Coexistence of peptides with classical neurotransmitters

In the present article the fact is emphasized that neuropeptides often are located in the same neurons as classical transmitters such as acetylcholine, 5-hydroxy-tryptamine, catecholamines, gamma-aminobutyric acid (GABA) etc. This raises the possibility that neurons produce, store and release more than one messenger molecule. The exact functional role of such coexisting peptides is often difficult to evaluate, especially in the central nervous system. In the periphery some studies indicate apparently meaningful interactions of different types with the classical transmitter, but other types of actions including trophic effects have been observed. More recently it has been shown that some neurons contain more than one classical transmitter, e.g. 5-HT plus GABA, further underlining the view that transfer of information across synapses may be more complex than perhaps hitherto assumed.     

Nervous control of smooth muscle by transmitters,cotransmitters and modulators

Conclusion The part played by peripheral neuroeffector control mechanisms has been underestimated. These are additional to central and ganglionic control mechanisms and are much more elaborate than originally thought. While the classical view is that the autonomic nervous system consists largely of antagonistic cholinergic and adrenergic nerves, about sixteen putative neurotransmitters have been proposed in autonomic nerves in the past few years, including various monoamines, polypeptides, purines and amino acids. Modulatory transmitter mechanisms have also been recognized, including prejunctional inhibition or enhancement of transmitter release, postjunctional modulation of transmitter action, and the secondary involvement of locally synthesized hormones and prostaglandins. The existence of more than one transmitter substance in some nerves is now widely recognized, and suggestions have been made about the ways that this can lead to differential peripheral control mechanisms at nerve terminals themselves. The cotransmitters always have synergistic actions on postjunctional effector cells, but two different operating mechanisms are postulated. 1) If both substances are stored in the same vesicles (for example, ACh or NA with ATP), release is closely parallel at all impulse frequencies. Upon release, the cotransmitter, in addition to having a direct action on postjunctional cells, may facilitate the action of the other transmitter and/or act as an inhibitor of its release. Differential actions at different impulse frequencies are achieved post-junctionally by ATP and NA acting via EJP-spike and spike-independent mechanisms, respectively. 2) If the two substances are stored in separate vesicle types (for example ACh or NA with some peptides), then differential release is possible at different impulse frequencies; the peptides released at higher frequencies modulate the role of the classical transmitter, by both prejunctional enhancement of its release and post-junctional facilitation of its action.     

Cephalopod myocardial receptors: Pharmacological studies on the isolated heart ofSepia officinalis (L.)

Summary This paper presents a synopsis of the information available about the pharmacological action of various substances on the cephalopod heart, with special emphasis on the central heart ofSepia officinalis. Threshold concentrations, EC₅₀ values and maximum effective concentrations have been experimentally determined. Studies with various transmitter substances, analogous compounds and antagonists have led to the following picture: Acetylcholine is the natural inhibitory transmitter substance; it acts via receptors with nicotinic properties which can be blocked by d-tubocurarine and -bungarotoxin. The probable excitatory transmitter system is represented by a noradrenergic innervation. Noradrenaline has a positive inotropic and a positive chronotropic action on in vitro heart preparations. A positive inotropic response can also be evoked by serotonin (5-HT); this effect is not due to stimulation of the catecholamine receptor, as is shown by cross-over experiments with specific blocking agents. Furthermore, a peptidergic receptor system has been described which reacts with the molluscan cardioactive peptide FMRF amide most effectively. It is assumed that cardioactive peptides may reach the central heart in the circulating blood; the sites of synthesis and release are still unknown. Possibly the NSV-layer of the vena cava is involved in hormonal cardiovascular regulation processes.     

Blocking by picrotoxin of nigra-evoked inhibition of neurons of ventromedial nucleus of the thalamus

Summary The transmitter substance released by nigro-thalamic fibres is proposed to be -aminobutyric acid, since picrotoxin blocked nigra-evoked monosynaptic inhibition of thalamic neurons.Supported by grants Nos 212009 and 311410 from Ministry of Education of Japan.The authors wish to thank Dr Marjorie Anderson, University of Washington, Seattle, for improving the English.     

Inhibition by tetanus and botulinum A toxin of the release of [3H]noradrenaline and [3H]GABA from rat brain homogenate

Summary Rat brain homogenate was preloaded with [³H]noradrenaline or [³H]GABA and stimulated with high K⁺. Tetanus toxin and botulinum A neurotoxin partially prevent the evoked [³H]noradrenaline release in the same range of toxin concentrations starting below 10^–10M. In contrast, release of -amino butyric acid (GABA) is much more sensitive to tetanus than to botulinum A toxin.     

GABAergic inhibition of neurons in the ventral tegmental area.

Stimulation of the nucleus accumbens evokes a potent inhibition in neurons of the ventral tegmental area. GABA is likely to act as a transmitter in this descending inhibitory system.     

GABAergic inhibition of neurons in the ventral tegmental area

Summary Stimulation of the nucleus accumbens evokes a potent inhibition in neurons of the ventral tegmental area. GABA is likely to act as a transmitter in this descending inhibitory system.     

The use of 5-fluorocytosine and ketoconazole in the culture of the erythrocytic stages ofPlasmodium falciparum and some tumor cell lines

Summary In vitro culture systems are often contaminated by bacteria and fungi. It is therefore often necessary to supplement culture media with agents such as penicillin/streptomycin, gentamycin or amphotericin B. The latter cannot be used in the in vitro culture of erythrocytic stages ofP. falciparum, and thus anti-fungal agents have not been regularly used in this system. We describe the prophylactic use of 5-fluorocytosine (5-FC) and ketoconazole (KTZ) in tissue cultures at concentrations up to 300 and 10 g/ml respectively which have no effect on the growth ofP. falciparum (FCR-3 strain). A melanoma cell line (C32) and a line of uterine carcinoma (C41) were also unaffected by similar concentrations of 5-FC and KTZ. When dissolved in complete culture medium (RPMI 1640) with 10% human plasma, the minimum inhibitory concentration of 5-FC for a susceptible strain ofCandida remained below 2 g/ml. These experiments suggest that 5-FC (at 50 g/ml) alone or in combination with KTZ (at 1 g/ml) is a useful addition to the armamentarium of antimicrobials available to the tissue culture biologist for a variety of cell culture systems.     

Polarity of meiotic gene conversion in fungi: Contrasting views

The frequency of meiotic gene conversion often varies linearly from one end of the gene to the other. This phenomenon has been called polarity. In this review, we will primarily discuss studies of polarity that have been done in the yeastSaccharomyces cerevisiae (ARG4 and HIS4 loci) and inAscobolus (b2 locus) with an emphasis on possible mechanisms. The genetic and physical data obtained at these hotspots of recombination strongly suggests that the formation of a polarity gradient reflects both the frequency of heteroduplex formation and the processing of this recombination intermediate by mismatch-repair-dependent processes.This article is dedicated to the memory of Seymour Fogel.     

Bovine microvascular endothelial cells of separate morphology differ in growth and response to the action of interferon-γ

Five cell types recently isolated from the bovine corpus luteum differed in their epithelioid morphology and their cytoskeleton, but shared common criteria of microvascular endothelial cells^1,2. To give strong evidence for the separate entity, the growth rate of the 5 phenotypically different cells was studied. They were seeded at low density on day 0. Most of these cells were treated with 200 to 1000 U recombinant bovine interferon- (IFN-) for 3 days. The untreated remainder served as controls. Cell counts were made for all cultures on days 4, 7, 10 and 13. morphology: 13 d after treatment with IFN- senescent cells as well as intact cells occurred in cultures of cell types 1 to 4. Cultures of cell type 5 were apparently unchanged and resembled their untreated counterparts. Desminpositive cells in cultures of cell type 2 developed cell processes. Growth rate: In the absence of IFN-, the growth rate was high for cell types 3 and 4, moderate for cell type 1, and low for cell types 2 and 5. The presence of IFN- caused anti-proliferative effects. These were higher for cell types 3 and 4 than for cell types 1 and 2. IFN- could be cytotoxic on cell type 3. In contrast, the cytokine tended to support the cell growth of cell type 5. These findings substantiate the postulate that endothelial cells exhibiting separate morphology in culture also function differently.     

Reserpin und γ-Aminobuttersäuregehalt des Gehirns

Summary 1. In mice,reserpine (5 mg/kg) causes a long-lasting depletion of the brain for -aminobutyric acid (GABA), which corresponds temporally to the lowered seizure threshold (electroshock).2.Iproniazid prohibits both the depletion of GABA and the lowering of seizure threshold.3. Relations between amine- and GABA-metabolism of the brain are pointed out.     

Neural stem cells in Parkinson’s disease: a role for neurogenesis defects in onset and progression

Parkinson’s disease (PD) is the second most common neurodegenerative disorder, leading to a variety of motor and non-motor symptoms. Interestingly, non-motor symptoms often appear a decade or more before the first signs of motor symptoms. Some of these non-motor symptoms are remarkably similar to those observed in cases of impaired neurogenesis and several PD-related genes have been shown to play a role in embryonic or adult neurogenesis. Indeed, animal models deficient in Nurr1, Pitx3, SNCA and PINK1 display deregulated embryonic neurogenesis and LRRK2 and VPS35 have been implicated in neuronal development-related processes such as Wnt/β-catenin signaling and neurite outgrowth. Moreover, adult neurogenesis is affected in both PD patients and PD animal models and is regulated by dopamine and dopaminergic (DA) receptors, by chronic neuroinflammation, such as that observed in PD, and by differential expression of wild-type or mutant forms of PD-related genes. Indeed, an increasing number of in vivo studies demonstrate a role for SNCA and LRRK2 in adult neurogenesis and in the generation and maintenance of DA neurons. Finally, the roles of PD-related genes, SNCA, LRRK2, VPS35, Parkin, PINK1 and DJ-1 have been studied in NSCs, progenitor cells and induced pluripotent stem cells, demonstrating a role for some of these genes in stem/progenitor cell proliferation and maintenance. Together, these studies strongly suggest a link between deregulated neurogenesis and the onset and progression of PD and present strong evidence that, in addition to a neurodegenerative disorder, PD can also be regarded as a developmental disorder.     

Activité tuberculostatique de thiouréesortho- etméta-substituées

Summary A large number of substituted thioureas and related compounds, the molecular structure of which diverges more or less from that of the classical 4-4-disubstituted thiocarbanilides, have been tested forin-vitro tuberculostatic activity; many of them have proved effective at a concentration of 10^–5.     

Redefining tumour suppressor genes: exceptions to the two-hit hypothesis

Knudsons two-hit model of tumour suppressor genes supposes that two mutations are required to cause a tumour, one occurring in each of the two alleles of the gene. Many such cancer genes exhibiting biallelic disruption and truncating point mutations have been identified, revealing the success of the model. Despite changes in our concept of cancer genes, two inactivating point mutations are still considered the hallmark of tumour suppressor genes. Recently, however, more and more reports describe candidate tumour suppressors that do not conform to this standard definition, including haploinsufficient genes requiring inactivation of only one allele, and genes inactivated not by mutation but rather epigenetic hypermethylation. This review describes some of these exceptions and proposes a revised tumour suppressor gene definition to facilitate the identification of this new generation of tumour suppressor loci.Received 21 January 2003; received after revision 26 March 2003; accepted 1 April 2003     

The detection of fraud and fakery

Summary Fraud is often found in science, especially in what is termed, fringe science. There are several reasons why scientists should be aware of the fact that they, too, can be deceived, both by subjects in experiments and by themselves. The will to believe is strong even among hard-headed academics, and is often the factor that causes them to publish results that do not stand up to subsequent examination and/or attempts to replicate. In some cases, scientists would be well advised to consult with such experts as conjurors, when skilled frauds are in a position to mislead them.     

Action ofβ-(4-chlorophenyl-GABA) on uptake and metabolism of GABA in different subcellular fractions of rat brain

Summary -(4-chlorophenyl)-GABA, a GABA mimetic compound, acts as an inhibitor of GABA metabolism in both synaptosomal and extrasynaptosomal compartments. It has no significant action on GABA or Glu uptake by synaptosomes.     

The mensuration of quadrilaterals and the generation of Pythagorean triads: A mathematical,heuristical and historical study with special reference to Brahmagupta's rules

Summary The ancient rule for the area of a quadrilateral, , is examined to show its inaccuracy and its arbitrariness, and in order to see how those using it might have become aware of its shortcomings. Consideration ofBrahmagupta's vastly more sophisticated rule, , and of the Hindu schedule of recognized quadrilateral types, leads to the question of the proper assessment to be made of this strand of Indian mathematics. The work on quadrilaterals was intimately connected with the generation of Pythagorean triangles out ofbja (=seed) numbers by the same method as had probably been used by the mathematicians of Old Babylonia. Ways in which this procedure could have arisen by induction from particular numerical calculation are shown and the rest of the study consists primarily of an investigation as to whether the same kind of approach might not also have been used to obtain the remarkable rules on quadrilaterals given byBrahmagupta. It is found that there is no compelling need to adopt the common assumption thatBrahmagupta must have had access to Alexandrian mathematics. But even if he did chance to learn of some helpful items from the works ofHero orPtolemy, it still seems necessary for a proper appreciation of his understanding of the mensuration of quadrilaterals to suppose that he would have worked such items into the contemporary Indian mathematical context in some such way as is indicated here. In particular, it is argued thatBrahmagupta, far from indulging in reckless generalization, could well have proceeded with great caution, from one amenable type of quadrilateral to another, verifying his inductions by comparing them with results given by alternative calculation methods.     

Neuroprotective effects of the gliopeptide ODN in an in vivo model of Parkinson’s disease

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by a progressive loss of dopamine (DA) neurons through apoptotic, inflammatory and oxidative stress mechanisms. The octadecaneuropeptide (ODN) is a diazepam-binding inhibitor (DBI)-derived peptide, expressed by astrocytes, which protects neurons against oxidative cell damages and apoptosis in an in vitro model of PD. The present study reveals that a single intracerebroventricular injection of 10 ng ODN 1 h after the last administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) prevented the degeneration of DA neurons induced by the toxin in the substantia nigra pars compacta of mice, 7 days after treatment. ODN-mediated neuroprotection was associated with a reduction of the number of glial fibrillary acidic protein-positive reactive astrocytes and a strong inhibition of the expression of pro-inflammatory genes such as interleukins 1β and 6, and tumor necrosis factor-α. Moreover, ODN blocked the inhibition of the anti-apoptotic gene Bcl-2, and the stimulation of the pro-apoptotic genes Bax and caspase-3, induced by MPTP in the substantia nigra pars compacta. ODN also decreased or even in some cases abolished MPTP-induced oxidative damages, overproduction of reactive oxygen species and accumulation of lipid oxidation products in DA neurons. Furthermore, DBI knockout mice appeared to be more vulnerable than wild-type animals to MPTP neurotoxicity. Taken together, these results show that the gliopeptide ODN exerts a potent neuroprotective effect against MPTP-induced degeneration of nigrostriatal DA neurons in mice, through mechanisms involving downregulation of neuroinflammatory, oxidative and apoptotic processes. ODN may, thus, reduce neuronal damages in PD and other cerebral injuries involving oxidative neurodegeneration.     

Using genetically-defined rodent strains for the identification of hippocampal traits relevant for two-way avoidance behavior: a non-invasive approach

Summary Genetically-defined rodent strains permit the identification of hippocampal traits which are of functional relevance for the performance of two-way avoidance behavior. This is exemplified here by analyzing the relationship between infrapyramidal mossy fibers (a tiny projection terminating upon the basal dendrites of hippocampal pyramidal neurons) and two-way avoidance learning in about 800 animals. The necessary steps include 1) identification of structural traits sensitive to selective breeding for extremes in two-way avoidance, 2) testing the robustness of the associations found by studying individual and genetical correlations between hippocampal traits and behavior, 3) establishing causal relationships by Mendelian crossing of strains with extreme structural traits and studying the behavioral consequences of such structural randomization, 4) confirming causal relationships by manipulating the structural variable in inbred (isogenic) strains, thereby eliminating the possibility of genetic linkage, and 5) ruling out the possibility of spurious associations by studying the correlations between the hippocampal trait and other behaviors known to depend on hippocampal functioning.In comparison with the classical lesion approach for identifying relationships between brain and behavior, the present procedure appears to be superior in two aspects: it is non-invasive, and it focuses automatically on those brain traits which are used by natural selection to shape behaviorally-defined animal populations, i.e., it reveals the natural regulators of behavior.     

Snake venom action: Are enzymes involved in it?

Summary Enzymes were the first clearly recognized components of snake venoms. When several more were discovered, attempts were made to correlate venom action with enzymic functions. The last few years have seen most successful efforts in the identification, isolation and structural elucidation of highly toxic polypeptides present in snake venoms, in particular of neurotoxins and membrane-active toxins. Following this development the polypeptides were called the true toxic components and the enzymes lost their previous central position in venom pharmacology. The time, therefore, has come to re-evaluate the role of enzymes in the complex interaction between snake and prey. While highly active polypeptides indeed dominate the action of hydrophiid venoms, they appear to play a lesser role in crotalid venom action as compared with enzyme components. Enzymes are involved in many levels of venom action, e. g. by serving as spreading factors, of by producing very active agents, such as bradykinin and lysolecithins in tissues of preys or predators. Some toxins, e. g. the membrane-active polypeptides appear to participate in the interaction between membrane phospholipids and venom phospholipases. The classical neurotoxin, -bungarotoxin, has been recognized as a powerful phospholipase. Several instances are known which indicate that some enzymes potentiate the toxic action of others; the analysis of a single enzyme may, therefore, not fully reveal its biofunction. For 3 enzymes, ophidianl-amino acid oxidase, ATPpyrophosphatase, and acetylcholinesterase, some of the problems pertaining to venom toxicity are discussed.