Theoretical and experimental derivation of the function relating the size distribution of spherical particles in a volume element to that obtained from images of sections taken through it

Summary The mathematical formulation of three classes of theories concerning the problem outlined in the title of this study was critically assessed and experimentally evaluated. It was found that only one class of the theories describes the relation between the distribution of particles in a volume element to that observed in sections through this volume in a satisfactory way. The errors in the remaining two classes could be traced and the corrections made after a mathematically rigorous analysis brought these theories to comply with a model which, as we could prove experimentally, deserves a high level of confidence.Supported by a grant from the Medical Research Council of Canada.In partial fulfillment of the requirements for obtention of the degree of a Master of Science. Supported by a Studentship from the Medical Research Council of Canada.Scholar of the Medical Research Council of Canada.     

Application of optimal multichannel filtering to simulated nerve signals

The optimal linear filters derived in the preceding paper can be thoroughly evaluated using computer simulations, based on the properties of mammalian sensory and motor nerve fibres. Using reasonable values for action potential waveforms, conduction velocity and electrode noise, good separation of motor and sensory signals can be obtained. The performance of the filters is degraded by 1) increasing the electrode noise, 2) introducing dispersion in the conduction velocities, or 3) variation in the waveform of the action potentials from that used in designing the filters. However, the variations needed to seriously degrade performance are quite large compared to those which are likely to be present in mammalian nerves. Use of these filters to distinguish different classes of sensory (or motor) signals based on conduction velocity is discussed.This work was partially supported by the Technical Research Council of Denmark (Grant 516-6703.E406), the Medical Research Council of Canada (Grant MRC-MT3307) and the National Research Council of Canada (Grant NRC A-4345)     

Possible posttranslational modification,and its genetic control,in flax genotroph isozymes

Environmentally induced flax genotrophs L and S show heritable shifts in the relative mobilities of peroxidase, esterase, and acid phosphatase isozymes, plus a number of nonspecific glycoproteins. All L isozymes migrated faster than corresponding S isozymes in 10% acrylamide gels. Various aspects of these shifts are reviewed here; it is proposed that posttranslational modification, probably of the carbohydrate moieties of these glycoproteins, underlies the shifts. This proposal is discussed in relation to the switch model for genotroph induction.The financial assistance of the Natural Sciences and Engineering Research Council of Canada is acknowledged with thanks.     

Autosomal determination of erythrocyte glucose 6-phosphate dehydrogenase in domestic chickens and ring-necked pheasants

Erythrocyte glucose 6-phosphate dehydrogenase isozymes of domestic chickens, ring-necked pheasants, and their hybrids were studied, using the starch gel zone electrophoresis technique. In domestic chickens G6PD isozymes were represented by two fast-moving bands and an indistinct third band, whereas in ring-necked pheasants a slow-moving broad band which seemed to consist of two closely apposed G6PD isozymes was observed. The F₁ hybrids showed three distinct bands combining the characteristic mobility pattern of the two parents, which seemed to indicate that both parental alleles are expressed in F₁ hybrids. Since both male and female hybrids exhibited strikingly similar isozyme patterns representing both sire and dam, it was assumed that the genes controlling the production of G6PD in chicken and pheasant red blood cells are located on the autosomes.This study was supported in part by a research grant from the National Research Council of Canada.     

Comparative studies on human skin fibroblasts: Life span and lipid metabolism in medium containing fetal bovine or human serum

Summary Three strains of human skin fibroblasts were cultivated in nutrient medium supplemented either with human serum or fetal bovine serum, and growth and lipid synthesis were compared. Rates of cellular growth were similar in both kinds of medium, but the replicative life spans of all three strains were curtailed significantly in human-serum medium. Incorporation of label into the major classes of neutral lipids from [¹⁴C]acetate and³H₂O was increased also in human-serum medium. Since human serum contained higher concentrations of cholesterol known to reduce endogenous cholesterol synthesis, these results were unexpected. Nonlipid factors in human serum may account for the shortened cellular life spans and increased lipogenesis and perhaps for the potential to develop atherosclerosis. Supported by grants from the Ontario Heart Foundation and Medical Research Council of Canada during the tenure of a Senior Research Fellowship from the Ontario Heart Foundation (J.T.C.) and a Scholarship from the Medical Research Council of Canada (S.G.).     

Optimal filtering of nerve singnals

Recording from multiple electrodes at different sites along a peripheral nerve permits the application of powerful filtering methods to extract the activity of populations of fibres within the nerve which differ in temporal or spectral characteristics. The design of optimal linear filters is initially treated as a general problem in the calculus of variations in which the signals from one population of nerve fibres are extracted so as to minimize those from a second population of nerve fibres or from other sources (noise). A particularly important application arises when the signals at two electrodes are related by weighting functions. In the simplest example the weighting function represents the time delay for nerve impulses to conduct from one electrode to the other, but explicit results are also derivable when there are a range of conduction delays with probabilities distributed according to well-known functions such as the sinc² function.This work was partially supported by the National Research Council of Canada and Medical Research Council of Canada by Grant NRC A-4345 to MNO and Grant MRC MA-3307 to RBS through the University of Alberta     

Some ring-trap mutants of the fungusDactylella brochopaga drechsler

Mutagenesis with nitrosoguanidine yielded two classes of ring trap mutants in the predacious HyphomyceteDactylella brochopaga: strains which could make no traps and those with a proportion of giant, functional traps. A third strain, derived from a trapless strain made abnormally small functional traps. The giant traps are described, together with developmental abnormalities they sometimes display. The characteristics of the chief mutant strains are discussed.This research was supported by a grant from the National Research Council of Canada which is gratefully acknowledged     

Fructose bisphosphatase isozymes of the mouse. I. Inheritance

Electrophoretically detectable polymorphisms of fructose bisphosphatase (EC 3.1.3.11) have been found in the mouse. One polymorphism, found among inbred strains of Mus musculus and feral animals, affects the isozymes found in the muscle and in most other tissues examined but is not expressed in kidney, liver, or testis. These tissues have other electrophoretically distinct isozymes which are monomorphic in Mus musculus but are present as a different electromorph in the sympatric species Mus spretus. Breeding data have established that the genetic control of the muscle enzyme is expressed by an autosomal structural locus Fbp-1 which is distinct from that expressing the liver, kidney, and testis enzyme, Fbp-2. The organ-specific expression of the two loci suggests possible functional differences between the two products.This work was supported by the Medical Research Council.     

Circadian rhythm of alkaline phosphatase activity in the Golgi zone of mouse duodenal enterocytes

Summary Alkaline phosphatase activity has been analyzed by biochemical methods on mouse duodenal homogenates and by cytophotometric method over the Golgi region of the duodenal cells, at different time periods of the day in fasting and nonfasting animals. A circadian variation of the activity has been observed with a peak at 9.00 h and a nadir at 15.00 h in the homogenates. On the contrary, the cytophotometric measurements have shown a maximal activity over the Golgi zone at 15.00 h and a minimal activity at 9.00 h. These observations are compared with other circadian variations of intestinal enzymes.This work was supported by a research grant of the Medical Research Council of Canada.M. Laurendeau D. is a recipient of a studentship of the Medical Research Council of Canada.     

Mathematical analysis of optimal multichannel filtering for nerve signals

This paper extends recent analyses (Roberts and Hartline, 1975; Ouztöreli and Stein, 1977) of optimal linear filters for separating neural signals from more than one electrode site. Roberts and Hartline's result, using a matched filter criterion, represents one of a class of optimal filters with different, but symmetrical, output waveforms derived by Ouztöreli and Stein (1977). Another narrow bandwidth filter of this class will give the optimal results according to an energy criterion, but may be less useful in practical situations.This work was partially supported by the Medical Research Council of Canada (Grant MRC-MT3307), the Technical Research Council of Denmark (Grant 516-6703 E406) and the National Research Council of Canada (Grant NRC A-4345)     

The effects of growth conditions on the esterases of Paramecium aurelia

The esterase isozymes of Paramecium aurelia grown in the presence and absence of bacteria were examined by starch gel electrophoresis. Where present, bacteria make a positive contribution to the esterase zymograms. Different bacteria contribute different esterases. Paramecia growing in axenic medium possess a different esterase which is not produced by the same parmecia growing in the presence of bacteria. This axenic esterase disappears when bacteria are added back to the medium.Supported by a research grant from the Science Research Council.     

Smooth endoplasmic reticulum proliferation in mouse enterocytes induced by fructose feeding

Summary Adult male mice receiving a fructose diet show, after three days, a large proliferation of the smooth endoplasmic reticulum in the jejunal absorptive cells. This extension is a secondary stage of the trememdous increase of the glucose-6-phosphatase activity and seems to result from a crypt regulation. Glucose feeding does not provoke the same morphologic changes. This work was supported by a research grant from the Medical Research Council of Canada. Dr. D. Maestracci Ph. D. is a recipient of a Centennial Fellowship of the Medical Research Council of Canada. Mr. D. Ménard is a recipient of a studentship of the Medical Reserach Council of Canada. The authors are greatly indebted to Mrs. S. Sinave for her skillful technical assistance.     

Peroxidase and leucine-aminopeptidase in diploidMedicago species closely related to alfalfa: Multiple gene loci,multiple allelism,and linkage

Summary The genetics of peroxidase and leucine-aminopeptidase isozymes was studied utilizing starch gel electrophoresis in the diploidsMedicago sativa L. (M. coerulea Less.) andM. falcata L. Three anodal and one cathodal sets of peroxidase isozymes identify four linked loci. In addition, two anodal sets of leucine-aminopeptidase isozymes identify two loci that may be linked. The allozymes at each of the loci segregated as expected for monomeric enzymes. However in several crosses there were deficiencies in the number of progeny in particular genotypic classes. This could result from the segregation of recessive deleterious genes linked to some of the allozyme alleles. This is the first report of multiple loci and multiple alleles determining isozymes inMedicago. Supported by grants from the Alberta Research Council (No. D1B02 to R.C. von Borstel) and the Computer Use and Policy Committee, University of Alberta     

Evolutionary games for spatially dispersed populations

An evolutionary game model is developed that incorporates both spatial dispersion and density effects in the evolutionary dynamic. It is shown that a stable equilibrium (e.g. an evolutionarily stable strategy) of the non-dispersed frequency dynamic becomes a stable equilibrium of the larger system if population density stabilizes at these fixed frequencies. It is also shown, by example, that other equilibria, whose frequencies change from one location to another, may appear when dispersal rates are relatively small.Research supported by Natural Sciences and Engineering Research Council of Canada Operating Grant A6187Research supported by Natural Sciences and Engineering Research Council of Canada Operating Grant A7822     

The dye-exclusion test for cell viability: Persistence of differential staining following fixation

Summary A method is described whereby the differential staining of viable and nonviable unfixed cells, as observed by the dye-exclusion method, can be reproduced in glutaraldehyde-fixed preparations by staining with alcian blue. The results suggest that the differential staining is due, at least in part, to structural differences that are retained following aldehyde fixation. This work was supported by grants from the National Cancer Institute of Canada and the National Research Council of Canada. Recipient of a Research Studentship from the National Cancer Institute of Canada.     

Malate dehydrogenase isozymes in flax genotroph leaves: Differences in apparent molecular weight and charge between and within L and S

Ferguson plots demonstrated that corresponding malate dehydrogenase (MDH) isozymes of Durrant's L and S flax genotrophs differ in apparent molecular weight (MW) and also in net negative charge. The MW differences explain heritable differences in electrophoretic relative mobility (R _m) between corresponding L and S isozymes. The MW for each MDH isozyme was higher for L than for S and resulted in a slowerR _m for L. The net negative charge for each isozyme was higher for L than for S. MDH isozymes also differ in MW within L and S. MW was lower for isozymes in leaves from the bottom of the stem than in leaves from the top of the stem, particularly in L. Integration of information on the MDH isozyme system in the flax genotrophs and information on the peroxidase system suggests the possibility that common modifier loci may controlR _m in both enzymes.The financial assistance of the Natural Sciences and Engineering Research Council of Canada is acknowledged with thanks.     

Electron microscopic localization of monoamine oxidase in the rat liver

Summary Two methods have been employed to localize monoamine oxidase activity in the cells of rat liver, using either 2-(2′-benzothiazolyl)-5-stryl-3-(4′-phtalhydrazidyl) tetrazolium chloride (BSPT) or ferricyanide as electron acceptor. With both methods monoamine oxidase activity was found both in the inner and the outer mitochondral membrane, although the outer membrane appeared the most probable location. In addition the BSPT method but not the ferricyanide method, revealed monoamine oxidase activity in the endoplasmatic reticulum. The results obtained by the two methods have been compared and are discussed in view of available biochemical data on monoamine oxidase. Supported by research grants from the National Research Council of Canada (A 3651), The Swedish Medical Research Council (4145) and M. Bergwall's Foundation, Stockholm.     

The effect of variable mechanical impedance on the control of antagonistic muscles

Most models of muscle have assumed that the series elastic element has a constant stiffness, although experimentally this is not true, either at the level of individual cross-bridges or that of the whole muscle. In this paper elastic and viscous elements are introduced whose properties vary systematically with activity levels as has been found experimentally. The effects of these nonlinear variations on the methods for optimally controlling a pair of antagonistic muscles are calculated. Although the nonlinearities add some complexity to the derivation and are important to the mechanism of force generation in the muscle, they do not qualitatively change the overall control of movement.This work was partly supported by the Natural Sciences and Engineering Research Council of Canada NSERC OGP-4345 and by the Medical Research Council of Canada Grant PG-47 through the University of Alberta     

Persistence in predator-prey systems with ratio-dependent predator influence

Predator-prey models where one or more terms involve ratios of the predator and prey populations may not be valid mathematically unless it can be shown that solutions with positive initial conditions never get arbitrarily close to the axis in question, i.e. that persistence holds. By means of a transformation of variables, criteria for persistence are derived for two classes of such models, thereby leading to their validity. Although local extinction certainly is a common occurrence in nature, it cannot be modeled by systems which are ratio-dependent near the axes. Research partially supported by the Natural Sciences and Engineering Research Council of Canada, Grant No. NSERC A4823. Research carried out while visiting the University of Alberta.     

Predator-prey systems with group defence: The paradox of enrichment revisited

The main concern of this paper is with survival or extinction of predators in models of predator-prey systems exhibiting group defence of the prey. It is shown that if there is no mutual interference among predators, enrichment could result in their extinction. However, if there is mutual interference, the predator population survives (at least deterministically). Research partially supported by the Natural Sciences and Engineering Research Council of Canada, Grant No. NSERC A 4823. Research partially supported by a Natural Sciences and Engineering Research Council of Canada postdoctoral fellowship.