Gene expression in Chromobacterium violaceum

The repertoire of 4,431 open reading frames (ORFs), eight rRNA operons and 98 tRNA genes of Chromobacterium violaceum must be expressed in a regulated manner for successful adaptation to a wide variety of environmental conditions. To accomplish this feat, the organism relies on protein machineries involved in transcription, RNA processing and translation. Analysis of the C. violaceum genome showed that transcription initiation, elongation and termination are performed by the five well-known RNA polymerase subunits, five categories of sigma 70 factors, one sigma 54 factor, as well as six auxiliary elongation and termination factors. RNA processing is performed by a variety of endonucleases and exonucleases, such as ribonuclease H, ribonuclease E, ribonuclease P, and ribonuclease III, in addition to poly(A) polymerase and specific methyltransferases and pseudouridine synthases. ORFs for all ribosomal proteins, except S22, were found. Only 19 aminoacyl-tRNA synthetases were found, in addition to three aminoacyl-tRNA synthetase-related proteins. Asparaginyl-tRNA (Asn) is probably obtained by enzymatic modification of a mischarged aminoacyl-tRNA. The translation factors IF-1, IF-2, IF-3, EF-Ts, EF-Tu, EF-G, RF-1, RF-2 and RF-3 are all present in the C. violaceum genome, although the absence of selB suggests that C. violaceum does not synthesize selenoproteins. The components of trans-translation, tmRNA and associated proteins, are present in the C. violaceum genome. Finally, a large number of ORFs related to regulation of gene expression were also found, which was expected, considering the apparent adaptability of this bacterium

Paracoccidioidomycoses: a sequential histopathologic study of lesions in experimentally infected rats

Foram utilizados ratos albinos, fêmeas, para o estudo histopatológico sequencial da paracoccidioidomicose experimental. Os animais foram inoculados intraperitonealmente com uma cepa de Paracoccidioides brasiliensis na fase leveduriforme e sacrificados, em determinados intervalos, a partir de 1 a 168 dias pós-infecçäo;cada animal recebeu um inóculo de 4 x 10 células em 0,8 ml de salina. Os animais controles receberam salina contendo raspado do meio de cultura. Foram estudados tecidos correspondentes à área de inoculaçäo. Analisou-se pela microscopia óptica o processo inflamatório granulomatoo em todo o seu conjunto, estudando a populaçäo celular, a matriz extracellular e apresença e características do fungo. Os resultados possibilitaram desmembrar a cinética da resposta inflamatória em três fases: 1) neutrofílica ou macrofágica-neutrofílica; 2) pré-granulomatosa; 3) granulomatosa. A síntese de matriz extracelular iniciou=se pela deposiçäo de material fibrinóide, intensificando-se de modo gradativo com depósito de colágeno, de proteoglicanos e glicoproteínas. Os parasitos estavam presentes em todas as fases estudadas. Períodos de reativaçäo da doença eram nitidamente evidenciados através da concomitância de granulomas recém-formados com granulomas mais antigos, indicando que o processo granulomatoso neste modelo näo resolve a doença, nem täao pouco consegue limitar a disseminaçäo do fungo por um período prolongado

Intrinsic vascularization of granuloma in experimental paracoccidioidomycosis

Rats infected with Paracoccidioides brasiliensis exhibited vascularized granulomas during the granulomatous stage, with more intensity on the 49 th day after infection. These data change the classical belief that the granuloma is always an avascular structure. The authors suggest that the granuloma is under the balanced influence of angiogenic or angiostatic factors, with the usual predominance of the latter, with the consequent advantage of limited antigen diffusion to the vascular system

Congenital and nursing effects on the evolution of Schistosoma mansoni infection in mice

Modification of the immune response to schistosomal infection in children or offspring born to mother R infected with Schistosoma mansoni has been demonstrated in human and in experimental schistosomiasis. One of the hypothesis to explain this fact could be the transfer of circulating antigens and antibodies from mother to foetus through the placenta or from mother to child by milk. The results of this spontaneous transference are controversial in the literature. In an attempt to investigate these questions, we studied one hundred and twenty offspring (Swiss mice), sixty born to infected-mothers (group A) and sixty born to non-infected mothers (group B). These were percutaneously infected with 50 cercariae/mouse, and divided in six sub-groups (20 mice/sub-group), according to the following schedule: after birth (sub-groups A.I and B.I), 10 days old (sub-groups A.II and B.II) and 21 days old (sub-groups A.III and B.III). After the exposure period, the young mice returned to their own mothers for nursing. Six weeks later, the mice were killed. We obtained the following results: 1) There is transference of antibody to cercariae (CAP), adult worms (SWAP) and egg antigens (SEA) from the infected mothers to the offspring, probably through placenta and milk; 2) Offspring born to infected mothers exhibit much less coagulative hepatic necrosis and show a lower number of eggs in the small intestine and a less intense and predominant exsudative stage of the hepatic granulomas when compared with the exsudative-productive stage of the control groups. The findings suggest that congenital and nursing factors can interfere on the development of the schistosomiasis infection, causing an hyporesponse to the eggs.