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Biomedical subjects

Z Chen

Publications and source records attributed to Z Chen.

At least 1,261 records · Page 70Linked to original sources
PubMed1995

[Experimental research on using macromolecule sodium hyaluronate to prevent flexior tendon adhesion].

With chicken paw as an animal model, we studied the effects of sodium hyaluronate product (SHP) on the heal of injured tendon and the formation of post-surgical tendon adhesions. The function of digit flexion angle and moving function of the tendon in SHP group were remarkably superior to those of tendons in physiological salt solution control group (P < 0.01). Tendons of the experiment group healed well, their surface was smooth without adhesion. False sheath was formed around the tendon, and there was also a gap between the false sheath and the tendon. However, the adhesion between the tendon and its surrounding tissue in the control group was donse with clear boundary. These results suggest that SHP has a protective effect against the formation of adhesion in healing tendon.

Animals↗
PubMed1995

[Cervico-scapulo-dorsal reverse axial flap with pedicle including the transverse cervical artery].

The anatomy of the transverse cervical artery and its branches were studied on 52 arteries in 26 cadavers. It was confirmed that blood in the transverse cervical artery might flow reversely into the suprascapular artery and the posterior intercostal perforators through anastomic branches. An axial skin flap in the cervico-scapulo-dorsal area could be adequately supplied by this artery. We have used this flap in reconstruction for burn scar contractures of the neck in 20 cases, and in one patient bilateral flaps were used. There was partial necrosis of the tip in 4 flaps, while all others survived completely.

Adolescent↗
PubMed1995

[Clinical study of the venous flaps].

Seven venous flaps were used clinically. Of them six flaps survived completely, one saphenous venous flap had partial necrosis of the derma. The size of the largest survived flap was 5 cm x 15 cm. Three principles regarding the flap application were emphasized: 1) The tissue surrounding the recipient site should be normal. High venous pressure and oxygen tension in the recipient veins are needed. 2) Rich venous network and an axial vein are required in the recipient site. 3) Reliable fixation of the flap is necessary to avoid any damage to new blood vessels.

Adolescent↗
PubMed1995

[Construction of genomic library of L. interrogans serovar lai and preliminary study of recombinant plasmid pDC38].

A genomic library, consisting of approximate 12 000 recombinants, has been constructed for the Leptospira interrogans serovar lai in E. coli. using pUC18 as the vector. Hybridization analysis with the DNA fragment containing OmpL1 gene was performed and 10 positive clones were screened from the genomic library. One of the positive clones, designated pDC38, showed hybridization signal with the DNA of 7 serovars 8 strains of pathogenic leptospires, but not with the DNA of nonpathogenic leptospires (L. biflexa), Leptonama illini, E. coli., and 2 strains of L. interrongans.

DNA, Recombinant↗
PubMed1995

[Influence of microiontophoretic morphine on nociceptive responses of Pf neurons after lesion of SmI].

Neuronal responses in thalamic nucleus parafasciculus (Pf) to microiontophoretic morphine were examined in 20 wistar rats after lesion of SmI. Extracellular recordings were made with five-barreled glass microelectrodes. The results showed that the spontaneous responses of Pf neurons were not statistically changed (n = 11, P > 0.05), but their nociceptive responses were attenuated at 0-8 minutes after iontophoretic morphine (n = 11, P < 0.05). There were statistically significant differences in nociceptive responses between morphine and saline groups at 0-8 minutes after iontophoresis. The results suggest that morphine may be involved in corticofugal modulation of nociceptive responses in thalamic Pf neurons.

Animals↗
PubMed1995

[Effect of streptomycin placing in the fenestra of semicircular canals on the function and morphology of the normal and hydropic ears in guinea pigs].

The effect of streptomycin placed in the fenestra of lateral semicircular canal (LSC) on the function and morphology of the normal and artificial hydropic inner ears in guinea pigs was studied in order to explore the method and possibility of treating Meniere's disease by using aminoglycosides. After placing the drug in the fenestra of LSC, no change in AP threshold of ECochG in normal ears but an increase of that in hydropic ears were found caloric induced nystagmus in both groups were disappeared. Under light microscope, severe damage of vestibular epithelium of three canal cristae and utricular macula was noted, while no insult of cochlear hair cells was found in normal ears. More severe damage of vestibular epithelium with part of them degenerated and atrophied and lesions of cochlear hair cells in basal turns and part of second turns occurred in hydropic ears. These demonstrated that the ototoxicity of streptomycin was higher in hydropic ears than in normal ears. In order to destroy vestibular function and preserve cochlear function, further study for adequate dosage of streptomycin and correct route of administration is needed.

Animals↗
PubMed1995

Effects of intracerebroventricular injection of histamine and its related compounds on rectal temperature in mice.

Effects of intracerebroventricular injection of histamine and its related compounds on rectal temperature were studied in mice. Histamine (0.1-1.0 mu g) and histidine (500-1,000 mg/kg) caused a dose-related hypothermia. H1 agonist, 2-methylhistamine and 2-thiazolylethylamine also displayed a dose-dependent hypothermia. In addition, H2 agonists, 4-methylhistamine and dimaprit elicited a decrease in body temperature. Preinjection of not only H1-antagonists (diphenhydramine and chlorpheniramine) but also H2 antagonists (cimetidine and ranitidine) abolished histamine-induced hypothermia. Either intracerebroventricular or intraperitoneal injection of thioperamide, a histamine H3 antagonist, showed hypothermia. The hypothermic effect produced by intracerebroventricular injection of thioperamide was significantly blocked by (R)-alpha-methylhistamine, a selective H3 agonist. In addition, the effect induced by thioperamide was inhibited by H1 and H2 antagonists, indicating that the H3 receptor also participates in histamine-induced hypothermia.

Animals↗
PubMed1995

[The study of the relationship between the granule size of immunoliposomes and the conjugate ratio of F(ab')2 of McAb HI30 (CD45)].

The immunoliposomes were prepared by conjugating the F(ab')2 of monoclonal antibodies HI30(CD45) labelled by 125I with the liposomes labelled by 131I, and then were separated by a sephacryl S-300 column. The chromatography showed that the liposomes prepared by ultrasonic method were not homogeneous, and the liposomes of smaller granule size had a higher conjugate ratio. It was also found that the fragment F(ab')2 of McAb conjugated to liposomes could enlarge their granule size.

Animals↗
PubMed1995

[Management of the dry eye with parotid duct transplantation: a summary on 40 cases].

PURPOSE: As today the effect of parotid duct transplantation is clinically regarded as uncertainty, and there is still absent of effective managenent of the dry eye, this paper tries to clarify its value, and see if it can be used clinically. METHODS: Forty dry eyes were operated with a follow up of 3 weeks to more than 6 years in the past 42 years. The pre- and postoperative changes of tear flow and vision, and the cause of dry eye, operative method, length of parotid duct and complications of bilateral operation were briefly summarized. RESULTS: Of these 40 operated eyes postoperatively, 82.5% had tearing, but no tearing occurred in 27.5%. Finally: vision increased in 72.5% with out any decrease. There was no difference in the results whether the procedure done extraorally or intraorally. The parotid duct being shorter was only seen in 7.5%, which were satisfactorily managed by tube making with oral mucosa. Four cases operated binocularly and silmutaneously, only 1 occurred aveolar abscess with complaining dry mouth, but cured 1 week later. After operation, profusive tearing occurred in 25 dry eyes caused by trachoma during eating and 96% usually, but tearing stopped finally in 3 eyes (2, due to infection). Four dry eyes with ocular pemphigoid failed. Among 9 dry eyes resulted from Stevens-Johnson syndrome, 6 had little tearing postoperatively, 2 of which attained a nearly normal results. One of the two dry eyes resulted from alkali eye burn failed and the other, occurred tearing but only followed-up for 1 month, the result was uncertain. CONCLUSION: As the technique of the parotid duct transplantation is simple and easy with no much complications, and for treating the dry eye, there is up to now still absent of effective management, therefore, the parotid duct transplantation should be considered to be indicated in dry eyes esp, caused by Stevens-Johnson syndrome. Though its success rate is lower than that of traucomatous ones, the satisfactory result of nearly normal postoperative tearing may be got. In ocular pemphigoid, however, it is contraindicated.

Follow-Up Studies↗
PubMed1995

[An analysis of causes of recurrence, matastasis and death of retinoblastoma].

PURPOSE: To discuss the relationship between diagnosis, treatment and recurrence, metastasis, death of Rb patients. METHODS: To analyse the data of 46 Rb patients treated in our center from July 1967 to May 1992, who had either recurrence, metastasis or died. RESULTS: The main factors affecting Rb prognosis are: 1 early or late diagnosis: 2 the mortality rate increased with the degree of optic nerve involvement: 3 involvement of orbit, cranial cavity and choroid by Rb; 4 clinically, secondary glaucoma often accompanied by optic nerve involvement. CONCLUSIONS: Delay in diagnosis and treatment will result in Rb recurrence, metastasis and death. Early diagnosis and treatment is very important for survival rate.

Child↗
PubMed1994

Adding a positive charge at residue 46 of Drosophila alcohol dehydrogenase increases cofactor specificity for NADP+.

We previously reported that the D39N mutant of Drosophila alcohol dehydrogenase (ADH), in which Asp-39 is replaced with asparagine, has a 60-fold increase in affinity for NADP+ and a 1.5-fold increase in kcat compared to wild-type ADH [Chen et al. (1991) Eur. J. Biochem. 202, 263-267] and proposed that this part of ADH is close to the 2'-phosphate on the ribose moiety of NADP+. Here we report the effect of replacing Ala-46 with an argine residue, and A46R mutant, on binding of NADP+ to ADH and its catalytic efficiency with the NADP+ cofactor, and a modeling of the three-dimensional structure of the NAD(+)-binding region of ADH. The A46R mutant has a 2.5-fold lower Km(app)NADP+ and a 3-fold higher kcat with NADP+ compared to wild-type ADH; binding of NAD+ to the mutant was unchanged and kcat with NAD+ was lowered by about 30%. For the A46R mutant, the ratio of kcat/Km of NAD+ to NADP+ is 85, over ten-fold lower than that for wild-type ADH. Our model of the 3D structure of the NAD(+)-binding region of ADH shows that Ala-46 is over 10 A from the ribose moiety of NAD+, which would suggest that there is little interaction between this residue and NAD+ and explain why its mutation to arginine has little effect on NAD+ binding. However, the positive charge at residue 46 can neutralize some of the coulombic repulsion between Asp-39 and the 2'-phosphate on the ribose moiety of NADP+, which would increase its affinity for the A46R mutant. We also constructed a double mutant, D39N/A46R mutant, which we find has a 30-fold lower Km(app)NADP+ and 8-fold higher kcat with NADP+ as a cofactor compared to wild-type ADH; binding of NAD+ to this double mutant was lowered by 5-fold and kcat was increased by 1.5-fold. As a result, kcat/Km for the double mutant was the same for NAD+ and NADP+. The principle effect of the two mutations in ADH is to alter its affinity for the nucleotide cofactor; kcat decreases slightly in A46R with NAD+ and remains unchanged or increases in the other mutants.

Alanine↗
PubMed1994

Purification and kinetic mechanism of a mammalian methionine synthase from pig liver.

Porcine hepatic methionine synthase has been purified to near homogeneity. The enzyme is isolated in two forms which were purified approximately 9,000- and approximately 7,000-fold and were obtained in 0.9 and 2.5% overall yield, respectively. The mammalian enzyme from pig liver is a large monomeric protein with a molecular mass of 151-155 kDa. It is characterized by the absence of any metals other than cobalt which is associated with the cofactor, cobalamin. This enzyme, like the methionine synthase from Escherichia coli is dependent on S-adenosylmethionine for activity. The steady state kinetic studies demonstrate that the reaction operates via an ordered sequential mechanism in which binding of CH3-H4-folate precedes homocysteine, and methionine is released prior to H4-folate.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1994

Direct imaging of interactions between an icosahedral virus and conjugate F(ab) fragments by cryoelectron microscopy and X-ray crystallography.

The binding properties of seven mouse monoclonal antibodies (McAbs) raised against cowpea mosaic virus (CPMV) were characterized by conventional and inhibition enzyme-linked immunosorbent assay (ELISA) technique. McAb binding to CPMV on electron microscope (EM) grids was also assayed with gold-labeled anti-mouse antibodies. Two of the seven McAbs (5B2 and 10B7) were found to bind tighter to CPMV than the others in the inhibition ELISA and the EM assay. F(ab) fragments from both of these McAbs were prepared and complexed with CPMV in solution. Electron micrographs of flash frozen (vitrified) samples of native CPMV and CPMV complexed with F(ab) fragments from McAbs 5B2 and 10B7 as well as IgGs from 5B2 were recorded and reconstructions were computed at 23 A resolution for the CPMV/F(ab) complexes and 30 A resolution for the CPMV/IgG complex. Structures of all three complexes clearly displayed the F(ab) fragments distributed with icosahedral symmetry on the surface of CPMV. The IgG bound in a monodentate fashion with only one F(ab) attached to the virus surface. F(ab) fragments from 5B2 and 10B7 bound to nearly identical positions. The refined 2.8 A X-ray structure of CPMV was used to identify the roughly 30 amino acids covered by the F(ab) fragments. The "footprint" spans a subunit interface and appears spatially similar to antigenic site 3B on poliovirus. In a previous, preliminary report of the CPMV/F(ab) 5B2 complex (Wang et al., 1992, Nature 355, 275-278) the wrong enantiomorph of the reconstruction was chosen. This was corrected and, since the F(ab) binds close to a mirror plane, the change in the footprint was minor.

Animals↗
PubMed1994

Crystal structure at 1.9-A resolution of human immunodeficiency virus (HIV) II protease complexed with L-735,524, an orally bioavailable inhibitor of the HIV proteases.

L-735,524 is a potent, orally bioavailable inhibitor of human immunodeficiency virus (HIV) protease currently in a Phase II clinical trial. We report here the three-dimensional structure of L-735,524 complexed to HIV-2 protease at 1.9-A resolution, as well as the structure of the native HIV-2 protease at 2.5-A resolution. The structure of HIV-2 protease is found to be essentially identical to that of HIV-1 protease. In the crystal lattice of the HIV-2 protease complexed with L-735,524, the inhibitor is chelated to the active site of the homodimeric enzyme in one orientation. This feature allows an unambiguous assignment of protein-ligand interactions from the electron density map. Both Fourier and difference Fourier maps reveal clearly the closure of the flap domains of the protease upon L-735,524 binding. Specific interactions between the enzyme and the inhibitor include the hydroxy group of the hydroxyaminopentane amide moiety of L-735,524 ligating to the carboxyl groups of the essential Asp-25 and Asp-25' enzymic residues and the amide oxygens of the inhibitor hydrogen bonding to the backbone amide nitrogen of Ile-50 and Ile-50' via an intervening water molecule. A second bridging water molecule is found between the amide nitrogen N2 of L-735,524 and the carboxyl oxygen of Asp-29'. Although other hydrogen bonds also add to binding, an equally significant contribution to affinity arises from hydrophobic interactions between the protease and the inhibitor throughout the pseudo-symmetric S1/S1', S2/S2', and S3/S3' regions of the enzyme. Except for its pyridine ring, all lipophilic moieties (t-butyl, indanyl, benzyl, and piperidyl) of L-735,524 are rigidly defined in the active site.

Aspartic Acid Endopeptidases↗
PubMed1994

Recent trends in hospital mortality of acute myocardial infarction--the Worcester Heart Attack Study. Have improvements been realized for all age groups?

BACKGROUND: While age-related differences in patterns of care for acute myocardial infarction have been demonstrated, temporal trends in clinical outcome for patients in different age groups have not been carefully examined. METHODS: We analyzed data collected as part of an ongoing communitywide study of 5480 patients hospitalized with validated acute myocardial infarction in Worcester, Mass, during 7 selected years spanning a 15-year period (1975 through 1990). Patients were stratified into three age groups: less than 65 years (n = 2220), 65 through 74 years (n = 1595), and 75 years or older (n = 1665). Within each age group, the odds of in-hospital death were determined by study year, with adjustments for selected demographic, clinical, and hospital characteristics. RESULTS: For patients less than age 65 years, the odds of dying during the acute hospital phase of myocardial infarction were reduced for all study years relative to the reference year (1975), reaching their lowest level in 1990 (adjusted odds ratio [OR], 0.16; 95% confidence interval [CI], 0.06 to 0.48). For patients aged 65 through 74 years, the odds of dying declined among patients hospitalized in 1978 (adjusted OR, 0.71; 95% CI, 0.39 to 1.29) and 1981 (adjusted OR, 0.36; 95% CI, 0.19 to 0.66) but remained essentially unchanged during the subsequent study years through 1990. For patients 75 years of age or older, the odds of dying declined through 1984 (adjusted OR, 0.42; 95% CI, 0.25 to 0.72) but increased over the following study years: 1986, 1988, and 1990. CONCLUSIONS: While the risk of in-hospital death following acute myocardial infarction has recently declined for patients less than 65 years of age, improvements have not been realized for older age groups. Current patterns of management of acute myocardial infarction in older patients require reexamination.

Age Factors↗
PubMed1994

Transcriptional enhancer factor 1 disruption by a retroviral gene trap leads to heart defects and embryonic lethality in mice.

We have used a retroviral gene trap in embryonic stem (ES) cells to derive a recessive embryonic lethal mouse strain, ROSA beta-geo5. Mutant embryos display an enlarged pericardial cavity, bradycardia, a dilated fourth ventricle in the brain, and die between embryonic days 11 and 12. Whereas heart development in the mutant embryos is extensive, the ventricular wall is abnormally thin with a reduced number of trabeculae. Cloning of the trapped gene indicates that proviral insertion creates a null mutation in the transcriptional enhancer factor 1 (TEF-1) gene. Although transcription of a number of muscle-specific genes believed to be TEF-1 targets appears normal, the defect in cardiogenesis is likely attributable to diminished transcription of one or several cardiac-specific genes.

Amino Acid Sequence↗