Effect of bacterial growth-inhibiting ingredients on the Ames mutagenicity of medicinal herbs

A solvent fractionation method was introduced to screen for mutagenicity in 10 medicinal herbs being consumed in Korea. The Ames mutagenicity test result of Scutellariae and Rhei was significantly increased by eliminating growth-inhibiting substances through solvent fractionation of the crude extract. It is suggested that a physicochemical pretreatment should reduce the false-negative results which are caused by the presence of growth-inhibiting substances in complex mixtures.     

Characterization of capsid and noncapsid proteins of B19 parvovirus propagated in human erythroid bone marrow cell cultures.

The major capsid and noncapsid proteins of the pathogenic parvovirus B19, propagated in vitro, were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoprecipitation, and immunoblot of the erythroid fraction of infected human bone marrow cell cultures. There were two capsid proteins of 58 kilodaltons (kDa; the major species) and 84 kDa (the minor species). Newly synthesized capsid viral proteins were present in the supernatants of infected cultures. The major noncapsid protein of 77 kDa was localized to the nucleus.     

Characterization of the Stimulation of Ethylene Production by Galactose in Tomato (Lycopersicon esculentum Mill.) Fruit

We have characterized the stimulation of ethylene production by galactose in tomatoes (Lycopersicon esculentum Mill.). The effect of concentration was studied by infiltrating 0, 4, 40, 100, 200, 400, or 800 micrograms galactose for each gram of fresh fruit weight into mature green `Rutgers' fruit. Both 400 and 800 micrograms per gram fresh weight consistently stimulated a transient increase in ethylene approximately 25 hours after infiltration; the lower concentrations did not. Carbon dioxide evolution of fruit infiltrated with 400 to 800 micrograms per gram fresh weight was greater than that of lower concentrations. The ripening mutants, rin and nor, also showed the transient increase in ethylene and elevated CO₂ evolution by 400 micrograms per gram fresh weight galactose. 1-Aminocyclopropane-1-carboxylic acid (ACC) content and ACC-synthase activity increased concurrently with ethylene production. However, galactose did not stimulate ACC-synthase activity in vitro. The infiltrated galactose in pericarp tissue was rapidly metabolized, decreasing to endogenous levels within 50 hours. Infiltrated galacturonic acid, dulcitol, and mannose stimulated transient increases in ethylene production similar to that of galactose. The following sugars produced no response: sucrose, fructose, glucose, rhamnose, arabinose, xylose, raffinose, lactose, and sorbitol.     

Effect of GA3 on the Cyclic AMP Biosynthesis in Maize Seedling

The effect of GA₃ on the biosynthesis of cAMP was studied toinvestigate the mechanism of gibberellic acid action. The presenceof cAMP in germinating maize seedlings was confirmed. The concentrationgradient of cAMP in maize seedlings inclined from shoot apexto root. The amount of cAMP in maize shoot was increased about3.3 times by exogenous GA₃. These results indicate that thebiosynthesis of cAMP is stimulated by GA₃. (Received June 17, 1986; Accepted January 22, 1987)     

Dynamics of populations with changing rates: generalization of the stable population theory

A general and complete exposition of the dynamics of populations with changing vital rates is given in the discrete time formulation. Results obtained are stronger than Lopez's or Hajnal's. In addition to the proof of existence of limits, an explicit expression for the age distribution is obtained by considering forward products of population projection matrices, while an explicit expression for the generalized reproductive values is obtained by considering backward products. The forward and backward characteristic equations respectively determine the forward and backward growth rates. The relative age distribution is compared to the alternative expression of Y.J. Kim (1986, Demography 23 (3), 451-461), which is the discrete version of S.H. Preston and A.J. Coale (1982, Pop. Index 48 (2), 217-259).     

Control by insulin and insulin-related growth factor 1 of protein synthesis in a cell-free translational system from chick-embryo fibroblasts.

Insulin and insulin-related growth factor 1 (IGF-1) increase by 1.5-1.6-fold the rate of [3H]leucine incorporation into protein in primary monolayer cultures of chick-embryo fibroblasts (CEF); half-maximal hormone concentrations are 10 and 0.25 nM respectively. To investigate the mechanism of this effect, a rapid method is used to prepare a lysate from CEF which is active in protein synthesis. Lysate derived from cells treated for 30-150 min with insulin synthesized protein at 1.8-3.0-fold greater rate than did controls; the increased rate persisted for 20 min in vitro. Pactamycin (0.5 microM), an inhibitor of peptide-chain initiation, inhibited protein synthesis by 50% in lysates derived from insulin-treated and control cells. Thus insulin and IGF-1 cause an increase in the protein-synthesis rate in vivo, which persists in cell-free protein-synthesizing lysates of CEF.     

Retinoic acid induction of stress proteins in fetal mouse limb buds

Retinoic acid (RA) is teratogenic in rodent embryos. Several teratogens have been shown to induce the synthesis of a subset of heat shock proteins (stress proteins) in Drosophila. To determine if RA induces the synthesis of these proteins in rodent embryos, pregnant ICR mice were dosed with 100 mg/kg RA on Day 11 of gestation. Forelimb buds were removed from embryos 2.5 hr post-RA-treatment and nuclei were isolated, stained, and sorted from stages of the cell cycle. Nuclear proteins were extracted and analyzed by two-dimensional polyacrylamide gel electrophoresis. Nuclear proteins with molecular weights of approximately 84 and 25 kDa were synthesized in embryos in the G0 + G1 phase after pregnant dams were treated with RA. Isoelectric points, molecular weights, immunochemical blotting, and polypeptide mapping demonstrated that these proteins are indistinguishable from stress proteins isolated under a variety of conditions from rat submaxillary glands and mouse lymphoma cells. These results suggest that treatment with RA induces the synthesis of a subset of stress proteins; the role of these proteins in the teratogenic effects of RA is not known.     

Molecular cloning and differential expression of somatic and testis-specific H2B histone genes during rat spermatogenesis

We have cloned cDNA of a testis-specific histone, TH2B (a variant of H2B), and rat somatic H2B gene to investigate regulation of testis-specific histone genes during rat spermatogenesis. The amino acid sequences deduced from DNA sequences show extensive sequence divergence in the N-terminal third of the two histones. The rest is highly conserved. One cysteine residue was found in TH2B. No cysteine is present in somatic histones except in H3 histone. We investigated the expression of TH2B and H2B genes using the regions of sequence divergence as hybridization probes. The TH2B gene is expressed only in the testis, and the expression of this gene is detected 14 days after birth, reaching a maximum at Day 20. The level of H2B mRNA shows a reciprocal pattern. This contrasting pattern can be explained by the gradually changing proportion of spermatogonia and spermatocytes with testicular maturation. In situ cytohybridization studies show that H2B gene is expressed primarily in proliferating spermatogonia and preleptotene spermatocytes, whereas TH2B gene is expressed exclusively in pachytene spermatocytes which first appear in testis about 14 days after birth. H2B and TH2B genes appear to be ideal markers for the study of proliferation and differentiation events in spermatogenesis and their regulatory mechanisms.     

Plasmodium falciparum: elicitation by peptides and recombinant circumsporozoite proteins of circulating mouse antibodies inhibiting sporozoite invasion of hepatoma cells

The immunodominant epitope region of the circumsporozoite protein of Plasmodium falciparum sporozoites contains 37 tandem repeats of the tetrapeptide Asn-Ala-Asn-Pro and 4 repeats of Asn-Val-Asp-Pro. Synthetic peptides and recombinant proteins of the repeat region were used to immunize mice using different doses and adjuvants. Antisera were tested for inhibition of sporozoite invasion of cultured human hepatoma cells. Synthetic peptides and recombinant proteins elicited high levels of antibodies that inhibited sporozoite invasion when emulsified with complete Freund's adjuvant. Since recombinant proteins with alum elicited a better antibody response to sporozoite invasion than they did without adjuvant, it may be that a recombinant protein containing 32 tandem copies of the tetrapeptide repeat combined with alum could be a candidate malarial vaccine suitable for human trials.