Christian Plath

Whole-body protein parameters in premature infants: a comparison of different 15N tracer substances and different methods.

[15N]glycine, [15N]leucine, and [15N]yeast protein thermitase hydrolysate (YPTH) as tracers for investigating the protein turnover rates in premature infants were studied in nine human milk-fed neonates (born after 32 to 34 wk of gestation) by paired comparison of the tracers. The 15N enrichment of total urinary nitrogen and ammonia after administration of a single oral dose of 15N was measured by emission spectrometry. Flux rates were calculated using a three-compartment model and the ammonia end product method. The mean whole-body protein synthesis rates, as determined by the three-compartment model derived from the three 15N tracers, differed significantly (p < 0.01) among [15N]glycine (15.9 g/kg/d), [15N] leucine (9.1 g/kg/d), and 15N-YPTH (5.9 g/kg/d). When the corresponding rates were determined from the excretion of label in ammonia, the results showed the opposite tendency; the lowest apparent synthesis rates were found after [15N]glycine (7.5 g/kg/d), followed by [15N]leucine (14.4 g/kg/d), and the highest figure resulted after [15N] YPTH (16.7 g/kg/d). The results of this comparison substantiate the assumption that there are methodologic errors in connection with the use of different tracers and models for the calculation of whole-body protein parameters in preterm infants, with respect to the main requirement for tracer kinetic studies; the tracer nitrogen must be representative of total amino acid nitrogen. Seen in this light, mixtures of completely labeled amino acids such as YPTH may represent the most reliable tracer substance. On the basis of the data obtained with 15N-labeled YPTH and with total 15N as the end product, there is no major difference in the order of magnitude of the protein flux between preterm and full-term infants.

15N tracer kinetic studies on the validity of various 15N tracer substances for determining whole-body protein parameters in very small preterm infants.

Reliable 15N tracer substances for tracer kinetic determination of whole-body protein parameters in very small preterm infants are still a matter of intensive research, especially after some doubts have been raised about the validity of [15N]glycine, a commonly used 15N tracer. Protein turnover, synthesis, breakdown, and further protein metabolism data were determined by a paired comparison in four preterm infants. Their post-conceptual age was 32.2 ± 0.8 weeks, and their body weight was 1670 ± 181 g. Tracer substances applied in this study were a [15N]amino acid mixture (Ia) and [15N]- glycine (Ib). In a second group of three infants with a post conceptual age of 15N-labeled 32.0 ± 1.0 weeks and a body weight of 1,907 ± 137 g, yeast protein hydrolysate (II) was used as a tracer substance. A three-pool model was employed for the analysis of the data. This model takes into account renal and fecal 15N losses after a single 15N pulse. Protein turnovers were as follows: 11.9 ± 3.1 g kg-1 d-1 (Ia), 16.2 ± 2.5 g kg-1 d-1 (Ib), and 10.8 ± 3.0 g kg-1 d-1 (II). We were able to demonstrate an over-estimation of the protein turnover when Ib was used. There was an expected correspondence in the results obtained from Ia and II. The 15N-labeled yeast protein hydrolysate is a relatively cheap tracer that allows reliable determination of whole-body protein parameters in very small preterm infants.

15N-tracer investigations into the nitrogen metabolism of preterm infants fed mother's milk and a formula diet.

Protein synthesis, protein breakdown, protein-N turnover, and other parameters describing the nitrogen metabolism were measured in five male preterm infants. The weight of the subjects at birth was 2,064 +/- 107 g and the measurements were performed at age 16.0 +/- 4.5 days in the case of the mothers milk diet and 27.4 +/- 6.8 days in the case of the formula diet containing 1.8% protein. The parameters were measured by means of the 15N-tracer technique using [15N]glycine (95 atom %) applied in a single oral dose of 20 mg/kg as a tracer. The three-pool model proposed by Winkler and Faust was used to calculate the whole body protein parameters. No difference in net protein gain, protein synthesis, protein breakdown, or the other protein metabolism parameters were recorded despite the different protein inputs. Renal nitrogen excretion and the rate of endogenous urea N excretion were significantly higher for the formula diet than for the mothers milk diet. The protein synthesis rate of 7.9 g X kg-1 X day-1 was, as has previously been observed, higher than in other age groups. The protein metabolism of the preterm infant older than 33 weeks of gestational age does not benefit from a formula diet based on cows milk that is richer in protein than mothers milk.

15N-tracer studies in formula-fed preterm infants: the role of glycine supply in protein turnover.

In preterm infants, protein-turnover rates obtained by [15N]glycine as a tracer are known to be overestimated. This may reflect the insufficient supply of dietary glycine. In this randomized study, the influence of a glycine-rich diet on whole body protein turnover rates in eight male preterm infants (29-32 weeks, 1,200-2,540 g birthweight) using the 15N-tracer technique on days 21 and 28 of life was investigated to evaluate the necessity of supplementing preterm infant formulas with proteins rich in glycine. Before and during the study, the infants were alternately fed with a commercial available preterm infant formula (I, 2% protein, 40 mg glycine/dl) and a variety of this formulation with glycine-rich proteins (II, 2% protein, 130 mg glycine/dl). The protein-turnover rates were computed after 15N-single-pulse labeling with the help of the three-compartment model (TCM) and the urinary ammonia end-product method (AEPM). The tracer used was [15N]glycine (dosage: 2 mg 15N/kg). For the determination of 15N-excess-excretion kinetics, fractionated urine specimens were collected over a 36-h period. The protein-turnover rate calculated by TCM was 8.8 +/- 1.6 g/kg/day (formula I) and 7.7 +/- 2.0 g/kg/day (formula II); using AEPM, the rate was 8.7 +/- 2.5 g/kg/day and 7.5 +/- 1.5 g/kg/day, respectively. We conclude that the presaturation of the precursor pool by an adequate glycine intake minimizes drawbacks that may arise when using [15N]-glycine as a tracer in preterm infants, and a protein concentration of 2%, as in formula I, and consequently, a 170% glycine content when compared with the same human milk volume, meets the glycine requirement.

Resistance of Bifidobacteria and Lactobacilli to tobramycin

Sir: The eradication of Bifidobacteria and other anaerobic micro-organisms of the intestinal microflora is an undesired and sometimes life-threatening side-effect of antibiotic treatment. The disappearance of these bacteria leads to the loss of colonization resistance which in turn is associated with the risk of adhesion and translocation of pathogenic germs [3]. We conducted studies on side-effects of penicillins, cephalosporins and other [3-1actam-antibi

Whole-body protein parameters in premature infants: a comparison of different 15N tracer substances and different methods

[15N]glycine, [15N]leucine, and [15N]yeast protein thermitase hydrolysate (YPTH) as tracers for investigating the protein turnover rates in premature infants were studied in nine human milk-fed neonates (born after 32 to 34 wk of gestation) by paired comparison of the tracers. The 15N enrichment of total urinary nitrogen and ammonia after administration of a single oral dose of 15N was measured by emission spectrometry. Flux rates were calculated using a three-compartment model and the ammonia end product method. The mean whole-body protein synthesis rates, as determined by the three-compartment model derived from the three 15N tracers, differed significantly (p less than 0.01) among [15N]glycine (15.9 g/kg/d), [15N] leucine (9.1 g/kg/d), and 15N-YPTH (5.9 g/kg/d). When the corresponding rates were determined from the excretion of label in ammonia, the results showed the opposite tendency; the lowest apparent synthesis rates were found after [15N]glycine (7.5 g/kg/d), followed by [15N]leucine (14.4 g/kg/d), and the highest figure resulted after [15N] YPTH (16.7 g/kg/d). The results of this comparison substantiate the assumption that there are methodologic errors in connection with the use of different tracers and models for the calculation of whole-body protein parameters in preterm infants, with respect to the main requirement for tracer kinetic studies; the tracer nitrogen must be representative of total amino acid nitrogen. Seen in this light, mixtures of completely labeled amino acids such as YPTH may represent the most reliable tracer substance.(ABSTRACT TRUNCATED AT 250 WORDS)

Die Peritonealdialyse zur Behandlung reifer und unreifer Neugeborener mit Atemnosyndrom

Some authors have recommended peritoneal dialysis to improve the therapy of the respiratory distress syndrome (RDS) of newborns. In 1968 we published a report estimated on a newborn suffering from RDS. As a pH of 6.73, was 2 hrs after birth, we administered standard therapy and peritoneal dialysis. The baby has survived and his development has been uneventful.This case and the results obtained by other authors in the treatment of RDS with peritoneal dialysis have led us to treat prematures and newborns suffering from severe RDS with peritoneal dialysis in addition to standard therapy (infusions of THAM, glucose, electrolytes, amino acids, administration of antibiotics and oxygen, and, when indicated, intermittent positive-pressure respiration). Peritoneal dialysis was carried out with bland hypertonic solution in continuous flow technics.We have treated 13 prematures and 1 newborn suffering from RDS and a premature suffering from erythroblastosis with hydrops and RDS. Except for the mature newborn, the gestational age was 25 to 33 weeks. Four prematures had birth weights below 1250 g. The Apgar score of 10 newborns was 3 or less 1 min after birth. Thirteen newborn needed resuscitation in the delivery room. Eight newborns were treated with respiration during the first few hours after birth and 4 other prematures at a later stage. Clinical and laboratory data after birth, on admission to the pediatric hospital and during the course of the disease are shown in tables and figures. The indications for the peritoneal dialysis are described in tables. In 2 patients we saw no positive effect, and we saw only a slight effect in 4 patients. Four prematures survived. The physical and psychological development was normal in 3 infants. One premature with a birth weight of 1200 g had recovered before she died of Candida sepsis at the age of 26 days.Results of the treatment and the efficacy and technical problems of peritoneal dialysis in RDS of newborns are discussed. Our opinion is that the peritoneal dialysis is a good additional aid in the treatment of RDS of prematures and newborns.ZusammenfassungMehrere Autoren haben die Peritonealdialyse zur Behandlung von Neugeborenen mit einem Atemnotsyndrom vorgeschlagen. Erste Versuche seit 1967, teils mit positivem Ergebnis, sowie die Resultate von Boda et al. veranlaßten uns zum Einsatz der Peritonealdialyse als Zusatz zu einer Standardtherapie beim Atemnotsyndrom reifer und unreifer Neugeborener mit schlechter Prognose.13 Frühgeborene, 1 Reifgeborenes sowie 1 Frühgeborenes mit einem Geburtsgewicht von 2750 g und Hydrops congenitus bei Morbus haemolyticus neonatorum wurden behandelt. Bei 2 Patienten war kein und bei 4 Patienten nur ein geringer Effekt zu beobachten. 4 Frühgeborene erholten sich von der Erkrankung. 3 dieser Kinder zeigten eine normale psychomotorische Entwicklung. 1 Frühgeborenes mit einem Geburtsgewicht von 1200 g starb im Alter von 26 Tagen an einer Pilzsepsis, nachdem es vom 6. bis 13. Lebenstag klinisch unauffällig war.Klinische und biochemische Angaben zu dem Krankheitsverlauf bei den Patienten sind in Tabellen und Abbildungen zu finden. Die Indikationen zur Peritonealdialyse sowie die Ergebnisse dieser Therapie sind in Tabellen aufgezeichnet.Wirkungsweise der Peritonealdialyse, Indikationen zur Peritonealdialyse sowie die Behandlungsergebnisse werden diskutiert. Unter Berücksichtigung von Aufwand und Nutzen wird die Peritonealdialyse als echte Ergänzung zur der üblichen Therapie des Atemnotsyndroms der reifen und unreifen Neugeborenen angesehen.