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.     

A leukocyte culture and chromosome preparation technique for avian species

Summary A technique for avian leukocyte culture and chromosome analysis is described. The method is simple and allows karyotypic analysis by a variety of chromosome banding methods. It is applicable to a wide variety of species and may be useful in determining the genetic sex of monotypic species in captivity or for population studies of specimens in the wild. This work was supported by Medical Research Council (Canada) Grant MA-4655. B. M. B. is a recipient of a Medical Research Council Fellowship.     

Morphological and cytochemical modifications induced by colchicine treatment in the duodenal epithelium of mouse

Summary S.W.R. adult male mice received one injection of colchicine and were killed at various time-intervals from 4 to 24 hours. Ultrastructural morphology and cytochemical activity of acid phosphatase, arylsulfatase and thiamine pyrophosphatase were recorded in the duodenal epithelium. Extensive damage was observed in the undifferentiated cells with formation of large heterophagosomes and in the absorptive cells with apparition of cytolysomes. The activity of the acid phosphatase and thiamine pyrophosphatase decreased after 6 hours of treatment. Moreover, the migration of the acid phosphatase content of the Golgi vesicles was restraint. These observations were related to the disruptive action of the alcaloid towards the microtubules.This work was supported by a grant from the Medical Research Council of Canada.Mr. Raymackers was a recipient of a studentship of the Medical Research Council of Canada. The authors are greatly indebted to Mr. Michel Couture and Pierre Magny for their skilful technical aid.     

Organ culture of adult mouse intestine

Summary Explants of adult mouse jejunum have been maintained in organ culture with or without fructose added to the medium in order to stimulate the intestinal glucose-6-phosphatase (G-6-Pase). When the fructose is added, at the beginning of the culture, a three-fold increase of G-6-Pase is measured during the first 24h. If the fructose is added after 24 h of culture, no significant increase of the G-6-Pase is registered in comparison with the controls. Proteins, DNA content and dissacharidase activities are not modified during the culture. Alkaline phosphatase activity presents a twofold increase in the controls and stimulated explants. The ultrastructural localization of the G-6-Pase is not altered during the culture.This work was supported by research grants from the Medical Research Council of Canada (J.S.H.) (D.M.)Mr. Chabot is a recipient of a studentship from the Medical Research Council of CanadaD. Ménard, Ph.D. is chercheur-boursier from the CRSQ     

Percoll centrifugation eliminates mold contaminants from cell cultures

This work was supported by a grant and research associateship to N.A. from the Medical Research Council of Canada and the National Cancer Institute of Canada.     

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.     

Effect of TRH (thyrotropin-releasing hormone) on the fine structure and replication of TSH and prolactin cells in the rat

Summary In intact male rats after TRH administration for 7 and 14 days, TSH cells showed similar morphological changes to those observed after thyroidectomy. These changes were paralleled by small numerical increases in TSH cell counts. After 34 days of TRH treatment, however, most of the TSH cells had a normal appearance and the number of TSH cells also had returned to normal. TRH treatment for 7, 14 and 34 days caused morphological changes in Prolactin cells similar to those obtained after a suckling stimulus. In the three groups these changes were also paralleled by small numerical increases in Prolactin cell counts. The cell replication after TRH for 7 and 14 days, as measured by incorporation of tritiated thymidine to obtain a labeling index, was slightly but significantly increased.This work was supported by grants MA-552 and MT-2701 from the Medical Research Council of Canada. The authors wish to thank Dr. D.A.J. Ives, Connaught Medical Research Laboratories, Toronto, for providing the TRH, and Mr. G. Penz for technical assistance.Fellow of the Medical Research Council of Canada.     

The endocrine cells of the upper gut mucosa in dogs with transplantation of the pyloric antrum to the colon

Summary A previous examination, done by others, of the endocrine cells of the canine pyloric antrum following its transplantation to the colon evidenced an increase in their number; the cell types involved, however, were not individualized. The present study further characterizes the changes occurring in the endocrine cells of the pyloric antrum of dogs following transplantation to the colon. The main change observed consists of hyperplasia of the enterochromaffin cells, with minor qualitative modifications in the antral gastrin-producing cells being noted only by electron microscopy. The response of the enterochromaffin cells cannot be readily explained but might be related to similar enterochromaffin cell hyperplasias found in human stomachs with peptic ulcers. Antrum transplantation to the colon in dogs appears to provide a promising experimental model for the study of the relationship between gastrin and other humoral factors (probably biogenic amines) in the mechanism of gastric secretion under normal as well as abnormal circumstances.Supported by a grant from the Medical Research Council of Canada. While performing this research, Dr. J. Lechago was a recipient of a fellowship from the Medical Research Council of Canada.     

Electron microscopic histochemistry of lysosomes in neurosecretory nerve endings and pituicytes of rat posterior pituitary

Summary Electron microscopic localization of acid phosphatase (AcPase) was carried out on posterior pituitary glands from rats. An estimated 5% of the neurosecretory nerve terminals contained structures which showed reaction product. Most of the lysosomes were small dense bodies, often with a membranous substructure. Other lysosomes were larger in size or were found within vacuoles. AcPase was also localized to lysosomes and the Golgi apparatus of pituicytes. Evidence is presented which would associate the large lipid droplets characteristic of pituicytes with AcPase-positive dense bodies. The present study indicates that hydrolytic activity by lysosomes occurs within the terminals of neurosecretory cells, and adds further support to the concept that this process represents a normal phenomenon of cells and their extensions in general.Supported by the Medical Research Council of Canada.Medical Research Associate of the Medical Research Council of Canada.     

Purification and properties of two distinct groups of ADH isozymes from Chinese hamster liver

Two major classes of alcohol dehydrogenase isozymes have been purified from Chinese hamster liver. The two isozyme classes have the same subunit molecular weights but different electrophoretic mobilities. They have a similar range of substrates but different KROM values and sensitivities to the inhibitor pyrazole. The ADHs are immunologically related as determined by Ouchterlony double diffusion experiments. These results suggest that the isozymes are encoded by different structural gene loci derived from a common ancestral gene.Financial support was provided by the National Cancer Institute of Canada and the Medical Research Council of Canada, Grant MT4860. J.-P. Thirion is a Research Scholar of the Science Research Council of Quebec.     

Adult rat pancreatic islet cells adherent to microcarrier beads: Evaluation of function and morphology

Summary Dispersed adult rat pancreatic islet cells were incubated with Cytodex-3 microcarrier beads for 72 h, during which time single cells adhered firmly to bead surfaces. Electron microscopy revealed well-preserved ultrastructure of attached A, B, and D cells. Perifusion of these cultures showed stable basal insulin release, brisk, biphasic insulin responses to 30-min glucose stimulation, and consistent, monophasic spikes of insulin release in response to repeated, brief pulses of glucose. These results indicate that adult rat islet cells attach to microcarriers and remain viable in culture. This preparation offers advantages for studies of hormone secretory dynamics of differentiated single islet cells, free from cell-to-cell interactions. This study was supported by grants from the Medical Research Council of New Zealand. D.W.H. was the recipient of a Novo Diabetes Research Scholarship.     

Mouse intestinal sensitivity to cycloheximide

Summary Cycloheximide 40 mg/kg was injected into adult male mice. Biochemical, histochemical and morphological modifications of the mucosal cells of the duodenum have been recorded after one or several injections. Biochemical experiments have shown a rapid decrease of alkaline phosphatase activity in the duodenum and a significant increase in the liver. Histochemical studies have shown a total disappearance of the alkaline phosphatase activity in the Golgi zone of the absorbing cells, two hours after one injection. Acid phosphatase, thiamine-pyrophosphatase and glucose-6-phosphatase did not exhibit the same pattern. Alterations of the ultrastructure of the villus cells have been observed after several injections. Atrophy of the Golgi cisternae, appearance of autophagic vacuoles and decrease of the goblet cells secretory granules have been the most frequent modifications.This work was supported by grants from the Medical Research Council of Canada and from the National Defense Board of Canada.The authors are greatly indebted to Mr. M. Couture for his skillful technical help.Mr. Charuel is a recipient of a studentship from the France-Quebec agreement.     

Functional diversity within the rudimentary locus of Drosophila melanogaster

Summary The rudimentary locus of Drosophila melanogaster is shown to be at least bifunctional. Mutants in different regions of the locus have either no CPSase or no ATCase activity; some mutants lack both activities. The results are discussed in correlation with the complementation and genetic map of the locus.Supported by National Research Council of Canada, grant A-1764 and National Cancer Institute of Canada, grant 6051 to D. T. Suzuki.Researcher, Centre National de la Recherche Scientifique, France and recipient of European Molecular Biology Organization Fellowship.     

Fluorescence coupling across lipid bilayer membranes

Summary An energy transfer between donor and acceptor fluorophores across single lipid bilayer membranes is demonstrated. Anilino-naphthalene sulfonate is used as the donor chromophore: its fluorescence is enhanced by the presence of lipid and thus indicates association with the purely lipid membranes of our preparation of vesicles in suspension. Light emit ted by the donor molecules excites fluorescence of acriflavine, a suitable acceptor enclosed inside the vesicles. Absorption and fluorescence spectra of this system, in its components and as a whole, are presented in evidence for an energy transfer.Supported by a grant from the Medical Research Council of Canada. The results of this work were presented, in part, at the 17th Annual Meeting of the Biophysical Society, February 27–March 2, 1973, Columbus, Ohio.Scholar of the Medical Research Council of Canada.     

Detection of feedback in the central nervous system using system identification techniques

An analysis method to detect the presence of feedback between biological signals, particularly those associated with the central nervous system, is presented. The technique is based on recent results in the system identification literature involving the concept of a feedback free process. It may be applied to volume conducted signals such as EEG and EMG, as well as to neuronal spike trains through the use of a data transformation procedure. The utility of the technique is then demonstrated in a study of the relationship between Parkinsonian tremor and certain tremor cells found in the thalamus of Parkinsonian patients, using data collected during thalamotomies. The results obtained suggest that feedback mechanisms may be an important factor contributing to Parkinsonian tremor.This research was supported by the Natural Sciences and Engineering Research Council of Canada, The Medical Research Council of Canada, and Bell-Northern Research     

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)     

Gap junctions in human sebaceous glands

Summary An examination of human sebaceous glands by transmission electron microscopy has revealed the presence of gap junctions. The junctions are found in abundance between differentiating cells, and annular forms are also seen. The possible significance of this new finding is briefly discussed.We thank the ENT consultant staff of Royal Prince Alfred Hospital, Sydney, for making tissue available. The co-operation of the director, Dr. D.J.H. Cockayne, and staff of the University of Sydney Electron Microscope Unit is gratefully acknowledged. Mr. E. Foster provided excellent assistance with the photography. -The project was supported by the Consolidated Medical Research Funds, University of Sydney, and the National Health and Medical Research Council of Australia. One of us (N.K.) was the recipient of the Phyllis Anderson Medical Research Fellowship awarded by the Faculty of Medicine, University of Sydney     

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 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