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Biomedical subjects

J Leng

Publications and source records attributed to J Leng.

At least 37 records · Page 2Linked to original sources
PubMed1998

CAS/Crk coupling serves as a "molecular switch" for induction of cell migration.

Carcinoma cells selected for their ability to migrate in vitro showed enhanced invasive properties in vivo. Associated with this induction of migration was the anchorage-dependent phosphorylation of p130CAS (Crk-associated substrate), leading to its coupling to the adaptor protein c-CrkII (Crk). In fact, expression of CAS or its adaptor protein partner Crk was sufficient to promote cell migration, and this depended on CAS tyrosine phosphorylation facilitating an SH2-mediated complex with Crk. Cytokine-stimulated cell migration was blocked by CAS lacking the Crk binding site or Crk containing a mutant SH2 domain. This migration response was characterized by CAS/Crk localization to membrane ruffles and blocked by the dominant-negative GTPase, Rac, but not Ras. Thus, CAS/Crk assembly serves as a "molecular switch" for the induction of cell migration and appears to contribute to the invasive property of tumors.

Animals↗
PubMed1998

Activation of Rac and Cdc42 by integrins mediates cell spreading.

Adhesion to ECM is required for many cell functions including cytoskeletal organization, migration, and proliferation. We observed that when cells first adhere to extracellular matrix, they spread rapidly by extending filopodia-like projections and lamellipodia. These structures are similar to the Rac- and Cdc42-dependent structures observed in growth factor-stimulated cells. We therefore investigated the involvement of Rac and Cdc42 in adhesion and spreading on the ECM protein fibronectin. We found that integrin-dependent adhesion led to the rapid activation of p21-activated kinase, a downstream effector of Cdc42 and Rac, suggesting that integrins activate at least one of these GTPases. Dominant negative mutants of Rac and Cdc42 inhibit cell spreading in such a way as to suggest that integrins activate Cdc42, which leads to the subsequent activation of Rac; both GTPases then contribute to cell spreading. These results demonstrate that initial integrin-dependent activation of Rac and Cdc42 mediates cell spreading.

3T3 Cells↗
PubMed1998

[Localization and quantitative analysis of insulin-like growth factor-I in placenta of extreme fetus].

OBJECTIVE: To investigate the immunohistochemical localization of insulin-like growth factor-I (IGF-I) in human placenta and to evaluate the role of IGF-I in fetal growth and placental growth. METHODS: In 72 tested samples, The cellular distribution of IGF-I in human placenta was determined by using immunohistochemistry. The relative area and mean absorbance were determined by using image analysis technique. Student's t-test was used to compare mean values between groups. RESULTS: IGF-I immunostaining was found in syncytiotrophoblast, cytotrophoblast and Hoffbauer's cells of chorionic villi and chorion of fetal membranes. The strongest immunoreactivity was observed in the syncytiotrophoblast and cytotrophoblast. The relative area and absorbance in placenta of SGA group were significantly lower than those of AGA group respectively (t = 4.65, P < 0.001; t = 2.15, P < 0.05). But the relative arca and absorbance of LGA were significantly higher than those of AGA (t = 8.72, P < 0.001; t = 7.82, P < 0.001). CONCLUSION: These results suggested that IGF-I in human placenta was principally synthsized and secreted by syncytiotrophoblast, cytotrophoblast, hoffbauer's cells of chorionic villi and chorion of fetal membranes. IGF-I is an improtant regulator of fetal and placental growth and development. It has the key role for macrosomia and IUGR forming.

Adult↗
PubMed1997

Overexpression of p53, EGFR, c-erbB2 and c-erbB3 in endometrioid carcinoma of the ovary.

OBJECTIVES: To determine overexpression of p53, EGFR, c-erbB-2 and c-erbB-3 in endometrioid carcinoma of the ovary and to evaluate the prognostic significance of these results, especially, coexisting overexpression of p53 and one of the member of type I growth factor receptor family. METHODS: Overexpressions of the p53, EGFR, c-erbB-2 and c-erbB-3 protein were studied by immunohistochemistry in paraffin-embedded tumor tissue from 28 patients with endometrioid carcinoma of the ovary. RESULTS: 11 (39.3%), 13 (46.4%), and 14 (50.0%) were stained positively with p53, c-erbB-2 and c-erbB-3 monoclonal antibodies. 13 (46.4%) was stained positively with EGFR polyclonal antibody. There were no relationship between p53, EGFR, C-erbB-2, c-erbB-3 and histologic grade, lymph node metastasis. The percentage of tumors with over expression of p53, EGFR, C-erbB-2 and c-erbB-3 was higher in those with stage II-III tumors compared with those with stage I, in patients with residual tumor after initial surgery compared with those without. A high survival rate was observed in patients without p53, EGFR, c-erbB-2 and c-erbB-3 overexpression respectively than those with. A highest survival rate was observed in patients with both p53 and one of EGFR, c-erbB-2 and c-erbB-3 negative compared with those both positive or either of both positive. CONCLUSION: Overexpression of p53, EGFR, c-erbB-2 and C-erbB-3 resulted in a poorer prognosis respectively. Overexpression of both p53 and one of the EGFR, c-erbB-2 and c-erbB-3 is a worse prognostic indicator in patients with endometrioid carcinoma of the ovary.

Adult↗
PubMed1996

[Expression of epidermal growth factor receptor (EGFR) in endometrioid carcinoma of the ovary].

OBJECTIVE: To determine the expression of EGFR expression in endometrioid carcinoma of the ovary and its relationship to clinicopathologic features and prognosis. METHODS: Expression of EGFR oncoprotein was studied by immunohistochemistry in paraffin-embedded tumor tissues from 28 patients with endometrioid carcinoma of the ovary. RESULTS: Tissues from 13 patients (46.4%) were stained positively with EGFR polyclonal antibody (1005). The staining was membranous and/or cytoplasmic. There was no relationship between EGFR expression and age at diagnosis, preoperative CA125 titer, clinical stage, histologic grade, and lymph node metastases. A higher expression rate was observed in patients with residual tumors (56.3% versus 33.3%). The mortality rate was higher in patients with EGFR expression than in those without EGFR expression (46.2% versus 14.3%), but the difference was not statistically significant. CONCLUSION: EGFR expression was not related to the clinicopathologic features in endometrioid carcinoma of the ovary, but was related to the poor prognosis of this disease.

Carcinoma, Endometrioid↗
PubMed1996

[The effect of splenectomy on alveolar macrophages morphology and function].

OBJECTIVE: To study the morphological and functional changes of pulmonary alveolar macrophages of rats after splenectomy, and the applied effects of splenic tissue autotransplantation in practice. METHODS: 87 Wistar rats were randomly divided into shamoperation group, splenectomy group and splenic tissue autotransplantation group. Six months after splenectomy, alveolar macrophges were subjected to brochoalveolar lavage described by Shennib. The dynamic survival and adherent rate of alveolar macrophages in culture, lysosomal enzyme content, hydrogen peroxide production and expression level of interleukin 1 (IL-1) activity of alveolar macrophages were quantitatively measured. The alveolar macrophages ultrastructure was observed by utilizing transmission electron microscope. RESULTS: The splenectomized rat's alveolar macrophages were different from alveolar macrophages of sham-operated rats. Their surface filopodia was reduced and shortened, lysosome fewer and its acid phosphatase quantity decreased, adherence postponed, hydrogen peroxide production and expression of IL-1 activity impaired. Splenic tissue autotransplantation fairly restored the splenic effects on maturation and function of alveolar macrophages. CONCLUSION: Splenic tissue autotransplantation is a simple useful operation for preserving splenic function after splenectomy.

Animals↗
PubMed1995

Isolation and cloning of a protein-serine/threonine phosphatase from an archaeon.

A divalent metal ion-stimulated protein-serine/threonine phosphatase, PP1-arch, was purified approximately 1,000-fold from the extreme acidothermophilic archaeon Sulfolobus solfataricus (ATCC 35091). Purified preparations contained 40 to 70% of total protein as PP1-arch, as determined by assay-ing sodium dodecyl sulfate-polyacrylamide gels for protein phosphatase activity. The first 25 amino acids of the protein's sequence were identified, as well as an internal sequence spanning some 20 amino acids. Using this information, we cloned the gene for PP1-arch via the application of PCR and conventional cloning techniques. The gene for PP1-arch predicted a protein of 293 amino acids that bore striking resemblance to the members of the major family of protein-serine/threonine phosphatases from members of the domain Eucarya, the PP1/2A/2B superfamily. The core of the protein, spanning residues 4 to 275, possessed 29 to 31% identity with these eucaryal protein phosphatases. Of the 42 residues found to be absolutely conserved among the known eucaryal members of the PP1/2A/2B superfamily, 33 were present in PP1-arch. If highly conservative substitutions are included, this total reached 37. The great degree of sequence conservation between molecules from two distinct phylogenetic domains implies that the members of this enzyme superfamily had evolved as specialized, dedicated protein phosphatases prior to the divergence of members of the Archaea and Eucarya from one another.

Amino Acid Sequence↗
PubMed1995

[Chemotherapy through selective pelvic artery catheterization complicated by mural thrombosis].

Through catheter on uterine artery digital subtractive angiography (DSA) intraarterial infusion of chemotherapeutic agents for the treatment of malignant trophoblastic diseases can raise local drug concentration, improve therapeutic results and reduce general side-effects. But mural thrombosis, a possible complication of intra arterial catheterization, should not be overlooked. This study reports 2 cases of mural thrombosis complication in selective pelvic artery catheterization for chemotherapy. The incidence, relevant factors to its occurrence such as technique of catheterization and the duration of catheter retention, as well as measures of prevention and treatment of mural thrombosis are discussed together with review of literature. With regards to prevention of mural thrombosis, stress is being laid on the importance of the technique of catheterization. Preliminary comments on the problem of heparin administration as a preventive measure of mural thrombosis are made.

Adult↗
PubMed1993

Identification of a serine/threonine-specific protein phosphatase from the archaebacterium Sulfolobus solfataricus.

We have observed that soluble extracts from the extreme acidothermophilic archaebacterium Sulfolobus solfataricus contained protein phosphatase activity that was greatly stimulated by the divalent metal ions Mn2+, Mg2+, Ni2+, or Co2+. This activity apparently arose from a single enzyme since (a) stimulation by these divalent metal ions was not additive and (b) protein phosphatase activity eluted as a single peak from both a DE52 ion-exchange column and a Sephadex G-100 gel filtration column. Its apparent molecular mass was approximately 28,000 daltons. The enzyme dephosphorylated a variety of phosphoserine-containing substrates including casein, histone H2a, phosphorylase kinase, or glycogen phosphorylase. The enzyme would not dephosphorylate either histone H1 or a number of phosphotyrosine-containing compounds. It removed only half the phosphate bound to histone H2b, which is phosphorylated at two sites by the cAMP-dependent protein kinase. Protein phosphatase activity was inhibited by EDTA, Cu2+, Zn2+, NaF, inorganic phosphate, or pyrophosphate; but was unaffected by other potential activators and inhibitors such as microcystin, okadaic acid, vanadate, polyamines, or sulfhydryl modifying reagents. This enzyme represents the first protein phosphatase to be identified in any member of the third and oldest phylogenetic kingdom in nature, the archaebacteria.

Enzyme Activation↗
PubMed1992

The MgATP-binding site on chicken gizzard myosin light chain kinase remains open and functionally competent during the calmodulin-dependent activation-inactivation cycle of the enzyme.

An ATP-like affinity labeling reagent, 5'-[p-(fluorosulfonyl)benzoyl]adenosine (FSBA), was used to probe the MgATP-binding site of smooth muscle myosin light chain kinase from chicken gizzard (smMLCK) and its calmodulin (CaM) complex. Native smMLCK has an absolute requirement for the binding of the calcium complex of CaM for expression of its catalytic activity. FSBA reacted with smMLCK-CaM and with the CaM-free, inactive enzyme as well. Both reactions were dependent on time and FSBA concentration. Reaction was accompanied by the incorporation of covalently bound [14C]FSBA into smMLCK protein at a molar ratio of approximately 1:1 in each case. p-(Fluorosulfonyl)benzoic acid, an analogue of FSBA lacking the adenosine targeting group, did not react at a significant rate with either form of smMLCK. Reaction of CaM-free and CaM-bound smMLCK with FSBA displayed saturation kinetics. The first-order rate constants for the conversion of the reversible, noncovalent enzyme-FSBA complex to form the irreversibly inhibited, covalently modified enzyme were similar for both smMLCK and smMLCK-CaM, 0.15 and 0.07 min-1, respectively. The concentrations of FSBA yielding the half-maximal rate of inactivation, KI, were essentially identical--0.65 and 0.64 mM, respectively--for smMLCK and smMLCK-CaM. MgATP, but not MgGTP or a substrate peptide, potently inhibited reaction with FSBA. Inhibition by MgATP was competitive. The measured inhibitory constant for MgATP was essentially the same--33 versus 34 microM--for both smMLCK and smMLCK-CaM. It therefore is concluded that the MgATP-binding site on smMLCK remains accessible and recognizable as such when the enzyme becomes inactivated upon dissociation of CaM.

Adenosine Triphosphate↗
PubMed1992

[A study of duck hepatitis B virus infection in Chinese ducklings].

Intraperitoneal inoculation of duck hepatitis B virus in three different dosages (9 x 10(7), 1.8 x 10(8), 9 x 10(8) DHBV particles) into 3 to 21 day-old Chinese ducklings provided from a DHBV free flock produced a persistent infection up to 93.3% in 60 animals. The serum and liver specimens of these ducklings were examined by DNA dot blot hybridization on the 30th day after inoculation. The results showed that: (1) examination of viral DNA in liver was more sensitive and reliable than estimation of the DNA in serum for detecting DHBV infection in inoculated ducklings; (2) the liver DHBV DNA level did not coincide with the degree of liver hepatitis induced; (3) 21-day-old Chinese ducklings were also susceptible to DHBV infection, the infection rate of this group was 100% (10/10).

Age Factors↗
PubMed1989

Amoxycillin/clavulanic acid ('Augmentin') compared with a combination of aminopenicillin, aminoglycoside and metronidazole in the treatment of pelvic inflammatory disease.

A randomized, multi-centre trial was carried out in 152 hospitalized women with pelvic inflammatory disease to evaluate the efficacy and tolerability of amoxycillin/clavulanic acid compared with that of a standard regimen using three antimicrobial agents (aminopenicillin, an aminoglycoside and metronidazole). Seventy patients initially received 3 to 4 intravenous doses per day of 1 g amoxycillin/200 mg clavulanic acid (mean 7.7 days) and then 4 to 6 tablets per day of 500 mg amoxycillin/125 mg clavulanic acid (mean 11.2 days). The other group of 82 patients initially received parenteral therapy daily (mean 7.7 days) with a combination of 3 to 4 g amoxycillin or ampicillin, 160 mg gentamicin (or 150 mg dibekacin or tobramycin) and 1.5 g metronidazole, and then oral therapy with 2 to 3 g amoxycillin or ampicillin and 1 to 1.5 g metronidazole daily (11.1 days). Clinical results, assessed at discharge from hospital (mean 10 days in both groups), were comparable in both groups, with 96% complete or partial response and no failures in the amoxycillin/clavulanic acid group, and 90% complete or partial successes and 5 failures with the triple therapy regimen. Both treatments were well tolerated and very few side-effects were reported.

Adult↗
PubMedDate not supplied

Carcinosarcoma arising from atypical endometriosis in a cesarean section scar.

Malignant change of endometriosis in a cesarean scar (CS) is rare. We report a case of carcinosarcoma arising from atypical endometriosis in a CS scar, which was successfully treated with complete excision of the lesion and repair of the abdominal wall defect with autologous skin-muscle flap graft. A 41-year-old woman presented with a recurrent endometriosis in a CS scar. Within 16 years it changed from benign to atypical endometriosis and finally to carcinosarcoma after three operations. Complete excision of the tumor was performed, with a big defect of abdominal wall successfully repaired by autologous pedicle skin-muscle graft. The diagnosis of carcinosarcoma arising from atypical endometriosis was confirmed histologically. The lesion recurred 6 months after the fourth operation. She died of disease 15 months after the fourth operation. This case demonstrated that long-standing recurrent scar endometriosis could undergo malignant changes and should be made aware. The primary treatment is complete surgical excision.

Abdominal Wall↗