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Biomedical subjects

X Ren

Publications and source records attributed to X Ren.

At least 37 records · Page 2Linked to original sources
PubMed2001

Electroosmotic properties of microfluidic channels composed of poly(dimethylsiloxane).

Microfluidic devices fabricated from polymers exhibit great potential in biological analyses. Poly(dimethylsiloxane) (PDMS) has shown promise as a substrate for rapid prototyping of devices. Despite this, disagreement exists in the literature as to the ability of PDMS to support electroosmotic (EO) flow and the stability of that flow over time. We demonstrate that in low ionic strength solutions near neutral in pH. oxidized PDMS had a four-fold greater EO mobility (mu(eo)) compared to native PDMS. The greater mu(eo) was maintained irrespective of whether glass or PDMS was used as a support forming one side of the channel. This enhanced mu(eo) was preserved as long as the channels were filled with an aqueous solution. Upon exposure of the channels to air, the mobility decreased by a factor of two with a half-life of 9 h. The EO properties of the air-exposed, oxidized PDMS were regenerated by exposure to strong base. High ionic strength, neutral in pH buffers compatible with living eukaryotic cells diminished the EO flow in the oxidized PDMS devices to a much greater extent than in the native PDMS devices. For analyses utilizing intact and living cells, oxidation of PDMS may not be an effective strategy to substantially increase the mu(eo).

Dimethylpolysiloxanes↗
PubMed2001

Cloning and expression of a single-chain catalytic antibody that acts as a glutathione peroxidase mimic with high catalytic efficiency.

Glutathione peroxidase (GPX) has a powerful role in scavenging reactive oxygen species. In previous papers we have developed a new strategy for generating abzymes: the monoclonal antibody with a substrate-binding site is first prepared, then a catalytic group is incorporated into the monoclonal antibody's binding site by using chemical mutation [Luo, Zhu, Ding, Gao, Sun, Liu, Yang and Shen (1994) Biochem. Biophys. Res. Commun. 198, 1240-1247; Ding, Liu, Zhu, Luo, Zhao and Ni (1998) Biochem. J. 332, 251-255]. Since then we have established a series of catalytic antibodies capable of catalysing the decomposition of hydroperoxides by GSH. The monoclonal antibody 2F3 was raised against GSH-S-2,4-dinitrophenyl t-butyl ester and exhibited high catalytic efficiency, exceeding that of rabbit liver GPX, after chemical mutation. To produce pharmaceutical proteins and to study the reason why it exhibits high catalytic efficiency, we sequenced, cloned and expressed the variable regions of 2F3 antibody as a single-chain Fv fragment (2F3-scFv) in different bacterial strains. The amounts of 2F3-scFv proteins expressed from JM109 (DE3), BL21 (DE3), and BL21 (coden plus) were 5-10%, 15-20% and 25-30% of total bacterial proteins respectively. The 2F3-scFv was expressed as inclusion bodies, purified in the presence of 8 M urea by Co(2+)-immobilized metal-affinity chromatography (IMAC) and renatured to the active form in vitro by gel filtration. The binding constants of the active 2F3-scFv for GSH and GSSG were 2.46 x 10(5) M(-1) and 1.03 x 10(5) M(-1) respectively, which were less by one order of magnitude than that of the intact 2F3 antibody. The active 2F3-scFv was converted into selenium-containing 2F3-scFv (Se-2F3-scFv) by chemical modification of the reactive serine; the GPX activity of the Se-2F3-scFv was 3394 units/micromol, which approaches the activity of rabbit liver GPX.

Amino Acid Sequence↗
PubMed2001

Facilitation of affiliation and pair-bond formation by vasopressin receptor gene transfer into the ventral forebrain of a monogamous vole.

Behaviors associated with monogamy, including pair-bond formation, are facilitated by the neuropeptide vasopressin and are prevented by a vasopressin receptor [V1a receptor (V1aR)] antagonist in the male prairie vole. The neuroanatomical distribution of V1aR dramatically differs between monogamous and nonmonogamous species. V1aR binding is denser in the ventral pallidal region of several unrelated monogamous species compared with nonmonogamous species. Because the ventral pallidum is involved in reinforcement and addiction, we hypothesize that V1aR activation in this region promotes pair-bond formation via a mechanism similar to conditioning. Using an adeno-associated viral vector to deliver the V1aR gene, we increased the density of V1aR binding in the ventral pallial region of male prairie voles. These males exhibited increased levels of both anxiety and affiliative behavior compared with control males. In addition, males overexpressing the V1aR in the ventral pallidal region, but not control males, formed strong partner preferences after an overnight cohabitation, without mating, with a female. These data demonstrate a role for ventral pallidal V1aR in affiliation and social attachment and provide a potential molecular mechanism for species differences in social organization.

Animals↗
PubMed2001

Kinetics study of a selenium-containing ScFv catalytic antibody that mimics glutathione peroxidase.

The steady-state kinetics study and some enzymatic characterization of a selenium-containing scFv catalytic antibody (Se-scFv2F3) were carried out. A novel reaction formula of this abzyme-catalyzed reaction was proposed and a rate equation was obtained according to the formula. The constants in the equation were compared with Dalziel's parameters and the exact meanings of these constants were analyzed. The obtained kinetics parameters from the kinetics study of Se-scFv2F3 were analyzed and compared with those of native glutathione peroxidase.

Antibodies, Catalytic↗
PubMed2001

Kinetics study of a selenium-containing ScFv catalytic antibody that mimics glutathione peroxidase.

The steady state kinetic study and some enzymic characterization of a selenium-containing scFv catalytic antibody (Se-scFv2F3) was carried out. A novel reaction formula of this abzyme-catalyzed reaction was proposed and a rate equation was gotten according to the formula. The constants in the equation were compared with Dalziel's parameters and the exact meanings of these constants were analyzed. The gotten kinetics parameters from the kinetics study of Se-scFv2F3 were analyzed and compared with that of native glutathione peroxidase.

Antibodies, Catalytic↗
PubMed2001

A novel glutathione peroxidase mimic with antioxidant activity.

Many diseases are associated with the overproduction of hydroperoxides that inflict cell damage. A novel cyclodextrin derivative, 6A,6B-diseleninic acid-6A',6B'-selenium bridged beta-cyclodextrin (6-diSeCD), was synthesized to be a functional mimic of glutathione peroxidase (GPX) that normally removes these hydroperoxides. The mimic had high catalytic GPX activity of 13.5 U/micromol, which is 13.6-fold higher than ebselen (PZ51), and was chemically and biologically stable in vitro. Antioxidant activity was studied by ferrous sulfate/ascorbate-induced mitochondria damage model system. These data show that the mimic has great antioxidant activity. Such mimics may result in better clinical therapies for diseases mediated by hydroperoxides.

Animals↗
PubMed2001

The ARG tyrosine kinase interacts with Siva-1 in the apoptotic response to oxidative stress.

The Abl family of mammalian nonreceptor tyrosine kinases consists of c-Abl and ARG (Abl-related gene). Certain insights are available regarding the involvement c-Abl in the response of cells to stress. ARG, however, has no known function in cell signaling. The present studies demonstrate that ARG associates with the proapoptotic Siva-1 protein. The functional significance of the ARG-Siva-1 interaction is supported by the finding that ARG is activated by oxidative stress and that this response involves ARG-mediated phosphorylation of Siva-1 on Tyr(48). The proapoptotic effects of Siva-1 are accentuated in cells stably expressing ARG and are inhibited in ARG-deficient cells. Moreover, the proapoptotic effects of Siva-1 are abrogated by mutation of the Tyr(48) site. We also show that the apoptotic response to oxidative stress is attenuated in ARG-deficient cells and that this defect is corrected by reconstituting ARG expression. These findings support a model in which the activation of ARG by oxidative stress induces apoptosis by a Siva-1-dependent mechanism.

Animals↗
PubMed2001

Gracilis muscle neosphincter for treating urinary incontinence.

The purpose of this study was to test the anatomical and functional feasibility of using a gracilis muscle free flap to create a urinary sphincter. Anatomical studies were performed in 12 human cadavers and short-term (n = 7) and long-term (n = 8) functional studies were performed in dogs. In the short-term functional studies, the left gracilis muscle was transferred into the pelvis and wrapped around the urethra and the right gracilis muscle was wrapped around a stent. A cuff electrode was placed on the muscle's nerve pedicle and used to stimulate the neosphincter while peak pressure, fatigue rate, and perfusion measurements were performed. In the long-term functional studies, intramuscular electrodes were inserted into the neosphincter to stimulate the flap. The flaps were wrapped around the urethra and dogs were followed for 16 weeks, during which time urodynamic measurements were performed. Our anatomical studies demonstrated that the gracilis muscle free flap could be transferred into the pelvis to create a urinary neosphincter. Our short-term functional study demonstrated that gracilis muscle free-flap function and perfusion were not compromised by transfer. In our long-term functional study, all neosphincters provided bladder outlet resistance pressures consistent with continence. Our anatomical, short-term, and long-term functional studies indicate that a gracilis muscle free-flap neosphincter is an effective procedure for treating urinary incontinence.

Animals↗
PubMed2001

Morphine tolerance and dependence in the nociceptin receptor knockout mice.

Here we report the involvement of nociceptin receptor in tolerance to morphine-induced antinociception and in morphine dependence. There was no different nociceptive perception and antinociceptive effects of morphine between wild-type and the nociceptin receptor knockout mice. Tolerance to morphine (10 mg/kg)-induced antinociception was developed in both wild-type and the nociceptin receptor knockout mice after administration of morphine (10 mg/kg) twice a day for 5 days. When naloxone (5 mg/kg) was administered to mice treated with morphine repeatedly on the 6th day, morphine withdrawal syndrome was observed in both wild-type and the nociceptin receptor knockout mice, which were accompanied by the elevation of cyclic AMP levels. While naloxone benzoylhydrazone (1 mg/kg), a putative antagonist for nociceptin receptor/naloxone benzoylhydrazone-sensitive sites, also induced the morphine withdrawal signs in both wild-type and the nociceptin receptor knockout mice, the jumping signs in the nociceptin receptor knockout mice were less severe than those in wild-type mice. Treatment with naloxone benzoylhydrazone in morphine-dependent wild-type mice caused a significant increase in cyclic AMP levels in the thalamus while it had no effect in the nociceptin receptor knockout mice. The analysis of opioid mu-receptor binding showed no difference between wild-type and the nociceptin receptor knockout mice. These results suggest that the nociceptin receptor/naloxone benzoylhydrazone-sensitive sites contribute to the induction of morphine withdrawal syndrome in part. Furthermore, it is demonstrated that morphine withdrawal syndrome excepting jumping can be induced by naloxone benzoylhydrazone without any changes in the cyclic AMP levels in the thalamus.

Analgesics, Opioid↗
PubMed2001

Involvement of cyclic AMP systems in morphine physical dependence in mice: prevention of development of morphine dependence by rolipram, a phosphodiesterase 4 inhibitor.

In this study, we examined whether morphine dependence was inhibited by rolipram, a cyclic AMP selective phosphodiesterase inhibitor in mice, since a role for the cyclic AMP systems in the development of morphine dependence has been reported. Mice, which received morphine (10 mg kg(-1) s.c.) twice a day for 5 days showed withdrawal syndromes such as jumping, rearing and forepaw tremor following naloxone challenge (5 mg kg(-1) i.p.) on the 6th day. Such mice exhibited a significant elevation of cyclic AMP levels in the thalamus compared to control mice. However, co-administration of rolipram (1 mg kg(-1) i.p.) with morphine for 5 days significantly attenuated the severity of the withdrawal syndrome and the increase in the cyclic AMP levels after the administration of naloxone. In naïve mice, acute morphine treatment (10 mg kg(-1) s.c.) decreased cyclic AMP levels in the thalamus and cerebral cortex 10 min later. The decrease of cyclic AMP levels induced by acute morphine treatment was blocked by co-administration of rolipram (1 mg kg(-1) i.p.). However, acute rolipram did not affect the naloxone-precipitated morphine withdrawal syndrome. These results suggest that the elevation of the cyclic AMP levels is involved in the development of morphine withdrawal syndrome and that blockade of the morphine-induced reduction of cyclic AMP levels by chronic rolipram inhibits the development of dependence and the behavioural and biochemical changes induced by naloxone. Furthermore, rolipram may be a useful drug for attenuating the development of morphine dependence.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2001

Bovine herpesvirus 1 tegument protein VP22 interacts with histones, and the carboxyl terminus of VP22 is required for nuclear localization.

The bovine herpesvirus 1 (BHV-1) UL49 gene encodes a viral tegument protein termed VP22. UL49 homologs are conserved among alphaherpesviruses. Interestingly, the BHV-1 VP22 deletion mutant virus is asymptomatic and avirulent in infected cattle but produces only a slight reduction in titer in vitro. Attenuation of the BHV-1 VP22 deletion mutant virus in vivo suggests that VP22 plays a functional role in BHV-1 replication. In herpes simplex virus type 1, the VP22 homolog was previously shown to interact with another tegument protein,VP16, the alpha-transinducing factor in vitro. In this report, we show that (i) the nuclear targeting of VP22 is independent of other viral factors, (ii) the carboxyl terminus of VP22 is required for its nuclear localization, (iii) VP22 associates with histones and nucleosomes, (iv) an antihistone monoclonal antibody cross-reacts with VP22, and (v) acetylation of histone H4 is decreased in VP22-expressing cells as well as virus-infected cells. Our data suggest that VP22 may have a modulatory function during BHV-1 infection.

Acetylation↗
PubMed2001

Tyrosine phosphorylation of bovine herpesvirus 1 tegument protein VP22 correlates with the incorporation of VP22 into virions.

Tyrosine phosphorylation has been shown to play a role in the replication of several herpesviruses. In this report, we demonstrate that bovine herpesvirus 1 infection triggered tyrosine phosphorylation of proteins with molecular masses similar to those of phosphorylated viral structural proteins. One of the tyrosine-phosphorylated viral structural proteins was the tegument protein VP22. A tyrosine 38-to-phenylalanine mutation totally abolished the phosphorylation of VP22 in transfected cells. However, construction of a VP22 tyrosine 38-to-phenylalanine mutant virus demonstrated that VP22 was still phosphorylated but that the phosphorylation site may change to the C terminus rather than be in the N terminus as in wild-type VP22. In addition, the loss of VP22 tyrosine phosphorylation correlated with reduced incorporation of VP22 compared to that of envelope glycoprotein D in the mutant viruses but not with the amount of VP22 produced during virus infection. Our data suggest that tyrosine phosphorylation of VP22 plays a role in virion assembly.

Animals↗
PubMed2001

Respiratory control in humans after 8 h of lowered arterial PO2, hemodilution, or carboxyhemoglobinemia.

In humans exposed to 8 h of isocapnic hypoxia, there is a progressive increase in ventilation that is associated with an increase in the ventilatory sensitivity to acute hypoxia. To determine the relative roles of lowered arterial PO2 and oxygen content in generating these changes, the acute hypoxic ventilatory response was determined in 11 subjects after four 8-h exposures: 1) protocol IH (isocapnic hypoxia), in which end-tidal PO2 was held at 55 Torr and end-tidal PCO2 was maintained at the preexposure value; 2) protocol PB (phlebotomy), in which 500 ml of venous blood were withdrawn; 3) protocol CO, in which carboxyhemoglobin was maintained at 10% by controlled carbon monoxide inhalation; and 4) protocol C as a control. Both hypoxic sensitivity and ventilation in the absence of hypoxia increased significantly after protocol IH (P < 0.001 and P < 0.005, respectively, ANOVA) but not after the other three protocols. This indicates that it is the reduction in arterial PO2 that is primarily important in generating the increase in the acute hypoxic ventilatory response in prolonged hypoxia. The associated reduction in arterial oxygen content is unlikely to play an important role.

Adult↗
PubMed2001

Genetic suppression of seizure susceptibility in Drosophila.

Despite the frequency of seizure disorders in the human population, the genetic and physiological basis for these defects has been difficult to resolve. Although many genetic defects that cause seizure susceptibility have been identified, the defects involve disparate biological processes, many of which are not neural specific. The large number and heterogeneous nature of the genes involved makes it difficult to understand the complex factors underlying the etiology of seizure disorders. Examining the effect known genetic mutations have on seizure susceptibility is one approach that may prove fruitful. This approach may be helpful both in understanding how different physiological processes affect seizure susceptibility and in identifying novel therapeutic treatments. In this study, we have taken advantage of Drosophila, a genetically tractable system, to identify factors that suppress seizure susceptibility. Of particular interest has been a group of Drosophila mutants, the bang-sensitive (BS) mutants, which are much more susceptible to seizures than wild type. The BS phenotypic class includes at least eight genes, including three examined in this study, bss, eas, and sda. Through the generation of double-mutant combinations with other well-characterized Drosophila mutants, the BS mutants are particularly useful for identifying genetic factors that suppress susceptibility to seizures. We have found that mutants affecting Na+ channels, mle(napts) and para, K+ channels, Sh, and electrical synapses, shak-B(2), can suppress seizures in the BS mutants. This is the first demonstration that these types of mutations can suppress the development of seizures in any organism. Reduced neuronal excitability may contribute to seizure suppression. The best suppressor, mle(napts), causes an increased stimulation threshold for the giant fiber (GF) consistent with a reduction in single neuron excitability that could underlie suppression of seizures. For some other double mutants with para and Sh(KS133), there are no GF threshold changes, but reduced excitability may also be indicated by a reduction in GF following frequency. These results demonstrate the utility of Drosophila as a model system for studying seizure susceptibility and identify physiological processes that modify seizure susceptibility.

Animals↗
PubMed2001

A comparison of long-term functional outcome after 2 middle cerebral artery occlusion models in rats.

BACKGROUND AND PURPOSE: Proven behavioral assessment strategies for testing potential therapeutic agents in rat stroke models are needed. Few studies include tasks that demand higher levels of sensorimotor and cognitive function. Because behavioral outcome and rate of recovery vary among ischemia models, there is a need to characterize and compare performance on specific tasks across models. METHODS: To this end, sensorimotor and cognitive deficits were assessed during a 5-week period after either permanent proximal middle cerebral artery occlusion (pMCAO) or permanent distal middle cerebral artery occlusion combined with a 90-minute occlusion of both common carotid arteries (dMCAO/tCCAO) in Sprague-Dawley rats. The EBST, hindlimb and forelimb placing, and cylinder tests were given at regular intervals postinjury to assess sensorimotor function. Cognitive function was assessed with a multitrial water navigation task. RESULTS: pMCAO, which caused both striatal and cortical damage, produced persistent sensorimotor and cognitive deficits. Limb placing responses and postural reflexes were impaired throughout the month of testing. A persistent bias for using the ipsilateral forelimb for wall movements in the cylinder test was observed as well as a bias for landing on the opposite forelimb. pMCAO rats were also impaired in the water navigation task. dMCAO/tCCAO, which caused only cortical damage, produced similar sensorimotor deficits, but these were greatly diminished by 2 weeks after injury. No impairment was found for water tank navigation. Correlations between forelimb placing (both models), water navigation performance (pMCAO model), and sensorimotor asymmetry (dMCAOtCCAO model) and infarct volume were observed. CONCLUSIONS: Based on the range of functions affected and stability of observed deficits, the pMCAO model appears to be preferable to the dMCAO/tCCAO model for use in assessing therapeutic agents for stroke.

Animals↗
PubMed2001

Differential patterns of cocaine-induced organ toxicity in murine heart versus liver.

To determine cocaine's toxicity in different organs, BALB/c mice were intraperitoneally injected daily for 15 days with either saline or cocaine: 10 mg/kg, 30 mg/kg, or 60 mg/kg. Cardiac function, hepatic pathophysiology, heart and liver apoptosis, and tumor necrosis factor (TNF-alpha) levels were analyzed. After administration of cocaine, cardiac function decreased. Inflammatory cell infiltration and eosinophilic contraction bands were visible in the hearts of mice treated with 60mg/kg cocaine. Moreover, histopathology demonstrated that cocaine caused hepatic necrosis. TdT-mediated dUTP nick end-labeling (TUNEL) staining and DNA ladder analysis indicated that cocaine caused apoptosis in both the heart and liver. Moreover, immunoassay showed that TNF-alpha levels significantly increased in the heart and liver with cocaine administration. However, our RT-PCR study showed that there was no significant difference in either the heart or liver in the levels of mRNA for TNF-alpha between cocaine-treated and saline control mice. The present study demonstrated that cocaine is toxic to multiple organs, and at low dose can induce hepatic damage without gross pathological injury to the heart. The results suggest that the liver is more sensitive than the heart to cocaine toxicity, and induction of apoptosis or TNF-alpha elevation may be a common mechanism responsible for cocaines toxicity.

Alanine Transaminase↗
PubMed2001

[Detection of positive-strand of transfusion transmitted virus fragment in the liver of cryptogenic hepatitis].

OBJECTIVE: To evaluate whether transfusion transmitted virus (TTV) replicates in the liver and to analyze the relationship between TTV and cryptogenic hepatitis. METHODS: A 3.2 kb TTV fragment was detected by nested polymerase chain reaction (PCR) in 31 serum samples of patients with cryptogenic hepatitis who came from a school where was in an outbreak area of cryptogenic hepatitis during 1996 and in 30 healthy individuals. A hybridization/nuclease protection assay was used to detect positive-strand TTV fragment from the liver specimens of the 7 patients. RESULTS: TTV DNA was detected in serum samples from 30 of 31 (96.9%) patients and from 18 of 30 (60%) healthy individuals, respectively. There was significant difference in the prevalence of TTV infection between the two groups. Based on hybridization/ nuclease protection assays, we detected positive-strand TTV fragment in all of 7 liver specimens of the patients. CONCLUSIONS: TTV is related possibly to cryptogenic hepatitis. TTV can replicate in the liver. Although TTV only causes mild liver damage, a few patients will suffer from chronic hepatitis.

Adult↗