Little is known about the biochemical mechanisms responsible for the biological aging process. Our previous results and those of others suggest that one possible mechanism is based on the loss of glutathione (GSH), a multifunctional tripeptide present in high concentrations in nearly all living cells. The recent finding that life-long dietary restriction of the GSH precursor methionine (Met) resulted in increased longevity in rats led us to hypothesize that adaptive changes in Met and GSH metabolism had occurred, leading to enhanced GSH status. To test this, blood and tissue GSH levels were measured at different ages throughout the life span in F344 rats on control or Met-restricted diets. Met restriction resulted in a 42% increase in mean and 44% increase in maximum life span, and in 43% lower body weight compared to controls (P < 0.001). Increases in blood GSH levels of 81% and 164% were observed in mature and old Met-restricted animals, respectively (P < 0.001). Liver was apparently the source for this increase as hepatic GSH levels decreased to 40% of controls. Except for a 25% decrease in kidney, GSH was unchanged in other tissues. All changes in GSH occurred as early as 2 months after the start of the diet. Altogether, these results suggest that dramatic adaptations in sulfur amino acid metabolism occur as a result of chronic Met restriction, leading to increases in blood GSH levels and conservation of tissue GSH during aging.
Many clinicians believe that de novo access is required when converting temporary hemodialysis (HD) catheters to long-term or permanent catheters. However, since vascular access sites are at a premium in the dialysis patient, it is important to preserve existing central venous catheters and conserve future access sites. In this retrospective study, data from 94 patients referred to interventional radiology for placement of long-term, tunneled HD catheters between July 2001 and September 2002 were reviewed. The study group consisted of 42 patients in whom the temporary catheter was exchanged for a peel-away sheath and a tunneled catheter inserted using the existing venous access site. The control group included 52 patients who received traditional de novo placement of permanent catheters. Based on available follow-up data, we report a 100% technical success rate, with 72% patency at 30 days in the study group (n = 32; mean age 58 years). By comparison, de novo catheter placement (n = 35; mean age 59 years) yielded a 100% technical success rate, with 83% patency at 30 days. The overall infection rate was 0.30 per 100 catheter-days (total 3036 catheter-days) and 0.36 per 100 catheter-days (total 3295 catheter-days), respectively (chi2 = 0.64, p > or = 0.05). There was no incidence of exit site infection, tunnel infection, or florid sepsis in either group. Likewise, no stenosis or bleeding complication was noted. Thus conversion of a temporary HD catheter to a tunneled catheter using the same venous insertion site is safe, does not increase the risk of infection, and allows conservation of other central venous access sites.
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