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Biomedical subjects

M F Ryan

Publications and source records attributed to M F Ryan.

At least 19 recordsLinked to original sources
PubMed1994

Characterisation of proteolytic activity of excretory-secretory products from adult Strongylus vulgaris.

An excretory-secretory (ES) preparation derived from adult Strongylus vulgaris in vitro was assessed for proteolytic activity using azocasein and synthetic, fluorogenic, peptide substrates. Fractionation was by molecular sieve fast protein liquid chromatography (molecular sieve FPLC) and resolution by gelatin-substrate sodium dodecyl sulphate-polyacrylamide gel electrophoresis (gelatin-substrate SDS-PAGE). The cysteine proteinase activator, dithiothreitol (DTT), enhanced azocaseinolysis and hydrolysis of carbobenzoxy-phenylalanyl-arginine-7-amido-4-methylcoumarin (Z-Phe-Arg-NMec) by the ES preparation and was a requirement for the detection of carbobenzoxy-arginyl-arginine-7-amido-4-methylcoumarin (Z-Arg-Arg-NMec) hydrolysis. Assays of FPLC-eluted fractions, with DTT, detected a broad peak of azocaseinolytic activity (22-24 kDa) and two peaks (24 and 18 kDa) of hydrolysis using the synthetic substrates. Hydrolysis by these peaks of Z-Phe-Arg-NMec was 50-fold greater than that of Z-Arg-Arg-NMec suggesting that their specificities are more like papain or cathepsin L rather than cathepsin B. In gelatin-substrate SDS-PAGE, DTT was required to detect proteolysis by the ES preparation which was optimal at pH 6.0 and resolved into eight bands (87-29 kDa). Cysteine proteinase inhibitors were the most effective in all assays. Collectively, these data indicate that cysteine-class proteolytic activity predominates in the ES preparation of adult S. vulgaris.

Animals↗
PubMed1993

Haemopoietic regrowth after chemotherapy for acute leukaemia: an immunohistochemical study of bone marrow trephine biopsy specimens.

AIM: To analyse haemopoietic regrowth and residual disease in bone marrow trephine biopsy specimens after treatment for acute leukaemia, using immunohistochemical staining. METHODS: Biopsy specimens before and after treatment were studied from patients diagnosed as having acute myeloid or lymphoblastic leukaemia. Specimens after treatment encompassed periods from two to 56 weeks from the start of treatment. Routine haematoxylin and eosin and Giemsa stained sections were evaluated in association with immunostained preparations. A panel of antibodies was used, which reacts with epitopes showing restricted expression dependent on the lineage or maturation stage of cells. Results were evaluated in the light of clinical, peripheral blood, and marrow aspirate findings. RESULTS: The speed and sequence of regrowth of haemopoietic cells were more variable than expected. Immunostaining highlighted features of dysplasia after treatment and in some cases assisted detection of residual or relapsed leukaemia. Peripheral blood and aspirate cell counts reflected accurately the amount of regrowth, but not the dysplasia, seen in biopsy samples. Delayed regrowth was associated with complex individual factors. CONCLUSIONS: Morphological and immunohistochemical study of trephine biopsy specimens from patients treated for acute leukaemia provides information complementary to that obtained from peripheral blood and aspirated marrow. Variation in the timing and sequence of regrowth is highlighted. Immunostaining can aid in the detection of relapse or minimal residual leukaemia. The clinical relevance of dysplastic changes in biopsy specimens after treatment is uncertain, but such changes may persist for long periods.

Acute Disease↗
PubMed1992

Clinical evaluation of a rapid parathyroid hormone assay.

Modifications to the incubation conditions of radioimmunoradiometric assay for whole molecule parathyroid hormone (PTH) permit accurate quantification of the hormone in the peripheral circulation within 1 h of sampling. We assessed the assay intraoperatively in 75 patients undergoing parathyroidectomy. Serum PTH concentration declined to less than 20% of its pre-operative value within 20 min of the successful completion of surgery provided that renal function was normal. In patients with chronic renal failure the rate of decline in serum PTH concentration after parathyroidectomy was slower in some cases. In four cases of unsuccessful parathyroidectomy, serum PTH concentration remained above 60% of its preoperative value. Intraoperative monitoring during parathyroidectomy using this rapid PTH assay offers considerable advantages to the surgeon over frozen section.

Adult↗
PubMed1991

The role of magnesium in clinical biochemistry: an overview.

Magnesium is the second most abundant intracellular cation. It is essential for a wide variety of metabolically important reactions, in particular those involving ATP. Hypomagnesaemia is surprisingly common in hospital populations but is sometimes either undetected or overlooked. Serum magnesium concentrations provide a guide to magnesium status but while hypomagnesaemia is a reliable indicator of magnesium deficiency, normomagnesaemia does not exclude magnesium depletion. A wide variety of conditions predispose to magnesium depletion. Clinical magnesium deficiency has potentially fatal consequences in vulnerable groups of patients and should be excluded in all such cases. Magnesium deficiency may result in hypokalaemia, hypocalcaemia or other disturbances of electrolyte homeostasis, refractory cardiac arrhythmias, or increased sensitivity to digoxin. The capacity to measure serum and urine magnesium concentrations rapidly, regularly and reliably should be part of the repertoire of all clinical chemistry laboratories involved in the care of critically ill patients.

Homeostasis↗
PubMed1990

Modification to a commercial immunoradiometric assay permitting intraoperative monitoring of parathyroid hormone levels.

We describe a modification to a commercially available immunoradiometric assay which reduces the turnaround time for parathyroid hormone (PTH) measurement to 1 h and permits intraoperative monitoring during parathyroidectomy. Alterations in PTH concentrations following removal of parathyroid tissue are compared with those of calcium, ionised calcium and phosphate. PTH measurements obtained intraoperatively permit definitive conclusions about the success of the operation within 1 h of sampling, allowing re-exploitation of the gland to take place immediately if necessary.

Calcium↗
PubMed1989

Serum hypomagnesaemia in an elderly day-hospital population.

Serum magnesium concentration was measured in 223 elderly patients attending a day-hospital. Patients with medical conditions or receiving medication (other than digoxin/diuretics) which could affect magnesium levels were strictly excluded from the study. All patients were living in the community and were medically stable. Ninety-five patients were on no therapy whilst 107 were on diuretic therapy. In spite of strict exclusion criteria, 10.3% of patients on no therapy had serum magnesium levels below normal. There were 61 patients receiving a combination of frusemide and amiloride and 11.9% of these patients had below normal levels of serum magnesium. We conclude that there is a significant prevalence of unexpected hypomagnesaemia among Dublin inner city day hospital elderly patients. Significant serum hypomagnesaemia may still occur in patients on potassium/magnesium sparing diuretics.

Aged↗
PubMed1984

Effects of diuretics on the renal handling of magnesium.

Diuretic-induced magnesium losses may contribute significantly to magnesium deficiency. Loop diuretics especially cause major losses of urinary magnesium. Our initial experiments in saline-loaded rats indicated that frusemide greatly increased magnesium excretion, while bendrofluazide caused no significant change and triamterene actually decreased magnesium excretion. Therefore, not all diuretics are magnesium-wasting. There is evidence that the potassium-sparing diuretic amiloride may also exert magnesium-sparing properties. In saline-loaded rats, the magnesium-sparing effect of amiloride was demonstrated when the drug was administered either alone or in combination with frusemide. Renal clearance studies in rats indicated that the magnesium-sparing effect of amiloride was a direct renal action and not secondary to possible extrarenal actions. A dose-response relationship has been established for the effect of amiloride in reducing fractional excretion of magnesium and potassium during frusemide diuresis in rats. Congestive heart failure patients being treated with frusemide were found to be both potassium- and magnesium-deficient, as indicated by reduced lymphocyte concentrations of potassium and magnesium. In these patients, amiloride reduced urinary magnesium and potassium, increased plasma magnesium and potassium, and also increased lymphocyte magnesium and potassium. The effects of amiloride most likely involve enhanced reabsorption of magnesium, but further studies are required to establish the precise mechanism(s) involved in the drug's magnesium-sparing properties.

Amiloride↗
PubMed1981

The effect of diuretics on lymphocyte magnesium and potassium.

Lymphocytes have advantages over other tissues, such as erythrocytes and muscle, for assessing intracellular magnesium and potassium. During experimental magnesium deficiency in rats, the magnitude of the magnesium loss from lymphocytes was similar to that of cardiac and skeletal muscle. During experimental potassium deficiency, cardiac muscle retained potassium more effectively than skeletal muscle. The magnitude of the potassium loss from lymphocytes was of similar magnitude to that of cardiac muscle. Chronic congestive heart failure patients being treated with the loop-blocking diuretic, furosemide, were found to have significantly reduced lymphocyte magnesium (p less than 0.05) and potassium (p less than 0.01) compared to values obtained in 20 control subjects. The effects of acute administration of the potassium-sparing diuretic, amiloride, were investigated in 10 congestive heart failure patients. Each patient was studied over a 6-day period comprising a 3-day control period involving furosemide administration, followed immediately by a 3-day test period when amiloride (10 mg twice daily) was added to the therapeutic regimen. Amiloride reduced urinary potassium and magnesium, and increased both plasma and lymphocyte potassium and magnesium. Under these conditions, amiloride exerted magnesium-sparing actions in addition to its well-established potassium-sparing actions. The magnesium-sparing actions may be beneficial in that many experimental studies have shown that magnesium is required for maintenance and restoration of cell potassium.

Aged↗
PubMed1970

Flour beetles: responses to extracts of their own pupae.

Two species of flour beetles, Tribolium confusum and Tribolium castaneum, respond to neutral pith disks impregnated with aqueous extracts of their pupae in such a way that the adults and larvae tend to select the extract of the other species. These findings have implications for the population ecology of Tribolium.

Aggression↗