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131.
Apical constriction is one of the fundamental mechanisms by which embryonic tissue is deformed, giving rise to the shape and
form of the fully-developed organism. The mechanism involves a contraction of fibres embedded in the apical side of epithelial
tissues, leading to an invagination or folding of the cell sheet. In this article the phenomenon is modelled mechanically
by describing the epithelial sheet as an elastic shell, which contains a surface representing the continuous mesh formed from
the embedded fibres. Allowing this mesh to contract, an enhanced shell theory is developed in which the stiffness and bending
tensors of the shell are modified to include the fibres’ stiffness, and in which the active effects of the contraction appear
as body forces in the shell equilibrium equations. Numerical examples are presented at the end, including the bending of a
plate and a cylindrical shell (modelling neurulation) and the invagination of a spherical shell (modelling simple gastrulation). 相似文献
132.
Bruna Martins Bezerra Antonio S. Souto Gareth Jones 《International journal of primatology》2010,31(5):759-778
The study of vocal behavior can reveal important aspects of how and why a species communicates in relation to ecological and
social challenges. We here focus on vocal communication in golden-backed uakaris (Cacajao melanocephalus), diurnal, pitheciine monkeys that exhibit fission-fusion social organization and typically inhabit dense forests that limit
the potential for visual communication. Moreover, the species spends little time engaged in tactile or olfactory communication,
e.g., social grooming and scent marking, respectively. Hence, vocalizations may be very important for the coordination of
social organization in these monkeys. We 1) categorized golden-backed uakari vocalizations, 2) ascertained their behavioral
context, and 3) investigated whether golden-backed uakari calls can encode information about the signaler. We observed the
monkeys during 2 wet seasons in the flooded igapó forest of Jaú National Park, Brazil. We showed that golden-backed uakaris
have 9 call types in their vocal repertoire, all distinguishable by ear and from analysis of spectrograms. Some calls, e.g.,
play-specific calls, were used only in particular behavioral contexts, and by individuals of specific age, whereas others
were emitted under a range of situations. The structure of the loud tchó call varied among individuals, and according to behavioral context, i.e., whether individuals were foraging/feeding, traveling,
or performing agonistic interactions. This knowledge of the species’ vocal repertoire is valuable for surveying the monkeys
acoustically in habitats where visual surveys are difficult. 相似文献
133.
The acoustic structure of echolocation pulses emitted by Japanese pipistrellePipistrellus abramus (Temminck, 1840) bats during different phases of aerial hawking is described here for the first time. Behavioural observations
of the foraging flight in conjunction with acoustical analysis of echolocation pulses indicated a flight path consisting of
four distinct phases following the reconnaissance or search phase. Short (∼4.68 ms) and relatively broadband frequencymodulated
(FM) pulses (∼23.55 kHz bandwidth) were emitted at a repetition rate of 15 Hz during presumed target approach. Presumed insect
capture consisted of an early and a late buzz phase. Both buzz types were emitted at high repetition rates (111 Hz in early
to 222 Hz in late) and consisted of very short, broadband FM pulses (1.26 ms in early to 0.3 ms in late). There was also a
characteristically sharp drop in both the peak and terminal frequencies of each echolocation pulse during the transition from
early to late buzz. No pulses were recorded during the final phase of foraging referred to as a “post-buzz pause”. Thus the
foraging behaviour of this species consisted of five sequential phases involving four broad types of echolocation pulses. 相似文献
134.
135.
Véronique Bolduc Gareth Marlow Kym M. Boycott Hiroshi Inoue Mitsuo Itakura Lucie Parent Kuniko Mizuta Isabelle Richard Ibrahim Mahjneh Rumaisa Bashir 《American journal of human genetics》2010,86(2):213-221
The recently described human anion channel Anoctamin (ANO) protein family comprises at least ten members, many of which have been shown to correspond to calcium-activated chloride channels. To date, the only reported human mutations in this family of genes are dominant mutations in ANO5 (TMEM16E, GDD1) in the rare skeletal disorder gnathodiaphyseal dysplasia. We have identified recessive mutations in ANO5 that result in a proximal limb-girdle muscular dystrophy (LGMD2L) in three French Canadian families and in a distal non-dysferlin Miyoshi myopathy (MMD3) in Dutch and Finnish families. These mutations consist of a splice site, one base pair duplication shared by French Canadian and Dutch cases, and two missense mutations. The splice site and the duplication mutations introduce premature-termination codons and consequently trigger nonsense-mediated mRNA decay, suggesting an underlining loss-of-function mechanism. The LGMD2L phenotype is characterized by proximal weakness, with prominent asymmetrical quadriceps femoris and biceps brachii atrophy. The MMD3 phenotype is associated with distal weakness, of calf muscles in particular. With the use of electron microscopy, multifocal sarcolemmal lesions were observed in both phenotypes. The phenotypic heterogeneity associated with ANO5 mutations is reminiscent of that observed with Dysferlin (DYSF) mutations that can cause both LGMD2B and Miyoshi myopathy (MMD1). In one MMD3-affected individual, defective membrane repair was documented on fibroblasts by membrane-resealing ability assays, as observed in dysferlinopathies. Though the function of the ANO5 protein is still unknown, its putative calcium-activated chloride channel function may lead to important insights into the role of deficient skeletal muscle membrane repair in muscular dystrophies. 相似文献
136.
Tuberculosis (TB), caused by Mycobacterium tuberculosis, is one of the most devastating bacterial diseases to affect humans. M. tuberculosis is a robust pathogen that has evolved the capacity to survive and grow inside macrophage phagosomes. A cocktail of antibiotics has long been successfully used against M. tuberculosis but is becoming less effective owing to the emergence of multidrug resistance. The only available preventive vaccine, using Mycobacterium bovis bacille Calmette-Guérin, is considered to be ineffective against adult pulmonary TB, the most prevalent form of the disease. Here, we review the potential use of biodegradable nanoparticle-based anti-TB drug delivery systems that have been shown to be more effective against M. tuberculosis in animal models than conventional antibiotic treatment regimens. This technology also has substantial potential for vaccination and other therapeutic strategies against TB and other infectious diseases. 相似文献
137.
Genetic mapping of the rice ionome in leaves and grain: identification of QTLs for 17 elements including arsenic, cadmium, iron and selenium 总被引:1,自引:0,他引:1
Gareth J. Norton Claire M. Deacon Lizhong Xiong Shaoying Huang Andrew A. Meharg Adam H. Price 《Plant and Soil》2010,329(1-2):139-153
Research into the composition of cereal grains is motivated by increased interest in food quality. Here multi-element analysis is conducted on leaves and grain of the Bala x Azucena rice mapping population grown in the field. Quantitative trait loci (QTLs) for the concentration of 17 elements were detected, revealing 36 QTLs for leaves and 41 for grains. Epistasis was detected for most elements. There was very little correlation between leaf and grain element concentrations. For selenium, lead, phosphorus and magnesium QTLs were detected in the same location for both tissues. In general, there were no major QTL clusters, suggesting separate regulation of each element. QTLs for grain iron, zinc, molybdenum and selenium are potential targets for marker assisted selection to improve seed nutritional quality. An epistatic interaction for grain arsenic also looks promising to decrease the concentration of this carcinogenic element. 相似文献
138.
139.
Stevens B Allen NJ Vazquez LE Howell GR Christopherson KS Nouri N Micheva KD Mehalow AK Huberman AD Stafford B Sher A Litke AM Lambris JD Smith SJ John SW Barres BA 《Cell》2007,131(6):1164-1178
During development, the formation of mature neural circuits requires the selective elimination of inappropriate synaptic connections. Here we show that C1q, the initiating protein in the classical complement cascade, is expressed by postnatal neurons in response to immature astrocytes and is localized to synapses throughout the postnatal CNS and retina. Mice deficient in complement protein C1q or the downstream complement protein C3 exhibit large sustained defects in CNS synapse elimination, as shown by the failure of anatomical refinement of retinogeniculate connections and the retention of excess retinal innervation by lateral geniculate neurons. Neuronal C1q is normally downregulated in the adult CNS; however, in a mouse model of glaucoma, C1q becomes upregulated and synaptically relocalized in the adult retina early in the disease. These findings support a model in which unwanted synapses are tagged by complement for elimination and suggest that complement-mediated synapse elimination may become aberrantly reactivated in neurodegenerative disease. 相似文献
140.
Marcelo R. de Carvalho Flávio A. Bockmann Dalton S. Amorim Carlos Roberto F. Brandão Mário de Vivo José L. de Figueiredo Heraldo A. Britski Mário C. C. de Pinna Naércio A. Menezes Fernando P. L. Marques Nelson Papavero Eliana M. Cancello Jorge V. Crisci John D. McEachran Robert C. Schelly John G. Lundberg Anthony C. Gill Ralf Britz Quentin D. Wheeler Melanie L. J. Stiassny Lynne R. Parenti Larry M. Page Ward C. Wheeler Julián Faivovich Richard P. Vari Lance Grande Chris J. Humphries Rob DeSalle Malte C. Ebach Gareth J. Nelson 《Evolutionary biology》2007,34(3-4):140-143