Population Life Tables Research Articles

Studies in aging. VI. Genes, developmental environment, and the expression of aging processes in Drosophila melanogaster.

The physiological performance of organisms is conditioned by their genotypes. It can be modified by interfering with the environment. Attempts have been made to study the effects of developmental environment on the adult physiology. Individuals of a known genotype were allowed to undergo embryonic or postembryonic development in different environments and the physiological effects on adult populations were studied under the normal or changed environmental conditions (there are recent reviews 2 and more recent studies3' 4). One of the main purposes of such studies is, and should be, to arrive at an understanding of the relationship that exists between development and aging. So far little insight has been gained into this relationship, let alone into the genetic mechanisms which are involved during development and which influence the physiology of adults. In the present experiments, a modest attempt has been made in this direction. Inbred and outbred populations of Drosophila have been allowed to develop in a changed environment, the effects of which have been studied by measuring the imaginal life span and fecundity under the normal environmental conditions. Thus, by observing the variation in the physiological parameters measured, the nature of relationship between the gene-controlled developmental processes and aging is deduced. Some of the experimental results have been described earlier.' Materials and Methods.-The Swedish-b8, Samarkand, and Canton-S inbred lines, kept in sib-matings for over 50, 200, and 30 generations, respectively, were employed. Two series of experiments were performed. In series I, the three synchronous experimental populations consisted of the Swedish-b8 and Samarkand inbred lines, and of a hybrid obtained by crossing Swedish-b8 females with Samarkand males. Series II consisted of only a hybrid that was raised asynchronously with populations in series I by crossing Swedish-b' females with Canton-S males. For brevity, the two inbred lines and the two first-generation hybrid populations will be referred to as Sw, Sam, Hy, and HY, respectiely. Parental populations were kept, in pairs, in food vials for 3-4 days after emergence at 25 + 1.00?C; thereafter each population was divided at random into two groups: one group was permitted to lay eggs at 16 i 1.00?C, and the other, at 25 4- 1.00?C. The offspring consisted of 4-7-day-old fertilized females allowed to lay eggs individually over 24-hr periods in half-pint milk bottles containing a medium of cornmeal, agar, and molasses, to which a suspension of living yeast was added. In series I, the eclosion times of individuals of both sexes at a lower, L, and at the normal, N, temperatures were recorded every day during the emergence periods. Individuals emerging within 3-7 days of the period of eclosion were collected, in pairs, in vials fitted with dual-purpose plastic stoppers containing the food medium. Additional males from each population were also obtained to serve as reserves. The two sets of each population, one that had developed at temperature L, and the other at N, were kept on the same shelf of the incubator at 25 i 1.00?C. The life tables for various populations were prepared by recording the number of deaths daily. In those vials in which males

Method of Construction of Attrition Life Tables for the Single Population Based on Two Successive Censuses

Abstract This paper describes a method of estimating the number of marriages during an inter-censal period among a group of never-married persons. Two alternative procedures are suggested: the first based on data on the never-married category and the second based on data on the ever-married category. The essential data needed are marital distributions by quinquennial age-groups from two successive censuses. The marital data from the 1951 and 1961 censuses of India are used to discuss the methodological problems involved in the estimation of marriage frequencies and in the construction of nuptiality tables based on them. Marriage and death are taken as the two attrition factors for decrement of single population. Gross and Net Attrition Tables for the single population of India are constructed for each sex. Section 5 describes various nuptiality measures derived from the Attrition Tables. It is suggested that the approach developed in this paper can be utilized for reliable marital and, subsequently, ferti...

Validity of centenarian data in the 1960 Census

This paper examines the question of how many genuine centenarians there actually are in the United States as compared with those reported in the census. It is concluded that the numbers of centenarians shown in various United States censuses are definite overstatements of the number of true centenarians. It seems likely that instead of the 10,326 centenarians reported in the 1960 census there were at most only about 3,700. Overstatement of ages seems to be particularly the case among those who claim to be aged 110 or over, and it is believed that there probably are no persons who are actually this old.The analysis has been made by projecting, through the me of population life table survival factors, the populations reported cit carious advanced age groups in one census to the next census and then comparing the results with the corresponding number reported in the latter census for the same age cohort. In general, the enumerated populations at ages below 95 are reasonably close to the projected populations, especially for white persons. On the other hand, at ages 95 and over-especially for centenarians-the enumerated populations significantly exceed the projected ones.As a subsidiary part of the analysis, the paper points out the significant differences at the older ages between the "full count" age distribution in the 1960 census and the corresponding "inflated 25 per cent sample" one. This is a subject that bears further investigation and explanation.The paper also discusses centenarians on the social security benefit rolls and concludes that the present data cannot be considered of substantial accuracy with regard to genuine centenarians, particularly the oldest ones. In a number of years, however, this program will provide excellent data, became the individuals involved will have been on the benefit rolls for many years and will have had their ages proved with reasonable accuracy.

On the Expectation of Life in the Late Tokugawa Period

No life table for the Japanese people before the Meiji Period has been constructed. Professor Naotaro Sekiyama recorded some tables of deaths by sex and age for some rural villages of Japan in the Tokugawa Period, in his KINSEI NIHONJINKO NO KENKYU (Studies on the Japanese population in pre-modern times). I found one of them suitable for constructing a life table. The material used is from the death records of inhabitants of Toraiwa Mura, Nagano Prefecture (Central Japan). The period when the deaths were recorded is from 1812 to 1815.The original data are shown in Table 1. Infant death records have usually many omissions in such old records, and Professor Sekiyama also pointed out serious omissions in infant death records of Toraiwa Mura. By complementing the deaths under 5 years as shown in Table 2, the total deaths may be given as 105 (males) and 95 (females). Using males for purposes of illustration, the life table for Toraiwa Mura was constructed as follows; starting with a population of 105, which I have called l″(0) (Table 3), 24 died before completing the first year, therefore 81, or l″(1), completed the first year; of the surviving 81, four died before completing the second year, therefore 77, or l″(2), completed the second year, and so on. Thus l″(x) was given as shown in Table 3. Then, I considered l″(0) as 1, 000, and computed the number surviving to the exact age x out of 1, 000 born alive, or l'(x) (Table 3). This l'(x) was graduated by two cubic curves and a Gompertz-Makeham's curve. The graduated number surviving l(x) is shown in Table 4. Based on this l(x) a life table was constructed as in Table 5. As to females the same methods were used.The expectation of life at birth is 36.8 years (males) and 36.5 years (females). This is about 6 (males) or 8 (females) years smaller than that of the first Life Table of Japanese population (1891-98). But as to the age period. 15-70 years, there are only a few differences between these two tables. At 75 and over the expectation of life of Toraiwa Mura was somewhat less.