Biosensors for environmental monitoring

Increasing environmental legislation which controls the release and the levels of certain chemicals in the environment has created a need for reliable monitoring of these substances in air, soil and especially water. Conventional analytical techniques, although highly precise, suffer from the disadvantages of high cost, the need for trained personnel and the fact that they are mostly laboratory bound. Biosensors because of their specificity, fast response times, low cost, portability, ease of use and a continuous real time signal, can present distinct advantages in certain cases. Their biological base makes them ideal for toxicological measurements which are suited for health and safety applications. Over the last 3-4 years there has been an increase in the number of publications concerning biosensors for environmental monitoring, especially in the field of pesticide measurements.This paper reviews some of the more important developments over the past 3-4 years.     

Cell-specific differences in membrane beta-glucosidase from normal and Gaucher cells.

Two isozymes of membrane-bound beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) with activity towards 4-methylumbelliferyl-beta-D-glucopyranoside have been identified in human cells. One of these isozymes was found to have a pH optimum of 5.0, a Km of 0.4 mM and to be rapidly inactivated at pH 4.0 ("acid-labile"). The second isozyme had a pH optimum of 4.5, a Km of 0.8 mM and was stable at pH 4.0 ("acid-stable"). Cultured long-term lymphoid lines and peripheral blood leukocytes contained both isozymes while cultured skin fibroblasts contained only the "acid-stable" form in detectable amounts. The specific activity of the "acid-stable" isozyme was severely reduced in cultured skin fibroblasts, cultured long-term lines and peripheral leukocytes from patients with Gaucher's disease. The specific activity of the "acid-labile" enzyme in the latter two cell types was apparently unaffected. The beta-glucosidase activity in all three cell types examined was predominantly particulate but the enzyme could be solubilized with low concentrations of Triton X-100. The solubilized enzyme required sodium taurocholate (0.2%) for maximum activity. Solubilized beta-glucosidase did not exhibit the cell-specific differences in pH optimum and Km shown by the membrane-bound enzyme.     

Persistent atrial paralysis: Case report with light microscopy and ultrastructural analyses

Persistent atrial paralysis in a patient with complete heart block and mild mitral insufficiency is presented. Left atrial specimens obtained during implantation of a permanent cardiac pulse generator showed evidence of hypertrophy and fibrosis; subcellular degenerative changes ranged from near normal to irreversible, thus suggesting that atrial paralysis may be due to the replacement of normal atrial muscle with nonfunctional fibrous tissue.     

Structure of bovine beta-lactoglobulin at 6A resolution.

Bovine β-lactoglobulin is a dimer with a molecular weight of 2 × 18,400. In solution it undergoes a pH-dependent transition at pH 7.0 between two alternative structures, named N and R. The structures of four different crystal forms have been determined by multiple isomorphous replacement with heavy-atoms. Two of them, lattices K and X, were crystallised at pH 6.5, corresponding to the N state in solution; and the other two, lattices Y and Z, were crystallised at pH 7.5, corresponding to the R state in solution. The figures of merit of the phase angles determined for these lattices were 0.76, 0.77, 0.80 and 0.80, respectively. The four structures that emerged are similar and show certain features suggestive of α-helices and pleated sheets, but the resolution is insufficient to trace the entire course of the polypeptide chain. No clear distinction can yet be made between the structures above or below pH 7.0, nor between the native molecule and the molecule from which the C-terminal leucine and histidine residues have been cleaved. Analyses at higher resolution are in progress.     

Bioenergetics of the range caterpillar,Hemileuca oliviae (Ckll.)

Summary The energy budget of the New Mexico range caterpillar, Hemileuca oliviae (Ckll.), was estimated on caterpillars reared on an artificial diet under constant conditions. There was a 54% average age-specific decrease in assimilation efficiency in the larval stages. Net production efficiency was relatively constant at 52%. Of the 26.77 cal/mg produced by the feeding larvae, 0.53 cal/mg were expended by the pupae and 0.59 cal/mg were expended by the adults. Since maintenance costs of the non-feeding stages accounted for only four percent of the larval production, that production was adequate for adult development and reproduction.     

Abscisic acid binding to subcellular fractions from leaves of Vicia faba

A centrifugation binding assay has been used to demonstrate the binding of [³H] (±) abscisic acid to membrane-rich fractions prepared from leaves of Vicia faba L. Kinetic analysis of this binding shows evidence of saturation of binding sites with increasing concentration of ligand. Scatchard analysis of these data yields a biphasic plot possibly indicating the presence of two types of binding sites. The dissocation constant for the high affinity site has been calculated to be 3.5×10^-8 mol 1^-1.     

Effects of radiation,temperature and humidity on photosynthesis,transpiration and water use efficiency of oilseed rape (Brassica campestris L.)

The net photosynthetic rate (F), transpiration rate (Q) and water use efficiency (F/Q) of oilseed rape (Brassica campestris L. cv. Span) was studied under a range of atmospheric conditions by gas exchange techniques. The plants were at the full bloom/pod initiation stage of development at the time of measurement. The environmental conditions consisted of various levels of photosynthetically active radiation (100 to 2800 (μmol m^?2 s^?1 PAK: 400–700 nm), air temperature (10 to 42°C) and vapour pressure deficit (0.7 to 2.1 kPa VPD). The peak values ofF were recorded at 1600 μmol m^?2 s^?1 PAR, 20°C air temperature and 1.2 kPa VPD of air in the chamber. Q increased with increasing PAR, air temperature and VPD. However, theF/Q remained high and almost constant from 600 to 1600 μmol m^?2 s^?1 PAR, but declined at the low and high photon flux densities.F/Q decreased progressively with increase in air temperature and VPD of air in the chamber.