Alpha1-adrenoceptor-mediated inhibition of cellular cAMP accumulation in neonatal rat ventricular myocytes

Summary We studied adrenergic regulation of cellular cAMP in neonatal rat ventricular myocytes. Since CAMP content depends on synthesis, breakdown and egress, the contribution of each of these mechanisms was assessed. In the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, cAMP accumulation stimulated by the -adrenoceptor agonist (–)-isoprenaline was diminished when the mixed + adrenoceptor agonist (–)-noradrenaline was coincubated with (–)-isoprenaline. Moreover, adenylyl cyclase activation stimulated by (–)-isoprenaline was decreased by (–)-noradrenaline and by the selective a₁-adrenoceptor agonists (–)-phenylephrine and methoxamine, suggesting that -adrenoceptor agonism regulates CAMP metabolism through its effect on the synthetic pathway. Evidence for ₁-adrenoceptor mediation of this response was enhancement of (–)-noradrenaline-induced cAMP generation by the selective ₁-adrenoceptor antagonist terazosin (10 nmol/l). The selective ₂-adrenoceptor antagonist yohimbine (10 nmol/l) had no effect. The ₁-adrenoceptor mediated depression of (–)-isoprenaline-stimulated CAMP generation and adenylyl cyclase activation was prevented by terazosin and in separate experiments markedly enhanced by pertussis toxin pretreatment, suggesting involvement of a guanine-nucleotide regulatory protein in this process.Occupation of the ₁-adrenoceptor by (–)-noradrenaline did not accelerate the rate of CAMP breakdown in the absence of phosphodiesterase inhibition. Furthermore, there was no enhancement of total phosphodiesterase activity by (–)-noradrenaline in the presence of (–)-propranolol. By contrast, pertussis toxin pretreatment augmented phosphodiesterase activity. Neither pertussis toxin nor (–)-noradrenaline increased CAMP egress.We conclude that in rat neonatal cardiac myocytes agonist occupation of the ₁-adrenoceptor inhibits -adrenoceptor stimulated CAMP accumulation most likely by coupling to a guanine nucleotide inhibitory protein.Supported by a grant from the Department of the Veterans Affairs Research Service and Program Project Grant HL 25847 from the National Heart, Lung and Blood Institute     

鄂西山区1592例成人泌尿系统疾病(USD)调查分析

本文对鄂西自治州一市二县三所医院近八年来(1980年元月～1987年12月)成人USD住院患者1592例的构成比作了回顾性调查分析.结果表明:USD患者占同期住院总人数的3.90%,其常见病种依次为尿路结石,尿路感染,慢性肾炎.急性肾炎、肾结核,慢性肾衰和肾病综合征;上尿路结石病人数有逐年上升趋势,且右侧显著高于左侧(P<0.001);慢性肾衰的病人数每隔1～2年有突然增高现象,1987年比1980年增加了四倍;急性肾炎和肾结核占有较大比例,肾结核为慢性肾衰病因的第三位.这些均为本组USD的临床流行病学特点.作者对各常见病种的特点进行了讨论.     

Coronary endothelium-protective effects of defibrotide in ischaemia and reperfusion

Summary Defibrotide is known to enhance prostacyclin (PGI₂) release from the vascular endothelium. We investigated the vasoactive effects of defibrotide in isolated rat hearts perfused at constant flow subjected to ischaemia and reperfusion. Defibrotide at 10^–7 or 100 g/ml did not exert any direct vasoactive effect on normal rats hearts. However, ischaemia and reperfusion resulted in an impaired vasodilation to acetylcholine, an endothelium-dependent vasodilator. In contrast, the vasodilator response to the endothelium-independent dilator, nitroglycerin, was unaffected. Defibrotide, at 10^–7 or 100 g/ml, markedly restored the vasodilation to acetylcholine 10^–7 nmol/l to 1 mol/l (P < 0.01) without influencing the vasodilator response to nitroglycerin (2 to 200 g/1). Haemoglobin (150 nmol/l) inhibited the dilation to acetylcholine in response to defibrotide. However, no evidence of (PGI₂) release was observed with acetylcholine-induced vasodilation in the presence or absence of defibrotide. Additionally, 10–100 g/ml of defibrotide did not significantly decrease superoxide radicals generated by a xanthine-xanthine oxidase synthetic system under conditions in which superoxide dismutase was effective. Thus, defibrotide appears to exert an endothelium-protective effect preserving endothelium-derived relaxing factor (EDRF) without directly scavenging free signals.Supported in part by Research Grant No. HL-25575 from the National Heart, Lung and Blood Institute of the NIH Send offprint requests to A. M. Lefer at the above address     

Evidence for two separate vasoconstriction-mediating nucleotide receptors,both distinct from the P2X-receptor,in rabbit basilar artery: a receptor for pyrimidine nucleotides and a receptor for purine nucleotides

Summary Uridine 5-triphosphate- (UTP-) and adenosine 5-triphosphate-(ATP) induced vasoconstriction was studied in the rabbit basilar artery. The arteries were incubated and perfused at a constant rate of flow. Vasoconstriction was measured as an increase in perfusion pressure.Serotonin, histamine and noradrenaline caused concentration-dependent vasoconstriction, with potency decreasing in that order. Of the nucleotides tested, UTP, UDP, UMP, CTP, ATP, ADP, adenosine 5-O-(3-thio)triphosphate (ATPS), and ,-imido adenosine 5-triphosphate (AMP-PNP) elicited concentration-dependent vasoconstriction, whereas AMP, 2-methylthio-ATP, , -methylene-ATP and ,-methylene-ATP up to 10^–3 mol/l caused no or only a very small increase in perfusion pressure. The order of potency of the pyrimidine nucleotides was: UTP = UDP UMP = CTP; that of the purine nucleotides was: ATPS > AMP-PNP > ATP > ADP > 2-methylthio-ATP = , -methylene-ATP = ,-methylene-ATP. The vasoconstrictor effects of UTP and ATP were not or only to a minor degree influenced by: phentolamine; a mixture of atropine, diphenhydramine and methysergide; indometacin; nordihydroguaiaretic acid; denervation by 6-hydroxydopamine; or mechanical removal of endothelium. Prolonged exposure to ,-methylene-ATP elicited only a very small vasoconstriction and did not change the constrictor effects of UTP or ATP. Prolonged exposure to ATPS elicited marked vasoconstriction; subsequently, responses to ATP were reduced whereas those to UTP were, if anything, slightly enhanced. Reactive blue 2 reduced neither the UTP- nor the ATP-induced vasoconstriction. ATP 10^–3 mol/l elicited marked additional vasoconstriction after precontraction with UTP 10^–3 mol/l, whereas UTP elicited only a very small additional vasoconstriction when its concentration was doubled from 10^–3 to 2 × 10^–3 mol/l.It is concluded that, in the rabbit basilar artery, the vasoconstrictor response to UTP is mediated by a pyrimidine nucleotide receptor which is distinct from the P₂-purinoceptor, and that the vasoconstrictor response to ATP is mediated by a P₂-receptor which is distinct from the known P₂-subtypes.Send offprint requests to I. v. Kügelgen at the above address     

Effects of GABAA receptor ligands on noradrenaline concentration and β-adrenoceptor binding in mouse cerebral cortex

The present experiments investigated changes in -adrenoceptor binding and noradrenaline stores in mouse cerebral cortex after single treatments with drugs which bind to the GABA_A receptor but which attenuate the actions of GABA. Neither the GABA antagonist, securinine, nor the picrotoxin/Cl^– channel ligand, picrotoxin, affected noradrenaline levels or -adrenoceptor binding. However, both the benzodiazepine inverse agonist, DMCM, and pentylenetetrazole increased noradrenaline levels 24 h after injection. Only pentylenetetrazol modified -adrenoceptor binding: there was a significant increase in receptor number 4 days after injection, but a significant decrease after 7 days. The anxiogenic, proconvulsant drug, yohimbine, was without effect. The changes induced by DMCM and pentylenetetrazole do not seem to be related to the behavioural effects of these drugs or to their affinity for binding to benzodiazepine receptors. The possibility that these compounds have actions in addition to those at the GABA_A receptor is discussed.     

The Liposome as a Model Membrane in Correlations of Partitioning with α-Adrenoceptor Agonist Activities

The apparent partition coefficients of a group of imidazoline -adrenoceptor agonists in liposome/buffer systems (K_m) and in the n-octanol/buffer system (P) have been compared in quantitative structure–activity relationships (QSAR) employing biological activities and receptor binding affinities. A parabolic relationship between log K _m and log P was found, and log K _m was greater than log P for all liposome compositions. In liposomes, log K _m decreased in the order, negatively charged > neutral > positively charged. Overall, hyper- and hypotensive activities of these drugs correlated better with log K _m than with log P; however, poor correlations were obtained between partition coefficients and in vitro binding affinities. Linear correlations of log K _m with hypotensive activities were obtained with negatively charged liposomes, whereas correlations with hypertensive activities were obtained using positively charged liposomes. Multiple regressions of biological activities with binding affinities showed positive correlations with hypotensive but not hypertensive activities with or without the inclusion of log K _m or log P. Thus, the liposome represents a more selective model membrane system than a bulk oil phase for predicting the biological activities of imidazoline -adrenoceptor agonists.     

Nongastrointestinal mucosa-associated lymphoid tissue (MALT) lymphomas: Clinical and therapeutic features of 24 localized patients

Background: Peripheral B-cell lymphoma of the marginal zone (MALT, low-grade), presenting as localized, extranodal disease, usually affects the elderly. The gastrointestinal tract is the most frequently involved extranodal location, representing 70% of all MALT lymphomas. Recently, numerous other extranodal sites involved by MALT lymphomas have also been described.Patients and methods: From January 1990 to October 1995, 24 patients with untreated nongastrointestinal low-grade MALT lymphoma were submitted to treatments ranging from the local approach of radiotherapy and local -interferon (-IFN) administration to chemotherapy. The tumours were located in the lung (seven cases), conjunctiva (four cases), lachrymal gland and orbital soft tissue (four cases), salivary glands (three cases), skin (three cases), breast (two cases)' and thyroid (one case). All patients had low-grade stage IE tumours.Results: Chemotherapy was administered in 11 patients (six with lung, three with salivary gland, one with breast, and one with thyroid locations); radiation therapy was employed in seven patients (three with lachrymal gland, three with skin, and one with breast locations); local -IFN administration was administered in five patients (four with conjunctival, and one with lachrymal gland sites); and surgery was employed in one patient with a lung tumour. All patients achieved complete remissions; three local recurrences and two relapses in other sites were observed. The global five-year survival rate was 100% with a relapse-free survival rate of 79%.Conclusions: These data confirm the significant efficacy of different therapeutic approaches to specific sites inbes obtaining a good remission rate for nongastrointestinal localized low-grade MALT lymphomas.     

Persistence of effects of nitric oxide synthase inhibitors: Comparisons on blood flow and plasma exudation in guinea pig skin

Plasma protein extravasation has been measured in guinea pig skin using

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-albumin and blood flow using

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enon (

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e) clearance. The nitric oxide (NO) synthase inhibitors N^G-nitro-

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-arginine methyl ester (

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-NAME), N^G-monomethyl-

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-arginine (l

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NMMA) and N^G-nitro-

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-arginine (

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-NOArg) and the α-adrenoceptor agonist, phenylephrine, inhibited bradykinin induced plasma protein extravasation when co-injected with the peptide. The inhibitory effects of

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-NAME and

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-NOArg lasted for up to 8 and 4 h, respectively, whereas phenylephrine and

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-NMMA had no persistent inhibitory effects. When co-injected with

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e,

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-NAME,

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-NMMA,

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-NOArg and phenylephrine, but not

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-NAME, produced significant reductions in skin blood flow. When injected prior to

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e,

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-NAME and

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-NOArg, but not phenylephrine or

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-NMMA, significantly reduced flow. The effect of

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-NAME on flow was not significant at 8 h. Thus, although the inhibitory effects of the NO synthase inhibitors on mediator induced plasma protein extravasation show correlations with their effects on blood flow, the persistent effect of

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-NAME on exudation appears to extend beyond its effect on flow.     

Purification of thrombospondin from human platelets

Summary Thrombospondins are a rapidly growing family of adhesive proteins that have diverse activities to modulate cellular growth, motility, and gene expression. Thrombospondin-1 (TSP) was the first identified member of this family and is the major form of thrombospondin in human platelets. A method is described to prepare TSP from human platelets in biologically active form with minimal degradation or contamination with other platelet proteins.     

Detection of allelic loss within the β1-interferon gene in childhood acute lymphoblastic leukemia using differential PCR

Summary Deletion of the short arm of chromosome 9p involving the 1-interferon (IFN) gene has been implicated in the process of malignant transformation in lymphomas and acute lymphoblastic leukemias. Since cytogenetic analysis is frequently unsuccessful in clinical samples, we used a recently described differential PCR technique to detect losses within the 1-IFN gene in 86 acute leukemias. Using differential PCR, no 1-IFN deletion was detected in 44 acute myeloid leukemia (AML) and eight control samples. However, five of 42 acute lymphoblastic leukemia (ALL) probes (12%) exhibited loss of the 1-IFN gene (three common ALL, two T-ALL). Cytogenetic analysis was performed independently in three of these five cases and revealed abnormalities of chromosome 9p in two samples. Two of five T-ALL cases exhibited a loss within the 1-IFN gene, compared with 3/29 c-ALLs, suggesting a predominance of IFN gene loss in T-ALLs. These data indicate that PCR can be used for rapid detection of gene dosage phenomena in clinical leukemia samples.