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Biomedical subjects

J Otsuka

Publications and source records attributed to J Otsuka.

At least 55 records · Page 3Linked to original sources
PubMed1987

Accumulation pattern of amino acid substitutions in protein evolution.

A simple method for the evolutionary analysis of amino acid sequence data is presented and used to examine whether the number of variable sites (NVS) of a protein is constant during its evolution. The NVSs for hemoglobin and for mitochondrial cytochrome c are each found to be almost constant, and the ratio between the NVSs is close to the ratio between the unit evolutionary periods. This indicates that the substitution rate per variable site is almost uniform for these proteins, as the neutral theory claims. An advantage of the present analysis is that it can be done without knowledge of paleontological divergence times and can be extended to bacterial proteins such as bacterial c-type cytochromes. It is suggested that the NVS of cytochrome c has been almost constant even over the long period (ca. 3.0 billion years) of bacterial evolution but that at least two different substitution rates are necessary to describe the accumulated changes in the sequence. This "two clock" interpretation is consistent with fossil evidence for the appearance times of photosynthetic bacteria and eukaryotes.

Amino Acid Sequence↗
PubMed1987

Theoretical analysis of single-round transcription experiments on trp leader region.

A kinetic model is proposed to reproduce the time courses of the concentration change in paused leader RNA, terminated leader RNA, and readthrough RNA in the single-round transcription experiments on trp leader region of Escherichia coli and its mutants, L132, L75, and L75L135 (Winkler, M. E., and C. Yanofsky, 1981, Biochemistry, 20:3738-3744; Fisher, R., and C. Yanofsky, 1983, J. Biol. Chem., 258:9208-9212). This model fits the experimental results well and also captures the essential aspects of the processes of transcriptional pausing and termination. In the wild type template, under optimal conditions, it is found that the transcription rate at the pause and attenuation sites is of the same order of magnitude, 10,000-fold lower than the transcription rate at the other sites, and the high termination level at the attenuation site is attributable to a higher dissociation rate. This analysis also provides a clue as to how the template base change, various concentrations of ribonucleoside triphosphates, and the presence or absence of L-factor affect the transcription and dissociation rates to yield different termination levels at the pause or attenuation site. It also discusses the molecular mechanism of the transcriptional pausing and termination.

DNA-Directed RNA Polymerases↗
PubMed1987

A possible mode of protein evolution. Role of the anti-sense strand in the generation of new proteins.

The possibility that a new functional protein may be generated during evolution by using the anti-sense strands of pre-existing genes is proposed. Sequence similarity between the anti-sense strand of one gene and the sense strand of another gene may provide evidence for this generation. The computer search for the "sense/anti-sense" strand similarities between nucleotide sequences for receptors and sequences available in a database was carried out. This type of similarity was found for various receptor genes, such as the low density lipoprotein receptor, lymphocyte receptor for IgE, asialoglycoprotein receptor (hepatic lectin), T-cell receptor, epidermal growth factor receptor, insulin receptor and estrogen receptor genes. Sequence similarities between the sense strands of receptor genes were also found. These results may suggest that the repertoire of proteins was increased by the utilization of the anti-sense or sense strands of pre-existing genes.

Amino Acid Sequence↗
PubMed1986

Theoretical evaluation of transcriptional pausing effect on the attenuation in trp leader sequence.

The effect of transcriptional pausing on attenuation is investigated theoretically on the basis of the attenuation control mechanism presented by Oxender et al. (Oxender, D. L., G. Zurawski, and C. Yanofsky, 1979, Proc. Natl. Acad. Sci. USA. 76:5524-5528). An extended stochastic model including the RNA polymerase pausing in the leader region is developed to calculate the probability of relative position between the RNA polymerase transcribing the trp leader sequence and the ribosome translating the transcript. The present study results in a new rationale that the transcriptional pausing site in the leader sequence makes the attenuation control both more sensitive as an on/off switch and less sensitive to variations in the concentration of cellular metabolites not connected with the need for expressing, or not expressing, the particular operon. It is also proposed that the transcriptional pausing diminishes the dependence of attenuation control characteristics on the number of nucleotides in the leader sequence. This result may be useful for understanding the attenuation control efficiencies of other amino acid leader sequences with different lengths of nucleotides.

Amino Acid Sequence↗
PubMed1986

Fine structure of the seminal vesicle epithelium of the mouse and golden hamster.

The seminal vesicle epithelium of the mouse and golden hamster was examined by light microscopy and by transmission and scanning electron microscopy. By transmission electron microscopy, in the seminal vesicle epithelium of both animals secretory epithelial cells which consisted of mostly light and a few dark cells were observed. The epithelial cells possessed secretory granules which contained a densely stained core. The secretory granules in the mouse epithelium reacted weakly with periodic acid-Schiff (PAS) stain and were slightly stained with alcian blue (AB), and those in the golden hamster exhibited strongly positive reactions with PAS and AB. The nuclei in the mouse tissue were spherical or ovoid, and those in the golden hamster tissue had a few lobes. By scanning electron microscopy, the apical surfaces of most of the epithelial cells were commonly flat or domed, and those of some epithelial cells protruded into the lumen as apocrine-like processes, or possessed small and large orifices. Besides the epithelial cells, there were cells characterized by pseudopodium-like cytoplasmic projections, a few membranous structures, an irregular nucleus, and cytoplasm containing a few dense bodies, in the basal portions of the epithelial cells, or between the basal lamina and the epithelial cells. These cells of the two species were similar in their features.

Animals↗
PubMed1986

Fine structure of the mandibular gland in Japanese field vole (Microtus montebelli).

The mandibular glands of the Japanese field vole were examined by light microscopy, and transmission and scanning electron microscopies. The acinar cells contained light and coarse secretory granules, and reacted with PAS and stained slightly with AB; they were considered to be seromucous in nature. The acinar epithelium was composed of light and dark cells containing many secretory granules. The intercalated duct cells consisted of light cells possessing a few dense granules. A few cytoplasmic crystalloides of moderate density were observed in occasional light cells. The striated ducts were comprized of two distinct portions, a secretory portion and a typical striated portion without secretory granules. The epithelium secretory portion consisted of light and dark cells containing acidophilic granules and exhibited a sexual dimorphism in these granules: The male epithelia contained the granules of low to high densities, while the female epithelia had only dense granules being smaller than those in the males. The epithelium of typical striated portion was composed of light and dark cells containing fine vacuoles and vesicles.

Animals↗
PubMed1985

Fine structure of the mandibular gland in pika (Ochotona rufescens rufescens).

The mandibular gland of the pika was examined by light microscopy, and transmission and scanning electron microscopies. The acinar cells were noted to be composed of serous cells and seromucous cells. The serous cells containing granules of moderate and high densities were slightly basophile and strongly positive to PAS, but were not stained with AB. The seromucous cells possessing less dense granules were light and moderately positive to PAS and AB. A sexual dimorphism was observed between these cells: Serous cells were considerably more frequent in males and seromucous cells were more numerous in females. Intercalated duct cells consisted of cuboidal light cells containing a few vesicles in the apical region. Striated ducts were comprised of two portions--a secretory portion and a typical striated portion without secretory granules. The secretory portion was composed of light and dark cells having secretory granules varying in size and density. The epithelium of typical striated portion consisted of light and dark cells containing fine vacuoles and vesicles.

Animals↗
PubMed1984

Fine structure of the mandibular gland of the Djungarian hamster (Phodopus sungarus).

The mandibular gland of the Djungarian hamster was examined by light microscopy, and transmission and scanning electron microscopies. Its acinar cells reacted with periodic acid-Schiff (PAS) and were weakly stained with alcian blue (AB). There were intercellular canaliculi between the acinar cells. These cells therefore appeared to be seromucous. The acinar epithelium was composed of light cells containing various spherical secretory granules. The granular cells of the mandibular gland possessed many acidophilic granules exhibiting a positive reaction to PAS stain. They were frequently observed at the junction of the acini and intercalated ducts in all mandibular glands examined. All of these cells were light and contained secretory granules of varying size and density. The intercalated ducts consisted exclusively of light cells possessing a few round granules of high density in the apical region. The striated ducts were comprised of two portions--a secretory portion and a typical striated portion without secretory granules. The secretory portion consisted of light, dark and specifically light epithelial cells containing acidophilic granules, which exhibited a strongly positive PAS reaction. The epithelium of typically striated portions was composed of light and dark cells containing fine vacuoles in the apical region. The mandibular gland of the Djungarian hamster revealed no histological differences between sexes.

Alcian Blue↗
PubMed1983

Fine structure of the parotid gland of Djungarian hamster (Phodopus sungarus).

The parotid glands of Djungarian hamster were examined by the light and electron microscopy. The acinar cells contained acidophile granules and reacted with the periodic acid-Schiff (PAS) and stained slightly with alcian blue (AB); they were thought to be seromucous in nature. The acinar epithelia were composed of light cells, dark cells and specific light cells containing spheroid granules. Cytoplasmic crystalloids of moderate to high densities were observed in nearly all light cells. The intercalated duct cells were composed of light cells alone, and contained the granules of moderate density in the apical and supranuclear regions. The striated duct cells consisted of light and dark cells. The most of these cells contained small granules of low to high densities in the apical and supranuclear regions. Myoepithelial cells were detected around the acini, and nerve terminals were observed among the adjacent acinar cells. The parotid gland of Djungarian hamster revealed no histological differences between the sexes.

Animals↗
PubMed1982

Fine structure of the mandibular gland of Chinese hamster (Cricetulus griseus).

The mandibular glands of the Chinese hamster were examined by light and electron microscopy. The mandibular acinar cells were noted to be categorized in a seromucous type, because the acinar cells stained slightly basophile and moderately positive for periodic acid-Schiff (PAS) and alcian blue (AB) reactions and the intercellular canaliculi were detected in the cells. The acini were composed exclusively of light cells containing various secretory granules. The acinar cells exhibited a sexual dimorphism; in the female AB staining was more intense, and also the granules having the matrix of a fine hair-like material were more numerous than in the male. Intercalated duct cells were composed exclusively of light cells and contained round and polygonal granules. The striated ducts consisted of two distinct portions, the secretory and typical striated portions without secretory granules. The epithelial cells of secretory portion were columnar in shape and contained acidophile granules which gave a strongly positive PAS reaction, and comprised light and dark cells containing secretory granules varying in size and density. The epithelium of typical striated portion was composed of both light and dark cells containing fine vacuoles and vesicles, but no secretory granules. No sexual dimorphism was detected in the striated duct.

Animals↗