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J Z Xu

Publications and source records attributed to J Z Xu.

At least 19 recordsLinked to original sources
PubMed2001

Quantitative analysis of agonist-dependent parathyroid hormone receptor trafficking in whole cells using a functional green fluorescent protein conjugate.

Many G-protein coupled receptors (GPCRs) undergo ligand-dependent internalization upon activation. The parathyroid hormone (PTH) receptor undergoes endocytosis following prolonged exposure to ligand although the ultimate fate of the receptor following internalization is largely unknown. To investigate compartmentalization of the PTH receptor, we have established a stable cell line expressing a PTH receptor-green fluorescent protein (PTHR-GFP) conjugate and an algorithm to quantify PTH receptor internalization. HEK 293 cells expressing the PTHR-GFP were compared with cells expressing the wild-type PTH receptor in whole-cell binding and functional assays. 125I-PTH binding studies revealed similar Bmax and kD values in cells expressing either the PTHR-GFP or the wild-type PTH receptor. PTH-induced cAMP accumulation was similar in both cell lines suggesting that addition of the GFP to the cytoplasmic tail of the PTH receptor does not alter the ligand binding or G-protein coupling properties of the receptor. Using confocal fluorescence microscopy, we demonstrated that PTH treatment of cells expressing the PTHR-GFP conjugate produced a time-dependent redistribution of the receptor to the endosomal compartment which was blocked by pretreatment with PTH antagonist peptides. Treatment with hypertonic sucrose prevented PTH-induced receptor internalization, suggesting that the PTH receptor internalizes via a clathrin-dependent mechanism. Moreover, co-localization with internalized transferrin showed that PTHR-GFP trafficking utilized the endocytic recycling compartment. Experiments using cycloheximide to inhibit protein synthesis demonstrated that recycling of the PTHR-GFP back to the plasma membrane was complete within 1-2 h of ligand removal and was partially blocked by pretreatment with cytochalasin D, but not nocodazole. We also demonstrated that the PTH receptor, upon recycling to the plasma membrane, is capable of undergoing a second round of internalization, a finding consistent with a role for receptor recycling in functional resensitization.

Algorithms↗
PubMed2001

A study on pathogenicity of hepatitis G virus.

AIM: To study the pathogenicity of hepatitis G virus (HGV) and observe the genesis and pathological process of hepatitis G. METHODS: HGV-RNA in serum was detected by RT-PCR assay. The immunohistochemical assays of liver tissue were performed with HGV monocoloned antibody (McAb) expressed from the region of HGV NS5 nucleic acid sequence. The clinical and pathological data of 52 patients with hepatitis G were discussed. In animal experiment, the Chinese Rhesus monkeys were infected with the serum of a patient with HGV infection. And the dynamic changes in serology and liver histology of animals were observed. RESULTS: One hundred and fifty-four patients with HGV-RNA positive were selected from 1552 patients with various kinds of hepatitis. Of 154 patients with HGV infection, 52 were infected with HGV only, which accounted for 33.8 (52/154) and 102 with positive HGV-RNA were super-infected with other hepatitis viruses, which accounted for 66.2 (102/154). The clinical and pathological observation showed that the acute and chronic hepatitis could be induced by HGV. The slight abnormality of transaminases ALT and AST in serum of monkeys lasted nearly 12 months and histological results showed a series of pathological changes. CONCLUSION: HGV is a hepatotropic virus and has pathogenicty.

Acute Disease↗
PubMed2000

Rat homolog of sulfonylurea receptor 2B determines glibenclamide sensitivity of ROMK2 in Xenopus laevis oocyte.

Recent studies showed that coexpression of Kir6.1 or Kir6.2 with the sulfonylurea receptor (SUR1, SUR2A, or SUR2B) reconstituted an inwardly rectifying, ATP-sensitive K(+) channel that was inhibited by glibenclamide (2, 15-17). Here we report the isolation of a rat homolog of mouse SUR2B (denoted rSUR2B) from a rat kidney cDNA library. The rSUR2B sequence contains a 4,635-bp open reading frame that encodes a 1,545-amino acid polypeptide, showing 67% shared identity with SUR1 (a pancreatic beta-cell isoform) and 98% with both SUR2A (a brain isoform) and SUR2B (a vascular smooth muscle isoform). Consistent with the predicted structures of other members of the ATP-binding cassette (ABC) superfamily, the sequence of rSUR2B contains 17 putative membrane-spanning segments. Also, predicted Walker A and B consensus binding motifs, present in other ABC members, are conserved in the rSUR2B sequence. RT-PCR revealed that rSUR2B is widely expressed in various rat tissues including brain, colon, heart, kidney, liver, skeletal muscle, and spleen. The intrarenal distribution of the rSUR2B transcript was investigated using RT-PCR and Southern blot of microdissected tubules. The rSUR2B transcript was detected in proximal tubule, cortical thick ascending limb, distal collecting tubule, cortical collecting duct, and outer medullary collecting duct, but not medullary thick ascending limb. This distal distribution overlaps with that of ROMK. Coexpression of rSUR2B with ROMK2 cRNA (in 1:10 ratio) in Xenopus laevis oocytes resulted in whole cell Ba(2+)-sensitive K(+) currents that were inhibited by glibenclamide (50% inhibition with 0.2 mM glibenclamide). In contrast, rSUR2B did not confer significant glibenclamide sensitivity to oocytes coinjected with ROMK1 or ROMK3. The interaction between ROMK2 and rSUR2B was further studied by coimmunoprecipitation of in vitro translated rSUR2B and ROMK2. In agreement with the functional data, the rSUR2B protein was coimmunoprecipitated with ROMK2 in the ROMK2-rSUR2B cotranslated samples. Our data demonstrate that ROMK2, but not ROMK1 and ROMK3, can interact with rSUR2B to confer a sulfonylurea-sensitive K(+) channel, implicating SUR proteins in forming and regulating renal ATP-sensitive K(+) channels. The ROMK isoform specificity of glibenclamide effects suggests that the NH(2) terminus of the ROMK protein mediates rSUR2B-ROMK2 interactions.

ATP-Binding Cassette Transporters↗
PubMed2000

[Regulation on growth and accumulation of total alkaloid in Leonurus artemisia (Lour.)S.Y. Hu by various microfertilizers].

OBJECTIVE: To trace the effects of various microfertilizers on the growth and accumulation of total alkaloid in Leonurus artemisia. METHOD: The total alkaloid was determined by spectrophotometry. RESULT: Microfertilizers of different concentrations could facilitate the growth of L. artemisia in various degrees and Mn-fertilizer of standard concentration and Cu-fertilizer of excessive concentration could help raise the output of the plant markedly by up to 43.6% and 55.2% respectively. Microfertilizers of different concentrations could improve the content of total alkaloid in L. artemisia: Mn-fertilizer of standard concentration and B-fertilizer of excessive concentration could enhance the contents of total alkaloid up to 2.15% and 2.09% respectively. Mn-fertilizer and Cu-fertilizer of standard concentration have been proved very useful in improving the resistibility and ability of the plant to survive summer safely, and Fe-fertilizer of standard concentration could bring the plant an obvious increase of output after surviving summer. CONCLUSION: Application of Mn-fertilizer of standard concentration is very important for cultivating L. artemisia of excellent quality and high output.

Alkaloids↗
PubMed1998

The A kinase anchoring protein is required for mediating the effect of protein kinase A on ROMK1 channels.

In the present study, we have used the two-electrode voltage-clamp and patch-clamp techniques to study the effects of forskolin and cAMP on the ROMK1 channels, which are believed to be the native K+ secretory channels in the kidney. Addition of 1 microM forskolin or 100 microM 8-bromo-cAMP, within 10 min, has no significant effect on the current of ROMK1 channels expressed in Xenopus oocytes. In contrast, application of 1 microM forskolin, within 3 min, significantly increased whole-cell K+ current by 35%, when ROMK1 channels were coexpressed with the A kinase anchoring protein AKAP79, which was cloned from neuronal tissue. Two lines of evidence indicate that the effect of forskolin is mediated by a cAMP-dependent pathway: (i) Addition of 100 microM 8-bromo-cAMP mimics the effect of forskolin and (ii) the effect of forskolin and cAMP is not additive. That AKAP is required for the effect of cAMP is further supported by experiments in which addition of ATP (100 microM) and cAMP (100 microM) restored the activity of run-down ROMK1 channels in inside-out patches in oocytes that coexpressed ROMK1 and AKAP79 but not in those that expressed ROMK1 alone. Moreover, when we used RII, the regulatory subunit of type II protein kinase A, in an overlay assay, we identified a RII-binding protein in membranes obtained from the kidney cortex but not in membranes from oocytes. This suggests that the insensitivity of ROMK1 channels to forskolin and cAMP is due to the absence of AKAPs. We conclude that AKAP may be a critical component that mediates the effect of protein kinase A on the ROMK channels in the kidney.

Adenosine Triphosphate↗
PubMed1998

Localization of the extracellular Ca2+/polyvalent cation-sensing protein in rat kidney.

We previously identified transcripts encoding a G protein-coupled, extracellular calcium/polyvalent cation-sensing receptor, RaKCaR, in rat kidney (D. Riccardi, J. Park, W.-S. Lee, G. Gamba, E. M. Brown, and S. C. Hebert. Proc. Natl. Acad. Sci. USA 92:131-135, 1994), which was proposed to provide the mechanism for modulating a variety of renal functions in response to changes in extracellular Ca2+ (E. M. Brown. In: Handbook of Physiology. Bethesda, MD: Am. Physiol. Soc., 1992, sect. 8, vol. 2, chapt. 39, p. 1841-1916; and S. C. Hebert. Kidney Int. 50: 2129-2139, 1996). Here, we examine the cellular and regional distribution of receptor protein by immunofluorescence microscopy using a polyclonal antibody raised against a 22 amino acid region of the NH2 terminus of the receptor. The most intense fluorescence was seen at the basolateral border of cortical thick ascending limb cells. Basolateral staining for the receptor was also detected in medullary thick ascending limbs, in macula densa cells identified by costaining with antibody to brain nitric oxide synthase, NOS-B1, and in distal convoluted tubule cells distinguished by costaining for the apical thiazide-sensitive Na(+)-Cl- cotransporter. Apical anti-RaKCaR staining was detected at the base of the brush border of proximal tubules with decreasing intensity from S1 to S3 segments. In cortical collecting ducts, anti-RaKCaR staining was detected in some, but not all, type A intercalated cells identified by costaining with anti-H(+)-ATPase and anti-AE1 Cl-/HCO3- exchanger antibodies. The present study demonstrates that RaKCaR protein is expressed in many different nephron segments and that the polarity of receptor expression varies with cell type along the nephron. These results suggest potential roles for the extracellular Ca2+/ polyvalent cation-sensing receptor in responding to both circulating and urinary concentrations of divalent minerals and potentially other polyvalent cations (e.g., aminoglycoside antibiotics) to modulate nephron function.

Animals↗
PubMed1998

Partially active channels produced by PKA site mutation of the cloned renal K+ channel, ROMK2 (kir1.2).

The activity of the cloned renal K+ channel (ROMK2) is dependent on a balance between phosphorylation and dephosphorylation. There are only three protein kinase A (PKA) sites on ROMK2, with the phosphorylated residues being serine-25 (S25), serine-200 (S200), and serine-294 (S294) (Z.-C. Xu, Y. Yang, and S. C. Hebert. J. Biol. Chem. 271: 9313-9319, 1996). We previously mutated these sites from serine to alanine to study the contribution of each site to overall channel function. Here we have studied each of these single PKA site mutants using the single-channel configuration of the patch-clamp technique. Both COOH-terminal mutations at sites S200A and S294A showed a decreased open channel probability (Po), whereas the NH2-terminal mutation at site S25A showed no change in Po compared with wild-type ROMK2. The decrease in Po for the S200A and S294A mutants was caused by the additional presence of a long closed state. In contrast, the occurrence of the S25A channel was approximately 66% less, suggesting fewer active channels at the membrane. The S200A and S294A channels had different kinetics compared with wild-type ROMK2 channels, showing an increased occurrence of sublevels. Similar kinetics were observed when wild-type ROMK2 was excised and exposed to dephosphorylating conditions, indicating that these effects are specifically a property of the partially phosphorylated channel and not due to an unrelated effect of the mutation.

Animals↗
PubMed1997

Localization of the ROMK protein on apical membranes of rat kidney nephron segments.

The ATP-sensitive, inwardly rectifying K+ channel, ROMK, has been suggested to be the low-conductance ATP-sensitive K+ channel identified in apical membranes of mammalian renal thick ascending limb (TAL) and cortical collecting duct (CCD). Mutations in the human ROMK gene (KIR 1.2) have been identified in kindreds with neonatal Bartter's syndrome. In the present study, we generated polyclonal antibodies raised against both a COOH-terminal (amino acids 252-391) ROMK-maltose binding protein (MBP) fusion protein and an NH2-terminal (amino acids 34-49) ROMK peptide. Affinity-purified anti-ROMK COOH-terminal antibody detected the 45-kDa ROMK protein in kidney tissues and HEK-293 cells transfected with ROMK1 cDNA. The antibody also recognized 85- to 90-kDa proteins in kidney tissue; these higher molecular weight proteins were abolished by immunoabsorption with ROMK-MBP fusion protein and were also detected on Western blots using anti-ROMK NH2-terminal antibody. Immunofluoresence studies using anti-ROMK COOH-terminal antibody showed intense apical staining along the loop of Henle and distal nephron; staining with preimmune and immunoabsorbed serum was negative. When colocalized with distal nephron markers [the thiazide-sensitive cotransporter (rTSC1), the bumetanide-sensitive cotransporter (rBSC1), the vacuolar type H(+)-ATPase, and neuronal nitric oxide synthase (NOS I)], the ROMK protein was found primarily at the apical border of cells in the TAL, macula densa, distal convoluted tubule, and connecting tubule. Within the CCD, the ROMK protein was expressed in principal cells and was absent from intercalated cells. The tubule localization and polarity of ROMK staining are consistent with the distribution of ROMK mRNA and provide more support for ROMK being the low-conductance K+ secretory channel in the rat distal nephron.

Amino Acid Sequence↗
PubMed1994

A new method, distribution-analyzing latex immunoassay (DALIA), to measure specific immunoglobulin G against mite and wheat allergen in human sera.

A distribution-analyzing latex immunoassay (DALIA), based on the agglutination of latex particles coupled with mite or wheat allergen, was developed to determine allergen-specific IgG in human sera. The immune complex between chemically coupled-allergen latex and specific IgG was agglutinated specifically and efficiently by employing an IgM-type monoclonal second antibody with strong amplification activity. The extent of agglutination was evaluated by determining the relative ratio of volumes (RV) of agglutinates to residual nonagglutinating particles with a particle counter. This method exhibited a high sensitivity (detection limit < or = 5 units/ml) in the determination of allergen-specific IgG, and no influence of inhibitory factors such as competitive antibodies (specific-IgA, -IgM) and nonspecific IgG (< or = 320 mg/ml) was observed. The concentrations of specific IgG against mite allergen in the sera of 130 allergy patients with atopic dermatitis and 52 normal subjects were 22.3 +/- 12.3 and 16.5 +/- 4.2 units/ml, respectively, and the concentrations of specific IgG against wheat allergen in the same two groups were 5.4 +/- 4.2 and 2.1 +/- 2.2 units/ml, respectively. The coefficients of variation of intra- and interassay ranged from 3.4% to 11.2% in both cases. The present method is an excellent homogeneous immunoassay which may be used as a routine assay that can measure 50 samples per hour without prior treatment.

Allergens↗
PubMed1993

Spectrophotometric assay of superoxide dismutase activity based on the activated autoxidation of a tetracyclic catechol.

A new spectrophotometric assay of superoxide dismutase (SOD) activity is described. The assay is based on the SOD-mediated increase in the rate of autoxidation of 5,6,6a,11b-tetrahydro-3,9,10-trihydroxybenzo[c]fluorene (BXT-01050) in aqueous alkaline solution. This autoxidation yields a chromophore with a maximal absorbance wavelength of 525 nm. The optimized assay of SOD activity is performed at pH 8.8, 37 degrees C, in 50 mM air-saturated 2-amino-2-methyl-1,3- propanediol buffer containing 3 mM boric acid and 0.1 mM diethylenetriaminepentaacetic acid. The kinetic measurement of 525-nm absorbance is performed for 1 min upon addition of BXT-01050. BXT-01050 is stabilized in stock solution acidified at pH 1.5. The SOD activity is determined from the Vs/Vc ratio of the autoxidation rates measured in the presence (Vs) and in the absence (Vc) of sample. One SOD activity unit (U-525) has been defined as the activity that doubles the autoxidation background (Vs/Vc = 2). The equation that fits the standard curve is the same with all studied SODs. Another reagent, 1,4,6-trimethyl-2-vinylpyridinium trifluoromethanesulfonate, directly eliminates interference due to sample mercaptans such as glutathione by means of a very fast alkylation reaction. A fast and reproducible measurement of SOD activity requires only a single determination per sample. At pH 8.8, an optimal assay sensitivity is achieved without strongly affecting the activity of known SODs such as Cu/Zn-, Mn-, or Fe-SOD.

Animals↗
PubMed1992

A conserved retina-specific gene encodes a basic motif/leucine zipper domain.

Using subtraction cloning, we have isolated a human cDNA, AS321, which is expressed in retina and retinoblastoma cell lines but not in any other tissue or cell line tested. AS321 mRNA is detected in all cells of neural retina, with a high level of expression in photoreceptors. The polypeptide sequence deduced from the cDNA reveals consensus phosphorylation sites for protein kinase A and proline-directed protein kinase. Its C-terminal region contains a basic motif and a leucine zipper domain similar to the DNA binding proteins of the jun and fos oncoprotein family, and it shows a strong similarity to the product of an avian retroviral oncogene, v-maf. The gene for AS321 is conserved during evolution and is expressed in vertebrate retina. We propose to name the gene NRL (neural retina leucine zipper.

Amino Acid Sequence↗
PubMed1992

[A study of cyclic nucleotide acids in the serum in patients with myasthenia gravis].

The levels of cAMP and cGMP in serum of 100 patients with myasthenia gravis have been measured by 125I-RIA. The results showed that cAMP and cGMP were higher in the patients than in the controls significantly (P < 0.001). In 33 cases of these patients after using anticholinesterase drugs and prednisone, the levels of cAMP and cGMP reduced significantly. According to our study, we presumed that there would be cyclic nucleotide acid metabolic disturbances in patients with MG and cAMP might play a regulatory role in morbidity of MG.

Cyclic AMP↗
PubMed1992

[Long-term results of small cell lung cancer treated by surgical resection and multimodality therapy].

241 patients with small cell lung cancer (SCLC) were operated in our hospital from 1957 to 1985. The early postoperative mortality was 1.7%. The 5-yr survival rate was 23.2% (56/241). The 10-yr survival rate was 16.5% (15/91) (only 4 patients died during 5-yr to 10-yr after surgery but none of them died of SCLC). We analysed the 5-yr survival group. The 5-yr survival rate for stage I patients was 52.3% (23/44), stage II 34.1% (14/41), stage III 12.8% (19/149) [IIIa12.3% (17/138),IIIb 18.2% (2/11)]. Stage IV 0 (0/3). The P value: I vs IIIaP < 0.001, II vs IIIaP < 0.01. 125 patients received chemotherapy (CT) and/or radiotherapy (RT) postoperatively (group A) and the other 112 cases received surgical resection only (group B). 4 patients (3 IIIa, 1 IIIb) who died in early postoperative period were not counted. The 5-yr survival rate for group A and B was 40.8% (51/125) and 4.5% (5/112) respectively, P < 0.001; for group A and B stage I was 71.4% (20/28) and 18.8% (3/16), P < 0.01;for group A and B stage II was 54.5% (12/22) and 10.5% (2/19), P < 0.01; for group A and B stage IIIa was 25.4% (17/67) and 0 (0/71), P < 0.001. There were no differences in 5-yr survival rate on types of surgical resection and locations of the disease. The present results revealed that the total 5-yr survival rate for SCLC was 23.2%, among them for resection only was 4.5% and for resection plus multimodality therapy was 40.8%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Comparison study of various traditional Chinese medicine therapy in acute phase of cor pulmonale].

This article is a retrospective summary of 419 cases of acute phase of cor pulmonale from 1978 to 1989. These patients were divided into 4 groups by various TCM therapy, as a part of whole treatment combining TCM with the western medicine. They were (1) clearing the lung heat and eliminating the phlegm; (2) clearing the lung heat, tonifying the Qi and activating the blood; (3) clearing the lung heat, tonifying the Qi and nourishing the Yin; (4) clearing the lung heat, nourishing the Yin, tonifying the Qi and activating the blood. Under a similar condition, comparing the effects of the 4 various therapies in clinical efficacy and blood gas analysis, the authors found that the 4th therapy was the best among the 4 groups. According to the relation of modern pharmacology study of each single therapy, the authors explored the principle of clearing the lung heat, nourishing the Yin, tonifying the Qi and activating the blood therapy. The authors held that the therapy is a better one to treat many pathological changes in acute phase of cor pulmonale.

Blood Gas Analysis↗
PubMed1990

Monoclonal antibody to human osteosarcoma: a novel Mr 26,000 protein recognized by murine hybridoma TMMR-2.

Three murine hybridomas (TMMR-1-3) were developed by repeated immunizations of mice with four different human osteosarcoma cell lines in an alternating sequence of inoculations. The monoclonal antibodies were screened for reactivities to cultured cell lines and tissue sections of osteosarcomas using flow cytometry and immunohistochemical techniques. TMMR-2 is a highly specific antibody (IgG1) that reacted with all 14 osteosarcoma tumors and eight human osteosarcoma cell lines tested, including the established human osteosarcoma cell lines HOS and Saos-2. Benign neoplastic cells from two osteoblastomas, osteoblasts from regions of reparative osteoid formation and neonatal new bone, are also reactive with TMMR-2. TMMR-1 has mesenchymal specificity while TMMR-3, although reactive with osseous differentiated cells, also reacted with mitotic cells of all cell types. Characterization of antigen structure by Western immunoblotting revealed that TMMR-2 reacted with a 100 degrees C heat labile mercaptoethanol-sensitive Mr 26,000 protein, and TMMR-3 recognized a mercaptoethanol-resistant Mr 97,000 protein whereas TMMR-1 reacted with a series of bands from 65,000 to 85,000 molecular weight, all of which were mercaptoethanol sensitive. TMMR-1 and TMMR-2 monoclonal antibodies showed complement-independent inhibition of [3H]thymidine incorporation into DNA, but did not exhibit cytotoxic activity. The results suggest that TMMR-2 is a specific antibody that recognizes an osteoblast/osteocyte surface antigen present in normal, reactive, and neoplastic disorders of bone. The inhibitory effects on DNA synthesis in cultured osteosarcoma cells by TMMR-2 indicate an important cell growth/proliferation role of this surface antigen. These monoclonal antibodies, in combination with other known antibodies, can be used to characterize mesenchymal cell surface antigenic structure and differentiation.

Animals↗
PubMed1988

[Surgical treatment of the second primary lung cancer].

1168 patients with primary carcinoma of lung had been treated by surgery in our hospital from 1976 to 1985. Among these patients we found 7 patients with second primary lung cancer. The incidence is 0.6% in this series. The criteria of the second primary lung cancer are: different histological type; synchronous lesion located in the contralateral lung or in different lobes or segments of the ipsilateral lung which must all be stage I; or prolonged interval between the initial and second resection (metachronous lesions), but the initial lesion must be proved as stage I. Lobectomy was the most common procedure for the initial and second resections. The result of the treatment was satisfactory with one patients surviving 6 years and 6 months. There was no operative mortality or complications. We consider that careful diagnosis is important and continued follow-up is necessary for all bronchogenic carcinomas.

Adenocarcinoma↗