Salt tolerance and glycerol accumulation of a respiration-deficient mutant isolated from the petite-negative, salt-tolerant yeast Zygosaccharomyces rouxii

A respiration-deficient (RD) mutant was isolated from the petite-negative, salt-tolerant yeast Zygosaccharomyces rouxii. One strain among sixteen glycerol-non-utilizing mutants exhibited vigorous liberation of CO2 but no uptake of O2. Furthermore, this strain lacked cytochrome aa3 and had a reduced level of cytochrome b. The few mitochondria found in cells of this strain contained few or no cristae. Salt tolerance and intracellular accumulation of glycerol by the RD strain were almost equal to that of the wild-type strain in media containing NaCl up to 2.5 M. In media with more than 3 M NaCl, the growth of the RD mutant was retarded and the intracellular accumulation of glycerol was depressed in spite of ample production.     

Scale Arrangement Pattern in a Lepidopteran Wing. 1. Periodic Cellular Pattern in the Pupal Wing of Pieris rapae

In most species of lepidopteran insects, anteroposterior rows formed by scales are arranged at regular intervals in the adult wing; within each row two kinds of scales are alternately arranged. To investigate the cellular basis for the scale arrangement pattern, we examined cell arrangement in the epidermal monolayer of the pupal wing of a small white cabbage butterfly, Pieris rapae , by scanning electron microscopy and light microscopy.
The arrangement of scale precursor cells, closely resembling that of scales in the adult wing, was observed in the wing epidermis of the early pupa. Scale precursor cells are proximodistally elongated and form anteroposterior rows. Within a row two kinds of scale precursor cells are nearly alternately arranged, which is not so precise as the alternation of scales in the adult wing. Individual rows of scale precursor cells are separated by rows of single or double undifferentiated general epidermal cells. Occasionally, arrangement abnormalities occur both in the adult and the pupal wing. The cellular basis for the regular spacing of scale rows is discussed.     

Evidence for the location of foreign genes in three different chromosomes in a plant obtained from direct DNA transfer

Tobacco mesophyll protoplasts were treated with plasmids, pCT2 (17.1 kbp) or pCT2T3 (18.3 kbp), which contained a chimeric aminoglycoside phosphotransferase II (APH(3′)II) gene and an intact nopaline synthase gene. Expression of two marker enzymes, APH(3′)II and nopaline synthase, were analyzed in transformed plants. Four out of 16 transformants obtained by pCT2T3 possessed both enzymes. Upon self-pollination, the progeny of one of transformants (T2) segregated to 153∶4 in terms of resistant and susceptible character to kanamycin, suggesting insertion of foreign genes into three independent chromosomes. The kanamycin resistant character in the rest of transformants showed 3∶1 segregation. DNA blot analysis of the T2 transformant and progenies indicated the presence of two marker genes.     

Requirement of c-kit for development of intestinal pacemaker system.

A discovery that the protooncogene encoding the receptor tyrosine kinase, c-kit, is allelic with the Dominant white spotting (W) locus establishes that c-kit plays a functional role in the development of three cell lineages, melanocyte, germ cell, and hematopoietic cell which are defective in W mutant mice. Recent analyses of c-kit expression in various tissues of mouse, however, have demonstrated that c-kit is expressed in more diverse tissues which are phenotypically normal in W mutant mice. Thus, whether or not c-kit expressed outside the three known cell lineages plays a functional role is one of the important questions needing answering in order to fully elucidate the role of c-kit in the development of the mouse. Here, we report that some of the cells in smooth muscle layers of developing intestine express c-kit. Blockade of its function for a few days postnatally by an antagonistic anti-c-kit monoclonal antibody (mAb) results in a severe anomaly of gut movement, which in BALB/c mice produces a lethal paralytic ileus. Physiological analysis indicates that the mechanisms required for the autonomic pacing of contraction in an isolated gut segment are defective in the anti-c-kit mAb-treated mice, W/Wv mice and even W/+ mice. These findings suggest that c-kit plays a crucial role in the development of a component of the pacemaker system that is required for the generation of autonomic gut motility.     

Comparative study of embryonic thermoresistance of two inbred strains of the medaka (Oryzias latipes)

Summary By using inbred strains (HO4C and HB32C) of the medaka,Oryzias latipes, the involvement of genetic factor(s) in the determination of thermoresistance of fish was investigated. The thermoresistance of embryos of the medaka was quantitated by the fraction of the embryos surviving 1 day after heat treatment. At early stages of development (st. 13 and st. 20–21), the HO4C strain was more resistant than the HB32C strain. At st. 20–21, the HO4C strain was more resistant than the HB32C strain at all temperatures used (42, 43, and 44°C). At later stages of development (st. 27 and st. 32), however, the HB32C strain was more resistant than the HO4C strain.The results of genetic cross experiments raised the following possibilities; the thermoresistance of embryos at early developmental stages can be lowered by some factor(s) inherited in the HO4C strain and/or increased by those in the HB32C strain. By contrast, the sensitivity of embryos at later stages of development was not affected by factor(s) of their parents, but by their own genetic constitution.     

Hepatic lesions in experimental Campylobacter jejuni infection of mice

Mice orally infected with Campylobacter jejuni developed focal infiltrative necrotic lesions in the liver, as determined by both histology and liver function tests. The initial histopathological feature was a focal infiltrative lesion in the parenchyma and portal triads. Foci of infiltrative lesions became necrotic between days 30 and 60 post-inoculation (p.i.). During this period, portal infiltrates increased in severity. From month 4 p.i., focal areas of infiltrative necrosis in the liver parenchyma became extensive. Study of liver function demonstrated mild elevations of transaminases, alkaline phosphatase and lactic dehydrogenase, and also the presence of hypoalbuminaemia. Although histopathological changes of the liver became gradually more marked after day 30 p.i., liver functions of infected mice were most affected at 2 months p.i. The capacity of C. jejuni to induce hepatic lesions seemed to be related to that of organisms to persist in the gall bladder; there was no correlation between biliary carriage in infected mice and positive faecal culture.     

A possible adenine nucleotide storage form in normal and ischaemic rat heart

Perfusion of Langendorff rat hearts with [¹⁴C]adenosine yields an acid-insoluble, radioactive product whose concentration falls during ischaemia. The properties of the substance show that it is a polyribonucleotide. It is suggested that it may be mitochondrial poly A acting as a storage form of adenine nucleotides.     

Forward mutation assay of V79 cells to 6-thioguanine resistance in a soft agar technique that eliminates effects of metabolic co-operation

A technique involving culture in soft agar was used for the assay of forward mutation of V79 cells to 6-thioguanine (6TG) resistance. The main reason for the use of soft agar was to prevent reduction in recovery of mutants depending on the cell density plated for mutation selection, which is the chief problem in the liquid method, and which results mainly from metabolic co-operation due to cell-to-cell contact.V79 cells grew well in fortified soft agar medium (DMEM + 20% FBS) showing cloning efficiencies (>80%) as high as in liquid culture. Therefore, V79/HGPRT mutagenesis could be assayed quantitatively in soft agar culture.The frequency of 6TG-resistant colonies in agar selective medium increased linearly with increase in concentration of EMS. Toxicity and mutagenic responses were greater in soft agar than in liquid culture.In cultures of untreated and EMS-treated cells, more than 95% of the 6TG-resistant colonies isolated were aminopterin-sensitive.Use of soft agar for selection prevented the reduction in the number of mutants with increase in the size of incula on plating up to 1?2 × 10⁶ cells per 9-cm dish: in liquid culture, even with a lower plating number (2 × 10⁵ cells per 9-cm dish), a notable reduction in numbers of mutants was observed. This character was re-examined in a reconstruction experiment. The results show that, when up to 2 × 10⁶ cells were plated per 9-cm dish, 6TG-resistant cells were almost completely recovered from the soft agar medium, whereas only 10% were recovered from liquid culture.     

A temperature-sensitive mutant in the gene rplX for ribosomal protein L24 and its suppression by spontaneous mutations in a 23S rRNA gene of Escherichia coli.

A temperature-sensitive mutant with an altered ribosomal protein L24 was analysed. Revertant analysis showed that the temperature-sensitive growth was correlated with the altered protein. A DNA segment containing the mutant rplX gene was cloned and sequenced. The GGC codon for glycine at the amino acid position 84 of the protein was found to be altered to a GAC codon for aspartic acid. By transforming the rplX mutant with a plasmid carrying the rrnB operon and by selecting for temperature-resistant transformants we obtained two spontaneous suppressor mutants in the gene for 23S rRNA. DNA sequence analysis of the region corresponding to the 5' end of the 23S rRNA showed a C to T alteration at position 33 in both mutants and an additional A to G alteration at position 466 in one of them. The results suggest intimate interaction of protein L24 and the 5' end of 23S rRNA in vivo and support a secondary structure model of the 23S rRNA which brings these mutational points into a close contact.