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Biomedical subjects

Z Meng

Publications and source records attributed to Z Meng.

At least 55 records · Page 3Linked to original sources
PubMed1998

[Treatment of arteriovenous malformation by linear accelerator radiosurgery].

OBJECTIVE: To summarize the effectiveness of radiosurgery for cerebral arteriovenous malformations (AVMs). METHOD: We treated with linear accelerator radiosurgery 17 patients harboring AVMs in the brain. 15 AVMs were located supratentorially and others infratentorially. All the patients were treated with single fraction. The doses at AVM margin were 15 to 30 Gy. RESULT: AVMs disappeared in 13 of the 17 patients, reduced in 3 and unchanged in only 1 at 2 year follow up. Vasogenic edema observed in 2 patients, their neurologic deficits were all improved with steroid. CONCLUSION: Linear accelerator radiosurgery is effective in dealing with cerebral AVMs. It provides with a new means of treatment for AVMs which can't be effectively treated with microsurgery and embolization.

Adolescent↗
PubMed1998

[Timosaponins E1 and E2].

By means of silica gel chromatography and HPLC, two compounds were isolated from Anemarrhena asphodeloides Bge.. On the basis of chemical and spectral (MS, 1H, 13CNMR, IR) analyses, their structures were elucidated as (25S)-26-O-beta-D-glucopyranosyl-22-hydroxy-5 beta-furost-3 beta, 15 alpha, 26-triol-3-O-beta-D-glucopyranosyl (1-->2)-beta-D-galactopyranoside (1), and (25S)-26-O-beta-D-glucopyranosyl-22-methoxy-5 beta-furost-3 beta, 15 alpha, 26-triol-3-O-beta-D-glucopyranosyl (1-->2)-beta-D-galactopyranoside (2). They are named as timosaponin E1 (1) and timosaponin E2 (2) respectively. The structure of anemarrhenasaponin-I (A) is briefly discussed. Timosaponins are the main active constituents of Anemarrhena asphodeloides, most of them were shown to can inhibit platelet aggregation.

Anemarrhena↗
PubMed1997

Synthetic strategies for the preparation of precursor polymers and of microcapsules suitable for cellular entrapment by polyelectrolyte complexation of those polymers.

The production of microcapsules suitable for the entrapment of mammalian cell by means of polyelectrolyte complexation has, of a necessity, led to the development of novel strategies for the preparation of relatively bioinert polymers which complex efficiently under unique conditions to produce a mechanically resilient membrane with efficient transport properties. In this communication we relate a brief overview of capsule-membrane forming systems for the immunoisolation (or potential immunoisolation) of mammalian cells, which are based upon the complexation of polyelectrolyte (PE) polymers; with emphasis on precursor synthesis and relationships between precursor polymer structure and capsule membrane stability.

Animals↗
PubMed1997

Chromosomal aberrations and micronuclei in lymphocytes of workers at a phosphate fertilizer factory.

The frequencies of chromosomal aberrations (CA) and micronuclei (MN) in peripheral blood lymphocytes of 40 workers at a phosphate fertilizer factory in North China, were studied. HF and SiF4 are the main air pollutants and small amounts of dust containing fluoride, NH3 and SO2 were also present in the factory. It was shown that the chemicals caused an increase in both CA and MN. The mean frequencies per 100 metaphase of major CA type (chromosome rings, translocations, and dicentrics) of the workers and the non-exposed controls were 0.91 and 0.24 (p < 0.01), respectively. The average percentages of lymphocytes with MN of the workers and the controls were 1.55 +/- 0.71 and 0.62 +/- 0.54 (p < 0.01), respectively. Both CA frequency and MN frequency of the workers increased with length of the chemical exposure period up to 10 years.

Air Pollutants, Occupational↗
PubMed1997

Effect of a chemical modification on the hydrated adenosine intermediate produced by adenosine deaminase and a model reaction for a potential mechanism of action of 5-aminoimidazole ribonucleotide carboxylase.

Using the hydrated adenosine intermediate (6R)-6-amino-1, 6-dihydro-6-hydroxy-9-(beta-D-ribofuranosyl)purine (2) produced by adenosine deaminase (ADA, EC 3.5.4.4) as a starting point, the active site probe and inhibitor platform 5-(formylamino)imidazole riboside (FAIRs, 4) was designed by removal of the-C6(OH)(NH2)-molecular fragment of 2 generated by the early events of the enzyme-catalyzed hydrolysis. FAIRs was synthesized directly from the sodium salt of 5-amino-1-(beta-D-ribofuranosyl)imidazole-4-carboxylic acid (CAIR) along a reaction sequence involving a tandem N-formylation/decarboxylation that may have a mechanistic connection to the Escherichia coli purE-catalyzed constitutional isomerization of N5-CAIR to CAIR. The physical and spectral properties of FAIRs were elucidated, its X-ray crystal and NMR solution structures were determined, and its interaction with ADA was investigated. Crystalline FAIRs exists solely as the Z-formamide rotamer and exhibits many of the same intramolecular hydrogen bonding events known to contribute to the association of Ado to ADA. In water and various organic solvents, however, FAIRs exists as NMR-distinct, slowly interconverting Z and E rotamers. This truncated enzymatic tetrahedral intermediate analog was determined to be a competitive inhibitor of ADA with an apparent Ki binding constant of 40 microM, a value quite close to that (33 microM) of the natural substrate's K(m). The actual species selected for binding by ADA, though, is likely the minor hydroxyimino prototropic form of Z-FAIRs possessing a far lower true Ki value. As the structural features of FAIRs appear well-suited to support its use as a template for constructing active site probes of both ADA and AIR carboxylases, a variety of carbohydrate-protected versions of FAIRs suitable for facile aglycon elaborations were synthesized. The N3-alkylation, N3-borane complexation, and C4-iodination of some of these were investigated in order to assess physicochemical properties that may assist in the elucidation of mechanisms for the AIR carboxylases. The survey of these properties taken together with a reasonable mechanism for the model CAIRs-->FAIRs synthetic transformation is interpreted to support a mechanism for the purE-catalyzed N5-CAIR-->CAIR biosynthetic one that involves a carboxylative sp3-rehybridization of the imidazole C4 atom rather than one possessing a dipole-stabilized C4 sp2 carbanionic intermediate.

Adenosine↗
PubMed1997

Effect of structural modification of enol-carboxamide-type nonsteroidal antiinflammatory drugs on COX-2/COX-1 selectivity.

Meloxicam (5), an NSAID in the enol-carboxamide class, was developed on the basis of its antiinflammatory activity and relative safety in animal models. In subsequent screening in microsomal assays using human COX-1 and COX-2, we discovered that it possessed a selectivity profile for COX-2 superior to piroxicam and other marketed NSAIDs. We therefore embarked on a study of enol-carboxamide type compounds to determine if COX-2 selectivity and potency could be dramatically improved by structural modification. Substitution at the 6- and 7-positions of the 4-oxo-1,2-benzothiazine-3-carboxamide, alteration of the N-methyl substituent, and amide modification were all examined. In addition we explored several related systems including the isomeric 3-oxo-1,2-benzothiazine-4-carboxamides, thienothiazines, indolothizines, benzothienothiazines, naphthothiazines, and 1,3- and 1,4-dioxoisoquinolines. While a few examples were found with greater potency in the COX-2 assay, no compound tested had a better COX-2/COX-1 selectivity profile than that of 5.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1997

Electrophysiological evidence that spinomesencephalic neurons in the cat may be excited via spinocervical tract collaterals.

Extracellular microelectrode recordings were made from spinomesencephalic tract (SMT) neurons in the lumbosacral spinal cord of cats anaesthetized with chloralose and paralysed with gallamine triethiodide. The SMT cells were antidromically fired from the posterolateral parts of the superior colliculus and the intercollicular region, were located in laminae IV to VIII, and had response properties and axonal conduction velocities similar to those described previously. The effects of stimulating the dorsolateral funiculus of the cervical cord at C3 and rostral C1, below and above the termination of spinocervical tract (SCT) axons in the lateral cervical nucleus, were examined on 33 SMT cells. The strength of stimulation was adjusted so that at C3 it was above threshold for antidromic activation of SCT cells and at C1 was below threshold for activation of the same cells. Seven (21%) SMT neurons were excited from C3 but not from C1. The remaining 26 (79%) were excited from both C3 and rostral C1 and 23 (70% of these) were excited significantly more from C3. That is, 91% of the total sample were either excited only from C3 or more strongly from C3 than from rostral C1. We discuss the possible neuronal systems involved and conclude that the greater excitatory effects from C3 are most likely due to antidromic activation of the SCT. The shortest latency effects from C3 indicate a monosynaptic linkage between SCT cells with the fastest axons and the SMT. The longer latency actions may be due to monosynaptic connexions from SCT cells with slower conducting axons, to di- or polysynaptic actions from SCT cells with fast axons, or a combination of both. SMT cells are another population of spinal neurons, in addition to postsynaptic dorsal column, spinothalamic and dorsal horn spinocerebellar neurons, which receive excitation via SCT collaterals.

Animals↗
PubMed1997

[Dynamic study of anti-NS5 and ALT in post-transfusion hepatitis C].

In order to study the character and dynamic changes of HCV NS5 antigen in post-transfusion hepatitis C, EIA was established with fusion protein, and different groups of population were investigated. The results showed the positive rate of whole blood donor, normal people, chronic hepatitis C patients and post transfusion hepatitis C patients is 0.0%, 1.66%, 50.7% and 70.5%, respectively. Serial blood samples of 25 cases of acute or chronic post-transfusion hepatitis C were detected, and the results indicated that the antibody of NS5 appeared relatively late, and the serum conversion time was 182.9 +/- 168.5 days. The anti-NS5 positive rate in 1, 3, 6, 12 and 24 months after HCV infection was 28%, 40%, 52%, 68% and 76%, respectively. The positive rate of anti-NS5 in sera with HCV RNA was 61.9%. Analysis on the appearance of antibody to the different antibody region of the gene, ALT and HCV RNA showed the dynamic changes of anti-NS5 were corresponding to the serum ALT in some cases, indicating antibody of NS5 appear later and may reflect the disease activity to some extent. The dynamic changes of anti-NS5 are of four kinds: transient positive, intermittent positive, persistent positive and persistent negative in during the two years period.

Alanine Transaminase↗
PubMed1997

[A prospective study on transfusion-related hepatitis C virus infection].

64 cases of blood recipients were followed-up for 6 months to study infection of hepatitis C virus. The infection rate of hepatitis C virus was 18.75% in total, including 8 cases of post-transfusion hepatitis C (PT-HC), 1 case of subclinical PT-HC, and 3 cases of anti-HCV sero conversion only. The time of initial ALT abnormality and anti-HCV sero conversion were 28 to 91 (51.9 +/- 20.9) days and 23 to 76 (42.4 +/- 15.9) days after blood transfusion respectively. There were 2 cases with cytomeglovirus infection and another 5 cases with unknown infectious agent were found in this study.

Enzyme-Linked Immunosorbent Assay↗
PubMed1997

[Molecular analysis of spontaneous and arsenite-induced mutations at the gpt locus in Chinese hamster ovary cells].

In this study, we examined the mutagenicity of sodium arsenite at the xathine-guanine phosphoribosyl transferase locus (gpt) in a pSV2 gpt-transformed CHO cell line AS52. The chemical induced a dose-dependent increase of mutant frequency at the locus. Nested PCR analysis revealed that the majority of arsenite-induced AS52 mutants had totally deleted the gpt gene. For the spontaneous, 50 mumol/L arsenite--and 100 mumol/L arsenite--induced mutants in AS52 cells, the percentages of total deletion of the gpt gene were 36.00%, 54.72% and 66.67% respectively. The PCR products of gpt gene from nine 100 mumo/L sodium bisulfite-induced mutants were analyzed with direct DNA sequence technology. The frameshift mutation was identified in two mutants (2/9). No genomic alteration could be found in the structural gene examined in the other 7 mutants, where their molecular alterations probably located in the promoter region.

Animals↗
PubMed1997

[The effect of phenytoin in healing of fracture of rabbits].

It was reported that the systemic use of phenytoin could promote healing of fracture. In order to observe the effect of local application of phenytoin in the healing of fracture, the experiment was performed. Seventy-two rabbits were divided into three groups. Fractures were created on both radius of all rabbits. Group 1, intraperitoneal injection of phenytoin with a dosage of 50 mg/kg per day; Group 2, local use of phenytoin with a dosage of 40 mg/kg was injected in the fracture site every seventy-two hours, and Group 3, injection mormal saline of in the control group. Eight rabbits in each group were sacrificed in the 9th, 16th and 30th days after operation respectively. By X-ray excuiualtion, the healing of fracture was observed. Dry and wet weights of the callus were determined. After HE and Mallory's stain, the samples were examined under microscope. Results showed that both local and systemic use of phenytoin promoted healing of fracture. The effects of phenytoin in the two groups were the same and had no significant difference.

Animals↗
PubMed1996

Head group analogs of arachidonylethanolamide, the endogenous cannabinoid ligand.

Several analogs of an endogenous cannabimimetic, arachidonylethanolamide (anandamide), were synthesized to study the structural requirements of the ethanolamide head group. CB1 receptor affinities of the analogs were evaluated by a standard receptor binding assay using tritiated CP-55,940 as the radioligand and compared to anandamide which was shown to have a Ki of 78 nM. Replacement of the amide carbonyl oxygen by a sulfur atom had a detrimental effect on the CB1 affinity. The thio analogs of both anandamide and (R)-methanandamide showed very weak affinity for CB1. The secondary nature of the amidic nitrogen was also shown to be important for affinity, indicating a possible hydrogen-bonding interaction between the amide NH and the receptor. Introduction of a phenolic moiety in the head group resulted in the loss of receptor affinity except when a methylene spacer was introduced between the amidic nitrogen and the phenol. A select group of analogs were also tested for their affinity for the CB2 receptor using a mouse spleen preparation and were found to possess low affinities for the CB2 sites. Notably, anandamide and (R)-methanandamide demonstrated high selectivity for the CB1 receptor. Overall, the data presented here show that structural requirements of the head group of anandamide are rather stringent.

Adjuvants, Immunologic↗
PubMed1996

Polymerase chain reaction-based deletion analysis of spontaneous and arsenite-enhanced gpt mutants in CHO-AS52 cells.

In this study, we have examined the mutagenicity of sodium arsenite at the xanthine-guanine phosphoribosyltransferase locus (ypt) in a pSV2 gpt-transformed CHO cell line, AS52. Our results provide very weak evidence for arsenite as a gene mutagen because the chemical at high doses and at high cytotoxicity enhances barely a doubling of mutant frequency (MF) and a doubling of the gpt gene deletion frequency compared to controls. We suggest that the increase in MF in arsenite-treated cells results from arsenic, as comutagen, enhancing the induction effect of any unknown endogenous or exogenous factors on the spontaneous mutagenesis of AS52 cells. Nested PCR analysis mutants has a total deletion of the gpt gene. For the spontaneous, 50 microM arsenite- and 100 microM arsenite-enhanced spontaneous mutants in AS52 cells, the percentages of total deletion of the gpt gene are 36.00%, 54.72% and 66.67%, respectively. We suggest that a high proportion of the gene deletion in arsenite-enhanced mutants may be due to the high cytotoxicity of the chemical.

Animals↗
PubMed1996

Effect of a nonsteroidal antiinflammatory drug on synovial fluid in osteoarthritis.

OBJECTIVE: The use of nonsteroidal antiinflammatory drug (NSAID) therapy in osteoarthritis (OA) is controversial because of suggestions that pure analgesics can be as effective as NSAID for pain relief. In addition, there is incomplete information whether antiinflammatory effects have any longterm benefit in OA. NSAID have been known to affect synovial fluid (SF) prostaglandins in rheumatoid arthritis. We describe the first examination of the effect of an NSAID, etodolac, on SF prostaglandins, cytokines, and cells in OA. METHODS: Joint fluids were studied before and 2 weeks after initiation of therapy with etodolac 400 mg tid. Leukocyte counts, prostaglandin, interleukin 6, and tumor necrosis factor were measured. RESULTS: Pretreatment features of SF did not predict clinical response. We found no change in the relatively low leukocyte counts. However, SF prostaglandin levels and interleukin 6 levels were significantly decreased and tumor necrosis factor alpha levels were increased after therapy with NSAID. CONCLUSION: This NSAID had potentially important local effects that could be either beneficial or deleterious. Further studies on effects of this and other NSAID on a broader variety of SF and synovial cytokines may help predict longterm effects of NSAID on progression of OA.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1996

[The progress of morphological research on the parabrachial nucleus].

In this paper, the progress of morphological research on the PBN, the cytoarchitecture of the PBN, and the fiber connections between the PBN and the spinal, the brainstem, the forebrain and the other nucleus were summarized. Its function in the relationship between the meridian and the internal organ was also assumed.

Animals↗
PubMed1996

[Preparation of fumitremorgin B].

In order to prepare fumitremorgin B (FTB), strains of Aspergillus fumigatus C4104 and 3656 were selected, based on the screening of high-FTB-production strains, and inoculated in rice medium of five kilograms and incubated for producing toxin. Cultures were extracted with ethyl acetate, dehydrated with anhydrous sodium sulfate, defatted with n-hexane, decolorized with activated charcoal, chromatographed in silica gel H column, recrystallized by methanol, and finally, four grams of colorless fine-needle shaped crystal were harvested. Two strains of the fungus could produce 800 mg of toxin per kilogram rice medium in average with a yield of approximately 20%, much higher than that reported in literatures (1.11%). Indentification with chemical analysis, such as melting point, ultraviolet, infrared, elemental analysis, mass spectrometry, as well as analyses of nuclear magnetic resonance hydrogen spectrum and carbon spectrum, showed consistency of the results with those in literatures, and confirmed it contained FTB with one molecule of H2O. Contribution of carbon and hydrogen to the molecular structure of self-prepared FTB was explored in the paper based on the spectrometric data.

Aspergillus fumigatus↗