An iterative procedure to estimate muscle lines of action in vivo

A method is described to estimate the line of action of muscles in the three-dimensional space from serial images of parallel muscle sections obtained in vivo by means of CT or MRI scanning. The external shape of a muscle, reconstructed from the series of parallel sections, is mathematically divided into a series of imaginary slices directed arbitrarily in the three-dimensional space. The line of action is estimated initially as a regression line through the centroids of these mathematical slices. A new series of mathematical slices is constructed perpendicular to the regression line and a new estimate of the line of action is obtained from their centroids. This procedure is repeated until the estimated line of action is perpendicular to the mathematical slices; it can then be considered as a reliable estimate of the line of action. The accuracy of the method has been tested for various reconstruction parameters and muscle shapes. The results of these tests show that the accuracy is relatively independent of the direction in which the sectional images have been made and that, except for relatively short and thick muscles, the estimated lines of action deviated less than about 2 degrees from the theoretical one. The presented method is a relatively simple mathematical technique which can be used easily for muscles reconstructed in vivo from routinely obtained sectional MRI or CT images.     

江豚耳蜗切片的计算机三维重建

在自己组装的微型机图象系统上,实现了对生物组织连续切片的三维重建。重建结果以灰度阴影方式在彩色显示器上显示,并可在打印机上以多灰度等级方式打印输出。结合一例江豚内耳的连续切片,对其耳蜗骨迷路部份进行了三维重建。并将重建结果以动态形式在显示器上转动,以便观察其各个侧面的情况。     

A microcomputer based system for three-dimensional reconstructions from tomographic or histologic sections

The reconstructions of three-dimensional (3-D) objects from serial two-dimensional (2-D) images can contribute to the understanding of many biologic structures, from organelles to organs and tissues. The 3-D reconstruction of sections can be divided into several major tasks: image acquisition, alignment of slices, internal object definition, object reconstruction and rotation of the completed image. A fast, versatile, interactive system was devised for the reconstruction of 3-D objects from serial 2-D images using a low-cost microcomputer, original programs and commercial software. The system allows reconstruction from any serial images, e.g., electron micrographs, histologic sections or computed tomograms. A photographic image or a microscopic field is acquired into the computer memory using a video digitizer. Slices are superimposed and aligned to each other using an operator-interactive program. A contour-(edge-) finding algorithm isolates an object of interest from the background image by "subtraction" of the image from an overlaid, slightly shifted identical image. Contours for each slice are input to a reconstruction procedure, which calculates the x, y and z coordinates of every point in a slice and the thickness and number of slices. It then calculates the illumination for every point using a given point source of light and an intensity-fading coefficient. Finally, the points are represented by cubes to provide dimension and reflective surfaces. A cube of appropriate shade and color represents in 2-D the equivalent of a 3-D object; this results in a very effective 3-D image. The reconstruction is rotated by recalculating the positions of every point defining the object and rebuilding the image.(ABSTRACT TRUNCATED AT 250 WORDS)     

生物组织显微结构三维重建的灰度阴影立体图对显示技术

本文描述了一种新的显示三维重建模型的方法—灰度阴影立体图对方法(shading-stereo-pair method).该方法根据连续切片三维重建的灰度阴影法和立体图对法的显示原理,导出了生成立体图对的视差公式.在灰度阴影法三维重建过程中,根据各切片所处的深度和其本身的厚度,按视差公式计算出它们在图对上的位移量并进行水平方向的移动,经过对各切片的叠加和重组,最后生成一幅具有视差信息的灰度阴影立体图对.在体视仪下观察,即可看到重建模型的三维实体图象.最后还讨论了进一步提高图象质量和改善观察效果所必须采取的措施.     

Top-down processes in object identification: evidence from experimental psychology,neuropsychology and functional anatomy.

Many models of object identification are bottom-up and serial in nature; processing at a first stage needs to be complete before it is passed on to a subsequent stage, and there is no top-down feedback from the later to the earlier stages. However, data on picture identification in normal observers contradict a strict serial account of processing, since effects of variables on early and late stages of object identification combine in an interactive rather than an additive manner. Recent neuropsychological and functional anatomical data also indicate that object identification involves top-down activation of earlier stages of visual processing. In neuropsychological patients, subtle perceptual deficits can produce naming problems, even when there is good access to associated semantic knowledge; in functional activation studies, there is increased activity in visual processing areas when conditions require object naming relative to object recognition. These studies provide evidence that increased visual processing occurs in identification tasks, suggesting that there is re-current feedback during the identification process.     

Ultrastructure and functional morphology of a nematalycid mite (Acari: Actinotrichida: Endostigmata: Nematalycidae): adaptations to mesopsammal life*

Nematalycid mites have undergone extreme changes of body shape in adaptating to life in tiny spaces between grains of fine sand. Because of their minute size, the morphology of these organisms can only be reconstructed from ultrathin serial sections. The cuticle forms regular alternating palettes on the surface; such a structure may also function as a plastron. Movement of the body is effected by a continuous secondary muscle layer beneath the epidermis which operates in connection with the cuticular palettes. This movement represents a hitherto unknown mode of reptation, which can be understood as an adaptation to moving among sand particles. The appendages have been reduced to a minute size. The morphology of the digestive tract is described and conclusions are drawn concerning nutrition.     

Motion from the past. A new method to infer vestibular capacities of extinct species

The vestibular system detects head movement in space and maintains visual and postural stability. The semicircular canal system is responsible for registering head rotation. How it responds to head rotation is determined by the rotational axis and the angular acceleration of the head, as well as the sensitivity and orientation of each semicircular canal. The morphological parameters of the semicircular canals are supposed to allow an optimal detection of head rotations induced by some behaviours, especially locomotor. We propose a new method of semicircular canal analysis, based on the computation of central streamlines of virtually reconstructed labyrinths. This method allows us to ascertain the functional structure of the semicircular canal system and to infer its capacity to detect particular head rotations, induced by particular behaviours. In addition, this method is well-suited for datasets provided by any kind of serial sectioning methods, from MRI to μCT scanning and even mechanical serial sectioning, of extant and extinct taxa.     

Method for Staining and Washing Thin Sections on Support Films

A procedure is described for staining large numbers of thin sections on support films for use with one-hole grids. The film is picked up, carried and protected using easily made plastic blocks. Loop-tipped forceps are then used to transfer tissue ribbons from the knife boat to the support film. A large number of tissue sections can then be stained and washed simultaneously in a modified Pyrex dish without damaging the film. After staining, the slot in the one-hole grid is centered over the tissue ribbon, and the grid is attached to the film. The method is suitable for serial reconstruction and the unobstructed viewing of large thin sections in the TEM.     

基于计算机三维图象技术的失语症病灶空间定位法

首次把计算机三维重建方法应用于失语症的研究中,主要有三方面的工作:(1)建立了一套精细程度较高的标准CT脑图,用三维重建方法建立了标准立体头颅,并用伪彩色显示不同的脑结构和语言区.(2)提出标准化应在三维空间内进行的观点,改进的标准化方法充分利用了CT所能提供的关于脑结构的信息,从而使病灶在每层标准CT脑图上的定位更加准确.(3)对两类临床表现不同但CT显示病灶位置相近的失语症病人共47例进行了研究.通过对标准化之后的病灶的统计处理,得到病灶的集中部位,并对其进行三维重建,在标准立体头颅中显示其空间位置的差别.     

Tomographic techniques for the study of exceptionally preserved fossils

Three-dimensional fossils, especially those preserving soft-part anatomy, are a rich source of palaeontological information; they can, however, be difficult to work with. Imaging of serial planes through an object (tomography) allows study of both the inside and outside of three-dimensional fossils. Tomography may be performed using physical grinding or sawing coupled with photography, through optical techniques of serial focusing, or using a variety of scanning technologies such as neutron tomography, magnetic resonance imaging and most usefully X-ray computed tomography. This latter technique is applicable at a variety of scales, and when combined with a synchrotron X-ray source can produce very high-quality data that may be augmented by phase-contrast information to enhance contrast. Tomographic data can be visualized in several ways, the most effective of which is the production of isosurface-based 'virtual fossils' that can be manipulated and dissected interactively.     

Interpretation of electron micrographs of single and serial sections

A method of securing serial sections for electron microscopy is described. Serial sections present certain anomalies of interpretation of a nature such that a complete and detailed three-dimensional reconstruction of the sectioned tissue cannot be made. These anomalies are discussed, as well as those which have been encountered in the interpretation of single sections. Observations of the following kinds have been made in an attempt to elucidate the interpretation of single and serial sections: differing methods of mounting adjacent sections, observation of the same section by high-angle stereoscopy, and examination of sections which have been shadowed prior to and subsequent to electron microscopy. It is found that the appearance of sections is independent of the choice of side to be placed against the formvar films. Stereoscopy shows that the appearance of fine structures is strongly dependent upon the direction of the penetrating electron beam with respect to the plane of the structures. Stereoscopy, combined with shadowing, shows quantitatively that extensive sublimation of polymer occurs upon normal exposure in the electron microscope. Observation of sections shadowed prior to electron microscopy indicates that varying amounts of material are removed between sections by the action of microtomy; i.e., it is probable that the sum of the thicknesses of several serial sections is considerably less than the total thickness of material removed from the block. It is believed that this effect, combined with the effect of sublimation, aids in explaining the failure of adjacent sections to exhibit continuity in their detailed structures.     

An electron microscopic study on the type I pneumocyte in the cat: Postnatal morphogenesis

This investigation describes the morphogenesis of the type I pneumocyte from the neonatal stage to the age of 3 months. Cells lining subpleural air spaces were photographed from electron microscopic serial sections and a three-dimensional representation of each cell was obtained by transferring the contours of the cell membranes from micrographs to transparent plastic sheets which were then spaced to scale and stacked. The portion of the reconstructed cell surface taking part in the formation of the blood-airbarrier increased extensively in postnatal stages when compared with reconstructed cells of prenatal stages. Reconstructed cell-surface irregularities decrease during distension. A cytoplasmic plate seen in the last stage studied may represent a forming alveolar pore.     

A method to estimate the DNA content of whole nuclei from measurements made on thin tissue sections

A microdensitometry method that allows estimation of the distribution of the DNA content of nuclei in thin tissue sections is described. The method is based on a theoretical model of Feulgen-stained spherical nuclei, of different sizes, in each of which the DNA is present as a homogeneous solution. In thin sections of nuclei of different sizes, the fraction of DNA per section is inversely proportional to the radius of the nucleus. Histograms of the product of DNA content and radius per nuclear section are independent of nuclear size but depend on total DNA content. The distribution of the total DNA content of nuclei in a section can be estimated from such a histogram. The results of the measurements of a Feulgen-stained rat liver section are described.     

True serial-sectioning of fossil material

A method of cutting serial sections of fossil material using a very thin diamond annular saw, clamped under tension and revolving at 3000 rev/min is described. A small skull of the therapsid reptile Endothiodon has been cut into 104 serial sections 0–6 mm thick. The technique is still in its infancy, but is described to show its potentialities.     

Fine reconstruction of the pancreatic ductular system at the onset of pancreatitis

The three-dimensional structure of the pancreatic ductular system (from the intercalated duct to the intercellular secretory canaliculus) is controversial and unclear. The aim of this study is to reveal the three-dimensional structure of the pancreatic ductular sysytem at the onset of pancreatitis. One day following rat pancreatic duct ligation, dilated lumina from the pancreatic ductular system were reconstructed by light microscopic and scanning electron microscopic examination of pancreatic tissue serial sections. The existence of the intra-acinar duct, which is formed only by centroacinar cells and interconnects the adjacent central lumina in an acinus, was demonstrated. The intercellular secretory canaliculi, which are the terminal parts of the pancreatic ductular system, anastomose and end blindly in the intercellular space located between adjacent lateral surfaces of the acinar cells. The intercalated ducts, the intra-acinar ducts, the central lumina, and the intercellular secretory canaliculi are arranged together in a complex connecting and branching system. However, there were no anastomoses found among the central lumina or acini.     

INTERPRETATIONS OF ELECTRON MICROGRAPHS OF SINGLE AND SERIAL SECTIONS

A method of securing serial sections for electron microscopy is described. Serial sections present certain anomalies of interpretation of a nature such that a complete and detailed three-dimensional reconstruction of the sectioned tissue cannot be made. These anomalies are discussed, as well as those which have been encountered in the interpretation of single sections. Observations of the following kinds have been made in an attempt to elucidate the interpretation of single and serial sections: differing methods of mounting adjacent sections, observation of the same section by high-angle stereoscopy, and examination of sections which have been shadowed prior to and subsequent to electron microscopy. It is found that the appearance of sections is independent of the choice of side to be placed against the formvar films. Stereoscopy shows that the appearance of fine structures is strongly dependent upon the direction of the penetrating electron beam with respect to the plane of the structures. Stereoscopy, combined with shadowing, shows quantitatively that extensive sublimation of polymer occurs upon normal exposure in the electron microscope. Observation of sections shadowed prior to electron microscopy indicates that varying amounts of material are removed between sections by the action of microtomy; i.e., it is probable that the sum of the thicknesses of several serial sections is considerably less than the total thickness of material removed from the block. It is believed that this effect, combined with the effect of sublimation, aids in explaining the failure of adjacent sections to exhibit continuity in their detailed structures.     

True serial-sectioning of fossil material

A method of cutting serial sections of fossil material using a very thin diamond annular saw, clamped under tension and revolving at 3000 rev/min is described. A small skull of the therapsid reptile Endothiodon has been cut into 104 serial sections 0–6 mm thick. The technique is still in its infancy, but is described to show its potentialities.     

Three-dimensional reconstruction and cross-sectional anatomy of the thigh musculature of the developing chick embryo (Gallus gallus)

The technique of graphical reconstruction by orthogonal projection of serial sections is used to generate three-dimensional models of embryonic chick thigh musculature at Hamburger-Hamilton ('51) stages 36 (day 10) and 39 (day 13). Unique and conserved anatomical landmarks are described, which can be used to specify position along the proximo-distal axis of the thigh from cross-sectional appearance. These landmarks provide an important reference for both current and future experimentation in which a precise developmental site must be systematically and repeatedly sampled.     

Preparation of serial sections of arthropods using 2,2-dimethoxypropane dehydration and epoxy resin embedding under vacuum

Improved methods are described for anatomical investigation of small insects and other arthropods using serial semithin sections. The specimens were dehydrated with acidified 2,2-dimethoxypropane and embedded in ERL 4206 epoxy resin under vacuum. This procedure ensures good resin impregnation of thin, long body compartments and appendages. Furthermore, it produces excellent overall preservation of the specimen and its fragile anatomical structures. This procedure saves time and gives excellent results when sectioning difficult arthropod material. A continuous recording of serial semithin sections is possible when diamond knives are used.     

Preparation of serial sections of arthropods using 2,2-dimethoxypropane dehydration and epoxy resin embedding under vacuum.

Improved methods are described for anatomical investigation of small insects and other arthropods using serial semithin sections. The specimens were dehydrated with acidified 2,2-dimethoxypropane and embedded in ERL 4206 epoxy resin under vacuum. This procedure ensures good resin impregnation of thin, long body compartments and appendages. Furthermore, it produces excellent overall preservation of the specimen and its fragile anatomical structures. This procedure saves time and gives excellent results when sectioning difficult arthropod material. A continuous recording of serial semithin sections is possible when diamond knives are used.