Distribution and size of the mojarra Diapterus rhombeus (Cuvier) (Actinopterygii, Gerreidae) in a Southeastern Brazilian bay

Diapterus rhombeus é uma das espécies de peixes mais abundantes na Baia de Sepetiba, ambiente costeiro de 520 km² de área semifechada no sudoeste do Brasil. O tamanho e distribuição dos indivíduos desta espécie foram descritos com o objetivo de determinar o uso das áreas de criação numa dimensão espacial e temporal (sazonal). Um programa de amostragem de arrasto de fundo foi conduzido mensalmente entre outubro 1998 a setembro 1999, em três zonas da baía (externa, central, interna), definidas através de gradientes de profundidade e salinidade. Diferenças altamente significativas foram encontradas para CPUEs (número e biomassa) entre estações do ano e zonas. O comprimento variou de 50 a 230 mm CT. Três grupos de tamanhos foram definidos de acordo com uma escala de maturação gonadal (n = 1435): 1 - imaturo (< 80 mm Comprimento Total - CT); 2- indivíduos em primeira maturação (L50) (80-90 mm CT); e 3 - adultos (L100) (&gt; 100 mm CT). Imaturos e indivíduos L50 foram abundantes (número e biomassa) durante o outono na zona interna, enquanto adultos (L100) predominaram durante o verão na zona externa. Evidências de movimento de indivíduos jovens (50-90 mm CT) da zona interna para zona externa foram detectadas conforme os animais foram atingindo maiores tamanhos (180 mm CT), no segundo ano de vida. A condição (k) aumentou em indivíduos maiores na zona externa durante a primavera, quando estes se tornam aptos a iniciar o processo reprodutivo. Duas coortes foram detectadas de acordo com a progressão modal: a primeira (menores tamanhos) mostrando crescimento mais rápido do que a segunda, evidenciando uma taxa menor de crescimento a medida que atingem maiores tamanhos. Diferentes classes de comprimento ocupando diferentes zonas da baía sugerem que grupos de idades otimizam sua coexistência compartilhando os recursos disponíveis e evitando competição intra-especifica.Diapterus rhombeus is one of the most abundant fish species in the Sepetiba bay, which is a 520 km² semi-closed coastal area in Southeastern Brazil. The size and distribution of this species have been described in order to assess the use of the area as a rearing ground in both spatial and temporal (seasonal) dimensions. A fish sampling program was conducted monthly by using an otter trawl between October 1998 and September 1999, in three bay zones (outer, middle and inner), defined according to depth and salinity gradient. Highly significant differences were found for CPUEs (number and biomass) among seasons and zones. Size ranged from 50 to 230 mm TL, and three size-groups were defined according to a maturation scale (n = 1435): 1 - immature (< 80 mm Total Length - TL); 2- individuals at the first maturation (L50) (80-90 mm TL), and 3 - adults (L100) (&gt; 100 mm TL). Immature and L50 individuals were more abundant (number and biomass) during Autumn in the inner zone, while adults (L100) predominated during Summer in the outer zone. Evidences of movements of young-of-the-year (50-90 mm TL) individuals from the inner to the outer zone were detected as they reach larger sizes (180 mm TL) in the second year of life. Condition (k) was higher in larger sized individuals in the outer zone during Spring, when they are apt to start the reproductive process. Two cohorts were detected according to modal progression: the first (smaller size) showing faster growth than the second, evidencing a slower growth rate as they reach larger size. Distinct size classes occupying different bay zones suggest that the age-groups optimize their coexistence by partitioning the available resources, avoiding intra-specific competition

Dopamine acting at D1-like, D2-like and α1-adrenergic receptors differentially modulates theta and gamma oscillatory activity in primary motor cortex

The loss of dopamine (DA) in Parkinson’s is accompanied by the emergence of exaggerated theta and beta frequency neuronal oscillatory activity in the primary motor cortex (M1) and basal ganglia. DA replacement therapy or deep brain stimulation reduces the power of these oscillations and this is coincident with an improvement in motor performance implying a causal relationship. Here we provide in vitro evidence for the differential modulation of theta and gamma activity in M1 by DA acting at receptors exhibiting conventional and non-conventional DA pharmacology. Recording local field potentials in deep layer V of rat M1, co-application of carbachol (CCh, 5 μM) and kainic acid (KA, 150 nM) elicited simultaneous oscillations at a frequency of 6.49 ± 0.18 Hz (theta, n = 84) and 34.97 ± 0.39 Hz (gamma, n = 84). Bath application of DA resulted in a decrease in gamma power with no change in theta power. However, application of either the D1-like receptor agonist SKF38393 or the D2-like agonist quinpirole increased the power of both theta and gamma suggesting that the DA-mediated inhibition of oscillatory power is by action at other sites other than classical DA receptors. Application of amphetamine, which promotes endogenous amine neurotransmitter release, or the adrenergic α1-selective agonist phenylephrine mimicked the action of DA and reduced gamma power, a result unaffected by prior co-application of D1 and D2 receptor antagonists SCH23390 and sulpiride. Finally, application of the α1-adrenergic receptor antagonist prazosin blocked the action of DA on gamma power suggestive of interaction between α1 and DA receptors. These results show that DA mediates complex actions acting at dopamine D1-like and D2-like receptors, α1 adrenergic receptors and possibly DA/α1 heteromultimeric receptors to differentially modulate theta and gamma activity in M1

Working mechanism underlying the reduction of the behavioral and accumbal dopamine response to cocaine by alpha-1-adrenoceptor antagonists

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Facilitation of Corticostriatal Plasticity by the Amygdala Requires Ca2+-Induced Ca2+ Release in the Ventral Striatum

Motor learning and habit formation are thought to depend on corticostriatal synaptic plasticity. Moreover, basolateral amygdala (BLA) activity facilitates consolidation of striatal-dependent memories. Accordingly, BLA stimulation in vitro facilitates long-term potentiation (LTP) induction at corticostriatal synapses onto medium spiny neurons (MSNs). Although these effects were found to depend on N-methyl-d-aspartate (NMDA) receptor activation at BLA synapses and consequent Ca2+ influx, it is unclear how this event can facilitate LTP at cortical synapses, even when the two inputs are not coactivated. Here, we aimed to shed light on this question, using whole cell recordings of MSNs in vitro. We first tested whether BLA inputs end at more proximal dendritic sites than cortical inputs. In this scenario, BLA synapses would experience stronger spike-related depolarizations and be in a strategic position to control the spread of second messengers. However, comparison of compound excitatory postsynaptic potentials and single-axon excitatory postsynaptic currents revealed that BLA and cortical synapses are intermingled. Next, we examined the sensitivity of cortical and BLA NMDA responses to ifenprodil because NR2A-containing NMDA receptors have faster kinetics than those containing NR2B subunits. However, the two inputs did not differ in this respect. Last, reasoning that propagating waves of Ca2+-induced Ca2+ release (CICR) could bridge temporal gaps between the two inputs, we tested the effects of CICR inhibitors on the BLA facilitation of corticostriatal LTP induction. Pharmacological interference with CICR blocked corticostriatal LTP induction. Thus our results are consistent with the notion that NMDA-dependent Ca2+ influx at BLA synapses initiates propagating waves of CICR, thereby biasing active corticostriatal inputs toward synaptic potentiation

Atomic spectrometry update: review of advances in atomic spectrometry and related techniques

This review covers developments in ‘Atomic Spectrometry’. It covers atomic emission, absorption, fluorescence and mass spectrometry, but excludes material on speciation and coupled techniques which is included in a separate review. It should be read in conjunction with the other related reviews in the series.1–6 A critical approach to the selection of material has been adopted, with only novel developments in instrumentation, techniques and methodology being included. Developments worthy of note include photochemical and electrochemical methods of vapour generation, single particle analysis using ICP-MS and the development of new methods for direct plasma generation in liquid samples. The use of MC-ICP-MS continues to grow in importance for isotope ratio measurements in fields as diverse as geochronology, nuclear forensics and biomedical research. Laser-based methods are also important in many fields, particularly for direct and stand-off analysis of solid samples