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Biomedical subjects

C Su

Publications and source records attributed to C Su.

At least 199 records · Page 11Linked to original sources
PubMed1971

[3H]adenosine triphosphate: release during stimulation of enteric nerves.

The isolated taenia coli of the guinea pig takes up tritiated adenosine, adenosine monophosphate, adenosine diphosphate, and adenosine triphosphate, in preference to tritiated inosine and adenine. After uptake, [(3)H]adenosine is converted and retained primarily as [(3)H]adenosine triphosphate. Tritium is released from taenia coli treated with [(3)H]adenosine upon activation of the nonadrenergic inhibitory nerves. These results are consistent with the previous evidence that adenosine triphosphate may be the transmitter from the nerves.

Adenine Nucleotides↗
PubMedDate not supplied

Association between IgE antibody against soluble egg antigen and resistance to reinfection with Schistosoma japonicum.

There is evidence that immunoglobulin (Ig) E antibody may be a critical component of protective immunity against Schistosoma mansoni and S. haematobium reinfection. In the present study, 555 individuals aged 3-67 years infected with S.japonicum received praziquantel treatment before the transmission season commenced; 45 d later, blood samples from 265 individuals who had no S. japonicum egg in their stool were examined by enzyme-linked immunosorbent assay for specific isotypic antibodies. Single, non-conditional logistic regression analysis showed that exposure intensity, age, soluble egg antigen (SEA)-IgE, SEA-IgM and soluble adult worm antigen-IgG4 were relevant to reinfection; multiple, non-conditional logistic regression analysis showed that exposure intensity was still a significant factor for reinfection while the SEA-IgE antibody level was associated with resistance to reinfection with S. japonicum, with a protective index of 2.00. It is suggested that this population in an area endemic for schistosomiasis japonica exhibits acquired immunity.

Adolescent↗
PubMedDate not supplied

Tyramine-induced contractions in the rabbit ear and basilar arteries.

This study examined in vitro tyramine (TY)-induced contractions of the isolated ring segments of the rabbit basilar and ear arteries in relation to their sympathetic innervations. The TY dose--response relationship in the basilar artery was not affected by cocaine, chronic sympathectomy, or reserpine pretreatment. However, these treatments shifted the TY dose--response relationship in the ear arteries significantly to the right. These results indicate that the TY-induced contraction in the basilar artery is due solely to its direct stimulation of the postsynaptic alpha-receptors, but in the ear artery it is due both to its indirect [release of norepinephrine (NE)] and direct actions. The failure of TY to induce contraction in the basilar artery by the indirect mechanism is probably in part due to a wide synaptic cleft distance and the reported insensitivity of alpha-receptors of this artery. These results suggest that the endogenous NE releasable from the sympathetic nerve in the basilar artery is insufficient to bring about vasoconstriction. This is turn favors our previous hypothesis that transmural-nerve-stimulation (TNS)-induced constriction of this artery is to a transmitter other than NE. It further suggests that the functional significance of the sympathetic innervations to different regions of the vessels is highly variable even when they are of the same ganglionic origin.

Animals↗
PubMedDate not supplied

Segmental variation of adrenergic innervation in rabbit mesenteric vasculature.

In order to characterize the segmental variation in vascular adrenergic innervation, histochemical, biochemical, and physiological parameters were determined in segments of the rabbit mesoduodenal arteries that averaged 1.23, 0.70, and 0.49 mm in outer diameter in situ. The catecholamine histofluorescence developed by glyoxylic acid in whole mount sections suggested that the thickness of superimposed nerve plexuses declined with vessel diameter. Smaller arteries contained less norepinephrine per wet weight. The absolute magnitude of the maximal constrictor response to transmural nerve stimulation also diminished with vessel diameter and tissue mass. While this response as a proportion of the maximal response to exogenous norepinephrine did not vary significantly, the smaller segments exhibited a greater contractile response/catecholamine content. Pretreatment of rabbits with reserpine practically abolished the norepinephrine contents, histofluorescence, and constrictor response to nerve stimulation, indicating that the constrictor nerve is adrenergic. While biochemical and histochemical analyses suggest that adrenergic innervation decreases distally in the mesenteric vasculature, in view of the constrictor responses, smaller segments appear to undergo more efficient neuroeffector transmission in a manner yet to be characterized.

Animals↗
PubMedDate not supplied

Reversal of adrenaline-induced contraction in the rabbit pulmonary artery by clonidine.

Characterization of clonidine which reversed the adrenaline-induced contractions was assessed using the rabbit pulmonary arterial segment. Clonidine in high concentrations (10(-5)-10(-4) mol/l) contracted this vascular tissue. Nevertheless, an adrenaline (3 X 10(-6)mol/l)-induced contraction, which can be markedly depressed by phentolamine, was reversed to relaxation by pre-addition of 3 X 10(-5)mol/l clonidine. This reversal was abolished by 10(-5) mol/l propranolol, a beta-adrenoceptor antagonist. The cumulative concentration-contraction curve for adrenaline was shifted to the right by 10(-5) mol/l clonidine without further alteration at 10(-4) mol/l, suggesting a partial agonistic feature of clonidine for alpha-adrenoceptors. Contractions evoked by 5 X 10(-5) mol/l clonidine alone were effectively reduced by prazosin (IC50 = 1.7 X 10(-7) mol/l) or yohimbine, (IC50 = 3.3 X 10(-5) mol/l) and those by phenylephrine (10(-5) mol/l) were suppressed as well (prazosin, IC50 = 3.4 X 10(-8) mol/l; yohimbine, IC50 = 5.0 X 10(-6) mol/l). However, the depolarization-induced contractions with 30 mmol/l KCl were virtually unaltered by both antagonists. These results suggest that the reversal action of clonidine on the adrenaline-induced contraction is primarily mediated by a partial agonistic property for postsynaptic alpha 1-adrenoceptors.

Animals↗
PubMedDate not supplied

Role of endothelium in dilator responses of spontaneously hypertensive rat arteries.

The possible role of endothelium in the vascular responses to vasodilator drugs was studied in relation to experimental hypertension. Short ring segments of the thoracic aorta and femoral artery were removed from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. They were rubbed on the intimal surface to destruct endothelial cells or unrubbed, and bathed in Krebs-bicarbonate solution for isometric recording of contractile and relaxant responses. The relaxant response to acetylcholine was abolished by rubbing all arteries tested. Rubbing also significantly attenuated the relaxation induced by adenosine in the SHR aorta and SHR and WKY femoral artery, and attenuated the relaxation by isoproterenol in the SHR femoral artery. In contrast, contractile response to norepinephrine was augmented by intimal surface rubbing in all arteries except the aorta of WKY. It is suggested that an endothelial compensatory mechanism develops to offset the diminished relaxant and/or increased contractile responsiveness of smooth muscle cells in the hypertensive rat arteries.

Acetylcholine↗