had experienced performance problems in the quarterly mailed proficiency testing (PT) program, reviewing the laboratories' analytical procedures by using carefully referenced samples to determine sources of errors and providing assistance in correcting them; 2) special assistance surveys in which carefully referenced samples were mailed to laboratories that had performed unsatisfactorily in routine mailed PT surveys and then telephone consultations were conducted to correct the problems; and 3) blind surveys in which carefully referenced samples were sent through normal patient sample acquisition routes to assess the actual day-to-day performance capability of the laboratories. Results suggest that on-site surveys by trained laboratory surveyors and special mailed assistance surveys can be very effective in identifying the source of analytical errors in laboratories previously found, through mailed PT surveys, to have performance problems. Blind-survey results indicate that good performance in mailed PT does not necessarily imply good laboratory performance with routine patient specimens. Although difficult to conduct, blind surveys should be conducted whenever the logistics can be worked out by contractors for laboratory services, clinicians using laboratory services, and the laboratories themselves to assure the continuation of quality service.

Blood Chemical Analysis↗
PubMed1981

Quantitative changes in adipocyte plasma membrane in response to nutritional manipulations.

The effects of changes in adipocyte size and the effects of nutritional manipulations on the quantity of plasma membrane per adipocyte were investigated. A method for estimating the quantity of plasma membrane was developed based on the specific labeling of adipocyte plasma membrane protein with the nonpermeable labeling agent 125I-labeled diazotized diiodosulfanilic acid. By studying rats (ranging in age from 50 to 125 days) fed a standard laboratory chow or a low fat diet or a high fat diet, a wide range of mean fat cell sizes was obtained. It was found that as the volume of the fat cell increased, the amount of plasma membrane increased in a linear fashion and that this linear relationship had the same slope whether the size of the adipocyte increased slowly with age or rapidly in response to a high fat diet. In contrast, fasting for up to 3 days caused a marked decrease in the mean volume of the adipocytes, but either no change or much less change in the amount of plasma membrane per cell than would have been predicted from the linear relationship between adipocytes, but either no change or much less change in the amount of plasma membrane per cell than would have been predicted form the linear relationship between adipocyte volume and amount of plasma membrane per cell obtained with fed rats, i.e., adipocytes from fasted rats contain more plasma membrane per cell than do fat cells of the same size from fed rats. Neither feeding a high fat diet nor fasting caused detectable changes in the protein and lipid composition of the adipocyte plasma membrane.

Adipose Tissue↗
PubMed1979

An assessment of the role of protein kinase and zymogen granule phosphorylation during secretion by the rat exocrine pancreas.

1. The levels of protein kinase activity and zymogen granule phosphorylation were studied in the adult rat during stimulus-coupled secretion in vitro. 2. The specific activity of protein kinase associated with intact zymogen granules was 11 pmol [32P]phosphate transferred to histone per min per mg protein. Most of this activity was recovered in purified granule membranes. 2. The addition of 10(-6) M cyclic AMP to a mixture of zymogen granules and the postmicrosomal supernatant resulted in a 5-fold increase in protein kinase activity associated with zymogen granules. The adsorbed activity was eluted from granules by 0.15 M NaCl. Cyclic GMP did not promote protein kinase binding to isolated granules. 4. Incubation of tissues with carbachol (10(-5) M), pancreozymin (0.1 unit/ml), caerulein (10(-8) M) or dibutyryl cyclic AMP (2.10(-4) M) between 2.5 and 60 min did not increase the levels of protein kinase activity in isolated zymogen granules above control values. 5. Protein phosphorylation of zymogen granule membranes and granule content was not detectable in tissues incubated with carbachol, pancreozymin-C-octapeptide, or caerulein. 6. These results suggest that neither the phosphorylation of zymogen granule membrane protein nor the adsorption of protein kinase activity to zymogen granules is an obligatory step in secretion.

Animals↗
PubMed1978

Glycoprotein synthesis in the adult rat pancreas. IV. Subcellular distribution of membrane glycoproteins.

Zymogen granule membranes from the rat exocrine pancreas displays distinctive, simple protein and glycoprotein compositions when compared to other intracellular membranes. The carbohydrate content of zymogen granule membrane protein was 5-10-fold greater than that of membrane fractions isolated from smooth and rough microsomes, mitochondria and a preparation containing plasma membranes, and 50-100-fold greater than the zymogen granule content and the postmicrosomal supernate. The granule membrane glycoprotein contained primarily sialic acid, fucose, mannose, galactose and N-acetylglucosamine. The levels of galactose, fucose and sialic acid increased in membranes in the following order: rough microsomes less than smooth microsomes less than zymogen granules. Membrane polypeptides were analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The profile of zymogen granule membrane polypeptides was characterized by GP-2, a species with an apparent molecular weight of 74 000. Radioactivity profiles of membranes labeled with [3H]glucosamine or [3H]leucine, as well as periodic acid-Schiff stain profiles, indicated that GP-2 accounted for approx. 40% of the firmly bound granule membrane protein. Low levels of a species similar to GP-2 were detected in membranes of smooth microsomes and the preparation enriched in plasma membranes but not in other subcellular fractions. These results suggest that GP-2 is a biochemical marker for zymogen granules. Membrane glycoproteins of intact zymogen granules were resistant to neuraminidase treatment, while those in isolated granule membranes were readily degraded by neuraminidase. GP-2 of intact granules was not labeled by exposure to galactose oxidase followed by reduction with NaB3H4. In contrast, GP-2 in purified granule membranes was readily labeled by this procedure. Therefore GP-2 appears to be located on the zymogen granule interior.

Animals↗
PubMedDate not supplied

A college nutrition science course as an intervention to prevent weight gain in female college freshmen.

The objective of this study was to test the hypothesis that a nutrition course that stresses fundamental principles of human physiology, energy metabolism, and genetics helps prevent weight gain during the first 16 months of college life. A randomized control trial was conducted from January 1997 to May 1998 using volunteers. Forty female college freshmen participated in the intervention (college course, n = 21) and control (no course, n = 19) groups. The intervention was a one-semester nutrition science college course. Body weight, nutrient intakes, and knowledge were measured at baseline, the end of the intervention (4 months from baseline), and 1 year later (16 months from baseline). Statistical analysis was conducted using a repeated-measure analysis of variance. Higher Body Mass Index (BMI) students (BMI > 24) in the intervention group (n = 11) reported lower fat (p =.04), protein (p =.03), and carbohydrate (p =.008) intakes compared with the higher BMI students in the control group (n = 6). Dietary changes reported by the higher BMI intervention students were associated with the maintenance of baseline body weight for 1 year in contrast with the higher BMI control students who gained 9.2 6.8 kg (p =.012). The findings suggest that nutrition education emphasizing human physiology and energy metabolism is an effective strategy to prevent weight gain in at-risk college students.

Adolescent↗
PubMedDate not supplied

Effects of estrogen and progesterone on plasma lipoproteins and experimental atherosclerosis in the baboon (Papio sp.).

We determined the effect of estrogen and progesterone on plasma cholesterol and lipoprotein cholesterol concentrations and on arterial lesions in 24 ovariectomized and hysterectomized baboons fed a high-cholesterol/high-saturated-fat diet. These baboons were divided into four groups: untreated control (C); estrogen, 100 micrograms/kg/week injected i.m. (E); progesterone, 3 mg/kg/day (P); and estrogen plus progesterone (E + P). The treatment regimen continued for 18 months. Cholesterol levels in plasma and lipoproteins were measured before hormone treatment and at 3, 10, and 18 months of treatment. Postheparin plasma lipoprotein lipase (LPL) activity was also measured during the treatment. After 18 months of hormone treatment, baboons were necropsied and arterial lesions were measured. Hormone treatment significantly influenced plasma cholesterol (P greater than C greater than [E + P] greater than E) and very low density lipoprotein plus low density lipoprotein (VLDL + LDL) cholesterol (P greater than C greater than [E + P] greater than E), with very little effect on high density lipoprotein (HDL) cholesterol concentration. The E + P group had a significantly higher HDL cholesterol concentration than did the P group. The (VLDL + LDL)/HDL cholesterol ratios in the E and E + P groups were significantly lower than those in the P and C groups. LPL activities were significantly lower in the E group compared with those in the E + P and P groups. Hormone treatment significantly influenced lesions in four (innominate, carotid, iliac, and abdominal aorta) of seven arteries. The P group had the most fatty streaks, and the E + P group had the least.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Deferred effects of preweaning diet on atherosclerosis in adolescent baboons.

We examined the effects of breast and formula feeding during infancy on the serum lipoproteins and on atherosclerosis in young adult baboons. Baboons were breast-fed (n = 13) or formula-fed (n = 32) until weaning at 16 weeks of age and thereafter they were fed a diet containing 1.7 mg cholesterol/kcal and 40% of calories as lard until 5 years of age. At 12 weeks of age, breast-fed baboons had higher serum high density lipoprotein cholesterol concentration (HDL-C, 68 vs. 51 mg/dl), lower serum triglyceride concentration (37 vs. 68 mg/dl), and lower very low density plus low density lipoprotein cholesterol (VLDL + LDL-C) to HDL-C ratio (0.65 vs. 0.98) than formula-fed infants. From weaning to 92 weeks of age, breast-fed baboons had a lower serum triglyceride concentration (23 vs. 38 mg/dl) than formula-fed baboons. After weaning, the VLDL + LDL-C/HDL-C ratio increased from 0.65 to 1.0 in breast-fed baboons, but decreased from 0.98 to 0.72 in formula-fed baboons. From 92 to 246 weeks of age, the VLDL + LDL-C/HDL-C ratio was consistently higher in breast-fed baboons compared to formula-fed baboons. At 5 years of age, baboons breast-fed as infants had a greater percentage of intimal surface area involved with atherosclerosis in the abdominal aorta, the iliac-femoral artery, the aortic arch, the brachial artery, and the carotid artery, than did those formula-fed as infants. The greater prevalence of lesions in breast-fed baboons was explained mainly by the higher VLDL + LDL-C/HDL-C ratio.

Animals↗
PubMedDate not supplied

Comparison of laboratory performance with blind and mail-distributed proficiency testing samples.

Simulated addict urine samples containing drugs were sent to collaborating hospital administrators and officials of methadone centers, who then forwarded the samples to their supporting laboratories as though they were ordinary specimens from patients. The laboratories, which were already participating in the proficiency testing program of the Center for Disease Control, received the identical test samples in the mail as part of a regular Center for Disease Control proficiency testing program. Most of the laboratories performed acceptably with the mail-distributed samples, but many performed poorly when the identical samples were sent to them as if they were specimens from patients. Because of the limitations of proficiency testing involving mail-distribution samples and the impracticality of extensive testing with blind samples on a national level, the Center for Disease Control proposes to compliment its regular proficiency testing program with a monitored, onsite program of performance evaluation.

Centers for Disease Control and Prevention, U.S.↗