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Biomedical subjects

W Zhai

Publications and source records attributed to W Zhai.

29 records · Page 2Linked to original sources
PubMed1997

[A study on type I, III and IV collagen production in CCl4 induced rat liver fibrosis].

OBJECTIVE: To study the dynamic changes of alpha 1 (I), alpha 1 (III) and alpha I (IV) procollagen mRNA and collagen-producing cells during CCl4 induced SD rat liver fibrogenesis (20 weeks). METHODS: The investigations were performed using Northern blot analysis, in situ hybridization and immunohistochemical techniques. RESULTS: The increased expression of alpha 1 (III) procollagen mRNA during fibrogenesis by Northern blot analysis was the most predominant among the three mRNAs studied. However, the increase of alpha 1 (IV) procollagen mRNA expression occurred earlier, while the expression of alpha 1 (I) mRNA did not increase until the middle stage of the experiment. Desmin positive and/or smooth muscle actin positive Ito cells and myofibroblasts (MFs) in and around the necrotic areas expressed alpha 1 (I), alpha 1 (III) and alpha 1 (IV) procollagen mRNA signals detected by in situ hybridization during the early stage of the experiment. All the three procollagen mRNAs were mostly localized in fibroblasts (Fbs) and MFs in the septa during the mid and late stages of fibrosis. CONCLUSIONS: Fbs and MFs were considered as important Col I, Col III and Col IV producing cells in liver fibrosis. Sinusoid endothelia were involved in Col IV synthesis in the fibrotic liver.

Animals↗
PubMed1996

Cloning, characterization and transient expression of the gene encoding a rice U3 small nuclear RNA.

A rice U3 small nuclear RNA (snRNA)-encoding gene has been isolated. The coding region of this gene contains all five conserved sequence boxes common to plant U3 snRNAs. The upstream and downstream regions of the gene harbour characteristic sequence elements required for transcription with RNA polymerase III (pol III), as well as three monocot-specific promoter (MSP) elements [Connelly et al., Mol. Cell Biol.14 (1994) 5910-5919], two of them comprising a palindromic G+C-rich segment. The sequence (TTTAAAA) of the TATA-box in this gene does not fit the established consensus [Marshallsay et al., Plant Mol. Biol. 19(1992) 973-983], making this gene unique among reported snRNA-encoding genes of plants. An RNase protection assay showed that the gene is expressed properly in cucumber protoplasts. We thus suggest that, with other promoter elements present, the TATA-box for RNA pol III-specific snRNA-encoding genes may not be as well conserved as that for RNA pol II-specific genes.

Base Sequence↗
PubMed1996

Antagonistic properties of centrally truncated analogs of [D-Trp(32)]NPY.

We have previously shown that [D-Trp(32)]NPY can competitively antagonize NPY-induced feeding in rats (Balasubramaniam et al. J. Med. Chem. 1994, 37, 811-815). This peptide, however, did not bind to SK-N-MC cells with Y-1 receptors. Since centrally truncated NPY analogs have been shown to bind Y-1 receptors, we synthesized similar analogs of [D-Trp(32)]NPY and investigated their Y-1 (SK-N-MC) and Y-2 (SK-N-BE2) receptor affinities and their properties in human erythroleukemia (HEL) cells. None of the analogs with D-Trp(32) mobilized intracellular calcium, [Ca2]i, in HEL cells. Although Des-AA(6-24)[Aoc(6)]NPY and the corresponding D-Trp(32) analog exhibited no affinity to Y-1 receptors, Des-AA(7-24)[Aoc(6),D-Trp(32)] NPY(6) exhibited weak binding. Replacing Pro(5) in 6 with D-Ala to stabilize the central chain reversal, and hence the antiparallel alignment of the N- and C-terminal regions known to be important for Y-1 binding, resulted in an analog, Des-AA(7-24)[D-Ala(5),Aoc(6),D-Trp(32)]NPY (7), which exhibited moderate antagonist potency in attenuating NPY effects on cAMP and [Ca2+]i, in SK-N-MC and HEL cells, respectively. This analog also shifted the dose-response curve of NPY on blood pressure in anesthetized rats. Deletion of only the 7-17 and/or the incorporation of N-Me-Ala(5), superior beta-turn stabilizer, in 7 did not improve the Y-1 receptor affinity. Des-AA(7-24)[D-Ala(5), Gly(6),D-Trp(32)]NPY exhibited an affinity similar to that of 7, suggesting that a long spacer arm is not necessary for efficient Y-1 receptor interaction. Locking the antiparallel alignment via a 2/26 or 2/27 lactam bridge did not improve the binding. Finally, replacement of D-Ala(5) in 7 with D-Trp dramatically increased both the binding and the antagonistic potencies. Modeling based on the avian pancreatic polypeptide X-ray structure suggested that analogs which have the N- and C-terminal regions in close proximity might exhibit good binding, and that the D-Trp(32) substitution may induce a beta-turn that could be important for exhibiting antagonism. A systematic investigation has resulted in the development of relatively potent Y-1 receptor antagonists. Further structure-activity studies with these compounds and those previously reported by us and other investigators should result in the development of long-acting and receptor selective antagonists.

Amino Acid Sequence↗
PubMed1996

Synthesis, structure, and antagonistic properties of des-Asn29[D-Trp28,32]NPY(27-36).

We have previously reported that [D-Trp32]NPY and its centrally truncated analogues such as des-AA7-24[D-Trp5,32,Aoc6]NPY can competitively antagonize NPY effects on rat hypothalamus and Y1 (SK-N-MC AND HEL) cells, respectively. In continuation of this work, we performed structure-activity studies with C-terminal decapeptide sequence keeping D-Trp at position 32 to develop lower molecular weight Y1-selective antagonists. This study led to the development of des-Asn29[D-Trp28,32]NPY(27-36), which bound to both Y1 (SK-N-MC, Ki > or = 10 microM) and Y2 (SK-N-BE2, Ki = 1.01 +/- 0.03 microM) receptors. This peptide did not exhibit any agonist activity at Y1 receptors, and exhibited comparable potencies in antagonizing the effects of NPY on the synthesis of cAMP and mobilization of [Ca2+]i in HEL cells. However, in SK-N-MC cells, it was more potent in antagonizing the mobilization of [Ca2+]i than inhibition of cAMP synthesis. Substitution of Nva for Gln34 to increase the hydrophobicity without altering the carbon skeleton substantially increased Y1 affinity (Ki = 0.33 +/- 0.15 microM) and imparted Y1 selectivity (Ki for Y2 affinity = 3.16 +/- 0.50). Moreover, this peptide exhibited good antagonistic potency in HEL cells. 2D NMR studies of des-Asn29[D-Trp28,32]NPY(27-36) revealed the existence of a fairly stable loop-like structure between residues 27 and 32 and a less stable one between residues 32 and 36. The increased Y1 affinity of des-Asn29[D-Trp28,32,Nva34]NPY(27-36) may be due to the stabilization of the 32-36 loop by Nva34. It appears therefore that stabilization of the loop structures in these peptides should result in the development of more potent Y1 receptor antagonists. Our investigations also suggest that HEL cells express a homogeneous population of NPY Y1 receptors whereas SK-N-MC cells express high- and low-affinity Y1 receptors coupled to Ca2+ and cAMP, respectively.

Animals↗
PubMed1996

PCR analysis of half-seeds of cereal crops and its application in marker-assisted selection and breeding.

A simple and rapid PCR method was adapted to DNA analysis of cereal seeds. Half-seeds of rice, wheat, and maize were treated with an extraction buffer and the resulting supernatants were used in PCR and RAPD reactions. PCR products amplified from the half-seed DNA extracts were identical with that from leaf tissue DNA extracts when the same specific primers were used in PCR reactions. The remaining half-seeds with embryos could still germinate normally. The half-seed PCR analysis was applied to the identification of resistant genotypes of rice bacterial blight, and it was proved effective in plant breeding and genetic studies.

Breeding↗
PubMed1995

[Study on cells associated with human liver fibrosis].

The cells which related to deposition of extracellular matrix (ECM) in human liver fibrogenesis were investigated with immunohistochemistry (IHC) and nucleic acid hybridization. Results showed that ECMs were high in chronic liver disease (CLD) tissues, particularly collagen III and its mRNA in active-CLD. In this group, cells positive for pre-collagen III pro-peptide (PIIIP) and collagen III mRNA were markedly increased and mostly located in the area connecting interstitium and parenchyma. These collagen producing cells were mainly the interstitial cells identified by IHC and electron microscopy as fat storing cells and associated myofibroblasts and fibroblasts. Their degree of hyperplasia was closely related to the infiltration of inflammatory cells.

Adipocytes↗
PubMed1994

Chromium-induced early changes in renal function among ferrochromium-producing workers.

Urinary biochemical indicators of renal injury were examined in 84 male and 38 female ferrochromium-producing workers exposed to water-soluble chromium compounds [Cr(VI)]. The indicators examined included urinary chromium (U-Cr), alkaline phosphatase (ALP), gamma-glutamyl transferase (gamma-GT), glutamic-oxalacetic and glutamic-pyruvic transaminases (GOT & GPT), lactate dehydrogenase (LDH), N-acetyl-beta-D-glucosaminidase (NAG), total protein (TPr) and beta 2-microglobulin (beta 2-MG). The U-Cr levels in the exposed group were approximately 1.8 times that of the control group. Compared to controls, the activities of gamma-GT, NAG, ALP, GOT and LDH in the urine of workers were significantly increased whenever U-Cr concentration exceeded 45 microgram/g creatinine. The activities of gamma-GT, GOT and NAG were elevated in workers employed for longer than ten years. However, no clear dose-response relationships nor time-effect relationships were found. The present results suggest that long-term exposure to water-soluble chromium [Cr(VI)] produces chronic renal injury. The site of the injury appears to mainly involve the proximal tubule. U-Cr concentrations of > 15 microgram/g creatinine can be proposed as a threshold dosage for nephrotoxicity, and gamma-GT, NAG and ALP are early sensitive indicators of the most valuable for evaluating the renal injury.

Acetylglucosaminidase↗
PubMed1993

Amplification and analysis of a male-specific SRY homologous sequence of cattle.

Based on the highly conserved region of human, rabbit and mouse SRY (sex-determining region Y) sequences, primers were designed for the amplification of the unknown homologous sequence of cattle by polymerase chain reaction (PCR). A 200-bp male-specific amplifying fragment was obtained. The fragment shares high homology with the known SRY gene. By using the cloned fragment as a probe to hybridize to the Southern blot of HindIII-digested cattle genomic DNA, a 1.7-kb male-specific fragment was detected, which is considered to contain the 200-bp fragment. When the same pair of primers was used in amplification of human and goat DNA samples, the 200-bp male-specific fragment could be detected.

Animals↗
PubMed1989

[The nucleotide sequence of the chloroplast psbA gene from Solanum nigrum atrazine resistant biotype and its relevant analysis].

The psbA gene cloned in pSB135 from Solanum nigrum atrazine-resistant biotype was sequenced. It has the same nucleotide sequence as the known atrazine resistance gene from another independent biotype of S. nigrum. On the basis of the deduced amino acid sequences the secondary structure of the 32kD proteins encoded by the psbA genes were compared between atrazine-resistant and susceptible biotypes, and some indications from the protein structure comparison were discussed.

Amino Acid Sequence↗