Differentiation and Multiplication of Dyskinetoplastic Trypanosoma cruzi in Tissue Culture and in the Mammalian Host*

SYNOPSIS. In cultures of the Y strain of Trypanosoma cruzi treated with acriflavine, a very high proportion of the crithidiae may be dyskinetoplastic. These crithidiae cannot be maintained in subcultures but are able to differentiate into (dyskinetoplastic) metatrypanosomes. In tissue cultures infected with these metatrypanosomes, or with blood trypanosomes and treated with acriflavine, dyskinetoplastic T. cruzi is able to go thru the whole sequence of stages that characterizes its cycle in the vertebrate host: penetration by trypanosomes into cells, differentiation into leishmaniae, multiplication in this phase and differentiation again into trypanosomes. The same may occur in the mammalian host itself. The physiological implications of these findings are discussed and special attention is called to polymorphism of blood forms of T. cruzi, which probably has the same significance it has in the brucei-evansi group of trypanosomes.     

Reserve Lipids in Stem Root Primordia of Poplar

Lipids are reserve substances in stem root primordia of poplarand occur as droplets approximately uniformly in all cells ofroot primordia. In ultrathin sections they appear as sphericalelectron-dense particles (0.5–1.4 µm diameter),filling up virtually all the available space in the cytoplasm.The presence of lipids in stem root primordia was demonstratedin several species of the genus Populus from the section Aigeirosand Tacamahaca, as well as in another representative of thefamily Salicaceae, viz. in the genus Salix.     

Production of Melanins by Ceruloplasmin

It was shown that ceruloplasmin, apart from the known oxidative conversion of dopamine into melanin, can also produce (DHI)-melanin from 5,6-dihydroxyindole and THP-melanin from tetrahydropapaveroline. Ceruloplasmin acts as an oxidase and the kinetic parameters for these oxidative reactions are reported. Since these ceruloplasmin-catalyzed reactions occur also at pH 7.4, they could have a significant physiological impact. This ceruloplasmin-oxidasic activity is enhanced by copper ions and inhibited by chelators, such as ethylenediaminetetraacetic acid (EDTA) and desferoxamine (DEF). Some possible implication of melanin production in blood are discussed.     

Activity and Compartmentation of Photosynthetic Carboxylases in Normal and Chloroplast-mutant Maize Leaves

The activity of ribulose-l,5-diphosphate carboxylase (RudiP-carboxylase) and phosphoenolpyruvate carboxylase (PEP-carboxylase) measured in vitro was independent from the chlorophyll content of the leaves. The relatively high activity of PEP-carboxylase as compared to the RudiP-carboxylase activity was particularly pronounced in the mutants. Realization of the potential (in vitro measured) carboxylating activities in fixation of CO₂in vivo was practically complete in normal leaves. In the mutants, however, CO₂ fixation was lower than the level permitted by the carboxylase activity. This could be explained only in part by the impaired rate of photophosphorylation. Compartmentation of PEP-carboxylase was different in normal and mutant leaves: in contrast to the normal ones, parenchyma-sheath cells of the mutants exhibited high PEP-carboxylase activity. Competition of PEP-carboxylase with RudiP-carboxylase for CO₂ in the mutants led to accumulation of organic acids, and can account for their low photosynthetic activity.     

Feeding and Resting Postures of Wild Northern Muriquis (Brachyteles hypoxanthus)

Increased body size in Brachyteles has been regarded as an important evolutionary adaptation that allowed a greater reliance on leaves compared to other more frugivorous Atelidae, but its association with muriqui positional behavior and substrate use is still unknown. Here, we present original data on the feeding and resting postures of the northern muriqui (Brachyteles hypoxanthus) and evaluate predictions about the relationships between body size, postural behavior, and substrate use derived from previously published data for other atelids (e.g. Alouatta, Ateles, and Lagothrix). The study was undertaken from August 2002 to July 2003 on a large group of well‐habituated muriquis inhabiting the Reserva Particular do Patrimônio Natural – Felíciano Miguel Abdala in Minas Gerais, Brazil. Consistent with our predictions, we found that B. hypoxanthus was highly suspensory during postural feeding (60.9%) and commonly used tail–hind limb suspension/horizontal tripod (38.0%) or tail–forelimb/hind limb suspension (21.4%). However, although tail‐suspensory postures permitted the muriquis to use the terminal canopy and small‐sized substrates, these areas were also accessed via tail‐assisted above‐branch postural behaviors involving multiple substrates. Unexpectedly, tail‐suspensory postures were found to be frequently associated with large substrates, tree trunks, and the understory. We suggest that Brachyteles’ ability to access food resources from all areas of a feeding tree and from tree crowns at different canopy levels may account for their ability to efficiently exploit food resources in seasonal disturbed forest fragments of the Brazilian Atlantic Forest today. Am. J. Primatol. 75:74‐87, 2013. © 2012 Wiley Periodicals, Inc.