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PubMed1994

Multivariate analyses of factors influencing the longevity of fixed partial dentures, retainers, and abutments.

In logistic regression models, variables were studied for possible influence on the longevity of fixed partial dentures, retainers, and abutments. The type of dental material was the most critical variable for change or removal of fixed partial dentures. Cantilever extension indicated no substantial increased risk of change or removal for the fixed partial dentures. The risk of removal for an abutment was influenced by the following variables: endodontic treatment, distal terminal position, placement in the mandible, and advanced marginal bone loss. Several variables were stronger multivariately than bivariately and this indicated that a combination of risk factors may be the most detrimental for the longevity of the restorations.

Adult↗

PubMed1984

Radiation-enhanced resistance to oxygen: a possible relationship to radiation-enhanced longevity.

Shortly after gamma-irradiation, flour beetles (Oklahoma strain of Tribolium confusum) exhibited a decline in resistance to oxygen toxicity. Beginning about two weeks after irradiation, however, the LD50 exposure time in pure oxygen was much greater than that of nonirradiated beetles, and this enhanced resistance persisted for about 6 months. The magnitude of the enhancement was a function of dose, and decreased with increasing age at irradiation. These characteristics of a radiation-enhanced resistance to a stress are comparable to the characteristics of radiation-enhanced longevity in Tribolium, in that after irradiation mortality rate is less than that of controls for about 6 months, the magnitude of the effect is dose-dependent, and older beetles are refractory to the effect. Irradiation under anoxic conditions reduced the development of oxygen resistance to the same degree that it reduced acute radiation lethality, suggesting that the amount of biological damage is the critical factor. These results are discussed in terms of the "induced repair" theory of radiation-enhanced longevity of insects.

Aging↗

PubMed1984

Developmental time and adult longevity in two strains of Drosophila melanogaster in a constant low-stress environment.

This study examines the life spans of wild type flies (Sevelen strain, n = 2991) and post-replication DNA repair-deficient flies (mei-41D5, n = 1607) as members of age-synchronized birth cohorts and as members of full sibships. Flies were individually housed from the time they were laid as eggs until they died as imagoes; environmental conditions were constant throughout the life span of these virgins. In this minimal stress experiment, developmental time and imaginal longevity were negligibly correlated (r = -0.09 to -0.25), even though developmental time was canalized at different levels in both strains. Previous research involving environmental perturbations during the life span of Drosophila (e.g. temperature, diet, population density) has demonstrated significant strong correlations, mostly positive, between developmental time and adult longevity. We have demonstrated that the duration of development and aging are not coupled in the absence of such stresses. We therefore suggest that related changes in the duration of the pre-imaginal and the adult stages of the lifecycle of Drosophila may have evolved through adaptation to environmental stresses.

Animals↗

PubMed1996

Genes that control longevity in Podospora anserina.

Two genetic methods were used to estimate the number of genes that potentially modulate longevity in the filamentous fungus Podospora anserina. First, life span of strains carrying mutations selected on criteria unrelated to senescence was measured. Second, strains bearing random mutations were generated by insertional mutagenesis. Life span of these strains was then measured. Surprisingly, both methods lead to the conclusion that a large number of genes (between 600 and 3000) can modulate life span. Among, the mutations that affect longevity, 50% increase life span and 50% diminish it.

Ascomycota↗

PubMed1995

Mechanical longevity estimation model for post-and-core restorations.

OBJECTIVES: The aim of this study was to integrate existing knowledge of in vitro strength of post-and-cores and masticatory loading to arrive at longevity estimates for post-and-core restorations when subjected to clinically relevant loads. METHODS: A biomechanical model was developed to predict the in vivo longevity. This method was applied to direct post-and-core restorations with amalgam or composite cores. Both experimental laboratory strength values and theoretical clinical strength values were used in the model. The restorations made in the laboratory were assumed to be of a higher quality than clinically made restorations, due to factors such as ease of manipulation, absence of saliva, etc. Both a high and low level of average masticatory loading were considered. The model was used to estimate the probability of mechanical failure before 5 X 10(6) load cycles (5 to 15 years) for all combinations of load range and manufacturing quality. RESULTS: The calculated failure probability was effectively zero for most combinations except for a clinical quality core subjected to loads in the high range. There the probability of mechanical failure before 5 X 10(6) cycles was estimated to be 2 X 10(-5) for amalgam and 5 X 10(-5) for composite cores. These results agree with the overall observed clinical failure rate of about 1% per year for post-and-core restorations. SIGNIFICANCE: The mechanical properties of the post-and-core restorations were adequate for clinically relevant loading conditions.

Biomechanical Phenomena↗

PubMed1989

Host association, on-host longevity and egg production of Ctenocephalides felis felis.

Host association, on-host longevity and egg production of Ctenocephalides felis felis (Bouché) were evaluated using fleas from a commercial laboratory colony and first generation, laboratory-reared, native Indiana fleas. Fleas were placed on cats that were declawed, fitted with Elizabethan collars and housed in specially designed metabolic cages. An average of 85% of the female and 58% of the male fleas stayed continuously on the cats for at least 50 days, indicating that the cat flea is a permanent ectoparasite. The maximum longevity of the cat flea was not determined, but it was shown that it can survive and reproduce on the cat for at least 113 days. A female cat flea may produce up to 1745 eggs during a 50-day period.

Animals↗

PubMed1994

Longevity effect of chromium picolinate--'rejuvenation' of hypothalamic function?

The first rodent longevity study with the insulin-sensitizing nutrient chromium picolinate has reported a dramatic increase in both median and maximal lifespan. Although the observed moderate reductions in serum glucose imply a decreased rate of tissue glycation reactions, it is unlikely that this alone can account for the substantial impact on lifespan; an effect on central neurohormonal regulation can reasonably be suspected. Recent studies highlight the physiological role of insulin as a modulator of brain function. I postulate that aging is associated with a reduction of effective insulin activity in the brain, and this contributes to age-related alterations of hypothalamic functions that result in an 'older' neurohormonal milieu; consistent with this possibility, diabetes leads to changes of hypothalamic regulation analogous to those seen in normal aging. Conversely, promoting brain insulin activity with chromium picolinate may help to maintain the hypothalamus in a more functionally youthful state; increased hypothalamic catecholamine activity, sensitization of insulin-responsive central mechanisms regulating appetite and thermogenesis, and perhaps trophic effects on brain neurons may play a role in this regard. Since both the pineal gland and thymus are dependent on insulin activity, chromium may aid their function as well. Thus, the longevity effect of chromium picolinate may depend primarily on delay or reversal of various age-related changes in the body's hormonal and neural milieu. A more general strategy of hypothalamic 'rejuvenation' is proposed for extending healthful lifespan.

Aging↗

PubMed2004

Impact of genetic complexity on longevity and gametocytogenesis of Plasmodium falciparum during the dry and transmission-free season of eastern Sudan.

Malaria in eastern Sudan is characterised by limited seasonal transmission, with the majority of the year remaining transmission-free. Some inhabitants who contract malaria during the transmission season retain long-lasting sub-patent infections, which probably initiate transmission the following year. Here we have monitored Plasmodium falciparum infection prevalence and gametocyte production during the dry season, and examined the impact of parasite genetic multiplicity on infection longevity. A cohort of 38 individuals who were infected with P. falciparum in November 2001 was monitored monthly by microscopy and PCR until December 2002. Reverse transcriptase polymerase chain reaction of the pfg377 gene was used to detect sub-patent gametocytes. In addition, all isolates were examined for msp-2 alleles and the mean number of parasite clones per infection was estimated. We found that a large proportion (40%) of the cohort retained gametocytes throughout the dry season. The majority of patients retained asexual infection for at least 7 months. Genetic multiplicity of P. falciparum significantly influenced longevity of asexual infection and its gametocyte production. Gametocytes from mixed genotype P. falciparum infections persisted three times longer than those from single genotype infections, suggesting that genetic diversity promotes persistence. These findings are discussed in the context of the parasite biology and malaria epidemiology in the study area.

Adult↗

PubMed2005

Yeast longevity and aging--the mitochondrial connection.

Studies of the yeast Saccharomyces cerevisiae reveal four processes determining life span: metabolism, stress resistance, chromatin-dependent gene regulation, and genome stability. The retrograde response, which signals mitochondrial dysfunction resulting in changes in nuclear gene expression, extends yeast life span and is induced during normal aging. This response involves extensive metabolic adaptations. The retrograde response links metabolism and genome stability during yeast aging. A reduction in the availability of nutrients also extends yeast life span. This metabolic mechanism operates by pathways distinct from the retrograde response, although it shares with the latter some longevity effectors. Life extension by calorie restriction entails re-modeling of mitochondrial function. The retrograde response appears to compensate for age changes, while calorie restriction may be a preventive mechanism. The maintenance of age asymmetry between the mother and daughter yeast cells also depends on mitochondrial function. Loss of this age asymmetry occurs during normal yeast aging and may be a paradigm for stem cell aging. The importance of mitochondrial integrity in yeast longevity is emphasized by the role of prohibition function in attenuating oxidative damage. Our studies point to the central role of mitochondria in yeast aging. They highlight the importance of the maintenance of mitochondrial membrane potential, which drives the transport of biosynthetic precursors derived from the Krebs cycle. Common threads weave their way through the studies of aging in yeast and in other model organisms. This suggests conserved features of aging across phyla.

Caloric Restriction↗

PubMed2001

Longevity determines sizes of an adult intertidal barnacle.

The small honeycomb barnacle Chamaesipho tasmanica Foster and Anderson often forms continuous sheets covering the substratum at mid-shore levels of sheltered rocky shores but also occurs in sparse distributions on exposed shores, and on higher levels of sheltered shores, in south-eastern Australia. Larger barnacles are generally found in more exposed and higher areas. Effects of each site on ultimate sizes of barnacles were therefore examined by measuring growth of barnacles of the same cohort at sheltered and exposed shores from the end of 1989 to the end of 1992. Because Chamaesipho varied in size among sites, and because size was not necessarily representative of age, three growth models were proposed to explain this size differential. While rates of growth and periods of growth did not differ, differences in longevity were found to influence size so that larger barnacles survived longer and were more abundant on the more exposed shores. In fact, when barnacles were aged, it was found that a greater proportion of older barnacles (>3 years of age) occupied these exposed areas. It seems that site-specific characteristics influenced longevity in some places so that larger Chamaesipho continued to predominate in these areas.

Journal Article↗

PubMed1998

Physiological trade-offs between reproduction, flight capability and longevity in a wing-dimorphic cricket, Modicogryllus confirmatus.

Physiological and morphological comparisons were made between the short-winged (SW) and long-winged (LW) morphs of a cricket, Modicogryllus confirmatus, to determine the cost of the flight capacity and the physiological mechanisms underlying trade-offs between different life history traits related to migration and reproduction. Both wingmorphs grew at a similar rate and no consistent correlation was found between nymphal development and adult body size. The metathoracic muscles at adult emergence represented 4.2% of the wet body weight in the SW morph and 10.5% in the LW morph. Fat content of the body at adult emergence was positively correlated to dry body weight, but no significant difference was found in mean fat content between the two wingmorphs or between sexes after body weight was adjusted. SW females fed ad libitum produced significantly more eggs than LW females during the first 20days of adult life. Egg production was not correlated to either body size or the duration of nymphal development. LW adults lived longer than SW ones when kept with water alone or when given various amounts of food on day 1 and otherwise kept with water alone. In females, a highly significant correlation was found between longevity and egg production, indicating the presence of a trade-off. LW females mainly allocated the energy from food to flight muscle development and general maintenance of the body rather than to egg production, whereas SW females used it for egg production and longevity. LW females that had been de-alated at adult emergence histolyzed the flight muscle and used the energy from food for egg production almost exclusively. These results suggest that energy allocation and trade-offs after adult emergence may play crucial roles in the functional differentiation of the two wingmorphs.

Journal Article↗

PubMed2005

[Can metal-on-metal bearings improve the longevity of total hip prostheses?].

PURPOSE OF THE STUDY: In total hip arthroplasty (THA), inter-series comparative clinical results cannot be considered worthy before at least 10 years of average follow-up, as shown in the Swedish Arthroplasty Register experience (1978-1993). Last generation metal-on-metal bearings were introduced in France only nine years ago (1995). To date, using mid term information, data from the literature, and our experience, one could assume that this bearing material has the capacity to improve THA longevity. Three types of information were analyzed: 1) comparative radiographic and EBRA studies published on early migration (<2 years) of acetabular implants; 2) preliminary comparative data on wear and osteolysis at the 8-year maximum follow-up; 3) clinical data on dislocation frequency and in vitro and in vivo observations of bearing separation and sliding. Study no 1: primary stability of these metal-on-metal acetabular cups was better than for polyethylene (PE) cups or alumina liners; study no 2: no detectable wear and less osteolysis were observed to date with metal-on-metal bearings versus their alumina-on-PE counterparts. Study no 3: less dislocation and less head sliding were measured with the metal-on-metal versus alumina-on-PR bearings possibly due to the interfacial forces provided by lubricating fluid (suction fit). CONCLUSION: According to current knowledge, this metal-on-metal bearing still represent, with alumina-on-alumina and highly crosslinked PE, a competitive and comprehensive option to improve THA longevity. The real pending problem concerns the frequency and above all the intensity of metal delayed hypersensitivity reaction and their potential effect on implant loosening.

Aluminum↗

PubMed2002

Techniques to maximize flexible ureteroscope longevity.

OBJECTIVES: To assess methods to improve the longevity and durability of flexible ureteroscopes by using the ureteral access sheath, 200-microm holmium laser fiber, and nitinol baskets or graspers during routine ureteroscopic procedures. Despite adequate advances in fiberoptics and endoscope design, the decreased size of currently available flexible ureteroscopes makes damage inevitable after repeated use. However, new auxiliary tools may be able to enhance ureteroscope durability. METHODS: The indications for performing flexible ureteroscopy were proximal ureteral stones (n = 32), renal calculi (n = 59), treatment of upper tract transitional cell carcinoma (n = 3), evaluation of hematuria or filling defect (n = 7), and treatment of ureteral strictures or ureteropelvic junction obstruction (n = 8). Using four new 7.5F flexible ureteroscopes, we prospectively evaluated the number of passes of each ureteroscope until more than 20 optical fibers were broken, more than a 25 degrees loss of deflection in either direction had occurred, or the instrument sustained injury requiring repair by the manufacturer. RESULTS: One hundred nine flexible ureteroscopic procedures (average 27.5 procedures per instrument; range 19 to 34) were performed with the four new flexible ureteroscopes before being sent for repair. Adjuncts to reduce scope damage during these procedures were the use of the ureteral access sheath (n = 109), nitinol devices allowing lower pole stone retrieval (n = 27), and the 200-microm holmium laser fiber for stone fragmentation, tumor ablation, and incision of ureteropelvic junction/ureteral stenoses (n = 91). The average number of passes until more than 20 optical fibers were broken was 15.3 (range 12 to 20), until more than a 25 degrees loss of deflection occurred was 50.3 (range 42 to 66), or until the scope required repair was 66.7 (range 46 to 82). CONCLUSIONS: Flexible ureteroscopy will be used increasingly to manage upper urinary tract pathologic findings. Historically, the number of procedures performed before a flexible ureteroscope requires repair averaged 6 to 15. By incorporating the new ureteroscopic accessories, such as nitinol devices, a ureteral access sheath, and the 200-microm holmium laser fiber into common practice, one can reduce the strain on these fragile 7.5F endoscopes, thereby maximizing their longevity.

Equipment Failure↗

PubMed2003

Effects of Equex from different sources on post-thaw survival, longevity and intracellular Ca2+ concentration of dog spermatozoa.

The aims of the present study were to compare the effects of two commercial preparations (Equex STM Paste or Equex Pasta), whose active ingredient is sodium dodecyl sulphate (SDS), added to a Tris-egg yolk-based extender, on post-thaw sperm survival and longevity, as well as on the intracellular Ca(2+) concentration of dog spermatozoa during incubation at 38 degrees C. One ejaculate was collected from each of eight dogs. Each ejaculate was centrifuged, the semen plasma discarded, and the sperm pellet rediluted with a Tris-glucose-egg yolk extender containing 3% glycerol (Ext-1) at a sperm concentration of 200 x 10(6) spermatozoa (spz)/ml. The diluted semen was divided in three aliquots of equal volume and allowed to equilibrate for 1h at 4 degrees C. After equilibration, the same volume of three different second extenders was added, respectively, to each of the three aliquots: (A) Ext-2A (same composition as Ext-1 except that it contained 7% glycerol and 1% Equex STM Paste), (B) Ext-2B (same composition as that of Ext-1 except that it contained 7% glycerol and 1% Equex Pasta), and (C) Ext-2 (CONTROL: same composition as that of Ext-1 except that it contained 7% glycerol). Semen samples were packed in 0.5 ml straws and frozen on a rack 4 cm above liquid nitrogen (LN(2)) in a styrofoam box. Thawing was at 70 degrees C for 8s. Sperm motility was evaluated after thawing and at 1 h intervals for 5h at 38 degrees C by subjective examination and by using a CASA system. Plasma membrane integrity and acrosomal status were evaluated at 1, 4 and 7h post-thaw using a triple staining procedure and flow cytometry. Intracellular Ca(2+) concentration of live spermatozoa was evaluated by flow cytometry at 1, 4 and 7h post-thaw after co-loading the sperm cells with the Ca(2+) indicators Fluo 3 AM and Fura Red AM, and with PI. Post-thaw sperm survival and longevity, as well as the quality of the sperm movement, were significantly better (P<0.005) when Ext-2A (containing Equex STM Paste) was used. There was no difference between Ext-2B (containing Equex Pasta) and Ext-2 (CONTROL). The mean intracellular Ca(2+) concentration (arbitrary units) of cryopreserved spermatozoa (range: 0.23+/-0.12 to 1.26+/-0.46) was higher than that of fresh spermatozoa (0.13+/-0.06). When using Ext-2A, the live spermatozoa frequently (P=0.012) appeared divided in two subpopulations, with high (1.26+/-0.46) and low (0.27+/-0.09) intracellular Ca(2+) content, respectively. When using Ext-2B or Ext-2, the live spermatozoa were more frequently seen in a single population with low intracellular Ca(2+) concentration (0.30+/-0.35 and 0.23+/-0.12, for Ext-2B and Ext-2, respectively).

Animals↗

PubMed1999

Comparison of the longevity of motility of stallion spermatozoa incubated at 38 degrees C in different capacitating media and containers.

This study was designed to compare the effects of different media and containers on longevity of motility of spermatozoa during in vitro incubation at 38 degrees C in either air or 5% CO2 atmosphere. Three ejaculates were collected from each of 4 stallions. The media tested were skim milk-glucose, modified Krebs/Ringer and Hank's salts solution for incubation in an air atmosphere, and modified Krebs/Ringer and Brackett and Oliphant (BO) defined medium for incubation in a 5% CO2 atmosphere. All samples were incubated in 5-mL borosilicate glass tubes filled with 3 mL of extended spermatozoa, 5-mL borosilicate tubes filled with 6 mL (topped) of extended spermatozoa, 35-mm Petri dishes filled with 3 mL of extended spermatozoa, and 35-mm Petri dishes with 200-microL microdroplets of extended spermatozoa under sterile mineral oil. For all treatments, individual samples were removed at 2, 4, 6 and 12 h of incubation to determine the percentage of motile cells. Overall, spermatozoa incubated in Petri dishes in both 3-mL and microdroplet treatments had significantly higher motility than those incubated in glass tubes (P<0.01). At 6 and 12 h of incubation in Petri dishes, progressive motility was significantly higher for spermatozoa extended in the Hank's salts solution than in the other media. Both the medium and container used significantly affected the longevity of motility of spermatozoa incubated at 38 degrees C.

Animals↗

PubMed1977

Effect of coronary bypass surgery on longevity in high and low risk patients. Report from the V.A. Cooperative Coronary Surgery Study.

There is considerable uncertainty about the effects of bypass surgery on the longevity of patients with coronary-artery disease and angina. The Cleveland Clinic has reported improved survival after surgical treatment; the Duke University study indicated improvement in a high-risk subgroup only. The Veterans Administration (V.A.) randomised study initially reported improved survival only for patients with significant left main artery (L.M.) disease. Further analysis of the V.A. study shows that survival in the high-risk subgroup was 87% for the surgically treated patients and 74% for those treated medically--a highly significant difference after four years of follow-up. However, exclusion of the L.M. group reduced the difference to a non-significant one of 84% versus 79%. For patients not in the high-risk subgroup, survival at four years (with L.M. excluded) was 93% for those treated surgically and 96% for those treated medically. For all patients the rates were 85% and 86%, respectively. These findings indicate that in the evaluation of the effects of bypass surgery on longevity the characteristics of the coronary-artery disease are critical.

Angina Pectoris↗

PubMed2000

Establishment of an Aging Farm of F344/N Rats and C57BL/6 Mice at the National Institute for Longevity Sciences (NILS).

In 1996 the National Institute for Longevity Sciences (NILS) started an aging/aged farm (Aging Farm), an animal farm for producing aging/aged laboratory rodents on inbred strains, F344/N rats and C57BL/6 mice at its Experimental Animal Facility Wing, based on plans prepared by the Laboratory Animal Research Facilities (LARF). The NILS Aging Farm, being well established, began internal supply of aging/aged laboratory rodents in 1999 to promote both aging and longevity science. This report describes development of the NILS Aging Farm under NILS Aging Farm Guide and the effectiveness of the Guide.

Journal Article↗

PubMed2002

Phosphorus saturation potential: a parameter for estimating the longevity of constructed wetland systems.

Phosphorus (P) adsorption capacities of materials derived from batch experiments can vary by several orders of magnitude depending on the method used, leading to potential misinterpretation of the P retention capacity on a long-term basis and unrealistic estimations of constructed wetland systems (CWS) longevity. The objective of this study was to determine if the P saturation of the material in a column could be used for this purpose with an improved accuracy. A 278-d column experiment with a synthetic P solution was conducted to investigate the long-term P retention capacity of electric arc furnace (EAF) steel slag up to its P saturation point. EAF slag showed a high affinity for P, reaching a saturation value of 1.35 g of P kg(-1). Investigations of the regeneration of the P adsorbing capacity by this material showed that, after 4 weeks of water desaturated resting, EAF steel slag was able to increase its initial P adsorptive capacity to 2.35 g of P kg(-1). A sequential P fractionation experiment was performed to quantify the proportion of P bound to mineral compounds in EAF. From the most loosely bound to the most strongly bound P fraction, P was associated with resin extractable (14%), Fe extractable (0.5 M Na2CO3, 47%), Al extractable (0.1 M NaOH, 1%), Ca extractable (1 M HCl, 12%), and Ca in a stable residual pool (concentrated hot HCl, 26.5%). X-ray fluorescence analyses of EAF steel slag chemical composition revealed that the continuous application of a P solution resulted in 75% and 59% increases in K2O and P2O5 respectively; Al2O3 and FeO increased by 8%, while the portion of CaO remained unchanged. The investigated properties (P retention potential, regeneration of P adsorption, P fractionation) provide useful data about the suitability of slag material as a media for long-term P removal and should enable an improved prediction of the longevity of full-scale CWS.

Adsorption↗