Cancer chemotherapy and somatic cell mutation

The occurrence of a second neoplasm is one of the major obstacles in cancer chemotherapy. The elucidation of the genotoxic effects induced by anti-cancer drugs is considered to be helpful in identifying the degree of cancer risk. Numerous investigations on cancer patients after chemotherapy have demonstrated: (i) an increase in the in vivo somatic cell mutant frequency (Mf) at three genetic loci, including hypoxanthine–guanine phosphoribosyl-transferase (hprt), glycophorin A (GPA), and the T-cell receptor (TCR), and (ii) alterations in the mutational spectra of hprt mutants. However, the time required for and the degree of such changes are quite variable among patients even if they have received the same chemotherapy, suggesting the existence of underlying genetic factor(s). Accordingly, some cancer patients prior to chemotherapy as well as patients with cancer-prone syndrome have been found to show an elevated Mf. Based on the information obtained from somatic cell mutation assays, an individualized chemotherapy should be considered in order to minimize the risk of a second neoplasm.     

Phenotypic Characterization of Adenovirus Type 12 Temperature-Sensitive Mutants in Productive Infection and Transformation

Eleven temperature-sensitive mutants of adenovirus type 12, capable of forming plaques in human cells at 33 C but not at 39.5 C, were isolated from a stock of a wild-type strain after treatment with either nitrous acid or hydroxyl-amine. Complementation tests in doubly infected human cells permitted a tentative assignment of eight of these mutants to six complementation groups. Temperature-shift experiments revealed that one mutant is affected early and most of the other mutants are affected late. Only the early mutant, H12ts505, was temperature sensitive in viral DNA replication. Infectious virions of all the mutants except H12ts505 and two of the late mutants produced at 33 C, appeared to be more heat labile than those of the wild type. Only H12ts505 was temperature sensitive for the establishment of transformation of rat 3Y1 cells. One of the late mutants (H12ts504) had an increased transforming ability at the permissive temperature. Results of temperature-shift transformation experiments suggest that a viral function affected in H12ts505 is required for “initiation” of transformation. Some of the growth properties of H12ts505-transformed cells were also temperature dependent, suggesting that a functional expression of a gene mutated in H12ts505 is required to maintain at least some aspects of the transformed state.     

Plant-growth regulators from common starfish (<Emphasis Type="Italic">Asterias amurensis</Emphasis> Lütken) waste

Starfish waste has been shown to be an effective compost material not only in the promotion of plant growth but also in terms of having insecticidal activity. In the present study, plant growth regulation by chemicals from starfish was examined. The aqueous fraction from a hot water extract of the starfish Asterias amurensis Lütken showed plant-growth activity, while the aqueous fraction from a methanol extract inhibited growth of Brassica campestris. The lipophilic fraction from the methanol extract also exhibited a plant growth-promoting effect. The active components from each extract were identified. Asterubine from the hot water extract promoted plant growth. A ceramide from the lipophilic fraction showed root growth promoting effect, and three glucocerebrosides had promotive effects on the entire plant. Asterosaponins were identified as the main growth inhibitors in the aqueous fraction of the methanol extract. These active compounds from starfish waste could be analyzed as potential plant growth regulators in agricultural applications in the future.     

Three types of vitronectin in human blood

Vitronectin is a cell-adhesive glycoprotein in serum and plasma, also termed serum spreading factor and complement S-protein. It consists of a mixture of a polypeptide of molecular weight 75 kilodalton (kDa) and its nicked product of 65 kDa plus 10 kDa. By a quantitative immunoblotting assay, human blood samples could be classified into three distinct vitronectin types; type I (58% of the population) was 75 kDa rich and 65 kDa poor, type II (35% of the population) contained approximately equal amounts of 75 kDa and 65 kDa, and type III (5% of the population) was 75 kDa poor and 65 kDa rich. The vitronectin type did not correlate with age, sex, or ABO blood type.     

Chromosomal mapping of 18S-28S rRNA genes and 10 cDNA clones of human chromosome 1 in the musk shrew (Suncus murinus).

The direct R-banding fluorescence in situ hybridization (FISH) method was used to map 18S-28S ribosomal RNA genes and 10 human cDNA clones on the chromosomes of the musk shrew (Suncus murinus). The chromosomal locations of 18S-28S ribosomal RNA genes were examined in the five laboratory lines and wild animals captured in the Philippines and Vietnam, and the genes were found on chromosomes 5, 6, 9, and 13 with geographic variation. The comparative mapping of 10 cDNA clones of human chromosome 1 demonstrated that human chromosome 1 consisted of at least three segments homologous to Suncus chromosomes (chromosomes 7, 10, and 14). This approach with the direct R-banding FISH method is useful for constructing comparative maps between human and insectivore species and for explicating the process of chromosomal rearrangements during the evolution of mammals.     

A molecular orbital study of the metabolic pathway with hydroquinone intermediate from benzene as carcinogen

A possible metabolic activation pathway of benzenein vivo is the nonenzymatic oxidation of hydroquinone producedvia the cytochrome P-450-mediate two-step oxidation of benzene. The mechanism of the further oxidation of hydroquinone and the nature of the most reactive intermediate have not yet been clarified, although it is speculated that the intermediate isp-benzoquinone and/orp-benzosemiquinone. The theoretical result of using molecular orbital calculations (ab initio and CNDO/2 methods) indicates that although the mechanism of the nonenzymatic oxidation of hydroquinone cannot yet be determined, the intermediate is thep-benzosemiquinone anion radical. It is also suggested that active-oxygen species such as hydroxyl radical, which accelerates the nonenzymatic oxidation, play an important role in the metabolic pathway in question.