Search PubMed⌕ Search

Biomedical subjects

Y Bao

Publications and source records attributed to Y Bao.

At least 91 records · Page 5Linked to original sources
PubMed1997

[Cataract extraction and intraocular lens implantation after vitrectomy].

OBJECTIVE: To study the characteristics of cataract extraction and surgical techniques in cases following vitrectomy. METHODS: Extra-capsular extraction/phacoemulsification of cataract and intra-ocular lens implantation were performed under vitreous irrigation. RESULTS: Of 37 cases (40 eyes), 31 eyes (77.5%) had obtained post-operative visual acuity > or = 0.1, 12 eyes (30.0%) > or = 0.3. The complications included nuclear dislocation into vitreous cavity (1 eye) and vitreous hemorrhage (1 eye) in the operation, and rubeosis iridis (1 eye) and pupillary capture (1 eye) after the operation. CONCLUSION: Anti-hypotony must be emphasized in the operation of cataract extraction after vitrectomy, and the vitreous irrigation is a good way against hypotony, extra-capsular extraction is more suitable than phacoemulsification in cases with hard nucleus.

Adolescent↗
PubMed1997

[Effects of the double chamber intra-aortic balloon pumping on the renal circulation].

The effects of the double chamber intra-aortic balloon (DIAB) and the single chamber intra-aortic balloon (SIAB) on the hemodynamic parameters in the kidney were studied. No negative effect of both cases was observed. Before and after removing the renal nerve system, the DIAB was used and the results had been compared. The pulse produced by pumping activized the renal nerve system and reduced the renal vascular resistance. Therefore the reduction of the renal vascular resistance is an important reason for increasing the renal blood flow during intra-aortic balloon pumping.

Animals↗
PubMed1997

[Lasting expression of hF IX mediated by myoblasts in mice].

OBJECTIVE: To develop experimentally gene therapy for hemophilia B by using C2C12 cells and C3H mice as models. METHODS: The retroviral vector containing MCK enhancer and hCMV promoter was constructed and was used to transfect PA317 cells. Then the viral particles were used to transfect C2C12 cells and select the G418r clones,which were further confirmed by Southern, Northern, Western blots. And then the C2C12 cells expressing hF IX protein were injected into C3H mice and hF IX expression in vivo was studied. RESULTS: The expression level of hF IX in vivo was positively correlated with the number of injected cells, and the in vitro expression level of these cell clones. The expression of hF IX could be enhanced and prolonged by immunosuppressive agents. CONCLUSION: Allogeneic myoblasts transplantation leads to immunorejection, but repeated injections at a longer intervals could improve the existing rate of transplanted cells. And this might be helpful to gain insight into the myoblast-mediated gene therapy for hemophilia B patients.

Animals↗
PubMed1997

Evidence for light/redox-regulated splicing of psbA pre-RNAs in Chlamydomonas chloroplasts.

Efficient splicing in vivo of most self-splicing group I introns is believed to require proteins, raising the possibility that splicing could be regulated; however, examples of such regulation have been lacking. The Chlamydomonas reinhardtii chloroplast psbA gene contains four large group I introns that self-splice efficiently in vitro, but only under nonphysiological conditions. The psbA gene encodes the D1 protein of photosystem II, which is synthesized at very high rates in the light in order to replace photodamaged protein. We show that psbA pre-mRNAs, containing one or more introns, accumulate in wild-type cells in the dark, apparently due to rate-limited splicing. Analysis of the pre-RNAs indicates that splicing of the four introns does not follow a strict order. Exposure of cells to light induced rapid (15-20 min) decreases in precursor levels of approximately 3-5-fold (depending on the intron), which were accompanied by transient increases in free intron levels. Because light also stimulated psbA transcription approximately 2-fold over the same period, the data suggests that light increases the splicing efficiency of psbA introns approximately 6-10-fold. Similar estimates of the extent of light stimulation were obtained by analyzing precursor decay rates in the presence of actinomycin D. The effect of light is specific for psbA introns, because levels of unspliced 23S pre-RNA did not decrease. The light-induced increase in psbA pre-RNA processing was abolished by inhibitors of photosynthetic electron transport, but not by the ATP synthesis inhibitor, carbonylcyanide m-chlorophenylhydrazone, which actually promoted pre-RNA processing in the dark. Finally, nonphotosynthetic mutants, including the tscA-lacking photosystem I mutant, H13, did not show evidence of light-stimulated RNA processing. However, the light response was restored in photosynthetic transformants of H13 that had been complemented with the tscA gene. These data suggest strongly that light coordinately stimulates splicing of all four psbA introns. Moreover, they demonstrate that this response to light is mediated by photosynthetic electron transport. The implications of these results for the regulation of psbA gene expression are discussed.

Animals↗
PubMed1997

An experimental study on application of PCR in detection of kala-azar.

A polymerase chain reaction (PCR) technique was developed to detect Kala-azar. Out of 25 patients, 24 were detected, a sensitivity of 96%. The specificity rate, false positive rate, false negative rate, coincidence rate and Youdent's index were 100% (60/60), 0, 4%, 99% and 0.96 respectively. It was shown that the PCR technique can directly detect Kala-azar in samples (1 microliter) from peripheral blood.

Animals↗
PubMed1997

Mucosal injury and disruption of intestinal barrier function in HIV-infected individuals with and without diarrhea and cryptosporidiosis in northeast Brazil.

OBJECTIVES: To determine the relative effects of AIDS-related diarrhea with or without cryptosporidiosis and microsporidiosis on intestinal function and injury. METHODS: We studied 40 HIV-infected patients (20 with and 20 without diarrhea) and 13 healthy volunteers, using the differential urinary excretion of ingested lactulose and mannitol as respective markers of barrier disruption and overall villous surface area. We also examined them for fecal leukocytes, lactoferrin, and alpha 1-antitrypsin. Fasting subjects drank test solution containing lactulose (5 g) and mannitol (1 g). Urine was collected for 5 h and tested for sugars by high-performance liquid chromatography with pulsed amperometric detection. RESULTS: HIV-positive patients with diarrhea had a 2.8-fold higher lactulose:mannitol excretion ratio (L:M) than HIV-positive patients without diarrhea (p = 0.01) and 10.4-fold higher than healthy volunteers (p = 0.004). This was accounted for by a 1.5- to 3.1-fold higher rate of lactulose excretion by HIV patients with diarrhea than by those without diarrhea or by healthy volunteers. Mannitol excretion was 32-55% less in patients with diarrhea than in those without diarrhea or in healthy volunteers. Patients with cryptosporidial diarrhea had a nearly 6-fold higher L:M ratio than those without diarrhea (p < 0.001) and nearly 3-fold higher than those with non-cryptosporidial diarrhea (p = 0.02). One patient with microsporidial infection had a nearly 3-fold higher L:M ratio than controls without diarrhea. Alpha 1-Antitrypsin was positive in 40% of HIV-positive patients with cryptosporidial infections and none of 12 HIV-positive patients with non-cryptosporidial diarrhea. Fecal lactoferrin or leukocytes were increased in all HIV patients with diarrhea. CONCLUSION: HIV infection is associated with intestinal dysfunction and injury, even in patients who do not have diarrhea. However, those with diarrhea, especially with cryptosporidiosis or microsporidiosis, have even greater disruption of intestinal barrier function with potentially important nutritional consequences.

AIDS-Related Opportunistic Infections↗
PubMed1996

Human glycogen debranching enzyme gene (AGL): complete structural organization and characterization of the 5' flanking region.

Glycogen debranching enzyme (gene symbol, AGL) is a multifunctional enzyme acting as 1,4-alpha-D-glucan:1,4-alpha-D-glucan 4-alpha-D-glycosyltransferase and amylo-1,6-glucosidase in glycogen degradation. Genetic deficiency of AGL activity causes glycogen storage disease type III (GSD-III). To determine the molecular basis of GSD-III and elucidate the mechanisms for controlling tissue-specific gene expression, we report the isolation and structural organization of the human chromosomal AGL gene. The gene is 85 kb in length and is composed of 35 exons, encoding a 7.0-kb mRNA. The first 2 exons and 68 bp of exon 3 contain 5' untranslated region. Translation begins in exon 3, which encodes the first 27 amino acids of the AGL. Exons 4 to 35 encode the remaining 1505 amino acids. Among the 6 isoforms identified, the major isoform (isoform 1) starts with exon 1 and is widely expressed, including expression in both liver and muscle. Muscle-specific isoforms (2, 3, and 4) begin with exon 2. Isoforms 5 and 6 are minor isoforms that begin further within the gene. Reporter assays revealed that promoter region 1 (for isoform 1) was functional in liver (HepG2 cells), muscle (C2C12 cells), and ovary (Chinese hamster ovary cells), and promoter region 2 (for muscle-specific isoforms) was active only in muscle. These results suggest that the human AGL gene contains at least 2 promoter regions that confer differential expression of isoform mRNAs in a tissue-specific manner.

Animals↗
PubMed1996

Direct analysis of mannitol, lactulose and glucose in urine samples by high-performance anion-exchange chromatography with pulse amperometric detection. Clinical evaluation of intestinal permeability in human immunodeficiency virus infection.

Clinically, the ratio of lactulose/mannitol excretion in urine after administration of these non-metabolized sugars has been used to evaluate the extent of malabsorption and intestinal permeability disruption in several infections and nutritional diseases, including human immunodeficiency virus (HIV) infection. A range of methodologies have been reported to determine the lactulose/mannitol ratio, including enzymatic assay, gas-liquid chromatography (GC), thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). Most published methods involve tedious sample preparations, rendering them unsuitable for routine or automated clinical laboratory testing. We describe in this paper a method in which weak anion-exchange high-performance liquid chromatography in conjunction with a pulsed amperometric detector was used. It requires very simple sample preparation and avoids interference by other components present in the urine. The linear range of determination for mannitol, lactulose and glucose are up to 10 nmol, in a single injection. The limits of detection are 8, 12, 47 and 52 pmol, respectively, for mannitol, glucose, lactose and lactulose. The separation and quantification using this method are highly reproducible, yielding standard errors of less than 2.5% for retention times and less than 3.5% for quantitation. The ratios of lactulose/mannitol recovery in controls and in HIV-infected subjects with and without diarrhea showed striking differences, which are in close agreement with the published results derived with similar HPLC methods.

Calibration↗
PubMed1996

Cloning, in vitro expression, and tissue distribution of a human prostaglandin transporter cDNA(hPGT).

We recently identified a cDNA in the rat that encodes a broadly expressed PG transporter (PGT). Because PGs play diverse and important roles in human health and disease, we cloned human PGT (hPGT) from an adult human kidney cDNA library. A consensus sequence (4.0 kb) derived from several clones, plus 3' polymerase chain reaction amplification, exhibited 74% nucleic acid identity and 82% amino acid identity compared to rat PGT. When transiently expressed in HeLa cells, a full-length clone catalyzed the transport of PGE1, PGE2, PGD2, PGF2alpha, and, to a lesser degree, TXB2. Northern blotting revealed mRNA transcripts of many different sizes in adult human heart, placenta, brain, lung, liver, skeletal muscle, pancreas, kidney, spleen, prostate, ovary, small intestine, and colon. hPGT mRNAs are also strongly expressed in human fetal brain, lung, liver, and kidney. The broad tissue distribution and substrate profile of hPGT suggest a role in the transport and/or metabolic clearance of PGs in diverse human tissues.

Amino Acid Sequence↗
PubMed1996

Mutations in exon 3 of the glycogen debranching enzyme gene are associated with glycogen storage disease type III that is differentially expressed in liver and muscle.

Glycogen storage disease type HI (GSD-III), an autosomal recessive disease, is caused by deficient glycogen debranching enzyme (GDE) activity. Most GSD-III patients are GDE deficient in both liver and muscle (type IIIa), and some GSD-III patients have GDE absent in liver but retained in muscle (type IIIb). The molecular basis for this enzymatic variability is largely unknown. In the present study, the analysis of the GDE gene in three GSD-IIIb patients by single-strand conformation polymorphism (SSCP), DNA sequencing, restriction analysis, and family studies, revealed each of them as being a compound heterozygote for two different mutations. The first mutant alleles in all three patients involved mutations in exon 3 at amino acid codon 6 of the GDE protein. Two had an AG deletion at nucleotides 17 and 18 of the GDE cDNA (17delAG) which resulted in change of subsequent amino acid sequence and a truncated protein (25X); the other had a C to T transition at nucleotide 16 of the cDNA which changed a Glutamine codon to a stop codon (Q6X). The 17delAG mutation was also found in 8 of the 10 additional GSD-IIIb patients. The Q6X mutation was found in one of the remaining two GSD-IIIb patients. These two mutations were not found in any of the 31 GSD-IIIa patients, 2 GSD-IIId patients, nor 28 unrelated normal controls. The second mutant alleles in each of the three GSD-IIIb patients were R864X, R1228X, and W68OX. The R864X and R1228X were not unique for GSD-IIIb as they were also found in GSD-IIIa patients (frequency of 10.3% and 5.2% in Caucasian patients, respectively). Our data demonstrated that both IIIa and IIIb had mutations in the same GDE gene and established for the first time the molecular basis of GSD-III that differentially expressed in liver and muscle. The striking and specific association of exon 3 mutations with GSD-IIIb may provide insight into mechanisms controlling tissue-specific expression of the GDE gene. The identification of exon 3 mutations has clinical significance as well because it distinguished GSD-IIIb from IIIa hence permitting diagnosis from a blood sample rather than a more invasive muscle biopsy.

Base Sequence↗
PubMed1996

Mapping nucleotides in the 126-kDa protein gene that control the differential symptoms induced by two strains of tobacco mosaic virus.

The differential symptom determinants of the Holmes' masked (M) and U1 strains of tobacco mosaic virus previously were mapped to the 5'-coterminal open reading frame (ORF) encoding the 126-kDa protein and the N-terminal two-thirds of the 183-kDa protein. Both proteins influence viral RNA accumulation, but the function of, and impact on, symptom formation by large domains within the 126-kDa gene, which are not conserved with sequences in analogous ORFs from other related viruses, are unknown. In the current study, cDNA clones representing each strain (i.e., MIC-TMV and U1-TMV) were mutated in these nonconserved domains to further define the nucleotides responsible for mosaic symptom induction on Nicotiana tabacum. Progeny virus of a mutant containing only eight nucleotide substitutions from the MIC-TMV sequence to the U1-TMV sequence within the 126-kDa protein ORF of MIC-TMV induced U1-TMV-like symptoms. Single or multiple substitutions among these eight nucleotides further defined residues critical for symptom modulation. Complementary substitutions in the MIC-TMV and U1-TMV sequences did not always yield progeny virus that induced complementary visual symptoms. Progeny of some mutants contained second-site spontaneous mutations at specific positions shown to influence symptom phenotype. For a subset of the stable site-directed mutants, there was no correlation between severity of systemic symptoms and chlorotic lesion size or virus accumulation in these chlorotic lesions on inoculated leaves.

Base Sequence↗
PubMed1996

Cloning of the rabbit homologue of mouse 'basigin' and rat 'OX-47': kidney cell type-specific expression, and regulation in collecting duct cells.

Monoclonal antibody '4D4' was generated against a gel-purified 43-50 kDa fraction of rabbit erythrocyte (RBC) ghosts. Immunoblots of rabbit RBCs, skeletal muscle, and kidney, and of a rabbit cortical collecting duct cell line (RC.SV3) yielded broad bands of 30-70 kDa that migrated at approximately 31 kDa after deglycosylation. In kidney sections, 4D4 labeled the basal plasma membranes of the proximal tubule, medullary thick ascending limb of Henle, cortical, medullary, and papillary collecting ducts, and papillary surface epithelium, as well as the lateral membranes of alpha and beta-type intercalated cells. Antibody 4D4 was used to clone a full-length kidney cDNA, which predicted a 31 kDa immunoglobulin-like glycoprotein with high homology to mouse 'gp42' or 'basigin', human 'M6' or 'EMMPRIN', rat 'OX-47' or 'CE-9', and avian 'neurothelin', 'HT7', or '5A11'. When heterologously expressed in HeLa cells, glycosylated immunoreactive protein was expressed at the plasma membrane. In the case of the endogenous protein in RC.SV3 cells, interferon-gamma and A23187 decreased, and fetal calf serum increased, steady-state mRNA levels. Thus, this molecule exhibits a high degree of cell type-specific expression in the kidney and undergoes regulation by cytokines and serum in kidney epithelial cells.

Amino Acid Sequence↗
PubMed1996

Hepatic and neuromuscular forms of glycogen storage disease type IV caused by mutations in the same glycogen-branching enzyme gene.

Glycogen storage disease type IV (GSD-IV) is an autosomal recessive disease resulting from deficient glycogen-branching enzyme (GBE) activity. The classic and most common form is progressive liver cirrhosis and failure leading to either liver transplantation or death by 5 yr of age. However, the liver disease is not always progressive. In addition, a neuromuscular type of the disease has been reported. The molecular basis of GSD-IV is not known, nor is there a known reason for the clinical variability. We studied the GBE gene in patients with various presentations of GSD-IV. Three point mutations in the GBE gene were found in two patients with the classical presentation: R515C, F257L, and R524X. Transient expression experiments showed that these mutations inactivated GBE activity. Two point mutations, L224P and Y329S, were detected in two separate alleles of a patient with the nonprogressive hepatic form. The L224P resulted in complete loss of GBE activity, whereas the Y329S resulted in loss of approximately 50% of GBE activity. The Y329S allele was also detected in another patient with the nonprogressive form of GSD-IV but not in 35 unrelated controls or in patients with the more severe forms of GSD-IV. A 210-bp deletion from nucleotide 873 to 1082 of the GBE cDNA was detected in a patient with the fatal neonatal neuromuscular presentation. This deletion, representing the loss of one full exon, was caused by a 3' acceptor splicing site mutation (ag to aa). The deletion abolished GBE activity. Our studies indicate that the three different forms of GSD-IV were caused by mutations in the same GBE gene. The data also suggest that the significant retention of GBE activity in the Y329S allele may be a reason for the mild disease. Further study of genotype/phenotype correlations may yield useful information in predicting the clinical outcomes.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1996

Position-dependent ATT initiation during plant pararetrovirus rice tungro bacilliform virus translation.

The expression of the rice tungro bacilliform virus open reading frame I was studied in transiently transfected protoplasts. Expression occurs despite the presence of a long leader sequence and the absence of a proper ATG initiation codon. Translation is initiated at an ATT codon. The efficiency of initiation in rice protoplasts depends strongly on the mechanism by which ribosomes reach this codon. From the effects of scanning-inhibiting structures inserted into different leader regions, it can be deduced that this mechanism is related to the ribosome shunt described for cauliflower mosaic virus 35S RNA. The process delivers initiation-competent ribosomes to the region downstream of the leader and is so precise that only the second of two potential start codons only 12 nucleotides apart is recognized. The ATT codon that is used when it is present downstream of the leader is hardly recognized as a start codon by ribosomes that reach it by scanning.

Base Sequence↗
PubMed1996

The 126- and 183-kilodalton proteins of tobacco mosaic virus, and not their common nucleotide sequence, control mosaic symptom formation in tobacco.

Nucleotide substitutions at two positions within the open reading frame encoding the 126-kDa protein in the attenuated masked (M) strain of tobacco mosaic tobamovirus (TMV) to those found in the virulent U1-TMV genome led to the induction of near U1-TMV-like symptoms on leaves of Nicotiana tabacum L. cv. Xanthi nn by progeny virus (M. H. Shintaku, S. A. Carter, Y. Bao, and R. S. Nelson, Virology 221:218-225, 1996). In this study, further site-directed mutations were made at these positions within the M strain cDNA to determine whether the protein or nucleotide sequence directly controlled the symptom phenotype. The protein and not the nucleotide sequence directly controlled the symptom phenotype when amino acid 360 within the 126-kDa protein sequence was altered and likely controlled the symptom phenotype when amino acid 601 was altered. The effects of the substitutions at amino acid position 360 on viral protein accumulation were studied by pulse-labeling proteins in infected protoplasts. Accumulation of the 126- and 183-kDa proteins was less for an attenuated mutant than for two virulent mutants, but the viral movement protein and coat protein accumulated to levels reported to be sufficient for normal systemic symptom development. The size of necrotic local lesions on N. tabacum L. cv. Xanthi NN was negatively correlated with symptom development and accumulation of the 126-kDa protein for these mutants. With reference to this last finding, an explanation of the cause of the differing symptoms induced by these viruses is presented.

Amino Acid Sequence↗
PubMed1996

Transient expression of oatp organic anion transporter in mammalian cells: identification of candidate substrates.

The cDNA for the rat liver organic anion-transporting polypeptide "oatp" has been shown to encode transport of bromosulfophthalein (BSP) and bile salts in Xenopus oocytes (E. Jacquemin, B. Hagenbuch, B. Stieger, A. W. Wolkoff, and P. J. Meier. Proc. Natl. Acad. Sci. USA 91: 133-137, 1994). Because oatp mRNA is expressed strongly in the kidney, we sought to determine whether renal oatp might play a role in the known secretion of a large variety of organic anions by the kidney. We transiently expressed a full-length oatp cDNA, cloned in pSPORT, in HeLa cell monolayers using the recombinant vaccinia virus vtf7-3. We tested an array of organic anions as candidate substrates by determining their ability to compete with tracer BSP for transport. HeLa cell monolayers transfected with the oatp cDNA transported tracer BSP and taurocholate at rates substantially higher than monolayers transfected with a control plasmid. Thus good expression can be obtained with the vaccinia-HeLa system using a standard plasmid cloning vector. BSP transport varied as a function of the medium albumin, ionic conditions, and pH in a fashion similar to that in Xenopus oocytes. Several organic anions known to be secreted by the classic secretory pathway, including p-aminohippurate (PAH), phenol red, and indigo carmine (10 microM) failed to inhibit oatp-mediated BSP transport. Direct testing using tracers revealed no oatp-mediated transport of sulfate, urate, PAH, several eicosanoids, or unconjugated or conjugated bilirubin. On the other hand, BSP transport was inhibited by approximately 50% by 10 microM corticosterone sulfate, spironolactone, and several other steroids. We conclude that the functional properties of oatp expressed in the HeLa cell/vaccinia transient expression system are comparable to those following expression in Xenopus oocytes and that steroids are likely to represent high-affinity endogenous oatp substrates. The latter hypothesis is addressed in greater detail in a companion paper.

Anion Transport Proteins↗
PubMed1996

Estradiol 17 beta-D-glucuronide is a high-affinity substrate for oatp organic anion transporter.

Although substantial evidence indicates that estradiol-17 beta (E2) is conjugated to the glucuronide in the kidney and then excreted by a direct tubular secretory route and that the liver transports E2 glucuronides via carrier-mediated mechanisms, the transporters involved in these processes have not been identified. The so-called "organic anion-transporting polypeptide" (i.e., oatp) has a number of known substrates, including bromosulfophthalein (BSP) and taurocholic acid (TCA) (E. Jacquemin, B. Hagenbuch, B. Stieger, A. W. Wolkoff, and P. J. Meier. Proc. Natl. Acad. Sci. USA 91: 133-137, 1994). In a companion study, we determined that steroid hormones represent a class of hormones that interact strongly with oatp when the latter is transiently expressed in vitro. Here, we studied more extensively steroids and steroid anion conjugates as candidate oatp substrates. In HeLa cell monolayers transfected with a full-length oatp cDNA, [3H]estradiol 17 beta-D-glucuronide ([3H]E2-17G) was transported with a signal-to-noise ratio of 15:1 over that of monolayers transfected with a control plasmid. The affinity of oatp for [3H]E2-17G was significantly higher than that for TCA (K(m) of 3 microM vs. 27 microM, respectively). In contrast to E2-17G, unconjugated estradiol (E2) was not significantly transported by oatp. Several unconjugated steroids and anionic steroid conjugates were tested for their ability to compete with tracer E2-17G for oatp-mediated transport. Conjugation at the 17 or 3 position with the anion of a strong acid (sulfate) resulted in a greater degree of inhibition of tracer E2-17G transport than did conjugation at the 17 or 3 position with an uncharged group (acetate), suggesting that the strength of the negative charge at these positions is an important determinant of the affinity of a given steroid conjugate for oatp. We conclude that the preferred substrates for oatp are steroids with a strong 17- or 3-position anionic group. Since steroid sulfotransferases and glucuronosyltransferases are expressed in the proximal tubule, as is oatp, the transporter may serve as an apical exit pathway for steroids following their conjugation within the tubule cell.

Anion Transport Proteins↗