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L F Saugstad

Publications and source records attributed to L F Saugstad.

32 records · Page 2Linked to original sources
PubMed1977

Heterozygote advantage for the phenylketonuria allele.

Mean weight at birth of unaffected (normal homozygous and PKU heterozygous) offspring of parents heterozygous for the phenylketonuria (PKU) allele averages significantly above that of Norwegian neonates, with no significant difference in mean age of mothers or in mean parity. It approaches the optimal birthweight--that which confers the minimum overall mortality in the pre-, peri-, and postnatal periods. This near-optimal birthweight together with the possibly higher effective fertility observed in PKU heterozygous couples (at least in those who married before 1940), has apparently more than outweighed the disadvantages of the allele in PKU homozygous offspring as shown, for example, in an excessive number of pre- and perinatal deaths among the total offspring of PKU heterozygotes, to say nothing of the PKU survivors who, often, used to die young. The two effects--fertility and viability--apparently both contribute in the same direction, to give a biological fitness in excess of 1 for the heterozygote. This heterozygote advantage presumably explains the presence of the allele at frequencies above those to be expected from the simple replacement of a homozygously-lethal allele by mutation alone.

Alleles↗
PubMed1977

Predominance of extreme geographical proximity of the spouses of heirs to independent farms in a mountain valley in Norway between 1600 and 1850.

The marriages contracted between 1600 and 1850 in the parishes Vang and Slidre in the mountain valley of Valdres in Norway were investigated, using the information in the genealogical and local history of the parishes and in various public archives. The parishes functioned as a marriage isolate, in spite of regular communication with neighbouring districts. Only 54 of 4334 marriages were with residents outside the parishes, and marriages with a non-farming class (clergy) were as rare (47); 1130 marriages were probably between offspring of crofters and independent farmers. The further analysis concerns 3103 marriages contracted by the eldest sons and other heirs to 463 of the 493 farms, with members of the farming class within the parishes. Because of the linear settlement with clusters of same-named farms along both sides of the river, marital distance was measured by counting the number of farm-clusters (neighbourhood steps) between places of birth. In comparison with expectation when the marriage partner is chosen at random, marriages within the cluster occurred 13 times more frequently than expected, with an adjoining cluster 8 times more frequently and with a neighbour 1-2 clusters away 6 times as frequently as expected. One-third of the 3103 marriages were contracted within a distance of two clusters or less, and 60% eight clusters or less apart. A marital distance of 15 clusters (= 7 km) included 74% of the marriages. The predominance of a marriage pattern based on such geographical proximity must necessarily imply similarity in genetic structure of the descendants. Close consanguineous mating was apparently consciously avoided. This extreme geographical proximity of the spouses of heirs to the independent farms is probably explained by the function of a marriage as a contract to benefit the farm: promoting good neighbourliness and preventing quarrels and lawsuits related to the already very complicated ownership of cultivated land.

Female↗
PubMed1977

Inbreeding in Norway.

In Norway specified information of marriages between second cousins and closer relations has been recorded in the marriage certificates since January 1889. In addition, information was collected in the 1891 census and in the Medical Registration of Births (established in 1967). A ratio of second- to first-cousin marriages equal to or greater than 2 has been taken as some evidence indicating reliability of the source of data. Using this criterion, the information in the Medical Registration of Births seems most reliable, and that in the 1891 census possibly of similar accuracy. On the other hand, from 1890 the marriage certificates are unreliable with regard to the proportion of second-cousin marriages (ratio less than 1), and with regard to the proportion of first-cousin marriages from 1919. The present inbreeding in Norway is low (alpha4 = 0-000242), approximately one-eighth of the estimated level according to the 1891 census. The greatest reduction in inbreeding probably occurred after 1920.

Consanguinity↗
PubMed1975

Frequency of phenylketonuria in Norway.

By January 1973, a total of 146 homozygotes (born between 1875 and 1972) for phenylketonuria (PKU) had been identified in Norway. This is an incomplete total, particularly in respect of PKU cases born before 1950, because of the PKU mortality rate. Between 1951 and 1972, the observed incidence of PKU was unchanged at 0.07 plus and minus 0.01 per 1000 live births. Haematological screening of about one-third of all births in Norway between 1966 and 1972 indicated an incidence of 0.07 plus and minus 0.02 per 1000 liveborn screened. As expected, this was well below the observed incidence of 0.11 plus and minus 0.01 per 1000 from screening data from Denmark, and considerably higher than the observed value of 0.03 plus and minus 0.01 per 1000 screened in Sweden. In comparison, indirect estimates, using the inbreeding coefficent of parents of PKUs and that of the general population in Norway in the corresponding years (1874-1972), suggested a fall in incidence of PKU in Norway from 0.14 plus and minus 0.15 per 1000 live births in 1918, to 0.08 plus and minus 0.08 per 1000 in 1941, and to 0.06 plus and minus 0.06 per 1000 live births in 1972. The present level of inbreeding in Norway (obtained from the Medical Registration of Bith) is discussed and compared with information in the 1891 census, with the parish registers between 1889and 1902, and with the parochial lists for the years 1903-1941.

Adolescent↗
PubMed1975

Anthropological significance of phenylketonuria.

The highest incidence rates of phenylketonuria (PKU) have been observed in Ireland and Scotlant. Parents heterozygous for PKU in Norway differ significantly from the general population in the Rhesus, Kell and PGM systems. The parents investigated showed an excess of Rh negative, Kell plus and PGM type 1 individuals, which makes them similar to the present populations in Ireland and Scotlant. It is postulated that the heterozygotes for PKU in Norway are descended from a completely assimilated sub-population of Celtic origin, who came or were brought here, 1ooo years ago. Bronze objects of Western European (Scottish, Irish) origin, found in Viking graves widely distributed in Norway, have been taken as evidence of Vikings returning with loot (including a number of Celts) from Western Viking settlements. The continuity of residence since the Viking age in most habitable parts of Norway, and what seems to be a nearly complete regional relationship between the sites where Viking graves contain western imported objects and the birthplaces of grandparents of PKUs identified in Norway, lend further support to the hypothesis that the heterozygotes for PKU in Norway are descended from a completely assimilated subpopulation. The remarkable resemblance between Iceland and Ireland, in respect of several genetic markers (including the Rhesus, PGM and Kell systems), is considered to be an expression of a similar proportion of people of Celtic origin in each of the two countries. Their identical, high incidence rates of PKU are regarded as further evidence of this. The significant decline in the incidence of PKU when one passes from Ireland, Scotland and Iceland, to Denmark and on to Norway and Sweden, is therefore explained as being related to a reduction in the proportion of inhabitants of Celtic extraction in the respective populations.

ABO Blood-Group System↗