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Biomedical subjects

S Zhu

Publications and source records attributed to S Zhu.

At least 235 records · Page 13Linked to original sources
PubMed1996

LAPTM5: a novel lysosomal-associated multispanning membrane protein preferentially expressed in hematopoietic cells.

While a large body of knowledge about cell membrane proteins exists, much less is known about the repertoire and function of integral membrane proteins of intracellular organelles. In looking for novel classes of genes that are functionally important to hematopoietic cells, we have cloned the cDNA for a gene preferentially expressed in adult hematopoietic tissues. During embryonic development the gene is expressed in both hematopoietic and nonhematopoietic tissues. In cell lines the gene is expressed specifically in hematopoietic lineages, whereas in normal adult tissues the mRNA is preferentially detected at high levels in lymphoid and myeloid tissues. The predicted protein is a pentaspanner with no homology to known genes and conserved across evolution. Immunocytological and cell fractionation studies with a specific antibody revealed a protein localizing in lysosomes. The gene, provisionally named LAPTM5, maps to chromosome 1p34. The expression pattern of the gene together with preliminary evidence that the protein interacts with ubiquitin indicates that the protein may have a special functional role during embryogenesis and in adult hematopoietic cells.

Adult↗
PubMed1996

Expression of vaccinia virus K3L protein in yeast inhibits eukaryotic initiation factor-2 kinase GCN2 and the general amino acid control pathway.

Phosphorylation of the alpha subunit of eukaryotic initiation factor-2 (eIF-2) is a well characterized mechanism regulating protein synthesis. Viral and cellular proteins have been identified that regulate the activity of the eIF-2alpha kinases. The regulatory protein, K3L, from vaccinia virus is homologous to the amino terminus of eIF-2alpha and is thought to inhibit the activity of the double-stranded RNA-dependent kinase suppressing the antiviral mechanism mediated by this kinase. We investigated whether K3L can inhibit the activity of the yeast eIF-2alpha kinase GCN2. Expression of K3L protein in yeast reduced the level of eIF-2alpha phosphorylation by GCN2 and blocked the stimulation of the general amino acid control pathway in response to starvation conditions. Accompanying in vitro studies showed that recombinant K3L protein reduced GCN2 autophosphorylation and phosphorylation eIF-2alpha. In agreement with the hypothesis that K3L inhibits eIF-2alpha kinases by functioning as a pseudosubstrate, we observed that K3L directly interacted with the kinase catalytic domain of GCN2. Together, these results indicate that K3L is a specific inhibitor of eIF-2alpha kinases from mammals and yeast and suggest that the kinases contain common structural features important for recognition of their substrate eIF-2alpha.

Amino Acid Sequence↗
PubMed1996

Adult alveolar type II cells lack cAMP and Ca(2+)-activated Cl-channels.

We investigated the presence of Ca(2+)-activated Cl-channels in adult rat alveolar type II (ATII) using patch-clamp techniques. Only one active channel each, with a single channel conductance of 50 pS and an opening probability (Po) of 0.76 was found among 130 successful cell-attached and 5 inside-out patches. Addition of CPT-cAMP into the bath (500 microM) induced one active patch from 33 silent cell-attached patches. Incubation of 9 ATII cells, with ionomycin (1 microM), failed to elicit chloride single currents in 9 cell-attached patches. Cl- currents were also absent from 35 whole cell patches, even after the addition of 10 microM terbutaline in the bath or 1 mM ATP and 5 mM MgCl2 in the pipette. These results indicate that only a very small fraction of adult rat ATII cells express CFTR and suggest that Cl- ions are passively transported across the cell junctions.

Adenosine Triphosphate↗
PubMed1996

Effects of inhalation anesthetics of Kainate-induced glutamate release from cerebellar granule cells.

The mechanisms of inhalation anesthesia may include inhibiting non NMDA excitatory amino acid neurotransmission. This possibility was addressed by measuring the effect of three anesthetics at clinically relevant concentration on kainate-induced glutamate release from cerebellar granule cells. Cerebellar granule cells were obtained from 8-day-old SD rats and maintained in vitro for 9-14 days. Medium glutamate concentrations were measured by HPLC after 90 minutes incubation with kainate or NMDA. Inhalation anesthetics were introduced by holding the cells under a continuous flow of air/anesthetic mixtures. All anesthetics tested did not effect NMDA-induced glutamate release. Halothane (1 MAC), isoflurane (1 MAC) inhibited kainate-induced glutamate release from the cultured cells whereas enflurane (1 MAC) had no effect on kainate-induced glutamate release. The difference between enflurane and the other anesthetics tested suggests that anesthesia is dependent on more than one process and the extent at which each function is perturbed is dependent on the specific anesthetic used. Halothane inhibition of kainate-induced glutamate release was not reversible by increasing kainate concentration, indicating halothane does not directly compete with kainate at its receptor.

Anesthetics, Inhalation↗
PubMed1996

Apolipoprotein E genotype distribution in schizophrenia.

We examined the hypothesis that apolipoprotein E (apoE) isoforms-besides their well-established role in the aetiology of early and late onset Alzheimer's disease (AD)-may be involved in the development of schizophrenia. We determined apoE genotypes in 98 schizophrenic patients and 98 sex and age matched controls. No significant difference in apoE allele frequencies were observed between schizophrenic patients, subpopulations of schizophrenics, or controls. There was also no difference in the mean age at onset depending on the number of apoE epsilon 4 alleles found in the patients. Our data do not support an association between AD and schizophrenia based on apoE acting as a common denominator in the pathogenesis of both diseases.

Adult↗
PubMed1996

Nitration of surfactant protein A results in decreased ability to aggregate lipids.

We assessed the extent to which nitration of surfactant protein (SP) A, isolated from the bronchoalveolar lavage of patients with alveolar proteinosis, alters its ability to enhance lipid aggregation, bind lipids, and act synergistically with surfactant apoproteins B and C (SP-B, SP-C) in lowering the surface activity of surfactant lipids. SP-A was treated with various concentrations of tetranitromethane (TNM) at pH 6, 7.4, 8, or 10. Depending on the pH, TNM acts either as a nitrating (pH > or = 7.4) or an oxidizing agent (pH < or = 6). Exposure of SP-A to TNM (0.1-1 mM) at pH 7.4 or 8 for 30 min resulted in dose-and pH-dependent increases in nitrotyrosine, detected by Western blotting, enzyme-linked immunosorbent assay, and direct amino acid analysis. Treatment of SP-A with 0.5 mM TNM decreased its ability to aggregate lipids by 30% at pH 7.4, and 90% at pH 8, but had no effect on the disulfide-dependent oligomeric state of SP-A. In contrast, SP-A exposed to 1 mM TNM at pH 6 had background levels of nitrotyrosine and exhibited normal lipid aggregation properties. TNM, but not a hydroxyl radical-generating system, resulted in a pH-dependent loss of SP-A fluorescence, suggesting that tryptophan also may have been nitrated. Nitration of SP-A did not affect its ability to bind lipids. In addition, SP-A (1-3% by weight), treated with 0.25-0.5 mM TNM at pH 8, restored the surface-active properties of calf lung surfactant extract, previously damaged by exposure to peroxynitrite. We conclude that tyrosine nitration selectively inhibits the SP-A-mediated lipid aggregation without affecting its ability to bind lipids.

Amino Acids↗
PubMed1996

Inhibition of alveolar type II cell ATP and surfactant synthesis by nitric oxide.

Alveolar type II (ATII) cells, are often exposed to increased concentration of endogenous and exogenous nitric oxide (.NO). Exposure of freshly isolated rat ATII cells for 2 h to 1-3 microM .NO, generated by S-nitroso-N-penicillamine (SNAP), spermine NONOate, or 3-morpholino-sydnonimine (SIN-1) in the presence of superoxide dismutase, resulted in approximately 60% decrease in the rate of surfactant synthesis, as measured by the rate of incorporation of [methyl-3H]choline into phosphatidylcholine, and 60-80% inhibition of cellular ATP levels, as determined by bioluminescence. Similar results were obtained after incubation of ATII cells with authentic peroxynitrite (0.5 mM) but not SIN-1, a putative generator of peroxynitrite. Addition into the medium of oxyhemoglobin (20 microM), which scavenged .NO, or enhancement of ATII glutathione levels by preincubation with glutathione ester (5 mM) totally prevented the NONOate (100 microM) inhibition of cellular ATP. In contrast to the in vitro findings, normal levels of ATP and lipid synthesis were measured in ATII cells isolated from the lungs of rats that breathed .NO gas (80 ppm) in 21% O2 for 2 h (n = 4). This lack of effect may be due either to the presence of various antioxidants (such as glutathione) in the epithelial lining fluid or to the relatively low concentrations of .NO reaching the alveolar epithelium. We conclude that .NO and peroxynitrite, at concentrations likely to be encountered in vivo during inflammation, decrease ATII cell energy stores and surfactant synthesis, which may lead to derangement of important physiological functions.

Adenosine Triphosphate↗
PubMed1996

[Management of anterior vitreous by high gluey Healon].

PURPOSE: To investigate the technique of managing anterior vitreous by high gluey Healon. METHODS: In 15 eyes of 15 cases having undertaken in situ phacoemulsification vitreous loss, 12 eyes of 12 cases in ECCE, 3 eyes of 2 cases in Marfan Syndrome, 13 eyes of 13 cases in eye injury, tunnel incision was made and PC-IOL implantation was performed after high gluey Healon managing anterior vitreous on all the cases. RESULTS: High gluey Healon managing anterior vitreous in 43 eyes, post capsule injuries was not enlarge, and cortex or fragments of len nuclear not fall in vitreous cavity. Visual acuity of 0.5 or better at postoperative one week were 72.1% and 59.1% respectively. CONCLUSION: The technique of managing anterior vitreous by high gluey Healon was worthy to be spread due to minimum injury, vitreous loss, and fast restoration of visual acuity.

Adolescent↗
PubMed1996

[Clinical application of intraoperative sustained limited expansion].

Since May 1993, the technique of intraoperative sustained limited expansion (ISLE) had been applied clinically in 21 cases for the immediate reconstruction of soft tissue defects. Satisfactory results were obtained in 18 cases (85.7%), and failed in 3 cases (14.3%). ISLE had been applied successfully in various regions of the body. It had been shown that the results were dependent on the extent of soft tissue defect, the extent of intraoperative tissue gain, and the time of intraoperative sustained expansion.

Adolescent↗
PubMed1996

Secretory expression of a single-chain insulin precursor in yeast and its conversion into human insulin.

A synthetic single-chain porcine insulin precursor (PIP) gene and an alpha-mating factor leader sequence (alpha MFL) gene obtained by the PCR method are inserted between the promoter and 3'-terminating sequence of the alcohol dehydrogenase gene ADH1 in plasmid pVT102-U to form plasmid pVT102-U/alpha MFL-PIP. The single-chain insulin precursor is expressed and secreted to the culture medium by Saccharomyces cerevisiae transformed by pVT102-U/alpha MFL-PIP. The precursor is purified and converted into human insulin by tryptic transpeptidation. The purified human insulin is fully active and can be crystallized. The overall yield of human insulin is 25 mg per liter of culture medium.

Base Sequence↗