Distribution of single-channel conductances in cultured rat hippocampal neurons

1. The nonhomogeneous spatial distribution of ionic channels in neurons has been implied from intracellular recordings at somatic and dendritic locations. These reports indicate that Na- and Ca-dependent regenerative currents are distributed differently throughout the neuron. Although a variety of K conductances and a noninactivating Na conductance have been described in intracellular studies, little is known about the spatial distribution of inward and outward currents throughout different regions of the neuron. 2. We recorded from cell-attached patches from cultured hippocampal cells from 1-day-old rats. The cells were cultured for 3-21 days. The spatial distribution of a variety of ionic channels was determined by comparing the conductances from somatic and dendritic membranes. Single-channel currents obtained from cell-attached patches were identified by the time course of ensemble (averaged) responses, voltage dependence, and the effect of channel blocking agents. 3. We consistently observed that only the rapidly inactivating inward current was localized to the soma. The other channel types that we studied, including an inward noninactivating, delayed rectifier and transient A-type currents, were observed in both the somatic and dendritic regions. 4. We suggest that the distribution of ionic conductances that we have observed may be functional in limiting excitability during development of neurons.     

Enhanced leptin-stimulated Pi3k activation in the CNS promotes white adipose tissue transdifferentiation

The contribution of different leptin-induced signaling pathways in control of energy homeostasis is only partly understood. Here we show that selective Pten ablation in leptin-sensitive neurons (Pten^ΔObRb) results in enhanced Pi3k activation in these cells and reduces adiposity by increasing energy expenditure. White adipose tissue (WAT) of Pten^ΔObRb mice shows characteristics of brown adipose tissue (BAT), reflected by increased mitochondrial content and Ucp1 expression resulting from enhanced leptin-stimulated sympathetic nerve activity (SNA) in WAT. In contrast, leptin-deficient ob/ob-Pten^ΔObRb mice exhibit unaltered body weight and WAT morphology compared to ob/ob mice, pointing to a pivotal role of endogenous leptin in control of WAT transdifferentiation. Leanness of Pten^ΔObRb mice is accompanied by enhanced sensitivity to insulin in skeletal muscle. These data provide direct genetic evidence that leptin-stimulated Pi3k signaling in the CNS regulates energy expenditure via activation of SNA to perigonadal WAT leading to BAT-like differentiation of WAT.     

Insulin action in AgRP-expressing neurons is required for suppression of hepatic glucose production

Insulin action in the central nervous system regulates energy homeostasis and glucose metabolism. To define the insulin-responsive neurons that mediate these effects, we generated mice with selective inactivation of the insulin receptor (IR) in either pro-opiomelanocortin (POMC)- or agouti-related peptide (AgRP)-expressing neurons of the arcuate nucleus of the hypothalamus. While neither POMC- nor AgRP-restricted IR knockout mice exhibited altered energy homeostasis, insulin failed to normally suppress hepatic glucose production during euglycemic-hyperinsulinemic clamps in AgRP-IR knockout (IR^ΔAgRP) mice. These mice also exhibited reduced insulin-stimulated hepatic interleukin-6 expression and increased hepatic expression of glucose-6-phosphatase. These results directly demonstrate that insulin action in POMC and AgRP cells is not required for steady-state regulation of food intake and body weight. However, insulin action specifically in AgRP-expressing neurons does play a critical role in controlling hepatic glucose production and may provide a target for the treatment of insulin resistance in type 2 diabetes.     

Cryptococcus Strains with Different Pathogenic Potentials Have Diverse Protein Secretomes

Secreted proteins are the frontline between the host and pathogen. In mammalian hosts, secreted proteins enable invasive infection and can modulate the host immune response. Cryptococcosis, caused by pathogenic Cryptococcus species, begins when inhaled infectious propagules establish to produce pulmonary infection, which, if not resolved, can disseminate to the central nervous system to cause meningoencephalitis. Strains of Cryptococcus species differ in their capacity to cause disease, and the mechanisms underlying this are not well understood. To investigate the role of secreted proteins in disease, we determined the secretome for three genome strains of Cryptococcus species, including a hypovirulent and a hypervirulent strain of C. gattii and a virulent strain of C. neoformans. Sixty-seven unique proteins were identified, with different numbers and types of proteins secreted by each strain. The secretomes of the virulent strains were largely limited to proteolytic and hydrolytic enzymes, while the hypovirulent strain had a diverse secretome, including non-conventionally secreted canonical cytosolic and immunogenic proteins that have been implicated in virulence. The hypovirulent strain cannot establish pulmonary infection in a mouse model, but strains of this genotype have caused human meningitis. To directly test brain infection, we used intracranial inoculation and found that the hypovirulent strain was substantially more invasive than its hypervirulent counterpart. We suggest that immunogenic proteins secreted by this strain invoke a host response that limits pulmonary infection but that there can be invasive growth and damage if infection reaches the brain. Given their known role in virulence, it is possible that non-conventionally secreted proteins mediate this process.     

Variability of the Ramularia collo‐cygni Population in Central Europe

The genetic structure of the fungal barley pathogen Ramularia collo‐cygni (Rcc) population in Central Europe involving the isolates from the Czech Republic, the Slovak Republic, Germany and Swiss was determined using amplified fragment length polymorphism (AFLP) analysis. One hundred and eighty‐four markers were chosen to determine genetic and genotypic diversity and to test the hypothesis of random mating and population differentiation of Rcc isolates. Among the 337 isolates collected, the overall gene diversity was moderate ( = 0.216). The level of multilocus genotypic diversity was higher within populations than among them. All individuals had unique multilocus genotypes. Genetic differentiation was significant among populations in localities, but at a moderate level (θ = 0.12; P < 0.001), suggesting that gene flow is occurring among populations. The isolates from all twelve clusters produced by Structure were found in all local populations, although at different frequencies. Therefore, the inferred clusters did not represent geographical populations. Although the null hypothesis of random mating in Rcc populations was rejected, the high level of genotypic diversity suggests that the Rcc population structure appears to be generated by a mixed reproductive system including both asexual and sexual reproduction, along with a rather high migration rate.     

Pyrazolone based TGFβR1 kinase inhibitors

Interruption of TGFβ signaling through inhibition of the TGFβR1 kinase domain may prove to have beneficial effect in both fibrotic and oncological diseases. Herein we describe the SAR of a novel series of TGFβR1 kinase inhibitors containing a pyrazolone core. Most TGFβR1 kinase inhibitors described to date contain a core five-membered ring bearing N as H-bond acceptor. Described herein is a novel strategy to replace the core structure with pyrazolone ring, in which the carbonyl group is designed as an H-bond acceptor to interact with catalytic Lys 232.