Contribution of different pathways to the supply of phosphatidylethanolamine and phosphatidylcholine to mitochondrial membranes of the yeast Saccharomyces cerevisiae

In the yeast, three biosynthetic pathways lead to the formation of phosphatidylethanolamine (PtdEtn): (i) decarboxylation of phosphatidylserine (PtdSer) by phosphatidylserine decarboxylase 1 (Psd1p) in mitochondria; (ii) decarboxylation of PtdSer by Psd2p in a Golgi/vacuolar compartment; and (iii) the CDP-ethanolamine (CDP-Etn) branch of the Kennedy pathway. The major phospholipid of the yeast, phosphatidylcholine (PtdCho), is formed either by methylation of PtdEtn or via the CDP-choline branch of the Kennedy pathway. To study the contribution of these pathways to the supply of PtdEtn and PtdCho to mitochondrial membranes, labeling experiments in vivo with [(3)H]serine and [(14)C]ethanolamine, or with [(3)H]serine and [(14)C]choline, respectively, and subsequent cell fractionation were performed with psd1Delta and psd2Delta mutants. As shown by comparison of the labeling patterns of the different strains, the major source of cellular and mitochondrial PtdEtn is Psd1p. PtdEtn formed by Psd2p or the CDP-Etn pathway, however, can be imported into mitochondria, although with moderate efficiency. In contrast to mitochondria, microsomal PtdEtn is mainly derived from the CDP-Etn pathway. PtdEtn formed by Psd2p is the preferred substrate for PtdCho synthesis. PtdCho derived from the different pathways appears to be supplied to subcellular membranes from a single PtdCho pool. Thus, the different pathways of PtdEtn biosynthesis play different roles in the assembly of PtdEtn into cellular membranes.     

A survey of the hybridisation status of Cervus deer species on the island of Ireland

Red deer (Cervus elaphus) did not recolonise Ireland after the last glaciation, but the population in Co. Kerry is descended from an ancient (c. 5000 BP) introduction and merits conservation. During the mid-19th century exotic species including North American wapiti (C. canadensis) and Japanese sika deer (C. nippon nippon) were introduced to Ireland, mainly via Powerscourt Park, Co. Wicklow. While wapiti failed to establish, sika thrived, dispersed within Co. Wicklow and were translocated to other sites throughout Ireland. Red deer and sika are known to have hybridised in Ireland, particularly in Co. Wicklow, but an extensive survey with a large, highly diagnostic marker panel is required to assess the threat hybridisation potentially poses to the Co. Kerry red deer population. Here, 374 individuals were genotyped at a panel of 22 microsatellites and at a single mtDNA marker that are highly diagnostic for red deer and Japanese sika. The microsatellites are also moderately diagnostic for red deer and wapiti. Wapiti introgression was very low [trace evidence in 2 (0.53 %) individuals]. Despite long-standing sympatry of red deer and sika in the area, no red deer-sika hybrids were detected in Co. Kerry suggesting strong assortative mating by both species in this area. However, 80/197 (41 %) of deer sampled in Co. Wicklow and 7/15 (47 %) of deer sampled in Co. Cork were red-sika hybrids. Given their proximity and that hybrids are less likely to mate assortatively than pure individuals, the Co. Cork hybrids pose a threat to the Co. Kerry red deer.     

Distinguishing Family from Friends

Kinship and friendship are key human relationships. Increasingly, data suggest that people are not less altruistic toward friends than close kin. Some accounts suggest that psychologically we do not distinguish between them; countering this is evidence that kinship provides a unique explanatory factor. Using the Implicit Association Test, we examined how people implicitly think about close friends versus close kin in three contexts. In Experiment 1, we examined generic attitudinal dispositions toward friends and family. In Experiment 2, attitude similarity as a marker of family and friends was examined, and in Experiments 3 and 4, strength of in-group membership for family and friends was examined. Findings show that differences exist in implicit cognitive associations toward family and friends. There is some evidence that people hold more positive general dispositions toward friends, associate attitude similarity more with friends, consider family as more representative of the in-group than friends, but see friends as more in-group than distant kin.     

724. BOMAREA DULCIS

Bomarea dulcis (Hook.) Beauv. is illustrated and details of its cultivation are given; its relationships to other members of subgenus Wichuraea are discussed.     

Studies on the mechanism of interaction of a bioresponsive endosomolytic polyamidoamine with interfaces. 1. Micelles as model surfaces

Polymers are appealing as pH-responsive elements of multicomponent systems designed to promote cytosolic delivery of macromolecular drugs (including proteins and genes), but so far the delivery efficiency achieved has been relatively modest. Therefore, the aim of this study was to apply several physicochemical techniques that are well established in the colloid field (surface tension measurements, small-angle neutron scattering (SANS), and electron paramagnetic resonance (EPR)) to probe the mechanism of endosomolytic polymer-surface interaction over the pH range 7.4 to 5.5 using the poly(amidoamine) (PAA) ISA23 x HCl and a series of "model" micelle surfaces. These micellar models were chosen to represent increasing complexity from simple, single surfactant sodium dodecylsulfate (SDS) micelles, surfactant mixtures containing bulky malono-bis-N-methylglucamide headgroups, or highly extended ethylene oxide headgroups. Spherical micelles composed of 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (lyso-PC) were also used. Changes in the onset of micellization, micelle surface fluidity, and in selected cases, the overall micelle shape and size were all quantified as a function of pH in the presence and absence of ISA23 x HCl. This amphoteric PAA is negatively charged at pH 7.4 and becomes gradually more protonated on exposure to lower pH values representative of the endosomal-lysosomal pathway. As expected, the strength of polymer interaction with anionic micelles increased with a decrease in pH, while for cationic micelles the opposite was observed. Addition of bulky, nonionic surfactant headgroups led to weaker interactions. The observations from surface tension and SANS studies showed a complex pattern of interaction with both an electrostatic and hydrophobic component. Using EPR it was confirmed that ISA23 x HCl perturbed the micelle palisade layer leading to a decrease in fluidity of the interface with a lower degree of headgroup hydration, and a significant change in micelle morphology. Surprisingly, there was no interaction between ISA23 x HCl and globular micelles formed from lyso-PC (a more biologically relevant model), and this suggests that the PAA structure could be better optimized to promote rapid interaction with endosomal membranes at the physiologically relevant pH 6.5.     

Rhabdomeric membrane and smooth endoplasmic reticulum in photoreceptors of Manduca sexta: modulations associated with the diurnal light/dark cycle and effects of chromophore deprivation

Summary Aberrations of photoreceptor ultrastructure resulting from carotenoid/retinoid (vitamin A) deprivation were studied in the retina of Manduca sexta. The syndrome of chromophore deficiency included hypertrophy of smooth endoplasmic reticulum, variable dilation of rhabdomeric microvilli, the insertion of endomembrane fingers into such enlarged microvilli, and the formation of rhabdomeric vacuoles, intracellular compartments containing microvilli similar to those of the rhabdomere. Retinas were processed either with conventional procedures employing preliminary aldehyde fixation followed by heavy metal postfixation, or by fixation and incubation in unbuffered OsO₄. The latter method deposits osmium throughout the endomembrane system, within the rhabdomeric vacuoles, and in the extracellular space of the rhabdom. However, the intravillous fingers were rarely impregnated with osmium, despite their continuity with densely stained cisternae of the smooth endoplasmic reticulum. We suggest that the insertion of endomembrane fingers into dilated microvilli results from a cytoskeleton-mediated link between cisternae of the smooth endoplasmic reticulum and the rhabdomeric membrane, an association that may be important in the turnover of photoreceptor membrane. We interpret endomembrane hypertrophy and development of rhabdomeric vacuoles as symptoms of disturbance in the pathway leading to the assembly of the rhabdomere resulting from reduced synthesis of visual pigment.