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  • 1
    Electronic Resource
    Electronic Resource
    Distribution of benthic algae and macroinvertebrates along a thermal stream gradient (1985)
    Springer
    Hydrobiologia 128 (1985), S. 13-21 
    Details
    ISSN: 1573-5117
    Keywords: algae ; benthic ; geothermal ; macroinvertebrates ; stream ; thermal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distribution and abundance of benthic algae and macroinvertebrates were examined along a natural thermal gradient formed by hot springs in Little Geysers Creek, Sonoma Co., California, USA. Maximum water temperatures ranged from 52 °C at the uppermost station to 23 °C at a station 400 m downstream. Benthic chlorophyll a decreased exponentially from 2.5 g m−2 at 52 °C to less than 0.1 g m−2 at 23 °C, a pattern of decline also exhibited by algal phaeophytin. Blue-green algae dominated at higher temperatures but were replaced by filamentous green algae and diatoms at lower temperatures. Macroinvertebrates were absent at temperatures ⩾45 °C; the highest density (〉 150 000 m−2, mainly Chironomidae) occurred at 34 °C, whereas biomass was highest (4.6 g m−2, as dry weight) at 23 °C and species richness (15 species) was highest at 27 °C. The two predominant macroinvertebrate populations (the midge Tanytarsus sp. and the caddisfly Helicopsyche borealis) occurred at sites that were several degrees below their lethal thermal threshold, suggesting that a temperature ‘buffer’ is maintained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00008935
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  • 2
    Electronic Resource
    Electronic Resource
    Bionomics of invertebrates within an extensive Potamogeton pectinatus bed of a California marsh (1992)
    Springer
    Hydrobiologia 234 (1992), S. 15-24 
    Details
    ISSN: 1573-5117
    Keywords: phytomacrofauna ; macrophyte-invertebrate associations ; macroinvertebrates ; microcrustaceans ; Potamogeton pectinatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fourteen samples of sago pondweed (Potamogeton pectinatus L.) and associated invertebrates were collected every two weeks over a single season of plant growth in a large monospecific pondweed-bed located in Coyote Hills Marsh (Alameda Co., California, USA), using pull-up samplers that collect plants, epiphytic macroinvertebrates, and microcrustaceans throughout the water column. The macro-invertebrate fauna was dominated by insects, primarily chironomids. Semi-aquatic neustonic taxa, including an aphid and a springtail, were common; this is in contrast with most aquatic plant-invertebrate studies, in which neustonic insects are seldom collected because of sampling bias. Over the entire season, P. pectinatus biomass and the densities of four insect taxa (Anopheles spp. mosquitoes, Hydrellia sp. brineflies, Ademon sp. parasitic wasps, and coenagrionid damselflies) were significantly correlated. These correlations resulted from both similar overall phenologies of the plant and each of the insect taxa, and ecological relationships in which P. pectinatus provides either a specialized habitat or food source. macroinvertebrate numbers were highest in mid-summer, when P. pectinatus forms a dense floating canopy; microcrustaceans were more common during plant senescence in early autumn. Individuals of some taxa may be distributed in proportion to plant biomass; this occurred commonly in damselflies, perhaps as a result of territoriality in these nymphs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010775
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  • 3
    Electronic Resource
    Electronic Resource
    Role of Enzymatic Lability in the Corneal and Conjunctival Penetration of Timolol Ester Prodrugs in the Pigmented Rabbit (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 728-733 
    Details
    ISSN: 1573-904X
    Keywords: prodrugs ; timolol ; enzymatic lability ; lipophilicity ; corneal penetration ; conjunctival penetration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The main objective of this study was to investigate how enzymatic lability would affect the extent of corneal and conjunctival penetration of a series of alkyl, cycloalkyl, and aryl ester prodrugs of timolol in the pigmented rabbit. Enzymatic lability of the prodrugs was studied in corneal epithelial and conjunctival homogenates, while their corneal and conjunctival penetration was determined using the isolated tissues in the modified Ussing chamber. The straight-chain alkyl and the unsubstituted cycloalkyl esters were hydrolyzed more rapidly than their corresponding branched-chain and substituted analogues as well as the aryl esters. The corneal and conjunctival penetration of all prodrugs, regardless of enzymatic lability, varied parabolically with lipophilicity. Moreover, the enzymatically more labile straight-chain alkyl esters penetrated the cornea and the conjunctiva more readily than the more stable branched-chain esters of comparable lipophilicity. Enzymatic lability is, therefore, an additional factor that should be considered in designing alkyl ester prodrugs with improved ocular drug delivery characteristics. Enzymatic lability does not, however, play as important a role as lipophilicity in the corneal and conjunctival penetration of cycloalkyl and aryl ester prodrugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015845916293
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  • 4
    Electronic Resource
    Electronic Resource
    Conjunctival Penetration of Insulin and Peptide Drugs in the Albino Rabbit (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 769-775 
    Details
    ISSN: 1573-904X
    Keywords: beta blockers ; conjunctival penetration ; enkephalins ; insulin ; paracellular penetration ; substance P ; transcellular penetration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An in vitro model was used to evaluate the conjunctival penetration of three peptides, [D-ala2]metenkephalinamide (YAGFM, MW 647), substance P (MW 1348), and insulin (MW 5778), in comparison with two nonpeptides, atenolol (MW 266) and timolol (MW 433). All three peptides were hydrolyzed to varying extents during penetration across the conjunctiva. The permeability coefficient for intact YAGFM and insulin was 4.5 ± 0.3 and 4.6 ± 0.7 µm sec−1, respectively. These values were about two to five times lower than those for atenolol and timolol. No permeability coefficient could be calculated for substance P, since its transconjunctival flux never reached steady state. The conjunctival penetration of YAGFM and insulin was improved by about two and three times, respectively, with the addition of 1% Na glycocholate. Increasing the Na glycocholate concentration was more effective than changing the type of bile salt in improving the conjunctival penetration of insulin. The maximum factor of improvement was 12, as the Na glycocholate concentration was raised to 4%. The way in which Na deoxycholate, glycocholate, and taurocholate affected the conjunctival penetration of atenolol, timolol, and insulin suggests that these three bile salts improved mainly the transcellular penetration of the compounds studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015803605621
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