Methane formation from fructose by syntrophic associations of Acetobacterium woodii and different strains of methanogens

When Acetobacterium woodii was co-cultured in continuous or in stationary culture with Methanobacterium strain AZ, fructose instead of being converted to 3 mol of acetate was converted to 2 mol of acetate and 1 mol each of carbon dioxide and methane, showing that interspecies hydrogen transfer occurred. In continous culture the organisms formed a close physical association in clumps; the doubling time for each organism was 6h at 33°C. Methane mainly was derived from carbon positions 3 and 4 of the sugar, but other carbons also yielded methane; this was shown to be due to carbon dioxide-acetate exchange reactions by A. woodii in a manner similar to that carried out by Clostridium thermoaceticum. Four other methanogens, Methanobacterium M.o.H. and M.o.H. G, Methanobacterium formicicum, and Methanosarcina barkeri (not acetate-adapted) also produced similar results, when co-cultured with A. woodii.     

Familial pseudohypoparathyroidism without somatic anomalies.

A family is described in which affected individuals showed pseudohypoparathyroidism, with hypocalcemia, hyperphosphatemia and increased serum levels of parathyroid hormone, but none of the somatic anomalies frequently associated with this disorder. The untreated individuals showed radiologic evidence of osteitis fibrosa. The administration of parathyroid hormone evoked only a slight increase in the excretion of cyclic adenosine monophosphate but no change in the renal tubular reabsorption of phosphate and no rise in the serum calcium level. The infusion of ethylenediamine tetra-acetic acid caused an appropriate increase in the serum level of parathyroid hormone, but again there was no apparent renal or skeletal response to the hormone. There were no associated abnormalities in calcitonin, thyrotropin or prolactin levels and no thyroid dysfunction. Therapy with vitamin D corrected the hypocalcemia but did not improve the renal and skeletal responsiveness to parathyroid hormone. The inheritance of the disorder in this family was compatible with an autosomal dominant mode with variable penetrance, but other modes could not be excluded.     

Complete degradation of carbohydrate to carbon dioxide and methane by syntrophic cultures of Acetobacterium woodii and Methanosarcina barkeri

Methanosarcina barkeri (strain MS) grew and converted acetate to CO₂ and methane after an adaption period of 20 days. Growth and metabolism were rapid with gas production being comparable to that of cells grown on H₂ and CO₂. After an intermediary growth cycle under a H₂ and CO₂ atmosphere acetateadapted cells were capable of growth on acetate with formation of methane and CO₂. When acetate-adapted Methanosarcina barkeri was co-cultered with Acetobacterium woodii on fructose or glucose as substrate, a complete conversion of the carbohydrate to gases (CO₂ and CH₄) was observed.Abbreviation CMC carboxymethyl cellulose     

Cleavage of single-stranded DNA by the A and A* proteins of bacteriophage phi X174.

The purified A protein and A* protein of bacteriophage phi X174 have been tested for endonuclease activity on single stranded viral phi X174 DNA. The A protein (55.000 daltons) nicks single-stranded DNA in the same way and at the same place as it does superhelical RFI DNA, at the origin of DNA replication. The A* protein (37.000 daltons) can cleave the single-stranded viral DNA at many different sites. It has however a strong preference for the origin of replication. Both proteins generate 3'OH ends and blocked 5' termini at the nick site.     

The measurement of ouabain binding and some related properties of digitonin-treated (Na+,K+)-ATPase.

1. Digitonin treated membrane preparations purified from dog kidney lose their (Na+,K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) activity, but the K+-phosphatase and Na+-dependent ADP-ATP exchange activities survive and remain ouabain-sensitive. Because the enzyme preparations consist largely of pure (Na+,K+)-ATPase, these effects of digitonin must be intrinsic to the Na+ pump. 2. Concomitant with these enzymatic changes, digitonin treatment alters the sensitivity of the phosphatase and exchange activities to ouabain. 3. Attempts to measure ouabain binding by the usual centrifugation or filtration methods proved unsuccessful. A filtration method involving a double 0.01 mum filter and omitting water washes is necessary to demonstrate ouabain binding. Under these conditions, ouabain binding capacity appears to be unchanged in the presence of digitonin, but the apparent dissociation constant is doubled. 4. Ouabain binding is rendered more reversible by digitonin treatment, since washing filters with water removes a large fraction of bound ouabain without affecting the retention of exchange activity. 5. The double filter method traps essentially all of the ADP-ATP exchange activity on the filter. However, a large and somewhat variable proportion of the K+-phosphatase activity passes through the filter. Sodium dodecyl sulfate polyacrylamide gel analysis of the filtrate shows that a small amount of filtrable protein catalyzed this phosphatase activity at greatly increased turnover rates. Both subunits of the (Na+, K+)-ATPase are present in this latter protein fraction.     

Flagellar ultrastructure and flagella-associated antigens of Campylobacter fetus.

Ultrastructural examinations of the flagellum of Compylobacter (Vibrio) fetus were performed throughout the growth cycle. Filament diameters, exceeding 17.6 nm during the exponential phase, were substantially greater than those reported for unsheathed flagella of other genera with the exception of Pseudomonas fluorescens. Filament diameters increased during growth, reaching a mean width of 21.2 nm in middle to late stationary phase. Internal flagellar structure, principally of the parallel lined variety, was observed during the later periods of growth but not during exponential or early stationary phase. Despite the unusually large filament sizes, no evidence of a flagellar sheath was observed after selected treatments (0.01 N HCl, 6 M urea, tris(hydroxymethyl) amino-methane-hydrochloride buffer, warm water) or examination of thin sections. To determine whether alterations in filament size and variable ability to demonstrate filament fine structure were correlated with progressive changes in serological activity, agglutination and immobilization tests were conducted with antisera directed against intact flagella, the principal flagellar antigen, the O antigen, and a superficial glycoprotein which has been found in association with the flagellum and the cell envelope. Significant differences in the serological activity of cells at different growth intervals were not noted with any of the sera employed.     

The effect of α-N-substituted histidine derivatives on bimolecular lipid membranes as related to their ability to uncouple oxidative phosphorylation

A series of α-N-alkyl and α-N-aryl histidines was synthesized. Several of the more lipophilic derivatives were shown to be uncouplers of oxidative phosphorylation. A direct relationship was noted for the α-N-alkyl series between carbon chain length on the α-nitrogen of histidine, organic/water partition coefficient, efflux rate from liposomes, ability to lower electrical resistance of bimolecular lipid membranes, ability to increase respiration in coupled mitochondria, and ability to lower P/O ratios in coupled mitochondria. The aromatic derivative α-N-salicyl histidine was the best uncoupler in the series but was still not as effective an uncoupler as 2,4-dinitrophenol.     

Engineering enzymes

Could we design and construct enzymes to catalyse any desired reaction? Compared with organic chemical catalysts, enzymes are highly specific and work in dilute aqueous solutions at ambient temperatures. Substrates are brought together from solution to precise orientations in the active site of an enzyme and the amino acid side-chains of the enzyme may assist catalysis by attacking or destabilizing substrate bonds. In principle, a novel enzyme could be constructed de novo or from pre-existing enzymes. Altering enzymes by recombinant DNA techniques offers most chance of success.     

Obstacle Avoidance,Visual Detection Performance,and Eye-Scanning Behavior of Glaucoma Patients in a Driving Simulator: A Preliminary Study

The objective of this study was to evaluate differences in driving performance, visual detection performance, and eye-scanning behavior between glaucoma patients and control participants without glaucoma. Glaucoma patients (n = 23) and control participants (n = 12) completed four 5-min driving sessions in a simulator. The participants were instructed to maintain the car in the right lane of a two-lane highway while their speed was automatically maintained at 100 km/h. Additional tasks per session were: Session 1: none, Session 2: verbalization of projected letters, Session 3: avoidance of static obstacles, and Session 4: combined letter verbalization and avoidance of static obstacles. Eye-scanning behavior was recorded with an eye-tracker. Results showed no statistically significant differences between patients and control participants for lane keeping, obstacle avoidance, and eye-scanning behavior. Steering activity, number of missed letters, and letter reaction time were significantly higher for glaucoma patients than for control participants. In conclusion, glaucoma patients were able to avoid objects and maintain a nominal lane keeping performance, but applied more steering input than control participants, and were more likely than control participants to miss peripherally projected stimuli. The eye-tracking results suggest that glaucoma patients did not use extra visual search to compensate for their visual field loss. Limitations of the study, such as small sample size, are discussed.