The α7β1-integrin accelerates fiber hypertrophy and myogenesis following a single bout of eccentric exercise

The α(7)β(1)-integrin is a heterodimeric transmembrane protein that adheres to laminin in the extracellular matrix, representing a critical link that maintains structure in skeletal muscle. In addition to preventing exercise-induced skeletal muscle injury, the α(7)-integrin has been proposed to act as an intrinsic mechanosensor, initiating cellular growth in response to mechanical strain. The purpose of this study was to determine the extent to which the α(7)-integrin regulates muscle hypertrophy following eccentric exercise. Wild-type (WT) and α(7)-integrin transgenic (α(7)Tg) mice completed a single bout of downhill running exercise (-20°, 17 m/min, 60 min), and gastrocnemius-soleus complexes were collected 1, 2, 4, and 7 days (D) postexercise (PE). Maximal isometric force was maintained and macrophage accumulation was suppressed in α(7)Tg muscle 1D PE. Mean fiber cross-sectional area was unaltered in WT mice but increased 40% in α(7)Tg mice 7D PE. In addition, a rapid and striking fivefold increase in embryonic myosin heavy chain-positive fibers appeared in α(7)Tg mice 2D PE. Although Pax7-positive satellite cells were increased in α(7)Tg muscle 1D PE, the number of nuclei per myofiber was not altered 7D PE. Phosphorylation of mammalian target of rapamycin (mTOR) was significantly elevated in α(7)Tg 1D PE. This study provides the first demonstration that the presence of the α(7)β(1)-integrin in skeletal muscle increases fiber hypertrophy and new fiber synthesis in the early time course following a single bout of eccentric exercise. Further studies are necessary to elucidate the precise mechanism by which the α(7)-integrin can enhance muscle hypertrophy following exercise.     

Effect of Halide Ions on t-[35S]Butylbicyclophosphorothionate Binding

The binding of t-[35S]butylbicyclophosphorothionate [( 35S]TBPS) to a site on the GABAA receptor complex is ion dependent. This study was conducted to determine the effects of ion species and concentration on the time course, affinity, and number of sites of [35S]TBPS binding. At a concentration of 200 mM ion, the time to equilibrium for [35S]TBPS binding was shortest for I-, followed by Br- less than Cl- less than F-. A similar rank order was observed for the concentration of ion required to produce half-maximal [35S]TBPS binding. Saturation binding experiments were conducted to evaluate the effect of increasing ion concentration on the KD and Bmax of [35S]TBPS binding. The Bmax was independent of both ion species and concentration. The receptor affinity, however, increased with increasing concentration for each ion. Calculated maximal affinity values were not different between ions; however, the EC50 to produce those values was different among ions and ranked in the same order as that for time course and maximal binding data. Association and dissociation rates for [35S]TBPS binding were greater in I- than in Cl-. These data emphasize the importance of ion selection and incubation times on [35S]TBPS binding.     

Isolation and characterization of an extracellular lipase from Mucor sp strain isolated from palm fruit

During our screening of lipolytic fungus which may play a role in the acidification of palm oil, we have recently isolated a Mucor sp strain. Culture conditions were optimized and the highest lipase production amounting to 57 U/ml was achieved after 6 days of cultivation. The extracellular lipase was purified 1050-fold by ammonium sulfate precipitation, carboxymethyl–sephadex chromatography and Sephadex G75 gel filtration to a final specific activity of 6600 IU/mg. The molecular weight of the homogenous lipase was determined about 42 kDa by gel filtration and SDS–polyacrylamide gel electrophoresis. The purified lipase was determined as a glycoprotein with a pI of 6.2. The Nt sequence was determined as AspGluIleGluThrValGlyXPheThrMetAspLeuProProAsnProPro and showed no homology with the sequences of the known lipases suggesting that the enzyme may be a new lipase. The purified lipase hydrolyzed both synthetic and natural triglycerides with the optimal activity recorded on trioctanoin and sunflower oil, respectively. Its activity was strongly inhibited by Triton X-100 and SDS. Metal ions such as Fe³⁺, Fe²⁺ and Hg²⁺ also decreased the lipase activity.     

Solid Phase Synthesis of Mitochondrial Triphenylphosphonium-Vitamin E Metabolite Using a Lysine Linker for Reversal of Oxidative Stress

Mitochondrial targeting of antioxidants has been an area of interest due to the mitochondria''s role in producing and metabolizing reactive oxygen species. Antioxidants, especially vitamin E (α-tocopherol), have been conjugated to lipophilic cations to increase their mitochondrial targeting. Synthetic vitamin E analogues have also been produced as an alternative to α-tocopherol. In this paper, we investigated the mitochondrial targeting of a vitamin E metabolite, 2,5,7,8-tetramethyl-2-(2′-carboxyethyl)-6-hydroxychroman (α-CEHC), which is similar in structure to vitamin E analogues. We report a fast and efficient method to conjugate the water-soluble metabolite, α-CEHC, to triphenylphosphonium cation via a lysine linker using solid phase synthesis. The efficacy of the final product (MitoCEHC) to lower oxidative stress was tested in bovine aortic endothelial cells. In addition the ability of MitoCEHC to target the mitochondria was examined in type 2 diabetes db/db mice. The results showed mitochondrial accumulation in vivo and oxidative stress decrease in vitro.     

Segregation analysis indicates a major gene in the control of interleukine-5 production in humans infected with Schistosoma mansoni.

The interleukine-5 (IL-5) is a hormone of the immune system that is the main regulator of eosinopoiesis, eosinophil maturation and activation, and immunoglobulin A production. Thus, IL-5 contributes in several ways to human immune defenses against various pathogens, including helminths and infectious agents of the digestive and respiratory tracts. On the other hand, the increase in eosinophil number and the activation of these cells, which both have been related to elevated IL-5 production, are the cause of severe pathological disorders, as in asthma or hypereosinophilic syndromes. Although the immunological pathways leading to IL-5 synthesis have been identified, the reasons for the large variability observed in IL-5 production among subjects exposed to comparable antigenic stimulation are unknown. To investigate the role of genetic factors in this variability, we conducted a segregation analysis in a Brazilian population infected by the helminth parasite Schistosoma mansoni. The analysis was performed on IL-5 levels produced by blood mononuclear cells of these subjects after in vitro restimulation with either parasite extracts (IL-5/schistosomula sonicates [SS] phenotype) or a T-lymphocyte mitogen (IL-5/phytohemagglutin [PHA]). The results provide clear evidence for the segregation of a codominant major gene controlling IL-5/SS and IL-5/PHA production and accounting for 70% and 73% of the phenotypic variance, respectively; the frequency of the allele predisposing to low IL-5 production was approximately .22 for both phenotypes. No significant relationship was found between these genes and the gene controlling infection intensities by S. mansoni detected in a previous study. Linkage studies are ongoing to locate those genes that would help to characterize the genetic factors involved in pathological conditions such as severe helminth infections and allergic diseases.     

The adaptive acid response in Mesorhizobium sp.

Mesorhizobium huakuii strain LL56 and Mesorhizobium sp. strain LL22, which nodulate Lotus glaber, developed an adaptive acid response during exponential growth upon exposure to sublethal acid conditions. The adaptive acid response was found to be dependent on the sublethal pH and the strain intrinsic acid tolerance: the lowest adaptation pH was 4.0 for strain LL56 and 5.7 for strain LL22, and the lowest pH values tolerated after adaptation were 3.0 and 4.0, respectively. Both complex and minimal medium allowed the development of the adaptive acid response, although in complex medium this response was more effective. Three low molecular weight polypeptides (LMWPs) showed increased expression in strain LL56 during the adaptation to pH 4.0. However, the adaptive acid tolerance was only partially dependent on de novo protein synthesis, and constitutive systems may play a significant role on the acid tolerance of Mesorhizobium huakuii strain LL56.     

Luteinizing hormone,progesterone and the morphological development of normal and superovulated corpora lutea in sheep

The development of granulosa-lutein cells was studied in 27 normal and 32 superovulated ewes between days 0-4(day 0 began with the preovulatory LH peak in normal animals and the HCG injection in superovulated ewes). The pattern of differentiation was similar in both groups. Following initial hormonal stimulation (0-12 hours after LH or HCG), granulosa cells were approximately 100 mu2 and contained small, pleomorphic nuclei with large amounts of clumped chromatin. Elongate cells lining the basement membrane possessed large, heterogeneous dense bodies, and a well-developed Golgi apparatus. Mitotic figures were observed up to 6 hours prior to ovulation. Sixteen to 20 hours following the LH surge or HCG injection, hypertrophy of granulosa cells was evident. Nuclei contained definitive nucleoli. Blood vessels in the theca interna were abundant and highly dilated. Ovulation occurred approximately 24 hours after the LH peak or HCG injection. Visible signs of luteinization were evident 6-12 hours after ovulation. A slight increase in serum progesterone levels was detected. The second post-ovulatory day was characterized by continuing hypertrophy of granulosa cells and extensive proliferation of smooth endoplasmic reticulum and mitochondria. Nuclei of granulosa cells were larger and possessed extremely large nucleoli. Numerous mitotic figures were apparent within the corpus luteum. Serum progesterone concentrations began increasing at 60-72 hours after hormone stimulation. By the end of the third post-ovulatory day, the corpus luteum consisted of large, pleomorphic, parenchymal cells, interspersed between capillaries and connective tissue elements. Only an occasional mitotic figure was apparent within the corpus luteum at 100 hours. Light microscopic autoradiography of 5, 10, and 15 day corpora lutea taken from ewes pulsed with 3H thymidine at specific times before and after ovulation revealed that granulosa cells did not undergo secondary mitoses following ovulation. In contrast, thecal, mesenchymal and endothelial cells did mitose on day 3.     

Mating‐Associated Changes in the Behaviour of Leptothorax gredleri Ant Queens

Throughout their lives, animals adapt their behaviour to environmental fluctuations and to their own requirements. In social insects, behavioural changes are often particularly conspicuous. For example, in many ant species, reproductive sexuals leave their maternal nests and engage in risky mating and dispersal activities. Female sexuals experience, during a short period of time, dramatic changes in terms of behaviour and environmental conditions. But because sexual activities of ants are not easily observed, few studies have quantified in detail how behaviour alters with maturation and mating. We studied how various behavioural traits of Leptothorax gredleri female sexuals, a species in which female sexuals attract males by ‘female calling’, change before and after mating. We tested the hypothesis that behavioural variation reflects the altered requirements of queens to adapt to a particular situation. To this end, we compared geotactic, phototactic and locomotor behaviour across a wide range of life stages from lightly coloured, unmated female sexuals to old, mated queens. The results showed that female sexuals of L. gredleri change conspicuously their geotactic, phototactic and locomotor behavioural traits over their life stages. Three different behavioural states were evident (1) from light to dark female sexuals, individuals have negative phototaxis and reduced locomotor activity; (2) mature female sexuals during the daily period of sexual activity have strong phototaxis, negative geotaxis and an important locomotor activity; and (3) freshly mated and old mated queens avoid light and decrease their locomotor activity. These sharp differences in behaviour between stages match the transition from the relative safety of the nest chamber to the adversary world outside the nest , and back.