The regeneration of the tail fin actinotrichia of carp (Cyprinus carpio, Linnaeus, 1758) under the action of naproxen / A regeneração das actinotriquias da nadadeira caudal da carpa (Cyprinus carpio, Linnaeus, 1758) sob a ação do naproxeno

A conglomerate of small, rigid, fusiform spicules known as actinotrichia sustains the edge of tail fins of teleost. After amputation, these structures show an extremely fast regenerative capacity. In this study we observed the effect of a nonsteroidal anti-inflammatory drug, naproxen, used in the treatment of degenerative articular diseases, during the process of actinotrichia regeneration. For this purpose, regenerating tissue from animals in contact with the drug was submitted to histochemical and ultrastructural analysis in comparison to tissue from animals under normal conditions, i.e., not in contact with the drug in question. Actinotrichia regeneration was similar in both animals, indicating that naproxen, at the dose used in the present study, did not interfere with actinotrichia synthesis during the regenerative process of the tail fin. This could be because naproxen did not influence the expression of the genes required for the regeneration process, such as the Sonic hedgehog (Shh) gene, which is involved in actinotrichia formation.

A borda da nadadeira caudal de teleósteo é sustentada por um conglomerado de espículas pequenas, rígidas e fusiformes chamadas actinotriquias. Essas estruturas, após a amputação, apresentam uma capacidade regenerativa extremamente rápida. Neste trabalho estudamos o efeito de uma droga anti-inflamatória não esteroide, o naproxeno, utilizada no tratamento de doenças articulares degenerativas, durante o processo de regeneração da actinotriquia. Para isso foram feitas análises histoquímicas e ultraestruturais do tecido em regeneração de animais em contato com a droga comparada com animais em condições normais, ou seja, sem contato com a droga em questão. Os animais em contato com a droga apresentaram a regeneração da actinotriquia de modo semelhante ao dos animais mantidos em condições normais, indicando que o naproxeno, na dose utilizada neste trabalho, não interferiu na síntese das actinotriquias durante o processo regenerativo da nadadeira caudal. Isto talvez seja porque o naproxeno não tenha influenciado a expressão dos genes necessários para o processo de regeneração, tal como o gene Sonic hedgehog (Shh), que está envolvido na formação da actinotriquia.

Histology of vitamin A induced ectopic limbs and normal hind limbs in tadpoles of Polypedates maculatus.

Marked histological similarities were observed between normal and vitamin A induced ectopic limb buds of P. maculatus. However, close association of nephric tubule and lateral plate mesoderm, as seen in normal hind limb bud does not seem to be essential for ectopic limb development. The ectopic limbs tend to develop in pairs.

Cross-contamination with tamoxifen induces transgene expression in non-exposed inducible transgenic mice

Inducible transgenic mouse models that impose a constraint on both temporal and spatial expression of a given transgene are invaluable. These animals facilitate experiments that can address the role of a specific cell or group of cells within an animal or in a particular window of time. A common approach to achieve inducibility involves the site-specific recombinase ‘Cre’, which is linked to a modified version of one of various steroid hormone-binding domains. Thus, the expression of Cre is regulated such that a functional nuclear transgene product can only be generated with the addition of an exogenous ligand. However, critical requirements of this system are that the nuclear localization of the transgene product be tightly regulated, that the dosage of the inducing agent remains consistent among experimental animals and that the transgene cassette cannot express in the absence of the inducing agent. We used the Cre ER(T2) cassette, which is regulated by the addition of the estrogen antagonist tamoxifen to determine whether cross-contamination of tamoxifen between animals housed together can be a significant source of spurious results. We found that cross-contamination of exogenous tamoxifen does occur. It occurred in all animals tested. We suggest that the mechanism of contamination is through exposure to tamoxifen in the general environment and/or to coprophagous behavior. These results have important implications for the interpretation and design of experiments that use ‘inducible’ transgenic animals.

Effects of intrathecal L-and N-type calcium channel blockers on the antinociception evoked by opioid agonists in the rat tail flick test

The effects of intrathecal administration of nimodipine or omega-conotoxin GVIA(L- and N-type calcium channel blockers, respectively) alone or followed by DAMGO, DADLE or bremazocine (mu-, delta- and kappa- opioid agonists, respectively) were studied on the rat tail flick test. The N- (16 to 64 pmoles), but not the L-type blocker (60 to 240 pmoles) produced a dose and time-dependent increase in the latency for the tail-flick reflex. DAMGO (30 to 120 pmoles) or bremazocine (190 to 560 pmoles), but not DADLE (50 to 200 pmoles), produced a dose-dependent increase in the latency for the tail-flick reflex. The effect of the highest dose of DAMGO was smaller, while the effects of DADLE and bremazocine were not changed after nimodipine (60 pmoles). The effects of DADLE were significantly potentiated, while the effects of DAMGO and bremazocine were not changed after omega-conotoxin GVIA (16 pmoles). The intrathecal administration of an N-type calcium channel blocker with a delta-opioid agonist seems to be the most effective combination to produce antinociception in the rat tail flick test.

Effect of acute footshock stress on the responsiveness of the isolated rat tail artery to phenylephrine and epinephrine

The effects of acute footshock stress on the sensitivity of the isolated rat tail artery were studied. Footshock stress applied to male Wistar rats (200-300 g) causes subsensitivity to the vasoconstrictor effects of phenylephrine and epinephrine. No significant changes in the pA2 cvalues of prozosin were detected, using epinephrine as the agonist. Footshock stress-induced subsensitivity ot epinephrine was not affected by the calcium entry blocker nifedipine. However, nifedipine significantly depressed the maximum response to epinephrine in tail arteries isolated from acute footshock-stressed rats. The present results suggest that acute footshock stress-induced reduced sensitivity to phenylephrine and epinephrine may not be only related to events at the alpha-adrenoreceptor level. The nifedipine-induced depression of the maximum response to epinephrine suggests a role for the calcium mobilization processess in the vascular responsiveness during acute stress

Participation of opioid receptors in the modulation of the analgesic response by adrenal and gonadal glands

The invovlement of opiodi receptors in the analgesic response was evaluated by the tail-immersion test in simultaneously adrenalectomized and ovariectomized female Wistar rats (210-250g). The reaction time (mean ñ SEM) for tail withdrawal from hot water decreased significantly 2 weeks after surgery (3.52 ñ 0.20 s) when compared to intact animals (6.09 ñ 0.23 s). Hormonal replacement with dexamethasone (50*/day) did not affect reaction time (3.38 ñ 0.19 s). However, this response was restored by combined adrenal and gonadal steroid substitution (estradiol 5*g/day and progesterone 1.5*g 6h before the test) therapy (5.11 ñ 0.45 s) in animal treated with dexamethasone plus estradiol and 5.04 ñ 0.43 s in animals treated with dexamethasone plus estradiol plus progesterone). Naloxone (2mg/Kg decreased the reaction time of animals treated with adrenal and gonadal steroids (5.11 ñ 0.45 vs 4.15 ñ 0.44 and 5.04 ñ 0.43 vs 3.87 ñ 0.28 s, respectively, before and after naloxone) but failed to decrease it in rats treated with dexamethasone only (3.88 ñ 0.18 vs 4.34 ñ 0.25 s, before and after naloxone). These observations indicate that gonadal steroids are the most important steroid factors involved in the reaction time to tail immersion in hot water and confirm other reports that the opioid pathways modulating the neuronal circuitry require the presence of these hormones