Prediction of Early Periprosthetic Joint Infection After Total Hip Arthroplasty.

Purpose: To develop a parsimonious risk prediction model for periprosthetic joint infection (PJI) within 90 days after total hip arthroplasty (THA). Patients and Methods: We used logistic LASSO regression with bootstrap ranking to develop a risk prediction model for PJI within 90 days based on a Swedish cohort of 88,830 patients with elective THA 2008-2015. The model was externally validated on a Danish cohort with 18,854 patients. Results: Incidence of PJI was 2.45% in Sweden and 2.17% in Denmark. A model with the underlying diagnosis for THA, body mass index (BMI), American Society for Anesthesiologists (ASA) class, sex, age, and the presence of five defined comorbidities had an area under the curve (AUC) of 0.68 (95% CI: 0.66 to 0.69) in Sweden and 0.66 (95% CI: 0.64 to 0.69) in Denmark. This was superior to traditional models based on ASA class, Charlson, Elixhauser, or the Rx Risk V comorbidity indices. Internal calibration was good for predicted probabilities up to 10%. Conclusion: A new PJI prediction model based on easily accessible data available before THA was developed and externally validated. The model had superior discriminatory ability compared to ASA class alone or more complex comorbidity indices and had good calibration. We provide a web-based calculator (https://erikbulow.shinyapps.io/thamortpred/) to facilitate shared decision making by patients and surgeons.

Regulated exocytosis: renal aquaporin-2 3D vesicular network organization and association with F-actin.

Regulated vesicle exocytosis is a key response to extracellular stimuli in diverse physiological processes, including hormone regulated short-term urine concentration. In the renal collecting duct, the water channel aquaporin-2 (AQP2) localizes to the apical plasma membrane as well as to small, subapical vesicles. In response to stimulation with the antidiuretic hormone, arginine vasopressin, aquaporin-2-containing vesicles fuse with the plasma membrane, which increases collecting duct water reabsorption and thus, urine concentration. The nanoscale size of these vesicles has limited analysis of their three-dimensional (3D) organization. Using a cell system combined with 3D superresolution microscopy, we provide the first direct analysis of the 3D network of aquaporin-2-containing exocytic vesicles in a cell culture system. We show that aquaporin-2 vesicles are 43 ± 3 nm in diameter, a size similar to synaptic vesicles, and that one fraction of AQP2 vesicles localized with the subcortical F-actin layer and the other localized in between the F-actin layer and the plasma membrane. Aquaporin-2 vesicles associated with F-actin and this association were enhanced in a serine 256 phospho-mimic of aquaporin-2, whose phosphorylation is a key event in antidiuretic hormone-mediated aquaporin-2 vesicle exocytosis.

Regulation of Plasma Membrane Nanodomains of the Water Channel Aquaporin-3 Revealed by Fixed and Live Photoactivated Localization Microscopy.

Several aquaporin (AQP) water channels are short-term regulated by the messenger cyclic adenosine monophosphate (cAMP), including AQP3. Bulk measurements show that cAMP can change diffusive properties of AQP3; however, it remains unknown how elevated cAMP affects AQP3 organization at the nanoscale. Here we analyzed AQP3 nano-organization following cAMP stimulation using photoactivated localization microscopy (PALM) of fixed cells combined with pair correlation analysis. Moreover, in live cells, we combined PALM acquisitions of single fluorophores with single-particle tracking (spt-PALM). These analyses revealed that AQP3 tends to cluster and that the diffusive mobility is confined to nanodomains with radii of ∼150 nm. This domain size increases by ∼30% upon elevation of cAMP, which, however, is not accompanied by a significant increase in the confined diffusion coefficient. This regulation of AQP3 organization at the nanoscale may be important for understanding the mechanisms of water AQP3-mediated water transport across plasma membranes.

Is length an appropriate estimator to characterize pulmonary alveolar capillaries? A critical evaluation in the human lung.

Stereological estimations of total capillary length have been used to characterize changes in the alveolar capillary network (ACN) during developmental processes or pathophysiological conditions. Here, we analyzed whether length estimations are appropriate to describe the 3D nature of the ACN. Semi-thin sections of five human lungs, previously investigated by Gehr et al. (Respir Physiol 1978; 32:121-140), were used to estimate alveolar capillary length using a "design-based" or a "model-based" stereological approach. The design-based approach involves counting of capillary profiles related to a defined area of the reference space. The model-based approach bases on the assumption that capillaries are round tubes and length was calculated from capillary volume and surface area. The model-based approach provided a mean of 6,950 km (SD: 3,108 km) for total capillary length, the design-based approach resulted in a mean of 2,746 km (SD: 722 km). Because of the geometry of the ACN both approaches carry an unpredictable bias. The bias incurred by the design-based approach is proportional to the ratio between radius and length of the capillary segments in the ACN, the number of branching points and the winding of the capillaries. The model-based approach is biased because of the real noncylindrical shape of capillaries and the network structure. In conclusion, the estimation of the total length of capillaries in the ACN cannot be recommended as the geometry of the ACN does not fulfill the requirements for stereological length estimation. Until new methods are being developed, the unbiased estimates of capillary volume, and surface area should be preferred.

An unbiased stereological method for efficiently quantifying the innervation of the heart and other organs based on total length estimations.

Quantitative information about the innervation is essential to analyze the structure-function relationships of organs. So far, there has been no unbiased stereological tool for this purpose. This study presents a new unbiased and efficient method to quantify the total length of axons in a given reference volume, illustrated on the left ventricle of the mouse heart. The method is based on the following steps: 1) estimation of the reference volume; 2) randomization of location and orientation using appropriate sampling techniques; 3) counting of nerve fiber profiles hit by a defined test area within an unbiased counting frame on paraffin sections stained immunohistochemically for protein gene product 9.5; 4) electron microscopic estimation of the mean number of axon profiles contained in one nerve fiber profile; 5) estimation of the degree of tissue shrinkage of specimens in paraffin; and 6) calculation of the total axon length within the reference volume, taking tissue shrinkage into account. In a set of five mouse hearts, the total length of axons ramifying between cardiomyocytes ranged between approximately 50 and 100 m, with a mean of 75.98 m (SD 23.73). The time required for the microscopical analysis was approximately 8 h/animal for an experienced observer. Using antibodies specific for different neuron subtypes and immunoelectron microscopy, this method is also suited to estimate the total axon length of neurons expressing different transmitters. This new and efficient method is particularly useful when structural remodeling takes place and is suspected to involve gain or loss of axons.