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Biomedical subjects

S T Yao

Publications and source records attributed to S T Yao.

At least 19 recordsLinked to original sources
PubMed2006

A spinal vasopressinergic mechanism mediates hyperosmolality-induced sympathoexcitation.

An elevation in plasma osmolality elicits a complex neurohumoral response, including an activation of the sympathetic nervous system and an increase in arterial pressure. Using a combination of in vivo and in situ rat preparations, we sought to investigate whether hypothalamic vasopressinergic spinally projecting neurones are activated during increases in plasma osmolality to elicit sympathoexcitation. Hypertonic saline (HS, i.v. bolus), which produced a physiological increase in plasma osmolality to 299 +/- 1 mosmol (kg water)(-1), elicited an immediate increase in mean arterial pressure (MAP) (from 101 +/- 1 to 121 +/- 3 mmHg) in vivo. Pre-treatment with prazosin reversed the HS-induced pressor response to a hypotensive response (from 121 +/- 3 to 68 +/- 2 mmHg), indicating significant activation of the sympathetic nervous system. In an in situ arterially perfused decorticate rat preparation, hyperosmotic perfusate consisted of either 135 mm NaCl, or a non-NaCl osmolyte, mannitol (0.5%); both increased lumbar sympathetic nerve activity (LSNA) by 32 +/- 5% (NaCl) and 21 +/- 1% (mannitol), which was attenuated after precollicular transection (7 +/- 3% and 1 +/- 1%, respectively). Remaining experiments used the NaCl hyperosmotic stimulus. In separate preparations the hyperosmotic-induced sympathoexcitation (21 +/- 2%) was also significantly attenuated after transection of the circumventricular organs (2 +/- 1%). Either isoguvacine (a GABA(A) receptor agonist) or kynurenic acid (a non-selective ionotropic glutamate receptor antagonist) microinjected bilaterally into the paraventricular nucleus (PVN) attenuated the increase in LSNA induced by the hyperosmotic stimulus (control: 25 +/- 2%; after isoguvacine: 7 +/- 2%; after kynurenic: 8 +/- 3%). Intrathecal injection of a V(1a) receptor antagonist also reduced the increase in LSNA elicited by the hyperosmotic stimulus (control: 29 +/- 6%; after blocker: 4 +/- 1%). These results suggest that a physiological hyperosmotic stimulus produces sympathetically mediated hypertension in conscious rats. These data are substantiated by the in situ decorticate preparation in which sympathoexcitation was also evoked by comparable hyperosmotic stimulation. Our findings demonstrate the importance of vasopressin acting on spinal V(1a) receptors for mediating sympathoexcitatory response to acute salt loading.

Adrenergic alpha-Antagonists↗
PubMed2003

Localisation of P2X2 receptor subunit immunoreactivity on nitric oxide synthase expressing neurones in the brain stem and hypothalamus of the rat: a fluorescence immunohistochemical study.

A large body of evidence suggests that nitric oxide (NO) and ATP act as neurotransmitters in the regulatory mechanisms concerning several autonomic functions at the level of both the hypothalamus and the brain stem. In the present study, we investigated whether neuronal NO synthase containing neurones also express P2X(2) receptor subunit of the ATP-gated ion channel via double-labelling fluorescence immunohistochemistry. Our data demonstrate that a high percentage of neuronal NO synthase-immunoreactive neurones are also P2X(2)-immunoreactive in the rostral ventrolateral medulla (98%) and supraoptic nucleus of the hypothalamus (92%). Significant numbers of neuronal NO synthase-immunoreactive neurones are also P2X(2)-immunoreactive in the subpostremal (48%) and commissural (65%) subdivisions of the nucleus tractus solitarius. In the caudal ventrolateral medulla and raphe obscurus, 96% and 89%, respectively, of neuronal NO synthase containing neurones also express P2X(2) receptor subunit. In contrast to the supraoptic nucleus, there was a lower percentage of co-localisation between NO synthase and P2X(2) receptor subunit in the paraventricular nucleus of the hypothalamus. In summary, this study demonstrates for the first time that there is a widespread co-localisation of neuronal NO synthase and P2X(2) receptor subunit in the hypothalamus and brain stem of the rat. Further studies are required to elucidate whether NO and ATP functionally interact within the hypothalamus and the brain stem.

Animals↗
PubMed2001

On the immunohistochemical distribution of ionotropic P2X receptors in the nucleus tractus solitarius of the rat.

ATP has been shown to excite neurones of the nucleus tractus solitarius (NTS) via the activation of P2X receptors. In the present study, the distribution of six P2X receptors (P2X(1)-P2X(6)) within the rat NTS was investigated by peroxidase immunohistochemistry. Immunopositive neurones for P2X receptor subtypes were detected in all divisions of the NTS, although the staining densities differed according to receptor subtype and sub-nuclei. P2X(1)-immunopositive cells were distributed throughout the rostro-caudal extent of the NTS, while varicose fibres were mainly located along the postremal border. P2X(2) immunoreactivity was present in neurones and fibres located throughout the NTS. In the commissural NTS intense staining was observed medial of the solitary tract while in the sub-postremal NTS neurones were observed along the postremal border. A high density of P2X(3)-positive neurones and fibres was observed in the sub-postremal NTS along the border of the area postrema and in the rostral NTS in the medial subdivision. In comparison to the staining observed with the other receptor antibodies, there was considerably reduced P2X(4) receptor immunoreactivity. P2X(4)-positive neurones tended to be more sparsely distributed, and found mainly in the intermediate portion of the commissural NTS, and along the postremal border. In contrast, we observed dense staining for the P2X(5) receptor subtype in a majority of regions within the NTS. The most striking staining was observed in the intermediate subdivision at the level of the sub-postremal NTS and the medial portion of the rostral NTS. P2X(6) immunoreactive neurones were observed in the medial commissural NTS, along the postremal border and in the dorso-medial and medial subdivisions of the rostral NTS.Taken together, our findings confirm the presence of six P2X receptor subtypes within the NTS of the rat, consistent with a neurotransmitter role for ATP in the rat NTS. These results indicate the need for more extensive functional studies to elucidate the roles of the individual and heterodimeric assemblies of P2X receptor subtypes within the NTS.

Animals↗
PubMed2001

[Studies on quality specification standards for Saposhnicovia divaricata (Turcz.) Schischk].

OBJECTIVE: To work out a qualitative-quantitative standard for Saposhnikovia divaricata. METHOD: TLC and HPLC were adopted. RESULT: Four chromone compounds were identified by TLC, and the contents of two chromone compounds were determined by HPLC. CONCLUSION: Prim-O-glucosylcimifugin, 4'-O-beta-D-glucosyl-5-O-methylvisamminol, sec-O-glucosylhamaudol and cimifugin should be present simultaneously in S. divaricata. The contents of prim-O-glucosylcimifugin and 4'-O-beta-D-glucosyl-5-O-methylvisamminol in S. divaricata should not be lower than 0.12% respectively.

Apiaceae↗
PubMed2000

Comparative study on the distribution patterns of P2X(1)-P2X(6) receptor immunoreactivity in the brainstem of the rat and the common marmoset (Callithrix jacchus): association with catecholamine cell groups.

The present study investigated the topographical distribution of P2X(1)-P2X(6) receptor subtypes in the rat and common marmoset hindbrain by immunohistochemistry. In addition, double-labeling immunofluorescence was used to determine the extent of colocalization between catecholamine cell groups and the various P2X receptors. The data demonstrate a widespread distribution pattern for all six P2X receptors throughout both the rat hindbrain and the marmoset hindbrain, although distinctions between species, brain nuclei, and P2X receptor subtypes exist. In rat, dense staining for the P2X receptors was found in the nucleus of the solitary tract (NTS), medial vestibular nucleus, and medial and lateral parabrachial nuclei. Moderate staining was observed in the hypoglossal nucleus, cuneate nucleus, inferior olive, prepositus hypoglossi, rostral ventrolateral medulla (RVLM), and locus coeruleus. Staining was also observed in the gracile nucleus, the mesencephalic trigeminal nucleus, and the central pontine gray. In marmoset, prominent P2X receptor-like immunoreactivity occurred in the NTS, medial cuneate nucleus, prepositus hypoglossi, and medial vestibular nucleus. Moderate staining was observed in the area postrema, dorsal motor nucleus of the vagus, lateral cuneate, lateral reticular, spinal trigeminal nucleus, RVLM, and inferior olive. Immunofluorescent double labeling of tyrosine hydroxylase (TH)-containing cells revealed that all subtypes of P2X receptors show some degree of colocalization with TH. The highest proportion of TH and P2X receptor double labeling was in the A5 region (with the P2X(2) subunit), whereas the lowest proportion of double-labeled cells occurred in the C2 region of the NTS for the P2X(5) subunit. These findings support a role for extracellular adenosine 5'-triphosphate in fast synaptic neurotransmission within the brainstem.

Adenosine Triphosphate↗
PubMed1999

Nitrergic stimulation of the locus coeruleus modulates blood pressure and heart rate in the anaesthetized rat.

To investigate whether nitric oxide is involved in the cardiovascular responses mediated via the locus coeruleus, the effects of microinjections of L-arginine and L-glutamate into the locus coeruleus on blood pressure and heart rate were investigated in sodium pentobarbitone-anaesthetized rats. Unilateral microinjection of L-arginine (25, 50 nmol) elicited dose-related depressor (-17 +/- 4, -25 +/- 4 mmHg) and bradycardic (13 +/- 3, 24 +/- 6 b.p.m.) effects. Furthermore, these effects were attenuated by prior local microinjection of N(G)-nitro-L-arginine (40 nmol). Peripheral muscarinic receptor blockade with atropine methyl nitrate (1 mg/kg, i.v.) attenuated the bradycardic but not the depressor responses to L-arginine. L-Glutamate (2 nmol) microinjections also mediated depressor (-27 +/- 6 mmHg) and bradycardic (53 +/- 23 b.p.m.) effects that were attenuated by microinjections of dizocilpine maleate (1 nmol) into the locus coeruleus. In addition, pretreatment with N(G)-nitro-L-arginine (40 nmol) also significantly attenuated the depressor response elicited by L-glutamate. These results suggest that nitrergic and glutamatergic pathways are operative within the locus coeruleus to modulate cardiovascular function, and also that a functional interaction may exist between the nitrergic and glutamatergic systems within the rat locus coeruleus.

Anesthesia, General↗
PubMed1976

An upper arm A-V fistula for hemodialysis patients with distal access failures.

The technique of creating an upper arm side-to-side A-V fistula in patients with forearm vascular access failures has been described. The procedure has been used extensively in patients in Japan with a high degree of success. The limited U.S. experience has confirmed that the procedure results in trouble-free, reliable vascular access. It is proposed as an alternative approach for patients with forearm access failures.

Adult↗