Type 2 segmental Darier disease.

A 45-year-old man had bilateral disseminated involvement of Darier disease, and two of his sisters likewise had lesions suggesting this trait. Remarkably the propositus showed, in addition, a unilateral, systematized, segmental pattern of excessively pronounced Darier lesions. This unusual case can be taken as an example of type 2 segmental Darier disease. In contrast to the type 1 segmental manifestation that develops from a new mutation occurring in an otherwise healthy embryo, the type 2 segmental involvement would originate in a heterozygous embryo from postzygotic loss of the corresponding normal allele, resulting in a cell clone that is either homozygous or hemizygous for the mutation. This concept would explain why the segmental lesions were excessively pronounced and superimposed on the ordinary trait. Future studies may show whether the concept of type 2 segmental Darier disease can be confirmed at the molecular level.

Site-specific phosphorylation of synapsin I by Ca2+/calmodulin-dependent protein kinase II in pancreatic betaTC3 cells: synapsin I is not associated with insulin secretory granules.

Increasing evidence supports a physiological role of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) in the secretion of insulin from the pancreatic beta-cell, but the precise sites of action are not known. A role of this enzyme in neuroexocytosis is implicated by its phosphorylation of a vesicle-associated protein, synapsin I. Because of emerging similarities to the neuron with respect to exocytotic mechanisms, the expression and phosphorylation of synapsin I in the beta-cell have been studied. Synapsin I expression in clonal mouse beta-cells (betaTC3) and primary rat islet beta-cells was initially confirmed by immunoblot analysis. By immunoprecipitation, in situ phosphorylation of synapsin I was induced in permeabilized betaTC3 cells within a Ca2+ concentration range shown to activate endogenous CaM kinase II under identical conditions. Proteolytic digests of these immunoprecipitates revealed that calcium primarily induced the increased phosphorylation of sites identified as CaM kinase II-specific and distinct from protein kinase A-specific sites. Immunofluorescence and immunogold electron microscopy verified synapsin I expression in betaTC3 cells and pancreatic slices but demonstrated little if any colocalization of synapsin I with insulin-containing dense core granules. Thus, although this study establishes that synapsin I is a substrate for CaM kinase II in the pancreatic beta-cell, this event appears not to be important for the mobilization of insulin granules.

Human papillomavirus-16 E6/E7 transfected retinal cell line expresses the Müller cell phenotype.

The introduction of viral transforming genes into mammalian cells has been used in establishing cultures of unlimited lifespan. Although Müller cells, the predominant glial cells in the mammalian retina, have been isolated using a variety of techniques, most of these cultures have limited capacity for cell division and are often contaminated by other cell types especially astrocytes, endothelial cells and microglial cells. We have established pure cultures of retinal cells which express Müller cell characteristics and exhibit unlimited growth in vitro. We now report the techniques involved in the propagation and characterization of these cultures. Mixed retinal cultures isolated from dystrophic rat retinas were infected with defective retroviruses coding for human papillomavirus (HPV) type 16 E6 and E7 proteins. The disabled viral constructs also contained the neomycin gene allowing selection of the cultures using Geneticin, a neomycin analogue. Pure cultures were then obtained from Geneticin-selected populations by limiting end-dilution techniques. The expression of the HPV-16 E6/E7 genes in the transfected cell line was established using an HPV-16 E6/E7 PCR product to probe Northern blots. Cloned cells were found to be highly reactive for Müller cell markers including S-100, carbonic anhydrase-C, cellular retinaldehyde binding protein, and glial fibrillary acidic protein but not for glutamine synthetase. Ultrastructural studies showed stacks of cells with long elaborate processes, short microvilli, coated pits, cytoplasmic filaments, abundant perinuclear rough endoplasmic reticulum, and smooth endoplasmic reticulum extending to the cell processes. Growth patterns of late passage cells (> 50 passages) showed a lag phase of 48 hr followed by exponential growth extending past visual confluence at day 5. Since the cultures have undergone more than 240 population doublings, they can be characterized as a continuous cell line with unlimited lifespan. The HPV-16 E6/E7 transfected Müller cell line may prove useful in studies requiring abundant and pure cultures of Müller cells.

Sedimentation rates measurements in former channels of the upper Rhône river using Chernobyl 137Cs and 134Cs as tracers.

Former river channels are aquatic ecosystems with a different geomorphology generated by fluvial dynamics more or less linked to the main channel. They present different ecological successions to become terrestrial ecosystems and are thus supposed to have different sedimentation rates. The aim of this paper is to assess this sedimentation rate using radioactive tracer methodology commonly used in lake studies. Chernobyl impacts, expressed in 137Cs concentration and 137Cs/134Cs ratio, were determined in sediment cores. Sites (21) were sampled in the alluvial plain of the Upper Rhône River from 1989 to 1994. The contamination presented a high spatial heterogeneity. The maximum values encountered by site ranged between 34 and 541 Bq/kg of dry matter. The method generally gave good core profiles. Sedimentation rate ranged between 0.14 and 0.70 cm/year for the former meanders and between 0.14 and 2.86 cm/year for the braided channels. The sediment accumulation rates ranged from 0.03 to 0.25 g/cm2 per year and 0.03 to 2.26 g/cm2 per year, respectively. These values are similar to those found for Lake Geneva. The importance of the former channels in relation to the main channel is enhanced by the higher contamination and radionuclides retention. The sediment accumulation rate is related to the organic carbon content in the sediment. A comparison between two former channels with different productivity showed that the the allogenous driven system presents a high organic sediment accumulation rate with a low organic content in the sediment and inversely, a low organic sediment accumulation rate with a high organic carbon content was found for the autogenous drive system.