Composition and turnover of contractile proteins in volume-overtrained skeletal muscle

The purpose of this study was to find the composition shift of myosin heavy chain (MyHC) isoforms in overtraining in fast- and slow-twitch skeletal muscles and different changes in MyHC isofom composition, synthesis and turnover rate between 4-week and 6-week overtraining. Male Wistar rats were randomly assigned to 4-week and 6-week endurance training, 4-week and 6-week overtraining groups. Plantaris (Pla), extensor digitorum longus (EDL), and soleus (Sol) muscles were studied. Daily excretion of 3-methylhistidine (3-MeHis) pool as an indicator for protein degradation increased in the 4-week and 6-week overtraining group to 4.04 +/- 0.21 and 4.32 +/- 0.23 %/day subsequently in comparison with the control group (2.16 +/- 14 %/day, p < 0.001). In Pla muscle MyHC I isoform synthesis rate was 33 200 +/- 2150 (after 6-week overtraining 27 100 +/- 1800, p < 0.05), IIa 32 600 +/- 2100; IId 27 300 +/- 1890 and IIb isoform 20 100 +/- 1600 (after 6-week overtraining 15 500 +/- 1400, p < 0.05) dpm/M leucine/min. Actin synthesis rate increased in fast-twitch muscles during 4- and 6-week overtraining, and in soleus muscle during 6-week overtraining. In EDL and Sol muscle MyHC isoform composition during 6-week overtraining did not change significantly. During the 6-week overtraining the relative content of MyHC I and IIb isoforms decreased and IIa and IId isoforms increased in Pla muscle. The initial increase of MyHC IIb isoform after 4-week overtraining shows the higher stability of this isoform in comparison with MyHC I isoform in fast-twitch muscles during high volume exercise.     

Low Particulate Type IV Phosphodiesterase Activity in Hypothyroid Rat Atria

Rats were made hypothyroid by adding propylthiouracil (PTU) to their drinking water. Some of the PTU-treated rats were given thyroid hormone injections for 5 days. Both soluble and particulate cAMP-phosphodiesterase activities of adipose and ventricular tissues were increased by 25-60% in hypothyroidism. In left atria, soluble cAMP-phosphodiesterase activity was not significantly altered in hypothyroidism, while total particulate cAMP-phosphodiesterase activity was lowered by 30%. This lowering was due to diminished isoenzyme IV activity, as studied with the isoenzyme specific inhibitors rolipram and SK&F 94836.In conclusion, the present results show decreased particulate type IV cAMP-phosphodiesterase activity in hypothyroid rat atria. This may explain the increased responsiveness to isoproterenol in hypothyroid atria.     

Behavioral characterization of mouse models for Smith-Magenis syndrome and dup(17)(p11.2p11.2)

Contiguous gene syndromes (CGS) refer to a group of disorders associated with chromosomal rearrangements in which the phenotype is thought to result from altered copy number of physically linked dosage-sensitive genes. Smith-Magenis syndrome and [dup(17)(p11.2p11.2)] are CGS associated with a heterozygous deletion or duplication of band p11.2 of chromosome 17, respectively. We previously constructed animal models for these CGSs by engineering rearranged chromosomes carrying a deletion/deficiency [Df(11)17] (Del mutant) or a duplication [Dp(11)17 ] (Dup mutant) of the syntenic region on mouse chromosome 11. Here we present a behavioral analysis of these models indicating that heterozygous male mice carrying the engineered deletion or the duplication are hypoactive or hyperactive, respectively. In addition, male Dup mutant mice, but not Del mutant mice, have impaired contextual fear conditioning. Circadian rhythm studies revealed period length differences in Del mutant mice, but not Dup mutant mice. These results indicate that some of the behavioral abnormalities are gene dosage sensitive, whereas other behavioral abnormalities are specific to mice carrying the deletion or the duplication and can be observed in a sex preferential manner. Our findings suggest that there is a gene(s) present in this defined genomic interval that is responsible for behavioral abnormalities in the mouse, as has been shown for the human syntenic region.     

Epilepsy in Estonia: a quality-of-life study

PURPOSE: To study the impact of epilepsy and its treatment on people with epilepsy in Estonia and to analyze how it is affected by the characteristics of epilepsy. METHODS: Clinical and demographic data about patients were obtained from medical notes and mailed self-completed questionnaires (including the RAND 36-Items Health Survey 1.0 (RAND-36)). RESULTS: Information was collected from 203 patients aged 20-74 years, who all had active epilepsy. A third of the respondents had been seizure free during the last year. Eighty-four percent were receiving monotherapy. More than half of respondents felt stigmatized by epilepsy, 24.7% of them highly so. A third were working full-time, 31.9% were underemployed workers, and 11%, unemployed. Sixty-two percent of these same unemployed or underemployed workers considered their epilepsy to be a significant reason for this situation. Overall, 44% believed they had been treated unfairly at work or when trying to get a job. Study respondents scored lower in all domains on the RAND-36 than did persons from the control group. The biggest differences were found in five domains: Social functioning, Role limitations-physical, Role limitations-emotional, General health, and Vitality. CONCLUSIONS: The clinical characteristics of this study were similar to those of most other series of prevalence cases of epilepsy. The level of employment among persons with epilepsy was not lower than that in the general population. The percentage of stigmatization was high. There were significant differences in the way respondents scored on the stigma scale and on the RAND-36 domains when measuring their health status, depending above all on seizure frequency and type.     

Tunable chiral triazole-based halogen bond donors: assessment of donor strength in solution with nitrogen-containing acceptors

Strong halogen bond (XB) donors are needed for the activation of neutral substrates. We demonstrate that XB donor properties of iodo-triazoles can be significantly enhanced by quaternization in combination with varying the counterion and aromatic substituent, exemplified by association constants with quinuclidine as high as 1.1 × 10⁴ M⁻¹.

Various structurally modified iodo-triazole based XB donors were screened with quinuclidine, displaying K_a values as high as 1.1 × 10⁴ M⁻¹.

Halogen bond (XB) based applications utilize the attractive interaction between a Lewis acidic halogen atom and a Lewis base.¹ From the turn of the century numerous publications have focused on the use of XBs in the solid state² and more recently, in solution as well.³ Among these applications the potential of XBs in catalysis⁴ and anion recognition should be highlighted.⁵ As shown by Huber et al. these fields can be closely associated, exemplified by halide abstraction reactions.⁶Compared to anion recognition, the recognition of neutral species in solution has received less attention. Studies with neutral acceptors have a primary focus on the fundamental nature of halogen bonding, such as the influence of the solvent and the structure of the XB donor/acceptor on the strength of XBs.⁷ Amines have usually been used as neutral acceptors in these studies for their high affinity towards XB donors. This property can potentially be utilized in the detection of biologically relevant amines by XBs.⁸ From the synthetic point of view, the activation of neutral species through XBs is also a topic of high interest.⁹ In general, compared to anions, neutral acceptors form weaker complexes with organic XB donors.^1d,3c Therefore, XB donors with stronger halogen bonding ability should be used for the activation of neutral compounds. From a catalyst design perspective, information on the extent different structural fragments affect XB donor ability is of great value.Recently, we became interested in applying XBs in asymmetric catalysis. Chiral 5-halo-1,2,3-triazoles are among the best candidates of catalysts to achieve this goal.^6b,9b,d The triazoles are readily available through a Cu-catalysed click reaction¹⁰ and access to a broad range of alkynes with the possibility to quaternize the triazole core makes it feasible to enhance the donor ability of the triazole. In addition, the availability of many chiral azides offers wide opportunities for the design of new chiral XB donor systems.¹¹ We have shown the potential of these compounds to interact with various possible substrates and in enantiodiscrimination.¹² Due to relatively low affinity constants with thiourea acceptors, it was difficult to fully assess how structural modifications affect XB donors'' binding ability. Therefore, a stronger XB acceptor has to be selected for this kind of analysis. Anionic species are known to give large affinity constants with halo-triazolium salts,¹³ however, in these complexes charge attraction plays a key role in XB formation. We therefore chose quinuclidine,^7d,h–k a neutral monodentate XB acceptor with a readily accessible lone pair, for screening of the effect of XB donor analogues (Fig. 1) on XB strength. Herein we describe the formation of complexes between triazole-based XB donors and quinuclidine in solution with emphasis on the influence of aromatic substituents and counterions on XB donor strength and investigate the XB donors'' ability to discriminate between enantiomers of chiral imines and amines.Open in a separate windowFig. 1XB donors and reference compound under study.A collection of monodentate XB donors shown in Fig. 1 were synthesized (see ESI^† for details). To determine the effect of structural changes, the triazolium salts were modified by introducing a perfluorophenyl or a p-nitrophenyl substituent instead of a phenyl substituent, changing the counterions and varying the halogen atoms. The XB donor ability of the synthesized compounds was determined through their respective association constants with quinuclidine in CDCl₃ based on ¹H NMR titration experiments. To evaluate the XB strength more accurately, the titration experiments were carried out in duplicate. The results are summarized in

Changes of local cerebral blood flow concomitant to lead-exposure in adult rabbits

Lead is considered a pathogenic factor of atherosclerosis and arterial hypertension, which are main risk factors of cerebrovascular disease. The brain microvasculature preferentially accumulates lead and its function is sensitive to its toxic effect. Influence of inorganic lead-exposure (20 mg/kg - I group, 40 mg/kg II group) for 10 days on local cerebral blood flow (1CBF) in hypothalamus (HYP) and cerebral cortex (CTX) of rabbits was studied by means of the hydrogen clearance method. Corresponding results were compared to sham operated group (III group). During lead-exposure 1CBF was reduced in both investigated regions. The reduction of 1CBF in HYP was reduced in both investigated regions. The reduction of 1CBF in HYP was 12.9% ( P <0.05) in I and 19.9% ( P < 0.001) in II group; corresponding changes in CTX were - 16.9 % (statistically non-significant - N) in I and 1.4% (NS) in II group. Present finding suggest that inorganic lead induces cerebral microvascular dysfunction with following changes in 1CBF. These alteration have a biphasic character Although these disturbances reveal a tendency towards normalization, it is possible to presume that higher concentrations of ingested lead cause more severe injury to endothelium of brain microvasculature.     

Dehydroepiandrosterone sulphate prevents oxygen-glucose deprivation-induced injury in cerebellar granule cell culture

Decreased levels of dehydroepiandrosterone sulphate have been hypothesized to contribute to increased vulnerability of the ageing or stressed human brain to ischemia. To help to address the question of whether of dehydroepiandrosterone sulphate has a possible neuroprotective effect against ischemic neuronal injury, we tested its effect on the neurodegeneration induced by oxygen-glucose deprivation in rat cultured cerebellar granule cells. Dehydroepiandrosterone sulphate added to the medium after injury demonstrated a neuroprotective effect with a median inhibitory concentration of 0.5 microM. At 10 microM concentration almost full neuroprotection was observed. Even more pronounced neuroprotective effect was found when dehydroepiandrosterone sulphate was added for 48h before injury. Furthermore, partial neuroprotection of dehydroepiandrosterone sulphate was also found against 1-methyl-4-phenylpyridinium, colchicine, glutamate and N-methyl-D-aspartate-induced toxicity. Further analysis demonstrated that dehydroepiandrosterone sulphate eliminated the apoptotic features of the oxygen-glucose deprivation-induced neuronal death: DNA fragmentation and nuclear condensation/fragmentation.Thus, our data suggest that dehydroepiandrosterone sulphate may have therapeutic potential in the prevention and treatment of ischemic/hypoxic neuronal damage. The neuroprotective action of dehydroepiandrosterone sulphate was inhibited by both a GABA(A) receptor-linked chloride channel agonist and an antagonist, pentobarbital and picrotoxin, respectively. It seems that GABA(A) receptor-mediated neuronal inhibition as well as neuronal excitation can reduce the neuroprotective action of dehydroepiandrosterone sulphate.     

Muscle protein turnover in endurance training: a review

There has been much debate about skeletal muscle capacity to adapt to long-lasting endurance exercise. Exercise in the aerobic zone of metabolism does not result in hypertrophy of skeletal muscle fibres but increases their oxidative capacity. The duration and intensity of an exercise session determines the time period of depressed muscle protein synthesis and increased degradation rate during the recovery period after exercise. Protein turnover characterizes the renewal processes of muscle proteins and the functional capacity of muscle. The turnover rate of myofibrillar proteins is slow in comparison with mitochondrial proteins and depends on the oxidative capacity of muscle fibres. The turnover rate of myofibrillar proteins in the same muscle is different and is also different within the myosin molecule between myosin heavy and light chain isoforms. The turnover rate of muscle proteins in endurance training shows the adaptation of skeletal muscle to long-lasting exercise via remodelling of muscle structures. Adaptational coordination between myofibrillar and mitochondrial compartments shows the physiological role and adaptational capacity of skeletal muscle to endurance training. It is challenging to use muscle protein turnover for the purposes of monitoring the training process of endurance athletes, optimizing training programs and preventing overtraining.