[Tumoral calcinosis at an unusual site in a haemodialysis patient]. / Calcinose pseudotumorale de localisation inhabituelle chez un patient hémodialysé.

BACKGROUND: Tumour-like calcinosis is a rare cause of tissue calcification in patients on maintenance haemodialysis for chronic renal failure. Its estimated incidence is between 0.5 and 7% of haemodialysis patients. PATIENTS AND METHODS: A 29-year-old male patient was referred to our department with a large cervical mass lesion increasing in size for two months. The patient had been on maintenance haemodialysis for one year for chronic renal failure during which time he reported multiple episodes of cervical trauma. Cervical MRI demonstrated a 11 x 9 cm calcified tumoral mass extending to the cervical muscles and the lower cervical spine (C6, C7, T1), accompanied by C6 osteolysis. Laboratory studies revealed secondary hyperparathyroidism with elevated calcium-phosphorus product. The patient underwent parathyroidectomy and several weeks later, there was a dramatic regression of the tumoral calcinosis. Renal transplantation was performed secondarily with no recurrence of the tumoral calcification after six years of follow-up. DISCUSSION: Tumour-like calcinosis of the lower cervical spine with osteolysis of the cervical vertebrae is very rare. The principal contributing factors are hyperparathyroidism, elevation of calcium-phosphorus product and local trauma. Optimal treatment of these calcifications remains controversial. While surgical resection of the mass is commonly recommended, in our case report, despite the initial aggressiveness of the lesion, surgery was not performed and treatment of hyperparathyroidism alone was sufficient to ensure dramatic improvement with complete resolution of the calcinosis within few weeks.

[Positive photobiological investigation in Jessner's lymphocytic infiltration of the skin]. / Photodéclenchement des lésions dans la maladie de Jessner-Kanof.

BACKGROUND: Jessner's lymphocytic infiltration of the skin is a rare and benign disorder. Its clinical course is cyclic with remissions and exacerbations. In this disease, photosensitivity was previously noticed by authors and recently demonstrated. We report four new cases with positive photobiological investigation. CASE REPORTS: Four patients (2 males, 2 females), with a mean age 36 years were seen with erythematous papules or discoid plaques on face, arms and upper trunk. The onset of disease occurred after sun exposure in summer. Skin biopsies showed perivascular lymphocytic infiltration in the dermis. All patients relapsed cyclically with incomplete healing during winter. Photobiological investigation elicited skin lesions in a broad spectrum of UV: UVB (2 cases), UVA (1 case), UVA and UVB (1 case). In all patients treatment with oral antimalarials and external photoprotection was effective. DISCUSSION: Our data suggest that photosensitivity history in patients with Jessner's lymphocytic infiltration of the skin should be searched for, and confirmed by provocative phototesting. This relevant event could guide the therapeutic strategy because antimalarials were effective for the Jessner's lymphocytic infiltration cases with photosensitivity.

Caenorhabditis elegans is a model host for Salmonella typhimurium.

The idea of using simple, genetically tractable host organisms to study the virulence mechanisms of pathogens dates back at least to the work of Darmon and Depraitère [1]. They proposed using the predatory amoeba Dictyostelium discoideum as a model host, an approach that has proved to be valid in the case of the intracellular pathogen Legionella pneumophila [2]. Research from the Ausubel laboratory has clearly established the nematode Caenorhabditis elegans as an attractive model host for the study of Pseudomonas aeruginosa pathogenesis [3]. P. aeruginosa is a bacterium that is capable of infecting plants, insects and mammals. Other pathogens with a similarly broad host range have also been shown to infect C. elegans [3,4]. Nevertheless, the need to determine the universality of C. elegans as a model host, especially with regards pathogens that have a naturally restricted host specificity, has rightly been expressed [5]. We report here that the enterobacterium Salmonella typhimurium, generally considered to be a highly adapted pathogen with a narrow range of target hosts [6], is capable of infecting and killing C. elegans. Furthermore, mutant strains that exhibit a reduced virulence in mammals were also attenuated for their virulence in C. elegans, showing that the nematode may constitute a useful model system for the study of this important human pathogen.

C. elegans dynamin-related protein DRP-1 controls severing of the mitochondrial outer membrane.

Little is known about the mechanism of mitochondrial division. We show here that mitochondria are disrupted by mutations in a C. elegans dynamin-related protein (DRP-1). Mutant DRP-1 causes the mitochondrial matrix to retract into large blebs that are both surrounded and connected by tubules of outer membrane. This indicates that scission of the mitochondrial outer membrane is inhibited, while scission of the inner membrane still occurs. Overexpressed wild-type DRP-1 causes mitochondria to become excessively fragmented, consistent with an active role in mitochondrial scission. DRP-1 fused to GFP is observed in spots on mitochondria where scission eventually occurs. These data indicate that wild-type DRP-1 contributes to the final stages of mitochondrial division by controlling scission of the mitochondrial outer membrane.

Recurrent painful hand crisis in a four-year-old girl, revealing an erythropoietic protoporphyria.

We report the case of a 4-year-old girl, who had been suffering for 2 years from a recurrent, painful crisis affecting both hands, following sun exposure. There were no obvious cutaneous lesions, which initially caused us to consider a diagnosis of a psychiatric disorder. However, the diagnosis of erythropoietic protoporphyria was then established by the demonstration of elevated levels of free protoporphyrin in erythrocytes. The present case illustrates the effectiveness of beta-carotene associated with canthaxanthin in erythropoietic protoporphyria.

Contribution of the GTPase domain to the subcellular localization of dynamin in the nematode Caenorhabditis elegans.

Caenorhabditis elegans dynamin is expressed at high levels in neurons and at lower levels in other cell types, consistent with the important role that dynamin plays in the recycling of synaptic vesicles. Indirect immunofluorescence showed that dynamin is concentrated along the dorsal and ventral nerve cords and in the synapse-rich nerve ring. Green fluorescent protein (GFP) fused to the N terminus of dynamin is localized to synapse-rich regions. Furthermore, this chimera was detected along the apical membrane of intestinal cells, in spermathecae, and in coelomocytes. Dynamin localization was not affected by disrupting axonal transport of synaptic vesicles in the unc-104 (kinesin) mutant. To investigate the alternative mechanisms that dynamin might use for translocation to the synapse, we systematically tested the localization of different protein domains by fusion to GFP. Localization of each chimera was measured in one specific neuron, the ALM. The GTPase, a middle domain, and the putative coiled coil each contribute to synaptic localization. Surprisingly, the pleckstrin homology domain and the proline-rich domain, which are known to bind to coated-pit constituents, did not contribute to synaptic localization. The GFP-GTPase chimera was most strongly localized, although the GTPase domain has no known interactions with proteins other than with dynamin itself. Our results suggest that different dynamin domains contribute to axonal transport and the sequestration of a pool of dynamin molecules in synaptic cytosol.

A new collection of thermosensitive endocytosis mutants in the cellular slime mold Dictyostelium discoideum.

We used a photoactivatable fluid-phase marker to isolate a new collection of thermosensitive endocytosis mutants in the cellular slime mold Dictyostelium discoideum. All the strains were thermosensitive for growth on bacteria or axenic medium at 27 degrees C. Initial rates of endocytosis rapidly decreased upon incubation at the restrictive temperature, but surprisingly most of the strains showed a transient recovery of activity with prolonged exposure to 27 degrees C. Endocytosis and exocytosis activities were uncoupled for some of the cell lines at 27 degrees C whereas the others had to be shifted to 29 degrees C. Further molecular analysis of these mutants could lead to the discovery of new proteins involved in endocytosis and its regulation.

Left atrial myxoma in the elderly: diagnosis by M-mode and bidimensional echocardiography.

Two cases are reported of left atrial myxoma in elderly patients, diagnosed by combined M-mode and bidimensional echocardiography. One patient was an 80-year-old man presenting with typical signs of mitral obstruction by an atrial tumor. His symptoms were erroneously attributed to chronic bronchitis until an echocardiogram was obtained. The other patient was a 70-year-old woman with atrial fibrillation of one year's duration. Left atrial myxoma, although rarely observed in the elderly, may be diagnosed easily by means of echocardiography. Some cases may prove amenable to surgical treatment.