Manifestaciones neuroftalmológicas como complicación de una infección por Mycoplasma pneumoniae y desarrollo posterior de una encefalitis aguda diseminada / Neuro-ophthalmological manifestations as complication of an infection with Mycoplasma pneumoniae and subsequent development of disseminated acute encephalitis

El objetivo es describir dos cuadros clínicos neuroftalmológicos en niños por infección sistémica por Mycoplasma pneumoniae (M. pneumoniae). Se presentan los casos de dos niñas de 14 y 12 años que acudieron a urgencias: la primera con oftalmoplejía internuclear y la segunda con pérdida de visión y cefalea. No presentaban otra focalidad neurológica. En la imagen de resonancia magnética se evidenciaron placas hiperintensas en ambas, sugerentes de cuadro desmielinizante. Al mes, los síntomas neuroftalmológicos se resolvieron y las resonancias magnéticas de control fueron normales. El diagnóstico fue encefalitis diseminada aguda secundaria a M. pneumoniae. El diagnóstico se hace por PCR (gold standard) y/o IgM en serología. Es importante pensar en esta posible etiología ante casos sugerentes de enfermedad desmielinizante. Existe controversia sobre el papel de los antibióticos y si se contemplan los corticoides. Como conclusión, M. pneumoniae debe ser diagnóstico diferencial en afectaciones neuroftalmológicas agudas en niños

The purpose of this article is to describe two paediatric neuro-ophthalmological clinical cases caused by a systemic infection due to Mycoplasma pneumoniae (M. pneumoniae). The cases are two girls aged 14 and 12 seen in the Emergency Department: The first one had internuclear ophthalmoplegia and second with loss of vision and headache. They had no other neurological foci. Magnetic resonance imaging showed hyperintense plaques in both, suggestive of a demyelinating disease. One month later, the neuro-ophthalmological symptoms resolved, with normal follow-up magnetic resonance imagings. The diagnosis was acute disseminated encephalitis secondary to M. pneumoniae. The diagnosis was made using PCR (gold standard) and/or IgM in serology. It is important to think about this possible aetiology in cases of suggestive demyelinating disease. There is controversy about the role of antibiotics and on whether corticosteroids are contemplated. In conclusion, M. pneumoniae must be a differential diagnosis in acute neuro-ophthalmological disorders in children

Neuro-ophthalmological manifestations as complication of an infection with Mycoplasma pneumoniae and subsequent development of disseminated acute encephalitis. / Manifestaciones neuroftalmológicas como complicación de una infección por Mycoplasma pneumoniae y desarrollo posterior de una encefalitis aguda diseminada.

The purpose of this article is to describe two paediatric neuro-ophthalmological clinical cases caused by a systemic infection due to Mycoplasma pneumoniae (M. pneumoniae). The cases are two girls aged 14 and 12 seen in the Emergency Department: The first one had internuclear ophthalmoplegia and second with loss of vision and headache. They had no other neurological foci. Magnetic resonance imaging showed hyperintense plaques in both, suggestive of a demyelinating disease. One month later, the neuro-ophthalmological symptoms resolved, with normal follow-up magnetic resonance imagings. The diagnosis was acute disseminated encephalitis secondary to M. pneumoniae. The diagnosis was made using PCR (gold standard) and/or IgM in serology. It is important to think about this possible aetiology in cases of suggestive demyelinating disease. There is controversy about the role of antibiotics and on whether corticosteroids are contemplated. In conclusion, M. pneumoniae must be a differential diagnosis in acute neuro-ophthalmological disorders in children.

The structural role of the carotenoid in the bacterial light-harvesting protein 2 (LH2) of Rhodonbacter capsulatus. A Fourier transform Raman spectroscopy and circular dichroism study.

In previous work (Zurdo J, Fernández-Cabrera C and Ramírez JM (1993) Biochem J 290: 531-537), it had been shown that selective extraction of the carotenoid from the light-harvesting protein 2 (LH2) of Rhodobacter capsulatus induced the dissociation of 800-nm absorbing bacteriochlorophyll (Bchl), a 10-nm red shift of 854-nm Bchl, and a decrease of the stability of the protein in detergent solution. In the present study, the Fourier transform Raman and near-infrared circular dichroism spectra of native and carotenoid-depleted LH2 membrane preparations were compared. It was found that while the coupled carbonyls of 854-nm Bchl remained specifically H-bonded to the peptides after carotenoid extraction, the optical activity of the near-infrared electronic transition was significantly altered. Given the excitonic origin of such optical activity, our data suggest that carotenoid extraction elicits a rearrengement of the chromophore cluster and of the associated polypeptide subunits. This implies a significant role of the carotenoid in maintaining the native quaternary structure of the protein, which would be consistent with the observed dissociation of 800-nm Bchl and the loss of solubilized LH2 stability that result from carotenoid removal. There is no evidence for a similar role of the carotenoid in the LH1 protein.

A structural role of the carotenoid in the light-harvesting II protein of Rhodobacter capsulatus.

The membrane-linked light-harvesting II protein (LHII) of Rhodobacter capsulatus was partly depleted of carotenoids by selective extraction with light petroleum. Carotenoid removal was accompanied by bleaching of the Qy(S1<--S0) absorption band of bacteriochlorophyll (Bchl) a near 800 nm, by a bathochromic shift and a broadening of the other Bchl Qy band at 850 nm, and by the formation of a weak Qy band of dissociated Bchl near 770 nm. The changes in the 800 and 850 nm bands seemed to reflect alterations in only those Bchl molecules that had lost their associated carotenoids, firstly, because the extent of the changes was closely correlated to the degree of carotenoid extraction, and, secondly, because the residual fraction of carotenoid-containing LHII, which could be almost quantitatively recovered from the membrane after detergent solubilization and ion-exchange chromatography, showed an unmodified LHII absorption spectrum. The Bchl responsible for the shifted 850 nm band remained bound to protein, since its visible (Qx) transition seemed to retain the induced optical activity of the native bound pigment. Besides, the shifted Bchl could act as an efficient acceptor of singlet excitation energy from the pigments of the intact LHII fraction. The close similarity between the spectroscopic Bchl changes that accompany carotenoid extraction and the differential spectral features of carotenoidless LHII of Rhodobacter mutants, previously reported, strongly suggests that the direct cause of the spectral modifications is the absence of carotenoid and not any independent effect of the experimental manipulation of the membrane. Several interpretations of the structural changes that underlie the observed spectral changes are possible. The simplest one is to assume that carotenoid removal elicits an alteration in the angle between the Qy transition moments of two strongly interacting Bchl molecules.

Enhancement of carotenoid-to-chlorophyll singlet energy transfer by carotenoid-carotenoid interaction.

The apparent quantum yield of singlet-singlet spirilloxanthin-to-bacteriochlorophyll a energy transfer increases linearly with the residual spirilloxanthin content in Rhodospirillum rubrum membrane vesicles from which this carotenoid has been partially removed. Since it has been previously shown that carotenoid-carotenoid interaction is a linear function of the residual spirilloxanthin level in the major pigment-protein complex of those vesicles (Zurdo, J., R. M. Lozano, C. Fernandez-Cabrera, and J. M. Ramirez. 1991. Biochem. J. 274:881-884), it appears that such degenerate interaction enhances singlet energy transfer. Part of the enhancement may be explained if the energy donor is the spirilloxanthin 1Bu----1Ag (S2----S0) transition, because exciton coupling probably brings its energy closer to that of the Qx (S2----S0) transition of bacteriochlorophyll. In contrast, it seems that the possible stabilization of the spirilloxanthin 2Ag (S1) state would hardly improve energy transfer, because this hidden state probably lies below the S1 bacteriochlorophyll state. In any case, the stabilizing effects of carotenoid-carotenoid interactions seem insufficient to explain the enhancement of energy transfer. Direct or indirect effects of carotenoid dimerization on the three-dimensional structure of the pigment cluster appear to be required to account for such enhancement.

Dimeric carotenoid interaction in the light-harvesting antenna of purple phototrophic bacteria.

The carotenoid content of intracytoplasmic membrane vesicles isolated from purple phototrophic bacteria was reduced to a variable extent by mild extraction with light petroleum. Using preparations obtained from Rhodobacter capsulatus strains that contained the Light Harvesting System I (LHI) complex as the only major photosynthetic holochrome, it was shown that the visible circular dichroism of the carotenoids increased with the square of the membrane carotenoid content, as expected from being caused by dimeric exciton interaction. No chirality resulting from twists of the individual planar chromophore was detected. Therefore the contribution to carotenoid optical activity of non-degenerate interactions with bacteriochlorophyll or the apoprotein does not appear to be significant. The broadening of the absorption band of the bound pigment, caused by the splitting of the monomer transition, was demonstrated in membrane vesicles of both Rb, capsulatus and Rhodospirillum rubrum as a decrease of the fine structure of the band. Furthermore, the dimeric organization of the carotenoid pigments in the bacterial LHI complex accounted for the observed quantitative relationship between the fine structure of the band and the carotenoid content of the membrane.

The contribution of the carotenoid to the visible circular dichroism of the light-harvesting antenna of Rhodospirillum rubrum.

The visible c.d. spectrum of wild-type Rhodospirillum rubrum shows positive bands [Dratz, Schultz & Sauer (1966) Brookhaven Symp. Biol. 19, 303-318] that are largely due to the B880 antenna pigments, bacteriochlorophyll a and carotenoids. The bacteriochlorophyll c.d. band was absent from the spectrum of R. rubrum G9, a mutant unable to synthesize coloured carotenoids, and could be partly restored by adding extracted carotenoids to freeze-dried membrane vesicles isolated from that mutant. Therefore it seems to arise from either bacteriochlorophyll-carotenoid interactions or bacteriochlorophyll-protein interactions that are induced by the carotenoid. The more complex carotenoid c.d. band had different shapes in native and reconstituted carotenoid-containing membranes. Such differences suggest that the optical activity of the carotenoid in the B880 antenna arises from both non-degenerate and degenerate interactions.

The ftsA gene product: a possible connection between DNA replication and septation in Escherichia coli.

The study of Escherichia coli strain D-2, which harbours the ftsA2(ts) allele, has shown that temperature-induced filaments of this strain can divide, at 30 degrees C, in the absence of DNA replication and translation. Strain D-2 is thermosensitive during a period coincident with that in which the termination protein should be synthesized and exert its action. The ftsA gene product, which participates in the structure of the septum, needs for its synthesis a short period of DNA replication. The FtsA protein could be involved in a mechanism that coordinates chromosome replication and cell division by a pathway different from and independent of the SOS-induced response.