Medical hypotheses
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Risk in SCUBA diving is often associated with the presence of gas bubbles in the venous circulation formed during decompression. Although it has been demonstrated time-after-time that, while venous gas emboli (VGE) often accompany decompression sickness (DCS), they are also frequently observed in high quantities in asymptomatic divers following even mild recreational dive profiles. Despite this VGE are commonly utilized as a quantifiable marker of the potential for an individual to develop DCS. ⋯ Research suggests that the arterialization of VGE presents a greater risk for DCS than when emboli are eliminated by the pulmonary circuit before they have a chance to crossover. Laboratory studies have demonstrated that exercise increases the incidence of crossover likely through extra-cardiac mechanisms such as intrapulmonary arterial-venous anastomoses (IPAVAs). This effect of exercise has been repeated in the field with divers demonstrating a direct relationship between exercise and increased incidence of arterialization.
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The prevalence of kidney stones is increasing worldwide. Various etiologies may in part explain this observation including increased prevalence of diabetes, obesity and the metabolic syndrome, increased dietary protein and salt content, and decreased dietary dairy products. We hypothesize an additional and novel potential contributor to increasing kidney stone prevalence: migration to urban settings, or urbanization, and resultant exposure of the population to the higher temperatures of urban heat islands (UHIs). ⋯ However, demonstration of a convincing link between urbanization and kidney stones is confounded by many variables simultaneously affected by migration to cities, such as changes in occupation, income, and diet. No data have yet been published supporting this proposed association. We explore the plausibility and limitations of this possible etiology of increasing kidney stone prevalence.
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The autonomic nervous system and the hypothalamic-pituitary-adrenal axis have been shown to be dysfunctional in a number of chronic pain disorders. Spinal manipulation is a therapeutic technique used by manual therapists, which may have widespread neuro-physiological effects. The autonomic nervous system has been implicated to modulate these effects. ⋯ To substantiate our hypothesis we provide evidence from manual therapy studies, basic science and animal studies. According to the proposed theory, there will be measurable changes in the neuro-endocrinal mechanisms following a thoracic spinal manipulation. This has far-reaching implications for manual therapy practice and research and in the integration of spinal manipulation in the treatment of a wide array of disorders.
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Ketogenic diets are markedly neuroprotective, but the basis of this effect is still poorly understood. Recent studies demonstrate that ketone bodies increase neuronal levels of hypoxia-inducible factor-1α (HIF-1α), possibly owing to succinate-mediated inhibition of prolyl hydroxylase activity. Moreover, there is reason to suspect that ketones can activate Sirt1 in neurons, in part by increasing cytoplasmic and nuclear levels of Sirt1's obligate cofactor NAD(+). ⋯ Brain-permeable agents which activate AMP-activated kinase, such as metformin and berberine, as well as the Sirt1 activator nicotinamide riboside, can also boost neuronal autophagy, and may have potential for amplifying the impact of ketogenesis on this process. Since it might not be practical for most people to adhere to ketogenic diets continuously, alternative strategies are needed to harness the brain-protective potential of ketone bodies. These may include ingestion of medium-chain triglycerides or coconut oil, intermittent ketogenic dieting, and possibly the use of supplements that promote hepatic ketogenesis - notably carnitine and hydroxycitrate - in conjunction with dietary regimens characterized by long daily episodes of fasting or carbohydrate avoidance.
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Randomized controlled trials require hard work and financial commitment, whereas meta-analyses and systematic reviews can be relatively easy to perform and often get published in high impact journals. Many researchers might decide to devote themselves to the latter approach, resulting in a negative impact on clinical research. We have reviewed the number of indexed meta-analyses and systematic reviews on PubMed and compared it with the number of randomized controlled trials over the same period. ⋯ The ratio between RCTs and synthetic studies is quickly decreasing. These results suggest that a growing number of researchers might prefer to commit themselves to synthetic studies more than be involved in more time consuming and funds demanding observational trials. If we are unable to invert this trend, in the future we will have a growing number of synthetic studies utilizing someone else's original data and fewer raw data to base our knowledge upon.