Gene-manipulated embryonic stem cells for rat transgenesis

Embryonic stem cells (ESCs) are derived from blastocysts and are capable of differentiating into whole tissues and organs. Transplantation of ESCs into recipient blastocysts leads to the generation of germline-competent chimeras in mice. Transgenic, knockin, and knockout gene manipulations are available in mouse ESCs, enabling the production of genetically modified animals. Rats have important advantages over mice as an experimental system for physiological and pharmacological investigations. However, in contrast to mouse ESCs, rat ESCs were not established until 2008 because of the difficulty of maintaining pluripotency. Although the use of signaling inhibitors has allowed the generation of rat ESCs, the production of genetically modified rats has been difficult due to problems in rat ESCs after gene introduction. In this review, we will focus on some well-documented examples of gene manipulation in rat ESCs.     

Cisplatin-induced genes as potential markers for thyroid cancer

Despite the uncontested role of p53 in cycle arrest/cell death after cisplatin treatment, to date the question whether wild-type p53 confers a resistant or sensitive status on the cell is still a matter of debate. Isogenic and isophenotypic human thyroid papillary carcinoma cell line variants for p53 differently expressed cycle genes after cisplatin treatment. Seven genes (CDC6-related protein, CCNC, GAS1, TFDP2, MAPK10/JNK3, WEE1, RPA1) selected after expression on an Atlas human cell cycle array were analyzed by quantitative real-time PCR. While cisplatin treatment increased their expression in p53 wild-type cells it decreased it in cells with inactivated p53 and had no or less effect on cells with mutated p53. These results show that in a well-defined system, different alterations of p53 can lead to a different regulation of genes and hence to either resistance or sensitivity to cisplatin. Moreover for the first time, MAPK10/JNK3 was identified in human thyroid cells and tissue. Four of the genes (CDC6-related protein, CCNC, GAS1 and TFDP2) were decreased in human papillary carcinoma tissues. Relevance of these genes (especially a decrease in GAS1 in thyroid papillary carcinoma) in various malignant pathologies has already been shown. These genes may be explored as new markers in advanced thyroid cancer such as metastatic and anaplastic forms displaying p53 alterations.Received 26 July 2004; received after revision 14 September 2004; accepted 26 October 2004     

Laser microbeam-induced fixation for electronmicroscopy: Visualization of transient developmental features in nematode embryos

Summary In order to study development of embryos ofCaenorhabditis elegans at an ultrastructural level, a new method of fixation has been developed. With a laser microbeam coupled to a microscope the impermeable eggshell is punctured to allow penetration of the fixative. At specific stages of embryogenesis further development can be arrested at will under visual control. As fixation occurs instantaneously, transient events (e.g. different phases of mitosis and cytokinesis) can be visualized.     

New mechanism for regulation of genetic expression

DNA sequence studies of mutated and wild type alleles of an intron in the mosaic mitochondrial gene for cytochrome b have revealed the possible existence of a protein coded in the intron and involved in RNA splicing. This protein would be endowed with properties of intrinsic autotomy of its own messenger RNA.     

Masked polyphenols in the cuticle of a cyst forming nematode

Zusammenfassung Nach Methanol-HCl-Behandlung wurde gefunden, dass sich die Polyphenole im allgemeinen in der Endocuticula der Cyste der KartoffelnematodeHeterodera rostochiensis Wollenwerber finden.     

Large scale cultivation of a free-living nematode (Caenorhabditis elegans)

Summary A method is presented for the large scale cultivation of the free-living nematodeCaenorhabditis elegans, using continuous aeration and agitation in glass ware (stirrer flasks) developed for the continuous culture of suspended cells. With this technique, populations up to 10⁹ nematodes may be obtained in a 10 l culture in less than 6 weeks with an inoculum of some 50 worms. Costs can be reduced by using an inexpensive yeast extract, available from the food industry.     

Determination of the water content of nematode worms by interference microscopy

Zusammenfassung Das Interferenz-Mikroskop ist hier zum ersten Male bei Metazoen, nämlich lebenden Nematoden, zur Messung des Wassergehalts benutzt worden. Die Resultate werden beschrieben und die Möglichkeiten weiterer Anwendung diskutiert.     

Some properties of cholinesterase of the plant nematode Aphelenchoides ritzema-boosi.

Activity and properties of cholinesterase from Aphelenchoides ritzema-boosi, a plant feeding nematode, were investigated by testing the reaction of the enzyme with different substrates and inhibitors. Butyrylthiocholine was a better substrate than propionyl- and acetylthiochine. When compared with mammaliian erythrocyte and plasma cholinesterase, the nematode enzyme was found to be extremely insensitive towards a number of well-known organophosphorus and carbamate inhibitors.     

A spatial depiction for the systematically degenerate genetic code

Zusammenfassung Auf Grund von Literaturangaben und durch Deduktion haben wir ein dreidimensionales Schema (oder Modell) des systematisch degenerierten genetischen Codes entworfen, aus dem man in einfacher Weise ablesen kann, welche Aminosäuresubstitutionen aus der Veränderung einer Base folgen.     

Prokaryotic genetic code

The prokaryotic genetic code has been influenced by directional mutation pressure (GC/AT pressure) that has been exerted on the entire genome. This pressure affects the synonymous codon choice, the amino acid composition of proteins and tRNA anticodons. Unassigned codons would have been produced in bacteria with extremely high GC or AT genomes by deleting certain codons and the corresponding tRNAs. A high AT pressure together with genomic economization led to a change in assignment of the UGA codon, from stop to tryptophan, in Mycoplasma.