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Biomedical subjects

G Liu

Publications and source records attributed to G Liu.

At least 451 records · Page 25Linked to original sources
PubMed1997

[Determination on the glycosyl sequence of gypenoside A by TLC-FABMS].

The glycosyl sequence of gypenoside A (A) isolated from Gynostemma pentaphyllum Makino was determinated by TLC-FABMS. The gypenoside A was hydrolysed with cellulase and the hydrolysate showed eight spots on a TLC plate, and the FABMS analysis of these spots indicated they corresponded to gypenoside A, A-Rham, A-Glu, A-Rham-Glu, A-Rham-Glu, A-Glu-Glu, A-Rham-2Glu, A-Rham-2Glu in order. Two chains can be determined to be Rham-Glu, and Glu-Glu, respectively. So the glycosyl sequence of gypenoside A was identical of gypenoside XLIII.

Chromatography, Thin Layer↗
PubMed1997

[Scale-up preparation of hydrophobic interaction chromatographic packing materials based on inorganic matrix].

Based on inorganic matrix controlled pore glass (CPG) and macro-pore silica sphere, by using polyethylene glycol (PEG 1000) as a ligand, a preparation method of hydrophobic interaction chromatographic (HIC) packing material was improved by adding a proper catalyst during the bonding process. The packing material can be synthesized in a scale-up batch, for example 150g for each batch, both for analytical and preparative columns. The retention of proteins, such as cytochrome C (Cyt-C), chymotrypsingen-A (Chy-A), lysozyme (Lys) and ribonuclease(Rnase), is increased with the increasing of (NH4)2SO4 concentration in the eluant 2.5 mol/L of salt concentration for the mobile phase was chosen by considering the separation efficiency and equipment life. After comparing the effect of pH for the retention of proteins it is found that the proteins are well separated at pH 7. The time of linear gradient elution program was optimized in considering the separation efficiency and speed. It is better to take 30 minutes of the gradient program for the separation. Six standard proteins can be well separated with the high-performance HIC column in the linear gradient elution program from 2.5 to 0 mol/L of (NH4)2SO4 in 50 mmol/L of phosphate buffer solution within 30 minutes. Cyt-C, Rnase, Lys and Chy-A can be separated by the HIC column based on CPG matrix. Six proteins, Cyt-C, Rnase, Lys, Chy-A, insulin(Ins) and lipase (Lip) can be well separated on the column based on silica matrix with gradient elution program. The recovery of trypsin detected with BAEE method is over 95% after purification with the HIC column.

Chromatography↗
PubMed1997

[Preparation and characterization of sinopak-s-DEAE weak-anion exchange packing for high performance liquid chromatography].

High-performance ion exchange chromatography (HPIEC) is extensively used in the separation of peptides and proteins, especially in the biotechnology process. The principle of separation of proteins is based on the changes of pH and salt concentration in the mobile phase for the chromatographic model. A new synthetic method with the help of a catalyst for the bounding of diethylaminoethyl group on a home-made macro-pore silica sphere (the trade mark is Sinopak-s, with sphere size of 5 microm and pore diameter of 100 nm) was developed in our laboratory for the application of the scale-up separation of biotechnological target products in China. The Sinopak-s-DEAE weak anion ion exchange matrix for HPLC was prepared and characterized with various proteins. The pH value and reaction time were discussed for the reaction efficiency of ligand to the silica sphere. The coverage of the DEAE ligand on the silica surface were among 1.6 to 2.1 micromol/m2 for six batches of packings. The influences of the pH value and the salt concentration in mobile phase upon the retention of proteins on the DEAE column were also discussed. A bio-activity recovery up to 98% for trypsin was arrived after purification with the DEAE column under the chosen chromatographic conditions. The capacity of matrix for BSA was 80 mg/g. The column was successfully applied to separate a mixture of several standard proteins in a linear gradient elution condition from 0 to 0.4 mol/L of NaCl in a 50 mmol/L of Tris/HCl buffer (pH 7.0) at 1.0 mL/min flow rate and detected at 280 nm wavelength.

Anion Exchange Resins↗
PubMed1997

[The microspectra of chromosome].

The spectra of radicle chromosome of broad bean, marrow cell chromosome and marrow cell micro-nucleus of small white mouse were measured within the range of visible light by microspectrum technique. The differences among the spectra were found.

Animals↗
PubMed1997

Experimental evidence for the origin of ductal-type adenocarcinoma from the islets of Langerhans.

To investigate the role of the islets of Langerhans in pancreatic carcinogenesis, freshly isolated islets from male Syrian hamsters were transplanted into the right submandibular glands of 50 female hamsters that were or were not pre-treated with streptozotocin. Thyroid gland fragments, cellulose powder, and immortal hamster pancreatic ductal cells were injected into the left submandibular gland of the same hamsters. All recipient hamsters were then treated with the potent pancreatic carcinogen N-nitrosobis(2-oxopropyl)amine weekly at a dose of 40 mg/kg of body weight for 3 weeks. Between 3 and 8 weeks later, 18 of 75 (24%) hamsters developed large ductal-type adenocarcinomas in the submandibular gland region, where islets were transplanted, but none developed tumors in the left submandibular gland. In 9 of 18 hamsters, tumors were multiple so that a total of 31 cancers were found. Eleven of these carcinomas were in the vicinity of transplanted islets, eight of which showed intra-insular ductular or cyst formation as seen in the pancreas of hamsters during pancreatic carcinogenesis. The formation of ductular structures within islets was also demonstrated in vitro. Some tumor cells in the vicinity of these islets were reactive with anti-insulin. Y chromosome message was found by polymerase chain reaction analysis in one of the three tumors examined. Also, like the induced pancreatic tumors, all three submandibular gland tumors that were examined had the mutation of the c-Ki-ras oncogene at codon 12 and all tumors expressed blood group A antigen. These and other findings strongly suggest that some components of islets, most probably stem cells, are the origin of ductal-type adenocarcinomas in this model.

Adenocarcinoma↗
PubMed1997

Sample size calculations for studies with correlated observations.

Correlated data occur frequently in biomedical research. Examples include longitudinal studies, family studies, and ophthalmologic studies. In this paper, we present a method to compute sample sizes and statistical powers for studies involving correlated observations. This is a multivariate extension of the work by Self and Mauritsen (1988, Biometrics 44, 79-86), who derived a sample size and power formula for generalized linear models based on the score statistic. For correlated data, we appeal to a statistic based on the generalized estimating equation method (Liang and Zeger, 1986, Biometrika 73, 13-22). We highlight the additional assumptions needed to deal with correlated data. Some special cases that are commonly seen in practice are discussed, followed by simulation studies.

Biometry↗
PubMed1997

Expression of proliferating cell nuclear antigen in Wilms' tumor.

OBJECTIVE: To investigate the expression of proliferating cell nuclear antigen (PCNA) and its clinical significance in Wilms' tumor. METHODS: PCNA immunoreactivity on paraffin-embedded tissues was assessed retrospectively in 35 cases using labelled streptaridin biotin (LSAB) procedure, and its association with clinical and other biological features was studied. RESULTS: Twelve tumors (34.29%) expressed PCNA. Expression rate increased with the advance of stage (P < 0.05). The S-phase fraction and proliferation index (PI) in children with PCNA positive expression were higher than those in children with negative PCNA expression (P < 0.05). The survival rate (16.67%) in patients with positive PCNA expression was significantly lower than that (73.91%) in no-expression ones (P < 0.01). CONCLUSION: PCNA is a sensitive indicator for cell proliferation and is clinically useful in identifying a poor prognostic group of patients with Wilms' tumor.

Child↗
PubMed1997

Polymorphisms of vitamin D receptor gene and its association with bone mineral density and osteocalcin in Chinese.

OBJECTIVE: To explore the distribution frequencies of vitamin D receptor (VDR) gene polymorphisms in Chinese and the relationship between VDR genotypes and bone mineral density (BMD) or serum osteocalcin level in Chinese women. METHODS: Polymorphisms of VDR gene were analyzed by polymerase chain reaction (PCR) to amplify the DNA sequence and three restriction enzymes (namely BsmI, ApaI and TaqI) to digest the PCR products in 223 subjects. Some of the VDR genotypes were also confirmed by Southern hybridization analysis. BMD was measured at the spine and proximal femur by dual-energy X-ray absorptiometry (DEXA). Serum osteocalcin concentrations were determined by radioimmunoassay. RESULTS: Chinese had high frequencies of "b,a,T" alleles, 95%, 75% and 95% respectively, which were much different from Caucasians. "BB" or "AA" genotype had tendency for higher BMD at some sites in the group of young women, whereas in the group of postmenopausal women, "bb" or "aa" genotype had relationship with lower BMD at femoral neck and trochanter. Furthermore, no relationship were found between VDR genotypes and the serum osteocalcin level in Chinese women. CONCLUSIONS: Allele frequencies of VDR gene in Chinese are different from those in Caucasians. VDR gene polymorphisms are associated with BMD in Chinese, but in a different pattern from other reports. Further study on predicting function of VDR for osteoporosis is necessary.

Adult↗
PubMed1997

Effect of TNF-alpha and IFN-alpha on the proliferation and cytotoxicity of lymphokine-activated killer cells in patients with bladder cancer.

OBJECTIVE: To investigate the effects of interleukin-2 (IL-2) combined with either tumor necrosis factor-alpha (TNF-alpha) or alpha-interferon (IFN-alpha) on the proliferation and cytolysis to bladder tumor cells of lymphokine-activated killer (LAK) cells in patients with bladder cancer. METHODS: LAK cells were generated by ficoll-paque density-centrifugation from 21 patients with bladder cancer and cultured in medium containing IL-2. LAK cell proliferation was assayed in the presence of various concentrations of either TNF-alpha or IFN-alpha by cell count in 96-well plates. Bladder cancer cell lines BIU-87 and EJ were cultured as target cells and the cytotoxicity of LAK cells was determined by 3-(4,5-dimethylthiazol-2-yl)-2, 5 diphenyltetrazolium bromide (MTT) assay. RESULTS: The proliferation of LAK cells induced by IL-2 was enhanced by TNF-alpha in a dose-responsive fashion. The direct growth support for the LAK cells was also observed with IFN-alpha at the concentration of 1000 U/ml after 48 hours of culture. TNF-alpha (5000 U/ml) resulted in an increase in the cytotoxicity of LAK cells to BIU-87 and EJ cells. However, the change of cytotoxicity of LAK cells treated with IFN-alpha was not statistically significant. CONCLUSIONS: TNF-alpha and IFN-alpha enhance the proliferation and activation of LAK cells and influence their antitumor cytotoxicity in patients with bladder cancer.

Carcinoma, Transitional Cell↗
PubMed1997

The embryonic development of the human lamina cribrosa.

OBJECTIVE: To investigate the embryonic development of lamina cribrosa of human eyes. METHODS: The lamina cribrosa of 291 eyes were studied including 260 eyes taken from embryos and fetus of 7 weeks to full term and 31 eyes from infants under 1 year of age by using light microscopy (LMS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). RESULTS: From observations, it was found that the development of the lamina cribrosa was lagged behind the development of the optic nerve. CONCLUSIONS: In eyes taken from embryos or fetus less than 4 months of pregnancy, only ectodermal primordium of the lamina cribrosa could be seen. The initial scleral part of the lamina cribrosa began its formation in the 5th month of fetus. The fibrous tissue originating from the choroid and optic nerve sheath contributed to the formation of the lamina cribrosa in the 8th month fetus. At this time, the morphology of the lamina cribrosa is similar to that of an adult, however the thickness of the structure is still getting increased up to one year after birth.

Choroid↗
PubMed1997

[Diagnostic value of serum IGA-fibronectin aggregates to IGA nephropathy].

In order to demonstrate the diagnostic value of serum IgA-fibronectin (FN) aggregates in IgA nephropathy, serum samples from 91 patients with IgA nephropathy, 14 patients with Henoch-Schonlein purpura, 117 patients with non-IgA nephritis, 24 random in-patients and 234 normal controls were examined for IgA-FN aggregates by using ELISA. The results showed that the level of IgA-FN aggregates increased markedly in the serum of patients with IgA nephropathy and 61.5% of them reached the positive standard. Only 8.8% of the patients with non-IgA nephritis, none of the in-patients with non-renal diseases and 5.1% of the normal controls were beyond the positive criteria. But the level of IgA-FN aggregates were also elevated in the serum of patients with Henoch-Schonlein purpura and lupus nephritis. These data indicate that serum IgA-FN aggregates may be useful in the diagnosis of IgA nephropathy, but Henoch-Schonlein purpura and lupus nephritis should be ruled out.

Adolescent↗
PubMed1997

[Effect of microinjection of GABA into the caudate nucleus on electrical discharges of nociceptive neurons in caudate nucleus of rat].

The characteristics of glass microelectrode recorded electrical activity of nociceptive neurons in the caudate nucleus elicited by microinjection of GABA and blockage by picrotoxin (PIC) were studied in 53 Wistar rats. The results showed that GABA (25, 50, 100 micrograms/2 microliters every 2 min) inhibited the activity of pain excitation neurons (PEN), as shown by decreased frequency and increased latency, but enhanced the activity of pian, inhibition neurons (PIN), as shown by shortened duration and increased discharge frequency. Both activities are highly dose-dependent and could be blocked by PIC (i.p. 250 micrograms, 1 ml/1 min).

Animals↗
PubMed1997

[Reconstruction of lacrimal passage in repair of oblique facial cleft].

For the reconstruction of lacrimal passage in obligue facial cleft, three methods were performed in 4 cases. According to the difference in local pathology canaliculorhinestomy, transfer of vein or oral mucosa, or modified dacryocystorhinostomy was performed. The patients were followed for 6 to 12 months with satisfacting results.

Abnormalities, Multiple↗
PubMed1996

Mutation of phosphoserine 389 affects p53 function in vivo.

To study the importance of phosphorylation for p53 transactivation function, we generated mutations at each of its known phosphorylated serine amino acids. Mutations of murine p53 serine residues individually to either alanine or glutamic acid at positions 7, 9, 12, 18, 37, 312, and 389 resulted in equivalent levels of transcriptional activation in standard transient transfection experiments. However, when p53 transcriptional activity was measured in cells that attain G1 arrest upon contact inhibition, wild-type p53 was inactive, and only alteration at serine 389 to glutamic acid resulted in a functional p53 protein. This Ser --> Glu mutant also has an increased ability to bind DNA. Elimination of the phosphorylation site by substitution of an alanine amino acid resulted in loss of transcriptional activity. We also demonstrated that specific phosphorylation of p53 at serine 389 is induced by cyclin E overexpression in high-density cells. Our data establish for the first time that phosphorylation of p53 at serine 389 is important in activating its function in vivo.

3T3 Cells↗
PubMed1996

Structural studies of imidazole-cytochrome c: resonance assignments and structural comparison with cytochrome c.

Two-dimensional nuclear magnetic resonance spectroscopy (2D NMR) was used to obtain extensive proton resonance assignments of Im-cyt c complex which is a possible analog of a late folding intermediate of cytochrome c. Assignments were made nearly completely for the main-chain and the side-chain protons (all except Gly29). As starting points for the assignment of the Im-cyt c, a limited set of protons was initially assigned by use of 2D NMR magnetization transfer methods to correlated resonances in the Im-cyt c with assigned resonances in the native cyt c. The subsequent search focused on recognition of main-chain NOE connectivity patterns, with use of previously assigned residues to place NOE-connected segments within the amino acid sequence. The observed patterns of main-chain NOEs provided some structural information and suggested potentially significant differences between Im-cyt c and the native cyt c. Differences in NOEs involving side-chain protons were reported and analyzed. There was evidence for conformational changes induced by the breakage of Fe-S bond. It was concluded that the Im-cyt c had undergone a rearrangement of several regions forming the heme pocket of the protein. The structural understanding of these effects of the mutation may be essential to elucidate the changes in function and kinetic mechanism of cyt c folding.

Animals↗
PubMed1996

Reversing effect of dimethyl-4,4'-dimethoxy-5,6,5', 6'-dimethylenedioxybiphenyl-2,2'-dicarboxylate (DDB) on the phenotypes of human hepatocarcinoma cells line.

When human Bel-7402 hepatocarcinoma cell line grew in a medium containing 10(-4) M dimethyl-4,4'-dimethoxy-5,6,5', 6'-dimethylenedioxybiphynyl-2,2'-dicarboxylate (DDB), the secretion of alpha-fetoprotein (AFP) was significantly lower than the control cells, whereas the albumin (ALB) secretion was markedly higher. The activity of gamma-glutamultranspepeidase (gamma-GT) in DDB-treated cells markedly decreased in comparison with the control cells. On the contrary, the activity of tyrosine-alpha-ketoglutarate transaminase (TAT) was higher in DDB-treated cells than in control cells. DDB (10(-4) M) could significantly increase the content of cAMP in Bel-7402 cells, and also enhance the expression of anti-oncogene p53. The results suggest that DDB has reversing effects on the phenotypes of the human Bel-7402 hepatocarcinoma cell line.

Biphenyl Compounds↗
PubMed1996

Mechanisms for the transport of alpha,omega-dicarboxylates through the mitochondrial inner membrane.

alpha,omega-Dicarboxylates have antibacterial properties, have been used in the treatment of hyperpigmentary disorders, are active against various melanoma cell lines, and can also undergo beta-oxidation. Little, however, is known about their transport. In this paper, we examine the mitochondrial transport of alpha, omega-dicarboxylates ranging from oxalate (DC2) to sebacate (DC10). DC2-DC10 are transported by the inner membrane anion channel (IMAC). DC6-DC10 are also transported by an electroneutral mechanism that appears to reflect transport of the acid through the lipid bilayer. At 37 degrees C and pH 7.0, DC10 is transported very rapidly at 3 micromol/min.mg, and respiring mitochondria swell in the K+ salts of these acids. This transport mechanism is probably the major pathway by which the longer dicarboxylates enter cells, bacteria, and mitochondria. We also demonstrate that DC5-DC10 can also be transported by an electroneutral mechanism mediated by tributyltin, a potent inhibitor of IMAC. The mechanism appears to involve electroneutral exchange of a TBT-dicarboxylate-H complex for TBT-OH. Finally, we present evidence that of all the dicarboxylates tested only DC2-DC4 can be transported by the classical dicarboxylate carrier.

Animals↗