Digital surface scanning in flap perfusion

Monitoring vascular perfusion of transferred tissue is essential in reconstructive surgery to recognize early flap failure. The aim of this study was to evaluate the ability of a digital surface scanner to detect vascular perfusion disorders through the monitoring of skin colour changes. A total of 160 surface scans of the forearm skin were performed with a TRIOS 3D scanner. Vascular compromise was simulated at different time-points by intermittent occlusion of the blood supply to the forearm skin (first the arterial blood supply and then the venous blood supply). Skin colour changes were examined according to the hue, saturation, and value colour scale. Colour differences were analysed with a paired t-test. Significant differences were observed between the colour of the normal skin and that of the vascular compromised skin (P < 0.01). The surface scanner could distinguish between arterial occlusion and venous congestion (P < 0.01). A digital surface scan is an objective, non-invasive tool to detect early vascular perfusion disorders of the skin.     

From clock to functional pacemaker

In mammals, the central pacemaker that coordinates 24‐hr rhythms is located in the suprachiasmatic nucleus (SCN). Individual neurons of the SCN have a molecular basis for rhythm generation and hence, they function as cell autonomous oscillators. Communication and synchronization among these neurons are crucial for obtaining a coherent rhythm at the population level, that can serve as a pace making signal for brain and body. Hence, the ability of single SCN neurons to produce circadian rhythms is equally important as the ability of these neurons to synchronize one another, to obtain a bona fide pacemaker at the SCN tissue level. In this chapter we will discuss the mechanisms underlying synchronization, and plasticity herein, which allows adaptation to changes in day length. Furthermore, we will discuss deterioration in synchronization among SCN neurons in aging, and gain in synchronization by voluntary physical activity or exercise.     

Pathological responses to single‐pulse electrical stimuli in epilepsy: The role of feedforward inhibition

Delineation of epileptogenic cortex in focal epilepsy patients may profit from single‐pulse electrical stimulation during intracranial EEG recordings. Single‐pulse electrical stimulation evokes early and delayed responses. Early responses represent connectivity. Delayed responses are a biomarker for epileptogenic cortex, but up till now, the precise mechanism generating delayed responses remains elusive. We used a data‐driven modelling approach to study early and delayed responses. We hypothesized that delayed responses represent indirect responses triggered by early response activity and investigated this for 11 patients. Using two coupled neural masses, we modelled early and delayed responses by combining simulations and bifurcation analysis. An important feature of the model is the inclusion of feedforward inhibitory connections. The waveform of early responses can be explained by feedforward inhibition. Delayed responses can be viewed as second‐order responses in the early response network which appear when input to a neural mass falls below a threshold forcing it temporarily to a spiking state. The combination of the threshold with noisy background input explains the typical stochastic appearance of delayed responses. The intrinsic excitability of a neural mass and the strength of its input influence the probability at which delayed responses to occur. Our work gives a theoretical basis for the use of delayed responses as a biomarker for the epileptogenic zone, confirming earlier clinical observations. The combination of early responses revealing effective connectivity, and delayed responses showing intrinsic excitability, makes single‐pulse electrical stimulation an interesting tool to obtain data for computational models of epilepsy surgery.     

Comparative studies of Toll-like receptor signalling using zebrafish

Zebrafish model systems for infectious disease are increasingly used for the functional analysis of molecular pattern recognition processes. These studies benefit from the high conservation level of all innate immune factors in vertebrates. Zebrafish studies are strategically well positioned for this because of the ease of comparisons with studies in other fish species of which the immune system also has been intensively studied, but that are currently still less amendable to detailed genetic or microscopic studies. In this paper we focus on Toll-like receptor (TLR) signalling factors, which currently are the best characterized in mammalian systems. We review the knowledge on TLR signalling in the context of recent advances in zebrafish studies and discuss possibilities for future approaches that can complement studies in cell cultures and rodent models. A focus in these comparisons is the role of negative control mechanisms in immune responses that appear very important in a whole organism to keep adverse systemic responses in check. We also pay much attention to comparisons with studies in common carp that is highly related to zebrafish and that because of its large body mass can complement immune studies in zebrafish.     

TRPC6 channel translocation into phagosomal membrane augments phagosomal function

Defects in the innate immune system in the lung with attendant bacterial infections contribute to lung tissue damage, respiratory insufficiency, and ultimately death in the pathogenesis of cystic fibrosis (CF). Professional phagocytes, including alveolar macrophages (AMs), have specialized pathways that ensure efficient killing of pathogens in phagosomes. Phagosomal acidification facilitates the optimal functioning of degradative enzymes, ultimately contributing to bacterial killing. Generation of low organellar pH is primarily driven by the V-ATPases, proton pumps that use cytoplasmic ATP to load H⁺ into the organelle. Critical to phagosomal acidification are various channels derived from the plasma membrane, including the anion channel cystic fibrosis transmembrane conductance regulator, which shunt the transmembrane potential generated by movement of protons. Here we show that the transient receptor potential canonical-6 (TRPC6) calcium-permeable channel in the AM also functions to shunt the transmembrane potential generated by proton pumping and is capable of restoring microbicidal function to compromised AMs in CF and enhancement of function in non-CF cells. TRPC6 channel activity is enhanced via translocation to the cell surface (and then ultimately to the phagosome during phagocytosis) in response to G-protein signaling activated by the small molecule (R)-roscovitine and its derivatives. These data show that enhancing vesicular insertion of the TRPC6 channel to the plasma membrane may represent a general mechanism for restoring phagosome activity in conditions, where it is lost or impaired.Chronic infection and inflammation in the airways in cystic fibrosis (CF), as well as chronic obstructive pulmonary disease (COPD), tuberculosis, and asthma are now among the most common chronic diseases. Pulmonary infection associated with these diseases has historically been treated with antibiotics that kill bacteria but also select for development of resistance in the pathogen in the chronically infected lung (1, 2). One solution to antimicrobial drug resistance is to target the host rather than the pathogen. This strategy necessitates finding alternative targets or signaling strategies amplifying or restoring bactericidal capacity in the cells charged with the task of resolving chronic infection.Mononuclear phagocytes orchestrate the innate immune response in the lung through the combinatorial interplay between the phagocytic uptake and killing of bacterial invaders, clearance of apoptotic cells, antigen presentation, and secretion of vesicle-bound signaling molecules to recruit help in the resolution of infection. Ionic fluxes across the phagosomal membrane that encloses the pathogen produce a hostile acidic environment developed through the action of a V-ATPase proton translocation. However, a positive intraphagosomal membrane potential generated by proton translocation minimizes the proton content of the phagosome. An influx of Cl⁻ via Cl⁻ channels reduces the membrane potential generated by the proton pump, thereby, allowing maximal acidification of the phagolysosomal compartment, which in turn maximizes the activation of lysosomal degradative enzymes, generation of hypochlorous acid, and consequent bacterial killing (3, 4). We have previously demonstrated that murine alveolar macrophages (AMs) use the anion channel cystic fibrosis transmembrane conductance regulator (CFTR) as a Cl⁻ permeation pathway in the phagosomal membrane. In CF, loss of functional CFTR in the AM alkalinizes the phagosomal lumen and allows antimicrobial-resistant bacterial pathogens to survive macrophage surveillance.Not all tissue macrophages use CFTR as a charge compensation pathway in phagolysosomal acidification (4). In fact, recent data suggest that multiple V-ATPase charge-shunt pathways can exist in diverse macrophage lineages (5) via lysosomal recruitment and membrane insertion upon particle uptake. This observation led us to search for possible alternative charge-shunt pathways in pulmonary macrophages and how they might be activated or targeted to the maturing phagosome. Could a pharmacological tool circumvent the defect in CF AMs and activate alternative pathways to rescue both organellar acidification and bactericidal activity in cells expressing mutations in CFTR? Such a tool might activate parallel charge-shunt pathways used in peritoneal macrophages for maximum acidification, thereby allowing them to clear bacteria independently of CFTR expression as well as amplify the microbicidal response in the presence of functional CFTR. The transport proteins and channels active in peritoneal macrophage bacterial clearance have not been described but may involve a K⁺/H⁺ exchanger important in promoting excitatory synaptic vesicle filling (6) or a cation channel moving positive charge out of the phagolysosomal compartment, as has been suggested for macrophage cell lines (7).We began our investigations pursuing a novel pharmacological strategy to identify compounds that would resolve bacterial infection in the CF lung without the use of antimicrobials. We picked a cellular defect in CF because of the availability of animal models and extended our observations to non-CF human pulmonary cells. We designed screening assays of phagosome function, which could be used in a clinical setting as both diagnostic and investigational tools. We interrogated host function by studying surface receptor-mediated mechanisms that might provide parallel signaling pathways in subcellular organellar function in the resolution of disease.We report that a series of small molecules first identified in chemotherapeutics, (R)-roscovitine [2-(R)-(1-ethyl-2-hydroxyethylamino)-6-benzylamino-9-isopropylpurine] and its derivatives, restore microbicidal function to compromised AMs in CF and enhance function in non-CF cells. The compounds use a G protein-mediated signaling pathway, which results in the mobilization of transient receptor potential canonical-6 (TRPC6) calcium-permeable, nonselective cation channels to the plasma membrane and subsequently to the phagosomal membrane. Members of the TRP channel family have been implicated in a number of critical phagocytic functions, including particle uptake, migration, and reactive oxygen species (ROS) production (5, 8–11). Numerous studies (12–15) have suggested TRP channels as potential targets for the development of therapies in pulmonary inflammation because of their abundant and diverse cellular expression throughout the respiratory tree. Although TRPC6 channels have been previously identified in lung macrophages and shown to be up-regulated in COPD, their precise role in the pathophysiology of the disease is yet to be determined (16). Perhaps more relevant to our study, a TRPC6-mediated Ca²⁺ influx is increased in human CF airway epithelial cells, possibly because of a functional association between CFTR and TRPC6 that is lost in CF (17), with unknown consequences. To our knowledge, this study is the first to associate TRPC6 channels a specific drug-targeting strategy for the resolution chronic pulmonary infection.     

AIDS and Infection Control: Amsterdam Dentists Surveyed

In March 1988 all Amsterdam dentists (N = 470) were sent a questionnaire to assess the extent of compliance with guidelines from the Health Council to prevent HIV transmission in dental practice. Response rate was 62 percent. Gloves, masks, and other protective garments were widely used. Other infection control procedures, like sterilizing instruments, were often not followed in ways recommended by the Health Council. To date, 60 percent of the respondents did not spend more than US$2,500 for protective garments or special equipment. Planned expenditure is substantially higher. One-quarter of the respondents were certain to have one or more HIV-seropositive patients, and 35 percent believed they did. When taking the medical history, almost one-third of the dentists ask questions to assess whether a patient is possibly HIV seropositive. Forty percent of the dentists hold the opinion that it is necessary for a dentist to know whether a patient is HIV seropositive. This is against Health Council views. Thirty percent of the respondents are definitely fearful of AIDS infection and want additional information or training on this topic.     

Posterior mandibular residual ridge resorption in patients with conventional dentures and implant overdentures

PURPOSE: This study investigated the effects of certain systemic and local factors on resorption of the posterior mandibular residual ridge under conventional dentures and overdentures supported by 2 implants. MATERIALS AND METHODS: Proportional area measurements of the posterior mandible were made on rotational tomograms taken immediately before and 5 years after treatment. The area was bounded by a line joining gonion to the lowest point of the mental foramen and the crest of the residual ridge and was expressed as a proportion of an area that was not dependent on the ridge. The use of proportions rather than actual measurements minimized errors related to magnification and distortion. RESULTS: The estimated average reduction in height was 1.25 mm in 5 years (1.63 mm for conventional denture groups and 0.69 mm for implant overdenture groups, ie, almost 1 mm less in the overdenture group). DISCUSSION AND CONCLUSION: Female gender was a risk factor for greater resorption. Other factors, such as the number of years a patient had been edentulous, initial height of the mandible, and the number of dentures used, failed to show an association with resorption of the residual posterior mandibular ridge, while the statistically significant effect of age was unlikely to be clinically significant.