A direct interaction of axonin-1 with NgCAM-related cell adhesion molecule (NrCAM) results in guidance, but not growth of commissural axons.

An interaction of growth cone axonin-1 with the floor-plate NgCAM-related cell adhesion molecule (NrCAM) was shown to play a crucial role in commissural axon guidance across the midline of the spinal cord. We now provide evidence that axonin-1 mediates a guidance signal without promoting axon elongation. In an in vitro assay, commissural axons grew preferentially on stripes coated with a mixture of NrCAM and NgCAM. This preference was abolished in the presence of anti-axonin-1 antibodies without a decrease in neurite length. Consistent with these findings, commissural axons in vivo only fail to extend along the longitudinal axis when both NrCAM and NgCAM interactions, but not when axonin-1 and NrCAM or axonin-1 and NgCAM interactions, are perturbed. Thus, we conclude that axonin-1 is involved in guidance of commissural axons without promoting their growth.

Intellectual property. Publication rights in the era of open data release policies.

The open data release policy adopted by the large-scale DNA sequencing centers has made accessible valuable information that facilitates research. Herein, we argue that the data producers' rights to receive credit for at least some portion of the analyses of the data must be protected. We suggest that this protection take the form of a specification of the probable content of the primary paper the data producers intend to publish when the data gathering is complete. Rights to publish that paper ought then be restricted to the producers unless they give permission otherwise.

Transmission and scanning EM-immunogold labeling of Leishmania major lipophosphoglycan in the sandfly Phlebotomus papatasi.

Previous studies using immunostaining and light microscopy demonstrated expression of Leishmania major lipophosphoglycan (LPG) on parasites developing in the sandfly gut from 2 days post infection. By days 4 to 7 post infection, there appeared to be large amounts of parasite-free LPG deposited on/in the microvilli and epithelial cells lining the thoracic midgut, while forward migration of parasites and the morphological changes which accompany metacyclogenesis were associated with developmental modification of the LPG molecules. Studies presented here examine this process with much greater precision using electron microscopy and immunogold labeling techniques to study the different developmental forms (nectomonads, haptomonads, paramastigotes, and metacyclics) of promastigotes in the sandfly gut. Results obtained using LPG-specific monoclonal antibodies (WIC79.3, 45D3 and the metacyclic-specific 3F12) show (1) gold labeling over the cell surface, within the flagellar pocket, and extending along the entire length of the flagellum of electron-dense nectomonads observed in the abdominal and thoracic midgut regions on days 4 and 7 post infection, and of electron-lucid haptomonads in the foregut, (2) dense labeling around the flagellar tips, by which nectomonad forms bind to the midgut microvilli, but not on the microvilli themselves or within the epithelial cells lining the midgut, (3) significant metacyclic-specific (3F12) labeling on nectomonad forms in the lumen of the midgut and attached to the microvilli, and (4) dense labeling on the cell surface of electron-lucid paramastigotes in the esophagus and in the filamentous matrix surrounding paramastigote and metacyclic forms in the esophagus and pharynx. These results are discussed in the light of the proposed roles for LPG in parasite attachment to, and survival in, the sandfly gut.

A sensitive repetitive DNA probe that is specific to the Leishmania donovani complex and its use as an epidemiological and diagnostic reagent.

Leishmania donovani (HU3 strain) metacyclic promastigotes generated in vitro were used to construct a cDNA library in the bacteriophage vector lambda gt10. A cDNA clone (Lmet 2), was isolated by differential screening with metacyclic-derived or log-phase promastigote-derived cDNA. The clone insert was comprised predominantly of four copies of an imperfect 60-bp repeat motif, which was represented in the genome by multiple tandem repeats distributed among at least six chromosomes. The corresponding mRNA transcript was a developmentally regulated 12-kb doublet. The Lmet 2 sequence was entirely specific to L. donovani donovani, L. donovani (East Africa), L. donovani infantum and L. donovani chagasi, even when genomic Southern blots and slot blots of other Leishmania species were washed at low stringencies. Twenty-two strains of L. donovani were clearly detected by radiolabelled Lmet 2 cDNA probe, with signals of approximately equal intensity, irrespective of geographical origin, which encompassed widely dispersed endemic regions. The probe could detect DNA from fewer than 100 organisms and identified small numbers of promastigotes in infected sand flies. Amastigotes were also detected in impression smears of organs from infected hamsters. The Lmet 2 probe is likely to be a valuable reagent for clinical diagnosis and epidemiological investigations.

Reduced longevity and fecundity in Leishmania-infected sand flies.

Phlebotomus papatasi and P. langeroni were infected with Leishmania major and L. infantum by membrane feeding. Each sand fly ingested approximately 200 parasites per blood meal. Higher mortality in both sand fly species was seen with mixed infections than with a single parasite species. There was no significant difference between infections with either L. major or L. infantum in their natural vectors or experimental hosts. Infection significantly depressed the mean number of eggs laid per female.

Phlebotomus (Phlebotomus) duboscqi (Diptera: Phlebotominae), naturally infected with Leishmania major in southern Ethiopia.

In a survey of Leishmania infections in phlebotomine sandflies in visceral leishmaniasis focus at Aba Roba, Segen Valley, southern Ethiopia, Phlebotomus duboscqi was found naturally infected with L. major (zymodeme MON-74). This is the first isolation of L. major from a vector sandfly in Ethiopia, from an area where human and/or rodent infections with L. major are, so far, unknown.

Comparative vectorial efficiency of Lutzomyia evansi and Lu. longipalpis for transmitting Leishmania chagasi.

The infection rates and development of Leishmania chagasi in two sandfly species, Lutzomyia evansi and Lutzomyia longipalpis, were evaluated under natural and experimental conditions. Natural infection rates of Lu. evansi in San Andrés de Sotavento (Colombia) and Montañas de Peraza (Venezuela) (0.05 and 0.2%, respectively) were similar to those previously recorded for this species in Colombia and Venezuela and for Lu. longipalpis in many foci of American Visceral Leishmaniasis (AVL). Both sand fly species were able to support the development of two Colombian strains of L. chagasi experimentally acquired from dogs, hamsters or membrane feeders. However, the experimental infection rates and the sequence of parasite development in the guts of these sand flies revealed that parasite colonisation, differentiation, migration and attachment were more frequent and uniform in Lu. longipalpis than in Lu. evansi. This is consistent with a more recent association between L. chagasi and Lu. evansi, and these results might help to explain the irregularity of AVL outbreaks in foci where Lu. evansi has been reported as the sole vector.

Coadaptation of male aedeagal filaments and female spermathecal ducts of the old world phlebotomine sand flies (Diptera: Psychodidae).

The morphology of insect genitalia is often highly species-specific, and its variation has been suggested as an important impetus for evolution. Structural variation of the male genitalia and the female spermathecae in Phlebotomine sand flies is unique among the blood sucking Diptera. We describe the fine structures involved in mating for Phlebotomus papatasi (Scopoli). Relationships among the length of the spermathecal duct and aedeagal filament were studied in 26 species of Old World phelebotomine sand flies comprising 12 subgenera. In most taxa the aedeagal filaments were very long allowing direct insemination into the spermathecae, indicating that intrasexual competition among males occurs as sperm precedence. There was a positive correlation between the lengths of the spermathecal ducts and aedeagal filaments, indicating that an evolutionary "arms race" occurs between males and females over the control of fertilization. The pattern of genitalia variation in phlebotomine sand flies also indicated that differences in the lengths of the spermathecal ducts and aedeagal filaments are distributed unevenly among closely related species. Genital differences do not seem to occur in populations of the Phlebotomus argentipes Annandale & Brunetti complex, whereas differences showed strongly in closely related Phlebotomus papatasi and P. bergeroti Parrot, and in sympatric Phlebotomus martini Parrot and P. celiae Minter.

Scanning electron microscopy of eggs of Phlebotomus (synphlebotomus) martini and P. (Syn.) celiae (Diptera: Phlebotominae).

The eggs of the two closely related species, Phlebotomus (Synphlebotomus) martini and P. (Syn.) celiae have clearly distinguishable chorionic sculpturing. A new category of egg shell sculpturing in sandflies is proposed to include these species and P. duboscqi.

Geographical and age-related variation in the activity of some enzymes associated with insecticide detoxification in sandflies (Diptera: Phlebotominae).

The activity of glutathione s-transferase (GST), glucose 6-phosphate dehydrogenase (G6PD), and esterases (EST1, EST2) was measured using microtitre plate assays of laboratory colonised Phlebotomus papatasi originating in Afghanistan, Cyprus, India, Iraq, Saudi Arabia, Spain and Tunisia. The mean enzyme activity of the seven populations was significantly different. Enzyme activity did not vary significantly with age in sandflies, unlike some mosquitoes. A baseline enzyme activity for susceptibility is proposed for P. papatasi.

The field response of Sri Lankan sandflies & mosquitoes to synthetic cattle-derived attractants.

This study examines the effect of synthetic cattle-derived odours, presented with Communicable Diseases Centre (CDC) miniature light traps for mosquitoes and also with sticky traps for sandflies, in Sri Lanka. The odours alone did not increase the trapping of mosquitoes and it is concluded that other stimuli, such as CO2, must also be present to obtain a positive response. Neither CDC light traps nor sticky traps were suitable for collecting large numbers of sandflies.

The contribution of sandfly control to leishmaniasis control.

Without doubt the single most important constraint on assessing the value of vector control in leishmaniasis control is the lack of well documented examples of intervention; information is usually anecdotal and therefore it is simply not possible to evaluate precisely the significance of sandfly control in disease control. Where the vector is peri-domestic, house spraying with residual insecticides has been employed, but this has usually been as a by-product of anti-malarial control (e.g. N.E.India). Increasing incidence of leishmaniasis following the cessation of mosquito control is cited as evidence of efficacy. However, habitat modification such as the destruction of mammal reservoirs and their burrows, has been effective in arid regions of the Middle East and Central Asia, and forest clearance in combination with insecticides in French Guiana. There have been several imaginative attempts at controlling sandflies by applying insecticides to non-domestic resting sites (eg. emergent trees in rain-forest; termite hills in Kenya and S. Ethiopia) but these have met with varying degrees of success. Fortunately there is little evidence of insecticide resistance. Therefore, there is still scope for exploring control methods based on either the systematic application of insecticides alone, the impregnation of nets or curtains, or even the use of insecticides or chemosterilants in conjunction with an attractant (eg. sugar or pheromones).

Bloodmeal digestion in the midgut of Phlebotomus papatasi and Phlebotomus langeroni.

Bloodmeal digestion in midguts of the sandflies Phlebotomus papatasi and Phlebotomus langeroni (Diptera: Psychodidae) was investigated in optimized assays to detect general protease, trypsin and aminopeptidase activities using synthetic substrates. Optimal activity occurred at pH 8-9 for all enzymes examined in both species. Protease activity peaked at 24-34 h post human bloodmeal in midguts of P. papatasi and 34-48 h in P. langeroni; all endo- and exoprotease activities were completed by 50 h in P. papatasi compared to 72 h in P. langeroni. Hydrolysis of two chymotrypsin substrates was < 2% of trypsin activity in both species. Aminopeptidase activity was associated mainly with the midgut wall, whereas trypsin activity was confined to the midgut lumen. A feature of digestion in P. langeroni was the high level of aminopeptidase recorded within 10 h of the bloodmeal.

Influence of Leishmania infection on blood-meal digestion in the sandflies Phlebotomus papatasi and P. langeroni.

The presence of amastigote-initiated infections of Leishmania major parasites caused a significant suppression in alkaline protease, trypsin and aminopeptidase activity during the first 30 h after ingestion of the infected bloodmeal in Phlebotomus papatasi, the natural vector of L. major. Protease levels were significantly higher in infected flies after 72 h than in the control group, where digestion had ceased. Evidence for the suppression of protease activity in infected P. langeroni, a sympatric but un-natural vector of L. major, was less clear; there was no difference in alkaline protease activity between control and infected groups in the first 24 h. However, protease, trypsin and aminopeptidase activities were elevated after 72 h in infected P. langeroni, indicating a delay in the time to the end of digestion and passage of the bloodmeal. The potential advantages for parasite development in suppressing protease activity and extending the period of bloodmeal digestion are discussed.