Aspergilosis En Colombia

Resumen Se presentan 15 casos de aspergilosis recolectados en diferentes ciudades del país. Doce fueron casos autopsiados. Los tres restantes se refieren a pacientes en quienes se efectuó una lobectomía pulmonar superior derecha por aspergiloma gigante intracavitario. En los doce primeros existía una enfermedad básica que había alterado seriamente el estado general del paciente; once de ellos habían recibido antibióticos, cinco habían recibido esteroides, y dos, agentes citotóxicos. Se cree que, tanto el estado general del paciente, como la administración de dichas drogas, favorecieron la infección micótica. De los tres casos con aspergiloma intracavitario gigante, se cree que, en uno, la micosis se implantó en una caverna tuberculosa cicatrizada. En los otros dos, la cavidad era un bronquio localmente dilatado y se consideró que no existía una infección tuberculosa.ElAspergillus posee un amplio espectro de patogenicidad. Se le puede observar en lesiones que van desde una localización intrabronquial, acompañada de mínima o nula reacción inflamatoria, hasta casos en los cuales existen lesiones pulmonares necrotizantes con diseminación hematógena a otros órganos (sistema nervioso central, hígado, riñón).     

Effect of lead on blood protoporphyrin levels of a group of ring teal ducks (Callonetta leucophrys)

This research determined the relationships between blood lead level and zinc protoporphyrin (ZnPROTO), protoporphyrin IX (PROTO), and free erythrocyte protoporphyrin (FEP) levels in a group of 18 ring teal ducks. Blood samples were drawn from two groups of ring teal ducks as part of the routine health maintenance program of the New York Zoological Park. One group of six teals had been exposed to what is believed to be lead-contaminated dust, while the second group of twelve teals was unexposed. Blood samples were analyzed for lead by flameless atomic absorption and for protoporphyrins by fluorescence. Blood lead level and log blood lead level had positive correlations with each of the protoporphyrins: the logarithmic correlations were better than the nonlogarithmic correlations, and PROTO correlated better than ZnPROTO. With one exception, PROTO levels were higher than ZnPROTO levels. The results suggest that PROTO, FEP, or ZnPROTO could serve as a biological indicator of lead poisoning in ring teal ducks.     

Nucleic acid scanning-by-hybridization of enterohemorrhagic Escherichia coli isolates using oligodeoxynucleotide arrays.

Nucleic acid scanning by hybridization (NASBH) is a non-electrophoretic typing strategy that uses gridded oligonucleotides to reproducibly characterize arbitrarily amplified nucleic acid sequences. Membrane-bound arrays of terminally-degenerate oligonucleotides were hybridized to DNA amplification fingerprinting (DAF) products from enterohemorrhagic Escherichia coli O157:H7 isolates. Numerical and cluster analysis of 64 isolates, selected by DAF to represent a single dominant amplification type identified 14 hybridization types. Results show that NASBH is a powerful alternative for the identification of closely related bacteria, can be used successfully in epidemiological studies, and holds potential in general nucleic acid diagnostics.     

Formation of intracytoplasmic lipid inclusions by Rhodococcus opacus strain PD630

An oleaginous hydrocarbon-degrading Rhodococcus opacus strain (PD630) was isolated from a soil sample. The cells were able to grow on a variety of substrates and to produce large amounts of three different types of intracellular inclusions during growth on alkanes, phenylalkanes, or non-hydrocarbon substrates. Electron microscopy revealed large numbers of electron-transparent inclusions with a sphere-like structure. In addition, electron-dense inclusions representing polyphosphate and electron-transparent inclusions with an elongated disc-shaped morphology occurred in small amounts. The electron-transparent inclusions of alkane- or gluconate-grown cells were composed of neutral lipids (98%, w/w), phospholipids (1.2%, w/w), and protein (0.8%, w/w). The major component of the cellular inclusions was triacylglycerols; minor amounts of diacylglycerols and probably also some free fatty acids were also present. Free fatty acids and/or fatty acids in acylglycerols in cells of R. opacus amounted up to 76 or 87% of the cellular dry weight in gluconate- or olive-oil-grown cells, respectively. The fatty acid composition of the inclusions depended on the substrate used for cultivation. In cells cultivated on n-alkanes, the composition of the fatty acids was related to the substrate, and intermediates of the β-oxidation pathway, such as hexadecanoic or pentadecanoic acid, were among the acylglycerols. Hexadecanoic acid was also the major fatty acid (up 36% of total fatty acids) occurring in the lipid inclusions of gluconate-grown cells. This indicated that strain PD630 utilized β-oxidation and de novo fatty acid biosynthesis for the synthesis of storage lipids. Inclusions isolated from phenyldecane-grown cells contained mainly the non-modified substrate and phenylalkanoic acids derived from the hydrocarbon oxidation, such as phenyldecanoic acid, phenyloctanoic acid, and phenylhexanoic acid, and approximately 5% (w/w) of diacylglycerols. The lipid inclusions seemed to have definite structures, probably with membranes at their surfaces, which allow them to maintain their shape, and with some associated proteins, probably involved in the inclusion formation. Received: 22 December 1995 / Accepted: 12 March 1996     

Construction of a Pseudomonas hybrid strain that mineralizes 2,4,6-trinitrotoluene.

A bacterium, Pseudomonas sp. strain C1S1, able to grow on 2,4,6-trinitrotoluene (TNT), 2,4- and 2,6-dinitrotoluene, and 2-nitrotoluene as N sources, was isolated. The bacterium grew at 30 degrees C with fructose as a C source and accumulated nitrite. Through batch culture enrichment, we isolated a derivative strain, called Pseudomonas sp. clone A, which grew faster on TNT and did not accumulate nitrite in the culture medium. Use of TNT by these two strains as an N source involved the successive removal of nitro groups to yield 2,4- and 2,6-dinitrotoluene, 2-nitrotoluene, and toluene. Transfer of the Pseudomonas putida TOL plasmid pWW0-Km to Pseudomonas sp. clone A allowed the transconjugant bacteria to grow on TNT as the sole C and N source. All bacteria in this study, in addition to removing nitro groups from TNT, reduced nitro groups on the aromatic ring via hydroxylamine to amino derivatives. Azoxy dimers probably resulting from the condensation of partially reduced TNT derivatives were also found.     

Molecular cloning and characterization of the Bacillus subtilis spore photoproduct lyase (spl) gene, which is involved in repair of UV radiation-induced DNA damage during spore germination.

Upon UV irradiation, Bacillus subtilis spore DNA accumulates the novel thymine dimer 5-thyminyl-5,6-dihydrothymine. Spores can repair this "spore photoproduct" (SP) upon germination either by the uvr-mediated general excision repair pathway or by the SP-specific spl pathway, which involves in situ monomerization of SP to two thymines by an enzyme named SP lyase. Mutants lacking both repair pathways produce spores that are extremely sensitive to UV. For cloning DNA that can repair a mutation in the spl pathway called spl-1, a library of EcoRI fragments of chromosomal DNA from B. subtilis 168 was constructed in integrative plasmid pJH101 and introduced by transformation into a mutant B. subtilis strain that carries both the uvrA42 and spl-1 mutations, and transformants whose spores exhibited UV resistance were selected by UV irradiation. With a combination of genetic and physical mapping techniques, the DNA responsible for the restoration of UV resistance was shown to be present on a 2.3-kb EcoRI-HindIII fragment that was mapped to a new locus in the metC-pyrD region of the B. subtilis chromosome immediately downstream from the pstI gene. The spl coding sequence was localized on the cloned fragment by analysis of in vitro-generated deletions and by nucleotide sequencing. The spl nucleotide sequence contains an open reading frame capable of encoding a 40-kDa polypeptide that shows regional amino acid sequence homology to DNA photolyases from a number of bacteria and fungi.     

Damage to living trees contributes to almost half of the biomass losses in tropical forests

Accurate estimates of forest biomass stocks and fluxes are needed to quantify global carbon budgets and assess the response of forests to climate change. However, most forest inventories consider tree mortality as the only aboveground biomass (AGB) loss without accounting for losses via damage to living trees: branchfall, trunk breakage, and wood decay. Here, we use ~151,000 annual records of tree survival and structural completeness to compare AGB loss via damage to living trees to total AGB loss (mortality + damage) in seven tropical forests widely distributed across environmental conditions. We find that 42% (3.62 Mg ha⁻¹ year⁻¹; 95% confidence interval [CI] 2.36–5.25) of total AGB loss (8.72 Mg ha⁻¹ year⁻¹; CI 5.57–12.86) is due to damage to living trees. Total AGB loss was highly variable among forests, but these differences were mainly caused by site variability in damage-related AGB losses rather than by mortality-related AGB losses. We show that conventional forest inventories overestimate stand-level AGB stocks by 4% (1%–17% range across forests) because assume structurally complete trees, underestimate total AGB loss by 29% (6%–57% range across forests) due to overlooked damage-related AGB losses, and overestimate AGB loss via mortality by 22% (7%–80% range across forests) because of the assumption that trees are undamaged before dying. Our results indicate that forest carbon fluxes are higher than previously thought. Damage on living trees is an underappreciated component of the forest carbon cycle that is likely to become even more important as the frequency and severity of forest disturbances increase.     

Genetic variation in the Y chromosome and sex-biased DNA methylation in somatic cells in the mouse

Mammalian Genome - Several lines of evidence suggest that the presence of the Y chromosome influences DNA methylation of autosomal loci. To better understand the impact of the Y chromosome on...     

Canopy tree mortality depends on the proportion of crown exposed to sunlight,but this effect varies with species' wood density

Understanding what drives changes in tree mortality as well as the covariates influencing trees' response is a research priority to predict forest responses to global change. Here, we combined drone photogrammetry and ground-based data to assess the influence of crown exposure to light (relative to total crown area), growth deviations (relative to conspecifics), tree size, and species' wood density (as a surrogate for light-demanding and shade-tolerant life-history strategies) on the mortality of 984 canopy trees in an Amazon terra firme forest. Trees with lower wood density were less prone to die when their proportion of crown was more exposed to sunlight, but this relationship with relative crown exposure weakened and slightly reversed as wood density increased. Trees growing less than their species average had higher mortality, especially when the species' wood density decreased. The role of wood density in determining the survival of canopy trees under varying light conditions indicates differential responses of light-demanding versus shade-tolerant species. Our results highlight the importance of accounting for life-history strategies, via plant functional types, in vegetation dynamic models aiming to predict forest demography under a rapidly changing climate. Abstract in Spanish is available with online material.