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Biomedical subjects

M Zhang

Publications and source records attributed to M Zhang.

At least 217 records · Page 12Linked to original sources
PubMed2001

Chelation of hypocrellin B with zinc ions with electron paramagnetic resonance (EPR) evidence of the photodynamic activity of the resulting chelate.

Hypocrellin B (HB), a perylenequinone derivative, is an efficient phototherapeutic agent. The chelation of HB with Zinc ions (Zn2+) results in a metal chelate (Zn-HB) which exhibits considerable absorption (lambda max = 612 nm) in the phototherapeutic window. The structure of this chelate has been characterized by UV-Vis, IR and mass spectra. The redox potentials of the Zn-HB chelate were Eox = +1.1 V (vs. SCE) and Ere = -0.7 V (vs. SCE) as measured using the circle volt curve. The quantum yield of singlet oxygen generated by the Zn-HB chelate was 0.86, which both the electron spin trap (EPR) method and the chemical trap method show to be about 0.1 higher than that of its parent compound HB. In irradiated oxygen-saturated solutions of Zn-HB chelate, superoxide radical anions and hydroxyl radicals were detected by EPR spectroscopy using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as the spin-trapping agent.

Chelating Agents↗
PubMed2001

HveC (nectin-1) is expressed at high levels in sensory neurons, but not in motor neurons, of the rat peripheral nervous system.

The entry of herpes simplex virus (HSV)-1 into cells is a complex process mediated in part by the binding of the HSV glycoprotein D (gD) to a specific cellular receptor identified as HveC, or nectin-1. We examined the distribution of HveC in sensory and motor neurons of the peripheral nervous system (PNS) by immunocytochemistry. HveC is expressed at high levels in sensory neurons of dorsal root ganglion and their peripheral axons, at lower levels in motor neurons of spinal cord, and without detectable expression in motor nerve terminals at the neuromuscular junction. These results have implications regarding the tropism of HSV to specific neuronal populations, and for the construction of HSV-based vectors for the peripheral nervous system.

Animals↗
PubMed2001

Promoter Extraction from GenBank (PEG): automatic extraction of eukaryotic promoter sequences in large sets of genes.

UNLABELLED: Promoter Extraction from GenBank (PEG) extracts promoter sequences for large sets of genes using information present in GenBank. For a gene whose promoter sequence is not found, PEG will attempt to extract promoter sequences of the orthologous genes instead. AVAILABILITY: It is freely available to academic users at ftp://cshl.org/pub/science/mzhanglab/theresa/. CONTACT: zhangt@cshl.org; mzhang@cshl.org

Databases, Nucleic Acid↗
PubMed2001

Expression and localization of luteinizing hormone receptor in the female mouse reproductive tract.

The presence of the LH receptor (LHR) in nongonadal tissues of the reproductive tract has been reported, but localization studies have not been performed. Our objectives were to demonstrate the presence of LHR in the reproductive tract and to localize receptor expression. Reproductive age rats and mice were obtained and (125)I-hCG binding assays were performed on membrane preparations from the uterus, ovary, liver, and testis. In situ hybridizations were performed using (35)S-labeled antisense and sense RNA probes prepared from nucleotides 1-591 of the mouse LHR cDNA. Specific hCG binding was detected in membrane preparations from the ovary, uterus, and testis but not in the liver in both the rat and mouse. In the ovary, LHR mRNA was localized in theca cells, large follicles, and corpora lutea as expected. In the uterus, LHR mRNA was expressed in stromal cells of the endometrium and in the uterine serosa. Uterine smooth muscle cells had low levels of expression, and the endometrial epithelium was negative. In the oviduct, high levels of LHR expression were noted on the serosa and in subepithelial cells. Oviductal smooth muscle had low expression, and the epithelium was negative. We conclude that functional, nongonadal LHR are expressed in the mouse reproductive tract. The presence and localization of LHR expression in the mouse reproductive tract lay the foundation for transgenic models to address the physiologic role of these receptors.

Animals↗
PubMed2001

Expression and function of the HSD-3.8 gene encoding a testis-specific protein.

The nucleotide sequence of the full length HSD-3.8 cDNA (accession number AF311312), encoding a human sperm component, was determined to consist of 3818 bp with a reading frame of 2778 bp encoding a deduced polypeptide composed of 926 amino acids. A 0.7 kb fragment containing three immunological epitopes of HSD-3.8 cDNA was prepared and used to construct recombinant expression vectors. The constructs were transformed into E.coli BL-21, and the fusion proteins were expressed, isolated and purified. Using the polyclonal antibodies raised against the purified expressed fusion proteins, positive immunostaining occurred over the surface of the postacrosomal zone of human spermatozoa and of germ cells within the seminiferous epithelium of human testis. Intense staining of large pachytene primary spermatocytes occurred. The capacity of the recombinant protein to reduce fertility as an immunogen in adult female rats was assessed. Immunized animals were infertile or exhibited marked reduction in their fertility. Analysis of the deduced HSD-3.8 polypeptide revealed the presence of a tetratricopeptide repeat (TPR) motif, a P-loop sequence that acts as a binding site for ATP/GTP and phosphorylation sites for PKC, CK2 and cAMP/cGMP-dependent protein kinases. A blot overlay assay with [alpha-(32)P]GTP showed that the polypeptide encoded by the 0.7 kb fragment of HSD-3.8 is a GTP binding protein. It was also shown to possess GTPase activity and to be phosphorylated by PKC in vitro. In conclusion, HSD-3.8 is a GTP binding protein and its activity may be regulated by phosphorylation.

Adenosine Triphosphate↗
PubMed2001

Fetuin, a negative acute phase protein, attenuates TNF synthesis and the innate inflammatory response to carrageenan.

Activation of the innate immune system, even by relatively innocuous stimuli, stimulates the release of cytokines (e.g. TNF) that can injure or kill the host. To maintain homeostasis, mammals have evolved a counter-regulatory response that suppresses the development of excessively robust inflammation. Fetuin, a 66-kD negative acute phase glycoprotein, was first identified in 1944. We recently discovered an anti-inflammatory role for fetuin, because it suppressed the release of TNF from lipopolysaccharide- (LPS) stimulated macrophages. Here the anti-inflammatory effects of fetuin were studied in vivo in an LPS-independent model of acute inflammation caused by administration of carrageenan. Administration of fetuin (5-500 mg/kg intraperitoneally) dose-dependently attenuated the development of paw edema as compared to either asialofetuin (500 mg/kg) or bovine albumin (500 mg/kg). TNF production in the carrageenan-injected paws was significantly inhibited by administration of fetuin (586+/-98 pg TNF/paw) as compared to either asialofetuin (1018+/-186 pg TNF/paw) or saline (1,005+/-172 pg TNF/paw). When specific anti-fetuin IgG was administered into the paw prior to the application of carrageenan, the development of edema formation was significantly increased as compared to irrelevant IgG, indicating that endogenous fetuin normally attenuates the inflammatory response. These results now reveal a previously unrecognized anti-inflammatory role of fetuin in counter-regulating the innate immune response, and suggest that it may be possible to use fetuin as an experimental anti-inflammatory agent.

Acute-Phase Proteins↗
PubMed2001

The relationship between quality and outcomes in routine depression care.

OBJECTIVE: This longitudinal, nonexperimental study examined whether depression treatment provided in concordance with guidelines developed by the Agency for Healthcare Research and Quality (AHRQ) is associated with improved clinical outcomes. METHODS: The medical, insurance, and pharmacy records of a community-based sample of 435 subjects who screened positive for current major depression were abstracted to ascertain whether depression treatment was received and whether it was provided in accordance with AHRQ guidelines. Regression analyses estimated the impact of guideline-concordant treatment on the change in depression severity and on mental and physical health over a six-month period. An instrumental variables analysis was used to check the sensitivity of the results to selection bias. RESULTS: A total of 106 subjects were treated for depression by 105 different primary care and specialty providers. Sixty percent of the sample had current major depression, and about 40 percent had subthreshold depression. Only 29 percent of the patients received guideline-concordant treatment. For patients with major depression, guideline-concordant care was significantly and substantially associated with improved depression severity but not with improvements in overall mental or physical health. The instrumental variables analysis indicated that the standard regression analysis underestimated the treatment effect by 21 percent. For those with subthreshold depression, guideline-concordant care was not associated with improved outcomes. DISCUSSION AND CONCLUSIONS: This community-based, nonexperimental study found a positive relationship between the quality of care for depression and clinical outcomes for patients with major depression in routine practice settings.

Adult↗
PubMed2001

Provider choice and utility loss due to selective contracting in rural and urban areas.

An econometric model estimated the disutility of traveling long distances for depression treatment, and simulations calculated the utility loss associated with selective contracting in rural and urban areas. A representative sample of depression patients (n = 106) and all practicing providers (n = 3,710) in Arkansas were identified and the distances between them were calculated. Using discrete choice analysis, patient preferences for provider type and travel distance were estimated. Simulations calculated the utility loss associated with alternative scenarios of selective contracting. Provider type and distance were significant predictors of provider choice. To equate the utility loss associated with selective contracting in rural and urban areas, a slightly higher proportion of rural physicians and a substantially higher proportion of rural mental health specialists must be contracted. To avoid further reductions in geographic access, managed care organizations should contract with a higher proportion of rural providers than urban providers.

Arkansas↗
PubMed2001

Identification and implantation stage-specific expression of an interferon-alpha-regulated gene in human and rat endometrium.

Implantation of the developing blastocyst is regulated by multiple effectors, such as steroid hormones, growth factors, and cytokines. To understand how these diverse signaling pathways interact to modulate uterine gene expression, we employed a gene expression screen technique to identify the molecules that are induced in the periimplantation rat uterus. Here we report the isolation of a complementary DNA representing a novel gene, interferon-regulated gene 1 (IRG1). This gene exhibits significant homology to interferon (IFN)-alpha/beta-inducible human genes p27 and 6-16, indicating that these genes may belong to the same family. Consistent with this finding, expression of IRG1 messenger RNA (mRNA) in rat uterus increased about 20-fold in response to IFNalpha. Uterine expression of IRG1 was also stimulated by estrogen and was partially inhibited by an antiestrogen, ICI 182,780. In pregnant rats, IRG1 expression was high on day 1, but declined on days 2 and 3. The level of IRG1 mRNA again rose transiently on day 4 immediately preceding implantation. In situ hybridization analysis localized the IRG1 mRNA expression in the endometrial epithelium and the surrounding stroma. Interestingly, the expression of p27, which shows high homology to IRG1, was strongly enhanced in human endometrium during the midsecretory phase of the menstrual cycle, overlapping the putative window of implantation. Both IRG1 and p27 mRNAs are therefore induced in the endometrium in an implantation stage-specific manner. We also observed a synergistic interaction between IFNalpha and estrogen receptor signaling pathways that led to maximal induction of p27 mRNA in Ishikawa cells. Although the functional roles of IRG1 and p27 remain unclear, we describe for the first time, identification of a gene family regulated by IFNalpha in both rodent and human uteri. More importantly, our studies reveal that a complex interplay between the steroid hormone and IFN pathways regulates the expression of these genes in the endometrium at the time of implantation.

Adult↗
PubMed2001

Copper staining method for extracting biologically active proteins from native gels.

An attempt was made to make protein bands visible on native gel using copper staining, since such a mild staining procedure would make the entire native gel electrophoresis process non-denaturing. Copper staining not only was able to detect various proteins on native gel with reasonable sensitivity, but also made extraction and recovery of active proteins possible from the gel using a gentle procedure.

Chromatography, Gel↗
PubMed2001

The dose-response effects of ethanol on the human fetal osteoblastic cell line.

Alcohol is a risk factor for the development of osteoporosis, especially in men. Chronic alcohol abuse decreases bone mass, which contributes to the increased incidence of fractures. To better understand the mechanism of action of ethanol on bone metabolism, we have studied the dose-response effects of ethanol on conditionally immortalized human fetal osteoblasts (hFOB) in culture. Ethanol treatment had no significant effects on osteoblast number after 1 day or 7 days. Ethanol treatment did not reduce type I collagen protein levels at either time point at any dose but slightly reduced alkaline phosphatase activity after 7 days. The messenger RNA (mRNA) levels for alkaline phosphatase, type I collagen, and osteonectin were unaltered by 24 h of ethanol treatment but a high dose (200 mM) reduced mRNA levels for the two bone matrix proteins after 7 days. Ethanol treatment led to dose-dependent increases in transforming growth factor beta1 (TGF-beta1) mRNA levels and decreases in TGF-beta2 mRNA levels. The concentration of ethanol in the medium decreased with time because of evaporation but there was little degradation caused by metabolism. These results, which show that cultured osteoblasts are less sensitive than osteoblasts in vivo, suggest that the pronounced inhibitory effects of ethanol on bone formation are not caused by direct cell toxicity.

Alkaline Phosphatase↗
PubMed2001

Prolactin-Stimulated X-linked inhibitor of apoptosis protein expression during S phase cell cycle progression in rat Nb2 lymphoma cells.

The rat Nb2 lymphoma is useful for studying prolactin (PRL) receptor signaling to mitogenesis and apoptosis suppression. Previous results showed that PRL rapidly induced expression of several apoptosis suppressor genes during the G1 phase of cell cycle in this model. The X-linked inhibitor of apoptosis protein (XIAP) gene product acts to suppress apoptosis by direct inhibition of caspases. The present study was conducted to determine whether PRL alters XIAP expression in lactogen-dependent Nb2-11 or -independent Nb2-SFJCD1 cells. Stationary Nb2-11 cultures expressed detectable levels of an 8.9-kb XIAP transcript. PRL (20 ng/mL) stimulated its expression, reaching maximal levels within 12 h. Expression of XIAP was also evaluated in Nb2-SFJCD1 cells subsequent to treatment with differentiating agents (sodium butyrate [2 mM, 72 h], all trans-retinoic acid [10 microM, 72 h], or 1,25-dihydroxycholecalciferol [100 nM, 24 h]). PRL significantly increased XIAP expression in cells previously treated with these compounds. Further analysis revealed that PRL stimulated XIAP expression during S phase of the cell cycle. To determine whether XIAP suppressed apoptosis, its cDNA was stably transfected into Nb2-11 cells. Compared to controls, cells overexpressing XIAP exhibited substantially less DNA fragmentation when apoptosis was induced by PRL deprivation or glucocorticoids. We conclude that PRL-stimulated XIAP expression likely serves to suppress apoptosis as cells progress through the later phases of the cell cycle.

Animals↗
PubMed2001

Spectroscopic studies and photodynamic actions of hypocrellin B in liposomes.

Hypocrellin B (HB), a lipid-soluble natural pigment of perylenequinone derivative, is considered as potential photosensitizer for photodynamic therapy. Liposomes loaded with HB can constitute a simple model system, appropriate for better understanding the photodynamic action of HB in vivo. The steady-state absorption and emission spectra, quantum yield and lifetime of fluorescence of HB incorporated into egg L-a-phosphatidyl-choline (EPC) liposome were examined. The photochemical properties (Type I and/or Type II) of HB have also been studied in aqueous dispersions of small unilamellar liposomes of EPC using electron paramagnetic resonance and spectrophotometric methods, respectively. The quantum yield of 1O2 generated by HB is ca 0.76 in chloroform solution and it did not change upon the incorporation of HB into liposomes of EPC. The superoxide anion radical was generated by the electron transfer from the anion radical of HB (HB.-) to oxygen. The disproportionation of O2.- can generate H2O2 and ultimately the highly reactive .OH via the Fenton reaction. It could be that the disproportionation proceeded too fast, so we could not detect O2.- directly in aqueous dispersions of liposome EPC. Moreover, the self-sensitized photooxygenation of HB embedded in liposomes was studied, and almost fully (87%) inhibiting this reaction of HB by p-benzoquinone (as the quencher of O2.-) in aqueous dispersion of liposome EPC indicated that the radical mechanism (Type I) might be mainly involved in this oxygenation. All these findings suggested that the photodynamic action of HB proceeded via both Type-I and -II mechanisms, but Type-I mechanism might play a more important role in the aqueous dispersion.

Electron Spin Resonance Spectroscopy↗
PubMed2001

Photobleaching of hypocrellin B and its butylamino-substituted derivative in solutions.

The photobleaching of hypocrellin B (HB) and its derivative butylamino-substituted hypocrellin B (BAHB), both of which are potent sensitizers for photodynamic therapy (PDT), were investigated by studies of absorption spectra and quenching experiments and by the determination of photoproducts. Control experiments indicated that the sensitizer, oxygen and light were essential for the photobleaching of HB and BAHB, which suggested that it was a photodynamic process, e.g. the photobleaching processes of both HB and BAHB were mainly self-sensitized photooxidations. The illumination of HB with visible light in oxygenated nonpolar solvents generated singlet oxygen efficiently [phi(1O2) = 0.76] which in turn attacked the sensitizer HB with the subsequent formation of an endoperoxide product. The endoperoxide of HB is unstable at room temperature and undergoes loss of singlet oxygen with regeneration of the parent HB. The singlet oxygen released from the endoperoxide of HB was detected with chemical trapping experiments. The quenching experiments indicated that in increasingly polar solvents the superoxide anion mechanism (type I) as well as the singlet oxygen mechanism (type II) contributed to the photobleaching of HB. The introduction of the electron-donating butylamino group not only enhanced the yield of the superoxide anion generation but also altered the position of attack in the BAHB molecule by the activated oxygen species. No endoperoxide product was observed, and no singlet oxygen released from the photobleaching process of BAHB was detected. The photobleaching process of BAHB was more complex. Both the singlet oxygen and superoxide anion mechanism played important roles in the photobleaching of BAHB in all organic solvent used here, even in aerobic nonpolar solvents such as CHCl3.

Electron Transport↗
PubMed2001

Probabilistic risk assessment of cotton pyrethroids: III. A spatial analysis of the Mississippi, USA, cotton landscape.

Estimates of potential aquatic exposure concentrations arising from the use of pyrethroid insecticides on cotton produced using conventional procedures outlined by the U.S. Environmental Protection Agency's Office of Pesticide Programs Environmental Fate and Effects Division seem unrealistically high. Accordingly, the assumptions inherent in the pesticide exposure assessment modeling scenarios were examined using remote sensing of a significant Mississippi, USA, cotton-producing county. Image processing techniques and a geographic information system were used to investigate the number and size of the water bodies in the county and their proximity to cotton. Variables critical to aquatic exposure modeling were measured for approximately 600 static water bodies in the study area. Quantitative information on the relative spatial orientation of cotton and water, regional soil texture and slope, and the detailed nature of the composition of physical buffers between agricultural fields and water bodies was also obtained. Results showed that remote sensing and geographic information systems can be used cost effectively to characterize the agricultural landscape and provide verifiable data to refine conservative model assumptions. For example, 68% of all ponds in the region have no cotton within 360 m and 92% of the ponds have no cotton within 60 m. Only 2% of ponds have cotton present in all directions around the ponds and within 120 m. These are significant modifications to conventional pesticide risk assessment exposure modeling assumptions and exemplify the importance of using landscape-level risk assessments to better describe the Mississippi cotton agricultural landscape. Incorporating spatially characterized landscape information into pesticide aquatic exposure scenarios is likely to have greater impact on the model output than many other refinements.

Animals↗
PubMed2001

Analysis of ubiquitination in vivo using a transgenic mouse model.

The primary pathway for the proteolytic destruction of cellular proteins is through ubiquitin-mediated targeting to the proteasome. This pathway is pivotal not only in the elimination of damaged or misfolded proteins but also in the temporal, developmental, or signal-mediated destruction of normal cellular substrates. The list of known substrates of the ubiquitin/proteasome pathway is long, but most substrates have been identified in yeast or, more recently, in cultured mammalian cells. It is likely that many mammalian substrates with developmental or disease relevance have yet to be identified because their ubiquitination occurs in tissue or organ systems that cannot be adequately modeled in vitro. We have developed a transgenic mouse model that will allow the isolation and identification of these substrates. The human UbC promoter was used to drive expression of a hexahistidine-tagged version of human ubiquitin in a variety of mouse tissues from early embryonic stages, as assessed by a green fluorescent protein marker. Cleavage of the fusion protein by endogenous enzymes produced epitope-tagged ubiquitin that was detected both in monomeric form and conjugated to cellular proteins. This mouse model should facilitate in the analysis of normal and disease-related ubiquitination events in vivo.

Animals↗
PubMed2001

Insulin activates ATP-sensitive K(+) channels in pancreatic beta-cells through a phosphatidylinositol 3-kinase-dependent pathway.

Insulin is known to regulate pancreatic beta-cell function through the activation of cell surface insulin receptors, phosphorylation of insulin receptor substrate (IRS)-1 and -2, and activation of phosphatidylinositol (PI) 3-kinase. However, an acute effect of insulin in modulating beta-cell electrical activity and its underlying ionic currents has not been reported. Using the perforated patch clamp technique, we found that insulin (1-600 nmol/l) but not IGF-1 (100 nmol/l) reversibly hyperpolarized single mouse beta-cells and inhibited their electrical activity. The dose-response relationship for insulin yielded a maximal change (mean +/- SE) in membrane potential of -13.6 +/- 2.0 mV (P < 0.001) and a 50% effective dose of 25.9 +/- 0.1 nmol/l (n = 63). Exposing patched beta-cells within intact islets to 200 nmol/l insulin produced similar results, hyperpolarizing islets from -47.7 +/- 3.3 to -65.6 +/- 3.7 mV (P < 0.0001, n = 11). In single cells, insulin-induced hyperpolarization was associated with a threefold increase in whole-cell conductance from 0.6 +/- 0.1 to 1.7 +/- 0.2 nS (P < 0.001, n = 10) and a shift in the current reversal potential from -25.7 +/- 2.5 to -63.7 +/- 1.0 mV (P < 0.001 vs. control, n = 9; calculated K(+) equilibrium potential = -90 mV). The effects of insulin were reversed by tolbutamide, which decreased cell conductance to 0.5 +/- 0.1 nS and shifted the current reversal potential to -25.2 +/- 2.3 mV. Insulin-induced beta-cell hyperpolarization was sufficient to abolish intracellular calcium concentration ([Ca(2+)](i)) oscillations measured in pancreatic islets exposed to 10 mmol/l glucose. The application of 100 nmol/l wortmannin to inactivate PI 3-kinase, a key enzyme in insulin signaling, was found to reverse the effects of 100 nmol/l insulin. In cell-attached patches, single ATP-sensitive K(+) (K(ATP)) channels were activated by bath-applied insulin and subsequently inhibited by wortmannin. Our data thus demonstrate that insulin activates the K(ATP) channels of single mouse pancreatic beta-cells and islets, resulting in membrane hyperpolarization, an inhibition of electrical activity, and the abolition of [Ca(2+)](i) oscillations. We thus propose that locally released insulin might serve as a negative feedback signal within the islet under physiological conditions.

Adenosine Triphosphate↗