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101.
A Magnetic Signature at Io: Initial Report from the Galileo Magnetometer   总被引:1,自引:0,他引:1  
During the inbound pass of the Galileo spacecraft, the magnetometer acquired 1 minute averaged measurements of the magnetic field along the trajectory as the spacecraft flew by Io. A field decrease, of nearly 40 percent of the background jovian field at closest approach to Io, was recorded. Plasma sources alone appear incapable of generating perturbations as large as those observed and an induced source for the observed moment implies an amount of free iron in the mantle much greater than expected. On the other hand, an intrinsic magnetic field of amplitude consistent with dynamo action at Io would explain the observations. It seems plausible that Io, like Earth and Mercury, is a magnetized solid planet.  相似文献   
102.
In our ongoing search for new pharmacologically active leads from Solomon organisms, we have examined the sponge Theonella swinhoei. Herein we report the isolation and structure elucidation of swinholide A (1) and one new macrolide, swinholide J (2). Swinholide J is an unprecedented asymmetric 44-membered dilactone with an epoxide functionality in half of the molecule. The structural determination was based on extensive interpretation of high-field NMR spectra and HRESIMS data. Swinholide J displayed potent in vitro cytotoxicity against KB cells (human nasopharynx cancer) with an IC(50) value of 6 nM.  相似文献   
103.
Cnidarian toxins represent a rich source of biologically active compounds. Since they may act via oxidative stress events, the aim of the present study was to verify whether crude venom, extracted from the jellyfish Pelagia noctiluca, elicits inflammation and oxidative stress processes, known to be mediated by Reactive Oxygen Species (ROS) production, in rats. In a first set of experiments, the animals were injected with crude venom (at three different doses 6, 30 and 60 µg/kg, suspended in saline solution, i.v.) to test the mortality and possible blood pressure changes. In a second set of experiments, to confirm that Pelagia noctiluca crude venom enhances ROS formation and may contribute to the pathophysiology of inflammation, crude venom-injected animals (30 µg/kg) were also treated with tempol, a powerful antioxidant (100 mg/kg i.p., 30 and 60 min after crude venom). Administration of tempol after crude venom challenge, caused a significant reduction of each parameter related to inflammation. The potential effect of Pelagia noctiluca crude venom in the systemic inflammation process has been here demonstrated, adding novel information about its biological activity.  相似文献   
104.
The effects of lactation on the fertility of dairy cows   总被引:1,自引:0,他引:1  
Lactation has been negatively associated with fertility because pregnancy rates in maiden heifers exceed those obtained after first or subsequent calvings. The extent of this difference is less in pasture-fed dairy cows (<10%) than in American Holsteins (>20%) fed grain and conserved forages. The latter cows have pregnancy rates to first insemination and oestrus detection rates of only 40 to 45%. This suggests that the subsequent fertility of inherently fertile Holstein heifers may be severely compromised by high levels of milk production. International comparisons show that pasture-fed dairy cows may experience extended periods of anovulatory anoestrum but have normal fertility (60% pregnancy rate to first insemination) once cycling. The high-producing American Holstein may ovulate within 4 weeks postpartum but is more likely to continue ovulating without being detected in oestrus. Both situations are associated with negative energy balances (NEB) during early lactation. The severity and duration of this NEB may vary with body condition at calving, age or parity, ration formulation, production level and environmental factors. Relative daily milk yield is not an absolute indicator of NEB, because some lower producing cows within a herd have lower feed intakes and more severe energy deficits. NEB is not simple to measure; nonetheless, it is correlated with genetic improvement for milk yield. A positive energy balance, greater weight gain and higher body condition score have all been shown to be positively correlated with plasma progesterone concentrations in early lactation. No studies have investigated the possibility that the rapid increase in metabolic rate at this time may also alter steroid concentrations with consequent effects on oestrous behaviour and fertility. Studies to more precisely define the effects of increasing milk yields in early lactation, especially in Holsteins, may need to be completed in Australia and New Zealand. Oestrus detection rates and pregnancy rates for American Holsteins of less than 50% are accepted widely in the USA. Such low detection rates confound studies on fertility. The objective should be to increase these 2 rates to at least 80% and 60% respectively. This may involve the use of controlled breeding, especially if oestrous behaviour is less overt in high-producing Holstein cows.  相似文献   
105.
106.
This research aimed to investigate erythrodiol, uvaol, oleanolic acid, and maslinic acid scavenging capacities and their effects on cytotoxicity, cell proliferation, cell cycle, apoptosis, reactive oxygen species (ROS) level, and oxidative DNA damage on human MCF-7 breast cancer cell line. The results showed that erythrodiol, uvaol, and oleanolic acid have a significant cytotoxic effect and inhibit proliferation in a dose- and time-dependent manner. At 100 μM, erythrodiol growth inhibition occurred through apoptosis, with the observation of important ROS production and DNA damage, whereas uvaol and oleanolic acid growth inhibition involved cell cycle arrest. Moreover, although all tested triterpenes did not show free radical scavenging activity using ABTS and DPPH assays, they protected against oxidative DNA damage at the concentration 10 μM. Uvaol and oleanolic and maslinic acids, tested at 10 and 100 μM, also reduced intracellular ROS level and prevented H(2)O(2)-induced oxidative injury. Overall, the results suggest that tested triterpenes may have the potential to provide significant natural defense against human breast cancer.  相似文献   
107.
Infectious diseases pose an important extinction risk for a number of endangered carnivore populations. Wild canids are particularly susceptible to generalist pathogens transmitted from domestic dogs - particularly rabies virus and canine distemper virus (CDV). Here we present a review of rabies as a threat to Ethiopian wolves, an endangered canid restricted to a few isolated Afro-alpine ranges in the Ethiopian highlands, and the impact of rabies on the largest population in the Bale Mountains. In the Bale Mountains, two confirmed rabies outbreaks among Ethiopian wolves in 1991-1992 and 2003-2004 were each responsible for over 70% mortality among focal packs and a third rabies outbreak was suspected in 1990. This review also presents an integrated disease management strategy for Ethiopian wolves combining long-term population monitoring, disease surveillance, conventional and emergency vaccination programs, and advanced modelling techniques.  相似文献   
108.
A study of nutrient distribution in the flowering stem of proteas was carried out in commercial protea plantations of each of the cultivars ‘Scarlett Ribbon’, ‘High Gold’, ‘Veldfire’, and ‘Sunrise’ of Leucospermum cordifolium, and of the species L. patersonii located in a subtropical zone (La Palma Island, Canarian Archipelago). Flowering stems were cut into different parts: flower bud, leaves from half proximal stem to the flower bud, leaves from half distal stem to the flower bud, half proximal stem to the flower bud, and half distal stem to the flower bud. Nutrient content of the different parts of the flowering stems of the cultivar and the species gave significant differences in some cases, depending on the nutrient and the cultivar. Occasional dissimilarities among the levels of nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), sodium (Na), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) were determined in comparisons among half proximal stems and half distal stems, independent of the cultivar. The same trend was observed when nutrient contents of the leaves from the half distal and the half proximal stems were compared. Phosphorus exhibited the lowest concentrations of all macronutrients in the different organs. Flower buds presented the smallest levels of macro-and micronutrients, while the leaves of the half distal and half proximal stems showed the highest values. The influence of nutrients of leaves from the half proximal stems on the stems length varied among cultivars.  相似文献   
109.
Precision agriculture (PA) technologies allow us to assess field variability and support site-specific (SSP) application of inputs. The joint application of PA and organic farming practices might be synergetic. The objective of this 3-year study was to propose a multivariate statistical and geostatistical approach, to evaluate the effects of SSP nitrogen (N) fertilization on durum wheat in transition to organic farming. Soil parameters were measured to assess soil fertility level before the SSP fertilization on wheat, which was carried out by management zones in the third year. Radiometric measurements were performed with a hyperspectral spectroradiometer and N-uptake at anthesis and grain yield were determined. The expected values and 95 % confidence intervals of the soil parameters, N-uptake and yield data were estimated with polygon kriging for each management zone. Reflectance data were reduced through principal component analysis and the retained principal components were submitted to factorial co-kriging analysis to estimate orthogonal scale-dependent factors. Comparisons between N-uptake and yield and between the retained regionalized factors (F1) and yield were performed. The spatial pattern of F1 at shorter scales was mostly reproduced in the N-uptake map, suggesting the predictive capacity of hyperspectral data for crop N-status. Within-cluster variance for yield was reduced, quite probably as a combined effect of meteorological pattern and management. The preliminary results seem to be promising in the perspective of PA. Moreover, an inverse relationship between grain yield and crop N-status was observed.  相似文献   
110.
A case of non‐syndromic, complete syndactyly involving all four limbs is described in a three‐month‐old male crossbreed dog for the first time. Syndactyly is a rare condition in most animal species, in dogs it has been infrequently reported. Findings of clinical, radiographic and cytogenetic analyses are described and demonstrate probably for the first time that numerical and structural chromosome aberrations are not involved in the pathogenesis of this case of syndactyly.  相似文献   
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