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Biomedical subjects

A St John

Publications and source records attributed to A St John.

35 records · Page 2Linked to original sources
PubMed1992

Determinants of intact parathyroid hormone and free 1,25-dihydroxyvitamin D levels in mild and moderate renal failure.

Parameters of calcium and phosphate metabolism were measured in 27 patients with mild renal failure [glomerular filtration rate (GFR) 40-90 ml/min], 12 patients with moderate renal failure (GFR 20-39 ml/min) and in 12 healthy subjects. GFR was determined by technetium-99m diethylenetriamine penta-acetic acid clearance. Intact parathyroid hormone (PTH) was measured by a sensitive immunochemiluminometric assay and somatomedin-C was determined by radioimmunoassay. Both 1,25-dihydroxyvitamin D [1,25(OH)2D] and vitamin-D-binding protein were measured allowing calculation of the free 1,25(OH)2D index. By linear regression and multivariate analysis, PTH was negatively and independently correlated with GFR, plasma bicarbonate and 25-hydroxyvitamin D [25(OH)D] while free 1,25(OH)2D was positively correlated with GFR. Increased PTH secretion and reductions in 1,25(OH)2D were present in mild renal failure patients before any changes in plasma calcium, phosphate and bicarbonate were noted. Plasma alkaline phosphatase was significantly higher in mild chronic renal failure patients compared to normal subjects, possibly indicating early effects of the secondary hyperparathyroidism on the skeleton. Somatomedin-C did not correlate with the free 1,25(OH)2D index or a measure of 1,25(OH)2D production. It is concluded that the secondary hyperparathyroidism which occurs very early in the onset of chronic renal failure may be due to a reduction in the circulating concentration of 1,25(OH)2D consequent upon the renal failure. Low plasma bicarbonate and 25(OH)D also appear to be determinants of a raised PTH concentration. The compensatory increase in PTH presumably maintains extracellular calcium and phosphate levels constant but with possible deleterious effects on the skeleton.

Adult↗
PubMed1992

Painful ophthalmoplegia secondary to a mucocele involving the sella turcica, superior orbital fissure, and sphenoid sinus.

A case of painful ophthalmoplegia associated with an extensive lesion involving the sella turcica, superior orbital fissure, and sphenoid sinus in a 57-year-old man is reported. Even though nasal and ocular symptoms and signs represent the usual features of sphenoidal mucoceles, extension to the intracranial cavity as seen in this lesion is rare. Surgical exploration via a sublabial, transseptal approach revealed a mucocele of the sphenoid sinus. This case exhibited extensive and aggressive behavior simulating a malignant neoplasm.

Bone Diseases↗
PubMed1991

Acute effects of an oral calcium load in pregnancy and lactation: findings on renal calcium conservation and biochemical indices of bone turnover.

An oral calcium (Ca) tolerance test was used to compare the acute calcaemic, calciuric, parathyroid and bone turnover responses in 21 women at 36 weeks of pregnancy, 27 breast-feeding women studied 22 weeks postpartum and 27 control women. In all groups the oral Ca load increased plasma Ca and urinary calcium excretion (CaE), reduced intact PTH concentration (and consequently reduced renal phosphate and cyclic AMP excretion) and reduced hydroxyproline excretion (HypE, a biochemical index of bone resorption). There were no changes in the biochemical indices of bone formation, serum osteocalcin (elevated in the lactating group) and alkaline phosphatase, in any group. The pregnant women had the same fall in HypE and a greater calcaemic response than the controls. These results suggest that there is increased intestinal Ca absorption efficiency and a normal rate of bone resorption in late pregnancy. In contrast, the lactating women had a greater fall in HypE (from a baseline twice that of controls) and a significantly lower (p less than 0.001) rise in CaE, despite a calcaemic response similar to that of controls. Therefore, in lactation there is increased bone turnover and an increased capacity to reabsorb Ca in the renal tubule, compared to controls. An oral calcium supplement may benefit breast-feeding women, by reducing lactation-related elevated rate of bone resorption and consequent loss of trabecular bone.

Absorption↗
PubMed1990

A monoclonal antibody-purified soluble target cell antigen inhibits nonspecific cytotoxic cell activity.

We have previously reported the characterization of mAb derived against NC-37 target cells. mAb 18C2 and 1E7 inhibit fish cytotoxicity by binding to target cells and thus preventing the formation of conjugates with fish nonspecific cytotoxic cells (NCC). It was therefore presumed that these inhibitory mAb were specific for the target cell Ag necessary for effector cell recognition. mAb 1D4 and 7C6 bind to NC-37 cells but do not inhibit fish cytotoxic activity. We now report the isolation and purification of the Ag recognized by mAb 18C2 (inhibitor) and 1D4 (noninhibitor) by affinity chromatography of solubilized NC-37 target cell extracts. The 18C2-purified soluble target Ag (STAg) caused inhibition of cytotoxicity when preincubated with fish NCC. This inhibitory activity was reversible and dose-dependent ranging from 20 to 70% inhibition with 25 to 100 micrograms 18C2 purified STAg/10(6) NCC. STAg purified by 1D4 affinity chromatography had no effect on fish cytotoxicity. mAb 18C2 and 1E7 preabsorbed with 18C2 STAg lost their inhibitory activity when tested in the fish NCC cytotoxicity assay. Preabsorption of the same mAb with 1D4 STAg had no effect on their activity.

Acetylglucosamine↗
PubMed1988

Comparison of the performance and clinical utility of a carboxy-terminal assay and an intact assay for parathyroid hormone.

A comparison of the performance of a two-site immunochemiluminometric assay for intact parathyroid hormone with that of an in-house radioimmunoassay for carboxy terminal parathyroid hormone has been performed on samples from unselected patients being investigated for hypercalcaemia. The intact parathyroid hormone assay was found to be a simple and robust technique with a broad working assay range (CV less than 10% between 1.8-212 pmol/l) and a detection limit of 0.2 pmol/l. Clinically it is superior to the carboxy terminal assay in its ability to distinguish between patients with hyperparathyroidism from those with other causes of hypercalcaemia especially in the presence of impaired renal function.

Adult↗
PubMed1988

Characterization by monoclonal antibodies of a target cell antigen complex recognized by nonspecific cytotoxic cells.

Fish nonspecific cytotoxic cells (NCC)3 recognize and lyse a large variety of human and mouse transformed cells. In an effort to determine the Ag recognized by NCC on these targets, mAb were raised against NC-37 target cells. Four anti-NC-37 mAb were chosen for further characterization based on their effects on NCC lysis of target cells. Purified mAb 18C2 and 1E7 (IgM isotype) inhibited NCC killing of the following targets: U937, MOLT-4, K562, HL-60, DAUDI, NC-37, P815, and YAC-1. The dose-dependent inhibitory activity occurred at the target cell level and ranged from 50 to 70% at a concentration of 50 micrograms/well when compared to noninhibitory mAb 7C6 and 1D4 (IgG isotype). Similarly, mAb 18C2 protected the fish parasite Tetrahymena pyriformis from lysis by NCC when compared to mAb 7C6. Adsorption experiments demonstrated that the inhibitory effect on NC-37 lysis by NCC could be removed in a titratable fashion by incubation of mAb 1E7 with any one of the other target cell lines, but it could not be removed by incubation with effector cells. The inhibitory activity of mAb 1E7 and 18C2 was shown to be caused by the inhibition of conjugate formation between effector and NC-37 target cells. The relative membrane concentration of the antigenic determinants recognized by these mAb on the target cells was studied by flow cytometry using FITC-labeled mAb. These experiments showed that all four mAb bound to the surface of the cells tested. Biochemical analysis with Western blots and immunoprecipitation showed that mAb 18C2 and 1E7 recognize two Ag in NC-37 lysates: a larger protein of around 80 kDa and a smaller one of 42 kDa.

Animals↗
PubMed1988

Identification of a putative antigen receptor on fish nonspecific cytotoxic cells with monoclonal antibodies.

In the present study mAb were derived against flow cytometry (FCM) purified fish (Ictalurus punctatus) nonspecific cytotoxic cells (NCC). mAb 5C6.10.4 and 6D3.2.10 produced 60 to 65% inhibition of lysis of NC-37 target cells (a human B-lymphoblastoid cell line) by unfractionated NCC. mAb 2B2.4.9 and 6D3.4.4 were noninhibitors of cytotoxicity. All mAb were the same isotype (IgM) and were cloned by limiting dilution (2x). Inhibitory activity was specific for the effector cells because the mAb had no effect on NCC cytotoxicity when only the target cells were treated. Inhibition could be produced by preincubation of the mAb with NCC or by no preincubation, and inhibition was not reversible. Killing by FCM-sorted NCC of NC-37 target cells was inhibited almost 100% by mAb 5C6.10.4. Inhibitor mAb also significantly reduced NCC killing of MOLT-4, K562, P815, U937, Daudi, YAC-1, and HL-60 cells. Experiments also were conducted to determine at which stage of the lytic cycle the mAb acted. Both inhibitor mAb significantly inhibited conjugate formation between effector and NC-37 target cells. The technique of FCM was combined with competitive binding experiments to determine that the Ag recognized by both inhibitor and noninhibitor mAb was found on the membranes of the same cells. These results were confirmed by demonstrating (by using FCM) that FITC-labeled inhibitor and biotinylated noninhibitor mAb bound to the same cells. FCM also was next used to determine mAb binding to various effector cell populations. Inhibitor and noninhibitor mAb bound to approximately 25% (5C6.10.4) and 39% (6D3.4.4) of fish anterior kidney cells; to 42% (5C6.10.4) and 54% (6D3.4.4) of fish spleen cells; and to 2.5% (5C6.10.4 and 6D3.4.4) of fish peripheral blood. mAb were used to purify the target cell binding structure found on NCC. Con A-Sepharose purified mAb were used as the fixed ligand for Affi-Gel-10 affinity chromatography experiments. FCM-purified NCC were solubilized and the receptor was purified by using this technique. Analysis of the NCC-purified receptor by 12% SDS-PAGE indicated that the mAb purified structure may be composed of a dimeric molecule consisting of 41 kDa and 38 kDa proteins. The same dimer was purified by using either inhibitory (6D3.2.10) or noninhibitory (6D3.4.4) mAb. Similar results were obtained with immunoprecipitation experiments by using mAb 5C6.10.4. These studies demonstrate that the Ag-binding receptor structure on fish NCC may be comprised of a dimeric complex.

Animals↗
PubMed1988

Comparison of poly- and monoclonal antibodies as labels in a two-site immunochemiluminometric assay for intact parathyroid hormone.

We have evaluated the potential of monoclonal antibodies in the development of a non-isotopic immunometric assay for intact human parathyroid hormone (PTH). The assay has been designed to utilise a chemiluminescent acridinium ester labelled anti-aminoterminal (anti-N) antibody and a solid-phase anti-carboxyterminal antibody in order to measure specifically the intact hormone. In this system the characteristics of the labelled antibody proved crucial to the performance of the assay. A low affinity monoclonal reagent yielded insufficient analytical sensitivity, while a higher affinity monoclonal reagent cross-reacted poorly with the intact molecule relative to the amino terminal PTH fragment to which it was raised. Neither antibody could therefore match the performance of an affinity-purified polyclonal anti-N PTH reagent. These results highlight the problems to be addressed in the selection of suitable reagents for immunometric assay development when specificity and sensitivity are crucial requirements.

Animals↗
PubMed1982

Investigation into paediatric bilirubin analyses in Australia and New Zealand.

A small regional survey of direct spectrophotometric methods and a larger Australian and New Zealand survey of paediatric bilirubin analyses are described. The overall performance of both groups was unsatisfactory with an unacceptable high interlaboratory variation. This interlaboratory variation was reduced significantly by the use of a spectrophotometric method with a common standard of methyl orange. The Australian and New Zealand survey also examined the "state of the art" for the measurement of conjugated bilirubin and showed that laboratories could not adequately measure conjugated bilirubin.

Australia↗
PubMed1981

Lysosomes and proteolytic enzyme activities in cultured striated muscle cells.

Primary cell cultures prepared from chick embryonic skeletal muscle and the rat myogenic line L6 were examined morphologically and biochemically during several stages of development. The L6 cells were cultured to provide three morphologically distinct populations: prefusion, postfusion, and a subclone of cells that did not fuse even at high density. Ultrastructural studies revealed the characteristic morphology of healthy myoblasts. Acridine orange staining and cytochemical localization of acid phosphatase suggest the presence of presumptive lysosomal material. Enzymatic studies of lysosomal cathepsins B, D, H, and L revealed unusually high enzyme specific activities in these homogeneous myoblast populations. No activity was detected for the two nonlysosomal enzymes Ca2+-proteinase and serine proteinase. It is suggested that the lysosomal apparatus and its complement of enzymes play a significant role in the differentiation of muscle myotubes.

Animals↗
PubMed1979

An inter-laboratory survey of paediatric bilirubin analyses.

A regional quality control trial of paediatric bilirubin analyses is described. The overall performance of the group was unsatisfactory with an unacceptably high inter-laboratory variation. The use of a common standard produced improvement in performance but it is concluded that the poor performance was also due to methodological problems. This lack of agreement between laboratories is a major problem when patients are transferred between hospitals.

Adult↗
PubMedDate not supplied

Study of intact (1-84) parathyroid hormone secretion in patients undergoing parathyroidectomy.

Patterns of intact (1-84) parathyroid hormone (intact PTH) elimination and subsequent recovery of parathyroid function were studied in 12 patients undergoing parathyroidectomy. Nine patients had primary hyperparathyroidism (HPT), with single gland disease in 6 and multiple gland disease in 3. Two patients had subtotal parathyroidectomy for HPT secondary to chronic renal failure and 1 underwent excision of a hyperfunctioning parathyroid autograft. Using a sensitive 2-site immunochemiluminometric assay, serum intact PTH levels were measured preoperatively, intraoperatively, and postoperatively. A dual phase pattern of hormone clearance was found in 10 of the 12 patients, including the patient undergoing autograft excision. A monoexponential clearance pattern was seen in the remaining 2 patients, both of whom had subtotal parathyroidectomies for multiple gland disease. In the patients with primary HPT due to single gland disease, the early phase of intact PTH clearance had a half-life (T1/2) of 3.3 (+/- standard deviation 0.9) minutes and a late T1/2 of 96.4 (+/- standard deviation 92.7) minutes. Calculation of decay curves and half-lives for the patients undergoing subtotal parathyroidectomy was more difficult because of the inherent uncertainty in determining time zero. Nevertheless, in all but 2 patients, the clearance pattern was biexponential and the T1/2 measurements were very similar to those encountered in patients with single-gland disease. In the 2 patients with monoexponential clearance, the T1/2 figures were 86.7 minutes and 26.7 minutes, respectively. In the patients undergoing parathyroidectomy for primary HPT, levels of intact PTH were lowest at 1-3 hours after surgery, recovering to normal in the majority of patients by 18-40 hours.

Half-Life↗
PubMedDate not supplied

Serum ionized calcium, serum and intracellular phosphate, and serum parathormone concentrations in acute malaria.

Previous studies have shown depressed serum corrected calcium and phosphate concentrations in acute falciparum malaria. To characterize malaria-associated disturbances in mineral homoeostasis further, serum ionized calcium and intracellular phosphate were measured in 18 patients (10 with falciparum malaria, 8 with vivax malaria) and 10 healthy controls. Six patients (4 falciparum, 2 vivax) had admission serum ionized calcium concentrations below the absolute control range (< 1.15 mmol/litre) and a further six (3 falciparum, 3 vivax) developed ionized hypocalcaemia during treatment. The patients with falciparum malaria had the lowest values at presentation (median [95% confidence intervals in brackets]: 1.17 [1.12-1.23] vs. 1.20 [1.18-1.24] mmol/litre in controls, P = 0.035) in the presence of depressed simultaneous serum parathormone concentrations (1.2 [0.6-1.9] vs. 1.6 [1.1-2.6] pmol/litre; P = 0.05). Admission serum phosphate concentrations were lower in the malaria patients (P = 0.007 vs. controls), especially in those with falciparum malaria (0.85 [0.7-1.1] vs. 1.2 [1.1-1.3] mmol/litre in controls; P = 0.002); patients with falciparum malaria also had significantly lower intracellular phosphate than controls (0.74 [0.58-0.90] vs. 0.88 [0.66-1.04] mmol/litre red cells; P = 0.047). There was a weak association between serum corrected and ionized calcium in the malaria patients (rs = 0.31, n = 18, P > 0.1), but serum and intracellular phosphate correlated significantly (rs = 0.71, n = 17, P < 0.001) with a regression line slope of 0.49 and intercept of 0.27 mmol/litre of red cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMedDate not supplied

Connectivity: the key to point-of-care testing.

For the point-of-care testing market to grow successfully the advances in whole blood sensing technology must be accompanied by improvements in information technology to link the analytical devices to data management systems. A common connectivity standard for all instruments is being developed to replace the myriad of proprietary and incompatible solutions that currently exist.

Point-of-Care Systems↗