Sensory Spots of Echinoderes capitatus (Zelinka, 1928) (Kinorhyncha,Cyclorhagida)

The sensory spots of Echinoderes capitatus from the Gulf of Trieste were examined by transmission and scanning electron microscopy. Their arrangement is bilaterally symmetrical and is species-specific. At the cuticle surface the sensory spot appears as a rounded to ovoid area of small cuticular papillae in which two pores open. The sensory organ consists of two different sensory cells, the monociliary receptor and the collar receptor, and one sheath cell. The course of the axons and their connections to the nervous system are described. A survey of collar receptors among invertebrates is given. A comparison of the sensory spots within Kinorhyncha and a comparison with the flosculi of Priapulida and the N-flosculi of Loricifera is made. A possible homology of these three structures is discussed.     

Tuning of electron delocalization in polynuclear mixed-valence clusters by super-exchange and double exchange

 Values for the exchange-coupling constant J and the double-exchange parameter B have been estimated for dimeric and hexameric mixed-valence iron clusters. For sulfur-bridged species the range of J values is 300–450 cm^–1, and B values vary between 320 and 400 cm^–1. For an OH-bridged diiron cluster B is as large as 1300 cm^–1. Received and accepted: 23 January 1996     

Hydroxyl Radical-Mediated Oxidation of Serotonin: Potential Insights into the Neurotoxicity of Methamphetamine

Abstract: When incubated with a hydroxyl radical (HO^?)-generating system (ascorbic acid/Fe²⁺-EDTA/O₂/H₂O₂), 5-hydroxytryptamine (5-HT; serotonin) is rapidly oxidized initially to a mixture of 2,5-, 4,5-, and 5,6-dihydroxytryptamine (DHT). The major reaction product is 2,5-DHT, which at physiological pH exists as its keto tautomer, 5-hydroxy-3-ethylamino-2-oxindole (5-HEO). Rapid autoxidation of 4,5-DHT gives tryptamine-4,5-dione (T-4,5-D), which reacts with the C(3)-centered carbanion of 5-HEO to give 3,3′-bis(2-aminoethyl)-5-hydroxy-[3,7′-bi-1H-indole]-2,4′,5′-3H-trione (7). The latter slowly cyclizes to 3′-(2-aminoethyl)-1′,6′,7′,8′-tetrahydro-5-hydroxyspiro[3H-indole-3,9′-[9H]pyrrolo[2,3-f]quinoline]-2,4′,5′(1H)- trione (9). A minor amount of T-4,5-D dimerizes to give 7,7′-bi-(5-hydroxytryptamine-4-one) (7,7′-D). In the presence of GSH, the reaction of T-4,5-D with 5-HEO is diverted and, in the presence of sufficient concentrations of this tripeptide, completely blocked. This is because GSH preferentially reacts with T-4,5-D to give 7-S-glutathionyltryptamine-4,5-dione (11). The results of this investigation suggest that 5,6-DHT, 5-HEO, 7, and 9 are products unique to the HO^?-mediated oxidation of 5-HT. Thus, the observation of other investigators that 5,6-DHT is formed in the brains of rats following a large dose of methamphetamine (MA) suggests that this drug might evoke HO^? formation. However, the present in vitro study indicates that 5,6-DHT is a rather minor, unstable product of the HO^?-mediated oxidation of 5-HT and suggests that detection of 5-HEO, 7/9, and 11 in rat brain following MA administration could provide additional support for HO^? formation. Furthermore, one or more of the intermediates and major products of oxidation of 5-HT by HO^? might, in addition to 5,6-DHT, contribute to the MA-induced degeneration of serotonergic neurons.     

Biochemical and immunocytochemical characterization of monoclonal antibody TOP 35 raised against purified tonoplast from cress root

The vacuolar membrane, the tonoplast, is a proteinrich membranehitherto only few proteins in it have been identified. As anapproach for the identification of tonoplast proteins by monoclonalantibodies (MABs), purified tonoplast from cress roots (Lepidiumsativum L.) were used for immunization and plasma membranesas a control membrane to test the absence of antigen. The MABTOP 35 identified a glycoprotein of about 35 kDa in purifiedtonoplast of cress roots. Triton X-114 phase separation showedthat it was a hydrophobic integral membrane protein. In immunocytochemistrythe MAB TOP 35 strongly labelled the vacuolar membrane. Theabsence of cell wall or plasma membrane labelling by TOP 35indicates a distinct biosynthetic pathway of this protein tothe vacuolar membrane in plants. Key words: Immnocytochemistry, Lepidium sativum, monoclonal antibody, secretion, vacuole     

5-Hydroxy-3-Ethylamino-2-Oxindole Is Not Formed in Rat Brain Following a Neurotoxic Dose of Methamphetamine: Evidence that Methamphetamine Does Not Induce the Hydroxyl Radical-Mediated Oxidation of Serotonin

Abstract: Oxygen radicals have been implicated in the neurodegenerative and other neurobiological effects evoked by methamphetamine (MA) in the brain. It has been reported that shortly after a single large subcutaneous dose of MA to the rat, the serotonergic neurotoxin 5,6-dihydroxytryptamine (5,6-DHT) is formed in the cortex and hippocampus. This somewhat controversial finding suggests that MA potentiates formation of the hydroxyl radical (HO^?) that oxidizes 5-hydroxytryptamine (5-HT) to 5,6-DHT, which, in turn, mediates the degeneration of serotonergic terminals. A major and more stable product of the in vitro HO^?-mediated oxidation of 5-HT is 5-hydroxy-3-ethylamino-2-oxindole (5-HEO). In this investigation, a method based on HPLC with electrochemical detection (HPLC-EC) has been developed that permits measurement of very low levels of 5-HEO in rat brain tissue in the presence of biogenic amine neurotransmitters/metabolites. After intracerebroventricular administration into rat brain, 5-HEO is transformed into a single major, but unknown, metabolite that can be detected by HPLC-EC. One hour after administration of MA (100 mg/kg s.c.) to the rat, massive decrements of 5-HT were observed in all regions of the brain examined (cortex, hippocampus, medulla and pons, midbrain, and striatum). However, 5-HEO, its unidentified metabolite, or 5,6-DHT were not detected as in vivo metabolites of 5-HT. MA administration, in particular to rats pretreated with pargyline, resulted in the formation of low levels of N-acetyl-5-hydroxytryptamine (NAc-5-HT) in all brain regions examined. These results suggest that MA does not potentiate the HO^?-mediated oxidation of 5-HT. Furthermore, the rapid MA-induced decrease of 5-HT might not only be related to oxidative deactivation of tryptophan hydroxylase, as demonstrated by other investigators, but also to the inhibition of tetrahydrobiopterin biosynthesis by NAc-5-HT. The massive decrements of 5-HT evoked by MA are accompanied by small or no corresponding increases in 5-hydroxyindole-3-acetic acid (5-HIAA) levels. This is due, in part, to the relatively rapid clearance of 5-HIAA from the brain and monoamine oxidase (MAO) inhibition by MA. However, the loss of 5-HT without corresponding increases in its metabolites point to other mechanisms that might deplete the neurotransmitter, such as oxidation by superoxide radical anion (O₂^??), a reaction that in vitro does not generate 5-HEO or 5,6-DHT but rather another putative neurotoxin, tryptamine-4,5-dione. One hour after administration, MA evokes large depletions of norepinephrine (NE) throughout the brain but somewhat smaller decrements of dopamine (DA) that are restricted to the nigrostriatal pathway. Furthermore, MA evokes a major shift in the metabolism of both NE and DA from the pathway mediated by MAO to that mediated by catechol-O-methyltransferase. The profound and widespread effects of MA on the noradrenergic system, but more anatomically localized influence on the dopaminergic system, suggests that NE in addition to DA, or unusual metabolites of these neurotransmitters, might play roles in the neurodegenerative effects evoked by this drug.     

Interaction of metabolic inhibitors with actin fibrils

Summary The dependence of the arrangement of fibrillar actin in cultured endothelial cells on metabolic conditions was investigated with cellular elements derived from the heart of Xenopus laevis tadpoles. Either primary culture or an established cell line (XTH-2) were used in these studies The metabolic stage of the cells was influenced by inhibiting respiration and lactate production. The actin pattern was revealed either by indirect immunofluorescence or by tetramethylrhodaminyl (TRITC)-phalloidin fluorescence. Total block of energy supply causes in all cases a distinct loss of actin fibrils, while inhibition of respiration alone increases the variability of actin organization. In primary XTH cells but not in XTH-2 cells cyanide disintegrates most of the actin fibres during 3 h of treatment. This effect is independent of the inhibition of respiration, since actin gels prepared from skeletal muscle also undergo destruction in the presence of cyanide. It is concluded that the actin fibrils of the primary cells and the established line behave differently to changing metabolic conditions and to application of KCN.     

An automatic method for determination of urinary 3-methylhistidine: normal values.

A system for automatic analysis of urinary 3-methylhistidine is described, applying ion-exchange chromatography and using an automatic sample injector, a motoric selector valve, and a diode programmer, which controls the analytical system. The method permits a sampling rate of 22 samples/day. 3-Methylhistidine was completely separated from histidine in 37 min whereas 1-methylhistidine was eluted together with ammonia. The 3-methylhistidine concentration was linear up to 150 nmol/ml and no appreciable sample interaction was found at automatic sequential runs. The error, in a single determination based on duplicate samples, was 4.61% and, in duplicated determinations, 3.26%. The mean urinary 3-methylhistidine output was 299.4 ± 23.8 μmol/day in 12 healthy females and 545.5 ± 35.2 μmol/day in 12 healthy males. The 3-methylhistidine excretion was significantly higher in males than in females, when expressed as the absolute daily output or as the estimated ratio to body weight, body surface area, or creatinine.