Clinical chemistry of vitamin B12.
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Absorption↗
Biomedical subjects
R E Davis
Publications and source records attributed to R E Davis.
Dephosphorylation of thiamin pyrophosphate by fresh human plasma.
Thiamin pyrophosphate was added to human plasma and serum. After various incubations, aliquots were assayed by the thiochrome method. This revealed that fresh human plasma dephosphorylated thiamin pyrophosphate by a reaction that was time and temperature dependent and inhibited by the presence of ethylenediaminetetraacetic acid (EDTA). Fresh plasma did not dephosphorylate pyridoxal-5-phosphate nor the protein bound thiamin pyrophosphate of red cells.
Edetic Acid↗
Fortification of sorghum beer with thiamin.
The consumption of indigenous cereal-based fermented beer is widespread throughout Africa and other parts of the world. In some countries such beer is brewed commercially as well as at home. As evidence of beri-beri may occur in habitual consumers of the beer, the thiamin content of beer brewed commercially from a mixture of sorghum and maize was investigated. Thiamin concentration in beer averaged 0.33 mg/l, with more than 95% in the cellular fraction, mainly live yeast cells. The thiamin in the cells is not generally available for absorption and the cells take up thiamin added to the beer. At low concentrations (0.25-0.5 mg/l) up to 90% of added 14C-thiamin was taken up by the cells but with concentrations in excess of 2.5 mg/l, the uptake was less than 30%. These results indicate that fortification of sorghum beer with thiamin is feasible. The addition of 2.5 mg/l would supply up to 1.6 mg of absorbable thiamin and thus meet the recommended daily allowance in the target group of habitual consumers.
Beer↗
Systemic colchicine inhibits goldfish optic nerve regeneration.
Experiments were carried out to further investigate the regenerating goldfish optic nerve as a preparation for screening drugs or environmental toxins for adverse effects on neuronal circuit development. Regeneration was induced by unilateral retrobulbar optic nerve crush, and the opposite eye was kept intact. The time to recovery of vision was measured, as an index of regeneration and neurotoxicity, by an improved behavioral technique. The visual stimulus was changed to eliminate extraretinal photoresponding and to permit testing for vision with the right or left eye independently in a trial. Visual recovery occurred within 14 to 25 days. Colchicine, a potent inhibitor of microtubules and axonal transport, was administered semiweekly by ip injection, as in earlier experiments, to study the efficacy of the protocol. The drug resulted in an inhibition of regeneration at doses up to 0.2 micrograms/g body wt which did not impair responding with the control eye. Administration of beta-lumicolchicine, a photoisomer of colchicine that is a weak inhibitor of microtubules or axonal transport, up to 2.0 micrograms/g body wt, had no effect on regeneration or maintenance of visual responding. The results support the thesis that regenerating circuits are more sensitive indicators of neurotoxicity than are established circuits and confirm that the regenerating optic nerve can be used to screen molecules that may impair neuronal circuit development in vivo and to measure their relative potency.
Animals↗
Visual recovery in goldfish following unilateral optic tectum ablation: evidence of competition between optic axons for tectal targets.
Anatomical studies suggest that regenerating optic axons which invade the ipsilateral lobe of the optic tectum following ablation of the contralateral lobe compete with resident optic axons for synaptic sites on tectal neurons. Invader optic axons are initially uniformly distributed over the entire tectal lobe. With time, the invader and resident optic axons progressively segregate so that the invaders are localized in bands or islands separated by areas that are innervated mainly by the residents. When the resident optic axons are destroyed by ablating the eye opposite to the experimental eye, the invader axons remain continuously distributed and the segregation process apparently does not occur. We investigated the relationship between the segregation process and the recovery of visual function by the invader axons. Visual recovery was measured with a behavioral method in which the index of vision was the occurrence of a branchial suppression response to a moving spot of red light that was classically conditioned to an electric shock stimulus. The minimum time to reappearance of vision following ablation of the contralateral lobe of the tectum in two-eye fish was similar to the reported time of onset of the segregation process. Visual recovery occurred sooner when the opposite eye was removed. The restored vision in both groups disappeared following subsequent ablation of the remaining lobe of the tectum. These results suggest that the goldfish optic tectum normally contains no free synaptic sites for anomalous optic afferents and that the invader axons must compete for targets with the resident optic afferents. The invader axons can apparently remain unconnected or non-functional for several weeks following their arrival in the ipsilateral tectal lobe.
Animals↗
Evaluation of an enzyme-linked antiglobulin test for the detection of red cell antibodies.
An enzyme-linked antiglobulin test (ELAT) using low ionic strength saline for the initial red cell sensitisation phase, and alkaline phosphatase conjugated antiglobulin (AP-AHG), has been compared with a conventional low ionic strength antiglobulin test in testing 222 red cell antibodies of various specificities. A wide variation in absorbance values was observed at all levels of haemagglutination strength. Relatively higher absorbance values were obtained with anti-K compared with the agglutination gradings. Haemolysis was eliminated by modifying the substrate buffer used for diluting the AP-AHG, since fixation of red cells prior to sensitisation significantly reduced the sensitivity of the ELAT. Five commercial AP-AHG reagents compared to tests with D, Fya, K and Jka antibodies varied markedly in performance, some being unsatisfactory. The ELAT can be effectively used for antibody detection as well as quantitative determinations but requires automation to realise its full potential.
Alkaline Phosphatase↗
Vitamin B6 intake and plasma pyridoxal phosphate concentrations in the first 2 weeks of life.
Plasma pyridoxal phosphate concentrations were measured in 178 hospitalised neonates. A reference interval for neonates less than 7 day old, of 25 to 78 nmol/l has been established. Vitamin B6 intakes did not correlate well with plasma pyridoxal concentrations despite 26 neonates receiving less than the Recommended Allowance (0.3 mg/d) and 19 receiving amounts below which convulsions have been associated (0.1 mg/d). Ten percent of those infants fed breast milk had plasma pyridoxal phosphate levels below the reference interval compared with only 4% of those fed milk formulae. Breast milk from mothers with babies less than 14 days old had a total vitamin B6 contents reference interval of 5 to 40 micrograms/l. Twenty percent of breast milk samples had virtually no vitamin B6 detected.
Bilirubin↗
Intestinal absorption of thiamin in man compared with folate and pyridoxal and its subsequent urinary excretion.
off intestinal absorption of thiamin was compared with that of folate and pyridoxal in six healthy volunteers using an oral dose of each vitamin equivalent to ten times the recommended daily allowance. Folate and pyridoxal were rapidly absorbed and following the oral dose, serum concentrations rose from a mean basal level of 10.9 micrograms/liter and 17.5 micrograms/liter to 174.8 micrograms/liter and 315.2 micrograms/liter respectively--an increases of 1,500% for folate and 1,701% for pyridoxal. The mean serum level of thiamin rose only marginally from 5.1 micrograms/liter to 7.2 micrograms/liter, an increase of 42%. One hour following the oral test dose of thiamin, the vitamin was actively excreted in the urine of all volunteers, with a mean creatinine/thiamin renal clearance ratio of 2.4. Active excretion continued for up to six hours. In contrast, folate was only actively cleared for a short period in two volunteers. Thiamin absorption appeared to be controlled and limited, and modest increases in the serum concentration were accompanied by active renal clearance.
Administration, Oral↗
Results of computerized tomography, psychometric testing and dietary studies in social drinkers, with emphasis on reversibility after abstinence.
The frequency of abnormal results of cranial computerized tomography (CT), psychometric testing and dietary studies was established in a prospective study of 39 light-to-moderate drinkers (below 120 g/day) of both sexes. Thirty-one subjects showed some degree of cerebral atrophy on CT scan and, of these, 25 also showed abnormalities on psychometric testing. Psychometric deficits were found in three subjects with a normal CT scan. Cerebral atrophy was reversed in 10 of 11 subjects who abstained from alcohol for between three and 12 months. On re-examination after six months, five of the 11 subjects showed improved performance in most psychometric tests. Sixteen subjects were deficient in some dietary factor and all but one of these had abnormal results of CT scan or psychometric testing. The deficiencies found were in kilojoules (six subjects), iron (five subjects), protein (four subjects), calcium (seven subjects), thiamin (six subjects), and ascorbic acid (one subject). Eight subjects had multiple dietary deficiencies; all but one were women. Four had a low red blood cell level of thiamin, but normal serum levels. This was thought to reflect an impairment in the metabolism of this vitamin due to the effect of alcohol. All four subjects with a low red blood cell thiamin level were found to have cerebral atrophy on CT scan and two had psychometric deficits.
Adolescent↗
Systemic apomorphine reverses intrastriatal dopamine-induced contralateral deviation.
Contralateral deviation induced by unilateral injection of 25 micrograms or 100 micrograms dopamine into the dorsal CPU was reversed to ipsilateral deviation by apomorphine administered systemically (1 mg/kg s.c.) before, at the same time, or after the dopamine. Contralateral deviation to a unilateral intrastriatal injection of 6.25 micrograms apomorphine was also reversed to ipsilateral deviation by systemically administered apomorphine. No significant effects on postural deviation were found when a control solution was injected unilaterally into the striatum, followed by systemic apomorphine. Contralateral deviation to the unilateral intrastriatal dopamine injection continued following a further bilateral intrastriatal injection of either dopamine or apomorphine. These results suggest that intrastriatal dopamine indirectly affects sites receptive to dopamine outside the striatum.
Animals↗
Influence of iron-deficiency anaemia on the glycosylated haemoglobin level in a patient with diabetes mellitus.
Iron-deficiency anaemia in a 68-year-old female patient with diabetes mellitus was associated with a marked rise in glycosylated haemoglobin level (from 10.7% to 15.4%). After treatment of the iron-deficiency anaemia, the glycosylated haemoglobin level fell to 11.0%. Control of her diabetes, as assessed by other measures, appeared to be satisfactory throughout.
Aged↗
Applying the correlation between glycosylated haemoglobin and plasma glucose levels.
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Blood Glucose↗
Circumvention of extraretinal photoresponses in assessing recovery of vision following optic nerve crush in goldfish.
Earlier experiments indicated that a conditioned light stimulus that was used to investigate the recovery of vision following optic nerve crush could evoke an extraretinal photoresponse. The present experiments sought to identify a visual stimulus that does not evoke a response following removal of both eyes for use in experiments on optic nerve regeneration. A stimulus consisting of a slight up-down movement of a small ring of light, that was kept stationary between conditioning trials, was classically conditioned to shock in eyed fish and the conditioned response consisted of a suppression of branchial ventilation movements. Following bilateral enucleation or a sham operation the fish received additional sessions of conditioning trials over a period of 3 weeks. Postoperative responding to the moving light stimulus was blocked in the enucleated but not the sham-operated fish. When the ring of light was turned on and off as a conditioned stimulus, responding was extensively but not completely eliminated following enucleation. The investigation confirms that extraretinal photostimulation can be classically conditioned to shock in at least some goldfish, and it shows that such conditioning can be circumvented by using a small moving light as the conditioned stimulus.
Animals↗
Clinical chemistry of vitamin B6.
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Animals↗
In vitro susceptibility of spiroplasmas to heavy-metal salts.
The susceptibility of six spiroplasma strains to heavy-metal salt was characterized in terms of minimal inhibitory concentrations and minimal biocidal concentrations in broth tube dilution tests. The strains were most susceptible to mercuric chloride and silver nitrate; less susceptible to copper sulfate, cobalt chloride, lead nitrate, and cadmium sulfate; and least susceptible to nickel chloride and zinc sulfate. Spiroplasma citri strains Maroc R8A2 and C189 were the most susceptible to five of eight heavy-metal salts, and honeybee spiroplasma strain AS576 and Spiroplasma floricola strain 23-6 were generally the least susceptible. The difference between the minimal biocidal concentrations and the minimal inhibitory concentrations was greater for certain heavy-metal salts than for others.
Hydrogen-Ion Concentration↗
Enumeration and Localization of N(2)-Fixing Bacteria Associated with Roots of Spartina alterniflora Loisel.
Numbers and possible locations of N(2)-fixing bacteria were investigated in roots of Spartina alterniflora Loisel, which support nitrogenase activity in the undisturbed native habitat. N(2)-fixing bacteria were recovered in cultures both from S. alterniflora roots and from the surrounding sediment, and they formed a greater proportion of the bacteria recovered from root homogenates than from salt-marsh sediment. N(2)-fixing bacteria were recovered in high numbers from the rhizoplane of S. alterniflora after roots were treated with 1 or 5% chloramine-T for 1 h or with 1% NaOCl for 1 or 2 h. Immersing S. alterniflora roots in 5% NaOCl for 1 h was more effective in distinguishing bacteria inside the roots since this treatment nearly eliminated N(2)-fixing bacteria recoverable from the rhizoplane, although high numbers of N(2)-fixing bacteria were recovered from homogenates of roots treated with 5% NaOCl for 1 h. However, this treatment was less effective with roots of Zea mays L. (Funks G4646) and Sorghum bicolor (L.) Moench (CK-60 A), indicating that techniques to surface sterilize roots should be evaluated for different plants. Bacteria were observed by light and electron microscopy inter- and intracellularly in the cortex and in the aerenchyma of S. alterniflora roots. This study clearly shows that bacteria, including N(2) fixers, colonize the interior of roots of S. alterniflora growing in a Chesapeake Bay, Maryland, salt marsh.
Journal Article↗
Chemically defined medium for cultivation of several epiphytic and phytopathogenic spiroplasmas.
A chemically defined medium, LD82, was formulated for in vitro cultivation of spiroplasmas. Medium LD82 supported good growth for four epiphytic and insect-pathogenic spiroplasmas, Spiroplasma floricola 23-6, Spiroplasma sp. strain SR3, Spiroplasma sp. strain brevi, and Spiroplasma sp. strain AS576, and of the phytopathogenic spiroplasmas Spiroplasma citri Maroc R8A2 and PC1. Titers of all six strains grown in defined medium LD82 reached 2.0 x 10 to 6.0 x 10 CFU/ml of culture. All spiroplasma strains tested formed colonies readily on agar medium LD82. None of the spiroplasmas formed typical fried-egg colonies. All formed diffuse colonies, but the forms of colonies differed somewhat among the spiroplasma strains. In preliminary studies of nutritional requirements, phospholipids slightly enhanced the growth of the epiphytic and insect-pathogenic strains in medium LD82 and were found essential for good growth of S. citri.
Journal Article↗