A Clinico-Pathologic Study of Botulism in Ring-Necked Pheasants

Toxins were produced from 6 strains of Cl. Botulinum, 2 of which killed pheasants. Inoculated birds were observed and a description of the progression of signs of the disease is given. Juvenile pheasants were inoculated with Types A and C toxin intramuscularly and were given the toxin orally. These birds were observed and their clinical signs noted. Adult pheasants were inoculated with toxoid prepared from type C toxin and commercial toxoid; injections were repeated in 21 days. Fourteen days following the final injection, the birds were challenged with toxin. Those protected with toxoid survived, while those receiving saline succumbed. Gross necropsy findings, bacteriologic and histopathologic examinations on all birds were negative

Scabies Research with Injectable Ivermectin

Scabies is a parasitic skin disease caused by tiny mites resulting in skin irritation. These mites are spread from animal to animal by direct contact. The mites puncture the skin and feed on the body fluids released from the wounds. These fluids ooze from wounds and dry to form scabs. Hence the name “scabies.” This disease costs the cattle industry millions of dollars each year. Cattle with scabies lick, rub and scratch themselves to relieve the intense itching. They often lose weight and are more susceptible to complications such as pneumonia. As the number of mites increase, the animal’s hair falls out or is rubbed off and lesions spread. If not treated, large areas of the body may be covered with thick, rough crusts. Scabies is a year-round problem. However, in warm weather skin lesions may disappear because mites are less active. This improvement is only temporary; and, as environmental temperature gets colder, the mites become active and lesions return. Under normal conditions, mites will survive for a maximum of 3 days off the host animal. It is possible for mites to spread from fences or trucks that have been in contact with infected animals. However, the greatest possibility of spread is directly animal to animal

Systolic and Diastolic Left Ventricular Mechanics during and after Resistance Exercise

PURPOSE: To improve the current understanding of the impact of resistance exercise on the heart, by examining the acute responses of left ventricular (LV) strain, twist and untwisting rate ('LV mechanics'). METHODS: LV echocardiographic images were recorded in systole and diastole before, during and immediately after (7-12 s) double leg press exercise at two intensities (30% and 60% of maximum strength, 1-repetition-maximum, 1RM). Speckle tracking analysis generated LV strain, twist and untwisting rate data. Additionally, beat-by-beat blood pressure was recorded and systemic vascular resistance (SVR) and LV wall stress were calculated. RESULTS: Responses in both exercise trials were statistically similar (P > 0.05). During effort, stroke volume decreased while SVR and LV wall stress increased (P 0.05). Immediately following exercise, systolic LV mechanics returned to baseline levels (P < 0.05) but LV untwisting rate increased significantly (P < 0.05). CONCLUSIONS: A single, acute bout of double leg-press resistance exercise transiently reduces systolic LV mechanics, but increases diastolic mechanics following exercise, suggesting that resistance exercise has a differential impact on systolic and diastolic heart muscle function. The findings may explain why acute resistance exercise has been associated with reduced stroke volume but chronic exercise training may result in increased LV volumes

The effect of heat stress, dehydration and exercise on global left ventricular function and mechanics in healthy humans

This thesis examined the effect of heat stress, dehydration and exercise on global left ventricular (LV) function and LV twist, untwisting and strain (LV mechanics) in healthy individuals. The primary aim was to identify whether the different haemodynamics induced by heat stress, dehydration and exercise would be associated with alterations in systolic and diastolic LV mechanics as assessed by two-dimensional speckle tracking echocardiography. Study one showed that enhanced systolic and diastolic LV mechanics during progressively increasing heat stress at rest likely compensate in part for a lower venous return, resulting in a maintained stroke volume (SV). In contrast, heat stress during knee-extensor exercise did not significantly increase LV twist, suggesting that exercise attenuates the increase in LV mechanics seen during passive heat stress. Study two revealed that dehydration enhances systolic LV mechanics whilst diastolic mechanics remain unaltered at rest, despite pronounced reductions in preload. The maintenance of systolic and diastolic LV mechanics with dehydration during knee-extensor exercise further suggests that the large decline in SV with dehydration and hyperthermia is caused by peripheral cardiovascular factors and not impaired LV mechanics. During both, heat stress and dehydration, enhanced systolic mechanics were achieved solely by increases in basal rotation. In contrast, the third study demonstrated that when individuals are normothermic and euhydrated, systolic and diastolic basal and apical mechanics increase significantly during incremental exercise to approximately 50% peak power. The subsequent plateau suggests that LV mechanics reach their peak at sub-maximal exercise intensities. Together, the present findings emphasise the importance of acute adjustments in both, basal and apical LV mechanics, during periods of increased cardiovascular demand.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The effect of heat stress, dehydration and exercise on global left ventricular function and mechanics in healthy humans

This thesis examined the effect of heat stress, dehydration and exercise on global left ventricular (LV) function and LV twist, untwisting and strain (LV mechanics) in healthy individuals. The primary aim was to identify whether the different haemodynamics induced by heat stress, dehydration and exercise would be associated with alterations in systolic and diastolic LV mechanics as assessed by two-dimensional speckle tracking echocardiography. Study one showed that enhanced systolic and diastolic LV mechanics during progressively increasing heat stress at rest likely compensate in part for a lower venous return, resulting in a maintained stroke volume (SV). In contrast, heat stress during knee-extensor exercise did not significantly increase LV twist, suggesting that exercise attenuates the increase in LV mechanics seen during passive heat stress. Study two revealed that dehydration enhances systolic LV mechanics whilst diastolic mechanics remain unaltered at rest, despite pronounced reductions in preload. The maintenance of systolic and diastolic LV mechanics with dehydration during knee-extensor exercise further suggests that the large decline in SV with dehydration and hyperthermia is caused by peripheral cardiovascular factors and not impaired LV mechanics. During both, heat stress and dehydration, enhanced systolic mechanics were achieved solely by increases in basal rotation. In contrast, the third study demonstrated that when individuals are normothermic and euhydrated, systolic and diastolic basal and apical mechanics increase significantly during incremental exercise to approximately 50% peak power. The subsequent plateau suggests that LV mechanics reach their peak at sub-maximal exercise intensities. Together, the present findings emphasise the importance of acute adjustments in both, basal and apical LV mechanics, during periods of increased cardiovascular demand.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The effect of an acute bout of resistance exercise on carotid artery strain and strain rate

Arterial wall mechanics likely play an integral role in arterial responses to acute physiological stress. Therefore, this study aimed to determine the impact of low and moderate intensity double-leg press exercise on common carotid artery (CCA) wall mechanics using 2D vascular strain imaging. Short-axis CCA ultrasound images were collected in 15 healthy men (age: 21 ± 3 years; stature: 176.5 ± 6.2 cm; body mass; 80.6 ± 15.3 kg) before, during, and immediately after short-duration isometric double-leg press exercise at 30% and 60% of participants’ one-repetition maximum (1RM: 317 ± 72 kg). Images were analyzed for peak circumferential strain (PCS), peak systolic and diastolic strain rate (S-SR and D-SR) and arterial diameter. Heart rate (HR), systolic and diastolic blood pressure (SBP and DBP) were simultaneously assessed and arterial stiffness indices were calculated post hoc. A two-way repeated measures ANOVA revealed that during isometric contraction, PCS and S-SR decreased significantly (P < 0.01) before increasing significantly above resting levels post-exercise (P < 0.05 and P < 0.01 respectively). Conversely, D-SR was unaltered throughout the protocol (P = 0.25). No significant differences were observed between the 30% and 60% 1RM trials. Multiple regression analysis highlighted that HR, BP and arterial diameter did not fully explain the total variance in PCS, S-SR and D-SR. Acute double-leg press exercise is therefore associated with similar transient changes in CCA wall mechanics at low and moderate intensities. CCA wall mechanics likely provide additional insight into localized intrinsic vascular wall properties beyond current measures of arterial stiffness

Ventricular structure, function, and mechanics at high altitude: chronic remodeling in Sherpa vs. short-term lowlander adaptation

Short-term, high-altitude (HA) exposure raises pulmonary artery systolic pressure (PASP) and decreases left-ventricular (LV) volumes. However, relatively little is known of the long-term cardiac consequences of prolonged exposure in Sherpa, a highly adapted HA population. To investigate short-term adaptation and potential long-term cardiac remodeling, we studied ventricular structure and function in Sherpa at 5,050 m (n = 11; 31 ± 13 yr; mass 68 ± 10 kg; height 169 ± 6 cm) and lowlanders at sea level (SL) and following 10 ± 3 days at 5,050 m (n = 9; 34 ± 7 yr; mass 82 ± 10 kg; height 177 ± 6 cm) using conventional and speckle-tracking echocardiography. At HA, PASP was higher in Sherpa and lowlanders compared with lowlanders at SL (both P < 0.05). Sherpa had smaller right-ventricular (RV) and LV stroke volumes than lowlanders at SL with lower RV systolic strain (P < 0.05) but similar LV systolic mechanics. In contrast to LV systolic mechanics, LV diastolic, untwisting velocity was significantly lower in Sherpa compared with lowlanders at both SL and HA. After partial acclimatization, lowlanders demonstrated no change in the RV end-diastolic area; however, both RV strain and LV end-diastolic volume were reduced. In conclusion, short-term hypoxia induced a reduction in RV systolic function that was also evident in Sherpa following chronic exposure. We propose that this was consequent to a persistently higher PASP. In contrast to the RV, remodeling of LV volumes and normalization of systolic mechanics indicate structural and functional adaptation to HA. However, altered LV diastolic relaxation after chronic hypoxic exposure may reflect differential remodeling of systolic and diastolic LV function. exposure to high altitude (HA) challenges the cardiovascular system to meet the metabolic demand for oxygen (O2) in an environment where arterial O2 content is markedly reduced. The drop in arterial O2 has both direct and indirect consequences for the heart, including depressed inotropy of cardiac muscle (40, 44), changes in blood volume and viscosity, and vasoconstriction of the pulmonary arteries (33). Despite these broad physiological changes, which have been reviewed previously (28, 49), there is evidence that the heart copes relatively well at HA (29, 34). Short-term HA exposure in lowland natives is characterized by a decreased plasma volume (PV), an increased sympathetic nerve activity, and pulmonary vasoconstriction (17, 30, 37), all of which have considerable impact on cardiac function and in time, could stimulate cardiac remodeling. Himalayan native Sherpa, who are of Tibetan lineage and have resided at HA for ∼25,000 yr (2), are well adapted to life at HA, demonstrating greater lung-diffusing capacity (11) and an absence of polycythemia compared with acclimatized lowlanders (4). Previous studies have also reported Sherpa to have higher maximal heart rates (HRs) and only moderate pulmonary hypertension compared with lowlanders at HA (11, 25). Due to their longevity at HA, Sherpa provide an excellent model to investigate the effects of chronic hypoxic exposure. Despite this, neither the acute nor lifelong effects of HA on right- and left-ventricular (RV and LV, respectively) structure and function have been fully assessed in lowlanders or the unique Sherpa population. Due to the unique arrangement of myofibers, cardiac form and function are intrinsically linked, as reflected in the cardiac mechanics (LV twist and rotation and ventricular strain) that underpin ventricular function. In response to altered physiological demand, ventricular mechanics acutely change (16, 41) and chronically remodel (31, 42) to reduce myofiber stress and achieve efficient ejection (5, 47). Therefore, concomitant examination of myocardial mechanics and ventricular structure in both the acute and chronic HA setting will provide novel insight into human adaptation to hypoxia. To investigate the effects of chronic hypoxic exposure, we compared ventricular volumes and mechanics in Sherpa at 5,050 m with lowlanders at sea level (SL). In addition, to reveal potential stimuli for remodeling and to examine the time course of adaptation, we compared Sherpa with lowlanders after short-term HA exposure. We hypothesized that: 1) Sherpa would exhibit smaller LV volumes and a higher RV/LV ratio than lowlanders at SL, 2) LV mechanics in Sherpa will closely resemble those of lowlanders at SL, and 3) following partial acclimatization to HA, LV volumes would be reduced in lowlanders and LV mechanics acutely increased

Carotid artery wall mechanics in young males with high cardiorespiratory fitness

The influence of cardiorespiratory fitness (CRF) on arterial stiffness in young adults remains equivocal. Beyond conventional measures of arterial stiffness, 2D strain imaging of the common carotid artery (CCA) provides novel information related to the intrinsic properties of the arterial wall. Therefore, this study aimed to assess the effect of CRF on both conventional indices of CCA stiffness and 2D strain parameters, at rest and following a bout of aerobic exercise in young healthy males. Short‐axis ultrasound images of the CCA were recorded in 34 healthy men [22 years (95%CI, 19–22)] before, and immediately after 5‐minutes of aerobic exercise (40% VO2max). Images were analysed for arterial diameter, peak circumferential strain (PCS), and peak systolic and diastolic strain rates (S‐SR, D‐SR). Heart rate (HR), systolic and diastolic blood pressure (SBP, DBP) were simultaneously assessed and Petersons' elastic modulus (Ep) and Beta stiffness (β1) were calculated. Participants were separated post hoc into moderate and high fitness groups [VO2max: 48.9 ml.kg‐1 min‐1 (95%CI, 44.7–53.2) vs. 65.6 ml.kg‐1 min‐1 (95%CI, 63.1–68.1); P 0.13) but were elevated in the moderate‐fitness group post‐exercise (P 0.05). High‐fit individuals exhibit elevated CCA PCS and S‐SR, which may reflect training‐induced adaptations that help to buffer the rise in pulse‐pressure and stroke volume during exercise

Aortic haemodynamics: the effects of habitual endurance exercise, age and muscle sympathetic vasomotor outflow in healthy men

PURPOSE: We determined the effect of habitual endurance exercise and age on aortic pulse wave velocity (aPWV), augmentation pressure (AP) and systolic blood pressure (aSBP), with statistical adjustments of aPWV and AP for heart rate and aortic mean arterial pressure, when appropriate. Furthermore, we assessed whether muscle sympathetic nerve activity (MSNA) correlates with AP in young and middle-aged men. METHODS: Aortic PWV, AP, aortic blood pressure (applanation tonometry; SphygmoCor) and MSNA (peroneal microneurography) were recorded in 46 normotensive men who were either young or middle-aged and endurance-trained runners or recreationally active nonrunners (10 nonrunners and 13 runners within each age-group). Between-group differences and relationships between variables were assessed via ANOVA/ANCOVA and Pearson product-moment correlation coefficients, respectively. RESULTS: Adjusted aPWV and adjusted AP were similar between runners and nonrunners in both age groups (all, P > 0.05), but higher with age (all, P < 0.001), with a greater effect size for the age-related difference in AP in runners (Hedges’ g, 3.6 vs 2.6). aSBP was lower in young (P = 0.009; g = 2.6), but not middle-aged (P = 0.341; g = 1.1), runners compared to nonrunners. MSNA burst frequency did not correlate with AP in either age group (young: r = 0.00, P = 0.994; middle-aged: r = − 0.11, P = 0.604). CONCLUSION: There is an age-dependent effect of habitual exercise on aortic haemodynamics, with lower aSBP in young runners compared to nonrunners only. Statistical adjustment of aPWV and AP markedly influenced the outcomes of this study, highlighting the importance of performing these analyses. Further, peripheral sympathetic vasomotor outflow and AP were not correlated in young or middle-aged normotensive men