Effect Of Vitamin B12 Research Articles

The Aeration-Dependent Effect of Vitamin B12on DNA Biosynthesis in Methylobacterium dichloromethanicum

The effect of vitamin B12 (cobalamin) on DNA biosynthesis in Methylobacterium dichloromethanicum was studied. When cultivated in media with methanol or dichloromethane, the bacterium produced approximately 10 micrograms corrinoids per g dry biomass, compared to about 7 micrograms/g when cultivated on ethanol or succinate. Exogenous adenosylcobalamin (AdoCbl) stimulated DNA biosynthesis in M. dichloromethanicum cells grown under poor aeration, the effect being mediated by AdoCb1-linked ribonucleotide reductase. In vitro studies showed that M. dichloromethanicum also has AdoCbl-independent ribonucleotide reductase. Under good aeration, exogenous AdoCbl had no effect on DNA biosynthesis, while hydroxyurea suppressed it. These data suggest that AdoCbl-independent ribonucleotide reductase, which is likely to be activated by oxygen, plays an important part in DNA biosynthesis when M. dichloromethanicum is cultured with good aeration, whereas AdoCbl-dependent ribonucleotide reductase is active under the conditions of poor aeration.

Effect of vitamin B6 on oxygen radicals, mitochondrial membrane potential, and lipid peroxidation in H2O2-treated U937 monocytes

Vitamin B6 (Vit.B6) supplementation has been shown to be beneficial in reducing diabetic complications, cognitive aging, and in the prevention of coronary heart disease. It was hypothesized that Vit.B6 compounds may function as antioxidants and thus offer protection against oxidative stress under various pathophysiological and or experimental conditions. To test this hypothesis, U937 monocytes were cultured with pyridoxine (P), pyridoxal phosphate (PP) and pyridoxamine (PM) and H2O2, either alone or together for 2 h. Oxidative stress was determined by measuring superoxide radical production, lipid peroxidation, and mitochondrial transmembrane potential. Results demonstrate that Vit.B6 compounds can prevent the oxygen radical generation and lipid peroxidation caused by hydrogen peroxide in U937 monocytes, and that some of the protective effect of Vit.B6 may occur via modification of mitochondrial function.

Effect of vitamin B1 and mixtures of B1 with other vitamins on cytostatic efficiency of sanazole under irradiation. A study in vitro

Experiments in vitro, using bacteria Escherichia coli (AB 1157) as a biological model, showed that the cytostatic efficiency of sanazole (AK-2123, a nitrotriazole-type radiosensitizer) in radiation treatment can be strongly influenced by the presence of various vitamins. In airfree media the sanazole action is increased by a factor of 2.5 in the presence of vitamin (vit.) B1, vit. C E-acetate and β-carotene, whereas vit. B1 used individually possesses a 2.7-times higher cytostatic activity than sanazole itself. In media containing air the highest increase of sanazole action is observed in the presence of vit. B1 and C, whereas the individual use of vit. B1 shows a radiation protection effect. In media saturated with N 2O the addition of the vit. B1 and C causes a 1.8-times larger sanazole activity, but the application of vit. B1 alone brings about a very high radiation protection. From studies of vit. B1-radiolysis it can be concluded that OH radicals are the major primary transients leading to substrate degradation. The results are of interest for the radiation therapy of cancer.

Modulation of Intracellular Ca2+ Concentration by Vitamin B12 in Rat Thymocytes

ABSTRACTWe have studied several novel effects of vitamin B12 (cyanocobalamin) on cellular Ca2+ homeostasis in rat thymocytes. We determined the effect of various concentrations of vitamin B12 on intracellular Ca2+ concentration ([Ca2+]i) and parameters of Ca2+in signaling using the fluorescent dye Fura-2. The basal [Ca2+]i in Ca2+-containing media was 115 ± 5 nM but in vitamin B12 (10 nM)-treated thymocytes [Ca2+]i was decreased to 60 ± 15 nM (mean ± SEM) during the first 5 min. The decline in [Ca2+]i was accompanied by an increase in the endoplasmic reticulum Ca2+ store, presumably as a result of Ca-ATPase activation. At the same time 100 nM–10 mM B12 induced the accumulation of Ca2+ in mitochondria. Somewhat higher concentrations of B12 (1–10 μM) had no effect on [Ca2+]i. A further increase in B12 concentration with range from 50 μM to 1 mM caused a dose-dependent elevation of [Ca2+]i from the basal level (115 ± 5 nM) up to 200 ± 50 nM in thymocytes, and this elevation was partially blocked in Ca2+-free media. This high concentration of vitamin B12 caused a gradual decrease of endoplasmic reticulum Ca2+ stores by means of Ca-ATPase inhibition. The B12-induced increase in [Ca2+]i was not observed after depletion of intracellular Ca2+ stores, induced by addition of 2′,5′-di(tert-butyl)-1,4-benzohydroquinone (BHQ), an inhibitor of endoplasmic reticulum Ca 2+-ATPase, concanavalin A, or arachidonic acid. These studies show that vitamin B12 regulates [Ca2+]i via several different mechanisms at different B12 concentrations. Participation of G proteins and calmodulin activity in B12-mediated [Ca2+]i increase is discussed.

Modest efficacy of folic acid and the lack of an additional effect of vitamin B12 in hyperhomocystinaemic patients with coronary artery disease Jo Griffiths, Manohara Senaratne. University of Alberta, Grey Nuns Hospital, Edmonton, AB, Canada

Modest efficacy of folic acid and the lack of an additional effect of vitamin B12 in hyperhomocystinaemic patients with coronary artery disease Jo Griffiths, Manohara Senaratne. University of Alberta, Grey Nuns Hospital, Edmonton, AB, Canada

The Effects of Vitamin B6 and Folate on The Level of Plasma Homocysteine and Brachial Artery Dilation in Healthy Subjects

Background:Elevation in plasma homocysteine has been widely studied as an independent risk factor for atherosclerosis. Additionally, epidemiologic studies have demonstrated that persons who take the folate and vitamin B6 have a lower incidence of atherosclerotic vascular disease and lower plasma homocysteine llevels. However, the effects of vitamin B6 and folate on the level of plasma homocysteine and brachial artery dilation on healthy subjects have not yet been evaluated. Methods:We evaluated the effects of 50 mg of vitamin B6 and 1 mg of folate on endothelial, function and plasma homocysteine levels in two healthy postmenoausal women and twenty-one men enrolled in a randomized, double-blind, placebo-controlled, crossover design study. Results:Despite a significant lowering of plasma homocysteine level (placebo:folate=6.56±1.55 mol/L vs. 5.37±1.04 mol/L, p=0.001), the supplement of vitamin B6 and folate had no statistically significant incremental effect on flow-mediated dilation (FMD) of healthy subjects as compared to the placebo (placebo: folate=5.12±3.26% vs. 6.69±2.60%, p=0.070). Conclusion:Despite the lowering of the plasma homocysteine level, vitamin B6 and folate had no significant effect in regards to improving the flow-mediated (eg, nitric oxide dependent) vasodilation of healthy persons. (Korean Circulation J 2001;31(3):305-310)

The effect of vitamin B6 and folate supplements on plasma homocysteine and serum lipids levels in patients on regular hemodialysis.

Hyperhomocysteinemia is an independent risk factor for cardiovascular events. The aim of this study was to show the results of the reduction of homocysteine in end stage renal failure patients on hemodialysis, as it is known, have higher levels of homocysteine than other groups of subjects. Plasma homocysteine concentration was determined before and after the administration of vitamin B6 and folic acid in 12 patients (males: 6) on regular dialysis therapy. Mean monthly fasting serum concentrations of total cholesterol (TCHOL), HDL-chol, LDL-chol and triglycerides (TRG) were determined for a period 68 months (12-120 months) before and 26 months after the administration of vitamin B6 and folic acid. Mean serum concentrations for folic acid and vitamin B12 before and after the administration were: folic acid: 5.03 +/- 4.9 and 18.0 +/- 19.2 ng/mL, (p < 0.0001) and B12: 456 +/- 257 and 514.38 +/- 307 pg/mL respectively). Plasma homocysteine was reduced significantly after the administration of above drugs (from 47 +/- 14 to 29 +/- 9 micromol/mL, p < 0.001). This reduction of homocysteine resulted in a modification of the patients' lipidemic profile: Serum LDL-chol was decreased significantly (119 +/- 38 mg/dL to 110 +/- 35 mg/dL, p<0.005). TCHOL and TRG were also decreased but not significantly (190 +/- 45 mg/dL to 187 +/- 43 mg/dL and 116 +/- 63 mg/dL to 108 +/- 47 mg/dL respectively)). Serum concentrations HDL-chol were increased significantly (from 42 +/- 10 mg/dL to 47 +/- 10 mg/dL, p < 0.001). The atherogenic index for cholesterol, LDL/HDL, was 1.6 times lower after the drugs receiving (before: LDL/HDL = 3.1 and after: LDL/HDL = 2.5, p < 0.001). These results indicate that the folate and vitamin B6 supplementation resulted in reduction of homocysteine levels and improvement of lipidemic profile in regular dialysis patients.

The Effect of Vitamin B12 on the Cultivation of T vaginalis in Diamond Medium

The Effect of Vitamin B12 on the Cultivation of T vaginalis in Diamond Medium

Homocysteine and renal disease.

Hyperhomocysteinemia refers to an elevated circulating level of the sulfur-containing amino acid homocysteine and has been shown to be a risk factor for vascular disease in the general population. In patients with renal failure, hyperhomocysteinemia is a common feature. The underlying pathophysiological mechanism for this phenomenon is unknown. Proposed mechanisms include reduced renal elimination of homocysteine and impaired nonrenal disposal, possibly because of inhibition of crucial enzymes in the methionine-homocysteine metabolism by the uremic milieu. Absolute or relative deficiencies of folate, vitamin B6, or vitamin B12 may also play a role. Several case-control and prospective studies have now indicated that hyperhomocystenemia is an independent risk factor for atherothrombotic disease in patients with predialysis and end-stage renal disease. In renal patients, plasma homocysteine concentration can be reduced by administration of folic acid in doses ranging from 1 to 15 mg per day. In more than 50% of the cases, however, the homocysteine concentration remains above 15 micromol/L. The effects of vitamin B12 or vitamin B6 are unclear. Large intervention trials are now needed to establish whether homocysteine-lowering therapy will reduce atherothrombotic events in patients with renal failure. These studies are now planned or are ongoing.

Effects of vitamin B6 deficiency on cytokine levels and lymphocytes in mice.

The effects of vitamin B6 (B6) deficiency on cytokine levels and proportions of lymphocyte subsets in BALB/c mice were investigated. The proportion of lymphocytes from the thymus and spleen of mice given no B6, that were CD4+ CD8- T cells, was larger than in mice given B6, and the ratio of CD8+ to CD4+ T cells in the thymus of mice given no B6 was lower. The concentrations of interleukin-5 and -10 in spleen cells stimulated in vitro with concanavalin A were significantly higher in the mice with B6 deficiency, as was their plasma corticosterone concentrations. These results suggested that B6 is necessary to maintain cytokine levels and lymphoid function in the thymus and spleen of mice.

Effect of Vitamin B12 on the Sleep-Wake Rhythm Following an 8-Hour Advance of the Light-Dark Cycle in the Rat

Kiuchi, T., H. Sei, H. Seno, A. Sano and Y. Morita. Effect of vitamin B12 on the sleep-wake rhythm following an 8-hour advance of the light-dark cycle in the rat. Physiol Behav 61(4) 551–554, 1997.—We have studied the effect of vitamin B12 (VB12) on the sleep-wake rhythm following an 8-h advance of the light-dark (LD) cycle in the rat. The electroencephalogram and electromyogram were recorded on chart paper via a two-channel telemetry system. Infusion of VB12 (Mecobalamin; 0.25 μg/h) or saline into the abdominal cavity was performed using an implanted miniosmotic pump. Before the phase shift, there was no significant difference between the two groups in terms of the mean daily amount of each vigilance stage. Following the phase advance, in the saline group, wake gradually decreased and nonrapid-eye-movement (NREM) sleep and REM sleep increased. In the VB12 group, no significant change was seen in any of the vigilance states, except for REM sleep on day 3. The results suggest that VB12 may maintain homeostasis of sleep and/or wake amount following an 8-h advance of the LD cycle in the rat.

Neurogenic Impotence and Lower Urinary Tract Symptoms Due to Vitamin B1 Deficiency in Chronic Alcoholism

No AccessJournal of UrologyClinical Urology: Case Report1 Mar 1997Neurogenic Impotence and Lower Urinary Tract Symptoms Due to Vitamin B1 Deficiency in Chronic Alcoholism Bernard S. Tjandra and Rudi A. Janknegt Bernard S. TjandraBernard S. Tjandra More articles by this author and Rudi A. JanknegtRudi A. Janknegt More articles by this author View All Author Informationhttps://doi.org/10.1016/S0022-5347(01)65098-5AboutFull TextPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail "Neurogenic Impotence and Lower Urinary Tract Symptoms Due to Vitamin B1 Deficiency in Chronic Alcoholism." The Journal of Urology, 157(3), pp. 954–955 References 1 : Studies on metabolism of pyruvic acid in normal and vitamin B1-deficient states; accumulation of pyruvic acid and other carbonyl compounds in beri-beri and effect of vitamin B1. Biochem. J.1939; 33: 1525. Google Scholar 2 : Vasculogenic impotence evaluated by high-resolution ultrasonography and pulsed Doppler spectrum analysis. Radiology1985; 155: 777. Google Scholar 3 : Sacral signal tracing: the electrophysiology of the bulbocavernosus reflex. J. Urol.1978; 122: 661. Google Scholar 4 : Evoked responses from the pudendal nerve. J. Urol.1982; 128: 974. Link, Google Scholar 5 : Comparison of Hoffmann reflex with quantitative assessment of cutaneous sensation in diabetic neuropathy. Acta Neurol. Scand.1986; 74: 121. Google Scholar 6 Tjandra, B. S., Van de Beek, C. and Janknegt, R. A.: Treatment of impotency with thiamine point-puncture. Proceedings of the 2nd Asian Congress of Urology, Bangkok, Thailand, December 1993. Google Scholar Departments of Urology, University of Indonesia, Djakarta, Indonesia, and University Hospital Maastricht, Maastricht, The Netherlands© 1997 by American Urological Association, Inc.FiguresReferencesRelatedDetails Volume 157Issue 3March 1997Page: 954-955 Advertisement Copyright & Permissions© 1997 by American Urological Association, Inc.MetricsAuthor Information Bernard S. Tjandra More articles by this author Rudi A. Janknegt More articles by this author Expand All Advertisement PDF downloadLoading ...

Effects of Vitamin B12 on performance and circadian rhythm in normal subjects

This preliminary study investigates effects of methyl- and cyanocobalamin on circadian rhythms, well-being, alertness, and concentration in healthy subjects. Six women (mean age 35 years) and 14 men (mean age 37 years) were randomly assigned to treatment for 14 days with 3 mg cyano-(CB12) or methylcobalamin (MB12) after 9 days of pre-treatment observation. Levels in the CB12 group increased rapidly in the first, then slowly in the second treatment week, whereas increase in the MB12 group was linear. Urinary aMT6s excretion was reduced by both forms of vitamin B12 over 24 hours with a significant decrease between 0700-1100 hours, whereas urinary excretion of potassium was significantly increased between 0700-1100 hours. Activity from 2300-0700 hours increased significantly under both forms of vitamin B12. Sleep time was significantly reduced under MB12 intake. In this group the change in the visual analogue scales items "sleep quality," "concentration," and "feeling refreshed" between pretreatment and the first week of treatment showed significant correlations with vitamin B12 plasma levels. Cortisol excretion and temperature were not affected by either medication. We conclude that vitamin B12 exerts a direct influence on melatonin. Only MB12 has a positive psychotropic alerting effect with a distribution of the sleep-wake cycle toward sleep reduction.

Side effects of diazepam administered to prevent febrile seizure recurrence

and nonrecurrence groups. Seizures recurred at least once in six the potential clinical applications of vitamin B6. Our study was patients (11.5%) receiving diazepam and in 17 patients (48.0%) designed to assess the clinical effectiveness of vitamin B6 for the receiving chloral hydrate (P < 0.005). prevention of repeated convulsions during one febrile episode. Conclusion. Intermittent rectal diazepam for the prevention of febrile convulsion recurrence was more effective than rectal chloral hydrate.

Vitamin therapy of hyperhomocysteinaemia in chronic renal failure

s 1933 Vitamin therapy of hyperhomocysteinaemia in chronic renal failure M. Hages, K. Pietrzik Institut fur Ernahrungswissenschaft, Abt. Pathophysiologie der Ernahrung des Menschen. Rheinische Friedrich-Wilhelms-Universitat. Bonn, Germany In patients with chronic renal failure, plasma homocysteine levels are already elevated significantly at an early stage and show a negative correlation with the glomerular filtration rate and serum creatinine concentration, respectively. End-stage renal disease patients on dialysis have homocysteine levels threeor fourfold above normal [1,2]. In several studies moderate hyperhomocysteinemia has been identified as a potential independent risk factor for premature cardiovascular disease, a frequent complication of advanced renal diseases. The mechanism of the atherogenic action of homocysteine is not clearly understood, but it is theorized that homocysteine is cytotoxic to the endothelial wall and promotes the oxidative modification of LDL cholesterol [3]. The elevated homocysteine concentration in patients with renal failure is mainly caused by the decreased catabolism of homocysteine in the proximal tubular cells due to reduced filtration and to tubular dysfunction. Additionally, the extrarenal homocysteine metabolism is decreased due to inhibition by retained metabolites [4]. Homocysteine is an amino acid, which is formed as an intermediate in the metabolism of methionine. Homocysteine can be remethylated to methionine with folic acid as methyl-donor and vitamin B12 as co-factor. Additionally, it can be converted to cystathionine by condensation with serin in an irreversible reaction. This metabolic step requires vitamin B6 as cofactor. The status of vitamin B6, B12, and folic acid is regarded as an important factor influencing the homocysteine level. However, many renal patients with elevated homocysteine concentrations have normal baseline serumand red cell folate levels, as well as normal serum B12 and B6 concentrations. Therefore, it is unlikely that manifest vitamin deficiencies contribute to the elevated homocysteine levels in patients with uraemia and end-stage renal disease. Nevertheless, the folic acid and vitamin B12 status in these patients is negatively correlated with their plasma homocysteine concentration [5,6]. Patients with renal failure, especially dialysis patients, frequently show vascular dysfunction as manifested by an elevated plasma level of von-Willebrand factor (vWF)-antigen, which is reported to be one of the specific markers of endothelial activation and inflammation. The elevated concentration of this indicCorrespondence and offprint requests to: M. Hages, Institut fur Ernahrungswissenschaft, Abt. Pathophysiologie der Ernahrung des Menschen, Rheinische Friedrich-Wilhelms-Universitat, Bonn, Germany. ator of endothelial damage is not only due to the reduced clearance in renal failure because there is no correlation between GFR and the blood level of this factor. Moreover, the level of von-Willebrand factor antigen in dialysis patients is negatively correlated with the duration (years) of hemodialysis [7]. These observations suggest the possibility of endothelial injury. There is in-vitro evidence that homocysteine promotes the release of von-Willebrand factor antigen [8]. However, in most studies, the fasting homocysteine plasma concentration and von-Willebrand factor don't correlate [9]. But after methionine loading test (0.1 g methionine/kg BW), the post-load homocysteine levels showed a significant relationship to the endothelial function parameter [9]. A methionine loading test stresses the pathway involved in homocysteine metabolism and is a valid diagnostic test for an abnormal homocysteine handling. Treatment with high doses of folic acid (5 mg/d) significantly lowers [10,11] the elevated homocysteine concentrations, both in non-dialyzed and in haemodialyzed patients, by the stimulation of the remethylation of homocysteine. This can be observed even in the absence of evident folate deficiency. In patients with mild hyperhomocysteinaemia and peripheral arterial occlusive disease, the vitamin is also able to reduce the elevated levels of von-Willebrand factor and appears to ameliorate the endothelial function [9]. Corresponding studies with renal failure patients are missing. Separate or additive effects of vitamin B6 and/or vitamin B12 on the homocysteine concentration in patients with renal failure have not been observed so far. Further research is needed to identify the optimal therapeutic dose and/or combination of vitamins in the therapy of hyperhomocysteinemia due to renal insufficiency.

The effect of vitamin B6 on the systolic blood pressure of rats in various animal models of hypertension

To investigate whether a dietary supplement of vitamin B6 could attenuate the elevation of systolic blood pressure (SBP) in Zucker obese or spontaneously hypertensive rats, or rats ingesting sucrose. Zucker obese rats (fa/fa), Sprague-Dawley rats with sucrose-induced elevation of SBP, spontaneously hypertensive rats (SHRs) and their corresponding controls were tested for the effects of vitamin B ingestion in different ways: (1) vitamin B6 was included as a supplement (five times the normal intake) from the start of the experiment until the development of hypertension; (2) vitamin B6 supplement was removed from the diet of Zucker obese and Zucker lean control groups after 16 weeks on the dietary treatments; and (3) a diet deficient in vitamin B6 was instituted in SHRs and control Wistar-Kyoto (WKY) rats. The SBP of rats in all groups was monitored in the conscious animal by tail-cuff plethysmography. The effects of the various treatments on the uptake of calcium by caudal artery segments were examined. Male Zucker obese rats (fa/fa) of age 6 weeks fed a commercial rat chow developed hypertension in 3-4 weeks, whereas their lean controls (Fa/Fa) did not. The inclusion of a vitamin B6 supplement (five times the normal intake) resulted in a complete attenuation of the hypertension in the obese strain. Removal of the vitamin B6 supplement from the diet of these obese rats resulted in the return of hypertension within 2 weeks. Similar changes in SBP were also observed in the Zucker lean controls treated with vitamin B6. The ingestion of sucrose by male Sprague-Dawley rats resulted in modest elevation of SBP that was attenuated by the inclusion of the vitamin B6 supplement in their diet. In contrast, there was no response to the inclusion or removal of dietary vitamin B6 supplement in the SHRs. However, the WKY control rats responded to both these conditions in a similar manner to that seen in the Sprague-Dawley strain. Increased peripheral resistance resulting from increased permeability of vascular smooth muscle plasma membrane to Ca2+ is thought to be one of the mechanisms of hypertension. Changes in SBP correlated with changes in the uptake of calcium by caudal artery segments in all the groups studied. The Zucker obese and sucrose-induced hypertensive rats have abnormalities in carbohydrate metabolism. The vitamin B6 supplement decreased the random or fasting blood glucose levels in the Zucker obese and sucrose-fed rats respectively. This is the first observation that animal models of hypertension can be classified on the basis of their response to a vitamin B6 supplement. On this basis, the etiology of hypertension in SHRs is quite distinct from that in Zucker obese rats and in rats ingesting sucrose.

Effects of vitamin B12, folate, and vitamin B6 supplements in elderly people with normal serum vitamin concentrations

SummaryIn a prospective, multicentre, double-blind controlled study, the effect of an intramuscular vitamin supplement containing 1 mg vitamin B12, 1·1 mg folate, and 5 mg vitamin B6 on serum concentrations of methylmalonic acid (MMA), homocysteine (HCYS), 2-methylcitric acid (2-MCA), and cystathionine (CYSTA) was compared with that of placebo in 175 elderly subjects living at home and 110 in hospital. Vitamin supplement and placebo were administered eight times over a 3-week period. Vitamin supplement but not placebo significantly reduced all four metabolite concentrations at the end of the study in both study groups. The maximum effects of treatment were usually seen within 5-12 days. Initially elevated metabolite concentrations returned to normal in a higher proportion of the vitamin than of the placebo group: 92% vs 20% for HYCS; 82% vs 20% for MMA; 62% vs 25% for 2-MCA; and 42% vs 25% for CYSTA.The response rate to vitamin supplements supports the notion that metabolic evidence of vitamin deficiency is common in the elderly, even in the presence of normal serum vitamin levels. Metabolite assays permit identification of elderly subjects who may benefit from vitamin supplements.

Effect of thiamine on the processes responsible for acetylcholine secretion in the frog neuromuscular synapses

The effect of vitamin B1 (thiamine, 10−10–10−3 M) on direct (transmitter secretion) and recurrent (resynthesis of the transmitter and its storage in synaptic vesicles) processes of acetylcholine (ACh) secretion was studied in the frog neuromuscular junction. In Ca2+-containing extracellular medium, the facilitatory effects of thiamine and α-latrotoxin (an increase in the frequency of miniature end-plate potentials, MEPP) were additive, regardless of the sequence of their application. After partial exhaustion of the synaptic vesicle stores caused by α-latrotoxin (2 nM) in Ca2+-free extracellular medium, thiamine accelerated the Ca2+-induced recovery of the ACh secretion. In the presence of thiamine, there were two phases in the dependence of quantum content of an end-plate potential (EPP) on stimulation frequency, which are typical of the effects of Sr2+ and Ba2+ on the ACh secretion. Under conditions of depression and postdepression recovery, the effect of thiamine on the time course of the changes in EPP amplitude was similar to that produced by Ba2+. Possible mechanisms of the effects of vitamin B1 on the processes responsible for the ACh secretion and the dependence of the MEPP frequency on the concentrations of thiamine and thiamine diphosphate are discussed in light of the above results.

Effects of vitamin B12 on biological rhythms and sleepiness

Effects of vitamin B12 on biological rhythms and sleepiness

Ultrastructure of nuclear chomatin in hepatocytes from regenerating guinea pig liver: effect of vitamin B12

Ultrastructure of nuclear chomatin in hepatocytes from regenerating guinea pig liver: effect of vitamin B12