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1.
Nielsen J; Peixoto AA; Piccin A; Costa R; Kyriacou CP; Chalmers D 《Molecular biology and evolution》1994,11(6):839-853
The region of the clock gene period (per) that encodes a repetitive tract
of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran
species both within and outside the Drosophilidae. All the non-
Drosophilidae sequences in this region are short and present a remarkably
stable picture compared to the Drosophilidae, in which the region is much
larger and extremely variable, both in size and composition. The
accelerated evolution in the repetitive region of the Drosophilidae appears
to be mainly due to an expansion of two ancestral repeats, one encoding a
Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and
asparagine or threonine. In some drosophilids the expansion involves a
duplication of the pentapeptide sequence, but in Drosophila pseudoobscura
both the dipeptide and the pentapeptide repeats are present in larger
numbers. In the nondrosophilids, however, the pentapeptide sequence is
represented by one copy and the dipeptide by two copies. These observations
fulfill some of the predictions of recent theoretical models that have
simulated the evolution of repetitive sequences.
相似文献
2.
We have used the method of disequilibrium pattern analysis to examine associations between the threonine-glycine (Thr-Gly) encoding repeat region of the clock gene period (per) of Drosophila melanogaster, and polymorphic sites both upstream and downstream of the repeat, in a number of European fly populations. The results are consistent with the view that selection may be operating on various haplotypes which share the Thr-Gly length alleles encoding 17, 20 and 23 dipeptide pairs, and that the repeat itself may be the focus for selection. These conclusions lend support to a number of other population and behavioural investigations which have provided evidence that selection is acting on the Thr-Gly region. The linkage analysis was also used to infer an approximate mutation rate (mu) for the repeat, of 10(-5) < mu < 4 x 10(-5) per gamete per generation. Direct measurements of the mutation rate using the polymerase chain reaction in a pedigree analysis of tens of thousands of individuals do not contradict this value. Consequently, the Thr-Gly repeat does not have a mutation rate that is as high as some of the non-coding minisatellites, but it is several orders of magnitude higher than the nucleotide substitution rate. The implications of this elevated mutation rate for linkage disequilibria and selection are discussed. 相似文献
3.
Mehnert KI Beramendi A Elghazali F Negro P Kyriacou CP Cantera R 《Developmental neurobiology》2007,67(4):415-421
In Drosophila melanogaster, as in most other higher organisms, a circadian clock controls the rhythmic distribution of rest/sleep and locomotor activity. Here we report that the morphology of Drosophila flight neuromuscular terminals changes between day and night, with a rhythm in synaptic bouton size that continues in constant darkness, but is abolished during aging. Furthermore, arrhythmic mutations in the clock genes timeless and period also disrupt this circadian rhythm. Finally, these clock mutants also have an opposing effect on the nonrhythmic phenotype of neuronal branching, with tim mutants showing a dramatic hyperbranching morphology and per mutants having fewer branches than wild-type flies. These unexpected results reveal further circadian as well as nonclock related pleiotropic effects for these classic behavioral mutants. 相似文献
4.
5.
Pozidis C Chalkiadaki A Gomez-Serrano A Stahlberg H Brown I Tampakaki AP Lustig A Sianidis G Politou AS Engel A Panopoulos NJ Mansfield J Pugsley AP Karamanou S Economou A 《The Journal of biological chemistry》2003,278(28):25816-25824
Type III protein secretion (TTS) is catalyzed by translocases that span both membranes of Gram-negative bacteria. A hydrophilic TTS component homologous to F1/V1-ATPases is ubiquitous and essential for secretion. We show that hrcN encodes the putative TTS ATPase of Pseudomonas syringae pathovar phaseolicola and that HrcN is a peripheral protein that assembles in clusters at the membrane. A decahistidinyl HrcN derivative was overexpressed in Escherichia coli and purified to homogeneity in a folded state. Hydrodynamic analysis, cross-linking, and electron microscopy revealed four distinct HrcN forms: I, 48 kDa (monomer); II, approximately 300 kDa (putative hexamer); III, 575 kDa (dodecamer); and IV, approximately 3.5 MDa. Form III is the predominant form of HrcN at the membrane, and its ATPase activity is dramatically stimulated (>700-fold) over the basal activity of Form I. We propose that TTS ATPases catalyze protein translocation as activated homo-oligomers at the plasma membrane. 相似文献
6.
Oliveira S Bottecchia M Bauzer L Souza N Ward R Kyriacou C Peixoto A 《Memórias do Instituto Oswaldo Cruz》2001,96(3):403-405
Lutzomyia longipalpis (Lutz & Neiva, 1912) (Diptera: Psychodidae: Phlebotominae) is a vector of visceral leishmaniasis in the Americas and it might represent a complex of sibling species. Reproductive isolation between closely related species often involves differences in courtship behaviour. cacophony (cac) and period (per) are two Drosophila genes that control features of the "lovesong" males produce during courtship that has been implicated in the sexual isolation between closely related species. We are using gene fragments from L. longipalpis' homologues of these two genes to study the speciation process in this putative species complex. 相似文献
7.
Kyriacou SK Mohamed A Miller K Neff S 《Biomechanics and modeling in mechanobiology》2002,1(2):151-164
Brain biomechanics has been investigated for more than 30 years. In particular, finite element analyses and other powerful
computational methods have long been used to provide quantitative results in the investigation of dynamic processes such as
head trauma. Nevertheless, the potential of these methods to simulate and predict the outcome of quasi-static processes such
as neurosurgical procedures and neuropathological processes has only recently been explored. Some inherent difficulties in
modeling brain tissues, which have impeded progress, are discussed in this work. The behavior of viscoelastic and poroelastic
constitutive models is compared in simple 1-D simulations using the ABAQUS finite element platform. In addition, the behaviors
of quasi-static brain constitutive models that have recently been proposed are compared. We conclude that a compressible viscoelastic
solid model may be the most appropriate for modeling neurosurgical procedures.
Received: 19 March 2002 / Accepted: 6 June 2002
Work is supported by a generous grant from the Whitaker Foundation. We would like to also thank Dr. Christos Davatzikos (Johns
Hopkins School of Medicine, Baltimore, Maryland) for his help. 相似文献
8.
Kozower BD Christofidou-Solomidou M Sweitzer TD Muro S Buerk DG Solomides CC Albelda SM Patterson GA Muzykantov VR 《Nature biotechnology》2003,21(4):392-398
Vascular immunotargeting may facilitate the rapid and specific delivery of therapeutic agents to endothelial cells. We investigated whether targeting of an antioxidant enzyme, catalase, to the pulmonary endothelium alleviates oxidative stress in an in vivo model of lung transplantation. Intravenously injected enzymes, conjugated with an antibody to platelet-endothelial cell adhesion molecule-1, accumulate in the pulmonary vasculature and retain their activity during prolonged cold storage and transplantation. Immunotargeting of catalase to donor rats augments the antioxidant capacity of the pulmonary endothelium, reduces oxidative stress, ameliorates ischemia-reperfusion injury, prolongs the acceptable cold ischemia period of lung grafts, and improves the function of transplanted lung grafts. These findings validate the therapeutic potential of vascular immunotargeting as a drug delivery strategy to reduce endothelial injury. Potential applications of this strategy include improving the outcome of clinical lung transplantation and treating a wide variety of endothelial disorders. 相似文献
9.
BACKGROUND: Primary melanoma of the lung is an extremely rare pathological entity and sparsely reported in the literature. CASE PRESENTATION: A case of primary malignant melanoma of the lung in a 41-year-old female is reported. The clinical, radiological and histopathological features are discussed. The initial symptom was cough, whereas the chest radiography showed a round opacity of the right lung. The computed tomography of the chest revealed a well-demarcated mass lesion in the right upper lobe. Endobronchial mass causing obstruction of the upper lobar bronchus was the bronchoscopic finding. Patient underwent pneumonectomy. A diagnosis of melanoma was confirmed postoperatively after the immunohistochemistry. Primary nature of the tumour in the lung results from the demonstration of characteristic junctional pattern of melanoma cells beneath the bronchial epithelium on histopathology, and from exclusion of other potential primary sites in the clinical, paraclinical and laboratory examination. CONCLUSIONS: Primary melanoma of the lung represents a rare pathological entity. Careful interpretation of histopathological information in correlation with all other findings from clinical and paraclinical studies can establish a diagnosis. Follow-up is necessary in order to diagnose potential dissemination or secondary sites of the disease. Due to the small number of cases reported in the literature, there is no experience on the management and the prognosis of the disease, but surgical resection remains the cornerstone of the treatment. 相似文献
10.
In the light of experimental results showing significant forward centre of mass (CoM) displacements within the base of support,
this study investigated if whole body reaching movements can be executed whilst keeping the CoM fixed in the horizontal axis.
Using kinematic simulation techniques, angular configurations were recreated from experimental data imposing two constraints:
a constant horizontal position of the CoM and an identical trajectory of the hand to grasp an object. The comparison between
recorded and simulated trials showed that stabilisation of the CoM was associated with greater backward hip displacements,
which became more marked with increasing object distance. This was in contrast to recorded trials showing reductions in backward
hip displacements with increasing distance. Results also showed that modifications to angular displacements were necessary
only at the shoulder and hip joints, but that these modifications were within the limits of joint mobility. The analysis of
individual joint torques revealed that the pattern and timing of simulated trials were similar to those recorded experimentally.
Peak joint torque values showed particularly that keeping the CoM at a constant horizontal position resulted in significantly
smaller ankle peak flexor and extensor torques. It may be concluded from this study that `stabilising' the CoM during human
whole body reaching represents a feasible strategy, but not the one chosen by subjects under experimental conditions. Our
results also do not support the idea of the CoM as the stabilised reference value for the coordination between posture and
goal-directed movements.
Received: 22 September 1998 / Accepted in revised form: 2 June 1999 相似文献