Biomedical subjects

L Zhang

Publications and source records attributed to L Zhang.

At least 397 records · Page 22Linked to original sources

PubMed2001

Impact of localized treatment in reducing risk of progression of low-grade oral dysplasia: molecular evidence of incomplete resection.

Currently, there is no consensus on the appropriate treatment for low-grade oral dysplasia. This is mainly due to the difficulty in predicting outcome for this heterogeneous group of lesions. In this study, we constructed a detailed clinical history of 66 mild and moderate dysplasias in order to determine how treatment affected outcome, and to evaluate the effect of treatment on lesions with different genetic profiles, which are defined by patterns of loss of heterozygosity (LOH) associated with low, intermediate and high risk of progression [Clin. Cancer Res., 6, 357-62, 2000]. The results showed that although treatment guided by clinical removal of leukoplakia reduced cancer progression risk in all three risk groups, the amount of reduction in our study group did not reach statistical significance. To assess whether completeness of lesion removal was a major factor in recurrence, repeat biopsies at the primary sites were analyzed for persistent LOH status on chromosomes 3p, 4q, 8p, 9p, 11q, 13q and 17p. Strikingly, eight of 17 cases judged clinically removed contained the same molecular clones in the initial and subsequent biopsies, suggesting incomplete removal. When molecular information was included in the assessment of lesion removal, treatment significantly reduced the risk of progression for cases with intermediate (P=0.043) and high risk (P=0.001) genetic profiles, but not cases with low-risk profiles. A 9.1-fold decrease in progression risk was observed for those with high-risk profile. Altogether, these data suggest the use of molecular profiles to guide the treatment of low-grade dysplasia. Our data also suggest that currently an inadequate margin may in part be responsible for the high rate of recurrence, especially in high-risk lesions.

Adult↗

PubMed2001

Evaluation of mushroom dietary fiber (nonstarch polysaccharides) from sclerotia of Pleurotus tuber-regium (Fries) singer as a potential antitumor agent.

Mushroom dietary fiber or nonstarch polysaccharides (NSPs) that were soluble in hot alkali and belonged to the beta-glucan type were isolated from the sclerotia of an edible mushroom, Pleurotus tuber-regium. The mushroom NSPs were further separated into a number of fractions [hot alkali extracts (HAEs)] with weight-average molecular weights (M(w)) ranging from 1 x 10(4) to 42.2 x 10(4). The HAE fractions [with M(w) of (5.8-17.1) x 10(4)] administered intraperitoneally at a dose of 20 mg/kg of body weight to BALB/c mice implanted with solid tumor Sarcoma 180 were found to be effective in inhibiting tumor proliferation with an inhibition ratio of > or =50%. In vitro experiments using human tumor cell lines HL-60 and HepG2 had shown that HAE fractions with M(w) of (5.8-42.2) x 10(4) also had antiproliferative activity at three different concentrations (50, 100, and 200 microg/mL) toward the tumor cell lines tested. All HAE fractions did not inhibit the growth of a normal kidney cell line (Vero) from monkey. It is therefore postulated that the antitumoral effect of NSPs from the sclerotia of P. tuber-regium is probably host-mediated and cytocidal.

Animals↗

PubMed2001

Accumulation of barley stripe mosaic virus is significantly reduced in transgenic wheat plants expressing a bacterial ribonuclease.

An rnc70 gene encoding a mutant bacterial ribonuclease III (RNase III) was introduced into wheat (Triticum aestivum cv. Bobwhite) by microprojectile bombardment. T1, T2, and T3 plants regenerated from three transgenic callus lines were challenged with barley stripe mosaic virus. Plants expressing RNase III exhibited a high level of resistance to the virus infection. This resistance was evidenced by the absence of virus symptoms and reduced accumulation of virions in these plants. The result demonstrates that this pathogen-targeted resistance strategy can be effectively employed in conferring resistance to viral diseases of cereal crops.

Blotting, Western↗

PubMed2001

Loss of heterozygosity: a potential tool in management of oral premalignant lesions?

Oral leukoplakia, a heterogeneous group of lesions, demonstrates a varying degree of risk for cancer progression. Histology (presence and degree of dysplasia), the current gold standard for assessing this risk, is reasonably effective in judging the malignant risk of high-grade pre-invasive lesions. It is, however, a poor predictor for lesions without dysplasia, or with minimal dysplasia, as only a few of these lesions will progress to cancer. This poses an enormous dilemma for clinicians as to whether these lesions should be aggressively treated or not. Recent studies show that loss of specific chromosomal regions (loss of heterozygosity, LOH) that contain known or presumptive tumor suppressor genes is an early predictor of subsequent progression of oral premalignant lesions. Incorporation of LOH findings into staging of oral premalignancy could improve our ability to identify and manage high-risk premalignant lesions, particularly those with relatively benign histology but high-risk genetic changes (high-risk LOH pattern).

Carcinoma, Squamous Cell↗

PubMed2001

Ran stimulates spindle assembly by altering microtubule dynamics and the balance of motor activities.

The guanosine tri-phosphatase Ran stimulates assembly of microtubule spindles. However, it is not known what aspects of the microtubule cytoskeleton are subject to regulation by Ran in mitosis. Here we show that Ran-GTP stimulates microtubule assembly by increasing the rescue frequency of microtubules three- to eightfold. In addition to changing microtubule dynamics, Ran-GTP also alters the balance of motor activities, partly as a result of an increase in the amount of motile Eg5, a plus-end-directed microtubule motor that is essential for spindle formation. Thus, Ran regulates multiple processes that are involved in spindle assembly.

Animals↗

PubMed2001

Nicastrin binds to membrane-tethered Notch.

The presenilins and nicastrin, a type 1 transmembrane glycoprotein, form high molecular weight complexes that are involved in cleaving the beta-amyloid precursor protein (betaAPP) and Notch in their transmembrane domains. The former process (termed gamma-secretase cleavage) generates amyloid beta-peptide (Abeta), which is involved in the pathogenesis of Alzheimer's disease. The latter process (termed S3-site cleavage) generates Notch intracellular domain (NICD), which is involved in intercellular signalling. Nicastrin binds both full-length betaAPP and the substrates of gamma-secretase (C99- and C83-betaAPP fragments), and modulates the activity of gamma-secretase. Although absence of the Caenorhabditis elegans nicastrin homologue (aph-2) is known to cause an embryonic-lethal glp-1 phenotype, the role of nicastrin in this process has not been explored. Here we report that nicastrin binds to membrane-tethered forms of Notch (substrates for S3-site cleavage of Notch), and that, although mutations in the conserved 312-369 domain of nicastrin strongly modulate gamma-secretase, they only weakly modulate the S3-site cleavage of Notch. Thus, nicastrin has a similar role in processing Notch and betaAPP, but the 312-369 domain may have differential effects on these activities. In addition, we report that the Notch and betaAPP pathways do not significantly compete with each other.

Alzheimer Disease↗

PubMed2001

A high frequency of allelic loss in oral verrucous lesions may explain malignant risk.

Verrucous carcinoma (VC), a variant of squamous cell carcinoma (SCC), is distinct from SCC in morphology and behavior. The underlying genetic changes involved in the development of VC and its precursor verrucous hyperplasia (VH) are unknown. This study determined whether chromosomal regions frequently lost during the development of SCC are also lost in the VH/VC variant. Twenty-five VH and 17 VC were analyzed for loss of heterozygosity (LOH) at 19 loci on 7 chromosome arms using microsatellite analysis. These data were compared with those from 47 reactive hyperplasias, 92 dysplasias (54 low- and 38 high-grade), and 41 SCCS: The results showed that VC/VH shared many of the losses present in dysplasia/SCC but differed in two aspects. First, VC/VH showed early acquisition of loss, compared with a gradual accumulation of losses from dysplasias to SCC. The LOH pattern of VH was similar to that of high-grade dysplasia and sharply different from reactive hyperplasia. The loss in VH often involved multiple arms (in 60% of VH vs 0% of reactive lesions). Only a marginal elevation of loss was observed at 9p (p = 0.06) and 4q (p = 0.05) from VH to VC because of the high degree of loss already present in VH. Second, a strikingly lower frequency of loss at 17p was noted in VH/VC compared with dysplasia/SCC and may indicate human papillomavirus (HPV) involvement. The finding of high-risk LOH profiles in VH may partly account for the high-progression risk seen for VH and also has potentially important clinical implications. The difficult pathological diagnosis of VH/VC from reactive hyperplasia frequently requires repeated biopsies and results in delay in diagnosis and significantly increased mortality/morbidity. Microsatellite analysis might facilitate this differential diagnosis.

Aged↗

PubMed2001

Alpha-1-antitrypsin and a broad spectrum metalloprotease inhibitor, RS113456, have similar acute anti-inflammatory effects.

There is increasing evidence that antiproteases are able to affect the inflammatory response. To further examine this question, we administered human alpha-1-antitrypsin (alpha1AT) or a synthetic metalloprotease inhibitor (RS113456) to C57 mice followed by a single intratracheal dose of quartz, a dust that evokes a marked, lasting, polymorphonuclear leukocyte (PMN) infiltrate. At 2 hours after dust administration, both antiproteases completely suppressed silica-induced PMN influx into the lung and macrophage inflammatory protein-2 (MIP-2)/monocyte chemotactic protein-1 (MCP-1) (neutrophil/macrophage chemoattractant) gene expression, partially suppressed nuclear transcription factor kappaB (NF-kappaB) translocation, and increased inhibitor of NF-kappaB (IkappaB) levels. By 24 hours, PMN influx and connective tissue breakdown measured as lavage desmosine or hydroxyproline were still at, or close to, control levels after antiprotease treatment, and increases in NF-kappaB translocation and MIP-2/MCP-1 gene expression were variably suppressed. At both time points, neither agent prevented silica-induced increases in amount of whole lung MIP-2 or MCP-1 protein, but both did prevent increases in whole lung intercellular adhesion molecule-1 (ICAM-1) at 24 hours. Inactivating the alpha1AT by oxidation to the point that it no longer possessed antiproteolytic properties did not affect its ability to suppress inflammation. Both antiproteases also prevented the silica-induced acute inflammatory response in mice with knocked out genes for macrophage metalloelastase (MME -/-), mice that develop inflammation, but not connective tissue breakdown, and the pattern of alpha1AT breakdown fragments was identical in control and MME -/- animals. These findings suggest that, in this model of acute PMN mediated inflammation, a serine protease inhibitor and a metalloprotease inhibitor have similar anti-inflammatory properties, that inflammation is not mediated by proteolysis with generation of chemotactic matrix fragments, and that classic antiproteolysis (complexing of protease to antiprotease) probably does not play a role in suppression of inflammation. The antiproteolytic effects of these agents do not seem to be mediated by protection of endogenous alpha1AT.

Animals↗

PubMed2001

Noradrenaline-induced changes in intracellular Ca(2+) and tension in mesenteric arteries from diabetic rats.

1. The purpose of this investigation was to determine whether enhanced contractile responses to noradrenaline (NA) of mesenteric arteries from rats with chronic streptozotocin-induced diabetes are associated with increases in mean cytosolic [Ca(2+)]i. 2. [Ca(2+)]i was measured with fura 2-AM, and was monitored simultaneously with tension in perfused endothelium-denuded mesenteric arterial rings from 12 - 14 week diabetic rats and age- and gender-matched control rats. 3. Basal [Ca(2+)]i (expressed as R(n), the normalized fura 2 ratio) was not significantly different in arteries from control and diabetic rats. Similarly, no differences between control and diabetic arteries in the tension or [Ca(2+)]i responses to 80 mM KCl in the presence of phentolamine were detected. 4. The rate of tension development, peak tension and integrated tension in response to 30 microM NA were all significantly greater in diabetic than control arteries. However, this was not associated with enhancement of the corresponding [Ca(2+)]i responses in the diabetic arteries. 5. Peak contractile responses to perfusion with both 0.3 and 3 microM NA, but peak [Ca(2+)]i only in response to 0.3 microM NA, were significantly greater in diabetic than control arteries. 6. NA (30 microM) produced a greater increase in both peak tension and [Ca(2+)]i in diabetic than control arteries perfused with Ca(2+)-free solution containing 1 mM EGTA. Neither the rate nor the magnitude of NA-induced Ca(2+) influx appeared to be altered in the diabetic arteries. 7. The enhanced sustained contractile response of diabetic arteries to NA appears to be dissociated from increases in [Ca(2+)]i, and may be due to other factors, such as an increase in the Ca(2+) sensitivity of the contractile proteins.

Animals↗

PubMed2001

HER-2 expression is a prognostic factor in patients with metastatic breast cancer treated with a combination of high-dose cyclophosphamide, mitoxantrone, paclitaxel and autologous blood stem cell support.

The expression levels of a circulating extracellular domain of HER-2 can be detected in the plasma and serum of patients with metastatic breast cancer using an enzyme immunoassay (ELISA) method. In this study, we evaluated the clinical significance of high and low levels of HER-2 in the plasma of 46 patients with metastatic breast cancer enrolled in a clinical trial of high-dose chemotherapy (HDCT) using cyclophosphamide, mitoxantrone, and paclitaxel with autologous stem cell transplantation (ASCT). Using 2500 U/ml as the cut-point, 20 patients (46%) had elevated HER-2 levels (HER-2 positive). Our results suggest that patients with metastatic breast cancer and high soluble plasma HER-2 have a significantly poorer overall (OS) and progression-free survival (PFS) following high-dose chemotherapy with paclitaxel and ASCT. The median OS of patients with low levels of HER-2 was significantly longer (P < 0.01) than the median OS of patients with high levels of HER-2 (29.8 months vs 15.9 months). PFS was also significantly longer (P < 0.01) for patients who were HER-2-negative, than for patients who were HER-2-positive (13.0 vs 8.6 months). Univariate analysis showed that patients with liver or lung metastases had significantly reduced OS and PFS. Patients with metastases to two or more sites also had a significantly reduced time to disease progression, but not OS. In multivariable analysis, lung metastases contributed along with HER-2-positive status to determine a group of patients with significantly poorer OS. However, HER-2-positive status remained the only independent predictor of PFS.

Adult↗

PubMed2001

Inhibition of phosphatidylinositol-3 kinase/Akt or mitogen-activated protein kinase signaling sensitizes endothelial cells to TNF-alpha cytotoxicity.

Bovine carotid artery endothelial (BAE) cells are resistant to tumor necrosis factor-alpha (TNF), like most other cells. We examined if mitogen-activated protein (MAP) kinase and phosphatidylinositol-3 (PI3) kinase/Akt pathways are involved in this effect. In BAE cells, TNF activates MAP kinase in a MAP kinase kinase 1 (MEK1) manner and Akt in PI3-kinase-dependent manner. Pretreatment with either the MEK1 inhibitor U0126 or PI3-kinase inhibitor LY294002 sensitized BAE cells to TNF-induced apoptosis. Neither U0126 nor LY294002 pretreatment affected TNF-induced activation of NF-kappaB, suggesting that the MAP kinase or PI3-kinase/Akt-mediated anti-apoptotic effect induced by TNF was not relevant to NF-kappaB activation. Both MAP kinase and PI3-kinase/Akt -mediated signaling could prevent cytochrome c release and mitochondrial transmembrane potential (Deltapsi) decrease. PI3-kinase/Akt signaling attenuated caspase-8 activity, whereas MAP kinase signaling impaired caspase-9 activity. These results suggest that TNF-induced MAP kinase and PI3-kinase/Akt signaling play important roles in protecting BAE cells from TNF cytotoxicity.

Animals↗

PubMed2001

Designing gene therapy vectors: avoiding immune responses by using tissue-specific promoters.

Attempts to correct genetic disorders by gene therapy have been hindered by various problems including unwanted immune responses against the gene product. It has been shown that immune responses with DNA vaccines after i.m. injection of antigen-encoding plasmid DNA are primed solely by professional antigen-presenting cells (APC), even though myocytes are the primary type of cell transfected. This possibly involves direct transfection of some APC in regional lymph nodes draining the injected muscle. Here we have used plasmid DNA vaccines that express hepatitis B surface antigen (HBsAg) to evaluate the possibility of abrogating these immune responses by use of a tissue-specific promoter that does not drive expression in APC. We show that HBsAg-specific humoral or cell-mediated responses are not induced in mice when the muscle-specific human muscle creatine kinase promoter is used in place of the ubiquitous cytomegaloviral promoter to drive expression of HBsAg. This may have significance in the field of gene therapy where one aims to achieve stable expression of the desired gene product without interference from the host immune response.

Animals↗

PubMed2001

Frequent demonstration of human herpesvirus 8 (HHV-8) in bone marrow biopsy samples from Turkish patients with multiple myeloma (MM).

In order to investigate the frequency of HHV-8 in MM patients from another geographic location, we obtained fresh bone marrow (BM) biopsies from Turkish patients with MM (n = 21), monoclonal gammopathy of undetermined significance (MGUS) (n = 2), plasmacytoma (n = 1) with BM plasma cell infiltration, various hematological disorders (n = 6), and five healthy Turkish controls. The frequency of HHV-8 was analyzed by polymerase chain reaction (PCR) in two independent laboratories in the USA and in Turkey. Using fresh BM biopsies, 17/21 MM patients were positive for HHV-8 whereas all five healthy controls, and six patients with other hematological disorders were negative. Two patients with MGUS, and one patient with a solitary plasmacytoma were also negative. The data from the two laboratories were completely concordant. Also using primer pairs for v IRF and v IL-8R confirmed the results observed with the KS330233 primers. Furthermore, sequence analysis demonstrated a C3 strain pattern in the ORF26 region which was also found in MM patients from the US. Thus, HHV-8 is present in the majority of Turkish MM patients, and the absence of the virus in healthy controls further supports its role in the pathogenesis of MM.

Biopsy↗

PubMed2001

Study of the separation and determination of monosaccharides in soluble coffee by capillary zone electrophoresis with electrochemical detection.

A simple, fast and reliable method, based on capillary electrophoresis with electrochemical detection, for the separation and determination of six monosaccharides, namely glucose, galactose, arabinose, fructose, xylose and ribose, in soluble coffees was developed. A copper disk electrode was used as the working electrode. The optimum conditions for separation and detection were 50 mmol L-1 sodium hydroxide buffer (pH 12.7), separation voltage 5 kV and detection potential 0.65 V (vs. Ag/AgCl). The linear ranges were from 5.0 x 10(-3) to 0.5 mmol L-1 for all six sugars. All regression coefficients were > 0.99. The detection limits for all the sugars were 1.0 x 10(-3) mmol L-1. The RSD of the peak current was < 4.2% (n = 5). The proposed method was applied directly to the separation and determination of the six sugars without prior derivatization, and the assay results were satisfactory.

Journal Article↗

PubMed2001

Covalent modification of glassy carbon electrode with glutamic acid for simultaneous determination of uric acid and ascorbic acid.

A novel covalently modified glassy carbon electrode with glutamic acid has been fabricated via an electrochemical oxidation procedure and was applied to the catalytic oxidation of uric acid (UA) and ascorbic acid (AA), reducing the overpotentials by about 0.2 V and 0.3 V, respectively. Based on its strong catalytic function toward the oxidation of UA and AA, the modified electrode resolved the overlapping voltammetric response of UA and AA into two well-defined voltammetric peaks with both cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which can be used for the simultaneous determination of these species in a mixture. The catalytic peak current obtained from DPV was linearly dependent on the UA and AA concentration in the range 2 x 10(-6)-4 x 10(-4) mol L-1 and 1.0 x 10(-6)-4 x 10(-4) mol L-1 with correlation coefficients of 0.996 and 0.997, respectively. The detection limits (3 delta) for UA and AA were 1.1 x 10(-6) mol L-1 and 9.2 x 10(-7) mol L-1, respectively. The modified electrode shows good sensitivity, selectivity and stability, and has been applied to the determination of UA and AA simultaneously in human urine samples with satisfactory results.

Ascorbic Acid↗

PubMed2001

Separation and determination of protocatechuic aldehyde and protocatechuic acid in Salivia miltorrhrza by capillary electrophoresis with amperometric detection.

Capillary electrophoresis with amperometric detection was applied to separate and determine protocatechuic aldehyde and protocatechuic acid in Salivia miltorrhrza preparations. The electrode used was a 0.3 mm diameter carbon disk electrode fixed in a wall-jet with amperometric detection. Under the optimum conditions, the two analytes were separated completely within 8 min. Excellent linearity was obtained in the concentration ranges of 0.25-100.0 microg ml(-1) and 0.50-100.0 microg ml(-1) for protocatechuic aldehyde and protocatechuic acid, respectively. The detection limits were 0.10 microg ml(-1) of protocatechuic aldehyde and 0.25 microg ml(-1) of protocatechuic acid, which were found to be lower than those of other methods that determine protocatechuic aldehyde (3,4-dihydroxybenzaldehyde) and protocatechuic acid (3,4-dihydrobenzoic acid) simultaneously. The mean recoveries of protocatechuic aldehyde and protocatechuic acid were 97.4% and 103.3%. This method has been successfully applied to monitor these two components in real samples such as Salivia miltorrhrza and its two traditional Chinese medicinal preparations.

Anticarcinogenic Agents↗

PubMed2001

Structural and functional studies of cinnamomin, a new type II ribosome-inactivating protein isolated from the seeds of the camphor tree.

Cinnamomin is a new type II ribosome-inactivating protein (RIP). Its A-chain exhibits RNA N-glycosidase activity to inactivate the ribosome and thus inhibit protein synthesis, whereas the glycosylated B-chain is a lectin. The primary structure of cinnamomin, which exhibits approximately 55% identity with those of ricin and abrin, was deduced from the nucleotide sequences of cDNAs of cinnamomin A- and B-chains. It is composed of a total of 549 amino-acid residues: 271 residues in the A-chain, a 14-residue linker and 264 residues in the B-chain. To explore its biological function, the cinnamomin A-chain was expressed in Escherichia coli with a yield of 100 mg per L of culture, and purified through two-step column chromatography. After renaturation, the recovery of the enzyme activity of the expressed A-chain was 80% of that of native A-chain. Based on the modeling of the three-dimensional structure of the A-chain, the functional roles of five amino acids and the only cysteine residues were investigated by site-directed mutagenesis or chemical modification. The conserved single mutation of the five amino-acid residues led to 8-50-fold losses of enzymatic activity, suggesting that these residues were crucial for maintaining the RNA N-glycosidase activity of the A-chain. Most interestingly, the strong electric charge introduced at the position of the single cysteine in A-chain seemed to play a role in enzyme/substrate binding.

Algal Proteins↗

PubMed2001

Phase-coupled oscillator models can predict hippocampal inhibitory synaptic connections.

What factors are responsible for propagating electrical activity in the hippocampus? Using an intact, isolated hippocampus preparation, it is possible to observe spontaneous delta (< or = 4 Hz) waves of rhythmic field potentials. These rhythmic potentials are inhibitory in nature, mediated by GABAergic inhibitory potentials originating from a population of principal neurons. They start in the ventro-temporal region and move longitudinally towards the dorso-septal region with a phase lag of approximately 10% between the extracellular recordings. We use the mathematical framework of phase-coupled oscillators (PCO) to gain some insight into the underlying network system. A chain of 15 nearest-neighbour bidirectionally coupled PCOs is used where each oscillator refers to a segment of the CA1 region of the hippocampus that can generate these slow field potentials. We find that ventro-dorsal delta waves exist if there is a dominance in coupling strength in one direction. Without a one-way coupling dominance, ventro-dorsal waves can still exist, but then the coupling strengths need to be much larger. The relationship between entrained and intrinsic frequencies and the variation of propagation speeds along the longitudinal axis can be used to determine which case applies. Currently available experimental data supports one of the cases, predicting that there is a stronger ventral to dorsal inhibitory effect.

Action Potentials↗