The mutation of Pro789 to Leu reduces the activity of the fast-twitch skeletal muscle sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA1) and is associated with Brody disease

Brody disease is a rare inherited disorder of fast-twitch skeletal muscle function and is characterized by a lifelong history of exercise-induced impairment of skeletal muscle relaxation, stiffness, and cramps. The autosomal recessive inheritance of mutations in ATP2A1, the gene encoding SERCA1, which is the fast-twitch skeletal muscle sarcoplasmic reticulum Ca2+ ATPase, has been associated with Brody disease in three of six Brody families in which ATP2A1 has been sequenced. In the present analysis of the ATP2A1 gene in four unrelated families with autosomal recessive inheritance of Brody disease, three mutations were found in two families, leading to premature stop codons and truncated SERCA1. In a third family, the homozygous substitution of T for C2366 led to the missense mutation of Pro789 to Leu. The Pro789 to Leu mutant was readily expressed in HEK-293 cells, but it demonstrated an almost complete loss of Ca2+ transport activity because of reduced Ca2+ affinity. In a fourth family, the heterozygous substitution of T for C2455, mutating Arg819 to Cys, was identified. This mutation was also readily expressed in HEK-293 cells and shown to have near normal Ca2+ transport activity, indicating that it is not causal for Brody disease. These results confirm the genetic heterogeneity of Brody disease and emphasize the importance of a functional test for mutant SERCA1; immunostaining of skeletal muscle to detect the loss of SERCA1a protein is not adequate for the diagnosis of ATP2A1-linked Brody disease.     

Knowledge and power in the clinical setting

In this paper we consider the three categories offered by Howard Brody for understanding power in medicine. In his book, The Healer's Power Brody separates out power in medicine into the categories of Aesculapian, Social, and Charismatic power. We examine these three categories and then apply them to a case. In this case set in an Obstetric ward, a junior member of the medical staff makes a clinical decision about a patient. This clinical decision is overruled by a senior medical staff member who then carries out his plan with disastrous consequences for the woman and her baby. This case challenges the three categories of power offered by Brody and highlights the need for a further category of Hierarchical power to be added to Brody's framework. We conclude by suggesting that there is a need to recognise the discrepancy in power not only between physician and patient but also between senior and junior staff in a clinical setting.     

Knowledge and Power in the Clinical Setting

In this paper we consider the three categories offered by Howard Brody for understanding power in medicine. In his book, The Healer's Power Brody separates out power in medicine into the categories of Aesculapian, Social, and Charismatic power. We examine these three categories and then apply them to a case. In this case set in an Obstetric ward, a junior member of the medical staff makes a clinical decision about a patient. This clinical decision is overruled by a senior medical staff member who then carries out his plan with disastrous consequences for the woman and her baby. This case challenges the three categories of power offered by Brody and highlights the need for a further category of Hierarchical power to be added to Brody's framework. We conclude by suggesting that there is a need to recognise the discrepancy in power not only between physician and patient but also between senior and junior staff in a clinical setting.     

Characterization of the Gene Encoding Human Sarcolipin (SLN), a Proteolipid Associated with SERCA1: Absence of Structural Mutations in Five Patients with Brody Disease

Sarcolipin (SLN) is a low-molecular-weight protein that copurifies with the fast-twitch skeletal muscle sarcoplasmic reticulum Ca²⁺ATPase (SERCA1). Genomic DNA and cDNA encoding human sarcolipin (SLN) were isolated and characterized and theSLNgene was mapped to chromosome 11q22–q23. Human, rabbit, and mouse cDNAs encode a protein of 31 amino acids. Homology of SLN with phospholamban (PLN) suggests that the first 7 hydrophilic amino acids are cytoplasmic, the next 19 hydrophobic amino acids form a single transmembrane helix, and the last 5 hydrophilic amino acids are lumenal. The cytoplasmic and transmembrane sequences are not well conserved among the three species, but the lumenal sequence is highly conserved. Like SERCA1, SLN is highly expressed in rabbit fast-twitch skeletal muscle, but it is expressed to a lower extent in slow-twitch muscle and to an even lower extent in cardiac muscle, where SERCA2a and PLN are highly expressed. It is expressed in only trace amounts in pancreas and prostate.SLNandPLNgenes resemble each other in having two small exons, with their entire coding sequences lying in exon 2 and a large intron separating the two segments. Brody disease is an inherited disorder of skeletal muscle function, characterized by exercise-induced impairment of muscle relaxation. Mutations in theATP2A1gene encoding SERCA1 have been associated with the autosomal recessive inheritance of Brody disease in three families, but not with autosomal dominant inheritance of the disease. A search for mutations in theSLNgene in five Brody families, four of which were not linked toATP2A1,did not reveal any alterations in coding, splice junction or promoter sequences. The homozygous deletion of C438 in the coding sequence ofATP2A1in Brody disease family 3, leading to a frameshift and truncation following Pro₁₄₇in SERCA1, is the fourthATP2A1mutation to be associated with autosomal recessive Brody disease.     

Mathematical modelling of intra- and extracellular potentials generated by active structures with short regions of increased diameter

The Hodgkin-Huxley (1952) model was used to calculate intracellular potentials by the method of Joyner et al. (1978). Extracellular potentials were estimated on the basis of a mathematical model proposed by us. It has shown that, irrespective of practical isopotentiality of the membrane of a local inhomogeneity, the latter affects extracellular potentials in two ways: 1) through changes in the potential profile in the region of the structure before the inhomogeneity; 2) through its own potential profile. The first effect is considerably greater than the second one, but the second is greater than the effect of the equal portion of the thin fibre. Increase in the diameter or length of an inhomogeneity is combined with such changes in the potential profile, that the effect of the inhomogeneity on the extracellular potential amplitude is practically independent of its actual size. The extracellular potential waveform substantially depends on the ratio of the diameters of the two parts of the structure and on the position of the inhomogeneity in relation to the sealed structure end. Registration of the positive-negative potentials having a large positive phase should not be considered as an indication of passive properties of the structure.     

Effect of local pulmonary blood flow control on gas exchange: theory

The effect of local pulmonary blood flow control by local alveolar O2 tension on steady-state pulmonary gas exchange is analyzed with techniques derived from control theory. In a single homogeneous lung unit with normal inspired and mixed venous blood gas composition, the homeostatic effect on local ventilation-perfusion ratios (VA/Q) regulation occurs over a restricted range of VA/Q. The homeostatic effect is maximal at a moderately low VA/Q (about 0.4) due to the slope of the O2 dissociation curve. In a multicompartment lung with a lognormal distribution of VA/Q, regulation of arterial O2 tension varies with the extent of inhomogeneity. At mild degrees of inhomogeneity where local pulmonary blood flow (Q) control acts predominantly on the lower VA/Q of the Q distribution, the regulatory effect is best. At severe degrees of inhomogeneity where local Q control acts mainly on the higher VA/Q of the Q distribution, the regulatory effect is worse, and positive-feedback behavior may occur. Local Q control has the potential of reducing the deleterious effects of lung disease on pulmonary gas exchange particularly when it operates in association with other regulatory mechanisms.     

Attenuation and smoothness of injected signals in a Rijlant network]

The V.C.G. methods must handle the E.K.G. information through weighing systems, because of the volume and the eccentric location of the heart in the chest, of the inhomogeneity of the surrounding tissues and of the irregular shape of the body surface. Most of these weighing systems use compensating networks. On the other hand, Rijlant simulates an homogeneous medium where the cardiac currents spread and where remote observation would eliminate much of the distorsions. In order to understand how such a simulated medium operates, we drive it by means of sinusoidal waves and we observe how the amplitude and the phase of the signals change when we switch on the different leads. Each value recorded at a same level in the network may be considered as the sum of a true proximity effect added to an other component depending upon the lead orientation. The latter is referred to a mixed result of the driving waves that we call "the modulus effect". From the injection level to the other levels, the proximity effect rapidly vanishes while the modulus effect does not disappear until grounded level is reached. The decrease of the modulus effect either to zero (grounded level) or to a finite value (free end of the network) is not expressed as a formula because Rijlant's network does not simulate an euclidian space. We conclude that, at least as the proximity effect is concerned, the instrument performs what it is expected to do.     

Life and Death Decision Making, by Baruch A. Brody

Veatch considers the pluralistic casuistry theory advocated by Baruch Brody in his 1988 book, Life and Death Decision Making, to be an important contribution to the secular medical ethics literature. The casuistic and pluralistic elements of Brody's new model are described as intriguing but controversial because Brody both excludes several ethical appeals (i.e., classical Hippocratic ethics, virtue theory) and/or limits other questionable appeals (i.e., consequences for families and others in society, the virtue of integrity) without accounting for these decisions. Veatch also questions Brody's use of intuitional judgment to determine what ought to be done after examination of various appeals and their significance because Brody's approach raises serious problems about how various appeals are counted. Veatch does affirm the rich assessment of medical ethical problems made possible by Brody's pluralistic approach but notes the difficulties it raises.     

Linear behaviour in the aperture pupil of single photoreceptors: Consequences related to the degree of inhomogeneity

An exact treatment of the initial field falling on the entrance face of a photoreceptor, so that the scattered field far from the latter vanishes, is presented. Its physical interest and some consequences are discussed. By establishing certain similarities between the behaviour of the photoreceptor as light penetrates into and propagates along, and an optical linear system, it is possible to define a spatial transverse impulse response containing information on the diffraction capability of each individual receptor. The distribution of this function across a transverse plane depends upon the particular form of the refractive index in the photoreceptor. Thus, certain differences are seen to occur between the case of an homogeneous receptor and an inhomogeneous one, for particular values in the degree of inhomogeneity. This fact allows to interpret the presence of inhomogeneities in the photoreceptor structure.     

Identification of a missense mutation in the bovine ATP2A1 gene in congenital pseudomyotonia of Chianina cattle: an animal model of human Brody disease

Congenital pseudomyotonia in Chianina cattle is a muscle function disorder very similar to that of Brody disease in humans. Mutations in the human ATP2A1 gene, encoding SERCA1, cause Brody myopathy. The analysis of the collected Chianina pedigree data suggested monogenic autosomal recessive inheritance and revealed that all 17 affected individuals traced back to a single founder. A deficiency of SERCA1 function in skeletal muscle of pseudomyotonia affected Chianina cattle was observed as SERCA1 activity in affected animals was decreased by about 70%. Linkage analysis showed that the mutation was located in the ATP2A1 gene region on BTA25 and subsequent mutation analysis of the ATP2A1 exons revealed a perfectly associated missense mutation in exon 6 (c.491G > A) leading to a p.Arg164His substitution. Arg164 represents a functionally important and strongly conserved residue of SERCA1. This study provides a suitable large animal model for human Brody disease.     

Scroll-wave dynamics in human cardiac tissue: lessons from a mathematical model with inhomogeneities and fiber architecture

Cardiac arrhythmias, such as ventricular tachycardia (VT) and ventricular fibrillation (VF), are among the leading causes of death in the industrialized world. These are associated with the formation of spiral and scroll waves of electrical activation in cardiac tissue; single spiral and scroll waves are believed to be associated with VT whereas their turbulent analogs are associated with VF. Thus, the study of these waves is an important biophysical problem. We present a systematic study of the combined effects of muscle-fiber rotation and inhomogeneities on scroll-wave dynamics in the TNNP (ten Tusscher Noble Noble Panfilov) model for human cardiac tissue. In particular, we use the three-dimensional TNNP model with fiber rotation and consider both conduction and ionic inhomogeneities. We find that, in addition to displaying a sensitive dependence on the positions, sizes, and types of inhomogeneities, scroll-wave dynamics also depends delicately upon the degree of fiber rotation. We find that the tendency of scroll waves to anchor to cylindrical conduction inhomogeneities increases with the radius of the inhomogeneity. Furthermore, the filament of the scroll wave can exhibit drift or meandering, transmural bending, twisting, and break-up. If the scroll-wave filament exhibits weak meandering, then there is a fine balance between the anchoring of this wave at the inhomogeneity and a disruption of wave-pinning by fiber rotation. If this filament displays strong meandering, then again the anchoring is suppressed by fiber rotation; also, the scroll wave can be eliminated from most of the layers only to be regenerated by a seed wave. Ionic inhomogeneities can also lead to an anchoring of the scroll wave; scroll waves can now enter the region inside an ionic inhomogeneity and can display a coexistence of spatiotemporal chaos and quasi-periodic behavior in different parts of the simulation domain. We discuss the experimental implications of our study.     

Transfer of the Excitation Energy in Anacystis nidulans Grown to Obtain Different Pigment Ratios

The blue-green alga, Anacystis nidulans, was grown in lights of different colors and intensities, and its absorption and fluorescence properties were studied. Strong orange light, absorbed mainly by phycocyanin, causes reduction in the ratio of phycocyanin to chlorophyll a; strong red light, absorbed mainly by chlorophyll, causes an increase in this ratio. This confirms the earlier findings of Brody and Emerson (12) on Porphyridum, and of Jones and Myers (8) on Anacystis. Anacystis cultures grown in light of low intensity show, upon excitation of phycocyanin, emission peaks at 600 mmu and 680 mmu, due to the fluorescence of phycocyanin and chlorophyll a, respectively. Changes in the efficiency of energy transfer from phycocyanin to chlorophyll a are revealed by changes in the ratios of these two bands. A decrease in efficiency of energy transfer from phycocyanin to chlorophyll a seems to occur whenever the ratio of chlorophyll a to phycocyanin deviates from the normal. Algae grown in light of high intensity show, upon excitation of phycocyanin, only a fluorescence band at 660 mmu and no band at 680 mmu. This suggests reduced efficiency of energy transfer from phycocyanin to the strongly fluorescent form of chlorophyll a (chlorophyll a(2)) and perhaps increased transfer to the weakly fluorescent form of chlorophyll a (chlorophyll a(1)).     

Inhomogeneity during deflation of excised canine lungs. I. Alveolar pressures

Factors both intrinsic and extrinsic to the lung may cause inhomogeneity of alveolar pressures during deflation. Wilson et al. (J. Appl. Physiol. 59: 1924-1928, 1985) predicted that any such inhomogeneity would be limited by interdependence of regional expiratory flows. To test this hypothesis and to explore how the pleural pressure gradient might affect inhomogeneity of alveolar pressures, we deflated at submaximal flows excised canine lobes that first were suspended in air and then were immersed in foams that simulated the vertical gradient of pleural pressure. Interregional inhomogeneity of regional transpulmonary pressures was measured with use of an alveolar capsule technique. Flow-dependent inhomogeneity of alveolar pressures was present, with differences in alveolar pressure quickly relaxing to a constant limiting value at each flow. Foam immersion increased inhomogeneity at a given flow. We conclude that factors intrinsic to the lung cause significant inhomogeneity of alveolar pressures at submaximal expiratory flows and that this inhomogeneity is enhanced by the extrinsic gradient of pleural pressure. These observations are consistent with the interdependence of flow proposed by Wilson et al.     

A biological system for studies on mixing in bioreactors

A method for studying bioreactor inhomogeneity is suggested. Oxygen depletion in an E. coli cultivation leads to mixed acid fermentation with hydrogen gas production. Using a palladium metal-oxide semiconductor (Pd-MOS) hydrogen sensor on line in the effluent gas, it is shown that in a batch culture of 1 m³ hydrogen gas was evolved even before the dissolved oxygen tension (DOT) as measured by the probe reached zero. This suggests an appreciable degree of inhomogeneity with respect to DOT. Using measurements performed off line, it was observed that the lag time for hydrogen to appear became greater if the cells had been subjected to oxygen depletion. Lack of oxygen also resulted in a lowered hydrogen evolution capacity of the cells.     

Ventilation-perfusion inhomogeneity increases gas uptake: theoretical modeling of gas exchange.

Ventilation-perfusion (VA/Q) inhomogeneity was modeled to measure its effect on gas exchange in the presence of inspired mixtures of two soluble gases using a two-compartment computer model. Theoretical studies involving a mixture of hypothetical gases with equal solubility in blood showed that the effect of increasing inhomogeneity of distributions of either ventilation or blood flow is to paradoxically increase uptake of the gas with the lowest overall uptake in relation to its inspired concentration. This phenomenon is explained by the concentrating effects that uptake of soluble gases exert on each other in low VA/Q compartments. Repeating this analysis for inspired mixtures of 30% O(2) and 70% nitrous oxide (N(2)O) confirmed that, during "steady-state" N(2)O anesthesia, uptake of N(2)O is predicted to paradoxically increase in the presence of worsening VA/Q inhomogeneity.     

The Effect of Spatial Inhomogeneity of the Cornea on the Deformation Properties of the Eyeball and the Results of Maklakoff Applanation Tonometry

A two-component model of the eyeball that represents the cornea as a momentless, linearly elastic deformable surface and the scleral region, as an elastic element that responds to intraocular pressure changes by volume changes, has been used to analyze the effect of spatial inhomogeneity in the distribution of effective corneal stiffness on the mechanical properties of the eye. The effective stiffness of the cornea characterized both the elastic properties and the thickness of the cornea within the framework of the model. Various axisymmetric forms of the effective stiffness distribution characterized by monotonic increase along the arc between a point on the corneal surface and the apex of the cornea were studied. The considered distributions simulated both natural inhomogeneity and apical region weakening due to surgical interventions. Numerical simulation yielded the dependences of deformation parameters on intraocular pressure changes. These parameters characterized the deformation properties of both the cornea (apex displacement) and the eyeball as a whole (intraocular volume change). In the case of moderate inhomogeneity, the dependences were only slightly different from those for a homogeneous cornea with an effective stiffness equal to the mean value for the corresponding inhomogeneous distribution. A noticeable increase in the integral response of the cornea and the eyeball as a whole to changes in pressure was observed if the effective stiffness amplitude was very high (two or more times higher than the mean value). The effect of inhomogeneity on the results of tonometric measurements with a Maklakoff tonometer (flat stamp) was studied. The tonometric difference, that is, the difference between the tonometric pressure (in the loaded eye) and the true pressure (before loading), mainly depended on the average stiffness of the cornea in this case as well, with a substantial increase observed at very high stiffness amplitudes only. Apical weakening of the cornea led to an increase (although not very pronounced) of the tonometric difference.     

Effects of mechanical interaction between two rabbit cardiac muscles connected in parallel

The hypothesis that myocardium mechanical inhomogeneity produces a substantial effect on mechanical function was tested. Muscle inhomogeneity was studied in isolated papillary muscles or trabeculae excised from rabbit right ventricle and connected in a parallel duplex. Each muscle was placed in a separate perfusion bath. One end of each muscle was fastened to an individual force transducer and the other to the common lever of a servomotor. This arrangement allowed both muscles, being excited independently, to pull jointly a load applied to the lever. Separate electrodes for each perfusion bath allowed to stimulate muscles with a time delay. Tension developed in the individual muscles and their interaction were studied. Developed tension was critically dependent on the timing and sequence of excitation. Using mathematical modeling, patterns of tension distribution experimentally observed in parallel duplexes were simulated. These results suggest that changes both in Ca(2+) transients and in the time course of Ca(2+)-troponin complexion due to the duplexed muscles interaction offset the effect of mechanical inhomogeneity.     

Comparison of non-linear models to describe the lactation curves for milk yield and composition in buffaloes (Bubalus bubalis)

In order to describe the lactation curves of milk yield (MY) and composition in buffaloes, seven non-linear mathematical equations (Wood, Dhanoa, Sikka, Nelder, Brody, Dijkstra and Rook) were used. Data were 116 117 test-day records for MY, fat (FP) and protein (PP) percentages of milk from the first three lactations of buffaloes which were collected from 893 herds in the period from 1992 to 2012 by the Animal Breeding Center of Iran. Each model was fitted to monthly production records of dairy buffaloes using the NLIN and MODEL procedures in SAS and the parameters were estimated. The models were tested for goodness of fit using adjusted coefficient of determination root means square error (RMSE), Durbin–Watson statistic and Akaike’s information criterion (AIC). The Dijkstra model provided the best fit of MY and PP of milk for the first three parities of buffaloes due to the lower values of RMSE and AIC than other models. For the first-parity buffaloes, Sikka and Brody models provided the best fit of FP, but for the second- and third-parity buffaloes, Sikka model and Brody equation provided the best fit of lactation curve for FP, respectively. The results of this study showed that the Wood and Dhanoa equations were able to estimate the time to the peak MY more accurately than the other equations. In addition, Nelder and Dijkstra equations were able to estimate the peak time at second and third parities more accurately than other equations, respectively. Brody function provided more accurate predictions of peak MY over the first three parities of buffaloes. There was generally a positive relationship between 305-day MY and persistency measures and also between peak yield and 305-day MY, calculated by different models, within each lactation in the current study. Overall, evaluation of the different equations used in the current study indicated the potential of the non-linear models for fitting monthly productive records of buffaloes.     

Attraction and repulsion of spiral waves by inhomogeneity of conduction anisotropy—a model of spiral wave interaction with electrical remodeling of heart tissue

Various forms of heart disease are associated with remodeling of the heart muscle, which results in a perturbation of cell-to-cell electrical coupling. These perturbations may alter the trajectory of spiral wave drift in the heart muscle. We investigate the effect of spatially extended inhomogeneity of transverse cell coupling on the spiral wave trajectory using a simple active media model. The spiral wave was either attracted or repelled from the center of inhomogeneity as a function of cell excitability and gradient of the cell coupling. High levels of excitability resulted in an attraction of the wave to the center of inhomogeneity, whereas low levels resulted in an escape and termination of the spiral wave. The spiral wave drift velocity was related to the gradient of the coupling and the initial position of the wave. In a diseased heart, a region of altered transverse coupling corresponds with local gap junction remodeling that may be responsible for stabilization-destabilization of spiral waves and hence reflect potentially important targets in the treatment of heart arrhythmias.     

Ventilation-perfusion inhomogeneity increases gas uptake in anesthesia: computer modeling of gas exchange.

Ventilation-perfusion (VA/Q) inhomogeneity was modeled to measure its effect on overall gas exchange during maintenance-phase N(2)O anesthesia with an inspired O(2) concentration of 30%. A multialveolar compartment computer model was used based on physiological log normal distributions of VA/Q inhomogeneity. Increasing the log standard deviation of the distribution of perfusion from 0 to 1.75 paradoxically increased O(2) uptake (VO(2)) where a low mixed venous partial pressure of N(2)O [high N(2)O uptake (VN(2)O)] was specified. With rising mixed venous partial pressure of N(2)O, a threshold was observed where VO(2) began to fall, whereas VN(2)O began to rise with increasing VA/Q inhomogeneity. This phenomenon is a magnification of the concentrating effects that VO(2) and VN(2)O have on each other in low VA/Q compartments. During "steady-state" N(2)O anesthesia, VN(2)O is predicted to paradoxically increase in the presence of worsening VA/Q inhomogeneity.