Laryngeal papillomas: local cellular immune response,keratinization and viral antigen

Virchows Archiv B Cell Pathology - Various parameters of the local cellular response have been studied in 16 laryngeal papillomas from ten patients with recurrent papillomas as well as normal...     

Ontogeny of the photoreceptors in the embryonic retina of the viviparous guppy,Poecilia reticulata P. (Teleostei)

Summary Ultrastructural analyses of retinal development in the guppy embryo show that at midgestation all types of photoreceptors are differntiated in the fundus, and at birth differentiation extends over the whole retina. Formation of discs of outer segments is more rapid in rods than in cones. Double cones differentiate simultaneously with long single cones and are formed by the adhesion of two primordial inner segments; short single cones develop last. Wherever cones are differentiated, they are arranged in an adult-type square mosaic. The rods in the embryo, as opposed to the adult, are likewise regularly arranged within the mosaic unit.These results are at variance with the generally held opinion that adult teleosts which possess duplex retinae have larvae with pure cone retinae, and that rods, double cones and mosaics appear in late larval life or only at metamorphosis.In the double cones of the guppy embryo subsurface cisternae develop along the adjoining primordial inner segments. Additionally, regularly distributed subsurface cisternae are formed in the regions of intimate contact of long single cones with double cones and rods.We suggest that the early development of rods and double cones, and a square-mosaic with regular distribution of rods and subsurface cisternae, provide the newly born with a fully functional optical apparatus, especially suited to perception of movements. This is necessary for its survival against predatory, especially maternal, attacks.This work was in part subsidized by a grant from the Medical Research Council of Ireland to Y.W.K.     

Étude expérimentale des variations de la teneur en eau au cours de la déshydratation et de la réhydratation chez la Fougère:Notochlaena vellea R. Br.

Experimental Study of changes in water content during dehydration and rehydration of the Fern: Notochlaena vellea R. Br.—This study takes place after studies made on otherPolypodiaceen Ferns. We have shown that, in these ferns, the survival duration was longer for the subterranean organs than for aerial ones. The problem was to show that this difference is due to a lower dehydration of the subterranean tissues. As far as we looked at the total water deficiency, we did not find any significant difference between the leaves and the meristematic parts of the subterranean organs: the main difference is the rate of rehydration which is higher in subterranean parts.     

Growth-related gene expression in Nicotiana tabacum mesophyll protoplasts

Eight cDNAs whose genes are more strongly expressed in suspension cells in growth phase than in stationary phase and at a low level in mature leaves have been isolated. The corresponding mRNAs are abundantly accumulated in young plant organs and in germinating seeds but are almost undetectable in mature plant tissues and dry seeds. Six of these cDNAs were characterized by comparison of nucleotide and protein sequences to the EMBL and SWISSPROT databanks. These eight growth-related genes are expressed in protoplasts isolated from Nicotiana tabacum mesophyll cells shortly after preparation (4 h). Two of them are expressed in freshly isolated protoplasts (early genes), while the other six are detected after 4 h of culture (late genes). Seven are more abundantly expressed in protoplasts than in growing plant organs while one growth-related gene is weakly expressed in protoplasts, as is the histone H₄ gene. They seem to be induced in protoplasts by a synergistic effect of wounding and maceration. Sustained expression of the early genes is dependent on the presence of sucrose in the culture medium.     

In vivo isolation of a pPJ3a-λ cosmid mediated by the Tn2307 transposon

From an E. coli cell harboring plasmid pPJ3b (= pPJ3a::Tn2301) and infected with phage λ, we have isolated two defective phages having inserted pPJ3a DNA and Tn2301 in their genomes. One of them has been extensively characterized: it behaves like a cosmid, i.e., upon injection into the cell, its DNA circularizes and replicates as a plasmid (pPJ10); it can be packaged again in λ heads, provided the presence of a phage helper. Furthermore, heteroduplex analysis has shown that in pPJ10, the transposon Tn2301 is inverted compared to its direction in pPJ3b. We give evidence suggesting that this type of inversion is in part mediated by Tn2301.     

Nonsense mutations in the amylomaltase gene and other loci of Streptococcus pneumoniae

Molecular Genetics and Genomics - Maltose-negative mutations in the amylomaltase gene of Streptococcus pneumoniae were examined for the presence of nonsense mutations. Out of 28 single-site mutants...     

Regulation of thymidine kinase synthesis during the cell cycle of Physarum polycephalum by the heat-sensitive system which triggers mitosis and S phase

Temperature shifts from 22 to 32 °C perturb one of the systems responsible for mitosis triggering in the plasmodia of Physarum (Myxomycetes). In order to determine if the same regulatory mechanism could also be involved in some other cell cycle events, the effects of temperature shifts on the peak of thymidine kinase (EC 2.7.1.21, ATP : thymidine 5′-phosphotransferase) synthesis have been studied. At 22 °C, the increase in thymidine kinase (tdk) activity begins shortly before mitosis and is thus always associated with the end of the G2 phase, the mitosis and the beginning of the S phase. The consequences of temperature shifts depend upon their position in the cell cycle. In all cases, a peak of tdk occurs concomitantly with the 32 °C mitosis. But, when the temperature shift is applied 90-15 min before the control metaphase at 22 °C, another peak of tdk is observed at 32 °C in absence of mitosis, but at the same time as the control mitosis at 22 °C. These results indicate that the increase in the synthesis of tdk is controlled by the heat-sensitive regulatory system which plays a role in the onset of mitosis and S phase. We further suggest that the increase in the synthesis of tdk and the triggering of mitosis are both controlled by the amount of a heat-sensitive effector. But the former takes place when the amount of the effector reaches a critical value lower than the value necessary to trigger mitosis.     

Decouverte de Septorella brachycera grambast et de Septorella ultima Grambast (Charophytes,Clavatoracees) dans le Maestrichtien superieur des Petites Pyrenees. Consequences stratigraphiques

The discovery of an assemblage of Clavatoraceae including Septorella brachycera and S. ultima in the “Marnes d'Auzas” (upper Maestrichtian) of the Petites Pyrénées constitutes the first element of comparison between the upper Cretaceous of the Petites Pyrénées and Provence, but creates a problem with regard to the subdivision of the provencial Rognacian, based, in part, on the superposition of these two species.     

What is hidden in the pannexin treasure trove: the sneak peek and the guesswork

Connexins had been considered to be the only class of the vertebrate proteins capable of gap junction formation; however, new candidates for this function with no homology to connexins, termed pannexins were discovered. So far three pannexins were described in rodent and human genomes: Panx1, Panx2 and Panx3. Expressions of pannexins can be detected in numerous brain structures, and now found both in neuronal and glial cells. Hypothetical roles of pannexins in the nervous system include participating in sensory processing, hippocampal plasticity, synchronization between hippocampus and cortex, and propagation of the calcium waves supported by glial cells, which help maintain and modulate neuronal metabolism. Pannexin also may participate in pathological reactions of the neural cells, including their damage after ischemia and subsequent cell death. Recent study revealed non-gap junction function of Panx1 hemichannels in erythrocytes, where they serve as the conduits for the ATP release in response to the osmotic stress. High-throughput studies produced some evidences of the pannexin involvement in the process of tumorigenesis. According to brain cancer gene expression database REMBRANDT, PANX2 expression levels can predict post diagnosis survival for patients with glial tumors. Further investigations are needed to verify or reject hypotheses listed.