Identification of a Strong Promoter of Bacteriophage MB78 that Lacks Consensus Sequence Around Minus 35 Region and Interacts with Phage Specific Factor

A strong promoter of bacteriophage MB78 does not have minus 35 consensus sequence although it has a TGn motif immediately upstream of minus 10 sequence as well as the AT rich UP element. It is efficiently recognised by the sigma 70 RNA polymerase, however, a phage-specific factor competes with sigma 70 RNA polymerase for binding to this region, the binding of the factor being stronger than that of the polymerase. Contrary to the reports in the literature the polymerase appears not to bind to the UP element whereas the phage-specific factor does. The latter seems to be involved in the regulation of the promoter activity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sequence analysis of exons 1, 2, 3, 4 and 5 of the HLA-B5/35 cross-reacting group

The HLA-B5/35 cross-reacting group (CREG) is a set of closely related antigens including HLA-B35, B51, B52, B53 and B78. The nucleotide sequences of exon 1 through 5 of the B5/35 CREG were determined to assess the level of polymorphism. For exons 2 and 3, the previously described sequence-based typing (SBT) strategy was applied, the nucleotide sequences of exon 1, 4 and 5 were determined by allele-specific sequencing. A total of 225 unrelated individuals were HLA-B typed by heterozygous sequencing of exons 2 and 3. In the B5/35 CREG, 26 different alleles were identified, whereas 63 non-B5/35 CREG alleles were sequenced. The SBT strategy was proven to be reliable and efficient for high resolution typing of the B5/35 CREG. The nucleotide sequences of exon 1, 4 and 5 were determined for the 26 different B5/35 CREG alleles to establish the level of polymorphism. For seven different alleles, of which the exon 1, 4 and 5 sequences were hitherto unknown, the sequences were elucidated and in agreement with the known B5/35 sequences. Nineteen HLA-B5/35 CREG alleles with previously published exon 1, 4 and 5 sequences were sequenced in at least two individuals. Three new alleles were identified. The first, B*5204, showed a difference at position 200 compared to B*52011, which was previously considered a conserved position. The other two alleles, B*3542 and B*51015, showed exon 2 and 3 sequences identical to B*35011 and B*51011, but differences in exons 1 and 4, respectively. B*3542 had differences at position 25 and 72 and B*51015 showed a difference at position 636. More polymorphism might be present outside exons 2 and 3 than previously thought.     

The effects of compounds related to γ-aminobutyrate and benzodiazepine receptors on behavioural responses to anxiogenic stimuli in the rat: Punished barpressing

Rats were trained to press a bar for sucrose reward on a random-interval (RI) schedule and footshock punishment was then introduced for 3-min intrusion periods (signalled by a tone) on an independent RI schedule. Shock intensity was individually adjusted to produce stable intermediate levels of response suppression during the tone for each animal. Groups of animals were then allocated to a number of separate experiments in which they were systemically injected with anxiolytics (chlordiazepoxide HCl or sodium amylobarbitone), GABA antagonists (picrotoxin or bicuculline), the GABA_A agonist muscimol, the GABA_B agonist baclofen, an antagonist (RO 15-1788) at the benzodiazepine receptor and, an inverse agonist (FG 7142) at this receptor. The results showed that the alleviation of punishment-induced suppression of barpressing produced by chlordiazepoxide was blocked or partially blocked by RO 15-1788, picrotoxin and bicuculline but not by FG 7142; that picrotoxin (but not FG 7142) increased the suppression of responding by punishment; that neither muscimol nor baclofen affected responding on their own, but their combination weakly but reliably released punished responding from suppression; and that the anti-punishment effect of amylobarbitone was unaffected by either picrotoxin or bicuculline, though the barbiturate reversed the punishment-enhancing effect of picrotoxin. These results are discussed in the light of the hypothesis that anxiolytic behavioural effects are due to increased GABAergic inhibition.     

Pharmacological characterization of type 1α metabotropic glutamate receptor-stimulated [35S]-GTPγS binding

1. The activation of G proteins by type 1α metabotropic glutamate receptors (mGluRs) in membranes from recombinant baby hamster kidney cells expressing the cloned rat mGluR1α receptor has been studied by use of a [³⁵S]-guanosine 5′-[γ-thio]triphosphate ([³⁵S]-GTPγS) binding assay.
2. L-Glutamate increased the rate of [³⁵S]-GTPγS binding in a concentration-dependent manner (−logEC₅₀ (M) 5.25±0.07), with an optimal (62.4±1.6%) increase over basal binding being observed following 60 min incubation at 30°C with 70 pM [³⁵S]-GTPγS, 1 μM GDP, 10 mM MgCl₂, 100 mM NaCl and 100 μg membrane protein ml⁻¹. The L-glutamate (100 μM)-stimulated increase in [³⁵S]-GTPγS binding was totally prevented in the presence of the group I mGluR antagonist (S)-4-carboxy-3-hydroxyphenylglycine (300 μM).
3. Quantitative analysis of the affinity and number of G proteins activated by a maximally effective concentration of L-glutamate revealed an equilibrium dissociation constant (K_D) for [³⁵S]-GTPγS binding of 0.76±0.20 nM and a maximal number of GTPγS-liganded G proteins (B_max) of 361±30 fmol mg⁻¹ protein.
4. Metabotropic glutamate receptor agonists, quisqualate (−logEC₅₀ (M) 6.74±0.06), 1S,3R-ACPD (4.64±0.08) and (S)-3,5-dihydroxyphenylglycine (5.16±0.23) also increased [³⁵S]-GTPγS binding in a concentration-dependent manner, with the latter two agents behaving as partial agonists.
5. (+)-α-Methylcarboxyphenylglycine (300 μM) caused a parallel rightward shift of the L-glutamate concentration-effect curve for [³⁵S]-GTPγS binding, allowing an antagonist equilibrium dissociation constant (K_D) of 34.0±7.8 μM to be calculated for this mGluR antagonist.
6. Pretreatment of BHK-mGluR1α cells with a concentration of pertussis toxin (PTX) shown to be maximally effective (100 ng ml⁻¹, 24 h) before membrane preparation resulted in a marked decrease in agonist-stimulated [³⁵S]-GTPγS binding (by 66.0±0.9%), and an altered concentration-effect relationship for agonist-stimulated [³⁵S]-GTPγS binding by the residual PTX-insensitive G-protein population.
7. The modulation of [³⁵S]-GTPγS binding by agonists and antagonists in membranes from recombinant cells provides an excellent system in which to study mGluR interactions with PTX-sensitive and -insensitive G proteins.

     

Subtype specificity of γ-aminobutyric acid type A receptor antagonism by clozapine

Clozapine, an atypical neuroleptic, functionally antagonizes the -aminobutyric acid-induced chloride uptake via the main central inhibitory receptor, -aminobutyric acid type A (GABA_A) receptor, in brain vesicles. GABA_A antagonism by micromolar concentrations of clozapine is more efficient in rat cerebrocortical and hippocampal membranes than in cerebellar membranes, as evidenced by clozapine reversal GABA-inhibition of [³⁵S]t-butylbicyclophosphorothionate ([³⁵S]TBPS) binding. A typical neuroleptic, haloperidol, failed to antagonize GABA in any of these brain regions, while the specific GABA_A antagonist 2-(3-carboxy-2,3-propyl)-3-amino-6-p-methoxyphenylpyrazinium bromide (SR 95531) was efficient in all three brain regions. Clozapine action on [³⁵S]TBPS binding was unaffected by the benzodiazepine receptor antagonist flumazenil. Clozapine inhibited the binding of [³H]muscimol and [³H]SR 95531 to the GABA recognition site, but this effect only partially correlated with the regional differences in and the potency of clozapine antagonism of GABA-inhibition of [³⁵S]TBPS binding, suggesting that also other than GABA sites may mediate clozapine actions. Autoradiography of [35S]TBPS binding revealed GABA antagonism by clozapine in most brain regions. Main exceptions were cerebellar granule cell and molecular layers, olfactory bulb external plexiform and glomerular layers and primary olfactory cortex, where clozapine antagonized GABA inhibition less than average, and lateral hypothalamic and preoptic areas where its antagonism was greater than average. Recombinant 622 receptors, the predominant 6 subunit-containing receptor subtype in cerebellar granule cells, failed to show GABA antagonism by clozapine up to 100 M. In contrast, recombinant 122 receptors, forming the predominant receptor subtype in the brain, were clozapine sensitive. Recombinant 622 and 632 receptors resulted in clozapine-insensitive receptors, whereas 612 receptors were clozapine sensitive. The efficacy of clozapine to antagonize GABA in 1x2 receptors decreased in the order of 112>122>132. The results indicate that clozapine antagonizes the function of most GABA_A receptor subtypes, and that the interaction is determined by the interaction of the and subunit variants. GABA antagonism is a unique property of clozapine, not shared by haloperidol, which might be involved in the pharmacological mechanism for the increased seizure susceptibility associated with clozapine treatment.     

Actions of roxindole at recombinant human dopamine D2, D3 and D4 and serotonin 5-HT1A, 5-HT1B and 5-HT1D receptors

Roxindole is a potential antidepressant agent. The present study determined its affinity and agonist efficacy at recombinant human (h) dopamine hD₂, hD₃ and hD₄ and serotonin (5-HT) h5-HT_1A, h5-HT_1B and h5-HT_1D receptors. Roxindole exhibited high affinity at hD₃ as well as at hD₂ (short isoform) and hD₄ (4-repeat isoform) receptors (pK _i values 8.93, 8.55 and 8.23, respectively). Further, it displayed high affinity at h5-HT_1A receptors (pK _i = 9.42) but modest affinity at 5-HT_1B and 5-HT_1D receptors (pK _i values 6.00 and 7.05, respectively). In [³⁵S]GTPγS binding experiments, roxindole was >20-fold more potent in stimulating [³⁵S]GTPγS binding at hD₃ than at hD₂ or hD₄ receptors (pEC₅₀ = 9.23 vs. 7.88 and 7.69). However, whereas roxindole exhibited partial agonist activity at hD₃ and hD₄ sites (E _max = 30.0% and 35.1%, respectively, relative to dopamine = 100%), it only weakly activated hD₂ receptors (E _max = 10.5%). Roxindole potently blocked dopamine-stimulated [³⁵S]GTPγS binding at hD₂ receptors (pK _B = 9.05). In comparison, the dopamine receptor agonist, (-)quinpirole, acted as a partial agonist at hD₃ and hD₄ sites (E _max = 67.4% and 66.3%, respectively) but surpassed the efficacy of dopamine at hD₂ receptors (E _max = 132%). At h5-HT_1A receptors, roxindole behaved as a high affinity (pK _i = 9.42) partial agonist (E _max = 59.6%, relative to 5-HT = 100%), whereas (-)quinpirole had negligible activity. The selective 5-HT_1A antagonist, WAY 100,635, blocked roxindole (100 nM)-stimulated [³⁵S]GTPγS binding at h5-HT_1A receptors in a concentration-dependent manner (pK _B = 9.28). Roxindole only weakly stimulated [³⁵S]GTPγS binding at 5-HT_1B and 5-HT_1D receptors (E _max = 27.1% and 13.7%). The present data suggest that roxindole activates mainly D₃ vs. D₂ or D₄ receptors and 5-HT_1A vs. 5-HT_1B or 5-HT_1D receptors. Activation of D₃ and/or 5-HT_1A receptors may thus contribute to its potential antidepressant properties. Received: 4 February 1999 / Accepted: 29 March 1999     

Thermodynamics and kinetics of t-butylbicyclophosphorothionate binding differentiate convulsant and depressant barbiturate stereoisomers acting via GABAA ionophores

The temperature dependence of [³⁵S]-t- butylbicyclophosphorothionate (TBPS) binding to the convulsant sites of the GABA_A receptor complex was studied in membrane preparations of rat forebrain. Although specific [³⁵S]TBPS binding was maximal around 20° C, the rate constants of dissociation decreased monotonously between 37°C and 2° C. The displacing potencies of the convulsant S(+) enantiomer of 1-methyl-5-phenyl-5-propyl-barbituric acid (MPPB) (IC₅₀ = 1250 ± 30 M) and the depressant R(–) MPPB (IC_5O = 310 ± 5 M) did not show significant changes between 19° C and 37° C. Therefore barbiturate binding seems to be driven by entropic, rather than enthalpic changes. An excess of MPPB enantiomers elicited accelerated and polyphasic dissociations of [³⁵S]TBPS as compared to the monophasic dissociation by TBPS. Arrhenius analysis was applied to the measurable initial rate constants of dissociation. Arrhenius plots were linear between 2° C and 37° C. Activation parameters were similar when [³⁵S] TBPS dissociation was triggered by the convulsants TBPS and S(+) MPPB. It can be attributed to similar conformations of the closed ionophore complex. In contrast, the depressant R(–) MPPB strongly decreased the activation energy of TBPS dissociation from the open ionophore ternary complex.In whole-cell patch-clamp experiments R(–) MPPB, but not S(+) MPPB, elicited chloride currents in rat primary cortical cultures with an EC₅₀ value of 560 ± 30 M and a Hill coefficient of 2.9 ± 0.2. These currents were similar to those elicited by GABA and blocked by TBPS. A kinetic scheme is proposed for the dissociation of TBPS and to explain the different effects of MPPB enantiomers. Submillimolar R(–) MPPB is supposed to bind to (about three) barbiturate sites on GABA_A-ionophores and to open them in a cooperative manner to result in a decreased activation energy for accelerated displacement of convulsant binding.     

HLö 7 dimethanesulfonate,a potent bispyridinium-dioxime against anticholinesterases

HLö 7 dimethanesulfonate (1-[[[4-(aminocarbonyl)pyridinio] methoxy] methyl] -2,4-bis [(hydroxyimino) methyl]pyridinium dimethanesulfonate) is a broad-spectrum reactivator against highly toxic organophosphorus compounds. The compound was synthesized by a new route with the carcinogenic bis(chloromethyl)ether being substituted by the non-mutagenic bis(methylsulfonoxymethyl)ether. The very soluble dimethanesulfonate of obidoxime was also prepared by this way. HLö 7 dimethanesulfonate is the first water-soluble salt of HLö 7 that should be suitable for the wet/dry autoinjector technology, because aqueous solutions of HLö 7 are not very stable (calculated shelf-life 0.2 years when stored at 8°C, 1 M solution, pH 2.5). The crystalline preparation contains 96% of thesyn/syn-isomer, less than 2% of thesyn/anti-isomer and some minor identified by-products. HLö 7 was very efficient in reactivating acetylcholinesterase (AChE) blocked by organophosphates as long as ageing did not prevent dephosphylation. HLö 7 was superior to HI 6 (1-[[[4-(aminocarbonyl)pyridinio]methoxy]methyl]-2-[(hydroxyimino)methyl]pyridinium dichloride) in reactivating soman and sarin-inhibited AChE from erythrocytes, and literature data indicate that HLö 7 exceeds HI 6 by far in reactivating tabun-inhibited AChE. In atropine-protected, soman-poisoned mice HLö 7 was three times more potent than HI 6 (protective ratio 5 versus 2.5), and in sarin-poisoned mice HLö 7 was 10 times more potent than HI 6 (protective ratio 8 for both oximes). In atropine-protected guinea-pigs HLö 7 was less effective than HI 6 (protective ratio: 2.3 versus 5.2 for soman; 5.2 versus 6.8 for sarin; 4.3 versus 3.8 for tabun). The mean survival time of anaesthetized guinea-pigs exposed to 5 LD₅₀ soman (6.3 min) was increased by atropine (27 min) and atropine + HLö 7 (57 min). HLö 7 alone did not prolong the survival. The most impressive effect of HLö 7 was on respiration: 3 min after i.v. injection of HLö 7 and atropine, the depressed respiration increased rapidly to 60% of control and remained at that level during the observation period (60 min). With atropine alone, respiration recovered only slowly. Behavioural and physiologic parameters were determined in atropine-protected mice exposed to a sublethal soman dose. The running performance was significantly improved by HLö 7. Even central symptoms, e.g. hypothermia and convulsions, were decreased markedly by HLö 7 (evaluation 60 min after poisoning). The pharmacokinetic data for HLö 7 in male beagle dogs are similar to those of HI 6. After i.v. injection: t_1/2 = 5 min; t_1/2ß = 46 min; V_D = 0.24 1/kg; Cl_p1 = 3.7 ml x min^–1 x kg^–1; Cl_ren= 3.2 ml x min^–1 x kg^–1; renal excretion of unchanged HLö 7 = 86%. After i. m. injection: t_1/2abs = 14 min; t_1/2ß = 48 min; Vd = 0.27 1/kg; Cl_p1= 3.9 ml x min^–1 x kg^–1; Cl_ren= 2.7 ml x min^–1 x kg^–1; renal excretion of unchanged HLö 7 = 76%; bioavailability >95%. Plasma protein binding was <5%; HLö 7 did not permeate into red cells. A dose of 20 mol/kg was well tolerated both after i.v. and i.m. administration. In anaesthetized dogs (chloralose) HLö 7 i.v. (20 (imol/kg) showed marginal hypotensive effects, whereas 50 mol/kg resulted in decreased mean blood pressure (–15%) and blood flow (–30%) without reflex tachycardia. One out of four dogs developed a circulatory shock syndrome with anuria. Respiration varied only transiently. Blood gases and pH were not influenced. Similar cardiovascular effects were observed in anaesthetized (urethane) guinea-pigs. In isolated guinea-pig hearts (Langendorff) sinus and ventricular heart rate were not influenced by HLö 7 <500 M. HLö 7 antagonized both carbachol and nicotine effects. Red cell AChE was inhibited by HLö 7 by up to 50%; C₅₀ about 100 M. Previously, HLö 7 was shown to block ganglionic transmission (IC₅₀= 500 M), probably due to ion-channel blockade. These data indicate that HLö 7 combines ganglion blocking, anticholinergic and indirect cholinergic properties like other bispyridinium compounds. The results suggest that HLö 7 may be tolerated by man at a dose of 10 mol/kg. Vital functions are not expected to be impaired. At such a dose (250–500 mg), which can be injected by an autoinjector, HLö 7 is expected to be superior to HI 6.Part of thesis     

Specific activation of the mu opioid receptor (MOR) by endomorphin 1 and endomorphin 2

The recently discovered endomorphin 1 (Tyr-Pro-Trp-Phe-NH2) and endomorphin 2 (Tyr-Pro-Phe-Phe-NH2) were investigated with respect to their direct receptor-binding properties, and to their ability to activate G proteins and to inhibit adenylyl cyclase in both cellular and animal models. Both tetrapeptides activated G proteins and inhibited adenylyl cyclase activity in membrane preparations from cells stably expressing the mu opioid receptor, an effect reversed by the mu receptor antagonist CTAP (D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2), but they had no influence on cells stably expressing the delta opioid receptor. To further establish the selectivity of these peptides for the mu opioid receptor, brain preparations of mice lacking the mu opioid receptor gene were used to study their binding and signalling properties. Endomorphin 2, tritiated by a dehalotritiation method resulting in a specific radioactivity of 1.98 TBq/mmol (53.4 Ci/mmol), labelled the brain membranes of wild-type mice with a Kd value of 1.77 nM and a Bmax of 63.33 fmol/mg protein. In membranes of mice lacking the mu receptor gene, no binding was observed, and both endomorphins failed to stimulate [35S]guanosine-5'-O-(3-thio)triphosphate ([35S]GTPgammaS) binding and to inhibit adenylyl cyclase. These data show that endomorphins are capable of activating G proteins and inhibiting adenylyl cyclase activity, and all these effects are mediated by the mu opioid receptors.