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M J Hutchings

Publications and source records attributed to M J Hutchings.

8 recordsLinked to original sources
PubMed1997

A review of the effects of bromate on aquatic organisms and toxicity of bromate to oyster (Crassostrea gigas) embryos.

A critical literature review has been undertaken of the effects that bromate (BrO3-) has on aquatic organisms. Chronic (multigeneration) studies using four marine phytoplankton species indicate a stimulation of cell division at concentrations up to 13.6 mg BrO3- liter-1, such that the EC50 is > 13.6 mg BrO3- liter-1 (exposure period unspecified). No published data were available for any freshwater algal or phytoplankton species. For freshwater invertebrates, the available data are limited to acute studies using two species: the water flea, Daphnia magna, with a 48-h LC50 of 179 mg BrO3- liter-1; and the planarian ("flatworm"), Polycelis nigra, with a 48-h LC50 of 2258 mg BrO3- liter-1. For saltwater invertebrates, there is a greater variety in the spread of species sensitivity to bromate. For crustaceans, the lowest reported acute value is a 24-h LC50 of 176 mg BrO3- liter-1 for mysid shrimp. For molluscs, the published data are somewhat contradictory, with different workers reporting EC50 values to oyster embryo-larvae of either 0.05-0.1 or 30 mg BrO3- liter-1. Following repeated attempts to resolve these differences using the Pacific oyster (Crassostrea gigas) embryo development assay, a 24-h EC50 of 170 mg BrO3- liter-1 was observed. Reported 96-h LC50 values for juvenile saltwater fish range from 427 to 512 mg BrO3- liter-1, while a 10-day LC50 of 279 mg BrO3- liter-1 is also reported. For fish early lifestages, newly hatched larvae are more sensitive than embryo hatching, with a larval 96-h LC50 of 31 mg BrO3- liter-1 being observed. Less severe effects have been reported for older larvae (pro-larvae), for which a 96-h LC50 of 404 mg BrO3- liter-1 is reported. In conclusion, a number of studies provide evidence for the acute toxicity of bromate to invertebrates and fish in the lowest region of 30 mg BrO3- liter-1. Applying the factor of 10 used to extrapolate from acute to potential chronic toxicity, the available data suggest that to protect aquatic organisms from long-term adverse effects, concentrations should not exceed approximately 3.0 mg BrO3- liter-1.

Animals↗
PubMed1994

Harmonic generation in "non-linear" biological systems.

We describe a high performance, low frequency Fourier Transform based spectrum analyser, with design features particularly suited to the harmonic analysis of the non-linear amplitude transfer functions of various biological systems. A previous published method, using general purpose systems to produce reference and signal plus reference "power" spectra, was susceptible to ambiguous interpretation of results. Unlike that design, the present spectrometer derives quantitative complex voltage (amplitude and phase) harmonics of sampled voltage data, maintaining potentially important information. Based on the use of a basic IBM or compatible PC, it features high sensitivity, high speed data processing and large dynamic range, is compact, easy to use, flexible in operation and low in cost. Its precision current signal source eliminates harmonics generated at the drive electrodes from the measurement. Use of the instrument leads us to conclude that, contrary to previous assertions, no repeatable dielectric or conductive non-linearity is exhibited in the bulk cell suspensions tested under the field and frequency conditions reported.

Electric Impedance↗
PubMed1994

Harmonic 'signatures' of microorganisms.

The frequency/amplitude effect of various microorganisms exposed to periodic (time varying) electric fields, when proximate to immersed electrodes, has been studied using a novel analytical instrument. The harmonic distribution, in complex signals caused by cells exposed to harmonic free waveforms and occupying part of the electrode/suspension interface volume, was shown to be almost entirely due to the change in the standing interfacial transfer function by the (dielectrically nonlinear) presence of cells. Thus, the characteristic interfacial non-linearity is viewed as variable, being uniquely modulated by the presence of particular cells in the interfacial region. Little can be attributed to bulk (far field) effects. The tendency for subtle (characteristic) signal distortion to occur as a function of particulate (cell or molecular) occupancy of the near electrode interfacial region under controlled current conditions leads to the method of sample characterisation by harmonic (Fourier) analysis. We report here, as a sequel to our original studies (Hutchings et al., 1993; Hutchings and Blake-Coleman, 1993), preliminary results of the harmonic analysis of microbial suspensions under controlled signal conditions using a three-electrode configuration. These data provide three-dimensional graphical representations producing harmonic 'surfaces' for various microorganisms. Thus, cell type differences are characterised by their 'harmonic signature'. The visual distinction provided by these 'surface' forming three-dimensional plots is striking and gives a convincing impression of the ability to identify and enumerate specific microorganisms by acquisition of cell-modulated electrode interfacial Fourier spectra.

Candida↗
PubMed1987

Pharmacokinetics and metabolism of salbutamol in premature labour.

1 The pharmacokinetics of salbutamol and its sulphate conjugate were examined during intravenous and steady-state oral administration in nine patients receiving the drug for the prevention or treatment of premature labour. 2 Uterine contractions were inhibited by plasma salbutamol concentrations in the range 8-33 ng ml-1 in six of the seven patients who were receiving intravenous drug. 3 By comparison with our previous study in a control group of healthy males and nonpregnant females, the total clearance of salbutamol in premature labour (501; s.d. 185 ml min-1) was similar to that in the control group (480; s.d. 123 ml min-1). Renal salbutamol clearance (208; s.d. 51 ml min-1), however, was significantly less than that in the control group (283; s.d. 51 ml min-1). 4 The systemic availability (n = 3), urinary recovery of unchanged oral salbutamol and area under the plasma curve during the oral dosage interval (n = 5) were all only slightly lower (10-20%) than control values, suggesting slightly lower oral absorption. 5 Formation and elimination of the sulphate conjugate were similar to those observed in control subjects suggesting that first-pass sulphation in the gut wall is unchanged in pregnancy. Overall there were only minor differences in salbutamol pharmacokinetics between control subjects and patients in premature labour.

Administration, Oral↗