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At least 505 records · Page 28Linked to original sources
PubMed2005

Enhancement of anaerobic carbon tetrachloride biotransformation in methanogenic sludge with redox active vitamins.

Carbon tetrachloride (CT) is an important groundwater pollutant which is only subject to biotransformation in the absence of oxygen. The anaerobic biotransformation of CT is influenced by electron shuttling compounds. The purpose of this study was to evaluate the impact of redox active vitamins on CT (100 microM) metabolism in a methanogenic sludge consortium (0.5 g VSS l(-1)) supplied with volatile fatty acids as electron donor (0.2 g COD l(-1)). The redox active vitamins, tested at concentrations ranging from 0.5 to 20 microM, were riboflavin (RF) and two forms of vitamin B12, cyanocobalamin (CNB12) and hydroxycobalamin (HOB12), and these were compared with a redox mediating quinone, anthraquinone-2,6-disulfonate (AQDS). Substoichiometric concentrations of RF, CNB12, HOB12 at molar ratios of vitamin: CT as low as 0.005 significantly increased rates of CT-bioconversion. These are the lowest molar ratios of vitamin B12 reported having an impact on dechlorination. Additionally, this study constitutes the first report of RF having a role in reductive dechlorination. At molar ratios of 0.1 vitamin: CT, RF, CNB12, HOB12 increased the first order rate constant of CT bioconversion by 4.0-, 13.3-and 13.6-fold, respectively. The redox active vitamins also enhanced the rates of abiotic CT conversion in heat killed sludge treatments, but the rates were approximately 4- to 5-fold lower than the corresponding vitamin enhanced rates of biological CT conversion. The addition of CNB12 or HOB12 to the live methanogenic sludge consortium increased the yield of inorganic chloride (Cl-) from CT-converted. Chloroform was a transient intermediate in CNB12 or HOB12 supplemented cultures. In contrast, the addition of RF increased the yield of chloroform from CT-converted. Taken as a whole the results clearly demonstrate that very low concentrations of redox active vitamins could potentially play an important role in accelerating the anaerobic the bioremediation of CT as well as influencing the proportions of biotransformation products formed.

Anaerobiosis↗
PubMed1975

A erimetric technique believed to test receptive field properties: sequential evaluation glaucoma and other conditions.

We used a technique to simplify and speed up a perimetric test (Westheimer function). Through sequential testing, the technique was successfully used to evaluate pathologic findings and partially to evaluate treatment regimens in three subjects. One patient had an onset of kinetic field changes and Westheimer function alteration with primary open-angle glaucoma. Temporary remissions of alterations in the Westheimer function and kinetic visual field loss occurred in patients with glaucoma and tobacco-alcohol (complicated) amblyopia. Using these techniques it is possible to localize an anomaly in the outer retinal layer, the inner retinal layer, and central to the optic nerve head. We divided the inner and outer retinal layers on a vascular support basis.

Aged↗
PubMed1983

An appraisal of the value of vitamin B12 in the prevention of motion sickness.

Unpublished reports have suggested that hydroxycobalamin (B12, i.m.) prevents motion sickness. Some biomedical evidence supports this contention in that B12 influences the metabolism of histidine and choline; dietary precursors to neurotransmitters with established roles in motion sickness. Susceptibility to motion sickness was evaluated after B12 (1000 micrograms, i.m.). Subjects initially completed vestibular function and motion sickness susceptibility tests to establish normal vestibular function. The experimental motion stressor was a modified coriolis sickness susceptibility test. Subjects executed standardized head movements at successively higher RPM until a malaise III endpoint was reached. Following two baseline tests with this motion stressor, subjects received a B12 injection, a second injection two weeks later, and a final motion sickness test three weeks later. No significant differences in susceptibility were noted after B12. Hematological parameters revealed no B12 deficiency before injection. The possibility that patients with B12 deficiencies are more susceptible to motion sickness cannot be ruled out.

Aerospace Medicine↗
PubMed1987

Hemes and hemoproteins. 3. The reaction of microperoxidase-8 with cyanide: comparison with aquocobalamin and hemoproteins.

The monomeric heme octapeptide from cytochrome c, microperoxidase-8, (MP-8), coordinates CN- with log K = 7.55 +/- 0.04 at 25 degrees C in 20% (v/v) aqueous methanol. Log K values are independent of pH between 6 and 9. A spectrophotometric titration of cyanoMP-8 between pH 5.5 and 13.8 gave a single pKa greater than or equal to 13.5 ascribed to ionization of the proximal His ligand. A study of the kinetics of the reaction of MP-8 with cyanide between pH 5.5 and 12, at 25 degrees C and mu = 0.1, indicates that formation of cyanoMP-8 occurs via three routes: attack of CN- on Fe(III) (k1 = 6.0 +/- 0.3 X 10(5) M-1 sec-1); attack of HCN on Fe(III) (k2 = 4.8 +/- 2.0 X 10(3) M-1 sec-1), followed by deprotonation and isomerization to form the C-bound species; and displacement of OH- by CN- when the proximal His ligand is ionized (k5 = 1.8 +/- 0.1 X 10(5) M-1 sec-1). These results are compared with available data for the reaction of cyanide with aquocobalamin and with various hemoproteins.

Animals↗