Search PubMed⌕ Search

Biomedical subjects

Y Hu

Publications and source records attributed to Y Hu.

At least 145 records · Page 8Linked to original sources
PubMed2001

[Synergetic protective effects of glial cell line-derived neurotrophic factor combined with neurotrophin-3 in F-actin on hair cell after noise trauma].

OBJECTIVE: To investigate if glial cell line-derived neurotrophic factor (GDNF) combined with neurotrophin-3 (NT-3) provides synergetic protection in filamentous actin (F-actin) on hair cell (HC) from acoustic trauma. METHODS: Guinea pigs were exposed to 4 kHz narrow band noise at 115 dB SPL for 4 h. Test group (n = 12) with a mixture of GDNF (100 ng/ml) and NT-3(2.5 micrograms/ml) or control group (n = 9) with artificial perilymph (AP) was delivered to the scala tympani via a mini-osmotic pump (0.5 microliter/h) for a total of 14 days. Auditory function was assessed by measuring thresholds of auditory brainstem responses (ABRs) elicited by clicks prior to surgery, 3 days after surgery (1 day before noise exposure) and 10 days following noise exposure (before animals were sacrificed), respectively. F-actin, labeled by rhodamine-phalloidin, was examined in the guinea pig cochlea using fluorescence microscopy for quantitative assessment of hair cell damage. RESULTS: There was a statistically significant increase the survival of out hair cell(P < 0.001, P < 0.01) and inner hair cell(P < 0.01, P < 0.01) and decrease in ABR threshold (P < 0.05, P < 0.01) in both the GDNF and NT-3 treated and untreated ear of animals. CONCLUSION: Our findings indicate that GDNF combined with NT-3 may effectively protect the inner ear from noise--induced hearing loss.

Actins↗
PubMed2001

[Important prognostic factors in patients with skull base erosion from nasopharyngeal carcinoma after radiotherapy].

OBJECTIVE: To evaluate the long-term outcome and prognostic factors in patients with skull base erosion from nasopharyngeal carcinoma (NPC) after initial radiation therapy. METHODS: From January 1985 to December 1986, 100 patients (71 male, 29 female) with the diagnosis of NPC were found to have skull base erosion from computed tomography (CT). The mean age was 41 (16-66) years. Ninety-six patients had World Health Organization (WHO) type III undifferentiated carcinoma while four had type I carcinomas. Metastatic workup including chest radiography, liver ultrasound and liver function test were negative. All patients underwent external beam radiotherapy alone to 66-80 Gy over 6-8 weeks. Daily fraction size of 2 Gy was delivered utilizing cobalt-60 or linear accelerator. No patient received chemotherapy. All patients were followed up at regular intervals after irradiation. Median follow-up was 22.3 months (2 months-174 months). Overall survival of the cohort was computed by the Kaplan-Meier method. Potential prognostic factors on survival were examined. Multivariate analyses was performed using Cox regression model. RESULTS: One, three, five, and ten year overall survival rates for the cohort were 79%, 38%, 27% and 13%, respectively. However, in the sub-group of patients with both anterior cranial nerves (I-VIII) and posterior cranial nerve (IX-XII) involvement had a five-year survival of only 7.7%. Causes of death included local recurrence (59 patients), distant metastases (21 patients), both local recurrence and distant metastases (1 patient) and unrelated causes (5 patients). After multivariate analysis, complete recovery of cranial nerve involvement, cranial nerves palsy and recovery of headache after irradiation were found to be independent prognostic factors in this cohort. CONCLUSION: This report presents one of the longest follow-ups of patients with nasopharyngeal carcinoma invading skill base. It demonstrates the importance of cranial nerves involvement as well as recovery of headache and cranial nerve palsy. These factors should be evaluated carefully from history and physical examination as well as imaging studies. Currently available magnetic resonance imaging (MRI) is highly recommended as an additional test. A subgroup of patients with skull base involvement had long-term survival after radiotherapy alone. More aggressive strategy such as combined chemo-radiotherapy and altered fractionation radiotherapy may improve outcome in patients with poor prognostic factors.

Adolescent↗
PubMed2001

Experimental study of the morphology of cerebral bridging vein.

OBJECTIVE: To investigate the morphological properties of pig cerebral bridging vein. METHODS: The morphology and fibre arrangement of 15 cerebral bridging veins obtained from 7 Danish Yorkshire landrace pigs were observed. RESULTS: There was a narrow region at the junction of the cerebral bridging veins and superior sagittal sinus termed "outflow cuff segment". The diameter and length of outflow cuff segment were much smaller and the thickness was higher than those of the cerebral bridging veins ( P < 0.01), and circumferential collagen fibres were most dense in the outflow cuff segment. The opening angle of the outflow cuff segment and the cerebral bridging veins were 115 +/- 4 degrees and 120 +/- 4 degrees ( P > 0.05). CONCLUSIONS: There were differences in fibre arrangement and morphological properties between the outflow cuff segment and the cerebral bridging vein, just like a resistance valve, the outflow cuff segment may play an important role in stabilizing cerebral venous outflow and regulating intracranial pressure.

Animals↗
PubMed2001

[Research on the resistivity of the HFCVD diamond films].

Resistivity of the diamond films by HFCVD technology is analyzed and studied. The I-V curve of the film is depicted in vertical direction using electrode of aluminum film plated on the surface of the diamond films. Further the resistivity of the films is determined. The following conclusion is derived on the basis of the analysis of Raman, SEM and XRD. The resistivity of the diamond films is in relation to the size of the grains and grain orientation of the surface of the films. The larger in average the grain of the films has, the greater the resistivity of the films is. Besides, the film with grain orientation of (110) has a larger resistivity. In addition, the fewer the defect and impurity of the film has, the larger the resistivity of the films is. Therefore, it is important to add the grain size of the film in average, and to increase the grain orientation rate of (110)/(111) in order to gain diamond films that have larger resistivity and good property of insulation. To reduce the content of structure defect and impurity is also an effect way to raise the resistivity of the films.

Aluminum↗
PubMed2001

[Study on postpartum hemorrhage in cesarean section in Nanjing].

OBJECTIVE: To investigate postpartum blood lose of cesarean section (CS) within 24 hrs in Nanjing area. METHODS: Stratified samples were collected from hospitals of different levels and located at different districts. The amount of postpartum blood loss was precisely measured by methods of weight, volume and area. RESULTS: There were 1,125 CS in a total of 4 171 deliveries. The main indications for CS were cephalo-pelvic disproportion, fetal distress, breech presentation, and there was 10.4% of CS without definite causes. The average amount of blood loss was 520 ml in CS, which was far more than that in vaginal delivery (n = 3 046). If postpartum hemorrhage (PPH) is defined as blood lose of 500 ml or more, the incidence of PPH was 53.7%; if it is defined as 700 ml, the incidence was 19.8%. CONCLUSIONS: Cesarean section is an important cause of PPH, and CS without proper indication should be avoided. It seems reasonable to defined the criteria of PPH in CS as 700 ml or more.

Cesarean Section↗
PubMed2001

[The impact of arsenic trioxide or all-trans retinoic acid treatment on coagulopathy in acute promyelocytic leukemia].

OBJECTIVE: To study the effect of arsenic trioxide (As2O3) or all-trans retinoic acid (ATRA) on coagulopathy in patients with acute promyelocytic leukemia (APL), and the mechanism of hemorrhage in these patients. METHODS: Thrombomodulin (TM) or tissue factor (TF) transcription of mRNA of freshly isolated bone marrow blast from APL patients was detected by semi-quantitative RT-PCR. The parameters of coagulation and cell procoagulation activity (PCA) were assessed in plasmic levels. Bleeding symptom was observed during As2O3 or ATRA treatment. RESULTS: TM expression in the APL cell surface was significantly upregulated from (14.31 +/- 1.60) ng/10(7) to (21.61 +/- 6.82) ng/10(7) cells. The levels of P-selectin, soluble fibrin monomer complex (SFMC) and D-dimer (D-D) decreased after ATRA or As2O3 treatment. Abnormal high expression of TF in APL cell was downregulated in patients treated with ATRA or As2O3. The expression level was (14.81 +/- 6.23) ng/L before treatment, but undetected after 20 days of treatment. In addition, the membrane PCA of fresh APL cells was predominantly FVII-dependent after ATRA or As2O3 treatment. Bleeding symptom was ameliorated during As2O3 or ATRA treatment. CONCLUSION: Bleeding symptom was controlled in patients with APL after As2O3 or ATRA treatment.

Adult↗
PubMed2000

Roles of Se and NO in apoptosis of hepatoma cells.

Mice inoculated with hepatoma cell (H22) suspension subcutaneously at their right axilla were administered orally with kappa-selenocarrageenan (Se) solution, the inoculated hepatoma's growth was suppressed. Different concentrations of Se solution added in human hepatoma cell line culture could inhibit proliferation and induce apoptosis in hepatoma cells. Meanwhile Se solution could increase the activity of glutathione peroxidase (GSH-Px) in the mice's plasma and the content of NO in the mice's sera and the hepatoma cell culture supernatant as well. Therefore, apoptosis in hepatoma cell induced by Se solution may be associated with the increase in antioxidative activity, the suppression free radical's intervention, and the excessive release of NO by stress.

Animals↗
PubMed2000

Rho(0) tumor cells: a model for studying whether mitochondria are targets for rhodamine 123, doxorubicin, and other drugs.

A human osteosarcoma cell line devoid of mitochondrial DNA (rho(0)) and its wild-type parental cell counterpart (wt) are presented as a model to investigate drug targeting. By virtue of the absence of mitochondrial DNA, rho(0) cells cannot perform electron transport or oxidative phosphorylation. Since most of the drugs studied are transported by the efflux pumping systems controlled by the MDR1 and MRP1 genes, both cell lines were examined for the expression of these genes, and it was found that no MDR1 and only low amounts of MRP1 were expressed. Growth inhibition experiments indicated that doxorubicin (Dox), vinblastine, and paclitaxel were equitoxic in these cell lines. On the other hand, the IC(50) for rhodamine 123 (Rho 123) in rho(0) cells was 50 times higher than in wt cells. This result correlates with a lower accumulation of Rho 123 in rho(0) cells as measured by fluorescence microscopy and flow cytometry (3 times less than in wt cells). In contrast, when stained with Dox, both cell types accumulated similar amounts. Surprisingly, in these non-P-glycoprotein expressing cells, verapamil increased both Dox and Rho 123 retention. Overall, these data suggest that: (i) functional mitochondria do not appear to be targets for the growth inhibitory activities of Dox, paclitaxel, or vinblastine; (ii) for lipophilic cations like Rho 123, however, normal functioning mitochondria and maintenance of a normal mitochondrial membrane potential (Deltapsi(mt)) appear to play a critical role in the intracellular accumulation and subsequent cytotoxicities of these compounds; and (iii) verapamil increases drug accumulation in non-P-glycoprotein expressing cell lines, most likely by direct action on Deltapsi(mt) for Rho 123 and safranin O, and on heretofore unidentified plasma membrane transporters, as well as via interaction with low levels of MRP1, for Dox. These results should be considered when Rho 123 and verapamil are used to detect P-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Thermal cycling aids folding of a recombinant human beta-casein with four extra N-terminal amino acid residues.

Due to the limited secondary structure, it is believed that the caseins of milk, particularly the beta-caseins (beta-CN), may be in a mostly random-coil conformation or in various structures that result from random association of hydrophobic residues. However, the self-association of the human proteins with increasing temperature (T) and in the presence of Ca2+ is reproducible, implying that they normally fold into fixed tertiary structures. A nonphosphorylated recombinant human beta-CN with four extra amino acids at the N-terminus (GSHM-) was prepared and studied by laser light scattering, analytical ultracentrifugation, fluorescence spectroscopy, turbidity, and circular dichroism. In 3.3 M urea or at 4 degrees C, the protein was monomeric, as expected. Increasing T both without and with the addition of Ca2+ ions caused self-association as it does for the nonphosphorylated native beta-CN but with a somewhat different interaction pattern. However, returning the protein to its monomeric state by reequilibration at 4 degrees C followed again by increasing T caused a shift in the pattern. Such thermal cycling eventually caused the protein to equilibrate to a particular conformation where no more change could be observed. The resulting interaction pattern was similar to that of the native protein but differed particularly in that there was more extensive self-association for the recombinant mutant. The equilibration to a stable conformation was more rapid in the presence of Ca2+ ions. This suggests that the native protein normally folds into a particular conformation which may be aided by Ca2+ in the mammary gland. Further study of a recombinant form with the native amino acid sequence is needed.

Amino Acids↗
PubMed2000

Structure-expression relationships of the 15-kDa selenoprotein gene. Possible role of the protein in cancer etiology.

Selenium has been implicated in cancer prevention, but the mechanism and possible involvement of selenoproteins in this process are not understood. To elucidate whether the 15-kDa selenoprotein may play a role in cancer etiology, the complete sequence of the human 15-kDa protein gene was determined, and various characteristics associated with expression of the protein were examined in normal and malignant cells and tissues. The 51-kilobase pair gene for the 15-kDa selenoprotein consisted of five exons and four introns and was localized on chromosome 1p31, a genetic locus commonly mutated or deleted in human cancers. Two stem-loop structures resembling selenocysteine insertion sequence elements were identified in the 3'-untranslated region of the gene, and only one of these was functional. Two alleles in the human 15-kDa protein gene were identified that differed by two single nucleotide polymorphic sites that occurred within the selenocysteine insertion sequence-like structures. These 3'-untranslated region polymorphisms resulted in changes in selenocysteine incorporation into protein and responded differently to selenium supplementation. Human and mouse 15-kDa selenoprotein genes manifested the highest level of expression in prostate, liver, kidney, testis, and brain, and the level of the selenoprotein was reduced substantially in a malignant prostate cell line and in hepatocarcinoma. The expression pattern of the 15-kDa protein in normal and malignant tissues, the occurrence of polymorphisms associated with protein expression, the role of selenium in differential regulation of polymorphisms, and the chromosomal location of the gene may be relevant to a role of this protein in cancer.

3' Untranslated Regions↗
PubMed2000

Effects of environmental enrichment on gene expression in the brain.

An enriched environment is known to promote structural changes in the brain and to enhance learning and memory performance in rodents [Hebb, D. O. (1947) Am. Psychol. 2, 306-307]. To better understand the molecular mechanisms underlying these experience-dependent cognitive changes, we have used high-density oligonucleotide microarrays to analyze gene expression in the brain. Expression of a large number of genes changes in response to enrichment training, many of which can be linked to neuronal structure, synaptic plasticity, and transmission. A number of these genes may play important roles in modulating learning and memory capacity.

Animals↗
PubMed2000

Trends in colorectal cancer rates in urban shanghai, 1972-1996, in relation to dietary changes.

PURPOSE: In urban Shanghai, the largest industrial and commercial city in China, the age-adjusted (world standard) incidence rates for colorectal cancer increased from 14.5 to 23.3 per 10(5) men and from 12.1 to 20.3 per 10(5) women between 1972 and 1996. This change was even more pronounced for colon cancer, whose incidence rates doubled from 5.95 to 13.7 per 10(5) men and from 5.77 to 12.5 per 10(5) women. The reasons for the rapid increases in cancer rates are not fully understood, but may involve dietary exposures that have changed substantially over the past two decades.METHODS: We calculated Pearson correlation coefficients (r) between colorectal cancer rates and the dietary factors of grain, vegetable oil, pork, poultry and vegetable consumption over the period of 1972 through 1996 in urban Shanghai.RESULTS: Statistically significant positive associations were observed between colon cancer rates and per capita consumption of vegetable oil (r = 0.91 for men, r = 0.94 for women), poultry (r = 0.90 for men, r = 0.90 for women), and pork (r = 0.78 for men, r = 0.81 for women). The correlation coefficients were not statistically significant between colon cancer and per capita consumption of grain (r = 0.38 for men, r = 0.37 for women) or vegetables (r = 0.16 for men, r = 0.14 for women). Similar weaker associations were observed between rectal cancer rates and vegetable oil, pork and poultry consumption.CONCLUSIONS: The findings in our study suggest that increases in dietary fat, poultry and pork intake may play a role in the rising colorectal cancer rates in Shanghai.

Journal Article↗
PubMed2000

Site-directed sulfhydryl labeling of the lactose permease of Escherichia coli: helix VII.

Site-directed sulfhydryl modification in situ is employed to investigate structural and dynamic features of transmembrane helix VII and the beginning of the periplasmic loop between helices VII and VIII (loop VII/VIII). Essentially all of the Cys-replacement mutants in the periplasmic half of the helix and the portion of loop VII/VIII tested are labeled by N-[(14)C]ethylmaleimide (NEM). In contrast, with the exception of two mutants at the cytoplasmic end of helix VII, none of the mutants in the cytoplasmic half react with the alkylating agent. Labeling of most of the mutants is unaltered by ligand at 25 degrees C. However, at 4 degrees C, conformational changes induced by substrate binding become apparent. In the presence of ligand, permease mutants with a Cys residue at position 241, 242, 244, 245, 246, or 248 undergo a marked increase in labeling, while the reactivity of a Cys at position 238 is slightly decreased. Labeling of the remaining Cys-replacement mutants is unaffected by ligand. Studies with methanethiosulfonate ethylsulfonate (MTSES), a hydrophilic impermeant thiol reagent, show that most of the positions that react with NEM are accessible to MTSES; however, the two NEM-reactive mutants at the cytoplasmic end of helix VII and position 236 in the middle of the membrane-spanning domain are not. The findings demonstrate that positions in helix VII that reflect ligand-induced conformational changes are located in the periplasmic half and accessible to the aqueous phase from the periplasmic face of the membrane. In the following papers in this issue (Venkatesan, P., Lui, Z., Hu, Y., and Kaback H. R.; Venkatesan, P., Hu, Y., and Kaback H. R.), the approach is applied to helices II and X.

Amino Acid Sequence↗
PubMed2000

Site-directed sulfhydryl labeling of the lactose permease of Escherichia coli: N-ethylmaleimide-sensitive face of helix II.

Cys-scanning mutagenesis of helix II in the lactose permease of Escherichia coli [Frillingos, S., Sun, J. et al. (1997) Biochemistry 36, 269-273] indicates that one face contains positions where Cys replacement or Cys replacement followed by treatment with N-ethylmaleimide (NEM) significantly inactivates the protein. In this study, site-directed sulfhydryl modification is utilized in situ to study this face of helix II. [(14)C]NEM labeling of 13 single-Cys mutants, including the nine NEM-sensitive Cys replacements, in right-side-out membrane vesicles is examined. Permease mutants with a single-Cys residue in place of Gly46, Phe49, Gln60, Ser67, or Leu70 are alkylated by NEM at 25 degrees C in 10 min, and mutants with Cys in place of Thr45 and Ser53 are labeled only in the presence of ligand, while mutants with Cys in place of Ile52, Ser56, Leu57, Leu62, Phe63, or Leu65 do not react. Binding of substrate leads to a marked increase in labeling of Cys residues at positions 45, 49, or 53 in the periplasmic half of helix II and a slight decrease in labeling of Cys residues at positions 60 or 67 in the cytoplasmic half. Labeling studies with methanethiosulfonate ethylsulfonate (MTSES) show that positions 45 and 53 are accessible to solvent in the presence of ligand only, while positions 46, 49, 67, and 70 are accessible to solvent in the absence or presence of ligand. Position 60 is also exposed to solvent, and substrate binding causes a decrease in solvent accessibility. The findings demonstrate that the NEM-sensitive face of helix II participates in ligand-induced conformational changes. Remarkably, this membrane-spanning face is accessible to the aqueous phase from the periplasmic side of the membrane. In the following paper in this issue [Venkatesan, P., Hu, Y., and Kaback, H. R. (2000) Biochemistry 39, 10656-10661], the approach is applied to helix X.

Alanine↗
PubMed2000

Site-directed sulfhydryl labeling of the lactose permease of Escherichia coli: helix X.

Helix X in the lactose permease of Escherichia coli contains two residues that are irreplaceable with respect to active transport, His322 and Glu325, as well as Lys319, which is charge-paired with Asp240 in helix VII. Structural and dynamic features of transmembrane helix X are investigated here by site-directed thiol modification of 14 single-Cys replacement mutants with N-[(14)C]ethylmaleimide (NEM) in right-side-out membrane vesicles. Permease mutants with a Cys residue at position 326, 327, 329, 330, or 331 in the cytoplasmic half of the transmembrane domain are alkylated by NEM at 25 degrees C, a mutant with Cys at position 315 at the periplasmic surface is labeled in the presence of substrate exclusively, and mutants with Cys at positions 317, 318, 320, 321, 324, 328, 332, or 333 do not react with NEM under the conditions tested. Binding of substrate causes increased labeling of a Cys residue at position 315 and decreased labeling of Cys residues at positions 326, 327, and 329. Studies with methanethiosulfonate ethylsulfonate indicate that Cys residues at positions 326, 329, 330, and 331 in the cytoplasmic half are accessible to the aqueous phase from the periplasmic face of the membrane. Ligand binding results in clear attenuation of solvent accessibility of Cys at position 326 and a marginal increase in accessibility of Cys at position 327 to solvent. The findings indicate that the cytoplasmic half of helix X is more reactive/accessible to thiol reagents and more exposed to solvent than the periplasmic half. Furthermore, positions that reflect ligand-induced conformational changes are located on the same face of helix X as Lys319, His322, and Glu325.

Amino Acid Sequence↗
PubMed2000

Conservation of early odontogenic signaling pathways in Aves.

Teeth have been missing from birds (Aves) for at least 60 million years. However, in the chick oral cavity a rudiment forms that resembles the lamina stage of the mammalian molar tooth germ. We have addressed the molecular basis for this secondary loss of tooth formation in Aves by analyzing in chick embryos the status of molecular pathways known to regulate mouse tooth development. Similar to the mouse dental lamina, expression of Fgf8, Pitx2, Barx1, and Pax9 defines a potential chick odontogenic region. However, the expression of three molecules involved in tooth initiation, Bmp4, Msx1, and Msx2, are absent from the presumptive chick dental lamina. In chick mandibles, exogenous bone morphogenetic protein (BMP) induces Msx expression and together with fibroblast growth factor promotes the development of Sonic hedgehog expressing epithelial structures. Distinct epithelial appendages also were induced when chick mandibular epithelium was recombined with a tissue source of BMPs and fibroblast growth factors, chick skin mesenchyme. These results show that, although latent, the early signaling pathways involved in odontogenesis remain inducible in Aves and suggest that loss of odontogenic Bmp4 expression may be responsible for the early arrest of tooth development in living birds.

Animals↗
PubMed2000

Gene therapy approaches for modulating bone regeneration.

Following injury, bone has the ability to regenerate itself to a form and function nearly indistinguishable from the pre-injury state. However, if the injury is beyond a critical limit, recovery will not occur without therapeutic interventions. Autografts and implants with banked bone continue as the treatments of choice, although each exhibits limitations and liabilities. Alternatives have included the utilization of bone-graft substitutes that may incorporate bone derivatives and soluble signaling molecules such as mitogens and morphogens. In addition, an evolving treatment modality, gene therapy, offers an exciting avenue for bone regeneration. This review presents some of the current concepts for developing a rational gene therapy approach in bone regeneration.

Animals↗