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Biomedical subjects

J E Pierce

Publications and source records attributed to J E Pierce.

At least 37 records · Page 2Linked to original sources
PubMed1982

Prevention of hyaline membrane disease in premature lambs by apneic oxygenation and extracorporeal carbon dioxide removal.

Hyaline membrane disease is found only in lungs where pulmonary ventilation has been established, i.e. after birth. We delivered eleven fetal lambs of a gestational age of 128-130 days but instead kept their lungs in total apnea and inflated to constant pressure, while removing all metabolically produced carbon dioxide with an extracorporeal membrane lung. Oxygen was provided by the membrane lung, and by apneic oxygenation through the natural lungs. Hence, arterial blood gases remained always normal, without any pulmonary ventilation. After 6-66 h the lungs had sufficiently cleared to allow normal mechanical pulmonary ventilation in 10 our of 11 lambs so treated. In a control group treated with mechanical ventilation alone, five of seven lambs died within the first 24 h of severe hyaline membrane disease.

Animals↗
PubMed1982

Regional myocardial blood flow in left ventricular hypertrophy. An experimental investigation in Newfoundland dogs with congenital subaortic stenosis.

To test the hypothesis that left ventricular hypertrophy (LVH) may predispose the subendocardium to ischemia, we studied regional myocardial blood flow in dogs with the fibrous ring form of subvalvular aortic stenosis and concentric LVH. Radioactive microspheres, 9 +/- 1 mu in diameter, were used. Eleven dogs with LVH (left ventricular body weight ratio of 6.35 +/- 0.46 gm/kg [mean +/- SEM] and peak left ventricular outflow gradient of 51 +/- 7 mm Hg) were compared to 12 normal dogs (left ventricular/body weight ratio of 3.41 +/- 0.12 gm/kg and peak left ventricular outflow gradient of 6 +/- 3 mm Hg). The two groups of dogs were subjected to comparable experimental interventions including (1) tachycardia produced by atrial pacing (221 +/- 4 beats/min), (2) ascending aortic constriction producing systolic hypertension (212 +/- 5 mm Hg), and (3) creation of an aortic-right atrial fistula lowering diastolic blood pressure (38 +/- 3 mm Hg). Basal regional myocardial blood flow was distributed similarly for LVH and normal dogs (endocardial/epicardial ratio = 0.90 +/- 0.05 and 0.94 +/- 0.03, respectively). During experimental interventions, regional blood flow remained equal to all myocardial layers in normal dogs; however, the endocardial/epicardial ratio diminished in LVH dogs during atrial tachycardia to 0.61 +/- 0.08, during systolic hypertension to 0.68 +/- 0.06, and during diastolic hypotension to 0.50 +/- 0.09. When the diastolic/systolic pressure time index ratio (DPTI/SPTI) was less than 0.8, subendocardial ischemia occurred in dogs with LVH (endocardial/epicardial ratio = 0.66 +/- 0.04) but not in normal dogs (endocardial/epicardial ratio = 0.92 +/- 0.03) (p less than 0.0001). Animals with infracoronary obstruction and LVH demonstrate greater susceptibility to development of subendocardial ischemia for identical hemodynamic interventions than do normal animals.

Animals↗
PubMed1981

Massive pulmonary infarction during total cardiopulmonary bypass in unanesthetized spontaneously breathing lambs.

We provided total cardiopulmonary support for 1-18 hours in unanesthetized tethered lambs by peripheral vascular cannulation, using a roller pump and the spiral membrane lung. Respirations were allowed to remain spontaneous and unaided. A Swan-Ganz catheter was placed for retrograde pulmonary artery blood flow sampling. Within a few minutes following induced ventricular fibrillation the PCO2 of sampled blood flowing retrograde through the lungs fell below 10 mm Hg, the PO2 rose to near 150 mm Hg, the pH rose to above 7.8, and the glucose level fell to less than 20 mg %. All of these values later gradually shifted, approaching mixed venous blood values within minutes. After 1-18 hrs of perfusion the animals went into shock and were sacrificed. At autopsy, the lungs of animals breathing room air were beefy and hemorrhagic. In lambs that were "breathing" CO2 enriched air the retrograde pulmonary artery blood pH and PCO2 was usually maintained close to the mixed venous blood values. The observed pulmonary changes were considerably less abnormal, and the microscopic abnormalities were at times nonexistent. We believe the integrity of pulmonary blood flow is vital to the survival of the lungs as a functioning organ. Cessation of total forward pulmonary blood flow (unlike partial cardiopulmonary bypass), combined with spontaneous pulmonary ventilation, rapidly leads to massive, pulmonary infarctions, shock, and death.

Alkalosis, Respiratory↗
PubMed1980

Hemoglobin switching in sheep: a comparison of the erythropoietin-induced switch to HbC and the fetal to adult hemoglobin switch.

Stimulation of sheep erythropoietic progenitor cells by erythropoietin (epo) has been studied with regard to its effect on the pattern of hemoglobin production. An analysis of hemoglobin (Hb) synthesis in BFU-E- and CFU-E-derived colonies from fetuses either homozygous for HbA (AA) (homozygous also for the beta c gene responsible for HbC production) or HbB (BB) (lacking the beta c gene) indicated the following. Colonies derived from precursor cells from 51- and 89-day fetuses exhibited small but detectable increments of HbB synthesis with prolonged incubation in vitro. This response was not dependent on the epo concentration. Erythropoietic precursor cells from a 124-day BB fetus were already committed to HbB synthesis, since HbF production was replaced by HbB on successive days in vitro as erythroid colonies matured; this switch was not affected by varying the epo concentration. In contrast, progenitor cells from a 124-day AA fetus responded to higher doses of epo by forming colonies in which more HbC was made at the expense of both HbF and HbA. Erythropoietic stress did not result in induction of HbF in vivo or in erythroid colonies derived from CFU-E in young adult BB sheep, whereas our prior studies had shown induction of HbC synthesis under analogous conditions in colonies derived from young adult AA sheep. We conclude that the epo-induced HbF (or HbA) to HbC switch and the fetal to adult hemoglobin switch are regulated by different mechanisms.

Animals↗
PubMed1978

Discrete subaortic stenosis in Newfoundland dogs: association of infective endocarditis.

Necropsy findings are described in eight Newfoundland dogs from the same colony with discrete subaortic stenosis. Infective endocarditis involving the aortic valve occurred in four dogs and in each it proved fatal. Damage to the aortic valve cusps by the jet of blood ejected through the discretely narrowed left ventricular outflow tract predisposes to the development of infective endocarditis in both dogs and human beings with discrete subaortic stenosis. Severe abnormality of the intramural coronary arteries in the ventricular septum, which also occurs in patients with hypertrophic cardiomyopathy, was present in all eight dogs. Myocardial fiber disorganization and asymmetric septal hypertrophy, two other findings observed in patients with hypertrophic cardiomyopathy, were absent in each of the eight Newfoundland dogs with discrete subaortic stenosis.

Animals↗
PubMed1978

Ultrastructure of the fibrous subaortic "ring" in dogs with discrete subaortic stenosis.

The subaortic fibrous "ring" in Newfoundland dogs with discrete subaortic stenosis is characterized by the presence of large, uni- and multinucleated, rounded connective tissue cells that resemble chondrocytes in several respects. Connective tissue adjacent to these cells is rich in acid mucopolysaccharides, small but cross-banded collagen fibrils, and small, poorly developed elastic fibers. The chondrocyte-like cells contain numerous cisternae of rough surfaced endoplasmic reticulum and prominent Golgi complexes, and they are surrounded by thick, concentrically arranged layers of basement membrane-like material. The differentiation of cellular and extracellular components of connective tissue in subaortic fibrous rings clearly differs in humans and in dogs with discrete subaortic stenosis.

Animals↗
PubMed1978

An alternative to breathing.

If carbon dioxide is removed by an extracorporeal membrane lung ventilated with room air, the natural lung can be used for oxygen transport alone; we have demonstrated this in lambs by maintaining lungs "inflated" with 100 percent oxygen at constant pressure and removing all carbon dioxide through the membrane lung. This process is a variant of "apneic oxygenation" without its disadvantages, because the arterial pH, PCO2, and PO2 all remain normal. No nitrogen washout is needed. These studies were carried out in five lambs anesthetized and paralyzed for 24 hours. For carbon dioxide removal, blood from the subclavin artery was pumped through an extracorporeal membrane lung and was returned into the external jugular vein. For oxygen delivery, the lungs were inflated through a tracheostomy tube with 100 percent oxygen to a pressure of 5 cm. H2O. There was no significant change in arterial blood PO2 after perfusion had begun or at the end of the perfusion 24 hours later. The arterial PCO2 remained steady, and there was no change in acid-base balance. The functional residual capacity (FRC) and static lung compliance remained unchanged. The total dead space was 10 to 15 ml. All animals recovered and survived in good health. At equilibrium, alveolar nitrogen partial pressure was always equal to the partial pressure of nitrogen in the ventilating gas of the membrane lung and was the sole determining factor in controlling alveolar oxygen concentration. Direct measurement of pulmonary gas showed alveolar gas at the level of the carina.

Animals↗
PubMed1978

Effects of repeated assessment on standardized test performance by infants.

Infant-intervention programs that evaluate their effectiveness by repeatedly testing infants with standardized tests may confound intervention effects with repeated-testing effects. Further, maternal participation in testing may increase infants' test scores, either directly by giving infants practice with test-like items at home between test administrations or indirectly by helping infants adapt to the test setting. Thirty-five infants were tested at 3-month intervals between 4 and 28 months of age with the Bayley Scales of Infant Development and at 31 months of age with the Stanford-Binet; 25 infants were tested with the Bayley at 4 months and the Stanford-Binet at 31 months. Mothers of some infants in each group participated in the testing process. Between-subjects analysis on the Stanford-Binet revealed no effects for repeated testing or maternal participation. Within-subjects analyses for repeatedly tested groups demonstrated that maternal presence during testing, but not repeated testing, was associated with significantly higher Bayley scores. It was concluded that maternal presence is a potent influence on Bayley performance, that repeated experience with the Bayley biased neither performance on another standardized test of development nor subsequent Bayley performance, and that infant intervention programs are not likely to confound their evaluation designs by testing infants repeatedly.

Age Factors↗
PubMed1977

Blood compatibility of methyl, methyl vinyl, methyl phenyl, and trifluoropropylmethylvinyl silicone rubber without silica fillers in the spiral-coiled membrane lung.

Spiral-coiled membrane lungs of 0.6 m2 surface area were fabricated from silicone rubber membranes coated with four types of commercially available pure-gum polysiloxane rubber: 1) polytrifluoropropylmethylvinylsiloxane, 2) polymethylphenylsiloxane, 3) polymethylvinylsiloxane, and 4) polydimethylsiloxane. Membranes lungs were tested in an arteriovenous shunt without added heparin after bypass was begun. All group 4 had major rise in resistance to blood flow or clotting in over 33% of the membrane lungs studied, after 6 hr of bypass. Membrane lungs with polydimethylsiloxane (group 4) had no rise in resistance to blood flow during 24 hr of bypass and had the least amount of changes in blood platelet count.

Animals↗
PubMed1977

Hemoglobin switching in sheep and goats: induction of hemoglobin C synthesis in cultures of sheep fetal erythroid cells.

Synthesis of HbF (alpha2gamma2) is replaced by synthesis of Hb A (alpha2betaA2) shortly before birth in sheep homozygous for the betaA globin chain whereas Hb C (alpha2betaC2) is produced transiently during the neonatal period. We have obtained a Hb F-to-Hb C switch by generating erythroid colonies at high erythropoietin concentration in plasma clot cultures of mid-gestation fetal bone marrow or liver. Furthermore, high erythropoietin concentration appeared specifically to activate the gene for betaC and not those for betaA or betaB globin in colonies grown from cells of an animal heterozygous for the betaA and betaB genes. Erythropoietic stress in the form of periodic bleeding or erythropoietin injection in utero did not stimulate production of Hb C (alpha2betaC2) in fetal sheep until shortly before birth, and then only in two of six animals. Thus, factors other than erythropoietin may influence the potential for betaC globin synthesis in vivo in fetal sheep.

Animals↗
PubMed1977

Control of breathing using an extracorporeal membrane lung.

Various amounts of carbon dioxide were removed through an extracorporeal membrane lung in spontaneously breathing lambs. The decrease in alveolar ventilation was proportional to the fraction of total carbon dioxide removed by the membrane lung. When extracorporeal CO2 removal approximated CO2 production (VCO2), alveolar ventilation almost ceased. Pulmonary ventilation can be controlled by extracorporeal carbon dioxide removal.

Animals↗
PubMed1976

Hemoglobin switching in sheep and goats. VI. Commitment of erythroid colony-forming cells to the synthesis of betaC globin.

Bone marrow from mature goats and sheep was cultured in plasma clots, and three erythropoietin (ESF)-dependent responses-growth (colony formation), differentiation (globin production), and initiation of hemoglobin C (alpha2beta2C) synthesis--were quantitated. ESF concentrations below 0.01 U/ml supported colony growth and adult hemoglobin production in cultures of goat marrow, while maximal hemoglobin C synthesis (70%), as measured between 72 and 96 h in culture, required a 100-fold higher ESF concentration. Sheep marrow was cultured in a medium enriched to enhance growth and to permit complete maturation of colonies. These colonies active in hemoglobin synthesis between 24 and 96 h produced mainly adult hemoglobin, and only between 96 and 120 h did sheep colonies develop which produced mainly hemoglobin C (up to 70%). A similar heterogeneity may exist among goat colonies. Thus, when goat bone marrow was fractionated by unit gravity sedimentation, more hemoglobin C synthesis was observed in colonies derived from cells of intermediate sedimentation velocity than in colonies derived from the most rapidly sedimenting cells. Brief exposure of sheep (in vivo) and goat (in vitro) bone marrow to a high ESF concentration committed precursor cells to the generation of colonies which, even at low ESF concentration, produced hemoglobin C. Committment to hemoglobin phenotype appears to be an early and probably irreversible event in the development of an erythroid cell.

Animals↗