Attention to neglect

Patients with spatial neglect fail to attend to stimuli in the contralesional visual world. He et al. used fMRI to reveal how disrupted functional connectivity, independent of task-evoked activation, in ventral and dorsal attentional networks may explain behavioral impairment in neglect and recovery from acute neglect.     

Construction of the genetic map of the polyoma genome.

Seven early mutants, three late mutants, and one plaque morphology mutant of polyoma have been mapped by marker rescue using wild-type restriction endonuclease fragments. The early mutants map between 1.0 and 26.4 units from the Eco RI site, a region previously shown to correspond to the 3'-OH termainal half of "early" RNA (Kamen et al., 1974). The late mutants as well as the plaque morphology mutant map between 26.6 and 45.4 map units, a region previously shown to correspond to the 3'-OH terminal half of "late" RNA (Kamen et al., 1974). Analysis of the genotype of rescued virus demonstrated that the modification of the mutant DNA during marker rescue was limited to the region of the genome covered by the wild-type restriction endonuclease fragment tested.     

Complexation of Arsenite with Phytochelatins Reduces Arsenite Efflux and Translocation from Roots to Shoots in Arabidopsis

Complexation of arsenite [As(III)] with phytochelatins (PCs) is an important mechanism employed by plants to detoxify As; how this complexation affects As mobility was little known. We used high-resolution inductively coupled plasma-mass spectrometry and accurate mass electrospray ionization-mass spectrometry coupled to HPLC to identify and quantify As(III)-thiol complexes and free thiol compounds in Arabidopsis (Arabidopsis thaliana) exposed to arsenate [As(V)]. As(V) was efficiently reduced to As(III) in roots. In wild-type roots, 69% of As was complexed as As(III)-PC₄, As(III)-PC₃, and As(III)-(PC₂)₂. Both the glutathione (GSH)-deficient mutant cad2-1 and the PC-deficient mutant cad1-3 were approximately 20 times more sensitive to As(V) than the wild type. In cad1-3 roots, only 8% of As was complexed with GSH as As(III)-(GS)₃ and no As(III)-PCs were detected, while in cad2-1 roots, As(III)-PCs accounted for only 25% of the total As. The two mutants had a greater As mobility, with a significantly higher accumulation of As(III) in shoots and 4.5 to 12 times higher shoot-to-root As concentration ratio than the wild type. Roots also effluxed a substantial proportion of the As(V) taken up as As(III) to the external medium, and this efflux was larger in the two mutants. Furthermore, when wild-type plants were exposed to l-buthionine sulfoximine or deprived of sulfur, both As(III) efflux and root-to-shoot translocation were enhanced. The results indicate that complexation of As(III) with PCs in Arabidopsis roots decreases its mobility for both efflux to the external medium and for root-to-shoot translocation. Enhancing PC synthesis in roots may be an effective strategy to reduce As translocation to the edible organs of food crops.Arsenic (As) contamination in the environment is caused by both geogenically and/or anthropogenically derived activities. This problem is the most serious in South and Southeast Asia where As-contaminated groundwater has been extracted for drinking and for irrigating rice (Oryza sativa) crops (Brammer and Ravenscroft, 2009). As contamination in soil can cause phytotoxicity and consequently yield losses (Panaullah et al., 2009) and elevated levels of As in rice grain that may pose a significant risk to human health (Meharg and Rahman, 2003; Zhu et al., 2008; Meharg et al., 2009). To develop mitigation strategies to reduce the transfer of As to the food chain requires a better understanding of the mechanisms of As uptake, translocation, and detoxification. It is known that As accumulation varies greatly among different plant species (e.g. Raab et al., 2007) and also among different genotypes within a species (e.g. Norton et al., 2009). Since root-to-shoot translocation is often the bottleneck for the accumulation of metal(loid)s in the shoots (Zhao and McGrath, 2009), understanding what controls As translocation within plants is important for designing strategies to decrease As concentrations in the edible parts of food crops.With the exception of As hyperaccumulating plants, translocation of As from roots to shoots is generally restricted in most plant species (for review, see Zhao et al., 2009). An explanation for this limited translocation is that arsenate [As(V)] is rapidly reduced to arsenite [As(III)] in roots, followed by complexation of As(III) with phytochelatins (PCs) and subsequent sequestration in root vacuoles (Dhankher et al., 2006; Raab et al., 2007; Zhao et al., 2009). The extent of As(III) complexation may therefore determine its mobility in roots. To test this hypothesis, we used the model plant Arabidopsis (Arabidopsis thaliana) mutants defective in glutathione (GSH) or PC synthesis, as well as manipulation of thiol synthesis in wild-type plants by the use of the specific inhibitor l-buthionine sulfoximine (BSO) and sulfur (S) deprivation. Both the PC-deficient mutant cad1-3 and the GSH-deficient mutant cad2-1 were isolated by their phenotype of cadmium (Cd) sensitivity (Howden et al., 1995a, 1995b). cad1-3 is a recessive loss-of-function mutant with a mutation in the PC synthase gene (AtPCS1; Ha et al., 1999) and is unable to synthesize PCs in response to Cd exposure (Howden et al., 1995b). cad2-1 has a deletion in the gene encoding the γ-glutamylcysteine synthetase, resulting in 60% to 85% lower levels of GSH compared with the wild type and little production of PCs in response to Cd exposure (Howden et al., 1995a; Cobbett et al., 1998).As(III) has a high affinity to thiol groups, and there is strong evidence that PCs play a constitutive role in the detoxification of As through complexation of As(III) in As nonhyperaccumulator plants. As strongly induces PC synthesis (Grill et al., 1987; Sneller et al., 1999; Schmöger et al., 2000). Both cad1-3 and cad2-1 are hypersensitive to As(V) (Ha et al., 1999; Li et al., 2006). Inhibition of GSH and PC synthesis by BSO results in As hypersensitivity in a number of plant species (Schmöger et al., 2000; Hartley-Whitaker et al., 2002; Schat et al., 2002). It has been shown that overexpression of PCS enhances As tolerance in transgenic plants, but interestingly not As accumulation (Li et al., 2004; Gasic and Korban, 2007). Furthermore, a range of intact As(III)-PC complexes has been identified in sunflower (Helianthus annuus) and Thunbergia alata plants after exposure to As(V) or As(III) (Raab et al., 2005; Bluemlein et al., 2008). In contrast, As hyperaccumulators, such as Pteris vittata, appear not to rely mainly on PC-dependent strategies for As detoxification, as very small proportions of As in roots and fronds are complexed with thiols (Webb et al., 2003; Zhao et al., 2003; Raab et al., 2004; Pickering et al., 2006). Lack of As(III)-PC complexation in P. vittata may be one of the important reasons for the highly efficient translocation of As from roots to fronds (Su et al., 2008; Zhao et al., 2009).While the role of PCs in As sensitivity is well established, how they influence As mobility in plants is not clear. Gong et al. (2003) showed that PCs may be transported from roots to shoots in a study involving root-specific expression of the wheat (Triticum aestivum) PCS gene (TaPCS1) in the Arabidopsis cad3-1 mutant. Furthermore, both root-specific and ectopic expression of TaPCS1 was found to enhance long-distance transport of Cd from roots to stems and rosette leaves, suggesting that PCs may be carriers of Cd in xylem transport. However, direct measurements of the xylem sap collected from As-exposed sunflower showed only traces of nonreactive oxidized PC₂ and oxidized glutathione (GSSG) with no evidence of As-PC complexation (Raab et al., 2005). Similarly, only trace levels of PCs were detected in the xylem sap from Cd-exposed Brassica napus (Mendoza-Cózatl et al., 2008). The role of PCs in the xylem mobility of As has not been investigated in detail. Interestingly, recent studies have shown that GSH, PCs, and other thiol peptides can be transported from shoots to roots via phloem (Chen et al., 2006; Li et al., 2006). High levels of PCs, GSH, and Cd were found in the phloem sap of B. napus, suggesting that thiol peptides may be carriers of Cd in the long-distance phloem transport (Mendoza-Cózatl et al., 2008).Here, we present evidence that decreasing As(III)-PC complexation in Arabidopsis roots led to greater As mobility, manifested by enhanced As(III) efflux to the external medium and enhanced As translocation from roots to shoots.     

Universality splitting in distribution of number of miRNA co-targets

In a recent work (Basu et al., in EPL 105:28007, 2014) it was pointed out that the link-weight distribution of microRNA co-target network of a wide class of species are universal up to scaling. The number cell types, widely accepted as a measure of complexity, turns out to be proportional to these scale-factor. In this article we discuss additional universal features of these networks and show that, this universality splits if one considers distribution of number of common targets of three or more number of microRNAs. These distributions for different species can be collapsed onto two distinct set of universal functions, revealing the fact that the species which appeared in early evolution have different complexity measure compared to those appeared late.     

Patterns in Cortical Connectivity for Determining Outcomes in Hand Function after Subcortical Stroke

Background and Purpose

Previous studies have noted changes in resting-state functional connectivity during motor recovery following stroke. However, these studies always uncover various patterns of motor recovery. Moreover, subgroups of stroke patients with different outcomes in hand function have rarely been studied.

Materials and Methods

We selected 24 patients who had a subcortical stroke in the left motor pathway and displayed only motor deficits. The patients were divided into two subgroups: completely paralyzed hands (CPH) (12 patients) and partially paralyzed hands (PPH) (12 patients). Twenty-four healthy controls (HC) were also recruited. We performed functional connectivity analysis in both the ipsilesional and contralesional primary motor cortex (M1) to explore the differences in the patterns between each pair of the three diagnostic groups.

Results

Compared with the HC, the PPH group displays reduced connectivity of both the ipsilesional and contralesional M1 with bilateral prefrontal gyrus and contralesional cerebellum posterior lobe. The connectivity of both the ipsilesional and contralesional M1 with contralateral primary sensorimotor cortex was reduced in the CPH group. Additionally, the connectivity of the ipsilesional M1 with contralesional postcentral gyrus, superior parietal lobule and ipsilesional inferior parietal lobule was reduced in the CPH group compared with the PPH group. Moreover, the connectivity of these regions was positively correlated with the Fugl-Meyer Assessment scores (hand+wrist) across all stroke patients.

Conclusions

Patterns in cortical connectivity may serve as a potential biomarker for the neural substratum associated with outcomes in hand function after subcortical stroke.     

Partitioning variability in animal behavioral videos using semi-supervised variational autoencoders

Recent neuroscience studies demonstrate that a deeper understanding of brain function requires a deeper understanding of behavior. Detailed behavioral measurements are now often collected using video cameras, resulting in an increased need for computer vision algorithms that extract useful information from video data. Here we introduce a new video analysis tool that combines the output of supervised pose estimation algorithms (e.g. DeepLabCut) with unsupervised dimensionality reduction methods to produce interpretable, low-dimensional representations of behavioral videos that extract more information than pose estimates alone. We demonstrate this tool by extracting interpretable behavioral features from videos of three different head-fixed mouse preparations, as well as a freely moving mouse in an open field arena, and show how these interpretable features can facilitate downstream behavioral and neural analyses. We also show how the behavioral features produced by our model improve the precision and interpretation of these downstream analyses compared to using the outputs of either fully supervised or fully unsupervised methods alone.     

Functional Improvement after Photothrombotic Stroke in Rats Is Associated with Different Patterns of Dendritic Plasticity after G-CSF Treatment and G-CSF Treatment Combined with Concomitant or Sequential Constraint-Induced Movement Therapy

We have previously shown that granulocyte-colony stimulating factor (G-CSF) treatment alone, or in combination with constraint movement therapy (CIMT) either sequentially or concomitantly, results in significantly improved sensorimotor recovery after photothrombotic stroke in rats in comparison to untreated control animals. CIMT alone did not result in any significant differences compared to the control group (Diederich et al., Stroke, 2012;43:185–192). Using a subset of rat brains from this former experiment the present study was designed to evaluate whether dendritic plasticity would parallel improved functional outcomes. Five treatment groups were analyzed (n = 6 each) (i) ischemic control (saline); (ii) CIMT (CIMT between post-stroke days 2 and 11); (iii) G-CSF (10 μg/kg G-CSF daily between post-stroke days 2 and 11); (iv) combined concurrent group (CIMT plus G-CSF) and (v) combined sequential group (CIMT between post-stroke days 2 and 11; 10 μg/kg G-CSF daily between post-stroke days 12 and 21, respectively). After impregnation of rat brains with a modified Golgi-Cox protocol layer V pyramidal neurons in the peri-infarct cortex as well as the corresponding contralateral cortex were analyzed. Surprisingly, animals with a similar degree of behavioral recovery exhibited quite different patterns of dendritic plasticity in both peri-lesional and contralesional areas. The cause for these patterns is not easily to explain but puts the simple assumption that increased dendritic complexity after stroke necessarily results in increased functional outcome into perspective.     

Phytochelatin Synthesis Is Essential for the Detoxification of Excess Zinc and Contributes Significantly to the Accumulation of Zinc

The synthesis of phytochelatins (PCs) is essential for the detoxification of nonessential metals and metalloids such as cadmium and arsenic in plants and a variety of other organisms. To our knowledge, no direct evidence for a role of PCs in essential metal homeostasis has been reported to date. Prompted by observations in Schizosaccharomyces pombe and Saccharomyces cerevisiae indicating a contribution of PC synthase expression to Zn²⁺ sequestration, we investigated a known PC-deficient Arabidopsis (Arabidopsis thaliana) mutant, cad1-3, and a newly isolated second strong allele, cad1-6, with respect to zinc (Zn) homeostasis. We found that in a medium with low cation content PC-deficient mutants show pronounced Zn²⁺ hypersensitivity. This phenotype is of comparable strength to the well-documented Cd²⁺ hypersensitivity of cad1 mutants. PC deficiency also results in significant reduction in root Zn accumulation. To be able to sensitively measure PC accumulation, we established an assay using capillary liquid chromatography coupled to electrospray ionization quadrupole time-of-flight mass spectrometry of derivatized extracts. Plants grown under control conditions consistently showed PC2 accumulation. Analysis of plants treated with same-effect concentrations revealed that Zn²⁺-elicited PC2 accumulation in roots reached about 30% of the level of Cd²⁺-elicited PC2 accumulation. We conclude from these data that PC formation is essential for Zn²⁺ tolerance and provides driving force for the accumulation of Zn. This function might also help explain the mysterious occurrence of PC synthase genes throughout the plant kingdom and in a wide range of other organisms.Both essential and nonessential metal ions can be toxic when present in excess. Zinc (Zn) ions, for instance, are used in biological systems as catalytic or structural components in a myriad of proteins (Frausto da Silva and Williams, 2001). In humans, about 10% of genes encode Zn-dependent proteins (Andreini et al., 2006) and it is reasonable to postulate similar numbers for plants. When the Zn-buffering capacity of a cell is exceeded, however, aberrant binding of Zn ions to thiols or other functional groups can occur, which disrupts the function of proteins. Also, Zn ions can displace other essential metal ions from their binding sites (Krämer and Clemens, 2005). Toxicity thresholds for Zn were found to range between 100 and 300 μg g⁻¹ dry weight depending on plant species and physiological state (Marschner, 1995). Ions of the nonessential metal cadmium (Cd) have a high affinity for various functional groups in biological molecules, in particular thiols. When taken up into a cell they can inactivate proteins by uncontrolled binding or cause oxidative stress by depleting glutathione pools (Clemens, 2006a).Because of the potential toxicity of metal ions, all living systems possess mechanisms to tightly regulate the distribution of metal ions and to minimize damage under conditions of excess metal supply (Eide, 2006; Grotz and Guerinot, 2006). Principally, detoxification of excess metal ions is assumed to be achieved by efflux, sequestration, and chelation. For instance, in the past few years evidence has been reported for a contribution of AtMTP1 (At2g46800) to vacuolar sequestration of Zn²⁺ (Kobae et al., 2004; Desbrosses-Fonrouge et al., 2005) and of AtHMA4 (At2g19110) to effluxing Zn²⁺ (Mills et al., 2005). Furthermore, the Arabidopsis halleri ortholog of HMA4 is essential for Zn and Cd hypertolerance (Hanikenne et al., 2008). Loss of ZIF1, a transporter of the major facilitator superfamily, results in Zn²⁺ hypersensitivity in Arabidopsis (Arabidopsis thaliana; Haydon and Cobbett, 2007).The synthesis of phytochelatins (PCs), glutathione-derived metal-binding peptides, represents a major detoxification mechanism for Cd and arsenic (As) ions in various species. More recently, PCs have also been implicated in long-distance transport of Cd in the phloem (Mendoza-Cozatl et al., 2008). Formation of PCs is catalyzed by PC synthases (PCS) and genes encoding this enzyme have been cloned from plants, fungi, and nematodes (Clemens et al., 1999, 2001; Ha et al., 1999; Vatamaniuk et al., 1999, 2001). Mutant lines of Arabidopsis, Schizosaccharomyces pombe, or Caenorhabditis elegans that are deficient in PC synthesis show a severe loss of Cd and As tolerance (Clemens et al., 1999; Ha et al., 1999; Vatamaniuk et al., 2001). For other metal ions only minor effects have been reported (Cobbett and Goldsbrough, 2002). Arabidopsis cad1-3 mutant plants, which are defective in AtPCS1, showed about a 2-fold increase in copper (Cu) and mercury sensitivity and no significant increase in Zn sensitivity (Ha et al., 1999). S. pombe PCS-deficient mutants are slightly more Cu²⁺ sensitive than wild-type cells (Clemens et al., 1999). PC-metal complexes have been detected in plant cells only with Cd, silver, Cu, and As (Maitani et al., 1996; Schmöger et al., 2000) even though synthesis of PCs is activated by a wide range of metal ions both in vivo and in vitro (Grill et al., 1987; Vatamaniuk et al., 2000; Oven et al., 2002). Thus, the role of PC synthesis in metal detoxification has so far been seen as being confined to Cd and As (Cobbett and Goldsbrough, 2002). This, however, leaves the question as to why PCS genes are so widespread and why the enzyme is expressed constitutively throughout the plant (Rea et al., 2004). It is not clear how the sporadic need to sequester excess Cd or As ions could have provided the selective pressure to maintain PCS expression throughout the plant kingdom and beyond (Clemens, 2006b). One explanation could be the second enzymatic function of PCS, i.e. breakdown of glutathione conjugates (GS conjugates) to the corresponding β-glutamyl-Cys conjugates (Blum et al., 2007). The catalytic activity of bacterial PCS-like proteins is similar (Harada et al., 2004; Tsuji et al., 2004; Vivares et al., 2005). Another possibility is involvement of PC synthesis in essential metal homeostasis, which has been discussed occasionally (Steffens et al., 1986; Rauser, 1990; Steffens, 1990). As early as 1986, Steffens et al. suggested this based on the observation that small amounts of PCs were detectable in tomato (Solanum lycopersicum) cell cultures in the absence of excess metals. Similarly, Grill et al. reported the induction of PC synthesis by Cu and Zn ions after transfer of cultured cells into fresh medium. The amount of detectable PCs was correlated linearly with the Zn²⁺ concentration in the culture medium and an involvement of PC synthesis in metal homeostasis was proposed (Grill et al., 1987, 1988). However, no genetic evidence for such a role of PCs has been reported to date. Here we present evidence that PC formation indeed contributes significantly to Zn²⁺ detoxification in Arabidopsis and enhances Zn accumulation.     

The spectrum of covariance matrices of randomly connected recurrent neuronal networks with linear dynamics

A key question in theoretical neuroscience is the relation between the connectivity structure and the collective dynamics of a network of neurons. Here we study the connectivity-dynamics relation as reflected in the distribution of eigenvalues of the covariance matrix of the dynamic fluctuations of the neuronal activities, which is closely related to the network dynamics’ Principal Component Analysis (PCA) and the associated effective dimensionality. We consider the spontaneous fluctuations around a steady state in a randomly connected recurrent network of stochastic neurons. An exact analytical expression for the covariance eigenvalue distribution in the large-network limit can be obtained using results from random matrices. The distribution has a finitely supported smooth bulk spectrum and exhibits an approximate power-law tail for coupling matrices near the critical edge. We generalize the results to include second-order connectivity motifs and discuss extensions to excitatory-inhibitory networks. The theoretical results are compared with those from finite-size networks and the effects of temporal and spatial sampling are studied. Preliminary application to whole-brain imaging data is presented. Using simple connectivity models, our work provides theoretical predictions for the covariance spectrum, a fundamental property of recurrent neuronal dynamics, that can be compared with experimental data.     

Behavioral attributes influence annual mating success more than morphological traits in male collared lizards

Traits that potentially influence mating success (MS) may be"static" with low lability once they develop or "dynamic" withhighly modifiable expression. We used principal components (PCs)analyses of dynamic behavioral and morphological traits thatare static over the short term to determine their relative contributionsto the ability of territorial male collared lizards to acquireaccess to females and obtain high MS. We estimated annual MSof males as the relative frequency with which they engaged incourtship with reproductively active resident females. ThreePCs explained statistically significant phenotypic variationamong males. Morphological traits loaded significantly on 2PCs that explained 26.3% and 13.0% of the variance, respectively,whereas behavioral variables loaded significantly on a differentcomponent that explained 15.7% of the variance in male traits.The frequency with which males initiated aggressive encounterswith same-sex competitors did not load significantly on thesePC axes. Males having behavioral PC scores above the mean hadsignificantly higher MS than those with behavioral scores belowthe mean, whereas male MS was not related to component scoresfor either of the axes describing static morphological variables.Results indicate that in our population behavior patterns associatedwith advertisement, particularly to females, influence maleMS more strongly than morphological traits or the initiationof direct aggression with same-sex competitors.     

Protein sequence classification using feature hashing

Recent advances in next-generation sequencing technologies have resulted in an exponential increase in the rate at which protein sequence data are being acquired. The k-gram feature representation, commonly used for protein sequence classification, usually results in prohibitively high dimensional input spaces, for large values of k. Applying data mining algorithms to these input spaces may be intractable due to the large number of dimensions. Hence, using dimensionality reduction techniques can be crucial for the performance and the complexity of the learning algorithms. In this paper, we study the applicability of feature hashing to protein sequence classification, where the original high-dimensional space is "reduced" by hashing the features into a low-dimensional space, using a hash function, i.e., by mapping features into hash keys, where multiple features can be mapped (at random) to the same hash key, and "aggregating" their counts. We compare feature hashing with the "bag of k-grams" approach. Our results show that feature hashing is an effective approach to reducing dimensionality on protein sequence classification tasks.     

A Novel Method for Assessing Proximal and Distal Forelimb Function in the Rat: the Irvine,Beatties and Bresnahan (IBB) Forelimb Scale

Several experimental models of cervical spinal cord injury (SCI) have been developed recently to assess the consequences of damage to this level of the spinal cord (Pearse et al., 2005, Gensel et al., 2006, Anderson et al., 2009), as the majority of human SCI occur here (Young, 2010; www.sci-info-pages.com). Behavioral deficits include loss of forelimb function due to damage to the white matter affecting both descending motor and ascending sensory systems, and to the gray matter containing the segmental circuitry for processing sensory input and motor output for the forelimb. Additionally, a key priority for human patients with cervical SCI is restoration of hand/arm function (Anderson, 2004). Thus, outcome measures that assess both proximal and distal forelimb function are needed. Although there are several behavioral assays that are sensitive to different aspects of forelimb recovery in experimental models of cervical SCI (Girgis et al., 2007, Gensel et al., 2006, Ballerman et al., 2001, Metz and Whishaw, 2000, Bertelli and Mira, 1993, Montoya et al., 1991, Whishaw and Pellis, 1990), few techniques provide detailed information on the recovery of fine motor control and digit movement.The current measurement technique, the Irvine, Beatties and Bresnahan forelimb scale (IBB), can detect recovery of both proximal and distal forelimb function including digit movements during a naturally occurring behavior that does not require extensive training or deprivation to enhance motivation. The IBB was generated by observing recovery after a unilateral C6 SCI, and involves video recording of animals eating two differently shaped cereals (spherical and doughnut) of a consistent size. These videos were then used to assess features of forelimb use, such as joint position, object support, digit movement and grasping technique.The IBB, like other forelimb behavioral tasks, shows a consistent pattern of recovery that is sensitive to injury severity. Furthermore, the IBB scale could be used to assess recovery following other types of injury that impact normal forelimb function.     

The emergence of patterned movement during late embryogenesis of Drosophila

Larval behavioral patterns arise in a gradual fashion during late embryogenesis as the innervation of the somatic musculature and connectivity within the central nervous system develops. In this paper, we describe in a quantitative manner the maturation of behavioral patterns. Early movements are locally restricted "twitches" of the body wall, involving single segments or parts of segments. These twitches occur at a low frequency and have low amplitude, reflecting weak muscle contractions. Towards later stages twitches increase in frequency and amplitude and become integrated into coordinated movements of multiple segments. Most noticeable among these is the peristaltic wave of longitudinal segmental contractions by which the larva moves forward or backward. Besides becoming more complex as development proceeds, embryonic movements also acquire a pronounced rhythm. Thus, late embryonic movements occur in bursts, with phases of frequent movement separated by phases of no movement at all; early movements show no such periodicity. These data will serve as a baseline for future studies that address the function of embryonic lethal genes controlling neuronal connectivity and larval behavior. We have analyzed behavioral abnormalities in two embryonic lethal mutations with severe neural defects, tailless (tll), which lacks the protocerebrum, and glial cells missing (gcm), in which glial cells are absent. Our results reveal prominent alterations in embryonic motility for both of these mutations, indicating that the protocerebrum and glial cells play a crucial role in the neural mechanism controlling larval movement in Drosophila.     

A novel role for Greatwall kinase in recovery from DNA damage

Activation of the DNA damage response (DDR) is critical for genomic integrity and tumor suppression. The occurrence of DNA damage quickly evokes the DDR through ATM/ATR-dependent signal transduction, which promotes DNA repair and activates the checkpoint to halt cell cycle progression (Halazonetis et al., 2008; Motoyama and Naka, 2004; Zhou and Elledge, 2000). The "turn off" process of the DDR upon satisfaction of DNA repair, also known as "checkpoint recovery", involves deactivation of DDR elements, but the mechanism is poorly understood. Greatwall kinase (Gwl) has been identified as a key element in the G2/M transition (Archambault et al., 2007; Jackson, 2006; Zhao et al., 2008; Yu et al., 2004; Yu et al., 2006; Zhao et al., 2006) and helps maintain M phase through inhibition of PP2A/B55δ (Burgess et al., 2010; Castilho et al., 2009; Goldberg, 2010; Lorca et al., 2010; Vigneron et al., 2009), the principal phosphatase for Cdk-phosphorylated substrates. Here we show that Gwl also promotes recovery from DNA damage and is itself directly inhibited by the DNA damage response (DDR). In Xenopus egg extracts, immunodepletion of Gwl increased the DDR to damaged DNA, whereas addition of wild type, but not kinase dead Gwl, inhibited the DDR. The removal of damaged DNA from egg extracts leads to recovery from checkpoint arrest and entry into mitosis, a process impaired by Gwl depletion and enhanced by Gwl over-expression. Moreover, activation of Cdk1 after the removal of damaged DNA is regulated by Gwl. Collectively, these results defines Gwl as a new regulator of the DDR, which plays an important role in recovery from DNA     

The heme oxygenase system and its functions in the brain.

The heme oxygenase (HO) system was identified in the early 1970s as a distinct microsomal enzyme system that catalyzes formation of bile pigments (Maines and Kappas, 1974). Up to the early 1990s the system was considered only as a "molecular wrecking ball" (Lane, 1998) for degradation of the heme molecule and production of toxic waste products, CO and bile pigments. For those years, the HO system remained relatively unknown to the research community. In a rather short span of the past 10 years following the discovery of high levels of a second form of the enzyme, HO-2, in the brain, suggesting that "heme oxygenase in the brain has functions aside from heme degradation" (Sun et al., 1990); concomitant with finding that another toxic gas, NO, is a signal molecule for generation of cGMP (Ignarro et al., 1982), the system was propelled into main stream research. This propulsion was fueled by the realization of the multiple and diverse functions of heme degradation products. Heme oxygenase has now found relevance in all kinds of human pathophysiology ranging from stroke, cancer, multiple sclerosis, and malaria to transplantation and immune response. As it turns out, its potential benefits are mesmerizing investigators in diverse fields (Lane, 1998). The most recent findings with HO-2 being a hemoprotein and potentially an intracellular "sink" for NO (McCoubrey et al., 1997a; Ding et al., 1999), together with the discovery of the third form of the enzyme, HO-3 (McCoubrey et al., 1997b), are likely to insure the widespread interest in the enzyme system in the coming years. The present review is intended to highlight molecular properties of HO isozymes and their likely functions in the brain. Extended reviews of the system are found in Maines (1992, 1997).     

Utilization of a new index to distinguish heterozygous thalassemic syndromes: comparison of its specificity to five other discriminants

In 1984, a new index (the Makris index) combining erythrocytic and platelet parameters was described for the discrimination of the heterozygous thalassemic syndromes (beta and alpha). The algorithm is [(MCV/RDW)/(MPV/PDW)] divided by the RBC count in millions and requires for input the MCV, RDW, MPV, PDW, and RBC. The critical value used for separating the heterozygous thalassemic subjects is 1.84, which is the mean value plus 2 SD of our heterozygous subjects (confidence limit 95%). Because this index utilizes a confidence limit that includes 95% of affected persons, all individuals with values smaller than this need further investigation. It should be noted that the specificity of the index can be increased using the mean value of our heterozygous group plus 3 SD (X + 3 SD = 1.30 + 3*0.27 = 2.11, confidence limit 99%). In a series of 1510 "normal" subjects examined, 154 were designated as abnormals. None of the rest had abnormalities of cellular morphology or red cells osmotic resistance. The algorithm is readily incorporated into the software of an automated, whole blood analyzer. Using an expert system, we compared the sensitivity and specificity of the Makris index to five other discriminants (Mentzer, Shine et al., England et al., Green, and Bessman et al.). The Makris index distinguished between heterozygotes and normals without misdiagnosis.     

Stem Cell Mediation of Functional Recovery after Stroke in the Rat

Background

Regenerative strategies of stem cell grafting have been demonstrated to be effective in animal models of stroke. In those studies, the effectiveness of stem cells promoting functional recovery was assessed by behavioral testing. These behavioral studies do, however, not provide access to the understanding of the mechanisms underlying the observed functional outcome improvement.

Methodology/Principal Findings

In order to address the underlying mechanisms of stem cell mediated functional improvement, this functional improvement after stroke in the rat was investigated for six months after stroke by use of fMRI, somatosensory evoked potentials by electrophysiology, and sensorimotor behavior testing. Stem cells were grafted ipsilateral to the ischemic lesion. Rigorous exclusion of spontaneous recovery as confounding factor permitted to observe graft-related functional improvement beginning after 7 weeks and continuously increasing during the 6-month observation period. The major findings were i) functional improvement causally related to the stem cells grafting; ii) tissue replacement can be excluded as dominant factor for stem cell mediated functional improvement; iii) functional improvement occurs by exclusive restitution of the function in the original representation field, without clear contributions from reorganization processes, and iv) stem cells were not detectable any longer after six months.

Conclusions/Significance

A delayed functional improvement due to stem cell implantation has been documented by electrophysiology, fMRI and behavioral testing. This functional improvement occurred without cells acting as a tissue replacement for the necrotic tissue after the ischemic event. Combination of disappearance of grafted cells after six months on histological sections with persistent functional recovery was interpreted as paracrine effects by the grafted stem cells being the dominant mechanism of cell activity underlying the observed functional restitution of the original activation sites. Future studies will have to investigate whether the stem cell mediated improvement reactivates the original representation target field by using original connectivity pathways or by generating/activating new ones for the stimulus.