The cause of the elevated outflow resistance and consequent ocular hypertension characteristic of glaucoma is unknown. To investigate possible causes for this flow resistance, we used atomic force microscopy (AFM) with 10-µm spherical tips to probe the stiffness of the inner wall of Schlemm’s canal as a function of distance from the tissue surface in normal and glaucomatous postmortem human eyes, and 1-µm spherical AFM tips to probe the region immediately below the tissue surface. To localize flow resistance, perfusion and imaging methods were used to characterize the pressure drop in the immediate vicinity of the inner wall using giant vacuoles that form in Schlemm’s canal cells as micropressure sensors. Tissue stiffness increased with increasing AFM indentation depth. Tissues from glaucomatous eyes were stiffer compared with normal eyes, with greatly increased stiffness residing within ∼1 µm of the inner-wall surface. Giant vacuole size and density were similar in normal and glaucomatous eyes despite lower flow rate through the latter due to their higher flow resistance. This implied that the elevated flow resistance found in the glaucomatous eyes was localized to the same region as the increased tissue stiffness. Our findings implicate pathological changes to biophysical characteristics of Schlemm’s canal endothelia and/or their immediate underlying extracellular matrix as cause for ocular hypertension in glaucoma.

Members of the family Halobacteriaceae in the domain Archaea are obligate extreme halophiles. They occupy a variety of hypersaline environments, and their cellular biochemistry functions in a nearly saturated salty milieu. Despite extensive study, a detailed analysis of their growth kinetics is missing. To remedy this, Arrhenius plots for 14 type species of the family were generated. These organisms had maximum growth temperatures ranging from 49 to 58°C. Nine of the organisms exhibited a single temperature optimum, while five grew optimally at more than one temperature. Generation times at these optimal temperatures ranged from 1.5 h (Haloterrigena turkmenica) to 3.0 h (Haloarcula vallismortis and Halorubrum saccharovorum). All shared an inflection point at 31 ؎ 4°C, and the temperature characteristics for 12 of the 14 type species were nearly parallel. The other two species (Natronomonas pharaonis and Natronorubrum bangense) had significantly different temperature characteristics, suggesting that the physiology of these strains is different. In addition, these data show that the type species for the family Halobacteriaceae share similar growth kinetics and are capable of much faster growth at higher temperatures than those previously reported.The family Halobacteriaceae in the domain Archaea presently is comprised of 18 genera and 49 validly described species (International Committee on Systematics of Prokaryotes [http://www.the-icsp.org]). All members are extreme halophiles, requiring at least 1.5 M NaCl for growth, but grow optimally in 2.0 to 4.5 M NaCl (6, 20). All have exceptionally high internal cation concentrations that approach 6 M in some species (e.g., Halobacterium salinarum) (21). In addition to exhibiting halophilicity, four genera (Natronococcus, Natronomonas, Natronorubrum, and Natronobacterium) are also alkaliphilic, growing optimally between pH 9.5 and 10.0 (20). These organisms have been isolated from a wide variety of environments, including the sediment of a cold, hypersaline lake in Antarctica (Halorubrum lacusprofundi) (3), the Dead Sea (Haloferax volcanii) (16), the Great Salt Lake (Halorabdus utahensis) (31), a hypersaline soda lake in Egypt (Natronomonas pharaonis) (27), and a salt crystal from a Permian halite deposit (Halosimplex carlsbadense) (30). There is also a report of haloarchaeal 16S rDNA amplified from inside a black smoker (28), but no haloarchaeons have been cultured from this source. All haloarchaea grow aerobically, and one species (Halobacterium salinarum) can grow phototrophically using bacteriorhodopsin as a light-driven proton pump (19).Since ". . .growth is the core of bacterial physiology. . ." (11) and since all experiments in cellular regulation are fundamentally physiological, it is essential to understand the growth physiology of the organism one is studying. Toward this goal we generated a complete Arrhenius plot for the haloarchaeon Haloferax mediterranei (22, 25; J. L. Robinson and R. F. Shand, unpublished data [http://jan.ucc.nau.edu/ϳshand]). This growth ...

No abstract

The Pteraspidiformes are an order of armoured agnathans of Silurian and Devonian age composed of five families: the Anchipteraspididae, Protopteraspididae, Pteraspididae, Protaspididae and Psammosteidae. Relationships within the order are poorly known and although past attempts have been made to represent the state of knowledge in this area none have attempted a rigorous computer-based analysis. Here we present the results of the cladistic analysis on a matrix comprising 25(+1) taxa and 59 characters using W INCLADA . The first analysis was run without any representative of the Psammosteidae and supports the presence of five groups within the order although one, the 'Protopteraspididae', is paraphyletic and a second, the Gigantaspididae, is newly recognized. In a second analysis the addition of the psammosteid Drepanaspis gemuendenensis results in a better resolved tree in which the basal family, the Anchipteraspididae, are clearly monophyletic and in which the Psammosteidae, as represented by Drepanaspis , is the next less inclusive. This is contrary to the previous view that the psammosteids were an advanced clade within the Pteraspidiformes.

Three new species and genera of pteraspidids (Agnatha, Heterostraci), Tuberculaspis elyensis, Pirumaspis lancasteri, and Lamiaspis longiripa, are described from the Sevy Dolomite, east-central Nevada. They form part of a vertebrate fauna of typical Early Devonian aspect that indicates a correlation with previously described faunas from the Beartooth Butte and Water Canyon Formations of Utah and Wyoming, thus improving the known distribution and diversity of these faunas. Correlation with an accurately dated fauna in Death Valley, California, enables this fauna to be dated to the late Emsian (inversus–serotinus Zones).