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Biomedical subjects

W Y Zhu

Publications and source records attributed to W Y Zhu.

At least 19 recordsLinked to original sources
PubMed2006

Effect of different plant extracts and natural substances (PENS) against membrane damage induced by enterotoxigenic Escherichia coli K88 in pig intestinal cells.

Pig weaning period is frequently associated with infectious disease, mainly caused by enterotoxigenic Escherichia coli (ETEC) K88. Plant extracts exert different beneficial effects and may represent antibiotic alternatives to reduce piglet infection. In this study, plant extracts and other natural substances (PENS) have been evaluated on the pig intestinal IPEC-1 cells, for potential protection against ETEC K88 induced membrane damage. Several PENS have been considered: yeast extract, yeast nucleotides, unsaturated oligo-mannuronic acid, ulvan, bromelain and three fractions of bovine colostrums, as anti-inflammatory and immunomodulatory compounds; daidzein and Chlorella vulgaris extract, as anti-oxidant compounds; allicin, cinnamaldehyde and carvacrol, as anti-bacterial compounds. First, possible toxic effect of PENS on cell membrane permeability was verified by assessing the transepithelial electrical resistance (TEER) and paracellular flux of the extracellular marker phenol red. The highest non-toxic PENS concentration was added to ETEC infected cells to test the protection against membrane damage. The results showed that yeast extract, daidzein, bovine colostrum, bromelain and allicin protected the cells against the increased membrane permeability caused by ETEC, whereas the other PENS did not show this ability. Allicin protection was not due to its anti-bacterial activity, since ETEC growth was unaffected by the presence of allicin.

Animals↗
PubMed2006

Changes of bacterial diversity and main flora in chilled pork during storage using PCR-DGGE.

This study was designed to explore the bacterial diversity and the main flora in chilled pork by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Longissimus muscle was removed from pork carcasses at 24 h postmortem. The muscle was tray- and vacuum-packaged at 4 degrees C for 2, 4, 7 days to extract the bacteria total DNA, respectively. The results indicated that the bacterial diversity of chilled pork decreased with storage time regardless of packaging method. Nine types of bacteria were identified, including Arthrobacter sp., Enterococcus sp., Staphylococcus sp., Moraxella sp., Pseudomonas sp., Lactobacillus sp., Aeromonas sp., Acinetobacter sp., Brochothrix thermosphacta. For tray-packaged pork, Pseudomonas sp. and B. thermosphacta were the dominant micro-organisms. The differences in the species found were related with the presence of Lactobacillus sp. in vacuum-packaged meat. The results of the present study might be useful to study the changes of the contaminating bacteria and their characteristics in chilled pork.

Animals↗
PubMed2006

Generalized granuloma annulare associated with chronic hepatitis B virus infection.

We describe a 63-year-old Chinese woman with generalized granuloma annulare (GGA) associated with chronic hepatitis B virus (HBV) infection for 10 years. She developed non-annular papule lesions after a previous infection of hepatitis B virus. Since then, her clinical course was aggressive with involvement of the trunk, extremities and neck. Histologically, granulomatous inflammations were found in the upper to mid dermis. The HBV DNA in these lesions was demonstrated by polymerase chain reaction (PCR). GGA was totally regressed after treatment of interferon-alpha for 3 months. To the best of our knowledge, GGA associated with chronic HBV infection has never been reported in literature. The prognostic significance of the association of granulomatous inflammation and virus infection is reviewed.

Antiviral Agents↗
PubMed2001

The rate of folate receptor alpha (FR alpha) synthesis in folate depleted CHL cells is regulated by a translational mechanism sensitive to media folate levels, while stable overexpression of its mRNA is mediated by gene amplification and an increase in transcript half-life.

DC-3F/FA3 cells (FA3) were obtained by selection of Chinese hamster lung fibroblasts for growth in folic acid free media, supplemented with 15 pM [6S]-5-formyltetrahydrofolic acid. These cells, as a result of low level gene amplification and RNA stabilization, were found to overexpress folate receptor alpha (FR alpha) mRNA by more than five hundred fold. The expression level of the receptor, a 43 kDa GPI-linked plasma membrane glycoprotein, was found to be inversely related to changes in media folate concentrations while its steady state mRNA level remained unaffected. In low folate, the rate of receptor synthesis was found to increase by more than three fold, while its half-life stabilized as compared to that observed in high folate media. Although DC-3F cells were found to contain low amounts of FR alpha mRNA, receptor expression was undetectable, and changing media folate concentrations had no effect on the expression of either. Hence, while selection for growth in low folate leads to stable overexpression of FR alpha mRNA, receptor expression is regulated at the level of protein synthesis by a mechanism sensitive to media folate levels.

Amino Acid Sequence↗
PubMed2001

Basal levels of metallothionein I and II expression in mouse embryo fibroblasts enhance growth in low folate through a cell cycle mediated pathway.

The impact of basal (non-induced) expression levels of metallothionein I and II on the growth of mouse embryo fibroblasts in standard DMEM/F-12 containing 8.8 microm folic acid, and in DMEM/F12 without hypoxanthine, thymidine or folic acid, containing 15 nm or 15 pm[6S]-folinic acid, was assessed by comparing wild-type MT (+/+) and homozygous null MT (-/-) cell lines. No difference in growth rate was observed between the two in DMEM/F12, although MT (-/-) cells displayed a 6-fold decrease in p27(Kip1), a two fold increase in p53 and a slight increase in p21(Waf1). After 6 days in culture, the growth rate for MT (-/-) cells in 15 nm or 15 pm[6S]-folinic acid was half that of MT (+/+). After an additional 6 days in 15 n m folate, both MT (+/+) and (-/-) cells maintained their respective growth rates, while those in 15 pm had ceased to grow. During the initial 6 days in 15 nm folate, neither cell population displayed an increase in apoptosis or a change in cell cycle distribution, even though MT (-/-) cells sustained an additional 4-fold increase in p21(Waf1)and a 6-fold decrease in cyclin E expression. At day 12, however, the MT (-/-) population, but not MT (+/+), underwent a 7-fold increase in apoptosis coupled with a 3 fold increase in S phase cells. Hence, the basal level of MT I and II constitutively expressed in MT (+/+) cells enhances growth in 15nM [6S]-folinic acid by preventing S phase arrest and apoptosis.

Animals↗
PubMed1999

Metallothionein is overexpressed by hamster fibroblasts selected for growth in 15 pm folinic acid and provides a growth advantage in low folate.

DC-3F/FA3 (FA3) cells, selected for growth in folic acid-free medium containing dialyzed serum and 15 pM [6S]-folinic acid, and parental DC-3F cells were compared by mRNA differential display to identify genetic changes occurring during selection. One of the genes found to be overexpressed in FA3 cells was metallothionein II (MT-II). Northern blots using a full-length hamster MT-II cDNA probe that recognizes both MT-I and MT-II RNA showed that the steady-state level of MT mRNA was elevated at least 10-fold in FA3 cells and in two other selected clones, FA7 and FA14, as well. Southern blot analysis of HindIII-digested genomic DNA indicated that amplification of neither the MT-I nor MT-II gene had occurred, and measurements of MT mRNA decay rates in the presence of actinomycin D suggested that no changes in its half-life had taken place. Hence, overexpression was due to an increase in transcription from the normal gene complement. In FA3 cells, the MT mRNA expression level was found to be directly sensitive and inversely proportional to media folate concentrations, whereas in DC-3F cells it was not, suggesting that MT gene expression is differentially regulated in these two cell lines. Overexpression of MT-II in transfected DC-3F cells was unable to support growth in 15 pM folinic acid. However, when plated in 15 nM folinic acid, a growth rate similar to FA3 cells was observed, whereas sham-transfected controls and double transfectants expressing antisense MT-II RNA and control levels of MT-II protein ceased to grow. Hence, overexpression of MT-II provides a growth advantage in low folate.

Animals↗
PubMed1999

Retinoic acid increases tyrosine phosphorylation of focal adhesion kinase and paxillin in MCF-7 human breast cancer cells.

Treatment of estrogen receptor (ER)-positive MCF-7 human breast cancer cells with retinoic acid (RA) inhibited cell growth and increased cell adhesion to fibronectin. In contrast, ER- MDA-MB-231 cells failed to respond. Western blot analysis showed that tyrosine phosphorylation of two major bands at Mr 125,000 and Mr 68,000 was induced by RA in ER+ MCF-7 human breast carcinoma cells. However, this induction was a late phenomenon detectable at 12 and 24 h, but not within 3 h. A similar increase of tyrosine phosphorylation by RA was observed in ER+ human breast cancer cell lines T-47D and ZR-75-1, but not in the ER- cell lines MDA-MB-231, MDA-MB-453, and MDA-MB-468. Focal adhesion kinase and paxillin, which localize in focal adhesion plaques and may play important roles in the integrin signaling pathway, were identified as the major proteins showing RA-induced tyrosine phosphorylation. The retinoid X receptor-selective compound SR11237 failed to induce tyrosine phosphorylation, indicating that retinoid X receptor activation is not involved in this phenomenon. In contrast, stable overexpression of a truncated RA receptor (RAR) alpha cDNA, RARalpha403, with strong RAR dominant negative activity prevented the increase in tyrosine phosphate, suggesting that RAR signaling is involved in RA-induced tyrosine phosphorylation. Tyrosine phosphorylation was induced the most by the RAR-alpha (193836), followed by RAR-gamma (194433), but was not significantly induced by RAR-gamma (193174)-selective retinoids. This study demonstrates a coordinated albeit relatively late effect of RA on cell adhesion and tyrosine phosphorylation in ER+ human breast cancer cells and suggests RAR-alpha as the major responsible retinoid receptor.

Antineoplastic Agents↗
PubMed1999

Evidence of a role for plant proteases in the degradation of herbage proteins in the rumen of grazing cattle.

Protein breakdown in the rumen is generally regarded as a two-stage process in which proteases produced by rumen microorganisms cleave plant protein into peptides and amino acids. However, many of the fiber-degrading cellulolytic species in the rumen are not in fact proteolytic, and the proteolytic activity of the entire rumen microbial population is only moderate when compared to the gastric and pancreatic secretions in the abomasum. Moreover, plant cell walls remain largely intact after initial chewing (particularly in cattle), presenting a physical barrier that must be breached prior to their effective colonization. The present study considers the hypothesis that the plant enzymes are at least partly responsible for herbage protein degradation in grazing ruminants. Ryegrass, red clover, white clover, and bird's-foot trefoil were incubated in the presence and absence of rumen microorganisms. The production of volatile fatty acids indicated the level of microbial activity, whereas the relative disappearance of the large subunit of ribulose 1,5 bisphosphate carboxylase/oxygenase (Rubisco LSU) indicated proteolytic activity. In all incubations, the relative abundance of the Rubisco LSU decreased as the incubation progressed. When rumen microorganisms were absent, low molecular weight peptides (below 20 kDa) accumulated as the incubation progressed. This accumulation was not observed in the presence of rumen microorganisms. Therefore we suggest that the intrinsic plant proteases contribute to the initial stages of proteolysis of grazed herbage.

Animal Feed↗
PubMed1997

Retinoic acid inhibition of cell cycle progression in MCF-7 human breast cancer cells.

Cell cycle analysis indicates that retinoic acid (RA) inhibition of MCF-7 cell growth occurs through induction of G1 arrest with a concomitant reduction in the proportion of cells in S and G2 + M phases. RA did not affect cyclins D1, A, and E and cyclin-dependent kinase 2 (CDK2) expression, but significantly reduced cyclin D3 and CDK4 expression after 24 h. RA also inhibited cyclin B1 and CDC2 expression, possibly responsible for the reduction of the proportion of cells in G2 + M and S phases. RA did not induce p16 and p27 expression, but obviously reduced p21 level in MCF-7 cells. The retinoid markedly reduced pRB protein level and abrogated pRB phosphorylation after 48 h; it also reduced transcription factor E2F1 expression at both the mRNA and protein levels. E2F1 promoter activity was reduced by 60%, which is probably responsible, at least in part, for the reduction of E2F1 expression in RA-treated MCF-7 cells. These observations demonstrate a marked effect of RA on some of the key cell cycle regulatory proteins in MCF-7 cells. Cyclin D3 and CDK4 are likely the early targets of RA, followed by reduced pRB expression and phosphorylation, as well as by the inhibition of the E2F1 transcription factor which controls progression from G1 to S phase. Most of these events precede the observed reduction in MCF-7 cell growth, which begins at Day 3 of RA treatment.

Breast Neoplasms↗
PubMed1997

Dilution rate increases production of plant cell-wall degrading enzymes by anaerobic fungi in continuous-flow culture.

The gut anaerobic fungi,Neocallimastix hurleyensis and aOrpinomyces sp., were grown in 100 mL batch and continuous-flow cultures on wheat straw at a concentration of 80 g dry matter/L of culture liquid. In batch cultures,N. hurleyensis and Orpinomyces sp. degraded only ca. 9% and 5% of the wheat straw, respectively. In continuous-flow cultures, however, the two fungi degraded 52-56% of the apparent dry matter of wheat straw. Both fungi were able to produce greater quantities (up to x 30) of cell-wall degrading enzymes (CMCase, xylanase, beta-glucosidase and beta-xylosidase) in continuous-flow cultures than in the corresponding batch cultures. Increasing the dilution rate in continuous-flow culture resulted in the production of increased enzyme activity for all the measured cell-wall degrading enzymes, with proportional relationships between dilution rate and the cumulative activities of beta-glucosidase and beta-xylosidase. Dilution rates, however, had no consistent effect on the cumulative production of the fermentation end-products, acetate, formate, D- and L-lactate from both fungi. In addition to acetate and formate,N. hurleyens is produced D- and L-lactate in both batch and continuous-flow cultures, whereas only trace amounts of L-lactate were detected in the Orpinomyces sp. cultures.

Journal Article↗
PubMed1996

Ultrastructure and human papillomavirus DNA in papillomatosis of external auditory canal.

BACKGROUND: A viral etiology has been suspected in papillomatosis of the external auditory canal (PEAC), but virus particles have not been detected so far, although they are easily demonstrable in skin warts. The purpose of the study was to solve this discrepancy by the use of polymerase chain reaction (PCR). MATERIALS AND METHODS: Specimens from the external auditory canal of 14 patients with PEAC, but no human papilloma virus infection of the genital areas, were examined histologically by light and electron microscopy, as well as by PCR to detect viral DNA. RESULTS: Histologically, papillomatosis was present in all specimens. Vacuolated cells were found in the upper part of the stratum malpighii in five cases. On electron microscopy, the numbers of perichromatin and interchromatin granules were increased, but no viral granules were observed. In all specimens, DNA of HPV 6 was detected using PCR, but there was no evidence of DNA of other HPV. CONCLUSIONS: Papilloma of the external auditory canal is produced by infection with HPV 6.

Adult↗
PubMed1995

Detection with the polymerase chain reaction of human papillomavirus DNA in condylomata acuminata treated with CO2 laser and microwave.

BACKGROUND: The recurrence rates of condyloma acuminata are high. The reasons for the relatively high relapse rates with different treatments are unknown. METHODS: Twelve specimens of condylomata acuminata of the vulva were excised from 12 patients and divided into three parts. One part was untreated, the second and the third parts were treated with CO2 laser and microwave, respectively. DNA was then extracted from tissue by proteolytic digestion and amplified by the polymerase chain reaction. Dot blots were performed with the use of radiolabeled consensus and human papilloma virus (HPV) type-specific probes. RESULTS: HPV DNA was amplified in 100% of untreated specimens (6-HPV 6; 6-HPV 11), and in 83.3% and 50% of specimens treated with CO2 laser and microwave, respectively. There was a significant difference in detection between untreated and microwave-treated specimens (chi 2 = 4.18, P < 0.05). CONCLUSION: Microwave damages HPV DNA more effectively than CO2 laser.

Carbon Dioxide↗
PubMed1995

[Effect of insulin on the function of pancreatic exocrine].

Pancreatic function was determined in the diabetic rats prepared with STZ, a compound specifically damaging B-cells of the islets. The results indicated that in STZ rats the amylase content and the level of amylase mRNA in pancreas were significantly decreased. Studies in vitro showed that the binding of 125I-insulin with diabetic acini was much higher than that of control (P < 0.01). The uptake of the 3H-glucose, the incorporation of 3H-leucine in acini, and the Na(+)-K+ ATPase activity in acinar membrane of diabetic rats were also significantly lower than that of the control rats (P < 0.01). However, the above-mentioned alternations could be reversed by replacement of insulin. These results indicate that insulin plays an important regulating role on the function of pancreatic acini.

Amylases↗
PubMed1995

[Inhibitory effect of interleukin-1 beta on insulin release from isolated rat pancreatic islets and the reversal action of testosterone].

Insulin release from pancreatic islet cells of neonatal rats could be markedly inhibited by a previous incubation of cells with interleukin-1 beta (5-20 U/ml) for 20 h even under high glucose (20 mmol/L) stimulation. This inhibitory effect of IL-1 beta on insulin release could be reversed by testosterone (10(-10) mol/L), which was accompanied by an increase of the insulin content in islet cells.

Animals↗
PubMed1994

Hirsutoid papillomas of vulvae: absences of human papilloma virus (HPV) DNA by the polymerase chain reaction.

We have analyzed the specimens from 16 women with hirsutoid papillomas of the vulvae for the presence of HPV DNA using the polymerase chain reaction. The subjects' ages ranged from 27 to 43 years. In all cases, smooth or filiform papules were symmetrically located on the inner surface of both labia minora. Histologically, the lesions consist of acanthosis or papillomatosis without koilocytes and mitotic activity. Eight of 16 specimens were studied by transmission electron microscopy (TEM). No HPV granules were found in the nuclei of keratinocytes. HPV DNA could not be detected in all specimens. Positive controls were present in each assay. These results suggest that the papules of hirsutoid papillomas of the vulvae are unrelated to HPV. Chronic irritants and inflammation may play an important role in pathogenesis.

Adult↗
PubMed1994

Helical growth of hyphae of Candida albicans.

When grown on a range of surfaces in conditions favouring hyphal growth, hyphae of Candida albicans grew in a right-handed helical fashion. This phenomenon was observed with eight strains and with two nutrient media. It is suggested that this is a result of rotation of the hyphal apex as it extends, which on some surfaces results in a helical hyphal wall, but which in a liquid results in a straight hypha. The consequence is that on a surface, a helically growing hypha will be exposed to a more diverse environment than a straight hypha. This phenomenon may have significance in the colonization of tissue by C. albicans.

Anti-Bacterial Agents↗