Induced astigmatism in extracapsular cataract extraction: long-term follow-up

PURPOSE: To study the long-term behavior of induced astigmatism in a series of patients who underwent extracapsular extraction in which a superoposterior limbal incision sutured with interrupted 10-0 mononylon sutures was performed. METHODS: 38 eyes of 35 patients were studied, 21 females and 17 males, with ages varying from 47 to 85 year (average = 70.17 year). All cases were operated by the same surgeon. The postoperative follow-up ranged from 15 to 33 months (average = 22.07 months). None of the cases had any of the sutures sectioned or removed. All patients recovered a corrected visual acuity equal or superior to 0.5. To calculate the induced astigmatism in each case, the preoperative and postoperative keratometric readings were considered and a program developed by Jaffe was used. RESULTS: The induced astigmatism ranged from 0.13 diopters (D) to 2.74D (average = 1.19D). Regarding the axis, there was induction of with-the-rule astigmatism in the majority of cases (60.52%). A significant shift in the dioptric power of the induced astigmatism was observed when the preoperative keratometric readings were compared with the keratometric readings recorded at the second postoperative week, between the first and the third postoperative months, between the third and the sixth postoperative months and after the twelfth postoperative month. CONCLUSION: When mononylon 10-0 is used as suture material in extracapsular extraction, the initially observed values of with-the-rule induced astigmatism tend to decrease during the post operative period.OBJETIVO: Estudar o comportamento do astigmatismo induzido a longo prazo em uma série de pacientes submetidos à cirurgia extracapsular da catarata, nos quais foi utilizada incisão límbica posterior superior suturada com pontos separados de mononylon 10-0. MÉTODOS: Foram estudados 38 olhos, de 35 pacientes, sendo 21 do sexo feminino e 14 do sexo masculino, com idades variando entre 47 e 85 anos (média = 70,17 anos). Todos os casos foram operados pelo mesmo cirurgião. O período de acompanhamento pós-operatório variou de 15 a 33 meses (média = 22,07 meses). Nenhum dos casos teve qualquer dos pontos seccionado ou removido. Todos os pacientes atingiram acuidade visual corrigida igual ou superior a 0,5. Para o cálculo do astigmatismo induzido foram consideradas as medidas ceratométricas pré e pós-operatórias e foi utilizado um programa desenvolvido por Jaffe. RESULTADOS: O astigmatismo induzido variou de 0,13 dioptria (D) a 2,74 D (média = 1,19 D). Em relação aos eixos, na maioria dos casos houve indução de astigmatismo a favor da regra (60,52%). Foi observada mudança significativa no valor dióptrico do astigmatismo quando foram comparadas as leituras ceratométricas registradas pré-operatoriamente até a segunda semana pós-operatória, entre o primeiro e o terceiro meses pós-operatórios, entre o terceiro e o sexto meses pós-operatórios e após o décimo-segundo mês pós-operatório. CONCLUSÃO: Quando o mononylon 10-0 é utilizado como material de sutura na cirurgia extracapsular da catarata, os valores de astigmatismo a favor da regra inicialmente observados tendem a diminuir com o tempo.Universidade Federal do Rio de JaneiroUniversidade Federal de São Paulo (UNIFESP)UNIFESPSciEL

The ladder-shaped polyether toxin gambierol anchors the gating machinery of Kv3.1 channels in the resting state

Voltage-gated potassium (Kv) and sodium (Nav) channels are key determinants of cellular excitability and serve as targets of neurotoxins. Most marine ciguatoxins potentiate Nav channels and cause ciguatera seafood poisoning. Several ciguatoxins have also been shown to affect Kv channels, and we showed previously that the ladder-shaped polyether toxin gambierol is a potent Kv channel inhibitor. Most likely, gambierol acts via a lipid-exposed binding site, located outside the K(+) permeation pathway. However, the mechanism by which gambierol inhibits Kv channels remained unknown. Using gating and ionic current analysis to investigate how gambierol affected S6 gate opening and voltage-sensing domain (VSD) movements, we show that the resting (closed) channel conformation forms the high-affinity state for gambierol. The voltage dependence of activation was shifted by >120 mV in the depolarizing direction, precluding channel opening in the physiological voltage range. The (early) transitions between the resting and the open state were monitored with gating currents, and provided evidence that strong depolarizations allowed VSD movement up to the activated-not-open state. However, for transition to the fully open (ion-conducting) state, the toxin first needed to dissociate. These dissociation kinetics were markedly accelerated in the activated-not-open state, presumably because this state displayed a much lower affinity for gambierol. A tetrameric concatemer with only one high-affinity binding site still displayed high toxin sensitivity, suggesting that interaction with a single binding site prevented the concerted step required for channel opening. We propose a mechanism whereby gambierol anchors the channel’s gating machinery in the resting state, requiring more work from the VSD to open the channel. This mechanism is quite different from the action of classical gating modifier peptides (e.g., hanatoxin). Therefore, polyether toxins open new opportunities in structure–function relationship studies in Kv channels and in drug design to modulate channel function

Tecnologie informatiche e handicap nella scuola italiana

Informazione, reperibilità, standardizzazione: tre punti chiave per facilitare l’introduzione delle tecnologie informatiche nella scuola a sostegno degli alunni disabil

Channels as taste receptors in vertebrates

Taste reception is fundamental for proper selection of food and beverages. Chemicals detected as taste stimuli by vertebrates include a large variety of substances, ranging from inorganic ions (e.g., Na+, H+) to more complex molecules (e.g., sucrose, amino acids, alkaloids). Specialized epithelial cells, called taste receptor cells (TRCs), express specific membrane proteins that function as receptors for taste stimuli. Classical view of the early events in chemical detection was based on the assumption that taste substances bind to membrane receptors in TRCs without permeating the tissue. Although this model is still valid for some chemicals, such as sucrose, it does not hold for small ions, such as Na+, that actually diffuse inside the taste tissue through ion channels. Electrophysiological, pharmacological, biochemical, and molecular biological studies have provided evidence that indeed TRCs use ion channels to reveal the presence of certain substances in foodstuff. In this review, we focus on the functional and molecular properties of ion channels that serve as receptors in taste transduction

Electrophysiological heterogeneity in a functional subset of mouse taste cells during postnatal development

Taste cells in adult mammals are functionally heterogeneous as to the expression of ion channels. How these adult phenotypes are established during postnatal development, however, is not yet clear. We have addressed this issue by studying voltage-gated K+ and Cl- currents (I-K and I-Cl, respectively) in developing taste cells of the mouse vallate papilla. I-K and I-Cl underlie action potential waveform and firing properties, and play an important role in taste transduction. By using the patch clamp technique, we analyzed these currents in a specific group of cells, called Na/OUT cells and thought to be sensory. In adult mice, three different electrophysiological phenotypes of Na/OUT cells could be detected: cells with I-K (K cells); cells with both I-K and I-Cl (K+Cl cells); and cells with I-Cl (Cl cells). In contrast, at early developmental stages (2-4 postnatal days, PD) there were no Cl cells, which appeared at PD 8. Our findings indicate a mechanism that contributes to building-up the functional heterogeneity of mammalian taste cells during the postnatal development