Plasma β-endorphin, cortisol and immune responses to acute exercise are altered by age and exercise training in horses

REASONS FOR PERFORMING STUDY

Ageing appears to affect immune and neuroendocirne function in horses and response to acute exercise. No studies have examined the combined effects of training and ageing on immune and neuroendocirne function in horses.

HYPOTHESIS

To ascertain whether training and age would affect the plasma beta-endorphin (BE) and cortisol (C) as well as immune function responses to acute exercise in Standardbred mares.

METHODS

Graded exercise tests (GXT) and simulated race tests (SRT) were performed before and after 12 weeks training at 60 % HRmax. BE and C were measured at rest and at 5, 10, 20, 40, 60 and 120 min post GXT. Leucocyte cell number, CD4+ and CD8+ lymphocyte subsets, and mitogen stimulated lymphoproliferative response (LPR), were measured in jugular blood before and after the SRTs.

RESULTS

Cortisol rose by 5 min post GXT in young (Y) and middle-age (MA) mares (P<0.05) and remained elevated until 40 and 60 min post GXT, respectively during both pre- and post training GXT. There was no rise in C in old (0) mares after either GXT (P>0.05). Pretraining BE rose (P<0.05) by 5 min post GXT in all mares. After training, BE was higher in Y and O vs. MA (P<0.05) at 5 min post GXT. Post training BE was higher at 5 min post GXT in Y and O vs. pretraining (P<0.05). After SRT, lymphocyte number rose in all mares (P<0.05); however, lower lymphocyte numbers (P<0.05) were seen in MA vs. Y and O vs. MA (P<0.05). The O had reduced LPR to Con A and PHA stimulation (P<0.05) compared to Y and MA after the SRT after both pre- and post training SRT. LPR to PWM was lower (P<0.05) in O vs. Y and MA after the pretraining SRT. Training caused an increase in resting LPR to PWM in MA only (P<0.05).

CONCLUSION

Both age and training altered the plasma beta-endorphin and cortisol responses as well as and immune responses to acute exercise.

POTENTIAL RELEVANCE

This study provides important information on the effects of ageing and training that will aid in the management and care of an increasing number of active older horses.

Neurosciences intensive care medicine in initial neurosurgical training

The authors describe a novel 4-month clinical placement in neurosciences intensive care medicine (NICM) undertaken in the first specialty registrar (ST1) year of neurosurgical training as part of a clinical neurosciences themed training year. Neurosurgery is unique among British surgical specialties in having pioneered themed early years in run-through training to replace basic surgical training in general surgical specialties as part of Modernising Medical Careers. After describing events leading to the new neurosurgical training, the knowledge, skills and attitudes acquired in NICM are highlighted alongside discussion of logistic aspects and future directions from an inaugural experience.

Muscle, tendon, and somatotropin responses to the restriction of muscle blood flow induced by KAATSU-walk training

OBJECTIVE

The efficacy of KAATSU training has been demonstrated in human athletes, both as a therapeutic method as well as a training aid. The purpose of this study was to investigate the effects of slow walk training combined with restriction of muscle blood flow (KAATSU) on muscle and tendon size.

METHODS

Six healthy, unfit Standardbred mares performed walking (240 m/min for 10 min and then 5 min recovery) with KAATSU, and 6 mares performed walking without KAATSU. A specially designed elastic cuff1 was placed at the most proximal position of the forelegs and inflated to a pressure of 200-230 mmHg throughout the walking and recovery sessions. The training was conducted once a day, 6 days/week for 2 weeks. Skeletal muscle thickness and tendon thickness were measured using B-mode ultrasound at baseline and after 2 weeks of training. Venous blood samples were obtained before the first acute exercise and 5, 15 and 60 min afterwards. Serum somatotropin concentration was determined using a commercially available equine-specific ELISA kit.

RESULTS

The acute increase in plasma somatotropin was 40% greater (P<0.05) in the KAATSU-walk group than in the Control-walk group 5 min after exercise and remained elevated (P<0.05) at 15 and 60 min post exercise compared with the Control-walk group. After 2 weeks of training, muscle thickness increased (P<0.05) 3.5% in the KAATSU-walk group but did not change in the Control-walk group (0.7%). Tendon thickness did not change (P>0.05) in either group.

CONCLUSIONS

These data demonstrate that KAATSU training can induce muscle hypertrophy in horses and suggest that KAATSU training may provide significant therapeutic/ rehabilitative value in horses, as has been shown in man.

Acute vascular occlusion in horses: effects on skeletal muscle size and blood flow

The purpose of this study was to demonstrate whether acute vascular occlusion was safe and if it would result in changes to limb muscle size in horses. Six healthy, unfit Standardbred mares were used. Horses (standing at rest) wore an occlusion cuff at the most proximal position of the left forelimb. The right forelimb was used as control. An occlusion pressure of 200 mmHg was set for 5 min followed by a 2 min recovery. Three sets of occlusions were given to each horse. Muscle thickness was measured using B-mode ultrasound. The circumference of the forelimb and first phalanx was measured using a flexible tape measure. Pulsed-wave Doppler was performed on the radialis artery with a 5–10 MHz mechanical transducer at baseline and at each occlusion. Peak flow velocity (PFV) and the flow velocity integral (FVI) were measured each time. Mid-forelimb, but not first phalanx, girth was increased (P<0.05) in the occluded but not in the control leg following occlusion. Extensor and flexor muscle thickness was increased (P<0.05) in the occluded but not in the control leg. There were no changes (P>0.05) in PFV or FVI at any measurement time point. Acute vascular occlusion may be a suitable and safe model for studying muscle hypertrophy in horses.

Effect of chronic clenbuterol administration and exercise training on immune function in horses

Effects of longitudinal exercise training and acute intensive exercise (simulated race test) on immune function have not been reported in horses. Clenbuterol, a beta2-adrenergic agonist, is used to manage inflammatory airway disease in horses. This study investigated the interaction of 8 wk of exercise training with or without 12 wk of clenbuterol administration in horses. Twenty-three untrained standardbred mares (10 +/- 3 yr, Mean +/- SE) were used and divided into four experimental groups. Horses given clenbuterol plus exercise (CLENEX; n = 6) and clenbuterol alone (CLEN; n = 6) received 2.4 microg/kg BW of clenbuterol twice daily (in an average volume of 20 mL) on a schedule of 5 d on and 2 d off for 12 wk. The CLENEX group was also aerobically trained 3 d/wk. Mares given exercise alone (EX; n = 5) were aerobically trained for 3 d/wk, and the control group (CON; n = 6) remained sedentary. Both EX and CON horses were administered similar volumes (approximately 20 mL) of molasses twice daily. A simulated race test (SRT) resulted in an elevation in lymphocyte number postexercise (P < 0.05). There was no significant difference after acute exercise in either monocyte or granulocyte number. Acute exercise resulted in a decrease (P < 0.05) in the percentage of CD4+ and an increase (P < 0.05) in the percentage of CD8+ cells. The SRT resulted in a decreased lymphoproliferative response to pokeweed mitogen (P < 0.05). A SRT had no effect on antibody production in response to equine influenza vaccine. The EX group demonstrated greater cortisol concentrations at rest and at all other time points postexercise after completing the training regimen compared with CLENEX horses (P < 0.05). Preexercise (SRT) peripheral blood monocyte number was lower in CLENEX horses than in other treatment groups (P < 0.05). Clenbuterol and exercise training did not significantly affect post-SRT changes in leukocyte numbers. Exercise training resulted in a decrease (P < 0.05) in the percentage of CD8+ cells post-SRT compared with other groups, but the percentage of CD4+ cells was not altered by either clenbuterol or exercise conditioning. Lymphocyte proliferative response was not affected by clenbuterol or exercise treatment. Horses demonstrated responses to bouts of acute exercise as noted with other species, namely humans and rodents.

Sex differences in whole body skeletal muscle mass measured by magnetic resonance imaging and its distribution in young Japanese adults

OBJECTIVES

To determine sex differences in the distribution of regional and total skeletal muscle (SM) using contiguous whole body magnetic resonance imaging (MRI) data, and to examine the relations between fat free mass (FFM) and total and regional SM masses.

METHODS

A total of 20 Japanese college students (10 women and 10 men) volunteered for the study. FFM was measured by two compartment densitometry. Whole body MRI images were prepared using a 1.5 T scanner. Contiguous transverse images with 1.0 cm slice thickness were obtained from the first cervical vertebra to the ankle joints. All MRI scans were segmented into four components (SM, subcutaneous adipose tissue, bone, and residual tissues). In each slice, the SM tissue cross sectional areas (CSAs) were digitised, and the muscle tissue volume per slice was calculated by multiplying muscle CSA by slice thickness. SM volume units (litres) were converted into mass units (kg) by multiplying the volumes by the assumed constant density (1.041 mg/ml) for SM.

RESULTS

The SM distribution pattern (shape of curve) from the contiguous whole body slices was essentially similar for the two sexes, with two large peaks and three smaller peaks (arms excluded). However, the largest peak was observed at the upper portion of the thigh for women and at the level of the shoulder for men. Men had larger (p<0.01) total and regional SM mass than women. All regional SM masses correlated highly (r=0.90-0.99, p<0.01) with total SM mass. A strong positive correlation was observed between FFM and total and regional SM masses in both sexes (women, r=0.95; men, r=0.90; all p<0.01). As FFM increased, there was a corresponding increase in SM/FFM ratio for all subjects (r=0.86, p<0.01).

CONCLUSIONS

Sex differences in total SM/FFM ratio and regional SM distributions are associated with the degree of absolute FFM accumulation in men and women.

Whole body muscle hypertrophy from resistance training: distribution and total mass

OBJECTIVE

To examine the absolute and relative changes in skeletal muscle (SM) size using whole body magnetic resonance imaging (MRI) in response to heavy resistance training (RT).

METHOD

Three young men trained three days a week for 16 weeks.

RESULTS

MRI measured total SM mass and fat free mass (FFM) had increased by 4.2 kg and 2.6 kg respectively after resistance training.

CONCLUSIONS

RT induces larger increases in SM mass than in FFM. RT induced muscle hypertrophy does not occur uniformly throughout each individual muscle or region of the body. Therefore the distribution of muscle hypertrophy and total SM mass are important for evaluating the effects of total body RT on muscle size.

Chronic clenbuterol administration alters myosin heavy chain composition in standardbred mares

The purpose of this study was to examine changes in myosin heavy chain (MHC) composition due to chronic clenbuterol administration with or without exercise in mares. Unfit Standardbred mares (aged 10+/-3 years) were divided into four groups: clenbuterol (2.4 micro/kg BW twice daily) plus exercise (3 days/week for 20 min at 50% VO(2max); CLENEX; n=6), clenbuterol only (CLEN; n=6), exercise only (EX; n=5), and control (CON; n=6). Muscle biopsies were obtained from gluteus medius muscle before and after the eight-week training/administration period. MHC composition was determined via SDS gel electrophoresis and quantified using a scanning and densometric system. CLENEX and CLEN exhibited significant (P<0.05) MHC changes while EX and CON did not. MHC type IIA decreased (29.8+/-6.1 to 19.3+/-4.0%, CLENEX; and 36.8+/-12.4 to 26.4+/-7.9%, CLEN) and MHC type IIX increased (59.4+/-7.2 to 71.8+/-5.8%, CLENEX; and 50.5+/-12.5 to 62.0+/-9.3%, CLEN). Chronic clenbuterol administration with and without exercise resulted in a significant shift in MHC profile in Standardbred mares.

Overview of horse body composition and muscle architecture: implications for performance

Locomotion requires skeletal muscle to sustain and generate force. A muscle's force potential is proportional to its weight. Since the larger the muscle the larger its potential power output, a better understanding of the proportion of skeletal muscle a horse possesses may lead to a better understanding of horse performance. Several techniques exist to assess body composition, which include dual energy X-ray absorption, underwater (hydrostatic) weighing, derivation from total body water, bio-electric impedance, air displacement, body condition scoring, cadaver dissection and ultrasound. The relevance of each method to the equine industry will be discussed as will the practical information that the existing horse body composition studies have provided. Attention will be given to the data regarding the implications of body composition on the performance horse. The limited number of studies discussing different varieties of muscle architectures and the functional importance of these muscles will also be addressed. These body composition data may provide a better understanding of important issues in horse care that can lead to more optimal horse care techniques and a healthier and safer environment for horses.

Plasma aldosterone concentration and renal sodium excretion are altered during the first days of training

The purpose of the present study was to determine whether the training-induced hypervolaemic response seen in the horse is associated with aldosterone-mediated renal mechanisms affecting sodium conservation during the first days of training. Five healthy, Standardbred mares (weight 450-500 kg, age 4-8 years) that were unfit, but accustomed to running on the treadmill, were used to test the hypothesis that repeated submaximal exercise would alter plasma aldosterone (ALDO) concentration and renal excretion of electrolytes in horses within the first 3 days of training. The experiment consisted of a 2 week housing equilibration period followed by a 1 week control period and a 3 day exercise training period (30 min/day at 60% VO2max). During control, ALDO and renal fluid and electrolyte losses were measured for 24 h on 3 separate days. Renal function (urine volume [UV], 24 h excretion of Na+, K+ and Cl- [UNA+ V, UK+ V, UCl- V], clearance of Na+ [CNa+], K+ [CK+] and Cl- [CCl-], creatinine [CCr], osmotic substances [Cosm], and solute-free water [FWC], and the fractional excretion of Na+, K+ and Cl-) and ALDO were measured for an additional 3 consecutive days during the training period. There were no differences (P>0.05) in any variable during the control period. Plasma volume increased (+18.7%, P<0.05) after 3 days of training. During training, there were no significant changes in plasma osmolality, electrolyte concentrations or CCr. Training caused decreases (P<0.05) in UV (-30%), UNA+ V (-73%), UK+ V, (-55%) and UCl- V (-70%). Training also caused decreases (P<0.05) in Cosm (-30%), through decreases in CNa+ (-60%), CK+ (-60%), and CCl- (-66%). Interestingly, FWC increased (+30%, P<0.05), whereas, there were significant decreases in the fractional excretion of Na+ (-59%), K+ (-48%) and Cl- (-60%). Training caused substantial elevations in both pre-exercise (967%, P<0.05) and postexercise (+3013%, P<0.05) plasma ALDO concentrations suggesting an increase in both basal levels and the responsiveness to acute exercise. Together, these observations suggest that mechanisms affecting tubular conservation of electrolytes contribute to the early response to training. However, it is also concluded that renal mechanisms appear to be only part of the mechanism for conserving sodium and water intake as well as training-induced changes in gastrointestinal mechanisms affecting electrolyte and water balance.

Relationship between body composition, blood volume and maximal oxygen uptake

It has long been known that body mass and, more specifically, lean body mass are strongly correlated with maximal oxygen uptake (VO2max) in man and animals. However, there are no data to date describing this phenomenon in the horse. The purpose of this paper is to examine the relationship between body composition and VO2max in the horse. Twenty-three healthy and unfit Standardbred mares performed an incremental exercise test (GXT) to measure VO2max. Rump fat thickness (RTH), a measure of fat covering, was measured using B-mode ultrasound. Plasma volume, total blood volume and red cell volume were determined, using the Evan's Blue dye dilution technique and packed cell volume. VO2max was correlated with body mass (r = 0.541; P<0.01) and exercise haematocrit (exHCT; r = 0.407; P<0.05) but not RTH or the other haematological variables. To eliminate the influence of body mass on the individual variables, a regression analysis was performed on the mass-residuals of VO2max, RTH, plasma volume and exHCT. The residuals of VO2max were correlated negatively with the residuals of RTH (r = -0.687; P = 0.0003) and positively with the residuals of exHCT (r = 0.422; P = 0.045) but not plasma volume. VO2max could be predicted from a linear combination of the residuals of RTH and exHCT (r = 0.767; P<0.0001). These data indicate that VO2max in the horse is significantly related to fat-free mass (FFM), independent of body mass. Red blood cells from the splenic reserve constitute an important factor in the horse's ability to achieve a high VO2max. Therefore, lean body mass may be a more appropriate basis for assessing metabolic function in the athletic horse.

Effects of ageing and training on maximal heart rate and VO2max

The purpose of this study was to test the hypotheses that ageing would result in a decline in maximal heart rate (HRmax) and maximal aerobic capacity (VO2max) and, secondarily, that those effects would be reversible with training. Eighteen, healthy, unfit Standardbred mares representing 3 age groups: young (Y = mean +/- s.e. 6.8 +/- 0.4 years, n = 6); middle-aged (MA = 15.2 +/- 0.4 years, n = 6); and old (O = 27.0 +/- 0.2 years, n = 6) were used. HRmax, VO2max and oxygen pulse at VO2max (OPmax) and the velocities producing HRmax (VHRmax) and VO2max (VVO2max) were measured during pretraining and post-training incremental exercise tests (GXT). During training, mares exercised 3 days/week (Weeks 1-8) and 4 days/week (Weeks 9-12) at a submaximal intensity (approximately 60% HRmax) for approximately 30 min/day. There were no differences (P>0.05) between Y and MA, before (218 +/- 2 vs. 213 +/- 3 beats/min; 116 +/- 3 vs. 109 +/- 3 ml/kg bwt/min; 0.55 +/- 0.01 vs. 0.52 +/- 0.02 ml/kg/beat; 9.0 +/- 0.3 vs. 9.3 +/- 0.2 ms; 8.8 +/- 0.2 vs. 8.8 +/- 0.2 m/s) or after training (224 +/- 2 vs. 218 +/- 2 beats/min; 131 +/- 3 vs. 120 +/- 2 ml/kg bwt/min; 0.58 +/- 0.01 vs. 0.55 +/- 0.01 ml/kg/beat; 10.5 +/- 0.2 vs. 9.5 +/- 0.1 ms; 10.6 +/- 0.2 vs. 9.5 +/- 0.1 m/s) for HRmax, VO2max, OPmax, VHRmax or VVO2max, respectively. Old horses had lower HRmax, VO2max and OPmax and reached them at lower velocities compared to Y and MA (P<0.05), both before (193 +/- 3 beats/min; 83.2 +/- 2.0 ml/kg bwt/min; 0.43 +/- 0.01 ml/kg/beat; 7.8 +/- 0.1 m/s; 7.2 +/- 0.1 m/s) and after training (198 +/- 2 beats/min; 95 +/- 2 ml/kg bwt/min; 0.48 +/- 0.01 ml/kg/beat; 8.2 +/- 0.2 m/s; 8.0 +/-0.2 m/s). Training did not alter HRmax in any age group (P>0.05) but did cause increases in VO2max, OPmax and VVO2max for all groups (P<0.05). Interestingly, training increased VHRmax only in Y (P<0.05). These data demonstrate that there is a reduction in HRmax, VO2max, OPmax, VHRmax and VVO2max in old horses, and that training can partially reverse some effects of ageing.

Effect of training on age-related changes in plasma insulin and glucose

The purpose of the study was to determine whether 12 weeks of exercise training would affect plasma glucose and plasma insulin concentrations in young and older Standardbred mares. Eighteen healthy, unfit mares representing 3 age groups were used: young (Y = 6.8 +/- 0.4 years; n = 6), middle-aged (MA = 15.2 +/- 0.4; n = 6), and old (O = 27.0 +/- 0.2; n = 6). Pre- and post-training incremental exercise tests (GXT) were performed to measure plasma glucose and insulin concentration from immediately after, until 120 min postexercise. Training consisted of exercise 3 days/week (weeks 1-8) and 4 days/week (weeks 9-12) at a submaximal intensity (approximately 60% of pretraining HRmax) for approximately 30 min/day. Old mares had lower levels of glucose after the GXT when compared to Y and MA mares (P<0.05). There was also a time-by-age interaction (P = 0.003) in that, at 120 min post-GXT, glucose levels had not returned to pre-exercise values. Plasma glucose concentrations, in response to acute exercise, were not altered by training for any age group (P>0.05). Prior to exercise training, O mares had higher plasma insulin compared to Y and MA mares at 120 min postexercise (P<0.05), and insulin was also elevated in O mares compared to all other time points at 120 min post-GXT (P<0.05). Training resulted in increased plasma insulin concentrations at 120 min post-GXT in all age groups (P<0.05). In conclusion, age affected glucose and insulin responses to acute exercise prior to and after 12 weeks of exercise training. With regards to insulin, 12 weeks of exercise training resulted in a postexercise rebound hyperinsulinaemia, which may be related to an increased need for glycogen repletion in the muscle. These factors are important in considering the ability of an older horse to tolerate exercise.

Fat-free mass is related to one-mile race performance in elite standardbred horses

This study examined whether body composition was predictive of competitive success in elite standardbreds (STB). Rump fat and muscle thickness (MTH) (vastus lateralis/intermedius [VL], extensor carpi radialis [ECR]) were measured in vivo in male n=6; female n=8 by B-mode ultrasound. Percentage body fat (%fat) was calculated from rump fat. There were no gender differences for age, body mass (males 432+/-11 kg; females 443+/-13 kg), fat-free mass (FFM) (males 400+/-12 kg; females 400+/-11 kg), ECR MTH (males 61+/-2 cm; females 60+/-2 cm) or race time (RT) (males 113+/-3 s; females 114+/-2 s). Males had less (P<0.05) fat mass (males 32+4 kg; females 44+/-3 kg) and %fat (males 7.4+/-0.9%; females 9.9+/-0.5%) and larger (P<0.05) VL MTH (males 88+/-7 cm; females 81+/-3 cm). RT was correlated to %fat and fat mass in males (r=0.89; r=0.82, P<0.05) not females (r=0.51; r=0.14). FFM tended to relate to RT in males (r=-0.76, P=0.07) and females (r=-0.59, P=0.12). Combined %fat and FFM data were correlated to RT (%fat r=0.70, P<0.01; FFM r=-0.65, P<0.01). RT was not correlated to MTH (VL r=-0.28; ECR r=-0.31). In conclusion, FFM was related to RT in elite STB with %fat negatively related to RT in males.

Chronic administration of therapeutic levels of clenbuterol acts as a repartitioning agent

The purpose of this study was to examine the effect of therapeutic levels of clenbuterol, with and without exercise training, on body composition. Twenty-three unfit Standardbred mares were divided into four experimental groups: clenbuterol (2.4 microg/kg body wt twice daily) plus exercise (ClenEx; 20 min at 50% maximal oxygen consumption 3 days/wk; n = 6), clenbuterol only (Clen; n = 6), exercise only (Ex; n = 5), and control (Con; n = 6). Rump fat thickness was measured at 2-wk intervals by using B-mode ultrasound, and percent body fat (%fat) was calculated by using previously published methods. For Ex, body fat decreased (P < 0.05) at week 4 (-9.3%), %fat at week 6 (-6.9%), and fat-free mass (FFM) increased (P < 0.05) at week 8 (+3.2%). On the other hand, Clen had significant changes in %fat (-15.4%), fat mass (-14.7%), and FFM (+4.3%) at week 2. ClenEx had significant decreases in %fat (-17.6%) and fat mass (-19.5%) at week 2, which was similar to Clen; however, this group had a different FFM response, which significantly increased (+4.4%) at week 6. Con showed no changes (P > 0.05) in any variable at any time. These results suggest that exercise training and clenbuterol have additive effects with respect to %fat and fat mass but antagonistic effects in terms of FFM. Furthermore, chronic clenbuterol administration causes significant repartitioning in the horse, even when administered in therapeutic doses.

Architectural characteristics of dominant leg muscles in junior soccer players

The preferential use of dominant over non-dominant limbs produces muscle hypertrophy in the dominant limb. The purpose of this study was to investigate the architectural characteristics of the muscle that are associated with dominant leg use in junior soccer players. Fascicle length, pennation angle and muscle thickness of the medial gastrocnemius (MG) were measured by B-mode ultrasound in 26 junior soccer players [mean (SD) age: 16.5 (0.6) years] and 20 control college students [age: 18.5 (0.5) years]. Lower leg circumference and MG muscle thickness were significantly (P < 0.05) greater in the soccer players than in the controls. The percent difference (dominant minus non-dominant legs) in muscle thickness and fascicle length were significantly (P < 0.01) larger in the soccer players than in the controls, but the percent difference in pennation angle was similar between groups. The difference (dominant leg minus non-dominant leg) in muscle thickness was significantly correlated (r = 0.55; P < 0.05) with the difference in muscle fascicle length in the soccer players, but not in the controls (r = 0.18). In conclusion, the preferential use of one limb over another, as seen in junior soccer players, results in a greater difference in muscle thickness between the dominant and non-dominant legs. This difference in muscle size was associated with longer fascicle lengths of the dominant leg. Thus, it appears possible that fascicle length may be further influenced by physical training in dominant legs.

Muscle enlargement in sumo wrestlers includes increased muscle fascicle length

Skeletal muscle architecture was measured in 28 college sumo wrestlers (Sumo) and 30 control subjects. Pennation angle (PAN) and muscle thickness (MTH) of the triceps long head (TL), vastus lateralis (VL) and gastrocnemius medialis (MG) and lateralis (LG) muscles were measured by B-mode ultrasonography, and fascicle length (FAL) was estimated. Sumo wrestlers had a significantly greater percentage body fat [mean (SD) 33.9 (9.4)%], fat mass [41.7 (18.5) kg], and fat-free mass [76.8 (7.5) kg] than the controls [15.6 (2.5)%, 9.3 (2.4) kg, and 49.9 (6.2) kg, respectively]. MTH was between 18 and 35% greater in sumo wrestlers than in controls. The sumo wrestlers had a significantly greater PAN in the TL, MG and LG muscles than did the controls, but not in the VL. There were significant correlations between PAN and MTH for the sumo wrestlers (r values from 0.33 to 0.57), suggesting that PAN is a function of the relative state of muscle enlargement. FAL was greater (P < 0.01) in the Sumo group for TL (7.26 cm vs 6.13 cm), VL (10.01 cm vs 6.97 cm) and MG (6.41 cm vs 5.53 cm) than in the controls, but not for LG (7.61 cm vs 7.04 cm). Relative FAL correlated significantly with MTH for these muscles in the Sumo group [r values from 0.45 (P < 0.05) to 0.71 (P < 0.01)]. There appear to be architectural differences in the muscle fascicles between sumo wrestlers and controls, with sumo wrestlers having longer fascicles. A greater FAL appears to limit the degree of change in PAN associated with the extreme muscle enlargement seen in sumo wrestlers. This architectural alteration may ultimately improve the expression of the force/cross-sectional area relationship with extreme muscle enlargement.

Cross reactivity between human erythropoietin antibody and horse erythropoietin

Erythropoietin (EPO) is the primary hormone of erythropoiesis. Administration of recombinant human erythropoietin (rhuEPO) to improve racing performance in the horse represents a new form of blood doping, which has been associated with increased mortality. While immunoassay kits have become plentiful, very few commercial hormone assays are made specifically for equine research. There is a strong degree of sequence homology reported for EPO among species, which has allowed antibodies designed for human EPO research to be used to determine EPO concentration in other species. The objective of the present study was to use Western blot analysis to determine whether the antibody to rhuEPO, provided in a commercial radioimmunoassay (RIA) kit, recognizes horse EPO. Western blot analysis of purified rhuEPO and horse plasma was conducted, using the polyclonal goat-antihuman EPO antibody supplied in the Incstar EPO Trac RIA as the primary antibody. Immunoblot analysis revealed a major band at approximately 52 kDa for both rhuEPO and the horse plasma. Our results demonstrate that a human EPO antibody recognizes equine EPO. These findings show that the Incstar EPO Trac RIA hormone assay system can be used to measure equine EPO.

Comparison of cerebral oximeter and evoked potential monitoring in carotid endarterectomy

PURPOSE

To assess the cerebral oximeter, which measures regional oxygen saturation (rSO2) continuously and noninvasively, as a cerebral monitor during carotid endarterectomy (CEA). The rSO2 was compared with Somatosensory Evoked Potentials (SSEPs) as an indicator for shunting and as a predictor of postoperative neurological deficits.

METHODS

Seventy-two consenting patients undergoing CEA with general anaesthesia were studied. Normocarbia, normothermia and normotension were maintained. Cerebral monitoring consisted of bilateral median nerve SSEPs and the INVOS 3100 cerebral oximeter with the sensor pad placed on the ipsilateral forehead. Decreases in SSEP amplitude of 50% and in rSO2 of 10% were considered clinically significant. Neurological assessment was performed at emergence from anaesthesia, 24 hr postoperatively and at discharge. The rSO2 changes were compared with SSEP changes and with neurological deficits. Statistical analysis was with chi square and analysis of variance P < 0.05 was considered significant.

RESULTS

During carotid artery clamping, rSO2 decreased from 72 +/- 8% to 68 +/- 9% and mean arterial blood pressure increased from 92 +/- 14 mmHg to 98 +/- 14 mmHg. In four patients, the carotid artery was shunted because of SSEP changes after cross-clamping. Five patients had > or = 10% decreases in rSO2 following clamp application. Changes in both SSEP and rSO2 occurred in two patients. Three of the four shunted patients had transient postoperative neurological deficits. One patients had a transient deficit without changes in either monitor. There were no persistent postoperative deficits. Compared with SSEPs, rSO2 had a sensitivity of 50% and a specificity of 96%.

CONCLUSION

Clinical experience with this evolving technology is ongoing. Its role in neurovascular procedures has yet to be established.

The effect of subhypnotic doses of propofol on the incidence of pruritus after intrathecal morphine for caesarean section

The effect of subhypnotic doses of propofol on intrathecal morphine-induced pruritus was studied in a prospective, randomly allocated, double-blind controlled trial. Fifty-eight women undergoing elective lower segment Caesarean section for a singleton fetus received spinal anaesthesia with 2.5 ml hyperbaric 0.5% bupivacaine and 0.2 mg of preservative-free morphine. They then received propofol 1 ml (10 mg) or Intralipid 1 ml (control group) intravenously after delivery. Pruritus was assessed using a five-point verbal rating scale at hourly intervals for 8 h. A second dose of their allocated treatment drug was administered at the first recording of significant pruritus. The pruritus score was reassessed after 5 min and the treatment was repeated if pruritus remained. There were no differences between the groups in the onset of pruritus or its successful treatment. No adverse side-effects were associated with this dose of propofol. There were no differences in the incidence of post-operative nausea and vomiting between the two groups. Subhypnotic propofol is not an effective treatment for intrathecal morphine-induced pruritus in women following Caesarean section.