Effect of hepatic cytosol on postnatal drug metabolism

Postnatal maturation for indomethacin O-demethylation in freshly isolated hepatocytes and 10,000 g liver homogenates of rabbit was found to be significantly different from that observed in rabbit hepatic microsomes. Addition of hepatic cytosol (100,000 g supernatant) from day 10 postnatal rabbits significantly inhibited indomethacin O-demethylation by hepatic microsomes from adult rabbits. Kinetic studies demonstrated that the inhibition was competitive and consistent with the concentration of cytosol. The pattern of postnatal maturation for hepatic microsomal drug metabolism may in part be related to changes in the concentration of endogenous cytosolic inhibitors.

Serum, retinal, choroidal vitreal vitamin E concentrations in human infants

Vitamin E is being used as an antioxidant in preterm neonates in an attempt to decrease the severity of retinopathy of prematurity. However, its efficacy may depend on many factors, a major one being its concentration in the retina. There is very little information available on the alpha-tocopherol levels in the human eye tissue. The present study was carried out to determine the total alpha-tocopherol levels in the retina, choroid, and vitreous and to compare the retinal levels with the serum levels obtained at the time of death. Thirteen whole eye donations were available during the past 22 months for the study. The data from this small number of cases showed that retinal levels of alpha-tocopherol were higher than choroidal and vitreal levels; higher serum levels were associated with higher retinal levels; and both serum and retinal alpha-tocopherol levels were lower in the unsupplemented (group A) infants. Further studies on pharmacokinetics of vitamin E in human newborns and its distribution are needed.

Resuscitation and respiratory management of infants weighing less than 1000 grams

Care of the tiny neonate with regard to assisted ventilation and possible surfactant therapy is discussed in this review. Management in the delivery room and after is also included.

Purification and properties of two DNA ligases from human placenta

Two DNA ligase activities have been separated, purified, and characterized. The resolution of the two enzymes from crude extracts was initially achieved through Polymin P precipitation. The ligation activity precipitating with the nucleic acids on treatment with Polymin P is designated as DNA ligase I, and an activity remaining in the supernatant fraction, as DNA ligase II. DNA ligase I and II are ATP and Mg2+-dependent enzymes with pH optima of 7.8 and 8.0 and isoelectric points of 6.9 and 7.6, respectively. The purified I and II DNA ligase activities have molecular weights of 83,000 and 89,000, respectively. Both activities are inhibited by dATP and inorganic pyrophosphate. However, in the presence of optimum rATP levels, dATP stimulates DNA ligase II activity, whereas DNA ligase I is inhibited under the same conditions. Both activities are DNA specific and ligation follows reaction steps similar to those described for the Escherichia coli DNA ligase.

Effect of tolazoline on renal function in newborn puppies

Tolazoline is used in pulmonary hypertension and hypoperfusion syndrome during the neonatal period. Some of the side effects of tolazoline are hypotension, bleeding disorders and renal dysfunction. The present study was designed to investigate the effect of hypoxia and tolazoline on renal function in newborn puppies. The data in normal animals administered tolazoline alone did not reveal any statistically significant changes in blood pressure or in renal function. In the hypoxia group changes in renal function were noticed in spite of normal blood pressure. When tolazoline was administered to the hypoxic animals, a marked decrease in blood pressure resulted. Indeed, changes in renal function were more profound in the hypoxic animals receiving tolazoline than in hypoxic animals not receiving tolazoline, even though some of the renal functional values did not reach statistical significance.

Transcutaneous oxygen and carbon dioxide monitoring in sick neonates using a combined sensor

Using a combined O2-CO2 sensor, we evaluated the effect of cathode size and membrane thickness and incorporation of correction factor upon transcutaneous O2-CO2 readings. The present studies were carried out in three phases in newborns less than a week of age. The data from these studies indicate that a combined O2-CO2 sensor with a smaller cathode, Teflon membrane and with a built-in correction factor can accurately reflect arterial O2 and CO2 tension and can replace the present two heated sensors.

Tissue pH monitoring by a disposable sensor in critically ill neonates

Using a new disposable polymer sensor, tissue pH was continuously monitored successfully in 33 critically ill neonates. Tissue pH correlated well with the arterial pH at wide pH ranges [n = 476; r = .84; y = 0.46 + (0.94)x]. Tissue pH changes accurately reflected the arterial pH during both respiratory and metabolic acidosis and alkalosis. During severe metabolic acidosis (arterial pH less than 7.10) tissue pH was lower than arterial pH. No complications were encountered during or after monitoring. Compared with earlier studies using a glass electrode, this electrode reflects a marked technologic improvement because of its ease of application, longevity of use, disposability, and decreased risk of complications in small preterm infants. Unlike transcutaneous oxygen and carbon dioxide sensors, this device is invasive but is not heated and does not require frequent site changes.

Bovine surfactant (surfactant TA) therapy in immature baboons with hyaline membrane disease

As a prelude to clinical trials with a bovine surfactant (surfactant TA), in human infants with hyaline membrane disease, pulmonary and hemodynamic changes following its instillation in premature baboons were investigated. Baboons, delivered by cesarean section at 141 +/- 3.5 days (mean +/- SD, 77% gestation), were provided with intensive care. At 2 hours of age in one group (n = 10), 100 mg/kg of surfactant TA (reconstituted bovine surfactant, Tokyo Tanabe Co., Tokyo) was instilled into the lungs. Sequential measurements and monitoring of pulmonary and hemodynamic variables were carried out in these ten baboons and in a control group of five baboons for 16 hours, at which time the experiments were electively terminated. At birth, the pulmonary compliance, findings of chest radiographs, ratio of arterial PO2 to alveolar PO2, and respirator variables needed to maintain normal blood gas and acid base status were identical in both groups and indicative of severe hyaline membrane disease. Following surfactant instillation, the treated group demonstrated a rapid increase in PO2 with significantly improved ratio of arterial PO2 to alveolar PO2 (from a mean +/- SD pretreatment value of 0.21 +/- 0.11 to 0.45 +/- 0.11 by 16 hours). Pulmonary compliance improved similarly (from pretreatment value of 0.18 +/- 0.06 mL/cm H2O/kg to 0.27 +/- 0.09 mL/cm H2O/kg). Significant reduction in respirator support variables could be achieved in all treated animals; however, in the control animals, the pulmonary status worsened as evidenced by increasing mean airway pressure and respirator variables to keep normal blood gas and acid base status, thus worsening compliance. At autopsy, pulmonary pressure-volume curves were significantly different with large hysteresis obtained in the surfactant-treated group. Although no deleterious effect on hemodynamics was noted in surfactant TA-treated animals, a large patent ductus arteriosus was demonstrated by aortography. Increased lung blood flow, probably due to a large patent ductus arteriosus flow, was demonstrated by radiolabeled microsphere technique. The physiologic significance and clinical relevance of these findings in premature baboons treated with surfactant TA are discussed.

Uptake of taurocholate by freshly isolated hepatocytes from fetal and newborn rabbits

During early postnatal maturation a significant increase in the rate constant of translocation (Michaelis-Menten constant; Km) for taurocholate uptake occurs in isolated rabbit hepatocytes. This age-dependent change is related to a decrease in the efficiency of uptake for taurocholate and is probably associated with changes in the receptor or its microenvironment within the plasma membrane. Cholic acid conjugates (taurocholic and glycocholic acids) are the predominant bile acids found in the premature and neonatal human. It is therefore of interest that in the fetal and neonatal rabbit we have found a developmentally dependent alteration of taurocholic acid transport.

Colloid osmotic pressure in infants with hyaline membrane disease

Colloid osmotic pressure (COP) was measured serially in 81 critically ill neonates with hyaline membrane disease (HMD) during the first five days of life, and these changes were correlated with the birth weight, gestational age, serum protein level, clinical status, and outcome. Colloid osmotic pressure correlated better with the total protein level (n = 81; r = 0.54) than with birth weight (r = 0.23) and gestational age (r = 0.31; n = 81). Seventy-one of 81 neonates survived. Among the survivors, COP increased significantly by day 5, whereas changes in the total protein level were not significant during the same period. Colloid osmotic pressure decreased significantly in nine of ten nonsurvivors (mean +/- SE, 11 +/- 0.5 to 8 +/- 0.55 mm Hg), whereas the total protein level did not show a similar change. Thus, COP cannot be accurately predicted by measuring serum protein during acute illness. Serial measurement of COP was a better prognostic indicator than the total protein level in infants with HMD.

Age-related difference in cerebral perfusion pressure response to acute hypoxia in neonatal puppies

Acute hypoxia is known to increase cerebral blood flow and intracranial pressure in the fetus and newborn. The combined effects of these changes on cerebral perfusion pressure are unknown. We investigated cerebral perfusion pressure changes in newborn puppies of two age groups (group I, mean age 28 days, group II, mean age 11 days) during acute, severe hypoxia. The results indicate that (1) in both groups the intracranial pressure increases within seconds following the onset of hypoxia; (2) the mean arterial blood pressure drops almost precipitantly in older animals, whereas in group II, the blood pressure is maintained near baseline values up to 4 min, and (3) because of differences in blood pressure responses the cerebral perfusion pressure falls dramatically in group I, whereas in younger animals normotensive response to hypoxia helps maintain the cerebral perfusion pressure for a longer period. We conclude that in young animals early normotensive response to hypoxia assures adequate transmural pressure for the perfusion of brain which may be a built-in protective factor.

Nerve damage in leprosy-a teased fibre study of sciatic nerves in experimental mice

The extent of nerve damage was assessed in the sciatic nerves of CBA/J mice with experimental leprosy by the teased single fibre preparations. Morphological changes in the fibres were observed upto 15 months of infection and compared with control animals of the same age groups. During 4 to 9 months period, the fibres showed paranodal enlargements, widening of the Schmidt-Lantermann incisures, paranodal and whole segmental demyelination. In addition, fragmentation of axons with the formation of myelin ovoids in the schwann tubes was also observed in animals with 9 to 15 months of infection. While segmental demyelination was predominant early in infection, axonal degeneration was more evident in advanced infection. These findings may possibly, explain the underlying mechanism of nerve damage in human leprosy.

Neonatal abdominal aortic thrombosis

Thromboembolism of abdominal aorta and its branches after umbilical artery catheterization has been previously reported. In the past, total occlusion of the abdominal aorta and its major branches was associated with high mortality. Successful aortic thrombectomy in the neonatal period has been reported only once in English literature. The successful management of 2 infants described here shows the need for early diagnosis and aggressive approach, including surgical thrombectomy when indicated. Thromboembolism of abdominal aorta and iliac arteries can be diagnosed by noninvasive methods, such as 2-dimensional echoaortography and Doppler blood flow measurement.

Indomethacin metabolism in isolated neonatal and fetal rabbit hepatocytes

Metabolism of indomethacin was examined in freshly isolated hepatocytes prepared by liver collagenase perfusion of fetal (28) and neonatal rabbits of 3, 5, 10, 12, and 25 days of age. Initial cell viability was more than 90% and linear rates of metabolism were observed for up to 2 hr of incubation. Deacylation of indomethacin to desbenzoyl indomethacin showed a rapid increase early in postnatal development while microsomal O-demethylation to desmethyl indomethacin was increased significantly only in the hepatocytes from 25-day-old rabbits. Glucuronide conjugates of indomethacin and indomethacin metabolites accounted for less than 8% of the total metabolites in hepatocytes from 25-day-old rabbits. The maturational development of indomethacin in metabolism may account for previously reported gestational dependent half-life of the drug in the premature infant (9). However, the factors that regulate development of indomethacin metabolism appear to be under more that one control system.

Simultaneous tissue pH and transcutaneous carbon dioxide monitoring in critically ill neonates

Clinical usefulness and factors affecting transcutaneous CO2 (PtcCO2) monitoring were studied in 22 critically ill neonates. In 10 of 22 infants, both tissue pH (pHt) and PtcCO2 were monitored simultaneously using Roche pHt and CO2 electrodes. Arterial blood gases were obtained from umbilical artery catheter. The effect of variations in blood pressure, oxygenation, arterial pH (pHa) pHt, and medications on PtcCO2 were studied. There was a linear correlation between pHt and pHa (n = 108, r = 0.85, slope 1.08), PtcCo2 and PaCO2 (n = 188, r = 0.85, slope 1.49). The pHt changes correlated better with PtcCO2 than with arterial CO2 (r = 0.78, slope 1.35). The major factors affecting the PtcCO2 relationship were (a) hypoxia and (b) acidosis. When PaO2 less than 40 torr, PtcCO2 correlated poorly to PaCO2 (n = 23, r = 0.48, slope 0.72) whereas, during normoxia (PaO2 greater than 40 torr), it correlated well, r = 0.85, slope 1.51 similarly. When pHt was greater than 7.30, PtcCO2 correlated better with PaCO2 (r = 0.88, slope 1.37) than during tissue acidosis (r = 0.71, slope 1.51). Mean blood pressure down to 30 mm Hg and administration of dopamine and tolazoline did not affect the PtcCO2 to PaCO2 relationship (n = 69, r = 0.86, slope 1.6). Clinically, both continuous pHt and PtcCO2 were found to be very useful in the management of critically ill neonates.

Critical care problems in neonates. Colloid osmotic pressure in healthy and sick neonates

Clinical usefulness of colloid osmotic pressure (COP) measurements in adults has been well established. However, data in healthy and sick neonates are sparse. The present study established the COP changes in healthy term and preterm infants and in critically ill neonates. COP in healthy term (16.9 +/- 1.9 mm Hg) and preterm (15.4 +/- 1.3) infants was significantly lower than adults (21.6 +/- 3.6). Even in sick neonates, COP correlated with gestational age (n = 78, r = 0.63, p less than 0.001 , birth weight (r = 0.58, p less than 0.001) and total protein (n = 71, r = 0.58, p less than 0.001). Critically ill preterm infants with hyaline membrane disease had the lowest COP (11.5 +/- 1.2). Administration of 10% albumin failed to increase the COP significantly. In critically ill preterm infants who survived, the COP increased during the first postnatal week, whereas in nonsurvivors COP decreased significantly to less than 10 mm Hg.

Continuous tissue pH monitoring in critically ill neonates

Continuous tissue pH was measured using a minaturized glass electrode in 21 sick term and preterm infants. Tissue pH correlated well with arterial (r = 0.87) and capillary pH (r = 0.90) during the steady state. However, tpH was lower than arterial pH during hypoperfusion and state of shock. Improvement in tissue perfusion resulted in improvement in tpH and good correlation with arterial pH. The electrode was also sensitive to changes in carbon dioxide tension and adminitration of buffer. The good correlation with arterial pH and the feasibility of continuous recording of tissue pH makes it a useful instrument for monitoring the acid-base status of critically ill neonates.

Structural changes induced in glycogen phosphorylase b by the binding of glucose and caffeine

The allosteric inhibitors glucose and caffeine cause significant structural alterations in glycogen phosphorylase b (1,4-alpha-D-glucan:orthophosphate alpha-D-glucosyltransferase, EC 2.4.1.1). Both cause a masking of two sulfhydryl groups and a reduction of binding affinity for AMP. Caffeine produces an alteration in the microenvironment of the binding site for 1-anilin-naphthalene-8-sulfonate, resulting in a decrease of quantum yield of fluorescence and a change in spectral distribution. The binding of glucose is exothermic with an enthalpy of binding of -6.0 kcal/mol. Glucose causes a change in the molecular ellipticity in the pyridoxal-5'-phosphate region. The implications of these results are discussed.

Gestational age and indomethacin elimination in the neonate

The disposition of oral indomethacin was studied in 9 premature infants with significant patent ductus arteriosus (sPDA) with birth weights ranging from 800 to 1,960 gm and gestational ages of 28 to 36 wk. Peak plasma concentrations in most of the subjects were not observed until 3 to 4 hr after administration and ranged from 0.027 to 0.31 microgram/ml. Plasma half-life (t1/2) of indomethacin ranged from 11 to 20 hr and correlated with gestational age. Plasma protein binding studies, in samples from the premature infant using radiolabeled indomethacin, showed no difference in binding from values obtained with adult plasma (greater than 98%). Absorption of orally administered indomethacin appears to be incomplete and plasma clearance much longer than in the adult.

Disposition of indomethacin in preterm infants

Indomethacin is currently used for the pharmacologic closure of PDA in preterm infants with respiratory distress syndrome. However, the response to the drug has been variable and the disposition of the drug in preterm infants is not well understood. We studied the pharmacokinetics of indomethacin in nine preterm infants with birth weights ranging from 800 to 1,960 gm and gestational ages of 28 to 36 weeks. Three different dose schedules (0.1, 0.25, 0.3 mg/kg dose) were used. The plasma half-life of indomethacin ranged from 11 to 20 hours. Peak levels were achieved within four hours and ranged from 0.027 to 0.310 microgram/ml. The half-life in infants less than 32 weeks' gestation was significantly prolonged compared to that in infants greater than 32 weeks. Protein-binding studies with 14C indomethacin showed that 98% of indomethacin was protein bound. Absorption of orally administered indomethacin appears to be poor and incomplete. No immediate major complications could be correlated to indomethacin therapy in this study.

Ligand binding and self-association of phosphorylase b

The mutual influence of ligand binding and self-association has been examined for phosphorylase b in the presence of a series of small ligands. The stepwise equilibrium constants describing the mutual dependence have been evaluated and discussed in terms of possible molecular mechanisms.

Immediate and long-term outcome of infants less than 1000 grams

In order to assess the immediate and long-term outcome of very low birth weight infants, a retrospective analysis of clinical and biochemical parameters of 100 consecutive newborns with birth weights less than 1000 g was carried out. Overall neonatal mortality for this group was 69%. For infants between 751 to 1000 g, the mortality rate was 52%. Of the 23 infants who were discharged, neurodevelopmental assessment was performed in 16. Twelve of the 16 were neurologically normal. The data indicate a favorable prognosis for infants with birth weight less than 1000 g.