Physiological effects of crude oil exposure in the striped mullet, Mugil cephalus

Juvenile mullet ($\text{Mugil cephalus}$) were exposed to a surface slick of Empire Mix crude oil for a three week period in a simulated estuarine ecosystem. Liver weight to body weight ratios were increased in the mullet from the oil-treated ponds when compared to those from the control ponds. Activities of alkaline phosphatase, which were elevated in gill and muscle of oil-treated mullet, and β-glucuronidase, which was elevated in the muscle of oil-treated mullet, may be related to the degree of stress the animals were experiencing. Malic dehydrogenase, which was depressed in the livers and elevated in the muscle of oil-treated organisms, indicate changes in aerobic metabolism in response to the stress of crude oil exposure. Muscle acetylcholinesterase was not affected by oil exposure.     

Synthesis of alpha subunit of human chorionic gonadotrophin by presumptive HeLa cells

Summary Several cell lines, originally thought to be derived from a human placenta at term but possibly HeLa-contaminated, have been studied. These cells secrete a protein indistinguishable immunochemically from the alpha subunit of chorionic gonadotropin but not the beta subunit of chorionic gonadotropin or placental lactogen. Complete chorionic gonadotropin was detected but amounted to less than 1% of the level of the alpha subunit. The cells also produce an alkaline phosphatase similar to placental alkaline phosphatase in immunochemical, gel-electrophoretic, and heat-denaturation properties. They induce tumor growth when inoculated into nude mice. These cells are aneuploid and have a model chromosome number of 66. The common HeLa karyologic markers, designated 1, 2, and 3, and A-type glucose-6-phosphate dehydrogenase are present in these cells. HeLa cells have not previously been shown to secrete theα subunit of hCG.     

Organization of ribosomal protein genes in Escherichia coli: II. Mapping of ribosomal protein genes by in vitro synthesis of ribosomal proteins using DNA fragments of a transducing phage as templates

The structural genes for six ribosomal proteins (r-proteins) located in the str-spc region around 64 minutes on the Escherichia coli chromosome have been mapped physically with respect to each other and the neighboring genes aroE and trkA. The genes code for the 30 S r-proteins S4 (ram), S5 (spc), S8, S11, S13 and S14. Furthermore, regions coding for unidentified 50 S r-proteins have been indicated.The mapping was performed by biochemical methods employing DNA from the specialized transducing phage λspc1, which carries the aroE-trkA-spc region of the E. coli chromosome. The phage DNA was cleaved by restriction endonucleases, and the generated DNA fragments used as templates for synthesis of r-proteins in a DNA-dependent cell-free system. Since the relative order of the DNA fragments created by the restriction endonucleases is known, a genetic map could be constructed.     

A comparison of the structures of apo dogfish M4 lactate dehydrogenase and its ternary complexes

Details are recorded of the X-ray diffraction data collection, heavy atom refinement and preliminary structure refinement for two different dogfish M₄ lactate dehydrogenase structures. One of these is the 2.0 Å resolution apoenzyme structure; the other is a 3.0 Å resolution abortive ternary complex. Two other ternary substrate inhibitory complexes (LDHase²: NAD: oxalate and LDHase: NADH: oxamate), isomorphous with the abortive ternary complex (LDHase: NAD-pyruvate), have also been examined. The apo-LDHase and LDHase: NAD-pyruvate structures are systematically compared to determine significant differences in their conformation. These are related to differences in structure amongst the three studied ternary complexes. These differences all occur in regions of the protein around the active site, particularly the flexible loop covering the active center pocket and the C-terminal helix αH. The changes are suggestive of a domino effect whereby the closing of the loop on binding coenzyme and substrate triggers the critical reactive residues into assuming their catalytically active positions.     

Nest box revealed habitat preferences of arboreal mammals in box‐ironbark forest

Habitat preferences need to be understood if species are to be adequately managed or conserved. Habitat preferences are presumed to reflect requirements for food, shelter and breeding, as well as interactions with predators and competitors. However, one or more of these requirements may dominate. Tree‐cavity‐dependent wildlife species are one example where shelter or breeding site requirements may dominate. We installed 120 nest boxes across 40 sites to target the vulnerable Brush‐tailed Phascogale (Phascogale tapoatafa) and the non‐threatened Sugar Glider (Petaurus breviceps). The provision of shelter sites where few of quality are available may enable better resolution of habitat preferences. Over three years, we observed the Brush‐tailed Phascogale at 17 sites, whereas the Sugar Glider was observed at 39 sites. We tested four broad hypotheses (H1–H4) relating to habitat that may influence occupancy by these species. There was no influence of hollow (cavity) abundance (H1) on either species suggesting our nest boxes had satisfied their shelter requirements. There was no influence of habitat structure (canopy and tree proximity) (H2) immediately around the nest box trees. We found no influence of distance to the forest edge (H3). Variables at and away from the nest box site that appear to reflect foraging substrates (H4) were influential on the Brush‐tailed Phascogale. Sugar Glider occupancy was only influenced by a single variable at the nest box site. The lack of influence of any other variables is consistent with the very high occupancy observed, suggesting most of the forest habitat is suitable when shelter sites are available. We found no evidence that the Sugar Glider reduced site use by the Brush‐tailed Phascogale.     

Structure Analysis of Proteins and Peptides by Difference Circular Dichroism Spectroscopy

The Protein Journal - Difference circular dichroism (CD) spectroscopy was used here to characterize changes in structure of flexible peptides upon altering their environments. Environmental changes...