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Biomedical subjects

Y M Zhang

Publications and source records attributed to Y M Zhang.

At least 19 recordsLinked to original sources
PubMed1992

Glycosylation using a one-electron-transfer, homogeneous reagent. Application to an efficient synthesis of the trimannosyl core of N-glycosylproteins.

Double glycosylation of methyl 2,4-di-O-benzyl-beta-D-mannopyranoside with ethyl 2-O-benzoyl-3,4,6-tri-O-benzyl-1-thio-alpha-D-mannopyranoside using as promoter tris(4-bromophenyl)ammoniumyl hexachloroantimonate, a stable, commercial, and crystalline radical cation, afforded after debenzoylation methyl 2,4-di-O-benzyl-3,6-di-O-(3,4,6-tri-O-benzyl-alpha-D-mannopyranoside in excellent yield. Other mannosyl donors were also investigated.

Carbohydrate Sequence↗
PubMed1992

Preparation and in vitro antiviral activity of liposomes of lipophilic esters of acyclovir.

The long chain acyclovir such as the acyclovir laurate and acyclovir palmitate were prepared directly from acyclovir by application of the usual esterification methods with appropriate acyl chlorides. The lipophilic prodrugs were found to be retained easier by liposomes whereas acyclovir escaped readily from liposomes. When assayed in African green monkey cell cultures against herpes simplex virus type I strain, the acyclovir palmitate liposomes proved to be more active compared with the parent drug and its liposome, suggesting an enhanced compatibility between the ester and liposomal lipids and an increased uptake of encapsulated prodrug by infected cells.

Acyclovir↗
PubMed1991

Studies of the effect on tumor and normal cells in vitro with bioactive materials isolated from algae by a microcalorimetric method.

Recently much attention has been focused on the human physiological actions with bioactive materials from algae to enhance immunocompetence and to strengthen antineoplastic activity. In the study reported in this paper an MS 80 standard Calvet microcalorimeter was used for measuring the thermogram of HeLa, human breast carcinoma (Bcap-37) and diploid fibroblasts from human feral lung (2BS) under conditions with or without the presence of bioactive materials (Sp) from algae. At the same time, the cell number was counted, the inhibition rate of growth and the death rate were obtained. It has been shown that the Sp (100 micrograms/ml) was the growth inhibitor and lethal to tumor cells (Bcap-37 and HeLa), but had no influence on the normal (2BS) cells under the same conditions in vitro.

Biological Factors↗
PubMed1991

Both nonstructural proteins NS2B and NS3 are required for the proteolytic processing of dengue virus nonstructural proteins.

The cleavages at the junctions of the flavivirus nonstructural (NS) proteins NS2A/NS2B, NS2B/NS3, NS3/NS4A, and NS4B/NS5 share an amino acid sequence motif and are presumably catalyzed by a virus-encoded protease. We constructed recombinant vaccinia viruses expressing various portions of the NS region of the dengue virus type 4 polyprotein. By analyzing immune precipitates of 35S-labeled lysates of recombinant virus-infected cells, we could monitor the NS2A/NS2B, NS2B/NS3, and NS3/NS4A cleavages. A polyprotein composed of NS2A, NS2B, and the N-terminal 184 amino acids of NS3 was cleaved at the NS2A/NS2B and NS2B/NS3 junctions, whereas a similar polyprotein containing only the first 77 amino acids of NS3 was not cleaved. This finding is consistent with the proposal that the N-terminal 180 amino acids of NS3 constitute a protease domain. Polyproteins containing NS2A and NS3 with large in-frame deletions of NS2B were not cleaved at the NS2A/NS2B or NS2B/NS3 junctions. Coinfection with a recombinant expressing NS2B complemented these NS2B deletions for NS2B/NS3 cleavage and probably also for NS2A/NS2B cleavage. Thus, NS2B is also required for the NS2A/NS2B and NS2B/NS3 cleavages and can act in trans. Other experiments showed that NS2B was needed, apparently in cis, for NS3/NS4A cleavage and for a series of internal cleavages in NS3. Indirect evidence that NS3 can also act in trans was obtained. Models are discussed for a two-component protease activity requiring both NS2B and NS3.

Amino Acid Sequence↗
PubMed1991

[Clinical and experimental study of burns treated locally with Chinese herbs].

According to the multiple pharmacological functions of Chinese herbs for treating burns, the authors selected some traditional herbs to cure the burning wound, which had not only the function of improving the local microcirculation of the burned surface and their bactericidal action, but also the function of changing the bacterial growth milieu action. Coptis chinensis 40%, Herba Taraxaci 40%, Fructus Mume 10% and Salvia miltiorrhizae 10% were boiled, infiltrated and disinfected. The mixture thus made was called as Burn II, which were applied on the burned surface daily, 97.1% of 103 patients were cured. Through the experiment of 60 rabbits burned by irons, which were divided into 6 groups (n = 10 in each group) and each 2 groups infected respectively with Bacillus pyocyaneus, Bacillus Coli and Staphylococcus Aureus, took one of each infected group as control group. After 14 days, the infected burned surfaces which were applied with Burn II daily. The results showed that the effect of Burn II was not only significant, but also its usage was not highly restricted by the medical condition.

Administration, Topical↗
PubMed1991

[Protective effects of nicorandil on myocardial mitochondria function during ischemia and reperfusion].

Experiment with recirculating blood perfusion device showed that nicorandil 0.15 mmol/L significantly counteracted the harmful effect of ischemic and reperfused injury on the respiratory function of myocardial mitochondria. The oxidative phosphorylation efficiency (ADP/O) was increased 19% (p less than 0.01), the respiratory control rate(RCR) was also increased 40% (p less than 0.01); while the content of myocardial calcium and Ca/Mg were decreased; and the ischemia and reperfusion-induced increase of myocardial water content was abolished as compared with solvent control. The results indicate that nicorandil has protective effect on myocardial mitochondria function during ischemia and reperfusion, which may be the result of blocking Ca2+ from entering the cell and prevent lipid peroxidation.

Animals↗
PubMed1991

[Studies on RESA in Plasmodium falciparum culture medium].

P. falciparum grown in the complete RPMI 1640 medium (containing about 10% normal rabbit serum) for 24 h was collected at about 5% parasitemia. The medium was centrifuged at 500g for 20 min and the supernatant was then centrifuged once more at 40,000g for 30 min. Ten serum samples from falciparum malaria patients with anti-RESA antibodies collected from Yunnan Province were mixed with different dilutions of the culture supernatant, incubated at 37 degrees C for 2h and then at 4 degrees C overnight, and used for conducting RESA-IFA test. The titers of RESA-IFA test of all samples were reduced as compared with controls. When heated supernatant was used in the test, the inhibitory activity remained unchanged. The results indicate that RESA in the supernatants was soluble and heat-stable. To establish the origin of the reacting antigens in the inhibition experiments, the soluble fraction of sonicated merozoite-enriched collection and sonicates of ghost made from normal O phenotype erythrocytes were used in the inhibition RESA-IFA test with sera containing anti-RESA antibodies. The results showed that merozoite-enriched preparations were fully inhibitory at the concentration of 3.1 micrograms/ml, while no inhibition was observed at 0.2 micrograms/ml. In contrast, similar extracts made from normal erythrocyte ghosts were not inhibitory until concentrations about 30 times higher than that of merozoite antigen.

Adolescent↗
PubMed1990

[Protective effects of nicorandil on lipid peroxidation in ischemic and reperfused myocardium of rabbits].

The experiments of recirculating blood perfusion device showed that nicorandil (Nic) 0.15 mmol/L significantly decreased the content of malondialdehyde (MDA), inhibited the release of creatine kinase (CK), counteracted the increase of coronary vascular resistance (CR), and abolished the reperfusion-induced arrhythmias in isolated rabbit hearts during ischemia and reperfusion. The results indicate that Nic has protective effects on myocardial ischemic and reperfused damage, which may relate to the prevention of lipid peroxidation.

Animals↗
PubMed1989

Microcalorimetric measurements of tissue cells in vitro.

A culture flask was designed for the microcalorimetric measurements of tissue cells by an MS 80 standard calvet microcalorimeter. Tissue cells cultured in this flask behaved in the same manner as in the common culture flask used in cytobiological studies. The thermograms of human adenocarcinoma gastric cells (SGc 7901) and HeLa cells were obtained. The heat output power of SGc 7901 cells continuously increased for 70 h with an initial cell number of 3.0 X 10(5). The thermogram was reproducible under strictly controlled conditions. The relationship between the heat output power and the number of SGc 7901 cells within 48 h was obtained. The heat output power was 40 pW/cell to 49 pW/cell when the cell number was in the range 4.5 X 10(5) to 10.4 X 10(5). It was 62.3 +/- 2.9 pW/cell for HeLa cells when the cell number was 6 X 10(5).

Adenocarcinoma↗
PubMed1989

Dengue virus-specific murine T-lymphocyte proliferation: serotype specificity and response to recombinant viral proteins.

Definition of the T-lymphocyte responses to dengue viruses should aid in the development of safe and effective vaccines and help to explain the pathophysiology of dengue hemorrhagic fever and dengue shock syndrome. In this study, we demonstrated that dengue virus-specific T lymphocytes were detected in spleen cells from dengue virus-immune mice using an in vitro proliferation assay. Following immunization with a single dose of infectious dengue virus, murine lymphocytes showed increased proliferation when incubated in the presence of viral antigens of the same serotype but not in the presence of control antigens. Depletion experiments with antibody and complement showed that the population of responding cells expressed the Thy1+ L3T4+ Lyt2- phenotype. This indicates that the predominant proliferating cells are T lymphocytes of the helper-inducer phenotype. Dengue virus-specific memory lymphocyte responses were detectable for at least 22 weeks after immunization. The response to primary infection was primarily serotype specific, with some serotype cross-reactivity present at a low level. We demonstrated that lymphocytes from mice immunized with dengue 4 virus proliferate in response to a combination of dengue 4 virus C, pre-M, E, NS1, and NS2a proteins expressed in Sf9 cells with a recombinant baculovirus, and, to a lesser extent, to the dengue 4 virus E protein alone.

Animals↗
PubMed1989

[Studies on the chemical constituents of Piper macropodum C.DC].

Piper macropodum is used in Chinese folk medicine for the treatment of rheumatism, toothache, epilepsy and stomach ache. From the ethanolic extract of the viny stem of this plant five components were isolated, a new compound and four known compounds. On the basis of spectroscopic analysis (IR, UV, MS, 1HNMR and 13CNMR) the structure of this new compound was elucidated as (2E,4E)-N-isobutyl-2,4-icosadienamide (I). The other four compounds were identified as piperine (II), piperyline (III), daucosterol (IV) and beta-sitosterol (V). All of them were isolated from this species for the first time.

Chemical Phenomena↗
PubMed1989

Dot-immunobinding assay (DIBA) with integral Plasmodium falciparum as antigen in immuno-diagnosis of falciparum malaria.

Among the available immuno-diagnostic methods of parasitoses, dot-immunobinding assay (DIBA) has been proved to be promising for its high sensitivity and specificity, easy performance, lack of need of special equipment, and consequently its practical usage in field work. In previously reported tests, soluble antigen was used, thus a sonicator and an ultracentrifuge were required to produce the antigen. This paper reports the application of integral P. falciparum as antigen in DIBA to detect antibodies in falciparum malaria cases. Of 52 sera from falciparum malaria patients tested, 49 (94.2%) showed positive reactions, which was similar to the result using soluble antigen in DIBA (96.2%) and was higher than that in IFA (86.5%) and ELISA (80.8%). No false positive was revealed in 48 control sera from healthy individuals and sera from visceral leishmaniasis, paragonimiasis, fasciolopsiasis and schistosomiasis patients.

Animals↗
PubMed1988

Immunization of mice with dengue structural proteins and nonstructural protein NS1 expressed by baculovirus recombinant induces resistance to dengue virus encephalitis.

We have constructed a recombinant baculovirus containing a 4.0-kilobase dengue virus cDNA sequence that codes for the three virus structural proteins, capsid (C) protein, premembrane (PreM) protein, and envelope glycoprotein (E), and nonstructural proteins NS1 and NS2a. Infection of cultured Spodoptera frugiperda cells with this recombinant virus resulted in the production of E and NS1 proteins that were similar in size to the corresponding viral proteins expressed in dengue virus-infected simian cells. Other dengue virus-encoded proteins such as PreM and C were also synthesized. Rabbits immunized with the dengue virus protein products of the recombinant virus developed antibodies to PreM, E, and NS1, although the titers were low, especially to PreM and E. Nevertheless, the dengue virus antigens produced by the recombinant virus induced resistance in mice to fatal dengue encephalitis.

Animals↗
PubMed1987

The nucleotide sequence of dengue type 4 virus: analysis of genes coding for nonstructural proteins.

We recently cloned a full-length DNA copy of the dengue type 4 virus genome. Analysis of the 5' terminal nucleotide sequence suggested that the three-virion structural proteins are synthesized by proteolytic cleavage of a polyprotein precursor which is encoded in one open reading frame. We now present the remaining sequence of the dengue type 4 virus genome which codes for the nonstructural proteins. The entire genome, which is 10,644 nucleotides in length, contains one long open reading frame which codes for a single large polyprotein 3386 amino acids in length. Alignment of the dengue nonstructural protein sequence with that of other flaviviruses, including yellow fever and West Nile viruses, revealed that significant homology exists throughout the entire nonstructural region of the dengue genome and this allowed tentative assignment of individual nonstructural proteins in the following order: NS1, NS2a, NS2b, NS3, NS4a, NS4b, and NS5-COOH. Processing of the nonstructural proteins appears to involve two types of proteolytic cleavage: the first occurs after a long hydrophobic signal sequence and the second occurs at a junction between two basic amino acids and a small polar amino acid. A notable exception is the cleavage at the N-terminus of the dengue NS3 which may take place at the junction between Gln-Arg and Ser. Comparative analysis suggests that dengue NS3 and NS5 may be involved in enzymatic activities related to viral replication and/or transcription. Putative nonstructural proteins NS2a, NS2b, NS4a, and NS4b are extremely hydrophobic, suggesting that these proteins are most likely associated with cellular membranes.

Amino Acid Sequence↗