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).     

Substrate-dependent degradation patterns in the decay of wheat straw and beech wood by ligninolytic fungi

Summary The ability of 45 fungal strains to degrade wheat straw and beech wood was studied. Degradation patterns were defined in terms of chemical evolution of substrates and changes in lignin and polysaccharides. Trametes versicolor produced an important degradation of lignin and increased substrate digestibility, but it caused high weight losses and gave rise to similar decay patterns on both substrates. A preferential degradation of lignin was produced during straw transformation by Pleurotus eryngii. The increase of soluble lignin and decreases of lignin content and H/C ratio defined the degradation tendency after principal component analysis. The cation exchange capacity and water and alkali solubility presented the highest loading factors for the characterization of fungal transformation of beech wood. Offprint requests to: A. T. Martínez     

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.     

Artificial hybridization within Saxifraga pentadactylis (Saxifragaceae)

Saxifraga pentadactylis subsp. almanzorii , an endemic to the subalpine nucleus of Sierra de Gredos (central Spain), differs from its closest relative, subsp. willkommiana , by its less showy petals. An artificial crossing program was carried out in order to assess the degree of reproductive isolation between the subspecies. To facilitate interpretation of the results, the program was extended to 10 other interspecific hybrid combinations within sect. Saxifraga . All the data gathered are congruent with the occurrence of two evolutionary scenarios. Interspecific crossings, rendering moderate to high seed-set (in obtaining the F₁), and vigorous but relatively sterile F₁ offspring, reveal reproductive barriers at the level of the F₁ fertility, probably originated as a byproduct of divergent evolution. In contrast, intraspecific crossings within S. pentadactylis resulted in seed-set values lower than expected (in obtaining the F₁), in a majority of weak non-viable F₁ offspring but also in a few fertile F₁ hybrid specimens which were able to originate F₂ offspring. This second pattern reveals reproductive barriers at the level of the F₁ vitality, probably arisen in a quite abrupt fashion. The lower P/O for subsp. almanzorii as compared to subsp. willkommiana , together with the rest of the evidence suggest that the reproductive barriers between them might be the product of active selection against hybridization achieved by incrementing the levels of autogamy in the former.     

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.     

Organization of the origins of replication of the chromosomes of Mycobacterium smegmatis, Mycobacterium leprae and Mycobacterium tuberculosis and isolation of a functional origin from M. smegmatis

The genus Mycobacterium is composed of species with widely differing growth rates ranging from approximately three hours in Mycobacterium smegmatis to two weeks in Mycobacterium leprae. As DNA replication is coupled to cell duplication, it may be regulated by common mechanisms. The chromosomal regions surrounding the origins of DNA replication from M. smegmatis, M. tuberculosis, and M. leprae have been sequenced, and show very few differences. The gene order, rnpA-rpmH-dnaA-dnaN-recF-orf-gyrB-gyrA, is the same as in other Gram-positive organisms. Although the general organization in M. smegmatis is very similar to that of Streptomyces spp., a closely related genus, M. tuberculosis and M. leprae differ as they lack an open reading frame, between dnaN and recF, which is similar to the gnd gene of Escherichia coli. Within the three mycobacterial species, there is extensive sequence conservation in the intergenic regions flanking dnaA, but more variation from the consensus DnaA box sequence was seen than in other bacteria. By means of subcloning experiments, the putative chromosomal origin of replication of M. smegmatis, containing the dnaA-dnaN region, was shown to promote autonomous replication in M. smegmatis, unlike the corresponding regions from M. tuberculosis or M. leprae.     

Lethality and mutagenicity inHalobacterium mediterranei caused by N-methyl-N′-nitro-N-nitrosoguanidine

Compared withEscherichia coli, Halobacterium mediterranei was highly resistant to the lethal effect of N-methyl-N-nitro-N-nitrosoguanidine (nitrosoguanidine), but it was sensitive to the mutagenic action of this chemical agent. Nitrosoguanidine at 500 g ml^–1 gave a cell survival level between 1% and 10%, and this allowed us to obtain more Josamycin-resistant mutants compared with lower concentrations, which gave higher survival rates but fewer mutants. The efficiency of the mutagenicity obtained with the nitrosoguanidine treatment was examined under a variety of conditions. The optimal conditions for obtaining Josamycinresistant mutants were achieved by exposing, in darkness and without shaking, a suspension of about 10⁸ log-phase cells to 500 g nitrosoguanidine in 1 ml of 50 mM modified saline Tris-maleate buffer at pH 7.5, or in 1 ml of 5 mM modified saline Tris-citrate-maleate for 30 min at 37°C.     

Copper distribution in the normal human brain

Copper concentration was determined in samples from 38 areas of 7 normal human brains. The grey matter contained higher concentrations of copper than the white matter. Identical areas of the grey and white matter of the cerebral cortex showed significant differences between individuals. In the caudate nucleus the highest concentrations of copper were found in the tail followed by the body and the head, respectively. A negative linear regression between age and brain copper levels was demonstrated.