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Biomedical subjects

H E Enesco

Publications and source records attributed to H E Enesco.

At least 19 recordsLinked to original sources
PubMed1991

Effect of dietary restriction and aging on polyploidy in rat liver.

Liver polyploidy levels were compared as a function of age and diet in male Fischer 344 rats between 1 and 24 months of age. Dietary restriction was imposed on one group by reducing their food intake to 60% of ad libitum food intake. Histological sections of the livers of animals at each age and diet were examined. Diploid, tetraploid and octaploid nuclei were observed, and their size and frequency established. There were no differences in the diameter or volume of these size classes as a function of age or diet. An age-related decline in the percentage of diploid nuclei, coupled with an increase in the percentage of tetraploid and octaploid nuclei was observed in both groups. The major difference between the two groups was that the adult level of liver polyploidy was attained more slowly in the animals on dietary restriction as compared to the ad libitum fed controls. Polyploid cell formation in the liver is under the control of growth hormone, thyroid hormone and thymus, all of which might be influenced by dietary restriction.

Aging↗
PubMed1990

Spontaneous activity level and life span in rotifers: lack of support for the rate of living theory.

Spontaneous activity level was measured in rotifers of the species Asplanchna brightwelli on each day of their 5-day life span. No correlation was seen in group data between activity level and life span. However, data from individuals showed a positive correlation between life span and activity level in the latter half of the life span on 3 days out of 5. This tendency toward greater activity in the longer-lived rotifers is not consistent with the rate of living theory of aging.

Aging↗
PubMed1989

The relationship between lifespan and reproduction in the rotifer Asplanchna brightwelli.

Lifespan is strongly correlated (0.7009) with the length of the reproductive period in the rotifer Asplanchna brightwelli. Lifespan is correlated to a lesser degree with the number of offspring produced (0.5545). When lifespan is extended by experimental means, it is the length of the reproductive period which is increased. Extension of the reproductive period appears to be the most important determinant of lifespan extension. These findings do not support most of the reproduction theories, but support the concept that the end of the reproductive period signals the end of the lifespan.

Animals↗
PubMed1989

Cortisone extends life span in the rotifer Asplanchna brightwelli.

Cortisone at 100 and 200 microM concentrations produced a significant increase in both life span and reproduction in the rotifer Asplanchna brightwelli. Two possible mechanisms are discussed to explain these results: (1) cortisone stabilization of lysosomal membranes, or (2) recognition of cortisone as a hormone capable of altering resource allocation by the rotifers.

Animals↗
PubMed1986

Influence of low tryptophan diet on survival and organ growth in mice.

Greater survival and reduced growth were found to characterize mice on a tryptophan deficient diet as compared to fully fed control mice. The 50% survival point was reached by the tryptophan restricted group at 683 days, and by the control group at 616 days. Measurements of body weight, organ weight, and DNA level were made at 8, 12, 24, 36, 52 and 78 weeks of age. Both whole body weight and organ weight of liver, kidney, heart and spleen were about 30% lower in the tryptophan restricted group as compared to the controls, so that the ratio of organ weight to body weight remained at a constant value for both groups. There was no significant change in cell number as determined by DNA measurements, as a result of the tryptophan restriction.

Aging↗
PubMed1986

Influence of dietary protein restriction on cell number, cell size and growth of mouse organs during the course of aging.

Groups of male Swiss albino mice on diets of 4%, 8% and 26% protein were sacrificed at 6, 12, 42 and 84 weeks of age to determine the extent to which cell number and cell size were influenced by dietary protein restriction in the course of aging. The results show that cell number is reduced by low protein diets only in liver and kidney: that is, in expanding cell populations. Cell number in the static cell populations of brain and heart was not influenced by diet. Increase in organ size is brought about by a variety of mechanisms. Heart size increases in mice on a higher protein diet by means of increase in cell size; a cellular hypertrophy. Liver size increases both through cell addition and formation of larger polyploid cells. The kidney was the only organ in which there was a continuous addition of new cells of constant size throughout the life span. Dietary protein restriction reduced the rate of cell size increase and of growth. Although it slowed the growth process, it did not alter any of the aging or growth patterns.

Animals↗
PubMed1985

Influence of diet on plasma tryptophan and brain serotonin levels in mice.

Groups of mice were maintained for up to 78 weeks on tryptophan restricted, protein restricted and control diets. Plasma tryptophan levels were significantly reduced by both forms of dietary restriction. Brain serotonin levels were significantly reduced only in mice on the tryptophan restricted diet, but not for mice on the protein restricted diet. The protein-restricted diet contains less of the large neutral amino acids which compete with tryptophan to enter the brain. It is known that protein restriction and tryptophan restriction extend lifespan. The results presented here suggest that extension of lifespan and lowering of brain serotonin are not related.

Aging↗
PubMed1985

Life span and age-related changes in activity level of the rotifer Asplanchna brightwelli: influence of curare.

The rotifer Asplanchna brightwelli shows a continuous decline in swimming activity through the course of its 5-day life span. This activity loss occurs at a slower rate when rotifers are treated with very low dosages (0.00025% to 0.0005%) curare. Rotifers treated with these low dosages of curare have a significantly longer life span than that of untreated control rotifers.

Activity Cycles↗
PubMed1984

Effects of U.V. radiation on the lifespan of the rotifer Asplanchna brightwelli.

Groups of rotifers of the species Asplanchna brightwelli were exposed to U.V. irradiation at dosages ranging from 50 to 4800 J/m2. The lifespan of the rotifers was significantly reduced by exposure to U.V. in the range of 200 to 4800 J/m2. A logarithmic decline in lifespan was seen as the U.V. dose increased. Rotifers were most sensitive to U.V. exposure during the prereproductive stage at the beginning of their lifecycle. Exposure of rotifers to visible light following U.V. radiation provided no evidence that photoreactivation could influence lifespan in this species.

Aging↗
PubMed1984

A study of dietary restriction and lifespan in the rotifer Asplanchna brightwelli monitored by chronic neutral red exposure.

The rotifer Asplanchna brightwelli could be exposed to concentrations of neutral red at 0.1 to 0.75 microgram/ml for two consecutive generations with no adverse effect on the lifespan or fecundity of either generation. Chronic exposure to higher concentrations of neutral red caused reductions in both lifespan and fecundity of the rotifers. Because neutral red stains the Paramecium which serve as a food source for the rotifers, the extent of red coloration in each rotifer's gut gave an approximation of how much food that rotifer had consumed. The Paramecium concentration had to be reduced to 100 per ml before pale gut coloration provided clear evidence of reduced food intake or dietary restriction. The group of rotifers with reduced food intake had a significantly longer lifespan than any other group. Their lifespan was 14.2% longer than that of control rotifers.

Aging↗
PubMed1984

The effect of light, dark or altered circadian cycle on the lifespan of the rotifer Asplanchna brightwelli.

Rotifers were maintained in various light conditions for at least 20 generations. In the first set of experiments lifespan and fecundity data were compared for groups of rotifers maintained under LL (continuous light), DD (continuous dark) or LD 12:12 (control, 12 hr. light 12 hr. dark). The mean lifespan of the rotifers cultured in DD conditions was significantly increased as compared to the LL or LD 12:12 groups but there were no fecundity differences. There was no alteration in lifespan or fecundity of the LL group as compared to the LD 12:12 control. In a second set of experiments, an LD 6:18 cycle was imposed to determine whether a shift in the circadian cycle would influence lifespan. Rotifers exposed to the LD 6:18 cycle and to the DD conditions showed an 18% and 22% increase in mean lifespan respectively. The results are interpreted to demonstrate that lifespan is influenced by the circadian cycle.

Animals↗
PubMed1984

Vitamin E extends lifespan in the short-lived rotifer Asplanchna brightwelli.

Supplementation with vitamin E at a concentration of 25 micrograms/ml significantly increased the mean lifespan of the rotifer Asplanchna brightwelli. Of the three life stages, the prereproductive, reproductive and postreproductive, only the prereproductive stage was significantly extended by vitamin E supplementation. Vitamin E supplemented rotifers were larger than control rotifers in their early stages of life, but both groups attained the same size by the end of their lifespan.

Animals↗
PubMed1983

Liver polyploidy: influence of age and of dietary restriction.

Polyploidy increases with age in mammalian liver. Since dietary restriction increases lifespan, the question posed in this study was whether liver polyploidy would be influenced by dietary protein restriction. Restricted mice were fed a 4% protein diet, while control mice received a 26% protein diet. Polyploidy was determined from measurements of nuclear diameter on liver of 3 week, 1 1/2, 3, 10, 20 and 24-1/2 month old Swiss albino mice. The percentage of polyploid cells increased steadily with age. The rate of increase, expressed as the polyploidization index, was greater in the fully fed control animals as compared to the animals on protein restriction. Protein restriction thus retards the age associated process of polyploidization of liver nuclei. Nuclear diameter increased slightly with age, but was not influenced by protein restriction.

Aging↗
PubMed1982

The effect of temperature and of dietary restriction on lifespan and reproduction in the rotifer Asplanchna brightwelli.

In this study, the effects of different environmental temperatures and of dietary restriction on the lifespan, reproductive cycle, and fecundity of the rotifer Asplanchna brightwelli were examined. When temperature effects were analyzed, it was observed that the mean lifespan and the times at which the reproductive cycle started and ended all increased as environmental temperatures decreased. When dietary restriction was imposed by increasing the interval between feeding times from 12 to 36 hours, there was an increase both in the mean lifespan and in the length of the reproductive period in this rotifer.

Animals↗
PubMed1982

Maternal age and lifespan do not influence longevity in the rotifer Asplanchna brightwelli.

An analysis of the mean lifespans among the progeny of the viviparous rotifer Asplanchna brightwelli produced during four generations has revealed that longevity of the offspring is not affected by maternal age of the parent or by the parent's lifespan. The production of viable offspring at any time during the parent's reproductive period may be of importance in assuring the continuity of clones of this short-lived rotifer species.

Animals↗
PubMed1982

The effect of dietary restriction on cell division potential, DNA content and enzyme levels in the rotifer Asplanchna brightwelli.

Dietary restriction in the rotifer Asplanchna brightwelli, carried out by lengthening the interval between feedings, causes an increase both in mean lifespan and in the length of the reproductive period. In the present study, we found that the rate of nuclear division in the gastric glands and vitellarium of the rotifer, as determined by daily nuclear counts, was retarded by dietary restriction. Spectro-fluorimetric measurements show that total DNA content remains constant from the beginning to the end of the lifespan, and is unaffected by dietary restriction. Lactic dehydrogenase and malic dehydrogenase activities were also measured throughout the lifespan of the rotifer, and were not affected by dietary restriction.

Aging↗