Cytoplasmic filaments and cellular wound healing in amoeba proteus

The flexibility and self-healing properties of animal cell surface membranes are well known. These properties have been best exploited in various micrurgical studies on living cells (2, 3), especially in amoebae (7, 20). During nuclear transplantation in amoebae, the hole in the membrane through which a nucleus passes can have a diameter of 20-30 μm, and yet such holes are quickly sealed, although some cytoplasm usually escapes during the transfer. While enucleating amoebae in previous studies, we found that if a very small portion of a nucleus was pushed through the membrane and exposed to the external medium, the amoeba expelled such a nucleus on its own accord. When this happened, a new membrane appeared to form around the embedded portion of the nucleus and no visible loss of cytoplasm occurred during nuclear extrusion. In the present study, we examined amoebae that were at different stages of expelling partially exposed nuclei, to follow the sequence of events during the apparent new membrane formation. Unexpectedly, we found that a new membrane is not formed around the nucleus from inside but a hole is sealed primarily by a constriction of the existing membrane, and that cytoplasmic filaments are responsible for the prevention of the loss of cytoplasm.     

Differential cytokine expression in myocytes and non-myocytes after myocardial infarction in rats

The proinflammatory cytokines interleukin (IL)-1 and IL-6 are increased after acute myocardial infarction (MI). Moreover, serum IL-6 level is elevated after MI, but has also been associated with heart failure. In the present study, heart function was monitored in a rat model of chronic MI. Cytokine expression in the infarcted and non-infarcted myocardium as well as in hearts of sham-operated controls was measured by the ribonuclease-protection assay. To identify the cells contributing to the increased cytokine expression, we further analyzed myocytes and non-myocytes isolated in the acute phase as well as during congestive heart failure (CHF) after MI. There was a strong induction in cytokine expression in the myocytes of the infarct area 6 h after MI. In the non-infarcted myocardium, cytokine expression increased only slightly in the non-myocytes after 6 h. This was not different from sham-operated controls and may, therefore, be induced by stress and catecholamines. In CHF, however, cytokine expression level in myocytes was normal. It increased slightly but significantly in the non-myocytes 4 and 8 weeks after MI. In conclusion, we suggest that pro-inflammatory cytokines, produced by the ischemic myocytes may be involved in the initiation of wound healing of the necrotic area, whereas the effect of pro-inflammatory cytokines in CHF, if any, seems not to be crucial.     

A preliminary study of keratinophilic fungi from Abaco Island,the Bahamas

The soil of two Bahamian communities on Abaco Island was examined for keratinophilic fungi. Isolated fungal species in soil identifies possible causal agents of dermatophytoses. Inhabitants of the area may have contaminated the soil, or species present may represent a potential source of new clinical cases. Fungal pathogens have been reported as free living soil saprophytes.     

Effect of various antibiotics on gastrointestinal colonization and dissemination by Candida albicans

Mice were treated orally with various antibiotics to determine which members of the indigenous intestinal microflora normally suppress Candida albicans colonization and dissemination from the gastrointestinal (GI) tract. The mice were given penicillin, clindamycin, vancomycin, erythromycin, or gentamicin for 3 days, and then challenged orally with C. albicans. Penicillin, clindamycin, and vancomycin, but not gentamicin or erythromycin, decreased the total anaerobic bacterial populations in the animals ceca, and increased the enteric bacilli population levels. All three of the former antibiotics allowed C. albicans to proliferate in the gut and, subsequently, disseminate from the GI tract to visceral organs. The ability of C. albicans to associate with intestinal mucosal surfaces was also tested. It was found that antibiotics which reduced anaerobic population levels, but not enteric bacilli or aerobes, also predisposed animals to mucosal association by C. albicans. It is suggested that the strictly anaerobic bacterial populations which predominate in the gut ecosystem are responsible for the inhibition of C. albicans adhesion, colonization and dissemination from the GI tract.     

Effects of heterogeneous and clustered contact patterns on infectious disease dynamics

The spread of infectious diseases fundamentally depends on the pattern of contacts between individuals. Although studies of contact networks have shown that heterogeneity in the number of contacts and the duration of contacts can have far-reaching epidemiological consequences, models often assume that contacts are chosen at random and thereby ignore the sociological, temporal and/or spatial clustering of contacts. Here we investigate the simultaneous effects of heterogeneous and clustered contact patterns on epidemic dynamics. To model population structure, we generalize the configuration model which has a tunable degree distribution (number of contacts per node) and level of clustering (number of three cliques). To model epidemic dynamics for this class of random graph, we derive a tractable, low-dimensional system of ordinary differential equations that accounts for the effects of network structure on the course of the epidemic. We find that the interaction between clustering and the degree distribution is complex. Clustering always slows an epidemic, but simultaneously increasing clustering and the variance of the degree distribution can increase final epidemic size. We also show that bond percolation-based approximations can be highly biased if one incorrectly assumes that infectious periods are homogeneous, and the magnitude of this bias increases with the amount of clustering in the network. We apply this approach to model the high clustering of contacts within households, using contact parameters estimated from survey data of social interactions, and we identify conditions under which network models that do not account for household structure will be biased.     

Studien über das „knallen” der alpheiden. Nach untersuchungen an alpheus dentipes guérin und synalpheus laevimanus (Heller)

Ohne Zusammenfassung     

Construction, database integration, and application of an Oenothera EST library

Coevolution of cellular genetic compartments is a fundamental aspect in eukaryotic genome evolution that becomes apparent in serious developmental disturbances after interspecific organelle exchanges. The genus Oenothera represents a unique, at present the only available, resource to study the role of the compartmentalized plant genome in diversification of populations and speciation processes. An integrated approach involving cDNA cloning, EST sequencing, and bioinformatic data mining was chosen using Oenothera elata with the genetic constitution nuclear genome AA with plastome type I. The Gene Ontology system grouped 1621 unique gene products into 17 different functional categories. Application of arrays generated from a selected fraction of ESTs revealed significantly differing expression profiles among closely related Oenothera species possessing the potential to generate fertile and incompatible plastid/nuclear hybrids (hybrid bleaching). Furthermore, the EST library provides a valuable source of PCR-based polymorphic molecular markers that are instrumental for genotyping and molecular mapping approaches.     

Critical Role of Perforin-dependent CD8+ T Cell Immunity for Rapid Protective Vaccination in a Murine Model for Human Smallpox

Vaccination is highly effective in preventing various infectious diseases, whereas the constant threat of new emerging pathogens necessitates the development of innovative vaccination principles that also confer rapid protection in a case of emergency. Although increasing evidence points to T cell immunity playing a critical role in vaccination against viral diseases, vaccine efficacy is mostly associated with the induction of antibody responses. Here we analyze the immunological mechanism(s) of rapidly protective vaccinia virus immunization using mousepox as surrogate model for human smallpox. We found that fast protection against lethal systemic poxvirus disease solely depended on CD4 and CD8 T cell responses induced by vaccination with highly attenuated modified vaccinia virus Ankara (MVA) or conventional vaccinia virus. Of note, CD4 T cells were critically required to allow for MVA induced CD8 T cell expansion and perforin-mediated cytotoxicity was a key mechanism of MVA induced protection. In contrast, selected components of the innate immune system and B cell-mediated responses were fully dispensable for prevention of fatal disease by immunization given two days before challenge. In conclusion, our data clearly demonstrate that perforin-dependent CD8 T cell immunity plays a key role in MVA conferred short term protection against lethal mousepox. Rapid induction of T cell immunity might serve as a new paradigm for treatments that need to fit into a scenario of protective emergency vaccination.     

Completely serum-free and chemically defined adipocyte development and maintenance

Background aims

In vitro engineered adipose tissue is in great demand to treat lost or damaged soft tissue or to screen for new drugs, among other applications. However, today most attempts depend on the use of animal-derived sera. To pave the way for the application of adipose tissue–engineered products in clinical trials or as reliable and robust in vitro test systems, sera should be completely excluded from the production process. In this study, we aimed to develop an in vitro adipose tissue model in the absence of sera and maintain its function long-term.