Long-term cultivation of amphibian melanophores. In vitro ageing and spontaneous transformation to a continuous cell line

Pure melanophore populations isolated from the tail skin of the tadpole, Rana catesbeiana, were mass cultured for a period of 2-3 years. All cell lines of amphibian melanophores studied exhibited growth crisis (in vitro ageing) followed by spontaneous transformation to a continuous cell line, as shown by changes in growth characteristics in mass culture and in clone culture, by the appearance of the cells, and by measurements of cell volumes. Even after becoming a continuous cell line, amphibian melanophores continued to have a diploid chromosome number (2n = 26) in three of four cell lines examined. The chromosome mode in one cell line, however, changed to thirty. Measurement of melanin dispersion after the addition of alpha-melanocyte-stimulating hormone suggested that the mechanism for melanin dispersion in melanophores changed during in vitro ageing.     

Physiological Effects of a and {alpha} Sexual Agglutination Substances on Mating Reaction in the Yeast Saccharomyces cerevisiae

The sex-specific glycoprotein agglutination substance, responsiblefor sexual agglutination, solubilized from the surface of haploidcells of a or a mating type by the autoclave method had thefollowing effects on mating reaction in Saccharomyces cerevisiae.Sexual agglutination was inhibited by the agglutination substanceof the opposite mating type in living cells as well as in heat-killedcells. Formation of zygotes was completely inhibited, when botha and a cells were treated with the agglutination substanceof the opposite mating type. The a and a agglutination substanceswere inactivated by cells of the opposite mating type, withthe degree of inactivation being greater for the former. Theenzyme responsible for the inactivation of a agglutination substanceseems to be carboxypeptidase Y. ¹ This paper is dedicated to the late Professor J. Ashida, KyotoUniversity. ² Present address: Department of Plant Pathology, Universityof California, Davis, CA. 95616, U.S.A. (Received November 1, 1982; Accepted January 19, 1983)     

Mapping of the human gene for epidermal growth factor receptor (EGFR) on the p13 leads to q22 region of chromosome 7

We previously reported that the structural gene for epidermal growth factor receptor (EGFR) can be mapped to the p22 leads to qter region of human chromosome 7 (Shimizu et al., 1979, 1980). In the present study, we produced two series of human-mouse cell hybrids by fusing mouse A9 cells that are deficient in EGFR with the human diploid fibroblast lines GM1356, 46,XX,t(1;7)(p34;p13), and GM2068, 46,XX,t(6;7)(q27;q22), both of which possess EGF receptors. Expression of EGF binding ability in the former series of cell hybrids was correlated with the retention of the human translocation chromosome containing the 7p13 leads to qter region, and in the latter series of cell hybrid it was correlated with the retention of the human translocation chromosome containing the 7pter leads to q22 region. Therefore, the EGFR gene can be localized in the p13 leads to q22 region of chromosome 7.     

Cytogenetics of ticks (Acari: Ixodoidea)

Chromosomes and sex determination of 9 species of Haemaphysalis assigned to 4 subgenera are described. H. (tAlloceraea) kitaokai possesses an XX∶XO sex chromosome system with 18 autosomes plus XX in females; 18 plus X in males. H. (Kaiseriana) hystricis has 18 +XX and 18 + XY in females and males, respectively, in most specimens, but a supernumerary chromosome is present in some individuals. A supernumerary chromosome was also observed in 1 male H. (Aborphysalis) formosensis. These two species are the second and third species of ticks reported to have supernumerary chromosomes. H. formosensis, H. (Kaiseriana) bispinosa, H. (Haemaphysalis) campanulata, H. (H.) flava, H. (H.) megaspinosa, H. (H.) japonica, and H. (H.) pentalagi possess 20 autosomes plus 2 sex chromosomes in females and 20+1 sex chromosomes in males. Phylogenetic relationships within the genus Haemaphysalis are briefly discussed.     

Solution properties of synthetic polypeptides. V. Helix–coil transition in poly(β-benzyl L-aspartate)

Simple approximate expressions have been derived from the theory of Zimm and Bragg for use in the analysis of experimental data on the helix-coil transition in polypeptide. On the basis of the resulting expressions practical procedures are proposed to determine two basic parameters characterizing a thermally induced transition, i.e., helix initiation parameter σ and enthalpy change for helix formation, ΔH. They have been applied to the data for poly(β-benzyl L -aspartate) (PBLA) with the result: σ = 1.6 × 10^?4 and ΔH = ?450 cal/mole for PBLA in m-cresol; σ = 0.6 × 10^?4 and ΔH = 260 cal/mole for PBLA in chloroform containing 5.7 vol-% of dichloroacetic acid. This result gives evidence that σ may change not only from one polypeptide to another but also for a given polypeptide in different solvents. The change in limiting viscosity number [η] accompanying the transition was measured in the same solvents. The curve of [η] versus helical content had a relatively monotonic shape for the chloroformdichloroacetic acid solutions as compared with that for the m-cresol solutions, indicating that [η] depended largely on σ. Provided that [η] is a direct measure of the mean-square radius of gyration, 〈S²〉, the results are consistent with the theoretical predictions of Nagai and of Miller and Flory for 〈S²〉.     

Electrocardiographic studies in the Japanese monkey (Macaca fuscata) with special reference to the effect of anesthesia with barbiturates

The electrocardiograms of 157 healthy Japanese monkeys (Macaca fuscata), covering a wide range of ages in both sexes, were recorded under light pentobarbital (Nembutal) anesthesia. Although results were generally similar to those reported for other macaque species, some quantitative differences were observed.The heart rate was about 160 per minute in all monkeys examined; the P-Q interval was 0.11±0.06 sec.; the duration of QRS was 0.04±0.01 sec.; the Q-T interval was 0.24±0.06 sec. The mean axis of QRS was +59° and the pattern of the QRS complex was qR type in most cases.The comparison with the human electrocardiogram shows that the heart rate ofM. fuscata is about twice that of man, while the P-Q, QRS, and Q-T intervals were about one-half of those found in human subjects. In the monkey, however, the P wave was sharp and the T wave flat.In order to estimate the effect of anesthesia on the electrocardiogram, the records of several monkeys before, during, and after intravenous administration of barbiturates were compared. Although some animals showed extrasystoles after barbiturate was administered, generally no essential changes were noted in the records, except for the retardation of the rate and proportional prolongation of intervals.This work was presented at the 10th Annual Meeting of the Primate Research Association held in Inuyama, March 13, 1966.     

Fine Structure of Healthy and TMV-Infected Tobacco Cells Grown in Tissue Culture

Three types of tobacco (Nicotiana tabacum cv. Havana 38) callus: 1) healthy stem callus, 2) TMV-infected stem callus, 3) TMV-infected leaf callus; and leaves differentiated from healthy stem callus, and from TMV-infected leaf callus were compared for fine structure. In addition, the fine structure was observed of plastids in cells of leaves differentiated from callus isolated from stem sections of TMV-infected hybrid tobacco plants (N. tabacum cv. Havana 38 ×N. glutinosa) grown under high temperature. The cytoplasmic organelles in tissue cultured cells were similar to those in cells of greenhouse-grown tobacco plants. Except for plastids, TMV infection did not noticeably affect morphologically other cellular organelles in tissue culture cells. In TMV-infected leaf callus, numerous small bodies were seen in plastid-like bodies, while vesicle-like structures were observed in the stroma of plastids in leaves differentiated from callus of hybrid tobacco inoculated with TMV. Morphological variations of mitochondria, such as swelling and vacuolization of the inner matrix, occurred frequently in TMV-infected leaf callus. Needle-like crystalline inclusions or looped inclusions composed of many fine, long filaments were considered TMV particles orientated parallel to each other. The TMV particles were detected in the cytoplasm of tissue culture cells.