Showing papers by "Laval University published in 1984"
868 citations
TL;DR: Human leukocytes and platelets were preincubated with inhibitors of the oxidative metabolism of arachidonic acid and indomethacin was the best inhibitor of the platelet cyclooxygenase as assessed by measurement of 12-hydroxy-heptadecatrienoic acid (HHT).
258 citations
TL;DR: In this article, retrograde transport of horseradish peroxidase (HRP) and fluorescent tracers after injections in various thalamic nuclei was used to investigate the relative density of retrogradely labeled cells in different districts of reticularis thalami (RE) nuclear complex of cat.
Abstract: The retrograde transport of horseradish peroxidase (HRP) and fluorescent tracers after injections in various thalamic nuclei was used to investigate the relative density of retrogradely labeled cells in different districts of reticularis thalami (RE) nuclear complex of cat. The RE nucleus was left virtually free of labeling only after injections localized into the anterior nuclear group; in those experiments, heavy retrograde labeling was obtained in mammillary nuclei. The major targets of RE cells proved to be centralis lateralis-paracentralis (CL-PC) and centrum medianum-parafascicularis (CM-PF) intralaminar nuclei. The projections to various intralaminar nuclei mainly arise in the rostral pole and rostrolateral part of RE nucleus and are reciprocal to intralaminar-RE pathways disclosed by Jones ('75). The RE territories labeled following injections in relay and associational nuclei are more restricted and are located contiguously and slightly anteriorly to a given nucleus. There was a very small proportion of doubly labeled RE cells after injections with fluorescent tracers in different nuclei. This was not due to a technical failure since many double-labeled neurons were found in the same material in medial globus pallidum after thalamic and midbrain injections (see companion paper by Parent and Steriade, '84). We conclude that most individual RE axons arborize in only one thalamic nucleus or nuclear group. An additional finding was the existence of intralaminar-to-relay (CL-PC to VA-VL) projections.
238 citations
TL;DR: This study established a converging sequence of evidence concerning the internal structure of fourteen broad categories of medical disorders as stored in the long‐term memories of pre‐clinical medical students and experienced doctors.
Abstract: According to recent research on categorization, knowledge of a given category is structured in memory around key cases or clear examples, referred to as the prototypes, which capture the core meaning of the category. The purpose of this study was to establish a converging sequence of evidence concerning the internal structure of fourteen broad categories of medical disorders as stored in the long-term memories of pre-clinical medical students and experienced doctors. It was shown that the mental representation of the categories was better described by the overlapping features of the prototype view of categorization than the criterial features of the classical view. It is argued that the prototype view may help facilitate the understanding of the learning and problem-solving process in medicine.
203 citations
TL;DR: The exercise program significantly lowered the adiposity of men and increased adipocyte epinephrine maximal stimulated lipolysis in women and men, respectively, and in both sexes, a significant increase in ESL was observed after training.
Abstract: In order to assess the effect of endurance training on adipose-tissue morphology and lipolysis, 22 adult subjects (11 men and 11 women) took part in a 20-week ergocycle training program, four to five days a week, 40 minutes a day, at 80% of their maximal heart rate. Before and after training, they were submitted to an adipose-tissue biopsy in the suprailiac region. Fat cell weight (FCW), and lipolytic activity were determined on isolated fat cells. For the whole sample, training significantly reduced FCW (pre: 0.40 +/- 0.13 (mean +/- SD) versus post: 0.36 +/- 0.13 micrograms; P less than 0.05), percentage of fat (pre: 22.0 +/- 8.3 versus post: 19.7 +/- 8.1%; P less than 0.05), and increased adipocyte epinephrine maximal stimulated lipolysis (ESL) (pre: 1.08 +/- 0.49 versus post: 1.69 +/- 0.67 mumol glycerol/30 min/10(6) cells; P less than 0.001). No changes were observed in fat cell number. In women, however, training induced no changes in the fatness indicators (% fat, sum of skinfolds, FCW). The exercise program significantly lowered the adiposity of men (% fat: P less than 0.001; sum of skinfolds: P less than 0.01; FCW: P less than 0.05). In both sexes, a significant increase in ESL was observed after training. ESL of men, however, responded better than that of women to training (ESL of women: 1.36 +/- 0.67 versus ESL of men: 2.02 +/- 0.50 mumol glycerol/30 min/10(6) cells; P less than 0.05), with increases over pre-training values of 46% and 66% in women and men, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
166 citations
TL;DR: Results suggest that immunoreactive material related to porcine NPY is present in the human hypothalamus, with a distribution similar to that observed in the rat.
Abstract: In order to study the distribution of neuropeptide Y-like immunoreactivity in the human hypothalamus, an immunocytochemical localization of this peptide was performed. Using antibodies developed against synthetic porcine neuropeptide Y (NPY), we have been able to localize immunoreactivity in neuronal cell bodies located exclusively in the infundibular nucleus. Immunostained fibers were found in several regions in the hypothalamus with a high concentration in the periventricular areas. Fibers were also found in the neurovascular zone of the median eminence, the pituitary stalk and the posterior pituitary. These results suggest that immunoreactive material related to porcine NPY is present in the human hypothalamus, with a distribution similar to that observed in the rat.
136 citations
TL;DR: In this paper, strong base and chlorotrimethylsilane were used to convert α, β- β, γ-unsaturated esters to the corresponding mixed vinylketene acetals.
133 citations
TL;DR: The hypothesis that NPY can act as a neurotransmitter or neuromodulator is supported by Ultrastructural studies using both the pre- and post-embedding immunoperoxidase techniques that showed NPY-like immunoreactivity could be observed in neuronal cell bodies, dendrites and axonal processes.
122 citations
TL;DR: It is concluded that tonically discharging bulbar reticular neurons with identified projections to the midbrain and thalamic nuclei act synergically with rostrally projecting MRF neurons as sources of thalamocortical activation.
Abstract: Neurons histologically localized in the gigantocellular (Gc) and magnocellular (Mc) fields of the bulbar reticular formation were tested for antidromic invasion by stimulating the ventromedial (VM) and intralaminar (centralis lateralis, CL, and centrum medianum, CM) thalamic nuclei, midbrain reticular formation (MRF), and reticulospinal tract. An overwhelming majority (94%) of antidromically identified cells projected either to rostral structures (MRF, medial and intralaminar thalamic nuclei) or to the spinal cord, while only 6% had bifurcating axons. Rostrally projecting bulbar reticular neurons were investigated during various wake-sleep behavioral states. (a) Phasic neurons were related to PGO waves, eye and head movements, and were localized in both Gc and Mc fields. (b) The majority of tonic neurons projected to MRF and VM and they were localized within Mc in a proportion of 85%. In order to test their possible role in activation of thalamocortical processes (as betrayed by EEG desynchronization), the activity of tonically discharging cells was separately evaluated in periods with and without phasic motor events. Half of the tonically discharging neurons had a high selectivity of discharge during paradoxical sleep without REM bursts (PS-); the ratio of their mean discharge rate during PS- to that in quiet wakefulness ( QW ) or slow-wave sleep (SWS) was 8 and 6, respectively. The other half of the tonic neurons equally increased firing rates from SWS to either QW or PS. The firing rate of rostrally projecting bulbar reticular neurons with tonic discharge patterns was analyzed during transitions from SWS to PS. An increase in discharge rate was found about 30 to 60 s prior to the first sign of EEG desynchronization in PS, during fully synchronized sleep with PGO waves (S-PGO). Statistical testing showed that the increased firing rate was not associated to PGO waves, but was temporally related to the appearance of EEG desynchronization at PS onset. We conclude, on the basis of these and other recent data, that tonically discharging bulbar reticular neurons with identified projections to the midbrain and thalamic nuclei act synergically with rostrally projecting MRF neurons as sources of thalamocortical activation.
112 citations
TL;DR: Stromal myofibroblasts from invasive ductal breast carcinomas rich in actin and readily identified by IF, were most numerous in the “young” edematous mesenchyme, areas corresponding to early stromal invasion or the peripheral invasive cellular front, suggesting that my ofibro Blasts may be more closely related to fibroblast than to smooth muscle cells.
Abstract: The intermediate filament cytoskeleton of stromal myofibroblasts from a series of twenty-eight infiltrating ductal breast carcinomas was examined by transmission electron microscopy (TEM) and indirect immunofluorescence (IF), the latter using antibodies to desmin, vimentin and prekeratin. Three cases of fibromatoses, selected as an additional source of myofibroblasts, were processed in the same manner. Stromal myofibroblasts from invasive ductal breast carcinomas rich in actin and readily identified by IF, were most numerous in the "young" edematous mesenchyme, areas corresponding to early stromal invasion or the peripheral invasive cellular front. Within the central sclerotic zone wherein clusters of neoplastic epithelial cells were surrounded by abundant collagen, most stromal cells corresponded by TEM to fibroblasts. In like fashion, myofibroblasts were most numerous in cellular, poorly collagenized portions of fibromatoses. By IF the only detectable intermediate filament protein of myofibroblasts in these two settings was vimentin. Since the appearance of stromal myofibroblasts appears to be associated with stromal invasion by malignant epithelium, their development by modulation of pre-existent periductal fibroblasts is postulated. With the exception of vascular smooth muscle cells and endothelial cells, the only periductal mesenchymal cells shown to contain vimentin were fibroblasts. The lack of desmin in myofibroblasts constitutes evidence against an origin from vascular smooth muscle cells. Because the molecular markers (intermediate filament proteins) of stromal cell differentiation presented quantitative but not qualitative modifications, the transformation of fibroblasts into myofibroblasts is quite likely, suggesting that myofibroblasts may be more closely related to fibroblasts than to smooth muscle cells.
100 citations
TL;DR: In this paper, a new model is proposed for liquid water, based on recent studies of the Raman spectra as a function of temperature, which features two kinds of hydrogen bonds: in addition to the well known linear hydrogen bonds (LHB), predominant in cold water, there are some bifurcated hydrogen bonds between three water molecules.
Abstract: A new model is proposed for liquid water, based on recent studies of the Raman spectra as a function of temperature. It features two kinds of hydrogen bonds: in addition to the well known linear hydrogen bonds (LHB), predominant in cold water, there are some bifurcated hydrogen bonds (BHB) between three water molecules. These three-centered bonds, mainly electrostatic, have an average energy of 2.5 kcal mol−1, about half of that of the LHB. Their characteristic OH stretching frequency is around 3420–3440 cm−1, compared with 3220 cm−1 for the LHB. In addition, there are a few percent of nearly free OH groups, i.e. non-hydrogen-bonded (NHB), with a stretching frequeney of ca 3615 cm−1. Reorientation between these three states occurs through rotation of the H2O molecules about one of their OH bonds. Thus, on melting, one third of the hydrogen atoms move out of the tetrahedral framework to occupy interstitial sites in the open ‘shafts’ characteristic of the ice structure. As in the case of ice, Fermi resonance between the ν1 and 2ν2 levels has little impact on the vibrational spectra of liquid water and iee. The hybrid molecule, HDO, does not form LHB with H2O or D2O, hence its simpler spectra. The BHB model can account much better than previous models for the thermodynamic anomalies of water.
TL;DR: There are considerable interindividual differences in the level of endowment for endurance performance and this genetic effect remains, however, quite modest when compared with other phenotypes, such as the skeletal dimensions of the body.
Abstract: Performance in endurance sports is affected by a variety of factors, including exercise-training habits, nutrition and other lifestyle components. Endurance performance can also be seen as a multifactorial phenotype influenced by genetic and non-genetic factors. Current models in quantitative genetics and experimental data available in the sport sciences literature suggest that the effects of genetic variation on endurance performance can be observed as (a) the consequence of a character highly determined by the genotype which is correlated with endurance performance, (b) inherited differences in endurance performance exhibited by individuals of a sample or population, and (c) genotype-dependent individual differences in the response to endurance training. This review considers the evidence for genetic effects in several determinants of endurance performance, namely: body measurements and physique, body fat, pulmonary functions, cardiac and circulatory functions, muscle characteristics, substrate utilisation, maximal aerobic power and others. Moreover, the response to aerobic training of indicators of aerobic work metabolism and endurance performance is reviewed, with emphasis on the specificity of the response and the individual differences observed in trainability. It is concluded that there are considerable interindividual differences in the level of endowment for endurance performance. This genetic effect remains, however, quite modest when compared with other phenotypes, such as the skeletal dimensions of the body. Moreover, while trainability of the capacity for endurance performance is quite high on the average, there are important individual differences in the sensitivity to endurance training. Recent data suggest that this sensitivity to aerobic training is largely genotype-dependent.
TL;DR: In this paper, a Gaussian Laguerre (or Hermite) beam that propagates in a straight line at a light velocity remaining focused for all time is presented.
Abstract: We have obtained packetlike solutions to the free-space homogeneous-wave equation. These solutions are Gaussian Laguerre (or Hermite) beams that propagate in a straight line at a light velocity remaining focused for all time.
TL;DR: In intact animals, neutralization of the inhibitory feedback action of endogenous androgens leads to an increased LH and testosterone secretion, which partly overcomes the direct action of the antiandrogen at the level of the prostate and seminal vesicles, which requires prevention of this escape phenomenon through inhibition of LH secretion.
Abstract: The nonsteroidal antiandrogen RU 23908 ( Anandron ) weakly interacts with the prostatic cytosolic androgen receptor and shows a fast dissociation rate. When administered to immature castrated rats up to the daily dose of 100 mg/kg, it is devoid of any androgenic activity but efficiently blocks the growth-promoting activity of androgens on ventral prostate and seminal vesicle weight, thus showing the characteristics of a pure antiandrogen. In intact animals, on the other hand, the antiandrogen administered alone exerts only a partial inhibition of prostate and seminal vesicle weight. This is due to the property of the pure antiandrogen to neutralize the inhibitory feedback effect of androgens at the pituitary level on the LH responsiveness to LHRH, as illustrated in vitro in rat anterior pituitary cells in culture as well as in vivo in intact and castrated animals. In intact animals, neutralization of the inhibitory feedback action of endogenous androgens leads to an increased LH and testosterone secretion, which partly overcomes the direct action of the antiandrogen at the level of the prostate and seminal vesicles. In fact, the plasma testosterone concentration is more than doubled 6 hr after the administration of 10 mg of RU 23908 while plasma LH and testosterone levels are increased by 7- and 17-fold, respectively, after 14 days of similar daily treatment. Efficient neutralization of the androgenic action at the prostatic level in intact animals thus requires prevention of this escape phenomenon through inhibition of LH secretion. Although inhibition of LH release can be achieved by estrogen and progestins, an optimal inhibitory effect on the prostate is obtained by the combined administration of the antiandrogen with an LHRH agonist that causes a specific blockage of testicular androgen biosynthesis as well as an inhibition of the LH responsiveness to LHRH.
TL;DR: Two methods are considered: Coherent superposition and decision making in multidimensional space and multiple circular harmonic components of the same target can be used jointly to discriminate between the target and other objects.
Abstract: Multiple circular harmonic components of the same target can be used jointly to discriminate between the target and other objects. Two methods are considered: Coherent superposition and decision making in multidimensional space. Experimental results for the discrimination between a tank and a truck are given.
TL;DR: The study showed that selecting the DLS ewes for extended breeding season may have altered the reproductive performance of the rams of that breed, and Rams within breeds differed significantly in the seminal characteristics studied.
Abstract: Breeding activity (libido), testicular size, testosterone levels and seminal characteristics of 10 DLS adult rams (a population of 1/2 Dorset, 1/4 Leicester and 1/4 Suffolk selected for extended breeding season) were compared with those of 10 adult Suffolk rams. The study lasted 18 mo during which the data were recorded over 30 collection periods. All characteristics varied significantly with the season of the year, being lowest during the summer and highest during the fall. Suffolk rams had higher libido but lower testosterone levels than the DLS rams throughout the study. Testosterone increased earlier and decreased later in the breeding season in DLS compared with Suffolk rams, the interaction breed X period being significant. Testosterone concentration was highly associated with testicular size and libido, accounting for 65 and 28% of the variation in the Suffolk and 37 and 18% in the DLS rams, respectively. Seminal output and quality (motility and percentage of live spermatozoa) were highest in October and November and lowest in April and May. Rams within breeds differed significantly in the seminal characteristics studied. Results of the study showed that selecting the DLS ewes for extended breeding season may have altered the reproductive performance of the rams of that breed.
TL;DR: The data showed that accuracy of judgment reached a fairly high level even at very brief exposure times and that human observers are especially competent to process very rapid changes in facial appearance.
Abstract: The purpose of this experiment was to study the accuracy of judgment of facial expressions of emotions that were displayed for very brief exposure times. Twenty university students were shown facial stimuli that were presented for durations ranging from 10 to 50 msec. The data showed that accuracy of judgment reached a fairly high level even at very brief exposure times and that human observers are especially competent to process very rapid changes in facial appearance.
TL;DR: It is concluded that bladder cancer is associated with aluminium smelting (primarily with the Soderberg process) and there is a synergistic effect when cigarette smoking and BaP exposure are combined; the numbers in the population are too small to determine whether this interaction effect is multiplicative or additive.
TL;DR: Results show that arginine esterase of dog seminal plasma is a serine protease composed of two different chains linked by disulfide bridges, one of the chains contains the reactive serine group.
Abstract: This work was undertaken to determine the identity of the major androgen-dependent 15,000 molecular weight protein previously observed on SDS polyacrylamide gel electrophoresis of both dog prostate cytosol and dog seminal plasma. The protein was identified as one of the two chains of arginine esterase on the basis of its ability to bind 3H-diisopropylphosphofluoridate (DFP), an active site titrant of serine proteases. Furthermore, since the other polypeptide chain was heterogeneous, at least five distinct peaks of arginine esterase activity could be separated by chromatofocusing under nonreducing conditions. The molecular weight of the seminal plasma protein was estimated at 29,500 by Sephadex G-100 gel filtration, and at 25,000 by SDS polyacrylamide gel electrophoresis in the absence of mercaptoethanol. In the presence of mercaptoethanol, two major peaks were observed with molecular weights of 15,000 and 14,000. These results show that arginine esterase of dog seminal plasma is a serine protease composed of two different chains linked by disulfide bridges. One of the chains contains the reactive serine group. The other one is probably glycosylated since it presents several isoelectric points.
TL;DR: In this article, the authors discuss methods originally proposed by Adams and Miovic in 1968 for calculating the output elasticity of useful energy consumption (ϵ), and show that this methodological approach is quite dubious.
Abstract: The present paper discusses methods originally proposed by Adams and Miovic in 1968 (then refined and used later by many other authors) for calculating the output elasticity of useful energy consumption (ϵ). We first show that this methodological approach is quite dubious. Better alternative methods of estimation are then proposed. We also stress that, since the marginal rate of interfuel substitution depends on the GDP functional form, the simulataneous use of several functional forms of GDP in energy studies leads obviously to misleading interpretations. Using thermal efficiency coefficients and OECD countries figures for the 1959–73 period, we finally found that ϵ did steadily fall from high values to values which are still higher than one.
TL;DR: The generalized homomorphic transformation to make signal-dependent noise independent of the signal is combined with a local-statistics image restoration technique to process images degraded by signal- dependent noise.
Abstract: The generalized homomorphic transformation to make signal-dependent noise independent of the signal is combined with a local-statistics image restoration technique to process images degraded by signal-dependent noise. Experimental results are given for images degraded by film-grain noise and by multiplicative noise.
TL;DR: Treatment with an antiandrogen in castrated men inhibit the formation of adrenal androgens due to a blockade at the level of 17, 20-desmolase, and the efficiency of the new combined antihormonal therapy aimed at complete androgen neutralization in prostate cancer is further facilitated.
Abstract: The basal plasma levels of cortisol, dehydroepiandrosterone (DHEA), DHEA sulfate (DHEA-S), and testosterone were studied in 20 patients with advanced prostatic cancer receiving combined treatment with an LHRH agonist and an antiandrogen [5,5-dimethyl-3-[4-nitro-3-(trifluoromethyl)-phenyl]-2 4-imidazolidinedione]. After 60 days of combined antihormonal therapy, plasma levels of testosterone decreased from 5.44 +/- 0.44 (SEM) to 0.136 +/- 0.052 ng/ml (2.5% of control). Somewhat unexpectedly, the plasma concentrations of the adrenal androgens DHEA and DHEA-S were reduced to 45 +/- 7 and 64 +/- 4% of control, respectively. The maximal reduction in plasma adrenal androgen levels occurred between 2 and 4 weeks of treatment. Whereas the increase in serum cortisol, 17-hydroxypregnenolone, and 17-hydroxyprogesterone concentrations 2 1/2 h after the injection of 0.25 mg human ACTH 1-24 was not affected by the combined treatment, the increment of DHEA and androstenedione after the same stimulus was reduced from 3.1 +/- 0.98 and 0.73 +/- 0.11 to 1.48 +/- 0.5 and 0.31 +/- 0.05 ng/ml, respectively. The reduced levels of serum DHEA and DHEA-S were not due to the LHRH agonist by itself, since similarly low levels of serum DHEA and DHEA-S were found in patients surgically castrated and receiving the same antiandrogen. These data suggest that treatment with an antiandrogen in castrated men inhibit the formation of adrenal androgens due to a blockade at the level of 17, 20-desmolase. The efficiency of the new combined antihormonal therapy (castration and antiandrogen) aimed at complete androgen neutralization in prostate cancer is thus further facilitated.
TL;DR: Results showed that the administration of folic acid during gestation could appreciably improve the reproductive performance of sows.
Abstract: Two-hundred nine sows were used in a 2 X 2 split-plot unbalanced design to measure the effect of folic acid against control, and flushing against a normal level of feeding, between weaning and mating on the following variables: serum folates at weaning and at 60 d of gestation, blood hemoglobin (Hb) and hematocrit (Ht) after 15 wk of gestation and reproductive performance at farrowing. Folic acid was administered im according to a schedule that maintained serum folates at approximately the same level between weaning and 60 d of gestation. The treatments had no effect on Hb or Ht after 15 wk of gestation. Average live litter size was 12.0 piglets/litter for sows receiving the folic acid and flushing treatments as compared with 10.5 for sows without any treatment; the main effect of folic acid was significant (P less than or equal to .04). Intralitter variation in birth weight and total litter weight tended to be increased by folic acid administration. Results showed that the administration of folic acid during gestation could appreciably improve the reproductive performance of sows.
TL;DR: Radioautography results indicate that in the anterior pituitary CRF receptors are restricted to corticotrophs (as identified by electron microscopy) and that, after binding to the plasma membrane, CRF is rapidly internalized to Golgi elements and lysosomes.
Abstract: In order to identify the anterior pituitary cell type(s) containing corticotropin-releasing factor (CRF) receptors and to study the internalization processes of this peptide by the target cells, radioautography was performed on rat anterior pituitaries removed at specific intervals (2-60 min) after intracarotid injection of [125I]iodo-CRF into intact and adrenalectomized female rats. In intact animals, all corticotrophs were labeled, whereas in the adrenalectomized animals about 80% of the hypertrophied corticotrophs (adrenalectomy cells) were. In control animals injected with both iodinated CRF and an excess of unlabeled peptide, no specific reaction could be detected. The time-course study in intact animals showed that 2 min after injection most silver grains were found over or within 160 nm of the plasma membrane. At the 5-min time intervals, grains were observed both over the plasma membrane and within the cytoplasm, associated with lysosomes, and the Golgi apparatus. Fifteen minutes after injection, grains were mostly found over lysosomes and the Golgi apparatus, whereas at the longest time intervals (30 and 60 min) almost no labeling could be detected. The results obtained in this study indicate that in the anterior pituitary CRF receptors are restricted to corticotrophs (as identified by electron microscopy) and that, after binding to the plasma membrane, CRF is rapidly internalized to Golgi elements and lysosomes.
TL;DR: The composition of Chroococcidiopsis cell envelopes was characterized by cytochemical tests for detection of sporopollenin-like compounds, and acid, sulphated and beta-linked polysaccharides, positively charged glycoproteins, lipids and proteins, which were present as very elaborate structures in the envelope of cells from stones and in desiccated cultures.
Abstract: Chroococcidiopsis sp. cells present hypolithically in quartz flints collected in the Negev Desert (Israel) and in wet and desiccated laboratory cultures were examined by light and transmission electron microscopy. The composition of Chroococcidiopsis cell envelopes was characterized by cytochemical tests for detection of sporopollenin-like compounds, and acid, sulphated and beta-linked polysaccharides, positively charged glycoproteins, lipids and proteins. These compounds were present as very elaborate structures in the envelope of cells from stones and in desiccated cultures. An increased envelope thickness is probably useful in the prevention of water loss, although it could cause cell death by reducing exchange with the environment. Isolated living cells that occurred in desiccated cultures might be regarded as resting forms allowing the survival of the cyanobacterium.
TL;DR: The process of spring fat accumulation is summarized, together with a comparison of fattening rates in birds using either Scirpus or Spartina marshes, to establish whether the recent range expansion into the Spartina habitat has affected the accumulation of fat reserves essential for these birds to reach their breeding grou s in peak condition.
Abstract: -The influence of habitat on fat storage by Greater Snow Geese (Chen caerulescens atlanticus) on their St. Lawrence River estuary spring staging grounds was studied in 1979 and 1980. In all, 373 individuals (two-year old and older birds only) were collected in two types of marsh during the six-week staging halt: the traditionally-occupied fresh-water, Scirpus-dominated marshes of the upper estuary (SCI) and in the newly-invaded (after the early 1960s) salt-water, Spartina-dominated marshes (SPA) of the lower estuary. The birds reached SPA a few days later than SCI in early April, at which time their total fat reserves amounted to about 10% of their body weight. Fattening at SCI increased steadily throughout the staging period, while at SPA, it slowed markedly in females and stopped completely in males around the middle of the staging period. In birds departing for the arctic around 18-20 May, the total fat reserves amounted to 19-20% of the body weight. Males departing from SCI carried 23% more fat on the average than those of SPA (P 0.05). It appears unlikely that the geese could increase these reserves after leaving the St. Lawrence estuary and before reaching their higharctic nesting grounds. In arctic-nesting geese, energy reserves available to birds at the beginning of the breeding season constitute one of the major determinants of reproductive success (Hanson 1962; Ryder 1967, 1970; Newton 1977; Raveling 1978). This has been shown for Lesser Snow Geese (Chen c. caerulescens; Harvey 1971, Ankney 1977, Ankney and MacInnes 1978) and Canada Geese (Branta canadensis; Raveling and Lumsden 1977, Raveling 1979). However, until recently little attention had been paid to the process of fat accumulation in the spring (Wypkema and Ankney 1979, McLandress and Raveling 1981). The Greater Snow Goose (Chen caerulescens atlanticus) is unique among arctic-nesting North American geese because it makes only a single known stop during spring migration. The spring population has increased in recent years from 25,400 in 1965 to 170,000 and 180,000 in 1979 and 1980, respectively (Anon. 1981), and the geese have also expanded their staging area. Traditionally, they used the bulrush-dominated (Scirpus americanus) tidal marshes of the upper St. Lawrence River estuary around Cap Tourmente and Montmagny, Quebec (Lemieux 1959; see Fig. 1). Since the 1960s the geese have progressively invaded the cordgrass (Spartina sp.)-dominated tidal marshes of the lower estuary, and by 1980, approximately 20% of the spring population used this newly invaded habitat (J. Bedard, unpubl. observ.). Preliminary observations in 1978 indicated that geese responded differently to the conditions prevailing in these two types of marshes. To investigate these responses, a comparative study of the birds' food habits, movements, time and energy budget was conducted in 1979 and 1980. In this article, we summarize one aspect of that larger investigation, the process of spring fat accumulation, together with a comparison of fattening rates in birds using either Scirpus or Spartina marshes. In this way, we hope to establish whether the recent range expansion into the Spartina habitat has affected the accumulation of fat reserves essential for these birds to reach their breeding grou s in peak condition.
TL;DR: In this paper, the number and weight average molecular weights of the fulvic acids (∼5000 and ∼22,000 daltons respectively) were lower than those of the humic acids ( ∼20,000 and ∼75,000 Daltons, respectively).
Abstract: SUMMARY. 1. Between February and September 1974, concentrations of fulvic and humic acids in waters from a cryoboreal region of the Precambrian Shield in Quebec varied between 0.5–6.1 mg 1−1 and 0.1–6.5 mg 1−1 respectively. Whereas the fulvic acids usually remained relatively constant during this period, humic acids showed appreciable increases.
2. The number and weight average molecular weights of the fulvic acids (∼5000 and ∼22,000 daltons respectively) were lower than those of the humic acids (∼20,000 and ∼75,000 daltons respectively). The average molecular weight of the aquatic humic matter often decreased during late summer and early autumn. During spring floods the molecular weight of fulvic acids increased and that of humic acids declined.
3. Because the aquatic humic acids were more intensely coloured than fulvic acids, they contributed more than 30% of the colour of the water even though they accounted for only 15% of the concentration of humic matter. The colour intensity of both fulvic and humic acids generally appeared to increase during the latter part of the summer, when there was normally a decrease in the value of the colour quotient (E4/E6 ratio), indicating the accumulation in the waters of more humified material.
TL;DR: Proprietes d'un racemique fait de poly-S et poly-R poly(α-methyl α-ethyl β-propiolactone) isotactiques (PMEPL).
Abstract: Proprietes d'un racemique fait de poly-S et poly-R poly(α-methyl α-ethyl β-propiolactone) isotactiques (PMEPL). Etude du comportement de melanges poly-S/poly-R PMEPL contenant un exces de poly-S ou de poly-R (melanges binaires). Comportement de melanges ternaires de PMEPL racemique, poly-S PMEPL et poly-R PMEPL. Fusion et proprietes morphologiques de ces melanges et nombre limite de donnees cristallographiques
TL;DR: It is found that under low light intensity (0.17 lux) adult creek chub fed as efficiently as under high lightintensity (22 lux) and several possible hypotheses to explain the evolution of the two different strategies exhibed by adult and juvenile creek chubs are discussed.
Abstract: Juvenile creek chub, Semotilus atromaculatus, differed ecologically from adults. They were essentially diurnal, fed on small prey (adult diptera and aquatic adult coleoptera) and were found mainly in shallow littoral water (0.8 m depth) of a Quebec oligotrophic lake. In contrast, adults were principally nocturnal, fed on larger prey (Gammaridae, diptera larvae, diptera pupae and ephemeroptera larvae) and were found in deeper water (1.2, 2.0 and 2.9 m depth). The overlap in diet between juvenile and adult fish was 10 percent. We found that predation by brook charr, Salvelinus fontinalis, upon creek chub was low, as only 5 chart stomachs of the 302 examined contained a total of 16 juvenile chub and none contained adult chub. Laboratory observations revealed that under low light intensity (0.17 lux) adult creek chub fed as efficiently as under high light intensity (22 lux). Several possible hypotheses to explain the evolution of the two different strategies exhibed by adult and juvenile creek chub are discussed.