Search PubMed⌕ Search

Biomedical subjects

A Takashima

Publications and source records attributed to A Takashima.

At least 181 records · Page 10Linked to original sources
PubMed1987

Nicardipine-sensitive enhancement of high K+ -evoked dopamine release in PC12 cells pretreated with 12-O-tetradecanoylphorbol 13-acetate.

The effects of the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA) on stimulus-evoked dopamine release were studied in PC12 cells. Pretreatment of the cells with TPA resulted in an enhancement of dopamine release which could be further stimulated by high concentrations of K+, A23187, but not with carbamylcholine. TPA-dependent, high-K+ -evoked enhancement of dopamine release was studied in detail: a maximum release was observed (169% of control) in response to 50 mM KCl upon treatment with 10(-7) M TPA for 5 min at 37 degrees C. This enhancement of dopamine release was associated with the concomitant reduction of the concentration rise of intracellular Ca2+ ([Ca2+]i) induced by a high concentration of K+ monitored by a fluorescent indicator, fura2. Thus, these data provide an example for alteration in the efficiency of stimulus-secretion coupling as pointed out in our previous paper. Moreover, we have shown that nicardipine, CdCl2, and CoCl2 inhibit high-K+ -evoked dopamine release more effectively in TPA treated cells than that of untreated cells, and that the TPA-dependent, high-K+ -evoked dopamine release observed in TPA treated cells is completely abolished by the presence of nicardipine, Cd2+ or Co2+, but is only partially inhibited in the presence of verapamil. These relevant findings suggest the possible involvement of protein kinase C in regulating the efficiency of a high-K+ -evoked dopamine release through the modification of nicardipine-sensitive Ca2+ channels.

Adrenal Gland Neoplasms↗
PubMed1987

Disposition of moxalactam and N-methyltetrazolethiol in rats and monkeys.

The disposition of moxalactam (MOX) and N-methyltetrazolethiol (NMTT) in rats and monkeys after intravenous injection was investigated, focusing on the in vivo liberation of NMTT, by using [NMTT-14C]MOX and [14C]NMTT. After [NMTT-14C]MOX injection, MOX levels in plasma quickly became high in both rats and monkeys and then declined, with half-lives at the beta phase of 18.8 and 67.1 min, respectively. The levels of NMTT liberated from MOX were much lower than those of MOX, but the apparent elimination was significantly slow. The levels of MOX and NMTT in rat liver were almost comparable but lower than those in plasma. With [14C]NMTT administration, the level of NMTT in plasma declined, with half-lives at the beta phase of 21.5 min in rats and 54.0 min in monkeys. After [NMTT-14C]MOX injection, most of the radioactivity was excreted in urine as MOX, with 11% of the dose in rats and 8% of the dose in monkeys eliminated as NMTT until 24 h. Total biliary excretion was 26% of the injected radioactivity in rats, and most of it was due to MOX. In one monkey, the total biliary excretion was only 0.2% of the injected radioactivity. With [14C]NMTT administration, most radioactivity was excreted in the urine as unchanged NMTT in both animals. Oral administration in rats showed that part of the biliary-excreted MOX was degraded to NMTT in the intestine and then absorbed. Repeated administration of [NMTT-14C]MOX to rats did not change the levels of MOX and NMTT in plasma or liver nor did it change the excretion profiles. Thus, accumulation of MOX and NMTT did not occur.

Animals↗
PubMed1987

Interactions of cholecystokinin, beta-endorphin, and their antagonists on passive avoidance behavior in rats.

The effects of cholecystokinin octapeptide (CCK-8), cholecystokinin tetrapeptide amide (CCK-4), beta-endorphin, proglumide, and naloxone on passive avoidance behavior were studied in rats. Intracerebroventricular (i.c.v.) injection of beta-endorphin (1-10 micrograms) had no significant influence on the latency of the avoidance response in intact rats. Also, beta-endorphin (0.05-5 micrograms, i.c.v.) did not affect the response in rats treated with electroconvulsive shock (ECS). The preventive effect of CCK-8 (0.1-1.0 micrograms, i.c.v.) on ECS-induced amnesia was partly antagonized by beta-endorphin (0.05-10 micrograms, i.c.v.). Intraperitoneal (i.p.) injection of naloxone (1-10 mg/kg) could not prevent ECS-induced amnesia, but continuous subcutaneous infusion of this drug (2 mg/day, 7 days) completely abolished the amnesia. Naloxone (1 and 10 mg/kg, i.p.) also partly antagonized amnesia induced by proglumide (1 and 10 micrograms, i.c.v.) and prevented it when induced by CCK-4 (5 and 10 micrograms, i.c.v.). The results indicate the facilitating action of naloxone and the inhibitory effect of beta-endorphin on memory, suggesting that the endogenous opiate systems are involved in some way in the memory processes.

Amnesia↗
PubMed1987

Activation of keratinocyte fibronectin receptor function during cutaneous wound healing.

Keratinocytes freshly isolated from unwounded skin could not attach and spread on fibronectin (FN)-coated culture dishes and could not bind and phagocytose FN-coated beads. These adhesive functions were activated, however, in keratinocytes that were isolated from healing wounds. Moreover, adhesiveness of basal keratinocytes to FN substrata was activated during epidermal cell or explant culture. Activation was specific for attachment to FN compared to other adhesion ligands, and occurred even when epidermal cells were cultured on collagen, basement membrane matrix, or lectin-coated substrata. Biochemical studies showed that keratinocytes have a 140 x 10(3) Mr FN receptor analogous to the fibroblast receptor for FN, and that this receptor is expressed in activated keratinocytes but not in keratinocytes freshly isolated from unwounded skin. The absence of FN receptors from keratinocytes in unwounded skin is not surprising since the basal keratinocytes of the epidermis are attached to a basement membrane containing laminin and type IV collagen. During wound repair, however, these cells migrate over or through a FN-coated matrix. Consequently, expression of FN receptors may be an essential feature of healing. Believing that FN is the required substratum for keratinocyte migration during wound healing, we have initiated clinical studies to determine if topical application of FN is useful as a therapy for non-healing cutaneous ulcers.

Cell Adhesion↗
PubMed1986

Morphological appearance of epidermal cells cultured on fibroblast-reorganized collagen gels.

Human foreskin fibroblasts were used to reorganize hydrated collagen gels into a dermal-like matrix, after which freshly isolated keratinocytes isolated from rabbit ear skin were placed on the surfaces of the matrices and cultured for up to 12 days. Transmission electron microscopy revealed 8-12 cell layers of epidermal cells organized in three distinct strata. The basal stratum consisted of cuboidal to columnar cells with typical complement of organelles, oval nuclei, and prominent tonofilaments inserting into desmosomes. Mitotic cells often were found at this level. There was no well-defined basement membrane region; rather, many of the cells appeared to be in close contact with collagen fibrils. The intermediate stratum of suprabasal cells consisted of elongated cells that had reduced organelles, but still were connected to each other by desmosomes. Finally, the superficial stratum of suprabasal cells contained cells that were completely flattened and often appeared to be sloughing off the apical surfaces of the cultures. Indirect immunofluorescence studies carried out on frozen sections revealed bullous pemphigoid antigen associated with basal epidermal cells; pemphigus vulgaris antigen around the epidermal cells of all strata, and keratin present in the epidermal cells of all strata. Filaggrin was observed in punctate and fibrillar arrangements in suprabasal cells. Fibronectin was found in a linear deposit at the dermal-epidermal junction and around the fibroblasts in the reorganized collagen gels. Type-IV collagen and laminin, however, were not detected.

Antigens↗
PubMed1986

Activation of rabbit keratinocyte fibronectin receptor function in vivo during wound healing.

Freshly isolated rabbit keratinocytes expressed low fibronectin (pFN) receptor function as shown by their poor ability to attach and spread on pFN-coated substrata or to bind and ingest pFN-coated beads. Following in vitro culture of these cells, however, pFN receptor function was activated. The cultured cells appeared to be normal, based on their ability to reepithelialize rapidly full-thickness cutaneous wound beds. Freshly isolated keratinocytes that had low pFN receptor function were autotransplanted onto full-thickness wound beds. Two days after transplantation, keratinocytes recovered from these wounds were observed to express increased pFN receptor function. This activity was maximal in keratinocytes isolated 3 days after transplantation and declined in keratinocytes isolated at later times. By 10 days after transplantation, the transplanted cells had formed a multilayered hyperplastic epidermis and reconstituted their laminin and type IV collagen-containing basement membrane. It is proposed that initiation of pFN receptor function in keratinocytes is a crucial mechanism necessary for them to attach to and migrate through the pFN-rich wound bed comprised of granulation tissue. After reepithelialization is complete, and the basement membrane re-forms, pFN receptor function declines markedly because it is no longer essential to the cells.

Animals↗
PubMed1986

Cell cycle-dependent modulation of biosynthesis and stimulus-evoked release of catecholamines in PC12 pheochromocytoma cells.

Catecholamine biosynthesis and its stimulus-evoked release in PC12 pheochromocytoma cells were studied as a function of cell cycle by means of HPLC with electrochemical detection. We found that 3,4-dihydroxyphenylethylamine (dopamine) levels in PC12 cells remained constant throughout the period of cell cycle. In contrast, the noradrenaline content was dependent on the cell cycle: it increased during the S + G2 phase followed by a decrease in the M phase. These results were confirmed further by measuring the activities catalyzing the catecholamine biosynthesis. Thus, activities of tyrosine 3-monooxygenase and 3,4-dihydroxyphenylalanine decarboxylase were independent of the cell cycle, whereas both soluble and membrane-bound dopamine beta-monooxygenase activities were modulated during the cell cycle. On the other hand, release of the catecholamines stimulated with 50 mM KCl increased in the G1 phase, reached a maximum in the late G1, and then gradually decreased in later periods. We also found that carbamylcholine-induced release of the catecholamines occurred maximally in the early S + G2 phase followed by a decrease during the M phase. Cell cycle dependence of the catecholamine release was in good agreement with that of 45Ca2+ uptake. Thus, this study provides evidence that the catecholamine biosynthesis and its release in PC12 cells are modulated during the period of cell cycle.

Animals↗
PubMed1986

[Differences in the immunostimulatory activity and antitumor therapeutic effect of OK-432 and N-CWS].

Immunobiological activities of OK-432 and N-CWS were studied in BALB/c-Meth-A and C3H-MH 134 systems. Peritoneal exudate cells obtained from mice injected i.p. with OK-432 or N-CWS showed stronger in vitro cytotoxicity against Meth-A and YAC-1 cells than did those from non-treated mice. Spleen cells from OK-432 or N-CWS-treated mice exhibited lower Con A mitogenic response in comparison with those from non-treated mice. When Meth-A or MH-134 tumor cells were admixed with OK-432 or N-CWS, the intradermally inoculated tumor cells showed no or slower growth than did those admixed with saline only. There were no significant differences in all the above mentioned activities between OK-432 and N-CWS, and there was no difference in the direct tumor inhibitory activity of the two agents in vitro. However, the administration of N-CWS had no therapeutic effect against i.p.-inoculated tumor cells while OK-432 showed a strong therapeutic effect by the same treatment schedule. Further studies are required to clarify the mechanisms responsible for the difference in the therapeutic effect of the two agents.

Animals↗
PubMed1986

The roles of the recurrent nerve and the ventral nerve cord in the feeding response of the blowfly, Phormia regina M.

The interaction of sensory activities from internal stretch receptors and from external sugar receptors was studied in relation to proboscis extension and sucrose intake of the blowfly. The tarsal threshold for proboscis extension was elevated in flies after the recurrent nerve was cut. Cutting either the recurrent nerve or the ventral nerve cord did not alter the labellar thresholds for proboscis extension but did influence sucrose intake by prolonging the duration of intake. After the ventral nerve cord was cut, the flies did not stop ingestion as long as sugar receptors in the interpseudotracheal papillae were stimulated. Tonic impulse discharges from the intact recurrent nerve were divided into efferent and afferent types. Efferent impulses from the brain were thought to be transmitted to the hypocerebral ganglion-corpus cardiacum complex for regulation of opening and closing of the foregut valves, of peristaltic movements in the foregut. Afferent impulses were thought to be discharged from the foregut stretch receptors which detected peristaltic movements in the foregut.

Animals↗
PubMed1985

Relationship between dopamine content and its secretion in PC12 cells as a function of cell growth.

The PC12 cell line derived from a rat adrenal medullary tumor is known to synthesize dopamine and to release it in response to cholinergic agonists or depolarizing agents. In this report, we have studied the relationship between dopamine biosynthesis and its stimulus-induced secretion in PC12 cells as a function of cell growth. The endogenous dopamine content was found to depend on cell growth, and reached a maximum in the stationary phase. This increase was associated both with an increase in the specific activity of tyrosine 3-monooxygenase, and with an increase of DOPA-decarboxylase in the cells. On the other hand, the maximal release of dopamine occurred in the late exponential phase before the endogenous dopamine was maximally synthesized in the cells. Moreover, the uptake of 45Ca2+ stimulated with either carbamylcholine or high K+ was also regulated by cell division: the maximal uptake took place in the same period of culture in which the maximal release of dopamine was observed. Thus, this report offers new evidence that the biosynthesis and secretion of dopamine are separately regulated in PC12 cells.

Adrenal Gland Neoplasms↗
PubMed1985

Fibronectin-mediated keratinocyte migration and initiation of fibronectin receptor function in vitro.

Cell suspensions of human keratinocytes, freshly isolated from skin specimens, did not express plasma fibronectin (pFN) receptor function in short-term assays for cell attachment and spreading on pFN-coated culture dishes and binding and phagocytosis of pFN-coated latex beads. These activities were expressed, however, by the cells harvested from primary keratinocyte cultures after 2-4 days of culture. Analysis of the cell types arising during primary culture, based on staining with antikeratin antibodies and bullous pemphigoid (BP) serum, revealed that about 90% of the originally isolated cell population consisted of keratinocytes (keratin-positive) and 30% were basal cells (BP antigen-positive). After 2 days of culture, 95% of the cells were keratinocytes and 70% were basal cells. In vitro initiation of pFN receptor function also was observed in cells harvested from epidermal explants. After 9 days in culture, the cells that migrated out of the explants also were active in short-term cell adhesion assays, while cells remaining in the central region of the explant had much less activity. In related studies, the role of pFN in epidermal cell migration was analyzed, and it was found that anti-pFN antibodies inhibited migration of keratinocytes out of epidermal explants. Addition of preimmune IgG, however, had no effect. It appears, therefore, that pFN is important in all aspects of keratinocyte adhesion, and the expression of pFN receptor function may be a critical activation step necessary for basal cell phagocytosis and migration during wound healing.

Antibodies, Anti-Idiotypic↗
PubMed1984

Human keratinocyte adhesion and phagocytosis promoted by fibronectin.

Epidermal cells from human foreskin or cadaver skin were found to bind and phagocytose fibronectin-coated latex beads but not serum albumin-coated beads. Three lines of evidence suggested that the beads actually were internalized by the cells and not bound only at the cell surfaces. First, the fibronectin coat on internalized beads could be detected with antifibronectin antibodies only if the cells were permeabilized prior to indirect immunofluorescence staining. Second, the internalized beads were not released from the cells by trypsin treatment. Finally, electron microscopic observations showed that the internalized beads were packaged individually and in clusters inside endocytic vesicles in the perinuclear region of the cells. These vesicles had the typical appearance of lysosomes, and, based on the release of trichloroacetic acid-soluble radioactive fragments of fibronectin into the incubation medium, it was concluded that degradation of the fibronectin on the bead surfaces occurred. The epidermal cells that phagocytosed the fibronectin-coated beads were confirmed as keratinocytes according to their electron microscopic appearance and prominent immunofluorescence staining with antikeratin but not anti-plasma fibronectin antibodies. Fibronectin also was found to promote the attachment and spreading of keratinocytes on culture dishes, although the concentration of fibronectin required for half-maximal activity (approximately 5 micrograms/ml) was severalfold higher than the concentration of fibronectin required for spreading of human fibroblasts (approximately 1 microgram/ml). The results suggest the possible importance of fibronectin in mediating adhesion and phagocytosis by keratinocytes, which may be important for the migration of these cells during wound repair.

Antibodies↗
PubMed1984

Clonal variability of PC12 pheochromocytoma cells with respect to catecholamine biosynthesis.

Clonal variants of PC12 cells with respect to catecholamine biosynthesis were isolated, and the catecholamine content was measured by high performance liquid chromatography with electrochemical detection. The dopamine content of 13 subclones, which were selected and isolated in tyrosine-free medium, was substantially higher than the control level: 0.91 +/- 0.10 nmol/mg protein (mean +/- SEM; n = 3). In contrast, the noradrenaline content showed a marked heterogeneity: only two subclones contained noradrenaline levels similar to or higher than the control level: 0.40 +/- 0.05 (n = 5). The rest of them contained below the level of 0.20, and only negligible amounts of noradrenaline were found in four subclones. Thus, the noradrenaline-to-dopamine ratio varied widely between 0.003:1 and 0.53:1. This divergence of the noradrenaline content appears to be related to differing levels of dopamine beta-monooxygenase activity. The administration of ascorbate to the medium alone, however, did not restore the level of noradrenaline to the normal level in a subclone. Heterogeneity of the response to applied glucocorticoid was also demonstrated.

Adrenal Gland Neoplasms↗