Biomedical subjects

L Ma

Publications and source records attributed to L Ma.

At least 145 records · Page 8Linked to original sources

PubMed2001

[An epidemiological study of spongiform leucoencephalopathy among heorin abusers].

OBJECTIVE: To understand the distribution and related risk factors of heroin spongiform leucoencephalopathy among drug users in coastland of Guangdong Province. METHODS: A cross-sectional study was conducted in four thousand four hundred and twenty eight drug users from eighteen detoxification organizations in six cities on coastland of Guangdong, using clustered random sampling methods. The six cities are Chaoyang (714), Heyuan (462), Shantou (572), Huidong (1286), Guangzhou (871) and Zhanjiang (523) and heroin abuse was considered serious in these cities. Questionnaire was used to collect the data on sex (man 3632, 82 percent; woman 795, 18 percent), age (minimum 15y, maximum 54y), duration of using heroin (minimum 1 month, maximum 150 months), daily dosage (minimum 0.02 g, maximum 6.0 g) and manner of using heroin. In addition, the neurological examination was taken in all of them and cerebral MRI was carried out in those with signs of cerebellar ataxia. RESULTS: Results showed that the total incidence of heroin spongiform leucoencephalopathy in six cities is 3.16 per thousand. Poisson regression analysis showed that the incidence was related to residential areas. In comparison with other cities, there are higher incidences in Chaoyang and Heyuan. Our investigation also showed that all the patients with this disease used heroin by inhaling the pyrolysate. The incidence of heroin spongiform leucoencephalopathy was unrelated to the daily inhaling amount of heroin and the duration of inhaling heroin. No differences could be observed between the groups of different age and sex. CONCLUSIONS: Spongiform leucoencephalopathy after inhalation of heroin is a rare complication and has never been reported in mainland of China before. The lesions are symmetrical and spongiform, but not necrotic and the cerebellum is invariably involved--a feature consistent with the clinical presentation that begins with ataxia. Cerebral CT showed symmetrical non-enhancing hypodense areas in both cerebellar hemispheres. Cerebral MRI showed the corresponding areas with decreased signal intensity on T1 weighted images and increased signal intensity on T2 weighted images. There was no contrast enhancement. When it occurs, several cases are affected as a small epidemic. It is suggested that the aetiology is related to the heroin batch and could perhaps be a toxic effect of a substance which came from heroin pyrolysis.

Administration, Inhalation↗

PubMed2000

Heterologous activation of protein kinase C stimulates phosphorylation of delta-opioid receptor at serine 344, resulting in beta-arrestin- and clathrin-mediated receptor internalization.

The purpose of the current study is to investigate the effect of opioid-independent, heterologous activation of protein kinase C (PKC) on the responsiveness of opioid receptor and the underlying molecular mechanisms. Our result showed that removing the C terminus of delta opioid receptor (DOR) containing six Ser/Thr residues abolished both DPDPE- and phorbol 12-myristate 13-acetate (PMA)-induced DOR phosphorylation. The phosphorylation levels of DOR mutants T352A, T353A, and T358A/T361A/S363S were comparable to that of the wild-type DOR, whereas S344G substitution blocked PMA-induced receptor phosphorylation, indicating that PKC-mediated phosphorylation occurs at Ser-344. PKC-mediated Ser-344 phosphorylation was also induced by activation of G(q)-coupled alpha(1A)-adrenergic receptor or increase in intracellular Ca(2+) concentration. Activation of PKC by PMA, alpha(1A)-adrenergic receptor agonist, and ionomycin resulted in DOR internalization that required phosphorylation of Ser-344. Expression of dominant negative beta-arrestin and hypertonic sucrose treatment blocked PMA-induced DOR internalization, suggesting that PKC mediates DOR internalization via a beta-arrestin- and clathrin-dependent mechanism. Further study demonstrated that agonist-dependent G protein-coupled receptor kinase (GRK) phosphorylation sites in DOR are not targets of PKC. Agonist-dependent, GRK-mediated receptor phosphorylation and agonist-independent, PKC-mediated DOR phosphorylation were additive, but agonist-induced receptor phosphorylation could inhibit PKC-catalyzed heterologous DOR phosphorylation and subsequent internalization. These data demonstrate that the responsiveness of opioid receptor is regulated by both PKC and GRK through agonist-dependent and agonist-independent mechanisms and PKC-mediated receptor phosphorylation is an important molecular mechanism of heterologous regulation of opioid receptor functions.

Arrestins↗

PubMed2000

The importance of erythroid expansion in determining the extent of apoptosis in erythroid precursors in patients with beta-thalassemia major.

Beta-thalassemia major is characterized by ineffective erythropoiesis leading to severe anemia and extensive erythroid expansion. The ineffective erythropoiesis is in part due to accelerated apoptosis of the thalassemic erythroid precursors; however, the extent of apoptosis is surprisingly variable. To understand this variability as well as the fact that some patients undergoing allogeneic marrow transplantation are resistant to the myeloablative program, we attempted more quantitative analyses. Two groups of patients totaling 44 were studied, along with 25 healthy controls, and 7 patients with hemolysis and/or ineffective erythropoeisis. By 2 flow cytometric methods, thalassemic erythroid precursors underwent apoptosis at a rate that was 3 to 4 times normal. Because thalassemic marrow has between 5- to 6-fold more erythroid precursors than healthy marrow, this translated into an absolute increase in erythroid precursor apoptosis of about 15-fold above our healthy controls. In searching for the causes of the variability in thalassemic erythroid precursor apoptosis, we discovered tight direct correlations between the relative and absolute extent of apoptosis and the extent of erythroid expansion as measured either by the absolute number of marrow erythroid precursors or by serum soluble transferrin receptor levels. These results could mean that the most extreme rates of erythroid proliferation lend themselves to cellular errors that turn on apoptotic programs. Alternatively, extreme rates of erythroid hyperplasia and apoptosis might be characteristic of more severely affected patients. Lastly, extreme erythroid hyperplasia could generate such numbers of apoptotic erythroid precursors that marrow macrophages are overwhelmed, leaving more apoptotic cells in the sample.

Adolescent↗

PubMed2000

Two tandem verprolin homology domains are necessary for a strong activation of Arp2/3 complex-induced actin polymerization and induction of microspike formation by N-WASP.

All WASP family proteins share a common C terminus that consists of the verprolin homology domain (V), cofilin homology domain (C), and acidic region (A), through which they activate Arp2/3 complex-induced actin polymerization. In this study, we characterized the Arp2/3 complex-mediated actin polymerization activity of VCA fragments of all of the WASP family proteins: WASP, N-WASP, WAVE1, WAVE2, and WAVE3. All of the VCA fragments stimulated the nucleating activity of Arp2/3 complex. Among them, N-WASP VCA, which possesses two tandem V motifs, had a more potent activity than other VCA proteins. The chimeric protein experiments revealed that the V motif was more important to the activation potency than the CA region; two V motifs were required for full activity of N-WASP. COS7 cells overexpressing N-WASP form microspikes in response to epidermal growth factor. However, when a chimeric protein in which the VCA region of N-WASP is replaced with WAVE1 VCA was overexpressed, microspike formation was suppressed. Interestingly, when the N-WASP VCA region was replaced with WAVE1 VCA, having two V motifs, this chimeric protein could induce microspike formation. These results indicate that strong activation of Arp2/3 complex by N-WASP is mainly caused by its two tandem V motifs, which are essential for actin microspike formation.

Actin-Related Protein 2↗

PubMed2000

Synthesis and antiviral activity of oxaselenolane nucleosides.

As dioxolane and oxathiolane nucleosides have exhibited promising antiviral and anticancer activities, it was of interest to synthesize isoelectronically substituted oxaselenolane nucleosides, in which the 3'-CH(2) is replaced by a selenium atom. To study structure-activity relationships, various pyrimidine and purine oxaselenolane nucleosides were synthesized from the key intermediate, (+/-)-2-benzoyloxymethyl-1,2-oxaselenolane 5-acetate (6). Among the synthesized racemic nucleosides, cytosine and 5-fluorocytosine analogues exhibited potent anti-HIV and anti-HBV activities. It was of interest to obtain the enantiomerically pure isomers to determine if they have differential antiviral activities. However, due to the difficult and time-consuming nature of enantiomeric synthesis, a chiral HPLC separation was performed to obtain optical isomers from the corresponding racemic mixtures. Each pair of enantiomers of Se-ddC and Se-FddC was separated by an amylose chiral column using a mobile phase of 100% 2-propanol. The results indicate that most of the anti-HIV activity of both cytosine and fluorocytosine nucleosides resides with the (-)-isomers.

Anti-HIV Agents↗

PubMed2000

Resuscitative effects of polynitroxylated alphaalpha-cross-linked hemoglobin following severe hemorrhage in the rat.

alphaalpha-Cross-linked hemoglobin (alphaalphaHb) is an example of a hemoglobin-based oxygen carrier (HBOC) with significant cardiovascular activity. This may compromise the safety and efficacy of this HBOC by causing systemic hypertension and reducing blood flow to some organs. The present work is based on the hypothesis that incorporating antioxidant activity into an HBOC in the form of a covalently attached nitroxide may prevent these effects. We have tested this hypothesis by adding antioxidant activity to alphaalphaHb with 2,2,6,6-tetramethyl-piperidinyl-1-oxyl (Tempo) to create polynitroxylated alphaalphaHb (PN-alphaalphaHb). The new compound PN-alphaalphaHb acts as an antioxidant in our in vitro and in vivo assays. In this study urethane-anesthetized rats were hemorrhaged to a mean arterial pressure (MAP) of 35-40 mmHg and maintained for 30 min. Animals were resuscitated with solutions of (1) 10% PN-alphaalphaHb (43 mmHg), (2) 10% alphaalphaHb (43 mmHg), (3) 7.5% albumin (43 mmHg), (4) 300% Ringers lactate (RL), and (5) 0. 9% normal saline equal to the shed blood volume (SBV). Hemodynamics and regional blood circulation was measured at baseline, following hemorrhage, and at 30 and 60 min postresuscitation using a radioactive microsphere technique. Base deficit (BD) was measured at baseline, following hemorrhage, and at 60 min following resuscitative fluid infusion. Finally survival was determined as the time following resuscitation until secession of heart rhythm. Saline and 300% RL resuscitation did not improve BD, systemic hemodynamics, or regional blood circulation. PN-alphaalphaHb, alphaalphaHb, and albumin significantly improved these parameters, however, only PN-alphaalphaHb and alphaalphaHb improved survival. PN-alphaalphaHb was found to be less hypertensive than alphaalphaHb due to blunted increases in both cardiac output and systemic vascular resistance. This study demonstrates that, by using alphaalphaHb as a scaffold for polynitroxylation, improvement in vasoactivity and resuscitative efficacy may be possible. In conclusion, the addition of antioxidant activity in the form of polynitroxylation of a low molecular weight Hb (alphaalphaHb) may create a safe and efficacious resuscitative fluid.

Animals↗

PubMed2000

A correlation of erythrokinetics, ineffective erythropoiesis, and erythroid precursor apoptosis in thai patients with thalassemia.

The variety of patients with thalassemia in Thailand offers an opportunity to fully characterize the kinetic causes of the anemia and to study apoptosis of marrow erythroid precursors as a possible factor contributing to its severity. Kinetic studies showed that in hemoglobin H (HbH) disease, the extent of hemolysis, as well as the minimally ineffective erythropoiesis, usually falls within the compensatory capacity of normal erythropoiesis; therefore, anemia in patients with HbH partly represents a failure to expand erythropoiesis adequately. Hemoglobin Constant Spring (HbCS), a common variant of alpha thalassemia in Bangkok, causes more severe hemolysis and a distinct increase in ineffective erythropoiesis. Ineffective erythropoiesis plays a much more prominent role in beta thalassemia/hemoglobin E (beta-thal/HbE) disease, in which the variability of the anemia is puzzling. We compared mild and severe cases and found that patients with severe disease had a maximal marrow erythropoietic response that failed to compensate for very short survival of red blood cells and a marked quantitative increase in ineffective erythropoiesis. Analysis of apoptosis of marrow erythroid precursors done both on shipped samples and in Bangkok showed a moderate increase in HbH disease, consistent with the small increase in ineffective erythropoiesis. In patients with homozygous HbCS, there was a further increase in apoptosis, consistent with the additional increase in ineffective erythropoiesis. Patients with beta-thal/HbE disease had the most ineffective erythropoiesis and the most erythroid apoptosis. Thus, it appears that alpha-chain deposition in erythroid precursors, either alpha(A) or alpha(cs), leads to accelerated apoptosis and ineffective erythropoiesis.

Adolescent↗

PubMed2000

Characterization of the human cysteinyl leukotriene 2 receptor.

The contractile and inflammatory actions of the cysteinyl leukotrienes (CysLTs), LTC(4), LTD(4), and LTE(4), are thought to be mediated through at least two distinct but related CysLT G protein-coupled receptors. The human CysLT(1) receptor has been recently cloned and characterized. We describe here the cloning and characterization of the second cysteinyl leukotriene receptor, CysLT(2), a 346-amino acid protein with 38% amino acid identity to the CysLT(1) receptor. The recombinant human CysLT(2) receptor was expressed in Xenopus oocytes and HEK293T cells and shown to couple to elevation of intracellular calcium when activated by LTC(4), LTD(4), or LTE(4). Analyses of radiolabeled LTD(4) binding to the recombinant CysLT(2) receptor demonstrated high affinity binding and a rank order of potency for competition of LTC(4) = LTD(4) LTE(4). In contrast to the dual CysLT(1)/CysLT(2) antagonist, BAY u9773, the CysLT(1) receptor-selective antagonists MK-571, montelukast (Singulair(TM)), zafirlukast (Accolate(TM)), and pranlukast (Onon(TM)) exhibited low potency in competition for LTD(4) binding and as antagonists of CysLT(2) receptor signaling. CysLT(2) receptor mRNA was detected in lung macrophages and airway smooth muscle, cardiac Purkinje cells, adrenal medulla cells, peripheral blood leukocytes, and brain, and the receptor gene was mapped to chromosome 13q14, a region linked to atopic asthma.

Adrenal Medulla↗

PubMed2000

Characterization of Hoxa-10/Hoxa-11 transheterozygotes reveals functional redundancy and regulatory interactions.

Hox genes show related sequences and overlapping expression domains that often reflect functional redundancy as well as a common evolutionary origin. To accurately define their functions, it has become necessary to compare phenotypes of mice with single and multiple Hox gene mutations. Here, we focus on two Abd-B-type genes, Hoxa-10 and Hoxa-11, which are coexpressed in developing vertebrae, limbs, and reproductive tracts. To assess possible functional redundancy between these two genes, Hoxa-10/Hoxa-11 transheterozygotes were produced by genetic intercrosses and analyzed. This compound mutation resulted in synergistic defects in transheterozygous limbs and reproductive tracts, but not in vertebrae. In the forelimb, distal radial/ulnar thickening and pisiform/triangular carpal fusion were observed in 35 and 21% of transheterozygotes, respectively, but were effectively absent in Hoxa-10 and Hoxa-11 +/- forelimbs. In the hindlimb, distal tibial/fibular thickening and loss of tibial/fibular fusion were observed in >80% of transheterozygotes but in no Hoxa-10 or Hoxa-11 +/- hindlimbs, and all transheterozygotes displayed reduced medial patellar sesamoids, compared to modest incidences in Hoxa-10 and Hoxa-11 +/- mutants. Furthermore, while the reproductive tracts of Hoxa-10 and Hoxa-11 single heterozygous mutants of both sexes were primarily unaffected, male transheterozygotes displayed cryptorchidism and abnormal tortuosity of the ductus deferens, and female transheterozygotes exhibited abnormal uterotubal junctions and narrowing of the uterus. In addition we observed that the targeted mutations of Hoxa-10 and Hoxa-11 each affected the expression of the other gene in the developing prevertebra and reproductive tracts. These results provide a measure of the functional redundancy of Hoxa-10 and Hoxa-11 and a deeper understanding of the phenotypes resulting in the single mutants and help elucidate the regulatory interactions between these two genes.

Animals↗

PubMed2000

Combinatorial screening of enzyme activity by using multiplexed capillary electrophoresis.

Efficient and comprehensive screening of enzyme activity was accomplished in a combinatorial array of 96 reaction microvials. Quantitation of the extent of the reaction at well-defined time intervals was achieved by using 96-capillary array electrophoresis coupled with a multiplexed absorption detector. Capillary electrophoresis provides high separation resolution to isolate the product from the reactants. Absorption detection provides universal applicability to combinatorial screening. For the conversion of NADH to NAD+, the catalytic activity of LDH was confirmed to be the highest at pH 7. This scheme should be useful for high-throughput drug discovery, clinical diagnosis, substrate binding, as well as combinatorial synthesis.

Electrophoresis, Capillary↗

PubMed2000

Polynitroxyl-albumin (PNA) plus tempol attenuate lung capillary leak elicited by prolonged intestinal ischemia and reperfusion(1).

Stable nitroxyl radicals (nitroxides) are potential antioxidant drugs, and we have previously reported that linking nitroxide to biological macromolecules can improve therapeutic activity in at least two ways. First, polynitroxylated compounds such as polynitroxyl human serum albumin (PNA) are a novel class of high molecular weight, extracellular antioxidants. Second, compounds such as PNA can prolong the half-life of free (unbound, low molecular weight) nitroxides such as 4-hydroxy-2,2,6, 6-tetramethylpiperidine-N-oxyl (Tempol) in vivo. Unlike PNA, Tempol can readily access the intracellular compartment. Thus PNA can act alone in the extracellular compartment, or in concert with Tempol, to provide additional antioxidant protection within cells. In this study, we compared the abilities of PNA, Tempol, and the combination of PNA + Tempol to prevent lung microvascular injury secondary to prolonged gut ischemia (I, 120 min) and reperfusion (R, 20 min) in the rat. Pulmonary capillary filtration coefficient (K(f,c)) and lung neutrophil retention (tissue myeloperoxidase activity, MPO) were measured in normal, isolated rat lungs perfused with blood harvested from I/R rats. Blood donor rats were treated with drug during ischemia. Gut I/R resulted in a marked increase in pulmonary capillary coefficient and lung MPO. PNA + Tempol, but not PNA alone or Tempol alone, at the doses used, prevented the development of lung leak. None of the treatments had an effect on lung neutrophil retention. Anti-inflammatory therapeutic activity appeared to correlate with blood Tempol level: in the presence of PNA, blood Tempol levels were maintained in the 50-100 microM range vs. essentially undetectable levels shortly after Tempol was administered alone. In this model of lung injury secondary to prolonged gut I/R, lung capillary leak was prevented when the membrane-permeable compound Tempol was maintained in its active, free radical state by PNA.

Albumins↗

PubMed2000

Cdc42 is required for PIP(2)-induced actin polymerization and early development but not for cell viability.

BACKGROUND: Cdc42 and other Rho GTPases are conserved from yeast to humans and are thought to regulate multiple cellular functions by inducing coordinated changes in actin reorganization and by activating signaling pathways leading to specific gene expression. Direct evidence implicating upstream signals and components that regulate Cdc42 activity or for required roles of Cdc42 in activation of downstream protein kinase signaling cascades is minimal, however. Also, whereas genetic analyses have shown that Cdc42 is essential for cell viability in yeast, its potential roles in the growth and development of mammalian cells have not been directly assessed. RESULTS: To elucidate potential functions of Cdc42 mammalian cells, we used gene-targeted mutation to inactivate Cdc42 in mouse embryonic stem (ES) cells and in the mouse germline. Surprisingly, Cdc42-deficient ES cells exhibited normal proliferation and phosphorylation of mitogen- and stress-activated protein kinases. Yet Cdc42 deficiency caused very early embryonic lethality in mice and led to aberrant actin cytoskeletal organization in ES cells. Moreover, extracts from Cdc42-deficient cells failed to support phosphatidylinositol 4,5-bisphosphate (PIP(2))-induced actin polymerization. CONCLUSIONS: Our studies clearly demonstrate that Cdc42 mediates PIP(2)-induced actin assembly, and document a critical and unique role for Cdc42 in this process. Moreover, we conclude that, unexpectedly, Cdc42 is not necessary for viability or proliferation of mammalian early embryonic cells. Cdc42 is, however, absolutely required for early mammalian development.

Actins↗

PubMed2000

Exposure to cigarette smoke increases apoptosis in the rat gastric mucosa through a reactive oxygen species-mediated and p53-independent pathway.

Cigarette smoking is a major risk factor for gastric cancer and peptic ulcer. The aim of our study was to investigate the relationship between exposure to cigarette smoke and apoptosis in the rat gastric mucosa and the mechanism involved. Rats were exposed to different concentrations of cigarette smoke (0, 2, and 4%) once daily for a different number of 1 h periods (1, 3, 6, and 9 d). Apoptosis was identified by the terminal deoxy-transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) method and caspase-3 activity. The mucosal xanthine oxidase (XO) activity and p53 level were also measured. The results showed that exposure to cigarette smoke produced a time- and concentration-dependent increase in apoptosis in the rat gastric mucosa that was accompanied by an increase in XO activity. The increased apoptosis and XO activity could be detected after even a single exposure. In contrast, the level of p53 was elevated only in the later stage of cigarette smoke exposure. The apoptotic effect could be blocked by pretreatment with an XO inhibitor (allopurinol, 20 mg/kg intraperitoneally) or a hydroxyl free radical scavenger (DMSO, 0.2%, 1 ml/kg intravenously). However, neither of these treatments had any effect on the p53 level of the mucosa. In summary, we conclude that exposure to cigarette smoke can increase apoptosis in the rat gastric mucosa through a reactive oxygen species- (ROS) mediated and a p53-independent pathway.

Allopurinol↗

PubMed2000

[Effects of zinc deficiency on the c-fos gene expression and transcription in the epiphyses of fetal mouse long bone in culture].

The effects of zinc on c-fos gene expression and transcription in the epiphyses of fetal long bone were studied in mice. The long bones of 16-day fetal mouse were cultured for 48 hours(in medium GBJb) and then used for measuring c-fos gene expression and transcription by immunohistochemistry and in situ hybridization. The result was analyzed by an imaged-analyses system. The experiment was divided into zinc control group(ZC), zinc deficiency group(ZD), zinc deficiency replenish group(ZDR) and zinc stimulatory group(ZS) respectively. The result showed that 1) zinc deficiency caused c-fos protein and mRNA expression and the number of reactive cell decreased. 2) when zinc concentration of medium was 100 mumol/L, the expression and transcription of c-fos gene were increased in hypertrophic, proliferative and resting zone of epiphyses. The research suggested that zinc could affect the expression of c-fos gene in mouse fetal long bone.

Animals↗

PubMed2000

Role of lipooligosaccharide in Opa-independent invasion of Neisseria gonorrhoeae into human epithelial cells.

Lipooligosaccharide (LOS) has been implicated in the adhesion and invasion of host epithelial cells. We examined the adhesive and invasive abilities of isogenic gonococcal opacity-associated outer membrane protein-negative, pilus-positive (Opa-Pil+) Neisseria gonorrhoeae strains expressing genetically defined LOS. Strain F62 (Opa-Pil+), expressing the lacto-N-neotetraose and the galNac-lacto-N-neotetraose LOS, and its isogenic derivative that expressed only the lacto-N-neotetraose LOS (F62 Delta lgtD), adhered to, and invaded, to the same extent the human cervical epidermoid carcinoma cell line, ME180. While the adhesive abilities of Opa-Pil+ isogenic strains that express LOS molecules lacking the lacto-N-neotetraose structure were similar to that seen for F62, their invasive abilities were much lower than the strains expressing lacto-N-neotetraose. Fluorescence microscopy studies showed that the adherence of F62, but not the strains lacking lacto-N-neotetraose, induced the rearrangement of actin filaments under the adherent sites. Electron microscopy studies demonstrated that F62, but not the strains lacking lacto-N-neotetraose, formed extensive and intimate associations with epithelial cell membranes. Thus, in the absence of detectable Opa protein, the lacto-N-neotetraose LOS promotes gonococcal invasion into ME180 cells. The data also suggest that LOS is involved in the mobilization of actin filaments in host cells, and in the formation of a direct interaction between the bacterial outer membrane and the plasma membrane of ME180 cells.

Actins↗

PubMed2000

Cholecystokinin-B receptor antagonists attenuate morphine dependence and withdrawal in rats.

The possible effect of a cholecystokinin-8 agonist (caerulein) and antagonists (MK-329 and L365,260) on the development of morphine dependence and withdrawal were investigated in rats. Caerulein treatment (0.01 and 0.1 mg/kg) increased the incidence of naloxone-induced withdrawal syndromes and delayed the extinction of morphine-conditioned place preference in morphine-dependent animals. The signs of the morphine withdrawal syndromes and the formation of morphine-conditioned place preference were suppressed by pretreatment with L365,260 (0.1 and 1 mg/kg) and not affected by pretreatment with MK-329 (0.1 and 1 mg/kg). The present study demonstrated CCK, acting on CCK-B receptors, participates in the development of the opiate dependence. These findings suggest that CCK-B receptor antagonists might be of some value in the treatment and prevention the relapse of opiate addicts.

Animals↗

PubMed2000

Role of capsaicin sensory nerves and EGF in the healing of gastric ulcer in rats.

Accumulating evidence indicates that capsaicin sensitive afferent fibers play a pivotal role not only in gastroprotection but also in ulcer healing. Denervation of capsaicin sensitive afferent fibers exerts an adverse action on these effects. However, whether such an action is mediated through a depression on epidermal growth factor (EGF) is undefined. In this study, the effects of denervation of sensory neurons with capsaicin (100 mg/kg, s.c.) on acetic acid-induced chronic gastric ulcers and their relationship with the EGF expression in salivary glands, serum and gastric mucosa were investigated. Capsaicin significantly increased ulcer size, decreased gastric mucosal cell proliferation at the ulcer margin, angiogenesis in the granulation tissue and also gastric mucus content. Ulcer induction by itself dramatically elevated EGF levels in salivary glands and serum on day 1 and 4, and also in the gastric mucosa on day 4. However, capsaicin completely abolished these effects. It is concluded that stimulation of EGF expression in salivary glands and serum may be one of the mechanisms by which capsaicin sensitive nerves contribute to the gastroprotective and ulcer healing actions in the stomach.

Animals↗

PubMed2000

Identification of a human brain-specific isoform of mammalian STE20-like kinase 3 that is regulated by cAMP-dependent protein kinase.

A novel isoform of mammalian STE20-like kinase 3 (MST3) with a different 5' coding region from MST3, termed MST3b, was identified by searching through expressed sequence tag data base and obtained by rapid amplification of cDNA 5'-ends. MST3b was assigned to the long arm of human chromosome 13, D13S159-D13S280, by use of the National Center for Biotechnology Information sequence-tagged sites data base. Reverse transcription-polymerase chain reaction and Northern blot analysis with a probe derived from 5' distinct sequence of MST3b revealed that the expression of MST3b mRNA is restricted to the brain, in contrast to ubiquitous distribution of MST3 transcript. Western analysis confirmed the brain-specific expression of MST3b protein. In situ hybridization of rat brain sections with a MST3b-specific probe indicated that MST3b is widely expressed in different brain regions, with especially high expression in hippocampus and cerebral cortex. When expressed in human embryonic kidney 293 (HEK293) cells, MST3b effectively phosphorylated myelin basic protein, as well as undergoing autophosphorylation. Interestingly, expression of MST3, but not MST3b, in HEK293 cells was able to activate the endogenous p42/44 mitogen-activated protein kinase (MAPK) up to 4-fold, whereas neither isoform activated p38 MAPK under the same conditions. Further experiments demonstrated that MST3b, but not MST3, was effectively phosphorylated by activation of cyclic AMP-dependent protein kinase (PKA) in both in vivo and in vitro assays. The mutation of Thr-18 into Ala in MST3b (T18A), a putative PKA phosphorylation site that is absent in MST3, abolished its phosphorylation by PKA. Consequently, expression of the T18A mutant in HEK293 cells led to partial activation of p42/44 MAPK, indicating that MST3b is under the regulation of PKA. Taken together, our data provide evidence that the two isoforms of STE20-like kinase 3 are differentially distributed and regulated.

Animals↗