VEGF is an essential retrograde trophic factor for motoneurons.

VEGF was initially discovered due to its angiogenic activity and therefore named "vascular endothelial growth factor." However, its more recently discovered neurotrophic activity may be evolutionarily more ancient. Our previous work showed that all the changes produced by axotomy on the firing activity and synaptic inputs of abducens motoneurons were completely restored after VEGF administration. Therefore, we hypothesized that the lack of VEGF delivered by retrograde transport from the periphery should also affect the physiology of otherwise intact abducens motoneurons. For VEGF retrograde blockade, we chronically applied a neutralizing VEGF antibody to the lateral rectus muscle. Recordings of extracellular single-unit activity and eye movements were made in alert cats before and after the application of the neutralizing antibody. Our data revealed that intact, noninjured abducens motoneurons retrogradely deprived of VEGF exhibited noticeable changes in their firing pattern. There is a general decrease in firing rate and a significant reduction in eye position and eye velocity sensitivity (i.e., a decrease in the tonic and phasic components of their discharge, respectively). Moreover, by means of confocal immunocytochemistry, motoneurons under VEGF blockade showed a marked reduction in the density of afferent synaptic terminals contacting with their cell bodies. Altogether, the present findings demonstrate that the lack of retrogradely delivered VEGF renders abducens motoneurons into an axotomy-like state. This indicates that VEGF is an essential retrograde factor for motoneuronal synaptic drive and discharge activity.

Proprioceptors in extraocular muscles.

Proprioception is the sense that lets us perceive the location, movement and action of the body parts. The proprioceptive apparatus includes specialized sense organs (proprioceptors) which are embedded in the skeletal muscles. The eyeballs are moved by six pairs of eye muscles and binocular vision depends on fine-tuned coordination of the optical axes of both eyes. Although experimental studies indicate that the brain has access to eye position information, both classical proprioceptors (muscle spindles and Golgi tendon organ) are absent in the extraocular muscles of most mammalian species. This paradox of monitoring extraocular muscle activity in the absence of typical proprioceptors seemed to be resolved when a particular nerve specialization (the palisade ending) was detected in the extraocular muscles of mammals. In fact, for decades there was consensus that palisade endings were sensory structures that provide eye position information. The sensory function was called into question when recent studies revealed the molecular phenotype and the origin of palisade endings. Today we are faced with the fact that palisade endings exhibit sensory as well as motor features. This review aims to evaluate the literature on extraocular muscle proprioceptors and palisade endings and to reconsider current knowledge of their structure and function.

Early antitermination in the atypical coliphage mEp021 mediated by the Gp17 protein.

The coliphage mEp021 belongs to a phage group with a unique immunity repressor, and its life cycle requires the host factor Nus. mEp021 has been classified as non-lambdoid based on its specific characteristics. The mEp021 genome carries a gene encoding an Nλ-like antiterminator protein, termed Gp17, and three nut sites (nutL, nutR1, and nutR2). Analysis of plasmid constructs containing these nut sites, a transcription terminator, and a GFP reporter gene showed high levels of fluorescence when Gp17 was expressed, but not in its absence. Like lambdoid N proteins, Gp17 has an arginine-rich motif (ARM), and mutations in its arginine codons inhibit its function. In infection assays using the mutant phage mEp021ΔGp17::Kan (where gp17 has been deleted), gene transcripts located downstream of transcription terminators were obtained only when Gp17 was expressed. In contrast to phage lambda, mEp021 virus particle production was partially restored (>1/3 relative to wild type) when nus mutants (nusA1, nusB5, nusC60, and nusE71) were infected with mEp021 and Gp17 was overexpressed. Our results suggest that RNA polymerase reads through the third nut site (nutR2), which is more than 7.9 kbp downstream of nutR1.

BDNF Influence on Adult Terminal Axon Sprouting after Partial Deafferentation.

BDNF is a neurotrophin family member implicated in many different neuronal functions, from neuronal survival during development to synaptic plasticity associated with processes of learning and memory. Its presence in the oculomotor system has previously been demonstrated, as it regulates afferent composition of extraocular motoneurons and their firing pattern. Moreover, BDNF expression increases after extraocular motoneuron partial deafferentation, in parallel with terminal axon sprouting from the remaining axons. To elucidate whether BDNF could play an active role in this process, we performed partial deafferentation of the medial rectus motoneurons through transection of one of the two main afferents, that is, the ascending tract of Deiters, and injected BDNF into the motoneuron target muscle, the medial rectus. Furthermore, to check whether BDNF could stimulate axon sprouting without lesions, we performed the same experiment without any lesions. Axon terminal sprouting was assessed by calretinin immunostaining, which specifically labels the remaining afferent system on medial rectus motoneurons, the abducens internuclear neurons. The results presented herein show that exogenous BDNF stimulated terminal axon growth, allowing the total recovery of synaptic coverage around the motoneuron somata. Moreover, calretinin staining in the neuropil exceeded that present in the control situation. Thus, BDNF could also stimulate axonal sprouting in the neuropil of intact animals. These results point to an active role of BDNF in plastic adaptations that take place after partial deafferentation.

Novel Aspects of cAMP-Response Element Modulator (CREM) Role in Spermatogenesis and Male Fertility.

Spermatogenesis is a very complex process with an intricate transcriptional regulation. The transition from the diploid to the haploid state requires the involvement of specialized genes in meiosis, among other specific functions for the formation of the spermatozoon. The transcription factor cAMP-response element modulator (CREM) is a key modulator that triggers the differentiation of the germ cell into the spermatozoon through the modification of gene expression. CREM has multiple repressor and activator isoforms whose expression is tissue-cell-type specific and tightly regulated by various factors at the transcriptional, post-transcriptional and post-translational level. The activator isoform CREMτ controls the expression of several relevant genes in post-meiotic stages of spermatogenesis. In addition, exposure to xenobiotics negatively affects CREMτ expression, which is linked to male infertility. On the other hand, antioxidants could have a positive effect on CREMτ expression and improve sperm parameters in idiopathically infertile men. Therefore, CREM expression could be used as a biomarker to detect and even counteract male infertility. This review examines the importance of CREM as a transcription factor for sperm production and its relevance in male fertility, infertility and the response to environmental xenobiotics that may affect CREMτ expression and the downstream regulation that alters male fertility. Also, some health disorders in which CREM expression is altered are discussed.

Evidence of requirement for homologous-mediated DNA repair during Ambystoma mexicanum limb regeneration.

BACKGROUND: Limb regeneration in the axolotl is achieved by epimorphosis, thus depending on the blastema formation, a mass of progenitor cells capable of proliferating and differentiating to recover all lost structures functionally. During regeneration, the blastema cells accelerate the cell cycle and duplicate its genome, which is inherently difficult to replicate because of its length and composition, thus being prone to suffer double-strand breaks. RESULTS: We identified and characterized two remarkable components of the homologous recombination repair pathway (Amex.RAD51 and Amex.MRE11), which were heterologously expressed, biochemically characterized, and inhibited by specific chemicals. These same inhibitors were applied at different time points after amputation to study their effects during limb regeneration. We observed an increase in cellular senescent accompanied by a slight delay in regeneration at 28 days postamputation regenerated tissues; moreover, inhibitors caused a rise in the double-strand break signaling as a response to the inhibition of the repair mechanisms. CONCLUSIONS: We confirmed the participation and importance of homologous recombination during limb regeneration. The chemical inhibition induces double-strand breaks that lead to DNA damage associated senescence, or in an alternatively way, this damage could be possibly repaired by a different DNA repair pathway, permitting proper regeneration and avoiding senescence.

A Systematic Review of Interventions Based on Judeo-Christian Principles for Patients with Substance Dependence.

Substance use disorders have significant consequences for patients and those around them. A qualitative systematic review was conducted to examine the effectiveness of religiosity and spirituality (R/S) interventions based on Judeo-Christian principles during the multidisciplinary treatment of patients with substance dependence disorder. Studies of patients of both sexes, at any age, of any nationality, and from any geographic location who were participating in treatment programs with religious elements explicitly tied to Christianity or Judaism were eligible for inclusion. Other religious interventions were excluded. Seven electronic databases were searched to identify eligible intervention studies published in English until August 2021. Two reviewers independently screened studies and extracted data. JBI tools were used to assess risk of bias. Of 146 articles retrieved for full text reading, five were ultimately included in this review published from July 2008 to August 2021. The R/S interventions used in the included studies were music therapy in a religious context, reading of the Bible or Torah, reflexive readings, personal prayer and reflection, and religiously integrated cognitive behavioral psychotherapy with or without a comparison group. Despite the broad search, there were found only a small number of studies and little homogeneity in the data of patients that reported positive impacts of treatments. Well-designed controlled studies are needed to truly investigate the efficacy of Judeo-Christian religious interventions for helping people with substance use problems, so as to strengthen the evidence of the benefits of these type of approaches in the treatment of drug addicts.

MIF versus SIF Motoneurons, What Are Their Respective Contribution in the Oculomotor Medial Rectus Pool?

Multiply-innervated muscle fibers (MIFs) are peculiar to the extraocular muscles as they are non-twitch but produce a slow build up in tension on repetitive stimulation. The motoneurons innervating MIFs establish en grappe terminals along the entire length of the fiber, instead of the typical en plaque terminals that singly-innervated muscle fibers (SIFs) motoneurons establish around the muscle belly. MIF motoneurons have been proposed to participate only in gaze holding and slow eye movements. We aimed to discern the function of MIF motoneurons by recording medial rectus motoneurons of the oculomotor nucleus. Single-unit recordings in awake cats demonstrated that electrophysiologically-identified medial rectus MIF motoneurons participated in different types of eye movements, including fixations, rapid eye movements or saccades, convergences, and the slow and fast phases of the vestibulo-ocular nystagmus, the same as SIF motoneurons did. However, MIF medial rectus motoneurons presented lower firing frequencies, were recruited earlier and showed lower eye position (EP) and eye velocity (EV) sensitivities than SIF motoneurons. MIF medial rectus motoneurons were also smaller, had longer antidromic latencies and a lower synaptic coverage than SIF motoneurons. Peristimulus time histograms (PSTHs) revealed that electrical stimulation to the myotendinous junction, where palisade endings are located, did not recurrently affect the firing probability of medial rectus motoneurons. Therefore, we conclude there is no division of labor between MIF and SIF motoneurons based on the type of eye movement they subserve.SIGNIFICANCE STATEMENT In addition to the common singly-innervated muscle fiber (SIF), extraocular muscles also contain multiply-innervated muscle fibers (MIFs), which are non-twitch and slow in contraction. MIF motoneurons have been proposed to participate only in gaze holding and slow eye movements. In the present work, by single-unit extracellular recordings in awake cats, we demonstrate, however, that both SIF and MIF motoneurons, electrophysiologically-identified, participate in the different types of eye movements. However, MIF motoneurons showed lower firing rates (FRs), recruitment thresholds, and eye-related sensitivities, and could thus contribute to the fine adjustment of eye movements. Electrical stimulation of the myotendinous junction activates antidromically MIF motoneurons but neither MIF nor SIF motoneurons receive a synaptic reafferentation that modifies their discharge probability.

Sirtuin GdSir2.4 participates in the regulation of rRNA transcription in the Giardia duodenalis parasite.

Giardia duodenalis is a parasite of great medical interest due to the number of infections it causes worldwide each year. Although research on epigenetic mechanisms in this protist has only begun recently, epigenetic regulation has already been shown to have important roles in encystation, antigenic variation, and resistance to antibiotics in Giardia. In this work, we show that a Giardia ortholog of Sir2, GdSir2.4, is involved in the silencing of rRNA expression. Our results demonstrate that GdSir2.4 localizes to the nucleolus, and its binding to the intergenic spacer region of the rDNA is associated with the deacetylation of the chromatin in this region. Given the importance of the regulation of rRNA expression to maintain adequate levels of ribosomes and genomic stability within the cells, GdSir2.4 can be considered a target to create new therapeutic agents against this parasite.

Implementation of a tunable t-CRISPRi system for gene regulation in Giardia duodenalis.

Giardia duodenalis, is a binuclear and microaerophilic protozoan that causes giardiasis. Up to date, several molecular approaches have been taken to understand the molecular mechanisms of diverse cellular processes in this parasitic protozoan. However, the role of many genes involved in these processes needs further analysis. The CRISPR interference (CRISPRi) system has been widely used, as a constitutive expression system for gene silencing purposes in several parasites, including Giardia. The aim of this work was to implement a tunable t-CRISPRi system in Giardia to silence abundant, moderately and low expressed genes, by constructing an optimized and inducible plasmid for the expression of both gRNA and dCas9. A doxycycline inducible pRan promoter was used to express dCas9 and each gRNA, consistently dCas9 expression and nuclear localization were confirmed by Western-blot and immunofluorescence in transfected trophozoites. The transcriptional repression was performed on α-tubulin (high expression), giardipain-1 (moderate expression) and Sir2 and Sir4 (low expression) genes. The α-tubulin gene knock-down caused by dCas9 doxycycline-induction was confirmed by a decrease in its protein expression which was of 50% and 60% at 24 and 48 h, respectively. This induced morphological alterations in flagella. The giardipain-1 knock down, showed a decrease in protein expression of 40 and 50% at 12 and 24 h, respectively, without affecting trophozoites viability, consistent with this a zymogram analysis on giardipain-1 knock down revealed a decrease in giardipain-1 protease activity. When repressing sirtuins expression, a total repression was obtained but trophozoites viability was compromised. This approach provides a molecular tool for a tailored repression to produce specific gene knockdowns.

Cancer in Amphibia, a rare phenomenon?

Compared to other animals, the spontaneous occurrence of tumors in wild amphibians is relatively rare, generally limited to specific populations or species. The number of reports of spontaneous tumors in amphibians known up to 1986 was 491 cases in anurans and about 253 cases in urodeles. Similarly, there have been many, unsuccessful attempts to chemically or biologically induce tumors in amphibians. With these considerations, it is inevitable to wonder: do urodeles and anurans have an inherent resistance to cancer? Here, we review the spontaneous and induced occurrence of tumors in amphibians in a timeline, as well as failed attempts to induce tumors in these amphibians. Indeed, recent studies seem to indicate that there is a relationship between regeneration and cancer because regenerating tissues seem to resist tumorigenesis, as opposed to nonregenerative tissues of the same amphibian models. Although the mechanisms that allow regenerating tissues to resist tumorigenesis have not been elucidated, it is worth to note that, in addition to the apparent relationship between regeneration and cancer, amphibians possess characteristics that could contribute to their ability to resist the development of neoplastic events. The implications of these features in cancer susceptibility are discussed.

Functional diversity of motoneurons in the oculomotor system.

Extraocular muscles contain two types of muscle fibers according to their innervation pattern: singly innervated muscle fibers (SIFs), similar to most skeletal muscle fibers, and multiply innervated muscle fibers (MIFs). Morphological studies have revealed that SIF and MIF motoneurons are segregated anatomically and receive different proportions of certain afferents, suggesting that while SIF motoneurons would participate in the whole repertoire of eye movements, MIF motoneurons would contribute only to slow eye movements and fixations. We have tested that proposal by performing single-unit recordings, in alert behaving cats, of electrophysiologically identified MIF and SIF motoneurons in the abducens nucleus. Our results show that both types of motoneuron discharge in relation to eye position and velocity, displaying a tonic-phasic firing pattern for different types of eye movement (saccades, vestibulo-ocular reflex, vergence) and gaze-holding. However, MIF motoneurons presented an overall reduced firing rate compared with SIF motoneurons, and had significantly lower recruitment threshold and also lower eye position and velocity sensitivities. Accordingly, MIF motoneurons could control mainly gaze in the off-direction, when less force is needed, whereas SIF motoneurons would contribute to increase muscle tension progressively toward the on-direction as more force is required. Anatomically, MIF and SIF motoneurons distributed intermingled within the abducens nucleus, with MIF motoneurons being smaller and having a lesser somatic synaptic coverage. Our data demonstrate the functional participation of both MIF and SIF motoneurons in fixations and slow and phasic eye movements, although their discharge properties indicate a functional segregation.

DNA repair during regeneration in Ambystoma mexicanum.

The remarkable regenerative capabilities of the salamander Ambystoma mexicanum have turned it into one of the principal models to study limb regeneration. During this process, a mass of low differentiated and highly proliferative cells, called blastema, propagates to reestablish the lost tissue in an accelerated way. Such a process implies the replication of a huge genome, 10 times larger than humans, with about 65.6% of repetitive sequences. These features make the axolotl genome inherently difficult to replicate and prone to bear mutations. In this context, the role of DNA repair mechanisms acquires great relevance to maintain genomic stability, especially if we consider the necessity of ensuring the correct replication and integrity of such a large genome in the blastema cells, which are key for tissue regeneration. On the contrary, DNA damage accumulation in these cells may result in senescence, apoptosis and premature differentiation, all of them are mechanisms employed to avoid DNA damage perpetuation but with the potential to affect the limb regeneration process. Here we review and discuss the current knowledge on the implications of DNA damage responses during salamander regeneration.

Giardiavirus: an update.

Giardiavirus is the only virus that infects Giardia duodenalis, a highly prevalent parasite worldwide, especially in low-income and developing countries. This virus belongs to the Totiviridae family, being a relative of other viruses that infect fungi and protozoa. It has a simple structure with only two proteins encoded in its genome and it appears that it can leave the cell without lysis. All these characteristics make it an interesting study model; however, its research has unfortunately made little progress in recent years. Thus, in this review, we summarize the currently available data on Giardiavirus, from their structure, genome and main proteins, to the uses that have been given to them and the possible health applications for the future.

Nicotinamide induces G2 cell cycle arrest in Giardia duodenalis trophozoites and promotes changes in sirtuins transcriptional expression.

Giardia duodenalis is a flagellated unicellular eukaryotic microorganism that commonly causes diarrheal disease throughout the world. Treatment of giardiasis is limited to nitroheterocyclic compounds as metronidazole and benzimidazoles as albendazole, where remarkably treatment failure is relatively common. Consequently, the need for new options to treat this disease is underscored. We predicted by a bioinformatic approach that nicotinamide inhibits Giardia sirtuins by the nicotinamide exchange pathway, and since sirtuins are involved in cell cycle control, they could be related with arrest and decrease of viability. When trophozoites were treated with nicotinamide (NAM), a strong arrest of Giardia trophozoites in G2 phase was observed and at the same time changes in transcriptional expression of sirtuins were produced. Interestingly, the G2 arrest is not related to double-strand breaks, which strengthens the role of sirtuins in the control of the Giardia cell cycle. Results with NAM-treated trophozoites as predicted demonstrate antigiardial effects and thus open new options for the treatment of giardiasis, either with the combination of nicotinamide with another antigiardial drug, or with the design of specific inhibitors for Giardia sirtuins.

Effects of Selective Deafferentation on the Discharge Characteristics of Medial Rectus Motoneurons.

Medial rectus motoneurons receive two main pontine inputs: abducens internuclear neurons, whose axons course through the medial longitudinal fasciculus (MLF), and neurons in the lateral vestibular nucleus, whose axons project through the ascending tract of Deiters (ATD). Abducens internuclear neurons are responsible for conjugate gaze in the horizontal plane, whereas ATD neurons provide medial rectus motoneurons with a vestibular input comprising mainly head velocity. To reveal the relative contribution of each input to the oculomotor physiology, single-unit recordings from medial rectus motoneurons were obtained in the control situation and after selective deafferentation from cats with unilateral transection of either the MLF or the ATD. Both MLF and ATD transection produced similar short-term alterations in medial rectus motoneuron firing pattern, which were more drastic in MLF of animals. However, long-term recordings revealed important differences between the two types of lesion. Thus, while the effects of the MLF section were permanent, 2 months after ATD lesioning all motoneuronal firing parameters were similar to the control. These findings indicated a more relevant role of the MLF pathway in driving motoneuronal firing and evidenced compensatory mechanisms following the ATD lesion. Confocal immunocytochemistry revealed that MLF transection produced also a higher loss of synaptic boutons, mainly at the dendritic level. Moreover, 2 months after ATD transection, we observed an increase in synaptic coverage around motoneuron cell bodies compared with short-term data, which is indicative of a synaptogenic compensatory mechanism of the abducens internuclear pathway that could lead to the observed firing and morphological recovery.SIGNIFICANCE STATEMENT Eye movements rely on multiple neuronal circuits for appropriate performance. The abducens internuclear pathway through the medial longitudinal fascicle (MLF) and the vestibular neurons through the ascending tract of Deiters (ATD) are a dual system that supports the firing of medial rectus motoneurons. We report the effect of sectioning the MLF or the ATD pathway on the firing of medial rectus motoneurons, as well as the plastic mechanisms by which one input compensates for the lack of the other. This work shows that while the effects of MLF transection are permanent, the ATD section produces transitory effects. A mechanism based on axonal sprouting and occupancy of the vacant synaptic space due to deafferentation is the base for the mechanism of compensation on the medial rectus motoneuron.

DNA damage induced by metronidazole in Giardia duodenalis triggers a DNA homologous recombination response.

The mechanisms underlying metronidazole (MTZ) resistance in Giardia duodenalis have been associated with decreased activity of the enzymes implicated in its activation including nitroductase-1, thioredoxin reductase and pyruvate-ferredoxin oxidoreductase (PFOR). MTZ activation generates radicals that can form adducts with proteins such as thioredoxin reductase and α- and -ß giardins as well as DNA damage resulting in trophozoite's death. The damage induced in DNA requires a straight forward response that may allow parasite survival. Here, we studied changes in histone H2A phosphorylation to evaluate the DNA repair response pathway after induction of double strand break (DSB) by MTZ in Giardia DNA. Our results showed that the DNA repair mechanisms after exposure of Giardia trophozoites to MTZ, involved a homologous recombination pathway. We observed a significant increase in the expression level of proteins GdDMC1B, which carries out Rad51 role in G. duodenalis, and GdMre11, after 12 h of exposure to 3.2 µM MTZ. This increase was concomitant with the generation of DSB in the DNA of trophozoites treated MTZ. Altogether, these results suggest that MTZ-induced DNA damage in Giardia triggers the DNA homologous recombination repair (DHRR) pathway, which may contribute to the parasite survival in the presence of MTZ.

Expression and secretion of the Giardia duodenalis variant surface protein 9B10A by transfected trophozoites causes damage to epithelial cell monolayers mediated by protease activity.

Giardia duodenalis is the protozoan parasite responsible for most cases of parasitic diarrhea worldwide. The pathogenic mechanisms of giardiasis have not yet been fully characterized. In this context parasite's excretory/secretory products have been related to the damage induced by the parasite on enterocytes. Among these is the Variable Surface Proteins (VSPs) family involved in antigenic variation and in the induction of protective response. In proteomic analyses carried out to identify the proteases with high molecular weight secreted by Giardia trophozoites during the initial phase of interaction with IEC-6 cell monolayers we identified the VSP9B10A protein. In silico bioinformatics analyses predicted a central region in residues 324-684 displaying the catalytic triad and the substrate binding pocket of cysteine proteases. The analysis of the effect of the VSP9B10A protein on epithelial cell monolayers using trophozoites that were transfected with a plasmid carrying the vsp9b10a gene sequence under the control of a constitutive promoter showed that transfected trophozoites expressing the VSP9B10A protein caused cytotoxic damages on IEC-6 and MDCK cell monolayers. This was characterized by loss of cell-cell contacts and cell detachment from the substrate while no damage was observed with trophozoites that did not express the VSP9B10A protein. The same cytotoxic effect was detected when IEC-6 cell monolayers were incubated only with supernatants from co-cultures of IEC-6 cell monolayers with VSP9B10A transfected trophozoites and this effect was not observed when transfected trophozoites were incubated with a monospecific polyclonal antibody anti-VSP9B10A previous to interaction with IEC-6 monolayers. These results demonstrate that the VSP9B10A protein secreted upon interaction with epithelial cells caused damage in these cells. Thus this protein might be considered as a conditional virulence factor candidate. To our knowledge this is the first report on the proteolytic activity from a Giardia VSP opening new research lines on these proteins.

Ubiquitin-like Atg8 protein is expressed during autophagy and the encystation process in Naegleria gruberi.

Members of the Naegleria genus are free-living amoebae, and the only pathogenic specie described to date for humans is N. fowleri. However, as the complete genome of this specie has not been reported, non-pathogenic N. gruberi is employed to describe molecular pathways in N. fowleri. Regardless, certain mechanisms, such as autophagy, have not yet been characterized in N. gruberi. Autophagy is involved in different cellular processes in some protozoa, including the recycling of unnecessary organelles, development, and cell differentiation. In this work, we characterized autophagy in N. gruberi using the specific inducer rapamycin. The formation of autophagy vacuoles in treated trophozoites was observed by ultrastructural analysis, and real time quantitative PCR demonstrated overexpression of the atg8 gene. In addition, we detected an increase in the vacuolar acidification of treated amoebae using the LysoTracker. Finally, confocal microscopy was utilized to identify Atg8 protein signal in the cytoplasm of N. gruberi trophozoites induced with rapamycin and even in trophozoites induced to encyst. In conclusion, N. gruberi possesses an Atg8 protein homolog that is overexpressed during the autophagic mechanism induced by rapamycin and also during encystation of this free-living amoeba.

Functional Diversity of Neurotrophin Actions on the Oculomotor System.

Neurotrophins play a principal role in neuronal survival and differentiation during development, but also in the maintenance of appropriate adult neuronal circuits and phenotypes. In the oculomotor system, we have demonstrated that neurotrophins are key regulators of developing and adult neuronal properties, but with peculiarities depending on each neurotrophin. For instance, the administration of NGF (nerve growth factor), BDNF (brain-derived neurotrophic factor) or NT-3 (neurotrophin-3) protects neonatal extraocular motoneurons from cell death after axotomy, but only NGF and BDNF prevent the downregulation in ChAT (choline acetyltransferase). In the adult, in vivo recordings of axotomized extraocular motoneurons have demonstrated that the delivery of NGF, BDNF or NT-3 recovers different components of the firing discharge activity of these cells, with some particularities in the case of NGF. All neurotrophins have also synaptotrophic activity, although to different degrees. Accordingly, neurotrophins can restore the axotomy-induced alterations acting selectively on different properties of the motoneuron. In this review, we summarize these evidences and discuss them in the context of other motor systems.