Taenia crassiceps: Fate of cysticerci following ingestion by the mouse

Cysticerci of Taenia crassiceps were administered to mice by gavage to determine whether enteral or parenteral infections would establish consistently. Some worms survived in the small intestine up to 16 days, whereas others penetrated through the gut wall into the peritoneal cavity within 24 hr. Similar proportions of different doses of worms reached the peritoneal cavity regardless of the size of the inoculum and sex or strain of mice used. In addiiton, it was shown that mice may acquire an intraperitoneal infection with T. crassiceps by eating the carcass of an infected mouse.     

A population‐based temporal logic gate for timing and recording chemical events

Engineered bacterial sensors have potential applications in human health monitoring, environmental chemical detection, and materials biosynthesis. While such bacterial devices have long been engineered to differentiate between combinations of inputs, their potential to process signal timing and duration has been overlooked. In this work, we present a two‐input temporal logic gate that can sense and record the order of the inputs, the timing between inputs, and the duration of input pulses. Our temporal logic gate design relies on unidirectional DNA recombination mediated by bacteriophage integrases to detect and encode sequences of input events. For an E. coli strain engineered to contain our temporal logic gate, we compare predictions of Markov model simulations with laboratory measurements of final population distributions for both step and pulse inputs. Although single cells were engineered to have digital outputs, stochastic noise created heterogeneous single‐cell responses that translated into analog population responses. Furthermore, when single‐cell genetic states were aggregated into population‐level distributions, these distributions contained unique information not encoded in individual cells. Thus, final differentiated sub‐populations could be used to deduce order, timing, and duration of transient chemical events.     

Three Members of the 6-cys Protein Family of Plasmodium Play a Role in Gamete Fertility

The process of fertilization is critically dependent on the mutual recognition of gametes and in Plasmodium, the male gamete surface protein P48/45 is vital to this process. This protein belongs to a family of 10 structurally related proteins, the so called 6-cys family. To identify the role of additional members of this family in Plasmodium fertilisation, we performed genetic and functional analysis on the five members of the 6-cys family that are transcribed during the gametocyte stage of P. berghei. This analysis revealed that in addition to P48/45, two members (P230 and P47) also play an essential role in the process of parasite fertilization. Mating studies between parasites lacking P230, P48/45 or P47 demonstrate that P230, like P48/45, is a male fertility factor, consistent with the previous demonstration of a protein complex containing both P48/45 and P230. In contrast, disruption of P47 results in a strong reduction of female fertility, while males remain unaffected. Further analysis revealed that gametes of mutants lacking expression of p48/45 or p230 or p47 are unable to either recognise or attach to each other. Disruption of the paralog of p230, p230p, also specifically expressed in gametocytes, had no observable effect on fertilization. These results indicate that the P. berghei 6-cys family contains a number of proteins that are either male or female specific ligands that play an important role in gamete recognition and/or attachment. The implications of low levels of fertilisation that exist even in the absence of these proteins, indicating alternative pathways of fertilisation, as well as positive selection acting on these proteins, are discussed in the context of targeting these proteins as transmission blocking vaccine candidates.     

Food perception with age and its relationship to pleasantness

Differences between elderly subjects (n = 46, 61-86 years) and young subjects (n = 36, 18-25 years) in food perception and food liking were investigated. Intensity and liking ratings were assessed for custard dessert, in which flavor enrichment, textural change, and irritant addition were incorporated as strategies to compensate for sensory losses with increasing age. The sensory acuity (taste, olfaction, irritation, chewing efficiency) of both young and elderly subjects was measured with the help of different sensitivity tests. The elderly perceived the custards differently from the young, mainly as less intense in flavor (cherry/vanilla) and less intense in creaminess/swallowing effort. Several of the observed interaction effects were different for the elderly and the young. The majority of these differences manifested as lower intensity slopes for the elderly. Losses in sensitivity to taste and to olfactory and trigeminal stimuli as well as a reduced chewing efficiency were observed on average for the elderly compared with the young. Furthermore, subgroups of the elderly were observed in which the compensatory strategies flavor enrichment, textural change, and irritant addition led to an increase in food liking. However, these subgroups did not differ in their sensory acuity. The present study does not support the assumption that age-associated changes in food perception-caused by losses in sensory acuity-inevitably reduce the food liking of the elderly.     

Caveolin-1 interacts with 5-HT2A serotonin receptors and profoundly modulates the signaling of selected Galphaq-coupled protein receptors

5-Hydroxytryptamine 2A (5-HT(2A)) serotonin receptors are important for a variety of functions including vascular smooth muscle contraction, platelet aggregation, and the modulation of perception, cognition, and emotion. In a search for 5-HT(2A) receptor-interacting proteins, we discovered that caveolin-1 (Cav-1), a scaffolding protein enriched in caveolae, complexes with 5-HT(2A) receptors in a number of cell types including C6 glioma cells, transfected HEK-293 cells, and rat brain synaptic membrane preparations. To address the functional significance of this interaction, we performed RNA interference-mediated knockdown of Cav-1 in C6 glioma cells, a cell type that endogenously expresses both 5-HT(2A) receptors and Cav-1. We discovered that the in vitro knockdown of Cav-1 in C6 glioma cells nearly abolished 5-HT(2A) receptor-mediated signal transduction as measured by calcium flux assays. RNA interference-mediated knockdown of Cav-1 also greatly attenuated endogenous Galpha(q)-coupled P2Y purinergic receptor-mediated signaling without altering the signaling of PAR-1 thrombin receptors. Cav-1 appeared to modulate 5-HT(2A) signaling by facilitating the interaction of 5-HT(2A) receptors with Galpha(q). These studies provide compelling evidence for a prominent role of Cav-1 in regulating the functional activity of not only 5-HT(2A) serotonin receptors but also selected Galpha(q)-coupled receptors.     

The influence of olfactory concept on the probability of detecting sub- and peri-threshold components in a mixture of odorants.

The headspace of apple juice was analysed to obtain an ecologically relevant stimulus model mixture of apple volatiles. Two sets of volatiles were made up: a set of eight supra-threshold volatiles (MIX) and a set of three sub-threshold volatiles. These sets were used to test the hypothesis that sub-threshold components can change the quality of a familiar smelling mixture of odorants when added to this mixture. In order to test this hypothesis, three successive dilutions of the sub-threshold volatiles were prepared in such a way that the strongest was at the threshold concentration and the two lower concentrations were below the threshold. The detection probabilities of the sub-threshold components in a blank stimulus were compared with the detectabilities in MIX. The sub- and peri-threshold volatiles were detected no better in MIX than in a blank. On the contrary, sub- and peri-threshold volatiles were better detected alone than when added to MIX. However, when the group of subjects was split into two sub-groups, employing either a rough or a detailed concept definition of the target stimulus, respectively, the subjects with highly refined concepts were better able to detect the presence of sub-threshold volatiles in MIX than those with poorly refined stimulus concepts. The effect of stimulus concept definition occurred independently of the proportions of correct detections of sub-threshold volatiles in a blank.     

Development and application of a positive–negative selectable marker system for use in reverse genetics in Plasmodium

A limitation of transfection of malaria parasites is the availability of only a low number of positive selectable markers for selection of transformed mutants. This is exacerbated for the rodent parasite Plasmodium berghei as selection of mutants is performed in vivo in laboratory rodents. We here report the development and application of a negative selection system based upon transgenic expression of a bifunctional protein (yFCU) combining yeast cytosine deaminase and uridyl phosphoribosyl transferase (UPRT) activity in P.berghei followed by in vivo selection with the prodrug 5-fluorocytosine (5-FC). The combination of yfcu and a positive selectable marker was used to first achieve positive selection of mutant parasites with a disrupted gene in a conventional manner. Thereafter through negative selection using 5-FC, mutants were selected where the disrupted gene had been restored to its original configuration as a result of the excision of the selectable markers from the genome through homologous recombination. This procedure was carried out for a Plasmodium gene (p48/45) encoding a protein involved in fertilization, the function of which had been previously implied through gene disruption alone. Such reversible recombination can therefore be employed for both the rapid analysis of the phenotype by targeted disruption of a gene and further associate phenotype and function by genotype restoration through the use of a single plasmid and a single positive selectable marker. Furthermore the negative selection system may also be adapted to facilitate other procedures such as ‘Hit and Run’ and ‘vector recycling’ which in principle will allow unlimited manipulation of a single parasite clone. This is the first demonstration of the general use of yFCU in combination with a positive selectable marker in reverse genetics approaches and it should be possible to adapt its use to many other biological systems.     

Echinococcus multilocularis: responses to infection in Mongolian gerbils

Mongolian gerbils (Meriones unguiculatus) inoculated intraperitoneally with three acephalic cysts of Echinococcus multilocularis were very susceptible to infection. Aspects of the responses of gerbils to this infection were examined to determine if they could be related to the progress of the infection. Hematologic changes observed during the infection included anemia, reticulocytosis, lymphocytopenia, neutrophilia, monocytosis, and eosinopenia; these changes were related to the size of the infection. Infected gerbils also produced specific protein-A binding antibodies to E. multilocularis. At 14 weeks after inoculation, infected gerbils showed splenomegaly and somewhat elevated serum transaminase levels, although serum 5'-nucleotidase levels were normal.