Observing Dynamic Conformational Changes within the Coiled-Coil Domain of Different Laminin Isoforms Using High-Speed Atomic Force Microscopy

Laminins are trimeric glycoproteins with important roles in cell-matrix adhesion and tissue organization. The laminin α, ß, and γ-chains have short N-terminal arms, while their C-termini are connected via a triple coiled-coil domain, giving the laminin molecule a well-characterized cross-shaped morphology as a result. The C-terminus of laminin alpha chains contains additional globular laminin G-like (LG) domains with important roles in mediating cell adhesion. Dynamic conformational changes of different laminin domains have been implicated in regulating laminin function, but so far have not been analyzed at the single-molecule level. High-speed atomic force microscopy (HS-AFM) is a unique tool for visualizing such dynamic conformational changes under physiological conditions at sub-second temporal resolution. After optimizing surface immobilization and imaging conditions, we characterized the ultrastructure of laminin-111 and laminin-332 using HS-AFM timelapse imaging. While laminin-111 features a stable S-shaped coiled-coil domain displaying little conformational rearrangement, laminin-332 coiled-coil domains undergo rapid switching between straight and bent conformations around a defined central molecular hinge. Complementing the experimental AFM data with AlphaFold-based coiled-coil structure prediction enabled us to pinpoint the position of the hinge region, as well as to identify potential molecular rearrangement processes permitting hinge flexibility. Coarse-grained molecular dynamics simulations provide further support for a spatially defined kinking mechanism in the laminin-332 coiled-coil domain. Finally, we observed the dynamic rearrangement of the C-terminal LG domains of laminin-111 and laminin-332, switching them between compact and open conformations. Thus, HS-AFM can directly visualize molecular rearrangement processes within different laminin isoforms and provide dynamic structural insight not available from other microscopy techniques.

Structural heterogeneity of the ion and lipid channel TMEM16F

Transmembrane protein 16 F (TMEM16F) is a Ca2+-activated homodimer which functions as an ion channel and a phospholipid scramblase. Despite the availability of several TMEM16F cryogenic electron microscopy (cryo-EM) structures, the mechanism of activation and substrate translocation remains controversial, possibly due to restrictions in the accessible protein conformational space. In this study, we use atomic force microscopy under physiological conditions to reveal a range of structurally and mechanically diverse TMEM16F assemblies, characterized by variable inter-subunit dimerization interfaces and protomer orientations, which have escaped prior cryo-EM studies. Furthermore, we find that Ca2+-induced activation is associated to stepwise changes in the pore region that affect the mechanical properties of transmembrane helices TM3, TM4 and TM6. Our direct observation of membrane remodelling in response to Ca2+ binding along with additional electrophysiological analysis, relate this structural multiplicity of TMEM16F to lipid and ion permeation processes. These results thus demonstrate how conformational heterogeneity of TMEM16F directly contributes to its diverse physiological functions.

Dynamics of Target DNA Binding and Cleavage by Staphylococcus aureus Cas9 as Revealed by High-Speed Atomic Force Microscopy

Programmable DNA binding and cleavage by CRISPR-Cas9 has revolutionized the life sciences. However, the off-target cleavage observed in DNA sequences with some homology to the target still represents a major limitation for a more widespread use of Cas9 in biology and medicine. For this reason, complete understanding of the dynamics of DNA binding, interrogation and cleavage by Cas9 is crucial to improve the efficiency of genome editing. Here, we use high-speed atomic force microscopy (HS-AFM) to investigate Staphylococcus aureus Cas9 (SaCas9) and its dynamics of DNA binding and cleavage. Upon binding to single-guide RNA (sgRNA), SaCas9 forms a close bilobed structure that transiently and flexibly adopts also an open configuration. The SaCas9-mediated DNA cleavage is characterized by release of cleaved DNA and immediate dissociation, confirming that SaCas9 operates as a multiple turnover endonuclease. According to present knowledge, the process of searching for target DNA is mainly governed by three-dimensional diffusion. Independent HS-AFM experiments show a potential long-range attractive interaction between SaCas9-sgRNA and its target DNA. The interaction precedes the formation of the stable ternary complex and is observed exclusively in the vicinity of the protospacer-adjacent motif (PAM), up to distances of several nanometers. The direct visualization of the process by sequential topographic images suggests that SaCas9-sgRNA binds to the target sequence first, while the following binding of the PAM is accompanied by local DNA bending and formation of the stable complex. Collectively, our HS-AFM data reveal a potential and unexpected behavior of SaCas9 during the search for DNA targets.

Unfolding and identification of membrane proteins in situ

Single-molecule force spectroscopy (SMFS) uses the cantilever tip of an AFM to apply a force able to unfold a single protein. The obtained force-distance curve encodes the unfolding pathway, and from its analysis it is possible to characterize the folded domains. SMFS has been mostly used to study the unfolding of purified proteins, in solution or reconstituted in a lipid bilayer. Here, we describe a pipeline for analyzing membrane proteins based on SMFS, that involves the isolation of the plasma membrane of single cells and the harvesting of force-distance curves directly from it. We characterized and identified the embedded membrane proteins combining, within a Bayesian framework, the information of the shape of the obtained curves, with the information from Mass Spectrometry and proteomic databases. The pipeline was tested with purified/reconstituted proteins and applied to five cell types where we classified the unfolding of their most abundant membrane proteins. We validated our pipeline by overexpressing 4 constructs, and this allowed us to gather structural insights of the identified proteins, revealing variable elements in the loop regions. Our results set the basis for the investigation of the unfolding of membrane proteins in situ, and for performing proteomics from a membrane fragment.

Simulation atomic force microscopy for atomic reconstruction of biomolecular structures from resolution-limited experimental images

Atomic force microscopy (AFM) can visualize the dynamics of single biomolecules under near-physiological conditions. However, the scanning tip probes only the molecular surface with limited resolution, missing details required to fully deduce functional mechanisms from imaging alone. To overcome such drawbacks, we developed a computational framework to reconstruct 3D atomistic structures from AFM surface scans, employing simulation AFM and automatized fitting to experimental images. We provide applications to AFM images ranging from single molecular machines, protein filaments, to large-scale assemblies of 2D protein lattices, and demonstrate how the obtained full atomistic information advances the molecular understanding beyond the original topographic AFM image. We show that simulation AFM further allows for quantitative molecular feature assignment within measured AFM topographies. Implementation of the developed methods into the versatile interactive interface of the BioAFMviewer software, freely available at www.bioafmviewer.com, presents the opportunity for the broad Bio-AFM community to employ the enormous amount of existing structural and modeling data to facilitate the interpretation of resolution-limited AFM images.

Macrocyclic Peptide-Conjugated Tip for Fast and Selective Molecular Recognition Imaging by High-Speed Atomic Force Microscopy

Fast and selective recognition of molecules at the nanometer scale without labeling is a much desired but still challenging goal to achieve. Here, we show the use of high-speed atomic force microscopy (HS-AFM) for real-time and real-space recognition of unlabeled membrane receptors using tips conjugated with small synthetic macrocyclic peptides. The single-molecule recognition method is validated by experiments on the human hepatocyte growth factor receptor (hMET), which selectively binds to the macrocyclic peptide aMD4. By testing and comparing aMD4 synthesized with linkers of different lengths and rigidities, we maximize the interaction between the functionalized tip and hMET added to both a mica surface and supported lipid bilayers. Phase contrast imaging by HS-AFM enables us to discriminate nonlabeled hMET against the murine MET homologue, which does not bind to aMD4. Moreover, using ligands and linkers of small size, we achieve minimal deterioration of the spatial resolution in simultaneous topographic imaging. The versatility of macrocyclic peptides in detecting unlimited types of membrane receptors with high selectivity and the fast imaging by HS-AFM broaden the range of future applications of this method for molecular recognition without labeling.

A Retrospective Comparative Analysis of Latissimus Dorsi (LD) Flap Versus Thoracodorsal Artery Perforator (TDAP) Flap in Total Breast Reconstruction with Implants: A Pilot Study

INTRODUCTION

 In breast surgery, an autologous flap combined with implant may reduce the risk or repair the soft-tissue defects in several cases. Traditionally, the preferred flap is the myocutaneous latissimus dorsi (LD) flap. In the perforator flap era, the evolution of LD flap is the thoracodorsal artery perforator (TDAP) flap. The aim of this study is the comparison between LD flap and TDAP flap with implants in terms of early complications and shoulder function.

METHODS

 We performed a retrospective cohort study in accordance with the STROBE guidelines. Between January 1 2015 and January 1 2020, 27 women underwent a unilateral total breast reconstruction with LD or TDAP flap combined with an implant at our institution. 15 women were operated with LD flap and 12 with TDAP flap. The most frequent indications for intervention were results of mastectomy and radiation-induced contracture. We evaluated several data in terms of clinical and demographical characteristics, operative and perioperative factors, and follow-up variables. We assessed shoulder function through the Disability of the Arm, Shoulder and Hand Questionnaire (DASH).

RESULTS

 The rate of complications was significantly lower in the TDAP group compared with the LD group (16.7% vs 60.0%, p = 0.047. Table 3). Although the small sample size limited further detailed statistical analyses, we particularly noticed no cases of donor site seroma in the TDAP group, as compared with four in the LD group. Patients in the TDAP group had an ∼11-point lower mean DASH score compared with the LD group (9.8 vs 20.5). This difference was statistically significant (p = 0.049).

CONCLUSIONS

 TDAP flap seems to be a reliable technique for soft-tissue coverage in total breast reconstruction with implants. In comparison with the traditional LD flap, it could be a more favorable option in terms of less complications and better quality of life.

An ultra-wide scanner for large-area high-speed atomic force microscopy with megapixel resolution

High-speed atomic force microscopy (HS-AFM) is a powerful tool for visualizing the dynamics of individual biomolecules. However, in single-molecule HS-AFM imaging applications, x,y-scanner ranges are typically restricted to a few hundred nanometers, preventing overview observation of larger molecular assemblies, such as 2-dimensional protein crystal growth or fibrillar aggregation. Previous advances in scanner design using mechanical amplification of the piezo-driven x,y-positioning system have extended the size of HS-AFM image frames to several tens of micrometer, but these large scanners may suffer from mechanical instabilities at high scan speeds and only record images with limited pixel numbers and comparatively low lateral resolutions (> 20–100 nm/pixel), complicating single-molecule analysis. Thus, AFM systems able to image large sample areas at high speeds and with nanometer resolution have still been missing. Here, we describe a HS-AFM sample-scanner system able to record large topographic images (≤ 36 × 36 µm²) containing up to 16 megapixels, providing molecular resolution throughout the image frame. Despite its large size, the flexure-based scanner features a high resonance frequency (> 2 kHz) and delivers stable operation even at high scans speeds of up to 7.2 mm/s, minimizing the time required for recording megapixel scans. We furthermore demonstrate that operating this high-speed scanner in time-lapse mode can simultaneously identify areas of spontaneous 2-dimensional Annexin A5 crystal growth, resolve the angular orientation of large crystalline domains, and even detect rare crystal lattice defects, all without changing scan frame size or resolution. Dynamic processes first identified from overview scans can then be further imaged at increased frame rates in reduced scan areas after switching to conventional HS-AFM scanning. The added ability to collect large-area, high-resolution images of complex samples within biological-relevant time frames extends the capabilities of HS-AFM from single-molecule imaging to the study of large dynamic molecular arrays. Moreover, large-area HS-AFM scanning can generate detailed structural data sets from a single scan, aiding the quantitative analysis of structurally heterogenous samples, including cellular surfaces.

The permeation mechanism of organic cations through a CNG mimic channel

Several channels, ranging from TRP receptors to Gap junctions, allow the exchange of small organic solute across cell membrane. However, very little is known about the molecular mechanism of their permeation. Cyclic Nucleotide Gated (CNG) channels, despite their homology with K+ channels and in contrast with them, allow the passage of larger methylated and ethylated ammonium ions like dimethylammonium (DMA) and ethylammonium (EA). We combined electrophysiology and molecular dynamics simulations to examine how DMA interacts with the pore and permeates through it. Due to the presence of hydrophobic groups, DMA enters easily in the channel and, unlike the alkali cations, does not need to cross any barrier. We also show that while the crystal structure is consistent with the presence of a single DMA ion at full occupancy, the channel is able to conduct a sizable current of DMA ions only when two ions are present inside the channel. Moreover, the second DMA ion dramatically changes the free energy landscape, destabilizing the crystallographic binding site and lowering by almost 25 kJ/mol the binding affinity between DMA and the channel. Based on the results of the simulation the experimental electron density maps can be re-interpreted with the presence of a second ion at lower occupancy. In this mechanism the flexibility of the channel plays a key role, extending the classical multi-ion permeation paradigm in which conductance is enhanced by the plain interaction between the ions.

Very Early Development and Recognition of Coronary Involvement in a Febrile Infant with Typical Signs of Kawasaki Disease

Kawasaki disease (KD) is an acute, self-limited, inflammatory disease affecting medium-sized arteries and particularly the coronary arteries in about 25% of untreated cases. KD is a clinical diagnosis based on the presence of ≥5 days of fever and the presence of ≥4 of the 5 principal clinical criteria. We described, for the first time to our knowledge, a case of a very early development (on day 1) of typical KD with transient coronary involvement, diagnosed on day 2 of disease and treated with aspirin and steroids on day 3, with complete resolution of clinical signs and coronary involvement.

Giant Cell Lesion of the Jaw. Case Report

A case is presented of a male patient affected by a giant cell lesion of the jaw, which had two recurrences in 8 years. Histologically, the lesion appeared to be composed of giant cells and mononuclear cells. Histoenzymatic study demonstrated acid phosphatase in both types of cells, and beta-glucuronidase in giant cells only. In some nuclei of giant cells, ultrastructural investigation showed filaments or microtubular structures of variable length, with irregular transverse periodicity, in addition to other expected findings. These characteristic features, found in giant cells of some giant cell tumors of the long bones, have never before been reported in a giant cell lesion of the jaw. The results are considered in order to assess the diagnosis, and the pathologic profiles of giant cell reparative granuloma, and of giant cell tumor are critically discussed.

History, rare, and multiple events of mechanical unfolding of repeat proteins

Mechanical unfolding of proteins consisting of repeat domains is an excellent tool to obtain large statistics. Force spectroscopy experiments using atomic force microscopy on proteins presenting multiple domains have revealed that unfolding forces depend on the number of folded domains (history) and have reported intermediate states and rare events. However, the common use of unspecific attachment approaches to pull the protein of interest holds important limitations to study unfolding history and may lead to discarding rare and multiple probing events due to the presence of unspecific adhesion and uncertainty on the pulling site. Site-specific methods that have recently emerged minimize this uncertainty and would be excellent tools to probe unfolding history and rare events. However, detailed characterization of these approaches is required to identify their advantages and limitations. Here, we characterize a site-specific binding approach based on the ultrastable complex dockerin/cohesin III revealing its advantages and limitations to assess the unfolding history and to investigate rare and multiple events during the unfolding of repeated domains. We show that this approach is more robust, reproducible, and provides larger statistics than conventional unspecific methods. We show that the method is optimal to reveal the history of unfolding from the very first domain and to detect rare events, while being more limited to assess intermediate states. Finally, we quantify the forces required to unfold two molecules pulled in parallel, difficult when using unspecific approaches. The proposed method represents a step forward toward more reproducible measurements to probe protein unfolding history and opens the door to systematic probing of rare and multiple molecule unfolding mechanisms.

The gating mechanism in cyclic nucleotide-gated ion channels

Cyclic nucleotide-gated (CNG) channels mediate transduction in several sensory neurons. These channels use the free energy of CNs' binding to open the pore, a process referred to as gating. CNG channels belong to the superfamily of voltage-gated channels, where the motion of the α-helix S6 controls gating in most of its members. To date, only the open, cGMP-bound, structure of a CNG channel has been determined at atomic resolution, which is inadequate to determine the molecular events underlying gating. By using electrophysiology, site-directed mutagenesis, chemical modification, and Single Molecule Force Spectroscopy, we demonstrate that opening of CNGA1 channels is initiated by the formation of salt bridges between residues in the C-linker and S5 helix. These events trigger conformational changes of the α-helix S5, transmitted to the P-helix and leading to channel opening. Therefore, the superfamily of voltage-gated channels shares a similar molecular architecture but has evolved divergent gating mechanisms.

High-Resolution and High-Speed Atomic Force Microscope Imaging

The advent of high-speed atomic force microscopy (HS-AFM) over the recent years has opened up new horizons for the study of structure, function and dynamics of biological molecules. HS-AFM is capable of 1000 times faster imaging than conventional AFM. This circumstance uniquely enables the observation of the dynamics of all the molecules present in the imaging area. Over the last 10 years, the HS-AFM has gone from a prototype-state technology that only a few labs in the world had access to (including ours) to an established commercialized technology that is present in tens of labs around the world. In this protocol chapter we share with the readers our practical know-how on high resolution HS-AFM imaging.

Structural Heterogeneity of CNGA1 Channels Revealed by Electrophysiology and Single-Molecule Force Spectroscopy

The determination at atomic resolution of the three-dimensional molecular structure of membrane proteins such as receptors and several ion channels has been a major breakthrough in structural biology. The molecular structure of several members of the superfamily of voltage-gated ionic channels such as K⁺ and Na⁺ is now available. However, despite several attempts, the molecular structure at atomic resolution of the full cyclic nucleotide-gated (CNG) ion channel, although a member of the same superfamily of voltage-gated ion channels, has not been obtained yet, neither by X-ray crystallography nor by electron cryomicroscopy (cryo-EM). It is possible that CNG channels have a high structural heterogeneity, making difficult crystallization and single-particle analysis. To address this issue, we have combined single-molecule force spectroscopy (SMFS) and electrophysiological experiments to characterize the structural heterogeneity of CNGA1 channels expressed in Xenopus laevis oocytes. The unfolding of the cytoplasmic domain had force peaks, occurring with a probability from 0.2 to 0.96. Force peaks during the unfolding of the transmembrane domain had a probability close to 1, but the distribution of the increase in contour length between two successive force peaks had multiple maxima differing by tens of nanometers. Concomitant electrophysiological experiments showed that the rundown in mutant channels S399C is highly variable and that the effect of thiol reagents when specific residues were mutated was consistent with a dynamic structural heterogeneity. These results show that CNGA1 channels have a wide spectrum of native conformations that are difficult to detect with X-ray crystallography and cryo-EM.

Soft-tissue defects of the Achilles tendon region: Management and reconstructive ladder. Review of the literature

INTRODUCTION

Defects of the Achilles tendon region represent a challenge for reconstructive surgeons. Several options are available but there is still no reconstructive ladder for this specific and tricky area. An up-to-date reconstructive ladder according to local and general conditions is proposed based on our multicentre experience and an extensive review of the English literature on PubMed.

MATERIALS AND METHODS

An extensive review of the English literature was performed on PubMed using the following key-words: "Achilles region", "heel", "soft-tissue reconstruction", "flaps", "grafts" and "dermal substitutes".

RESULTS

A total of 69 complete papers were selected, covering the last thirty years' literature. Although most of the studies were based on limited case-series, local and general conditions were always reported. A comprehensive reconstructive ladder of all the available reconstructive techniques for the Achilles region has been created based on our personal multicentre experience and the results of the literature review.

CONCLUSIONS

The reconstructive ladder is a concept that is still a mainstay in plastic surgery and guides decisions in the repair strategy for soft tissue defects. The optimal solution, according to the experience of the surgeon and the wishes of the patient, is the one that implies less sacrifice of the donor site. Perforator flaps should be the first-line option for small-to-moderate defects; the distally-based sural flap is the most reported for moderate-to-large defects of the Achilles region, and free flaps should be reserved mainly for complex and wide reconstructions.

Tibialis anterior muscle needle biopsy and sensitive biomolecular methods: a useful tool in myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a neuromuscular disorder caused by a CTG repeat expansion in 3'UTR of DMPK gene. This mutation causes accumulation of toxic RNA in nuclear foci leading to splicing misregulation of specific genes. In view of future clinical trials with antisense oligonucleotides in DM1 patients, it is important to set up sensitive and minimally-invasive tools to monitor the efficacy of treatments on skeletal muscle. A tibialis anterior (TA) muscle sample of about 60 mg was obtained from 5 DM1 patients and 5 healthy subjects through a needle biopsy. A fragment of about 40 mg was used for histological examination and a fragment of about 20 mg was used for biomolecular analysis. The TA fragments obtained with the minimally-invasive needle biopsy technique is enough to perform all the histopathological and biomolecular evaluations useful to monitor a clinical trial on DM1 patients.

A structural, functional, and computational analysis suggests pore flexibility as the base for the poor selectivity of CNG channels

Cyclic nucleotide-gated (CNG) ion channels, despite a significant homology with the highly selective K(+) channels, do not discriminate among monovalent alkali cations and are permeable also to several organic cations. We combined electrophysiology, molecular dynamics (MD) simulations, and X-ray crystallography to demonstrate that the pore of CNG channels is highly flexible. When a CNG mimic is crystallized in the presence of a variety of monovalent cations, including Na(+), Cs(+), and dimethylammonium (DMA(+)), the side chain of Glu66 in the selectivity filter shows multiple conformations and the diameter of the pore changes significantly. MD simulations indicate that Glu66 and the prolines in the outer vestibule undergo large fluctuations, which are modulated by the ionic species and the voltage. This flexibility underlies the coupling between gating and permeation and the poor ionic selectivity of CNG channels.

Giant congenital melanocytic naevi: review of literature

Giant congenital pigmented naevi is a great reconstructive challenge for the pediatric and plastic surgeons. Due to the increased risk of malignant transformation in such lesions, many procedures have been used to remove giant congenital naevi like dermoabrasion, laser treatment or surgical excision combined with reconstruction through skin expansion or skin grafting; among these, only a complete excision can offer an efficacious treatment. In our centre we use the "tissue expansion" technique in order to achieve a sufficient quantity of normal skin to perform a both staged and radical excision of these giant lesions.

Proton transfer unlocks inactivation in cyclic nucleotide-gated A1 channels

KEY POINTS

Desensitization and inactivation provide a form of short-term memory controlling the firing patterns of excitable cells and adaptation in sensory systems. Unlike many of their cousin K(+) channels, cyclic nucleotide-gated (CNG) channels are thought not to desensitize or inactivate. Here we report that CNG channels do inactivate and that inactivation is controlled by extracellular protons. Titration of a glutamate residue within the selectivity filter destabilizes the pore architecture, which collapses towards a non-conductive, inactivated state in a process reminiscent of the usual C-type inactivation observed in many K(+) channels. These results indicate that inactivation in CNG channels represents a regulatory mechanism that has been neglected thus far, with possible implications in several physiological processes ranging from signal transduction to growth cone navigation.

ABSTRACT

Ion channels control ionic fluxes across biological membranes by residing in any of three functionally distinct states: deactivated (closed), activated (open) or inactivated (closed). Unlike many of their cousin K(+) channels, cyclic nucleotide-gated (CNG) channels do not desensitize or inactivate. Using patch recording techniques, we show that when extracellular pH (pHo ) is decreased from 7.4 to 6 or lower, wild-type CNGA1 channels inactivate in a voltage-dependent manner. pHo titration experiments show that at pHo  < 7 the I-V relationships are outwardly rectifying and that inactivation is coupled to current rectification. Single-channel recordings indicate that a fast mechanism of proton blockage underlines current rectification while inactivation arises from conformational changes downstream from protonation. Furthermore, mutagenesis and ionic substitution experiments highlight the role of the selectivity filter in current decline, suggesting analogies with the C-type inactivation observed in K(+) channels. Analysis with Markovian models indicates that the non-independent binding of two protons within the transmembrane electrical field explains both the voltage-dependent blockage and the inactivation. Low pH, by inhibiting the CNGA1 channels in a state-dependent manner, may represent an unrecognized endogenous signal regulating CNG physiological functions in diverse tissues.

A sneaky surgical emergency: Acute compartment syndrome. Retrospective analysis of 66 closed claims, medico-legal pitfalls and damages evaluation

BACKGROUND

Acute compartment syndrome (ACS) is a clinical condition with potentially dramatic consequences, therefore, it is important to recognise and treat it early. Good management of ACS minimises or avoids the sequelae associated with a late diagnosis, and may also reduce the risk of malpractice claims. The aim of this article was to evaluate different errors ascribed to the surgeon and to identify how the damage was evaluated.

MATERIALS AND METHODS

A total of 66 completed and closed ACS cases were selected. The following were analysed for each case: clinical management before and after diagnosis of ACS, imputed errors, professional fault, damage evaluation and quantification. Particular attention was paid to distinguishing between impairment because of primary injury and iatrogenic impairment. Statistical analyses were performed using Fisher's exact test and Pearson's correlation.

RESULTS

The most common presenting symptom was pain. Delay in the diagnosis, and hence delay in decompression, was common in the study. A total of 48 out of 66 cases resolved with the verdict of iatrogenic damage, which varied from 12% to 75% of global capability of the person. A total of $394,780 out of $574,680 (average payment) derived from a medical error.

CONCLUSIONS

ACS is a clinical emergency that requires continuous clinical surveillance from both medical and nursing staff. The related damage should be evaluated in two parts: damage deriving from the trauma, so that it is considered inevitable and independent from the surgeon's conduct, and damage deriving from a surgeon's error, which is eligible for an indemnity payment.

Surgical excision of Infantile Haemangiomas: a technical refinement to prevent bleeding complications

PURPOSE

The aim of the study is to improve operative speed and precision of haemangiomas excision.

METHODS

CASE-REPORT

haemangioma is a common affection of the 8% of the population during the neonatal period. In complicated cases and involution sequelae surgical treatment is the first choice. The Authors propose a surgical refinement to prevent intraoperative bleeding.

METHODS

several suture stitches were placed around the hemangioma. The edges of the lesion became more defined, thus allowing accurate excision.

RESULTS AND CONCLUSIONS

Haemangiomas are characterized by rich blood supply. Surgery is often hindered by massive bleeding and Temporary placement of full-thickness sutures, surrounding the hemangioma, allowed a noticeable improvement in hemostasis precision and greater definition of the margins of the hemangioma.

Multiple mechanisms underlying rectification in retinal cyclic nucleotide-gated (CNGA1) channels

In cyclic nucleotide-gated (CNGA1) channels, in the presence of symmetrical ionic conditions, current–voltage (I-V) relationship depends, in a complex way, on the radius of permeating ion. It has been suggested that both the pore and S4 helix contribute to the observed rectification. In the present manuscript, using tail and gating current measurements from homotetrameric CNGA1 channels expressed in Xenopus oocytes, we clarify and quantify the role of the pore and of the S4 helix. We show that in symmetrical Rb⁺ and Cs⁺ single-channel current rectification dominates macroscopic currents while voltage-dependent gating becomes larger in symmetrical ethylammonium and dimethylammonium, where the open probability strongly depends on voltage. Isochronal tail currents analysis in dimethylammonium shows that at least two voltage-dependent transitions underlie the observed rectification. Only the first voltage-dependent transition is sensible to mutation of charge residues in the S4 helix. Moreover, analysis of tail and gating currents indicates that the number of elementary charges per channel moving across the membrane is less than 2, when they are about 12 in K⁺ channels. These results indicate the existence of distinct mechanisms underlying rectification in CNG channels. A restricted motion of the S4 helix together with an inefficient coupling to the channel gate render CNGA1 channels poorly sensitive to voltage in the presence of physiological Na⁺ and K⁺.

A 'migrant' mass of the forehead: diagnosis and treatment

BACKGROUND

Primary cutaneous large B-cell lymphoma, leg type, is a rare and aggressive neoplasm as defined by the World Health Organization/European Organisation for Research and Treatment of Cancer classification of cutaneous lymphomas. In some cases this disease may simulate other forms of benign or malignant solid tumours.

MATERIAL

We present a case of a 74-year-old man showing a quickly 'migrant' mass on his forehead. First skin biopsy, ultrasound and magnetic resonance images were not significant. A deeper biopsy revealed a pathology consistent with a primary cutaneous diffuse large B-cell lymphoma leg type.

RESULTS

The patient was successfully treated with only local radiotherapy (total dose: 32.4 Gy). At 1-year follow-up there were no recurrences.

DISCUSSION

To the best of our knowledge, this is the second case of a primary cutaneous diffuse large B-cell lymphoma leg type developed as a quickly 'migrant' lesion. In contrast with the first report, our case developed in a non-leg site. From these two cases, we should bear in mind that aggressive and quickly migrant cutaneous or subcutaneous masses might mask a lymphomatous disease.

Failure by congestion of pedicled and free flaps for reconstruction of lower limbs after trauma: the role of negative-pressure wound therapy

Lower limb reconstruction with pedicled or free flaps can be commonly compromised by venous insufficiency. This complication often leads to partial/complete flap necrosis and increases the risk of superinfection. Negative-pressure wound therapy (NPWT) is known to increase local blood flow, decrease edema, promote tissue granulation, and reduce the likelihood of soft tissue infection. This study aims to evaluate the effectiveness of NPWT in the treatment of congested pedicled and free flaps of the lower limb after reconstructions in lower limb traumas. A retrospective analysis was performed on four congested (pedicled and free) flaps on the lower limbs. NPWT was applied in all cases after partial flap debridement. NPWT was able to improve and resolve tissue edema and venous insufficiency, avoid further flap necrosis, and promote granulation. On NPWT removal, a split-thickness skin graft was applied on the wound, achieving complete and uneventful healing. NPWT is a useful instrument in managing flaps affected by venous insufficiency in lower limb reconstruction, although larger studies are necessary to better define the effectiveness and indications of NPWT in this setting.

A ring of threonines in the inner vestibule of the pore of CNGA1 channels constitutes a binding site for permeating ions

Cyclic nucleotide-gated (CNG) channels and K+ channels have a significant sequence identity and are thought to share a similar 3D structure. K+ channels can accommodate simultaneously two or three permeating ions inside their pore and therefore are referred to as multi-ion channels. Also CNGA1 channels are multi-ion channels, as they exhibit an anomalous mole fraction effect (AMFE) in the presence of mixtures of 110 mM Li+ and Cs+ on the cytoplasmic side of the membrane. Several observations have identified the ring of Glu363 in the outer vestibule of the pore as one of the binding sites within the pore of CNGA1 channels. In the present work we identify a second binding site in the selectivity filter of CNGA1 channels controlling AMFE. Here, we show also that Cs+ ions at the intracellular side of the membrane block the entry of Na+ ions. This blockage is almost completely removed at high hyperpolarized voltages as expected if the Cs+ blocking site is located within the transmembrane electric field. Indeed, mutagenesis experiments show that the block is relieved when Thr359 and Thr360 at the intracellular entrance of the selectivity filter are replaced with an alanine. In T359A mutant channels AMFE in the presence of intracellular mixtures of Li+ and Cs+ is still present but is abolished in T360A mutant channels. These results suggest that the ring of Thr360 at the intracellular entrance of the selectivity filter forms another ion binding site in the CNGA1 channel. The two binding sites composed of the rings of Glu363 and Thr360 are not independent; in fact they mediate a powerful coupling between permeation and gating, a specific aspect of CNG channels.

Mammaplasties and medicolegal issues: 50 cases of litigation in aesthetic surgery of the breast

BACKGROUND

Aesthetic surgery procedures are increasing all over the world, and so are related medicolegal questions and litigation cases. Aesthetic mammaplasties represent a very important part of this field and consequently many cases of error appear. Most of these errors lead to litigation from which plastic surgeons rarely can be exonerated. The aim of this article was to evaluate different errors ascribed to the plastic surgeon, the rate of cases in which professional responsibility has been identified, and the type of guilt imputed.

METHODS

Each case is based on the evaluation of both documentation used by the judge and the relationships of two specialists involved in the assessment of the presumed error. In every case, problems complained about by the patient and the eventually related error of the surgeon were analyzed. Moreover, the eventual identification of professional responsibility, the quantified damage, and its possible reduction by another corrective operation were considered.

RESULTS

The cases studied (N=50) were divided into 34 cases of augmentation mammaplasty, 11 cases of reduction mammaplasty, and 5 cases of mastopexy. Most of the problems complained about by patients were in the preoperative and intraoperative phases. In only 10% of the cases was the informed consent contested and an expected reduction of the damage was individuated in less than half of cases.

CONCLUSIONS

The evaluation of aesthetic damage is a tricky question due to different aspects such as the psychological component or the frequent lack of adequate photographic documentation of the patient before the operation. Moreover, whenever possible reduction of the damage is proposed, the patient's willingness to undergo another operation, with all its related costs and benefits, must be considered.

Giant congenital nevi of the scalp and forehead treated by skin expansion

Congenital giant melanocytic nevi of the scalp and forehead are rare lesions present at birth. These lesions are associated with risk of malignant transformation, but they primarily represent a psychological problem to both patient and parents and merit early excision and reconstruction. In this study we report our own experience: seven patients, aged 8 months to 9 years, with congenital pigmented nevi involving forehead and scalp, and a 4-year old patient with congenital pigmented nevus of periorbital region and nose were treated successfully with excision and expanded skin flap reconstructions. The mean expansion procedures were 2 (range, 1 to 3), with an average of 8,8 injections for each expansion procedure (range, 6 to 11). In only one patient simultaneous expanders were placed in the scalp and forehead. Follow-up ranged from 4 months to 15 years. We had no rupture, extrusion or infection of the skin expanders. Complications included eyebrow ptosis and asymmetry in two patients underwent correction at a final procedure. In our opinion tissue expansion is an excellent technique for the treatment of giant nevi of the scalp and forehead because it offers the best aesthetic and functional outcomes.

Increased frequency of immunoglobulin (Ig)A-secreting cells following Toll-like receptor (TLR)-9 engagement in patients with Kawasaki disease

Kawasaki disease (KD) is an acute vasculitis affecting mainly infants and children. Human B cells express Toll-like receptor (TLR)-9, whose natural ligands are unmethylated cytosine-guanine dinucleotide (CpG) motifs characteristic of bacterial DNA. The aim of this study was to clarify the pathogenesis of KD analysing the activation status of peripheral blood mononuclear cells (PBMC), focusing on B lymphocyte activation and functions. Ten patients and 10 age-matched healthy donors were recruited from the Bambino Gesù Hospital of Rome, Italy and enrolled into this study. We determined phenotype profile and immunoglobulin (Ig) production of PBMC from KD patients and age-matched controls. We found that the frequency of CD19(+) B lymphocytes and CD19(+) /CD86(+) activated B lymphocytes from KD patients during the acute phase before therapy was increased significantly. Moreover, B lymphocytes of acute-phase KD patients were more prone to CpG oligodeoxynucleotide (ODN) activation compared with the age-matched controls, as assessed by a significant increase of the number of IgA-secreting cells (SC). In the same patients we found a marked increase of IgM, IgG, interleukin (IL)-6 and tumour necrosis factor (TNF)-α production compared with the control group. In addition, in two convalescent KD patients, conventional treatment with intravenous immunoglobulin (IVIG) restored the normal frequency of CD19(+) B cells, the number of IgA-, IgM- and IgG-SC and the production of IL-6 and TNF-α. Our findings indicate that the percentages of peripheral B lymphocytes of acute-phase KD patients are increased and are prone to bacterial activation in terms of increased numbers of IgA-SC and increased production of IL-6 and TNF-α inflammatory cytokines. Thus, our data support the hypothesis of an infectious triggering in KD.

The pollicization of the index finger in the aplasia of the thumb

We have examined 11 patients with aplasia of the thumb and we have treated by pollicization of the index finger. We have conducted a follow up of 5 years. The total absence of the thumb may be an isolated anomaly, but it is often associated with some other congenital malformation. The absent thumb is as an autosomal dominant pathology or may be sporadic. It is frequently observed in the Holt-Oram syndrome, Fanconi's anemia, and ring D chromosome abnormalities. It is occasionally observed in the Rothmund syndrome, trisomy, thalidomide embryopathology and other congenital syndromes. An absent radius is almost always associated with an absent thumb, except in thrombocytopenia radial aplasia (Fanconi's syndrome), where the thumb is present even when the radius is absent. The treatment in most cases of the absent thumb is to perform a pollicization of the index finger. Our isolated congenital absence of the thumb patients have been treated with pollicization as described by Buck-Gramcko works well. It is a beautiful operation for the congenitally deformed, aplastic, or missing thumb. Pollicization of the index finger gives good functional and cosmetic results which are maintained.

CONCLUSIONS

The total absence of the thumb in the congenitally pathology gives the hand of the patient insufficient in the functional movement and no cosmetic. So the pollicization with the second index fined gives a good reconstruction for the neo-thumb. In our five years follow-up, the 11 young patients that were treated with the pollicization, they are satisfy and use the neo-thumb like normal thumb. In congenitally absent thumbs clearly support the fact that the pollicized digit is used by most patients and is not ignored or bypassed.

Second toe transplantation to reconstruct digits

In congenital absence of fingers or in post-traumatic amputations of the thumb or fingers, reconstruction by microsurgical toe-to-hand transfer is becoming a common treatment for these difficult problems. In case of congenital absence of the thumb, fingers, or both, these transfers can provide acceptable growth, function and sensation of the transferred toes with a current success rate usually greater than 95%. The most commonly transplanted toe is the second toe, since it is the longest toe and combines all the useful characteristics of a finger (such as joint, a nail, sensitive pulp tissue, and the ability to growth) with a good reliable blood supply. In this article, we discuss the rationale for this treatment approach, by considering the indications to treatment, the patient's preoperatory assessment, and the long-term results. We also report a case of a 4-year-old female child, suffering from congenital partial absence of second finger of the left hand, who underwent reconstruction by transfer of the second toes of foot.

Impact of leukapheresis cell composition on immunomagnetic cell selection with the Baxter Isolex 300i device: a statistical analysis

Immunomagnetic cell selection (ICS) of CD34(+) cells is increasingly adopted in allogeneic and autologous transplant settings. Because many variables can affect the final results of ICS, we focused our study toward the influence exerted by the leukapheresis (LKF) cell composition on recovery, purity, and log of T and B depletion of the immunoselected cells. A total of 39 consecutive CD34(+) ICS were performed with the Isolex 300i (Baxter) device on 39 LKF from 9 HLA haploidentical donors and 20 patients. Flow cytometric analysis was performed both on the leukapheresis content and on the immunoselected cells. The statistical analysis was performed utilizing the Pearson's correlation test and the Mann-Whitney U test. The median purity and recovery of the immunoselected CD34(+) cells were 95.3% (IR: 93.0-99.0) and 55.1% (IR: 41.8-68.2), respectively. The median log of T and B depletion were 3.87 (IR: 3.5-4.3) and 2.9 (IR: 2.5-3.5), respectively. Our data indicate that not only the CD34(+) cell load but also the ratio among the cells belonging to the starting fraction can influence the results of ICS. LKF collection protocols have to be addressed to collect an high number of CD34(+) cells (>500 x 10(6)) without taking care of the contaminating cells when the Baxter Isolex 300i device is employed.

[Cutaneous head and neck carcinomas: biological characteristics, natural history and clinical classification]

In cutaneous carcinoma of the Head and Neck there is a 7% of cases that often suffer substantial morbidity and even mortality. The identification of the "high-risk patient" may derive from the study of the prognostic factors which have been published in Literature. The problem has to be differentiated between the basal cells carcinoma (BCC) and the squamous cells carcinoma (SCC) due to the locally limited aggressiveness of the first and the potential for metastatization of the latter. The evaluation of the different variables confirms the inadequacy of the present TNM Classification for Cutaneous carcinoma; nevertheless the opportunity of a new and omni-comprehensive proposal is questionable.

[Hypercalcitoninemia and disorders of dentition development. A family study]

INTRODUCTION

A lot of factors interfere in the physiopathology of the exfoliation of the primary teeth. One of the most important factors is bone shuffle which is due to osteoclastic activity; this activity is controlled by a hormonal equilibrium.

CLINICAL CASE

The aim of the present study was to correlate primary teeth's exfoliation delay in two brothers with their hypercalcitoninemia. They had a positive familiar anamnesis for thyroid medullar cancer; this disease is notoriously associated with hypercalcitoninemia.

CONCLUSIONS

The connection between a high basal and after-stimulation seric level of calcitonin and a lower activity of osteoclasis is evident. Thus, i also appeared evident to us the connection between the hormonal disease of the two children and the delay of exfoliation of their primary teeth. In these cases, it is important to control periodically the patients in order to prevent or to diagnose early isolated medullar thyroid cancer or a multiple endocrine adenomatosis.

[Multiple peg-shaped teeth associated with acrocephalosyndactyly. A variant of the Saethre-Chotzen syndrome? A clinical case]

INTRODUCTION

The SC syndrome is relatively common among craniosynostosis syndromes, and it is transmitted as an autosomal dominant trait. The syndrome was first recognized and described by S. and C. (1931-1932), but that most extensive discussion of the disorder was published by Pantke et al. in 1975. He systematically described the most and the least common marks of that syndrome.

CLINICAL CASE

We thought it right to report a case we met and observed, because together with the S.C. syndrome's marks, there was the presence of multiple peg-shaped teeth. This peculiar mark is common to many orger craniosynostotic syndromes, but, we think it has never been described in "acrocephalosyndactyly type three" clinical cases. As a matter of fact, in literature, they have described in that syndrome, only lateral incisors shape anomalies.

CONCLUSIONS

Even if in our patient the syndrome had a poor expressivity (there were scarce cranio-facial anomalies), and even if it came out there was no familiarity, it was peculiar because of the presence of multiple peg-shaped teeth. Besides, we think it is important to recognize that syndrome (which diagnosis is today still clinical because of the absence of peculiar laboratory aids), in such a way as to advice the female patient and to suggest her, in case of pregnancy, to go to a Uman Genetic Service for a an advice.

[Oral hygiene in subjects treated with diphenylhydantoin: effects of a professional program]

The purpose of the present study was to investigate, on a longitudinal basis, the effectiveness of a specific preventive dental program for patients who are taking phenytoin for seizure control. The results confirm that a preventive dental program, consisting on frequent prophylaxis and plaque control, is effective in minimizing clinically gingival enlargement associated with phenytoin therapy, even in patients who present histological aspects of gingival hyperplasia.