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Biomedical subjects

M Araki

Publications and source records attributed to M Araki.

At least 199 records · Page 11Linked to original sources
PubMed1986

Alterations in the differentiation of chick retina caused by an intraocular injection of an alkaline phosphatase inhibitor.

Intense alkaline phosphatase (ALPase) activity has been localized in the outer plexiform layer of the developing chick retina. To elucidate the functional significance of this enzymatic activity, we have injected an ALPase inhibitor, levamisole, into embryonic eyes on either the 13th or 15th day of incubation. The retina was fixed between the 15th and 20th day of incubation and examined by electron microscopy. Levamisole injection on the 13th day caused various morphological alterations in retinal development, including the appearance of solitary photoreceptor cells in the subretinal space as well as folding of both the outer plexiform and outer nuclear layers. Pedicles of photoreceptor cells in the outer plexiform layer displayed rather smooth configurations with a reduced number of invaginations by post-synaptic neurites. The outer plexiform layer was thinned and the neuritic extensions in this layer appeared much less developed than in the control (PBS-injected) retina. Photoreceptor outer segments were seldom observed. Besides these alterations, layers of optic fibers and ganglion cells were also affected, as shown by evidence of degeneration in the ganglion cells and thinning of the nerve-fiber layer. Injection of levamisole into day 15 embryonic eyes exerted less influence on retinal development, but some photoreceptor cells were still found in the subretinal space. Some of these observations have been reported in the retinas of aged normal animals or in retinas with hereditary or induced retinal dystrophy. It is suggested that ALPase activity in the outer plexiform layer of the developing chick retina may be important for the onset of normal development of synapses in the outer plexiform layer and differentiation of the photoreceptor cells.

Alkaline Phosphatase↗
PubMed1986

Expression of hepatitis B virus core antigen gene in Saccharomyces cerevisiae: synthesis of two polypeptides translated from different initiation codons.

Two recombinant plasmids were constructed that allow expression of the hepatitis B core (HBc) antigen gene in the yeast Saccharomyces cerevisiae under the control of the repressible acid phosphatase promoter. One plasmid was designed to produce polypeptide I, which consists of 183 amino acids, and the other plasmid was designed to produce polypeptide II, which has an additional 29-amino-acid sequence at the amino terminus of polypeptide I. The viral genome may code for either one or both of these two polypeptides, depending upon the selection of initiation codons. Both polypeptides produced in yeast cells reacted with anti-HBc antibody and were assembled into spherical particles approximately 27 nm in diameter. Particles made of polypeptide I were stable, whereas those made of polypeptide II readily dissociated when exposed to high salt levels. The antigenicity of the HBc (as defined by its reactivity to anti-HBc antibody in the reversed passive hemagglutination assay) disappeared as the particle dissociated, leaving materials that sedimented slowly and that reacted to anti-hepatitis B e antibody. These observations strongly suggest that native viral cores are mostly (if not all) made of polypeptide I, because it is reasonably stable, and that the N-terminal portion of this polypeptide has some, but not a profound, influence on the assembly of polypeptides into particles.

Capsid↗
PubMed1986

A novel oncogene from a human hepatocellular carcinoma.

Primary human hepatocellular carcinomas (HCC) were surveyed for oncogenes by transformation assays using NIH 3T3 cells and calcium phosphate coprecipitation method. One new transforming DNA, called lca (for liver cancer) was obtained, and its properties were studied in detail. The lca DNA, localized in a 10.5 kb DNA fragment, was assigned to human chromosome 2. It showed identical restriction enzyme cleavage profiles as its counterpart DNA obtained from normal tissue, indicating that there is no extensive DNA rearrangement associated with activation process of the lca DNA. The normal counterpart DNA shows no transforming activity. Recombinant genes of the laca and its normal counterpart made in vitro have allowed localization of the site of "activation" to a limited region of the 10.5 kb fragment. An independently obtained transforming DNA from another HCC exhibited identical restriction enzyme cleavage profiles. Thus, lca DNA is likely to represent a commonly encountered transforming DNA in HCC.

Animals↗
PubMed1985

Striatonigral and pallidonigral pathways studied by a combination of retrograde horseradish peroxidase tracing and a pharmacohistochemical method for gamma-aminobutyric acid transaminase.

The pharmacohistochemical neuronal staining method for gamma-aminobutyric transaminase (GABA-T) combined with retrograde horseradish peroxidase (HRP) staining was used to define more precisely the descending striatonigral and pallidonigral pathways. Previous studies have established that GABA-T intensive cells in the basal ganglia and other structures correspond with reported glutamic acid decarboxylase (GAD)-containing cells and are therefore presumed to use GABA as their neurotransmitter. Following injection of HRP into the substantia nigra, many HRP-labeled cells were detected in the caudate-putamen and globus pallidus. Two separate groups of cells were doubly labeled for GABA-T and HRP and seemed to represent two distinct GABA-T-rich descending pathways to the substantia nigra. One component came from medium-sized cells in the lateral aspect of the globus pallidus. It represented a majority of all descending cells from that nucleus. The other came from the lateral aspect of the caudate-putamen and represented only a minority of descending cells from that structure. These data suggest that the majority of striatonigral fibers are non-GABA containing while the majority of pallidonigral fibers are GABA-containing. The precise location of the GABA-T intensive cells making up these two pathways helps to explain much confusing data in the literature on the source of descending GABA fibers to the substantia nigra.

4-Aminobutyrate Transaminase↗
PubMed1985

Differential effect of kainic acid on somatostatin, GABAergic and cholinergic neurons in the rat striatum.

Kainic acid was injected into the rat striatum and its effects on presumptive striatal cholinergic, GABAergic and somatostatin-containing neurons were examined with three histochemical staining methods. Presumptive cholinergic and GABAergic neurons are damaged to a similar extent, but somatostatin neurons are more sensitive to the neurotoxic effect of kainic acid and are more severely affected.

4-Aminobutyrate Transaminase↗
PubMed1984

Retrograde HRP tracing combined with a pharmacohistochemical method for GABA transaminase for the identification of presumptive GABAergic projections to the habenula.

A pharmacohistochemical method for GABA-transaminase (GABA-T), the key enzyme for GABA metabolism, has been combined with retrograde tracing by horseradish peroxidase, to a study of projections to the lateral habenula. The results indicate that projections to the lateral habenula arise from both GABA-T intensive and non-GABA-T staining cells in the rostral entopeduncular nucleus and the lateral hypothalamus suggesting that these projections contain GABAergic elements, as indicated by previous work, but also involve other neurotransmitters. A few GABA-T intensive cells in the lateral preoptic area were also found to project to the lateral habenula by this double staining technique.

4-Aminobutyrate Transaminase↗
PubMed1984

Functional heterogeneity of the descending limbs of Henle's loop. I. Internephron heterogeneity in the hamster kidney.

By using the in vitro microperfusion technique, were examined functions of the descending limbs of Henle's loop obtained from either the short-loop nephron (SDL) or the upper portion of the long-loop nephron of hamsters (LDLu). Morphological distinctions between these segments were confirmed by light and electron microscopic observations. Both segments were highly permeable to water. The LDLu was highly permeable to sodium and to chloride: efflux coefficients (10(-7) cm2 x s-1) for 22Na and 36Cl were 41.0 +/- 5.4 and 3.8 +/- 0.6, respectively. The SDL were less permeable to sodium and to chloride: efflux coefficient for 22Na and 36Cl were 2.9 +/- 1.4 and 0.9 +/- 0.2, respectively. In contrast, the SDL was more permeable to urea as compared to the LDL, efflux coefficients for urea being 5.1 +/- 1.4 vs 1.4 +/- 0.3, respectively. When composition of the perfusate was identical to that of the bathing fluid, no transepithelial voltage was demonstrated. The volume flux was very small or undetectable. From these observations, we propose that the internephron heterogeneity must be taken into consideration for constructing a model of countercurrent system in the renal medulla.

Animals↗
PubMed1984

Immunocytochemical study on photoreceptor cell differentiation in the cultured retina of the chick.

Photoreceptor cell differentiation was investigated in a dissociated monolayer culture of chick embryonic retinas with electron microscopic immunohistochemistry. The antibody was raised against bovine rhodopsin purified on SDS-polyacrylamide gel electrophoresis. In the developing retina, immunoreactivity was first recognized on the 14th day of incubation and was localized on the plasma membrane of the growing inner segment. On the 16th day, immunoreactivity was observed on some differentiating outer segments but not on inner segments. In the culture from 6 1/2-day-old embryonic retinas, immunoreactivity was found on the 7th day of culturing on the plasma membrane of large-sized neurons. Electron microscopic observations confirmed that such stained cells showed reaction product on the plasma membrane, and that they displayed fine structures characteristic of intact photoreceptor cells. They had a number of microvillous processes and often one thick process, both of which were intensely stained. Outer segment formation, however, was not observed in the present monolayer culture. These results indicate that opsin synthesis and its transport to the plasma membrane begins prior to and probably independently of outer segment formation.

Animals↗