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PubMed2005

Effect of temperature on reproductive parameters and longevity of Tyrophagus putrescentiae (Acari: Acaridae).

The effect of temperature on reproductive parameters and longevity of the mold mite, Tyrophagus putrescentiae (Schrank) was examined at seven constant temperatures, ranging from 10 to 34 degrees C, and a relative humidity of 90 +/- 5%. Preoviposition period and fecundity were adversely affected by extreme temperatures and the oviposition period increased as temperature was reduced. Different patterns were observed for longevity data for males and females, with greater longevities for males at intermediate temperatures and more similar values for both sexes at extreme temperatures. Polynomial and non-linear models provided a good fit of the relationship of reproductive and longevity parameters with temperature. The effect of temperature on the intrinsic rate of increase of T. putrescentiae populations was established by the non-linear Lactin model. The optimum temperature for development was obtained at 30 degrees C. At this temperature, the population doubling time is 1.75 days. The lower and upper thresholds for T. putrescentiae populations were established at 10.4 and 34.8 degrees C, respectively. Altogether, these data provide basic information to develop sound physical control strategies of the mold mite.

Acaridae↗
PubMed1993

Molecular mechanism of the lipid vesicle longevity in vivo.

An important, if not the chief, condition for the prolongation of the circulation times of lipid vesicles in vivo is the suppression of macromolecular adsorption onto the surface of such vesicles. This adsorption can be prevented very efficiently by a zone of suitably designed and mobile steric hindrances near the lipid layer surface. Lipid vesicles with such a surface coat, cryptosomes, thus circulate in blood for very long periods of time after systemic applications. Lipid vesicles composed of phosphatidylcholine molecules and of suitable polyoxyethylene (PEG) derivatives of phosphatidylethanolamine, for example, remain in the blood circulation 8-10-times longer than standard liposomes made of phosphatidylcholine only: in mice the half-lives of the former and latter vesicles, after an i.v. administration, are approx. 0.6 h and between 5.9 and 13.8 h, respectively. Vesicle longevity is not destroyed by the phosphatidylcholine chains fluidity. Vesicles consisting of a mixture of distearoylphosphatidylethanolamine-PEG (DSPE-PEG) with distearoylphosphatidylcholine or cryptosomes made of DSPE-PEG and soy-bean phosphatidylcholine, consequently, have a very similar fate in vivo. Furthermore, the cryptosome longevity is not affected directly by the presence of the net charges on the lipid membranes and is little sensitive to the details of the group coupling the PEG-headgroups and the lipidic (hydrophobic) anchor. However, the life-time and the distribution of the stabilized lipid vesicles in vivo depend quite sensitively on the surface density of the sterically active headgroups; often (if not always) the resistance to plasma components adsorption as well as the resulting longevity in vivo both show a maximum near the same lipid/stabilizer molar ratio. Optimum bilayer composition may differ for the different combinations of the main and sterically active membrane components. Its position is probably determined by the variations in the molecular mobility and the effective surface-coverage effects: both must be sufficiently high for the vesicle phagocytosis and accumulation in the reticulohystiocytic system to be suppressed. On the contrary, the bilayer surface hydrophilicity, which hitherto has been believed to be of paramount importance for the liposome longevity in vivo, is per se not relevant for the biological fate of the lipid vesicles, provided that this hydrophilicity exceeds some minimum value.

Adsorption↗
PubMed1991

The politics of psychiatric self-help: political factions, interactional support, and group longevity in a social movement.

This paper examines data from a national sample of 104 groups in the former mental patient self-help movement in terms of how differences in group longevity are related to patterns of interactional social support within the different political factions in the movement. Community organization theory, which explains self-help group longevity in terms of interactional support from external community organizations, would suggest that the oldest groups should be the most conservative groups. This contradicts the de facto existence of old radical groups. Mental patient movement activists claim that the oldest groups are the most radical groups that began the movement in the early 1970s. This ignores the existence of some equally old conservative groups and offers no explanation of group longevity. Data are presented that show the longevity of conservatively affiliated groups to be an artifact of their propensity toward external community interactional support and their lack of involvement in organizational interaction within the self-help movement. The data also show that the existence of some of the oldest groups in the movement within the most radical factions is associated with the perpetuation of radical, anti-psychiatric ideology within the movement. These groups are shown to be actively involved in radical social movement activities (organizational interaction) and to eschew involvement in the development of institutional interaction. Thus, these findings show that some self-help groups can and do find needed social systemic and moral support within the movement itself and do not require external official institutional support for their long-term survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Group Processes↗
PubMed2006

White matter grade and ventricular volume on brain MRI as markers of longevity in the cardiovascular health study.

High white matter grade (WMG) on magnetic resonance imaging (MRI) is a risk factor for dementia, stroke and disability. Higher ventricular size is a marker of brain "atrophy." In the Cardiovascular Health Study (CHS) (n=3245) mean age 75 years, 50% black and 40% men, we evaluated WM and ventricular grade (VG), total, cardiovascular and noncardiovascular mortality and longevity before and after adjusting for numerous determinants of longevity over an approximate 10-12 years of follow-up. A low WMG and VG was a marker for low total, cardiovascular and noncardiovascular mortality and for increased longevity over 10+ years of follow-up. We estimated that a 75-year-old with WMG below median would have about a 5-6 years greater longevity and for VG about 3 years, than above the median even after adjustment for numerous risk factors. Low WMG and VG on MRI is a powerful determinant of long-term survival among older individuals.

Aged↗
PubMed2004

Dentists' molar restoration choices and longevity: a web-based survey.

STATEMENT OF PROBLEM: The increasing trend toward esthetics has led to controversy as to the longevity of esthetic restorations and the wisdom of having traditional restorations replaced for esthetic reasons. With the assumption that the way dentists treat their own teeth may be a good indication of the accumulated wisdom of the profession, knowledge of dentists' own restorative choices may provide guidance in selecting the most appropriate restorations. PURPOSE: The purpose of this article was to determine restorative choices of dentists for personal molars and estimate restoration longevity. MATERIAL AND METHODS: Information about dentists' molars was obtained from a Web-based survey designed to receive dentists' demographic data and charting of 8 molar teeth with estimated longevity. Approximately 12,000 e-mails asking to access the website were sent to dentists' addresses randomly selected from a commercial database. Nonrespondents received 1 reminder. The responses were statistically analyzed with a chi-square analysis (alpha=.05). RESULTS: Seven hundred fifty-seven valid replies provided information for 6,034 teeth (22% unrestored, 75% restored, 2% missing). Restorations reported included amalgam (36%), gold inlay/onlay (13%), complete veneer crown (CVC) (10%), metal-ceramic crown (MCC) (8%), and composite (7%). Other esthetic options accounted for less than 3%. Restorations with more than 20 years longevity included amalgam restorations (58%), gold inlays/onlays (48%) and crowns (23%). Fifty-six percent of esthetic restorations and 5% of amalgams were placed in the last 5 years. The following restorations were placed in the last year (n=186): 38% esthetic, 29% crowns (18% MCC; 11% CVC), and 17% gold inlay/onlay or amalgam. Significant differences (P<.001) were identified for dentist's gender, year of graduation and practice location. CONCLUSIONS: Most dentists have not replaced traditional metallic restorations with esthetic alternatives. Dentists still choose nonesthetic options for significant numbers of their own restorations.

Attitude of Health Personnel↗
PubMed2002

Paradigms and pitfalls of yeast longevity research.

Over the past 10 years, considerable progress has been made in the yeast aging field. Multiple lines of evidence indicate that a cause of yeast aging stems from the inherent instability of repeated ribosomal DNA (rDNA). Over 16 yeast longevity genes have now been identified and the majority of these have been found to affect rDNA silencing or stability. Environmental conditions such as calorie restriction have been shown to modulate this mode of aging via Sir2, an NAD-dependent histone deacetylase (HDAC) that binds at the rDNA locus. Although this mechanism of aging appears to be yeast-specific, the longevity function of Sir2 is conserved in at least one multicellular organism, Caenorhabditis elegans (C. elegans). These findings are consistent with the idea that aging is a by-product of natural selection but longevity regulation is a highly adaptive trait. Characterizing this and other mechanisms of yeast aging should help identify additional components of longevity pathways in higher organisms.

Animals↗
PubMed2005

Extending the longevity of fluorescence-based sensor arrays using adaptive exposure.

Fluorescent microbead sensor arrays were prepared to determine sensor array longevity. Sensor longevity is limited by photobleaching of the dyes attached to the microbeads and presents one of the biggest drawbacks of most fluorescent dye-based arrays. Responses of an array of organic vapor sensors were acquired for 2 weeks to evaluate the sensor performance over time. Photobleaching effects were overcome in two ways: (1) by limiting the excitation light power and gradually increasing the power at a rate comparable to the sensor photobleaching rates and (2) by illuminating subsections of the array through an optical slit. Both approaches extended the longevity of a sensor array. During the longevity study, the sensor arrays were employed to test their ability to correctly distinguish between responses to seven vapors. A high classification accuracy (99.8%) was obtained after 17,700 exposures for vapor responses collected over two weeks using only approximately 8% of the array's surface area.

Journal Article↗
PubMed2000

Longevity in vitro of human CD4+ T helper cell clones derived from young donors and elderly donors, or from progenitor cells: age-associated differences in cell surface molecule expression and cytokine secretion.

The effectiveness of the adaptive immune system relies upon extensive proliferation of an initially small number of antigen-specific T cells. At the end of a successful response, the majority die by apoptosis and a small minority joins the memory cell pool. Upon re-challenge with antigen, these memory cells must again undergo clonal expansion in order to mediate an effective response. Thus, T cells are subjected to marked proliferative stress which may result in clonal exhaustion due to replicative senescence. In other systems made up of rapidly proliferating cells (e.g. in the gut) individual clones are identical and are replaced at the end of their lifespan by differentiation from a stem cell reservoir. However, because of the unique clonal distribution of antigen receptors on T cells, mere replacement with other T cells is not sufficient to maintain the integrity of the system. Moreover, the very source of new T cells decreases with age (due to thymic involution). Therefore, the adaptive immune system may be uniquely susceptible to the deleterious effects of replicative senescence. Particularly in humans, in vivo studies of the behaviour of individual T-cell clones in the body is difficult. However, T-cell longevity, measured as proliferative capacity in terms of population doublings, can be usefully modelled at the clonal level in vitro. This paper discusses the surprisingly little that is known about the average longevity, variation between clones, and the maximal longevity of human T cells under clonal culture conditions in vitro. From our own studies, we show that average lifespan of human T cells is as little as 17 PD; however, established clones reach 35 PD on average, with maximum longevity generally in the region of 60-80 PD, regardless of the source of the cloned cells. Expression of surface molecules in general did not differ strikingly between young and old donors, but the frequency of clones secreting IL-10, and the amount secreted per clone was higher in the elderly than in the young. Conversely, the frequency of clones secreting IL-6 and the amount secreted per clone was higher in the young.

Adult↗
PubMed1997

Genetic trade-off between early fecundity and longevity in Bactrocera cucurbitae (Diptera: Tephritidae).

The response to selection on age at reproduction was measured to test for a genetic trade-off between early fecundity and longevity in the melon fly Bactrocera cucurbitae (Coquillett). Three replicate lines were selected for propagation by breeding from young (Y-lines) and old (O-lines) adults, respectively. Selection was continued for 24 and 9 generations for Y- and O-lines, respectively. Females from O-lines lived longer than Y-line females as an indirect response to selection, indicating that longevity is a trait under genetic control. Females from Y-lines had higher fecundity early in the lifespan, a shorter preoviposition period, and a shorter prepeak fecundity period than females from O-lines. However, total fecundity did not differ between lines from the two selection regimes. These results suggest the existence of a genetic trade-off between early fecundity and longevity in the population examined, which may be controlled by pleiotropy. The larval period of the O-lines was longer than that of the Y-lines, whereas there were no significant effects of selection regime on egg hatchability or preadult survival rate. The trade-off relationship between early fecundity and longevity is discussed in relation to mass production of the melon fly for the sterile insect technique programme.

Journal Article↗
PubMed2006

Relationship between seed bank expression, adult longevity and aridity in species of Chaetanthera (Asteraceae) in central Chile.

BACKGROUND AND AIMS: Broad surveys have detected inverse relationships between seed and adult longevity and between seed size and adult longevity. However, low and unpredictable precipitation is also associated with seed bank (SB) expression in semi-arid and arid areas. The relationship between adult longevity, SB formation, seed mass and aridity is examined in annual and perennial herbs of Chaetanthera (Asteraceae) from the Chilean Mediterranean-type climate and winter-rainfall desert areas over a precipitation range of one order of magnitude. METHODS: Seeds of 18 species and subtaxa (32 populations) were buried in field locations, and exhumed after two successive germination periods. Seeds not germinating in the field were tested in a growth chamber, and remnant intact seed tested for viability. Seed banks were classed as transient or persistent. The effect of life form, species, population and burial time on persistent SB size was assessed with factorial ANOVA. Persistent seed bank size was compared with the Martonne aridity index (shown to be a surrogate for inter-annual variation in precipitation) and seed size using linear regression. ANCOVA assessed the effect of life-form on SB size with aridity as covariate. KEY RESULTS: Three species had a transient SB and 15 a persistent SB. ANOVA revealed a significant effect of life-form on SB size with annuals having larger SB size and greater capacity to form a persistent SB than perennials. Significant inter-population variation in SB size was found in 64% of cases. Seed mass was negatively correlated with persistent SB size. Persistent seed bank size was significantly correlated with the Martonne aridity index in the perennial and annual species, with species from more arid areas having larger persistent SBs. However, when aridity was considered as a covariate, ANCOVA revealed no significant differences between the annual and perennial herbs. CONCLUSIONS: Persistent seed bank size in Chaetanthera appears to reflect environmental selection rather than any trade-off with adult longevity.

Asteraceae↗
PubMed1999

Interorganelle signaling is a determinant of longevity in Saccharomyces cerevisiae.

Replicative capacity, which is the number of times an individual cell divides, is the measure of longevity in the yeast Saccharomyces cerevisiae. In this study, a process that involves signaling from the mitochondrion to the nucleus, called retrograde regulation, is shown to determine yeast longevity, and its induction resulted in postponed senescence. Activation of retrograde regulation, by genetic and environmental means, correlated with increased replicative capacity in four different S. cerevisiae strains. Deletion of a gene required for the retrograde response, RTG2, eliminated the increased replicative capacity. RAS2, a gene previously shown to influence longevity in yeast, interacts with retrograde regulation in setting yeast longevity. The molecular mechanism of aging elucidated here parallels the results of genetic studies of aging in nematodes and fruit flies, as well as the caloric restriction paradigm in mammals, and it underscores the importance of metabolic regulation in aging, suggesting a general applicability.

Antifungal Agents↗
PubMed2001

Genetic mapping of quantitative trait loci governing longevity of Caenorhabditis elegans in recombinant-inbred progeny of a Bergerac-BO x RC301 interstrain cross.

Recombinant-inbred populations, generated from a cross between Caenorhabditis elegans strains Bergerac-BO and RC301, were used to identify quantitative trait loci (QTL) affecting nematode longevity. Genotypes of young controls and longevity-selected worms (the last-surviving 1% from a synchronously aged population) were assessed at dimorphic transposon-specific markers by multiplex polymerase chain reaction. The power of genetic mapping was enhanced, in a novel experimental design, through map expansion by accrual of recombinations over several generations, internally controlled longevity selection from a genetically heterogeneous, homozygous population, and selective genotyping of extremely long-lived worms. Analysis of individual markers indicated seven life-span QTL, situated near markers on chromosomes I (tcbn2), III (stP127), IV (stP13), V (stP6, stP23, and stP128), and X (stP41). These loci were corroborated, and mapped with increased precision, by nonparametric interval mapping-which supported all loci implicated by single-marker analysis. In addition, a life-span QTL on chromosome II (stP100-stP196), was significant only by interval mapping. Congenic lines were constructed for the longevity QTL on chromosomes III and X, by backcrossing the Bergerac-BO QTL allele into an RC301 background with selection for flanking markers. Survival data for these lines demonstrated consistent and significant effects of each QTL on life span.

Alleles↗
PubMed1998

Differences in root longevity of some tree species.

Although the importance of root production and mortality to nutrient fluxes in ecosystems is widely recognized, the difficulties associated with root measurements have limited the availability of reliable data. We have used minirhizotrons and image analysis to measure root longevity of Prunus avium L., Picea sitchensis (Bong.) Carrière, Acer pseudoplatanus L. and Populus x canadensis cv. Beaupre directly in cohorts of roots. Major differences in the longevity of roots among species were identified. For example, 40% of Prunus avium roots but only 6% of Picea sitchensis roots survived for more than 14 days. Survival analysis of cohorts of roots of Prunus avium and Populus x canadensis revealed differences in the distribution of longevity among cohorts. Genetic, biotic and abiotic factors that may influence longevity are discussed.

Journal Article↗
PubMed2000

Decreased needle longevity of fertilized Douglas-fir and grand fir in the northern Rockies.

Changes in nutrient availability significantly affect canopy dynamics in conifers. To elucidate these effects, we experimentally fertilized mixed conifer stands at several sites across the northern Rocky Mountains. We measured needle longevity, total branch length and foliated length along the main branch axis, and determined mean retained cohort length on mid-canopy branches of shade-intolerant Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) and shade-tolerant grand fir (Abies grandis Lindl.). Needle longevity ranged from 6 to 8 years in Douglas-fir and from 7 to 8 years in grand fir on unfertilized plots. Fertilization significantly decreased needle longevity by 26 and 27% in Douglas-fir and grand fir, respectively. However, the foliated branch length remained unchanged following fertilization and was similar for both species, indicating a 33% increase in mean branch length per needle cohort in Douglas-fir and a 27% increase in grand fir. These data are consistent with the theory that foliated branch length and needle longevity are a result of the ecological light compensation point (ELCP), which links the inherent physiology of the leaf with the availability of resources in the leaf environment. Mid-canopy ELCP was approximately 74 and 71 cm from the branch terminus in Douglas-fir and grand fir, respectively, regardless of fertilization. We hypothesize that fertilization-enhanced needle production and annual shoot growth resulted in a higher rate of shading of older needles. The shaded needles were unable to maintain a positive carbon balance and abscised. The results demonstrate that foliated branch length of Douglas-fir and grand fir in the northern Rocky Mountains can be treated as a homeostatic response to fertilization, whereas foliar turnover is plastic.

Journal Article↗
PubMed2001

Changes in fine root production and longevity in relation to water and nutrient availability in a Norway spruce stand in northern Sweden.

Effects of irrigation and liquid fertilization on fine root (< 1 mm) production and longevity, and fine root (< 0.5-2 mm) biomass were studied in a Norway spruce (Picea abies (L.) Karst.) stand in northern Sweden. Fine root length production and longevity were measured by the minirhizotron technique at 0-10 cm depth in the following treatments: irrigation (I), liquid fertilization (IL) and control (C). Standing root biomass and root length density (RLD) were studied in the litter-fermented humus (LFH) layer and at depths of 0-10, 10-20 and 20-30 cm using soil cores in solid fertilized (F) and C plots. Minirhizotrons were installed in October 1994 and measurements recorded monthly from July to September 1995 and during the growing season in 1996. Soil cores were sampled in 1996. Fine root production increased significantly in IL plots compared with C plots, but the I treatment did not increase root production. Root mortality increased significantly in IL plots compared with C plots. Fine root longevity in IL plots was significantly lower compared with C and I plots. No significant difference was found between longevity of fine roots in I and C plots. Compared with C, F treatment increased fine root biomass in the LFH and mineral soil layers, and increased the amount of fine roots in mineral soil layers relative to the LFH layer. Furthermore, F increased RLD and the number of mycorrhizal root tips significantly.

Biomass↗
PubMed1990

The interaction between leaf longevity and shoot growth and foliar biomass per shoot in Pinus contorta at two elevations.

Leaf longevity ranged from an average of 5 to 18 years in individual trees of lodgepole pine (Pinus contorta Dougl. ssp. latifolia D.K. Bailey) from six even-aged stands in central Colorado, USA, of which three were at an elevation of 2800 and three at an elevation of 3200 m. Leaf longevity was 38% greater and annual shoot growth increment was 33% less in trees growing at 3200 m than in trees growing at 2800 m elevation. There was no difference in leaf biomass per shoot between the trees at the two elevations. These results suggest that leaf longevity is greater on shoots with low annual growth potential. Thus, a slow-growing tree at high elevation (low annual shoot growth potential) can have the same amount of foliage per shoot as a fast-growing tree at lower elevation. This plasticity in leaf longevity enables a consistency in foliar biomass per shoot, which may contribute to the wide range of sites and environments that lodgepole pine occupies successfully.

Journal Article↗
PubMed2004

Longevity of balloon-stabilized skin-level gastrostomy device.

OBJECTIVE: The gastrostomy button is increasingly used in patients requiring long-term enteral feeding. No data are available addressing the longevity of balloon-type gastrostomy buttons. The aim of this study was to evaluate the longevity of balloon-type gastrostomy buttons in children and the cause of the button removal. PATIENTS AND METHODS: During a period of 2.5 years, 165 gastrostomy (Mic-Key, Medical Innovations Corporation, Draper, Utah, U.S.A.) buttons were inserted in 84 children. In all patients, the button replaced a standard tube gastrostomy. The first button was usually inserted under general anesthesia at least 2 months after the insertion of a surgical gastrostomy tube. Additional replacement was performed without sedation. RESULTS: Mean longevity of balloon-type gastrostomy buttons was 5 months (range, 14 days-14 months). Causes of button removal were: inner balloon rupture (n = 101, 61%); leak around button or deflation of the balloon (n = 23, 14%); accidental removal (n = 20, 12%); device damage (n = 5), and obstruction (n = 3). When considering the subgroup with inner balloon rupture, the longevity of the button was 6 months (range, 1-13 months). No correlation was found between duration of gastrostomy button and underlying disease, age of the patient, or the use of antisecretory drugs. CONCLUSION: Although the Mic-Key button has the advantage of an easy insertion, its major limitation is the high frequency of inner balloon rupture, which was the primary main reason for removal.

Adolescent↗
PubMed2000

Sperm velocity and longevity trade off each other and influence fertilization in the sea urchin Lytechinus variegatus.

The theoretical prediction that fast sperm should be more effective at fertilizing eggs has never been documented empirically. Interspecific comparisons suggest an inverse relationship between sperm velocity and sperm longevity but this trade-off has never been demonstrated within a species. Here I investigate how sperm velocity and sperm longevity influence the patterns of fertilization in the sea urchin Lytechinus variegatus. In the laboratory I examined 11 male female pairs of sea urchins for variation in sperm velocity and sperm longevity, and determined the correlations of these traits with the percentage of eggs fertilized with serially diluted sperm. Males with faster sperm had higher rates of fertilization than males with slower sperm. Within individual males, as sperm aged they slowed down and showed a reduced percentage activity and lower rates of fertilization. Across males, the average velocity of freshly spawned sperm was inversely related to sperm longevity. These results establish the possibility that sperm traits are adapted for varying conditions along a continuum from sperm limitation to sperm competition.

Animals↗