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  • Articles  (16)
  • Life and Medical Sciences  (12)
  • Rotifera  (4)
  • 1995-1999  (16)
  • 1950-1954
  • 1
    Electronic Resource
    Electronic Resource
    Effects of turbidity and biotic factors on the rotifer community in an Ohio reservoir (1998)
    Springer
    Hydrobiologia 287-388 (1998), S. 215-223 
    Details
    ISSN: 1573-5117
    Keywords: reservoir ; Rotifera ; spatial distribution ; temporal variation ; turbidity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In reservoirs physical horizontal gradients may affect zooplankton distributions as well as the biotic interactions that potentially regulate zooplankton abundance and species composition. We examined patterns of rotifer abundance and population dynamics along a turbidity gradient over a 4-year period in an Ohio reservoir. To analyze the effect of turbidity on rotifer populations we compared rotifer abundance patterns, species composition, birth and death rates at two sites with high turbidity (river site) and low turbidity (dam site) conditions. Because of the potentially important biotic interaction between rotifers and cladocerans, we also compared cladoceran abundance patterns and species composition. Our results suggest no effect of turbidity on rotifers in Acton Lake. Rotifer and cladoceran abundance patterns were similar at low and high turbidity sites. Similarity indices revealed few differences in rotifer and cladoceran species composition between sites. Rotifer birth and death rates were also similar at low and high turbidity sites. In contrast to these homogeneous spatial patterns, among year comparisons indicate high temporal variability in all parameters measured. Mean rotifer densities were similar from 1993 to 1995, but in 1996 density increased 4-fold. Rotifer species assemblages were dominated by Brachionus spp. from 1993 to 1995, while Keratella cochlearis and Polyarthra spp. were numerically dominant in 1996. Mean cladoceran density also increased in 1996 compared to previous years. Cladoceran species composition was dominated by Diaphanosoma birgei from 1993 to 1995, while Daphnia parvula and Bosmina longirostris dominated the 1996 cladoceran community. Comparison of rotifer population parameters in years of contrasting D. parvula abundance suggests that exploitative competition may be an important mechanism regulating rotifer communities in Acton Lake. Interannual variation in Daphnia abundance may in turn be controlled by variation in fish biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017041826108
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  • 2
    Electronic Resource
    Electronic Resource
    Rotifer responses to increased acidity: long-term patterns during the experimental manipulation of Little Rock Lake (1998)
    Springer
    Hydrobiologia 287-388 (1998), S. 141-152 
    Details
    ISSN: 1573-5117
    Keywords: Rotifera ; community ; acidification ; whole-lake experiments ; Little Rock Lake ; Wisconsin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Little Rock Lake, Wisconsin, U.S.A. has been the site of a whole-ecosystem experiment since 1983. It was divided into a treatment basin that was acidified in three, two-year stages and a reference basin. The rotifer community in the treatment basin exhibited a variety of responses to the manipulation. Many species decreased in abundance under reduced pH conditions but other rotifers increased at the same time such that there were ultimately increases with acidification in total rotifer biomass, and quite conspicuously, in the proportion that rotifers comprised of total zooplankton biomass. Ten rotifer species decreased at some stage during the acidification (e.g., Kellicottia longispina, Asplanchna priodonta and Keratella cochlearis) while four species increased dramatically (e.g., Synchaeta sp. and Keratella taurocephala ). Similarity indices and total rotifer biomass differences measured between the two basins exhibited very different temporal patterns of response to acidification. Similarity decreased regularly beginning with the earliest stages of acid additions while biomass was nearly the same between the basins until the late stages of the experiment. Comparisons with other nearby lakes indicate, however, that acid conditions are not the only factors generating among-lake differences in rotifer community characteristics. Changes observed with acidification in Little Rock Lake were such that its total rotifer biomass grew more similar to that in a nearby acidic-bog lake and different from that in a near-neutral-pH lake. At the same time, abundance patterns for individual rotifer species in Little Rock Lake were not particularly similar to those in the other lakes. It appears that, although they are important, acid conditions alone can not account for all observed rotifer community differences among lakes. Higher proportions of rotifer biomass and high populations of K. taurocephala do seem to be common features of many low pH habitats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017055307027
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of turbidity and biotic factors on the rotifer community in an Ohio reservoir (1998)
    Springer
    Hydrobiologia 387-388 (1998), S. 215-223 
    Details
    ISSN: 1573-5117
    Keywords: reservoir ; Rotifera ; spatial distribution ; temporal variation ; turbidity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In reservoirs physical horizontal gradients may affect zooplankton distributions as well as the biotic interactions that potentially regulate zooplankton abundance and species composition. We examined patterns of rotifer abundance and population dynamics along a turbidity gradient over a 4-year period in an Ohio reservoir. To analyze the effect of turbidity on rotifer populations we compared rotifer abundance patterns, species composition, birth and death rates at two sites with high turbidity (river site) and low turbidity (dam site) conditions. Because of the potentially important biotic interaction between rotifers and cladocerans, we also compared cladoceran abundance patterns and species composition. Our results suggest no effect of turbidity on rotifers in Acton Lake. Rotifer and cladoceran abundance patterns were similar at low and high turbidity sites. Similarity indices revealed few differences in rotifer and cladoceran species composition between sites. Rotifer birth and death rates were also similar at low and high turbidity sites. In contrast to these homogeneous spatial patterns, among year comparisons indicate high temporal variability in all parameters measured. Mean rotifer densities were similar from 1993 to 1995, but in 1996 density increased 4-fold. Rotifer species assemblages were dominated by Brachionus spp. from 1993 to 1995, while Keratella cochlearis and Polyarthra spp. were numerically dominant in 1996. Mean cladoceran density also increased in 1996 compared to previous years. Cladoceran species composition was dominated by Diaphanosoma birgei from 1993 to 1995, while Daphnia parvula and Bosmina longirostris dominated the 1996 cladoceran community. Comparison of rotifer population parameters in years of contrasting D. parvula abundance suggests that exploitative competition may be an important mechanism regulating rotifer communities in Acton Lake. Interannual variation in Daphnia abundance may in turn be controlled by variation in fish biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017041826108
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  • 4
    Electronic Resource
    Electronic Resource
    Rotifer responses to increased acidity: long-term patterns during the experimental manipulation of Little Rock Lake (1998)
    Springer
    Hydrobiologia 387-388 (1998), S. 141-152 
    Details
    ISSN: 1573-5117
    Keywords: Rotifera ; community ; acidification ; whole-lake experiments ; Little Rock Lake ; Wisconsin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Little Rock Lake, Wisconsin, U.S.A. has been the site of a whole-ecosystem experiment since 1983. It was divided into a treatment basin that was acidified in three, two-year stages and a reference basin. The rotifer community in the treatment basin exhibited a variety of responses to the manipulation. Many species decreased in abundance under reduced pH conditions but other rotifers increased at the same time such that there were ultimately increases with acidification in total rotifer biomass, and quite conspicuously, in the proportion that rotifers comprised of total zooplankton biomass. Ten rotifer species decreased at some stage during the acidification (e.g., Kellicottia longispina, Asplanchna priodonta and Keratella cochlearis) while four species increased dramatically (e.g., Synchaeta sp. and Keratella taurocephala ). Similarity indices and total rotifer biomass differences measured between the two basins exhibited very different temporal patterns of response to acidification. Similarity decreased regularly beginning with the earliest stages of acid additions while biomass was nearly the same between the basins until the late stages of the experiment. Comparisons with other nearby lakes indicate, however, that acid conditions are not the only factors generating among-lake differences in rotifer community characteristics. Changes observed with acidification in Little Rock Lake were such that its total rotifer biomass grew more similar to that in a nearby acidic-bog lake and different from that in a near-neutral-pH lake. At the same time, abundance patterns for individual rotifer species in Little Rock Lake were not particularly similar to those in the other lakes. It appears that, although they are important, acid conditions alone can not account for all observed rotifer community differences among lakes. Higher proportions of rotifer biomass and high populations of K. taurocephala do seem to be common features of many low pH habitats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017055307027
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  • 5
    Electronic Resource
    Electronic Resource
    Spinal cord central canal of the German shepherd dog: Morphological, histological, and ultrastructural considerations (1995)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 224 (1995), S. 205-212 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study deals with some macroscopical, microscopical, and ultrastructural aspects of the spinal cord central canal of the German shepherd dog. The caudal end of the spinal cord is constituted by the conus medullaris, which may extend to the first sacral vertebra, the terminal ventricle, and the filum terminale. The latter structure is considered as internum (second to third sacral vertebrae) or externum (fifth caudal vertebra), according to its relation to the dura mater. Occasionally, there is a second anchorage which is close to the level of the sixth caudal vertebra. The central canal is surrounded by a ciliated ependymal epithelium, which differs depending upon the levels. The most caudal part of the filum terminale bears a columnar ciliated ependymal epithelium surrounded by two layers of glia and pia mater, which separate the central canal from the subarachnoid space. Microfil injections show a communication between the cavity and the subarachnoid space, as the plastic is able to pass through the ependymal epithelium. At the level of the terminal ventricle there are real separations of the ependymal epithelium, which seem to connect the lumen of the spinal canal with the subarachnoid space. These structures probably constitute one of the drainage pathways of the cerebrospinal fluid. The diameter of the central canal is related to the age of the animal. However, even in very old animals the spinal cord central canal reaches the tip of the filum terminale and remains patent until death. At the ultrastructural level the ependymal cells present villi, located on cytoplasmic projections, cilia, dense mitochondria, and oval nuclei. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052240209
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  • 6
    Electronic Resource
    Electronic Resource
    Seasonal variation in ovarian histology of the viviparous lizard Sceloporus torquatus torquatus (1995)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 226 (1995), S. 103-119 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Changes in ovarian histology during the reproductive cycle of the viviparous lizard Sceloporus torquatus torquatus are described. In general, the variation in follicular histology observed during the seasonal cycle is similar to that of other lizards. Sceloporus t. torquatus exhibits a cycle in which small, previtellogenic follicles exist in the ovary from December to August. Vitellogenesis occurs between September and November, followed by ovulation from late November to early December. Parturition occurs the following spring. After ovulation, the remaining follicular cells form the corpus luteum and luteolysis did not occur until April-May. Follicular atresia is commonly observed in previtellogenic follicles with polymorphic granulosa, but occurs less frequently in follicles during late vitellogenesis. There are two germinal beds in each ovary. The yolk nucleus is evident in young oocytes as is a vacuolated ooplasma prior to vitellogenesis. Extensive polymorphism is observed in yolk platelets. Mast cells and secretory cells are observed in the thecal layer of the follicular wall as are melanocytes in the ovarian stroma. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052260107
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  • 7
    Electronic Resource
    Electronic Resource
    Overexpression of an epitope- tagged β-tubulin in Chinese hamster ovary cells causes an increase in endogenous α-tubulin synthesis (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 259-272 
    Details
    ISSN: 0886-1544
    Keywords: microtubules ; transfection ; hemagglutinin antigen ; autoregulation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A Chinese hamster β-tubulin cDNA, engineered to express a 9 amino acid epitope from the influenza hemagglutinin antigen (HA), was transfected into Chinese hamster ovary (CHO) cells. The recombinant protein (HAβ1-tubulin) appeared to behave normally by the following criteria: immunofluorescence indicated that HAβ1-tubulin incorporated into all classes of interphase and spindle microtubules as well as microtubule organizing centers. The sensitivity of the cells expressing HAβ1-tubulin to Colcemid and taxol was unchanged. A 210 kD microtubule associated protein (MAP) remained associated with microtubules that incorporate HAβ1-tubulin. The synthesis of both endogenous β-tubulin and HAβ1-tubulin was repressed by colchicine. The HAβ1-tubulin incorporated into microtubules to the same extent as the endogenous β-tubulin, and the overall extent of microtubule assembly in transfected cells was unchanged. Finally, trasfected cells had normal growth rates and morphologies. When effects on endogenous tubulin production were measured, it was found that expression of the HAβ1-tubulin reduced the synthesis of endogenous wild-type β-tubulin but increased the synthesis of α-tubulin. At steady state, a small increase in total tubulin consistent with the increased synthesis of α-tubulin was found. The results indicate that expression of excess exogenous β-tubulin perturbs the synthesis of endogenous α-tubulin in a manner that is not easily explained by current models of tubulin regulation. The changes in tubulin synthesis along with degradation of excess tubulin subunits may reflect mechanisms that exist to ensure coordinate levels of α- and β-tubulin for assembly. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970310403
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  • 8
    Electronic Resource
    Electronic Resource
    Order-disorder in T, T′, and T* phase: Superconductors and related materials (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 30 (1995), S. 193-207 
    Details
    ISSN: 1059-910X
    Keywords: Superconductivity ; n-type superconductors ; Nonstoichiometry ; Superconducting oxides ; T, T′ ; T* structures ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: After reviewing microstructural studies on superconducting materials showing T, T′, and T* structural types, results are presented on the microstructure of some n-type superconductors and related materials prepared with accurate control of the oxygen stoichiometry. Electron microscopy is used to describe the ordering of interstitial oxygen defects in T-type La2NiO4+δ leading to the formation of the n = 2 term of a homologous series with the general formula La8nNi4nO16n+1. Structural transitions and superstructure formation in the Pr2-x-yCexSryCuO4-δ system are reported, where T, T′:;, and T* phases are isolated as a function of both Ce and Sr content. © 1995 Wiley-Liss, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070300302
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  • 9
    Electronic Resource
    Electronic Resource
    Role of amino acid-induced changes in ion fluxes in the regulation of hepatic protein synthesis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 163 (1995), S. 277-284 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Alanine is a powerful stimulator of hepatic protein synthesis whose mechanism of action has not yet been ascertained. The present work aimed to elucidate whether rate changes in ion fluxes accompanying the transport of this amino acid could play a role in the stimulation of protein synthesis. In perfused livers, the utilization of alanine produced a net uptake of K+ of 1.5 μMol/min/liver, a progressively increasing efflux of Ca2+ to reach a maximum of 0.9 μMol/min/liver, and alkalization of the extracellular medium. Inhibition of Na+/K+ exchange by ouabain reversed only the uptake of K+, indicating that this is the main way for the efflux of Na+ cotransported with alanine. In isolated hepatocytes, the uptake of alanine increased the intracellular content of K+ and the cell volume. The following observations suggest that these changes, and not an increased intracellular concentration of Na+, are associated with the stimulation of protein synthesis: 1) Ouabain inhibited the alanine stimulation of L-[3H]-valine incorporation into protein without altering the basal rate of protein labeling; 2) ouabain had no effects on alanine uptake indicating that Na+ influx is not involved in the alanine stimulation of protein synthesis; 3) disruption of Na+ gradient across the plasma membrane by specific ionophores, monensin and gramicidin D, inhibited both basal and alanine-stimulated protein synthesis, but substitution of extracellular Na+ by K+ did not prevent the stimulatory action of alanine. The observation that hypotonic buffer enhanced protein synthesis to the same degree than alanine in liver cells indicates that alanine-induced cell swelling could be sufficient to stimulate protein synthesis. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041630208
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  • 10
    Electronic Resource
    Electronic Resource
    DNA Sequence Analysis of a 23 002 bp DNA Fragment of the Right Arm of Saccharomyces cerevisiae Chromosome VII (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 13 (1997), S. 357-363 
    Details
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; yeast genome ; genome sequencing ; chromosome VII ; QCR9 ; UBR1 ; TYS1 ; TFG1 ; HGH1 ; BUB1 ; tRNALeu3 ; tRNATrp ; tRNALys1 ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We report the sequence of a 23 002 bp fragment located on the right arm of Saccharomyces cerevisiae chromosome VII. Analysis of this region revealed 14 complete open reading frames (ORFs) with more than 300 base pairs. Six of them correspond to previously known genes. G7164 is the QCR9 gene coding for subunit 9 of the cytochrome c reductase; G7168 is UBR1, encoding an ubiquitin protein ligase; G7522 is the TYS1 gene, which encodes for the tyrosyl tRNA synthetase; G7526 is TFG1, the gene coding for the RNA polymerase transcription initiation factor TFIIF (factor G); G7538 is the gene HGH1 which encodes a protein related to the mammalian HMG1 and HMG2 proteins. G7542 is the BUB1 gene which encodes a ser/thr protein kinase involved in spindle assembly during the cell cycle. One of the ORFs, G7553, shares significant homologies with the gene UTR2 from S. cerevisiae. None of the seven remaining ORFs shows similarity to any of the sequences within the public databases. Three ORFs are internal ORFs of the above-described known genes, and two small ORFs are completely contained in larger ORFs on the complementary strand, and therefore probably do not correspond to real genes. This region also contains three genes specifying tRNAs for Leu, Lys and Trp, and several LTR elements. The sequence described in this paper has been deposited in the EMBL data library under the Accession Number X99074. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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