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Biomedical subjects

X Zhu

Publications and source records attributed to X Zhu.

At least 343 records · Page 19Linked to original sources
PubMed1999

Alpha5beta1 integrin controls cyclin D1 expression by sustaining mitogen-activated protein kinase activity in growth factor-treated cells.

Cyclin D1 expression is jointly regulated by growth factors and cell adhesion to the extracellular matrix in many cell types. Growth factors are thought to regulate cyclin D1 expression because they stimulate sustained extracellular signal-regulated kinase (ERK) activity. However, we show here that growth factors induce transient ERK activity when added to suspended fibroblasts and sustained ERK activity only when added to adherent fibroblasts. Cell attachment to fibronectin or anti-alpha5beta1 integrin is sufficient to sustain the ERK signal and to induce cyclin D1 in growth factor-treated cells. Moreover, when we force the sustained activation of ERK, by conditional expression of a constitutively active MAP kinase/ERK kinase, we overcome the adhesion requirement for expression of cyclin D1. Thus, at least in part, fibroblasts are mitogen and anchorage dependent, because integrin action allows for a sustained ERK signal and the expression of cyclin D1 in growth factor-treated cells.

3T3 Cells↗
PubMed1999

Structure of acutolysin-C, a haemorrhagic toxin from the venom of Agkistrodon acutus, providing further evidence for the mechanism of the pH-dependent proteolytic reaction of zinc metalloproteinases.

The structure of acutolysin-C, a haemorrhagic zinc metalloproteinase from the venom of Agkistrodon acutus, has been analyzed and refined at 2.2 A resolution. The space group of the crystal is P2(1)2(1)2(1), with unit-cell dimensions a = 46.84, b = 49.52, c = 95.34 A. One molecule was found in each asymmetric unit. The phasing problem was solved by the molecular-replacement program AMoRe. Crystallographic refinement was performed using X-PLOR, leading to final R and free R factors of 0.176 and 0.272, respectively. The residue sequence of acutolysin-C was determined mainly by electron density. No density was found for the first residue at the N--terminus and the last two residues at the C-terminus, which was also the case for most other P-I class snake-venom metalloproteinases (SVMPs). Acutolysin-C has two highly conserved characteristic sequences His142-Glu143-X-X-His146-X-X-Gly149-X-X-His15 2 and Cys162-Ile163-Met164. The enzyme has three disulfide bridges: Cys117-Cys195, Cys157-Cys179 and Cys159-Cys162. The entire structure shows good agreement with that of other reported P-I class SVMPs and has two subdomains with a cleft in which one catalytic zinc ion is localized. However, the local conformation (especially the disulfide configurations), the coordination of the catalytic water molecules and some residue side chains differ compared with other P-I class SVMPs. The proteolytic activities of SVMPs are sensitive to the pH value. The molecular superpositions around the proteolytic active sites of all the P-I class SVMP crystal structures show that the distances between the zinc ion and its ligands are not correlated with the crystallization pH values, although the contact distances between the catalytic water molecule and the O atoms of the Glu143 carboxylate group in the neutral and weakly alkaline structures are shorter than those in weakly acidic structures, and the closer the crystallization pH value of one enzyme is to its optimal activity pH value, the shorter the contact distances. Overall, all P-I class SVMPs have similar conformations in the active-site cleft. The size of the active site is not correlated with the crystallization pH values or the proteolytic activities. The disulfide bridge Cys117-Cys195 is conserved in all crystal structures of P-I class SVMPs, whereas the conformation and number of disulfide bridges in the C-terminal subdomain differ. Acutolysin-C has no structural calcium ion, which may not affect the proteolytic activity or haemorrhagic activity directly.

Agkistrodon↗
PubMed1999

An in-home nurse-administered geriatric assessment for hypoalbuminemic older persons: development and preliminary experience.

BACKGROUND: Although malnutrition in older persons is a common, potentially treatable condition, few data indicate that treatments for this disorder can be effective. OBJECTIVE: To develop and preliminarily evaluate a two-component intervention that includes a nurse-administered, in-home assessment to identify potentially remediable causes of hypoalbuminemia and protocols to treat these problems. DESIGN: A pre-test post-test case-series. SETTING: An academic geriatrics practice. PARTICIPANTS: Seventeen persons aged 65 and older with serum albumin levels < or = 3.8 g/dL; eight of the participants received pre-and post-test outcome measures. INTERVENTION: Nurse-administered standardized assessment and intervention protocols. MEASUREMENTS: Serum albumin, Medical Outcome Study (MOS) SF-36, serum IL-1a and b, TNF alpha, IL-6, and lymphocyte markers of immune function. RESULTS: The assessment took 87 minutes, on average, and generated a mean 4.2 recommendations. Among the eight subjects with pre- and post-test measures, serum albumin increased by 0.2 g/dL (P = .035). Compared with baseline, two T cell markers of immune function demonstrated changes consistent with better function. CONCLUSIONS: These preliminary data support the potential benefit of a nurse-administered assessment coupled with protocols to address remediable contributors to hypoalbuminemia.

Aged↗
PubMed1999

Comparative analysis and serovar-specific identification of multiple-banded antigen genes of Ureaplasma urealyticum biovar 1.

Ureaplasma urealyticum is a causative agent of nongonococcal urethritis and is implicated in the pathogenesis of several other diseases. The species is divided into 14 serovars and two biovars, of which biovar 1 is most commonly isolated from clinical specimens. Reported associations between individual serovars and diseases have been difficult to confirm because of practical difficulties with serotyping. The multiple-banded antigen (MBA) is the predominant U. urealyticum antigen recognized during infections in humans and probably has a significant role in virulence. The 5' end of the MBA gene is relatively conserved but contains biovar, and possibly serovar, specificity. The 5' ends of the MBA genes of standard strains of U. urealyticum biovar 1, consisting of serovars 1, 3, 6, and 14, were amplified, cloned into pUC19, and sequenced to identify serovar-specific differences. The 5' end of the MBA gene sequence of serovar 3 was identical with the previously published sequence and differed by only three bases from that of serovar 14. Significant differences between the MBA gene sequences allowed biovar 1 to be divided into two subgroups, containing serovars 3/14 and serovars 1 and 6, respectively, using primers UMS-125-UMA269 and UMS-125-UMA269'. Serovars 1 and 6 were distinguished by restriction enzyme analysis of the amplicon and/or by PCR specific for serovar 6. These methods were used to identify and type U. urealyticum in 185 (46.3%) of 400 genital specimens from women. Biovar 1 was detected in 89.2% and biovar 2 in 18.3% of positive specimens. Of 165 specimens containing U. urealyticum biovar 1, 22.2% contained more than one serovar and 46.7, 46.1, and 25.5% contained serovars 1, 3/14, and 6, respectively. U. urealyticum was found in a significantly higher proportion of pregnant women than in sex workers and other women attending a sexually transmissible diseases clinic (P < 0.01). The methods described are relatively rapid, practicable, and specific for serotyping isolates and for direct detection and identification of individual serovars in clinical specimens containing U. urealyticum biovar 1.

Antigens, Bacterial↗
PubMed1999

Structural requirements and dynamics of mitosin-kinetochore interaction in M phase.

Mitosin is a 350-kDa human nuclear protein which transiently associates with centromeres and spindle poles in M phase. Ultrastructure studies reveal that it is located at the outer kinetochore plate. In this work, we explored the detailed structural basis and dynamics of the mitosin-kinetochore interaction. Two major regions important for targeting to centromeres were identified by analyzing different deletion mutants expressed in CHO cells: (i) the "core region" between amino acids 2792 and 2887, which was essential for the centromere localization of mitosin; and (ii) the internal repeats between residues 2094 and 2487, which cooperated with the core region to achieve strong mitosin-kinetochore interaction. The core region is characteristic of two leucine zipper motifs. Deletion of either motif abolished the centromere localization activity. In addition, Cys2864, adjacent to the second motif, was also essential for the activity of the core region. In contrast, the internal repeats alone were insufficient for centromere localization. We propose that this region may serve as a regulatory domain to facilitate interaction of the core region with the kinetochore. We showed that mitosin molecules entering nuclei after nuclear envelope breakdown (NEBD) were not assembled onto kinetochores efficiently, suggesting that the mitosin-kinetochore interaction is stabilized prior to NEBD. This result supports the idea of an ordered process for kinetochore assembly. Our data also suggest that mitosin might interact with chromatin in interphase. Evidence for coordinated regulation between the centromere-targeting and the putative chromatin-binding activities is also provided.

Amino Acid Sequence↗
PubMed1999

Cloning of Trp1beta isoform from rat brain: immunodetection and localization of the endogenous Trp1 protein.

The Trp gene product has been proposed as a candidate protein for the store-operated Ca2+ channel, but the Trp protein(s) has not been identified in any nonexcitable cell. We report here the cloning of a rat brain Trp1beta cDNA and detection and immunolocalization of the endogenous and expressed Trp1 protein. A 400-bp product, with >95% homology to mouse Trp1, was amplified from rat submandibular gland RNA. Rat-specific primers were used for cloning of a full-length rat brain Trp1beta cDNA (rTrp1), encoding a protein of 759 amino acids. Northern blot analysis demonstrated the transcript in several rat and mouse tissues. The peptide (amino acids 523-536) was used to generate a polyclonal antiserum. The affinity-purified antibody 1) immunoprecipitated human Trp1 (hTrp1) from transfected HEK-293 cells, 2) reacted with a protein of approximately 92 kDa, but not with hTrp3, in membranes of hTrp3-expressing HEK-293 cells, and 3) reacted with proteins of 92 and 56 kDa in human and rat brain membranes. Confocal microscopy and cell fractionation demonstrated that endogenous and expressed hTrp1 and expressed hTrp3 proteins were localized in the plasma membrane of HEK-293 cells, consistent with their proposed role in Ca2+ influx. The data demonstrate for the first time the presence of Trp1 protein in a nonexcitable cell.

Amino Acid Sequence↗
PubMed1999

Augmentation of eosinophil degranulation and LTC(4) secretion by integrin-mediated endothelial cell adhesion.

We examined the effect of eosinophil ligation to cultured human umbilical vein endothelial cells (HUVECs) in augmenting the stimulated secretion of leukotriene (LT) C(4) and eosinophil peroxidase (EPO). The effects of adhesion were compared before and after specific blockade with monoclonal antibodies directed against eosinophil surface integrins or endothelial counterligands. Adhesion to HUVECs augmented EPO release caused by formyl-methionyl-leucyl-phenylalanine plus cytochalasin B from 403 +/- 15.3 (BSA control) to 778 +/- 225 ng/10(6) cells for eosinophils exposed to interleukin-1alpha-treated HUVECs (P < 0.05) and also caused a twofold increase in stimulated LTC(4) secretion (P < 0.05). To determine whether augmented secretion resulted directly from adhesive ligation, studies were also performed with paraformaldehyde-treated HUVECs; stimulated secretion of LTC(4) from eosinophils was comparable to that for living HUVECs. Our study is the first demonstration that adhesion to HUVECs through ligation to alpha(4)- or beta(2)-integrin on the eosinophil surface causes augmentation of stimulated secretion of both EPO and LTC(4) and that blockade of adhesion molecules on either eosinophils or HUVECs prevents the priming effect on eosinophil secretion.

Antibodies, Monoclonal↗
PubMed1999

Inhibition of cPLA2 translocation and leukotriene C4 secretion by fluticasone propionate in exogenously activated human eosinophils.

We examined the effect of the highly lipophilic corticosteroid, fluticasone propionate (FP), in causing (1) inhibition of nuclear translocation of cytosolic phospholipase A2 (cPLA2), and (2) blockade of leukotriene C4 (LTC4) synthesis in isolated human eosinophils in vitro. Eosinophils were isolated from peripheral blood, treated with either buffer or 10(-)10 M to 10(-)6 M FP in the presence of 10 pg/ml human recombinant interleukin-5 (rhIL-5) and activated with formyl-met-leu-phe (FMLP) + cytochalasin B (CB). At 24 h, stimulated LTC4 secretion from eosinophils was unchanged; however, when corrected for cell viability, LTC4 secretion decreased from 1,429 +/- 327 pg/10(6) cells to 762 +/- 113 pg/10(6) cells for eosinophils treated for 48 h with >/= 10(-)8 M FP (p < 0.003). FMLP/CB-stimulated translocation of cPLA2 to the nuclear envelope assessed by specific immunohistochemical staining also was blocked by FP. By contrast, membrane expression of annexin-1, which was not minimal at 30 min, was substantial at 48 h for eosinophils treated with > 10(-)10 M FP, and inhibition of LTC4 synthesis was reversed by exogenous arachidonic acid (AA). We find that FP causes a decrease in stimulated eosinophil secretion of LTC4 that is regulated by phospholipase A2 (PLA2). Inhibition of LTC4 synthesis precedes the global cytotoxic effects of FP as indicated by the simultaneous upregulation of annexin-1 expression. Inhibited stimulated secretion corresponds to inhibited translocation of cPLA2 to the nuclear envelope during cellular activation.

Administration, Topical↗
PubMed1999

Bidirectional FcRn-dependent IgG transport in a polarized human intestinal epithelial cell line.

The MHC class I-related Fc receptor, FcRn, mediates the intestinal absorption of maternal IgG in neonatal rodents and the transplacental transport of maternal IgG in humans by receptor-mediated transcytosis. In mice and rats, expression of FcRn in intestinal epithelial cells is limited to the suckling period. We have recently observed, however, clear expression of FcRn in the adult human intestine, suggesting a function for FcRn in intestinal IgG transport beyond neonatal life in humans. We tested this hypothesis using the polarized human intestinal T84 cell line as a model epithelium. Immunocytochemical data show that FcRn is present in T84 cells in a punctate apical pattern similar to that found in human small intestinal enterocytes. Solute flux studies show that FcRn transports IgG across T84 monolayers by receptor-mediated transcytosis. Transport is bidirectional, specific for FcRn, and dependent upon endosomal acidification. These data define a novel bidirectional mechanism of IgG transport across epithelial barriers that predicts an important effect of FcRn on IgG function in immune surveillance and host defense at mucosal surfaces.

Adult↗
PubMed1999

Roles of Gi and Gq/11 in mediating desensitization of the luteinizing hormone/choriogonadotropin receptor in porcine ovarian follicular membranes.

Although desensitization of most guanine nucleotide-binding (G) protein receptors is triggered by phosphorylation of the receptor, desensitization of the LH/CG receptor (-R) in porcine follicular ovarian membranes appears to be independent of LH/CG-R phosphorylation. We therefore evaluated whether desensitization of the LH/CG-R reflected a direct inhibition of adenylyl cyclase (AC) activity by either the alpha-subunit of Gi or betagamma-subunits derived from any of the membrane G proteins activated in response to LH/CG-R activation or whether desensitization reflected a competition between Gs and a G protein that activated phospholipase C for binding sites on the LH/CG-R. The results showed that follicular membrane AC activity was not inhibited upon activation of the LH/CG-R despite evidence that the ACs in follicular membranes, when maximally activated by forskolin, could be inhibited when membrane G proteins were activated by guanyl-5'-yl imidodiphosphate, and that pertussis toxin pretreatment of membranes raised forskolin-stimulated AC activity, consistent with a tonic inhibition of follicular membrane AC activity. Similarly, agonist-stimulated desensitization of LH/CG-R-stimulated AC activity was not inhibited by pertussis toxin. Therefore, desensitization is not the result of inhibition of AC mediated by an inhibitory Gi subunit. Follicular membrane AC was also not inhibited by Gbetagamma subunits freed with activation of Gs Gq/11, or G13, based on the inabilities of exogenous Gbetagamma to promote desensitization and of a protein that sequesters Gbetagamma to inhibit desensitization. Desensitization was also not inhibited by a Gq/11 C-terminal peptide or antiserum directed toward the C-terminus of Gq/11, nor was it reversed with the addition of Gbetagamma to membranes exhibiting desensitized LH/CG-R, suggesting that desensitization is independent of coupling of the LH/CG-R to Gq/11. These results indicate that agonist-dependent desensitization of LH/CG-R-stimulated AC activity is mediated by a unique mechanism.

Adenylate Cyclase Toxin↗
PubMed1999

Identification of epi-1 locus as a laminin alpha chain gene in the nematode Caenorhabditis elegans and characterization of epi-1 mutant alleles.

A new genetic locus, epi-1, has been identified and mapped, which affects epithelialization of various tissues in the nematode, Caenorhabditis elegans. Seven independent epi-1 mutant alleles have been obtained. These mutants have a wide spectrum of abnormalities, all seem to be caused by a primary defect of basement membrane. We have identified the epi-1 gene as a structural gene of laminin alpha chain. The sequence analyses of the gene and cDNAs revealed that the gene consists of 15 exons and encodes a protein of 3704 amino acids in an open reading frame of 11115 base pairs. The nematode alpha chain is similar to its vertebrate and fly orthologs in the domain structure. The mRNA is trans-spliced to SL1 leader RNA as many of the nematode mRNAs. Mutation sites have been identified in four alleles. Two alleles have nonsense mutations and produce truncated proteins lacking the domain necessary for the formation of a heterotrimeric laminin molecule. The other two alleles have missense mutations in domains VI and IIIb, respectively.

Alleles↗
PubMed1999

Intravenous infusion ascitic fluid during hemodialysis: a study of 108 treatments in 13 uremic cases.

Nephrogenic ascites is a clinical diagnosis defined as persistent ascites in an uremic patient without evidence for a causative underlying disease. It imperils the patient's life with intradialytic hypotension, however there is no effective therapy other than renal transplantation so far. In 13 cases, 108 treatments with i.v. ascites infusion were performed with hemofilter alone or combined with plasmafilter during hemodialysis over past 7-years. The ascitic fluid was filtrated and dialyzed before it was intravenously infused into the blood compartment of the hemofilter. There were a mean of 8.38 treatments per patient in a period of 56 days and 3,275.9 +/- 1,359.5 ml of ascitic fluid were removed per treatment. The patients' appetite and physical ability were considerably improved and the intradialytic hypotensions disappeared immediately following the initiation of ascitic fluid infusions. In this study, one patient was transplanted successfully. The longest interval without ascitic fluid infusion was 127 days. Main side effect was light pyrogenic reaction, which was presented in 12.96% of the total treatments. It is concluded that this method permits to continue hemodialysis, improves the nutritional condition and prolongs the lifespan by conserving and reusing the ascites protein.

Adult↗
PubMed1999

[Relationships of angiotensinogen gene M235T variant with diabetic nephropathy in Chinese type 2 diabetes mellitus].

OBJECTIVE: To investigate whether angiotensinogen(AGT) gene M235T variant is associated with type 2 diabetes mellitus without nephropathy (DM) and/or diabetic nephropathy (DN) in Chinese type 2 diabetes. METHODS: AGT genotypes of 84 cases with DM, 96 with DN and 98 controls were determined by polymerase chain reaction (PCR) amplification and restriction fragment length polymorphism analysis of the region of the variant. RESULTS: Increased frequencies of T allele (0.82) and TT genotype (0.70) were observed in 96 subjects with DN, compared with those observed in 98 control subjects (0.63 and 0. 43 respectively, P = 0.003, P = 0.0004). The odds ratio associated with TT genotype was 3.47 (95% CI 1.51-7.94, P = 0.0033) for DN in analysis adjusted for several DN risk factors. There was no difference in allele distribution between 84 DM patients and the controls. CONCLUSION: TT genotype of the AGT gene might be an independent risk factor of diabetic nephropathy in Chinese patients with type 2 diabetes mellitus.

Adult↗
PubMed1999

[Monitoring of serum lidocaine concentration in tumescent liposuction infiltrated with high-dosage lidocaine and its clinical significance].

OBJECTIVE: This study was carried out to determine the maximum and safe dosage of lidocaine administered in tumescent liposuction. METHODS: In 14 cases of tumescent liposuction using high-dosage, low-concentration lidocaine as local infiltration anesthetic, serum lidocaine concentrations were monitored with automated fluorescence polarization analysis. RESULTS: The time-concentration curve together with clinical manifestations indicated that in tumescent liposuction, lidocaine, under a concentration of 0.1 mg/ml mixed with 1/1,000,000 to 1/2,000,000 epinephrine, could be administered with a dosage of 35 mg/kg body weight as a local infiltration anesthetic while the serum lidocaine was still within the safety limit and no signs of intoxication manifested. The resulting diminution both in pain and blood loss during the operation enhanced the overall operation safety and suction volume. CONCLUSION: This study provides the basis for high-dosage lidocaine administration in tumescent liposuction.

Adult↗
PubMed1999

[The expression of ICAM-1 on the keratinocytes in second degree human burn skin].

OBJECTIVE: To investigate the significance of changes in intercellular adhesion molecule-1 (ICAM-1) expression on keratinocytes(KCs) during wound healing of second degree burn. METHODS: With immunohistochemistry technique, the ICAM-1 expression in second degree burn wounds in patients were investigated at four different postburn periods. The normal skins from 6 burn patients (BNG), the normal skins from 8 healthy volunteers (HVG) and the scar tissues (SG) from 8 patients served as controls. RESULTS: There was poor expression of ICAM-1 on basal cells in normal skins of healthy volunteers, while the expression of ICAM-1 enhanced in normal skins of burn patients. On basal cells in second degree burn wounds, the expression of ICAM-1 slightly increased in the first week postburn, obviously enhanced in the second week, and in the third or fourth week, the expression continued to keep strong. In addition, the ICAM-1 in KCs showed polar distribution, and the expression of ICAM-1 markedly enhanced on the multilayer KCs in neogenetic epithelium and the positive cells arranged columnarly. CONCLUSION: The enhanced expression of ICAM-1 on KCs in second degree burn wounds might be related to invasion of inflammatory cells beneath wound. It might play a role in inducing proliferation and migration of KCs and accelerating epithelization.

Burns↗
PubMed1999

[Human preadipocyte culture and the establishment of hyperplasia and hypertrophy model].

OBJECTIVE: To better understand hyperplasia and hypertrophy properties of human adipose tissue. METHODS: Using an "adhesion-ceiling" culture strategy, fibroblast-like cells from adult pure adipose granules were successfully cultured. RESULTS: The cells were highly homogeneous, highly proliferative and with a high differentiation rate. Their dynamic morphological changes, growth curve, glycerophosphate dehydrogenase pattern, oil red O staining, and reaction to insulin and dexamethasone all verified their preadipocyte identity. Under controlled conditions, the preadipocytes replayed their in vivo hyperplasia and hypertrophy process. CONCLUSION: In mature human adipose tissue there exist functionally active fractions that can be modified. This study laid the basis for further probing into obesity and fat autotransplantation.

Adipocytes↗