ISSN:0031-3998    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The cellular distribution of the cystic fibrosis transmembrance conductance regulator (CFTR) in human fetal digestive respiratory mucosa has been studied by immunohistochemistry. The streptavidin-biotin immunoperoxidase method was applied to paraffin-embedded specimens collected from normal fetuses ranging from 7 to 39 wk of gestation. By the 7th wk, CFTR protein was strongly detected in the yolk sack; in contast, the staining was weak in the undifferentiated epithelium of the intestine and the airways. At 23 wk, the intestine showed strongly and diffusely stained enterocytes and a basal cytoplasmic reactivity in the first secretory cells. During development, only slight changes could be detected in the digestive epithelial distribution of CFTR. In the airways, the CFTR distribution followed the cephalocaudal maturation. In the tracheal ciliated cells, the CFTR protein was diffusely detected in the cytoplasm as early as 7 wk. After 24–25 wk, CFTR was also present in the collecting ducts and in the glands of the airways, predominantly in the periphery of the acini. Our data suggest that the CFTR is present as early as 7 wk during organogenesis and probably plays an important role during fetal life. There is an evolution in the CFTR distrubution during airway development whereas in the intestine, CFTR is highly expressed through the epithelium as early as 22 wk and keeps the same distribution until birth.

ISSN:0031-3998    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

To better understand the role of enteric nerves in the regulation of colonic ion transport in neonates, we examined the effects of endogenous and exogenous neurotransmitters on ion transport across distal colonic tissues of piglets. Tissues were obtained from full-term fetuses; newborns; suckling piglets killed 1 d, 5 d, and 14 d after birth; and 21-d-old piglets that had been weaned for 2 d. Colonic tissues were stripped of external muscle layers and mounted in Ussing flux chambers. Short-circuit current (Isc), a measure of active ion transport, and transmural potential difference were lowest in fetal colons and increased during postnatal development. Tissue conductance remained constant throughout development until d 14 and then rose sharply after weaning. Blockade of enteric neural transmission with tetrodotoxin reduced basal Isc compared with control tissues in fetal, newborn, and 1-d-old piglets but had no effect in older animals. The Na+-channel blocker amiloride had no effect on basal Isc in fetal tissues but significantly reduced Isc in all other groups, with the effect increasing with age. Isc responses to electrical field stimulation of enteric neurons were similar in fetal through 14-d-old piglets and then increased after weaning. Increases in Isc after serosal additions of carbachol (10 μM), serotonin (10 μM), or norepinephrine (10 μM) in fetal and newborn piglets were as great or greater than in the older piglets. For serotonin and norepinephrine, Isc responses rose sharply immediately after weaning. In 1-d-old piglets, Isc responses to all stimuli were reduced significantly by removal of Cl-ions from the bathing solutions. At all ages Isc responses were inhibited by bumctanide (10 μM) but were not affected by amiloride. These results demonstrate that colonic CI secretion evoked by endogenous or exogenous addition of neurotransmitters is well developed at an early age in piglets.

ISSN:0031-3998    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Evidence suggests that IGF and their binding proteins play a role in fetal growth, but more knowledge concerning their regulation is essential. We examined the expression of IGF and their binding proteins in experimental intrauterine growth-retarded (lUGR) rat fetuses of hypoxic dams (13–14% oxygen, d 14–21 of gestation). The mean body weight of the fetuses (d 21 of gestation, n = 72) of the six hypoxic dams was 24% lower [p < 0.0001) than the mean weight of the fetuses of six control dams (n = 82). Wet liver weights demonstrated a 20% decrease (p < 0.0001) and placentas a 10% decrease (p < 0.01) compared with control fetuses. The mean serum concentrations of immunoreactive IGF-I in both groups were low but did not differ significantly. The mean serum concentrations of immunoreactive IGF-II, however, were higher in IUGR fetuses. As assessed by Northern blot analysis, there was a 4-fold increase in insulin-like growth factor binding protein-1 (IGFBP-1) mRNA expression in the livers of the IUGR fetuses compared with controls. IGFBP-2 mRNA expression was 6-fold increased in IUGR fetal livers. No difference was found in IGFBP-4 mRNA. An increase in IGFBP-1, −2, and −4 concentrations could be seen by Western ligand blotting in the serum of growth-retarded fetuses compared with control fetuses. This finding was verified by immunoprecipitation with specific antibodies, which demonstrated increases in IGFBP-1 and IGFBP-2. Our results validate the use of maternal hypoxia as an experimental model of intrauterine growth retardation and indicate that increased IGFBP-1 and −2 expression may be of importance in the etiology of fetal growth retardation caused by maternal hypoxia.

ISSN:0031-3998    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

IGF-I, IGF-II, and IGF binding proteins (IGFBP) were characterized in porcine serum, colostrum, and milk on d 1–28 postpartum. IGF-I and -II were measured by heterologous RIA. Scrum IGFBP were characterized by Western ligand blotting and milk IGF binding activity by [125I]-IGF binding assay. IGF-II accounted for 70–85% of serum IGF and rose 2-fold between d 1 and d 28. Serum IGF-I was unaffected by duration of lactation. Milk IGF-II concentrations were higher than IGF-I concentrations on d 1–7 postpartum. After d 10, milk IGF-I and IGF-II contents were not significantly different. Serum contained IGFBP with M, of 43, 39, 34, 28, and 24 kD. Over the course of lactation, the 43− and 39-kD bands increased, the 24-kD band decreased, and the 34− and 28-kD bands were unchanged. Milk IGF binding activity increased between d 1 (28%) and d 3 (44%), then declined until d 28 (7%). Serum and milk were separated by isoelectric focusing into 20 fractions, across a gradient from pH 3 to 10, that were screened for IGFBP by Western ligand blotting. Milk contained six IGFBP of similar Mr as serum IGFBP; however, the relative amounts of the IGFBP and their apparent isoelectric points differed. In conclusion, porcine milk contains both IGF-I and -II, with IGF-II predominating. Several IGFBP with similar Mras those found in serum are present in milk. IGF peptide concentrations were highest in prepartum secretions and colostrum, whereas IGF binding activity peaked on d 4 of lactation.

ISSN:0031-3998    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The growth hormone-releasing hexapeptide (GHRP-6) specifically stimulates growth hormone (GH) secretion in several animal species and humans. The mechanism of action of GHRP-6 is largely unknown, although experimental evidence indicates that it may modulate growth hormone-releasing hormone (GHRH) and somatostatin actions at the pituitary or hypothalamic level. To gain more insight into the mechanism(s) of action of GHRP-6, we studied the infant rat, an animal model highly responsive to GH-releasing stimuli. In 14-d-old rats GHRP-6 (32–600 μg/kg, s. c.) induced a marked and dose-dependent rise in plasma GH concentrations, maximal stimulation occurring with the dose of 300 μg/kg. Neither GHRH nor somatostatin antiserum prevented or modified the GH release elicited by GHRP-6. In pups passively immunized with GHRH antibodies, a 5-d treatment with GHRP-6 (80 μg/kg, s. c, twice daily) completely counteracted the inhibitory effect of GHRH deprivation on GH mRNA expression. In vitro GHRP-6 (10-7and 10-6M) induced a small and transient stimulation of GH release from cultured pituitary cells. These results indicate the following: 1) GHRP-6 is a potent stimulator of GH release in rat pups; 2) it stimulates GH gene expression in the GHRH-deprived pup; 3) during the neonatal period its action is not mediated by GHRH or somatostatin; and 4) its actions are not directed at the somatotrophs.

ISSN:0031-3998    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

In the pig, the gastrointestinal tract grows rapidly after birth and undergoes a short postnatal maturation. The objective of the present work was to assess the metabolic characteristics of the small intestinal mucosa during this period by investigating glucose, galactose, and glutamine metabolism in pig isolated enterocytes. Piglets were used immediately after birth or at various stages during suckling or postweaning. Fed animals were taken in a postabsorptive state. The jejunoileum was excised and perfused with an EDTA (5 mM)-containing buffer. The epithelial cell layer was further dissociated in the presence of hyaluronidase (0.01%). The resulting cell suspension (95% absorbing enterocytes; viability greater than 90%) was incubated with14C-labeled substrates to measure14CO2production in parallel with substrate disappearance. The capacity to utilize glutamine was high and remained steady during the suckling period. Glucose utilization capacity was limited at birth and increased more than 3-fold during the first week of suckling. Such an increase was not observed in piglets kept unsuckled since birth. Galactose utilization capacity remained steady during the first week but afterward gradually disappeared. Lactate and pyruvate production through glycolysis was the major pathway accounting for glucose or galactose disappearance. A capacity for a net glucose production from galactose was evidenced during the first week of suckling. Thus, isolated newborn pig enterocytes exhibit specific and transient metabolic characteristics during the first postnatal week.

ISSN:0031-3998    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

When a 12-y-old girl suffering from isovaleric acidemia was treated with L-carnitine, there was a considerable increase in her blood and urine concentration of isovalerylcarnitine. When later the patient received an infusion of glycine in place of carnitine, isovalerylcarnitine reverted toward the low levels found in a normal subject. At the end of either treatment, erythrocyte calpain was measured and found to be decreased after carnitine therapy (140 versus 96 U/mg Hb with glycine or carnitine, respectively). Because we have previously shown that the activity of calpain isolated from erythrocytes was markedly modified by isovalerylcarnitine, the present results might be seen as the consequence of the chronic exposure of the patient's red blood cells to high levels of isovalerylcarnitine. The lowered calpain activity was also proved by an increase in erythrocyte band 3 phosphorylation together with an increased erythrocyte fragility after calcium loading in the presence of the ionophore A-23187. Calpastatin, the natural inhibitor of calpain, was only slightly modified.

ISSN:0031-3998    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The effect of bone marrow transplantation (BMT) on enzyme and glycosaminoglycan levels of various tissues and isolated parenchymal cells of lethally irradiated gusmps/gysmpsmice was studied. These mice have an inherited deficiency of the lysosomal enzyme β-glucuronidase with less than 1% of normal enzyme activity present in all tissues and represent a model of human mucopolysaccharidosis type VII. Tissues were evaluated 200 d after BMT and liver parenchymal cells 300 d after BMT. Normal levels of β-glucuronidase activities were present in spleen and peripheral blood leukocytes of gusmps/gusmpsmice that underwent transplantations. Intermediate activities were found in lung (73%), kidney (4%), liver (10%), heart (53%), muscle (55%), brain (6%), and liver parenchymal cells (10% of normal controls). A concomitant decrease in activity of the secondarily increased enzyme -hexosaminidase was observed. BMT also led to a substantial reduction in storage of glycosaminoglycans in lung (130 to 100%), heart (350 to 106%), kidney (439 to 217%), brain (177 to 91%), liver (613 to 125%), and liver parenchymal cells (443 to 161% of normal controls). These findings were supported by electron microscopy. A normalization of the storage process was seen in the visceral organs spleen and liver and in the histiocytes of the heart. The kidney showed variable improvement depending on the cell type. In the brain, a substantial improvement of neuronal storage was observed, but BMT apparently had no effect on storage in glial cells. The subcellular localization of β-glucuronidase was investigated in liver parenchymal cells of mice that underwent transplantation. Subcellular fractionation provided evidence for a lysosomal localization of β-glucuronidase, indicating that transfer of β-glucuronidase of donor origin to the lysosomal compartment of parenchymal cells might at least partly be responsible for the observed decrease in storage of glycosaminoglycans in these cells.

ISSN:0031-3998    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Methylmalonic acid and total honnxyslcine in plasma and scrum have previously been used as indicators of intracellular cobalamin function in adults. To assess the usefulness of quantitation of these metabolites in the diagnosis of dietary cobalamin deficiency in infants, they were determined in plasma from 41 infants (aged l0–20 mo) on a macrobiotic diet and in 50 healthy group-matched omnivorous controls. In the macrobiotic infants, both methylmalonic acid and total homocysteine were markedly increased compared with controls (8-fold and 2-fold, respectively). Both metabolites showed an inverse relation to the plasma cobalamin level. The very low cobalamin content of the macrobiotic diet and low plasma cobalamin in macrobiotic infants makes an impaired cobalamin function likely in these infants. We therefore used dietary group as an independent indicator of cobalamin status. Different test parameters for cobalamin status were evaluated by comparing their ability to discriminate between the two dietary groups. Logistic regression analysis showed that methylmalonic acid followed by total homocysteine and cobalamin, in that order, were the strongest predictors of dietary group. Mean corpuscular volume and Mb had low discriminative power. We conclude that the determination of methylmalonic acid and total homocysteine represents a sensitive and specific test for the diagnosis and follow-up of nutritional cobalamin deficiency in infants. Furthermore, the finding of high methylmalonic acid and total homocysteine in plasma of most macrobiotic infants demonstrates a functional cobalamin deficiency in these subjects.

ISSN:0031-3998    

出版商:OVID    

年代:1994

数据来源: OVID