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Linear growth in the early neonatal period
71 Stevens, J.C., Webb, H.D., Smith, M.E., Buffin, J.T. and Ruddy, H. (1987): Clin. Physiol. Meas., 8, 95-104. Kemp, D., Bray, P., Alexander, L. and Brown, A.M. (1986): Stand. Audiol., Suppl. 25. Stevens, J.C. (1987): Br. J. Audiol., 22, 45-49.
Pinsma rerdn and renin substrate concentrations
in the very premature
and T.J. Stephenson’, Department of Obstetrics Health, Queen’s Medical Centre, Nottingham, U.K.
and Gynaecology
buman baby. F.B. Pipkin and *Department of Child
The renin-angiotension system (RAS) may be of greatest significance in cardiovascular homeostasis in fetal and newborn animals. The limited studies of the RAS in the premature human infant have concentrated on plasma renin activity, a measure of the blood’s capacity to generate angiotensin I, and have not examined enzyme (PRC) and substrate (PRS) separately. These are under different control mechanisms about which nothing is known at this age. We are therefore studying the RAS in infants beween 24 and 34 weeks gestation during the first postnatal week in whom blood sampling is being undertaken for clinical indications. Data from 37 samples are available at present, of which 28 are paired from 14 babies at a 48-h interval. Mean birthweight is 1.33 + 0.40 kg (mean f S.E.M.) at a gestation age of 29.8 f 2.5 weeks. PRC is grossly raised in these babies (range 12-300 ng ml-l h-l compared with 1.0-4.5 ng ml-l h-l in adults) and is inversely proportional to gestation age (GA; r = -0.37, P = 0.026). PRS is also raised, but to a lesser extent (range 0.7-15.9 c(g ml-l cf 0.1-4.0 pg ml-‘) and rises with GA (r = 0.48, P = 0.003). It seems probable that PRS is rate-limiting under these circumstances. Neither PRC nor PRS differed in spontaneously-premature, compared with the other babies. There was a strong inverse correlation between log,,, PRC (LPRC) and the haemoglobin concentration (r = -0.56, P = 0.001). Haemorrhage is known to be a potent stimulus to the RAS. A high Fr. Na excretion was associated with significantly-raised LPRC both overall (r = 0.67, P = 0.005) and in the spontaneously premature infants (r = 0.96, P = 0.002); the macula densa is thus functional at this age, although subsequent reabsorption does not take place. Log,,, PRS is inversely proportional to FE, high FE, the PRS is being utilized in the production of angiotensin and hence aldosterone.
Linear growth in the early neonatal period. N. Bishop, F. King, A. Lucas, MRC Dunn Nutrition
Unit, Cambridge, U.K. Changes in body weight after birth are well documented, yet there is little corresponding information on linear growth. Such data are required to understand the control of somatic growth and the specific nutrient needs of infants during the period of intensive adaptation post partum. Crown-heel length, ulna length, weight and occipitofrontal circumference was measured daily for up to 8 days in 45 infants of appropriate weight for gestation. There was a mean weight loss of 205 (S.E. 10) g, corresponding to a mean decrease in body weight of 6%; there was also an initial decrease in head circumference. Despite this, crown-heel and ulna length increased rapidly and linearly from the first day of age, with mean gains during the first week of 11.5 mm (S.E. 1.3 mm; mean Vo increase in length 2.5%) and 2.5 mm (S.E. 0.5 mm; increase 3%). The observed rate of skeletal growth in the first week, which is similar to that described in the third trimester, represents the most rapid rate found ex utero, yet it occurs at a time when nutrient supply has fallen abruptly. These data suggest that linear growth is ‘programmed’ to continue after birth despite faltering in body weight, and that skeletal growth may be fuelled at the expense of other body tissues.
Pinsma rerdn and renin substrate concentrations
in the very premature
and T.J. Stephenson’, Department of Obstetrics Health, Queen’s Medical Centre, Nottingham, U.K.
and Gynaecology
buman baby. F.B. Pipkin and *Department of Child
The renin-angiotension system (RAS) may be of greatest significance in cardiovascular homeostasis in fetal and newborn animals. The limited studies of the RAS in the premature human infant have concentrated on plasma renin activity, a measure of the blood’s capacity to generate angiotensin I, and have not examined enzyme (PRC) and substrate (PRS) separately. These are under different control mechanisms about which nothing is known at this age. We are therefore studying the RAS in infants beween 24 and 34 weeks gestation during the first postnatal week in whom blood sampling is being undertaken for clinical indications. Data from 37 samples are available at present, of which 28 are paired from 14 babies at a 48-h interval. Mean birthweight is 1.33 + 0.40 kg (mean f S.E.M.) at a gestation age of 29.8 f 2.5 weeks. PRC is grossly raised in these babies (range 12-300 ng ml-l h-l compared with 1.0-4.5 ng ml-l h-l in adults) and is inversely proportional to gestation age (GA; r = -0.37, P = 0.026). PRS is also raised, but to a lesser extent (range 0.7-15.9 c(g ml-l cf 0.1-4.0 pg ml-‘) and rises with GA (r = 0.48, P = 0.003). It seems probable that PRS is rate-limiting under these circumstances. Neither PRC nor PRS differed in spontaneously-premature, compared with the other babies. There was a strong inverse correlation between log,,, PRC (LPRC) and the haemoglobin concentration (r = -0.56, P = 0.001). Haemorrhage is known to be a potent stimulus to the RAS. A high Fr. Na excretion was associated with significantly-raised LPRC both overall (r = 0.67, P = 0.005) and in the spontaneously premature infants (r = 0.96, P = 0.002); the macula densa is thus functional at this age, although subsequent reabsorption does not take place. Log,,, PRS is inversely proportional to FE, high FE, the PRS is being utilized in the production of angiotensin and hence aldosterone.
Linear growth in the early neonatal period. N. Bishop, F. King, A. Lucas, MRC Dunn Nutrition
Unit, Cambridge, U.K. Changes in body weight after birth are well documented, yet there is little corresponding information on linear growth. Such data are required to understand the control of somatic growth and the specific nutrient needs of infants during the period of intensive adaptation post partum. Crown-heel length, ulna length, weight and occipitofrontal circumference was measured daily for up to 8 days in 45 infants of appropriate weight for gestation. There was a mean weight loss of 205 (S.E. 10) g, corresponding to a mean decrease in body weight of 6%; there was also an initial decrease in head circumference. Despite this, crown-heel and ulna length increased rapidly and linearly from the first day of age, with mean gains during the first week of 11.5 mm (S.E. 1.3 mm; mean Vo increase in length 2.5%) and 2.5 mm (S.E. 0.5 mm; increase 3%). The observed rate of skeletal growth in the first week, which is similar to that described in the third trimester, represents the most rapid rate found ex utero, yet it occurs at a time when nutrient supply has fallen abruptly. These data suggest that linear growth is ‘programmed’ to continue after birth despite faltering in body weight, and that skeletal growth may be fuelled at the expense of other body tissues.