摘要:

Clinical testing of growth hormone (GH) sufficiency is a controversial area in endocrinology. Due to the episodic nature of endogenous GH secretion, diagnosis of GH deficiency has been defined as a failure to achieve normal GH levels in response to at least two stimuli. This testing is associated with significant patient morbidity and cost. We analyzed our experience over a 4-y period to determine whether clinical or biochemical variables could be used to predict the results of a specific GH testing procedure. Of 180 cases analyzed (67% male, mean age 8.89 ± 4.39 y, range neonate-16 y), eight cases had incomplete GH testing results. Of the remaining 172, 19 were GH deficient (GH level <7 ng/mL). Younger age, higher body mass index and a greater degree of bone age delay were characteristic of the GH-deficient population; however, none of these variables alone was of diagnostic utility. Serum IGF-I level was below the normal range for 81% of the GH deficient and 47% of the GH-sufficient children; and was the only single variable that provided a reasonable between-group distinction. Discriminant analysis resulted in development of a new variable, based on IGF-I z scores, chronologic age, degree of bone age delay, and body mass index, which would have allowed exclusion of GH deficiency without provocative testing for 58% of the GH sufficient population, whereas permitting the diagnosis of GH deficiency for all GH-deficient subjects. Our data are dependent on the IGF-I assay method and the clinical definition for GH deficiency; therefore, the calculated predictive values are not applicable to all clinical populations. However, our data provide a new perspective on the integration of IGF-I levels and clinical information in predicting GH sufficiency.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The effect of hypoxia on plasma met-enkephalin and catecholamine levels was studied in chronically catheterized fetal sheep. Maternal and fetal hypoxia was maintained for 20 min. We found hypoxia significantly increased the plasma levels of large mol wt met-enkephalin containing peptides from 1755 ± 229 pg/mL during baseline to 4408 ± 1426 pg/mL by 15 minutes of hypoxia. The levels of the met-enkephalin pentapeptide were unchanged during hypoxia from a baseline value of 168 ± 56 pg/mL. Norepinephrine and epinephrine levels increased 5- and 10-fold, respectively, by 15 min of hypoxia. These observations suggest cosecretion of the large mol wt met-enkephalin peptides with catecholamines during stress in developing animals.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

We determined the extent to which ligating both maternal uterine arteries affects fetal hepatic energy and redox states in the fetal rat. Bilateral maternal uterine artery ligation on d 18 of the rat's 21.5-d gestation significantly inhibits fetal growth; sham surgery limits growth to a lesser extent. Within 12 h of surgery and persisting to d 19, small-for-gestational age (SGA) fetuses had significantly diminished ATP/ADP and adenylate charge ratios, whereas sham fetuses had values intermediate between SGA and normal. Hepatic mitochondrial redox state demonstrated similar changes. Cytosolic redox state in SGA fetuses at 12 and 24 h after surgery was significantly elevated. SGA fetuses had significantly diminished plasma insulin and elevated glucagon concentrations. On d 19 and 20, hepatic ATP/ADP and cytosolic NAD+/NADH correlated directly for sham and normal but not SGA fetuses. Alterations in glucose, insulin, and glucagon availability and hypoxia were responsible for the changes in energy and redox states. They may also have disassociated hepatic cytosolic from mitochondrial redox states and altered the equilibrium between adenine and nicotinamide nucleotides. These altered cellular functions retarded fetal growth. Newborn SGA, sham, and normal rat pups had similar hepatic ATP/ADP, cytosolic, and mitochondrial redox states at 10 and 240 min after delivery suggesting that the hypoglycemia which developed in SGA pups was not attributable to alterations in these variables.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

We studied healthy and saline lavaged rabbits during high frequency oscillatory ventilation to determine what combination of frequency (f), tidal volume (Vt), and mean airway pressure (Paw) produced the lowest peak-to-peak alveolar pressure amplitude (Palv) and physiologic blood gas tensions. Sinusoidal volume changes were delivered through a tracheostomy by a piston pump driven by a linear motor. Tracheal pressure amplitude (Ptr) was measured through a tracheal catheter and alveolar pressure amplitude was measured in a capsule glued to the right lower lobe. Pao2, Paco2, Ptr, and Palvwere measured at the following settings: FiO2=0.5, frequency 2-28 Hz, V, 1-3 mL/kg (50 150% dead space) and Paw5-15 cm H2O. Many combinations of frequency and Vtresulted in the same Pao2 and Paco2. Paw had a large effect on Palvand minimal effect on blood gas tensions. In lavaged rabbits, the composite variable f X V,2 described the trends in Pa)v and blood gas tensions. As the product of fx Vt2 increased, Pao2initially increased and then decreased, whereas Paco2decreased and Palvincreased. No single combination of frequency, Vtand Paw simultaneously provided the lowest Palvand physiologic blood gas tensions. Adequate blood gas tensions and low Palvwere obtained at frequencies less than 12 Hz, a V, of 2 mL/kg and a Paw of 10 cm H2O. In healthy and lavaged rabbits Pao2increased and Paco2decreased as frequency increased at lower V1Pao2decreased as frequency increased at higher Vtin lavaged rabbits only. Palvtended to be greater in lavaged rabbits.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

We studied the effect of positive pressure mechanical ventilation on the pulmonary clearance (k) of99mtechnetium diethylenetriamine pentaacetate (99mTc- DTPA) in lambs. Twelve lambs were anesthetized and ventilated with air at 25 breaths/min and with end expiratory airway pressure at 2 cm H2O for a minimum period of 8 h. Four lambs received normal pressure ventilation with peak airway pressure at 17 ± 3 cm H2O and eight received high pressure ventilation with peak airway pressure at 41 ± 2 cm H2O. Three99mTc-DTPA clearance studies were done in each lamb; at the start and after 4 and 8 h of mechanical ventilation. All clearance measurements were made at normal peak airway pressure 16 ± 3 cm H2O. Baseline clearance rate, k, (n=12) was 1.2 ± 0.5% (SD). During normal pressure ventilation, k increased from 1.0 ± 0.5 to 2.2 ± 0.8% after 4 h and to 2.7 ± 0.8% after 8 h. During high pressure ventilation, k increased from 1.4 ± 0.4 to 3.6 ± 1.3% after 4 h and to 4.8 ± 1.2% after 8 h. To see if 8 h of mechanical ventilation was associated with other evidence of lung epithelial injury, we determined the movement of I125labeled albumin from the interstitium into the airspace, lung water content, lung histology, and lung lavage constituents in the lambs at the end of the study. All variables were similar between ventilated and four unventilated lambs, except the percentage of alveolar macrophages recovered by lavage, which was more in the ventilated lambs. We conclude that positive pressure mechanical ventilation results in a continuous increase in the pulmonary clearance of99mTc-DTPA and the duration and magnitude of positive pressure applied tended to increase the value of k.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Lactic acidosis and accumulation of 3-hydroxybutyrate and other citric acid cycle intermediates were found in an infant with a lethal syndrome of metabolic acidosis and renal tubular acidosis. Nevertheless, the patient was relatively well for 4 mo of life. The activity of the pyruvate dehydrogenase complex, 2-oxoglutarate dehydrogenase, and branched-chain keto acid dehydrogenase were all reduced to levels 9 to 29% of control. In contrast, the activity of lipoamide dehydrogenase was normal. The conversion of l-14C-leucine and l-I4C-valine to14CO2and of U-L-14C-valine to its major metabolic product 3-hydroxyisobutyric acid by fibroblasts derived from the patient was less than 5% of control. Cultivation of the patient's fibroblasts in medium enriched with lipoic acid markedly improved these in vitro conversions of leucine and valine.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Taurine, required by the fetus for nutrition and neurological development, is inadequately synthesized by the fetus and substantial quantities of the amino acid are supplied by the mother. Maternal to fetal unidirectional taurine transport was studied inin vitroperfused human placentae from normal term deliveries. To determine whether the placenta can achieve and maintain a chemical gradient for taurine, recirculating equimolar maternal and fetal perfusions were performed. The ratio of fetal/maternal taurine concentration increased over 75 min and was maintained at 1.38 ± 0.14 (SEM) through 2.25 h (n=6). To determine the rate of taurine transport against a concentration gradient, flux was determined with maternal taurine constant at 50 μM whereas the fetal taurine concentration varied from 0 to 500 μM in a nonrecirculating system (n=5). Despite increasing the chemical gradient tenfold, taurine was transported at a constant rate of 1.75 ± 0.75 (SEM) nmol/min/g. Nonrecirculating perfusions were performed with B-alanine (»=13) and hypotaurine (w=10), both B-carrier competitors, and no inhibition of taurine transport could be detected, taurine flux being 104.1 ± 6.0% (SEM) of baseline in the presence of Balanine and 106.0 ± 7.0% (SEM) with hypotaurine. Finally, ouabain inhibited transport (n=3) by 58.1 ± 5.4% (SEM). We conclude that taurine is transported in the human placenta by an active carrier mechanism.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Taurine is a cerebral osmoprotective molecule during chronic hypernatremic dehydration. In these experiments, we investigated the role of taurine in osmoregulation during acute hyponatremia. Taurine deficiency was induced in experimental cats (n=6) by feeding a taurine-free diet for 8-10 wk, whereas control counterparts (n=6) consumed a regular diet. Hyponatremia was provoked in all cats over 54 h by daily injections of 5% dextrose in water (7.5% body wt) and vasopressin (20 U/d). The serum Na+ concentration was abruptly lowered to 110 ± 3 and 117 ± 2 mmol/L, in experimental and control animals, respectively. The cerebral total and intracellular water compartment sizes were reduced from 486 ± 11 to 441 ± 11 ml/100 g dry wt and from 357 ± 7 to 309 ± 12 mL/100 g dry wt, respectively, in control versus experimental cats, p<0.05. There was a significant linear relationship between cerebral taurine content and the intracellular water compartment size in all animals,p<0.02. Taurine displayed a similar osmoprotective capacity in muscle tissue in these studies. We conclude that taurine is an osmoregulatory molecule in cerebral and extracerebral tissues during severe hyponatremia. Reductions in tissue taurine content may complement decreases in cytosolic electrolyte levels during adaptation to more prolonged hyponatremia.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The metabolism of individual dietary n-3 fatty acids was studied in n-3 fatty acid-deficient newly hatched chicks. Laying hens were fed the n-6 fatty acid, ethyl linoleate, as the only source of polyunsaturated fat. Chicks were then fed the n-3-deficient hens' diet, or one of three other diets supplemented with the ethyl ester of 18:3n-3, 20:5n-3 [eicosapentaenoic acid (EPA)], or 22:6n- 3 [docosahexaenoic acid (DHA)] at 0.44% of calories. At the end of 0, 1, 2, and 3 wk, the fatty acid composition of the brain, retina, liver, and serum was determined. Dietary EPA and DHA were equally effective at raising levels of DHA in the brain and retina. Dietary 18:3 was relatively ineffective in restoring brain and retina DHA. In the n-3- deficient chicks fed EPA or DHA, levels of DHA recovered to control values in both the brain and retina by 3 wk. Very little EPA accumulated in the brain or retina of chicks fed EPA. Hepatic synthesis of DHA from EPA appeared low, suggesting that the brain and retina synthesized the DHA that accumulated rapidly in these tissues after the feeding of EPA. The 6-4-desaturase enzyme was apparently very active, then, in the brain and retina. Retroconversion of dietary 22:6 to 22:5 and 20:5 was evident in the serum, liver, and retina but not in the brain. Thus, it was possible to study the relative metabolism and especially the interconversion of n-3 fatty acids in a environment uncomplicated by existing stores of these essential fatty acids. This study would suggest that 18:3 as the sole source of n-3 fatty acids in the diets of animals, including the human infant, may not be adequate for the biochemical development of the brain and retina and that dietary DHA is the preferred fatty acid of the n-3 series.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Total body water (TBW) is an indicator of fat-free mass and thus of nutritional status but cannot be measured readily in children in developing countries who are at greatest risk of becoming malnourished. We therefore developed equations to predict 18O TBW from bioelectrical impedance (Z), wt, and ht in well and malnourished infants and children whom we considered characteristic of children evaluated in nutritional surveillances in Peru. Children 3 to 30 mo of age, whose wt were 3.4 to 14.4 kg, which was —2.8 to +1 SD wt-for-ht, were randomly assigned to group I (n=30) to develop equations to predict TBW or to group II («=14) to cross-validate the predictive equations. Mean TBW measured by 180 dilution was 4.8 ± 1.2 kg in group I, and 5.6 ± 1.7 kg in group II. TBW ranged from 57 to 78% of body wt (65 ± 6%) in group I and from 56 to 80% (64 ± 6%) in group II, indicating no statistically significant differences in body composition. The following equation was developed and cross-validated: TBW, kg=0.48 + 0.68 ht2/Z; standard error estimate=0.36; r=0.98). A slight improvement was achieved by the addition of body wt (TBW, kg=0.76 + 0.18 ht2/Z + 0.39 wt; standard error estimate=0.23; r=0.99).

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID