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R M Viscardi

Publications and source records attributed to R M Viscardi.

30 records · Page 2Linked to original sources
PubMed1989

Cholinephosphate cytidylyltransferase in fetal rat lung cells: activity and subcellular distribution in response to dexamethasone, triiodothyronine, and fibroblast-conditioned medium.

The initiation of pulmonary surfactant synthesis during fetal development has been shown to be under hormonal control. Using cultured lung cells isolated from 19-day-gestation fetal rats, we evaluated the effects of various hormones on the activity and subcellular distribution of cholinephosphate cytidylyltransferase, a rate-controlling enzyme in phosphatidylcholine synthesis. The cells were incubated in medium containing 10% carbon-stripped fetal bovine serum to which dexamethasone, triiodothyronine, and/or conditioned medium from dexamethasone-treated fetal rat lung fibroblasts were added for 48 h. Dexamethasone and fibroblast-conditioned medium increased microsomal enzyme activity 169% +/- 6% (mean +/- SE, p less than 0.01) and 150% +/- 2% (p less than 0.05) over control levels, respectively. Further, dexamethasone increased cytosolic specific activity 160% +/- 17% (p less than 0.05). Addition of T3 to the fibroblast-conditioned medium caused a further increase in microsomal activity, but T3 alone had no effect. Increased microsomal cytidylyltransferase activity correlated with an increased rate of [3H]choline incorporation into disaturated phosphatidylcholine. Hormonal induced increases in enzyme activity were not adequately explained by simple translocation of enzyme from cytosol to microsomes. Cycloheximide (5 micrograms/ml) inhibited enzyme stimulation by dexamethasone and fibroblast-conditioned medium, suggesting that protein synthesis of new enzyme or regulatory proteins is involved. We conclude that hormones modulate cytidylyltransferase activity of isolated fetal lung cells. Dexamethasone and fibroblast-conditioned medium exert their major effects by stimulating microsomal activity.

Animals↗
PubMed1989

Adult respiratory distress syndrome in full-term newborns.

Since 1984, 11 newborns with severe respiratory distress have been treated whose clinical characteristics appear distinctive. Characteristics of these neonates were as follows: (1) they were full term by obstetric and neonatal criteria, (2) they had diffuse bilateral alveolar opacification on chest radiographs during the acute illness, (3) each had an acute perinatal triggering insult, (4) the neonates required continuous positive pressure ventilation for at least 48 hours with FiO2 greater than 0.50 for at least 12 hours, (5) they needed positive end-expiratory pressure of 6 cm of H2O or greater within three days of the triggering event, (6) there were no other known causes of these clinical conditions. Ten (91%) neonates had evidence of other organ dysfunction in addition to the lungs. Trials of hyperventilation in nine and tolazoline in five failed to improve oxygenation. Ten infants who underwent trials of increased positive end-expiratory pressure greater than or equal to 6 cm of H2O without other concurrent changes in ventilator settings responded with prompt increases in PaO2 (median increase 84 mm Hg, range 22 to 196 mm Hg). All 11 babies survived but required prolonged mechanical ventilation and supplemental oxygen. We suggest that adult respiratory distress syndrome can and does occur in newborns. A trial of positive end-expiratory pressure greater than or equal to 6 cm of H2O should be considered in full-term infants with severe respiratory distress in whom other causes can be excluded.

Acute Disease↗
PubMed1988

Intraventricular hemorrhage in preterm twin gestation infants.

The incidence of intraventricular hemorrhage (IVH) in twin pregnancy infants with birthweights less than 1500 g in a 5 year period was examined retrospectively. Of the 70 infants in this birthweight category (for which IVH status was known) born at the University of Michigan Medical Center between January 1980 and December 1984, 20 had IVH (29%) (p = NS). The only significant association with IVH was respiratory distress. Presentation, route of delivery, a low 5 minute Apgar score, and time between first and second delivery were not significant factors. However, a multiple logistic regression of the infants categorized by IVH status demonstrated significant effects of twinship itself and of birth order within a given twinship. The unexpected low incidence of IVH in this high risk group suggests that better obstetric and neonatal management of low birthweight preterm twins at tertiary care centers may result in improved survival and decreased morbidity including intraventricular hemorrhage.

Birth Order↗
PubMed1985

Partial pyruvate decarboxylase deficiency with profound lactic acidosis and hyperammonemia: responses to dichloroacetate and benzoate.

We describe the successful use of sodium benzoate in a neonate with hyperammonemia associated with congenital lactic acidosis caused by a partial deficiency of the E1 component of pyruvate dehydrogenase (PDH); of note, this biochemical disturbance has not been previously described in PDH deficiency. The pyruvate dehydrogenase complex in skin fibroblasts had 48% of normal activity with a deficiency of the E1 component. The infant presented with rapid onset of a severe metabolic lactic acidosis, hyperventilation, hyperammonemia, and coma. At 30 hours of age continuous peritoneal dialysis was started; however, plasma NH3 concentrations remained in the 300-400 micrograms/dl range over the next 12 hours. Sodium benzoate, 250 mg/kg, was infused intravenously with a decrease in plasma ammonia of 25 micrograms/dl/hr. Hippurate was documented in the urine and peritoneal fluid after benzoate therapy. At 10.5 months of age, 50 mg/kg dichloroacetate was administered orally under fasting conditions, which resulted in a 56 and 62% reduction in the serum lactate and pyruvate levels, respectively; after 2 weeks on dichloroacetate his fasting levels were significantly decreased. Fibroblast PDH activity responded similarly to this drug. In our patient sodium benzoate was rapidly effective in producing a decline in plasma ammonia that was associated with clinical improvement. We feel that its use in organic acidemias deserves further evaluation and, furthermore, that any child with suspected PDH deficiency requires a clinical trial of dichloroacetate.

Acidosis↗
PubMedDate not supplied

Fetal androgen exposure inhibits fetal rat lung fibroblast lipid uptake and release.

Fetal lung fibroblasts provide lipid substrate for type II cell surfactant phospholipid synthesis. This process is developmental and glucocorticoid dependent. Previous studies in our laboratory demonstrating sex differences in several aspects of lung maturation suggest that these differences may be due to effects of fetal androgens. Based on these studies, we hypothesized that fetal lung fibroblast triglyceride metabolism is determined by opposing effects of fetal androgens and glucocorticoids. To model the effects of androgens on fetal lung fibroblast triglyceride metabolism, pregnant rats were treated with dihydrotestosterone (DHT) 1 mg/kg/day from the days 15 to 20 of gestation, and changes in triglyceride content of freshly isolated fetal rat lung fibroblasts (FRLF) and rates of uptake and prostaglandin E2 (PGE2)-mediated release by cultured FRLF in response to glucocorticoids in the presence or absence of DHT in vitro were measured. During lung development, the triglyceride content and rate of uptake of female-derived FRLF increased 3.5- and 4.8-fold, respectively, between days 18 and 20 of gestation. From days 19 to 22, male FRLF trigyclyceride content and rate of uptake were lower than the content and uptake by female FRLF. Maternal DHT treatment inhibited the normal developmental increase in fibroblast triglyceride content and rate of uptake between days 19 and 22 by both male and female FRLF. In the absence of maternal DHT, in vitro dexamethasone stimulated triglyceride uptake 3-fold by day 21 in FRLF. This effect was blocked by maternal pretreatment with DHT. Maternal DHT exposure prevented stimulation of triglyceride release by PGE2. Although in vitro dexamethasone stimulated triglyceride release by maternal DHT-exposed fibroblasts, it did not enhance the response to PGE2. These data suggest that in utero exposure to androgens (1) delay the developmental increase in triglyceride content and (2) oppose the effects of glucocorticoid on cultured FRLF triglyceride uptake and PGE2-mediated release.

Animals↗
PubMedDate not supplied

Developmental changes in phosphatidylinositol transfer protein concentration and phospholipid transfer activities in rat type II cells.

The phospholipid transfer proteins (PLTPs) are cytosolic proteins that have been characterized by their ability to facilitate the transfer of phospholipids between membranes in vitro. The goals of this study were to determine whether PITP alpha concentration and phospholipid transfer activities are enriched in type II cells compared with whole lung and to determine the developmental changes in PITP alpha concentration and phospholipid transfer activities during late gestation and newborn period. The concentration of PITP alpha in type II cell cytosol measured by enzyme-linked immunosorbent assay (ELISA) increased during late fetal gestation to 2.2-fold adult levels and declined 41% during the first postnatal day. However, compared to whole adult lung cytosol, type II cell cytosol was not significantly enriched with PITP alpha. Phospholipid transfer activities were determined by a vesicle-rat lung membrane transfer assay. In adult lung, transfer activities for all the phospholipids were enriched in adult type II cell cytosol compared to whole lung cytosol (phosphatidylglycerol [PG], 12.5-fold; phosphatidylinositol [PI], 9.2-fold; phosphatidylcholine [PC], 6.5-fold; and phosphatidylethanolamine [PE], 6.6-fold; P < .05 in each case). The rate of phospholipid transfer in type II cell cytosol increased during late fetal gestation to levels 4.9 (PG), 3.7 (PI), and 2.8 (PC) times greater than adult levels. In cytosol from cells from different stages, the order of transfer rate was PG > PI > PC > PE. PITP alpha immunodepletion of adult type II cytosol did not significantly affect phospholipid transfer activities, suggesting that other PLTPs are responsible for the majority of the observed transfer activities in these cells. Developmental increases in PITP alpha concentration and other PLTPs parallel developmental changes in type II cell surfactant phospholipid metabolism, suggesting a possible role of these transfer proteins in the unique function of the type II cell.

Animals↗
PubMedDate not supplied

Reproducible isolation of type II pneumocytes from fetal and adult rat lung using nycodenz density gradients.

Isolating fresh, relatively pure type II pneumocytes from the lung, particularly of fetal origin, is a difficult process. Separation by buoyant density gradient centrifugation has been used successfully to isolate adult type II cells. There is concern, however, that Percoll, a gradient medium that is commonly used for type II cell isolation, may be toxic to cells. We evaluated a new gradient medium, Nycodenz, that is (1) a true solution, (2) transparent, (3) not metabolized by cells, and (4) nontoxic to cells. Type II pneumocytes were isolated from 19- and 21-day gestation fetal and adult rat lung by elastase digestion and separated on preformed isotonic Nycodenz gradients (2 mL each of 27.6, 20.7, 13.8, and 4.6 (w/v) solutions). Type II pneumocytes were recovered from the density range 1.057-1.061 and identified by binding of FITC-conjugated and gold-complexed Maclura pomifera lectin. Cells derived from 19-day fetal lung contained abundant glycogen and reacted with a monoclonal antibody to the cytokeratins 8 and 18, which are markers of the fetal type II cell. Adult type II cells reacted with antibodies to cytokeratins 8, 18, and 19. Type II cell purity was 79.7 +/- 2.4%, 83.8 +/- 2.8%, and 82.6 +/- 1.8% (means +/- SEM) for 19- and 21-day gestation fetal and adult lung preparations, respectively. Cell viability was greater than 95%. The final cell yield for adult preparations was 17.8 +/- 2.7 x 10(6)/rat (means +/- SEM). To determine if the freshly isolated type II pneumocytes were functionally active, the incorporation of [3H]choline into phosphatidylcholine was measured. The percent saturation of phosphatidylcholine was high for both populations of freshly isolated cells. However, adult type II pneumocytes incorporated [3H]choline into phosphatidylcholine more rapidly than 21-day gestation fetal cells (5.97 x 10(-3) dpm/10(6) cells/h vs. 0.32 x 10(-3) dpm/10(6) cells/h, P less than .005). We have demonstrated that, using the Nycodenz isolation method, it is possible to obtain a high yield of relatively pure viable type II cells from fetal and adult lung that can be used for immediate study or cultured with an excellent plating efficiency (39 +/- 6.3%).

Animals↗
PubMedDate not supplied

Delayed primary tooth eruption in premature infants: relationship to neonatal factors.

Previous studies suggest that primary tooth eruption (PTE) in preterm infants is related primarily to gestational age, but the impact of other neonatal factors has not been studied. In a prospective longitudinal study, the timing and sequence of PTE were documented by a pictorial PTE record completed by the parents and by frequent oral exams in 14 preterm infants whose first tooth erupted at < or = 10 months chronologic age (normal group) and 21 preterm infants whose first tooth erupted at > 10 months (late group). Initial eruption sequence in both groups was the same as full-term infants, with the two lower central incisors erupting first. PTE occurred significantly later in children with BW < 1000 g (t = 3.4, P < 0.01) or < or = 30 weeks (t = 2.41, P < 0.05). Factors related to nutrition appeared to be important. Age at first tooth correlated significantly with age when full enteral feedings were attained, age when oral vitamin supplementation was started, and with average weight gain per day. Five neonatal factors (duration of oral intubation, birthweight, gestational age, age when full enteral feedings were attained, and apnea of prematurity) explained 44% (R = 0.67, P < 0.05) of the variability in age at which the first tooth erupted. Of that 44%, 77% was explained by a single factor, duration of oral intubation. These results suggest that factors related to severity of neonatal illness and postnatal nutrition as well as degree of prematurity affect timing of primary tooth eruption.

Apnea↗
PubMedDate not supplied

Effect of position on pulmonary mechanics in healthy preterm newborn infants.

Preterm infants are often placed in the supine position to facilitate care and observation. Prone positioning may positively affect later neurodevelopmental outcome, but it may also affect pulmonary function. Using a computerized system, we examined the effect of positioning on pulmonary mechanics in spontaneously breathing healthy preterm infants. Eleven infants with a mean birth weight (+/- SD) of 1523 +/- 171 gm and a mean gestational age (+/- SD) of 31.7 +/- 1.5 weeks were studied during the first 2 weeks of life. Pulmonary mechanic measurements were obtained in both supine and prone positions by mask pneumotachography and esophageal balloon technique. Respiratory rate and oxygen saturation were unaffected by positioning. There was a statistically, but not clinically, significant increase in heart rate in the prone position. However, there were no significant differences in tidal volume, minute ventilation, pulmonary resistance, or dynamic compliance between positions. The contribution of intrasubject variability of serial measurements was assessed in a separate group of four infants studied three times in the same position. There was no significant difference in respiratory rate, tidal volume, dynamic compliance per kilogram, or total pulmonary resistance in the same infant when studied in the same position over time (p > or = 0.24). The maximum variability (95% confidence limit) was 25.5% for tidal volume, 21% for dynamic compliance, and 44.3% for resistance. Because prone positioning did not adversely affect pulmonary mechanics or oxygen saturation in these healthy preterm infants, we suggest that prone position be used to facilitate the developmental needs of these infants.

Birth Weight↗
PubMedDate not supplied

Inflammatory cytokine mRNAs in surgical specimens of necrotizing enterocolitis and normal newborn intestine.

Coagulation necrosis, inflammation, and hemorrhage are pathologic hallmarks of necrotizing enterocolitis (NEC). Because cytokines are peptides that mediate inflammatory cell recruitment and amplify the immune response, several of the inflammatory cytokines have been implicated in NEC. We hypothesized that mRNA levels for the interrelated cytokines interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), IL-6, and the neutrophil chemotactic factor IL-8 would be increased in NEC and would be associated with the presence of inflammation. In this study, we determined the relative levels and localization of mRNA for these cytokines in surgical pathology archival intestinal tissue from 29 premature infants with acute NEC and 15 control infants with congenital intestinal malformations using a novel quantitative in situ hybridization technique. Compared with controls, there were higher IL-1 beta mRNA levels in full-thickness sections and higher TNF-alpha mRNA levels in full-thickness and mucosa sections of acute NEC samples, suggesting a potential role for these cytokines in the pathogenesis of local inflammation in NEC. IL-6 and IL-8 mRNA levels were similar in samples of control and acute NEC cases. Analysis of covariance including all subjects showed that the presence of acute inflammation was associated with increased IL-1 beta mRNA levels in mucosa (P = .035) and increased IL-8 in full-thickness sections (P = .005) and mucosa (P = .01). In four of five NEC cases in which intestinal specimens were available from reanastomosis surgery, cytokine mRNA levels decreased to low or undetectable levels. These data suggest that the inflammatory cytokines are involved in neutrophil recruitment and augmentation of the inflammatory response in neonatal intestine.

Cytokines↗