Serotonergic modulation of neurotransmission in the rat subicular cortex in vitro: a role for 5-HT1B receptors

Summary We have studied the effect of serotonin on synaptic transmission in rat hippocampal subiculum slices. Electrical stimulation of the alveus induced a field potential in the subiculum. The non-NMDA glutamate receptor antagonist, NBQX (3 × 10^–6 mol/l) suppressed the response by 78%, indicating that the signal involves glutamatergic neurons. Application of serotonin suppressed (EC₅₀ = 3.6 × 10^–6 mol/l) the amplitude of he evoked potentials in a reversible, concentration-dependent manner. The responses to 5-HT were not altered after pretreatment with the 5-HT uptake blocker, fluvoxamine (10^–5 mol/l) or a combination of the MAO inhibitor pargyline (10^–5 mol/l) and ascorbic acid (10^–4 mol/l). The responses to 5-HT were also unaffected by pretreatment with the 5-HT_1A selective antagonist NAN-190 (10^–6 mol/l), the 5-HT_2A antagonist ketanserin (10^–6 mol/l) or the 5-HT₃/5-HT₄ antagonist ICS 205–930 (10^–6 mol/l).The 5-HT_1B selective agonist CP 93,129 mimicked the effects of serotonin, but was more potent (EC₅₀ 4.1 × 10^–7 mol/l). The 5-HT_1B receptor antagonist, (±)21-009 (3 × 10^–7 mol/l), antagonized the response to 5-HT and CP 93,129 with a pK_B value of 7.1 and 7.2, respectively. These results suggest that the effect of 5-HT in the rat subiculum is mediated by 5-HT_1B receptors.Correspondence to: H.W.G.M. Boddeke at the above address     

The Protein Expression of Bcl-2, Bax, Fas/Apo-1 in Acute Myeloid Leukemia

Homeostasisof11ematopoiesisiscontrollednotoillybytheproliferationanddifferentiationofcells,butalsobycelldeath.Inadditiontolossofcontrolofcellproliferation,disruptionofapoptosis--inducedf[lnctionalsocontributestotumordevelopment.Althoughdiversesignalscaninduceapoptosisinawidevarietyofcelltypes,anumberofevolutionarilyconservedgenesregulateafinalcommoncelldeathpathway,thatisconservedinmanyspeciesfromwormstohumansll].Thehcf--2proto--oncogeneisoneofthecrucialapoptosisantagonizinggenes.Highlevelofhc…     

Altered neuropeptide Y Y1 responses in mesenteric arteries in rats with congestive heart failure

The aim of the present study was to elucidate if the potentiating effect of neuropeptide Y on various vasoactive agents in vitro is (1) altered in mesenteric arteries from rats with congestive heart failure and (2) mediated by the neuropeptide Y Y₁ receptor. The direct vascular effects of neuropeptide Y and its modulating effects on the contractions induced by endothelin-1-, noradrenaline-, 5-hydroxytryptamine (5-HT)-, U46619-(9, 11-dideoxy-11, 9-epoxymethano-prostaglandin F₂) and ATP, and acetylcholine-induced dilatations were studied in the presence and absence of the neuropeptide Y Y₁ antagonist, BIBP3226 (BIBP3226{(R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]- -arginine-amide}). Neuropeptide Y, per se, had no vasoactive effect in the arteries. The potency of endothelin-1 was significantly decreased in congestive heart failure rats. Neuropeptide Y and neuropeptide Y-(13–36) potentiated the endothelin-1-induced contraction in congestive heart failure mesenteric arteries. In 20% of the congestive heart failure rats, sarafotoxin 6c induced a contraction of 31±4%. Neuropeptide Y also potentiated U46619- and noradrenaline-induced contractions but not 5-HT-induced contractions in congestive heart failure arteries. In sham-operated animals neuropeptide Y potentiated noradrenaline- and 5-HT-induced contractions. These potentiations were inhibited by BIBP3226. Acetylcholine induced an equipotent relaxation in both groups which was unaffected by neuropeptide Y. In conclusion, neuropeptide Y responses are altered in congestive heart failure rats. The potentiating effect differs between vasoactive substances. Neuropeptide Y Y₁ and non-neuropeptide Y₁ receptors are involved.     

A single gene copy merozoite surface antigen and immune evasion?

During the course of chronic malaria infection antigenic variants of a parasite antigen are expressed and exposed on the surface of infected erythrocyte membranes. There also exists a number of apparently invariant single gene copy blood-stage antigens, exposed or non-exposed, which have been shown to afford immunity under experimental conditions. To determine why the host, presented with invariant 'protective' antigens, is unable to control infections effectively, immunity to a representative single gene copy antigen, the merozoite surface protein 1 (MSP1) was investigated in Plasmodium chabaudi chabaudi AS, a murine model of chronic malaria. Immunization with monoclonal antibody affinity purified native MSP1 resulted in enhanced control of parasitaemia on challenge, irrespective of the parasite inoculum size; challenge with a single parasite, however, suggested that expansion of resistant parasite subpopulations was not occurring. Challenge of mice immunized with recombinant fusion proteins encoding N- or C-terminal regions of the P.c. chabaudi AS MSP1 produced inconsistent effects, often parasitaemias were indistingishable from controls despite significant anti-MSP1 antibody responses. The not unlikely contamination of MSP1 native preparations with erythrocyte (E) components was considered. Immunization with a mixture of the MSP1 C-terminus recombinant polypeptide and a Triton X-100 solubilized lysate of normal E resulted in enhanced control of parasitaemia, however, no effect was seen after administration of either component on its own. Co-immunization of E with the N-terminus polypeptide reversed the inhibition seen, on this occasion with this construct alone.     

Superoxide dismutases of muscle in mitochondrial encephalomyopathies

Lmmunohistochemical analyses were made of the superoxide dismutases (Mn-SOD and CuiZn-SOD) in biopsied muscles from 7 patients with mitochondrial encephalomyopathies that included mitochondrial encephalomyopathy, lactic acidosis and strokelike episodes (MELAS), and chronic progressive external ophthalmoplegia (CPEO). Mn-SOD mainly was present in the subsarcolemmal region, but it also was found in a coarsely granular, reticular, or diffuse pattern of staining within the muscle fibers. These Mn-SOD-positive fibers corresponded almost completely to the ragged-red fibers. The immunoreaction for CuiZn-SOD was weakly positive in some of the muscle fibers positive for Mn-SOD. In CPEO, Mn-SOD-positive fibers predominantly showed decreased cytochrome c oxidase (COX) activity. In MELAS, Mn-SOD-positive fibers tended to be stained deeply for COX although a few were COX-negative. These findings suggest that Mn-SOD-positive fibers can be used to make a differential diagnosis between CPEO and MELAS and that in mitochondrial encephalomyopathies Mn-SOD in the raggedred fibers may protect against oxidative stress. © John Wiley & Sons, Inc.     

PET examination of [11C]NNC 687 and [11C]NNC 756 as new radioligands for the D1-dopamine receptor

The benzazepines NNC 687 and NNC 756 have in animal studies been described as selective D₁-dopamine receptor antagonists. Both compounds have been labeled with¹¹C for examination by positron emission tomography (PET). In the present study central receptor binding was studied in monkeys and healthy men. After IV injection of both radioligands in Cynomolgus monkeys radioactivity accumulated markedly in the striatum, a region with a high density of D₁-dopamine receptors. This striatal uptake was displaced by high doses of the selective D₁-antagonist SCH 23390 (2 mg/kg) but not by the 5HT₂-antagonist ketanserin (1.5 mg/kg) or the selective D₂-antagonist raclopride (3 mg/kg). The cortical uptake after injection of [¹¹C]NNC 687 was not reduced in displacement experiments with ketanserin. The cortical uptake of [¹¹C]NNC 756 was reduced in displacement and protection experiments with ketanserin by 24–28% (1.5 mg/kg), whereas no reduction could be demonstrated on striatal uptake. In healthy males both compounds accumulated markedly in the striatum. For [¹¹C]NNC 687 the ratio of radioactivity in the putamen to cerebellum was about 1.5. For [¹¹C]NNC 756 the ratio was about 5. This ratio of 5 for [¹¹C]NNC 756 is the highest obtained so far for PET radioligands for the D₁-dopamine receptor.     

Proteolytic Processing Mechanisms in the Biosynthesis of Neuroendocrine Peptides: The Subtilisin-like Proprotein Convertases

The recent discovery of a novel family of precursor processing endoproteases has greatly accelerated progress in understanding the complex mechanisms underlying the maturation of prohormones, neuropeptides, and many other precursor-derived proteins. At least six members of this family have been found thus far in mammalian species, several having alternatively spliced isoforms, and related enzymes have been identified in many invertebrates, including molluscs, insects, nematodes, and coelenterates. The proprotein convertases are all dependent on calcium for activity and all possess highly conserved subtilisin-like domains with the characteristic catalytic triad of this serine protease (ordered Asp, His, and Ser along the polypeptide chain). Two members of this family, PC2(SPC2) and PC1/PC3(SPC3), appear to play a preeminent role in neuroendocrine precursor processing. Both convertases are expressed only in the brain and in the extended neuroendocrine system, while another important family member—furin/PACE (SPC1)—is expressed more ubiquitously, in almost all tissues, and at high levels in liver. SPC2 and SPC3 exhibit acidic pH optima and other properties which enhance their activity in the acidic, calcium-enriched environment of the dense-core secretory granules of the regulated pathway in neuroendocrine cells, while furin has a neutral pH optimum and is localized predominantly to the trans Golgi network where it is retained by a C-terminal transmembrane domain. Furin processes a wide variety of precursors in the constitutive pathway, such as those of growth factors, receptors, coagulation factors, and viral glycoproteins. Recent findings on the processing of proopiomelanocortin, proinsulin, proglucagon, and several other neuroendocrine precursors by SPC2 and SPC3 are discussed, along with information on the structure, properties, evolution, developmental expression, and regulation or the convertases. An inherited defect in the fat/fat mouse which affects the processing of proinsulin, and probably also many other prohormones, due to a point mutation in carboxypeptidase E has recently been identified and has begun to provide new insights into the functional integration of the individual processing steps.     

Are cytokines possible mediators of cancer cachexia?

The possible role of cytokines in the development of cancer cachexia was reviewed from the literature. Tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, IL-6, interferon (IFN)-gamma and leukemia inhibitory factor (LIF) can elicit many but not all host changes seen in cancer cachexia, including loss of appetite, loss of body weight, and the induction of acute-phase protein synthesis. However, these cytokines are not always demonstrated in the circulation of the cancer patients. The inability to detect circulating cytokines may be due to their low rate of production, their short half-life and rapid clearance from plasma, or their mode of action (autocrine or paracrine). Different cytokines are induced to stimulate the same response. This is very different from hormonal regulation, where a hormone acts on a cell directly through a specific receptor without depending on other mediators. Specific antibodies including anti-IFN-gamma, anti-TNF and anti-IL-6 antibodies, as well as the cyclooxygenase inhibitor indomethacin, have been used to reverse cancer cachexia. Overlapping physiologic activities make it unlikely that a single substance is the sole cause of cancer cachexia. It is hoped that further investigation on other cytokines and their possible relationships with hormones will help to clarify the mechanisms of cancer cachexia in the near future.This work was supported by a grant from the Japan-Sweden Foundation in 1991.     

CYP1A2 activity, gender and smoking, as variables influencing the toxicity of caffeine

We have investigated several factors that might be related to the occurrence of toxic effects during the performance of a urinary test with caffeine (300  mg p.o), in 120 healthy volunteers. A total of 218 toxic effects were self-reported by eighty-two (68%) subjects. Females and nonsmokers were at the highest risk (chi-square test, P =0.01). Furthermore, two nonsmoking females experienced a symptomatology with delirium, restlessness, muscle tremor, vomiting and wakefulness. Among females and nonsmokers, those subjects who experienced toxic effects had lower caffeine N3-demethylation index (CYP1A2 activity) compared with unaffected females (1.87±0.51 vs 1.47±0.27, P <0.0005) and nonsmokers (1.69±0.23 vs 1.49±0.31, P <0.02). Caffeine N1- and N7-demethylations indices were also lower among females ( P <0.0005) and nonsmokers ( P <0.02) who reported toxic symptoms. We conclude that CYP1A2 activity, gender and smoking are variables to be considered as influencing the toxicity of caffeine.     

Immediate ultrastructural effects of endothelin-1 on rabbit basilar artery

Summary In this study intra-arterial Endothelin-1 was applied to rabbit basilar arteries and morphological findings were compared between two groups who were either perfusion fixed or immersion fixed. We planned to establish the quantitative dimension of the drug-induced morphological alterations, independent of the fixation technique's effect.There was an abundance of collagenous fibres deposited among the smooth muscle cells which was not observed in control arteries and after immersion fixation. These degenerative changes are similar to the finding following subarachnoid haemorrhage. The only fixation-related difference was the fact that lamina elastica interna was not corrugated in the perfusion fixation group.It is concluded that, the observed changes in the connective tissue of the arterial wall alter the passive elastic properties and so affect the degree of the response to the vasoactive messengers.