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Biomedical subjects

Y Bi

Publications and source records attributed to Y Bi.

47 records · Page 3Linked to original sources
PubMed1998

[Direct vision mitral valve reconstruction: a long-term follow-up of 46 cases].

OBJECTIVE: To improve the long-term results of direct vision mitral valve reconstruction. METHOD: From July 1983 through July 1995, 46 patients with mitral valve disease were treated by a direct vision reconstructive techniques. Rheumatic valve stenosis and incompetence were noted in 39 (patients), nonrheumatic insufficiencies in 5, and congenital disease in 2. According to leaflet pliability, type I normal leaflet motion was notedin 17 patients, type II leaflet prolapse in 3 and type III restricted leaflet motion in 29. Cardiac function (NYHA classification) showed class II in 2, class in 25 III, and class IV in 19. Valvuloplasty and annuloplasty were performed with various techniques according to the pathanatomical changes of the valve. Prosthetic obturators self made were employed in 29 patients. RESULT: The operative mortality rate was 6% (3/46). In the mitral valve replacement group it was 10% (27/265). Two to 10 years (mean 65 months) follow-up showed grade I cardiac function in 6 patients, grade II in 17, grade III in 8, and grade IV in 3. CONCLUSION: Good long-term results can be achieved by valve reconstruction with lower mortality and incidence of thromboembolism than.

Adolescent↗
PubMed1997

Ritanserin administration potentiates amphetamine-stimulated dopamine release in the rat prefrontal cortex.

1. Administration of serotonin 5-HT2 receptor antagonists increases the basal release of dopamine in the mesocorticolimbic pathway. 2. Treatment with dopamine D2 receptor antagonists increases impulse-dependent basal dopamine release in the nigrostriatal pathway. D2 antagonists also potentiate carrier-mediated increases in DA efflux from this pathway. 3. The present study compared the effects of a 5-HT2A/C antagonist (ritanserin) and a D2 antagonist (haloperidol) on carrier-mediated (amphetamine-induced) DA release in the mesocortical system. 4. In vivo microdialysis was used to recover extracellular fluid from the medial prefrontal cortex of conscious rats. Samples were then assayed for dopamine content by HPLC with electrochemical detection. Haloperidol or ritanserin were administered systemically (i.p.) 30 min before d-amphetamine (5.0 mg/kg i.p.). 5. Results demonstrated that 5.0 mg/kg ritanserin, but not 1.0 mg/kg, potentiated amphetamine-induced DA release in the prefrontal cortex. Similar to previous findings in the striatum, haloperidol (1.0 mg/kg) also augmented amphetamine-stimulated DA efflux in the cortex. 6. These results suggest that 5-HT2 and D2 receptor antagonists increase impulse-mediated dopamine release in the rat prefrontal cortex which in turn potentiates carrier-mediated release.

Amphetamine↗
PubMed1997

Rolipram, a selective phosphodiesterase type-IV inhibitor, prevents induction of heat shock protein HSP-70 and hsp-70 mRNA in rat retrosplenial cortex by the NMDA receptor antagonist dizocilpine.

The non-competitive NMDA receptor antagonists, such as (+)-MK-801 (dizocilpine), cause the expression of heat shock protein HSP-70 and pathomorphological damage in the retrosplenial cortex of the rat brain. However, the precise mechanism(s) underlying the neurotoxicity of NMDA receptor antagonists is unknown. The present study was undertaken to examine the role of phosphodiesterase type IV in the expression of heat shock genes induced by dizocilpine. Heat shock protein HSP-70, which is known as a sensitive marker of neuron injury, was induced in the retrosplenial cortex of the rat brain 24 h after a single administration of dizocilpine (1 mg/kg). Pretreatment with the specific phosphodiesterase type IV inhibitor rolipram (2.5, 5 or 10 mg/kg, 15 min before dizocilpine) attenuated the expression of HSP-70 and hsp-70 mRNA induced by dizocilpine (1 mg/kg) in a dose-dependent manner. Furthermore, another phosphodiesterase type IV inhibitor, Ro 20-1724 (5 or 10 mg/kg, 15 min before dizocilpine), and a non-selective phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX) (5 or 10 mg/kg, 15 min before dizocilpine), significantly attenuated the expression of HSP-70 protein and hsp-70 mRNA induced in the retrosplenial cortex by dizocilpine. However, the induction of the immediate early gene c-fos and microglial activation in the retrosplenial cortex after administration of dizocilpine was not attenuated by pretreatment with rolipram (5 or 10 mg/kg, 15 min before dizocilpine). Moreover, histopathological study indicated that pretreatment with rolipram (5 or 10 mg/kg, 15 min before dizocilpine) did not prevent the formation of vacuoles caused by treatment with dizocilpine. The present findings suggest that phosphodiesterase type IV may play a significant role in the expression of HSP-70 protein and hsp-70 mRNA in the rat retrosplenial cortex after administration of dizocilpine, and that phosphodiesterase type IV may not play a role in the neurotoxicity of NMDA receptor antagonists such as dizocilpine.

Animals↗
PubMed1997

[The effects of ethinyl estradiol on glucose metabolism in postmenopausal women].

OBJECTIVE: To study the effects of ethinyl estradiol on glucose metabolism in postmenopausal women. METHODS: Postmenopausal women were randomized as nine cases (group A) receiving 0.025 mg ethinyl estradiol (EE) and ten cases (group B) receiving EE 0.05 mg for three months. The oral glucose tolerance test (OGTT) and frequently sampled intravenous glucose tolerance test (FSIGT) were performed before and after EE respectively. The levels of plasma glucose, insulin were measured and the area under curve (AUC) and insulin sensitivity indexes (SI) were calculated. RESULTS: Both two dosages of EE administration effectively decreased the levels of fasting plasma glucose and insulin and significantly reduced the AUC of insulin. SI was increased significantly. There were no significant differences in AUC of glucose before and after treatment in group A, but in group B the AUC of glucose significantly increased after treatment. CONCLUSIONS: EE may significantly reduce the levels of fasting plasma glucose and insulin concentrations and abate the insulin resistance in postmenopausal women; 0.05 mg EE possibly causes the deterioration in glucose tolerance, suggesting the use of 0.025 mg EE as an appropriate dosage.

Blood Glucose↗
PubMed1996

Prevention of methamphetamine-induced behavioral sensitization in rats by a cyclic AMP phosphodiesterase inhibitor, rolipram.

Effects of an interaction between rolipram, a cyclic adenosine 3', 5'-monophosphate (cyclic AMP) phosphodiesterase inhibitor, and methamphetamine on the development of behavioral sensitization were observed in rats. In vivo microdialysis showed that a single dose of 4 mg/kg methamphetamine (i.p.) significantly increased striatal dopamine levels while coadministration with 4 mg/kg rolipram (i.p.) did not affect these levels. Also, methamphetamine alone did not alter striatal cyclic AMP levels but coadministration with rolipram and rolipram alone significantly increased these levels. The administration of 4 mg/kg methamphetamine (i.p.) once a day for 5 days significantly enhanced hyperlocomotion and rearing induced by a 2-mg/kg methamphetamine challenge (i.p.) after a 1-week withdrawal period, compared with controls or coadministration with 4 mg/kg rolipram (i.p.). Striatal dopamine levels, detected by in vivo microdialysis, were increased following the challenge but were comparable between the groups. These findings suggest that rolipram prevents methamphetamine-induced behavioral sensitization by increasing cyclic AMP levels while not affecting dopamine-releasing processes.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1996

Preparation and evaluation of a compressed tablet rapidly disintegrating in the oral cavity.

In order to make a compressed tablet which can rapidly disintegrate in the oral cavity, microcrystalline cellulose and low-substituted hydroxypropylcellulose were used as disintegrants, and ethenzamide and ascorbic acid were chosen as poorly and easily water soluble model drugs, respectively. The mixture of microcrystalline cellulose and low-substituted hydroxypropylcellulose was compressed at 100--500 kgf in the absence of an active ingredient. The properties of these tablets, such as hardness, porosity, the time required for complete wetting of a tested tablet (wetting time), water uptake and disintegration time determined by a new disintegration apparatus, were investigated to elucidate the wetting and disintegration characteristics of these tablets, When the MCC/L-HPC ratio was in the range of 8:2 to 9:1, the shortest disintegration time was observed. The disintegration of tablets containing ethenzamide or ascorbic acid was examined next. Tablet disintegration time in the oral cavity was also tested, and good correlation between the disintegration behaviors in vitro and in the oral cavity was recognized.

Ascorbic Acid↗
PubMed1992

Molecular yardsticks. Rigid probes to define the spatial dimensions of the benzodiazepine receptor binding site.

A series of rigid planar azadiindoles (8a, 8b, and 8d), benzannelated pyridodiindoles (11a, 11b, and 11d), and indolopyridoimidazoles (11c, 20, and 24) were synthesized from 4-oxo-1,2,3,4-tetrahydro-beta-carboline 5 via the Fischer indole cyclization with the appropriate arylhydrazines. These analogues were employed as probes ("molecular yardsticks") to define the spatial dimensions of the lipophilic regions of the benzodiazepine receptor (BzR) binding cleft. Benzannelated indoles 11a-d and indolopyridoimidazoles 20 and 24 were important in establishing an area of negative interaction (S1, see Figure 6, part b) in the binding cleft common to the interactions of both inverse agonists and agonists. Data from this chemical and computer-assisted analysis of the pharmacophore (see Figure 6) indicates that inverse agonists and agonists bind to the same binding region, but the pharmacophoric descriptors required for the two activities are different, in keeping with previous studies with these planar ligands. However, the hydrogen bond donating site H1 and the lipophilic region L1 in the receptor binding site are common interactions experienced by both series of ligands. The low affinities of both indolo[3,2-c]carbazole (3a) and indolo[3,2-b]isoquinoline (3b) for the BzR are consonant with the requirements of a hydrogen bond acceptor interaction at donor site H1 and a hydrogen bond donor interaction at acceptor site A2 for potent inverse agonist activity in the beta-carboline series. The hydrochloride salts of 1-aza- 8a (IC50 10.6 nM), 2-aza- 8b (IC50 51.5 nM), and 4-azadiindole 8d (IC50 11.2 nM) were found to be much more soluble in water than the corresponding salt of the parent diindole 2. Moreover, aza analogues 8a and 8b were shown to be partial inverse agonists with proconvulsant potencies comparable to that of the parent diindole 2.

Animals↗
PubMed1989

Histamine selective microelectrode based on a synthetic organic liquid ion exchanger.

A two-barrel organic ion-sensitive microelectrode has been developed to electrochemically detect histamine activity. The synthesis of the histamine-sensitive liquid ion exchanger, composed of tetrafluorophenylboron histamine plus 3-nitro-o-xylol, and the construction of the two-barrel microelectrode (0.1-0.5 micron tip diameter) sensitive to histamine based on such an exchanger is reported. The calibration curves, their slope, selectivity, stability and detection limits for different solutions are described. High selectivity for Na+, K+, Ca2+ was observed.

Biosensing Techniques↗
PubMedDate not supplied

Two-barrel bile-acids-sensitive microelectrodes based on liquid ion exchanger.

Several liquid membrane microelectrodes sensitive to bile acids (two barrel, tip diameter about 0.5 micron) are described. The results of different liquid ion exchangers such as Aliquat 336/decanol, trioctylmethylammonium/decanol, hexadecyltrimethylammonium/decanol, benzyldimethylhexadecylammonium/decanol, hexadecyltributylammonium/5% hexachlorobenzene + 0.5% bromoacetanilide in o-dichlorobenzene are compared with each other, and the better one among them is the mixture of benzyldimethylhexadecylammonium cholate/decanol with hexadecyltributylammonium taurocholate/5% hexachlorobenzene + 0.5% bromoacetanilide in o-dichlorobenzene because of its quicker response time and low drift. The calibration curves, slopes, test limits, selective coefficients, drifts, and response times of the various bile-acids-sensitive microelectrodes in different calibration solutions were demonstrated and compared with each other.

Bile Acids and Salts↗
PubMedDate not supplied

Small leucine-rich proteoglycans in the aging skeleton.

Small Leucine-Rich Proteoglyans (SLRPs) are major skeletal extracellular matrix (ECM) components that comprise a family of 13 members containing repeats of a leucine-rich motif. To examine SLRP function, we generated mice deficient in one or more member and analyzed them at the tissue, cell and molecular levels. This review outlines the novel research findings uncovered using these new animal models.

Aging↗