The C-Terminal Domain of the mGluR1 Metabotropic Glutamate Receptor Affects Sensitivity to Agonists

Abstract: The metabotropic glutamate receptor (mGluR) subtype 1 exists as at least three variants (−1a, −1b, and −1c) generated by alternative splicing at the C-terminal domain. Fluorometric Ca²⁺ measurements were used to compare the concentration dependency of agonist-induced rises in intracellular free Ca²⁺ concentration ([Ca²⁺]_i) in human embryonic HEK 293 cells transiently expressing rat mGluR1a, mGluR1b, or mGluR1c. The rank order of agonist potencies was quisqualate ≫ (2 S, 1' S, 2' S )-2-(carboxycyclopropyl)glycine (L-CCG-I) > (1 S, 3 R )-1-aminocyclopentane-1,3-dicarboxylic acid [(1 S, 3 R )-ACPD] and did not differ among the splice variants. However, agonists were consistently more potent at mGluR1a than at mGluR1c and mGluR1b. In the same system, we characterized the agonist pharmacology of two chimeric rat mGluR3/1 receptors where the first and/or the second intracellular loop(s) and the C-terminal domain were exchanged with the corresponding mGluR1a or mGluR1c sequences and that were previously shown to mediate elevations in [Ca²⁺]_i in response to agonists. The potency of agonists was higher at the chimera having the C-terminus of mGluR1a as compared with those having the mGluR1c C-terminus. Both chimeric mGluR3/1 receptors had the same rank order of agonist potencies: L-CCG-I ≫ (1 S, 3 R )-ACPD ∼ quisqualate. These data support the hypothesis that the C-terminal domain of mGluRs plays a role in determining the potency of agonists for inducing mGluR-mediated functional responses.     

Recovery,structure, and function of dog granulocytes after freeze-preservation with dimethylsulfoxide

The recovery, structure and function of dog granulocytes were determined before and after freeze-preservation. Leucocytes were isolated from defibrinated or anti-coagulated whole blood and subsequent erythrocyte sedimentation on a column of 2:1 dextran (6%)-isopaque (33.9%). Granulocytes isolated by these procedures were examined for changes in O₂ consumption associated with phagocytosis, in vitro directed migration (chemotaxis), bactericidal activity, and ultrastructure before and after freezing. Granulocytes were frozen in DMSO (7.5%) and autologous serum or HBSS-minus and 20% autologous serum at the rate of ?1 °C/min to ?80 °C and stored in liquid N₂ vapor.After freeze-preservation, O₂ consumption associated with phagocytosis was decreased by 54 and 64% for granulocytes isolated from defibrinated or from ACD-anticoagulated blood, respectively. Bactericidal activity is only slightly depressed in samples from either isolation method after freeze-preservation when compared to the prefreeze controls, but granulocytes isolated from defibrinated blood are significantly less effective in killing bacteria than those from ACD-anticoagulated blood. Chemotactic response after freeze-preservation was completely inhibited in granulocytes isolated from defibrinated blood. Exposure of granulocytes to ACD inhibited chemotaxis prior to freezing, but the granulocytes responded chemotactically after freeze-thaw and additional washing. The ultrastructure of granulocytes observed before and after freeze-thaw was similar for cells isolated by both methods. However, nuclear, cytoplasmic, and granular changes observed were slightly greater in granulocytes isolated from defibrinated blood. Dog granulocytes isolated by either method withstood freeze-preservation in DMSO to a degree not previously reported.It is concluded that dog granulocytes freeze-preserved by these methods are functional in vitro, but that phagocytic, directed migration, and bactericidal functions and ultrastructure are impaired to different degrees, according to the method of isolation and preparation for storage. These results indicate the need for continued investigation on the effects of storage variables on the preservation of granulocytes.     

Arysulfatase A modulation with pH in multiple sulfatase deficiency disorder fibroblasts.

It has been observed that multiple sulfatase deficiency disorder (MSDD) fibroblasts contained from profoundly deficient to near normal amounts of arylsulfatase (ARS) A depending on the medium in which they were cultured. Our present findings show that the major factor determining the enzyme level is the pH of the medium during growth. In media which became acidic or was maintained at low pH (less than 7), the cells expressed the enzymopathy, while in high pH media (7.4), the cells produced enzyme. The high and low enzyme states were reversible. The ARS A deficiency in MSDD must, therefore, be a secondary manifestation of a mutation in another system.     

The modification of cortical reorganization and chronic pain by sensory feedback

Recent neuroscientific evidence has revealed that the adult brain is capable of substantial plastic change in areas such as the primary somatosensory cortex that were formerly thought to be modifiable only during early experience. We discuss research on phantom limb pain as well as chronic back pain that revealed functional reorganization in both the somatosensory and the motor system in these chronic pain states. In phantom limb pain patients, cortical reorganization is correlated with the amount of phantom limb pain; in low back pain patients the amount of reorganizational change increases with chronicity. We present a model of the development of chronic pain that assumes an important role of somatosensory pain memories. In phantom limb pain, we propose that those patients who experienced intense pain prior to the amputation will later likely develop enhanced cortical reorganization and phantom limb pain. We show that cortical plasticity related to chronic pain can be reduced by behavioral interventions that provide feedback to the brain areas that were altered by somatosensory pain memories.     

Effects of Fe deficiency on the protein profile of Brassica napus phloem sap

The aim of this work was to study the effect of Fe deficiency on the protein profile of phloem sap exudates from Brassica napus using 2DE (IEF‐SDS‐PAGE). The experiment was repeated thrice and two technical replicates per treatment were done. Phloem sap purity was assessed by measuring sugar concentrations. Two hundred sixty‐three spots were consistently detected and 15.6% (41) of them showed significant changes in relative abundance (22 decreasing and 19 increasing) as a result of Fe deficiency. Among them, 85% (35 spots), were unambiguously identified. Functional categories containing the largest number of protein species showing changes as a consequence of Fe deficiency were signaling and regulation (32%), and stress and redox homeostasis (17%). The Phloem sap showed a higher oxidative stress and significant changes in the hormonal profile as a result of Fe deficiency. Results indicate that Fe deficiency elicits major changes in signaling pathways involving Ca and hormones, which are generally associated with flowering and developmental processes, causes an alteration in ROS homeostasis processes, and induces decreases in the abundances of proteins involved in sieve element repair, suggesting that Fe‐deficient plants may have an impaired capacity to heal sieve elements upon injury.     

The ESX-4 substrates,EsxU and EsxT,modulate Mycobacterium abscessus fitness

ESX type VII secretion systems are complex secretion machineries spanning across the mycobacterial membrane and play an important role in pathogenicity, nutrient uptake and conjugation. We previously reported the role of ESX-4 in modulating Mycobacterium abscessus intracellular survival. The loss of EccB4 was associated with limited secretion of two effector proteins belonging to the WXG-100 family, EsxU and EsxT, and encoded by the esx-4 locus. This prompted us to investigate the function of M. abscessus EsxU and EsxT in vitro and in vivo. Herein, we show that EsxU and EsxT are substrates of ESX-4 and form a stable 1:1 heterodimer that permeabilizes artificial membranes. While expression of esxU and esxT was up-regulated in M. abscessus-infected macrophages, their absence in an esxUT deletion mutant prevented phagosomal membrane disruption while maintaining M. abscessus in an unacidified phagosome. Unexpectedly, the esxUT deletion was associated with a hyper-virulent phenotype, characterised by increased bacterial loads and mortality in mouse and zebrafish infection models. Collectively, these results demonstrate that the presence of EsxU and EsxT dampens survival and persistence of M. abscessus during infection.     

Metabotropic glutamate receptor subtype 7 controls maternal care,maternal motivation and maternal aggression in mice

The group III metabotropic glutamate receptor subtype 7 (mGlu7) is an important regulator of glutamatergic and GABAergic neurotransmission and known to mediate emotionality and male social behavior. However, a possible regulatory role in maternal behavior remains unknown to date. Adequate expression of maternal behavior is essential for successful rearing and healthy development of the young. By understanding genetic and neural mechanisms underlying this important prosocial behavior, we gain valuable insights into possible dysregulations. Using genetic ablation as well as pharmacological modulation, we studied various parameters of maternal behavior in two different mouse strains under the influence of mGlu7. We can clearly show a regulatory role of mGlu7 in maternal behavior. Naïve virgin female C57BL/6 mGlu7 knockout mice showed more often nursing postures and less spontaneous maternal aggression compared to their heterozygous and wildtype littermates. In lactating C57BL/6 wildtype mice, acute central activation of mGlu7 by the selective agonist AMN082 reduced arched back nursing and accelerated pup retrieval without affecting maternal aggression. In addition, in lactating CD1 wildtype mice the selective mGlu7 antagonist XAP044 increased both pup retrieval and maternal aggression. With respect to receptor expression levels, mGlu7 mRNA expression was higher in lactating vs virgin C57BL/6 mice in the prefrontal cortex, but not hypothalamus or hippocampus. In conclusion, these findings highlight a significant role of the mGlu7 receptor subtype in mediating maternal behavior in mice. Region‐dependent studies are warranted to further extend our knowledge on the specific function of the brain glutamate system in maternal behavior.     

Molecular Epidemiology of Human Oral Chagas Disease Outbreaks in Colombia

Background

Trypanosoma cruzi, the causative agent of Chagas disease, displays significant genetic variability revealed by six Discrete Typing Units (TcI-TcVI). In this pathology, oral transmission represents an emerging epidemiological scenario where different outbreaks associated to food/beverages consumption have been reported in Argentina, Bolivia, Brazil, Ecuador and Venezuela. In Colombia, six human oral outbreaks have been reported corroborating the importance of this transmission route. Molecular epidemiology of oral outbreaks is barely known observing the incrimination of TcI, TcII, TcIV and TcV genotypes.

Methodology and Principal Findings

High-throughput molecular characterization was conducted performing MLMT (Multilocus Microsatellite Typing) and mtMLST (mitochondrial Multilocus Sequence Typing) strategies on 50 clones from ten isolates. Results allowed observing the occurrence of TcI, TcIV and mixed infection of distinct TcI genotypes. Thus, a majority of specific mitochondrial haplotypes and allelic multilocus genotypes associated to the sylvatic cycle of transmission were detected in the dataset with the foreseen presence of mitochondrial haplotypes and allelic multilocus genotypes associated to the domestic cycle of transmission.

Conclusions

These findings suggest the incrimination of sylvatic genotypes in the oral outbreaks occurred in Colombia. We observed patterns of super-infection and/or co-infection with a tailored association with the severe forms of myocarditis in the acute phase of the disease. The transmission dynamics of this infection route based on molecular epidemiology evidence was unraveled and the clinical and biological implications are discussed.     

Diverse cellulolytic bacteria isolated from the high humus, alkaline-saline chinampa soils

Aiming at learning the functional bacterial community in the high humus content, saline-alkaline soils of chinampas, the cellulolytic bacteria were quantified and 100 bacterial isolates were isolated and characterized in the present study. Analysis of 16S-23S IGS (intergenic spacer) RFLP (restriction fragment length polymorphism) grouped the isolates into 48 IGS types and phylogenetic analysis of 16S rRNA genes identified them into 42 phylospecies within 29 genera and higher taxa belonging to the phyla Actinobacteria, Firmicutes and Proteobacteria, dominated by the genera Arthrobacter, Streptomyces, Bacillus, Pseudomonas, Pseudoxanthomonas and Stenotrophomonas. Among these bacteria, 63 isolates represent 26 novel putative species or higher taxa, while 37 were members of 17 defined species according to the phylogenetic relationships of 16S rRNA gene. Except for the novel species, the cellulolytic activity was not reported previously in 9 of the 17 species. They degraded cellulose in medium at pH?4.5–10.0 or supplied with NaCl up to 9 %. In addition, 84.8 and 71.7 % of them degraded xylan and Avicel, respectively. These results greatly improved the knowledge about the diversity of cellulolytic bacteria and demonstrated that the chinampa soils contain diverse and novel cellulolytic bacteria functioning at a wide range of pH and salinity levels, which might be a valuable biotechnological resource for biotransformation of cellulose.