Tidal flows and sediment budgets for a salt-marsh system,Essex, England

Studies of tidal flows in salt-marsh creeks in Essex, England, show large variations in water velocity during different tidal cycles, particularly between tides below, at, and above marsh level. Water level, velocity and suspended sediment concentration have been monitored at 5-min intervals during 700 tidal cycles during the year March 1982–March 1983, and the data are being used to calculate sediment budgets for the creek system studied. Completed analyses for two of the tidal cycles show a large positive sediment flux. Because of the importance of velocity in controlling total discharge through a creek cross-section, and hence its effect on total sediment movement, we cannot extrapolate from these two below-marsh tides to any general conclusions about marsh erosion or accretion. We use these preliminary data both to demonstrate our methods and to indicate some of the complexities involved in the analysis.Acknowledgements: This work has been supported by the Natural Environment Research Council. We thank the Philip Lake Fund for financial assistance and the Department of Geography, Cambridge University, for much material support. Mr D. J. Fisher kindly gave access to his land, and Mr W. Bailey helped us greatly. We also thank Mr A. St Joseph for his help, Mr M. Diver for practical support, and Dr J. S. Pethick for discussion.     

Solid-state 15N NMR of oriented lipid bilayer bound gramicidin A'

Highly oriented samples of lipid and gramicidin A' (8:1 molar ratio) have been prepared with the samples extensively hydrated (approximately 70% water v/w). These preparations have been shown to be completely in a bilayer phase with a transition temperature of 28 degrees C, and evidence is presented indicating that the gramicidin is in the channel conformation. An estimate of the disorder in the alignment of the bilayers parallel with the glass plates used to align the bilayers can be made from the asymmetry of the nuclear magnetic resonances (NMR). Such an analysis indicates a maximal range of disorder of +/- 3 degrees. Uniformly 15N-labeled gramicidin has been biosynthesized by Bacillus brevis grown in a media containing 15N-labeled Escherichia coli cells as the only nitrogen source. When prepared with labeled gramicidin, the oriented samples result in high-resolution 15N NMR spectra showing 12 resonances for the 20 nitrogen sites of the polypeptide. The frequency of the three major multiple resonance peaks has been interpreted to yield the approximate orientation of the N-H bonds in the peptide linkages with respect to the magnetic field. These bond orientations are only partially consistent with the extant structural models of gramicidin.     

Inhibitory effect of the flavonoid silymarin on the erythrocyte hemolysis induced by phenylhydrazine

The flavonoid silymarin, which is used as a therapeutical agent in the treatment of liver diseases, can inhibit the hemolysis and lipid peroxidation induced by phenylhydrazine on erythrocytes obtained from rats treated with the flavonoid. This effect is ascribed to the antioxidant properties as a free radical scavenger exhibited by the flavonoid. Silymarin failed to inhibit the glutathione depletion induced by phenylhydrazine on erythrocytes. It is proposed that the flavonoid acts at the membrane level of the cell avoiding the lipid peroxidative and fluidizing effect of phenylhydrazine.     

Identification of a complex of the three forms of the rat liver asialoglycoprotein receptor

We have generated antibodies against synthetic peptides which represent the carboxyl terminus of either the major, or the two minor, forms of the rat hepatic lectin which recognizes galactose-terminated glycoproteins (asialoglycoproteins). The antibodies were shown to be specific for the form of the lectin containing the immunizing peptide sequence by the following: reaction with purified lectin after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoprecipitation of sodium dodecyl sulfate-denatured lectin, immunoprecipitation of lectin synthesized in vitro. These antibodies, however, precipitated all three rat hepatic lectin forms from nonionic detergent extracts of hepatocytes labeled with 125I via the lactoperoxidase catalyzed technique. A similar result was obtained if antibody was bound to intact cells prior to solubilization with detergent and collection of the immune complexes. We conclude that at least the plasma membrane-associated fraction of the rat hepatic lectin forms exists as a heterotypic complex.     

Congenital diverticulum of the ileum in a rat.

A congenital diverticulum of the ileum (Meckel's diverticulum), approximately 10 mm long, was detected in a rat and examined histologically. The histological findings were basically the same as in the ileum. Although Meckel's diverticulum is uncommon in the rat, the present report demonstrated the possibility of discovering new cases.     

Quantitative determination of the induction of apoptosis in a murine B cell line using flow cytometric bivariate cell cycle analysis.

WEHI-231 cells have been used extensively as a model of tolerance induction in B cells. Recent evidence has shown that anti-IgM treatment of WEHI-231 cells resulted in the induction of apoptosis. In this study, using acridine orange staining and flow cytometric analysis, we demonstrated that apoptotic cells are detected as a distinct population of cells separate from the cells in normal cell cycle progression. The validity of analysis gates was confirmed by cell sorting of the apoptotic population versus normal cells and subsequent gel analysis. Using this technique, we have demonstrated that F(ab')2 anti-mu, A23187, or PMA induced apoptosis in the WEHI-231 cells. The addition of LPS reversed apoptotic induction as seen previously with the WEHI-231 cell line. In contrast, however, PMA did not prevent the induction of apoptosis in anti-mu-treated cells. Additionally, we were interested in determining if the induction of apoptosis was restricted to a specific phase of cell cycle. Since growth inhibition results in most cells arresting in the G1 phase of cell cycle, we wanted to demonstrate apoptosis as a G1-dependent event. This was examined with WEHI-231 cells treated with known cell cycle inhibitors. Interestingly, inhibition of cells in each phase of cycle resulted in the induction of apoptosis. LPS was able to inhibit the induction of apoptosis with each of the cell cycle inhibitors except actinomycin D. Furthermore, we have demonstrated that the WEHI-231 cells contain a Ca(2+)-Mg(2+)-dependent preexisting endonuclease.