Room-Temperature Plasticity of a Nanosized GaN Crystal.

GaN wurtzite crystal is commonly regarded as eminently brittle. However, our research demonstrates that nanodeconfined GaN compressed along the M direction begins to exhibit room-temperature plasticity, yielding a dislocation-free structure despite the occurrence of considerable, irreversible deformation. Our interest in M-oriented, strained GaN nanoobjects was sparked by the results of first-principles bandgap calculations, whereas subsequent nanomechanical tests and ultrahigh-voltage (1250 kV) transmission electron microscopy observations confirmed the authenticity of the phenomenon. Moreover, identical experiments along the C direction produced only a quasi-brittle response. Precisely how this happens is demonstrated by molecular dynamics simulations of the deformation of the C- and M-oriented GaN frustum, which mirror our nanopillar crystals.

Expression profile of human porcine endogenous retrovirus A receptors (HuPAR-1, HuPAR-2) and transcription factor activator protein-2γ (TFAP-2C) genes in infected human fibroblasts-Model in vitro.

BACKGROUND: Xenotransplantation of porcine tissues raises concerns, especially in the context of the potential interspecies transmission of porcine endogenous retroviruses (PERVs). To date, the possibility of PERV infections of various human cells has been confirmed in vitro. PERVs infect cells coupling viral Env protein with adequate functional receptor on the surface of the host cell. So far, two PERV-A receptors have been described in humans: HuPAR-1 and HuPAR-2. TFAP-2C was described as one of the transcription factors engaged in the expression of HuPAR-2. METHODS: Bacterial LPS, well known as a strong inflammation inducer, was used in this study to stimulate changes of the expression profile of inflammation-related genes in human cells in vitro. The aim of the study was to investigate the expression profile of HuPAR-1 and HuPAR-2 and TFAP-2C genes in human NHDF cells treated with LPS and/or infected with PERVs from PK15 cells. PERV infection and expression was confirmed by qPCR and RTqPCR. The expression of HuPAR-1, HuPAR-2, and TFAP-2C genes was studied using HGU 133A 2.0 microarrays and RTqPCR. RESULTS: NHDF cells expressed both HuPAR-1 and HuPAR-2 genes with a higher expression of HuPAR-1. LPS down-regulated the expression of HuPAR-1 and TFAP-2C in NHDF cells, but had no effect on HuPAR-2 expression. These changes induced by LPS were more pronounced in the presence of PERV infection. CONCLUSION: As reported previously, treatment of NHDF cells with LPS decreased PERV-A provirus integration and increased PERV-A mRNA expression. PERV infection alone did not modulate the expression of HuPAR-1, HuPAR-2, and TFAP-2C. This is the first study analyzing the expression profile of HuPAR-1, HuPAR-2, and TFAP-2C in NHDF cells treated by LPS and/or infected by PERVs.

Familial or Sporadic Idiopathic Scoliosis - classification based on artificial neural network and GAPDH and ACTB transcription profile.

BACKGROUND: Importance of hereditary factors in the etiology of Idiopathic Scoliosis is widely accepted. In clinical practice some of the IS patients present with positive familial history of the deformity and some do not. Traditionally about 90% of patients have been considered as sporadic cases without familial recurrence. However the exact proportion of Familial and Sporadic Idiopathic Scoliosis is still unknown. Housekeeping genes encode proteins that are usually essential for the maintenance of basic cellular functions. ACTB and GAPDH are two housekeeping genes encoding respectively a cytoskeletal protein ß-actin, and glyceraldehyde-3-phosphate dehydrogenase, an enzyme of glycolysis. Although their expression levels can fluctuate between different tissues and persons, human housekeeping genes seem to exhibit a preserved tissue-wide expression ranking order. It was hypothesized that expression ranking order of two representative housekeeping genes ACTB and GAPDH might be disturbed in the tissues of patients with Familial Idiopathic Scoliosis (with positive family history of idiopathic scoliosis) opposed to the patients with no family members affected (Sporadic Idiopathic Scoliosis). An artificial neural network (ANN) was developed that could serve to differentiate between familial and sporadic cases of idiopathic scoliosis based on the expression levels of ACTB and GAPDH in different tissues of scoliotic patients. The aim of the study was to investigate whether the expression levels of ACTB and GAPDH in different tissues of idiopathic scoliosis patients could be used as a source of data for specially developed artificial neural network in order to predict the positive family history of index patient. RESULTS: The comparison of developed models showed, that the most satisfactory classification accuracy was achieved for ANN model with 18 nodes in the first hidden layer and 16 nodes in the second hidden layer. The classification accuracy for positive Idiopathic Scoliosis anamnesis only with the expression measurements of ACTB and GAPDH with the use of ANN based on 6-18-16-1 architecture was 8 of 9 (88%). Only in one case the prediction was ambiguous. CONCLUSIONS: Specially designed artificial neural network model proved possible association between expression level of ACTB, GAPDH and positive familial history of Idiopathic Scoliosis.

Quantitative analysis of porcine endogenous retroviruses in different organs of transgenic pigs generated for xenotransplantation.

The pig appears to be the most promising animal donor of organs for use in human recipients. Among several types of pathogens found in pigs, one of the greatest problems is presented by porcine endogenous retroviruses (PERVs). Screening of the source pig herd for PERVs should include analysis of both PERV DNA and RNA. Therefore, the present study focuses on quantitative analysis of PERVs in different organs such as the skin, heart, muscle, and liver and blood of transgenic pigs generated for xenotransplantation. Transgenic pigs were developed to express the human α-galactosidase, the human α-1,2-fucosyltransferase gene, or both genetic modifications of the genome (Lipinski et al., Medycyna Wet 66:316-322, 2010; Lipinski et al., Ann Anim Sci 12:349-356, 2012; Wieczorek et al., Medycyna Wet 67:462-466, 2011). The copy numbers of PERV DNA and RNA were evaluated using real-time Q-PCR and QRT-PCR, respectively. Comparative analysis of all PERV subtypes revealed the following relationships: PERV A > PERV B > PERV C. PERV A and B were found in all samples, whereas PERV C was detected in 47 % of the tested animals. The lowest level of PERV DNA was shown in the muscles for PERV A and B and in blood samples for PERV C. The lowest level of PERV A RNA was found in the skin, whereas those of PERV B and C RNA were found in liver specimens. Quantitative analysis revealed differences in the copy number of PERV subtypes between various organs of transgenic pigs generated for xenotransplantation. Our data support the idea that careful pig selection for organ donation with low PERV copy number may limit the risk of retrovirus transmission to the human recipients.

Vitamin D receptor gene (VDR) transcripts in bone, cartilage, muscles and blood and microarray analysis of vitamin D responsive genes expression in paravertebral muscles of juvenile and adolescent idiopathic scoliosis patients.

BACKGROUND: VDR may be considered as a candidate gene potentially related to idiopathic scoliosis susceptibility and natural history. Transcriptional profile of VDR mRNA isoforms might be changed in the structural tissues of the scoliotic spine and potentially influence the expression of VDR responsive genes. The purpose of the study was to determine differences in mRNA abundance of VDR isoforms in bone, cartilage and paravertebral muscles between tissues from curve concavity and convexity, between JIS and AIS and to identify VDR responsive genes differentiating juvenile and adolescent idiopathic scoliosis in paravertebral muscles. METHODS: In a group of 29 patients with JIS and AIS, specimens of bone, cartilage, paravertebral muscles were harvested at the both sides of the curve apex together with peripheral blood samples. Extracted total RNA served as a matrix for VDRs and VDRl mRNA quantification by QRT PCR. Subsequent microarray analysis of paravertebral muscular tissue samples was performed with HG U133A chips (Affymetrix). Quantitative data were compared by a nonparametric Mann Whitney U test. Microarray results were analyzed with GeneSpring 11GX application. Matrix plot of normalized log-intensities visualized the degree of differentiation between muscular tissue transcriptomes of JIS and AIS group. Fold Change Analysis with cutoff of Fold Change ≥2 identified differentially expressed VDR responsive genes in paravertebral muscles of JIS and AIS. RESULTS: No significant differences in transcript abundance of VDR isoforms between tissues of the curve concavity and convexity were found. Statistically significant difference between JIS and AIS group in mRNA abundance of VDRl isoform was found in paravertebral muscles of curve concavity. Higher degree of muscular transcriptome differentiation between curve concavity and convexity was visualized in JIS group. In paravertebral muscles Tob2 and MED13 were selected as genes differentially expressed in JIS and AIS group. CONCLUSIONS: In Idiopathic Scolioses transcriptional activity and alternative splicing of VDR mRNA in osseous, cartilaginous, and paravertebral muscular tissues are tissue specific and equal on both sides of the curve. The number of mRNA copies of VDRl izoform in concave paravertebral muscles might be one of the factors differentiating JIS and AIS. In paravertebral muscles Tob2 and Med13 genes differentiate Adolescent and Juvenile type of Idiopathic Scoliosis.

Concomitant ipsilateral femoral neck and shaft fractures--analysis of cases.

Concomitant ipsilateral shaft and femoral neck or pertrochanteric fractures are uncommon. They result from high-energy traumas and the mechanism of injury is usually complex. The proximal fracture is often not displaced and may be hardly visible on x-rays. Overlooking the proximal fracture may result in therapeutic problems. The best method of treatment is by closed stabilization of both fractures with a reconstruction nail. In our opinion, concomitant neck and femoral shaft fractures demand particular alertness in x-ray analysis, precision in fracture stabilization and usually longer patient rehabilitation.

Porcine Endogenous Retrovirus (PERV) - Molecular Structure and Replication Strategy in the Context of Retroviral Infection Risk of Human Cells.

The xenotransplantation of porcine tissues may help overcome the shortage of human organs for transplantation. However, there are some concerns about recipient safety because the risk of porcine endogenous retrovirus (PERV) transmission to human cells remains unknown. Although, to date, no PERV infections have been noted in vivo, the possibility of such infections has been confirmed in vitro. Better understanding of the structure and replication cycle of PERVs is a prerequisite for determining the risk of infection and planning PERV-detection strategies. This review presents the current state of knowledge about the structure and replication cycle of PERVs in the context of retroviral infection risk.

Microscale's relationship between Young's modulus and tissue density. Prediction of displacements.

The study presents an experimental verification of Wagner et al.'s relationship in microscale and proposes a modification of this relationship. For this purpose, 11 cubic specimens were microcomputed tomography scanned and mechanically tested with the displacement full-field measurements using a digital image correlation system. Then, numerical simulations of the compression tests were performed using a finite elements method. The Young's modulus distributions assigned to the finite elements models were calculated using both of Wagner et al.'s relationships: original and modified. Comparison of the experimental and numerical results indicated the accuracy of numerical solutions for both relationships.

Lead content in the femoral heads of inhabitants of Silesia (Poland).

Lead content was evaluated in spongious and cortical bone as well as in cartilage surface of human femoral heads obtained during hip arthroplasty from 45 inhabitants (11 males and 34 females) of the industrial region of Upper Silesia. The average age of this group was 63.9+/-14.4 years. Lead content was assessed using microwave mineralization with the graphite furnace atomic absorption spectrometry (GFAAS) method. The average lead content in the specimens from spongious bone was 2.56 microg/g, 3.05 microg/g in cortical bone and 3.53 microg/g in cartilage surface. The calculated average Pb/Ca ratio was 1783x10(-8) in spongious bone, 1623x10(-8) in cortical bone, and 2512x10(-8) in the cartilage. Both lead concentration and Pb/Ca ratio increased with the age of the patients. Higher lead content was found in the specimens from male hips and in the group of cigarette smokers.

Effect of 2'-deoxyisoguanosine on the growth of human tumor and normal cell lines.

AIM: To test the effect of 2'-deoxyisoguanosine as a specific substrate of HIV reverse transcriptase on the growth of cultured normal and cancer cells. METHODS: The effect of 2'-deoxyisoguanosine on the growth of cells of two normal (telomerase-negative) and five cancer cell lines have been tested. Cell viability was assessed by MTT assay. RESULTS: We have found that this nucleoside analogue has low potency and specificity in inhibiting tumor cell growth. IC50 ranged from 0.5 mM to 2 mM for tumor cells, and from 1 mM to more than 4 mM for normal cells. CONCLUSIONS: 2'-deoxyisoguanosine has low potency and specificity in inhibiting tumor cell growth, similar to other telomerase inhibitors.

Transforming growth factor-beta (TGF- ß) signaling in paravertebral muscles in juvenile and adolescent idiopathic scoliosis.

Most researchers agree that idiopathic scoliosis (IS) is a multifactorial disease influenced by complex genetic and environmental factors. The onset of the spinal deformity that determines the natural course of the disease, usually occurs in the juvenile or adolescent period. Transforming growth factors ß (TGF-ßs) and their receptors, TGFBRs, may be considered as candidate genes related to IS susceptibility and natural history. This study explores the transcriptional profile of TGF-ßs, TGFBRs, and TGF-ß responsive genes in the paravertebral muscles of patients with juvenile and adolescent idiopathic scoliosis (JIS and AIS, resp.). Muscle specimens were harvested intraoperatively and grouped according to the side of the curve and the age of scoliosis onset. The results of microarray and qRT-PCR analysis confirmed significantly higher transcript abundances of TGF-ß2, TGF-ß3, and TGFBR2 in samples from the curve concavity of AIS patients, suggesting a difference in TGF-ß signaling in the pathogenesis of juvenile and adolescent curves. Analysis of TGF-ß responsive genes in the transcriptomes of patients with AIS suggested overrepresentation of the genes localized in the extracellular region of curve concavity: LTBP3, LTBP4, ITGB4, and ITGB5. This finding suggests the extracellular region of paravertebral muscles as an interesting target for future molecular research into AIS pathogenesis.

Prediction of Young׳s modulus of trabeculae in microscale using macro-scale׳s relationships between bone density and mechanical properties.

According to the literature, there are many mathematical relationships between density of the trabecular bone and mechanical properties obtained in macro-scale testing. In micro-scale, the measurements provide only the ranges of Young׳s modulus of trabeculae, but there are no experimentally tested relationships allowing the calculation of the distribution of Young׳s modulus of trabeculae within these experimental ranges. This study examined the applicability of relationships between bone density and mechanical properties obtained in macro-scale testing for the calculation of Young׳s modulus distribution in micro-scale. Twelve cubic specimens from eleven femoral heads were cut out and micro-computed tomography (micro-CT) scanned. A mechanical compression test and Digital Image Correlation (DIC) measurements were performed to obtain the experimental displacement and strain full-field evaluation for each specimen. Five relationships between bone density and Young׳s modulus were selected for the test; those were given by Carter and Hayes (1977), Ciarelli et al. (2000), Kaneko et al. (2004), Keller (1994) for the human femur, and Li and Aspden, 1997. Using these relationships, five separate finite element (FE) models were prepared, with different distribution of Young׳s modulus of trabeculae for each specimen. In total, 60 FE analyses were carried out. The obtained displacement and strain full-field measurements from numerical calculations and experiment were compared. The results indicate that the highest accuracy of the numerical calculation was obtained for the Ciarelli et al. (2000) relationship, where the relative error was 17.87% for displacements and 50.94 % for strains. Therefore, the application of the Ciarelli et al. (2000) relationship in the microscale linear FE analysis is possible, but mainly to determine bone displacement.

Arthroplasty in patients with congenital hip dysplasia--early evaluation of a treatment method.

BACKGROUND: Developmental hip dysplasia (DHD) is the most common cause of secondary hip osteoarthritis (OA). It often leads to OA in young, active and working adults. The aim of our study is to evaluate the results of THA in patients with DHD. MATERIAL AND METHODS: Total hip arthroplasty was performed in 15 patients with DHD - 13 women (average age - 39) and 2 men (average age - 44) between June 2010 to June 2011. Patient's hips were estimated by Crowe classification to evaluate the severity of degenerative arthritis. Patients we reassessed with Harris Hip Score before and after the surgery. RESULTS: The mean preoperative score was 44.6 points, directly after surgery 62.4 pts., 6 months after 78.6 points. After artrhroplasty, improvement was noted in walking stairs without railing, walking without support, sitting on chair for more than 1 hour. Before the surgery average difference in limbs" length was 4 cm After the treatment it was reduced to 0.5 cm. Mean hip flexion was 40 ° before, 90 ° after the surgery, mean abduction was respectively 0° and 25°. Our study proves that total hip arthroplasty in patients with developmental dysplasia of hip helps to improve stability and mobility of joint and to reduce the pain. CONCLUSIONS: 1. In the type 1 and 2 according to Crow's classification, good clinical results may be achieved using standard prosthesis stem sizes and press-fit acebutalar component with possibly the smallest diameter providing stable placing. 2. In the case of ty pe III good results are observed using acetabular press-fit method for fixing, after reconstruction of bone defects with osteogenous bone graft. 3. The usage of big head dimensions gives beneficial effects on the osseointegration of the acetabular component and reduces the risk of dislocation. 4. A short follow-up period of the group of patients presented requires further prospective study to evaluate the long-term results.

Locked intramedullary nailing in the treatment of non-union following humeral shaft fractures. Cases study.

The paper presents an analysis of cases of treatment of humeral shaft fracture non-union following operative treatment. Non-union was treated by locked intramedullary nailing in all patients. Bone destruction at the fracture site is an indication for using bone grafts. In our opinion autologous bone marrow injection to the fracture site is an effective method of bone union stimulation, and this non-invasive procedure may be repeated several times. Stable osteosynthesis promotes callus formation and remodeling, and enables early rehabilitation.

Intracranial subdural hematoma and pneumocephalus after spinal instrumentation of myelodysplastic scoliosis.

To report a case of acute intracranial subdural hematoma, pneumocephalus, and pneumorachis, which occurred because of cerebrospinal fluid (CSF) leak caused by a malpositioned transpedicular screw during spinal surgery for severe myelodysplastic scoliosis accompanied with hydrocephalus. Intracranial hemorrhage may occur as a consequence of dural sac penetration and CSF leakage after various medical procedures at the spinal level. The awareness of this severe complication is especially important during spinal instrumentation procedures in which inadvertent dural sac violation and CSF loss may be overlooked. A case report and literature review are presented here. A 12-year-old girl with a history of myelomeningocele and hydrocephalus underwent instrumentation for severe myelodysplastic scoliosis. Postoperatively, she became aphasic and increasingly somnolent. An urgent computed tomographic scan of the head and spine showed massive intracranial hematoma, pneumocephalus, pneumorachis, and a malpositioned pedicular screw that caused CSF leakage, intracranial hypotension, and bleeding remote from the surgical site. The patient needed neurosurgical cranial decompression and subsequent spinal reoperation with dural tear repair. The final outcome was an uneventful complete recovery. The increasing use of pedicular screws in spinal surgery carries a potential risk of occult dural sac violation with subsequent CSF leakage, intracranial hypotension, and the possibility of intracranial bleeding and pneumocephalus remote from the surgical site. This potentially fatal complication should always be considered after spinal surgery in the presence of early signs of neurological deterioration and necessitates an urgent cranial and spinal imaging to confirm the diagnosis and to make adequate treatment decisions.

Deconfinement leads to changes in the nanoscale plasticity of silicon.

Silicon crystals have an important role in the electronics industry, and silicon nanoparticles have applications in areas such as nanoelectromechanical systems, photonics and biotechnology. However, the elastic-plastic transition observed in silicon is not fully understood; in particular, it is not known if the plasticity of silicon is determined by dislocations or by transformations between phases. Here, based on compression experiments and molecular dynamics simulations, we show that the mechanical properties of bulk silicon and silicon nanoparticles are significantly different. We find that bulk silicon exists in a state of relative constraint, with its plasticity dominated by phase transformations, whereas silicon nanoparticles are less constrained and display dislocation-driven plasticity. This transition, which we call deconfinement, can also explain the absence of phase transformations in deformed silicon nanowedges. Furthermore, the phenomenon is in agreement with effects observed in shape-memory alloy nanopillars, and provides insight into the origin of incipient plasticity.

The value of computed tomography with 3D reconstruction for the diagnosis of pelvic and spine fractures following a sports injury--a case report.

The paper presents the case of a young snowboarder injured after falling down on a hill slope. Pelvis and spine computed tomography with 3D reconstruction visualised fractures not visible on standard radiographs. Not all injuries to the pelvis can be seen on a-p radiographs. It is due to its complex spatial anatomy and the presence of gas-filled tissue overlying the bony shadows. Fracture detection may be a diagnostic problem in elderly osteoporotic patients and in young patients with multiple injuries. We believe that computed tomography with 3D reconstruction should be performed when there is a strong suspicion of fracture in spite of a negative standard radiological examination.

Rabbit cortical bone tissue increases its elastic stiffness but becomes less viscoelastic with age.

Bone is dynamic tissue undergoing changes in its composition, structure and functional properties during growth. It has been proposed that especially changes in the collagen phase of bone are responsible for making the bone more fragile, and potentially less viscoelastic with age. Hence, robust methods to measure viscoelasticitiy are needed. This study aimed to characterize the development of the elastic and viscoelastic mechanical properties of rabbit bone during maturation and growth, as assessed by nanoindentation. The humeri from female New Zealand white rabbits of varying age (newborn, 11 days, 4 weeks, 3 and 6 months old, n=8 per group) were investigated. Mid-diaphyseal cortical bone samples were cut, dehydrated, embedded and polished. Nanoindentation probing, semi-dynamic testing with a frequency of 20 Hz and creep with a dwell time of 60 s were performed under load control to quantify the elastic and the time-dependent viscoelastic mechanical properties of bone. The elastic moduli were evaluated with all three methods and the viscoelastic parameters were assessed using the phase-shift and the creep time constant. The elastic stiffness of bone increased significantly with each consecutive age group, from 11 days to 6 months of age, based on the reduced modulus from the indentation probing, the storage modulus from the semi-dynamic test, and the first elastic parameter from the creep test. These elastic parameters correlated significantly (R=0.88-0.94, p<0.01). The values of viscoelastic parameters, the phase-shift and time creep constant, decreased significantly with age. The viscous properties determined by the creep and the semi-dynamic testing correlated significantly (R=0.90, p<0.01), however, no correlation was found between the phase-shift and the creep time constant. Additionally, the present results showed specific associations with tissue composition, as measured with Fourier Transform Infrared spectroscopy of the same samples. In summary, the present results reveal significant changes in material properties of rabbit cortical bone with age. The elastic modulus of bone tissue increased by approximately 60%, whereas the viscoelastic parameters decreased by 10% to 25% during the first 6 months of the rabbit's life. Together, this indicates significant structural and functional maturation of the bone matrix during growth of the rabbit.

Precision of nanoindentation protocols for measurement of viscoelasticity in cortical and trabecular bone.

Nanoindentation has recently gained attention as a characterization technique for mechanical properties of biological tissues, such as bone, on the sub-micron level. However, optimal methods to characterize viscoelastic properties of bones are yet to be established. This study aimed to compare the time-dependent viscoelastic properties of bone tissue obtained with different nanoindentation methods. Bovine cortical and trabecular bone samples (n=8) from the distal femur and proximal tibia were dehydrated, embedded and polished. The material properties determined using nanoindentation were hardness and reduced modulus, as well as time-dependent parameters based on creep, loading-rate, dissipated energy and semi-dynamic testing under load control. Each loading protocol was repeated 160 times and the reproducibility was assessed based on the coefficient of variation (CV). Additionally, three well-characterized polymers were tested and CV values were calculated for reference. The employed methods were able to characterize time-dependent viscoelastic properties of bone. However, their reproducibility varied highly (CV 9-40%). The creep constant increased with increasing dwell time. The reproducibility was best with a 30s creep period (CV 18%). The dissipated energy was stable after three repeated load cycles, and the reproducibility improved with each cycle (CV 23%). The viscoelastic properties determined with semi-dynamic test increased with increase in frequency. These measurements were most reproducible at high frequencies (CV 9-10%). Our results indicate that several methods are feasible for the determination of viscoelastic properties of bone material. The high frequency semi-dynamic test showed the highest precision within the tested nanoindentation protocols.

An electric current spike linked to nanoscale plasticity.

The increase in semiconductor conductivity that occurs when a hard indenter is pressed into its surface has been recognized for years, and nanoindentation experiments have provided numerous insights into the mechanical properties of materials. In particular, such experiments have revealed so called pop-in events, where the indenter suddenly enters deeper into the material without any additional force being applied; these mark the onset of the elastic-plastic transition. Here, we report the observation of a current spike--a sharp increase in electrical current followed by immediate decay to zero at the end of the elastic deformation--during the nanoscale deformation of gallium arsenide. Such a spike has not been seen in previous nanoindentation experiments on semiconductors, and our results, supported by ab initio calculations, suggest a common origin for the electrical and mechanical responses of nanodeformed gallium arsenide. This leads us to the conclusion that a phase transition is the fundamental cause of nanoscale plasticity in gallium arsenide, and the discovery calls for a revision of the current dislocation-based understanding of nanoscale plasticity.