ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Blackwell Science Ltd  (308)
  • 2000-2004  (308)
  • 1980-1984
  • 2004  (308)
  • 1
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Goldfish Carassius auratus embryos were subjected to artificial ultraviolet-B (UVB) radiation (280–320 nm) at various times during development to evaluate the effects on production of anatomically normal larvae. The UVB radiation used in these experiments included a higher proportion of shorter wavelengths compared to the natural spectrum. The development of embryos exposed to UVB for 2 or 4 h at 26 h post-fertilization was severely impaired whereas similar exposures at 50 or 74 h post-fertilization had no effect. A 2 h exposure to UVB commencing at 2 h post-fertilization did not adversely affect embryonic development whereas a 4 h exposure to a lower dose did. At 50 h post-fertilization, when embryos were normally resistant to UVB, denial of access to visible light and UVA before, during and after exposure to UVB caused impairment of development. Analysis of DNA fragment length after incubation with an endonuclease suggested that UVB damage at 50 h was caused by formation of pyrimidine dimers. This study demonstrated that the sensitivity of goldfish embryos to UVB varied during development and that resistance to UVB in later developmental stages included a photorepair mechanism.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The sequencing of the entire genetic complement of Streptomyces coelicolor A3(2) has been completed with the determination of the 365 023 bp sequence of the linear plasmid SCP1. Remarkably, the functional distribution of SCP1 genes somewhat resembles that of the chromosome: predicted gene products/functions include ECF sigma factors, antibiotic biosynthesis, a gamma-butyrolactone signalling system, members of the actinomycete-specific Wbl class of regulatory proteins and 14 secreted proteins. Some of these genes are among the 18 that contain a TTA codon, making them targets for the developmentally important tRNA encoded by the bldA gene. RNA analysis and gene fusions showed that one of the TTA-containing genes is part of a large bldA-dependent operon, the gene products of which include three proteins isolated from the spore surface by detergent washing (SapC, D and E), and several probable metabolic enzymes. SCP1 shows much evidence of recombinational interactions with other replicons and transposable elements during its history. For example, it has two sets of partitioning genes (which may explain why an integrated copy of SCP1 partially suppressed the defective partitioning of a parAB-deleted chromosome during sporulation). SCP1 carries a cluster of probable transfer determinants and genes encoding likely DNA polymerase III subunits, but it lacks an obvious candidate gene for the terminal protein associated with its ends. This may be related to atypical features of its end sequences.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Seven years of carbon dioxide flux measurements indicate that a ∼90-year-old spruce dominated forest in Maine, USA, has been sequestering 174±46 g C m−2 yr−1 (mean±1 standard deviation, nocturnal friction velocity (u*) threshold 〉0.25 m s−1). An analysis of monthly flux anomalies showed that above-average spring and fall temperatures were significantly correlated with greater monthly C uptake while above-average summer temperatures were correlated with decreased net C uptake. Summer months with significantly drier or wetter soils than normal were also characterized by lower rates of C uptake. Years with above-average C storage were thus typically characterized by warmer than average spring and fall temperatures and adequate summer soil moisture.Environmental and forest–atmosphere flux data recorded from a second tower surrounded by similar forest, but sufficiently distant that flux source regions (‘footprints’), did not overlap significantly showed almost identical temperature and solar radiation conditions, but some differences in energy partitioning could be seen. Half-hourly as well as integrated (annual) C exchange values recorded at the separate towers were very similar, with average annual net C uptake differing between the two towers by 〈6%. Interannual variability in net C exchange was found to be much greater than between tower variability. Simultaneous measurements from two towers were used to estimate flux data uncertainty from a single tower. Carbon-flux model parameters derived independently from each flux tower data set were not significantly different, demonstrating that flux towers can provide a robust method for establishing C exchange model parameters.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Grass and forage science 59 (2004), S. 0 
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Annual ryegrass (Lolium multiflorum Lam.) is a primary forage resource for livestock producers throughout the south-eastern USA during the winter-growing season. It is important for livestock producers to begin grazing annual ryegrass as early as possible and any management practices maximizing early season production could be beneficial. To assess the impact of seeding rate on subsequent yield, yield distribution, quality, seedling density, and end-of-season plant and tiller density, a 2-year study was initiated at four locations in Louisiana. Three annual ryegrass cultivars, varying in seed size, were established at four seeding rates based on pure live seed (PLS) rates of 400, 800, 1200 and 1600 PLS m−2. There was no advantage in total yield from increasing seeding rates beyond 800 PLS m−2. However, first-harvest yields increased from 360 to 930 kg dry matter (DM) ha−1 as seeding rate increased from 400 to 1600 PLS m−2. Crude protein and neutral-detergent fibre concentrations, and in vitro DM digestibility, were not affected by seeding rate. Seedling density and end-of-season plant numbers increased as seeding rate increased. However, stems per plant decreased as seeding rate increased, indicating compensatory tillering for the reduced plant numbers observed at the lower seeding rates. These results indicate first-harvest yield can be increased by planting at higher seeding rates but total yields are not increased.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Perch Perca fluviatilis recruitment (based on the catch per unit effort, CPUE, of 2 or 3 year male perch) varied greatly from 1941 to 1995 in Windermere, U.K., with year class strengths strongly synchronous between the two basins of this temperate, mesotrophic lake. Statistically significant modified Ricker (Saila-Lorda) stock-recruitment curves could be fitted to data from three of four sampling sites, while the presence of widespread disease and late summer water temperature were also important explanatory variables. Multiple-regression analyses revealed no influences of pike Esox lucius recruitment, zooplankton abundance, or the climatic influences (i.e. North Atlantic Oscillation and displacement of the summer position of the Gulf Stream) on perch recruitment over and above associated influences from temperature. Fitted models realistically explained up to c. 60% of the observed variation in perch recruitment.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The sagitta of Kurtus gulliveri was ovate, moderately thick with the following attributes: lateral surface convex, mesial surface flat; dorsal margin sinuate, posterior margin rounded ventrally, ventral margin rounded and irregular; sulcus divided into ostium and cauda by constriction of dorsal and ventral margins, heterosulcoid, colliculum heteromorph; dorsal depression large and distinct, ventral groove close to margin in larger otoliths; rostrum broad and antirostrum small, separated by wide, shallow excisural notch. Otolith size was moderate, average 4·6% standard length (LS), typical for a perciform. Annuli on 78 whole sagittae were read, and 15% of these were transversely sectioned for verification of the annuli. Males ranged from 94 to 235 mm LS and females from 95 to 284 mm LS. There was little difference in size distribution of the sample between the sexes, perhaps due to a 6 month spawning season over which young were continually added to the population. Some sexual dimorphism was noted, however, as age 2 year females were significantly larger than males of the same age. The largest fish aged was a 284 mm LS, 3 year-old female, and the oldest age reached was 4 years by two males. It appears likely that most spawning females are ≥2 years old, but some larger 1 year old fish may attain sexual maturity.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Depending on population, wild Fraser River sockeye salmon Oncorhynchus nerka travel distances of 〈100 km to 〉1100 km and ascend elevations ranging from near sea-level to 1200 m to reach spawning areas. Populations embarking on distant, high elevation migrations (i.e. Early Stuart, Chilko and Horsefly populations) began their upriver spawning migrations with higher densities of somatic energy (c. 9·2 to 9·8 MJ kg−1) and fewer eggs (c. 3200 to 3800) than populations making shorter, low elevation migrations (i.e. Weaver and Adams; c. 7·1 to 8·3 MJ kg−1 gross somatic energy and c. 4300 to 4700 eggs). Populations making difficult upriver migrations also had morphologies that were smaller and more fusiform than populations making less difficult migrations, traits that may facilitate somatic energy conservation by reducing transport costs. Indeed, fish travelling long distances expended less somatic energy per unit of migratory difficulty than those travelling shorter distances (2·8 to 3·8 kJ v. 10–1400 kJ). Consistent with evolutionary theory, difficult migrations appear to select for energy efficiency but ultimately fish making more difficult migrations produce fewer eggs, even when differences in body length have been accounted for. Despite large among-population differences in somatic energy at the start of upriver migration, all populations completed migration and spawning, and subsequently died, with c. 4 MJ kg−1 of energy remaining, a level which may reflect a threshold to sustain life.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1474-8673
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Chemistry and Pharmacology , Medicine
    Notes: 1 Prolonged bed rest or exposure to microgravity may cause several alterations in autonomic nervous system response (ANSR). 2 Hindlimb unloading (HU) rats were used as an animal model of simulated microgravity to investigate ANSR changes. The experiments were carried out to investigate the effects of simulated microgravity on the autonomic nervous response of the perfused mesenteric vascular bed (MVB), vas deferens and the colon and duodenum from 2-week HU rats. 3 In MVB preparations of HU rats, the frequency-dependent increases in perfusion pressure with perivascular nerve stimulation (PNS; 8–40 Hz) were inhibited, whereas the noradrenaline (NA) concentration-dependent (1–100 μm) perfusion pressure increases were potentiated. The latter most probably reflected up-regulation of α-adrenergic receptor function. Relaxant responses of NA-precontracted MVB to PNS (4–30 Hz) or isoprenaline were not different between control and HU preparations, while vasodilation induced by the endothelial agonist ACh was reduced. 4 Transmural stimulation (2–40 Hz) induced frequency-dependent twitches of the vas deferens which were reduced in vas deferens of HU rats, while the sensitivity to NA-induced contraction was significantly increased. 5 In the gastroenteric system of HU rat, direct contractile responses to carbachol or tachykinin as well as relaxant or contractile responses to nervous stimulation appeared unchanged both in the proximal colon rings and in duodenal longitudinal strips. 6 In conclusion, HU treatment affects peripheral tissues in which the main contractile mediators are the adrenergic ones such as resistance vessels and vas deferens, probably by reducing the release of neuromediator. This study validates NA signalling impairment as a widespread process in microgravity, which may most dramatically result in the clinical phenotype of orthostatic intolerance.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 49 (2004), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Persistence of zebra mussel populations in river systems probably depends upon the presence of upriver sites capable of hosting self-recruiting adult populations that act as sources of larvae. In this paper we examine the importance of Lake Pepin, a natural riverine lake in the Upper Mississippi River, as an upriver source of larvae to the downstream populations of zebra mussels.2. Field studies and modelling suggest that Lake Pepin plays a major role in maintaining zebra mussel populations in the Upper Mississippi River. Long water residence times in Lake Pepin allow for self-recruitment under the right hydraulic conditions. Larval abundance was low to absent upstream of the lake but increased dramatically downriver in all 3 years of the study. Travel time estimates in the Upper Mississippi River show that newly fertilised larvae drifting out of Lake Pepin can contribute substantially to the major downstream peak in larval abundance. In contrast, backwater and other off-channel sites are unlikely to drive main-channel abundance patterns. Larval abundances in off-channel sites were less than or equal to those in the main channel.3. A key factor in assessing the importance of Lake Pepin as a source population was the abundance of early stage, unshelled larvae. Studies that consider only abundances of older shelled stages (visible by cross polarised lighting) may yield misleading results. Results of this study suggest that efforts to control zebra mussels in the Upper Mississippi River should focus on controlling adult populations within Lake Pepin and reducing or eliminating larvae exiting the lake.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...