Further morphological characterization and structural proteins of infectious bursal disease virus.

An outer layer surrounding the capsid of infectious bursal disease virus was evident from electron micrographs of intact virus particles having diameters of 62 to 63 nm. The capsid was found to be composed of large morphological units or capsomeres, measuring about 12 nm in diameter. The architecture of the capsid appears to be that of T = 3 symmetry, with a probable 32 morphological units by rotational enhancement of image detail. Structural proteins of infectious bursal disease virus consist of seven species, two major and five minor polypeptides. These are P1 to P7, with molecular weights of 133 x 10(3), 124 x 10(3), 98 x 10(3), 51 x 10(3), 33 x 10(3), 26 x 10(3), and 23 x 10(3), respectively.     

Non-random distribution of transduction termini in transductants from the integrated R plasmid, R100-1

Summary Tra ⁺and tra ^–derivatives of drug resistance plasmid, R100-1, were isolated by phage P1 from an Hfr donor with integrated R100-1 and then analyzed by complementation tests with tra ^–point mutants of Flac. Tra ⁺derivatives of R100-1 carrying tetracycline resistance alone and those carrying all six drug-resistance genes could support transfer of tra ^–point mutants of Flac except Flac traJ, whereas all of tra ^–derivatives of R100-1 failed to complement any one of tra ^–point mutants of Flac. This suggests that these tra ^–derivatives of R100-1 carrying tetracycline resistance gene are deleted for all the transfer genes impaired in the Flac point mutants tested. We assume a hot point, probably a specific base sequence similar to an IS element, at the left of the tetracycline gene (Fig. 1) becomes a transduction terminus in transduction of the integrated R100-1 by phage P1. Complementation analysis of tra ^–derivatives carrying five resistance genes except the tetracycline gene led us to a supposition that a gene(s), probably analogous to traJ of the F plasmid, is located on R100-1 near the tetracycline gene which plays an important regulatory role for self-transfer as well as for the complementation of tra ^–Flac mutants.     

Dose-response relations for dicentric yields in G0 lymphocytes on man and crab-eating monkey following acute and chronic γ-irradiations

A comparison has been made of dicentric yields in G₀ lymphocytes between man and crab-eating monkey, Macaca fascicularis, after acute and chronic γ-irradiations. With acute irradiation (49.6 rad/min) there was no significant difference between them, but for the chronic irradiation (17.1 rad/h) a significant difference was observed between the species. When the dose-response relations were fitted to the linear-quadratic model (Y = αD + βD²), the species-difference observed for chronic irradiation was almost entirely due to change in the value of β. In addition, after chronic irradiation the β-value for monkey was almost negligible, but that for man was significant. Post-irradiation incubation experiment showed that cells with dicentrics were partly eliminated during the course of chronic irradiation, because there were appreciable reductions of dicentric yields (ca. 25% for both man and monkey at 400 rad) together with mitotic indices (ca. 30% and 60% for man and monkey, respectively, at 400 rad). Accordingly, it would be reasonable to postulate that G₀ repair for dicentrics other than selection mechanism must play a major role in the effects of low dose rate. It can be further suggested that G₀-repair capacity for chromosal damages leading to dicentrics may be different among different primate species.     

Dicentric yields induced by gamma-radiation and chromosome arm number in primates.

To evaluate the effect of the chromosome arm number on the yield of dicentric chromosomes, frequencies of gamma-ray-induced chromosome aberrations were examined with peripheral lymphocytes from three different primate species, Saimiri sciureus (arm number, 77), Macaca fascicularis (arm number, 83) and Nycticebus coucang (arm number, 99). Irradiated blood samples were cultured by the same standard technique as that commonly used for human lymphocytes. The yields of dicentrics and dicentrics plus rings at doses of 100, 200 and 300 rad of gamma-irradiation were not significantly different among the three species, in spite of the difference in the chromosome arm number. Furthermore, dose-response relationships for these species were consistent with that for man. Statistical analysis indicated that the expected dicentric yields calculated from the arm number model were significantly different from the observed yields at 200 and 300 rad doses (P less than 0.01). From these results it can be pointed out that there is no correlation between the yield of dicentrics and the effective chromosome arm number, and that the chromosomal radiosensitivity of these primates is essentially the same as that of man, at least in the lymphocyte system.     

Regional replication of the bacterial chromosome induced by derepression of prophage lambda

Summary Derepression of prophage in E. coli strain K12 results in constitutive synthesis of the enzymes directed by the nearby bacterial operon, gal (escape synthesis). Phage 82 fails to cause escape synthesis despite that it lysogenizes the strain K12 at the site identical to that of on the host chromosome. The reason for the observed difference between 82 and is studied in the light of the recent finding that escape synthesis in -lysogen is closely associated to phage-promoted replication of bacterial chromosome contiguous to the prophage including gal operon (escape replication). Excision-defective mutants from 82, 82int or 82xis, do initiate escape synthesis, suggesting that the prophage 82 is normally excised too quickly after induction to allow sufficient escape replication. In support of this, much more DNA hybridizable to bacterial DNA contained in gal accumulates after induction of 82int than after induction of 82. Studies with various hybrid phages between 82 and have suggested: 1. The occurrence of gal escape synthesis depends on the nature of the region between b2 and N in the map. 2. Regions of the 82 genome on both sides of the attachment site contribute independently to prevent gal escape synthesis. Implications of these results are discussed with regard to the factors involved in the prophage excision.The IIIrd article of this series is in Molec. Gen. Genet. 159, 185–190 (1978)     

Purification and partial characterization of cytochrome b5 from Tetrahymena pyriformis

With the use of detergents and successive column chromatographies, Tetrahymena b-type cytochrome was purified from microsomes to a specific content of 36.0 nmol per mg of protein. The purified form showed a single band on SDS-polyacrylamide gel with molecular weight of 22,000. The spectral properties of the reduced b-type cytochrome, the α-peak of which is situated at 560 nm and asymmetric with a shoulder at 556 nm, was different from that of rat liver microsomal cytochrome b₅. However, it was reducible by NADH in the presence of NADH-cytochrome b₅ reductase purified from rat liver microsomes.The results indicated that the microsomal b-type cytochrome should be designated as cytochrome b₅ of a ciliated protozoan, Tetrahymena pyriformis.     

Cyclin B in fish oocytes: its cDNA and amino acid sequences, appearance during maturation, and induction of p34cdc2 activation.

Under the influence of maturation-inducing hormone (MIH) secreted from follicle cells, oocyte maturation is finally triggered by maturation-promoting factor (MPF), which consists of a homolog of the cdc2+ gene product of fission yeast (p34cdc2) and cyclin B. Two species of cyclin B clones were isolated from a cDNA library constructed from mature goldfish oocytes. Sequence comparisons revealed that these two clones are highly homologous (95%) and were found to be similar to Xenopus cyclin B1. Using monoclonal antibodies against Escherichia coli-produced goldfish cyclin B and the PSTAIR sequence of p34cdc2, we examined the levels of cyclin B and p34cdc2 proteins during goldfish oocyte maturation induced in vitro by 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17 alpha, 20 beta-DP), a natural MIH in fish. Protein p34cdc2 was found in immature oocyte extracts and did not remarkably change during oocyte maturation. Cyclin B was not detected in immature oocyte extracts and appeared when oocytes underwent germinal vesicle breakdown. Cyclin B that appeared during oocyte maturation was labelled with [35S]methionine, indicating its de novo synthesis. Introduction of E. coli-produced cyclin B into immature oocyte extracts induced p34cdc2 (MPF) activation. Although the possibility that immature goldfish oocytes contain an insoluble cyclin B is not completely excluded, these results strongly suggest that 17 alpha, 20 beta-DP induces oocytes to synthesize cyclin B, which in turn activates preexisting p34cdc2, forming active MPF.     

A three-dimensional computerized reconstruction of the rectum, anus and surrounding muscles of the rat fetus at the 20th gestation day

Using fetuses of Wistar/I rats on the 20th gestation day. We designed a three-dimensional computerized reconstruction of the rectum, anus and the surrounding muscles. The tissues were fixed in Bouin's solution sagittally sectioned serially were stained with hematoxylin-eosin. Light microscopic pictures at 40 x magnification were subjected to the analysis using a three-dimensional image processing system, consisting of a drum-scanner, a general purpose computer (Micro VAX II), and a color image processor. The results showed that this system clearly reconstructed the three-dimensional image of the rectum, anus and the surrounding muscles and suggested the presence of the puborectal muscle sling.     

A novel cDNA clone for acid invertase in tomato fruit.

The sequence of a novel cDNA clone, Aiv-1, for tomato acid invertase was similar to that of TIV1 (Klann et al., 1992) for the enzyme except for a unique intron-like insertion. It is considered that Aiv-1 is derived from either an alternatively spliced mRNA for an isozyme or a pre-mRNA of TIV1.     

Frequency of a 9-bp deletion in the mitochondrial DNA among Asian populations.

Individuals of the following Asian populations were surveyed for the presence of a 9-base-pair deletion of mitochondrial DNA (mtDNA): Ainu, Japanese, Korean, Negrito, and Vedda. Although the variation was detected in every population except the Vedda, the frequencies of the variation differed widely among the populations, suggesting a geographic cline.