ABSTRACT
The crystal of barium pentacyanonitrosylferrate trihydrate [barium nitroprusside trihydrate, Ba[Fe(CN)5(NO)] x 3H2O] has been studied by neutron diffraction at 20 K. The study was performed to characterize the structural phase generated by the phase transition undergone by the crystals at 80 K, at which temperature the unit-cell volume doubles. This crystal phase still exists at 20 K. The crystal structure, in space group P1, is completely ordered. The positional changes of the water molecules in the present structure with respect to those of the compound at 105 K are presented.
ABSTRACT
Crystals of barium pentacyanonitrosylferrate trihydrate (barium nitroprusside trihydrate), Ba[Fe(CN)(5)(NO)].3H(2)O, have been studied by neutron diffraction in order to examine the structural behaviour of the compound in the 20-120 K temperature range and to determine the structure at 105 K. The results show the existence of a new crystal phase of the compound at 80 K (with a duplicated a parameter), which still exists at 20 K. The crystal structure at 105 K shows a rearrangement of the water molecules, which results in an ordered structure with P1 symmetry. Two of the four independent nitroprusside cations are rotated by 4.5 degrees around the [100] direction.
Subject(s)
Barium Compounds/chemistry , Nitroprusside/analogs & derivatives , Water/chemistry , Hydrogen Bonding , Models, Molecular , Molecular Structure , Neutron Diffraction , TemperatureABSTRACT
The opportunistic yeast Malassezia pachydermatis is commonly recovered from both normal and diseased skin of warm-blooded animals. The diversity of M pachydermatis isolates obtained from a wide range of hosts was investigated by the partial sequencing of the large subunit (LSU) ribosomal RNA. Among 100 isolates examined, seven types (Ia-Ig) were discriminated on the basis of nucleotide sequence diversity. The seven types differed by one to five mutations, all of them corresponding to transitions. The predominant sequence, type Ia, appeared to be ubiquitous since it was observed in isolates recovered from domestic and wild carnivora, from a monkey and from man. In contrast the sequence types Ic, Id and Ig seemed to be more host-specific; they included isolates recovered exclusively from rhinoceros, dogs and ferrets, respectively. None of the seven sequence types correlated with isolation from healthy skin or a particular lesion (otitis externa or other dermatitis). The study indicated that the skin of an animal may be colonised by more than one type of M pachydermatis.
Subject(s)
Malassezia/genetics , Malassezia/isolation & purification , RNA, Ribosomal/analysis , Tinea Versicolor/veterinary , Animals , Animals, Domestic , Animals, Wild , Base Sequence , Carnivora , Cats , Dermatitis/epidemiology , Dermatitis/veterinary , Dogs , Ferrets , Haplorhini , Humans , Molecular Sequence Data , Mutation , Otitis Externa/epidemiology , Otitis Externa/veterinary , RNA, Ribosomal/chemistry , RNA, Ribosomal/genetics , Swine , Tinea Versicolor/epidemiologyABSTRACT
Peptidolytic activity was studied in the broken-cell extracts of 17 isolates of pathogenic fungi tested with phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-Arg (PZ-PLGPA) as a substrate. All the fungi studied except Candida spp., Cryptococcus neoformans and two actinomycetes hydrolyzed the substrate and therefore contained a so-called PZ-peptidase activity. Of all the positive strains, Trichophyton schoenleinii, a pathogenic fungus showed the highest activity and was therefore chosen as a source for PZ-peptidase purification. The four chromatographic steps, a 'negative' dye column, a 'positive' dye column, hydroxyapatite Ultrogel, and modified TSK (HW 55), gave a highly purified peptidase with a 12% overall yield. Inhibitor studies suggested that the 82 000 M(r) PZ-peptidase is a metalloproteinase. Moreover it cleaved native rat type I collagen. Partial peptide sequencing showed a strong sequence homology to regions of two metalloproteinases previously identified in the yeast Saccharomyces cerevisiae and in rat.
Subject(s)
Fungi/enzymology , Metalloendopeptidases/isolation & purification , Amino Acid Sequence , Animals , Arthrodermataceae/enzymology , Collagenases/isolation & purification , Metalloendopeptidases/chemistry , Molecular Sequence Data , Protease Inhibitors/pharmacology , Rats , Sequence Homology, Amino Acid , Trichophyton/enzymology , YeastsABSTRACT
On the basis of the numbers of Nocardia strains referred to the National Reference Center for Mycoses and Antifungal Agents (NRC), Institut Pasteur, Paris, in the period from 1987 to 1990, it was estimated that between 150 and 250 cases of nocardiosis are diagnosed in France each year. A total of 63 clinical isolates were referred to the NRC and identified as Nocardia asteroides (66.7%), Nocardia farcinica (23.8%), Nocardia brasiliensis (3.2%), Nocardia otitidiscaviarum (4.8%) and Nocardia carnea (1.5%). Nocardia asteroides accounted for 71.4% of pulmonary infections, 80.0% of central nervous system infections and 80.0% of systemic infections. Patients infected with Nocardia farcinica died in 57.1% of cases, compared with 17.6% of patients infected with Nocardia asteroides. Corticosteroid therapy represented a significant factor in mortality. Isolates of Nocardia asteroides revealed variable resistance, whereas isolates of Nocardia farcinica were resistant to most antimicrobial agents. Only amoxicillin/clavulanic acid, imipenem, cefoxitin, kanamycin, amikacin, minocycline and vancomycin showed activity against both species. Nocardiosis caused by Nocardia farcinica may be a growing problem because of the relatively high incidence in AIDS patients and the resistance of this species to most antimicrobial agents.
