Search PubMed⌕ Search

Biomedical subjects

H Yao

Publications and source records attributed to H Yao.

At least 145 records · Page 8Linked to original sources
PubMed1995

Direct sequencing of SSP-PCR-amplified cDNA to identify new alleles in the DR52-associated DRB1 group: identification of DRB1*1115, DRB1*1117 and DRB1*1319.

Low and high resolution sequence specific oligonucleotide probe hybridization patterns were used to design an approach to direct sequencing of allele specific amplified cDNA. Several PCR amplifications were used to derive overlapping sequence fragments to define complete first domain sequences for a single allele. This method has been used to characterize three new DRB1 alleles in the DR52 family, DRB1*1115, DRB1*1117, and DRB1*1319. All three alleles carry polymorphisms previously observed in other DRB alleles and underscore the importance of utilizing a directed sequencing approach for obtaining unambiguous typing results in matching for bone marrow transplantation between unrelated donor and recipient.

Alleles↗
PubMed1995

Brain infarction developed in hypertensive and normotensive patients during hospitalization--hemodynamic factors.

To determine the effects of changes in blood pressure (BP) on the development of ischemic stroke, 17 patients who developed acute brain infarction during hospitalization were analyzed in relation to the vascular risk factors such as hypertension, previous stroke, diabetes mellitus, and hyperlipidemia. Their BPs were retrospectively referred to the onset of stroke. The average values of mean arterial blood pressure (MABP) on admission were 137 mmHg in hypertensive patients (HT; n = 9) and 101 mmHg in normotensives (NT; n = 8). HT patients received antihypertensive treatment after admission and MABP decreased by 22 mmHg (14%) prior to the ictus (three to sixty-five days after admission). MABP in NT patients remained constant before the attack (-1.4 mmHg, four to one hundred ten days after admission). Similarly, MABP decreased by 17 mmHg (four to ninety-three days) before the ictus in patients with previous stroke (n = 9), whereas it changed only a little in patients without history of stroke (n = 8). BP in each group elevated immediately after the stroke and gradually decreased to 90% of the resting level after two weeks. An excessive reduction of BP may induce brain infarction in HT or chronic stroke patients or cause it to recur.

Acute Disease↗
PubMed1995

[Effects of cytokines on hippocampus in central nervous system].

Cytokines consist of a group of polypeptides, whose main functions are considered to be mediating the non-specific immune reaction and promoting differentiation, proliferation and growth of white blood cells. But according to recent studies, these cytokines such as interleukin-1 (IL-1), interleukin-2 (IL-2) and interleukin-6 (IL-6) and their receptors are also found in the central nervous system (CNS) and may play a role in modulating the physiological functions of neuronal and glial cells in CNS. In review, we summarize the representative studies concerning mainly the interleukins' effects on the hippocampus.

Acetylcholine↗
PubMed1995

Electrochemical dehydrogenase-based homogeneous assays in whole blood.

An electrochemical method has been developed for determining NADH in whole blood for dehydrogenase-based assays by flow-injection analysis. NADH generated by dehydrogenase is oxidized by an electron-transfer coupling reagent, 2,6-dichloroindophenol (DCIP). The reduced form of DCIP (DCIPH2) is measured amperometrically by flow-injection analysis. Endogenous interferents were inhibited by p-hydroxymercuribenzoate. Electrode fouling by proteins was not observed under assay conditions. The Emit theophylline enzyme immunoassay and the hexokinase glucose assay were used as models. For the glucose assay, the intraassay CVs were 15% at 0.31 g/L and 3.5% at 1.82 g/L. Recoveries of glucose from whole blood (compared with that for aqueous standards) were 109%, 97.9%, and 101% at 0.050, 2.00, and 5.00 g/L glucose, respectively, and 104%, 101%, and 102% for theophylline at concentrations of 5.0 (low), 16.4 (medium), and 30.2 (high) mg/L, respectively, with corresponding precisions of 12%, 9.5%, and 8.8%. Both assays correlated well with results by reference methods. These studies demonstrate that this method can measure NADH in whole blood without prior separation and that it is potentially applicable to other dehydrogenase-based assays in whole blood.

2,6-Dichloroindophenol↗
PubMed1994

G(i) alpha 2- and G(o) alpha-mediated signaling in the Pit-1-dependent inhibition of the prolactin gene promoter. Control of transcription by dopamine D2 receptors.

Dopaminergic signaling in pituitary lactotrophs is dependent on coupling of D2 receptors to several inhibitory G-protein subtypes, resulting in the activation of multiple signaling pathways. In prolactin-secreting GH4 cells that express cloned D2 receptors, dopamine selectively inhibits the activity of the prolactin gene promoter, a response mediated in part by the pituitary transcription factor Pit-1. Transfected gain-of-function mutants of the G alpha subtypes, Gi alpha 2 (Q205L) and G(o) alpha (Q205L), mimic the promoter-specific and Pit-1-dependent inhibition by dopamine. Whereas the activated Gi alpha 2 subtype suppresses cAMP levels, the G(o) alpha mutant does not, demonstrating a cAMP-independent pathway in the inhibition of the prolactin gene. This alternate pathway could involve other regulators, possibly calcium. Interestingly, in Ltk- cells in which cloned D2 receptors modestly suppress cAMP, but elevate [Ca2+]i, the activity of the prolactin promoter is enhanced rather than inhibited by dopamine. The response is promoter-specific, dependent on Pit-1, and completely blocked by low concentrations of EGTA, consistent with a calcium-regulated pathway. Last, in GH4 cells, the absence of additivity between Gi alpha 2 and G(o) alpha mutants suggests a convergent mechanism in the reduction of prolactin promoter activity, in which either signaling pathway may be sufficient for maximum inhibition. This apparent redundancy in inhibitory control mechanisms may be of physiological importance for maintaining efficient tonic suppression of prolactin synthesis.

Animals↗
PubMed1994

Slow relaxation process in the main transition of phosphatidylcholines studied with heat capacity spectroscopy. I. Multilamellar vesicles.

Extremely slow relaxation processes have been examined near the main transition of multilamellar vesicle samples of dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC) with a heat capacity spectroscopic technique. The dynamic heat capacity showed a significant frequency dependence in the studied frequency region of 0.5 mHz to 50 mHz. The relaxation observed here has been analyzed with the Cole-Cole equation. The mean relaxation times were 120 s in DMPC, and 260 s in DPPC. The relaxation showed a polydispersive character. The parameter beta was around 0.5 in both DMPC and DPPC.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1994

Glutamate antagonist MK-801 attenuates incomplete but not complete infarction in thrombotic distal middle cerebral artery occlusion in Wistar rats.

The purpose of this study was to investigate the effects of a non-competitive N-methyl-D-aspartate antagonist, MK-801, on incomplete infarction (selective neuronal necrosis), a zone of which had been found previously in a thrombotic distal middle cerebral artery (MCA) occlusion model in Wistar rats. Male Wistar rats were treated with 1 mg/kg of MK-801 or saline 30 min before MCA occlusion. Laser irradiation with intravenous administration of Rose Bengal dye was used to cause thrombotic distal MCA occlusion. The ipsilateral common carotid artery was occluded permanently and the contralateral carotid artery for 60 min. Head temperature was controlled at 36 degrees C. Cerebral blood flow (CBF) was determined with laser-Doppler flowmetry. Three days after the ischemic insult, brains were perfusion-fixed and volumes of cortical (complete and incomplete) infarction were determined. There were no significant differences in physiological variables or CBF between the two groups. Volumes of complete infarction were equivalent between the two groups (94.9 +/- 15.6 mm3 and 91.6 +/- 14.0 mm3 in the control and MK-801 treated groups, respectively). In MK-801 treated group, the volume of incomplete infarction was reduced by 44% (6.4 +/- 1.7 mm3 vs. 3.6 +/- 2.1 mm3 in control and MK-801 treated groups, respectively, P < 0.05). Although the zone responsive to MK-801 was small in this thrombotic MCA occlusion model, our present study revealed that MK-801 has a beneficial effect on the tissue zone containing selective neuronal alterations (incomplete infarction). Our results support the concept that this drug is effective in the area of less severe ischemia.

Animals↗
PubMed1994

[Effects of interleukin-1 and interleukin-2 on electrophysiological characteristics of rat hippocampal neurons in culture].

The effects of recombinant human interleukin-1 beta (rhIL-1 beta) and interleukin-2 (rhIL-2) on the cultured rat hippocampal neurons were investigated with intracellular recording and extracellular micropressure ejection techniques. Experimental results showed that all of the neurons tested with rhIL-1 beta (100 U/ml) exhibited a 4.20 +/- 1.86 mV membrane hyperpolarization. 50% of the neurons treated with rhIL-2 (100 U/ml) showed a depolarization of 11.12 +/- 3.71 mV accompanied by bursting activity, while in a still higher concentration (1,000 U/ml) a 3.25 +/- 0.63 mV hyperpolarization was observed. All the above effects of rhIL-1 beta and rhIL-2 on the hippocampal neurons were completely reversible. The membrane resistance of the neurons was not significantly affected by these cytokines. These results suggest that the effects of cytokines IL-1 and IL-2 on the excitability of hippocampal neurons may be a way by which the immune system exerts a regulatory action on hippocampal function.

Animals↗
PubMed1993

Isradipine attenuates the ischemia-induced release of dopamine in the striatum of the rat.

We examined the effect of isradipine, a blocker of L-type voltage-sensitive Ca2+ channels (VSCCs), on the ischemia-induced release of dopamine in the rat striatum. Perfusion of 200 micrograms/ml isradipine in the striatum did not alter extracellular dopamine concentrations monitored by microdialysis. However, a marked increase (145-fold) in dopamine level during forebrain ischemia, developed by bilateral carotid artery occlusion, was attenuated significantly by 37% by isradipine whereas the intensity of ischemia, monitored by striatal blood flow, was unchanged. These results suggest that isradipine attenuates the ischemia-induced release of dopamine via blockade of L-type VSCCs on dopaminergic neurons.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Four years' experience with the treatment of all-trans retinoic acid in acute promyelocytic leukemia.

A retrospective analysis was done on 43 patients with acute promyelocytic leukemia (APL) at our hospital from June 1987 to August 1992. All-trans retinoic acid was used to induce these patients to differentiation. In the early period of induction there were risks of severe hemorrhage, which was the main cause of early death. Treatments combined with platelets and heparin or aminomethylbenzoic (PAMBA) were given to patients with abnormal coagulation. As a result only 4 out of 43 patients died of intracranial bleeding at 4-12 days when their white blood cell (WBC) counts peaked. The combination of retinoic acid (RA) and HA chemotherapy could reduce hyperleukocytosis during the RA induction course. None of 7 patients died at early stage with this treatment combination. Our studies showed that it could predict the onset of remission at early stage through observations on the successive changes of karyotypes and morphology of the bone marrow and peripheral blood cells. Our studies also showed that the growth of CFU-F could be inhibited by RA. We think that it may play a role in the RA-induced differentiation. In 4 years of follow-up the overall leukemia-free survival (LFS) was 80% with a relapse rate of 45%. Thirty-five patients out of 43 cases were still alive in remission, and one was alive in relapse. All 11 out of 43 patients relapsed within 3 years, but the relapses occurred later, after 3 years duration of remission (P < .01). Retinoic acid failed to induce 5 patients who relapsed with the continuation treatment of RA and chemotherapy alternatively. In order to overcome the resistance to RA, the continuation treatment of simple chemotherapy had been administered following CR. Two cases achieved remission in this way. The difference of resistant events to RA reached significance between these 2 groups of different continuation treatment.

Adolescent↗
PubMed1993

Induction of an adaptive response to dominant lethality and to chromosome damage of mouse germ cells by low dose radiation.

In the present paper, dominant lethal mutations, chromosome aberrations in spermatocytes and reciprocal translocations in stem spermatogonia were analyzed after whole body exposure of mice to X-radiation. Results both from chromosome aberrations in spermatocytes and for reciprocal translocations in spermatogonia showed that pre-exposure to low doses up to 200 mGy could induce a significant dose-dependent reduction in adapted mice compared to the non-adapted mice; the lower the adaptive dose, the greater the reduction. For dominant lethal mutations, it was found that spermatogonia (both stem cells and differentiated cells) and spermatocytes adapted to 50 mGy X-rays could show an adaptive response, but spermatids and spermatozoa could not.

Adaptation, Physiological↗
PubMed1993

Condition for the appearance of the metastable P beta' phase in fully hydrated phosphatidylcholines as studied by small-angle x-ray diffraction.

In the ripple phase of fully hydrated multilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC), two kinds of small-angle x-ray diffraction profiles are observed on cooling through the main transition. One is a seemingly normal profile similar to that observed on heating and the other is the superposition of the diffraction profiles for the primary (normal) and the secondary ripple structures. We found that the profile obtained depended on the cooling rate. Increasing the cooling rate from 0.1 degrees C/min to 1 degrees C/min caused the peaks originating from the secondary ripple structure to diminish. After a cooling scan at 43 degrees C/min, the profile became similar to that of the normal ripple structure, although a trace of the secondary ripple structure remains. The results are interpreted in terms of the rise and fall of three-dimensional correlated domains composed of both primary and secondary ripple structures. At slow cooling rates, correlated domains of both kinds of ripple structures develop. As the cooling rate is increased, the domain of the primary ripple structure remains correlated, while that of the secondary ripple structure becomes less correlated. In addition, the multipeak profile appears even at rapid cooling rates, if the final low temperature lies just below the Tm for the main transition. This results suggests that formation of the correlated domains of the secondary ripple structure requires a certain time interval during which the DPPC vesicles experience the temperature just below the main transition. The secondary ripple structure takes place in phosphatidylcholines having more than 15 carbons in each hydrocarbon chain upon cooling through the main transition.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1993

Ischemia-induced changes in brain monoamine metabolism in aged spontaneously hypertensive rats.

Effects of aging on monoamine metabolism in transient cerebral ischemia were studied using adult and aged female spontaneously hypertensive rats (SHRs). Tissue monoamine contents in discrete brain areas were quantified after 20 min of cerebral ischemia with or without 30-min recirculation. Cerebral blood flow (CBF) was determined with a hydrogen clearance method in separate experiments. Dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) contents in the striatum, nucleus accumbens and septum decreased in ischemic aged SHRs, compared with those in ischemic adult SHRs. After 30-min recirculation, DA contents were actually unchanged with inconsistently increased DOPAC levels. Ischemic CBF decreased to < 20% of the resting CBF in the striatum and cortex, which was not different between the two age groups of SHRs. These results indicate that aging is primarily responsible for more severely impaired DA metabolism during cerebral ischemia in aged SHRs.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Cerebral blood flow and ischemia-induced neurotransmitter release in the striatum of aged spontaneously hypertensive rats.

BACKGROUND AND PURPOSE: We found age-related vulnerability to cerebral ischemia in the hippocampus and striatum in spontaneously hypertensive rats. Further study revealed that ischemia-induced release of hippocampal taurine, an inhibitory amino acid, was reduced by 40% in aged rats compared with adult rats, which suggested an impaired inhibitory function against excitotoxicity in aged rats. The purpose of this study was to examine whether ischemia-induced neurotransmitter release is altered in the striatum of aged spontaneously hypertensive rats. METHODS: Five adult (5-6 months) and five aged (18-22 months) female spontaneously hypertensive rats were subjected to 20 minutes of cerebral ischemia induced by bilateral carotid artery occlusions and 120 minutes of recirculation under amobarbital anesthesia (100 mg/kg i.p.). Cerebral blood flow was determined using the hydrogen clearance method, and extracellular concentrations of neurotransmitters were determined with the brain dialysis technique in the striatum. RESULTS: During ischemia, cerebral blood flow in aged rats decreased to 8.7 +/- 1.2 (mean +/- SEM) mL/100 g per minute (11% of the resting), which was not different from 5.2 +/- 1.7 mL/100 g per minute (8% of the resting) in adult rats, and extracellular dopamine and amino acids (glutamate, aspartate, and taurine) increased by approximately 170- and 10-30-fold, respectively, and returned to baseline after 20-40 minutes of recirculation. These values of neurotransmitters, however, were not different between aged and adult rats during ischemia and reperfusion. CONCLUSIONS: It is unlikely that a presynaptic mechanism is involved in age-related vulnerability in the striatum of hypertensive rats.

Aging↗