Search PubMed⌕ Search

Biomedical subjects

Y Z Liu

Publications and source records attributed to Y Z Liu.

At least 37 records · Page 2Linked to original sources
PubMed1997

Membrane formation and cellular response on the surface of lenses implanted in rabbit eyes.

PURPOSE: To study the pathogenesis of membrane formation and cellular response on the surface of posterior chamber intraocular lenses (IOLs) implanted in rabbits. SETTING: Department of Histology and Embryology, Pathology, Ophthalmology. The First Military Medical University, Guangzhou, P.R. China. METHODS: Thirty rabbits had extracapsular lens extraction and posterior chamber IOL implantation. The IOLs were removed 4, 7, 15, 30, and 90 days postoperatively. Membrane formation and cellular response on IOL surfaces were evaluated using light (n = 25), transmission (n = 5), and scanning electron (n = 5) microscopy. RESULTS: On 30 IOLs, the incidence of cellular adhesion was 100%. Cellular components comprised macrophages, fibroblast-like cells, epithelioid cells, giant cells, ultralarge giant cells, and lymphocytes. A thin, proteinaceous film was also seen on the surface of the IOLs. The membrane of the IOL surface comprised fibrin, collagen fibrils, macrophages, fibroblast-like cells, giant cells, and fibroblasts. CONCLUSION: The findings of this study might apply to humans because cellular elements and membranes have been reported in humans.

Animals↗
PubMed1996

The ability of the inhibitory domain of the POU family transcription factor Oct-2 to interfere with promoter activation by different classes of activation domains is dependent upon the nature of the basal promoter elements.

The Oct-2 transcription factor contains an inhibitory domain which is able to repress transcription following DNA binding. Here we show that within the neuronally expressed Oct-2.5 form, the inhibitory domain can strongly inhibit activation by transcription factor activation domains which are either composed predominantly of acidic residues or contain the HOB motif, whereas it has a weaker effect or no effect on proline-rich activation domains and on a glutamine-rich domain. In contrast, the isolated inhibitory domain of Oct-2 can efficiently repress all types of activation domains. This effect is observed however, only on TATA box-containing promoters and not on promoters containing an initiator motif. This widespread inhibition of different activation domains and its dependence on the nature of the basal promoter elements indicate that the inhibitory domain is likely to act by contacting a common downstream target of activation domains within the basal transcriptional complex bound at the TATA box rather than quenching specific activation domains by direct interaction. These effects are discussed in terms of the functional role of the inhibitory domain within Oct-2.5 and the mechanism by which it acts.

Animals↗
PubMed1996

The ability of POU family transcription factors to activate or repress gene expression is dependent on the spacing and context of their specific response elements.

The different forms of the Oct-2 and Brn-3 POU family transcription factors can have distinct effects on their target promoters involving both the activation and repression of gene expression. To investigate the requirements for these effects we have altered both the context and spacing of the two TAATGARAT binding sites for these factors within the herpes simplex virus immediate-early 3 gene promoter. We show that the activation of this promoter by Brn-3a and its repression by Brn-3b is dependent on the correct spacing of these binding sites. In contrast, repression of the promoter by Oct-2.4 and Oct-2.5 is dependent on both the spacing and context of these sites with the requirements for repression by Oct-2.4 or Oct-2.5 being different. These effects are discussed in the context of the mechanisms by which POU factors activate or repress their target genes.

Animals↗
PubMed1996

Alternative splicing of the Brn-3a and Brn-3b transcription factor RNAs is regulated in neuronal cells.

The closely related and functionally antagonistic POU family transcription factors Brn-3a and Brn-3b are encoded by two distinct genes that are expressed primarily in neuronal cells. In addition, however, the primary transcript of each of these genes is alternatively spliced to produce two distinct mRNAs encoding long and short isoforms that differ at the N-terminus of the protein. We show that this process is regulated so that different proportions of the mRNAs encoding the long and short forms of either Brn-3a or Brn-3b are produced in different rat tissues. Similarly, the ratio of each of these forms can be modulated by specific stimuli in both a neuronal cell line and primary neurons. The significance of these effects is discussed in relation to the functional differences between the two forms of each factor.

Alternative Splicing↗
PubMed1996

Functional interaction between the HIV-1 Tat transactivator and the inhibitory domain of the Oct-2 cellular transcription factor.

OBJECTIVES: To examine the interaction of the HIV Tat protein and the inhibitory domain of the cellular transcription factor Oct-2. DESIGN: HIV reporter plasmids were co-transfected with expression vectors encoding wild-type and mutant Tat proteins and vectors encoding the inhibitory domain either alone or linked to a DNA-binding domain. METHODS: The activity of the different reporters was compared in the presence or absence of Tat or the inhibitory domain, or both. RESULTS: In the presence of the Tat protein, the Oct-2 inhibitory domain enhances the activation of Tat-responsive promoters by Tat. This effect is not observed when either the inhibitory domain or Tat cannot bind to the target gene, but is observed when one or both of the factors can bind. No activation is observed when the Oct-2 domain is co-transfected with Tat mutants that lack the Tat activation domain, indicating that the Oct-2 domain cannot substitute for the Tat activation domain. CONCLUSION: These data indicate that the Oct-2 inhibitory domain can functionally interact with Tat to form a complex with enhanced transactivating ability.

DNA-Binding Proteins↗
PubMed1995

Activation of the herpes simplex virus immediate-early gene promoters by neuronally expressed POU family transcription factors.

Herpes simplex virus immediate-early (IE) promoters contain the TAATGARAT motif which acts as a target site for the cellular POU family transcription factors Oct-1 and Oct-2. Here we show that other members of the POU family that are expressed in sensory neurons can also affect IE promoter activity. In particular, two members of the Brn-3 family of POU proteins Brn-3a and Brn-3c can activate the IE-1 and IE-3 promoters when co-transfected into fibroblasts and neuronal cells whereas a third member Brn-3b represses IE promoter activity. In contrast, Brn-3 proteins cannot overcome the inhibitory effect of neuronal Oct-2 on IE promoter activity in co-transfections nor do they prevent transactivation of the IE promoters by the Oct-1-Vmw65 complex. The potential regulation of the IE promoters by several different neuronally expressed POU proteins during the initiation, maintenance and re-activation of latent infection in sensory neurons is discussed.

Animals↗
PubMed1995

Regulated splicing of the Oct-2 transcription factor RNA in neuronal cells.

The primary RNA transcript derived from the gene encoding the Oct-2 transcription factor is alternatively spliced to yield a number of different mRNAs which encode different isoforms of this protein. The mRNAs encoding two such isoforms Oct-2c and mini Oct-2 were originally detected in neuronal cells. We show here that the mRNAs encoding these forms also occur in other tissues with the proportion of the mini Oct-2 mRNA being much higher in the spleen than in the brain. However, the levels of the mini Oct-2 mRNA increase in neuronal cell lines in response to differentiation-inducing stimuli and decrease upon exposure to growth factors. Hence the splicing of the Oct-2 transcript can be regulated in both a tissue specific manner and in neuronal cells in response to specific stimuli. The significance of this effect is discussed in terms of the differing ability of different forms of Oct-2 to activate or inhibit gene expression.

Animals↗
PubMed1994

Radical scavenger effect of Boschniakia rossica.

To elucidate the mechanism of the invigorating and antisenile action of the dried herb of Boschniakia rossica (Boschniakiae Herba), the free radical scavenging activity of its 50% ethanol extract (BR) was examined using an electron spin resonance spectrometer. The scavenging activity of plasma from Fisher-334 rats with continuous administration of BR was also examined. The concentrations showing 50% inhibition of the free radical of BR on the 1,1-diphenyl-2-picrylhydrazil (DPPH) radical, superoxide radical and hydroxyl radical were 0.003%, 0.06% and 9.67%, respectively. Plasma from the rats with BR administered clearly showed higher free radical scavenging activity compared with that of normal control rats. These findings suggest that Boschniakia rossica has strong free radical scavenging activity and consequently it has inhibitory effects on the disorders caused by free radical production in living tissue.

Administration, Oral↗
PubMed1994

Reinforcement effects of Boschniakia rossica on discrimination learning in cholinergic lesions of rats.

The dried herb or stem of Boschniakia rossica (Boschniakiae Herba) has been used as an antisenile agent in the Jilin Province of China. To elucidate the effects of Boschniakiae Herba on decreased learning ability and memory weakness, a 50% ethanol extract of Boschniakiae Herba was administered to rats whose nucleus basalis of Meynert had been destroyed by the injection of ibotenic acid. This administration showed a significant improvement in the decrease of the ratio of correct responses caused by destruction of the nucleus basalis of Meynert. These results suggest that B. rossica would be therapeutic in senility.

Animals↗
PubMed1994

Tannins and related polyphenols of euphorbiaceous plants. XI. Three new hydrolyzable tannins and a polyphenol glucoside from Euphorbia humifusa.

Three new hydrolyzable tannins, euphormisins M1, M2, and M3, were isolated from Euphorbia humifusa WILLD., and respectively characterized as 1,3,6-tri-O-galloyl-4-O- brevifolincarboxyl-beta-D-glucose (19), an oxidative metabolite (23) of geraniin, and 1,3,6-tri-O-galloyl-alpha-D-glucose (18), by spectroscopic and chemical methods. A new ellagic acid glucoside (16) and fifteen known tannins, including geraniin (8) and four dimers [euphorbins A (13), B (14), excoecarianin (15) and eumaculin A (12)], were also isolated.

Flavonoids↗
PubMed1994

[Complications following Nd: YAG laser posterior capsulotomy].

We used neodymium-YAG laser to perform discissions of the posterior capsules in 221 eyes of 203 patients who had undergone previous extracapsular cataract extractions. After a follow-up period ranging from 1-96 months, in the mean 10.5 months, 47.06% of the eyes achieved corrected visual acuities of > or = 0.5. The complications included rhegmatogenous retinal detachment in 3 eyes (1.36%) and bullous keratopathy in one eye (0.45%). Although cystoid macular edema and glaucoma were not seen in this series, they had been reported. The author suggests that patients undergoing Nd: YAG laser capsulotomies require ongoing medical observations to detect and treat these complications.

Adolescent↗
PubMed1994

[Natural history of corneal astigmatism following posterior chamber intraocular lens implantation].

The natural history of corneal astigmatism in 118 eyes following extracapsular cataract extraction and PC IOL implantation demonstrated that the average surgery induced with-the-rule astigmatism of 3.37D one week after the operation declined at a rate of 0.60, 0.63 and 0.39D during the 1st, 2nd and 3rd months respectively, indicating that the with-the-rule astigmatism of 2.00-3.00D would be corrected spontaneously to the normal or physiological status. The relationship between the changes in astigmatism and postoperative vision and the intraocular pressure was discussed.

Aged↗
PubMed1993

[Intraoperative control of corneal astigmatism during cataract extraction with PC IOL implantation].

The surgical keratoscope and Terry surgical keratometer were used in 29 (group a) and 34 (group b) eyes respectively during cataract extraction with PC IOL implantation to monitor the corneal astigmatism and to adjust the tension of sutures. Two weeks after the operation, the corneal astigmatism in group a was 3.50 +/- 1.70D, and that in group b was 2.56 +/- 1.60D. Two months after the operation, 55.2% of the eyes in group a and 38.2% of the eyes in group b had corneal astigmatism > 2.00D, differing significantly from the higher percentage in the controls. The authors opined that the intraoperative use of the surgical keratoscope and Terry surgical keratometer helped reduce the corneal astigmatism following the intraocular operation.

Aged↗
PubMed1992

[Perfusion lung scan in unexplained pulmonary hypertension].

Thirty-two patients were diagnosed as unexplained pulmonary hypertension by clinical history, physical examination, hemodynamics, pulmonary angiography and perfusion lung scanning. The findings of pulmonary scans in twenty patients (62.5%) showed patchy heterogeneous perfusion defects, which suggested chronic silent pulmonary thromboembolism (CSPT) and in twelve cases (37.5%) demonstrated normal or equally diffuse radionuclide scattering due to primary pulmonary hypertension (PPH). This result corresponded with the pathological data in some of the relevant references. Pulmonary perfusion scan is a noninvasive, safe and simple procedure for determining whether CSPT or PPH is the causative factor in patients with unexplained pulmonary hypertension.

Adolescent↗
PubMed1992

[Postoperative cardiac intensive care for patients with thoracic cancer: analysis of 430 cases].

430 patients with thoracic cancer were given intensive care after major thoracic surgery. Of those 188 (43.72%) developed cardiac complication during their stay in ICU and 2 (0.46%) died. The results indicated that postoperative cardiac complications were closely related to the patients age, preoperative concomitant cardiovascular diseases, duration of operation, hypoxemia, hypercapnia, and surgical complications. Postoperative cardiac intensive care could reduce the mortality rate.

Adult↗
PubMed1991

[Phenolic constituents of licorice. IV. Correlation of phenolic constituents and licorice specimens from various sources, and inhibitory effects of licorice extracts on xanthine oxidase and monoamine oxidase].

The roots and/or rhizomes of Glychyrrhiza uralensis, G. glabra and G. inflata, and commercial licorice specimens from various regions or countries were analyzed by high-performance liquid chromatography (HPLC), and classified into three types based on their phenolic constituents. i) Type A: The roots and rhizomes of G. uralensis, commercial licorice specimens from northwestern region of China (Seihoku-kanzo) and from northeastern region of China (Tohoku-kanzo) in Japanese markets, and also several licorice specimens from Chinese markets. They contain licopyranocoumarin (6), glycycoumarin (7) and/or licocoumarone (8), which were not found in G. glabra and G. inflata. ii) Type B: The root and rhizome of G. glabra, and the licorice specimens imported from the Soviet Union and Afghanistan. They contain glabridin (9) and glabrene (10), which were not found in the samples of the other two Glycyrrhiza species. A root sample of Glycyrrhiza species from Turkey also contains 9 and 10. iii) Type C: The root sample of G. inflata. They contain licochalcones A (11) and B (12), which were not found in the samples of the other two Glycyrrhiza species. Commercial licorice specimens obtained in Japan, which were imported from Sinkiang of China (Shinkyo-kanzo), and some licorice specimens obtained from Chinese markets, have also been found to contain 11 and 12. The phenolics 6-12, characteristic constituents of types A, B or C, were not found in a specimen of cortex-free licorice from a Japanese market (kawasari-kanzo). Extracts of some licorice specimens of types A and B, and all of the licorice specimens of type C inhibited 40-56% of the xanthine oxidase activity at the concentration of 30 micrograms/ml. Extracts of some licorice specimens of types A and B also showed inhibitory effects on monoamine oxidase (44-64% inhibition, at the concentration of 30 micrograms/ml), which were slightly weaker than that of harmane hydrochloride.

Chromatography, High Pressure Liquid↗