Inhibition of the transthylakoid gradient of electrochemical proton potential by the local anesthetic dibucaine

The effects of the local anesthetic dibucaine on coupling between electron transport and ATP synthesis-hydrolysis by the coupling-factor complex (CF₀CF₁ ATPase) were investigated in thylakoid membranes from Spinacia oleracea L. cv. Monatol. Evidence is presented that inhibition of ATP synthesis was produced by a specific uncoupling mechanism which was based on dibucaine-membrane surface interactions rather than on the interaction of dibucaine with the ATPase complex. Dibucaine reduced the osmotic space of thylakoid vesicles. At low pH of the medium it stimulated ATP hydrolysis beyond the rates obtained with optimum concentrations of ‘classical’ uncouplers. After addition of dibucaine, there was displacement of membrane-bound Mg²⁺ and strong thylakoid stacking in the presence of only low Mg²⁺ concentrations. Inhibition of ATP synthesis and transmembrane pH gradient increased with medium pH. Hydrolysis of ATP by isolated CF₁ and the CF₀CF₁ complex was only slightly affected by dibucaine. The data are discussed assuming the involvement of localized proton channels on the membrane surface in protonic coupling of electron transport and ATP synthesis. A hypothesis for the mechanisms of action of local anesthetics at the thylakoid membrane is presented.     

Comparison of diagnostic methods for detection of low infestation levels ofVarroa jacobsoni in honey-bee (Apis mellifera) colonies

Thirty-five honey-bee colonies, originally free fromVarroa jacobsoni (Oudemans) were monitored approximately every third week for the presence of the mite during 16 months following an initial introduction of five to eight adultVarroa females in early July. Investigations of hive debris detected the presence ofV. jacobsoni in 22 colonies (63%) within three months of the mite introduction. During the first winter period (October–April), mites were found in the hive debris of 13 colonies (37%). In terms of detectingVarroa during the summer in colonies with sealed brood, investigations of hive debris were more effective than sampling of brood. Brood sampling was more effective than sampling of live bees. In colonies without sealed brood, investigations of hive debris or of live bee samples seemed approximately equally efficient. The highest correlation between sampling methods was found between daily mite downfall and mites per live bee (r=0.81) in colonies with sealed brood. During the winter, investigations of dead bees and hive debris were approximately equally efficient in detectingVarroa.     

Extracellular Overflow of Neuroactive Amino Acids During Severe Insulin-Induced Hypoglycemia: In Vivo Dialysis of the Rat Hippocampus

Hypoglycemia-evoked changes in levels of extracellular excitatory and inhibitory amino acids were studied using the microdialysis technique. A newly designed dialysis probe was inserted stereotaxically into the rat hippocampus. Animals were then subjected to insulin-induced hypoglycemia; then blood glucose levels were restored by glucose injections after a 30-min period of isoelectric electroencephalography. Dialysates were collected before, during, and after the isoelectric period. Amino acids in the dialysates were analyzed by liquid chromatography and fluorescence detection following automatic precolumn derivatization with o-phthaldialdehyde. During the isoelectric phase, the concentration of aspartate increased 15-fold, whereas glutamate, gamma-amino-butyric acid, taurine, and phosphoethanolamine levels were elevated three- to sixfold. Smaller increases were observed for nonneuroactive amino acids such as asparagine, alanine, and phenylalanine. In contrast to all other amino acids, the glutamine content was reduced to less than 30% of preisoelectric values. The concentrations of the neuroactive amino acids were restored to normal in the post-isoelectric phase. These data demonstrate that there is an extracellular overflow of neuroactive amino acids, especially aspartate, during severe hypoglycemia.     

Evolution of catalytic proteins

Summary It is believed that all present-day organisms descended from a common cellular ancestor. Such a cell must have evolved from more primitive and simpler precursors, but neither their organization nor the route such evolution took are accessible to the molecular techniques available today. We propose a mechanism, based on functional properties of enzymes and the kinetics of growth, which allows us to reconstruct the general course of early enzyme evolution. A precursor cell containing very few multifunctional enzymes with low catalytic activities is shown to lead inevitably to descendants with a large number of differentiated monofunctional enzymes with high turnover numbers. Mutation and natural selection for faster growth are shown to be the only conditions necessary for such a change to have occurred.     

The Electrical Conductivity of Bovine Milk in Mastitis Diagnosis

The electrical conductivity (EC) of milk is mainly a function of the electrolyte concentration in the milk and therefore raised in mastitis. The present investigation was aimed at elaborating, if possible, a diagnostic model for screening purposes based on EC determinations and consistent with the diagnostic procedures and interpretations commonly used in laboratory milk diagnosis in the Nordic countries (Klastrup 1975). According to this diagnosis (here called reference diagnosis) cell numbers above 300,000/ml (cell count or the corresponding CMT-score) in foremilk quarter samples during the main part of the lactation period and significantly above the lowest value on within-udder comparison during late lactation are considered indicative of mastitis and bacteriological examinations are made when called for.     

Distichia acicularis sp. nov. – a new cushion forming Juncaceae from the high Andes of Ecuador

Distichia acicularis is described as a new species of Juncaceae. It occurs in the high Andes of Ecuador between 3200 m and 4200 m above sea level. Its closest relative is D. muscoides Nees & Meyen from which it is distinct through its narrow, linear, mucronate leafblades and its 1–3 mm long auricles at the junction of the leafsheath to the blade.     

Stability of solvent formation in Clostridium acetobutylicum during repeated subculturing

Summary Clostridium acetobutylicum ATCC 824 was submitted to repeated subculturing at 24-hour intervals for 218 days. The organism retained its ability to form solvents, although the fermentation slowly became increasingly acidogenic during the first 200 days. Except for the initial spore inoculum, the cultures were not subjected to heat shocking between the serial transfers. When the inoculum volume was doubled from 3.3% to 6.7% after 200 days of subculturing, the product formation pattern quickly shifted back from acids to primarily butanol. Acetone production also resumed after being undetectable for more than 50 days. The relative formation of acetate and ethanol remained nearly constant throughout the experiments, while the formation of butyrate mirrored that of butanol.     

Die Chaetophoralen der Binnengewässer

Ohne Zusammenfassung     

Virulence of Salmonella enteritidis phage type 4 is related to the possession of a 38 MDa plasmid

Nine strains of Salmonella enteritidis phage type 4 were examined for virulence in BALB/c mice. The possession of a 38 MDa plasmid was necessary for full virulence. Strains carrying this plasmid had LD50 values of less than 20 bacteria whilst plasmid-free strains had LD50 values of greater than 10(6) bacteria when challenged intraperitoneally. Pathogenesis of disease involved the widespread distribution of bacteria throughout the tissues. Possession of the 38 MDa plasmid could not be linked with the ability of strains to express novel outer membrane proteins, to produce toxins affecting Vero, Y1, HeLa, Henle or HEp-2 cells, or to invade HEp-2 cells. Furthermore, the 38 MDa plasmid did not encode an aerobactin-mediated iron uptake system or the production of a haemolysin. Strains of S. enteritidis PT4 isolated in 1967, 1978 or 1979 and possessing the 38 MDa plasmid showed the same virulence properties as the current plasmid-carrying strains. This suggests that the enhanced virulence of the current strains for poultry is unlikely to be the result of changes in the 38 MDa plasmid.