In Vivo and In Vitro Toxicity Profiles of Hexane Extract of Alpinia malaccensis Rhizome in Rat and Cell Line Models.

The objective of the study was to evaluate the potential toxicity of crude n-hexane extract of Alpinia malaccensis rhizome. The in vivo acute oral toxicity was evaluated by administering a single oral dose of the extract at 0, 300, or 2000 mg/kg body weight to female Wistar rats according to modified OECD Test Guideline 423. For the in vitro cytotoxicity study, A549, HepG2, 3T3, and COS-7 cell lines were exposed to different doses of A. malaccensis extract and cell viability was assessed adopting MTT assay followed by AO/EB staining, Hoechst staining, and comet assay with a view to compare the cellular and molecular mechanisms underlying the toxicity, if any. It was found that administration of 2000 mg/kg bw dose in in vivo oral acute toxicity study did not produce significant toxicity or mortality. No significant (p < 0.05) differences were observed for body weight and hematological and biochemical parameters compared to control after 14 days of treatment. No changes in behavior, body weight, hematological and biochemical parameters, and aspects of histopathology were observed when compared to the control. Thus, the possible oral lethal dose for A. malaccensis extract is above 2000 mg/kg body weight. The in vitro cytotoxicity analysis showed nontoxicity concentrations of the extract to be 2, 1.4, 30, and 1.4 µg/mL for A549, HepG2, 3T3, and COS-7 cells, respectively, where no apoptotic/necrotic cell death and DNA damage were observed. In conclusion, the extract of rhizome of A. malaccensis did not produce apparent cytotoxicity or acute oral toxicity, confirming the scope to use A. malaccensis as a safe food preservative and a natural therapeutic product after further subacute and chronic toxicity studies.

The effect of mental fatigue on the performance of Australian football specific skills amongst amateur athletes.

OBJECTIVES: This study investigated the effects of induced mental fatigue on the performance of Australian football (AF) specific skills amongst amateur AF players. DESIGN: Randomised cross over trial. METHODS: Twenty-five amateur AF players performed a series of standardised tests from the Australian Football League (AFL) Draft Combine after completing a 30-min Stroop test (mental fatigue condition) or 30-min control condition. The AFL Draft Combine tests included the standing vertical jump test, running vertical jump test, agility test, 20m sprint, Matthew Lloyd clean hands test, Brad Johnson goal kicking test and a Yo-Yo Intermittent Recovery Level 1 (Yo-Yo IR1) test. RESULTS: The Stroop test score decreased during the Stroop test (first five trials: mean=84.7, SD=3.5; last five trials: mean=82.2, SD=5.0, p=0.03). The Yo-Yo IR1 test (mental fatigue: median=920m, IQR=400; control: median=1040m, IQR=760; p=0.03) and Brad Johnson goalkicking test (mental fatigue: median=19.0, IQR=5.0; control: median=25.0, IQR=10.0, p=0.048) were negatively affected by mental fatigue. No other Draft Combine tests demonstrated a negative affect from mental fatigue. CONCLUSIONS: Mental fatigue had a detrimental influence on the performance of AF specific skills. The findings may have implications for AF players who are required to sustain attention and concentration for prolonged periods before and during matches.

Between session reliability of intramuscular electromyography for segments of gluteus medius and minimus during gait and stepping tasks.

Between-session reliability of electromyographic data is important for confidence in interpreting the role of muscles in functional tasks but critical if these data are to be compared before and after an intervention that seeks to change pathological patterns of muscle activity. The gluteus medius (GMed) and minimus (GMin) are known to have functionally discrete segments that are highly active during stance phase of gait and stepping tasks. This study measured the between-session reliability of activity patterns, mean amplitudes and time to peak (TTP) activity of these muscle segments. Intramuscular electrodes were placed in 3 segments of GMed and 2 segments of GMin in 10 healthy young adults for each of two testing sessions held two weeks apart. Participants completed six repetitions of comfortable speed walking trials, step-up and step-down tasks with activity patterns for each muscle segment time- and amplitude-normalized and averaged across trials. Re-test reliability for was high for activity patterns (coefficient of mean correlation ranging from 0.890 to 0.998) across all tasks and muscle segments and only two pairwise comparisons showing differences in amplitude between sessions. With standardized data collection and analysis procedures, GMed and GMin muscle segment activity patterns show good between-session reliability for weightbearing tasks.

Antimicrobial activity and phytochemical screening of Alpinia malaccensis (Ran-kiriya) against food-borne bacteria.

AIMS: Investigation of antimicrobial activity and phytochemicals of Alpinia malaccensis (Ran-kiriya) against foodborne bacteria Staphyloccocus aureus, Listeria monocytogenes, Escherichia coli and Salmonella Typhimurium. METHODS AND RESULTS: Antibacterial activity was tested on the above four foodborne bacteria using agar disc diffusion and broth dilution assay. Alpinia malaccensis rhizome extract chemical composition was determined using gas chromatography-mass spectrometry (GCMS). Active compound was identified using thin-layer chromatography (TLC) and confirmed by nuclear magnetic resonance spectroscopy (NMR). The A. malaccensis rhizome hexane crude extract showed significantly (P < 0·05) higher diameter of inhibition (DIZ) 40 ± 0·52, 38 ± 0·96 and 36 ± 1·45 mm for S. aureusSA113, MSSASS25D and methicillin-resistant S. aureus compared with other tested bacteria. The minimum inhibition concentration and minimum bactericidal concentration were 0·625 and 5 mg ml-1 for S. aureus 113. TLC showed DIZ 39 ± 0·12 mm only for one fraction. The crude extract showed 82·87% a major compound by GCMS which is the active fraction. This purified active fraction was confirmed as 1'acetoxychavicol acetate (1'ACA) by NMR. No significantly different inhibition was observed for crude extract and purified compound. CONCLUSIONS: Bioactive 1'ACA of A. malaccensis showed strong antibacterial activity against S. aureus strains including MRSA strain. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is the first to identify 1'ACA from A. malaccensis. The crude or purified compound could potentially be developed as antimicrobials.

The effect of high-frequency cutaneous vibration on different inputs subserving detection of joint movement.

Stimuli that preferentially activate rapidly adapting cutaneous receptors impair proprioception in the fingers. These experiments assessed potential mechanisms. The ability to detect passive movements about interphalangeal joints of the fingers was measured when vibrotactile stimuli were applied to the moving digit or to an adjacent digit at a high frequency (300 Hz) and low amplitude (50 microm peak-to-peak) that favours activation of Pacinian corpuscle (PC) afferents. Detection of movement was significantly impaired when vibration was applied to either digit. However, vibration applied to an anaesthetized adjacent digit caused no impairment. Impairment of proprioception was still observed when only skin and joint (but not muscle) afferents could contribute to detection, but was not significant with only muscle afferents intact during anaesthesia of the moving digit. We suggest that activation of PC afferents, either in or near the moving digit, impairs movement detection through an interaction predominantly between the classes of cutaneous afferents.

Local subcutaneous and muscle pain impairs detection of passive movements at the human thumb.

Activity in both muscle spindle endings and cutaneous stretch receptors contributes to the sensation of joint movement. The present experiments assessed whether muscle pain and subcutaneous pain distort proprioception in humans. The ability to detect the direction of passive movements at the interphalangeal joint of the thumb was measured when pain was induced experimentally in four sites: the flexor pollicis longus (FPL), the subcutaneous tissue overlying this muscle, the flexor carpi radialis (FCR) muscle and the subcutaneous tissue distal to the metacarpophalangeal joint of thumb. Tests were conducted when pain was at a similar subjective intensity. There was no significant difference in the ability to detect flexion or extension under any painful or non-painful condition. The detection of movement was significantly impaired when pain was induced in the FPL muscle, but pain in the FCR, a nearby muscle that does not act on the thumb, had no effect. Subcutaneous pain also significantly impaired movement detection when initiated in skin overlying the thumb, but not in skin overlying the FPL muscle in the forearm. These findings suggest that while both muscle and skin pain can disturb the detection of the direction of movement, the impairment is site-specific and involves regions and tissues that have a proprioceptive role at the joint. Also, pain induced in FPL did not significantly increase the perceived size of the thumb. Proprioceptive mechanisms signalling perceived body size are less disturbed by a relevant muscle nociceptive input than those subserving movement detection. The results highlight the complex relationship between nociceptive inputs and their influence on proprioception and motor control.

Group III and IV muscle afferents differentially affect the motor cortex and motoneurones in humans.

The influence of group III and IV muscle afferents on human motor pathways is poorly understood. We used experimental muscle pain to investigate their effects at cortical and spinal levels. In two studies, electromyographic (EMG) responses in elbow flexors and extensors to stimulation of the motor cortex (MEPs) and corticospinal tract (CMEPs) were evoked before, during, and after infusion of hypertonic saline into biceps brachii to evoke deep pain. In study 1, MEPs and CMEPs were evoked in relaxed muscles and during contractions to a constant elbow flexion force. In study 2, responses were evoked during elbow flexion and extension to a constant level of biceps or triceps brachii EMG, respectively. During pain, the size of CMEPs in relaxed biceps and triceps increased (by approximately 47% and approximately 56%, respectively; P < 0.05). MEPs did not change with pain, but relative to CMEPs, they decreased in biceps (by approximately 34%) and triceps (by approximately 43%; P < 0.05). During flexion with constant force, ongoing background EMG and MEPs decreased for biceps during pain (by approximately 14% and 15%; P < 0.05). During flexion with a constant EMG level, CMEPs in biceps and triceps increased during pain (by approximately 30% and approximately 26%, respectively; P < 0.05) and relative to CMEPs, MEPs decreased for both muscles (by approximately 20% and approximately 17%; P < 0.05). For extension, CMEPs in triceps increased during pain (by approximately 22%) whereas MEPs decreased (by approximately 15%; P < 0.05). Activity in group III and IV muscle afferents produced by hypertonic saline facilitates motoneurones innervating elbow flexor and extensor muscles but depresses motor cortical cells projecting to these muscles.

Impairment of human proprioception by high-frequency cutaneous vibration.

These experiments assessed whether the impairment in proprioceptive acuity in the hand during 'interfering' cutaneous stimulation could be caused by inputs from Pacinian corpuscles. The ability to detect passive movements at the proximal interphalangeal joint of the index finger was measured when vibrotactile stimuli were applied to the adjacent middle finger and thenar eminence at frequencies and amplitudes that favour activation of rapidly adapting cutaneous afferents. Inputs from Pacinian corpuscles are favoured with high-frequency vibration (300 Hz), while those from Meissner corpuscles are favoured by lower frequencies (30 Hz). Detection of movement was significantly impaired when 300 Hz (20 microm peak-to-peak amplitude) complex vibration or 300 Hz (50 microm) sinusoidal vibration was applied to the middle finger and thenar eminence. In contrast, detection of movements was not altered by low-frequency sinusoidal vibration at 30 Hz with an amplitude of 50 microm or with a larger amplitude matched in subjective intensity to the 300 Hz sinusoidal stimulus. Thus it is unlikely that the impairment in detection was due to attention being diverted by vibration of an adjacent digit. In addition, an increase in amplitude of 300 Hz vibration led to a greater impairment of movement detection, so that the impairment was graded with the input. The time taken to nominate the direction of applied movement also increased during 300 Hz but not during 30 Hz sinusoidal vibration. These findings suggest that stimuli which preferentially activate Pacinian, but not Meissner corpuscles, impair proprioceptive acuity in a movement detection task.

Force matching errors following eccentric exercise.

During eccentric exercise contracting muscles are forcibly lengthened, to act as a brake to control motion of the body. A consequence of eccentric exercise is damage to muscle fibres. It has been reported that following the damage there is disturbance to proprioception, in particular, the senses of force and limb position. Force sense was tested in an isometric force-matching task using the elbow flexor muscles of both arms before and after the muscles in one arm had performed 50 eccentric contractions at a strength of 30% of a maximum voluntary contraction (MVC). The exercise led to an immediate reduction of about 40%, in the force generated during an MVC followed by a slow recovery over the next four days, and to the development of delayed onset muscle soreness (DOMS) lasting about the same time. After the exercise, even though participants believed they were making an accurate match, they made large matching errors, in a direction where the exercised arm developed less force than the unexercised arm. This was true whichever arm was used to generate the reference forces, which were in a range of 5-30% of the reference arm's MVC, with visual feedback of the reference arm's force levels provided to the participant. The errors were correlated with the fall in MVC following the exercise, suggesting that participants were not matching force, but the subjective effort needed to generate the force: the same effort producing less force in a muscle weakened by eccentric exercise. The errors were, however, larger than predicted from the measured reduction in MVC, suggesting that factors other than effort might also be contributing. One factor may be DOMS. To test this idea, force matches were done in the presence of pain, induced in unexercised muscles by injection of hypertonic (5%) saline or by the application of noxious heat to the skin over the muscle. Both procedures led to errors in the same direction as those seen after eccentric exercise.

Force-matching errors after eccentric exercise attributed to muscle soreness.

1. Experiments were performed to test the ability of human subjects to match forces in their elbow flexor muscles following eccentric exercise of one arm and, in a second series, after biceps brachii of one arm had been made sore by injection of hypertonic saline. 2. In the force-matching task, the elbow flexors of one arm, the reference arm, generated 30% of maximum voluntary contraction (MVC) under visual control. Subjects matched that level with their other arm, the indicator arm, without visual feedback. 3. After eccentric exercise of elbow flexors of the indicator arm, subjects felt they had achieved a satisfactory match while indicating forces that were significantly lower, by approximately 5%, than the reference level. Errors were in the opposite direction (i.e. forces were overestimated) when the reference arm was exercised. 4. Errors were reduced when matching forces were expressed as fractions of the sessional MVC rather than the pre-exercise MVC. Residual errors from 24 h postexercise onwards were attributed to muscle soreness from the exercise. 5. In support of this view, a similar pattern of matching errors was observed when an unexercised arm was made sore by injection of hypertonic saline into the biceps. 6. It is concluded that muscle soreness can interfere with a subject's ability to match forces, perhaps as a result of a reduced excitability of motor cortex. It implies that muscle soreness may contribute to the weakness experienced after a period of unaccustomed eccentric exercise.

Force matching at the elbow joint is disturbed by muscle soreness.

These experiments are concerned with the ability of human subjects to match isometric torque in their elbow flexor muscles when biceps of one arm is made sore. Pain was induced by injection of hypertonic saline. Subjects were asked to generate a level of torque, 30% of maximum, with one arm, the reference arm. To achieve the required torque, subjects were given visual feedback. Subjects were then asked to match this torque with their other arm, the indicator arm. In control measurements, subjects were consistent in their matching ability and often were quite accurate. However, when biceps of one arm was made sore, subjects consistently and significantly underestimated the level of torque being generated by the sore arm. Painful heat applied to the skin over biceps produced a similar pattern of errors. Heating skin remote from elbow flexors had no significant effect. One interpretation of these findings is that the nociceptive input from the sore region of skin or muscle leads to reduced excitability of the motor cortex. That, in turn, disturbs the relationship between the centrally generated effort and motor output, leading to matching errors.

Matching different levels of isometric torque in elbow flexor muscles after eccentric exercise.

Human subjects generated a specified level of isometric torque with elbow flexor muscles of one arm, the reference arm, under visual feedback. They were then asked to generate what they perceived to be the same level, with the other arm, the indicator, but with no visual feedback. A number of torque levels, between 2% and 30% of maximum were used in the matching trials. Elbow flexors of one arm were then exercised eccentrically on a dynamometer. Immediately after the exercise, there was a large (40%) drop in maximum voluntary torque, as well as some soreness and swelling 24 h later, indicative of muscle damage. When the torque-matching experiment was repeated after the indicator arm had been exercised, the indicator signalled torque levels significantly below the reference level (P<0.05). When the reference arm was exercised, errors were in the opposite direction. Over the 4 days of testing post-exercise, errors became less as torque levels returned to normal. When errors were expressed in terms of maximum torque post-exercise, they were significantly reduced. This suggested that subjects were using as a matching cue the perceived effort required to generate a given level of torque rather than the level of torque itself. Persisting matching errors, from 24 h onwards after the eccentric contractions, were proposed to include a component attributable to the muscle soreness. Changes in electromyogram recorded after eccentric exercise were consistent with the effort-matching hypothesis. The muscle's torque-angle relationship was used to estimate matching ability in the absence of fatigue. One forearm was placed at various angles and its reference torque was matched by the other, the indicator, always at 90 degrees. Again, matching errors were consistent with an interpretation based on a match of effort rather than torque.

Changes in passive tension of muscle in humans and animals after eccentric exercise.

1. This is a report of experiments on ankle extensor muscles of human subjects and a parallel series on the medial gastrocnemius of the anaesthetised cat, investigating the origin of the rise in passive tension after a period of eccentric exercise. 2. Subjects exercised their triceps surae of one leg eccentrically by walking backwards on an inclined, forward-moving treadmill. Concentric exercise required walking forwards on a backwards-moving treadmill. For all subjects the other leg acted as a control. 3. Immediately after both eccentric and concentric exercise there was a significant drop in peak active torque, but only after eccentric exercise was this accompanied by a shift in optimum angle for torque generation and a rise in passive torque. In the eccentrically exercised group some swelling and soreness developed but not until 24 h post-exercise. 4. In the animal experiments the contracting muscle was stretched by 6 mm at 50 mm s(-1) over a length range symmetrical about the optimum length for tension generation. Measurements of passive tension were made before and after the eccentric contractions, using small stretches to a range of muscle lengths, or with large stretches covering the full physiological range. 5. After 150 eccentric contractions, passive tension was significantly elevated over most of the range of lengths. Measurements of work absorption during stretch-release cycles showed significant increases after the contractions. 6. It is suggested that the rise in passive tension in both human and animal muscles after eccentric contractions is the result of development of injury contractures in damaged muscle fibres.

Large-fiber mechanoreceptors contribute to muscle soreness after eccentric exercise.

Muscles subjected to eccentric exercise, in which the contracting muscle is forcibly lengthened, become sore the next day (delayed onset muscle soreness). In subjects who had their triceps surae of 1 leg exercised eccentrically by walking backwards on an inclined moving treadmill, mapping the muscle 48 hours later with a calibrated probe showed sensitive areas were localized but not restricted to the muscle-tendon junction. Injection of 5% sodium chloride into a sensitive site in the exercised leg did not produce more pain than injections into the unexercised leg, suggesting that nociceptor sensitization was not responsible. Applying controlled indentations to a sensitive area showed that the pain could be exacerbated by 20-Hz or 80-Hz vibration. In an unexercised muscle, vibration had the opposite effect; it reduced pain. Pain thresholds were measured before, during, and after a pressure block of the sciatic nerve. The block affected only large-diameter nerve fibers, as evidenced by disappearance of the H reflex and a weakened voluntary contraction, leaving painful heat and cold sensations unaltered. Pain thresholds increased significantly during the block. It is concluded that muscle mechanoreceptors, including muscle spindles, contribute to the soreness after eccentric exercise.