Conditional Gene Targeting in Mouse Pancreatic β-Cells: Analysis of Ectopic Cre Transgene Expression in the Brain

B. W. and M. B. Contributed equally to this manuscript Corresponding authors

Treatment of diaphyseal non-unions of the ulna and radius

Non-unions of the forearm often cause severe dysfunction of the forearm as they affect the interosseus membrane, elbow and wrist. Treatment of these non-unions can be challenging due to poor bone stock, broken hardware, scarring and stiffness due to long-term immobilisation. We retrospectively reviewed a large cohort of forearm non-unions treated by using a uniform surgical approach during a period of 33 years (1975-2008) in a single trauma centre. All non-unions were managed following the AO-principles of compression plate fixation and autologous bone grafting if needed. The study cohort consisted of 47 patients with 51 non-unions of the radius and/or ulna. The initial injury was a fracture of the diaphyseal radius and ulna in 22 patients, an isolated fracture of the diaphyseal ulna in 13, an isolated fracture of the diaphyseal radius in 5, a Monteggia fracture in 5, and a Galeazzi fracture-dislocation of the forearm in 2 patients. Index surgery for non-union consisted of open reduction and plate fixation in combination with a graft in 30 cases (59%), open reduction and plate fixation alone in 14 cases (27%), and only a graft in 7 cases (14%). The functional result was assessed in accordance to the system used by Anderson and colleagues. Average follow-up time was 75 months (range 12-315 months). All non-unions healed within a median of 7 months. According to the system of Anderson and colleagues, 29 patients (62%) had an excellent result, 8 (17%) had a satisfactory result, and 10 (21%) had an unsatisfactory result. Complications were seen in six patients (13%). Our results show that treatment of diaphyseal forearm non-unions using classic techniques of compression plating osteosynthesis and autologous bone grafting if needed will lead to a high union rate (100% in our series). Despite clinical and radiographic bone healing, however, a substantial subset of patients will have a less than optimal functional outcom

Indications for implant removal after fracture healing: a review of the literature

Introduction: The aim of this review was to collect and summarize published data on the indications for implant removal after fracture healing, since these are not well defined and guidelines hardly exist. Methods: A literature search was performed. Results: Though there are several presumed benefits of implant removal, such as functional improvement and pain relief, the surgical procedure can be very challenging and may lead to complications or even worsening of the complaints. Research has focused on the safety of metal implants (e.g., risk of corrosion, allergy, and carcinogenesis). For these reasons, implants have been removed routinely for decades. Along with the introduction of titanium alloy implants, the need for implant removal became a subject of debate in view of potential (dis)advantages since, in general, implants made of titanium alloys are more difficult to remove. Currently, the main indications for removal from both the upper and lower extremity are mostly 'relative' and patient-driven, such as pain, prominent material, or simply the request for removal. True medical indications like infection or intra-articular material are minor reasons. Conclusion: This review illustrates the great variety of view points in the literature, with large differences in opinions and practices about the indications for implant removal after fracture healing. Since some studies have described asymptomatic patients developing complaints after removal, the general advice nowadays is to remove implants after fracture healing only in symptomatic patients and after a proper informed consent. Well-designed prospective studies on this subject are urgently needed in order to form guidelines based on scientific evidence

Global Mapping of DNA Methylation in Mouse Promoters Reveals Epigenetic Reprogramming of Pluripotency Genes

DNA methylation patterns are reprogrammed in primordial germ cells and in preimplantation embryos by demethylation and subsequent de novo methylation. It has been suggested that epigenetic reprogramming may be necessary for the embryonic genome to return to a pluripotent state. We have carried out a genome-wide promoter analysis of DNA methylation in mouse embryonic stem (ES) cells, embryonic germ (EG) cells, sperm, trophoblast stem (TS) cells, and primary embryonic fibroblasts (pMEFs). Global clustering analysis shows that methylation patterns of ES cells, EG cells, and sperm are surprisingly similar, suggesting that while the sperm is a highly specialized cell type, its promoter epigenome is already largely reprogrammed and resembles a pluripotent state. Comparisons between pluripotent tissues and pMEFs reveal that a number of pluripotency related genes, including Nanog, Lefty1 and Tdgf1, as well as the nucleosome remodeller Smarcd1, are hypomethylated in stem cells and hypermethylated in differentiated cells. Differences in promoter methylation are associated with significant differences in transcription levels in more than 60% of genes analysed. Our comparative approach to promoter methylation thus identifies gene candidates for the regulation of pluripotency and epigenetic reprogramming. While the sperm genome is, overall, similarly methylated to that of ES and EG cells, there are some key exceptions, including Nanog and Lefty1, that are highly methylated in sperm. Nanog promoter methylation is erased by active and passive demethylation after fertilisation before expression commences in the morula. In ES cells the normally active Nanog promoter is silenced when targeted by de novo methylation. Our study suggests that reprogramming of promoter methylation is one of the key determinants of the epigenetic regulation of pluripotency genes. Epigenetic reprogramming in the germline prior to fertilisation and the reprogramming of key pluripotency genes in the early embryo is thus crucial for transmission of pluripotency

Identification of Arx transcriptional targets in the developing basal forebrain

Mutations in the aristaless-related homeobox (ARX) gene are associated with multiple neurologic disorders in humans. Studies in mice indicate Arx plays a role in neuronal progenitor proliferation and development of the cerebral cortex, thalamus, hippocampus, striatum, and olfactory bulbs. Specific defects associated with Arx loss of function include abnormal interneuron migration and subtype differentiation. How disruptions in ARX result in human disease and how loss of Arx in mice results in these phenotypes remains poorly understood. To gain insight into the biological functions of Arx, we performed a genome-wide expression screen to identify transcriptional changes within the subpallium in the absence of Arx. We have identified 84 genes whose expression was dysregulated in the absence of Arx. This population was enriched in genes involved in cell migration, axonal guidance, neurogenesis, and regulation of transcription and includes genes implicated in autism, epilepsy, and mental retardation; all features recognized in patients with ARX mutations. Additionally, we found Arx directly repressed three of the identified transcription factors: Lmo1, Ebf3 and Shox2. To further understand how the identified genes are involved in neural development, we used gene set enrichment algorithms to compare the Arx gene regulatory network (GRN) to the Dlx1/2 GRN and interneuron transcriptome. These analyses identified a subset of genes in the Arx GRN that are shared with that of the Dlx1/2 GRN and that are enriched in the interneuron transcriptome. These data indicate Arx plays multiple roles in forebrain development, both dependent and independent of Dlx1/2, and thus provides further insights into the understanding of the mechanisms underlying the pathology of mental retardation and epilepsy phenotypes resulting from ARX mutations

Current perspectives of the signaling pathways directing neural crest induction

The neural crest is a migratory population of embryonic cells with a tremendous potential to differentiate and contribute to nearly every organ system in the adult body. Over the past two decades, an incredible amount of research has given us a reasonable understanding of how these cells are generated. Neural crest induction involves the combinatorial input of multiple signaling pathways and transcription factors, and is thought to occur in two phases from gastrulation to neurulation. In the first phase, FGF and Wnt signaling induce NC progenitors at the border of the neural plate, activating the expression of members of the Msx, Pax, and Zic families, among others. In the second phase, BMP, Wnt, and Notch signaling maintain these progenitors and bring about the expression of definitive NC markers including Snail2, FoxD3, and Sox9/10. In recent years, additional signaling molecules and modulators of these pathways have been uncovered, creating an increasingly complex regulatory network. In this work, we provide a comprehensive review of the major signaling pathways that participate in neural crest induction, with a focus on recent developments and current perspectives. We provide a simplified model of early neural crest development and stress similarities and differences between four major model organisms: Xenopus, chick, zebrafish, and mouse

Antitermitic Properties of Cellulose Pads Treated with Bark Extractives

A study was undertaken to evaluate the feasibility of using bark extractives as a preservative treatment for wood to inhibit subterranean termite activity. Bark samples were collected from eleven species: Pinus strobus, P. virginiana, Tsuga canadensis, Quercus alba, Q. velutina, Q. prinus, Sassafras albidum, Juglans nigra, Carya ovata, Liriodendron tulipifera, and Robinia pseudoacacia.Cellulose paper pads (unbleached kraft) were treated with one of two bark extracts (A:H:W or 1% NaOH/Na2S) at 0.16, 0.67, and 0.83 g/ml treatment levels and evaluated for antitermitic properties.Complete termite mortality was observed after 4 weeks for paper pads treated with A:H:W bark extracts from the species Q. prinus, P. strobus, C. ovata, and S. albidum at both the 0.67 and 0.83 g/ml treatment levels. In addition, no termite survival was observed for paper pads treated with the A:H:W bark extracts from the species Q. alba, L. tulipifera, and T. canadensis at the 0.83 g/ml treatment level. Termite survival was observed for paper pads treated with A:H:W extracts at the 0.16 g/ml treatment level and with alkali extracts at the 0.16, 0.67, and 0.83 g/ml treatment levels for all bark species examined.No significant difference in termite mortality was observed between A:H:W bark extracts obtained from fresh or 1-year-old harvested bark. Feeding preference trials indicate that termites are attracted to A:H:W extracts obtained from C. ovata and J. nigra. Antitermitic trials with pentachlorophenol, copper naphthenate, and bark extracts at the 0.67 g/ml treatment level exhibited complete termite mortality; but the termites consumed more cellulose treated with bark extractives than with commercial preservatives.These results indicate that A:H:W bark extracts from the species Q. prinus, S. albidum, P. strobus and C. ovata show promise as a wood preservative, but additional studies are needed to isolate and identify the antitermitic extracts

A Study of Loblolly Pine Growth Increments—Part III Refining Characteristics of Tracheids from Kraft Pulps

Growth increments of loblolly pine were divided into five growth zones and kraft-pulped according to four different digestion schedules of 1 1/2, 1 3/4, 2, and 3 hours. Each of the 20 pulps was subjected to four periods of beating and Canadian Standard Freeness (CSF) was determined for each. It was found that all pulps independent of the extent of digestion or origin of wood from the growth ring had about the same CSF after short periods of beating. After 35 minutes in the beater, latewood pulp freeness was drastically reduced whereas earlywood pulps changed very little. In general, significantly less energy, as indicated by shorter beating times, was needed for latewood pulps to achieve a specific CSF level than for earlywood pulp. Pulps of low yield were easier to refine than those of high yield. Scanning electron microscopic observations revealed that all pulps underwent a tracheid cell-wall peeling sequence. The layer removed from latewood tracheids by beating separated into long fibrillar bundles while earlywood lamellae freed from tracheids remained intact. The influence of this external fibrillation was attributed to differences between the pulps in refining

Temporal and thermal effects on deformation potentials in bone.

There were 44 freshly excised adult rat femora subjected to mechanical deformation in a 4-point bending jig while the load/deformation curves and the electrical potentials generated were recorded simultaneously. Serial testing was repeated after storage of specimens up to 30 days at 25 degrees C and -15 degrees, and after heating for 1 h at 70 degrees, 80 degrees, and 85 degrees C. The amplitude of the potential decreased shortly after the femora had been excised until, by 4-7 days, it reached a plateau which was 10-20% of the initial value. In some cases polarity reversal occurred. These changes were not prevented by freezing or drying nor were they accompanied by increased stiffness. It is presumed that they are related to more subtle changes in the mechanical properties of bone or to alterations in the generating or conducting mechanisms. Heating caused a significant increase in potential without a change in the waveform. A corresponding increase in the deformation occurred due to softening of the bone which could, in itself, be responsible for the increased potential without a basic alteration in the transducer mechanism