The tof-guard neuromuscular transmission monitor and its use in horses

Quando da utilização de bloqueadores neuromusculares, já foi enfatizado na literatura médica humana, que é de vital imporância a monitoração do bloqueio neuromuscular e que estes agentes nunca devem ser utilizados sem a mesma. O objetivo deste estudo foi o de avaliar o uso do monitor da transmissão neuromuscular TOF-Guard em eqüinos. Para tanto, doze eqüinos foram separados aleatoriamente para receberem como bloqueadores neuromusculares o pancurônio ou o atracúrio. Todos os eqüinos foram pré-medicados com romifidina, induzidos com diazepam e quetamina e mantidos com halotano. Foi administrado o atracúrio ou o pancurônio, seguindo-se a apnéia e início da ventilação mecânica controlada. O tempo entre a administração do relaxante muscular e a obtenção de um bloqueio máximo (T1=0), o retorno do T1 para 25% e da razão do TOF para 0,7 e o tempo do retorno do T1 de 25 para 75% foram mensurados. Concluiu-se que é de grande importância a monitoração do bloqueio neuromuscular quando da utilização de um bloqueador neuromuscular não-despolarizante, uma vez que ela torna o ato anestésico e cirúrgico mais seguro, com a utilização de doses adequadas que inviabilizam a superficialização do bloqueio durante o procedimento cirúrgico. O monitor TOF-Guard mostrou ser uma boa opção para a monitoração do bloqueio neuromuscular em eqüinos.

Influence of temperature upon effects of crotoxin and gamma-irradiated crotoxin at rat neuromuscular transmission

The influence of temperature upon the effects of crotoxin (CTX)? from Crotalus durissus terrificus venom, and gamma-irradiated (Co-60, 2000 Gy) crotoxin (iCTX) was studied in rat neuromuscular transmission 'in vitro'. Indirect twitches were evoked in the phrenic-diaphragm preparation by supramaximal strength pulses with a duration of 0.5 ms and frequency of 0.5 Hz. The phospholipase A(2) (PLA(2)) enzymatic activity of CTX and iCTX was assayed against phosphadityl choline in Triton X-100. At 27 degrees C, CTX (14 mu g/ml) did not affect the amplitude of indirectly evoked twitches. However, at 37 degrees C, CTX induced a time-dependent blockade of the neuromuscular transmission that started at 90 min and was completed within 240 min, iCTX (14 mu g/ml) was inneffective on the neuromuscular transmission either at 27 or 37 degrees C. The PLA(2) enzymatic activity of CTX at 37 degrees C was 84 and that at 27 degrees C was 27 mu mol fatty acid released/min/mg protein, and that of the iCTX at 37 degrees C was 39 mu mol fatty acid released/min/mg protein. Thus, it was concluded that the mechanism of detoxification of CTX by gamma radiation at the neuromuscular level relies on the loss of its PLA(2) enzymatic activity. 2000 Elsevier B.V. Ireland Ltd. All rights reserved.

Amplification of neuromuscular transmission by methylprednisolone involves activation of presynaptic facilitatory adenosine A(2A) receptors and redistribution of synaptic vesicles

The mechanisms underlying improvement of neuromuscular transmission deficits by glucocorticoids are still a matter of debate despite these compounds have been used for decades in the treatment of autoimmune myasthenic syndromes. Besides their immunosuppressive action, corticosteroids may directly facilitate transmitter release during high-frequency motor nerve activity. This effect coincides with the predominant adenosine A(2A) receptor tonus, which coordinates the interplay with other receptors (e.g. muscarinic) on motor nerve endings to sustain acetylcholine (ACh) release that is required to overcome tetanic neuromuscular depression in myasthenics. Using myographic recordings, measurements of evoked [H-3]ACh release and real-time video microscopy with the FM4-64 fluorescent dye, results show that tonic activation of facilitatory A(2A) receptors by endogenous adenosine accumulated during 50 Hz bursts delivered to the rat phrenic nerve is essential for methylprednisolone (03 mM)-induced transmitter release facilitation, because its effect was prevented by the A(2A) receptor antagonist, ZM 241385 (10 nM). Concurrent activation of the positive feedback loop operated by pirenzepine-sensitive muscarinic M-1 autoreceptors may also play a role, whereas the corticosteroid action is restrained by the activation of co-expressed inhibitory M-2 and Al receptors blocked by methoctramine (0.1 mu M) and DPCPX (2.5 nM), respectively. Inhibition of FM4-64 loading (endocytosis) by methylprednisolone following a brief tetanic stimulus (50 Hz for 5 s) suggests that it may negatively modulate synaptic vesicle turnover, thus increasing the release probability of newly recycled vesicles. Interestingly, bulk endocytosis was rehabilitated when methylprednisolone was co-applied with ZM241385. Data suggest that amplification of neuromuscular transmission by methylprednisolone may involve activation of presynaptic facilitatory adenosine A(2A) receptors by endogenous adenosine leading to synaptic vesicle redistribution. (C) 2014 Elsevier Ltd. All rights reserved.

Ação do extrato bruto da Tabernaemontana catharinensis e de seu alcalóide isolado sobre as atividades de fosfolipases A2 ofídicas em preparação neuromuscular de camundongos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Neuromuscular effects of venoms and crotoxin-like proteins from Crotalus durissus ruruima and Crotalus durissus cumanensis

A myographic study was performed to compare the neuromuscular effects of venoms and crotoxin-like proteins from Crotalus durissus ruruima and Crotalus durissus cumanensis in mice phrenic-diaphragm preparation. It was concluded that both venoms present neurotoxic activity as a consequence of their crotoxin content. Furthermore, crotoxin from C.d. cumanensis is more potent than that from C.d. ruruima venom. At the concentration range in which both venoms express neurotoxic activity, only C.d. cumanensis venom also manifest a direct myotoxic effect that probably involves the synergic participation of other components than crotoxin. (C) 2015 Elsevier Ltd. All rights reserved.

MOTOR NERVE CONDUCTION and REPETITIVE NERVE STIMULATION IN CAPTIVE RING-TAILED COATI (NASUA NASUA)

There are few electrophysiologic studies in wild animals. The aim of this study was to determine normal data for motor nerve conduction studies and repetitive stimulation in sciatic-tibial and ulnar nerves in clinically normal captive coati. Eight adult ring-tailed coatis (Nasua nasua), two females and six males weighing 68 kg, were used. Average nerve conduction velocity was 70.81 m/sec (standard deviation [SD] = 3.98) and 56.93 m/sec (SD = 4.31) for the sciatic-tibial and ulnar nerves, respectively. Repetitive stimulation responses demonstrated minimal variations of the area of the compound muscle action potentials at low (3 Hz) and high (20 Hz) frequencies. The maximal obtained decremental area response was 8%. These normal data of conduction studies may be used in assessing abnormalities for clinical diagnosis. In addition, the obtained normal repetitive stimulation data were similar to dogs and humans and may be used for post- and presynaptic disturbances of the neuromuscular transmission in coatis.

Ação neuro-muscular do veneno crotálico: dados preliminares

Estudamos 6 pacientes, 2 cães e um coelho com intoxicação crotálica. Avaliamos a condução nervosa periférica sensitiva e motora, a transmissão neuromuscular e eletromiografias. As biópsias de músculo foram processadas por histoquímica. Os 6 pacientes apresentaram mononeuropatia sensitiva no nervo periférico adjacente ao local da inoculação do veneno e encontramos evidências histoquímicas de miopatia mitocondrial. Os defeitos da transmissão neuromuscular foram mínimos. A maioria dos autores admite que veneno crotálico determina síndrome miastênica. Nossos achados indicam que ptose palpebral, facies miastênico e fraqueza muscular observados após acidente crotálico, correspondem provavelmente a miopatia mitocondrial, muitas vezes transitória e reversível.

Avaliação eletroneuromiográfica em gatos normais e submetidos ao hiperparatireoidismo secundário nutricional

O trabalho teve por objetivos estudar a condução nervosa motora e a transmissão neuromuscular e eletromiografia de repouso em gatos normais (grupo I), submetidos a hiperparatireoidismo secundário nutricional (grupo II). Para estudo normativo (grupo I), foram utilizados 10 gatos, aparentemente saudáveis, sem raça definida, sendo seis machos e quatro fêmeas, com idades entre 4 e 5 meses e peso médio de 1,67kg. No grupo II, empregaram-se 10 gatos, sem raça definida, sendo cinco machos e cinco fêmeas, com idade aproximada inicial entre 2 e 3 meses e peso inicial médio de 820 gramas. Após um período de adaptação de 10 dias, foram alimentados por 60 dias com coração bovino moído e cru, visando a indução de hiperparatireoidismo secundário nutricional. Foi possível concluir que latência, amplitude e velocidade de condução nervosa motora e os achados eletromiográficos das atividades insercional e espontânea de gatos com hiperparatireoisdismo secundário nutricional, apresentaram um padrão similar aos de gatos normais da mesma idade. Para estimulações repetitivas a 3Hz, observou-se tendência global a decremento dos potenciais de ação musculares compostos e a 10 Hz houve tendência de incremento ou decremento; entretanto, tais variações apresentaram-se dentro dos limites de normalidade.

Structure and biological activities of eumenine mastoparan-AF (EMP-AF), a new mast cell degranulating peptide in the venom of the solitary wasp (Anterhynchium flavomarginatum micado)

A new mast cell degranulating peptide, eumenine mastoparan-AF (EMP-AF), was isolated from the venom of the solitary wasp Anterhynchium flavomarginatum micado, the most common eumenine wasp found in Japan. The structure was analyzed by FAB-MS/MS together with Edman degradation, which was corroborated by solid-phase synthesis. The sequence of EMP-AF, Ile-Asn-Leu-Leu-Lys-Ile-Ala-Lys-Gly-Ile-lle-Lys-Ser-Leu-NH(2), was similar to that of mastoparan, a mast cell degranulating peptide from a hornet venom; tetradecapeptide with C-terminus amidated and rich in hydrophobic and basic amino acids. In fact, EMP-AF exhibited similar activity to mastoparan in stimulating degranulation from rat peritoneal mast cells and RBL-2H3 cells. It also showed significant hemolytic activity in human erythrocytes. Therefore, this is the first example that a mast cell degranulating peptide is found in the solitary wasp venom. Besides the degranulation and hemolytic activity, EMP-AF also affects on neuromuscular transmission in the lobster walking leg preparation. Three analogs EMP-AF-1 similar to 3 were snythesized and biologically tested together with EMP-AF, resulting in the importance of the C-terminal amide structure for biological activities. (C) 2000 Elsevier B.V. Ltd. All rights reserved.

Gabaergic-benzodiazepine system is involved in the crotoxin-induced anxiogenic effect

The behavioral effects of crotoxin (CTX), the major component of Crotalus durissus terrificus venom, were studied in rats submitted to the open field, holeboard, and social interaction tests. CTX (100, 250, and 500 mu g/kg, IP) was administered 2 h before the tests. In the open field, CTX reduced ambulation (250 mu g/kg) and rearing (250 and 500 mu g/kg) and increased grooming (100 and 250 mu g/kg) and freezing (250 mu g/kg). In the holeboard and social interaction, all the CTX doses evaluated decreased, respectively, head dip and head dipping, and social interaction time. The CTX-induced behavioral alterations could be attributed to its neuromuscular transmission blockade, but this possibility was ruled out because CTX (250 and 500 mu g/kg, IP, 2 h before the rotarod test) was unable to modify the rotarod performance of rats. The involvement of the benzodiazepine receptor in the CTX-induced behavioral alterations was investigated through the pretreatment (30 min before the tests, IP) of the animals with diazepam (1.2 mg/kg), or flumazenil (4 and 10 mg/kg). Both diazepam and flumazenil antagonized the CTX induced behavioral alterations in the open field, holeboard, and social interaction tests. This study demonstrated that: (1) CTX is an anxiogenic compound; and (2) the gabaergic-benzodiazepine system may play a role in the CTX-induced anxiogenic effect. (C) 1999 Elsevier B.V.

Dissociation of enzymatic and pharmacological properties of piratoxins-I and -III, two myotoxic phospholipases A(2) from Bothrops pirajai snake venom

Piratoxins (PrTX) I and III are phospholipases A(2) (PLA(2)s) or PLA(2) homologue myotoxins isolated from Bothrops pirajai snake venom, which also induce myonecrosis, bactericidal activity against Escherichia coli, disruption of artificial membranes, and edema. PrTX-III is a catalytically active hemolytic and anticoagulant Asp49 PLA(2), while PrTX-I is a Lys49 PLA, homologue, which is catalytically inactive on artificial substrates, but promotes blockade of neuromuscular transmission. Chemical modifications of His, Lys, Tyr, and Trp residues of PrTX-I and PrTX-III were performed, together with cleavage of the N-terminal octapeptide by CNBr and inhibition by heparin and EDTA. The lethality, bactericidal activity, myotoxicity, neuromuscular effect, edema inducing effect, catalytic and anticoagulant activities, and the liposome-disruptive activity of the modified toxins were evaluated. A complex pattern of functional differences between the modified and native toxins was observed. However, in general, chemical modifications that significantly affected the diverse pharmacological effects of the toxins did not influence catalytic or membrane disrupting activities. Analysis of structural changes by circular dichroism spectroscopy demonstrated significant changes in the secondary structure only in the case of N-terminal octapeptide cleavage. These data indicate that PrTX-I and PrTX-III possess regions other than the catalytic site, which determine their toxic and pharmacological activities. (C) 2001 Academic Press.

Guanidine Affects Differentially the Twitch Response of Diaphragm, Extensor Digitorum Longus and Soleus Nerve-Muscle Preparations of Mice

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Tempo de latencia do rocuronio e da succinilcolina e condicoes de intubacao traqueal

Background and Objectives - Pulmonary aspiration of gastric content during induction of anesthesia for emergency surgical procedures is a serious complication; fast endotracheal intubation under these circumstances is of vital importance to secure the airways. Despite its numerous side effects, succinylcholine is used for this purpose. Rocuronium is the most recently introduced aminoesteroid neuromuscular blocking drug with short onset. The objective of this study was to compare the onset time and intubating conditions of rocuronium and succinylcholine. Methods - After informed consent, forty-five patients were randomly allocated into three groups of 15: Group I (GI) = succinylcholine 1 mg.kg-1; Group II (GII) = rocuronium 0.6 mg.kg-1; Group III (GIII) = rocuronium 0.9 mg.kg-1. Every patient was premedicated with midazolam 15 mg per os and induction of anesthesia was made with fentanyl 10 μg.kg-1 and etomidate 0.3 mg.kg-1. The neuromuscular block was monitored with the TOP-Guard neuromuscular transmission monitor. The TOP-Guard neuromuscular monitor uses an accelerometer to measure the response to nerve stimulation. The stimulating electrodes were placed close to the course of the ulnar nerve at the wrist. The onset time was considered as the time between the end of neuromuscular drug injection and the twitch height (T1) decrease to 10%. Heart rate and arterial blood pressure were registered at 6 moments before and after induction of anesthesia. Results - The onset time results were: Group I, 71 s; Group II, 120 s and Group III, 70 s or GI = GIII < GII (F = 8.862; p < 0.01). There were 43 patients exhibiting excellent intubating conditions and 2 with good intubating conditions. Heart rate and arterial blood pressure showed alterations due to induction of anesthesia and intubation. Conclusions - Rocuronium 0.9 mg.kg-1 can be used in rapid sequence induction because it has a short onset time which is similar to that of succnylcholine. It is likely that rocuronium would be a good indication in patients with high intracranial pressure, burns and neuromuscular diseases.

Bothropstoxin-I reduces evoked acetylcholine release from rat motor nerve terminals: Radiochemical and real-time video-microscopy studies

Understanding the biological activity profile of the snake venom components is fundamental for improving the treatment of snakebite envenomings and may also contribute for the development of new potential therapeutic agents. In this work, we tested the effects of BthTX-I, a Lys49 PLA2 homologue from the Bothrops jararacussu snake venom. While this toxin induces conspicuous myonecrosis by a catalytically independent mechanism, a series of in vitro studies support the hypothesis that BthTX-I might also exert a neuromuscular blocking activity due to its ability to alter the integrity of muscle cell membranes. To gain insight into the mechanisms of this inhibitory neuromuscular effect, for the first time, the influence of BthTX-I on nerve-evoked ACh release was directly quantified by radiochemical and real-time video-microscopy methods. Our results show that the neuromuscular blockade produced by in vitro exposure to BthTX-I (1 μM) results from the summation of both pre- and postsynaptic effects. Modifications affecting the presynaptic apparatus were revealed by the significant reduction of nerve-evoked [3H]-ACh release; real-time measurements of transmitter exocytosis using the FM4-64 fluorescent dye fully supported radiochemical data. The postsynaptic effect of BthTX-I was characterized by typical histological alterations in the architecture of skeletal muscle fibers, increase in the outflow of the intracellular lactate dehydrogenase enzyme and progressive depolarization of the muscle resting membrane potential. In conclusion, these findings suggest that the neuromuscular blockade produced by BthTX-I results from transient depolarization of skeletal muscle fibers, consequent to its general membrane-destabilizing effect, and subsequent decrease of evoked ACh release from motor nerve terminals. © 2012 Elsevier Ltd.

Estudos estruturais com fosfolipases A2 isoladas de venenos de serpentes dos gêneros Bothrops e Crotalus

Pós-graduação em Ciências Biológicas (Genética) - IBB