The process of bone formation, remodelling and healing involves a coordinated action of various cell types. Advances in understanding the biology of osteoblast cells during these processes have been ...enabled through the use of various in vitro culture models from different origins. In an era of intensive bone tissue engineering research, these cell models are more and more often applied due to limited availability of primary human osteoblast cells. While they are a helpful tool in developing novel therapies or biomaterials; concerns arise regarding their phenotypic state and differences in relation to primary human osteoblast cells. In this review we discuss the osteoblastic development of some of the available cell models; such as primary human, rat, mouse, bovine, ovine and rabbit osteoblast cells; as well as MC3T3-E1, MG-63 and SaOs-2 cell lines, together with their advantages and disadvantages. Through this, we provide suggestions on the selection of the appropriate and most relevant osteoblast model for in vitro studies, with specific emphasis on cell-material based studies.
Development of an optimal interface between bone and orthopaedic and dental implants has taken place for many years. In order to determine whether a newly developed implant material conforms to the ...requirements of biocompatibility, mechanical stability and safety, it must undergo rigorous testing both in vitro and in vivo. Results from in vitro studies can be difficult to extrapolate to the in vivo situation. For this reason the use of animal models is often an essential step in the testing of orthopaedic and dental implants prior to clinical use in humans. This review discusses some of the more commonly available and frequently used animal models such as the dog, sheep, goat, pig and rabbit models for the evaluation of bone-implant interactions. Factors for consideration when choosing an animal model and implant design are discussed. Various bone specific features are discussed including the usage of the species, bone macrostructure and microstructure and bone composition and remodelling, with emphasis being placed on the similarity between the animal model and the human clinical situation. While the rabbit was the most commonly used of the species discussed in this review, it is clear that this species showed the least similarities to human bone. There were only minor differences in bone composition between the various species and humans. The pig demonstrated a good likeness with human bone however difficulties may be encountered in relation to their size and ease of handling. In this respect the dog and sheep/goat show more promise as animal models for the testing of bone implant materials. While no species fulfils all of the requirements of an ideal model, an understanding of the differences in bone architecture and remodelling between the species is likely to assist in the selection of a suitable species for a defined research question.
Fracture-related infection (FRI) is a common and serious complication in trauma surgery. Accurately estimating the impact of this complication has been hampered by the lack of a clear definition. The ...absence of a working definition of FRI renders existing studies difficult to evaluate or compare. In order to address this issue, an expert group comprised of a number of scientific and medical organizations has been convened, with the support of the AO Foundation, in order to develop a consensus definition.
The process that led to this proposed definition started with a systematic literature review, which revealed that the majority of randomized controlled trials in fracture care do not use a standardized definition of FRI. In response to this conclusion, an international survey on the need for and key components of a definition of FRI was distributed amongst all registered AOTrauma users. Approximately 90% of the more than 2000 surgeons who responded suggested that a definition of FRI is required. As a final step, a consensus meeting was held with an expert panel. The outcome of this process led to a consensus definition of FRI.
Two levels of certainty around diagnostic features were defined. Criteria could be confirmatory (infection definitely present) or suggestive. Four confirmatory criteria were defined: Fistula, sinus or wound breakdown; Purulent drainage from the wound or presence of pus during surgery; Phenotypically indistinguishable pathogens identified by culture from at least two separate deep tissue/implant specimens; Presence of microorganisms in deep tissue taken during an operative intervention, as confirmed by histopathological examination. Furthermore, a list of suggestive criteria was defined. These require further investigations in order to look for confirmatory criteria.
In the current paper, an overview is provided of the proposed definition and a rationale for each component and decision. The intention of establishing this definition of FRI was to offer clinicians the opportunity to standardize clinical reports and improve the quality of published literature. It is important to note that the proposed definition was not designed to guide treatment of FRI and should be validated by prospective data collection in the future.
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Teaching has been characterised as a stressful profession that is prone to burnout. Less is known about the specific ways in which teachers experience and navigate stressors associated with their ...work. This study aimed to qualitatively understand how teachers who perceive high and low levels of burnout characterise their lived experiences in school environments. Data were collected through interviews with 28 inservice teachers (11 male, 17 female) from the US Midwest who reported high- or low-burnout on a psychometric survey. Data were analysed by two experienced qualitative researchers. Results indicated that (a) low-burnout teachers perceived nurturing teaching environments, (b) high-burnout teachers perceived combative and constraining teaching environments, and (c) all teachers had to manage workplace stress. Building from these findings, we present a model for understanding how the school environment influences teacher burnout. This model highlights the importance of developing optimal working conditions that nurture teacher development.
Abbreviation: MBI-ES = Maslach Burnout Iventory-Educators Survey; IEP = Individualized Education Plan
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Cannabinoid hyperemesis syndrome (CHS) is a challenging clinical disorder. CHS patients frequently present to the emergency department and may require treatment for intractable emesis, dehydration, ...and electrolyte abnormalities. Thought to be a variant of cyclic vomiting syndrome, CHS has become more prevalent with increasing cannabis potency and use, as enabled by various states having legalized the recreational use of cannabis.
This aim of this review is to investigate the pathophysiology of CHS and evaluate the published literature on pharmacologic treatment in the emergency department. This information may be helpful in providing evidence-based, efficacious antiemetic treatment grounded in knowledge of antiemetic medications’ mechanisms of action, potentially precluding unnecessary tests, and reducing duration of stay.
The endocannabinoid system is a complex and important regulator of stress response and allostasis, and it is occasionally overwhelmed from excessive cannabis use. Acute episodes of CHS may be precipitated by stress or fasting in chronic cannabis users who may have pre-existing abnormal hypothalamic–pituitary–adrenal axis feedback and sympathetic nervous system response. The reasons for this may lie in the physiology of the endocannabinoid system, the pathophysiology of CHS, and the pharmacologic properties of specific classes of antiemetics and sedatives. Treatment failure with standard antiemetics is common, necessitating the use of mechanistically logical sedating agents such as benzodiazepines and antipsychotics.
Despite the increasing prevalence of CHS, there is a limited body of high-quality research. Benzodiazepines and antipsychotics represent logical choices for treatment of CHS because of their powerful sedating effects. Topical capsaicin holds promise based on a totally different pharmacologic mechanism. Discontinuation of cannabis use is the only assured cure for CHS.
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Contaminated or infected bone defects remain serious challenges in clinical trauma and orthopaedics, and a bone substitute with both osteoconductivity and antibacterial properties ...represents an improvement for treatment strategy. In this study, quaternized chitosan (hydroxypropyltrimethyl ammonium chloride chitosan, HACC) was grafted to 3D-printed scaffolds composed of polylactide-co-glycolide (PLGA) and hydroxyapatite (HA), in order to design bone engineering scaffolds endowed with antibacterial and osteoconductive properties. We found that both the PLGA/HA/HACC and PLGA/HACC composite scaffolds decreased bacterial adhesion and biofilm formation under in vitro and in vivo conditions. Additionally, ATP leakage assay indicated that immobilizing HACC on the scaffolds could effectively disrupt microbial membranes. Using human bone marrow-derived mesenchymal stem cells (hBMSCs), we demonstrated that HA incorporated scaffolds, including PLGA/HA and PLGA/HA/HACC, favoured cell attachment, proliferation, spreading and osteogenic differentiation compared to HA-free PLGA or PLGA/HACC scaffolds. Finally, an in vivo biocompatibility assay conducted on rats, showed that HA incorporated scaffolds (including PLGA/HA and PLGA/HA/HACC scaffolds) exhibited good neovascularization and tissue integration. Taken together, our findings support the approach for developing porous PLGA/HA/HACC composite scaffold with potential clinical application in the treatment of infected bone.
Although plenty of conductive scaffold biomaterials have been exploited to improve bone regeneration under infection, potential tissue toxicity under high concentration and antibiotic-resistance are their main deficiencies. This study indicated that HACC-grafted PLGA/HA composite scaffold prepared using an innovative 3D-printing technique and covalent grafting strategy showed significantly enhanced antibacterial activities, especially against the antibiotic-resistant strains, together with good osteogenic activity and biocompatibility. Therefore, it provides an effective porous composite scaffold to combat the infected bone defect in clinic with decreased risks of bacterial resistance and open a feasible strategy for the modification of scaffold interfaces involved in the bone regeneration and anti-infection.
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Despite the importance of early diagnosis and treatment of HIV, only a small fraction of HIV-exposed infants in low- and middle-income countries are tested for the disease. The gold standard for ...early infant diagnosis, DNA PCR, requires resources that are unavailable in poor settings, and no point-of-care HIV DNA test is currently available. We have developed a device constructed of layers of paper, glass fiber, and plastic that is capable of performing isothermal, enzymatic amplification of HIV DNA. The device is inexpensive, small, light-weight, and easy to assemble. The device stores lyophilized enzymes, facilitates mixing of reaction components, and supports recombinase polymerase amplification in five steps of operation. Using commercially available lateral flow strips as a detection method, we demonstrate the ability of our device to amplify 10 copies of HIV DNA to detectable levels in 15 min. Our results suggest that our device, which is designed to be used after DNA extraction from dried-blood spots, may serve in conjunction with lateral flow strips as part of a point-of-care HIV DNA test to be used in low resource settings.
We have developed a device made of plastic and paper that performs recombinase polymerase amplification of HIV DNA with a limit of detection of 10 DNA copies in 15 min.
In 2011, Lake Erie experienced the largest harmful algal bloom in its recorded history, with a peak intensity over three times greater than any previously observed bloom. Here we show that long-term ...trends in agricultural practices are consistent with increasing phosphorus loading to the western basin of the lake, and that these trends, coupled with meteorological conditions in spring 2011, produced record-breaking nutrient loads. An extended period of weak lake circulation then led to abnormally long residence times that incubated the bloom, and warm and quiescent conditions after bloom onset allowed algae to remain near the top of the water column and prevented flushing of nutrients from the system. We further find that all of these factors are consistent with expected future conditions. If a scientifically guided management plan to mitigate these impacts is not implemented, we can therefore expect this bloom to be a harbinger of future blooms in Lake Erie.
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Estimated trends in relative stock abundance are a primary input to fish stock assessments. Accurate and precise estimates are essential for successful conservation and management. Scientifically ...designed data collection ensures that estimates of relative abundance are unbiased. However, the statistical efficiency of a design-based estimator may be low under certain circumstances. We apply a recently developed spatiotemporal model that incorporates habitat variables to estimate a model-based abundance index for northern shrimp (Pandalus borealis) in the Gulf of Maine. We contrast this spatiotemporal index with a classical design-based index and evaluate the impacts of differences between the two abundance indices on the stock assessment. We show that using the spatiotemporal index in the assessment model greatly alters the estimates of recruitment and spawning stock biomass and the determination of stock status. Also, incorporating the spatiotemporal index leads to less retrospective bias and outperforms the model with design-based index in terms of predictive performance through a retrospective cross-validation test. Our results suggest that temporal variability of population abundance could be exaggerated by the design-based estimator, and such imprecision may greatly affect the performance of a stock assessment and subsequent development of management decisions.
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Breeding for high water-use efficiency Condon, A.G; Richards, R.A; Rebetzke, G.J ...
Journal of experimental botany,
11/2004, Volume:
55, Issue:
407
Journal Article, Conference Proceeding
Peer reviewed
Open access
There is a pressing need to improve the water-use efficiency of rain-fed and irrigated crop production. Breeding crop varieties with higher water-use efficiency is seen as providing part of the ...solution. Three key processes can be exploited in breeding for high water-use efficiency: (i) moving more of the available water through the crop rather than it being wasted as evaporation from the soil surface or drainage beyond the root zone or being left behind in the root zone at harvest; (ii) acquiring more carbon (biomass) in exchange for the water transpired by the crop, i.e. improving crop transpiration efficiency; (iii) partitioning more of the achieved biomass into the harvested product. The relative importance of any one of these processes will vary depending on how water availability varies during the crop cycle. However, these three processes are not independent. Targeting specific traits to improve one process may have detrimental effects on the other two, but there may also be positive interactions. Progress in breeding for improved water-use efficiency of rain-fed wheat is reviewed to illustrate the nature of some of these interactions and to highlight opportunities that may be exploited in other crops as well as potential pitfalls. For C3 species, measuring carbon isotope discrimination provides a powerful means of improving water-use efficiency of leaf gas exchange, but experience has shown that improvements in leaf-level water-use efficiency may not always translate into higher crop water-use efficiency or yield. In fact, the reverse has frequently been observed. Reasons for this are explored in some detail. Crop simulation modelling can be used to assess the likely impact on water-use efficiency and yield of changing the expression of traits of interest. Results of such simulations indicate that greater progress may be achieved by pyramiding traits so that potential negative effects of individual traits are neutralized. DNA-based selection techniques may assist in such a strategy.
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