Search

Exploiting species-specific behavioural responses of fish to light is an increasingly promising technique to reduce the entrainment or impingement of fish that results from the diversion of water for human activities, such as hydropower or irrigation. Whilst there is some evidence that white light can be an effective deterrent for Chinook salmon smolts, the results have been mixed. There is a need to test the response of fish to different spectra and strobing frequencies to improve deterrent performance. We tested the movement and spatial response of groups of four fish to combinations of light-emitting diode (LED) spectra (red, green, blue and white light) during the day and night, and strobing frequencies (constant and 2Hz) during the day, using innovative LED technology intended as a behavioural guidance device for use in the field. Whilst strobing did not alter fish behaviour when compared to constant light, the red light had a repulsive effect during the day, with fish under this treatment spending significantly less time in the half of the arena closest to the behavioural guidance device compared to both the control and blue light. Importantly, this effect disappeared at night, where there were no differences in movement and space use found between spectra. There was some evidence of a potential attractive response of fish to the blue and green light during the day. Under these light treatments, fish spent the highest amount of time closest to the behavioural guidance device. Further tests manipulating the light intensity in the different spectra are needed to verify the mechanistic determinants of the observed behaviours. Results are discussed in reference to the known spectral sensitivities of the cone and rod photopigments in these fish, and further experiments are suggested to better relate the work to mitigating the effects on fish of infrastructure used for hydropower and irrigation. more...

The effects of ethanol on blood flow in the coronary arteries, the major blood vessels supplying the heart, and the dimensions of the coronary arteries were examined in 29 patients with coronary artery disease and six normal subjects. Blood flow was measured in the coronary sinus, a large vein that drains coronary arteries, before and during a 15- to 30-minute infusion of dextrose, or sugar, into the hearts of 15 subjects and an infusion of 5 percent ethanol in dextrose solution in 20 subjects. In subjects receiving dextrose, heart rate, arterial pressure, and coronary sinus blood flow were unchanged. In subjects receiving ethanol, coronary sinus flow increased about 27 percent, and resistance in the coronary blood vessels to flow decreased 17 percent. In the ethanol group, there were also changes in the oxygen content in the coronary artery sinus and artery, but no changes in the coronary artery dimensions. The results show that ethanol increases coronary blood flow and decreases resistance without causing any changes in dimensions, suggesting that the effects of ethanol result from dilation of the small blood vessels called arterioles, which cause resistance to flow. (Consumer Summary produced by Reliance Medical Information, Inc.) more...

Hatchery‐reared age 1+ and 4+ lake sturgeon (Acipenser fulvescens) were assayed to determine the effectiveness of coloured, strobing LED light guidance device (LGD) at achieving behavioural guidance for attraction or avoidance responses. Based on an initial y‐maze dichotomous choice study in age 1+ fish during daytime, we selected green, blue, orange, and full‐spectrum white light, all strobing at 1 Hz, for further testing. During nighttime light guidance trials, age 1+ sturgeon demonstrated the fastest entries and greatest proportion of entries to the cone of illumination in the experimental raceway when the LGD was producing blue light, and the lowest proportion of entries in response to orange light. Conversely, they also spent the greatest amounts of time under illumination during orange light trials. Blue light was associated with the greatest proportion and total numbers of complete passages through the illuminated zone, although passage rates through this area were observed during the unilluminated control trials. White light resulted in the least time spent in the illuminated zone, and the lowest rates of passage. Under the nighttime testing scenario, the age 4+ sturgeon, by contrast, demonstrated strong avoidance of blue light and white light. While their behaviour was negatively phototactic in general, orange light was the least repulsive. For the behavioural guidance of lake sturgeon moving at night, we recommend the use of blue light strobing at 1 Hz for the attraction of the 1+ age class and white light strobing at 1 Hz for their repulsion. For age 4+ fish, we recommend the use of blue light or white light strobing at 1 Hz for repulsion and caution that (a) light as a behavioural guidance tool appears most effective as a repulsive stimulus, and (b) further testing under both laboratory and field conditions are required. [ABSTRACT FROM AUTHOR] more...

In the United States cocaine is commonly used as a topical anesthetic for nasal surgery. Some of the side effects of cocaine may include high blood pressure, heart arrhythmia (abnormal heartbeat rhythm), and increased oxygen demand of the myocardium (heart muscle). In cardiac patients, ischemia (inadequate oxygen supply) or myocardial infarction (heart attack) may be induced by cocaine. Abuse of the drug is also associated with serious cardiac episodes. The effect of intranasal cocaine was observed in 45 patients, aged 36 to 67 years, whose evaluation for chest pain included cardiac catheterization (makes possible clear X-ray imaging of the heart and coronary arteries which supply oxygen to the myocardium). Measurements, taken before and 15 minutes after the intranasal administration of cocaine included: heart rate, arterial pressure (within arteries), blood flow in the coronary sinus (vein that empties into the right atrium), and the diameter of the left coronary artery (supplies the left ventricle). The results of the data indicated that cocaine increased the heart rate and systemic arterial pressure, which resulted in increasing the myocardial demand for oxygen. Simultaneously, cocaine reduced myocardial oxygen supply by decreasing the coronary sinus blood flow. None of these measurements changed after the administration of a saline placebo and there was no difference in the results between patients who were or were not ultimately diagnosed with diseased coronary arteries. Constriction of the coronary artery was relieved by phentolamine, an alpha-adrenergic blocking agent. The metabolic, hemodynamic, and arteriographic findings confirmed that cocaine induced the coronary artery vasoconstriction. Researchers concluded that similar but more serious adverse effects could be anticipated with higher doses of cocaine which are typical in recreational use of the drug. more...