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.     

Effect of IL-2 in vitro on CTL generation in spleen cells of young and old mice: asialo GM1+ cells are required for the apparent restoration of the CTL response

The role of asialo GM1+ (ASGM1+) cells and exogenous IL-2 in the age-related decline in allospecific CTL activity was evaluated. Primary CTL were generated in mixed leukocyte culture (MLC) [BALB/cANN (H-2d) anti C57BL/6N (H-2b)] and tested for allospecific lytic activity against the EL-4 (H-2b) cell culture line, and for non-MHC-restricted activity against WEHI-3 (H-2d) and YAC-1 (H-2a). Cultures included responder cell populations which had been treated with antibody to ASGM1 plus complement or complement alone, and irradiated stimulator cells, in the presence or absence of rIL-2 or crude IL-2-containing supernatants. The amount of rIL-2 used to accommodate the age-related decline in IL-2 production was determined empirically to be 500 U by assessing IL-2 production in MLCs containing responder cells from young versus old animals. rIL-2 appeared to restore the allospecific CTL activity generated by spleen cells of old mice to the level of that of young. However, treatment with anti-ASGM1 antibody revealed that this restoration was due to an effect of the IL-2 on ASGM1+ cells. The allospecific target cells, EL-4, were not sensitive to lymphokine-activated killer (LAK) cells induced by IL-2 alone under the conditions used. It is suggested that the apparent restoration was due to increased LAK-like (or MHC-nonrestricted) activity mediated by an ASGM1+ cell in the CTL precursor population.     

Sequences of cDNAs for human salivary and pancreatic α-amylases

The nucleotide sequences of the cloned human salivary and pancreatic α-amylase cDNAs correspond to the continuous mRNA sequences of 1768 and 1566 nucleotides, respectively. These include all of the amino acid coding regions. Salivary cDNA contains 200 bp in the 5′-noncoding region and 32 in the 3′-noncoding region. Pancreatic cDNA contains 3 and 27 bp of 5′- and 3′-noncoding regions, respectively. The nucleotide sequence humology of the two cDNAs is 96% in the coding region, and the predicted amino acid sequences are 94% homologous.Comparison of the sequences of human α-amylase cDNAs with those previously obtained for mouse α-amylase genes (Hagenbuchle et al., 1980; Schibler et al., 1982) showed the possibility of gene conversion between the two genes of human α-amylase.     

Studies on the Metabolic Activity of Muscle Proteins

The activities of glutamic oxaloacetic transaminase and Ca⁺⁺ ion-activated ATPase of muscle in the adult rats fed a protein-free diet for 8, 16 and 24 days were measured in order to clarify their metabolic responses with respect to reserve proteins. It was found that these enzyme activities, or presumably their enzyme proteins, decreased at the stage as early as the 8th day of protein depletion following the same pattern as seen in reserve proteins. Their responses, particularly those in unit activity, were somewhat different from each other. The metabolic significance of those responses was discussed in relation to protein nutrition.     

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.     

Feedbacks between nutrient cycling and vegetation predict plant species coexistence and invasion

To investigate the role of species‐specific litter decomposability in determining plant community structure, we constructed a theoretical model of the codevelopmental dynamics of soil and vegetation. This model incorporates feedback between vegetation and soil. Vegetation changes the nutrient conditions of soil by affecting mineralization processes; soil, in turn, has an impact on plant community structure. The model shows that species‐level traits (decomposability, reproductive and competitive abilities) determine whether litter feedback effects are positive or negative. The feedback determines community‐level properties, such as species composition and community stability against invasion. The model predicts that positive feedback may generate multiple alternative steady states of the plant community, which differ in species richness or community composition. In such cases, the realized state is determined by initial abundance of co‐occurring species. Further, the model shows that the importance of species‐level traits depends on environmental conditions such as system fertility.     

Pulse-labeled, small closed circular DNA in cultured mouse and human cells

Mouse (erythroleukemia, TSA8, and FM3A) cells and human (HeLa and HL-60) cells were pulse-labeled with [3H]thymidine and covalently closed circular DNA in the extrachromosomal fraction was analyzed by fluorography following polyacrylamide gel electrophoresis. Two discrete bands for mouse and at least one, different, band for human cells emerged in the position to which small circular DNA (less than 1 kb) migrate, suggesting there to be species-specific, preferentially labeled, small circular DNA in mammalian cells. The incorporation of [3H]thymidine into the DNA was inhibited by cycloheximide but unaffected by aphidicolin. Restriction enzyme (AluI) digestion of the DNA fraction from MEL cells produced approximately 120-, 100-, and 50-bp labeled DNA fragments. The origin of the pulse-labeled DNAs is discussed.     

The isolation and culture of lily pollen protoplasts

Methods for the enzymatic isolation of lily protoplasts and their successful culture are described. When pre-anthesis binucleate pollen (immature pollen grains) was treated in enzyme solution containing macerozyme and cellulase, up to 80% lost their exine and gave rise to intact protoplasts within 1 h. These pollen protoplasts were uniform in size and densely cytoplasmic with two prominent generative and vegetative nuclei. The isolated pollen protoplasts regenerated a cell wall within 1 day of culture and produced a structure resembling a pollen tube after 10–12 days of culture. During this culture period, dividing generative nuclei or 2 sperm nuclei were observed in many protoplasts with regenerated cell walls.