Biomedical subjects

R Zhang

Publications and source records attributed to R Zhang.

At least 109 records · Page 6Linked to original sources

PubMed2001

[Simulation and display methods of spatial data in landscape ecology].

Simulating and display ecological data over large geographic areas require much time, many resources, and considerable special training. Based on the latest researches all over the world, 7 simulation methods of ecological spatial data and 4 data display formats were reviewed, and several sampling ways were also discussed. Sample density and its spatial distribution, spatial dependence, and estimation accuracy were primarily considered to be the major factors influencing surface representation.

Computer Simulation↗

PubMed2001

[Ossifying fibromyxoid tumor of soft parts: a clinicopathological analysis of eight cases].

OBJECTIVE: To study the morphological characteristics and immunophenotype of ossifying fibromyxoid tumor of soft parts (OFT) with a discussion of its histogenesis. METHODS: The clinical, pathological and immunohistochemical features of 8 cases of OFT were evaluated. RESULTS: All 8 cases were middle to old aged patients, ranged from 43 -- 78 years (mean 63 years). Clinically, the majority presented as slowly growing painless masses that located in subcutis of the proximal extremities. Histologically, the tumor was characterized by the following three unique features which have diagnostic value. (1) The tumor was well circumscribed and encapsulated with an incomplete bony shell composed of metaplastic bone within the capsule in most cases; (2) The tumor parenchyma consisted of lobules of variable size and cellularity. The tumor cells within each lobule were rounded to short spindled with pale-staining or eosinophilic cytoplasm; (3) The tumor cells arranged in nests, cords, or laciform pattern, and were embedded in a characteristic fibromyxoid to collagenized stroma. Immunohistochemically, all 7 cases tested were positive for vimentin and NSE, while 6 cases expressed S-100 protein and 2 cases expressed desmin. Follow-up information showed recurrences in two patients 2 and 15 years after local excision. CONCLUSIONS: OFT is a distinctive soft tissue tumor of potentially low-grade malignancy which occurred predominantly in middle to old aged patients. The characteristic bony shell, the unique cytological appearance and arrangement of the cells are pathognomonic features of OFT. Our immunohistochemical result supported a Schwann-cell origin.

Adult↗

PubMed2001

[Pyruvate oxidase gene from Streptococcus sanguis: molecular cloning and sequence analysis of the gene].

OBJECTIVE: To clone and sequence the gene of pyruvate oxidase (Sopox) from Streptococcus sanguis. METHODS: The PCR primers for Sopox gene were designed and synthesized according to the sequence of pyruvate oxidase (spxB) gene of S. pneumonia. The amplified PCR product was cloned into pUC18 and then subcloned into M13mp18 and M13mp19. The DNA sequence of the gene was analyzed. RESULTS: Sopox gene was successfully amplified from S. sanguis ATCC10557. The nucleotide sequence of the whole gene was revealed to be 1788 base pairs with one open reading frame coding pyruvate oxidase with 591 amino acid residuals. CONCLUSION: The clone and DNA sequence of Sopox gene were obtained which could serve as a foundation on which to elucidate the molecular mechanisms of hydrogen peroxide production and its regulation by oral streptococci.

Base Sequence↗

PubMed2001

[Addition internal standard method in chromatographic quantitative analysis].

Internal standard method is a conventional chromatographic quantitative method which requires one or several internal standards added. The internal standard component must not be contained in the sample and need a good separation between the internal standard and sample components. In many cases selecting an internal standard is not convenient or even restricted by the seperation of components. In this paper, we try to combine the internal standard method and the addition method to form a new chromatographic quantitation method named addition internal standard method. The principles of addition internal standard method are suitable to not only chromatographic quantitation but also polarography etc. The related theory and foundation of the method are defined. The operation steps and the conditions suitable to the method are discussed. The advantages and disadvantages of this method are explained in detail.

Chromatography↗

PubMed2001

[Inhibitory effects of melatonin on the development of 17-beta-estradiol induced prolactinoma in relation to plasma prolactin and peroxidative lipid contents].

In the present study, we have examined inhibitory effects of melatonin on the development of pituitary prolactin-producing tumors (prolactinoma) induced by 17-beta-estradiol (E(2)) in vivo. The prolactinomas were established by implanting E(2)-laden silastic capsules subcutaneously in Sprague-Dawley male rats weighing 80 approximately 100 g. Melatonin (0.05, 0.25, 0.50, 1.00, and 2.00 mg/0.1 ml/rat) was administrated subcutaneously at l8:00 h for 90 days, beginning from d 7 prior to tumor induction. Controls were given equal volumes of 4 percent; alcohol in 0.9 percent; saline. Our results showed: (1) In control group and groups given respectively 0.05, 0.25, 0.50, 1.00 and 2.00 mg melatonin, the weight of prolactinoma was 115.0+/-71.0, 85.2+/-41.0, 58.9+/-24.1, 72.7+/-23.6, 79.3+/-56.1, 74.5+/-46.8 mg respectively; the plasma prolactin (PRL) content was 493.46+/-33.3, 373.78+/-26.5, 125.13+/-13.3, 201.79+/-11.2, 418.88+/-41.3, 281.94+/-36.4 ng/ml respectively; the plasma peroxidative lipid content was 1.21+/-0.23, 0.89+/-0.32, 0.92+/-0.27, 0.64+/-0.24, 0.41+/-0.14 and 0.43+/-0.21 delta233/ml respectively. (2) The correlation coefficients between tumor weight and plasma PRL content, tumor weight and plasma peroxidative lipid content, and plasma PRL content and plasma peroxidative lipid content were 0.8738, 0.5550 and 0.2141 respectively. These results indicate: (1) The dosages of 0.25 (P<0.01) and 0.50 (P<0.05) mg, but not 0.05 (P>0.05), 1.00 (P>0.05) and 2.00 (P>0.05) mg, melatonin significantly inhibited the development of the E(2)-induced prolactinoma and the secretion of PRL in comparison with the matched control. (2) The levels of 0.05 approximately 2.00 (P<0.05 approximately 0.00l) mg melatonin showed a dose-dependent antioxidative action. (3) There are positive correlation between tumor weight and plasma PRL content (P<0.05), but no correlation between tumor weight and plasma peroxidative lipid content (P>0.05), and plasma PRL content and plasma peroxidative lipid content (P>0.05). Therefore, our experiments demonstrate that the inhibition of the development of E(2)-induced prolactinoma by adequate dosage of melatonin may be related to the inhibitory effects of MLT on the secretion of PRL, but not to the antioxidative action of MLT.

Animals↗

PubMed2001

[Study on apoE gene polymorphism in Chinese type II b hyperlipidemia].

OBJECTIVE: To study apolipoprotein(apo) E polymorphism and its relationship with plasma lipids and apolipoproteins levels in Chinese patients with type II b hyperlip oproteinemia. METHODS: apoE genotypes were assayed by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method, serum lipids were determined by enzyme method, and apolipoproteins were measured by radial immunodiffusion assay in 74 type II b hyperlipidemia patients whose fasting serum lipids levels were TG > or = 2.26 mmol/L, TC > or = 6.21 mmol/L and in 230 healthy subjects whose fasting serum lipids levels were TG < 1.82 mmol/L, TC < 6.21 mmol/L from a population of Chinese Han nationality in Chengdu area. RESULTS: Compared with the control group, the serum TG, TC, LDLC, nHDLC, apoA II, apoB100, apoC II, apoC III, apoE levels and TG/HDLC ratio in patients with type II b hyperlipidemia were significantly increased(P < 0.001), and the serum HDLC levels and apoE/apoC III ratio were significantly decreased (P < 0.05). ApoE3/3 genotype and allele epsilon 3 frequency in type II b hyperlipidemia group and control group were both the highest. In type II b hyperlipidemia group, allele epsilon 2 frequency tended to increase and allele epsilon 4 frequency tended to decrease as compared with those in the control group (P > 0.05). In type II b hyperlipidemia group the genotype of apoE2 was associated with higher serum TG, apoC II, apoE levels and apoE/apoC III ratio when compared with the genotype of apoE3; the genotype of apoE4 was associated with higher serum TC, nHDLC and apoE levels when compared with the genotypes E3 and E2 (P < 0.001). CONCLUSION: The alleles epsilon 2 and epsilon 4 are associated with serum TG, TC, nHDLC, apoC II and apoE levels to some extent in type II b hyperlipide in Chinese population.

Adult↗

PubMed2001

[Expression of pyruvate oxidase gene sopox from Streptococcus sanguis in E. coli].

OBJECTIVE: To reconstruct the expression plasmid of Sopox gene for further understanding the regulation of its expression. METHODS: Sopox was recombined with expression vector pBV220 and the expression of Sopox in E. coli JM105 was observed after transformation. RESULTS: pBV220/Sopox/JM105 expressed a protein with molecular weight of 65 kd on SDS-PAGE after induction, and the expression reached the maximal amount with induction at 42 degrees C for 4 hours. CONCLUSION: Sopox was successfully cloned into pBV220 and expressed in E. coli JM105.

Cloning, Molecular↗

PubMed2001

[Study on extraction process of aqueous part of radix Salvia miltiorrhiza].

OBJECTIVE: To find out the optimum extraction process for total salvianolic acid part of radix Salviae miltiorrhizae. METHOD: The extraction process was studied by orthogonal design with the danshen su content determined by RP-HPLC as index. RESULT: A3B3C2D1 is the best extraction condition of aqueous part from radix Salvia miltiorrhiza. CONCLUSION: This extraction process shows total salvianolic acid has high content and good stability.

Chemistry, Pharmaceutical↗

PubMed2000

Identification of the major positional isomer of pegylated interferon alpha-2b.

Interferons display a wide range of antiviral, antiproliferative, and immunomodulatory activities on a variety of cell types and have been used to treat many diseases including hairy-cell leukemia and hepatitis B and C and have also been applied to other therapeutic areas. To improve the pharmacological properties of interferon (IFN) alpha-2b, a long-acting pegylated form (PEG-IFN) has been developed [PEG, monomethoxy poly(ethylene glycol) with average molecular mass of 12 000 Da]. PEG-IFN is a mixture of pegylated proteins with differing sites of PEG attachment. To identify the major positional isomer in the pegylated material [PEG-IFN(His-34)], NMR studies were conducted on a subtilisin-digested N-acetylated peptide of the major positional isomer [PEG-IFN(His-34)dig], synthetic peptide analogues containing His-34, as well as unmodified IFN and PEG-IFN(His-34). Our studies reveal a novel interferon-polymer attachment site as a histidine-linked interferon conjugate. We show that the major component of PEG-IFN is pegylated in the imidazole side chain of histidine-34. Chemical shift data suggest that pegylation occurs mainly at the N(delta)(1) position in the imidazole side chain of this residue. This positional isomer, PEG-IFN(His-34), comprises approximately 47% of the total pegylated species when PEG-IFN is synthesized under the current experimental conditions at pH 6.5 with an electrophilic derivative of PEG, succinimidyl carbonate PEG. The reversibility of the histidine modification was examined. The PEG-imidazole adduct in the intact protein, PEG-IFN(His-34), is labile but much more stable than in the peptide, PEG-IFN(His-34)dig. Apparently, the tertiary structure of the intact protein protects the His(34)-imidazole ring from depegylation.

Drug Stability↗

PubMed2000

Identification of a novel ligand-receptor pair constitutively activated by ras oncogenes.

The Ras signaling pathway is thought to control the expression of a subset of yet to be defined genes that are crucial for cell growth and differentiation. Here we have identified by differential display a novel oncogenic Ras target, mob-5, encoding a 23-kDa cytokine-like secreted protein. Mob-5 expression could be induced by oncogenic Ha-ras and Ki-ras, but not by normal ras activation. Inhibitors of both Ha-Ras and mitogen-activated protein kinase kinase completely abolished the mob-5 expression in ras transformed cells, with concomitant loss of the transformation phenotype. Using an alkaline phosphatase-tagged Mob-5 as ligand, a putative Mob-5 receptor was identified on the cell surface of oncogenic ras transformed cells. Thus, the Mob-5/Mob-5 receptor may represent a novel putative autocrine loop coordinately activated by ras oncogenes.

Amino Acid Sequence↗

PubMed2000

Biphenylsulfonamide endothelin receptor antagonists. 2. Discovery of 4'-oxazolyl biphenylsulfonamides as a new class of potent, highly selective ET(A) antagonists.

The synthesis and structure-activity relationship (SAR) studies of a series of 4'-oxazolyl-N-(3,4-dimethyl-5-isoxazolyl)[1, 1'-biphenyl]-2-sulfonamide derivatives as endothelin-A (ET(A)) receptor antagonists are described. The data reveal a remarkable improvement in potency and metabolic stability when the 4'-position of the biphenylsulfonamide is substituted with an oxazole ring. Additional 2'-substitution of an acylaminomethyl group further increased the binding activity and provided one of the first subnanomolar ET(A)-selective antagonists in the biphenylsulfonamide series (17, ET(A) K(i) = 0.2 nM). Among the compounds described, 3 (N-(3,4-dimethyl-5-isoxazolyl)-4'-(2-oxazolyl)[1, 1'-biphenyl]-2-sulfonamide; BMS-193884) had the optimum pharmacological profile and was therefore selected as a clinical candidate for studies in congestive heart failure.

Administration, Oral↗

PubMed2000

Crystal structure of human stem cell factor: implication for stem cell factor receptor dimerization and activation.

Stem cell factor (SCF) plays important roles in hematopoiesis and the survival, proliferation, and differentiation of mast cells, melanocytes, and germ cells. SCF mediates its biological effects by binding to and activating a receptor tyrosine kinase designated c-kit or SCF receptor. In this report we describe the 2.3-A crystal structure of the functional core of recombinant human SCF. SCF is a noncovalent homodimer composed of two slightly wedged protomers. Each SCF protomer exhibits an antiparallel four-helix bundle fold. Dimerization is mediated by extensive polar and nonpolar interactions between the two protomers with a large buried surface area. Finally, we have identified a hydrophobic crevice and a charged region at the tail of each protomer that functions as a potential receptor-binding site. On the basis of these observations, a model for SCF small middle dotc-kit complex formation and dimerization is proposed.

Amino Acid Sequence↗

PubMed2000

Neurokinin A, calcitonin gene-related peptide, and dynorphin A (1-8) in spinal dorsal horn contribute to descending inhibition evoked by nociceptive afferent pathways: an immunocytochemical study.

Immunocytochemical technique was used to compare the contents of neurokinin A (NKA), calcitonin gene-related peptide (CGRP), and dynorphin A (1-8) (DynA) on two sides of the lumbar dorsal horn of rats in which the unilateral thoracic dorsalateral funiculus (DLF) was transected while formalin (0.2 ml, 0.5%) was injected equally into two hindpaws. The results showed that all the NKA-like, CGRP-like, and DynA (1-8)-like immunoreactivities were significantly lower in the superficial laminae of the dorsal horn on the side ipsilateral to the lesioned DLF than that on the side with intact DLF. This implies that peripheral noxious inputs activate the supraspinal descending inhibitory systems which in turn modulate the transmission of noxious message at the spinal level by changing the release of related neuropeptides.

Afferent Pathways↗

PubMed2000

An assay for angiotensin-converting enzyme using capillary zone electrophoresis.

A sensitive and rapid method was developed for angiotensin-converting enzyme (ACE) activity determination by capillary zone electrophoresis. Hippuryl-l-histidyl-l-leucine, a synthetic tripeptide, was used as the ACE-specific substrate. Capillary zone electrophoresis was employed to separate the products of the enzymatic reaction and the ACE activity was determined by quantification of hippuric acid, a result of the enzymatic reaction on the tripeptide. The capillary electrophoresis was performed in a 27 cm x 75 micrometer i.d. fused-silica capillary using 200 mM boric acid-borate buffer (pH 9.0) as a run buffer with an applied voltage of 8.1 kV at a capillary temperature of 23 degrees C. The electrophoresis was monitored at 228 nm. Each electrophoretic run requires only a nanoliter of the enzymatic reactant solution, at only 6 min, rendering a powerful tool for the ACE assay.

Calibration↗

PubMed2000

Two diastereomeric saponins with cytotoxic activity from Albizia julibrissin.

Two diastereomeric saponins, julibrosides J1 (1) and J9 (2), both of which show cytotoxic activity, were obtained from the stem bark of Albizia julibrissin Durazz. On the basis of chemical and spectral evidence [L.B. Ma et al., Carbohydr. Res., 281 (1996) 35-46], the structure of 1 was revised as 3-O-[beta-D-xylopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->6) -beta-D-glucopyranosyl]-21-O-[(6S)-2-trans-2-hydroxymethyl-6-methyl-6-O- [4-O-((6R)-2-trans-2,6-dimethyl-6-O-(beta-D-quinovopyranosyl)-2,7- octadienoyl)-beta-D-quinovopyranosyl]-2,7-octadienoyl] acacic acid-28-O-beta-D-glucopyranosyl-(1-->3)-[alpha-L-arabinofuranosyl-(1-->4 )]-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl ester. The diastereoisomer 2 of 1 was identified as 3-O-[beta-D-xylopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->6) -beta-D-glucopyranosyl]-21-O-[(6S)-2-trans-2-hydroxymethyl-6-methyl-6-O- [4-O-((6S)-2-trans-2,6-dimethyl-6-O-(beta-D-quinovopyranosyl)-2,7- octadienoyl)-beta-D-quinovopyranosyl]-2,7-octadienoyl] acacic acid-28-O-beta-D-glucopyranosyl-(1-->3)-[alpha-L-arabinofuranosyl-(1-->4 )]-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl ester. Saponin 2 is a new saponin named julibroside J9. Both julibrosides J1 and J9 show good inhibitory action against the KB cancer cell line in vitro.

Antineoplastic Agents↗

PubMed2000

NF-kappa B is required for H-ras oncogene induced abnormal cell proliferation and tumorigenesis.

Oncogenic mutations in ras lead to constitutive activation of downstream signaling pathways that modulate the activities of transcription factors. In turn, these factors control the expression of a subset of genes responsible for neoplastic cell transformation. Recent studies suggest that transcription factor NF-kappa B contributes to cell transformation by inhibiting the cell death signal activated by oncogenic Ras. In this study, inhibition of NF-kappa B activity by forced expression of a super-repressor form of I kappa B alpha, the major inhibitor of NF-kappa B, markedly decreased the growth rate, saturation density and tumorigenicity of oncogenic H-Ras transformed rat embryo fibroblasts. Such clonally isolated cells overexpressing I kappa B alpha super-repressor not only were viable but also exhibited no sign of spontaneous apoptosis. Inhibition of NF-kappa B in these cells was functionally demonstrated by both the loss of cytokine induced DNA binding activity and a profoundly increased sensitivity to cell death in response to TNF-alpha treatment. In contrast, inhibition of NF-kappa B activity in non-transformed fibroblasts had minimal effect on growth, but rendered the cells resistant to a subsequent transformation by H-ras oncogene. Similar results were also obtained with rat intestinal epithelial cells harboring an inducible ras oncogene. Taken together, these findings suggest that NF-kappa B activity is essential for abnormal cell proliferation and tumorigenicity activated by the ras oncogene and highlight an alternative functional role for NF-kappa B in oncogenic Ras-mediated cell transformation that is distinct from its anti-apoptotic activity. Oncogene (2000) 19, 841 - 849.

Animals↗

PubMed2000

Ca(2+) channel modulation by recombinant auxiliary beta subunits expressed in young adult heart cells.

L-type Ca(2+) channels contribute importantly to the normal excitation-contraction coupling of physiological hearts, and to the functional derangement seen in heart failure. Although Ca(2+) channel auxiliary beta(1-4) subunits are among the strongest modulators of channel properties, little is known about their role in regulating channel behavior in actual heart cells. Current understanding draws almost exclusively from heterologous expression of recombinant subunits in model systems, which may differ from cardiocytes. To study beta-subunit effects in the cardiac setting, we here used an adenoviral-component gene-delivery strategy to express recombinant beta subunits in young adult ventricular myocytes cultured from 4- to 6-week-old rats. The main results were the following. (1) A component system of replication-deficient adenovirus, poly-L-lysine, and expression plasmids encoding beta subunits could be optimized to transfect young adult myocytes with 1% to 10% efficiency. (2) A reporter gene strategy based on green fluorescent protein (GFP) could be used to identify successfully transfected cells. Because fusion of GFP to beta subunits altered intrinsic beta-subunit properties, we favored the use of a bicistronic expression plasmid encoding both GFP and a beta subunit. (3) Despite the heteromultimeric composition of L-type channels (composed of alpha(1C), beta, and alpha(2)delta), expression of recombinant beta subunits alone enhanced Ca(2+) channel current density up to 3- to 4-fold, which argues that beta subunits are "rate limiting" for expression of current in heart. (4) Overexpression of the putative "cardiac" beta(2a) subunit more than halved the rate of voltage-dependent inactivation at +10 mV. This result demonstrates that beta subunits can tune inactivation in the myocardium and suggests that other beta subunits may be functionally dominant in the heart. Overall, this study points to the possible therapeutic potential of beta subunits to ameliorate contractile dysfunction and excitability in heart failure.

Adenoviridae↗

PubMed2000

Crystal structure of human procathepsin X: a cysteine protease with the proregion covalently linked to the active site cysteine.

Human cathepsin X is one of many proteins discovered in recent years through the mining of sequence databases. Its sequence shows clear homology to cysteine proteases from the papain family, containing the characteristic residue patterns, including the active site. However, the proregion of cathepsin X is only 38 residues long, the shortest among papain-like enzymes, and the cathepsin X sequence has an atypical insertion in the regions proximal to the active site. This protein was recently expressed and partially characterized biochemically. Unlike most other cysteine proteases from the papain family, procathepsin X is incapable of autoprocessing in vitro but can be processed under reducing conditions by exogenous cathepsin L. Atypically, the mature enzyme is primarily a carboxypeptidase and has extremely poor endopeptidase activity. We have determined the three-dimensional structure of the procathepsin X at 1.7 A resolution. The overall structure of the mature enzyme is characteristic for enzymes of the papain superfamily, but contains several novel features. Most interestingly, the short proregion binds to the enzyme with the aid of a covalent bond between the cysteine residue in the proregion (Cys10p) and the active site cysteine residue (Cys31). This is the first example of a zymogen in which the inhibition of enzyme's proteolytic activity by the proregion is achieved through a reversible covalent modification of the active site nucleophile. Such mode of binding requires less contact area between the proregion and the enzyme than observed in other procathepsins, and no auxiliary binding site on the enzyme surface is used. A three-residue insertion in a highly conserved region, just prior to the active site cysteine residue, confers a significantly different shape on the S' subsites, compared to other proteases from papain family. The 3D structure provides an explanation for the rather unusual carboxypeptidase activity of this enzyme and confirms the predictions based on homology modeling. Another long insertion in the cathepsin X amino acid sequence forms a beta-hairpin pointing away from the active site. This insertion, thought to be an equivalent of cathepsin B occluding loop, is located on the side of the protein, distant from the substrate binding site.

Amino Acid Sequence↗