DNA replication in vivo of linear DNA killer plasmids pGKL1 and pGKL2 in Saccharomyces cerevisiae

Abstract Electron microscopic observation demonstrated that linear DNA plasmids, pGKL1 and pGKL2, were replicated by a strand displacement mechanism similar to adenovirus and Bacillus subtilis ø 29 phage. Moreover, their DNA replication was prevented by α-factor, a mating hormone which prevents the replication of chromosomal DNA and 2 μm plasmid in Saccharomyces cerevisiae mating type a cells. This result suggests that the replication of pGKL plasmids is controlled by the same genes that control the initiation or maintenance of chromosomal DNA and 2 μm plasmid replications.     

Effect of d-Limonene and related compounds on bile flow and biliary lipid composition in rats and dogs

d-Limonene enhanced bile flow in rats and dogs with a dose response correlation. The choleretic activity was much higher in the metabolites of d-limonene such as p-mentha-1,8-dien-10-ol, p-menth-1-ene-8,9-diol and p-mentha-1,8-dien-6-ol than d-limonene, and this suggested that the choleretic activity of d-limonene was attributable at least in part to its metabolites.The choleretic activities of esters of p-menth-1-ene-8,9-diol with acetic acid, propionic acid, stearic acid, palmitic acid, linoleic acid, benzoic acid, salicylic acid, α-naphthylacetic acid and nicotinic acid were also investigated in rats. Among these compounds, acetate, propionate and nicotinate possessed considerable, but lesser activities than the original diol. In dogs, however, the choleretic activity of p-menth-l-ene-8,9-diol acetate and propionate was much higher than that of original diol, suggesting that the choleretic activity of these esters is attributable to the esters themselves.d-Limonene decreased the ratio of biliary bile salts and phospholipids to cholesterol, whereas p-menth-l-ene-8,9-diol increased it.     

The spinal nerves innervate putative chemosensory cells in the ventral skin of desert toads, Bufo alvarius

Toads normally obtain water by absorption across their skin from osmotically dilute sources. When hyperosmotic salt solutions are presented as a hydration source to dehydrated desert toads, they place the ventral skin onto the source but soon afterwards escape to avoid dehydration. The escape behavior coincides with neural excitation of the spinal nerves that innervate putative chemosensory cells in the ventral skin. In the present study, fluorescent dye translocated through the spinal nerves to those receptor cells in the epidermis was photoconverted in the presence of 3, 3'-diaminobenzidine tetrahydrochloride for electron-microscopic observation of the cells and associated nerve terminals. Most of the photoconverted cells were located in the deepest layer of the epidermis, with some being in more intermediate layers. No labeled cell was seen in the outermost layer of living cells. In desert toads, flask cells and Merkel cells are occasionally seen in the epidermis. An association of nerve fibers with these epidermal cells has been reported in some species of the anurans. In the present study, however, the cytological features of the photoconverted cells are neither reminiscent of flask cells nor Merkel cells, but are similar to those of surrounding epithelial cells in each layer of the epidermis. We hypothesize a sensory function for these cells, because they have a close association with nerve fibers and participate in the transepithelial transport of salts that must pass through all cell layers of the skin.     

Molecular cloning of Saccharomyces cerevisiae MGC1/YDR473c gene which is essential for cell growth

Saccharomyces cerevisiae haploid cells undergo morphological changes in response to mating pheromones, a- and -factors, during sexual conjugation. As a first step to elucidate the mechanism, I had previously identified the mgc1 mutation which affected the morphogenesis induced by mating pheromones. The mutation had been designated mgc1 for morphogenesis control. In the present study I cloned the MGC1 gene. Sequencing analysis indicates that the MGC1 gene corresponds to the YDR473c gene. The MGC1 gene was shown to be essential for cell growth and required for the transition from the G1 to S phase of cell cycle. Protein-protein interaction of Mgc1 protein was shown by using yeast two-hybrid system. Mgc1 protein was also proposed to be localized in the nucleus in yeast cells.     

Taste Disks are Induced in the Lingual Epithelium of Salamanders during Metamorphosis

Morphological changes of oral cavity during metamorphosis withspecial reference to the taste organ were examined in Ezo salamanders(Hynobius retardatus) and axolotls (Ambystoma mexicanum), andcompared with those in bullfrogs (Rana catesbeiana). The non-distensibletongue of salamanders changed the structure progressively duringmetamorphosis: a small area of the rostrum protruded and developedcaudally with recession of the flat area of the tongue. Theprotrusion that developed on the tongue had numerous papillae,as seen in the frog tongue. The apical region of the papillaeoccasionally had a cell mass similar to the taste disk of frogs(termed a taste disk-like cell mass). On the flat area of thetongue, the barrel-shaped taste buds of larval salamanders weretransformed into taste buds with a wider receptor area. Thebarrel-shaped taste buds decreased progressively during metamorphosis,while taste disk-like cell masses increased. Neuronal labelingwith an antibody to neuron-specific enolase and fluorescentcarbocyanine dye showed that the taste disk-like cell massesin metamorphosed salamanders were innervated by the glossopharyngealnerve (nerve IX). Nerve IX responded to taste stimulation aswell as mechanical stimulation applied to the rostral tongue.During metamorphosis the salamanders undergo transformationand rearrangement of taste organs on the tongue possibly asan adaptation to the terrestrial environment. Chem. Senses 22:535–545, 1997.     

Axolotl hemoglobin: cDNA-derived amino acid sequences of two alpha globins and a beta globin from an adult Ambystoma mexicanum

Erythrocytes of the adult axolotl, Ambystoma mexicanum, have multiple hemoglobins. We separated and purified two kinds of hemoglobin, termed major hemoglobin (Hb M) and minor hemoglobin (Hb m), from a five-year-old male by hydrophobic interaction column chromatography on Alkyl Superose. The hemoglobins have two distinct alpha type globin polypeptides (alphaM and alpham) and a common beta globin polypeptide, all of which were purified in FPLC on a reversed-phase column after S-pyridylethylation. The complete amino acid sequences of the three globin chains were determined separately using nucleotide sequencing with the assistance of protein sequencing. The mature globin molecules were composed of 141 amino acid residues for alphaM globin, 143 for alpham globin and 146 for beta globin. Comparing primary structures of the five kinds of axolotl globins, including two previously established alpha type globins from the same species, with other known globins of amphibians and representatives of other vertebrates, we constructed phylogenetic trees for amphibian hemoglobins and tetrapod hemoglobins. The molecular trees indicated that alphaM, alpham, beta and the previously known alpha major globin were adult types of globins and the other known alpha globin was a larval type. The existence of two to four more globins in the axolotl erythrocyte is predicted.