Amoebic gill diseases (AGD) caused primarily by the amphizoic Neoparamoeba spp. have been identified as significant to fish health in intensive aquaculture. These diseases have consequently received significant attention with regard to disease pathophysiology. Neoparamoeba perurans has been putatively identified as the aetiological agent in salmonids, with other species such as turbot Psetta maxima and sea bass Dicentrarchus labrax also affected. Similarly, Neoparamoeba spp. have also been identified in co-infections with other gill diseases in salmonids. While infection of the gills results in an acute multifocal hyperplastic host response, reduced gill surface area and increased mucous cell densities, ion regulation and respiration in terms of blood gasses are only marginally affected. This may be partially attributed to reserve respiratory capacity and a reduction in mucous viscosity allowing for a greater flushing of the gill, so reducing the gill mucus boundary layer. Clinical and acute infections result in significant cardiovascular compromise with increases in aortic blood pressure, and systemic vascular resistance in Atlantic salmon, Salmo salar, which are not seen in rainbow Oncorhynchus mykiss and brown trout Salmo trutta. Increases in vascular resistance appear to be due to vascular constriction potentially reducing blood flow to the heart in compromised fishes, the overall effect being to lead to a compensatory tissue remodelling and change in cardiac shape in chronically infected fishes. The combined effect of reduced gill surface area and cardiovascular compromise leads to a significant reduction in swimming performance and increases in the routine metabolic rate that lead to an increase in the overall metabolic cost of disease.
The occurrence of spinal deformity in aquaculture can be considerable, and a high rate of deformity has been suggested in triploid smolts in Tasmania. However, the physiological performance of fish with skeletal deformities has not been addressed. The swimming performance and oxygen consumption of triploid Atlantic salmon smolts with either a vertebral fusion (platyspondyly) or multifocal scoliosis were compared to normal (non-deformed) triploid smolts. Fish with vertebral fusion attained swim speeds similar to normal fish, whereas scoliotic fish were unable to attain comparable swim speeds. Routine and maximum oxygen consumption was higher for deformed fish compared with normal fish, translating into apparent increased routine metabolic scope in vertebral fusion fish, and equivocal scope in scoliotic fish compared with normal controls. Deformed fish developed a lower excess post-exercise oxygen consumption compared to non-deformed fish, suggesting they are either incapable of sustained anaerobic activity or possess an increased recovery capacity. These data suggest that skeletal deformity has differential effects on swimming performance depending upon the type of deformity but imposes a significant metabolic cost on salmon smolts.
In light of the limited resources available in the criminal justice system, and given the financial costs and inmate mental health risks associated with disciplinary segregation, the practice warrants testing and evaluation. Limited research exists on the effect disciplinary segregation has on subsequent inmate misconduct in state prisons. Institutional violation rates for a cohort of male inmates incarcerated by the Oregon Department of Corrections were analyzed. Controlling for other factors, the results of this study indicate that disciplinary segregation was not a significant predictor of subsequent institutional misconduct. The findings also indicate that the experience of disciplinary segregation does not reduce subsequent prison inmate misconduct and therefore suggest that it may not be an effective institutional practice. These results signal that disciplinary segregation should be used in a more judicious and informed manner and that further research should be performed to determine whether disciplinary segregation has a general deterrent effect.
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