Biomedical subjects

R G Cutler

Publications and source records attributed to R G Cutler.

At least 19 recordsLinked to original sources

PubMed2000

Uric acid and serum antioxidant capacity: a reaction to atherosclerosis?

BACKGROUND: the evidence of a potential beneficial role of antioxidants in preventing atherosclerotic disease is not entirely consistent. OBJECTIVE: to assess the longitudinal association of serum total antioxidant capacity and serum antioxidants with the presence of subclinical carotid atherosclerosis. METHODS: Prospective case-control study nested within an historical cohort. Cases were 150 individuals with elevated carotid intimal-medial thickness measured by B-mode ultrasound at the first two examinations of the Atherosclerosis Risk in Communities Study (1987-92). Controls were 150 age-gender-matched individuals with low carotid intimal-medial thickness. Serum antioxidant vitamins, uric acid, and serum total antioxidant capacity were measured in frozen serum samples collected from the same individuals in 1974 (13-15 years prior to the determination of case-control status). RESULTS: Compared to controls, atherosclerosis cases had significantly higher levels of serum total antioxidant capacity in 1974 than controls. This difference was almost entirely explained by increased serum concentration of uric acid in cases. In contrast with cross-sectional results, uric acid serum concentration in 1974, was significantly higher in cases than in controls, even after adjusting for the main cardiovascular risk factors. Cases had significantly lower levels of alpha-carotene in the 1974 sera than controls, but no other differences in serum antioxidant vitamin concentrations were observed. CONCLUSIONS: The higher serum uric acid concentration seemed associated with elevated total serum antioxidant capacity among individuals with atherosclerosis. This finding is consistent with experimental evidence suggesting that hyperuricemia may be a compensatory mechanism to counteract oxidative damage related to atherosclerosis and aging in humans.

Antioxidants↗

PubMed1998

Mouse embryonic stem cells carrying one or two defective Msh2 alleles respond abnormally to oxidative stress inflicted by low-level radiation.

Chronic oxidative stress may play a critical role in the pathogenesis of many human cancers. Here, we report that mouse embryonic stem (ES) cells deficient in DNA mismatch repair responded abnormally when exposed to low levels of ionizing radiation, a stress known to generate oxidative DNA damage. ES cells derived from mice carrying either one or two disrupted Msh2 alleles displayed an increased survival following protracted exposures to low-level ionizing radiation as compared with wild-type ES cells. The increases in survival exhibited by ES cells deficient in DNA mismatch repair appeared to have resulted from a failure to efficiently execute cell death (apoptosis) in response to radiation exposure. For each of the ES cell types, prolonged low-level radiation treatment generated oxidative genome damage that manifested as an accumulation of oxidized bases in genomic DNA. However, ES cells from Msh2(+/-) and Msh2(-/-) mice accumulated more oxidized bases as a consequence of low-level radiation exposure than ES cells from Msh2(+/+) mice. The propensity for normal cells with mismatch repair enzyme deficiencies, including cells heterozygous for inactivating mismatch repair enzyme gene mutations, to survive promutagenic genome insults accompanying oxidative stresses may contribute to the increased cancer risk characteristic of the hereditary nonpolyposis colorectal cancer syndrome.

Alleles↗

PubMed1998

Release of nitric oxide from a spin trap, N-tert-butyl-alpha-phenylnitrone, under various oxidative conditions.

Nitric oxide (NO) generation from a spin trap, N-tert-butyl-alpha-phenylnitrone (PBN) under various oxidative conditions was examined. The absorbance of PBN at 295 nm decreased with time of UV-irradiation, showing that PBN was decomposed by UV irradiation. The hydroxyl radical formed from a Fenton reagent also decomposed PBN, but there was little effect by a peroxyl radical and a superoxide. Nitrite, an oxidative product of NO, in PBN solution was determined using a NOx analyzer based on Griess reaction. UV-irradiation and the hydroxyl radical also formed nitrite. Direct detection of NO from the sample on reaction with hydroxyl radical was successful using a GC/MS/SIM on the UV-irradiated sample. NO generated in PBN solutions activated guanylate cyclase. From these results, PBN is viewed as a new kind of medicine which acts as an antioxidant and as an NO donor in vivo.

Animals↗

PubMed1998

A spin trap, N-tert-butyl-alpha-phenylnitrone extends the life span of mice.

To characterize the pharmacological effects of N-tert-butyl-alpha-phenylnitrone (PBN) on life span, we administered PBN in drinking water to 24.5-month-old mice, and the survivors were counted. Their water consumption and body weights were measured as biological markers. PBN-treated animals as compared with control animals had prolonged mean and maximum life spans. Their water consumption decreased but no significant change was found in their body weights, indicating that the metabolism was improved. Results showed that PBN indeed affects physiological functions and extends life span. We propose that nitric oxide release from PBN may be involved in altering the aging process.

Animals↗

PubMed1997

The risk of developing lung cancer associated with antioxidants in the blood: ascorbic acid, carotenoids, alpha-tocopherol, selenium, and total peroxyl radical absorbing capacity.

Lung cancer cases diagnosed during the period 1975 through 1993 and matched controls were identified in the rosters of Washington County, Maryland residents who had donated blood for a serum bank in 1974 or 1989. Plasma from participants in the 1989 project was assayed for ascorbic acid; serum or plasma was assayed for participants in either project for alpha- and beta-carotene, cryptoxanthin, lutein/zeaxanthin, lycopene, alpha-tocopherol, selenium, and peroxyl radical absorption capacity. Among the total group of 258 cases and 515 controls, serum/plasma concentrations were significantly lower among cases than controls for cryptoxanthin, beta-carotene, and lutein/zeaxanthin with case-control differences of -25.5, -17.1, and -10.1%, respectively. Modest nonsignificant case-control differences in a protective direction were noted for alpha-carotene and ascorbic acid. There were only trivial differences for lycopene, alpha-tocopherol, selenium, and peroxyl radical absorption capacity. Findings are reported for males and females and for persons who had never smoked cigarettes, former smokers, and current smokers at baseline. These results and those from previous studies suggest that beta-carotene is a marker for some protective factor(s) against lung cancer; that cryptoxanthin, alpha-carotene, and ascorbic acid need to be investigated further as potentially protective factors or associates of a protective factor; and that lycopene, alpha-tocopherol, selenium, and peroxyl radical absorption capacity are unlikely to be associated with lung cancer risk. Until specific preventive factors are identified, the best protection against lung cancer is still the avoidance of airborne carcinogens, especially tobacco smoke; second best is the consumption of a diet rich in fruits and vegetables.

Adult↗

PubMed1996

Calorie restriction lowers body temperature in rhesus monkeys, consistent with a postulated anti-aging mechanism in rodents.

Many studies of caloric restriction (CR) in rodents and lower animals indicate that this nutritional manipulation retards aging processes, as evidenced by increased longevity, reduced pathology, and maintenance of physiological function in a more youthful state. The anti-aging effects of CR are believed to relate, at least in part, to changes in energy metabolism. We are attempting to determine whether similar effects occur in response to CR in nonhuman primates. Core (rectal) body temperature decreased progressively with age from 2 to 30 years in rhesus monkeys fed ad lib (controls) and is reduced by approximately 0.5 degrees C in age-matched monkeys subjected to 6 years of a 30% reduction in caloric intake. A short-term (1 month) 30% restriction of 2.5-year-old monkeys lowered subcutaneous body temperature by 1.0 degrees C. Indirect calorimetry showed that 24-hr energy expenditure was reduced by approximately 24% during short-term CR. The temporal association between reduced body temperature and energy expenditure suggests that reductions in body temperature relate to the induction of an energy conservation mechanism during CR. These reductions in body temperature and energy expenditure are consistent with findings in rodent studies in which aging rate was retarded by CR, now strengthening the possibility that CR may exert beneficial effects in primates analogous to those observed in rodents.

Aging↗

PubMed1996

Longevity and the genetic determination of collagen glycoxidation kinetics in mammalian senescence.

A fundamental question in the basic biology of aging is whether there is a universal aging process. If indeed such a process exists, one would expect that it develops at a higher rate in short- versus long-lived species. We have quantitated pentosidine, a marker of glycoxidative stress in skin collagen from eight mammalian species as a function of age. A curvilinear increase was modeled for all species, and the rate of increase correlated inversely with maximum life-span. Dietary restriction, a potent intervention associated with increased life-span, markedly inhibited glycoxidation rate in the rodent. On the assumption that collagen turnover rate is primarily influenced by the crosslinking due to glycoxidation, these results suggest that there is a progressive age-related deterioration of the process that controls the collagen glycoxidation rate. Thus, the ability to withstand damage due to glycoxidation and the Maillard reaction may be under genetic control.

Aging↗

PubMed1996

The utilization of 5-hydroxyl-2-amino valeric acid as a specific marker of oxidized arginine and proline residues in proteins.

Alteration of cellular proteins by oxidative modification could represent an important mechanism leading to cellular dysdifferentiation and age-related diseases. There is difficulty in testing this hypothesis because of a lack of specific assays that can measure the extent proteins are oxidized in nonpurified tissue preparations. Some methods used to measure carbonyl groups in nonpurified samples have serious limitations because of interference from other sources of carbonyl groups not being a product of oxidation-mediated damage. Oxidation of arginine and proline residues has been reported to produce gamma-glutamyl semialdehyde, which on reduction and acid hydrolysis, was predicted to form 5-hydroxy-2-amino valeric acid (HAVA). In this article we confirm this prediction using a GC/MS/SIM technique, and carry out additional experiments to determine if HAVA may be a useful marker of oxidative damage in proteins. These experiments utilized purified preparations of arginine, proline, histidine, and lysine amino acid homopolymers and six different purified proteins preparations in nonoxidized and oxidized states. Results demonstrate that HAVA compares well with the carbonyl group formation as a specific marker of oxidized protein, and that the GC/MS/SIM technique can detect HAVA reliably to 150 femtomoles per injection. Thus, HAVA as a specific marker of oxidized arginine and proline could prove to be a useful assay in pure and nonpurified samples.

Amino Acids↗

PubMed1996

Comparison of 5-hydroxy-2-amino valeric acid with carbonyl group content as a marker of oxidized protein in human and mouse liver tissues.

Previous studies indicate that 5-hydroxy-2-amino valeric acid (HAVA) is an excellent marker of oxidized arginine and proline in purified proteins. We report here experiments testing the specificity of the HAVA assay technique using the unpurified 100,000 x g supernatant fraction prepared from mice and human liver tissue. Results are compared to carbonyl group analysis on the same tissue samples. Mice at ages 3, 12, and 30 months were exposed to 100% oxygen. Results showed a significant increase of HAVA content in each age group. No significant changes were found in carbonyl group content. Because it has been reported that carbonyl group content increases with age, we applied the HAVA assay to reexamine this question. Using mice of 1 to 30 months of age, we failed to detect any significance difference in either HAVA or carbonyl group content. However, on using human liver samples a significant decrease from age 16 to 40 years and then an increase to 85 years of age was found for both HAVA and carbonyl groups. Liver proteins may be oxidized from hydrogen peroxide produced from the cytochrome P450 detoxification system. This possibility was supported by a significant positive correlation found between HAVA and cytochrome P450 content in 18 human individuals of different ages.

Aging↗

PubMed1995

Protein oxidation and aging. I. Difficulties in measuring reactive protein carbonyls in tissues using 2,4-dinitrophenylhydrazine.

A current hypothesis explaining the aging process implicates the accumulation of oxidized protein in animal tissues. This hypothesis is based on a series of reports showing an age-dependent increase in protein carbonyl content and an age-dependent loss of enzyme function. This hypothesis is also supported by the report of a novel effect of N-tert-butyl-alpha-phenylnitrone (PBN) in reversing these age-dependent changes. Here we specifically study the method that was used to measure reactive protein carbonyls in tissues. This method uses 2,4-dinitrophenylhydrazine (DNPH) and includes a washing procedure. Our results indicate that reactive protein carbonyls in normal crude tissue extracts cannot be reliably measured by this method, although it does reliably measure reactive carbonyls in purified proteins which have been oxidatively modified in vitro. The nucleic acids in tissues could be a major problem encountered in the assay. Using the streptomycin sulfate treatment combined with a dialysis step, we were successful in removing most nucleic acids from a crude tissue extract, but then the reactive carbonyl level in the crude tissue extract was too low to be reliably measured. This streptomycin sulfate treatment procedure, however, had no effect on the reactive carbonyl measurement of an oxidized protein sample. The unwashed free DNPH was another major problem in the assay because of its very strong absorption around 370 nm, where reactive carbonyls were quantitated. Nevertheless, on using the procedure described in the literature to measure total "reactive carbonyls" in rat liver and gerbil brain cortex, no change with age or PBN treatment was found. Then, we investigated a HPLC procedure which uses sodium dodecyl sulfate in the mobile phase but this was also found to be unsuitable for the reactive protein carbonyl assay in tissues.

Aging↗

PubMed1995

Protein oxidation and aging. II. Difficulties in measuring alkaline protease activity in tissues using the fluorescamine procedure.

A current hypothesis explaining the aging process implicates the accumulation of oxidized protein in animal tissues. This is primarily based on a series of reports showing an age-dependent increase in protein carbonyl content and an age-dependent decrease in the activities of enzymes, especially of alkaline proteases, which preferentially degrade oxidatively modified protein. Recently, this hypothesis was strongly supported by the report of a novel effect of the spin-trapping compound N-tert-butyl-alpha-phenylnitrone (PBN) in reversing these age-dependent changes. However, we found that the reactive protein carbonyls could not be reliably measured in tissues by using the 2,4-dinitrophenylhydrazine procedure described in the PBN study. We now focus on the alkaline protease activity assay and show that alkaline protease activity cannot be reliably measured in crude tissue extracts by using the fluorescamine procedure also described in the PBN study. We were, however, able to reliably measure a protease activity in crude tissue extracts at alkaline pH by using a synthetic fluorogenic peptide substrate, but no effect of aging or PBN treatment was found on the protease activity in rat brain cortexes. Thus, the reported age-dependent changes in protein carbonyl formation and alkaline protease activity remain to be confirmed.

Aging↗

PubMed1995

Effects of aging and dietary restriction on activity of monkey serum in promoting fibroblast migration.

In order to determine whether serum modified cellular aging in vivo, we previously studied the effects of serum from various mammals of different ages on cell functions such as proliferation and migration, and reported that cell migration was more greatly inhibited by serum from old donors than cell proliferation [1]. Moreover, since dietary restriction has been reported to extend lifespan and slow the aging rate of some animals [2], we wondered whether sera from dietary restricted and control monkeys of various ages might exhibit reduced aging effects on cell migration. When serum from young adult (3-5 years old) monkeys was added to plain medium, the migration of human fetal skin fibroblasts was very strongly inhibited compared to FBS. Surprisingly, sera from adult (6-11 years old) and old (more than 18 years old) monkeys caused significantly less migration-inhibitory activity than serum from young adult monkeys although sera from adult and old monkeys were much more inhibitory to cell migration than FBS. Dietary restriction only caused marginal effects on serum migration-promoting activity in a few monkey groups. The inhibition of cell migration caused by monkey serum was not brought about by cytotoxic effects since monkey serum stimulated cell proliferation as well as fetal bovine serum. These results indicate that the effects of aging on monkey serum migration-promoting activity are much more pronounced than those of dietary restriction.

Aging↗

PubMed1995

Influence of age, sex, and dietary restriction on intracellular free calcium responses of CD4+ lymphocytes in rhesus monkeys (Macaca mulatta).

The influence of aging and dietary restriction on increase in intracellular free calcium ([Ca2+]i) of CD4+ lymphocytes from Macaca mulatta was examined after stimulation with anti-CD3 mAb. We used a flow cytometric assay with the dye indo-1 and either direct or reciprocal immunofluorescent staining to identify CD4+ cells. After stimulation with anti-CD3 mAb, intracellular free calcium responses were reduced in CD4+ lymphocytes from old male and female ad libitum fed monkeys compared to young and adult male or female monkeys. Old female monkeys had significantly lower [Ca2+]i than did old male monkeys. The reduced responses were in part related to a decreased percentage of responding cells. Dietary restriction of males over a four-year period did not alter [Ca2+]i response compared to ad libitum fed male monkeys. Female monkeys of all ages (which were restricted only for four months) also had similar [Ca2+]i responses to ad libitum fed controls. Our data suggest that age-related changes in [Ca2+]i responses are similar between humans and M. mulatta, and that over these intervals, no effects of caloric restrictions can be detected.

Aging↗

PubMed1995

Energy balance in rhesus monkeys (Macaca mulatta) subjected to long-term dietary restriction.

Male rhesus monkeys of various age groups representative of the species life span were fed ad libitum amounts (controls) or 30% less food than control monkeys of comparable age and body weight. Despite significantly lowered energy intake and body weight, the amount of energy lost in the feces, and fecal energy density (concentration) were not altered in diet-restricted (DR) monkeys, compared to age- and weight-matched controls. Absolute energy expenditure (EE; 24-hr) was consistently lower in DR monkeys, but this trend was not statistically significant. Expressed as a function of metabolic mass (body weight, metabolic body size, lean mass), 24-hr EE was not different in monkeys subjected to long-term DR, compared to controls. Calculations of net energy (intake-loss), as an index of energy balance, revealed that energy expenditure generally exceeded energy intake in all juvenile and adult group monkeys. However, this discrepancy was not statistically different from zero, suggesting that most animals were in energy balance. Also, there was no difference between control and DR animals with respect to energy balance. Diet restriction induced significant reductions in the absolute amount of lean body mass; however, percent (of total weight) lean and fat mass did not differ from controls.

Animals↗

PubMed1995

Aging and food restriction alter some indices of bone metabolism in male rhesus monkeys (Macaca mulatta).

Food restriction increases life span, reduces aging rate and affects a wide variety of biological functions. In rats, food restriction delays bone growth and reduces bone density and mineral content. We report the effects of aging and long-term (> 6.0 y) food restriction on several indices of bone growth and metabolism in rhesus monkeys (Macaca mulatta). Food allotments for controls approximated free access consumption, whereas food-restricted monkeys received 30% less food on a body weight basis. Cross-sectional and longitudinal age effects on serum alkaline phosphatase paralleled those reported for humans. Food restriction induced a significant delay in the developmental decline (to adult levels) in total alkaline phosphatase and significantly suppressed serum interleukin 6 concentrations, particularly in younger monkeys. Also, food restriction slowed skeletal growth, as reflected by shorter crown-rump length, and significantly reduced total body bone mineral content, but not bone mineral density, measured by dual energy X-ray absorptiometry. Analyses of serum parathyroid hormone, calcium, phosphate and osteocalcin concentrations suggested that the effects on skeletal growth were not related to alterations in calcium and phosphate homeostasis or a primary defect in bone formation. These findings suggest that long-term food restriction delays skeletal development in male rhesus monkeys while allowing the development of a reduced but otherwise normal skeleton.

Aging↗

PubMed1995

Diet restriction in rhesus monkeys lowers fasting and glucose-stimulated glucoregulatory end points.

Male rhesus monkeys (Macaca mulatta) of different age groups representing the species life span were fed ad libitum or a 30% reduced calorie diet over a 7-yr period. During the first 2-3 yr of this longitudinal study, glucose and insulin levels were not altered by diet restriction (DR). However, reductions in fasting blood glucose became apparent in DR animals after 3-4 yr. At the end of the 6th yr of study, glycated hemoglobin was measured, and intravenous glucose tolerance tests (IVGTTs) were conducted. Maximum glucose levels reached during IVGTTs increased with age but were lower in DR animals compared with controls. Several measures of the insulin response (baseline, maximum, and integrated areas under curve) increased with age and were lower in DR monkeys. With the exception of glycated hemoglobin, which was not different in monkeys subjected to DR, these findings confirm previous studies in rodents demonstrating that DR alters glucose metabolism and may be related to the antiaging action of this intervention.

Aging↗

PubMed1993

The effect of caloric restriction on the lateral diffusion constant of hepatocyte membrane proteins in C57BL/6 male mice of different ages: FRAP studies on liver smears.

The lateral mobility of proteins in hepatocyte plasma membranes was compared in calorically restricted and ad libitum (AL)-fed C57BL/6 male mice in age groups from 7 to 28 months. Caloric restriction was achieved by means of the every-other-day (EOD) feeding regimen, maintained for various periods from 1 to 15 months. Protein lateral diffusion constant (D) in hepatocyte membranes was measured by means of fluorescence recovery after photobleaching (FRAP) in liver smears. The peroxide-induced autofluorescence (PIAF) was utilized as a fluorescent label. A mild (1 mM for 10 min) H2O2 treatment of liver smears produces oxidation of riboflavin that is bound to all proteins of the cell membrane. Using this technique, the average lateral diffusion constant (D) and the fractional recovery (FR) of these proteins can be measured. EOD feeding resulted in a significant decrease in body weights and also a significant increase in the values of D in all age groups after 1 month of EOD feeding. After 3.5 months of EOD feeding a further increase of D was observed (up to about 15%). Nevertheless no further change in D occurred if the EOD feeding was maintained for 6.5 or even 15 months. The negative linear age correlation of D observed in the AL-fed animals was present also under the EOD feeding; however, the whole regression equation shifted towards higher values. These experiments indicate that caloric restriction influences the lateral diffusion constant of membrane proteins in hepatocytes. The results are interpreted as a result of an increased protein turnover caused by the caloric restriction.

Aging↗

PubMed1993

Nitric oxide formation during light-induced decomposition of phenyl N-tert-butylnitrone.

Phenyl N-tert-butylnitrone (PBN) is a spin trap commonly employed in free radical research. PBN has been shown to have adverse and beneficial effects on various biological systems. We report here evidence that photolysis (or even ambient light) decomposes PBN to nitric oxide in aqueous solutions. Non-heme and heme proteins have been employed to form nitrosyl complexes, which were detected using EPR spectroscopy. Concomitantly, nitrite formation was detected after light-induced decomposition of PBN. In addition, we found that tert-nitrosobutane and decomposed PBN caused an activation of guanylate cyclase. We propose a mechanism where PBN is decomposed by light to tert-nitrosobutane. The latter compound is, in turn, decomposed to nitric oxide. This study suggests the possibility that PBN or PBN radical adducts may be sources of nitric oxide in biological environments. When using PBN as a spin trap in biological samples, not only is the trapping of reactive free radicals operative, but nitric oxide produced from PBN decomposition may play an important role in altering biological functions.

Animals↗