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Biomedical subjects

E J Clegg

Publications and source records attributed to E J Clegg.

At least 19 recordsLinked to original sources
PubMed2001

Starting, spacing and stopping in the reproductive histories of outer Hebridean families.

Maternal ages at the first maternity (starting), at the last maternity (stopping) and the lengths of intervals between maternities (spacing) have been studied in the Outer Hebridean islands of Harris and Barra for births between the years of 1855 and 1990, a period during which a considerable 'fertility transition' occurred. There was a tendency in each island for increases with time in the ages at starting among less-fecund women (although after 1936 starting ages declined), and highly significant heterogeneity of covariance: adjusted means dependent on the total numbers of maternities experienced. The same result was seen for the ages at stopping. Lengths of reproductive life (the difference between ages at starting and stopping) rose to 1876-1895, and then fell, apart from a short-lived rise in Barra during 1956-1975, possibly due to the papal encyclical Humaneae Vitae. Intervals between marriage and first maternity and between successive maternities were studied by hazard function survival analysis. The marriage first birth interval remained very constant, unaffected by total maternities. The father's occupation and the mother's age at first maternity showed no significant relationships. In Barra there was a weak negative relationship with the date of the marriage. For intervals between maternities in both islands, total maternities and the death of a previous infant were associated with shorter, and birth order with longer intervals. In Harris, there were tendencies for intervals to be consistently long or short in families, and for the age of the mother and date at first maternity to be negatively related to the length of the interval. In Barra, a previous multiple birth was followed by a longer interval. The date of the previous maternity, father's occupation, maternal age at the previous maternity, the sex of the previous child, and the duration of the marriage appeared to have no influence on maternity intervals. Evidence for an effect of economic deprivation during the 19th century on the variables considered was equivocal. During the 20th century, it is suggested that economic depression during the inter-war years, the spread of contraception, and improvements in health care may have acted 'synergistically' to produce the lower ages of childbearing and the shortening of maternity intervals and reproductive lives.

Adolescent↗
PubMed1999

Probabilities of marriage in two outer Hebridean islands, 1861-1990.

A study has been made of the probabilities of marriage of females and males aged 15-49 (either as a whole or in 5-year age groups) in two Outer Hebridean islands, Harris and Barra. The results were compared with ages of marriage and with the frequencies of permanent celibacy. The marriages took place between 1861 and 1990. Median ages of marriage rose to maxima in the 1930s and 1940s, then fell steeply, levelling out latterly. Permanent celibacy was consistently high among females, but rose from much lower levels in males to maxima in the 1970s and 1980s. It is concluded that in these populations age at marriage and the extent of permanent celibacy are largely independent of one another. In both islands the overall probabilities of females marrying fell until the 1920s, and then rose. The last decades showed stability (Barra) and a fall (Harris). Males showed only slight falls to about 1910; data were absent for between 1911 and 1960, but subsequently there was little rise in probability. These overall changes seemed to be associated with reciprocal variations in probabilities in the younger and older age groups. Declining overall probabilities were associated with declines in younger and increases in older age-group probabilities, and vice versa. Non-parametric correlations between median ages of marriage and probability of marriage were negative and generally significant for the 15-19 age group. Among the older age groups coefficients were generally positive. There was some evidence of an association between probability of marriage and sex ratio in any group of potential mates. The effect appeared more marked among 15- to 19-year-old females. Local factors which might explain at least part of the decline in nuptiality for the greater part of the period under study include the decline in the fishing industry and the 'land hunger' which existed until the late 1920s. This decline is interpreted as a 'Malthusian' response to economic and social conditions, but it coexisted with a 'neo-Malthusian' strategy, in the shape of declining marital fertility. The 'Malthusian' strategy seems to have been largely abandoned around the 1950s, but it may have reappeared during the 1980s.

Adolescent↗
PubMed1998

Some factors affecting marital distances in the Outer Hebrides.

Some factors affecting marital distances have been studied in two Outer Hebridean islands, Harris (843 marriages) and Barra (444 marriages), over the period 1855-1990. In each island marital distances fell before 1900, but then rose to their greatest values after the 1950s. Fisherman generally married at the shortest distances and men in land-based occupations at the longest. The depression in the fishing industry during the 1880s and early 1890s was associated with reductions in marital distances, especially among fisherman. In the different regions of Harris, marital distances were least in the south-east, where settlement was most dense, and greatest in the south-west where it was most sparse. When the association between marital frequencies and inter-settlement distances was studied, it was found that for Harris there was, overall, a trend to endogamous and short-distance marriage. However, this trend was only slight during 1955-90. For Barra a similar trend was found before 1955, but thereafter there appeared to be virtually no connection between marital frequency and inter-settlement distance. Thus the only constraint on marriage was the spatial distribution of settlements. In this situation the chances of random mating with respect to distance are maximised. Application of 'Central Place' theory suggested that only since 1946 can any tendency be detected to regard Tarbert in Harris or Castlebay in Barra as Central Places, at least as far as marriage is concerned. In each island the tendency appears to be limited to the settlements closest to the Central Place.

Demography↗
PubMed1995

Religion and fertility in the Outer Hebrides.

Estimates of fertility in Protestant Barra and Catholic Harris, islands in the Outer Hebrides, over the period 1856-1985, show that in both islands fertility declined, although marital fertility was generally greater than in Scotland as a whole, and illegitimate fertility was less. However, in Barra during 1966-75 there were pronounced rises in all the indices; illegitimate fertility showed the smallest rise. The publication of the papal encyclical Humanae Vitae may have played a part in this change in fertility, although other, probably local, factors must have been acting, as the first rise in numbers of births occurred before the publication of the encyclical. Other than this transient rise, the religious difference between Harris and Barra had little effect on changes in fertility over the whole period. Indices of proportions married showed declines until after World War 2, followed by steep increases. The marked decline in fertility in both islands may be due in part to this low nuptiality. In addition, a trend of occupation away from traditional crofting and fishing towards more skilled mercantile and professional employment may have played a role.

Adolescent↗
PubMed1994

Aspects of neonatal death in St Kilda, 1830-1930.

Neonatal death (mainly due to tetanus) was common in St Kilda until 1891. Two aspects of this phenomenon are studied; factors which predicted death, and the impact of neonatal death on family building. Maternal age appeared to be a predictive factor for death of the first child, but only in children of high birth order were other factors, particularly the number of previous neonatal deaths, important. The first birth interval appeared to be determined mainly by the date of the first birth, independent of neonatal mortality levels. For later intervals, the neonatal death of the previous child appeared to be the main determining factor.

Birth Intervals↗
PubMed1983

Morphometric studies of the spleen of the hypoxic mouse.

Adult male mice were exposed for periods of up to 7 days at atmospheric pressures of either 72 or 52 kPa (540 or 390 mm mercury). Changes in body weights, spleen weights and red and white splenic pulp weights were compared with those in normoxic controls. Contrary to expectation, spleen weights and amounts of red pulp were greater (in terms of experimental-control differences) in the animals kept at 72 kPa, suggesting that at 52 kPa loss of overall fitness reduced the adaptive erythropoietic response. However, in view of the fact that increased erythropoiesis has disadvantages as well as advantages, the lesser response at the lower pressure may not be wholly disadvantageous. Coefficients of variation of the spleen variables examined showed a tendency to decrease in the animals at 72 kPa, but rose markedly at 52 kPa. This finding was interpreted as indicating that at 72 kPa spleen and red pulp changes are adaptive, but at 52 kPa they indicate an overall relative failure of adaptive mechanisms, with consequent reduced somatic fitness.

Animals↗
PubMed1979

The survival and implantation of mouse blastocysts at varying degrees of reduced atmospheric pressure.

Pregnant mice were exposed to reduced atmospheric pressures ranging from 630 to 390 mm Hg during the pre-implantation and implantation periods and the numbers of embryos surviving 85 hours post coitum compared with those in litter-mate controls. Even at a pressure of 630 mm Hg (= 1,550 mm Hg) there was a significant fall in numbers of normal blastocysts and rise in abnormal forms before implantation, and implantation sites were reduced in number. The numbers of abnormal forms increased and implantation sites decreased at lower pressures, suggesting strongly that the hypoxia of reduce atmospheric pressure was responsible for the abnormalities observed. The pre-implantation period appears to be one during which the fertilised ovum is at particular risk, both of hypoxic damage and of failure to implant. Implantation may afford a degree of protection against hypoxia.

Animals↗
PubMed1978

The influence of family characteristics on the heights, weights and skinfolds of highland and lowland children in Ethiopia.

In Ethiopian children residing at either high or low altitude, the relationship between growth (in stature, body weight and skinfold thickness) and age and family size (broken down into birth rank and number of younger sibs) was examined. Contrary to expectation, when children were grouped for similar ages, the impact of family characteristics appeared to be small. However, there was some evidence that among low-altitude girls, growth was significantly and positively related to the number of younger sibs. It is suggested tentatively that the relative lack of observed effects is due to the nuclear family being subsumed in a larger kinship group which forms the principal economic unit.

Adolescent↗