Effects of cannabinoids on dopamine release in the corpus striatum and the nucleus accumbens in vitro

Cannabinoid receptors are widely distributed in the nuclei of the extrapyramidal motor and mesolimbic reward systems; their exact functions are, however, not known. The aim of the present study was to characterize the effects of cannabinoids on the electrically evoked release of endogenous dopamine in the corpus striatum and the nucleus accumbens. In rat brain slices dopamine release elicited by single electrical pulses was determined by fast cyclic voltammetry. Dopamine release was markedly inhibited by the OP2 opioid receptor agonist U-50488 and the D2/D3 dopamine receptor agonist quinpirole, indicating that our method is suitable for studying presynaptic modulation of dopamine release. In contrast, the CB1/CB2 cannabinoid receptor agonists WIN55212-2 (10(-6) M) and CP55940 (10(-6)-10(-5) M) and the CB1 cannabinoid receptor antagonist SR141716A (10(-6) M) had no effect on the electrically evoked dopamine release in the corpus striatum and the nucleus accumbens. The lack of a presynaptic effect on terminals of nigrostriatal and mesolimbic dopaminergic neurons is in accord with the anatomical distribution of cannabinoid receptors: The perikarya of these neurons in the substantia nigra and the ventral tegmental area do not synthesize mRNA, and hence protein, for CB1 and CB2 cannabinoid receptors. It is therefore unlikely that presynaptic modulation of dopamine release in the corpus striatum and the nucleus accumbens plays a role in the extrapyramidal motor and rewarding effects of cannabinoids.

Familial clustering of infantile cirrhosis in Northern Germany: A clue to the etiology of idiopathic copper toxicosis

Two cases of infantile liver cirrhosis of unknown origin occurred in a circumscribed rural area of Northern Germany. Both children had increased dietary copper exposure. The search for additional cases of what appeared to be idiopathic copper toxicosis (ICT) revealed a cluster of affected infants in this region, raising questions about the relative importance of genetic and environmental factors that are considered to be etiologic. We gathered clinical and pathologic data concerning the patients, analyzed the pedigrees of affected families, and searched for possible environmental factors contributing to the pathologic process. We encountered 8 cases of infantile liver cirrhosis in 5 families in Emsland, a circumscribed and predominantly rural area of Northern Germany; ICT was definitely proven in 2 cases. Clinical presentation and liver pathology in 6 additional cases were consistent with the diagnosis of ICT. Pedigrees of affected families revealed complex relationships with occasional consanguinity of parents, suggesting autosomal recessive inheritance. The households were served by private wells with water of low pH flowing through copper pipes, suggesting the possibility of increased alimentary copper exposure. These findings support earlier conclusions that ICT develops when an infant with a genetic predisposition is exposed to a copper-enriched diet.

Direct interaction between the ARF-specific guanine nucleotide exchange factor msec7-1 and presynaptic Munc13-1

Msec7-1, a mammalian homologue of yeast sec7p, is a specific GDP/GTP exchange factor for small G-proteins of the ARF family. Overexpression of msec7-1 in Xenopus neuromuscular junctions leads to an increase in synaptic transmitter release that is most likely caused by an increase in the pool of readily releasable vesicles. However, the molecular mechanisms by which msec7-1 is targeted to presynaptic compartments and enhances neurotransmitter release are not known. In the present study, we demonstrate that msec7-1 interacts directly with Munc13-1, a phorbol ester-dependent enhancer of neurotransmitter release that is specifically localized to presynaptic transmitter release zones. Given that Munc13-1 and msec7-1 participate in very similar presynaptic processes and because Munc13-1 is specifically targeted to presynaptic active zones, we suggest that the msec7-1/Munc13-1 interaction serves to colocalize the two proteins at the active zone, a subcellular compartment with extremely high membrane turnover.

Wrap-around arterialized venous flap for salvage of an avulsed finger

The case of an avulsed finger with extensive soft-tissue trauma is presented. The digit was salvaged using an arterialized wrap-around flow-through venous flap from the forearm.

Prevalence of risk factors of coronary heart disease in Turks living in Germany: The Giessen Study

Turkish people represent the majority of immigrants in Germany. Even though a high proportion of Turks has been living in Germany since about 20 years, little is known about risk factors of coronary heart disease (CHD) in this population. In this study a sample of 325 male and 155 female Turks are investigated, who voluntarily underwent a health check-up in Germany. Data about the presence of CHD, risk factors and blood parameters were collected. Mean residence time was 21 and 17 years (males/females). A low percentage of female participants was observed compared to the general Turkish population in Germany. Age adjusted prevalence of CHD reached 9.5% in males and 6.7% in females, respectively. Dyslipoproteinemia (DLP) showed the highest prevalence of all risk factors investigated in both genders. Total cholesterol (TC) levels were comparable to those of other western countries and remarkably higher than reported for the population in Turkey. Besides this, low high density lipoprotein-cholesterol (HDL-C) and apolipoprotein A-I (ApoA-I) levels could be found in the majority of the sample. The highest odds ratios for CHD were estimated for stress and hypertension in males and obesity in females. It is concluded that Turkish immigrants in Germany showed an assimilation of lipid pattern to western populations. However, reasons for low HDL-C levels remain unclear. Changes in the lipid metabolism chiefly seem to contribute to the risk factor pattern of Turkish immigrants in Germany.

Pantoprazole lacks induction of CYP1A2 activity in man

OBJECTIVE

This drug-drug interaction study investigated the potential influence of the proton pump inhibitor pantoprazole on the CYP1A2 activity as assessed by urinary excretion of caffeine metabolites.

SUBJECTS, MATERIALS AND METHODS

12 healthy, non-smoking volunteers underwent two treatment periods of 7 days each in randomized order with once-daily oral intake of 40 mg pantoprazole (test) or placebo (reference). On days 6 and 7 of both periods, 200 mg caffeine was administered two hours after pantoprazole intake, i.e. at the expected t(max) of pantoprazole serum concentrations. Urinary excretion of the caffeine metabolites 1X, 1U, AFMU, 17U was measured up to 8 hours after caffeine intake. In accordance with recent guidelines on drug-drug interactions, lack of interaction was handled as an equivalence problem.

RESULTS

Point estimate and 90% confidence intervals (CI) of the respective ratios test/reference were 0.91 (0.81, 1.03) for (1X + 1U + AFMU)/17U, indicative for CYP1A2 activity, 1.03 (0.94, 1.13) for AFMU/1X (N-acetyl transferase activity) and 1.01 (0.94, 1.09) for 1U/1X (xanthine oxidase activity).

CONCLUSION

Pantoprazole does not induce CYP1A2 activity, consistent with previous findings following theophylline administration, nor does it have any influence on N-acetyl-transferase or xanthine oxidase activity.

A presynaptic role for the ADP ribosylation factor (ARF)-specific GDP/GTP exchange factor msec7-1

ADP ribosylation factors (ARFs) represent a family of small monomeric G proteins that switch from an inactive, GDP-bound state to an active, GTP-bound state. One member of this family, ARF6, translocates on activation from intracellular compartments to the plasma membrane and has been implicated in regulated exocytosis in neuroendocrine cells. Because GDP release in vivo is rather slow, ARF activation is facilitated by specific guanine nucleotide exchange factors like cytohesin-1 or ARNO. Here we show that msec7-1, a rat homologue of cytohesin-1, translocates ARF6 to the plasma membrane in living cells. Overexpression of msec7-1 leads to an increase in basal synaptic transmission at the Xenopus neuromuscular junction. msec7-1-containing synapses have a 5-fold higher frequency of spontaneous synaptic currents than control synapses. On stimulation, the amplitudes of the resulting evoked postsynaptic currents of msec7-1-overexpressing neurons are increased as well. However, further stimulation leads to a decline in amplitudes approaching the values of control synapses. This transient effect on amplitude is strongly reduced on overexpression of msec7-1E157K, a mutant incapable of translocating ARFs. Our results provide evidence that small G proteins of the ARF family and activating factors like msec7-1 play an important role in synaptic transmission, most likely by making more vesicles available for fusion at the plasma membrane.

Left ventricular diastolic function in infants, children, and adolescents. Reference values and analysis of morphologic and physiologic determinants of echocardiographic Doppler flow signals during growth and maturation

OBJECTIVES

The aim of this study was to set up reference values for Doppler flow-derived left ventricular filling parameters and to evaluate physiologic determinants of changes in signal expression related to maturation.

BACKGROUND

In left ventricular diastolic function studies, age-related modulations in signal expression are observed. Assuming degenerative myocardial changes to be absent during childhood and adolescence, the determinants of these modulations must be different from those suspected in adults.

METHODS

Pulsed wave Doppler signals from the mitral valve tip region were recorded in 329 healthy subjects aged 2 months to 39 years. Multiple linear regression was used to evaluate statistical relations between Doppler flow signals and stroke volume in the mitral valve area.

RESULTS

Increasing early filling time velocity integral throughout maturation caused a decrease in atrial filling fraction from 0.34+/-0.06 to 0.24+/-0.04 (p < 0.005). Peak flow velocities during atrial systole decreased from infancy to adolescence (66+/-15 to 41+/-10 cm/s). Main effects on signal modulation were caused by heart rate, stroke volume and mitral ring area with a linear model fit (R2) of 0.79 for early filling phase (E)-time velocity integral, 0.6 for atrial filling phase peak velocity 0.84 for total E duration and 0.73 for E deceleration time. Atrial filling phase-time velocity integral, albeit significantly dependent on heart rate, was stable throughout growth.

CONCLUSIONS

During infancy and childhood, the stroke volume crossing the mitral valve is a main modulator for early filling phase (E)-time velocity integral and diastolic time intervals during early filling, whereas atrial filling phase parameters are mainly dependent on heart rate. This results in a more pronounced atrial filling during infancy and childhood.

Pantoprazole does not interact with the pharmacokinetics of carbamazepine

OBJECTIVE

Pantoprazole is a H+/K+-ATPase inhibitor with a minimized potential of interaction with the cytochrome P450 system. Imidazole derivatives such as cimetidine and omeprazole have been shown to markedly interact with carbamazepine, a major anticonvulsant with a narrow therapeutic range. Therefore, the influence of steady-state pantoprazole on the pharmacokinetics of carbamazepine was investigated.

SUBJECTS AND METHODS

N = 20 healthy volunteers (12 male/8 female) completed a double-blind, placebo-controlled, randomized crossover study. During the test period they received 40 mg pantoprazole p.o. once daily for 11 days and concomitantly a single oral dose of 400 mg carbamazepine on day 5. In the reference period placebo was administered instead of pantoprazole.

RESULTS

Serum concentrations of carbamazepine and its active metabolite carbamazepine-10,11-epoxide were measured until day 11. Geometric means of AUC (extent characteristic) and Cmax/AUC (rate characteristic) of carbamazepine were 292 and 287 mgxh/l, and 0.0150 and 0.0144 l/h (reference and test), respectively. Point estimates and 90% confidence intervals of the ratios were 0.98 (0.95, 1.01) for AUC, and 0.96 (0.92, 1.00) for Cmax/AUC, respectively. Since the 90% confidence intervals of the primary characteristics, AUC and Cmax/AUC were entirely within the predefined equivalence range of 0.80 - 1.25, lack of interaction of pantoprazole with the pharmacokinetics of carbamazepine was demonstrated. Equivalence was also demonstrated for carbamazepine-10,11-epoxide using the characteristics AUC and Cmax.

CONCLUSION

No dose adjustment of carbamazepine is therefore required during concomitant treatment with pantoprazole.

Spontaneous secretion of interleukin 1 receptor antagonist (IL-1ra) by cells isolated from herniated lumbar discal tissue after discectomy

In the study presented, cells of a herniated lumbar disc were cultivated in vitro and analysed for interleukin 1beta (IL-1beta) and interleukin 1 receptor antagonist (IL-1Ra) production. The objective of this study was the detection of IL-1beta and IL-1Ra secreted by herniated lumbar discal cells after discectomy. The involvement of cytokines in the degeneration of intervertebral discs and in the pathophysiology of radiculopathy is established. Antagonizing proteins, e.g. IL-1Ra are thought to have considerable therapeutic potential. In the present study, a 51-year-old male with massive sequestrated lumbar disc herniation at L5/S1 was treated by microsurgical discectomy. Discal cells were isolated, cultures and culture supernatants immunochemically analysed for IL-1beta and IL-1Ra secretion. Spontaneous secretion of IL-1Ra was found. IL-1beta was not detected. Our findings might contradict recent studies on the role of IL-1beta and IL-1Ra. A possible therapeutic role of exogenous IL-1Ra in disc degeneration needs further research.

P2-receptor-mediated inhibition of noradrenaline release in the rat pancreas

The aim of the study was to find out whether, and if so through which receptors, nucleotides modulate the release of noradrenaline in the rat pancreas. Segments of the pancreas were preincubated with [3H]-noradrenaline, superfused with medium containing desipramine (1 microM) and yohimbine (1 microM), and stimulated electrically, in most experiments by 60 pulses/l Hz. The adenosine A1-receptor agonist N6-cyclopentyl-adenosine (CPA; EC50 32 nM), the non-subtype-selective adenosine receptor agonists adenosine (EC50 15 microM) and 5'-N-ethylcarboxamidoadenosine (NECA; EC50 135 nM), and the nucleotides ATP (EC50 13 microM), adenosine-5'-O-(3-thiotriphosphate) (ATPgammaS; EC50 19 microM) and adenosine-5'-O-(2-thiodiphosphate) (ADPbetaS; EC50 16 microM) decreased the evoked overflow of tritium. The adenosine A2A-agonist 2-p-(2-carboxyethyl)-phenethylamino-5 '-N-ethylcarboxamido-adenosine (CGS 21680) caused no change. The concentration-response curve of CPA was shifted to the right by the A -antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX 10 nM; pKd 9.1) but, like the concentration-response curve of adenosine, hardly affected by the P2-receptor antagonist cibacron blue 3GA (30 microM). Combined administration of a high concentration of DPCPX (1 microM) and 8-phenyltheophylline (10 microM) abolished the effects of CPA and NECA. The concentration-response curves of ATP and ADPbetaS were shifted to the right by both DPCPX (10 nM; pKd 8.7 and 8.9, respectively) and cibacron blue 3GA (30 microM; pKd 5.0 and 5.2, respectively). The antagonist effects of DPCPX (10 nM) and cibacron blue 3GA (30 microM) against ATP were additive in a manner compatible with the blockade of two separate receptors for ATP. In the presence of the high concentration of DPCPX (1 microM) and 8-phenyltheophylline (10 microM), ATP and ADPbetaS still decreased evoked tritium overflow, and this decrease was attenuated by additional administration of cibacron blue 3GA (30 microM). The P2-antagonists cibacron blue 3GA, reactive blue 2, reactive red 2, and to a limited extent also suramin and 8-(3,5-dinitro-phenylenecarbonylimino)- 1,3,5-naphthalenetrisulphonate (XAMR0721), increased the evoked overflow of tritium by up to 114%. Pyridoxalphosphate-6-azophenyl-2',4'-disulphonate (PPADS) caused no change. The results indicate that the postganglionic sympathetic axons of the rat pancreas possess A1-adenosine and P2-receptors. Both receptors mediate an inhibition of noradrenaline release. The presynaptic P2-receptors are activated by an endogenous ligand, presumably ATP, during appropriate trains of action potentials. This is the first demonstration of presynaptic P2-receptors at postganglionic sympathetic neurons that are located in prevertebral ganglia.

Ulnar nerve compression in Guyon's canal due to a haemangioma of the ulnar artery

A case of ulnar nerve compression in Guyon’s canal due to a haemangioma of the ulnar artery is reported.

X-chromosomal (p21) muscular dystrophy and left ventricular diastolic and systolic function

In order to screen for cardiac abnormalities, we prospectively studied 15 patients (age 8-25 years, mean 15.5 years) with Duchenne's (DMD) (n = 9) and Becker's (BMD) (n = 6) muscular dystrophy using the echocardiogram. Data were compared to a control group of 92 healthy individuals (age 7.9-25 years, mean 14.3 years). Left ventricular filling in diastole showed a different pattern when comparing echocardiographic Doppler results in patients and controls: Patients had lower peak velocity of early left ventricular diastolic filling (E-vmax)(P < 0.0001) and smaller time velocity integral of the E-wave (E-tvi)(P < 0.0001). In contrast, the atrial component (A-vmax, A-tvi) of diastolic filling in DMD/ BMD showed no significant difference to controls. The mean area of the mitral valve orifice was significantly larger in patients (P < 0.0001) without presence of mitral regurgitation. Systolic left ventricular function was significantly impaired in the DMD/BMD group; we found lower heart rate corrected fiber shortening velocity VCFc (P < 0.001) and higher peak systolic wall stress (P < 0.001) in DMD/BMD. In 8 of 15 patients, peak systolic wall stress was above 95th percentile of controls. In 6 of 15 patients, VCFc was lower than the 5th percentile of controls. Systolic and diastolic myocardial impairment was found even in young patients and at low stages of disability--equally among patients with DMD or BMD. Diastolic left ventricular impairment predominantly affected the early diastolic filling, but atrial compensation was poor. Peak systolic wall stress measurements were particularly useful in patients with CMP, reflecting the left ventricular afterload.

The excitation of NMR transitions by the current in a sample and the proposals for its detection

A new magnetic resonance technique for investigating conducting samples is described. NMR transitions are excited by the magnetic field of alternating current which flows across the sample. The dissipation of the energy caused by NMR transitions results in a change of the impedance of the sample. The NMR signal is detected as an associated change of the voltage drop across a sample while passing through the resonance region. It is predicted that the resonance can be detected by state-of-the-art low-noise superconducting quantum interference device (SQUID)-based NMR spectrometers. The method is believed to be useful for investigations of small-volume samples which are inaccessible by other NMR techniques.

Importance of the serovar-specific plasmid for virulence of salmonella strains in calves

To evaluate the influence of serovar-specific plasmids on salmonella virulence in calves, experiments were performed involving infection, by the oral route, with mixtures of strains containing equal counts of a plasmid-carrying and a plasmid-free strain of the same serovar. The concentration ratio between the plasmid-carrying and the plasmid-free strain which had developed in the organs of the infected animals was used for a comparative evaluation of virulence and pathogenetic behaviour of the strains. While in the S. typhimurium strains studied, the presence of the plasmid was accompanied by a significantly increased colonization and multiplication of the agent in the host's body, examination of S. enteritidis and S. dublin revealed that the plasmid-free strains exhibited identical or even significantly higher bacterial counts than the plasmid-carrying strains in organs. The fact that plasmid-free salmonella strains with a high virulence for calves have been found demonstrates that the presence of a serovar-specific plasmid is not an indispensable requirement for the development of salmonellosis in calves.

P2-receptor-mediated inhibition of serotonin release in the rat brain cortex

The possibility of a P2-receptor-mediated modulation of the release of serotonin in the rat brain cortex was investigated in occipito-parietal slices preincubated with [3H]serotonin and then superfused and stimulated electrically (10 pulses, 1 Hz). Adenosine receptor agonists decreased the stimulation-evoked overflow of tritium at best slightly; the selective A1 agonist N6-cyclopentyl-adenosine caused no change. Several nucleotides had more marked effects: ATP (3-1000 microM), adenosine-5'-O-(3-thiotriphosphate) (3-300 microM) and P1,P5-di(adenosine-5')-pentaphosphate (3-300 microM) decreased the evoked overflow by up to ca 35%. AMP, alpha,beta-methylene-ATP and UTP produced smaller decreases and 2-methylthio-ATP and UMP caused no change. The inhibition by ATP was attenuated both by the P1-receptor antagonist 8-(p-sulphophenyl)-theophylline (100 microM) and by the P2-receptor antagonist suramin (300 microM) but was not changed by indomethacin (10 microM) and NG-nitro-L-arginine (10 microM). We conclude that the release of serotonin in the rat brain cortex is inhibited through presynaptic P1-receptors (which are not A1) as well as P2-receptors. Inhibition of release via P2-receptors has been previously shown for noradrenaline (brain cortex and hippocampus) and dopamine (neostriatum) and, hence, may be widespread. Differences between transmitter systems exist, however, in the degree of their sensitivity to presynaptic P2-receptor-mediated modulation.

[In vitro transfer of genes in spinal tissue]

INTRODUCTION

It is well known that cytokines are involved in the induction of intervertebral disc and articular cartilage destruction. Therapeutic proteins are of great potential as locally produced drugs after transfer of their cognate genes to the sites of interest.

METHODS

Chondrocytic cells from bovine os coccygis and discal chondrocytes from 6 wistar rats were isolated and cultured in vitro. The bacterial beta-galactosidase (LacZ) gene and the cDNA of the human interleukin-1 receptor antagonist (IL-1ra) were introduced into the cells by retrovirus mediated gene transfer. LacZ activity was determined by Xgal staining, IL-1ra protein was determined by ELISA.

RESULTS

Our study confirms that isolation and cultivation of bovine chondrocytic end plate cells and of rat discal cells in possible. Transfer of both LacZ and of the IL-1ra cDNA to cultured cells was successfull.

DISCUSSION

The introduction of exogenous therapeutical genes into cells from the intervertebral disc and the end plate opens the possibility for a local gene therapy of IVD degeneration. This therapy has the potential to be specific, effective and appropriate to the chronicity of the disease.

Identification of 2,5-dimethyl-4-hydroxy-3[2H]-furanone beta-D-glucuronide as the major metabolite of a strawberry flavour constituent in humans

2,5-Dimethyl-4-hydroxy-3[2H]furanone (Furaneol, DMHF) [3658-77-3], an important flavour constituent of strawberry fruit, was administered to four male and two female volunteers using fresh strawberries as a natural DMHF source. The amount excreted was determined by measuring urinary levels of DMHF and DMHF glucuronide. DMHF glucuronide was synthesized and the structure elucidated by mens of 1H, 13C and two dimensional nuclear magnetic resonance, as well as mass spectral data. Identification and quantification of DMHF glucuronide in human urine were achieved after solid phase extraction on XAD-2 using reverse-phase reverse-phase HPLC with either on-line UV/VIS or electrospray tandem mass spectrometry detection. Male and female volunteers excreted 59-69% and 81-94%, respectively, of the DMHF dose (total of free and glycosidically bound DMHF in strawberries) as DMHF glucuronide in urine within 24 hr. The amount of DMHF excretion was independent of the dose size and the ratio of free to glycosidically bound forms of DMHF in strawberry fruit. DMHF, DMHF glucoside and its 6'-O-malonyl derivative, naturally occurring in strawberries, were not detected in human urine.

P2-receptor-mediated inhibition of noradrenaline release in the rat hippocampus

Experiments on hippocampal slices were carried out in order to find out whether the release of noradrenaline in the hippocampus can be modulated through P2-receptors. The slices were preincubated with [3H]-noradrenaline, superfused with medium containing desipramine (1 microM), and stimulated electrically, in most experiments by 4 pulses/100 Hz. The adenosine A1-receptor agonist N6-cyclopentyl-adenosine (CPA) and the nucleotides ATP, adenosine-5'-O-(3-thiotriphosphate) (ATP gamma S) and adenosine-5'-O-(2-thiodiphosphate) (ADP beta S) decreased the evoked overflow of tritium by up to 55%. The adenosine A2a-agonist 2-p-(2-carboxyethyl)-phenethylamino-5'-N-ethylcarboxamido-adenosin e (CGS 21680; 0.003-0.3 microM) caused no change. The concentration-response curve of CPA was shifted to the right by the A1-antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; 3 nM) but not by the P2-receptor antagonists cibacron blue 3GA (30 microM) and reactive blue 2 (30 microM); the apparent pKB value of DPCPX against CPA was 9.0. In contrast, the concentration-response curve of ATP was shifted to the right by DPCPX (3 nM), apparent pKB 8.7, as well as by cibacron blue 3GA (30 microM), apparent pKB 5.2, and reactive blue 2 (30 microM), apparent pKB 5.6; the antagonist effects of DPCPX and cibacron blue 3GA were additive in a manner compatible with the blockade of two separate receptors for ATP. The same pattern was obtained with ATP gamma S: its concentration-response curve was shifted to the right by DPCPX as well as by cibacron blue 3GA and reactive blue 2. Suramin (300 microM) antagonized neither the effect of ATP nor that of ATP gamma S. The 5'-nucleotidase inhibitor alpha, beta-methylene-ADP (100 microM) did not change the effect of ATP. Only cibacron blue 3GA (30 microM) but not reactive blue 2 (30 microM), given alone, consistently caused a small increase of the evoked overflow of tritium. Hippocampal slices degraded exogenous ATP, and this degradation was reduced by cibacron blue 3GA (30 microM), reactive blue 2 (30 microM) and suramin (300 microM). The results indicate that the noradrenergic terminal axons of the rat hippocampus possess P2-receptors in addition to the known A1-adenosine receptors. The presynaptic P2-receptors mediate an inhibition of noradrenaline release, are activated by nucleotides but not nucleosides, and are blocked by cibacron blue 3GA and reactive blue 2. ATP and ATP gamma S act at both the A1- and the P2-receptors. An autoreceptor function of cerebral presynaptic P2-receptors remains doubtful.

Magnetocardiography and 32-lead potential mapping: repolarization in normal subjects during pharmacologically induced stress

Signals from 37 magnetocardiographic sensors and simultaneously recorded 32 ECG leads were obtained in three healthy male subjects (including two reinvestigations). After recordings at rest, the heart rate was increased by pharmacologic stress (117 to 142 beats/min). Comparison of the repolarization of rest and stress showed substantial changes in the magnetocardiogram (MCG) up to T wave inversions during stress. In the ECG only junctional ST-T segment shifts were present. For quantification, correlation coefficients between pairs of rest and stress MCG and rest and stress ECG distributions were calculated for the same time instant at the beginning of T wave under rest and stress conditions. In addition, equivalent electrical current dipole moment and magnetic dipole moment vectors were calculated from the MCG, and their change from rest to stress evaluated. Correlation coefficients for MCG comparison ranged from 0.3 to 0.5; ECG comparison suggested much less change from stress, ranging from 0.7 to 1.0. Current dipole moment changes at T wave onset were marginal; in contrast, the magnetic dipole moment changed substantially. Since the magnetic dipole reflects vortex currents, changes in its intensity and/or orientation during repolarization suggest this as the biophysical basis of the striking difference in the response of the MCG and ECG to pharmacologic stress. Normal ECG findings at rest and under stress in healthy subjects support the conclusion that the repolarization changes in the MCG were of nonpathologic origin.

Circulatory changes after surfactant bolus instillation in lung-lavaged adult rabbits

Following surfactant instillation in infants treated for respiratory distress syndrome, a mean arterial blood pressure (MABP) decrease is often observed. Its etiology and pathogenesis are still unknown. In this study various circulatory parameters were recorded continuously after surfactant instillation to elucidate the role of pulmonary vascular resistance as one possible cause for the MABP drop. Seven anesthetized adult New Zealand white rabbits were artificially ventilated after tracheotomy. Arterial and right atrial pressure were recorded continuously. Pulmonary artery pressure and cardiac output were determined by means of a thermodilution catheter. After inducing surfactant deficiency by repeated saline lavages, 200 mg/kg body weight of a natural surfactant preparation was administered by tracheal bolus instillation. PaO2 increased rapidly from 8.0 +/- 1.3 kPa to 51.2 +/- 8.8 kPa (mean +/- standard deviation) within 2 min (p < .05). MABP dropped from 12.1 +/- 1.9 kPa to 8.9 +/- 2.3 kPa within 2 min (p < .05). Pulmonary artery pressure, cardiac output, and right atrial pressure did not change during the observation period of 60 min. The results suggest that a peripheral vasodilatation is the most likely cause for the drop in MABP.