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  • 1
    Electronic Resource
    Electronic Resource
    Effect of temperature on the occluding junctions of monolayers of epithelioid cells (MDCK) (1984)
    Springer
    The journal of membrane biology 79 (1984), S. 175-184 
    Details
    ISSN: 1432-1424
    Keywords: epithelial monolayers ; MDCK cells ; occluding junctions ; intramembrane particles ; electrical resistance ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary In previous works it was demonstrated that the monolayer of MDCK cells behaves as a leaky epithelium where the electrical resistance across reflects the sealing capacity of the occluding junction. In the present work we study whether this sealing capacity can be modified by temperature and whether this is accompanied by changes in the structure of the occluding junction. Monolayers were prepared on disks of nylon cloth coated with collagen and mounted as a flat sheet between two Lucite chambers. The changes in resistance elicited by temperature were large (306% between 3 and 37°C), fast (less than 2 sec), and reversible. An Arrhenius plot of conductance versus the inverse of temperature shows a broken curve (between 22 and 31°C), and the activation energies calculated (3.2 and 4.0 kcal·mol−1) fall within the expected values for processes of simple diffusion. The morphology of the occuluding the number of evaluated in freeze-fracture replicas by counting the number of strands and the width of the band occupied by the junction every 133 nm. In spite of the change by 306% of the electrical resistance and the phase transition, we were unable to detect any appreciable modification of the morphology of the occluding junction. Since the freeze-fracture replicas also show a density of intramembrane particles (IMP) different in the apical from that in the basolateral regions of the plasma membrane, as well as differences between faceE and faceP, we also investigated whether this is modified by temperature. Cold increases the population of IMP, but does not affect their polarization with the incubation time it takes to elicit changes in electrical resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01872121
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  • 2
    Electronic Resource
    Electronic Resource
    Reproduction of Diaeretiella rapae on Russian wheat aphid hosts at different temperatures (1997)
    Springer
    Entomologia experimentalis et applicata 82 (1997), S. 159-166 
    Details
    ISSN: 1570-7458
    Keywords: Diaeretiella rapae ; reproduction ; life-tables ; temperature ; Diuraphis noxia ; biological control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Diaeretiella rapae (M'Intosh), a polyphagous and cosmopolitan parasite of aphids, was imported from China to the USA for biological control of Diuraphis noxia (Mordwilko), a pest of small grains. We studied several aspects of its biology on D. noxia hosts in the laboratory at 3 constant temperatures, 10.0, 21.1, and 26.7 °C. Females lived significantly longer than males at all 3 temperatures, and longevity was greatest at 10 °C, followed by 21.1 and 26.7 °C. Fecundity (= number of mummies) did not differ significantly among the 3 temperatures studied. The ovarian egg-load was 129.1 ± 9.3, and was significantly affected by the size of adult females. A pre-oviposition period ± 0.26 days) was detected at 10 °C, but not at the other temperatures. Pre-imaginal survivorship was similar among temperatures, while R o and T c decreased with temperature, and r m increased with temperature. The offspring sex ratio (proportion females) was lowest at 26.7 °C, and similar between 10.0 and 21.1 °C. In addition, the offspring sex ratio significantly declined with the age of the female parent. The suitability of D. rapae for colonization against D. noxia in North America is discussed in relation to its responses to temperature and the climate of its home range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1002929500786
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of temperature and food concentration on body size, weight and lipid content of two Calanoid copepod species (1988)
    Springer
    Hydrobiologia 167-168 (1988), S. 201-210 
    Details
    ISSN: 1573-5117
    Keywords: copepods ; temperature ; food ; size ; weight ; lipid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two species of Copepoda Temora longicornis (Müller) and Pseudocalanus elongatus (Boeck) were cultured continuously in the laboratory. Four and three generations, respectively, were raised at 16 different combinations of temperature and food concentration. Prosome length and ash-free dry weight were measured in the adult stage and in Pseudocalanus also in copepodite stage I, and the relation between length and weight was established. In Pseudocalanus also the relative amount of lipid was estimated. Prosome length and length-specific body weight (condition factor) were positively correlated with food concentration. Lipid content in Pseudocalanus was also strongly affected by the concentration of food. Prosome length was negatively correlated with temperature. However, length-specific body weight in Temora was positively correlated with temperature. Therefore, at higher temperature Temora was smaller, but heavier per unit body length. In Pseudocalanus a similar but less significant influence of temperature on length-specific weight was found; lipid content was not significantly influenced by the temperature. Females of Temora had larger length-specific weights than males. In Pseudocalanus the opposite was found, coinciding with a higher lipid content in males than in females. It is discussed that at natural concentrations of phytoplankton body size and weight of copepods are reduced in the North Sea during the major part of the growing-season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026306
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  • 4
    Electronic Resource
    Electronic Resource
    On the Influence of Hot-Water Discharges on Phytoplankton Communities from a Coastal Zone of the Gulf of Mexico (2000)
    Springer
    Water, air & soil pollution 119 (2000), S. 209-230 
    Details
    ISSN: 1573-2932
    Keywords: microalgal communities ; photosynthesis ; temperature ; thermal pollution ; tropical coast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The influence of thermal discharges on thephytoplankton community from a coastal zone of theGulf of Mexico was evaluated through their structureand photosynthetic behaviour focusing on responses tochanges in light and temperature. Biological andphysicochemical parameters were measured over a periodof two years in an area with permanent hot waterdischarges from a thermoelectric plant. Thetemperature in the sampling area ranged from 23.5 to36 °C with differences between the coldest andthe hottest station from 5.3 to 9.2 °C.Photosynthetically active radiation (PAR) were reducedin the discharge area water column, due to turbulence.One hundred and one different taxa were identifiedwith a strong predominance of Diatoms. The chlorophylla concentration ranged from 0.3 to 6.1 μgL-1, with highest values of thephaeophytin:chlorophyll ratio found at the hottest station.The community structure did not show significativedifferences among sampling stations with respect totemperature variations. However, in the algalassemblages influenced by thermal discharges, it waspossible to observe alterations in the photosynthesisbehaviour. Phytoplankton response to short termphotosynthesis experiments was segregated according tocomposition and origin of microalgal assemblages.Samples with larger heterogeneous composition had moreconsistent oxygen production responses. Algalcommunities exposed to hot effluent showed differentdegrees of photosynthesis rate reduction,higher light requirements (〉500 μE m2 s-1)and lower temperature (25 °C) to achieve Pmaxthan algae sampled in sites without such exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005161309609
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  • 5
    Electronic Resource
    Electronic Resource
    Pollen content study of the lower atmosphere in León (Spain) by use of a tethered balloon (2000)
    Springer
    Aerobiologia 16 (2000), S. 187-191 
    Details
    ISSN: 1573-3025
    Keywords: aerobiology ; airborne pollen ; León (Spain) ; lower atmosphere ; meteorology ; mixing ratio ; relative humidity ; tethered balloon ; temperature ; wind speed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was undertaken in order to understand thebehaviour of airborne pollen grains, namely therelationship between their concentrations andconcomitant meteorological parameters, at differentaltitudes (ground level, 200, 400 and 600 m) of thelower atmosphere and its daily variations over onesite (the experimental farm of the University ofLeón). The experimental design involved a tetheredballoon (2.25 m3), an ADAS remote meteorologicalstation and an original radio controlled three headedpollen and spore sampler (called GABIS) using theRotorod design. Each head sampled a differentaltitude, while two control samples were taken atground level. Twenty-one takeoffs could be realized inthe 5 weeks period between end of May and end of June1997. Sampling was done early in the morning and sampling time at each altitudewas of 15 minutes. Results show that 45 differenttypes of pollen grains could be collected at this timeof the year and that significant variations could beobserved in the behaviour of the pollen cloud on a dayto day basis, probably because of differentmeteorological situations. Contrary to what isgenerally believed, pollen was in most cases moreabundant at higher altitude – on average by 30% ascompared to ground level – making evident anaerobiological layer of transport at about 500 m aboveground. This was especially the case for trees (Quercus and Castanea). The atmosphere MixingRatio was the most explicative factor at 200 m, whiletemperature dominated significance analysis at both400 and 600 m.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007685513925
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