961 resultados para life-span
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Vigilance, anxiety, epileptic activity, and muscle tone can be modulated by drugs acting at the benzodiazepine (BZ) site of gamma-aminobutyric acid type A (GABAA) receptors. In vivo, BZ sites are potential targets for endogenous ligands regulating the corresponding central nervous system states. To assess the physiological relevance of BZ sites, mice were generated containing GABAA receptors devoid of BZ sites. Following targeted disruption of the gamma 2 subunit gene, 94% of the BZ sites were absent in brain of neonatal mice, while the number of GABA sites was only slightly reduced. Except for the gamma 2 subunit, the level of expression and the regional and cellular distribution of the major GABAA receptor subunits were unaltered. The single channel main conductance level and the Hill coefficient were reduced to values consistent with recombinant GABAA receptors composed of alpha and beta subunits. The GABA response was potentiated by pentobarbital but not by flunitrazepam. Diazepam was inactive behaviorally. Thus, the gamma 2 subunit is dispensable for the assembly of functional GABAA receptors but is required for normal channel conductance and the formation of BZ sites in vivo. BZ sites are not essential for embryonic development, as suggested by the normal body weight and histology of newborn mice. Postnatally, however, the reduced GABAA receptor function is associated with retarded growth, sensorimotor dysfunction, and drastically reduced life-span. The lack of postnatal GABAA receptor regulation by endogenous ligands of BZ sites might contribute to this phenotype.
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Human diploid fibroblast cells cease growth in culture after a finite number of population doublings. To address the cause of growth cessation in senescent IMR-90 human fibroblast cells, we determined the level of oxidative DNA damage by using 8-oxoguanine excised from DNA and 8-oxo-2'-deoxyguanosine in DNA as markers. Senescent cells excise from DNA four times more 8-oxoguanine per day than do early-passage young cells. The steady-state level of 8-oxo-2'-deoxyguanosine in DNA is approximately 35% higher in senescent cells than in young cells. Measurement of protein carbonyls shows that senescent cells did not appear to have elevated protein oxidation. To reduce the level of oxidative damage, we cultured cells under a more physiological O2 concentration (3%) and compared the replicative life span to the cells cultured at the O2 concentration of air (20%). We found that cells grown under 3% O2 achieved 50% more population doublings during their lifetime. Such an extension of life span resulted from the delayed onset of senescence and elevation of growth rate and saturation density of cells at all passages. The spin-trapping agent alpha-phenyl-t-butyl nitrone (PBN), which can act as an antioxidant, also effectively delayed senescence and rejuvenated near senescent cells. The effect is dose-dependent and is most pronounced for cells at the stage just before entry into senescence. Our data support the hypothesis that oxidative DNA damage contributes to replicative cessation in human diploid fibroblast cells.
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Multiple mammary epithelial cell (MEC) types are observed both in mammary ducts in vivo and in primary cultures in vitro; however, the oncogenic potential of different cell types remains unknown. Here, we used human papilloma virus 16 E6 and E7 oncogenes, which target p53 and Rb tumor suppressor proteins, respectively, to immortalize MECs present in early or late passages of human mammary tissue-derived cultures or in milk. One MEC subtype was exclusively immortalized by E6; such cells predominated in late-passage cultures but were rare at early passages and apparently absent in milk. Surprisingly, a second cell type, present only in early-passage tissue-derived cultures, was fully immortalized by E7 alone. A third cell type, observed in tissue-derived cultures and in milk, showed a substantial extension of life span with E7 but eventually senesced. Finally, both E6 and E7 were required to fully immortalize milk-derived MECs and a large proportion of MECs in early-passage tissue-derived cultures, suggesting the presence of another discrete subpopulation. Identification of MECs with distinct susceptibilities to p53- and Rb-targeting human papillomavirus oncogenes raises the possibility that these cells may serve as precursors for different forms of breast cancer.
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Cancer in a parent or caregiver is an event that affects the whole family. The roles and responsibilities of the diagnosed parent, as well as those of each family member, are affected at the time of diagnosis and throughout the progression of the illness. According to the American Cancer Society, there will be an estimated 1,665,540 new cancer cases diagnosed and 585,720 cancer deaths in 2014. This staggering statistic means there are a number of cancer diagnoses that will directly affect thousands of parents and their children. Past research suggests this upheaval in the system is particularly stressful on children and can lead to a number of responses including anxiety, depression, distress, and other negative reactions. Despite the large number of parents and caregivers diagnosed with cancer in the United States each year, there are relatively few support groups aimed at supporting children affected by parental cancer. Support groups provide opportunities to serve this population in a number of advantageous ways by providing safety, support, and a sense of community. Additionally, support groups allow this population of young people to express their fears and worries, connect to others going through similar circumstances, and explore their parent's diagnosis in a context that is helpful and developmentally appropriate. Past research has found that children who do not receive support during this life-changing event can be negatively affected throughout the life span. On the other hand, this event can be a time to build a child's resilience and provide the structure through which they may thrive in adversity. Support groups offer the opportunity to address this difficult event and lead to positive results. Kids Alive! is one such group that has been proactive in support for children of parents diagnosed with cancer since 1995. Kids Alive!, a support group that runs out of Porter Hospital in Denver Colorado, uses Joseph Campbell's Hero's Journey to structure monthly groups. The Hero's Journey, described in Campbell's The Hero with a Thousand Faces (1949), focuses on a set pattern that all heroes must go through during their journey towards an ultimate victory and self-discovery. Kids Alive! incorporates this journey into a curriculum aimed at helping children explore their thoughts and feelings around their parent's cancer and leads to a realization that they are not alone on this journey. Over the course of eight months, children in Kids Alive! receive support and solidarity that leads to life-changing experiences and an understanding of what a diagnosis of cancer in a parent can mean. Kids Alive! consists of professionals and volunteers who take time to recognize and support this underserved population. The program has led to positive outcomes for nearly two decades and consistently increases the numbers of children and families served. The purpose of this paper is to describe the Kids Alive! program as an exemplar program that addresses these problems by utilizing protective factors research has found in this population. Further, this paper will discuss areas of future research while providing the model of an effective program aimed at serving an important population. Additionally, the model of Kids Alive! will be described through this paper in a way that allows for other oncology settings to consider this relatively simple program that provides consistently positive results.
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Energy harvesting devices are widely discussed as an alternative power source for todays active implantable medical devices. Repeated battery replacement procedures can be avoided by extending the implants life span, which is the goal of energy harvesting concepts. This reduces the risk of complications for the patient and may even reduce device size. The continuous and powerful contractions of a human heart ideally qualify as a battery substitute. In particular, devices in close proximity to the heart such as pacemakers, defibrillators or bio signal (ECG) recorders would benefit from this alternative energy source. The clockwork of an automatic wristwatch was used to transform the hearts kinetic energy into electrical energy. In order to qualify as a continuous energy supply for the consuming device, the mechanism needs to demonstrate its harvesting capability under various conditions. Several in-vivo recorded heart motions were used as input of a mathematical model to optimize the clockworks original conversion efficiency with respect to myocardial contractions. The resulting design was implemented and tested during in-vitro and in-vivo experiments, which demonstrated the superior sensitivity of the new design for all tested heart motions.
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Living Heterostegina depressa were found in the Persian Gulf on shallows and sides of islands in the Central Basin. Preliminary culture experiments furnished information on life span, salinity tolerances and population density of species. Reproduction processes (probably asexual) could be observed several times. A possible carbonate production of ca. 150 g/year/m**2 has been estimated.
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Indiana Department of Transportation, Indianapolis
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Federal Railway Administration, Office of Safety, Washington, D.C.
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Federal Highway Administration, Washington, D.C.
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Oklahoma Department of Transportation, Oklahoma City
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Texas Department of Transportation, Austin
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Federal Highway Administration, Office of Research, Washington, D.C.
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Federal Transit Administration, Washington, D.C.
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National Highway Traffic Safety Administration, Washington, D.C.
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Transportation Department, Secretary of Transportation, Washington, D.C.