A new case for a presynaptic role of dendrites: An immunocytochemical study of the N. Raphé Dorsalis

The distribution of serotonin (5-HT) was determined by the application of the prembedding peroxidase-anti-peroxidase (PAP) technique in vibratome and ultrathin sections of the brain stem. The antiserum stained the neuronal groups B₁ to B₉. Somata, dendrites and axons of multipolar and bipolar neurons were recognized in the usual locations. The most commonly found profiles in the area of the n.raphe dorsalis were dendrites. The search for axon terminals was unsuccesful. The labeled dendrites appear in synaptic contact with unlabeled endings containing round or pleomorphic vesicles, and occasionally some large dense core vesicles. Contacts between two labeled dendrites or processes were not found. Occasionally a dendrodendritic junction between a 5-HT labeled dendrite and an unlabeled dendrite has been found. There are areas of the dendritic membrane free of synaptic junctions and free of glial insulation. Results are discussed in relation with the previously proposed presynaptic role of the dendrites in the neuronal circuitry of then. raphé dorsalis.Special Issue dedicated to Prof. Eduardo De Robertis.Research supported by grants from the CONICET and SECYT, Argentina.     

Sirt3-mediated deacetylation of evolutionarily conserved lysine 122 regulates MnSOD activity in response to stress

Genetic deletion of the mitochondrial deacetylase sirtuin-3 (Sirt3) results in increased mitochondrial superoxide, a tumor-permissive environment, and mammary tumor development. MnSOD contains a nutrient- and ionizing radiation (IR)-dependent reversible acetyl-lysine that is hyperacetylated in Sirt3?/? livers at 3 months of age. Livers of Sirt3?/? mice exhibit decreased MnSOD activity, but not immunoreactive protein, relative to wild-type livers. Reintroduction of wild-type but not deacetylation null Sirt3 into Sirt3?/? MEFs deacetylated lysine and restored MnSOD activity. Site-directed mutagenesis of MnSOD lysine 122 to an arginine, mimicking deacetylation (lenti-MnSOD(K122-R)), increased MnSOD activity when expressed in MnSOD?/? MEFs, suggesting acetylation directly regulates function. Furthermore, infection of Sirt3?/? MEFs with lenti-MnSOD(K122-R) inhibited in vitro immortalization by an oncogene (Ras), inhibited IR-induced genomic instability, and decreased mitochondrial superoxide. Finally, IR was unable to induce MnSOD deacetylation or activity in Sirt3?/? livers, and these irradiated livers displayed significant IR-induced cell damage and microvacuolization in their hepatocytes.     

Acute pre-learning stress and declarative memory: impact of sex,cortisol response and menstrual cycle phase

This study explores the influence of pre-learning stress on performance on declarative memory tasks in healthy young adults in relation to sex and menstrual cycle phase. The sample was composed of 119 students (32 men and 87 women) from 18 to 25 years of age. The women were tested in different hormonal stages (30 in follicular phase, 34 in luteal phase, and 23 using oral contraceptives). The participants were exposed to the Trier Social Stress Test (TSST) or a control condition. Afterwards, their memory performance was measured using a standardized memory test (Rey's Auditory Verbal Learning Test). In the control condition, all groups of women recalled more words than men, but these differences disappeared in the group exposed to TSST because men's performance on the memory test improved, but only to the level of women. In addition, our data suggest that in women the relationship between cortisol and memory can be modulated by sex hormone levels, since in luteal women a negative relationship was found between memory performance and peak cortisol level. These results confirm that sex differences need to be considered in the relationship between pre-learning stress and memory performance.     

TCR engagement induces proline-rich tyrosine kinase-2 (Pyk2) translocation to the T cell-APC interface independently of Pyk2 activity and in an immunoreceptor tyrosine-based activation motif-mediated fashion

The relocation of kinases in T lymphocytes during their cognate interaction with APCs is essential for lymphocyte activation. We found that the proline-rich tyrosine kinase-2 (Pyk2) is rapidly translocated to the T cell-APC contact area upon T cell-specific recognition of superantigen-pulsed APCs. Stimulation with anti-CD3-coated latex microspheres was sufficient for Pyk2 reorientation, and the coengagement of CD28 boosted Pyk2 redistribution. Nevertheless, Pyk2 translocation did not result in its recruitment to lipid rafts. Two results support that Pyk2 translocation was independent of its kinase activity. First, Lck activity was required for TCR-induced Pyk2 translocation, but not for TCR-induced Pyk2 activation. Second, a kinase-dead Pyk2 mutant was equally translocated upon TCR triggering. In addition, Lck activity alone was insufficient to induce Pyk2 reorientation and activation, requiring the presence of at least one intact immunoreceptor tyrosine-based activation motif (ITAM). Despite the dependence on functional Lck and on phosphorylated ITAM for Pyk2 translocation, the ITAM-binding tyrosine kinase zeta-associated protein 70 (ZAP-70) was not essential. All these data suggest that, by translocating to the vicinity of the immune synapse, Pyk2 could play an essential role in T cell activation and polarized secretion of cytokines.     

Chronic Cadmium Exposure Lead to Inhibition of Serum and Hepatic Alkaline Phosphatase Activity in Wistar Rats

Alkaline phosphatase (ALP) activity in the serum and liver from rats administered with cadmium (Cd) in drinking water was studied. After metal administration, Cd showed a time‐dependent accumulation in the liver, meanwhile metallothionein had a maximum increase at 1 month, remaining in this level until the end of the study. On the other hand, serum and liver ALP activity was decreased after 3 months exposure. To determine if Cd produced an inhibition on enzyme, apo‐ALP prepared from both nonexposed and exposed rats was reactivated with Zn, showing 60% more activity as compared with the enzyme isolated from nonexposed rats. In vitro assays showed that Cd‐ALP was partially reactivated with Zn; however, in the presence of cadmium, Zn‐ALP was completely inhibited. Kinetic studies indicate a noncompetitive inhibition by Cd; these results suggest that Cd can substitute Zn, and/or Cd can interact with nucleophilic ligands essential for the enzymatic activity.     

Hidden diversity of Acoelomorpha revealed through metabarcoding

Animals with bilateral symmetry comprise the majority of the described species within Metazoa. However, the nature of the first bilaterian animal remains unknown. As most recent molecular phylogenies point to Xenacoelomorpha as the sister group to the rest of Bilateria, understanding their biology, ecology and diversity is key to reconstructing the nature of the last common bilaterian ancestor (Urbilateria). To date, sampling efforts have focused mainly on coastal areas, leaving potential gaps in our understanding of the full diversity of xenacoelomorphs. We therefore analysed 18S rDNA metabarcoding data from three marine projects covering benthic and pelagic habitats worldwide. Our results show that acoels have a greater richness in planktonic environments than previously described. Interestingly, we also identified a putative novel clade of acoels in the deep benthos that branches as sister group to the rest of Acoela, thus representing the earliest-branching acoel clade. Our data highlight deep-sea environments as an ideal habitat to sample acoels with key phylogenetic positions, which might be useful for reconstructing the early evolution of Bilateria.     

Blood transfusion and iatrogenic risks in Mexico City. Anti-Trypanosoma cruzi seroprevalence in 43,048 blood donors, evaluation of parasitemia, and electrocardiogram findings in seropositive

Iatrogenous transmission of Trypanosoma cruzi by blood transfusion was suggested as a potential risk by Pellegrino (1949). Seropositive blood donors in Mexico were first reported in 1978, however, limited information is available due to small sampling, the use of heterogeneous serologic assays, and geographically limited studies. A wide survey carried out in 18 out of the 32 states of Mexico, showed a national mean of 1.6% seropositive among 64,969 donors, ranging from 0.2 to 2.8%. In the present study, we have screened 43,048 voluntary blood donors in a period of five years at the Instituto Nacional de Cardiología I. Chávez, a concentration hospital located in Mexico city which serves mainly the metropolitan area and accepts from all over the country. Standardized ELISA and IIF were used to identify seropositive individuals in addition to hemoculture, PCR and standard 12 lead ECG tests that were applied to a group of seropositive patients (29/161). The result showed a seropositivity of 0.37% (161/43,048). From the group of seropositive individuals 40% (12/29) were potential carriers of T. cruzi at the donation time and 5/29 had subclinical ECG abnormalities. Parasitological tests performed in 70 erythrocyte and platelet fractions from seropositive units (70/161) showed negative results. Our findings strongly support T. cruzi screening in the transfusion medicine practice and identify subclinical heart disease among seropositive blood donors.     

Neural Differentiation Modulates the Vertebrate Brain Specific Splicing Program

Alternative splicing patterns are known to vary between tissues but these patterns have been found to be predominantly peculiar to one species or another, implying only a limited function in fundamental neural biology. Here we used high-throughput RT-PCR to monitor the expression pattern of all the annotated simple alternative splicing events (ASEs) in the Reference Sequence Database, in different mouse tissues and identified 93 brain-specific events that shift from one isoform to another (switch-like) between brain and other tissues. Consistent with an important function, regulation of a core set of 9 conserved switch-like ASEs is highly conserved, as they have the same pattern of tissue-specific splicing in all vertebrates tested: human, mouse and zebrafish. Several of these ASEs are embedded within genes that encode proteins associated with the neuronal microtubule network, and show a dramatic and concerted shift within a short time window of human neural stem cell differentiation. Similarly these exons are dynamically regulated in zebrafish development. These data demonstrate that although alternative splicing patterns often vary between species, there is nonetheless a core set of vertebrate brain-specific ASEs that are conserved between species and associated with neural differentiation.