Immunohistochemical and functional studies on calcium-sensing receptors in rat uterine smooth muscle

1. Activation of calcium‐sensing receptors (CaS) leads to relaxation of vascular smooth muscle. However, the role of CaS in uterine smooth muscle is unknown. Therefore the aim of the present study was to investigate the expression and function of CaS in the uterus. 2. The expression of CaS in the oestrogen‐dominated rat uterus was investigated using immunohistochemistry. The effects of putative CaS ligands on oxytocin‐induced contractions of longitudinally orientated uterine strips from oestrogen‐dominated rats were determined at reduced extracellular Ca²⁺concentrations using conventional organ bath techniques. 3. Immunohistochemical evidence showed the presence of CaS in the endometrium and smooth muscle layers of the rat uterus. Oxytocin‐induced contractions were inhibited by cations (Gd³⁺ > Ca²⁺ = Mg²⁺), polyamines (spermine > spermidine) and the positive allosteric modulators cinacalcet and calindol. However (R)‐ and (S)‐cinacalcet were equipotent, indicating a lack of stereoselectivity, and the negative allosteric modulator calhex‐231 also caused dose‐dependent relaxation. In addition, although intermediate‐conductance calcium‐activated potassium channels and cytochrome P450‐dependent signal transduction have been implicated in CaS‐induced relaxation of vascular smooth muscle, neither Tram‐34 nor miconazole (1 μmol/L), which block these pathways, respectively, had any effect on the ability of cinacalcet to inhibit oxytocin‐induced contractions. 4. Calcium‐sensing receptors are expressed in smooth muscle layers of the rat uterus and their ligands produce potent relaxation of longitudinally orientated uterine strips. However, the pharmacological profile of inhibition of contractility by CaS ligands is not consistent with a role for CaS in the regulation of uterine contractility in the rat.     

Ccdc66 null mutation causes retinal degeneration and dysfunction

Retinitis pigmentosa (RP) is a group of human retinal disorders, with more than 100 genes involved in retinal degeneration. Canine and murine models are useful for investigating human RP based on known, naturally occurring mutations. In Schapendoes dogs, for example, a mutation in the CCDC66 gene has been shown to cause autosomal recessively inherited, generalized progressive retinal atrophy (gPRA), the canine counterpart to RP. Here, a novel mouse model with a disrupted Ccdc66 gene was investigated to reveal the function of protein CCDC66 and the pathogenesis of this form of gPRA. Homozygous Ccdc66 mutant mice lack retinal Ccdc66 RNA and protein expression. Light and electron microscopy reveal an initial degeneration of photoreceptors already at 13 days of age, followed by a slow, progressive retinal degeneration over months. Retinal dysfunction causes reduced scotopic a-wave amplitudes, declining from 1 to 7 months of age as well as an early reduction of the photopic b-wave at 1 month, improving slightly at 7 months, as evidenced by electroretinography. In the retina of the wild-type (WT) mouse, protein CCDC66 is present at highest levels after birth, followed by a decline until adulthood, suggesting a crucial role in early development. Protein CCDC66 is expressed predominantly in the developing rod outer segments as confirmed by subcellular analyses. These findings illustrate that the lack of protein CCDC66 causes early, slow progressive rod-cone dysplasia in the novel Ccdc66 mutant mouse model, thus providing a sound foundation for the development of therapeutic strategies.     

Adipose Tissue Plasticity During Catch-Up Fat Driven by Thrifty Metabolism: Relevance for Muscle-Adipose Glucose Redistribution During Catch-Up Growth

OBJECTIVE

Catch-up growth, a risk factor for later type 2 diabetes, is characterized by hyperinsulinemia, accelerated body-fat recovery (catch-up fat), and enhanced glucose utilization in adipose tissue. Our objective was to characterize the determinants of enhanced glucose utilization in adipose tissue during catch-up fat.

RESEARCH DESIGN AND METHODS

White adipose tissue morphometry, lipogenic capacity, fatty acid composition, insulin signaling, in vivo glucose homeostasis, and insulinemic response to glucose were assessed in a rat model of semistarvation-refeeding. This model is characterized by glucose redistribution from skeletal muscle to adipose tissue during catch-up fat that results solely from suppressed thermogenesis (i.e., without hyperphagia).

RESULTS

Adipose tissue recovery during the dynamic phase of catch-up fat is accompanied by increased adipocyte number with smaller diameter, increased expression of genes for adipogenesis and de novo lipogenesis, increased fatty acid synthase activity, increased proportion of saturated fatty acids in triglyceride (storage) fraction but not in phospholipid (membrane) fraction, and no impairment in insulin signaling. Furthermore, it is shown that hyperinsulinemia and enhanced adipose tissue de novo lipogenesis occur concomitantly and are very early events in catch-up fat.

CONCLUSIONS

These findings suggest that increased adipose tissue insulin stimulation and consequential increase in intracellular glucose flux play an important role in initiating catch-up fat. Once activated, the machinery for lipogenesis and adipogenesis contribute to sustain an increased insulin-stimulated glucose flux toward fat storage. Such adipose tissue plasticity could play an active role in the thrifty metabolism that underlies glucose redistribution from skeletal muscle to adipose tissue.The pattern of growth early in life is now recognized to be an important predictor of chronic metabolic diseases. In particular, people who had low birth weight or whose growth faltered during infancy and childhood, but who subsequently showed catch-up growth, had higher propensity for the development of abdominal obesity, type 2 diabetes, and cardiovascular diseases later in life (1–8). The mechanistic basis of the link between catch-up growth and risks for these chronic diseases is poorly understood. There is, however, compelling evidence that mammalian catch-up growth is characterized by a disproportionately higher rate of body fat than lean tissue gain (9) and that an early feature of such “preferential catch-up fat” is concomitant hyperinsulinemia (10).Using a rat model of semistarvation-refeeding (11), in which catch-up fat is studied in the absence of hyperphagia, we previously showed that the hyperinsulinemic state of catch-up fat preceded the development of excess adiposity and could be linked to suppressed thermogenesis, per se, in the absence of hyperphagia (12). Subsequent studies of hyperinsulinemic-euglycemic clamps during catch-up fat showed that in vivo insulin-mediated glucose utilization was diminished in skeletal muscle but enhanced in white adipose tissue (WAT), suggesting that preferential catch-up fat is characterized by glucose redistribution from skeletal muscle to WAT (13). Consistent with this hypothesis are the demonstrations, in this rat model of catch-up fat, of diminished mitochondrial mass and lower insulin receptor substrate (IRS)-1–associated phosphatidylinositol-3-kinase (PI3K) activity in the skeletal muscle (14,15). Furthermore, ex vivo studies in WAT have previously shown that glucose uptake and utilization are enhanced during refeeding after fasting or caloric restriction (16,17).Elucidating the mechanisms that underlie such enhancement in glucose uptake and glucose flux toward lipid synthesis in WAT is therefore of central importance in understanding the mechanisms of glucose redistribution during catch-up fat. In addressing this topic, we have characterized our rat model of catch-up fat for changes in adipose tissue morphometry (adipocyte size and number) and fatty acid composition given their importance as determinants of WAT responsiveness to the action of insulin on glucose utilization. Indeed, it is established that small adipocytes have a greater capacity for insulin-mediated glucose uptake and de novo lipogenesis than larger ones (18–22), while alterations in adipocyte membrane phospholipid composition in favor of a high ratio of polyunsaturated fatty acids (PUFAs) to saturated fatty acids (SFAs) correlates with increased rate of insulin-stimulated glucose transport and glucose flux toward de novo lipogenesis in WAT (23–24). We have therefore investigated here the extent to which differences in adipocyte number and diameter, key gene markers for adipocyte proliferation, as well as the fatty acid composition of phospholipid and triglyceride lipid fractions of WAT, might be involved in the enhanced glucose flux toward lipogenesis. Furthermore, given the importance of insulin signaling in adipocyte growth (25) and in controlling glucose flux toward lipogenesis (26,27), we have also evaluated the in vivo insulinemic response to glucose and investigated proximal insulin signaling in WAT under basal and in vivo insulin-stimulated conditions during catch-up fat.     

Detected peritoneal fluid in small bowel obstruction is associated with the need for surgical intervention

Background

Predicting the clinical course in adhesional small bowel obstruction is difficult. There are no validated clinical or radiologic features that allow early identification of patients likely to require surgical intervention.

Methods

We conducted a retrospective review of 100 patients consecutively admitted to a tertiary level teaching hospital over a 3-year period (2002–2004) who had acute adhesional small bowel obstruction and underwent computed tomography (CT). The primary outcomes that we assessed were conservative management or the need for surgical intervention. We investigated time to physiologic gastrointestinal function recovery as a secondary outcome. We examined independent predictors of surgical intervention in a bivariate analysis using a stepwise logistic regression analysis.

Results

Of the 100 patients investigated, we excluded 12. Of the 88 remaining patients, 58 (66%) were managed conservatively and 30 (34%) underwent surgery. Peritoneal fluid detected on a CT scan (n = 37) was associated more frequently with surgery than conservative management (46% v. 29%, p = 0.046, χ²). Logistical regression identified peritoneal fluid detected on a CT scan as an independent predictor of surgical intervention (odds ratio 3.0, 95% confidence interval 1.15–7.84).

Conclusion

The presence of peritoneal fluid on a CT scan in patients with adhesional small bowel obstruction is an independent predictor of surgical intervention and should alert the clinician that the patient is 3 times more likely to require surgery.     

Finite element analysis of side branch access during bifurcation stenting

Stent implantation has become a widely accepted endovascular intervention for the treatment of stenosed arteries. This minimally invasive technique has shown excellent results in unbranched arteries. However, stenting bifurcation lesions remains a challenge in coronary intervention as it is associated with a lower success rate. Many different techniques have been proposed in medical practice but all the suggested methodologies have specific limitations. Numerical simulations may help to understand and eliminate the shortcomings of current clinical techniques and devices.In this study, one of the currently applied techniques is analysed which involves the implantation of a stent in the main branch, followed by subsequent inflation of a balloon through the side of the stent. This improves the side branch patency and provides access to the side branch for later stent implantations. The impact of using different balloon sizes and stent designs was investigated. The stent cell through which the balloon is inflated increases considerably and as intuitively expected, using a larger balloon results in a larger opening. Furthermore, it was observed that this procedure may compromise the downstream main branch lumen. These observations correspond well with previously reported results, which were based on in vitro studies. The added value of the proposed numerical model is the ability to study many different techniques/stents, without the need for various expensive stent samples.     

Imagerie osseuse du patient insuffisant rénal chronique : un nouvel outil ?

Bone damage in patients with chronic kidney disease (CKD), in the spectrum of chronic kidney disease-mineral and bone disorders (CKD-MBD), represents a daily challenge for nephrologists. The impact of CKD on bone health may be immediate (biological equilibrium) or delayed (fractures and vascular calcifications). Histomorphometry remains the gold standard to evaluate bone but it is rarely perfomed in clinical practice. A real measurement of bone mineral density (BMD) by dual X-ray absorptiometry (DXA) is currently performed to evaluate bone mass. However, this technique presents some limitations. In 2000, the National Institute of Health (NIH) defined new "quality" criteria for the diagnosis of osteoporosis in addition to a decreased bone mass. Bone strength actually integrates two concepts: bone density and bone quality (i.e., microarchitectural organization, bone turnover, mineralization and microfractures). These quality criteria cannot be evaluated by DXA. New bone imaging techniques have thus been developed, leading to an improvement in bone evaluation.