Delineating the relationship between immune system aging and myogenesis in muscle repair

Recruited immune cells play a critical role in muscle repair, in part by interacting with local stem cell populations to regulate muscle regeneration. How aging affects their communication during myogenesis is unclear. Here, we investigate how aging impacts the cellular function of these two cell types after muscle injury during normal aging or after immune rejuvenation using a young to old (Y‐O) or old to old (O‐O) bone marrow (BM) transplant model. We found that skeletal muscle from old mice (20 months) exhibited elevated basal inflammation and possessed fewer satellite cells compared with young mice (3 months). After cardiotoxin muscle injury (CTX), old mice exhibited a blunted inflammatory response compared with young mice and enhanced M2 macrophage recruitment and IL‐10 expression. Temporal immune and cytokine responses of old mice were partially restored to a young phenotype following reconstitution with young cells (Y‐O chimeras). Improved immune responses in Y‐O chimeras were associated with greater satellite cell proliferation compared with O‐O chimeras. To identify how immune cell aging affects myoblast function, conditioned media (CM) from activated young or old macrophages was applied to cultured C2C12 myoblasts. CM from young macrophages inhibited myogenesis while CM from old macrophages reduced proliferation. These functional differences coincided with age‐related differences in macrophage cytokine expression. Together, this study examines the infiltration and proliferation of immune cells and satellite cells after injury in the context of aging and, using BM chimeras, demonstrates that young immune cells retain cell autonomy in an old host to increase satellite cell proliferation.     

Chemical modification of lysine residues in lysozyme may dramatically influence its amyloid fibrillation

Studies on the aggregation of mutant proteins have provided new insights into the genetics of amyloid diseases and the role of the net charge of the protein on the rate, extent, and type of aggregate formation. In the present work, hen egg white lysozyme (HEWL) was employed as the model protein. Acetylation and (separately) citraconylation were employed to neutralize the charge on lysine residues. Acetylation of the lysine residues promoted amyloid formation, resulting in more pronounced fibrils and a dramatic decline in the nucleation time. In contrast, citraconylation produced the opposite effect. In both cases, native secondary and tertiary structures appeared to be retained. Studies on the effect of pH on aggregation suggested greater possibilities for amorphous aggregate formation rather than fibrillation at pH values closer to neutrality, in which the protein is known to take up a conformation more similar to its native form. This is in accord with reports in the literature suggesting that formation of amorphous aggregates is more favored under relatively more native conditions. pH 5 provided a critical environment in which a mixture of amorphous and fibrillar structures were observed. Use of Tango and Aggrescan software which describe aggregation tendencies of different parts of a protein structure suggested critical importance of some of the lysine residues in the aggregation process. Results are discussed in terms of the importance of the net charge in control of protein–protein interactions leading to aggregate formation and possible specific roles of lysine residues 96 and 97.     

Olfactory response of predatory mite Phytoseiulus persimilis to synthetic methyl salicylate

We studied the role of methyl salicylate as an important part of volatile blends in searching behaviour of the predatory mite, Phytoseiulus persimilis (Athias-Henriot). We showed that Methyl Salicylate (MeSa) attracted the predatory mites (1 h starved) in a dose range of 0.02–20?μg. The highest attraction was recorded at the dose of 0.2?μg. The dose of 0.002?μg was considered under the detection level of the predator. P. persimilis could not detect the extra amount of MeSa (100 and 200?μg). The probable effect of starvation period on the predator response is discussed.     

Sperm biology and control of reproduction in sturgeon: (II) sperm morphology, acrosome reaction, motility and cryopreservation

In the present review, sperm morphology, acrosome reaction, motility, short-term storage and cryopreservation are summarized and discussed in sturgeon (Chondrostei, Acipenseriformes). The elongated head of spermatozoon comprises an acrosome with 8?C12 posterolateral projections. Usually three endonuclear canals are observed in the nucleus. Proximal and distal centrioles and 3?C6 mitochondria are located in the midpiece region. The flagellum consists of an axoneme with a typical ??9?+?2?? structure of microtubules and presents a ribon-like structure due to two lateral membranous fins. Egg water, Ca²⁺ and Mg²⁺ can trigger acrosome reaction. Trypsin- and chymotrypsin-like activities are reported in sturgeon sperm. These physiological properties of sturgeon sperm are identified as serine activity with 33?kDa molecular mass and can be inhibited by their respective inhibitors. The K⁺ prevents sperm activation in seminal plasma, and hypo-osmolality or decrease of extracellular K⁺ triggers sperm activation. Extracellular Ca²⁺ is involved in flagellar beating pattern and sperm velocity. After activation, sperm motility, velocity, and flagellar beating frequency, wavelength and amplitude decrease, while number of waves and curvature increase. Sturgeon sperm can be stored for several days at 4?°C; however it is better to add K⁺ into the immobilizing medium because it prevents sperm activation during incubation. Regarding sperm cryopreservation, methanol is a better cryoprotectant than DMSO. Either short-term storage or cryopreservation of sperm generates damage to spermatozoa that lead to reduction of sperm motility performance. Some studies suggest using an activation medium containing Ca²⁺ for enhancing sperm motility performance of incubated or frozen-thawed sperm.     

Bacterial inoculation speeds zinc release from ground tire rubber used as Zn fertilizer for corn and sunflower in a calcareous soil

Background and Aims

We tested the utility of some biological treatments to hasten degradation of waste tire rubber in soil and thus the release of zinc and sulfur for plant uptake.

Methods

Three rates of ground tire rubber (0, 150, and 300?mg?kg^?1) were incorporated into a Zn-deficient calcareous soil. Before addition to the soil, ground rubber was given four microbial treatments including no inoculation, inoculation with Rhodococcus erythropolis, inoculation with R. erythropolis+Escherichia coli, and inoculation with R. erythropolis+E. coli+Acinobacter calcoaceticus. In the pot experiment, corn (Zea mays L. Hybrid Single Cross 500) and sunflower (Helianthus annuus L. cv. Record) plants were exposed to three rates of ground rubber (0, 150, and 300?mg?kg^?1) or 3?mg zinc kg^?1 as ZnSO₄. Before addition to the soil, ground rubber and ZnSO₄ were inoculated or non-inoculated with R. erythropolis+E. coli+A. calcoaceticus.

Results

Ground rubber and microbial inoculation treatments reduced soil pH and the magnitude of this reduction increased over time. Ground rubber in combination with microbial inoculation increased DTPA-extractable soil Zn and Fe. The amount of DTPA-extractable Zn and Fe of rubber-amended soils increased over time so that the highest concentration of available Zn and Fe was found at week 10. Application of microbial inoculated ground tire rubber significantly increased shoot Zn concentration of each plant species.

Conclusions

Bacterial inoculation of ground rubber was effective in hastening increase in DTPA-extractable Zn in the studied calcareous soil and in enhancing Zn uptake by plants.     

Connexin 43 phosphorylation and degradation are required for adipogenesis

Connexin-43 (Cx43) is a membrane phosphoprotein that mediates direct inter-cellular communication by forming gap junctions. In this way Cx43 can influence gene expression, differentiation and growth. Its role in adipogenesis, however, is poorly understood. In this study, we established that Cx43 becomes highly phosphorylated in early adipocyte differentiation and translocates to the plasma membrane from the endoplasmic reticulum. As preadipocytes differentiate, Cx43 phosphorylation declines, the protein is displaced from the plasma membrane, and total cellular levels are reduced via proteosomal degradation. Notably, we show that inhibiting Cx43 degradation or constitutively over-expressing Cx43 blocks adipocyte differentiation. These data reveal that transient activation of Cx43 via phosphorylation followed by its degradation is vital for preadipocyte differentiation and maturation of functional adipocytes.     

Systematic discovery of pseudomonad genetic factors involved in sensitivity to tailocins

Tailocins are bactericidal protein complexes produced by a wide variety of bacteria that kill closely related strains and may play a role in microbial community structure. Thanks to their high specificity, tailocins have been proposed as precision antibacterial agents for therapeutic applications. Compared to tailed phages, with whom they share an evolutionary and morphological relationship, bacterially produced tailocins kill their host upon production but producing strains display resistance to self-intoxication. Though lipopolysaccharide (LPS) has been shown to act as a receptor for tailocins, the breadth of factors involved in tailocin sensitivity, and the mechanisms behind resistance to self-intoxication, remain unclear. Here, we employed genome-wide screens in four non-model pseudomonads to identify mutants with altered fitness in the presence of tailocins produced by closely related pseudomonads. Our mutant screens identified O-antigen composition and display as most important in defining sensitivity to our tailocins. In addition, the screens suggest LPS thinning as a mechanism by which resistant strains can become more sensitive to tailocins. We validate many of these novel findings, and extend these observations of tailocin sensitivity to 130 genome-sequenced pseudomonads. This work offers insights into tailocin–bacteria interactions, informing the potential use of tailocins in microbiome manipulation and antibacterial therapy.Subject terms: Functional genomics, Microbial ecology, Bacterial genetics, Soil microbiology     

Cannabinoids and Their Interactions with Diazepam on Modulation of Serum Corticosterone Concentration in Male Mice

Experimental results indicate a mutual interaction between cannabinoidergic and GABAergic systems; however, the interaction between these systems on corticosterone release has not been fully investigated. In this study, we treated male mice with either cannabinoid compounds alone or in combination with diazepam. Blood samples were collected at 60 min post-injection. The serum corticosterone (CORT) level was measured using ELISA technique. Acute treatment of mice by cannabinoid receptor agonist WIN55212-2 (2.5 mg/kg; i.p.) resulted in a significant reduction of CORT, while treatment with either endocannabinoid reuptake inhibitor AM404 or endocannabinoid degradation enzyme inhibitor URB597 increased CORT compared to control group. Co-administration of AM404 or URB597 with cannabinoid CB1 receptor antagonist AM251 blocked the effect of these compounds on CORT. Treatment of mice with different doses of diazepam alone did not alter CORT compared to control group. However, co-administration of diazepam and either AM404 or WIN55212-2 significantly reduced CORT compared to the respective group treated with cannabinoid compound alone. Co-administration of ineffective dose of URB597 and ineffective dose of diazepam increased CORT level compared to groups treated with each compound alone. In conclusion, our findings suggest that the endogenous cannabinoid system is active as a modulator of CORT in mice and diazepam can alter the effect of cannabinoid system in the modulation of neuroendocrine functions.     

Structural and enzymatic characterization of a glycoside hydrolase family 31 α-xylosidase from Cellvibrio japonicus involved in xyloglucan saccharification

The desire for improved methods of biomass conversion into fuels and feedstocks has re-awakened interest in the enzymology of plant cell wall degradation. The complex polysaccharide xyloglucan is abundant in plant matter, where it may account for up to 20% of the total primary cell wall carbohydrates. Despite this, few studies have focused on xyloglucan saccharification, which requires a consortium of enzymes including endo-xyloglucanases, α-xylosidases, β-galactosidases and α-L-fucosidases, among others. In the present paper, we show the characterization of Xyl31A, a key α-xylosidase in xyloglucan utilization by the model Gram-negative soil saprophyte Cellvibrio japonicus. CjXyl31A exhibits high regiospecificity for the hydrolysis of XGOs (xylogluco-oligosaccharides), with a particular preference for longer substrates. Crystallographic structures of both the apo enzyme and the trapped covalent 5-fluoro-β-xylosyl-enzyme intermediate, together with docking studies with the XXXG heptasaccharide, revealed, for the first time in GH31 (glycoside hydrolase family 31), the importance of a PA14 domain insert in the recognition of longer oligosaccharides by extension of the active-site pocket. The observation that CjXyl31A was localized to the outer membrane provided support for a biological model of xyloglucan utilization by C. japonicus, in which XGOs generated by the action of a secreted endo-xyloglucanase are ultimately degraded in close proximity to the cell surface. Moreover, the present study diversifies the toolbox of glycosidases for the specific modification and saccharification of cell wall polymers for biotechnological applications.