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51.
Biosynthesis of phytoene from isopentenyl pyrophosphate by a Neurospora enzyme system. 总被引:1,自引:0,他引:1
An enzyme system catalyzing the conversion of isopentenyl pyrophosphate to phytoene has been isolated from Neurospora crassa mycelia. This enzyme system shows an absolute requirement for Mg?, but no other cofactors. Cultures of N. crassa exhibit a low level of phytoene synthesizing activity when grown in the dark. A 2-min in vivo blue light irradiation results in a ninefold increase in activity after 24 h. This increase is dependent on the duration of the light treatment and is inhibited by cycloheximide. A similar blue light-induced elevation of phytoene synthesizing activity was demonstrated in an albino-1 mutant. This enzyme activity was not found in either dark-grown or irradiated cultures of an albino-2 or an albino-3 mutant. 相似文献
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R Podstawski DJ Choszcz S Konopka J Klimczak M Starczewski 《Biology of sport / Institute of Sport》2014,31(4):315-321
The aim of the study was to evaluate anthropometric characteristics as determinants of 500 m rowing ergometer performance in physically inactive collegiate females. In this cross-sectional study, which included 196 collegiate females aged 19-23 years not participating in regular physical activities, body mass (BM), body height (BH), length of upper limbs (LA), length of lower limbs (LL), body mass index (BMI), slenderness index (SI), and the Choszcz-Podstawski index (CPI) were measured and a stepwise multiple regression analysis was performed. Participants performed 500 m maximal effort on a Concept II rowing ergometer. BM, BH, LA, LL, and the BMI, SI and CPI indices were found to be statistically significant determinants of 500 m performance. The best results (T) were achieved by females whose BH ranged from 170 to 180 cm, with LA and LL ranging from 75 to 80 cm and 85 to 90 cm, respectively. The best fitting statistical model was identified as: T = 11.6793 LR – 0.1130 LR2 – 0.0589 LN2 + 29.2157 CPI2 + 0.1370 LR·LN - 2.6926 LR·CPI – 211.7796. This study supports a need for additional studies focusing on understanding the importance of anthropometric differences in rowing ergometer performance, which could lead to establishing a better quality reference for evaluation of cardiorespiratory fitness tested using a rowing ergometer in collegiate females. 相似文献
54.
Spurgeon DW 《Environmental entomology》2012,41(2):415-419
Several aspects of the basic biology of the western tarnished plant bug, Lygus hesperus Knight, are poorly known despite the economic importance of this species. Among these are the factors regulating the adult diapause. Reports of recent studies questioned the validity of earlier reports of diapause in L. hesperus, in part because of the demonstrated loss of diapause response in insects obtained from long-standing laboratory colonies. However, use of laboratory reared insects would facilitate additional diapause research, so long as those insects exhibit a diapause response similar to that of the field population. L. hesperus, originating as eggs from field-collected insects, were reared in the laboratory for four generations to examine corresponding changes in selected biological characteristics. Over the course of the four generations, incidence of diapause in both L. hesperus genders decreased whereas the frequency of oviposition by virgin females increased. Measurable changes were not observed in frequency of occurrence of a specific fat body type (glass bead fat) or nymphal development time. These results suggest L. hesperus used in diapause research should be as close to the field population as possible, but no further removed than three generations. Results further demonstrate variability among different biological characteristics in their responses to selection from laboratory rearing. Collectively, these findings demonstrate the importance of understanding the influences of rearing on specific biological characteristics under study, and the need to verify the similarity of laboratory-reared insects to their native counterparts in studies used to draw inferences regarding the field population. 相似文献
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Willem Proesmans Christopher Andrews Alan Gray Rob Griffiths Aidan Keith Uffe N. Nielsen David Spurgeon Richard Pywell Bridget Emmett Adam J. Vanbergen 《Ecology and evolution》2022,12(4)
Cattle grazing profoundly affects abiotic and biotic characteristics of ecosystems. While most research has been performed on grasslands, the effect of large managed ungulates on forest ecosystems has largely been neglected. Compared to a baseline seminatural state, we investigated how long‐term cattle grazing of birch forest patches affected the abiotic state and the ecological community (microbes and invertebrates) of the soil subsystem. Grazing strongly modified the soil abiotic environment by increasing phosphorus content, pH, and bulk density, while reducing the C:N ratio. The reduced C:N ratio was strongly associated with a lower microbial biomass, mainly caused by a reduction of fungal biomass. This was linked to a decrease in fungivorous nematode abundance and the nematode channel index, indicating a relative uplift in the importance of the bacterial energy‐channel in the nematode assemblages. Cattle grazing highly modified invertebrate community composition producing distinct assemblages from the seminatural situation. Richness and abundance of microarthropods was consistently reduced by grazing (excepting collembolan richness) and grazing‐associated changes in soil pH, Olsen P, and reduced soil pore volume (bulk density) limiting niche space and refuge from physical disturbance. Anecic earthworm species predominated in grazed patches, but were absent from ungrazed forest, and may benefit from manure inputs, while their deep vertical burrowing behavior protects them from physical disturbance. Perturbation of birch forest habitat by long‐term ungulate grazing profoundly modified soil biodiversity, either directly through increased physical disturbance and manure input or indirectly by modifying soil abiotic conditions. Comparative analyses revealed the ecosystem engineering potential of large ungulate grazers in forest systems through major shifts in the composition and structure of microbial and invertebrate assemblages, including the potential for reduced energy flow through the fungal decomposition pathway. The precise consequences for species trophic interactions and biodiversity–ecosystem function relationships remain to be established, however. 相似文献
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Evolution at the tip and base of the X chromosome in an African population of Drosophila melanogaster 总被引:1,自引:0,他引:1
Hitchhiking effects of advantageous mutations have been invoked to explain
reduced polymorphism in regions of low crossing-over in Drosophila. Besides
reducing DNA heterozygosity, hitchhiking effects should produce strong
linkage disequilibrium and a frequency spectrum skewed toward an excess of
rare polymorphisms (compared to the neutral expectation). We measured DNA
polymorphism in a Zimbabwe population of D. melanogaster at three loci,
yellow, achaete, and suppressor of forked, located in regions of reduced
crossing-over. Similar to previously published surveys of these genomic
regions in other populations, we observed low levels of nucleotide
variability. However, the frequency spectrum was compatible with a neutral
model, and there was abundant evidence for recombination in the history of
the yellow and ac genes. Thus, some aspects of the data cannot be accounted
for by a simple hitchhiking model. An alternative hypothesis, background
selection, might be compatible with the observed patterns of linkage
disequilibrium and the frequency spectrum. However, this model cannot
account for the observed reduction in nucleotide heterozygosity. Thus,
there is currently no satisfactory theoretical model for the data from the
tip and base of the X chromosome in D. melanogaster.
相似文献
60.
Oligogalacturonic acids (OGAs), derived from plant cell wall pectin, have
been implicated in a number of signal transduction pathways involved in
growth, development and defense responses of higher plants. This study
investigates the size range of OGAs capable of inducing ethylene synthesis
in tomato plants, and demonstrates that in contrast with many other
effects, only short chain OGAs are active. Oligomers across a range of DP
from 2-15 were separated and purified to homogeneity by QAE-Sephadex anion
exchange chromatography using a novel elution system. The OGAs were applied
to tomato plants and assayed for their ability to induce ethylene gas
release and changes in steady state levels of mRNA encoding the ethylene
forming enzyme aminocyclopropane-1-carboxylic acid oxidase (ACO). The study
demonstrated that only OGAs in the size range of DP4-6 were active both in
eliciting ACO expression and in the production of ethylene.
相似文献