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H Kamiya

Publications and source records attributed to H Kamiya.

At least 379 records · Page 21Linked to original sources
PubMed1988

Synthetic omega-conotoxin blocks synaptic transmission in the hippocampus in vitro.

The effects of some organic calcium channel blockers and a toxin on synaptic transmission were examined in hippocampal slices from the guinea pig. omega-Conotoxin fraction GVIA, a novel peptide that blocks N and L type voltage-sensitive calcium channels, blocked synaptic transmission from mossy fibers to CA3 neurons at very low concentration (100 nM). However, organic calcium channel blockers such as verapamil (100 microM) and nifedipine (10 microM), which block L type calcium channels, had little effect on the synaptic transmission. Phenytoin (100 microM, T type calcium channel blocker) was also ineffective to block the synaptic transmission. These results suggest that presynaptic calcium channels which cause transmitter release may be N type calcium channel.

Animals↗
PubMed1988

Cingulate gyrus of the cat receives projection fibers from the thalamic region ventral to the ventral border of the ventrobasal complex.

Direct projections to the cingulate gyrus from the thalamic region lying just ventrally to the ventral border of the ventrobasal complex (VB) were found in the cat by two sets of experiments that used WGA-HRP (wheat germ agglutinin-horseradish peroxidase conjugate). In the first set of experiments, WGA-HRP was injected into the thalamic region around the ventral border of the VB. When the site of injection involved the thalamic region lying ventrally to the ventral border of the VB at the levels of the caudal two thirds of the VB, the cerebral cortex in the rostral part of the cingulate gyrus ipsilateral to the WGA-HRP injection contained fine HRP-positive granules, which indicated anterograde labeling of axon terminals. These labeled presumed axon terminals were mainly distributed to the superficial part of layer I, deep part of layer II, layer IV, and the most superficial part of layer V in the cingulate cortex. In the second set of experiments, WGA-HRP was injected into the cerebral cortex of the rostral part of the cingulate gyrus. When the site of injection involved the region of the cingulate gyrus, where presumed axon terminals had been labeled in the first set of experiments, the thalamic region just ventral to the ventral margin of the caudal two-thirds of the VB ipsilateral to the WGA-HRP injection contained neuronal cell bodies labeled retrogradely. The results indicate that some neurons that are located in the thalamic region just ventral to the ventral border of the caudal two-thirds of the VB send their axons to the cerebral cortex in the rostral part of the cingulate gyrus. The possible significance of the thalamocingulate projection found in the present study is discussed with relation to nociceptive behavior and function.

Animals↗
PubMed1988

The supramammillary region of the cat sends substance P-like immunoreactive axons to the hippocampal formation and the entorhinal cortex.

A combined method of the tracing of WGA-HRP (wheat germ agglutinin-conjugated horseradish peroxidase) and the immunohistochemistry of substance P (SP) showed that many SP-like immunoreactive neurons in the supramammillary nucleus of cat hypothalamus sent their axons to the hippocampal formation. SP-like immunoreactive axons in the hippocampal formation and entorhinal cortex were markedly reduced in number ipsilaterally after placing an electrothermic lesion in the supramammillary region of the hypothalamus.

Animals↗
PubMed1988

Somatosensory and auditory relay nucleus in the rostral part of the ventrolateral medulla: a morphological study in the cat.

A nucleus that possibly relays both somatosensory and auditory information was identified in the well-known autonomic control region in the rostral part of the ventrolateral medulla (RVL) of the cat by four sets of experiments using the WGA-HRP (wheat germ agglutinin-horseradish peroxidase conjugate) method. First, after injecting WGA-HRP into the dorsal column nuclei (DCN), anterograde and retrograde labeling was found bilaterally within and around a small cluster of medium-sized neurons in the RVL; more labeled neuronal cell bodies were seen in the cluster ipsilateral to the injection than in the contralateral cluster, whereas labeled axon terminals were distributed more densely on the contralateral side than on the ipsilateral side. The neuronal cluster in the RVL was located close to the ventrolateral surface of the medulla oblongata, constituting a short, slender column extending from a caudal level of the facial nucleus to the level of the rostral one-third of the inferior olive. This cluster of neurons was named the ventrolateral medullary nucleus (VLMN). In the second set of experiments, WGA-HRP was injected into the VLMN. Labeled neuronal cell bodies were seen in the reticular zone of the DCN bilaterally, with a slight dominance on the side contralateral to the injection, and further in the anteroventral division of the cochlear nuclei (CN) bilaterally, with a predominantly contralateral distribution. Labeled presumed axon terminals were seen bilaterally not only in the DCN and granular layer of the CN but also in the intercollicular region (IcR), lateral division of the posterior group of the thalamus (Pol), and medial geniculate nuclei (MG). Labeled terminals in the DCN were more numerous on the side ipsilateral to the injection than on the contralateral side, whereas those in other regions were distributed with a clear-cut contralateral dominance. In the third set of experiments, WGA-HRP injection into the CN resulted in anterograde and retrograde labeling in the VLMN. The labeling was bilateral, but more marked in the VLMN contralateral to the injection. In the fourth set of experiments, after WGA-HRP injection into the IcR, Pol, or MG, labeled neuronal cell bodies were located in the VLMN bilaterally with a dominant contralateral distribution. The results indicate that the VLMN possibly relays somatosensory and auditory information from the reticular zone of the DCN and anteroventral division of the CN to the IcR, Pol, and MG.

Afferent Pathways↗
PubMed1988

Dimerization of neurokinin A and B COOH-terminal heptapeptide fragments enhanced the selectivity for tachykinin receptor subtypes.

We have synthesized dimeric analogues of neurokinin A and B COOH-terminal heptapeptide fragments and evaluated their biological activities to contract isolated smooth muscle preparations of the guinea-pig ileum and rat vas deferens. The dimers were fairly active and showed two-fold increased selectivity for receptors in the guinea-pig ileum as compared with monomers. Extremely slow dissociation indicated a possible bivalent interaction between dimer and receptor.

Amino Acid Sequence↗
PubMed1988

A highly selective ligand for brain delta opiate receptors, a cyclopropyl(E)Phe(4)-enkephalin analog, suppresses mu receptor-mediated thermal analgesia by morphine.

[D-Ala(2)(2R,3S)-delta(E)Phe(4)Leu(5)]enkephalin (CP-OH) [delta denoting cyclopropyl; superscript E indicating the E-configuration about the cyclopropane ring], a highly selective opioid ligand for delta receptors in rat brain, but not for those in the mouse vas deferens, was examined for in vivo biological activities by intracerebroventricular administration. CP-OH (5-20 micrograms) showed no analgesic activity in the hot plate (51 degrees C) test using rats. However, it suppressed completely the analgesic effects of intraperitoneally administered morphine (3 mg/kg rat) in a dose-dependent manner. CP-OH showed no binding affinity for brain kappa receptors to which dynorphin, an opioid peptide that inhibits morphine analgesia, binds predominantly. These results suggest that, besides the conventional delta receptors which mediate analgesia, the rat brain contains another delta-like receptor which has a modulatory role to attenuate morphine-induced analgesia mediated through the mu receptors, and that this modulatory receptor does not exist in the mouse vas deferens.

Analgesia↗
PubMed1988

Well-maintained reflex responses of sympathetic nerve activity to stimulation of baroreceptor, chemoreceptor and cutaneous mechanoreceptors in neonatal capsaicin-treated rats.

Neonatal treatment with capsaicin (CAP) reduced the content of substance P-like immunoreactivity in the area of the nucleus tractus solitarii and the dorsal horn of the spinal cord in rats. The resting values of the mean arterial blood pressure and heart rate of CAP-treated rats were not significantly different from those of control rats. Reflex responses of the renal sympathetic nerve activity to stimulation of baroreceptor, chemoreceptor and cutaneous mechanoreceptor were compared in CAP- and vehicle-treated rats. Under these conditions the reflex responses were quite well maintained in CAP-treated rats.

Animals↗
PubMed1988

Additive feature of long-term potentiation and phorbol ester-induced synaptic enhancement in the mossy fiber-CA3 synapse.

Application of phorbol esters, selective activators of protein kinase C (PKC), causes a long-lasting enhancement of synaptic transmission in the hippocampus. We examined the relationship between this phorbol ester-induced enhancement of synaptic transmission and long-term potentiation (LTP) quantitatively in the mossy fiber-CA3 synapse of the guinea pig hippocampus in vitro. Potentiating action of 0.5 microM phorbol 12,13-diacetate (PDAc) on synaptic transmission was almost unaffected by preceding tetanic stimuli which had caused a full development of LTP. Tetanic stimulation induced LTP even after synaptic transmission had been enhanced by 0.5 microM PDAc. Quantitative estimations revealed that PDAc-induced synaptic enhancement and LTP were simply additive to each other. The relation between LTP and PKC activation is discussed.

Action Potentials↗
PubMed1988

Effect of aspirin on haloperidol-induced cataleptic behavior in mice.

Haloperidol given intraperitoneally dose-dependently elicited cataleptic behavior, evaluated by high bar and four-cork tests, in mice. The haloperidol-induced cataleptic behavior was reduced dose-dependently after oral treatment with aspirin, a cyclooxygenase inhibitor. The intra-cerebroventricular administration of prostaglandin F2a produced cataleptic behavior of long duration determined by the high bar test. It is suggested that prostaglandins may participate in the induction of cataleptic behavior in part.

Animals↗
PubMed1988

Purification and properties of agglutinins from conger eel, Conger Myriaster (Brevoort), skin mucus.

The skin mucus of the conger eel, Conger myriaster, contains galactose-specific agglutinins. Hemagglutinating activity is independent of divalent cations and is destroyed by heating at 50 degrees C for 15 min. The mucus agglutinins, named congerins, are a mixture of proteins with different electrical charges. Three of these molecules were isolated by affinity chromatography on acid-treated Sepharose 4B and by ion-exchange chromatography. They are simple proteins with the same molecular weight of 30,000 and consisting of two subunits (each 13,000 daltons). The agglutinins inhibited the normal embryonic development of the starfish Asterina pectinifera, and lysed the fertilized eggs at a concentration of 25 micrograms protein/ml. They also agglutinated but did not inhibit the growth of a marine bacterium, Vibrio anguillarum.

Agglutinins↗
PubMed1988

Sequence-dependent antitumor effect of VP-16 and 1-beta-D-arabinofuranosylcytosine in L1210 ascites tumor.

The sequence-dependence of the antitumor effect of etoposide (VP-16) and 1-beta-D-arabinofuranosylcytosine (ara-C) was investigated against the L1210 ascites tumor in BDF1 mice. Treatment with VP16 (7.5 or 15 mg/kg) and ara-C (25 or 500 mg/kg) was administered intraperitoneally on days 1, 4 and 7 after tumor inoculation. Six hour pretreatment with 15 mg/kg VP16 followed by 500 mg/kg ara-C yielded a 100% cure rate, but only a 20% cure rate was obtained with the reverse sequence. Simultaneous administration of 15 mg/kg of VP-16 and 500 mg/kg ara-C interacted synergistically, producing a 70% cure rate. In contrast with the results obtained with VP-16 and 500 mg/kg ara-C, simultaneous administration of 25 mg/kg ara-C neither antagonized nor potentiated the antitumor effect of VP-16. Twenty-five mg/kg ara-C was too low to produce any antitumor effect with VP-16 in simultaneous administration. At every dose investigated, pretreatment with VP-16 followed by ara-C was the most effective antitumor schedule in L1210 leukemia. This sequence of drug administration did not cause greater toxicity as measured by weight loss or toxic death.

Animals↗
PubMed1988

Phorbol esters potentiate glucocorticoid-induced cytotoxicity in CEM-C7 human T-leukemia cell line.

Phorbol ester tumor promoter, such as 12-O-tetradecanoylphorbol-13-acetate (TPA), is synergistic with dexamethasone to cause growth inhibition of CEM-C7 human T-leukemia cell line. A specific saturable binding component which may mediate the phorbol ester effects has been identified by using [20-(3)H]phorbol 12,13-dibutyrate in a whole cell binding assay. Saturation of the specific binding occurs at a concentration (approx. 100 nM) consistent with causing maximal cytotoxicity. Scatchard analysis of the binding after 15 min at 37 degrees C demonstrates a single class of binding sites. The number is 194,000 sites per cell. Other phorbol esters are also cytotoxic to CEM-C7 cell in the presence of 30 nM dexamethasone in an approximate proportion to their activity in competing for [20-(3)H]phorbol 12,13-dibutyrate binding. Phorbol 12, 13-didecanoate, 4-O-methyl PMA, 4-beta-phorbol do not compete for specific binding. The synergism of phorbol esters and dexamethasone on CEM-C7 cells is reversible by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine(H-7). However, by treating CEM-C7 cells with TPA for 48 h there is not any increase in the affinity or levels of glucocorticoid receptor. It is tentatively concluded that phorbol esters may play an important role linked to the glucocorticoid-induced growth inhibition in CEM-C7 human T-leukemic cell.

Binding, Competitive↗
PubMed1988

Conversion of the guanine nucleotide binding sites of ras protein resulting in the reduction of base specificity.

A gene coding for the novel ras protein, p21X, in which the domains of guanine binding and phosphate binding were exchanged, was constructed and expressed in Escherichia coli. The gene product, p21X, showed GTP binding activity, but no GPTase activity. In addition, p21X revealed binding activity toward ATP and CTP. In a competitive binding assay, [3H]GTP binding to p21X was inhibited in the presence of ATP, CTP and UTP, ITP as well as GDP, GTP and dGTP.

Amino Acid Sequence↗
PubMed1988

Incorporation of N4-behenoyl-1-beta-D-arabinofuranosylcytosine into DNA as 1-beta-D-arabinofuranosylcytosine.

BHAC is a newly synthesized lipophilic derivative of ara-C. To clarify its pharmacological mode of action, P388 murine leukemic cells were incubated with two different types of 14C-labeled BHAC, [cytosine-2-14C]BHAC and [acyl-1-14C]BHAC, and DNA was extracted with phenol. The phenol-extracted DNA was then hydrolyzed by nuclease P1 and analyzed with high-performance liquid chromatography (HPLC). The radioactivity of DNA, from the cells incubated with [cytosine-2-14C]BHAC, was detected as ara-CMP. But the radioactivity of DNA, from the cells incubated with [acyl-1-14C]BHAC, was hardly detected. On the other hand, the main radioactivity of the acid soluble fraction was determined as ara-CTP. On the basis of our results, BHAC is not phosphorylated directly to produce N4-behenoyl-ara-CTP, but is mainly converted to ara-C which subsequently produces ara-CTP, the active metabolite of the drug, and which is then incorporated into DNA.

Animals↗