Vascular and arterial calcification in peritoneal dialysis patients--state-of-the-art 2012.

Vascular calcification is a major challenge to the long-term health of many patients with chronic kidney disease, and patients receiving peritoneal dialysis therapy are no exception to this. The mechanisms behind vascular calcification are complex and diverse. There are several different imaging techniques that can be used to interrogate the vasculature in these patients, and the relative merits of these as research and screening tools we discuss. There are some recent epidemiological studies which throw fresh light on the implications of the development or progression of vascular calcification. Finally, an animal model experiment is reported which one day may open up the possibility of a successful therapeutic intervention.

The influence of human settlements on the parasite community in two species of Peruvian tamarin.

Although there is a growing recognition that the transfer of diseases between humans and non-human primates can be of great significance for conservation biology, there have been only a few studies focusing on parasites. In this study, saddleback (Saguinus fuscicollis) and moustached tamarin (Saguinus mystax) from the rainforest of the Peruvian lowlands were used as models to determine helminth parasite associations between canopy-dwelling primate species and a nearby human settlement. The human population showed high prevalences of infestation with a number of nematodes, including Ascaris lumbricoides (88.9%), Trichuris trichiura (37%) and hookworms (55.6%). However, the ova of these geohelminths were not detectable in tamarin faeces. Thus, no direct parasite transfer from humans to non-human primates could be documented. However, tamarin groups with more frequent contact to humans and their facilities had significantly higher prevalences and egg output of Prosthenorchis elegans, an important primate pathogen, than a forest group. In contrast, a cestode was significantly more common with more egg output in sylvatic than in human-associated groups. Human alteration of the habitat is likely to play a major role in determining the occurrence, prevalence and intensity of helminth infestation of wild non-human primates.

Can phenology explain the scarcity of folivory in New World primates?

I evaluated the hypothesis that the scarcity of folivorous neotropical primate taxa is due to fruiting and leafing occurring in phase in the New World. I compiled phenological information from different primatological studies, and correlated patterns of fruiting and leafing. Contrary to the prediction of the hypothesis, at most sites there was no synchronization of fruiting and leafing. Thus, the scarcity of folivorous platyrrhine taxa can not be attributed to specific phenological patterns of the neotropics. Some potential alternative hypotheses are suggested.

Denitrification of groundwater with methane as sole hydrogen donor.

It was examined, whether methane can be used as hydrogen donor for an in situ denitrification of groundwater. It is demonstrated, that groundwater can serve as liquid medium and that the denitrification can occur at 10 degrees C. Efforts to enrich methanotrophic bacteria under anoxic conditions have not been successful. No methane oxidation occurred in the absence of oxygen. For this reason, the denitrification with methane must be performed in a two-stage process with aerobic methanotrophic bacteria producing metabolites, that are used as hydrogen donor by non-methanotrophic bacteria in anoxic areas. This kind of indirect denitrification was proved by quantifying nitrogen and nitrous oxide in enrichment cultures that were not stirred or shaken. Large numbers of non-methanotrophic bacteria being able to denitrify with methanol, acetate or proteins as sole hydrogen donor were enriched besides the methanotrophic bacteria under these conditions.

Interspecific variation of scent-marking behaviour in wild tamarins, Saguinus mystax and Saguinus fuscicollis.

The scent-marking behaviour of sympatric moustached, Saguinus mystax, and saddle-back tamarins, Saguinus fuscicollis, was compared in order to explore interspecific differences and potential sources of variation. The author examined basic patterns of scent marking (types, intensity, complexity), substrate use (type, orientation, height), and social patterning of scent marking in three groups of S. mystax and one group of S. fuscicollis at the Estación Biológica Quebrada Blanco, Peruvian Amazonia. S. mystax and S. fuscicollis differed significantly in the relative frequency of different types, and in the intensity and complexity of scent marking. Only S. fuscicollis showed allomarking. They also differed significantly in the type, orientation and height of substrates used for scent marking which corresponded to general differences in substrate use. In S. fuscicollis, but very rarely in S. mystax, two or more group members marked the same site sequentially or simultaneously. 'Collective scent marking', i.e. simultaneous scent marking by most or all group members, occurred only in S. fuscicollis. Since both tamarin species live sympatrically in mixed-species groups, ecological factors are unlikely to account for the differences found in scent-marking behaviour (except for differences in substrate use). They probably relate to as yet unknown differences in social and reproductive strategies of the two species.

The behavioural ecology of mixed-species troops of callitrichine primates.

This review summarizes information on the behavioural ecology of mixed-species troops (interspecific associations) formed by different species of callitrichines, small New World monkeys, in western and central Amazonia. The formation of mixed-species troops is an integral part of the biology of several species of this subfamily. Niche separation between associated species is obtained through vertical segregation which results in differences in the prey spectrum. The degree of niche separation is a predictor for the stability of mixed-species troops. Individuals may benefit from the formation of mixed-species troops through increased safety from predators, increased foraging efficiency, and/or increased resource defence. Costs of mixed-species troop formation are probably very low and mainly relate to patterns of interspecific behavioural interactions. We point to gaps in our knowledge and suggest pathways for future research into mixed-species troops.

Vertebrate predation by sympatric tamarins, Saguinus mystax and Saguinus fuscicollis.

Vertebrate predation was examined in sympatric moustached tamarins (Saguinus mystax) and saddle-back tamarins (Saguinus fuscicollis) in the Amazon rainforest of northeastern Peru. Both species prey on frogs and lizards, and very rarely on nestling birds. As a result of divergent foraging strategies, S. mystax primarily exploited frogs at higher strata of the forest, while S. fuscicollis predominantly preyed on reptiles in the lower strata and on the ground. This difference may strengthen the niche differentiation between these two tamarin species that exists with regard to other prey.

Infanticide in a group of wild saddle-back tamarins, Saguinus fuscicollis.

An infanticide was observed in a group of wild saddle-back tamarins, Saguinus fuscicollis. The newborn singleton was killed by its mother after it had fallen from the carrier several times. This infanticide may represent a case of parental manipulation: the mother terminated investment in an offspring that probably had a low chance of survival. Also, stress associated with the simultaneous pregnancy of another adult female in the group may have played a role.

Field observations of the golden-mantled tamarin, Saguinus tripartitus, on the Río Curaray, Peruvian Amazonia.

During a primatological survey on the Río Curaray in north-eastern Peruvian Amazonia, observations on the ecology and behaviour of the golden-mantled tamarin, Saguinus tripartitus, were made. Two groups consisting of 6 and 9 individuals were observed. The diet of one group that was observed in some detail consisted of fruit, insects (tettigoniid orthopterans) and gums. Patterns of height use were very similar to those observed in saddle-back tamarins, Saguinus fuscicollis. This similarity and the lack of evidence for sympatry with either S. fuscicollis or S. nigricollis lead to the suggestion that S. tripartitus should be reconsidered as a subspecies of S. fuscicollis rather than a species on its own; alternatively, other subspecies of S. fuscicollis should be raised in taxonomic rank.

Estimation of inhibitory organophosphates with purified pig liver carboxylesterase.

Organophosphates that inhibit acetylcholinesterase normally also inhibit pig liver carboxylesterase irreversibly. Since this liver esterase is well characterized and easily accessible in large amounts, we propose the use of this enzyme for the quantitation of low concentrations of such organophosphates. The principle of two estimation methods is described. Both methods involve the addition of an unknown amount of organophosphate to an assay mixture of purified esterase, buffer and a low affinity esterase substrate. In the first of these methods, the inhibitor concentration is calculated from the esterase activities before and after the addition of the inhibitor. In the second method, the amounts of inhibitor or of enzyme are changed in several assays, until equimolar conditions can be detected from the observed reaction kinetics. The theoretical background of these methods is discussed and practical examples for the estimation of paraoxon (order of 0.1 nmoles) are given.

The relationship between body size and mixed-species troops of tamarins (Saguinus spp.).

While Saguinus fuscicollis forms mixed-species troops with sympatric tamarin species in parts of its geographic range, in other parts it does not. The question is addressed whether body size divergence is a critical factor for this difference. Analysis of body size (head-body length) data shows that body size divergence ranges between 8 and 17% for associated species and between 1 and 4% for non-associated species. In associated species, the degree of body size divergence seems to correlate with the stability of mixed-species troops (i.e., time spent in interspecific association). It is concluded that body size plays an important role for niche differentiation, sympatric coexistence and the formation of mixed-species troops in tamarins.

Hydrolysis of parabenes by extracts from differing layers of human skin.

We could distinguish four carboxylesterases capable of hydrolyzing 4-hydroxy-benzoic acid esters in human skin and subcutaneous fat tissue. The highest specific activities were found in an extract from subcutaneous fat tissue. The most prominent esterase of this tissue prefers the methyl ester of 4-hydroxybenzoic ester (methyl parabene). Its activity decreases with increasing chain length of the alcohol moiety of the parabenes. The existence of a second parabene esterase in subcutaneous fat is concluded from organophosphate inhibition characteristics. Another prominent parabene esterase was characterized in extracts from transformed keratinocytes. It prefers butyl parabene and its activity decreases with decreasing chain length of the alcohol moiety. The fourth parabene esterase is an enzyme of blood which contaminates the tissue extracts used here. All of the tissue extracts were active at pH 8.0, no parabene hydrolyzing activity could be demonstrated at pH 5.0.

A note on the identity of porcine liver carboxylesterase and prolyl-beta-naphthylamidase.

Prolyl-beta-naphthylamidase from porcine liver is compared with the two prevalent isoenzymes of pig liver carboxylesterase by isoelectrofocusing experiments and by inhibition studies with phenyl-methyl-sulfonyl fluoride. The results suggest that prolyl-beta-naphthylamidase is identical with the amide-cleaving isoenzyme of carboxylesterase, not with the usually predominant methyl butyrate-hydrolysing isoenzyme. It is questionable whether the recently published sequence of prolyl-beta-naphthylamidase does belong to this enzyme or to the predominant carboxylesterase without amidase activity. Surprisingly, the amide-cleaving carboxylesterase isoenzymes from rat liver have almost no activity with prolyl-beta-naphthylamide.

Organophosphate sensitive and insensitive carboxylesterases in human skin.

The influence of paraoxon and bis(4-nitrophenyl)phosphate (BNPP) on carboxylesterases of human skin is assayed. Both organophosphates have frequently been used as inhibitors of carboxylesterases of the B-esterase type. Homogenates from carefully washed skin have no paraoxon-cleaving activity and very little phosphodiesterase activity with BNPP. However, a number of skin enzymes are irreversibly inhibited by these compounds. Three zones of carboxylesterase bands can be detected in the soluble fraction of skin homogenate by isoelectric focusing. One zone containing 5 esterase bands in the pI-range of 6.7-7.0 and another zone at pI 4.9 are insensitive to organophosphate inhibition. The zone with the main esterase activities contains at least 6 bands in the range of pI 5.7-6.2. All of these are quickly and completely inhibited by paraoxon. The complex inhibition kinetics with BNPP and observations with differing substrates point to a functional heterogeneity. The esterases with pI-values in the range of 5.7 to 6.2 and the esterase with pI 4.9 can be enriched using anion exchange chromatography and FPLC. From the data presented here it is concluded that human skin contains at least four different carboxylesterases which act on simple aromatic esters.