Innervation zone location of the biceps brachii,a comparison between genders and correlation with anthropometric measurements

Avoiding the innervation zone (IZ) is important when collecting surface electromyographic data. The purposes of this study were threefold: (1) to examine the precision of two different techniques for expressing IZ location for the biceps brachii, (2) to compare these locations between men and women, and (3) to determine if IZ movement with changes in elbow joint angle is related to different anthropometric measures. Twenty-four subjects (mean ± SD ages = 21.8 ± 3.5 yr) performed isometric contractions of the right forearm flexors at each of three separate elbow joint angles (90°, 120°, and 150° between the arm and forearm). During each contraction, the location of the IZ for the biceps brachii was visually identified using a linear electrode array. These IZ locations were expressed in both absolute (i.e. as a distance (mm) from the acromion process) and relative (i.e. as a percentage of humerus length) terms. The results suggested that the estimations of IZ location were more precise when expressed in relative versus absolute terms, and were generally different for men and women. The shift in IZ location with changes in elbow joint angle was not, owever, related to height, weight, or humerus length.     

Test-retest reliability of barbell velocity during the free-weight bench-press exercise

The purpose of this study was to calculate test-retest reliability statistics for peak barbell velocity during the free-weight bench-press exercise for loads corresponding to 10-90% of the 1-repetition maximum (1RM). Twenty-one healthy, resistance-trained men (mean ± SD age = 23.5 ± 2.7 years; body mass = 90.5 ± 14.6 kg; 1RM bench press = 125.4 ± 18.4 kg) volunteered for this study. A minimum of 48 hours after a maximal strength testing and familiarization session, the subjects performed single repetitions of the free-weight bench-press exercise at each tenth percentile (10-90%) of the 1RM on 2 separate occasions. For each repetition, the subjects were instructed to press the barbell as rapidly as possible, and peak barbell velocity was measured with a Tendo Weightlifting Analyzer. The test-retest intraclass correlation coefficients (model 2,1) and corresponding standard errors of measurement (expressed as percentages of the mean barbell velocity values) were 0.717 (4.2%), 0.572 (5.0%), 0.805 (3.1%), 0.669 (4.7%), 0.790 (4.6%), 0.785 (4.8%), 0.811 (5.8%), 0.714 (10.3%), and 0.594 (12.6%) for the weights corresponding to 10-90% 1RM. There were no mean differences between the barbell velocity values from trials 1 and 2. These results indicated moderate to high test-retest reliability for barbell velocity from 10 to 70% 1RM but decreased consistency at 80 and 90% 1RM. When examining barbell velocity during the free-weight bench-press exercise, greater measurement error must be overcome at 80 and 90% 1RM to be confident that an observed change is meaningful.     

The effects of diverting activities on recovery from fatiguing concentric isokinetic muscle actions

The purpose of this study was to examine the effects of diverting activities on recovery from fatiguing concentric isokinetic muscle actions. On 3 separate occasions, 11 men (mean ± SD age = 22.2 ± 1.5 years) and 8 women (mean ± SD age = 22.2 ± 2.1 years) performed 2 bouts of 50 consecutive maximal concentric isokinetic muscle actions of the dominant leg extensors. Between these bouts, the subjects either performed math problems (mental diverting activity), contralateral dynamic constant external resistance (DCER) leg extensions (physical diverting activity), or rested quietly (control). For each trial, the peak torque data from the first and second bouts of 50 muscle actions served as the pretest (Pre) and posttest (Post) data, respectively. The results indicated that when the subjects rested quietly or performed contralateral DCER leg extensions between the fatiguing bouts, the initial peak torque values observed for Post were significantly less than those for Pre. When the subjects performed math problems, however, no decline in the initial peak torque values was observed, thus indicating better recovery. In addition, a decline in the average torque values was observed from Pre to Post for the control trial but not for the math problem or contralateral exercise trials. No differences were observed among the trials for final peak torque, percent decline, or the linear slope of the decline in peak torque. These findings demonstrated that performing either mental or physical diverting activities after fatiguing isokinetic muscle actions enhanced recovery.     

Differential expression of virulence and stress fitness genes during interaction between Listeria monocytogenes and Bifidobacterium longum

Bifidobacterium is well known to have an inhibitory effect on the survival, growth, and proliferation of various foodborne pathogens, but the mechanism of the molecular action of B. longum in blocking the invasion of Listeria monocytogenes is not yet well defined. In the present study, following RNA extraction and cDNA synthesis, differential expression of virulence and stress fitness genes in L. monocytogenes and B. longum was determined by real-time PCR. The results indicate that L. monocytogenes virulence factors, including actA, hly, inlA, and plcA, showed significantly downregulated expression during co-incubation of B. longum and L. monocytogenes in phosphate-buffered saline. The relative mRNA levels of oppA and serpin, two stress fitness genes in B. longum, were significantly higher than for the control group. These results indicate that downregulation of L. monocytogenes virulence factors during co-incubation with B. longum might be responsible for the inhibitory effects.     

An Artificial Aril Designed to Induce Seed Hauling by Ants for Ecological Rehabilitation Purposes

Ants are effective at moving seeds toward their nests, something that may benefit the seeds. We evaluated whether seed movements that may be useful for the rehabilitation of degraded pastures in Colombia can be enhanced by local ants. An artificial aril was prepared and then evaluated in six open cattle pasture farms. Twenty paper disks (each holding seeds with an artificial aril, honey, tuna oil, and control) were set up along linear transects at each farm, and monitored five times in 48 hours. A total of 340 out of 480 seeds were moved from the experimental units by ants. Seeds with tuna oil and an artificial aril were removed twice as frequently as the control and honey smeared seeds. Ectatomma ruidum, Solenopsis geminata, and Pheidole sp. removed the majority of seeds. Advantages of the artificial aril over tuna oil are discussed. This inexpensive technique can enhance seed movement by generalist ants in degraded pastures, likely contributing to regeneration and ecological rehabilitation.     

Torque-related changes in mechanomyographic intensity patterns for the superficial quadriceps femoris muscles

The purpose of this study was to investigate changes in mechanomyographic (MMG) intensity patterns for the vastus lateralis (VL), rectus femoris (RF) and vastus medialis (VM) during submaximal to maximal concentric isokinetic, eccentric isokinetic and isometric muscle actions of the leg extensors. Eleven men (mean ± SD age = 20.1 ± 1.1 years) performed concentric, eccentric and isometric muscle actions of the dominant leg extensors on 3 separate days. Surface MMG signals were detected from the VL, RF and VM, processed with a wavelet analysis and examined with a trend plot. The results indicated that the trend plot was capable of tracking systematic changes in MMG amplitude and frequency with an increase in torque. However, these changes were statistically significant in only 26% of the cases. There were also no consistent differences between muscles or contraction types for the significance of the trend plots.     

Decline in local ecological knowledge in the Colombian Andes may constrain silvopastoral tree diversity

Local ecological knowledge (LEK) can play an important role in ecological restoration by guiding landholder decision‐making towards more ecologically oriented land management. Silvopastures are a promising option for restoring ecological function to degraded landscapes because they increase tree cover and diversity, moderating the impacts of cattle production on ecological processes. Some silvopastoralists possess considerable LEK that can shape silvopastoral tree communities, but little is known about the temporal trends of this knowledge base. We followed up on a survey of workers, managers, and owners of silvopastoral farms in the Colombian Andes 6 years later and found that the ability to identify native trees and describe their uses, and interest in tree planting, were significantly lower. Importantly, the likelihood that an individual would plant a species was linked directly to the number of uses they listed for that species. Furthermore, the utility of species became more important for influencing the probability of planting native trees over time, as general interest in planting trees declined. We show that knowledge about the uses of native trees is critical for promoting cultivation of diverse tree species in silvopastoral systems, and that multipurpose trees are most likely to be planted. Moreover, our results suggest that the socio‐economic changes driving declines in ecological knowledge elsewhere, including outmigration and limited transmission of knowledge to younger generations, appear to erode LEK among Colombian silvopastoralists. Preserving LEK is therefore a critical factor for ensuring silvopastoral and other agro‐ecosystems can contribute to efforts to restore ecological integrity to degraded landscapes.     

Facilitation by pioneer shrubs for the ecological restoration of riparian forests in the Central Andes of Colombia

Riparian vegetation has great functional importance in agroscapes because it establishes physical connections between natural ecosystems embedded in an agricultural matrix. Throughout the tropics, the historical demand for cropland and pastures in the lands adjacent to streams has led to the replacement of forests by exotic grasses. In order to find new methods for initiating the restoration of riparian forests, we evaluated the use of the pioneer shrubs Tithonia diversifolia and Piper auritum as nurse species for their effects on (1) competition with dominant grasses; (2) natural regeneration and the ecological facilitation of six native tree species of different successional stages; and (3) influence on microclimate. Over a period of 15 months, 4.4% coverage of P. auritum was insufficient to inhibit grasses. In contrast, 81% coverage of T. diversifolia limited the growth of dominant grasses such as Cenchrus purpureus, Paspalum paniculatum, and Cynodon plectostachyus likely by intercepting more than 90% of photosynthetically active radiation (PAR), even though other factors cannot be ruled out. T. diversifolia showed simultaneous effects of facilitation and competition by promoting higher survival of the planted native trees while slowing the growth of pioneer species and inhibiting the regeneration of native woody plants probably as a result of high light interception. This study suggests that planting T. diversifolia as a nurse shrub may facilitate early stages of restoration by inhibiting the growth of pastures, but requires pruning, both to increase light availability and promote the growth of planted trees and the recruitment of woody plants.     

Effects of changes in left ventricular contractility on indexes of contractility in mice

Measurement of left ventricular (LV) function is often overlooked in murine studies, which have been used to analyze the effects of genetic manipulation on cardiac phenotype. The goal of this study was to address the effects of changes in LV contractility on indexes of contractility in mice. LV function was assessed in vivo in closed-chest mice by echocardiography and by LV catheterization using a conductance pressure-volume (P-V) catheter with three different interventions that alter contractility by 1) atrial pacing to increase inotropy by augmentation of the force-frequency relation (modest increment of inotropy), 2) dobutamine to maximize inotropy, and 3) esmolol infusion to decrease contractility. Load-independent parameters derived from P-V relations, such as slope of end-systolic P-V relations (ESPVR) and slope of the first maximal pressure derivative over time (dP/dt(max))-end-diastolic volume relation (dP/dt-EDV), and standard echocardiographic parameters were measured. The dP/dt-EDV changed the most among parameters after atrial pacing and dobutamine infusion (percent change, 162.8 +/- 95.9% and 271.0 +/- 44.0%, respectively). ESPVR was the most affected by a decrease in LV contractility during esmolol infusion (percent change, -49.8 +/- 8.3%). However, fractional shortening failed to detect changes in contractility during atrial pacing and esmolol infusion and its percent change was <20%. This study demonstrated that contractile parameters derived from P-V relations change the most during a change in LV contractility and should therefore best detect a small change in contractility in mice. Heart rate has a modest but significant effect on P-V relationship-derived indexes and must be considered in the evaluation of murine cardiac physiology.