Showing papers by "McGill University published in 1971"

Satellite cells as the source of nuclei in muscles of growing rats.

Abstract: The source of the new nuclei appearing during the growth of muscle fibers was examined in the tibialis anterior muscle of young Sherman rats (14–17 days of age) using radioautography at various intervals after a single injection of a small, non-toxic dose of 3H-thymidine (2 μCi/g body weight). Two techniques were employed: (1) labeled nuclei were detected in 1 μ thick radioautographs examined in the light microscope, and identified by simultaneous electron microscope examination of an adjacent section. The nuclei were then classified either as “true” muscle nuclei (within the plasmalemma of the fibers) or as belonging to “satellite cells” (which are mononucleated cells with scanty cytoplasm wedged between plasmalemma and basement membrane). (2) Muscle fibers freed by collagenase digestion were radioautographed one hour after 3H-thymidine injection in order to determine the total number of labeled nuclei (true muscle nuclei plus those of satellite cells) per unit length of fiber. Certain nuclei within the basement membrane of muscle fibers are labeled one hour after 3H-thymidine and, therefore, synthesize DNA. The electron microscope demonstrates that these nuclei invariably belong to satellite cells, never to true muscle nuclei. Furthermore, the total number of labeled nuclei per unit length of fiber doubles between 1 and 24 hours; and, therefore, the labeled satellite cell nuclei undergo mitosis. Following mitosis, half of the daughters of satellite cells are incorporated into the fibers to become true muscle nuclei. The remaining half divides again later; and half of their daughter cells are incorporated. Thus, satellite cells in young rats divide repeatedly and function as a source of true muscle nuclei.

On the language of pain

Abstract: The purpose of this study was to develop new approaches to the problem of describing and measuring pain in human subjects. Words used to describe pain were brought together and categorized, and an attempt was made to scale them on a common intensity dimension. The data show that: 1) there are many w

Primary auditory stream segregation and perception of order in rapid sequences of tones

Abstract: A recent finding of the inability of listeners to judge the order of three or four nonspeech sounds presented in a repetitive cycle is explained by the concept of stream segregation. Two experiments showed that at high presention rates of a short cycle of six tones (three high and three low), 5s invariably segregated the tone sequences into streams based on frequency and could perceive only those patterns relating elements of the same subjective stream.

The spermatogonial stem cell population in adult rats. I. Their morphology, proliferation and maturation.

Abstract: Whole mounted segments of seminiferous tubules from rat testes have been used to investigate the morphology and proliferative activity of the undifferentiated type A spermatogonial population. This has led to the formulation of a new model for spermatogonial stem cell renewal. Three groups of undifferentiated A spermatogonia were classified according to their topographical arrangements as isolated, paired, and aligned spermatogonia. It was proposed that the isolated (as well as a few paired) spermatogonia, which were always present throughout the seminiferous epithelium, are the functional stem cells and should therefore be designated as As. Through sporadic divisions, the As spermatogonia both maintain their own numbers and give rise to pairs of cells which are destined to eventually differentiate. The latter undergo several synchronous divisions in succession, thereby forming increasingly longer chains of aligned spermatogonia. The proliferation of these chains, primarily in stages I–V, leads to a gradual expansion in the size of the undifferentiated type A population. When the population attains its maximal size in stage V, mitotic activity among the aligned cells ceases, and all of these cells morphologically transform without further division into typical A1 spermatogonia. Subsequently, the cohort of A1 cells synchronously divides in stage IX to begin the long process of spermatogonial maturation. The isolated (and a few paired) cells, which do not undergo this transformation and remain quiescent during the stage IX peak of mitosis, form a residual stock of stem cells, that, during the course of another cycle, rebuild the population of aligned A spermatogonia. In this way, a continual supply of type A1 spermatogonia which will cyclically differentiate is insured.

Managerial Work: Analysis from Observation

Abstract: The progress of management science is dependent on our understanding of the manager's working processes. A review of the literature indicates that this understanding is superficial at best. Empirical study of the work of five managers supported by those research findings that are available led to the following description: Managers perform ten basic roles which fall into three groupings. The interpersonal roles describe the manager as figurehead, external liaison, and leader; the information processing roles describe the manager as the nerve center of his organisation's information system; and the decision-making roles suggest that the manager is at the heart of the system by which organizational resource allocation, improvement, and disturbance decisions are made. Because of the huge burden of responsibility for the operation of these systems, the manager is called upon to perform his work at an unrelenting pace, work that is characterized by variety, discontinuity and brevity. Managers come to prefer issues that are current, specific, and ad hoc, and that are presented in verbal form. Aa a result, there is virtually no science in managerial work. The management scientist has done little to change this. He has been unable to understand work which has never been adequately described, and he has poor access to the manager's information, most of which is never documented. We must describe managerial work more precisely, and we must model the manager as a programmed system. Only then shall we be able to make a science of management.

Electrohydrodynamic Deformation and Burst of Liquid Drops

Abstract: In 60 Hz electric fields, liquid drops suspended in a second immiscible liquid deformed into prolate spheroids oriented in the direction of the field in 22 drop/medium combinations studied experimentally. In steady fields, oblate or prolate spheroids were formed depending upon the dielectric constants and resistivities of the drop and medium. In systems yielding oblate spheroids, a critical frequency existed at which the drop remained spherical at all field strengths. Electrohydrodynamic streaming near the surface of the drop occurred as predicted by Taylor. A theory, valid for both steady and alternating fields, was developed which predicts the conditions leading to oblate and prolate spheroids and which reduces to Taylor's equations for conducting dielectrics in steady fields and to the equations for perfect dielectrics in steady and alternating fields. The theory explains the general types of deformation and electrohydrodynamic flow which were observed and predicts several interesting new modes of behaviour. In most cases the measured deformations were greater than calculated from the theory; various explanations for this discrepancy are advanced, but no definite conclusions are reached. At high field strengths the drops burst in two basically different ways which we have designated as electric and electrohydrodynamic burst, the first caused by electric stresses alone and the second by a combination of electric and hydrodynamic stresses.

Renewal of the epithelium in the descending colon of the mouse. I. Presence of three cell populations: vacuolated-columnar, mucous and argentaffin.

Abstract: The epithelium of the descending colon was examined in the mouse using one-micron thick Epon embedded sections of formaldehyde-fixed tissues stained with the periodic acid-Schiff and iron-hematoxylin techniques, and radioautographed at various time intervals after a single injection of tritium labeled thymidine. Four cell types may be described: vacuolated cells located in the lower twothirds of the crypts, columnar cells in the upper third and on the surface, mucous cells and argentaffin (granule-containing) cells distributed throughout crypt and surface. One hour after injection of 3H-thymidine, only some vacuolated and mucous cells are labeled; cells of both types may show mitotic figures, but only in the lower two-thirds of the crypts. By 36 hours, label appears in cells of the upper third of the crypts; some of these cells are intermediate between vacuolated and columnar, while others are full-fledged columnar cells. Labeled mucous cells also appear at this level. Occasionally, a labeled argentaffin cell may be found at that time toward the base of the crypts. By three days, labeled columnar and mucous cells are found on the surface. Extrusion of such labeled cells is usually seen toward the fourth day. It is concluded that the epithelium of the descending colon of the mouse includes three cell lines. In the first one, vacuolated cells divide to produce more vacuolated cells, but as they migrate upwards, they lose their vacuoles while ceasing to divide and become typical columnar cells. Together they make up the vacuolated-columnar cell line. The mucous cells arise from mitosis of cells with a small amount of mucus. As daughter cells migrate upwards, their theca swells, presumably because production of mucus exceeds release, whereas, on the surface, the theca becomes narrow as release predominates. In the third cell line, the argentaffin cells do not divide and appear to originate from poorly differentiated vacuolated cells at the base of the crypts. The latter cells may also give rise to the young mucous cells capable of division. The three cell lines would thus have a common stem cell.

The spermatogonial stem cell population in adult rats. II. A radioautographic analysis of their cell cycle properties.

Abstract: Radioautographed whole mounted seminiferous tubules from adult rat testes were used to analyse undifferentiated type A spermatogonia at various intervals up to 81 hr following a single injection of 3H-TdR. the data obtained led to the identification of the spermatogonial stem cell and to the formulation of a new model for spermatogonial renewal and differentiation. Undifferentiated type A cells were morphologically alike, but were topographically classified as (1) isolated or (2) paired and aligned. Although labeled isolated A cells were scattered over most stages of the seminiferous epithelium, their proliferative activity varied with the stage; their labeling index was 20-30% in stages I and II, but less than 1% in stages VII and VIII. By tracing the labeled divisions of isolated A spermatogonia in time, it was seen that some daughter cells became separated from one another to form two new isolated cells, while others remained together as paired A spermatogonia. Analysis of two successive waves of labeled mitoses revealed that most paired A spermatogonia continued to proliferate forming four aligned A cells, many of which divided again to produce a chain of eight and so on. the greatest incidence of labeling among paired and aligned A spermatogonia occurred in stages XIII-III. In stage I, where the labeling index was 50%, the calculated proliferative fraction was 1 for these spermatogonia. Between stages II and V, they began to leave mitotic cycle, and during stage V this entire cohort morphologically transformed into A1 spermatogonia. Labeled metaphase curves for undifferentiated A spermatogonia were distinct from any of the curves previously constructed for the six classes of differentiating spermatogonia, especially because of particularly long S and G2 phases in the former. the cell cycle time of paired and aligned A cells was 55 hr, compared to an average of 42 hr for differentiating types A2 to B.

Motion of entrained particles in gas streams

Abstract: Recent work on the drag experienced by an entrained particle in relative motion through a fluid is reviewed. It is shown that fluid turbulence, acceleration, particle shape and orientation, and particle-fluid mass transfer can all have a significant effect on the value of the drag force, particularly when the non-idealities cause a change in the flow pattern around the particle. Conditions under which the drag force can be predicted with certainty are still very limited, and some potentially valuable directions for future research are suggested. On fait une revue des travaux recents sur la trainee a la quelle est sujette une particule entrainee dans un mouvement relatif dans un fluide. On voit que la turbulence du fluide, l'acceleration, la forme et l'orientation des particules et le transfert de masse entre les particules et le fluide sont des facteurs qui peuvent tous avoir un effet appreciable sur la valeur de la force de trainee, surtout lorsque l'absence de conditions ideales produit un changement dans l'allure de l'ecoulement autour de la particule. Les conditions qui permettent de predire avec certitude la force de trainee sont encore tres limitees et l'on propose des directives potentiellement valables pour les travaux futurs de recherche.

Meeting Abstracts Phantom Limb PainImplications for Treatment of Pathologic Pain

Abstract: The mechanisms underlying pathologic pain states such as phantom limb pain remain a mystery. Observations that 1) pain may persist indefinitely; 2) trigger zones may spread to healthy parts of the body; and 3) pain may be abolished by either decreasing or increasing the sensory input cannot be explained solely in terms of peripheral causes or abnormal activity restricted to the spinal cord. This paper proposes that a portion of the brainstem reticular formation exerts a tonic inhibitory effect on transmission at all levels of the somatic projection system. The loss of sensory input after amputation would decrease the tonic inhibition and increase the probability of self-sustaining neural activity. The self-sustaining activity, its capacity to recruit adjacent neurons, and its occurrence at several transmission levels would underlie prolonged pain and spread of trigger zones. Modulation of the sensory input by anesthetic blocks or intense stimulation would abolish the self-sustaining activity and produce pain relief.

On the Representation of Modules by Sheaves of Factor Modules

Abstract: Throughout this paper we consider associative rings with unity elements. In §1 various results on the representation of rings by rings of sections of special rings are compared. In particular, it is shown that results enunciated by Dauns and Hofmann, Koh, and the present author may all be deduced from one statement, the proof of which appears in §3.

A system for rapid digital aeromagnetic interpretation

Abstract: In this paper, we describe a system for the collection and interpretation of aeromagnetic data. The great interdependence of the detection instrumentation, the navigation instrumentation, the compilation procedures, and the interpretation techniques is defined. Doppler radar is the basis for aircraft navigation; it drives the recording devices to produce spatial‐domain data. A digital system provides a means for rapid computer interpretation. A distinction is made between data‐processing techniques that aid in interpretation and those that are involved in the actual definition of magnetic anomalies in terms of the horizontal and vertical position of the causative bodies. The computerized interpretation technique described herein is an extension of a technique first described by S. Werner of the Geological Survey of Sweden. Depths are calculated for all geologic events with some elongation, regardless of the events’ strike, dip, and remanent magnetization; and the calculations are valid at any magnetic inc...

Particle motions in non-Newtonian media

Abstract: An experimental study of the behaviour of rigid and deformable particles suspended in pseudoplastic and elasticoviscous liquids undergoing slowCouette flow was undertaken. The velocity profiles deviated slightly from those obtained forNewtonian fluids, but the measured angular velocities of rigid spheres showed that the rotation of the field was equal to half the velocity gradient. While the measured angular velocities of rods and discs were in accord with theory applicable toNewtonian liquids, in both non-Newtonian media there was a steady drift in the orbit towards an asymptotic value corresponding to minimum energy dissipation in the flow. Furthermore, discs in elasticoviscous solutions of polyacrylamide at higher shear stresses aligned themselves in the direction of the flow and ceased to rotate. Migration of rigid particles across the planes of shear in the annul us of theCouette was also observed. In pseudoplastic liquids, the migration was towards the region of higher shear, whereas the opposite was true in elasticoviscous liquids. The deformation, orientation and burst of pseudoplastic drops inNewtonian liquids and that ofNewtonian drops in pseudoplastic fluids were similar to those previously in completelyNewtonian systems. With elasticoviscous drops, however, the deformation was smaller than given by theory. As in elasticoviscous fluids, two-body collisions of rigid uniform spheres in the pseudoplastic liquids were unsymmetrical and irreversible, thus differing from collisions inNewtonian systems where complete reversibility is observed. While some of the observed phenomena in elasticoviscous suspensions could be qualitatively interpreted, particle behaviour in the pseudoplastic liquids could not be explained in terms of the known rheological properties of the fluids.

Elaboration of the matrix glycoprotein of enamel by the secretory ameloblasts of the rat incisor as revealed by radioautography after galactose-3h injection

Abstract: The elaboration of enamel matrix glycoprotein was investigated in secretory ameloblasts of incisor teeth in 30–40-g rats. To this end, the distribution of glycoprotein was examined histochemically by the use of phosphotungstic acid at low pH, while the formation of glycoprotein was traced radioautographically in animals sacrificed 2.5–30 min after galactose-3H injection. Histochemically, the presence of glycoprotein is observed in ameloblasts as well as in the enamel matrix; in ameloblasts glycoprotein occurs within the Golgi apparatus in amounts increasing from the outer to the inner face of the stacks of saccules, and is concentrated in condensing vacuoles and secretory granules; in the enamel matrix, glycoprotein is observed within linear subunits. Radioautographs at 2.5 min after injection demonstrate the uptake of galactose-3H label by Golgi saccules, indicating that galactose-3H is incorporated into glycoprotein within this organelle. After 5–10 min, the label collects in the condensing vacuoles and secretory granules of the Golgi region. By 20–30 min, the label appears in the secretory granules of the apical (Tomes') processes, as well as in the enamel matrix (next to the distal end of the apical processes, and at the tips of matrix prongs). In conclusion, galactose contributes to the formation of glycoprotein within the Golgi apparatus. The innermost saccules then distribute the completed glycoprotein to condensing vacuoles, which later evolve into secretory granules. These granules rapidly migrate to the apical processes, where they discharge their glycoprotein content to the developing enamel.

The motion of long slender bodies in a viscous fluid. Part 2. Shear flow

Abstract: A long slender axisymmetric body is considered placed at rest in a general linear flow in such a manner that the undisturbed fluid velocity is identically zero on the body axis. Formulae for the total force and torque on the body are found as an expansion in terms of a small parameter κ defined as the radius-to-length ratio of the body. These general results are used to determine the resistance to axial rotation of the body and also the equivalent axis ratio of the body for motion in a shear flow.

Application of Gas-Liquid Chromatography to the Thermodynamics of Polymer Solutions

Abstract: It has been well established that gas—liquid chromatography (glc) can give accurate thermodynamic data on binary solutions where the components differ considerably in volatility or molecular weight. The substance of lower molecular weight (component 1) is injected into the moving gas phase and dissolves at effectively infinite dilution in the stationary liquid phase. This is formed by the higher molecular weight material, for example, squalane, biphenyl, dinonyl phthalate, glycerol, or the higher n-alkanes such as C16, C24, C36, etc. The convenience of the technique is such that activity coefficient data have already been obtained for hundreds of systems. In contrast, activity data are available for far fewer high polymer systems, in part certainly because of the need to use the laborious vapor sorption technique. While that technique gives activity data as a function of concentration, it would still be desirable to have data at infinite dilution for a variety of systems in order to test contempo...

A NEW CHONDRODYSTROPHIC MUTANT IN MICE : Electron Microscopy of Normal and Abnormal Chondrogenesis

Abstract: The occurrence of a new mutation affecting cartilage and bone in mice is reported. The gene is lethal, shows autosomal recessive inheritance, and has high penetrance. It is not allelic to shorthead and probably not to phocomelia or achondroplasia. It results in a foreshortened face, cleft palate, defective trachea, and shortened long bones with flared metaphyses. Chondrocytes of epiphyseal cartilage from the mutant are not aligned in columns, and there is a decrease in the usual staining of the cartilage matrix. Electron microscope observations show large, wide collagen fibrils with "native" banding in the matrix of mutant cartilage, which are not present in normal cartilage. Possible explanations for the expression of this genetic disorder of cartilage development are put forward.

Radioautographic study of in vivo and in vitro incorporation of fucose-3h into thyroglobulin by rat thyroid follicular cells

Abstract: The incorporation of fucose-3H in rat thyroid follicles was studied by radioautography in the light and electron microscopes to determine the site of fucose incorporation into the carbohydrate side chains of thyroglobulin, and to follow the migration of thyroglobulin once it had been labeled with fucose-3H. Radioautographs were examined quantitatively in vivo at several times after injection of fucose-3H into rats, and in vitro following pulse-labeling of thyroid lobes in medium containing fucose-3H. At 3–5 min following fucose-3H administration in vivo, 85% of the silver grains were localized over the Golgi apparatus of thyroid follicular cells. By 20 min, silver grains appeared over apical vesicles, and by 1 hr over the colloid. At 4 hr, nearly all of the silver grains had migrated out of the cells into the colloid. Analysis of the changes in concentration of label with time showed that radioactivity over the Golgi apparatus increased for about 20 min and then decreased, while that over apical vesicles increased to reach a maximum at 35 min. Later, the concentration of label over the apical vesicles decreased, while that over the colloid increased. Similar results were obtained in vitro. It is concluded that fucose, which is located at the end of some of the carbohydrate side chains, is incorporated into thyroglobulin within the Golgi apparatus of thyroid follicular cells, thereby indicating that some of these side chains are completed there. Furthermore, the kinetic analysis demonstrates that apical vesicles are the secretion granules which transport thyroglobulin from the Golgi apparatus to the apex of the cell and release it into the colloid.

‘Sephadex’ Column Chromatography as an Adjunct to Competitive Protein Binding Assays of Steroids

Abstract: THE remarkably specific binding properties of certain proteins make possible competitive protein binding (CPB) assays for many hormones1,2. Various kinds of binding proteins have been used, including plasma proteins, tissue proteins, antibodies (radio-immunoassay) and enzymes (radio-enzymatic assay), but no protein has been found which binds only a single substance—each can be shown to bind a series of closely related analogues. To measure a single ligand in the complex mixtures present in biological fluids, it is therefore often necessary to separate the competing analogues. This is especially true in the use of the plasma proteins for the assay of steroids, for each binds two distinct groups of steroid—the corticosteroid binding globulin (CBG) binds corticoids and progestins and the sex hormone binding globulin (SHBG) binds androgens and oestradiol. Because all the bound steroids are of biological interest, however, it is often desirable to be able to measure all of them, so that the diversity of binding can be an advantage if the steroids can be adequately separated before assay.

Finite-element solution of 2-dimensional exterior-field problems

Abstract: A new method, based on the finite-element method of discretisation and compatible with existing finite-element techniques, is described for the solution of field problems in which the region of prime interest is embedded in an infinitely extending region where Laplace's equation holds. The essence of this method lies in representing the infinitely extending region by a single finite element, which may be included in an element assembly descriptive of the finite region of major interest. No iterative computation is necessary, and the computing effort required for solution is essentially the same as that required for solving the interiorfield problem alone.

The in vivo effects of semipermeable microcapsules containing L-asparaginase on 6C3HED lymphosarcoma.

Abstract: SEMIPERMEABLE microcapsules are spherical ultrathin polymer membranes of cellular dimensions each enveloping a micro-droplet of protein solution or suspension1,2. Microencapsulated enzymes, while prevented from leaking out to give rise to hypersensitivity or immunological reactions, can act on external substrates dialysing across the semipermeable membranes3,4. Microencapsulated enzymes include those present in erythrocyte haemolysates, urease, catalase, trypsin, uricase and L-asparaginase1,4. L-Asparaginase suppresses the growth of certain asparagine dependent tumours5 by depleting the extracellular supply of asparagine. Recent reviews6–9 suggest that parenterally injected Escherichia coli asparaginase is removed rapidly as foreign protein and that there appears to be a relationship between the antitumour activity and the plasma half-life of L-asparaginase. In addition, E. coli asparaginase may give rise to hypersensitivity and immunological reactions. Because microencapsulated L-asparaginase acts efficiently in vitro and in vivo on asparagine which dialyses across the microcapsule membranes10, we have examined the effects of microencapsulated asparaginase on 6C3HED lymphosarcoma cells implanted in mice.