Biotic and abiotic factors determining the distribution of two prawn species: Palaemon adspersus and P. squilla

Summary The reasons behind the absence of the prawn Palaemon adspersus and the presence of P. squilla in rockpools and on bare sand bottoms were studied. Some maximal abundances in different habitats are given. Introduction experiments into natural and artificial rockpools and measurements of tolerance towards low oxygen levels showed that nocturnal hypoxia excluded P. adspersus which was significantly more sensitive to oxygen depletion. Respiration rates measured by the closed-bottle method showed no interspecific difference.On bare sand bottoms P. aspersus was probably excluded by predators, since predator exclusion experiments in cages and predator inclusion experiments in containers showed that P. adaspersus was more vulnerable to predation than P. squilla.The costs for being able to cope with a wide array of habitat in P. squilla are probably balanced by the benefits of access to habitats such as intertidal rockpools, very shallow bottoms and deeper sand bottoms. Tolerance towards abiotic factors extends its habitat range upwards into shallower waters, and tolerance towards biotic factors, i.e. predation, extends it downwards.     

Solid-phase peptide synthesis of somatostatin using mild base cleavage of N alpha-9-fluorenylmethyloxycarbonylamino acids

Experimental details for the "Fmoc solid phase peptide synthesis" of somatostatin are described. The 9-fluorenylmethyloxycarbonyl group was rapidly and quantitatively cleaved by 55% piperidine in dimethylformamide and monitored (u.v.) manually. For a kinetic study, a centrifugal reactor with a photometric control system and reference cell was used at each stage. The symmetrical anhydride coupling reaction was rapid and either acetic anhydride or fluorescamine termination was incorporated to minimize formation of deletion peptides. Anchor-bond cleavage was effected with trifluoroacetic acid which simultaneously removed all the acid labile tert.-butyl side chain protecting groups. N alpha-9-fluorenylmethyloxycarbonyl peptides may be obtained by omitting the piperidine deprotection step after the last cycle of synthesis. From several syntheses, analytically pure di-S-protected somatostatin 14-peptide was obtained in 55-60% overall yield. The S-protecting groups were removed and the product was purified by gel filtration to give homogeneous dihydrosomatostatin (91%) yield. Oxidation of dihydrosomatostatin with potassium ferricyanide and purification by countercurrent distribution provided analytically pure homogeneous somatostatin.     

Palynological study of a holocene peat and a miocene coal deposit from NW Borneo

The development of a Holocene peat near Marudi (Sarawak) and a Miocene coal near Berakas (Brunei) is studied pollen-analytically and stratigraphically by comparison with present-day swamp vegetation along the NW Bornean coast. A number of 76 pollen and spore types were recognized and are briefly diagnosed.The Marudi profile starts on mangrove sediment and shows a succession which is closely comparable to the present-day zonation of the large raised bog of which it forms part.The Berakas profile starts on fluviatile sediments and remains in the mixed swamp forest stage. This small deposit has remained close to the coast and peat growth is terminated by marine transgression.The floristic composition of the mixed swamp forest stage in both bogs, separated in age by approximately seven million years is closely comparable. Minor differences which exist can be attributed to differences in size, ecologic conditions and accessibility from mainland reservoirs.Only on spore type, Stenochlaena areolaris has become extinct in Borneo.     

Gaze-dependent evidence accumulation predicts multi-alternative risky choice behaviour

Choices are influenced by gaze allocation during deliberation, so that fixating an alternative longer leads to increased probability of choosing it. Gaze-dependent evidence accumulation provides a parsimonious account of choices, response times and gaze-behaviour in many simple decision scenarios. Here, we test whether this framework can also predict more complex context-dependent patterns of choice in a three-alternative risky choice task, where choices and eye movements were subject to attraction and compromise effects. Choices were best described by a gaze-dependent evidence accumulation model, where subjective values of alternatives are discounted while not fixated. Finally, we performed a systematic search over a large model space, allowing us to evaluate the relative contribution of different forms of gaze-dependence and additional mechanisms previously not considered by gaze-dependent accumulation models. Gaze-dependence remained the most important mechanism, but participants with strong attraction effects employed an additional similarity-dependent inhibition mechanism found in other models of multi-alternative multi-attribute choice.     

New insights in the cellular processing of platinum antitumor compounds, using fluorophore-labeled platinum complexes and digital fluorescence microscopy

The cellular distribution and processing pathways of two platinum compounds, modeling the antitumor drug cisplatin (cDDP) in human osteosarcoma (U2-OS) cells is reported. A [Pt(en)Cl] entity has been covalently linked to a carboxyfluorescein diacetate (CFDA) moiety and to a dinitrophenyl (DNP) moiety. The two different constructs were administered to living cell cultures that were analyzed using digital fluorescence microscopy. The non-fluorescent CFDA construct becomes fluorescent after cellular uptake and subsequent acetate hydrolysis by esterases, and is therefore suitable to monitor platinum in living cells; the DNP construct can be visualized by immunocytochemistry and consequently serves as a control. Both complexes were readily internalized by the cells, and localized throughout the whole cell. After 2-3 h the complex accumulated in the nucleus, but 6-8 h after incubation a punctuate staining of a cytoplasmic region was observed, that persisted and became more pronounced after 24 h. The overall fluorescence in the cell decreased over time, implying a secretion of the platinum complex. Surprisingly, the accumulation remained visible after 72 h. Co-localization experiments with a Golgi apparatus-selective stain indicate the involvement of Golgi vesicles in intracellular processing of cisplatin-derived complexes. Immunocytochemical studies, using the DNP derivative, resulted in very similar images as obtained with the CFDA construct. CFDA-boc (a non-platinum-containing fluorescein derivative) was used as control: a faint staining throughout the whole cell was observed. Cisplatin-resistant U2-OS/Pt cells showed staining patterns very similar to the U2-OS cells using both platinum constructs. This study illustrates that only a very small portion of the platinum complex eventually remains bound to DNA, as after 24 h no significant fluorescence could be observed in the nucleus. Cisplatin-derived complexes with fluorescent tags afford a new insight into the cellular processing of these complexes and therefore may contribute to further unraveling of the mechanism of platinum antitumor complexes.     

Proteomic analysis of microvesicles from plasma of healthy donors reveals high individual variability

Healthy blood plasma is required for several therapeutic procedures. To maximize successful therapeutic outcomes it is critical to control the quality of blood plasma. Clearly initiatives to improve the safety of blood transfusions will have a high economical and social impact. A detailed knowledge of the composition of healthy blood plasma is essential to facilitate such improvements. Apart from free proteins, lipids and metabolites, blood plasma also contains cell-derived microvesicles, including exosomes and microparticles from several different cellular origins. In this study, we have purified microvesicles smaller than 220nm from plasma of healthy donors and performed proteomic, ultra-structural, biochemical and functional analyses. We have detected 161 microvesicle-associated proteins, including many associated with the complement and coagulation signal-transduction cascades. Several proteases and protease inhibitors associated with acute phase responses were present, indicating that these microvesicles may be involved in these processes. There was a remarkably high variability in the protein content of plasma from different donors. In addition, we report that this variability could be relevant for their interaction with cellular systems. This work provides valuable information on plasma microvesicles and a foundation to understand microvesicle biology and clinical implications.