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91.
92.
Changes in the Distribution of Fibronectin During Limb Regeneration in Newts Using Immunocytochemistry 总被引:1,自引:0,他引:1
LILLIAN A. REPESH THOMAS J. FITZGERALD LEO T. FURCHT 《Differentiation; research in biological diversity》1982,22(1-3):125-131
The distribution of fibronectin in regenerating newt limbs was studied using immunocytochemistry. At appropriate intervals after the initial amputation at the elbow (10–30 days), animals were reamputated at the shoulder and processed for light microscopy. The peroxidase-antiperoxidase technique was used to localize affinity-purified antibodies to fibronectin in limb tissues. At the amputation site, fibronectin was associated with basal laminae and connective tissues adjacent to dedifferentiating limb tissues destined to form the regeneration blastema. Accumulation and growth of the blastema was accompanied by the apparent de novo synthesis of fibronectin, where it appeared randomly in the interstitium between blastemal cells. The onset of chondrogenesis was characterized by a central condensation of prechondroblasts that formed the cartilage anlagen. Fibronectin formed an amorphous network between presumptive chondroblasts. As the mature cartilage phenotype was expressed and chondrocytes became isolated in lacunae, fibronectin was greatly reduced and then disappeared. The extracellular matrix surrounding undifferentiated blastemal cells still contained fibronectin. Fibronectin was also found in high concentrations between differentiating myoblasts. A condensation of fibronectin was also observed beneath the epidermis at the distal limb tip at the onset of digit formation. These observations are consistent with the hypothesis that fibronectin may play a key role in the morphogenetic events that result in the spatial organization and subsequent differentiation of cells during pattern formation in the regenerating limb. 相似文献
93.
Higher-level snake phylogeny inferred from mitochondrial DNA sequences of 12S rRNA and 16S rRNA genes 总被引:3,自引:0,他引:3
Portions of two mitochondrial genes (12S and 16S ribosomal RNA) were
sequenced to determine the phylogenetic relationships among the major
clades of snakes. Thirty-six species, representing nearly all extant
families, were examined and compared with sequences of a tuatara and three
families of lizards. Snakes were found to constitute a monophyletic group
(confidence probability [CP] = 96%), with the scolecophidians (blind
snakes) as the most basal lineages (CP = 99%). This finding supports the
hypothesis that snakes underwent a subterranean period early in their
evolution. Caenophidians (advanced snakes), excluding Acrochordus, were
found to be monophyletic (CP = 99%). Among the caenophidians, viperids were
monophyletic (CP = 98%) and formed the sister group to the elapids plus
colubrids (CP = 94%). Within the viperids, two monophyletic groups were
identified: true vipers (CP = 98%) and pit vipers plus Azemiops (CP = 99%).
The elapids plus Atractaspis formed a monophyletic clade (CP = 99%). Within
the paraphyletic Colubridae, the largely Holarctic Colubrinae was found to
be a monophyletic assemblage (CP = 98%), and the Xenodontinae was found to
be polyphyletic (CP = 91%). Monophyly of the henophidians (primitive
snakes) was neither supported nor rejected because of the weak resolution
of relationships among those taxa, except for the clustering of Calabaria
with a uropeltid, Rhinophis (CP = 94%).
相似文献
94.
Many mainland populations of kiwi are declining because stoats (Mustela erminea) kill most of their chicks. Stoats are often trapped during conservation programmes, but the long-term effectiveness of trapping has not been measured. During continuous trapping of mammalian predators in the 9800?ha Whangarei Kiwi Sanctuary, the survival of brown kiwi (Apteryx mantelli) chicks declined over time. Following the use of sodium fluoroacetate (1080) to kill rats (Rattus spp.) and possums (Trichosurus vulpecula) and likely secondary poisoning of stoats, chick survival at Riponui increased from 5% to 56%, and the 62% chick survival at Rarewarewa was better than the 20% recorded in a trapped-only area nearby. We suggest that untrappable stoats accumulate in areas subjected to continuous predator trapping. Conservation managers should build into their long-term pest control programmes a periodic pulse of an alternative tool to kill pests that, for whatever reason, actively avoid the primary control tool. 相似文献
95.
TOBY J. HIBBITTS LEE A. FITZGERALD 《Biological journal of the Linnean Society. Linnean Society of London》2005,85(3):363-371
Similar morphologies between species may be due to shared ancestry or convergent evolution . Understanding instances of morphological and ecological convergence is central to evolutionary ecology because they help us understand the fit between organism and environment. Two species of stream-dwelling natricine snakes, Thamnophis rufipunctatus and Nerodia harteri present a model system for studying ecological and morphological convergence and adaptation. The species are allopatric and both live in shallow riffles in streams and forage visually for fish. We studied morphological similarity, trait evolution and functional significance of ecologically relevant traits in these and related species, and used mitochondrial DNA sequences for the ND4 gene to estimate their phylogenetic relationships. Character mapping of head length and head width supported the hypothesis of independent evolution of head shape in T . rufipunctatus and N . harteri . The elongate snout is a derived trait in these two taxa that is associated with reduced hydrodynamic drag on the snakes' heads when in a swift current, compared to other species with the ancestral blunt snout. We hypothesize that lower hydrodynamic drag facilitates prey capture success in these species that are known to forage by holding their position in currents and striking at fish prey. The elongate snout morphology has also resulted in a diminished binocular vision field in these snakes, contrary to the hypothesis that visually orientated snakes should exhibit relatively greater binocular vision. Convergent evolution of the long snout and reduced hydrodynamic drag in T. rufipunctatus and N. harteri are consistent with the hypothesis that the long snout is an adaptation to foraging in a swift current. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 363–371. 相似文献
96.
M A EASTERBROOK J D FITZGERALD C PINCH J TOOLEY X-M XU 《The Annals of applied biology》2003,143(3):325-331
The development rates and fecundity of three important pests of strawberry in the UK were determined over a range of temperatures. Development time of the strawberry tarsonemid mite, Phytonemus pallidus, from egg lay to adult, ranged from a mean of 28.4 days at 12.5°C to 8.8 days at 25°C. No nymphs developed to adult at 10°C. Females lived for up to 45 days and laid a mean of 24.3 and 28.5 eggs at 20°C and 25°C respectively. Total development time from egg lay to adult for the strawberry blossom weevil, Anthonomus rubi, ranged from a mean of 95.7 days at 10°C to 18.2 days at 25°C. Mean fecundity at 20°C was 157.6 eggs, and the oviposition period averaged 71.6 days. When nymphs were reared on strawberry, development of the European tarnished plant bug, Lygus rugulipennis, from egg lay to adult, ranged from 83.8 days at 15°C to 28.8 days at 25°C. Development times on groundsel were shorter and ranged from 65.6 to 22.2 days at 15°C and 25°C. Only two nymphs developed to adults at 10°C; no eggs hatched at that temperature. Mean fecundity at 20°C was 75.4 eggs, but ranged from 23 to 179. Under a fluctuating temperature regime of 10°C for 12 h:20°C for 12 h, nymphs of L. rugulipennis took 40.3 days to become adult on strawberry, and 33.4 days on groundsel. Simple linear models fitted the developmental rate ‐ constant temperature relationship well for all species, accounting for 95–98% of the total variation in observed developmental rates. Development under fluctuating temperatures illustrated the potential problem of extrapolating linear models beyond the conditions of the experiment. 相似文献
97.
L. D. GRAHAM I. P. HAYWARD M. FITZGERALD J. M. WHITELOCK J. A. BINGLEY J. H. CAMPBELL P. A. UNDERWOOD 《Cell biology international》1997,21(9):585-594
The testing of a 30-mer dG-rich phosphorothioate oligodeoxynucleotide (LG4PS) for effects on the behaviour of vascular smooth muscle cells (VSMC)in vitroandin vivois described. LG4PS at 0.3μm inhibited significantly the phenotype modulation of freshly isolated rabbit VSMC, and cell outgrowth from pig aortic explants was inhibited ~80% by 5μm LG4PS. The growth of proliferating rabbit and pig VSMC was inhibited ~70% by 0.3μm and 5μm LG4PS, respectively. Though less marked, the antiproliferative effects of LG4PS on human VSMC were comparable to those obtained with heparin. The cytotoxic effects of LG4PS on VSMCin vitrowere low. Despite these promising results, adventitial application of 2–200nmol LG4PS in pluronic gel failed to reduce vascular hyperplasia in balloon-injured rabbit carotid arteries, and the highest dose caused extensive mortality. 相似文献
98.
David M Markusic Niek P van Til Johan K Hiralall PJ Oude Ronald Elferink Jurgen Seppen 《BMC biotechnology》2009,9(1):85
Background
Lentiviral vectors are well suited for gene therapy because they can mediate long-term expression in both dividing and nondividing cells. However, lentiviral vectors seem less suitable for liver gene therapy because systemically administered lentiviral vectors are preferentially sequestered by liver macrophages. This results in a reduction of available virus and might also increase the immune response to the vector and vector products. 相似文献99.
Background
Leucine-rich repeats are one of the more common modules found in proteins. The leucine-rich repeat consensus motif is LxxLxLxxNxLxxLxxLxxLxx- where the first 11–12 residues are highly conserved and the remainder of the repeat can vary in size Leucine-rich repeat proteins have been subdivided into seven subfamilies, none of which include members of the epidermal growth factor receptor or insulin receptor families despite the similarity between the 3D structure of the L domains of the type I insulin-like growth factor receptor and some leucine-rich repeat proteins. 相似文献100.
A Bell OA Rodríguez LA de Castro e Paula MB Padua J Hernández-Cerón CG Gutiérrez A De Vries PJ Hansen 《BMC veterinary research》2008,4(1):22