Biomedical subjects

C Nicol

Publications and source records attributed to C Nicol.

At least 19 recordsLinked to original sources

PubMed2006

Changes in the soleus muscle architecture after exhausting stretch-shortening cycle exercise in humans.

This study focused on the architectural changes in the muscle-tendon complex during the immediate and secondary (delayed) reductions of performance (bimodal recovery) caused by an exhaustive rebound type stretch-shortening cycle (SSC) exercise. The isometric plantar flexor torque during maximum voluntary contraction (MVC) was measured together with recording of electromyography (EMG) and ultrasonography from the soleus muscle before (BEF), after (AFT), 2 h (2H), 2 and 8 days (2D, 8D) after the SSC exercise (n=8). The performance variables (MVC torque and EMG activation) followed the bimodal recovery patterns. This was not the case in the changes of the fascicle length and muscle thickness. The relative torque changes in MVC correlated positively (R=0.78, P=0.02) to the corresponding averaged EMG changes between BEF and 2H (BEF-->2H); the significance disappeared in the comparison between 2H and 2D (2H-->2D), during which period MVC showed a secondary reduction. The relative torque changes in MVC showed no correlation with the changes in muscle thickness between BEF-2H. However, this correlation between 2H-2D was negative (R=-0.85, P<0.01). The fascicle shortening/average EMG ratio in MVC increased at 2H, and then decreased more at 2D than 2H (P<0.05). Thus, the secondary performance decline was not related to the corresponding EMG reduction but to the increased muscle thickness, which peaked at 2D. The results suggest clearly that the secondary decline in MVC could be related to the increase in muscle volume.

Adult↗

PubMed2005

Campylobacter spp. in New Zealand raw sheep liver and human campylobacteriosis cases.

Sheep liver samples were tested for the presence and numbers of Campylobacter jejuni and C. coli during both spring and autumn. Over the same period, isolates were obtained from human clinical cases from the same geographical area as where the food samples were purchased. A subset of the C. jejuni isolates was typed by both Penner serotyping and pulsed field gel electrophoresis using the restriction enzyme SmaI, to estimate the proportion of liver isolate types that were also isolated from human cases of campylobacteriosis. Of the 272 liver samples tested, 180 (66.2%) contained Campylobacter. Most of the positive samples contained <3 MPN/g of the organism, and only 12 (6.7%) were contaminated at a level exceeding 100 MPN/g. A total of 180 C. jejuni isolates were obtained from sheep liver and another 200 from human faeces. Of these, 212 isolates were randomly selected for typing, half from raw liver and half from human faeces. More than half (61.1%) of the 106 C. jejuni isolates from liver were of subtypes that were also isolated from human cases. While the C. jejuni present in sheep liver were mostly of subtypes also isolated from human cases, the significance of this food as a vehicle of human campylobacteriosis needs to be examined further in respect to other factors such as dose-response information, consumption data, frequency of undercooking and cross contamination.

Animals↗

PubMed2005

Sesame seed products contaminated with Salmonella: three outbreaks associated with tahini.

In November 2002, the first of three outbreaks of Salmonella Montevideo infection in Australia and New Zealand was identified in New South Wales, Australia. Affected persons were interviewed, and epidemiologically linked retail outlets inspected. Imported tahini was rapidly identified as the source of infection. The contaminated tahini was recalled and international alerts posted. A second outbreak was identified in Australia in June-July 2003 and another in New Zealand in August 2003. In a total of 68 S. Montevideo infections, 66 cases were contacted. Fifty-four (82%) reported consumption of sesame seed-based foods. Laboratory analyses demonstrated closely related PFGE patterns in the S. Montevideo isolates from human cases and sesame-based foods imported from two countries. On the basis of our investigations sesame-based products were sampled in other jurisdictions and three products in Canada and one in the United Kingdom were positive for Salmonella spp., demonstrating the value of international alerts when food products have a wide distribution and a long shelf life. A review of the controls for Salmonella spp. during the production of sesame-based products is recommended.

Australia↗

PubMed2005

The occurrence of Campylobacter subtypes in environmental reservoirs and potential transmission routes.

AIM: To identify potential reservoirs and transmission routes of human pathogenic Campylobacter spp. METHODS AND RESULTS: An enrichment PCR method for the detection and identification of Campylobacter jejuni and/or Campylobacter coli in faecal, food and river water samples was applied to 1450 samples of 12 matrix types obtained from a defined geographical area. PCR-positive samples were cultured to yield isolates for typing, and the data for 616 C. jejuni isolates obtained. Serotyping and SmaI macrorestriction profiling using pulsed field gel electrophoresis revealed a high level of diversity within the isolates from each matrix. Campylobacter jejuni and C. coli subtypes indistinguishable from those obtained from human cases were detected in most of the matrices examined. No Campylobacter isolates were isolated from possum faeces. CONCLUSIONS: Ten of the 12 matrices examined may be involved in the transmission of human campylobacteriosis as they contained Campylobacter subtypes also isolated from clinical cases. SIGNIFICANCE AND IMPACT OF THE STUDY: Results indicate that, for this rural population, a range of potential transmission routes that could lead to campylobacteriosis exist. Their relative importance needs to be assessed from an exposure assessment standpoint.

Animals↗

PubMed2004

[Delayed post effort muscle soreness].

Muscle intolerance to exercise may result from different processes. Diagnosis involves confirming first the source of pain, then potential pathological myalgia. Delayed-onset muscle soreness (DOMS), commonly referred as tiredness, occurs frequently in sport. DOMS usually develops 12-48 h after intensive and/or unusual eccentric muscle action. Symptoms usually involve the quadriceps muscle group but may also affect the hamstring and triceps surae groups. The muscles are sensitive to palpation, contraction and passive stretch. Acidosis, muscle spasm and microlesions in both connective and muscle tissues may explain the symptoms. However, inflammation appears to be the most common explanation. Interestingly, there is strong evidence that the progression of the exercise-induced muscle injury proceeds no further in the absence of inflammation. Even though unpleasant, DOMS should not be considered as an indicator of muscle damage but, rather, a sign of the regenerative process, which is well known to contribute to the increased muscle mass. DOMS can be associated with decreased proprioception and range of motion, as well as maximal force and activation. DOMS disappears 2-10 days before complete functional recovery. This painless period is ripe for additional joint injuries. Similarly, if some treatments are well known to attenuate DOMS, none has been demonstrated to accelerate either structural or functional recovery. In terms of the role of the inflammatory process, these treatments might even delay overall recovery.

Exercise↗

PubMed2003

Effects of long- and short-term fatiguing stretch-shortening cycle exercises on reflex EMG and force of the tendon-muscle complex.

This study examined the fatigue effects of stretch-shortening cycle exercises of different intensity and duration on stretch reflex EMG and mechanical responses of the triceps surae muscle. Twelve subjects performed either a 10-km run ( n=6) or short but exhaustive rebound exercise on a sledge apparatus ( n=6). Passive reflex tests (mechanically induced ankle dorsiflexions) were examined before, after as well as 2 h, 2 and 7 days after exercise. Mechanical reflex responses were recorded from the ergometer torque signal. An acute contractile failure was observed as large reductions in twitch responses, especially in the sledge subgroup who showed high post-exercise peak blood lactate and an increased EMG/torque ratio. Independently of the exercise, the delayed fatigue analysis revealed strong relationships between the reflex-induced EMG and mechanical changes. In addition to muscle damage, these results may be explained by inhibitory effects via the sensitisation of small muscle afferents particularly during the exercise-induced delayed recovery process.

Adolescent↗

PubMed2003

Motor unit activation patterns during isometric, concentric and eccentric actions at different force levels.

Motor unit activation patterns were studied during four different force levels of concentric and eccentric actions. Eight male subjects performed concentric and eccentric forearm flexions with the movement range from 100 degrees to 60 degrees in concentric and from 100 degrees to 140 degrees elbow angle in eccentric actions. The movements were started either from zero preactivation or with isometric preactivation of the force levels of 20, 40, 60 and 80% MVC. The subjects were then instructed to maintain the corresponding relative force levels during the dynamic actions. Intramuscular and surface EMG was recorded from biceps brachii muscle. Altogether 28 motoneuron pools were analyzed using the intramuscular spike-amplitude frequency (ISAF) analysis technique of Moritani et al. The mean spike amplitude was lower and the mean spike frequency higher in the isometric preactivation phase than in the consequent concentric and eccentric actions. When the movements started with isometric preactivation the mean spike amplitude increased significantly (P<0.001) up to 80% in isometric and concentric actions but in eccentric actions the increase continued only up to 60% (P<0.01). The mean spike frequency in isometric preactivation and in concentric action with preactivation was lower only at the 20% force level (P<0.01) as compared to the other force levels while in eccentric action with preactivation the increase between the force levels was significant (P<0.01) up to 60%. When the movement was started without preactivation the mean spike amplitude at 20% and at 40% force level was higher (P<0.01) in eccentric action than in concentric actions. It was concluded that the recruitment threshold may be lower in dynamic as compared to isometric actions. The recruitment of fast motor units may continue to higher force levels in isometric and in concentric as in eccentric actions which, on the other hand, seems to achieve the higher forces by increasing the firing rate of the active units. At the lower force levels mean spike amplitude was higher in eccentric than in concentric actions which might indicate selective activation of fast motor units. This was, however, the case only when the movements were started without isometric preactivation.

Adult↗

PubMed2002

Interaction between pre-landing activities and stiffness regulation of the knee joint musculoskeletal system in the drop jump: implications to performance.

The purpose of the present study was to investigate the interaction between the pre-landing activities and the stiffness regulation of the knee joint musculoskeletal system and the takeoff speed during a drop jump (DJ). Nine healthy male subjects performed a DJ test from the height of 50 cm. The surface electromyographic (EMG) activity of the vastus lateralis (VL) muscle was recorded to evaluate both the pre-landing and post-landing muscle activation levels. Simultaneous recording of the jumping motion and ground reaction force was performed by a high-speed video camera (100 frames x s(-1)), and a force platform was employed to allow joint moment analysis. Joint stiffness was calculated by a linear regression of the knee joint moment/angle relationship. Elasticity of the knee extensor muscle during DJ was estimated by means of a four-element muscle model consisting of a parallel elastic component, a series elastic component (SEC), a viscous damper, and a contractile element. DJ performance correlated positively with the positive peak power of the knee joint (P < 0.01) and with the moment of the knee joint at the end of stretch (P < 0.01). However, there was no significant relationship between DJ performance and the positive peak power of the ankle joint. The knee joint moment at the end of stretch correlated with the SEC stiffness during the transmission phase from the end of the initial impact to the onset of the concentric action (P < 0.01) and with the maximum rate of isometric force development of the knee extensors (P < 0.01). Multiple regression analysis showed that the SEC stiffness during the transmission phase of the knee joint can be explained by a combination of the pre-activity of the VL muscle and the knee joint angular velocity at touchdown (F = 5.76, P < 0.05). These results seem to emphasize the functional significance of the pre-programmed activity for controlling the subsequent stiffness regulation and then contributing to the performance in DJ. Thus, it can be suggested that the centrally pre-programmed activity and the associated elastic behavior of the SEC in the knee extensor muscle in conjunction with the muscle contractile property play a major role in regulating the performance in DJ.

Adult↗

PubMed2002

Acute and prolonged reduction in joint stiffness in humans after exhausting stretch-shortening cycle exercise.

The purpose of the present study was to examine the acute and long-term fatigue effects of exhausting stretch-shortening cycle (SSC) exercise on the stiffness of ankle and knee joints. Five subjects were fatigued on a sledge apparatus by 100 maximal rebound jumps followed by continuous submaximal jumping until complete exhaustion. Neuromuscular fatigue effects were examined in submaximal hopping (HOP) and in maximal drop jumps (DJ) from 35 (DJ35) and 55 cm (DJ55) heights on a force plate. Additional force and reflex measurements were made using an ankle ergometer. Jumping tests and ankle ergometer tests were carried out before, immediately after, 2 h (2H), 2 days and 7 days (7D) after the SSC exercise. Kinematics, force and electromyography (EMG) recordings were complemented with inverse dynamics, which was used to calculate joint moments. The quotient of changes in joint moment divided by changes in joint angle was used as a value of joint stiffness (JS). In addition, blood lactate concentrations and serum creatine kinase activities were determined. The exercise induced a clear decrease in knee joint stiffness by [mean (SD)] 29 (13)% (P < 0.05) in HOP, 31 (6)% (P < 0.05) in DJ35 and 34 (14)% (P < 0.05) in DJ55. A similar trend was observed in the ankle joint stiffness with significant post-exercise reductions of 22 (8)% (P < 0.05) in DJ35 and of 27 (19)% (P < 0.05) at 2H in DJ55. The subsequent recovery of JS was slow and in some cases incomplete still at 7D. Generally, all the EMG parameters were fully recovered by 2H, whereas the force recovery was still incomplete at this time. These data indicate that the immediate reduction in JS was probably related to the effects of both central (neural) and peripheral (metabolic) fatigue, whereas the prolonged impairment was probably due to peripheral fatigue (muscle damage).

Adult↗

PubMed2002

An epidemic of salmonellosis caused by Salmonella Typhimurium DT160 in wild birds and humans in New Zealand.

AIM: This study reports an outbreak of salmonellosis due to S. Typhimurium DT160 which caused extensive mortality in wild birds and enteric disease in humans in New Zealand during the winter and spring months of the year 2000. METHODS: Necropsies were performed and microbiological examinations undertaken on wild birds from populations in which mass mortality was reported, and on captive indigenous birds which died suddenly during the winter and spring of 2000. Affected tissues were examined histologically and isolates of S. Typhimurium were phage typed and examined using pulsedfield gel electrophoresis (PFGE). Isolates of S. Typhimurium obtained from cases of human enteric disease which occurred during these months were phage typed, examined using PFGE and compared with the bird isolates. RESULTS: Central and northern areas of the South Island and the southern North Island were worst affected with die-offs of several hundreds of sparrows and other birds reported in rural areas. Mortalities reached a peak in winter (July-August) 2000 and decreased to small numbers during the spring and early summer. The birds usually died of an acute septicaemia with multifocal necrotising lesions in the liver and spleen. Human cases throughout the country increased gradually over the same period. Isolates from birds, livestock and humans examined using PFGE were indistinguishable from one another. CONCLUSION: This strain of Salmonellahas emerged as a major cause of septicaemia in wild birds in New Zealand. Because of the close association between house sparrows (Passer domesticus) and humans, the organism also poses a serious zoonotic risk. The possibility that the infection may spread to involve indigenous species needs investigation.

Journal Article↗

PubMed2001

Tympanic temperature and heart rate changes in firefighters during treadmill runs performed with different fireproof jackets.

Six well-trained firefighters performed six treadmill runs at 70% of the velocity at VO2max (Maximal aerobic velocity MAV = 13.2+/-0.3 km h(-1)). A recovery time of 1 week was allowed between trials. The first session was performed by subjects wearing only shorts (i.e. no fire jacket, J0). A similar protocol was applied subsequently to test the physiological effects associated with the wearing of one of five different fire jackets: one leather (J1) and four textile-type jackets: VTN with membrane (J2), VTN without membrane (J3), Vidal with Kermel HTA (Haute Teneur en Aramide i.e. high density in Aramide) (J4); and Rolland with Kermel HTA (J5). All sessions were performed in a randomized order and in laboratory conditions. Exercise with the fireproof jackets resulted in higher tympanic temperature (Tty), heart rate (HR) and body mass loss (BML) changes compared to J0 (p<0.001). The magnitudes of these changes depended on the type of the jacket. Exercise in the leather jacket (J1) resulted in the highest Tty and HR, which differed significantly from values in all other conditions (p<0.001). The exercise-induced increases in Tty wearing jackets J3 and J5 were also significantly (p < 0.05) higher than those observed with jackets J2 and J4. In conclusion, textile jackets induced less HR and Tty stresses than the leather one. The magnitude of the physiological responses induced by textile jackets were correlated to jacket weight. J2 and J4 jackets were more effective in limiting hyperthermia and any potential detrimental effect on the exercise capacity.

Adult↗

PubMed2000

Isolation of shiga toxin-producing Escherichia coli (STEC) from foods using EHEC agar.

Enterohaemorrhagic Escherichia coli (EHEC) agar was evaluated for its ability to recover one isolate of each of three serotypes (O157:H7, O26 and O113:H21) of shiga toxin-producing E. coli (STEC) from raw mince, pasteurized milk and salami after enrichment. The method detected around one colony-forming unit (cfu) in 25 ml in milk, but was less sensitive with salami, requiring 10-1000 cfu 25 g-1 (depending on serotype) for detection. In raw minced beef any enterohaemolysin-producing colonies were outnumbered by other colonies and only one of 12 enrichments yielded the inoculum serotype. Additional tests were conducted on 15 retail meat products. One 25-g sample of each product was processed as purchased, while another was inoculated with 157-185 cfu of a cocktail of E. coli O157, O113 and O26 cultures. Recovery was easily achieved with cooked meat products and salami. Recovery from raw minced meat was again difficult, but sometimes possible. Testing more suspect colonies than were tested in this study would presumably increase the sensitivity of the method.

Animals↗

PubMed1999

Effect of exhausting stretch-shortening cycle exercise on the time course of mechanical behaviour in the drop jump: possible role of muscle damage.

The purpose of the present study was to investigate the effect of stretch-shortening-cycle-induced muscle damage on the time course of mechanical behaviour in the drop jump. Ten healthy male subjects performed submaximal stretch-shortening cycle (SSC) exercise on a special sledge apparatus. Exhaustion occurred on average within 3 min. A drop jump (DJ) test from a 50-cm height was performed before and immediately after the sledge exercise as well as 2 h, 2 days and 4 days later. The fatigue exercise showed relatively high blood lactate concentration [12.5 (SD 2.6) mmol x l(-1)] and an increase of serum creatine kinase (CK) activity delayed by 2 days [540 (SD 407) U x l(-1)]. The initial decline in the jump performance (before - immediately after) was related negatively to the early recovery in performance (immediately after 2 h) (P < 0.05). The early recovery of the knee joint moment at the end of stretch showed a negative correlation to the delayed decrease in DJ performance (2 h 2 days) (P < 0.01). Thus, the DJ performance showed an initial decline followed by an early recovery and a secondary decline. Both the initial decline and early recovery in the knee joint moment at the end of stretch were related to the corresponding initial (after 2 h) (P < 0.05) and secondary increases (2 h - 2 days) (P < 0.01) in CK. It is suggested that the early recovery as well as the initial decline in the knee joint function could depend on the degree of muscle damage. Delayed decrease in initial stiffness (2 h - 2 days) was negatively related to the corresponding changes in the knee joint angle at touch down in DJ (P < 0.001). These interactions would imply that the decrease in the stiffness regulation and the modulation of the prelanding motor control might be attributable to secondary muscle damage during 2 days after the SSC exercise. Therefore, it may be suggested that the changes in the DJ performance after the exhausting SSC exercise accompany the progress of muscle damage observed by the corresponding increase in serum CK concentration and the corresponding deterioration of stiffness regulation and motor control in DJ.

Adult↗

PubMed1999

Plasma catecholamine responses to four resistance exercise tests in men and women.

The plasma adrenaline ([A]) and noradrenaline ([NA]) concentration responses of nine men and eight women were investigated in four resistance exercise tests (E80, E60, E40 and E20), in which the subjects had to perform a maximal number of bilateral knee extension-flexion movements at a given cycle pace of 0.5 Hz, but at different load levels (80%, 60%, 40% and 20% of 1 repetition maximum, respectively). The four test sessions were separated by a minimal interval of 3 rest days. The number of repetitions (Repmax), the total work (Wtot) done normalized for the lean body mass and the heart rate (HR) responses were similar in the two groups in each test. In addition, no differences were found between the two groups in [A] and [NA] either before or after the exercise tests. The postexercise [NA], both in the men [10.8 (SD 7.0) nmol x l(-1)] and in the women [11.7 (SD 7.4) nmol x l(-1)], was clearly the highest in E20, where also the Repmax, WtOt, the total amount of integrated electromyograph activity in the agonist muscles and the peak postexercise blood lactate concentration [men 8.3 (SD 1.6) vs women 7.3 (SD 0.9) mmol x l(-1), ns] were significantly higher than in the other tests. Although the postexercise [A] in E20 both in the men [7.1 (SD 6.0) nmol x l(-1)] and in the women [5.2 (SD 2.0) nmol x l(-1)] were higher than in E80 [men 3.1 (SD 4.2), women 2.1 (SD 2.0) nmol x l(-l)] (P < 0.05), they were not significantly different from E60 [men 3.6 (SD 1.9), women 4.0 (SD 3.3) nmol x l(-1)] and E40 [men 3.8 (SD 4.1), women 5.8 (SD 4.0) nmol x l(-1)] in either group. The present study did not indicate any sex differences in performance and in plasma catecholamine responses in different exhausting resistance exercise tests performed with the knee extensor muscles. In both groups the plasma [NA] response was clearly the largest in the longest exercise with the greatest amount of muscle activity and work done, and with the largest blood lactate response. The differences in the plasma [A] responses between the exercises tended to be somewhat smaller.

Adult↗

PubMed1999

Seasonal variation of Campylobacter types from human cases, veterinary cases, raw chicken, milk and water.

During August 1996 (winter) and February 1997 (summer), a total of 180 Campylobacter isolates from a restricted geographical area were obtained from human and veterinary cases, raw milk and chicken, and untreated water. Isolates were typed by Penner serotyping and pulsed-field gel electrophoresis (PFGE) of restriction enzyme-produced DNA fragments. Differences were noted between the August and February serotypes with the most, and fourth most frequently isolated serotypes in February being completely absent in August. Two other serotypes were more frequently found in the February isolates, while the reverse was true for two others. In contrast to the serotyping data, one PFGE restriction profile type was dominant in both seasons, and the pattern of distribution of isolates among the other restriction patterns was similar. Five groups of isolates in each month were indistinguishable by both typing methods. Only one group was common to both months. Another group, which was absent in August, dominated the February isolates. Marked differences in the types isolated in the two seasons were therefore evident. Some isolates from human cases were indistinguishable from others isolated from water and raw chicken, indicating possible routes of infection for humans.

Animals↗

PubMed1999

Understanding equine stereotypies.

It is frequently asserted that equine stereotypies, such as crib-biting, wind-sucking and weaving, are caused by boredom. However, this explanation is too general to be of practical use in discerning the causes of each stereotypy or in devising management practices to prevent their occurrence. The majority of equine stereotypes start within one month of weaning when both the nutritional and social environment of the foal are substantially altered. Epidemiological research has revealed that the provision of low quantities of forage and minimal opportunities for social contact are associated with a higher reported prevalence of stereotypic behaviour. Experimental data also suggest that oral stereotypies develop in response to a low forage diet but this may be partially adaptative. Oral stereotypies may increase salivary flow therefore reducing the acidity of gastric tract and speeding the transit of ingested feed. Stereotypic horses may be less reactive to short-term aversive stimulation. Neither direct nor circumstantial evidence confirms anecdotal reports that horses copy stereotypies from each other. Surgical and pharmacological methods of prevention should not be attempted unless the underlying causes are removed.

Animal Feed↗

PubMed1998

Significance of passively induced stretch reflexes on achilles tendon force enhancement.

An in vivo buckle transducer technique was applied to study the reflex contribution to ATF enhancement during passive dorsiflexion stretches. Single stretches led to a linear ATF increase in the absence of an EMG reflex response, whereas clear ATF enhancement over the passive component occurred 13-15 ms after the onset of EMG responses. To quantify the reflexly induced increase in ATF, the stretched position was maintained. The mean reflex effect was two to four times greater than the passive stretch effect.

Achilles Tendon↗

PubMed1998

Physiological and behavioral consequences associated with short-term prevention of crib-biting in horses.

Crib-biting in the horse is frequently prevented in the short-term by horse-owners using physical means. Because it has been proposed that crib-biting may function to reduce stress, the effect of prevention of crib-biting and/or eating on the behaviour, heart rate, and plasma cortisol and beta-endorphin concentrations was measured in six crib-biting and six normal horses. When crib-biters were unable to crib-bite, they showed an increase in ingestive behaviour. When crib-biters were prevented from crib-biting and eating, a relative stasis in the motility of the foregut occurred, suggesting that normal gut function in these animals depends on ad libitum access to food and to suitable crib-biting substrates. There was no significant difference in the mean baseline levels of normal and crib-biting horses but, contrary to expectations, beta-endorphin levels were higher in crib-biting horses than in normal horses when crib-biting was prevented. Mean baseline levels of cortisol were higher, under a variety of test and control conditions, in crib-biting than in normal horses, but there was no significant rise in cortisol levels in crib-biters during periods when crib-biting was prevented, suggesting that the function of this oral stereotypy does not lie in stress-reduction.

Animals↗