Tissue-specific expression of male-transmitted mitochondrial DNA and its implications for rates of molecular evolution in Mytilus mussels (Bivalvia: Mytilidae).

Mytilus and other bivalves exhibit an unusual system of mitochondrial DNA (mtDNA) transmission termed doubly uniparental inheritance (DUI). Specifically, males transmit the mtDNA they have received from their fathers to their sons. Females transmit their mother's mtDNA to both sons and daughters. Males are normally heteroplasmic and females are normally homoplasmic, but not exclusively. This system is associated with an unusual pattern of molecular evolution. Male-transmitted mtDNA (M type) evolves faster than female-transmitted (F type) mtDNA. Relatively relaxed selection on the M type has been proposed as an explanation for this phenomenon. To further evaluate the selective forces acting upon the M-type genome, we used RT-PCR to determine where it is expressed. M-type mtDNA expression was detected in all gonad samples and in 50% of somatic tissues of males, and in a single female tissue. F-type mtDNA expression was detected in all female tissues, all male somatic tissues, and all but one male gonad sample. We argue that the expression of M-type mtDNA in male somatic and male gonad tissues has implications for the strength of selection acting upon it.     

A mercapto analogue of 5'-noraristeromycin.

5'-Noraristeromycin and its enantiomer have been found to possess a wide range of antiviral effects. In the search for analogues of and with improved activity, the synthesis of both enantiomers of 5'-mercapto-5'-deoxy-5'-noraristeromycin ( and ) has been accomplished. While (+)-7 was inactive, (-)- did show marginal activity against vaccinia virus, but not any other virus.     

No effect of parental quality or extrapair paternity on brood sex ratio in the blue tit (Parus caeruleus)

Sex allocation theory predicts that parents should manipulatebrood sex ratio in order to maximise the combined reproductivevalue of their progeny. Females mating with high quality malesshould, therefore, be expected to produce brood sex ratiosbiased towards sons, as male offspring would receive a relativelygreater advantage from inheritance of their father's characteristicsthan would their female siblings. Furthermore, it has been suggested that sex allocation in chicks fathered through extrapair fertilizations should also be biased towards sons. Contraryto these predictions, we found no evidence that the distributionof sex ratios in a sample of 1483 chicks from 154 broods ofblue tits (Parus caeruleus) deviated significantly from thatof a binomial distribution around an even sex ratio. In addition,we found no significant effect on brood sex ratio of the individualquality of either parent as indicated by their biometrics, feather mite loads, time of breeding, or parental survival. This suggeststhat females in our population were either unable to manipulateoffspring sex allocation or did not do so because selectionpressures were not strong enough to produce a significant shiftaway from random sex allocation. The paternity of 986 chicks from 103 broods was determined using DNA microsatellite typing.Extrapair males sired 115 chicks (11.7%) from 41 broods (39.8%).There was no significant effect of paternity (within-pair versusextrapair) on the sex of individual offspring. We suggest that,in addition to the weakness of selection pressures, the possiblemechanisms responsible for the allocation of sex may not besufficiently accurate to control offspring sex at the levelof the individual egg.     

Baeyer-Villiger oxidations of representative heterocyclic ketones by whole cells of engineered Escherichia coli expressing cyclohexanone monooxygenase

Whole cells of an Escherichia coli strain overexpressing Acinetobacter sp. NCIB 9871 cyclohexanone monooxygenase (CHMO; E.C. 1.14.13.22) have been used for the Baeyer-Villiger oxidation of representative heterocyclic six-membered ketones to probe the potential impact of nitrogen, sulfur and oxygen on the chemoselectivity of these reactions. The fact that all of these heterocyclic systems were accepted as substrates by the enzyme and gave normal Baeyer-Villiger products broadens the synthetic utility of the engineered E. coli strain and emphasizes the chemoselectivity achievable with enzymatic oxidation catalysts.     

Murine phosphatidylserine-specific phospholipase A1 (Ps-pla1) maps to Chromosome 16 but is distinct from the lpd (lipid defect) locus

We have previously generated a mouse transgenic line with an insertional mutation designated lpd that demonstrates a phenotype of hypertriglyceridemia and fatty liver. Since the recently identified phosphatidylserine-specific phospholipase A1 (PS-PLA1) demonstrates significant homology to triglyceride lipases, we reasoned that the mouse Ps-pla1 gene may be the disrupted gene within the lpd locus. Using a rat PS-PLA1 cDNA sequence to search the EST database, we identified a mouse EST homolog AA839424. Sequencing analysis of AA839424 revealed a putative Ps-pla1 protein of 456 amino acids with extensive overall structural conservation with human and rat PS-PLA1 and with triglyceride lipases. Conserved sequences in Ps-pla1 include a lipase consensus sequences G×S×G, a catalytic triad, and eight of the ten conserved cysteine residues that are required for tertiary structure. Mouse Ps-pla1 carries a phosphatidylserine-binding motif that is absent in all triglyceride lipases. Using a mouse whole-genome radiation hybrid (WG-RH) mapping panel (T31), we mapped mouse Ps-pla1 to Chromosome (Chr) 16 between genetic markers D16Mit194 and D16Mit38, which is 17.1 cM centromeric to the lpd locus. On the basis of chromosome location, we conclude that Ps-pla1 and lpd are distinct genes in lipid metabolism. Received: 31 May 2000 / Accepted: 5 October 2000     

Studies on the energy metabolism of opossum Didelphis virginiana erythrocytes--II. Comparative aspects of 2-deoxy-D-glucose catabolism in opossum and human red cells in vitro

1. G-6-P, F-6-P, F-1, 6-P, DHAP and GA-3-P in opossum erythrocytes were found at levels above those reported in human red cells. 2. About 1% of the radioactivity provided as [1-14C] DOG to red cells of both species was recovered as 14CO2 in 1 hr. 3. Unlike [1-14C] DOG, radiochromatography of extracts of cells incubated DOG revealed two diffusible radiolabelled compounds in the supernatant of cell suspensions. 4. The catabolism of DOG was quantitatively and qualitatively similar in opossum and human erythrocytes under the conditions of this study.     

Testing the Role of Climate Change in Species Decline: Is the Eastern Quoll a Victim of a Change in the Weather?

To conserve a declining species we first need to diagnose the causes of decline. This is one of the most challenging tasks faced by conservation practitioners. In this study, we used temporally explicit species distribution models (SDMs) to test whether shifting weather can explain the recent decline of a marsupial carnivore, the eastern quoll (Dasyurus viverrinus). We developed an SDM using weather variables matched to occurrence records of the eastern quoll over the last 60 years, and used the model to reconstruct variation through time in the distribution of climatically suitable range for the species. The weather model produced a meaningful prediction of the known distribution of the species. Abundance of quolls, indexed by transect counts, was positively related to the modelled area of suitable habitat between 1990 and 2004. In particular, a sharp decline in abundance from 2001 to 2003 coincided with a sustained period of unsuitable weather over much of the species’ distribution. Since 2004, abundance has not recovered despite a return to suitable weather conditions, and abundance and area of suitable habitat have been uncorrelated. We suggest that fluctuations in weather account for the species’ recent decline, but other unrelated factors have suppressed recovery.