Highly mobile users and paging: optimal polling strategies

We consider the problem of minimizing average paging cost subject to delay constraints in a wireless system. Previous work assumed the unit to be found did not move during the paging process whereas here the unit may change location during polling events. We show that the conditionally most probable locations, given that the unit has not yet been found, should be searched first. We find the optimal sequential paging strategies for given maximum delay constraints and compute both paging and delay costs as a function of the time between polling events. The results show that sequential paging strategies are beneficial in all but the extremely high-mobility cases where polling failures provide little information about the unit location. It is observed that optimal sequential paging strategies substantially lower the paging cost compared to the classical blanket polling at the expense of a small degradation in the average delay performance     

Type C retrovirus released from porcine primary peripheral blood mononuclear cells infects human cells

As part of the evaluation of porcine cells, tissues, and organs intended for transplantation into humans, we investigated the conditions required to induce expression and release of porcine endogenous retrovirus (PoEV) from primary cells. Pigs contain endogenous retroviral sequences encoding infectious retrovirus, yet little is known about the conditions required to activate the expression and release of PoEV from primary cells. We show here that mitogenic activation of peripheral blood mononuclear cells (PBMC) isolated from the National Institutes of Health (NIH) miniature pig and the Yucatan pig resulted in the activation and release of an infectious type C retrovirus. Coculture of activated porcine PBMC with pig or human cell lines resulted in the transfer and expression of PoEV-specific sequences and the establishment of a productive infection. Sequence comparison of portions of the PoEV pol gene expressed in pig cell lines productively infected with virus derived from NIH miniature pig and Yucatan pig PBMC revealed marked similarity, suggesting that one or a few loci may be capable of being activated to yield an infectious virus. These findings demonstrate that the presence of endogenous viruses in source animals needs to be carefully considered when the infectious disease potential of xenotransplantation is being assessed.     

Apolipoprotein E antibodies affect the retention of passive avoidance memory in the chick

Isoforms of apolipoprotein E (ApoE) have been implicated as risk factors in Alzheimer's disease. We have, therefore, examined the possible role of ApoE in memory formation, using a one-trial passive avoidance task in day-old chicks. Birds were trained on the task and then at various times pre or post-training were injected intracerebrally with anti-ApoE. Immunofluorescence staining demonstrated the presence of the antibody bound to the neuropil, close to the injection site and adjacent to the ventricle, with a residence time in the brain of up to 30 min. Chicks that were injected 30 min pre-training or just post-training with 5 micrograms/hemisphere of the antibody learned the task, but were amnesic when tested at 30 min or at subsequent times up to 24 hr post-training. When tested at 24 hr, birds injected 5.5 hr post-training showed unimpaired retention. Birds injected with 5 micrograms/hemisphere of anti-ApoA-I (which has a brain distribution similar to that of anti-ApoE) at 30 min pretraining showed no amnesia, indicating the specificity of the effect to the ApoE. Possible mechanisms for this effect are discussed.     

Surface and interface characterization of chlorinated polyolefin coated thermoplastic polyolefin

Laser scanning confocal fluorescence microscopy measurements were performed on thermoplastic polyolefin (TPO) substrates that were coated with chlorinated polyolefin (CPO). The TPO investigated was a blend of high modulus polypropylene with an ethylene-butene copolymer (EBR9) containing 9 wt% butene. The CPO was a maleated chlorinated polypropylene containign 20 wt% Cl. The purpose of these experiments was to obtain detailed mechanistic information about the CPO-TPO interaction. To achieve acceptable contrast in these measurements, a fluorescent dye was covalently attached to a small portion of the CPO. Solvent wiping of the TPO substrates with isopropyl alcohol followed by xylenes prior to coating with CPO increased the mean roughness of the TPO surface by more than 100 nm; but it had a much larger effect on the roughness of the (several micrometers) CPO-TPO interface after coating. The EBR component of the TPO was shown to be exclusively responsible for the roughness increase. We also found evidence of a diffuse interface between the CPO and ERB components that was localized to sites in which the EBR was present at the TPO surface.     

Calibrating the sociometer: The relational contingencies of self-esteem.

A longitudinal daily diary study examined how chronic perceptions of a partner's regard for oneself might affect the day-to-day relational contingencies of self-esteem. Married partners each completed a diary for 21 days, and completed measures of satisfaction twice over the year. Multilevel analyses revealed that people who chronically felt more positively regarded compensated for one day's acute self-doubts by perceiving greater acceptance and love from their partner on subsequent days. In contrast, people who chronically felt less positively regarded by their partner internalized acute experiences of rejection, feeling worse about themselves on days after they feared their partner's disaffection. Over the year, such self-esteem sensitivity to rejection predicted declines in the partner' s satisfaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gaining control: family members relate to persons with severe mental illness

Nine isolates of methicillin-resistant Staphylococcus aureus (MRSA) collected in a Warsaw hospital in 1996 were typed by phenotypic (resistograms) and genotypic (PFGE and plasmid restriction analysis-REAP) methods. Twenty-four (MRSA) strains collected in this hospital during a period of the same duration in 1992 and typed earlier using resistograms and PFGE were also typed by REAP. Comparison of typing results obtained for isolates from 1992 and 1996 showed that strains characterised by PFGE patterns of two distinct types described as specific of the two clonally related groups of Polish MRSA in a multicentre study in 1992 are continuously present in the hospital. However, MRSA strains representing PFGE patterns not observed before were also found within the collection from 1996. REAP typing has proved to have a discriminatory power similar to that of PFGE analysis. Nevertheless, due to the lack of plasmids or difficulties in plasmid DNA isolation in 3 out of 33 studied strains, the typability of REAP turned out to be lower than that of PFGE.     

Cytotoxic activities of Mannich bases of chalcones and related compounds

Various Mannich bases of chalcones and related compounds displayed significant cytotoxicity toward murine P388 and L1210 leukemia cells as well as a number of human tumor cell lines. The most promising lead molecule was 21 that had the highest activity toward L1210 and human tumor cells. In addition, 21 exerted preferential toxicity to human tumor lines compared to transformed human T-lymphocytes. Other compounds of interest were 38, with a huge differential in cytotoxicity between P388 and L1210 cells, and 42, with a high therapeutic index when cytotoxicity to P388 cells and Molt 4/C8 T-lymphocytes were compared. In general, the Mannich bases were more cytotoxic than the corresponding chalcones toward L1210 but not P388 cells. A ClusCor analysis of the data obtained from the in vitro human tumor screen revealed that the mode of action of certain groups of compounds was similar. For some groups of compounds, cytotoxicity was correlated with the sigma, pi, or molar refractivity constants in the aryl ring attached to the olefinic group. In addition, the IC50 values in all three screens correlated with the redox potentials of a number of Mannich bases. X-ray crystallography and molecular modeling of representative compounds revealed various structural features which were considered to contribute to cytotoxicity. While a representative compound 15 was stable and unreactive toward glutathione (GSH) in buffer, the Mannich bases 15, 18, and 21 reacted with GSH in the presence of the pi isozyme of glutathione S-transferase, suggesting that thiol alkylation may be one mechanism by which cytotoxicity was exerted in vitro. Representative compounds were shown to be nonmutagenic in an intrachromosomal recombination assay in yeast, devoid of antimicrobial properties and possessing anticonvulsant and neurotoxic properties. Thus Mannich bases of chalcones represent a new group of cytotoxic agents of which 21 in particular serves as an useful prototypic molecule.     

Modeling unfolded states of proteins and peptides. II. Backbone solvent accessibility

Buried surface area is often used as a measure of the contribution to protein folding from the hydrophobic effect. Quantitatively, the surface buried upon folding is reckoned as the difference in area between the native and unfolded states. This calculation is well defined for a known structure but model-dependent for the unfolded state. In a previous paper [Creamer, T. P., Srinivasan, R., & Rose, G. D. (1995) Biochemistry 34, 16245-16250], we developed two models that bracket the surface area of the unfolded state between limiting extremes. Using these extrema, it was shown that earlier models, such as an extended tripeptide, overestimate the surface area of side chains in the unfolded state. In this sequel to our previous paper, we focus on backbone surface in the unfolded state, again adopting the strategy of trapping the area between limiting extrema. A principal conclusion of this present study is that most backbone surface in proteins is buried within local structure.