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Biomedical subjects

Y Fukui

Publications and source records attributed to Y Fukui.

At least 433 records · Page 24Linked to original sources
PubMed1987

Movement of the actin filament bundle in Mytilus sperm: a new mechanism is proposed.

An actin filament bundle approximately 2-5 microns in length is present in the sperm of the blue mussel, Mytilus. In unfired sperm this bundle extends from the midpiece through a canal in the center of the nucleus to terminate on the membrane limiting the inside of the cone-shaped acrosomal vacuole. The bundle is composed of 45-65 actin filaments which are hexagonally packed and regularly cross-bridged together to form an actin paracrystal so well ordered that it has six nearly equal faces. Upon induction of the acrosomal reaction, a needle-like process is formed in a few seconds. Within this process is the actin filament bundle which appears unchanged in filament number and packing as determined by optical diffraction methods. Using fluorescein-conjugated phalloidin we were able to establish that the bundle does not change length but instead is projected anteriorly out of the midpiece and nuclear canal like an arrow. Existing mechanisms to explain this extension cannot apply. Specifically, the bundle does not increase in length (no polymerization), does not change its organization (no change in actin twist), does not change filament number (no filament sliding), and cannot move by myosin (wrong polarity). Thus we are forced to look elsewhere for a mechanism and have postulated that at least a component of this movement, or cell elongation, is the interaction of the actin filament bundle with the plasma membrane.

Actin Cytoskeleton↗
PubMed1987

Follicle culture enhances fertilizability and cleavage of bovine oocytes matured in vitro.

The fertilization and cleavage of bovine oocytes matured by intra- or extra-follicular methods were investigated. Oocytes were fertilized in vitro or in the rabbit oviduct and cleavage was assessed after in vitro culture of in vitro fertilized oocytes and after in vivo culture (rabbit oviducts) of xenogenously fertilized oocytes. The effect of fertilization with fresh-diluted or frozen-thawed semen were also examined. The intra-follicular method did not increase the nuclear maturation rate as compared with the extra-follicular method (57.9 and 52.7%, respectively). However, the proportions of in vitro fertilized eggs (54.8%) and of cleaved eggs (two to eight cells; 34.6%) in the rabbit oviduct for 48 h after xenogenous fertilization were higher (P less than .025) in the intra-follicular oocytes than those of the extra-follicular oocytes (37.1 and 21.3%, respectively). It was also found that the use of fresh-diluted semen resulted in more cleaved eggs from the rabbit oviduct than the use of frozen-thawed semen (43.4 and 23.3% in the intra-follicular oocytes, P less than .025; 31.0 and 7.8% in the extra-follicular oocytes, P less than .05), while the appearance of cleaved eggs following in vitro fertilization was extremely low (0 to 6.6%). The present results demonstrated that the intra-follicular culture method of bovine oocytes provided a physiological environment for cytoplasmic maturation leading to higher fertilizability and development than the conventional in vitro culture of extra-follicular oocytes.

Animals↗
PubMed1986

Role of a ras homolog in the life cycle of Schizosaccharomyces pombe.

We have analyzed the function of the only ras homolog in S. pombe detectable by Southern blotting, ras1, which is homologous to mammalian ras genes and has been cloned. We have disrupted the ras1 gene and have replaced it with ras1Val17, which corresponds to a transforming variant of mammalian ras. Loss of ras1 activity by disruption results in the complete inability to mate. The cell body of a ras1- strain is extensively deformed, and a ras1-/ras1- diploid sporulates very poorly. Unlike RAS1 and RAS2 of S. cerevisiae, ras1 of S. pombe appears to have no effect on adenylate cyclase activity. This suggests that the target enzymes presumably modulated by ras proteins in signal transduction are not the same for all organisms.

Adenylyl Cyclases↗
PubMed1986

Mating pheromone-like diffusible factor released by Schizosaccharomyces pombe.

We demonstrate that a diffusible factor is secreted by h cells of the fission yeast Schizosaccharomyces pombe, whose mating pheromones have not been described. This factor, tentatively named the h-factor, affects hS. pombe cells and induces their elongation under nitrogen-depleted conditions. Circumstantial evidence suggests its physiological significance in the mating process. Despite their sterility, hras1 cells secrete this factor. However, hras1 cells have apparently lost the ability to respond to it. This may suggest that the gene product of S. pombe ras1, a homologue of mammalian ras oncogenes, is involved in the mechanism for responding to mating pheromones.

Journal Article↗
PubMed1986

Detection of delta 9-THC in saliva by capillary GC/ECD after marihuana smoking.

A method is described for the determination of delta 9-tetrahydrocannabinol (delta 9-THC) in the saliva by the use of a combination of moving-precolumn injector and glass capillary gas chromatograph with electron capture detector (GC/ECD). There were no interfering peaks due to impurities around the peak of pentafluoropropyl derivative of delta 9-THC (delta 9-THC-PFP). This GC/ECD method was linear over the range of 5-200 ng/ml of delta 9-THC-PFP. The lower detection limit was approximately 1 ng/ml. delta 9-THC content in the saliva after experimental marihuana smoking was measured by this method. It was demonstrated that for at least 4 h after smoking the level of delta 9-THC was sufficient for detection.

Adult↗
PubMed1986

The adenovirus type 12 early-region 1B 58,000-Mr gene product is required for viral DNA synthesis and for initiation of cell transformation.

An E1B 58K mutant of adenovirus type 12 (Ad12), dl207, was constructed by the deletion of 852 base pairs in the E1B 58K coding region. The mutant could grow efficiently in 293E1 cells but not in HeLa, KB, or human embryo kidney (HEK) cells. Viral DNA replication of dl207 was not detected in HeLa and KB cells and was seldom detected in HEK cells. Analysis of viral DNA synthesis in vitro showed that the Ad12-DNA-protein complex replicated by using the nuclear extract from Ad12 wild-type (WT)-infected HeLa cells but not by using the nuclear extract from dl207-infected cells. In dl207-infected HeLa and KB cells, early mRNAs were detected, but late mRNAs were not detected. The mutant induced fewer transformed foci than the WT in rat 3Y1 cells. Cells transformed by dl207 could grow efficiently in fluid medium, form colonies in soft agar culture, and induce tumors in rats transplanted with the transformed cells at the same efficiency as WT-transformed cells. Tumors were induced in hamsters injected with WT virions but were not induced in hamsters injected with dl207 virions. The results indicate that the E1B 58K protein is required both for viral DNA replication in productive infection and for initiation of cell transformation, but not for maintenance of the transformed phenotype.

Adenovirus Early Proteins↗
PubMed1986

Analysis of structure and activation of some receptor-type tyrosine kinase oncogenes.

We first describe the characterization of proto-oncogene of v-ros in chicken and human genomes. v-ros sequence of UR2 avian sarcoma virus carries a hydrophobic short stretch upstream of the kinase domain, suggesting that its proto-oncogene encodes for a receptor molecule. Using v-ros DNA as a probe we isolated chicken and human c-ros proto-oncogenes. These c-ros DNAs contained a tyrosine kinase domain, transmembrane domain and a part of an extracellular domain carrying an N glycosylation site which was not acquired by UR2 sarcoma virus. These results strongly suggest that proto-oncogene c-ros encodes for a receptor of cell growth or differentiation factor(s) and that the v-ros sequence is a truncated form of this receptor molecule. Structural alteration and overexpression under the control of viral promoter may be crucial for transforming activity of v-ros gene. We then report another example where a receptor-type oncogene is qualitatively and quantitatively activated. By screening with various onc probes we detected two human glioblastomas which have amplification of structurally altered c-erbB1 (epidermal growth factor (EGF) receptor) gene. c-erbB1 gene in these tumors bears a small deletion within the extracellular domain, and the gene product 140 kd protein shorter than the normal 170 kd EGF receptor was heavily phosphorylated on tyrosine residue even without ligand in in vitro phosphorylation reaction. Thus, these mutated EGF receptors seem to be fixed as a "switch-on" form in signal transduction for cell growth and might be involved in the transformation of glial cells.

Amino Acid Sequence↗
PubMed1986

Tetrahydro-beta-carbolines in human urine and rat brain--no evidence of formation by alcohol drinking.

1-Methyl-1,2,3,4-tetrahydro-beta-carboline (1-MeTHBC) and 6-methoxy-1-methyl-1,2,3,4-tetrahydro-beta-carboline (6-M-1-MeTHBC) were identified and quantified in the urine of 131 healthy volunteers by gas chromatography/mass spectrometry (GC/MS) with a chemically-bonded glass-capillary column. 1-MeTHBC was present naturally in the human urine, whereas 6-M-1-MeTHBC was observed in only 20% of all subjects at a much lower level. No significant relationship was observed between these substances and alcohol consumption in the subjects. Various foods and alcoholic beverages were found to contain 1-MeTHBC but not 6-M-1-MeTHBC; thus, the urinary 1-MeTHBC detected could be of dietary origin. Salsolinol, on the other hand, was significantly elevated in the urine without increase of THBCs by long-term moderate drinking. 1-MeTHBC and 6-M-1-MeTHBC were also analysed in the brains of rats following inhalation of ethanol and acetaldehyde for four days. No evidence of formation of these compounds was observed in any regions of the brain.

Acetaldehyde↗
PubMed1985

Molecular cloning and sequence analysis of a ras gene from Schizosaccharomyces pombe.

We have cloned a ras gene homologue from fission yeast Schizosaccharomyces pombe and determined its nucleotide sequence. A putative coding sequence for 219 amino acids was found. The sequence contained one set of splicing signals: GTAAGT for a donor sequence, ACTAA for a unique sequence found in introns of yeast genes and TAG for an acceptor sequence, indicating the existence of an intron. The amino-terminal one third of the predicted S. pombe ras protein was nearly perfectly homologous and the next one third moderately homologous to those of mammalian ras proteins. The carboxy-terminal one third showed no homology but terminated with a short conserved sequence Cys-X-X-Z (X being a hydrophobic amino acid) as in other ras proteins. The result of Southern analysis of S. pombe DNA under nonstringent hybridization conditions using our clone as a probe indicated that no other closely related gene may be present in the S. pombe genome. The transcript of this gene could be detected by Northern analysis.

Amino Acid Sequence↗