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P F Ryan

Publications and source records attributed to P F Ryan.

At least 37 records · Page 2Linked to original sources
PubMed1992

Use of historical assessment for evaluation of process-based model projections of future environmental change: Lake acidification in the Adirondack mountains, New York, USA.

Because of the considerable uncertainties associated with modeling complex ecosystem processes, it is essential that every effort be made to test model performance prior to relying on model projections for assessment of future surface water chemical response to environmental perturbation. Unfortunately, long-term chemical data with which to validate model performance are seldom available. The authors present here an evaluation of historical acidification of lake waters in the northeastern United States, and compare historical changes in a set of lakes to hindcasts from the same watershed model (MAGIC) used to estimate future changes in response to acidic deposition. The historical analyses and comparisons with MAGIC model hindcasts and forecasts of acid-base response demonstrate that the acidic and low-ANC lakes in this region are responsive to strong acid inputs. However, the model estimates suggest lakewater chemistry is more responsive to atmospheric inputs of sulfur than do the estimates based on paleolimnological historical analyses. A 'weight-of-evidence approach' that incorporates all available sources of information regarding acid-base response provides a more reasonable estimate of future change than an approach based on model projections alone. The results of these analyses have important implications for predicting future surface water chemical change in response to acidic deposition, establishing critical loads of atmospheric pollutants, and other environmental assessment activities where natural variation often exceeds the trends under investigation (high noise-to-signal ratio). Under these conditions, it is particularly important to evaluate future model projections in light of historical trends data.

Journal Article↗
PubMed1992

Sensitivity to change for low-ANC eastern US lakes and streams and brook trout populations under alternative sulfate deposition scenarios.

A weight-of-evidence approach was used by the US National Acid Precipitation Assessment Program (NAPAP) to assess the sensitivity of chemistry and biology of lakes and streams to hypothesized changes in sulfate deposition over the next 50 years. The analyses focused on projected effects in response to differences in the magnitude and the timing of changes in sulfate deposition in the north-eastern United States, the Mid-Appalachian Highlands, and the Southern Blue Ridge Province. A number of tools was used to provide the weight of evidence that is required to have confidence in an assessment that has many uncertainties because of the complexity of the systems for which the projections of future conditions were made and because of limited historical data. The MAGIC model provided the projections of chemical changes in response to alternative deposition scenarios. Projected chemical conditions were input into biological models that evaluate effects on fish populations. The sensitivity of water chemistry and brook trout resources to the hypothesized changes in deposition was found to be greatest in the Adirondacks and Mid-Atlantic Highlands. Under the hypothesized sulfur deposition reduction scenarios, chemical conditions suitable for fish were projected to improve 20-30 years sooner than with the scenario that assumed no new legislated controls. Other lines of evidence, e.g. other models, field observations, and paleolimnological findings, were used to evaluate uncertainty in the projections. Model parameter/calibration uncertainty for the chemical models and population sampling uncertainty were explicitly quantified. Model structural uncertainties were bracketed using model comparisons, recent measured changes, and paleolimnological reconstructions of historical changes in lake chemistry.

Journal Article↗
PubMed1989

Calcific periarthritis.

Although the radiological detection of soft tissue calcification is common and of little clinical significance a number of distinctive rheumatological syndromes are associated with release of certain calcium salts from tendons into the surrounding soft tissues and joints (calcific periarthritis). Research has shown that calcium crystals, too, may be of importance in chronic degenerative joint disease.

Calcinosis↗
PubMed1988

Neuropsychiatric manifestations of systemic lupus erythematosus.

Forty-six episodes of major neuropsychiatric manifestations of systemic lupus erythematosus occurring in 35 patients over a ten-year period were reviewed. The frequency of central nervous system SLF was lower than that reported from overseas referral centres. Glucocorticosteroid treatment did not precipitate psychiatric problems in this group. Whilst neuropsychiatric recovery was the rule, such features indicated a subgroup of SLE with high short-term mortality.

Adolescent↗
PubMed1984

Red cell ferritin content: a re-evaluation of indices for iron deficiency in the anaemia of rheumatoid arthritis.

In iron deficiency anaemia basic red cell content of ferritin is appreciably reduced. This variable was determined in 62 patients with rheumatoid arthritis to evaluate conventional laboratory indices for iron deficiency in the anaemia of rheumatoid arthritis. For 23 patients with rheumatoid arthritis and normocytic anaemia irrespective of plasma ferritin concentration, red cell ferritin content did not differ significantly from that for non-anaemic patients with rheumatoid arthritis. For 27 patients with rheumatoid arthritis and microcytic anaemia, the mean red cell ferritin content for patients with a plasma ferritin concentration in the 13-110 micrograms/l range was appreciably reduced. It was indistinguishable from that for patients with rheumatoid arthritis and classical iron deficiency anaemia, indicated by plasma ferritin concentrations of less than 12 micrograms/l. In contrast, the mean red cell ferritin content for patients with rheumatoid arthritis, microcytic anaemia, and plasma ferritin concentrations above 110 micrograms/l did not differ from that for patients with rheumatoid arthritis and normocytic anaemia. Oral treatment with iron in patients with rheumatoid arthritis, microcytic anaemia, and appreciably reduced red cell ferritin concentrations was accompanied by significant increases in haemoglobin concentration (p less than 0.01), mean corpuscular volume (p less than 0.01), and red cell ferritin contents (p less than 0.05). This treatment, however, did not produce any appreciable change in haemoglobin concentration in patients with rheumatoid arthritis, normocytic anaemia, and normal red cell ferritin contents. These findings suggest that the indices for iron deficiency in patients with rheumatoid arthritis and anaemia should include peripheral blood microcytosis together with a plasma ferritin concentration of less than 110 micrograms/l.

Adolescent↗
PubMed1983

Post partum nephrotic syndrome in mixed essential cryoglobulinemia.

The clinical and histological findings of a patient with mixed essential cryoglobulinemia (MECG) who developed post partum renal failure and the nephrotic syndrome are described. The renal insufficiency responded dramatically to intensive plasma exchange and longer term immunosuppression with associated resolution of the renal histological changes. To our knowledge deterioration of renal function in the post partum period has not been previously described in the syndrome of MECG.

Adult↗
PubMed1982

Adult-onset Still's disease. Twenty-year followup and further studies of patients with active disease.

Eleven female patients with adult-onset Still's disease were followed for 7-36 years (mean 20.2 years) after the onset of their illness. Ten of these patients had a chronic course characterized by remissions and exacerbations of arthritis associated with fever and rash. Five patients had terminal interphalangeal involvement, and carpal ankylosis was demonstrated on x-ray film in 10. Two patients developed a widespread polyarthritis, and renal amyloidosis was diagnosed 10 years after disease onset in the most severely affected patient. In 4 patients studied during an exacerbation of the disease, circulating immune complexes were detected by the staphylococcal A binding assay, but not by the C1q binding assay. Synovial fluid analysis in 1 patient revealed a low C3 level and total hemolytic complement (CH50) together with immune complexes and IgG rheumatoid factor. Immune complexes were not identified in the characteristic Still's rash by immunofluorescence or electron microscopy, although mast cell degranulation, neutrophil lysis, and perivascular fibrin deposition were reminiscent of immune complex--mediated vascular injury. The clinical and laboratory features as well as the long-term course of adult- and juvenile-onset systemic Still's disease are similar, but further studies of genetic markers and immunopathology are required to establish a common pathophysiology.

Adult↗
PubMed1982

Kinetics of heat damaged autologous red blood cells. Mechanism of clearance from blood.

The kinetics of radiolabelled heat damaged red cell (HDRBC) distribution have been studied in humans using a gamma camera, and compared with the kinetics of other blood cells. Liver uptake of 111In labelled HDRBC was completed within about 10 min of injection; splenic uptake was biphasic with a half time of about 5 min over the first 20 min following injection, and a later half time much longer than this. Activity initially present in the lung fields cleared within 24 h. The rate constants of liver uptake of 99mTc labelled HDRBC and of 111In labelled platelets were very similar; the rate constants of splenic uptake of these 2 particles were also very similar up to about 20 min following injection when the splenic platelet levels became constant and the HDRBC level continued to slowly rise. Splenic uptake and blood clearance of red cells coated with IgG (IgG-RBC), in contrast to HDRBC, were monoexponential. It was concluded that: (1) the blood clearance of HDRBC was due to pooling within, and to irreversible extraction by, the spleen; (2) liver uptake of HDRBC, which was irreversible, was completed within 10 min of injection; (3) IgG-RBC clearance was due to irreversible extraction by the spleen; (4) HDRBC uptake in the lung was unrelated to reticuloendothelial function, and represented prolonged transit through the lung microvasculature.

Blood Platelets↗
PubMed1981

Analysis of heat-damaged erythrocyte clearance curves.

The rate of clearance from the blood of heat-damaged erythrocytes (HDE) is used routinely as a quantitative assessment of splenic function. The time taken for the value at 3 min to fall by 50% (t0.5)is usually taken as the index of function. The clearance of HDE is dependent on three processes: splenic blood flow, splenic HDE extraction ratio and intrasplenic transit time of "unextracted' HDE, returning to the circulation. Exponential analysis of the clearance curve can resolve these three functions. Simple methods of analysis, however, such as t0.5, which are applied directly to the curve, may be weighted in favour of any one of them. In this paper, a large number of clearance curves have been analysed and the components of splenic function resolved. The t0.5, the percentage fall in HDE between 8 and 28 min (C20), the rate constant at 8 min (K8) and the rate constant of the tail of the curve (alpha 2) have been correlated with these components. K8 showed a close correlation with splenic blood flow, and alpha 2 with the rate of HDE phagocytosis. In general, the correlation between the various components of splenic function was better with C20 than with t0.5. This is explained predominantly by the fact that the t0.5 includes liver clearance. The t0.5 should therefore be used with caution as an estimate of splenic function, which can be usefully assessed by applying alternative simple methods of analysis described.

Erythrocytes↗
PubMed1981

Measurement of splenic function in humans using heat damaged autologous red blood cells.

Functional hyposplenism, a clinical entity which has only recently been recognised, is usually assessed quantitatively by the rate of clearance of radiolabelled heat damaged erythrocytes (HDE) from the circulation. Based on recent observations on the kinetics of HDE, we have developed a 3 compartmental model of HDE distribution between the spleen and blood, and calculated, in a large series of clearance curves, splenic blood flow, HDE intrasplenic transit time and splenic HDE extraction ratio. Transit time (about 15 min) was of the same order as platelet transit time and extraction ratio (about 35%) was similar to that recorded in animals. Thr relationships between blood flow, transit time and extraction ratio provided evidence in support of 2 separate functional compartments, of which only one was engaged in phagocytosis, present within the spleen.

Erythrocytes↗
PubMed1980

Splenic function in non-renal systemic lupus erythematosus.

The reticuloendothelial clearance of autologous heat-damaged red blood cells was assessed in 10 patients with systemic lupus erythematosus (SLE) but without clinical nephritis. Although in nine patients the disease was clinically active at the time of the test, only one patient had a prolonged half-clearance time (T 1/2). One patient who had persistently high titers of circulating immune complexes, but whose disease was clinically inactive, had a normal T 1/2. There was no correlation between the patients' age, duration of disease, disease activity, therapy or titer of circulating immune complexes and the T 1/2. It appears that a general defect in splenic function is not a universal feature of SLE and that high titers of circulating immune complexes may be found in the presence of efficient reticuloendothelial phagocytic ability.

Adult↗