Midsummer heat wave effects on lacustrine plankton: Variation of assemblage structure and fatty acid composition

The effects of the 2003 European heat wave on a freshwater plankton assemblage and its fatty acid (FA) composition were investigated. Composition and FA profiles of four size categories of planktonic organisms collected in 2003 were compared to those of the colder year 2002.     

Cluster analysis of behavioural and event-related potentials during a contingent negative variation paradigm in remitting-relapsing and benign forms of multiple sclerosis

Background  

Event-related potentials (ERPs) may be used as a highly sensitive way of detecting subtle degrees of cognitive dysfunction. On the other hand, impairment of cognitive skills is increasingly recognised as a hallmark of patients suffering from multiple sclerosis (MS). We sought to determine the psychophysiological pattern of information processing among MS patients with the relapsing-remitting form of the disease and low physical disability considered as two subtypes: 'typical relapsing-remitting' (RRMS) and 'benign MS' (BMS). Furthermore, we subjected our data to a cluster analysis to determine whether MS patients and healthy controls could be differentiated in terms of their psychophysiological profile.     

Centrifugation of 2-cell mouse ova: cytoplasm stratification and recovery

Summary Two-cell mouse ova, which were centrifuged for l h at 70 000–90 000xg, showed a precise stratification of the cytoplasm and an elongation of the nucleus. The ova were fixed at different times and observed by light and electron microscopy using cytochemical methods and detergent extractions. Within 40 min after centrifugation the normal-looking morphology was recovered except for the persisting lipid caps at the centripetal poles of the blastomeres. Cleavage, compaction and blastulation were not prevented by centrifugation. Treatments with colcemid or cytochalasin D delayed but did not impair recovery. These results suggest that a resilient cytoskeletal structure may be involved in this kind of embryonic regulation.     

Stringent regulation of human growth hormone expression in cultured murine C2C12 myoblasts by theE. coli lac repressor

Summary Gene transfer techniques can be used to encode the production of a polypeptide product, such as human growth hormone (hGH), that is missing in an acquired or inherited disease state such as growth hormone deficiency. In one model system, engineered C2C12 myoblasts are injected intramuscularly into a mouse and subsequently secrete hGH into the circulation. In this regard, a gene-expression regulatory system that functions in myoblasts would be of interest. We demonstrate that theEscherichia coli lac operon system can be used to stringently regulate the expression of hGH in engineered C2C12 myoblasts in tissue culture. A DNA segment encoding hGH was linked to a DNA segment containing an SV40 enhancer and promoter. The latter components were positioned between two syntheticlac operators.Lac repressor expression was driven by a simian cytomegalovirus promoter. In transient co-transfection assays, hGH expression from cultured C2C12 myoblasts could be modulated up to 60-fold (P = 0.002) with the inducing agent, isopropyl-β-d-thiogalactoside (IPTG). In the absence of IPTG, hGH expression was almost fully repressed. These results show that the components of theE. coli lac operon provide a stringent regulatory system for use in myoblasts. The system might prove to be useful for the regulation of transferred genes in animals.     

Sequences isolated from aDrosophila early-ecdysone puff are expressed in rat liver

We have studied the presence of a cloned fragment of DNA from Drosophila melanogaster in other organisms by means of nucleic acid hybridization analysis. The isolated region is localized in polytene chromosomes at the 63F subdivision. This region includes a puff that responds within minutes to ecdysone stimulation. We have found that 63F DNA from D. melanogaster hybridizes 'in situ' to both DNA and RNA from D. simulans, D. teissieri, and D. hydei. In all these species the isolated DNA remains associated with one early-ecdysone stimulated puff. The isolated Drosophila recombinant DNA is also complementary to polyadenylated RNA from foetal and adult rat liver but fails to hybridize to the nonpolyadenylated RNA classes from both sources and to polyadenylated RNA from rat mammary glands.     

Cloning and expression of hepatitis B surface antigen in the yeastKluyveromyces lactis

Summary The gene coding for the major surface antigen of the hepatitis B virus was integrated into the genome ofKluyveromyces lactis and expressed up to levels of 0.4% of the total soluble protein.