Recent studies on aspergillosis in turkey poults

A review of the studies on aspergillosis in turkey poults at the National Animal Disease Center include limited field studies, pathogenicity studies, and vaccine development. Natural ventilation in turkey rearing houses was effective in reducing airborne propagules of four major fungal genera, but the effectiveness of ventilation appeared to be limited by the width of the building. Aspergillus fumigatus was more effective than A. flavus in producing mortalities in aerosol exposed poults. Toxigenicity of A. flavus did not enhance its pathogenicity, and no apparent aflatoxin production occurred during pathogenesis in infected turkey poults. Spores of A. fumigatus were disseminated quite rapidly in poults exposed to aerosols, and alveolar macrophages from respiratory lavages taken immediately after exposure contained spores of A. fumigatus. Vaccines produced from germlings of A. fumigatus and administered to turkey poults were the most efficacious of five vaccines tested against challenge exposure to aerosols of A. fumigatus spores.     

Effects of stressors on blood glucose and hepatic glycogen concentrations in turkey poults.

1. The putatively stressful procedures of sexing, toe trimming, snood removal, beak trimming and injection of antibiotic solution, as performed in a commercial hatchery, elevated blood glucose levels and depressed hepatic glycogen levels in newly-hatched turkey poults. 2. The first procedure performed, cloacal sexing, was sufficient to elevate blood glucose, but all procedures were required before depression of hepatic glycogen occurred. 3. Blood glucose levels declined in both untreated (INITIAL) and fully-treated (FINAL) poults over a 24 hr holding period. 4. Hepatic glycogen declined with 24 hr holding of INITIAL poults but increased with holding of FINAL poults.     

Toxicity of 2-hydrazinoethanol in turkey poults

1. Toxicity of 2-hydrazinoethanol was investigated in turkey poults 2-6 weeks posthatch. 2. Significant depression of body wt was evident at concentrations of the drug as low as 10 ppm. 3. Severe anorexia closely paralleled a highly significant decrease in water intake. 4. A significant increase in the ratio of granulocytes to agranulocytes was seen in poults fed the drug at a dose of 50 ppm. 5. Under the conditions of this experiment, none of the tissues sampled exhibited pathologic changes consistent with drug injury.     

Effect of heavy exercise on spectral baroreflex sensitivity, heart rate, and blood pressure variability in well-trained humans

The aim of the study was to assess the instantaneous spectral components of heart rate variability (HRV) and systolic blood pressure variability (SBPV) and determine the low-frequency (LF) and high-frequency baroreflex sensitivity (HF-BRS) during a graded maximal exercise test. The first hypothesis was that the hyperpnea elicited by heavy exercise could entail a significant increase in HF-SBPV by mechanical effect once the first and second ventilatory thresholds (VTs) were exceeded. It was secondly hypothesized that vagal tone progressively withdrawing with increasing load, HF-BRS could decrease during the exercise test. Fifteen well-trained subjects participated in this study. Electrocardiogram (ECG), blood pressure, and gas exchanges were recorded during a cycloergometer test. Ventilatory equivalents were computed from gas exchange parameters to assess VTs. Spectral analysis was applied on cardiovascular series to compute RR and systolic blood pressure power spectral densities, cross-spectral coherence, gain, and alpha index of BRS. Three exercise intensity stages were compared: below (A1), between (A2), and above (A3) VTs. From A1 to A3, both HF-SBPV (A1: 45 +/- 6, A2: 65 +/- 10, and A3: 120 +/- 23 mm2Hg, P < 0.001) and HF-HRV increased (A1: 20 +/- 5, A2: 23 +/- 8, and A3:40 +/- 11 ms2, P < 0.02), maintaining HF-BRS (gain, A1: 0.68 +/- 0.12, A2: 0.63 +/- 0.08, and A3: 0.57 +/- 0.09; alpha index, A1: 0.58 +/- 0.08, A2: 0.48 +/- 0.06, and A3: 0.50 +/- 0.09 ms/mmHg, not significant). However, LF-BRS decreased (gain, A1: 0.39 +/- 0.06, A2: 0.17 +/- 0.02, and A3: 0.11 +/- 0.01, P < 0.001; alpha index, A1: 0.46 +/- 0.07, A2: 0.20 +/- 0.02, and A3: 0.14 +/- 0.01 ms/mmHg, P < 0.001). As expected, once VTs were exceeded, hyperpnea induced a marked increase in both HF-HRV and HF-SBPV. However, this concomitant increase allowed the maintenance of HF-BRS, presumably by a mechanoelectric feedback mechanism.     

Evaluation of allopurinol as a cardioprotectant in ethanol-fed turkey poults

Cardioprotectant effects of allopurinol were investigated in ethanol-fed poults during induction of cardiomyopathy and during a period of ethanol abstinence. In young poults fed ethanol, allopurinol has an additive effect on depression of growth but has little or no effect on caloric consumption. Allopurinol significantly depresses heart weight and heart weight to body weight ratios in young poults. In poults 5 weeks and older, allopurinol depresses significantly body weight and caloric consumption. Although allopurinol depresses heart weight in older poults, it appears to have little or no effect on heart weight to body weight ratios. Cardioprotective effect of allopurinol is more apparent during the inductive process than during the recovery phase.     

Changes in blood pressure, heart rate and blood constituents during heat exposure in men with elevated blood pressure

Although the vascular volume response of hypertensive men during exercise has been rather well characterized, the effect of resting heat exposure in this patient population has not been examined. This was done in the present report in seven men with high blood pressure (BP) (i.e., diastolic pressure greater than 12 kPa (90 mmHg) upon initial interview) and 5 normotensive control subjects. 50 min after each subject had consumed an amount of water equal to 1% of his body weight, he reclined on a cot. 10 min later the subject was carried into an environmental chamber equilibrated at Tdb = 45 degrees C, Twb = 28 degrees C. Free-flowing venous blood samples were obtained from a cubital vein, and BP and heart rate were measured, before the heat exposure and at 15 min intervals during the experiment. Within 30 min systolic, diastolic and mean BP of the high BP subjects had decreased to normal levels; no BP changes were detected in normotensive subjects. Accompanying this depressor response was an exaggerated elevation in plasma glucose concentration. No alterations were found with haematocrit, plasma osmolality or electrolytes, or total protein and albumin. The data suggest that heat exposure may have been more stressful for the subjects with high BP than for their controls. This finding implies that phasic depressor responses may be as important as phasic pressor episodes in the aetiology of established essential hypertension.     

Ultrastructural features of ethanol-induced cardiomyopathy in turkey poults

Alcoholic cardiomyopathy, characterized by cardiac hypertrophy, was induced in young turkey poults with 5% ethanol. Ultrastructural features included accumulation of glycogen, swollen mitochondria, myofibrillar lysis, increased number of lysosomes, dilated sarcoplasmic reticulum and dense myofibers. Similarity of these alterations to those described in human alcoholic cardiomyopathy confirms the usefulness of the turkey poult as an animal model for this disease syndrome.     

The effect of dietary aflatoxin on wild turkey poults

Aflatoxins, toxic metabolites of Aspergillus flavus or Aspergillus parasiticus, cause poor feed utilization, decreased weight gains, depressed immune function, liver dysfunction, coagulation abnormalities, and death in a wide variety of species including humans. Conservationists have become concerned that increasingly popular wildlife feeding or baiting practices could expose wildlife to toxic amounts of aflatoxin-contaminated grains. In particular, the effects of aflatoxins on the wild turkey (Meleagris gallopova silvestris) are of concern because the conspecific domestic turkey is highly susceptible to aflatoxins. To evaluate the effect of dietary aflatoxin on wild turkeys, four groups of 4-mo-old wild turkeys were fed diets containing either 0, 100, 200, or 400 micrograms aflatoxin/kg feed for 2 wk in September and October 1996. Aflatoxin-fed poults had decreased feed consumption and weight gains as compared with control poults. Decreased liver-to-body weight ratios, liver enzyme alterations, slightly altered blood coagulation patterns, and mild histologic changes indicated low-level liver damage. Compromise of cell-mediated immunity was indicated by decreased lymphoblast transformation. The effects were apparent in all treatment groups to variable levels, but significant differences most often were found at 400 micrograms aflatoxin/kg feed. This study shows that short-term aflatoxin ingestion by wild turkeys can induce undesirable physiologic changes; therefore, exposure of wild turkeys to feeds containing aflatoxin levels of 100 micrograms aflatoxin/kg feed or more should be avoided.     

Effect of head-down-tilt bed rest and hypovolemia on dynamic regulation of heart rate and blood pressure

Adaptation to head-down-tilt bed rest leads to an apparent abnormality of baroreflex regulation of cardiac period. We hypothesized that this "deconditioning response" could primarily be a result of hypovolemia, rather than a unique adaptation of the autonomic nervous system to bed rest. To test this hypothesis, nine healthy subjects underwent 2 wk of -6 degrees head-down bed rest. One year later, five of these same subjects underwent acute hypovolemia with furosemide to produce the same reductions in plasma volume observed after bed rest. We took advantage of power spectral and transfer function analysis to examine the dynamic relationship between blood pressure (BP) and R-R interval. We found that 1) there were no significant differences between these two interventions with respect to changes in numerous cardiovascular indices, including cardiac filling pressures, arterial pressure, cardiac output, or stroke volume; 2) normalized high-frequency (0.15-0.25 Hz) power of R-R interval variability decreased significantly after both conditions, consistent with similar degrees of vagal withdrawal; 3) transfer function gain (BP to R-R interval), used as an index of arterial-cardiac baroreflex sensitivity, decreased significantly to a similar extent after both conditions in the high-frequency range; the gain also decreased similarly when expressed as BP to heart rate x stroke volume, which provides an index of the ability of the baroreflex to alter BP by modifying systemic flow; and 4) however, the low-frequency (0.05-0.15 Hz) power of systolic BP variability decreased after bed rest (-22%) compared with an increase (+155%) after acute hypovolemia, suggesting a differential response for the regulation of vascular resistance (interaction, P < 0.05). The similarity of changes in the reflex control of the circulation under both conditions is consistent with the hypothesis that reductions in plasma volume may be largely responsible for the observed changes in cardiac baroreflex control after bed rest. However, changes in vasomotor function associated with these two conditions may be different and may suggest a cardiovascular remodeling after bed rest.     

侧脑室及下丘脑视前区微量注射孤啡肽对大鼠血压、心率的影响

孤啡肽（OrphaninFQ,OFQ）是1995年底发现的内阿片肽,一级结构与强啡肽A很相似,但生物学作用与其它内阿片肽有所不同。本工作采用侧脑室及核团微量注射的方法,观察了中枢OFQ对大鼠心血管活动的影响。结果表明：侧脑室注射1、10μgONQ可明显降低大鼠平均动脉压（MAP）及心率（HR）;侧脑室预先注射4μg纳洛酮不影响1μgOWQ的降压及减慢心率的效应。下丘脑视前区（POA）微量注射1μgOFQ也可降低血压、减慢心率。结果表明,中枢OFQ与其它内阿片肽相似,可抑制心血管活动,且其抑制作用不是通过μ、δ、κ阿片受体介导。POA为中枢OFQ抑制心血管活动的靶区之一。     

Artificial arterial blood pressure artifact models and an evaluation of a robust blood pressure and heart rate estimator

Background  

Within the intensive care unit (ICU), arterial blood pressure (ABP) is typically recorded at different (and sometimes uneven) sampling frequencies, and from different sensors, and is often corrupted by different artifacts and noise which are often non-Gaussian, nonlinear and nonstationary. Extracting robust parameters from such signals, and providing confidences in the estimates is therefore difficult and requires an adaptive filtering approach which accounts for artifact types.     

Effect of acutely-induced lactic acidemia on fetal breathing movements, heart rate, blood pressure, ACTH and cortisol in sheep.

Experiments were conducted in 8 chronically-catheterized fetal sheep at 125-135 days gestation in order to determine the effect of exogenously administered lactic acid to the fetus on fetal heart rate, blood pressure, breathing movements (FBM), electrocortical activity (ECOG), plasma immunoreactive (IR-ACTH) and cortisol concentrations. When fetal arterial pH decreased from 7.37 +/- 0.01 during the control period to 7.20 +/- 0.01, there was an initial bradycardia followed by tachycardia but no change in blood pressure. The amplitude of FBM increased 2-fold initially in association with an increase in PCO2 from 47.9 +/- 2.1 mmHg to 58.8 +/- 3.6 mmHg at 5 min into the lactate infusion. There was no change in the incidence of FBM or low-voltage ECOG and there was no change in the plasma concentrations of IR-ACTH and cortisol with the infusion of lactate. We conclude that the major effects of acutely elevating circulatory lactate concentrations in fetal sheep are to increase the amplitude of FBM and to cause an initial bradycardia followed by a tachycardia.     

Methylphenidate increases heart rate,blood pressure and plasma epinephrine in normal subjects

Following an intravenous infusion of methylphenidate (0.3mg/kg) there were significant increases in plasma epinephrine, heart rate, systolic and diastolic pressure, but there was no change in plasma norepinephrine. This pattern of response differs from that seen with D-amphetamine or caffeine.