Maria Castello

Objectives: This study aimed to assess the effects of a virtual Mindful Self-compassion (MSC) intervention on mindfulness, self-compassion, empathy, stress, and well-being in Uruguayan primary school teachers. Methods: A quasi-experimental, longitudinal study was conducted with an active control intervention (Kundalini Yoga, KY). Uruguayan volunteer female teachers were randomly assigned to MSC or KY 9-weeks virtual training and completed self-reports and an empathy for pain task (EPT) at pre-, post-training, and follow-up (3 months). Results: After MSC training, mindfulness (ES: observing= -0.836; non-reactivity= -0.476; total mindfulness= -0.655), self-compassion (ES: self-kindness= 0.745; common humanity= -0.588; mindfulness= -0.487) and self-judgment (ES= -0.463) significantly (p<0.05) increased. Furthermore, perspective-taking increased (ES= -0.505) and personal distress decreased (ES= -0.587), while stress decreased (ES= -0.450) and well-being increased (ES= -0.612) after t...

This paper describes the peripheral mechanisms involved in signal processing of self- and conspecific-generated electric fields by the electric fish Gymnotus carapo. The distribution of the different types of tuberous electroreceptor and the occurrence of particular electric field patterns close to the body of the fish were studied. The density of tuberous electroreceptors was found to be maximal on the jaw (foveal region) and very high on the dorsal region of the snout (parafoveal region), decaying caudally. Tuberous type II electroreceptors were much more abundant than type I electroreceptors. Type I electroreceptors occurred exclusively on the head and rostral trunk regions, while type II electroreceptors were found along as much as 90 % of the fish. Electrophysiological data indicated that conspecific- and self-generated electric currents are ‘funnelled’ by the high conductivity and geometry of the body of the fish. These currents are concentrated at the peri-oral zone, where mo...

SUMMARY Some fish emit electric fields generated by the coordinated activation of electric organs. Such discharges are used for exploring the environment and for communication. This article deals with the development of the electric organ and its discharge in Gymnotus, a pulse genus in which brief discharges are separated by regular silent intervals. It is focused on the anatomo-functional study of fish sized between 10 and 300 mm from the species of Gymnotus, in which electrogenic mechanisms are best known. It was shown that: (1) electroreception and electromotor control is present from early larval stages; (2) there is a single electric organ from larval to adult stages; (3) pacemaker rhythmicity becomes similar to that of the adult when the body length becomes greater than 45 mm and (4) there is a consistent developmental profile of the electric organ discharge in which waveform components are added according to a programmed sequence. The analysis of these data allowed us to iden...

SUMMARYPulse electric fish evaluate successive electrosensory images generated by self-emitted electric discharges, creating a neural representation of the physical world. Intervals between discharges (system resolution) are controlled by a pacemaker nucleus under the influence of reafferent signals. Novel sensory stimuli cause transient accelerations of the pacemaker rate(novelty responses). This study describes quantitatively the effect of changes in contrast of reafferent electrosensory signals on the amplitude and probability of novelty responses. We found that: (i) alterations of a single image in an otherwise homogeneous series cause a novelty response; (ii) the amplitude of the elicited novelty response is a linear function of the logarithm of the change in image contrast; (iii) the parameters of this function, threshold and proportionality constant, allowed us to evaluate the transference function between change in stimulus amplitude and the amplitude of the novelty response...

The fast electrosensory pathway (FEP) of gymnotiform fish is mediated by tuberous electroreceptor organs innervated by ganglion cells that synapse with spherical cells of the electrosensory lateral line lobe (ELL). Spherical cells project to the magnocellular mesencephalic nucleus. The electrosensory environment was represented somatotopically within ELL. The mandibular (MN) and the supraorbital (SON) nerves projected to rostral ELL (occupying 19-28% and 4-10%, respectively), and the posterior branch of the anterior lateral line nerve (pALLN) projected to caudal ELL (occupying 56-64%). Labeling with horseradish peroxidase or biotinylated dextran-amine demonstrated three kinds of synaptic endings coupling primary afferents to spherical cells: multiple synaptic knobs, medium-sized calyxes, and very large calyxes. Multiple synaptic knobs arose from MN and SON primary afferents and were found in a narrow rostral area covering the centrolateral (CLS) and lateral (LS) segments of ELL. Medium and large calyxes, proceeding from the same nerves, predominated in the remaining parts of the three segments of ELL containing spherical cells. Calyx-type endings were also found in the LS-occupying regions in which the pALLNs projected. Calyx-type endings formed gap junctions but also contained vesicles and showed submembrane specializations typical of chemical synapses. The postsynaptic spherical cells were linked by dendrosomatic gap junctions and were also contacted by unlabeled en passant synaptic boutons, whose fine structure suggested chemical transmission. Electrophysiological studies indicated that spherical cell responsiveness diminished after electrosensory stimulation. This apparently inhibitory phenomenon may be subserved by the unlabeled synaptic boutons, which possibly originate from interneurons that have yet to be identified.

Local electric fields generated by the electric organ discharge of Gymnotus carapo were explored at selected points on the skin of an emitter fish (‘local self-generated fields’) and on the skin of a conspecific (‘local conspecific-generated fields’) using a specially designed probe. Local self-generated fields showed a constant pattern along the body of the fish. At the head, these fields were collimated, much stronger than elsewhere on the fish, and had a time waveform that was site-independent. This waveform consisted of a slow head-negative wave followed by a faster head-positive wave. In contrast, time waveforms in the trunk and tail regions were site-specific, with field vectors that changed direction over time. Local conspecific-generated fields were similar to the head-to-tail field, but their spatio-temporal pattern at the skin depended on the relative orientation between the receiving fish and the emitting fish. Because self-generated fields had a slow early component at t...

SUMMARY One difficulty in understanding the brain is that of linking the structure of the neurons with their computational roles in neural circuits. In this paper we address this subject in a relative simple system, the fast electrosensory pathway of an electric fish, where sensory images are coded by the relative latency of a volley of single spikes. The main input to this path is a stream of discrete electric images resulting from the modulation of a self-generated carrier by the environment. At the second order cell level, a window of low responsiveness, reducing potential interference from other stimuli, follows activation of the path. In the present study, we further characterize the input–output relationship at the second order neurons by recording field potentials, and ascertain its cellular basis using in vitro whole cell patch recordings. The field potentials from freely behaving, socially interacting fish were obtained from chronically implanted fish restrained in a mesh p...

Early sensory relay circuits in the vertebrate medulla often adopt a cerebellum-like organization specialized for comparing primary afferent inputs with central expectations. These circuits usually have a dual output, carried by center ON and center OFF neurons responding in opposite ways to the same stimulus at the center of their receptive fields. Here, we show in the electrosensory lateral line lobe of Gymnotiform weakly electric fish that basilar pyramidal neurons, representing ‘ON’ cells, and non-basilar pyramidal neurons, representing ‘OFF’ cells, have different intrinsic electrophysiological properties. We used classical anatomical techniques and electrophysiological in vitro recordings to compare these neurons. Basilar neurons are silent at rest, have a high threshold to intracellular stimulation, delayed responses to steady-state depolarization and low pass responsiveness to membrane voltage variations. They respond to low-intensity depolarizing stimuli with large, isolated...

Global attempts to renew scientific education aim to stop the decline of young people's interest in science and technology, and to promote the development of citizens' scientific literacy for sustainable development. Among other changes, these aims require the adaptation of K12 Biological Science Teacher’s training to meet the new objectives.Scientific literacy involves knowing science and how knowledge is developed and validated, recognizing the interactions between science, technology and society, that is, the nature of science (NoS; a set of meta-scientific contents that encompass historical, epistemological and sociological aspects of science with great value for scientific education). It also involves grasping of cognitive skills underlying critical thinking (CT; a set of cognitive abilities, including self-regulation and metacognitive processes) and creative problem solving. Therefore, scientific literacy contributes to making informed decisions, facilitating the parti...

The anatomical organization of African Mormyrids' brain is a clear example of departure from the average brain morphotype in teleosts, probably related to functional specialization associated to electrosensory processing and sensory-motor coordination. The brain of Mormyrids is characterized by a well-developed rhombencephalic electrosensory lobe interconnected with relatively large mesencephalic torus semicircularis and optic tectum, and a huge and complex cerebellum. This unique morphology might imply cell addition from extraventricular proliferation zones up to late developmental stages. Here we studied the ontogeny of these brain regions in Mormyrus rume proboscirostris from embryonic to adult stages by classical histological techniques and 3D reconstruction, and analyzed the spatial-temporal distribution of proliferating cells, using pulse type BrdU labeling. Brain morphogenesis and maturation progressed in rostral-caudal direction, from 4day old free embryos, through larvae, to juveniles whose brain almost attained adult morphological complexity. The change in the relative size of the telencephalon, and mesencephalic and rhombencephalic brain regions suggest a developmental shift in the relative importance of visual and electrosensory modalities. In free embryos, proliferating cells densely populated the lining of the ventricular system. During development, ventricular proliferating cells decreased in density and extension of distribution, constituting ventricular proliferation zones. The first recognizable one was found at the optic tectum of free embryos. Several extraventricular proliferation zones were found in the cerebellar divisions of larvae, persisting along life. Adult M. rume proboscirostris showed scarce ventricular but profuse cerebellar proliferation zones, particularly at the subpial layer of the valvula cerebelli, similar to lagomorphs. This might indicate that adult cerebellar proliferation is a conserved vertebrate feature.

Teleosts are a numerous and diverse group of fish showing great variation in body shape, ecological niches and behaviors, and a correspondent diversity in brain morphology, usually associated with their functional specialization. Weakly electric fish are a paradigmatic example of functional specialization, as these teleosts use self-generated electric fields to sense the nearby environment and communicate with conspecifics, enabling fish to better exploit particular ecological niches. We analyzed the development of the brain of the pulse type gymnotid Gymnotus omarorum, focusing on the brain regions involved directly or indirectly in electrosensory information processing. A morphometric analysis has been made of the whole brain and of brain regions of interest, based on volumetric data obtained from 3-D reconstructions to study the growth of the whole brain and the relative growth of brain regions, from late larvae to adulthood. In the smallest studied larvae some components of the ...

It has been shown that Fasciculins (FAS), polypeptides isolated from the venom of the green mamba Dendroaspis angusticeps, provoke a powerful inhibition of peripheral acetylcholinesterase (AChE). In the present study, 0.5 microliter of increasing concentrations (10-500 micrograms/ml) of FAS were injected into the striatum of rats. Micropunches taken 2 mm around the injection site showed 90% inhibition of AChE up to 24 h after FAS injection (500 micrograms/ml). AChE activity was about 50% of controls at the 7th day without apparent cell loss. Assessment of AChE activity in the whole striatum showed no inhibition. It is postulated that, due to this potent, localized and long-lasting central nervous system AChE inhibition, FAS could become a useful tool for the study of central cholinergic pathways.

Weakly electric fishes "electrically illuminate" the environment in two forms: pulse fishes emit a succession of discrete electric discharges while wave fishes emit a continuous wave. These strategies are present in both taxonomic groups of weakly electric fishes, mormyrids and gymnotids. As a consequence one can distinguish four major types of active electrosensory strategies evolving in parallel. Pulse gymnotids have an electrolocating strategy common with pulse mormyrids, but brains of pulse and wave gymnotids are alike. The beating strategy associated to other differences in the electrogenic system and electrosensory responses suggests that similar hardware might work in a different mode for processing actively generated electrosensory images. In this review we summarize our findings in pulse gymnotids' active electroreception and outline a primary agenda for the next research.

Fasciculin 2 (FAS) an anticholinesterase peptide isolated from the venom of the Green mamba (Dendroaspis angusticeps) was injected into the right striatum of albino rats (1.5 micrograms total amount). The inhibition of acetylcholinesterase (AChE) activity was 86 and 60% 24 h and 7 days after FAS injection, respectively. The treatment with apomorphine (APO) (2 mg/kg s.c.) 24 h after FAS provoked a moderate circling towards the lesioned side that was reverted by atropine (30 mg/kg i.p.). The same dose of APO 7 days after FAS, provoked an inconstant contralateral circling. Neither dopamine nor serotonin nor their metabolites were significantly affected 24 h or 7 days after FAS injection. Radioligand binding assays of dopamine, muscarinic and benzodiazepine receptors only showed a decrease of the density of the muscarinic ones 7 days after FAS. These results are interpreted as showing that the changes provoked by FAS would be compensated but the system would remain in an unsteady state only demonstrable after pharmacological challenge. The chronic down-regulation of muscarinic receptors would compensate the increased cholinergic activity and would therefore block its behavioral expression.

Local electric fields generated by the electric organ discharge of Gymnotus carapo were explored at selected points on the skin of an emitter fish ('local self-generated fields') and on the skin of a conspecific ('local conspecific-generated fields') using a specially designed probe. Local self-generated fields showed a constant pattern along the body of the fish. At the head, these fields were collimated, much stronger than elsewhere on the fish, and had a time waveform that was site-independent. This waveform consisted of a slow head-negative wave followed by a faster head-positive wave. In contrast, time waveforms in the trunk and tail regions were site-specific, with field vectors that changed direction over time. Local conspecific-generated fields were similar to the head-to-tail field, but their spatio-temporal pattern at the skin depended on the relative orientation between the receiving fish and the emitting fish. Because self-generated fields had a slow earl...

This paper describes the peripheral mechanisms
involved in signal processing of self- and conspecificgenerated
electric fields by the electric fish Gymnotus
carapo. The distribution of the different types of tuberous
electroreceptor and the occurrence of particular electric
field patterns close to the body of the fish were studied. The
density of tuberous electroreceptors was found to be
maximal on the jaw (foveal region) and very high on the
dorsal region of the snout (parafoveal region), decaying
caudally. Tuberous type II electroreceptors were much
more abundant than type I electroreceptors. Type I
electroreceptors occurred exclusively on the head and
rostral trunk regions, while type II electroreceptors
were found along as much as 90 % of the fish.
Electrophysiological data indicated that conspecific- and
self-generated electric currents are ‘funnelled’ by the high
conductivity and geometry of the body of the fish. These
currents are concentrated at the peri-oral zone, where most
electroreceptors are located. Moreover, within this region,
field vector directions were collimated, constituting the
most efficient stimulus for electroreceptors. It can be
concluded that the passive properties of the fish tissue
represent a pre-receptor device that enhances exafferent
and reafferent electrical signals at the fovea–parafoveal
region.

A highly specific proteinase, converting dynorphin A (1-17) to enkephalins, was isolated from the human spinal cord and subjected to further characterization. The enzyme was found to be a thiol-dependent protein with a relative molecular mass of 50 kDa and a pH optimum between 5.0 and 5.5. This proteinase appears to exclusively convert dynorphin A (1-17) to Leu-enkephalin and its COOH-terminal extensions Leu-enkephalin-Arg' (which was a major conversion product) and Leu-enkephalin-Arg6-Arg7 but not the other prodynorphin-or proenkephalin-derived peptides. This high specificity toward a single structure is suggested to be involved in a distinct processing pathway associated with the generation of the opioid peptides with selectivity for &opioid receptors.

Local electric fields generated by the electric organ
discharge of Gymnotus carapo were explored at selected
points on the skin of an emitter fish (‘local self-generated
fields’) and on the skin of a conspecific (‘local conspecificgenerated
fields’) using a specially designed probe. Local
self-generated fields showed a constant pattern along the
body of the fish. At the head, these fields were collimated,
much stronger than elsewhere on the fish, and had a time
waveform that was site-independent. This waveform
consisted of a slow head-negative wave followed by a faster
head-positive wave. In contrast, time waveforms in the
trunk and tail regions were site-specific, with field vectors
that changed direction over time. Local conspecificgenerated
fields were similar to the head-to-tail field, but
their spatio-temporal pattern at the skin depended on the
relative orientation between the receiving fish and the
emitting fish. Because self-generated fields had a slow early
component at the head region, they displayed a lowfrequency
peak in their power spectral density histograms.
In contrast, the conspecific-generated fields had time
waveforms with a sharper phase reversal, resulting in a
peak at higher frequency than in the self-generated field.
Lesions in emitting fish demonstrated that waveform
components generated by the trunk and tail regions of
the electric organ predominate in conspecific-generated
fields, whereas waveform components generated by
the abdominal region prevail in self-generated fields.
Similar results were obtained from Brachyhypopomus
pinnicaudatus. These results suggest that, in pulse-emitting
gymnotids, electrolocation and electrocommunication
signals may be carried by different field components
generated by different regions of the electric organ.

Pulse-discharging, weakly electric fish actively electrolocate by emitting electric organ discharges and sensing changes provided by objects on transepidermal self-generated electric fields. In this way they create a series of discrete electric images on a cutaneous electroreceptive mosaic (Lissmann, 1958; cf. Bullock, 1986, 1999; Bastian, 1986). In this study we examine how fish discriminate between electrosensory images of different contrast. This kind of analysis requires unambiguous definition and measurement of the stimulus (input) and of the related performance of a sensory system (output; Marr, 1982). Our recent knowledge of electric image generation mechanisms allowed us to control and measure the

One difficulty in understanding the brain is that of
linking the structure of the neurons with their
computational roles in neural circuits. In this paper we
address this subject in a relative simple system, the fast
electrosensory pathway of an electric fish, where sensory
images are coded by the relative latency of a volley of
single spikes. The main input to this path is a stream of
discrete electric images resulting from the modulation of a
self-generated carrier by the environment. At the second
order cell level, a window of low responsiveness, reducing
potential interference from other stimuli, follows
activation of the path.
In the present study, we further characterize the
input–output relationship at the second order neurons by
recording field potentials, and ascertain its cellular basis
using in vitro whole cell patch recordings. The field
potentials from freely behaving, socially interacting fish
were obtained from chronically implanted fish restrained
in a mesh pen. In addition, at the end of some experiments
the fish was curarized and the fast electrosensory path
responses to artificial stimuli were further explored. These
in vivo approaches showed that larger stimuli cause larger
and longer windows of low responsiveness. The simple
spherical geometry of the second order cells allowed us to
unveil the membrane mechanisms underlying this
phenomenon in vitro. These spherical cells respond with a
single spike at the onset of current steps of any amplitude
and duration, showing inward and outward rectification,
and a long refractory period. We postulate that a lowthreshold
K+ conductance generates the outward
rectification. The most parsimonious interpretation of our
data indicates that slow deactivation of this conductance
causes the long refractory period. These non-linear
properties of the membrane explain the single spiking
profile of spherical cells and the low-responsiveness
window observed in vivo. Since the electric organ
discharges are emitted at intervals slightly longer than the
duration of the low-responsiveness window, we propose
that the described cellular mechanisms allow fish
streaming self-generated images.

Some fish emit electric fields generated by the
coordinated activation of electric organs. Such discharges
are used for exploring the environment and for
communication. This article deals with the development of
the electric organ and its discharge in Gymnotus, a pulse
genus in which brief discharges are separated by regular
silent intervals. It is focused on the anatomo-functional
study of fish sized between 10 and 300·mm from the
species of Gymnotus, in which electrogenic mechanisms are
best known. It was shown that: (1) electroreception and
electromotor control is present from early larval stages;
(2) there is a single electric organ from larval to adult
stages; (3) pacemaker rhythmicity becomes similar to that
of the adult when the body length becomes greater than
45·mm and (4) there is a consistent developmental profile
of the electric organ discharge in which waveform
components are added according to a programmed
sequence. The analysis of these data allowed us to identify
three main periods in post-natal development of
electrogenesis: (1) before fish reach 55·mm in length, when
maturation of neural structures is the main factor
determining a characteristic sequence of changes observed
in the discharge timing and waveform; (2) between 55 and
100·mm in length, when peripheral maturation of the
effector cells and changes in post-effector mechanisms due
to the fish’s growth determine minor changes in waveform
and the increase in amplitude of the discharge and (3)
beyond 100·mm in length, when homothetic growth of the
fish body explains the continuous increase in electric
power of the discharge.

This article deals with the electric organ and its discharge in Gymnotus coropinae, a representative species of one of the three
main clades of the genus. Three regions with bilateral symmetry are described: (1) subopercular (medial and lateral columns of
complex shaped electrocytes); (2) abdominal (medial and lateral columns of cuboidal and fusiform electrocytes); and (3) main
[four columns, one dorso-lateral (containing fusiform electrocytes) and three medial (containing cuboidal electrocytes)].
Subopercular electrocytes are all caudally innervated whereas two of the medial subopercular ones are also rostrally innervated.
Fusiform electrocytes are medially innervated at the abdominal portion, and at their rostral and caudal poles at the main portion.
Cuboidal electrocytes are always caudally innervated. The subopercular portion generates a slow head-negative wave (V1r)
followed by a head-positive spike (V3r). The abdominal and main portions generate a fast tetra-phasic complex (V2345ct). Since
subopercular components prevail in the near field and the rest in the far field, time coincidence of V3r with V2 leads to different
waveforms depending on the position of the receiver. This confirms the splitting hypothesis of communication and exploration
channels based on the different timing, frequency band and reach of the regional waveforms. The following hypothesis is
compatible with the observed anatomo-functional organization: V1r corresponds to the rostral activation of medial subopercular
electrocytes and V3r to the caudal activation of all subopercular electrocytes; V2, and part of V3ct, corresponds to the successive
activation of the rostral and caudal poles of dorso-lateral fusiform electrocytes; and V345ct is initiated in the caudal face of cuboidal
electrocytes by synaptic activation (V3ct) and it is completed (V45ct) by the successive activation of rostral and caudal faces by the
action currents evoked in the opposite face.

Adult neurogenesis, an essential mechanism of brain plasticity, enables brain development along postnatal life, constant addition of new neurons, neuronal turnover, and/or regeneration. It is amply distributed but negatively modulated during development and along evolution. Widespread cell proliferation, high neurogenic, and regenerative
capacities are considered characteristics of teleost brains during adulthood. These anamniotes are promising models to depict factors that modulate cell proliferation, migration, and neurogenesis, and might be intervened to promote brain plasticity in mammals. Nevertheless, the migration path of derived cells to their final destination was not studied in various teleosts, includingmost weakly electric fish. In this group adult brain morphology is attributed to sensory specialization, involving the concerted evolution of peripheral electroreceptors and electric organs, encompassed by the evolution of neural networks involved in electrosensory information processing. In wave type gymnotids
adult brain morphology is proposed to result from lifelong region specific cell proliferation and neurogenesis. Consistently, pulse type weakly electric gymnotids and mormyrids show widespread distribution of proliferation zones that persists in adulthood, but their neurogenic potential is still unknown. Here we studied the migration process and
differentiation of newborn cells into the neuronal phenotype in the pulse type gymnotid Gymnotus omarorum. Pulse labeling of S-phase cells with 5-Chloro-2′-deoxyuridine thymidine followed by 1 to 180 day survivals evidenced long distance migration of newborn cells from the rostralmost telencephalic ventricle to the olfactory bulb, and between layers of all cerebellar divisions. Shorter migration appeared in the tectum opticum and torus semicircularis. In many brain regions, derived cells expressed early neuronal markers doublecortin (chase: 1–30 days) and HuC/HuD (chase: 7–180 days).
Some newborn cells expressed the mature neuronal marker tyrosine  hydroxylase in the subpallium (chase: 90 days) and olfactory bulb (chase: 180 days), indicating the acquisition of a mature neuronal phenotype. Long term CldU labeled newborn cells of the granular layer of the corpus cerebelli were also retrogradely labeled “in vivo,” suggesting  their insertion into the neural networks. These findings evidence the neurogenic capacity of telencephalic, mesencephalic, and  rhombencephalic brain proliferation zones in G. omarorum, supporting the phylogenetic conserved feature of adult neurogenesis and its functional significance.