On the contribution of MMP-2 and MMP-9 to the postnatal cerebellar corticogenesis

The development of the cerebellar cortex is dependent on orchestrated cell-cell, cell-matrix interactions, as well as intrinsic genetic programs. Matrix metalloproteinases (MMPs) are proteolytic enzymes that degrade ECM molecules and are involved in neuronal migration, process extension, and synaptic plasticity. The current study investigated (1) the developmental expression and activity of MMP-2 and MMP-9, and (2) the effect of blocking the activity of MMP-2 and MMP-9 by a specific inhibitor on the histogenesis of the cerebellar cortex. Cerebella were collected from rat pups every three days starting at postnatal day 3 (P3) until P25---a period equivalent to the third gestational trimester in humans. Temporal analysis of MMP activity by gelatinase assay showed that both the active and latent forms were present in the developing cerebellum. The mRNA analysis by real-time quantitative PCR indicated that the expression pattern of MMP-2 and MMP-9 mRNA agreed with their gelatinase activity. In situ zymography was localized in the EGL, the PCL, and IGL. The EGL, Bergamnn glial fibers, and the PCL showed immunoreactivity for MMP-2, whereas MMP-9 immunoreactivity was detected only in PC and the EGL. Exposure of organotypic slices to a specific MMP-2/MMP-9 inhibitor (1.6, 3.2 or 6.4 muM) altered the activity of MMP-2 and 9 and caused a significant increase in the thickness of the EGL, and a decrease in migrating granule neurons in the molecular layer. Our study suggests that MMP-2 and MMP-9 play a role in the postnatal cerebellar histogenesis

Ancient properties of spider silks revealed by the complete gene sequence of the prey-wrapping silk protein (AcSp1).

Spider silk fibers have impressive mechanical properties and are primarily composed of highly repetitive structural proteins (termed spidroins) encoded by a single gene family. Most characterized spidroin genes are incompletely known because of their extreme size (typically >9 kb) and repetitiveness, limiting understanding of the evolutionary processes that gave rise to their unusual gene architectures. The only complete spidroin genes characterized thus far form the dragline in the Western black widow, Latrodectus hesperus. Here, we describe the first complete gene sequence encoding the aciniform spidroin AcSp1, the primary component of spider prey-wrapping fibers. L. hesperus AcSp1 contains a single enormous (∼19 kb) exon. The AcSp1 repeat sequence is exceptionally conserved between two widow species (∼94% identity) and between widows and distantly related orb-weavers (∼30% identity), consistent with a history of strong purifying selection on its amino acid sequence. Furthermore, the 16 repeats (each 371-375 amino acids long) found in black widow AcSp1 are, on average, >99% identical at the nucleotide level. A combination of stabilizing selection on amino acid sequence, selection on silent sites, and intragenic recombination likely explains the extreme homogenization of AcSp1 repeats. In addition, phylogenetic analyses of spidroin paralogs support a gene duplication event occurring concomitantly with specialization of the aciniform glands and the tubuliform glands, which synthesize egg-case silk. With repeats that are dramatically different in length and amino acid composition from dragline spidroins, our L. hesperus AcSp1 expands the knowledge base for developing silk-based biomimetic technologies

Inelastic Displacement Ratios of SSI Systems

This paper presents the effect of soil-structure interaction on seismic inelastic displacement ratios of Single Degree of Freedom (SDOF) systems. Existing methods used in the past assumes the soil to be rigid. Through simplified equivalent fixed-base methods, the effect of soil-structure interaction (SSI) on the inelastic behaviour of structures is evaluated for different soil parameters using effective period and damping values. Using a degrading modified Clough model, the influence of different types of degradation is accounted for, for SDOF systems with periods ranging from 0.2 to 1.4 s. In total 300 different earthquake motions recorded on firm soil condition with magnitudes greater than 5 and peak ground acceleration (PGA) values greater than 0.08 g were selected. These records were scaled to the same hazard level and applied on five experimentally-tested reinforced concrete columns selected from the Pacific Earthquake Engineering Research Centre database. A total of 384,000 dynamic analyses were conducted. The results of the soil interacting systems are compared with the fixed-base case for different strength reduction factors (R) and foundation aspect ratios (h/r) for a range of NEHRP soil types C and D properties. These results show that the maximum inelastic displacements for soil type D are greater than those of soil type C and the fixed-base case. Particularly for periods less than 0.6 s with large aspect ratios, the effects of soil-structure interaction should be accounted for. Finally, the collected data was used to derive mathematical expressions for inelastic displacement ratios of SSI systems, suitable for use in performance-based seismic evaluation of structures

Metabolic Bone Disease of Infancy in the Offspring of Mothers With Bariatric Surgery: A Series of 5 Infants in Contested Cases of Child Abuse

Background and aims: Metabolic Bone Disease of Infancy is a multifactorial disorder of bone fragility in infants who typically present under 6 months of age with multiple unexplained fractures. Major risk factors for this disorder relate to the fetal time period and include decreased provision of the essential nutrients for bone formation during pregnancy (calcium, phosphate, vitamin D, and protein), prema- turity, and decreased fetal bone loading. Methods: This study presents 5 infants with multiple unexplained fractures born to women who had prior bariatric surgery in which child abuse was alleged, and the alleged perpetrator denied wrong doing. Results: The radiographic findings showed poor bone mineralization and were consistent with Metabolic Bone Disease of Infancy. Conclusions: Using the Utah Paradigm to understand risk factors for MBDI, the authors believe the nutritional deficiencies that accompany bariatric surgery likely contribute to the bone fragility in these 5 infants. Other risk factors for MBDI were appreciated in 4 of the 5 cases. 1,25 dihydroxyvitamin D was elevated or high-normal suggesting calcium deficiency in 2 cases. We believe infants born to mothers who have had prior bariatric surgery are at increased risk for bone fragility and MBDI during the first 6 months of life

Blueprint for a high-performance biomaterial: full-length spider dragline silk genes.

Spider dragline (major ampullate) silk outperforms virtually all other natural and manmade materials in terms of tensile strength and toughness. For this reason, the mass-production of artificial spider silks through transgenic technologies has been a major goal of biomimetics research. Although all known arthropod silk proteins are extremely large (>200 kiloDaltons), recombinant spider silks have been designed from short and incomplete cDNAs, the only available sequences. Here we describe the first full-length spider silk gene sequences and their flanking regions. These genes encode the MaSp1 and MaSp2 proteins that compose the black widow's high-performance dragline silk. Each gene includes a single enormous exon (>9000 base pairs) that translates into a highly repetitive polypeptide. Patterns of variation among sequence repeats at the amino acid and nucleotide levels indicate that the interaction of selection, intergenic recombination, and intragenic recombination governs the evolution of these highly unusual, modular proteins. Phylogenetic footprinting revealed putative regulatory elements in non-coding flanking sequences. Conservation of both upstream and downstream flanking sequences was especially striking between the two paralogous black widow major ampullate silk genes. Because these genes are co-expressed within the same silk gland, there may have been selection for similarity in regulatory regions. Our new data provide complete templates for synthesis of recombinant silk proteins that significantly improve the degree to which artificial silks mimic natural spider dragline fibers

Dramatic expansion of the black widow toxin arsenal uncovered by multi-tissue transcriptomics and venom proteomics.

BackgroundAnimal venoms attract enormous interest given their potential for pharmacological discovery and understanding the evolution of natural chemistries. Next-generation transcriptomics and proteomics provide unparalleled, but underexploited, capabilities for venom characterization. We combined multi-tissue RNA-Seq with mass spectrometry and bioinformatic analyses to determine venom gland specific transcripts and venom proteins from the Western black widow spider (Latrodectus hesperus) and investigated their evolution.ResultsWe estimated expression of 97,217 L. hesperus transcripts in venom glands relative to silk and cephalothorax tissues. We identified 695 venom gland specific transcripts (VSTs), many of which BLAST and GO term analyses indicate may function as toxins or their delivery agents. ~38% of VSTs had BLAST hits, including latrotoxins, inhibitor cystine knot toxins, CRISPs, hyaluronidases, chitinase, and proteases, and 59% of VSTs had predicted protein domains. Latrotoxins are venom toxins that cause massive neurotransmitter release from vertebrate or invertebrate neurons. We discovered ≥ 20 divergent latrotoxin paralogs expressed in L. hesperus venom glands, significantly increasing this biomedically important family. Mass spectrometry of L. hesperus venom identified 49 proteins from VSTs, 24 of which BLAST to toxins. Phylogenetic analyses showed venom gland specific gene family expansions and shifts in tissue expression.ConclusionsQuantitative expression analyses comparing multiple tissues are necessary to identify venom gland specific transcripts. We present a black widow venom specific exome that uncovers a trove of diverse toxins and associated proteins, suggesting a dynamic evolutionary history. This justifies a reevaluation of the functional activities of black widow venom in light of its emerging complexity

Untangling spider silk evolution with spidroin terminal domains

<p>Abstract</p> <p>Background</p> <p>Spidroins are a unique family of large, structural proteins that make up the bulk of spider silk fibers. Due to the highly variable nature of their repetitive sequences, spidroin evolutionary relationships have principally been determined from their non-repetitive carboxy (C)-terminal domains, though they offer limited character data. The few known spidroin amino (N)-terminal domains have been difficult to obtain, but potentially contain critical phylogenetic information for reconstructing the diversification of spider silks. Here we used silk gland expression data (ESTs) from highly divergent species to evaluate the functional significance and phylogenetic utility of spidroin N-terminal domains.</p> <p>Results</p> <p>We report 11 additional spidroin N-termini found by sequencing ~1,900 silk gland cDNAs from nine spider species that shared a common ancestor > 240 million years ago. In contrast to their hyper-variable repetitive regions, spidroin N-terminal domains have retained striking similarities in sequence identity, predicted secondary structure, and hydrophobicity. Through separate and combined phylogenetic analyses of N-terminal domains and their corresponding C-termini, we find that combined analysis produces the most resolved trees and that N-termini contribute more support and less conflict than the C-termini. These analyses show that paralogs largely group by silk gland type, except for the major ampullate spidroins. Moreover, spidroin structural motifs associated with superior tensile strength arose early in the history of this gene family, whereas a motif conferring greater extensibility convergently evolved in two distantly related paralogs.</p> <p>Conclusions</p> <p>A non-repetitive N-terminal domain appears to be a universal attribute of spidroin proteins, likely retained from the origin of spider silk production. Since this time, spidroin N-termini have maintained several features, consistent with this domain playing a key role in silk assembly. Phylogenetic analyses of the conserved N- and C-terminal domains illustrate dramatic radiation of the spidroin gene family, involving extensive duplications, shifts in expression patterns and extreme diversification of repetitive structural sequences that endow spider silks with an unparalleled range of mechanical properties.</p

A Predictive Structural Model of Standards-Based School Evaluation on Student Outcome

The current study examined the relationship between school leadership, school environment, teaching and learning strategies, and students’ performance on national assessment in math and science. In addition, it examined the mediating role of teaching and learning strategies in its relation to school leadership, school environment, and students’ performance in math and science as well. Study data was utilized from two datasets. First, the School Evaluation Standards scale (SES), which includes three subscales: school leadership, school environment, and teaching and learning strategies was utilized from a total of 711 schools that were randomly chosen from Saudi Arabia. Second, these school average scores in national assessment of math and science were collected. The finding revealed that there were direct and indirect effects of school leadership, school environment, teaching and learning strategies on students’ performance in math and science. Furthermore, teaching and learning strategies played as mediator between school leadership and school environment and students performance in math and science. The results of the research provided insights on how school evaluation standards (SES) affect academic performance and learning outcomes. Educational policy makers can benefit from the results of this study by evaluating school performance assessment standards and the level of practices to gauge the degree of application in real world practices and determine the room for improvements