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Biomedical subjects

F A Lints

Publications and source records attributed to F A Lints.

At least 37 records · Page 2Linked to original sources
PubMed1985

Growth rate and life spain in Drosophila. IV. Role of cell size and cell number in the biphasic relationship between life span and growth rate.

The patterns of variation of wing cell size and number were studied under developmental conditions leading to a biphasic relationship between life span and growth rate while duration of development remained constant (development on an agar-only medium with a varying added yeast amount, constant temperature (25 degrees C) and constant larval density). Across the yeast range, a 125% increase of body weight was accompanied by a roughly 30% increase in the wing linear dimensions, wing cell size and wing cell number while estimated duration of cell division and its reciprocal mitotic division rate remained constant. Furthermore, cell size (but not cell number) varied with growth rate in a similar biphasic pattern to that observed for life span. Finally, from a simultaneous examination of the covariation patterns of life span, growth rate, cell size and cell number with decreasing yeast amount, it became apparent that there was a "critical" yeast amount, approximately 125 mg/120 eggs, below which: (a) cell number abruptly started to decrease linearly from a roughly constant value; (b) the rate of the slow decrease of cell size now tripled and that of growth rate increased even more; and (c) life span which, in the upper yeast range, increased slowly with decreasing yeast, apparently reached a maximum at the critical yeast level and decreased three times faster below that level. These data taken together suggest that: (i) the decrease of all parameters (including life span) below the critical yeast level results from a presumably suboptimal or disturbed development because of and in proportion to the lack of nutrients and (ii) the increase of life span with decreasing yeast amount above the critical yeast level has not been definitely explained but some possibilities are suggested such as changes in subcellular organelle numbers, size and/or functional properties, or other changes due to a phenomenon equivalent to food restriction in rats, probably without changes in overall metabolic rate of the flies.

Aging↗
PubMed1985

Growth rate and life span in Drosophila V. The effect of prolongation of the period of growth on the total duration of life (J.H. Northrop, 1917)--revisited.

Sixty-eight years ago Northrop observed a constant life span in Drosophila after a progressive increase of the duration of development of the flies achieved by using a yeastless nutrient medium to which he added yeast with a progressively increasing delay. This evidence against the more recent concept of an increased life span following an experimentally decreased developmental rate has generally been ignored due, presumably, to the imprecise methodology employed by Northrop at a time that Drosophila research was just commencing. We describe here a study that aimed at re-examining and extending Northrop's work by developing the flies in either a yeastless or a lightly yeasted medium. While in a yeastless medium development of flies was virtually arrested until yeast was added, in the yeasted medium a slow growth of the larvae was possible before yeast was added. With another method, larval growth rate was reduced over the entire developmental period by adding a relatively low amount of yeast in four portions and with various delays between portions (the first portion being added without delay). Our study confirmed the "Northrop-effect", i.e. the absence of an effect on life span from increased duration of development by a virtual arrest of growth of the larvae for a number of days. Further, it showed that manipulation of growth rate by portioning the yeast amount did not unequivocally support the concept that a lower growth rate leads to an increased life span.

Animals↗
PubMed1984

Growth rate and life span in Drosophila. II. A biphasic relationship between growth rate and life span.

The relationship between growth rate and life span was studied in Drosophila by varying the amount of yeast available to each developing larva at constant temperature, 25 degrees C. With one approach the larvae developed in a standard medium at constant larval density and a varying amount of yeast added on the medium. Across the entire growth rate range covered in this way (10-100 micrograms/day, male flies) imaginal life span depended on growth rate in a biphasic way, the relationship having a parabolic form with a maximum at about 55 to 60 micrograms/day. Similar covariation of growth rate and life span was obtained by varying larval density at a constant amount of added yeast. With both these approaches growth rate variation was due to opposite variations of both components of growth rate, i.e. duration of development and body size. However, development in a medium without nutrients but with a varying amount of added yeast at constant larval density led to a similar biphasic relationship between growth rate and life span although duration of development did not vary. Therefore, the present results are not compatible with the hypothesis that there is a single causal negative relationship between growth rate and life span and demonstrate that duration of development is not a causative factor of the biphasic relationship between growth rate and life span established here.

Animals↗
PubMed1984

Growth rate and life span in Drosophila. III. Effect of body size and developmental temperature on the biphasic relationship between growth rate and life span.

The previous finding of a biphasic relationship between life span and growth rate of Drosophila, developed at 25 degrees C, was confirmed at other temperatures in the usual range (19-28 degrees C) and for development in either a standard medium or one deprived of nutrients but with varying amounts of yeast added on the medium. The role of body size in this relationship was studied by developing flies in a nutrient-less medium with a constant, submaximal amount of added yeast and varying temperature. It was found that under these conditions, which abolished the usual inverse relationship between body size and developmental temperature, body size variations did not account for the observed variations in life span. Thus, corroborating previous studies from this laboratory, body size was ruled out as a causative factor in the life span-growth rate relationship.

Animals↗
PubMed1984

Growth rate and life span in Drosophila. I. Methods and mechanisms of variation of growth rate.

It has been suggested that development and ageing may be linked and it has been shown, in Drosophila, under conditions of varying developmental temperature and larval crowding that the rate of development may be inversely related with the duration of adult life. In order to test this hypothesis systematically, precise methods were devised for varying, in Drosophila, either growth rate or each of its components, i.e. body weight and duration of development, while holding the other constant. These methods are described in the present paper. Moreover, we report studies that shed some light on the mechanisms underlying the effects of temperature and larval crowding on Drosophila development. The major novel findings from these studies were: (a) the restriction of the amount of yeast per larva as larval density increases accounts entirely for the effect of larval crowding on duration of development but only for about two-thirds of its effect on body size; and (b) the increased size of flies grown at lower temperatures may be due to assimilation of more food rather than to more efficient assimilation of food.

Aging↗
PubMed1984

Does a relationship exist between spontaneous locomotor activity, fitness and lifespan in Drosophila melanogaster?

Spontaneous locomotor activity (SLA), fecundity, fertility and lifespan were measured in a wild laboratory strain of Drosophila melanogaster in order to ascertain whether there is a genetic correlation between these traits. In females there is no correlation either between SLA and fecundity or between SLA and lifespan. It is concluded that, although a high level of SLA probably constitutes a favorable behavioral component of fitness, this does not mean that more active females have a larger number of offspring and live longer than less active ones.

Animals↗
PubMed1984

A longitudinal study of the effects of age on spontaneous locomotor activity in Drosophila melanogaster.

The spontaneous locomotor activity of Drosophila melanogaster was observed longitudinally, in both sexes, at young and old age, during a photophase of 12 h. 75 observations of each fly (n = 200 at young age, n = 98 at old age) were made during each photophase. At a populational level and with increasing age the difference between the maximal and minimal percentages of flies active during the photophase diminishes seriously; moreover, the scattering of the observations increases with increasing age. At an individual level females are more active than males at both ages and the scores of activity of both males and females decrease with increasing age. The effects observed, both at the populational and at the individual level, are due solely to age; they are not due to a differential survival depending on or linked to the score of activity exhibited at young age.

Aging↗
PubMed1984

Spontaneous locomotor activity and life span. A test of the rate of living theory in Drosophila melanogaster.

The spontaneous locomotor activity and life span of approximately 600 individuals of both sexes and of three widely different genotypes of Drosophila melanogaster have been measured. Neither at the individual nor at the populational level could a significant correlation between spontaneous locomotor activity and life span be found. The results are discussed in relation with Pearl's [The rate of living, London University Press, London 1928] rate of living theory. That theory has been tested in relation with environmental temperature, oxygen consumption and activity. It is shown that the theory has received no definite confirmation until now.

Aging↗
PubMed1983

Does the female life span exceed that of the male? A study in Drosophila melanogaster.

A survey of all the papers relating to life span in Drosophila melanogaster published in Experimental Gerontology from its origin in 1964 to 1981 shows that, contrary to a common belief, the mean life span of females exceeds that of males in only approximately 50% of the cases. It is shown that mean life span, as it is measured in most experiments, is a poor estimate of the potential life span of a Drosophila strain. However, the analysis of four extensive studies of Drosophila melanogaster life span strongly suggests that the potential (or maximal) life span is consistently higher for females than it is for males. That analysis also shows that, vis-à-vis the controlled or uncontrolled variations of the environment, the males have a broader norm of reaction or, in other words, a smaller homeostasis than the females. A model, mainly based on these two results, allows us to explain how the mean life span of males is so often higher than that of females.

Aging↗
PubMed1982

Influence of preimaginal constant and alternating temperatures on growth rate and longevity of adults of five genotypes in Tribolium castaneum.

The longevity of adults of five genotypes of Tribolium castaneum differing in their body weights was measured at a single constant temperature, 35 degrees C, after they had developed at three constant temperatures, 25, 30 or 35 degrees C, and one alternating temperature 25/35 degrees C (mean = 30 degree C). Two genotypes had been naturally selected for heavy and light body weights, two had been artificially selected for extreme pupal weights and one was the pygmy mutant. The main results are as follows. (1) There is a negative correlation between growth rate and imaginal longevity for four of the five genotypes, when the variations in growth rate are due to the influence of constant developmental temperatures. (2) The genotype has a marked effect on mean longevity and on the slope of the regression of longevity on growth rate. (3) Growth rate is larger and longevity is longer when the larvae are raised at alternating 25/35 degrees C than when they are raised at a constant 30 degrees C. These results seem to confirm the developmental theory of ageing.

Animals↗
PubMed1981

Studies on the descendancy of four populations of Koekelaere pines: Pinus nigra Arnold, subsp. laricio (Poiret) Maire, cv. Koekelaere. II. Heritability as a function of parental age.

The variations of heritability as a function of parental age are studied in Koekelaere pines [Pinus nigra Arnold, laricio (Poiret) Maire, cv. Koekelaere]. The age of the parental trees varies between 26 and 101 years. 16 different traits are analysed. It is shown that heritability does not vary as a function of parental age. These results are discussed in relation with the problems of ageing in trees and of the theories of ageing.

Aging↗
PubMed1979

An attempt to select for increased longevity in Drosophila melanogaster.

Eight generations of selection towards a higher longevity were made in a wild strain of Drosophila melanogaster. Two control lines were also observed. Absolutely no response to selection was obtained whilst a major increase in longevity occurred between F2 and F4 in the three lines under observation. It is shown that the major increase in longevity is due neither to genetic drift, nor to changes in classical environmental conditions. The absence of response to selection is demonstrated to be due neither to a too low selection differential, nor to the absence of genetic variability in the strain, nor to inaccuracy in the measurements, nor to recurrent reproduction at an old age. The impossibility to select towards a higher longevity and the total absence of relation between parental and offspring longevities demonstrate that the very large phenotypic variability displayed by longevity in wild strains of D. melanogaster does not depend on a precise set of specific genes or polygenes with additive action. The results are briefly discussed in relation with inbreeding depression and heterosis for longevity and with similar results obtained in experiments of selection for duration of development.

Animals↗
PubMed1975

Longevity, growth rate and related traits among strains of Tribolium castaneum.

Longevity of eight laboratory strains of the flour beetle Tribolium castaneum, with various geographic backgrounds, was studied under constant laboratory conditions of 33 degrees C and 70% relative humidity in standard medium (95% whole wheat flour and 5% dried yeast) during a period of 227 days starting from the egg stage. The eggs were collected from the same parents, first a few days after emergence and afterwards at intervals of 13, 9, 10 and 11 days. Mean survival time (MST) was found to be strain-specified. It ranges from 128.6 days for KJ (Kyoto, Japan) to 174.2 days for ES (Edinburgh, Scotland). MST was highly correlated with the percentage of adults alive after 227 days, which did not change the ranking order of strain longevity. Parental age had no effect on longevity. The mean adult longevity of the strains was correlated with the available data on adult weight, growth rate, viability and productivity. There was no relationship between adult weight and longevity. LIfe span was found to depend on growth rate (measured as 13-day larval weight), percent viability (from 13-day larvae to adulthood) and productivity. Developmental time was also found to influence adult life span within certain limits (two extreme strains deviated). The data suggest that ageing and death in T. castaneum is under genetic control and support the idea that ageing, allied to development, is genetically controlled.

Age Factors↗