Biomedical subjects

H Gao

Publications and source records attributed to H Gao.

At least 163 records · Page 9Linked to original sources

PubMed1997

Sympathetic nervous system and hypertension during prolonged TxA2/PGH2 receptor activation in rats.

The thromboxane A2 (TxA2)/prostaglandin H2 (PGH2) receptor mimetic U-46619 (0.6 microgram.kg-1.min-1) was infused into conscious rats receiving a high-salt diet. U-46619 increased the mean arterial pressure (MAP) over 13 days by 25 +/- 2 mmHg, whereas the MAP of vehicle-infused controls did not change (-2 +/- 2 mmHg). In subgroups infused with U-46619, cardiac output was unchanged, whereas renal blood flow was reduced (before: 8.5 +/- 0.8; day 4: 5.7 +/- 0.7 ml/min; P < 0.01). Ifetroban (a specific TxA2/PGH2 receptor antagonist) reduced MAP to basal levels in the group receiving U-46619 when infused intravenously (1-100 micrograms/kg) but not intracerebroventricularly (1-100 ng/kg). Hexamethonium (10 mg/kg i.v., a ganglionic blocking agent) and prazosin (0.1 mg/kg, an alpha-adrenergic antagonist) decreased MAP significantly (P < 0.05) more in the experimental group (hexamethonium, U-46619: -55 +/- 3 vs. vehicle: -43 +/- 4 mmHg; and prazosin, U-46619: 28 +/- 3 vs. vehicle: 17 +/- 2 mmHg). In conclusion, hypertension during prolonged infusions of U-46619 into conscious, salt-loaded rats is accompanied by an increase in total and renal vascular resistance and is dependent on peripheral but not central TxA2/PGH2 receptors and on the autonomic and alpha 1-adrenergic peripheral sympathetic nervous systems.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1997

Role of AVP in pressor responses during activation of central TxA2/PGH2 receptors.

Administration of thromboxane A2/prostaglandin H2 (TxA2/PGH2)-receptor agonist U-46619 (2.86 nmol/kg i.v.) to conscious rats increased mean arterial pressure (MAP) by 17 +/- 2 mmHg (n = 6; P < 0.001) and plasma arginine vasopressin (AVP) by 3.5 +/- 1.1 IU/ml (n = 6; P < 0.001). Ifetroban (TxA2/PGH2 antagonist; intracerebroventricularly) prevented both responses. Intracerebroventricular U-46619 increased MAP in Long-Evans rats (n = 6) more than in AVP-deficient Brattleboro rats. AVP V1-receptor antagonist d(CH2)5Tyr(Me)AVP (3 microg/kg i.v.) blocked 67 +/- 5% and 69 +/- 7% of pressor response to intravenous AVP and intracerebroventricular U-46619, respectively. AVP (10 ng/kg i.v.) increased AVP by 4.7 +/- 0.5 pg/ml, comparable to the increase of 3.5 +/- 1.2 pg/ml with intracerebroventricular U-46619 (2.86 nmol/kg), but the rise in MAP was only one-half as great (+8 +/- 3 mmHg for AVP vs. +17 +/- 2 mmHg for U-46619; P < 0.05). In conclusion, U-46619 raises blood pressure and releases AVP by activating brain receptors. AVP explains approximately one-half of the pressor response.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1997

Central thromboxane receptors: mRNA expression and mediation of pressor responses.

These studies tested whether activation of central thromboxane (Tx)A2/prostaglandin (PG) H2 receptors raises blood pressure (BP). Messenger RNA for TxA2/PGH2 receptors was detected in normal Sprague-Dawley rat brain and in rat neuronal and astroglial brain cells in culture. The mean arterial blood pressure (MAP) was recorded in conscious rats during graded administration of the TxA2/PGH2 receptor agonist U-46,619 given intracerebroventricularly or intravenously. Because the pressor responses to intracerebroventricular (but not intravenous) U-46,619 were significantly greater in-high-salt compared with low-salt rats, high-salt rats were used for subsequent studies. The rise in MAP with intracerebroventricular administration of U-46,619 was greater than with intravenous administration and was more sustained. A comparison of plasma radioactivity after intracerebroventricular or intravenous injection of [3H]U-46,619 demonstrated that approximately 35% of the drug reached the systemic circulation by 5-15 min after intracerebroventricular administration. Coadministration of a TxA2/PGH2 antagonist, ifetroban, by intravenous or intracerebroventricular routes blocked the pressor responses induced by U-46,619. The half-maximal inhibition for blockade of responses was substantially lower for intracerebroventricular than for intravenous responses (intracerebroventricular: 0.03 +/- 0.01 vs. intravenous: 3.1 +/- 0.6 micrograms/kg; P < 0.001). The intravenous administration of ifetroban (10 micrograms/kg) caused a greater (P < 0.02) inhibition of pressor responses to U-46,619 (1 microgram/kg) given intravenously (81 +/- 3%) compared with U-46,619 given intracerebroventricularly (40 +/- 13%). In conclusion, TxA2/PGH2 receptor mRNA is expressed in neurons, glial, and brain stem of normal rats. The central administration of a TxA2/PGH2 mimetic raises blood pressure by interaction with specific central and peripheral receptors. This response is augmented in rats fed a high-salt compared with a low-salt diet.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1997

[The comparison of selenium status between the children suffered from pneumonia and the normal children from kindergarten].

In order to investigate the relationship between selenium (Se) status and pneumonia children, the levels of Se and glutathione peroxidase (GSH-Px) in plasma and white blood cells and Se content in urine were determined in 57 cases with pneumonia and 85 control children under 10 years old. The results showed that the levels of Se and GSH-Px in plasma and white blood cell in the group of pneumonia were significantly lower, but the content of Se in urine was higher. Se content and GSH-Px activity in white blood cells of patients during crisis were significantly lower than those of patients during convalescence.

Adolescent↗

PubMed1997

[Clinical study on myxoma and chordoma in the skull base].

OBJECTIVE: The clinical manifestation, neuroimaging properties, and pathologic changes of myxoma and chordoma were studied. METHODS: Their neuroimaging properties and pathologic changes of myxoma 7 cases and chordoma 13 cases were analyzed. RESULTS: (1) Clinical manifestation: the injury of oculomotor nerve and exorbitism is dominant in myxoma, but the injury of posterior cranial nerves is dominant in chordomas. (2) Plain skull X-ray film: local irregular punctate calcification and osseous necrosis were common in myxoma. Clivus invasion moruloid calcification and cauliflower-like calcification are always seen in chordoma. (3) CT and MRI: Location of the tumor and their relations with the adjacent structure were clear. (4) Pathologic changes: Cells are punctately arranged in myxoma, and vesicularly arranged in chordoma. CONCLUSION: The clinical study of myxoma and chordoma is not only useful for their differiental diagnosis, but can provide valuable clues for their surgical approach as well.

Adolescent↗

PubMed1997

Combined effect of noise and vibration on articulation of Chinese syllable.

To study combined effect of noise and vibration on articulation, changes of the speech features of Chinese single syllabic utterances were investigated under combined factors. The experiments were conducted under four conditions: combined noise and vibration, simple noise, simple vibration and control. A set of signal processing system was established, programs for speech signal analysis and statistics were developed. The results showed that, as compared with simple noise , simple vibration or control condition, the fundamental frequency, energy and duration of articulation under combined conditions increased significantly. It suggests that the effect of noise and vibration should be considered in the design of aerospace speech recognition system.

Aerospace Medicine↗

PubMed1997

Dynamics of a microcarrier particle in the simulated microgravity environment of a rotating-wall vessel.

Rotating-wall vessel (RWV), a low-shear, low turbulence microcarrier culture system provides a simulated microgravity environment suitable for 3-dimensional tissue culture. In this paper, the motion of a microcarrier particle in the rotating fluid has been analytically/numerically studied. If the microcarrier is less dense than the surrounding liquid medium, it eventually migrates towards an equilibrium state in the fluid. This state corresponds to a stationary location in the inertial frame of reference or equivalently, a circular orbit about the rotational axis in a rotating frame. If the particle is denser, it may move away indefinitely to reach or collide with the outer wall of the rotating vessel (outer boundary of the rotating fluid). Such a collision may damage the cells and could be undesirable for tissue culture. We have calculated migration times for a denser microcarrier to reach the outer wall of the vessel. Several factors--rotational speed, fluid viscosity, density difference between that of the microcarrier and the fluid, microcarrier radius, and the initial position of the microcarrier--were found to affect this migration time. We have also evaluated the variation of the fluid shear stress on the microcarrier surface. Decreasing the density difference between the microcarrier and the fluid, and decreasing the size of the microcarrier, can both decrease the maximum shear stress. The results for a solid, a hollow, and a hollow-porous microcarrier show that with a denser microcarrier material, the hollow or hollow-porous spherical microcarriers are preferable in order to increase the suspension time and decrease the maximum shear stress. The results of this study are thought to be useful for the development of optimal conditions for cell growth and metabolism in RWVs.

Cell Culture Techniques↗

PubMed1997

[Character of emergence for the seeds of Ephedra sinica].

The experimental results on the germinating of Ephedra sinica seeds and sowing show: the seeds of E. sinica are not sensitive to illumination, but very sensitive to humidity; the effects of soil, the depth of sowing and irrigation on emergence are very notable, but not remarkable to covering which can be used to prevent measure.

Ephedra sinica↗

PubMed1997

[Clinical application study of intraoral high-level mandibular neurotomy: Reported of 19 cases]

Trigeminal neuralgia is a common disease in clinical practice. The recurrence rate after avulsion is relatively high. In order to reduce the recurrence rate, the author developed a new method and operated on 19 cases with intraoral high level trigeminal neurotomy based on 21 cases of adult human skull anatomy. The method is simple, safe and in good condition. The author emphasized that the proper management of the buccal branch during operation may have a close relation with the post-operative recurrence rate.

Journal Article↗

PubMed1997

Elevated mRNA expression of brain-derived neurotrophic factor in retinal ganglion cell layer after optic nerve injury.

PURPOSE: Recent studies show that exogenous brain-derived neurotrophic factor (BDNF) can promote retinal ganglion cell survival in vivo and in vitro. BDNF is expressed by a subpopulation of cells in the ganglion cell layer (GCL). To investigate whether endogenous BDNF may play a role in neuronal protection after ganglion cell trauma, BDNF expression in the retina was examined after optic nerve (ON) injury. METHODS: The optic nerve in Sprague-Dawley rats was crushed intraorbitally posterior to the optic disc. For controls, the optic nerve on the opposite side in each animal was similarly exposed but was not crushed. After intervals of 6 hours to 6 weeks, eye tissues were processed for in situ hybridization, Northern blot, and RNase protection assay using radiolabeled rat riboprobes. RESULTS: After ON injury, BDNF expression was significantly elevated in cells restricted to the GCL, and more cells demonstrated expression of BDNF than were observed in the controls. Elevated BDNF expression was first observed at 24 hours, peaked at 48 hours, and declined to the basal level 2 weeks after ON injury. Quantitative analysis showed a fivefold to sixfold increase in the number of BDNF-positive cells and a 54% increase in BDNF signal intensity in individual cells in the GCL 48 hours after ON injury. In control retinas without ON injury, BDNF expression was localized to some cells in the GCL, as was observed in normal eyes without surgery. Northern blot and RNase protection assay demonstrated a 38% elevation in BDNF expression above control levels 48 hours after ON injury. CONCLUSIONS: These results indicate that cells in the GCL can upregulate gene expression of BDNF in response to ganglion cell axonal injury and suggest that endogenous BDNF may contribute to a natural neuroprotective process after ON injury.

Animals↗

PubMed1997

The role of polymorphonuclear neutrophils (PMNs) in clearance of granulocyte colony-stimulating factor (G-CSF) in vivo and in vitro.

Previous studies have suggested that in vivo granulocyte colony-stimulating factor (G-CSF) pharmacokinetics may change over time. We studied three patients treated with high-dose chemotherapy followed by autologous bone marrow transplantation (ABMT) for metastatic breast cancer after intravenous administration of recombinant human (rh) G-CSF (5 or 16 microg/kg/day). We investigated plasma G-CSF concentrations and absolute neutrophil counts (ANCs/pL) in these patients on three separate days. G-CSF plasma clearance increased with time post-ABMT with no change in the apparent volume of distribution (Vd) of G-CSF. Regression analysis of G-CSF plasma clearance and ANCs revealed a linear relationship, with r2 = 0.85 (p = 0.00025). We further investigated this phenomenon in vitro by estimating pharmacokinetic parameters for rhG-CSF using a model in which polymorphonuclear neutrophils (PMNs) were incubated with rhG-CSF. We found that, at low G-CSF concentrations in vitro, there was an increase in G-CSF clearance with increasing ANCs, but at higher G-CSF concentrations this relationship did not hold. We suggest that this finding resulted from aggregation and polymerization of G-CSF at high concentrations when kept at 37 degrees C for 24-48 hours in vitro. Using fluorescence staining techniques, our data suggest there are changes over time in the amount of G-CSF bound to PMNs. These changes may reflect reexpression or recycling of the G-CSF receptor, and could explain the continuing clearance of G-CSF by PMNs in vitro. The strong positive correlation between G-CSF plasma clearance and ANCs in vivo is compatible with the hypothesis that neutrophils mediate one of the major pathways for rhG-CSF clearance.

Bone Marrow Transplantation↗

PubMed1997

[Oxygen free radical on interleukin-1 activity of hemorrhage/resuscitation rat].

OBJECTIVE: To investigate the effects of oxygen free radical on the enhancement of IL-1 activity in vivo and in vitro on hemorrhagic and resuscitated rat. METHODS: 30% of rats total blood volume was withdraw by carotid artery catheter and resuscitated with 2 times of lost blood volume 1 h later. RESULTS: Plasm IL-1 activity and MDA content increased and SOD activity decreased significantly 1-4 hours after resuscitation. There was a marked correlation between IL-1 activity and MDA content as well as SOD activity. Treatment with SOD as resuscitation prevented the postresuscitation increase in plasma IL-1 activity significantly. Hemorrhage and resuscitation also caused significant decrease of SOD activity and elevation of MDA in peritoneal macrophage 2 hours after resuscitation. After preincubation with SOD for 1 hour, the macrophage presented a much lowered capacity to release IL-1. CONCLUSION: Oxygen free radical may be one of the most important factors that contribute to elevation of IL-1 level after hemorrhage and resucitation.

Animals↗

PubMed1997

[Modulation mechanism of IL-1 in hemorrhagic shock in relation to endotoxin].

The modulation mechanism of IL-1 in relation to endotoxin (ET) was investigated in hemorrhangic shock rat. It was found that within 4 h after hemorrhagic shock, SD rat showed a significant increase in both ET and IL-1, the latter taking place earlier than the former. While SD rat reared in germ free condition showed an obvious increas in IL-1 but without marked change in ET, no matter whether the rats reared in different condition were pretreated with lactuolsc or anti-ET. Within 5 d after reinfusion of lost blood to the ordinary shock rat, IL-1 and ET changed in a parallel manner. When shock rats were treated with lactulose or anti-ET, both IL-1 and ET showed significant decrease as compared with the control. It is suggested from the above observation that ET is not an important factor in enhancing IL-1 activity in the early stage of hemorrhagic shock, but does contribute to the increased IL-1 activity in the later phase of hemorrhagic shock. The ET comes mainly from the gut in hemorrhagic state.

Animals↗

PubMed1996

Binding of THZif-1, a MAZ-like zinc finger protein to the nuclease-hypersensitive element in the promoter region of the c-MYC protooncogene.

A detailed analysis is reported of the binding of the zinc finger protein THZif-1 to the nuclease-hypersensitive element (NHE) in the promoter region of the c-MYC gene using the electrophoretic mobility shift assay and a series of mutants of a fusion protein composed of glutathione S-transferase and THZif-1. The THZif-1 protein bound specifically to the single-stranded (ss) pyrimidine-rich DNA of the NHE (ss c-myc NHE-C) with an apparent dissociation constant (Kd (app)) of 0.077 microM. By contrast, no binding to the single-stranded purine-rich DNA of the NHE (ss c-myc NHE-G) was detected. Moreover, the binding affinity of THZif-1 protein was 2-fold higher for the single-stranded 5-methyl-2'-deoxycytidine derivative of NHE (ss c-myc NHE-me5C) than for the unmethylated NHE. In the case of the binding of THZif-1 to methylated double-stranded (ds) NHE (ds c-myc NHE-me5CG), no significant binding to the DNA was observed. The decrease in binding to DNA of THZif-1 was significant in the case of mutated ds c-myc NHE, in which more than two sites of deoxycytidine residues were methylated. However, the binding affinity of THZif-1 protein for methylated and for unmethylated triple-helical DNA of the NHE was almost identical. Moreover, the domain of the THZif-1 protein that made the major contribution to binding to ss c-myc NHE-C or ss c-myc NHE-me5C corresponded to the amino-terminal second zinc finger motif. Taken together, the results indicate that the THZif-1 protein exhibits preferential DNA-binding activity with ss c-myc NHE-C, ds c-myc NHE-CG, and ts c-myc NHE but not with ss c-myc NHE-G and ds c-myc NHE-me5CG in vitro.

Chromosome Mapping↗

PubMed1996

Basic fibroblast growth factor: increased gene expression in inherited and light-induced photoreceptor degeneration.

In a recent study, we reported that bFGF content and mRNA expression levels are elevated in degenerating photoreceptors in the rd mouse retina as compared to the levels in photoreceptors in age matched normal retinas (Gao and Hollyfield, 1995). To determine whether bFGF up-regulation is a general feature of degenerating photoreceptors, bFGF expression was examined with in situ hybridization in several rodent models with retinal degeneration: (a) the normal mouse retina in which cGMP metabolism had been disrupted pharmacologically using an inhibitor of phosphodiesterase or an analog of cGMP, (b) the rds mouse with an inherited photoreceptor degeneration that does not involve alterations in cGMP metabolism, (c) light-damaged BALB/c mice subjected to bright constant light, and (d) light-stressed albino rats subjected to bright cyclic light. In each of these models, we observed dramatic up-regulation of bFGF gene expression in photoreceptors, although the relative levels varied among the different models and followed different temporal patterns. We conclude that increased expression of bFGF in photoreceptors during their degeneration is a general phenomenon occurring in rd, rds, light-damaging and light-stressing conditions. These observations indicate that bFGF can be up-regulated by a variety of photoreceptor insults. We speculate that endogenous bFGF may function as a photoreceptor protection/rescue factor that is activated in response to photoreceptor stress.

Animals↗

PubMed1996

Direct determination of iron in ferritin using the polarographic catalytic current.

A new method for the determination of iron in ferritin using the polarographic catalytic current has been developed. Iron is released in NaOH and triethanolamine (TEA) solution and subsequently determined based on the polarographic catalytic wave in the presence of bromate with the peak potential of -1.0 V (vs.SCE). The 2.5-derivative peak height of iron is linearly proportional to its concentration in the range of 8.0 x 10(-8)-1.0 x 10(-6) g/ml with a correlation coefficient of 0.9991. The method has been applied to the determination of iron in human fetal liver and horse-spleen ferritin and the recovery is 95-112%.

Journal Article↗

PubMed1996

Neurotrophins and Alzheimer's disease: beyond the cholinergic neurons.

Improvement of the cholinergic deficit in Alzheimer's disease (AD) by intracerebral application of nerve growth factor (NGF) serves as a paradigmatic example for a novel approach to the treatment of neurodegeneration. The first part of this paper presents and discusses experiments which were performed in our laboratory to study the NGF receptor response after intracerebral NGF treatment in vivo. We found that intraparenchymal NGF elicits prolonged tyrosine phosphorylation of Trk type NGF receptors. Our results indicate that intraparenchymal injections are preferable to intraventricular application for targeting specific neuronal populations with minimal side effects. Besides the cholinergic deficit, severely disturbed brain energy metabolism, particularly in cortical association areas, is another consistent feature of AD. Metabolic hypofunction is observed early in the disease progression and correlates with the cognitive impairment. Cell culture findings are presented which indicate that brain-derived neurotrophic factor (BDNF), and other neurotrophins with activity on the TrkB tyrosine kinase receptor, increase mRNA levels and biochemical activity of enzymes of the glycolytic pathway in brain cells. Treatment with these factors was also found to stimulate glucose utilization in rat embryonic cortex cells in primary cultures. Our observations suggest that selected neurotrophins should become useful not only for the treatment of the cholinergic deficit in AD, but also of the cortical metabolic hypofunction associated with this disease.

Alzheimer Disease↗

PubMed1996

Effects of hypoxia/reoxygenation on aortic vasoconstrictor responsiveness.

The purpose of the present study was to assess the effects of hypoxia/reoxygenation (H/R) on vasoconstrictor effectiveness, in vitro. Aortic rings were obtained from rats and placed on isometric force transducers in oxygenated Krebs buffer (95% O2/5% CO2, PO2 > 500 torr). Cumulative concentration/effect relationships to norepinephrine, G-protein activation by AlICl3/NaF, depolarization by KCl or BayK-8644, mobilization of intracellular calcium by caffeine, and protein kinase C activation by l-indolactam were evaluated. Hypoxia (PO2 < 5 torr) was induced by rapidly bubbling the Krebs buffer with 95% N2/5% CO2 for 15 min. Vessel rings were reoxygenated for 30 min and concentration/effect relationships reevaluated. The dissociation constant (KA) for norepinephrine was also determined. The pD2 for maximal norepinephrine responsiveness decreased from 7.7 to 7.3 following H/R. Maximal tension generation was significantly decreased following H/R. Endothelium denudation or nitric oxide synthesis inhibition did not prevent the right shift in norepinephrine concentration/effect relationship caused by H/R. The combination of superoxide dismutase and catalase prevented the dextral shift in the concentration/effect curve. The dissociation constant for norepinephrine increased from 0.16 to 0.32 microM following H/R, suggesting decreased affinity of adrenergic receptor. H/R did not alter AlCl3/NaF, KCl, BayK-8644 or l-indolactam-induced vasoconstriction. Caffeine-induced vasoconstriction was significantly impaired following H/R, suggesting that release of calcium from the sarcoplasmic reticulum is compromised. These results suggest that H/R leads to an endothelium independent, oxidant-mediated decrease in vascular norepinephrine responsiveness that may be related to defects in the mobilization of intracellular calcium from the sarcoplasmic reticulum pool.

Animals↗