Model of gas transport during high-frequency ventilation

We analyze gas exchange during high-frequency ventilation (HFV) by a stochastic model that divides the dead space into N compartments in series where each compartment has a volume equal to tidal volume (V). We then divide each of these compartments into alpha subcompartments in series, where each subcompartment receives a well-mixed concentration from one compartment and passes a well-mixed concentration to another in the direction of flow. The number of subcompartments is chosen on the basis that 1/alpha = (sigma t/-t)2, where -t is mean transit time across a compartment of volume, and sigma t is standard deviation of transit times. If (sigma t/-t)D applies to the transit times of the entire dead space, the magnitude of gas exchange is proportional to (sigma t/-t)D, frequency, and V raised to some power greater than unity in the range where V is close to VD. When V is very small in relation to VD, gas exchange is proportional to (sigma t/-t)2D, frequency, and V raised to a power equal to either one or two depending on whether the flow is turbulent or streamline, respectively. (sigma t/-t)D can be determined by the relation between the concentration of alveolar gas at the air outlet and volume expired as in a Fowler measurement of the volume of the dead space.     

Hypothalamic orexin--a neurons are involved in the response of the brain stress system to morphine withdrawal

Both the hypothalamus-pituitary-adrenal (HPA) axis and the extrahypothalamic brain stress system are key elements of the neural circuitry that regulates the negative states during abstinence from chronic drug exposure. Orexins have recently been hypothesized to modulate the extended amygdala and to contribute to the negative emotional state associated with dependence. This study examined the impact of chronic morphine and withdrawal on the lateral hypothalamic (LH) orexin A (OXA) gene expression and activity as well as OXA involvement in the brain stress response to morphine abstinence. Male Wistar rats received chronic morphine followed by naloxone to precipitate withdrawal. The selective OX1R antagonist SB334867 was used to examine whether orexins' activity is related to somatic symptoms of opiate withdrawal and alterations in HPA axis and extended amygdala in rats dependent on morphine. OXA mRNA was induced in the hypothalamus during morphine withdrawal, which was accompanied by activation of OXA neurons in the LH. Importantly, SB334867 attenuated the somatic symptoms of withdrawal, and reduced morphine withdrawal-induced c-Fos expression in the nucleus accumbens (NAc) shell, bed nucleus of stria terminalis, central amygdala and hypothalamic paraventricular nucleus, but did not modify the HPA axis activity. These results highlight a critical role of OXA signalling, via OX1R, in activation of brain stress system to morphine withdrawal and suggest that all orexinergic subpopulations in the lateral hypothalamic area contribute in this response.     

Changes in the "shape reaction" and "orientation reaction" of cell nuclei as a consequence of neoplastic transformation

Reactions of cell nuclei on curvature of cylindrical surfaces (curvature radii 333, 75 or 61 mcm) in 9 lines of cultured transformed human, Syrian hamster, rat and murine fibroblasts were studied quantitatively. The nuclear elongation was assessed as a ratio of long to short axes. Contact orientation was characterized by values derived from the angles, formed by long nuclear axes with the direction of cylinder axis. Due to transformation, cells lost the ability to elongate their nuclei in response to cultivation on cylindrical surfaces. The ability of cells cultured on cylindrical surfaces to increase the contact orientation values was also lost or weakened considerably.     

Can one angle be simply subtracted from another to determine range of motion in three-dimensional motion analysis?

To determine the range of motion of a joint between an initial orientation and a final orientation, it is convenient to subtract initial joint angles from final joint angles, a method referred to as the vectorial approach. However, for three-dimensional movements, the vectorial approach is not mathematically correct. To determine the joint range of motion, the rotation matrix between the two orientations should be calculated, and angles describing the range of motion should be extracted from this matrix, a method referred to as the matrical approach. As the matrical approach is less straightforward to implement, it is of interest to identify situations in which the vectorial approach leads to insubstantial errors. In this study, the vectorial approach was compared to the matrical approach, and theoretical justification was given for situations in which the vectorial approach can reasonably be used. The main findings are that the vectorial approach can be used if (1) the motion is planar (Woltring HJ. 1994. 3-D attitude representation of human joints: a standardization proposal. J Biomech 27(12): 1399–1414), (2) the angles between the final and the initial orientation are small (Woltring HJ. 1991. Representation and calculation of 3-D joint movement. Hum Mov Sci 10(5): 603–616), (3) the angles between the initial orientation of the distal segment and the proximal segment are small and finally (4) when only one large angle occurs between the initial orientation of the distal segment and the proximal segment and the angle sequence is chosen in such a way that this large angle occurs on the first axis of rotation. These findings provide specific criteria to consider when choosing the angle sequence to use for movement analysis.     

3D-DIASemb: a computer-assisted system for reconstructing and motion analyzing in 4D every cell and nucleus in a developing embryo

A computer-assisted three-dimensional (3D) system, 3D-DIASemb, has been developed that allows reconstruction and motion analysis of cells and nuclei in a developing embryo. In the system, 75 optical sections through a live embryo are collected in the z axis by using differential interference contrast microscopy. Optical sections for one reconstruction are collected in a 2.5-s period, and this process is repeated every 5 s. The outer perimeter and nuclear perimeter of each cell in the embryo are outlined in each optical section, converted into beta-spline models, and then used to construct 3D faceted images of the surface and nucleus of every cell in the developing embryo. Because all individual components of the embryo (i.e., each cell surface and each nuclear surface) are individually reconstructed, 3D-DIASemb allows isolation and analysis of (1) all or select nuclei in the absence of cell surfaces, (2) any single cell lineage, and (3) any single nuclear lineage through embryogenesis. Because all reconstructions represent mathematical models, 3D-DIASemb computes over 100 motility and dynamic morphology parameters for every cell, nucleus, or group of cells in the developing embryo at time intervals as short as 5 s. Finally, 3D-DIASemb reconstructs and motion analyzes cytoplasmic flow through the generation and analysis of "vector flow plots." To demonstrate the unique capabilities of this new technology, a Caenorhabditis elegans embryo is reconstructed and motion analyzed through the 28-cell stage. Although 3D-DIASemb was developed by using the C. elegans embryo as the experimental model, it can be applied to other embryonic systems. 3D-DIASemb therefore provides a new method for reconstructing and motion analyzing in 4D every cell and nucleus in a live, developing embryo, and should provide a powerful tool for assessing the effects of drugs, environmental perturbations, and mutations on the cellular and nuclear dynamics accompanying embryogenesis.     

Orientation and function of the nuclear-centrosomal axis during cell migration

A hallmark of polarity in most migrating cells is the orientation of the nuclear centrosomal (NC) axis relative to the front-back cellular axis. Here, we review 'effector functions' associated with the NC axis during cell migration. We highlight recent research that has demonstrated that the orientation of the NC axis depends upon the coordinated, but separate positioning of the nucleus and the centrosome. We stress the importance of environmental factors such as cell-cell contacts and substrate topology for NC axis orientation. Finally, we summarize tests of the significance of this axis for cell migration and disease.     

Acetabular morphology and resurfacing design

The bony surfaces of 18 archaeological hemipelves were scanned using a 3D laser surface scanner and CyDir™ software on a Silicon Graphics workstation. The acetabular area was selected and point data from the approximately spherical bone surface saved. These data were input to a MATLAB routine that calculated the radius and centre of the best-fit sphere. The goodness of fit was estimated using the mean and standard deviation of the distance of the bone surface points from the sphere surface. Eight points, at approximately equal distances around the acetabular rim, were selected with reference to bony landmarks. A plane containing three of these points served as an orientation reference plane. The vectors joining the eight rim points to the centre of the best-fit sphere were found. The angles between these vectors and the normal to the reference plane were calculated. Paired angles were summed to give the angle subtended by the acetabular rim in four directions. The overall mean angle was 158° (range of mean angles 145°–173°). The largest individual angles, some exceeding 180°, were in the superior–inferior direction, while the mean angle in the anterior–posterior direction, i.e. that controlling flexion-extension, was 152°. Males had larger subtended angles than females, although the difference was not statistically significant. Simulated reaming increased all angles by approximately 10°. The subtended angles are important parameters in the design of the acetabular component of a hip replacement and particularly important in resurfacing hip replacement when the volume available is tightly constrained.     

Control analysis of transition times in metabolic systems.

The transition time, tau, of a metabolic system is defined as the ratio of the metabolite concentrations in the system, sigma, to the steady-state flux, J. Its value reflects a temporal characteristic of the system as it relaxes towards the steady state. Like other systemic properties, the value of tau will be a function of the enzyme activities in the system. The influence of a particular enzyme activity on tau can be quantified by a Control Coefficient, C tau ei. We show that it is possible to derive a Summation Theorem sigma ni = 1 C tau ei = -1 and a Connectivity Theorem sigma ni = 1 C tau ei.epsilon viSk = -Sk/sigma. We establish a 'sign rule' that predicts the order of positive and negative Control Coefficients in a sequence.     

Monoplastidic mitosis in the mossTimmiella barbuloides (Bryophyta)

Summary Mitotic cell division of monoplastidic sporogones was investigated in the mossTimmiella barbuloides (Brid.) Moenk. (Pottiales, Bryophyta) by TEM. Division polarity of sporogones is established by the interphase position of the single oblong cup-shaped plastid, which is orientated with its long axis parallel to one of the cell walls. In preprophase the plastid elongates and its extremities bend at right angles. Plastid growth is directed by microtubules and accompanied by plastid tubules. The plastid begins the process of duplication by constricting centrally in the plane of the future cytokinetic septum. There is no preprophase band of microtubules at the division site. The large central nucleus becomes fusiform and aligned parallel to the main plastid axis. By the end of prophase the daughter plastids are positioned at the opposite poles of the nucleus where they probably function as nucleating or organizing centres for the spindle microtubules. Metaphase and anaphase spindles contain long sheets of ER. Cytokinesis involves the formation of a well developed phragmoplast.Abbreviations TEM transmission electron microscopy - PPB preprophase band of microtubules - ER endoplasmic reticulum     

Crystalloid inclusions in the Sertoli cell of the koala,Phascolarctos cinereus (Marsupialia)

Summary Crystalloid inclusions are a common feature in the basal region of Sertoli cells in the koala, Phascolarctos cinereus. Generally located near the nucleus, they are non membrane-bounded, slender rectangular structures composed of tubules which are orientated at right angles to the long axis of the crystalloid and regularly arranged in rows parallel to this long axis. The tubules in adjacent rows are offset from one another at definite angles and extensively interconnected by filaments. Neither the composition nor function of the crystalloids has been determined, but their association with tonofilaments and the presence of ribosomes in the vicinity suggests that they are most likely proteinaceous.The authors would like to thank Mr. D. Harbrow, Mr. S. Brown and Ms. B. Canty for technical assistance; the Queensland National Parks and Wildlife Service and the Victorian Ministry of Conservation (Fisheries and Wildlife Division) for providing permits to work on this protected species; the staff of the Lone Pine Koala Sanctuary, Brisbane, for their assistance in obtaining animals. This work was supported by a grant from the Australian Research Grants Committee, Number DI-77/15525     

Preprophasic establishment of division polarity in monoplastidic mitosis of hornworts

Summary Preprophase in the monoplastidic mitotic cells ofPhaeoceros andNotothylas is characterized by the establishment of a division site in the absence of a typical preprophase band. The future cytokinetic plane is predicted by plastid orientation and development of an elaborate preprophasic microtubule system perpendicular to the division plane. Division of the single plastid is initiated early in preprophase and the constricting plastid migrates to a position perpendicular to the future plane of division. Plastid orientation assures that division of the plastid by mid-constriction will result in distribution of a plastid to each daughter cell. Microtubules parallel the long axis of the plastid and are most numerous adjacent to the nucleus which becomes elongated in the future spindle axis. We conclude that the division site is a fundamental component of the cytokinetic apparatus involved in the determination of cleavage plane prior to nuclear division.     

Reorientation response of cells to repeated stretch and recoil of the substratum

The effect of directional stretching of the substratum on cell orientation was investigated using Earle's L strain fibroblasts. An apparatus was constructed that caused a silicon rubber substratum to undergo periodic elongation and recoil at 15 sec intervals. This substratum was contained within a flask that also held a control (static) substratum of the same material. Examination of the pattern of cells by scanning electron microscopy (SEM), made after 18–24 h incubation, showed a highly significant preponderance over the controls of cells on the stretching substrata arranged with their long axis at right angles to the direction of stretching. The observation is interpreted as an avoidance reaction to stretching based on the cells' adhesion by linear focal contacts, which run parallel to the long axis of the cells, and which are associated with microfilaments.     

Negative staining of myosin molecules

A reproducible method has been developed for the negative staining of myosin molecules. The dimensions of stained molecules are in close agreement with those obtained by metal shadowing. Sharp bends in the tail, indicative of hinge regions, were observed at two positions 44 nm and 76 nm from the head-tail junction. The tail was often ill-defined at the position of the first (44 nm) bend. The bend positions may be sites of proteolytic cleavage that result in the production of long and short myosin subfragment S2. About half the molecules exhibited bending to various degrees at one or both of these positions, but cases where the tail folded back on itself in a 180 degrees bend were comparatively rare (approximately equal to 10%). However, in the absence of EGTA, a large fraction of the molecules (approximately equal to 80%) exhibited 180 degrees bends. A small region, approximately 20 nm long, at the tip of the tail often appears to be significantly different from the rest. The heads are about 19 nm long and roughly pear-shaped. Although sometimes straight, more often they show a pronounced curvature. Both senses of curvature were observed, but those curved in a clockwise manner were the most common, indicating preferential binding of one side of the head to the carbon substrate. An analysis of the different combinations of head shapes in individual molecules indicates that each head can rotate independently around its long axis. No preferred angle of orientation between the two heads in a molecule, or between either head and the tail could be found. Substructure has been observed within the heads.     

Structure of Paramecium tetraurelia calmodulin at 1.8 A resolution.

The crystal structure of calmodulin (CaM; M(r) 16,700, 148 residues) from the ciliated protozoan Paramecium tetraurelia (PCaM) has been determined and refined using 1.8 A resolution area detector data. The crystals are triclinic, space group P1, a = 29.66, b = 53.79, c = 25.49 A, alpha = 92.84, beta = 97.02, and gamma = 88.54 degrees with one molecule in the unit cell. Crystals of the mammalian CaM (MCaM; Babu et al., 1988) and Drosophila CaM (DCaM; Taylor et al., 1991) also belong to the same space group with very similar cell dimensions. All three CaMs have 148 residues, but there are 17 sequence changes between PCaM and MCaM and 16 changes between PCaM and DCaM. The initial difference in the molecular orientation between the PCaM and MCaM crystals was approximately 7 degrees as determined by the rotation function. The reoriented Paramecium model was extensively refitted using omit maps and refined using XPLOR. The R-value for 11,458 reflections with F > 3 sigma is 0.21, and the model consists of protein atoms for residues 4-147, 4 calcium ions, and 71 solvent molecules. The root mean square (rms) deviations in the bond lengths and bond angles in the model from ideal values are 0.016 A and 3 degrees, respectively. The molecular orientation of the final PCaM model differs from MCaM by only 1.7 degrees. The overall Paramecium CaM structure is very similar to the other calmodulin structures with a seven-turn long central helix connecting the two terminal domains, each containing two Ca-binding EF-hand motifs. The rms deviation in the backbone N, Ca, C, and O atoms between PCaM and MCaM is 0.52 A and between PCaM and DCaM is 0.85 A. The long central helix regions differ, where the B-factors are also high, particularly in PCaM and MCaM. Unlike the MCaM structure, with one kink at D80 in the middle of the linker region, and the DCaM structure, with two kinks at K75 and I85, in our PCaM structure there are no kinks in the helix; the distortion appears to be more gradually distributed over the entire helical region, which is bent with an apparent radius of curvature of 74.5(2) A. The different distortions in the central helical region probably arise from its inherent mobility.     

Orientation of paramecium swimming in a DC magnetic field

We found that a ciliated protozoan, Paramecium, swam perpendicular to a static (DC) magnetic field (0.68 T). The swimming orientation was similar even when the ionic current through the cell membrane disappeared after saponin treatment. To determine the diamagnetic anisotropy of intracellular organs, macronuclei, cilia, and secretory vesicles, trichocysts, were selectively isolated. Both cilia and trichocysts tended to align their long axis parallel to the magnetic field (0.78 T). Paramecium mutants that lack trichocysts also swam perpendicular to the magnetic field, although the proportion fraction was smaller than the normal population. Since large numbers of cilia and trichocysts are arranged at right angles to the long axis of the cell, the diamagnetic anisotropies of cilia and trichocysts cause the long axis of the cell to align perpendicular to the magnetic field. In contrast to the DC magnetic field, an alternative (AC) magnetic field (60 Hz, 0.65 T) had almost no effect on the swimming orientation of Paramecium.     

基底周期拉伸引起ECV-304细胞形态学变化的分析

对ECV-304细胞施以最大应变10％、0.67Hz的周期拉伸,利用计算机图像处理系统,对周期拉伸过程中ECV-304细胞的取向调整进行了形态学分析,结果显示：周期拉伸能引起细胞长轴取向垂直于最大主应变方向;加载12h内细胞长短径比增加,12-24h之间长短径比下降,随后趋于稳定;细胞在周期拉伸最大主应变方向上的最大截距缩短,而在垂直于最大主应变方向上的最大截距延长;取向调整的过程与长短径比增大的过程有显著的相关性。表明在周期拉伸过程中的取向调整是一个细胞具有方向差异性的变形过程,而不是刚性的旋转或位移。     

Synthesis and pharmacological evaluation of 6-piperidino- and 6-piperazinoalkyl-2(3H)-benzothiazolones as mixed sigma/5-HT(1A) ligands

In an effort to produce new pharmacological probes with mixed sigma/5-HT(1A) affinity, we have synthesized a series of 12 original 6-piperidino- or piperazino-alkyl-2(3H)-benzothiazolones and their receptor binding profile (sigma, 5-HT(1A), 5-HT(2A), 5-HT(3), D(2), H(1), and M(1)) was determined. The best mixed sigma/5-HT(1A) affinity profile was found within the piperidine series with 4-benzyl substitution associated to linker methylene chain n=2 (K(i) 5 and 4nM, respectively). Moreover, a highly selective sigma2 ligand was obtained with a 3,4-dichlorobenzyl substitution associated to n=4 (K(i) 2nM, selectivity ratio sigma1/sigma2=70).     

朱顶红精细胞超微结构观察

精细胞是双受精作用的直接参与者,是生殖生物学中的重点研究对象之一。以往的研究表明,应用连续超薄切片和计算机辅助三维重组技术,结合免疫荧光定位,发现两个精细胞在体积和细胞器含量上存在着差异,即精子的二型性,而且与营养细胞核三者构成紧密功能单位即雄性生殖单位（ＭＧＵ）,微管对精细胞的性状的确定、运动和维持ＭＧＵ的动态结构稳定具有重要的作用。本文应用透射电镜,详细观察了朱顶红花粉管中精细胞的超微结构,并着重微管结构及其分布的观察。朱顶红成熟花粉为两细胞型。成熟花粉于２６℃、黑暗条件下,在液体培养基（含１０％蔗糖和１００ｐｐｍ硼酸）中培养１３－１８小时,然后收集花粉管,固定,供电镜观察并照相。朱顶红成熟花粉培养１３小时后,生殖细胞在花粉管中完成核分裂和胞质分裂等两个过程。形成两个精细胞。初形成的两个精细胞前后排列,营养核前导并靠近花粉管顶端。领头的精细胞的细胞质以很大的表面与营养核相互贴合（图版Ⅰ－１,２）,有时营养核与两个精细胞彼此穿插、缠绕（图版Ⅰ－３）。两精细胞之间的共同壁上具有很多胞质通道和含均质电子密度中等的基质（图版Ⅱ－４）。精细胞质在核与共同壁之间的区域染色较深,经高倍放大,观察到此处含丰富的微管,基     

Spindle orientation in animal cell mitosis: roles of integrin in the control of spindle axis

The orientation of mitotic spindles, which determines the plane of cell division, is tightly regulated in polarized cells such as epithelial cells, but it has been unclear whether there is a mechanism regulating spindle orientation in non-polarized cultured cells. In adherent cultured cells, spindles are positioned at the center of the cells and the axis of the spindle lies in the longest axis of the cell. Thus, cell geometry is thought to be one of cues for spindle orientation and positioning in cultured cells because this defines the center and the long axis of the cell. Recent work provides a new insight into the spindle orientation in cultured cells; spindles are aligned along the axis parallel to the cell-substrate adhesion plane. Concomitantly, integrin-mediated cell adhesion to the extracellular matrix (ECM), rather than gravitation, cell-cell adhesion or cell geometry, has shown to be essential for this mechanism of spindle orientation. Several independent lines of evidence confirm the involvement of cell-ECM adhesion in spindle orientation in both cultured cells and in developing organisms. The important future challenge is to identify a molecular mechanism(s) that links integrin and spindles in the control of spindle axis.     

A motion-decomposition approach to address gimbal lock in the 3-cylinder open chain mechanism description of a joint coordinate system at the glenohumeral joint

In this study, the standard-sequence properties of a joint coordinate system were implemented for the glenohumeral joint by the use of a set of instantaneous geometrical planes. These are: a plane that is bound by the humeral long axis and an orthogonal axis that is the cross product of the scapular anterior axis and this long axis, and a plane that is bounded by the long axis of the humerus and the cross product of the scapular lateral axis and this long axis. The relevant axes are updated after every decomposition of a motion component of a humeral position. Flexion, abduction and rotation are then implemented upon three of these axes and are applied in a step-wise uncoupling of an acquired humeral motion to extract the joint coordinate system angles. This technique was numerically applied to physiological kinematics data from the literature to convert them to the joint coordinate system and to visually reconstruct the motion on a set of glenohumeral bones for validation.