Kinematics of metachronous walking. I. Configurations]

?The notion of configuration of legs' spatial distribution is presented. The relationships between the legs' spatial distribution and the features of meachronal activity in the ipsilateral legs row of some less than abstract greater than animal's locomatory system were investigated on the basis of theoretical analysis of different configurations. Some hypotheses about the control of legs' metachronal activity are proposed.     

Kinematics of metachronous walking. III. Invariants]

The concept of a kinematic space for a locomotor system is introduced and regime of locomotion is defined as a continued one-dimensional manifold of this space. The problem of describing of locomotion is set (settled) by kinematic invariants. It is shown that metachrony of such millipedes as Scolopendra and Julus can be considered as a special case of some "relativity principle", on the basis of which the expression of metachrony invariant has come out. The attempt is made to use this principle for the determination of step's invariants of each individual leg too.     

Kinematics of walking in the hermit crab,Pagurus pollicarus

Hermit crabs are decapod crustaceans that have adapted to life in gastropod shells. Among their adaptations are modifications to their thoracic appendages or pereopods. The 4th and 5th pairs are adapted for shell support; walking is performed with the 2nd and 3rd pereopods, with an alternation of diagonal pairs. During stance, the walking legs are rotated backwards in the pitch plane. Two patterns of walking were studied to compare them with walking patterns described for other decapods, a lateral gait, similar to that in many brachyurans, and a forward gait resembling macruran walking.Video sequences of free walking and restrained animals were used to obtain leg segment positions from which joint angles were calculated. Leading legs in a lateral walk generated a power stroke by flexion of MC and PD joints; CB angles often did not change during slow walks. Trailing legs exhibited extension of MC and PD with a slight levation of CB. The two joints, B/IM and CP, are aligned at 90° angles to CB, MC and PD, moving dorso-anteriorly during swing and ventro-posteriorly during stance. A forward step was more complex; during swing the leg was rotated forward (yaw) and vertically (pitch), due to the action of TC. At the beginning of stance, TC started to rotate posteriorly and laterally, CB was depressed, and MC flexed. As stance progressed and the leg was directed laterally, PD and MC extended, so that at the end of stance the dactyl tip was quite posterior. During walks of the animal out of its shell, the legs were extended more anterior-laterally and the animal often toppled over, indicating that during walking in a shell its weight stabilized the animal.An open chain kinematic model in which each segment was approximated as a rectangular solid, the dimensions of which were derived from measurements on animals, was developed to estimate the CM of the animal under different load conditions. CM was normally quite anterior; removal of the chelipeds shifted it caudally. Application of forces simulating the weight of the shell on the 5th pereopods moved CM just anterior to the thoracic-abdominal junction. However, lateral and vertical coordinates were not altered under these different load conditions. The interaction of the shell aperture with proximal leg joints and with the CM indicates that the oblique angles of the legs, due primarily to the rotation of the TC joints, is an adaptation that confers stability during walking.     

Helical motion analysis of the knee--II. Kinematics of uninjured and injured knees during walking and pivoting

The knee kinematics of eight individuals with uninjured knees and of seven individuals with ruptured anterior cruciate ligaments have been investigated during walking and pivoting. The kinematics were measured using a six degree of freedom goniometer and quantitated using helical motion analysis. The helical motion variables reveal clearly that the knee is definitely neither a hinge nor a planar joint and its dynamic behavior changes over the stride. Ligamentous loss results in more adduction and external rotation during certain periods of the stride. Also, the range of translation of the tibia in the medial/lateral direction is reduced, and its average translation is more medial.     

Kinematics of lower limbs during walking are emulated by springy walking model with a compliantly connected,off-centered curvy foot

The dynamics of the center of mass (CoM) during walking and running at various gait conditions are well described by the mechanics of a simple passive spring loaded inverted pendulum (SLIP). Due to its simplicity, however, the current form of the SLIP model is limited at providing any further information about multi-segmental lower limbs that generate oscillatory CoM behaviors and their corresponding ground reaction forces. Considering that the dynamics of the CoM are simply achieved by mass-spring mechanics, we wondered whether any of the multi-joint motions could be demonstrated by simple mechanics. In this study, we expand a SLIP model of human locomotion with an off-centered curvy foot connected to the leg by a springy segment that emulates the asymmetric kinematics and kinetics of the ankle joint. The passive dynamics of the proposed expansion of the SLIP model demonstrated the empirical data of ground reaction forces, center of mass trajectories, ankle joint kinematics and corresponding ankle joint torque at various gait speeds. From the mechanically simulated trajectories of the ankle joint and CoM, the motion of lower-limb segments, such as thigh and shank angles, could be estimated from inverse kinematics. The estimation of lower limb kinematics showed a qualitative match with empirical data of walking at various speeds. The representability of passive compliant mechanics for the kinetics of the CoM and ankle joint and lower limb joint kinematics implies that the coordination of multi-joint lower limbs during gait can be understood with a mechanical framework.     

Heteromorphism of corynebacteria. II. Microcells]

The formation of microcells is one of the manifestations of the heteromorphism of Corynebacterium. It can occur in 6 ways, of these, 3 are possible during septation (chaotic septation of gigantic macroforms, irregular multiseptation of elongated organisms, and microcells appearing as inserts at the sites of the septum formation), and 3 in undividing cells (microcells at the edge segments of the protoplast, exogemmation, endogemmation). The analysis of the ultrastructure of microcells indicated the possibility of their independent existence for a certain period of time.     

Kinematics of plant growth.

Many of the concepts and equations which have been used in the study of compressible fluids can be applied to problems of plant development. Growth field variables, i.e. functions of position in the plant and of time, can be specified in either Eulerian (spatial) or Lagrangian (material) terms. The two specifications coincide only when the spatial distribution of the variable is steady, and steady patterns are most likely to emerge when an apex is chosen as origin of the co-ordinate system. The growth field itself can be described locally by the magnitude and orientation of the principal axes of the rate of strain tensor and by the vorticity tensor. Material derivatives can be calculated if the temporal and spatial variation in both growth velocity, u (rate of displacement from a material origin), and the variable of interest are known. The equation of continuity shows the importance of including both growth velocity, u, and growth rate, ▽ ·u in estimates of local biosynthesis and transport rates in expanding tissue, although the classical continuity equation must be modified to accommodate the compartmentalized distributions characteristic of plant tissue. Relatively little information on spatial variation in plant organs can be found in the botanical literature, but the current availability of interactive computer graphics equipment suggests that analysis of the spatial distribution of growth rates at least is no longer difficult.     

Gaits of monkeys and horses: A methodological critique

In a previous paper it was shown that the traditional methodology used to analyze quadrupedal gaits is inadequate when applied to the gaits of monkeys. The traditional methods were modified for use with the monkey sample (Prost, '65). Was the modification a general improvement of the traditional approach or was it dictated by peculiarities of monkey locomotion? The traditional analysis receives its support primarily from its usefulness in handling horse gaits. If it can be shown that the modified methods improve the analysis for horses, then it can be claimed that the system is not a special case designed uniquely for use with monkeys. Motion pictures were taken of an American Saddle Bred, five-gaited horse performing several classic gaits. The films were analyzed using the modified methods developed to analyze monkey gaits. The analysis was superior to the traditional approach. All of the organizing principles which structure horse gaits were found to be identical to those which structure monkey gaits.     

Development of a robotic walking simulator for gait rehabilitation]

Restoration of gait is a major concern of rehabilitation after stroke or spinal cord injury. Modern concepts of motor learning favour a task-specific repetitive approach, i.e. "whoever wants to learn to walk again must walk." However, the physical demands this places on the therapist, is a limiting factor in the clinical routine setting. This article describes a robotic walking simulator for gait training that enables wheelchair-bound subjects to freely carry out repetitive practicing of an individually adapted gait pattern under simulation of the manual guidance of an experienced therapist. The technical principle applied makes use of programmable footplates with permanent foot/machine contact in combination with compliance control. The solution chosen comprises a planar parallel-serial hybrid kinematic system with three degrees of freedom that moves the feet in the sagittal plane. Gait analysis while floor walking and stair climbing, clinical practicability and safety aspects were the basis for the design. A variable compliance control enables man-machine interaction, ranging from purely position controlled movement to full compliance during swing phase above a virtual ground profile. In full compliance mode the robotic walking simulator behaves like a haptic device. The concept presented offers new prospects for individualized gait rehabilitation.     

Ultrastructure of L-forms. II. L-forms of Listeria monocytogenes]

A study was made of ultrathin sections of the stable l-forms of listeria obtained under the action of penicillin in meat-peptone-liver broth. A marked cellular polymorphism was found in the L-form culture: within the same colony cells differed in size, shape and fine structure. It is supposed that polymorphism could be partially explained by a different plasticity and premeability of cytoplasmic membrane in different types of cells of the same L-colony. The three-layer structure of the membrane does not always display the same distinctness in various L-colony cells and also in different areas of the cell surface. Structureless material of low electron density, possibly a defective murein or its precursor, was revealed on the membrane surface. Electrondense inclusion bodies, mesosomes of ring-shaped or more complicated structure and two-contour vesicles were found in the cytoplasm. The cells multiplied by budding, by binary and anomalies division participation of mesosomes in this process was not proved by the L-forms.     

Work of the human visual system. II. Color]

In the first part of this work [1] the author presented the expression for so called adequate visual stimulus. This expression describing the change of relative space - time differences of light actions in different retinal points defines the conditions necessary for producing visual sensations. In this paper author makes a statement that the quality of visual sensation (the percieved colour) can be evaluated by integrating the expression for the adequate visual stimulus both in time and in space. The integration in space is fulfilled starting from the extreme periphery of the retina, which is usually illuminated by scattered light averaged over the whole visual field. Human visual system works in such a way that the light action in the extreme periphery plays a role of the unit for scaling of visual sensations.     

Ultrastructure of the silkworm testis. II. Ductus deferens]

Ultrastructure of the silkworm's ducts defferens is described after spermatozoa went out of lobulli testis and after the end of secretion. D. defferens is composed of an external layer of the ring and longitudinal muscles and of an internal layer of glandular cells. Both layers are separated by structurless lamina--tunica propria. Z-discs of irregular form are placed at the borders of sarcomeres. M-lines are absent. Sarcolemma intrudes into the muscle fibers at the level of Z-discs and gives origin to T-system the tubes of which together with sarcoplasmic reticulum form dyades. Structures like intercalate discs are observed in muscle tissue at the level of Z-discs. Glandular cells have unusually developed nucleoli, many ribosomes, lysosome-like and residual bodies. There are comb desmosomes between the glandular cells.     

The pathogenesis of chronic lymphocytic leukemia. II]

Starting from a survey of the present knowledge of morphological, immunological and biochemical characteristics of lymphocytes degenerated in leukamic respect and their kinetics, proposals are made for the pathogenesis of chronic lymphatic leukaemia (CLL). The fact that a progressing restriction of the functional immunological variety will occur in the typical CLL is discussed. Besides normal T and B cells there are elements similar to B and T cells whose percentage of proportion changes in the course of the illness with diminution of function and increasing immunological defect.     

Electrophysiological studies of chemoreceptors sensitive to pyridine on the crayfish walking leg. II. Characteristics of inhibitory molecules

The effect of substituted pyridines on the response of singlepyridine-sensitive cells from crayfish walking legs was investigatedelectrophysiologically. Seven p-substituted pyridines, actingreversibly, were identified as specific antagonists at the pyridinereceptor. The maximum saturation frequency of the response toagonists was reached in the presence of antagonists but thedose–response curves of the agonists were shifted in parallelto the right along the concentration axis. Schild plots of threehighly effective antagonists with six agonists were linear witha slope close to one, indicating competitive antagonism. Theinhibition constants yielded a K₁ value of {small tilde}4–8µmol for the most effective antagonist, 4-(4-nitrobenzyl)pyridine,which had only one order of magnitude lower affinity than themost effective agonist 2,3'-bipyridyl. The antagonists 2,4'-bipyridyland 4-benzylpyridine had K¹ values of 6–10 µmol,followed by 4-acetylpyridine with a K¹ value of 30–70µmol. The rank order of inhibitory potency of the differentantagonists was found to be the same for all units tested. Comparingelectronic effects (Hammett values and pKa values) of the substitutentsin p- and m-position showed that inhibitory effectiveness decreasedwith a decrease in pKa and an increase in Partition coefficientswere determined for 10 agonists and the antagonists which weregenerally more lipophilic than the agonists. A hypotheticalreceptor site is proposed.