摘要:

SummaryKnowledge of the quality and speed of recovery after thoracotomy is crucial for studies of the early changes in cardiovascular function in the neonatal period. We studied the early recovery period after thoracotomy with pericardiotomy, but without ventriculotomy, in 21 lambs operated on between 2–24 days after birth. In 15 lambs, we measured resting pH, PaO2, PaCO2, O2consumption, cardiac output, heart rate, and aortic and pulmonary arterial pressures, before and after thoracotomy, daily for 1 wk. We found that, except for PaO2(82versus87 torr), all variables returned to normal by the third day after thoracotomy. Four lambs were exposed to hypoxia (FIO20.09 for 1 h) before and 3 days after thoracotomy; hypoxia-induced changes were not different at the two different periods. Six other lambs, undergoing thoracotomy within the first 3 days after birth and exposed to hypoxia on the third postoperative day, had hypoxia-induced responses similar to six age-matched nonthoracotomized lambs. These findings indicate recovery of cardiovascular function by 48–72 h after thoracotomy. We believe, therefore, that reliable studies of the circulation in lambs are possible as early as 3–4 days after birth, even if thoracotomy is required for making measurements. Speculation Thoracotomy, often required for the study of cardiovascular function, has adverse effects for a certain period of time. In newborn and young animals this period is only 2–3 days, thereby permitting essentially uninterrupted longitudinal studies despite thoracotomy.

ISSN:0031-3998    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Summary[3H]-Palmitate labeled natural lamb surfactant and free [14C]-choline were mixed with the lung fluid of 11 term lambs at cesarean section, before the first breath. After receiving the isotope, the lambs were delivered, allowed to breathe spontaneously, and were subsequently sacrificed from 5 min to 96 h of age. Alveolar washes, lung homogenates, microsomal and lamellar body fractions of lungs, and pulmonary alveolar macrophages were examined for the presence of labeled phosphatidylcholine. Analysis of the labeled natural surfactant kinetic data revealed an apparent t1/2of phosphatidylcholine in the whole lung of 6.0 days. This half-life can be interpreted only as a rough estimate. Appearance of considerable [3H] labeled phosphatidylcholine in the lung homogenates demonstrated uptake of phosphatidylcholine from alveoli into lung tissue. The surfactant-associated label in homogenates was localized preferentially to lamellar body fractions. Some of the administered [14C]-choline appeared in phosphatidylcholine. Almost all of this labeled phosphatidylcholine was associated with the homogenate. Extremely small % of administered [3H] and [14C] were found in pulmonary alveolar macrophages. Speculation The prolonged t1/2measured in this study indicates very slow turnover of alveolar phosphatidylcholine and/or considerable reutilization of label and possibly of the entire phosphatidylcholine molecule. The concentration of label in lamellar bodies raises the possibility that alveolar phosphatidylcholine may be degraded and its components utilized for synthesis of new phosphatidylcholine or that alveolar phosphatidylcholine may be absorbed into type-2 alveolar cells and resecreted intact. The finding of [14C] labeled phosphatidylcholine in lung homogenate but not in alveolar wash indicates that, even if choline were released by intra-alveolar degradation of surfactant, it is not used to a significant degree for synthesis of new surfactant phosphatidylcholine.

ISSN:0031-3998    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

SummaryUterine blood flow and its distribution to uterus, placenta and subplacental structures was measured in 18 pregnant guinea pigs studied under chronic steady-state conditions. Maternal cardiac output averaged 266 ± 14 ml/min. Placenta) blood flow (PBF) remained less than 4 ml/min until 50 days gestation, after which it increased rapidly, attaining flows of 16 ml/min at term. PBF also increased linearly with placental weight (r = 0.76,P< 0.001); however, the increase in PBF with gestational age is evident even in narrow weight ranges, indicating hyperperfusion of term placentas relative to those earlier in gestation. Fetal weight correlated with measured placental blood flow supplying the corresponding placenta after 50 days gestation (r = 0.72,P< 0.001). Speculation Placental blood flow appears to be an important independent determinant of spontaneous fetal size. Measurement of uteroplacental blood flow under unstressed conditions accurately describes normal uteroplacental blood flow and may provide more reliable characterizations of the relationships between uteroplacental blood flow, placental size, and fetal growth.

ISSN:0031-3998    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

SummaryThe right ventricular (RV) and left ventricular (LV) free wall weights, ornithine decarboxylase (ODC) specific activity and polyamine content were determined in fetal, 1–, 2–, 7–, 14–, and 21–day-old rabbit hearts. There was a significant increase in the LV free wall weight and a decrease in RV free wall weight between 1–7 days. By day 7 the LV/RV mass ratio doubled and reached a ratio comparable to that seen in adult rabbit hearts. The rate of change in the LV and RV free wall weights were comparable after day 7.There was a significant increase in LV ODC specific activity and a decrease in RV ODC specific activity after birth. The LV ODC specific activity was significantly greater than RV ODC specific activity in both 1 and 2 day old rabbit hearts whereas they were not significantly different in 7 and 14 day old rabbit hearts.The molar content (nmoles/mg wet weight or nmoles/mg protein) of putrescine decreased approximately 3-fold fter birth in the RV but increased approximately 2-fold in the LV. The molar content of spermidine and spermine was transiently increased after birth (1 day old) in both RV and LV with approximately a 2-fold increase in spermidine and a 2.5-fold (LV) and 4-fold (RV) increase in spermine content. The increase in LV putrescine content after birth was due, at least in part, to the observed increase in ODC specific activity in the LV free wall. The putrescine/spermidine ratio increased in the LV and decreased in the RV immediately after birth up to day 7. As opposed to the shortlived increase in spermidine and spermine observed in both the RV and the LV free wall, increased ODC specific activity and putrescine accumulation uniquely characterized the preferential growth of the LV between day 1 and 7.Speculation The postnatally developing heart affords an ideal model for studying the relationship between pressure loading and adaptive myocardial growth because paired comparisons of left and right ventricular parameters are possible. Age-related changes in left ventricular (LV) growth, ornithine decarboxylase (ODC) specific activity and putrescine accumulation occur immediately after birth and were clearly different from the right ventricle. This increase in LV ODC activity and putrescine synthesis may be secondary to the alterations in hemodynamic loading of the LV in the newborn. If cellular hyperplasia accounts for this preferential growth of the LV in the developing rabbit heart, as has been reported to be the case in the developing rat heart, it is speculated that polyamine metabolism may play a role in myocardial cellular hyperplasia.

ISSN:0031-3998    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

SummaryMucosal samples from rabbit jejunum were incubated (30 min, 25°C) with (125I) glycinin in the presence of buffer, soybean lectin (50 μg/ml) soyasaponins (1 mg/ml), or both lectin and saponins. The mueosal uptake of (125I) glycinin was negligible with buffer, and increased progressively with additions of soybean lectin (P< 0.05), soyasaponins (P< 0.005), and both (P< 0.0001). The stimulation of uptake by lectin and saponins together was greater than the sum of their individual effects (P< 0.0005). The effect of soybean lectin on glycinin uptake was concentration dependent, reaching a maximum at approximately 50 μg/ml for the stimulation of uptake in the presence of saponins, and was inhibited by D-GaINAc. Although the mechanisms involved in mucosal uptake of glycinin cannot be described from these data, we have assumed the presence of two independent pathways for lectin-stimulated and saponin-induced uptakes. In addition, we have proposed that soybean lectin, by binding to terminal galactoside sites at the enterocyte apical membrane, enhances a crenator effect of saponins that leads to increasing leakage of glycinin into the cell.Speculation Soyasaponins are heat resistant and their cellular lytic and trypsin inhibiting activities are known to increase after heat processing. Soybean lectin is heat labile, but remains at appreciable concentrations in inadequately processed and crude soy extracts. Interactions and effects similar to those occurring with mueosal tissuesin vitrocould also take place in the jejunumin vivoupon ingestion of such soy products.

ISSN:0031-3998    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

SummaryThe effects of severe hypoxemia on blood coagulation factor activities and other physiologic parameters were examined in ten near-term chronically catheterized fetal lambs (135–140 days gestation). Six lambs were subjected to a mean Po2of 13.8 ± 1.4 mmHg for 60 min. The other four served as controls. Before, during and after hypoxemia, the white blood cell count, hemoglobin, hematocrit, platelet count, pH, Pco2, Po2, mean arterial pressure, heart rate, norepinephrine and epinephrine were measured. Measures of coagulation factor activities including platelet counts, partial thromboplastin times, prothrombin times and quantitation of plasma activities for factors I, II, V, VII, VIII, IX, X, XI, XII, fibrin degradation products (FDP), antithrombin III, fibrin monomer and ristocetin cofactor activity were also done. An increase in mean arterial pressure from 48 ± 2 mmHg to 56 ± 2 mmHg, and an increase in epinephrine from 22 ± 9 pg/dl to 419 ± 199 pg/dl, and norepinephrine from 431 ± 98 pg/dl to 2408 ± 868 pg/dl occurred in the hypoxemic animals. There was also a slight decrease in the pH from 7.37 ± 0.01 to 7.32 ± 0.03 in the hypoxemic animals. The only significant change in blood coagulation factors during hypoxemia was a slight increase in fibrin monomer from 5.6 ± 0.8 ±g/ml to 12.6 ± 2.0 μg/ml. After the experiment, the animals were allowed to go to term and deliver spontaneously. Delivery occurred from 2–12 days after the experiment (mean 6 days). Blood coagulation factor activities I, II, V, VII, VIII, IX, X, XI, XII, antithrombin III, fibrin monomer, and fibrin degradation products were measured after delivery in the hypoxemic and control animals. Except for factor XII, values obtained from ten previously catheterized control fetal lambs after spontaneous delivery did not differ from the current control animals after delivery.Values on postdelivery samples for the two control groups were therefore pooled for analysis. Factors VIII, and IX were found to show increased activity during the 2 wk after delivery in hypoxemic animals when compared with controls. In contrast, the values for factors II, V, VII, X and fibrinogen showed lower activity in hypoxemic as compared to control animals during the early neonatal period. The study demonstrates that though there are no severe acute effects on blood coagulation during severe hypoxemia in the near-term fetus except perhaps transient low-grade disseminated intravascular coagulation, the episode of hypoxemia appears to alter the future development of blood coagulation factor activities during the early neonatal period.Speculation Hypoxemia in the near-term fetus delays the normal development of prothrombin, factors V, VII, X, and fibrinogen during the early neonatal period and accelerates the development of factors VIII and IX. The differences in factor responses may help explain the variable results reported in human infants. The results also suggest that both thrombotic and hemorrhagic tendencies might be a consequence of prenatal hypoxemia.

ISSN:0031-3998    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

SummaryWe report a stable isotope dilution method for the accurate measurement of methylmalonic acid (MMA) in amniotic fluid and its successful application to the prenatal diagnosis of methylmalonic acidemia. The stable isotopically-labeled analogue of MMA, (2-[2H3]methyl)malonic acid, was synthesized and used as an internal standard. Samples were extracted, methylated, and analyzed by chemical ionization gas chromatography-mass spectrometry (CI-GC-MS) operated in the selected ion monitoring (SIM) mode. The analytical method is rapid (8 h), ultrasensitive (lower limit ~10 ng/ml), linear over three orders of magnitude, and reproducible. The concentration of MMA in amniotic fluids from normal pregnant women was 38 ± 15 ng/ml (mean ± 1 S.D.). This value is 20-fold less than our previous estimate by gas chromatographic analysis, indicating that interference by co-eluting materials was eliminated by use of SIM in the present method. Amniotic fluids from eight at-risk pregnancies were examined. MMA concentration in six of the pregnancies was in the normal range whereas the concentration in the remaining two pregnancies was elevated by greater than two orders of magnitude (125–250-fold). Analysis of urine from ten at-risk pregnancies showed a smaller (31/2–9-fold) but significant increase in urinary MMA excretion in two women carrying affected fetuses. A control group of normal pregnant women had a mean urinary MMA excretion of 1.7 ± 0.5 μg/mg creatinine, in excellent agreement with previous estimates. There was concordance in prenatal diagnosis of fetal status in all cases between amniotic fluid cell studies and MMA measurements in amniotic fluid and/or maternal urine. Amniotic fluid MMA determination by the stable isotope dilution technique provides a highly accurate technique for prenatal diagnosis of methylmalonic acidemia that is complementary to amniotic fluid cell studies, and may supplant such studies in selected instances.Speculation The stable isotope dilution method may be extended to prenatal diagnosis of other inborn errors of metabolism in which low molecular weight metabolites accumulate in amniotic fluid. The concentrations of metabolites, which accumulate in some of these disorders, are below the sensitivity limits of currently available analytical techniques and it is thus impossible to distinguish differences that may be present in pregnancies carrying affected and unaffected fetuses. The enhanced sensitivity of the stable isotope dilution method may permit the desired discrimination.

ISSN:0031-3998    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

SummaryThis report explored the possibility that maternal hyperglycemia during pregnancy might produce a competition between glucose (G) and ascorbic acid (AA) and reduce the transfer of AA to the fetus using anin vivosingle-pass placental perfusion technique in the guinea pig. Levels of G in maternal plasma increased from 104 ± 4 mg/dl (x ± S.E.) before AA + G infusion to 370 ± 19 mg/dl at the end of each study (P< 0.001). Preinfusion levels of AA in maternal and fetal plasma were 0.29 ± 0.02 mg/dl and 0.46 ± 0.03 mg/dl, respectively. Maternal infusion of AA or AA + G produced significant increases in maternal plasma AA (P< 0.025) and fetal plasma AA (P< 0.001); however, fetal plasma AA from dams infused with AA + G were significantly below fetal plasma values obtained when only AA was infused (P< 0.005) suggesting that when maternal plasma G is increased, the placental transport of AA to the fetus is reduced. Preinfusion levels of AA in placental tissue were 10.8 ± 0.5 mg/dl and infusion of AA or AA + G produced significant increases in AA in this organ (P< 0.001). Comparison of the AA in placental tissue from fetuses of dams infused with either solution demonstrates that significantly less AA was present after AA + G infusion (P< 0.005). Additionally, when AA + G was infused a significant decrease in AA transferred across the placenta was found (P< 0.001) as maternal plasma G increased beyond 200 mg/dl. The data suggest that in the guinea pig glucose may compete with ascorbic acid transfer across the placenta and that maternal hyperglycemia may reduce the bioavailability of AA to the fetus.Speculation An acute episode of maternal hyperglycemia interferes with the placental transfer of ascorbic acid. Therefore, maternal hyperglycemia during gestational diabetes may result in a decreased supply of ascorbic acid to the fetus.

ISSN:0031-3998    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

SummaryA supplement of the branched chain amino acids, valine, isoleucine, and leucine (VIL) was administered orally to patients with phenylketonuria, either together with unrestricted diet of natural protein or with a low phenylalanine diet. The VIL supplement brought about a significant reduction of the cerebrospinal fluid-serum ratio of phenylalanine from a mean value of 0.254 without VIL to 0.204 with VIL. The reduction varied from 15–40% (mean 21%). Concentrations of glycine, lysine, methionine, threonine, tryptophan, and tyrosine were within normal limits in serum and cerebrospinal fluid of infants with phenylketonuria. No amino acid imbalance was created by the supplement and no adverse effects from VIL were observed.Speculation The branched chain amino acids and phenylalanine share a common transport system. High levels of phenylalanine in brain of children with phenylketonuria may be reduced by administration of a supplement of valine, isoleucine and leucine (VIL). Supplementation of the low-phenylalanine diet with VIL during the first 2 years of life may add a measure of protection to the developing brain beyond that which can be achieved by diet alone. In older children, VIL supplementation may permit liberalization of the diet without unfavorable behavioral consequences.

ISSN:0031-3998    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

SummaryThein vivoabsorption of L-valine was studied in segments of the jejunum and ileum using a one-pass perfusion technique in normal suckling (2-week-old), weanling (3-week-old) and adolescent (6-week-old) rats. In both the jejunum and the ileum, rate of absorption (μmoles/h/g wt) of L-valine declined with age. The relationship between absorption rate and luminal concentration suggested the presence both of a saturable carrier mediated (Jmax[C]/Kt+ [C]) and diffusive (KD.[C]) processes for absorption of L-valine. In both the jejunum and the ileum, rates ‘of carrier mediated and of diffusive absorption of L-valine were over 2-fold greater in the suckling than in the adolescent rats. Rates of absorption were not significantly different in the jejunum and ileum at all three age periods. Although values of Jmaxand KDwere greater in segments of the suckling rats, values of the apparent Ktwere similar at all 3 age periods, suggesting that the mechanism (affinity of the carrier macromolecules) of carrier mediated absorption of L-valine did not change with age but the passive permeability of the intestinal mucosa to L-valine and relative number of L-valine absorbing sites (number of carrier macromolecules) decreased per unit weight of intestine with increasing age. Serum and intestinal tissue concentration of L-valine at the end of the perfusion period were greater in the 2-week-old than in the older rats. After parentral injection of [14C]-L-valine rate of secretion of L-valine was several-fold greater in the jejunum and the ileum of the suckling than of the adolescent rats.Speculation The decline in the ability of the small intestine to absorb L-valine (per unit weight) with increasing age appears to be due to a decrease in the passive permeability of the mucosal membrane to L-valine as well as to a relative decrease in the number of absorbing sites (carrier macromolecules) per unit weight of intestine. The decline in the passive permeability suggests a change in the biochemical composition or the ultrastructure of the mucosal membrane during maturation. The decline in the absorbing capacity of the small intestine with age could be due to a relative increase in number of villus epithelial cells not involved in absorption of amino acid; however, it is more likely to be due to a decrease in number of amino acid absorbing sites (carrier macromolecules) per villus epithelial cell.

ISSN:0031-3998    

出版商:OVID    

年代:1982

数据来源: OVID