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At least 1,297 records · Page 72Linked to original sources
PubMed2003

Floral longevity and nectar secretion of Platanthera chlorantha (Custer) Rchb. (Orchidaceae).

Flowering and nectar secretion were studied in Platanthera chlorantha in two years. Nectar was secreted and accumulated in this orchid's spur, originating from part of the labellum. The nectary spur was, on average, 32 mm long. It produced 6.86 micro l nectar in 1999 and 7.84 micro l in 2000. The number of flowers per inflorescence and the volume of nectar secreted per flower were not correlated. Nectar secretion and flower longevity differed depending on pollination and flower position in the inflorescence. Among pairs of pollinated and unpollinated flowers there was no difference in the volume of nectar produced; however, the life span of pollinated flowers was shorter than that of unpollinated ones. Within an inflorescence, the lowest-positioned flowers had the largest nectar production and the longest life compared with flowers positioned higher up.

Flowers↗
PubMed2001

eEF1A Controls ascospore differentiation through elevated accuracy, but controls longevity and fruiting body formation through another mechanism in Podospora anserina.

Antisuppressor mutations in the eEF1A gene of Podospora anserina were previously shown to impair ascospore formation, to drastically increase life span, and to permit the development of the Crippled Growth degenerative process. Here, we show that eEF1A controls ascospore formation through accuracy level maintenance. Examination of antisuppressor mutant perithecia reveals two main cytological defects, mislocalization of spindle and nuclei and nuclear death. Antisuppression levels are shown to be highly dependent upon both the mutation site and the suppressor used, precluding any correlation between antisuppression efficiency and severity of the sporulation impairment. Nevertheless, severity of ascospore differentiation defect is correlated with resistance to paromomycin. We also show that eEF1A controls fruiting body formation and longevity through a mechanism(s) different from accuracy control. In vivo, GFP tagging of the protein in a way that partly retains its function confirmed earlier cytological observation; i.e., this factor is mainly diffuse within the cytosol, but may transiently accumulate within nuclei or in defined regions of the cytoplasm. These data emphasize the fact that the translation apparatus exerts a global regulatory control over cell physiology and that eEF1A is one of the key factors involved in this monitoring.

Alleles↗
PubMed2005

Mitochondrial iron detoxification is a primary function of frataxin that limits oxidative damage and preserves cell longevity.

Friedreich ataxia is a severe autosomal-recessive disease characterized by neurodegeneration, cardiomyopathy and diabetes, resulting from reduced synthesis of the mitochondrial protein frataxin. Although frataxin is ubiquitously expressed, frataxin deficiency leads to a selective loss of dorsal root ganglia neurons, cardiomyocytes and pancreatic beta cells. How frataxin normally promotes survival of these particular cells is the subject of intense debate. The predominant view is that frataxin sustains mitochondrial energy production and other cellular functions by providing iron for heme synthesis and iron-sulfur cluster (ISC) assembly and repair. We have proposed that frataxin not only promotes the biogenesis of iron-containing enzymes, but also detoxifies surplus iron thereby affording a critical anti-oxidant mechanism. These two functions have been difficult to tease apart, however, and the physiologic role of iron detoxification by frataxin has not yet been demonstrated in vivo. Here, we describe mutations that specifically impair the ferroxidation or mineralization activity of yeast frataxin, which are necessary for iron detoxification but do not affect the iron chaperone function of the protein. These mutations increase the sensitivity of yeast cells to oxidative stress, shortening chronological life span and precluding survival in the absence of the anti-oxidant enzyme superoxide dismutase. Thus, the role of frataxin is not limited to promoting ISC assembly or heme synthesis. Iron detoxification is another function of frataxin relevant to anti-oxidant defense and cell longevity that could play a critical role in the metabolically demanding environment of non-dividing neuronal, cardiac and pancreatic beta cells.

Amino Acids↗
PubMed2004

Epitope specificity and longevity of a vaccine-induced human T cell response against HPV18.

Persistent human papillomavirus (HPV) type 16 and 18 infection can lead to pre-malignant and malignant diseases of the lower genital tract. Several lines of evidence suggest that T cell responses can control HPV infection. However, relative to other human viruses, strong effector memory T cell responses against HPV have been difficult to detect. We used an in vitro stimulation step prior to enzyme-linked immunospot assays to identify IFN-gamma-secreting T cells specific for HPV16 and 18 E6/E7 peptides. This allowed the detection of HPV-specific CD4+ T cells that were not evident in direct ex vivo assays. T cell responses against HPV16 or 18 peptides were detected in healthy volunteers (7/9) and patients with lower genital tract neoplasia (10/20). Importantly, this assay allowed tracking of vaccine-induced T cell responses in nine patients, following inoculation with a live recombinant vaccinia virus (HPV16 and 18 E6/E7, TA-HPV). Novel vaccine-induced T cell responses were demonstrated in five patients, but no clinical responses (lesion regressions) were seen. For one vaccinated patient, the T cell response was mapped to a single dominant HPV18 E7 epitope and this response was sustained for >3 years. Our data suggest that systemic memory T cells against HPV16 and 18, induced naturally or by TA-HPV vaccination, are relatively rare. Nevertheless, the assay system developed allowed estimation of magnitude, epitope specificity, and longevity of vaccine-induced CD4+ T cell responses. This will be useful for vaccine design and measurement of immunological endpoints in clinical trials.

Adult↗
PubMed2005

Context-dependent codon bias and messenger RNA longevity in the yeast transcriptome.

Context-dependent codon bias and its relationship with messenger RNA (mRNA) longevity was examined in 4,648 mRNA transcripts of the Saccharomyces cerevisiae transcriptome for which mRNA half-lives have been empirically determined. Surprisingly, rare codon usage (codons used <13 times per 1,000 codons in the genome) increased with mRNA half-life. However, it is shown that this pattern was not due to preference for rare codon use within codon families containing both rare and nonrare codons. Rather, the pattern was due to an increase in the frequency of amino acids encoded solely by rare codons, and a decrease in the frequency of amino acids never encoded by rare codons, with mRNA half-life. When standardized by open reading frame length, the use of consecutive rare codons was also positively correlated with mRNA half-life. There was negative correlation between the usage of synonymous A|T dinucleotides spanning codon boundaries and mRNA half-life, despite the fact that the frequency of AT dinucleotide usage overall, and AT dinucleotide usage at other codon position contexts (e.g., 1-2, 2-3, or 3|1 total), was not correlated with mRNA half-life. The use of A|T dinucleotides at synonymous dicodon boundaries could potentially allow for more efficient 3'-5' degradation by endonucleolytic cleavage.

Codon↗
PubMed1990

Treatment of spermagglutination with proteolytic enzymes. I. Sperm motility, vitality, longevity and successful disagglutination.

The treatment of antibody-mediated spermagglutination by corticosteroid therapy has a high incidence of side-effects and sperm washing is often followed by re-agglutination. The possibility of enzymatic disagglutination was therefore investigated. In the first part of the study the effects of four proteases on sperm motility, vitality and longevity were evaluated. Subtilisin had prohibitively detrimental effects even at 10 U/ml. However, chymotrypsin (less than or equal to 500 U/ml), trypsin (less than or equal to 500 U/ml) and papain (less than or equal to 50 U/ml) had no adverse effects. In the second series of experiments one or more of these latter three enzymes was found to disagglutinate spermatozoa which had previously been incubated with sperm-agglutinating antibody-positive sera in 87% of cases. Although further investigation is required, enzymatic disagglutination may be beneficial for the treatment of immunologically mediated spermagglutination.

Cell Membrane↗
PubMed2002

Chloroplast transformation with modified accD operon increases acetyl-CoA carboxylase and causes extension of leaf longevity and increase in seed yield in tobacco.

Acetyl-CoA carboxylase (ACCase) in plastids is a key enzyme regulating the rate of de novo fatty acid biosynthesis in plants. Plastidic ACCase is composed of three nuclear-encoded subunits and one plastid-encoded accD subunit. To boost ACCase levels, we examined whether overexpression of accD elevates ACCase production. Using homologous recombination, we replaced the promoter of the accD operon in the tobacco plastid genome with a plastid rRNA-operon (rrn) promoter that directs enhanced expression in photosynthetic and non-photosynthetic organs, and successfully raised the total ACCase levels in plastids. This result suggests that the level of the accD subunit is a determinant of ACCase levels, and that enzyme levels are in part controlled post-transcriptionally at the level of subunit assembly. The resultant transformants grew normally and the fatty acid content was significantly increased in leaves, but not significantly in seeds. However, the transformants displayed extended leaf longevity and a twofold increase of seed yield over the control value, which eventually almost doubled the fatty acid production per plant of the transformants relative to control and wild-type plants. These findings offer a potential method for raising plant productivity and oil production.

Acetyl-CoA Carboxylase↗
PubMed2006

2006 Frank Stinchfield Award: grafting of biocompatible polymer for longevity of artificial hip joints.

Aseptic loosening induced by wear particles from the polyethylene liner is likely the most common cause of long-term total hip arthroplasty failure. We developed a novel hip polyethylene liner with the surface graft of a biocompatible phospholipid polymer, 2-methacryloyloxyethyl phosphorylcholine (MPC), and previously reported the grafting decreased the short-term production of wear particles and the subsequent bone resorptive responses. For clinical application, we investigated the stability of the 2-methacryloyloxyethyl phosphorylcholine grafting during sterilization and the wear resistance of the sterilized liner during longer loading comparable to clinical usage. Radiographic spectroscopy confirmed the stability of the 2-methacryloyloxyethyl phosphorylcholine polymer on the liner surface after the gamma irradiation. We used a hip wear simulator up to 1 x 10(7) cycles to test sterilized cross-linked polyethylene liners with and without 2-methacryloyloxyethyl phosphorylcholine grafting. The 2-methacryloyloxyethyl phosphorylcholine grafting markedly decreased the friction, the production of wear particles, and the wear of the liner surface. These data suggest a marked improvement in the wear resistance of the polyethylene liner by the 2-methacryloyloxyethyl phosphorylcholine grafting for clinically relevant periods after sterilization, indicating 2-methacryloyloxyethyl phosphorylcholine grafting is a promising technology for extending longevity of artificial hips.

Gamma Rays↗
PubMed2006

Effects of a 14-day healthy longevity lifestyle program on cognition and brain function.

OBJECTIVE: The objective of this study was to determine the effects of a 14-day healthy longevity lifestyle program on cognition and cerebral metabolism in people with mild age-related memory complaints. METHODS: Seventeen nondemented subjects, aged 35-69 years (mean: 53 years, standard deviation: 10) with mild self-reported memory complaints but normal baseline memory performance scores were randomly assigned to 1) the intervention group (N = 8): a program combining a brain healthy diet plan, relaxation exercises, cardiovascular conditioning, and mental exercise (brain teasers and verbal memory training techniques); or 2) the control group (N = 9): usual lifestyle routine. Pre- and postintervention measures included self-assessments of memory ability, objective tests of cognitive performance, and determinations of regional cerebral metabolism during mental rest with [fluorine-18]fluorodeoxyglucose (FDG) positron emission tomography (PET). RESULTS: Subjects in the intervention group objectively demonstrated greater word fluency. Concomitantly, their FDG-PET scans identified a 5% decrease in activity in the left dorsolateral prefrontal cortex. The control group showed no significant change in any of the measures. CONCLUSIONS: A short-term healthy lifestyle program combining mental and physical exercise, stress reduction, and healthy diet was associated with significant effects on cognitive function and brain metabolism. Reduced resting activity in left dorsolateral prefrontal cortex may reflect greater cognitive efficiency of a brain region involved in working memory.

Adult↗
PubMed2025

Hormetic nutrient stress promotes longevity by orchestrating histone acetylation on key lipid catabolism and antioxidant defense genes.

Exposure to low levels of environmental challenges, known as hormetic stress, such as nutrient deprivation and heat shock, fosters subsequent stress resistance and promotes healthy aging in later life. However, specific mechanisms governing transcriptional reprogramming upon hormetic nutrient stress remain elusive. In this study, we identified histone H3 lysine 27 acetylation (H3K27ac) as a crucial driver of transcriptomic adaptation to hormetic fasting. Beyond its immediate function of enhancing lipid catabolism for alternative energy sources, stress-induced H3K27ac activates lifelong antioxidant defenses, thereby reducing reactive oxygen species (ROS) produced by stress-induced fatty acid oxidation and their accumulation during aging. The increase in H3K27ac, mediated by pioneer factor PHA-4/FOXA and cooperating transcription factor NHR-49/HNF4, is crucial for lifespan extension under hermetic nutrient stress in Caenorhabditis elegans. Our findings establish H3K27ac as a key transcriptional switch that bridges nutrient status with transcriptomic reprogramming, underpinning the pro-longevity effects of hormetic fasting through orchestrating lipid catabolism and antioxidative defenses.

Journal Article↗
PubMed1999

The SIR2/3/4 complex and SIR2 alone promote longevity in Saccharomyces cerevisiae by two different mechanisms.

The SIR genes are determinants of life span in yeast mother cells. Here we show that life span regulation by the Sir proteins is independent of their role in nonhomologous end joining. The short life span of a sir3 or sir4 mutant is due to the simultaneous expression of a and alpha mating-type information, which indirectly causes an increase in rDNA recombination and likely increases the production of extrachromosomal rDNA circles. The short life span of a sir2 mutant also reveals a direct failure to repress recombination generated by the Fob1p-mediated replication block in the rDNA. Sir2p is a limiting component in promoting yeast longevity, and increasing the gene dosage extends the life span in wild-type cells. A possible role of the conserved SIR2 in mammalian aging is discussed.

DNA, Fungal↗
PubMed2004

Analysis of natural allelic variation of Arabidopsis seed germination and seed longevity traits between the accessions Landsberg erecta and Shakdara, using a new recombinant inbred line population.

Quantitative trait loci (QTL) mapping was used to identify loci controlling various aspects of seed longevity during storage and germination. Similar locations for QTLs controlling different traits might be an indication for a common genetic control of such traits. For this analysis we used a new recombinant inbred line population derived from a cross between the accessions Landsberg erecta (Ler) and Shakdara (Sha). A set of 114 F9 recombinant inbred lines was genotyped with 65 polymerase chain reaction-based markers and the phenotypic marker erecta. The traits analyzed were dormancy, speed of germination, seed sugar content, seed germination after a controlled deterioration test, hydrogen peroxide (H2O2) treatment, and on abscisic acid. Furthermore, the effects of heat stress, salt (NaCl) stress, osmotic (mannitol) stress, and natural aging were analyzed. For all traits one or more QTLs were identified, with some QTLs for different traits colocating. The relevance of colocation for mechanisms underlying the various traits is discussed.

Abscisic Acid↗
PubMed2004

Vitamin E is essential for seed longevity and for preventing lipid peroxidation during germination.

Tocopherols (vitamin E) are lipophilic antioxidants synthesized by all plants and are particularly abundant in seeds. Despite cloning of the complete suite of tocopherol biosynthetic enzymes and successful engineering of the tocopherol content and composition of Arabidopsis thaliana leaves and seeds, the functions of tocopherols in plants have remained elusive. To address this issue, we have isolated and characterized two VITAMIN E loci (VTE1 and VTE2) in Arabidopsis that when mutated result in tocopherol deficiency in all tissues. vte1 disrupts tocopherol cyclase activity and accumulates a redox-active biosynthetic intermediate, whereas vte2 disrupts homogentisate phytyl transferase activity and does not accumulate pathway intermediates. Mutations at either locus cause significantly reduced seed longevity compared with the wild type, indicating a critical role for tocopherols in maintaining viability during quiescence. However, only vte2 mutants exhibited severe seedling growth defects during germination and contained levels of lipid hydroperoxides and hydroxy fatty acids elevated up to 4- and 100-fold, respectively, relative to the wild type. These data demonstrate that a primary function of tocopherols in plants is to limit nonenzymatic lipid oxidation during seed storage, germination, and early seedling development. The vte mutant phenotypes also explain the strong selection for retention of tocopherol biosynthesis during the evolution of seed-bearing plants.

Alkyl and Aryl Transferases↗
PubMed1998

A multilevel analysis of factors affecting the longevity of fixed partial dentures, retainers and abutments.

There is a methodological problem in analysis of data belonging to different hierarchical levels, e.g. patient, arch, and tooth. A method for multilevel modelling (MLM) that resolves this problem is available. This method which is presented in this article, was used to reanalyse previously published long-term treatment results concerning the longevity of fixed partial dentures, retainers and abutments. The main results were consistent, indicating that no great faults were committed when using the conventional logistic regression method. There were, however, differences when calculating the combined risks for various situations. The conventional method was found to over- and underestimate probabilities of survival in different cases, compared to the MLM method. Especially when the most negative factors were combined, the conventional method had a tendency to underestimate the risk. For example, if an abutment had the combination 'endodontically treated'; 'FPD placed by 'another dentist''; 'distal abutment'; and 'marginal bone loss > 50%'; the probability of the tooth remaining after 18-23 years was only 20% according to the MLM method but 35% according to the conventional method. It was concluded that MLM is the method of choice for many situations in dental research where data belonging to different levels are to be analysed.

Dental Abutments↗
PubMed1985

Injectable collagen implant: histopathologic identification and longevity of correction.

This prospective study reports the results of the longevity of the correction achieved in 312 patients receiving injectable collagen implant and the histopathologic identification of the implant in the six who experienced reactions at the treatment sites. In reporting results in cosmetic patients, certain ones can be considered objective or factual, and other must be judged subjective. This study reports both kinds of results and proposes a new theory to explain the duration of the improvement.

Adult↗
PubMed1980

Longevity comparisons among lithium anode power cells for cardiac pacemakers.

Of over 10,000 lithium-powered pacemakers followed by a commercial transtelephone monitoring service, 148 have been explanted due to rate decline. A breakdown according to the power cell manufactures shows that the longevity is not uniform, indicating that significant differences exist among the power cell designs even though all have lithium anodes. One tenth of all lithium-powered pacemakers in the study were explanted for rate declines within 4 years.

Data Collection↗
PubMedDate not supplied

The role of pannus in the longevity of an Ionescu-Shiley pericardial bioprosthesis.

As the population ages, bioprosthetic heart valves are increasingly being used to replace diseased native valves. Bioprosthetic valve durability depends on patient age and other factors, but rarely exceeds 15 years. Explanted bioprosthetic valves commonly show tissue degeneration, tears, and calcification. Host tissue overgrowth (pannus), to the extent of interfering with their function, is another finding in bioprostheses that have been in place for long periods. We present a case in which a bovine pericardial valve was explanted after more than 20 years of implantation. The longevity of this pericardial valve may have been related to excessive pannus growth, which most likely protected the valve from earlier failure.

Aortic Valve Stenosis↗
PubMed1988

Dental restoration longevity: survival functions and statistical indices in low and high failure rate groups.

A group of 71 patients was examined to determine the longevity of restorations placed at the University of North Carolina School of Dentistry. Patients with an overall restorations failure rate of equal to or greater than 40 per 1000 restoration-yr were categorized as having a "high failure rate" and those below that were considered "low failure rate". An investigation was made to determine statistical differences between these two groups of patients using survival analysis and various statistical indices. Time of exposure and age of patients for both groups were similar. High rate patients had a greater number of anterior restorations and anterior teeth restored. In addition, the number of restorations per tooth was significantly greater in anterior and posterior teeth of the high failure rate group. No single variable was found to account for the differences in the failure rates in the two groups of patients. A prospective study is needed in order to examine possible causes for restoration failures.

Dental Restoration, Permanent↗