Publications by authors named "Josephine Chiu"

Pre-surgical psychological assessments are becoming common in the United States and are recommended or required prior to surgical/spinal cord stimulator intervention for chronic back pain. Psychological testing is often recommended for these evaluations and the various versions of the Minnesota Multiphasic Personality Inventory (MMPI) have demonstrated utility for predicting outcomes in this setting. This investigation sought to extend that literature with the newest version of the MMPI, the MMPI-3.

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While the majority of host cell protein (HCP) impurities are effectively removed in typical downstream purification processes, a small population of HCPs are particularly challenging. Previous studies have identified HCPs that are challenging for a variety of reasons. Lipoprotein lipase (LPL)-a Chinese hamster ovary (CHO) HCP that functions to hydrolyze esters in triglycerides-was one of ten HCPs identified in previous studies as being susceptible to retention in downstream processing.

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Prior work in animals and humans suggests that muscle mechanoreceptor control of sympathetic activation [muscle sympathetic nerve activity (MSNA)] during exercise in heart failure (HF) patients is heightened compared with that of healthy humans and that muscle mechanoreceptors are sensitized by metabolic by-products. We sought to determine whether cyclooxygenase products and/or endogenous adenosine, two metabolites of ischemic exercise, sensitize muscle mechanoreceptors during rhythmic handgrip (RHG) exercise in HF patients. Indomethacin, which inhibits the production of prostaglandins, and saline control were infused in 12 HF patients.

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HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase inhibitors (statins) have been shown to reduce serum cholesterol and cardiovascular morbidity and mortality. The mechanisms of these beneficial effects are reviewed. Altered inflammatory responses and improved endothelial function mediated by statins are thought to be, in part, responsible for the reduction in cardiovascular events.

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Evidence in healthy animals and humans is accumulating that the muscle mechanoreceptors play an important role in mediating sympathetic activation during exercise, especially rhythmic exercise. Furthermore, muscle mechanoreceptors appear to be sensitized acutely during exercise by metabolic by-products, although the identity of these by-products remains unknown. The purpose of this study was to determine whether the metabolic by-products 1) prostaglandins and/or 2) adenosine sensitize muscle mechanoreceptor control of muscle sympathetic nerve activity (MSNA) in normal humans during rhythmic exercise.

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Article Synopsis
  • Previous research indicates that muscle mechanoreceptors in heart failure (HF) patients might be more sensitive, leading to increased sympathetic activation during exercise.
  • The study sought to explore whether this enhanced mechanoreceptor control occurs in HF patients and if lactic acid, a metabolic by-product, sensitizes these receptors during exercise.
  • Results showed that MSNA (muscle sympathetic nerve activity) increased earlier in HF patients during exercise and that muscle mechanoreceptors displayed heightened sensitivity, while lactic acid was not a major factor in this sensitization.
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Recent studies have implicated reactive oxygen species (ROS) in the pathogenesis of hypertension and activation of the sympathetic nervous system (SNS). Because nitric oxide (NO) exerts a tonic inhibition of central SNS activity, increased production of ROS could enhance inactivation of NO and result in activation of the SNS. To test the hypothesis that ROS may modulate SNS activity, we infused Tempol (4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl), a superoxide dismutase mimetic, or vehicle either intravenously (250 microg x kg(-1) x min(-1)) or in the lateral ventricle (50 microg x kg body wt(-1) x min(-1)), and we determined the effects on blood pressure (BP), norepinephrine (NE) secretion from the posterior hypothalamus (PH) measured by the microdialysis technique, renal sympathetic nerve activity (RSNA) measured by direct microneurography, the abundance of neuronal NO synthase (nNOS)-mRNA in the PH, paraventricular nuclei (PVN), and locus coeruleus (LC) measured by RT-PCR, and the secretion of nitrate/nitrite (NO(x)) in the dialysate collected from the PH of Sprague-Dawley rats.

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