Progress in brain research
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Human death is a unitary phenomenon that physicians can determine in two ways: (1) showing the irreversible cessation of all brain clinical functions; or (2) showing the permanent cessation of circulatory and respiratory functions. Over the last 40 years the determination of human death using neurological tests ("brain death") has become an accepted practice throughout the world but has remained controversial within academic circles. Brain death has a rigorous biophilosophical basis by defining death as the irreversible loss of the critical functions of the organism as a whole. ⋯ Among physicians, the area of greatest controversy in death determination now is the use of circulatory-respiratory tests, particularly as applied to organ donation after circulatory death. Circulatory-respiratory tests are valid only because they produce destruction of the whole brain, the criterion of death. Clarifying the distinction between the permanent and irreversible cessation of circulatory and respiratory functions is essential to understanding the use of these tests, and explains why death determination in organ donation after circulatory death does not violate the dead donor rule.
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The search for a "magic bullet" drug targeting a single receptor for the treatment of stroke or traumatic brain injury (TBI) has failed thus far for a variety of reasons. The pathophysiology of ischemic brain injury and TBI involves a number of mechanisms leading to neuronal injury, including excitotoxicity, free radical damage, inflammation, necrosis, and apoptosis. Brain injury also triggers auto-protective mechanisms, including the up-regulation of anti-inflammatory cytokines and endogenous antioxidants. ⋯ Laboratories around the world have shown that progesterone and allopregnanolone act through numerous metabolic and physiological pathways that can affect the injury response in many different tissues and organ systems. Furthermore, progesterone is a natural hormone, synthesized in both males and females, that can act as a pro-drug for other metabolites with their own distinct mode of action in CNS repair. These properties make progesterone a unique and compelling natural agent to consider for testing in clinical trial for CNS injuries including TBI and stroke.
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Perceptual decision making is the process by which information gathered from sensory systems is combined and used to influence our behavior. Importantly, however, the route from perception to action is not a one-way street, rather, perception and action interact continuously. ⋯ We conclude that there is evidence for the liaison of action and perception in simple decision-making tasks. This framework may also be extended to reward-based decision making in humans.
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This chapter describes current findings from the research into postoperative cognitive dysfunction (POCD) following cardiac and non-cardiac surgery in older adults. The evidence suggests that a significant proportion of patients show POCD in the early weeks following surgery and anesthesia. Specific domains of cognition are affected, especially memory. ⋯ Increasing age is among the most consistently reported patient-related risk factor. Other factors more directly related to the surgery and anesthesia are likely to contribute to the pathogenesis of POCD, including inflammatory processes triggered by the surgical procedure. Animal studies have provided valuable findings otherwise not possible in human studies; these include a correlation between the inflammatory response in the hippocampus and the development of POCD in rodents.
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Impaired urinary dilution leading to water retention and hyponatremia may occur in patients with cardiac failure, cirrhosis, pregnancy, hypothyroidism, glucocorticoid and mineralocorticoid deficiency. The mechanisms for these defects predominantly involve the non-osmotic stimulation of arginine vasopressin release with upregulation of aquaporin 2 water channel expression and trafficking to the apical membrane of the principal cells of the collecting duct. ⋯ They may involve several factors, such as impaired counter-current concentration secondary to downregulation of Na-K-2Cl co-transporter. Vasopressin-resistant downregulation of aquaporin 2 expression has also been described as a factor in impaired urinary concentration.