Michael Y. Tsai

Amniotic fluid phosphatidylglycerol in diabetic and control pregnant patients at different gestational lengths

Phosphatidylglycerol (PG) and lecithin/sphingomyelin (L/S) ratios were simultaneously determined in 1770 samples of amniotic fluid. PG was defined as present when it appeared in at least 2% of the total phospholipids. Comparison of the appearance of PG in samples of amniotic fluid obtained from diabetic and nondiabetic pregnant patients according to L/S ratios showed that samples from diabetic patients were less likely to have PG present than those from nondiabetic patients, particularly at L/S ratios between 3.1 and 4.0. Because of that, further studies compared the appearance of PG according to gestation in 186 diabetic patients with that in a group of 238 control patients that was composed only of those who underwent repeat cesarean section. Rh-sensitized patients were not included in the control group, since they had delayed appearance of PG. The results showed that the appearance of PG was delayed in patients with Classes B, C, and D-F-R diabetes. In patients with Class A diabetes, the appearance of PG was not significantly different from that in control patients over the entire gestational period, although the appearance of PG may be delayed during early gestation. In contrast, there were no significant differences in L/S ratios in various classes of diabetic pregnant patients and control patients at different gestations.

The effect of prenatal dexamethasone on fetal rat lung prostaglandin synthesis

[14C]Arachidonic acid conversions were studied in homogenates of lungs from 20, 21, and 22 day fetuses with or without prenatal dexamethasone treatment. The major metabolites were in all cases 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE), 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), prostaglandin E2 (PGE2), and 12-L-hydroxy-5,8,10-heptadecatrienoic acid (HHT). Prostaglandin F2 alpha (PGF2 alpha), prostaglandin D2 (PGD2), and thromboxane B2 (TxB2) were present in small amounts. Dexamethasone treatment significantly stimulated the conversion of [14C]-arachidonic acid in fetal lung homogenates to 6-keto-PGF1 alpha, PGE2, 12-HETE, and HHT, at 20 days gestational age. This effect was dependent on the dose of dexamethasone. These results suggest that dexamethasone accelerates the maturation of the enzymes involved in prostaglandin synthesis. Because dexamethasone is also known to inhibit phospholipase A2, further studies are required to determine the overall in vivo effect of prenatal dexamethasone therapy on fetal lung prostaglandin synthesis.

Effect of dexamethasone or fetal lung 15-hydroxy-prostaglandin dehydrogenase: Possible mechanism for the prevention of patent ductus arteriosus by maternal dexamethasone therapy

Prenatal maternal glucocorticoid treatment has been reported to reduce the incidence of patent ductus arteriosus in prematurely born infants. Patency of the ductus arteriosus is thought to be maintained primarily by the vasodilatory effect of PGE2 both in utero and in prematurely born infants, and lung is a major source of PGE2 in fetuses and neonates. 15-Hydroxy-prostaglandin dehydrogenase (15-PGDH) catalyzes the initial reaction in converting biologically active PGE2 to its inactive analogue, 15-keto-PGE2. In the present study, effect of prenatal dexamethasone treatment on the activity of fetal rat lung 15-PGDH was studied at 20, 21 and 22 days of gestation. Activity of fetal lung 15-PGDH more than doubled from 20 to 22 days of gestation. Dexamethasone treatment at 0.4 mg/kg and 0.8 mg/kg significantly increased the activity of 15-PGDH in both 20- and 21-day fetuses but had no effect on 22-day fetuses. We speculate that the clinical observation that prenatal glucocorticoid treatment reduces the incidence of patent ductus arteriosus in premature infants may in part be due to the stimulatory effect of glucocorticoid on the activity of 15-PGDH in fetal and neonatal lung and possibly other organs.

Clinical manifestations of mannosidosis--a longitudinal study.

Mannosidosis is a partially defined disorder of glycoprotein metabolism; less than 20 cases have been reported in the literature. In this work, a longitudinal study of five new patients is presented in an attempt to delineate the phenotype and clinical course of this unusual storage disease. The data on our patients and those in the literature indicate that people with mannosidosis appear normal at birth and that their typical phenotype develops by two years of age. This is characterized by a distinctive coarse facies and dysostosis multiplex. Although recurrent infections, hearing loss and mental retardation occur, the course in this storage disorder generally is stable and is compatible with adult life. The diagnosis is confirmed by the presence of a deficiency in alpha-D-mannosidase activity in leukocytes or fibroblasts, by the presence of vacuolated lymphocytes in peripheral blood and foam cells in bone marrow, and an increased excretion of mannose-rich oligosaccharides in urine.

Fetal rat lung phosphatidylcholine synthesis in diabetic and normal pregnancies: A comparison of prenatal dexamethasone treatments

The effects of maternal diabetes upon fetal lung surfactant phospholipid metabolism were studied using 19-day gestational age fetal rats from mothers with streptozotocin-induced diabetes mellitus. In this experimental animal model, maternal glucose intolerance significantly impaired fetal body and lung development. However, incorporation of [14C]palmitate and [3H]choline into lung total and disaturated phosphatidylcholine was unimpaired in offspring of diabetic mothers. Dexamethasone, which is known to promote fetal lung maturation in normal pregnancies, was administered to diabetic and control mothers during late gestation. Prenatal dexamethasone inhibited lung growth in both diabetic and control pregnancies. While this agent slightly stimulated [14C]palmitate incorporation into total phosphatidylcholine and markedly enhanced [3H]choline incorporation into both disaturated and total phosphatidylcholine in control pregnancies, it failed to stimulate incorporation of either precursor into fetal lung from diabetic pregnancies.

Glucocorticoid and prostaglandin: lack of an inhibitory effect by dexamethasone on the synthesis of 6-ketoprostaglandin F1α in rat lung

High doses of dexamethasone (1-12 mg/kg twice daily) were administered to pregnant rats for 2 days. The effect of dexamethasone on fetal and maternal lung prostaglandin metabolism was examined on day 21 of gestation. Dexamethasone treatment at all dosages significantly increased conversion of [14C]-arachidonic acid to 6-ketoprostaglandin F1 alpha in both fetal and maternal lung homogenates. This finding is similar to our earlier finding using lower dosages of dexamethasone and suggests that dexamethasone enhances lung prostaglandin synthetase activity. Because dexamethasone is known to inhibit the activity of phospholipases, we also measured lung immunoreactive 6-ketoprostaglandin F1 alpha. The results showed that dexamethasone treatment did not diminish lung 6-keto-prostaglandin F1 alpha level even at the highest dosage used (12 mg/kg). These results suggest that high dosages of dexamethasone, such as those used in the clinical treatment of septic shock, do not inhibit synthesis of lung prostaglandin.

Delayed pulmonary phosphatidylglycerol synthesis and reversal by prenatal dexamethasone in fetal rats of streptozotocin-diabetic mothers.

Lung slices from fetal rats of streptozotocin-diabetic mothers incorporated [3H]glycerol and [3H]choline into phosphatidylglycerol and disaturated phosphatidylcholine, respectively. When compared to age-matched fetuses from nondiabetic mothers, lung phosphatidylglycerol synthesis of 21-day fetuses of diabetic mothers was significantly diminished, although [3H]glycerol incorporation into other phospholipids was not impaired. Synthesis of disaturated phosphatidylcholine was not diminished in lungs of 20-, 21-, or 22-day fetuses of diabetic mothers. Prenatal dexamethasone partially reversed the diminished phosphatidylglycerol synthesis at 21 days of gestation; the degree of stimulation was the same as that seen in 21-day fetuses of normal mothers but the maximal rate of [3H]glycerol incorporation was about 60% of that in 21-day fetuses of normal mothers. Fetal lung disaturated phosphatidylcholine synthesis was not stimulated by dexamethasone in diabetic pregnancies, in contrast to that seen in nondiabetic pregnancies. These data suggest that maternal diabetes interferes with the ability of fetal lungs to synthesize phosphatidylglycerol, a finding consistent with the delayed appearance of phosphatidylglycerol in the amniotic fluid of human diabetic pregnancies. In addition, maternal diabetes impairs the responsiveness of disaturated phosphatidylcholine synthesis to dexamethasone. Since phosphatidylglycerol synthesis is enhanced by prenatal dexamethasone, this therapy may still be effective for reducing the adverse impact of maternal diabetes on fetal lung development.

Disturbance of pulmonary prostaglandin metabolism in fetuses of alloxan-diabetic rabbits

[14C]Arachidonic acid conversion in lung homogenates of 28-day fetuses from control and alloxan-diabetic rabbits was studied. The major metabolites were 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid and prostaglandin E2. Small amounts of 6-ketoprostaglandin F1 alpha, prostaglandin F2 alpha, and thromboxane B2 were also observed. Lung homogenates from fetuses of alloxan-diabetic rabbits convert significantly less [14C]arachidonic acid to prostaglandin E2, whereas all other metabolites were present in similar quantities compared to fetuses of non-diabetic rabbits. These studies suggest that the decreased arachidonic acid conversion to prostaglandin E2 could be partially responsible for the functional delay of lung maturation in offspring of alloxan-diabetic rabbits.

Identification of metabolites diagnostic for organic acidurias by simultaneous dual-column capillary gas chromatography

To offer a procedure with increased resolution compared to packed-column gas chromatography, we developed a dual-capillary method of gas chromatography for diagnosing organic acidurias. We derivatized and injected organic acids repeatedly on two different bonded phase columns (DB-1, DB-1701) to establish a table of methylene units. Compounds in urine specimens were identified by their characteristic pair of methylene units. With this method, we are able to identify 120 metabolites in urine. Accordingly, the procedure provides a cost-effective alternative to routine gas chromatography-mass spectrometry.

Identification of human DNA sequences complementary to chromosomal RNA with an improved RNA/DNA gradient hybridization technique

Native DNA components in the human genome were identified with an improved RNA/DNA gradient hybridization technique. 3H-Labelled complementary RNA transcribed from total human DNA was hybridized to homologous DNA which had been mildly sheared to generate single-stranded ends. Unhybridized RNA was eliminated from the reaction mixture by column chromatography before the hybrids were subjected to CsCl gradient centrifugation. Nine radioactive peaks representing RNA/DNA hybrids were reproducibly found at buoyant densities of 1.687, 1.693, 1.696, 1.699, 1.702, 1.705, 1.708, 1.711 and 1.715 g/cm3. The technique was also utilized to hybridize I125-labelled human chromosomal RNA to DNA. Three distinct radioactive peaks were found at the heavy buoyant densities of 1.702, 1.705, and 1.708 g/cm3, suggesting a differential enrichment of DNA components with sequences complementary to chromosomal RNA.