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Biomedical subjects

Q Zhou

Publications and source records attributed to Q Zhou.

At least 397 records · Page 22Linked to original sources
PubMed1989

Attenuation of phosphoinositidase activity and phosphatidylinositol bisphosphate level of bovine retinal capillary pericytes in high glucose.

Both phosphoinositidase (PIase) and individual species of inositol phospholipid (IPL) of bovine retinal capillary pericytes (BRCP) were quantitatively determined. When glucose in growth medium was increased from 5- to 15- or 30 mM, PIase activity was attenuated to 82% or 55%, respectively. In contrast, when glucose (5-, 15-, 30 mM) was added to an enzyme extract from cells grown in the standard growth medium (5 mM glucose, 0.04 mM myo-inositol) the PIase activity was not changed, indicating that the reduced PIase activity was not due to the direct effect of glucose. When IPLs from BRCP were analysed by HPLC and TLC, we observed reduction of the total and newly formed IPLs including the substrate of PIase. Phosphatidylinositol bisphosphate (PIP2). Reduced levels of IPLs were associated with a decrease in myo-inositol and an increase in sorbitol. The changes in IPL metabolism were reversed by adding either free myo-inositol or AL1576, an aldose reductase inhibitor (ARI), to the high-glucose medium. However, the addition of myo-inositol to the growth medium with a standard concentration of glucose only caused a marked increase in phosphatidylinositol, but not in PIP or PIP2, while the supplement of AL1576 in the standard medium did not cause any changes in IPL formation. These findings suggest that the alteration in IPL metabolism in BRCP may be related to insufficient myo-inositol or activated sorbitol pathway under high-glucose conditions. Further explanation of the role of the altered hydrolysis of PIP2 triggered by PIase may provide clues to understanding of the mechanism of decreased pericyte viability in the presence of high glucose concentrations.

1-Phosphatidylinositol 4-Kinase↗
PubMed1989

DNA-synthesis regulation and correlation with inositol trisphosphate levels in cultured bovine retinal capillary pericytes.

Inositol phosphate (IP), inositol bisphosphate (IP2) and inositol trisphosphate (IP3) in cultured bovine retinal capillary pericytes (BRCP) were quantitated by an ion-pair reverse-phase HPLC. BRCP were grown in media with standard (5 mM) or high (30 mM) glucose, and were either labeled with myo-[2-3H]inositol (20 microCi ml-1) for 60 hr or with dual isotopes (20 microCi ml-1 myo-[2-3H]inositol and 2 microCi ml-1 [14C]glycerol) for 8 hr. In parallel, BRCP in different glucose-media were incubated with 1 microCi ml-1 [3H]thymidine for 4 hr. High glucose significantly suppressed the accumulation of [3H]label in IP, IP2 and IP3, and specifically reduced the incorporation of [14C]glycerol into inositol phospholipids, but not that of neutral lipids and other types of phospholipids. The reduced IP3 level correlated with the decrease in the incorporation of [3H]thymidine into DNA. Both the reduced IP3 formation and DNA synthesis which were induced by high glucose were significantly reversed by adding either myo-inositol or AL1576, an aldose reductase inhibitor (ARI). However, the addition of neither myo-inositol nor ARI stimulated IP3 formation and/or DNA synthesis when BRCP were grown in the standard medium (5 mM glucose). These findings indicate that myo-inositol metabolism and the polyol pathway affect inositol phospholipid-mediated pericyte division in vitro only under the high-glucose condition. These data are compatible with the hypothesis that altered inositol phospholipid metabolism accounts for the loss of pericytes in diabetic retinopathy.

Animals↗
PubMed1989

Sp1 activates transcription without enhancing DNA-binding activity of the TATA box factor.

We have studied the interactions of the Sp1 and IID transcription factors with a simple RNA polymerase II promoter. The adenovirus E1B core promoter consists essentially of a GC box and a TATA box, binding sites for the Sp1 and IID transcription factors, respectively. The E1B promoter is accurately transcribed in vitro using a mammalian transcription system. Sp1 activates E1B transcription in vitro in reactions using IID factor isolated from either human or yeast cells. In DNase I footprinting studies, Sp1 bound rapidly to its recognition sequence even at 0 degrees C (t1/2 less than 1 min). In contrast, yeast IID bound more slowly (t1/2 approximately 6 min at 25 degrees C) and required thermal energy for stable binding to the TATA box sequence. Dissociation rates were measured by the addition of specific oligonucleotide competitors to preformed DNA-protein complexes. Sp1 dissociates rapidly (t1/2 less than 1 min) at 25 degrees C, while yeast IID dissociates with an estimated t1/2 of 1 h at 25 degrees C. Sp1 and yeast IID bound to the E1B promoter simultaneously but independently. The rates of binding and dissociation of these factors were not significantly affected by the presence of the other factor. Bound Sp1 factor did not alter or enhance the yeast IID footprint. Oligonucleotide challenge of in vitro transcription reactions indicated that Sp1 also did not enhance the binding of the human IID factor to the E1B promoter. Thus the Sp1 factor activates transcription of the E1B gene by a mechanism that does not enhance the DNA-binding activity of the IID factor. Sp1 factor activates E1B transcription by 5- to 10-fold in vitro. Under these in vitro transcription conditions, transcripts due to reinitiation from an individual promoter complex contribute only a small portion of the total yield of E1B transcripts. Thus Sp1 cannot activate transcription by increasing the rate of initiation events per complex. Instead it appears that Sp1 acts by increasing the number of productive transcription complexes formed in vitro.

Adenoviridae↗
PubMed1989

Interspecific protoplast fusion of Streptomyces hygroscopicus var. yingchengenisis with Streptomyces qingfengmyceticus and biological characterization of their recombinants.

The frequency of recombination between Streptomyces hygroscopicus var. yingchengensis and Streptomyces qingfengmyceticus as a result of interspecific protoplast fusion was 4.5 x 10(-4). Characterization of biological properties revealed differences in spore mass color, drug resistance, antimicrobial activity, and antibiotic production capacity between the recombinants and their parents. Two recombinant strains, FL-42 and FL-48, exhibited production of the antibiotics originally elaborated by the two parents individually. They also produced two compounds with antimicrobial activity that their parents could not synthesize.

Anti-Bacterial Agents↗
PubMed1987

Reduction of inositol triphosphate in retinal microvessels by glucose and restimulation by myo-inositol.

The formation of inositol phospholipids (IPLs) and inositol phosphate esters (IPEs) in response to glucose was studied in isolated retinal microvessels from porcine eyes. Retinal microvessels incubated from 60 hr with myo-[3H]inositol were sequentially extracted to obtain IPLs and IPEs. [3H]Inositol-labelled IPLs were deacylated to produce the corresponding glycero derivatives. Both deacylation products and water-soluble IPEs were monitored by anion-exchange chromatography. In the presence of high glucose (30 mM) the labelling in inositol triphosphate (IP3) was reduced to 77% and was restimulated by adding myo-inositol (final concentration 0.4 mM) to 158% of the control under physiological conditions of glucose (5 mM) and myo-inositol (0.04 mM). With a fixed glucose concentration (5 mM), IPE accumulation was observed with increasing concentrations of exogenous myo-inositol. Under physiological conditions (glucose 5 mM, myo-inositol 0.04 mM) the distribution (percentage) of radioactivity in phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-phosphate (PIP2) was 63:19:18. The myo-inositol concentration dependence of IPL formation was also demonstrated. A decrease in IP3 in response to high glucose without changing PIP2 but with a reduction in PI indicated that PI may act as a reservoir to replace a possible loss of PIP2. These findings suggest that availability of myo-inositol by retinal microvessels may be essential to maintain the normal signal transduction and cell proliferation associated with IPL turnover under high glucose concentration.

Animals↗