Electromyogram and force during stimulated fatigue tests of muscles in dominant and non-dominant hands

Mechanical and electrical properties were studied for the first dorsal interosseous muscle of the dominant (d-FDI) and non-dominant hand (nd-FDI). Observations were made before, during and after a fatigue test, fatigue being evoked by percutaneous electrical stimulation of the ulnar nerve. The test consisted of 30 Hz bursts of ten supramaximal 0.1 ms pulses, repeated once a second for 5 min. The measurements included the amplitude of the first and fifth compound muscle action potentials (M-waves) within bursts, the peak burst force and the amplitude and time course of single twitches. At the end of the fatigue test, burst force had decreased to about the same extent in the FDI of both hands. The final decline in first M-wave amplitude was, however, significantly more pronounced for the nd-FDI than for the d-FDI. There were no longer any significant discrepancies between the two muscles after a subsequent recovery-period of 15 min. Comparisons among nd-FDI of various individuals demonstrated the presence of significant inter-individual differences in fatigue-related force-drop without any associated differences in M-wave decline. Intra-individual variability was similar for fatigue-related force-drop and M-wave decline.     

A non-toxic method to combat incipient decay of CCA- and creosote-treated poles in soil-contact

A non-chemical means of preventing premature pole failure in soil-contact was investigated by applying open-ended cylindrical sleeves of heat-shrink polyethylene to the soil-contact surfaces of Eucalyptus grandis poles as physical barriers to fungal colonisation from soil in sub-tropical South Africa. The test site was managed under flood-irrigation to represent vineyard conditions. After exposure for 26 weeks all untreated unsleeved poles had failed, whereas sleeved poles were colonised by fungi but remained relatively sound. Unsleeved poles treated with 16 kg CCA m⁻³ were colonised by fungi at their soil-contact surfaces, whereas their sleeved counterparts were uncolonised. Unsleeved poles treated with 100 kg creosote m⁻³ were extensively covered by biofilm and showed incipient decay at their soil-contact surfaces, whereas their sleeved counterparts were uncolonised.     

The XcpR protein of Pseudomonas aeruginosa dimerizes via its N-terminus

Extracellular protein secretion by the main terminal branch of the general secretory pathway in Pseudomonas aeruginosa requires a secretion machinery comprising the products of at least 12 genes. One of the components of this machinery, the XcpR protein, belongs to a large family of related proteins distinguished by the presence of a highly conserved nucleotide binding domain (Walker box A). The XcpR protein is essential for the process of extracellular secretion and amino acid substitutions within the Walker A sequence result in inactive XcpR. The same mutations exert a dominant negative effect on protein secretion when expressed in wild-type bacteria. Transdominance of XcpR mutants suggests that this protein is involved in interactions with other components of the secretion machinery or that it functions as a multimer. In this study, the amino-terminal portion of the cI repressor protein of phage λ was used as a reporter of dimerization in Escherichia coli following fusion to full-length as well as a truncated form of XcpR. The cI–XcpR hybrid proteins were able to dimerize, as demonstrated by the immunity of bacteria expressing them to killing by λ phage. The full-length XcpR as well as several deletion mutants of XcpR were able to disrupt the dimerization of the chimeric cI–XcpR protein. The disruption of cI–XcpR dimers using the deletion mutants of XcpR, combined with the analysis of their dominant negative effects on protein secretion, was used to map the minimal dimerization domain of XcpR, which is located within an 85 amino acid region in its N-terminal domain. Taken together, the data presented in this paper suggest that the XcpR protein dimerizes via its N-terminus and that this dimerization is essential for extracellular protein secretion.     

Expression patterns of loricrin in various species and tissues

Abstract. In this study we analyzed the expression patterns of loricrin in various species and tissues using immunohistochemistry, immunoblotting and Northern blots. Loricrin is a glycine-, serine- and cysteine-rich protein expressed very late in epidermal differentiation in the granular layers of normal mouse and human epidermis. Later on in differentiation, loricrin becomes cross-linked as a major component into the cornified cell envelope by the formation of N^ɛ -(γ-glutamyl)lysine isopeptide bonds. This process either occurs directly or by the intermediate accumulation in L-keratohyaline granules of mouse epidermis and human acrosyringia. Loricrin was identified in all mammalian species analyzed by virtue of its highly conserved carboxy-terminal sequences revealing an electric mobility of ∼60 kDa in rodents, rabbit and cow and of ∼35 kDa in lamb and human on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Loricrin is expressed in the granular layer of all mammalian orthokeratinizing epithelia tested including oral, esophageal and fore-stomach mucosa of rodents, tracheal squamous metaplasia of vitamin A deficient hamster and estrogen induced squamous vaginal epithelium of ovary ectomized rats. Loricrin is also expressed in a few parakeratinizing epithelia such as BBN [N-butyl-N-(4–hydroxybutyl)nitrosamine]-induced murine bladder carcinoma and a restricted subset of oral and single vaginal epithelial cells in higher mammals. Our results provide further evidence that the program of squamous differentiation in internal epithelia of the upper alimentary tract in rodents and higher mammals differ remarkably. In addition, we also have noted the distinct distribution patterns of human loricrin and involucrin, another major precursor protein of the cornified cell envelope.     

Reintroducing the European Beaver to Britain: nostalgic meddling or restoring biodiversity?

The European Beaver Castor fiber once occurred throughout Europe, but in many countries was exterminated or greatly reduced by over-hunting. In the UK, Beavers were last recorded in Scotland in the sixteenth century. Thirteen countries have carried out reintroduction programmes to restore the range of the Beaver in Europe, We provide a basis for discussing the feasibility and desirability of reintroducing the Beaver to Britain. The basic biology of the Beaver is described, followed by summaries of reintroductions in Europe and an evaluation of their successes and failures. We address the fundamental questions of propagule size, habitat requirements, habitat size and provenance of Beavers to be released, before examining in theory whether reintroducing Beavers to Britain is likely to fulfil UKCINC and IUCN criteria relating to environmental impact, socioeconomics and conservation. We then make suggestions as to how a reintroduction to Britain could proceed. Essential work outstanding includes site assessment and public consultation. The restoration of the Beaver to Britain could be a fitting start to the millennium.     

Association of the type II cAMP-dependent protein kinase with a human thyroid RII-anchoring protein. Cloning and characterization of the RII-binding domain.

The type II cAMP-dependent protein kinase (PKA) is localized to specific subcellular environments through binding of the dimeric regulatory subunit (RII) to anchoring proteins. Subcellular localization is likely to influence which substrates are most accessible to the catalytic subunit upon activation. We have previously shown that the RII-binding domains of four anchoring proteins contain sequences which exhibit a high probability of amphipathic helix formation (Carr, D. W., Stofko-Hahn, R. E., Fraser, I. D. C., Bishop, S. M., Acott, T. E., Brennan, R. G., and Scott J. D. (1991) J. Biol. Chem. 266, 14188-14192). In the present study we describe the cloning of a cDNA which encodes a 1015-amino acid segment of Ht 31. A synthetic peptide (Asp-Leu-Ile-Glu-Glu-Ala-Ala-Ser-Arg-Ile-Val-Asp-Ala-Val-Ile-Glu-Gln-Val -Lys-Ala-Ala-Tyr) representing residues 493-515 encompasses the minimum region of Ht 31 required for RII binding and blocks anchoring protein interaction with RII as detected by band-shift analysis. Structural analysis by circular dichroism suggests that this peptide can adopt an alpha-helical conformation. Both Ht 31 (493-515) peptide and its parent protein bind RII alpha or the type II PKA holoenzyme with high affinity. Equilibrium dialysis was used to calculate dissociation constants of 4.0 and 3.8 nM for Ht 31 peptide interaction with RII alpha and the type II PKA, respectively. A survey of nine different bovine tissues was conducted to identify RII binding proteins. Several bands were detected in each tissues using a 32P-RII overlay method. Addition of 0.4 microM Ht 31 (493-515) peptide to the reaction mixture blocked all RII binding. These data suggest that all anchoring proteins bind RII alpha at the same site as the Ht 31 peptide. The nanomolar affinity constant and the different patterns of RII-anchoring proteins in each tissue suggest that the type II alpha PKA holoenzyme may be specifically targeted to different locations in each type of cell.