Transform-Limited-Pulse Representation of Excitation with Natural Incoherent Light

We study the natural excitation of molecular systems, applicable to, for example, photosynthetic light-harvesting complexes, by natural incoherent light. In contrast with the conventional classical models, we show that the light need not have random character to properly represent the resultant linear excitation. Rather, thermal excitation can be interpreted as a collection of individual events resulting from the system's interaction with individual, deterministic pulsed realizations that constitute the field. The derived expressions for the individual field realizations and excitation events allow for a wave function formalism, and therefore constitute a useful calculational tool to study dynamics following thermal-light excitation. Further, they provide a route to the experimental determination of natural incoherent excitation using pulsed laser techniques.Comment: 5 pages, 3 figures, 1 page supplementary information. Comments welcom

Prolonging disuse in aged mice amplifies cortical but not trabecular bones’ response to mechanical loading

Objective: Short-term neurectomy-induced disuse (SN) has been shown to restore load responses in aged mice. We examined whether this restoration was further enhanced in both cortical and trabecular bone by simply extending the SN. Methods: Following load: strain calibration, tibiae in female C57BL/J6 mice at 8, 14 and 20 weeks and 18 months (n=8/group) were loaded and bone changes measured. Effects of long-term SN examined in twenty-six 18 months-old mice, neurectomised for 5 or 100 days with/without subsequent loading. Cortical and trabecular responses were measured histomorphometrically or by micro-computed tomography. Results: Loading increased new cortical bone formation, elevating cross-sectional area in 8, 14 and 20 week-old (p <0.05), but not 18 month-old aged mice. Histomorphometry showed that short-term SN reinstated load-responses in aged mice, with significant 33% and 117% increases in bone accrual at 47% and 37%, but not 27% of tibia length. Cortical responses to loading was heightened and widespread, now evident at all locations, following prolonged SN (108, 167 and 98% at 47, 37 and 27% of tibial length, respectively). In contrast, loading failed to modify trabecular bone mass or architecture. Conclusions: Mechanoadaptation become deficient with ageing and prolonging disuse amplifies this response in cortical but not trabecular bone

Sclerostin does not play a major role in the pathogenesis of skeletal complications in type 2 diabetes mellitus

In contrast to previously reported elevations in serum sclerostin levels in diabetic patients, the present study shows that the impaired bone microarchitecture and cellular turnover associated with type 2 diabetes mellitus (T2DM)-like conditions in ZDF rats are not correlated with changes in serum and bone sclerostin expression. INTRODUCTION: T2DM is associated with impaired skeletal structure and a higher prevalence of bone fractures. Sclerostin, a negative regulator of bone formation, is elevated in serum of diabetic patients. We aimed to relate changes in bone architecture and cellular activities to sclerostin production in the Zucker diabetic fatty (ZDF) rat. METHODS: Bone density and architecture were measured by micro-CT and bone remodelling by histomorphometry in tibiae and femurs of 14-week-old male ZDF rats and lean Zucker controls (n = 6/group). RESULTS: ZDF rats showed lower trabecular bone mineral density and bone mass compared to controls, due to decreases in bone volume and thickness, along with impaired bone connectivity and cortical bone geometry. Bone remodelling was impaired in diabetic rats, demonstrated by decreased bone formation rate and increased percentage of tartrate-resistant acid phosphatase-positive osteoclastic surfaces. Serum sclerostin levels (ELISA) were higher in ZDF compared to lean rats at 9 weeks (+40 %, p < 0.01), but this difference disappeared as their glucose control deteriorated and by week 14, ZDF rats had lower sclerostin levels than control rats (-44 %, p < 0.0001). Bone sclerostin mRNA (qPCR) and protein (immunohistochemistry) were similar in ZDF, and lean rats at 14 weeks and genotype did not affect the number of empty osteocytic lacunae in cortical and trabecular bone. CONCLUSION: T2DM results in impaired skeletal architecture through altered remodelling pathways, but despite altered serum levels, it does not appear that sclerostin contributes to the deleterious effect of T2DM in rat bone

Chronic administration of Glucagon-like peptide-1 receptor agonists improves trabecular bone mass and architecture in ovariectomised mice

Some anti-diabetic therapies can have adverse effects on bone health and increase fracture risk. In this study, we tested the skeletal effects of chronic administration of two Glucagon-like peptide-1 receptor agonists (GLP-1RA), increasingly used for type 2 diabetes treatment, in a model of osteoporosis associated bone loss and examined the expression and activation of GLP-1R in bone cells. Mice were ovariectomised (OVX) to induce bone loss and four weeks later they were treated with Liraglutide (LIR) 0.3 mg/kg/day, Exenatide (Ex-4) 10 μg/kg/day or saline for four weeks. Mice were injected with calcein and alizarin red prior to euthanasia, to label bone-mineralising surfaces. Tibial micro-architecture was determined by micro-CT and bone formation and resorption parameters measured by histomorphometric analysis. Serum was collected to measure calcitonin and sclerostin levels, inhibitors of bone resorption and formation, respectively. GLP-1R mRNA and protein expression were evaluated in the bone, bone marrow and bone cells using RT-PCR and immunohistochemistry. Primary osteoclasts and osteoblasts were cultured to evaluate the effect of GLP-1RA on bone resorption and formation in vitro. GLP-1RA significantly increased trabecular bone mass, connectivity and structure parameters but had no effect on cortical bone. There was no effect of GLP-1RA on bone formation in vivo but an increase in osteoclast number and osteoclast surfaces was observed with Ex-4. GLP-1R was expressed in bone marrow cells, primary osteoclasts and osteoblasts and in late osteocytic cell line. Both Ex-4 and LIR stimulated osteoclastic differentiation in vitro but slightly reduced the area resorbed per osteoclast. They had no effect on bone nodule formation in vitro. Serum calcitonin levels were increased and sclerostin levels decreased by Ex-4 but not by LIR. Thus, GLP-1RA can have beneficial effects on bone and the expression of GLP-1R in bone cells may imply that these effects are exerted directly on the tissue

Economic impact of frost in the Australian wheatbelt

[Introduction]: Extreme temperatures can cause severe reductions in wheat yield, including in Australia where temperatures are highly variable within and across growing seasons. A single post head-emergence frost (PHEF) event has the potential to devastate individual wheat crop by damaging stems and killing whole head. Management of crop phenology to avoid PHEF is very important in many parts of the world where frost risk is high. Breeding for improved reproductive frost tolerance could allow greater yield and economic benefits to be achieved, by (i) reducing direct frost damage and (ii) allowing earlier sowing to reduce risks of late-season drought and/or heat stresses (Fig. 1). This study aims to provides insights into the frost impact and economic benefits of different improved frost tolerance levels across the Australian wheatbelt

Non-invasive mechanical joint loading as an alternative model for osteoarthritic pain

OBJECTIVE: Mechanisms responsible for osteoarthritic pain remain poorly understood and current analgesic therapies are often insufficient. We have characterized and pharmacologically tested the pain phenotype of a non-invasive mechanical joint loading (MJL) model of osteoarthritis thus providing an alternative murine model for osteoarthritic pain. METHODS: The right knees of male mice (12-week-old, C57BL/6) were loaded at 9N or 11N (40 cycles, three times/week for two weeks). Behavioural measurements of limb disuse, mechanical and thermal hypersensitivity were acquired before MJL and monitored for six weeks post-loading. The severity of articular cartilage lesions was determined post-mortem with the OARSI grading scheme. Furthermore, 9N-loaded mice were treated for four weeks with diclofenac (10mg/kg), gabapentin (100mg/kg) or anti-Nerve Growth Factor (3mg/kg). RESULTS: Mechanical hypersensitivity and weight-bearing worsened significantly in 9N- and 11N-loaded mice two weeks post-loading compared to baseline values and non-loaded controls. Maximum OA scores of ipsilateral knees confirmed increased cartilage lesions in 9N- (2.8±0.2) and 11N-loaded (5.3±0.3) mice compared to non-loaded controls (1.0±0.0). Gabapentin and diclofenac restored pain behaviours to baseline values after two weeks of daily treatment, with gabapentin being more effective than diclofenac. A single injection of anti-NGF alleviated nociception two days after treatment and remained effective for two weeks with a second dose inducing stronger and more prolonged analgesia. CONCLUSION: Our results show that MJL induces OA lesions and a robust pain phenotype that can be reversed using analgesics known to alleviate OA pain in patients. This establishes the use of MJL as an alternative model for osteoarthritic pain

Unambiguous Formulation for Heat and Work in Arbitrary Quantum Evolution

Given a trajectory described by a time-dependent density matrix of an arbitrary open quantum system, we formulate a general and unambiguous method to separate the internal energy change of the system into one part which entails pure entropy change and another part with no entropy change. We identify these parts as heat and work, respectively. Using a universal dynamical equation for a trajectory, we specify a dissipative part of the energy change of work type, which contains a counterdibatic drive term naturally arising from the dynamics along the given trajectory. This enables us to attribute heat and work, respectively, to dissipative and coherent parts of the universal dynamical equation. We illustrate our formalism with an example.Comment: 6+2 page