Biomedical subjects

M Ikegami

Publications and source records attributed to M Ikegami.

At least 109 records · Page 6Linked to original sources

PubMed1998

Direct fetal glucocorticoid treatment alters postnatal adaptation in premature newborn baboons.

Abnormalities of premature newborn adaptation after preterm birth result in significant perinatal mortality and morbidity. We assessed the effects of short-term (24 h) fetal betamethasone exposure on preterm newborn baboon pulmonary and cardiovascular regulation and renal sodium handling during the first 24 h after birth. Male fetal baboons (Papio) (124-day gestation, term 185 days) received ultrasound-guided intramuscular injections of saline (n = 5) or betamethasone (0.5 mg/kg; n = 5). Fetuses were cesarean delivered 24 h later, treated with 100 mg/kg surfactant, and ventilated by adjusting peak inspiratory pressures to maintain PCO2 values of 35-50 mmHg for 24 h. Betamethasone- vs. saline-treated mean +/- SE newborn body weights (0.45 +/- 0.02 vs. 0.41 +/- 0.01 kg) were similar. Although prenatal betamethasone did not affect postnatal lung function (PCO2, arterial/alveolar O2 gradient, or dynamic compliance), plasma hormone (cortisol or thyroxine), or catecholamine levels, mean arterial pressure (25 +/- 1 vs. 32 +/- 1 mmHg), plasma sodium concentration (132 +/- 2 vs. 138 +/- 1 meq/l), glomerular filtration rate (0.07 +/- 0.02 vs. 0.16 +/- 0.02 ml.min-1.kg-1), and renal total sodium reabsorption (1.5 +/- 0.5 vs. 16.0 +/- 3.0 mu eq.min-1.kg-1) values were significantly lower in saline-treated than in betamethasone-treated newborns at 24 h. We conclude that despite the fact that there are no pulmonary and endocrine effects, antenatal glucocorticoid exposure alters premature newborn baboon vascular and renal glomerular function and improves sodium reabsorption after preterm delivery.

Adaptation, Physiological↗

PubMed1998

Effect of ventilation style on cardiovascular and renal adaptation in preterm newborn lambs.

Renal adaptive responses during the 24 h after delivery in term newborn lambs include marked increases in both glomerular filtration rate (GFR) and sodium reabsorption. This study investigated the effects of ventilation style on cardiovascular, renal, and endocrine adaptations in preterm newborn lambs. Lambs (n = 62) were delivered by cesarean section at 131 days gestation (term = 150 days), treated with surfactant, and randomized to one of three ventilation strategies: high-frequency oscillation (12 Hz), high rate (50 breaths/min; tidal volume = 8 ml/kg), or low rate (15 breaths/min; tidal volume = 15 ml/kg). Lambs (5 or 6/group) were ventilated for 2, 5, 10, and 24 h to maintain arterial PCO2 between 45 and 50 mmHg. Plasma vasopressin levels decreased to <25 pg/ml by 10 h, and fractional sodium excretion decreased to <1% by 16 h in all groups. However, cardiac output, renal plasma flow, and GFR values did not change over time for any of the groups. The style of ventilation employed had no measurable effects on overall cardiovascular, renal, or endocrine function. We conclude in ventilated preterm lambs that 1) the ventilation style does not affect the time course for postnatal adaptation, 2) adaptive changes in renal tubular sodium reabsorption are evident by 16 h after birth, and 3) changes in preterm newborn renal sodium reabsorption occur in the absence of postnatal changes in renal plasma flow or GFR.

Absorption↗

PubMed1998

Repetitive prenatal glucocorticoid therapy reduces oxidative stress in the lungs of preterm lambs.

Repetitive courses of maternal prenatal glucocorticoids are often used in high-risk pregnancies with threatening preterm labor to induce lung maturation, but the effects on the cellular oxidant-antioxidant balance in the fetal lung have not been evaluated. We investigated the effect of repetitive treatment with glucocorticoids, beginning early in gestation, on oxidative stress in the preterm ovine lung. Pregnant ewes were randomized to receive one, two, three, or four doses of 0.5 mg/kg betamethasone or saline placebo at 7-day intervals on 104, 111, 118, and 124 days gestation (n = 11 for each group). All lambs were delivered preterm at 125 days gestation, and lung tissue was assayed for antioxidant enzymes, lipid hydroperoxides, and carbonyl proteins. Lung manganese superoxide dismutase, catalase, and glutathione peroxidase activity increased after 1 dose of betamethasone given at 104 days gestation, whereas copper-zinc superoxide dismutase activity increased after 2 doses given at 104 and 111 days gestation. The activity of all four antioxidant enzymes further increased with additional doses and was maximal after four doses of betamethasone. Lung lipid hydroperoxide levels and carbonyl protein content decreased stepwise after each dose of betamethasone and were lowest after four doses. Repetitive prenatal glucocorticoid therapy increases antioxidant enzyme activity and reduces oxidative stress in the lungs of preterm lambs, and these effects begin early in gestation and persist for 2-3 wk.

Animals↗

PubMed1998

Lung function in premature lambs and rabbits treated with a recombinant SP-C surfactant.

We evaluated the efficacy of a recombinant surfactant protein-C (rSP-C) surfactant in vitro and in vivo, using ventilated preterm lambs and rabbits. The surface tension measured with a Wilhelmy balance of the rSP-C surfactant was lower than the surface tension of natural sheep surfactant (containing SP-B and SP-C). The rSP-C and natural surfactants were equivalently sensitive to inhibition by plasma. Over a 5-h study period, lambs treated with 100 mg/kg rSP-C and natural surfactants at birth had similar PCO2, lung mechanics, and FRC values. Indicators of injury also were not different. In preterm rabbits ventilated with 3 cm H2O positive end-expiratory pressure (PEEP), similar compliance responses were measured for the rSP-C and natural surfactant. Large-aggregate surfactants recovered from alveolar washes of the lambs treated with rSP-C or natural surfactant retained their function when tested in preterm rabbits. In conclusion, the rSP-C surfactant was effective in preterm animals with surfactant deficiency.

Animals↗

PubMed1998

Effects of ventilation style on surfactant metabolism and treatment response in preterm lambs.

We investigated whether the style of ventilation would influence respiratory physiology or surfactant metabolism in surfactant-treated preterm lambs. Preterm lambs were delivered at 131 +/- 1 d gestation and treated with an organic solvent extract of sheep surfactant (100 mg/kg). The lambs were randomized to ventilation peiods of 2 h, 5 h, 10 h, or 24 h, and to ventilation with a low rate (15 breaths/min) and high VT (15 ml/kg), with a high rate (50 breaths/min) and low VT (8 ml/kg), or with high-frequency oscillatory ventilation (HFOV). Gas exchange and lung volumes were similar across time and for the different ventilation styles. Saturated phosphatidylcholine (SatPC) in alveolar lavage was lower for the HFOV group than for the other ventilation groups at 10 h and 24 h. The rate of loss of surfactant protein B (SP-B) from these preterm animals' lungs was slow and not influenced by ventilation style. The percentages of surfactants in large-aggregate forms were not changed by style of ventilation, and the large-aggregate surfactants had excellent function when tested in surfactant-deficient preterm rabbits. Alveolar lavage protein was low (30 ml/kg), and tissue hyaluronan did not change with time or ventilation style. In preterm lambs ventilated without causing injury, the extreme styles of ventilation examined in the study had minimal effects on lung function, surfactant function, or surfactant metabolism.

Animals↗

PubMed1998

Surfactant homeostasis in corticotropin-releasing hormone deficiency in adult mice.

Glucocorticoids are essential for lung maturation and pharmacologic doses of glucocorticoids increase surfactant in adult rats. Therefore, we asked if glucocorticoid deficiency in corticotropin-releasing hormone-deficient mice (CRH-/-) with very low plasma corticosterone levels would alter surfactant pool sizes and precursor incorporation into saturated phosphatidylcholine (Sat PC). Alveolar and lung tissue Sat PC pool sizes were not different for CRH-/- mice and wild-type mice. The incorporation of [3H]choline into Sat PC also was similar for the two strains of mice. Glucocorticoids are not a major regulator of surfactant homeostasis in the adult mouse.

Animals↗

PubMed1998

Abnormal surfactant metabolism and function in preterm ventilated baboons.

We evaluated surfactant metabolism and function and the effects of antenatal glucocorticoids in very preterm baboons. Pregnant baboons were randomized to receive saline (controls) or 6 mg betamethasone (beta) 48 and 24 h before delivery at 125 +/- 2 d gestation (term is 184 d). The newborn baboons were treated with [14C]dipalmitoylphosphatidylcholine-labeled surfactant and ventilated for 6 d. Lung function for six control and six betamethasone-treated animals was similar. Recoveries of 14C-saturated phosphatidylcholine (Sat PC) were similar: 4.8% (control) and 3.6% (beta) in alveolar wash and 15.4% (control) and 17.7% (beta) in total lungs. Alveolar and total lung pool sizes of Sat PC were about 23 and 190 micromol/kg, respectively. The preterm baboons secreted 8.7% (control) and 6.5% (beta) of de novo synthesized Sat PC labeled with 3H-palmitate from Day 5 to Day 6. These preterm baboons had high estimated Sat PC synthetic and net tissue accumulation rates but low secretion of Sat PC. The large aggregate surfactant fractions from the preterm baboons had high minimal surface tensions and were less effective when used to treat surfactant-deficient preterm rabbits than surfactant from newborn or adult baboons. Ventilation of the preterm baboon was associated with surfactant functional and metabolic abnormalities that were not altered by antenatal glucocorticoids.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1998

Surfactant protein-C in ventilated premature lamb lung.

Although surfactants containing only lipids and surfactant protein C (SP-C) or SP-C analogs can be effective for the treatment of surfactant deficiency in animal models, there is no information concerning the alveolar or lung clearance of SP-C. Because the other lipid and protein components of surfactant are cleared very slowly from the preterm lung, we hypothesized that SP-C also would be cleared slowly. Therefore, we compared the losses of iodinated native SP-C (nSP-C) and a recombinant SP-C analog (rSP-C, phenylalanines in positions 4 and 5 and isoleucine in position 32 of the human sequence) to [14C]dipalmitoylphosphatidylcholine (DPPC) after airway administration at birth of trace or treatment doses of surfactant given to preterm lambs. In preterm lambs given trace doses at 134-136 d gestation, alveolar [14C]DPPC and [125I]rSP-C decreased to 14.7% recovery for DPPC and 8.3% recovery for rSP-C after 2 h ventilation. There was no loss of [14C]DPPC from the total lungs (alveolar wash + lung tissue), and approximately 20% of the [125I]rSP-C was lost from the lungs. For 128 d gestational age lambs treated with 100-mg/kg doses of surfactants containing nSP-C or 2% rSP-C, the alveolar and total lung recoveries for [125I]nSP-C or [125I]rSP-C were equivalent to that of [14C]DPPC after 5 h ventilation. These results demonstrate that nSP-C and rSP-C have alveolar clearances and accumulations into preterm lung tissue that are similar to those of DPPC.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1998

Molecular evolution of a host-range gene in geminiviruses infecting asexual populations of Eupatorium makinoi.

Asexual plants of Eupatorium makinoi is frequently infected with tobacco leaf curl geminivirus (TLCV). The host range of TLCV is narrow, and ORF C4 is considered to function as a host range determinant. Using this TLCV-Eupatorium system, we tested the expectation that the rate of amino acid replacements will be accelerated in ORF C4 if resistant genes of the host plants drive molecular evolution in ORF C4. ORF C4 is entirely contained within a longer ORF C1 encoding a replication protein. We analyzed 21 sequences containing ORF C4 and a part of ORF C1. While per-site number of synonymous substitutions exceeded that of replacements in ORF C1, per-site number of replacements exceeded that of synonymous substitutions in ORF C4. However, this excess of per-site replacement in ORF C4 was mostly explained by the overlap gene nature, because most synonymous substitutions in ORF C1 change amino acid of ORF C4. In conclusion, not positive but negative selection is a predominant mode characterizing molecular evolution of ORF C4.

Asteraceae↗

PubMed1998

Fetal versus maternal and gestational age effects of repetitive antenatal glucocorticoids.

BACKGROUND: Although single courses of antenatal glucocorticoids decrease respiratory distress syndrome and mortality, repetitive courses of antenatal glucocorticoids are being given to women at risk of preterm delivery without evidence of benefit or appreciation of potential risks. OBJECTIVES: To evaluate the effects of single and repetitive antenatal glucocorticoid exposures on fetal growth and postnatal lung function in sheep. METHODS: Pregnant ewes were randomized to three protocols that included one or three doses (at 7-day intervals) of 0.5 mg/kg of betamethasone (beta) given to the ewe or fetus beginning at gestations ranging from 104 to 128 days' gestation with delivery at 125, 135, and 146 days' gestation. Postnatal assessments included measurements of gas exchange, compliance, ventilation efficiency, static lung volume, and lung tissue and alveolar wash saturated phosphatidylcholine. RESULTS: Single or repetitive maternal beta but not fetal beta caused fetal growth retardation at delivery at 125, 135, and 146 days' gestation. Single-dose fetal beta had no effect on postnatal lung function whereas single-dose maternal beta significantly increased compliance, lung volume, and tissue and alveolar surfactant after preterm delivery. Although three-dose fetal beta improved all indicators of postnatal lung function, three-dose maternal beta resulted in larger responses. The added benefits of repetitive beta relative to a single-dose beta on postnatal lung function after preterm delivery were not as great when therapy was begun later in gestation. Postnatal lung function after delivery at 146 days' gestation (term is 150 days) was improved after repetitive maternal beta at early gestational age. CONCLUSIONS: In sheep, single or repetitive maternal beta causes growth retardation from 104 to 121 days' gestation and the growth retardation persists to term. In contrast, single or repetitive fetal beta does not cause fetal growth retardation and is less potent at improving postnatal lung function and increasing surfactant pools. There are potential benefits as well as risks for the use of repetitive antenatal glucocorticoids. Randomized, controlled trials in humans are essential given the widespread use of repetitive courses of antenatal glucocorticoids in women at risk of preterm delivery. respiratory distress syndrome, maturation, prematurity, growth retardation, surfactant.

Animals↗

PubMed1998

Effects of shaking on the sensitivity of neuromuscular transmission in vitro to d-tubocurarine and neomycin in mice.

The effects of continuous shaking after birth were examined on the sensitivity of neuromuscular transmission to d-tubocurarine (dTc) and neomycin (NMC) in various nerve-muscle preparations from male mice of the ddY strain. Newborn mice were subjected to continuous reciprocal shaking with an amplitude of 2.5 cm at a frequency of 2 cycles per second until they reached 13 weeks of age. Some of them were returned to conventional breeding conditions for 4 weeks at 13 weeks of age. Nerve-muscle preparations were made from the left phrenic nerve and the diaphragm muscle (DPH), the sciatic nerve and the soleus muscle (SOL), and the sciatic nerve and the extensor digitorum lungus muscle (EDL) of 13- or 17-week-old male mice. The results revealed that the shaking augmented the sensitivity of SOL and DPH to dTc, it reduced the sensitivity of all the preparations to NMC, it reduced the rate of spontaneous release of transmitter in SOL and it increased the rate of evoked release of transmitter in DPH. Furthermore, these alterations disappeared upon cessation of shaking. These results suggest diversity in the plasticity of neuromuscular transmission and, moreover, that some changes might be reversible.

Animals↗

PubMed1998

[Effect of ultrasound contrast medium in color Doppler of blood flow in transplant kidneys].

We have so far performed color Doppler echography to make diagnosis in renal transplantation. The ultrasound contrast agent in color Doppler developed and used recently has made possible the recording and measuring of low velocity wave in transplant kidneys. As characteristics of that, mention can be made of improvement in detection of the flow, reliability of assessment of the velocity, space resolving power. It is useful particularly for the peripheral blood vessels on chronic rejection and the interlobar artery on acute vascular rejection. With that put to practical use, imaging diagnosis in the field of renal transplantation has improved in its diagnosing ability and is expected to make further development in the future.

Contrast Media↗

PubMed1997

Rescue of SP-B knockout mice with a truncated SP-B proprotein. Function of the C-terminal propeptide.

The function of the 102-amino acid C-terminal propeptide of surfactant protein B (SP-B) was analyzed by characterizing the phenotype associated with loss of expression of this peptide domain in transgenic mice. A construct encoding the signal peptide, N-terminal propeptide, and mature peptide of human SP-B (hSP-BDeltac) was cloned under the control of the 3.7-kilobase human SP-C promoter and injected into fertilized eggs of the FVB/N mouse strain. Founder mice expressing the hSP-BDeltac transgene were bred with heterozygous SP-B knockout mice (SP-B +/-). Offspring containing the transgene and one allele of mouse SP-B were identified and subsequently crossed to generate a transgenic line that expressed SP-BDeltac in a null background (SP-B(-/-)/hSP-BDeltac(+/+)). Expression of hSP-BDeltac in SP-B(-/-) mice was restricted to type II cells and resulted in a 2-fold increase in mature SP-B relative to wild type littermates. These mice survived without any evidence of respiratory problems and had normal lung function, normal alveolar surfactant phospholipid pool sizes, and typical tubular myelin indicating that the 102-residue C-terminal propeptide of SP-B is not required for normal structure and function of extracellular surfactant. However, proteolytic processing of the SP-C proprotein was perturbed resulting in the accumulation of a processing intermediate, Mr = 11,000, similar to the phenotype detected in SP-B(-/-) mice; furthermore, lamellar bodies in type II cells of SP-B(-/-)/hSP-BDeltac(+/+) mice were much larger than in the wild type animal and saturated phosphatidylcholine content in lung tissue was significantly increased although the incorporation of choline into saturated phosphatidylcholine was normal. Collectively, these results demonstrate a role for the C-terminal propeptide of SP-B in SP-C proprotein processing and the maintenance of lamellar body size. The C-terminal propeptide may be an important determinant of intracellular surfactant pool size.

Animals↗

PubMed1997

Preterm lung function after retreatment with antenatal betamethasone in preterm lambs.

OBJECTIVE: We hypothesized that two doses of betamethasone administered 1 week apart would further enhance postnatal pulmonary function in preterm lambs (compared with a single dose). STUDY DESIGN: Fetal sheep (121 days' gestation) randomly received saline solution or betamethasone (0.5 mg/kg) as a single injection. Six days later fetal sheep were retreated with either saline solution or corticosteroid, and postnatal lung function was evaluated 1 day later. RESULTS: Betamethasone improved compliance and ventilation efficiency index nearly 50%, and total lung volume increased twofold. No effects of treatment-to-delivery interval (1 vs 7 days) or corticosteroid retreatment on pulmonary function were apparent. Although surfactant pool sizes increased as a function of duration of exposure, no additional effect of corticosteroid retreatment was noted. Antenatal betamethasone increased messenger ribonucleic acid levels for the surfactant proteins A and C, and retreatment augmented surfactant protein B messenger ribonucleic acid levels but suppressed surfactant protein A and C messenger ribonucleic acid. CONCLUSION: Improved postnatal lung function resulting from antenatal betamethasone was not augmented by retreatment.

Animals↗

PubMed1997

Surfactant metabolism in surfactant protein A-deficient mice.

In the present study we asked if surfactant metabolism was altered in surfactant protein (SP) A-deficient mice in vivo. Although previous studies in vitro demonstrated that SP-A modulates surfactant secretion and reuptake by type II cells, mice made SP-A deficient by homologous recombination grow and reproduce normally and have normal lung function. Alveolar and lung tissue saturated phophatidylcholine (Sat PC) pools were 50 and 26% larger, respectively, in SP-A(-/-) mice than in SP-A(+/+) mice. Radiolabeled choline and palmitate incorporation into lung Sat PC was similar both in vivo and for lung tissue slices in vitro from SP-A(+/+) and SP-A(-/-) mice. Percent secretion of radiolabeled Sat PC was unchanged from 3 to 15 h, although SP-A(-/-) mice retained more labeled Sat PC in the alveolar lavages at 48 h (consistent with the increased surfactant pool sizes). Clearance of radiolabeled dipalmitoylphosphatidylcholine and SP-B from the air spaces after intratracheal injection was similar in SP-A(-/-) and SP-A(+/+) mice. Lack of SP-A had minimal effects on the overall metabolism of Sat PC or SP-B in mice.

Animals↗

PubMed1997

Preferential uptake of small-aggregate fraction of pulmonary surfactant in vitro.

Homeostasis of pulmonary surfactant requires metabolic clearance of surfactant forms with decreased surface activity. Rabbit pulmonary surfactant was labeled in vivo with rhodamine-labeled dipalmitoylphosphatidylethanolamine (R-DPPE), isolated, and fractionated into large- and small-aggregate subfractions by differential centrifugation. Endocytosis of large (LA)- and small (SA)-aggregate surfactant by a mouse lung epithelial cell line (MLE-12) was evaluated in vitro by epifluorescence microscopy. More SA than LA surfactant was taken up by MLE-12 cells. Endocytosis of SA and LA surfactant was inhibited by preincubation of the subfractions with surfactant protein A and 3.3 mM Ca2+. The difference in uptake between SA and LA surfactant was lost for reconstituted organic extracts of the subfractions. Much of the difference in uptake of SA and LA surfactant may be attributed to the greater concentration of surfactant protein A in LA surfactant.

Animals↗

PubMed1997

Surfactant metabolic consequences of overexpression of GM-CSF in the epithelium of GM-CSF-deficient mice.

Granulocyte macrophage colony-stimulating factor (GM-CSF) is a regulator of surfactant metabolism because GM-CSF-deficient mice have abnormally slow clearance and catabolism of saturated phosphatidylcholine (Sat PC) and surfactant protein (SP)-A in airspaces and lung tissue. Overexpression of GM-CSF only in respiratory epithelial cells of mice deficient in GM-CSF using the SP-C promotor (GM-/-,SP-C-GM+/+) resulted in increased type II cell numbers and normalization of alveolar Sat PC pool sizes. Metabolic measurements demonstrated that incorporation of radiolabeled choline and palmitate was increased more than twofold, but the amount of radiolabeled Sat PC that accumulated in airspaces relative to the amount incorporated was decreased by 50% relative to normal GM+/+ mice. The clearance of dipalmitoylphosphatidylcholine and SP-B from the airspaces was more rapid for GM-/-,SP-C-GM+/+ mice than for GM+/+ mice. Loss of Sat PC and SP-B from the lungs (alveolar plus lung tissue) was similar in the two strains of mice. The normal surfactant pools in the GM-/-,SP-C-GM+/+ mice were achieved by the net effects of increases in type II cell numbers, increased incorporation, decreased accumulation, and increased reuptake rates for surfactant components, demonstrating the multiple effects of GM-CSF on surfactant metabolism.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1997

Pulmonary dysfunction in neonatal SP-B-deficient mice.

Pulmonary function was assessed in newborn wild-type and homozygous and heterozygous surfactant protein B (SP-B)-deficient mice after birth. SP-B +/+ and SP-B+/- mice became well oxygenated and survived postnatally. Although lung compliance was decreased slightly in the SP-B+/- mice, lung volumes and compliances were decreased markedly in homozygous SP-B-/- mice. They died rapidly after birth, failing to inflate their lungs or oxygenate. SP-B proprotein was absent in the SP-B-/- mice and was reduced in the SP-B+/- mice, as assessed by Western analysis. Surfactant protein A, surfactant proprotein C, surfactant protein D, and surfactant phospholipid content in lungs from SP-B+/- and SP-B-/- mice were not altered. Lung saturated phosphatidylcholine and precursor incorporation into saturated phosphatidylcholine were not influenced by SP-B genotype. Intratracheal administration of perfluorocarbon resulted in lung expansion, oxygenation, and prolonged survival of SP-B-/- mice and in reduced lung compliance in SP-B+/+ and SP-B+/- mice. Lack of SP-B caused respiratory failure at birth, and decreased SP-B protein was associated with reduced lung compliance. These findings demonstrate the critical role of SP-B in perinatal adaptation to air breathing.

Animals↗