Biomedical subjects

M Kozuka

Publications and source records attributed to M Kozuka.

At least 55 records · Page 3Linked to original sources

PubMed1993

[Vestibular changes due to barotrauma].

Morphological vestibular changes caused by barotrauma were studied in guinea pigs. Animals were exposed to rapid decompression from 2 absolute atmospheric pressures (ATA) to 1 ATA, which causes inner ear barotrauma in the guinea pig. During decompression, spontaneous nystagmus was recorded, which consisted of irritative symptoms initially, followed by paralytic nystagmus. After pressure loading and observation to confirm the absence of Preyer's reflex with vertigo, the animals were tested for caloric nystagmus using ice water and then sacrificed at varying intervals. Then, morphological changes in vestibular organs and the organ of Corti were studied. Half of the experimental animals showed canal paresis on caloric testing. Damage to the organ of Corti was severe while that to vestibular organs was very slight. Damage to the sensory cells of the vestibular organs was not clear on light microscopy, despite a partial collapse of labyrinthine membranes. Under scanning electron microscopy, local damage was observed in a portion of the crista ampullaris of the semicircular canals. In this area, incomplete or complete disappearance of kinocilia and stereocilia, similar to that seen after rotatostimulation, was observed. However, no damage to sensory hairs was seen in the utricles and saccules. The observed vestibular organ damage, resulting from inner ear barotrauma, suggested effects on endolymphatic flow.

Animals↗

PubMed1992

Affinity chromatographic purification of bovine lung endothelin receptor using biotinylated endothelin and avidin-agarose.

Endothelin receptor was purified from bovine lung by affinity chromatography using biotinylated endothelin and avidin-agarose. Endothelin was biotinylated with sulphosuccinimidyl 2-(biotinamido)ethyl-1,3-dithiopropionate, a reactive form of biotin with a cleavable spacer arm containing a disulphide bond designed for a simple elution by thiols. Starting from 3.5 kg of bovine lung, about 200 micrograms of pure receptor were obtained.

Amino Acid Sequence↗

PubMed1992

Antitumor agents, 135. Structure and stereochemistry of polacandrin, a new cytotoxic triterpene from Polanisia dodecandra.

A new dammarane triterpene, polacandrin [1], has been isolated from Polanisia dodecandra. The structure of 1 was established as 1 beta, 3 alpha, 12 beta, 25-tetrahydroxy-20(S),24(S)-epoxydammarane by chemical and spectroscopic methods, which included the concerted application of a number of 2D nmr techniques that involved 1H-1H COSY, HETCOR, NOESY, and long-range HETCOR. Single-crystal X-ray analysis of polacandrin pentahydrate verified the complete structure and stereochemistry. Polacandrin showed potent cytotoxicities against KB (ED50 = 0.60 microgram/ml), P-388 (ED50 = 0.90 microgram/ml), and RPMI-7951 (ED50 = 0.62 microgram/ml) tumor cells.

Animals↗

PubMed1992

Anti-tumor-promoting activities of afromosin and soyasaponin I isolated from Wistaria brachybotrys.

Afromosin [1] and soyasaponin I [2] isolated from Wistaria brachybotrys exhibited remarkable inhibitory effects on mouse skin tumor promotion, and afromosin also exhibited a significant inhibitory effect on pulmonary tumor promotion. The combined effects of these compounds on the two-stage skin carcinogenesis were also examined, and it was concluded that the combination of 1 with 2 enhanced the inhibitory effect.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1992

Properties and localization of endothelin-1-specific receptors in rat testicles.

The characterization and localization of rat testicular endothelin receptors were studied. Receptor binding assay with radiolabeled members of the endothelin family revealed that endothelin-1-specific receptors were present in rat testes; a maximal binding capacity of 250 +/- 62 fmol/mg protein and a dissociation constant value of 0.35 +/- 0.06 nM were calculated from the Scatchard plot. The affinities for endothelin analogues were endothelin-1 = endothelin-2 much greater than endothelin-3 much greater big endothelin-1 for the membrane-bound receptors. Receptors of endothelin-1 were localized in peritubular myoid cells and interstitial cells of rat testis by 125I-labeled endothelin-1 autoradiography; the receptors were undetectable in spermatogenic cells. The presence of endothelin-1 receptors in the rat testis raises the possibility that one or more of the endothelins may play a physiological role in the regulation of testicular function.

Animals↗

PubMed1992

Studies on inhibitors of skin tumor promotion. XI. Inhibitory effects of flavonoids from Scutellaria baicalensis on Epstein-Barr virus activation and their anti-tumor-promoting activities.

To search for possible anti-tumor-promoters, fourteen flavones obtained from the root of Scutellaria baicalensis were examined for their inhibitory effects on the Epstein-Barr virus early antigen (EBV-EA) activation by a short-term in vitro assay. Among these flavones, 5,7,2'-trihydroxy- and 5,7,2',3'-tetrahydroxyflavone showed remarkable inhibitory effects on the EBV-EA activation, and the effect of the latter on Raji cell cycle was also examined by flow cytometer. These two flavones exhibited remarkable inhibitory effects on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test.

Animals↗

PubMed1992

Pulmonary intralobar sequestration accompanied by aneurysm of an anomalous arterial supply.

A 47-year-old woman presented with hemoptysis and her chest X-ray films showed an opacity suggesting a mass in the left lower lung field. Based on radiographic investigations, the mass was diagnosed as an aneurysm develop in an anomalous vessel and was considered to be a Pryce type I pulmonary intralobar sequestration. Resection of the left lower lobes was performed and the aneurysm was found to be filled with thrombus. It is rare for an aneurysm to form in an aberrant vessel. This complication may have been the result of regional sclerosis affecting the anomalous artery as well as systemic atherosclerosis.

Aneurysm↗

PubMed1991

Purification and characterization of bovine lung endothelin receptor.

Endothelin receptor was purified from bovine lung by a rapid and simple two-step procedure: 1) solubilization with the detergent 3[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate and digitonin and 2) affinity chromatography using biotinylated endothelin and avidin-agarose. Starting from 3.5 kg of bovine lung, about 200 micrograms of pure receptor were obtained. Microsequencing of tryptic fragments of the purified protein revealed a high sequence similarity with the rat endothelin ETB receptor that has very recently been cloned by expression cloning and shown to be nonselective in terms of the ligand specificity. Purification of the receptor in the presence of low (1 mM) and high (50 mM) concentrations of EDTA yielded, as a major form, 34- and 52-kDa species, respectively, indicating that the lower Mr species (34 kDa) is a proteolytic product of the 52-kDa species. Interestingly, this metal proteinase-mediated limited proteolysis did not affect the ligand binding properties of the receptor.

Amino Acid Sequence↗

PubMed1991

Identification of G protein-coupled endothelin receptors in cultured bovine endothelial cells.

Autocrine and paracrine regulation of vascular endothelial cells by endothelins has been postulated and has been the target of many recent investigations. In the present study, we demonstrated, by affinity labeling, the presence of endothelin-1- and endothelin-3-specific receptors on cultured bovine endothelial cells that secrete endothelin; the endothelin-3 receptor was the major form. Analysis using the GTP analogue guanosine 5'-O- (thiotriphosphate) indicated that these receptors are coupled to G proteins.

Animals↗

PubMed1991

Inhibitory effects of 3-nitro-2,4,6-trihydroxybenzamides on Epstein-Barr virus early antigen induction.

Inhibitory effects of a series of 3-nitro-2,4,6-trihydroxybenzamides on Epstein-Barr virus early antigen (EBV-EA) induction were examined using Raji cells. Some of the tested compounds showed highly inhibitory activity, the N-octyl amide derivative being the most active among them. These results suggest the possibility that 3-nitro-2,4,6-trihydroxybenzamides might be listed as novel inhibitors of tumor promotion.

Antigens, Viral↗

PubMed1991

Separation and purification of 34- and 52-kDa species of bovine lung endothelin receptors and identification of the 34-kDa species as a degradation product.

We solubilized bovine lung endothelin receptors in a nonaggregated state and identified 34- and 52-kDa species of endothelin receptor by affinity labeling. The ratio of 34-kDa species to 52-kDa species varied widely from sample to sample, suggesting that the 34-kDa species is a proteolytic product; we therefore examined the effect of various proteinase inhibitors and found that EDTA (greater than 50 mM) was very effective in preventing the conversion. These results indicate that the lower Mr species arose from the 52-kDa receptor as a result of limited proteolysis by metal proteinase(s). The resulting 34-kDa species had endothelin-binding activity, was very stable, and was not processed further even in the absence of proteinase inhibitors. We therefore first tried to purify the 34-kDa species by affinity chromatography. Bovine lung extracts were mixed with biotinylated endothelin and the ligand-receptor complexes formed were isolated with avidin-agarose. Starting from 3.5 kg of bovine lung, approximately 200 micrograms of the pure receptor was obtained. Microsequencing of two well-separated tryptic fragments yielded the following partial amino acid sequences: Ala-Asn-Asp-His-Gly-Tyr-Asp-Asn-Phe and Ser-Gly-Met-Gln-Ile-Ala-Leu-Asn-Asp-His-Leu-Lys.

Amino Acid Sequence↗

PubMed1991

Inhibition of 12-O-tetradecanoylphorbol-13-acetate-promoted mouse skin papilloma by saponins.

Papillomas in mouse skin were initiated with 390 nmol of 7,12-dimethylbenz(a)anthracene and 1 week later, were promoted 2 times a week with 4.1 nmol of 12-O-tetradecanoylphorbol-13-acetate (TPA). Five saponin-related compounds used as potential anti-inflammatory agents were applied in the same position with 82 nmol. Saponin-related compounds effectively inhibited tumor formation in the sensitive mouse stock even when these compounds were given 1 h prior to TPA treatment. These results suggested that there was a general correlation between the anti-inflammatory and antitumor-promoting activities of saponins.

Animals↗

PubMed1990

Solubilization of endothelin receptors from bovine lung plasma membranes in a non-aggregated state and estimation of their minimal functional sizes.

Bovine lung endothelin receptors were solubilized in a non-aggregated state and characterized in terms of their minimal functional size and chemical nature of the ligand-binding site. A variety of detergents and their combinations were tested for their efficiency to solubilize endothelin receptors from bovine lung plasma membranes, and a combination of 0.4% digitonin and 0.25% CHAPS was found to be very effective in obtaining highly dispersed receptor solution. Gel filtration of the CHAPS/digitonin-solubilized receptors revealed the presence of two receptor species eluting at the positions corresponding to 34 and 52 kDa. These values were in good agreement with those estimated by affinity labeling and SDS-polyacrylamide gel electrophoresis, establishing that they represent minimal functional units. Chemical modification of ligand-occupied and free receptors with p-chloromercuriphenylsulfonic acid revealed that both 34 and 52 kDa receptors have SH group(s) essential for the receptor activity in their ligand-binding sites.

Affinity Labels↗

PubMed1990

70-kilodalton heat shock protein induction in cerebellar astrocytes and cerebellar granule cells in vitro: comparison with immunocytochemical localization after hyperthermia in vivo.

Induction of the 70-kDa heat shock protein, hsp70, was evaluated in cultured cerebellar astrocytes and granule cell neurons subjected to a hyperthermic stress, using a monoclonal antibody and an oligonucleotide probe that selectively recognize stress-inducible species of hsp70-related proteins and RNAs, respectively. Immunoblots of cultures enriched in either granule cells or astrocytes, and immunocytochemical localization studies in cocultures of these cell types, demonstrated that hsp70 induction was restricted to the astrocyte population. Amino acid incorporation experiments showed little difference in the loss and recovery of overall protein synthesis activity in these two cell types following transient hyperthermic stress. RNA blot hybridizations confirmed the preferential glial induction of hsp70. In vivo immunocytochemical studies in brains of adult rats following hyperthermia were consistent with earlier observations that suggested a primarily glial and vascular localization of the heat shock response in most brain regions, although the intense immunoreactivity in the cerebellar granule cell layer suggests that there is induction of hsp70 in these neurons under in vivo conditions. These results suggest the potential value of such defined cell cultures in identifying mechanisms responsible for differences in the heat shock response of various cell types in vitro, and in revealing factors that may account for the apparent absence of the stress response in cultured cerebellar granule cell neurons.

Animals↗

PubMed1990

Structures of euglobal-G1, -G2, and -G3 from Eucalyptus grandis, three new inhibitors of Epstein-Barr virus activation.

Three new euglobals with acylphloroglucinol-monoterpene structures, named euglobal -G1 (1), -G2 (2), and -G3 (3) were isolated from the chloroform extract of the juvenile leaves of Eucalyptus grandis (Myrtaceae). The structures of these new compounds were determined on the basis of their spectral data. The compounds strongly inhibited the Epstein-Barr virus activation.

Antiviral Agents↗

PubMed1990

Inhibitors of skin-tumor promotion. VIII. Inhibitory effects of euglobals and their related compounds on Epstein-Barr virus activation. (1).

Twelve euglobals from Eucalyptus globulus and their twenty-six related compounds were examined for their inhibitory effects on Epstein-Barr virus activation by a short-term in vitro assay. The results showed that most of the euglobals having monoterpene structures, and euglobal-III (8) had strong inhibitory activity. Grandinol (18), homograndinols (19 and 20), and compounds 26, 27, 28, and 32 showed stronger inhibitory effects. Based on the results, the structural requirements for the activity of these compounds were discussed.

Antineoplastic Agents, Phytogenic↗

PubMed1990

Cumulative effect of repeated ischemia on brain edema in the gerbil. Biochemical and physiological correlates of repeated ischemic insults.

Using a bilateral carotid artery occlusion model in the gerbil, we evaluated the cumulative effect of repeated ischemic insults on various physiological and biochemical parameters in brain. The most striking consequence of repeated occlusions is a profound, delayed increase in brain edema between 6- and 24-hr recirculation, after a series of three 5-min occlusions carried out at 1-hr intervals. This increment in brain water is accompanied by morphological evidence of compressed capillaries with increased filling of larger vessels, consistent with impaired microcirculation even though total blood flow and total vascular volume return toward control levels. The effect on edema is most severe when occlusions are repeated during the period of postischemic hypoperfusion, although the mechanisms responsible for this effect remain to be determined. Histograms of cerebral cortical oxygen tension show a shift toward progressively lower values during the recirculation interval after each occlusion, suggesting that secondary hypoxia accompanying hypoperfusion may worsen the impact of successive ischemic intervals. Although levels of PCr and ATP indicate adequate recovery of energy metabolism between occlusions, slight elevations of brain lactate persist, consistent with continued hypoxia. Under the conditions employed in these studies, repeated occlusions give rise to progressively more prolonged deficits in brain protein synthesis activity, which may thus provide a useful index of the severity of the accumulated ischemic insult. Continued studies using this well-defined model should provide further insight into the pathophysiology of ischemic brain edema.

Animals↗

PubMed1989

Stimulation of Na-K-Cl cotransport in cultured vascular endothelial cells by atrial natriuretic peptide.

Vascular endothelial cells have been shown to contain atrial natriuretic peptide (ANP)-sensitive Na-K-Cl cotransport system whose activity is regulated by intracellular cGMP levels. Addition of ANP to culture medium stimulated 86Rb+ uptake in bovine endothelial cells with a concomitant increase in cGMP contents. This action of ANP was mimicked by 8-bromo-cGMP and completely diminished by furosemide. These results indicate that ANP selectively activates the Na-K-Cl cotransporter in vascular endothelial cells via cGMP and offer new insight into the physiological significance of endothelial ANP receptors.

Animals↗