Synechocystis sp. PCC 6803 — a useful tool in the study of the genetics of cyanobacteria

The cyanobacterium Synechocystis sp. PCC 6803 was the first phototrophic organism to be fully sequenced. The genomic sequence has revealed the structure of the genome and its gene constituents (3167 genes), as well as the relative map positions of each gene. The functions of nearly half of the genes has been deduced using similarity searches. The genome sequence has also allowed for the implementation of systematic strategies to study gene function and the mechanisms of gene regulation on a genome-wide level. Two genome databases, CyanoBase and CyanoMutants, have been established and act as a central repository for information on gene structure and gene function, respectively. As a result of the genome sequencing and the establishment of these databases, Synechocystis sp. PCC 6803 provides an extremely versatile and easy model to study the genetic systems of photosynthetic organisms. This revised version was published online in June 2006 with corrections to the Cover Date.     

Angioleiomyosarcoma – a very rare malignant tumour from the soft tissue

In the article we describe a case of a 12-year old boy with the tumour in the small pelvis. The only one abnormality in laboratory tests was a 3-numeral ESR and a big solid tumour probably extended from the urine bowel, found on radiological examination. On surgery the tumour was found to extend from the ascendent colon. On pathological examination, it was described as angioleiomyosarcoma with metastases in the lymph nodes. The boy was treated with IX courses consisting of ifosfamide, vepeside or ifosfamide, adriamycine and vincristine. At present, the child is in the first complete remission, 7 months after completion chemotherapy.     

Embryonic induction: Is the Nieuwkoop centre a useful concept?

Regionalisation of the amphibian embryo is classically thought to involve induction by the Spemann organiser, itself induced by the Nieuwkoop centre. This model has now been extended to teleosts, with the identification of a gene that appears to define the zebrafish equivalent of the Nieuwkoop centre.     

K. H. Rechinger — a life devoted to botany

K. H. Rechinger's great botanical life-work and its impulses on plant geography and taxonomy are estimated.Address toKarl Heinz Rechinger, held on October 18, 1986.     

Captive breeding—a useful tool in the preservation of biodiversity?

Within the next decades species extinction may eliminate between 20 and 50% of the Earth's species. Captive breeding has often been claimed to be a useful tool in preservation of biodiversity. The role of zoos in conservation work and the value of captive breeding are discussed; the latter exemplified by the Peregrine Falcon (Falco peregrinus) Programme and the Arabian oryx (Oryx leucoryx) Programme. Captive breeding programmes are very resource demanding and can only be afforded for a very small number of species, which limits their value significantly. Zoos deal mainly with vertebrates, but these comprise less than 3% of the described species, and although the 878 zoos considered hold more than 20 000 specimens of 140 threatened mammal species, they probably only contribute to the conservation of 20 full species. The situation for birds, reptiles and amphibians is even worse. Zoos face serious problems with minimum viable population sizes and hybridization. However, zoos can make a major contribution to preservation of biodiversity through educating and informing the public. Today, where the crisis of extinction of species has reached such daunting dimensions, captive breeding and otherex situ conservation tools should be the last resort for preserving biodiversity, and captive breeding must not become an excuse to avoid dealing with preservation of habitats.     

Is virtual reality a useful tool in the teaching of physiology?

This opinion statement points out some of the considerations and pitfalls in using virtual reality computer programs in the teaching of life sciences. Emphasis is placed on the possibility of such programs leading to reductionist thinking including how reductionist thinking could foster the formation of misconceptions. Negative feedback is used as the classic example of reductionist thinking in physiological regulation, including how classic negative feedback is inconsistent with evidence of complexity in living systems. This statement concludes that virtual reality can be a useful tool in the teaching of physiology so long as the complexity of living systems is taken into account.     

Is LEAFY a useful marker gene for the flower-inflorescence boundary in the Euphorbia cyathium?

The flower-like reproductive structure of Euphorbia s.l. (Euphorbiaceae) is widely believed to have evolved from an inflorescence, and is therefore interpreted as a special type of pseudanthium, termed a cyathium. However, fuzzy morphological boundaries between the inflorescence, individual flowers, and organs have fuelled the suggestion that the cyathium does not merely superficially resemble a flower but could actually share developmental genetic pathways with a conventional flower. To test this hypothesis, immunolocalizations of FLORICAULA/LEAFY (LFY), a protein associated with floral identity in many angiosperm species, were performed in developing cyathia of different species of Euphorbia. Expression of the LFY protein was found not only in individual floral primordia (as predicted from results in the model organisms Arabidopsis and Anthirrhinum), but also in the cyathium primordium and in the primordia of partial male inflorescences. These results provide further evidence that the evolution of floral traits in pseudanthial inflorescences often involves expression of floral development genes in the inflorescence apex. This finding blurs the conventional rigid distinction between flowers and inflorescences.     

CNS stem cells: Where's the biology (a.k.a. beef)?

Central nervous system (CNS) stem cells have become the subject of many laboratories' efforts, presentations, and publications. Yet, in the stem cell world, CNS cells are viewed with skepticism. This is likely due to a dearth of biology (in vivo function) to accompany a flurry of phenomenological and restorative neurology studies. In this article, we compare and contrast the biological knowledge of adult forebrain epidermal growth factor-responsive neural stem cells that has emerged from our laboratories with that of hematopoietic stem cells, using two recent papers in the latter field as specific examples. A comparison of stem cell location, lineage, and repopulation suggests that our understanding of CNS stem cell biology is immature. We conclude that a greater focus on in vivo biology will enhance our knowledge and understanding of CNS stem cells. © 1998 John Wiley & Sons, Inc. J Neurobiol 36: 307–314, 1998     

Visual system: prostriata - a visual area off the beaten path

Recent work establishes that Prostriata, a little-studied area of the visual cortex neighboring V1, has distinct but hybrid visual properties which are suggestive of an unsuspected role in the rapid analysis and integration of peripheral visual stimuli.     

Two group I introns with a C.G basepair at the 5' splice-site instead of the very highly conserved U.G basepair: is selection post-translational?

In virtually all of the 200 group I introns sequenced thus far, the specificity of 5' splice-site cleavage is determined by a basepair between a uracil base at the end of the 5' exon and a guanine in an intron guide sequence which pairs with the nucleotides flanking the splice-site. It has been reported that two introns in the cytochrome oxidase subunit I gene of Aspergillus nidulans and Podospora anserina are exceptions to this rule and have a C.G basepair in this position. We have confirmed the initial reports and shown for one of them that RNA editing does not convert the C to a U. Both introns autocatalytically cleave the 5' splice-site. Mutation of the C to U in one intron reduces the requirement for Mg2+ and leads to an increase in the rate of cleavage. As the C base encodes a highly conserved amino acid, we propose that it is selected post-translationally at the level of protein function, despite its inferior splicing activity.     

The monoclonal antibody GB 42 — a useful marker for the differentiation of myofibroblasts

The expression patterns of a variety of cytoskeletal antigens were studied in normal human tissues (placenta, umbilical cord, myometrium, colon, mammary gland, testis, skeletal muscle, myocardium) as well as in abnormal human tissues (palmar fibromatosis, fibrocystic disease of the mammary gland, mammary carcinoma). The immunohistochemical binding patterns of the monoclonal antibody GB 42 were compared to those of commerical antibodies directed against vimentin, desmin, smooth muscle myosin, pan actin, -smooth muscle actin and -smooth muscle actin. Methods applied comprised immunohistochemistry on cryostat sections and paraffin sections. Immunogold immunocytochemistry was performed on Lowicryl sections. The patterns of GB 42-binding were confirmed biochemically by SDS-PAGE and Western-blotting, and quantitative amino acid analysis. Our data suggest that the monoclonal antibody GB 42 recognizes an actin isoform which is identical to, or closely related to, -smooth muscle actin. Unlike the commercially available antibody against -smooth muscle actin, GB 42 does not cross-react with -skeletal or -cardiac actins. The GB 42-antigen is expressed in smooth muscle cells, myoepithelial cells and in later stages of differentiation of myofibroblasts, in all the tissues investigated. Throughout the development of smooth muscle cells and myofibroblasts, the appearance of the GB 42-antigen occurs after the expression of vimentin, desmin and -smooth muscle actin, but prior to the expression of smooth muscle myosin. GB 42 is a reliable marker for higher stages of differentiation of smooth muscle cells and myofibroblasts.     

Effects of a plume front on the distribution of inorganic and organic matter off the Rhône River

Hydrological and chemical structures off the Rhône River estuary resulting from the introduction of the river flow into the Mediterranean Sea are described. The effect of the fresh-water/sea-water interface on the distribution of inorganic and organic matter off the Rhône river is investigated. Strong vertical gradients of inorganic and dissolved organic matter such as lipids characterized the first few meters in this area (from 83.7 to 0.6 N-NO₃ µgat l^–1, from 6.39 to 0.92 N-NH₄ µgat l^–1 and from 299 to 73 µg l^–1 of total dissolved lipids). At the interface, substantial increases of particulate organic (PON: from 45 µg l^–1 at surface to 118 µg l^–1 at the interface, POC: from 462 to 876 µg l^–1, total particulate lipids: from 33 to 648 µg l^–1) and suspended matter in general (from 18 to 22.2 mg l^–1) were observed. High phytoplanktonic production may account for some of this enrichment, although passive accumulation might also be involved.