Non-random reef use by fishes at two dominant zones in a tropical, algal-dominated coastal reef

Habitat use and the processes which determine fish distribution were evaluated at the reef flat and reef crest zones of a tropical, algal-dominated reef. Our comparisons indicated significant differences in the majority of the evaluated environmental characteristics between zones. Also, significant differences in the abundances of twelve, from thirteen analyzed species, were observed within and between-sites. According to null models, non-random patterns of species co-occurrences were significant, suggesting that fish guilds in both zones were non-randomly structured. Unexpectedly, structural complexity negatively affected overall species richness, but had a major positive influence on highly site-attached species such as a damselfish. Depth and substrate composition, particularly macroalgae cover, were positive determinants for the fish assemblage structure in the studied reef, prevailing over factors such as structural complexity and live coral cover. Our results are conflicting with other studies carried out in coral-dominated reefs of the Caribbean and Pacific, therefore supporting the idea that the factors which may potentially influence reef fish composition are highly site-dependent and variable.

Effects of Ischemia and Reperfusion on P2X(2) Receptor Expressing Neurons of the Rat Ileum Enteric Nervous System

Purpose We investigated the effects of ischemia/reperfusion in the intestine (I/R-i) on purine receptor P2X(2)-immunoreactive (IR) neurons of the rat ileum. Methods The superior mesenteric artery was occluded for 45 min with an atraumatic vascular clamp and animals were sacrificed 4 h later. Neurons of the myenteric and submucosal plexuses were evaluated for immunoreactivity against the P2X(2) receptor, nitric oxide synthase (NOS), choline acetyl transferase (ChAT), calbindin, and calretinin. Results Following I/R-i, we observed a decrease in P2X(2) receptor immunoreactivity in the cytoplasm and surface membranes of neurons of the myenteric and submucosal plexuses. These studies also revealed an absence of calbindin-positive neurons in the I/R-i group. In addition, the colocalization of the P2X(2) receptor with NOS, ChAT, and calretinin immunoreactivity in the myenteric plexus was decreased following I/R-i. Likewise, the colocalization between P2X(2) and calretinin in neurons of the submucosal plexus was also reduced. In the I/R-i group, there was a 55.8% decrease in the density of neurons immunoreactive (IR) for the P2X(2) receptor, a 26.4% reduction in NOS-IR neuron, a 25% reduction in ChAT-IR neuron, and a 47% reduction in calretinin-IR neuron. The density of P2X(2) receptor and calretinin-IR neurons also decreased in the submucosal plexus of the I/R-i group. In the myenteric plexus, P2X(2)-IR, NOS-IR, ChAT-IR and calretinin-IR neurons were reduced in size by 50%, 49.7%, 42%, and 33%, respectively, in the I/R-i group; in the submucosal plexus, P2X(2)-IR and calretinin-IR neurons were reduced in size by 56% and 72.6%, respectively. Conclusions These data demonstrate that ischemia/reperfusion of the intestine affects the expression of the P2X(2) receptor in neurons of the myenteric and submucosal plexus, as well as density and size of neurons in this population. Our findings indicate that I/R-i induces changes in P2X(2)-IR enteric neurons that could result in alterations in intestinal motility.

TLR2 and TLR4 expression after kidney ischemia and reperfusion injury in mice treated with FTY720

Ischemia and reperfusion injury (IR) is an antigen independent inflammatory process that causes tissue damage. After IR, kidneys up-regulate leukocyte adhesion molecules and toll-like receptors (TLRs). Moreover, injured kidneys can also secrete factors (i.e. heat shock protein) which bind to TLRs and trigger intracellular events culminating with the increase in the gene expression of inflammatory cytokines. FTY720 is an immunomodulatory compound and protects at least in part kidneys submitted to IR. The mechanisms associated with FTY720`s beneficial effects on kidneys after IR remain elusive. We investigated whether FTY720 administration in mice submitted to kidney IR is associated with modulation of TLR2 and TLR4 expression. C57BL/6 mice submitted to 30 min of renal pedicles clamp were evaluated for serum parameters (creatinine, urea and nitric oxide), kidney histology, spleen and kidney infiltrating cells expression of TLR2 and TLR4, resident kidney cells expression of TLR2 and TLR4 and IL-6 protein expression in kidney. FTY720-treated mice presented decrease in serum creatinine, urea and nitric oxide, diminished expression of TLR2 and TLR4 both in spleen and kidney infiltrating cells, and reduced kidney IL-6 protein expression in comparison with IR non-treated mice. However, acute tubular necrosis was present both in IR non-treated and IR + FTY720-treated groups. Also, FTY720 did not prevent TLR2 and TLR4 expression in kidney resident cells. In conclusion, FTY720 can promote kidney function recovery after IR by reducing the inflammatory process. Further studies are needed in order to establish whether TLR2 and TLR4 down regulation should be therapeutically addressed as protective targets of renal function and structure after IR. (C) 2011 Elsevier B.V. All rights reserved.

Eugenol modifies the excitability of rat sciatic nerve and superior cervical ganglion neurons

Eugenol is a phenylpropene obtained from the essential oils of plants such as clove and basil which has ample use in dentistry. Eugenol possesses analgesic effects that may be related to the inhibition of voltage-dependent Na(+) channels and/or to the activation of TRPV1 receptors or both. In the present study, electrophysiological parameters were taken from the compound action potentials of the isolated rat sciatic nerve and from neurons of the superior cervical ganglion (SCG) impaled with sharp microelectrodes under current-clamp conditions. In the isolated rat sciatic nerve, eugenol inhibited the compound action potential in a concentration-dependent manner. Action potentials recorded from SCG neurons were inhibited by eugenol with an IC(50) of 0.31 mM. At high concentrations (2 mM), during brief applications. eugenol caused significant action potential blockade while it did not interfere with the resting membrane potential or the membrane input resistance. Surprisingly, however, at low eugenol concentrations (0.6 mM), during long time applications, a reversible reduction (by about 50%) in the input membrane resistance was observed, suggesting the possible involvement of a secondary delayed effect of eugenol to reduce neuronal excitability. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

Single Synapse Information Coding in Intraburst Spike Patterns of Central Pattern Generator Motor Neurons

Burst firing is ubiquitous in nervous systems and has been intensively studied in central pattern generators (CPGs). Previous works have described subtle intraburst spike patterns (IBSPs) that, despite being traditionally neglected for their lack of relation to CPG motor function, were shown to be cell-type specific and sensitive to CPG connectivity. Here we address this matter by investigating how a bursting motor neuron expresses information about other neurons in the network. We performed experiments on the crustacean stomatogastric pyloric CPG, both in control conditions and interacting in real-time with computer model neurons. The sensitivity of postsynaptic to presynaptic IBSPs was inferred by computing their average mutual information along each neuron burst. We found that details of input patterns are nonlinearly and inhomogeneously coded through a single synapse into the fine IBSPs structure of the postsynaptic neuron following burst. In this way, motor neurons are able to use different time scales to convey two types of information simultaneously: muscle contraction (related to bursting rhythm) and the behavior of other CPG neurons (at a much shorter timescale by using IBSPs as information carriers). Moreover, the analysis revealed that the coding mechanism described takes part in a previously unsuspected information pathway from a CPG motor neuron to a nerve that projects to sensory brain areas, thus providing evidence of the general physiological role of information coding through IBSPs in the regulation of neuronal firing patterns in remote circuits by the CNS.

The kidney in different stages of the cardiovascular continuum

Patients with chronic kidney disease are at higher risk of developing cardiovascular disease. The complex, interaction between the kidney and the cardiovascular system is incompletely understood, particularly at the early stages of the cardiovascular continuum. The overall aim of this thesis was to clarify novel aspects of the interplay between the kidney and the cardiovascular system at different stages of the cardiovascular continuum; from risk factors such as insulin resistance, inflammation and oxidative stress, via sub-clinical cardiovascular damage such as endothelial dysfunction and left ventricular dysfunction, to overt cardiovascular death. This thesis is based on two community-based cohorts of elderly, Uppsala Longitudinal Study of Adult Men (ULSAM) and Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS). The first study, show that higher insulin sensitivity, measured with euglycemic-hyperinsulinemic clamp technique was associated to improve estimated glomerular filtration rate (eGFR) in participants with normal fasting plasma glucose, normal glucose tolerance and normal eGFR. In longitudinal analyses, higher insulin sensitivity at baseline was associated with lower risk of impaired renal function during follow-up. In the second study, eGFR was inversely associated with different inflammatory markers (C-reactive protein, interleukin-6, serum amyloid A) and positively associated with a marker of oxidative stress (urinary F2-isoprostanes). In line with this, the urinary albumin/creatinine ratio was positively associated with these inflammatory markers, and negatively associated with oxidative stress. In study three, higher eGFR was associated with better endothelial function as assessed by the invasive forearm model. Further, in study four, higher eGFR was significantly associated with higher left ventricular systolic function (ejection fraction). The 5th study of the thesis shows that higher urinary albumin excretion rate (UAER) and lower eGFR was independently associated with an increased risk for cardiovascular mortality. Analyses of global model fit, discrimination, calibration, and reclassification suggest that UAER and eGFR add relevant prognostic information beyond established cardiovascular risk factors in participants without prevalent cardiovascular disease. Conclusion: this thesis show that the interaction between the kidney and the cardiovascular system plays an important role in the development of cardiovascular disease and that this interplay begins at an early asymptomatic stage of the disease process.

A rede de marcação e recaptura: o caso de borboletas do gênero heliconius

(The Mark and Recapture Network: a Heliconius case study). The current pace of habitat destruction, especially in tropical landscapes, has increased the need for understanding minimum patch requirements and patch distance as tools for conserving species in forest remnants. Mark recapture and tagging studies have been instrumental in providing parameters for functional models. Because of their popularity, ease of manipulation and well known biology, butterflies have become model in studies of spatial structure. Yet, most studies on butterflies movement have focused on temperate species that live in open habitats, in which forest patches are barrier to movement. This study aimed to view and review data from mark-recapture as a network in two species of butterfly (Heliconius erato and Heliconius melpomene). A work of marking and recapture of the species was carried out in an Atlantic forest reserve located about 20km from the city of Natal (RN). Mark recapture studies were conducted in 3 weekly visits during January-February and July-August in 2007 and 2008. Captures were more common in two sections of the dirt road, with minimal collection in the forest trail. The spatial spread of captures was similar in the two species. Yet, distances between recaptures seem to be greater for Heliconius erato than for Heliconius melpomene. In addition, the erato network is more disconnected, suggesting that this specie has shorter traveling patches. Moving on to the network, both species have similar number of links (N) and unweighed vertices (L). However, melpomene has a weighed network 50% more connections than erato. These network metrics suggest that erato has more compartmentalized network and restricted movement than melpomene. Thus, erato has a larger number of disconnected components, nC, in the network, and a smaller network diameter. The frequency distribution of network connectivity for both species was better explained by a Power-law than by a random, Poissom distribution, showing that the Power-law provides a better fit than the Poisson for both species. Moreover, the Powerlaw erato is much better adjusted than in melpomene, which should be linked to the small movements that erato makes in the network