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Biomedical subjects

K Shimamura

Publications and source records attributed to K Shimamura.

At least 91 records · Page 5Linked to original sources
PubMed1996

Endothelium-dependent relaxation by alpha 2-adrenoceptor agonists in spontaneously hypertensive rat aorta.

Differences in alpha(2)-adrenoceptor-induced relaxation of the aorta between stroke-prone spontaneously hypertensive rats (SHRSP) and control normotensive Wistar Kyoto rats (WKY) were studied. Changes in the tension of ring preparations of the aortas were measured isometrically. Relaxation was observed in the preparations precontracted in the presence of ONO-11113, a thromboxane A(2) analogue. The alpha(2)-agonist clonidine and UK-14304 induced dose-dependent relaxation in both the WKY and SHRSP preparations. The relaxation was impaired in the SHRSP preparation. A modified sandwich experiment showed that the relaxing substance from the SHRSP endothelium was decreased. Acetylcholine (ACh) also induced dose-dependent relaxation, and the relaxation was impaired in the SHRSP preparations. alpha(2)-Agonists induced a greater degree of impairment in the relaxation than did ACh. The relaxation induced by alpha(2)-agonists and by ACh was blocked by N G-nitro-L-arginine (L-NNA). Indomethacin improved the relaxation induced by ACh but not that induced by alpha(2)-agonists in the SHRSP aortas. These results suggest that the impairment of relaxation by alpha(2)-agonists in SHRSP is not caused by the increase in the release of endothelium-derived contracting factor (EDCF) but by the reduction in the release of nitric oxide (NO). Alteration of the alpha(2)-adrenoceptors and/or the intracellular mechanism through which NO is synthesized by stimulation of the alpha(2)-adrenoceptors may be the cause of the reduction in relaxation.

Acetylcholine↗
PubMed1996

Monitoring of procainamide and N-acetylprocainamide concentration in saliva after oral administration of procainamide.

The aim of this study was to evaluate saliva as a potential monitoring medium for procainamide (PA) and its metabolite, N-acetylprocainamide (NAPA). Saliva concentrations of PA and NAPA were determined both in single and repeated oral administration of PA in four healthy subjects. PA and NAPA were detected both in serum and saliva after 500 mg of single oral administration of PA. After single oral administration, serum and saliva concentrations of PA and NAPA reached peak levels at about 1 h and declined thereafter. The mean half-lives of PA were 2.35 h in serum and 1.28 h in saliva. The mean half-lives of NAPA were 5.29 h in serum and 5.01 h in saliva. In this study, PA and NAPA concentrations in saliva were nearly twice as high as those in serum upon chronic oral administration as well as those in a single oral dose of PA. Significant correlation coefficients were observed between serum and saliva concentrations of PA (r = 0.78, p < 0.001, n = 21) and NAPA (r = 0.76, p > 0.001, n = 21) in single oral administration of PA. Significant correlation coefficients were also observed between serum and saliva concentrations of PA (r = 0.89, p < 0.001, n = 17) and NAPA (r = 0.87, p > 0.001, n = 19) after repeated oral administration of PA. The saliva-to-serum ratios of PA and NAPA maintained nearly constant at 1 h after oral administration. It would appear from this study that saliva is a suitable medium for monitoring PA and NAPA concentration regarding acetylator status.

Journal Article↗
PubMed1996

Effects of cyclopiazonic acid and thapsigargin on electromechanical activities and intracellular Ca2+ in smooth muscle of carotid artery of hypertensive rats.

1. The effects of cyclopiazonic acid (CPA) and thapsigargin (TG), both of which are known to inhibit sarcoplasmic reticular Ca(2+)-ATPase, on the mechanical activities, intracellular Ca2+ level and electrical activities of smooth muscle of the carotid artery of stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar Kyoto rats (WKY) were compared. 2. Both CPA and TG induced elevation of tension of the smooth muscle, which was composed of a phasic and a tonic component. The level of tension attained, especially the tonic component, was greater in the preparation from SHRSP. 3. The elevation of tension was associated with an increased intracellular Ca2+ level. Both the elevation of tension and the increase in intracellular Ca2+ were diminished by the removal of extracellular Ca2+ or by the application of verapamil. 4. The resting membrane potential of the preparations from SHRSP were depolarized to a greater extent than those from WKY.CPA depolarized the smooth muscle from both SHRSP and WKY, and the final level was also more depolarized in the preparation from SHRSP. 5. These results indicate that the elevation of tension induced by these drugs is mainly due to increased Ca2+ influx through voltage-dependent Ca2+ channels, and the difference in the action between the preparation from SHRSP and that from WKY can be explained mainly by the changes in the channels. 6. Thus, differences in the action of these drugs on the tension of smooth muscle between preparations from WKY and SHRSP can mainly be explained by the difference in the membrane potential which is related to the difference in voltage-dependent Ca2+ influx.

Animals↗
PubMed1996

Progesterone inhibits superoxide radical production by mononuclear phagocytes in pseudopregnant rats.

This study investigated the changes in superoxide radical production by mononuclear phagocytes in the corpus luteum (CL) during pseudopregnancy in rats. Activity of superoxide radical production was determined by the conversion of nitro blue tetrazolium (NBT) to blue formazan deposit. Rats received 10 mg NBT via the abdominal aorta on day 3, 7, or 13 of pseudopregnancy and were autopsied 1 min later to prepare the histological sections. The cells with blue formazan deposits (NBT-positive cells) in the CL were scarce on days 3 and 7 of pseudopregnancy and significantly increased on day 13 of pseudo-pregnancy. On the other hand, simultaneous administration of 100 micrograms phorbol 12-myristate 13-acetate, which activates mononuclear phagocytes to produce superoxide radical, significantly increased the numbers of NBT-positive cells in the CL on day 7 of pseudopregnancy, but not in the CL on day 3 or 13 of pseudopregnancy. To study the possibility that superoxide radical production by mononuclear phagocytes is inhibited by progesterone on day 7 of pseudopregnancy, peritoneal mononuclear phagocytes prepared on day 7 or 13 of pseudopregnancy were preincubated with 10, 50, or 100 ng/ml progesterone for 6 h and then stimulated with phorbol 12-myristate 13-acetate. Superoxide radical production was measured by the cytochrome c reduction method. One hundred nanograms per ml progesterone significantly inhibited superoxide radical production by mononuclear phagocytes, and this inhibitory effect of progesterone was significantly blocked by the simultaneous addition of RU486 (10(-7) M). These results suggested that progesterone inhibited superoxide radical production by the mononuclear phagocytes in the CL during midpseudopregnancy in rats.

Animals↗
PubMed1996

Changes in interleukin-1 production of peritoneal macrophages during estrous cycle in golden hamsters.

The present study demonstrated the change in interleukin-1 (IL-1) production of peritoneal macrophages during the estrous cycle in golden hamsters and discussed its possible roles in ovarian function. Macrophages were collected from the peritoneal cavity at 0900 h on various days of the estrous cycle and incubated for 6 h in the presence of ovine pituitary LH (500 ng/ml). The IL-1 concentration in the media was measured by bioassay with the A375S2 human melanoma cell line. The number of macrophages significantly (P < 0.01) increased on estrus and proestrus compared with diestrus 1 or diestrus 2. LH-induced production of IL-1 was also greater (P < 0.01) on proestrus (292 +/- 36 pg/10(6) cells/ ml) and estrus (222 +/- 30 pg/10(6) cells/ml) than on diestrus 1 (34 +/- 15 pg/10(6) cells/ml) or diestrus 2 (117 +/- 16 pg/10(6) cells/ml). To clarify the factor inducing the changes in peritoneal macrophages, hamsters were ovariectomized on diestrus 1, and 3 weeks later the animals were treated with s.c. injections of progesterone (200 micrograms/day), testosterone (100 micrograms/day), estradiol (10 micrograms/day) or sesame oil for three days. The hamsters were killed 24 h after the last injection, and the number and IL-1 producing capacity of macrophages were determined. The number of macrophages and their response to LH to produce IL-1 were increased significantly (P < 0.01) by estradiol treatment but not by progesterone or testosterone treatment. It was concluded that the peritoneal macrophages became more sensitive to LH to produce IL-1 on proestrus and estrus in cyclic hamsters, and that these changes in macrophages, probably induced by estradiol, would play important roles in ovarian function.

Animals↗
PubMed1996

Blood pressure and age-dependent changes of endothelium-dependent tension oscillations in different strains of spontaneously hypertensive rats.

The influence of blood pressure and age of spontaneously hypertensive rats on endothelium-dependent tension oscillation of aortic preparation were studied. Rats with different blood pressures, normotensive Wistar Kyoto rats (WKY), spontaneously hypertensive rats (SHR), stroke-prone SHR (SHRSP) and malignant type of SHRSP (M-SHRSP), were used. The effects of antihypertensive treatment of SHRSP on the tension oscillation were also studied. High doses of noradrenaline induced tension oscillations in endothelium-intact preparations of all strains of young rats. The rate of the occurrence of the tension oscillation decreased age-dependently. The decrease was faster when the blood pressure of the rats was higher. Application of acetylcholine in the presence of noradrenaline induced a relaxation and tension oscillations, both of which were negatively dependent on age and blood pressure. Antihypertensive treatment of hypertensive rats with hydralazine or captopril prevented a decrease in incidence of the tension oscillation. These influences of age and blood pressure as well as antihypertensive treatments on the tension oscillation resembled those on the endothelium-dependent relaxation and are thought to be brought about by functional changes of the endothelium.

Acetylcholine↗
PubMed1996

A study of the luteolytic mechanism of the antiprogesterone RU486 during the late-luteal phase in pseudopregnant rats.

The purpose of this study was to examine the possible mechanism through which RU486 induces luteolysis during the late-luteal phase in pseudopregnant (PSP) rats. PSP rats received a subcutaneous injection of RU486 in sesame oil (5 mg/kg body weight) or sesame oil alone once a day between day 9 and day 11 of pseudopregnancy. Serial blood samples were collected on days 5, 9, 10, 11 and 12 and assayed for progesterone content. To examine the possible action of RU486 through a uterine and/or a pituitary (prolactin-dependent) mechanism, PSP rats and chronic hysterectomized PSP rats which had been hysterectomized before PSP induction received a subcutaneous injection of RU486 in sesame oil (5 mg/kg body weight), sesame oil alone, prolactin in 50% polyvinylpyrrolidone (15 IU/day), or RU486 and prolactin once a day between day 9 and day 11 of pseudopregnancy. Serial blood samples were collected on days 5, 9, 10 and 11 and assayed for progesterone content. Blood samples were also collected at 0400 h on day 12 and used for prolactin and progesterone determinations. To examine the direct effect of RU486 on corpus luteum and/or pituitary, hysterectomized rats underwent hypophysectomy and pituitary autotransplantation on dioestrus 1 and received a subcutaneous injection of RU486 in sesame oil or sesame oil alone for 3 days between day 21 and day 23 after surgery. Serial blood samples were collected on days 10, 21, 22, 23 and 24 and assayed for progesterone and prolactin contents. In ordinary PSP rats, serum progesterone levels were significantly (P < 0.01) lower in the RU486-treated group than in the control group (9 +/- 1 vs 53 +/- 7 ng/ml; mean +/- S.E.M.) on day 11. Serum prolactin levels at 0400 h on day 12 of pseudopregnancy were significantly (P < 0.05) lower in the RU486-treated group than in the control group (16 +/- 4 vs 154 +/- 44 ng/ml; mean +/- S.E.M.). The concomitant prolactin treatment reversed the luteolytic effects of RU486 on day 11 of pseudopregnancy. In hysterectomized PSP rats, RU486 also suppressed serum prolactin levels, and the concomitant prolactin treatment again reversed the luteolytic effects of RU486. In hysterectomized rats which were hypophysectomized and pituitary autotransplanted, RU486 treatment did not induce any significant changes in serum progesterone and prolactin levels. These results indicated that RU486 induced luteolysis during the late-luteal phase in PSP rats by suppressing prolactin secretion via a hypothalamic mechanism.

Animals↗
PubMed1996

Attenuation of intrinsic active tone by endothelium-derived nitric oxide in aortae of spontaneously hypertensive rats with different levels of blood pressure.

The influences of endothelium on the basal tone of aortae from various strains of spontaneously hypertensive rats with different blood pressure (SHR, SHRSP, M-SHRSP) were studied. Endothelium-intact preparations of aortae from spontaneously hypertensive rats exhibited spontaneous active tone, which was greater in the order of SHR < SHRSP < M-SHRSP. The active tone of the M-SHRSP preparations was about 40% of high-K(+)-induced contraction, while that of normotensive WKY was less than 5%. The active tone was enhanced by the removal of endothelium. The active tone was sensitive to extracellular Ca2+ and abolished by verapamil. The application of N(G)-monomethyl-L-arginine caused the increase in the active tone which was counteracted by L-arginine. These results indicate that the active tone of smooth muscle increases as the blood pressure of the rat increases, and that endothelium attenuates the active tone by releasing nitric oxide (NO) spontaneously. It was also demonstrated that the attenuating action of endothelium was impaired depending on the blood pressure level.

Animals↗
PubMed1996

[Involvement of stimulatory effect of prostaglandin F2 alpha on superoxide radical production by macrophages in corpus luteum regression].

The effect of prostaglandin F2 alpha (PGF2 alpha) on superoxide radical production by macrophages was studied in pseudopregnant rats. Peritoneal macrophages prepared on day 7 or 13 of pseudopregnancy (psp) were incubated with various doses of PGF2 alpha for 90 min, and the production of superoxide radical was measured by the cytochrome C reduction method. PGF2 alpha significantly stimulated superoxide radical production by macrophages on day 13 of psp, but not on day 7 of psp. The pretreatment of macrophages with an inhibitor of protein kinase C (H7), Ca2+ channel blocker (Verapamil), Ca2+ chelators (EGTA, BAPTA), and an inhibitor of GTP-binding protein (pertussis toxin) prevented the stimulatory effects of PGF2 alpha on superoxide radical production. In conclusion, PGF2 alpha stimulated superoxide radical production by macrophages through the intracellular signal transduction pathway including activation of protein kinase C through the GTP-binding protein and Ca2+ influx, which would play important roles in the luteolytic process in psp rats.

Animals↗
PubMed1996

Sensitive detection of oxidatively modified low density lipoprotein using a monoclonal antibody.

We have established a new method capable of measuring the very low concentrations of oxidized low density lipoprotein (OxLDL). In our previous study, we obtained a novel murine monoclonal antibody against oxidized lipoproteins (Itabe, H. et al. 1994. J. Biol. Chem. 269: 15274-15279). The epitope of this antibody resides in oxidized products of phosphatidylcholine that can form complexes with polypeptides, including apolipoprotein B. When the monoclonal antibody was precoated onto microtiter wells prior to carrying out a sandwich ELISA using an anti-human apolipoprotein B antibody, it was possible to detect 0.5 ng protein of copper-induced OxLDL. The detection of OxLDL was dependent on the presence of monoclonal antibody and was blocked by oxidized phosphatidylcholine (OxPC). Under the same sandwich ELISA condition, native LDL showed a dose-dependent increase of absorbance that was inhibited by complex of OxPC with BSA. These results suggest the possible occurrence of oxidative modification of human plasma LDL, which is recognized by the antibody against OxPC. The level of LDL oxidation of normal human subjects was found to be 0.52 +/- 0.35 units per 5 mu g protein of LDL, where one unit was defined as the reactivity corresponding to 1 ng of copper-induced OxLDL by this assay. Furthermore, we found that the LDL oxidation level in patients who had been receiving hemodialysis treatment was increased more than eightfold over that of normal subjects. We suggest that LDL in human plasma is oxidatively modified under certain conditions and this method for measurement of OxLDL could be used to study the relationship between in vivo oxidation reaction and various pathological conditions.

Antibodies, Monoclonal↗
PubMed1995

Null mutation of Dlx-2 results in abnormal morphogenesis of proximal first and second branchial arch derivatives and abnormal differentiation in the forebrain.

Genetic analysis of the development and evolution of the vertebrate head is at a primitive stage. Many homeo box genes, including the Distal-less family, are potential regulators of head development. To determine the function of Dlx-2, we generated a null mutation in mice using gene targeting. In homozygous mutants, differentiation within the forebrain is abnormal and the fate of a subset of cranial neural crest cells is respecified. The latter causes abnormal morphogenesis of the skeletal elements derived from the proximal parts of the first and second branchial arches. We hypothesize that the affected skull bones from the first arch have undergone a transformation into structures similar to those found in reptiles. These results show that Dlx-2 controls development of the branchial arches and the forebrain and suggests its role in craniofacial evolution.

Animals↗
PubMed1995

Cadherin-11 expressed in association with mesenchymal morphogenesis in the head, somite, and limb bud of early mouse embryos.

Cadherin-11 (cad-11) is a novel member of the cadherin family of cell adhesion molecules, having recently been identified by means of the polymerase chain reaction. To study the function and expression of this molecule, we cloned mouse, cad-11 cDNA. Transfection of L cells with cDNA led them to acquire a typical cadherin-dependent cell-cell adhesiveness, and the L cells expressing cad-11 did not coaggregate with L cells expressing E-, P-, N-, or R-cadherin when they were mixed, indicating that this novel cadherin has a homophilic binding specificity, as found for other cadherins. To determine the developmental expression pattern of this molecule, we performed in situ hybridization analysis on early mouse embryos. Cad-11 first appeared in mesodermal layers only in the head and tail regions at the mid-to-late primitive streak stages. In the head, this appearance was followed by strong expression in mesenchymal tissues including branchial arches. In the trunk, the paraxial mesoderm initially did not express cad-11. However, as the somites formed, they expressed cad-11, and this expression was strictly correlated with their initial condensation and segregation from the presomitic mesoderm. The cad-11 expression in the somites was eventually restricted to sclerotome cells. As the limb buds developed, cad-11 appeared in the distal portion of the limb mesenchyme, and, at later stages, its expression was most evident at the peripheral mesenchyme. Cad-11 was thus expressed by restricted populations of mesenchymal cells in early embryos, although it was also expressed in parts of the neural tube, such as the optic vesicle and dorsal midline, and in part of the otic vesicle. As a step to investigate the role of cad-11 in mesenchymal cell adhesion, we dissociated the limb bud mesenchyme into single cells, pelleted them, and cultured them as aggregates. In these cultures, cad-11-positive cells clearly sorted out of the negative cell population, suggesting that cad-11 might be involved in selective association of mesenchymal cells. For comparison, we studied the expression of N-cadherin and found that the expressions of these two cadherins were differential, and complementary in some tissues. These results suggest that cad-11 is involved in specific associations of subsets of mesenchymal cells and also of some neural cells during early embryogenesis.

Amino Acid Sequence↗
PubMed1995

Effects of fibroblasts of different origin on long term maintenance of xenotransplanted human epidermal keratinocytes in immunodeficient mice.

We examined effects of fibroblasts of different origin on long-term maintenance of xenotransplanted human epidermal keratinocytes. A suspension of cultured epidermal cells, originating from adult human trunk skin, was injected into double mutant immunodeficient (BALB/c nu/scid) mice subcutaneously, with or without cultured fibroblastic cells of different origin. At one week after transplantation, the epidermal cells generated epidermoid cysts consisting of human epidermis-like tissue. When the epidermal cells were injected alone or together with fibroblastic cells derived from human bone marrow, muscle fascia, or murine dermis, organized epidermoid cysts regressed within 6 weeks. In contrast, when the epidermal cells were injected together with human dermal fibroblasts, generated epidermoid cysts were maintained in vivo for more than 24 weeks. Histological examination showed that the reorganized epidermis, after injection of both epidermal keratinocytes and dermal fibroblasts, retained normal structures of the original epidermis during 6 to 24 weeks after transplantation. The results indicate that human dermal fibroblasts facilitate the long-term maintenance of the reorganized epidermis after xenotransplantation of cultured human epidermal keratinocytes by supporting self renewal of the human epidermal tissue in vivo.

Animals↗
PubMed1995

T-brain-1: a homolog of Brachyury whose expression defines molecularly distinct domains within the cerebral cortex.

The mechanisms that regulate regional specification and evolution of the cerebral cortex are obscure. To this end, we have identified and characterized a novel murine and human gene encoding a putative transcription factor related to the Brachyury (T) gene that is expressed only in postmitotic cells. T-brain-1 (Tbr-1) mRNA is largely restricted to the cerebral cortex, where during embryogenesis it distinguishes domains that we propose may give rise to paleocortex, limbic cortex, and neocortex. Tbr-1 and Id-2 expression in the neocortex have discontinuities that define molecularly distinct neocortical areas. Tbr-1 expression is analyzed in the context of the prosomeric model. Topological maps are proposed for the organization of the dorsal telencephalon.

Amino Acid Sequence↗
PubMed1995

Immortalisation of human oesophageal epithelial cells by a recombinant SV40 adenovirus vector.

We introduced the origin-defective SV40 early gene into cultured human oesophageal epithelial cells by infection of a recombinant SV40 adenovirus vector. The virus-infected cells formed colonies 3-4 weeks after infection in medium containing fetal calf serum. When the cells derived from 'serum-resistant' colonies were then maintained in the serum-free medium with a low calcium ion concentration, some of them passed the cell crisis and kept growing for over 12 months. These cells, regarded as immortalised cells, resembled the primarily cultured oesophageal epithelial cells in morphology and had some of their original characteristics. Treatment of the cells with a high calcium concentration induced phenotypic changes. These cells still responded to transforming growth factor beta. When the immortalised cells were injected into severe combined immunodeficient mice, they transiently formed epithelial cysts, although the typical differentiation pattern of the oesophageal epithelium was not observed. These cysts regressed within 2 months without development into tumours. The results indicated that human oesophageal epithelial cells were reproducibly immortalised by infection with a recombinant SV40 adenovirus vector at relatively high efficiency. The immortalised cells should be useful in studies on oesophageal carcinogenesis and in assessing the cooperative effects with other oncogene products or carcinogens.

Animals↗
PubMed1995

Prolonged survival of mice with human gastric cancer treated with an anti-c-ErbB-2 monoclonal antibody.

A monoclonal antibody (MAb), 4D5, specifically recognising an extracellular epitope of the c-ErbB-2 protein, inhibited the growth of human gastric cancer overexpressing c-ErbB-2 severe combined immunodeficient (SCID) mice. This antibody also reduced the mass of established tumours xenografted into SCID mice, whereas gastric cancer not expressing c-ErbB-2 exhibited no regression in response to 4D5 treatment. In addition, administration of 4D5 prevented colonisation of cancer cells and prolonged the survival of host SCID mice inoculated i.v. with c-ErbB-2-overexpressing tumour cells. This is the first reported study to show that treatment with a single antibody specific to c-ErbB-2 prolongs the survival of host SCID mice bearing xenotransplanted tumours.

Animals↗
PubMed1995

Alteration in the release of endothelium-derived relaxing factors by alpha-adrenoceptor stimulation in the aorta of stroke-prone spontaneously hypertensive rats.

1. Endothelium-dependent relaxation by alpha-adrenoceptor agonists was examined in the thoracic aorta from normotensive Wistar-Kyoto (WKY) rats and stroke-prone spontaneously hypertensive rats (SHRSP). 2. In ring preparations from both strains, noradrenaline-induced contraction was increased by L-nitro arginine (L-NNA), a NO synthesis inhibitor. 3. L-NNA increased the contraction induced by phenylephrine, an alpha1-adrenoceptor agonist. UK-14304 and clonidine, alpha2-adrenoceptor agonists, did not contract the preparations with intact endothelium. However, these agents contracted preparations when NO synthesis was inhibited. 4. In a precontracted preparation, clonidine and UK-14304 induced relaxations. The relaxations in SHRSP aorta were smaller than those in WKY aorta. 5. These results indicate that alpha-agonists release NO from endothelium in WKY and SHRSP aorta. The mechanism related to NO release by alpha2-adrenoceptor agonist is impaired in SHRSP aorta.

Adrenergic alpha-Agonists↗