Evans function computation for the stability of travelling waves.

In recent years, the Evans function has become an important tool for the determination of stability of travelling waves. This function, a Wronskian of decaying solutions of the eigenvalue equation, is useful both analytically and computationally for the spectral analysis of the linearized operator about the wave. In particular, Evans-function computation allows one to locate any unstable eigenvalues of the linear operator (if they exist); this allows one to establish spectral stability of a given wave and identify bifurcation points (loss of stability) as model parameters vary. In this paper, we review computational aspects of the Evans function and apply it to multidimensional detonation waves.This article is part of the theme issue 'Stability of nonlinear waves and patterns and related topics'.

Attentional resource allocation during a cued saccade task.

Attentional selection of sensory information and motor output is critical for successful interaction with one's surroundings. However, organization of attentional processes involved in selection of salient visual information, decision making, and movement planning has not yet been fully elucidated. We hypothesized that attentional processes involved in these tasks can function independently and draw from separate resources. If true, challenging the capacity limit of one attentional process would not affect performance of others. Healthy participants performed a cued saccade task in which target cues were embedded in a central stream of letters in a Rapid Serial Visual Presentation (RSVP). Participants performed saccades as quickly and as accurately as possible to a peripheral target location based on cue presentation within the central letter stream. To challenge visual attention, we parametrically varied the duration at which each letter of the RSVP was presented (50-200ms). In a separate experiment we challenged motor attention by increasing the number of possible saccade trajectories (1-6 peripheral targets). As expected, increasing attentional load in one domain of the task negatively affected performance in that domain, while performance in other domains was unaffected. We interpret our results as support for the independent allocation of attentional resources, at least in the early stages of processing, required across components of a cued saccade task. Deciphering the contributions of attention during visuomotor tasks is a critical step to understanding how humans process information necessary to successfully interact with the environment.

Biology of Pseudoligosita plebeia (Hymenoptera: Trichogrammatidae), an egg parasitoid of Homalodisca spp. (Hemiptera: Cicadellidae) collected from northwestern Mexico as a potential biocontrol agent of H. Vitripennis in California.

Pseudoligosita plebeia (Perkins) (Hymenoptera: Trichogrammatidae) is a candidate biological control agent targeting the glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), in California. Little is known about the biology of P. plebeia. Here we report the results of laboratory studies describing the longevity of P. plebeia adults provided alternative food resources, their ability to parasitize H. vitripennis eggs of different ages, lifetime offspring production when provided steady access to excess host eggs, and levels of mature ovarian eggs present when wasps were held without access to hosts. P. plebeia is a gregarious parasitoid, with up to six adults emerging from a single H. vitripennis egg. When provided with honey and water, water alone, or no food or water, P. plebeia adult females lived an average of 64.1, 2.3, and 2.0 d, respectively. P. plebeia were able to successfully parasitize all ages of H. vitripennis eggs (1-8 d old), with higher parasitism in younger host eggs (1-3 d old) than in older host eggs (5-7 d old). An increasing trend in offspring production was seen for P. plebeia from adult age 2-26 d followed by a decreasing trend with offspring produced up to age 75 d. P. plebeia females are at least partially synovigenic, as they contained fewer mature eggs at younger ages (1 and 3 d old) than at older ages (5, 11, 15, and 31 d old). Our results provide foundational information regarding the biology of P. plebeia useful for its further evaluation as a potential biological control agent in California.

Non-exposed bisphosphonate-related osteonecrosis of the jaw: a critical assessment of current definition, staging, and treatment guidelines.

Non-exposed bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a newly reported complication arising from bisphosphonate therapy that presents with atypical symptoms and no apparent mucosal fenestration or exposure of necrotic bone. The clinical observation of the presence of necrotic bone underneath normal epithelial coverage was not conclusive for the diagnosis of BRONJ based on current guidelines established by the American Association of Oral and Maxillofacial Surgeons (AAOMS) and the American Society for Bone and Mineral Research (ASBMR), which specify the presence of clinically exposed necrotic bone for more than 8 weeks. Hence, the purpose of this review is to critically assess the current guidelines for diagnosis and management of BRONJ and propose a modified staging system and treatment guidelines to properly address the non-exposed variant of BRONJ lesions.

Target mRNAs are repressed as efficiently by microRNA-binding sites in the 5' UTR as in the 3' UTR.

In animals, microRNAs (miRNAs) bind to the 3' UTRs of their target mRNAs and interfere with translation, although the exact mechanism of inhibition of protein synthesis remains unclear. Functional miRNA-binding sites in the coding regions or 5' UTRs of endogenous mRNAs have not been identified. We studied the effect of introducing miRNA target sites into the 5' UTR of luciferase reporter mRNAs containing internal ribosome entry sites (IRESs), so that potential steric hindrance by a microribonucleoprotein complex would not interfere with the initiation of translation. In human HeLa cells, which express endogenous let-7a miRNA, the translational efficiency of these IRES-containing reporters with 5' let-7 complementary sites from the Caenorhabditis elegans lin-41 3' UTR was repressed. Similarly, the IRES-containing reporters were translationally repressed when human Ago2 was tethered to either the 5' or 3' UTR. Interestingly, the method of DNA transfection affected our ability to observe miRNA-mediated repression. Our results suggest that association with any position on a target mRNA is mechanistically sufficient for a microribonucleoprotein to exert repression of translation at some step downstream of initiation.

Small nuclear RNAs encoded by Herpesvirus saimiri upregulate the expression of genes linked to T cell activation in virally transformed T cells.

Seven small nuclear RNAs of the Sm class are encoded by Herpesvirus saimiri (HVS), a gamma Herpesvirus that causes aggressive T cell leukemias and lymphomas in New World primates and efficiently transforms T cells in vitro. The Herpesvirus saimiri U RNAs (HSURs) are the most abundant viral transcripts in HVS-transformed, latently infected T cells but are not required for viral replication or transformation in vitro. We have compared marmoset T cells transformed with wild-type or a mutant HVS lacking the most highly conserved HSURs, HSURs 1 and 2. Microarray and Northern analyses reveal that HSUR 1 and 2 expression correlates with significant increases in a small number of host mRNAs, including the T cell-receptor beta and gamma chains, the T cell and natural killer (NK) cell-surface receptors CD52 and DAP10, and intracellular proteins--SKAP55, granulysin, and NKG7--linked to T cell and NK cell activation. Upregulation of three of these transcripts was rescued after transduction of deletion-mutant-HVS-transformed cells with a lentiviral vector carrying HSURs 1 and 2. These changes indicate an unexpected role for the HSURs in regulating a remarkably defined and physiologically relevant set of host targets involved in the activation of virally transformed T cells during latency.

Premature termination codons do not affect the rate of splicing of neighboring introns.

Introduction of a premature termination codon (PTC) into an exon of a gene can lead to nonsense-mediated decay of the mRNA, which is best characterized as a cytoplasmic event. However, increasing evidence has suggested that PTCs may also influence the nuclear processing of an RNA transcript, leading to models of nuclear surveillance perhaps involving translating nuclear ribosomes. We used quantitative RT-PCR to measure the in vivo steady-state levels of every exon-intron junction in wild-type, PTC-containing, and missense-containing precursor mRNAs of both the nonrearranging dihydrofolate reductase (DHFR) and the somatically rearranging Ig- micro genes. We find that each exon-intron junction's abundance and, therefore, the rate of intron removal, is not significantly affected by the presence of a PTC in a neighboring exon in either the DHFR or Ig- micro pre-mRNA. Similarly, the abundance of the uncleaved Ig- micro polyadenylation sites does not differ between wild-type and PTC-containing Ig- micro pre-mRNAs. Our Ig- micro data were confirmed by RNase protection analyses, and multiple cell isolates were examined to resolve differences with previously published data on steady-state pre-mRNA levels. We conclude that the presence of a PTC affects the rate of neither splicing nor the cleavage step of 3' end formation during pre-mRNA processing in the nucleus. Our results are discussed with respect to existing evidence for nuclear surveillance mechanisms.

Domains on the hepatitis C virus internal ribosome entry site for 40s subunit binding.

The internal ribosome entry site (IRES) of the hepatitis C virus (HCV) RNA is known to interact with the 40S ribosomal subunit alone, in the absence of any additional initiation factors or Met-tRNAi. Previous work from this laboratory on the 80S and 48S ribosomal initiation complexes involving the HCV IRES showed that stem-loop III, the pseudoknot domain, and some coding sequence were protected from pancreatic RNase digestion. Stem-loop II is never protected by these complexes. Furthermore, there is no prior evidence reported showing extensive direct binding of stem-loop II to ribosomes or subunits. Using direct analysis of RNase-protected HCV IRES domains bound to 40S ribosomal subunits, we have determined that stem-loops II and III and the pseudoknot of the HCV IRES are involved in this initial binding step. The start AUG codon is only minimally protected. The HCV-40S subunit binary complex thus involves recognition and binding of stem-loop II, revealing its role in the first step of a multistep initiation process that may also involve rearrangement of the bound IRES RNA as it progresses.

Specific cleavage of hepatitis C virus RNA genome by human RNase P.

We have found that RNase P from HeLa cells specifically and efficiently cleaves hepatitis C virus (HCV) transcripts in vitro. The evidence includes identification of the 5'-phosphate polarity of the newly generated termini at position A(2860) as well as immunological and biochemical assays. Active cleavage has been shown in five dominant sequences of HCV "quasispecies" differing at or near the position of cleavage, demonstrating that this is a general property of HCV RNA. During the analysis, a second cleavage event was found in the 3' domain of the internal ribosome entry site. We have found that HCV RNA competitively inhibits pre-tRNA cleavage by RNase P, suggesting that HCV RNA has structural similarities to tRNA. This finding sets HCV apart from other pathogens causing serious human diseases and represents the first description of human RNase P-viral RNA cleavage. Here we discuss the possible meaning of these RNase P-accessible structures built into the viral genome and their possible role in vivo. Moreover, such structures within the viral genome might be vulnerable to attack by therapeutic strategies.

Occlusal disease revisited: Part I--Function and parafunction.

This article will address the evolution of occlusal disease from childhood and the deciduous dentition forward. It will include the evolution of anterior wear with emphasis on "cross over" of the mandible. Having classified the types and extent of occlusal disease, new evidence will be shown, on the adult dentition with pathognomonic manifestations, of cross-over or bruxed-braced occlusal disease. Its potential effect on restorative dentistry and dental implants will be discussed.

Occlusal disease revisited: Part II.

In part I of this article, the evolution of bruxism from childhood was discussed. Further, the different types of anterior tooth wear were reviewed. Specifically, the type of wear noted in bruxed-braced or cross-over position was pointed out. Examples were illustrated to allow the practitioner to recognize the type of parafunction in advance of treatment. This article will continue the discussion of cross over with moderate to extreme examples. Suggestions for treatment are discussed depending on the severity of the problem. Restorative failure and the implications for implant dentistry are noted.

The ribosome binding site of hepatitis C virus mRNA.

Hepatitis C virus (HCV) infects an estimated 170 million people worldwide, the majority of whom develop a chronic infection which can lead to severe liver disease, and for which no generally effective treatment yet exists. A promising target for treatment is the internal ribosome entry site (IRES) of HCV, a highly conserved domain within a highly variable RNA. Never before have the ribosome binding sites of any IRES domains, cellular or viral, been directly characterized. Here, we reveal that the HCV IRES sequences most closely associated with 80S ribosomes during protein synthesis initiation are a series of discontinuous domains together comprising by far the largest ribosome binding site yet discovered.

Hepatitis C virus internal ribosome entry site RNA contains a tertiary structural element in a functional domain of stem-loop II.

The internal ribosome entry site (IRES) of hepatitis C virus (HCV) RNA contains >300 bases of highly conserved 5'-terminal sequence, most of it in the uncapped 5'-untranslated region (5'-UTR) upstream from the single AUG initiator triplet at which translation of the HCV polyprotein begins. Although progress has been made in defining singularities like the RNA pseudoknot near this AUG, the sequence and structural features of the HCV IRES which stimulate accurate and efficient initiation of protein synthesis are only partially defined. Here we report that a region further upstream from the AUG, stem-loop II of the HCV IRES, also contains an element of local tertiary structure which we have detected using RNase H cleavage and have mapped using the singular ability of two bases therein to undergo covalent intra-chain crosslinking stimulated by UV light. This pre-existing element maps to two non-contiguous stretches of the HCV IRES sequence, residues 53-68 and 103-117. Several earlier studies have shown that the correct sequence between bases 45 and 70 of the HCV IRES stem-loop II domain is required for initiation of protein synthesis. Because features of local tertiary structure like the one we report here are often associated with protein binding, we propose that the HCV stem-loop II element is directly involved in IRES action.

Use of plants for toxicity assessment of estuarine ecosystems.

Estuarine ecosystems are being rapidly degraded by environmental toxicants from municipal and industrial wastes, agricultural runoff, recreational boating, shipping, and coastal development, ranking them as the most anthropogenically degraded habitat types on earth. Toxicity tests are used to establish links between adverse ecological effects and the toxicity of environmental chemicals. However, most toxicity tests used for regulating the release of chemicals into the environment have used animals as test species, with the erroneous assumption that toxicant levels protective of fish or invertebrates are also protective of plants. Most plant toxicity tests have used terrestrial crop plants, whereas the few aquatic test species used have been primarily freshwater algae. Even though estuarine and marine vascular plants are highly vulnerable to environmental chemicals, phytotoxicity studies using native coastal plants have been limited, and no such studies are required for testing by regulating agencies. The relevance of toxicity tests of estuarine sediments and of wastes entering the estuary should depend on the use of estuarine and marine plant species. This review summarizes toxicity testing of marine plants used in biomonitoring, phytotoxicity, biotransformations of toxicants, bioaccumulation, and phytoremediation. Challenges to marine plant testing are discussed and include developing standard test protocols, identifying species with minimal salinity and toxicant interaction, defining and choosing a suitable sediment for sediment-bound toxicant testing, selecting endpoints with low variability, producing viable seeds, and culturing test plants. Progress in acquiring a suitable database is being made, but at a rate that is inadequate to create the sound, scientific foundation needed for safeguarding our estuarine ecosystems in the near future.

Microleakage of a consolidated silver direct filling material.

Microleakage of an experimental direct filling material comprised of a chemically precipitated silver powder that had been surface treated with a dilute acid to promote cold welding upon consolidation was evaluated. Microleakage was compared to both dispersed-phase and spherical amalgam by use of an in vitro gas-diffusion method and in class 5 restorations placed in extracted human teeth. The effect of two cavity varnishes and two dentin adhesives as cavity liners on microleakage was also evaluated using extracted teeth. Microleakage of silver powder consolidated with dental instruments was less than that found with dental amalgam. The use of copal or polyamide cavity varnish resulted in the lowest combination of microleakage on dentin and enamel margins.

Life-cycle toxicity of bis(tributyltin) oxide to the sheepshead minnow (Cyprinodon variegatus).

The effects of tributyltin (TBT) to the life cycle of the estuarine fish Cyprinodon variegatus were examined in a 180-day flow-through exposure. The study was initiated with embryos less than 24 h postfertilization and monitored through hatch, maturation, growth, and reproduction under continuous exposure to mean measured TBT concentrations of 5.4, 3.2, 1.3, 0.66, and 0.41 microg TBT/L. Progeny isolated at the onset of reproduction by the parental generation (F0) were monitored for survival as embryos, survival as fry/juveniles, and growth 30 days postisolation. TBT, at a concentration of 5.4 microg/L, significantly reduced embryo survival of the F0 generation sheepshead minnows. By day 145 of the exposure, significant effects to the survival of this generation increased and included all test concentrations >/=0.66 microg/L. Survival of 0.66 microg/L was reduced 59% relative to control survival by termination of the F0 generation. Growth of F0 generation organisms as measured by standard length was significantly reduced only on day 90 at 3.2 microg/L, however no significant reductions of wet or dry weight related to treatment concentration were detected. Due to complete mortality of organisms exposed to 5.4 microg/L by study day 7, effects to fecundity and progeny were monitored at measured concentrations of 3.2, 1.3, 0.66, and 0.41 microg TBT/L. Fecundity, as measured by the production of viable eggs produced per female per day, was unaffected by any of the test treatments. All F1 generation embryos isolated from treatment chambers into 3.2 microg/L died. Survival, standard length, wet and dry weight of the F1 generation at the remaining treatment concentrations were unaffected. The results of this study indicate that exposure to TBT reduced survival of the F0 generation sheepshead minnow and establishes the lowest observed effect concentration (LOEC) as 0.66 microg TBT/L, and the no observed effect concentration (NOEC) as 0.41 microg TBT/L for this species.http://link.springer-ny. com/link/service/journals/00244/bibs/37n2p258.html

Characterization of failure to imbibe in infants.

The term failure to imbibe is proposed to describe infants with failure to thrive due to poor feeding. Feeding assessment was performed in 128 patients: 43 healthy controls, 53 diseased controls, 12 with nonorganic failure to thrive, and 20 with failure to imbibe. Infants with failure to imbibe required a significantly longer time to feed compared with other infants. In contrast to other infants with nonorganic failure to thrive, patients with failure to imbibe were more likely to need pediatric subspecialty care and nasogastric or gastrostomy tube feeding. Since these patients may have treatable conditions, infants with failure to imbibe merit further investigation.