Infraspecific variation in Cerastium alpinum s. lat. (Caryophyllaceae) in Central Norway

Within Cerastium alpinum s. lat., several taxa have been circumscribed. Three infraspecific taxa are currently recognized in Nordic literature, but the opinions have varied about their taxonomic levels and relations to each other. Populations of these three taxa — alpinum, glabratum and lanatum — were investigated in Central Norway to elucidate taxonomic relationships on a regional scale. Morphometric analyses (PCA ordination) based on two data sets; one with 61 characters, and one without the 35 indumentum characters, gave different results. The former partly support the use of a higher rank for glabratum , but this analysis may put too much weight on indumentum characters. The reduced data set gave a more continuous transition between the three taxa, with no special status for glabratum. Crossing experiments between the taxa indicated full cross compatibility as far as relative seed set was concerned. Finally, vegetation analysis (DCA ordination) indicated that the three taxa have somewhat different ecological demands. This suggests that they, in spite of hybridization abilities, normally are maintained as separate entities due to habitat differences. A delimitation of three infraspecific taxa at the same level within C. alpinum s. lat. is thus supported by this study. Whether these taxa should be treated as subspecies or varieties strongly depends upon the definitions of these categories. Viewed in a wide geographical context, however, the arguments for subspecific rank are strengthened.     

Cloning and expression of a cDNA encoding a catalytically active fragment of calf thymus DNA polymerase alpha

A calf thymus cDNA expression library was constructed in the EcoRI site of lambda gt11 and probed with an antibody raised against calf thymus DNA polymerase alpha. Three classes of antibody-reactive clones were isolated. The largest class carried a 1.9 kilobase calf cDNA insert and expressed a 165-175 kilodalton beta-galactosidase:calf fusion protein which displayed DNA polymerase activity. The characteristic responses of the polymerase activity to alpha-specific inhibitors and antibodies identified the 1.9 kilobase cDNA as a sequence specifically derived from the structural gene encoding the pol alpha catalytic core.     

The effect of triacontanol on growth, photosynthesis and photorespiration in Chlamydomonas reinhardtii and Anacystis nidulans

Chlamydomonas reinhardtii Dangerad 11–32(90) (−), which exhibits C3 properties, and Anacystis nidulans (Strain no. UTEX 625), which exhibits C4 properties, were used to study the effects of triacontanol on growth, photosynthesis and photorespiration. Photosynthetic rate was measured as CO2 uptake and the O2 inhibition of photosynthesis was used as a measure of photorespiration. Triacontanol dissolved in chloroform and dispersed in Tween-20 and triacontanol colloidally dispersed in an aqueous solution of sodium tallow alkyl sulfate were tested. Chlamydomonas cultures increased significantly in cell number after 4 days, and in chlorophyll content after 3 days of treatment with 2.3 × 10⁻⁸ M TRIA in chloroform/Tween-20. In cultures of Anacystis the chlorophyll content became significantly higher 3 days after treatment with 2.3 × 10⁻⁹ M TRIA and the cell number was noticeably higher than the controls.
CO₂ uptake by triacontanol-treated Chlamydomonas cultures was about the same in both 2 and 21% O2, and the O2 inhibition was significantly reduced as compared with the controls. Photosynthesis in Anacystis was O2-insensitive under the experimental condition used. When Anacystis was treated with triacontanol there was no change in the rate of CO2 uptake and no change in the O2 sensitivity of its CO2 uptake. It appears that triacontanol affects some process which regulated the balance between photosynthesis and photorespiration, but other processes which result in increased growth are probably also affected.     

Performance of a perforated plate column as a multistage continuous fermentor

Microorganisms were continuously cultivated in multistage column consisting of ten perforated plate sections to which medium and air were supplied concurrently from the bottom. At steady state the cell concentration in the various stages was gradationally differentiated from the bottom to the top in the direction of medium flow. RNA content per unit cell concentration at each sage was determined. The cells in the lower stages were higher in RNA content than those from the upper stages. Wash out was observed to occur in the column at dilution rates which do not result in wash out in a single stage chemostat system. A study of the flow characteristics revealed that the overall performance of the plate column was equivalent to that of a multistage system, when hole diameter and hole area to column cross sectional area ratio were properly selected. This was true even in highly aerated conditions. These results indicated that the perforated plates in the column hindred intermixing through the plates, and that each stage functioned as an independent stirred vessel. Industrial and research application of this type fermentor was discussed.     

Genetic differentiation in endemic Lobularia (Brassicaceae) in the Canary Islands

Patterns of genetic diversity were examined in five endemic subspecies of the Lobularia canariensis complex from six of the Canary Islands. The taxa are interfertile, insect-pollinated outbreeders with wind dispersal. Electrophoretic analysis revealed a high level of genetic polymorphism at ten loci coding soluble enzymes, with a mean of 2.38 alleles per locus, 73.7 % polymorphic loci, and a mean heterozygosity of 0.279. Excesses of homozygotes, indicating inbreeding, were observed in small populations. The average total diversity was high, F.,=0.518. Among-population diversity, F_ST=0.318, contributed more to the total diversity than within-population diversity, F_IS=0.222. Little geographic or taxonomic patterning of the allozyme variation was observed. The mean genetic identitity for pairwise comparisons of the 19 populations was 0.76, with a range of 0.51–0.96 and c. 17 % of the comparisons below 0.67 and c. 8 % above 0.90. The results contrast with the many cases of high genetic identities reported for populations of endemic plants on oceanic islands. High levels of allozyme divergence suggest a relatively old origin of the L. canariensis complex and a long period of isolation of some of the populations.     

Subject: Migration

Research Notes on Avian Biology 1994: Selected Contributions from the 21st International Ornithological CongressGeneral Biology: Migration

Subject: Migration     

Scanning electron microscopic study of spermatozoa from gossypol-treated rats

Summary Spermatozoa from the cauda epididymidis of gossypol-treated rats exhibit distinctive departures from the morphology of spermatozoa from control rats: wrinkled and disorganized cell membrane in the head and tail regions, cell membrane missing from segments of the tail midpiece and principal piece regions, malformed heads, decapitate spermatozoa, retention of a cytoplasmic droplet at variable loci along tail midpieces, and looped tails. The observations suggest that gossypol exerts its contraceptive effect during spermatocytogenesis and spermiogenesis, including the posttesticular development and maturation of spermatozoa in the epididymis.     

Interplay between the RNA binding‐protein Musashi and developmental signaling pathways

Musashi comprises an evolutionarily conserved family of RNA‐binding proteins (RBP) that regulate cell fate decisions during embryonic development and play key roles in the maintenance of self‐renewal and differentiation of stem cells and adult tissues. More recently, several studies have shown that any dysregulation of MSI1 and MSI2 can lead to cellular dysfunctions promoting tissue instability and tumorigenesis. Moreover, several reports have characterized many molecular interactions between members of the Musashi family with ligands and receptors of the signaling pathways responsible for controlling normal embryonic development: Notch, Transforming Growth Factor Beta (TGF‐β), Wingless (Wnt) and Hedgehog Signaling (Hh); all of which, when altered, are strongly associated with cancer onset and progression, especially in pediatric tumors. In this context, the present review aims to compile possible cross‐talks between Musashi proteins and members of the above cited molecular pathways for which dysregulation plays important roles during carcinogenesis and may be modulated by these RBP.