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Biomedical subjects

C Qin

Publications and source records attributed to C Qin.

At least 37 records · Page 2Linked to original sources
PubMed2000

Intrapericardiac injections of algogenic chemicals excite primate C1-C2 spinothalamic tract neurons.

Extracellular potentials of 38 C1-C2 spinothalamic tract (STT) neurons in anesthetized monkeys (Macaca fascicularis) were examined for responses to intrapericardiac injections of an algogenic chemical mixture (adenosine, 10(-3) M; bradykinin, prostaglandin E(2), serotonin, histamine, each 10(-5) M). Chemical stimulation of cardiac/pericardiac receptors increased activity of 21 cells, decreased activity of 5 cells, and did not change activity of 12 cells. Cells excited by chemical stimuli received input from noxious mechanical stimulation of somatic fields; most receptive fields included the neck, inferior jaw, or head areas. Nerve ablations in 11 cells excited by intrapericardiac chemicals showed that cardiac input activated by algogenic chemicals traveled primarily in vagal afferent fibers to C1-C2 segments; phrenic or cardiopulmonary sympathetic inputs were predominant in 2 of 11 cells. These results supported the concept that activation of cardiac vagal afferents might lead to the production of referred pain sensation in somatic fields innervated from high cervical segments.

Afferent Pathways↗
PubMed2000

[Expression and plasma activity of plasminogen activator inhibitor-1 infibrotic liver tissues].

OBJECTIVE: To study plasminogen activator inhibitor-1 (PAI-1) gene expression and protein synthesis in fibrotic liver tissues and plasma activity levels. METHODS: Plasma PAI-1 activity was detected by chromogenic activity assay kit. The messenger RNA (mRNA) of PAI-1 and PAI-1 protein was detected on serial biopsied liver specimens of normal, HBV-related chronic hepatitis and cirrhosis by in situ hybridization and immunohistochemistry. The semi-quantitative results of the protein expression to immunohistochemistry staining were analysed in contrast with the stage of hepatic fibrosis. RESULTS: The plasma PAI-1 activity levels decreased with the progression of hepatic fibrosis. PAI-1 mRNA and protein were expressed in the extracellular matria deposition of the portal areas, focal necrotic areas, fibrous septa and hepatocytes as well as the hepatocellular cytoplasm adjacent to the areas described above. CONCLUSION: Localization of PAI-1 is not only in interstitial cells but also hepatocytes, suggesting an intense relationship between PAI-1 and hepatic fibrosis.

Adolescent↗
PubMed2000

Determining functions of multiple phospholipase Ds in stress response of Arabidopsis.

Phospholipase D (PLD) is encoded by a multiple gene family, and several PLDs from Arabidopsis have been characterized at the molecular biological and biochemical levels. PLDalpha is the most abundant plant PLD and exhibits a number of different biochemical properties to the other isoforms. The other PLDs have many overlapping catalytic properties but display some unique patterns of expression during development and in response to stress cues. Accumulating data indicate that different PLDs have multiple and different roles in plant responses to stress.

Abscisic Acid↗
PubMed1999

Convergence of trigeminal input with visceral and phrenic inputs on primate C1-C2 spinothalamic tract neurons.

Trigeminal, spinal and vagal afferent fibers overlap in C1-C2 segments. We hypothesized that trigeminal input from the superior sagittal sinus (SSS) can excite C1-C2 spinothalamic tract (STT) neurons receiving thoracic visceral or phrenic inputs. Effects of SSS stimulation were evenly divided among cells responding to each nerve stimulus; magnitude of responses to ipsilateral vagal input was greater in neurons excited by SSS input. Somatic fields of 80% of neurons responding to SSS stimulation included face areas innervated by the trigeminal nerve, whereas somatic fields of 89% of neurons unaffected by SSS stimulation were located only on areas innervated by cervical spinal nerves. Results are consistent with the idea that pain referred to trigeminal areas could originate in thoracic organs.

Animals↗
PubMed1999

Synthesis, structural characterization and antitumor activity evaluations of copper complex with tetraazamacrocyclic ligand.

Cu (II) complex with 1,4,7,10-tetrakis(2-cyanoethyl-)-1,4,7,10-tetraazacyclododecane was prepared and characterized by X-ray diffraction. Four nitrogen atoms of macrocyclic ligand and oxygen atom of water molecule defined a tetragonal pyramidal polyhedron surrounding the central copper atom. Preliminary pharmacological tests showed that it had antitumor activity against P388 and BEL-7404 cell lines in vitro. Also it exhibited perturbation effects to K562 tumor cell lines at G0-G1 stage and further studies showed that it can cleave supercoiled DNA (pBR 322) to nicked and linear DNA in aerobic condition.

Antineoplastic Agents↗
PubMed1999

Substrate specificity and stereoselectivity of rat brain microsomal anandamide amidohydrolase.

Anandamide amidohydrolase (AAH) catalyzes the hydrolysis of arachidonylethanolamide (anandamide), an endogenous cannabinoid receptor ligand. To delineate the structural requirements of AAH substrates, rat brain microsomal AAH hydrolysis of a series of anandamide congeners was studied using two reverse-phase high-performance liquid chromatography (RP-HPLC) assays developed in our laboratory. Arachidonamide (1) was found to be the best substrate with an apparent Km of 2.34 mM and a Vmax of 2.89 nmol/min/mg of protein. Although anandamide (2) has a similar Km value, its Vmax is approximately one-half that of arachidonamide. N, N-Bis(2-hydroxyethyl)arachidonamide (3) was not hydrolyzed, suggesting specificity for unsubstituted or mono-N-substituted arachidonamides. Analogues with a methyl group at the 1'-position of the ethanolamido headgroup were also found to have greater resistance to enzymatic turnover and therefore increased metabolic stability. The enzyme exhibited high stereoselectivity as the rate of hydrolysis of (R)-alpha-methanandamide (2.4%) (anandamide = 100%) was about 10-fold lower than that of its (S)-enantiomer (23%). In contrast, (R)-beta-methanandamide was 6-times more susceptible (121%) than the (S)-beta-enantiomer (21%). Interestingly, an inverse correlation was shown between AAH stereoselectivity and the brain cannabinoid receptor affinity as the enantiomers with high receptor affinity displayed low susceptibility to hydrolysis by AAH. Metabolic stability is also imparted to analogues with a short hydrocarbon headgroup as well as to those possessing 2-monomethyl or 2,2-dimethyl substituents. 2-Arachidonylglycerol and racemic 1-arachidonylglycerol were shown to be excellent AAH substrates. To identify AAH inhibitors, hydrolysis of anandamide was also studied in the presence of a select group of cannabimimetics. Of these, (-)-Delta8-THC and SR141716A, a biarylpyrazole CB1 antagonist, were found to inhibit enzymatic activity. These newly defined enzyme recognition parameters should provide a foundation for the rational development of stable, therapeutically useful anandamide analogues with high receptor affinity.

Amidohydrolases↗
PubMed1999

Chemical activation of cervical cell bodies: effects on responses to colorectal distension in lumbosacral spinal cord of rats.

We have shown that stimulation of cardiopulmonary sympathetic afferent fibers activates relays in upper cervical segments to suppress activity of lumbosacral spinal cells. The purpose of this study was to determine if chemical excitation (glutamate) of upper cervical cell bodies changes the spontaneous activity and evoked responses of lumbosacral spinal cells to colorectal distension (CRD). Extracellular potentials were recorded in pentobarbital-anesthetized male rats. CRD (80 mmHg) was produced by inflating a balloon inserted in the descending colon and rectum. A total of 135 cells in the lumbosacral segments (L(6)-S(2)) were activated by CRD. Seventy-five percent (95/126) of tested cells received convergent somatic input from the scrotum, perianal region, hindlimb, and tail; 99/135 (73%) cells were excited or excited/inhibited by CRD; and 36 (27%) cells were inhibited or inhibited/excited by CRD. A glutamate (1 M) pledget placed on the surface of C(1)-C(2) segments decreased spontaneous activity and excitatory CRD responses of 33/56 cells and increased spontaneous activity of 13/19 cells inhibited by CRD. Glutamate applied to C(6)-C(7) segments decreased activity of 10/18 cells excited by CRD, and 9 of these also were inhibited by glutamate at C(1)-C(2) segments. Glutamate at C(6)-C(7) increased activity of 4/6 cells inhibited by CRD and excited by glutamate at C(1)-C(2) segments. After transection at rostral C(1) segment, glutamate at C(1)-C(2) still reduced excitatory responses of 7/10 cells. Further, inhibitory effects of C(6)-C(7) glutamate on excitatory responses to CRD still occurred after rostral C(1) transection but were abolished after a rostral C(6) transection in 4/4 cells. These data showed that C(1)-C(2) cells activated with glutamate primarily produced inhibition of evoked responses to visceral stimulation of lumbosacral spinal cells. Inhibition resulting from activation of cells in C(6)-C(7) segments required connections in the upper cervical segments. These results provide evidence that upper cervical cells integrate information that modulates activity of distant spinal neurons responding to visceral input.

Action Potentials↗
PubMed1999

Transcriptional activation of insulin-like growth factor-binding protein-4 by 17beta-estradiol in MCF-7 cells: role of estrogen receptor-Sp1 complexes.

Insulin-like growth factor-binding protein-4 (IGFBP-4) is expressed in MCF-7 human breast cancer cells, and treatment of these cells with 17beta-estradiol (E2) resulted in induction of IGFBP-4 gene expression (>3-fold) and protein secretion (>6-fold). To identify genomic sequences associated with E2 responsiveness, the 5'-promoter region (-1214 to +18) of the IGFBP-4 gene was cloned into a vector upstream from the firefly luciferase reporter gene, and E2 induced a 10-fold increase in luciferase activity in MCF-7 cells transiently transfected with this construct. Deletion analysis of this region of the IGFBP-4 gene promoter identified two GC-rich sequences at -559 to -553 and -72 to -64 that were important for E2-induced trans-activation. Gel mobility shift assays using 32P-labeled -569 to -540 and -83 to -54 oligonucleotides from the IGFBP-4 gene promoter showed that Sp1 protein bound these oligonucleotides to form a retarded band, and the intensity of the band was competitively decreased after coincubation with unlabeled IGFBP-4-derived and consensus Sp1 oligonucleotides. Mutation of the GC-rich sites within these sequences resulted in loss of the retarded band formation. Wild-type human estrogen receptor did not bind directly to the IGFBP-4 oligonucleotides; however, human estrogen receptor enhanced Sp1-DNA binding in a concentration-dependent manner. The results of this study demonstrate that at least two GC-rich sequences at -559 to -553 and -72 to -64 are required for induction of IGFBP-4 gene expression by E2 in MCF-7 cells.

Estradiol↗
PubMed1999

Development of selective aryl hydrocarbon receptor modulators for treatment of breast cancer.

The aryl hydrocarbon receptor (AhR) is a basic helix-loop-helix DNA-binding protein that forms a transcriptionally-active heterodimer with the AhR nuclear translocator (Arnt) protein. The nuclear AhR complex is a ligand-induced transcription factor and the environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a high affinity ligand for the AhR. TCDD induces a diverse spectrum of tissue-, sex- and species-specific biochemical and toxic responses in Ah-responsive cells/tissues including the inhibition of 17beta-oestradiol (E2)-induced gene expression in the rodent uterus and mammary and in human breast cancer cell lines. TCDD also inhibits spontaneous and carcinogen-induced mammary tumour formation and growth in rodent models. Research in this laboratory has utilised the AhR as a target for developing anticancer drugs for treatment of breast cancer and two different structural classes of selective AhR modulators (SAhRMs) have been developed. Alternate-substituted (1,3,6,8- and 2,4,6,8-) alkyl polychlorinated dibenzofurans (PCDFs) and substituted diindolylmethanes (DIMs) bind the AhR and induce a pattern of AhR-oestrogen receptor (ER) inhibitory cross-talk similar to that observed for TCDD including inhibition of mammary tumour growth at doses < 1.0 mg/kg/day. In contrast, effective doses of these compounds do not induce hepatic CYP1A1-dependent activity or other AhR-mediated toxic responses induced by TCDD. These results indicate that SAhRMs may be an important new class of drugs for clinical treatment of breast cancer via AhR-ER inhibitory cross-talk.

Journal Article↗
PubMed1999

[A study on the etiology of Budd-Chiari syndrome].

OBJECTIVE: To investigate the etiology of Budd-Chiari syndrome (BCS) with finding in surgical operation. METHODS: Thirteen patients with BCS undertook direct vision membranectomy and reconstruction of inferior vena cava. The specimens were studied with light microscopy, electron microscope and immunohistochemistry. RESULTS: Membranous occluding changes, which thickness varying from 2 to 20mm, were found in the posthepatic segment of inferior vena cava during the operation. Thrombi in inferior vena cava were found in 7 cases, 3 of them with thrombi evenly extending to the root of hepatic vein. The compromised venous wall showed proliferation of fibrous connective tissue, hyalinization or mucoid degeneration under light microscopy, 9 of the 13 cases showed chronic infiltration of inflammatory cells. Copious collagenous fibers, few endothelial cells and mitochondria swelling were found with electron microscope. No immune complex (IgA, IgG, IgM) was observed by immunohistochemistry. CONCLUSION: It is concluded that in these cases of BCS, occluding and stenosing lesions in the inferior vena cava were the outcome of thrombosis and its sequelae and local inflammation might be one of the reasons of thrombosis. There was no evidence of congenital malformation.

Adult↗
PubMed1999

[Study on chemical constituents of essential oil of Michelia leaves by gas chromatography-mass spectrometry].

The essential oil in Michelia leaves was extracted by steam distillation. The oil obtained was dried with anhydrous magnesium sulfate. The chemical constituents were analyzed by GC-MS. Thirty three peaks were separated by GC, and 27 of them were identified by MS with NBS mass spectral data and Wiley/NBS registry of mass spectral data. The structure of linalool was further verified by GC/FTIR. The identified constituents represent 97% of the peak area of the essential oil on FID. The major chemical constituent of them are linalool, trans-caryophyllene and diethyl-o-phthalate.

Acyclic Monoterpenes↗
PubMed1998

Novel analogues of arachidonylethanolamide (anandamide): affinities for the CB1 and CB2 cannabinoid receptors and metabolic stability.

Several analogues of the endogenous cannabinoid receptor ligand arachidonylethanolamide (anandamide) were synthesized and evaluated in order to study (a) the structural requirements for high-affinity binding to the CB1 and CB2 cannabinoid receptors and (b) their hydrolytic stability toward anandamide amidase. The series reported here was aimed at exploring structure-activity relationships (SAR) primarily with regard to stereoelectronic requirements of ethanolamido headgroup for interaction with the cannabinoid receptor active site. Receptor affinities, reported as Ki values, were obtained by a standard receptor binding assay using [3H]CP-55,940 as the radioligand, while stability toward the amidase was evaluated by comparing the Ki of each analogue in the presence and absence of phenylmethanesulfonyl fluoride (PMSF), a serine protease blocker and inhibitor of anandamide amidase. Introduction of a methyl group in the 1'- and 2'-positions or substitution of the ethanolamido headgroup with a butylamido group gave analogues with vastly improved biochemical stability. This is accomplished in some cases with increased receptor affinity. Conversely, oxazolyl and methyloxazolyl headgroups led to low-affinity analogues. Substitution of the hydroxyl group with electronegative substituents such as fluoro, chloro, allyl, and propargyl groups significantly increased receptor affinity but did not influence the biochemical stability. The 2'-chloro analogue of anandamide was found to have the highest affinity for CB1. Additionally, reversing the positions of the carbonyl and NH in the amido group produces retro-anandamides possessing considerably higher metabolic stability. Replacement of the arachidonyl tail with oleyl or linoleyl results in analogues with low affinities for both receptors. All of the analogues in this study showed high selectivity for the CB1 receptor over the peripheral CB2 receptor. The most potent analogues were tested for their ability to stimulate the binding of [35S]GTPgammaS to G-proteins and were shown to be potent cannabimimetic agonists. The results are discussed in terms of pharmacophoric features affecting receptor affinity and enzymatic stability.

Amidohydrolases↗
PubMed1998

Determination of anandamide amidase activity using ultraviolet-active amine derivatives and reverse-phase high-performance liquid chromatography.

Anandamide amidase catalyzes the hydrolysis of anandamide (AEA) to arachidonic acid (AA) and ethanolamine (EA). Recently, we published a method for determining anandamide amidase activity based on the measurement of arachidonic acid with direct UV detection at 204 nm. However, this method cannot be used to determine the hydrolysis of non-UV-active AEA analogs. It also cannot be used to study AEA amidase inhibitors that contain the arachidonic acid tail, and which are also enzyme substrates. Here we report a novel, more general method for measuring amidase activity by o-phthaldialdehyde (OPA) precolumn derivatization and reverse-phase high-performance liquid chromatography (HPLC). The hydrolysis product, ethanolamine, after separation from protein was derivatized with OPA to form a UV-active isoindole derivative which was then detected at 230 nm. The detection limit for derivatized ethanolamine was 1.0 pmol and retention times were typically less than 8 min. Our new method can detect non-UV-active analogs through derivatization of the amine product. It can thus be used after careful selection of the HPLC conditions in competition experiments between AEA and AEA analogs possessing different head groups. The most effective competitive inhibitor tested was (R)-N-(1-methyl-2-hydroxyethyl)arachidonylamide (AM356), which is resistant to enzymatic hydrolysis and yet inhibits AEA hydrolysis in a competition experiment by 43%. Moreover, this method offers several advantages over existing methodologies using radioisotopes or solvent extraction procedures. Our work to date has shown that small structural changes in the AEA molecule can result in significant variation in both affinity and turnover rate for each analog with respect to AEA amidase.

Amidohydrolases↗
PubMed1996

High-performance liquid chromatographic determination of anandamide amidase activity in rat brain microsomes.

A rapid, sensitive, and reliable method for measuring anandamide amidase activity in rat brain microsomes by reversed-phase high-performance liquid chromatography (RP-HPLC) and its applications are described. Enzymatic activity was assayed by the determination of the rates of hydrolysis of anandamide or its analogs at 37 degrees C. The reaction products were separated using an ODS guard column eluted with aqueous phosphoric acid-acetonitrile and quantitated with uv detection at 204 nm and an external standard method. Baseline separation of the acid products from their substrates was completed in less than 2 min. The detection limits were 1.4 pmol for arachidonic acid and 0.22 pmol for anandamide at a signal to noise ratio of 4:1. The stability of anandamide in the acidic mobile phase was tested, and no significant decomposition was observed up to 1 h. The method was successfully applied to the examination of substrate specificity as well as for testing the ability of amidase inhibitors to block its hydrolysis. Kinetic constants obtained for (S)-methanandamide were an apparent Km of 8.6 +/- 1.3 microM and a Vmax of 362 +/- 16 pmol/min/mg of protein. A highly potent inhibitor, palmitylsulfonyl fluoride (PSF), was found to have an IC50 of 50 nM. PSF is 210 times as potent as phenylmethylsulfonyl fluoride. The method offers several advantages over existing methodology using radioisotopes or a solvent extraction procedure.

Amidohydrolases↗
PubMed1996

Investigations into the loss of glutathione from lenses in organ culture.

PURPOSE: To investigate possible causes and implications of the decrease in glutathione concentration in rat lenses during organ culture. METHODS: Freshly excised lenses were incubated in modified TC-199 medium. Ellman's Reagent or the GSH-400 assay were used to assay glutathione levels in lenses cultured for different times and under a variety of altered culture conditions. RESULTS: In lenses from young rats the glutathione decrease was not ameliorated by reduction of oxygen tension in the incubator, nor by supplementation of the culture medium with various antioxidants or sulfhydryl compounds, nor with the amino acid precursors of glutathione. Addition of 2-mercaptoethanol stimulated cysteine transport into the lens but had only a modest effect in maintaining the level of glutathione. The decrease in glutathione concentration was less in cultured lenses from older rats. Lenses from rhesus monkeys exhibited no decrease in glutathione levels when maintained in organ culture for up to 48 h. CONCLUSIONS: The basis for the decreased glutathione in cultured young rat lenses is still uncertain. The data from the present study indicate a definite relationship between glutathione loss and age for cultured rat lenses, with young lenses being much more susceptible. The resistance of cultured monkey lenses to loss of glutathione demonstrates species differences in this property which may be relevant to previously reported differences in susceptibility to oxidative damage.

Aging↗