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51.
Extrapair paternity and egg hatchability in tree swallows: evidence for the genetic compatibility hypothesis? 总被引:8,自引:5,他引:3
Kempenaers Bart; Congdon Brad; Boag Peter; Robertson Raleigh J. 《Behavioral ecology》1999,10(3):304-311
Tree swallows (Tachycineta bicolor) show one of the highestlevels
of extrapair paternity in birds, and there is evidencethat females have
control over who fathers their offspring.However, it is unclear which
benefits female tree swallows obtainfrom mating with multiple males. Using
microsatellite DNA fingerprinting,we studied extrapair paternity in relation
to nesting successand male, female, and offspring characteristics. More than
70%of all nests contained extrapair young, and more than half ofall
offspring were extrapair. Within broods, the extrapair youngwere often
fathered by several males. Despite screening allresident and some floater
males, we could identify the biologicalfather of only 21% of all extrapair
offspring. All identifiedextrapair males were close neighbors. Extrapair
males did notdiffer from within-pair males in any of the measured
characteristics,except that the former had larger cloacal protuberances than
thelatter. Extrapair males were equally successful in gaining paternityin
their own broods as males that did not father extra young.In nests with mixed
paternity, extrapair young did not differfrom within-pair young in body size
or mass. However, nestswith extrapair young had higher hatching success than
nestswithout extrapair young. All examined unhatched eggs were fertilizedand
thus hatch failure resulted from embryo mortality. The availabledata are in
accordance with the genetic diversity and the geneticcompatibility
hypothesis, but not with the good genes hypothesis. 相似文献
52.
53.
54.
Jiaping Gu Erin E. Congdon Einar M. Sigurdsson 《The Journal of biological chemistry》2013,288(46):33081-33095
Aggregated Tau proteins are hallmarks of Alzheimer disease and other tauopathies. Recent studies from our group and others have demonstrated that both active and passive immunizations reduce Tau pathology and prevent cognitive decline in transgenic mice. To determine the efficacy and safety of targeting the prominent 396/404 region, we developed two novel monoclonal antibodies (mAbs) with distinct binding profiles for phospho and non-phospho epitopes. The two mAbs significantly reduced hyperphosphorylated soluble Tau in long term brain slice cultures without apparent toxicity, suggesting the therapeutic importance of targeting the 396/404 region. In mechanistic studies, we found that neurons were the primary cell type that internalized the mAbs, whereas a small amount of mAbs was taken up by microglia cells. Within neurons, the two mAbs were highly colocalized with distinct pathological Tau markers, indicating their affinity toward different stages or forms of pathological Tau. Moreover, the mAbs were largely co-localized with endosomal/lysosomal markers, and partially co-localized with autophagy pathway markers. Additionally, the Fab fragments of the mAbs were able to enter neurons, but unlike the whole antibodies, the fragments were not specifically localized in pathological neurons. In summary, our Tau mAbs were safe and efficient to clear pathological Tau in a brain slice model. Fc-receptor-mediated endocytosis and the endosome/autophagosome/lysosome system are likely to have a critical role in antibody-mediated clearance of Tau pathology. 相似文献
55.
56.
A characteristic feature of the sperm P1 protamines of eutherian mammals is
the constant presence of six to nine cysteine residues per molecule. During
spermiogenesis these residues become oxidized to form a three-dimensional
network of disulfide bridges between, and within, protamine molecules in
the sperm chromatin. This covalent cross linking strongly stabilizes
eutherian sperm nuclei. In contrast, protamines sequenced from teleost
fish, birds, monotremes, and marsupials all lack cysteine residues and
their sperm nuclei, without the stabilizing cross links, are easily
decondensed in vitro. We have now found that one genus of tiny, shrewlike
dasyurid marsupials, the Planigales, possess P1 protamines containing five
to six cysteine residues. These residues appear to have evolved since the
divergence of Planigales from other members of the family Dasyuridae, such
as the marsupial mouse, Sminthopsis crassicaudata. We believe this
constitutes a case of convergent evolution in a subfamily of dasyurid
marsupials toward the cysteine-rich eutherian form of sperm protamine P1.
相似文献
57.
A model of human muscle action is presented for a maximally fast, large-amplitude forearm movement to target. the inputs to the model are approximately the biceps and triceps EMG envelopes over a single movement. The model's output gives the corresponding displacement angle of the forearm about a fixed elbow position as a function of time. The idea of the model is to conceive of both EMG input drives as successions of millisecond input pulses, with each pulse resulting in a muscle tension twitch. Every twitch is amplitude-scaled, parametrically-shaped, and duration-limited as a function of the muscle's contractile history thus far in the movement. The muscle tension at any time t is the sum of the residual tension levels of all twitches begun before t. The model was developed and tested with special reference to two subjects: one, according to the model dynamics, was a comparatively slow-twitch type, and the other modelled as a fast-twitch type. Good agreement was found between model output and subject response data whenever the subject's EMG's were synchronous. The model can be used to characterize each subject's responses by a suite of twitch characteristics. This will enable us to check the accepted but now suspect correlation between muscle biopsy-and performance-determined muscle twitch type.This study was supported by contract DAMD 17-80-C-0101 from the U.S. Army Medical Research and Development Command. The views, opinions and/or findings contained in this report are those of the authors and should not be construed as an official Department of the Army position, policy, or decision, unless so designated by other documentation 相似文献
58.
Christopher L Rowe William A Hopkins Caralyn Zehnder Justin D Congdon 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2001,129(3):275-283
Recent studies of several vertebrates and an invertebrate have shown elevated standard metabolic rate (SMR) following chronic exposure to a mixture of trace elements in a contaminated habitat. In this study, we examined whether another invertebrate, a crayfish (Procambarus acutus), also experienced elevated SMR in response to the same contaminants. We compared SMR of individuals inhabiting the contaminated site with SMR of individuals from uncontaminated reference sites. We also examined SMR of individuals collected from the reference areas and exposed in the laboratory for 50 days to sediment and food derived from the contaminated site. Individuals collected from the contaminated site had elevated SMR compared to individuals collected from the unpolluted areas (25.1 vs. 19.2 J g?1 day?1). Individuals exposed to contaminated sediment and food in the laboratory experienced elevations in SMR compared to controls after 27 days of exposure (35.2 vs. 29.4 J g?1 day?1), but after 50 days of exposure, metabolic rate no longer differed between treatments. Growth of contaminant-exposed individuals was lower than growth of reference animals throughout the laboratory study. Elevated SMR associated with contaminant exposure may reflect energy-demanding mechanisms required to combat deleterious effects of contaminants. Our results support the prediction that increases in energy expenditure in the contaminated habitat would negatively influence production processes, such as growth. Results from this study in conjunction with observations from other species suggest that increased SMR is a common response among several taxa to the mixture of contaminants in the study site. 相似文献
59.
Bradley C Congdon Kurniasih Bernard A Franzmann Adam T Hardy 《Australian Journal of Entomology》2002,41(2):106-103
Sequence variation in the internal transcribed spacer (ITS-1) ribosomal DNA subunit was examined for sorghum midge obtained from introduced and native hosts in south-eastern and central Queensland. No variation was observed relative to host plant or geographical distance for midges collected from two introduced hosts, grain sorghum ( Sorghum bicolor ) and Johnson grass ( S. halepense ); however, sequence differences were observed between midges from introduced and native hosts and among midges from a single native host, slender bluegrass ( Dichanthium affine ). No evidence was observed of introduced midges on native hosts, or vice versa. These results agree with previously hypothesised host distributions for native and introduced midges in Australia, and expand the sample of introduced hosts to include Johnson grass. They suggest that Stenodiplosis sorghicola , the principal midge infesting grain sorghum, is also the most common species on Johnson grass. This confirms that Johnson grass plays a role in the population dynamics of S. sorghicola and suggests that midges originating from Johnson grass may influence levels of infestation in grain sorghum. 相似文献
60.
A historical perspective is given of the current paradigm that does not explicitly protect nonhuman biota from radiation but instead relies on the concept that if dose limits are set to protect humans, then the environment is automatically protected as well. We summarize recent international questioning of this paradigm and briefly present three frameworks for protecting biota that are being considered by the U.S. Department of Energy, the Canadian Nuclear Safety Commission, and the International Commission on Radiological Protection. We point out a controversial component in each of the three frameworks and suggest topics that need additional research. We emphasize that to properly address radiation protection of the environment, we need to understand how effects are integrated across different levels of biological organization. We caution that the proposed use of molecular end points to estimate ecological risks from radioactive contamination is applicable only if we understand the extent of the impact that molecular damage has on individual organisms and populations of exposed biota. To accomplish the latter, enhanced collaborations are required among the traditionally separate disciplines of radiation biology and radiation ecology. 相似文献