Altered proteasome function and subunit composition in aged muscle

Myofibrillar protein degradation is mediated through the ubiquitin-proteasome pathway. To investigate if altered proteasome activity plays a role in age-related muscle atrophy, we examined muscle size and proteasome function in young and aged F344BN rats. Significant age-related muscle atrophy was confirmed by the 38% decrease in cross-sectional area of type 1 fibers in soleus muscle. Determination of proteasome function showed hydrolysis of fluorogenic peptides was equivalent between ages. However, when accounting for the 3-fold increase in content of the 20S catalytic core in aged muscle, the lower specific activity suggests a functional loss in individual proteins with aging. Comparing the composition of the catalytic beta-subunits showed an age-related 4-fold increase in the cytokine-inducible subunits, LMP2 and LMP7. Additionally, the content of the activating complexes, PA28 and PA700, relative to the 20S proteasome was reduced 50%. These results suggest significant alterations in the intrinsic activity, the percentage of immunoproteasome, and the regulation of the 20S proteasome by PA28 and PA700 in aged muscle.     

Cellular redox activity of coenzyme Q10: effect of CoQ10 supplementation on human skeletal muscle

In this paper, we report results obtained from a continuing clinical trial on the effect of coenzyme Q 10 (CoQ 10 ) administration on human vastus lateralis (quadriceps) skeletal muscle. Muscle samples, obtained from aged individuals receiving placebo or CoQ 10 supplementation (300 mg per day for four weeks prior to hip replacement surgery) were analysed for changes in gene and protein expression and in muscle fibre type composition. Microarray analysis (Affymetrix U95A human oligonucleotide array) using a change in gene expression of 1.8-fold or greater as a cutoff point, demonstrated that a total of 115 genes were differentially expressed in six subject comparisons. In the CoQ 10 -treated subjects, 47 genes were up-regulated and 68 down-regulated in comparison with placebo-treated subjects. Restriction fragment differential display analysis showed that over 600 fragments were differentially expressed using a 2.0-fold or greater change in expression as a cutoff point. Proteome analysis revealed that, of the high abundance muscle proteins detected (2086 ±115), the expression of 174 proteins was induced by CoQ 10 while 77 proteins were repressed by CoQ 10 supplementation. Muscle fibre types were also affected by CoQ 10 treatment; CoQ 10 -treated individuals showed a lower proportion of type I (slow twitch) fibres and a higher proportion of type IIb (fast twitch) fibres, compared to age-matched placebo-treated subjects. The data suggests that CoQ 10 treatment can act to influence the fibre type composition towards the fibre type profile generally found in younger individuals. Our results led us to the conclusion that coenzyme Q 10 is a gene regulator and consequently has wide-ranging effects on over-all tissue metabolism. We develop a comprehensive hypothesis that CoQ 10 plays a major role in the determination of membrane potential of many, if not all, sub-cellular membrane systems and that H 2 O 2 arising from the activities of CoQ 10 acts as a second messenger for the modulation of gene expression and cellular metabolism.     

Regulation and dysregulation of fibrosis in skeletal muscle

In response to skeletal muscle injury, distinct cellular pathways are activated to repair the damaged tissue. Activation and restriction of these pathways must be temporally coordinated in a precise sequence as regeneration progresses if muscle integrity and homeostasis are to be restored. However, if tissue injury persists, as in severe muscular dystrophies, the repair process becomes uncontrolled leading to the substitution of myofibers by a non-functional mass of fibrotic tissue. In this review, we provide an overview of how muscle responds to damage and aging, with special emphasis on the cellular effectors and the regulatory and inflammatory pathways that can shift normal muscle repair to fibrosis development.     

按摩对兔骨骼肌损伤修复自由基相关酶的活性的影响

目的通过检测按摩对兔骨骼肌钝挫伤修复过程中谷胱甘肽过氧化物酶(GSH-Px)、髓过氧化物酶(MPO)活力值,及细胞磷脂酶A2(PLA2)mRNA表达的影响,探讨按摩加快清除肌肉损伤修复过程中自由基的作用机制。方法选取新西兰大白兔42只,随机分为4组,即正常对照组(A组,n=3)、损伤组(B组,n=3)、按摩组(C组,n=18,包括损伤后第5d和第10d各9只)和自然恢复组(D组,n=18,包括损伤后第5d和第10d各9只)。A组实验兔不作处理,作为正常对照;B、C、D组实验动物用自制打击器来制备兔左后肢股四头肌损伤模型。C组于造模后第4天用按摩器施以按摩治疗,1次/天至处死取材;B、D组不进行按摩。各组于伤后5d及10d活体心脏取血,用于进行生化指标检测GSH-Px和MPO的活力值;取股四头肌样本,进行HE染色和实时荧光定量PCR法检测PLA2mRNA的相对表达量,并同A组正常股四头肌检测结果进行比较。结果正常组、损伤组、伤后5d及10d按摩组和自然恢复组的GSH-Px和MPO活力值经比较,按摩组较自然恢复组明显减少(P0.05);经按摩干预后,各组的PLA2mRNA表达量也显示,按摩组明显比自然恢复组减少(P0.05)。结论按摩可促进兔股四头肌损伤的修复过程,其机制可能是按摩能够通过加快清除损伤后自由基的产生,使中性粒细胞浸润减少,降低PLA2活性来保护细胞结构完整性,减轻疼痛。     

Effect of age on acetylcholinesterase and other hemolymph proteins in Aplysia

Summary Hemolymph was examined in young (ca. 86 days old), mature (ca. 163 days old), and old (ca. 294 days old) Aplysia for age-related changes in constituent proteins. In young, mature, and old animals protein concentrations were 1.6±0.27, 1.41±0.53, and 1.45±0.43 mg·ml^-1, respectively. The copper-containing respiratory protein, hemocyanin, measured by determining the copper concentration, was found to increase significantly from young (0.98±0.51 g·ml^-1) to mature (2.02±0.95 g·ml^-1) Aplysia, with little change between mature and old (1.92±0.43 g·ml^-1) animals. These findings were consistent with the results obtained when hemocyanin was directly measured by spectrophotometric absorption at 340 nm. Acetylcholinesterase (AChE) was present in the hemolymph of Aplysia. Its activity was highest in mature animals (3121±1627 units·mg^-1) and least in old animals (1463±599 units·mg^-1). Young animals had intermediate levels (2080±762 units·mg^-1). SDS-PAGE revealed a distinct pattern of protein bands for hemolymph from each age group; hemolymph from the young group contained six prominent protein bands with molecular weights (MW) from 13 to 300 kDa. Hemolymph of mature and old animals exhibited four and three prominent protein bands, respectively, with MW between 45 and 300 kDa. A prominent band at 97 kDa was present in samples from the mature group, but was faint in samples from the old group and absent in samples from the young group. Under non-denaturing conditions the hemolymph protein band patterns for each group differed from the others, thereby demonstrating that the age-dependent differences in the protein profiles are intrinsic to hemolymph in vivo. Isoelectric focusing of the hemolymph samples revealed that the proteins were all acidic (pI ca. 3.0–6.5). The hemolymph from the young differed from the other two groups in having an additional acidic protein (pI ca. 4.0). A possible link between age-related changes in hemolymph proteins and age-related changes in the nervous system is proposed.Abbreviations 2-ME 2-mercaptoethanol - AChE acetylcholinesterase - FMRFamide amidated tetrapeptide containing phenylalanine, methionine, arginine and phenylalanine - MW molecular weight - PAS periodic acid-Schiff - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - TRIS tris-(hydroxymethyl)-aminomethane     

Effect of deuterium oxide on contraction characteristics and ATPase activity in glycerinated single rabbit skeletal muscle fibers

We studied the effect of deuterium oxide (D₂O) on contraction characteristics and ATPase activity of single glycerinated muscle fibers of rabbit psoas. D₂O increased the maximum isometric force P₀ by about 20%, while the force versus stiffness relation did not change appreciably. The maximum shortening velocity under zero load V_max did not change appreciably in D₂O, so that the force-velocity (P-V) curve was scaled depending on the value of P₀. The Mg-ATPase activity of the fibers during generation of steady isometric force P₀ was reduced by about 50% in D₂O. Based on the Huxley contraction model, these results can be accounted for in terms of D₂O-induced changes in the rate constants f₁ and g₁ for making and breaking actin-myosin linkages in the isometric condition, in such a way that f₁/(f₁+g₁) increases by about 20%, while (f₁+g₁) remains unchanged. The D₂O effect at the molecular level is discussed in connection with biochemical studies on actomyosin ATPase.     

Effect of Simulated Acid Rain on Bursaphelenchus xylophilus Infection of Pine Seedlings

White, Scots, and Austrian 3-year-old pine seedlings were treated with conditions simulating acid rain and inoculated with the white pine specific pathotype of Bursaphelenchus xylophilus, VPSt-1. Oleoresin concentration increased slightly and carbohydrate concentration decreased in all seedlings treated with simulated acid rain (SAR). The changes were significantly increased after inoculation of SAR-treated white and Scots pine seedlings with VPSt-1. Wilting was delayed and nematode reproduction decreased in SAR-treated white pine seedlings inoculated with VPSt-1. SAR-treated Austrian pine seedlings were resistant to VPSt-1, but SAR-treated Scots pine seedlings lost tolerance to VPSt-1 and wilted 50-60 days after inoculation.     

Prevention of congenital Chagas through treatment of girls and women of childbearing age

It is currently unknown whether treatment of Chagas disease decreases the risk ofcongenital transmission from previously treated mothers to their infants. In a cohortof women with Chagas disease previously treated with benznidazole, no congenitaltransmission of the disease was observed in their newborns. This finding providessupport for the treatment of Chagas disease as early as possible.     

Effect of Temperature on Growth, Development and Reproduction of Meloidogyne hapla in Lettuce

Temperature was an important factor in growth, development and reproduction of Meloidogyne hapla in lettuce. Growth, as measured by increase in diameter of females, was not appreciably different at the intermediate (21.1 C night and 26.7 C day) and high (26.7 C night and 32.2 C day) temperature regimes, but was considerably less at the low temperature regime (15.5 C night and 21.1 C day) than at the two higher temperature regimes. Second-stage female larvae developed into adults 14 days after inoculation at the high, 18 days at the intermediate and 34 days at the low temperature regime. Eggs were observed 20 days after inoculation at the high, 26 days at the intermediate and 54 days at the low temperature regime. Number of eggs and larvae after 6 weeks was greater at the high than at the intermediate temperature regime and no eggs or larvae occurred at the low temperature regime during the observed 6 weeks.     

IP3 receptor blockade restores autophagy and mitochondrial function in skeletal muscle fibers of dystrophic mice

Duchenne muscular dystrophy (DMD) is characterized by a severe and progressive destruction of muscle fibers associated with altered Ca²⁺ homeostasis. We have previously shown that the IP₃ receptor (IP₃R) plays a role in elevating basal cytoplasmic Ca²⁺ and that pharmacological blockade of IP₃R restores muscle function. Moreover, we have shown that the IP₃R pathway negatively regulates autophagy by controlling mitochondrial Ca²⁺ levels. Nevertheless, it remains unclear whether IP₃R is involved in abnormal mitochondrial Ca²⁺ levels, mitochondrial dynamics, or autophagy and mitophagy observed in adult DMD skeletal muscle. Here, we show that the elevated basal autophagy and autophagic flux levels were normalized when IP₃R was downregulated in mdx fibers. Pharmacological blockade of IP₃R in mdx fibers restored both increased mitochondrial Ca²⁺ levels and mitochondrial membrane potential under resting conditions. Interestingly, mdx mitochondria changed from a fission to an elongated state after IP₃R knockdown, and the elevated mitophagy levels in mdx fibers were normalized. To our knowledge, this is the first study associating IP₃R1 activity with changes in autophagy, mitochondrial Ca²⁺ levels, mitochondrial membrane potential, mitochondrial dynamics, and mitophagy in adult mouse skeletal muscle. Moreover, these results suggest that increased IP₃R activity in mdx fibers plays an important role in the pathophysiology of DMD. Overall, these results lead us to propose the use of specific IP₃R blockers as a new pharmacological treatment for DMD, given their ability to restore both autophagy/mitophagy and mitochondrial function.     

Effect of Membrane Tension on Gap Junctional Conductance of Supporting Cells in Corti's Organ

The effects of turgor pressure-induced membrane tension on junctional coupling of Hensen cell isolates from the inner ear were evaluated by input capacitance or transjunctional conductance measurement techniques. Turgor pressure was altered by changing either pipette pressure or the osmolarities of extracellular solutions. Both positive pipette pressure and extracellular applications of hypotonic solutions, which caused cell size to concomitantly increase, uncoupled the cells as indicated by reduced input capacitance and transjunctional conductance. These changes were, in many cases, reversible and repeatable. Intracellular application of 50 μM H-7, a broad-based protein kinase inhibitor, and 10 mM BAPTA did not block the uncoupling effect of positive turgor pressure on inner ear gap junctions. The transjunctional conductance at a holding potential of −80 mV was 53.6 ± 5.8 nS (mean ± SEM, n = 9) and decreased ∼40% at a turgor pressure of 1.41 ± 0.05 kPa. Considering the coincident kinetics of cell deformation and uncoupling, we speculate that mechanical forces work directly on gap junctions of the inner ear. These results suggest that pathologies that induce imbalances in cochlear osmotic pressure regulation may compromise normal cochlear homeostasis.     

Effect of antioxidant vitamin supplementation on muscle function after eccentric exercise

This study investigated the effects of antioxidant vitamin supplementation upon muscle contractile function following eccentric exercise and was performed double blind. Twenty-four physically active young subjects ingested either placebo (400 mg; n = 8), vitamin E (400 mg; n=8) or vitamin C (400 mg; n = 8) for 21 days prior to and for 7 days after performing 60 min of box-stepping exercise. Contractile function of the triceps surae was assessed by the measurement of maximal voluntary contraction (MVC) and the ratio of the force generated at 20 Hz and 50 Hz tetanic stimulation before and after eccentric exercise and for 7 days during recovery. Following eccentric exercise, MVC decreased to 75 (4) % [mean (SE); n = 24; P < 0.05] of the preexercise values and the 20/50 Hz ratio of tetanic tension from 0.76 (0.01) to 0.49 (0.03) [mean (SE); n = 24; P<0.05). Compared to the placebo group no significant changes in MVC were observed immediately post-exercise, though recovery of MVC in the first 24 h post-exercise was greater in the group supplemented with vitamin C. The decrease in 20/50 Hz ratio of tetanic tension was significantly less (P < 0.05) post-exercise and in the initial phase of recovery in subjects supplemented with vitamin C but not with vitamin E. These data suggest that prior vitamin C supplementation may exert a protective effect against eccentric exercise-induced muscle damage.     

Effect of electrical stimulation-induced muscle force and streptomycin treatment on muscle and trabecular bone mass in early-stage disuse musculoskeletal atrophy

Objectives:

The aim was to determine whether daily muscle electrical stimulation (ES) and streptomycin treatment would have positive or negative effects on trabecular bone mass in disuse rats.

Methods:

Seven-week-old male F344 rats were randomly divided into five groups of eight animals each: an age-matched control group (CON); a sciatic denervation group (DN); a DN + direct electrical stimulation group (DN+ES); a DN + streptomycin treatment group (DN+SM); and a DN+ES+SM group. The tibialis anterior (TA) muscles in all ES groups were stimulated with 16mA at 10Hz for 30 min/day, six days/week, for one week. Bone volume and structure were evaluated using micro-CT, and histological examinations of the tibiae were performed.

Results:

Direct ES significantly reduced the disuse-induced trabecular bone loss. Osteoid thickness were also significantly greater in the ES groups than in the DN group. Micro CT and histomorphological parameters were significantly lower in the DN+ES+SM group than in the DN+ES group, while there were no significant differences between the DN and DN+SM groups.

Conclusions:

These results suggest that ES-induced muscle force reduced trabecular bone loss, and streptomycin treatment did not induce bone loss, but attenuated the effects of ES-induced muscle force on reducing the loss of disused bone.     

Effects of temperature on electromyogram and muscle function

The effects of 30 min of cooling (15 degrees C water) and warming (40 degrees C water) on arm muscle function were measured. A reference condition (24 degrees C air) was included. Of nine young male subjects the maximal grip force (Fmax), the time to reach 66% of Fmax (rate of force buildup) and the maximal rhythmic grip frequency were determined, together with surface electromyographic activity (EMG) of a forearm muscle (flexor digitorum superficialis). The results showed that in contrast to warming, cooling resulted in a significant decrease of 20% in the Fmax and a significant 50% decrease in force build-up time and the maximal rhythmic grip frequency. The relationship between the root mean square value (rms) of the EMG and the static grip force did not change due to temperature changes. The median power frequency (MPF) in the power spectrum of the EMG signal decreased by 50% due to cooling but remained unchanged with heating. During a sustained contraction at 15% of Fmax (Fmax depending on the temperature) the increase in the rms value with contraction time was 90% larger in the warm condition and 80% smaller in the cold condition compared to the increase in the reference condition. The MPF value remained constant during the warm and reference conditions but in the cold it started at a 50% lower value and increased with contraction time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of Quadrat and Core Sizes on Determining the Spatial Pattern of Criconemella sphaerocephalus

An unmanaged pasture was sampled on four occasions (A, B, C, D) with five different quadrat sizes for Criconemella sphaerocephalus by removing a constant soil core volume of 75 cm³ (A) and 300 cm³ (C) from increasing quadrat areas of 0.5-8 m², and removing soil core volumes of increasing size - 75-1,200 cm³ (B) and 300-4,800 cm³ (D) - proportionally with an increase in quadrat area (0.5-8 m²). Frequency counts of C. sphaerocephalus were fitted to six probability distributions. The index of aggregation (b) for Taylor''s power law and Morisita''s index of dispersion were also calculated where appropriate. Twelve of nineteen of the sampling combinations were best described by negative binomial distribution (P = 0.05). Criconemella sphaerocephalus appeared more highly aggregated when sampled with constant soil core volumes (A and C) than from increasing soil core volumes (B and D) based on Taylor''s index of aggregation (b). Morisita''s index of dispersion indicated aggregation at the smallest quadrat area (0.5 m²) for all sampling occasions (A, B, C, D).     

Effect of low frequency fatigue on human muscle strength and fatigability during subsequent stimulated activity

Fatiguing contractions of the adductor pollicis muscle were produced by intermittent supramaximal stimulation of the ulnar nerve in a set frequency pattern, in six normal subjects. At the end of an initial fatiguing contraction series, low frequency fatigue (LFF) had been induced and persisted at 15 min of recovery. Stimulated fatiguing activity was then repeated in an identical fashion to the initial series. At high frequencies, declines in force were similar for both series. At low frequencies, declines in force were greater during the second series despite similar changes in compound muscle action potential amplitude. This confirmation that LFF persists during subsequent stimulated activity, and reduces low but not high frequency fatigue resistance, suggests that the impaired endurance of fatigued muscle during voluntary activity primarily results from peripheral changes at low frequency. These findings also have implications for therapeutic electrical stimulation of muscle.     

The effect of changes in muscle function and bone growth on muscle migration

The elastic sleeve model of the periosteum of a long bone presents the periosteum as a structure which, because it is attached to the epiphyses rather than the diaphysis, expands interstitially and equally at all points as the bone grows at its ends. Structures attached to the periosteum are seen as essentially passive hitchhikers on the expanding periosteum. Two corollaries of this model are tested here. First, that changes in the magnitude or direction of the force that an attached structure exerts on the periosteum do not affect the migration of the structure. Second, that changes in the proportion of growth that occur at each end of the bone do not affect the migration of attached structures. Experiments performed on rabbits to test these corollaries include muscle paralysis, muscle transection, changes in the direction pull of a muscle, and epiphysiodesis. The results are in agreement with the hypotheses. This model should have applicability to functional and comparative anatomy, since it postulates that differences in positions of attachment of muscles and ligaments to bones reflect underlying genetic differences (phylogeny) rather than the effects of differences in behavior of the animal (ontogeny).     

Effects of age,sex, and heredity on measures of bone mass in baboons (Papio hamadryas)

Abstract: Bone mass and bone density were estimated in 219 pedigreed baboons (Papio hamadryas) by radiographic morphometry of the left second metacarpal. Compact bone width (total bone width – medullary canal diameter) and bone ratio (compact bone width/total bone width) decreased with increasing age squared in both sexes. The heritability of medullary canal diameter was 0.64±0.11, of compact bone width was 0.40±0.15 and of bone ratio was 0.67±0.13. The results indicate baboons are a useful model for studies of age, sex and genetic effects on bone mass.     

Effect of Weak Acid Hypochlorous Solution on Selected Viruses and Bacteria of Laboratory Rodents

Weak acid hypochlorous solution (WAHS) is known to have efficacy for inactivatingpathogens and to be relatively safe with respect to the live body. Based on theseadvantages, many animal facilities have recently been introducing WAHS for daily cleaningof animal houses. In this study, we determined the effect of WAHS in inactivating specificpathogens of laboratory rodents and pathogens of opportunistic infection. WAHS with anactual chloride concentration of 60 ppm and a pH value of 6.0 was generated usingpurpose-built equipment. One volume of mouse hepatitis virus (MHV), Sendai virus,lymphocytic choriomeningitis virus, Bordetella bronchiseptica,Pasteurella pneumotropica, Corynebacterium kutscheri,Staphylococcus aureus, and Pseudomonas aeruginosa wasmixed with 9 or 99 volumes of WAHS (×10 and ×100 reaction) for various periods (0.5, 1,and 5 min) at 25°C. After incubation, the remaining infectious viruses and live bacteriawere determined by plaque assay or culture. In the ×100 reaction mixture, infectiousviruses and live bacteria could not be detected for any of the pathogens examined evenwith the 0.5-min incubation. However, the effects for MHV, B.bronchiseptica, and P. aeruginosa were variable in the ×10reaction mixture with the 0.5- and 1-min incubations. Sufficient effects were obtained byelongation of the reaction time to 5 min. In the case of MHV, reducing organic substancesin the virus stock resulted in the WAHS being completely effective. WAHS is recommendedfor daily cleaning in animal facilities but should be used properly in order to obtain asufficient effect, which includes such things as using a large enough volume to reduceeffects of organic substances.     

Effect of Host Plant Age on Population Development and Pathogenicity of Ditylenchus destructor on Peanut

The effect of inoculating peanut, Arachis hypogaea cv. Sellie, with Ditylenchus destructor at timed intervals after planting and with different initial nematode population densities (Pi) was tested in greenhouse experiments. Final nematode population densities (Pf) in hulls and seeds were greater (Pf < 0.001) in plants inoculated at or before 9 weeks after planting. Pod disease symptoms correlated positively with the Pf in the pods. The seedgrade of peanuts inoculated at or before 9 weeks after planting was reduced, whereas grade of peanuts from plants inoculated at 15 weeks or later was not reduced. Peanut plants inoculated 12 weeks after planting with a Pi of 10-100 had a lower Pf (P < 0.05) than plants with a Pi of 250 to 8,000. Seed of plants with a Pi of 250 or less could be marketed as choice edible seed, whereas those with a Pi of 500 or more were of reduced seedgrade. These results suggest that as few as 500 nematodes per plant at 12 weeks after planting can build up to injurious levels before harvest. A nematicide should therefore be active for longer than 12 weeks after planting to sufficiently suppress the population.