Lactobezoar formation in two premature infants receiving medium-chain triglyceride formula.

We describe two cases of premature infants who developed clinical and radiologic evidence of gastric lactobezoars within the same month in our neonatal intensive care unit while both were receiving medium-chain triglyceride-rich formula as part of the management of chylothoraces.

Binding of epidermal growth factor (EGF) to a cultured human glioma cell line.

We have studied binding of 125I-EGF to the human malignant glioma cell line U-343 MG aCl2:6, which is planned to be used as a model system in studies of toxic effects of EGF conjugates. Special care has been taken to fulfil the requirements for a correct Scatchard analysis of binding parameters. Binding as a function of time, temperature and pH was investigated as well as dissociation and internalization of bound EGF. The stability of EGF during incubation was also determined. After binding to the receptor, EGF is rapidly internalized and degraded at physiological temperature. We found that binding experiments should be performed at 4 degrees C, since at this temperature practically no internalization took place, whereas dissociation occurred. From displacement experiments using increasing concentrations of unlabelled EGF competing with 125I-EGF for binding, binding parameters were calculated using a computerized, nonlinear, least-squares regression analysis of binding data. We found that EGF bound to a class of high affinity receptors with an apparent dissociation constant KD of about 4 x 10(-10) M. The mean number of receptors was 25,000 per cell. In experiments where receptors were saturated with 125I-EGF an additional class of low affinity receptors was detected. This had an apparent KD of 1 x 10(-8) M with a mean receptor number per cell of 780,000. We also noticed enhanced dilution-induced dissociation of bound 125I-EGF in the presence of excess unlabelled EGF, suggesting negative cooperativity.

Effects of 131I-EGF on cultured human glioma cells.

Malignant glioma cells often have more epidermal growth factor (EGF) receptors than normal cells and targeting of toxic substances to the receptor might therefore be an attractive therapeutical approach. Radiation effects were analysed on human glioma cells growing as monolayers after exposure to 131I-EGF. Unspecific effects were analysed with 131I-BSA or after presaturation with nonradioactive EGF. The radiation effects were compared to the effects obtained by external 60Co gamma irradiation. Administration of the highest radioactive concentrations, 0.2-0.5 MBq/ml in the culture medium, corresponded, after 20 min incubation, to a binding of about 1.0-2.5 dpm/cell. Such an exposure to 131I decays gave effects on cell survival corresponding to about 2.5 Gy of external gamma irradiation. Somewhat less than half of this effect came from the specific bound radioactivity and the rest from nonbound radioactivity. When administrating lower concentrations of radioactivity both the binding and the radiation effects were smaller. The observations showed that it is possible to inactivate cell-proliferation of glioma cells with specific bound 131I-EGF. The possibilities to fractionate the treatments and of binding also other toxic agents than 131I to the EGF receptor are discussed.

Bioluminescent assay of lactate dehydrogenase and its isoenzyme-1 activity.

A bioluminescent assay based on the bacterial luciferase reaction has been developed for the determination of total lactate dehydrogenase and heart-specific lactate dehydrogenase isoenzyme-1 activity in serum. The lactate dehydrogenase-catalyzed reaction was measured in both directions, but NADH formation (lactate----pyruvate) is recommended because it allows the use of optimal reaction conditions. Internal calibration with a known amount of NADH accounts for possible interference from samples when both NADH formation and consumption are followed. The bioluminescent method is sensitive, has good precision, and is readily automated. Serum lactate dehydrogenase isoenzyme-1 was immunochemically isolated and the activity was assayed by bioluminescence. A good correlation between the bioluminescent assays and the conventional spectrophotometric procedure used as reference was obtained.

Pharmacokinetic evaluation of a new maintenance solution for severely injured patients.

Nine severely injured patients (SIP) and 9 healthy controls received 20 min iv infusions of Aminoplasmal-LS-10 (2.15 ml/kg body wt containing 0.215 g amino acids). Employing the values of the plasma amino acid (AA) concentrations 3, 7, 15, 30, 45, 70, and 150 min after the end of the infusion, we calculated the elimination half-life (t 1/2), the elimination constant (k2), the total clearance (Cltot), and the transfer of the individual AA. The AA showed t 1/2 between 6 (Glu) and 23 (Thr) min. Comparing the metabolic kinetics of healthy controls and SIP, there were no statistical differences in t 1/2 or in k2. In the SIP, nearly all plasma AA showed increased transfer and Cltot, significantly for Thr (p < 0.05), Pro, Gly, Ala, Arg (p < 0.02), Glu (p < 0.01), and Met (p < 0.005). In contrast, the Cltot for Phe and Tyr were decreased. Except for Phe, Tyr, Met (enhanced values) and Arg (no change), the fasting values of AA concentrations in the SIP were diminished compared to those in the healthy controls. Based on the measured transfer, we have developed a new maintenance solution adapted to SIP. Compared with Aminoplasmal, it is necessary to apply AA concentrations which are increased in Lys, His, Phe, Tyr, Val, Ala, and Ser, and reduced in Arg, Pro, Leu, Ile, and Gly.