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David W. Thomas Amabile K. Matida Célio L. Silva Thuioshi Ioneda 《Chemistry and physics of lipids》1979,23(3):267-282
The purification procedure of 6,6′-diesters of trehalose from Corynebacterium diphtheriae was modified and the isolated substance was analysed by mass spectrometry as its permethylated derivative. The fatty acid moiety released from the glycolipid after alkaline hydrolysis was studied by mass spectral analysis of the O-methylated and O-acetylated methyl ester derivatives. By argentation thin-layer chromatography, three species of O-acetylated methyl esters were recognized, corresponding to saturated, mono-unsaturated and di-unsaturated α-branched-β-hydroxylated fatty acids. The double bond was located by ozonolysis of the O-acetylated methyl ester derivatives, by gas chromatography of the reaction product and mass spectrometry of the effluent from the gas chromatograph. The main components of each species of α-branched-β-hydroxylated fatty acids found in the gly colipid fraction of C. diphtheriae were 2-tetradecyl-3-hydroxyoctadecanoic acid (C32H64O3, corynomycolic acid), 2-tetradecyl-3-hydroxy-11-octadecenoic acid (C32H62O3, corynomycolenic acid), 2-tetradec-7′-enyl-3-hydroxy octadecanoic acid (C32H62O3) and 2-tetradec-7′-enyl-3-hydroxy-11-octadecenoic acid (C32H60O3, corynomycoldienic acid). The glycolipid fraction from C. diphtheriae is obviously a complex mixture of 6,6′-diesters of trehalose. 相似文献
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Márcia M. Medeiros Henrique B. da Silva Aramys S. Reis Renato Barboza Joanne Thompson Maria Regina D'Império Lima Cláudio R. F. Marinho Carlos E. Tadokoro 《PloS one》2013,8(11)
It is postulated that accumulation of malaria-infected Red Blood Cells (iRBCs) in the liver could be a parasitic escape mechanism against full destruction by the host immune system. Therefore, we evaluated the in vivo mechanism of this accumulation and its potential immunological consequences. A massive liver accumulation of P. c. chabaudi AS-iRBCs (Pc-iRBCs) was observed by intravital microscopy along with an over expression of ICAM-1 on day 7 of the infection, as measured by qRT-PCR. Phenotypic changes were also observed in regulatory T cells (Tregs) and dendritic cells (DCs) that were isolated from infected livers, which indicate a functional role for Tregs in the regulation of the liver inflammatory immune response. In fact, the suppressive function of liver-Tregs was in vitro tested, which demonstrated the capacity of these cells to suppress naive T cell activation to the same extent as that observed for spleen-Tregs. On the other hand, it is already known that CD4+ T cells isolated from spleens of protozoan parasite-infected mice are refractory to proliferate in vivo. In our experiments, we observed a similar lack of in vitro proliferative capacity in liver CD4+ T cells that were isolated on day 7 of infection. It is also known that nitric oxide and IL-10 are partially involved in acute phase immunosuppression; we found high expression levels of IL-10 and iNOS mRNA in day 7-infected livers, which indicates a possible role for these molecules in the observed immune suppression. Taken together, these results indicate that malaria parasite accumulation within the liver could be an escape mechanism to avoid sterile immunity sponsored by a tolerogenic environment. 相似文献
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Felipe Silva de Andrade Thiago Ribeiro de Carvalho Lucas Borges Martins Ariovaldo Antonio Giaretta 《Studies on Neotropical Fauna and Environment》2017,52(2):157-167
In this study, we re-describe the advertisement and territorial calls of Boana pardalis, carry out an acoustic comparison between the studied species and the other congeners of the B. faber group, and report for the first time the tympanic amplexus for the studied species. The advertisement call of B. pardalis can be used to supplement its diagnosis in the B. faber group based on temporal call traits, e.g. emission rate and emission pattern, as well as the call envelope. 相似文献
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C L Marcelo 《Experimental cell research》1979,120(1):201-210
Primary keratinocyte cultures free of dermal fibroblasts were used to investigate the effect of varying cyclic AMP (cAMP) concentrations on epidermal cell function. Addition of 10?3, 10?4 or 10?5 M dibutyryl cAMP to plated cells (day 1) results by day 5 in a dose dependent increase of [3H]TdR incorporation into DNA as determined by increases in both the labeling index and incorporation of 3H label into an isolated DNA fraction. 8-Bromo cAMP, another cAMP analogue, likewise induced keratinocyte proliferation. The proliferative response was dose and time dependent, and 5- to 6-fold increases in 3H label incorporated into DNA were seen at day 6, 8 and up until day 15 of culture. Moreover, elevation of cellular cAMP by addition of cholera toxin, an irreversible stimulator of adenylate cyclase, also demonstrated a time dependent stimulation of [3H]TdR uptake into DNA and increased the labeling index. Specific histochemical staining for keratinaceous protein (Kreyberg technique) demonstrated that elevated cAMP levels also enhance the production of specialized (differentiated) epidermal cells. Determination of the level of cAMP and cyclic GMP (cGMP) by RIA of partially purified fractions of the cultures revealed that addition of 8-bromo cAMP or cholera toxin to the cultures increased the levels of cAMP but not of cGMP. Addition of 8-bromo cGMP to the keratinocytes on day 1 at concentrations of 10?6, 10?7 or 10?8 M had no effect on culture proliferation on days 4, 6 and 8, although qualitative changes in the electron microscopic pattern of the culture stratification and specialization were observed. The results indicate (1) both large and moderate increases in cellular cAMP levels induce keratinocyte culture proliferation and specialization in the absence of fibroblasts or dermal influences, (2) the quantitative enhancement of keratinocyte growth and specialization occurs without apparent participation of cGMP, (3) cGMP may be a qualitative effector of epidermal cell differentiation. 相似文献
29.
A. R. Marques G. W. Fernandes I. A. Reis R. M. Assunç;ão 《Plant biology (Stuttgart, Germany)》2002,4(1):94-103
Abstract: This study focuses on the sex ratio and spatial distribution of males and females in three populations of the endemic and restricted tropical dioecious shrub, Baccharis concinna (Asteraceae) in the mountainous region of Serra do Cipó, southeastern Brazil. The proportion of female plants in the population at lower elevation (1000 m a.s.l.) was significantly greater than of male plants. At this elevation of P/N and Ca/Al ratios in the soil were also greater indicating better nutritional status of the soils. The concentration of aluminium increased significantly with the elevation ( p < 0.001), perhaps rendering soils less conducive to female plants at higher elevations. Female plants are possibly adversely affected to a greater extent by soil quality than male plants. The spatial distribution of the populations within habitat was tested by the K(t) function, where the neighbourhood of a given individual was defined by a circle with a radius (t) up to 3 m. Despite the strong tendency for aggregation, the distribution of the sexes within habitats was random and the hypothesis was not supported. The independent distribution of the sexes within habitats may be explained by nutrient homogeneity of the soils, as well as by an absence of antagonism between the sexes. Nevertheless, we found a trend for males and females to be aggregated according to their gender. 相似文献
30.
Patricia Pacheco Daniel J. Crawford Tod F. Stuessy Mario Silva O. 《American journal of botany》1991,78(4):534-543
Leaf flavonoid chemistry was examined from the three subgenera and 11 species of the endemic genus Dendroseris (Compositae, Lactuceae) of the Juan Fernandez Islands, Chile. Eight of the species are restricted to the older island (Masatierra, ca. 4 million years old), which is also closer to the mainland. Three species, one from each subgenus, are restricted to Masafuera, which is younger geologically (1–2 million years old) and 145 km further west of Masatierra. A total of 16 compounds was identified, with the 7-0-glucosides of the flavones apigenin and luteolin accounting for 12 of the constituents. Two glucosides of the flavonol quercetin were detected. Despite considerable interpopulation variation within species, six of the taxa have distinctive flavonoid profiles. Although there are few absolute differences among the subgenera, they can be distinguished chemically. Subgenus Rea contains the greatest number of compounds, and a previous cladistic analysis based on morphological features suggested this subgenus as most primitive. Subgenus Phoenicoseris is considered highly derived morphologically, and it has a reduced flavonoid chemistry. Very little reduction in flavonoid diversity was seen in the morphologically specialized subg. Dendroseris as compared to subg. Rea. A trend in reduction of numbers of compounds was seen for two of the three species on the younger island of Masafuera when compared to their presumed ancestors on Masatierra. Flavonoids of selected species of Hieracium and Hypochaeris, presumptive mainland progenitors of Dendroseris, reveal a close chemical affinity with the former genus. 相似文献