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Biomedical subjects

L Yan

Publications and source records attributed to L Yan.

At least 109 records · Page 6Linked to original sources
PubMed2000

Identification and characterization of hydra metalloproteinase 2 (HMP2): a meprin-like astacin metalloproteinase that functions in foot morphogenesis.

Several members of the newly emerging astacin metalloproteinase family have been shown to function in a variety of biological events, including cell differentiation and morphogenesis during both embryonic development and adult tissue differentiation. We have characterized a new astacin proteinase, hydra metalloproteinase 2 (HMP2) from the Cnidarian, Hydra vulgaris. HMP2 is translated from a single mRNA of 1.7 kb that contains a 1488 bp open reading frame encoding a putative protein product of 496 amino acids. The overall structure of HMP2 most closely resembles that of meprins, a subgroup of astacin metalloproteinases. The presence of a transient signal peptide and a putative prosequence indicates that HMP2 is a secreted protein that requires post-translational processing. The mature HMP2 starts with an astacin proteinase domain that contains a zinc binding motif characteristic of the astacin family. Its COOH terminus is composed of two potential protein-protein interaction domains: an "MAM" domain (named after meprins, A-5 protein and receptor protein tyrosine phosphatase mu) that is only present in meprin-like astacin proteinases; and a unique C-terminal domain (TH domain) that is also present in another hydra metalloproteinase, HMP1, in Podocoryne metalloproteinase 1 (PMP1) of jellyfish and in toxins of sea anemone. The spatial expression pattern of HMP2 was determined by both mRNA whole-mount in situ hybridization and immunofluorescence studies. Both morphological techniques indicated that HMP2 is expressed only by the cells in the endodermal layer of the body column of hydra. While the highest level of HMP2 mRNA expression was observed at the junction between the body column and the foot process, immunofluorescence studies indicated that HMP2 protein was present as far apically as the base of the tentacles. In situ analysis also indicated expression of HMP2 during regeneration of the foot process. To test whether the higher levels of HMP2 mRNA expression at the basal pole related to processes underlying foot morphogenesis, antisense studies were conducted. Using a specialized technique named localized electroporation (LEP), antisense constructs to HMP2 were locally introduced into the endodermal layer of cells at the basal pole of polyps and foot regeneration was initiated and monitored. Treatment with antisense to HMP2 inhibited foot regeneration as compared to mismatch and sense controls. These functional studies in combination with the fact that HMP2 protein was expressed not only at the junction between the body column and the foot process, but also as far apically as the base of the tentacles, suggest that this meprin-class metalloproteinase may be multifunctional in hydra.

Amino Acid Sequence↗
PubMed2000

Adhesion-dependent control of matrix metalloproteinase-2 activation in human capillary endothelial cells.

The growth and regression of capillary blood vessels during angiogenesis is greatly influenced by changes in the activity of matrix metalloproteinases (MMPs), which selectively degrade extracellular matrix (ECM) and thereby modulate capillary endothelial cell shape, growth and viability. However, changes in cell-ECM binding and cell spreading have also been reported to alter MMP secretion and activation. Studies were carried out to determine whether changes in integrin binding or cell shape feed back to alter MMP-2 processing in human capillary endothelial (HCE) cells. Catalytic processing of proMMP-2 to active MMP-2 progressively decreased when HCE cells were cultured on dishes coated with increasing densities of fibronectin (FN), which promote both integrin binding and cell spreading. Conversely, the highest levels of active MMP-2 were detected in round cells cultured on low FN. When measured 24 hours after plating, this increase in active MMP-2 was accompanied by a concomitant rise in mRNA and protein levels for the membrane-type 1 MMP (MT1-MMP), which catalyzes the cleavage of proMMP-2. To determine whether proMMP-2 processing was controlled directly by integrin binding or indirectly by associated changes in cell shape, round cells on low FN were allowed to bind to microbeads (4.5 microm diameter) coated with a synthetic RGD peptide or FN; these induce local integrin receptor clustering without altering cell shape. ProMMP-2 activation was significantly decreased within minutes after bead binding in these round cells, prior to any detectable changes in expression of MT1-MMP, whereas binding of beads coated with control ligands for other transmembrane receptors had no effect. This inhibitory effect was mimicked by microbeads coated with activating antibodies against alphaVbeta3 and beta1 integrins, suggesting a direct role for these cell-surface ECM receptors in modulating proMMP-2 activation. Similar inhibition of proMMP-2 processing by integrin binding, independent of cell spreading, was demonstrated in cells that were cultured on small, microfabricated adhesive islands that prevented cell spreading while presenting a high FN density directly beneath the cell. Interestingly, when spread cells were induced to round up from within by disrupting their actin cytoskeleton using cytochalasin D, proMMP-2 processing did not change at early times; however, increases in MT1-MMP mRNA levels and MMP-2 activation could be detected by 18 hours. Taken together, these results suggest the existence of two phases of MMP-2 regulation in HCE cells when they adhere to ECM: (1) a quick response, in which integrin clustering alone is sufficient to rapidly inhibit processing of proMMP-2 and (2) a slower response, in which subsequent cell spreading and changes in the actin cytoskeleton feed back to decrease expression of MT1-MMP mRNA and, thereby, further suppress cellular proteolytic activity.

Capillaries↗
PubMed2000

Effect of vanadyl ions on calcineurin and its A subunit.

Calcineurin (CN) exhibits a bimodal regulation by different concentrations of vanadyl ions (VO2+) in the presence of Mn2+. Low concentrations of VO2+ inhibit the enzyme, with 50 microM VO2+ completely inhibiting CN activity, while high concentrations, up to 500 microM VO2+, stimulate the CN activity. A similar bimodal regulation of CN was not observed with either calcium or vanadate under the same conditions. X-band electron spin resonance spectroscopy, used to study the binding of VO2+ to the catalytic subunit A of calcineurin, show that there are two kinds of binding sites in the A subunit.

Animals↗
PubMed2000

A clinical investigation on zhi ling tang for treatment of senile dementia.

Zhi Ling Tang (ZLT [symbol: see text], a TCM prescription designed for replenishing essence, supplementing marrow, invigorating qi, warming yang, removing blood stasis and phlegm, tonifying the brain, and invigorating mental activity) was used in 32 cases of senile dementia (SD). After treatment, the levels of serum cholesterol (Tch), triglyceride (TG), and plasma lipid peroxides (LPO) were lowered; the content of high density lipoprotein (HDL) and the activity of superoxide dismutase (SOD) in RBC significantly elevated, the cerebral blood flow was increased; latent period of P300 and P3 waves was shortened while the amplitude of P3 elevated; and topographic electroencephalogram, revised Hasegawa dementia scales (HDS) scores (P < 0.05-0.01) and clinical symptoms were improved. The total effective rate was 81.3%, indicating that ZLT exhibits relatively good therapeutic effects for treating senile dementia.

Aged↗
PubMed2000

[Applied anatomy of the transverse rectus abdominis musculocutaneous (TRAM) flap in relation to the eleventh or twelfth thoracic nerve].

OBJECTIVE: To observe the distribution of the terminal branches of the eleventh and twelfth thoracic nerve(T11, T12) for the anatomical basis and operation key points of the transverse rectus abdominis musculocutaneous(TRAM) flap with T11, T12. METHODS: The anterior abdominal wall was investigated through anatomical dissection in 22 embalmed cadavers. RESULTS: Cutaneous nerve distribution in the TRAM flap came mainly from T11, T12. They run obliquely between transverse abdominis and obliquus internus abdominis muscle. At the lateral edge of the rectus abdominis, they piece the anterior rectus sheath into the muscle. While supplying the muscle they pass on to supply the anterior rectus sheath and the overlying skin. CONCLUSION: It is possible to preserve T11, T12 in the TRAM flap, which would favour rapid return of flap sensation.

Female↗
PubMed2000

Change of apoptotic status in the human colorectal adenoma-carcinoma sequences and its correlation with carcinogenesis and prognosis.

OBJECTIVE: To assess apoptotic status during the development of colorectal cancer and its prognostic value. METHODS: The apoptotic frequency of 168 fresh adenocarcinoma specimens and primary cultured cells at 2, 12, 24 and 48 hours (9 normal mucosa, 4 adenomas and 9 adenocarcinomas) were measured by flow cytometry (FCM). Apoptotic indices (AI) in situ for 25 adenomas and 77 adenocarcinomas were visualized by TdT-mediated dUTP nick end labeling (TUNEL), Ki-s5 labeling indices (KI), bcl-2, bax, waf1 and p53 were immunostained with ABC method. RESULTS: The culture-related apoptosis at 24-48 hours in vitro was obviously decreased in cultured tumor cells when compared with mucosa cells. Spontaneous apoptosis in situ occurred more frequently in tumor with aneuploid type at late stage. There was positive relationship between apoptosis and proliferative activity, determined by both TUNEL and FCM methods. The well-differentiated or early stage lesions with intensive bcl-2/bax expression were significantly more likely to have low AI. p53 accumulation and waf1 depression were mainly related to KI, whereas bax and waf1 overexpression led to a comparatively higher AI/KI ratio. bcl-2 and KI were found to be independent risk factors. CONCLUSIONS: The data suggest that the depressed susceptibility to inductive apoptosis may contribute to the initial phase of tumorigenesis, and spontaneous apoptosis in vivo may serve as a marker of tumor progression. The bcl-2 and KI may be valuable in predicting prognosis in colorectal cancer.

Adenocarcinoma↗
PubMed2000

Design and clinical application of cervical hollow threaded fixator.

OBJECTIVE: Cervical hollow threaded fixator (CHTF) was designed and applied to stabilize the cervical spine following anterior decompression due to cervical spondylosis or acute cervical disc herniation. METHODS: Medical use titanium alloy with no magnetism was made into a hollow threaded structure with holes on the wall of the fixator. Forty-two patients with cervical spondylosis and acute cervical disc herniation were stabilized using the CHTF technique after anterior decompression. X-ray films and CT scans were taken after the operation to observe the stability and fusion rate of the segments. RESULTS: Patients were allowed to walk one day after the operation and were followed up for 6 to 36 months. The operated segments were stable and solid fusion was observed 3-6 months after surgery. CONCLUSIONS: Immediate stability of the operated segments can be obtained using the CHTF technique. Patients were easy to manage after the operation and returned to their jobs in a short time. The CHTF technique is safe and simple to perform and eliminates the complications of an autograft. It may be an alternative to traditional cervical interbody fusion with bone graft.

Adolescent↗
PubMed2000

[Surgery for patients with primary liver cancer: report of 1,038 patients].

OBJECTIVE: To investigate methods for enhancing safety of and improving the survival in patients with primary liver cancer (PLC). METHODS: One thousand and thirty eight patients with PLC were treated in our hospital from January 1990 to December 1998. The early period group (from January 1990 to December 1996) consisted of 731 patients [312 patients (42.7%) receiving liver resection]; the late period group (from January 1997 to December 1998) included 307 patients [217 patients (70.7%) receiving liver resection]. RESULTS: The mortality within one month after hepatectomy was 2.24% in the early group and 0.74% in the late group. The 1-, 3- and 5-year survival rates were 73.1%, 54.2%, and 34.0% respectively in patients undergoing hepatectomy in the early group and 91.1%, 63.8% and 40.2% in the late group. CONCLUSIONS: Regular follow-up of high risk patients is helpful to discover small PLC. High proportion of small PLC, progress of perioperative management, and improvement of operative techniques including hepatopetal blood occlusion of half liver or in vitro-bypass through bio-pump during hepatectomy might be important approaches to enhance the safety of surgical treatment and improve the prognosis of patients with PLC.

Adolescent↗
PubMed2000

[The relationship between effects and radiation doses of intra-arterial phosphorus-32 glass microspheres embolization therapy for patients with advanced liver cancer].

OBJECTIVE: To evaluate the relationship between effects and internal radiation of phosphorus-32 glass microspheres embolization therapy for liver cancer patients. METHODS: From 1994 to 1998, 44 patients with unresectable liver cancer received intra-arterial radio-embolization therapy using (32)P-GMS. Preoperative and postoperative function and energy level of the liver were tested by liver function test and arterial blood ketone body ratio (AKBR). CT, single photon emission computer tomography (SPECT), and AFP were used to judge the effect of the therapy; multivariate analysis was made. RESULTS: In the moderate dose group, low incidence of complication, high tumor shrinking rate and AFP decreasing rate, and long-term survival rate were observed. In the larger dose group, high incidence of liver failure, high tumor shrinking rate and AFP decreasing rate, and long-term survival rate were also observed. In the low dose group, low incidence of complication, but low tumor shrinking rate and AFP decreasing rate and long-term survival rate were not observed. CONCLUSIONS: The reasonable radiation doses for liver cancer patients may be about 30 Gy; if liver cirrhosis is serious, the doses can be reduced.

Adult↗
PubMed2000

[Expression of proliferation and apoptosis related genes in colorectal adenoma with malignant transformation].

OBJECTIVE: The effect of proliferation and apoptosis related genes of colorectal adenoma with malignant transformation and its clinicopathologic significance was studied. METHODS: p53, bcl-2, Fas, bax expression were detected immunohistochemically in 61 cases of colorectal adenoma with either mild or severe dysplasia and carcinoma. The rate of proliferation was evaluated with Ki-67 and apoptosis with TUNEL. RESULTS: The positive rates for p53 and bcl-2 protein in carcinomatous area, adenoma with severe and mild dysplasia were 67.2%, 57.4%, 19.7% and 77.1%, 80.3%, 49.2% respectively. The mean Ki-67 index and PCD index were 38.4%, 36.5%, 16.1% and 2.2%, 1.9%, 0.5% respectively. The difference of the expression of p53 protein, bcl-2 protein and Ki-67 index, PCD index in carcinomatous region and adenoma with severe dysplasia compared with mild dysplasia was statistically significant (P < 0.05). CONCLUSION: It is apparent that both apoptosis inhibition and abnormal proliferation play an important role in tumor formation. Adenoma with severe dysplasia is a lesion very close to carcinoma in nature, which possesses active tendency to become fully malignant. Detection of these proteins is important in the early diagnosis of malignant transformation of an adenoma.

Adenoma↗
PubMed2000

[The relations of cellular DNA content to lymph node metastasis in gastric carcinoma].

The objectives of this study were to evaluate the relations of cellular DNA content, S-phase fraction (SPF) and G2/M-phase(G2/MPF) to lymph node metastasis in gastric carcinoma by using flow cytometry. The results showed that the incidence of lymph node metastasis and SPF were significantly higher in aneuploid carcinoma than in diploid carcinoma(P < 0.05). But the G2/MPF values did not correlate with lymph node metastasis. These findings suggest that correlations between cellular DNA content, SPF and the extent of lymph node metastasis are present.

Adenocarcinoma↗
PubMed2000

[Expression of human papillomavirus DNA in cholesteatoma of the middle ear].

OBJECTIVE: To reveal the role of HPV in the occurrence and development of cholesteatoma of the middle ear. METHOD: PCR and nuclear acid hybridization were applied in screening 44 cases of middle ear cholesteatoma for detection of HPV DNA, and a comparison analysis with the pathological results of 35 cases of middle ear cholesteatoma was made. RESULTS: Pathologically, the characteristics of HPV induced-lesions was found in 12 of 35 specimens (34.3%). 44 cases of middle ear cholesteatoma were examined with consensus primers PCR and digoxigenin labeled HPV general probes. HPV DNA positive rates were 29.5% (13/44) and 25.0% (11/44) respectively. HPV DNA positive rate was 58.3% (7/12) and 13.0% (3/23) respectively in 12 cases with pathological characteristics of HPV induced-lesions and in 23 cases without those characteristics. There was significant difference(chi 2 = 7.926, P < 0.005). CONCLUSIONS: HPV infection can arouse the cleavage and proliferation of cholesteatoma epithelium and may play certain role in the occurrence and development of middle ear cholesteatoma. Aggressive, papillomatous growth and koilocytes can be served as the initial proof of HPV infection in cholesteatoma of the middle ear.

Adolescent↗
PubMed2000

Final report about Stage II Collaboration Project on Leprosy Rehabilitation.

OBJECTIVE: To undertake the pilot experiments of prevention of disability (POD) in 14 different geographical areas to serve as examples for future development of rehabilitation work in China and in Asia. METHODS: According to the principles and national criterion, 27 000 people affected by leprosy were selected and assessed using disability record forms at beginning and followed up regularly for observing changes of different indicators. RESULTS: A total of 197 neuritis cases were detected and treated with prednisolone out of 1 407 new or active cases. Self-care training of eyes, hands and feet were conducted for 10 500 disabled people affected by leprosy. Comprehensive therapy was given to 1 804 cases having complicated ulcers of which 1 055 cases have got their ulcers healed. Out of 706 prostheses, 613 were given to patients with satisfactory results. Surgical treatment was given to 269 cases and 251 have shown good progress. CONCLUSION: Most of patients have got benefit from the project in function or appearance which is very helpful for their going back to the society and agreed by foreign experts during the final evaluation. The experiences from the project can be implemented in the whole country.

China↗
PubMed1999

Nonstatistical binding of a protein to clustered carbohydrates.

Carbohydrate-derivatized self-assembled monolayers (SAMs) are used as a model system to address issues involving cell-surface carbohydrate-protein interactions. Here we examine the influence of carbohydrate surface density on protein-binding avidity. We show that the binding selectivity of Bauhinia purpurea lectin switches from one carbohydrate ligand to another as the surface density of the carbohydrate ligands increases from values of chi(sugar) approximately 0.1-1.0. Polyvalent binding is possible at all surface densities investigated; hence, the switch in selectivity is not due simply to the achievement of a critical density that permits polyvalent contacts. Instead, secondary interactions at high surface densities promote a switch in carbohydrate-binding selectivity. These findings may have implications for how changes in the composition and the density of cell-surface carbohydrates influence biological recognition processes and regulatory pathways.

Carbohydrate Metabolism↗
PubMed1999

Characterization of the enzymatic properties of the first and second domains of metallocarboxypeptidase D.

Carboxypeptidase D (CPD) contains three domains with homology to other metallocarboxypeptidases. To further characterize the various domains, we constructed a series of point mutants with a critical active site Glu of duck CPD converted to Gln. The proteins were expressed in the baculovirus system, purified to homogeneity, and characterized. Point mutations within both the first and second domains eliminated enzyme activity, indicating that the third domain is inactive toward dansyl-Phe-Ala-Arg. CPD removed only the C-terminal Lys or Arg from peptides, with the first domain more efficient toward Arg and the second domain more efficient toward Lys. Peptides containing Pro in the penultimate position were poorly cleaved by either domain. Cleavage of a peptide with Ala in the penultimate position was most efficient, with the relative order Ala >/= Met > Ser, Phe > Tyr > Trp > Thr >/= Gln, Asp, Leu, Gly >> Pro for CPD with both domains active. There were only minor differences between the first and the second domains regarding the influence of the penultimate amino acid. The first domain was optimally active at pH 6.3-7.5, whereas the second domain was optimally active at pH 5. 0-6.5. Thus, the first and second carboxypeptidase domains have complementary enzyme activities. Furthermore, the finding that CPD with both domains active shows a broad activity to a wide range of substrates is consistent with a role for this enzyme in the processing of many proteins that transit the secretory pathway.

Animals↗
PubMed1999

Dietary supplementation with secoisolariciresinol diglycoside (SDG) reduces experimental metastasis of melanoma cells in mice.

We investigated the effect of dietary supplementation with secoisolariciresinol diglycoside (SDG), a lignan precursor isolated from flaxseed, on experimental metastasis of B16BL6 murine melanoma cells in C57BL/6 mice. Four diets were compared: a basal diet (control group) and the basal diet supplemented with SDG at 73, 147 or 293 micromol/kg (equivalent to SDG provided in the 2.5, 5 or 10% flaxseed diet). Mice were fed the diet for 2 weeks before and after an intravenous injection of 0.6 x 10(5) tumor cells. At necropsy, the number and size of tumors that formed in the lungs were determined. The median number of tumors in the control group was 62, and those in the SDG-supplemented groups were 38, 36 and 29, respectively. The last was significantly different from the control (P < 0.01). Dietary supplementation with SDG at 73, 147 and 293 micromol/kg also decreased tumor size (tumor cross-sectional area and volume) in a dose-dependent manner compared with the control values. These results show that SDG reduced pulmonary metastasis of melanoma cells and inhibited the growth of metastatic tumors that formed in the lungs. It is concluded that dietary supplementation with SDG reduces experimental metastasis of melanoma cells in mice.

Animals↗
PubMed1999

[Comparison of three methods in detection of rotavirus infection in neonates].

OBJECTIVE: To compare, three methods in detection of rotavirus infection in neonates. METHODS: 252 fecal samples from neonates with acute gastroenteritis, healthy neonates and under 4-month-old babies with diarrhoea were detected with ELISA, PAGE and EM. RESULTS: Using ELISA and PAGE to check 5 fecal samples from neonates with diarrhoea, the positive number of ELISA was 4 and the PAGE was all negative. One fecal sample from neonate of one month old with diarrhoea detected with ELISA was strong positive and result with EM was negative. By checking 119 fecal samples from normal neonates of less than ten days old, the positive rate of ELISA was 54.6% and results of PAGE were all RNA negative. 128 fecal samples from less than 4-month-old babies with diarrhoea showed coincident detection rate of ELISA and PAGE (81.2%), but which was going up with increasing of their ages. We also checked 55 fecal samples from less than 4-month-old babies with diarrhoea by ELISA, PAGE, EM and the positive rates were 27.3%, 38.2% and 20% respectively, the coincident rate of the three was 63.6% and the differentiation rate 36.4%. CONCLUSION: The differentiation rate between ELISA and PAGE was obvious, as in the elisa there showed a sirong positive and in PAGE the weak. The diffesence went down with increasing of the ages of the babies with diarrhoea. This indicated that the false positive rate of ELISA existed. PAGE is more reliable and objective and is the better method to check neonate diarrhoea.

Electrophoresis, Polyacrylamide Gel↗