Breeding biology and flower visitors of the rare White River penstemon, Penstemon scariosus var. albifluvis (Scrophulariaceae)

We studied the breeding system and flower visitors of White River penstemon, a rare endemic from the Uintah Basin of eastern Utah and western Colorado. Bagging treatments and hand-pollination treatments showed that Penstemon scariosus var. albifluvis has a mixed mating system: while some seeds and fruits are produced through selfpollination (both autogamy and geitonogamy), significantly more are produced when flowers are cross-pollinated. The primary flower visitors, and likely pollinators, were several species of native twig- and ground-nesting bees in the families Apidae, Halictidae, and Megachilidae. We found no differences in fruit or seed production between open-pollinated controls and hand-outcrossed flowers, suggesting that pollinator visits were sufficient to maximize female reproductive success. Management plans to conserve White River penstemon must recognize that full reproductive success of this rare plant taxon relies on a suite of pollinating bees, and that the species richness and abundances of bee visitors should be maintained.     

Modèles écologiques et aménagement de l'espace

Summary With the increased impact of man's activities resulting from the industrial revolution, the fall-out of his actions widens in both space and time. It is impossible to proceed any further in the exploitation of Nature on the basis of economic concepts founded on the pursuit of sectorial short-term profit. We must on the contrary observe the rules governing the biosphere and the ecosystems.Economic development must not upset the energetic equilibrium of the biosphere. This is possible on condition that we use essentially balanced energy sources, instead of the energy released by potential sources.The whole organization of economy is based on a linear principle, resulting in the exhaustion of basic materials and overload by often polluting waste. The acceleration of the circuit is artificially induced by publicity factors which, pretexting fashion, regards as garbage still usable goods. The perenniality of ecosystems is ensured by the recycling of materials, an economy founded on the same principle can alone ensure the future of mankind.The sectorial development of economy and of professional training contributes to make it more difficult to organize the healthy management of natural resources.The obstacles to the achievement of a healthy policy of resource management are not technical, but pedagogic, economic and political.     

Heterozygous missense mutations in BSCL2 are associated with distal hereditary motor neuropathy and Silver syndrome

Distal hereditary motor neuropathy (dHMN) or distal spinal muscular atrophy (OMIM #182960) is a heterogeneous group of disorders characterized by an almost exclusive degeneration of motor nerve fibers, predominantly in the distal part of the limbs. Silver syndrome (OMIM #270685) is a rare form of hereditary spastic paraparesis mapped to chromosome 11q12-q14 (SPG17) in which spasticity of the legs is accompanied by amyotrophy of the hands and occasionally also the lower limbs. Silver syndrome and most forms of dHMN are autosomal dominantly inherited with incomplete penetrance and a broad variability in clinical expression. A genome-wide scan in an Austrian family with dHMN-V (ref. 4) showed linkage to the locus SPG17, which was confirmed in 16 additional families with a phenotype characteristic of dHMN or Silver syndrome. After refining the critical region to 1 Mb, we sequenced the gene Berardinelli-Seip congenital lipodystrophy (BSCL2) and identified two heterozygous missense mutations resulting in the amino acid substitutions N88S and S90L. Null mutations in BSCL2, which encodes the protein seipin, were previously shown to be associated with autosomal recessive Berardinelli-Seip congenital lipodystrophy (OMIM #269700). We show that seipin is an integral membrane protein of the endoplasmic reticulum (ER). The amino acid substitutions N88S and S90L affect glycosylation of seipin and result in aggregate formation leading to neurodegeneration.     

The impact of cyclin-dependent kinase 5 depletion on poly(ADP-ribose) polymerase activity and responses to radiation

Cyclin-dependent kinase 5 (Cdk5) has been identified as a determinant of sensitivity to poly(ADP-ribose) polymerase (PARP) inhibitors. Here, the consequences of its depletion on cell survival, PARP activity, the recruitment of base excision repair (BER) proteins to DNA damage sites, and overall DNA single-strand break (SSB) repair were investigated using isogenic HeLa stably depleted (KD) and Control cell lines. Synthetic lethality achieved by disrupting PARP activity in Cdk5-deficient cells was confirmed, and the Cdk5^KD cells were also found to be sensitive to the killing effects of ionizing radiation (IR) but not methyl methanesulfonate or neocarzinostatin. The recruitment profiles of GFP-PARP-1 and XRCC1-YFP to sites of micro-irradiated Cdk5^KD cells were slower and reached lower maximum values, while the profile of GFP-PCNA recruitment was faster and attained higher maximum values compared to Control cells. Higher basal, IR, and hydrogen peroxide-induced polymer levels were observed in Cdk5^KD compared to Control cells. Recruitment of GFP-PARP-1 in which serines 782, 785, and 786, potential Cdk5 phosphorylation targets, were mutated to alanines in micro-irradiated Control cells was also reduced. We hypothesize that Cdk5-dependent PARP-1 phosphorylation on one or more of these serines results in an attenuation of its ribosylating activity facilitating persistence at DNA damage sites. Despite these deficiencies, Cdk5^KD cells are able to effectively repair SSBs probably via the long patch BER pathway, suggesting that the enhanced radiation sensitivity of Cdk5^KD cells is due to a role of Cdk5 in other pathways or the altered polymer levels.     

Relations phénétiques entre les familles d'Hamamelididae

Summary The phenetic relationships between the families of the Hamamelididae subclass were studied by using the following multifactorial analytical methods: principal components analysis (PCA) and reciprocal averaging (RA). The results obtained agree appreciably with Takhtajan's classification system.

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Remerciements. Nous remercions Mlle Sylvie Laliberté, Institut botanique de l'Université de Montréal, pour sa révision du manuscrit; M. Michel Labrecque, Institut botanique de l'Université de Montréal, pour avoir dessiné les figures; de même que M. André Bouchard, Jardin Botanique de Montréal et Institut botanique de l'Université de Montréal, de nous avoir permis d'utiliser les programmes dont il se sert pour ses travaux d'écologie.     

Prostaglandin-like substances inPropionibacterium acnes. IV. Effect on isolated human vessels

Summary The present study demonstrates a powerful vasoconstrictor activity of prostaglandin-like substances (PLS), extracted fromP. acnes, on human blood vessels. PLS is about equipotent to PGE₂ in its effect on human umbilical vessels, but the contractile response pattern is different. PLS therefore seems to have specific and different physiological characteristics.     

Rate of tryptophan hydroxylation in vivo in brain nuclei of genetically hypertensive rats of the Lyon strain

The rate of tryptophan hydroxylation in vivo is unaltered in brain areas of 5, 9 and 21 week-old Lyon genetically Hypertensive (LH) rats as compared to both Lyon Normotensive (LN) and Low Blood Pressure (LL) rats, except for a decrease in the C1 area of the medulla oblongata in 9 week-old animals.