Response of protozoans to detergent-enzymes

Summary These studies were divided into two parts: (1) time until death curves in which Paramecium caudatum Ehrenberg was exposed to selected concentrations of the detergent-enzyme Axion, and (2) exposure of fresh-water protozoan communities to selected concentrations of Axion. The former were carried out in test tubes, the latter in plastic troughs with a constantly flowing fluid. Both types of bioassays were carried out with filtered water from Douglas Lake, Michigan, U.S.A. at a temperature of about 25° C. One hundred percent of an exposed population of Paramecium caudatum was killed in 20 to 30 minutes at a concentration of 100 ppm of Axion. No appreciable change in the controls was noted during these tests. The bioassays with fresh-water protozoan communities were carried out in plastic troughs with a constant flow of Douglas Lake water. During the exposure period the lake water flow was stopped and a flow of Axion solution was substituted for approximately three hours. After this exposure period lake water flow were restored. The number of species was determined before and at intervals following exposure. Appropriate controls were maintained. A three hour exposure to 56 ppm (introduced concentration) of Axion caused a 35 percent reduction in the number of species in less than five hours with recovery to the original number in approximately 145 hours; a three hour exposure to 75 ppm caused a 54% reduction in number of species in less than five hours with recovery to the original number in approximately 240 hours; 100 ppm produced a 55 percent reduction with recovery in approximately 200 hours; 125 ppm produced a 48% reduction with recovery in approximately 148 hours; 200 ppm caused a 78% reduction with recovery in about 140 hours. Response patterns vary as do those of bioassays with single species. However, it is important to note that each test community had different types of species present, and it is quite likely that some communities had a higher percentage of sensitive species than others. Since this variation also occurs in nature the tests are probably representative of the differences that exist when natural communities are exposed to wastes. Variation in control troughs was less than ± 10 percent in the number of species.     

Repeated Cocaine Alters Glutamate Receptor Subunit Levels in the Nucleus Accumbens and Ventral Tegmental Area of Rats that Develop Behavioral Sensitization

Increased glutamate transmission in the nucleus accumbens and ventral tegmental area has been proposed as a mechanism underlying sensitized behavioral responses to repeated cocaine administration. GluR1, GluR2/3, and NMDAR1 subunits of glutamate receptors were quantified from immunoblots in these brain nuclei in rats at 24 h and 3 weeks after discontinuing 1 week of daily cocaine injections. Motor behavior was monitored after the first and last injections of daily cocaine, and those rats that showed >20% increase in motor activity after the last compared with the first injection were considered to have developed behavioral sensitization. The subjects that developed behavioral sensitization showed a significant increase in GluR1 levels in the nucleus accumbens at 3 weeks but not at 24 h of withdrawal. Conversely, sensitized animals showed a significant increase in NMDAR1 and GluR1 levels in the ventral tegmental area at 1 day but not at 3 weeks of withdrawal. None of these increases occurred in the rats exposed to daily cocaine that did not develop behavioral sensitization (<20% increase in motor activity), and no changes were measured in the level of GluR2/3 in any treatment group. The functional importance of the increases in glutamate receptor subunit levels is suggested by the fact that the changes were present only in rats that developed behavioral sensitization to repeated cocaine administration.     

Structure prediction of a complex between the chromosomal protein HMG-D and DNA

Non-histone chromosomal proteins are an important part of nuclear structure and function due to their ability to interact with DNA to form and modulate chromatin structure and regulate gene expression. However, the understanding of the function of chromosomal proteins at the molecular level has been hampered by the lack of structures of chromosomal protein–DNA complexes. We have carried out a molecular dynamics modeling study to provide insight into the mode of DNA binding to the chromosomal HMG-domain protein, HMG-D. Three models of a complex of HMG-D bound to DNA were derived through docking the protein to two different DNA fragments of known structure. Molecular dynamics simulations of the complexes provided data indicating the most favorable model. This model was further refined by molecular dynamics simulation and extensively analyzed. The structure of the corresponding HMG-D-DNA complex exhibits many features seen in the NMR structures of the sequence-specific HMG-domain-DNA complexes, lymphoid enhancer factor 1 (LEF-1) and testis determining factor (SRY). The model reveals differences from these known structures that suggest how chromosomal proteins bind to many different DNA sequences with comparable affinity. Proteins 30:113–135, 1998. © 1998 Wiley-Liss, Inc.     

Particulate versus integrated evolution of the upper body in late pleistocene humans: A test of two models

Evolutionary biologists are largely polarized in their approaches to integrating microevolutionary and macroevolutionary processes. Neo-Darwinians typically seek to identify population-level selective and genetic processes that culminate in macroevolutionary events. Epigeneticists and structuralists, on the other hand, emphasize developmental constraints on the action of natural selection, and highlight the role of epigenetic shifts in producing evolutionary change in morphology. Accordingly, the ways in which these paradigms view and address morphological contrasts between classes of related organisms differ. These paradigms, although seldomly explicitly stated, emerge in paleoanthropology as well. Considerations of postcranial morphological contrasts between archaic and modern humans typically fall into one of two broad interpretive models. The first derives from the neo-Darwinian perspective and holds that evolution in the postcranial skeleton was largely mosaic (operating in a particulate manner), and that temporal change in specific traits informs us about behavioral shifts or genetic evolution affecting isolated anatomical regions (i.e., adaptive behavioral inferences can be made from comparative studies of individual trait complexes). The alternative model follows from the epigeneticist paradigm and sees change in specific postcranial traits as correlated responses to change in overall body form (involving shifts in regulation of skeletal growth, or selective and developmental responses to broad adaptive shifts). By this view, integration of functional systems both constrains and directs evolution of various traits, and morphological contrasts inform us about overall change in body form related to change in such things as overall growth patterns, climatic adaptation, and technological dependency. These models were tested by confirmatory factor analysis using measures of upper body form and upper limb morphological traits in Eurasian Neandertal and early modern fossils and recent human samples. Results indicate (1) a model of morphological integration fits the data better than a model of no integration, but (2) this integration accounts for less than half of the variance in upper limb traits, suggesting a high degree of tolerance for particulate evolution in the context of an integrated upper body plan. Significant relationships were detected between joint shapes and body size, between humeral shaft shape and body size and chest shape, and between measures of biomechanical efficiency and robusticity. The observed morphological differences between late archaic and early modern humans reflect particulate evolution in the context of constraints imposed by genetic and morphological integration. While particulate approaches to interpreting the fossil record appear to be justified, attention must also be paid to delineating the nature and extent of morphological integration and its role in both constraining and producing observed patterns of variation between groups. Confirmatory factor analysis provides a means of examining trait covariance matrices, and serves as a useful method of identifying patterns of integration in morphology. © 1996 Wiley-Liss, Inc.     

Niemann-Pick disease type C1 is a sphingosine storage disease that causes deregulation of lysosomal calcium

Niemann-Pick type C1 (NPC1) disease is a neurodegenerative lysosomal storage disorder caused by mutations in the acidic compartment (which we define as the late endosome and the lysosome) protein, NPC1. The function of NPC1 is unknown, but when it is dysfunctional, sphingosine, glycosphingolipids, sphingomyelin and cholesterol accumulate. We have found that NPC1-mutant cells have a large reduction in the acidic compartment calcium store compared to wild-type cells. Chelating luminal endocytic calcium in normal cells with high-affinity Rhod-dextran induced an NPC disease cellular phenotype. In a drug-induced NPC disease cellular model, sphingosine storage in the acidic compartment led to calcium depletion in these organelles, which then resulted in cholesterol, sphingomyelin and glycosphingolipid storage in these compartments. Sphingosine storage is therefore an initiating factor in NPC1 disease pathogenesis that causes altered calcium homeostasis, leading to the secondary storage of sphingolipids and cholesterol. This unique calcium phenotype represents a new target for therapeutic intervention, as elevation of cytosolic calcium with curcumin normalized NPC1 disease cellular phenotypes and prolonged survival of the NPC1 mouse.