Showing papers by "McGill University published in 1970"

The motion of long slender bodies in a viscous fluid Part 1. General theory

Abstract: A solid long slender body is considered placed in a fluid undergoing a given undisturbed flow. Under conditions in which fluid inertia is negligible, the force per unit length on the body is obtained as an asymptotic expansion in terms of the ratio of the cross-sectional radius to body length. Specific examples are given for the resistance to translation of long slender bodies for cases in which the body centre-line is curved as well as for those for which the centre-line is straight.

Use of the Kolmogorov-Smirnov, Cramer-Von Mises and Related Statistics without Extensive Tables

Abstract: SUMMARY This paper gives modifications of eleven statistics, usually used for goodness of fit, so as to dispense with the usual tables of percentage points. Some test situations are illustrated, and formulae given for calculating significance levels.

Electron microscopic identification of three classes of oligodendrocytes and a preliminary study of their proliferative activity in the corpus callosum of young rats.

Abstract: In recent electron microscope studies of the corpus callosum in 60–80 gm male rats, some of the cells were identified as microglia by staining with the weak silver carbonate method of del Rio-Hortega, and others as astrocytes by staining with the gold chloride sublimate method of Ramon y Cajal. In the present work, the cells which did not belong in one of these two groups were examined in the light microscope using semithin sections stained with toluidine blue and in the electron microscope using thin sections stained with uranyl-lead. These cells make up a large, somewhat heterogeneous group, but they have a few common features: regular nucleus, cytoplasm rich in ribosomes and microtubules, and a variable number of narrow, non-branching fine processes of uniform diameter. Because of these features, the cells are all taken to be oligodendrocytes. Three classes may be described within this group of cells: (a) light oligodendrocytes, which are large cells with pale nucleus, a large nucleolus, a cytoplasm containing rather small organelles as well as many free ribosomes, and giving off numerous fine processes; they make up about 6% of the glial cells in the corpus callosum; and they undergo mitosis at a rapid rate; (b) medium-shade oligodendrocytes, which are somewhat smaller cells with moderately dense nucleus and cytoplasm, containing well developed organelles, and giving off a fair number of fine processes; they make up about a quarter of the glial cells; and they undergo mitosis at a moderate rate; (c) dark oligodendrocytes, which are even smaller cells with very dense nucleus and cytoplasm, containing a prominent Golgi and structures referred to as lamellar bodies, and giving off very few fine processes; these cells make up about 40% of the glial cells; they do not undergo mitosis and probably arise from divisions of medium oligodendrocytes.

Nature of dividing nuclei in skeletal muscle of growing rats

Abstract: Much is known about the early stages of muscle development-the proliferation of myoblasts, their fusion into myotubes, and the transformation of myotubes into young muscle fibers . However, the mode of growth of muscle in the young animal remains obscure . It is known that muscle growth is extensive (e .g . in the chicken the pectoralis muscle enlarges from 0.7 g at hatching to 300 g in the adult) and is mainly the result of hypertrophy of the fibers (1), with little, if any, increase in their number (2) . Moreover, it is generally assumed that, unlike what happens in most other tissues, there is no division of the nuclei and, consequently, no increase in their number (3) . This view is supported by experiments showing that, while myoblasts can divide at early stages of development, they lose this ability once they have been incorporated into myotubes (4) . Furthermore, during muscle regeneration following injury, myoblasts appear which take up thymidine-'H, indicating their ability to divide, whereas the nuclei of muscle fibers do not (5) . Hence the prevalent opinion has been that new nuclei are not produced in skeletal muscle fibers during growth . This view was questioned when DNA determinations revealed a considerable increase in the number of fiber nuclei during growth in rats (6) and chickens (1), and mitotic figures were observed within the muscle fibers of growing rats (7) . Furthermore, after an injection of thymidine3H, radioautography revealed labeled nuclei within the confines of the basement membrane of muscle fibers (7, 8). In the hope of reconciling these apparently conflicting observations, it was suggested that the muscle nuclei which take up thymidine 3H and undergo mitosis are not true muscle nuclei but belong to \"muscle satellite cells\" (7). Such cells, which had been observed only in the electron microscope (9), consist of a single nucleus surrounded by scanty cytoplasm and are located between the basement membrane and the plasmalemma of the fibers, whereas true muscle nuclei are within the plasmalemma . Since satellite cell nuclei are eaily distinguished from true muscle nuclei in the electron microscope, it was decided to examine radioautographs in this instrument following thymidine 3H injection . Six male rats aged 17 days and weighing 25-30 g were given a single injection of 25-60 )uCi of thymidine 3H; g body weight and sacrificed at intervals varying from I to 72 hr later . The tibialis anterior muscle was fixed by immersion in glutaraldehyde paraformaldehyde (10), postfixed in osmium tetroxide, and embedded in Epon . Thin (silver to gold) sections were prepared for radioautography in the electron microscope with Ilford L4 emulsion (11-13) and poststained with lead citrate (14) . Electron microscopy revealed the existence of two types of nuclei within the basement membrane of the fiber . The nuclei of the first type (85-90% of the total) are in direct contact with the myofibril-containing cytoplasm ; they are the true muscle nuclei. The nuclei of the second type are surrounded by a small amount of cytoplasm, which is separated from the myofibril-containing cytoplasm by an intercellular space; these are the satellite cell nuclei ; they are usually smaller and darker than true muscle nuclei . In radioautographs obtained I hr after injection of thymidine 3H, approximately 3% of the nuclei within the basement membrane were labeled . These invariably belonged to satellite cells (Fig. 1) . Not one of the true muscle nuclei was labeled at that time. The results were similar at 6 and 10 hr after injection (Table I) . It was, therefore, concluded that satellite cell nuclei, but not true muscle nuclei, were able to synthesize DNA . Moreover, since it is known that DNA synthesis precedes mitosis (8), it may be concluded that the mitotic figures previously observed in the muscle fibers of growing rats (7) must belong to satellite cells . This conclusion is in accord with a recent report that, after colchicine treatment of 30-g rats, arrested mitoses of the nuclei of satellite cells, but not of true muscle nuclei, may be observed (15) . By 24 hr, a few true muscle nuclei were also labeled (Table I). At 48 hr, the labeling frequency of true muscle nuclei was increased, and by 72

Role of spermatogonia in the repair of the seminiferous epithelium following x-irradiation of the rat testis.

Abstract: In the normal adult rat testis, type A0 spermatogonia do not appear to participate to a significant extent in the production of spermatocytes, while type A1 spermatogonia periodically initiate a series of divisions resulting in the production of spermatocytes and new type A1 spermatogonia. The behavior of type A0 and A1 spermatogonia was investigated following administration of a single dose of x-rays (300 r) to the testis. Using whole mounts of seminiferous tubules, the type A0 and A1 cells were counted at various intervals after irradiation. At 8 and 13 days after irradiation, type A1 spermatogonia reached lowest values, i.e., 6% and 3% of non-irradiated control, while type A0 reached the lowest value, i.e., 62% of control at eight days. Thereafter the numbers of type A0 and A1 progressively increased to return to normal at 39 days. It was thus concluded that the type A0 were comparatively more resistant to x-irradiation than type A1 spermatogonia. To verify if the surviving type A0 proliferated in the irradiated testis, animals were injected with 3H-thymidine three hours before they were sacrificed at various times after x-irradiation. In irradiated testes the labeling indices of the surviving type A (A0, A1–A4) were the same as in the non-irradiated testes except in stages V-VI of the cycle of the seminiferous epithelium. While in the controls only 2% of type A cells were labeled at these two stages of the cycle, after irradiation the labeling index of type A reached a maximum of 31% at 13 days to return to control values by 39 days. Since at 13 days after irradiation type A0 spermatogonia were the predominant component of the spermatogonial population, it was concluded that these cells must have incorporated 3H-thymidine and thereby contributed to the reconstruction of the spermatogonial population partially destroyed by irradiation.

Finite Element Solution of Saturable Magnetic Field Problems

Abstract: This paper reports on initial numerical experiments for the solution of the nonlinear magnetic field problem by the method of finite elements, a new technique that permits great freedom in prescribing boundary shapes and does not suffer from the deceleration of convergence that plagues the relaxation methods [9]. The sizes of the triangular elements can be freely chosen so that dense clusters of smaller elements exist in the principal regions of interest (usually the iron parts) and fewer large ones in remote air spaces.

Glutamate and γ -Aminobutyric Acid in Brain

Abstract: Evidence is accumulating that, in the brain, the amino–acids L-glutamate and γ-aminobutyric acid (GABA) are essential agents of communication and not just elements of an alternate metabolic pathway, as was generally believed for some years.

Factors influencing villus size in the small intestine of adult rats as revealed by transposition of intestinal segments.

Abstract: As an index of villus size, the number of epithelial cells per representative villus section was counted in longitudinal sections of the rat small intestine. Villus size was found to decrease gradually along the length of the small intestine, with villi being nearly three times as large in upper duodcnum as in terminal ileum. The influence of various surgical operations on villus size was then examined. In ileal segments inserted into the jejunum, villi enlarged to the size of local jejunal villi. In jejunal segments inserted into the ileum, villi decreased almost to the size of local ileal villi. Thus, villus size was influenced by the environment, that is, most probably by the different types of chyme in jejunum and ileum. In duodenal segments inserted into the ileum, villi did not decrease in size, and distally located ileal villi enlarged. This and other experiments indicated that the duodenum produced secretions which not only neutralized the villus-reducing effect of the ileal environment, but also exerted a potent villus-enlarging effect. Pyloric secretions had a similar villus-enlarging effect. Segments of intestine were made into blind sacs by closing their proximal end and joining their distal end to the colon, so as to remove the influence of the chyme. Villus size decreased in sacs of jejunum and lower duodenum (without the duodenal papilla), but increased in sacs of ileum. Thus in the three types of sacs, there was a tendency for villi to acquire an intermediate size. In conclusion, an intermediate villus size, which is postulated to exist in chyme-free, non-functional intestine, would normally be modified by two types of factors: villusenlarging factors present mainly in pyloric and duodenal secretions, and villus-reducting factors present in the ileal chyme. Interaction between these factors would result in the gradient of villus size along the small intestine.

The distribution of lignin in Birch wood as determined by ultraviolet microscopy.

Abstract: The distribution of lignin in black spruce has been determined quantitatively by the study of 0.5 μm transverse sections in a UV microscope. The average lignin concentration in the compound middle lamella was about twice that in the secondary wall. The lignin concentration of the middle lamella at the cell corners of adjacent tracheids was nearly four times that in the secondary wall but the volume of the secondary wall was much greater than the volume of the middle lamella. Thus, for earlywood, 72% of the total lignin was in the secondary wall leaving only 28% in the compound middle lamella and cell corner middle lamella regions. The corresponding values for latewood were 82% and 18% respectively. Use of oblique longitudinal sections of 0.1 μm thick permitted the resolution of the compound middle lamella. The lignin concentration in the true middle lamella was found to be equal to that in the cell corner middle lamella and the primary wall lignin content to be about twice that in the secondary wall.

Ultrasonic Method for Measuring Elastic Coefficients of Bone and Results on Fresh and Dried Bovine Bones

Abstract: The elastic stiffness coefficients of dried bovine phalanx and femur and of fresh bovine phalanx were measured by an ultrasonic technique. An analysis of the electrical behavior and the crystallographic and morphological character of bone showed that it is a texture which has the same form of the elastic coefficient matrix as a hexagonal single crystal. The five elastic stiffness coefficients of fresh phalanx are: C 11 = 1.97, C 12 = 1.21, C 13 = 1.26, C 33 = 3.20, shear moduli as a function of direction were calculated.

Formation of cell coat material for the whole surface of columnar cells in the rat small intestine, as visualized by radioautography with L-fucose-3H.

Abstract: Some 30 years ago, Chambers proposed that the cell surface is covered by a thin amphous `cell coat\" (1) . The evidence in support of this view was mostly indirect until the cell coat was demonstrated in numerous rat cells by light microscopy with the periodic acid-Schiff or colloidal iron procedure (2) and by electron microscopy with periodic acid-silver methenamine (3) or phosphotungstic acid at low pH (4) . The staining of the cell coat by these techniques was attributed to the presence of glycoprotein material (3) tightly attached to the outer leaflet of the plasma membrane (4) . The cell coat was found to be most prominent at the apical surface of cells which are in contact with a lumen (3, 5) . In the small intestine of cat and some other species, a thick coating of periodic acid-Schiffpositive fuzzy material was described on the tips and sides of the microvilli making up the apical surface of columnar cells (5) . To investigate the formation of this material, Ito (6) incubated pieces of cat intestine with glucose3H and, using electron microscope radioautography, observed a reaction first over the cytoplasm and, after 1 hr, along the apical surface . Light microscope radioautographic studies carried out in our department showed that, minutes after injection of galactose 3H into young rats, the label was localized in the Golgi region of duodenal columnar cells and, soon after, was present at the apical border (7, 8) . The early localization of the galactose label to the Golgi apparatus of intestinal cells was later confirmed in the electron microscope (9-11) . These investigations led to the belief that the apical surface of intestinal columnar cells is characterized by a rapidly forming carbohydrate layer. In the course of a recent study of this problem with galactose 3H (11), there were indications that the label appeared not only at the apical surface, but also at the other cell surfaces . However, this phenomenon was not so clear as one might wish because of scattered labeling in the cytoplasm . This scatter may be explained by unpublished observations of A . Weinstock showing rapid passage of some galactose label into glucose, which would then be utilized for glycogen synthesis or, after transformation into amino acids, for protein synthesis . On the other hand, recent experience

A general rotation criterion and its use in orthogonal rotation

Abstract: Measures of test parsimony and factor parsimony are defined Minimizing their weighted sum produces a general rotation criterion for either oblique or orthogonal rotation The quartimax, varimax and equamax criteria are special cases of the expression Two new criteria are developed One of these, the parsimax criterion, apparently gives excellent results It is argued that one of the most important factors bearing on the choice of a rotation criterion for a particular problem is the amount of information available on the number of factors that should be rotated

Dynamics of Tubular Cantilevers Conveying Fluid

Abstract: In Part 1 a general theory is presented to account for the small, free, lateral motions of a vertical, uniform, tubular cantilever conveying fluid, with the free end being either below the clamped one (‘hanging’ cantilever) or above it (‘standing’ cantilever) Gravity forces are not considered to be negligibleIt is shown that, when the velocity of the fluid exceeds a certain value, the cantilever in all cases becomes subject to oscillatory instability In the case of hanging cantilevers buckling instability does not occur Standing cantilevers, on the other hand, may buckle under their own weight; it is shown that in some cases flow (within a certain range of flow velocities) may render stable a system which would buckle in the absence of flowExtensive complex frequency calculations were conducted to illuminate the dynamical behaviour of the system with increasing flow The conditions of stability have also been extensively calculated and stability maps constructed It is shown that dissipative forces m

Role of Heterogeneity of the Solvation Site in Electronic Spectra in Solution

Abstract: The emission spectra of polar aromatic molecules in rigid, polar solution are shown to depend on the exciting wavelength. Occurrence of the phenomenon depends on both the excited-state lifetime of the chromophore and the degree of rigidity of the medium. The results are interpreted in terms of a model which stresses the contribution of micro-environmental heterogeneity to electronic absorption and emission spectra.

The comparative ultrastructure of the algal chloroplast

Abstract: In preparing this paper, I had two big decisions to make. First, whose classification of the algae should I use, and second, which terminology should I use to describe chloroplast ultrastructure? I decided to use Christensen’s classification of the algae because overall it correlates fairly well with chloroplast ultrastructure. Since Christensen’s classification of the algae has not yet been mentioned in this conference, I will summarize it briefly. Christensen separates the algae into four divisions: the Cyanophyta, comprising one class, the Cyanophyceae; the Rhodophyta, comprising one class, the Rhodophyceae; the Chromophyta, comprising nine classes, the Cryptophyceae, Dinophyceae, Raphidophyceae (the Chloromonads) , Chrysophyceae, Haptophyceae, Craspedophyceae (the collared flagellates, which I will not mention again since none are known to have chloroplasts), the Bacillariophyceae, Xanthophyceae, and Phaeophyceae; and the Chlorophyta, into which he puts four classes. These are the Euglenophyceae, the Chlorophyceae, and two groups of algae that he removed from the green algae because of ‘differences in flagellation, the Prasinophyceae and Loxophyceae. The differences between these two classes are not clear-cut, and in this paper I will follow Peterfi and Manton * and lump the Loxophyceae with the Prasinophyceae. The question of which terminology of chloroplast ultrastructure to use is a more difficult one. For all other cell organelles, electron microscopists have now more or less agreed on a standard terminology. Who, for example, would still call the endoplasmic reticulum alpha cytomembranes? However, if you want to describe only the membranes of a chloroplast, you have a dozen odd terms to choose from-discs, thylakoids, frets, partitions, lamellae, lamellations, stacks, grana, bands-despite the fact that the membranes of all chloroplasts are built on a basic structural plan. The basic unit of the chloroplast is a flattened membrane-limited sac which Menke has named a thylakoid. Others, myself included, have called these sacs discs. In the interest of a uniform terminology, I propose that we abandon the word disc and use thylakoid henceforth. I propose to use the wbrd granum specifically to refer to a stack of appressed thylakoids, many of which are short and round and of approximately equal diameter, whereas others, which are interspersed with these, extend across the stroma to form part of a neighboring granum or even of the same granum. This leaves the problem of what to call the groups of two or three appressed or loosely associated thylakoids which extend across the chloroplasts of most algae. Stacks is probably the most descriptive word, but it is not a very euphonious one, and it implies a pile of some height rather than an extended flat layer.

The Dissonance Model in Post-Decision Product Evaluation:

Abstract: Post-decision cognitive reevaluation of instant coffee was primarily influenced by confirmation-disconfirmation experience with the product. Prior information resulting from brand familiarity influ...

Capacitance and Field Distributions for Interdigital Surface-Wave Transducers

Abstract: : A boundary-shift technique used in conjunction with relaxation solutions of Laplace's equation allows the convenient numerical evaluation of the potential in the neighborhood of interdigital comb structures. With this method, the area of computation in the unbounded problem can be restricted to the region of interest near the electrode and interface surfaces. Because of the point-by-point nature of the calculation, a wide range of geometries can be studied with the inclusion of the effects of finger thickness and shape, and of any layers present. Capacitance values for many single interface and layered configurations of surface-wave transducers are presented along with a few representative examples of potential and field maps. (Author)

Release of Alkaline Phosphatase from Cells of Pseudomonas aeruginosa by Manipulation of Cation Concentration and of pH

Abstract: Pseudomonas aeruginosa ATCC 9027 contains an inducible alkaline phosphatase. The enzyme is readily removed from 14-hr cells by washes in 0.2 m MgCl(2), pH 8.4. Similar washes in tris(hydroxymethyl)aminomethane buffer, 20% sucrose, monovalent ions, or water partially release enzyme from the cells. The release of alkaline phosphatase is correlated with an increased release of protein and retention of internal enzymes. The effect of 0.2 m MgCl(2) washing upon the cells is minimal since both viability and growth rates remain unchanged as compared to water washing. Although cells are plasmolyzed in both 0.2 m MgCl(2) and 20% sucrose, it is evident that plasmolysis alone is unable to account for total enzyme release and that a divalent metal, i.e. Mg(2+), augments the release pattern. Growing cells in the presence of increasing concentrations of MgCl(2) or at increased pH values results in an almost total secretion of the enzyme to the culture filtrate. The findings suggest that P. aeruginosa alkaline phosphatase is linked to the exocytoplasmic region through divalent metal ion, presumably Mg(2+), bridges.

Handedness : proficiency versus stated preference

Abstract: An investigation of performance factors of developed hand preference was undertaken. Measurements taken from both the preferred and nonpreferred hands of 50 males and 50 females yielded scores on 6...

Epidemiology of primary malignant mesothelial tumors in Canada.

Abstract: All fatal malignant mesothelial tumors known to patholgosts in Canada between 1959 and mid-1968 were registered. They numbered 165 (1 per million population per annum); two thirds were in males. Occupational and residential histories were obtained “blind” from relatives and friends of 90% of the cases and 2 matched control series. An association with definite or probable occupational exposure to absestos was clearly demonstrated, but only 20% of male cases and one female case had any such contact. Almost all the excess was in the manufacture and industrial application of absestos rather than in mining or milling. No association was found with lesser degrees of occupational exposure or residence in absestos-mining areas, but there was a small excess of possible domestic exposures the smoking histories in the mesothelial tumor and main control groups were almost identical and unlike those for cases of primary lung cancer.

An Algorithm for Detecting Unimodal Fuzzy Sets and Its Application as a Clustering Technique

Abstract: An algorithm is presented which partitions a given sample from a multimodal fuzzy set into unimodal fuzzy sets. It is proven that if certain assumptions are satisfied, then the algorithm will derive the optimal partition in the sense of maximum separation.

A cytochrome-related inherited disorder of the nervous system and muscle

Abstract: INVESTIGATION of an unusual hereditary disease of the nervous system and muscle revealed a marked reduction in the demonstrable cytochrome b content of the muscle mitochondria and other abnormalities of the cytochrome system. The purpose of this report is to present the clinical, morphological, and biochemical studies of the two patients in whom these unique defects were found, in the hope that these studies will contribute to the further understanding of the pathogenesis of similar neurological disorders. Report of Cases CASE 1.— This 46-year-old man was in excellent health until age 33, when his gait became unsteady and his speech became slurred. Shortly thereafter, movements of his hands became clumsy and his handwriting deteriorated, and, within two years, he experienced weakness of the muscles of his legs and shoulders. All of these symptoms were insidiously progressive, but cramplike muscle pains, which persisted for approximately six years after the onset of

Migration of bone marrow lymphocytes demonstrated by selective bone marrow labeling with thymidine‐H3

Abstract: Thymidine-H3 was injected into the femoral and tibial marrow (labeled marrow) of guinea pigs while the hind limb circulation was arrested temporarily and non-radioactive thymidine was administered systemically. Blood and lymphoid tissue radioautographs were subsequently examined for the presence of marrow-derived labeled cells. Small lymphocytes in the labeled marrow showed a wave of labeling, maximal at two to three days. Concurrently, labeled small lymphocytes appeared in the blood and lymphoid tissues, mainly the spleen and mesenteric lymph node. Their numbers were greatest at four to five days, and declined rapidly thereafter. At first they appeared predominantly in the splenic red pulp and throughout the lymph node cortex, including the subcapsular sinus. By four to five days they were also concentrated in the splenic white pulp, including periarteriolar lymphoid sheaths, and in the lymph node medullary cords. They were detected within medullary sinuses, hilar lymphatics and thoracic duct lymph. Labeled monocytes and large lymphoid cells also appeared in the blood and lymphoid tissues, mainly in the spleen. It is concluded that bone marrow is a major source of circulating newly-formed small lymphocytes many of which migrate rapidly into the spleen and mesenteric lymph node.