Physiology and pathophysiology of nitric oxide in the nervous system,with special mention of the islands of Calleja and the circunventricular organs

Nitric oxide (NO) has been recognized as a key regulatory factor in many physiological processes, including central nervous system function, development, and phatophysiology. NO is produced by a class of enzymes known as NO synthases (NOS) and in normal adult animals only the neuronal isoform (nNOS) is detectable. During cortical development, nNOS was found at E14 in neuroblasts of the marginal zone and its expression raised to a zenith by P5, decreasing afterwards until reaching a steady level by P10. At that time, nNOS was found mainly in pyramidal neurons. Interestingly, the inducible isoform of the enzyme (iNOS) was also active from P3 to P7, but it disappeared almost completely by P20. The neurodegeneration observed during normal aging and following hypoxic accidents seems to be the result of cumulative free radical damage, and excessive production of NO may be at the basis of the cascade. After ischemic events we observed an elevation in the number of neurons expressing nNOS coincident with an elevation in Ca2+-dependent NOS activity for up to 120 min. After this period, nNOS activity began to decrease but it was substituted by a rapid increase in Ca2+-independent activity coincident with the histological appearance of previously undetectable iNOS-immunoreactive neurons. These increases in NO production were accompanied by specific patterns of protein nitration, a process that seems to result in loss of protein function. In particular, we observed a correlation between exposure to ischemia-reperfusion and nitration of cytochrome c. This process was coincident with the exit of the cytochrome from the mitochondria to the surrounding cytoplasm, an early event in neuronal apoptosis. Interestingly, most of the morphological and molecular changes associated with ischemic damage were prevented by treatment with inhibitors of NO production, indicating a clear path in the search for efficacious drugs in the battle against cerebrovascular accidents.     

Molecular cloning and functional characterization of Cynomolgus monkey (Macaca fascicularis) CC chemokine receptor,CCR3

We have cloned and performed the first functional characterization of the chemokine receptor, CCR3, of Cynomolgus monkey (Macaca fascicularis). The deduced amino acid sequence of the cloned Cynomolgus CCR3 was found to be more similar to that of a previously-reported Rhesus (Macaca mulatta) CCR3 (99.4%) than that of a reported Cynomolgus CCR3 (98.0%). Stably-transfected Cynomolgus CCR3 bound human eotaxin (CCL11) with similar kinetics (Kd 240 pM) and was responsive to human CCR3 ligands (eotaxin [CCL11], eotaxin-2 [CCL24], and MCP4 [CCL13]) in Ca(2+) mobilization and chemotaxis assays, thus provides a useful alternative species model system for the analysis of modulators of eotaxin--CCR3 induced signaling and activation.     

Mortality risk prediction of high-sensitivity C-reactive protein in suspected acute coronary syndrome: A cohort study

BackgroundThere is limited evidence on the use of high-sensitivity C-reactive protein (hsCRP) as a biomarker for selecting patients for advanced cardiovascular (CV) therapies in the modern era. The prognostic value of mildly elevated hsCRP beyond troponin in a large real-world cohort of unselected patients presenting with suspected acute coronary syndrome (ACS) is unknown. We evaluated whether a mildly elevated hsCRP (up to 15 mg/L) was associated with mortality risk, beyond troponin level, in patients with suspected ACS.Methods and findingsWe conducted a retrospective cohort study based on the National Institute for Health Research Health Informatics Collaborative data of 257,948 patients with suspected ACS who had a troponin measured at 5 cardiac centres in the United Kingdom between 2010 and 2017. Patients were divided into 4 hsCRP groups (<2, 2 to 4.9, 5 to 9.9, and 10 to 15 mg/L). The main outcome measure was mortality within 3 years of index presentation. The association between hsCRP levels and all-cause mortality was assessed using multivariable Cox regression analysis adjusted for age, sex, haemoglobin, white cell count (WCC), platelet count, creatinine, and troponin.Following the exclusion criteria, there were 102,337 patients included in the analysis (hsCRP <2 mg/L (n = 38,390), 2 to 4.9 mg/L (n = 27,397), 5 to 9.9 mg/L (n = 26,957), and 10 to 15 mg/L (n = 9,593)). On multivariable Cox regression analysis, there was a positive and graded relationship between hsCRP level and mortality at baseline, which remained at 3 years (hazard ratio (HR) (95% CI) of 1.32 (1.18 to 1.48) for those with hsCRP 2.0 to 4.9 mg/L and 1.40 (1.26 to 1.57) and 2.00 (1.75 to 2.28) for those with hsCRP 5 to 9.9 mg/L and 10 to 15 mg/L, respectively. This relationship was independent of troponin in all suspected ACS patients and was further verified in those who were confirmed to have an ACS diagnosis by clinical coding. The main limitation of our study is that we did not have data on underlying cause of death; however, the exclusion of those with abnormal WCC or hsCRP levels >15 mg/L makes it unlikely that sepsis was a major contributor.ConclusionsThese multicentre, real-world data from a large cohort of patients with suspected ACS suggest that mildly elevated hsCRP (up to 15 mg/L) may be a clinically meaningful prognostic marker beyond troponin and point to its potential utility in selecting patients for novel treatments targeting inflammation.Trial registrationClinicalTrials.gov - {"type":"clinical-trial","attrs":{"text":"NCT03507309","term_id":"NCT03507309"}}NCT03507309

Amit Kaura and colleagues investigate whether mildly elevated high sensitivity C-reactive protein is associated with mortality risk in patients with suspected acute coronary syndromes.     

Tyrosine 981, a novel ret autophosphorylation site, binds c-Src to mediate neuronal survival

The glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) are neurotrophic factors that influence several aspects of the developing and injured nervous system. GFLs signal through a common receptor tyrosine kinase (Ret) and one of the four ligand-binding co-receptors (GFRalpha1 to 4). Ligand-induced translocation of Ret to lipid rafts, where it interacts with the nonreceptor tyrosine kinase Src, is a prerequisite for full biological activity of these neurotrophic factors. This interaction and subsequent activation of Src are required for GFL-mediated neuronal survival, neurite outgrowth, or cell proliferation. Here we show by multiple approaches that Ret tyrosine 981 constitutes the major binding site of the Src homology 2 domain of Src and therefore the primary residue responsible for Src activation upon Ret engagement. Other tyrosines such as 1015 and 1029 may contribute to the overall interaction between Ret and Src, as judged by overexpression experiments. By generating a phosphospecific antibody, we demonstrate that tyrosine 981 is a novel autophosphorylation site in Ret. Importantly, we also show that this tyrosine becomes phosphorylated in dissociated sympathetic neurons after ligand stimulation. Mutation of tyrosine 981 to phenylalanine reduces GDNF-mediated survival in a transfected cerebellar granule neuron paradigm.     

Pollen analogues are transported across greater distances in bee‐pollinated than in hummingbird‐pollinated species of Justicia (Acanthaceae)

Several hummingbird‐pollinated plant lineages have been demonstrated to show increased rates of diversification compared to related insect‐pollinated lineages. It has been argued that this pattern is produced by a higher degree of specialization on part of both hummingbirds and plants. We here test an alternative hypothesis: The often highly territorial hummingbirds may on average carry pollen over shorter distances than other pollinators and drive diversification by reducing gene flow distances. We present experimental data from pollen analogue tracking showing shorter dispersal distances in hummingbird‐pollinated than in bee‐pollinated species among ten Neotropical species of Justicia (Acanthaceae). Abstract in Spanish is available with online material.     

Phenotypical and functional heterogeneity of neural stem cells in the aged hippocampus

Adult neurogenesis persists in the hippocampus of most mammal species during postnatal and adult life, including humans, although it declines markedly with age. The mechanisms driving the age‐dependent decline of hippocampal neurogenesis are yet not fully understood. The progressive loss of neural stem cells (NSCs) is a main factor, but the true neurogenic output depends initially on the actual number of activated NSCs in each given time point. Because the fraction of activated NSCs remains constant relative to the total population, the real number of activated NSCs declines in parallel to the total NSC pool. We investigated aging‐associated changes in NSCs and found that there are at least two distinct populations of NSCs. An alpha type, which maintains the classic type‐1 radial morphology and accounts for most of the overall NSC mitotic activity; and an omega type characterized by increased reactive‐like morphological complexity and much lower probability of division even under a pro‐activation challenge. Finally, our results suggest that alpha‐type NSCs are able to transform into omega‐type cells overtime and that this phenotypic and functional change might be facilitated by the chronic inflammation associated with aging.     

Ovarian response in sheep superovulated after pretreatment with growth hormone and GnRH antagonists is weakened by failures in oocyte maturation

The administration of growth hormone (GH) or GH plus GnRH antagonists (GnRHa) in sheep allows the enhancement of the pool of gonadotrophin-responsive follicles present in the ovaries and may be useful to increase yields obtained in embryo programmes. The objective of the current study was to evaluate the ability of follicles recruited in response to treatment with GH and GnRHa to grow in response to exogenous follicle stimulating hormone (FSH) and the competence of their oocytes to resume meiosis. Seven females were treated with two doses of GnRHa (days 0 and 3) and three doses of 15 mg of GH (days 3, 4 and 5). Thereafter, this group and a second group (n = 7) were treated with three doses of 1.5 ml of FSH 12 h apart. A third group (control; n = 4) did not receive GH/GnRHa or FSH. The mean number of follicles aspirated on day 7 was higher in ewes treated with GH and GnRHa prior to the stimulation with exogenous FSH than in ewes treated with FSH without pretreatment and in untreated control sheep (20.4 +/- 2.6 vs 17.7 +/- 3.9 and 11.5 +/- 0.8, p < 0.05 and p < 0.01, respectively). The number of recovered cumulus-oocyte complexes after follicular aspiration was higher in the GH/GnRHa + FSH group (8.7 +/- 0.9 vs 6.8 +/- 1.3 in FSH group, n.s., and 4.5 +/- 0.8 in control, p < 0.05), but there were no differences found in the resumption of meiosis (63.1 +/- 9.5% for GH/GnRHa + FSH vs 79.5 +/- 6.3% for FSH and 60.0 +/- 8.8% for control). These results indicate that GH and GnRHa would be useful to increase the number of gonadotrophin-responsive follicles in the ovary, but adjustment of later FSH treatment allowing further development of follicles may be necessary prior to its use in superovulatory protocols.     

Plant–mycorrhizal fungus co‐occurrence network lacks substantial structure

The interactions between plants and arbuscular mycorrhizal fungi (AMF) maintain a crucial link between macroscopic organisms and the soil microbial world. These interactions are of extreme importance for the diversity of plant communities and ecosystem functioning. Despite this importance, only recently has the structure of plant–AMF interaction networks been studied. These recent studies, which used genetic data, suggest that these networks are highly structured, very similar to plant–animal mutualistic networks. However, the assembly process of plant–AMF communities is still largely unknown, and an important feature of plant–AMF interactions has not been incorporated: they occur at an extremely localized scale. Studying plant–AMF networks in a spatial context seems therefore a crucial step. This paper studies a plant–AMF spatial co‐occurrence network using novel methodology based on information theory and a unique set of spatially explicit species‐level data. We apply three null models of which only one accounts for spatial effects. We find that the data show substantial departures from null expectations for the two non‐spatial null models. However, for the null model considering spatial effects, there are few significant co‐occurrences compared with the other two null models. Thus, plant–AMF spatial co‐occurrences seem to be mostly explained by stochasticity, with a small role for other factors related to plant–AMF specialization. Furthermore, we find that the network is not significantly nested or modular. We conclude that this plant–AMF spatial co‐occurrence network lacks substantial structure and, therefore, plants and AMF species do not track each other over space. Thus, random encounters seem more important in the first step of the assembly of plant–AMF communities. Synthesis The symbiotic interaction between plants and arbuscular mycorrhizal fungi (AMF) is crucial for ecosystem functioning. However, the factors affecting the assembly of plant‐AMF communities are poorly understood. An important factor of the assembly of plant‐AMF communities has been overlooked: plant‐AMF interactions occur at a localized spatial scale. Our study investigated the importance of space in the structure of plant‐AMF communities. We studied a plant‐AMF spatial co‐occurrence network using a unique set of spatially explicit data and applied three null models. We found that plant‐AMF spatial co‐occurrences seem to be mostly explained by stochasticity. In particular, our study shows that this plant‐AMF spatial co‐occurrence network lacks substantial structure and, therefore, plants and AMF species do not track each other over space. Thus, random encounters seem to drive the assembly of plant‐AMF communities.     

Expression of nitrergic system and protein nitration in adult rat brains submitted to acute hypobaric hypoxia.

Changes in the nitric oxide (NO) system of the rat cerebral cortex were investigated by immunohistochemistry, immunoblotting, and NO synthase (NOS) activity assays in adult rats submitted for 30 min to hypoxia, in a hypobaric chamber at a simulated altitude of 38,000 ft (11000 m) (154.9 mm Hg). The cerebral cortex was studied after different survival times, 0 and 24 h, 5, 8, 15, and 30 days of reoxygenation. This situation led to morphological alterations in the large type I interneurons, as well as immunoreactive changes in the appearance and number of the small neurons (type II), both containing neuronal NOS (nNOS). Some of these small neurons showed immunoreactive cytoplasm and short processes; others, the more numerous during all reoxygenation periods, contained the immunoreactive product mainly related to a perinuclear ring. Ultrastructurally, these small neurons exhibited changes in nuclear structures as in the shape of the nuclear membrane, in the distribution of heterochromatin, and in the nucleolar morphology. The reaction product for nitrotyrosine, as a marker of protein nitration, showed modifications in distribution of the immunoreactive product. No expression was found for inducible NOS (iNOS). All these modifications were accompanied by increased nNOS and nitrotyrosine production as demonstrated by Western blotting and calcium-dependent activity, returning to control conditions after 30 days of reoxygenation, suggesting a reversible NO mechanism of action.