Biomedical subjects

R Zhang

Publications and source records attributed to R Zhang.

At least 379 records · Page 21Linked to original sources

PubMed1996

Solid-phase synthesis, metal binding and folding properties of caulimovirus-related 'zinc finger'.

A 17-residue peptide containing the caulimovirus-related "zinc finger' was prepared by solid-phase peptide synthesis. Fluorescence measurements showed that the tryptophan quantum yield was Zn(2+)-dependent, allowing a 1:1 a stoichiometry for the complex to be determined. The structure of the peptide was characterized using circular dichroic spectroscopy, which indicates that the peptide exhibits a random coiled conformation in the absence of zinc but appears to form an ordered structure in the presence of zinc.

Amino Acid Sequence↗

PubMed1996

Identification of a minimal hydrophobic domain in the herpes simplex virus type 1 scaffolding protein which is required for interaction with the major capsid protein.

Recent biochemical and genetic studies have demonstrated that an essential step of the herpes simplex virus type 1 capsid assembly pathway involves the interaction of the major capsid protein (VP5) with either the C terminus of the scaffolding protein (VP22a, ICP35) or that of the protease (Pra, product of UL26). To better understand the nature of the interaction and to further map the sequence motif, we expressed the C-terminal 30-amino-acid peptide of ICP35 in Escherichia coli as a glutathione S-transferase fusion protein (GST/CT). Purified GST/CT fusion proteins were then incubated with 35S-labeled herpes simplex virus type 1-infected cell lysates containing VP5. The interaction between GST/CT and VP5 was determined by coprecipitation of the two proteins with glutathione Sepharose beads. Our results revealed that the GST/CT fusion protein specifically interacts with VP5, suggesting that the C-terminal domain alone is sufficient for interaction with VP5. Deletion analysis of the GST/CT binding domain mapped the interaction to a minimal 12-amino-acid motif. Substitution mutations further revealed that the replacement of hydrophobic residues with charged residues in the core region of the motif abolished the interaction, suggesting that the interaction is a hydrophobic one. A chaotropic detergent, 0.1% Nonidet P-40, also abolished the interaction, further supporting the hydrophobic nature of the interaction. Computer analysis predicted that the minimal binding motif could form a strong alpha-helix structure. Most interestingly, the alpha-helix model maximizes the hydropathicity of the minimal domain so that all of the hydrophobic residues are centered around a Phe residue on one side of the alpha-helix. Mutation analysis revealed that the Phe residue is absolutely critical for the binding, since changes to Ala, Tyr, or Trp abrogated the interaction. Finally, in a peptide competition experiment, the C-terminal 25-amino-acid peptide, as well as a minimal peptide derived from the binding motif, competed with GST/CT for interaction with VP5. In addition, a cyclic analog of the minimal peptide which is designed to stabilize an alpha-helical structure competed more efficiently than the minimal peptide. The evidence suggests that the C-terminal end of ICP35 forms an alpha-helical secondary structure, which may bind specifically to a hydrophobic pocket in VP5.

Amino Acid Sequence↗

PubMed1996

Virus-specific interaction between the human cytomegalovirus major capsid protein and the C terminus of the assembly protein precursor.

We previously identified a minimal 12-amino-acid domain in the C terminus of the herpes simplex virus type 1 (HSV-1) scaffolding protein which is required for interaction with the HSV-1 major capsid protein. An alpha-helical structure which maximizes the hydropathicity of the minimal domain is required for the interaction. To address whether cytomegalovirus (CMV) utilizes the same strategy for capsid assembly, several glutathione S-transferase fusion proteins to the C terminus of the CMV assembly protein precursor were produced and purified from bacterial cells. The study showed that the glutathione S-transferase fusion containing 16 amino acids near the C-terminal end was sufficient to interact with the major capsid protein. Interestingly, no cross-interaction between HSV-1 and CMV could be detected. Mutation analysis revealed that a three-amino-acid region at the N-terminal side of the central Phe residue of the CMV interaction domain played a role in determining the viral specificity of the interaction. When this region was converted so as to correspond to that of HSV-1, the CMV assembly protein domain lost its ability to interact with the CMV major capsid protein but gained full interaction with the HSV-1 major capsid protein. To address whether the minimal interaction domain of the CMV assembly protein forms an alpha-helical structure similar to that in HSV-1, peptide competition experiments were carried out. The results showed that a cyclic peptide derived from the interaction domain with a constrained (alpha-helical structure competed for interaction with the major capsid protein much more efficiently than the unconstrained linear peptide. In contrast, a cyclic peptide containing an Ala substitution for the critical Phe residue did not compete for the interaction at all. The results of this study suggest that (i) CMV may have developed a strategy similar to that of HSV-1 for capsid assembly; (ii) the minimal interaction motif in the CMV assembly protein requires an alpha-helix for efficient interaction with the major capsid protein; and (iii) the Phe residue in the CMV minimal interaction domain is critical for interaction with the major capsid protein.

Animals↗

PubMed1996

Evidence for the presence of a proteinase-activated receptor distinct from the thrombin receptor in vascular endothelial cells.

The thrombin receptor was the first cloned G protein-coupled receptor reported to be activated by proteolytic cleavage of its extracellular amino terminus. A second proteinase-activated receptor (PAR-2) was cloned recently and expressed in Xenopus laevis oocytes. PAR-2 was activated by trypsin and by a peptide (SLIGRL) derived from the new amino terminus. Since PAR-2 mRNA was detected in highly vascularized organs, we compared the physiological functions of the thrombin receptor and PAR-2 in vascular endothelium. Thrombin and trypsin both elicited endothelium-dependent relaxations in prostaglandin F2alpha (PGF2alpha)-contracted strips of porcine coronary artery. Whereas high doses of both thrombin or trypsin (10 U/mL) caused homologous desensitization, trypsin caused further relaxation of thrombin-desensitized tissues. Thrombin and PAR-2-derived peptides (SFLLRN and SLIGRL) both induced endothelium-dependent relaxations in PGF2alpha-contracted porcine coronary arteries. SFLLRN or SLIGRL (30 micronmol/L) also showed homologous desensitization but not cross desensitization. In the presence of the NO synthase inhibitor NG-monomethyl-L-arginine (1 mmol/L), both SFLLRN- and SLIGRL-induced relaxations were partially inhibited. SFLLRN elicited weak contraction in coronary arteries without endothelium, whereas SLIGRL had no effect. Intravenous injection of SFLLRN (1 mg/kg, bolus) into anesthetized rats elicited a transient depressor response followed by pronounced pressor response. In contrast, intravenous administration of SLIGRL (1 mg/kg, bolus) produced only a marked depressor response. Consistent with the in vivo data, SFLLRN contracted the endothelium-rubbed rat aortic rings and aggregated human platelets in vitro, whereas SLIGRL had no effect. The finding that both trypsin and SLIGRL induced endothelium-dependent relaxations indicates the presence of PAR-2 on endothelial cells. In addition, both trypsin and SLIGRL elicited relaxations in thrombin- or SFLLRN-desensitized tissue, suggesting that PAR-2 is distinct from thrombin receptor in vascular endothelium. The lack of PAR-2-mediated platelet aggregation or smooth muscle contraction suggested it might not share the pathogenic properties associated with the thrombin receptor in the vasculature.

Animals↗

PubMed1996

Developmental regulation of unique adenosine 3',5'-monophosphate-specific phosphodiesterase variants during rat spermatogenesis.

Previous studies from our laboratory have shown that messenger RNAs (mRNAs) coding for a cAMP-specific phosphodiesterase (PDE4A) are present in mature rat and mouse germ cells. However, no information is available about the properties of the expressed proteins. To determine their structure and regulation, the PDE4A isoforms expressed in the rat testis were identified and compared to the variants expressed in the brain. Western blot analysis using an antiserum specific for PDE4A demonstrated the presence in testis extracts of two distinct proteins with apparent masses of 98.8 and 86 kDa. The electrophoretic mobilities of these proteins differ from those of proteins detected in the brain extracts (113 and 76 kDa). Reverse transcriptase-PCR of the different splicing mRNA variants expressed in testis confirmed the presence of at least one novel PDE4A mRNA that is distinct from the PDE4A splicing variants identified in the brain and other tissues. Expression of the complementary DNA encoding this variant in a heterologous system resulted in an increase in PDE activity and the appearance of an immunoreactive protein with a mass of 98.8 kDa. No 86-kDa protein could be generated with this transfection. Upon fractionation of testis extracts by HPLC diethylaminoethyl-chromatography, a peak of cAMP-PDE activity coeluted with the two immunoreactive species. During testicular development, the 98.8-kDa protein is present in trace amounts at 10 days, and its level increases with the age of the animals, reaching a plateau at 40 days. The 86-kDa protein appears at 20 days of age and reaches its maximum at 40 days. Studies on the cellular site of expression demonstrated that the two polypeptides are most abundant in round spermatids and are expressed in trace amounts in pachytene spermatocytes, whereas they could not be detected in Sertoli or interstitial cells. The 98.8-kDa, but not the 86-kDa, protein was also expressed in epididymal spermatozoa. These data demonstrate the expression of novel cAMP-specific PDEs coded by the PDE4A gene. The expression of these isoforms is maximal in round spermatids and is maintained in mature spermatozoa. The genesis of the lower mol wt species remains to be determined.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1996

Protective effect of vitamin E on liver damage induced by 2-chloro-1, 3-butadiene.

The present study was performed to determine the influence of lipid peroxidation and perturbance of Ca2+ homeostasis on liver damage induced by 2-chloro-1, 3-butadiene (CBD) and the protective effects of vitamin E in Wistar rats. Animals were given intraperitoneally different doses (8,40 or 200 mg.kg.-1 daily) of CBD for 21 days, and the following dose-dependent events were observed: liver damage, significant increase in liver lipid peroxides, and decreases in activities of erythrocytic glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD). The pretreatment of rats with vitamin E (po 150 mg.kg-1) before administering CBD (ip 60 mg.kg-1) daily for 21 days prevented the following CBD-induced changes, the increase in serum cholyglycine (CG), hepatic LP, hepatic mitochondrion LP, hepatic oxidized glutathione (GSSG) (while the significant increase of reduced glutathione (GSH) was not affected) and the decrease in activities of erythrocytic SOD and hepatic mitochondrial calcium sequestration. These results suggest that lipid peroxidation and perturbance of Ca2+ homeostasis appear to contribute to the hepatotoxicity of CBD, and vitamin E might prevent the liver damage induced by CBD. The decrease in activities of GSH-Px and SOD in erythrocytes might be used as biomarkers for adverse effects of CBD on defense system against lipid peroxidation.

Animals↗

PubMed1996

[Supra-aortic arch esophagogastrostomy through esophageal bed in treating patients with middle and lower esophageal carcinoma].

A new surgical procedure of esophagogastrostomy was carried out in 162 cases with middle or lower thoracic esophageal carcinoma in our department from January, 1992 to December, 1994. Esophagogastrostomy was performed at supra-aortic arch site by pulling the stomach along the esophageal bed instead of putting it before aortic arch in the thoracic cavity. The procedure may keep the normal physiological function of the organs in the chest. It may help fully distend the left lung so as to reduce impairement of pulmonary function because the thoracic stomach was kept within the mediastinum. No resection mortality or anastomotic leakage occurred in the series. Since the esophagus and the stomach were anastomosed in a linear fashion without angulation, the evenly distributed intracavitary pressure may help prevent anastomotic leakage from occurrence. It is also easy to be dilated if anastomotic stricture occurs. In addition, the new procedure may be helpful in promoting gastric emptying, preventing gastric reflux, depressing and stopping the blood oozing in the mediastinum and air leakage from the ruptured lungs, as well as in distinguishing pleural effusion from gastric retention. Compared with other procedures, it is more difficult to perform the anastomosis. Once anstomotic leakage occurs, drainage is not easy.

Adult↗

PubMed1996

[Diagnosis and treatment of pleural mesothelioma: a report of 40 cases].

Forty patients with pleural mesothelioma confirmed pathologically including 2 benign and 38 malignant lesions are reported. In the 38 malignant mesotheliomas, 12 were histopathologically defined while the rest were unclassified. In this series, 33 surgical resections and 3 thoracotomy biopsies were carried out, whereas 4 patients were not operated. In 36 thoracotomies, there was one death with an operative mortality of 2.8% (1/36). Of 33 surgical resections, 10 (31%) received combined therapy. Of the 3 thoracotomy biopsy cases, postoperative irradiation was given to one, irradiation plus chemotherapy to the second and no treatment to the third. In 4 who were not operated, one died without treatment, two accepted chemotherapy and the fourth was treated with irradiation plus chemotherapy. Only two (5%) of these 40 patients had history of exposure to asbestos. The pre- and intra-operative diagnostic conformity rate was 50%. Ten patients were lost from follow-up. The longest survival was twelve years and one month. The authors sum-up their 31-year (1963-1994) experience of this disease and discuss the occupational factors in etiology, clinical diagnosis, treatment options and the significance of pathological types on prognosis of pleural mesothelioma.

Adolescent↗

PubMed1996

Prognostic significance of lymph node metastasis in surgical resection of esophageal cancer.

OBJECTIVE: Although surgery is relatively successful in eradicating local tumor, post-resection five-year survival rate for esophageal cancer is still lower than 30%. Multiple factors are found to influence the long-term results after surgical treatment. However, recent investigations have focused on the significance of lymph node matastasis (LNM), which seems to be one of the most important factors leading to poor survival. Hence, the prognostic significance of LNM in surgical resection of esophageal cancer was studied. METHODS: The rate and degree of LNM were evaluated and their prognostic significance was investigated through a retrospective study of 474 patients with esophageal cancer treated by surgery alone. RESULTS: LNM was positive in 211 patients, with an incidence of 44.5% (211/474). A total of 5382 lymph nodes were resected and studied pathologically, among which metastasis was found in 690 nodes with an overall LNM degree of 12.8% (690/5382). The 5-year survival rate was 30.6% (145/474) in the entire series, 12.8% (27/211) in patients with LNM, and 44.9% (118/263) in those without LNM. CONCLUSIONS: Surgery remains the first choice of treatment for carcinoma of the esophagus, and that meticulous lymph node dissection is an important practice of surgical oncology. However, in more advanced cases of this disease, surgery alone is of limited value in eradicating all cancer compromized tissue, and therefore the routine practice of extensive lymph node dissection in such cases may not be rewarding.

Adult↗

PubMed1996

Pharmacokinetics and tissue disposition of a chimeric oligodeoxynucleoside phosphorothioate in rats after intravenous administration.

Antisense oligonucleotides represent a novel therapeutic principle for designing drugs against various diseases. Oligonucleotides can be chemically modified to improve their pharmacokinetics and in vivo stability, and it is important to understand the effect of these modifications. In the present study, the pharmacokinetics of a 25-mer phosphorothioate oligonucleotide containing four contiguous, internucleotide, methylphosphonate linkages at the 3'- and 5'-ends (chimeric oligonucleotide) were determined in rats after i.v. administration of the 35S-labeled oligonucleotide at a dose of 30 mg/kg. Plasma disappearance of the oligonucleotide could be described by a two-compartment model, with half-lives of 0.38 and 52.9 hr. The intact chimeric oligonucleotide was detected in plasma up to 6 hr after dosing. Urinary excretion represented the major elimination pathway, with approximately 21% of the administered dose being excreted within 24 hr and 35% being excreted over a 240-hr period after dosing. The majority of the radioactivity in urine was associated with the intact oligonucleotide within 6 hr after dosing and with increasing degradation products thereafter. Fecal excretion was a minor elimination pathway. The oligonucleotide was widely distributed in tissues, with the majority of the radioactivity in most tissues being intact up to 48 hr after dosing. Compared with oligodeoxynucleotide phosphorothioates, the chimeric oligonucleotide was significantly more stable in vivo. The presence of intact oligonucleotide in plasma and tissues even 12 hr after dosing is a significant advantage over an "all"-phosphorothioate analog. Thus, the chimeric oligonucleotide could provide a longer duration of action as an antisense agent after its administration.

Animals↗

PubMed1996

[The most important prognostic factors for 736 patients with adenocarcinoma of the gastric cardia: a multivariate analysis using COX proportion hazard model].

A prognostic study was done in 736 patients with primary resectable adenocarcinoma of the gastric cardia whose postoperative survival time was longer than three months. The 3-, 5-, and 10-year cumulative survival rate was 32.2%, 20.2% and 12.2%, respectively. Thirty individual variables were evaluated statistically using the cumulative survival rate by the computer's COX multivariate analysis model. The results showed that the most important prognostic variables for predicting overall survival included maximal tumor diameter, type of resection, depth of invasion and paracardial lymph node metastasis. Sex and preoperative radiotherapy did not influence prognosis.

Adenocarcinoma↗

PubMed1996

[The colorimetric method for measuring activities of lipoprotein lipase and hepatic lipase in plasma].

To study the pathogenesis of hyperlipoidemia and atheromatosis and the metabolism of lipoprotein, we have developed a colorimetric method for simultaneously determining the activities of post-heparinplasma lipoprotein lipase (LPL) and hepatic lipase (HL). The intralipid was kept for LPL and HL at 37 degrees C, pH8.3 for 30 min, with 100 microliters post-heparin plasma. The LPL and HL in the post-heparin plasma could hydrolyse the triglyceride in intralipid into glycerine and free fatty acid (FFA). Determining the amount of FFA by copper-reagent method, we could measure the activities of LPL and HL. The kinetics of LPL and HL in post-heparin plasma was observed. K(m) values for LPL and HL were 0.9 mumol/L and 2.4 mumol/L respectively. The C. V. for LPL and HL were 4.5% (n = 4), 2.9% (n = 6) and 6.4% (n = 6), 4.8% (n = 6) respectively.

Animals↗

PubMed1996

[Treatment and prognosis of soft tissue sarcoma].

The treatment and prognosis of 121 patients with primary and locally recurrent soft tissue sarcomas of the extremities and trunk were analyzed. The most common histologic type was malignant fibrous histocytoma (32 patients, 26.4%). Ninety-three patients had high grade sarcomas (76.9%) and 28 had low grade sarcomas (23.1%). Adjuvant radiotherapy and chemotherapy were applied to 37 and 41 patients respectively. In 28 patients who had local recurrence after surgery, the 5-year local control rate was 72.3%. The overall 5-year survival rate was 59.9% for all patients, and 59.1% for 96 patients with locally recurrent lesions. The independent risk factors affecting the overall survival included high grade, tumor of upper extremity, perioperative blood transfusion, and tumor size of > or = 10 cm. We conclude that (1) wide excision is the most accepted operative procedure for treatment of soft tissue sarcoma of the extremity and trunk unless the lesions are locally advanced (In the advanced cases amputation should be performed); (2) in patients with local recurrence only, there is an almost same rate of long-term salvage as that in patients with primary tumors; (3) avoiding unnecessary perioperative blood transfusion may improve survival; and (4) further investigation of more effective regimen of adjuvant radiotherapy and chemotherapy needs to be taken.

Adolescent↗

PubMed1996

[Research of clinic and laboratory of face acupuncture effect and the exploration of their afferent pathways].

This paper shows that face acupuncture point (Liver point through gallbladder point) has significant effect of promoting bile secretion on the patients of cholecystectomy and choledochotomy and drainage. Special different point is that face acupuncture stimulation has very obvious posteffect comparing with other three body acupuncture groups and this posteffect lasts more than fifty minuts. The results also show that the successful rate of face acupuncture anesthesia is better than body acupuncture anesthesia during the ligation of oviduct and subtotal gastrectomy. The above results are all analysed statistically and there is a very significant difference among them. During the research on domestic dog anesthesiaed by face acupuncture, the successful rate is 86.5%, moreover the analgesic effect of face acupuncture can be blocked by blocking bilateral postganglionic fibre of trigeminal ganglion with 2% procaine. The results imply that trigeminal ganglion is the main afferent way of stimulation information of face acupuncture.

Acupuncture Analgesia↗

PubMed1996

[Reconstruction of right ventricular outflow tract using transannular patch in 52 children with tetralogy of Fallot].

52 children with tetralogy of Fallot received reconstruction of right ventricular outflow tract (RVOT) by using transannular patch. The indications for using transannular patch to reconstruct RVOT, patch materials, and the standard of enlargement pulmonary annulus were studied. The indications were held correctly for reconstruction of RVOT with transannular patch. The autologous pericardium was the most acceptable material for patch. All patients showed no obstruction of RVOT during early and late postoperative follow-up, althought most of them had certain degree of pulmonary regurgitation (PR) in first postoperative year, whicli was gradually attenuated as their life time long-drawn, with better exertion tolerance.

Adolescent↗

PubMed1996

[Measurement of serum apoA I and apoA II in 438 male healthy subjects aged 40-70 in Chengdu area].

Using the method of immunoturbidimetric assay (INA) for apoA 1 and the method of radial immunodiffusion assay (RID) for apoA II developed by ourselves, we measured the serum apoA I and apoA II concentrations in 438 male healthy subjects aged 40-70 in Chengdu area. The contents of serum apoA I and apoA II for male aged 40-70 were 130.1 +/- 22.0 mg/dl (n = 438) and 29.9 +/- 4.90 mg/dl (n = 437) respectively. The serum apoA I and A II levels showed no significant increase with age and had a normal distribution.

Adult↗

PubMed1996

[Surgical treatment of aortoesophageal fistula induced by foreign body in esophagus].

It is well known that there is no effective therapy to cure aortoesophageal fistula induced by a foreign body in the esophagus all over the world. In 220 cases of foreign body in esophagus, 4 developed the life-threatening complication of aortoesophageal fistula as the foreign body eroded through the esophageal wall and perforated the aorta. Although 3 of 4 patients were operated upon, only one survived by means of profound hypothermia and circulatory arrest. According to the successful experience and a review of the literature, the authors considered that some patients with aortoesophageal fistula may be saved if an emergency operation is undertaken immediately after the diagnosis made. Meanwhile, they divided this disease into 3 pathological types, and suggested the optimal operation procedure individualized to the different pathological types.

Adult↗

PubMed1996

[A study of corneal transplantation and human leukocyte antigen matching].

OBJECTIVE: The effect of human leukocyte antigen (HLA) matching on immune rejection after keratoplasty was studied. METHODS: Immunoserologic HLA typing was performed on thirty-three eyes with corneal vascularization of 33 high-risk patients before keratoplasty, and HLA matching was made before the surgery. The donor corneas used for these cases were selected on the basis of obtaining a negative HLA cross-match test and matched ABO antigen compatibility of blood group before surgery. The mean follow-up was fifteen months. RESULTS: The findings suggested that there should be highly statistic significance (t = 7.36, P < 0.01) between the rate of rejection of well matched group and that of the poorly matched one. There was no correlation between the number of HLA antigen matched and the rejection rate (t = 0.917, P > 0.05). CONCLUSION: Lower incidence of corneal graft failure from allograft rejection occurs when well HLA matching is used for selecting donor in high-risk patients with corneal vascularization.

Adult↗