Genetic dissection of the Leishmania paraflagellar rod, a unique flagellar cytoskeleton structure

1999 ◽  
Vol 112 (16) ◽  
pp. 2753-2763 ◽  
Author(s):  
J.A. Maga ◽  
T. Sherwin ◽  
S. Francis ◽  
K. Gull ◽  
J.H. LeBowitz
Keyword(s):  
Cell Motility ◽  
Previous Analysis ◽  
Complex Structure ◽  
The Other ◽  
Genetic Dissection ◽  
Null Mutant ◽  
Leishmania Mexicana ◽  
Stable Association ◽  
Protein Components ◽  
Null Mutants

The paraflagellar rod (PFR) is a unique network of cytoskeletal filaments that lies alongside the axoneme in the flagella of most trypanosomatids. While little is known about how two major Leishmania mexicana PFR protein components, PFR1 and PFR2, assemble into this complex structure, previous analysis of PFR2 null mutants demonstrated that the PFR is essential for proper cell motility. The structural roles of PFR1 and PFR2 are now examined through comparison of PFR2 null mutants with new PFR1 null mutant and PFR1/PFR2 double null mutant parasites. Both PFR1 and PFR2 were essential for PFR formation and cell motility. When elimination of one PFR gene prevented assembly of a native PFR structure, the other PFR protein accumulated at the distal flagellar tip. Comparison of PFR substructures remaining in each mutant revealed that: (1) fibers that attach the PFR to the axoneme did not contain PFR1 or PFR2, and assemble in the absence of a PFR. (2) PFR1 was synthesized and transported to the flagella in the absence of PFR2, where it formed a stable association with the axoneme attachment fibers. (3) PFR2 was synthesized and transported to the flagella in the absence of PFR1, though it was not found associated with the axoneme attachment fibers. (4) PFR1 and PFR2 were located throughout the subdomains of the PFR. These data suggest that while PFR filaments contain both PFR1 and PFR2, the PFR is attached to the axoneme by interaction of PFR1 with the axoneme attachment fibers.

scholarly journals Glucose Transporters and Virulence inLeishmania mexicana

mSphere ◽  
2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Xiuhong Feng ◽  
Khoa D. Tran ◽  
Marco A. Sanchez ◽  
Hakima Al Mezewghi ◽  
Scott M. Landfear
Keyword(s):  
Endoplasmic Reticulum ◽  
Glucose Transporter ◽  
Glucose Transporters ◽  
Null Mutant ◽  
Leishmania Mexicana ◽  
Wild Type ◽  
Content Type ◽  
Intracellular Amastigotes ◽  
Null Mutants

ABSTRACTGlucose transporters are important for viability and infectivity of the disease-causing amastigote stages ofLeishmania mexicana. The Δgt1-3null mutant, in which the 3 clustered glucose transporter genes,GT1,GT2, andGT3, have been deleted, is strongly impaired in growth inside macrophagesin vitro. We have now demonstrated that this null mutant is also impaired in virulence in the BALB/c murine model of infection and forms lesions considerably more slowly than wild-type parasites. Previously, we established that amplification of thePIFTC3gene, which encodes an intraflagellar transport protein, both facilitated and accompanied the isolation of the original Δgt1-3null mutant generated in extracellular insect-stage promastigotes. We have now isolated Δgt1-3null mutants without coamplification ofPIFTC3. These amplicon-negative null mutants are further impaired in growth as promastigotes, compared to the previously described null mutants containing thePIFTC3amplification. In contrast, the GT3 glucose transporter plays an especially important role in promoting amastigote viability. A line that expresses only the single glucose transporter GT3 grows as well inside macrophages and induces lesions in animals as robustly as do wild-type amastigotes, but lines expressing only the GT1 or GT2 transporters replicate poorly in macrophages. Strikingly, GT3 is restricted largely to the endoplasmic reticulum in intracellular amastigotes. This observation raises the possibility that GT3 may play an important role as an intracellular glucose transporter in the infectious stage of the parasite life cycle.IMPORTANCEGlucose transport plays important roles forin vitrogrowth of insect-stage promastigotes and especially for viability of intramacrophage mammalian host-stage amastigotes ofLeishmania mexicana. However, the roles of the three distinct glucose transporters, GT1, GT2, and GT3, in parasite viability inside macrophages and virulence in mice have not been fully explored. Parasite lines expressing GT1 or GT2 alone were strongly impaired in growth inside macrophages, but lines expressing GT3 alone infected macrophages and caused lesions in mice as robustly as wild-type parasites. Notably, GT3 localizes to the endoplasmic reticulum of intracellular amastigotes, suggesting a potential role for salvage of glucose from that organelle for viability of infectious amastigotes. This study establishes the unique role of GT3 for parasite survival inside host macrophages and for robust virulence in infected animals.

scholarly journals A Study of the Effects of Rain, Snow and Hail on the Atmospheric Electric Field near Ground

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 996
Author(s):  
Athanasios Karagioras ◽  
Konstantinos Kourtidis
Keyword(s):  
Frequency Distribution ◽  
Complex Structure ◽  
Potential Gradient ◽  
Weather Conditions ◽  
The Other ◽  
Fair Weather ◽  
Northern Greece ◽  
Rain Events ◽  
The Impact ◽  
Bounce Back

The purpose of the present study is to investigate the impact of rain, snow and hail on potential gradient (PG), as observed in a period of ten years in Xanthi, northern Greece. An anticorrelation between PG and rainfall was observed for rain events that lasted several hours. When the precipitation rate was up to 2 mm/h, the decrease in PG was between 200 and 1300 V/m, in most cases being around 500 V/m. An event with rainfall rates up to 11 mm/h produced the largest drop in PG, of 2 kV/m. Shortly after rain, PG appeared to bounce back to somewhat higher values than the ones of fair-weather conditions. A decrease in mean hourly PG was observed, which was around 2–4 kV/m during the hail events which occurred concurrently with rain and from 0 to 3.5 kV/m for hail events with no rain. In the case of no drop, no concurrent drop in temperature was observed, while, for the other cases, it appeared that, for each degree drop in temperature, the drop in hourly mean PG was 1000 V/m; hence, we assume that the intensity of the hail event regulates the drop in PG. The frequency distribution of 1-minute PG exhibits a complex structure during hail events and extend from −18 to 11 kV/m, with most of the values in the negative range. During snow events, 1-minute PG exhibited rapid fluctuations between high positive and high negative values, its frequency distribution extending from −10 to 18 kV/m, with peaks at −10 and 3 kV/m.

scholarly journals Comparing climate change indices between a northern (arid) and a southern (humid) basin in Mexico during the last decades

2018 ◽  
Vol 15 ◽  
pp. 231-237 ◽  
Author(s):  
Martín José Montero-Martínez ◽  
Julio Sergio Santana-Sepúlveda ◽  
Naydú Isabel Pérez-Ortiz ◽  
Óscar Pita-Díaz ◽  
Salvador Castillo-Liñan
Keyword(s):  
Climate Change ◽  
River Basin ◽  
Arid Region ◽  
Climate Changes ◽  
Previous Analysis ◽  
Environmental Issues ◽  
The Other ◽  
The World ◽  
Humid Area ◽  
Different Parts

Abstract. It is a matter of current study to determine potential climate changes in different parts of the world, especially in regions like a basin which has the potential to affect socioeconomic and environmental issues in a defined area. This study provides a comparison between several climate change indices trends of two very different basins in Mexico, one located in the northern arid region (the Conchos River basin) and the other in the southern humid area (the Usumacinta River basin). First, quality control, homogenization, and completion of the missing data were applied before calculating the climate change indices and their respective trends for the combined period 1961–1994. A clear warming signal was found for the two basins in addition to an increment in the DTR, in agreement with other studies in Mexico. Also, the Conchos River basin was found to be more humid and the Usumacinta River basin drier, in accordance to a supposed seesaw behavior indicated in previous analysis.

Regulation of Capsule Synthesis and Cell Motility in Salmonella enterica by the Essential Gene igaA

Genetics ◽  
2002 ◽  
Vol 162 (4) ◽  
pp. 1513-1523
Author(s):  
David A Cano ◽  
Gustavo Domínguez-Bernal ◽  
Alberto Tierrez ◽  
Francisco Garcia-del Portillo ◽  
Josep Casadesús
Keyword(s):  
Cell Motility ◽  
Gene Product ◽  
Regulatory Network ◽  
Salmonella Enterica ◽  
Essential Gene ◽  
Fibroblast Cells ◽  
Null Mutant ◽  
Functional Interaction ◽  
Cells In Culture ◽  
System A

Abstract Mutants of Salmonella enterica carrying the igaA1 allele, selected as able to overgrow within fibroblast cells in culture, are mucoid and show reduced motility. Mucoidy is caused by derepression of wca genes (necessary for capsule synthesis); these genes are regulated by the RcsC/YojN/RcsB phosphorelay system and by the RcsA coregulator. The induction of wca expression in an igaA1 mutant is suppressed by mutations in rcsA and rcsC. Reduced motility is caused by lowered expression of the flagellar master operon, flhDC, and is suppressed by mutations in rcsB or rcsC, suggesting that mutations in the igaA gene reduce motility by activating the RcsB/C system. A null igaA allele can be maintained only in an igaA+/igaA merodiploid, indicating that igaA is an essential gene. Lethality is suppressed by mutations in rcsB, rcsC, and yojN, but not in rcsA, suggesting that the viability defect of an igaA null mutant is mediated by the RcsB/RcsC system, independently of RcsA (and therefore of the wca genes). Because all the defects associated with igaA mutations are suppressed by mutations that block the RcsB/RcsC system, we propose a functional interaction between the igaA gene product and either the Rcs regulatory network or one of its regulated products.

scholarly journals Revising Stanley’s footsteps: encountering the ‘other’ in Darkest England (1996) by Christopher Hope

Literator ◽  
2000 ◽  
Vol 21 (1) ◽  
pp. 85-98
Author(s):  
H. Roos
Keyword(s):  
Nineteenth Century ◽  
Complex Structure ◽  
Frame Of Reference ◽  
Point Of View ◽  
The Other ◽  
Central Theme ◽  
Post Colonial ◽  
Black Africa ◽  
Colonial Texts ◽  
Travel Writings

As has now become a familiar image in Hope’s writings, once again ttie idea of looking at a society from the position of an outsider and an exile forms the central theme of Darkest England (1996). In this satirical novel, the tradition of nineteenth-century travel writings set in a colonial context is reversed, undermined, and then remarkably recreated to portray the present-day manifestation of encounters and relations between (black) Africa and the (white) West. Presenting the (fictional) journals of a Khoisan leader, David Mungo Booi, within a dynamic frame of reference to classical colonial texts by, among others, Livingstone and Stanley. Hope writes a new travel report. This essay discusses how, by the reversal of point of view, a change in time and space, and creating a satirical mood, the colonizer and the colonized are interchanged and the original texts are evoked to be rewritten. The notions of Self/Other, colonial /(post-)colonial and primitive/civilized are placed in new and disturbing contexts, adding to the complex structure of this fascinating text.

scholarly journals A NEW SPECIES OF MALDIVEA GERLACH, 1962 (NEMATODA, OXYSTOMINIDAE) FROM FELIDHOO ATOLL (MALDIVES, INDIAN OCEAN) AND AN EMENDED DIAGNOSIS OF THE SUB-FAMILY AND GENUS

2019 ◽  
Vol 20 ◽  
pp. 1-9
Author(s):  
Federica Semprucci ◽  
Maria Balsamo
Keyword(s):  
New Species ◽  
Indian Ocean ◽  
Type Species ◽  
Distal Part ◽  
Complex Structure ◽  
Dorsal Side ◽  
The Other ◽  
Ventral Part ◽  
Endemic Genus ◽  
A New Species

Maldivea Gerlach, 1962 is a possible endemic genus of the Maldivian archipelago for which only M. xarifae Gerlach, 1962 has been described so far. A new species of this genus, M. complexa n.sp., was recently found in Felidhoo atoll. It reveals a more complex structure of gubernaculum than in type species which appears to be divided into two pieces: one is a sort of long wing in the ventral part of the spicule and the other one, more complex, is characterized by several curved stripes which envelop the dorsal side of the spicule distal part. According to the present considerations, diagnoses of Paroxystomininae and Maldivea are emended.

Identification and diagnosis of Leishmania mexicana complex isolates by polymerase chain reaction

Parasitology ◽  
1994 ◽  
Vol 109 (4) ◽  
pp. 423-433 ◽  
Author(s):  
S. Eresh ◽  
S. M. McCallum ◽  
D. C. Barker
Keyword(s):  
Polymerase Chain Reaction ◽  
Dna Sequences ◽  
The Other ◽  
South American ◽  
Kinetoplast Dna ◽  
Leishmania Mexicana ◽  
Chain Reaction ◽  
Potential Host ◽  
Oligonucleotide Primers ◽  
Polymerase Chain

SUMMARYFollowing cloning of Leishmania (L.) amazonensis kinetoplast DNA two recombinant clones were identified: one specific for L. (L.) amazonensis and the other specific for L. (L.) amazonensis and closely related isolates. DNA sequences from these clones were compared with those of other kinetoplastids and oligonucleotide primers were designed to be used in the polymerase chain reaction. A pair of these primers has been shown not only to be highly specific for L. mexicana complex isolates but can also be used to distinguish between L. (L.) mexicana and L. (L.) amazonensis isolates. These primers have been tested with water-lysed cultures, crude DNA extracts from human patients, potential host reservoirs, sandfly vectors and with cell pellets after isoenzyme characterization. The results of these tests indicate that the primers can be used specifically in the presence of excess host DNA originating from the majority of South American countries.

Structural constraints of secondary asymmetry in male external genitalia of Noctuidae

2013 ◽  
Vol 44 (3-4) ◽  
pp. 349-372 ◽  
Author(s):  
Zoltán Varga ◽  
László Ronkay
Keyword(s):  
Reproductive Success ◽  
Complex Structure ◽  
External Genitalia ◽  
The Other ◽  
Structural Constraints ◽  
Asymmetric Structures ◽  
Other Hand ◽  
Spatial Geometry ◽  
Male External Genitalia ◽  
Working Hypotheses

The basic architecture of the external genitalia of Noctuidae (“genital capsula”) is bilaterally symmetric. Secondary asymmetry is well-known in different subfamilies and tribes. We review and interpret the functions and processes which may be responsible for secondary asymmetry (i.e., dissymmetry) of these structures in terms of structural vs. behavioural working hypotheses. We consider the genital structures as correlated elements of a complex structure (“bauplan”) in which some changes in details can be explained by selection due to optimization of the reproductive success. Major pathways of changes are, however, delimited by some structural constraints which appear in parallel in different phyletic lines of trifine Noctuidae. One of these constraints is the subsistence of symmetry in structures with own musculature. On the other hand, some rigid parts without own musculature can evolve more rapidly and divergently in connection with the different allocation of functions. Such asymmetric structures may have some selective advantages due to the more effective stimulation, on one side, and fixation of genital parts during copulation, on the other. Asymmetric structures can effectively enhance the variations of the spatial geometry but without change of the “bauplan” which can be preserved in parallel in different taxonomical groups. It means that the originally symmetric “bauplan” with its homologies can be considered as a phyletic “heritage”, while the functional dissymmetrisation driven by selective optimization is the “habitus” in which numerous homoplasies can occur.

Anti-glycation defences in yeast

2003 ◽  
Vol 31 (6) ◽  
pp. 1409-1412 ◽  
Author(s):  
A. Ponces Freire ◽  
A. Ferreira ◽  
R. Gomes ◽  
C. Cordeiro
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Kinetic Modelling ◽  
Reductase Activity ◽  
Glycolytic Flux ◽  
Glyoxalase I ◽  
Cellular Model ◽  
Null Mutant ◽  
Glycolytic Activity ◽  
State Concentration ◽  
Null Mutants

Saccharomyces cerevisiae is an outstanding cellular model for metabolic studies in glycation. Due to its high glycolytic activity, it produces methylglyoxal, a highly reactive intracellular glycation agent, at a rate of approx. 0.1% of the glycolytic flux. We investigated methylglyoxal metabolism in Saccharomyces cerevisiae cells, using haploid null mutants. Growth studies showed that the most sensitive strains to 2-oxoaldehydes were the null mutants for GSH1 and GLO1, coding for glutathione synthase I and glyoxalase I respectively. The GRE3 null mutant, lacking aldose reductase activity, is as sensitive as the control strain. Kinetic modelling and computer simulation of this type of experiment were also performed, and we concluded that the most important parameters for controlling the intracellular concentration of methylglyoxal are the activity of glyoxalase I and the GSH concentration. Moreover, our model predicts an intracellular steady-state concentration of methylglyoxal of approx. 2 μM. Our results show that the glyoxalase pathway is the main detoxification pathway for 2-oxoaldehydes in yeast, and is likely to be the key enzymatic anti-glycation agent in these cells.

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