Genetic analysis of five sedentary fish species in middle Laranjinha River (upper Paraná River basin): A case study.

Most studies of diversity and genetic structure in neotropical fish have focused on commercial species from large rivers or their reservoirs. However, smaller tributaries have been identified as an important alternative migratory route, with independent pools of genetic diversity. In this context, the present study aimed to evaluate genetic diversity and structure in five neotropical fish species from a region of Laranjinha River in the upper Paraná River basin. PCR-RAPD (random amplified polymorphic DNA) markers were used to characterize around 40 individuals of each species distributed upstream and downstream of Corredeira Dam that interrupts the river. The descriptive index of genetic diversity (P = 30.5-82%; HE 0.122-0.312) showed that the populations have acceptable levels of genetic diversity. The values for Nei's genetic distance (DN min 0.0110 and max 0.0306) as well as the genetic structure index and the analysis of molecular variance (AMOVA, ϕST min 0.0132 and max 0.0385) demonstrated low, but significant levels of genetic structure. Bayesian analysis of assignment found two k clusters, including several individuals with mixed ancestry for all populations from the five species analyzed. These findings along with historical data on rainfall and the low dimensions of the dam studied here support the hypothesis that periodic floods enable the transit of individuals between different localities mitigating the differentiation process between populations.

Inhibition of sodium appetite by lipopolysaccharide: involvement of alpha2-adrenoceptors.

Lipopolysaccharide (LPS), an endotoxin from the wall of Escherichia coli, produces a general behavioral inhibition and affects several aspects of fluid-electrolyte balance. LPS inhibits thirst; however, it is not clear if it also inhibits sodium appetite. The present results show that LPS (0.3-2.5 mg/kg body wt) injected intraperitoneally produces a dose-dependent reduction of sodium appetite expressed as 0.3 M NaCl intake induced by sodium depletion (furosemide plus removal of ambient sodium for 24 h). The high doses of LPS (1.2-2.5 mg/kg) also produced transient hypothermia at the beginning of the sodium appetite test; however, no dose produced hyperthermia. LPS also increased the stomach liquid content (an index of gastric emptying) after a load of 0.3 M NaCl given intragastrically by gavage to sodium-depleted rats. The α(2)-adrenoceptor antagonist yohimbine (5 mg/kg ip) abolished the effect of LPS on 0.3 M NaCl intake, without changing the effect of LPS on gastric emptying. Injection of RX-821002 (160 nmol), another α(2)-adrenoceptor antagonist, in the lateral cerebral ventricle (LV) also reversed the inhibition of sodium appetite produced by LPS. Yohimbine intraperitoneally or RX-821002 in the LV alone had no effect on sodium intake. Although yohimbine plus LPS produced a slight hypotension, RX-821002 plus LPS produced no change in arterial pressure, suggesting that the blockade of the effects of LPS on sodium intake by the α(2)-adrenoceptor antagonists is independent from changes in arterial pressure. The results suggest an inhibitory role for LPS in sodium appetite that is mediated by central α(2)-adrenoceptors.

Contribuição ao entendimento da patogenia da sepse / A contribution to the understanding of the phatogenesis of sepsis

O choque vaso dilatador mais frequente resulta de sepse, uma inflamação sistêmica em resposta a uma infecção que se caracteriza por hipotensão, hiporreatividade às catecolaminas e coagulação intravascular disseminada. A causa mais comum de sepse é a infecção por bactérias Gram-negativas, principalmente de Escherichia coli, resultando na liberação de lipopolissacarídeos (endotoxinas) da parede celular, quando da morte ou lise do microrganismo, com o envolvimento de muitos mediadores, incluindo o óxido nítrico. Mais tarde descobriu-se que os níveis sanguíneos de vasopressina,em pacientes com sepse, eram anormalmente baixos, e observou-se que alguns destes pacientes, com choque séptico avançado, eram extremamente sensíveis às ações pressóricas da vasopressina exógena.

Potencialização do efeito antiinflamatório e antinociceptivo do diclofenaco e da nimesulida por vitaminas do complexo B / Potentiating effect of pretreatment with some B vitamins on the anti-inflammatory and antinociceptive properties of nimesulide and diclofenac

Investigou-se os efeitos de algumas vitaminas B associadas ao diclofenaco ou nimesulida, na contorção abdominal em camundongos e edema de pata em ratos apenas com a nimesulida ou sua associação com algumas vitaminas B.Verificou-se que o pré-tratamento com as vitaminas tiamina[B1], piridoxina[B6] e cianocobalamina [B12], isoladasou administradas conjuntamente, não inibiu o edema de pata produzido pela carragenina em ratos, nem as contorções abdominais produzidas pelo ácido acético em camundongos. Por outro lado, a nimesulida [5mg/kg]reduziu o edema de pata em ratos, e a associação das três vitaminas à este fármaco, mas não as vitaminas administradas isoladamente, potencializou seus efeitos nos tempos de duas, três e quatro horas após a carragenina. As contorções abdominais em camundongos foram inibidas pelas doses de 25 ou 50mg/kg de diclofenaco. A associação das três vitaminas ou apenas da cianocobalamina, potencializou as duas doses do diclofenaco utilizadas. As contorções abdominais foram reduzidas também pelo nimesulida [5mg/kg] e a associação das três vitaminas, oucada uma das vitaminas administradas isoladamente, foram capazes de potencializar os efeitos do nimesulida. É provável que a diferença no mecanismo de ação destes fármacos sejaresponsável pela diferença dos efeitos das vitaminas. O presente trabalho aponta para a realização de novos estudos com o uso destes antiinflamatórios, combinados com as vitaminas tiamina[B1], piridoxina[B6] e cianocobalamina [B12], em doenças inflamatórias crônicas, na tentativa dereduzir a dose destes fármacos e consequentemente diminuindo seus efeitos colaterais.

The effects of a combination of some B vitamins and diclofenac or nimesulide on chemical nociception in mice or paw edema in rats were investigated. While the vitamins alone had no effect, combination of thiamine (B1), pyridoxine (B6) and cyanocobalamin (B12), given i.p. in doses of 100mg and 5mg/kg, respectively, potentiated the inhibition by nimesulide (5mg/kg) of paw edema induced by carrageenin in rats. Antinociceptive effects of diclofenac and nimesulide (inhibition of abdominal writhing induced by acetic acid in mice) were also potentiated by the combination of the vitamins B1, B6 and B12. Thiamine, pyridoxine and cyanocobalamin given singly were effective in potentiating antinociceptive effects of nimesulide, but only cyanocobalamin potentiated these effects of diclofenac, probably reflecting the differing mechanisms of action of the two drugs. The results document the positive influence of B vitamins on the antinociceptive effects of diclofenac or nimesulide and support the use of B vitamins to shorten the treatment time and reduce the daily dose of anti-inflammatories.

Efeito do tratamento com algumas vitaminas B na potencialização do efeito antiinflamatório e antinociceptivo do diclofenaco e da talidomida / Potentiating effect of treatment with some B vitamins on the anti-inflammatory and antinociceptive properties of diclofenac and thalidomide

Mostrou-se que o pré-tratamento com as vitaminas tiamina[B1], piridoxina[B6] e cianocobalamina [B12], isoladas ou administradas conjuntamente, não inibiu o edema de pata produzido pela carragenina em ratos, nem as contorções abdominais produzidas pelo ácido acético em camundongos.Por outro lado, o diclofenaco [25 ou 50mg/kg] ou talidomida [45mg/kg] inibiram o edema de pata em ratos, e a associação das três vitaminas à estas drogas, mas não as vitaminas administradas isoladamente, potencializou os efeitos do diclofenaco [25 ou 50mg/kg] no tempo de quatro horas e a talidomida [45mg/kg], nos tempos de duas, três e quatro horas após a carragenina.As contorções abdominais em camundongos foram inibidas pelas doses de 25 ou 50mg/ kg de diclofenaco.A associação das três vitaminas ou apenas da cianocobalamina, potencializou as duas doses do diclofenaco utilizadas.As contorções abdominais foram inibidas também pela talidomida [45mg/kg] e a associação das três vitaminas, ou cada uma das vitaminas administradas isoladamente, foram capazes de potencializar os efeitos da talidomida.É provável que a diferença no mecanismo de ação destas drogas seja responsável por esta diferença dos efeitos das vitaminas.O presente estudo preconiza o uso de antiinflamatórios, combinados com as vitaminas tiamina[B1], piridoxina[B6] e cianocobalamina [B12], em doenças crônicas, diminuindo assim a dose destas drogas e seus efeitos colaterais

Effect of n(ômega)nla, an inhibitor of No-synthase, on the release of tissue-plasminogem activator from rat aorta

Fibrinólise é um mecanismo de defesa do organismo que serve para controlar a deposição de fibrina no leito vascular. O endotélio controla o tonus da musculatura lisa subjacente, liberando fatores como NO e sendo também metabolicamente ativo, sintetizando o ativador de plasminogênio tecidual (AP-t), que inicia a fibronólise. É desconhecido o mecanismo pelo qual é liberado o AP-t. Estudos em diversas espécies de animais sugerem a implicação de mediadores químicos na ativação e liberação do AP-t. Medimos a atividade fibrinolítica (AF) produzida por segmento de aorta de rato, em placas de fibrina. O inibidor de NO N(ômega)NLA, inibiu significativamente a liberação de AP-t (grupo II) comparado com o grupo (I) tratado com salina. A administração de L-arginina (grupo III) restaurou a liberação de AP-t, em ratos tratados com N(ômega)NLA, sugerindo que a liberação de AP-t é influenciada pelo óxido nítrico.

Effect of dipyrone, L-NAME and L-arginine on endotoxin-induced rat paw edema.

Paw edema was induced in male Wistar rats (200-250 g) by intraplantar (ipl) administration of 2.5 micrograms endotoxin (Etx). Etx, like carrageenin, produced two distinct edema formation phases, an early phase (75 min) followed by a late phase (7 h). We showed that the edema formation in the early phase was antagonized by dipyrone (80 mg/kg, i.p.) and indomethacin (1 mg/kg, i.p.) by 52% and 55%, respectively, and that the late phase was resistant to these drugs. These results suggest that in the early phase prostaglandins appear to be involved in the process. However, the activation of the kinin cascade leading to the release of other mediators may be involved in the increase of edema in the late phase. To test this hypothesis, we investigated whether the release of nitric oxide (NO) is involved in the mechanism of endotoxin-induced rat paw edema during the late phase, using N omega-nitro-L-arginine methyl ester (L-NAME) (50 micrograms, ipl) as inhibitor of NO synthase and L-arginine (1 mg, ipl) as substrate of NO synthase. The paw edema induced by Etx was inhibited by L-NAME by 56% and increased by L-arginine by 81%. Furthermore, L-arginine given in combination with L-NAME completely reversed the inhibition of Etx-induced edema produced by L-NAME. These results support the hypothesis that in the late phase NO production is associated with the edema evoked by Etx.

Effect of dipyrone, L-NAME and L-arginine on endotoxin-induced rat paw eddema

Paw edema was induced in male Wistar rats (200-250 g) by intraplantar (ipl) administration of 2.5 mug endotoxin (Etx). Etx, like carrageenin, produced two distinct edema formation phases, an early phase (75 min) followed by a late phase (7 h). We showed that the edema formation in the early phase was antagonized by dipyrone (80 mg/kg, ip) and indomethacin (1 mg/kg, ip) by 52 per cent and 52 per cent, respectively, and that the late phase was resistant to these drugs. These result suggest that in the early phase prostaglandins appear to be involved in the process. However, the activation of the kinin cascade leading to the release of other mediators may be involved in the increase of edema in the late phase. To test this hypothesis, we investigated whether the release of nitric oxide (NO) is involved in the mechanism of endotoxin-induced rat paw edema during the late phase, using Nw-nitro-L-arginine methyl ester (L-NAME) (50 mug, ipl) as inhibitor of NO synthase and L-arginine (1 mg, ipl) as substrate of NO synthase. The paw edema induced by Etx was inhibited by L-NAME by 56 per cent and increased by L-arginine by 81 per cent. Furthermore, L-arginine given in combination with L-NAME completely reversed the inhibitions of Etx-induced edema produced by L-NAME. These results support the hypothesis that in the late phase NO production is associated with the edema evoked by Etx.

Lesion of the anteroventral third ventricle region abolishes the beneficial effects of hypertonic saline on hemorrhagic shock in rats.

The effect of intravenous infusion of hypertonic saline (HS, 7.5% NaCl) on the recovery of mean arterial pressure (MAP) during hemorrhage was studied in sham-operated rats and in rats with electrolytic lesion in the anteroventral third ventricle (AV3V) region. After intravenous infusion of 7.5% NaCl (4 ml/kg b.wt.), MAP increased from about 60 to 90 mmHg in sham rats and became stable at this level during all the time of observation (30 min). In AV3V-lesioned rats, after the same infusion, the MAP increased to 80 mmHg, but returned to the pre-infusion levels within 30 min. These results show that the integrity of the AV3V region is important for the beneficial effect of HS during hemorrhagic shock in rats. The AV3V lesion disrupts neural pathways involved in the maintenance of fluid balance and these changes probably abolish the effect of hypertonic saline.

Central lesion abolishes the beneficial effect of hypertonic saline on circulatory shock produced by compound 48/80 in rats.

The purpose of the present study was to examine the protective action of a 7.5% hypertonic NaCl solution (HS) on the circulatory shock produced by compound 48/80 (48/80) in rats and to determine the effect of the AV3V lesion on the protective action of HS. Intravenous injection of 48/80 into sham-operated rats resulted in an immediate drop of mean arterial pressure (MAP). In sham-operated rats, intravenous injection of HS prevented the drop of MAP produced by 48/80, but HS was ineffective in AV3V-lesioned rats. These results show that HS had a protective action on the circulatory shock produced by 48/80 and that the AV3V region plays an important role in this protective action.

Central lesion abolishes the beneficial effect of hypertonic saline on circulatory shock produced by compound 48/80 in rats

The purpose of the presente study was to examine the protective action of a 7.5% hypertonic NaCl solution (HS) on the ciruclatory shock produced by compound 48/80 (48/80) in rats and to determine the effect of the AV3V lesion on the protective action of HS. Intravenous injection of 48/80 into sham-operated rats resulted in an innediate drop of mean arterial pressure (In sham-operated rats, intravenous inection of HS prevented the drop of MAP produced by 48/80, but HS was ineffective in AV3V-lesioned rats. These results show that HS had a protective action on the circularory shock produced by 48/80 and that the AV3V region plaus an important role in this protective action

Influence of temperature on the release of plasminogen activator.

Fibrinolysis is a basic defense mechanism of the organism designed to control the deposition of fibrin in the vascular system and elsewhere. Fibrinolytic activity was measured by the fibrin plate method for three groups of rats (N = 6) that were maintained at room temperature, 20-25 degrees C, 3 degrees C or 38 degrees C for 4 h before testing. Based on measurement of fibrinolytic activity, the level of plasminogen activator released from isolated aortic segments of rats maintained at room temperature (24-28 degrees C) differed significantly from that of the 38 degrees C group. The animals maintained at 3 degrees C did not release plasminogen activator, suggesting that the fibrinolytic response was impaired at low temperature.

Contribution of adrenaline to the fibrinolytic activity evoked by E. coli endotoxin in the rat.

Intravenous injection of E. coli endotoxin (ETX), of adrenaline (AD) or of carbamylcholine (CBCH), caused fibrinolytic activity (FA), directly detectable on plasminogen-rich fibrin plates, to appear in the plasma of the rat. Adrenodemedullation abolished responses to ETX or CBCH, but enhanced those to AD. Rats given ETX exhibited marked hypotension, followed by a compensatory phase of normotension abolished by adrenodemedullation and significantly attenuated by phenoxybenzamine, an alpha-adrenergic blocking agent which however failed to block FA caused by either ETX or AD. Aspirin, but not indomethacin, inhibited FA evoked by ETX, AD or CBCH. These results suggest that FA evoked by ETX in the rat is caused by AD released from the adrenal gland and does involve the fatty acid cyclooxygenase system.