Biomedical subjects

N Wu

Publications and source records attributed to N Wu.

At least 91 records · Page 5Linked to original sources

PubMed1996

[Determination of estrogen receptor and progesterone receptor of the sinonasal malignant neoplasms].

To examine the relationship between sex steroid receptor and sinonasal malignant neoplasms, estrogen receptor (ER) and progesterone receptor (PR) were determined in 25 cases of sinonasal malignant neoplasms, 10 cases of sinonasal papillomas, 31 cases of nasal polyps and 12 cases of normal nasal mucosa. The determination of ER and PR was done by radioligand binding assay of receptors (RBAR). The results indicated that sinonasal malignant neoplasms had higher concentrations of ER and PR binding protein, while sinonasal papillomas, nasal polyps and normal nasal mucosa were found to contain lower concentration of ER and PR, and the differences were significant. (P < 0.01). It is suggested that sinonasal malignant neoplasms might depend on ER and PR.

Adolescent↗

PubMed1996

[The principle of nasal defects repair based on the frontal and temporal vessels anatomy].

After dissection of 9 corpes' (18 sides) vessels of the forehead, nose and temporal, we have discovered that the superatrochlear arteries run upward bilaterally, the branches of the supertrochelear arteries, the superficial branches of the supraorbital arteries and the front branches of the superficial temporal form a network--the frontal artery anastomotic net. The main trank and the parital branches of the superficial temporal arteries give off 2-3 ear branches. Based on these findings, we have made a series of explor atire researches, designed several new kinds of skin flaps for repairing the nasal defects, and improved a number traditional skin flaps. Guided by the above mentioned principles, we have successfully reconstructed 32 different kinds of nasal defects and achieved good results.

Adolescent↗

PubMed1996

[Bi-pedical and bi-muscle flap reconstruction of the laryngeal function].

The method of reconstruction of laryngeal function by bi-pedical and bi-muscle flap (DP-DMF) was presented. The DP-DMF was obtained from sternohyoid muscle, sternothyroid muscle and thyrohyoid muscle. It had enough length, width and plasticity, applicable to all patients with T3 and T4 laryngeal carcinoma. Up to now, 102 patients were treated by expanded horizontal hemilaryngectomy and repaired with unilateral or bilateral DP-DMF. After operation, the swallow function returned to normal in 7 to 11 days. The tracheal tube extraction rate was 66.7% (72/108). The 5-year survival rate was 76.5% (62/81), and recurrence rate was 13.9% (15/108). With the application of DP-DMF, the patients who might have been treated formerly by total laryngectomy could be treated by partial laryngectomy. This method expanded the indication of partial laryngectomy, improved the life quality and survival rate.

Adult↗

PubMed1995

Somatic mutations of the WAF1/CIP1 gene in primary prostate cancer.

The WAF1/CIP1 gene, a potential tumor suppressor gene, has recently been cloned and identified as a p53 mediator and an inhibitor for G1 cyclin-dependent kinases (CDKs). We undertook this study to investigate the possible role of the WAF1/CIP1 gene in human prostatic carcinoma. Matched normal and cancer tissues from 18 patients with prostate cancer were screened for WAF1/CIP1 mutation by nested reverse transcription-polymerase chain reaction/single strand conformational polymorphism (RT-PCR/SSCP) and DNA sequencing. Shifted bands from three tumor, but not the matched normal specimens, were observed. Subsequent direct DNA sequencing of the PCR fragments identified four sequence alterations including a cytosine (C) to adenine (A) transversion and a guanine (G) to A transition and two A insertions. Our results demonstrated that mutations of the WAF1/CIP1 gene occur and may be important during the pathogenesis of human prostate cancer. This is the first report of WAF1/CIP1 mutation in a primary human cancer.

Base Sequence↗

PubMed1995

On-line NMR detection of amino acids and peptides in microbore LC.

The combination of liquid chromatography (LC) and nuclear magnetic resonance (NMR) offers the potential of unparalleled chemical information from analytes separated from complex mixtures. However, the application of LC-NMR has been hindered by poor detection sensitivity. We develop a theoretical model for predicting signal-to-noise ratio (SNR) performance while scaling NMR detection cells for flowing experiments. The model includes the effects of separation parameters, coil geometry, and NMR acquisition parameters on SNR performance. Although the detector cell should be as large as possible to ensure adequate efficiency for a given separation, reducing the detector cell volume does not significantly degrade SNR. For example, our model predicts a 2-fold reduction in SNR for a 400-fold reduction in cell volume. The results of static NMR measurements of amino acids and peptides in a 50-nL-volume cell (approximately 1 microgram of each) demonstrate the performance of such a small-volume NMR microcell. Using this 50-nL detector cell with microbore LC, two-dimensional LC-NMR chromatograms are shown for amino acid and peptide separations.

Amino Acid Sequence↗

PubMed1995

[Experimental studies of protective effects of ischemic myocardium preconditioning and its mechanism].

Recent research has shown that repeated brief myocardial ischemia (RBMI) can increase the tolerance of myocardium to a subsequent sustained ischemia and have protective effects on myocardial cells. With the isolated rat heart Langendorff model, we investigated the effects of RBMI on myocardial morphology, systolic function, coronary flow rates (CFR), myocardial membrane phospholipid (PL) content and its marker enzyme's activity (5'-AMPase). The results showed: After ischemia-reflow, the HR, LVP and CFR in control and experimental groups had no significant difference (P > 0.05). But the PL content and specific activity of 5'-AMPase were significantly higher in the experimental group than that in control group (P < 0.01, P < 0.05). And the observations of ultrastructure suggested that the myocardium of the experimental group was preserved better than that in control group. It was also shown that RBMI had protective effects on myocardial membrane structure, and however effective had no relation to CFR.

Animals↗

PubMed1995

[Studies on the transcription regulation by upstream sequence of human heat shock protein 90 beta gene].

Using a pair of synthetic oligonucleotide as primers, human peripheral lymphocyte lambda GEM-11 genomic DNA library as template, a fragment spanning -1102/+68bp of human heat shock protein 90 beta gene was amplified by polymerase chain reaction (PCR) and cloned into pGEM-4Z vector. The cloned fragment was truncated and ligated to an eukaryotic expression vector containing luciferase as a reporter gene. These subclones were transfected into Jurkat cells and the cellular luciferase activity and mRNA level were measured under either heat shock or PHA activation. Our results suggest that: (1) 5' flanking sequences of hsp90 beta mediates a relatively higher basal level expression via promotor region; (2) under heat shock, presence of the fragment surprisingly reduced luciferase activity, a heat shock induced negative regulatory element was restricted to -554/-171bp; and (3) PHA activation requires distal 5' sequence.

Base Sequence↗

PubMed1995

[The cloning and expression of human secreted interleukin 2 receptor alpha chain gene in eukaryotic cells].

By deleting the sequences encoding the cytoplasmic domain, transmembrane domain and the 5' untranslated region, human interleukin-2 receptor alpha cDNA fragment was subcloned into an eukaryotic expression vector pRc/CMV. The recombinant plasmid was then transfected into CHO cells by either electroporation or calcium phosphate precipitation. 11 G418-resistent clones were randomly selected for detection of mRNA expression. 5 clones out of the 11 were proved to be positively hybridyzed with IL-2R alpha cDNA probe. All of the 5 positive cell lines also expressed sIL-2R alpha in their supernatants as detected by ELISA. The establishment of rhsIL-2R alpha cell lines is of importance in the detection and purification of IL-2 based on the ability of affinity binding between IL-2 and its recombinant receptor.

Animals↗

PubMed1994

The Fanconi anemia polypeptide FACC is localized to the cytoplasm.

Fanconi anemia (FA) is an autosomal recessive disease characterized by congenital anomalies, aplastic anemia, and chromosomal instability. A cDNA encoding the FA complementation group C (FACC) polypeptide was recently cloned [Strathdee, C. A., Gavish, H., Shannon, W. R. & Buchwald, M. (1992) Nature (London) 356, 763-767]. To further characterize this polypeptide, we generated a rabbit polyclonal antiserum against its carboxyl terminus. We used this antiserum to analyze the FACC polypeptide from normal or mutant (FA) lymphoblast cell lines. By immunoprecipitation, the wild-type FACC was a 60-kDa protein, consistent with its predicted molecular mass. FA group C cell lines expressed full-length FACC, truncated FACC, or no detectable FACC polypeptide. In addition, the antiserum specifically immunoprecipitated a 50-kDa and a 150-kDa FACC-related protein (FRP-50 and FRP-150). Unexpectedly, cell fractionation and immunofluorescence studies demonstrated that the FACC polypeptide localizes to the cytoplasm. In conclusion, we have generated an antiserum specific for the human FACC polypeptide. The antiserum should be useful for screening FA cells for mutant FACC polypeptides and for identifying and cloning FACC-related proteins.

Base Sequence↗

PubMed1994

Enhanced separation and detection of serum bilirubin species by capillary electrophoresis using a mixed anionic surfactant-protein buffer system with laser-induced fluorescence detection.

The four major bilirubin species in serum are separated by capillary electrophoresis and detected using laser-induced fluorescence detection. The optimum buffer system consists of 40 mM sodium dodecyl sulfate (SDS)-0.012 mM bovine serum albumin (BSA). The use of the SDS-BSA mixture in the mobile phase allows for the separation of four major bilirubin species at physiological pH with untreated capillaries. The results show that the use of BSA as a run buffer modifier in SDS solution improves separation efficiency and increases sample solubility via pH changes of the run buffer. The limits of detection for the bilirubin species using laser-induced fluorescence are between 30 and 150 nM, depending on the bilirubin species; not only is this approximately two orders of magnitude lower than with visible-light absorption methods, it allows the bilirubin species in normal sera to be quantitatively measured without sample pretreatment.

Adult↗

PubMed1994

Hydrazine-mediated DNA damage: role of hemoprotein, electron transport, and organic free radicals.

The hydrazines represent an important class of xenobiotic agents encountered in the environment, in industrial settings, and in medical therapeutics. Agents with a hydrazine functionality are metabolized to toxic intermediates capable of damaging cellular macromolecules and stimulating proteolysis. Phenylhydrazine (PH), methylhydrazine (MH), hydrazine (HY), and the therapeutic agents phenelzine (PZ) and hydralazine (HD) were examined for their ability to undergo metabolism via HbO2 and to cause damage to added supercoiled phi x174 RF DNA. The hydrazines, when incubated in hemolysate, caused a time- and concentration-dependent strand scission of DNA as monitored using phi x174 RF DNA. The rank order for hydrazine-mediated damage was phenylhydrazine > phenelzine > hydrazine > hydralazine > methylhydrazine. In addition, hydrazine-mediated damage to DNA increased in proportion to protein concentration (i.e., HbO2 content) of the hemolysate. To examine whether the DNA damage resulted primarily from organic free radicals or reactive oxygen free radical species, a series of mechanistic studies employing antioxidants and a free radical scavenger was initiated. The antioxidants dimethylfuran, dimethyl sulfoxide, and dimethylthiourea failed to inhibit hydrazine-mediated DNA damage in hemolysate. In contrast, the free radical spin trap agent dimethylpyrrolidin-N-oxide effectively inhibited PH-mediated DNA damage, while the free radical scavenger N-acetylcysteine also showed a protective effect against PH-, PZ-, HD-, HY-, and MH-mediated DNA strand scission. Potassium ferricyanide-mediated methemoglobin formation and imidazole, a ligand for the heme moiety of hemoglobin, both inhibited PH-stimulated DNA damage in hemolysate demonstrating the importance of oxyhemoglobin to the process. These results suggest that organic free radicals play a dominant role, relative to oxygen free radical species, in hydrazine-mediated DNA strand scission.

DNA Damage↗

PubMed1994

Effects of magnesium citrate and phytin on reducing urinary calcium excretion in rats.

The aim of this study was to determine and compare the effects of both magnesium citrate and phytin on reducing urinary calcium excretion under high-calcium-diet conditions during single and combined treatments. An animal experiment was carried out over a period of 4 weeks in 35 male rats. Urinary calcium excretion was reduced significantly by magnesium citrate and/or phytin in rats fed on high-calcium diets. The hypocalciuric effect of magnesium citrate was more evident than that of phytin. Urinary magnesium excretion was high in all experimental groups. However, the urinary magnesium/calcium ratios showed a consistent increase only in the groups treated with magnesium citrate. Urinary citrate excretion showed a relative increase with the introduction of magnesium citrate plus phytin; however, in both the high-calcium-diet group and the magnesium-citrate group this was found to be reduced. Urinary phosphate excretion was slightly higher in the groups treated with phytin. There was no definite difference in urinary oxalate concentration between the groups. No significant change was noted in the serum concentration of calcium, magnesium, or phosphate.

Animals↗

PubMed1994

A Sertoli cell-secreted paracrine factor(s) stimulates proliferation and inhibits steroidogenesis of rat Leydig cells.

Previous studies have shown that disruption or damage to the seminiferous tubules by radiation, antiandrogen, vitamin A deficiency or experimental cryptorchidism causes Leydig cell hypertrophy and hyperplasia, suggesting that Sertoli cells secrete a mitogenic factor(s) that stimulates Leydig cell proliferation. To study the possible paracrine regulation of Leydig cell proliferation by Sertoli cells, highly purified Leydig cells and Sertoli cells were co-cultured in a two-chambered co-culture system. Our results revealed that co-culture of immature rat Sertoli cells with Leydig cells stimulated Leydig cell DNA synthesis by 19-fold, increased cell number by about 3.9-fold and increased the labeling index from 0.5% to 15.8%. In addition to these changes, co-culture reduced Leydig cell testosterone formation and luteinizing hormone (LH) receptor levels, and dramatically altered the morphology of Leydig cells. The addition of concentrates from Sertoli cell conditioned medium (SCCM) mimicked these biological effects. The Leydig cell mitogenic activity in SCCM was trypsin sensitive and inactivated by boiling for 2 h, suggesting that it is a protein. However, it was resistant to acid and dithiothreitol. The molecular weight of this putative factor(s) is above 10 kDa. The responsiveness of Leydig cells to this mitogenic protein(s) decreased with age, whereas the secretion of this protein(s) by Sertoli cells in culture did not change with age. The addition of 10 ng/ml of follicle stimulating hormone (FSH) dramatically decreased the mitogenic activity in SCCM, indicating that the secretion of this mitogenic factor(s) is inhibited by FSH. This paracrine factor(s) may be as yet an unidentified testicular growth factor(s) because it differs in molecular weight, stability and other characteristics from all previously reported Sertoli cell-produced or expressed growth factors.

Animals↗

PubMed1994

[Radiofrequency transcatheter ablation of dual atrioventricular nodal reentrant tachycardia].

24 cases of dual atrioventricular nodal reentry tachycardia (DAVNRT) were identified by EPS. Radiofrequency transcatheter ablation (RFCA) was applied to interrupt the slow pathways (SP) conduction with a large tip catheter in all the cases. The records from the ablation catheter in the first 8 cases were analysed retrospectively; a low amplitude, relatively slow spike ("B" wave) was found in all the successful cases. In the following 16 cases, "B" waves were purposely sought for the site of ablation, which was usually on the middle and proximal third of the line between His bundle and coronary sinus OS. AB interval was measured, it ranged from 35 to 65 ms with an average of 29 ms, being shorter than the AH interval. "B" wave usually followed the "jump" from the fast to SP, and was not eliminated by RFCA. As compared with the original ablation method, less energy (22.8 vs 26.1 W, P < 0.01) and shorter time of X-ray exposure were needed, if the RF current was applied at "B" site. During the ablation, A wave should be much smaller than V wave, in order not to damage the AVN. The appearance of junctional rhythm usually indicates a successful ablation of SP, SP were eliminated in all the 24 cases. After a follow-up of more than 2 months, recurrence was found in one patient, who underwent a second ablation. Complete AV block occurred in 1 patient, who had a pacemaker implanted. The presence of "B" wave possibly indicates the existence of a short pathway between the fast and SP. RF current applied at that site was safe and more effective.

Adolescent↗

PubMed1994

High frequency of mutator phenotype in human prostatic adenocarcinoma.

Mutator phenotype of nucleotide repeats has been implicated to be involved in human cancer and other diseases. This type of instability may be the direct result of DNA replication and/or repair errors. To examine mutator phenotype during the development of human prostate cancer, we undertook this study to screen 57 patients with prostatic adenocarcinoma for possible mutator phenotype at 18 microsatellite marker loci on 12 chromosomes (3p, 5q, 6p, 7p, 8p, 10q, 11p, 13q, 16q, 17p, 18q and Xq). Overall, in 37 of 57 patients, we have found positive mutator phenotype in at least one of the loci analysed. A significantly greater number of cases were found to be positive for this phenotype among the poorly differentiated than the moderately- and well-differentiated prostatic adenocarcinomas. Our data suggest that mutator phenotype may play an important role in the development and progression of human prostate cancer.

Adenocarcinoma↗

PubMed1993

Developmental progression of DNA puffs in Sciara coprophila: amplification and transcription.

DNA amplification for two major DNA puffs (II/2B and II/9A) of the fungus fly Sciara coprophila increases steeply from 17 to 19 days after hatching (18 degrees C), resulting in almost 20-fold more DNA at these loci in mature larval salivary glands than in adult tissues. At 19 days after hatching when gene amplification reaches a plateau, there is a burst in the amount of mRNA encoded by these two DNA puffs. Expansion of the two puffs coincides with the increase in transcription rather than reinitiation of DNA replication. In contrast, an RNA puff (III/9B) undergoes no DNA amplification, and the burst in RNA produced by this locus occurs slightly later, at 20 days after hatching. The progression of cytological puffing and associated molecular events of DNA amplification and transcription correlate with features of the external phenotype of the larvae, especially the number of pigment granules in the eyespots that are the anlage to the adult eyes. The sequential and coordinated regulation of DNA puff replication and transcription is discussed.

Animals↗

PubMed1993

Biphasic effect of basic fibroblast growth factor on 125I-human chorionic gonadotropin binding to cultured immature Leydig cells.

The present studies examined the effects of basic fibroblast growth factor (bFGF or FGF-2) on 125I-human chorionic gonadotropin (hCG) binding to cultured immature rat Leydig cells. We found that low concentrations of bFGF (0.1-1.0 ng/ml) inhibited 125I-hCG binding to cultured immature Leydig cells in a dose- and time-dependent manner; however, this inhibition was reversed partially at higher bFGF concentrations (10-200 ng/ml). The decline in 125I-hCG binding by bFGF was due to a reduction in the number of binding sites per cell and not to a change in receptor affinity for the ligand. The inclusion of 10 micrograms/ml heparin (a concentration that is reported to block bFGF binding to heparan sulfate proteoglycans) with increasing bFGF concentrations had no effect on the inhibition of 125I-hCG binding by low bFGF concentrations, but completely blocked the secondary increase in binding by higher bFGF concentrations. In addition, neither varying heparin concentrations (0.1-25 micrograms/ml) nor insulin or insulin-like growth factor-I had any effect on the inhibition of 125I-hCG binding by 1 ng/ml bFGF. These studies suggest that receptor-mediated actions of bFGF (inhibition of hCG binding by low bFGF concentrations) on cultured immature Leydig cells are unaffected by heparin; however, the secondary increase in 125I-hCG binding observed with higher bFGF concentrations (mediated by bFGF binding to heparan sulfate proteoglycans) is blocked by heparin.

Animals↗

PubMed1993

Basic fibroblast growth factor-induced increase in 125I-human chorionic gonadotropin binding to luteinizing hormone receptors in cultured immature Leydig cells is mediated by binding to heparan sulfate proteoglycans.

Previous studies have shown that basic fibroblast growth (bFGF) has a biphasic effect on 125I-hCG binding to LH receptors in cultured Leydig cells from immature rats. Low concentrations of bFGF (0.1-1.0 ng/ml) progressively decreased binding, while higher concentrations (10-100 ng/ml) progressively increased binding above nadir levels. In the present studies, treatment of cultured immature Leydig cells with heparinase I and/or heparinase III, which enzymatically remove heparan sulfate proteoglycans, had no effect on basal binding of 125I-hCG to LH receptors or the decrease in binding due to treatment with low bFGF concentrations; however, this treatment dramatically reduced the secondary increase in binding following the addition of higher bFGF concentrations. These results strongly support the idea that the secondary increase in 125I-hCG binding to LH receptors elicited by treatment with higher bFGF concentrations is mediated by bFGF binding to heparan sulfate proteoglycans associated with the plasma membrane and/or extracellular matrix.

Animals↗