Maturation of Thermoregulatory and Thermogenic Mechanisms in Fetal Sheep

Gluckman, P. D.; Gunn, Tania R.; Johnston, Barbara M.; Power, GG; Ball, K. T.

doi:10.1007/978-3-642-72975-1_26

Cited by 3 publications

(2 citation statements)

References 10 publications

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“…1984;GUM et af. 1985) but show little evidence of increased heat production (Gluckman et al 1985;Power 1989), partly because of the low foetal oxygen tensions (Power et al 1986;Power 1989), and possibly also through the action of a putative inhibitor of thermogenesis thought to be produced by the placenta (Gluckman et al 1988;Power 1989). The existence of such a placental inhibitor is an attractive idea, first because it would ensure that heat production remains low in utero, thereby reducing the thermogenic load on the mother and conserving foetal energy reserves required for heat production after birth; secondly because severance of the umbilical cord at birth would remove the source of such an inhibitor and allow appropriate thermogenic responses.…”

Section: Foetal Thermogenesismentioning

confidence: 99%

Some aspects of perinatal maturation and adaptation

Mellor

1993

Equine Veterinary Journal

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Physiological challenges facing the perinatal individual are huge. This is partly because of the marked and abrupt change from the intrauterine to the extrauterine environment, but also because the physiological responses to that change depend upon systems whose maturation is affected markedly by birth. Perinatal maturation appears, therefore, both to precede and accompany the physiological adaptations required for neonatal survival. This review does not provide a comprehensive coverage of perinatal physiology but directs attention towards evaluating constraints on foetal and neonatal thermogenesis, especially those imposed by postnatal availability of metabolic fuels in body reserves deposited before birth and acquired in colostrum and milk after birth. The relative importance of the supply of carbohydrate from body reserves and colostrum is examined. Carbohydrate is the major rate-limiting substrate with respect to heat production. It is shown that in the normal birth environments of several species, including the horse, colostral supply of lactose is not adequate to meet the entire carbohydrate needs of the neonate. It must, therefore, draw on its body glycogen reserves to sustain the required rates of heat production during the first day after birth. Gastrointestinal maturation and growth play a major part in the initial and continued provision of substrates for general metabolism and growth. Pre-natal and post-natal development of the stomach and intestines in a number of species are considered, including their disproportionately large growth compared with the body as a whole during the first 1-3 days after birth. Possible contributions to gastro intestinal growth and body growth of milk-borne growth factors such as epidermal growth factors and the insulin-like growth factors are considered. The role, as a possible significant stimulus to gastrointestinal growth and maturation immediately after birth, of the high levels of these growth factors in colostrum is evaluated. References Alexander, G. (1962) Temperature regulation in the new-born lamb. IV. The effect of wind and evaporation of water from the coat on metabolic rate and body temperature. Ausr J. agr. Res. 13. 82-99. Alexander. G. (1979) Cold thermogenesis. Inf. Rev. Physiol. environ. Physiol. Ill. 20, 43-155. Alexander, G. and Williams, D. (1968) Shivering and non-shivering thennogenesis during summit metabolism in young lambs. Stimulatory effects of epidermal growth factor on deoxyribonucleic acid synthesis in the gasmintestinal tract of the suckling mouse. Comp. Biochem. Physiol. 868, 123-127. Asplund, J.M., Grummer, R.H. and Phillips, P.H. (1962) Absorption of colostral gamma-globalins and insulin by the newborn pig. Immunoreactive somatomedii-C/insulin-lie growth factor I and its binding protein in human milk. J. clin. Endocr. 58,955-959. Bell, A.W., Cranwell, P.D. and Hansky, J. (1984) Plasma gastrin in the foetal and neonatal lamb and the pregnant and lactating ewe. Can. J . Anim. Sci. 64, (Suppl.) 97-99. Berseth, C.L. (1987) Enhancement of int...

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Section: Foetal Thermogenesismentioning

confidence: 99%

Some aspects of perinatal maturation and adaptation

Mellor

1993

Equine Veterinary Journal

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“…All these data showed that adaptation to low environmental temperature exists even among mammalian embryos at different stages of their development, and this phenomenon might be considered as persisting from embryos of lower vertebrates. It seems that adaptation to hypothermia at early developmental stages reflects, perhaps, the cell resistance to low temperature because the central mechanisms for responding to a cold stress have differentiated well only at the late stages of foetal development (Bruck, 1988;Gluckman et al, 1988;Zeisberger & Roth, 1988).…”

Section: Embryonic Resistance To Chemical and Physical Factorsmentioning

confidence: 99%

Embryonic Resistance to Chemical and Physical Factors: Manifestation, Mechanism, Role in Reproduction and in Adaptation to Ecology

Zusman

Ornoy²

1990

Biological Reviews

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Chemical and physical factors may adversely affect embryonic development. As an example of chemical factors, the effects of diabetic metabolic factors on embryonic development in mammals was reviewed. The existence of a stage-dependent reaction of embryos was found. At preimplantation stages diabetic metabolic factors are embryotoxic and lethal, and the blastocysts reacted by an "all-or-none" response. Early somite embryos showed a higher resistance to the effects of diabetic metabolic factors resulting in various types of malformations. Both groups of embryos showed a very high sensitivity to the effects of combined diabetic metabolic factors. Congenital defects in term foetuses were lower than those observed during middle phases of pregnancy because some of the severely malformed embryos resorb during gestation. The effects of temperature on embryonic development were presented as an example of physical influences. In man, hyperthermia in pregnancy seems to correlate with defects in the development of the nervous and skeletal systems. In domestic animals, changes in environmental temperature correlated with depressions of reproduction rate. In laboratory animals, hyperthermia caused the development of congenital malformations. Stage-dependent as well as genetic differences in embryonic susceptibility to hyperthermia were found. Critical periods in sensitivity of embryos to hyperthermic influences were also observed. It has been shown that, in spite of similar external manifestations of the reaction of embryos to effects of diabetes and hyperthermia, the mechanism of these reactions was different. High resistance of early reptile and bird embryos to influences of temperature was considered as an example of morphofunctional adaptations in early embryogenesis of vertebrates to their development in terrestrial conditions.

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Growth Hormone and Prolactin

Gluckman¹,

Pinal²

2004

Fetal and Neonatal Physiology

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Maturation of Thermoregulatory and Thermogenic Mechanisms in Fetal Sheep

Cited by 3 publications

References 10 publications

Some aspects of perinatal maturation and adaptation

Some aspects of perinatal maturation and adaptation

Embryonic Resistance to Chemical and Physical Factors: Manifestation, Mechanism, Role in Reproduction and in Adaptation to Ecology

Growth Hormone and Prolactin

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