Showing papers by "Queen's University published in 1984"

Adaptive response of mammalian skeletal muscle to exercise with high loads.

Abstract: This review is concerned with the effects on muscle of chronic exercise using high loads. An attempt is made to assess the nature of the training stimulus, the rate of response of the tissue to the stimulus and the underlying biochemical and neurological mechanisms of the response. In order to clarify the later discussion it is useful here to begin with a few operational definitions. A muscle generates 'force' when it attempts to accelerate a load or some other form of resistance. The term 'load' refers to the mass moved during a single contraction and 'work' has its usual physical meaning. Active use of energy by a muscle is usually referred to as a 'contraction' even if no actual contraction of muscle length occurs. Two main types of muscle contractions are commonly distinguished. In 'isometric' or 'static' contractions, muscle force is developed at a constant muscle length. In 'dynamic' contractions muscle shortening ( 'concentric' contraction) or lengthening ( 'eccentric' contraction) occurs. Dynamic contractions are usually termed 'isotonic' if the load is preset and the velocity of the contraction measured, and 'isokinetic' if the velocity is preset and the load measured. Under isotonic conditions involving the lifting of weights, a rough estimate of strength is the weight which can be lifted by a particular muscle group once only without a rest. For the purposes of this review the 'strength' of a particular muscle group is defined

Theory of the magnetisation process in ferromagnets and its application to the magnetomechanical effect

Abstract: A theory of the magnetisation process in ferromagnets, based on existing ideas of domain rotation and domain wall motion is presented. This has been developed via a consideration of the various energy terms into a mathematical description of the process leading to an equation of state for a ferromagnet. The differential equation has been solved and a solution containing terms up to the second order presented, showing the essential features of ferromagnetic hysteresis. The theory has then been used to explain the effects of stress on magnetisation. It has been found that the magnetisation approaches the anhysteretic curve when a ferromagnet is subjected to stress and this is the underlying principle behind such changes in magnetisation. The change of magnetisation with stress can not be predicted solely on the basis of the magnetostriction coefficient except in special cases when the initial (zero stress) conditions of magnetisation lie on the anhysteretic. This condition is also approximately satisfied at higher fields.

High Frequency Ventilation

Abstract: High-frequency ventilation (HFV) is a difficult subject to deal with because we still lack a definition of high frequency. Basically HFV comes in three flavors: high-frequency positive pressure ventilation (HFPPV) introduced by Jonzon et al. (1); high-frequency jet ventilation (HFJV) introduced by Klain et al. (2); and high-frequency oscillation (HFO) introduced by Lunkenheimer et al. (3). The definition of high frequency depends on the system: HFPPV generally operates at 60+/min, HFJV at 150+/min and HFO at 900+/min. They can all achieve effective gas exchange in the normal lung. There are, as yet, no good comparative studies between the systems, nor any convincing evidence that any of them are superior to conventional mechanical ventilation (CMV) in diffuse parenchymal lung disease with hypoxia in humans. Despite this there are compelling theoretical reasons to suspect that HFV may be superior to CMV in this group of diseases. CMV creates large phasic volume distensions in sick lungs which have a nonuniform distribution of compliance, inevitably creating local overdistension. This can, at the macroscopic level, lead to air leaks (pneumothorax, etc.) and at the microscopic level cause hyaline membrane formation. Therefore, a mode of ventilation which reduces the magnitude of the volume distension might reduce the degree of barotrauma.

Trainsdermal nitroglycerin in angina pectoris

Abstract: The hemodynamic and antianginal efficacy of transdermal nitroglycerin (TGTN) patches were assessed in patients with chronic, stable angina pectoris. In 11 patients, acute dosing with 10,20 and 30 cm 2 of TGTN (designed to deliver 5,10 and 15 mg GTN over 24 hours) improved treadmill walking time 2 and 4 hours after application, but no clinical effects were seen at 24 hours. In a second study in 6 patients with doses of 30, 60 and 90 cm 2 of TGTN treadmill walking time was improved at 2 and 4 hours, but no changes were seen at 24 hours except with the 90-cm 2 preparation. After daily therapy with 30-cm 2 patches of TGTN for 1 to 2 weeks, exercise tolerance was similar to that seen during daily placebo therapy. These results suggest that TGTN patches are of inadequate size to produce 24-hour antianginal protection. During sustained therapy, tolerance develops to the antianginal efficacy of this form of GTN administration.

Recurrent patterns of natural selection in a population of Darwin's finches

Abstract: The adaptive significance of morphological traits can be assessed by measuring and identifying the forces of selection acting on them Boag and Grant documented directional selection in a small population of Darwin's medium ground finches, Geospiza fortis, on I Daphne Major, Galapagos, in 1977 Large beak and body size were favoured at a time of diminishing food supply and high adult mortality We show here that in two subsequent periods of moderate to high adult mortality (1980 and 1982), the population was subject to the same selection We have used a recently developed technique to ascertain the targets of direct selection Beak depth and body weight were commonly under direct selection to increase but, surprisingly, beak width was directly selected to decrease, over all three periods of mortality The results have implications for our understanding of evolutionary change in morphological traits of Darwin's finches

Classic and generalized variants of Pick's disease: A clinicopathological, ultrastructural, and immunocytochemical comparative study

Abstract: Six sporadic cases of dementia with lobar atrophy and neuronal cytoplasmic inclusions (Pick's disease) could be separated into two groups on the basis of the involvement of subcortical structures, the distribution and the histochemical, immunochemical, and ultrastructural characteristics of the inclusions, and possibly the age at onset. The first group (classic) was characterized by predominantly cortical atrophy and the presence in the hippocampus and neocortex of argyrophilic cytoplasmic inclusion bodies that reacted with a monoclonal antibody against neurofilament proteins and antitubulin antisera. Ultrastructurally the bodies were composed of straight fibrils of variable diameter, averaging 15 nm, and long-period constricted fibrils. The second group (generalized) showed subcortical as well as cortical atrophy. Cortical and subcortical cytoplasmic inclusions contained RNA and stained poorly with silver and antibodies against neurofilaments and microtubules. Ultrastructurally the straight fibrils composing the bodies were coated with granular material, presumed to be derived from ribosomes. The generalized cases occurred in younger patients than did the classic cases in this series.

Morphology and internal structure of sandwaves in the Bay of Fundy

Abstract: Intertidal sandwaves in the Minas Basin and Cobequid Bay, Bay of Fundy, occur under a wide range of conditions (mean grain size 0.274-1.275 mm; velocity strength index (V1)0.46-3.34; and velocity symmetry index (V2) 0.011-0.294), and they vary from symmetrical to strongly asymmetrical in cross-section. Heights and wavelengths average 0.81 and 37.9 m respectively. They are straight to weakly sinuous and laterally continuous in plan, occasionally show crestal branching reminiscent of wave ripples, and are commonly skewed relative to the strongest currents because of differential migration rates along their length. The average migration rate is 0.11 m/tidal cycle. Megaripples occur on each sandwave crest, at least during spring tides, but the areal extent, sinuosity and size of the megaripples increases as the dominant current speed increases. The megaripples have heights averaging 24% of the sandwave height, are oriented perpendicular to the fastest dominant currents, and have life spans of several tidal cycles. They are believed to be in quasi-equilibrium with the sandwaves and play a key role in sandwave dynamics and internal structure formation: periods of lee face steepening and rapid forward migration (megaripple crest at sandwave brink) alternate with times of non-deposition or erosion and slowed or reversed migration (trough at brink). Dominant-current cross-bedding predominates in the two intergradational varieties of translation structure observed: Inclined Cross-Bedding—decimetre-scale cross-beds separated by gently inclined (9° average) erosional surfaces; and Large-Scale Foresets—cross-beds with thicknesses greater than half the sandwave height, interrupted by weakly erosional to conformable discontinuity surfaces. These are overlain by a vertical growth or repair structure, Complex Cross-Bedded Cosets, that consists of nearly equal volumes of dominant- and subordinate-current cross-beds stacked without a preferred set-boundary dip. The translation structures correspond well to forms predicted by Allen (1980a, fig. 8) but the inclined set boundaries and discontinuity surfaces (master bedding planes) are produced by megaripple troughs rather than by current reversals. Consequently, Allen's regime diagram is unable to predict structure occurrences. The repair structures suggest that ‘curvature-related mass-transport’ (Allen, 1980a, b) is important in tidal sandwave maintenance, although it is not necessarily responsible for sandwave initiation.

A qualitative approach to the study of a teacher's beliefs

Abstract: This article describes a qualitative study of the beliefs and principles of one science teacher. The study employs the Repertory Grid Technique of Kelly (The psychology of personal constructs, New York: Norton, 1955). This technique is illustrated thoroughly by the case study, and ample segments from an interview with the teacher concerned are provided. All relevant information obtained from working with this teacher is used to establish the dominant beliefs held by her. The significance of the study is argued within the framework of curriculum and instructional innovation and implementation.

Proliferation of mature oligodendrocytes after trauma to the central nervous system.

Abstract: It has long been thought that mature oligodendrocytes in the adult mammalian central nervous system (CNS) are post-mitotic and are unable to proliferate in response to injury. The implications of this have been profound, because it has been suggested that this failure of oligodendrocytes to undergo mitosis is perhaps one of the reasons for the failure of the human CNS to undergo remyelination after demyelinating disease. This is in contrast with the normal peripheral nervous system in which there is consistent remyelination, and brisk Schwann cell mitosis. Although it has recently been shown that oligodendrocytes can be regenerated following some specific instances of demyelination, it has long been accepted that unlike mature astrocytes and microglia (macrophages), oligodendrocytes do not proliferate in response to general conditions damaging the nervous system. Here we show that mature oligodendrocytes in adult animals, as well as astrocytes and microglia, are able to respond to damage in the CNS following trauma by incorporating tritiated thymidine into their nuclei.

Orthopaedic bone cutting jig and alignment device

Abstract: An orthopaedic bone cutting jig and alignment frame for facilitating a series of controlled, precise bone cuts to fit selected prosthetic knees which promote bone imgrowth and do not rely upon cement for fixation.

Measurement of reaction time following minor head injury.

Abstract: A four-choice reaction time test was carried out on 45 minor head injury cases, 24 hours after the injury and 6 weeks later. Twenty-eight subjects were re-tested after a six month interval. Reaction time measures were also obtained in a matched, general practice control group. The concussion cases displayed significantly poorer performances than the matched controls in four measures, at day 0 and at 6 weeks. The patients also showed serial improvement in these measures up to six months after the injury, when their scores excelled those of the matched controls.

Differential effects of scopolamine on working and reference memory of rats in the radial maze

Abstract: Anticholinergics have often been found to impair choice accuracy in the radial maze. Some researchers have suggested that this indicates involvement of cholinergically innervated structures in cognitive mapping while others argue that these structures mediate working memory. However, most results are open to either interpretation since the baiting method did not allow a distinction between reference and working memory errors. To further test these hypotheses this study examined the effects of systemic scopolamine on radial maze performance, using a 4-out-of-8 baiting procedure. Food-deprived Wistar rats were pretrained until working memory choice accuracy stabilized to a criterion of 87% or better. Scopolamine (0.1, 0.4 and 0.8 mg/kg, IP, 30 min before a session) significantly increased the number of working memory errors (re-entries into baited arms) whereas reference memory errors (entries into never baited arms) did not change significantly. Observed deficits appeared not to be attributable to a drug-induced disruption of motivational systems. Results confirm the behavioural similarities between the memorial effects of hippocampectomy and anticholinergics, and implicate cholinergically innervated structures in working memory.

Post-Exercise Reduction of Blood Pressure in Hypertensive Men is Not Due to Acute Impairment of Baroreflex Function

Abstract: 1. Two experiments were carried out in male subjects. In the first experiment heart rate and blood pressures were measured before, during and for 90 min after a 50 min period of intermittent exercise in seven hypertensive subjects. After exercise there was a marked reduction in systolic and diastolic blood pressures; this effect lasted throughout the 90 min observation period and was unaccompanied by tachycardia. 2. In the second experiment heart rate and blood pressures were measured before and during the rest periods in a 50 min session of intermittent exercise in nine hypertensive and nine normotensive subjects. Following the first 10 min bout of exercise, resting blood pressures were significantly reduced in the hypertensive subjects; the reduction in blood pressure progressively increased following successive exercise periods. The normotensive subjects did not show a significant reduction in resting blood pressures until the fifth bout of exercise had been completed. 3. In the second experiment also, the competence of baroreflexes was assessed by measuring cardiovascular responses to lower body sub-atmospheric pressure (LBSP) 30 min before and 30 and 60 min after exercise. The post-exercise reduction in blood pressure was not due to exercise-induced impairment of baroreflex mechanisms since the reduced blood pressure after exercise was well maintained during lower body sub-atmospheric pressure. Furthermore, after exercise, exposure to lower body subatmospheric pressure elicited greater increases in heart rate and forearm vascular resistance than were seen before exercise.

Creep damage mechanics and micromechanisms

Abstract: Creep fracture is the end result of the accumulation of damage during creep. In this paper, micromechanisms of damage are classified, and a methodology of analysis is developed. For each mechanism, a damage-evolution law and a creep-law is derived. The result is a pair of differential equations, with the same form as that of the continuum treatment of Kachanov and Rabotnov. The equations can be integrated to give the shape of the creep curve, the time and strain to fracture, residual life, and so forth. Each mechanism exhibits a characteristic shape of creep curve, with an associated Monkman-Grant constant and creep ductility; these give guidance in selecting and using the appropriate equations. Progress is made in unifying the continuum and micromechanistic approaches to creep fracture, and a method is presented for identifying the dominant damage mechanism (or class of mechanism) from the shape of the tensile creep curve. An overview of the contents of this paper can be obtained by reading Sections 1, 2, 3 and 5.

Recruitment and the timing of reproduction in Lesser Snow Geese (Chen caerulescens caerulescens)

Abstract: Pour trois des sept saisons d'observation, les oiseaux issus de couvees precoces ont un taux plus grand de recrutement que les couvees tardives ou intermediaires entre precoces et tardives. Pour les autres saisons, pas de differences nettes

Possible epigenetic mechanisms of tumor progression: induction of high-frequency heritable but phenotypically unstable changes in the tumorigenic and metastatic properties of tumor cell populations by 5-azacytidine treatment.

Abstract: Treatment of a variety of highly tumorigenic mouse lines in vitro with chemical mutagens, such as ethyl methane sulfonate (EMS) or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), can result in extraordinarily high frequencies (sometimes in excess of 90%) of strongly immunogenic clones unable to grow progressively in normal syngeneic hosts. These clones will, however, grow in immunosuppressed hosts and gradually regain tumorigenic ability in normal mice if maintained in long-term (several months-1 year) culture, i.e., they are often phenotypically unstable. These features--phenotypic drift and high frequency--make it unlikely that point mutations are the underlying mechanism involved in the generation of the variants. Results presented here demonstrate that these observations can be reproduced on the same tumor lines using 5-azacytidine--an analogue of cytidine which can be incorporated into DNA causing subsequent extensive hypomethylation of cytosine residues in the absence of any significant mutagenic effects. Furthermore, 5-azacytidine treatment of a nonmetastatic mouse mammary tumor led to the emergence of a small number of heritable but unstable tumor clones capable of spontaneous metastatic spread. Because it is known that DNA hypomethylation can lead to transcriptional activation of normally silent genes, that altered methylation patterns can be somatically replicated with a high but not perfect fidelity, and that mutagens can cause DNA hypomethylation, we propose that DNA hypomethylation followed by de novo methylation represents a plausible mechanism to account not only for the induction of the nontumorigenic variants but for a number of aspects of tumor progression and tumor heterogeneity, as well. In particular, we refer to heritable phenotypic alterations in tumor cell populations which occur at very high frequency but which are not necessarily stable over very long periods of time.

Human monoclonal antibodies

Abstract: The technology for the production of murine monoclonal antibodies has been refined enormously since its introduction in 1975. However, the technology for generating human monoclonal antibodies has only recently come into its own. In this review, three currently available approaches to the production of human monoclonal antibodies are described. These include the hybridoma technique, based on the fusion of antibody-producing human B lymphocytes with either mouse or human myeloma or lymphoblastoid cells; the EBV immortalization technique, based on the use of Epstein-Barr virus (EBV) to ‘immortalize’ antigen-specific human B lymphocytes; and the EBV-hybridoma technique, based on a combination of the first two methods. The EBV-hybridoma system retains the advantageous features of the other two systems while overcoming their pitfalls and may be the current method of choice for producing human monoclonal antibodies with a defined specificity.

Transdermal isosorbide dinitrate in angina pectoris: effect of acute and sustained therapy.

Abstract: Twelve patients with chronic, stable angina pectoris underwent hemodynamic investigations and treadmill exercise testing before and during a 24-hour period after the application of 100 mg of transdermal isosorbide dinitrate (ISDN) and matching placebo. Compared with placebo, there were no changes in systolic blood pressure or heart rate at rest or during exercise; but treadmill walking time to the onset of angina and to the development of moderate angina was significantly prolonged at 2,4 and 8 hours, but not at 24 hours, after drug application. Patients subsequently received these same treatment regimens for 7 to 10 days and underwent repeat exercise testing. During this sustained phase of the investigation, treadmill walking time to the onset of angina and to the development of moderate angina was similar 4, 8 and 24 hours after application of ISDN and placebo. Thus, transdermal ISDN in a dose of 100 mg is effective for 8 hours during acute therapy, but during sustained therapy tolerance developed and no antianginal effects of ISDN persisted.