Phylogenetic analysis of 1.5 Mbp and platypus EST data refute the Marsupionta hypothesis and unequivocally support Monotremata as sister group to Marsupialia/Placentalia

The extant mammalian groups Monotremata, Marsupialia and Placentalia are, according to the 'Theria' hypothesis, traditionally classified into two subclasses. The subclass Prototheria includes the monotremes and subclass Theria marsupials and placental mammals. Based on some morphological and molecular data, an alternative proposition, the Marsupionta hypothesis, favours a sister group relationship between monotremes and marsupials to the exclusion of placental mammals. Phylogenetic analyses of single genes and even multiple gene alignments have not yet been able to conclusively resolve this basal mammalian divergence. We have examined this problem using one data set composed of expressed sequence tags (EST) and another containing 1 510 509 nucleotide (nt) sites from 1358 inferred cDNA genomic sequences. All analyses of the concatenated sequences unambiguously supported the Theria hypothesis. The Marsupionta hypothesis was rejected with high statistical confidence from both data sets. In spite of the strong support for Theria, a non-negligible number of single genes supported either of the two alternative hypotheses. The divergence between monotremes and therian mammals was estimated to have taken place 168–178 Mya, a dating compatible with the fossil record. Considering the long common evolutionary branch of therians, it is surprising that sequence data from many thousand amino acid sites were needed to conclusively resolve their relationship to monotremes. This finding draws attention to other mammalian divergences that have been taken as unequivocally settled based on much smaller alignments. EST data provide a comprehensive random sample of protein coding sequences and an economic way to produce large amounts of data for phylogenetic analysis of species for which genomic sequences are not yet available.     

An unreported RFLP for probe 218 EP6 that is useful in linkage analysis of adult polycystic kidney disease

Probe 218 EP6 is known to recognise two restriction fragment length polymorphisms (RFLPs) after digestion of genomic DNA withPvuII. We report a rare allele that segregates in Mendelian fashion, in a family where adult polycystic kidney disease was being tracked using linked polymorphisms.     

Effect of prostacyclin on perfusion pressure, electrical activity, rate and force of contraction in isolated rat and rabbit hearts.

Prostacyclin when added to medium perfusing rat and rabbit hearts caused an increase in perfusion pressure at concentrations from 1 pg/ml ? 1 ng/ml (2.8 × 10^?12 ? 2.8 × 10^?9M) and a decrease at higher concentrations. Rhythm disturbances were observed with low prostacyclin concentrations in 6 of 10 rat hearts and 2 of 5 rabbit hearts studied. Increased heart rates were seen in the isolated rat hearts but not in the rabbit hearts. Force of contraction of isolated rat hearts was increased with increasing prostacyclin concentrations up to 100 pg/ml. Higher concentrations decreased contractile force. No inotropic effects were seen with rabbit hearts.     

Periodicity in Atlantic salmon Salmo salar L. smolt migration

Behavioural and physiological mechanisms postulated for the control of downstream migration of Atlantic salmon smolts are reviewed briefly, and some new evidence is presented for their refusal to undergo sustained swimming. Although these mechanisms imply passive displacement as the primary means of emigration, it is likely that active components must also exist as the rates of travel of smolts through loch systems are only slightly slower than those recorded for river systems. The timing of these movements within 24 h periods is reviewed and it is shown that the predominantly nocturnal emigration pattern is evident on occasions in alevin, fry and parr stages also. Thus at migration the diel periodicity probably represents a seasonal locomotor rhythm which, under changed behavioural and physiological circumstances, results in downstream displacement.     

Attenuation of radiation-induced genomic instability by free radical scavengers and cellular proliferation.

To investigate the mechanisms of radiation-induced chromosomal instability, cells were irradiated in the presence of the free radical scavengers DMSO, glycerol, or cysteamine, in the presence of DMSO while frozen, or held in confluence arrest post-irradiation to permit cells to repair potentially lethal DNA damage. Clones derived from single progenitor cells surviving each treatment were then analyzed for the subsequent development of chromosomal instability. The presence of scavengers (+/- freezing) during irradiation, and the recovery from potentially lethal damage after irradiation led to an increase in cell survival that was accompanied by a decrease in the initial yield of chromosomal rearrangements. Furthermore, analysis of over 400 clones and 80,000 metaphases indicates that these same treatments reduced the incidence of instability at equitoxic doses when compared to controls irradiated in the absence of scavengers at ambient temperature. Results suggest that preventing reactive species from damaging DNA, promoting chemical repair of ionized DNA intermediates, or allowing enzymatic removal of genetic lesions, represent measures that reduce the total burden of DNA damage and reduce the subsequent onset of radiation-induced genomic instability.