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Rock Substrate (rock + substrate)
Selected AbstractsContribution of ROCK in contraction of trabecular meshwork: Proposed mechanism for regulating aqueous outflow in monkey and human eyesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2005Emi Nakajima Abstract Aqueous outflow in the conventional outflow pathway is regulated by the contraction and relaxation of the ciliary muscle (CM) and the trabecular meshwork (TM). Rho-associated coiled coil-forming protein kinase (ROCK) is thought to regulate actomyosin-based contractility in many types of cells by phosphorylation of ROCK substrates. In animal models, ROCK inhibitor Y-39983 relaxed CM and TM and decreased intraocular pressure (IOP). Thus, ROCK is implicated in the regulation of aqueous outflow and IOP. However, the site of action of ROCK in monkey and man is unknown. In the present communication, RT-PCR analysis of monkey tissues showed higher levels of mRNAs for ROCK and ROCK substrates in TM compared to CM. Human TM also showed higher levels of mRNAs for ROCK and ROCK substrates compared to CM. Differences between TM and CM in human were not as high as in monkey. ROCK inhibitor Y-39983 led to a dose-dependent relaxation of carbachol-induced, contracted TM from monkey. In contrast, Y-39983 was only slightly effective in relaxing CM. Our results suggested that TM was one of the major sites for regulating IOP by ROCK. ROCK inhibitor Y-39983 might be a candidate drug for lowering IOP by increasing conventional outflow and producing fewer side effects on accommodation and miosis. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:701,708, 2005 [source] Soil production in heath and forest, Blue Mountains, Australia: influence of lithology and palaeoclimateEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2005Marshall T. Wilkinson Abstract An Erratum has been published for this article in Earth Surfaces Processes and Landforms 25(13) 2005, 1683,1686. Recent determinations of soil production from in situ cosmogenic nuclides indicate that production decreases exponentially with soil depth. This contrasts with a long-held assumption that maximum soil production occurs under a soil cover of finite depth. Sites in the Blue Mountains, Australia, show a sharp decrease of soil depth where vegetation changes from forested plateau surfaces to heath-covered spurs, and bands of bare rock in the heath suggest that soil production depends on presence of a finite depth of soil. The substrate varies from hard ferruginized sandstone to soft saprolite. In situ 10Be determinations indicate that apparent rates of erosion and soil production are greater under the relatively thin heath soil than under the thicker forest soil but, in contrast to other studies, these sites do not show significant depth-dependence of apparent soil production. The pattern reflects both hardness variation in the rock substrate and the effect of Late Quaternary climatic change. Optically stimulated luminescence (OSL) dating indicates that soil ,30 cm depth is of Holocene age whereas the deeper soil is substantially older. The age-break coincides with a stone line interpreted as a former surface lag deposit. Assuming that pre-Holocene soil depths were 30 cm less than today, recalculated soil production tends to decrease with increasing depth. Soil production at this site requires soil cover but bare rock patches and vegetation comprise a shifting mosaic. In the long term, average rates of erosion and soil production decrease with increasing soil depth. Copyright © 2005 John Wiley & Sons, Ltd. [source] Living on the bottom: Kinematics of benthic station-holding in darter fishes (Percidae: Etheostomatinae)JOURNAL OF MORPHOLOGY, Issue 1 2010Rose L. Carlson Abstract Darters represent a substantial radiation of freshwater fishes that live in close association with the substrate in North American streams and rivers. A key feature of any darter species is therefore its ability to stay in place or to "hold station" in flowing water. Here, we quantify the station-holding performance of two morphologically divergent darter species, the fantail darter Etheostoma flabellare and the Missouri saddled darter Etheostoma tetrazonum. We also characterize the primary kinematic responses of the two species when holding station in flow speeds ranging from 4 to 56 cm s,1 in a flow tank on either plexiglas or small rock substrate. We then present a series of hypotheses about the potential hydrodynamic and functional consequences of the observed postural changes and the links among morphology, posture, and station-holding performance. On both substrates, E. tetrazonum was able to hold station at higher flow speeds than E. flabellare. On rocks, E. tetrazonum slipped at an average speed of 55.7 cm s,1 whereas E. flabellare slipped at 40.2 cm s,1. On plexiglas, E. tetrazonum slipped at an average speed of 24.7 cm s,1 whereas E. flabellare slipped at 23.1 cm s,1. We measured body and fin positions of the two species from individual frames of high-speed video while holding station on rocks and plexiglas. We found that on both substrates, the two species generally exhibited similar kinematic responses to increasing flow: the head was lowered and angled downward, the back became more arched, and the median and caudal fin rays contracted as water flow speed increased. The ventral halves of the pectoral fins were also expanded and the dorsal halves contracted. These changes in posture and fin position likely increase negative lift forces thereby increasing substrate contact forces and reducing the probability of downstream slip. J. Morphol., 2010. © 2009 Wiley-Liss, Inc. [source] Rock weathering creates oases of life in a High Arctic desertENVIRONMENTAL MICROBIOLOGY, Issue 2 2010Sara Borin Summary During primary colonization of rock substrates by plants, mineral weathering is strongly accelerated under plant roots, but little is known on how it affects soil ecosystem development before plant establishment. Here we show that rock mineral weathering mediated by chemolithoautotrophic bacteria is associated to plant community formation in sites recently released by permanent glacier ice cover in the Midtre Lovénbreen glacier moraine (78°53,N), Svalbard. Increased soil fertility fosters growth of prokaryotes and plants at the boundary between sites of intense bacterial mediated chemolithotrophic iron-sulfur oxidation and pH decrease, and the common moraine substrate where carbon and nitrogen are fixed by cyanobacteria. Microbial iron oxidizing activity determines acidity and corresponding fertility gradients, where water retention, cation exchange capacity and nutrient availability are increased. This fertilization is enabled by abundant mineral nutrients and reduced forms of iron and sulfur in pyrite minerals within a conglomerate type of moraine rock. Such an interaction between microorganisms and moraine minerals determines a peculiar, not yet described model for soil genesis and plant ecosystem formation with potential past and present analogues in other harsh environments with similar geochemical settings. [source] | ||||||||||