Division and gametophytic tissue formation from protoplasts of young sporophytes in fern Lygodium japonicum

Protoplasts isolated enzymatically from juvenile leaflets of sporophytes in fern Lyqodium japonicum were inoculated in a MS medium containing NAA 2.7 m, BAP 2.2 m, 0.6 M mannitol, and 0.05 M sucrose. Cell division took place within 8 days of culture initiation, and after 30 days cell-clusters with 10–15 cells were observed. When the cell-clusters were transferred into fresh hormone-free medium containing no mannitol, they developed rhizoids and protonema-like regenerants. About 2 months later, cordate prothallia developed bearing both antheridia and archegonia.Abbreviations MS Murashige and Skoog (1962) - NAA naphthalene acetic acid - BAP 6-benzylaminopurine     

Types,rates, origin and expressivity of chromosome mutations involving 13q14 in retinoblastoma patients

Summary A cytogenetic survey of 200 retinoblastoma (Rb) patients revealed that approximately 8.5% of the fresh germinal mutations were microscopically detectable chromosome mutations, either interstitial deletions or rearrangements, involving 13q14. They showed a strong bias toward paternal origin, indicating a significant contribution of errors in paternal meiotic processes. The incidence of patients with Rb due to such chromosome mutations was estimated to be 1.9 x 10^-6 of live births. Age-specific incidence of Rb tumors suggested that the Rb mutations by such chromosomal mechanisms had a lower carcinogenic potential, as indicated by the later onset of disease, than other Rb mutations of germinal origin.     

Electron microscopic observations on the formation of elastic fibres in cultures of aortic medial cells and adventitial cells

The formation of elastic fibres was observed in the cultured cells derived from the tunica media and the tunica adventitia of mouse aorta. Bundles of myofilaments with dense bodies were abundantly observed in the cytoplasm of the cultured medial cells, and numerous bundles of microfibrillar components were present in the intercellular spaces. Fine granules of approximately 50 nm in diameter were observed in the bundles of microfibrillar components. It was supposed that these fine granules of elastin fused with each other and formed elastic aggregates and then formed large elastic clumps. Numerous bundles of microfibrillar components were also present in the intercellular spaces of the cultured adventitial cells. Elastic aggregates were scarcely observed in the bundles of microfibrillar components. However, large elastic clumps as observed in the medial cell culture could not be found in the adventitial cell culture. It is suggested that the formation of large elastic clumps might be related to the sheet structures or lamellae of elastic fibres in the tunica media.     

DNA fragments of 300 base pairs released from metaphase chromosomes by digestion with deoxyribonuclease I

DNase I digestion of metaphase chromosomes, that have been extensively digested with Hae III, further released chromosomal DNA and proteins; 3.3% and 10.8% of the chromosomal DNA and proteins, respectively, remained insoluble. However, digestion of chromosomes first with DNase I followed by Hae III caused most of the proteins to remain in the insoluble fraction. DNase I released DNA fragments of 300 base pairs long which were not released by Hae III digestion. These DNA fragments may be protected by protein components from further fragmentation by DNase I.     

Increase in the frequency of gamma-ray induced chromosomal aberrations in mammalian cells by post-treatment with novobiocin

The effect of novobiocin (an inhibitor of DNA topoisomerase and polymerase) on the frequency of chromosomal aberrations was examined in Chinese hamster V79 cells irradiated with gamma-rays in the plateau phase of growth and subcultured in the presence of novobiocin until the first mitosis after irradiation. Novobiocin alone affected cell survival, DNA synthesis and the mitotic frequency of unirradiated cells in a dose-dependent manner, without causing any significant increase in the frequency of chromosome- or chromatid-type aberrations. The frequency of chromosome-type aberrations induced by gamma-radiation was not influenced by novobiocin at 200 microM, but the frequency of chromosome deletions (but not rings and dicentrics) showed a two-fold increase when 300 microM novobiocin was present. Irradiation produced a low level of chromatid-type aberrations and post-treatment with novobiocin at concentrations greater than 100 microM significantly increased the frequency of chromatid gaps and breaks. The results support the idea that different radiation-induced lesions lead to chromosome- as opposed to chromatid-type aberrations.     

Muscarinic acetylcholine receptors in rat gastric mucosa

Summary The muscarinic cholinergic innervation of the rat gastric mucosa was investigated by localizing the muscarinic receptors using a tritiated muscarinic antagonist, pirenzepine. Radioautography was performed by freeze drying stomach tissue, which was then embedded in Epon and wet sectioned with ethylene glycol, and dry mounting on emulsion film by the wire-loop method to prevent loss of the labelled substance during fixation and the radioautographic procedure. Light and electron microscopy showed that the specific pirenzepine-binding sites were localized predominantly on parietal cells, chief cells and perivascular plexuses. Analysis of the grain distribution on parietal cells revealed that the silver grains corresponding to the pirenzepine-binding sites were mainly on the basolateral plasma membrane. On the other hand, the surface mucous or mucous neck cells had few pirenzepine-binding sites.     

Electrophoretic variants of blood proteins in Japanese. IV. Prevalence and enzymologic characteristics of glucose-6-phosphate dehydrogenase variants in Hiroshima and Nagasaki

Summary Electrophoretic screening of glucose-6-phosphate dehydrogenase (EC 1.1.1.49, G6PD) was conducted one sample of 9,260 children born to the atomic bomb survivors in Hiroshima (Honshu) and Nagasaki (Kyushu). The prevalence of electrophoretic variants was 0.11% in males and 0.42% in females in Hiroshima, and 0.16% in males and 0.31% in females in Nagasaki. Enzymologic characteristics of 10 variants obtained from three males and seven hemizygous fathers of heterozygous females were examined. As a result, three new types of G6PD variants were identified among five variants detected in Hiroshima, and three new types among five variants in Nagasaki. All the variants except one belonged to Class 3, as defined by Yoshida et al. (1971).     

Formation and removal of benzo[a]pyrene metabolites--DNA adducts in cultured normal human fibroblasts using a microsome-activating system

The rate of removal of DNA adducts of several benzo[a]pyrene metabolites from nuclear DNA was compared by introducing a microsome-activating system in human fibroblast cells. Confluent human fibroblasts were exposed to benzo[a]pyrene in the presence of a microsomal activating system and DNA adducts were formed in the nuclear DNA. The adducts present in DNA were determined after 1 h of incubation and 48 h later. There was no difference in the rate of removal between 7S- and 7R -N2-[10-(7 beta, 8 alpha-trihydroxy-7,8,9,10- tetrahydrobenzo[a]pyrene)yl]deoxyguanosine, 7R -N2-[10(7beta, 8 alpha, 9 beta-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene)yl]deoxyguanosine and the covalent adduct of 9-hydroxybenzo[a]pyrene-4,5-epoxide to guanosine. This finding does not agree with the idea that metabolites forming 'persistent DNA adducts' are always responsible for the carcinogenicity of their parent compound.