Induction of endoreduplication in Chinese hamsters V79 cells by cytosine arabinoside

Endoreduplication (ER) could be induced very effectively in Chinese hamster V79 cells exposed to cytosine arabinoside (1-β-D-arabinofuranosylcytosine; Ara-C). Cells were cultured for 48 hours in Ara-C containing medium. ER frequency increases rapidly after Ara-C release. About 60% of metaphase cells were endoreduplicated at 8–10 hours after release from Ara-C (5 μg/ml). Induction of ER also depends on Ara-C concentrations.     

Cytological evidence for holocentric chromosomes of the silkworms,Bombyx mori and B. mandarina, (Bombycidae,Lepidoptera)

The nature of the centromere and the orientation in meiosis of silkworm chromosomes were investigated using the trivalent of the F₁ hybrid between the wild and domestic silkworm and X-ray-induced aberrant chromosomes as well as normal silkworm chromosomes. The results of the experiments were as follows: (1) Pro-metaphase chromosomes showed no distinct primary constriction even after treatment with hypotonic solution, (2) sister chromatids separated in parallel along the entire length of the chromosome at mitotic anaphase, (3) chiasmata underwent complete terminalization during diakinesis and thus chromosome dyads were always connected end-to-end by a terminal chiasma at metaphase I, (4) radiation-induced aberrant chromosomes were stably transmitted throughout a number of cell generations, and (5) although the homomorphic bivalents generally orientated axially at metaphase I and equatorially at metaphase II, this normal sequence tended to be inverted or modified in the X-ray-induced aberrant chromosomes and in the trivalent of the F₁ hybrid silkworms. These observations may be best interpreted by assuming the holocentric nature of silkworm chromosomes.     

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〉.     

Chemiluminescent assay of various enzyme activites and its application to enzyme immunoassays

A highly sensitive chemiluminescent assay for NAD(P)H have been developed. The principle of the method is as follows; NAD(P)H reduces molecular oxygen to superoxide anion (O) and hydrogen peroxide (H₂O₂) in the presence of 1-methoxy-5-methylphenazinium methyl sulphate (1-MPMS) as electron mediator. The produced O and H₂O₂ can be measured by chemiluminescent reaction using isoluminol (IL) and microperoxidase (m-POD). A linear relationship between chemiluminescence intensity and NAD(P)H concentration (log/log) was obtained ranged from 10^?9 mol/I to 10^?5 mol/I. This chemiluminescent reaction has been coupled to the assay of glucose-6-phosphate dehydrogenase (G6PDH), β-D -galactosidase (β-Gal) and alkaline phosphatase (ALP). The detection limits of G6PDH, β-Gal and ALP were 10^?18 mol, 10^?20 mol and 10^?18 mol per assay, respectively. The chemiluminescent assay of these enzymes applied to chemiluminescent enzyme immunoassay for 17α-hydroxy-progesterone and DNA hybridization assay using these enzymes as label.