Ultrafast coherent generation of hot electrons studied via band-to-acceptor luminescence in GaAs.
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Journal Article↗
Biomedical subjects
G Boehm
Publications and source records attributed to G Boehm.
Heat treatment of infant formula: effect on postprandial serum alpha-amino-nitrogen concentrations in very-low-birth-weight infants.
Several different types of heat treatment are used in the production of commercial infant formulas. The extent of heat treatment can have different physicochemical effects on the milk proteins and will affect their solubility and digestibility. In the present study, 40 very-low-birth-weight infants were randomized at the age of 2 weeks to be given one test feed of either fresh, human milk protein-fortified human milk, a conventional canned sterilized liquid formula, a spray-dried powder formula, or an ultra-high-temperature (UHT)-treated liquid formula. The mean volume of the nasogastric test feed was adjusted so that protein intake was the same in each study group (0.45 g/kg). Venous blood samples were taken preprandially and at 30, 60, and 120 min after the test meal. alpha-amino-nitrogen in serum was assayed by the ninhydrin reaction. The concentration of alpha-amino-nitrogen rose rapidly after the fortified human milk feed, reaching a peak at 30 min. After the peak was reached, the serum values progressively declined, reaching baseline values at 120 min after the start of the test meal. The areas under the curve for all formulas were significantly different from that found for fortified human milk. At 30 min, all formulas had significantly lower alpha-amino-nitrogen values than fortified human milk; at 60 min, all formulas had significantly higher mean concentrations than fortified human milk. At 120 min, none of the formula-fed infants had reached baseline values; in particular, canned sterilized formula was still significantly above baseline values.(ABSTRACT TRUNCATED AT 250 WORDS)
Amino Acids↗
Is the [15N]methacetin liver function test suited to estimate environmental effects on the maturity of neonates?
Clinical and paraclinical data of 91 neonates of the Saxon regions of Leipzig and of Torgau/Elbe were reviewed and correlated to the environmental conditions of the places of residence of their mothers during pregnancy. One of the parameters investigated was the hepatic detoxification capacity of the neonates measured by 15N elimination rates in the [15N]methacetin urine test. Because of heavy air pollution in the places of residence of some of the pregnant women, a distinct reflection of environmental influence in the parameters was expected. While some of the parameters considered, such as birth weight and bilirubin levels, did not correlate with mean exposure data of the residences of the pregnant women, the mean rate of the age-dependent maturation of hepatic 15N elimination did. This maturation was seen to be significantly decreased in heavily polluted districts of the Leipzig region compared to lower polluted places of Leipzig and to the lowly polluted region of Torgau/Elbe.
Acetamides↗
Nitrogen and fat balances in very low birth weight infants fed human milk fortified with human milk or bovine milk protein.
The study was designed to compare two different human milk fortifiers in a group of very low birth weight (VLBW) infants by analysing nitrogen and fat balances, serum concentrations of alpha-amino-nitrogen, urea, and prealbumin as well as growth rates when human milk enriched with one of the two studied fortifiers was fed to the infants. Fortifier A contained different bovine proteins, peptides and amino acids and had an amino acid composition comparable to that of the nutritional available proteins in human milk, with carbohydrates, and minerals. Fortifier B was composed of freeze-dried skimmed human milk and minerals to achieve a similar macronutrient composition in both fortifiers. Eleven infants were fed with human milk enriched with fortifier A and 13 with fortifier B. After a 10-day equilibration period, a 3-day metabolic balance was performed. On the 14th day of the study blood was obtained preprandially for serum analysis and growth rates were estimated. The nitrogen absorption rate (93.8% vs 93.5%) as well as the retention rate (80.8% vs 78.5%) were no different between the groups. The fat absorption rate (92.3% vs 91.5%) as well as the weight gain (32.1 vs 31.1 g/day) were similar and there were no differences in the serum parameters studied. The results indicate that feeding VLBW infants with human milk enriched with a well-balanced bovine fortifier fulfil their nutritional requirements as well as diets composed exclusively of human milk protein.
Birth Weight↗
Protein quality of human milk fortifier in low birth weight infants: effects on growth and plasma amino acid profiles.
Serum preprandial essential amino acid, urea and prealbumin concentrations, and growth rates were studied in appropriate for gestational age low birth weight infants fed one of three regimens: (1) human milk enriched with human milk protein (n = 17); (2) bovine whey protein hydrolysate (n = 18; and (3) a mixture of bovine proteins, peptides and amino acids designed to have an amino acid composition close to that of human milk proteins (n = 18). Energy and nitrogen intakes were similar in all groups. Growth rates and gross metabolic responses did not differ between the feeding groups. There were also no differences in the amino acid profiles between those infants fed human milk protein fortifier and mixed bovine protein fortifier. Infants fed the whey fortifier had significantly higher threonine concentrations in comparison to those fed exclusively human milk protein (287 +/- 63 mumol/l vs 168 +/- 26 mumol/l) whereas the levels of some other essential amino acids (i.e. valine, leucine, lysine, histidine, phenylalanine and tryptophan) were lower. The results indicate that growth rates and gross metabolic indices do not depend on the protein quality of human milk fortifiers. However, the addition of well balanced mixtures of bovine proteins to human milk results in amino acid profiles similar to those observed in LBW infants fed similar amounts of human milk proteins.
Amino Acids, Essential↗
Postmenstrual age correlates to indices of protein metabolism in very low birth weight infants.
In 14 infants who were normal in weight for gestational age and 14 infants who were small for gestational age, the plasma essential amino acid profiles and serum urea concentrations were studied between the 30th and 46th weeks of postmenstrual age. All infants were of very low birth weight (< 1,500 g) and were fed with fresh human milk fortified with 6 g freeze-dried human milk per 100 ml (mean protein intake 3.1 g/kg/day, mean energy intake 130 kcal/kg/day). With the exception of threonine, all measured plasma essential amino acid concentrations increased significantly with increasing postmenstrual age (appropriate for gestational age infants: r = 0.861, p < 0.01; small for gestational age infants: r = 0.772, p < 0.001). No differences in this increase could be found between the infants who were small or appropriate for gestational age. The serum urea concentrations also increased with increasing postmenstrual age without differences between the study groups (appropriate for gestational age infants: r = 0.658, p < 0.01; small for gestational age infants: r = 0.604, p < 0.05). The results indicate that very low birth weight infants of similar weights may have very different protein requirements, depending on their postmenstrual ages. Thus, postmenstrual age is of greater importance than birth weight when protein nutrition is planned for very low birth weight infants.
Amino Acids↗
[Post-conceptional age. Effect on protein requirements of premature infants].
In 12 preterm infants (mean gestational age: 28.9 weeks; mean birthweight: 1230 g) (Group 1) the serum concentrations of urea and alpha-amino-nitrogen were studied during the 32nd and between the 36th and 37th week of post-conceptional age. In 9 preterm infants with a mean gestational age of 34.6 weeks (mean birthweight: 1860 g) (Group 2) the same parameters were estimated during the 36th or 37th week of postconceptional age. In all male infants (group 1: n = 6; group 2: n = 5) the excretion of nitrogen in urine and stools were measured during a 48 h balance period. During the study all infants were fed with human milk enriched with 3 g of a bovine human milk fortifier (Eoprotin, Milupa AG, Germany) per 100 ml human milk (mean protein intake: 3.4 g/kg.day; mean caloric intake: 132.5 kcal/kg.day). Despite the similar protein and energy intakes on all study days the serum concentrations of urea and alpha-amino-nitrogen were significantly higher during the 36th or 37th postconceptional week if compared to those found during the 32nd postconceptional week. This was accompanied by elevated renal excretion of total nitrogen due to an increased excretion of urea in the older infants. The nitrogen excretions in stools were low during both study periods. During the period 36 and 37 weeks of postconceptional age no differences could be found for all parameters studied between the both groups of different gestational ages. The data of the present study suggest that in preterm infants with postconceptional age of 37 weeks or more protein intakes of 3.4 g/kg.day and more may exceed the requirements of these infants. Thus, supplementation of human milk with protein is not necessary after the 37th week of postconceptional age if feeding volumes of 170 ml/kg.day or more are tolerated.
Amino Acids↗
[Effect of the amino acid content of breast milk supplements on the amino acid profile in the plasma of newborn infants: human albumin in comparison with Eoprotin].
The influence of amino acid composition of two human milk fortifiers (Eoprotin, Milupa AG, Germany, and human albumin) on plasma amino acid profiles was studied in 28 preterm infants after a 14-day feeding period. The concentrations of total essential amino acids increased in both feeding groups significantly if compared to the period without supplementation; only the concentrations of methionine and phenylalanine in the eoprotin group and those of threonine, methionine and isoleucine in the human albumin group did not increase significantly. However, only the concentrations of isoleucine (Eoprotin: 79 +/- 19 mumol/l; human albumin: 45 +/- 20 mumol/l, p < 0.001) and methionine (Eoprotin: 26 +/- 10 mumol/l, human albumin: 16 +/- 10 mumol/l, p = 0.014) were significantly different between the two feeding groups. There was a significant correlation between the differences in the serum concentrations and the ones of each essential amino acid concentration in the fortifiers (r = 0.951). The results indicate that the amino acid composition of human milk fortifiers must be taken into consideration to achieve optimal nutritional management of preterm infants.
Amino Acids↗
Postnatal development of liver and exocrine pancreas in polycythemic newborn infants.
In 35 newborn infants appropriate for gestational age the influence of neonatal polycythemia (venous hematocrit greater than 60% measured between the second and fourth hour of life) on development of enterohepatic circulation of bile acids, activities of pancreatic enzymes in duodenal juice, and the effects of hemodilution were studied during the second week of life. A significant correlation was found between the initial hematocrit and both the bile acid concentration in serum and lipase and trypsin activity in duodenal juice. Of 35 infants, 10 were not treated with hemodilution due to asymptomatic polycythemia; they had the highest concentration of serum bile acids associated with the lowest lipase and trypsin activity in duodenal juice. However, the 25 infants treated with hemodilution also showed serum bile acid concentrations and lipase and trypsin activity in duodenal juice out of the normal range when compared to normocythemic infants. These data indicate that, during the first days of life, polycythemia results in a delayed postnatal development of enterohepatic circulation of bile acids and exocrine pancreas functions independently from the occurrence of clinical symptoms. Thus, it can be concluded that, on the first day of life, all polycythemic infants should be treated with hemodilution. Moreover, the nutritional management of these infants must also account for the limited functional capacity of the gastrointestinal tract.
Algorithms↗
Macromolecular absorption in small-for-gestational-age infants.
Using human alpha-lactalbumin as a marker protein, macromolecular absorption was studied in 40 preterm infants, appropriate for gestational age (AGA), in 12 AGA term infants and in 18 preterm infants, small for gestational age (SGA). The absorption of alpha-lactalbumin was measured as concentration in serum after a human milk feed and expressed as micrograms alpha-lactalbumin/l serum/l human milk/kg body weight on day 7, 14, 21 and 42 after delivery. The serum concentration of alpha-lactalbumin was correlated negatively with maturity and postnatal age. In the SGA infants, the concentration of alpha-lactalbumin was significantly higher than in the AGA infants of similar gestational age. The data show that intrauterine growth retardation causes a delayed postnatal decrease in macromolecular absorption. This may indicate delayed intestinal maturation.
Birth Weight↗
Tomographic imaging of opaque and low-contrast objects in range-independent waveguides.
A feasibility study is presented for acoustic tomographic imaging of arbitrarily shaped objects in range-independent oceanic waveguides. One of the main obstacles in the efficient use of tomographic imaging is that tomographic systems usually allow for a number of different independent solutions which satisfy the same systems of equations. This adverse property of acoustic tomography is especially pronounced in underdetermined systems characterized by null spaces of tomographic matrices which relate measured data to an unknown sound-speed distribution. In fact, acoustic tomography is usually underdetermined and the null space problem becomes critical in many applications. Acoustic tomography in many instances yields blurred images precluding its efficient use for mapping underwater objects in oceanic waveguides. How to improve the resolving power of tomographic imagery in waveguides is shown. A new technique based on the sliding window approach is suggested which uses constrained traveltime inversion. The method will be tested on mapping opaque and low-contrast acoustic objects placed in range-independent waveguides. The method is fast since it does not directly invert tomographic matrices of large rank but instead carries out summation over nonzero elements of tomographic matrices. It can be proved that constrained inversion compensates for limited angular aperture recording and thus can be applied to practical problems with incomplete angular aperture. This work is limited to processing of transmitted signals. A separate study will be devoted to the analysis of reflection data.
Acoustics↗
Doxycycline tolerance study. Incidence of nausea after doxycycline administration to healthy volunteers: a comparison of 2 formulations (Doryx' vs Vibramycin').
In a randomised, double-blind, 3-way cross-over trial, the incidence of nausea associated with 2 doxycycline 100 mg formulations (Doryx' and Vibramycin') were compared. The original study cohort comprised 103 healthy male volunteers, with 97 subjects completing the trial. Subjects were randomly allocated to 1 of 3 treatment sequences and received a single dose of Doryx', Vibramycin' or placebo, with a 7-day washout prior to cross-over. At half-hourly intervals, from 0 to 2 h post-dose, subjects completed questionnaires to indicate if they felt nauseous. Data were analysed according to a log-linear method for the analysis of cross-over trials with categorical responses. Seventeen, 29 and 11 subjects experienced nausea with Doryx', Vibramycin' and placebo, respectively. A significantly greater number of volunteers indicated a positive response with Vibramycin' vs Doryx' and vs placebo; the positive response frequency was not significantly different for the Doryx' vs the placebo regimen. Treatment sequence had no significant effect on response, although a marked first-dose effect was noted; the first (vs the second and vs the third) regimen was 1.5-2 times more likely to induce a positive response.
Adult↗
Activities of lipase and trypsin in duodenal juice of infants small for gestational age.
In 18 low birth weight infants, small for gestational age, with different degrees of intrauterine growth retardation the activities of pancreatic lipase and trypsin and the concentrations of bile acids were measured in preprandially aspirated duodenal juice. The results were compared to those of 24 low birth weight infants, appropriate for gestational age, with comparable birth weights and postnatal ages. The activities of both measured pancreatic enzymes were negatively correlated with the degree of intrauterine growth retardation, expressed as the difference between the individual birth weight and the weight of the 10th percentile of the intrauterine growth curve (lipase: r = -0.697, p less than 0.001; trypsin: r = -0.739, p less than 0.001). The activity of trypsin in the small for gestational age infants was within the range of that found in the infants appropriate for gestational age. However, the lipase activity was decreased in infants who presented with growth retardation of greater than 400 g/kg birthweight. The concentrations of bile acids were similar in both groups (4.60 +/- 2.51 and 4.55 +/- 2.26 mmol/L, respectively) and sufficient for activating the bile salt stimulated lipase in human milk. The data suggest that in intrauterine growth retarded infants the lipase activity in the duodenal juice can be a limiting factor for optimal fat digestion. This should be considered in the nutritional management of such infants.
Duodenum↗
Effects of two antibiotics on hepatic function in low birth weight infants: ampicillin vs. cefotaxime.
In 21 low birth weight infants with two regimens of antibiotic therapy during the first 3 days of life possible hepatotoxic side effects were studied 8 days after the last administration of the tested drugs. Fourteen of the infants were treated with ampicillin/gentamicin and 7 received cefotaxime/gentamicin. The serum concentrations of total bile acids, the activities of transaminases in serum and the cumulative 15N excretion in urine after administration of 3 mg of 15N-labeled methacetin/kg of body weight were used as markers of hepatotoxic side effects. Neither the concentrations of total bile acids (22.6 +/- 12.1 and 19.4 +/- 10.8 mM, respectively) nor the activities of transaminases (alanine aminotransferase, 0.27 +/- 0.06 vs. 0.30 +/- 0.09 mumol/second/liter; aspartate aminotransferase, 0.46 +/- 0.11 vs. 0.49 +/- 0.10 mumol/second/liter) were different between the two groups. In contrast the cumulative 15N excretion in urine was significantly lower in the group treated with cefotaxime/gentamicin than in the group treated with ampicillin/gentamicin (17.2 +/- 6.4 vs. 33.0 +/- 5.1% of intake; P less than 0.01) and also lower than the reported age-related reference values. On the 28th day of life no differences could be found between the cumulative 15N excretion in the urine of the infants treated with cefotaxime/gentamicin and the reported age-related reference values of this test. The results indicate a limited capacity of the monooxygenase system of the liver of low birth weight infants during the first weeks of life and a specific reversible influence of cefotaxime on this hepatocellular system. Further investigations are required to evaluate the clinical relevance of this drug-specific inhibition of the hepatic monooxygenase pathway.
Acetamides↗
Development of urea-synthesizing capacity in preterm infants during the first weeks of life.
The urea-synthesizing capacity of the liver was studied in 20 healthy preterm infants during the first month of life. The urea-synthesizing capacity was estimated by the ratio of 15N abundances of ammonia and urea in the 6-hour urine after administration of 3 mg 15N-labelled ammonium chloride/kg body weight. The ratio increases with increasing protein intakes from the 2nd to the 3rd week of life. On protein intakes of more than 3 g/kg/protein day from the 3rd week to the end of the 2nd month of life, the ratio decreases suggesting a maturation of the urea cycle during the first weeks of life.
Age Factors↗
[Neonatal nutrition with enriched human milk. EOPROTIN 60 in comparison with human albumin].
The influence of feeding fresh human milk supplemented either with EOPROTIN (n = 13) or human albumin (n = 15) on biochemical parameters and growth were studied in preterm infants with gestational ages below 32 weeks p.m. up to the 42nd day of postnatal life. In both feeding groups the intakes of protein, energy and electrolytes were similar. The serum concentrations of bile acids, alpha-amino-nitrogen and prealbumin, the renal excretion of total nitrogen, alpha-amino-nitrogen, urea and ammonia as well as the growth in weight and length were studied in all infants. The supplementation of the fresh human milk with EOPROTIN results in significant lower serum concentrations of alpha-amino-nitrogen (1.56 +/- 0.21 vs 2.03 +/- 0.27 mmol/l; p less than 0.01), higher serum concentrations of prealbumin (89.8 +/- 20.3 vs 72.7 +/- 13.3 mg/l; p less than 0.02), and lower urinary excretion of total nitrogen (7.4 +/- 0.9 vs 8.9 +/- 1.1 mmol/kg/day); if compared to the results found in the infants fed human albumin supplemented human milk. The higher nitrogen retention in the EOPROTIN than in the human albumin fed infants was associated by a significant higher growth in weight (16.6 +/- 1.4 vs 13.7 +/- 1.9 g/kg/day; p less than 0.01) as well as in length (1.02 +/- 0.08 vs 0.87 +/- 0.1 cm/week; p less than 0.01). The results indicate that the bioavailability of EOPROTIN is higher than that of human albumin. The observed differences in the nutritional response between the two human milk supplements may be based on differences in the amino acids composition which is in EOPROTIN adapted to the nutritional available part of the protein in human milk.
Albumins↗
Influence of casein feeding to very-low-birth weight infants on the plasma amino acid concentrations and the renal amino acid excretion.
The response of plasma and urine amino acid concentrations to a casein formula and to supplemented human milk (both 1.4 gm protein/100 ml) was measured in very-low-birth weight (VLBW) infants (less than 1500 gm) at a postconceptional age of 36 and 40 weeks, respectively. A control group of infants was fed exclusively with fresh human milk (HM). Casein feeding to VLBW infants resulted in prefeeding plasma amino acid profiles and renal amino acid excretions which were not markedly different from those found in infants fed supplemented HM. In comparison with the control feeding group, the infants fed casein or supplemented HM responded with higher total plasma amino acid concentrations (114.4 +/- 33.7 vs 171.0 +/- 36.1 or 167.1 +/- 27.1 mumol/100 ml, respectively) reflecting the higher amount of protein provided by these two feedings. The critical amino acids (sulfur-containing and aromatic amino acids) were metabolized efficiently in infants fed the casein formula. Furthermore, a highly significant relationship (r = 0.795; p less than 0.001) between the plasma concentrations of tyrosine and valine was achieved in all infants independent of the food applied. This relationship could represent a control mechanism to prevent an inordinate influx of aromatic amino acids into the brain. In VLBW infants at a postconceptional age of 36-40 weeks, the metabolic and functional maturity reaches levels which were similar to those found in term newborns.
Aging↗
Postnatal development of urea- and ammonia-excretion in urine of very-low-birth-weight infants small for gestational age.
In 12 very-low-birth-weight (VLBW) infants with intrauterine growth retardation and in 14 VLBW-infants appropriate for gestational age (AGA) fed a human milk (HM) formula (HM enriched with 6 g freeze dried HM per 100 ml) the renal excretion of urea and ammonia was studied on the 10th, 21st and 42nd days of life. The lowest excretion of urea was found in both groups on the 10th day of life. Up to the 42nd day of life the excretion raised significantly more in the AGA- than in the small for gestational age (SGA)-infants. In contrast to the urea excretion the excretion of ammonia was highest on the 10th day of life in both groups, but the excretion was significantly higher in the SGA-infants if compared to the AGA-infants. In the AGA-infants excretion of ammonia decreased with postnatal age whereas in the SGA-infants the high excretion remained up to the 42nd day of life. The data suggest that in VLBW-infants the urea synthesizing capacity is decreased and develops within the first weeks of postnatal life. The postnatal development is delayed in SGA-infants when compared to AGA-infants. The differences are more pronounced with increasing degree of intrauterine growth retardation.
Ammonia↗