Genetic characterization of the mei-41 locus in Drosophila melanogaster

Summary The mutagen-sensitive mutant mus(1)104 ^D1 of Drosophila melanogaster maps to a position on the X chromosome very close to the meiotic mutant mei-41 ^D5 . Both mutants have been characterized as mutagen-sensitive and defective in post-replication repair. In the present report we show by complementation studies that mus(1)104 and mus(1)103 are allelic with mei-41. In addition, two reported alleles of mus(1)104 lie between the mei-41 alleles A10 and D5. The size of the mei-41 locus is estimated to be about 0.1 centimorgans (cM). Because several alleles of mei-41 have been shown to reduce recombination and increase meiotic chromosome loss and nondisjunction, mus(1)104 ^D1 females were examined for defects in meiosis. Although there was no evidence for reduced recombination on the second chromosome in homozygous mus(1)104 ^D1 females, heterozygous mus(1)104 ^D1 /mei-41 ^>D5 and mus(1)104 ^D1 /deficiency females showed reduced levels of recombination. However, there was no evidence of an increase in nondijunction in these females.We dedicate this article to the memory of Larry Sandler, who passed away suddenly on February 7, 1987     

The complete sequence of the rice (Oryza sativa) chloroplast genome: intermolecular recombination between distinct tRNA genes accounts for a major plastid DNA inversion during the evolution of the cereals

Summary The entire chloroplast genome of the monocot rice (Oryza sativa) has been sequenced and comprises 134525 bp. Predicted genes have been identified along with open reading frames (ORFs) conserved between rice and the previously sequenced chloroplast genomes, a dicot, tobacco (Nicotiana tabacum), and a liverwort (Marchantia polymorpha). The same complement of 30 tRNA and 4 rRNA genes has been conserved between rice and tobacco. Most ORFs extensively conserved betweenN. tabacum andM. polymorpha are also conserved intact in rice. However, several such ORFs are entirely absent in rice, or present only in severely truncated form. Structural changes are also apparent in the genome relative to tobacco. The inverted repeats, characteristic of chloroplast genome structure, have expanded outward to include several genes present only once per genome in tobacco and liverwort and the large single copy region has undergone a series of inversions which predate the divergence of the cereals. A chimeric tRNA pseudogene overlaps an apparent endpoint of the largest inversion, and a model invoking illegitimate recombination between tRNA genes is proposed which accounts simultaneously for the origin of this pseudogene, the large inversion and the creation of repeated sequences near the inversion endpoints.     

Conformational change of bovine serum albumin by heat treatment

The thermal denaturation of bovine serum albumin (BSA) was studied at pH 2.8 and 7.0 in the range of 2–65°C. The relative proportions of -helix, -structure, and disordered structure in the protein conformation were determined as a function of temperature, by the curve-fitting method of circular dichroism spectra. With the rise of temperature at pH 7.0, the proportion of -helix decreased above 30°C and those of -structure and disordered structure increased in the same temperature range. The structural change was reversible in the temperature range below 45°C. However, the structural change was partially reversible upon cooling to room temperature subsequent to heating at 65°C. On the other hand, the structural change of BSA at pH 2.3 was completely reversible in the temperature range of 2–65°C, probably because the interactions between domains and between subdomains might disappear due to the acid expansion. The secondary structure of disulfide bridges-cleaved BSA remained unchanged during the heat treatment up to 65°C at pH 2.8 and 7.0.     

Potentiation of harringtonine cytotoxicity by calcium antagonist diltiazem and biscoclaurine alkaloid cepharanthine in adriamycin-resistant P388 murine leukemia and K562 human leukemia cells

Harringtonine showed cross resistance in adriamycin-resistant murine leukemia P388 (P388/ADM) and human leukemia K562 (K562/ADM) cells. The relative resistance of the P388/ADM and K562/ADM cells to harringtonine was about 7 and 40, respectively. Calcium influx blockers, diltiazem and the biscoclaurine alkaloid cepharanthine enhanced the cytotoxicity of harringtonine in P388/ADM and K562/ADM cells. The extent of enhancement was different for the two drugs, and up to a 9- to 10-fold increase in harringtonine cytotoxicity occurred in P388/ADM cells, and 14- to 22-fold enhancement in K562/ADM cells with diltiazem or cepharanthine. Harringtonine resistance of P388/ADM was circumvented completely, and the resistance of K562/ADM was circumvented partially, by diltiazem or cepharanthine. The mechanism of enhanced cytotoxicity by diltiazem and cepharanthine is probably inhibition of active efflux of harringtonine in P388/ADM and K562/ADM cells.     

NADPH production from NADP+ with a glucose dehydrogenase system involving whole cells and immobilized cells of Gluconobacter suboxydans

Summary A convenient and efficient method of NADPH production from NADP⁺ has been established using a glucose dehydrogenase system involving whole cells and immobilized cells of Gluconobacter suboxydans IFO 3172. Using airdried cells of the bacterium, the optimum conditions for NADPH production were examined, including the cell and glucose concentrations, NADP⁺ concentration, pH, buffer and reaction temperature. Under suitable conditions, the conversion ratio and the amount of NADPH accumulated reached about 100% and 73 mg/ml of the reaction mixture, respectively, after 1-h reaction. Intact cells of the bacterium also showed high NADPH production even in the reaction mixture without a surfactant. The addition of Triton X-100 to the reaction mixture and freeze-thawing treatment of intact cells enhanced the production. The NADPH production method was further improved by using cells of the bacterium immobilized by entrapment in a -carrageenan gel lattice. The immobilized cells had almost the same enzymatic properties as the air-dried cells. The conditions for the continuous production of NADPH with an immobilized cell column were also investigated. NADPH was produced in a good yield (about 95%) with this continuous process.     

Purification and characterization of a protein that binds to the recombination signal sequence of the immunoglobulin J kappa segment.

A protein that binds to the recombination signal sequence (RS) of the immunoglobulin J kappa segment was purified almost to homogeneity from the nuclear extract of a murine pre-B cell line 38B9. A similar binding protein was found in lymphoid cell lines but not in non-lymphoid cell lines. The binding activity was associated with a polypeptide with a molecular weight of 60,000. DNase I footprinting analysis demonstrated that this binding protein interacted with the heptamer and several 3' bases close to the heptamer. The Kd value of the J kappa RS binding protein to the J kappa RS was 1 nM. One base substitution in the heptamer of the J kappa RS greatly reduced the affinity of the J kappa RS binding protein. The high specificity of the binding site of the J kappa RS binding protein suggests that this protein may be involved in V-J recombination.     

Proluminal movement of 3H-androgen across the epididymal epithelium in the rat after hypophysectomy and gonadotropin supplementation

The effects of hypophysectomy and gonadotropin replacement on transepithelial movement of 3H-androgen in the rat epididymis were examined by in vivo microperifusion of 3H-testosterone followed by in vivo micropuncture to obtain peritubular and intraluminal fluid. In the caput epididymidis of normal rats, intraluminal 3H-androgen concentrations were approximately 300% of those in the interstitial space. In contrast, proluminal movement of 3H-androgen into rat caput epididymal tubules was significantly decreased 10 days after hypophysectomy. 3H-Testosterone movement across the caput epididymal epithelium was completely returned to normal by supplementation with 24 micrograms/day follicle-stimulating hormone (FSH) or 24 micrograms/day luteinizing hormone (LH). However, neither 0.12 micrograms/day FSH nor 250 micrograms/day prolactin returned proluminal androgen movement to normal. It is speculated that epididymal uptake of peritubular testosterone is mediated by androgen-binding protein, which is known to be secreted by Sertoli cells after stimulation by FSH or testosterone.     

Primary structure of an N-linked sugar chain derived from glucoamylase of Rhizopus niveus

The primary structure of the N-linked sugar chain of Rhizopus niveus glucoamylase (major component) was investigated. The carbohydrate moiety was released from the polypeptide backbone by Flavobacterium sp. endo-beta-N-acetylglucosaminidase digestion. Studies using the method of exoglycosidase digestion of the fluorescent pyridylamino derivative, gel-permeation chromatography on Bio-Gel P-4 and 400-MHz 1H-NMR spectroscopy revealed that the most abundant structure is (Man)8-GlcNac-ol.     

Variation of glycosaminoglycan in the growth of transplantable tumors derived from a spontaneous ddY mouse mammary tumor

The components and variations of glycosaminoglycan (GAG) in the growth of transplantable tumors derived from a spontaneous mouse mammary tumor were investigated. A 45-week-old ddY female mouse, obtained from Shizuoka Laboratory Animal Center, was found to have a bean-sized mass at the third mammary gland of the left side. The tumor mass was surgically excised and used for transplantation in the present study. This mammary tumor was histologically found to be Type B-adenocarcinoma. Transplantable mammary tumors consisted of the fibrous or edematous interstitium contained a large amount of GAG components, which was mainly hyaluronic acid (HA), dermatan sulfate (DS) and chondroitin sulfate A/C (ChS). In the analysis of GAG components, HA content was present in a large amount in logarithmic growth phase of transplanted mammary tumors, but it was markedly decreased in stationary phase. On the other hand, the contents of DS and ChS increased in stationary phase of the tumor growth, and these increases corresponded, histologically, with the propagation of the fibrous interstitial tissues.