Biomedical subjects

D E Demello

Publications and source records attributed to D E Demello.

5 recordsLinked to original sources

PubMed1998

Computerized morphometry of the pulmonary vasculature over a range of intravascular pressures.

Recent availability of computerized image analysis has fostered hope that barium injection and landmarking of pulmonary arteries would be unnecessary for morphometric assessment when using this technique. We reasoned that if barium injection altered morphometric variables, it would do so in a linear fashion correlating with incremental increases in injection pressure of the barium. The two goals of the present study were to determine whether barium injection into arteries affected morphometric measurements and to determine whether incremental increases in injection pressure correlated with alterations in morphometric measurements in a linear fashion. Computerized image analysis was used to measure the internal elastic lamina (IEL) and external elastic lamina (EEL). Medial area (MA), luminal area (LA), percentage of medial thickness, IEL square root of MA, and idealized LA were calculated. Barium injection did not alter morphometric variables in a linear fashion correlating with incremental increases in injection pressure of the barium except the percentage of arteries that filled with barium. Maximum recruitment for pre-acinar arteries occurred at 40 mmHg pressure and 60 mmHg distending pressure for intra-acinar arteries. Incremental increases in injection pressure did not affect IEL, EEL, or calculated morphometric variables. However, IEL, medial thickness, and MA were all smaller in injected vessels than in uninjected vessels. IEL square root of MA and the ratio of measured vs. idealized LA were both increased in injected lungs. We suspect that vascular injection selects for evaluation, a population of smaller, thin-walled vessels, which in the uninjected lungs are collapsed and hence excluded from analysis.

Angiography↗

PubMed1997

Thyrotropin-releasing hormone accelerates fetal mouse lung ultrastructural maturation via stimulation of extra thyroidal pathway.

Maternal administration of TSH-releasing hormone (TRH) in the euthyroid mouse accelerates fetal lung ultrastructural maturation. However, the mechanism(s) of TRH in fetal lung development remains unclear; it could be due to its neuroendocrine and/or neurotransmitter effects. Although the neuroendocrine effect of TRH is mediated via stimulation of the fetal pituitary-thyroid axis, the neurotransmitter effect is mediated via stimulation of fetal autonomic nervous system activity. In the hyt/hyt mouse there is a point mutation in the beta subunit of the TSH receptor in the thyroid gland of the Balb-c mouse. In these mice TSH does not bind to its receptors, leading ultimately to the development of primary hypothyroidism, which is transmitted as an autosomal recessive trait. A maturational delay in the lung ultrastructure of the hyt/hyt mouse fetus has been observed. This investigation was undertaken to study the effect of maternal TRH treatment on lung ultrastructural maturation in the hyt/hyt mouse fetus. If the effect of TRH is mediated via stimulation of fetal pituitary-thyroid axis, TRH treatment should not enhance lung maturity in the hyt/hyt fetus and vice versa. Adult hyt/hyt mice made euthyroid by triiodothyronine supplementation were mated to carry hyt/hyt pups. Saline or TRH (0.4 or 0.6 mg/kg/dose) was administered to the mother (i.p.) on d 16 and 17 (b.i.d.) and on d 18 of pregnancy 1 h before killing (term, approximately 20 d). The fetal lung electron micrographs were subjected to ultrastructural morphometric analysis of the number of lamellar bodies and glycogen/nuclear ratio in type II cells, and the alveolar/parenchymal ratio by Chalkley point counting with an interactive computerized image analyzer (Optimas, Bioscan). Fetal lungs exposed to the lower dose of TRH (n = 7) showed no significant difference in their ultrastructural maturation when compared with saline-treated controls (n = 5). However, fetal lungs exposed to a higher dose of TRH (n = 6) showed increased numbers of lamellar bodies per type II cell, an increase in the alveolar/parenchymal ratio, larger air spaces, thinner alveolar septa, presence of tubular myelin, and increased numbers of air-blood barriers. We conclude that the effect of TRH in accelerating fetal mouse lung maturation is at least in part mediated via stimulation of extra thyroidal pathways.

Animals↗

PubMed1994

Chronic platelet-activating factor induces a decrease in pulmonary vascular compliance, hydroxyproline, and loss of vascular matrix.

We have previously demonstrated that chronic intravenous platelet-activating factor (PAF) induces morphologic remodeling of pulmonary arteries characterized by a decrease in internal and external elastic lamina circumference, pulmonary arterial contracture, and internal elastic lamina duplication. The mechanism of PAF-induced arterial contracture is unknown. In this study we determined whether PAF caused arterial contracture through cell loss by calculating the number of cell nuclei/total cross-sectional area of arteries. The nuclear ratio was increased in intra- and preacinar pulmonary arteries of PAF-treated rabbits. Hydroxyproline content of lungs stratified by anatomic region was significantly reduced in intra-acinar tissue of PAF-treated rabbits, indicating that PAF-induced vascular contracture was associated with loss of interstitial collagen. We next tested whether these morphologic alterations were associated with decreased pulmonary vascular compliance and increased resistance. Compliance and resistance were determined in isolated, perfused lungs from rabbits chronically treated with PAF. Compliance was calculated: (1) from the slope of the venous occlusion trace (CVO), (2) by increasing left atrial pressure (CLA), (3) by increasing flow (CHF), and (4) by the classic static technique (CAV) of adding volume (2 ml) to a passively drained lung. Vascular compliance was significantly reduced in PAF-treated lungs when measured by all four methods; however, pulmonary vascular resistance was unchanged. We conclude that structural changes that result from chronic intravenous PAF infusion affect the elastic modulus to a greater extent than factors that influence pulmonary vascular resistance.

Animals↗

PubMed1993

Effect of maternal diabetes on the expression of genes regulating fetal brain glucose uptake.

Diabetes alters adult brain glucose uptake and glucose transporter 1 gene expression. To investigate the effect of diabetes on genes regulating fetal brain glucose uptake, we examined the effect of moderate (blood glucose 10-16.7 mM, normoinsulinemia) and severe (blood glucose > 16.8 mM, hypoinsulinemia) maternal diabetes on the expression of genes regulating fetal brain glucose uptake in the genetically nonobese diabetic mouse. In the moderately diabetic state, a 50% decline in fetal brain GLUT1 mRNA levels was associated with a 20% increase in the corresponding GLUT1 protein levels. Simultaneously, although fetal brain GLUT3 mRNA and protein levels were barely detectable, no change in hexokinase I enzyme mRNA, protein (115,000 and 100,000 M(r)) or activity, was noted. In the severe form of maternal diabetes GLUT1 protein was unchanged, GLUT3 protein levels remained low, and a 2- to 3-fold increase in the lower molecular form of the hexokinase I protein (100,000 M(r)) and enzyme activity occurred. These observations suggest that moderate and severe forms of maternal diabetes do not affect the fetal brain glucose transporter levels to a physiologically significant extent. The severe form of maternal diabetes, however, enhances 1.5- to 3-fold the expression and activity of hexokinase I. This enzyme mediates the rate-limiting step in brain glucose metabolism, namely the intracellular conversion of glucose to glucose-6-phosphate.

Animals↗

PubMed1987

Effects of indomethacin in utero on the pulmonary vasculature of the newborn guinea pig.

The clinical syndrome of persistent pulmonary hypertension of the newborn results from failure of the normal perinatal vascular adaptation, and functionally is characterized by persistent right to left shunting of blood through the foramen ovale and ductus arteriosus. Exposure of the fetus to drugs that inhibit prostaglandin synthesis and cause closure of the ductus arteriosus has been suggested as one cause of persistent pulmonary hypertension of the newborn. We attempted to produce a functional and structural model of persistent pulmonary hypertension of the newborn by administration of indomethacin, a cyclooxygenase inhibitor, to pregnant guinea pigs. Five pregnant guinea pigs received 3.5 mg/kg indomethacin intravenously twice each day for the 12 to 19 days before delivery and seven controls received saline. Hemodynamic studies were performed in eight "treated" newborns and in 12 controls. After sacrifice, the ductus was ligated and, for morphometric studies, the pulmonary arteries were distended with barium/gelatin. The treated animals did not show the intraacinar structural or hemodynamic changes of persistent pulmonary hypertension of the newborn. It seems that the indomethacin did cross the placenta because lung structure was modified. The radical alveolar count and alveolar/artery ratio were increased and the preacinar arteries dilated, with more increase in muscle mass. This could be explained by increased pulmonary blood flow because of ductal constriction but direct effect of indomethacin cannot be excluded.

Animals↗