The Stability Principle and global weak solutions of the free surface semi-geostrophic equations in geostrophic coordinates.

The semi-geostrophic equations are used widely in the modelling of large-scale atmospheric flows. In this note, we prove the global existence of weak solutions of the incompressible semi-geostrophic equations, in geostrophic coordinates, in a three-dimensional domain with a free upper boundary. The proof, based on an energy minimization argument originally inspired by the Stability Principle as studied by Cullen, Purser and others, uses optimal transport techniques as well as the analysis of Hamiltonian ODEs in spaces of probability measures as studied by Ambrosio and Gangbo. We also give a general formulation of the Stability Principle in a rigorous mathematical framework.

On the relationship between stratospheric structure and tropospheric blocking patterns.

Prediction of long-lived anomalous behaviour in the atmosphere is fundamental to extended range and seasonal forecasting. Prediction of changes in the climatology of such anomalous behaviour is also fundamental to regional climate modelling. Anomalous atmospheric behaviour is often related to mid-latitude tropospheric 'blocking' patterns, where the normal westerly flow associated with the temperature difference between the Poles and the Equator is disrupted. Following recent work on stratosphere-troposphere coupling, we show that the vertical structure of the atmosphere can strongly influence the climatology of tropospheric blocking. We invoke dynamical theory to argue that the development and decay of anomalous circulations is most efficient for a preferred aspect ratio of the flow, implying that the development of large-scale anomalies requires a large vertical scale. Evidence for this link comes from the observed evolution of the geopotential height. In particular, we find that the development of the large-scale tropospheric anomalies associated with blocking requires a vertical scale extending well into the stratosphere. This process is inhibited during periods of high stratospheric activity, when the vertical scale of tropospheric developments is restricted, leading to the persistence of large horizontal scales.

Aberrant expression of CD19 in AML with t(8;21) involves a poised chromatin structure and PAX5.

Correct hematopoietic differentiation requires the tightly regulated execution of lineage-specific and stage-restricted gene expression programs. This process is disturbed in hematological malignancies that typically show incomplete differentiation but often also display a mixed lineage phenotype. Co-expression of lymphoid and myeloid molecules is a well-known feature of acute myeloblastic leukemia (AML) with t(8;21). These cells consistently express the B-cell-specific transcription factor PAX5, and the B-cell-specific cell surface protein CD19. However, the functional consequences of PAX5 expression are unknown. To address this question, we studied the chromatin features of CD19, which is a direct target of PAX5 in cells with and without the t(8;21) chromosomal translocation. We show that CD19 chromatin exists in a poised configuration in myeloid progenitors and that this poised chromatin structure facilitates PAX5-dependent CD19 activation. Our results also show a positive correlation between PAX5 and CD19 expression in t(8;21)-positive AML cells and demonstrate that PAX5 binds to the promoter and enhancer of CD19 gene and remodels chromatin structure at the promoter. This study shows that expression of PAX5 in leukemic cells has functional consequences and points to an important role of a progenitor-specific chromatin configuration in myeloid leukemia.

Large eddy simulation of the atmosphere on various scales.

Numerical simulations of the atmosphere are routinely carried out on various scales for purposes ranging from weather forecasts for local areas a few hours ahead to forecasts of climate change over periods of hundreds of years. Almost without exception, these forecasts are made with space/time-averaged versions of the governing Navier-Stokes equations and laws of thermodynamics, together with additional terms representing internal and boundary forcing. The calculations are a form of large eddy modelling, because the subgrid-scale processes have to be modelled. In the global atmospheric models used for long-term predictions, the primary method is implicit large eddy modelling, using discretization to perform the averaging, supplemented by specialized subgrid models, where there is organized small-scale activity, such as in the lower boundary layer and near active convection. Smaller scale models used for local or short-range forecasts can use a much smaller averaging scale. This allows some of the specialized subgrid models to be dropped in favour of direct simulations. In research mode, the same models can be run as a conventional large eddy simulation only a few orders of magnitude away from a direct simulation. These simulations can then be used in the development of the subgrid models for coarser resolution models.

Hypoglycaemia in an adult male: a surprising finding in pursuit of insulinoma.

A 50-year-old man who had suffered several episodes of early morning sweats and tremors was diagnosed as having hyperinsulinaemic hypoglycaemia. Cross-sectional imaging and endoscopic ultrasound revealed no pancreatic lesion. A selective intra-arterial calcium infusion study showed a two-fold increase of insulin secretion after infusion of the splenic and superior mesenteric arteries. Laparotomy was performed, no lesion was identified after full mobilisation of the pancreas, and nothing was evident with intra-operative ultrasound. A distal pancreatectomy was performed. Microscopically, the pancreas exhibited diffuse islet cell hyperplasia consistent with nesidioblastosis. The patient remains euglycaemic eight months post-operatively.

Neurocysticercosis: a rare cause of seizure.

Neurocysticercosis is endemic in certain parts of the world, is rare in Europe and has never previously been described in the Irish healthcare setting. We report the case of a healthy male, originally from Guatemala, who presented to our hospital with a generalized tonic-clonic seizure presumed secondary to neurocysticercosis.

The cost of managing diabetic foot ulceration in an Irish hospital.

BACKGROUND: Little is known about the economic impact of diabetic foot ulceration in the Irish healthcare setting. AIM: Audit of diabetic foot ulcer admissions in St James's Hospital between April 2001 and March 2002. METHODS: Hospital charts were reviewed and costs were calculated on the length of patients' hospital stay and the cost of individual investigations performed. RESULTS: Thirty patients were admitted with diabetic foot ulceration as the primary complaint. Amputation was performed in eight patients, two patients with a non-healing ulcer died. The average duration of each hospital admission was 20.3+/-30.7 days. Net in-hospital expenditure was 704,689, an average of 23,489.63 per hospital admission. CONCLUSIONS: The management of diabetic foot ulceration has a significant economic impact on the Irish healthcare budget. Treatment should therefore be focused on primary prevention through specialised foot clinics and a multidisciplinary team approach to reduce this economic burden.

Muscle fibre breakdown in venom-induced muscle degeneration.

We studied the early stages of the degeneration of skeletal muscles using the venom of Notechis scutatus as the myotoxic agent. The venom was used at a dose equivalent to the LD50 in the mouse. There was no mortality amongst the rats. Electron microscopy was used to show the progressive hypercontraction of sarcomeres and the loss of alignment of myofibrils in individual muscle fibres. Between areas of hypercontraction sarcomeres were torn, shedding loosened myofilaments into the cytosol. Western blotting and Coomassie staining were used to compare the respective rates of loss of desmin, titin, actin, myosin and dystrophin. We showed that desmin and titin were the first proteins to be degraded with a time to 50% loss of approximately 1 h and 3 h, respectively. The loss of major contractile proteins, myosin and actin, was rather slower. The loss of dystrophin was also slower than the loss of desmin and titin. Early damage to the plasma membrane of the muscle fibre caused the cells to depolarize, probably promoting the hypercontraction of the sarcomeres, but actual loss of membrane was incomplete even at 24 h. We suggest that the early degradation of desmin and titin was responsible for the disaggregation of the sarcomeres; the liberated contractile proteins myosin and actin were shed into the cytosol, where they were degraded. Phagocytic cells that had invaded the degenerating muscle fibres were primarily involved in the clearance of damaged mitochondria.

The Healthline pilot: call centre triage in New Zealand.

AIMS: To acquaint New Zealand doctorsabout nurse telephone triage using call centre technology, and to report the activities of Healthline, a pilot call centre telephone triage project in New Zealand. METHODS: Data for the second quarter of Healthline's activities are reported. RESULTS: Healthline received about 100 calls a day, mostly after hours, and typically from symptomatic patients seeking health advice. Women and children were the most frequent users; Maori used the service in proportion to their representation in the population. Common symptoms were to those encountered in primary medical care. Requests for specific health information were usually about the health issues of the day Callers were more often directed to contact general practitioners than any other careproviders. The triage advice provided was often different from the caller's original intention about the timing and and ofcare they would have sought. Satisfaction with the service among Maori and non-Maori callers was high. CONCLUSIONS: Healthline is providing a safe and acceptable primary care triage service in its pilot regions and appears to be meeting its first objective of providing timely and appropriate access to health advice and services.

Calcium currents and transients in co-cultured contracting normal and Duchenne muscular dystrophy human myotubes.

1. The goal of the present study was to investigate differences in calcium movements between normal and Duchenne muscular dystrophy (DMD) human contracting myotubes co-cultured with explants of rat spinal cord with attached dorsal root ganglia. Membrane potential, variations of intracellular calcium concentration and T- and L-type calcium currents were recorded. Further, a descriptive and quantitative study by electron microscopy of the ultrastructure of the co-cultures was carried out. 2. The resting membrane potential was slightly less negative in DMD (-61.4 +/- 1.1 mV) than in normal myotubes (-65.5 +/- 0.9 mV). Both types of myotube displayed spontaneous action potentials (mean firing frequency, 0.42 and 0.16 Hz, respectively), which triggered spontaneous calcium transients measured with Indo-1. 3. The time integral under the spontaneous Ca(2+) transients was significantly greater in DMD myotubes (97 +/- 8 nM s) than in normal myotubes (67 +/- 13 nM s). 4. The L- and T-type current densities estimated from patch-clamp recordings were smaller in DMD cells (2.0 +/- 0.5 and 0.90 +/- 0.19 pA pF(-1), respectively) than in normal cells (3.9 +/- 0.7 and 1.39 +/- 0.30 pA pF(-1), respectively). 5. The voltage-dependent inactivation relationships revealed a shift in the conditioning potential at which inactivation is half-maximal (V(h,0.5)) of the T- and L-type currents towards less negative potentials, from -72.1 +/- 0.7 and -53.7 +/- 1.5 mV in normal cells to -61.9 +/- 1.4 and -29.2 +/- 1.4 mV in DMD cells, respectively. 6. Both descriptive and quantitative studies by electron microscopy suggested a more advanced development of DMD myotubes as compared to normal ones. This conclusion was supported by the significantly larger capacitance of the DMD myotubes (408 +/- 45 pF) than of the normal myotubes (299 +/- 34 pF) of the same apparent size. 7. Taken together, these results show that differences in T- and L-type calcium currents between normal and DMD myotubes cannot simply explain all observed alterations in calcium homeostasis in DMD myotubes, thus suggesting that other transmembrane calcium transport mechanisms must also be altered in DMD myotubes compared with normal myotubes.

Urocortin, corticotropin releasing factor-2 receptors and energy balance.

Although there is considerable information regarding the role of brain CRF in energy balance, relatively little is known about the role of urocortin (UCN), which is an equally potent anorexic agent. Therefore, the effects of intracerebroventricular (icv) administration of UCN (0.01-1 nmol/day) on food intake and body weight were assessed over a period of 13 days and compared with data from CRF-infused counterparts. Although both peptides dose dependently reduced food intake and weight gain, the effects of CRF were much greater in magnitude than those of UCN, particularly on body weight. Pair-feeding studies suggested that, while the effects of CRF on body weight could not be completely explained by appetite suppression, the effects of UCN appeared to be due to its initial impact on food intake. CRF increased brown adipose fat pad and adrenal weights, whereas it reduced thymus and spleen weights. CRF also increased serum corticosterone, triglyceride, FFA, and cholesterol levels, whereas it reduced glucose. UCN did not produce any consistent changes in any of these indices of sympathetic nervous system activation. Concurrent administration of the CRF(2)-selective antagonist, antisauvagine-30 (ASV-30) (30 nmol/day) completely reversed or attenuated the effects of UCN and CRF (1 nmol/day) on food intake and body weight. ASV-30 did not significantly attenuate any of the above CRF-induced changes in tissue weights or serum chemistry. These data suggest that the central CRF(2) receptor may primarily mediate the anorexic, but not the metabolic effects of CRF.

Growth factor supplemented matrigel improves ectopic skeletal muscle formation--a cell therapy approach.

Following damage to skeletal muscle, satellite cells become activated, migrate towards the injured area, proliferate, and fuse with each other to form myotubes which finally mature into myofibers. We tested a new approach to muscle regeneration by incorporating myoblasts, with or without the exogenous growth factors bFGF or HGF, into three-dimensional gels of reconstituted basement membrane (matrigel). In vitro, bFGF and HGF induced C2C12 myoblast proliferation and migration and were synergistic when used together. In vivo, C2C12 or primary i28 myoblasts were injected subcutaneously together with matrigel and growth factors in the flanks of nude mice. The inclusion of either bFGF or HGF increased the vascularization of the gels. Gels supplemented with bFGF showed myogenesis accompanied by massive mesenchymal cell recruitment and poor organization of the fascicles. Samples containing HGF showed delayed differentiation with respect to controls or bFGF, with increased myoblast proliferation and a significantly higher numbers of cells in myotubes at later time points. HGF samples showed limited mesenchymal cell infiltration and relatively good organization of fascicles. The use of both bFGF and HGF together showed increased numbers of nuclei in myotubes, but with bFGF-mediated fibroblast recruitment dominating. These studies suggest that an appropriate combination of basement membrane components and growth factors could represent a possible approach to enhance survival dispersion, proliferation, and differentiation of myogenic cells during muscle regeneration and/or myoblast transplantation. This model will help develop cell therapy of muscle diseases and open the future to gene therapy approaches.

A unique metabolic syndrome causes obesity in the melanocortin-3 receptor-deficient mouse.

The central melanocortin system is critical for the long term regulation of energy homeostasis. Null mutations of the melanocortin-4 receptor (MC4-R) are associated with hyperphagia, obesity, and accelerated longitudinal growth in mice and humans. However, little is known about the function of another central melanocortin receptor, the MC3-R. To assess the role of the MC3-R in energy homeostasis, the majority of the mc3r coding sequence was deleted from the mouse genome. In contrast to the MC4-R knockout, which exhibits increased food intake, increased somatic growth, and defects in metabolism, mc3r-/- mice exhibit an exclusively metabolic syndrome. Homozygous null mc3r mice, while not significantly overweight, exhibit an approximately 50% to 60% increase in adipose mass. Mc3r-/- mice also exhibit an unusual increase in respiratory quotient when transferred onto high fat chow, suggesting a reduced ratio of fat/carbohydrate oxidation. Furthermore, male mc3r-/- mice also exhibit an approximately 50% reduction in locomotory behavior on the running wheel, suggesting reduced energy expenditure.

Distinct patterns of dystrophin organization in myocyte sarcolemma and transverse tubules of normal and diseased human myocardium.

BACKGROUND: Genetic mutations of dystrophin and associated glycoproteins underlie cell degeneration in several inherited cardiomyopathies, although the precise physiological role of these proteins remains under discussion. We studied the distribution of dystrophin in relation to the force-transducing vinculin-rich costameres in left ventricular cardiomyocytes from normal and failing human hearts to further elucidate the function of this protein complex. METHODS AND RESULTS: Single- and double-label immunoconfocal microscopy and parallel high-resolution immunogold fracture-label electron microscopy were used to localize dystrophin and vinculin in human left ventricular myocytes from normal (n=6) and failing hearts (idiopathic dilated cardiomyopathy, n=7, or ischemic heart disease, n=5). In control cardiomyocytes, dystrophin had a continuous distribution at the peripheral sarcolemma, with concentrated bands corresponding to the vinculin-rich costameres. Intracellular labeling extended along transverse (T) tubule membranes. Fracture-label confirmed this distribution, showing significantly greater label on plasma membrane fractures overlying I-bands (I-band 4.1+/-0.3 gold particles/micrometer A-band 3.3+/-0.2 gold particles/micrometer mean+/-SE, P=0.02). Hypertrophied myocytes from failing hearts showed maintenance of this surface distribution except in degenerating cells; there was a clear increase in intracellular dystrophin label reflecting T-tubule hypertrophy. CONCLUSIONS: Dystrophin partially colocalizes with costameric vinculin in normal and hypertrophied myocytes, a distribution lost in degenerating cells. This suggests a primarily mechanical role for dystrophin in maintenance of cell membrane integrity in normal and hypertrophied myocytes. The presence of dystrophin in the cardiac T-tubule membrane, in contrast to its known absence in skeletal muscle T-tubules, implies additional roles for dystrophin in membrane domain organization.

Role of corticotropin-releasing factor (CRF) receptors in the anorexic syndrome induced by CRF.

Genetic manipulations of corticotropin-releasing factor (CRF)(1) and CRF(2) receptors have resulted in data suggesting that the CRF(2) receptor could mediate the effects of CRF on appetite or satiety. We have attempted to obtain pharmacological evidence for this hypothesis by comparing the ability of a high-affinity peptide, mixed CRF antagonist [cyclo 30-33,f12,L18,21E30, A32,K33]sucker fish urotensin (12-41)NH(2) [cUTSN (12-41)] with a small-molecule CRF(1)-selective antagonist, NBI-27914, and a CRF(2)-selective peptide antagonist, antisauvagine-30, to attenuate the anorexic effects of CRF. We also monitored other behaviors that accompanied CRF-induced anorexia. CRF-induced anorexia was significantly correlated with a reduction in locomotor activity and an increase in freezing behavior and piloerection. cUTSN (12-41) and antisauvagine-30 significantly attenuated the effects of CRF (0.04 nmol) on food intake along with the behavioral syndrome that accompanied anorexia. In contrast, NBI-27914 did not attenuate either of the above-mentioned CRF-induced phenomena when given centrally at doses ranging from 0.13 to 10 nmol/2.5 microl or when given orally at 20 to 40 mg/kg. Although these data support the hypothesis that the CRF(2) receptor mediates the appetite suppression induced by CRF, they also suggest that the CRF(2) receptor could mediate the stress-like behaviors that accompany CRF-induced appetite suppression.

Plasma membrane cytoskeleton of muscle: a fine structural analysis.

The discovery of dystrophin and its definition as the causative molecule in Duchenne Muscular Dystrophy has led to a renewed interest in the molecular structure of the muscle fiber plasma membrane and its association with the extracellular basal lamina. The original identification of dystrophin gave credence to the possibility that the plasma membrane of the muscle fiber may be highly organized and involved in maintaining appropriate homeostasis in this actively contracting cellular system. In this review, we examine the currently known members of the muscle fiber plasma membrane cytoskeleton and the interactions that occur between the different members of this complex using histological, electron microscopic, and confocal methods. From our studies and others cited in this review, it is clear that the dystrophin cytoskeletal complex is not completely understood and component molecules continue to be discovered. Perhaps equally importantly, currently defined molecules (such as alpha-actinin or neuronal nitric oxide synthase) are being recognized as being specifically associated with the complex. What is striking from all of the studies, to date, is that while we are able to identify members of the dystrophin cytoskeletal complex and while we are able to associate mutations of individual molecules with disease(s), we are still unable to truly define the roles of each of the molecules in maintaining the normal physiology of the muscle fiber.

Systemically and topically administered leptin both accelerate wound healing in diabetic ob/ob mice.

Leptin is a 16 kD protein that is produced by adipocytes and induces weight loss in both normal and genetically obese ob/ob mice. ob/ob mice are obese, have multiple metabolic abnormalities, and exhibit impaired wound healing. Exogenous administration of leptin to these animals induces weight loss and corrects their metabolic defects. Leptin's effect on wound repair, however, has not been studied. Systemic administration of leptin at doses ranging from 0.1 to 10 mg/kg/day induced a highly significant acceleration in wound repair in ob/ob mice (p<0.0001), but not in db/db mice, indicating that leptin's effects on wound repair were mediated through the leptin receptor. We then investigated the possibility that leptin was acting directly at the wound site by administering leptin topically, and found that topical leptin also induced a dose dependent acceleration in wound repair (p<0.0001). In addition, we found that all forms of leptin receptor, including the signal transducing long form, were present in skin by RNase protection assay, and that leptin receptor localized to subcutaneous vessels of wounded skin by in situ hybridization. Finally, we investigated the possibility that leptin stimulated angiogenesis in wounds by analyzing wound hemoglobin and wound vessel density. Neither systemic nor topical leptin induced any significant changes in either parameter, suggesting that leptin accelerates wound repair by a mechanism other than stimulation of angiogenesis. In summary, both systemic and topical leptin accelerate wound repair in diabetic ob/ob mice, possibly via the direct interaction of leptin with its receptors in wounded skin, but do not appear to significantly stimulate wound angiogenesis. Further studies to better elucidate the mechanisms of leptin's effects on wound repair are warranted.

Compliance by collaboration: effectively addressing problems of treatment adherence.

BACKGROUND: Poor treatment compliance is a major problem in general practice. GPs need to develop strategies to identify and manage this problem as part of their clinical skills. OBJECTIVES: This paper provides an overview of the frequency and underlying causes of poor treatment compliance, highlighting strategies that can be utilised for its enhancement and promoting an understanding of the cycle of motivational change as it may apply to treatment compliance. DISCUSSION: General practitioners should consider the use of multiple strategies to manage adherence problems. General practitioners should develop an individualised understanding of why a patient does not adhere to appropriate treatment.

Calcium homeostasis and ultrastructural studies in a patient with limb girdle muscular dystrophy type 2C.

There is increasing evidence that gamma-sarcoglycan is absent and other sarcoglycans are reduced in patients with the limb-girdle muscular dystrophy type 2C (LGMD2C) form of severe childhood autosomal recessive muscular dystrophy. In the present investigation, we combined microspectrofluorimetry and electron microscopy techniques to investigate the physiological function and the ultrastructure of control and LGMD2C myotubes. Results obtained from Ca2+ measurements showed that the resting level of the cytosolic free calcium ([Ca2+ ]i ) in control myotubes was 73+/-3.4 nmol/l (mean+/-se, n=35) and in LGMD2C myotubes was 69+/-4 nmol/l (n=44). Carbachol (CCh, 10 micromol/l ) induced a 335+/-10 nmol/l (n=8) rise in [Ca2+ ]i in control myotubes and 531.9+/-32 nmol/l (n=23) in LGMD2C myotubes. Similarly, elevations of [Ca2+ ]i by 35 mmol/l K+ were 324+/-32 nmol/l (n=8) in control myotubes and 442.8+/-24 nmol/l (n=22) in LGMD2C myotubes. Caffeine (10 mmol/l) activated similar [Ca2+]i peaks in control and LGMD2C myotubes but induced a biphasic response in LGMD2C in four out of 12 myotubes and only a monophasic response in control myotubes. The ultrastructural results showed that the plasma membrane was abnormally indented and convoluted in both the LGMD2C biopsy and the LGMD2C cultured myotubes. It is suggested that the reduction in components of the dystrophin-glycoprotein complex results in the instability and an increase in the surface area of the plasma membrane, which may result in a higher population of Ca2+ channels in the LGMD2C myotubes.