NAP prevents hippocampal oxidative damage in neonatal rats subjected to hypoxia-induced seizures.

Neonatal seizures in which hypoxic-ischemic encephalopathy is the main triggering etiology have a challenging diagnosis and limited efficacy of treatment. NAP (NAPVSIPQ) has shown extensive neuroprotective and antioxidant capacity in vitro and in vivo. To evaluate its neuroprotective role in the context of seizures associated with perinatal hypoxia, we assessed the integrity of DNA and lipid membranes as well as the redox status in the hippocampus of 10-day-old rats exposed to hypoxia-induced seizures (HS) with and without NAP treatment. Rats were exposed to transient global hypoxia (12 min exposure to 5-7% O2 was able to induce electrographic seizures) or room air with subsequent intraperitoneal NAP (0.03, 0.3 or 3 microg/g) or vehicle administration. Results showed elevated DNA damage immediately after the insult until 72 h post-HS, while oxidized bases were only detected 3, 6 and 24 h later. In addition, thiobarbituric acid reactive species peaked at 6 h in parallel with decreased levels of reduced glutathione between 3 and 72 h post-HS insult. Our findings expand on the knowledge about the time course of HS-induced oxidative damage and demonstrate for the first time that a single NAP injection dose-dependently prevents HS-induced oxidative damage to DNA and lipid membranes, in correlation with modulation of the glutathione system. Hence, NAP may represent a promising therapeutic strategy for avoiding HS-induced oxidative damage.

Assessing cochlear evoked potentials after electrocautery-induced trauma to the utricle.

UNLABELLED: Utriculostomy is a new surgical alternative for Ménière's disease. The basis of this procedure is that the outcome of an electrocautery-induced utricular trauma does not affect cochlear function. However, a demonstration of the hypothesis that this approach to the utricle would preserve hearing is still pending. OBJECTIVE: To determine whether any changes would occur in the electrical potentials evoked in the cochlea and auditory nerve before, during, and 1 month after a surgical procedure in the utricule in an animal model. MATERIALS AND METHODS: An experimental study. Eight sheep underwent electrocautery-induced utricular trauma, and their cochlear function was assessed by electrocochleography--recording of electrical evoked potentials, in the preoperative, immediate postoperative and medium-term postoperative periods. The results were analyzed statistically. RESULTS: There were no statistically significant variations in amplitude (p = 0.099) and latency (p = 0.591) before and 1 month after the surgical procedure. There was a statistically significant change in the summation of the potential/action potential area ratio (p = 0.0122), a calculated loss of 11.8 dB. CONCLUSION: The intervention performed in this study enabled us to conclude that, taking into account the impaired electrophysiological responses observed during and 1 month after the surgical procedure, hearing was preserved in the operated sheep.

Alterations in cochlear function during induced acute hyperinsulinemia in an animal model.

UNLABELLED: Hyperinsulinism secondary to peripheral insulin resistance has been described as the most frequent etiologic factor in cochlear and vestibular syndromes. AIM: This experimental study recorded and analyzed evoked auditory potential changes using transtympanic electrocochleography (EcochG) during induced acute hyperinsulinism in an animal model. MATERIALS AND METHODS: Six adult male sheep were randomly divided into 2 groups. The animals were submitted to EcochG under general anesthesia, and a peripheral blood sample was collected to measure glycemia and insulinemia. Animals in the intervention group (n=3) received regular human insulin IV (0.1 U/kg). The control group (n=3) received saline solution. Glycemia and insulinemia were measured simultaneously with the recording of evoked potentials at 10-minute intervals during 90 minutes. RESULTS: The intervention group experienced a progressive suppression in action potential amplitude when compared to the control group (p=0.001). CONCLUSION: Data strongly suggest that acute induced hyperinsulinism suppresses cochlear function. Results may be attributed to loss of Na+K+ATPase activity in the stria vascularis, leading to loss of endocochlear potential and subsequent depolarization of cochlear hair cells as well as of neural cells in the auditory portion of cranial nerve VIII.

Avaliação dos potenciais evocados cocleares após lesão do utrículo por eletrocauterização / Assessing cochlear evoked potentials after electrocautery-induced trauma to the utricle

A utriculostomia é uma nova alternativa cirúrgica para a doença de Ménière. A hipótese cirúrgica desse procedimento é a de que o desfecho de uma lesão do utrículo por eletrocauterização não interfere na função coclear. Contudo, a hipótese de que essa abordagem do utrículo preserva a audição ainda não foi comprovada. OBJETIVO: Determinar se ocorrem mudanças nos potenciais elétricos evocados na cóclea e no nervo auditivo antes, durante e 1 mês após o procedimento cirúrgico no utrículo em modelo animal. MATERIAIS E MÉTODOS: Estudo experimental: Oito ovelhas foram submetidas à lesão do utrículo por eletrocauterização e sua função coclear foi avaliada por meio de eletrococleografia, registrando-se os potenciais elétricos evocados nos períodos pré-operatório, pós-operatório imediato e pós-operatório de médio prazo. Os resultados foram analisados estatisticamente. RESULTADOS: Não houve variação estatisticamente significativa na amplitude (p = 0,099) e na latência (p = 0,591) antes e 1 mês após o procedimento cirúrgico. Houve alteração estatisticamente significativa na razão entre potencial de somação/potencial de ação (p = 0,0122), representando uma perda calculada de 11,8 dB. CONCLUSÃO: A intervenção realizada no utrículo neste estudo permite concluir que, tendo em conta respostas eletrofisiológicas deficientes observadas durante e 1 mês após o procedimento cirúrgico, houve preservação da audição nas ovelhas operadas.

Utriculostomy is a new surgical alternative for Ménière's disease. The basis of this procedure is that the outcome of an electrocautery-induced utricular trauma does not affect cochlear function. However, a demonstration of the hypothesis that this approach to the utricle would preserve hearing is still pending. OBJECTIVE: To determine whether any changes would occur in the electrical potentials evoked in the cochlea and auditory nerve before, during, and 1 month after a surgical procedure in the utricule in an animal model. MATERIALS AND METHODS: An experimental study. Eight sheep underwent electrocautery-induced utricular trauma, and their cochlear function was assessed by electrocochleography - recording of electrical evoked potentials, in the preoperative, immediate postoperative and medium-term postoperative periods. The results were analyzed statistically. RESULTS: There were no statistically significant variations in amplitude (p = 0.099) and latency (p = 0.591) before and 1 month after the surgical procedure. There was a statistically significant change in the summation of the potential/action potential area ratio (p = 0.0122), a calculated loss of 11.8 dB. CONCLUSION: The intervention performed in this study enabled us to conclude that, taking into account the impaired electrophysiological responses observed during and 1 month after the surgical procedure, hearing was preserved in the operated sheep.

Tratamento cirúrgico da doença de Ménière por meio de Shunts labirínticos: Passado e presente / Surgical treatment of Meniere disease via labyrinth Shunt: Past and present

Introdução: As cirurgias dos shunts endolinfáticos empregadas para o tratamento da vertigem na doença de Ménière incapacitante permanece um tópico controverso. Portmann, em 1926, foi o primeiro a executar a cirurgia, incisando o saco endolinfático com o objetivo de diminuir a pressão endolinfática da orelha interna. Planejadas para criar uma fístula que conecte o espaço endo e perilinfático, as saculotomias foram descritas por FICK em 1964, por CODY em 1969 e por SCHUKNECHT (cocleossaculotomia) em 1982, entretanto foram paulatinamente abandonadas devido à alta incidência de perda auditiva. Uma nova e promissora opção cirúrgica dos shunts, em caráter experimental, é a utriculostomia, realizada por LAVINSKY em 1999. Objetivo: Realizar uma revisão da literatura sobre as principais técnicas cirúrgicas dos shunts endolinfáticos empregados no tratamento da doença de Ménière, seus resultados e o que há de avanços no entendimento desses procedimentos. Método: Com base nos dados da literatura, são discutidas as principais técnicas cirúrgicas dos shunts endolinfáticos e sua racionalidade no tratamento da doença de Ménière incapacitante. Conclusão: Existe muita controvérsia sobre a efetividade dos procedimentos cirúrgicos dos shunts endolinfáticos para o tratamento da doença de Ménière incapacitante, e muitos deles causam danos à orelha interna. A cirurgia experimental utriculostomia, portanto, parece-nos uma opção promissora. Futuras pesquisas poderão fornecer a resposta para essa questão...

Introduction: The surgerys of the endolymphatic shunt are employed in the treatment of the vertigo of Meniere disease disabling, remains a controversial topic. Portmann in 1926, was the first to perform the surgery, incising the endolymphatic sac aimming the decrease of the endolymphatic pressure of the inner ear. Planned to create a fistula that connects the endo and perilymphatic space, the sacculotomy were described by Fick in 1964, by Cody in 1969 e by Schuknecht (cochleosacculotomy) in 1982, however they were gradually abandoned because of the high incidence of hearing loss. A new and promising surgery option of shunt, still experimental is utriculostomy, performed by LAVINSKY in 1999. Objective: Make a review of literature about the main surgical techniques of endolymphatic shunt, used in the treatment of Meniere disease, its results and the advance in the understanding of these procedures. Methods: Based on the literature data, the main surgical techniques of endolymphatic shunt are discussed and its rationality in the treatment of Meniere's disabling disease. Conclusion: There are a lot of controversy over the effectiveness of surgical procedures of endolymphatic shunt for the treatment of Meniere's disabling disease, and a lot of them damage the inner ear. The experimental surgery of utriculostomy, so it seems, a promising option. Future research can give an answer to this matter...

Alterations in cochlear function during induced acute hyperinsulinemia in an animal model / Alterações na função coclear durante a indução aguda de hiperinsulinismo em um modelo animal

Hyperinsulinism secondary to peripheral insulin resistance has been described as the most frequent etiologic factor in cochlear and vestibular syndromes. AIM: This experimental study recorded and analyzed evoked auditory potential changes using transtympanic electrocochleography (EcochG) during induced acute hyperinsulinism in an animal model. MATERIALS AND METHODS: Six adult male sheep were randomly divided into 2 groups. The animals were submitted to EcochG under general anesthesia, and a peripheral blood sample was collected to measure glycemia and insulinemia. Animals in the intervention group (n=3) received regular human insulin IV (0.1 U/kg). The control group (n=3) received saline solution. Glycemia and insulinemia were measured simultaneously with the recording of evoked potentials at 10-minute intervals during 90 minutes. RESULTS: The intervention group experienced a progressive suppression in action potential amplitude when compared to the control group (p=0.001). CONCLUSION: Data strongly suggest that acute induced hyperinsulinism suppresses cochlear function. Results may be attributed to loss of Na+K+ATPase activity in the stria vascularis, leading to loss of endocochlear potential and subsequent depolarization of cochlear hair cells as well as of neural cells in the auditory portion of cranial nerve VIII.

O hiperinsulinismo secundário à resistência periférica à insulina tem sido apontado como o fator etiológico mais frequente de síndromes tanto vestibulares como cocleares. OBJETIVO: Este estudo experimental registrou e analisou as alterações dos potenciais evocados auditivos através da eletrococleografia (ECoG) transtimpânica durante o hiperinsulinismo agudo induzido em um modelo animal. MATERIAL E MÉTODO: 6 ovelhas macho adultas foram divididas randomicamente em 2 grupos. Os animais submeteram-se ao exame de ECoG sob anestesia geral, e sangue periférico foi coletado para determinação de glicemia e hiperinsulinemia. Os animais do grupo intervenção (n=3) receberam insulina regular humana IV (0.1U/kG). O grupo controle (n=3) recebeu solução salina. Glicemia e insulinemia foram determinadas simultaneamente com o registro dos potenciais evocados a intervalos de 10 minutos, durante 90 minutos. RESULTADO: O grupo intervenção apresentou uma progressiva supressão da amplitude do potencial de ação quando comparado ao grupo controle (p=0.001). CONCLUSÃO: Os dados sugerem fortemente que o hiperinsulinismo agudo induzido suprime a atividade coclear. Os resultados podem ser atribuídos à perda da atividade da enzima Na+K+ATPase na estria vascular, levando à perda do potencial endococlear e da despolarização subsequente das células ciliadas assim como das células neurais que compõem a porção auditiva do VIII par craniano.