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Biomedical subjects

J Ren

Publications and source records attributed to J Ren.

At least 73 records · Page 4Linked to original sources
PubMed2001

Choline acetyltransferase activity parallels the pressure gradient in the feline pharyngo-esophageal region.

Pressures generated by the pharyngeal constrictor muscles and proximal esophagus involve acetylcholine-induced muscle contractions. We hypothesized that the pharyngo-esophageal pressure gradient is related to choline acetyltransferase activity. In nine anesthetized cats, hypopharyngeal pressure and proximal esophageal pressure were recorded with a solid state transducer assembly. Enzymatic activities in the thyropharyngeus, cricopharyngeus, and proximal esophageal muscles were measured. Hypopharyngeal pressure was higher than the proximal esophagus (p < 0.01), and choline acetyltransferase activity was higher in the cricopharyngeus compared to the proximal esophagus ( p < 0.05). The pressure gradient between the hypopharynx and proximal esophagus may be influenced by the activity of choline acetyltransferase.

Acetylcholinesterase↗
PubMed2001

2-Amino-6-arylsulfonylbenzonitriles as non-nucleoside reverse transcriptase inhibitors of HIV-1.

A series of 2-amino-5-arylthiobenzonitriles (1) was found to be active against HIV-1. Structural modifications led to the sulfoxides (2) and sulfones (3). The sulfoxides generally showed antiviral activity against HIV-1 similar to that of 1. The sulfones, however, were the most potent series of analogues, a number having activity against HIV-1 in the nanomolar range. Structural-activity relationship (SAR) studies suggested that a meta substituent, particularly a meta methyl substituent, invariably increased antiviral activities. However, optimal antiviral activities were manifested by compounds where both meta groups in the arylsulfonyl moiety were substituted and one of the substituents was a methyl group. Such a disubstitution led to compounds 3v, 3w, 3x, and 3y having IC50 values against HIV-1 in the low nanomolar range. When gauged for their broad-spectrum antiviral activity against key non-nucleoside reverse transcriptase inhibitor (NNRTI) related mutants, all the di-meta-substituted sulfones 3u-z and the 2-naphthyl analogue 3ee generally showed single-digit nanomolar activity against the V106A and P236L strains and submicromolar to low nanomolar activity against strains E138K, V108I, and Y188C. However, they showed a lack of activity against the K103N and Y181C mutant viruses. The elucidation of the X-ray crystal structure of the complex of 3v (739W94) in HIV-1 reverse transcriptase showed an overlap in the binding domain when compared with the complex of nevirapine in HIV-1 reverse transcriptase. The X-ray structure allowed for the rationalization of SAR data and potencies of the compounds against the mutants.

Anti-HIV Agents↗
PubMed2001

Sensitive and universal indirect chemiluminescence detection for capillary electrophoresis of cations using cobalt(II) as a probe ion.

Highly sensitive and universal indirect chemiluminescence detection for capillary electrophoresis of cations was described. This novel method is based on use of the ultrasensitive cobalt(II) as a probe ion in the running buffer. A strong and stable background chemiluminescent signal can be generated by the luminol-hydrogen peroxide reaction catalyzed by cobalt(II) ion. Displacement of the cobalt(II) probe ion in the running buffer by a migrating sample cation results in a quantifiable decrease in the background signal. The conditions for electrophoresis and the chemiluminescent reaction were systematically investigated using a commercial capillary electrophoresis instrument with an in-house-built chemiluminescence detector. Under the optimal conditions, the detection limits of the concentration for manganese(II), cadmium(II), nickel(II), lead(II), and 14 lanthanides were (3.0-6.0) x 10(-9) mol/L (S/N = 3), which was approximately 3 orders of magnitude better than indirect UV detection and 2 orders better than indirect laser-induced fluorescent detection. A mixture of 18 metal ions including 14 lanthanides was efficiently separated within 3.5 min using lactate to partially complex the metal ions. Our data demonstrated that CE with indirect CL detection was a powerful and universal tool for analysis of inorganic and organic cations.

Journal Article↗
PubMed2001

The c-Src tyrosine kinase regulates signaling of the human DF3/MUC1 carcinoma-associated antigen with GSK3 beta and beta-catenin.

The DF3/MUC1 mucin-like glycoprotein is aberrantly overexpressed in most human carcinomas. The cytoplasmic domain of MUC1 interacts with glycogen synthase kinase 3 beta (GSK3 beta) and thereby decreases binding of MUC1 and beta-catenin. The present studies demonstrate that MUC1 associates with the c-Src tyrosine kinase. c-Src phosphorylates the MUC1 cytoplasmic domain at a YEKV motif located between sites involved in interactions with GSK3 beta and beta-catenin. The results demonstrate that the c-Src SH2 domain binds directly to pYEKV and inhibits the interaction between MUC1 and GSK3 beta. Moreover and in contrast to GSK3 beta, in vitro and in vivo studies demonstrate that c-Src-mediated phosphorylation of MUC1 increases binding of MUC1 and beta-catenin. The findings support a novel role for c-Src in regulating interactions of MUC1 with GSK3 beta and beta-catenin.

Antigens, Neoplasm↗
PubMed2001

Characterization of contractile function in diabetic hypertensive cardiomyopathy in adult rat ventricular myocytes.

Diabetes and hypertension both produce myocardial dysfunction that accelerates cardiovascular morbidity and mortality. Coexistence of the two often results in a more severe cardiomyopathy than either process alone. The purpose of this study was to characterize the contractile function of diabetic hypertensive cardiomyopathy at the single myocyte level. Adult spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were made diabetic with a single injection (55 mg/kg) of streptozotocin (STZ). Contractile properties of ventricular myocytes were evaluated, including peak shortening (PS), time-to-peak shortening (TPS), time-to-90% relengthening (TR90) and maximal velocities of shortening/relengthening (+/-dL/d t). The experimental animals exhibited enlarged heart size, elevated blood glucose and systolic blood pressure. PS was unchanged (SHR), enhanced (WKY-STZ) or depressed (SHR-STZ) compared to control (WKY). Myocytes from all experimental groups displayed prolonged TPS and TR90 compared to the WKY group, although only those from the hypertensive groups (SHR, SHR-STZ) were associated with reduced +/-dL/d t. Additionally, myocytes from the WKY-STZ but not the SHR or the SHR-STZ groups exhibited impaired responsiveness to increased extracellular Ca2+. Myocytes from the SHR-STZ group displayed a leftward shift of the stimulus frequency-peak shortening response curve compared to the WKY group. These results confirmed observations at the multicellular levels that combination of diabetes and hypertension results in a greater impairment of cardiac contractile function than is seen with either disease alone.

Animals↗
PubMed2001

Functional analysis of the putative peroxidase domain of FANCA, the Fanconi anemia complementation group A protein.

Fanconi anemia (FA) is an autosomal recessive disorder manifested by chromosomal breakage, birth defects, and susceptibility to bone marrow failure and cancer. At least seven complementation groups have been identified, and the genes defective in four groups have been cloned. The most common subtype is complementation group A. Although the normal functions of the gene products defective in FA cells are not completely understood, a clue to the function of the FA group A gene product (FANCA) was provided by the detection of limited homology in the amino terminal region to a class of heme peroxidases. We evaluated this hypothesis by mutagenesis and functional complementation studies. We substituted alanine residues for the most conserved FANCA residues in the putative peroxidase domain and tested their effects on known biochemical and cellular functions of FANCA. While the substitution mutants were comparable to wild-type FANCA with regard to their stability, subcellular localization, and interaction with FANCG, only the Trp(183)-to-Ala substitution (W183A) abolished the ability of FANCA to complement the sensitivity of FA group A cells to mitomycin C. By contrast, TUNEL assays for apoptosis after exposure to H2O2 showed no differences between parental FA group A cells, cells complemented with wild-type FANCA, and cells complemented with the W183A of FANCA. Moreover, semiquantitative RT-PCR analysis for the expression of the peroxide-sensitive heme oxygenase gene showed appropriate induction after H2O2 exposure. Thus, W183A appears to be essential for the in vivo activity of FANCA in a manner independent of its interaction with FANCG. Moreover, neither wild-type FANCA nor the W183A mutation appears to alter the peroxide-induced apoptosisor peroxide-sensing ability of FA group A cells.

Alanine↗
PubMed2001

Sequence and stress-response analyses of the DNA mismatch repair gene hexA in Lactococcus lactis.

The DNA mismatch repair gene hexA was identified in Lactococcus lactis by PCR amplification by using a pair of primers homologous to the DNA-binding Dps protein. The gene in its entirety, including the regulatory regions, was sequenced, by using a strategy of chromosomal walking based on two PCR protocols. The open reading frame of 2526 bp was preceded by a strong ribosome-binding site (AGGAAG) and was followed by a potential transcription terminator (hairpin loop structure). The 5' terminus of the hexA mRNA was located 135 bp upstream of the start codon, and putative -10 and -35 regions were identified. The deduced amino acid sequence revealed two motifs, the ATP/GTP-binding site (P-loop) and the "MutS family signature". The hexA promoter was cloned into pMU1327, which contained a promoter-less CAT reporter gene, and the promoter activity was examined under oxidative-stress conditions. It appears that the promoter activity is down-shifted by H2O2 at 4 mM.

Amino Acid Sequence↗
PubMed2001

An octakis-intercalating molecule.

Herein we report the synthesis and characterization of a polyintercalator with eight potential intercalating l,4,5,8-naphthalenetetracarboxylic diimide (NDI) units linked in a head-to-tail arrangement via a peptide linker. UV spectroscopy and viscometry measurements indicated the molecule binds to double-stranded DNA with all eight NDI units intercalated simultaneously. Competition dialysis and DNAse 1 footprinting studies revealed a preference for GC-rich regions of DNA, and circular dichroism studies revealed significant distortion of B-form DNA upon binding. Our so-called "octamer" represents, to the best of our knowledge, the first intercalator that binds as an octakis-intercalator, capable of spanning at least 16 base pairs of DNA.

Animals↗
PubMed2001

Immunohistochemical detection of verotoxin receptors in nervous system.

Verotoxin receptor is a globotriaosylceramide (Gb3) present on vascular endothelial cells, in which the toxin causes hemolytic uremic syndrome. We established a sensitive method of immunohistochemical staining in serial sections using monoclonal antibodies (mAbs) against verotoxin and glycolipids that includes Gb3 and galactosylGb3 (GalGb3). With it, we showed co-localization of the verotoxin receptor and Gb3 in dorsal root ganglia (DRG) of humans, rabbits, rats and mice. We also used a very simple method to identify the presence of lipofuscin-like autofluorescence which complicates fluorescence microscopy observation of aged human nervous tissues.

Animals↗
PubMed2001

GM2 ganglioside regulates the function of ciliary neurotrophic factor receptor in murine immortalized motor neuron-like cells (NSC-34).

We previously reported that ciliary neurotrophic factor (CNTF) increased the serum-free cell survival of immortalized motor neuron-like cells (NSC-34), and addition of the exogenous ganglioside GalNAc beta4(Neu5Ac alpha3)Gal beta4GlcCer (GM2) facilitated cell survival together with CNTF. Moreover beta 1,4 N-acetylgalactosaminyltransferase (GM2 synthase) activity increased in NSC-34 cells cultured with CNTF. We now have examined whether CNTF-induced cell survival is associated with the collaboration between GM2 and the CNTF receptor (CNTF-R). Despite the presence of CNTF (50 ng/ml), anti-CNTF-R antibody caused cell death and prevented the up-regulation of GM2 synthase expression. The addition of GM2 (1 to 20 microM) abrogated the anti-CNTF-R antibody effect which shortened cell survival and blocked GM2 synthase activation. Use of [125I]CNTF showed the specificity of CNTF binding in NSC-34 cells in situ. GM2 produced a 5-fold increase in the CNTF binding affinity per cell but did not change the binding site number. The study by metabolic labeling with [1-(14)C]N-acetyl-D-galactosamine ([14C]GalNAc) showed that biosynthesized GM2 was involved in the immunoprecipitation of CNTF-R. These findings indicate that up-regulated GM2 synthesis induces functional conversion of CNTF-R to the activated state, in which it has affinity for CNTF. We conclude that GM2 is a bio-regulating molecule of CNTF-R in motor neurons.

Animals↗
PubMed2001

Ginsenosides Rb1 and Re decrease cardiac contraction in adult rat ventricular myocytes: role of nitric oxide.

1. Panax ginseng is used to enhance stamina and relieve fatigue as well as physical stress. Ginsenoside, the effective component of ginseng, regulates cardiovascular function. This study was to examine the effect of ginsenosides Rb1 and Re on cardiac contractile function at the cellular level. Ventricular myocytes were isolated from adult rat hearts and were stimulated to contract at 0.5 Hz. Contractile properties analysed included: peak shortening (PS), time-to-90%PS (TPS), time-to-90% relengthening (TR90), and fluorescence intensity change (DeltaFFI). Nitric oxide synthase (NOS) activity was determined by the 3H-arginine to 3H-citrulline conversion assay. 2. Both Rb1 and Re exhibited dose-dependent (1-1000 nM) inhibition in PS and DeltaFFI, with maximal inhibitions between 20-25%. Concurrent application Rb1 and Re did not produce any additive inhibition on peak shortening amplitude (with a maximal inhibition of 24.9+/-6.1%), compared to Rb1 or Re alone. Pretreatment with the NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 microM) abolished the effect of Rb1 and Re. Both Rb1 and Re significantly (P<0.05) stimulated NOS activity concentration-dependently. 3. This study demonstrated a direct depressant action of ginsenosides on cardiomyocyte contraction, which may be mediated in part through increased NO production.

Animals↗
PubMed2001

Galanin suppresses calcium conductance and activates inwardly rectifying potassium channels in myenteric neurones from guinea-pig small intestine.

Whole-cell patch-clamp recording methods were used to investigate the ionic mechanisms underlying the hyperpolarizing action of galanin in enteric neurones. Galanin suppressed calcium current (ICa) and activated inwardly rectifying potassium current (IK,ir) in AH-type myenteric neurones of guinea-pig small intestine. Both suppression of ICa and activation of IK,ir were concentration-dependent, with an EC50 of 1.4 nmol L-1 and 55 nmol L-1, respectively. Pretreatment with pertussis toxin eliminated both actions of galanin, suggesting that both galanin-induced inhibition of ICa and galanin-induced activation of IK,ir involved activation of Gi/Go proteins. Both suppression of ICa and activation of IK,ir by galanin were mimicked by the N-terminal fragment of galanin, galanin-(1-16) suggesting that the first 16 amino acids of the peptide were sufficient for both actions. The galanin receptor antagonist galantide suppressed the galanin-induced activation of IK,ir with an EC50 of 16 nmol L-1. However, galantide alone suppressed ICa. The results suggest two mechanisms of action for galanin: one is opening of inwardly rectifying potassium channels and the second is blockade of voltage-activated calcium channels.

Adjuvants, Immunologic↗
PubMed2001

Studies on the effects of lactate transport inhibition, pyruvate, glucose and glutamine on amino acid, lactate and glucose release from the ischemic rat cerebral cortex.

A rat four vessel occlusion model was utilized to examine the effects of ischemia/reperfusion on cortical window superfusate levels of amino acids, glucose, and lactate. Superfusate aspartate, glutamate, phosphoethanolamine, taurine, and GABA were significantly elevated by cerebral ischemia, then declined during reperfusion. Other amino acids were affected to a lesser degree. Superfusate lactate rose slightly during the initial ischemic period, declined during continued cerebral ischemia and then was greatly elevated during reperfusion. Superfusate glucose levels declined to near zero levels during ischemia and then rebounded beyond basal levels during the reperfusion period. Inhibition of neuronal lactate uptake with alpha-cyano-4-hydroxycinnamate dramatically elevated superfusate lactate levels, enhanced the ischemia/reperfusion evoked release of aspartate but reduced glutamine levels. Topical application of an alternative metabolic fuel, glutamine, had a dose dependent effect. Glutamine (1 mM) elevated basal superfusate glucose levels, diminished the decline in glucose during ischemia, and accelerated its recovery during reperfusion. Lactate levels were elevated during ischemia and reperfusion. These effects were not evident at 5 mM glutamine. At both concentrations, glutamine significantly elevated the superfusate levels of glutamate. Topical application of sodium pyruvate (20 mM) significantly attenuated the decline in superfusate glucose during ischemia and enhanced the levels of both glucose and lactate during reperfusion. However, it had little effect on the ischemia-evoked accumulation of amino acids. Topical application of glucose (450 mg/dL) significantly elevated basal superfusate levels of lactate, which continued to be elevated during both ischemia and reperfusion. The ischemia-evoked accumulations of aspartate, glutamate, taurine and GABA were all significantly depressed by glucose, while phosphoethanolamine levels were elevated. These results support the role of lactate in neuronal metabolism during ischemia/reperfusion. Both glucose and glutamine were also used as energy substrates. In contrast, sodium pyruvate does not appear to be as effectively utilized by the ischemic/reperfused rat brain since it did not reduce ischemia-evoked amino acid efflux.

Amino Acids↗
PubMed2001

Interaction of an acridine dimer with DNA quadruplex structures.

The reactivation of telomerase activity in most cancer cells supports the concept that telomerase is a relevant target in oncology, and telomerase inhibitors have been proposed as new potential anticancer agents. The telomeric G-rich single-stranded DNA can adopt an intramolecular G-quadruplex structure in vitro, which has been shown to inhibit telomerase activity. The C-rich sequence can also adopt a quadruplex (intercalated) structure (i-DNA). Two acridine derivatives were shown to increase the melting temperature of the G- quadruplex and the C-quadruplex at 1 microM dye concentration. The increase in Tm value of the G-quadruplex was associated with telomerase inhibition in vitro. The most active compound, "BisA", showed an IC(50) value of 0.75 microM in a standard TRAP assay.

Acridines↗
PubMed2001

Influence of ATP-sensitive K+ channel modulation on the mechanical properties of diabetic myocardium.

ATP-sensitive K+ (KATP) channels are therapeutic targets for hypertension and diabetes. KATP channel opening elicits vasorelaxation and myocardial protection, whereas its closing stimulates insulin secretion. The cardiac KATP conductance is believed altered under diabetes. This study was to evaluate the influence of KATP channel openers and blocker on myocardial contractile dysfunction in diabetes. Adult rats were made diabetic with streptozotocin (55 mg/kg) and maintained for eight weeks. Contractile properties were studied using isolated papillary muscles in the absence or presence of KATP channel openers (BRL 38227 and pinacidil) and KATP blocker (glyburide). Experimental diabetes led to hyperglycemia, reduced growth, cardiac hypertrophy and hepatomegaly. Mechanical properties exhibited prolonged duration and reduced velocity of both contraction and relaxation in diabetic myocardium, characteristic of diabetic cardiomyopathy. Acute exposure to both KATP channel openers induced concentration-dependent negative inotropic effects (NIE) on myocardial contraction. The magnitude of the NIE was similar between the normal and diabetic groups and was fully reversible upon washout for BRL 38227 although not for pinacidil. Both KATP channel openers depressed the velocity of contraction and relaxation, whereas exerted no effect on the duration of contraction and relaxation, in myocardium from both groups. Acute exposure to glyburide, a KATP channel blocker, failed to alter any of the mechanical parameters measured. These data suggest that acute modulation of KATP channel with channel opener or blocker had little influence on diabetic cardiomyopathy, at least in the setting of multicellular preparations.

Adenosine Triphosphate↗
PubMed2001

Influence of gender and diabetes on vascular and myocardial contractile function.

Premenopausal women have a lower cardiovascular risk than men or postmenopausal women. However, this "female advantage" is lost in diabetes, a condition characterized by cardiac and vascular contractile dysfunction. This study was designed to compare the influence of diabetes on vascular and myocardial contractile function between genders. Adult male and female rats were made diabetic with streptozotocin (55 mg/kg) and maintained for 8 weeks. Tension development was examined in thoracic aortic rings and left ventricular papillary muscles. KCl-induced vasoconstriction, acetylcholine (ACh)-induced endothelium dependent or sodium nitroprusside (SNP)-induced endothelium-independent vasorelaxation, duration and maximal velocity of myocardial contraction and relaxation duration (TPT/RT90 and +/- VT) were similar between males and females. Diabetes augmented KCl-induced vasoconstriction at low doses, reduced SNP-induced vasorelaxation and had little effect on ACh-induced vasorelaxation in aortic rings from both genders. Diabetes prolonged TPT and RT90 in both genders, and reduced +/- VT in males but not females. Acute increase in extracellular Ca2+ (2.7 mM to 5.4 mM) shortened TPT in diabetic myocardium from both genders, whereas it had no effect on other myocardial mechanical indices in normal or diabetic groups of either gender. In addition, acute exposure to the Na+/K(+)-ATPase inhibitor ouabain shortened TPT/RT90 and enhanced +/- VT in myocardium from normal female, whereas it had no effect on male or diabetic myocardium. In conclusion, these data suggest that in the vasculature, there is no difference in diabetes-induced contractile dysfunction between genders, however several gender-specific differences are evident in the myocardium.

Acetylcholine↗
PubMed2001

Bis(2,2-bipyridine-N,N')tetra-mu-chloro-tetracopper(I).

A novel centrosymmetric chair-like dimer, bis(2,2'-bipyridine)-1kappa(2)N,N';3kappa(2)N,N'-tetra-mu-chloro-1:2kappa(2)Cl;2:3kappa(2)Cl;3:4kappa(2)Cl;1:4kappa(2)Cl-tetracopper(I), [Cu(4)Cl(4)(C(10)H(8)N(2))(2)], has been solvothermally synthesized and structurally characterized. The complex self-assembles into a three-dimensional network via C-H.Cl hydrogen bonds, pi-pi stacking and weak Cu.Cl electrostatic interactions.

Journal Article↗