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Biomedical subjects

G Bao

Publications and source records attributed to G Bao.

At least 37 records · Page 2Linked to original sources
PubMed1999

[Subtenon's infiltration anesthesia for intraocular surgery].

PURPOSE: To study the efficiency of Subtenon's anesthesia for intraocular surgery. METHODS: Subtenon's infiltration anesthesia was performed in the following ocular surgeries: Extracapsular cataract extraction combined with intraocular lens(IOL) implantation (14 eyes), cataract aspiration with IOL implantation(5 eyes), iridectomy(2 eyes), trabeculetomy(3 eyes), and removal of silicon band after scleral buckle for retinal detachment (1 eye). After superficial anesthesia with 0.5% Dicaine solution and incision of limbal conjunctira were performed, a 22 gauge blunt connected with a 5 ml syringe containing a mixture of 2% lidocain and 0.75% of Bupivacaine was introduced posteriorly along with the surface of the sclera towards both 10:00 and 2:00 o'clock direction, under Tehon's capsule at tabout 10-15 mm away from the limbus. A slow injection of 1.5-2.0 ml of the anesthesia was made at the equator of the globe. RESULTS: According to the standard made by Pang chenjiu, the efficiency of anesthesia was as follows: Grade I: 20 eyes(80%), Grade II: 4 eyes (16%), Grade III: 1 eye (4%). CONCLUSION: It is an effective, safe and simple anesthetic method for intraocular surgery especially for those with single eye, glaucoma eye in absolute stage and old patient with insufficient heart function.

Adult↗
PubMed1999

[Diathermic high-frequency capsulorhexis in cataract surgery].

PURPOSE: To evaluate the efficiency of diathermic high-frequency capsulorhexis in cataract surgery. METHODS: After injection of viscoelastic material into the anterior chamber, a continuous circular capsulotomy (CCC) was performed using a diathermic high-frequency capsulorhexis machine in 34 eyes of 30 cataract patients during extracapsular cataract extraction (ECCE) combined with intraocular lens (IOL) implantation. RESULTS: Successfully CCC was made in 31 eyes. A small peripheral radial capsular tear was detected in 3 eyes. No postoperative corneal edema and other complications were found in all eyes. The postoperative corrected visual acuity > or = 0.5 was accounted for 91.2%. CONCLUSION: Diathermic high-frequency capsulorhexis is a simple, safe and effective method for ECCE (or Phacoemulsification) combined with IOL implantation. It is especially indicated for those eyes with hypermature cataract, traumatic cataract and children with congenital cataract.

Aged↗
PubMed1998

Rhizobium mongolense sp. nov. is one of three rhizobial genotypes identified which nodulate and form nitrogen-fixing symbioses with Medicago ruthenica [(L.) Ledebour].

Medicago ruthenica [(L.) Ledebour] is native to inner Mongolia where rhizosphere samples were collected for the isolation of 106 rhizobial cultures. Besides nodulating the original trap host, the isolates formed nitrogen-fixing symbioses with Phaseolus vulgaris. Only half of the isolates nodulated alfalfa (Medicago sativa), but these did not form nitrogen-fixing symbioses. Rhizobium tropici also formed nitrogen-fixing symbioses with Medicago ruthenica. A total of 56 distinctive multilocus electrophoretic types (ETs) were identified among 94 of the 106 isolates which were analysed for variation in electrophoretic mobility of 12 enzyme loci. One isolate (USDA 1920) possessed a unique ET, while the ETs of the other isolates formed two weakly divergent subgroups approximately equal in size. It was concluded from small subunit rRNA gene sequences of eight isolates of Medicago ruthenica that they belonged to the genus Rhizobium and not to the genus Sinorhizobium which is more commonly associated with Medicago. Genomic similarity, determined from DNA hybridization analysis, between USDA 1920 and the strain representing the remaining isolates (USDA 1844) was lower than 20%. Based upon these observations it was concluded that at least three genomic species of rhizobia form nitrogen-fixing symbioses with Medicago ruthenica. One of these genomic species is R. tropici, another is represented by the single isolate USDA 1920 and the name Rhizobium mongolense is proposed for the third genomic species represented by USDA 1844.

Alleles↗
PubMed1998

[Experimental studies on human lung cancer gene-therapy with HSV-TK/GCV system].

OBJECTIVE: Evaluate the clinical potential of HSV-TK/GCV system in gene-therapy of tumors by using this system to treat human lung cancer A549 cells in vitro and in vivo. METHOD: The in vitro sensitivity levels of A549/TK (TK-tranfered A549) cells and wild type A549 cells to GCV were expressed as IC50 which was measured with MTT assay after treating both cells for 72 hrs. In vivo study, The nude mice bearing A549/TK tumor or A549 tumor were used as experimental models. All the animals were divided into 3 groups. Group 1, the animals bearing A549/TK tumor would be treated with GCV. Group 2, The animals bearing A549/TK tumor would be treated with saline. Group 3, The animals bearing A549 tumor would be treated with GCV. When the tumors reached to 200-300 mg the animals would be injected intraperitoneally with GCV solution (100 mg.kg-1.day-1) or equal volume of saline for two weeks. In this period and the following four weeks, the tumor weights were measured and calculated with the experience formula once every three or four days. RESULT: In vitro study showed that the A549/TK cells were apparently killed in a 20 mumol/L GCV solution while the wild type A549 cells grew normally under the same condition. The IC50 of A549/TK cells in GCV solution was 0.5 mumol/L and that of A549 cells 500 mumol/L, showing a 1,000 fold difference (P < 0.01). In vivo experiment GCV had compelled the A549/TK tumors to lead to a regression of 92%, meanwhile the A549 tumors treated with GCV increased 3.9 times in weight in the first seventeen days of experiment. Group 2 tumors A549/TK tumors which were treated with saline, grew as well as group 3 did. There was a significant difference (P < 0.01) between group 1 and other groups. CONCLUSION: GCV could specifically and effectively kill the TK-transfered A549 cells in vitro and in vivo. This result suggested that the HSV-TK/GCV system may have a clinical potential for gene therapy of lung cancer.

Adenocarcinoma↗
PubMed1998

[Effect of SNP on KCa of resistance vascular smooth muscle cell membrane in SHRsp].

OBJECTIVE: To investigate the effect of sodium nitroprusside (SNP) on calcium activated potassium channels (KCa) of mesenteric arterial A4-A5 branches resistence vascular smooth muscle cell membrane in Stroke-prone Spontaneously Hypertensive Rats (SHRsp) and its normotensive control WKY rats. METHODS: Cell-attached patch clamp technique was used. RESULTS: It was found that SNP could activate the KCa of the resistance vascular smooth muscle in both SHRsp and WKY. Under the same dose of SNP (1 nmol/L), the conductance and channel current amplitude etc. of the activated KCa in SHRsp were smaller than that in WKY rats. Given the same dose of 8-Br-cGMP (10 mumol/L), the cGMP activation of SHRsp KCa was less potentiated than that of WKY, appeared very similar to SNP/NO activation. CONCLUSIONS: The results suggested the KCa of hypertensive resistance vascular smooth muscle membrane appearing weaker response to relaxing factor EDRF/NO.

Animals↗
PubMed1997

Hypertension caused by chronic intermittent hypoxia--influence of chemoreceptors and sympathetic nervous system.

BACKGROUND: The sleep apnea syndrome (SAS) is a common health problem with a 30% prevalence among patients with so-called essential hypertension. OBJECTIVE: Prompted by this epidemiologic link we tried to find out whether there is a cause-effect relationship between SAS and systemic hypertension. DESIGN: We developed an animal model to simulate defined aspects of the SAS. Rats were exposed to chronic repetitive hypoxia for 7 h per day and their blood pressure was measured by invasive methods. RESULTS: We found that 30 days of intermittent hypoxia sufficed for the development of a significant elevation of blood pressure. The co-exposure to hypoxia and hypercapnia had no additional effect. Surgical denervation of peripheral chemoreceptors prevented the increase in arterial blood pressure. Adrenal demedullation and chemical denervation of the peripheral sympathetic nervous system by 6-hydroxy dopamine also prevented the increase. CONCLUSIONS: Our data imply that repetitive hypoxemia in SAS is probably the cause of the high prevalence of systemic hypertension in this population and that peripheral chemoreceptors and the sympathetic nervous system play important roles in this pathophysiologic process.

Adrenal Medulla↗
PubMed1997

Acute blood pressure elevation during repetitive hypocapnic and eucapnic hypoxia in rats.

Using a rat model, we investigated whether episodic eucapnic hypoxia was a more potent stimulus to acute blood pressure (BP) elevation and bradycardia than episodic hypocapnic hypoxia. We also investigated the role of sympathetic and parasympathetic nervous system in this cardiovascular response. Sprague-Dawley (SD) and Wistar Kyoto (WKY) rats were exposed to repetitive 30-s cycles of hypocapnic or eucapnic hypoxia before and after intravenous injection of the alpha1-adrenergic blocker prazosin, alpha2-adrenergic blocker yohimbine, or atropine. Eucapnic hypoxia caused a threefold elevation in systolic BP from baseline (83.5 +/- 3.5 mmHg in WKY, 70.6 +/- 4.6 mmHg in SD) and greater bradycardia (-178 +/- 20 beats/min in WKY, -178 +/- 21 beats/min in SD) compared with hypocapnic hypoxia (29.8 +/- 3.6 mmHg and -43 +/- 15 beats/min in WKY, 19.0 +/- 4.1 mmHg and -45 +/- 12 beats/min in SD). After prazosin, the BP increase from eucapnic hypoxia was blunted, yohimbine showed no effect, and atropine blocked the bradycardia. Direct measurement of sympathetic nerve activity confirmed that adding CO2 to the hypoxic gas mixture caused a 61% increase in sympathetic nerve activity. WKY rats seem more vulnerable than SD rats to both hypoxia exposures in terms of the elevation in BP. We conclude that, in the rat, eucapnic hypoxia is a more potent stimulus to acute BP elevation and bradycardia than is hypocapnic hypoxia. An increased sympathetic tone appears to be involved in the BP response to acute episodic hypoxia.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1997

Blood pressure response to chronic episodic hypoxia: role of the sympathetic nervous system.

Previous studies in several strains of rats have demonstrated that 35 consecutive days of recurrent episodic hypoxia (7 h/day) cause an 8- to 13-mmHg persistent increase in diurnal systemic blood pressure (BP). Carotid chemoreceptors and the sympathetic nervous system have been shown to be necessary for development of this BP increase. The present study was undertaken to further define the role of renal artery sympathetic nerves and the adrenal medulla in this BP increase. Male Sprague-Dawley rats had either adrenal medullectomy, bilateral renal artery denervation, or sham surgery. Rats from each of these groups were subjected to episodic hypoxia for 35 days. Control groups received either compressed air or were left unhandled. Adrenal demedullation or renal artery denervation eliminated the chronic diurnal mean BP response (measured intra-arterially) to episodic hypoxia, whereas sham-operated controls continued to showed persistent elevation of systemic BP. Plasma and renal tissue catecholamine levels at the end of the experiment confirmed successful adrenal demedullation or renal denervation in the respective animals. The chronic episodic hypoxia-mediated increase in diurnal BP requires both intact renal artery nerves as well as an intact adrenal medulla.

Adrenal Medulla↗
PubMed1997

Potassium channels on cardiomyocytes of selenium iodine deficiency rats and iodine deficiency rats.

Using diet control method to feed the weaning male Wistar rats with selenium and iodine deficiency Keshan endemic area food for 8 weeks to set up animal model. Singal channel recording in cell attached model was used to measure cardiac cell membrane potassium channel conductances, which coincide with the cardiac cell membrane potassium channel conductances in normal Wistar rats. The potassium channel conductance on selenium and iodine deficiency rat cardiac cell membrane is showing current-voltage increasing lineally in the range of clamping voltage 0 +/- 30 mV with channel conductance of 43.4 pS. The channel current does not increase depending on the clamping voltage that is showing the rectifying characteristic and the channel current amplitude can be augmented by added KIOa 5 mmol/L in bath solution. A kind of inward rectifying potassium channel activity was recorded, but this channel activity disappeared after lasting 6-10 minutes only. Then an inward rectifying potassium channel with the conductance of 14.2 pS was activated by KIOa 5 mmol/L introduced to bath solution. Both conductances are less than that of normal Wistar rats.

Animals↗
PubMed1997

[A seroepidemiological study of hepatitis viruses among the patients with different types of liver disease in Qinhuangdao].

This article described a seroepidemiological surveillance in 326 patients with different clinical types of liver disease (acute hepatitis, AH; chronic hepatitis, CH; liver cirrhosis, LC; hepatocellular carcinoma, HCC) from hospitals in Qinhuangdao city during 1992-1995. The results showed that HAV infection could not develop chronic hepatitis. Among 238 patients of CH, LC, and HCC, anti-HAV IgM was not detected. HBV infection was the main pathogenic factor of CH, LC, and HCC with an infection rates of 77.78%, 84.21%, and 94.29%, respectively, the average rate of infection was 3.8 times higher than that in AH. HCV infection rate was increased gradually with development of chronic liver syndrome. Anti-HCV positive rate was 5.56% in CH, but 14.74% and 20.00% in LC and HCC respectively. HEV infection was found in patients with all types of liver disease with an average positive rate of 13.19%. It was not found that single HEV infection developed in CH, LC, and HCC. The average rate of super infection was 17.18% among all the patients, but the super infection rate in LC and HCC was 1.93 times higher than that in AH and CH. It seems that the super infection of HBV and HCV was the main factor for worsened liver symptoms and for developing LC and HCC.

Adolescent↗
PubMed1996

Curved beam model of the proximal femur for estimating stress using dual-energy X-ray absorptiometry derived structural geometry.

The investigation of individual differences in hip strength requires a method to measure structural geometry in vivo and a valid analytical approach to calculate mechanical stress. We developed a method for deriving structural geometry of the femur from the proximal shaft through the femoral neck, using data from dual energy X-ray absorptiometry. The geometric properties are employed in a two-dimensional curved beam model of the proximal femur to estimate stresses on the lateral and medial bone surfaces. Stresses calculated by this method are compared with those from the conventional flexure formula and with results produced from a cadaver femur with use of three-dimensional finite element analysis of computed tomography data. Loading conditions simulating a one-legged stance and a fall on the greater trochanter are employed. Stresses calculated by curved beam theory are in much better agreement with three-dimensional finite element analysis than are those for which the conventional straight beam formula was used. In simulation of a fall on the greater trochanter, all three methods show peaks of stress at the femoral neck but only the curved beam and finite element analysis methods show an additional peak at the medial intertrochanteric margin. Both neck and trochanter regions correspond to common failure sites for hip fractures in the elderly. The curved beam treatment of hip structure derived from dual-energy X-ray absorptiometry provides an approach for the in vivo engineering analysis of hip structure that is not practical by other methods.

Absorptiometry, Photon↗
PubMed1996

Effects of chronic episodic hypoxia on monoamine metabolism and motor activity.

Chronic episodic hypoxia produces a wide array of cardiovascular dysfunctions in rats, including increases in blood pressure, heart rate, and sympathetic nerve activity. The action of episodic hypoxia might be related to low oxygen itself (hypoxemia) and/or combined with low CO2 (hypocapnia) resulting from hyperventilation. It is unknown whether or not the cardiovascular abnormalities are related to alterations in the central nervous system (CNS) that may be manifested as neurotransmitter and/or behavioral changes. In this study, we investigated effects of episodic eucapnic and hypocapnic hypoxia on monoamine metabolism in both CNS and adrenal glands, and on motor behavioral activity. Thirty-five male rats were divided into 3 groups. Experimental rats were exposed 8 h daily to varying fractional concentrations of inspired oxygen (FiO2) and carbon dioxide (FiCO2) for 35 days. These consisted of brief exposures (3-6s) of episodic (twice every min) eucapnic (3.5% FiO2 and 10% FiCO2, n = 6) or hypocapnic (3.5% FiO2 and 0% FiCO2, n = 14) hypoxia, or room air (21% FiO2 and 0.03% FiCO2, n = 15). Norepinephrine, dopamine, serotonin, and their metabolites in the hypothalamus, hippocampus, and adrenal glands were measured by high-performance liquid chromatography (HPLC). Spontaneous behavioral activity was assessed for 30 min by automated activity monitors. Episodic hypocapnic hypoxia produced a decrease in dopamine turnover and eucapnic hypoxia increased norepinephrine levels in the hypothalamus. Animals exposed to hypocapnic hypoxia also exhibited a consistent increase in horizontal (walking) and vertical (rearing) activity, as well as in total activity time. From these results, it is concluded that episodic eucapnic and hypocapnic hypoxia may affect metabolism of different neurotransmitters in the CNS.

Amines↗
PubMed1996

Effect of episodic eucapnic and hypocapnic hypoxia on systemic blood pressure in hypertension-prone rats.

Repetitive episodic (18-24 s twice per minute) hypocapnic hypoxia (HH) administered chronically (7 h/day, 35 days) to Sprague-Dawley or Wistar-Kyoto rats results in a sustained increase in daytime blood pressure (BP). We examined acute and chronic BP response to episodic HH and eucapnic hypoxia (EH) in borderline hypertensive rats [first generation (F1) cross between spontaneously hypertensive and Wistar-Kyoto rats]. We hypothesized that episodic HH and EH would create a greater increase in acute and chronic BP in this breed of rat than in previously studied strains. We also examined neural mechanisms by which BP changes from hypoxia are induced. BP and heart rate were examined acutely in nine F1 rats during baseline, HH, EH, EH with prazosin, and EH with prazosin and atropine. Five groups of male F1 rats were studied after 35-day exposure to the following: Unhandled (n = 8): no treatment; Sham (n = 10): episodic compressed air; HH (n = 14): daily episodic hypoxia (2.7%); EH1 (n = 12); hypoxia 2.9%, CO2 8.4%; and EH2 (n = 11): hypoxia 2.8% and CO2 10.5%. Under acute conditions, HH caused a 34.2-mmHg and EH a 77.9-mmHg increase in mean BP. Prazosin partially blocked the increase in BP. Under chronic conditions, HH caused a 10.3-mmHg increase in daytime mean BP, whereas EH caused a fall in mean BP of 16.6 and 9.3 mmHg in the two separately studied groups. In the F1 rat, acute EH causes an elevation of BP but chronic EH causes a fall in BP. The acute response to EH is not predictive of what occurs after chronic exposure in the hypertension-prone F-1 rat.

Animals↗
PubMed1996

The rat as a model of chronic recurrent episodic hypoxia and effect upon systemic blood pressure.

The systemic arterial blood pressure response to obstructive sleep apnea (OSA) in humans is usually repetitive (with each apnea) acute elevation with return to near baseline following the apnea. In addition, it is believed by most investigators that chronic diurnal elevation of systemic blood pressure may result from repetitive nightly apneas in humans, resulting in systemic hypertension in about 50-70% of sleep apnea patients. Mechanisms of the chronic elevation in blood pressure are difficult to investigate in humans because it may take many years of repetitive apneas for sustained daytime blood pressure to develop. The rat is an especially good animal to use to investigate these mechanisms because of its use as a model in many types of hypertension. The authors have examined the response to chronic episodic hypoxia (for 35 consecutive days) in several strains of rats, discovering that systemic blood pressure (BP) remains chronically elevated in the absence of hypoxic stimulation after this period. This manuscript reviews the findings in this model after various interventions in the neurochemical and neuroendocrine mechanisms controlling BP in this animal.

Animals↗
PubMed1996

Nonlinear property membrane rectifier potassium channel and inhibitory effects of oxygen free radical.

There are at least eight kinds of different potassium channels on cardiac cell membrane. This paper presents a nonlinear property membrane outward current going rectifying potassium channel and the inhibitory effects of oxygen free radical on this channel. The current-voltage relation of this nonlinear-membrane can be defined by an equation I = 8a3/(0.01v2 + 4a2)2 and the maximum conductance of this channel is -75.3 pS.

Animals↗
PubMed1995

Role of bradykinin in the antihypertensive and cardioprotective actions of converting enzyme inhibitors.

Angiotensin converting enzyme inhibitors (ACEIs) not only reduce angiotensin II synthesis but also potentiate endogenous kinins. In addition to their antihypertensive actions, accumulated evidence has demonstrated an improvement by ACEIs of cardiac function, cardiac structural and metabolic status, and myocardial blood flow in conditions such as cardiac ischemia, left ventricular hypertrophy, and myocardial infarction. The mechanisms underlying the antihypertensive and cardioprotective actions of ACEIs are under intensive investigation. A reduction of angiotensin II synthesis is undoubtedly responsible for a major part of the antihypertensive effects of ACEIs. However, in experimental renal hypertension but not in genetic hypertension, bradykinin potentiation has been shown to partially mediate the acute and chronic antihypertensive actions of these drugs. In addition, experimental observations suggest that bradykinin potentiation plays a pivotal role in the cardioprotective effects of ACEIs.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1995

Effect of recurrent episodic hypocapnic, eucapnic, and hypercapnic hypoxia on systemic blood pressure.

We have described a rat model that responds to chronic (8 h/day, 35 days) repetitive nonapneic episodic (cycled every 30 s) hypocapnic hypoxia with sustained increase in systemic blood pressure. Because the usual blood gas change of apnea is mildly increased CO2, we hypothesized that episodic hypoxia ranging from eucapnea to hypercapnia might cause a greater chronic increase in blood pressure than hypocapnic hypoxia in this model. Five groups of male Sprague-Dawley rats were studied: unhandled group received no treatment, sham group received compressed air in their chambers, hypocapnic hypoxic group received episodic hypoxia for 35 days, eucapnic hypoxic group received the same level of hypoxia but with 7-10% inspired fraction of CO2, and hybercarbic hypoxic group received hypoxia with 11-14% inspired fraction of CO2. Mean arterial blood pressure was measured in unrestrained conscious animals at baseline and after 35 days under their respective study conditions. Neither episodic eucapnic nor hypercarbic hypoxia had any additional effect on the changes in chronic diurnal blood pressure compared with hypocapnic hypoxia. These results suggest that the sympathetic nervous system or other neurohumoral systems contributing to chronic diurnal blood pressure elevation may be maximally stimulated by hypoxia or there may be some protective mechanism limiting the blood pressure response to asphyxia in this rat model.

Animals↗