Forward and inverse problems for creep models in viscoelasticity.

This study examines a class of time-dependent constitutive equations used to describe viscoelastic materials under creep in solid mechanics. In nonlinear elasticity, the strain response to the applied stress is expressed via an implicit graph allowing multi-valued functions. For coercive and maximal monotone graphs, the existence of a solution to the quasi-static viscoelastic problem is proven by applying the Browder-Minty fixed point theorem. Moreover, for quasi-linear viscoelastic problems, the solution is constructed as a semi-analytic formula. The inverse viscoelastic problem is represented by identification of a design variable from non-smooth measurements. A non-empty set of optimal variables is obtained based on the compactness argument by applying Tikhonov regularization in the space of bounded measures and deformations. Furthermore, an illustrative example is given for the inverse problem of isotropic kernel identification. This article is part of the theme issue 'Non-smooth variational problems with applications in mechanics'.

Levy geometric graphs.

We present a family of graphs with remarkable properties. They are obtained by connecting the points of a random walk when their distance is smaller than a given scale. Their degree (number of neighbors) does not depend on the graph's size but only on the considered scale. It follows a gamma distribution and thus presents an exponential decay. Levy flights are particular random walks with some power-law increments of infinite variance. When building the geometric graphs from them, we show from dimensional arguments that the number of connected components (clusters) follows an inverse power of the scale. The distribution of the size of their components, properly normalized, is scale invariant, which reflects the self-similar nature of the underlying process. This allows to test if a graph (including nonspatial ones) could possibly result from an underlying Levy process. When the scale increases, these graphs never tend towards a single cluster, the giant component. In other words, while the autocorrelation of the process scales as a power of the distance, they never undergo a phase transition of percolation type. The Levy graphs may find applications in community detection and in the analysis of collective behaviors as in face-to-face interaction networks.

Effective epidemic model for COVID-19 using accumulated deaths.

The severe acute respiratory syndrome COVID-19 has been in the center of the ongoing global health crisis in 2020. The high prevalence of mild cases facilitates sub-notification outside hospital environments and the number of those who are or have been infected remains largely unknown, leading to poor estimates of the crude mortality rate of the disease. Here we use a simple model to describe the number of accumulated deaths caused by COVID-19. The close connection between the proposed model and an approximate solution of the SIR model provides estimates of epidemiological parameters. We find values for the crude mortality between 10 - 4 and 10 - 3 which are lower than estimated numbers obtained from laboratory-confirmed patients. We also calculate quantities of practical interest such as the basic reproduction number and subsequent increment after relaxation of lockdown and other control measures.

Potentiation of an anthrax DNA vaccine with electroporation.

DNA vaccines are a promising method of immunization against biothreats and emerging infections because they are relatively easy to design, manufacture, store and distribute. However, immunization with DNA vaccines using conventional delivery methods often fails to induce consistent, robust immune responses, especially in species larger than the mouse. Intramuscular (i.m.) delivery of a plasmid encoding anthrax toxin protective antigen (PA) using electroporation (EP), a potent DNA delivery method, rapidly induced anti-PA IgG and toxin neutralizing antibodies within 2 weeks following a single immunization in multiple experimental species. The delivery procedure is particularly dose efficient and thus favorable for achieving target levels of response following vaccine administration in humans. These results suggest that EP may be a valuable platform technology for the delivery of DNA vaccines against anthrax and other biothreat agents.

Enhancement of immune responses to an HBV DNA vaccine by electroporation.

These studies document the ability of electroporation (EP)-based DNA vaccination to induce multi-specific CTL responses to hepatitis B virus (HBV) DNA vaccination in normal mice and marked immune responses to multivalent HBV DNA immunization in larger animal species. These results suggest that electroporation-mediated HBV DNA vaccination is worth pursuing as a treatment for chronic HBV infection.

Structure and expression of 12-oxophytodienoate reductase (subgroup I) genes in pea, and characterization of the oxidoreductase activities of their recombinant products.

Recently, we observed that expression of a pea gene (S64) encoding an oxophytodienoic acid reductase (OPR) was induced by a suppressor of pea defense responses, secreted by the pea pathogen Mycosphaerella pinodes. Because it is known that OPRs are usually encoded by families of homologous genes, we screened for genomic and cDNA clones encoding members of this putative OPR family in pea. We isolated five members of the OPR gene family from a pea genomic DNA library, and amplified six cDNA clones, including S64, by RT-PCR (reverse transcriptase-PCR). Sequencing analysis revealed that S64 corresponds to PsOPR2, and the amino acid sequences of the predicted products of the six OPR-like genes shared more than 80% identity with each other. Based on their sequence similarity, all these OPR-like genes code for OPRs of subgroup I, i.e., enzymes which are not required for jasmonic acid biosynthesis. However, the genes varied in their exon/intron organization and in their promoter sequences. To investigate the expression of each individual OPR-like gene, RT-PCR was performed using gene-specific primers. The results indicated that the OPR-like gene most strongly induced by the inoculation of pea plants with a compatible pathogen and by treatment with the suppressor from M. pinodes was PsOPR2. Furthermore, the ability of the six recombinant OPR-like proteins to reduce a model substrate, 2-cyclohexen-1-one (2-CyHE), was investigated. The results indicated that PsOPR1, 4 and 6 display robust activity, and PsOPR2 has a most remarkable ability to reduce 2-CyHE, whereas PsOPR3 has little and PsOPR5 does not reduce this compound. Thus, the six OPR-like proteins can be classified into four types. Interestingly, the gene structures, expression profiles, and enzymatic activities used to classify each member of the pea OPR-like gene family are clearly correlated, indicating that each member of this OPR-like family has a distinct function.

Kidney-targeted naked DNA transfer by retrograde injection into the renal vein in mice.

We recently developed a novel kidney-targeted gene transfer technique in rats, using the retrograde renal vein injection of naked plasmid DNA. Many animal disease models are created in mice by transgenic or knockout technologies. However, it is much harder to perform renal vein injection in mice than in rats because they have a thin and short vein. Here we transferred the mouse interleukin (IL)-10 gene into mice by retrograde renal vein injection, using an IL-10 and immunoglobulin fusion protein (IL-10/Fc) (96-kDa) expression plasmid, pCAGGS-IL10/Fc. We observed a dose-response relationship between serum IL-10 levels and the amount of injected DNA. The serum IL-10 levels peaked at day 1 and then were sustained for at least 2 weeks. These results demonstrate that the kidney-targeted naked plasmid DNA transfer of mice by retrograde renal vein injection can be achieved, and the kidney serves as a depot organ for the production of large proteins.

Hydrodynamics-based transfer of PCR-amplified DNA fragments into rat liver.

A high level of plasmid DNA expression in rat liver can be achieved by the rapid injection of a large volume of a naked DNA solution into the tail vein, called the 'hydrodynamics-based procedure.' The preparation of PCR-amplified DNA fragments is easier than that of naked DNA. In this paper we evaluated the effects of expressing the erythropoietin (Epo) gene in the rat liver by injecting fCAGGS-Epo, an Epo-expressing PCR-amplified DNA fragment, via the tail vein. After injection of 5 pmol fCAGGS-Epo (10 microg) or pCAGGS-Epo (18.4 microg), plasmid DNA, the serum Epo levels peaked at week 1, then persisted for at least 12 weeks. Transgene-derived Epo secretion resulted in significant erythropoiesis. These results demonstrated that transfer of PCR-amplified DNA fragments into the rat liver via rapid tail vein injection can be achieved. This method may provide a useful means for studying the physiologic function of a putative gene.

A novel family of hairpin peptides that inhibit IgE activity by binding to the high-affinity IgE receptor.

A family of structured peptides that bind to FcepsilonRIalpha, the alpha-chain of the high-affinity receptor for IgE, has been identified. Binding selections using FcepsilonRIalpha and polyvalent peptide-phage libraries yielded a dominant 18-residue peptide-phage clone, as well as related sequences that did not resemble fragments of IgE. Synthetic peptides based on these sequences inhibited IgE binding to its receptor, and were found by NMR analysis to adopt a stable beta-hairpin structure in solution. Optimized peptides with micromolar receptor affinity exhibited high stability in biological fluids and inhibited cellular histamine release in an in vitro bioassay of IgE activity. The structure-activity relationships of these peptides, which are less than 1% of the size of IgE, suggest an overlap between their binding site and that of IgE on FcepsilonRI. Thus, the peptides demonstrate that blocking a small epitope on this receptor chain is sufficient to block IgE activity. Such structured peptides represent a possible starting point for the design of novel antagonists, and offer the potential for testing in vivo a new approach for treating allergic disease.

Binding protein-3-selective insulin-like growth factor I variants: engineering, biodistributions, and clearance.

Insulin-like growth factor I (IGF-I) is a potent anabolic peptide that mediates most of its pleiotropic effects through association with the IGF type I receptor. Biological availability and plasma half-life of IGF-I are modulated by soluble binding proteins (IGFBPs), which sequester free IGF-I into high affinity complexes. Elevated levels of specific IGFBPs have been observed in several pathological conditions, resulting in inhibition of IGF-I activity. Administration of IGF-I variants that are unable to bind to the up-regulated IGFBP species could potentially counteract this effect. We engineered two IGFBP-selective variants that demonstrated 700- and 80,000-fold apparent reductions in affinity for IGFBP-1 while preserving low nanomolar affinity for IGFBP-3, the major carrier of IGF-I in plasma. Both variants displayed wild-type-like potency in cellular receptor kinase assays, stimulated human cartilage matrix synthesis, and retained their ability to associate with the acid-labile subunit in complex with IGFBP-3. Furthermore, pharmacokinetic parameters and tissue distribution of the IGF-I variants in rats differed from those of wild-type IGF-I as a function of their IGFBP affinities. These IGF-I variants may potentially be useful for treating disease conditions associated with up-regulated IGFBP-1 levels, such as chronic or acute renal and hepatic failure or uncontrolled diabetes. More generally, these results suggest that the complex biology of IGF-I may be clarified through in vivo studies of IGFBP-selective variants.

The use of schematic knowledge about sources in source monitoring.

Source monitoring refers to mental processes leading to attributions regarding the origin of information. We tested Johnson, Hashtroudi, and Lindsay's (1993) assumption that prior source-relevant knowledge is used in some source-monitoring tasks. In two experiments using different domains of schematic knowledge, two sources presented information that was expected for one source and somewhat unexpected for the other. In a later source-monitoring test, participants decided whether items had been presented by Source A, by Source B, or were new. The results of both experiments show that source identification is better for expected items than for somewhat unexpected items. Multinomial modeling analyses revealed that when participants do not remember the source of information, they guess that it was presented by the expected source. These results provide evidence for the claim that source monitoring can be based on prior knowledge and support a guessing hypothesis.

Eosinophilia of dystrophin-deficient muscle is promoted by perforin-mediated cytotoxicity by T cell effectors.

Previous investigations have shown that cytotoxic T lymphocytes (CTLs) contribute to muscle pathology in the dystrophin-null mutant mouse (mdx) model of Duchenne muscular dystrophy through perforin-dependent and perforin-independent mechanisms. We have assessed whether the CTL-mediated pathology includes the promotion of eosinophilia in dystrophic muscle, and thereby provides a secondary mechanism through which CTLs contribute to muscular dystrophy. Quantitative immunohistochemistry confirmed that eosinophilia is a component of the mdx dystrophy. In addition, electron microscopic observations show that eosinophils traverse the basement membrane of mdx muscle fibers and display sites of close apposition of eosinophil and muscle membranes. The close membrane apposition is characterized by impingement of eosinophilic rods of major basic protein into the muscle cell membrane. Transfer of mdx splenocytes and mdx muscle extracts to irradiated C57 mice by intraperitoneal injection resulted in muscle eosinophilia in the recipient mice. Double-mutant mice lacking dystrophin and perforin showed less eosinophilia than was displayed by mdx mice that expressed perforin. Finally, administration of prednisolone, which has been shown previously to reduce the concentration of CTLs in dystrophic muscle, produced a significant reduction in eosinophilia. These findings indicate that eosinophilia is a component of the mdx pathology that is promoted by perforin-dependent cytotoxicity of effector T cells. However, some eosinophilia of mdx muscle is independent of perforin-mediated processes.

High prevalence of Chlamydia trachomatis, Neisseria gonorrhoeae and Mycoplasma genitalium in female commercial sex workers in Japan.

Our objectives were to explore the prevalence of Chlamydia trachomatis, Neisseria gonorrhoeae, and Mycoplasma genitalium in Japanese female commercial sex workers (CSWs), in comparison with pregnant women as controls. A high-risk group of 174 female CSWs and 90 asymptomatic pregnant women were enrolled in this study. Detection of C. trachomatis, N. gonorrhoeae, and M. genitalium on the endocervix of the women was performed mainly by using polymerase chain reaction (PCR)-based assays. The prevalence rates of C. trachomatis, N. gonorrhoeae, and M. genitalium were 19.0%, 32.8%, and 12.6%, respectively, in the CSWs, compared with 5.6%, 0%, and 1.1% respectively, in the pregnant women. These results suggest a high prevalence of C. trachomatis, N. gonorrhoeae, and M. genitalium in Japanese CSWs. We conclude that continued close monitoring of the prevalence of C. trachomatis, N. gonorrhoeae, and M. genitalium infection in CSWs is important for preventing the dissemination of these microorganisms, and that further investigation of M. genitalium as a sexually transmitted pathogen in women is needed.

Expression of the 180-kD ribosome receptor induces membrane proliferation and increased secretory activity in yeast.

Expression of the canine 180-kD ribosome receptor (p180) in yeast cells resulted in a marked proliferation of intracellular membranes. The type of membranes observed varied with the expression of specific portions of p180. Rough membranes predominated when the ribosome binding domain of p180 was present, whereas expression constructs lacking this region resulted in smooth membranes. Northern analysis indicated that expression of the NH(2)-terminal 767 amino acids (DeltaCT), which include the ribosome binding domain, upregulated the transcription and translation of genes involved in exocytosis. The membranes that were proliferated were functional as these cells overcame a temperature-sensitive translocation defect. Most significantly, cells that overexpressed DeltaCT and proliferated rough endoplasmic reticulum exhibited severalfold higher levels of secretion of an ectopically expressed secretory protein. We conclude that p180 expression triggers a cascade of events leading to an increase in secretory potential akin to the terminal differentiation of mammalian secretory cells and tissues.

Correlation between microvessel density and tumor cell proliferation with clinical factors in breast carcinomas.

Fifty-nine methacarn-fixed, paraffin-embedded human breast carcinomas were immunostained by QB-END/10 (an antibody to CD34 antigen) to observe microvessels and by PC10 (an antibody to proliferating cell nuclear antigen; PCNA) to determine tumor cell proliferation; 9 normal human breast tissue specimens were also immunostained by QB-END/10. The number of microvessels in the periphery of the breast carcinoma was significantly greater than both that in the center of the breast carcinoma and that in the normal breast. There was also a significant relationship between the number of microvessels in the periphery of breast carcinomas and the histological tumor size and lymph node status. However, there was no significant relationship between the tumor cell proliferation activity (PCNA positive cell ratio) and any clinical or histopathological variables. The number of microvessels and the tumor cell proliferation activity showed a weak negative correlation.

Ablation depths and morphological changes in human enamel and dentin after Er:YAG laser irradiation with or without water mist.

OBJECTIVE: This investigation was performed quantitatively to determine the ranges of ablation and to evaluate the morphological changes in human enamel and dentin irradiated by Er:YAG laser with or without water mist. SUMMARY BACKGROUND DATA: Recently, several infrared lasers have been introduced in the dental clinic to remove carious dental hard tissues in anticipation of replacing the high-speed dental drill. Among them, the Er:YAG laser has shown the most promise for hard tissue ablation. METHODS: An Er:YAG laser was used to ablate human dental hard tissues using a pulse energy that ranged from 100 to 400 mJ at a frequency of 2 Hz for 5 seconds. Ablation rates with or without water mist at different pulse energies were measured, and the morphological changes on enamel and dentin were also investigated by stereomicroscopy and scanning electron microscopy (SEM). RESULTS: The relationship between ablation depths and energies was almost linear at both enamel and dentin samples. The irradiation with water mist reduced the ablation depths, but only minimally, when compared to those irradiated without water mist. Morphological findings by SEM indicated that Er:YAG laser irradiation with water mist could produce the cavities without signs of thermal damage to the surrounding enamel and dentin. CONCLUSIONS: The results of this study suggest that addition of a fine water mist directed at the ablation sites does not greatly decrease the ablation, and does not cause any carbonization and melting in the surrounding dental hard tissues.

Genetic and immunologic characterization of viruses infecting MN-rgp120-vaccinated volunteers.

Proviral sequences were determined and immunologic characterization was carried out for envelope glycoproteins from 7 vaccinees who became infected with human immunodeficiency virus type 1 (HIV-1), through high-risk behavior, while participating in clinical trials of MN-rgp120, a candidate HIV-1 vaccine. All 7 infections resulted from subtype B viruses; however, only 3 of the viruses possessed the MN serotype-defining V3 domain sequence, IGPGRAF, prevalent in 60%-70% of US infections. Six of the 7 viruses differed from MN-rgp120 at a neutralizing epitope in the C4 domain, and all 7 differed from MN-rgp120 at a neutralizing epitope in the V2 domain. Recombinant gp120 was prepared from each breakthrough specimen and tested for binding to a panel of neutralizing monoclonal antibodies. The results suggest that 6 of 7 breakthrough infections may be related to incomplete immunization or to infection with viruses that differed from the vaccine immunogen at important virus-neutralizing epitopes.

Solution structure of an ATP-binding RNA aptamer reveals a novel fold.

In vitro selection has been used to isolate several RNA aptamers that bind specifically to biological cofactors. A well-characterized example in the ATP-binding RNA aptamer family, which contains a conserved 11-base loop opposite a bulged G and flanked by regions of double-stranded RNA. The nucleotides in the consensus sequence provide a binding pocket for ATP (or AMP), which binds with a Kd in the micromolar range. Here we present the three-dimensional solution structure of a 36-nucleotide ATP-binding RNA aptamer complexed with AMP, determined from NMR-derived distance and dihedral angle restraints. The conserved loop and bulged G form a novel compact, folded structure around the AMP. The backbone tracing of the loop nucleotides can be described by a Greek zeta (zeta). Consecutive loop nucleotides G, A, A form a U-turn at the bottom of the zeta, and interact with the AMP to form a structure similar to a GNRA tetraloop, with AMP standing in for the final A. Two asymmetric G. G base pairs close the stems flanking the internal loop. Mutated aptamers support the existence of the tertiary interactions within the consensus nucleotides and with the AMP found in the calculated structures.

Protection of MN-rgp120-immunized chimpanzees from heterologous infection with a primary isolate of human immunodeficiency virus type 1.

Three chimpanzees immunized with recombinant gp120 from human immunodeficiency virus type 1 (HIV-1) strain MN and 1 control animal were challenged intravenously with a primary isolate of HIV-1SF2. Viral infection was detected in the control animal by viral culture, polymerase chain reaction, and multiple serologic assays beginning 2 weeks after infection. Markers of HIV-1 infection were not detected in any of the gp120-vaccinated animals during 12 months of follow-up. Antisera from the gp120-immunized chimpanzees were unable to neutralize the challenge virus cultured in peripheral blood mononuclear cells (PBMC). These studies demonstrate that immunization with recombinant gp120 derived from a T cell-adapted isolate prevented infection by a heterologous primary isolate of HIV-1. The results suggest that in vitro virus neutralization assays utilizing primary isolates cultured in PBMC may be imperfect indicators of protection in vivo.