A covariotide model explains apparent phylogenetic structure of oxygenic photosynthetic lineages

The aims of the work were (1) to develop statistical tests to identify whether substitution takes place under a covariotide model in sequences used for phylogenetic inference and (2) to determine the influence of covariotide substitution on phylogenetic trees inferred for photosynthetic and other organisms. (Covariotide and covarion models are ones in which sites that are variable in some parts of the underlying tree are invariable in others and vice versa.) Two tests were developed. The first was a contingency test, and the second was an inequality test comparing the expected number of variable sites in two groups with the observed number. Application of these tests to 16S rDNA and tufA sequences from a range of nonphotosynthetic prokaryotes and oxygenic photosynthetic prokaryotes and eukaryotes suggests the occurrence of a covariotide mechanism. The degree of support for partitioning of taxa in reconstructed trees involving these organisms was determined in the presence or absence of sites showing particular substitution patterns. This analysis showed that the support for splits between (1) photosynthetic eukaryotes and prokaryotes and (2) photosynthetic and nonphotosynthetic organisms could be accounted for by patterns arising from covariotide substitution. We show that the additional problem of compositional bias in sequence data needs to be considered in the context of patterns of covariotide/covarion substitution. We argue that while covariotide or covarion substitution may give rise to phylogenetically informative patterns in sequence data, this may not always be so.      

Using ontologies to describe mouse phenotypes

The mouse is an important model of human genetic disease. Describing phenotypes of mutant mice in a standard, structured manner that will facilitate data mining is a major challenge for bioinformatics. Here we describe a novel, compositional approach to this problem which combines core ontologies from a variety of sources. This produces a framework with greater flexibility, power and economy than previous approaches. We discuss some of the issues this approach raises.     

Effluxes of 3,4-Dihydroxyphenylalanine, 3,4-Dihydroxyphenylglycol, and Norepinephrine from Four Blood Vessels During Basal Conditions and During Nerve Stimulation

Abstract: Effluxes of 3,4-dihydroxyphenylalanine, 3,4-dihydroxyphenyglycol, and norepinephrine from four superfused canine blood vessels (saphenous and portal veins and mesenteric and pulmonary arteries) were studied under basal conditions and during nerve stimulation. From quantification of the compounds a series of indices of activities at neuroeffector junctions are proposed. These are (a) basal overflow of 3,4-dihydroxyphenylglycol as an index of vesicular-cytoplasmic translocation of norepinephrine, (b) the increase in 3,4-dihydroxyphenyglycol overflow attributable to nerve stimulation as an index of neuronal reuptake of norepinephrine released by stimulation, (c) the sum of the increases in overflows of norepinephrine and 3,4-dihydroxyphenylglycol attributable to nerve stimulation as an index of evoked release of norepinephrine, and (d) the efflux of 3,4-dihydroxyphenylalanine as an index of the activity of tyrosine hydroxylase, the rate-limiting enzyme in the synthesis of norepinephrine. There were clear differences between these indices in the vessels. Correlation coefficients of the indices among vessels indicated that a high tissue norepinephrine level was associated with high biosynthetic capacity and high vesicular-cytoplasmic exchange but not with high release. There was no evidence suggesting feedback inhibition of synthesis by neuroplasmic norepinephrine—whether arising from vesicular-cytoplasmic translocation or from reuptake from the junctional cleft. The major value of these indices will probably be in determining the intergrated effects of pharmacologic agents at neuroeffector junctions in different blood vessels.     

Olfactory sensitivity in tsetse flies: a daily rhythm

The diurnal tsetse Glossina morsitans morsitans bites especially in early morning and late afternoon; around midday feeding is at a low. In laboratory apparatus that measures the amount of locomotion under constant conditions over the photophase, the flies display a similar patterning of activity levels. The profile of daily rhythms for G. morsitans reported in the literature includes a number of motor and sensory motor systems that fluctuate cophasically. Lacking is a study on the patterning of the senses' response levels. In this paper we present the first instance of a daily modulation in the sense of smell. We stimulated the antennae with concentration series of host-derived odours and measured the spiking rate of cells at different times during the photophase. The concentration-response curves suggest that the sensitivity of antennal olfactory cells flows in parallel with the other daily rhythms. This was also reflected in electroantennograms (EAGs). The electroantennography was extended to G. fuscipes fuscipes, whose level of spontaneous locomotor activity--instead of following a U- shaped pattern--rises gradually over the photophase. Again, the EAGs appeared to parallel the species' locomotor activity. What we believe happens is that the organism tones down the sensitivity of its odour receptors during periods of anticipated inactivity for reasons of economy.      

In vitro development of bovine embryos as affected by different lots of bovine serum albumin and citrate

The effect of bovine serum albumin (BSA) lots on the development of in vitro-derived bovine embryos in synthetic oviductal fluid was investigated. Citrate concentration was determined for each lot of BSA, and then correlated with differences noted in the ability of BSA lots to support embryo development. Development of bovine embryos to the blastocyst stage was also compared after culture in chemically-defined medium with varying levels of citrate. There were distinct differences in the ability of the different BSA lots to support embryo development to the blastocyst stage (P相似文献   

Addition of penicillamine, hypotaurine and epinephrine (PHE) or bovine oviductal epithelial cells (BOEC) alone or in combination to bovine in vitro fertilization medium increases the subsequent embryo cleavage rate

The cleavage rate of in vitro-matured bovine oocytes was compared after fertilization in 1) TALP medium alone (control); 2) in TALP + BOEC; 3) in TALP + PHE; or 4) in TALP + BOEC and PHE. The overall cleavage rate at 45 h post insemination was greater for embryos in Treatments 2 (52%), 3 (55%) and 4 (66%) than for Treatment 1 (32%). The oocyte cleavage rates for Treatments 2 and 3 were similar, but were lower than that of Treatment 4. Addition of PHE or BOEC, alone or in combination, to the fertilization medium resulted in more embryos at the 3- or 4-cell stage than the 2-cell stage by 45 h post insemination. After 5 d of co-culture with BOEC in M-199 medium, 21, 28, 25 and 35% of the cleaved embryos in Treatments 1, 2, 3 and 4, respectively, developed to the morula or blastocyst stage. The rate of development to morulae and blastocysts was similar among Treatments 1, 2 and 3, and between Treatments 2 and 4. Across treatments, a correlation of 0.98 was noted between the portion of embryos that had reached the 3- or 4-cell stage by 45 h post insemination and the percentage of embryos in each treatment that continued to develop to the morula or blastocyst stage in vitro.     

The specific activity of retained and released norepinephrine in dog saphenous vein prelabeled with radiolabeled norepinephrine

The specific activities of released and retained norepinephrine (NE) in the isolated superfused dog saphenous vein preparation, prelabeled with [³H]NE, have been determined. Norepinephrine was isolated from extracts of vein superfusate and its concentrations were measured by high pressure liquid chromatography with electrochemical detection. The specific activity of NE in superfusate collected under basal conditions was lower than that of NE in veins after electrical stimulation or in parallel unstimulated veins. However, NE released during electrical stimulation had a specific activity 1.5 to 3 times higher than the NE in the veins. Thus, NE taken up by neuronal uptake in the prelabeling procedure enters a pool from which is preferentially released by electric stimulation. In addition, NE is released from different compartments during basal conditions and during electric stimulation.     

Acetyl-L-carnitine supplementation restores decreased tissue carnitine levels and impaired lipid metabolism in aged rats

The effects of long-term carnitine supplementation on age-related changes in tissue carnitine levels and in lipid metabolism were investigated. The total carnitine levels in heart, skeletal muscle, cerebral cortex, and hippocampus were approximately 20% less in aged rats (22 months old) than in young rats (6 months old). On the contrary, plasma carnitine levels were not affected by aging. Supplementation of acetyl-l-carnitine (ALCAR; 100 mg/kg body weight/day for 3 months) significantly increased tissue carnitine levels in aged rats but had little effect on tissue carnitine levels in young rats. Plasma lipoprotein analyses revealed that triacylglycerol levels in VLDL and cholesterol levels in LDL and in HDL were all significantly higher in aged rats than in young rats. ALCAR treatment decreased all lipoprotein fractions and consequently the levels of triacylglycerol and cholesterol. The reduction in plasma cholesterol contents in ALCAR-treated aged rats was attributable mainly to a decrease of cholesteryl esters rather than to a decrease of free cholesterol. Another remarkable effect of ALCAR was that it decreased the cholesterol content and cholesterol-phospholipid ratio in the brain tissues of aged rats. These results indicate that chronic ALCAR supplementation reverses the age-associated changes in lipid metabolism.