Dietary practices,site-specific tumors,and age-at-death relationships

When rats are given freedom of dietary choice, the quantity and composition of the diet selected varies from animal to animal, but the risk to the individual of developing a variety of neoplasms is greatly increased over that of rats fed fixed diets. The increase in frequency of tumors cannot be explained on the basis of the amount or the composition of the diet selected. However, the application of “variable selection” statistical procedures shows that there are combinations of temporal-specific interacting dietary and dietary-dependent variables that are closely linked with cancer mortality. The multi-variable statistical model for animals dying with one type of tumor is not applicable to those dying with tumors of other types or sites. In every case, the only data required to characterize the dates of death of tumor-bearing individuals are those describing the dietary practices and growth responses prior to maturity. The model for animals with pancreatic tumors is used to illustrate the extent to which dietary practices of early life are linked with the animals’ survival.     

Some evidence of the enzymatic conversion of bovine suppressor phosphoseryl-tRNA to selenocysteyl-tRNA

In order to clarify the mechanisms of selenocysteine incorporation into glutathione peroxidase, some evidence to show the in vitro conversion of phosphoseryl-tRNA to selenocysteyl-tRNA is reported. [³H]Phosphoseryl-tRNA was incubated in a reaction mixture composed of SeO₂, glutathione and NADPH in the presence of selenium-transferase partially purified. Analyses of amino acids on the product tRNA showed that a part (4%) of [³H]phosphoseryl-tRNA was changed to [³H]selenocysteyl-tRNA. The conversion from seryl-tRNA^su or major seryl-tRNA_IGA was not found. Selenium-transferase was essential for the conversion. [³H]Selenocysteine, liberated from the tRNA, was modified with iodoacetic acid. The product was confirmed to be carboxymethyl-selenocysteine by two-dimensional TLC. Selenocysteyl-tRNA^su should be used to synthesize glutathione peroxidase by co-translational mechanisms.     

Some effects of fructose-1,6-diphosphate on rat myocardial tissue related to a membrane-stabilizing action

This study aims at elucidating the mechanism of action of extracellular fructose-1,6-diphosphate (FDP). FDP is able to inhibit Ca++ entry into the myocardial tissue with an IC50 value of 11.5 mM and in addition, it is bound by rat heart slices, the binding being activated by Zn and conditions of chemical hypoxia induced by KCN and iodoacetate. The overall effect of extracellular FDP includes an increase of frequency and amplitude of contraction of perfused heart at concentration below 1 mM, and, in general, a stimulation of the oxygen consumption of the tissue. The antihaemolytic effect of FDP suggests its action as a membrane stabilizer. The effects of extracellular FDP on the myocardial cell can be interpreted both on the basis of a limited permeability of the cell membrane to it and as a purely extracellular effect transduced through the cell membrane with a final response consisting of an increase in the intracellular FDP.     

Geographic variation of flavonoids in Phlox carolina

Non-anthocyanin flavonoid expression was determined among 64 continuous range and nine disjunct range populations of Phlox carolina. The species contains four flavone nuclei and a total of 25 derivatives, most of which are $\text{C-}\text{glycosides}$. Nearly all populations express unique flavone patterns. Using a qualitative similarity index of minimum biosynthetic step distance (MBSD), the average population contains only ca. 50% of the overall substitutional diversity. The separate ranges are distinctive in the % occurrence of most compounds but only weakly divergent in comparative mean MBSD. Proximity and MBSD are significantly correlated overall but local variability is extensive and no discrete racism is apparent. Within the continuous range 18 compounds are distributed in independent but overlapping gradients and 13 of these extend consistently through the disjunct range. The patch-work continuum of flavone variation is the apparent consequence of dissection and contraction of a historically more widespread distribution. Other general aspects of the variation patterns are discussed.     

Highly enantioselective kinetic resolution of trans-2-(phenylthio)cyclohexanol derivatives by immobilized Candida antartica B lipase

Candida antartica B (immobilized CAL-B) mediated resolutions of trans-2-(phenylthio)cyclohexanol derivatives using vinyl acetate as acylating agent and MTBE as solvent provide excellent enantioselectivity (up to >99%) and high yield of both the enantiomers in short reaction time.     

Investigations of the possible role of proteases in altering surface proteins of virally transformed hamster fibroblasts

Virally transformed fibroblasts have on their surfaces zero or reduced amounts of a large external transformation-sensitive (LETS) glycoprotein. This protein is extremely sensitive to proteolysis. When prelabeled normal fibroblasts are cocultivated with transformed cells, the LETS glycoprotein of the normal cells shows an increased rate of turnover. Experiments are described which investigate the possibility that this phenomenon and the absence of LETS glycoprotein are due to proteolysis by the transformed cells. In particular, the role of plasminogen activation is examined by the use of protease inhibitors and plasminogen-depleted serum. It is concluded that activation of plasminogen is not required for the disappearance of the LETS glycoprotein although the involvement of other proteases cannot be ruled out. The role of proteases in affecting cell growth and behavior is discussed.     

Thermodynamic investigations of proteins. I. Standard functions for proteins with lysozyme as an example.

A direct method is proposed for obtaining thermodynamic standard functions for native and denatured proteins using experimental data from scanning calorimetry, isothermal calorimetry and potentiometric titrations. The possibility of this approach is demonstrated on the example of lysozyme in the range of pH 1.5-7.0 and temperature 0-100 degrees C. Tests for the validity of the obtained functions of enthalpy and entropy are presented in the form of cyclic processes using experimental data obtained from thermodynamically different pathways. The Gibbs function is checked by comparison with results of an independent method. The methodic problems in determining and checking standard functions for proteins are discussed in detail.