Evidence for thermoregulatory behavior during self-paced exercise in the heat

The primary objective of this investigation was to test the hypothesis that voluntary reductions in exercise intensity in heat improve heat exchange between the body and the environment, and are thus thermoregulatory behaviors. This was accomplished by observing the conscious selection of exercise intensity and the accompanying thermal outcomes of eleven moderately active males when exposed to an uncompensably hot (UNCOMP) and a compensable (COMP) thermal environment. Evidence for thermoregulatory behavior was defined relative to the specific, pre-determined definition. Self-selected exercise intensity (power output) was unanimously reduced in UNCOMP over time and relative to COMP in all the subjects. These voluntary responses were found to modify metabolic heat production over time and therefore heat exchange between the body and the environment. Likewise, the observed reductions in power output were, at least in part, due to a conscious action, that was found to be inversely related to the total body heat storage and thermal discomfort. There was no evidence for thermoregulatory behavior in COMP. These data uniquely indicate that voluntary reductions in exercise intensity improves heat exchange over time, and therefore contributes to the regulation of body temperature. These findings suggest that reductions in exercise intensity in heat are, by definition, thermoregulatory behaviors.     

Telemetered heart rate responses of the rat during free and learned behavior

To assess the effect of recording on the heart rate and on the behavior of the free moving rat, the electrocardiogram was recorded with the aid of radiotelemetry or through wire leads attached to the animal in different behavioral situations. Adaptation of heart rate both within and across sessions in the home cage and in a novel environment (open-field) was observed in rats bearing a transmitter. No adaptation occurred in rats attached to wire leads. The pattern of heart rate changes appeared to be independent of the mode of recording during passive avoidance behavior and when the rats displayed various motor activities like walking, sniffing, rearing or grooming in the open-field. The heart rate of rats attached to wire leads, however, was always higher. These data indicate that radiotelemetry is preferable to the use of wire connections for recording cardiac activity during behavioral studies in the rat.     

Building a bird brain: Sculpting neural circuits for a learned behavior

Development in animals is frequently characterized by periods of heightened capacity for both neural and behavioral change. So-called sensitive periods of development are windows of opportunity in which brain and behavior are most susceptible to modification. Understanding what factors regulate sensitive periods constitutes one of the main goals of developmental neuroscience. Why is the ability to learn complex behavioral patterns often restricted to sensitive periods of development? Songbirds provide a model system for unraveling the mysteries of neural mechanisms of learning during development. Like many songbirds, zebra finches (Taeniopygia guttata) learn a specific vocal pattern during a restricted period early in life. Young birds must hear songs produced by members of their species; this auditory experience is thought to engender specific changes in the brain to guide the process of vocal learning. Many studies of the songbird system have focused on examining relationships between brain development and learning. One goal of this work is to elucidate mechanisms that regulate basic processes of neural development, and in so doing to shed light on factors governing the emergence of a complex learned behavior.     

Evidence for early endosome-like fusion of recently endocytosed synaptic vesicles

Early endosomes are well-established acceptor compartments of endocytic vesicles in many cell types. Little evidence of their existence or function has been obtained in synapses, and it is generally believed that synaptic vesicles recycle without passing through an endosomal intermediate. We show here that the early endosomal SNARE proteins are enriched in synaptic vesicles. To investigate their function in the synapse, we isolated synaptic nerve terminals (synaptosomes), stimulated them in presence of different fluorescent markers to label the recycling vesicles and used these vesicles in in vitro fusion assays. The recently endocytosed vesicles underwent homotypic fusion. They also fused with endosomes from PC12 and BHK cells. The fusion process was dependent upon NSF activity. Moreover, fusion was dependent upon the early endosomal SNAREs but not upon the SNAREs involved in exocytosis. Our results thus show that at least a fraction of the vesicles endocytosed during synaptic activity are capable of fusing with early endosomes and lend support to an involvement of endosomal intermediates during recycling of synaptic vesicles.     

Long-term retention of a poorly learned saccharin aversion : Evidence for an incubation effect

The retention of a weak conditioned saccharin aversion was tested using independent groups over a 14-day period. The delay between CS (saccharin 0.1 %) and US (LiCl 0.15 M) was 6 hours. Significant variations in the retention function were observed, in particular an improvement of memory - i.e. an incubation effect - over the 14-day period. This result suggests that retention of conditioned taste aversion may share common features with the retention of more classical aversive conditioning.     

Afferent influences on cell death and birth during development of a cortical nucleus necessary for learned vocal behavior in zebra finches

Forebrain nuclei that control learned vocal behavior in zebra finches are anatomically distinct and interconnected by a simple pattern of axonal pathways. In the present study, we examined afferent regulation of neuronal survival during development of the robust nucleus of the archistriatum (RA). RA projection neurons form the descending motor pathway of cortical vocal-control regions and are believed to be directly involved in vocal production.RA receives afferent inputs from two other cortical regions, the lateral magnocellular nucleus of the anterior neostriatum (lMAN) and the higher vocal center (HVC).However, because the ingrowth of HVC afferent input is delayed, lMAN projection neurons provide the majority of afferent input to RA during early vocal learning. lMAN afferent input to RA is of particular interest because lMAN is necessary for vocal learning only during a restricted period of development. By making lesions of lMAN in male zebra finches at various stages of vocal development (20-60 days of age) and in adults (>90-days old), we asked whether the survival of RA neurons depends on lMAN afferent input, and if so whether such dependence changes over the course of vocal learning. The results showed that removal of lMAN afferent input induced the loss of over 40% of RA neurons among birds in early stages of vocal development(20 days of age). However, lMAN lesions lost the ability to induce RA neuron death among birds in later stages of vocal development (40 days of age and older). These findings indicate that many RA neurons require lMAN afferent input for their survival during early vocal learning, whereas the inability of lMAN lesions to induce RA neuron death in older birds may indicate a reduced requirement for afferent input or perhaps the delayed ingrowth of HVC afferent input (at approx. 35 days of age)provides an alternate source of afferent support. Removal of lMAN afferent input also dramatically increased the incidence of mitotic figures in RA, but only among 20-day-old birds at 2 days post-lesion. The early, acute nature of the mitotic events raises the possibility that cell division in RA may be regulated by lMAN afferent input.     

The transmission of learned behavior: An observational study of father-child interactions during fishing

Mechanisms of transmission of learned behavior were described in terms of the behavioral interactions between fathers and their children as they fished from a pier on Maryland's Eastern Shore. Verbal and nonverbal behaviors and the patterns of association in the behavioral repertoire were described in detail. Groupings of associated behaviors ranged from clusters suggestive of modeling or simple showing to complex combinations of behaviors involved in teaching. There were indications that the transmission behaviors varied with the content of the transmitted information and the role of the performer. Role differentiation in the transmission behaviors suggested the occurrence of two distinct patterns in the ontogeny of complex behaviors.     

Evidence for a major gene controlling susceptibility to tegumentary leishmaniasis in a recently exposed Bolivian population.

Tegumentary leishmaniasis due to Leishmania braziliensis is a parasitic disease that occurs in two stages after the infected sandfly bite: (1) a primary cutaneous lesion followed by (2) a secondary mucosal involvement generally resulting in severe facial deformities. In order to investigate the genetic and environmental factors involved in the development of the cutaneous lesion, a familial study was performed in a region of Bolivia in which the disease is endemic. Complete selection of 118 nuclear families (703 subjects, with 241 patients), each with at least one cutaneous affected subject, was achieved; 41 families were of native origin, and 77 (herein designated "migrant") recently had settled in the area. For the analysis, the trait under study was the time to onset of the primary cutaneous lesion. The start of the follow-up was birth, for native population, or date of arrival in the endemic area, for migrant population. Segregation analysis was performed by use of a model based on survival analysis methods that allows joint estimation of genetic and environmental effects and accounts for gene x covariate interactions. A significant effect of gender, home-forest distance, and forest-related activity was found. In the 77 migrant families there was evidence for a recessive major gene controlling the onset of the primary cutaneous lesion, with residual familial dependences and age x genotype interaction. Penetrance estimations show that young subjects are genetically more susceptible than older subjects, suggesting that this genetic component could concern mechanisms involved in the development of individual protection during childhood. There was also a significant genetic heterogeneity of the sample according to the native/migrant origin of the families, and no major-gene effect was found in the native subsample.     

Effects of apomorphine on the expression of learned helplessness behavior

Dopaminergic system and its D1 as well as D2 receptors are involved in the modulation of emotional behavior. This experiment investigated the role of dopaminergic activity in the inescapable stress-induced learned helplessness, a widely used depression animal model, by using the pharmacological manipulation through the apomorphine (APO), an agonist for D1 and D2 receptors, and sulpiride (SUL), a selective D2 antagonist. Male Sprague Dawley rats were used and tested in a shuttle box. In the day-1 session, the rats received a 10-trial (1 min/trial) inescapable stressor: a 3 sec conditioned stimulus (CS; 75 db sound and 250 lux red light) followed by a 10 sec unconditioned stimulus (UCS; electrical foot shock, 0.5 mA). In the day-2 session, a 15-trial active avoidance test, 3 sec CS followed by UCS, was performed 30 min after the administration of APO (0, 0.05, 0.5, 1, and 5 mg/kg, i.p.). The number of failures was counted and the UCS was stopped when the rats did not escape after 15 sec UCS. The results showed that APO at the dosage of 0.5 mg/kg had a tendency to enhance the avoidance behavior. In contrast, the treatment of higher dose of APO, 1 and 5 mg/kg, reduced the number of escape but increased the number of failure. Pretreatment of SUL (5 mg/kg, i.p.), 10 min before 1 mg/kg of APO, significantly enhanced the failure behavior. The present data suggest that the activity of D2 receptor may be associated with the adaptive or protective role in the prevention of escape deficits after exposure to inescapable stress. However, the excessive stimulation of D1 receptor may participate in the failure of coping behavior leading to learned helplessness and therefore in the pathophysiological mechanisms underling the development of depression.     

Risk-taking behavior of bull-headed shrikes that recently colonized islands

Individuals which have invaded urbanized environments are reported to engage in riskier behaviors, possibly influenced by the scarcity of predators in urbanized areas. Here, we studied the risk-taking behavior of birds which had invaded a new natural environment, rather than an artificial urban environment, using recently established populations of the bull-headed shrike Lanius bucephalus, which naturally colonized three subtropical islands in Japan. We compared flight initiation distance (FID), the distance at which an individual approached by a human initiates flight, between the islands and the temperate mainland. FID was longer for the insular shrikes compared with the mainland shrikes after controlling for other factors, indicating that the individuals which had invaded a new natural environment had a lower propensity for risk-taking. A possible explanation for these results is that low risk-taking behavior might be adaptive on the islands due to predation by the black rat Rattus rattus, an unfamiliar predator not found in shrike habitats on the temperate mainland. Further studies are needed to examine the nest predation rate, predator species, and nest site selection of these insular shrike populations.     

Diurnal variation of physiological rhythms in a patient with sleepwalking

The association between sleepwalking, a non-rapid-eye-movement parasomnia, and biological rhythms has not been subject of research in the past, although shift work is a known risk factor of the disorder. We present the case of a 36-year-old policeman who suffered for years from sleepwalking and was referred to the hospital for polysomnography. All standard investigations including multiple sleep latency or maintenance wakeful test were normal. On the contrary, chronobiological assessment revealed phase delay of vital functions and body temperature, whereas acrophases of melatonin and cortisol remained stable. We postulate an increase in sleep fragmentation due to shift work, but further research is needed to substantiate the hypothesis.     

雌性信息素在麻点豹天牛成虫交尾行为中的作用

通过对麻点豹天牛Coscinesthes salicisGressitt成虫交尾行为的观察,发现雌、雄成虫间明显存在着性引诱物质的诱导现象,作者采用溶剂从雌虫体上提取出该物质,并对其生物活性及雄虫的感应方式进行检测,结果证明该信息素提取物在成虫的交尾行为中起着较为关键的作用,雄虫依靠此信息物来寻找和识别雌虫。应用提取物对雄虫所诱发的交尾行为反应与正常状态下的行为相似,经测定雄虫对该性信息素提取物的感应方式主要是接触感应。     

Endocrine control of amphibian sexual behavior: Evidence for a neurohormone-androgen interaction

The incidence of sexual behavior increased after an injection of arginine-8 vasotocin or arginine-8 vasopressin into intact male newts (Taricha granulosa). Administration of arginine vasopressin to males that were castrated 35 days earlier enhanced sexual behaviors in only those males implanted with androgen.     

Evidence for differential DNA endoreplication during the development of a molluscan brain

The DNA content of neurons in the cerebral ganglion of Achatina fulica was determined by the two-wavelength method of microspectrophotometry using Feulgen-stained sections. DNA measurements of mouse hepatocytes were used as a control of the methods. All sampled neurons with a nuclear diameter greater than 7 microns were polyploid. The shape of the frequency histogram of DNA contents is not compatible with an interpretation that assumes one or more simple duplications of the genome. It is suggested, instead, that the results are due to either the underreplication of some DNA sequences or the selective amplification of genes. Additional experiments using [3H]-thymidine autoradiography showed that the incidence of neuronal DNA synthesis is highest during the period of the animal's greatest growth and then declines rapidly near the onset of sexual maturity. The mesocerebrum incorporated greater amounts of [3H]-thymidine than the rest of the brain, whereas the procerebrum remained diploid throughout the course of the study.     

Evidence for a tetrahedral intermediate complex during serpin-proteinase interactions

Proteinase inhibitors in the serpin family form complexes with serine proteinases by interactions between the gamma-OH group at serine 195 of the enzyme and a specific peptide bond within the reactive site loop of the inhibitor. However, the type of complex formed (i.e. Michaelis, acyl, or tetrahedral) is unknown. Until now, 13C NMR spectroscopy studies have only been useful in examining complexes formed with either peptide-related or small protein inhibitors, where 13C-labeled amino acids can be inserted semi-synthetically. Recombinant DNA technology has, however, made it possible to specifically enrich larger proteins with 13C. In the case of serpins we have examined the structure of the complex formed between human alpha 1-proteinase inhibitor uniformally labeled with [13C]methionine and porcine pancreatic elastase. 13C NMR spectroscopic studies revealed a large upfield chemical shift of the carbonyl signal of Met-358 upon complex formation suggesting for the first time that a tetrahedral adduct is formed between a serpin inhibitor and a serine proteinase.     

Vocal turn-taking in a non-human primate is learned during ontogeny

Conversational turn-taking is an integral part of language development, as it reflects a confluence of social factors that mitigate communication. Humans coordinate the timing of speech based on the behaviour of another speaker, a behaviour that is learned during infancy. While adults in several primate species engage in vocal turn-taking, the degree to which similar learning processes underlie its development in these non-human species or are unique to language is not clear. We recorded the natural vocal interactions of common marmosets (Callithrix jacchus) occurring with both their sibling twins and parents over the first year of life and observed at least two parallels with language development. First, marmoset turn-taking is a learned vocal behaviour. Second, marmoset parents potentially played a direct role in guiding the development of turn-taking by providing feedback to their offspring when errors occurred during vocal interactions similarly to what has been observed in humans. Though species-differences are also evident, these findings suggest that similar learning mechanisms may be implemented in the ontogeny of vocal turn-taking across our Order, a finding that has important implications for our understanding of language evolution.     

Evidence for ancient genetic subdivision among recently fragmented populations of the endangered shrub Grevillea caleyi (Proteaceae)

The genetic effects of population fragmentation cannot be interpreted without understanding the underlying pattern of genetic variation resulting from historic population processes. We used AFLP markers to determine genetic structure and distribution of genetic diversity among populations of an endangered Australian shrub Grevillea caleyi (Proteaceae). Populations that occurred historically on four ridges have new been fragmented to varying degrees, producing some large, relatively pristine populations and very small populations consisting of fewer than 10 adult plants. We found marked population genetic structure (65.9% of genetic variation was among populations) and a significant relationship between genetic and geographic distance (rm=0.564, P=0.004). However, only 14% of overall genetic differentiation was attributable to variation among ridges, compared with 52% among populations within ridges. Moreover, genetic diversity within samples of plants did not vary with either population size or degree of isolation. Thus, the present genetic structure of populations is probably almost entirely the product of historical events. Fine-scale structuring within populations prior to fragmentation may have been caused by limited seed and pollen dispersal, despite a complex suite of (mostly avian) pollinators, and a mixed mating system that allows a large amount of selfing. The combined effects of adult longevity and a soil-stored seed bank may have buffered the recently fragmented populations against the effects of dramatic reductions in numbers of adult plants.     

Evidence of a responsible gene for the thermosensibility during laying-season with Drosophila melanogaster

Summary A recessive gene that makes oogenesis and development heat sensitive has been found in a laboratory strain of Drosophila melanogaster homozygous for sepia. The new mutation called pts (ponte thermosensible) is located on chromosome III, near the locus of sepia. When eggs are collected from females kept at 30°C, two observations can be made:The rate of egg laying is reduced, oogenesis being stopped reversibly at stage 7 of ovarian cystes.Eggs which have gone through this stage before the temperature was raised are deposited, but fail to hatch, even when their own genotype is heterozygous pts/pts ⁺.Heat shocks applied at later periods to pts/pts homozygous show the existence of two others periods of temperature sensitivity located respectively at the beginning of embryogenesis and of larval stage.

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Directeur: Ph. L'Héritier

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Mémoire présenté par E. Hadorn