The phagocytic function of leucocytes in anæmia

Knott, F. A.; Hartfall, S. J.

doi:10.1002/path.1700350609

Cited by 4 publications

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“…(The fact that in the totals, mean litter weight is greater for litter orders 2-4 than for 5 and over reflects the difference in distribution by litter size.) The conclusion that length of gestation increases with parity is consistent with most reports on the cow [Knott, 1932;Braude & Walker, 1949], the horse [Mauch, 1937;Howell & Rollins, 1951], and the sheep [Terrill, 1944]. In man, with increasing parity, length of gestation was reported to increase in multiple pregnancy and to decrease slightly in single pregnancy [McKeown & Record, 1954].…”

supporting

confidence: 86%

The Influence of Litter Size and Litter Order on Length of Gestation and Early Postnatal Growth in the Guinea-Pig

McKeown¹,

MacMahon²

1956

Journal of Endocrinology

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The influence of litter size and litter order on length of gestation and early postnatal growth of offspring has been examined on records of sixty-six female guinea-pigs which delivered 440 litters.It is shown that:(a) The association between foetal weight and length of gestation is not the same for different litter sizes: in small litters weight increases with length of gestation; in large litters weight decreases. It is suggested that weight influences time of parturition in large litters, but not in small ones.(b) Length of gestation increases with litter order. This result is shown to be independent of litter size and weight.(c) As litter size increases, weight of young at 28 days after birth decreases, but rate of postnatal growth (weight at 28 days expressed as a percentage of birth weight) increases.(d) Rate of postnatal growth (to 28 days) is lowest for first-born young, increases after the first birth, and falls again after the fourth.Litter size and litter order are among the variables known to influence the maturity of the foetus at birth. This influence is manifested partly by an effect on the rate of jjrenatal growth, and partly by an effect on the length of gestation. Of these two effects, the second has had less attention than the first, and we here use data for the guinea-pig to examine the influence of litter size and order on duration of gestation. The observations include the weight of young at 28 days after birth, and so permit inspection of the effect of the two variables on early postnatal development.The data were made available to us by Dr I. W. Rowlands, who has described the methods used in their collection [1949]. In an investigation of economical breeding methods, female guinea-pigs were allowed to mate, deliver and rear their young in cages from which males were not removed. As a result animals usually became pregnant on the day on which they delivered a litter. Observations recorded included dates of delivery ; number, sex and weight of young at birth and at 28 days after birth. The data used in the present inquiry are derived from the breeding histories of sixtysix females kept in six pens. They had 440 litters.Length of gestation Duration of gestation is unknown in respect of first litters (time of mating was not recorded), and in respect of the subsequent 374 litters it is derived from the dates of consecutive deliveries. In sixty-eight pregnancies, for which the interval between consecutive deliveries was more than 71 days, it was assumed that animals had not

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supporting

confidence: 86%

The Influence of Litter Size and Litter Order on Length of Gestation and Early Postnatal Growth in the Guinea-Pig

McKeown¹,

MacMahon²

1956

Journal of Endocrinology

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“…That weight of foetus has relatively little influence on time of onset of calving is also suggested by the fact that gestation is only a little shorter in multiple than in single pregnancy [Knott, 1932], unlike man, in which the difference is marked.…”

Section: Discussionmentioning

confidence: 90%

“…2), and in the relative proportions of males and females delivered at different stages of gestation (see Fig. 7, which has been prepared from data published by Knott [1932]). …”

Section: Discussionmentioning

confidence: 99%

“…The most satisfactory data refer to the cow, in which a large number of investigations have indicated that pregnancy is longer for males than for females. The four largest series [Knott, 1932 ;Ineichen, 1946 ;Ward & Castle, 1947 ;Lazarus & Anantakrishnan, 1952] are each based on more than 1000 pregnancies, and suggest that the sex difference is about a day. There have been fewer reports on the horse, but they suggest that male pregnancies are a little more than a day longer than female pregnancies [Uppenborn, 1933;Staffe, 1934;Gonnerman, 1935;Mauch, 1937].…”

mentioning

confidence: 98%

“…7. Distribution of calves according to duration of gestation (from Knott, 1932). nearly be joined by a straight line.…”

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confidence: 98%

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Sex Differences in Length of Gestation in Mammals

McKeown¹,

MacMahon²

1956

Journal of Endocrinology

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Observations on length of gestation of males and females are presented for man, the guinea-pig, sheep, pig and rabbit; from the literature, data are also available for the cow, horse, camel and goat. Pregnancy is longer for males than for females in the cow, horse and possibly the sheep and camel; it is longer for females than for males in man and possibly the guinea-pig. No definite conclusion is reached about the pig and rabbit, in which litter-size is normally large, or about the goat, in which the number of observations on record is small. The sex differences in length of gestation are reflected in the sex ratios of offspring born after different periods of gestation, and in the percentage distribution of the sexes by duration of gestation.The difference in length of gestation can be attributed to a sex difference in foetal weight in man, but not in the guinea-pig or in species such as the cow, in which gestation is longer for males than for females. It is suggested that in the cow the longer male gestation may be due to the fact that the proportion of males conceived is higher if mating takes place early, rather than late, in heat. (The only alternative explanation is a sex difference, attributable to something other than weight of foetus, in the period between fertilization and birth.) In man the earlier birth of males is apparently due to their greater weight, attributable wholly or in part to a sex difference in rate of prenatal growth. This observation does not exclude the possibility that in man, as in the cow, the proportion of males conceived is higher if mating occurs early in the cycle, since the method of recording length of gestation (from onset of menstruation) gives no information about time of mating.Recorded sex differences in length of gestation in mammals are small, and no parti¬ cular significance has hitherto been attached to them. In man, for example, the mean period of gestation is shorter for males than for females, but the difference is only a fraction of a day, and has been generally regarded as of statistical rather than biological interest. Two observations suggested that the matter might be worth further investigation. The first was a fairly marked association, in the guinea-pig and in man, between length of gestation and sex ratio of offspring. The second was the fact that the relationship between sex and gestation is not the same in different species ; in the cow, for example, males are born later than females. This last observation suggested that in one species at least the sex difference in time of parturition could not be attributed to a sex difference in foetal weight (perhaps the most obvious explanation of the earlier birth of the human male foetus), and might be due to variation in the time of mating, rather than to variation in the interval between fertilization and birth. MATERIAL

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Physiologie der Leukocyten nach den Arbeiten von 1929–1940

Glanzmann¹

1941

Ergebnisse der Physiologie und exper. Pharmakologie

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The phagocytic function of leucocytes in anæmia

Cited by 4 publications

References 2 publications

The Influence of Litter Size and Litter Order on Length of Gestation and Early Postnatal Growth in the Guinea-Pig

The Influence of Litter Size and Litter Order on Length of Gestation and Early Postnatal Growth in the Guinea-Pig

Sex Differences in Length of Gestation in Mammals

Physiologie der Leukocyten nach den Arbeiten von 1929–1940

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