Biomedical subjects

I R Doyle

Publications and source records attributed to I R Doyle.

28 records · Page 2Linked to original sources

PubMed1997

Surfactant proteins-A and -B are elevated in plasma of patients with acute respiratory failure.

Surfactant protein-A (SP-A) leaks into the circulation of patients with acute respiratory distress syndrome (ARDS) or acute cardiogenic pulmonary edema (APE) in a manner inversely related to lung function. Since surfactant protein-B (SP-B) is synthesized as a precursor considerably smaller than alveolar SP-A, we investigated whether it enters the circulation more readily. Reactivities consistent with SP-B proprotein (approximately 42 to approximately 45 kD) and the approximately 25 kD processing intermediate were detected in plasma. Plasma immunoreactive SP-B levels were significantly higher in ARDS (8,007+/-1,654 ng/ml [mean+/-SEM], n = 22) and APE (3,646+/-635 ng/ml, n = 10) patients compared with normal subjects (1,685+/-58 ng/ml, n = 33) and ventilated patients with no cardiorespiratory disease (1,829+/-184 ng/ml, n = 7). All groups had plasma SP-B/SP-A ratios approximately 6- to approximately 8-fold higher than in normal lavage or ARDS tracheal aspirate fluid, consistent with protein sieving. During admission, both plasma SP-B and the SP-B/SP-A ratio were inversely related to blood oxygenation (PaO2/FIO2) (p < 0.0001 and p < 0.025, n = 260 from 39 patients; Spearman) and static respiratory system compliance (deltaV/deltaP) (p < 0.0001 and p < 0.01, n = 168 from 25 patients). We describe in detail three patients and conclude that immunoreactive SP-B enters more readily than SP-A, is cleared acutely, and provides a better indicator of lung trauma.

Acute Disease↗

PubMed1996

Expression and distribution of surfactant proteins and lysozyme after prolonged hyperpnea.

We have induced prolonged hyperpnea in rats and examined the distribution of surfactant-associated proteins (SP-A and SP-B) and lysozyme in lamellar bodies (lb) and two alveolar fractions, one tubular myelin rich (alv-1) and the other tubular myelin poor (alv-2). We have also examined the expression of SP-A, SP-B, SP-C, and lysozyme mRNA in lung tissue and alveolar type II cells. Hyperpnea resulted in significant increases in lb SP-A, lysozyme, and phospholipid (PL) but no change in the protein-to-PH ratios, suggesting that lb stoichiometry is constant. The SP-A and SP-B-to-PL ratios were 33 and 18 times greater, respectively, in control alv-1 than in lb, suggesting that alv-1 is enriched with these proteins. In contrast, the lysozyme-to-PL ratio was similar in control alv-1 and lb. Hyperpnea did not alter the alv-1 SP-A or SP-B-to-PL ratios, suggesting some constant stoichiometry to their lipid association; however, the lysozyme-to-PL ratio was reduced. Whereas hyperpnea significantly elevated the PL, SP-A, and lysozyme levels in alv-2, the SP-B level was unchanged. We suggest that surfactant-associated lysozyme is secreted with lb, the majority of SP-A is linked to lipid secretion but not necessarily with lb, and the majority of SP-B secretion is independent of PL secretion. Hyperpnea did not alter the mRNA expression of SP-A, SP-B, SP-C, or lysozyme in alveolar type II cells, but expression of SP-A and SP-B mRNA was significantly increased in lung tissue.

Animals↗

PubMed1996

Differential changes in SP-A and disaturated phospholipids in the isolated perfused rat lung and in vivo.

Alveolar disaturated phospholipids (DSPA) increase in vivo in rats with hyperpnea and in isolated perfused lungs (IPL) in response to either salbutamol or increasing tidal volume (VT). Because surfactant protein-A (SP-A) may play a role in surfactant homeostasis, we have examined the relationship between SP-A and DSP in the alveolus lamellar bodies (LB-A), and in a vesicular (LB-B) lung subfraction. Whereas 2 h swimming increased total DSPA (approximately 48%), it had no effect on alveolar SP-A (SP-AA). In the IPL, salbutamol increased total DSPA (approximately 30%) and SP-AA (approximately 41%); increasing VT (2.5-fold) only increased DSPA (approximately 22%). SP-A and DSP also varied differentially in the tubular myelin-rich and -poor subfractions. In both the IPL and in vivo, we found inverse relationships between DSPA and SP-AA/DSPA, indicating that although SP-AA and DSPA are related, they vary independently. Whereas total SP-AA/DSPA varied between 0.046 and 0.074, it remained constant in LB-A (approximately 0.015) and LB-B (approximately 0.010), suggesting that DSP and SP-A are secreted differentially and that only a small portion of SP-AA is derived from lamellar bodies.

Animals↗

PubMed1995

Calcium oxalate crystal matrix extract: the most potent macromolecular inhibitor of crystal growth and aggregation yet tested in undiluted human urine in vitro.

Demineralization of calcium oxalate (CaOx) crystals precipitated from human urine in vitro yields an organic crystal matrix extract (CME) consisting predominantly of a single protein which we originally named crystal matrix protein but have subsequently shown to be a urinary form of prothrombin activation peptide fragment 1 (F1). The aim of this study was to determine whether CME is a promoter or inhibitor of CaOx crystallization. The effect of CME on CaOx crystal growth and aggregation was tested using a standard seeded crystallization system, and its effect quantified by use of particle size analysis and a computer model. In addition, the effect of CME on the crystallization of CaOx was tested in undiluted, ultrafiltered human urine using Coulter Counter analysis and scanning electron microscopy. It was shown that CME is a potent inhibitor of CaOx crystal growth and aggregation in a seeded metastable solution. However, of greater significance is that at a concentration of 10 mg/l it completely reversed the formation of large crystalline aggregates that form upon the removal of urinary macromolecules from undiluted urine. It was concluded that CME is the most potent macromolecular urinary inhibitor yet to be tested in urine in vitro. By preventing the aggregation of newly formed crystals, the components of CME may significantly reduce the probability of particle retention in vivo and therefore the occurrence of urolithiasis.

Calcium Oxalate↗

PubMed1995

Serum surfactant protein-A levels in patients with acute cardiogenic pulmonary edema and adult respiratory distress syndrome.

Detection of alveolo-capillary damage has important implications for treatment modalities in ventilated patients. Although surfactant protein-A (SP-A) is normally only found in appreciable amounts in the lung, we describe significantly elevated concentrations in the sera of patients with acute cardiogenic pulmonary edema (median, 250 ng/ml; range, 180 to 364; n = 10) and in those with the adult respiratory distress syndrome (ARDS) (median, 378 ng/ml; range, 215 to 1,378; n = 15) relative to healthy control subjects (median, 175 ng/ml; range, 123 to 248; n = 15) and ventilated patients with no cardiorespiratory disease (median, 169 ng/ml; range, 126 to 253; n = 6) (p < 0.01, in all cases). Serum SP-A was inversely related to blood oxygenation and to static respiratory system compliance both at the time of the patient's entry into the study (p < 0.005, rs = -0.51, n = 31; p < 0.001, rs = 0.82, n = 17; respectively) and during the course of admission (p < 0.001, rs = -0.34, n = 168; p < 0.001, rs = -0.50, n = 111; respectively). In addition, we describe in detail three cases of ARDS where lung function either improved, remained static, or deteriorated. We conclude that serum SP-A is an acute indicator of lung function and alveolo-capillary membrane injury.

Adult↗

PubMed1994

Composition of human pulmonary surfactant varies with exercise and level of fitness.

We have tested the hypothesis that the composition of alveolar surfactant varies with pattern of breathing and level of fitness. We examined three major components of surfactant, surfactant protein A (SP-A), disaturated phospholipids (DSP), and cholesterol (CHOL) in bronchoalveolar lavage (BAL) fluid from 12 healthy men before and after exercise. Fitness was assessed as work load/heart rate ([kpm.min-1]/[HR.HRmax-1]) achieved during cycling for 30 min at 90% theoretical maximal heart rate. Using a bronchoscope, four 20-ml vols of 0.15 M NaCl at 37 degrees C were instilled and then recovered from first a right upper and then a right lower lobe segmental bronchus. As we found no differences in the BAL from upper and lower lobes, the fluid was combined. We found a direct relationship between CHOL and DSP (rs = 0.84, p < 0.001), SP-A and CHOL (rs = 0.40, p < 0.025), and between SP-A and DSP (rs = 0.44, p < 0.025). The change in the ratios CHOL/DSP, SP-A/CHOL, and SP-A/DSP immediately after exercise was correlated with fitness (rs = -0.56, p < 0.025; rs = 0.75, p < 0.005; rs = 0.62, p < 0.025, respectively). We conclude that the composition of surfactant can change rapidly with exercise in a manner related to fitness, and we suggest that this is consistent with the existence of at least two pools of tissue surfactant of different composition supplying the alveolar compartment.

Adult↗

PubMed1994

Distribution of surfactant protein A in rat lung.

Although surfactant protein A (SP-A) is an integral component of alveolar surfactant, its relative abundance in lamellar bodies, regarded as the intracellular storage organelles for surfactant, remains contentious. We have previously shown that lamellar bodies, isolated from rat lung by upward flotation on a sucrose gradient, can be subfractionated into classic-appearing lamellar bodies (Lb-A) and a vesicular fraction (Lb-B), which we have speculated may be a second release form of surfactant. In the present study, we have used two-dimensional protein electrophoresis and immunochemical analysis to clarify the origin and the composition of these two subcellular fractions. In addition, we have examined the hypothesis that the secretion of SP-A and surfactant phospholipids occurs by independent pathways by examining the distribution of SP-A, total protein, and disaturated phospholipids (DSP) in the tubular myelin-rich (Alv-1) and tubular myelin-poor (Alv-2) fractions separated from lavaged material and in Lb-A and Lb-B isolated from both lung homogenate and purified alveolar type II cells. Our findings indicate that Lb-B is derived from type II cells, although they do not indicate whether it is a secretory form of surfactant, a reuptake vesicle, or a mixture of both. We found that the lung has a large tissue pool of immunoreactive SP-A. The %SP-A/DSP of total lamellar bodies isolated from type II cells was 0.96 +/- 0.1 (mean +/- SE), intermediate between that in Lb-A (1.67 +/- 0.13) and in Lb-B (0.65 +/- 0.04). In contrast, the %SP-A/DSP was 11.16 +/- 0.84 in whole lung homogenate and 13.14 +/- 1.71 in whole type II cells. In the alveolar compartment, the %SP-A/DSP was 17.38 +/- 3.40 in Alv-1, 6.34 +/- 0.31 in Alv-2, and 10.49 +/- 1.43 in macrophages, values an order of magnitude greater than found with the lamellar bodies. Our results indicate that only a relatively small portion of alveolar SP-A is derived from lamellar bodies, and we suggest that secretion of SP-A and DSP occurs via independent pathways.

Animals↗

PubMed1994

Urinary glycosaminoglycans are selectively included into calcium oxalate crystals precipitated from whole human urine.

Urinary glycosaminoglycans are selectively included into calcium oxalate (CaOx) crystals precipitated from whole human urine: The presence of glycosaminoglycans (GAGs) in the organic matrix of urinary stones, and their known effects on CaOx crystallization have prompted speculation regarding their role in CaOx urolithiasis. The aim of this study was to examine the involvement of GAGs in the early stages of CaOx crystallization in human urine. Urine samples were collected from healthy men and CaOx crystallization was induced by the addition of a sodium oxalate load. The crystals were harvested and demineralized, and the GAG content of the resulting extract analysed by cellulose acetate electrophoresis. Only one GAG, heparan sulphate (HS) was detected in the organic matrix of the crystals; chondroitin sulphate (ChS), the most abundant urinary GAG, was conspicuously absent. Further experiments, in which varying amounts of HS and ChS were added to ultrafiltered (10,000 Da) urine prior to induction of calcium oxalate crystallization, showed that ChS was included into the crystals only when HS was absent from the urine. It was concluded that the selective inclusion of GAGs into crystals and stones is a function related more to relative binding affinity than to ambient GAG concentration and that HS and ChS compete for specific binding sites on the crystal surface.

Adult↗

PubMed1993

Immunohistochemical distribution and quantification of crystal matrix protein.

The aim of this study was to determine the immunohistochemical distribution and quantification of crystal matrix protein (CMP). CMP, a 31 kDa glycoprotein, is the principal macromolecule found in calcium oxalate crystals generated in human urine, and is a potent inhibitor of crystal aggregation. A polyclonal rabbit anti-human CMP antibody was used to examine renal tissue by immunohistochemical techniques and light microscopy (N = 45). Twenty-five other human organs were similarly assessed. Quantification was performed using a visual analogue scale. CMP was visible as cytoplasmic staining in the epithelial cells of the TALH and the distal convoluted tubule including the macula densa in a subgroup of nephrons. CMP was not identified elsewhere in the urinary tract or in the extrarenal organs examined. Despite a trend indicating that the kidneys of normal men had more CMP than those of normal women, the difference failed to reach significance (P = 0.11). There was, however, more CMP in the stone formers group compared with either normal men (P < 0.01) or normal women (P < 0.01). This protein may be an important determinant of calcium oxalate kidney stone disease.

Aged↗

PubMed1991

Inclusion of proteins into calcium oxalate crystals precipitated from human urine: a highly selective phenomenon.

The abundance of protein in the matrix of calcium oxalate uroliths has fueled speculation regarding its role in stone genesis. In this study, we wanted to characterize the composition of the proteins associated with early stages of calcium oxalate crystallization in urine. Calcium oxalate crystallization was induced in urine from healthy men and women by the addition of an oxalate load. The crystals were harvested and demineralized, and the proteins remaining were separated and characterized by polyacrylamide gel electrophoresis and Western blotting. Most urinary proteins were not detected in the crystals or were present in only small quantities. The most abundant urinary macromolecule, Tamm-Horsfall glycoprotein, was notably absent from the crystal extracts. The predominant protein associated with the crystals, a previously unknown urinary constituent that we call crystal matrix protein (CMP; molecular mass, 30,000 Da), was more prevalent in the crystals derived from female urine. We conclude that most urinary proteins play no direct role in calcium oxalate crystal formation. However, the protein CMP exhibits a remarkable affinity for calcium oxalate crystals and may be important in stone pathogenesis.

Blotting, Western↗