Effects of deuterium substitution on the chronotropic responses to some sympathomimetic amines in the isolated rat atria

Summary In spontaneously beating rat atria the potencies for the chronotropic effects of the following deuterated phenylethylamine derivatives were higher than the potencies of the corresponding non-substituted (protio-) amines: ,,d₂--phenylethylamine; ,,,-d₄-p-tyramine; ,,,-d₄-m-tyramine; ,,-d₃-p-octopamine. In contrast, ,,-d₃-noradrenaline and ,,-d₃-m-octopamine were equipotent with the corresponding protio-amines. Experiments performed in atria depleted of endogenous noradrenaline by pretreatment with reserpine and in atria exposed to the monoamine oxidase (MAO) inhibitor pargyline indicated: a. p-octopamine had both direct and indirect effects, but the chronotropic responses to p-octopamine in tissues with normal MAO activity depended mostly on the direct action of the amine; deuterium substitution enhanced the indirect component of action of p-octopamine; b. m-octopamine possessed considerable indirect effects while d₃-m-octopamine behaved as an amine of direct action. The substitution of deuterium for hydrogens in the -carbon of the alkyl-side chain of phenylethylamines decreases the rate of deamination by MAO. Therefore, the results obtained with all the amines, except for m-octopamine and ,,p-d₃-m-octopamine, could be interpreted in terms of the direct, indirect or mixed action of those compounds and/or of the influence that MAO activity has on the chronotropic responses to these amines. The results obtained with protio-and deuterio-m-octopamine suggested that deuterium substitution, either at the - or the -carbon, can alter some other mechanisms in addition to the enzymatic deamination.Career Investigator on leave of absence from the Consejo de Investigaciones Cientificas y Técnicas, ININFA, Junín 956, 5°P, RA-1113 Buenos Aires, Argentina Send offprint requests to S. M. Celuch     

The physiological disposition of p-octopamine in man

Summary After oral administration of ³H-p-octopamine (8 mg300 Ci) more ³H-activity (93% of the dose) is excreted in the urine within 24 h than after intravenous infusion (2 mg300 Ci) over 2.5 h (82% of the dose). This proves that p-octopamine is absorbed quantitatively in man. The absorption proceeds rapidly, peak plasma levels are reached between 30 and 60 min.The only metabolic pathways for p-octopamine are deamination and conjugation. The predominant step is oxidative deamination by monoamine oxidase (MAO) to p-hydroxymandelic acid. This acid represents 2/3 of the urinary ³H-activity after both routes of admistration.A quantitative difference is seen in the fraction of free p-octopamine which equals the amount of conjugated amine after infusion but is only 1/20 after oral administration. This indicates a higher total clearance after an oral dose which consequently explains the diminished efficacy on blood pressure after this route.Hydroxylation to catecholamines was not found.     

Effect of hexachlorobenzene on enzymes of the steroid metabolism in rat liver

Adult female Wistar rats were fed with a diet containing 0.05% hexachlorobenzene. On the 60th day of this treatment the specific activities of NADPH: ⁴-3-oxosteroid-5-reductase and the 3-hydroxysteroid dehydrogenases in rat liver microsomes were diminished compared to control rats. The cytoplasmatic 5-reduction was higher in HCB treated rats than in control rats. These alterations of the steroid metabolism lead to increased formation of 5-H-steroids which are known to be inducers of the porphyrin biosynthesis.

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Zusammenfassung Erwachsene weibliche Wistar-Ratten wurden mit 0.05% Hexachlorbenzol enthaltendem Futter ernährt. Am 60. Tag dieser Behandlung waren die spezifischen Aktivitäten der NADPH: ⁴-3-oxosteroid-5-Reduktase und der 3-Hydroxysteroid-Dehydrogenasen in Lebermikrosomen, verglichen mit Kontroll-Ratten, vermindert. Die cytoplasmatische 5-Reduktion war bei HCB-behandelten Ratten höher als bei Kontroll-Ratten. Diese Veränderungen des Steroidmetabolismus führen zu vermehrter Bildung von 5-H-Steroiden, von denen bekannt ist, daß sie Induktoren der Porphyrin-Biosynthese sind.

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Abbreviations HCB Hexachlorobenzene - 5-DHT 5-Dihydrotestosterone (17-hydroxy-5-androstan-3-one) - 5-DHT 5-dihydrotestosterone (17-hydroxy-5-androstan-3-one) Dedicated to Prof. Dr. Hj. Staudinger on occasion of his 65th birthday     

Studies on the constituents of Scutellaria species (XXI): constituents of the leaves of Scutellaria strigillosa Hemsley

From the leaves of Scutellaria strigillosa, 14 compounds, chrysin, apigenin, 5,7,2-trihydroxyflavone, norwogonin, ursolic acid, 6-hydroxy-4-stigmasten-3-one, 6-hydroxy-4,22-stigmastadien-3-one, 2 R,4 R,8 R--tocopherol, (S)-5,5 -bi--tocopheryl, (R)-5,5 -bi--tocopheryl, solanachromene, tocopherylquinone, jodrellin T, and 14,15-dihydrojodrellin T were isolated. The structures were determined on the basis of chemical and spectral data.     

Differentiation of cardiac chronotropic and inotropic effects of β-adrenoceptor agonists

Summary The relative inotropic and chronotropic activity of -adrenoceptor agonists was studied in the noradrenaline-depleted, anaesthetized cat. Terbutaline, a selective ₂-adrenoceptor agonist, gave at a certain dose a more pronounced chronotropic than inotropic response, while a new ₁-selective adrenoceptor agonist (–)-H 80/62 produced the same degree of chronotropic and inotropic stimulation. The results indicate that there is some difference between the -adrenoceptors in the sinus node mediating chronotropic stimulation and -adrenoceptors in the ventricular myocardium mediating stimulation of the contractile force. It has been shown that there are both ₁- and ₂-adrenoceptors in the heart (Carlsson et al., 1972). In the light of this finding it is hypothetized that there are differences in the relative distribution of ₁- and ₂-adrenoceptors in the sinus node and in the myocardium. Although ₁ is the predominant type of -adrenoceptor in both regions, the ₁: ₂ concentration ratio seems to be higher in the myo-cardium, than in the sinus node.     

Catalepsy induced by α-methyl-p-tyrosine and d-amphetamine: The rÔle of catecholamine metabolism

The effect of inhibition of monoamine oxidase (MAO), catechol-O-methyltransferase (COMT) and Dopa-decarboxylase on the catalepsy induced by d-amphetamine in -methyl-p-tyrosine (-MpT) treated rats has been investigated.Administration of an MAO inhibitor concomitant with -MpT slightly antagonized the cataleptic state, but when given 2 h later was without an appreciable effect. Only when an inhibitor was injected at an extremely high dose level 18 h prior to -MpT did catalepsy fail to develop.Following COMT inhibition the cataleptic state was enhanced. After Dopa decarboxylase inhibition the catalepsy developed as usual for the first 3 h post-amphetamine, but then declined in intensity.It is concluded that neither deaminated nor O-methylated products are responsible for the development of catalepsy. In fact, the indication is that the catalepsy may be antagonised by an O-methylated derivative. A possible explanation for the action of the Dopa decarboxylase inhibitor is discussed.     

Evaluation of P2-purinoceptor antagonists at two relaxation-mediating P2-purinoceptors in guinea-pig taenia coli

The guinea-pig taenia coli possesses two relaxation-mediating receptors for nucleotides: a prototypic P_2Y-purinoceptor, which is activated by adenosine 5-O-(2-thiodiphosphate) (ADPßS), and a separate receptor for ,-methylene ATP (,-MeATP). Effects of several as yet incompletely characterized P₂-purinoceptor antagonists at these receptors were examined.The concentration-relaxation curve of ADPßS was shifted to the right by reactive blue 2, suramin, 8-(3,5-dinitro-phenylenecarbonylimino)-1,3,5-naphthalenetrisulphonic acid (XAMR0721; at 1000 M only), pyridoxalphosphate-6-azophenyl-2,5-disulphonic acid (iso-PPADS), pyridoxal 5-phosphate, trypan blue and Evans blue (at 320 M only). Schild plots for the antagonism of reactive blue 2, suramin, iso-PPADS and pyridoxal 5-phosphate against ADPßS had slopes <1. The concentration-relaxation curve of ,-MeATP was shifted to the right by reactive blue 2, suramin, XAMR0721, iso-PPADS, pyridoxal 5-phosphate and trypan blue but not by Evans blue (320 M). Schild plots for the antagonism of suramin, XAMR0721 and iso-PPADS against ,-MeATP had slopes >1. Only XAMR0721 differed clearly in potency against the two nucleotides: it was considerably more potent against ,-MeATP than against ADPßS. 2-Methylthio ATP (MeSATP; 1 M) and ATP (100 M) were degraded by pieces of taenia coli. All antagonists except trypan blue attenuated the degradation of either or one of the two nucleotides.The selective effect of XAMR0721 against ,-MeATP confirms the existence of two relaxation-mediating P₂-purinoceptors in guinea-pig taenia coli. Comparison of the apparent affinities of the antagonists for the two taenia coli receptors with affinities for the P_2X-purinoceptor of the rat vas deferens shows that reactive blue 2, suramin, iso-PPADS, pyridoxal 5-phosphate and trypan blue have little selectivity for any of the three receptors. XAMR0721, which has been shown to possess relatively high affinity for the P_2Y-purinoceptor in turkey erythrocytes, was very weak at the P_2Y-receptor of the taenia, thus supporting the existence of pharmacologic P_2Y-receptor subtypes. Evans blue, with little effect in the taenia coli but a marked effect in the rat vas deferens, is the most selective P_2X-(versus P_2Y-) purinoceptor antagonist presently known, although its effect on the degradation of nucleotides must be kept in mind.     

Comparative toxicity of four chlorinated dibenzo-p-dioxins (CDDs) and their mixture

There is presently no scientifically proven method to assess the toxicity of environmental samples containing complex mixtures of chlorinated dibenzo-p-dioxins (CDDs) of known composition. Their risk assessment is currently based on the interim concept of toxicity equivalency factors (TEFs), with the unproven assumption that all interactions of CDDs are additive. To address this problem we conducted acute toxicity studies with four different CDDs, viz 2,3,7,8-tetrachlorodibenzo-p-dioxin (tetra-CDD), 1,2,3,7,8-pentachlorodibenzo-p-dioxin (penta-CDD), 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (hexa-CDD) and 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (hepta-CDD), all containing chlorine substituents in the crucial 2,3,7,8-positions. The homologues, dissolved in corn oil/acetone, were administered to groups of five male Sprague Dawley rats at several doses (at least three) by gastric intubation. The obtained mortality data were employed to calculate the LD_20,50 and₈₀ for each homologue. These data were subsequently used to prepare equipotent doses (expected mortality of 20, 50 and 80%) of a mixture containing all four homologues, each of them contributing one fourth of the toxicity, under the assumption of additive toxicity. The obtained LD₅₀ value and (TEF) was for tetra-CDD 43 g/kg (1), penta-CDD 206 g/kg (0.2) hexa-CDD 887 g/kg (0.05) and hepta-CDD 6325 g/kg (0.007), respectively. The dose-response to the mixture confirmed the hypothesis of strict additivity in the acute toxicity of the four CDD homologues.Presented in part at the 30th Annual Meeting of the Society of Toxicology 1991, Dallas, TX, USA     

Effect of K+ channel blockers on the α2-adrenoceptor-coupled regulation of electrically evoked noradrenaline release in hippocampus

Summary The question whether presynaptic ₂-adrenoceptors regulating noradrenaline release in hippocampus directly couple to tetraethylammonium chloride (TEA) or -dendrotoxin (-DTX)-sensitive K⁺ channels was investigated. Hippocampal slices, prelabelled with [³H] noradrenaline, were superfused in the presence of (+)-oxaprotiline and electrically stimulated with 4 pulses delivered at 100 Hz, in order to avoid autoinhibition due to released noradrenaline.TEA enhanced the evoked [³H]noradrenaline release in rabbit hippocampus in a concentration-dependent manner, yielding an approximately 4-fold increase at 30 mmol/l, whereas the spontaneous outflow of tritium was only slightly affected at this concentration. The ₂-adrenoceptor agonist clonidine, at 10–100 nmol/l inhibited the evoked [³H]noradrenaline release between 77% and 96%. The inhibitory effect of the ₂-agonist was distinctly diminished in the presence of 30 mmol/l TEA but was restored in low Ca²⁺/high Mg²⁺ buffer. Therefore, the diminution of the ₂-agonist effect by TEA observed in experiments with normal Ca²⁺ can be explained by an increase of the Ca²⁺ availability for the release process due to the prolongation of action potentials. In rabbit hippocampus -DTX (10–200 nmol/l) did neither affect the evoked release of [³H]noradrenaline nor its ₂-agonist-induced modulation. However, in rat hippocampus -DTX significantly increased the evoked transmitter release and diminished the effect of clonidine.Taken together, the present data for the rabbit hippocampus exclude the possibility that activation of presynaptic ₂-adrenoceptors inhibits depolarization-evoked [³H]noradrenaline release by inducing an outward K⁺ current through TEA- or -DTX-sensitive K⁺ channels. However, there are species differences between the rabbit and the rat so that in the rat the ₂-adrenoceptors could actually be coupled to K⁺ channels — provided that the release-enhancing properties of -DTX do not account for the ₂-antagonism observed.Correspondence to C. Allgaier at the above address     

The Relationship of pK a and Acute Skin Irritation in Man

The relationship between pK _a and skin irritation in man is studied for a homologous series of benzoic acid derivatives, which permeate through human skin at comparable rates (15–88 µg/cm²/hr). Skin irritation and pK _a are correlated for pK _a 4. Laser Doppler velocimetric assessment of skin blood flow, color meter readings, erythema, edema, and the primary irritation index are all linearly correlated and related to pK _a, erythema at 24 hr appears to be the most sensitive parameter to variation in pK _a when pK _a 4.     

The depolarizing action of 5-hydroxytryptamine on rabbit isolated preganglionic cervical sympathetic nerves

Summary This study describes a depolarizing action of 5-hydroxytryptamine (5-HT) on rabbit isolated preganglionic cervical sympathetic nerves using an extracellular recording technique. From cumulative concentration-response curves for 5-HT (1 mol/1-1 mmol/1), the mean maximal depolarization was shown to be 277 ± 32 V and EC₅₀ was 9.4 mol/l(6.5–13.6 mol/l, geometric mean, 95% confidence limits, n = 42). The responses to 5-HT displayed marked tachyphylaxis. When cumulative concentration-response curves to 5-HT and 2-methyl-5-HT were determined in the same preparations (n = 4), the mean maximal response to 5-HT was 519 ± 167 V, EC₅₀ 32.2 mol/l (8.8–118 mol/l) and the mean maximal response to 2-methyl-5-HT was 317 ± 63 V, EC₅₀ 35.1 mol/l (12.9–95.5 mol/l, geometric means, 95 % confidence limits). The action of selective 5-HT antagonists was tested on repeated cumulative concentration-response curves to 5-HT. Neither methiothepin (0.1–1 mol/l, _n = 3) nor ketanserin (0.1–1 mol/l, n = 3) had an action on 5-HT responses. The selective 5-HT₃ antagonists MDL 72222, ICS 205-930 and SDZ 206–830 were all potent antagonists of the 5-HT depolarizations. The action of these antagonists was quantified by determining the apparent pA₂ from the dose ratios and a Schild plot. For MDL 72222 (1 nmol/1-0.1 mol/l), the apparent pA₂ was 9.1 ± 0.1 (n = 12), Schild plot: 9.2; for ICS 205–930 (0.1 nmol/l–3 nmol/1), the apparent pA₂ was 10.4 ± 0.1 (n = 11), Schild plot 10.3, and for SDZ 206–830 (0.03 nmol/l-1 nmol/1), the apparent pA₂ was 11.2 ± 0.1 (n = 12), Schild plot 11.2. 5-HT depolarizations were unaffected by hexamethonium (0.5 mmol/1). 5-HT depolarizations were reduced by superfusion with both Na-free (42 ± 8% of controls, n = 4) and Na/Ca-free media (35 ± 7% of controls, n = 4). It is concluded that 5-HT depolarizations of rabbit preganglionic cervical sympathetic nerve are mediated by 5-HT₃ receptors. The data with selective 5-HT₃ receptor antagonists suggest that the receptor profile may be more like that for the 5-HT₃ receptor on the terminals of sympathetic nerves than that for the 5-HT₃ receptor on the soma of superior cervical ganglion cells or on vagal afferent neurones. Send offprint requests to D. I. Wallis at the above address     

Two distinct adrenoceptor-biophases in the vasculature: One for α-and the other for β-agonists

Summary Strips of two canine vessels with different patterns of sympathetic innervation were used: the mesenteric artery which has an adventitio-medial plexus and the saphenous vein in which nerve terminals are distributed throughout the media.The pD₂ of (–)-adrenaline for -and -adrenoceptors was determined for both vessels (in the presence of 0.5 M propranolol and 7 M phentolamine, respectively; in the latter case the strips were contracted by 0.28 M prostaglandin F2) and found to be very similar: 6.96 and 7.01 in the saphenous vein and 6.77 and 6.91 in the mesenteric artery, respectively. The similarity of pD₂ for adrenaline acting on -and -adrenoceptors in both preparations allowed us to compare the effect of inhibition of neuronal uptake by 12 M cocaine with that of inhibition of COMT by 50 M dihydroxy-2-methyl propiophenone (U-0521) on: a) the potency of adrenaline (noradrenaline was used in the saphenous vein only) acting on -and -adrenoceptors and b) the time required by the strips to recover 50% in oil (t ₅₀) after contractions or relaxations caused by 0.23 M adrenaline. In the saphenous vein cocaine increased the potency of both adrenaline and noradrenaline for -effects more than for -effects (2.8 times vs. no increase for adrenaline; 7.1 vs. 1.9 times for noradrenaline) and U-0521 increased the potency of both adrenaline and noradrenaline for -effects more than for -effects (4.1 vs. 2.6 times for adrenaline; 1.8 times vs. no increase for noradrenaline); regarding the termination of action of adrenaline, cocaine prolonged the t ₅₀ 1.6 times after contraction and did not change it after relaxation, whereas U-0521 prolonged the t ₅₀ 6.9 times after relaxation and only 1.8 times after contraction.In the mesenteric artery only sensitivity experiments were done. Cocaine increased the potency of adrenaline by a factor of 2.1 for the -effects while there was no influence on its potency with regard to its -effects, and U-0521 increased the potency of adrenaline for the -effects more than for -effects (3.9 vs. 1.8 times, respectively).These results show that there are two different biophases for sympathomimetic agonists in the vasculature: one for -adrenoceptors which is more under the influence of the neuronal uptake and one for -adrenoceptors which is more under the influence of COMT activity. We conclude that -adrenoceptors are situated close to the nerve endings and -adrenoceptors close to COMT sites. Since these results do not differ qualitatively in two vessels with different patterns of innervation, we conclude that this asymmetry in the distribution of -and -adrenoceptors may be due to either an uneven distribution of cells with only one type of receptors each or due to an uneven distribution of receptors on the same cell.     

Role of catecholamines in the anorectic effects of amphetamine in rats

Inhibition of catecholamine synthesis with -methyl-p-tyrosine antagonized amphetamine-induced anorexia. This effect of -methyl-p-tyrosine was reversed by l-Dopa administration. Comparison of the anorectic potencies of the stereoisomers of amphetamine yielded a d-amphetamine to l-amphetamine ratio of 2.751. It is concluded that amphetamine produces anorexia through an action on catecholamines, with dopamine playing a major role.This work was supported in part by National Institute of Mental Health Grants MH01562 and MH08501 to Byron A. Campbell.     

Pharmacokinetics and safety of ILX23-7553, a non-calcemic-vitamin D3 analogue, in a phase I study of patients with advanced malignancies

Purpose: Differentiation therapy is an alternative to chemotherapy with potentially less toxicity, improved quality of life, and survival. We conducted a phase I trial of ILX23-7553, a formulation of 1,25-dihydroxy-16-ene-23-yne-vitamin D₃, a 1,25-dihydroxyvitamin D₃ analog with preclinically demonstrated antitumor and differentiating effects and diminished hypercalcemic effects. Patients and methods: The protocol consisted of five daily oral treatments during 14-day cycles at 15 dose levels from 1.3 to 45.0g/m²/day. We treated 42 heavily pretreated patients who had a variety of malignancies with 162 treatment cycles, and obtained pharmacokinetics from three patients at the two highest dose levels. Results: There were no grade 3 or 4 toxicities. Grade 1–2 toxicities included diarrhea, nausea, fatigue, constipation, and one grade 1 hypercalcemia. Average day 6 calcium was 9.26 ± 0.55mg/dl in cycle 1 and 9.30 ± 0.67mg/dl in cycle 2. Pharmacokinetics at dose levels 14 (40g/m²/day) (1 patient) and 15 (45g/m²/day) (2 patients) demonstrated an average C _max of 30.4 ± 7.8pg/ml (0.07nM) and 104 ± 38.2pg/ml (0.25nM), and AUCs of 222.5 ± 225.2pg·h/ml and 855 ± 536pgh/ml, respectively. Eight patients (19%) had stable disease. While in vitro effects have been reported at these concentrations, they were at least 10-fold lower than ED₅₀s, and the study was terminated before an MTD was reached. Conclusion: The drug is safe and has potential benefits at serum concentrations where effects begin to be noted in vitro. Further study is needed with a reformulated higher unit dose compound to determine the safety and efficacy of higher serum concentrations.     

Solasodine glycosides of Solanum unguiculatum (A.) Rich

Besides solasonine, three new glycosides, namely, 3-O--L-rhamnopyranosyl-(13)-solasodine, 3-O--L-rhamnopyranosyl-(12)--L-rhamnopyranosyl-(14)--D-galactopyranosyl solasodine, and 3-O--L-rhamnopyranosyl-(12)--D-galactopyranosyl solasodine, were isolated fromSolanum unguiculatum (A.) Rich. Their structures were determined on the basis of chemical and spectral methods.     

α-Adrenoceptor activity of arylalkylimidazoles is improved byα-methylation and impaired byα-hydroxylation

Summary To investigate the effects of hydroxyl and methyl substitution of the alkyl bridge bond on the-adrenoceptor activity of arylalkylimidazole derivatives, the cardiovascular effects of the molecules were studied in anaesthetized and pithed rats. The compounds studied were 4(5)-substituted imidazole derivatives with a methano, ethano or etheno bridge between the imidazole and the 2-, 2,3- or 2,6-methyl substituted phenyl rings. The hypotensive and bradycardic activities of the molecules in the anaesthetized rat were always reduced by-hydroxylation and usually augmented by-methylation of the bridge between the imidazole and phenyl rings. Hydroxylation was associated with a consistent, marked decrease in vasopressor and sympatho-inhibitory activity in the cardiovascular system of the pithed rat, but a methyl moiety as a bulky substituent in the-position of the alkyl bridge did not decrease but even caused an increase in-adrenoceptor activity in this test system. The detrimental effect of-hydroxylation of the compounds at ₁- and ₂-adrenoceptors supports the notion that the interaction of the imidazoles at-adrenoceptor is different from that of the classical, noradrenaline-like phenethylamines. The results also suggest that the alkyl bridge between the phenyl and imidazole rings of the imidazoles may contribute directly to the binding process.     

O-Acylated lysergol and dihydrolysergol-I derivatives as competitive antagonists of 5-HT at 5-HT2 receptors of rat tail artery

Summary Twelve ergolines (O-Ayated lysergol and dihydrolysergol-I derivatives) were synthesized to study their antagonism of 5-HT responses in comparison with methysergide and LY 53857 [6-methyl-l-(1-methylethyl)-8-ergoline carboxylic acid 2-hydroxy-l-methyl-propylester hydrogen maleate] in cylindrical segments of the isolated rat tail artery. With regard to (9.10-didehydro-6-methyl-8-ergoline)methyl R,S-2-methylbutyrate, the most potent new ergoline derivative, we examined the phenomenon of insurmountable antagonism to 5-HT by methysergide.O-Acylated lysergol and dihydrolysergol-I derivatives competitively antagonized 5-HT-induced contractions with calculated pA₂. values of 7.30 ± 0.42 for the weakest and 8.42 ± 0.35 for the most potent ergoline derivative in this series. N¹-isopropyl substitution did not generally enhance 5-HT₂ receptor affinities but lowered affinities for ₁ adrenoceptors in rat aorta. Methysergide and LY 53857 were insurmountable, antagonists of 5-HT in rat tail artery.Preincubation with (9.10-didehydro-6-methyl-8-ergoline)methyl R,S-2-methylbutyrate (1 mol/l) partially prevented the depression of 5-HT-induced contractions caused by methysergide (1–10 nmol/l). Methysergide (100 nmol/l) abolished the protective effect of (9.10-didehydro-6-methyl-8-ergoline)methyl R,S-2-methylbutyrate. (9.10-Didehydro-6-methyl-8-ergoline)methyl R,S-2-methylbutyrate (1 mol/l), concomitantly incubated with methysergide (30 nmol/l), partially restored the maximum response to 5-HT that had been depressed by methysergide (30 nmol/l). Partial restoration could not be mimicked by washout of methysergide. In view of this result, it is suggested that insurmountable antagonism by methysergide of 5-HT responses in rat tail artery is due to allosteric modulation of 5-HT₂ receptors rather than pseudoirreversible inhibition. Send offprint requests to H. Pertz at the above address     

Polyhalogenated dibenzo-p-dioxins and dibenzofurans and the immune system. 4. Effects of multiple-dose treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on peripheral lymphocyte subpopulations of a non-human primate (Callithrix jacchus)

Non-human primates (Callithrix jacchus) were treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) over a period of 30 weeks, and lymphocyte subpopulations of venous blood were monitored using monoclonal antibodies and flow cytometry (FACScan). There was no clear-cut change in the total lymphocyte population during this study. In the first part of the study the new-world monkeys (marmosets) were treated for 24 weeks with a weekly dose of 0.3 ng TCDD/kg body wt. At the end of this treatment period a level corresponding to an actual cumulative dose of about 2.5–2.7 ng TCDD/kg body wt was expected. The percentage and the absolute number of the CD4⁺CDw29⁺ cells (helper inducer or memory cells) surmounted the physiologically occurring increase. Concomitantly the percentage of the CD4⁺CD45RA⁺ cells (suppressor-inducer or naive cells) decreased. There was, at the same period, no change in the total T cell population (CD2⁺ cells) or in the cells carrying the CD8 or the CD4 epitope. When increasing the weekly dose to 1.5 ng TCDD/kg body wt, a transient increase in the percentage and the absolute number of the CD8⁺CD56⁺ cell population (cytotoxic T cells) was observed 3 weeks after the increase in dosing. At this time the expected decrease in the percentage or the absolute number of CD4⁺CDw29⁺ cells was just detectable and this decline was at its maximum 6 weeks after switching to the higher weekly doses. The reduction in the percentage and the absolute number of CD4⁺CDw29⁺ cells persisted 5 weeks after discontinuation of the dosing, but this cell population was again within normal limits 7 weeks later. Because the two subpopulations are changed in opposite directions, the ratio CD4⁺CDw29⁺/CD4⁺CD45RA⁺ is a very sensitive measure of the effect induced by TCDD. There was a pronounced decrease in the percentage of the CD20⁺ cells (B₁ cells), but their percentage and number rapidly normalized, in contrast to the CD4⁺CDw29⁺ cells, when the dosing was discontinued. At the end of the treatment period the apparent body burden was calculated to correspondt an actual dose of about 9–10 ng TCDD/kg body wt. Such an actual dose level might be assumed to be reached under steady-state conditions in chronic experiments with daily doses of about 135 pg TCDD/kg body wt (assuming a half-life for TCDD in the marmoset of 6–8 weeks). Er trapolations of the results obtained at higher doses to very low exposures is not justified with respect to the effect induced by TCDD on the immune system of marmosets. A lower doses the effect is clearly reversed.     

A Simple Rheological Method for the in Vitro Assessment of Mucin-Polymer Bioadhesive Bond Strength

A simple viscometric method was used to quantify mucin-polymer bioadhesive bond strength. Viscosities of 15% (w/v) porcine gastric mucin dispersions in 0.1 N HC1 (pH 1) or 0.1 N acetate buffer (pH 5.5) were measured with a Brookfield viscometer in the absence (_m) or presence (_t) of selected neutral, anionic, and cationic polymers (0.1–2.5%, w/v). Viscosity components of bioadhesion (1%) were calculated from the equation, _t = _m + _p + _b, where _p is the viscosity of corresponding pure polymer solution as measured by an Ostwald viscometer. The forces of bioadhesion (F) were calculated from the equation, F = _b, where is the rate of shear/sec. _b's and F's for polyelectrolytes, e.g., polyacrylic acid, cationic gelatin, and chitosan were always higher in acetate buffer than in HC1. Validity of the technique and the effect of ionic charge, polymer conformation, and rate of shear on _b and F are discussed, as is a comparison of this method to other methods for evaluating bioadhesive materials.     

Effects of (−)δ9-trans-tetrahydrocannabinol (δ9-THC) on memory,attention and subjective state

In a double blind study, cross-over design, on 37 volunteers several effects of an orally administered dosage of 15 mgs (–)- ⁹-trans-tetrahydrocannabinol ( ⁹-THC) were assessed. The results did bear out the hypotheses of this experiment that the impairment of attention and information storage in the long-term memory as well as depersonalization and temporal disintegration phenomena induced by ⁹-THC are interrelated. Furthermore, the sequence of information retrieval from memory was found to be changed by ⁹-THC.