9 research outputs found
Black portraits in African-American literature: A perpective from 1920â1996, including the midwest
Virulence Attenuation of a UDP-galactose/ N-acetylglucosamine ÎČ1,4 Galactosyltransferase Expressing Leishmania donovani Promastigote
Protozoan parasites of the genus Leishmania are
the causative agent of leishmaniasis, a disease whose
manifestations in humans range from mild cutaneous
lesions to fatal visceral infections. Human visceral leishmaniasis
is caused by Leishmania donovani. Long-term
culture in vitro leads to the attenuation of the parasite. This
loss of parasite virulence is associated with the expression
of a developmentally regulated UDP-Galactose/N-acetylglucosamine
ÎČ 1â4 galactosyltransferase and galactose
terminal glycoconjugates as determined by their agglutination
with the pea nut agglutinin (PNA). Thus, all promastigotes
passaged for more than 11 times were 100%
agglutinated with PNA, and represent a homogeneous
population of avirulent parasites. Identical concentrations
of PNA failed to agglutinate promastigotes passaged for â€5
times. These PNAâ promastigotes were virulent. Promastigotes
passaged from 5 to 10 times showed a mixed
population. The identity of populations defined by virulence
and PNA agglutination was confirmed by isolating
PNA+ avirulent and PNAâ virulent clones from the 7th
passage promastigotes. Only the PNA+ clones triggered
macrophage microbicidal activity. The PNA+ clones lacked lipophosphoglycan. Intravenous administration of [14C]
galactose-labeled parasite in BALB/c mice resulted in rapid
clearance of the parasite from blood with a concomitant
accumulation in the liver. By enzymatic assay and RT-PCR
we have shown the association of a UDP-Galactose/Nacetylglucosamine
ÎČ1,4 galactosyltransferase with only the
attenuated clones. By immunofluorescence we demonstrated
that the enzyme is located in the Golgi apparatus. By
western blot analysis and SDS-PAGE of the affinitypurified
protein, we have been able to identify a 29 KDa
galactose terminal protein from the avirulent clones
The Mars Atmosphere and Volatile Evolution (MAVEN) Mission
The MAVEN spacecraft launched in November 2013, arrived at Mars in September 2014, and completed commissioning and began its one-Earth-year primary science mission in November 2014. The orbiterâs science objectives are to explore the interactions of the Sun and the solar wind with the Mars magnetosphere and upper atmosphere, to determine the structure of the upper atmosphere and ionosphere and the processes controlling it, to determine the escape rates from the upper atmosphere to space at the present epoch, and to measure properties that allow us to extrapolate these escape rates into the past to determine the total loss of atmospheric gas to space through time. These results will allow us to determine the importance of loss to space in changing the Mars climate and atmosphere through time, thereby providing important boundary conditions on the history of the habitability of Mars. The MAVEN spacecraft contains eight science instruments (with nine sensors) that measure the energy and particle input from the Sun into the Mars upper atmosphere, the response of the upper atmosphere to that input, and the resulting escape of gas to space. In addition, it contains an Electra relay that will allow it to relay commands and data between spacecraft on the surface and Earth