摘要:

Uteroplacental insufficiency alters the anabolic metabolism of the fetus, resulting in intrauterine growth retardation (IUGR). The metabolic and physiologic factors that cause IUGR have long standing consequences after birth. Postnatal growth and glucose metabolism are altered in the IUGR infant. Skeletal muscle is an important component of growth and metabolizes up to 70% of i.v. glucose. The ability of skeletal muscle to metabolize glucose is affected by ATP availability. We hypothesized that gene expression and function of proteins involved in mitochondrial ATP production and distribution would be altered in juvenile IUGR muscle. To test this hypothesis, we used a model of IUGR, induced by bilateral uterine artery ligation in the pregnant rat, that mimics uteroplacental insufficiency in the human. RT-PCR was used to measure the mRNA levels of three important mitochondrial proteins; NADH-ubiquinone-oxireductase subunit 4L(ND-4L), subunit C of the F1F0-ATP synthase (SUC), and adenine nucleotide translocator 1(ANT1) in IUGR and control rats in fetal and juvenile life. In the fetus, mRNA levels of all three proteins were significantly increased in IUGR skeletal muscle. In contrast, in juvenile animals, mRNA levels of all three proteins were significantly decreased. mRNA levels of other metabolically important proteins, glucose-6-phosphate dehydrogenase and carnitine-palmitoyl-transferase II, were not significantly altered in IUGR juvenile animals. To assess if decreased gene expression is associated with altered mitochondrial function, we measured the mitochondrial NAD+/NADH ratio in d 21 juvenile control and IUGR muscle. At d 21, decreased gene expression if ND-4L, SUC, and ANT1 is associated with a decreased mitochondrial NAD+/NADH ratio. The results of our study suggest that the metabolic alterations associated with uteroplacental insufficiency in the rat result in altered fetal and postnatal muscle mitochondrial mRNA expression as well as altered postnatal mitochondrial function.Abbreviations: ANT1,adenine-nucleotide translocator-1;CPTII,carnitine-palmitoyl-transferase II;G6PD,glucose-6-phosphate dehydrogenase;IUGR,intrauterine growth retardation;ND-4L,NADH-ubiquinone oxireductase subunit 4L;RT,reverse transcriptase;SUC,subunit C of the F1F0-ATPase

ISSN:0031-3998    

出版商:OVID    

年代:1998

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Gaucher's disease, the inherited deficiency of glucocerebrosidase, manifests with vast phenotypic variation. Even among patients with type 2(acute neuronopathic) Gaucher's disease, there is a spectrum of clinical presentations. DNA samples from 14 patients with type 2 Gaucher's disease with a course ranging from intrauterine death at 22 wk of gestation to survival until age 30 mo were studied. L444P was the only common mutation identified, found in 15 patients' alleles. Sequencing of genomic DNA amplified by long template PCR revealed that mutation L444P occurred as a single point mutation in seven mutant alleles and as part of a recombinant allele in eight mutant alleles. Two patients had a deletion of 55 bp in exon 9; in one patient the deletion was part of a recombinant allele, and in a second the deletion occurred alone. Direct sequencing identified R120W on one allele, P415R on another, and one fetus was homoallelic for a deletion of a C nucleotide at codon 139 in exon 5. Eight of the mutant alleles remain unidentified. Northern blots revealed an appropriately sized mRNA in all except one of the patients studied. Of the 14 type 2 Gaucher patients, three had hydrops fetalis and diedin uteroor at birth, five had congenital ichthyosis, and seven survived 5 mo or more. Patients who died in the neonatal period had decreased protein detected by Western blot, regardless of genotype observed. These studies demonstrate that genotypic heterogeneity exists in patients with type 2 Gaucher's disease, even among infants with the most severe phenotypes.

ISSN:0031-3998    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Pyruvate carboxylase (PC) is a biotinylated mitochondrial enzyme that catalyzes the conversion of pyruvate to oxaloacetate. Children with inborn errors of PC metabolism have lactic acidosis, hypoglycemia, and mental retardation. The variable severity of the clinical phenotype is dependent on both genetic and environmental factors. Two consanguineous families with moderate forms of PC deficiency were characterized at the biochemical and molecular levels. In both families, the probands were found to have low PC activity (range, 2-25% of control) in blood lymphocytes and skin fibroblasts associated with either diminished or normal protein levels. In the first case, sequencing of patient-specific PC cDNA demonstrated a T to C substitution at nucleotide 434, which causes a valine to alanine change at amino acid residue 145. Direct sequencing of the parents showed that they are heterozygous for this mutation. In the second family, a brother and sister had mental retardation and episodes of severe lactic/ketoacidosis in early childhood. In these cases, a C to T substitution at nucleotide 1351 results in a cysteine for arginine substitution at amino acid residue 451; the parents were also found to be heterozygous for this mutation. In both families, no other mutations were found, and both substitutions occurred in relatively conserved amino acid residues. These mutations, located in the biotin carboxylase domain, provide a unique opportunity to analyze how natural occurring mutations affect PC function.Abbreviation: PC,pyruvate carboxylase

ISSN:0031-3998    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The mechanism(s) by which insulin enhance prematurely the activity of brush border membrane (BBM) hydrolases in rat immature intestine is unknown. Therefore, we have compared the responses of four BBM enzymes[sucrase-isomaltase (SI), maltase, lactase-phloridzine hydrolase (LPH), and aminopeptidase] with exogenous insulin, the analog B-Asp10, IGF-I, and antireceptor MAb [insulin-receptor (IR) MAb] given to preweaning pups. Low doses of insulin caused a precocious induction of SI and of SI mRNA and stimulated maltase activity without effect on LPH nor on aminopeptidase activities. IGF-I given at the same dose as that of insulin had no detectable effect on these enzymes. Administration to sucklings of IR MAb prevented the effect of endogenous insulin by inhibiting the expression of SI and maltase without effect on LPH activity. B-Asp10, an insulin analogue that exhibitsin vitroa 3.5-fold increase in receptor affinity with sustained signaling of the receptor tyrosine kinase, caused an overexpression of SI by 3.5-fold and of maltase by 1.5-fold compared with equivalent doses of normal insulin. The premature increases in SI activity, SI mRNA, and maltase activity in response to insulin were dose-dependent and were associated with dose-dependent increases in intracellular spermine and spermidine concentrations. In conclusion, these data suggest that the premature induction of SI by insulin is mediated by a dose-dependent signal initiated by binding of the hormone to its intestinal receptor, which after transduction into the cell indirectly triggers the transcription of the SI gene, possibly by changes in intracellular polyamine concentrations.Abbreviations: BBM,brush border membrane;IR,insulin receptor;SI,sucrase-isomaltase;LPH,lactase-phloridzine hydrolase;GAPDH,glyceraldehyde-3-phosphate dehydrogenase;ODC,ornithine decarboxylase

ISSN:0031-3998    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Suitability of a recently proposed noninvasive L-[13C]leucine breath test for assessment of whole body leucine oxidation in maple syrup urine disease (MSUD) was examined. Oral L-[1-13C]leucine loads (38 μmol/kg body weight) were performed in overnight fasted MSUD patients (n= 6, classical form), obligate heterozygote parents (n= 6), and control subjects (n= 10). Three-hour13CO2exhalation kinetics were evaluated using curve fitting procedures. Venous blood was obtained in most cases and analyzed for13C-labeled plasma metabolites. In control subjects, maximal13CO2exhalation was reached attmax= 55 ± 18 min. Cumulative13CO2output at 3 h amounted to 4.7 ± 0.7 μmol × (kg body weight)-1. Estimated total13CO2exhalation was 7.2± 1.4 μmol × (kg body weight)-1(19.0 ± 3.6% of the dose). Half of this amount was expired att1/2= 130± 18 min. The data show a considerable degree of intersubject variability. Intraindividual variability was comparable, however, when checked in two volunteers. In obligate heterozygotes,13CO2kinetics were similar to controls (tmax= 35 ± 8 min,t1/2= 95 ± 16 min). Total13CO2output[5.7 ± 1.4 μmol × (kg body weight)-1] tended to be in the lower control range. None of the MSUD patients under study exhibited a significant increase in13CO2output after load. Maximal increase of label in plasma 4-methyl-2-oxopentanoate, the physiologic precursor of13CO2, was 16.1 ± 3.5 MPE in control subjects. In MSUD, label dilution was increased and correlated with the patients' leucine/4-methyl-2-oxopentanoate plasma levels. Considering the generally high variability of13CO2output and the unstable substrate pools in MSUD, we discuss the limitations of whole body leucine oxidation measurements by noninvasive approaches.Abbreviations: APE,atom percent13C-label enrichment;BCAA,branched chain L-amino acids;BCOA,branched chain 2-oxo acids;BCOA-DH,branched-chain 2-oxo acid dehydrogenase complex;KIC,4-methyl-2-oxopentanoate;MPE,mole percent13C-label enrichment;MSUD,maple syrup urine disease;WBLO,whole body leucine oxidation

ISSN:0031-3998    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

In the presence of light, a multivitamin preparation is the main source of peroxides in solutions of total parenteral nutrition (TPN). This preparation contains two photosensitive products, 5′-phosphate flavin mononucleotide(FMN) and polysorbates (PS), as well as electron donors such as ascorbate(AH). We hypothesized that the admixture of FMN or PS with electron donors generates peroxides in TPN and alters the quality of nutrients. Using xylenol orange, peroxide concentrations were measured in solutions containing AH, FMN, and/or PS in water, a dextrose solution, an amino acid preparation, and a lipid emulsion. Thiol functions were evaluated by reduction of 5,5-dithiobis(2-nitrobenzoic acid) in the amino acid preparation. After 24-h light exposure, dextrose solutions with admixtures of AH + FMN or AH + FMN + PS generated peroxides at concentrations similar to those observed in a 1% multivitamin solution, and over three times higher than those observed with FMN, PS, or AH alone. However, in the presence of amino acids, FMN alone induced a generation of peroxides comparable to that observed with FMN + AH. In the lipid emulsion, peroxides increased over 3-fold in the presence of FMN or FMN + AH. The addition of catalase suggested that lipid peroxides and H2O2were produced, and the loss of thiol function suggested that an oxidation of amino acids occurred. When exposed to light, FMN induces reactions with amino acids, polyunsaturated fatty acids, and even AH, altering the quality of nutrients. Paradoxically, AH without FMN has a protective effect on peroxide generation in TPN.Abbreviations: AH,ascorbate;A&OV0254;,radical ascorbate;A,dehydroascorbate;Rf,riboflavin;FMN,5′-phosphate flavin mononucleotide;PS,polysorbates;TPN,total parenteral nutrition;TBH,tert-butylhydroperoxide;IL,Intralipid 20%

ISSN:0031-3998    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Changes in body composition, in particular the onset of obesity, may result from reductions in total daily energy expenditure (TDEE) as a consequence of relative physical inactivity. Children previously treated for acute lymphoblastic leukemia (ALL) become obese, yet the mechanism remains undefined. TDEE and physical activity levels [PAL = TDEE/basal metabolic rate(BMR)] were measured in 34 long-term survivors of ALL and compared with results from 21 survivors of other malignancies and 32 healthy sibling control subjects using the flex-heart rate technique. Body composition was measured by dual energy x-ray absorptiometry. The median TDEE was reduced in the ALL group(150 kJ·kg d-1) compared with other malignancies and controls(207 and 185 kJ·kg d-1, respectively,p< 0.01). This reduction was accounted for mainly by a relative decrease in the PAL of the ALL group (1.24) compared with both other malignancies and controls (1.58 and 1.47, respectively,p< 0.01). TDEE and PAL were correlated with percentage body fat (r= -0.39,p< 0.001 andr= -0.24,p< 0.05, respectively). Obesity in survivors of ALL may, in part, be explained by a reduction in TDEE as a consequence of reduced PAL. The cause of such reduction is uncertain.Abbreviations: ALL,acute lymphoblastic leukemia;BMI,body mass index;BMR,basal metabolic rateCI,confidence interval;DEXA,dual energy x-ray absorptiometry;FFM,fat free mass;HR,heart rate;PAL,physical activity level;RMR,resting metabolic rate;TDEE,total daily energy expenditure;NHL,non-Hodgkin's lymphoma;SDS,SD score

ISSN:0031-3998    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IGF-II plays a major role in the regulation of human fetal growth and development. However, more extensive information on the cellular sites of IGF-II synthesis in the fetus would provide more insight into its role in fetal organogenesis. Thus we have determined the sites of IGF-II synthesis in 18-26-wk gestation human fetal tissues usingin situhybridization with a digoxigenin-labeled cRNA probe to localize IGF-II mRNA in fetal liver, kidney, adrenal gland, cerebral cortex, costal cartilage, skeletal muscle, and lung, and in placental tissue. In human fetal tissues it has to date been impossible to clearly assign IGF-II mRNA to epithelial cells of entodermal origin. Besides their already known localization in cell matrix and a variety of mesodermal cell types, strong IGF-II mRNA-positive signals were detected in epithelial cells in the liver (hepatocytes), bronchial and bronchiolar epithelium, undifferentiated renal tubular epithelium, mature glomerular epithelium, pelvic urothelium, and adrenal epithelial cells of the zona persistens. To identify the cellular location of immunoreactive IGF-II, we also performed immunocytochemical studies in tissues of the same fetuses. Every tissue studied except the cerebral cortex contained immunoreactive cells; however, immunostaining was generally weaker thanin situhybridization signals. Our data show that the distribution of IGF-II in human fetal tissue is much more widespread than hitherto thought. A digoxigenin-labeled detection system for IGF-II is more capable of detecting the cellular expression pattern of IGF-II than radioactive probes and is suitable for analysis of routinely prepared paraffin-embedded material.Abbreviation: IGFBP,insulin-like growth factor binding protein

ISSN:0031-3998    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

We determined the placental transfer of TSH in anin vitromodel of dually perfused isolated lobule in 28 human term placentas by adding varying concentrations (5-60 μIU mL-1) of TSH as a single bolus dose to the closed maternal circulation. Transmembrane transfer of TSH was also studied by adding 45 μIU mL-1to the maternal or fetal compartment of a dual chamber of fetal membranes in culture. Passage of freely diffusible markers creatinine and antipyrine were also studied in this model. TSH concentration was measured by third generation chemiluminescence assay with a sensitivity of 10 mIU mL-1. In the perfusion experiments, at physiologic concentrations the slow decline of TSH in the maternal circulation was associated with a small linear increase in fetal levels to 0.11 ± 0.04% of initial dose at 2 h. The placental transfer rate was 0.08 μIU min-1. Increasing maternal concentrations of TSH were associated with proportional increases in transfer rate (y= 0.002x; R2= 0.99) and placental uptake (y= 0.01x; R2= 0.97). The placental permeability of TSH was 2.4·10-4mL min-1g-1and was proportional to its coefficients of diffusion in water and molecular size. The transmembrane transfer and permeability of TSH was comparable to those of the placenta. We conclude that TSH crosses the human term placenta and fetal membranes sparingly.Abbreviations: MAUC,maternal area under the curve;FAUC,fetal area under the curve;F/M,fetomaternal;TRH,TSH-releasing hormone

ISSN:0031-3998    

出版商:OVID    

年代:1998

数据来源: OVID