The catalytic bimodality of mammalian phosphoglycerate mutase

Rabbit muscle phosphoglycerate mutase, presumed to manifest an absolute cofactor requirement for activity, has been found to express catalysis (3 +/- 1% of optimum) in the absence of added D-glycerate-2,3-P2. Isotope experiments indicate that this catalysis proceeds through a binary phosphoryl enzyme-glycerate intermediate which dissociates into free enzyme and monophosphoglycerate. 32P-Labeled phosphoglycerate mutase is formed by reaction with either D-32P-glycerate-3-P or D-U32P-glycerate-2,3-P2. In each case, the acid lability and alkali stability of the covalent adduct, phosphoenzyme, is consistent with a phosphohistidyl residue having been formed within the active site. D-[U-14C]Glycerate reacts with phosphoenzyme to generate D-[U-14C]monophosphoglycerate which, in turn, can react further with phosphoenzyme to yield D-[U-14C]glycerate-2,3-P2. The pH profile for the cofactor-independent activity exhibits an optimum at 6.0 as opposed to 7.0 when D-glycerate-2,3-P2 is present in the reaction medium. Bisubstrate kinetics (pH 7.0, 23 degrees C) with D-glycerate-3-P concentration as the variable, yields a family of reciprocal plots which is in accord with a modified ping-pong mechanism when D-glycerate-2,3-P2 concentrations are greater than 10(-1) Km (where Km = 0.33 microM). Progressively diminishing concentrations (much less than Km) of D-glycerate-2,3-P2 produce curvilinear reciprocal plots that approach linearity as a limit in accordance with single substrate kinetics.     

The phylogeny of the hominoid primates: a statistical analysis of the DNA-DNA hybridization data

Sibley and Ahlquist compared the single-copy nuclear DNA sequences of the hominoid primates using DNA-DNA hybridization. From this data set they estimated a phylogeny that clusters man and chimpanzees using a distance Wagner procedure. However, no assessment of statistical confidence in this estimated phylogeny was made, despite the fact that their data set contains internal inconsistencies concerning the correct branching order. This paper presents a modification of Pielou's Q- statistic that allows one to make nonparametric tests of phylogenetic relationship from distance data. The results of this analysis indicate that the estimated phylogeny of Sibley and Ahlquist is without statistical significance owing to the internal inconsistencies of the data set. A survey and additional analyses of other types of molecular data indicate that the phylogeny that clusters chimpanzees and gorillas and has the human lineage splitting off earlier is statistically consistent with all the molecular data (including the DNA-DNA hybridization data), whereas the phylogeny estimated by Sibley and Ahlquist can be rejected at the 5% level using the data on restriction- endonuclease sites in the mitochondrial genome.      

Circulating immunologic complexes in blood sera of bronchial asthma patients treated with attenuated vaccine

The study included 20 patients (8 males and 12 females) with non-atopic bronchial asthma treated with attenuated vaccines. Circulating immune complexes were assayed with two methods prior to and after the treatment of each patient. No increase in serum circulating immune complexes was produced after the treatment. Clinical improvement was noted in 75% of treated patients. Circulating immune complexes were detected in the blood serum of three patients treated without an effect.     

Lack of correlation between in vitro and in vivo activation of complement in mice by infective Trichinella spiralis larvae

Very little is known about the role played by complement in vivo during Trichinella spiralis infections, although previous reports indicate that it binds readily to the surfaces of muscle stages of the parasite in vitro. In order to study the binding of complement to muscle-stage larvae in vivo, larvae were recovered from BALB-c inbred, NFR/N inbred, and Swiss white outbred mice from 20 to 95 days postinfection. The presence of C3 was examined by direct immunofluorescence and leucocyte- and erythrocyte-adherence tests. Complement was found on a few larvae from the outbred strain and only rarely on larvae from the 2 inbred strains. Histological sections prepared from inbred strains and used in immunofluorescence tests to study in situ complement activation and binding were negative. Larvae from all 3 mouse strains bound complement 100% of the time when it was added to the worms in vitro. The results indicate that extrapolation from in vitro to in vivo activation and binding of complement to T. spiralis larvae may not be valid.     

Interactions ofCandida albicans with bacteria and salivary molecules in oral biofilms

The yeastCandida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells.C. albicans andCandida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind toStreptococcus gordonii NCTC 7869 while two otherCandida species (Candida krusei andCandida kefyr) do not. Adherence ofC. albicans was greatest when the yeast had been grown at 30° C to mid-exponential growth phase. For 21 strains ofC. albicans there was a positive correlation between the ability to adhere toS. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence ofC. albicans toS. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins ofC. albicans are co-expressed.     

Effect of oxafun on the antibiosis between Bacillus subtilis and Phoma betae

The fungicide oxafun decreased the production of antibiotic substances active against Phoma betae, by Bacillus subtillis. This was confirmed by reduced effectiveness of antibiotic substances against Phoma infection in micropot experiment. Besides, the bacterial metabolites effected cell membrane permeability of mycelium and resulted in some relationships of fungicide and antibiotic substances.     

Monoclonal antibodies to rabbit liver cytochrome P-448

Cytochrome P-448 (mol wt 55,000 Daltons) from rabbit liver was purified to a specific content of 16.6 nmol/mg. Mice were immunised with this preparation, their spleens removed and dissociated lymphocytes hybridised with myeloma cells. Four monoclonal antibodies against cytochrome P-448 were raised and partially characterised. All four antibodies interacted with cytochrome P-448 in intact microsomal fractions and selectively immunoadsorbed cytochrome P-448 from solubilised microsomal preparations. One of the antibodies inhibited benzo[a] pyrene hydroxylase activity in a reconstituted system, one had no effect on activity and two increased activity. The possible applications of such antibodies are discussed.     

Selective enrichment of Shigella in the presence of Escherichia coli by use of 4-chloro-2-cyclopentylphenyl beta-D-galactopyranoside.

A procedure involving the use of citrate-buffered lactose broth (pH 6.5) containing an analogue of a beta-galactoside (4-chloro-2-cyclopentylphenyl beta-D-galactopyranoside) has been developed for the enrichment of Shigella in competition with a 100-fold higher population of Escherichia coli. The system makes use of the beta-galactosidase activity of E. coli which hydrolyzes the phenolic derivative of beta-galactoside to galactose and an aglycone moiety (4-chloro-2-cyclopentylphenol) which is toxic to E. coli but is tolerated by Shigella. The procedure is particularly effective in the enrichment of S. sonnei and S. flexneri; S. dynsenteriae and S. boydii are enriched to a lesser extent.