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Biomedical subjects

W Oh

Publications and source records attributed to W Oh.

At least 109 records · Page 6Linked to original sources
PubMed1992

Risk factors for early intraventricular hemorrhage in low birth weight infants.

Because earlier studies suggested that preterm infants with germinal matrix hemorrhage or intraventricular hemorrhage or both (GMH/IVH) present within the first 12 postnatal hours are at greatest risk for the development of high-grade hemorrhage and neurodevelopmental disability, we examined the risk factors for this insult among 229 neonates of 600 to 1250 gm birth weight in a multicenter study. All had echoencephalography (ECHO) within the first 11 hours and serially for the next 20 days; risk factor data were collected prospectively. Forty-three infants had GMH/IVH within the first 5 to 11 hours (mean age at ECHO 7.7 hours): 18 GMH and 21 grade II, 1 grade III, and 3 grade IV IVH. One hundred eighty-six infants did not have GMH/IVH at a mean age of 7.9 hours. Both groups of infants were similar in birth weight, gestational age, maternal risk factors, cord pH values, and surfactant therapy before ECHO. The group with early IVH had more vertex presentations than the group without early IVH (79% vs 55%, p = 0.043), less maternal tocolytic use (42% vs 60%, p = 0.029), and more vaginal deliveries (67% vs 44%, p = 0.005). In the first 21 days, severe IVH developed in 12 infants with early IVH and in 6 infants without early IVH (p < 0.001). There were more neonatal deaths (16% vs 6%, p = 0.035) and more deaths at any time during the primary hospitalization (23% vs 9%, p = 0.010) among the early IVH group than among the group without early IVH. Multivariate analysis indicated that the mode of delivery, fetal presentation, and birth weight were important and independent prognostic indicators of IVH.

Birth Weight↗
PubMed1992

Glucose kinetics following administration of an intravenous fat emulsion to low-birth-weight neonates.

To evaluate the mechanism(s) of the observed increase in plasma glucose concentration following the administration of an intravenous fat emulsion to the neonate, we measured glucose kinetics in eight low-birth-weight neonates by the prime constant rate infusion technique with D-[6,6-2H2]glucose at a rate of 0.22 +/- 0.01 mumol.kg-1 x min-1 (39.4 +/- 1.3 micrograms.kg-1 x min-1) while the neonates received 32 +/- 5 mumol.kg-1 x min-1 glucose (6.3 +/- 1.1 mg.kg-1 x min-1) plus an amino acid mixture (parenteral alimentation) alone and in combination with an intravenous fat emulsion (Intralipid). Following the latter combination, there were significant increases in plasma glucose concentration [4.07 +/- 0.11 (73 +/- 2 mg/dl) to 5.00 +/- 0.22 mmol/l (90 +/- 4 mg/dl); P < 0.01] and in plasma insulin concentration [72 +/- 14 (10 +/- 2 microU/ml) to 172 +/- 36 pmol/l (24 +/- 5 microU/ml); P < 0.05]. The parenteral alimentation and intravenous fat effusion combination did not affect the glucose production rate: 0.15 +/- 0.05 mumol.kg-1 x min-1 (0.03 +/- 0.01 mg.kg-1 x min-1) during the parenteral alimentation alone and 0.16 +/- 0.05 mumol.kg-1 x min-1 (0.03 +/- 0.01 mg.kg-1 x min-1) when parenteral alimentation was combined with an intravenous fat emulsion. We conclude that the increased plasma glucose concentration seen in association with administration of parenteral alimentation combined with an intravenous fat emulsion to the premature neonate is not due to enhanced glucose production but could be the result of alterations in glucose utilization.

Blood Glucose↗
PubMed1992

Group B Streptococcus-induced acidosis in newborn swine: regional oxygen transport and lactate flux.

To investigate the mechanism of metabolic acidosis resulting from group B streptococcal sepsis, oxygen metabolism and lactate flux of the cerebrum, hindlimb, liver, splanchnic organs, and systemic vascular bed as a whole were examined. Nine 3- to 5-day-old awake and spontaneously breathing piglets were studied before and after 3, 4, and 5 h of continuous live group B Streptococcus infusion. After 5 h, oxygen delivery was decreased to all organs and to the whole systemic vascular bed. Increased oxygen extraction compensated for reduced oxygen delivery in the liver and splanchnic organs; however, it only partially offset reduced oxygen delivery to the hindlimb and systemic vascular bed. Cerebral oxygen extraction did not increase. As a result, oxygen uptake was reduced in the cerebrum, hindlimb, and systemic vascular bed. At 5 h of bacterial infusion, arterial lactate concentration was increased with regional lactate efflux from the cerebrum and hindlimb and influx to the liver (P less than 0.05 vs. zero or no net flux). We conclude that group B Streptococcus-induced metabolic acidosis is associated with regional lactate efflux from vascular beds in which oxygen uptake is reduced. We speculate that the quantity of net lactate efflux from vascular beds with insufficient oxygen uptake exceeds the net influx into organs such as the liver, resulting in metabolic acidosis.

Acidosis↗
PubMed1992

Atrial natriuretic peptide in newborn piglets with a patent ductus arteriosus.

Atrial natriuretic peptide (ANP) is a hormone involved in fluid and blood pressure homeostasis. We studied the effects of left-to-right shunting through a patent ductus arteriosus on blood pressure changes and plasma ANP concentrations in newborn piglets. In five experimental piglets, the ductus arteriosus was bathed with PGE1 and infiltrated with formalin to maintain its patency. In four age-matched control piglets, the ductus arteriosus was ligated. Plasma ANP concentrations and blood pressure determinations were obtained prior to (base-line) and 25 +/- 1 h (day 1), and 48 +/- 1 h (day 2) after surgery. Radionuclide-microsphere determinations of left-to-right patent ductus arteriosus shunts were performed on days 1 and 2 in the 5 piglets with a patent ductus arteriosus. Plasma ANP concentrations were significantly elevated in the left atrium on day 1 and the right atrium on day 2 in the PDA piglets. No correlation was demonstrated between plasma ANP concentrations and right or left atrial pressures. We conclude that left and right plasma atrial ANP concentrations are significantly elevated in newborn piglets with left-to-right patent ductus arteriosus shunts.

Animals↗
PubMed1992

Changes in piglet auditory brainstem response amplitudes without increases in serum or cerebrospinal fluid neuron-specific enolase.

We studied the relationship between changes in auditory brainstem responses (ABR) and serum and cerebrospinal fluid levels of neuron-specific enolase (NSE) in hyperbilirubinemic 2- to 8-d-old piglets. Infusion of a stabilized solution of bilirubin resulted in serum bilirubin levels of 571.1 +/- 48.8 mumol/L (mean +/- SEM) after 6 h. ABR were obtained at baseline and then hourly until the piglets were killed. We measured peak amplitudes and latencies for waves I-V, as well as latency for the post-V trough. Changes in amplitudes and latencies were analyzed as slopes because of heterogeneous variances. Over time, a significant reduction was observed in peak II-V amplitudes of bilirubin-infused piglets, but not in those of corresponding controls. No change was observed in latencies. NSE was analyzed by RIA. Serum NSE remained stable throughout the experiment (means 5.1-6.6 micrograms/L) and did not differ between the groups. Cerebrospinal fluid NSE values also remained stable, and no differences that could be ascribed to hyperbilirubinemia were detected. We conclude that hyperbilirubinemia induced significant changes in piglet ABR amplitudes without concomitant evidence of severe neuronal compromise, as might have been indicated by significant increases in serum and/or cerebrospinal fluid NSE levels. This provides further support to the clinical impression that early ABR changes during hyperbilirubinemia may be reversible.

Animals↗
PubMed1991

Meconium for drug testing.

Samples of meconium from 28 neonates born to women suspected of drug abuse were tested for drugs of abuse (ie, cocaine, morphine, codeine, and marijuana). In each case, testing of urine from the mother, the newborn, or both had been ordered by the attending physician because of suspected maternal drug abuse. Seventeen (61%) of 28 meconium samples tested positive; 28 (60%) of 47 urine samples were positive. Meconium test results were concordant with the results of maternal or newborn urine testing in 24 (86%) of the 28 cases. In three cases, meconium was positive for cocaine when newborn urine was negative; in one case, meconium was negative when maternal urine was positive for cocaine. Compared with the combination of maternal and newborn urine testing, meconium testing had an 82% positive predictive value (14/17) and a 91% negative predictive value (10/11). Collection of meconium is simpler and more reliable than collection of urine, and testing of meconium was easily incorporated into routine procedures at a busy commercial laboratory. Meconium is a useful sample for drug detection in newborns.

Cocaine↗
PubMed1991

Neurodevelopmental and medical status of low-birthweight survivors of bronchopulmonary dysplasia at 10 to 12 years of age.

Thirty low-birthweight (less than 1500g) infants (15 with bronchopulmonary dysplasia (BPD), and 15 controls less than or equal to 5 days O2) and 15 fullterm controls were evaluated at 10 to 12 years of age. BPD children weighted less than fullterm children and had smaller head circumferences than either preterm or fullterm controls. They also had significantly more neurological abnormality than both control groups. BPD children and preterm controls had lower WISC-R arithmetic scores and lower Beery VMI scores, as well as greater need of resources and special education compared with fullterm controls. BPD survivors at 10 to 12 years of age continue to manifest sequelae related to their early pulmonary disease.

Achievement↗
PubMed1991

The cross-generation effect of neonatal macrosomia in rat pups of streptozotocin-induced diabetes.

To study the cross-generation effect of enhanced growth in macrosomic newborn rats, we induced mild hyperglycemia in 15 pregnant Sprague Dawley rats by intraperitoneal injection of streptozotocin, 35 mg/kg body weight, on the 5th d of gestation. As reported previously, we produced hyperinsulinemia and accelerated growth in the fetuses of hyperglycemic dams. We also showed that the macrosomic female pups (second generation) continued to have a higher growth rate through the first 12 wk of life. In this study, the second-generation female rats were mated with macrosomic second-generation males; they demonstrated glucose intolerance during late pregnancy and delivered pups (third generation) with higher birth weight and plasma insulin levels than the pups from control second-generation rats. When the macrosomic third-generation pups were raised under identical nutritional and environmental conditions as controls, the macrosomic rats showed accelerated growth and higher fat tissue weight during the first 12 wk of life. Furthermore, the macrosomia was associated with glucose intolerance and higher insulin to glucose ratios compared to controls. We also mated the offspring of second-generation streptozotocin-injected nonmacrosomic as well as the offspring of macrosomic pups of buffer-injected dams; none of the pups from these matings were significantly macrosomic. Therefore, we conclude that the perpetuation of obesity and possibly glucose intolerance across generations in this rat model is predominantly a result of abnormal intrauterine metabolic environment rather than genetic factor driven.

Animals↗
PubMed1991

Evaluation of insulin sensitivity in obese offspring of diabetic rats by hyperinsulinemic-euglycemic clamp technique.

Young adult macrosomic offspring of streptozotocin-induced mildly hyperglycemic rats exhibit accelerated growth through the first 10 wk of age. At 10 wk, oral glucose loading resulted in elevated plasma insulin and glucose concentrations compared to controls. To assess the mechanism of the abnormal glucose tolerance in vivo, hyperinsulinemic-euglycemic clamp studies were performed. Ten-wk-old rats were fasted overnight, and porcine insulin was infused (2.4 mU.kg-1.min-1). Glucose was infused concurrently at varying rates to maintain euglycemia for 40-60 min. Insulin levels were raised from a baseline value of 163 +/- 57 pmol/L (23 +/- 8 microU/mL) (SD) to 476 +/- 57 pmol/L (67 +/- 8 microU/mL) at steady state for males and from 178 +/- 43 pmol/L (25 +/- 6 microU/mL) to 454 +/- 43 pmol/L (64 +/- 6 microU/mL) for females. The results showed that the macrosomic male and female animals were significantly less sensitive to the effects of insulin than were their respective controls; this was evident by a lower increment in glucose disposal rate per unit increase in insulin (0.04 +/- 0.01 versus 0.11 +/- 0.03 for males and 0.05 +/- 0.03 versus 0.18 +/- 0.07 mg.kg-1 per microU/mL for females). The endogenous glucose production by the liver in the basal (fasted) state in the macrosomic group compared to controls was higher, suggesting possible hepatic insulin resistance. However, endogenous glucose production was suppressed to the same degree between the experimental and control groups during the hyperinsulinemic period, suggesting that the hepatic insulin resistance can be overcome by high insulin levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Hyperventilation restores autoregulation of cerebral blood flow in postictal piglets.

Autoregulation of cerebral blood flow is impaired in the postictal state. This loss of autoregulation may in part be mediated by a rise in perivascular hydrogen ion and carbon dioxide concentration. We hypothesized that hypocarbia with a concomitant reduction in perivascular hydrogen ion and carbon dioxide concentration would restore autoregulation during the postictal state. We studied autoregulation of cerebral blood flow in 13 ventilated, awake 3- to 4-d-old piglets during the postictal state under normocarbic and hypocarbic conditions. During the postictal state, cerebral blood flow was pressure-passive in normocarbic piglets, whereas the relationship between cerebral blood flow and cerebral perfusion pressure was described by a polynomial curve in hypocarbic piglets. Because hypocarbia restores cerebral blood flow autoregulation in postictal newborn piglets, we speculate that the perivascular hydrogen ion and carbon dioxide concentration contribute significantly to the state of cerebral autoregulation in the postictal subject.

Animals↗
PubMed1991

Fetal growth factors as determinants of intrauterine hepatic growth.

To understand mechanisms at the cellular level that may lead to the selective organomegaly seen in fetuses of diabetic mothers, we examined the role of insulin and autocrine-paracrine growth factors in the regulation of hepatic growth in the fetal rat. Analyses of fetal liver from the last one-third of gestation demonstrated the presence of specific mRNAs for the transforming growth factors (TGFs) TGF-alpha and TGF-beta. TGF-alpha, a homologue of epidermal growth factor (EGF), acts through EGF receptors. Levels of mRNA for TGF-alpha increased dramatically postnatally, whereas EGF receptor number increased just before term. In contrast, levels of mRNA for TGF-beta, an inhibitor of epithelial cell growth, were greater in fetal liver than in adult liver, as was TGF-beta-receptor binding. Other analyses demonstrated increases in tyrosine kinase activities of the insulin receptor, EGF receptor, and insulinlike growth factor I receptor as term approached. Proliferation of fetal rat hepatocytes in primary culture did not require mitogens or serum, consistent with production and activity of autocrine-paracrine growth factors. TGF-beta was a potent inhibitor of fetal hepatocyte proliferation in culture, whereas insulin potentiated fetal hepatocyte growth above "mitogen-independent" levels. The regulatory mechanisms controlling fetal hepatic growth involve a complex interaction between stimulatory and inhibitory factors. Growth factor expression, receptor expression, receptor tyrosine kinase activity, and postreceptor signal transmission represent potential loci for insulin action that might be involved in the pathogenesis of fetal macrosomia seen in diabetic pregnancies.

Animals↗
PubMed1990

Behavioral changes correlated with brain-stem auditory evoked responses in term infants with moderate hyperbilirubinemia.

The purpose of this study was to test the hypotheses that newborn infants with moderate serum bilirubin concentrations have depressed Brazelton scores and increased brain-stem conduction time and that serum bilirubin levels correlate with Brazelton behavior scores and brain-stem auditory evoked response changes. Fifty term infants who were enrolled into either a low serum bilirubin group (less than 8 mg/dl) or a moderate serum bilirubin group (10 to 20 mg/dl) were tested with the Brazelton Neonatal Behavioral Assessment Scale and a brain-stem auditory evoked response test. Partial correlation analysis controlling for phototherapy revealed that increased bilirubin concentration correlated negatively with the Brazelton orientation and with state range clusters and individual Brazelton test items that involve auditory processing. Increased bilirubin concentration correlated with an increased latency of brain-stem auditory evoked response wave 4, 5. An increased interpeak 1-5 (brain-stem conduction time) correlated with the decreased animate visual and auditory item. We conclude that moderate hyperbilirubinemia in term infants affects both infant behavior, as measured by specific components of the Brazelton test, and brain-stem conduction time, as measured by the brain-stem auditory evoked response test.

Arousal↗
PubMed1990

Hemodynamic changes in a term newborn piglet model of patent ductus arteriosus.

Patent ductus arteriosus (PDA) is a common form of congenital heart disease in full-term infants. To investigate the morbidities associated with a left to right PDA shunt, we produced a PDA in six full-term newborn piglets (less than 36 hours old) by bathing the ductus arteriosus with prostaglandin E (PGE) and infiltrating it with formalin. In five age-matched piglets, the ductus arteriosus was ligated to serve as controls. Microsphere determinations of left ventricular output (LVO) and regional blood flow (Q) were made on three consecutive days. We produced left to right shunts of 36 to 47% (mean) in the experimental piglets. The experimental piglets had a 22 to 36% increase in LVO with a one- to twofold reduction in percentage of LVO to the kidneys and carcass (p less than 0.05). Although percentage of LVO to the gastrointestinal tract was reduced (p less than 0.05), no reduction of absolute Q to the gastrointestinal tract was observed. Brain and heart Q were similar in both groups. We conclude that significant hemodynamic changes result from left to right shunting in the full-term newborn piglet with PDA. These hemodynamic changes, such as reduction in renal blood flow, are relevant information that will help explain the morbidities observed in infants with a hemodynamically significant PDA with a left to right shunt.

Animals↗
PubMed1990

The effects of acute uterine ischemia on fetal circulation.

The effects of acute maternal hemorrhage on uterine blood flow and fetal circulation were investigated in pregnant sheep. Nine chronically instrumented pregnant sheep (114-128 d gestation), phlebotomized from the iliac artery at the point of origin of the uterine artery, were studied at baseline, after acute hemorrhage, and immediately and two h after replacement of the blood. Maternal hemorrhage caused a reduction in uterine blood flow as well as both fetal hypoxemia and acidemia. Changes in fetal organ blood flow measured by radionuclide-labeled microspheres showed that blood flow to the brain, heart, and adrenal glands increased (p less than 0.05), whereas blood flow to the other major organs did not change significantly. Rapid replacement of blood restored all parameters to baseline values. We conclude that acute maternal hemorrhage causes a reduction in uterine blood flow, fetal hypoxemia, and acidemia with a secondary increase in blood flow to the high priority organs. Rapid replacement of blood reverses these effects.

Animals↗
PubMed1990

Glucose metabolism in adipocytes of obese offspring of mild hyperglycemic rats.

Six pregnant rats were made mildly hyperglycemic by intraperitoneal injection of streptozotocin on d 5 of gestation. Four control rats were injected with citrate buffer. Thirty pups born to experimental dams who had increased birth weight (birth weight greater than 1.7 SD of mean birth weight of pups from control dams) maintained accelerated growth through 10 wk of age. At 10 wk, oral glucose tolerance tests showed higher glucose and insulin levels than the controls (n = 37). In addition to the higher body weight, the experimental rats also had higher fat weight to body weight ratios. Adipocytes of epididymal fat from obese males and periovarian fat from obese females had higher lipid content with significantly larger cell size than the adipocytes of the controls. The adipocytes of macrosomic rats showed attenuated response to insulin-stimulated glucose conversion to total lipid and fatty acid when compared with the responses seen in the adipocytes of the control rats. Interestingly, although the insulin-stimulated glucose conversion to CO2 was similar in macrosomic and control males, the response in the macrosomic female was blunted when compared with that of the control females. Insulin receptor binding capacities of the macrosomic rats were lower than those of the controls, which is consistent with a phenomenon of down-regulation. However, the receptor affinities were higher in the experimental animals than in controls. Therefore, a postreceptor defect may account for the abnormality in glucose metabolism in the obese rats. In conclusion, the abnormal response to oral glucose loading in these experimental obese, hyperinsulinemic rats is due to peripheral tissue insulin resistance that is probably postreceptor in nature.

Adipose Tissue↗
PubMed1990

Multicenter trial of single-dose modified bovine surfactant extract (Survanta) for prevention of respiratory distress syndrome. Ross Collaborative Surfactant Prevention Study Group.

A multicenter, prospective randomized controlled trial was performed comparing the efficacy of a single intratracheal dose of modified bovine surfactant extract (Survanta, 100 mg/kg, Abbott Laboratory, North Chicago, IL) with air placebo in preventing respiratory distress syndrome. Infants were enrolled if they were estimated to be between 24 and 30 weeks' gestation, weighed between 750 and 1250 g, and were intubated and stabilized within 15 minutes after birth. A total of 160 infants were treated (79 with surfactant, 81 with air placebo) between 4 and 37 minutes after birth (median time 12 minutes). Of these, 5 infants were excluded from the final analysis. The 72-hour average values for the arterial-alveolar oxygen ratio, fraction of inspired oxygen, and mean airway pressure were calculated from the area under the curve of scheduled values measured throughout 72 hours. Clinical status was classified using five ordered categories (no supplemental oxygen or assisted ventilation, supplemental oxygen only, continuous positive airway pressure or assisted ventilation with intermittent mandatory ventilation less than or equal to 6 breaths/min, assisted ventilation with intermittent mandatory ventilation greater than 6 breaths/min, death). Chest radiographs at 24 hours were graded for severity of respiratory distress syndrome. Infants receiving Survanta had less severe radiographic changes at 24 hours of age and decreased average fraction of inspired oxygen (31% vs 42%, P = .002) compared with control infants. No differences were noted in the average arterial-alveolar oxygen ratio, mean airway pressure, or clinical status on days 7 and 28. A beneficial effect was noted in the incidence of pneumothorax (P = .057) and an increase was noted in the incidence of necrotizing enterocolitis (P = .052). No differences in incidence of patent ductus arteriosus, intraventricular hemorrhage, sepsis, or bronchopulmonary dysplasia were seen. According to results of a secondary analysis, there was improvement in the fraction of inspired oxygen and a greater number of survivors without bronchopulmonary dysplasia in the subgroup of infants weighing less than 1000 g who were treated with surfactant. It was concluded that a single dose of Survanta given shortly after birth resulted in decreased severity of chest radiographic findings 24 hours after treatment and improved oxygenation during 72 hours after treatment, but did not improve other acute measures of disease severity or clinical status later in the neonatal period. The group at highest risk for respiratory distress syndrome (infants with birth weights between 750 and 999 g) may benefit the most from preventive therapy.

Animals↗