Control of interneurone firing pattern by axonal autoreceptors in the juvenile rat cerebellum

Recent work has shown that certain neurones have axonal GABA_A receptors, whose tonic activation modifies their firing properties and neurotransmitter release capability. In addition, results obtained in interneurones of the molecular layer of the cerebellum indicate that action potential-released GABA binds back to the axon that released it, generating an autoreceptor current. In the present paper, we show that at physiological Cl⁻_i concentration (15 m m ) and at 34–36°C, the autoreceptor current generates a large amplitude (up to 21 mV) afterdepolarization that lasts for about 150 ms, and that occasionally leads to double firing. Furthermore we show that elimination of the afterdepolarization, by either blocking GABA_A receptors, or eliminating the autoreceptor currents through prolonged whole-cell recording, decreases burst firing. I _h (a hyperpolarization-activated current) was previously found to be prominent in interneurone axons. We show that blocking I _h leads to an increase in the amplitude of the autoreceptor current as well as of the associated afterdepolarization, suggesting a shunting effect of I _h on autoreceptor-mediated afterdepolarization. Conversely, blocking I _h accentuates burst firing. The effects of autoreceptor-mediated afterdepolarization on firing are prominent during a period of development when interneurone synapses are stabilized and vanish by postnatal day 17 (PN 17), together with the expression of the autoreceptor current. Altogether, this work reveals a new role for autoreceptors in the regulation of cell excitability and firing pattern, which may contribute to the development and stabilization of the cerebellar network.     

Black-fly assemblage distribution patterns in streams in disturbed areas in southern Brazil

Black flies (Simuliidae) are considered to be pests in rural and in some urban areas in the south of Brazil due to the bites of females. Little information exists on the factors that contribute to Simuliidae distribution in these areas. We sampled 39 streams in the state of Rio Grande do Sul in September 2004 to address ecological aspects. Of the 18 species collected, those that occurred in more than 50% of the streams were: Simulium subnigrum Lutz 1910, Simulium pertinax Kollar 1882, Simulium subpallidum Lutz 1910 and Simulium incrustatum Lutz 1910. Species richness was not influenced by any of the environmental or geographical variables considered, and there was no pattern of species co-occurrence, corroborating the hypothesis of a stochastic distribution of the Simuliidae assemblage. When analyzed individually, only three of seven species with occurrence frequency >30% were related to any of the variables measured. The probabilities of occurrence of Simulium jujuyense Paterson & Shannon 1927 and S. pertinax were higher in streams with high values of water pH and electrical conductivity, whereas the opposite was observed for S. incrustatum. Therefore, due to stochastic distribution, the population studies of Simuliidae are more suitable for predicting the occurrence of species in rural areas than are studies of assemblages.     

Gait parameters,functional mobility and fall risk in individuals with early to moderate primary open angle glaucoma: a cross-sectional study

Objective

This study investigated the influence of early to moderate primary open angle glaucoma on gait, functional mobility and fall risk.

Possible sleep bruxism,circadian preference,and sleep-related characteristics and behaviors among dental students

Objective: To assess sleep bruxism prevalence and its association with circadian preference and sleep-related characteristics among dental students.

Methods: Dental students of the Federal University of Minas Gerais participated in this cross-sectional study. Participants answered a scale assessing individuals' circadian preference, and a questionnaire regarding sleep-related characteristics and behaviors, history of muscle ache in the temporomandibular area, and history of bruxism.

Results: One hundred fifty-two students participated in the study. Sleep bruxism was reported by 11.3%. Most students (63.2%) were classified as intermediary, 34.9% as morningness, and 1.3% as eveningness. Individuals who reported muscle ache in the temporomandibular area in the morning (PR = 3.5; 95% CI = 1.1–11.5) were more likely to be in the group with sleep bruxism.

Conclusion: Muscle ache in the temporomandibular area is an important associated factor with sleep bruxism among dental students. Special attention should be paid to dental students’ circadian preference.     

Pediatric Liver Transplant Outcome Using Severe Hypernatremic Donors

IntroductionPediatric liver transplantation is limited by donation. In the last 5 years, urgent conditions have forced transplant teams to accept donors with minor suboptimal conditions, termed “extended donor criteria.” Among those, the risk of using severe hypernatremic donors (SHD) for liver transplant is not yet well established. The aim of this study is to report the outcome of pediatric patients receiving grafts from SHD.MethodsClinical records of patients transplanted in the last 3 years at Hospital Luis Calvo Mackenna, Santiago, Chile, were reviewed. Outcome was evaluated in terms of patient and graft survival and complications potentially associated to the donor condition.ResultsFive of 33 deceased donor transplants presented with SHD. All recipients were waiting transplant in an acute condition, one of them in acute liver failure (ALF). No living related donor was available. Donors' serum sodium was 169 to 193 mEq/L before medical management and between 157 and 172 mEq/L at procurement. One patient died from sepsis related to biliary complications, and the patient suffering ALF developed primary graft nonfunction, received a second transplant 2 weeks later, and recovered to stable medical condition. No other complication was registered in these patients.DiscussionOur findings allow us to postulate that hypernatremic deceased donors may be used for pediatric liver transplant under special circumstances.     

Pediatric Liver Transplantation Experience and Outcome in Chile

IntroductionIn 1994 our group began its experience with pediatric liver transplantation. The experience gained during this period is the largest in the country, positioning the Hospital Luis Calvo Mackenna and Clinica Las Condes as major referral centers in the public and private sectors. The aim of this study was to report our experience of our pediatric liver transplantation program during this period.MethodsThe liver transplantation database of Hospital Luis Calvo Mackenna and Clinica Las Condes between January 1994 and July 2011 was reviewed recording age, gender, indications for transplantation, surgical technique, complications, and survival. Survival rates were calculated using Kaplan-Meier analysis.ResultsDuring the period described 230 transplantations were performed in 189 pediatric patients. Fifty-five percent were male patients. The average age was 5 years. The main causes of transplantation were biliary atresia (50%), fulminant hepatic failure (25%), and other cholestatic diseases by 10%. Vascular and biliary complications were the leading cause of graft loss and retransplantation. The overall rate of retransplantation at 5 years was 20%. The technique of living donor was used in 28% of the cases. The 1-year patient actuarial survival rate was 80%, 73% at 5 years, and 68% at 10 years. In the last 3 years the survival rate at 1 year exceeds 90%.DiscussionOur program includes more than 90% of the national liver experience. The incorporation of living donor is a milestone that has enabled us to save many patients who previously died while waiting for an organ. Its use in cases of full acute liver failure has allowed us to dramatically reduce mortality on the waiting list. Our results in the last 3 years reflect the experience that results in a significant decrease in mortality, comparing favorably to other series published in the international literature.     

Health-related Quality of Life After Pediatric Liver Transplant: Single-Center Experience in Chile

IntroductionOrthotopic liver transplantation is the treatment of choice for most terminal liver diseases in children. Currently, the improved survival of these patients is well documented, but their quality of life post-transplant is not described. In Chile, Hospital Luis Calvo Mackenna (HLCM) has performed pediatric liver transplantation in children from around the country since 1994. The aim of this study is to evaluate our patients' and parents' current quality of life.MethodsA cross-sectional study was conducted between July 2010 and June 2011. All liver transplant patients currently in control at HLCM were invited to complete the PedsQL 4.0 report (Pediatric Quality of Life Inventory). For each group, average score was calculated and comparisons were done using Student t and χ² tests.ResultsForty-nine patients were enrolled. One-third of the patients were between 2 and 4 years, one-third between 5 and 12, and the rest were 13 to 18 years old. Half of the patients had their transplants for more than 3 years, 53% were female, 53% lived in cities far from the transplant center, 72.5% had chronic liver disease, 53% had received a liver from cadaveric donor, and 21% had received more than 1 liver transplant. Patients under 4 years referred good health-related quality of life (HRQOL) in all categories. All school-age patients had poor or very poor psychosocial HRQOL.DiscussionOur good results obtained in transplant patients under 4 years may be because the questionnaire was completed by caregivers. The school-age patients were affected in terms of school functioning, as they were not able to participate in all the activities. These findings need to be compared with HRQOL perception in other groups, such as children with other chronic conditions, and evaluated with other broader factors, as reported in international HRQOL publications.