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Biomedical subjects

R Hirota

Publications and source records attributed to R Hirota.

At least 19 recordsLinked to original sources
PubMed2003

Effect of alpha-ketobutyrate on microvascular thickness in the diabetic rat kidney.

The first objective of this study was to examine the intermediary metabolism of plasma amino acids and keto acids in streptozotocin (STZ)-treated rats. Plasma alpha-aminobutyrate (alpha-ABA) concentration in STZ rats was 1.5-fold greater than in control (CNT) animals at 1 month. In contrast, the level of plasma alpha-ketobutyrate (KB), which is transaminated to alpha-ABA, did not differ significantly between STZ and CNTs at 1 month, and also increased with age. Additionally, HPLC analysis revealed consistent profiles containing peaks of unknown origin. Two pathways exist for the formation of alpha-KB, either from the action of threonine dehydratase or via homocysteine, the latter metabolite being closely associated with the development of cardiovascular disease. These observations suggest that uncharacterized metabolites, including plasma alpha-KB, may be potential risk factors for the development of diabetic complications. We carried out preparatory experiments on non-diabetic rats to investigate the influence of alpha-KB and confirmed this metabolite had no adverse effects. The second aim of the study was to compare vascular wall thickness in diabetic rats treated or untreated with alpha-KB with CNT animals in order to determine the effects of alpha-KB on the renal microvasculature. The thickness of the medial wall of arterioles and small arteries differed significantly among all groups and was increased, especially in the small arterial walls of the diabetic rats treated with alpha-KB. Plasma renin activities (PRA) in both diabetic rats treated or untreated with alpha-KB were decreased significantly compared to CNT animals, while diabetic rats treated with alpha-KB had higher angiotensin converting enzyme (ACE) activity than the CNT group (p < 0.01). These results suggest that alpha-KB may have a role in the renal microvascular complications of diabetes.

Animals↗
PubMed2001

Localization of heme oxygenase-2 in the canine larynx.

The localization of heme oxygenase-2 (HO-2) in the larynx of the dog was investigated using immunohistochemistry. HO-2-positive cells were seen among neurons in intralaryngeal ganglia. Nerve fibers positive to HO-2 immunohistochemistry were seen surrounding laryngeal glands and arterioles and also in the adventitia of arterioles. HO-2-positive fibers were also seen running parallel to the mucosa in the lamina propria but no positive fibers were seen in the epithelium. Some of the intramuscular neurons found in the intrinsic laryngeal muscles were HO-2-positive, although no positive motor fibers were seen, and the neuromuscular junctions were also HO-2-negative. The results implicate the participation of HO-2-in the parasympathetic innervation of the larynx.

Animals↗
PubMed2000

Purification and inactivation by substrate of an allene oxide synthase (CYP74) from corn (Zea mays L.) seeds.

The allene oxide synthase (AOS) was purified from corn (Zea mays) seeds to homogeneity and characterized partially. The corn AOS was a hemoprotein cytochrome P450 with a molecular weight and pI of 53,000 and 6.0, respectively. The corn AOS was found to be irreversibly inactivated by a substrate, 13-hydroperoxyoctadienoic acid. The rate of the enzyme inactivation was higher at low pHs.

Intramolecular Oxidoreductases↗
PubMed2000

Leukocyte integrin-dependent and antibody-independent cytotoxicity of macrophage against allografts.

Macrophages (Mphis), but not T cells, infiltrating into the rejection site of either i.p. allografted Meth A (H-2d) fibrosarcoma cells in C57BL/6 (B6) (H-2b) mice or BALB/c (H-2d) skin onto B6 mice are cytotoxic against allografts with H-2d specificity. To determine the mechanisms of specific killing of allografts by allograft-induced Mphi (AIM), we raised approximately 5,000 rat monoclonal antibodies (mAbs) against AIM and selected three of them (R1-73, R2-40 and R1-34), each of which inhibited cytotoxic activity against allografts in a dose-dependent manner. The antigens recognized by R1-73, R2-40 and R1-34 mAbs were defined by immunoprecipitation and Western blot analyses as CD11a, CD18 and CD11b, respectively; and the allografts expressed CD54, a ligand of CD11a or CD11b, suggesting leukocyte integrin-dependent killing. Although Ab-dependent cellular cytotoxicity has been recognized as a mechanism of specific killing by Mphis, the infiltration of AIM into the rejection site of allografts far (approximately 6 days) preceded the appearance of serum IgG Ab specific for the allograft. AIM exhibiting full cytotoxic activity against allografts was also induced in the transplantation site of Fcgamma receptor knockout [(B6x129) F1] mice as well as B10.D2 (H-2 compatible with allograft) and B6-xid (X-linked immunodeficiency with B cell-specific defect) strains of mice. In the latter two strains of mice, the levels of serum IgG Ab to the allograft were negligible. Moreover, the cytotoxic activity of AIM against allografts was not affected by pretreatment of the cells with anti-mouse IgG serum, suggesting Ab-independent cytotoxicity.

Animals↗
PubMed2000

Physical map location of the multicopy genes coding for ammonia monooxygenase and hydroxylamine oxidoreductase in the ammonia-oxidizing bacterium Nitrosomonas sp. strain ENI-11.

Pulsed-field gel electrophoresis of PmeI digests of the Nitrosomonas sp. strain ENI-11 chromosome produced four bands ranging from 1,200 to 480 kb in size. Southern hybridizations suggested that a 487-kb PmeI fragment contained two copies of the amoCAB genes, coding for ammonia monooxygenase (designated amoCAB(1) and amoCAB(2)), and three copies of the hao gene, coding for hydroxylamine oxidoreductase (hao(1), hao(2), and hao(3)). In this DNA fragment, amoCAB(1) and amoCAB(2) were about 390 kb apart, while hao(1), hao(2), and hao(3) were separated by at least about 100 kb from each other. Interestingly, hao(1) and hao(2) were located relatively close to amoCAB(1) and amoCAB(2), respectively. DNA sequence analysis revealed that hao(1) and hao(2) shared 160 identical nucleotides immediately upstream of each translation initiation codon. However, hao(3) showed only 30% nucleotide identity in the 160-bp corresponding region.

Chromosome Mapping↗
PubMed2000

Mutational analysis of the multicopy hao gene coding for hydroxylamine oxidoreductase in Nitrosomonas sp. strain ENI-11.

The ammonia-oxidizing bacterium Nitrosomonas sp. strain ENI-11 contains three copies of the hao gene (hao1, hao2, and hao3) coding for hydroxylamine oxidoreductase (HAO). Three single mutants (hao1::kan, hao2::kan, or hao3::kan) had 68 to 75% of the wild-type growth rate and 58 to 89% of the wild-type HAO activity when grown under the same conditions. A double mutant (hao1::kan and hao3::amp) also had 68% of the wild-type growth and 37% of the wild-type HAO activity.

DNA Mutational Analysis↗
PubMed2000

HPLC analysis and optimization of enzymatic synthesis of 4'-O-(beta-D-glucopyranosyl)-D-pantothenic acid.

We analyzed beta-glucosidase-catalyzed transglucosylation to D-pantothenic acid using a reversed-phase HPLC system in order to obtain 4'-O-(beta-D-glucopyranosyl)-D-pantothenic acid (PaG) at a higher yield. The HPLC system was simpler and more straight-forward for the PaG analysis than the previously employed bioassay method and could also be adopted for efficient isolation of PaG. Penicillium decumbens naringinase showed the highest glucosyl transfer activity to D-pantothenic acid, and the reaction using smaller amounts of naringinase for prolonged periods of reaction time (70 h<) was important to attain higher yields of glucosyl transfer. Maximum overall yields of PaG of 10 and 4% (mol/mol, based on D-pantothenic acid) were obtained using beta, beta'-trehalose and cellobiose, respectively, as glucosyl donors. The value was 3.6- and 1.4-times higher, respectively, than that obtained by previous synthesis and isolation procedures.

Animals↗
PubMed1999

Isolation and characterization of two cryptic plasmids in the ammonia-oxidizing bacterium Nitrosomonas sp. strain ENI-11.

Two plasmids were discovered in the ammonia-oxidizing bacterium Nitrosomonas sp. strain ENI-11, which was isolated from activated sludge. The plasmids, designated pAYS and pAYL, were relatively small, being approximately 1.9 kb long. They were cryptic plasmids, having no detectable plasmid-linked antibiotic resistance or heavy metal resistance markers. The complete nucleotide sequences of pAYS and pAYL were determined, and their physical maps were constructed. There existed two major open reading frames, ORF1 in pAYS and ORF2 in pAYL, each of which was more than 500 bp long. The predicted product of ORF2 was 28% identical to part of the replication protein of a Bacillus plasmid, pBAA1. However, no significant similarity to any known protein sequences was detected with the predicted product of ORF1. pAYS and pAYL had a highly homologous region, designated HHR, of 262 bp. The overall identity was 98% between the two nucleotide sequences. Interestingly, HHR-homologous sequences were also detected in the genomes of ENI-11 and the plasmidless strain Nitrosomonas europaea IFO14298. Deletion analysis of pAYS and pAYL indicated that HHR, together with either ORF1 or ORF2, was essential for plasmid maintenance in ENI-11. To our knowledge, pAYS and pAYL are the first plasmids found in the ammonia-oxidizing autotrophic bacteria.

Amino Acid Sequence↗
PubMed1998

The influences of insulin and food intake on intestinal ornithine transcarbamylase activity in diabetic rats.

Intestinal ornithine transcarbamylase (OTC) activity was studied in rats with experimentally-induced diabetes. After the injection of streptozotocin, OTC activity was approximately 75% that of age-matched controls. Then we investigated the influences of (a) insulin treatment and (b) limiting food-intake, which was adjusted to the control level, on OTC activities in the three segments of the small intestine. (a) Insulin treatment resulted in OTC activities being restored to control levels in all segments of the small intestine, with the disappearance of intestinal epithelial hyperplasia. (b) In limited food-intake rats, OTC activities of the middle and distal segments normalized with insulin treatment. In the proximal segment, however, which showed epithelial hyperplasia, OTC activity was as low as that in untreated STZ rats. These observations suggest that altered regulation of intestinal epithelial over-growth and immoderate food-intake were normalized by insulin treatment, leading to the restoration of normal OTC activity in the small intestine.

Analysis of Variance↗
PubMed1997

Bone density and bone metabolic markers in active collegiate athletes: findings in long-distance runners, judoists, and swimmers.

We investigated the bone metabolic system status of 103 male and female volunteer collegiate athletes, who were actively pursuing one of three different sports: Long-distance running (LR); judo (JU); and swimming (SW). The following parameters were evaluated: total body bone mineral density (TMBD); bone-forming metabolic markers; serum procollagen type I C-peptide (PICP) levels; bone alkaline phosphatase (B-ALP) content; bone resorption markers, urinary pyridinoline (Pyd) and deoxypyridinoline (Dpd) levels. We found that the TBMD and urinary Dpd values in JU athletes were significantly higher (p < 0.001) than in athletes of the same sex in the other two groups. The urinary Pyd level in male JU athletes was also higher (p < 0.001) than that in the other two groups, but that in females JU athletes was only higher (p < 0.01) than that in female LR athletes. The PICP levels were similar to the TBMD values in all groups. No differences in bone density or in bone metabolic markers were seen in LR and SW athletes of the same sex. We thus conclude that differences in bone mineral density are in part due to the demands of the specific sport, and that they are reflected in bone metabolic markers. In addition, the status of bone metabolic turnover in male JU athletes in training may be hypermetabolic and as well as that of female JU athletes with regular menses cycles.

Adult↗
PubMed1995

Visible light-sensitized oxidation of arachidonic acid in the presence of inperatorin.

To understand the mechanism of the phototoxic effects of inperatorin, a psoralen derivative used as a pigmentation agent, we have investigated the photosensitized oxidation of arachidonic acid (ARA) by irradiation with visible light (> 400 nm) in the presence of inperatorin. HPLC and GC/MS analyses of the products showed the formation of many hydroperoxyeicosatetraenoic acids (HPETEs) including the products of lipoxygenase-catalyzed reactions such as 5- and 15-HPETEs, which are the precursors of chemical mediators such as leukotrienes and lipoxins, during the reaction. Active oxygen scavening agents such as D-mannitol, superoxide dismutase, and beta-carotene inhibited the formation of the oxidation products, indicating that the oxidation reaction was mediated by various active oxygen species. These results suggest that the phototoxic effects of inperatorin could also be induced by visible light and could be explained at least partially in terms of inflammation initiated by the biologically active HPETEs arising from photosensitized oxygenation reactions of ARA with the drug.

Arachidonic Acid↗
PubMed1991

Production of corticosterone and testosterone in scorbutic mutant rats: difference of in vivo production between adrenal gland and testis.

Effects of deficiency in ascorbic acid on in vivo production of corticosterone and testosterone were examined using a mutant strain of rats unable to synthesize ascorbic acid. The adrenal weight of scorbutic rats was larger, and corticosterone levels in plasma and adrenal tissues were higher than those of ascorbic acid-supplied (ascorbutic) rats. Acute and chronic stimulation with ACTH increased corticosterone levels in both ascorbutic and scorbutic rats. In contrast, weights of seminal vesicles and ventral prostates in unstimulated scorbutic rats were smaller, and testosterone levels in plasma and testicular tissues were lower than those in ascorbutic rats. Acute stimulation with hCG increased testosterone levels only slightly in plasma and not in testicular tissues of scorbutic rats, when testosterone levels in ascorbutic rats reached a maximum. Chronic stimulation with hCG increased testosterone levels remarkably in both ascorbutic and scorbutic rats. These findings seem to indicate that ascorbic acid is not essential for the synthesis of steroid hormones. The scurvy seems to increase plasma ACTH levels secondary to the stress, resulting in the stimulation of the adrenals. In contrast, a prolonged deficiency in ascorbic acid appears to decrease plasma gonadotropin levels, and may reduce the sensitivity of testes to gonadotropins.

Adrenal Glands↗
PubMed1989

Effect of physical training on thrombotic tendency in rats: decrease in thrombotic tendency measured by the He-Ne laser-induced thrombus formation method.

The effect of physical training on thrombotic tendency was assessed in rats. Exercise was done on a flat treadmill for 30 min at a rate of 1,400 m/h (submaximal speed), 5 times a week for either 1.5 or 3 months. The thrombotic tendency was measured by the He-Ne laser-induced thrombus formation method in microvessels of mesentery, i.e. measurement of the number of laser irradiations necessary to induce stasis of blood flow by occlusive thrombus formation. An increase in the number of irradiations necessary to induce occlusive thrombus formation was observed in arterioles, but not in venules after physical training for 1.5 and 3 months.

Animals↗
PubMed1982

Effect of cholecystokinin octapeptide and vasoactive intestinal polypeptide on adrenocortical secretion in the rat.

Intraperitoneal (i.p.) injection of C-terminal octapeptide of cholecystokinin (CCK-8) produced a dose-related increase in plasma corticosterone levels in intact rats, but not in vagotomized ones. Intracerebroventricular (i.c.v.) injection of CCK-8 was ineffective in stimulating the secretion of corticosterone, and in vitro experiment on ACTH release indicated that CCK-8 could not affect pituitary tissue directly. Since i.p. injection of non-sulfated CCK-8 failed to elevate plasma corticosterone levels, sulfated tyrosine residue in the CCK molecule is assumed to be indispensable for the stimulation of visceral organs. On the other hand, vasoactive intestinal polypeptide (VIP) was found to cause a dose-dependent increase in plasma corticosterone levels when administered centrally, but not after i.p. injection. However, VIP could not stimulate the release of ACTH from the pituitary tissue directly. The results suggest that VIP, but not CCK, stimulates the hypothalamic CRF neurons either directly or indirectly.

Adrenal Cortex↗
PubMed1982

Effect of intraventricular administration of vasoactive intestinal polypeptide on body temperature in the rat.

Intracerebroventricular injection of vasoactive intestinal polypeptide (VIP) into rat caused a temporary elevation of body temperature followed by a decrease to below the control level. Hypothermia induced by cholecystokinin octapeptide was abolished by simultaneous administration of VIP. Hypothermia following pentobarbital administration was reduced by successive injections of VIP. The results suggest that multiple interactions of neuropeptides are involved in central thermoregulation.

Animals↗
PubMed1981

Cholecystokinin-induced hypothermia in the rat.

Cholecystokinin-octapeptide (CCK-8) was shown to cause hypothermia after intracerebroventricular administration in the rat, and the hypothermic effect of CCK-8 was antagonized by simultaneous injection of TRH.

Animals↗