Trees on networks: resolving statistical patterns of phylogenetic similarities among interacting proteins

Background  

Phylogenies capture the evolutionary ancestry linking extant species. Correlations and similarities among a set of species are mediated by and need to be understood in terms of the phylogenic tree. In a similar way it has been argued that biological networks also induce correlations among sets of interacting genes or their protein products.     

Sexual reproduction and developmental adaptations in Xanthoria parietina

Thalli of Xanthoria parietina have been grown in cultures in the natural environment. In early phases of development the fungus associates with foreign algae and only later forms a symbiosis with Pseudotrebouxia . The lichen is shown to have a very effective mechanism for distribution by sexual spores followed by relichenization.     

Assignment of autosomal dominant spinocerebellar ataxia (SCA1) centromeric to the HLA region on the short arm of chromosome 6, using multilocus linkage analysis.

A 7-generation kindred with the HLA-linked form of spinocerebellar ataxia (SCA1) was studied to determine whether the SCA1 gene maps centromeric or telomeric to the HLA loci. The DNA markers flanking the HLA-(A-B) region were used for polymorphism studies and multilocus linkage analysis. These two markers are the cDNA for the beta-subunit of HLA-DP, which is centromeric to HLA-(A-B), and the cDNA for coagulation factor XIIIa (F13A), which is telomeric to HLA-(A-B). Haplotypes were constructed using multiple polymorphisms for these two DNA markers, and pairwise linkage analysis revealed a maximum lod score of 2.18 for SCA1 versus HLA-DP at a recombination fraction of .05 and a maximum lod score of 0 for SCA1 versus F13A at a recombination fraction of .50. A possible crossover between HLA-(A-B) and HLA-DP was identified, but lack of samples from key individuals hampered the analysis. To clarify the phase and improve the analysis, the two chromosomes 6 for the crossover individual were separated in somatic cell hybrids. The results strongly favored the probability that the crossover occurred between HLA-(A-B-DR) and HLA-DP with SCA1 segregating with HLA-DP, consistent with a location centromeric to HLA-(A-B). Multilocus linkage analysis was used to evaluate further the location of SCA1 relative to F13A, HLA-(A-B), and HLA-DP; the results indicated that the SCA1 gene locus is centromeric to HLA-DP with odds of 46:1 favoring this most likely location over the second most likely location, i.e., telomeric to HLA-(A-B) between the HLA complex and F13A.     

Prolonged submaximal exercise and L-carnitine in humans

Changes in the main physiological parameters and circulating indicators of carbohydrate, protein, lipid (and ketone body) metabolism were measured in ten exercising subjects before L-carnitine (L-carn) loading, after 4 weeks of daily loading with 2 g L-carn, and 6-8 weeks after terminating L-carn administration. Measurements were made on venous blood samples collected during each experiment at fixed time intervals over an initial rest of 45 min, 60 min bicycle exercise performed near 50% VO2max and 120 min recovery. Free and total plasma carnitine levels reached a plateau corresponding to an average rise of 25% for both fractions, 9-10 days after the beginning of the L-carn diet. These levels returned to their initial values 6-8 weeks after cessation of the supply. Generally L-carn supplementation did not significantly modify the physiological parameters and circulating metabolites. No distinct increase of the relative participation of endogenous lipids in the fuel supply of prolonged submaximal exercise was observed. In normal human subjects the increased demand for fatty acid oxidation resulting from exercise seems to be adequately supported by endogenous levels of carnitine.     

Effect of membrane cholesterol on dimyristoylphosphatidylcholine-induced vesiculation of human red blood cells

During incubation of intact human erythrocytes with sonicated dimyristoylphosphatidylcholine (DMPC) vesicles, the cells change their discoid morphology to form echinocytes and finally give rise to the release of membrane vesicles. In this process, the red cell membrane accumulates DMPC and loses up to 15% of its cholesterol. On the other hand, replacement of 25% of the endogenous phosphatidylcholine species by DMPC without affecting the cholesterol level of the erythrocytes can be achieved by incubation with DMPC/cholesterol (1:1, mol/mol) sonicated vesicles in the presence of the phosphatidylcholine-specific phospholipid-transfer protein from bovine liver. This replacement also gives rise to an echinocytic cell morphology, but no membrane vesiculation can be observed. However, the vesiculation process can as yet be initiated upon a subsequent decrease of the cholesterol level, by incubation of those modified cells in the presence of sonicated vesicles of pure egg phosphatidylcholine. Incubation of native erythrocytes with pure egg phosphatidylcholine vesicles, on the other hand, results in cholesterol depletion, but does neither induce the formation of echinocytes nor the release of membrane vesicles. Cellular ATP levels are not affected during these incubations. From these results, it can be concluded that a decrease in cholesterol content of the erythrocyte membrane is essential for the DMPC-induced vesiculation of those cells.     

Absence of sexual dimorphism in the goat: Induction of luteinizing hormone discharge in the castrated male and female and in the intersex with estradiol benzoate

Gonadectomized male (n = 5) and female (n = 5) and intact intersex goats (n = 2) were injected i.m. with 50 mug 17(beta)-estradiol benzoate (EB). After treatment, there was a transient 6- to 9-hr decrease in circulating levels of LH followed by a preovulatory-like discharge of LH in all goats. Release peaked at 12 to 18 hr after EB treatment. The magnitude of discharge and the time from treatment until peak of release were not influenced by the goat's sex. These findings suggested that the positive feedback effects of estrogen on LH release were not sexually differentiated in the goat. Since tonic concentrations of LH prior to EB treatment were not different among the groups, the studies also suggested that the intersex goats lacked the inhibitory gonadal influences on gonadotropin release that characterize intact animals.     

南瓜雌蕊与自花及远缘花粉的相互作用

南瓜柱头表面经去垢剂、蛋白酶及Con A处理后花粉不能萌发或花粉管生长受阻,Con A能专一地与柱头表面结合。柱头块加入培养液可促进花粉萌发。不同的远缘花粉授粉后在雌蕊不同部位受阻。在成熟南瓜雌蕊提取液中检测到血凝活性,凝集素可能参与雌蕊对远缘花粉的抑制。