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R G Cutler

Publications and source records attributed to R G Cutler.

81 records · Page 5Linked to original sources
PubMed1966

Synchronization of bacteria by a stationary-phase method.

Cutler, Richard G. (University of Houston, Houston, Tex.), and John E. Evans. Synchronization of bacteria by a stationary-phase method. J. Bacteriol. 91:469-476. 1966.-Cultures of Escherichia coli and Proteus vulgaris have been synchronized, with a high percentage phasing, in large volumes and at high cell densities by a method which takes advantage of a tendency of cells to synchronize themselves when entering the stationary phase of growth. The method consists of growing the bacteria to an early stationary phase, harvesting them quickly under minimal conditions of stress, and inoculating them into fresh medium at a dilution of about sevenfold. Cellular division is then partially synchronized. Four-generation cycles of a high percentage of phasing are obtained by repeating this procedure on the partially synchronized culture. Deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein analyses were made throughout all phases of the growth curve. Advantage has been taken of this method of synchrony to isolate selected segments of the bacterial genome in significant amounts. A working hypothesis to explain the synchrony suggests that the unfavorable conditions of growth as the bacteria near the stationary phase are detected by a decrease in the amino acid pool size, and that this results in a gradual decrease of DNA transcription activity through the inhibition of RNA polymerase by transfer RNA. The synchronizing method may be unique in producing cultures that grow both in cellular division and in genomic synchrony.

Bacterial Proteins↗
PubMedDate not supplied

The effects of idebenone on DNA and RNA contents as well as synthesis rates of total and poly(A)+ RNA in brain of normal, old C57BL/6J mice and in experimental partial cerebral ischemia of rats.

Effects of idebenone on RNA and DNA contents as well as on synthesis rates of total and poly(A)(+) RNA in the brain were measured in two animal models: (1) Normal young and old, male C57BL/6J mice (6 and 32 months). Idebenone suspended in 5% gum arabic was applied in 50 mg/kg/day dose to old mice for 1 month through a gastric tube. (2) Adult female CFY rats (14-18 months) in which experimental partial cerebral ischemia was induced by bilateral common carotid artery occlusion. Idebenone was administered intraperitoneally in two dose (10mg/kg and 100 mg/kg body weight) 30 min before the interruption of carotid blood flow. DNA content remained invariate during aging in the brain; idebenone treatment did not exert any influence on this parameter. RNA content as well as total and poly(A)(+) RNA synthesis rates, which were measured by incorporation of tritiated uridine into RNA, decreased significantly with age in brain. Idebenone treatment did not cause any essential change of the metabolism of RNA under the given conditions. The RNA and DNA contents of brain were influenced neither by experimental partial cerebral ischemia nor by treatment with idebenone during the ischemia. Partial cerebral ischemia decreased the rate of total and poly(A)(+) RNA synthesis in the brain about 15-45% depending on the methods and basis of expression. This decline could totally be prevented by intraperitoneal application of 10 mg/kg idebenone 30 min before the onset of the partial ischemia. The dose of 100 mg/kg idebenone also elevated the rate of RNA synthesis; however, this increase remained statistically insignificant.

Journal Article↗
PubMedDate not supplied

Expression of the intracisternal A particle endogenous retrovirus genes over the lifetime of mouse and Syrian hamster.

Transcription of intracisternal A particle genes in several tissues has been examined throughout the lifespan of inbred C57BL/6J and outbred wild-type mice and golden Syrian hamster. In both rodent species, expression of the genes occurs at all ages and in all tissues. Also, in both species, RNA transcripts of heterogeneous lengths are found that correspond in size not only to the proviral genes previously characterized but also to genes larger than those reported. In hamster, the size heterogeneity is more extensive than in the mouse, where discrete size transcripts are detectable over the heterogeneous signal. Transcription of these genes throughout the lifespan is not peculiar to the hamster or inbred laboratory mouse strain (C57BL/6J) but also occurs in many tissues of outbred wild-type Mus musculus at each age examined. Lifelong transcription of intracisternal A particle retrovirus genes raises the suggestion that retrovirus proteins and cDNA are continuously produced and could facilitate cumulative genomic rearrangements. This could lead to improper gene regulation and thus contribute to the age-dependent increase of cancer and more generally to the aging process itself.

Journal Article↗
PubMedDate not supplied

Recent progress in testing the longevity determinant and dysdifferentiation hypotheses of aging.

An overview of the longevity determinant and dysdifferentiation hypotheses is presented, highlighting some of the major postulates and predictions. Results of recent experiments testing these hypotheses are discussed, including the search for specific longevity determinant genes and evidence that cancer and aging may have common causative mechanisms of action and control. Regulation of oxidative stress is considered a potential longevity determinant mechanism and methods and results testing this prediction are reviewed. Possibility of enhancing protective mechanisms against oxidative stress is discussed by way of intervention of central regulatory mechanisms of antioxidants using the cyclase-arachidonic acidcyclooxygenase (GAC model).

Journal Article↗
PubMedDate not supplied

High concentrations of antioxidants may not improve defense against oxidative stress.

It is often assumed that the oxygen radical defense could be further improved by higher concentration of antioxidants. But this has not been demonstrated over a wide range of concentrations. There are different types of oxygen radicals produced in the body and the antioxidant protection against them may not positively related to their concentrations. We report here that by using H(2)O(2) with Cu(2+) as an hydroxyl-radical generator in vitro, ascorbic acid shows no oxygen-radical absorbing capacity. We also found that the net hydroxyl-radical absorbing capacity of a water soluble alpha-tocopherol analogue (Trolox) and uric acid increases with concentration only when the concentration is lower than the normal value found for alpha-tocopherol and uric acid in human serum. At higher concentrations, the hydroxyl-radical absorbing capacity of the alpha-tocopherol analogue and uric acid decreases. The mechanism involved in the decrease of hydroxyl radical absorbance capacity of Trolox and uric acid at high concentration may be related to their reaction with hydroxyl radicals or other oxygen radicals produced in the presence of both H(2)O(2) and Cu(2+). This kind of reaction could lead to the formation of additional many Trolox or uric acid radicals at the same time. These results may be important not only in evaluating antioxidant activities of antioxidants in vitro but also in studying the potential efficiency of antioxidants in vivo in affecting oxidative stress status.

Journal Article↗
PubMedDate not supplied

Evaluating measures of hematology and blood chemistry in male rhesus monkeys as biomarkers of aging.

Reliable and valid biomarkers of aging can provide valuable tools for examining the effectiveness of interventions that may influence the rate of aging processes. However, a standardized method for identifying biomarkers of aging has yet to be developed. The current analysis focused on hematology and blood chemistry variables obtained from a 5-year longitudinal study of male rhesus monkeys (N = 29) on a diet restriction regime known to retard aging processes and extend lifespan in laboratory rodents (70% of the diet intake of controls). For the current analysis, the major screening criteria for identifying candidate biomarkers of aging were cross-sectional and longitudinal correlation with chronological age (CA) and stability of individual differences. Six potential variables from the battery of blood chemistry tests were identified: 1) serum glutamic oxalacetic transaminase; 2) alkaline phosphatase; 3) total protein; 4) globulin; 5) blood urea nitrogen to creatinine ratio; and 6) phosphates. When submitted to principle component analysis, these variables loaded onto a single component that accounted for over 50% of the total variance to indicate marked covariance among them. By applying the factor score coefficients from the first principle component, an equation was derived for estimating a biological age score (BAS) for each individual monkey. A comparison of BAS between control and diet-restricted monkeys revealed no statistically significant difference at present; however, the slope of the regression of BAS onto CA appeared steeper for the control group compared to the experimental group. Thus, while demonstration of the validity of the candidate biomarkers awaits further evidence, a strategy by which additional biomarkers of aging can be identified is proposed as an improvement over past approaches.

Aging↗
PubMedDate not supplied

Preferential use of less toxic detoxification pathways by long-lived species.

This study was undertaken to determine whether the detoxification pathways producing the least oxidative stress appear to be favored in longer-lived mammalian species. Firstly, we focused on the cytochrome P-450 monooxygenase system. Although this system is an important component of the defenses that protect living organisms against toxic chemicals, some reactions catalyzed by the cytochrome P-450 system result in the formation of products that are highly reactive as well as active oxygen species. Our results suggest that the lower amount of hepatic cytochrome P-450 content found in longer-lived species may have evolved to reduce the toxic side-effect of this detoxification system. Support of the idea that the cytochrome P-450 system is an important source of oxidative stress is the positive correlation between cytochrome P-450 content and the amount of oxidized proteins found in liver of different human individuals. Secondly, we have measured the specific activity of other detoxification enzymes as a function of life span. Instead of a direct comparison of detoxification capabilities of the species, the approach used in this study was: (1) to select those detoxification enzymes which utilize the same substrate but differ in toxicity of the intermediate compounds formed in the reaction, and (2) to measure the levels of these enzymes in the two pathways to determine which pathway is dominant for each species. Our results suggest that the detoxification pathways producing the least oxidative stress do appear to be favored in longer-lived species.

Journal Article↗