Showing papers by "McGill University published in 1977"

Oscillation and Chaos in Physiological Control Systems

Abstract: First-order nonlinear differential-delay equations describing physiological control systems are studied. The equations display a broad diversity of dynamical behavior including limit cycle oscillations, with a variety of wave forms, and apparently aperiodic or "chaotic" solutions. These results are discussed in relation to dynamical respiratory and hematopoietic diseases.

The formalin test : a quantitative study of the analgesic effects of morphine, meperidine, and brain stem stimulation in rats and cats

Abstract: SUMMARYA method for assessing pain and analgesia in rats and cats is described. The procedure involves subcutaneous injection of dilute formalin into the forepaw, after which the animal's responses are rated according to objective behavioral criteria. The formalin test is a statistically valid techn

Meiotic and mitotic recombination in Aspergillus and its chromosomal aberrations.

Abstract: Publisher Summary This chapter analyzes the effects of one, or two, overlapping, reciprocal translocations on meiotic crossing-over and nondisjunction and to identify the processes of mitotic recombination in diploids with and without translocations, in triploids, and also in disomics from single and double translocation crosses, as well as the effects of inducing agents on these. It also assesses the various methods of genetic mapping, the uses of translocations for mapping, and the various problems arising from chromosomal aberrations for mapping by the parasexual cycle. The effects of chromosomal aberrations on meiotic recombination are of two general types. Based on an extensive analysis of effects by recombination-reducing aberrations on the disjunction of other chromosomes, two phases of pairing have been postulated for the meiosis of Drosophila : one early one, leading to and reinforced by chiasma formation, and a second one, “distributive pairing,” which involves all noncrossover chromosomes and may result in pairing of heterologous types. Several types of mitotic segregation which lead to spotting or variegation have been demonstrated in various organisms. In Aspergillus, two main types occur spontaneously: (1) Mitotic crossing-over, (2) Mitotic nondisjunction. A large variety of methods combining genetic, cytological, and biochemical techniques have been used in various organisms for the mapping of genes to specific chromosome segments. The chapter emphasizes the methods based on mitotic recombination that are new and especially useful in Aspergillus nidulans. In addition, techniques making use of translocations for genetic mapping in conjunction with meiotic and mitotic recombination are considered in detail.

Ia antigen expression on human epidermal Langerhans cells.

Abstract: IT has been proposed that the mammalian epidermal Langerhans cell is an epidermal equivalent of the cells of the reticulo-endothelial system, which are involved in binding and presentation of allergens in lymph nodes and the spleen1,2. The demonstration that these resident cells are capable of binding various allergens and migrate to the lymph vessels and local draining nodes, indicates a major function in the afferent arm of the primary immune response3,4 and has improved understanding of contact allergic hypersensitivity reactions. Much still remains to be discovered concerning the characteristics of the cell type, its reactivity with various antigens, and its relationship to other cells of the immune system. We show here that epidermal Langerhans cells react positively by immunofluorescence with antisera raised in rabbits against human B lymphoblastoid cell line membrane glycoproteins, which indicates the presence of Ia-like antigens on these dendritic cells.

Acetylene inhibition of nitrous oxide reduction and measurement of denitrification and nitrogen fixation in soil

Abstract: Reduction of N2O in moist soil was inhibited completely by 10−2 atm C2H2 and partially by 10−5 atm C2H2. The effect of C2H4 was 104 times less than that of C2H2. Denitrification of NO−3 occurred in anaerobically or aerobically incubated waterlogged soil and in anaerobic but not in aerobic moist soil. In the absence of C2H2 there was transient accumulation of N2O. In the presence of C2H2 there was stoichiometric conversion of NO−3 to N2O. Some kinetics of the reduction of N2O and of NO−3 to N2O are presented. Denitrification of 1 μg added NO−3-N.g− could be measured within 1 h. Stoichiometries of production of N2O from NO−2 and NO−3, respectively, and production of CO2 attributable to denitrification were consistent with reported energy yields. Reduction of C2H2 to C2H4 occurred immediately following complete denitrification of added NO−3. The incubation of soil in the presence and in the absence of C2H2 thus permits assay of both denitrification and N2 fixation and provides information on the mole fraction of N2O in the products of denitrification.

Trigger points and acupuncture points for pain: Correlations and implications

Abstract: Trigger points associated with myofascial and visceral pains often lie within the areas of referred pain but many are located at a distance from them. Furthermore, brief, intense stimulation of trigger points frequently produces prolonged relief of pain. These properties of trigger points--their widespread distribution and the pain relief produced by stimulating them--resemble those of acupuncture points for the relief of pain. The purpose of this study was to determine the correlation between trigger points and acupuncture points for pain on the basis of two criteria: spatial distribution and the associated pain pattern. A remarkably high degree (71%) of correspondence was found. This close correlation suggests that trigger points and acupuncture points for pain, though discovered independently and labeled differently, represent the same phenomenon and can be explained in terms of the same underlying neural mechanisms. The mechanisms that play a role in the genesis of trigger points and possible underlying neural processes are discussed.

Physical properties and supermolecular structure of perfluorinated ion‐containing (nafion) polymers

Abstract: The supermolecular structure and viscoelastic and diffusion properties of a perfluorinated polymer containing sulfonic acid (Nafion) were investigated. The breakdown of time–temperature super-position for the dry salt and and acid in the presence of 0.5 H2O/SO3H as well as the results of small-angle x-ray scattering suggest that the ions in this material are clustered. Above 180°C, the reestablishment of the time–temperature superposition in the salt suggests that ions in the clusters become mobile. Dynamic mechanical studies were performed over a temperature range from −190°C to above the glass transition temperatures Tg of the materials. The Tg of the salts is found at ca. 220°C, while in the acid it occurs at 110°C. A β peak in the acid is found at ca. 20°C, while in the salts it occurs between 140°C and 160°C. The β peak shifts to a lower temperature with the addition of water in both the acid and the salts, while the α and γ peaks are unaffected. The latter is located at ca. −110°C at 1 Hz. Dielectric behavior has also been studied as a function of water content for the acid sample and the potassium salt at frequencies of 100 Hz to 10 kHz. Two relaxations with different activation energies were observed. The position of both peaks shifts to a lower temperature as the water content increases. Finally, the diffusion of water in Nafion in the acid form has been determined. The diffusion coefficient can be represented by the equation

Degeneration of germ cells in normal, hypophysectomized and hormone treated hypophysectomized rats

Abstract: In normal adult rats some germ cells degenerate at several vulnerable steps of spermatogenesis. These are the type A spermatogonia, midpachytene spermatocytes, primary and secondary spermatocytes which degenerate during their respective maturation divisions and step 7 and 19 spermatitids. In the present study, these degenerating cells were examined under the electron microscope, and their frequency was determined in toluidine blue stained semithin sections of testes from normal, hypophysectomized (at 5.5 days after operation) and hypophysectomized rats injected with FSH and LH separately or in combination. With the exception of the step 19 spermatids, the degenerating germ cells underwent necrosis in vacuolated spaces delimited by Sertoli cells. In the case of the affected step 19 spermatids, an apical cytoplasmic process of the Sertoli cell initially ensheathed a long segment of their flagellum, and then each degeneration cell was drawn deep in the seminiferous epithelium where it was phagocytozed by the Sertoli cell. Soon after hypophysectomy the incidence of degenerating mid-pachytene spermatocytes, step 7 and 19 spermatids which are present in stages VII or VIII of the cycle of the seminiferous epithelium, increased significantly. In contrast the number of degenerating primary or secondary spermatocytes during the meiotic divisions seen in stage XIV of the cycle or of any other germinal cell was not significantly modified. While the injection of FSH alone had no influence on the number of degenerating cells in hypophysectomized rats, injections of LH at the two doses administered (0.7 microng or 20 microng) reduced significantly the number of degenerating cells seen in stages VII-VIII of the cycle; combined injections of FSH and LH (20 microng) reduced the number of these degenerating cells to the normal low values. Thus it appeared that the mid-pachytene spermatocytes and the step 7 and 19 spermatids, all present in the adluminal compartment of the seminiferous epithelium in stages VII or VIII of the cycle, were more sensitive to the presence of absence of gonadotropic hormones than the other germ cells present in the seminiferous epithelium.

Proteins of Myelin

Abstract: The protein composition of CNS myelin is relatively simple, with two protein fractions comprising 60–80% of the total membrane protein. These are the highly basic, histonelike protein (a single protein in most animals, two in some species) and the hydrophobic proteolipid protein fraction (predominantly a single protein). The remainder of the proteins fall into a heterogeneous group composed of some enzymes, glycoproteins, and an as yet undetermined number of minor proteins of unknown structure and function, most of which have a higher molecular weight than the two major protein fractions. These protein classes are readily separated in several different polyacrylamide electrophoretic systems. The most commonly used procedure is one which employs sodium dodecyl sulfate (SDS) and a high concentration of acrylamide. A typical separation pattern is presented in Fig. 1. The relative proportions and absolute amounts of each protein class can be determined by a spectrophotometric scan of stained or of unstained gels (Greenfield et al., 1971; Poduslo and Braun, 1975).

The tbilisi declaration

Abstract: Educational environment was the topic, discussed from a multitude of angles, at the Unesco Intergovernmental Conference held at Tbilisi, Georgia, USSR, in October 1977.

Phantom body pain in paraplegics: Evidence for a central “pattern generating mechanism” for pain

Abstract: Phantom body pain in paraplegic patients is the most mysterious of all pain phenomena. It has been traditionally assumed [45] that the essential cause of pain in any part of the body is activity in the receptor-fiber units that innervate it. In this paper, however, we shall describe paraplegic patients who had undergone removal of an entire section of the spinal cord (segmental cordectomy) in the attempt to alleviate phantom body pain, yet they still suffered severe pain in the denervated areas of the body. There is no reason to believe that the pain was due to depression or neurosis. Furthermore, the possibility that the pain was produced by nociceptive signals transmitted along the sympathetic chain is ruled out because the pain was not relieved by bilateral sympathetic blocks. The perception of severe, chronic pain in the absence of any input from those parts of the body in which pain is felt has profound implications for theories of pain. The purpose of this paper is to examine the properties of phantom body pains in paraplegics and to propose a theoretical concept to explain them.

Effects of surface roughness on wetting (theoretical)

Abstract: The effect of roughness of a solid surface on its wettability by a liquid has been studied theoretically using mechanistic arguments. By calculating the equilibrium shape of a liquid drop resting on a rough surface, we obtain the relation between the true (or microscopic) equilibrium contact angle at the three-phase contact line and the apparent contact angle observed macroscopically at the geometrical contour plane of the solid. By extending a proposal of Shuttleworth and Bailey, we provide a plausible explanation for hysteresis of the drop shape and contact angle which we evaluate for solid surfaces with concentric grooves. To calculate the equilibrium drop shape of a liquid on a solid surface whose roughness is more realistic than concentric grooves, we employ a perturbation method of solving approximately the Young-Laplace equation for the shape. Although the hysteresis in contact angle and drop shape cannot be evaluated by the method, the apparent contact angle and the local contact line positions are approximately predicted when the surface roughness has the form of cross grooves, hexagonal grooves, and radial grooves. Surfaces having random roughness are also considered and a modified form of the well-known Wenzel equation is derived which includes a factor for surface texture in addition to the conventional roughness factor.

The microrheology of colloidal dispersions VII. Orthokinetic doublet formation of spheres

Abstract: A theory is developed for the rate of doublet formation in dilute dispersions of spheres subjected to a simple shear flow of gradient G when Brownian motion can be neglected but taking account of both hydrodynamic and interparticle interactions. When Coulombic repulsive forces are negligible, the capture frequency is found to be approximately proportional toG 0.82; when they dominate the van der Waals attractive forces, the capture frequency is zero. When both attractive and repulsive forces are important no simple relationship exists, but the capture frequency can be calculated numerically. Experiments are described which are in qualitative agreement with the theory. Hamaker constants for polystyrene in water calculated from the measured doublet formation agree with those calculated by means of the present theory from experimental data of other workers, but are somewhat higher than those obtained from perikinetic coagulation rates.

Bilingualism and Aphasia

Abstract: Publisher Summary This chapter focuses on aphasia and bilingualism. Recovery is said to be antagonistic when one language regresses as the other progresses. Recovery is said to be successive when one language does not begin to reappear until another has been restored. Successive recovery may also be a part of a selective restitution pattern. The chapter presents a case study of a patient who first recovered from his Bulgarian mother tongue and then from German and Russian, but recovered from neither French nor English. Recovery is said to be selective when the patient does not regain one or more of his languages. It has also been observed that sometimes the language preferentially recovered is neither the mother tongue nor the most fluent language but the language of the patient's milieu, that is, the language spoken by the hospital staff. However, no single characteristic of the language preferentially restituted seems to be the determining factor of its recovery.

On convergence rates of subgradient optimization methods

Abstract: Rates of convergence of subgradient optimization are studied. If the step size is chosen to be a geometric progression with ratioρ the convergence, if it occurs, is geometric with rateρ. For convergence to occur, it is necessary that the initial step size be large enough, and that the ratioρ be greater than a sustainable ratez(μ), which depends upon a condition numberμ, defined for both differentiable and nondifferentiable functions. The sustainable ratez(μ) is closely related to the rate of convergence of the steepest ascent method for differentiable functions: in fact it is identical if the function is not too well conditioned.

Hair element content in learning disabled children

Abstract: Hair samples from 31 learning disabled and 22 normal children were analyzed for content of 14 elements. Significant group differences were determined and a discriminant function was completed which separated the groups with 98 per cent accuracy. Elevated lead and cadmium content in the learning disabled group is viewed as being of particular importance.

An Application of Relaxation Labeling to Line and Curve Enhancement

Abstract: A relaxation process is described and is applied to the detection of smooth lines and curves in noisy, real world images. There are nine labels associated with each image point, eight labels indicating line segments at various orientations and one indicating the no-line case. Attached to each label is a probability. In the relaxation process, interaction takes place among the probabilities at neighboring points. This permits line segments in compatible orientations to strengthen one another, and incompatible segments to weaken one another. Similarly, no-line labels are reinforced by neighboring no-line labels and weakened by appropriately oriented line labels. This process converges, in only a few iterations, to a condition in which points lying on long curves have achieved high line probabilities, while other points have high no-line probabilities, There is some tendency, under this process, for curves to thicken; however, a thinning procedure can be incorporated to counteract this. The process is effective even for curves of low contrast, and even when many curves lie close to one another.

Abnormal myelination in transplanted Trembler mouse Schwann cells

Abstract: AXON and Schwann cell interdependence has received increasing attention in recent years1,2. In normal nerves, axons influence Schwann cell proliferation3,4 and myelin formation5–8. These interactions may also be important in peripheral nerve disorders. Indeed, it has been suggested that in certain neuropathies, it is an axonal abnormality which is responsible for the failure of Schwann cells to maintain normal myelin9,10. An experimental approach to this question has become possible with the demonstration that, in nerve grafts from normal animals, Schwann cells which originate in donor nerves ensheath and myelinate axons arising from nerve cells in the host6,8,11. This demonstration of the feasibility of in vivo combinations of Schwann cells and axons, each originating from different animals, prompted the present experiments in which axons and Schwann cells from normal and abnormal mice were combined in sciatic nerve grafts. For the present study, abnormal nerves were obtained from Trembler mice (Tr)12. These mutants have a dominantly inherited neuropathy characterised by the presence of abnormally thin myelin sheaths and slow conduction in the peripheral nerves13, changes which have been considered to resemble those of human hypertrophic neuropathies14.

Migration, culture and mental health.

Abstract: The former belief that immigrants always suffer from an excess of mental disorder is no longer valid, and the old rivalry between social selection and social causation hypotheses has lost much of its relevance. The mental health of a migrant group is determined by factors relating to the society of origin, factors relating to the migration itself, and factors operating in the society of resettlement; and all three sets need to be considered if one seeks to reduce or merely to understand the level of mental disorder in any immigrant group. Illustrations from each set of factors are presented, with indications of whether they appear to have general relevance or be related to specific mental disorders.

The steady movement of a liquid meniscus in a capillary tube

Abstract: The steady movement of a liquid meniscus in a circular capillary tube has been examined theoretically for dynamic contact angles close to 90° with minute slippage of the liquid on the solid, thus relaxing the conventional no-slip boundary condition. The resulting flow field does not produce an unbounded force at the contact line, contrary to that with the no-slip condition. The interfacial velocity, wall stress, fluid pressure and the meniscus shape are calculated, and the significance of dynamic contact-angle measurements is discussed. A modified version of the classical Washburn equation which takes account of the meniscus also reveals the importance of slippage.

Enhanced Thyroxine Metabolism and High Uptake Goiters in Rats After a Single Dose of 2,3,7,8- Tetrachlorodibenzo-p-Dioxin11

Abstract: Nine days after treatment of rats with a single dose (25 μg/kg) of 2,3,7,8-tetrachlorodibenzo-p- dioxin (TCDD), the 1 h biliary excretion of [125I] - thyroxine (T4) was increased 4-fold and the [125I] T4 bile:plasma ratio and the biliary clearance rate of plasma [125I] T4 were increased 10-fold. The proportion of biliary 125I present as T4-glucuronide was larger in TCDD-treated rats. Unexpectedly, TCDD did not influence the 30 min biliary excretion of [125I] triiodothyronine (T3), the [125I] T3 bile: plasma ratio, and the biliary clearance rate of plasma [125I] T3. TCDD also elevated serum thyrotropin concentrations, produced goiters and increased thyroid 131I uptake. Serum T4 concentrations were reduced to half of normal in TCDDtreated animals, but their serum T3 levels were elevated. Sephadex uptake of serum [125I] T3 was reduced in the TCDD group.

Analysis of the disruption in hypothalamic-pituitary regulation in rats treated neonatally with monosodium L-glutamate (MSG): evidence for the involvement of tuberoinfundibular cholinergic and dopaminergic systems in neuroendocrine regulation.

Abstract: Adult rats which have received monosodium-L-glutamate (MSG) (4 mg/g body weight) on alternate days for the first ten days of life acquire neurotoxic lesions of the retina and arcuate nucleus and manifest an endocrine deficiency syndrome characterized by stunted growth, obesity, hypothyroidism, hypogonadism and pituitary atrophy. In the present study, the biochemical basis for the MSG-induced endocrine dysfunction has been examined and the findings of note are as follows: normal serum levels of TSH and LH despite hypothyroidism and gonadal atrophy, and significantly reduced serum GH levels in both males and females; elevated serum PRL levels in males, but not females; normal or augmented pituitary release of LH and TSH to exogenous LHRH and TRH. Within the central nervous system: a normal diurnal rhythm of pineal N-acetyltransferase activity despite optic atrophy; normal concentrations of LHRH, TRH and somatostatin within the medial basal hypothalamus; normal concentrations of norepinephrine (NE), choline ...