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L. Major (l + major)

Distribution by Scientific Domains

Medical Sciences	54%
Life Sciences	45%

Selected Abstracts

Fish distribution and diet in relation to the invasive macrophyte Lagarosiphon major in the littoral zone of Lake Dunstan, New Zealand

ECOLOGY OF FRESHWATER FISH, Issue 1 2008
T. O. Bickel
Abstract,,, Invasive macrophytes are usually associated with negative impacts on habitat quality and a threat to native biodiversity. However, they might provide the same beneficial functions of native macrophytes, i.e., the provision of food and shelter for fish, in the absence of native macrophytes. To assess the value of the invasive macrophyte Lagarosiphon major as a fish habitat, we investigated the spatio,temporal variation in the distribution of a small littoral fish species (common bully) in the littoral of Lake Dunstan, a New Zealand hydro lake. Large- and fine-scale common bully distribution could partly be explained by the occurrence of dense L. major stands. Additionally, variability in catch per unit effort was partly explained by season and recruitment. Diet analysis indicated that common bullies in the Lagarosiphon-dominated littoral fed on invertebrates (Mollusca, Trichoptera, Chironomidae) found on exotic L. major, therefore suggesting its role as a food provider in the system. These results indicated that invasive macrophytes can provide important ecosystem functions in disturbed habitats that are otherwise devoid of native macrophytes. Any macrophyte management strategy should therefore carefully consider the costs and benefits associated with macrophyte control. [source]

The development of effector and memory T cells in cutaneous leishmaniasis: the implications for vaccine development

IMMUNOLOGICAL REVIEWS, Issue 1 2004
Phillip Scott
Summary:,Leishmania major infections induce the development of a CD4+ T-helper 1 (Th1) response that not only controls the primary infection but also results in life-long immunity to reinfection. How that immunity is maintained is unknown, although because of the existence of infection-induced immunity, there has been an assumption that the development of a vaccine against leishmaniasis would be relatively easy. This has turned out not to be the case. One problem has been the finding that a large part of the immunity induced by a primary infection depends upon the presence of persistent parasites. Nevertheless, there are ample situations where immunologic memory persists without the continued presence of antigen, providing the prospect that a non-live vaccine for leishmaniasis can be developed. To do so will require an understanding of the events involved in the development of an effective protective T-cell response and, more importantly, an understanding of how to maintain that response. Here, we review work from our laboratory, describing how Th1 cells develop in L. major -infected mice, the nature of the memory T cells that provide protection to reinfection, and how that information may be utilized in the development of vaccines. [source]

Cover Picture: J. Biophoton.

JOURNAL OF BIOPHOTONICS, Issue 5-6 2010
6/2010
Green fluorescence from GFP+ L. major in cutaneous leishmaniasis lesions on the ear of BALB/c mouse (Picture: E. Latorre-Esteves et al., pp. 328,335 in this issue) [source]

Rhesus monkey model for Leishmania major transmitted by Phlebotomus papatasi sandfly bites

MEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2001
R. J. Probst
Summary Leishmaniasis research needs a near-human model for investigations of natural infection processes, immunological responses and evaluation of treatments. Therefore, we developed a reproducible system using Leishmania major Yakimoff & Schokhor (Trypanosomatidae: Kinetoplastida), the cause of Old World zoonotic cutaneous leishmaniasis (ZCL), transmitted to rhesus monkeys Macaca mulatta (Zimmerman) (Primates: Cercopithecidae) by sandfly bites of experimentally infected Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae). Eight monkeys of presumed Indian origin (Leishmania naïve) were exposed to bites of female sandflies that had been infected with L. major by membrane-feeding on human blood seeded with amastigotes isolated from hamster footpad lesions. Infection rates of membrane-fed sandflies averaged >,85% seven days after the infective feed, with uniformly high numbers of promastigotes in the stomodaeal valve region of the sandfly gut. Nodules and ulcerating dermal lesions developed on 7/8 monkeys 2,4 weeks post-bite and persisted for 3,7 months. Monkeys also developed satellite lesions beyond the area of sandfly bites on the head, but not on the chest. Three re-challenged monkeys developed lesions that healed faster than lesions from their primary challenges. After infection, monkeys developed delayed type hypersensitivity (DTH) responses to a panel of Leishmania skin test antigens (LSTA) and, when tested by ELISA and IFA, showed significant post-infection antibody titres which typically rose for ,170 days and then gradually receded during the next 100 days following the first challenge. After the second challenge, antibody titres spiked higher within ,50 days and receded more rapidly. In contrast, four rhesus macaques of Chinese origin developed no lesions following infected sandfly bites, although they raised antibodies and LSTA reactions, indicating subclinical infection. [source]

Characterization of the A2,A2rel gene cluster in Leishmania donovani: involvement of A2 in visceralization during infection

MOLECULAR MICROBIOLOGY, Issue 4 2001
Wen-Wei Zhang
The A2 gene family is present in Leishmania donovani, which causes fatal visceral leishmaniasis in human patients, but is not present in Leishmania major, which causes cutaneous leishmaniasis infections. The A2 genes in L. donovani are stage specific and are expressed at high levels in the amastigote stage in the mammalian host, but are not expressed in the promastigote stage in the insect sandfly vector. The A2 genes are tandem repeated with a distinct gene family termed the A2rel genes. In order to characterize the structure and function of the A2,A2rel gene clusters, the 5, and 3, DNA sequences flanking the A2,A2rel cluster were isolated, sequenced and used to generate mutants through gene targeting. Although it was possible to generate partial A2,A2rel gene clusters knock-out mutants, it was not possible to delete all the A2,A2rel gene clusters completely from the L. donovani genome, suggesting that, within this cluster, there are genes that are essential for survival in culture. Characterization of these mutants revealed that A2 and A2rel gene expression was compensated by amplifying the remaining intact A2 and A2rel genes, and the proliferation of these mutants in culture and their virulence in BALB/c mice were compromised. In order to explore further the biological role of A2, the L. donovani A2 gene was introduced into L. major. In comparison with the control L. major, the A2-expressing L. major parasites demonstrated an increased ability to survive in the spleen of BALB/c mice. These data suggest that A2 plays a role in the visceralization of infection associated with L. donovani. [source]

Schistosomiasis delays lesion resolution during Leishmania major infection by impairing parasite killing by macrophages

PARASITE IMMUNOLOGY, Issue 7 2002
Anne Camille La Flamme
Summary Infection of mice with Schistosoma mansoni delays the resolution of cutaneous lesions and parasitaemia during Leishmania major infection. In contrast, L. major infection does not appear to alter the course of schistosomiasis. Analysis of the cytokine responses in the draining lymph nodes (LN) indicates that, while L. major infection had no effect on schistosome-specific interleukin (IL)-4 production by mesenteric LN (MLN) cells, coinfection with S. mansoni resulted in decreased leishmania-induced interferon (IFN)-,, tumour necrosis factor-, and nitric oxide production by popliteal LN (PLN) cells 4 weeks after L. major infection. In addition, PLN cells produced higher levels of IL-4 4 weeks after L. major infection in coinfected mice. Finally, IFN-,-stimulated macrophages isolated from S. mansoni -infected mice were impaired in their ability to kill L. major after in vitro infection. These results suggest that pre-existence of a strong Th2 response-dominated infection can alter the responses to Th1-inducing pathogens at peripheral sites and impair Th1-mediated effector functions. [source]

Cutaneous Leishmaniasis: Three Children with Leishmania major Successfully Treated with Itraconazole

PEDIATRIC DERMATOLOGY, Issue 1 2006
J. M. L. White M.R.C.P.
Treatment was successful with oral itraconazole for the children and intralesional sodium stibogluconate for the mother. Cutaneous leishmaniasis should be considered in those with apparently sterile plaques returning from endemic areas. These results suggest that itraconazole, which is ideally suited for use in children, is an effective monotherapy for L. major. [source]

In vitro Leishmanicidal activity of naturally occurring chalcones

PHYTOTHERAPY RESEARCH, Issue 2 2001
Oliver Kayser
Abstract A variety of chalcones have been shown to exhibit activity against Leishmania parasites. In contrast to synthetic or semisynthetic chalcones, only a few plant-derived compounds have been investigated. To provide a scientific rational for the antiprotozoal potency of plants used in ethnomedicine and containing chalcones, and in the search for new antiprotozoal drugs, we have carried out a primary screening for in vitro leishmanicidal activity of 20 chalcones isolated from plants. The compounds were tested against extracellular promastigotes of Leishmania donovani, L. infantum, L. enrietii and L. major, and against intracellular amastigote L. donovani residing within murine macrophages. Against the extracellular Leishmania (L. donovani), most compounds were active with EC50 values between 0.07 and 2.01,µg/mL. Some of these chalcones, 2,,4,-dihydroxy-4-methoxychalcone, 2,-hydroxy-3,4-dimethoxychalcone and 2-hydroxy-4,4,-dimethoxychalcone also significantly inhibited the intracellular survival of L. donovani parasites with EC50 values between 0.39 and 0.41,µg/mL. When tested against murine bone marrow-derived macrophages as a mammalian host cell control, all compounds with antileishmanial activities also proved to be cytotoxic to varying extents (EC50 0.19,2.06,µg/mL). Correlations between molecular structures and antileishmanial activity are discussed in detail. Specific compounds are illustrated with emphasis on their mode of action and potential for the development of selective antiprotozoal agents. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Purification and enzymatic activity of an NADH-fumarate reductase and other mitochondrial activities of Leishmania parasites,

APMIS, Issue 12 2001
M. CHEN
A 65 kD membrane-associated NADH-fumarate reductase subunit, which has a molecular weight similar to that of one of the enzyme subunits from bacteria, was purified from Leishmania donovani promastigotes. NADH-fumarate reductase and other mitochondrial enzymatic activities of L. major and L. donovani promastigotes and amastigotes were investigated. The presence of NADH-fumarate reductase was demonstrated in digitonin-permeabilized L. major promastigotes and mitochondria of L. major and L. donovani promastigotes and amastigotes. The activity of solubilized NADH-fumarate reductase was measured in L. major and L. donovani promastigotes. Succinate exhibited a clear concentration-dependent inhibitory effect on fumarate reductase, whereas fumarate also exhibited a clear concentration-dependent inhibitory effect on succinate dehydrogenase. The data indicate that fumarate reductase is an obligatory component of the respiratory chain of the parasite. Since the enzyme is an important component in the intermediate metabolism in the Leishmania parasite and is absent in mammalian cells, it could be a potential target for antileishmanial drugs. [source]

Determination of intracellular efficacies of azithromycin against Leishmania major infection in human neutrophils in vitro

CELL BIOCHEMISTRY AND FUNCTION, Issue 1 2003
Mehmet Tanyuksel
Abstract Azithromycin is one of a new class of antibiotics known as azalides. Azithromycin has high tissue affinity and this feature is thought to be due to the presence of two basic tertiary amine groups. Leishmania major, one of the causative agents of cutaneous leishmaniosis, is an obligate intracellular parasite. In this in vitro study, the potential anti-leishmanial effect of azithromycin upon intracellular forms namely the amastigote of L. major in mice peritoneal macrophages was investigated. L. major promastigotes were propagated in RPMI-1640 supplemented with 20% fetal calf serum in the log phase. The percentage of phagocytosis and microbiacidal activity of azithromycin on macrophages was assessed in the control and study groups by fluorescence microscopy, using acridine orange. Our results showed that at all the concentrations used (0.05, 0.1, 0.3, 0.6,,g,ml,1) azithromycin had no inhibitory effect on the phagocytic capacity of mouse peritoneal macrophages. Although no significant difference was observed for leishmaniacidal activity between the study and the control groups at a concentration of 0.05,,g,ml,1 (p>0.05), a significant (p<0.05) increase in leishmaniacidal activity was detected at 0.1, 0.3 and 0.6,,g,ml,1. As a result, azithromycin does not provide any contribution to the phagocytosis of L. major promastigotes in macrophages in vitro, but it increases the intracellular killing rates of amastigotes. These results suggest that it has a potential anti-leishmanial effect, and may provide a significant advantage in the treatment of the disease. Copyright © 2002 John Wiley & Sons, Ltd. [source]