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PubMed2001

SNARE proteins are critical for regulated exocytosis of ECP from human eosinophils.

The SNARE hypothesis, describing a protein assembly-disassembly pathway, was recently proposed for the sequential steps of synaptic vesicle docking, activation, and fusion. To determine if SNARE proteins are involved in regulated exocytosis in eosinophils, the presence and functional role of SNAREs was examined in human blood eosinophils. Immunoblotting, subcellular fractionation, and immunocytochemistry documented that vesicle-associated membrane protein-2 (VAMP-2), a vesicle-SNARE, was expressed in human eosinophils. Syntaxin 4 and SNAP-25 were also detected. Sequencing of cloned RT-PCR products amplified from a domain conserved among VAMP isoforms revealed identity only to VAMP-2 but not to VAMP-1 or cellubrevin. Functional experiments revealed that tetanus toxin pretreatment, which cleaved VAMP-2 in eosinophils, significantly inhibited both IgE receptor- and phorbol ester-mediated exocytosis of eosinophil cationic protein (ECP) from streptolysin-O-permeabilized eosinophils. Thus, these results strongly suggest a critical role of SNAREs in regulated exocytosis in eosinophils.

Animals↗

PubMed1999

Blood mononuclear cells in patients with HTLV-I-associated myelopathy: lymphocytes are highly activated and adhesion to endothelial cells is increased.

We have investigated lymphocyte subpopulations and blood mononuclear cell (MNC) adhesion to activated endothelial monolayers in patients with human T lymphotropic virus type I (HTLV-I) associated myelopathy (HAM), in HTLV-I asymptomatic carriers (carriers), and in seronegative controls. HAM patients and carriers had higher levels of CD4(+)CD29(+) "memory cells" than controls (P < 0.05). The percentage of CD3(+)CD27(-) "primed T cell" was elevated in patients with HAM (P < 0.05), but not in carriers. HAM patients had higher levels of CD8(+)CD57(+) "cytotoxic cells" (P < 0.05) than controls and carriers. The percentages of CD4(+) cells coexpressing activation markers HLA-DR and CD25, and of CD8(+) cells expressing HLA-DR, were significantly higher in HAM patients and carriers than in controls. Functional experiments indicated that MNC from HAM patients adhered more to activated endothelial monolayers than MNC from carriers or controls. Blocking studies demonstrated that the adhesion molecules VLA-4 and ICAM-1 and also L-selectin all contributed to increased binding. Analysis of expression of molecules involved in adhesion indicated that in HAM patients, L-selectin (CD62L) expression on CD4(+) and CD8(+) subsets was lower than in controls. Interestingly, HAM patients had a lower percentage of CD4(+) subsets expressing L-selectin than carriers (P < 0.05). In contrast, the percentage of CD4(+) and CD8(+) cells expressing VLA-4 (CD49d) was found to be higher in both HAM patients and carriers compared with controls. After 2 days in culture without mitogen, the percentage of T cells expressing ICAM-1 (CD54) increased in culture in carriers and more profoundly in HAM, but not in controls (P < 0. 05). After culture, T cells expressing the early activation antigen CD69 were also increased in HAM and carriers (P < 0.05) but not in controls. Interestingly, the levels of CD8(+) cells coexpressing activation antigen HLA-DR and CD38 were higher in HAM patients compared with both carriers and controls (P < 0.05) after culture. These findings are consistent with the observations that HTLV-I produces chronic lymphocyte activation with increased adhesion. This may be sufficient to initiate events leading to central nervous system inflammation and ultimately to HAM.

Adult↗

PubMed1999

A role for xGCNF in midbrain-hindbrain patterning in Xenopus laevis.

Cells in the presumptive neural ectoderm of Xenopus are committed to neural fate through a process called neural induction, which may involve proteins that antagonize BMP signaling pathways. To identify genes that are induced by the BMP antagonists and that may be involved in subsequent neural patterning, we used a suppression PCR-based subtraction screen. Here we investigate the prospective activities and functions of one of the genes, a nuclear orphan receptor previously described as xGCNF. In animal cap assays, xGCNF synergizes with ectopic chordin to induce the midbrain-hindbrain marker engrailed-2 (En-2). In Keller explants, which rely on endogenous factors for neural induction, similar increases in En-2 are observed. Expression in embryos of a dominant interfering form of xGCNF reduces the expression of endogenous En-2 and Krox-20. These gain-of-function and prospective loss-of-function experiments, taken with the observation that xGCNF is expressed in the early neural plate and is elevated in the prospective midbrain-hindbrain region, which subsequently expresses En-2, suggest that xGCNF may play a role in regulating En-2 and thus midbrain-hindbrain identity.

Animals↗

PubMed2002

A novel invertebrate trophic factor related to invertebrate neurotrophins is involved in planarian body regional survival and asexual reproduction.

Trophic factors are a heterogeneous group of molecules that promote cell growth and survival. In freshwater planarians, the small secreted protein TCEN49 is linked to the regional maintenance of the planarian central body region. To investigate its function in vivo, we performed loss-of-function and gain-of-function experiments by RNA interference and by the implantation of microbeads soaked in TCEN49, respectively. We show that TCEN49 behaves as a trophic factor involved in central body region neuron survival. In planarian tail regenerates, tcen49 expression inhibition by double-stranded RNA interference causes extensive apoptosis in various cell types, including nerve cells. This phenotype is rescued by the implantation of microbeads soaked in TCEN49 after RNA interference. On the other hand, in organisms committed to asexual reproduction, both tcen49 mRNA and its protein are detected not only in the central body region but also in the posterior region, expanding from cells close to the ventral nerve chords. In some cases, the implantation of microbeads soaked in TCEN49 in the posterior body region drives organisms to reproduce asexually, and the inhibition of tcen49 expression obstructs this process, suggesting a link between the central nervous system, TCEN49, regional induction, and asexual reproduction. Finally, the distribution of TCEN49 cysteine and tyrosine residues also points to a common evolutionary origin for TCEN49 and molluscan neurotrophins.

Amino Acid Sequence↗

PubMed2000

Modular bacterial artificial chromosome vectors for transfer of large inserts into mammalian cells.

To facilitate the use of large-insert bacterial clones for functional analysis, we have constructed new bacterial artificial chromosome vectors, pPAC4 and pBACe4. These vectors contain two genetic elements that enable stable maintenance of the clones in mammalian cells: (1) The Epstein-Barr virus replicon, oriP, is included to ensure stable episomal propagation of the large insert clones upon transfection into mammalian cells. (2) The blasticidin deaminase gene is placed in a eukaryotic expression cassette to enable selection for the desired mammalian clones by using the nucleoside antibiotic blasticidin. Sequences important to select for loxP-specific genome targeting in mammalian chromosomes are also present. In addition, we demonstrate that the attTn7 sequence present on the vectors permits specific addition of selected features to the library clones. Unique sites have also been included in the vector to enable linearization of the large-insert clones, e. g., for optical mapping studies. The pPAC4 vector has been used to generate libraries from the human, mouse, and rat genomes. We believe that clones from these libraries would serve as an important reagent in functional experiments, including the identification or validation of candidate disease genes, by transferring a particular clone containing the relevant wildtype gene into mutant cells or transgenic or knock-out animals.

Animals↗

PubMed2000

Identification of ENV determinants in V3 that influence the molecular anatomy of CCR5 utilization.

The V3 loop of the ENV glycoprotein exerts a dominant influence on the interaction of gp120 with coreceptors. Primary env genes cloned from sequential isolates from two seroconverters revealed Pro-->Ala conversion in the conserved GPG motif of the V3 crown in seven of 17 R5 ENV. ENV containing the GPG motif in the V3 crown had fusogenic activity with chimeric receptors containing either the N terminus or loops of CCR5, whereas those with the GAG variant utilized only the former. Site-directed mutagenesis of multiple primary and prototypic R5 env genes demonstrated that the GPG motif was necessary for dual utilization of the N terminus and body of CCR5 in both gain and loss-of-function experiments. All ENV containing the GPG V3 crown showed CCR5 binding in the presence of soluble CD4, whereas it was not detected with the GAG variants. Molecular dynamic simulations of a V3 peptide predicts that the Pro-->Ala substitution results in a conformational change with loss of the crown structure. These studies demonstrate that sequences in the third hypervariable region determine the specificity of coreceptor utilization for fusion, and that a conserved motif in the crown directly influences the molecular anatomy of the interaction between gp120 and CCR5.

Amino Acid Motifs↗

PubMed1993

Protection by Cyclosporin A of ischemia/reperfusion-induced damage in isolated rat hearts.

Reperfusion following a period of ischemia can salvage the myocardium only if the ischemic episode has not exceeded a certain time limit; beyond this point damage becomes irreversible. A key feature of the transition from reversible to irreversible injury is mitochondrial dysfunction which may involve the opening of a non-specific pore in the mitochondrial inner membrane. Pore opening can be induced in vitro by exposure of isolated mitochondria to high [Ca2+] and Pi. Such pore formation is sensitized by adenine nucleotide depletion and oxidative stress and can be blocked by the immunosuppressant cyclosporin A. Here we show that in isolated perfused rat hearts subjected to 30 min ischemia and 15 min reperfusion, 0.2 microM cyclosporin A restored the ATP/ADP ratio and AMP content (decreased and increased respectively during ischemia) to pre-ischemic values. In separate experiments functional recovery was assessed by monitoring the restoration of left ventricular developed pressure (LVP) during reperfusion after 30, 40 or 45 min ischemia. LVP was substantially improved in the presence of 0.2 microM cyclosporin A but did not return to pre-ischemic levels. The cyclosporin analogues G and H were less effective than cyclosporin A in protecting the heart during reperfusion. This is consistent with their reduced ability to protect isolated mitochondria from damage caused by Ca2+ overload. Surprisingly, reperfusion of hearts with 1 microM cyclosporin A reversed the protective effect seen at 0.2 microM.

Adenine Nucleotides↗

PubMed1997

Deletion analysis of four of eighteen late gene expression factor gene homologues of the baculovirus, BmNPV.

Nucleotide sequence analysis of the genome of the baculovirus Bombyx mori nuclear polyhedrosis virus (BmNPV) identified 18 homologues of the Autographa californica NPV (AcNPV) lefs (late expression factor genes). These BmNPV lefs showed high (73-98%) amino acid sequence identities to AcNPV lefs and were localized to similar positions in the genome. One lef, p35, was previously characterized in AcNPV and BmNPV deletion experiments. Functional deletion of each of the BmNPV lef homologues was attempted here by insertion of a beta-galactosidase gene cassette into the coding region of each lef. Four of 18 BmNPV lef (39K, ie-2, lef-7, and p35) deletion mutants were successfully isolated, indicating that the other 14 BmNPV lefs were likely essential for viral replication in cell culture. Further analysis showed that deletion of lef-7, p35, and ie-2 resulted in lower levels of viral DNA replication, indicating that the BmNPV lef-7, p35, and ie-2 products have stimulating effects on DNA replication. Deletion of 39K resulted in a significantly lower level of late gene transcription and extremely low (over 10(2)-fold less at 48-80 hr p.i.) production of progeny budded virus in BmN cells. In contrast, the deletion did not affect viral DNA replication, indicating that BmNPV 39K is involved in late gene transcription. Reduced late gene expression presumably affected production and/or release of progeny budded virus particles. This was corroborated by transmission electron microscopy, which showed that virus replication was abnormal in BmN cells infected with a BmNPV mutant lacking 39K and virion production was low. Even though 39K deletion resulted in a loss of oral infectivity, the 39K deletion mutant replicated in silkworm larvae when injected into the body cavity, as did the ie-2, lef7, and p35 deletion mutants. In addition, a BmNPV homologue of the baculovirus very late expression factor gene (vif-1) found in AcNPV was essential, implying an essential function of the BmNPV vif-1 homologue at a step before the onset of very late gene expression.

Amino Acid Sequence↗

PubMed1999

Identification of a sequence element involved in AC2-mediated transactivation of the pepper huasteco virus coat protein gene.

The geminivirus AC2 gene product transactivates the expression of the coat and movement protein (CP and BV1) genes, and this effect seems to be mediated by specific although hitherto unknown cis-acting elements. In this work we examined regions from the CP and BV1 gene promoters of pepper huasteco virus (PHV) to define the sequence elements involved in regulation by AC2. Results from transient gene expression and transgenic plant assays suggest that a truncated 115-nt CP promoter is still responsive to the viral transactivator. This promoter contains three elements similar to a sequence motif termed conserved late element (CLE), which is found in the regulatory regions of many geminiviruses and that was previously suggested, on a theoretical basis, to be a potential functional target for AC2 (Argüello-Astorga et al. (1994), Virology 203, 90-100). To confirm these results, an oligonucleotide containing two CLE motifs was synthesized and characterized in gain-of-function experiments. Transient expression assays showed that this 29-nt sequence is able to confer AC2 responsiveness to heterologous promoters. A smaller oligonucleotide (16 nt) containing a single CLE also conferred this activity. In addition, when the CLE motifs were mutated in their original context (truncated 115-nt promoter), this modified promoter lost its ability to be transactivated by AC2. All these results support the involvement, at least in the case of PHV, of CLE sequences in the process of transactivation.

Capsid↗

PubMed2001

Mutations in the N-terminus of VP5 alter its interaction with the scaffold proteins of herpes simplex virus type 1.

During the assembly process of herpes simplex virus type 1 capsids, there is an essential interaction between the C-terminal tail of the scaffold proteins (22a and 21) and the major capsid protein (VP5). Recent studies of spontaneous revertant viruses that overcome a blocked maturation cleavage site of the scaffold proteins have shown that the N-terminus of VP5 is important for this interaction. One of the revertant viruses, PR7, encodes a second-site mutation at residue 69 of VP5 which unlike wild-type VP5 fails to interact with 22a and thus gives white colonies in the yeast two-hybrid assay. In the present study a small DNA fragment, encoding residues 1 to 85 of wild-type and PR7 VP5, was mutagenized using error-prone PCR. Mutagenized DNA was used in the yeast two-hybrid assay to identify mutations in wild-type VP5 that resulted in loss of 22a binding (white colonies), or in PR7 VP5 that resulted in a gain of function (blue colonies). For the loss of function experiments, using KOS VP5, a row of eight thymidine nucleotides (codons 37-40) resulted in many frameshift mutations, which led us to terminate the study without reaching a statistically significant result. For the PR7 experiment, 30 clones were identified that had single amino acid substitutions, and these mutations were localized to amino acids 27-45 and 63-84 of VP5. The most frequent mutation was a reversion back to wild-type. The next most frequent were E28K and N63S, and these gave the highest beta-galactosidase enzyme activities (indicative of PR7VP5-22a interaction), 30 and 20% of wild-type, respectively. When E28K and N63S were transferred into the wild-type VP5 background, that is, in the absence of the PR7 mutation, they gave rise to different phenotypes. The E28K mutation lost its ability to interact with the scaffold proteins as judged by this assay. Therefore, it may be acting as a compensatory mutation whose phenotype is only expressed in the presence of the original PR7 mutation. However, the N63S mutation in the wild-type VP5 background increased the interaction, as judged by the beta-galactosidase activity, by a factor of 9 relative to when the PR7 mutation was present. Even more surprising, in the absence of the PR7 mutation the enzyme activity was still greater, by a factor of 2, than that observed for wild-type VP5. This study provides further evidence that the N-terminus of VP5 is in intimate association with the C-terminus of the scaffold proteins.

Amino Acid Sequence↗

PubMed2005

Wnt signaling in lymphopoiesis.

Wnt signaling elicits changes in gene expression and cell physiology through beta-catenin and LEF1/TCF proteins. The signal transduction pathway regulates many cellular and developmental processes, including cell proliferation, cell fate decisions and differentiation. In cells that have been stimulated by a Wnt protein, cytoplasmic beta-catenin is stabilized and transferred to the nucleus, where it interacts with the nuclear mediators of Wnt signaling, the LEF1/TCF proteins, to elicit a transcriptional response. Loss-of-function and gain-of-function experiments in the mouse have provided insight into the role of this signaling pathway in lymphopoiesis. The self-renewal and maintenance of hematopoietic stem cells is regulated by Wnt signals. Differentiation of T cells and natural killer cells is blocked in the absence of LEF1/TCF proteins, and pro-B cell proliferation is regulated by Wnt signaling.

Animals↗

PubMed1991

Culture conditions dictate whether mouse fetal thymus lobes generate predominantly gamma/delta or alpha/beta T cells.

Thymus lobes from 14 day-old mouse embryos cultured submerged in r-IL-2 generated a mixture of CD8 alpha+/CD4- and CD8-/CD4- gamma delta TcR expressing cells (Ceredig et. al. 1989). Based upon Northern analysis with TcR constant region probes, no alpha beta T cells could be identified in these cultures. Submerged lobes also showed responsiveness to IL-7. In contrast, when cultured at an air liquid interface as organ cultures (OC), most cells appeared to express alpha beta TcR (Ceredig 1988). Thus depending on the mode of culture, fetal thymus lobes generate predominantly gamma delta or alpha beta T cells; it is unclear how this difference is regulated. Previous phenotypic and functional experiments suggested that gamma delta T cells may be present in OC. In order to study gamma delta T cells in both submerged lobe and OC, we have carried out three colour flow microfluorimetric analysis of gamma delta TcR, abTcR, CD3, J11d and CD8 beta expression by subpopulations of CD8 alpha and CD4 defined thymocytes. In addition, using V gamma-specific oligonucleotides and the polymerase chain reaction, we have begun identifying and sequencing the V gamma repertoire of gamma delta T cells in these mouse fetal thymus cultures.

Animals↗

PubMed1995

Evidence against a role of nitric oxide in the indirect negative inotropic-effect of M-cholinoceptor stimulation in human ventricular myocardium.

Nitric oxide (NO) has been reported to mediate several effects in response to muscarinic cholinergic stimulation in cardiovascular tissues. Recently, an attenuation of guinea pig cardiac myocyte contraction by NO has been described. The aim of the present study was to determine whether the indirect negative inotropic effect of M-cholinoceptor stimulation in human myocardium is in part due to an effect of endogenous NO. Therefore, the effect of carbachol was studied under control conditions and during inhibition of NO-synthase by pretreatment with NG-monomethyl-L-arginine (NMMA). Functional experiments were performed in isolated, electrically driven (1 Hz, 37 degrees C) left ventricular papillary muscle strips of human myocardium. Since cytokines have been reported to be increased in the serum of patients with heart failure and could induce NO-synthase activity in failing myocardium, we compared samples from nonfailing and terminally failing (classified as NYHA IV) hearts. The indirect negative inotropic effect of carbachol (10 mumol/l) was studied in the presence of the beta-adrenoceptor agonist isoprenaline (0.03 mumol/l). After stimulation with isoprenaline, carbachol significantly (P < 0.05) reduced force of contraction. This effect was diminished in failing myocardium compared to nonfailing, probably due to the diminished inotropic response most likely due to the lower cAMP levels in response to beta-adrenoceptor stimulation in the former condition. Pretreatment with NMMA (100 mumol/l) altered the antiadrenergic effect of carbachol neither in nonfailing nor in failing preparations. Furthermore, inhibition of guanylyl cyclase, the target enzyme of NO, by preincubation with methylene blue (10 mumol/l) for 30 min had no effect on the carbachol-induced decrease in force of contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine↗

PubMed1995

Functional consequences of inhibition of nucleotide breakdown in rat vas deferens: a study with Evans blue.

The effect of Evans blue on nucleotide breakdown, nucleotide-evoked contractions and electrically evoked contractions, overflow of ATP and overflow of tritium (after labelling with [3H]-noradrenaline) was studied in rat vas deferens. Pieces of vas deferens degraded 83 to 85% of added ATP, ADP and 2-methyl-thio ATP (all 100 microM) over 30 min. Evans blue (100 microM) reduced this degradation to 22 to 26%. Nucleotides elicited contraction with potency declining in the order alpha,beta-methylene ATP > 2-methylthio ATP > ATP > ADP. Evans blue (100 microM) shifted the concentration-response curve of alpha, beta-methylene ATP to the right and increased the maximum. Concentration-response curves of ATP, ADP and 2-methylthio ATP, in contrast, were shifted to the left and responses were much potentiated. In the presence of Evans blue, the rank order of potency was ATP > 2-methylthio ATP > alpha, beta-methylene ATP > ADP. Electrical field stimulation (100 pulses at 10 Hz) elicited contraction and an overflow of tritium and ATP. Evans blue (100 microM) did not alter the contraction and the evoked overflow of tritium but increased 24-fold the evoked overflow of ATP. The results indicate that Evans blue may serve as an-albeit impure-ecto-nucleotidase inhibitor in functional experiments. Such experiments demonstrate that the low potency of ATP (and also ADP and 2-methylthio ATP) in eliciting contraction, and the small size of the overflow of ATP upon sympathetic nerve stimulation, are due to rapid breakdown.

Adenosine Triphosphate↗

PubMedDate not supplied

Muscarinic cholinoceptors in the human heart: demonstration, subclassification, and distribution.

In human atrial and ventricular myocardium, the muscarinic cholinoceptor (M-cholinoceptor) populations were characterized by means of radioligand binding (with [N-methyl-3H]-scopolamine ([3H]-NMS) as the ligand) and functional experiments (negative inotropic effect of carbachol on isolated electrically driven right atrial and left papillary muscle preparations). (1) Binding of [3H]-NMS to human atrial and ventricular membranes was rapid, reversible and saturable (KD-values: 0.5-1.0 nmol/l). The maximal number of [3H]-NMS binding sites, however, was approximately 2.5-fold higher in right and left atrial membranes (200-250 fmol [3H]-NMS specifically bound/mg protein) than in right and left ventricular membranes (80-100 fmol/mg protein). (2) M-cholinoceptor antagonists inhibited [3H]-NMS binding to right atrial and left ventricular membranes with steep, monophasic competition curves indicating interaction with a single class of binding sites. In both tissues the order of potency was: atropine greater than AF-DX 116 greater than hexahydrosiladifenidol (HHSiD) greater than pirenzepine. (3) On isolated electrically driven right atrial and left papillary muscle preparations (with force of contraction enhanced by 10(-5) mol/l isoprenaline), carbachol (10(-8)-10(-4) mol/l) caused concentration-dependent decreases in force of contraction; the pD2-value for carbachol was 6.65 +/- 0.09 (n = 8, atria) and 6.62 +/- 0.08 (n = 10, papillary muscles). In both tissues M-cholinoceptor antagonists antagonized the negative inotropic effect of carbachol with an order of potency: atropine greater than AF-DX 116 greater than HHSiD greater than pirenzepine, identical to that obtained in radioligand binding experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbachol↗

PubMed1976

Alterations in the neurohypophysis of rats treated with chlorphentermine or tricyclic antidepressants.

Rats were treated with several amphiphilic, cationic compounds that are known to cause generalized lipidosis (chlorphentermine, iprindole, 1-chloro-amitriptyline, clomipramine). After prolonged drug treatment the neurohypophysis showed severe morphologic alterations particularly in Herring bodies (HB), perivascular cells, and pituicytes. HBs displayed the following abnormalities: (a) great accumulation of autophagic vacuoles that contained neurosecretory granules (NSG); (b) numerous coarse osmiophilic conglomerates; (c) masses of multilamellated material; (d) reduced numbers of intact NSGs. Perivascular cells accumulated large lamellated inclusion bodies. Pituicytes contained membrane-bound crystalloid inclusion bodies. The noxious effect of chlorphentermine and l-chloro-amitriptyline was more pronounced than that of iprindole and clomipramine. The alterations in perivascular cells and in pituicytes are typical of drug-induced lipidosis. The lesions in HBs are tentatively explained as follows: HBs were previously proposed to be the sites of normally occurring intraaxonal disposal of excess neurosecretory material. The present experimental conditions interfere with this catabolic process. Incomplete digestion of the axo-plasmic constituents due for disposal might result in abnormal accumulation of NSG-containing autophagic vacuoles, osmiophilic conglomerates, and multilamellated material. This eventually leads to degeneration of HBs. The functional implications of the neurohypophysial lesions remain to be elucidated by functional experiments.

Animals↗

PubMed1976

Enzyme activities in hepatic venous blood under strenuous physical exercise.

In order to study the influence of physical exercise on liver function, experiments were performed in healthy volunteers subjected to controlled major physical effort. Blood samples obtained by catheterization of hepatic vein during exercise were analyzed for activities of LD (thermostabile and thermolabile isoenzymes), AlAT, SDH, ICD, AP and CPK, and these activities were compared with corresponding values in arterial blood samples taken simultaneously. Hepatic blood flow and oxygen saturation of hepatic venous blood were measured. Physical exercise resulted both in diminished hepatic blood flow and a fall in hepatic venous oxygen saturation. These changes were accompanied by release of liver specific enzymes, indicating that exhausting exercise may induce an "increased hepatocyte membrane permeability" in man.

Adult↗

PubMed1986

Identity of inhibitory presynaptic 5-hydroxytryptamine (5-HT) autoreceptors in the rat brain cortex with 5-HT1B binding sites.

In rat brain cortex slices preincubated with [3H]5-HT, the potencies of 17 5-HT receptor agonists to inhibit the electrically evoked 3H overflow and the affinities of 13 antagonists (including several beta-adrenoceptor blocking agents) to antagonize competitively the inhibitory effect of unlabelled 5-HT on evoked 3H overflow were determined. The affinities of the compounds for 5-HT1B and 5-HT2 binding sites in rat brain cortex membranes (labelled by [125I]cyanopindolol = [125I]-CYP in the presence of 30 mumol/l isoprenaline and [3H]ketanserin, respectively), for 5-HT1A binding sites in pig and rat brain cortex membranes (labelled by [3H]8-hydroxy-2-(di-n-propylamino)tetralin = [3H]8-OH-DPAT) and for 5-HT1C binding sites in pig choroid plexus membranes (labelled by [3H]mesulergine) were also determined. The affinities of the drugs for the various 5-HT recognition sites ranged over 4-5 log units (the functional experiments revealed the same range of differences between the drugs). There were no significant correlations between the affinities of the drugs at 5-HT1C and 5-HT2 binding sites and their potencies or affinities, determined for the 5-HT autoreceptors. In contrast, significant correlations were found between the potencies or affinities of the drugs for the autoreceptors and their affinities at 5-HT1A or 5-HT1B binding sites; the best correlations were obtained with the 5-HT1B binding site. Some of the drugs investigated were not included in the correlation since their agonistic or antagonistic effects on the autoreceptors were weak and pEC30 or apparent pA2 values could not be determined (less than 5.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗