Practice compared--payment systems.
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Humans↗
Biomedical subjects
O Frank
Publications and source records attributed to O Frank.
Antioxidant survey to assess antagonism to redox stress using a prokaryotic and an eukaryotic system.
Using a prokaryote (Escherichia coli) and a metazoa-resembling eukaryote (Ochromonas danica), we surveyed antioxidants which might overcome redox stress imposed by menadione sodium bisulphite (MD) and buthionine sulphoximine (BSO). BSO oxidant stress was evident only in O. danica; MD oxidant stress was evident in both organisms. Glutathione, its precursors, e.g. cysteine, homocysteine, and 2-oxo-4-thiazolidine carboxylic acid, and red blood cells, emerged as prime antioxidants for relieving BSO and MD oxidant stress. BSO and MD oxidant activity and antioxidant-annulling effect in O. danica were judged comparable to those found in animal cells whereas the results E. coli were not entirely equivalent. The O. danica system emerged as a practical, rapid, and useful system for pinpointing oxidant stressors and antioxidants, and shows promise for studies with mammalian systems.
Antioxidants↗
Holotranscobalamins in B12 and non B12 requiring prokaryotes and eukaryotes.
Transcobalamins, vitamin B12 binding proteins, deliver B12 to cell surface receptors which then permit B12 to cross cell membranes for metabolic use. There is little documentation concerning B12 binding proteins in bacteria and protists. We found that prokaryotes and eukaryotes requiring B12, as well as those protists synthesizing B12, also produce several transcobalamins for functionally transporting B12 similar to humans.
Animals↗
Human plasma patterns during 14 days ingestion of vitamin E, beta-carotene, ascorbic acid, and their various combinations.
OBJECTIVE: We wanted to learn about plasma patterns of ascorbic acid (AA), beta carotene (BC), and vitamin E (vit E) when each or their various combinations were fed to humans. Conceivably, the combined absorption of these antioxidants could synergize maximum plasma redox potential. METHODS: Vit E (800 mg/day), BC (30 mg/day), and AA (1000 mg/day) were fed individually or in various combinations with each other to 91 volunteers divided into different feeding groups for 14 days. Plasma vit E, carotenes, and AA patterns were analyzed by standardized methods; values were compared with each group's baseline value. RESULTS: AA feeding did not significantly increase already saturated plasma AA concentrations above baseline. Intake of BC did not influence vitamin A (vit A) levels. Feeding of only vit E or only BC, with or without AA addition, or a combination of BC and vit E significantly increased plasma vit E and carotene levels after 2 days. A statistically (ANOVA) significant increase in plasma vit E above baseline was noted when vit E was ingested combined with AA or BC; this increase in plasma vit E was not significant when AA, BC and vit E were taken in combination. CONCLUSION: Our results show that BC or AA ingestion in combination with vit E significantly increases circulating vit E above that seen when vit E is individually ingested. Vit E in combination with BC or AA seems a practical means or increasing the circulating antioxidant potential afforded by vit E. Reasons why such synergism does not exist when an AA, BC, vit E combination is ingested is not yet obvious.
Adult↗
Eigenvalue density oscillations in separable microwave resonators.
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Journal Article↗
A guide to computer-generated prescriptions.
The use of computer systems to produce prescriptions offers many benefits at a reasonable cost. This article summarises the benefits and costs and the steps recommended for general practitioners who wish to start using a computer to generate their prescriptions.
Australia↗
The end of fertility: age, fecundity and fecundability in women.
Onset of capacity for childbearing in women is dated biologically by menarche, although actual onset may be delayed. The end of childbearing is less understood but recent demographic and biological research on fertility at older ages in clarifying the end of fertility. The demographic view of declining fertility with age is based on age-specific fertility in natural fertility populations, artificial insemination and pregnancy rates by age and World Fertility Survey data. New data from the Demographic and Health Surveys on exposure to the risk of pregnancy shows that whereas older women biologically need longer exposure to pregnancy, exposure declines on behavioural grounds such as duration of marriage. Actual fecundity is obscured by factors of fecundability. Recent research on medically assisted conception is adding to the understanding of declining fecundity with age, especially the relative contributions of endometrial and ovarian ageing. This paper reviews the available information on declining fertility with age and discusses the implications of the extension of fertility through new medical technologies.
Adult↗
Biocidal action of chlorhexidine is annulled by nicotinic acid.
An analytical system comprising a bacterium and a protozoan was used to pinpoint the metabolic lesion whereby chlorhexidine (CLX) produced cell death. Nicotinic acid but not nicotinamide annulled the biocidal action of CLX. The results suggest that CLX may not permit bioconversion of nicotinamide to nicotinic acid to annul the growth inhibition induced by CLX.
Animals↗
Electrophysiological evidence of Ranvier node clustering in human sensory nerve fascicles.
Thin concentric needle electrodes were used to explore intact median nerve fascicles in human subjects. In particular, the presence of single units, probably recorded from nodes of Ranvier, was studied in different parts of a fascicle. Single-unit activity in myelinated fibers was rarely found at numerous sites. In many other intrafascicular areas, a substantial number of single units could be discriminated in the same or nearby recording sites with the same technique. To account for the neurophysiological results, stochastic models and statistical tests were developed to test various hypotheses concerning intrafascicular nerve fiber arrangements. The acquired data suggested both an intrafascicular modality grouping of nerve fibers and a simultaneous clustering of the Ranvier nodes of these fibers within very restricted areas of a fascicle. It was further concluded that the yield when searching for units in different types of nerve preparations may depend upon the ultrastructure of the explored nerve segments.
Adult↗
Vitamin activities in human portal, hepatic and femoral blood after vitamin ingestion.
The dynamics of intestinal absorption, blood concentration and distribution of thiamin, biotin, nicotinate, riboflavin, pantothenate, various folates (folic acid, folinic acid, pteroyltriglutamate), vitamins A, E, C, B12, and B6 were monitored in 12 patients by multiple simultaneous sampling of blood obtained by combined catheterization of portal vein, hepatic vein, and femoral artery after vitamin ingestion. All water-soluble vitamins proved elevated after vitamin ingestion principally in portal blood within 10 minutes as compared with hepatic and femoral blood. Elevated vitamin levels in portal blood--compared to hepatic and femoral blood--remained high even after 120 min. indicating that absorption from the gut was still progressing. In contrast, ingestion of the fat-soluble vitamins A and E evoked no elevated vitamin activity in portal blood. Within 10 min. after vitamin ingestion, all folates were converted into reduced and methylated 5-methyltetrahydrofolate (5-CH3THF) on passage through the gut. At this time, portal blood elevation of 5-CH3THF persisted before its elevation in hepatic or femoral blood. Presumably, the elevation was not due to the flushing of stored 5-CH5THF from tissues but rather of folate conversion to 5-CH3THF upon gut passage. The significance of these findings is discussed.
Administration, Oral↗
Absorption and excretion of L-carnitine during single or multiple dosings in humans.
Changes of short-chain (free) and long-chain (acyl) carnitine activity (CA) in plasma, whole blood, red blood cells (rbc) and urine were induced (a) by ingestion of L-carnitine as a single dose of 500 mg, or 2500 mg, or (b) by ingestion of a daily dose of 2500 mg for 10 days. A single 500-mg dose induced insignificant increases of CA in blood constituents. However elevated free CA was noted in urine. Single or daily high doses--e.g. 2500 mg of carnitine--significantly increased free and acyl-CA in plasma, whole blood and urine, but these increases were low. Variations in dosage or frequency of carnitine intake led to no changes in rbc CA; presumably CA in plasma diffused only slowly into rbc. The apparent low absorption of carnitine suggests that oral therapy may not effect rapid repletion of body stores of CA.
Adult↗
Tissue concentrations of water-soluble vitamins in normal and diabetic rats.
Changes in circulating and tissue concentrations of several vitamins have been reported in diabetic animals and human subjects. In this study, the effect of short-term (2 weeks) streptozotocin diabetes on folate, B6, B12, thiamin, nicotinate, pantothenate, riboflavin and biotin in liver, kidney, pancreas, heart, brain and skeletal muscle of rats was investigated. The tissue distribution of vitamins varied widely in normal rats. Diabetes significantly lowered folate in kidney, heart, brain, and muscle; B6 in brain; B12 in heart; thiamin in liver and heart; nicotinate in liver, kidney, heart and brain; pantothenate in all tissues; riboflavin in liver, kidney, heart, and muscle. These results indicate that experimental diabetes causes a depression of several water-soluble vitamins in various tissues of rats.
Animals↗
Effect of cyclosporine treatment on carnitine and myo-inositol in diabetic rats.
1. The effect of long-term (20 wk) treatment of cyclosporine A (CyA) was studied in urine, blood, liver, kidney and pancreatic concentrations of acid-soluble carnitine and free myo-inositol in streptozotocin diabetic rats. 2. Diabetic rats excreted significantly higher concentrations of carnitine and myo-inositol; CyA prevented the urinary loss of carnitine but not myo-inositol. 3. Blood carnitine levels were not different between normal and diabetic rats, however, CyA significantly decreased these levels. Conversely, blood myo-inositol concentrations were higher in diabetic than in normal rats; CyA prevented this increase. 4. Hepatic concentrations of both carnitine and myo-inositol were increased in diabetic rats; CyA treatment caused even further increase. 5. Pancreas from diabetic rats contained less carnitine and myo-inositol compared to normal pancreas. CyA treatment did not affect pancreatic carnitine, but it normalized myo-inositol in diabetic rats. 6. The kidney carnitine or myo-inositol levels were not influenced either by diabetes or by CyA treatment. 7. These results suggest that CyA treatment causes changes in carnitine and myo-inositol concentrations in biologic fluids and certain tissues.
Animals↗
Effect of interleukin-2 on some micronutrients during adoptive immunotherapy for various cancers.
In 20 patients, we investigated the effect of interleukin-2 (IL-2) treatment during adoptive immunotherapy for various cancers on circulating levels of: thiamin; biotin; folate; pantothenate; riboflavin; nicotinate; vitamins A, B6, B12 and E; carotenes; free and total cholines; inositol; and free and total carnitines. Of the above micronutrients, only vitamins A, B6, B12, inositol, carotenes and folate varied markedly from normal levels (pre IL-2 exposure) to abnormal levels (post IL-2). Following IL-2 exposure, every patient's B12 level was significantly elevated; 50% of the levels were abnormally increased above 1000 pg/ml. Extreme significant elevations of inositol were also seen in 90% of the patients. In contrast, IL-2 exposure depressed normal vitamins A, B6, carotene, and folate levels to subnormal; 90% of the patients became B6 hypovitaminemic; 60% for vitamin A, 80% for carotene, and 45% for folate. Other micronutrients tested showed no clear deviations from normal levels post IL-2 exposure. Some reasons for micronutrient variations are discussed.
Adult↗
A jejunoileal bypass rat model for rapid study of the effects of vitamin malabsorption.
Jejunoileal bypass operation was originally done to promote weight loss for treatment of morbid obesity. We used such a model to determine if dietary vitamin absorption is compromised by such an operation. Six rats were subjected to a jejunoileal bypass, 6 control rats were pair-fed to bypassed rats; and 6 were fed ad libitum. Vitamin content of folic, B6, riboflavin, nicotinate, pantothenate, thiamin, biotin, B12, vitamins A, E, and carotene in blood and liver was determined after 8 postoperative weeks. Aside from riboflavin, blood vitamin levels were significantly depressed in bypassed rats. The deepest depression was seen for B12, carotene and vitamin E. Liver vitamin stores of folate, riboflavin, thiamin, B12, clearly were significantly depressed in the bypassed animals compared to the pair-fed and ad libitum-fed controls. This model can serve for rapidly studying micronutrient depletion due to malabsorption without dietary manipulation or antibiotics for gut sterilization.
Animals↗
Segregation by modality of myelinated and unmyelinated fibers in human sensory nerve fascicles.
Thin diameter concentric needle electrodes with a small recording surface were used to explore the characteristics of neighboring fibers in sensory median nerve fascicles. Fibers which were close neighbors in the fascicle, were not randomly distributed intraneurally. Instead there was an intrafascicular segregation by modality of both myelinated and unmyelinated fibers. In addition, evidence was obtained which suggested that the contents of different Schwann cells vary. Some Schwann cell systems envelop afferent C fibers whereas others hold efferent sympathetic C axons. The results imply a modality segregation amongst both A and C fibers in human peripheral sensory nerve fascicles.
Adult↗
Behavioural and biological determinants of fertility transition in sub-Saharan Africa.
In the transition from high to low fertility, different biological and behavioural proximate determinants play roles of varying importance in mediating the change. In most regions of the world, the practice of contraception has come to play the major role, so much so that there is a close relationship worldwide between the level of practice of contraception and the level of fertility. In sub-Saharan Africa, the prevalence of contraceptive practice is low, and fertility levels are exceptionally high for recorded levels of contraceptive practice, even where levels of contraceptive practice are comparable to other regions. The discrepancies are explained to a very large extent by differences between Africa and other regions in other proximate determinants--notably exposure to the risk of pregnancy, and abstinence after delivery. It would seem that transition in African countries will follow one of two patterns that are different to the pattern of transition observed in all other regions. First, fertility may rise before it declines, due to abandonment of traditional fertility regulation for some time prior to the eventual adoption of contraceptive practice. Second, the prevalence of contraceptive practice may rise for a time before there is an observable decline in fertility, because at the same time that contraception is adopted, traditional regulation of fertility is being abandoned, offsetting any effect on fertility. Kenya is an example of the first pattern, while Botswana, Ghana, and Zimbabwe are probably examples of the second.
Africa↗
Vitamin and micronutrient concentrations in cyclosporine-induced renal tumor from diabetic rats.
Concentrations of vitamins, biopterin, free inositol and acid-soluble carnitine were determined in cyclosporine A induced renal adenocarcinoma and uninvaded renal tissue from streptozotocin diabetic rats. Vitamin B6, thiamin, riboflavin, nicotinate, free inositol and acid-soluble carnitine were significantly decreased in tumor than nontumor tissue. Concentrations of folic acid, B12, biotin, pantothenate and biopterin were similar in both tissues. These studies suggest that renal adenocarcinoma affects concentrations of only certain vitamins and micronutrients.
Adenocarcinoma↗