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Biomedical subjects

B Feng

Publications and source records attributed to B Feng.

At least 73 records · Page 4Linked to original sources
PubMed1997

Ocular components measured by keratometry, phakometry, and ultrasonography in emmetropic and myopic optometry students.

Ocular components were measured by keratometry, phakometry, and ultrasonography on 176 young adults. Refractive error was measured by retinoscopy. Mean vitreous depth was greater and the cornea was steeper in myopes than in emmetropes. There were no significant differences between myopes and emmetropes in mean anterior chamber depth, crystalline lens thickness, anterior crystalline lens radius, posterior crystalline lens radius, or crystalline lens power. Coefficients of correlation were calculated for each of the ocular components with refractive error for the entire group of 176 subjects. The components that showed statistically significant correlations with refractive error were vitreous depth and anterior corneal radius. Eyes with greater vitreous depths tended to have flatter anterior corneal surfaces. The slope of the principal axis relating these two variables was significantly different in emmetropes and myopes. Eyes with greater vitreous depths tended to have lesser crystalline lens power. Vitreous depth showed a statistically significant correlation with posterior lens radius, but not with anterior lens radius.

Adolescent↗
PubMed1997

[Targeting delivery of liposomal adriamycin by intra-lymphatic infusion].

OBJECTIVE: To assess the feasibility of delivering liposomal adriamycin (lipo-ADM) to the regional lymph nodes via intralymphatic infusion in a rabbits model. METHODS: The plasma and tissue ADM levels were measured by high performance liquid chromatography (HPLC) at 0.5 hour, 1 hour, 6 hours, 12 hours, 1 day, 7 days, 14 days, 28 days. RESULTS: The maximum ADM level (Cmax) in the lymph nodes of lipo-ADM was 91.23 micrograms/g, which was 2 times higher than that of the free-ADM group. The area under the ADM concentrations-time curve (AUC) of the regional lymph nodes of lipo-ADM and free-ADM was 138.34 micrograms/day x g-1, 31.86 micrograms/day x g-1 respectively (P < 0.01). The pathological features showed that the lipo-ADM group had more microabscess, necrosis and fibrosis in the lymph nodes than those of the free-ADM group. The histological changes of heart were absent or slight in the lipo-ADM group. CONCLUSIONS: lipo-ADM has a high affinity for lymphatic tissue. Intralymphatic infusion of lipo-ADM may be useful for the treatment of lymphnode metastasis in ovarian cancer.

Animals↗
PubMed1997

Autoantibodies and anti-interferon antibody in patients with chronic viral hepatitis and its clinical significance: a preliminary investigation.

OBJECTIVE: To determine the antoantibodies and anti-interferon antibody in chronic viral hepatitis patients treated with interferon and the relation of the antibodies to the curative effect of interferon. METHODS: Forty chronic viral hepatitis patients (twenty cases for hepatitis B; twenty patients for hepatitis C) were studied. Indirect immunofluorescence assay (IFA) was used to measure the autoantibodies. Enzyme immunoassay (EIA) was used to measure the anti-interferon total antibody. RESULTS: Compared with normal groups, the autoantibodies in patients increased significantly (P < 0.01), and the anti-interferon antibody in chronic hepatitis B and hepatitis C patients had an obvious difference (P < 0.05). As for the curative effect, the presence or absence of autoantibodies did not have a distinct significance in patients treated with alpha-interferon, but the patients with anti-interferon antibody before or after therapy might have a different response to alpha-interferon. CONCLUSIONS: It was suggested that the presence of autoantibodies was not a contraindication to the use of interferon in patients with chronic viral hepatitis; the clinical significance of anti-interferon antibody should be further studied.

Antibodies↗
PubMed1996

Major groove (S)-alpha-(N6-adenyl)styrene oxide adducts in an oligodeoxynucleotide containing the human N-ras codon 61 sequence: conformations of the S(61,2) and S(61,3) sequence isomers from 1H NMR.

The (S)-alpha-(N6-adenyl)styrene oxide adducts at positions X6 in d(CGGACXAGAAG). d(CTTCTTGTCCG) and X7 in d(CGGACAXGAAG).d(CTTCTTGTCCG), incorporating codons 60, 61 (underlined), and 62 of the human n-ras protooncogene, were examined by 1H NMR. These were the S(61,2) and S(61,3) adducts. Chemical shift perturbations were in the 3'-direction from the sites of adduction; upfield changes associated with the styrene aromatic ring current were noted for S-SOA6 H2 and H1', T16 N3H, H6, and CH3 resonances in the S(61,2) oligomer. In the S(61,3) oligomer, S-SOA7 H1', T16 H1', C15 N4Ha, and H5 shifted upfield. The styrene aromatic rings flipped rapidly on the NMR time scale; under these conditions the ortho and meta aromatic protons were equivalent. A sequence effect, in which the S(61,2) adduct equilibrated between two conformers, while the S(61,3) adduct exhibited only a single conformation, was observed. Potential energy minimization of the S(61,2) adduct major conformation yielded a structure in which the styrene ring was oriented in the 3'-direction and interacted primarily with the complementary strand. For the S(61,3) adduct, 291 restraints were obtained from NOE data at three mixing times using relaxation matrix analysis. The emergent structures refined to an average rms difference of 1.3 A, determined by pairwise analysis. These were compared to NOE intensity data; the calculated sixth root residual index was 9.2 x 10-2 at 250 ms. In the refined structure, the styrene ring was also oriented in the 3'-direction and interacted with the complementary strand. The minor conformation of the S(61,2) adduct was not identified. These results contrasted with the diastereomeric R(61,2) and R(61,3) adducts, which underwent slow ring flips on the NMR time scale and for which small sequence effects involving the minimum energy conformation of the styrene ring were observed.

Adenine↗
PubMed1996

Differential effects of insulin-like growth factor-1 on neonatal canine gene expression.

To determine the effects of insulin-like growth factor-1 (IGF-1) and amylin on glucose homeostasis in vivo in newborn dogs, euglycemic hyper-IGF-1 clamps and hypoglycemic hyper-IGF-1 clamps were performed in newborn dogs. Northern blotting and radioimmunoassays were used to study the effects of the infused IGF-1 and/or hypoglycemia on the mRNA expression of the genes for phosphoenolpyruvate carboxykinase (PEPCK) and on the expression of the amylin gene in newborn dogs. Our results were that (1) Infused IGF-1 (plasma IGF-1 >/=1000 ng/ml) rapidly lowered the plasma glucose level, and 120 +/- 38 mg glucose/pup was co-infused during a 105-min clamp to maintain the plasma glucose at the basal level. (2) The infused IGF-1 rapidly reduced the liver cytosolic mRNA for the PEPCK gene to an almost undetectable level. (3) Hyper-IGF-1 had no effect on mRNA level of the amylin gene in pancreas, 106.7 +/- 14.2% vs 100.0 +/- 5.9% (controls), or on plasma amylin concentration, 56. 0 +/- 5.7 pg/ml vs 52.1 +/- 5.7 pg/ml (basal). (4) The amylin mRNA level, 127.8 +/- 3.9% vs 100.0 +/- 5.9% (controls) (P = 0.017), and the plasma amylin concentration, 132.3 +/- 18.3 pg/ml vs 110.0 +/- 10.8 pg/ml (controls) (P = 0.371), showed a parallel stimulation by hypoglycemia in the presence of hyper-IGF-1. We concluded that (1) IGF-1 acutely suppressed cytosolic PEPCK gene expression in liver of newborn dogs. (2) IGF-1 does not effect the expression of the pancreatic amylin gene. (3) Amylin may be involved in glucose homeostasis in newborn dogs and may play a role as a counterregulatory factor during the neonatal period. Unsuppressed amylin production may contribute to neonatal hyperglycemia.

Animals↗
PubMed1996

The regulatory protein NIT4 that mediates nitrate induction in Neurospora crassa contains a complex tripartite activation domain with a novel leucine-rich, acidic motif.

Expression of nit-3 and nit-6, the structural genes which encode nitrate reductase and nitrite reductase in Neurospora crassa, requires the global-acting NIT2 and the pathway specific NIT4 regulatory proteins. NIT4, which consists of 1090 amino-acid residues, possesses a Cys6/Zn2 zinc cluster DNA-binding-domain. NIT4 was dissected to localize transactivation domains by fusion of various segments of NIT4 to the DNA-binding domain of GAL4 for in vivo analysis in yeast. Three separate activation subdomains, and one negative-acting region, which function in yeast were located in the carboxyl-terminal region of NIT4. The C-terminal tail of 28 amino-acid residues was identified as a minimal activation domain and consists of a novel leucine-rich, acidic region. Most deletions which removed even small segments of the NIT4 protein were found to lead to the loss of NIT4 function in vivo in N. crassa, implying that the central region of the protein which lies between the DNA-binding and activation domains is essential for function. The yeast two-hybrid system was employed to identify regions of NIT4 responsible for dimer formation. A short isoleucine-rich segment downstream from the zinc cluster, predicted to form a coiled coil, allowed dimerization in vivo; this same isoleucine-rich region also showed dimerization in vitro when examined via chemical cross linking. The enzyme nitrate reductase has been postulated to exert autogenous regulation by directly interacting with the NIT4 protein. This possible nitrate reductase-NIT4 interaction was investigated with the yeast two-hybrid system and by direct in vitro binding assays; both assays failed to identify such a protein-protein interaction.

Amino Acid Sequence↗
PubMed1996

Immunohistoselective sequencing (IHSS) of p53 tumor suppressor gene in human oesophageal precancerous lesions.

Accumulation of p53 protein occurs in human oesophageal precancerous lesions and even in near-normal oesophageal epithelium. In some instances, p53 gene mutations have been detected. In many of the cases of p53 protein accumulation in early lesions, however, p53 mutations were not detected due to either the lack of mutation or the low abundance of cells with a mutation. In order to enrich p53 immunostain-positive cells for single strand conformation polymorphism (SSCP) analysis and DNA sequencing, an immunohisto-selective sequencing (IHSS) method was developed. Anti-p53 antibody-peroxidase stained oesophageal tissue sections were subjected to ultraviolet (UV) irradiation to damage the DNA in p53 immunostain-negative cells. The immunostain protected p53 immunostain-positive cells from the UV light and thus preserved the DNA in those cells for PCR amplification. Comparison of the SSCP results from sections with and without UV treatment showed that the IHSS method selectively enriched p53 immunostain-positive cells. With this method, we could analyse mutations in samples with as few as 30 p53 immunostain-positive cells per tissue section. Analysis was carried out on tissues with precancerous lesions from six surgically-resected oesophageal specimens and 13 oesophageal biopsies from symptom-free subjects. The results of mutation analysis for some of the samples were confirmed by microdissection to enrich the p53-positive cells. The mutations in tissues with precancerous lesions were compared with those in the corresponding squamous cell carcinomas. The IHSS method is shown to be a simple and effective way to analyse mutations in p53 immunostain-positive cells. IHSS may also be a general method for molecular analysis of biological specimens after immunohistochemical staining.

DNA↗
PubMed1996

Rat as an animal model carrying human hepatitis B virus in hepatocytes.

OBJECTIVE: To establish an experimental animal model of rat carrying human hepatitis B virus in the hepatocytes using a simple and reproducible method. MATERIALS AND METHODS: Human serum rich in hepatitis B virus was injected into portal veins and caudalis veins of young male Wistar rats. One and two months after the injection, liver biopsies were done. In situ hybridization and immunohistochemical study of liver specimens were carried out. Sera were also examined for HBV DNA by polymerase chain reaction. RESULTS: All of seven rats in this experiment were HBV DNA and HBV surface antigen (HBsAg) positive in their hepatocytes. Most HBV positive hepatocytes were distributed around the central vein and scattered in the liver lobules, and HBV DNA and HBsAg were located in cytoplasm. HBsAg exists mainly as the forms of diffuses and inclusion body. No hepatocytic damage or inflammation was observed. Neither viremia nor antigenemia was detected. CONCLUSIONS: Our studies showed for the first time that natural human HBV can enter Wistar rat liver cells through intravenous injection efficiently and express for a long period. This animal model can be used in the studies of HBV molecular biology, therapeutic regimens and prophylaxis against HBV. A possible mechanism of HBV entering rat hepatocytes is also proposed.

Animals↗
PubMed1996

[Acetaminophen absorption test for determination of diabetic gastroparesis and effects of erythromycin on gastric emptying].

The purpose of this study is to know the incidence of diabetic gastroparesis in diabetics and its relationship with diabetic neuropathy and to direct rational clinical treatment. Acetaminophen absorption test was performed for determination of gastric emptying function of liquid in 43 patients with diabetes mellitus (male 23, female 20, mean age 53.5 years). The patients were divided into two groups: diabetics with and without autonomic neuropathy. The change of gastric emptying time (GET) after intravenous administration of erythromycin (100 mg/h) was observed. The results showed that GET in diabetics was significantly prolonged. The incidence of abnormal gastric emptying function of liquid was 51.16%. GET in diabetics with neuropathy was significantly longer than that in those without neuropathy (42.83 +/- 13.80 min vs 26.00 +/- 11.42 min, P < 0.01). Its incidence was significantly increased in diabetic neuropathy and related to its severity. Delayed GET in diabetics was normalized after erythromycin administration (from 47.63 +/- 6.74 min to 20.53 +/- 7.43 min, P < 0.01). The results indicate that this test can be used as an objective indicator for diabetic gastric autonomic neuropathy and gastroparesis. Erythromycin accelerates gastric emptying.

Absorption↗
PubMed1995

Major groove (R)-alpha-(N6-adenyl)styrene oxide adducts in an oligodeoxynucleotide containing the human N-ras codon 61 sequence: conformations of the R(61,2) and R(61,3) sequence isomers from 1H NMR.

Conformations of (R)-alpha-(N6-adenyl)styrene oxide adducts at positions X6 in d(CGGACXAGAAG).d(CTTCTTGTCCG) and X7 in d(CGGACAXGAAG).d(CTTCTTGTCCG), incorporating codons 60, 61 (underlined), and 62 of the human n-ras protooncogene, were refined from 1H NMR data. These were the R(61,2) and R(61,3) adducts. Chemical shift perturbations were in the 5'-direction from the sites of adduction; large changes were observed for C5 H5 and H6 in the R(61,2) adduct. The styrene moieties were only partially defined by NOE data. Spectral overlap, particularly for the R(61,2) adduct, prevented complete assignments of the aromatic resonances; likewise, there were insufficient data to orient the CH2OH moieties. Ring flips were slow on the NMR time scale. For the R(61,2) adduct 260 restraints were obtained from NOE data at three mixing times using relaxation matrix analysis; for the R(61,3) adduct 230 restraints were obtained. Structures emergent from molecular dynamics/simulated annealing for the R(61,2) adduct converged to average and maximum pairwise rms differences of 1.3 and 1.7 A, respectively, while those for the R(61,3) adduct converged to average and maximum pairwise rms differences of 1.2 and 1.6 A. Sixth root residual indices of 7.5 and 6.8 x 10(-2) were measured between the refined structures and NOE intensities using relaxation matrix calculations for the R(61,2) and R(61,3) adducts, respectively. The styrene rings were in the 5'-direction from the lesion sites in the major groove. The preferred orientation calculated for the R(61,2) adduct placed the styrene ring edgewise and approximately orthogonal to C5, while that calculated for the R(61,3) duplex had the styrene ring approximately orthogonal to the major groove edges of base pairs A6.T17 and R-SOA7.T16.

Adenine↗
PubMed1995

Osteopontin (OPN) may facilitate metastasis by protecting cells from macrophage NO-mediated cytotoxicity: evidence from cell lines down-regulated for OPN expression by a targeted ribozyme.

Osteopontin (OPN) is a GRGDS-containing phosphoglycoprotein that is capable of facilitating cell adhesion and modulating gene expression via integrin receptors. Three hammerhead ribozymes designed to target three different regions of OPN mRNA were shown to cleave the message catalytically in vitro. Plasmid vectors that had been engineered to express the ribozymes in mammalian cells were used to generate stably transfected T24 H-ras-transformed NIH3T3 cells that normally express OPN at high levels. Northern and Western blot analyses showed that OPN mRNA and protein expression were reduced in a subset of these anti-OPN ribozyme-expressing cell lines. Cells whose ability to produce OPN had been impaired exhibited greater sensitivity to the cytotoxic action of activated RAW264.7 macrophage-like cells; they were also less effective at suppressing macrophage NO production. In agreement with previous reports, they were also less tumorigenic and metastatic in an experimental metastasis assay. These results are consistent with the hypothesis that OPN serves as a defense against NO-mediated host cell cytotoxicity and thereby augments the metastatic phenotype.

Animals↗
PubMed1995

Nuclear DNA-binding proteins which recognize the intergenic control region of penicillin biosynthetic genes.

The biosynthesis of penicillin, a secondary metabolite produced by Penicillium chrysogenum, is subject to sophisticated genetic and metabolic regulation. The structural genes, pcbC and pcbAB, which encode two of the penicillin biosynthetic enzymes are separated by a 1.16-kb intergenic region and transcribed divergently from one another. To identify and characterize nuclear proteins which interact with the pcbAB-pcbC intergenic promoter region, crude and partially purified nuclear extracts were used in mobility shift and DNA footprinting assays. Multiple DNA-binding proteins appear to bind to different regions of this DNA segment. An abundant nuclear protein, nuclear factor A (NF-A), binds at a single site in the intergenic promoter region and recognizes an 8-bp sequence, GCCAAGCC. Penicillin production is sensitive to nitrogen catabolite repression. The global-acting nitrogen regulatory protein NIT2 of Neurospora crassa binds strongly to the intergenic promoter region of the pcbAB and pcbC genes at a single site that contains two closely spaced GATA sequences.

Base Sequence↗
PubMed1995

Solution structure of an oligodeoxynucleotide containing the human n-ras codon 61 sequence refined from 1H NMR using molecular dynamics restrained by nuclear Overhauser effects.

The solution structure of the ras61 oligodeoxynucleotide duplex d(CGGACAAGAAG). d(CTTCTTGTCCG), which consists of codons 60, 61 (underlined), and 62 of the human n-ras protooncogene, was refined from 1H NMR data. The sequence contains a run of purines in the coding strand, with one R-Y step, A4.T19-->C5.G18, and one Y-R step, C5.G18-->A6.T17 (excluding the 5'-terminal base pair). The NMR data were consistent with a B-like helix as judged by characteristic internucleotide NOEs. The NOE intensities between purine H8 and purine anomeric protons were small as compared to the intensities between cytosine H5 and H6 protons, indicative of glycosyl torsion angles in the anti range. Cross-peaks were observed between purine H8 and pyrimidine H5 and CH3 protons on adjacent bases in the direction of purine (5'-->3') pyrimidine, but not in the direction pyrimidine (5'-->3') purine. Watson-Crick hydrogen bonding was intact and enabled the assignment of the exchangeable protons. A total of 226 experimental distance restraints were obtained. A restrained molecular dynamics and simulated annealing approach was utilized in the refinement. The data for 5 emergent molecular dynamics (MD) structures calculated from a B-form starting structure and 5 emergent MD structures calculated from an A-form starting structure refined to an average pairwise root-mean-square (rms) difference of 1.2 A, with maximum pairwise rmsd of 1.7 A. The accuracy of the emergent structures was assessed by complete relaxation matrix back-calculation. The sixth root residual index of 9.4 x 10(-2) was measured between the refined structures and the NOE data, suggesting that the former were in reasonable agreement with the data. The refined structures revealed an increased roll angle of 7 degrees in the codon 61 sequence at base step C5.G18-->A6.T17, which relieved the purine-purine clash in the minor groove, and in turn relieved the purine-purine clash in major groove between A4.T19 and C5.G18. A 3.7 A rise between C5.G18 and A6.T17 was calculated, which assisted in relieving the purine-purine clash. The local variations in the B-like conformation did not confer large structural alterations upon the ras61 sequence, but could be important in modulating the reactivity of the first as compared to the second adenine in codon 61.

Base Composition↗
PubMed1995

Sequence-specific DNA binding by NIT4, the pathway-specific regulatory protein that mediates nitrate induction in Neurospora.

The expression of the structural genes nit-3 and nit-6, which encode the nitrate assimilatory enzymes nitrate reductase and nitrite reductase, respectively, is highly regulated by the global-acting NIT2 regulatory protein. These structural genes are also controlled by nitrogen catabolite repression and by specific induction via nitrate. A pathway-specific regulatory protein, NIT4, appears to mediate nitrate induction of nit-3 and of nit-6. The NIT4 protein, composed of 1090 amino acids, contains a putative GAL4-like Cys-6 zinc cluster DNA-binding motif, which is joined by a short segment to a stretch of amino acids that appear to constitute a coiled-coil dimerization domain. Chemical crosslinking studies demonstrated that a truncated form of NIT4 forms homodimers. Mobility-shift and DNA-footprinting experiments have identified two NIT4-binding sites of significantly different strengths in the promoter region of the nit-3 gene. The stronger binding site contains a symmetrical octameric sequence, TCCGCGGA, whereas the weaker site has a related sequence. Sequences related to this palindromic element can be found upstream of the nit-6 gene.

Amino Acid Sequence↗
PubMed1995

Does the common bile duct dilate after cholecystectomy? Sonographic evaluation in 234 patients.

OBJECTIVE: The purpose of this study was to determine whether the common bile duct dilates after cholecystectomy. SUBJECTS AND METHODS: All 234 patients who had cholecystectomy at our hospital between October 1985 and April 1994 were included in this study. The luminal diameter of the proximal segment of the common bile duct was measured on antero-posterior transverse sonograms 4-15 days before cholecystectomy. In all patients, the luminal diameter was measured again on sonograms obtained 7-2160 days after surgery (mean, 393 days; median, 180 days; mode, 360 days). A diameter of 6 mm or less was considered normal. This study contained 197 patients with a normal common bile duct (< or = 6 mm) and 37 patients with a dilated common bile duct (> 6 mm). RESULTS: The mean diameter of the common bile duct measured on sonograms was 5.9 mm before cholecystectomy and 6.1 mm after cholecystectomy. This difference was statistically significant (p < .05). The diameter of the common bile duct increased in 110 patients, decreased in 61 patients, and stayed the same in 63 patients. Of the 234 patients, 197 (84%) had a normal preoperative diameter of the common bile duct, whereas 167 (71%) had a common bile duct with a normal diameter postoperatively. CONCLUSION: The diameters of the common bile duct as measured on sonograms increase slightly after cholecystectomy. Most patients do not have significant compensatory dilatation of the duct after cholecystectomy.

Adult↗
PubMed1995

[Study on the calibration model of electronystagmography (ENG) in the guinea pigs].

The passive calibration of ENG according to the gain of OKN evoked in guinea pigs was studied in this paper. The method was also verified by animal experiment and the comparison between active calibration and passive one in normal subjects. OKN was elicited by optokinetic drum with black and white strips at 10 intervals at velocity of 5-60 degrees/s. The calculating formula of passive calibration in animals obtained by mathematical corollary is K = G . ST sigma . DV/SA sigma. The slow-phase velocity of spontaneous nystagmus in a group of animals with acute loss of unilateral vestibular function recorded with this method showed typically a logarithmic decline within 24 hours. No significant difference between the values of active and passive calibration was found in normal subjects. The results demonstrated that the method described in the paper was accurate and reliable. It can be used in perivestibular experiments.

Animals↗
PubMed1995

[Preparation and characterization of liposomal adriamycin].

We established a more suitable methodology for preparing liposomal adriamycin (Lipo-ADM) by a remote loading technique. This procedure is convenient, simple with an entrapment efficiency of 95%. The mean diameter of liposome is about 100nm showing unilamellar spherical shape. The leakage ratio is about 10% within 24hr. Those characteristics fit for clinical demand.

Doxorubicin↗