Displacement Of Band Research Articles

Three-dimensional geometry and fabric of shear deformation-bands in unconsolidated Pleistocene sediments

We present an outcrop-based study on the 3D geometry and fabric of shear deformation-bands that developed in Middle Pleistocene, unconsolidated, glaciolacustrine delta sands in northern Germany. With a three dimensional model of a 3.38m³ outcrop we demonstrate deformation band geometries, analysis of band thickness and along-strike juxtaposition maps of beds against the deformation bands. The parallel thicknesses of the shear deformation-bands ranges from 0 to 8cm, with a mean of 1.5cm. Analysis of along-strike band displacement of intersecting shear deformation-bands proves the true displacement vector is close to dip-slip movement. The shear deformation-bands compensated a large lateral extension of ca. 10–20%. Though the deformation is unevenly distributed, this is a very high amount of deformation and this has wide implications when upscaled to the whole outcrop or locality. Grain size within the shear deformation-bands is identical to the grain-size distribution of the parent sediment. Conventional Fry analysis of grains in the shear deformation-bands shows strain ratios of 1.4. This, however, is an artifact of bulk grain-shape, since a normalized Fry plot shows strain close to unity. We observe a two-stage calcite overgrowth on the grains of the deformation band (radial sparite followed by micrite). We thus propose grain-boundary sliding (possibly aided by calcite-rich fluids) to be the dominant deformation mechanism. The deformation bands are very likely the product of young basement tectonics and may be related to movements in the crest of a salt anticline. In the study area, the observation of young basement tectonics is a novelty.

What are the most frequent complications of Fobi-Capella bariatric surgery and how to treat them?

The mortality rate of the Fobi-Capella bariatric surgery can reach up to 1% in large series and general complica-tions can occur in up to 40% of the cases. We will cite the most frequent complications and will attempt to describe the best way to prevent and treat them, to the best of our knowledge. 1. Gastrojejunal anastomosis fistula: it is a feared complication and difficult to diagnose. The pa-tient can have only tachycardia, in the beginning, and later develop dyspnea and pleural effusion. The last thing to be perceived is peritonitis. Its occurrence rate can be decreased by carrying out a careful anastomosis and performing a second plane of suture over the clamping of the small gastric chamber. The maneuver that consists of injecting saline solution with methylene blue through the orogastric tube can disclose small leaks in the anastomosis, which can be corrected during the intraoperative period. We also suggest the placement of drain in this region, exteriorized to the left flank, which diagnoses and guides the fistula when the latter appears. In cases where the patient did not receive a drain and fistula di-agnosis was suspected, we suggest an immediate surgical reapproach, with washing of the cavity, ample draining of the abdominal cavity and per-forming a gastrostomy in the large excluded gas-tric chamber for feeding. 2. Surgical wound hematoma-seroma: it can be minimized by carefully washing the surgical wound and subcutaneous approximation. Wear-ing an elastic abdominal support can also help decrease its incidence in the postoperative pe-riod. 3. Incisional herniation: its incidence is higher in the open surgery than in the one performed by videolaparoscopy. Aponeurosis must be pref-erably closed with nonabsorbable sutures and stitches should be placed closed to each other. Wearing an elastic abdominal support can help and must be encouraged for at least 60 days after surgery. 4. Pulmonary embolism: it is a rare complication, albeit a feared one. Its incidence can be decreased by wearing support hose or knee-high compres-sions stockings in immediate intra- and post-operative periods. Early ambulation must be encouraged and motor physical therapy must be prescribed as early as in the immediate post-operative period. Use of anticoagulants in the postoperative period is mandatory for 10 days after the surgery. 5. Postoperative atelectasis and pneumonia: can af-fect up to 3% of the cases and prophylactic an-tibiotic therapy and respiratory physical therapy must be carried out during the hospitalization. Physical therapy with positive-pressure must not be performed due to the risk of air ingestion and gastrointestinal suture rupture. 6. Persistent nausea and vomiting: can occasionally occur and, in these cases, Wernicke’s syndrome can appear. This is a severe syndrome and can re-sult in significant neurological sequelae. In these cases, vitamin B1 (thiamine) must be adminis-tered by IV route as long as the vomiting persists. 7. Gastrojejunal anastomosis stenosis: it is the most frequent one when round staples are used instead of linear ones, when performing the anastomo-sis. It tends to have a lower incidence in manual anastomoses. We recommend an anastomosis of approximately 3 cm or more in length to prevent stenosis. Treatment of stenosis is satisfactory through endoscopic dilatation. 8. Complications with the band: band rupture can occur, as well as band displacement with stom-ach obstruction or erosion when the band enters the gastric lumen. Due to these complications, we have decreased band use, indicating it only for super-obese patients. In individuals whose BMI < 50, the band is no longer used. 9. Intestinal obstruction: a severe complication that occurs due to small intestine herniation. Its treat -ment is surgical and must be carried out imme-diately. Treatment delay can lead to necrosis of

Low-temperature electrical conductivity and the superconductor-insulator transition induced by indium impurity states in (Pb0.5Sn0.5)1 − x In x Te solid solutions

A study is reported of the low-temperature electrophysical (including superconducting) characteristics of the (Pb0.5Sn0.5)1 − xInxTe semiconducting solid solutions with an indium content variable within x = 0.05–0.20. A decrease in the impurity content x in the material has been found to bring about a decrease in the superconducting transition temperature Tc and the onset of an “insulating” state of the material. These effects manifest themselves in an increase in the low-temperature (T = 4.2 K) resistivity of (Pb0.5Sn0.5)0.95In0.05Te by more than three orders of magnitude as compared to that of (Pb0.5Sn0.5)0.8In0.2Te. A decrease in the In content in the solid solution also gives rise to a radical change in the shape of the temperature dependence of the electrical resistivity from a metallic behavior in the material with x = 0.20 (decrease in the electrical resistivity with decreasing temperature in the range 300–4.2 K) to a semiconducting behavior in a sample with x = 0.05 (exponential increase in the resistivity at T < 25 K). This transition to the insulating state with decreasing content of the impurity should be assigned to the displacement of the impurity band of quasi-local indium states toward the top of the light-hole valence band of the material and its emergence into the band gap of the solid solution.

Structural importance of residue 334 in the stability of cytochromes P450 2B6 and 2B11

Human P450 2B6 and canine P450 2B11 play an important role in xenobiotic metabolism, bioremediation research, and activation of anti‐cancer prodrugs. Thorough biochemical and biophysical characterization of the enzymes has been impeded by relatively low stability compared to the extensively studied rat 2B1 and rabbit 2B4. Comparison of the amino acid sequences of N‐terminal truncated and C‐terminal His‐tagged constructs revealed seven sites that are conserved between the more stable 2B1 and 2B4 but different from those found in the less stable 2B6 and 2B11. Site‐directed mutagenesis at these positions showed that P334→ Ser substitution increased heterologous expression levels and thermal stability in both 2B6 and 2B11. The mechanism of this effect was explored with pressure‐perturbation spectroscopy. Compressibility of the heme pocket in the four P450 2B enzymes and their P334S (2B6 and 2B11) or S334P (2B1 and 2B4) mutants was assessed from the pressure induced displacement of the Soret band. The variants of all four enzymes containing proline at position 334 are characterized by lower compressibility than their more stable serine 334 counterparts. Therefore, the stabilizing effect of P334S is associated with increased conformational flexibility in the region of the heme pocket. Mutation of the non‐active site residue P334→ Ser could find applications in drug metabolism and gene therapy for cancer treatment.

A regional climate model simulation over West Africa: parameterization tests and analysis of land-surface fields

The West African Monsoon has been simulated with the regional climate model PROMES, coupled to the land-surface model ORCHIDEE and nested in ECMWF analysis, within AMMA-EU project. Three different runs are presented to address the influence of changes in two parameterizations (moist convection and radiation) on the simulated West African Monsoon. Another aim of the study is to get an insight into the relationship of simulated precipitation and 2-m temperature with land-surface fluxes. To this effect, data from the AMMA land-surface model intercomparison project (ALMIP) have been used. In ALMIP, offline simulations have been made using the same land-surface model than in the coupled simulation presented here, which makes ALMIP data particularly relevant for the present study, as it enables us to analyse the simulated soil and land-surface fields. The simulation of the monsoon depends clearly on the two analysed parameterizations. The inclusion of shallow convection parametrization affects the intensity of the simulated monsoon precipitation and modifies some dynamical aspects of the monsoon. The use of a fractional cloud-cover parameterization and a more complex radiation scheme is important for better reproducing the amplitude of the latitudinal displacement of the precipitation band. This is associated to an improved simulation of the surface temperature field and the easterly jets. However, the parameterization changes do not affect the timing of the main rainy and break periods of the monsoon. A better representation of downward solar radiation is associated with a smaller bias in the surface heat fluxes. The comparison with ALMIP land-surface and soil fields shows that precipitation and temperature biases in the regional climate model simulation are associated to certain biases in land-surface fluxes. The biases in soil moisture seem to be driven by atmospheric biases as they are strongly affected by the parameterization changes in atmospheric processes.

“Heavy Eye” syndrome in the absence of high myopia: A connective tissue degeneration in elderly strabismic patients

In axial high myopes with "heavy eye" syndrome, orbital MRI can be use to demonstrate degeneration of the lateral rectus-superior rectus (LR-SR) band, with the result that the lateral rectus muscle slips inferiorly and causes esotropia and hypotropia. We investigated whether this degeneration might also cause strabismus in nonmyopic elderly patients. Three elderly patients with strabismus, 3 strabismic high myopes, and 12 orthotropic elderly subjects underwent ophthalmic examinations and orbital MRI. The lateral rectus muscle position was determined relative to globe center from quasicoronal images and correlated with LR-SR band structure. MRI scans were compared with histology of 4 cadaveric orbits ranging in age from 17 months to 93 years. Two strabismic patients exhibited hypotropia; one exhibited esotropia. Mean axial length was 24.1 +/- 0.8 mm (mean +/- SD), compared with 31.6 +/- 1.4 mm for myopes. The lateral rectus muscle position of elderly strabismic subjects averaged 4.6 +/- 1.7 mm inferior to globe center, which was significantly lower than that of orthotropic elderly subjects (2.1 +/- 1.9 mm; p = 0.01) and similar to that of high myopes (5.1 +/- 3.2 mm). On MRI scanning, 100% of strabismic elderly orbits, 67% of strabismic myopic orbits, and 12.5% of control elderly orbits showed LR-SR band thinning, discontinuity, or displacement. LR-SR band degeneration was present histologically only in older cadavers. Age-related LR-SR band degeneration permits the lateral rectus muscle to slip inferiorly in elderly nonmyopes, a mechanism of strabismus similar to myopic "heavy eye" syndrome. Imaging may assist in diagnosing this mechanical cause of age-related strabismus.

Anion-Exchange Chromatographic Separation of Hg for Isotope Ratio Measurements by Multicollector ICPMS

A procedure is described for precise Hg isotope ratio measurements by solution nebulization multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). Hg was released from geological samples using aqua regia extraction and then separated from other matrix elements with the aid of anion-exchange chromatography using strongly basic Dowex 1-X8 anion-exchange resin. Performance of the chromatographic procedure was evaluated using various types of replacement anions for elution of mercury, including l-cysteine, thiourea, NO3-, and SO42-. A solution of 0.15% l-cysteine in 0.06 M HCl was found to be the most convenient eluent for subsequent MC-ICPMS measurements. The optimized procedure provides separation of Hg from virtually all concomitant matrix elements while maintaining quantitative (>95%) recovery. In addition, band displacement chromatographic experiments were conducted to assess whether the anion-exchange purification can produce Hg isotope fractionation artifacts. No isotope fractionation between the Hg(II)-l-cysteine complex in aqueous solution and Hg ions in the anion-exchange resin was observed. Hg isotope ratio measurements were performed using the bracketing standards approach and on-line correction for instrumental mass discrimination using Tl spiking and normalization to the 205Tl/203Tl ratio. The absence of spectral interference during Hg isotope ratio measurements was verified using a three-isotope plot. Uncertainties of Hg isotope ratio measurements for replication of the entire procedure, expressed as two standard deviations, are better than +/-0.08 per thousand/amu. The described procedure facilitates study of variations in the isotopic composition of Hg in nature.

Crystal chemistry of the divalent cation in alluaudite-type phosphates: A structural and infrared spectral study of the Na 1.5( [formula omitted]) 1.5Fe 1.5(PO 4) 3 solid solutions ( x=0 to 1, M2+=Cd 2+, Zn 2+)

Compounds of the Na 1.5(Mn 1− xM x 2+) 1.5Fe 1.5(PO 4) 3 ( M 2+=Cd 2+, Zn 2+) alluaudite-type solid solutions were synthesized by solid-state reactions in air, between 800 and 900 °C, and were investigated by X-ray powder diffraction and infrared spectroscopy. The site occupancy factors of the Na 1.5(Mn 1− x Cd x 2+) 1.5Fe 1.5(PO 4) 3 compounds, obtained from the Rietveld refinements of the X-ray powder patterns, indicate that the replacement of Mn 2+ by Cd 2+ takes place on the M(1) site for x=0.25 and 0.50, and then on the M(1) and M(2) sites for x=0.75 and 1.00. Small amounts of Cd 2+ were also detected on the A(1) site, compensated by small amounts of Na + occurring on M(1). This partially disordered distribution is probably due to the similar effective ionic radii of Cd 2+ and Na +. The cationic distributions in the Na 1.5(Mn 1− x Zn x 2+) 1.5Fe 1.5(PO 4) 3 solid solution indicate that Zn 2+ was first introduced in the M(2) site, before to replace Mn 2+ in the M(1) site. The unit-cell parameters show a significant increase when Mn 2+ is replaced by Cd 2+, and a significant decrease when it is replaced by Zn 2+. The variations of the β angle were also correlated with the M(1)– M(2) distances. The infrared spectra show the displacement of an absorption band at ca. 400–425 cm −1, which is assigned to the vibrations of the M 2+ cations localized on the M(1) site. This assignment is confirmed by the excellent correlations between the M(1)–O bond distances and the energy of the absorption band.

Ocular coherence tomography in acute posterior multifocal placoid pigment epitheliopathy

The authors report a case of typical acute posterior multifocal placoid pigment epitheliopathy in which an ocular coherence tomographic scan was performed through an acute lesion and then repeated through the same lesion 12 months later. The initial ocular coherence tomographic scan showed marked anterior displacement of both neuroretina and outer reflective band. A subsequent ocular coherence tomographic scan revealed resolution of the prior displacement, increased reflectance of the outer reflective band and mild disruption of the outer retinal layers. These findings are consistent with a primary choroiditis.

Estudo da degradação da intensidade de fotoluminescência de filmes finos de óxido de alumínio dopados com cério

Filmes finos de alumina dopados com cério depositados por spray-pirólise podem ser utilizados como emissores fotoluminescentes na faixa do violeta-azul (360 - 410 nm). Todos os espectros destes filmes apresentaram espectros assimétricos resultantes da superposição de dois picos centrados em 365 e 395 nm. Os filmes envelhecidos apresentaram intensidade de luminescência menor que a observada nas amostras como-depositadas. Além disto, foi observado nos espectros das amostras envelhecidas um desvio da banda de emissão para menores comprimentos de onda. O tratamento térmico a 300 ºC durante oito horas diminuiu a intensidade de luminescência tanto das amostras como-depositadas como envelhecidas. Os filmes tratados apresentaram ainda uma razão entre as áreas dos picos centrados em 365 e 395 nm, menor que a observada nos filmes não-tratados levando ao deslocamento da banda de emissão para maiores comprimentos de onda.

Anex vivoevaluation of resin-modified glass polyalkenoates and polyacid-modified composite resins as orthodontic band cements

The objective of this ex vivo study was to assess the use of resin-modified glass polyalkenoates and polyacid-modified composite resins, as orthodontic band cements. Plain stainless steel bands were cemented to 350 human extracted third molar teeth using 1 of 7 different cements. Following complete cement cure, half of each sample group was exposed to mechanical stress in a ball mill. Stressed and unstressed samples were tested in tension and the stress at which initial cement failure recorded. The mode of failure was recorded using an adhesive remnant evaluation. The mean band retention stresses offered by the cements studied ranged from 0.96 to 1.56 MPa. Fuji Ortho provided the highest mean band retention stress in "stressed" (1.56 MPa) and "unstressed" (1.45 MPa) states. Exposure to mechanical stress did not appear to significantly influence band retention or mode of cement failure for most cements. Fuji Ortho cement recorded the highest Weibull modulus for all cements tested. Virtually all samples failed at either the cement/enamel or cement band interface. Significant differences in band displacement stress values and mode of failure were demonstrated between the cements studied. However, generic comparisons were difficult to make.

Numerical simulation of the temperature dependence of the ionization energy of hydrogen-like impurities in semiconductors: Application to transmutation-doped Ge: Ga

An electrostatic model describing the dependence of the thermal ionization energy of impurities on their concentration, compensation factor, and temperature is developed. The model takes into account the screening of impurity ions by holes (electrons) hopping from impurity to impurity, the change in the impurity-band width, and its displacement with respect to the edge of the valence band for acceptors (conduction band for donors). The displacement of the impurity band is due to the functional dependence of the hole (electron) affinity of the ionized acceptor (donor) on the screening of the Coulomb field of the ions. The spatial distribution of the impurity ions over the crystal was assumed to be Poisson-like, and the energy distribution was assumed to be normal (Gaussian). For the relatively low doping levels under investigation, the behavior of the density of states at the edges of the valence and conduction bands was assumed to be the same as for the undoped crystal. The results of the numerical study are in agreement with the decrease in the ionization energy that is experimentally observed for moderately compensated Ge: Ga as the temperature and the doping level are decreased. It is predicted that the temperature dependence of the thermal ionization energy has a small anomalous maximum at small compensation factors.

Estudo histológico das estruturas periodontais comparando o afastamento gengival pelo uso do anel de cobre e godiva em relação ao uso do fio de algodão, em cães

This study carried out three dogs to gingival displacement comparing the copper band and compound gingival displacement and impression technique with string impregnated in aluminium chloride with gingival displacement technique, and single impression by condensing silicone impression material. The objective was to compare the periodontal biocompability between the two techniques. Blocks specimens including the teeth and the soft tissue were taken immediately, 0, 7, 14 and 21 days, and had histological analysis with stain hematoxilin and eosin. The results showed that all groups had reversible histological consequences.

Surface plasmon resonance of azobenzene‐incorporated polyelectrolyte thin films as an H+ indicator

AbstractAn azo‐dye‐incorporated polyionene was spin‐coated as thin films on silver evaporated glass substrates. The films were used in conjunction with surface plasmon resonance (SPR) spectroscopy to examine the utility of combining these techniques for optical H+‐ion sensing. A method suggested by Kano and Kawata was used to enhance the sensitivity of the classical SPR measurements toward absorption detection. With the exposure of the composite polyionene films to HCl vapor, changes in the reflectivity signal were obtained in proportion to the concentration of H+ ions and according to the analyzing wavelength. The transformation of the parent azobenzene into the azohydrazone polar form determined the displacement of the absorption band and was the basis for the absorption‐enhanced SPR measurements. The difference in the SPR signals for the neutral sample and that exposed to interaction with HCl was most demonstrated for the wavelength at which the sample spectrum changed from being nonabsorbing to absorbing. The results show that chromophoric polyionenes are good materials for the production of sensitive substrates and can be combined with SPR spectroscopy for the optical sensing of aggressive gaseous species. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1459–1464, 2002

Dynamic sonography of external snapping hip syndrome.

To evaluate the dynamic sonographic findings of external snapping hip syndrome. Five patients with 7 cases of painful external snapping hip (3 male and 2 female; age range, 14-32 years; mean, 19 years) were examined with sonography. Two patients had bilateral snapping. Dynamic sonographic examinations of hips were performed with a linear 5- to 12-MHz transducer during hip motion. Dynamic sonographic studies of the affected hip revealed causes of the external snapping hip in all cases. It was elicited by an abnormal jerky movement of the iliotibial band overlying the greater trochanter in 5 of 7 cases and of the gluteus maximus muscle in 2 cases. The iliotibial band over the greater trochanter was hypoechoic in 3 of the 5 cases and thickened in 1 case. Dynamic sonography showed good correlations between the jerky movements of the iliotibial band and the gluteus maximus muscle and the painful snapping reported by the patients. Dynamic sonography was helpful in the diagnosis of external snapping hip syndrome; it showed real-time images of sudden abnormal displacement of the iliotibial band or the gluteus maximus muscle overlying the greater trochanter as a painful snap during hip motion.

SEPARATION OF STABLE NITROGEN ISOTOPES BY ION EXCHANGE CHROMATOGRAPHY

ABSTRACT The ion exchange chromatography technique was used for the enrichment of nitrogen 15 (15N). A set of columns filled with the ion exchange resin Wofatit KPS (medium porosity type) with 5.4 cm I.D. and 1.5 m height was set up. Ammonia NH4 +/NH3 aq. was chosen as the isotopic exchange system. The ammonium bands formed in the columns were eluted by a solution of sodium hydroxide. The isotope separation factor, ϵ, was found to decrease with increasing temperature or ammonia concentration. Operational conditions of temperature and ammonium concentration were proposed as the optimum for the production of the enriched isotope by using the present process. Results showed that: (1) the rear part of the band is enriched in 15N, while the frontal part is depleted; (2) it is possible to obtain 7.6 at. % of 15N after a 60 m displacement of the ammonium band. The analytical determination of the samples was made by emission spectrometry (NOI-6E).

Stabilization of P450 2B4 by Its Association with P450 1A2 Revealed by High-Pressure Spectroscopy

We studied the effect of intermolecular interactions between cytochromes P450 1A2 (CYP1A2) and 2B4 (CYP2B4) on the barotropic inactivation of the ferrous carbonyl complexes of the hemoproteins. When taken separately, these hemoproteins reveal quite distinct barotropic behavior. While the 2B4(Fe2+)-CO complex is very sensitive to hydrostatic pressures and undergoes P450 → P420 transition at rather low pressures (P1/2 = 297 MPa, ΔV0 = −61 ml/mol), the 1A2(Fe2+)-CO is extremely resistant to barotropic inactivation. Only about 8% of the 1A2 was exposed to pressure-induced P450 → P420 transition (P1/2 = 420 MPa, ΔV0 = −28 ml/mol). The formation of the mixed oligomers of 2B4 and 1A2 was found to have a dramatic effect on the barotropic behavior of 2B4. In the heterooligomers of 1A2 and 2B4, the 2B4 hemoprotein appears to be largely protected from barotropic inactivation. In 1:1 mixed oligomers no more than 25% of the total P450 content undergoes P450 → P420 inactivation with the molar reaction volume value (ΔV0 = −26 ml/mol) similar to those found for pure 1A2. Moreover, interactions between 1A2 and 2B4 results in a displacement of the Soret band of the ferrous carbonyl complex of CYP2B4 to shorter wavelength (from 451.3 to 448.4 nm) and largely strengthens the dependence of the Soret band wavenumber on hydrostatic pressure below 200 MPa. This effect suggests an important hydration of the CYP2B4 heme moiety in response to the interactions with CYP1A2. We discuss these results in terms of the hypothesis that the heterooligomerization of cytochromes P450 in microsomes plays an important role in the control of the activity and coupling of the microsomal monooxygenase.

Photophysics of Nile red in solution: Steady state spectroscopy

Spectroscopic properties of Nile red (NR) in organic solvents, binary solvent mixtures have been studied. Remarkable shifts in the emission band positions have been observed as a function of the polarity of the medium. In solvent mixtures, these shifts can be explained by the process of specific solvation known as dielectric enrichment. The displacement of the fluorescence band was also measured as a function of temperature to obtain the thermochromic shifts (15 cm −1 K −1 in methyltetrahydrofuran and 13.8 cm −1 K −1 in butanol). Excited state dipole moments were calculated from these shifts.

Compartmentalization of the erythrocyte membrane by the membrane skeleton: intercompartmental hop diffusion of band 3.

Recent developments in microscopic instrumentation and probes have allowed the observation and manipulation of the movement of membrane proteins and lipids in the plasma membrane at the level of single molecules. These experiments are performed by tracking small colloidal gold particles attached to specific membrane proteins and lipids (single particle tracking) (Jacobson et al., 1995 ; Sheets et al., 1995 ; Kusumi and Sako, 1996 ; Saxton and Jacobson, 1997 ) or by dragging particle–protein complexes along the surface of the plasma membrane using laser tweezers (also termed an “optical trap” or OT) (Edidin et al., 1991 ; Kusumi and Sako, 1996 ; Kusumi et al., 1998 ). In optimal cases, a single protein molecule is attached to a 40-nm-diameter colloidal gold probe (Tomishige et al., 1998 ). These single molecule experiments have demonstrated that most membrane-spanning proteins do not undergo simple diffusion, but that a significant number are locally slowed or stopped, some are temporarily confined, and others are transported unidirectionally (Kusumi et al., 1993 ; Sheets et al., 1997 ; Sako et al., 1998 ; Simson et al., 1998 ). Previously, these processes had not been observed, because the methods used, e.g., fluorescence recovery after photobleaching, recorded the ensemble-averaged behavior of a large number of molecules. The underlying cellular mechanisms that induce nonrandom diffusion have remained largely unknown; however, we and others found that properties of the membrane skeleton network fundamentally affect the movement and distribution of certain membrane proteins, such as transferrin receptor, α2-macroglobulin receptor, MHC class I molecules, E-cadherin, and band 3, through corralling and binding effects imposed by the membrane skeleton network (Edidin et al., 1991 ; Luna and Hitt, 1992 ; Kusumi et al., 1993 ; Sako and Kusumi, 1994 , 1995 ; Sako et al., 1998 ; Tomishige et al., 1998 ). The results are particularly clear with band 3 in human erythrocyte ghost membranes, where the specimen consists of a lipid bilayer and its underlying membrane skeleton, which has been biochemically and biophysically well characterized (Golan, 1989 ; Bennett, 1990 ; Bennett and Gilligan, 1993 ; Mohandas and Evans, 1994 ). The results obtained by these studies support a “membrane skeleton fence model” in which the cytoplasmic portion of a membrane protein collides with the membrane skeletal “meshwork” because of steric hindrance, thus resulting in the temporal confinement of the protein within the mesh (compartment, Figure ​Figure1A).1A). Membrane proteins escape from these compartments and hop to adjacent ones because of the dynamic properties of the membrane skeleton. We predict that time-dependent fluctuations in the distance between the membrane and the skeleton are large or the membrane–skeleton network connections form and break continuously, as expected in a chemical equilibrium, providing membrane proteins with the opportunity to pass through the mesh barrier. In the case of band 3, macroscopic diffusion within the erythrocyte membrane occurs as the result of a series of such intercompartmental hops. Figure 1 (A) The model to explain the confined diffusion of band 3 in the membrane (the membrane skeleton fence model). (B) Movement of gold particles attached to band 3 in the erythrocyte membrane, observed with a temporal resolution of 8 ms (4 times greater ... The scientific content of this work has been published previously (Tomishige et al., 1998 ), and the purpose of the present essay is to give the reader a glimpse of the raw data from this study, as recorded by both normal and high-speed video microscopy. We hope the video sequences attached to this article will help the viewing audience develop a feel for how band 3 interacts with the membrane skeleton and undergoes intercompartmental hop diffusion within the erythrocyte ghost membrane.

Commentary

In the article by Alva and associates, the authors report their institutional experience with double-chambered right ventricle over an 8-year period. This report serves to expand our knowledge on the morphologic nature of this entity. Their objective was to study the muscular division of the right ventricle by correlating morphologic, echocardiographic, and angiographic findings. Double-chambered right ventricle, the partitioning of the right ventricle into 2 chambers, has been recognized since at least 18671Peacock T. Malformation of the human heart.in: Churchill and Sons, London1967: 75-79Google Scholar and is produced by prominent anomalous muscle bundles within the right ventricular cavity. Although frequently associated with membranous ventricular septal defects,2Simpson W Sade R Crawford F Taylor A Fyfe D. Double-chambered right ventricle.Ann Thorac Surg. 1987; 44: 7-10Abstract Full Text PDF PubMed Scopus (26) Google Scholar other anatomic forms have also been reported.3Baumstark A Fellows K Rosenthal A. Combined double chambered right ventricle and discrete subaortic stenosis.Circulation. 1978; 57: 299-303Crossref PubMed Scopus (41) Google Scholar, 4Gallucci V Scalia D Thiene G Mazzuco A Valfre C. Double-chambered right ventricle: surgical experience and anatomical considerations.Thorac Cardiovasc Surg. 1980; 28: 13-17Crossref PubMed Scopus (17) Google Scholar, 5Rowland T Rosenthal A Castaneda A. Double chamber right ventricle: Experience with 17 cases.Am Heart J. 1985; 89: 455-462Abstract Full Text PDF Scopus (67) Google Scholar Most recently, my colleagues and I6Moran AM Hornberger LK Jonas RA Keane JF. Development of a double-chambered right ventricle after repair of tetralogy of Fallot.J Am Coll Cardiol. 1998; 31: 1127-1133Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar reported our own institutional experience of the development of double-chambered right ventricle in postoperative patients with tetralogy of Fallot, with a minimal occurrence rate of 3.1%. An underlying anatomic substrate was recently suggested by Wong and colleagues.7Wong PC Sanders SP Jonas RA Colan SD Parness IA Geva T et al.Pulmonary valve–moderator band distance and association with development of double-chambered right ventricle.Am J Cardiol. 1991; 68: 1681-1686Abstract Full Text PDF PubMed Scopus (64) Google Scholar They described the presence of a displaced insertion of moderator band into the septal band. This pattern of insertion was recognized both in pathologic specimens and in clinical cases. The evaluation in human beings used 2-dimensional echocardiographic methods. This displacement of the moderator band was further quantified as the distance of the insertion point from the pulmonary valve indexed to the tricuspid valve. The report by Alva and colleagues furthers our understanding of this pathologic entity. They confirm the frequent association with membranous ventricular septal defects and even include a single patient after repair of tetralogy of Fallot. By evaluating several normal anatomic specimens, they highlight the variability in the presence of the moderator band (noting prominent septoparietal trabeculations without the presence of a discrete moderator band in 2). More important, they provide quantitative evidence of 2 distinct anatomic subtypes of double-chambered right ventricle, suggesting that these represent either displaced septoparietal trabeculations or moderator bands that undergo marked hypertrophy. Finally, they provide a quantitative method for assessing the position of such muscle bars relative to the long axis of the right ventricle using angiographic imaging. It is unfortunate that they were unable to attempt a similar analysis using echocardiography, since this is the initial imaging modality of choice in the current era. This inability is sure to reflect the retrospective nature of their study. Although this report increases our knowledge of this intriguing anatomic entity, several questions are left unanswered. The prospective application of previously described ratios (listed above) to identify at-risk patients is awaited. If successfully validated, this could lead to “prophylactic interventions” at the time of other cardiac operations. Clinically, the long-term follow-up of surgically treated patients warrants evaluation, because we6Moran AM Hornberger LK Jonas RA Keane JF. Development of a double-chambered right ventricle after repair of tetralogy of Fallot.J Am Coll Cardiol. 1998; 31: 1127-1133Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar have previously reported recurrence of such obstructions. Finally, the stimulus to hypertrophy in such patients is as yet unknown and may, in part, reflect altered flow dynamics. Further work is required.