Leonard Amby Maynard - November 5, 1887-June 22, 1972.
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History, 20th Century↗
Biomedical subjects
D A Roe
Publications and source records attributed to D A Roe.
Pharmacokinetics of pentamidine in Sprague-Dawley rats in late pregnancy.
To our knowledge, placental transfer of pentamidine has not been previously studied in vivo. In the present study, the pharmacokinetics of pentamidine were analyzed in late gestation (18 days) among Sprague-Dawley rats. Pentamidine's kinetics were assessed in the following maternal compartments over a 12-hour period in 16 timed-pregnant rats: serum, liver, and kidney. Placentas were also analyzed for pentamidine concentration as were fetal brain, liver, and kidney tissues. Significant placental transfer of the drug was found, with pentamidine reaching all fetal compartments studied. Notably, by the twelfth hour fetal brain tissue achieved pentamidine concentrations that were not significantly different from those of maternal serum at the second hour of the experiment. This is an interesting observation because adult mouse and rat brains were found to be unexposed to the drug.
Animals↗
Quantitative relationship between oral nitrate-reducing activity and the endogenous formation of N-nitrosoamino acids in humans.
Salivary nitrate and nitrate concentrations, in vitro kinetics of nitrate reduction in saliva, and numbers of salivary nitrate-reducing micro-organisms were each compared with N-nitrosoamino acid excretion in 16 humans eating controlled diets. N-Nitrosoproline (NPRO) and N-nitrosothiazolidine-4-carboxylic acid (NTCA) excretion were measured after intake of nitrate (5.24 mmol) and L-proline (4.35 mmol) before and after treatment with an oral antiseptic (Peridex, 0.12% chlorhexidine gluconate). Peridex treatment resulted in a 94% reduction in the numbers of salivary nitrate-reducing bacteria, a decline from 17 to 4% in the amount of salivary nitrate that was reduced to nitrite in vivo, and an 85% reduction in the rate of in vitro nitrate reduction by saliva. Concurrently, there were 62 and 74% inhibitions of endogenous NPRO and NTCA formation, respectively. Correlations of the numbers of nitrate reductase micro-organisms, in vivo oral nitrate reduction and salivary nitrite concentrations, with individual NPRO excretion, indicated that individuals with higher oral nitrate-reducing capacities formed more N-nitrosoamino acid endogenously. These data suggest that individual differences in oral nitrate reduction are a significant factor in gastric nitrosation and account for a large proportion of the interindividual variability in nitrosoamino acid excretion.
Administration, Oral↗
Riboflavin deficiency: mucocutaneous signs of acute and chronic deficiency.
Mucocutaneous lesions are present in both acute and chronic riboflavin deficiency. The distribution of the lesions varies with the age and gender of the patient. Lesions of acute riboflavin deficiency are similar to those observed in protein-energy malnutrition of the kwashiorkor type. In chronic riboflavin deficiency the cutaneous lesions resemble monilial intertrigo and the mucous membrane lesions include a characteristic glossitis. Prompt resolution of lesions after therapeutic doses of the vitamin are given confirms the diagnosis. Biochemical changes caused by riboflavin deficiency, which explain the dermatoses and mucous membrane lesions, have not as yet been determined. Lack of information in this area is explained by the difficulty of separating cutaneous changes caused by the deficiency from those caused by trauma or other proximate etiologic agents.
Acute Disease↗
Assessment of risk factors for carotenodermia and cutaneous signs of hypervitaminosis A in college-aged populations.
Carotenodermia occurs in individuals in a college-aged population who exhibit signs of anorexia and/or bulimia nervosa. It is caused by consuming large amounts of raw carrots. In the same population, athletes are at risk for hypervitaminosis A because of injudicious self-administration of high-potency vitamin preparations.
Adult↗
Metabolism of cocaine by human placentas: implications for fetal exposure.
To assess placental metabolism of cocaine, placentas were obtained at the time of delivery and the microsomes were extracted by ultracentrifugation within 2 hours. Placental microsomes were cultured with cocaine at physiologic plasma concentrations similar to those of cocaine users (0.75 micrograms/ml). Two control groups were established. In the first group an anticholinesterase was added to the culture to suppress enzyme activity, and in the second cocaine was cultured alone without placental microsomes to obtain baseline spontaneous conversion of the drug. The results indicate that cocaine is biotransformed by the human placenta, presumably by cholinesterase activity. This suggests that the placenta may provide a moderate degree of protection from cocaine-induced morbidity, such as abruptio placentae and fetal growth retardation, by converting cocaine into less active metabolites. These results also have pharmacogenetic implications because cholinesterase activity varies among individuals. Hence placentas that cannot transform the drug may place the conceptus at greater risk of developmental abnormalities.
Biotransformation↗
In-home nutritional assessment of inner-city elderly.
Aims of this research have been to obtain aggregate data on reported problems in food access that are experienced by homebound, inner-city elderly; to disaggregate the data to show which subgroups of elderly are at highest risk for these types of food insecurity; and to assess whether these elderly differ socioeconomically, medically, or nutritionally from homebound elderly who report that they eat regularly. Instruments were designed to measure population-based food insecurity and to ask respondents to provide information about their socioeconomic status and disabilities as well as the extent to which they have formal or informal assistance in obtaining food. The need to collect this information has been linked to a state-wide effort to target city nutritionally needy elderly for home-delivered meals. Findings have been that food insecurity in the inner-city homebound is linked to loss of mobility as well as to poverty and lack of in-home food assistance. Minority elderly whose questionnaire responses indicate food insecurity include diabetics whose disease control is adversely affected by irregular eating. When methods of home assessment have been used to examine the extent to which a home-delivered meals program meets the nutritional needs of recipients, it has been possible to demonstrate that meals recipients show less food insecurity than a comparison group on waiting lists to receive meals.
Aged↗
Geriatric nutrition.
The aging process alters body composition so that nutritional status changes as we get older. The aging process shows interindividual variability in its rate of development. Determinants of the rates of aging of systems and tissues are largely genetic. Premature aging of cells and tissues is due to genetic factors and to long-term exposure to physical or chemical environments that cause irreversible tissue damage. Whereas maximal lifespan is fixed for us all, individuals vary in life expectancy both because of variability in the risk of genetic disease which shortens life and because of variable capability for avoidance of those factors in our environment which cause early aging. Early aging as well as geriatric disease foreshorten life, but both can be prevented to some extent by diet or by diet and exercise. Diseases that can be nutritionally prevented, giving us a greater chance of achieving our genetically determined lifespans, include nutritional deficiency states and chronic diet-related diseases such as non-insulin-dependent diabetes, hypertension, coronary artery disease, and cancer. Disabilities resulting from these diseases and from degenerative arthritis are also subject to modulation by diet. The nutritional requirements of the elderly are mostly similar to those of younger people. Elderly usually need fewer calories and similar nutrient intakes compared with those of younger people. Elderly with higher needs for specific nutrients include homebound or institutionalized people who lack sunlight exposure and therefore require more vitamin D. Nutritional requirements to promote longer life expectancy and freedom from disabilities that result from chronic disease include restriction of food energy and fat. Nutritional assessment of the elderly is aimed at identifying not only the presence of deficiency states but also states of nutrient excess and chronic diet-related diseases. There are certain problems in carrying out nutritional assessment in the elderly, but techniques are now available which make valid assessment possible even in the oldest old. Those who live longest have less genetic risk of premature aging, but as a result of native intelligence, education, coping skills, and higher socioeconomic status, they also have a greater likelihood of eating a diet that best meets their long-term nutritional needs. Those most at risk for developing malnutrition as they get older are those who lack food access because of poverty, because of disability resulting from chronic geriatric disease, or because of a combination of these factors. Malnutrition is found in elderly in our society who live in their own homes if they are indigent, isolated, and homebound because of disability.(ABSTRACT TRUNCATED AT 400 WORDS)
Aged↗
Accuracy of heart-rate monitoring and activity diaries for estimating energy expenditure.
The accuracy of heart-rate monitoring and activity diaries for measuring energy expenditure in free-living individuals was studied in 12 women. Estimates of energy expenditure were calculated from heart-rate monitoring by use of four different prediction equations to describe the relationship between heart rate and energy expenditure. Estimates of energy expenditure from activity diaries were calculated using both individually measured and published values for the energy cost of activities. Energy intake adjusted for changes in body-energy stores was used as a reference. Heart-rate monitoring overestimated group energy expenditure from 2 to 9% and the errors in estimating individual energy expenditure ranged from -53 to 67%. Activity diaries underestimated group energy expenditure by 2-6% and the errors in estimating individual energy expenditure ranged from -39 to 56%. Heart-rate monitoring and activity diaries may prove useful for estimating the energy expenditure of groups but not individuals.
Activities of Daily Living↗
Body composition and energy intake: do overweight women overeat and underreport?
The relationship between energy consumption and body composition was evaluated in 63 women by use of energy-intake values that were precisely measured in a metabolic unit and corrected for deviations from energy balance. Energy requirement for the maintenance of body weight was not significantly correlated with adiposity expressed as percent body fat. However, energy requirement was positively associated with lean mass (p less than 0.0001) whereas fat mass added no predictive value to the same multivariate regression equation. Self-reported energy intake (before the experiments) was not correlated with lean mass and was underestimated by lean subjects at least as much as by obese subjects. Discrepant findings in the literature concerning relationships between obesity and energy intake may be explained by reporting error and by the relative lean mass of obese vs nonobese women but not by systematic underreporting unique to obese subjects.
Adult↗
The menstrual cycle's effect on the reliability of bioimpedance measurements for assessing body composition.
We examined the reliability of resistance (R) and body composition estimates measured by bioelectrical impedance analysis (BIA) in 25 women during their menstrual cycle. Weight and bioimpedance were measured daily for one cycle and sodium intake was assessed. The precision of bioimpedance measures was examined and subjects' average resistance, weight, Na intake, and calculated body composition during the four phases of menses were compared by using paired t tests. Significant differences were observed between phases 1 and 2 for R (p less than 0.001), weight (p less than 0.05), and fat-free mass (p less than 0.05) and differences were observed between phases 2 and 4 for R (p less than 0.05) and weight (p less than 0.05); no significant differences were observed for percent body fat. Changes in body weight (p less than 0.001) associated with Na intake explained a significant proportion of error in resistance measures. These data suggest the reliability of the BIA body composition approach during menses; small weight changes related to hydration status may, however, be a confounding influence.
Adipose Tissue↗
Ultraviolet light-induced reductions in plasma carotenoid levels.
The effects of ultraviolet (UV) irradiation on plasma levels of carotenoids and vitamin A in human subjects were investigated in two crossover trials. UV exposures were given on 11 r 12 days of a 2-wk period. The 12 female and 12 male subjects received mean cumulative UV-A (320-400 nm) doses of 17.8 +/- 1.9 J/cm2 and 21.0 +/- 3.3 J/cm2 to the anterior and posterior sides of the body, respectively. UV-B (280-320 nm) doses were equivalent to 10% of UV-A doses given. Significant reductions in plasma total carotenoid levels were observed in both female (p less than 0.004) and male (p less than 0.05) subjects after repeated irradiation. There was no significant effect on plasma vitamin A levels. It was concluded that UV treatment can reduce plasma carotenoid levels in vivo.
Adult↗
Andre Gerard van Veen (1903-1986).
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History, 20th Century↗
Effect of fiber supplements on the apparent absorption of pharmacological doses of riboflavin.
The effect of dietary fiber from wheat bran and psyllium gum on the apparent absorption of riboflavin was studied in 12 healthy women. The test fiber was consumed in crackers that contained approximately 7.5 gm fiber from psyllium gum, wheat bran, or a combination of the two sources. Each subject was given a riboflavin load test after consuming one of the three different fiber supplements or a control supplement that contained 1.3 gm fiber. Fractional urine collections were made for 24 hours, and riboflavin was measured by fluorometric techniques. The psyllium gum and combination supplements reduced the 24-hour apparent absorption of riboflavin from 31.8% to 25.4% and 26.1%, respectively (p less than .01). No effect of the wheat bran supplement on riboflavin was detected.
Absorption↗
Drug and nutrient interactions in the elderly diabetic.
Elderly diabetics take more drugs than other groups of elderly patients. Their multiple drug use is largely explained by the drugs that they take for complications of their primary disease; these include cardiovascular drugs for macrovascular disease and antibiotics for secondary infections. They also take more drugs for control of other conditions that are etiologically associated with the development and progression of their diabetes, including antihypertensive agents, antilipemic agents and steroids, and nonsteroidal antiinflammatory drugs (NSAIDs), which are taken for relief of joint pain that is intensified by arthritic joints bearing excess weight. Drugs taken by elderly diabetics that contribute to the high prevalence of drug-nutrient interactions include those taken as antidiabetic agents, including both insulin and sulfonylureas as well as calcium channel blockers; they also include thiazides, loop diuretics, sulfa drugs, cephalosporin antibiotics, tetracyclines, antifungal agents, cholestyramine and colestipol, niacin, prednisone and other corticosteroids, and NSAIDs. These drugs and drug combinations contribute to the risk of hyperglycemia, which can cause nonketotic hyperglycemia in the elderly; to the risk of hypoglycemia, which in the elderly carries the risk of inducing pseudo-stroke; to the risk of drug-induced nutritional deficiencies from antilipemics and cephalosporins, which can induce vitamin K deficiency; to the risk of acute incompatibility reactions, including flush reactions from chlorpropamide, niacin, and calcium channel blockers; and to the risk of edema, anemia, and hyperkalemia from NSAIDs.(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
Drug and nutrient interactions in elderly cardiac patients.
In the elderly, drug treatment is used for the prevention and control of cardiovascular disease. Prevention of cardiovascular disease includes management of hypercholesterolemia to reduce risk of myocardial infarction, treatment of acute myocardial infarction to reduce the risk of recurrence, and treatment of hypertension to reduce the risk of hypertensive heart disease and stroke. Management of chronic cardiovascular disease with permanent disability is the major therapeutic goal. The most commonly treated disorders of the heart and peripheral vascular system include congestive heart failure, arrhythmias, angina, and thromboses. Reduction of plasma lipid levels may be undertaken by drug therapy as a means of preventing myocardial infarction.
Aged↗
Effect of psyllium gum and wheat bran on spontaneous energy intake.
Energy intake, fecal energy output, and gastrointestinal symptoms were measured in 12 females who consumed either approximately 23 g/d supplementary fiber or a 4 g/d fiber control. Fiber supplements were crackers containing psyllium gum, wheat bran, or a combination of the two fiber sources. After 1 wk on the control cracker, subjects consumed the three high-fiber crackers and the control cracker for 2-wk periods in a balanced design. Gum and combination supplements gave increased bloating and flatulence. Increase in abdominal pain was reported with gum supplement. Mean daily fecal energy was 96 kcal/d with control crackers and was increased by 63 kcal with high-fiber crackers. Gum and combination supplements significantly decreased intake of digestible energy by 153 and 115 kcal/d, respectively. This suppression was not dependent upon fiber intolerance. Wheat bran supplement had no effect on energy intake.
Adult↗
Dietary fat and the regulation of energy intake in human subjects.
The role of dietary fat in the regulation of energy intake was assessed by manipulating a conventional diet and measuring spontaneous food consumption. Twenty-four women each consumed a sequence of three 2-wk dietary treatments in which 15-20%, 30-35%, or 45-50% of the energy was derived from fat. These diets consisted of foods that were similar in appearance and palatability but differed in the amount of high-fat ingredients used. Relative to their energy consumption on the medium-fat diet, the subjects spontaneously consumed an 11.3% deficit on the low-fat diet and a 15.4% surfeit on the high-fat diet (p less than 0.0001), resulting in significant changes in body weight (p less than 0.001). A small amount of caloric compensation did occur (p less than 0.02), which was greatest in the leanest subjects (p less than 0.03). These results suggest that habitual, unrestricted consumption of low-fat diets may be an effective approach to weight control.
Adult↗