Effects of stream-crossing by a pipeline on the benthic macroinvertebrate communities of a small mountain stream

Aquatic environmental impact associated with stream-crossing by a pipeline was monitored at Archibald Creek, B.C. for two years. Water chemistry and benthic macroinvertebrates were used as monitoring tools. Results indicated that impacts arising from stream-crossing were short-term and non-residual.Funded by a contract from Canadian Arctic Gas Study Limited, calgary, to Aquatic Environments Limited, Calgary.Aquatic Environments Limited, Calgary.Aquatic Environments Limited, Calgary.     

Gamma-crystallins of the human eye lens: expression analysis of five members of the gene family.

While only two gamma-crystallins have been identified in the human eye lens, molecular studies indicate that the human gamma-crystallins are encoded in a multigene family comprising at least seven closely related members. Sequence analysis of five of these genes has suggested that three (gamma 1-2, G3, and G4) are potentially active, while two (G1 psi and G2 psi) correspond to closely related pseudogenes. Here we report on the detailed structure of a sixth gamma-crystallin gene, G5, and our results obtained with transient expression assays to characterize both the promoter activity and translation products of five members of the gene family. We show that 5'-flanking sequences of G1 psi and G2 psi lacked detectable promoter activity, while the corresponding sequences of G3, G4, and G5 were able to direct high levels of expression of the bacterial chloramphenicol acetyltransferase gene in primary lens epithelia, but not in cultures of nonlens origin. Detailed sequence comparisons indicated that active genes contained several conserved sequence tracts 5' of the TATA box which may constitute functional elements of a lens-specific gamma-crystallin promoter. Expression of the gamma-crystallin coding sequences from the human metallothionein IIA promoter in nonlens cells facilitated characterization of the polypeptides encoded by individual gamma-genes and, in future studies, should permit comparison of these proteins with distinct gamma-crystallins in the human lens.     

Molecular basis of growth cone adhesion: anchoring of adheron- containing filaments at adhesive loci

Adhesive contacts made by filopodia of neuronal growth cones are essential for proper neurite elongation and may have a role in the formation of synaptic junctions. Previously we described the appearance of filamentous materials extending from growth cone surfaces that seem to be associated with the strongly adhesive behavior of filopodia (Tsui, H.-C., K. L. Lankford, and W. L. Klein. 1985. Proc. Natl. Acad. Sci. USA. 82:8256-8260). Here, we have used immunogold labeling to determine whether known adhesive molecules might be localized at points of adhesion and possibly be constituents of the filamentous material. Antibodies to an adhesive molecule (neural cell adhesion molecule [N-CAM]) and to an adhesive macromolecular complex of proteins and proteoglycans (adheron) were localized at the EM level in whole mounts of cultured avian retina cells. Labeling of fixed cells showed that N-CAM and adheron molecules were both present on growth cones and on filopodia. However, filamentous materials extending from the cell surface were labeled with anti-adheron but not with anti-N-CAM. If cells were labeled before fixation, patches of anti-N-CAM labeling occurred in random areas over the growth cones, but adheron antibodies concentrated at points of apparent adhesion. Particularly dense clustering of anti-adheron occurred at individual filopodial tips and at points of contact between pairs of filopodia. The different patterns of labeling imply that N-CAMS do not associate with the main antigenic components of adheron on the membrane surface. Most importantly, the data indicate the N-CAMs were mobile in the membrane but that constituents of adherons were anchored at adhesive loci. An appealing hypothesis is that molecules found in adheron preparations have an important role in establishing the adhesive junctions formed by growth cone filopodia.     

The role of integration host factor In gene expression in Escherichia coli

Integration host factor is a sequence-specific, histone-like, multifunctional DNA-binding and -bending protein of Escherichia coli. The characterization and functional analysis of this protein has been done mainly in bacteriophage lambda and other mobile genetic elements. Less is known concerning the role of integration host factor (IHF) in E. coli, although it has been implicated in a number of processes in this organism including DNA replication, site-specific recombination, and gene expression. This review presents recent work which suggests that IHF alters the activity of an unusually large number of operons in E. coli. We discuss the possible physiological relevance of the involvement of IHF in gene expression and the hypothesis that IHF is a member of a class of functionally redundant proteins that participate in chromosome structure and multiple processes involving DNA.     

The intrinsic pKa values for phosphatidylserine and phosphatidylethanolamine in phosphatidylcholine host bilayers.

Potentiometric titrations and surface potential measurements have been used to determine the intrinsic pKa values of both the carboxyl and amino groups of phosphatidylserine (PS) in mixed vesicles of PS and phosphatidylcholine (PC), and also of the amino group of phosphatidylethanolamine (PE) in mixed PE-PC vesicles. The pKa of the carboxyl group of PS in liposomes with different PS/PC lipid ratios measured by the two different methods is 3.6 +/- 0.1, and the pKa of its amino group is 9.8 +/- 0.1. The pKa of the amino group of PE in PE-PC vesicles, determined solely by surface potential measurements, is 9.6 +/- 0.1. These pKa values are independent of the aqueous phase ionic strength and of the effect of the liposome's surface potential due to the presence of these partially charged lipids.