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41.
When a species is introduced into a new location, it may escape, at least temporarily, from its natural enemies. In field surveys, we found that when the exotic, invasive mosquito, Aedes albopictus, invades new sites, it initially experiences reduced infection by its gut parasite, Ascogregarina taiwanensis. To determine the effect of this escape from parasitism on the competitive ability of A. albopictus, we performed a laboratory competition experiment in which infected and uninfected A. albopictus larvae were reared in microcosms alone and in competition with larvae of the native mosquito, Ochlerotatus triseriatus. We analyzed the effect of parasitism by A. taiwanensis on A. albopictus performance when subjected to intra- and interspecific competition across a range of larval densities, as well as the effect of A. albopictus parasitism by A. taiwanensis on the competitive impact of A. albopictus on O. triseriatus. At a density of 30 O. triseriatus larvae, O. triseriatus survivorship was significantly reduced by the addition of 30 unifected A. albopictus, but not by addition of 30 infected A. albopictus, and not by addition of 15 A. albopictus whether infected or uninfected. Although estimated finite rate of population increase (') showed similar trends, and was significantly affected by treatments, no pairwise differences in rate of increase were significant. Infection by A. taiwanensis also significantly prolonged A. albopictus female development time and reduced the intraspecific competitive effect of increased density of A. albopictus, but did not affect A. albopictus survivorship, mass, or estimated finite rate of population increase. Thus, when A. albopictus escapes from this parasite as it colonizes new sites, this escape may give it a small, but significant, added competitive advantage over O. triseriatus, which may facilitate range expansion of A. albopictus and enhance A. albopictus's initial impact on resident species.  相似文献   
42.
Measurement of fat mass using DEXA: a validation study in elderly adults.   总被引:4,自引:0,他引:4  
The accuracy of total body fat mass and leg fat mass measurements by fan-beam dual-energy X-ray absorptiometry (DEXA) was assessed in 60 healthy elderly subjects (aged 70-79 yr). Total fat and leg fat mass at four leg regions (total leg, thigh, midthigh, and calf) were measured with the QDR 4500A (Hologic, Waltham, MA). The four-compartment model and multislice computed tomography scans were selected as criterion methods for total fat and leg fat mass, respectively. Total fat mass from DEXA was positively associated with fat mass from the four-compartment model with a standard error of the estimate ranging from 1.4 to 1.6 kg. DEXA fan-beam tended to overestimate fat mass for total leg and total thigh fat mass, whereas only marginal differences in fat mass measurements at the midthigh and calf were demonstrated (相似文献   
43.
This article is a review of research and additional unpublished diseases that have been discovered and documented in naturally mummified remains recovered from South America. A new impetus in paleopathological studies was the work and discovery of a solution for rehydration of mummified tissues by Sir Marc Armand Ruffer in 1913. This solution allows the paleopathologist, after performing the autopsy, to process the tissues in a manner similar to current practices in pathology. In our studies, the most common diseases were infectious in nature, similar to the diseases that are most prominent today in the same regions.  相似文献   
44.
In laboratories, mice are housed at 20–24°C, which is below their lower critical temperature (≈30°C). This increased thermal stress has the potential to alter scientific outcomes. Nesting material should allow for improved behavioral thermoregulation and thus alleviate this thermal stress. Nesting behavior should change with temperature and material, and the choice between nesting or thermotaxis (movement in response to temperature) should also depend on the balance of these factors, such that mice titrate nesting material against temperature. Naïve CD-1, BALB/c, and C57BL/6 mice (36 male and 36 female/strain in groups of 3) were housed in a set of 2 connected cages, each maintained at a different temperature using a water bath. One cage in each set was 20°C (Nesting cage; NC) while the other was one of 6 temperatures (Temperature cage; TC: 20, 23, 26, 29, 32, or 35°C). The NC contained one of 6 nesting provisions (0, 2, 4, 6, 8, or 10g), changed daily. Food intake and nest scores were measured in both cages. As the difference in temperature between paired cages increased, feed consumption in NC increased. Nesting provision altered differences in nest scores between the 2 paired temperatures. Nest scores in NC increased with increasing provision. In addition, temperature pairings altered the difference in nest scores with the smallest difference between locations at 26°C and 29°C. Mice transferred material from NC to TC but the likelihood of transfer decreased with increasing provision. Overall, mice of different strains and sexes prefer temperatures between 26–29°C and the shift from thermotaxis to nest building is seen between 6 and 10 g of material. Our results suggest that under normal laboratory temperatures, mice should be provided with no less than 6 grams of nesting material, but up to 10 grams may be needed to alleviate thermal distress under typical temperatures.  相似文献   
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46.
Although numbers of giant anteaters within North American facilities have been steadily increasing for the last 15 years, the population now exhibits an unstable age distribution with genetically valuable individuals nearing reproductive senescence. Contributing to this issue is the Association of Zoos and Aquariums (AZA) described lack of standardization of breeding introduction practices and high risk of female injury occurring during such pairings. This report describes the development of a successful breeding protocol at Cleveland Metroparks Zoo based on hormone monitoring and efficient communication between science and animal management teams that minimizes risk of female injury. By training a female giant anteater for urine sample and body weight data collection, staff members accurately predicted estrus, and timed breeding introductions to facilitate positive interactions between the male and female. Such training also allowed for careful monitoring of two pregnancies through parturition (169–184 days from breeding) and post‐partum return to estrus (114–129 days from parturition). Urinary hormone monitoring revealed a sharp progestogen increase averaging >five‐fold over basal levels (0.52 ± 0.05 ng/mg creatinine) which was sustained throughout the second half of pregnancy. Mean regular estrous cycle length (n = 14 cycles), was calculated as 46.17 ± 1.39 days, measured as days between estrogen peaks of mean concentration 2.27 ± 0.19 ng/mg creatinine. This report summarizes impressive collaborative efforts among multiple zoological departments to achieve extensive hormonal and body weight monitoring from a female giant anteater, adding valuable information on reproductive parameters, and specifics for novel hormone assay techniques.  相似文献   
47.
Understanding mechanotransduction pathways leading to thrombosis will require progressive steps, including determination of the mechanical behavior of the platelet membrane in response to applied loads. The platelet membrane deformation capacity, as quantified by membrane progression into a borosilicate glass micropipette of defined internal diameter, was probed in murine platelets using a controlled range of negative pressure (0–7 cm H2O). Based on our observations that the platelet portion outside the micropipette was mostly spherical and that the platelet volume did not change upon aspiration, a novel continuum mechanics-based model of the platelet micropipette aspiration experiment was created, and a new hyperelastic isotropic material model including membrane residual tension was proposed for the platelet membrane. Murine platelet membranes maintained an average linear deformation behavior: L p/R p = 146,100p i × R p + 19.923, where L p is the platelet length aspirated in the micropipette (m), R p is micropipette radius (m) and p i is the aspiration pressure (Pa). The theoretical model was used to generate material constants for the murine platelet membrane that allowed for an accurate simulation of the micropipette aspiration experiments. From published results, another set of material constants was established for the human platelet membrane. Limited cases of platelet lysis upon aspiration were analyzed using the theoretical model to determine preliminary membrane tension strength values.  相似文献   
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49.
While the human gut microbiota are suspected to produce diffusible small molecules that modulate host signaling pathways, few of these molecules have been identified. Species of Bacteroides and their relatives, which often comprise >50% of the gut community, are unusual among bacteria in that their membrane is rich in sphingolipids, a class of signaling molecules that play a key role in inducing apoptosis and modulating the host immune response. Although known for more than three decades, the full repertoire of Bacteroides sphingolipids has not been defined. Here, we use a combination of genetics and chemistry to identify the sphingolipids produced by Bacteroides fragilis NCTC 9343. We constructed a deletion mutant of BF2461, a putative serine palmitoyltransferase whose yeast homolog catalyzes the committed step in sphingolipid biosynthesis. We show that the Δ2461 mutant is sphingolipid deficient, enabling us to purify and solve the structures of three alkaline-stable lipids present in the wild-type strain but absent from the mutant. The first compound was the known sphingolipid ceramide phosphorylethanolamine, and the second was its corresponding dihydroceramide base. Unexpectedly, the third compound was the glycosphingolipid α-galactosylceramide (α-GalCerBf), which is structurally related to a sponge-derived sphingolipid (α-GalCer, KRN7000) that is the prototypical agonist of CD1d-restricted natural killer T (iNKT) cells. We demonstrate that α-GalCerBf has similar immunological properties to KRN7000: it binds to CD1d and activates both mouse and human iNKT cells both in vitro and in vivo. Thus, our study reveals BF2461 as the first known member of the Bacteroides sphingolipid pathway, and it indicates that the committed steps of the Bacteroides and eukaryotic sphingolipid pathways are identical. Moreover, our data suggest that some Bacteroides sphingolipids might influence host immune homeostasis.  相似文献   
50.
Domestic guinea pigs (Cavia aperea f. porcellus) in laboratories have been shown to actively avoid the centers of their cages. This experiment tested a novel, dark-colored “shader” placed over the central portion of a cage. Based on the observed behavior of wild guinea pig species, it was hypothesized that utilization of the central portion of the cage would increase when the shader was present. Eleven male and 11 female albino, 3-week-old Hartley guinea pigs (Crl:HA) experienced the control and treatment conditions in a crossover study design. They spent more time in central cage sections when the shader was present and spent more time in and around the food hopper when the shader was absent (p < .001). Differences between sexes included increased inactivity in males versus females (p < .05) and a difference in time spent in a corner section of the cage (p < .001), likely associated with location in the room. We concluded that the presence of a shader increased utilization of cage space, which appeared to provide a similar increase in space utilization as structural enrichments.  相似文献   
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