Changes in nucleic acid metabolism in barley seedlings during vernalization

Changes in nucleic acid metabolism of barley seedlings duringvernalization were investigated using thymidine-³H and uridine-³H. DNA content increased in the early germination stage from the1st to 3rd week in vernalized seedlings. In unvernalized seedlings,the most rapid increase was found in the late germination stage.RNA content in the vernalized seedlings increased after 1 weekand reached maximum level after 3 weeks of vernalization treatment.The unvernalized seedlings had a comparatively high contentat 2 days' germination which then gradually increased. Much thymidine-³H was incorporated into DNA and uridine-³H intoRNA fractions in the seedlings during early vernalization. Onthe contrary, without vernalization, heavy incorporation ofthymidine-³H was delayed during the late germination stage.Incorporation of uridine-³H showed a linear increase. A more detailed distribution of thymidine-³H and uridine-³Hin the nucleic acids was examined by methylated albumin-coatedkieselguhr column chromatography. A considerable amount of theincorporated uridine-³H was found in the tenaciouslybound ribonucleicacid (TB-RNA) in the vernalized seedlings. (Received January 18, 1973; )     

Suppression of nucleic acid synthesis in mitochondrial and chloroplast fractions of Spirogyra during conjugation process

RNA- and DNA-synthesizing activities were much lower in conjugatingand zygote cells than in vegetatively growing cells. We suggestthat a certain factor(s) which may repress RNA and DNA Syntheseswas formed during the conjugation process. (Received December 24, 1971; )     

Changes in the nucleic acid and protein content of the Japanese quail during postnatal development

A study of growth activity in the Japanese quail showed the rate of growth to be the highest, in both sexes, between the ages of 5 and 20 days. Positive allometry was manifested in skeletal muscle development, negative allometry or isometry in the case of the liver and heart. The protein/P DNA ratio rose progressively with age in all the given tissues and attained the maximum prior to sexual maturation. The P RNA/P DNA ratio rose markedly in all the tissues after only a few days and remained high throughout the whole period of development. Growth dynamics in the both sexes followed the same course; the only exception were proteosynthesis indicators, which attained higher values in females, in correlation to their greater body weight.     

Changes in protein synthesis and morphology during acid adaptation of Propionibacterium freudenreichii

Survival of bacteria in changing environments depends on their ability to adapt to abiotic stresses. Microorganisms used in food technology face acid stress during fermentation processes. Similarly, probiotic bacteria have to survive acid stress imposed within the stomach in order to reach the intestine and play a beneficial role. Propionibacteria are used both as cheese starters and as probiotics in human alimentation. Adaptation to low pH thus constitutes a limit to their efficacy. Acid stress adaptation in the probiotic SI41 strain of Propionibacterium freudenreichii was therefore investigated. The acid tolerance response (ATR) was evidenced in a chemically defined medium. Transient exposure to pH 5 afforded protection toward acid challenge at pH 2. Protein neosynthesis was shown to be required for optimal ATR, since chloramphenicol reduced the acquired acid tolerance. Important changes in genetic expression were observed with two-dimensional electrophoresis during adaptation. Among the up-regulated polypeptides, a biotin carboxyl carrier protein and enzymes involved in DNA synthesis and repair were identified during the early stress response, while the universal chaperonins GroEL and GroES corresponded to a later response. The beneficial effect of ATR was evident at both the physiological and morphological levels. This study constitutes a first step toward understanding the very efficient ATR described in P. freudenreichii.     

Changes in the EEL intestine during seawater adaptation

• 1.1. Rate of fluid absorption by eel (Anguilla rostrata) intestinal sacs in vitro reached seawater adapted values 3 days after transfer from freshwater to seawater.
• 2.2. After 3 days in seawater oxygen consumption and Na-K-ATPase activity of intestinal mucosa had not increased over freshwater values.
• 3.3. The weight of intestinal mucosa increased 32% during seawater adaptation as a result of an increase in the number of mucosal cells (hyperplasia).
• 4.4. The rate of intestinal fluid absorption was reduced by 10⁻⁴ M ouabain and was not affected by 10⁻⁴ M acetazolamide.

     

Stability of division-related protein and nucleic acid fractions in synchronized Tetrahymena

The kinetics of RNA synthesis have been studied under various growth conditions using synchronized Tetrahymena pyriformis GL. The curves obtained are approximately linear in growth-supporting media but vary under other circumstances. The presence of amino acids in the medium stimulates RNA synthesis in Tetrahymena as it does in bacteria. Since these induced variations do not influence the essential features of the pre-cytokinetic period it is inferred that fluctuations in the rate of RNA synthesis described by others are probably not essential features of temperature-induced synchrony. In addition, the translational stability of division-related templates at synchronizing temperatures has been investigated. The synthesis of proteins necessary for cytokinesis is shown to be greatly reduced under conditions simulating a heat-shock. Inhibitor studies using cycloheximide indicate that protein synthesis is required longer into the cytokinetic phase than had previously been thought. Collectively the data are all compatible with the hypothesis that synthesis of division-related proteins is drastically reduced in heat-shocked Tetrahymena and that the basis for this reduction is hydrolysis of template RNA without concurrent translation.     

Changes in nucleic acid and protein synthesis during starvation and spherule formation inPhysarum polycephalum

Summary The synthesis of protein and nucleic acids was studied by isotope incorporation and dilution in the plasmodia ofPhysarum polycephalum during periods of growth and differentiation (spherule formation). The total protein content decreased during starvation, but protein synthesis still occurred, probably at the expense of proteins previously synthesized during growth. Studies on leucine incorporation showed that protein synthesized during growth had a greater turnover than did protein formed by starving cultures, when both types of cultures were transferred to starvation conditions. Protein synthesis after prolonged starvation was rapidly and markedly decreased following the inhibition of RNA synthesis, whereas no such direct dependence on RNA synthesis was observed in growing cultures or during early starvation.The kinetics of RNA synthesis and the types of RNA formed were also shown to differ in growth and starvation. RNA turnover was low in growing cultures but substantial in starving cultures that were returned to growth medium. Qualitative differences in pulse-labeled RNA extracted from growing or starving cultures were revealed by methylated-albumin-kieselguhr column chromatography and sucrose gradient centrifugation. In starving cultures proportionately more labeled RNA was found in the lighter, non-ribosomal region of the gradient, and RNA from this region hybridized with denatured DNA to a greater extent than did other RNA fractions.This work was supported in part by Grant CA-07175 from the National Cancer Institute and by a grant from the Alexander and Margaret Stewart Trust Fund. The authors express their appreciation to Dr. H. Kubinski for helpful suggestions.One of us (H.W.S.) was in part supported by the Deutsche Forschungsgemeinschaft.