Dendrites differ from axons in patterns of microtubule stability and polymerization during development

BACKGROUND: Dendrites differ from axons in patterns of growth and development, as well as in morphology. Given that microtubules are key structural elements in cells, we assessed patterns of microtubule stability and polymerization during hippocampal neuron development in vitro to determine if these aspects of microtubule organization could distinguish axons from dendrites. RESULTS: Quantitative ratiometric immunocytochemistry identified significant differences in microtubule stability between axons and dendrites. Most notably, regardless of developmental stage, there were high levels of dynamic microtubules throughout the dendritic arbor, whereas dynamic microtubules were predominantly concentrated in the distal end of axons. Analysis of microtubule polymerization using green fluorescent protein-tagged EB1 showed both developmental and regional differences in microtubule polymerization between axons and dendrites. Early in development (for example, 1 to 2 days in vitro), polymerization events were distributed equally in both the anterograde and retrograde directions throughout the length of both axons and dendrites. As development progressed, however, polymerization became biased, with a greater number of polymerization events in distal than in proximal and middle regions. While polymerization occurred almost exclusively in the anterograde direction for axons, both anterograde and retrograde polymerization was observed in dendrites. This is in agreement with predicted differences in microtubule polarity within these compartments, although fewer retrograde events were observed in dendrites than expected. CONCLUSION: Both immunocytochemical and live imaging analyses showed that newly formed microtubules predominated at the distal end of axons and dendrites, suggesting a common mechanism that incorporates increased microtubule polymerization at growing process tips. Dendrites had more immature, dynamic microtubules throughout the entire arbor than did axons, however. Identifying these differences in microtubule stability and polymerization is a necessary first step toward understanding how they are developmentally regulated, and may reveal novel mechanisms underlying neuron maturation and dendritic plasticity that extend beyond the initial specification of polarity

Comparing Vegetation Monitoring Methods in Shrublands: How Valuable is Grant’s Method in Shrub Communities?

Faced with managing extensive rangelands, land managers need reliable monitoring methods. Grant and others (2004) proposed a monitoring method that uses a floristic classification of dominant vegetation and assesses species frequency. The method was developed in native grass prairies with limited woody vegetation and is designed to provide more efficient repetitive monitoring. Our objective for this study was to determine if Grant’s method is useful in shrubland systems for a newly implemented baseline inventory and monitoring program. We conducted a study to compare Grant’s method and its efficacy to more commonly used line-point intercept in grass and shrub alliances at Brown’s Park National Wildlife Refuge, Colorado. In the summer of 2007 we conducted baseline inventory of vegetation characteristics on 39 permanent bottomland plots in six pre-determined grass and shrub vegetation alliances on the refuge. Within each plot, we monitored vegetation with line-point intercept and Grant’s method on three 50 m line transects. We compare data collected using these methods from a grassland (smooth brome dominated) and a shrubland (greasewood dominated) alliance. Results of this study indicate that data collected using Grant’s method is more variable than line-point intercept data in shrub systems. Bare ground was detected less using Grant’s than line-point intercept; however, Grant’s detected more herbaceous and invasive species overall than did the line-point intercept method. A complementary use of the methods for long-term monitoring is recommended that accommodates tradeoffs between incorporating detail versus efficiency of data collection efforts

National Educators' Workshop: Update 1996

This document contains a collection of experiments presented and demonstrated at the National Educators' Workshop: Update 96, held at Los Alamos National Laboratory, Los Alamos, New Mexico on October 27-30, 1996. The experiments related to the nature and properties of engineering materials and provided information to assist in teaching about materials in the education community

Urinary eicosanoid metabolites in HIV-infected women with central obesity switching to raltegravir: an analysis from the women, integrase, and fat accumulation trial.

Chronic inflammation is a hallmark of HIV infection. Eicosanoids reflect inflammation, oxidant stress, and vascular health and vary by sex and metabolic parameters. Raltegravir (RAL) is an HIV-1 integrase inhibitor that may have limited metabolic effects. We assessed urinary F2-isoprostanes (F2-IsoPs), prostaglandin E2 (PGE-M), prostacyclin (PGI-M), and thromboxane B2 (TxB2) in HIV-infected women switching to RAL-containing antiretroviral therapy (ART). Thirty-seven women (RAL = 17; PI/NNRTI = 20) with a median age of 43 years and BMI 32 kg/m(2) completed week 24. TxB2 increased in the RAL versus PI/NNRTI arm (+0.09 versus -0.02; P = 0.06). Baseline PGI-M was lower in the RAL arm (P = 0.005); no other between-arm cross-sectional differences were observed. In the PI/NNRTI arm, 24-week visceral adipose tissue change correlated with PGI-M (rho = 0.45; P = 0.04) and TxB2 (rho = 0.44; P = 0.005) changes, with a trend seen for PGE-M (rho = 0.41; P = 0.07). In an adjusted model, age ≥ 50 years (N = 8) was associated with increased PGE-M (P = 0.04). In this randomized trial, a switch to RAL did not significantly affect urinary eicosanoids over 24 weeks. In women continuing PI/NNRTI, increased visceral adipose tissue correlated with increased PGI-M and PGE-M. Older age (≥ 50) was associated with increased PGE-M. Relationships between aging, adiposity, ART, and eicosanoids during HIV-infection require further study

Isotope-reinforced polyunsaturated fatty acids improve Parkinson’s disease-like phenotype in rats overexpressing α-synuclein

Producción CientíficaLipid peroxidation is a key to a portfolio of neurodegenerative diseases and plays a central role in α-synuclein (α-syn) toxicity, mitochondrial dysfunction and neuronal death, all key processes in the pathogenesis of Parkinson's disease (PD). Polyunsaturated fatty acids (PUFAs) are important constituents of the synaptic and mitochondrial membranes and are often the first molecular targets attacked by reactive oxygen species (ROS). The rate-limiting step of the chain reaction of ROS-initiated PUFAs autoxidation involves hydrogen abstraction at bis-allylic sites, which can be slowed down if hydrogens are replaced with deuteriums. In this study, we show that targeted overexpression of human A53T α-syn using an AAV vector unilaterally in the rat substantia nigra reproduces some of pathological features seen in PD patients. Chronic dietary supplementation with deuterated PUFAs (D-PUFAs), specifically 0.8% D-linoleic and 0.3% H-linolenic, produced significant disease-modifying beneficial effects against α-syn-induced motor deficits, synaptic pathology, oxidative damage, mitochondrial dysfunction, disrupted trafficking along axons, inflammation and DA neuronal loss. These findings support the clinical evaluation of D-PUFAs as a neuroprotective therapy for PD

Au-Ag template stripped pattern for scanning probe investigations of DNA arrays produced by Dip Pen Nanolithography

We report on DNA arrays produced by Dip Pen Nanolithography (DPN) on a novel Au-Ag micro patterned template stripped surface. DNA arrays have been investigated by atomic force microscopy (AFM) and scanning tunnelling microscopy (STM) showing that the patterned template stripped substrate enables easy retrieval of the DPN-functionalized zone with a standard optical microscope permitting a multi-instrument and multi-technique local detection and analysis. Moreover the smooth surface of the Au squares (abput 5-10 angstrom roughness) allows to be sensitive to the hybridization of the oligonucleotide array with label-free target DNA. Our Au-Ag substrates, combining the retrieving capabilities of the patterned surface with the smoothness of the template stripped technique, are candidates for the investigation of DPN nanostructures and for the development of label free detection methods for DNA nanoarrays based on the use of scanning probes.Comment: Langmuir (accepted

Complexity and diversity in c-type cytochrome biogenesis systems

Abstract c-type cytochromes contain haem covalently attached to protein by thioether bonds formed posttranslationally and requiring a dedicated biogenesis apparatus. Three biogenesis systems, found in different cell types, are well known. Here we discuss emerging evidence for at least one additional system, for unanticipated diversity in the location of the systems and for the co-existence of multiple systems in some cells