Specimen-specific modeling of hip fracture pattern and repair

Hip fracture remains a major health problem for the elderly. Clinical studies have assessed fracture risk based on bone quality in the aging population and cadaveric testing has quantified bone strength and fracture loads. Prior modeling has primarily focused on quantifying the strain distribution in bone as an indicator of fracture risk. Recent advances in the extended finite element method (XFEM) enable prediction of the initiation and propagation of cracks without requiring a priori knowledge of the crack path. Accordingly, the objectives of this study were to predict femoral fracture in specimen-specific models using the XFEM approach, to perform one-to-one comparisons of predicted and in vitro fracture patterns, and to develop a framework to assess the mechanics and load transfer in the fractured femur when it is repaired with an osteosynthesis implant. Five specimen-specific femur models were developed from in vitro experiments under a simulated stance loading condition. Predicted fracture patterns closely matched the in vitro patterns; however, predictions of fracture load differed by approximately 50% due to sensitivity to local material properties. Specimen-specific intertrochanteric fractures were induced by subjecting the femur models to a sideways fall and repaired with a contemporary implant. Under a post-surgical stance loading, model-predicted load sharing between the implant and bone across the fracture surface varied from 59%:41% to 89%:11%, underscoring the importance of considering anatomic and fracture variability in the evaluation of implants. XFEM modeling shows potential as a macro-level analysis enabling fracture investigations of clinical cohorts, including at-risk groups, and the design of robust implants.     

Quadranguloside,a cycloartane triterpene glycoside from Passiflora quadrangularis

Quadranguloside, a new cyclopropane triterpene glycoside was isolated from the methanolic extract of the leaves of Passiflora quadrangularis. Its structure has been established as 9,19-cyclolanost-24Z-en-3β,21,26-triol-3,26-di-O-gentiobioside on the basis of hydrolysis and spectral evidence.     

TRAF3IP2 gene and systemic lupus erythematosus: association with disease susceptibility and pericarditis development

Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disease. Although genetic factors confer susceptibility to the disease, only 15 % of the genetic contribution has been identified. TRAF3IP2 gene, associated with susceptibility to psoriatic arthritis and psoriasis, encodes for Act1, a negative regulator of adaptive immunity and a positive signaling adaptor in IL-17-mediated immune responses. The aim of this study was to assess the role of TRAF3IP2 gene variability in SLE susceptibility and disease phenotype in an Italian population. Two hundred thirty-nine consecutive SLE patients were enrolled. Study protocol included complete physical examination; the clinical and laboratory data were collected. Two hundred seventy-eight age- and ethnicity-matched healthy subjects served as controls. TRAF3IP2 polymorphisms (rs33980500, rs13190932, and rs13193677) were analyzed in both cases and controls. Genotype analysis was performed by allelic discrimination assays. A case–control association study and a genotype–phenotype correlation were performed. The rs33980500 and rs13193677 resulted significantly associated with SLE susceptibility (P?=?0.021, odds ratio (OR)?=?1.71, and P?=?0.046, OR?=?1.73, respectively). All three TRAF3IP2 single nucleotide polymorphisms resulted associated with the development of pericarditis; in particular, rs33980500 showed the strongest association (P?=?0.002, OR 2.59). This association was further highlighted by binary logistic regression analysis. In conclusion, our data show for the first time the contribution of TRAF3IP2 genetic variability in SLE susceptibility, providing further suggestions that common variation in genes that function in the adaptive and innate arms of the immune system are important in establishing SLE risk. Our study also shows that this gene may affect disease phenotype and, particularly, the occurrence of pericarditis.     

Crystal structure of a minimal eIF4E-Cup complex reveals a general mechanism of eIF4E regulation in translational repression

Cup is an eIF4E-binding protein (4E-BP) that plays a central role in translational regulation of localized mRNAs during early Drosophila development. In particular, Cup is required for repressing translation of the maternally contributed oskar, nanos, and gurken mRNAs, all of which are essential for embryonic body axis determination. Here, we present the 2.8 Å resolution crystal structure of a minimal eIF4E–Cup assembly, consisting of the interacting regions of the two proteins. In the structure, two separate segments of Cup contact two orthogonal faces of eIF4E. The eIF4E-binding consensus motif of Cup (YXXXXLΦ) binds the convex side of eIF4E similarly to the consensus of other eIF4E-binding proteins, such as 4E-BPs and eIF4G. The second, noncanonical, eIF4E-binding site of Cup binds laterally and perpendicularly to the eIF4E β-sheet. Mutations of Cup at this binding site were shown to reduce binding to eIF4E and to promote the destabilization of the associated mRNA. Comparison with the binding mode of eIF4G to eIF4E suggests that Cup and eIF4G binding would be mutually exclusive at both binding sites. This shows how a common molecular surface of eIF4E might recognize different proteins acting at different times in the same pathway. The structure provides insight into the mechanism by which Cup disrupts eIF4E–eIF4G interaction and has broader implications for understanding the role of 4E-BPs in translational regulation.     

P2X7-mediated Increased Intracellular Calcium Causes Functional Derangement in Schwann Cells from Rats with CMT1A Neuropathy

Charcot-Marie-Tooth (CMT) is the most frequent inherited neuromuscular disorder, affecting 1 person in 2500. CMT1A, the most common form of CMT, is usually caused by a duplication of chromosome 17p11.2, containing the PMP22 (peripheral myelin protein-22) gene; overexpression of PMP22 in Schwann cells (SC) is believed to cause demyelination, although the underlying pathogenetic mechanisms remain unclear. Here we report an abnormally high basal concentration of intracellular calcium ([Ca²⁺]_i) in SC from CMT1A rats. By the use of specific pharmacological inhibitors and through down-regulation of expression by small interfering RNA, we demonstrate that the high [Ca²⁺]_i is caused by a PMP22-related overexpression of the P2X7 purinoceptor/channel leading to influx of extracellular Ca²⁺ into CMT1A SC. Correction of the altered [Ca²⁺]_i in CMT1A SC by small interfering RNA or with pharmacological inhibitors of P2X7 restores functional parameters of SC (migration and release of ciliary neurotrophic factor), which are typically defective in CMT1A SC. More significantly, stable down-regulation of the expression of P2X7 restores myelination in co-cultures of CMT1A SC with dorsal root ganglion sensory neurons. These results establish a pathogenetic link between high [Ca²⁺]_i and impaired SC function in CMT1A and identify overexpression of P2X7 as the molecular mechanism underlying both abnormalities. The development of P2X7 inhibitors is expected to provide a new therapeutic strategy for treatment of CMT1A neuropathy.Charcot-Marie-Tooth disease type 1 (CMT1)³ is a progressive hereditary motor and sensory neuropathy, characterized by distal muscle wasting and weakness, foot deformities, and severe slowing of nerve conduction, because of progressive demyelination (1). With a prevalence of 1 case in 2500, CMT1 is the most common hereditary neurologic disorder, and in the majority of cases (CMT1A) the disease is associated with a duplication on chromosome 17p11.2 of the gene for PMP22 (peripheral myelin protein 22) (2). PMP22 is a 22-kDa glycoprotein mainly expressed by myelinating Schwann cells (SC) and localized in compact myelin (3). The transgenic rat model of CMT1A, obtained by overexpression of PMP22 (4), confirms a role of PMP22 in the pathogenesis of CMT1A. Both PMP22 overexpression because of gene duplication and point mutations of PMP22 are associated with a CMT1A phenotype.The biochemical mechanisms correlating PMP22 dysfunction with demyelination are still unclear. Some reports indicate that a perturbed homeostasis of the intracellular Ca²⁺ concentration ([Ca²⁺]_i) might be causally involved in the demyelination process. Conditions inducing an increased [Ca²⁺]_i in SC impair cell differentiation and myelination (5, 6), similarly to what occurs in CMT1A. Incubation of intact rat nerves with Ca²⁺ and ionophores causes a progressive demyelination, spreading from the paranodes and invading regions of formerly compact myelin, which is dependent upon a rise in the [Ca²⁺]_i of SC (5).Additional evidence for the detrimental effect of a [Ca²⁺]_i elevation on myelin production by SC comes from application of ATP to murine SC monocultures, inducing an immediate and large increase in the [Ca²⁺]_i. As a result of ATP treatment, maturation and differentiation of SC, as well as expression of the myelin basic protein and production of compact myelin, are completely prevented (6). Taken together, the above observations indicate that abnormally elevated Ca²⁺ levels are causally related to impairment of myelin production by SC.In this study, we addressed the possible correlation between PMP22 overexpression and alteration of the [Ca²⁺]_i homeostasis in SC from a rat model of CMT1A. We recorded higher levels of basal [Ca²⁺]_i in affected than in control cells, and we identified the mechanisms responsible for the perturbation of the [Ca²⁺]_i levels in CMT1A SC. Experiments with pharmacological inhibitors and with small interfering RNA (siRNA) unequivocally demonstrated a correlation in CMT1A SC between overexpression of the purinergic receptor P2X7 and influx of extracellular [Ca²⁺]_i across this plasma membrane receptor/channel. In addition, correction of the abnormally elevated [Ca²⁺]_i levels by the use of a P2X7 antagonist or through down-regulation of the expression of P2X7 by transfection with siRNA or with short hairpin RNA-expressing plasmid (shRNA) restored the normal phenotype in CMT1A SC. These findings suggest that CMT1A should be considered as a “calcium disease.” Identification of P2X7 activation as the pathogenetic mechanism underlying demyelination may provide the rationale for a new therapeutic strategy for CMT1A, a disease with no currently available treatment.     

TimeClust: a clustering tool for gene expression time series

TimeClust is a user-friendly software package to cluster genes according to their temporal expression profiles. It can be conveniently used to analyze data obtained from DNA microarray time-course experiments. It implements two original algorithms specifically designed for clustering short time series together with hierarchical clustering and self-organizing maps. AVAILABILITY: TimeClust executable files for Windows and LINUX platforms can be downloaded free of charge for non-profit institutions from the following web site: http://aimed11.unipv.it/TimeClust.     

The genetics of feto-placental development: A study of acid phosphatase locus 1 and adenosine deaminase polymorphisms in a consecutive series of newborn infants

Background  

Acid phosphatase locus 1 and adenosine deaminase locus 1 polymorphisms show cooperative effects on glucose metabolism and immunological functions. The recent observation of cooperation between the two systems on susceptibility to repeated spontaneous miscarriage prompted us to search for possible interactional effects between these genes and the correlation between birth weight and placental weight. Deviation from a balanced development of the feto-placental unit has been found to be associated with perinatal morbidity and mortality and with cardiovascular diseases in adulthood.     

Bot1p is required for mitochondrial translation, respiratory function, and normal cell morphology in the fission yeast Schizosaccharomyces pombe

Maintenance of cell morphology is essential for normal cell function. For eukaryotic cells, a growing body of recent evidence highlights a close interdependence between mitochondrial function, the cytoskeleton, and cell cycle control mechanisms; however, the molecular details of this interconnection are still not completely understood. We have identified a novel protein, Bot1p, in the fission yeast Schizosaccharomyces pombe. The bot1 gene is essential for cell viability. bot1Delta mutant cells expressing lower levels of Bot1p display altered cell size and cell morphology and a disrupted actin cytoskeleton. Bot1p localizes to the mitochondria in live cells and cofractionates with purified mitochondrial ribosomes. Reduced levels of Bot1p lead to mitochondrial fragmentation, decreased mitochondrial protein translation, and a corresponding decrease in cell respiration. Overexpression of Bot1p results in cell cycle delay, with increased cell size and cell length and enhanced cell respiration rate. Our results show that Bot1p has a novel function in the control of cell respiration by acting on the mitochondrial protein synthesis machinery. Our observations also indicate that in fission yeast, alterations of mitochondrial function are linked to changes in cell cycle and cell morphology control mechanisms.