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Biomedical subjects

M Ikegami

Publications and source records attributed to M Ikegami.

At least 361 records · Page 20Linked to original sources
PubMed1981

Isolation and characterization of virus-specific double-stranded DNA from tissues infected by bean golden mosaic virus.

A double-stranded (ds) DNA which may be a replication intermediate was isolated from bean (Phaseolus vulgaris L. "Top Crop") leaves systemically infected with bean golden mosaic virus, a whitefly-transmitted plant virus with a genome of circular single-stranded (ss) DNA. The isolation method used phenol/chloroform extraction, hydroxyapatite column chromatography, and rate-zonal centrifugation. The dsDNA had sequences complementary to those of viral DNA. The guanine-plus-cytosine content was 35%, and the sedimentation coefficient in alkaline sucrose density gradients was similar to that of viral ssDNA. Digestion of the dsDNA by Hha I endonuclease produced fragments that corresponded exactly in number and size with those produced by complete digestion of circular viral ssDNA by Hha I, when the fragments were denatured and analyzed on polyacrylamide gels. The dsDNA molecule was a circular structure with one discontinuity in one strand; hybridization results suggest that some of a the dsDNA has a discontinuity in the viral strand and some has a discontinuity in the nonviral strand. On the basis of these structures for the dsDNA, a preliminary model for replication of viral DNA is discussed.

Journal Article↗
PubMed1981

Surface activity following natural surfactant treatment in premature lambs.

Premature lambs with respiratory failure [CO2 partial pressure (PCO2) greater than 70 Torr] were treated with 50 mg/kg 3H-labeled natural surfactant by tracheal instillation. Minimum surface tensions of sequential samples suctioned from the airways fell from 25 +/- 3 dyn/cm before treatment to 8 +/- 5 dyn/cm after treatment and again rose to 32 +/- 2 dyn/cm at death. Minimum surface tensions of alveolar wash samples taken at death were 27 +/- 4 dyn/cm, whereas surfactant fractions reisolated from the alveolar washes lowered surface tension to under 10 dyn/cm. The alveolar washes, surfactant reisolated from the alveolar washes, and natural surfactant had similar phospholipid compositions; however, the alveolar washes contained about 40 times more protein per micromole phosphatidylcholine. The natural surfactant used for treatment apparently was inactivated by an inhibitor of surfactant function. After intravenous injections of [14C]palmitic acid, labeled saturated phosphatidylcholine appeared on the airways, indicating endogenous synthesis and secretion. However, the specific activity of the 3H-labeled saturated phosphatidylcholine in the natural surfactant used for treatment decreased by only 30 +/- 4% in the alveolar wash; thus the treatment dose was not diluted to a large extent by endogenous pools.

Animals↗
PubMed1981

Duration and characteristics of treatment of premature lambs with natural surfactant.

Premature lambs were treated with 50 mg/kg of natural surfactant lipid by tracheal instillation either at birth or shortly thereafter when respiratory failure was documented. All lambs were delivered by cesarean section and supported on infant ventilators with 100% oxygen under conditions to mimic the care of human infants with the respiratory distress syndrome. The natural surfactant used for therapy was recovered by lavage from sheep lung. Six 120-d gestational age lambs treated at birth had an initial mean oxygen pressure (pO2) value of 270 +/- 35 mm Hg; this fell within 3 h to less than 100 mm Hg. By 8.3 +/- 0.3 h after birth the lambs were in severe respiratory failure with a mean pH less than 7.1 and a mean pCO2 greater than 70 mm Hg. Six untreated lambs had pH values below 7.0 within 40 min of life despite more intensive respiratory support than was given the treated animals. Treatment with natural surfactant of 17 lambs of 120 and 130 d gestational age after early respiratory failure resulted in a prompt increase in pO2 values from about 35 mm Hg to values over 200 mm Hg and a fall in pCO2 values to normal levels in the majority of animals. This response lasted only approximately 3 h, and a second treatment was less predictably effective.

Animals↗
PubMed1981

Sequential treatments of premature lambs with an artificial surfactant and natural surfactant.

To test an artificial surfactant in vivo, six 120-d gestational age lambs were treated at birth with a mixture of a 9:1 M ratio of [14C]dipalmitoyl phosphatidylcholine (DPC) and phosphatidylglycerol at a dose of 100 mg DPC/kg. Nine other lambs were not treated. The mean PO2 values of the lambs treated with artificial surfactant were 65.7 +/- 11 mm Hg vs. 24.8 +/- 1.6 mm Hg for the untreated lambs (P less than 0.001). All lambs then were treated with 50 mg/natural surfactant lipid per kg, which promptly improved PO2 in all lambs. The PO2 values of those lambs previously treated with artificial surfactant remained greater than 100 mm Hg for 2.5 +/- 0.5 h vs. 0.9 +/- 0.3 h for lambs untreated with artificial surfactant (P less than 0.01). The pH and PCO2 values were not strikingly different between the two groups of lambs. Airway samples taken from lambs treated with artificial surfactant before treatment with natural surfactant had minimal surface tensions of 32 +/- 2.9 dyn/cm, whereas the artificial surfactant reisolated from these samples by centrifugation had minimum surface tension of 0 dyn/cm. The minimum surface tension of artificial surfactant was inhibited by fetal lung fluid from the premature lambs, whereas the minimum surface tension of natural surfactant was much less sensitive to inhibition. Artificial surfactant did not improve the pressure-volume characteristics of unventilated premature lung, whereas natural surfactant did. The change in specific activity of [14C]DPC following treatment with natural surfactant indicated that approximately 50% of the DPC initially administered was no longer associated with the airways.

Animals↗
PubMed1981

The labeling of pulmonary surfactant phosphatidylcholine in newborn and adult sheep.

The labeling of the saturated phosphatidylcholine from surfactant with radiolabeled palmitic acid was characterized in seven newborn and seven adult sheep using a repetitive sampling technique. Each animal had a small cannula placed surgically in the trachea. Following the intravenous injection of (3H) palmitic acid, surfactant samples in saline were recovered from the distal airways of each animal with fine plastic catheters over a period of 10 days. The change in specific activity of the saturated phosphatidylcholine (cpm/mumol) was used to define the kinetics of secretion and then disappearance of the labeled saturated phosphatidylcholine. Labeled saturated phosphatidylcholine accumulated in a linear fashion without an apparent initial delay for 27 hr in adult and 44 hr in newborn sheep. The labeled saturated phosphatidylcholine then decayed with mean apparent biological half-life values of 45 hr and 54 hr in adult and newborn sheep, respectively. However, these half-life estimates are compromised by the long secretory phase of the labeling curves. The characteristics of the labeling of surfactant saturated phosphatidylcholine in sheep may be more representative of surfactant metabolism in large mammals than previous studies in small rodents.

Animals↗
PubMed1980

The in vivo labeling with acetate and palmitate of lung phospholipids from developing and adult rabbits.

The labeling with radiolabeled acetate and palmitate of lung, microsomes isolated from lung, and surfactant phospholipids from adult, 3-day-old, and newborn rabbits was studied. The half-life of phosphatidylcholine from lung and microsomal fractions was shorter when labeled with acetate than when labeled with palmitate. Half-time values similarly measured for phosphatidylglycerol, phosphatidylinositol or phosphatidylethanolamine were not different for the two labels. Acetate and palmitate-labeled phospholipids appeared in the surfactant fraction with similar accumulation curves. The relative specific activities of acetate-labeled phosphatidylcholine from adult, 3-day-old, and newborn rabbits, respectively, were 1.30, 1.86 and 1.77 times those measured for those measured for the palmitate label. Surfactant phosphatidylinositol and phosphatidylethanolamine from 3-day-old animals similarly were labeled preferentially with acetate. However, phosphatidylglycerol purified from the surfactant fraction contained equivalent relative amounts of the acetate and palmitate labels in 3-day-old and adult rabbits. These results suggest that the type II pneumocyte may use acetate preferentially for the synthesis of palmitic acid which then is incorporated into surfactant phospholipids.

Acetates↗
PubMed1980

Surfactant metabolism of newborn lamb lungs studied in vivo.

Surfactant, microsomal, and lamellar body fractions were isolated from the lungs of 5-day-old lambs 0.21-55 h after the intravenous injection of radiolabeled palmitic acid. The specific activities as cpm/mumol phospholipid phosphate of phosphatidylcholine, saturated phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine were measured. The palmitate-labeled phospholipids disappeared from the lung parenchyma with a half-life of approximately 50 h. The radiolabel disappeared from phosphatidylcholine, saturated phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine of microsomal fractions with initial half-life values of 4.5, 4.6, 1.9, and 23.9 h, respectively. The labeled phospholipids rapidly appeared in the lamellar body fraction and accumulated in the surfactant of the lambs in a linear fashion for 35 h. The curves for the labeling of surfactant with radiolabeled saturated phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine were similar to the curve for phosphatidylcholine.

Animals↗
PubMed1980

The quantity of natural surfactant necessary to prevent the respiratory distress syndrome in premature lambs.

Premature lambs at 118 to 122 days of gestation were delivered by caesarean section and received before the first breath 0, 19, 53 or 64 mg natural surfactant total lipid (TL) per kg body weight (BW). The seven lambs receiving no surfactant died within 40.1 +/- 7.5 min, whereas the lambs treated with surfactant survived the 2-hr experimental period. Nineteen mg surfactant TL per kg BW preserved lung function; the pH and blood gas measurements were similar to those measured in lambs receiving 53 mg TL per kg BW or more surfactant. Pressure volume and surface tension characteristics were significantly improved after the administration of 19 mg of surfactant, but surface activity was still poor when compared to lambs receiving 53 mg TL per kg BW or more surfactant. The dose of surfactant (53 mg TL per kg BW) that resulted in good surface activity measurements in vitjro was similar to other estimates of the amount of surfactant necessary to cover the alveolar space.

Animals↗
PubMed1979

Characterization of double-stranded ribonucleic acid in tobacco leaves.

Double-stranded RNA was isolated from tobacco leaves and characterized in terms of base composition, density, and nuclease resistance. Although its role in the plant's physiology is not clear, evidence was adduced that it is the product of the RNA-dependent RNA polymerase previously shown to occur in this and other plants. The fact that twice as much fully than partially double-stranded RNA appears to be made favors a regulatory role for the double-stranded RNA rather than a transcriptional intermediate role.

Journal Article↗
PubMed1979

The labelling of pulmonary surfactant phosphatidylcholine in 19-31-days-old lambs.

The labelling of surfactant phosphatidylcholine and disaturated phosphatidylcholine was studied in 19-31-days-old lambs. Following the placement of small bore tracheal catheters, the animals were given radioactively labelled palmitic acid and/or choline by intravenous injection and multiple samples were recovered from the distal airways of each animal via a small catheter. The specific activities of the phosphatidylcholine and/or disaturated phosphatidylcholine were measured in these samples of surfactant. The labelled phospholipids accumulated in the samples of surfactant in a linear fashion; the mean time required to reach maximal specific activities in phosphatidylcholine and saturated phosphatidylcholine with either palmitic acid or choline as precursor was 28 h. Subsequently the specific activities of the labelled phospholipids from the surfactant samples decreased semi-logarithmically. The mean t1/2 for phosphatidylcholine and disaturated phosphatidylcholine labelled with radioactive palmitic acid was 35 h. The saturated phosphatidylcholine labelled with radioactive choline had a t1/2 of 251 h. The results demonstrate that surfactant labelling studies can be done by multiple sampling of single large animals.

Animals↗
PubMed1978

RNA-dependent RNA polymerase of tobacco plants.

Several properties of RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) active fractions obtained from tobacco plants, be they uninfected, infected with tobacco mosaic virus, or infected with tobacco necrosis virus, were compared. By the seven criteria tested, the RNA-dependent RNA polymerase from these three sources behaved the same, although its activity is greatly but variably stimulated by the two virus infections. It thus appears probable that these two viruses do not code for this enzyme, but rely for their replication on their ability to stimulate production of a host enzyme. The conclusion that cells contain RNA replicating capability represents a modification of the central dogma of molecular biology.

Journal Article↗
PubMed1978

Effects of tracheal instillation of natural surfactant in premature lambs. I. Clinical and autopsy findings.

Ten pairs of twin lambs 118--122 days of gestation were given either natural surfactant or diluent endotracheally before the first breath. By using the premature twin lamb model, we have been able to show that instillation of natural surfactant produced 100% survival for the duration of the study period (2 hr); stable blood gases on room air; lungs that became increasingly compliant while on the respirator; generally well aerated lungs at autopsy; good lung pressure-volume relationships; normal lung surface tension measurements; and histologic evidence of good alveolar expansion with large amounts of free intraluminal phospholipid, no epithelial damage, and no hyaline membranes. It is concluded that tracheal instillation of natural surfactant into the premature lamb protects the lungs from developing many features characteristic of the respiratory distress syndrome.

Animals↗