Semi-automated quantitative analysis of the middle limiting membrane in tubercular serpiginous-like choroiditis using swept-source optical coherence tomography.

To analyze the longitudinal changes in the outer plexiform layer (OPL) in patients with tubercular serpiginous-like choroiditis (TB SLC) and compare it to the healthy control population. Clinical and imaging data of subjects with TB SLC (minimum 6-month follow-up) and healthy control subjects were reviewed. Optical coherence tomography (OCT) imaging obtained using swept-source device (DRI Triton, Topcon, Japan) from three visits (baseline, 3 months, and 6 months) were analyzed. Three OCT scans were chosen-one passing through the center of the fovea, one line above, and one line below. After random indexing to anonymize the images, they were pre-processed and fed into an automated pipeline to identify, crop, and measure the area of the OPL in the line scan. Longitudinal comparisons of OPL within the patient group were performed. The study included 32 eyes (16 patients; 11 males; mean age: 32.9 ± 7.8 years) with TB SLC. Twenty-eight eyes (14 subjects; 10 males: mean age: 31.1 ± 6.2 years) of healthy control subjects (age- and gender-matched) were also selected. The area of OPL was significantly different between the baseline and month 6 visit (6288 ± 1803 versus 5487 ± 1461; p = 0.0002) at the central scan passing through the fovea. For the scans above and below the fovea, the reduction in OPL area was significant at each visit (p < 0.0001). In comparison with healthy control subjects, OPL area values in patients with TB SLC were significantly lower at the month-3 (6116 ± 1441 versus 7136 ± 2539; p = 0.04) and the 6-month visit (5487 ± 1461 versus 7136 ± 2539; p < 0.001). The atrophied OPL at month 6 has been referred to as the "middle limiting membrane" (MLM). Subjects with TB SLC may develop progressive atrophy of the OPL resulting in formation of MLM, which is seen as a hyper-reflective line replacing the OPL. The analysis of longitudinal changes in the OPL may be useful in predicting anatomical and functional outcomes in these patients.

Membrana neovascular yuxtapapilar asociada a drusas del nervio óptico / Juxtapapillary neovascular membrane associated with optic nerve drusen

CASO CLÍNICO: Paciente de 14 años de edad concurre refiriendo una disminución progresiva de la agudeza visual del ojo izquierdo de 3 meses de evolución. Al examen presenta drusas de papila bilateral, asociadas a membrana neovascular yuxtapapilar, que comprometen seriamente la visión y el campo visual del ojo izquierdo. RESULTADO: El tratamiento con 3 inyecciones consecutivas de ranibizumab intravítreo resultó en la inactivación de la membrana neovascular con reabsorción de líquido subretiniano y mejora de la agudeza visual mejor corregida del ojo izquierdo. Después de 9 meses de seguimiento, esta fue 20/20 y estable. CONCLUSIÓN: Si bien las drusas de la cabeza del nervio óptico son consideradas benignas, las membranas neovasculares pueden ser una complicación. Los anti-VEGF son una alternativa eficaz para el tratamiento

CLINICAL CASE: Forteen year old patient presenting progressive decrease in visual acuity of the left eye after 3 months of evolution. On examination he presents bilateral drusen of papilla, associated with juxtapapillary neovascular membrane, which seriously compromises the vision and visual field of the left eye. RESULT: Treatment with 3 consecutive injections of intravitreal ranibizumab resulted in the inactivation of the neovascular membrane with reabsorption of subretinal fluid and improvement of the best corrected visual acuity of the left eye. After 9 months of follow-up, it was 20/20 and stable. CONCLUSION: Although optic nerve head drusen are considered benign, neovascular membranes can be a complication. Anti-VEGFs are an effective alternative for treatment

Does the induced membrane have antibacterial properties? An experimental rat model of a chronic infected nonunion.

INTRODUCTION: The Masquelet procedure proved its efficiency in treating infected nonunion filling bony gaps up to 25 cm. Yet the use of local antibiotics is still questionable in the daily practice with lack of evidence regarding its usefulness in controlling infection. An experimental rat model is put in place to study the antibacterial properties of the induced membrane produced during the first stage of Masquelet. METHOD: Twenty-three-month-old wistar male rats are inoculated with a 0.5 mL solution of 10^8 CFU/mL MRSA over a critical fracture done on the right femur. Six weeks later, remaining 11 rats exhibiting signs of a chronic infection with a sinus tract and oozing pus along with radiological nonunion are used for a first stage Masquelet procedure. They are randomly divided into two groups with six rats having no local antibiotic in the cement mixture and five rats having 3 g of vancomycin mixed with gentamycin loaded cement. Six weeks later (twelve weeks from baseline), all eleven rats are euthanized and blood samples for C-reactive protein are withdrawn. The induced membrane is identified and resected along with bone fragments and sent for cultures and pathology. RESULTS: MRSA is isolated in the cultures of all six rats in the first group where no local antibiotic was added. Altered polymorphonuclears with abscess and pus are noted on four of six pathology samples. However in the second group where local antibiotics were added, three out of five rats exhibited eradication of MRSA (p = 0.034) and all samples did not exhibit clear infection signs on pathology. A pyo-epithelioid over a foreign body reaction is seen predominantly in this group demonstrating a regenerative process. DISCUSSION: The induced membrane does not have antimicrobial properties capable of overcoming an infected nonunion on its own. When local antibiotics were added during the first stage of the Masquelet procedure, new bone formation occurred indicating the need to control an infection in order for bone union to occur. CONCLUSION: Local antibiotics use in adjunction to extensive debridement is advisable during the first stage of a Masquelet procedure for an infected nonunion.

Exosomes: The New Mediator of Peritoneal Membrane Function.

Fibrosis and angiogenesis are the most common processes that result in progressive peritoneal tissue remodeling and, eventually, peritoneal membrane dysfunction. The role of exosomes, which contributes to intercellular communication, in these processes has been neglected. Various biomolecules, including DNA, mRNA, proteins, lipids, and particular certain miRNAs, can be transferred by exosomes to local, neighboring and distal cells. Upon stimulation by cytokines or other microenvironment stimuli, donor cells release a mass of exosomes to peritoneal mesothelial cells, further affecting fibrosis and angiogenesis. This important exosomes-mediated intracellular communication is thought to regulate peritoneal membrane function. Understanding the molecular mechanisms of these processes, targeting changes in exosomes and regulating exosomal miRNAs will advance therapeutic methods for protecting peritoneal membrane function.

The Function of the Distal Interosseous Membrane and its Relevance to the Stability of the Distal Radioulnar Joint: An Anatomical and Biomechanical Review.

The purpose of this article is to review functional anatomy and biomechanics of the distal interosseous membrane (DIOM) and its relevance to the stability of the distal radioulnar joint. The intact DIOM constrained dorsal dislocation of the radius, but it seldom constrained palmar dislocation. A residual ulnar translation deformity of the radial shaft in distal radius fractures has the potential to cause the distal radioulnar joint instability when the triangular fibrocartilage complex injury is also present, because it may result in detensioning of DIOM. Ulnar shortening with the osteotomy performed proximal to the attachment of the DIOM had a more favorable effect on stability of the DRUJ compared with the effect of distal osteotomy, especially in the presence of the distal oblique bundle (DOB). The longitudinal resistance to ulnar shortening was significantly greater in proximal shortening than in distal shortening.

Genomewide molecular and biologic characterization of biomembrane formation adjacent to a methacrylate spacer in the rat femoral segmental defect model.

OBJECTIVES: This study focuses upon the morphologic and molecular features of the layer of cells, termed the "biomembrane," which forms around methacrylate spacers in bone segmental defects. The objective of this research was to assess the biomembrane formed in a novel rodent femoral segmental defect model at 4, 8, and 16 weeks with histologic and molecular studies. METHODS: Following Institutional Animal Care and Use Committee approval, a segmental defect was created in the rat femur and stabilized with the AO LockingRatNail and analyzed at 4, 8, and 16 weeks postsurgery using digital radiologic imaging, morphological and immunohistochemical studies, and genomewide gene expression studies employing microarray analysis. RESULTS: The biomembrane formed around the methacrylate spacer was rich in vasculature, which showed vascular endothelial growth factor immunolocalization. The biomembrane supported development of foci of bone and cartilage within it. Bone morphogenetic protein 2 immunolocalization and gene expression were positive within developing osseous and chondrocyte foci. Microarray analysis showed significant expression of key genes related to bone and cartilage formation and angiogenesis. CONCLUSIONS: This rat bone model was effective in creation of the biomembrane. Bone and cartilage foci were formed within the vascularized biomembrane with associated expression of genes critical for bone and cartilage development/formation and vascularization. The polymethyl methacrylate-induced biomembrane offers an exciting potential solution for segmental defects; the biomembrane, may act as a receptive bed and also serve as a source for mesenchymal stem cells, which could be recruited/directed for the healing process.

Quantification of transmembrane currents during action potential propagation in the heart.

The measurement, quantitative analysis, theory, and mathematical modeling of transmembrane potential and currents have been an integral part of the field of electrophysiology since its inception. Biophysical modeling of action potential propagation begins with detailed ionic current models for a patch of membrane within a distributed cable model. Voltage-clamp techniques have revolutionized clinical electrophysiology via the characterization of the transmembrane current gating variables; however, this kinetic information alone is insufficient to accurately represent propagation. Other factors, including channel density, membrane area, surface/volume ratio, axial conductivities, etc., are also crucial determinants of transmembrane currents in multicellular tissue but are extremely difficult to measure. Here, we provide, to our knowledge, a novel analytical approach to compute transmembrane currents directly from experimental data, which involves high-temporal (200 kHz) recordings of intra- and extracellular potential with glass microelectrodes from the epicardial surface of isolated rabbit hearts during propagation. We show for the first time, to our knowledge, that during stable planar propagation the biphasic total transmembrane current (I(m)) dipole density during depolarization was ∼0.25 ms in duration and asymmetric in amplitude (peak outward current was ∼95 µA/cm(2) and peak inward current was ∼140 µA/cm(2)), and the peak inward ionic current (I(ion)) during depolarization was ∼260 µA/cm(2) with duration of ∼1.0 ms. Simulations of stable propagation using the ionic current versus transmembrane potential relationship fit from the experimental data reproduced these values better than traditional ionic models. During ventricular fibrillation, peak I(m) was decreased by 50% and peak I(ion) was decreased by 70%. Our results provide, to our knowledge, novel quantitative information that complements voltage- and patch-clamp data.

Determinants of peritoneal membrane function over time.

Changes to peritoneal membrane function over time result in the development of ultrafiltration failure in a proportion of PD patients and pose a risk for the rarer condition of encapsulating peritoneal sclerosis. These changes are characterized by an increase in the transport rate for small solutes owing to increased vascularity and/or peritoneal blood flow and in more severe cases a reduction in the osmotic conductance of the membrane that likely reflects progressive fibrosis. Both of these processes are preceded by exposure of the membrane to glucose when using conventional dialysis solutions, although this usually is necessitated and likely exacerbated by loss of residual renal function and recurrent peritonitis. Mediators of membrane injury and thus potential biomarkers include inflammatory cytokines, notably local interleukin-6 production, which also appears to determine solute transport characteristics at the start of peritoneal dialysis, local production of vascular endothelial growth factor, and transforming growth factor ß-associated epithelial to mesenchymal transition of the mesothelium leading to membrane fibrosis. Low glucose degradation product solutions may ameliorate the mesothelial injury associated with high glucose exposure, but evidence that they prevent or delay changes in membrane function over time is lacking. In the meantime, avoidance of excessive glucose exposure, preservation of residual renal function, and prevention of peritonitis remain the most logical treatment strategies for this problem.

Postnatal development of carotid body glomus cell response to hypoxia.

This study examines developmental changes in CB glomus cell depolarization, intracellular calcium ([Ca(2+)](i)) and the magnitude of an O(2)-sensitive background ionic conductance that may play roles in the postnatal increase in oxygen sensitivity of glomus cells isolated from rats of 1-3 days and 11-14 days postnatal age. Using fura-2 and perforated patch whole cell recordings, we simultaneously measured [Ca(2+)](i) and membrane potential (E(m)) during normoxia and hypoxia. Resting E(m) in normoxia was similar at both ages. Hypoxia caused a larger E(m) depolarization and correspondingly larger [Ca(2+)](i) response in glomus cells from 11- to 14-day-old rats compared to 1-3-day-old rats. E(m) and [Ca(2+)](i) responses to 40mM K(+) were identical between the two age groups. Under normoxic conditions both age groups had similar background conductances. Under anoxic conditions (at resting membrane potential) background K(+) conductance decreased significantly more in cells from 11- to 14-day-old rats compared to cells from 1- to 3-day-old rats. Glomus cells from newborns therefore have less O(2)-sensitive background K(+) conductance. These results support the hypothesis that postnatal maturation of glomus cell O(2) sensitivity involves developmental regulation of the expression and/or O(2)-sensitivity of background ionic conductances.

Experimental studies of the effects of abnormal venous valves on fluid flow.

The effects of variations in the venous valve anatomy are studied experimentally using an artificial system that mimics the bicuspid valves normally found in veins in the lower extremities. The artificial valves are constructed from thin-walled, latex tubing and polyurethane film. The experimental variables in the study are the gap width between the leaflet attachments at the vein wall and the ratio of the sinus depth to vein diameter. The results show that the antegrade mass flow rate is not affected to the same degree when compared to retrograde flow by the various valve configurations examined in this study. The results also indicate that increases in the gap width, which serve to increase the degree of imperfect wall attachment, have less effect on retrograde mass flow rate in valves with deeper sinuses.

Disruption of hydrophobic stability of biomembranes is the earliest event in several clinical disorders.

Hydrophobic attractive force is the major force in maintaining the stability of biomembranes, yielding coordinated functionality to the embedded proteins that they contain. This force between the composite linear hydrocarbons of the biomembranes is a function of their length and their mutual parallel distance from each other, and is extremely sensitive to this distance. Extracellular, natural linear hydrocarbons of certain length and shape can intercalate into lipid matrix of the biomembranes, reducing their innate hydrophobic net strength in a concentration-dependent manner, making them loose, leaky, and thus gaining the credence of stimulus-generating agents. In physiological circulatory concentration, these molecules may have a role for the maintenance of cellular homeostasis. However, in stagnating physiological excess, these same agents can become acutely or chronically stimulating and, therefore, disease-precipitating. Such situations do exist in the clinical disorders of acne, atherosclerosis, acute pancreatitis, diabetes, diabetic retinopathy, homocysteinemea, and stress. A systematic approach, beginning with surface film studies with the suspect linear hydrocarbons, can be followed up with in vitro and in vivo studies. This should substantiate or negate the view presented here. Isolated information, along these lines, already exist in literature. The example of acne is a suitable starting point to elaborate this view, for sebaceous gland of the human pilosebaceous unit (PSU) contains all the exemplary, stimulus-inducing linear hydrocarbons to generate surface-reaction on the pilosebaceous ductal surface.

[Muscular genetic disorders caused by abnormal membrane excitability]. / Maladies musculaires génétiques causées par une excitabilité anormale de la membrane.

Ion channels are transmembrane proteins which enable ion exchanges between the inner and the outer part of the cell. During evolution, the property of ligand- or voltage-gating conferred cell excitability which permitted intercellular communication. The study of muscle diseases, periodic paralysis and myotonia, has led to the discovery of mutations in the genes encoding ion channels. The analysis of the functional consequences on muscle membrane gave insight into pathophysiology. A loss of function of sodium or calcium channels leads to hypokalaemic periodic paralysis. A gain of function of sodium channel results in hyperkalaemic periodic paralysis or paramyotonia, depending of its level. It is also known that mutations in other genes can cause membrane excitatibility such as the gene encoding perlecan (Schwartz-Jampel syndrome). The study of muscle channelopathies has opened a new field in neurological disorders. Molecular diagnosis is now possible and the efficacy of treatments is better understood.

Neutrophils are stimulated by syncytiotrophoblast microvillous membranes to generate superoxide radicals in women with preeclampsia.

OBJECTIVE: This study was undertaken to determine whether syncytiotrophoblast microvillous membranes (STBMs) stimulate maternal neutrophils to produce superoxide radicals in women with preeclampsia. STUDY DESIGN: Serum levels of tissue polypeptide antigen (TPA), which is a marker for STBM, were measured in 25 nulliparous women (10 with mild preeclampsia, 6 with severe preeclampsia, and 9 controls). Superoxide production by maternal neutrophils from cases and controls and by donor neutrophils cocultured with the STBMs from cases and controls was measured spectrophotometrically by reduction of ferricytochrome C. RESULTS: Maternal TPA levels were significantly greater among cases than controls (P=.005). Superoxide production by maternal neutrophils and donor neutrophils cultured with STBM from cases of preeclampsia was greater than controls (P values.006 and.019, respectively), and dose-response relationships were observed. Superoxide production by maternal leukocytes was correlated with superoxide induction by STBMs in culture (P=.007). CONCLUSION: STBMs in maternal blood induce neutrophils to generate superoxide radicals that may cause endothelial dysfunction in women with preeclampsia.

Clinical indices of in vivo biocompatibility: the role of ex vivo cell function studies and effluent markers in peritoneal dialysis patients.

Clinical indices of in vivo biocompatibility: The role of ex vivo cell function studies and effluent markers in peritoneal dialysis patients. Over the past 20 years, studies of the biocompatibility profile of peritoneal dialysis solutions (PDF) have evolved from initial in vitro studies assessing the impact of solutions on leukocyte function to evaluations of mesothelial cell behavior. More recent biocompatibility evaluations have involved assessments of the impact of PDF on membrane integrity and cell function in peritoneal dialysis (PD) patients. The development of ex vivo systems for the evaluation of in vivo cell function, and effluent markers of membrane integrity and inflammation in patients exposed both acutely and chronically to conventional and new PDF will be interpreted in the context of our current understanding of the biology of the dialyzed peritoneum. The available data indicate that exposure of the peritoneal environment to more biocompatible PDF is associated with improvements in peritoneal cell function, alterations in markers of membrane integrity, and reduced local inflammation. These data suggest that more biocompatible PDF will have a positive impact on host defense, peritoneal homeostasis, and the long-term preservation of peritoneal membrane function in PD patients.

Ion transport systems as targets of free radicals during ischemia reperfusion injury.

Oxidative stress is a recognized pathogenic factor in ischemia/reperfusion injury (IRI). Iron induced generation of reactive oxygen species (ROS) in vitro reduces both the Na+K+-ATPase activity and Na+-Ca2+ exchanger of synaptosomal membranes, concomitantly with alteration of physical state of membranes. Oxidative insult also leads to the loss of ability of endoplasmic reticular membranes (ER) to sequester Ca2+ as well as to the increase of Ca2+ permeability. Furthermore, ROS induces both lipid peroxidation and lipid-independent modifications of membrane proteins. Acute in vivo ischemia alters kinetic parameters of Na+K+-ATPase affecting mainly the dephosphorylation step of ATPase cycle with parallel changes of Na+-Ca2+ exchanger and alterations of physical membrane environment. Subsequent reperfusion after ischemia is associated with decrease of immuno signal for PMCA 1 isoform in hippocampus. In addition, incubation of non-ischemic membranes with cytosol from ischemic hippocampus decreases level of PMCA 1 in non-ischemic tissues. Loss of PMCA 1 protein is partially protected both by calpain- and by non-specific protease inhibitors which suggest possible activation of proteases in the reperfusion period. On the other hand, ischemia does not affect the level of Ca2+ pump (SERCA 2b) and calreticulin of intracellular Ca2+ stores. However, IRI resulted in a decrease of IP3 receptor I and altered active Ca2+ accumulation into the ER. A non-specific alteration of physical properties of total membranes such as the oxidative modifications of proteins as well as the content of lipoperoxidation products can also be detected after IRI. ROS can alter physical and functional properties of neuronal membranes. We discuss our results suggesting that ischemia-induced disturbation of ion transport systems may participate in or follow delayed death of neurons after ischemia.

[Long-standing high-transport membrane as a risk factor for EPS development after PD withdrawal: an analysis based on changes in peritoneal function during and after CAPD withdrawal].

The pathophysiology of encapsulating peritoneal sclerosis (EPS) that develops after withdrawal from long-standing dependence on CAPD remains unclear. The aim of this study was to clarify the risk factors for EPS as expressed in the peritoneal function. Fourteen patients who had shifted to standard hemodialysis after long-term CAPD (average, 105 months) were studied: 3 developed EPS after PD withdrawal while 11 did not. Analysis of the data obtained from the peritoneal equilibration test (PET) revealed that: (1) the dialysate/plasma creatinine ratio (D/Pcr) was significantly higher in the EPS group than in the non-EPS group during the course of PD as well as after PD withdrawal; and (2) eight patients, including the 3 with EPS, were classified as being in a high-transport membrane state (HTS) at PD withdrawal. The duration of HTS during PD was longer in those patients with EPS. During the periods after PD withdrawal, none of these EPS patients recovered from HTS, whereas 4 of the 5 non-EPS patients did. These data suggest that long-standing HTS during the course of PD as well as post-withdrawal, may be risk factors for EPS development. For this reason, it is indicated that PET has clinical relevance in examining sequential changes in peritoneal function and in detecting those patients at risk of EPS.

Changes in strain distribution along the radius and ulna with loading and interosseous membrane section.

The changes in strain distribution along the radius and ulna with loading and interosseous membrane (IOM) section were analyzed in this biomechanical study. Four cadaveric upper extremities were dissected and strain gauges applied. The forearm was loaded at the distal radius with a carpal implant after being positioned upright in neutral forearm rotation. Strain measurements were recorded before and after transection of the IOM. Before IOM transection, increased compressive strain was measured on the ulnar border of the ulna, while increased tensile strain was recorded on the dorsal aspect of the ulna, the dorsal aspect of the radius, and the lateral border of the radius when compared with the unloaded forearm. This suggests bowing of the radius and ulna with the convex side dorsally and bowing of the radius with the convex side radially. After IOM transection, increased tensile strain on the lateral border of the radius and the ulnar border of the ulna was measured when compared with the loaded forearm with an intact IOM. No change in strain patterns was measured by the strain gauges located on the dorsal aspect of the radius or ulna after IOM transection. The increased tensile strain during constant load application suggests increased bending moments acting on the radius and ulna after IOM transection.

Transcytotic vesicle fusion is reduced in cholestatic rats: redistribution of phospholipids in the canalicular membrane.

Cholestasis, which affects phospholipid trafficking, therefore would be expected to alter canalicular membrane phospholipid composition and fluidity, as well as fatty acid composition of membrane phospholipid. These alterations may affect transcytotic vesicle fusion and would be expected to cause variety of cholestatic phenomena. The aim of this study was to determine the effect of cholestasis on transcytotic vesicle fusion. Sprague-Dawley rats with extrahepatic and intrahepatic cholestasis were prepared by bile duct ligation (6 hr or three days) and phalloidin infusion (0.4 mg/kg body weight), respectively. Liposomes of phosphatidylserine/phosphatidylcholine were labeled with octadecyl rhodamine B chloride. Fusion of liposomes to canalicular membrane vesicle preparations from cholestatic and control rats was induced by the addition of calcium. The degree of fusion was evaluated by measuring the increase in rhodamine fluorescence. Membrane phospholipid content also was analyzed. Rates of liposomal fusion to membranes from cholestatic rats were decreased compared to controls. The saturated/unsaturated and saturated/polyunsaturated fatty acid ratios were increased in membrane phosphatidylcholine and decreased in membrane sphingomyelin from cholestatic rats. Cholesterol/phospholipid ratios were increased. Thus, in the presence of cholestasis, a redistribution of phospholipid species within canalicular membranes is associated with decreased transcytotic vesicle fusion. Cholestasis likely decreases membrane fluidity. The regulation of phospholipid species within hepatocellular membranes may play an important role in intrahepatic lipid transport.

Rotational instability and integrity of the interosseous membrane in cadaveric ulnar shaft fractures.

The stability of isolated ulnar shaft fractures required further investigation because no data were available for fractures in the middle third or on the effect on rotational stability. Ten intact cadaveric arms were used to study the pathomechanics of fractures of the middle ulna. In all of them a transverse osteotomy was performed (A), then in five of them, an additional osteotomy was done in order to create a third fragment (B). The interosseous membrane was subsequently divided for 2 cm on either side of the osteotomy (A-->C, C-->D). On radiographs the displacement was recorded in pronation and supination, and the rotational displacement was calculated. Rotational instability occurred in all fractures studied, even in the so-called stable ones. Also, dissection of the interosseous membrane was not followed by a displacement of more than 50%, and shortening of the ulna should also be considered in fractures with less than 50% displacement as a sign of instability.