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Biomedical subjects

S D Zhang

Publications and source records attributed to S D Zhang.

At least 19 recordsLinked to original sources
PubMed2000

Solid-phase synthesis of muramyl dipeptide (MDP) derivatives using a multipin method.

Solid-phase synthetic method of muramyl dipeptide derivatives is reported. A diverse library of muramyl dipeptides could be potentially synthesized by acylation, reductive alkylation, sulfonamide formation, urea formation, N-alkylation, amine addition, or component Ugi reactions based on this method for drug screening.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed2000

Posterior slope of tibial plateau in Chinese.

The posterior slope of tibial plateau in 25 pairs of Chinese cadaveric tibia was studied. A digital photograph of the lateral profile of each cadaveric tibia was taken, and the posterior slope angles of medial and lateral plateau relative to the anterior tibial cortex were measured. The posterior slope of the medial plateau was 14.8 degrees, and the posterior slope of the lateral plateau was 11.8 degrees. Lateral radiographs of each cadaveric tibia were taken, and the posterior tibial slope angles relative to simulated extramedullary and intramedullary alignment were determined. With radiographic measurement, the posterior slope was 11.5 degrees using intramedullary method, and it was 14.7 degrees using extramedullary method. The posterior slopes increased with the presence of degenerative changes.

Aged↗
PubMed1999

Universality and self-similarity of an energy-constrained sandpile model with random neighbors.

We study an energy-constrained sandpile model with random neighbors. The critical behavior of the model is in the same universality class as the mean-field self-organized criticality sandpile. The critical energy E(c) depends on the number of neighbors n for each site, but the various exponents are independent of n. A self-similar structure with n-1 major peaks is developed for the energy distribution p(E) when the system approaches its stationary state. The avalanche dynamics contributes to the major peaks appearing at E(p(k))=2k/(2n-1) with k=1,2,...,n-1, while the fine self-similar structure is a natural result of the way the system is disturbed.

Journal Article↗
PubMed1996

Pollux, a novel Drosophila adhesion molecule, belongs to a family of proteins expressed in plants, yeast, nematodes, and man.

Adhesion molecules have pivotal roles in cellular processes critical to the development and maintenance of multicellular organisms. Here we describe a new member of the adhesive repertoire encoded by the Drosophila pollux (plx) gene. Marked by a novel 74-amino-acid domain, Plx belongs to a highly conserved family with members in plants, yeast, nematodes, and man, including the human oncoprotein TRE17. Essential for viability, plx mutant analysis indicates that larval death is attributable to asphyxiation brought on by fluid-congested tracheal tubes. Ultrastructural examination of mutant tracheae reveals defects in cell-extracellular matrix contacts. During embryogenesis, Plx uniformly covers the apical surface of cellular blastoderm cells. It is later found regionally concentrated along subsets of central nervous system axon pathways and on the apical surface of the trachea's tubular epithelium. Cell attachment assays demonstrate that Plx can serve as a ligand for cell surface integrins. Plx also contains a motor neuron-selective adhesive site, multiple proteoglycan-binding motifs, and a leucine zipper: all suggest possible associations with additional components of the adhesion complex.

Amino Acid Sequence↗
PubMed1996

[Effect of thyrotropin-releasing hormone analogue (YM14673) on experimental brain contusion and edema in rats].

The effect of TRH analogue, YM14673: N alpha-[[(S)-4-oxo-2-azetidinyl]-carbonyl)-L-histidyl-L-prolinamide] dihydrate, on traumatic brain edema were studied in male Wistar rats. The cerebral contusion was produced by Feeney's dropping weight method. Animals were randomly divided into 4 groups: normal group and YM14673 (0.1 mg.kg-1, i.p.), YM14673 (1.0 mg.kg-1, i.p.) and a control group (given equal volume of physiological saline, i.p.) after cerebral contusion. Contents of water in brain tissue were measured. These results suggest that treatments with YM14673 significantly reduced brain edema than control group (P < 0.05).

Animals↗
PubMed1995

Misexpression of the white (w) gene triggers male-male courtship in Drosophila.

We report here that the general ectopic expression of a tryptophan/guanine transmembrane transporter gene, white (w), induces male-male courtship in Drosophila. Activation of a hsp-70/miniwhite (mini-w) transgene in mature males results in a marked change in their sexual behavior such that they begin to vigorously court other mature males. In transformant populations containing equal numbers of both sexes, most males participate, thus forming male-male courtship chains, circles, and lariats. Mutations that ablate the w transgene function also abolish this inducible behavior. Female sexual behavior does not appear to be altered by ectopic w expression. By contrast, when exposed to an active homosexual courtship environment, non-transformant males alter their behavior and actively participate in the male-male chaining. These findings demonstrate that, in Drosophila, both genetic and environmental factors play a role in male sexual behavior.

ATP-Binding Cassette Transporters↗
PubMed1993

Herpes simplex virus pathogenesis in transgenic mice is altered by the homeodomain protein Hox 1.3.

The DNA sequence TAAT is the core binding motif for the mouse homeodomain protein Hox 1.3 (proposed new name, Hoxa-5). These sequences are present within the multiple TAATGARAT regulatory motifs in the promoters of the immediate-early genes which control herpes simplex virus type 1 replication. To investigate the role of this homeodomain protein in the regulation of herpes simplex virus gene expression and pathogenesis, transgenic mice containing a mouse Hox 1.3 cDNA under the control of the virus- and interferon-inducible Mx 1 promoter were generated. After infection of transgenic mice with herpes simplex virus, Hox 1.3 RNA and protein were expressed at the sites of virus replication. In these transgenic mice, herpes simplex virus replication, spread of virus through the host, and virus-induced mortality were markedly enhanced. Increased spread and replication of herpes simplex virus were also observed in cultured fibroblasts from transgenic mice. This finding suggests that in vivo, Hox 1.3 may increase viral spread by increasing viral replication at the level of the individual infected cells. These results demonstrate that expression of a transgene encoding a single host protein, Hox 1.3, alters the pathogenesis of experimental herpes simplex virus infection. We conclude that a protein that belongs to a class of DNA-binding proteins which are best known for their role in regulating embryonic development may also regulate herpesvirus pathogenesis.

Animals↗
PubMed1992

castor encodes a novel zinc finger protein required for the development of a subset of CNS neurons in Drosophila.

Using an enhancer detection screen, we have identified castor, a new gene required for embryonic CNS development in Drosophila. Embryos that lack castor expression have a diminished CNS axonal network and express engrailed aberrantly late in CNS development. castor is unique among the previously described genes involved in Drosophila neurogenesis in that its expression is restricted to a subset of delaminated CNS neuroblasts and to ventral midline glial precursor cells. The putative castor gene product contains a novel zinc-binding domain and multiple transcriptional activation domains, suggesting that it acts as a transcription factor necessary for the development of a subset of CNS neuronal precursors.

Amino Acid Sequence↗
PubMed1992

Extracorporeal shock wave lithotripsy and methyl tert-butyl ether for gallbladder stones.

Twenty-one patients with gallbladder stones of 1.1-2.6 cm in diameter were treated by extracorporeal shock wave lithotripsy (ESWL) combined with dissolution using methyl tert-butyl ether (MTBE). In 18 of 21 patients, ESWLs were followed by MTBE instillation through a catheter placed percutaneously via the liver and the gallbladder bed under ultrasonographic and fluoroscopic guidance. As a result, 15 of the 18 patients were cleared of their stones after 54 minutes to 3 hours of dissolution. In the other three cases initially treated by MTBE, ESWLs were added because of no dissolution or poor efficacy. Consequently, after additional 3-5 hours of instillation, complete dissolution in one and subtotal dissolution in two were achieved. Our preliminary results indicated that ESWL followed by MTBE dissolution in the management of cholesterol gallbladder stones was reasonable. On the one hand, ESWL can enhance dissolution by increasing the surface area of stone, and on the other hand MTBE can instantly clear the fragments created by ESWL, so that long-term bile acid intake and potential side effects caused by fragment migration might be avoided.

Adult↗
PubMed1991

DNA-drug interactions. The crystal structures of d(TGTACA) and d(TGATCA) complexed with daunomycin.

The anticancer drug daunomycin has been co-crystallized with the hexanucleotide duplex sequences d(TGTACA) and d(TGATCA) and single crystal X-ray diffraction studies of these two complexes have been carried out. Structure solution of the d(TGTACA) and d(TGATCA) complexes to 1.6 and 1.7 Angstrom resolution, respectively, shows two daunomycin molecules bound to the DNA hexamer. Binding occurs via intercalation of the drug chromophore at the d(TpG) step, and hydrogen bonding interactions involving the drug, DNA and solvent molecules. The daunomycin sugar is located in the minor groove of the DNA hexamer and is stabilized by hydrogen bonds between the amino group of the sugar and functional groups on the floor of the groove. The amino sugar of the d(TGATCA) duplex interacts directly with the DNA sequence, while in the d(TGTACA) duplex, the interaction is via solvent molecules. Two other complexes d(CGTACG)-daunomycin and d(CGATCG)-daunomycin have previously been structurally characterized. Comparison of the four structures with daunomycin bound to the triplet sequences 5'TGT, 5'TGA, 5'CGT and 5'CGA reveals changes in the conformation of both the DNA hexamer and the daunomycin upon complexation, as well as the hydrogen bonding and van der Waals' interactions.

Binding Sites↗
PubMed1991

[Clinical trial on the effects of shikonin mixture on later stage lung cancer].

The shikonin mixture was used for 19 cases of later-stage lung cancer who were not the candidates for operation, radiotherapy and chemotherapy. The clinical observation showed that shikonin mixture could inhibit the growth of lung cancer and improve the immune function of the body. The tumors were reduced over 25% in diameter. The effective rate was 63.3%, remission rate 36.9%, survival rate of one year 47.3%. The intermedium survival period was about 10 months, including adenocarcinoma 10 months, squamous carcinoma 12 months. After treatment the life quality of patients were greatly improved. The patients got better appetite and their body weights were increased. They could manage themselves in daily life. The Karnofsky scores were enhanced by 20. The authors also observed that shikonin mixture could relieve such symptoms as cough, bloody sputum and chest pain caused by lung cancer. The levels of cells and interleukin-2 were increased (P less than 0.001). It had no harmful effects on peripheral blood picture, heart, kidney and liver. Shikonin mixture is safe and effective for later-stage cancer.

Adenocarcinoma↗
PubMed1991

[A review of 139 cases of acute necrotic pancreatitis].

One hundred and thirty-nine cases of acute necrotic pancreatitis were treated in our hospital from Oct. 1975 through Feb. 1990. The mode of treatment went through three stages: (1) From Oct. 1975 to Dec. 1980, application of early operation including necrosectomy, gastrostomy, jejunostomy, choledochostomy and postoperative local peritoneal irrigation, with a survival rate of 50%; (2) From Jan. 1981 through Dec. 1987, early operation with regular pancreatectomy as the operation of choice, and peripancreatic exploration, planned postoperative debridement performed at weekly intervals, with a survival rate of 65.45%; (3) From Jan. 1988 through Feb. 1990 the adoptation of the strategy of "Individualization" consisting of early operation for those with apparent signs of inflammation and complications, and late exploration for those without signs of infection and/or complication, with a survival rate rose to 72.41%.

Adolescent↗
PubMed1990

A new kalium channel blocker of Chinese medicinal origin--benzyltetrahydropalmatine hydrochloride.

Benzyltetrahydropalmatine hydrochloride (BTHP) exhibited antiarrhythmic action in animal models. I. Electrophysiological effects of BTHP were investigated in various heart preparations. 1) BTHP markedly prolonged functional refractory period and inhibited adrenaline-induced automaticity. It decreased spontaneously beating rate of right atrium and abolished ouabain-induced delayed afterdepolarization and triggered activity of papillary muscle. 2) In standard microelectrode and contractility experiments BTHP concentration-dependently prolonged the action potential duration (APD) and effective refractory period (FRP) between 1-100 mumol/L; the force of contraction remained unchanged. 3) In voltage clamp experiments BTHP 1-100 mumol/L inhibited in dose-dependent manner the Ik with IC50 of 13 mumol/L and inhibited also Is at high concentration. 4) In monophasic action potential (MAP) of feline ventricle MAPD50 and MAPD90 were prolonged by BTHP in normal myocardium, and shortened APD induced by ischemia and reperfusion was restored to normal level. 5) In ECG and His-bundle electrogram heart rate was reduced; P-R and A-H interval were prolonged, but H-V interval and V duration were unaffected. II. BTHP showed a competitive alpha 1-adrenoceptor-blocking effect with pA2 value of 5.8 and 5.86 in rat anococcygeus muscle and rabbit aortic strips respectively. Radioligand binding assays showed that BTHP had affinity for both alpha 1 and alpha 2-adrenoceptor. The results from these experiments show that BTHP is a new K+ channel blocker of Chinese medicinal origin with alpha 1-adrenoceptor-blocking action.

Alkaloids↗