Randomised trial of prophylactic daily aspirin in British male doctors

A six year randomised trial was conducted among 5139 apparently healthy male doctors to see whether 500 mg aspirin daily would reduce the incidence of and mortality from stroke, myocardial infarction, or other vascular conditions. Though total mortality was 10% lower in the treated than control group, this difference was not statistically significant and chiefly involved diseases other than stroke or myocardial infarction. Likewise, there was no significant difference in the incidence of non-fatal myocardial infarction or stroke—indeed, disabling strokes were somewhat commoner among those allocated aspirin. The lower confidence limit for the effect of aspirin on non-fatal stroke or myocardial infarction, however, was a substantial 25% reduction. Migraine and certain types of musculoskeletal pain were reported significantly less often in the treated than control group, but as the control group was not given a placebo the relevance of these findings was difficult to assess. There was no apparent reduction in the incidence of cataract in the treated group.The lack of any apparent reduction in disabling stroke or vascular death contrasts with the established value of antiplatelet treatment after occlusive vascular disease.     

Influence of Storage at Freezing and Subsequent Refrigeration Temperatures on β-Galactosidase Activity of Lactobacillus acidophilus

The ability of three strains of Lactobacillus acidophilus to survive and retain β-galactosidase activity during storage in liquid nitrogen at −196°C and during subsequent storage in milk at 5°C was tested. The level of β-galactosidase activity varied among the three strains (0.048 to 0.177 U/10⁷ organisms). Freezing and storage at −196°C had much less adverse influence on viability and activity of the enzyme than did storage in milk at 5°C. The strains varied in the extent of the losses of viability and β-galactosidase activity during both types of storage. There was not a significant interaction between storage at −196°C and subsequent storage at 5°C. The strains that exhibited the greatest losses of β-galactosidase activity during storage in milk at 5°C also exhibited the greatest losses in viability at 5°C. However, the losses in viability were of much greater magnitude than were the losses of enzymatic activity. This indicates that some cells of L. acidophilus which failed to form colonies on the enumeration medium still possessed β-galactosidase activity. Cultures of L. acidophilus to be used as dietary adjuncts to improve lactose utilization in humans should be carefully selected to ensure that adequate β-galactosidase activity is provided.     

Structure of phosphate-free ribonuclease A refined at 1.26 A

The structure of phosphate-free bovine ribonuclease A has been refined at 1.26-A resolution by a restrained least-squares procedure to a final R factor of 0.15. X-ray diffraction data were collected with an electronic position-sensitive detector. The final model consists of all atoms in the polypeptide chain including hydrogens, 188 water sites with full or partial occupancy, and a single molecule of 2-methyl-2-propanol. Thirteen side chains were modeled with two alternate conformations. Major changes to the active site include the addition of two waters in the phosphate-binding pocket, disordering of Gln-11, and tilting of the imidazole ring of His-119. The structure of the protein and of the associated solvent was extensively compared with three other high-resolution, refined structures of this enzyme.     

Multiple conformations of amino acid residues in ribonuclease A

The highly refined 1.26 A structure (R = 0.15) of phosphate-free bovine pancreatic ribonuclease A was modeled with 13 residues having discrete multiple conformations of side chains. These residues are widely distributed over the protein surface, but only one of them, Lys 61, is involved in crystal packing interactions. The discrete conformers have no unusual torsion angles, and their interactions with the solvent and with other atoms of the protein are similar to those residues modeled with a single conformation. For three of the residues--Val 43, Asp 83, and Arg 85--two correlated conformations are found. The observed multiple conformations on the protein surfaces will be of significance in analyzing structure-function relationships and in performing protein engineering.     

Characterization of Growth Stimulants in Corn Steep for Lactic Streptococci

The production of acid in milk cultures of lactic streptococci was stimulated by the addition of corn steep liquor. Separation by ion-exchange and paper chromatography indicated the presence of four major stimulatory components in the corn steep. Some variation was noted in the response of the lactic streptococci to the individual stimulatory components. The four components were further purified by paper and column chromatography. One of the four stimulatory components stained positively on chromatograms with ninhydrin. The remaining stimulatory components were detectable only by bioautography. All four components were unstable to acid hydrolysis and absorbed ultraviolet light between 230 and 275 nm in aqueous solution. The stimulatory components did not contain pentoses, suggesting that they were not nucleotides or nucleosides; however, they might be purine or pyrimidine bases.     

Biological response of lactic streptococci and lactobacilli to catalase

Addition of catalase to milk cultures of lactic streptococci resulted in increased rates of acid production, although it had no effect on cultures of lactobacilli. Milk cultures of both streptococci and lactobacilli produced detectable amounts of peroxide, which reached a maximum level in the early period of acid production followed by a drastic decrease as the acid production increased. Pyruvate and reduced glutathione decreased the amount of peroxide formed, but had little effect on acid production by the streptococci. Ferrous sulfate prevented the accumulation of peroxide and stimulated the rate of acid production by the streptococci to a greater extent than did catalase.     

Preparation of concentrated lactic streptococcus starters

Single-strain cultures of Streptococcus cremoris were grown in a semisynthetic medium with automatic pH control. After centrifugation, the cells were resuspended in sterile nonfat milk (2% of the original volume). There was no significant difference in the maximum population attained when cultures were grown at pH values of 5.5, 6.0, or 6.5 with sodium hydroxide as the neutralizer. With ammonium hydroxide as the neutralizer, maximum populations obtained were increased about twofold. In most cases, the acid-producing ability of the culture concentrates was comparable to that of fresh-milk cultures. There was some variation among strains of S. cremoris with respect to the effects of different neutralizers and levels of pH control on the biological activity of the culture concentrates. The culture concentrates were stored in liquid nitrogen for as long as 231 days without significant loss in biological activity.