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81.
Flagellar adhesion in chlamydomonas induces synthesis of two high molecular weight cell surface proteins 总被引:2,自引:2,他引:0
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Because our previous studies (Snell, W.J., and W.S. Moore, 1980, J. Cell Biol. 84:203- 210) on the mating reaction of chlamydomonas reinhardtii showed that there was an adhesion-induced turnover of proteins whose synthesis is induced during aggregation. Analysis by SDS PAGE and autoradiography showed that proteins of 220,000 M(r) and 165, 000 M(r) (designated A(1) and A(2) respectively) consistently showed a high rate of synthesis only in flagella or flagellar membrane-enriched fractions prepared from aggregating gametes. Since the two proteins were soluble in the non-ionic detergent NP-40 and were removed from intact cells by a brief pronase treatment, it is likely that A(1) and A(2) are membrane proteins expose on the cell surface. A(1) and A(2) were each synthesized by gametes of both mating types (mt(-) and mt(+)) and synthesis of these two proteins could be detected in the normal mating reaction (wild type mt(-) and mt(+)), in mixtures of mt(-) and impotent mt(+) gametes (which could aggregate but not fuse), and in mixtures of gametes of a single mating type with isolated flagella of the opposite mating type. Cells aggregating in tunicamycin, an inhibitor of protein glycosylation, lost their adhesiveness during aggregation and did not synthesize the 220,000 M(r) protein but instead produced a protein (possibly an underglycosylated form of A(1)) of slightly lower mol wt. The 220,000 and 165,000 M(R) proteins appeared to be flagellar proteins and not cell wall proteins because A(1) and A(2) did not co-migrate with previously identified cell wall proteins, and synthesis of the two proteins could not be detected in flagella-less (bald-2) mutant cells. Analysis of the adhesive activity of sucrose gradient fraction of detergent (octyl glucoside)-solubilized flagellar membranes revealed that fractions containing A(1) and A(2) did not have detectable adhesive activity. The possibility remains that A(1) and A(2) are adhesion molecules whose activity could not be measured in the assay we used. Alternatively, the 220,000 and 165,000 M(r) proteins may be inactivated adhesion molecules or else they may be flagellar surface proteins involved only indirectly in the adhesion process. 相似文献
82.
A molecular phylogeny for aplocheiloid fishes (Atherinomorpha, Cyprinodontiformes): the role of vicariance and the origins of annualism 总被引:2,自引:0,他引:2
Annual aplocheiloid killifish embryos possess a rare ability among
vertebrates to enter stages of developmental arrest (diapause) when
subjected to adverse environmental conditions. Previous morphological
analyses have presented disparate hypotheses regarding the evolution of the
intriguing life history associated with this phenomenon. We present a novel
hypothesis of aplocheiloid relationships based on 1,009 bp of sequence data
from three mitochondrial genes (cytochrome b, 12S rRNA, and 16S rRNA).
Phylogenetic analysis using maximum parsimony, neighbor- joining, and
maximum likelihood produce strongly congruent topologies. Our data confirm
the monophyly of the Neotropical family Rivulidae, while demonstrating a
paraphyletic Old World assemblage. The basal sister group position of
Indo-Malaysian and Madagascaran taxa relative to a monophyletic South
American/African dichotomy strongly indicates the role of vicariance in the
diversification of these fishes in spite of their definition as secondary
freshwater fish. The distribution of annualism onto this topology implies a
single early origin for this suite of characters, prior to the divergence
of South American and African taxa. If so, then annualism has since been
lost several times during the evolution of genera now residing in permanent
aquatic habitats. Paleoclimatic knowledge complements this scenario based
on molecular characters.
相似文献
83.
Reduced DNA repair in mouse satellite DNA after treatment with methylmethanesulfonate, and N-methyl-N-nitrosourea. 总被引:3,自引:3,他引:0
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We have measured DNA repair in mouse satellite and main band DNA as resolved by Ag+-Cs2SO4 centrifugation in response to treatment with the alkylating agents, methyl methanesulfonate, and N-methyl-N-nitrosourea. We find that there is a statistically significant lower incorporation of 3H-Tdr into the satellite DNA as compared to the main band at varying periods after treatment with the alkylating agents. This suggests a reduced repair activity in the satellite DNA. We have measured the extent of binding of 14C-methyl methanesulfonate to the satellite, and main band DNA, and no difference in binding was observed, indicating that the reduced repair activity of satellite DNA is not due to a difference in binding of alkylating agents. We believe that the reduced incorporation of 3H-Tdr into satellite DNA may be due to its location in the condensed chromatin fraction. 相似文献
84.
T Garma C Kobayashi F Haddad G R Adams P W Bodell K M Baldwin 《Journal of applied physiology》2007,102(1):135-143
The present study was undertaken to test the hypothesis that the contraction mode of action [static-isometric (Iso), shortening-concentric (Con), or lengthening-eccentric (Ecc)] used to stress the muscle provides a differential mechanical stimulus eliciting greater or lesser degrees of anabolic response at the initiation of a resistance training program. We performed an acute resistance training study in which different groups of rodents completed four training sessions in either the Iso, Con, or Ecc mode of contraction under conditions of activation and movement specifically designed to elicit equivalent volumes of force accumulation. The results of this experiment indicate that the three modes of contraction produced nearly identical cell signaling, indicative of an anabolic response involving factors such as increased levels of mRNA for IGF-I, procollagen III alpha1, decreased myostatin mRNA, and increased total RNA concentration. The resulting profiles collectively provide evidence that pure mode of muscle action, in and of itself, does not appear to be a primary variable in determining the efficacy of increased loading paradigms with regard to the initiation of selected muscle anabolic responses. 相似文献
85.
Mehmet Küçükaycan Michiel Van Krugten Herman-Jan Pennings Tom WJ Huizinga Wim A Buurman Mieke A Dentener Emiel FM Wouters 《Respiratory research》2001,3(1):1-7
Pulmonary surfactant is a complex mixture of phospholipids and proteins, which is present in the alveolar lining fluid and is essential for normal lung function. Alterations in surfactant composition have been reported in several interstitial lung diseases (ILDs). Furthermore, a mutation in the surfactant protein C gene that results in complete absence of the protein has been shown to be associated with familial ILD. The role of surfactant in lung disease is therefore drawing increasing attention following the elucidation of the genetic basis underlying its surface expression and the proof of surfactant abnormalities in ILD. 相似文献
86.
Carl N. Sprung Yan-Ping Wang Douglas L. Miller Donald D. Giannini Nauduri Dhananjaya William J. Bodell 《Mutation research》2001,484(1-2):77-86
We have investigated the genotoxic effects of 1-(2-hydroxyethyl)-1-nitrosourea (HENU). We have chosen this agent because of its demonstrated ability to produce N7-(2-hydroxyethyl) guanine (N7-HOEtG) and O6-(2-hydroxyethyl) 2′-deoxyguanosine (O6-HOEtdG); two of the DNA alkylation products produced by 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU). For these studies, we have used the Big Blue Rat-2 cell line that contains a lambda/lacI shuttle vector. Treatment of these cells with HENU produced a dose dependent increase in the levels of N7-HOEtG and O6-HOEtdG as quantified by HPLC with electrochemical detection. Treatment of Big Blue Rat-2 cells with either 0, 1 or 5 mM HENU resulted in mutation frequencies of 7.2±2.2×10−5, 45.2±2.9×10−5 and 120.3±24.4×10−5, respectively. Comparison of the mutation frequencies demonstrates that 1 and 5 mM HENU treatments have increased the mutation frequency by 6- and 16-fold, respectively. This increase in mutation frequency was statistically significant (P<0.001). Sequence analysis of HENU-induced mutations have revealed primarily G:C→A:T transitions (52%) and a significant number of A:T→T:A transversions (16%). We propose that the observed G:C→A:T transitions are produced by the DNA alkylation product O6-HOEtdG. These results suggest that the formation of O6-HOEtdG by BCNU treatment contributes to its observed mutagenic properties. 相似文献
87.
M Tangney GT Winters WJ Mitchell 《Journal of industrial microbiology & biotechnology》2001,27(5):298-306
The utilization of maltose by Clostridium acetobutylicum ATCC 824 was investigated. Glucose was used preferentially to maltose, when both substrates were present in the medium. Maltose
phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS) activity was detected in extracts prepared from cultures
grown on maltose, but not glucose or sucrose, as the sole carbon source. Extract fractionation and PTS reconstitution experiments
revealed that the specificity for maltose is contained entirely within the membrane in this organism. A putative gene system
for the maltose PTS was identified (from the C. acetobutylicum ATCC 824 genome sequence), encoding an enzyme IIMal and a maltose 6-phosphate hydrolase.
Journal of Industrial Microbiology & Biotechnology (2001) 27, 298–306.
Received 12 September 2000/ Accepted in revised form 30 November 2000 相似文献
88.
WJ Richardson DD van der Voort E Wilson JE Moore Jr. 《Molecular & cellular biomechanics : MCB》2013,10(3):245-265
Non-uniform stress and strain fields are prevalent in many tissues in vivo, and often exacerbated by disease or injury. These mechanical gradients potentially play a role in contributing to pathological conditions, presenting a need for experimental tools to allow investigation of cell behavior within non-uniformly stimulated environments. Herein, we employ two in vitro cell-stretching devices (one previously published; one newly presented) capable of subjecting cells to cyclic, non-uniform stretches upon the surface of either a circular elastomeric membrane or a cylindrical PDMS tube. After 24 hours of cyclic stretch, 10T1/2 cells on both devices showed marked changes in long-axis orientation, with tendencies to align parallel to the direction of minimal deformation. The degree of this response varied depending on location within the stretch gradients. These results demonstrated the feasibility of conducting cell mechanobiology investigations with the two novel devices, while also highlighting the experimental capabilities of non-uniform mechanical environments for these types of studies. Such capabilities include robust data collection for developing mechanobiological dose-response curves, signal threshold identification, and potential spatial targeting for drug delivery. 相似文献
89.
Zack Saud Victoria J. Tyrrell Andreas Zaragkoulias Majd B. Protty Evelina Statkute Anzelika Rubina Kirsten Bentley Daniel A. White Patricia Dos Santos Rodrigues Robert C. Murphy Harald Köfeler William J. Griffiths Jorge Alvarez-Jarreta Richard William Brown Robert G. Newcombe James Heyman Manon Pritchard Robert WJ. Mcleod Richard J. Stanton 《Journal of lipid research》2022,63(6):100208
The lipid envelope of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an essential component of the virus; however, its molecular composition is undetermined. Addressing this knowledge gap could support the design of antiviral agents as well as further our understanding of viral-host protein interactions, infectivity, pathogenicity, and innate immune system clearance. Lipidomics revealed that the virus envelope comprised mainly phospholipids (PLs), with some cholesterol and sphingolipids, and with cholesterol/phospholipid ratio similar to lysosomes. Unlike cellular membranes, procoagulant amino-PLs were present on the external side of the viral envelope at levels exceeding those on activated platelets. Accordingly, virions directly promoted blood coagulation. To investigate whether these differences could enable selective targeting of the viral envelope in vivo, we tested whether oral rinses containing lipid-disrupting chemicals could reduce infectivity. Products containing PL-disrupting surfactants (such as cetylpyridinium chloride) met European virucidal standards in vitro; however, components that altered the critical micelle concentration reduced efficacy, and products containing essential oils, povidone-iodine, or chlorhexidine were ineffective. This result was recapitulated in vivo, where a 30-s oral rinse with cetylpyridinium chloride mouthwash eliminated live virus in the oral cavity of patients with coronavirus disease 19 for at least 1 h, whereas povidone-iodine and saline mouthwashes were ineffective. We conclude that the SARS-CoV-2 lipid envelope i) is distinct from the host plasma membrane, which may enable design of selective antiviral approaches; ii) contains exposed phosphatidylethanolamine and phosphatidylserine, which may influence thrombosis, pathogenicity, and inflammation; and iii) can be selectively targeted in vivo by specific oral rinses. 相似文献
90.
Thomas J Lee Yannick Pouliot Valerie Wagner Priyanka Gupta David WJ Stringer-Calvert Jessica D Tenenbaum Peter D Karp 《BMC bioinformatics》2006,7(1):170-14