Influence of barium on rectification in rat neocortical neurons

The effect of low concentrations of barium on the membrane properties of rat neocortical neurons was studied in vitro. Potassium currents were examined using single-electrode current- and voltage-clamp techniques. Neurons responded to bath application of barium (10–100 μM) with a membrane depolarization associated with an increase in input resistance. Under voltage clamp conditions, an inward shift in holding current was observed. The effects of barium were rapidly reversible upon washing and persisted in the presence of TTX. The equilibrium potential for the barium-induced inward current was near −110 mV, suggesting that barium inhibited a tonically active potassium conductance. Measurements of current voltage relationships indicated an inward rectification of this conductance between −50 and −130 mV. These results provide strong evidence that barium blocks a persistent potassium ‘leak’ current in neocortical neurons that contributes to the resting potential of these cells

Expression Patterns of Arabidopsis DRG Genes: Promoter-GUS Fusions, Quantitative RT-PCR and Patterns of Protein Accumulation in Response to Environmental Stresses

DRGs are very highly conserved GTP-binding proteins. All eukaryotes contain DRG1 and DRG2 orthologs. Arabidopsis has three DRGs: AtDRG1 (At4g39520), AtDRG2 (At1g17470), and AtDRG3 (At1g72660). DRG2 and DRG3 encode proteins that are 95% identical; identity between DRG1 and DRG2/3 is 55%. The focus of this article is expression of Arabidopsis DRGs. DRG1 and DRG2 promoter-GUS constructs showed similar spatial expression in seedlings and mature organs, but gene-specific differences were noted. Quantitative real-time PCR experiments indicated similar levels of DRG1 and DRG2 mRNA accumulation in most tissues. DRG3 transcripts were very low in all tissues. Heat stress at 37 C led to a 10-fold increase in DRG1 transcripts and a 1000-fold increase in DRG3 transcripts. DRG1 antibodies recognized a 43-kD protein, and DRG2 antibodies recognized bands at 30, 43, and 45 kD. Plants were exposed to stresses (salt, heat, cold, UV light, osmotic, and other stresses) and examined by Western blotting. Only heat stress caused detectable changes. Heat did not affect DRG1, but DRG2 and a 72-kD protein recognized by DRG2 antibodies both increased. The modest changes in DRG mRNA and protein levels seen here suggest that other types of regulation, such as altered subcellular localization, may be important for their cellular functions

Update on the management of Lennox-Gastaut syndrome with a focus on rufinamide

Carl E StafstromSection of Pediatric Neurology, Departments of Neurology and Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, USAObjective: This review summarizes the treatment of Lennox-Gastaut syndrome, an intractable epileptic encephalopathy of early childhood. In particular, the review focuses on rufinamide, a recently released anticonvulsant medication with reported effectiveness in this epilepsy syndrome.Methods: A systematic literature search (PubMed) was performed to review the existing literature pertaining to the treatment of Lennox-Gastaut syndrome as well as studies involving rufinamide as an anticonvulsant medication.Results: The published literature to date documents a beneficial effect of rufinamide on children over 4 years old with Lennox-Gastaut syndrome. Studies indicate a significant decrease in tonic and atonic seizure frequency as well as total seizure frequency compared to placebo-treated children. Rufinamide appears to be well tolerated and a safe medication, somnolence and vomiting being the most common side effects.Conclusions: Rufinamide is a promising adjunctive therapy for Lennox-Gastaut syndrome, an intractable childhood epilepsy. To ensure its optimal effectiveness, clinicians must be familiar with the medication’s clinical response profile and potential for adverse effects.Keywords: pediatric, epilepsy, epileptic encephalopathy, Lennox-Gastaut syndrome, rufinamid

TCA Microsatellite Repeats in the 5’UTR of the Sat5 Gene of Wild and Cultivated Accessions of Pisum and of Four Closely Related Genera

PsSat5, a cDNA clone from Pisum sativum cv. Alaska, contained a microsatellite consisting of 15 TCA repeats within the 59UTR. This SSR microsatellite was immediately upstream of the presumptive ATG start codon. PCR amplification of genomic DNA from cv. Alaska yielded an identical sequence. This repeat region was analyzed from 10 additional wild and cultivated accessions of Pisum and from four closely related genera (Cicer, Lathyrus, Lens, and Vicia). All of the sequences were generally quite similar, with the exception of the number of TCA repeats (region 3) and a short domain immediately upstream of the repeats (region 2). Pisum humile-northern and Lathyrus each contained four TCA repeats (the fewest number observed). Similar to P. sativum-Alaska and other cultivated peas, Lens contained 15 repeats, the largest number observed. The number of TCA repeats does not appear to correspond to the established phylogeny of these accessions, so the cellular events that generated variable numbers of repeats probably have occurred repeatedly and have involved both expansions and contractions in the number of repeats. The mRNA corresponding to PsSat5 was found in all tissues of P. sativum-Alaska that were examined, but its abundance in leaves and sepals was low. The level of expression was similar in growing and nongrowing stems, roots, and axillary buds. Northern blot analysis of stems and leaves of all 15 accessions showed similar levels of expression. Therefore, there is not a clear correlation between the number of TCA repeats in the 59UTR and the level of Sat5 expression

Are Annulate Lamellae in the Drosophila Embryo the Result of Overproduction of Nuclear Pore Components?

Annulate lamellae are cytoplasmic organelles composed of stacked sheets of membrane containing pores that are structurally indistinguishable from nuclear pores. The functions of annulate lamellae are not well understood . Although they may be found in virtually any eucaryotic cell, they occur most commonly in transformed and embryonic tissues . In Drosophila, annulate lamellae are found in the syncytial blastoderm embryo as it is cleaved to form the cellular blastoderm . The cytological events of the cellularization process are well documented, and may be used as temporal landmarks when studying changes in annulate lamellae . By using morphometric techniques to analyze electron micrographs of embryos, we are able to calculate the number of pores per nucleus in nuclear envelopes and annulate lamellae during progressive stages of cellularization . We find that annulate lamellae pores remain at a low level while nuclear envelopes are expanding and acquiring pores in early interphase . Once nuclear envelopes are saturated with pores, however, the number of annulate lamellae pores increases more than 10-fold in 9 min . Over the next 30 min it gradually declines to the initial low level . On the basis of these results, we propose (a) that pore synthesis and assembly continues after nuclear envelopes have been saturated with pores; (b) that these supernumerary pores accumulate transiently in cytoplasmic annulate lamellae; and (c) that because these pores are not needed by the embryo they are subsequently degraded

Nocturnal foraging enhanced by enlarged secondary eyes in a net-casting spider

Animals that possess extreme sensory structures are predicted to have a related extreme behavioral function. This study focuses on one such extreme sensory structure—the posterior median eyes of the net-casting spider Deinopis spinosa. Although past research has implicated the importance of vision in the nocturnal foraging habits of Deinopis, no direct link between vision in the enlarged eyes and nocturnal foraging has yet been made. To directly test the hypothesis that the enlarged posterior median eyes facilitate visually based nocturnal prey capture, we conducted repeated-measures, visual occlusion trials in both natural and laboratory settings. Our results indicate that D. spinosa relies heavily on visual cues detected by the posterior median eyes to capture cursorial prey items. We suggest that the enlarged posterior median eyes benefit D. spinosa not only through increased diet breadth, but also by allowing spiders to remain active solely at night, thus evading predation by diurnal animals

Nocturnal foraging enhanced by enlarged secondary eyes in a net-casting spider

Animals that possess extreme sensory structures are predicted to have a related extreme behavioral function. This study focuses on one such extreme sensory structure—the posterior median eyes of the net-casting spider Deinopis spinosa. Although past research has implicated the importance of vision in the nocturnal foraging habits of Deinopis, no direct link between vision in the enlarged eyes and nocturnal foraging has yet been made. To directly test the hypothesis that the enlarged posterior median eyes facilitate visually based nocturnal prey capture, we conducted repeated-measures, visual occlusion trials in both natural and laboratory settings. Our results indicate that D. spinosa relies heavily on visual cues detected by the posterior median eyes to capture cursorial prey items. We suggest that the enlarged posterior median eyes benefit D. spinosa not only through increased diet breadth, but also by allowing spiders to remain active solely at night, thus evading predation by diurnal animals

The Ketogenic Diet as a Treatment Paradigm for Diverse Neurological Disorders

Dietary and metabolic therapies have been attempted in a wide variety of neurological diseases, including epilepsy, headache, neurotrauma, Alzheimer disease, Parkinson disease, sleep disorders, brain cancer, autism, pain, and multiple sclerosis. The impetus for using various diets to treat – or at least ameliorate symptoms of – these disorders stems from both a lack of effectiveness of pharmacological therapies, and also the intrinsic appeal of implementing a more “natural” treatment. The enormous spectrum of pathophysiological mechanisms underlying the aforementioned diseases would suggest a degree of complexity that cannot be impacted universally by any single dietary treatment. Yet, it is conceivable that alterations in certain dietary constituents could affect the course and impact the outcome of these brain disorders. Further, it is possible that a final common neurometabolic pathway might be influenced by a variety of dietary interventions. The most notable example of a dietary treatment with proven efficacy against a neurological condition is the high-fat, low-carbohydrate ketogenic diet (KD) used in patients with medically intractable epilepsy. While the mechanisms through which the KD works remain unclear, there is now compelling evidence that its efficacy is likely related to the normalization of aberrant energy metabolism. The concept that many neurological conditions are linked pathophysiologically to energy dysregulation could well provide a common research and experimental therapeutics platform, from which the course of several neurological diseases could be favorably influenced by dietary means. Here we provide an overview of studies using the KD in a wide panoply of neurologic disorders in which neuroprotection is an essential component

A low-voltage activated, transient calcium current is responsible for the time-dependent depolarizing inward rectification of rat neocortical neurons in vitro

Intracellular recordings were obtained from rat neocortical neurons in vitro. The current-voltage-relationship of the neuronal membrane was investigated using current- and single-electrode-voltage-clamp techniques. Within the potential range up to 25 mV positive to the resting membrane potential (RMP: –75 to –80 mV) the steady state slope resistance increased with depolarization (i.e. steady state inward rectification in depolarizing direction). Replacement of extracellular NaCl with an equimolar amount of choline chloride resulted in the conversion of the steady state inward rectification to an outward rectification, suggesting the presence of a voltage-dependent, persistent sodium current which generated the steady state inward rectification of these neurons. Intracellularly injected outward current pulses with just subthreshold intensities elicited a transient depolarizing potential which invariably triggered the first action potential upon an increase in current strength. Single-electrode-voltage-clamp measurements reveled that this depolarizing potential was produced by a transient calcium current activated at membrane potentials 15–20 mV positive to the RMP and that this current was responsible for the time-dependent increase in the magnitude of the inward rectification in depolarizing direction in rat neocortical neurons. It may be that, together with the persistent sodium current, this calcium current regulates the excitability of these neurons via the adjustment of the action potential threshold