cDNA cloning of eel (Anguilla anguilla) somatolactin.

The nucleotide sequence of the cDNA coding for eel somatolactin (SL), a pituitary hormone belonging to the growth hormone (GH)/prolactin (PRL) family, has been determined. The full-length eel SL cDNA (1213 bp) encodes a protein of 229 amino acids (aa), with a putative signal peptide of 24 aa and a mature protein of 204 aa. Eel SL contains seven Cys residues found to be characteristic of SLs, and two potential N-glycosylation sites. Significant sequence homology between eel and seven other fish SLs (42% aa identity, 63% aa similarity) reveal SL to be highly conserved. A higher sequence identity of SL to GH than PRL is suggested by the comparison of these hormones in eel and chum salmon.

Responses to desiccation in four Coleopterans from sub-Antarctic South Georgia.

RATES OF WATER LOSS WERE DETERMINED FOR FOUR COLEOPTERA SPECIES: the herbivores Hydromedion sparsutum, Perimylops antarcticus (Family Perimylopidae) and the carnivores Trechisibus antarcticus, Oopterus soledadinus (Family Carabidae) collected during summer from a range of terrestrial habitats at South Georgia. A recording microbalance enabled measurement of individual weight loss with time in <5% r.h. at 10, 20, 30 and 35 degrees C. Adults of T. antarcticus had significantly higher rates of water loss than any other species over all temperatures. Individuals of both herbivores exhibited the slowest water loss rates under the experimental conditions. Within species, rates at 10 or 20 degrees C were slower than at the higher temperatures. Adult P. antarcticus had significantly greater amounts of body water than adult H. sparsutum for each of the four temperatures. Within species and life-stages of both herbivores, body water contents after drying at 10 degrees C were significantly lower than individuals dried at 30-35 degrees C, but no such differences were observed for the carnivores. At each temperature, rates of water loss were negatively correlated with initial live weight in all four species, but this was not the case within species or between adults and larvae. Maximum survival times during desiccation declined as temperature increased, but did not differ between species at 10 degrees C. Over 30-35 degrees C, survival times of both herbivores were significantly longer than either of the carnivores. Smaller insects (e.g. the carabids) had faster rates of water loss than the larger perimylopids under the same environmental conditions. The latter had greater resistance to desiccation than the former. It is suggested that the larger body water content of P. antarcticus enables it to resist desiccation more than the other three species, which correlates with its ecological distribution. Differences in water contents after drying individuals at low and high temperatures may be caused either by the water binding properties of cells and tissues or by reduction in energy stores in order to maintain metabolism at lower environmental temperatures causing a body weight loss. Whilst both herbivores show some physiological adaptations to drying conditions, it is suggested that the two carnivorous beetles may have adapted behaviourally to the South Georgia environment.

Novel use of a selectable fusion gene as an "in-out" marker for studying genetic loss in mammalian cells.

Recent demonstrations of loss of heterozygosity in a wide variety of human cancers suggest that large multilocus genetic deletions (presumably including tumor suppressor genes) constitute a major class of genetic alteration in human carcinogenesis. Here we show that a bifunctional fusion gene (Hytk), suitable for both positive and negative selection, is an effective marker for studying genetic loss in mammalian cells with minimal interference from point-mutational changes. Studies with a transgenic V79 cell line in which a single functional copy of Hytk was stably inserted into the genome in a retroviral vector showed that loss of the marker (and presumably flanking cellular genetic material) could be induced efficiently by ionizing radiation (gamma-rays and fast neutrons) but only weakly by the powerful point-mutagen benzo[a]pyrene diol epoxide. In a first application of the system, we provide evidence that radiation-induced loss can occur through an indirect mechanism after a high-frequency event. Collectively, our results suggest that the Hytk marker should be a valuable tool for studying genome position effects on the tolerance of genetic loss in cultured human cells that represent different stages in clonal evolution and tumor progression.

Construction and characterization of a highly stable human: rodent monochromosomal hybrid panel for genetic complementation and genome mapping studies.

Human:rodent somatic cell hybrids carrying a single, intact, selectable human chromosome are valuable both for functional somatic cell genetic analysis and genome mapping procedures. Here, we describe the construction and detailed molecular cytogenetic characterization of a panel of 23 stable hybrids, representing all 22 human autosomes plus the X-chromosome. Individual normal human chromosomes have been tagged with a selectable fusion gene (Hytk) introduced into the chromosome in a small (4.2 kbp) retroviral vector. Use of the Hytk marker permits both positive and negative ("in-out") selection to be applied to the human chromosome in any mammalian cell background. The panel includes 18 new hybrids isolated by direct microcell transfer from normal human diploid fibroblasts into mouse A9 cells.

Young children's use of spatial categorization as a mnemonic strategy.

The interdependence of knowledge and strategic behavior is becoming increasingly well established. The purpose of this research was to determine whether young children could use spatial categorization--a cognitive skill well within the repertoire of even 2-year-olds--as a mnemonic strategy. The results of three studies revealed that young children are capable of spatially organizing objects as a strategy in the service of future retrieval. There were clear developmental trends in the strategic deployment of categorization. Although there was some evidence of the mnemonic use of perceptually defined categories by 2- and 3-year-olds, these children rarely executed the strategy effectively. Four-year-old children were quite successful at exploiting perceptually defined categories to aid retrieval. By five years of age, children were able, in addition, to actively construct physical categories based on an internal representation and use them in the service of memory.