From the Eye of the Albatrosses: A Bird-Borne Camera Shows an Association between Albatrosses and a Killer Whale in the Southern Ocean

Albatrosses fly many hundreds of kilometers across the open ocean to find and feed upon their prey. Despite the growing number of studies concerning their foraging behaviour, relatively little is known about how albatrosses actually locate their prey. Here, we present our results from the first deployments of a combined animal-borne camera and depth data logger on free-ranging black-browed albatrosses (Thalassarche melanophrys). The still images recorded from these cameras showed that some albatrosses actively followed a killer whale (Orcinus orca), possibly to feed on food scraps left by this diving predator. The camera images together with the depth profiles showed that the birds dived only occasionally, but that they actively dived when other birds or the killer whale were present. This association with diving predators or other birds may partially explain how albatrosses find their prey more efficiently in the apparently ‘featureless’ ocean, with a minimal requirement for energetically costly diving or landing activities

A comparison of responses to raised extracellular potassium and endothelium-derived hyperpolarizing factor (EDHF) in rat pressurised mesenteric arteries

The present study examined the hypothesis that potassium ions act as an endothelium-derived hyperpolarizing factor (EDHF) released in response to ACh in small mesenteric arteries displaying myogenic tone. Small mesenteric arteries isolated from rats were set up in a pressure myograph at either 60 or 90 mmHg. After developing myogenic tone, responses to raising extracellular potassium were compared to those obtained with ACh (in the presence of nitric oxide synthase and cyclo- oxygenase inhibitors). The effects of barium and ouabain, or capsaicin, on responses to raised extracellular potassium or ACh were also determined. The effects of raised extracellular potassium levels and ACh on membrane potential, were measured using sharp microelectrodes in pressurised arteries. Rat small mesenteric arteries developed myogenic tone when pressurised. On the background of vascular tone set by a physiological stimulus (i.e pressure), ACh fully dilated the small arteries in a concentration-dependent manner. This response was relatively insensitive to the combination of barium and ouabain, and insensitive to capsaicin. Raising extracellular potassium produced a more inconsistent and modest vasodilator response in pressurised small mesenteric arteries. Responses to raising extracellular potassium were sensitive to capsaicin, and the combination of barium and ouabain. ACh caused a substantial hyperpolarisation in pressurized arteries, while raising extracellular potassium did not. These data indicate that K+ is not the EDHF released in response to ACh in myogenically active rat mesenteric small arteries. Since the hyperpolarization produced by ACh was sensitive to carbenoxolone, gap junctions are the likely mediator of EDH responses under physiological conditions

PET and SPECT Imaging in Hyperkinetic Movement Disorders

Movement disorders can be classified in hypokinetic (e.g., Parkinson's disease, PD) and hyperkinetic disorders (e.g., dystonia, chorea, tremor, tics, myoclonus, and restless legs syndrome). In this chapter, we will discuss results from positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging studies in patients with tremor, tics, myoclonus, and restless legs syndrome. Most studies in patients with tremor included patients with essential tremor (ET): a bilateral, largely symmetric, postural or kinetic tremor mainly involving the upper limbs and sometimes the head. Other studies evaluated patients with orthostatic tremor (OT): an unusually high frequent tremor in the legs that mainly occurs when patients are standing still. Increased regional cerebral blood flow (rCBF) and increased glucose metabolism have been found in the cerebellum, sensorimotor cortex, and thalamus in both patients with ET and OT compared to controls. Both PET and SPECT studies have evaluated the dopamine system in patients with ET and OT. Most imaging studies in patients with ET showed no, or only subtle loss of striatal tracer binding to the dopamine transporter indicating that ET is not characterized by nigrostriatal cell loss. The serotonin and/or gamma-aminobutyric acid (GABA) systems may play a role in the pathophysiology of ET. PET and SPECT imaging of the dopamine and serotonin system in patients with OT showed no abnormalities. Tics, the clinical hallmark of Gilles de la Tourette syndrome (TS), are relatively brief and intermittent involuntary movements (motor tic) and sounds (phonic tic). The essential features of tics are that (1) they can be temporarily suppressed; after suppression a rebound usually occurs with a flurry of tics; (2) the patient experiences an urge to tic, and (3) the tic is followed by a short moment of relief. Using 18F-FDG PET, it was shown that TS is a network disorder where multiple brain areas are active or inactive at the same time. The exact composition of this network is yet to be determined. Using rCBF PET and SPECT many brain regions were found to be abnormal, however, tics mostly correlated with hypoperfusion of the caudate nucleus and cingulate cortex. Both dopamine and serotonin are likely to play a role in the pathophysiology of TS. It is hypothesized that TS is characterized by low serotonin levels that modulate increased phasic dopamine release. Myoclonus is defined as a brief muscle jerk and occurs in many neurologic and non-neurologic disorders. Imaging with PET and SPECT in patients with myoclonus mainly showed abnormalities consistent with the underlying disorder. We described PET and SPECT imaging results in patients in which myoclonus was a prominent symptom. Hypoperfusion and/or hypometabolism of the frontoparietal cortex was found in patients with negative epileptic myoclonus, Alzheimer's disease, corticobasal degeneration, Creutzfeldt-Jakob disease, fatal familiar insomnia, and posthypoxic myoclonus. Other findings that were frequently reported were decreased rCBF and/or glucose metabolism in the cerebellum and thalamus and abnormalities in the dopamine system. Restless legs syndrome (RLS) is defined as an urge to move the legs accompanied with an unpleasant sensation in the legs or in another body part that is especially present during the evening and night and that can be accompanied by periodic limb movements in sleep (PLMS). Imaging studies in these patients have mainly focused on the dopamine system. Most PET studies found decreased tracer binding to the dopamine transporter, although this was not found in SPECT studies. Both PET and SPECT studies showed conflicting results regarding dopamine D2/3 receptor binding: both increased and decreased tracer binding was reported. Furthermore, it is likely that the serotonin and opioid systems also play a role in the pathophysiology of RLS.</p