Experience-dependent upregulation of multiple plasticity factors in the hippocampus during early REM sleep

Sleep is beneficial to learning, but the underlying mechanisms remain controversial. The synaptic homeostasis hypothesis (SHY) proposes that the cognitive function of sleep is related to a generalized rescaling of synaptic weights to intermediate levels, due to a passive downregulation of plasticity mechanisms. A competing hypothesis proposes that the active upscaling and downscaling of synaptic weights during sleep embosses memories in circuits respectively activated or deactivated during prior waking experience, leading to memory changes beyond rescaling. Both theories have empirical support but the experimental designs underlying the conflicting studies are not congruent, therefore a consensus is yet to be reached. To advance this issue, we used real-time PCR and electrophysiological recordings to assess gene expression related to synaptic plasticity in the hippocampus and primary somatosensory cortex of rats exposed to novel objects, then kept awake (WK) for 60 min and finally killed after a 30 min period rich in WK, slow-wave sleep (SWS) or rapid-eye-movement sleep (REM). Animals similarly treated but not exposed to novel objects were used as controls. We found that the mRNA levels of Arc, Egr1, Fos, Ppp2ca and Ppp2r2d were significantly increased in the hippocampus of exposed animals allowed to enter REM, in comparison with control animals. Experience-dependent changes during sleep were not significant in the hippocampus for Bdnf, Camk4, Creb1, and Nr4a1, and no differences were detected between exposed and control SWS groups for any of the genes tested. No significant changes in gene expression were detected in the primary somatosensory cortex during sleep, in contrast with previous studies using longer post-stimulation intervals (>180 min). The experience-dependent induction of multiple plasticity-related genes in the hippocampus during early REM adds experimental support to the synaptic embossing theory.

Genetic group x ambient temperature interaction effects on physiological responses and growth performance of rabbits

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A physiological manoeuvre to improve the positivity of the gastro-oesophageal reflux scintigraphic test

One of the best examinations used routinely to detect gastro-oesophageal reflux (GOR) is scintigraphy and attempts are continuously being made to improve the performance of the test. We have tested a new manoeuvre to improve the results. Three hundred and twenty eight patients (190 males and 138 females, aged 1 month to 84 years, average 4.47 years) were studied after a 12 h fast period with 100 MBq of Tc-99(m)-Phytate, 50 ml volume, directly delivered into the stomach in a mixture of orange juice. All patients were strongly suspected of having GOR. Conventional acquisition was done for 20 min, at a rate of one frame every 20 s. in the middle of the examination, small children were put in the upright position and held there for a few seconds or released in a way that allowed movement; adults were asked to stand up and walk a few metres. The test was then continued for the remaining 10 min. The global index of positivity was 64.6% (76 positive cases in the first half of the examination and 134 positive cases only after the manoeuvre). The mean of GOR episodes observed in the positive cases without the manoeuvre was 0.5 per patient, significantly different from the mean of 1.59 noted after the manoeuvre (P<0.01). In 28 cases the manoeuvre increased either the intensity or the frequency of reflux previously detected without it. We believe that this manoeuvre should be performed in all scintigraphic tests aiming to detect GOR. In the present series, the manoeuvre increased the frequency of GOR episodes. ((C) 2001 Lippincott Williams & Wilkins)].

Aggressive behaviour traits predict physiological stress responses in Nile tilapia (Oreochromis niloticus)

This study tested whether aggressive behaviour can predict individual variation in stress responses of Nile tilapia Oreochromis niloticus. We used a mirror test to measure tendency to aggressive behaviour, and calculated the attack frequency and time until the first attack (latency) for each fish. One day later, we measured plasma cortisol and glucose, and two days later, we measured ventilatory frequency (VF) (pre-confinement responses). Immediately after the VF measure, we subjected the same fish to 30 min confinement, followed by measurements of cortisol, glucose, and VF (post-confinement responses). We found that post-confinement stress cortisol, glucose, and VF were higher than pre-confinement responses. Attack frequency was negatively correlated with VF and latency was positively correlated with baseline glucose and VF. Thus, we conclude that attack frequency and latency to a mirror reflection could be used to predict baseline levels of physiological stress indicators in Nile tilapia.

Chronic social stress in rainbow trout: Does it promote physiological habituation?

The effect of chronic social stress on growth, energetic substrates and hormones was tested in rainbow trout, Oncorhynchus mykiss. After a 14-day isolation period, the fish were paired for 8 days. In order to expose fish to chronic intermittent social contact during pairing, they were maintained in direct contact with each other during the first day. After that, a black plastic screen partition was introduced in each tank, preventing direct contact between animals. Every day the partition was removed for 30 min, allowing physical interaction between fish. At the end of pairing period, they were isolated again for 13 days. Fish were weighed and blood was sampled frequently during the experiment. Plasma levels of cortisol, growth hormone, glucose, total protein and free amino acids were quantified. Both dominants and subordinates had specific growth rate decreased during the pairing period, but only subordinates increased when the stressor was abolished (dominants: 0.32 +/- 0.21 and 0.24 +/- 0.41, subordinates: -0.77 +/- 0.29 and 0.37 +/- 0.31, respectively). Dominants showed a higher cortisol level one week after pairing condition had been abolished than subordinates (dominants: 56.76 +/- 13.26, subordinates: 31.89 +/- 13.36). We conclude that chronic condition of intermittent social stress represents a stressful condition for animals of both hierarchical ranks and a treatment of one daily short direct contact between conspecifics does not promote habituation in fish, as mentioned for other stressors. (C) 2007 Elsevier B.V. All rights reserved.

The 'club' cell and behavioural and physiological responses to chemical alarm cues in the Nile tilapia

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Morphological and physiological specialization for digging in amphisbaenians, an ancient lineage of fossorial vertebrates

Amphisbaenians are legless reptiles that differ significantly from other vertebrate lineages. Most species dig underground galleries of similar diameter to that of the animal. We studied the muscle physiology and morphological attributes of digging effort in the Brazilian amphisbaenid Leposternon microcephalum (Squamata; Amphisbaenia), which burrows by compressing soil against the upper wall of the tunnel by means of upward strokes of the head. The individuals tested (<72 g) exerted forces on the soil of up to 24 N. These forces were possible because the fibres of the longissimus dorsi, the main muscle associated with burrowing, are highly pennated, thus increasing effective muscle cross-sectional area. The muscle is characterized by a metabolic transition along its length: proximal, medial and distal fibres are fast contracting and moderately oxidative, but fibres closer to the head are richer in citrate synthase and more aerobic in nature. Distal fibres, then, might be active mainly at the final step of the compression stroke, which requires more power. For animals greater than a given diameter, the work required to compress soil increases exponentially with body diameter. Leposternon microcephalum, and probably some other highly specialized amphisbaenids, are most likely constrained to small diameters and can increase muscle mass and effective muscle cross-sectional area by increasing body length, not body diameter.

Locomotor performance of closely related Tropidurus species: relationships with physiological parameters and ecological divergence

Tropidurid lizards have colonized a variety of Brazilian open environments without remarkable morphological variation, despite ecological and structural differences among habitats used. This study focuses on two Tropidurus sister-species that, despite systematic proximity and similar morphology, exhibit great ecological divergence and a third ecologically generalist congeneric species providing an outgroup comparison. We quantified jumping capacity and sprint speed of each species on sand and rock to test whether ecological divergence was also accompanied by differences in locomotor performance. Relevant physiological traits possibly associated with locomotor performance metabolic scopes and fiber type composition, power output and activity of the enzymes citrate synthase, pyruvate kinase and lactate dehydrogenase of the iliofibularis muscle - were also compared among the three Tropidurus species. We found that the two sister-species exhibited remarkable differences in jumping performance, while Tropidurus oreadicus, the more distantly related species, exhibited intermediate values. Tropidurus psamonastes, a species endemic to sand dunes, exhibited high absolute sprint speeds on sand, jumped rarely and possessed a high proportion of glycolytic fibers and low activity of citrate synthase. The sister-species Tropidurus itambere, endemic to rocky outcrops, performed a large number of jumps and achieved lower absolute sprint speed than T. psamonastes. This study provides evidence of rapid divergence of locomotor parameters between sister-species that use different substrates, which is only partially explained by variation in physiological parameters of the iliofibularis muscle.

A laboratory study on feeding plasticity of the shredder Sericostoma vittatum Rambur (Sericostomatidae)

Since litter input and availability of leaves in many streams is highly seasonal in Portugal, we investigated whether Sericostoma vittatum, a typical shredder, was able to grow using alternative food sources. To test this hypothesis we fed S. vittatum with Alnus glutinosa (alder, CPOM, coarse particulate organic matter), leaf powder from A. glutinosa and Acacia dealbata and FPOM (fine particulate organic matter) from a 5th and a > 6th order river, the macrophyte Myriophyllum aquaticum and biofilm. Growth in S. vittatum was significantly influenced by the food item given (ANOVA, P = 0.0082). The food item promoting the highest growth was A. glutinosa, in the form of FPOM (6.48% day(-1)) and CPOM (4.24% day(-1)); all other forms of FPOM and biofilm provided relatively low growth rates (0.77-1.77% day(-1)). The macrophyte M. aquaticum was also used as food source by S. vittatum and promoted intermediate growth (1.96% day(-1)). Neither nitrogen, phosphorus nor caloric content was correlated with growth. However, since higher growth was achieved with alder, in the form of CPOM and FPOM, we concluded that the chemical content of food was more important for S. vittatum than the physical form of such food. This may partially explain why shredders are able to survive when leaves are scarce in streams.

Feeding selectivity of ichthyofauna in a tropical stream: space-time variations in trophic plasticity

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Action of permethrin on Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) semi-engorged females: Morpho-physiological evaluation of salivary glands

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Karyotype plasticity in crickets: Numerical, morphological, and nucleolar organizer region distribution pattern of Anurogryllus sp.

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Morpho-physiological analysis of the insect fat body: A review

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Time-course of photosynthetic induction in four tropical woody species grown in contrasting irradiance habitats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of light intensity and temperature on Cylindrospermopsis raciborskii (Cyanobacteria) with straight and coiled trichomes: growth rate and morphology

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)