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121.
The effects of temperature acclimation and acute temperature change were investigated in postprandial green shore crabs, Carcinus maenas. Oxygen uptake, gut contractions and transit rates and digestive efficiencies were measured for crabs acclimated to either 10 °C or 20 °C and subsequently exposed to treatment temperatures of 5, 15, or 25 °C. Temperature acclimation resulted in a partial metabolic compensation in unfed crabs, with higher oxygen uptake rates measured for the 10 °C acclimated group exposed to acute test temperatures. The Q10 values were higher than normal, probably because the acute temperature change prevented crabs from fully adjusting to the new temperature. Both the acclimation and treatment temperature altered the characteristics of the specific dynamic action (SDA). The duration of the response was longer for 20 °C acclimated crabs and was inversely related to the treatment temperature. The scope (peak oxygen consumption) was also higher for 20 °C acclimated crabs with a trend towards an inverse relationship with treatment temperature. Since the overall SDA (energy expenditure) is a function of both duration and scope, it was also higher for 20 °C acclimated crabs, with the highest value measured at the treatment temperature of 15 °C. The decline in total SDA after acute exposure to 5 and 25 °C suggests that both cold stress and limitations to oxygen supply at the temperature extremes could be affecting the SDA response. The contractions of the pyloric sac of the foregut region function to propel digesta through the gut, and contraction rates increased with increasing treatment temperature. This translated into faster transit rates with increasing treatment temperatures. Although pyloric sac contractions were higher for 20 °C acclimated crabs, temperature acclimation had no effect on transit rates. This suggests that a threshold level in pyloric sac contraction rates needs to be reached before it manifests itself on transit rates. Although there was a correlation between faster transit times and the shorter duration of the SDA response with increasing treatment temperature, transit rates do not make a good proxy for calculating the SDA characteristics. The digestive efficiency showed a trend towards a decreasing efficiency with increasing treatment temperature; the slower transit rates at the lower treatment temperatures allowing for more efficient nutrient absorption. Even though metabolic rates of 10 °C acclimated crabs were higher, there was no effect of acclimation temperature on digestive efficiency. This probably occurred because intracellular enzymes and digestive enzymes are modulated through different control pathways. These results give an insight into the metabolic and digestive physiology of Carcinus maenas as it makes feeding excursions between the subtidal and intertidal zones. 相似文献
122.
C E Grimshaw D A Matthews K I Varughese M Skinner N H Xuong T Bray J Hoch J M Whiteley 《The Journal of biological chemistry》1992,267(22):15334-15339
Kinetic constants for the interaction of NADH and NADPH with native rat dihydropteridine reductase (DHPR) and an Escherichia coli expressed mutant (D-37-I) have been determined. Comparison of kcat and Km values measured employing quinonoid 6,7-dimethyldihydropteridine (q-PtH2) as substrate indicate that the native enzyme has a considerable preference for NADH with an optimum kcat/Km of 12 microM-1 s-1 compared with a figure of 0.25 microM-1 s-1 for NADPH. Although the mutant enzyme still displays an apparent preference for NADH (kcat/Km = 1.2 microM-1 s-1) compared with NADPH (kcat/Km = 0.6 microM-1 s-1), kinetic analysis indicates that NADH and NADPH have comparable stickiness in the D-37-I mutant. The dihydropteridine site is less affected, since the Km for q-PtH2 and K(is) for aminopterin are unchanged and the 14-26-fold synergy seen for aminopterin binding to E.NAD(P)H versus free E is decreased by less than 2-fold in the D-37-I mutant. No significant changes in log kcat and log kcat/Km versus pH profiles for NADH and NADPH were seen for the D-37-I mutant enzyme. However, the mutant enzyme is less stable to proteolytic degradation, to elevated temperature, and to increasing concentrations of urea and salt than the wild type. NADPH provides maximal protection against inactivation in all cases for both the native and D-37-I mutant enzymes. Examination of the rat DHPR sequence shows a typical dinucleotide binding fold with Asp-37 located precisely in the position predicted for the acidic residue that participates in hydrogen bond formation with the 2'-hydroxyl moiety of all known NAD-dependent dehydrogenases. This assignment is consistent with x-ray crystallographic results that localize the aspartate 37 carboxyl within ideal hydrogen bonding distance of the 2'- and 3'-hydroxyl moieties of adenosine ribose in the binary E.NADH complex. 相似文献
123.
124.
Narimen Yousfi Raouf Nader Rekik Cristiano Eirale Rodney Whiteley Abdulaziz Farooq Montassar Tabben 《Chronobiology international》2013,30(10):1385-1390
ABSTRACTPrevious literature suggests that human behaviour and physiology are somehow altered by the moon-cycle, with particular emphasis on poorer sleep quality and increased aggressive behaviour during full moon. The latter variables can negatively impact athletes’ recovery and increase the likelihood of injury resulting from collision with another athlete. Therefore, the current study aimed to investigate the association between the lunar cycle and injury risk in professional football players (soccer). We monitored injuries and player exposure in the premier professional league in Qatar during four consecutive seasons (2013–2014 through 2016–2017). Acute (sudden-onset traumatic) injuries (n = 1184; 587 from contact with another player and 597 without player contact) recorded during matches and training were classified according to the lunar cycle characteristics on the date of injury: (i) moon illumination, (ii) lunar distance from earth and (iii) tidal coefficient, acquired from the lunar calendar and tide tables. We used a Poisson regression model to examine the relationship between injury risk and lunar cycle characteristics. We did not detect any association between injury risk and moon illumination, earth-to-moon distance or tidal coefficient, not for all acute injuries, nor for contact and non-contact injuries when examined separately. The findings suggest that the full moon or new moon or the gravitational pull have no effect on football injuries. Thus, organisers need not consult moon or tide tables when planning future event schedules. 相似文献
125.
Many biological processes in the cell are linked to RNA metabolism and therefore have implications for a wide range of biotechnological
applications. The processing and degradation of RNA plays an important role in RNA metabolism with often the same enzymes
being involved in both processes. In this review, we highlight the dynamic nature of the structural components of the Escherichia coli RNA degradosome which is a large multiprotein complex that plays an important role in RNA degradation. The activities of
the individual components of the degradosome are also discussed. The RNA degradosome forms part of the bacterial cytoskeleton
and associated proteins, such as molecular chaperones, may aid in the compartmentalization of enzymatic activities and cytoskeletal
organization. An enhanced understanding of the components of the RNA degradosome in other bacterial species will certainly
aid in their evaluation as potential antimicrobial agents. 相似文献
126.
DNA-RNA molecular hybridization experiments were performed to compare sequences of RNA that are present in the unfertilized egg, gastrula, trochophore, early veliger, mid-veliger, and adult with that population that is being synthesized by the midveliger. The conditions of annealing were designed to examine the more common RNA sequences that are complementary to the highly reiterated sequences of the genome. It was found that the RNA of the unfertilized egg competes extensively with RNA sequences that are being synthesized by this relatively late larval stage. These RNA sequences are present at a lower concentration in RNA preparations extracted from unfertilized eggs as compared to later stages. Autoradiographs of 3H-uridine labeled veligers indicate that the pulse-labeled RNA used in these experiments represents that synthesized by a wide variety of larval tissues. These results are discussed with respect to differences in RNA metabolism and determination between regulative and mosaic embryos. 相似文献
127.
Zachary L. Robinson Jason A. Coombs Mark Hudy Keith H. Nislow Benjamin H. Letcher Andrew R. Whiteley 《Molecular ecology》2017,26(17):4418-4433
Genetic rescue is an increasingly considered conservation measure to address genetic erosion associated with habitat loss and fragmentation. The resulting gene flow from facilitating migration may improve fitness and adaptive potential, but is not without risks (e.g., outbreeding depression). Here, we conducted a test of genetic rescue by translocating ten (five of each sex) brook trout (Salvelinus fontinalis) from a single source to four nearby and isolated stream populations. To control for the demographic contribution of translocated individuals, ten resident individuals (five of each sex) were removed from each recipient population. Prior to the introduction of translocated individuals, the two smallest above‐barrier populations had substantially lower genetic diversity, and all populations had reduced effective number of breeders relative to adjacent below‐barrier populations. In the first reproductive bout following translocation, 31 of 40 (78%) translocated individuals reproduced successfully. Translocated individuals contributed to more families than expected under random mating and generally produced larger full‐sibling families. We observed relatively high (>20%) introgression in three of the four recipient populations. The translocations increased genetic diversity of recipient populations by 45% in allelic richness and 25% in expected heterozygosity. Additionally, strong evidence of hybrid vigour was observed through significantly larger body sizes of hybrid offspring relative to resident offspring in all recipient populations. Continued monitoring of these populations will test for negative fitness effects beyond the first generation. However, these results provide much‐needed experimental data to inform the potential effectiveness of genetic rescue‐motivated translocations. 相似文献
128.
A new genus, Regiocrella, is described with two species, R. camerunensis and R. sinensis, based on specimens collected in Cameroon and China. Both species are parasitic on scale insects (Coccidae, Homoptera). Morphological and molecular evidence place the new genus in the Clavicipitaceae (Hypocreales), despite its combination of characters that are atypical of that family; Regiocrella is characterized by having perithecia partly immersed in a subiculum, noncapitate asci, unicellular fusiform ascospores and pycnidial-acervular conidiomata. The two new species, R. camerunensis and R. sinensis, are distinguished based on ascospore and perithecium size. Morphological characters were evaluated and compared to other genera in the Clavicipitaceae, especially those parasitic on scale insects or with pycnidial-acervular anamorphs or synanamorphs (i.e. Aschersonia, Ephelis or Sphacelia): Atkinsonella, Balansia, Claviceps, Epichl?e, Hypocrella, Myriogenospora and Neoclaviceps. The phylogenetic relationships of Regiocrella were examined with three gene loci: large subunit nuclear ribosomal DNA (LSU), translation elongation factor 1-alpha (TEF), and RNA polymerase II subunit 1 (RPB1). The results of this study confirm that Regiocrella is distinct from other genera in the Clavicipitaceae and that its two species form a monophyletic group. Regiocrella is shown to be closely related to the scale insect pathogen Hypocrella and the plant-associated genera Balansia, Claviceps, Epichl?e, Myriogenospora and Neoclaviceps. This study also provides insights into the evolution of pycnidial-acervular conidiomata and scale insect parasitism within the Clavicipitaceae. Plant-associated genera form a monophyletic group correlated with Clavicipitaceae subfamily Clavicipitoideae sensu Diehl. We also demonstrate that scale insect parasites have multiple evolutionary origins within the family and genera with pycnidial-acervular anamorphs or synanamorphs have a single origin. 相似文献
129.
130.
Q. Y. Deng B. Yang J. F. Wang C. G. Whiteley X. N. Wang 《Biotechnology letters》2009,31(10):1505-1509
A novel biological method for the synthesis of platinum nanoparticles using the horse spleen apoferritin (HSAF) is reported.
When HSAF was incubated with K2PtCl6 at 23°C) for 48 h followed by subsequent reduction with NaBH4 it resulted in the formation of spherical platinum nanoparticles, size 4.7 ± 0.9 nm, with narrow particle size distribution
confirmed by transmission electron microscopy and energy dispersive X-ray analysis. As the initial platinum concentration
increased through 0.155, 0.31, 0.465 to 0.62 mM the efficiency of its removal from solution by the apoferritin was 99, 99,
84 and 71% respectively. The maximum uptake of platinum salt per mM apoferritin was estimated at 12.7 mmol l−1 h−1. These results clearly indicate that the HSAF protein cage can successfully serve as a suitable size-constrained support
matrix for the biological synthesis of platinum nanoparticles. 相似文献