Biomechanical assessments of the effect of visual feedback on cycling for patients with stroke

Stroke patients exhibit abnormal pattern in leg cycling exercise. The aim of this study was to investigate the effects of visual feedback on the control of cycling motion in stroke patients from kinesiological, kinematic and kinetic aspects. The cycling performance derived from cycling electromyography (EMG), cycling cadence, and torque of forty stroke subjects was evaluated under conditions with and without visual feedback of cycling cadence. Kinesiological indices, shape symmetry index (SSI) and area symmetry index (ASI) were extracted from EMG linear envelopes to evaluate the symmetry of muscle firing patterns during cycling. Roughness index (RI) was calculated from cycling cadence to represent cycling smoothness from kinematic aspects. Averaged cycling power (Pav), the product of cadence and torque, was used to represent force output. The rectus femoris EMG showed significantly greater ASI with visual feedback, however, the difference in SSI between the two conditions was not significant. For the biceps femoris, there was a significant decrease in SSI with visual feedback, while the ASI was not affected significantly by the task conditions. The cycling smoothness was better and the average power generated was larger when visual feedback was provided. This study found that the addition of visual feedback improved both neuromuscular control and overall performance. Such improvement is likely to be the result of better control of the rectus femoris muscle activation and coordination of both legs.     

Anticipation mechanism in body sway control and effect of muscle fatigue

The aim of this work is to quantify the occurrence of an anticipatory mechanism in the control of quiet standing by measuring the lag between the myoelectric activity of the lateral gastrocnemius muscle and the stabilometric signal, as well as to determine the influence of the muscle fatigue on this process. Stabilometric and electromyographic (EMG) signals were synchronously collected from 22 subjects. Gastrocnemius fatigue was induced by a sustained plantar flexed posture until muscle failure. The data acquisition lasted for 120 s before and after the induced fatigue. After mean removal, the root mean square values of the EMG (RMS-EMG) were calculated for each 20 ms period. The normalized cross-correlation function was estimated to find the time delay between RMS-EMG and stabilometric signals. Anticipation values up to 1.62 s were found both before and after fatigue conditions (p < 0.05), indicating that this mechanism plays an important role in body sway control. The fatigue caused a significant increase in the latency between the myoelectric activity of the gastrocnemius muscle and the movements of the center of pressure (p < 0.05).     

Gastrocnemius and soleus muscle length, velocity, and EMG responses to changes in pedalling cadence

Several authors have shown different excitation patterns for soleus and gastrocnemius muscles in response to cadence manipulation during cycling. The purpose of this study was to examine gastrocnemius and soleus length and velocity change as a function of pedalling cadence to consider mechanisms underlying these excitation differences. Ten male and two female cyclists rode at five randomly assigned cadences (50, 65, 80, 95, and 110 rpm) at a nominal 200 W power output while EMG of the gastrocnemius and soleus and sagittal plane video were recorded. Joint-coordinate data for the knee and ankle were used with equations of Grieve et al. [Grieve D, Pheasant S, Cavanagh PR. Prediction of gastrocnemius length from knee and ankle joint posture, in: E. Asmussen, K. Jorgensen, editors. International Series on Biomechanics, vol. 2A, Baltimore: University Park Press; 1978. p. 405–412] to compute gastrocnemius and soleus length and velocity. Consistent with previous publications, gastrocnemius displayed a significant (p < 0.05) increase in integrated EMG with increased cadence, whereas cadence had no significant effect on integrated EMG of the soleus. The ankle became significantly (p < 0.05) more plantar flexed and reflected a reduced range of motion with increased cadence while the knee became significantly (p < 0.05) less extended. Soleus decreased its range of motion by 29%, whereas gastrocnemius decreased its range of motion by 9%. In contrast, soleus increased its velocity range by 32% and gastrocnemius increased by 45%. These data show that with increased cadence gastrocnemius operated over a narrower range of operating lengths but at a higher range of shortening velocity than soleus. The higher range of velocity may have resulted in the need for a relatively higher excitation, as indicated by the integrated EMG, as the muscle was working at a different range on its force–velocity curve. During the recovery portion of the pedalling cycle, the soleus was acting eccentrically while the gastrocnemius acted concentrically indicating the triceps surae complex did not always act in unison.     

The morphology of the medial gastrocnemius in typically developing children and children with spastic hemiplegic cerebral palsy

We collected 3D ultrasound images of the medial gastrocnemius muscle belly (MG) in 16 children with spastic hemiplegic cerebral palsy (SHCP) (mean age: 7.8 years; range: 4–12) and 15 typically-developing (TD) children (mean age: 9.5 years; range: 4–13). All children with SHCP had limited passive dorsiflexion range on the affected side with the knee extended (mean ± 1SD: −9.3° ± 11.8). Scans were taken of both legs with the ankle joint at its resting angle (RA) and at maximum passive dorsiflexion (MD), with the knee extended. RA and MD were more plantar flexed (p < 0.05) in children with SHCP than in TD children.

We measured the volumes and lengths of the MG bellies. We also measured the length of muscle fascicles in the mid-portion of the muscle belly and the angle that the fascicles made with the deep aponeurosis of the muscle. Volumes were normalised to the subject’s body mass; muscle lengths and fascicle lengths were normalised to the length of the fibula.

Normalised MG belly lengths in the paretic limb were shorter than the non-paretic side at MD (p = 0.0001) and RA (p = 0.0236). Normalised muscle lengths of the paretic limb were shorter than those in TD children at both angles (p = 0.0004; p = 0.0003). However, normalised fascicle lengths in the non-paretic and paretic limbs were similar to those measured in TD children (p > 0.05). When compared to the non-paretic limb, muscle volume was reduced in the paretic limb (p < 0.0001), by an average of 28%, and normalised muscle volume in the paretic limb was smaller than in the TD group (p < 0.0001).

The MG is short and small in the paretic limb of children with SHCP. The altered morphology is not due to a decrease in fascicle length. We suggest that MG deformity in SHCP is caused by lack of cross-sectional growth.     

Influence of PAHs in ambient air on chromosomal aberrations in exposed subjects: international study - EXPAH

The aim of this study was to determine the influence of carcinogenic polycyclic aromatic hydrocarbons (c–PAHs) in complex mixtures in ambient air on DNA damage (chromosomal aberrations) in occupationally exposed subjects measured as percent of aberrant cells (% AB.C.).

There were in total 203 exposed subjects and 150 respective controls in the whole project, allocated in three different European cities – Kosice (Slovakia), Prague (Czech Republic) and Sofia (Bulgaria). The studied population from Kosice (Slovakia) consisted of 106 subjects. From these 51 were exposed policemen and 55 were controls. The Czech population comprised 52 exposed policemen and 50 controls. In Bulgaria, there were two equally numerous exposed groups: 50 policemen and 50 professional bus drivers together with 45 controls. According to personal monitoring, policemen and bus drivers in the Bulgarian capital Sofia were exposed to the highest levels of c-PAHs amongst the exposed subject groups in the cities (45.3 ± 25.9 ng/m³ in policemen resp. 36.1 ± 31.6 ng/m³ in bus drivers in Sofia, 26.8 ± 39.8 ng/m³ for policemen in Kosice and 11.9 ± 11.2 ng/m³ for policemen in Prague), compared to the respective controls (24.9 ± 17.7 ng/m³ for controls in Sofia, 7.9 ± 3.8 ng/m³ for controls in Kosice and 6.2 ± 3.6 ng/m³ for controls in Prague).

We observed the following frequency of % AB.C. scored by conventional method: 2.60 ± 2.64 in exposed policemen and 2.14 ± 1.61 in controls in Kosice (p = n.s.); 2.33 ± 1.53 in exposed policemen and 1.94 ± 1.28 in controls in Prague (p = n.s.); 3.04 ± 1.64 in exposed policemen, respectively, 3.60 ± 1.63 in exposed bus drivers and 1.79 ± 0.77 in the control group in Sofia (p < 0.05, respectively, p < 0.05).

According to data from multiple regression analysis, and group comparison of smokers versus nonsmokers in Sofia also cigarette smoking (p = 0.055) and the age (p = 0.020) seem to play an important role within the aberrant cell formation in addition to the occupational c-PAHs exposure (p = 0.000). Smoking status was the modifying factor for % AB.C. in Kosice (p = 0.020) after multiple regression approach was employed.

In summary, we can say that subjects occupationally exposed to higher levels of c-PAHs in ambient air in Sofia are at greater genotoxic risk compared to those working indoors.     

Chromosomal aberrations by fluorescence in situ hybridization (FISH)--Biomarker of exposure to carcinogenic PAHs

The fluorescence in situ hybridization (FISH) technique with whole chromosome painting for chromosomes #1 and #4 was used to study the impact of air pollution containing higher concentrations of carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) in three European cities, Prague (Czech Republic), Kosice (Slovakia) and Sofia (Bulgaria). In each site were followed an exposed group, who were police officers or bus drivers who work usually through busy streets for at least 8 h, and a reference group, who spent more than 90% of their daily time indoors.

In Prague, a significant increase was observed in percentage of aberrant cells (% AB.C.) in the police officers compared to the reference group (0.33 ± 0.25 versus 0.24 ± 0.18, p < 0.05). In Kosice, the exposed group differed from reference in the endpoints F_G/100 1.52 ± 1.18 versus 1.12 ± 1.30, p < 0.05; % AB.C. 0.30 ± 0.19 versus 0.21 ± 0.20, p < 0.05; t/1000 3.91 ± 3.18 versus 2.84 ± 3.10, p < 0.05. In Sofia were followed two exposed groups: police officers and bus drivers. All FISH endpoints were significantly higher in police officers compared to reference group (F_G/100 1.60 ± 0.99 versus 0.82 ± 0.79, p < 0.01; % AB.C. 0.25 ± 0.14 versus 0.13 ± 0.13, p < 0.01; t/1000 4.19 ± 2.65 versus 2.13 ± 2.05, p < 0.05; rcp 1.46 ± 1.07 versus 0.70 ± 0.76, p < 0.05). In bus drivers compared to reference there was an increase in % AB.C. (0.25 ± 0.18 versus 0.13 ± 0.13, p < 0.05).

This is the first study when FISH method was used to analyze the impact of environmental air pollution. According to the original hypothesis it is expected that the most important group of chemicals responsible for the biological activity of air pollution represent c-PAHs.     

Consummatory behavior and metabolic indicators after central ghrelin injections in rats

Ghrelin, an endogenous ligand for the growth-hormone-secretagogue receptor, is a 28-amino acid peptide with a post-translational acyl modification necessary for its activity. It has central nervous system actions that affect appetite, body mass and energy balance. An intracerebroventricular (ICV) injection protocol of sub-nanomolar doses of ghrelin, known to alter the morphology of ACTH and GH producing pituicytes and plasma levels of these hormones, was used to provide an overview of metabolic changes linked to energy metabolism. Variables measured were: food intake (FI), water intake (WI), fecal mass, urine volume, body weight (BW), retroperitoneal (RP) and epididymal (EPI) white adipose tissue (WAT), and changes in serum leptin, insulin, triglycerides, cholesterol, and glucose. Five injections of rat ghrelin or PBS (n = 8 per group) were given ICV every 24 h (1 μg/5 μL PBS) to adult male rats. Ghrelin had a positive and cumulative effect on FI, WI and BW (p < 0.05), but not feces mass or urine volume (p > 0.05). Centrally applied ghrelin clearly increased RP WAT (by 235%, p < 0.001), EPI WAT (by 85%, p < 0.05) and serum insulin levels (by 43%, p < 0.05), and decreased serum leptin levels (by 77%, p < 0.05) without (p > 0.05) evoking changes in blood triglyceride cholesterol, or glucose levels.

These data and the available literature clearly document that exposure of the brain of normal rats, over time, to sub-nanomolar doses of ghrelin results in metabolic dysregulation culminating in increased body mass, consummatory behavior, and lipid stores as well as changes in blood leptin/insulin levels. Thus, modulation of central ghrelin receptors may represent a pharmacological approach for controlling multiple factors involved in energy balance and obesity.     

Ageing and dexamethasone associated sarcopenia: peculiarities of regeneration

The purpose of this study was to assess the development of ageing- and glucocorticoid-related sarcopenia on the level of myofibrillar apparatus, paying attention to the synthesis (SR) and degradation rate (DR) of contractile proteins, muscle strength, and daily motor activity. We also wanted to test the effect of ageing and dexamethasone (Dex) excess on the regeneration peculiarities of skeletal muscle autografts. Four and 30-month-old male rats of the Wistar strain were used. Ageing associated sarcopenia was calculated from gastrocnemius muscle relative mass decrease (from 5.6 ± 0.08 to 3.35 ± 0.04; p < 0.001). The SR of MyHC in old rats was 30% and actin 23% lower than in young rats. Dex treatment decreased SR of two main contractile proteins significantly in both age groups (p < 0.001) and increased DR during ageing from 2.11 ± 0.15 to 4.09 ± 0.29%/day (p < 0.001). Hindlimb grip strength in young rats was 5.90 ± 0.35 N/100 g bw and 2.64 ± 0.2 N/100 g bw (p < 0.001) in old rats.

Autografts of old rats have a higher content of adipose tissue 14.9 ± 1.1% in comparison with young rats 6.8 ± 0.51% (p < 0.001) and less muscle tissue 39.8 ± 2.6% and 48.3 ± 2.8%, respectively (p < 0.05).

Both, ageing and dex-caused sarcopenic muscles have diminished capacity for regeneration.     

Non-uniform electromyographic activity during fatigue and recovery of the vastus medialis and lateralis muscles

The aim of the study was to investigate EMG signal features during fatigue and recovery at three locations of the vastus medialis and lateralis muscles. Surface EMG signals were detected from 10 healthy male subjects with six 8-electrode arrays located at 10%, 20%, and 30% of the distance from the medial (for vastus medialis) and lateral (vastus lateralis) border of the patella to the anterior superior spine of the pelvic. Subjects performed contractions at 40% and 80% of the maximal force (MVC) until failure to maintain the target force, followed by 20 2-s contractions at the same force levels every minute for 20 min (recovery). Average rectified value, mean power spectral frequency, and muscle fiber conduction velocity were estimated from the EMG signals in 10 epochs from the beginning of the contraction to task failure (time to task failure, mean ± SD, 70.7 ± 25.8 s for 40% MVC; 27.4 ± 16.8 s for 80% MVC) and from the 20 2 s time intervals during recovery. During the fatiguing contraction, the trend over time of EMG average rectified value depended on location for both muscles (P < 0.05). After 20-min recovery, mean frequency and conduction velocity of both muscles were larger than in the beginning of the fatigue task (P < 0.05) (supernormal values). Moreover, the trend over time of mean frequency during recovery was affected by location and conduction velocity values depended on location for both muscles (P < 0.05). The results indicate spatial dependency of EMG variables during fatigue and recovery and thus the necessity of EMG spatial sampling for global muscle assessment.     

The influence of age on the use of potential enrichment objects and synchronisation of behaviour of pigs

This experiment aimed to identify how a pig's age affected the extent and synchrony of use of different environmental enrichment materials, and how this use changed over time. Ten diverse novel objects were each presented to three replicate litters of 3 weeks of age (sucklers) and three replicate groups of three animals of 5 (weaners) weeks and 13 (growers) weeks of age. Video recordings were made of the pigs’ behaviour over a period of 5 days and subsequently analysed for activity, inactivity and object directed behaviour of three animals per group on days 1 and 5. The observed performance of any given behaviour, when at least one other member of the group was also performing that behaviour, was compared with the probability that such concurrence occurred by chance and these results were used to calculate the degree of synchronisation. Gender had no effect on the duration of object use or approach latency. Growers displayed a shorter latency to approach the objects initially compared to sucklers and weaners (mean seconds; 2153 versus 2660 versus 980 for sucklers, weaners and growers, respectively, S.E.D. 542, p = 0.007). Sucklers used the objects to a much lesser extent than either the weaners or growers (mean duration object interaction (s); 129 versus 1253 versus 1412 for sucklers, weaners and growers, respectively, S.E.D. 93, p < 0.001). Overall object use decreased between days 1 and 5 (mean duration object interaction (s); 1326 versus 536 for days 1 and 5, respectively, S.E.D. 76, p < 0.001). All of the age groups synchronised their behaviour to a much greater extent than expected by chance. The sucklers showed a higher degree of synchrony of activity (K; 0.890 versus 0.776 versus 0.682 for sucklers, weaners and growers respectively, S.E.D. 0.013, p < 0.001) and inactivity (K; 0.963 versus 0.905 versus 0.909 respectively, S.E.D. 0.007, p < 0.001), but lower degree of synchrony for object directed behaviour (K; 0.149 versus 0.375 versus 0.370 respectively, S.E.D. 0.025, p < 0.001), than the weaners and growers. The degree of synchronisation of object directed behaviour decreased over the 5-day period, irrespective of age (K; 0.382 versus 0.214 for days 1 and 5 respectively, S.E.D. 0.020, p < 0.001). Significant correlations (r = 0.678–0.879) were found between the degree of synchrony and extent of object interaction only for the sucklers. Since pigs showed behavioural synchronisation, object availability should be considered when providing desirable enrichment in order to avoid excessive competition in larger commercial groups.     

Spatio-temporal processing of surface EMG signals from the sternocleidomastoideus muscle to assess effects of radiotherapy on motor unit conduction velocity and firing rate—A pilot study

Radiation therapy causes both muscle and nerve tissue damage. However, the evolution and mechanisms of these damages are not fully understood. Information on the state of active muscle fibres and motoneurons can be obtained by measuring sEMG signals and calculating the conduction velocity (CV) and firing rate of individual motor units, respectively. The aim of this pilot study was to evaluate if the multi-channel surface EMG (sEMG) technique could be applied to the sternocleidomastoideus muscle (SCM) of radiotherapy patients, and to assess if the CV and firing rate are altered as a consequence of the radiation.

Surface EMG signals were recorded from the radiated and healthy SCM muscles of 10 subjects, while subjects performed isometric rotation of the head. CV and firing rate were calculated using two recently proposed methods based on spatio-temporal processing of the sEMG signals. The multi-channel sEMG technique was successfully applied to the SCM muscle and CV and firing rates were obtained. The measurements were fast and simple and comfortable for the patients. Sufficient data quality was obtained from both sides of seven and four subjects for the CV and firing rate analysis, respectively. No differences in CV or firing rate were found between the radiated and non-radiated sides (p = 0.13 and p = 0.20, respectively). Firing rate and CV were also obtained from a myokymic discharge pattern. It was found that the CV decreased significantly (p = 0.01) during the bursts.     

Agonist and antagonist muscle activation during maximal and submaximal isokinetic fatigue tests of the knee extensors

The purpose of this study was to examine the differences in electromyographic activity of agonist and antagonist knee musculature between a maximal and a submaximal isokinetic fatigue protocol. Fourteen healthy males (age: 24.3 ± 2.5 years) performed 25 maximal (MIFP) and 60 submaximal (SIFP) isokinetic concentric efforts of the knee extensors at 60° s⁻¹, across a 90° range of motion. The two protocols were performed a week apart. The EMG activity of vastus medialis (VM), vastus lateralis (VL) and biceps femoris (BF) were recorded using surface electrodes. The peak torque (PT) and average EMG (aEMG) were expressed as percentages of pre-fatigue maximal value. One-way analysis of variance indicated a significant (p < 0.05) decline of PT during the maximal (45.7%) and submaximal (46.8%) protocols. During the maximal test, the VM and VL aEMG initially increased and then decreased. In contrast, VM and VL aEMG continuously increased during submaximal testing (p < 0.05). The antagonist (BF) aEMG remained constant during maximal test but it increased significantly and then declined during the submaximal testing. The above results indicate that agonist and antagonist activity depends on the intensity of the selected isokinetic fatigue test.     

Short term effects of dexamethasone on hyaluronidase activity and sperm characteristics in rams

The aim of this study was to determine the effects of dexamethasone on sperm characteristics and hyaluronidase activity of serum and semen. In this investigation, 14 healthy Akkaraman rams, at the age of 2 years and weighing between 50–60 kg, were used. The rams were randomly divided into two groups. After the last administration of dexamethasone intramuscularly at a dose of 0.25 mg/kg, semen and blood samples were taken at different times. The results showed that the serum hyaluronidase activity was increased significantly (p < 0.001) in the treatment group when compared with the control group except for the 1st hour. There was a significant difference (p < 0.001, 0.01, 0.05) in the hyaluronidase activity of semen between the treatment group and the control group. Furthermore, there was a significant difference (p < 0.01) in sperm concentration between both groups at all the times except the 96th hour. There were statistically significant (p < 0.05) differences in semen volume between the treatment and control groups. There were also significant differences (p < 0.05) in sperm motility between the treatment and control groups except for the 72 and 96th hours.

These findings indicate that dexamethasone increases hyaluronidase activity of serum and semen, but it decreases sperm concentration, semen volume and sperm motility in rams. Therefore the use of these drugs in breeding rams during breeding season is not suitable.     

Clusterin in cerebrospinal fluid: analysis of carbohydrates and quantification of native and glycosylated forms

Clusterin is suggested to be involved in the pathogenesis of Alzheimer's disease. Clusterin expression is increased in brain tissue in affected regions of Alzheimer patients, and intense clusterin staining is found in both senile plaques and in neuronal and glia cells. In contrast, the cerebrospinal fluid level of clusterin in Alzheimer patients has, thus far, been found unchanged. Clusterin is a glycosylated protein, and an alteration of its glycosylation in Alzheimer's disease might influence accurate quantification in cerebrospinal fluid through interference of antibody binding to the protein. Using enzymatic deglycosylation of clusterin isolated from cerebrospinal fluid, we found that the carbohydrates attached to clusterin were of the N-linked type and sialic acids. Based on this finding, cerebrospinal fluid samples from Alzheimer patients (n = 99) and controls (n = 39) were analysed. The samples were treated with peptide: N-glycanase F, cleaving off N-linked carbohydrates, and clusterin was quantified before and after deglycosylation using a new sandwich enzyme-linked immunosorbent assay. Clusterin was significantly increased in Alzheimer patients, in both native (7.17 ± 2.43 AU versus 5.73 ± 2.09 AU; p = 0.002), and deglycosylated samples (12.19 ± 5.00 AU versus 9.68 ± 4.38 AU; p = 0.004). Deglycosylation led to increased measured levels of clusterin by 70% (p < 0.001) in Alzheimer patients and 67% (p < 0.001) in controls. These findings indicate that glycosylation of proteins may interfere with their quantification. The results show that clusterin is significantly increased in cerebrospinal fluid from Alzheimer patients as a group, supporting that clusterin might be involved in the pathogenesis of Alzheimer's disease. However, the individual clusterin levels overlap between the two groups, and thus cerebrospinal fluid clusterin measurement is not suitable as a biochemical marker in the diagnosis of Alzheimer's disease.     

Identification of UDP-glucuronosyltransferase 1A10 in non-malignant and malignant human breast tissues

UGT1A10 was recently identified as the major isoform that conjugates estrogens. In this study, real-time PCR revealed high levels of UGT1A10 and UGT2B7 mRNA in human breast tissues. The expression of UGT1A10 in breast was a novel finding. UGT1A10 and UGT2B7 mRNAs were differentially expressed among normal and malignant specimens. Their overall expression was significantly decreased in breast carcinomas as compared to normal breast specimens (UGT1A10: 68 ± 26 vs. 252 ± 86, respectively; p < 0.05) and (UGT2B7: 1.4 ± 0.7 vs. 12 ± 4, respectively; p < 0.05). Interestingly, in African American women, UGT1A10 expression was significantly decreased in breast carcinomas in comparison to normals (57 ± 35 vs. 397 ± 152, respectively; p < 0.05). Among Caucasian women, UGT2B7 was significantly decreased in breast carcinomas in comparison to normals (1.1 ± 0.5 vs. 13.5 ± 6, respectively; p < 0.05). Glucuronidation of 4-hydroxylated estrone (4-OHE₁) was significantly reduced in breast carcinomas compared to normals (30 ± 15 vs. 106 ± 31, respectively; p < 0.05). Differential down-regulation of UGT1A10 and UGT2B7 mRNAs, protein, and activity in breast carcinomas compared to the adjacent normal breast specimens from the same donor were also found. These data illustrate the novel finding of UGT1A10 in human breast and confirm the expression of UGT2B7. Significant individual variation and down-regulation of expression in breast carcinomas of both isoforms were also demonstrated. These findings provide evidence that decreased UGT expression and activity could result in the promotion of carcinogenesis.     

The relationship between 8-oxo-7,8-dihydro-2'-deoxyguanosine level and extent of cytosine methylation in leukocytes DNA of healthy subjects and in patients with colon adenomas and carcinomas

It has been known for a long time that DNA hypomethylation occurs in many human cancers and precancerous conditions. However, the mechanisms of hypomethylation are largely unknown. It is possible that endogenous 8-oxo-7,8-dihydroguanine (8-oxoGua) level may be linked to aberrant DNA methylation of adjacent cytosine and in this way influences carcinogenesis. Therefore, the aim of the present study was to assess a possible link between 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) background level and 5-methylcytosine content in DNA from human leukocytes of healthy subjects (n = 105) as well as in patients with colon adenomas (n = 39) and carcinomas (n = 50).

Our results demonstrated statistically significant negative correlation between background level of 8-oxodG and 5-methylcytosine content in DNA isolated from leukocytes of healthy donors (r = −0.3436, p = 0.0003). The mean content of 5-methylcytosine was significantly lower, while 8-oxodG level was significantly higher in leukocytes DNA of patients with colon adenomas and carcinomas in comparison with healthy subjects. The mean values for 5-methylcytosine were: 3.59 ± 0.173% (healthy subjects), 3.38 ± 0.128% (patients with adenomas), 3.40 ± 0.208% (colon cancer patients). The mean values of 8-oxodG in DNA were, respectively: 4.67 ± 1.276, 5.72 ± 1.787, 5.76 ± 1.884 8-oxodG per 10⁶ dG molecules. DNA from affected tissue (colon) suffered from significant, about 10% reduction in cytosine methylation in comparison with leukocytes of the paired subjects.

Our work provides the first in vivo evidence suggesting that increased levels of 8-oxodG in DNA may lead to carcinogenesis not only via mispair/mutagenic potential of the modified base but also through its ability to influence gene expression by affecting DNA methylation.     

Comparison of electromyographic activity during eccentrically versus concentrically loaded isometric contractions

Electromyographic (EMG) amplitude and mechanical tension are directly related during isometric contraction. Maximal voluntary isometric contractions are typically elicited through two different procedures; resisting a load, which is eccentric in nature, and contracting against an immovable object, which is concentric in nature. A wealth of literature exists indicating that EMG amplitude during concentric contractions is greater than that of eccentric contractions of the same magnitude. However, the effects of different methods to elicit isometric contraction on EMG amplitude have yet to be investigated. The purpose of this study was to compare EMG amplitudes under different loading configurations designed to elicit isometric muscle contraction. Twenty healthy volunteers (10 males and 10 females, age = 23 ± 2 yrs, height = 1.7 ± 0.09 m, mass = 69.9 + 16.8 kg) performed a maximal voluntary plantarflexion effort for which the vertical ground reaction force (GRFv) sampled from a force plate and surface EMG of the soleus were recorded. Participants then performed isometric plantarflexion at 20%, 30%, 40%, and 50% GRFv_max in a seated position, from a neutral ankle position, under two different counterbalanced isometric loading conditions (concentric and eccentric). For concentric loading conditions, the subject contracted against an immovable resistance to the specified %GRFv identified via visual and auditory feedback. For eccentric loading conditions, subjects contracted against an applied load placed on the distal anterior thigh that produced the specified %GRFv. This applied load had the tendency to force the ankle into dorsiflexion. Therefore, plantarflexion force, in an attempt to maintain the ankle in a neutral position, resisted lengthening of the plantarflexor musculature, thus representing eccentric loading during an isometric contraction. Mean EMG amplitude was compared across loading levels and types using a 2 (loading type: concentric, eccentric) × 4 (loading level: 20%, 30%, 40%, 50% GRFv) repeated-measures ANOVA. The main effect for loading level was significant (p = 0.007). However, the main effect for loading type, and the loading type × loading level interaction were non-significant (p > 0.05). The present findings provide evidence that isometric muscle contractions loaded in either concentric or eccentric manners elicit similar EMG amplitudes, and are therefore comparable in research settings.     

Repair competence assay in studies of the influence of environmental exposure to c-PAHs on individual susceptibility to induction of DNA damage

Previous results from studies performed in three European cities suggested a decrease in DNA repair efficiency observed in lymphocytes of subjects occupationally exposed to environmental carcinogenic polycyclic aromatic hydrocarbons (c-PAHs). The aim of this study was to investigate whether a relationship between exposure to environmental c-PAHs and cellular vulnerability to the induction of DNA damage and its repair is confirmed in a pooled group of subjects from Prague, Košice and Sofia. The investigated pool consisted of 144 subjects occupationally exposed to environmental c-PAHs, who were municipal policemen or bus drivers. A control group of 115 matched individuals consisted of males unexposed at work to c-PAHs. The repair efficacy was evaluated by a comparison of the DNA damage detected by the single cell gel electrophoresis (SCGE) immediately after challenging the cells with X-ray irradiation, with residual damage (RD) being measured after an incubation period of 60 min. A stochastic concept for a mechanism of the interaction between DNA and various genotoxic exposures, was applied to analyze a relationship between exposure and biological effect in the studied sample. The outcome of the study confirms that the exposure to environmental c-PAHs or smoking cigarettes, significantly decreases DNA repair efficiency (repair efficiency in the pooled group of exposed individuals was 61.8 ± 11.8% versus 67.9 ± 9.9 in control, p < 0.001, and repair efficiency in group of smoking individuals was 63.0 ± 11.5% versus 65.9 ± 11.1 in nonsmokers, p < 0.005). The repair efficiency can be affected by a genetic polymorphism, such as subjects with a homozygous mutation in polymorphic CYP1A1_(Val/Val) enzyme, or slow NAT2 acetylators, who showed a considerably lower DNA repair efficiency (i.e. average repair efficiency in subgroups of fast acetylators was for the control subgroup 68.1% versus 66.5% in exposed subjects, while in the case of subgroups of slow acetylators, for the control group was 68.0% versus significantly less in the exposed subjects, 60.6%, p < 0.05). Smoking habits, or the diet's vitamin content, significantly affected the process. The results obtained confirm a potential value of the method as a biomarker of susceptibility in molecular epidemiology or preclinical studies, aimed at predicting susceptibility to various genotoxic exposures (environmental, occupational, therapeutic). To conclude, the research proved the influence of environmental c-PAHs, genotypes, and life styles on DNA damage and on its repair efficiency. Even low exposure to environmental c-PAHs altered DNA repair abilities of the subjects, which may result in an increased cancer risk. The findings confirm that c-PAHs should become pollutants that are subject to regulation.     

Allelopathic effects of Ulva lactuca on selected species of harmful bloom-forming microalgae in laboratory cultures

Allelopathic effects of the green macroalgae Ulva lactuca on the growth of three species of red tide microalgae, Heterosigma akashiwo, Alexandrium tamarense, and Skeletonema costatum were tested in laboratory co-cultures precluding the nutrient and light limitation and the effect of high pH. The growth of all three species of microalgae was significantly (p < 0.01) inhibited by fresh U. lactuca. In nutrient replete semicontinuous co-cultures with U. lactuca, H. akashiwo was completely dead in 12 days, and the growth of A. tamarense and S. costatum was reduced by 48 and 46%, respectively by U. lactuca within 12 days. The U. lactuca culture filtrate exhibited a significant (p < 0.05) inhibitory effect on the microalgae in the first 1 or 2 days, but growth resumed in the following days, and S. costatum growth was slightly (p > 0.05) promoted from day 3. The results suggested that the allelopathic compounds are quickly degradable and a long-term inhibition might need the continuous addition of compounds originated from macroalgae. Dried U. lactuca also exhibited inhibitory effects on the microalgae, and the normalized mean growth rates of microalgae decreased with the biomass of dried U. lactuca. The dependent relationships were y = −2.1208x² + 1.0159x + 0.9752 for H. akashiwo, y = 0.7133x² − 3.5813x + 1.1665 for A. tamarense, and y = −0.2114x² − 1.063x + 1.0873 for S. costatum, respectively. The potential feasibility of utilization of dried U. lactuca against red tide microalgae was 2.0 g dry wt L⁻¹. The present study shows that U. lactuca exhibits negative allelopathic effects on harmful bloom-forming microalgae.     

Attenuated feeding responses to circadian and palatability cues in mice lacking neuropeptide Y

Neuropeptide Y (NPY) is a potent orexigenic peptide that is implicated in the feeding response to a variety of stimuli. The current studies employed mice lacking NPY (Npy−/−) and their wild-type (Npy+/+) littermates to investigate the role of this peptide in the feeding response to circadian and palatability cues. To investigate the response to a circadian stimulus, we assessed food intake during the 4-h period following dark onset, a time of day characterized by maximal rates of food consumption. Compared to Npy+/+ controls, intake of Npy−/− mice was reduced by 33% during this period (0.6 ± 0.1 g versus 0.9 ± 0.1 g; p ≤ 0.05). In contrast, intake did not differ between genotypes when measured over a 24-h period (3.7 ± 0.2 g versus 3.5 ± 0.3 g; p = ns). Furthermore, reduced dark cycle 4 h food intake in Npy−/− mice was not evident after a 24-h fast (1.4 ± 0.1 g for both genotypes; p = ns), despite a pronounced delay in the initiation of feeding (636 ± 133 s versus 162 ± 29 s; p ≤ 0.05). To investigate the role of NPY in the feeding response to palatability cues, mice were presented with a highly palatable diet (HP) for 1 h each day (in addition to having ad libitum access to chow) for 18 days. Npy+/+ mice rapidly increased daily HP intake such that by the end of the first week, they derived a substantial fraction of daily energy from this source (41 ± 3%). By comparison, HP intake was markedly reduced in Npy−/− mice during the first week (24 ± 7% of daily energy intake, p ≤ 0.05 versus Npy+/+), although it eventually increased (by Day 9) to values comparable to those of Npy+/+ controls. These experiments suggest that NPY contributes to the mechanism whereby food intake increases in response to circadian and palatability cues and that mechanisms driving food intake in response to these stimuli differ from those activated by energy restriction.