Adsorption of Human Recombinant Erythropoietin on Dialysis Membranes In Vitro

Abstract: The adsorptive characteristics of 5 dialysis membranes for recombinant human erythropoietin (EPO) were studied in vitro in a closed circuit system. For 120 min, EPO added with bovine serum was significantly adsorbed by polymethylmetacrylate (PMMA) and polyacry–lonitrile (PAN) membranes but not by Cuprophan, ethylene vinyl alcohol (EVAL), or polysulfone (PS) membranes. In addition the EPO adsorptive rate, as well as that of β₂–microglobulin (β₂–MG), was greater with a PMMA membrane than with a PAN membrane. EPO was not detected in the ultrafiltrate at 15 min with 5 membranes. These results indicate that EPO was eliminated by membrane adsorption only with some dialysis membranes.     

Accumulation of cyanide and thiocyanate in haemodialysis patients.

BACKGROUND: Cyanide is a toxic agent, and its detoxification product, thiocyanate, may be a major pathogenetic substance in uraemia. Recent studies examining the myeloperoxidase(MPO)/thiocyanate system have suggested a link between thiocyanate and atherosclerosis. However, inaccuracies in conventional assays for cyanide and thiocyanate have limited the understanding of their metabolism in haemodialysis (HD) patients. METHODS: We used high-performance liquid chromatography to measure cyanide in erythrocytes and thiocyanate in plasma in 43 HD patients and in a group of 46 healthy controls that included 15 current smokers. To clarify the metabolic conversion of cyanide to thiocyanate in uraemic patients, we also measured cysteine and sulfate. We then used stepwise regression analysis to analyse factors that determine erythrocyte cyanide and plasma thiocyanate. RESULTS: Mean cyanide and thiocyanate were significantly greater in HD patients than in non-smoking controls. However, cyanide was far below lethal concentrations in dialysis patients. Thiocyanate was six to seven times greater in HD patients than in non-smoking controls, and decreases in thiocyanate following dialysis were only 19.3+/-3.5%. Multiple regression analysis showed a positive correlation between cyanide and thiocyanate in controls, but a negative correlation in HD patients. In patients, an inverse relationship between thiocyanate and BUN was also observed. CONCLUSIONS: The elevation of thiocyanate in patients undergoing dialysis probably is secondary to both limited efficiency of HD and deranged metabolism of cyanide and thiocyanate. Because thiocyanate is a preferred substrate for MPO, it may play a role in uraemic complications including cardiovascular events.     

Organization of gustatory sensitivities in hamster superior laryngeal nerve fibers

1. Mammalian taste receptors are distributed within several distinct subpopulations, innervated by branches of cranial nerves VII, IX, and X. Most gustatory electrophysiology has focused on input from the fungiform papillae on the anterior portion of the tongue, carried by the chorda tympani branch of the VIIth nerve. However, laryngeal taste buds in the hamster are as numerous as those in the fungiform papillae. Gustatory fibers in the hamster's chorda tympani and glossopharyngeal nerves have been well characterized. In comparison with these taste fibers, much less is known about the chemical sensitivities of fibers innervating laryngeal taste buds. 2. Action potentials were recorded from 65 individual fibers in the superior laryngeal nerve (SLN) of the hamster. Stimuli were distilled H2O and five concentrations each of sucrose, NaCl, HCl, and quinine hydrochloride (QHCl). All stimuli except the NaCl series were made in physiological saline (0.154 M NaCl) and were delivered from the laryngeal side of the epiglottis via a tracheal cannula. Responses were quantified as the number of impulses in 10 s minus the responses in the preceding 10 s of baseline activity during a rinse with physiological saline. 3. Distilled H2O, HCl, and NaCl were by far the most excitatory stimuli, with mean responses across all cells 5-10 times greater than those evoked by sucrose or QHCl. The order of effectiveness of the strongest concentrations of the stimuli was H2O greater than 0.03 M HCl greater than 1.0 M NaCl much greater than 0.03 M QHCl greater than 1.0 M sucrose. 4. The mean concentration-response function for NaCl was U shaped, with the greatest number of impulses to distilled H2O and 1.0 M NaCl. The responses diminished as the concentrations approached physiological levels (0.154 M NaCl), where there was no response, and increased as NaCl concentration rose above this level. Increasing concentrations of HCl above 0.0003 M elicited increasing responses in these fibers. 5. The mean time course of the responses to distilled H2O and to hypotonic NaCl solutions (0.01 and 0.03 M) peaked in the first few seconds and then declined slowly. This was distinct from the time course of the responses to hypertonic NaCl concentrations (0.3 and 1.0 M), which increased gradually throughout the 10-s response period. Responses to HCl peaked in the initial second and then decayed rapidly to a slowly declining plateau. These distinctively different time courses suggest different receptor mechanisms for water, salt, and acid stimuli. 6. The across-fiber pattern of the responses to hypotonic NaCl solutions correlated strongly to that elicited by distilled H2O.(ABSTRACT TRUNCATED AT 400 WORDS)     

Changes in Glucose Metabolism in Cerebral Cortex and Cerebellum Correlate With Tremor and Rigidity Control by Subthalamic Nucleus Stimulation in Parkinson's Disease: A Positron Emission Tomography Study

Objective. Employing [¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography (PET) to assess the correlation between the effect of deep brain stimulation (DBS) on the subthalamic nucleus (STN) and the regional cerebral metabolic rate of glucose (rCMRGlc) in advanced Parkinson's disease patients (N = 8). Materials and Methods. On the basis of patients’ diary records, we performed FDG‐PET during the off‐period of motor activity with on‐ or off‐stimulation by STN‐DBS on separate days and analyzed the correlation between changes in motor symptoms and alterations in the rCMRGlc. Result. When FDG‐PET was performed, the motor score on the unified Parkinson's disease rating scale (UPDRS) was 64% lower with on‐stimulation than with off‐stimulation (p < 0.001, Wilcoxon single‐rank test). STN‐DBS increased the rCMRGlc in the posterior part of the right middle frontal gyrus, which corresponded to the premotor area, and the right anterior lobe of the cerebellum (p < 0.005, paired t‐test). No region exhibited a decrease in rCMRGlc. Among the items of the UPDRS motor score, the changes in resting tremor and rigidity of the left extremities showed a significant correlation with the changes in rCMRGlc observed in the right premotor area (p < 0.02 and p < 0.05, respectively, Spearman's rank correlation). Conclusions. STN‐DBS either activates the premotor area or normalizes the deactivation of the premotor area. These FDG‐PET findings obtained are consistent with the idea that STN‐DBS modifies the activities of neural circuits involved in motor control.     

Abdominal vagotomy attenuates interleukin-1β-induced nitric oxide release in the paraventricular nucleus region in conscious rats

Nitric oxide (NO) has recently been shown to modulate the hypothalamic–pituitary–adrenal axis response to interleukin-1β (IL-1β). We measured levels of nitrite (NO₂⁻) and nitrate (NO₃⁻) in the hypothalamic paraventricular nucleus (PVN) region using an in vivo brain microdialysis technique in conscious rats. Intraperitoneally administered IL-1β produced a significant increase in both NO₂⁻ and NO₃⁻ levels in the PVN region. We also examined the possible involvement of the abdominal vagal afferent nerves in this effect. In abdominal-vagotomized rats, the increase was significantly attenuated compared to that in sham-operated rats. Our results suggest that the abdominal vagal afferent nerves are involved in intraperitoneally administered IL-1β-induced NO release in the PVN region.     

Overexpression of the Del1 gene causes dendritic branching in the mouse mesentery

In the present study, we established transgenic mice overexpressing Del1, a ligand of integrins, to examine the effect of overexpression of Del1 on vascular morphogenesis. In the wild-type mouse, mesenteric vessels are shaped like rakes consisting of a long stalk and short branches at the periphery. In contrast, those in transgenic mice showed typical dendritic architecture consisting of a few large primary branches with smaller spreading branches. The phenotype of mice overexpressing Del1 suggests the existence of a tissue-specific mechanism for branching morphogenesis in the mesentery.     

Paradoxical effect of L-arginine on nitric oxide (NO) synthesis and histopathological changes in 5/6 nephrectomized SD rats

Whether L-Arginine (L-ARG) ameliorates or aggravates renal function and histopathological changes in several models of renal disease remains controversial as L-ARG is the substrate for nitric oxide (NO) synthase as well as the precursor of proline and polyamines which cause renal fibrosis. These ambiguous results might be attributed to differences in the dose and period of L-ARG administration and the animal model used in each observation. Therefore, we tested the dose-dependent effect of L-ARG on mean blood pressure (MBP), 24-hour urinary excretion of protein (UP), NO metabolites (NO2(-) + NO3-) and cyclic GMP (cGMP), plasma asymmetrical dimethylarginine (ADMA), glomerular sclerosis index (SI) and % interstitial fibrosis area (%INT) in 5/6 nephrectomized SD rats. These 5/6 nephrectomized SD rats were divided into 4 groups: 1. L-ARG 0.2 g/kg/day (0.2 g ARG), 2. L-ARG 1 g/kg/day (1 g ARG), 3. L-ARG 2 g/kg/day (2 g ARG), 4. No administration of L-ARG(ARG(-)). Compared with ARG(-)MBP, UP and ADMA were significantly decreased and NO2(-) + NO3-, cGMP were significantly increased in the 0.2 g ARG. SI group and %INT were significantly increased in the 2 g ARG group and decreased in the 0.2 g ARG group. A small dose of L-ARG ameliorated glomerulosclerosis and interstitial fibrosis while a larger dose did not. SI, %INT and ADMA were inversely correlated with NO2(-) + NO3-. These data suggested that renal NO synthesis might attenuate glomerulosclerosis and interstitial fibrosis and the rise in ADMA and L-ARG might cause the decrease in NO.