Biomedical subjects

L Zhao

Publications and source records attributed to L Zhao.

At least 91 records · Page 5Linked to original sources

PubMed2001

Spectral karyotyping study of chromosome abnormalities in human leukemia.

Chromosomal analysis plays an important role in the diagnosis, treatment and prognosis of human leukemia. Currently, the GTG-banding technique (G-banding) is the most commonly used diagnostic method in clinical cytogenetics. G-banding analysis of subtle chromosomal rearrangements or complex karyotypes with multiple markers can be inadequate because of poor chromosome morphology and/or an insufficient yield of analyzable metaphases. Fluorescence in situ hybridization (FISH) is a highly sensitive and specific method to detect chromosomal alterations. Conventional FISH is used optimally in instances where only one or a few abnormalities are investigated. Spectral karyotyping (SKY), a novel cytogenetic technique, has been developed to unambiguously display and identify all chromosomes at one time using a spectrum of 24 different colors. This report presents the use of SKY for examination of the entire karyotype in specimens with complex chromosomal abnormalities from three leukemia patients. Conventional cytogenetic analysis (G-banding) showed complex hyperdiploid clones with multiple markers in each case. SKY was able to clarify and identify additional cryptic chromosomal translocations [e.g., t(2;10), t(3;10), t(5;7), t(7;18), t(9;17), t(10;12), t(13;16)] insertions [e.g., ins(17;9), ins(20;Y)], duplications [e.g., i(8)(q10), dup(4)(q31q35)] and marker chromosomes in each case. This study demonstrates that the combination of SKY and G-band techniques results in a more complete characterization of the complex chromosomal aberrations seen in leukemia.

Bone Marrow Cells↗

PubMed2001

Production, purification, and characterization of an intracellular aflatoxin-detoxifizyme from Armillariella tabescens (E-20).

Some Armillariella tabescens (E-20) multienzymes have previously been reported to present detoxifying activities against aflatoxins. In this paper, we describe the isolation purification of an intracellular enzyme, named aflatoxin-detoxifizyme, which exhibited detoxification activity on aflatoxin B(1) (AFB(1)). This aflatoxin-detoxifizyme exhibited a specific activity of 7.09 nmol min/mg at pH 6.0 and 28 degrees C. The apparent molecular mass was 51.8 kDa as determined by SDS-PAGE. The isoelectric point was estimated to be 5.4 and optimum activity for the enzyme was found at pH 6.8 and 35 degrees C. The activity of the purified enzyme was confirmed by Ames test.

Aflatoxin B1↗

PubMed2001

Gene therapy for hepatocellular carcinoma based on tumour-selective suicide gene expression using the alpha-fetoprotein (AFP) enhancer and a housekeeping gene promoter.

The aim of this study was to examine whether the human alpha-fetoprotein (AFP) enhancer could be used to induce hepatocellular carcinoma (HCC)-selective expression of the herpes simplex virus thymidine kinase (HSV-tk) gene which is under the control of the phosphoglycerate kinase (pgk) promotor. The human AFP enhancer was linked with the non-tissue-specific, human housekeeping pgk promoter in a retroviral vector. AFP-producing HCC cells infected with retroviruses carrying the HSV-tk gene under the control of the AFP enhancer/pgk promoter were much more susceptible to the prodrug, ganciclovir (GCV), than those infected with the same retroviruses without the AFP enhancer. Non-HCC cells infected with retroviruses carrying the HSV-tk gene under the control of the AFP enhancer/pgk promoter exhibited profoundly increased resistance to GCV compared with those infected with the same retroviruses without the AFP enhancer. Northern blot analysis revealed that the AFP enhancer caused enhanced HSV-tk expression in AFP-producing HCC cells and suppressed HSV-tk expression in non-HCC cells. Our results indicate that the AFP enhancer could give HCC selectivity to the pgk promoter, and that this novel strategy may be useful for HCC-selective cancer gene therapy.

Blotting, Northern↗

PubMed2001

Functional importance and caffeine sensitivity of ryanodine receptors in primary lymphocytes.

Calcium signaling patterns are important for the specific regulation of activation and effector function in lymphocytes. Studies of [Ca2+]i regulation in lymphocytes, including the involvement of ryanodine receptors (RyR) and the importance of caffeine-sensitive pools, have been carried out mainly in lymphocyte cell lines and the presence and functional importance of these pools in primary lymphocytes has not been addressed. Here we show by confocal microscopy that caffeine caused a prompt but transitory increase of [Ca2+]i in primary lymphocytes, an effect that was inhibited by pre-treatment with ryanodine. Furthermore, the increase of [Ca2+]i in CD4+ and CD8+ MLR T lymphocytes stimulated by 5 microg/ml concanavalin A was significantly inhibited by pretreatment with caffeine. In functional studies, caffeine decreased cytotoxicity against myocyte target cells which is probably related to an altered calcium signaling in CD8+ MLR lymphocytes. Caffeine also terminated spontaneous Ca2+ oscillations and induced a rise in [Ca2+]i in CD4- and CD8- MLR lymphocytes probably of B cell origin. These results demonstrate that caffeine alters Ca2+ signaling in primary lymphocytes, and suggest that RyR, probably the skeletal muscle receptor (RyR-1) and brain receptor (RyR-3), are involved in mediating this effect. It is also possible that blocking of inositol-1,4,5-triphosphate (IP3) receptors is involved in the effects of caffeine on lymphocyte activation.

Animals↗

PubMed2001

Cloning, sequencing, and heterologous expression of the elmGHIJ genes involved in the biosynthesis of the polyketide antibiotic elloramycin from Streptomyces olivaceus Tü2353.

Elloramycin A (1) belongs to a small family of naphthacenequinones characterized by a unique highly hydroxylated cyclohexenone moiety. A cosmid clone 16F4, harboring genes for the production of 1 from Streptomyces olivaceus Tü2353, has been previously isolated. DNA sequence analysis of a 3.2-kb fragment from 16F4 revealed four open reading frames--the elmGHIJ genes. Heterologous expressions of the elmGHI genes in either Escherichia coli or Streptomyces lividans, followed by biochemical characterizations of the ElmGHI proteins, established ElmG as tetracenomycin B2 oxygenase, ElmH as tetracenomycin F1 monooxygenase, and ElmI as tetracenomycin F2 cyclase. These results provide direct biochemical evidence for the hypothesis that the biosynthesis of 1 in S. olivaceus parallels that of tetracenomycin C (2) in Streptomyces glaucescens and support the notion that the biosynthesis of the highly hydroxylated cyclohexenone moiety in other polyketides most likely follows the same paradigm as the tetracenomycin B2 or A2 oxygenase.

Anthraquinones↗

PubMed2001

Tumoricidal activity of a novel anti-human DR5 monoclonal antibody without hepatocyte cytotoxicity.

A novel anti-human DR5 monoclonal antibody, TRA-8, induces apoptosis of most tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-sensitive tumor cells both in vitro and in vivo. In contrast to both the membrane-bound form of human TRAIL, which induced severe hepatitis in mice, and the soluble form of human TRAIL, which induced apoptosis of normal human hepatocytes in vitro, TRA-8 did not induce significant cell death of normal human hepatocytes. However, both primary hepatocellular carcinoma cells and an established liver cancer cell line were highly susceptible to the killing mediated by TRA-8. We show here that elevated levels of cell-surface expression of DR5 and increased susceptibility to DR5-mediated apoptosis are characteristics of malignant tumor cells. In contrast, DR5 alone is not sufficient to trigger apoptosis of normal hepatocytes. Therefore, selective, specific targeting of DR5 with an agonistic antibody might be a safe and effective strategy for cancer therapy.

Animals↗

PubMed2001

Effects of combining three different antiplatelet agents on platelets and leukocytes in whole blood in vitro.

1. Antiplatelet drugs have been demonstrated to reduce the incidence of recurrent events in patients with symptomatic vascular disease. However, there is no experimental data indicating the effects of these agents when given together on platelets and leukocytes. We investigated the ability of aspirin (an inhibitor of cyclo-oxygenase), dipyridamole (an inhibitor of phospodiesterases and adenosine uptake) and AR-C69931 (a direct acting P(2T) antagonist with effects similar to those of clopidogrel which can be used in vitro) when used alone or in combination to inhibit platelet and leukocyte function. 2. Measurements of platelet and leukocyte function were performed in blood taken from normal volunteers, and the inhibitory effects of aspirin (100 micromol l(-1)), dipyridamole (10 micromol l(-1)) and AR-C66931 (100 nmol l(-1)) were determined. Platelet aggregation was induced by stirring blood with and without adenosine diphosphate (ADP) or platelet activating factor (PAF) and measured by platelet counting. Platelet P-selectin expression, platelet-leukocyte conjugate formation, and leukocyte activation were determined by flow cytometry. 3. Dipyridamole, AR-C69931, dipyridamole and AR-C69931, dipyridamole and aspirin, AR-C69931 and aspirin, and all three agents together inhibited platelet aggregation induced by stirring, ADP and PAF (P<0.01). However, it was only the combination of all three agents inhibited P-selectin expression (P<0.01). Similarly, it was the combination of all three antiplatelet agents that most consistently inhibited platelet-monocyte and platelet-neutrophil conjugate formation and monocyte and neutrophil activation. 4. Since both platelets and leukocytes are thought to contribute to arterial thrombosis and atherosclerosis, it is possible that combinations of different antiplatelet agents with different mechanisms of action may afford better protection than individual or pairs of agents used on their own.

Adenosine Diphosphate↗

PubMed2001

Neuroprotective effects of pyridoxal phosphate and pyridoxal against ischemia in monkeys.

Previously, in monkeys undergoing 20 min whole brain ischemia we demonstrated that the activated calpain-induced lysosomal disruption with the resultant leakage of cathepsins B and L, causes neuronal death in the cornu Ammonis (CA) 1 sector on day 5. Selective cathepsin inhibitors significantly protected ischemic CA1 neurons from delayed necrosis. Recently, pyridoxal phosphate (PLP) and pyridoxal (hydrochloride) (PL) were demonstrated to inhibit cathepsins B and L in vitro, because the active aldehyde at position 4 of the pyridine ring has an affinity for the active site -SH of cysteine residues of cathepsins. Here, we studied whether PLP and PL can, in vivo, protect monkey CA1 neurons from ischemic insult. In monkeys undergoing 20 min whole brain ischemia, 15 mg/kg body weight/day of drugs were intravenously injected for 10 days before and after the ischemic insult. Histological analysis of the surviving CA1 neurons was done using the hippocampus resected on day 5 after ischemia. For PLP or PL, approximately 17% (P = 0.0639) or 54% (P < 0.0001) of the total population (100%) of control CA1 neurons were, respectively, saved from the ischemia-induced neuronal death, showing a remarkable contrast to the surviving neurons (approximately 3.9%) in non-treated monkeys. These data suggested that PL (perhaps PLP intracellularly) is useful as a novel neuroprotectant in primates.

Animals↗

PubMed2001

Proposal of the genera Anaerococcus gen. nov., Peptoniphilus gen. nov. and Gallicola gen. nov. for members of the genus Peptostreptococcus.

Members of genus Peptostreptococcus have previously been found to be distantly related to the type species, Peptostreptococcus anaerobius, on the basis of 16S rDNA sequence similarities. They were divided into three major phylogenetic groups, and their peptidoglycan structure and biochemical traits differed between groups. The reclassification of the species of these three groups into three new genera, Peptoniphilus gen. nov., Anaerococcus gen. nov. and Gallicola gen. nov., is proposed. The genus Peptoniphilus gen. nov. includes the following butyrate-producing, non-saccharolytic species that use peptone and amino acids as major energy sources: Peptoniphilus asaccharolyticus comb. nov. (type species), Peptoniphilus lacrimaris comb. nov., Peptoniphilus harei comb. nov., Peptoniphilus indolicus comb. nov. and Peptoniphilus ivorii comb. nov. The genus Anaerococcus gen. nov. contains the saccharolytic, butyrate-producing species Anaerococcus prevotii comb. nov. (type species), Anaerococcus tetradius comb. nov., Anaerococcus lactolyticus comb. nov., Anaerococcus hydrogenalis comb. nov., Anaerococcus vaginalis comb. nov. and Anaerococcus octavius sp. nov. The genus Gallicola gen. nov. contains a single species, Gallicola barnesae comb. nov.

Animals↗

PubMed2001

Vi-Suppressed wild strain Salmonella typhi cultured in high osmolarity is hyperinvasive toward epithelial cells and destructive of Peyer's patches.

Salmonella typhi GIFU10007-3 which lost a viaB locus on its chromosome became highly invasive in our previous study. To investigate the phenomenon, we controlled Vi expression in wild strain S. typhi GIFU10007, and studied the invasive phenotype both in vitro and in vivo. When the wild strain of S. typhi was cultured in 300 mM NaCl containing Luria-Bertani broth (LBH), the expression of Vi antigen was suppressed, but secretion of invasion proteins (SipC, SipB and SipA) was increased. In this condition, wild strain S. typhi became highly invasive toward both epithelial cells and M cells of rat Peyer's patches. When GIFU10007 was cultured under conditions of high osmolarity, the bacteria disrupted Peyer's patches and induced massive bleeding in these structures only 20 min after inoculation into the ileal loop. In contrast, Vi-encapsulated wild strain GIFU10007 cultured under low osmolarity was not destructive, even after 60 min. To understand the role of the type III secretion system under conditions of high osmolarity, we knocked out the invA and sipC genes of both GIFU10007 and GIFU10007-3. Neither invA nor sipC mutants could invade epithelial cells or M cells in a high osmolarity environment. Our data show that the highly invasive phenotype was only expressed when the wild strain S. typhi was cultured under high osmolarity, which induced a state of Vi suppression, and in the presence of the type III secretion system.

Animals↗

PubMed2001

Modeling of combined processing steps for reducing Escherichia coli O157:H7 populations in apple cider.

Probabilistic models were used as a systematic approach to describe the response of Escherichia coli O157:H7 populations to combinations of commonly used preservation methods in unpasteurized apple cider. Using a complete factorial experimental design, the effect of pH (3. 1 to 4.3), storage temperature and time (5 to 35 degrees C for 0 to 6 h or 12 h), preservatives (0, 0.05, or 0.1% potassium sorbate or sodium benzoate), and freeze-thaw (F-T; -20 degrees C, 48 h and 4 degrees C, 4 h) treatment combinations (a total of 1,600 treatments) on the probability of achieving a 5-log(10)-unit reduction in a three-strain E. coli O157:H7 mixture in cider was determined. Using logistic regression techniques, pH, temperature, time, and concentration were modeled in separate segments of the data set, resulting in prediction equations for: (i) no preservatives, before F-T; (ii) no preservatives, after F-T; (iii) sorbate, before F-T; (iv) sorbate, after F-T; (v) benzoate, before F-T; and (vi) benzoate, after F-T. Statistical analysis revealed a highly significant (P < 0.0001) effect of all four variables, with cider pH being the most important, followed by temperature and time, and finally by preservative concentration. All models predicted 92 to 99% of the responses correctly. To ensure safety, use of the models is most appropriate at a 0.9 probability level, where the percentage of false positives, i.e., falsely predicting a 5-log(10)-unit reduction, is the lowest (0 to 4.4%). The present study demonstrates the applicability of logistic regression approaches to describing the effectiveness of multiple treatment combinations in pathogen control in cider making. The resulting models can serve as valuable tools in designing safe apple cider processes.

Beverages↗

PubMed2001

Comparison of logistic regression and linear regression in modeling percentage data.

Percentage is widely used to describe different results in food microbiology, e.g., probability of microbial growth, percent inactivated, and percent of positive samples. Four sets of percentage data, percent-growth-positive, germination extent, probability for one cell to grow, and maximum fraction of positive tubes, were obtained from our own experiments and the literature. These data were modeled using linear and logistic regression. Five methods were used to compare the goodness of fit of the two models: percentage of predictions closer to observations, range of the differences (predicted value minus observed value), deviation of the model, linear regression between the observed and predicted values, and bias and accuracy factors. Logistic regression was a better predictor of at least 78% of the observations in all four data sets. In all cases, the deviation of logistic models was much smaller. The linear correlation between observations and logistic predictions was always stronger. Validation (accomplished using part of one data set) also demonstrated that the logistic model was more accurate in predicting new data points. Bias and accuracy factors were found to be less informative when evaluating models developed for percentage data, since neither of these indices can compare predictions at zero. Model simplification for the logistic model was demonstrated with one data set. The simplified model was as powerful in making predictions as the full linear model, and it also gave clearer insight in determining the key experimental factors.

Clostridium botulinum↗

PubMed2001

Potent, broad-spectrum inhibition of human immunodeficiency virus type 1 by the CCR5 monoclonal antibody PRO 140.

CCR5 serves as a requisite fusion coreceptor for clinically relevant strains of human immunodeficiency virus type 1 (HIV-1) and provides a promising target for antiviral therapy. However, no study to date has examined whether monoclonal antibodies, small molecules, or other nonchemokine agents possess broad-spectrum activity against the major genetic subtypes of HIV-1. PRO 140 (PA14) is an anti-CCR5 monoclonal antibody that potently inhibits HIV-1 entry at concentrations that do not affect CCR5's chemokine receptor activity. In this study, PRO 140 was tested against a panel of primary HIV-1 isolates selected for their genotypic and geographic diversity. In quantitative assays of viral infectivity, PRO 140 was compared with RANTES, a natural CCR5 ligand that can inhibit HIV-1 entry by receptor downregulation as well as receptor blockade. Despite their divergent mechanisms of action and binding epitopes on CCR5, low nanomolar concentrations of both PRO 140 and RANTES inhibited infection of primary peripheral blood mononuclear cells (PBMC) by all CCR5-using (R5) viruses tested. This is consistent with there being a highly restricted pattern of CCR5 usage by R5 viruses. In addition, a panel of 25 subtype C South African R5 viruses were broadly inhibited by PRO 140, RANTES, and TAK-779, although approximately 30-fold-higher concentrations of the last compound were required. Interestingly, significant inhibition of a dualtropic subtype C virus was also observed. Whereas PRO 140 potently inhibited HIV-1 replication in both PBMC and primary macrophages, RANTES exhibited limited antiviral activity in macrophage cultures. Thus CCR5-targeting agents such as PRO 140 can demonstrate potent and genetic-subtype-independent anti-HIV-1 activity.

Amides↗

PubMed2001

Steroidogenic factor 1 (SF1) is essential for pituitary gonadotrope function.

Knockout mice lacking the orphan nuclear receptor steroidogenic factor 1 (SF1) exhibit a complex endocrine phenotype that includes adrenal and gonadal agenesis, impaired expression of pituitary gonadotropins, and absence of the ventromedial hypothalamic nucleus (VMH). These multiple defects complicate efforts to delineate primary versus secondary effects of SF1 deficiency in different tissues, such that its direct role in gonadotropes remains uncertain. To define this role, we have expressed Cre recombinase driven by the promoter region of the common alpha subunit of glycoprotein hormones (alpha GSU), thereby inactivating a loxP-modified SF1 locus in the anterior pituitary gland. Although pituitary-specific SF1 knockout mice were fully viable, they were sterile and failed to develop normal secondary sexual characteristics. Their adrenal glands and VMH appeared normal histologically, but their testes and ovaries were severely hypoplastic. alpha GSU-Cre, loxP mice had normal levels of most pituitary hormones, but had markedly decreased expression of LH and FSH. Treatment with exogenous gonadotropins stimulated gonadal steroidogenesis, inducing germ cell maturation in males and follicular and uterine maturation in females--establishing that the gonads can respond to gonadotropins. The pituitary-specific SF1 knockout mice are a novel genetic model of hypogonadotropic hypogonadism that establishes essential role(s) of SF1 in pituitary gonadotropes.

Animals↗

PubMed2001

Production of poly(3-hydroxybutyrateco-3-hydroxyvalerate) from cottonseed oil and valeric acid in batch culture of Raistonia sp. strain JC-64.

A Ralstonia sp. strain JC-64 that is capable of accumulating poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P[3HB-co-3HV]) from cottonseed oil and valeric acid was isolated. By using a high limiting-nitrogen (HLN) mineral medium as the medium for the second stage of the fermentation process and by adding the two carbon sources at different times, a range of copolymers with 12-62 mol% of 3HV were produced from a series of HLN mineral mediums containing different compositions of cottonseed oil and valeric acid by Ralstonia sp. JC-64. The melting temperature (Tm) of polyhydroxybutyrate from cottonseed oil was 174 degrees C and that of P(3HB-co-3HV) with the highest 3HV-mol fraction (62%) was 81 degrees C.

Carbon↗

PubMed2001

[The use of limit amplitude technique in clinical cardiac electrical signal recording].

Based on the electrophysiologic mechanism of cardiac electrical action and the theory of voltage effect, the limit amplitude technique was employed to obtain the best clinical record effects. The results showed that limiter could limit the oversize signals overlapping each other and make the tiny signals magnification without distortion, such as the His bundle deflection in His Bundel Electrogram. At the same time, all signals recorded at multichannel physiologic recorder were clear and did not interfere with each other. Furthermore, the limiter not only improved the recording quality but also protected the cardiac electronic equipment because overdue stimulation signal was limited at a given electronic level during the recording of transesophageal pacing.

Electrocardiography↗

PubMed2001

[Effects of intestinal endotoxemia on the development of cirrhosis in rats].

OBJECTIVE: To explore the effect of endotoxin on the development of cirrhosis. METHODS: The cirrhosis model with intestinal endotoxemia was made by oral intake of 0.03% thioacetamide for four months to observe the effect of endotoxin on the hepatic collagen contents in both thioacetamide and thioacetamide + lipopolysaccharide groups and to detect the contents of tumor necrosis factor-alpha (TNF-alpha), endothelin-1 (ET-1), nitric oxide (NO), and malondialdehyde (MDA) in the plasma and the hepatic homogenate. RESULTS: The contents of TNF-alpha, ET-1, NO, and MDA in the plasma and the hepatic homogenate and the content of collagen in the hepatic tissue in the two groups were higher than those in the normal control group. CONCLUSIONS: Endotoxin can accelerate liver fibrosis and the formation of cirrhosis.

Animals↗

PubMed2001

[Cytotoxic T lymphocyte activity induced by genetic immunization with NV-HC/NS].

OBJECTIVE: To investigate the immunoprophylactic and immunotherapeutic effects of DNA vaccine (NV-HC/NS(3)) after inoculation of mice by target tumor loading technique. METHODS: Before or after inoculation with NV-HC/NS(3) intramuscularly, BALB/c mice in the experimental group were planted with target tumor cells (SP2/0-NS(3)), which were derived from BALB/c mice and stably transfected with the recombinant plasmid NV-HC/NS(3). Tumor growth and survival rate of the mice immunized with NV-HC/NS(3) were compared with those in the control group. RESULTS: Tumor mass grew well in all mice in the control group in a few days, while no visible tumor mass growth in 40% mice immunized with NV-HC/NS(3) could be seen. The survival rate and life span of mice in the experimental group were significantly longer than those in the control group. CONCLUSIONS: Specific immune activity could be induced by immunization with NV-HC/NS(3). Such effects are immunoprophylactic and immunotherapeutic.

Animals↗