Volatilization of mercury byThiobacillus ferrooxidans

Thiobacillus ferrooxidans became significantly more tolerant to mercury stress after culturing in media of increasing mercury(II) concentrations. When mercuric chloride was added to the growth medium, the resistant organisms were found to volatilize elemental mercury (Hg⁰).T. ferrooxidans may be an important factor in the natural mercury cycle, since the environments whereT. ferrooxidans is found typically contain elevated levels of heavy metals, including mercury.     

High biological activity of the synthetic replicates of somatostatin-28 and somatostatin-25

We have isolated form extracts of ovine hypothalami two molecules characterized as somatostatin-28 and somatostatin-4-28 (referred to as somatostatin-25). They were reproduced by solid hase synthesis. In equimolar ratio and depending upon the experimental conditions, synthetic somatostatin-28 ans somatostatin-25 are 3-14 times more potent than somatostatin-14 to inhibit the basal in vitro secretion of growth hormone or as stimulated by prostaglandin (PGE2). In early studies in vivo, somatostatin-28 and somatostatin-25 are also more potent than somatostatin-14 in inhibiting the secretion of growth hormone acutely stimulated in the rat by injection of morphine; somatostatin-28 is also longer-acting than somatostatin-14. These results suggest that somatostatin-14, as originally isolated, is a biologically active fragment of a larger molecule of greater specific activity; it should be considered as another form of somatostatin with high biological activity present in some tissues and likely secreted y the tissues along with somatostatin-14 and possibly other somatostatin-peptides of diverse sizes.     

Experiments on the abiotic amplification of optical activity

Our earlier experiments are briefly reviewed, involving the abiotic generation of optical activity by exposure of DL-amino acids to various chiral physical forces. The enantiomeric enrichments so obtained were low, however, and additional experiments were undertaken with the objective of abiotically enhancing such small enantiomeric excesses. DL Mixtures of leucine N-carboxy anhydride gave enantiomerically enriched polymers on partial polymerization, while valine NCA mixtures behaved oppositely. Leucine polymers were also found to hydrolyze stereoselectively, providing for additional enantiomenic enhancement. A repetitive sequence of partial polymerization-hydrolysis steps is suggested as a possible mechanism for the abiotic genesis of optically enriched polypeptides on the primitive Earth.     

Pubertal age,weight, and weight gain in the individual female new world monkey (Cebus albifrons)

From February 1972 to August 1974 ten immatureCebus albifrons monkeys were weighed and vaginal swabbing performed at monthly or shorter intervals to determine age and weight at the onset of puberty. The average weight (±S.E.M.) at birth and at puberty was 226±5.8 g and 1,617±32.45 g, respectively. The average age at puberty was 3.59±0.17 years. The average weight velocity for all ten monkeys shows the maximum rate of weight gain to occur shortly after birth and decrease rapidly to its smallest prepubertal increment at nine months of age (weaning). From nine months there is a post-weaning weight spurt which reaches its greatest velocity at an average age of 15 months. Thereafter, the weight velocity decreases to its lowest level. Individual weight velocity curves of each of the ten animals show a slight prepubertal weight spurt which is not obvious in the average growth curve.     

Application of CNDO2 theoretical calculations to interpretation of the chemical reactivity and biological activity of the syn and anti diolepoxides of benzo[a]pyrene

$\text{CNDO}\text{2}$ molecular orbital theoretical calculations performed on the anti and syn diolepoxides (1 and 2) of the potent carcinogen benzo[a]pyrene provide insight into the molecular structure and reactivity of these mutagenic and carcinogenic hydrocarbon metabolites. Hydrogen-bonded interaction between the 7-HO proton and the epoxide oxygen atom of 2 is shown to be absent in the normal semichair conformation of the tetrahydro ring, (H…O bond distance = 2.7 Å), but is energetically favored in a somewhat distorted puckered structure (H…O bond distance = 1.7 Å). Unexpectedly, internal H-bonding alters the relative electron density at C₉ and C₁₀, leading to prediction of the former as the more electrophilic center. Since all reactions of 2 take place exclusively at C₁₀, transannular H-bonding is concluded not to contribute significantly to the structure of 2. Diolepoxide reactions with both weak and strong nucleophiles and with DNA are discussed and the mechanisms interpreted in terms of molecular structure as determined by the theoretical calculations.     

Cytotoxic T lymphocytes in DBA/2 mice harboring L5178Y cells in a tumor-dormant state

Previous experiments have demonstrated a temporal relationship between the decline of cytotoxic T lymphocyte (CTL) activity in the peritoneal cavity of DBA/2 mice harboring L5178Y cells in a tumor-dormant state and the appearance of ascitic tumors. Some tumor-dormant mice remain clinically normal for many weeks after the decline of CTL activity, and this activity can be rapidly restimulated by an IP inoculation of irradiated L5178Y cells. We report here that the peritoneal cells from many tumor-dormant mice can be stimulated to cytolytic activity in vitro when cultured for 4 days either with or without the addition of irradiated L5178Y cells. Peritoneal cell populations which cannot be stimulated in vitro can suppress the generation of CTL in those populations which can be stimulated. The tumor-dormant state may terminate when suppressor cells in the peritoneal cavity of tumor-dormant mice inhibit the generation of CTL activity and permit tumor cells to produce an ascitic tumor.