摘要:

We examined the separate effects of acute hypercapnia and acute hypoxia on the electromyographic activity (EMG) of the costal and crural diaphragm in 6 anesthetized spontaneously breathing piglets (age 12–23 days, weight 3.00–4.37 kg). Bipolar wire electrodes were inserted into the anterior paratendinous costal diaphragm and the midportion of the crural diaphragm. EMG activity was quantified in arbitrary units (au) of peak moving time average while the animals breathed 50% O2/50% N2(baseline) and after 30 min of either hypercapnia (12% CO2) or hypoxia (12% O2) exposure. After 30 min of hypercapnia, the peak moving time average EMG increased in both parts of the diaphragm with the increase in crural diaphragm EMG activity (from baseline: 20 ± 2 au to 30 min 12% CO2: 83 ± 20 au) not being significantly different from that observed in the costal diaphragm (from baseline: 21 ± 2 au to 30 min 12% CO2: 72 ± 20 au,p= 0.17). Similarly, the peak moving time average EMG increased in both parts of the diaphragm after 30 min of hypoxia with the increase in the crural diaphragm EMG activity (from baseline: 21 ± 2 au to 30 min 12% O2: 28 ± 6 au) not being significantly different from that observed in the costal diaphragm (from baseline: 21 ± 1 au to 30 min 12% O2: 26 ± 7 au,p= 0.51). These data indicate that the inspiratory EMG activity of the diaphragm is not differentially distributed between its costal and crural components during chemically stimulated breathing in piglets.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Milk can be a significant source of lead (Pb) for young mammals, including humans. Certain essential trace elements have previously been shown to be specifically associated with particular milk components and such associations often increase bioavailability. Thus, the first goal of this study was to determine the distribution of Pb in cream, casein, and whey fractions of various milks under various conditions using203Pb as a tracer. In rat milk almost 90% of the Pb was found to be associated with the casein micelles, regardless of: 1) whether the milk was labeledin vivoorin vitro; b) whether the milk was fresh or frozen; and c) the added concentration of Pb (over the range 0.01–75 μ/ml). The remainder of the Pb was approximately equally distributed between cream and whey. A virtually identical pattern of Pb distribution was observed with bovine milk. Pb added to infant formula also associated predominantly with casein micelles, although the Pb content of this fraction was significantly less than with rat and bovine milks. The second goal of the study was to determine if Pb remained associated with casein as it traversed the gastrointestinal tract of infant rats. For this purpose, rat pups aged 15–16 days were gavaged with203Pb-labeled rat milk, and lumenal contents from the stomach and small intestine were collected 2 h later. Differential centrifugation of the homogenized lumenal contents showed that in the stomach the Pb was associated primarily with the casein curd. By the time chyme reached the distal small intestine, Pb was found predominantly in a fraction that was not precipitable by high-speed centrifugation (thus, not intact casein micelles), but was nondialyzable. We conclude that Pb in milk is protein bound and remains this way as it traverses the stomach and proximal small intestine of the infant rat.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

A mutation, resulting in a deficiency of liver GTP-cyclohydrolase activity, has been induced in the laboratory mouse. Mice homozygous for this mutation exhibit hyperphenylalaninemia under the following conditions: 1) early in life and 2) throughout life when exposed to phenylalanine. A phenylalanine loading regimen was used to discriminate between mutant and wild type mice on the basis of the resultant phenylalanine and tyrosine serum levels. Subjecting mice to this regimen reveals several distinguishing characteristics. Mutant mice exhibit approximately 2-fold higher peak phenylalanine levels than wild-type mice. In wild-type mice the hyperphenylalaninemic state is transient and rapidly abates while in mutant mice it is persistent and remains for a prolonged period. Mutant mice exhibit normal serum tyrosine levels after a loading challenge, while wild-type mice experience an increase in tyrosine levels. The loading regimen was also used to gauge the response of mutant hyperphenylalaninemic mice to exposure to chemical compounds required for normal phenylalanine catabolism (i.e.pteridine cofactors of the phenylalanine hydroxylase reaction). Mutant mice exposed to native enzyme cofactor or cofactor precursors exhibit a sharp decline in serum phenylalanine levels relative to their uninjected counterparts coupled with a tyrosine increase. By contrast, mutant mice exposed to nonprecursor compounds that are structurally related to the native cofactor, experience no diminution of serum phenylalanine levels.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

This study was designed to assess potential differences in ventilation homogeneity related to growth. One hundred thirty-three healthy subjects representing four stages of growth were studied: group 1, preschool, ages 34–74 months; group 2, preadolescent, ages 8–10 yr; group 3, postpubertal, ages 15–17 yr; group 4, young adult, ages 26–40 yr. Ventilation homogeneity was assessed by moment analysis of multibreath nitrogen washout with functional residual capacity, the ratio of the 1st to 0th moment (MR 1/0), and the ratio of the 2nd to 0th moment (MR 1/0) being the outcome variables of interest. Across the four groups functional residual capacity increased as a curvilinear function of height. At all heights functional residual capacity was larger in males than females and the slope of the regression was steeper in males than females (p< 0.001). Both MRs 1/0 and 2/0 were significantly higher in group 1 than the other groups, indicating that ventilation washout was less homogeneous in the preschool subjects than in older children or adults. Males of group 1 had significantly higher values for both moment ratios (more ventilation nonuniformity) than females. In the other groups there were no significant sex based differences although there was a trend for males to have a lower MR 1/0 than females in the young adults,p= 0.08. The results indicate that both age and sex are important determinants of the growth of distribution of ventilation.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The fetal respiratory and electrocortical effects of thyrotropin-releasing hormone (TRH) administered into the lateral cerebral ventricles, have been investigated in chronically catheterized unanesthetized fetal sheep at 125–140 days of gestation. Stimulatory effects on fetal breathing movements were seen at doses as low as a lug bolus. TRH given as a 5-μg bolus followed by a 10 μg/h infusion for 2 h induced a rapid switch to significantly faster, deeper, and continuous fetal breathing movements, while the electrocorticogram remained episodic. Fetal breathing movements did not stop during hypoxia. TRH given as a 2-μg bolus followed by a 4 μg/h infusion or as a 5-μg bolus followed by a 5 μg/h infusion induced the same stimulation of FBMs, but breathing essentially remained episodic, state related and inhibited by hypoxia. As hypothermia presumably induces a surge in TRH secretion at birth it is possible that TRH has some role in the switch from fetal to postnatal breathing patterns.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Vitamin A and its precursor β-carotene are naturally occurring antioxidants. The effects of diets deficient in β-carotene and vitamin A on the alveolar-capillary membrane were studied in young adult BALB/C mice before and after exposure to 65% oxygen. One of three diets (standard complete, β-carotene deficient, or β-carotene and vitamin A deficient) was fed for a 6-wk period. Mice were then exposed to 65% oxygen for 0, 3, or 6 days, sacrificed, and their lungs examined by electron microscopy using the morphometric techniques of Weibel. The arithmetic and the harmonic mean thicknesses of the alveolar-capillary membrane and its components (epithelium, interstitium, and endothelium) were measured to assess the influences of diet and of duration of exposure to 65% oxygen. Analysis of variance and multiple comparisons of means (Student-Neuman-Keuls statistics) were applied. Diet alone did not significantly affect membrane thickness. However, duration of oxygen exposure increased the thicknesses of both the epithelium and interstitium in the group fed a diet deficient in both β-carotene and vitamin A as compared to the other two groups although this was only significant for the epithelium. β-Carotene deficiency alone did not affect the respiratory membrane either before or after oxygen exposure. These results suggest that vitamin A may be an important nutrient in the protection against pulmonary oxygen toxicity.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Group B β-hemolytic Streptotocci cause pulmonary hypertension when injected into animals and may precipitate the persistent pulmonary hypertension syndrome in infected human neonates. We used chronically instrumented piglets to study the effects of repeated injections of heat-killed group B Streptococcus (GBS) type III. Daily exposure to GBS was associated with a 2-fold or greater potentiation of pulmonary and systemic hypertensive responses after 1 wk. Throughout experimentation, pulmonary pressure changes were more marked than systemic changes. After establishing a dose-response relationship, we chose a control dose that produced intermediate hypertensive responses. We then evaluated the effects of antibody and various drugs on the hypertensive responses. Preincubation of organisms with rabbit antiserum containing type-specific antibody enhanced the responses. Beta endorphin blockade with naloxone had little or no effect; leukotriene synthesis inhibition also did not affect responses. Both indomethacin, a cyclooxygenase inhibitor, and dazmegrel, a specific thromboxane synthesis inhibitor, blocked the hypertensive responses to GBS. It appears that repeated doses of GBS potentiate the hypertensive responses, a process that we hypothesize may be mediated by development of type-specific antibody as type-specific antibody levels rose during potentiation. It is likely that thromboxane A2is the effector of the pulmonary and systemic hypertensive responses to GBS injection, because thromboxane inhibition by dazmegrel was as effective as indomethacin in blocking these effects. Thromboxane synthesis blockade may prove useful in management of hemodynamic disturbances accompanying severe bacterial infections in humans.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Babies with chronic bronchopulmonary dysplasia (BPD) can sometimes develop pallor, systemic and pulmonary edema, oliguria, and hyponatremia not attributable to cardiopulmonary or renal impairment. These signs and symptoms might, however, be explained by inappropriate control of vasopressin secretion. To test this hypothesis, we measured plasma vasopressin and osmolality, serum sodium and potassium concentrations, urine output and osmolality, and free water clearance in 26 normoxic infants with BPD aged 1–4 months. All of these infants required supplemental oxygen (FiO20.41 ± 0.03, mean ± 1 SE) to maintain O2saturation of > 88%, and six infants also required mechanical ventilation. As controls, 10 infants of similar age but without BPD were also studied. None of the infants had been discharged from the nursery and was receiving any medications, and all were clinically stable when studied. Compared to control infants, infants with BPD had significantly elevated plasma vasopressin concentrations (control 5.2 ± 0.9 pg/ml; BPD 42.4 ± 5.1; mean ± SE,p> 0.05). Moreover, infants with BPD had hyponatremia and hypotonic plasma, and both urine output and free water clearance were significantly reduced. These data suggest that some infants with chronic BPD have elevated vasopressin levels that are functionally significant. We speculate that excessive stimulation of vasopressin secretion may explain some of the pulmonary and nonpulmonary signs and symptoms in infants with chronic BPD.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Urinary growth hormone (GH) excretion was quantitated in 12-h overnight urine collections obtained from 31 control children, ages 3 to 17 yr (group 1); 21 children, ages 5 to 19 yr with GH deficiency (group 2), and 30 subjects, ages 10 to 18 yr with idiopathic growth failure and normal GH stimulation tests (group 3). The output of urinary GH was measured in one acromegalic woman. The authenticity of urinary GH, 22 kDa, was confirmed by high-performance liquid chromatography. The elution pattern of urinary GH was identical to that of biosynthetic and pituitary-derived GH. The immunoreactive profiles characterized by monoclonal immunoradiometric GH assay and standard GH radioimmunoassay were identical. The quantity of GH (mean ± SEM per kg body weight) in group 1 (0.27 ± 0.02 ng/kg) was significantly greater than group 2 (0.08 ± 0.02 ng/kg) or group 3 (0.17 ± 0.02 ng/kg,p< 0.01). Approximately 50% of the subjects in group 3 had urinary GH measurements indistinguishable from those observed in the GH-deficient population. Twelve hypopituitary patients (group 2) excreted significantly greater amounts of urinary GH in the first 12 h after GH administration compared to the baseline period (0.41 ± 0.07versus0.12 ± 0.02 ng/kg,p< 0.01). Markedly elevated output of urinary GH (2.0 ng/kg) was documented in one acromegalic patient. The data suggest that measurements of urinary GH may be a useful, simple, and noninvasive screening test for identifying patients with GH deficiency or excess.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Previous studies have shown that salicylates and protein-calorie malnutrition compromise immunological responses in humans and experimental animals. The present study compared the effects of prenatal normal and low protein diets, with and without aspirin-like drug treatments, on lymphocyte blastogenesis measured by tritiated thymidine uptake for DNA synthesis in splenic lymphocytes from pregnant rats and their offspring following stimulation with the mitogens concanavalin A, phytohemagglutinin, and pokeweed mitogen. Aspirin treatment was associated with increased lymphocyte thymidine uptake for blastogenesis in pregnant rats fed the normal protein control diet and their offspring. The phytohemagglutinin-stimulated increase detected in offspring lymphocytes could not be statistically guaranteed. A low protein diet alone and a normal protein diet combined with salicylamide treatment was associated with decreased blastogenesis in pregnant rats but not in their offspring. Salicylamide or aspirin combined with a low-protein diet decreased blastogenesis in both dams and their offspring. Aspirin combined with a normal protein diet did not adversely affect blastogenesis in either pregnant rats or their offspring. This study suggests that low dietary protein and aspirin-like drugs may independently decrease lymphocyte blastogenesis of pregnant rats and in combination they may also reduce lymphocyte blastogenesis in offspring. The significance of increased lymphocyte blastogenesis in both mothers and offspring following aspirin treatment of pregnant rats fed a normal protein diet is unclear.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID