Fluoroscopically-guided manipulation of malfunctioning peritoneal dialysis catheters.
(17/1170)
OBJECTIVE: To review our experience with fluoroscopic evaluation and manipulation of malpositioned, malfunctioning, peritoneal dialysis (PD) catheters. MATERIALS AND METHODS: Thirty-one patients, over a 5-year period (1 May 1992 to 30 April 1997) with malfunctioning PD catheters, who had fluoroscopically-guided manipulation were reviewed. Catheters were manipulated using a malleable aluminum bar and, if necessary, guide wires or other stiffeners. Technical success was assessed on the basis of adequate, fluoroscopically verified, catheter placement at the time of the procedure and improved flows. A functional PD catheter at 30 days post manipulation was considered to be a clinically successful manipulation. RESULTS: There were 41 manipulations [33 initial (IM) and 8 remanipulations (RM)] for malpositioned or kinked catheters. In 31 (19 male, 12 female) patients ranging in age from 31 to 76 years (mean age 60 years), the initial technical success rate was 85% for IM (n = 28/33) and 63% (n = 5/8) for RM. The overall clinical success rate, or 30-day primary patency, was 55% for IM (n = 18/33) and 63% for RM. Catheter function (combined IM and RM) continued for a median 869 days (95% CI: 118, 1620). No early complications were noted. CONCLUSIONS: Fluoroscopic manipulation, including attempts at remanipulation, of PD catheters is a safe procedure. The technique is a simple, inexpensive, and effective way of prolonging PD catheter life, thereby reducing the number of surgical interventions. (+info)
Pamidronate therapy as prevention of bone loss following renal transplantation.
(18/1170)
BACKGROUND: Very rapid bone loss, osteopenia and skeletal morbidity after renal transplantation have been well documented and found to occur in a sex dependent fashion. Glucocorticoids, cyclosporine and pre-existing uremic osteodystrophy have been implicated in the pathogenesis of the skeletal lesions. Glucocorticoid induced osteopenia is also a serious clinical problem in patients with various nonrenal diseases and can be prevented, or at least attenuated, by pamidronate and other bisphosphonates. METHOD: We prospectively studied 26 male patients undergoing renal transplantation, and randomized them to receive either placebo or intravenous pamidronate (0.5 mg/kg) at the time of transplantation and again one month later. All patients received immunosuppression comprising prednisolone, cyclosporine and azathioprine. The bone mineral density (BMD) of the second, third and fourth lumbar vertebrae and of the femoral neck was measured at the time of transplantation and at three months and 12 months after transplantation using dual energy X-ray absorptiometry (DXA). RESULTS: Twelve months after transplantation, the mean (+/- SEM) BMD of the lumbar vertebrae in patients who received placebo had decreased 6.4% (P < 0.05). In contrast, patients who received pamidronate experienced no significant reduction of BMD at the lumbar vertebrae. At the femoral neck, placebo-treated patients showed a reduction of BMD of 9% (P < 0.005), whereas there was no significant change in the pamidronate treated group. The two study groups had similar patient profiles, serum parathyroid hormone (PTH) and aluminium concentrations. After transplantation, comparable falls in the serum creatinine and PTH concentration were found in the two groups. Apart from transient hypocalcemia in two patients, no significant adverse effects of pamidronate were noted. CONCLUSION: This study has shown that the early rapid bone loss that occurs in men during the first 12 months after renal transplantation can be prevented by two intravenous doses of pamidronate given at transplantation and one month later. The regimen was simple to administer, well tolerated and potentially applicable to other clinical groups of glucocorticoid treatment patients. (+info)
Oxidative stress and Alzheimer disease.
(19/1170)
Research in the field of molecular biology has helped to provide a better understanding of both the cascade of biochemical events that occurs with Alzheimer disease (AD) and the heterogeneous nature of the disease. One hypothesis that accounts for both the heterogeneous nature of AD and the fact that aging is the most obvious risk factor is that free radicals are involved. The probability of this involvement is supported by the fact that neurons are extremely sensitive to attacks by destructive free radicals. Furthermore, lesions are present in the brains of AD patients that are typically associated with attacks by free radicals (eg, damage to DNA, protein oxidation, lipid peroxidation, and advanced glycosylation end products), and metals (eg, iron, copper, zinc, and aluminum) are present that have catalytic activity that produce free radicals. beta-Amyloid is aggregated and produces more free radicals in the presence of free radicals; beta-amyloid toxicity is eliminated by free radical scavengers. Apolipoprotein E is subject to attacks by free radicals, and apolipoprotein E peroxidation has been correlated with AD. In contrast, apolipoprotein E can act as a free radical scavenger and this behavior is isoform dependent. AD has been linked to mitochondrial anomalies affecting cytochrome-c oxidase, and these anomalies may contribute to the abnormal production of free radicals. Finally, many free radical scavengers (eg, vitamin E, selegeline, and Ginkgo biloba extract EGb 761) have produced promising results in relation to AD, as has desferrioxamine-an iron-chelating agent-and antiinflammatory drugs and estrogens, which also have an antioxidant effect. (+info)
Expression of aluminum-induced genes in transgenic arabidopsis plants can ameliorate aluminum stress and/or oxidative stress.
(20/1170)
To examine the biological role of Al-stress-induced genes, nine genes derived from Arabidopsis, tobacco (Nicotiana tabacum L.), wheat (Triticum aestivum L.), and yeast (Saccharomyces cerevisiae) were expressed in Arabidopsis ecotype Landsberg. Lines containing eight of these genes were phenotypically normal and were tested in root elongation assays for their sensitivity to Al, Cd, Cu, Na, Zn, and to oxidative stresses. An Arabidopsis blue-copper-binding protein gene (AtBCB), a tobacco glutathione S-transferase gene (parB), a tobacco peroxidase gene (NtPox), and a tobacco GDP-dissociation inhibitor gene (NtGDI1) conferred a degree of resistance to Al. Two of these genes, AtBCB and parB, and a peroxidase gene from Arabidopsis (AtPox) also showed increased resistance to oxidative stress induced by diamide, while parB conferred resistance to Cu and Na. Al content of Al-treated root tips was reduced in the four Al-resistant plant lines compared with wild-type Ler-0, as judged by morin staining. All four Al-resistant lines also showed reduced staining of roots with 2',7'-dichloro fluorescein diacetate (H(2)DCFDA), an indicator of oxidative stress. We conclude that Al-induced genes can serve to protect against Al toxicity, and also provide genetic evidence for a link between Al stress and oxidative stress in plants. (+info)
Aluminum tolerance genes on the short arm of chromosome 3R are linked to organic acid release in triticale.
(21/1170)
Triticale, a hybrid between wheat and rye, shows a high degree of Al tolerance that is inherited from rye, but the mechanisms of high Al tolerance in both rye and triticale are unknown. We found that the short arm of chromosome 3R carries genes necessary for Al tolerance in triticale (x Triticosecale Wittmark cv Currency). Detailed comparative studies with a 3DS.3RL translocation line (ST22) and a non-substitution line (ST2) were conducted. Root elongation was similarly inhibited by Al in ST2 and ST22 during the first 12 h of Al treatment, but more strongly in ST22 than in ST2 at 18 h and thereafter. The root inhibition induced by other metals (Cu, Cd, and La) was similar between ST2 and ST22, suggesting that the action of the genes for Al tolerance on the short arm of triticale chromosome 3R is highly specific to Al. A 2-fold larger amount of malate and citrate was released from the roots of ST2 than from ST22 at 12 and 18 h after Al treatment, respectively. The marked lag phase in the inhibition of root elongation and the release of organic acids implies that the expression of genes on the short arm of triticale chromosome 3R is induced by Al, and that these genes are necessary for the release of organic acids. (+info)
Genotypical differences in aluminum resistance of maize are expressed in the distal part of the transition zone. Is reduced basipetal auxin flow involved in inhibition of root elongation by aluminum?
(22/1170)
Short-term Al treatment (90 microM Al at pH 4.5 for 1 h) of the distal transition zone (DTZ; 1-2 mm from the root tip), which does not contribute significantly to root elongation, inhibited root elongation in the main elongation zone (EZ; 2.5-5 mm from the root tip) to the same extent as treatment of the entire maize (Zea mays) root apex. Application of Al to the EZ had no effect on root elongation. Higher genotypical resistance to Al applied to the entire root apex, and specifically to the DTZ, was expressed by less inhibition of root elongation, Al accumulation, and Al-induced callose formation, primarily in the DTZ. A characteristic pH profile along the surface of the root apex with a maximum of pH 5.3 in the DTZ was demonstrated. Al application induced a substantial flattening of the pH profile moreso in the Al-sensitive than in the Al-resistant cultivar. Application of indole-3-acetic acid to the EZ but not to the meristematic zone significantly alleviated the inhibition of root elongation induced by the application of Al to the DTZ. Basipetal transport of exogenously applied [(3)H]indole-3-acetic acid to the meristematic zone was significantly inhibited by Al application to the DTZ in the Al-sensitive maize cv Lixis. Our results provide evidence that the primary mechanisms of genotypical differences in Al resistance are located within the DTZ, and suggest a signaling pathway in the root apex mediating the Al signal between the DTZ and the EZ through basipetal auxin transport. (+info)
Increased bone strontium levels in hemodialysis patients with osteomalacia.
(23/1170)
BACKGROUND: In this study, we report on the association between increased bone strontium levels and the presence of osteomalacia in end-stage renal failure patients treated by hemodialysis. METHODS: We performed a histologic examination and determined the strontium content and strontium/calcium ratios in bone biopsies of 100 hemodialysis patients recruited from various centers all over the world. Aside from the bone strontium concentration, the bone aluminum content was assessed. The bone zinc concentration, a nonrelevant element for bone toxicity, was also measured. RESULTS: Bone strontium levels and bone strontium/calcium ratios were increased in subjects with osteomalacia when compared with those with the other types of renal osteodystrophy. Bone strontium and bone calcium levels correlated with each other. The slope of the linear regression curve correlating these parameters was much steeper in the osteomalacic group (Y = 2.22X - 120) as compared with the other types of renal osteodystrophy (Y = 0.52X - 5.7). Within the group of patients with osteomalacia, bone strontium levels also significantly correlated with the bone aluminum content (r = 0.72, P = 0.018). No such correlation was found for the other types of renal osteodystrophy. The bone zinc concentration of subjects with normal renal function did not differ significantly from the values noted for the various types of renal osteodystrophy taken as separate groups, nor could increased bone zinc concentrations be associated with a particular bone lesion. CONCLUSIONS: Our data demonstrate an association between osteomalacia and increased bone strontium concentrations in dialysis patients. Further studies are warranted to establish whether strontium plays either a primary, secondary, or contributive role in the development of the latter type of renal osteodystrophy. (+info)
Oligomeric but not monomeric silica prevents aluminum absorption in humans.
(24/1170)
BACKGROUND: Soluble silica, a ubiquitous component of the diet, may be the natural ligand for dietary aluminum and may prevent its accumulation and toxicity in animals. However, previous studies on the inhibition of aluminum absorption and toxicity by soluble silica have produced conflicting results. We recently identified a soluble silica polymer, oligomeric silica, that has a much higher affinity for aluminum than does monomeric silica and that may be involved in the sequestration of aluminum. OBJECTIVE: By using (26)Al as a tracer, we investigated the effects of oligomeric and monomeric silica on the bioavailability of aluminum (study 1) and compared the availability of silicon from oligomeric and monomeric silica in the human gastrointestinal tract (study 2). DESIGN: In study 1, three healthy volunteers each ingested aluminum alone (control), aluminum with oligomeric silica (17 mg), and aluminum with monomeric silica (17 mg). In study 2, five healthy volunteers ingested both the oligomeric and monomeric forms of silica (34 mg). Serum and urine samples were analyzed for aluminum and silicon. RESULTS: Oligomeric silica reduced the availability of aluminum by 67% (P = 0.01) compared with the control, whereas monomeric silica had no effect (P = 0.40). Monomeric silica was readily taken up from the gastrointestinal tract and then excreted in urine (53%), whereas oligomeric silica was not detectably absorbed or excreted. CONCLUSIONS: The oligomeric, high-aluminum-affinity form of soluble silica reduces aluminum availability from the human gastrointestinal tract. Its potential role in the amelioration of aluminum toxicity in other biological systems requires attention. (+info)