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J I Bruce

Publications and source records attributed to J I Bruce.

At least 19 recordsLinked to original sources
PubMed2001

Experimental assessment of lanthanide ion donor preference: spectroscopic and theoretical dissection of static charge and dynamic polarisation contributions to axial ligation in a C4-symmetric chiral europium complex.

Measurements of the equilibrium constants for ligand exchange (MeCN, 295 K) involving the axial donor in a C4-symmetric, mono-capped, square antiprismatic cationic Eu complex, supported by calculations based on an electrostatic perturbation model, have been interpreted in terms of a predominant ligand polarisation interaction defined by observation of the hypersensitive delta J = 2 normalised emission intensity, in association with measurements correlating delta J = 1 band splitting and 1H NMR dipolar shifts that vindicate Bleaney's theory of magnetic anisotropy.

Journal Article↗
PubMed2000

Pharmacological evaluation of the role of cytochrome P450 in intracellular calcium signalling in rat pancreatic acinar cells.

We have investigated whether the cytochrome P450 system is involved in Ca(2+) signalling in rat pancreatic acinar cells. Intracellular free [Ca(2+)] ([Ca(2+)](i)) was measured in collagenase-isolated cells using fura-2 microspectrofluorimetry and imaging. The imidazole P450 inhibitor ketoconazole (5 - 50 microM) inhibited [Ca(2+)](i) oscillations induced by cholecystokinin octapeptide (CCK). However, ketoconazole also raised baseline [Ca(2+)](i) when applied in the absence of CCK. These effects were mimicked by 5 - 50 microM SKF96365, an imidazole widely used as an inhibitor of Ca(2+) entry. The non-imidazole P450 inhibitor proadifen (SKF525A) inhibited CCK-induced [Ca(2+)](i) oscillations at a concentration of 10 - 50 microM. Proadifen alone caused intracellular Ca(2+) release at 25 or 50 microM, but not at 10 microM. Octadecynoic acid and 1-aminobenzotriazole, structurally-unrelated non-imidazole P450 inhibitors, did not alter baseline [Ca(2+)](i) or CCK-evoked oscillations. We compared cumulative CCK dose-response relationship in control cells and in cells where P450 had been induced by prior injection of animals with beta-naphthoflavone. Only minor differences were apparent, with induced cells showing some decrease in responsiveness at moderate and higher concentration of CCK (30 pM - 3 nM). Direct assessment of depletion-activated Ca(2+) entry showed no clear differences between control and induced cells. In conclusion, we could find no compelling evidence for a role of P450 in controlling Ca(2+) signalling generally, or Ca(2+) entry in particular, in pancreatic acinar cells. Induction of P450 is therefore probably toxic to acinar cells via a Ca(2+)-independent mechanism.

Animals↗
PubMed1999

Molecular and functional identification of a Ca2+ (polyvalent cation)-sensing receptor in rat pancreas.

The balance between the concentrations of free ionized Ca2+ and bicarbonate in pancreatic juice is of critical importance in preventing the formation of calcium carbonate stones. How the pancreas regulates the ionic composition and the level of Ca2+ saturation in an alkaline environment such as the pancreatic juice is not known. Because of the tight cause-effect relationship between Ca2+ concentration and lithogenicity, and because hypercalcemia is proposed as an etiologic factor for several pancreatic diseases, we have investigated whether pancreatic tissues express a Ca2+-sensing receptor (CaR) similar to that recently identified in parathyroid tissue. Using reverse transcriptase-polymerase chain reaction and immunofluorescence microscopy, we demonstrate the presence of a CaR-like molecule in rat pancreatic acinar cells, pancreatic ducts, and islets of Langerhans. Functional studies, in which intracellular free Ca2+ concentration was measured in isolated acinar cells and interlobular ducts, show that both cell types are responsive to the CaR agonist gadolinium (Gd3+) and to changes in extracellular Ca2+ concentration. We also assessed the effects of CaR stimulation on physiological HCO3- secretion from ducts by making measurements of intracellular pH. Luminal Gd3+ is a potent stimulus for HCO3- secretion, being equally as effective as raising intracellular cAMP with forskolin. These results suggest that the CaR in the exocrine pancreas monitors the Ca2+ concentration in the pancreatic juice, and might therefore be involved in regulating the level of Ca2+ in the lumen, both under basal conditions and during hormonal stimulation. The failure of this mechanism might lead to pancreatic stone formation and even to pancreatitis.

Animals↗
PubMed1997

Analysis of calcium oscillations in pancreatic acinar cells.

Since they were first reported in hepatocytes in 1986, agonist-evoked oscillations in intracellular free calcium ([Ca2+]i) have been described in numerous cell types, including pancreatic exocrine and endocrine cells. Pancreatic acinar cells show both 'sinusoidal' [Ca2+]i oscillations (when stimulated with muscarinic agonists) and so-called 'baseline [Ca2+]i spiking' (when stimulated with cholecystokinin, bombesin or analogues of either peptide). These agonist-evoked [Ca2+]i oscillations present novel problems to the investigator, particularly since they show considerable cell-to-cell variability. In this review, we discuss the various approaches available for analysing [Ca2+]i oscillations, particularly with respect to assessing whether drugs or other experimental interventions alter the oscillation pattern.

Animals↗
PubMed1995

Persistence of Schistosoma haematobium infection despite multiple courses of therapy with praziquantel.

A 7-year-old boy, who had returned to the United States in June 1991 after a 3-year stay in Malawi, was evaluated in October 1991 because of hematuria. He was excreting Schistosoma haematobium eggs and was treated with praziquantel (PZQ; approximately 40 mg/kg). He may have spit up < or = 30% of this dose, and a concomitant Giardia lamblia infection might have caused malabsorption of PZQ. Because of persistent excretion of viable eggs, he was retreated with PZQ in January and May 1992. Egg excretion was first quantified 2 months following his second course of PZQ; at that time it was 35 eggs per 10 mL of urine. He excreted viable eggs at least as late as October 1992, 5 months after his third PZQ course. Experimental administration of chemotherapy to hamsters infected with the S. haematobium strain demonstrated that it was susceptible to PZQ. Repeated courses of therapy with PZQ may be necessary to cure S. haematobium infection, and both parasite and host factors should be considered if infection persists.

Animals↗
PubMed1992

Efficacy of Niclosamide as a potential topical antipenetrant (TAP) against cercariae of Schistosoma mansoni in monkeys.

A 1% (W/V) formulation of Niclosamide (2', 5-Dichloro-4-nitrosalicylanilide) (TAP) was tested on Cebus apella monkeys as a topical prophylactic against schistosomiasis mansoni. Two experiments were conducted using the same formulation. In the first experiment, the TAP provided complete protection against schistosomiasis for 3 days. Of the 4 monkeys treated with TAP 7 days before exposure to Schistosoma mansoni cercariae, 2 were completely protected. The remaining 2 monkeys of the 7 day treatment group had a 78% or greater reduction in adult worm burdens when compared to the placebo treated monkeys. The second experiment was designed to determine the time between day 3 and 7 when the TAP no longer provided complete protection. However, all of the TAP treated monkeys in this experiment were completely protected, even the monkeys treated 7 days earlier. In both experiments, all monkeys used as infection controls and those receiving only the placebo became infected and showed typical experimental schistosomiasis. These results demonstrate that the TAP could provide fast acting, short-term protection to people who must enter cercariae infested water.

Administration, Topical↗
PubMed1991

Giardia lamblia: phospholipid analysis of human isolates.

Thin layer chromatograms for phospholipids obtained from 11 human Giardia lamblia isolates and their culture media have shown that phosphatidylcholine and sphingomyelin are the predominant phospholipid classes in all samples. A decrease in the relative percentage of the different classes, especially of phosphatidylcholine, was noticed in the medium after Giardia growth. Fatty acid analysis of the parasite phosphatidylcholine demonstrated that while oleate and palmitate were the major fatty acids in most isolates, arachidonate predominated in two of those studied. Some isolates contained small amounts of myristate, which was not present in the phosphatidylcholine of the culture medium. Moreover, stearate and linoleate predominated in phosphatidylcholine obtained from both media types. The saturated/unsaturated fatty acid ratio also varied for the different isolates. These results appear to suggest heterogeneity in the metabolic activity and utilization of lipid molecules between Giardia isolates.

Animals↗
PubMed1991

Efficacy of alternating therapy with oxamniquine and praziquantel to treat Schistosoma mansoni in children following failure of first treatment.

Two hundred children infected with Schistosoma mansoni were treated with either 20 mg/kg oxamniquine or 60 mg/kg praziquantel. Cure rates (about 85%) were similar as was the percentage reduction (80%) in egg counts in uncured children. Treatment with the alternative drug of children not cured with the first treatment resulted in negative stools in 11 of 12 cases examined one month after the second round of therapy. In order to minimize the risk of the development of drug resistance, our data suggest that infected patients be treated with one drug, and therapeutic failures with another. Evidence from experiments in mice with isolates obtained after failures of one treatment in children suggests that therapeutic failure does not necessarily indicate the presence of drug-resistant schistosomes. The value of using mice to assess drug resistance in schistosomes is questioned.

Adolescent↗
PubMed1990

Inhibition of in vitro RNA synthesis by hycanthone, oxamniquine and praziquantel.

The schistosomicides, hycanthone, oxamniquine and praziquantel, were found to inhibit the in vitro RNA synthesis using isolated hamster liver nuclei. Preincubation of the nuclei with these drugs revealed that the inhibitory effect of oxamniquine was irreversible and progressed with time, whereas that of hycanthone and praziquantel was reversible. On the other hand, hycanthone and praziquantel have a high affinity for DNA but oxamniquine does not. The data indicate that the mechanism of inhibition by oxamniquine is different from that of hycanthone and praziquantel.

Animals↗
PubMed1989

The molluscicidal activity of Phytolacca dodecandra. I. Location of the activating esterase.

A number of methods have been used to extract molluscicidal saponins from the dried berries of Phytolacca dodecandra. The potency of the extract has been determined to depend on the release of an enzyme found only in the seed and breaking the seed is critical to the extraction process. The enzyme is inactivated by heat of alcohol. The highest potency extract is made from a cold water extraction of finely ground dried berries.

Animals↗
PubMed1989

The detection of IgE by radio allergosorbent technique (R.A.S.T.) and ELISA in Egyptian cases of schistosomiasis.

Studies were carried out on the radioallergosorbent test (R.A.S.T.) in comparison with the Elisa for the diagnosis of schistosomiasis. Using sera from known S. mansoni, S. haematobium and both S. mansoni and S. haematobium cases, R.A.S.T. showed high sensitivity; 72%, 55% and 75% respectively, in the detection and quantification of specific IgE antibodies. While in case of ELISA only 20% of patients were positive. With control sera, both tests showed 100% negative. It is concluded that R.A.S.T. is more specific and superior than ELISA for IgE detection in schistosomiasis.

Animals↗
PubMed1989

New trends in the sero-diagnosis of schistosomiasis in Egypt.

A comparison has been made of a newly modified diffusion-in-gel enzyme-linked immunosorbent technique (DIG-ELISA) and an established, standardized ELISA, using sera as well as whole blood adsorbed on filter paper discs. With known human cases of S. mansoni and/or S. haematobium, both tests showed great sensitivity in the diagnosis of schistosomiasis; 93%-95% positive for ELISA and 92%-93% positive by DIG-ELISA on using egg antigens, while 92% positive for ELISA and 91% positive by DIG-ELISA when worm antigens were used. DIG-ELISA is characterised by its technical simplicity, high sensitivity which make it an excellent screening serological technique especially in endemic areas. Moreover, the use of whole blood on filter paper discs (paper disc DIG-ELISA), rather than serum from venipuncture should add more advantages for its field application.

Animals↗
PubMed1989

Conventional Giemsa-stained and C-banded chromosomes of seven strains of Schistosoma mansoni.

Karyotypes stained with conventional Giemsa and with a C-banding method were compared among 7 strains of Schistosoma mansoni: 2 from Puerto Rico and 1 each from St. Lucia, Brazil, Venezuela, Egypt, and Kenya. A few differences were noted in relative lengths and centromeric indexes, but overall karyotypes of all strains were similar, with 2n = 16. The W chromosome of the female of all strains had a relatively large heterochromatic block, distinguishing the female from the male karyotype.

Animals↗