Showing papers by "Laval University published in 1978"

Potent antidopaminergic activity of estradiol at the pituitary level on prolactin release

Abstract: Prior incubation of rat anterior pituitary cells with 17beta-estradiol led to an almost complete reversal of the inhibitory effect of two dopamine agonists, dihydroergocornine and RU 24213, on both basal prolactin release and thyrotropin releasing hormone-induced prolactin release. These experiments thus demonstrate a direct interference of dopamine action by a peripheral hormone. Prolactin secretion by pituitary cells in primary culture could possibly serve as an easily accessible model of a system under dopaminergic control.

Atlas of the distribution of monoamine-containing nerve cell bodies in the brain stem of the cat.

Abstract: The distribution and morphological characteristics of monoamine (MA)-containing neuronal somata in the brain stem of kittens and of adult cats were studied by means of the Falck-Hillarp histofluorescence method This investigation has shown, among other things, that in the midbrain of the cat the catecholamine (CA) perikarya are chiefly confined to the pars compacta of the substantia nigra, the ventromedial tegmental area, the nucleus linearis rostralis and the nucleus parabrachialis pigmentosus Numerous CA neurons are also present in the dorsolateral part of the pontine tegmentum but also within the nucleus subcoeruleus, in nuclei lemnisci lateralis dorsalis and in nuclei parabrachialis lateralis and medialis In the medulla, a few CA neuronal somata are lying near the hypoglossal nucleus whereas a larger number of CA cell bodies occur at the level of nucleus reticularis lateralis and in nucleus paragigantocellularis lateralis On the other hand, most of the serotonin (5-HT) perikarya are confined to the raphe nuclei of the brain stem: nuclei raphe dorsalis, centralis superior, raphe pontis, raphe magnus, raphe pallidus and raphe obscurus Some 5-HT neuronal somata are also found lateral to the pyramidal tract and to the inferior olivary complex The various similarities and differences in respect to the pattern of the topographical distribution of MA neurons in the brain stem of the cat as compared to that of other mammals are discussed

Linear, annular, and radial focusing with axicons and applications to laser machining

Abstract: New optical combinations of axicons and axicons with spherical mirrors and lenses suitable for laser machining are presented. Linear and annular focusing, coaxially and radially to the laser beam, are possible. Most combinations allow continuous adjustment of exit beam parameters, focal line length, focal ring diameter, and magnification, by varying the relative position of one of the axicons. Potential new laser applications are also discussed in relation to these optical devices.

Cortical long-axoned cells and putative interneurons during the sleep-waking cycle

Abstract: Knowledge of the input-output characteristics of various neuronal types is a necessary first step toward an understanding of cellular events related to waking and sleep. In spite of the oversimplification involved, the dichotomy in terms of type I (long-axoned, output) neurons and type II (short-axoned, local) interneurons is helpful in functionally delineating the neuronal circuits involved in the genesis and epiphenomena of waking and sleep states. The possibility is envisaged that cortical interneurons, which are particularly related to higher neuronal activity and have been found in previous experiments to be more active during sleep than during wakefulness, might be involved in complex integrative processes occurring during certain sleep stages. Electrophysiological criteria for the identification of output cells and interneurons are developed, with emphasis on various possibilities and difficulties involved in recognizing interneurons of the mammalian brain. The high-frequency repetitive activity of interneurons is discussed, together with various possibilities of error to be avoided when interpreting data from bursting cells. Data first show opposite changes in spontaneous and evoked discharges of identified output cells versus putative interneurons recorded from motor and parietal association cortical areas in behaving monkeys and cats during wakefulness (W) compared to sleep with synchronized EEG activity (S): significantly increased rates of spontaneous firing, enhanced antidromic or synaptic responsiveness, associated with shorter periods of inhibition in type I (pyramidal tract, cortico-thalamic and cortico-pontine) cells during W versus significantly decreased frequencies of spontaneous discharge and depression of synaptically elicited reponses of type II cells during W compared to S. These findings are partly explained on the basis of recent iontophoretic studies showing that acetylcholine, viewed as a synaptic transmitter of the arousal system, excites output-type neurons and inhibits high-frequency bursting cells. Comparing W and S to the deepest stage of sleep with desynchronized EEG activity (D) in type I and type II cells revealed that: ( a ) the increased firing rates of output cells in D, over those in W and S, is substantially due to a tonic excitation during this state, and rapid eye movements (REMs) only contribute to the further increase of discharge frequencies; ( b ) in contrast, the increased rates of discharge in interneurons during D is entirely ascribable to REM-related firing. On the basis of experiments reporting that increased duration of D has beneficial effects upon retention of information acquired during W, the suggestion is made that increased firing rates of association cortical interneurons during REM epochs of D sleep are an important factor in maintaining the soundness of a memory trace.

Localization of alpha-melanocyte-stimulating hormone in rat brain and pituitary.

Abstract: The distribution of alpha-melanocyte-stimulating hormone (alpha-MSH) was studied in the rat brain with an immunoperoxidase technique. alpha-MSH-containing cells were found in the arcuate nucleus of the hypothalamus. Cells staining for alpha-MSH were also localized in the intermediate lobe of the pituitary. alpha-MSH-containing nerve fibers extended throughout regions of the hypothalamus, thalamus, and midbrain. Two weeks after hypophysectomy, alpha-MSH-positive cells anf fibers were still present in the brain. These results indicate that alpha-MSH of non-pituitary origin is synthesized and stored by neural structures in the rat brain. The detection of alpha-MSH by radioimmunoassay in the rat brain and pituitary supports these observations.

Ring pattern of a lens-axicon doublet illuminated by a Gaussian beam

Abstract: An axicon and a lens are combined to form an optical system producing a ring-shaped pattern. The purpose of this paper is to show that when a lens-axicon combination is illuminated by a Gaussian beam, the transverse distribution of the focal ring is also a Gaussian distribution. The typical width of this distribution was found to be, in the case of the lens-axicon combination, 1.65 times greater than the typical width of the Gaussian beam obtained by focusing the same beam using the lens alone. This focusing system is well suited for the drilling of good quality large diameter holes using a high power laser beam.

Inhibitory Effect of LHRH and Its Agonists on Testicular Gonadotrophin Receptors and Spermatogenesis in the Rat

Abstract: Treatment of adult male rats with the potent LHRH agonists [D-Leu6, des-Gly-NH210]LHRH ethylamide or [D-Ala6. des-Gly-NH210]LHRH ethylamide led to a marked reduction of testicular LH and prolactin receptor levels accompanied by decreased plasma testosterone levels and testis, seminal vesicle and prostate weight. Maximal inhibitory effects were seen at a dose of 50 ng. After a single injection, maximal inhibitory effects were seen at 2–4 days with return toward normal levels at later time intervals. Similar results were obtained with LHRH itself although 5 μg was required for maximal effects. When the LHRH analog was administered twice a week at the 100 ng dose, degenerative signs appeared in the seminiferous tubules after one week while at four weeks, degenerative changes were so advanced that almost all germ cells had disappeared leaving only Sertoli cells.

The organization of monoamine‐containing neurons in the brain of the sunfish (Lepomis gibbosus) as revealed by fluorescence microscopy

Abstract: The morphological organization of the monoamine-containing neurons in the brain of the sunfish (Lepomis gibbosus) was studied by means of the Falck-Hillarp histofluorescence method. No attempt was made to distinguish between norepinephrine and dopamine, both primary catecholamines (CA) yielding a similar yellow-green fluorescence after paraformaldehyde treatment. In the brain stem of this teleost fish, three groups of CA-containing neuronal somata have been found. First, there is a small collection of CA perikarya located just caudal to the obex of the fourth ventricle. The neurons of this medullo-sinal group give rise to numerous CA fibers many of which ascend within the central portion of the medulla. Intermingled with these CA fibers are some CA cells that constitute the central medullary group. The CA perikarya of this group are scattered between the levels of cranial nerves X and VIII. The tegmentum of the isthmus also contains a small group of very closely packed CA neurons. The large-sized CA cells of the isthmal group are located dorsolateral to the medial longitudinal fasciculus, partly within the periventricular gray. High densities of CA varicosities were also disclosed in various brain stem structures such as the optic tectum, the torus semicircularis and the cerebeller valvula. In addition, numerous serotonin (5-HT)-type neuronal somata were found in the raphe region of the brain stem, particularly at caudal mesencephalic, isthmal and rostral medullary levels. A large number of CA cell bodies were visualized in the sunfish hypothalamus. Most of them form two populations of small, round cells that are located along and partly within the ependymal walls of the posterior and lateral recesses of the third ventricle. These bipolar cells possess one short club-like process protruding into the ventricle and their thin ependymofugal processes contribute to the CA innervation of numerous hypothalamic regions. Large CA neurons apparently without direct CSF contact also occur in the area of nucleus posterior tuberis, at the level of the mesodiencephalic junction. Although the hypothalamic inferior lobes are devoid of CA cell bodies they are heavily innervated by CA axons. The sunfish telencephalon also receives a strikingly massive and complex monoaminergic innervation. Numerous CA fibers which are first observed at the level of the preoptic area, ascend through the central zone of the telencephalon and arborize profusely particularly within the medial zone of area dorsalis telencephali. Other CA fibers, as well as abundant fine 5-HT varicosities were found in the lateral zone of area dorsalis. Although the exact origin of the telencephalic CA afferents in Lepomis is not known, part of it may arise from the isthmal CA cell group which appears similar to the locus coeruleus of reptiles, birds and mammals.

β‐Adrenergic Receptors in Brown‐Adipose Tissue. Characterization and Alteratios during Acclimation of Rats to Cold

Abstract: 1 The capacity of brown adipose tissue to respond calorigenically to catecholamines increases markedly during cold-acclimation of adult rats. To investigate this phenomenon, we have used the potent radioactive ligand (-)-[3H]dihydroalprenolol to directly estimate the number, the density and the affinity of β-adrenergic receptors in brown adipose tissue membranes from control, cold-exposed and cold-acclimated rats. 2 Binding of (−)-[3H]dihydroalprenolol to unfractionated membranes was rapid, stable, saturable and reversible. It displayed the affinity, specificity and stereoselectivity expected of binding to adenylate cyclase-coupled β-adrenergic receptors. β-Adrenergic agonists competed for binding sites with an order of potency typical of the β1 subtype of adrenergic receptors: (−)-Isoproterenol > (−)-norepinephrine ≥ (−)-epinephrine. Binding exhibited a remarkable stereoselectivity, the (−)-isomers of β-adrenergic agonists and antagonists being 34 to 280 times more potent than the (+)-isomers in competing for (−)-[3H]dihydroalprenolol binding sites. 3 Total interscapular brown adipose tissue of the adult, warm-acclimated rat contained 1.12 ± 0.08 pmol of (−)-[3H]dihydroalprenolol binding sites. During cold-acclimation, growth of the tissue was accompanied by a 4–5-fold increase in the total number of recptor sites. However, this increase did not keep pace with the increse in brown adipose tissue cellularity (as estimated by total tissue DNA content), resulting in a 40–50% reduction in receptor density. The decrease in receptor density was associated with cold-exposure rather than with cold-acclimation. 4 The affinity of (−)-[3H]dihydroalprenolol receptor sites was not significantly altered by cold-acclimation. 5 The results of this study are interpreted as indicating that catecholamines released via activation of the sympathetic nervous system regulate both the density and the number of their own receptors in brown adipose tissue of cold-exposed animals. The development of the hyperadrenergic response of this thermogenic tissue during cold-acclimation may result from a marked organ hyperplasia associated with an increased number of β-adrenergic receptor sites and cannot be explained by alterations in receptor density or affinity.

Guidelines for Bacteriophage Characterization

Abstract: Publisher Summary Bacteriophages or phages occur in a wide range of prokaryotes, including bacteria and blue-green algae. With an estimated 1650 isolates studied by electron microscopy, they are the largest viral group described. This group is expanding at a rate of about 130 to 150 virus descriptions per year. These large numbers reflect the relative ease, with which the phages are isolated and their enormous importance for molecular biology, genetics, and epidemiology. For example, a recent review lists typing sets for about 70 bacterial species and serotypes. Although most work has been done on the phages of bacteria pathogenic to humans, there is presently a trend toward studying the phages of nonmedical and sometimes arcane bacteria. The isolation of the new phages raises problems for the investigators, the journal editors, and the scientific public alike. At present, there is no agreement on parameters, methods, and nomenclature. This has led to widely different, often unsatisfactory, phage descriptions and many identical names for different phages. In addition, much effort seems to be devoted to the study of obsolete parameters or properties that, for the lack of standard methods, cannot be compared with existing data. Such a situation is detrimental to comparative virology. The purpose of this chapter is to suggest the guidelines for phage characterization and nomenclature, and to set forth the minimum requirements for their description.

Inhibition of spermatogenesis in the rat by treatment with [D-Ala6, Des-Gly-NH210] LHRH ethylamide.

Abstract: The effect of treatment with a potent LHRH agonist, [D-Ala6, Des-Gly-NH2]LHRH ethylamide, injected at the low dose of 100 ng, twice a week, was evaluated on spermatogenesis in the rat. Significant degenerative changes of seminiferous tubules could be observed after two weeks of treatment. These changes were progressive and led to a marked inhibition of spermatogenesis after four to eight weeks of treatment. Testis weight was decreased to approximately 50% of control after eight weeks of treatment.

Actin- and myosin-like filaments in rat brain pericytes.

Abstract: Heavy meromyosin (HMM) labeling was used to identify the nature of the filaments which form bundles in the cytoplasm of the pericytes in brain tissue. Rat brain tissue pieces were incubated in glycerol solutions at 4 degrees and then transferred into buffer (pH 7.0), (1) without HMM, (2) with HMM, (3) with HMM + 5 mM ATP, and (4) with HMM + 2.5 mM Na+ pyrophosphate. In pericytes from untreated tissue, smooth-surfaced microfilaments, averaging 6 nm in diameter, appear to branch and anastomose and to anchor on the plasma membrane. After exposure to HMM, the number and the density of the microfilaments are strikingly increased. These tightly-packed microfilaments are now heavily coated with exogeneous HMM thus increasing in width to 18-20 mm. They intertwine in closely-woven networks. After incubation in HMM solutions containing ATP or Na+ phosphate, they are no longer coated with thick sidearms. It can thus be concluded that these microfilaments are of actin-like nature. In addition, after incubation in ATP, they are intermingled with, and converge onto the surfaces of, thick, tapered filaments, which we have tentatively identified as of myosin-like nature. Thus, it appears that certain of the major elements necessary for contraction are present in brain pericytes.

Mechanism of action of hypothalamic hormones in the anterior pituitary gland and specific modulation of their activity by sex steroids and thyroid hormones.

Abstract: Publisher Summary This chapter discusses the mechanism of action of hypothalamic hormones in the anterior pituitary gland and specific modulation of their activity by sex steroids and thyroid hormones. Although important information on the role of hypothalamic hormones in the control of anterior pituitary function could be obtained using hypothalamic extracts at different stages of purification, the relative ease of synthesis of these peptides and their analogs has opened new possibilities for studies of their mechanism of action. It has led to a rapid expansion of knowledge of the physiology of the hypothalamo-pituitary complex. The chapter focuses on the effects of three synthetic hormones—luteinizing-hormone-releasing hormone (LHRH), thyrotropin-releasing hormone, and somatostatin—on cyclic adenosine monophosphate accumulation in the anterior pituitary gland. Because LHRH stimulates the secretion of both luteinizing hormone and follicle stimulating hormone, the divergence frequently observed in vivo between the rates of secretion of the two gonadotropins can be best explained by differential effects of gonadal steroids at the pituitary level on the secretion of these two hormones. A combined in vivo and in vitro approach is used to assess the site of action and the characteristics of interaction of estrogens and thyroid hormone in the control of thyrotropin-stimulating hormone and prolactin secretion.

Identification of Human Anterior Pituitary Cells by Immunoelectron Microscopy

Abstract: An attempt was made to classify human pituitary cell types by electron microscopic immunohistochemistry. The immunoperoxidase technique involving the use of the peroxidase-antiperoxidase complex was applied to thin sections of human pituitaries removed surgically for breast cancer or diabetic retinopathy. Using specific antibodies against human PRL, GH, beta-FSH, beta-LH, beta-TSH, and porcine ACTH, the localization of each hormone was studied. Identification of 5 human pituitary cells was possible: 1) The PRL-secreting cell contains round or slightly ovoid secretory granules of a diameter of 275-350 nm. 2) The GH-secreting cell is densely granulated with granule diameters ranging from 350-500 nm. 3) The gonadotrophic cell, which stains for both beta-FSH and beta-LH, is characterized by the presence of a varying number of secretory granules ranging from 275-375 nm. 4) The cortico-lipotrophic cell has numerous granules of about 375-550 nm in diameter. 5) The TSH-secreting cell contains small secretory granules of about 125-200 nm in diameter. Another cell type of which the small secretory granules of about 100 nm in diameter could not be stained by any of the antisera was also observed. This ultrastructural identification of human pituitary cells should contribute to a better understanding of the pathophysiology of the human pituitary.

Influence of Imposed Metabolic Fatigue on Visual Capacity Components

Abstract: The present study was designed to investigate the effects of exercise to exhaustion on different components of visual capacity: visual field, and coincidence/anticipation capacity. 16 male subjects were first familiarized with the three visual tests, one day before being submitted to a prefatigue visual test. Metabolic fatigue was induced by working to exhaustion on a bicycle ergometer. Once fatigued, all subjects undertook the visual tests. Pre- and post-fatigue visual measurements were not significantly different. The results demonstrated the independence between metabolic fatigue and visual capacity.

Genetics and Medicine: an evolving relationship

Abstract: The rapid expansion of knowledge in human and medical genetics has revealed at least 6 percent average heterozygosity per structural gene locus, in excess of 2300 Mendelian (single gene) variants and several hundred chromosomal variants in man. This means that with the exception of monozygous twins, no two individuals are alike in their phenotype. Therefore, each person has a relative state of health, and genetic factors contribute significantly to disease. The ubiquity of genetic diversity requires the development of services for genetic screening, diagnosis, and counseling to prevent and treat a major portion of disease in modern society. Specific programs in Quebec and Canada illustrate how individuals and populations can be served by such services. Better education of citizens and health professionals in human genetics is essential for the further improvement of genetics services in society.

Frequency of Down syndrome in livebirths by single-year maternal age interval: results of a Massachusetts study.

Abstract: An analysis of rates of intra-state Down syndrome livebirths to Massachusetts residents by single-year maternal age interval in 1958-1965 inclusive was carried out. A gradual increase of rate of the Down syndrome occurred from age 20 to about age 31, and a steeper increase thereafter. Different regression equations were derived in the 20-31 and the 33-45 age group. The regression equations were ln y = 0.04515 x -1.45759 for those age 20-31 and ln y = 0.24302x-7.57870, for those age 33-45, where y = rate per 1,000 and x = maternal age. The regression-derived rates are slightly lower than those reported in similar analyses of data from Sweden and New York State, but they are not markedly discrepant.

Paraganglioma of the filum terminale.

Abstract: An unusual tumor arising in the filum terminale is described. The clinical data revealed an extensive and slowly growing lesion. The histologic picture was characterized by a proliferation of lobules and sheets of regular cells within a rich vascular network. Electron microscopic studies showed light and dark cells with sustentacular extensions. Typical neurosecretory granules were obsen'ed in both cell types, establishing the diagnosis of para-ganglioma. The glomus coccygeum could be the site of this tumor.