How does flowering magnitude affect seed survival in Shorea pilosa (Dipterocarpaceae) at the predispersal stage in Malaysia?

General flowering (GF), a supra-annual, irregular fluctuation in flowering and seeding at the community level, is a phenomenon unique to the tropical rainforests of South-East Asia. To test the animal pollination and predator satiation hypotheses, which are the main hypotheses that attempt to explain the ultimate cause of GF, we conducted a bagging experiment after the flowering of Shorea pilosa (Dipterocarpaceae). Seed survival at the predispersal stage was divided into two stages (1–30 days and > 30 days after flowering) and we compared the results between treatments and between GF and non-GF periods using a survival analysis. Survival during the GF period at both stages was significantly higher than during non-GF periods, suggesting that both hypotheses were supported and that synchronous flowering with GF benefits the reproductive success of S. pilosa .     

ENZYME ACTIVITIES ASSOCIATED WITH RIBOSOMES FROM SOYBEAN SEEDLINGS

Ribosomes from cotyledons of soybean seeds soaked overnightin water (resting-cotyledon ribosomes) and respective ribosomesfrom cotyledons (working-cotyledon ribosomes) and hypocotyls(hypocotyl ribosomes) of 5 day-old seedlings were prepared.These ribosomes mainly consisted of 80 S particles. However,hypocotyls contained 115 S particles in a small amount and working-cotyledonscontained 115 and 150 S particles which may correspond to thepolymers of ribosomes or polysomes. The abundant 80 S ribosomeswere fractionated by the sucrose density gradient centrifugation,and enzyme activities in the fractionated ribosomes were estimated.RNase, PDase, acid phosphatase, 5'-nucleotidase, XTPase, peroxidaseand ß-glucosidase were found in the ribosomes. Theenzyme activities were lower in the resting-cotyledon ribosomesand higher in the hypocotyl ribosomes. Working-cotyledon ribosomesshowed the middle of them. All these enzymes were also foundin the cytoplasmic solution (supernatant) of cotyledon and hypocotylcells. However, RNase, PDase, 5'-nucleotidase and peroxidasewere concentrated in ribosomes, and the specific activitiesof 5'-nucleotidase and ß-glucosidase were increasedby washing the ribosomes. The status of the enzymes found inthe ribosomes was discussed. (Received May 12, 1966; )     

Inhibition of Bacterial DNA Replication by 6-(<Emphasis Type="Italic">p</Emphasis>-Hydroxyphenylazo)-uracil

THE semi-conservative replication of DNA of Gram-positive bacteria is specifically inhibited by 6-(p-hydroxyphenyIazo)-uracil (HPUra; obtained from ICI) in an apparently novel mechanism^1–4. We have attempted to characterize the HPUra-sensitive site in replication using in vitro preparations of drug-sensitive bacteria. In particulate and soluble preparations of sensitive bacteria, however, HPUra at high concentration does not significantly inhibit polymerization of deoxyribonucleotides^2,4. Since these systems may not accurately represent the process of DNA replication as it occurs in vivo, we have examined the effect of HPUra on a more suitable, toluene-treated preparation of Bacillus subtilis described by Matsushita et al.⁵. In this preparation, DNA replication is ATP-dependent, utilizes deoxyribonucleotides to give biologically active DNA, semi-conservatively and sequentially in the proper gene order. HPUra can inhibit DNA replication by this system. We describe here the characteristics of HPUra inhibition and the conditions necessary for it to occur.     

MOUSE MUSCLE CELL DIFFERENTIATION IN CLONAL CULTURE

Clonal culture of muscle cells from thigh muscles of the term fetus of the mouse was undertaken. Myoblasts were spherical or spindle-shaped, and proliferated exponentially until day 4 in culture. The generation time of the muscle cells from 2 to 4 days' culture was 9.1 to 13.4 hr. The fusion of myoblasts began on day 4 in culture; many myotubes had been formed by day 6 and spontaneous contraction was observed on day 7. Clonal efficiency was 30%, and the proportion of muscle colonies in all the colonies was 72%.     

TOBACCO MOSAIC VIRUS IN CHLOROPLAST AND CYTOPLASM OF INFECTED TOBACCO LEAF

Chloroplasts containing Tobacco Mosaic Virus (TMV) were isolatedfrom TMV inoculated tobacco leaves, and TMV was extracted fromthem. The preparations from isolated chloroplasts of infectedleaves showed 30% increase in the optical density at 260 mµover those from healthy leaves. Most of infectivity was observedin chloroplast fraction 40 hr after inoculation. Thereafter,infectivity in the chloroplast fraction decreased and that ofcytoplasm increased with time. (Received April 6, 1964; )     

EFFECTS OF THE LENS CAPSULE ON CELLULAR FLATTENING, CELL GROWTH AND EXPRESSION OF THE DIFFERENTIATED TRAITS OF CHONDROCYTES CULTURED IN VITRO

The morphology, growth and differentiation of chondrocytes cultured on the lens capsule were studied. When incubated in Eagle's MEM with fetal serum, chondrocytes on the surface of the lens capsule became flattened with extended pseudopodia, but most cell remained spherical on the surface of a plastic dish. Thus, the lens capsule promoted cellular flattening of chondrocytes. When grown in Ham's FI2 medium, flattening of cells on the lens capsule was greater and the cells developed the features of fibroblasts without any detectable characteristics of chondrocytes, although their growth rate was not enhanced. This inhibitory effect of the lens capsule on differentiation in this medium was reversed when the cells were separated from the lens capsule and grown on a plastic substrate.     

A Comparison Between Melanotic and Amelanotic Retinal Pigment Epithelial Cells In Vitro Concerning the Effects of L-Dopa and Oxygen on Cell Cycle

Melanin precursors and free radicals, cytotoxic substances, are produced during melanin synthesis by tyrosinase. We compared these cytotoxic effects of L-dopa and oxygen on the cell cycle of melanotic retinal pigment epithelial (RPE) cells with amelanotic RPE cells because of the differences of tyrosinase activities between melanotic and amelanotic RPE cells. Flow cytometric DNA analysis of RPE cells exposed to L-dopa (100 μM and 250 μM) were conducted at several oxygen concentrations (20%, 10%, and 5%). The dose-dependent effect of L-dopa to arrest the cell cycle (the S phase) was more pronounced in melanotic than in amelanotic RPE cells, and oxygen caused arrest in the G₁ phase.     

Chromosome Replication in Toluenized <Emphasis Type="Italic">Bacillus subtilis</Emphasis> Cells

BIOCHEMICAL studies of chromosome replication have been hampered by the unavailability of an adequate in vitro system with the basic features of in vivo DNA replication. The criteria for such a system are: (1) semiconservative replication; (2) normal biological activity of newly synthesized DNA; (3) normal advancement of the original replication fork; (4) rate of DNA replication equivalent to in vivo; and (5) expected phenotypic behaviour of temperature-sensitive dna mutants. Systems in Escherichia coli, a membrane-DNA fraction¹, an agar-embedded cell lysate² and toluene-treated cells³ have met two or three of the requirements. Several laboratories have also reported the expected behaviour of ts-dna E. coli mutants in toluenized cells^3–5.     

STUDIES ON CHLOROPHYLLASE OF CHLORELLA PROTOTHECOIDESI. ENZYMATIC PHYTYLATION OF METHYL CHLOROPHYLLIDE

1. The relation between chlorophyll content and the hydrolyticactivity of chlorophyllase in Chlorella protothecoides was examined.An increase in the activity was parallel to that in chlorophyllcontent during the development of green colouration, or greeningcourse, in the bleached cells. The activity sharply declinedand a parallel disappearance of chlorophyll was also found duringbleaching of the green cells.
2. A partially purified water-solublepreparation of chlorophyllasewas obtained by n-butanol treatmentand fractionation with coldacetone. It showed high activityand hydrolyzed 2 mg chlorophylla per hr per mg protein.
3. Forseparation and identification of the pigments concernedin thechlorophyllase reaction, a new solvent system of paperchromatographywas introduced.
4. When methyl chlorophyllide a and phytol wereincubated withthe enzyme, two products were formed. By comparisonwith theRf values of isolated pure substances, one was identifiedaschorophyll a and the other as chlorophyllide a. This enzymedid not catalyze the phytylation of free chlorophyllide a, butit had the ability to attach phytol to methyl chlorophyllidea. The final step in the biosynthesis of chlorophyll a is brieflydiscussed.

¹ Contribution No. 158 from the Department of Biology, Facultyof Science, Kyushu University. Supported in part by a grant-in-aidfor Fundamental Scientific Research from the Ministry of Education.