Cinematographic analysis of contractile events produced in intrafusal muscle fibres by stimulation of static and dynamic fusimotor axons.
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1. Muscle spindles with an intact blood supply and uninterrupted connexions with ventral and dorsal spinal roots (Bessou & Pages, 1967, 1972) have been prepared in cat's tenuissimus muscles with the aim of cinephotographically recording intrafusal movements induced by the stimulation of single static or dynamic gamma axons; the time cours of these movements and the morphological kind of activated intrafusal muscle fibres have been established. 2. Displacements of spindle guiding marks in the equatorial region elicited by stimulating single static gamma axons are 4-20 times greater in amplitude than the ones elicited by stimulating dynamic gamma axons at the same frequency. 3. The dynamic gamma axons induced a contraction only in nuclear bag fibres which, in addition, never received any static gamma innervation. The static gamma axons evoked contractions either in nuclear bag fibres alone, or in nuclear chain fibres alone, or in both types of intrafusal fibres. Two thirds of static gamma axons supplied nuclear bag fibres. For various reasons, one half only of static gamma axons innervating nuclear bag fibres could be shown to simultaneously innervate nuclear chain fibres. Consequently, about one third of static gamma axons supplied both nuclear bag fibres and nuclear chain fibres, but it is highly probable that this latter figure is an underestimate. One third of static gamma axons produced contraction in nuclear chain fibres only. In this work, the distribution of fusimotor axons has been established in only one muscle spindle of the cluster of muscle spindles that each fusimotor axon is generally innervating. 4. Generally speaking, a static gamma axon elicits contraction of several intrafusal fibres whereas a dynamic gamma axon innervates only one intrafusal fibre and frequently only one pole of the fibre. 5. One third of static gamma axons evoked contractions in nuclear chain fibres that seemed to involve the whole pole. The other static gamma axons and all dynamic gamma axons produced, in the intrafusal fibres that they supplied, one or several foci of localized contractions. 6. The nuclear chain fibres contract and relax faster than nuclear bag fibres. The contractions of nuclear bag fibres supplied by static gamma axons are stronger and faster than those of nuclear bag fibres innervated by dynamic gamma axons. Nearly all nuclear bag fibres innervated by static gamma axons, like the nuclear chain fibres, show transient contractions at each pulse of a stimulation at low frequency (2-20/sec). 7. The results are discussed taking into account the available anatomical and physiological data on the muscle spindle. Their consequences with regard to intrafusal working are briefly considered. (+info)
Infectious diseases in cinema: virus hunters and killer microbes.
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The world of infectious diseases has been rarely presented in the cinema with accuracy. Apart from random biographies of scientists and retellings of stories about great epidemics from the past, most films focus on the dangers presented by outbreaks of unknown agents that originate from acts of bioterrorism, from laboratory accidents, or even from space. We review these films and underline the possible effect that they have on the public's perception of infection--a perception that, when misguided, could prove to be problematic in times of epidemics. (+info)
Quantification of left to right atrial shunts with velocity-encoded cine nuclear magnetic resonance imaging.
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OBJECTIVES: The purpose of this study was to evaluate the ability of velocity-encoded nuclear magnetic resonance (NMR) imaging to quantify left to right intracardiac shunts in patients with an atrial septal defect. BACKGROUND: Quantification of intracardiac shunts is clinically important in planning therapy. METHODS: Velocity-encoded NMR imaging was used to quantify stroke flow in the aorta and in the main pulmonary artery in a group of patients who were known to have an increased pulmonary to systemic flow ratio (Qp/Qs). The velocity-encoded NMR flow data were used to calculate Qp/Qs, and these values were compared with measurements of Qp/Qs obtained with oximetric data derived from cardiac catheterization and from stroke volume measurements of the two ventricles by using volumetric data from biphasic spin echo and cine NMR images obtained at end-diastole and end-systole. RESULTS: Two independent observers measured Qp/Qs by using velocity-encoded NMR imaging in 11 patients and found Qp/Qs ranging from 1.4:1 to 3.9:1. These measurements correlated well with both oximetric data (r = 0.91, SEE = 0.35) and ventricular volumetric data (r = 0.94, SEE = 0.30). Interobserver reproducibility for Qp/Qs by velocity-encoded NMR imaging was good (r = 0.97, SEE = 0.20). CONCLUSIONS: Velocity-encoded NMR imaging is an accurate and reproducible method for measuring Qp/Qs in left to right shunts. Because it is completely noninvasive, it can be used to monitor shunt volume over time. (+info)
The changes in configuration of the rib cage and abdomen during breathing in the anaesthetized cat.
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1. The external surface of the rib cage and abdominal wall in anaesthetized cats was surgically exposed in order to record their movements cinematographically in spontaneous breathing and in paralysed cats, during artificial positive pressure ventilation. 2. Cine-stereophotography was used to allow the recording of the movements of a set of markers placed on the external surface of the trunk wall and the corresponding stereometric data were numerically and graphically processed into three-dimensional drawings. The cine-film frames corresponding to the phases of maximum inflation and deflation of the lungs were analysed to reveal the changes in configuration associated with the respiratory movements of the trunk wall. 3. The changes in shape of the diaphragm and the diaphragm and the displacements of the abdominal viscera between extreme inflation and deflation were recorded by X-ray photography. 4. During spontaneous inspiratory movements, the ribs rotated outwards and rostrally about the costovertebral joints, bringing about an increase in the transverse dimensions of the cage all along its length; these movements were accompanied by a clear-cut caudad displacement of the sternum, caused by the straightening of the costal cartilages and by the widening of the angles defined at sternochondral joints between the sternum and each of the costal cartilages. 5. Neuromuscular blockade abolished muscle tone in the trunk wall, allowing the weight of the viscera markedly to deform its configuration. 6. The inspiratory rib movements of the paralysed animal during artificial inspiration were similar to those during spontaneous breathing but the movements of the sternum were inverted and showed small cranial displacements. 7. The loss of muscular tone under neuromuscular blockade made the abdominal wall more compliant than the rib cage to the positive lung pressure and allowed greater mobility of the viscera with consequent distortion of the shape of the diaphragm. 8. The role of rib cage muscle tone in meeting requirements of purely configurational character in such a shell-like structure is discussed in relation to the optimal mechanical performance of the diaphragm. (+info)
MOTION PICTURE STUDY OF THE TOXIC ACTION OF STREPTOLYSINS ON LEUCOCYTES.
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The initial morphologic alteration in rabbit polymorphonuclear leucocytes exposed to streptolysin is rapid and extensive lysis of cytoplasmic granules. The granules appear to rupture directly into the cell sap. Within a few minutes following degranulation, the leucocyte rounds up, filamentous processes appear on the cell membrane, the cytoplasm liquefies, and finally the nuclear lobes swell and fuse. Streptolysin O causes these changes in intact leucocytes when added in concentrations only slightly higher than those required for release of hydrolases from isolated liver lysosomes, and furthermore exerts its action on granulocytes promptly. On the other hand streptolysin S acts on white cells only after a 15 to 30 minute delay, and the levels necessary to disrupt granules in leucocytes are considerably higher than those which act on lysosome suspensions. Exposure of rabbit alveolar macrophages to streptolysin O also results in lysis of granules, soon followed by alterations in the cytoplasm and membrane. The observations are in accord with the hypothesis that streptolysins penetrate the leucocyte membrane and bring about lysis of granules. Autolytic enzymes released from the granules might then be responsible for the subsequent damage seen in various other cell structures. (+info)
MOTION PICTURE STUDIES ON DEGRANULATION OF HORSE EOSINOPHILS DURING PHAGOCYTOSIS.
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Horse eosinophil function has been studied in vitro by means of phase contrast cinemicrophotography. Locomotion of horse eosinophils was inhibited by serum factors reacting with glass surfaces. Under appropriate conditions which eliminated this inhibitory effect, eosinophils moved about and ingested some particles as rapidly as did neutrophils. Eosinophils were attracted to and readily engulfed such diverse materials as yeast cell walls, foreign erythrocytes, and antigen-antibody precipitates. Specific antibody was required for phagocytosis of red cells, and greatly accelerated the uptake of yeast cell walls. Horse eosinophil granules situated adjacent to material being engulfed disrupted with discharge of granule contents into or alongside the phagocytic vacuole. Granule disruption resulted in a clear zone and deposition of amorphous, phase-dense material. A heat-labile serum factor was required for degranulation of eosinophils ingesting foreign red cells, but not for degranulation during engulfment of yeast cell walls or antigen-antibody precipitates. Horse eosinophils were incapable under these conditions of engulfing an entire human red cell. The eosinophil commonly put out a large pseudopod to surround about half the red cell, and then appeared to constrict this pseudopod distally to cut the erythrocyte in half. It is concluded that eosinophils are phagocytic cells, resembling neutrophils in many of their properties. Any specific functions of eosinophils, distinguishing them from other phagocytes, remain to be discovered. (+info)
STUDIES ON CILIA. THE FIXATION OF THE METACHRONAL WAVE.
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Upon excision into spring water, the lateral cilia of the gill of the freshwater mussel Elliptio complanatus (Solander) stop beating, but 0.04 M potassium ion can activate the gill so that these cilia again beat with metachronal rhythm. One per cent osmium tetroxide quickly pipetted onto a fully activated gill fixes the lateral cilia in a pattern that preserves the form and arrangement of the metachronal wave, and permits the cilia to be studied with the electron microscope in all stages of their beat cycle. Changes are seen in the fixed active preparation that are not present in the inactive control, i.e., in the packing of the cilia, the position of the axis of the ciliary cross-section, and the diameter of the ring of peripheral filaments. Analysis of these parameters may lead to new correlations between ciliary fine structure and function. (+info)
CORONARY CINEANGIOGRAPHY. CLINICAL STUDIES FOR EVALUATION IN EQUIVOCAL CASES.
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Coronary cineangiography was helpful in the following circumstances:1. A patient with an abnormal electrocardiogram and no evidence of coronary artery disease.2. A patient with thoracic pain in whom the diagnosis of coronary artery disease was questioned.3. A patient with intractable angina pectoris who was being studied for possible surgical therapy.4. A patient with coronary insufficiency and aortic stenosis who was being evaluated for operation on the aortic valve. (+info)