Search PubMed⌕ Search

Biomedical subjects

Y Bao

Publications and source records attributed to Y Bao.

At least 109 records · Page 6Linked to original sources
PubMed1996

Regulation of renal oatp mRNA expression by testosterone.

A recently cloned cDNA encodes the so-called "organic anion-transporting polypeptide" (i.e., oatp), which is expressed in rat liver and in the kidney S3 proximal tubule. functional characterization of the cloned transporter indicates that estradiol 17 beta-D-glucuronide is a major substrate. Because the urinary excretion of glucuronidated steroids differs between males and females, we hypothesized that renal oatp expression may be under sex hormone control. Total RNA was isolated from male or female kidneys and probed with a digoxigenin-labeled oatp antisense riboprobe. Expression of oatp mRNA expression was quantitated by densitometry from Northern blots. Male kidneys expressed at least six distinct oatp transcripts (approximately 4.0, 3.2, 2.9, 2.6, 1.7, and 1.2 kb). Of these, the 3.2-kb band was consistently the strongest. In female rats, renal oatp mRNA expression was markedly less, such that only the 3.2-kb band was consistently detectable. Administering testosterone to female rats increased, and administering estradiol (E2) to male rats decreased, the steady-state levels of renal oatp mRNA. Gonadectomized male and female rats, as well as adrenalectomized male rats, were given pharmacological hormone replacement (testosterone, E2, or dexamethasone, respectively) by subcutaneous osmotic minipump. Castration of male rats produced a dramatic drop in the steady-state level of all six renal oatp transcripts. These were returned to normal by testosterone replacement. In contrast, there was no regulation of hepatic oatp mRNA expression by testosterone. Renal oatp mRNA expression in female rats was mildly increased by oophorectomy. Administration of E2 to oophorectomized females moderately suppressed renal oatp mRNA expression. Adrenalectomy produced a small decrease in oatp expression, but dexamethasone replacement failed to return expression to normal. We conclude that renal oatp mRNA expression is under strong (stimulatory) testosterone control and perhaps weaker (inhibitory) estrogen control. We speculate that this regulation of renal oatp expression is important in modulating the renal tubular secretion of conjugated E2.

Adrenalectomy↗
PubMed1996

Structural determinants of substrates for the prostaglandin transporter PGT.

We recently identified a broadly expressed transporter, PGT, that transports primarily prostaglandins E2 and F2 alpha (PGE2 and PGF2 alpha). In the current study, we examined the structural determinants of potential PGT substrates in detail. Rat PGT was transiently expressed in HeLa cells, the timed uptake of tracer PGE2 was determined in the presence of various concentrations of unlabeled prostanoids; and the resulting inhibitory constants (Ki) were determined by curve-fitting. PGE2 and PGF2 alpha, both known to be transported, had similar affinities for PGT (Ki = 49-50 nM). The strongest interaction (Ki = 13-19 nM) was obtained with prostanoids lacking the 9- or 11-position oxygen groups. A relatively high affinity was also obtained for the bicycloendoperoxides U44069, PGH2, and U46619 (Ki = 29-39 nM). However, a radioactive representative from this group, U46619, was not transported. Structural modifications that produced a moderately reduced affinity relative to that of PGE2 (Ki = 56-286 nM) included reduction in C5 = C6, the addition of a benzene group at position C18, and isomerization at the C8 position. In complementary studies, tracer isoprostane B-iso-PGF2 alpha was found to be transported at approximately 13% the rate of tracer PGE2. Substantially weaker interaction (Ki = > 700 nM) was seen when the 1-position COO- anionic group was neutralized or when the 15(S)-OH group was changed to 15(R)-OH or to 15-keto. These results with the cloned rat PGT are very similar to those previously reported in the in vitro perfused rat lung and indicate that PGT probably represents the predominant route by which certain prostanoids, including F2 isoprostanes, are transported across plasma membranes.

Animals↗
PubMed1996

Metabolism of hydroperoxy-phospholipids in human hepatoma HepG2 cells.

Two enzymatic mechanisms have been proposed for the metabolism of hydroperoxy-phospholipids: i) the combined action of phospholipase A2 and glutathione peroxidase, and/or ii) direct enzymatic reduction. The latter reaction may be catalyzed by selenium-dependent phospholipid hydroperoxide glutathione peroxidase and/or by glutathione S-transferase alpha. To study the pathway of this reaction, we used human hepatoma HepG2 cells into which was incorporated labeled, hydroperoxy-phospholipids. The major product of incorporated l-palmitoyl-2-(13-hydroperoxy-cis-9, trans-11-octadecadienoyl)-L-3-phosphatidylcholine was the corresponding hydroxy-phospholipid with no hydroxy- or hydroperoxy-fatty acids. The contributions to reduction of hydroperoxy-phospholipids in HepG2 cells from glutathione S-transferase Al and phospholipid hydroperoxide glutathione peroxidase were calculated to be 0.5% and 99.5%, respectively. Increasing selenium in the cell culture medium led to increases in selenium-dependent phospholipid hydroperoxide glutathione peroxidase activity but not in glutathione S-transferase alpha. This increase in the selenium-dependent enzyme was paralleled by a concomitant increase in the extent of reduction of the incorporated hydroperoxy-phospholipid. We conclude that the main metabolic fate of hydroperoxy-phospholipids in HepG2 cells is by direct reduction to hydroxy-phospholipids by phospholipid hydroperoxide glutathione peroxidase but also by glutathione S-transferase alpha, and that phospholipase A2/selenium-dependent glutathione peroxidase does not play a significant role in the reduction.

Carcinoma, Hepatocellular↗
PubMed1996

A study of platelet specific antibody (anti-Sib(a)).

OBJECTIVE: To screen and analyse the platelet-specific alloantibody form the sera of patients who received multiple platelet transfusions or experienced side effects after platelet transfusions. METHODS: 156 patients, who received multiple platelet transfusion or experienced side effects after platelet transfusion, were collected from hospitals in Shanghai. The simplified sensitized erythrocyte platelet serology assay (SEPSA) was used to screen the platelet antibodies and the identification of specificities of the platelet alloantibodies was performed with a platelet panel of known antigens and absorption tests. RESULTS: Seventy-four sera were found positive. Among them 59 sera (47.4%) contained HLA antibodies, two sera (2.7%) platelet-specific antibodies, and 13 sera both HLA and platelet-specific antibodies. One of 2 sera containing platelet-specific alloantibody, the serum Zhu, was confirmed to have a monospecific platelet-specific alloantibody, the anti-Sib(a) (HPA-2b). CONCLUSIONS: We report the first case of anti-Sib(a) in Chinese Han population. The antigen frequency of Sib(a) is considered as one of the most important antibodies which will cause the platelet transfusion refractoriness in China.

Antigens, Human Platelet↗
PubMed1996

[Occurrence of depression symptoms and their influence factors in perimenopausal women].

OBJECTIVE: To investigate the prevalence of depression symptoms and their influence factors in perimenopausal women. METHODS: Self-rating depression scale and general condition questionaire were used in 419 perimenopausal women aged 45-55 in Beijing city. RESULTS: The prevalence of depression symptoms in these women was 46.1%, among which 69.9% was mild and 30.1% moderate or severe. The occurrence of depression symptoms in worker group was higher than cadres or skilled person groups (P < 0.01). The incidence of depression symptoms in women with systemic diseases was higher than those without (P < 0.001). Women with decreased libido and dissatisfaction with their husbands, family income and living conditions had a higher incidence than those without (P < 0.05). CONCLUSIONS: The prevalence of depression symptoms in perimenopausal women was considerably high. Clinical doctors should pay attention to psychological problems especially for women with high risks during medical treatment.

Adult↗
PubMed1995

Identification and characterization of a prostaglandin transporter.

Carrier-mediated prostaglandin transport has been postulated to occur in many tissues. On the basis of sequence homology, the protein of unknown function encoded by the rat matrin F/G complementary DNA was predicted to be an organic anion transporter. Expression of the matrin F/G complementary DNA in HeLa cells or Xenopus oocytes conferred the property of specific transport of prostaglandins. The tissue distribution of matrin F/G messenger RNA and the sensitivity of matrin F/G-induced prostaglandin transport to inhibitors were similar to those of endogenous prostaglandin transport. The protein encoded by the matrin F/G complementary DNA is thus preferably called PGT because it is likely to function as a prostaglandin transporter.

Amino Acid Sequence↗
PubMed1995

Direct separation of hydroperoxy- and hydroxy-phosphatidylcholine derivatives: application to the assay of phospholipid hydroperoxide glutathione peroxidase.

We have developed a method for assaying the activity of phospholipid hydroperoxide glutathione peroxidase (PHGPx) which is both more sensitive and specific than the spectrophotometric assay. The assay is based on the direct detection of the enzymatic product 1-palmitoyl-2-(13-hydroxy-cis-9, trans-11-octadecadienoyl)-L-3-phosphatidylcholine by HPLC. Under the conditions used, baseline separation is achieved for product and substrate. The utility of the method is demonstrated by the measurement of PHGPx activity in crude extracts from human lenses and from human Hep G2 hepatoma cells. This method is also suitable for measuring the specificity of PHGPx for cofactors apart from glutathione. The assay was used to demonstrate that cysteine alone at pH 7.4 mimics PHGPx activity.

Chromatography, High Pressure Liquid↗
PubMed1995

Circulating factors and insulin resistance. I. A novel myoinositol 1,2-cyclic phosphate phosphoglycan insulin antagonist from human plasma is elevated in noninsulin-dependent diabetes mellitus.

A novel low mol wt inositol phosphoglycan inhibitor (M tau 1200-1500) of insulin action in rat adipocytes has been partially purified from normal human plasma. This inhibitor, termed fraction V after the first purification step and fraction V3 after the second, is different from other reported serum insulin antagonists. It contains myoinositol, galactosamine, and mannose in approximate molar ratios of 1:1:3.3. The myoinositol has a 1,2-cyclic phosphate substituent, which is essential for the inhibitory activity. Its inhibitory activity is significantly elevated (161%, P < 0.05 for fraction V; 278%, P < 0.05 for fraction V3) in plasma of humans with noninsulin-dependent diabetes mellitus as compared with plasma of nondiabetic controls. These findings represent the first report of a naturally occurring mammalian inositol 1,2-cyclic phosphate containing phosphoglycan related to insulin action.

Adipocytes↗
PubMed1995

Biodistribution and metabolism of internally 3H-labeled oligonucleotides. II. 3',5'-blocked oligonucleotides.

The pharmacokinetics and metabolism of four radiolabeled phosphodiester oligonucleotides with 3'- and 5'-blocked ends were studied in mice and compared with previously studied, unblocked, all-phosphodiester and all-phosphorothioate oligonucleotides. The radiolabel was a tritiated methyl group enzymatically attached at an internal cytidine. The ends of the blocked phosphodiester oligonucleotides were protected by cyclization or by incorporation of either phosphorothioate or methylphosphonate linkages. Although these modifications protected the blocked oligonucleotides from degradation by exonucleases present in mouse serum, degradation initiated by endonucleases was 50% complete in 0.5-5 hr. After intravenous injection, the blocked oligonucleotides were much less stable than the all-phosphorothioate oligonucleotide and only marginally more stable than the previously studied, unblocked phosphodiester oligonucleotide. Even a "chimeric" blocked oligonucleotide with 16 phosphorothioate linkages and eight contiguous phosphodiester linkages was rapidly degraded. Despite the favorable serum binding, tissue accumulation, and stability observed with phosphorothioate oligonucleotides, these properties did not provide the chimeric oligonucleotide access to a compartment where its phosphodiester linkages were stable. In other respects, the blocked and chimeric phosphodiester oligonucleotides also resembled the unblocked phosphodiester oligonucleotide; radiolabel was cleared rapidly from the blood, there was little evidence of tissue accumulation, high performance liquid chromatographic analysis of tissue extracts showed extremely rapid degradation to mononucleotides, and only mononucleotide metabolites were present in urine. In summary, blocked phosphodiester oligonucleotides are rapidly attacked by endonucleases present in mice. Unless this problem is less serious in primates, such blocked oligonucleotides will be relatively unattractive candidates for drug development.

Animals↗
PubMed1994

Replication intermediates of rice tungro bacilliform virus DNA support a replication mechanism involving reverse transcription.

Rice tungro bacilliform virus (RTBV) replication intermediates have been studied in rice plants infected with the virus. Unencapsidated virus-specific molecules were identified which had open circular, linear, supercoiled (SC), strong-stop, single-stranded, linear double-stranded hairpin, and double-stranded with single-stranded extension DNA forms. The structures of these different DNA forms were consistent with the replication model of cauliflower mosaic virus and support other results that reverse transcription is involved in the replication of RTBV. The existence of nonspecific and defective (+)-strand priming is suggested. The relative amount of SC DNAs differs in various tissues of the same plant and in the same tissue at different ages. This indicates host regulation of the virus replication cycle and a feedback regulatory mechanism in controlling the SC DNA level. There are no obvious differences in the composition of the replication intermediates between insect-infected and agroinoculated rice plants.

DNA Replication↗
PubMed1994

Purification and characterization of an oxygen-stable form of dinitrogenase reductase-activating glycohydrolase from Rhodospirillum rubrum.

Dinitrogenase reductase-activating glycohydrolase (DRAG) is responsible for removing the ADP-ribose moiety from post-translationally inactivated nitrogenase of Rhodospirillum rubrum. Using DRAG purified from an overexpressing strain (UR276), further properties of this enzyme were studied, including its u.v.-visible and fluorescence spectra and its stability in air. DRAG appears to require no covalently bound inorganic cofactors for its activity or regulation. Previously, purified DRAG was found to be rapidly inactivated in air. The air-catalysed lability originated with the presence of sodium dithionite and Mn2+ throughout the purification of the enzyme. This lability can be mimicked using H2O2, which is known to oxidatively inactivate proteins containing bivalent metals. Implications for the regulation of nitrogenase are discussed with respect to the lack of sensitivity to air of the regulatory enzyme, DRAG.

Electrophoresis, Polyacrylamide Gel↗
PubMed1994

Fine specificity of B-cell epitopes on Felis domesticus allergen I (Fel d I): effect of reduction and alkylation or deglycosylation on Fel d I structure and antibody binding.

The repertoire of B-cell epitopes on the major cat allergen, Fel d I, was analyzed with monoclonal antibodies (MoAbs) in topographic mapping studies and in immunoassays with antigen derived from other cat (Felidae) species. Four essentially nonoverlapping epitopes on Fel d I, designated Fd1A to D, were defined by use of 15 anti Fel d I MoAbs in cross-inhibition radioimmunoassay. Only MoAbs directed against epitope Fd1B bound to putative Fel d I homologues in hair and dander extracts from seven other feline species (Panthera species, [n = 5], Leptailurus serval, and Leopardus pardalus). Quantitative monosaccharide analysis showed that Fel d I was a glycoprotein, containing high levels of fucose, as well as glucosamine, galactose, and mannose. Binding of MoAbs and human IgG or IgE antibody to native, reduced and alkylated or deglycosylated Fel d I was compared by means of immunoprecipitation and immunoassay, and the effects of these treatments on the structure of Fel d I were analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis. On reduction and alkylation, Fel d I dissociated into 14 kd and 3.2 kd peptides, and deglycosylation with trifluoromethane sulfonic acid produced a 12 to 14 kd peptide. These procedures resulted in a 100- to 1000-fold loss in murine or human antibody binding activity and caused significant loss of secondary structure, as judged by circular dichroism spectroscopy. Treatment with potassium hydroxide also caused a marked loss in antigenic reactivity. In contrast, enzymatic deglycosylation generated a 9 kd peptide, which showed strong reactivity with murine and human antibodies, comparable to native Fel d I. The results show that MoAbs define a broad repertoire of B-cell epitopes on Fel d I, one of which is expressed by other cat species. These epitopes are conformational and do not appear to involve oligosaccharide residues.

Alkylation↗
PubMed1994

A further study of LDT and IFAT tests in evaluating the control of kala-azar in China.

Kala-azar (KA) used to be highly prevalent in Shandong Province in China and, according to the survey made in 1950, the average prevalence rate was 350 per million. Through mass treatment and sandfly control, the prevalence rate was brought down to 3 per 100,000 in 1958 and the disease was basically eliminated. Since 1972, only 18 residual patients have been detected and no newly infected cases have appeared. In the meantime, the vector density had been reduced to such a low level that sandflies could not be found in 85% of the villages. For further evaluation of the control measures, an immunological survey on a relatively large scale was conducted in 78 townships located in 24 counties of 13 prefectures and cities in 1990. A total of 10,239 rural residents of different ages had the Leishmanin dermal test (LDT). None of the people under 30 years of age was positive (0/8020), while in those aged above 30, the average positive rate was 4.4% (98/2219). During the survey, blood samples were also taken from 4232 people for indirect fluorescent antibody test (IFAT); results were all negative. This indicates that the transmission of KA had been completely interrupted since the early 1960s and the province is now a non-endemic area of KA. Further analyses of the data showed that LDT is of great value in epidemiological investigation of KA, for the evaluation of control measurements, the ascertainment of the past and present status of the disease, and detection of subclinical infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Preparation of poly(glycolic acid) bonded fiber structures for cell attachment and transplantation.

A novel method was developed to prepare three-dimensional structures with desired shapes used as templates for cell transplantation. The produced biomaterials are highly porous with large surface/volume and provide the necessary space for attachment and proliferation of the transplanted cells. The processing technique calls for the formation of a composite material with nonbonded fibers embedded in a matrix followed by thermal treatment and the selective dissolution of the matrix. To evaluate the technique, poly(glycolic acid) (PGA) fiber meshes were bonded using poly(L-lactic acid) (PLLA) as a matrix. The bonded structures were highly porous with values of porosity up to 0.81 and area/volume ratios as high as 0.05 micron-1.

Animals↗
PubMed1993

Mapping the 5'-terminus of rice tungro bacilliform viral genomic RNA.

The initiation site of the major transcript of rice tungro bacilliform virus (RTBV) has been located by mapping the 5' end of the RNA to nucleotides 7404 and 7405 of the RTBV genome using an RNase protection method. This was confirmed by the 5' RACE PCR procedure which mapped the 5' end of the RNA to nucleotide 7405. These results are consistent with data from our analysis of the strong-stop DNA of RTBV. A eukaryotic RNA polymerase II promoter sequence (TATATAA) was located at nucleotide 7373 of RTBV genome which is 31-32 nucleotides upstream from the proposed initiation site of the RTBV transcript.

Base Sequence↗