Biomedical subjects
Publications and source records attributed to K Heinonen.
In rats after neonatal thyroid destriction, cystathionae in liver and pancreas increased, but the enzyme activity in kidneys decreased. Substitution with thyroxine corrected these changes. Excess of thyroxine, too, had an effect on tissue cystathionase.
Well, appropriate-for-gestational age, low-birth-weight infants weighing 2,100 gm or less were divided into three gestational age groups and assigned randomly within each age group to one of five feeding regimens: pooled human milk; formula 1 (F1) = 1.5gm/dl protein, 60 parts bovine whey proteins: 40 parts bovine caseins; F2 = 3.0 gm/dl, 60:40; F3 = 1.5 gm/dl, 18:82; F4=3.0 gm/dl, 18:82. Plasma and urine concentrations of methionine and of cystathionine were higher in the infants fed F1 to F4 than in the infants fed BM. The plasma cystine concentrations of infants fed F2 (which had a cystine content at least twice that of any of the other formulas) were significantly higher than those of infants fed BM. Plasma taurine concentrations of infants fed F1 or F4, which were virtually devoid of taurine, decreased steadily during the course of study becoming lower than those of infants fed BM. Urine taurine concentrations of infants fed F1, F3, or F4 (but not F2 which had more taurine than F1, F3, or F4) were lower than those of infants fed BM. These results provide further evidence for the limited capacity of the preterm human infant to convert methionine to cystine, owing to delayed maturation of cytathionase, and suggest a limited capacity to convert cystine to taurine. The latter suggestion is consistent with low human hepatic cysteinesulfinic acid decarboxylase activity 0.26 (fetal) and 0.32 (adult) nmoles/mg protein/hour vs 468 in rat liver.
Well, appropriate-for-gestational age, low-birth-weight infants were divided into three gestational age groups and assigned randomly within each age group to one of five feeding regimens: pooled human milk (BM); formula 1 (F1) = 1.5 gm/dl protein, 60 parts bovine whey proteins: 40 parts bovine caseins; F2 = 3.0 gm/dl, 60:40; F3 = 1.5 gm/dl, 18:82; F4 = 3.0 gm/dl, 18:82. Plasma and urine concentrations of tyrosine and phenylalanine were far higher in the infants fed F1 to F4, especially F2 and F4, than in the infants fed BM. These findings offer further evidence for the limited capacity of the low-birth-weight infant to catabolize tyrosine. Infants fed F3 had significantly higher plasma tyrosine concentrations than infants fed F1, and those fed F4 had higher concentrations than those fed F2. Thus, increased plasma tyrosine concentrations in low-birth-weight infants are related directly both to the quantity and to the quality of the protein in their diets.
The optimal quantity and quality of protein for low-birth-weight infants is undefined. In this study, 106 well, appropriate-for-gestational-age, low-birth-weight infants weighing 2,100 gm or less were divided into three gestational age groups and assigned randomly within each age group to one of five feeding regimens: pooled human milk; formula 1 (protein content, 1.5 gm/100 ml- 60 parts bovine whey proteins to 40 parts bovine caseins); formula 2 (3.0 gm/100 ml, 60:40); formula 3 (1.5 gm/100 ml, 18:82); and formula 4 (3.0 gm/100 ml, 18:82). The concentrations of the free amino aicds in the plasma and urine of these infants were determined. The plasma concentrations of free amino acids were generally far greater in the infants fed the 3.0-gm/100 ml protein diets than they were in the infants fed pooled human milk. The plasma concentrations of free amino acids of the infants fed the 1.5-gm/100 ml protein diets were intermediate. In general, the concentrations of the free amino acids in the plasma of the infants fed the 3.0-gm/100 ml casein-predominant formula (F4) were furthest from those fed pooled human milk. Glutamate showed the highest plasma amino acid concentrations in infants fed the 3.0-gm/100 ml casein-predominant formula (F4) were furthest from those fed pooled human milk. Glutamate showed the highest plasma amino acid concentrations in infants fed both the high- and low-protein casein-predominant formulas. This was true despite the fact that the intake of glutamate on the high-protein, whey-predominant formula was twice that on the low-protein, casein-predominant formula. The differences between groups in the essential amino acids in plasma were generally greater than those of the nonessential amino acids. The concentrations of amino acids in the urine tended to parallel those of the plasma.
The optimal quantity and quality of protein for low-birthweight infants is undefined. In this study, 106 well, appropriate-for-gestational age, low-birthweight infants weighing 2,100 gm or less were grouped in three gestational age categories: T1 = 28 to 30 weeks; T2 = 31 to 33 weeks; T3 = 34 to 36 weeks. Each group was assigned randomly to either banked human milk (BM) or to one of four isocaloric formulas varying in quantity and quality of protein but not in mineral content or in fat content: formula 1 = 1.5 gm of protein per 100 ml, 60 parts bovine whey proteins to 40 parts bovine caseins; formula 2 = 3.0 gm of protein per 100 ml, 60:40; formula 3 = 1.5 gm of protein per 100 ml, 18:82; formula 4 = 3.0 gm of protein per 100 ml, 18:82. Caloric intake was 117 kcal/150 ml/kg/day for the formulas. Human milk was fed at 170 ml/kg/day in order to attain a caloric intake approximately equal to that of the formulas. No significant differences were found in the rate of growth in crown-rump length, in femoral length, in head circumference, or in rate of gain in weight from time of regaining birthweight to time of discharge at 2,400 gm. Blood urea nitrogen, urine osmolarity, total serum protein, serum albumin, and serum globulin varied directly with the quantity of protein in the diet: F2, F4 greater than F1, F3 greater than BM. Blood ammonia concentration varied with both quantity and quality of protein in the diet: F2, F3, F4 greater than F1, BM. Metabolic acidosis was more frequent, more severe, and more prolonged in the infants fed the casein-predominant formulas (F3,F4) than in those fed the whey protein-predominant formulas (F1, F2).
At the 18th day of gestation and thereafter foetal rat liver explants in organ culture showed the competence to respond to dexamethasone by increased cystathionase activity, whereas the ability to respond to dibutyryl cyclic AMP or glucagon became evident at a later developmental stage (during the last 2 days prior to term). Simultaneous incubation with cycloheximide inhibited the stimulatory effect of these agents on foetal rat liver cystathionase activity in vitro. Dexamethasone and glucagon were both capable of increasing liver cystathionase activity both in newborn and 3-day-old animals in vivo.
In hypothyroidism induced by radioiodine the activity of cystathionine synthase and the concentration of L-cytathionine in cerebrum and cerebellum of developing rat decreased markedly. The amount of taurine was significantly higher in cerebral and cerebellar tissue of hypothyroid rats than in corresponding parts of normal rat brain. Early substitution therapy with L-thyroxine corrected these changes.
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Incubation of liver explants from second-trimester human foetuses with dexamethasone, glucagon or dibutyryl cyclic AMP (plus theophylline) increased the activity of liver cystathionase from unmeasurable or trace values to adult values. Simultaneous incubation with cycloheximide or actinomycin D inhibited this effect.
High activity of cystathionase was present in rat liver but only low amounts of activity in rat brain during development. Triamcinolone had no effect on liver cystathionase activity in foetuses but increased the enzyme activity significantly in postnatal rats. l-Thyroxine decreased liver cystathionase activity significantly in newborn rats; administration of pyridoxal 5'-phosphate did not prevent this effect. l-Methionine significantly increased liver cystathionase activity in newborn rats.
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During the stall feeding period 1982-1983, it was established that serious fertility disturbances, indicating oestrogenic stimulation, had occurred in a herd of cattle in an area supported by the College of Veterinary Medicine's ambulatory clinic. Whilst investigating the cause of these disturbances it was proven that the silage administered during this period was prepared almost entirely from pure red clover aftergrowth. The oestrogenic isoflavone content of the silage (liquid chromatograph examination) and the oestrogenic strength (bioassay) were considerably great. When feeding with the fodder was subsequently discontinued the disturbances ceased to occur and the cows became pregnant more easily. On the basis of the aforementioned incidences it was ascertained that plant oestrogens were almost certainly the cause of the fertility disturbances.