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Biomedical subjects

D C Mitchell

Publications and source records attributed to D C Mitchell.

At least 19 recordsLinked to original sources
PubMed1998

Self-selected diets of lactating women often fail to meet dietary recommendations.

OBJECTIVE: To assess longitudinally nutrient intakes of lactating women during the postpartum period. DESIGN: Dietary data from lactating women were collected by means of 2-day food records at 3 and 6 months postpartum. Intake of energy and selected nutrients was tabulated and compared with dietary standards. SUBJECTS: The 52 lactating women enrolled in the study lived in a university community, were apparently healthy, had a body mass index within normal range, were successfully nursing a term infant, and planned to nurse for at least 6 months. STATISTICAL ANALYSES PERFORMED: Paired t tests and Stuart-Maxwell chi(2) analyses. RESULTS: Mean energy intakes were below the Recommended Dietary Allowance. Mean intakes of most nutrients met or exceeded recommended standards except for zinc and vitamins D and E at both 3 and 6 months postpartum. Calcium and folate intakes were also below standards at 6 months. Although mean iron intake exceeded the standard at both measurement times, there was a significant decline from 3 to 6 months. Relative frequencies of mothers meeting various percentages of standards differed significantly from 3 to 6 months for calcium; iron; folate; and vitamins E, D, and B-6. At 6 months, significant increases were noted in the number of women reporting calcium, folate, and vitamin B-6 intakes at less than one half of the recommended amounts. APPLICATIONS/CONCLUSIONS: Guidance for lactating women should stress food sources of nutrients likely to be limited in their diets: calcium; zinc; folate; and vitamins E, D, and B-6.

Adult↗
PubMed1998

Molecular order and dynamics in bilayers consisting of highly polyunsaturated phospholipids.

The time-resolved fluorescence emission and decay of fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) was used to characterize equilibrium and dynamic bilayer structural properties of symmetrically substituted phosphatidylcholines (PCs) with acyl chains containing no, one, four, or six double bonds and mixed-chain phosphatidylcholines with a saturated sn-1 chain and one, four, or six double bonds in the sn-2 chain. Both the Brownian rotational diffusion (BRD) model and the wobble-in-cone model were fit to all differential polarization data, and the descriptions of the data provided by the BRD model were found to be statistically superior. Global analysis of differential polarization data revealed two statistically equivalent solutions. The solution corresponding to a bimodal orientational distribution function, f(theta), was selected based on the effects of temperature on f(theta) and previous measurements on fixed, oriented bilayers. The overall equilibrium acyl chain order in these bilayers was analyzed by comparing the orientational probability distribution for DPH, f(theta) sin theta, with a random orientational distribution. Orientational order decreased and probe dynamics increased in mixed-chain species as the unsaturation of the sn-2 chain was increased. The degree of orientational order dropped dramatically in the dipolyunsaturated species compared with the mixed-chain phosphatidylcholines, which contained a polyunsaturated sn-2 chain. In terms of both orientational order and probe dynamics, the differences between the highly polyunsaturated species and the monounsaturated species were much greater than the differences between the monounsaturated species and a disaturated PC.

Diphenylhexatriene↗
PubMed1998

Effect of cholesterol on molecular order and dynamics in highly polyunsaturated phospholipid bilayers.

The effect of cholesterol on phospholipid acyl chain packing in bilayers consisting of highly unsaturated acyl chains in the liquid crystalline phase was examined for a series of symmetrically and asymmetrically substituted phosphatidylcholines (PCs). The time-resolved fluorescence emission and decay of fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) was used to characterize equilibrium and dynamic structural properties of bilayers containing 30 mol % cholesterol. The bilayers were composed of symmetrically substituted PCs with acyl chains of 14:0, 18:1n9, 20:4n6, or 22:6n3, containing 0, 1, 4, or 6 double bonds, respectively, and mixed-chain PCs with a saturated 16:0 sn-1 chain and 1, 4, or 6 double bonds in the sn-2 chain. DPH excited-state lifetime was fit to a Lorentzian lifetime distribution, the center of which was increased 1-2 ns by 30 mol % cholesterol relative to the cholesterol-free bilayers. Lifetime distributions were dramatically narrowed by the addition of cholesterol in all bilayers except the two consisting of dipolyunsaturated PCs. DPH anisotropy decay was interpreted in terms of the Brownian rotational diffusion model. The effect of cholesterol on both the perpendicular diffusion coefficient D perpendicular and the orientational distribution function f(theta) varied with acyl chain unsaturation. In all bilayers, except the two dipolyunsaturated PCs, 30 mol % cholesterol dramatically slowed DPH rotational motion and restricted DPH orientational freedom. The effect of cholesterol was especially diminished in di-22:6n3 PC, suggesting that this phospholipid may be particularly effective at promoting lateral domains, which are cholesterol-rich and unsaturation-rich, respectively. The results are discussed in terms of a model for lipid packing in membranes containing cholesterol and PCs with highly unsaturated acyl chains.

Cholesterol↗
PubMed1998

Venous allografts prepared from stripped long saphenous vein. Is there a need for antibiotic sterilisation?

AIM: Can useful lengths of vein be retrieved from varicose vein stripping procedures; is it necessary to sterilise this tissue prior to use as vein allografts? METHOD: Stripped long saphenous vein was retrieved at operation. Vein samples were cultured using direct plate inoculation and enrichment culture. Further samples were immersed in two low concentration antibiotic solutions and recultured. Smooth muscle viability was assessed after antibiotic immersion and storage by cryopreservation. RESULTS: High quality vein could be retrieved by vein stripping. Vein segments grew skin commensals on enrichment culture despite negative cultures with standard media plate inoculation (Chi-squared = 53.34 1 d.f. p < 0.001). Low concentration antibiotic solutions sterilised processed vein. Smooth muscle cell viability was reduced by cryopreservation, Mann-Whitney p = 0.008 (control 98% S.E. 0.93 vs. cryopreserved 64% S.E. 6.58), but prior exposure to antibiotics did not compound this effect. CONCLUSION: Useful lengths of vein grafts can be retrieved from varicose vein stripping procedures. Venous segments are frequently contaminated by skin commensals. Enrichment culture is required to detect contamination. Low concentration antibiotics sterilise venous-tissue without affecting smooth muscle cell viability.

Anti-Bacterial Agents↗
PubMed1998

Time and cost for recruiting older adults.

OBJECTIVES: The purpose of this study was to examine the time requirements and costs of recruiting older adults for participation in a medical center-/university-sponsored, home-based nutrition education study. A two-step recruitment strategy consisting of an introductory letter followed by a telephone call was used. DESIGN: A random selection of 1300 individuals aged 60 to 74 years was drawn from a patient database of a large, rural, tertiary care hospital to receive introductory letters and recruitment telephone calls. One week after the mailing, potential subjects were contacted by trained interviewers and asked to participate in a home-based nutrition education study. PARTICIPANTS: Men and women, aged 60 to 74 years, whose names appeared in a rural, tertiary care hospital database. MEASUREMENTS: Recruitment rate, time required for recruitment by telephone, and cost of the combined mailing and telephone recruitment effort. RESULTS: Of the 1300 individuals selected, 1077 (83%) people were contacted by phone and 223 (17%) people were unable to be reached. A total of 2895 calling attempts were required to determine the recruitment status of those identified as potential participants. Of those reached by phone, the recruitment rate was 45%. The total cost (mailing, telephone, and database management) per recruited subject was $8.56. CONCLUSION: This study has helped to establish the costs of recruitment for home-based education interventions using a two-step strategy of an introductory mailing and follow-up telephone interview.

Aged↗
PubMed1997

The effect of changes in dietary fat on the food group and nutrient intake of 4- to 10-year-old children.

OBJECTIVE: To determine how young children changed their overall diet when they changed their fat intake after 3 months of participating in a nutrition education demonstration study designed to lower low-density lipoprotein cholesterol and cardiovascular risk. METHODS: Three 24-hour dietary recalls were collected from 303 4- to 10-year-old children at baseline and 3 months later. At both times, mean number of servings from food groups, grams of fat contributed from food groups, and intake of calories and nutrients were calculated and compared among quartiles of children formed according to change in their percent of calories from total fat after 3 months. RESULTS: Children who reduced their percent of calories from total fat most (ie, by an average of 8.5%) after 3 months consumed fewer servings from meats, eggs, dairy, fats/oils, and breads but tended to increase their number of servings from lower-fat foods within those food groups, particularly from dairy foods. These children also increased their mean intake of fruits, vegetables, and desserts, and maintained average intakes of all nutrients (except vitamin D) in excess of two thirds of the respective recommended dietary allowance. CONCLUSIONS: Young children who reduced their percent of calories from total fat in accordance with the current National Cholesterol Education Program recommendations accomplished this by reducing their overall intake of higher-fat foods, replacing higher-fat foods with lower-fat foods within several food groups, particularly within the dairy group (eg, drinking skim milk instead of whole milk) and by consuming more servings of fruits, vegetables, and very-low-fat desserts. These behaviors did not compromise their mean calorie or nutrient intakes, showing that it is possible for young children to lower their fat intake safely to reduce their risk of future heart disease.

Child↗
PubMed1996

Primary alcohols modulate the activation of the G protein-coupled receptor rhodopsin by a lipid-mediated mechanism.

The visual pigment rhodopsin is a prototypical member of the G protein-coupled receptor superfamily. In this study, we have investigated the effect of a series of n-alcohols on the formation of metarhodopsin II (MII), the photoactivated conformation of rhodopsin, which binds and activates transducin. When rhodopsin was photolyzed in the presence of several n-alcohols, increased MII formation was observed in the order ethanol > butanol > hexanol, whereas longer chain n-alcohols inhibited MII formation with decanol > octanol. The magnitude of the stimulatory effects was greater in a more highly unsaturated phospholipid. Alcohols, which enhanced MII formation also increased phospholipid acyl chain packing free volume, while those that decreased this bilayer property inhibited MII formation. An apparent discontinuity in the effect of these alcohols results when their potency is calculated in terms of the total aqueous alcohol concentration. In sharp contrast, a continuous variation in their behavior is observed, when their potency is calculated in terms of the amount of alcohol partitioned in the membrane. Our findings strongly support a lipid-mediated mechanism of action for alcohols on rhodopsin and, by analogy, for other G protein-coupled receptors.

Alcohols↗
PubMed1996

A role for phospholipid polyunsaturation in modulating membrane protein function.

Visual transduction is one of the best characterized G protein--coupled signalling systems. In addition, about 50% of the disk membrane phospholipid acyl chains are 22:6n-3, making this system ideal for determining the role of polyunsaturation in modulating membrane-signalling systems. The extent of formation of metarhodopsin II (MII), the G protein--activating photointermediate of rhodopsin, was studied in phospholipid vesicles composed of a variety of phosphatidylcholines, differing in their acyl chain composition at the sn-2 position. The amount of MII formed increased progressively with the level of acyl chain unsaturation at the sn-2 position. The effect of added cholesterol was to reduce the amount of MII formed. The acyl chain packing free volume of the rhodopsin containing lipid vesicles was characterized by a fractional volume parameter fv derived from measurements of the time-resolved fluorescence anisotropy decay of the hydrophobic membrane probe 1,6-diphenyl-1,3,5-hexatriene. The relationship among sn-2 acyl chain unsaturation, cholesterol content, and MII formation is explained on the basis of variation in fv with bilayer lipid composition and a novel model for the packing of phospholipids containing polyenoic acyl chains, such as 22:6n-3.

Fats, Unsaturated↗
PubMed1996

Amphotericin B responsive Scedosporium apiospermum infection in a patient with acute myeloid leukaemia.

A 71 year old man with newly diagnosed acute myelomonocytic leukaemia developed a soft tissue infection of his foot during his first course of chemotherapy. Scedosporium apiospermum was isolated from the lesion, which resolved rapidly on treatment with intravenous amphotericin B despite being resistant in vitro to this agent. This observation suggests that sensitivity testing of S apiospermum should be interpreted with caution and that clinical response may be a better indicator of outcome.

Aged↗
PubMed1996

The dietary intake of children with IDDM.

OBJECTIVE: To assess the dietary intake of children with IDDM and to determine whether the intake meets the current nutritional recommendations for children with IDDM. RESEARCH DESIGN AND METHODS: A total of 66 children with IDDM who were < 10 years of age were recruited from two suburban Pennsylvania hospitals. To collect dietary intake data, subjects were asked, via telephone interview, to complete three random-day 24-h dietary recalls. Data were analyzed for the content of nutrients and other food components by a computerized database program. Intakes were expressed as a 3-day average intake for each subject. RESULTS: Overall mean intake of protein and cholesterol approximated the current recommendations. The mean intake of saturated fat exceeded recommendations, while fiber intake was less than the recommended level. Many of the children consumed levels of saturated fat well above recommendations. Energy, vitamin, and mineral intakes were adequate for the overall sample. However, from 10 to 40% of the sample had an inadequate intake of vitamin D, vitamin E, and zinc. The percentage of those with inadequate intakes of these nutrients decreased with age. CONCLUSIONS: These data suggest that, on average, among this sample of children with IDDM aged < 10 years, adherence to the current nutritional recommendations for children with IDDM was adequate, but some individual children had intakes that were not consistent with the recommendations for optimal management of IDDM.

Child↗
PubMed1994

Effect of ethanol on metarhodopsin II formation is potentiated by phospholipid polyunsaturation.

The role of phospholipids in modulating the effect of ethanol on membrane receptor activation was investigated by studying the extent of metarhodopsin II (MII) formation in vesicles formed POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and PDPC (1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine) and in native rod outer segment disk membranes as a function of ethanol concentration. The equilibrium concentration of MII, the G protein-activating form of photoactivated rhodopsin, was found to increase as a function of ethanol concentration in all three bilayers. Phospholipid composition had a marked effect on ethanol potency, with the presence of polyunsaturated phospholipid acyl chains increasing ethanol potency by 40%. The effects of ethanol on lipid acyl chain packing in POPC and PDPC were investigated using frequency domain anisotropy decay measurements of the fluorescent membrane probe 1,6-diphenyl-1,3,5-hexatriene. Enhanced formation of MII due to the presence of ethanol was correlated with the effects of ethanol on acyl chain packing properties. These findings support a phospholipid-mediated mechanism for the action of ethanol in modulating integral membrane receptor conformation.

Cell Membrane↗
PubMed1994

Myelomeningocele at the sacral level. Long-term outcomes in adults.

We reviewed the long-term outcome of thirty-six patients who had a myelomeningocele at the sacral level and whose average age was twenty-nine years (range, nineteen to fifty-one years). The patients were followed at our institution for an average of ten years (range, one to thirty-three years); however, the medical records from birth on were available for all of the patients. Instead of the expected outcome that function had been maintained in this group of patients, we found a decline in the ability to walk of eleven of the thirty-five patients who had been community ambulators initially. At the time of the most recent follow-up examination, five had become household ambulators, two were non-functional ambulators, and four were non-ambulators. The one patient who initially had been a household ambulator was a non-ambulator at the time of the most recent follow-up examination. A decrease in plantar flexion was found in fourteen patients and a decrease in plantar sensation, in fifteen. Breakdown of the skin and soft-tissue infections on the plantar surface of the metatarsal heads and of the heel were seen in twenty-seven and twenty-three patients, respectively, and were related to the absence of plantar sensation. Fifteen patients had osteomyelitis involving the lower extremity. Eleven patients had had a total of fourteen amputations: five involved one toe or more, four involved one ray or more, two were Syme amputations, and three were below-the-knee amputations. By the most recent follow-up examination, thirty-three patients had had a total of 371 orthopaedic procedures. The procedures included tendinous procedures; osteotomies; soft-tissue releases, transfers, and débridements; amputations; and arthrodeses of the lower extremities or spine.

Adult↗
PubMed1993

Low-dose aspirin fails to inhibit increased platelet reactivity in patients with peripheral vascular disease.

A study was performed to evaluate the effect of low-dose aspirin (75 mg/day) on platelet reactivity in patients with peripheral vascular disease. Platelet function was measured in 31 patients with advanced peripheral vascular disease requiring surgery. Shear-induced haemostasis and collagen-induced thrombus formation were used as indicators of platelet reactivity. They were measured in non-anticoagulated fresh whole blood samples ex vivo using a haemostatometer. Results were compared with those from 30 age- and sex-matched controls. Shear-induced haemostasis and collagen-induced thrombus formation were also measured in 18 of the 31 patients before the start of aspirin administration (before operation) and 1 week after surgery. Patients with advanced peripheral vascular disease were found to have increased platelet reactivity with a mean(s.e.m.) shear-induced haemostasis index of 1977(180) mmHg s compared with a control value of 3161(234) mmHg s (P < 0.001) and a mean(s.e.m.) collagen-induced thrombus formation index of 3980(460) mmHg s compared with a control value of 5350(420) mmHg s (P = 0.02). Perioperative low-dose aspirin failed to inhibit platelet function in patients with peripheral vascular disease.

Aged↗
PubMed1993

Beta carotene uptake into atherosclerotic plaque: enhanced staining and preferential ablation with the pulsed dye laser.

The yellow color of atherosclerotic plaque is due to the presence of carotenoids, which absorb light between 430-530 nm and account for the preferential ablation of plaque by the pulsed dye laser operating at 480 nm. This study was designed to examine tissue uptake of beta-carotene and the effect of uptake on arterial plaque ablation. Forty-two atherosclerotic NZW rabbits were given intravenous beta-carotene at a dose of 40 mg/kg, twice weekly and killed between 1 hour and 28 days after the initial injection. beta-carotene was not detected in control specimens but was significantly greater in plaque than in normal wall at all time points following beta-carotene injection (P < 0.04 Mann Whitney U test). The ablation threshold was significantly lower in beta-carotene treated plaque than in untreated plaque or normal arterial wall (P < 0.01, Fisher's exact test). In this model beta-carotene is preferentially taken up into arterial plaque, resulting in increased absorption of laser radiation at 480 nm and enhanced tissue ablation.

Adipose Tissue↗
PubMed1993

The role of fatty acid saturation on plasma lipids, lipoproteins, and apolipoproteins: I. Effects of whole food diets high in cocoa butter, olive oil, soybean oil, dairy butter, and milk chocolate on the plasma lipids of young men.

The present studies were conducted to evaluate the cholesterolemic effects of whole-food diets high in stearic acid. In study no. 1, normocholesterolemic young men were fed diets high in stearic acid provided by cocoa butter (CB); oleic acid provided by olive oil (OO); linoleic acid provided by soybean oil (SO); and myristic acid (and lauric acid) provided by dairy butter (B). In study no. 2, different subjects with similar baseline characteristics were fed diets high in stearic acid provided by milk chocolate (C), CB, CB+B (4:1, MIX), and myristic (and lauric) acid provided by B. Both studies used a randomized, crossover, double-blind experimental design, and experimental subjects (n = 18 for study no. 1 and n = 15 for study no. 2) in each study consumed every diet for 26 days with a 1-month wash-out period between each experimental period. The diets provided 37% of calories from fat, of which 81% was provided by the test fat. Ten ounces (280 g) C was provided daily by the C diet. In study no. 1, the B diet was hypercholesterolemic, whereas the SO diet was hypocholesterolemic, compared with the other diets. The OO and SO diets were hypocholesterolemic compared with the CB diet. Low-density lipoprotein (LDL) cholesterol levels, in general, paralleled the changes in plasma total cholesterol levels. SO significantly decreased apolipoprotein (apo) B levels compared with the other diets. Plasma very-low density lipoprotein (VLDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and apo A-I levels were unaffected by the experimental diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Time and cost analysis of a computer-assisted telephone interview system to collect dietary recalls.

This study, conducted in 1991, examined the time requirements and costs of obtaining 24-hour dietary recalls via telephone interviews using the University of Minnesota's microcomputer Nutrient Data System to conduct the interviews and compute the nutrient composition of the diets. The subjects were 156 hypercholesterolemic children (aged 4-10 years) and 102 hypercholesterolemic adults (aged 21-65 years), who were participating in ongoing cholesterol education programs. A total of 391 recalls were completed with the children and 278 with the adults. For each completed interview, 3.5 and 2.8 attempts were required, respectively. Evenings were the most productive time for completing interviews. All tasks associated with completing the interviews (attempts to call, interviews per se, and postinterview procedures) required an average of 39.7 and 35.5 minutes per completed interview with the children and adults, respectively. About half of these total times were actually devoted to conducting the interview. The costs per completed interview were $9.22 for the children versus $6.99 for the adults. This difference reflects the greater number of attempts required to reach the children, the longer duration of their interviews, and the higher intrastate toll rates for calls to them as compared with the interstate rates for calls to the adults.

Adult↗