Medical School, Newcastle upon Tyne, NE2 4HH1 The ability of D-cycloserine to act as a substrate for H+/amino acid symport has been tested in epithelial layers of Caco-2 human intestinal cells. 2 In Na+-free media with the apical bathing media held at pH 6.0, D-cycloserine (20 mM) is an effective inhibitor of net transepithelial transport (Jnet) of L-alanine (100 pM) and its accumulation (across the apical membrane) in a similar manner to amino acid substrates (L-alanine, /3-alanine, L-proline and glycine). In contrast L-valine was ineffective as an inhibitor for H'/amino acid symport. Both inhibition of L-alanine Jne, and its accumulation by D-cycloserine were dose-dependent, maximal inhibition being achieved by 5-10 mM. 3 Both D-cycloserine and known substrates for H+/amino acid symport stimulated an inward short circuit current (ISC) when voltage-clamped monolayers of Caco-2 epithelia, mounted in Ussing chambers, were exposed to apical substrate in Na+-free media, with apical pH held at 6.0. The D-cycloserine dependent increase in ISC was dose-dependent with an apparent Km = 15.8 + 2.0 (mean + s.e.mean) mm, and Vma,, = 373 + 21 nmol cm-2 h-'. 4 D-Cycloserine (20 mM) induced a prompt acidification of Caco-2 cell cytosol when superfused at the apical surface in both Na+ and Na+-free conditions. Cytosolic acidification in response to D-cycloserine was dependent upon superfusate pH, being attenuated at pH 8 and enhanced in acidic media. 5 The increment in ISC with 20 mM D-cycloserine was non-additive with other amino acid substrates for H+/amino acid symport.

This paper summarises a research investigation carried out on behalf of the Environment Agency. The investigation was concerned with the adaptation of flow measurement structures, designed in accordance with British or International Standards, to aid the upstream migration of fish. It was intended to ensure that these adaptations do not significantly degrade the accuracy of the combined structure as a hydrometric device. The research provided specifications for adaptations to benefit fish migration without significantly affecting hydrometric performance. This paper focuses on the key findings from the research.

Six approximate methods of calculating the torsional stiffness of prismatic beams of isosceles triangular cross section are compared with the exact solution for the cross section in the form of a sector of a circle.

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