(Table 2) Mercury and selenium concentration in the brain stem of wild polar bears (Ursus maritimus), east Greenland

Polar bears (Ursus maritimus) are exposed to high concentrations of mercury because they are apex predators in the Arctic ecosystem. Although mercury is a potent neurotoxic heavy metal, it is not known whether current exposures are of neurotoxicological concern to polar bears. We tested the hypotheses that polar bears accumulate levels of mercury in their brains that exceed the estimated lowest observable adverse effect level (20 µg/g dry wt) for mammalian wildlife and that such exposures are associated with subtle neurological damage, as determined by measuring neurochemical biomarkers previously shown to be disrupted by mercury in other high-trophic wildlife. Brain stem (medulla oblongata) tissues from 82 polar bears subsistence hunted in East Greenland were studied. Despite surprisingly low levels of mercury in the brain stem region (total mercury = 0.36 ± 0.12 µg/g dry wt), a significant negative correlation was measured between N-methyl-D-aspartate (NMDA) receptor levels and both total mercury (r = -0.34, p < 0.01) and methylmercury (r = -0.89, p < 0.05). No relationships were observed among mercury, selenium, and several other neurochemical biomarkers (dopamine-2, gamma-aminobutyric acid type A, muscarinic cholinergic, and nicotinic cholinergic receptors; cholinesterase and monoamine oxidase enzymes). These data show that East Greenland polar bears do not accumulate high levels of mercury in their brain stems. However, decreased levels of NMDA receptors could be one of the most sensitive indicators of mercury's subclinical and early effects.

Expression of membrane-associated carbonic anhydrase XIV on neurons and axons in mouse and human brain

Although long suspected from histochemical evidence for carbonic anhydrase (CA) activity on neurons and observations that CA inhibitors enhance the extracellular alkaline shifts associated with synaptic transmission, an extracellular CA in brain had not been identified. A candidate for this CA was suggested by the recent discovery of membrane CA (CA XIV) whose mRNA is expressed in mouse and human brain and in several other tissues. For immunolocalization of CA XIV in mouse and human brain, we developed two antibodies, one against a secretory form of enzymatically active recombinant mouse CA XIV, and one against a synthetic peptide corresponding to the 24 C-terminal amino acids in the human enzyme. Immunostaining for CA XIV was found on neuronal membranes and axons in both mouse and human brain. The highest expression was seen on large neuronal bodies and axons in the anterolateral part of pons and medulla oblongata. Other CA XIV-positive sites included the hippocampus, corpus callosum, cerebellar white matter and peduncles, pyramidal tract, and choroid plexus. Mouse brain also showed a positive reaction in the molecular layer of the cerebral cortex and granular cellular layer of the cerebellum. These observations make CA XIV a likely candidate for the extracellular CA postulated to have an important role in modulating excitatory synaptic transmission in brain.

Dos pombos descoordenados às rãs sem rumo: o ensino do encéfalo através dos manuais escolares de Ciências Naturais (1900-1950)

O objetivo principal deste trabalho é mostrar como o encéfalo foi abordado nos programas e manuais de Ciências Naturais publicados na primeira metade do século XX. Para tal, utilizou-se um método de caráter qualitativo assente no conceito de transposição didática de Chevallard. O conteúdo programático mostrou que o estudo do encéfalo foi sempre associado ao estudo do sistema nervoso. A descrição neuroanatómica e fisiológica do encéfalo nos manuais organizou-se em torno do bolbo raquidiano, cerebelo e cérebro. Os manuais publicados nas primeiras duas décadas do século XX (Aires, 1906, 1920) foram mais exaustivos na abordagem a esses órgãos do que os publicados entre as décadas de 30 e 50 (Primo, 1939; Soeiro, 1930, 1950; Lima & Soeiro,1950). A sua análise mostrou que a transposição didática do conhecimento científico sobre o encéfalo baseou-se na neuroanatomia, e menos na neurofisiologia, o que é revelador do avanço do conhecimento neuroanatómico deste órgão em comparação com a compreensão do seu funcionamento. Todos os autores ilustraram as funções dos órgãos que constituem o encéfalo através de observações e experiências realizadas em animais, como os pombos e as rãs.

Primary culture and characteristic morphologies of medulla terminalis neurons in the eyestalks of Chinese shrimp, Fenneropenaeus chinensis

A method for culturing medulla terminalis (MT) neurons in the eyestalk of Chinese shrimp, Fenneropenaeus chinensis, was first established. The neurons showed immediate outgrowth in the culture medium supplemented with glutamine, glucose and antibiotics. The cells grew for about 2-7 days and then sustained for a week or more. At least six types of neurons were distinguished on the basis of size and form of soma and outgrowth pattern of cells. (C) 2003 Elsevier Science B.V. All rights reserved.

De arte voluntatis, libri sex : in quibus platonicae, stoicae, & Christianae discipliné medulla digeritur, succo omni politioris philosophiae expresso ex Platone, Seneca, Epicteto, Dione, Chrysostome, Plotino, Iamblicho, & aliis. Quorum sensa subtiliora artificiosius ordinantur; nonnulla emendantur; plurima adducuntur noué, & arguté. Accedit ad calcem Historia panegyrica de tribis martyribus eiusdem Societatis, in Vrugai pro fide occisis

UANL

De sancto matrimonii sacramento : Editio novissima prae ceteris locupletior : in qua praeter duplicem indicem, alterum disputationum, alterum rerum scitu digniorum accessere nunc primum aphorismi ex decem libris commentariorum ejusdem auctoris de matrimonio in compendium redacti, velut medulla totius operis, deinde constitutiones SS. Domini NostriPapae Benedicti XIV. circa idem sacramentum editae.

UANL

Sacrae theologiae moralis medulla recens ad mentem celeberriorum PP. Salmanticensium

UANL

The neurochemically diverse intermedius nucleus of the medulla as a source of excitatory and inhibitory synaptic input to the nucleus tractus solitarii

Sensory afferent signals from neck muscles have been postulated to influence central cardiorespiratory control as components of postural reflexes, but neuronal pathways for this action have not been identified. The intermedius nucleus of the medulla (InM) is a target of neck muscle spindle afferents and is ideally located to influence such reflexes but is poorly investigated. To aid identification of the nucleus, we initially produced three-dimensional reconstructions of the InM in both mouse and rat. Neurochemical analysis including transgenic reporter mice expressing green fluorescent protein in GABA-synthesizing neurons, immunohistochemistry, and in situ hybridization revealed that the InM is neurochemically diverse, containing GABAegric and glutamatergic neurons with some degree of colocalization with parvalbumin, neuronal nitric oxide synthase, and calretinin. Projections from the InM to the nucleus tractus solitarius (NTS) were studied electrophysiologically in rat brainstem slices. Electrical stimulation of the NTS resulted in antidromically activated action potentials within InM neurons. In addition, electrical stimulation of the InM resulted in EPSPs that were mediated by excitatory amino acids and IPSPs mediated solely by GABA(A) receptors or by GABA(A) and glycine receptors. Chemical stimulation of the InM resulted in (1) a depolarization of NTS neurons that were blocked by NBQX (2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonoamide) or kynurenic acid and (2) a hyperpolarization of NTS neurons that were blocked by bicuculline. Thus, the InM contains neurochemically diverse neurons and sends both excitatory and inhibitory projections to the NTS. These data provide a novel pathway that may underlie possible reflex changes in autonomic variables after neck muscle spindle afferent activation.

Ventrolateral medulla mechanisms involved in cardiorespiratory responses to central chemoreceptor activation in rats

A rise in arterial PCO(2) stimulates breathing and sympathetic activity to the heart and blood vessels. In the present study, we investigated the involvement of the retrotrapezoid nucleus (RTN) and glutamatergic mechanisms in the Botzinger/C1 region (Botz/C1) in these responses. Splanchnic sympathetic nerve discharge (sSND) and phrenic nerve discharge (PND) were recorded in urethane-anesthetized, sino-aortic-denervated, vagotomized, and artificially ventilated rats subjected to hypercapnia (end-expiratory CO(2) from 5% to 10%). Phrenic activity was absent at end-expiratory CO(2) of 4%, and strongly increased when end-expiratory CO(2) reached 10%. Hypercapnia also increased sSND by 103 +/- 7%. Bilateral injections of the GABA-A agonist muscimol (2 mM) into the RTN eliminated the PND and blunted the sSND activation (Delta = +56 +8%) elicited by hypercapnia. Injections of NMDA receptor antagonist AP-5 (100 mM), non-NMDA receptor antagonist 6,7-dinitro-quinoxaline-2,3-dione (DNQX; 100 mM) or metabotropic glutamate receptor antagonist (+/-)-alpha-methyl-4-carboxyphenylglycine (MCPG; 100 mM) bilaterally into the Botz/C1 reduced PND (Delta = +43 +/- 7%, +52 +/- 6% or +56 +/- 11%, respectively). MCPG also reduced sSND (Delta = +41 +/- 7%), whereas AP-5 and DNQX had no effect. In conclusion, the increase in sSND caused by hypercapnia depends on increased activity of the RTN and on metabotropic receptors in the Botz/C1, whereas PND depends on increased RTN activity and both ionotropic and metabotropic receptors in the Botz/C1.

Role of catecholaminergic neurones of the caudal ventrolateral medulla in cardiovascular responses induced by acute changes in circulating volume in rats

Several findings suggest that catecholaminergic neurones in the caudal ventrolateral medulla (CVLM) contribute to body fluid homeostasis and cardiovascular regulation. The present study sought to determine the effects of lesions of these neurones on the cardiovascular responses induced by changes in circulating volume. All experiments were performed in male Wistar rats (320-360 g). Medullary catecholaminergic neurones were lesioned by microinjection of anti-dopamine beta-hydroxylase-saporin (6.3 ng in 60 nl; SAP rats, n = 14) into the CVLM, whereas sham rats received microinjections of free saporin (1.3 ng in 60 nl, n = 15). Two weeks later, rats were anaesthetized (urethane, 1.2 g kg(-1), I.V..), instrumented for measurement of mean arterial pressure (MAP), renal blood flow (RBF) and renal vascular conductance (RVC), and infused with hypertonic saline (HS; 3 M NaCl, 0.18 ml (100 g body weight)(-1), I.V.) or an isotonic solution (volume expansion, VE; 4% Ficoll, 1% of body weight, I.V.). In sham rats, HS induced sustained increases in RBF and RVC (155 +/- 7 and 145 +/- 6% of baseline, at 20 min after HS). In SAP rats, RBF responses to HS were blunted (125 +/- 6%) and RVC increases were abolished (108 +/- 5%) 20 min after HS. Isotonic solution increased RBF and RVC in sham rats (149 +/- 10 and 145 +/- 12% of baseline, respectively, at 20 min). These responses were reduced in SAP rats (131 +/- 6 and 126 +/- 5%, respectively, at 20 min). Pressor responses to HS were larger in SAP rats than in sham rats (17 +/- 5 versus 9 +/- 2 mmHg, at 20 min), whereas during VE these responses were similar in both groups (6 +/- 3 versus 4 +/- 6 mmHg, at 20 min). Immunohistochemical analysis indicates that microinjections of anti-D beta H-saporin produced extensive destruction within the A1/C1 cell groups in the CVLM. These results suggest that catecholaminergic neurones mediate the cardiovascular responses to VE or increases in plasma sodium levels.

Importance of angiotensinergic mechanisms for the pressor response to L-glutamate into the rostral ventrolateral medulla

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Kidney-Induced Hypertension Depends on Superoxide Signaling in the Rostral Ventrolateral Medulla

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ventrolateral medulla mechanisms involved in cardiorespiratory responses to central chemoreceptor activation in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)