Relationship between 22-kHz calls and testosterone in male rats

Ultrasonic calls in rats induced by the presence of a predator, referred to as “22-kHz calls,” are mainly emitted by socially dominant male rats. Testosterone levels are closely related to social dominance in male rats. In the present study, we investigated the relationship between the emission of stress-induced 22-kHz calls and circulating testosterone levels in male rats, using a combination of surgery (castration or sham operation) and chronic steroid administration (testosterone or cholesterol) to modify circulating testosterone levels. We also assessed the effects of androgen and/or estrogen receptor antagonists on the emission of 22-kHz calls in male rats. An air puff stimulus, known to reliably induce 22-kHz calls in rats, was used as a stressor. Castrated rats with cholesterol implants exhibited significantly fewer 22-kHz calls than rats that had received a sham operation and cholesterol implants, and there was no significant difference between castrated rats with testosterone implants and rats that had received a sham operation and cholesterol implants. Only male rats pretreated with a binary mixture of androgen and estrogen antagonists exhibited significantly fewer 22-kHz calls than controls. These results show that testosterone in male rats has a positive effect on the emission of stress-induced 22-kHz calls, and the calls may be regulated by the activation of both androgen and estrogen receptors.     

First evidence of pathogenicity of V234I mutation of hVAPB found in Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis is a motor neurodegenerative disease which is characterized by progressive loss of motor neurons followed by paralysis and eventually death. In human, VAMP-associated protein B (VAPB) is the causative gene of the familial form of ALS8. Previous studies have shown that P56S and T46I point mutations of hVAPB are present in this form of ALS. Recently, another mutation, V234I of hVAPB was found in one familial case of ALS. This is the first study where we have shown that V234I-VAPB does not form aggregate like other two mutants of VAPB and localizes differently than the wild type VAPB. It induces Ubiquitin aggregation followed by cell death. We propose that V234I-VAPB exhibits the characteristics of ALS in spite of not having the typical aggregation property of different mutations in various neurodegenerative diseases.     

miR-27a is up regulated and promotes inflammatory response in sepsis

MicroRNAs (miRNAs) are short, non-coding RNAs that regulate the expression of multiple target genes. Dysregulation of miRNAs is common in sepsis. Through microRNA microarray and qRT-PCR we found that the levels of miR-27a, miR-153 and miR-143 are up regulated, while let-7a, miR-218 and miR-129-5p are down regulated in lungs of septic mice. Knocking down of miR-27a down regulates expression levels of TNF-α and IL-6 significantly via reducing the phosphorylation level of NF-κB p65 and inhibiting its DNA binding activity. Furthermore, neutralisation of miR-27a up regulates PPARγ level, down regulates TNF-α expression, relieves pulmonary inflammation and promotes survival of septic mice, which demonstrates that miR-27a plays an important role in regulating inflammatory response in sepsis and provides a potential target for clinical sepsis research and treatment.     

The GIT–PIX complexes regulate the chemotactic response of rat basophilic leukaemia cells

Background information. Cell motility entails the reorganization of the cytoskeleton and membrane trafficking for effective protrusion. The GIT–PIX protein complexes are involved in the regulation of cell motility and adhesion and in the endocytic traffic of members of the family of G‐protein‐coupled receptors. We have investigated the function of the endogenous GIT complexes in the regulation of cell motility stimulated by fMLP (formyl‐Met‐Leu‐Phe) peptide, in a rat basophilic leukaemia RBL‐2H3 cell line stably expressing an HA (haemagglutinin)‐tagged receptor for the fMLP peptide. Results. Our analysis shows that RBL cells stably transfected with the chemoattractant receptor expressed both GIT1–PIX and GIT2–PIX endogenous complexes. We have used silencing of the different members of the complex by small interfering RNAs to study the effects on a number of events linked to agonist‐induced cell migration. We found that cell adhesion was not affected by depletion of any of the proteins of the GIT complex, whereas agonist‐enhanced cell spreading was inhibited. Analysis of agonist‐stimulated haptotactic cell migration indicated a specific positive effect of GIT1 depletion on trans‐well migration. The internalization of the formyl‐peptide receptor was also inhibited by depletion of GIT1 and GIT2. The effects of the GIT complexes on trafficking of the receptors was confirmed by an antibody‐enhanced agonist‐induced internalization assay, showing that depletion of PIX, GIT1 or GIT2 protein caused decreased perinuclear accumulation of internalized receptors. Conclusions. Our results show that endogenous GIT complexes are involved in the regulation of chemoattractant‐induced cell motility and receptor trafficking, and support previous findings indicating an important function of the GIT complexes in the regulation of different G‐protein‐coupled receptors. Our results also indicate that endogenous GIT1 and GIT2 regulate distinct subsets of agonist‐induced responses and suggest a possible functional link between the control of receptor trafficking and the regulation of cell motility by GIT proteins.     

Pif1- and Exo1-dependent nucleases coordinate checkpoint activation following telomere uncapping

Essential telomere 'capping' proteins act as a safeguard against ageing and cancer by inhibiting the DNA damage response (DDR) and regulating telomerase recruitment, thus distinguishing telomeres from double-strand breaks (DSBs). Uncapped telomeres and unrepaired DSBs can both stimulate a potent DDR, leading to cell cycle arrest and cell death. Using the cdc13-1 mutation to conditionally 'uncap' telomeres in budding yeast, we show that the telomere capping protein Cdc13 protects telomeres from the activity of the helicase Pif1 and the exonuclease Exo1. Our data support a two-stage model for the DDR at uncapped telomeres; Pif1 and Exo1 resect telomeric DNA <5 kb from the chromosome end, stimulating weak checkpoint activation; resection is extended >5 kb by Exo1 and full checkpoint activation occurs. Cdc13 is also crucial for telomerase recruitment. However, cells lacking Cdc13, Pif1 and Exo1, do not senesce and maintain their telomeres in a manner dependent upon telomerase, Ku and homologous recombination. Thus, attenuation of the DDR at uncapped telomeres can circumvent the need for otherwise-essential telomere capping proteins.     

Fruit and seed heteromorphism in the cold desert annual ephemeral Diptychocarpus strictus (Brassicaceae) and possible adaptive significance

Background and Aims

Diptychocarpus strictus is an annual ephemeral in the cold desert of northwest China that produces heteromorphic fruits and seeds. The primary aims of this study were to characterize the morphology and anatomy of fruits and seeds of this species and compare the role of fruit and seed hetermorphism in dispersal and germination.

Methods

Shape, size, mass and dispersal of siliques and seeds and the thickness of the mucilage layer on seeds were measured, and the anatomy of siliques and seeds, the role of seed mucilage in water absorption/dehydration, germination and adherence of seeds to soil particles, the role of pericarp of lower siliques in seed dormancy and seed after-ripening and germination phenology were studied using standard procedures.

Key Results

Plants produce dehiscent upper siliques with a thin pericarp containing seeds with large wings and a thick mucilage layer and indehiscent lower siliques with a thick pericarp containing nearly wingless seeds with a thin mucilage layer. The dispersal ability of seeds from the upper siliques was much greater than that of intact lower siliques. Mucilage increased the amount of water absorbed by seeds and decreased the rate of dehydration. Seeds with a thick mucilage layer adhered to soil particles much better than those with a thin mucilage layer or those from which mucilage had been removed. Fresh seeds were physiologically dormant and after-ripened during summer. Non-dormant seeds germinated to high percentages in light and in darkness. Germination of seeds from upper siliques is delayed until spring primarily by drought in summer and autumn, whereas the thick, indehiscent pericarp prevents germination for >1 year of seeds retained in lower siliques.

Conclusions

The life cycle of D. strictus is morphologically and physiologically adapted to the cold desert environment in time and space via a combination of characters associated with fruit and seed heteromorphism.