Is integer arithmetic fundamental to mental processing?: the mind's secret arithmetic

Unlike the ability to acquire our native language, we struggle to learn multiplication and division. It may then come as a surprise that the mental machinery for performing lightning-fast integer arithmetic calculations could be within us all even though it cannot be readily accessed, nor do we have any idea of its primary function. We are led to this provocative hypothesis by analysing the extraordinary skills of autistic savants. In our view such individuals have privileged access to lower levels of information not normally available through introspection.

Suppressive immunization with DNA encoding a self-peptide prevents autoimmune disease: modulation of T cell costimulation

Usually we rely on vaccination to promote an immune response to a pathogenic microbe. In this study, we demonstrate a suppressive from of vaccination, with DNA encoding a minigene for residues 139-151 of myelin proteolipid protein (PLP139-151), a pathogenic self-Ag. This suppressive vaccination attenuates a prototypic autoimmune disease, experimental autoimmune encephalomyelitis, which presents clinically with paralysis. Proliferative responses and production of the Th1 cytokines, IL-2 and IFN-gamma, were reduced in T cells responsive to PLP139-151. In the brains of mice that were successfully vaccinated, mRNA for IL-2, IL-15, and IFN-gamma were reduced. A mechanism underlying the reduction in severity and incidence of paralytic autoimmune disease and the reduction in Th1 cytokines involves altered costimulation of T cells; loading of APCs with DNA encoding PLP139-151 reduced the capacity of a T cell line reactive to PLP139-151 to proliferate even in the presence of exogenous CD28 costimulation. DNA immunization with the myelin minigene for PLP-altered expression of B7.1 (CD80), and B7.2 (CD86) on APCs in the spleen. Suppressive immunization against self-Ags encoded by DNA may be exploited to treat autoimmune diseases.

Efficacy of Solarization and Cabbage Amendment for the Control of Phytophthora spp. in North Florida

The effects of soil solarization with or without cabbage leaf amendments on the survival of Phytophthora spp. were evaluated in several North Florida soils. Soil temperature under solarization treatments reached a maximum of 47°C at a 10-cm depth, but only 41°C at 25 cm. Solarization with a clear, gas-impermeable film was as effective as methyl bromide in reducing populations of P. nicotianae at a 10-cm depth but had no effect on populations at a depth of 25 cm. Populations of P. capsici after solarization with either a clear, low-density polyethylene or a clear, gas-impermeable film were similar to methyl bromide treatment at the 10-cm depth, while at the 25-cm depth, no reduction in populations was observed. Incorporation of cabbage into the soil at a rate of 6.6 to 8.9 kg/m² did not enhance the effectiveness of solarization in reducing populations of either Phytophthora sp.

Effects of sample preparation conditions on biomolecular solid-state NMR lineshapes

Sample preparation conditions with the 46 kDa enzyme complex of 5-enolpyruvyl-shikimate-3-phosphate (EPSP) synthase, shikimate-3-phosphate (S3P) and glyphosate (GLP) have been examined in an attempt to reduce linewidths in solid-state NMR spectra. The linewidths of 31P resonances associated with enzyme bound S3P and GLP in the lyophilized ternary complex have been reduced to 150 +/- 12 Hz and 125 +/- 7 Hz respectively, by a variety of methods involving additives and freezing techniques.

On the mechanism of 5-enolpyruvylshikimate-3-phosphate synthase

5-Enolpyruvylshikimate-3-phosphate (EPSP) synthase catalyzes the condensation of shikimate 3-phosphate (S3P) and phosphoenolpyruvate (PEP) to form EPSP, a precursor for the aromatic amino acids. This paper examines a recent claim [Studelska, D. R., McDowell, L. M., Espe, M. P., Klug, C. A., and Schaefer, J. (1997) Biochemistry 36, 15555-15560] that the mechanism of EPSP synthase involves two covalent enzyme-intermediates, in complete contrast to a large body of literature that has already proven the involvement of a single noncovalent intermediate. The evidence in the paper of Studelska et al. is examined closely, and unequivocal proof is provided that those authors' NMR assignments to covalent structures are in error, and that in fact the species they observed were simply the product EPSP and a side-product EPSP ketal. Since those authors used rotational-echo double-resonance (REDOR) solid-state NMR to measure intermolecular and intramolecular distances in the proposed covalent intermediates, we have used REDOR to measure the same distances in enzyme-free and enzyme-bound preparations of purified EPSP, and enzyme-free preparations of purified EPSP ketal. The distance between the shikimate ring phosphorus atom and C8 in enzyme-free EPSP is 6.6 +/- 0.1 A, which lengthens to 7.4 +/- 0.1 A in the presence of the enzyme, and in enzyme-free EPSP ketal is 5.6 +/- 0.1 A. These are entirely consistent with those measured by Studelska et al., which were 7.5 +/- 0.5 A for a putative enzyme-enolpyruvyl species and 6.1 +/- 0.3 A for a putative enzyme-ketal species.

Composted Municipal Waste Reduces Infection of Citrus Seedlings by Phytophthora nicotianae

Most citrus nurseries and orchards in Florida are infested with Phytophthora nicotianae, the causal agent of Phytophthora root rot. Although fungicides control the disease and increase seedling growth and tree yields, they are not always economically or environmentally sustainable. Amendment of citrus soils with composted municipal waste (CMW) may provide an alternative to fungicides for disease management. Citrus seedling growth decreased with increasing proportions of one CMW source, indicating the potential for phytotoxicity from soluble salts and acetic acid when the proportion of CMW in soil exceeded 20% (vol/vol). When a citrus soil was amended (20% vol/vol) with certain sources of CMW, the incidence of infection of 5-week-old susceptible citrus seedlings by P. nicotianae was reduced from 95% to as low as 5%. Addition of fresh CMW to two different citrus soils reduced colony growth of P. nicotianae after the fungus was incubated in the amended soil for 6 days and then recovered on PARPH selective medium. If CMW was stored for more than 3 months before amendment, the soil mixtures did not suppress colony development. In general, extracts of fresh CMW reduced mycelial growth in vitro; whereas suppressiveness of CMW from the same batch was lost after storage. Acetic acid was detected at higher concentration in fresh CMW that suppressed colony growth than in CMW that lacked activity. A species of Acremonium was isolated from another source of CMW that was suppressive to P. nicotianae. This fungus parasitized hyphae of P. nicotianae in vitro. Thus, CMWs have the potential to at least temporarily suppress P. nicotianae through chemical and microbial agents depending on source and age of the CMW.

Short peptide-based tolerogens without self-antigenic or pathogenic activity reverse autoimmune disease

An immunodominant epitope of myelin basic protein (MBP), VHFFKNIVTPRTP (p87-99), is a major target of T cells in brain lesions of multiple sclerosis (MS), and this peptide can trigger experimental autoimmune encephalomyelitis (EAE). We designed truncated peptides based on this pathogenic 13-mer that are not antigenic. These short peptides reduced production of IFN-gamma and TNF-alpha in vivo. Moreover, paraplegic rats given the 7-mer FKNIVTP in soluble form showed total reversal of paralysis in 24 h. Truncated peptides that are too small to stimulate antigenic responses to pathogenic regions of myelin basic protein are nevertheless effective tolerogens and are able to anergize autoreactive T cells. Short peptide-based tolerogens, devoid of immunogenic and pathogenic potential, may be attractive for therapy of autoimmune diseases.

Histological Comparison of Fibrous Root Infection of Disease-Tolerant and Susceptible Citrus Hosts by Phytophthora nicotianae and P. palmivora

ABSTRACT Phytophthora nicotianae and P. palmivora infect and cause rot of fibrous roots of susceptible and tolerant citrus rootstocks in Florida orchards. The infection and colonization by the two Phytophthora spp. of a susceptible citrus host, sour orange (Citrus aurantium), and a tolerant host, trifoliate orange (Poncirus trifoliata), were compared using light and electron microscopy. Penetration by both Phytophthora spp. occurred within 1 h after inoculation, regardless of the host species. No differences were observed in mode of penetration of the hypodermis or the hosts' response to infection. After 24 h, P. palmivora had a significantly higher colonization of cortical cells in susceptible sour orange than in tolerant trifoliate orange. Intracellular hyphae of both Phytophthora spp. were observed in the cortex of sour orange, and cortical cells adjacent to intercellular hyphae of P. palmivora were disrupted. In contrast, the cortical cells of sour orange and trifoliate orange adjacent to P. nicotianae hyphae and the cortical cells of trifoliate orange adjacent to P. palmivora were still intact. After 48 h, the cortical cells of both hosts adjacent to either Phytophthora spp. were disrupted. After 48 and 72 h, P. palmivora hyphae colonized the cortex of sour orange more extensively than the cortex of trifoliate orange; P. palmivora also colonized both hosts more extensively than P. nicotianae. A higher rate of electrolyte leakage among host-pathogen combinations reflected the combined effects of greater cell disruption by P. palmivora than by P. nicotianae, and the higher concentration of electrolytes in healthy roots of trifoliate orange than of sour orange. Although cellular responses unique to the tolerant host were not observed, reduced hyphal colonization by both pathogens in the cortex of trifoliate orange compared with sour orange is evidence for a putative resistance factor(s) in the trifoliate orange roots that inhibits the growth of Phytophthora spp.

Local L-NAME decreases blood flow and increases leukocyte adhesion via CD18

Local inhibition of nitric oxide (NO) synthesis with L-arginine analogs such as NG-nitro-L-arginine methyl ester (L-NAME) decreased red blood cell velocity (VRBC) in capillaries and increased leukocyte adhesion in postcapillary venules in rat skeletal muscle. The goal of the present study was to determine the mechanism of this response to L-NAME. Using intravital videomicroscopy, we examined blood flow in the surface microvasculature of rat extensor digitorum longus muscle. L-NAME (30 mM in the pipette) locally applied to capillaries (300 microns from feeding arteriole) reduced VRBC [control VRBC = 244 +/- 53 (SE) microns/s; delta VRBC = -52 +/- 8%] and increased leukocyte adhesion (from 0.2 +/- 0.01 to 1.3 +/- 0.3 cells/100 microns) in control animals. Systemic pretreatment with fucoidan (selectin binder), superoxide dismutase and catalase (extracellular antioxidants), dimethylthiourea (intracellular antioxidant), or ketotifen (mast cell stabilizer) did not alter this response. Pretreatment with CL26, an anti-CD18 antibody, abolished the L-NAME response. Our results suggest that L-NAME increased leukocyte-endothelial interactions via an effect on CD11/CD18 or its ligand, intercellular adhesion molecule.

Beam splitting on weak illumination

We demonstrate, in both two and three dimensions, how a self-guided beam in a non-Kerr medium is split into two beams on weak illumination. We also provide an elegant physical explanation that predicts the universal character of the observed phenomenon. Possible applications of our findings to guiding light with light are also discussed.

Temperature Effects on the Attachment of Pasteuria penetrans Endospores to Meloidogyne arenaria Race 1

Pasteuria penetrans is a gram positive bacterium that prevents Meloidogyne spp. from reproducing and diminishes their ability to penetrate roots. The attachment of the endospores to the cuticle of the nematodes is the first step in the life cycle of the bacterium and is essential for its reproduction. As a preliminary study to a field solarization test, the effects of temperature on the attachment of P. penetrans on Meloidogyne arenaria race 1 were investigated. Preexposing second-stage juveniles (J2) of M. arenaria to approximately 30 degrees C in water before exposing them to endospores increased their receptivity to endospore attachment when compared to treating J2 at 25 degrees C or 35 degrees C. In tests with soil, highest attachment occurred when J2 were incubated in soil infested with endospores and maintained at 20 degrees C to 30 degrees C for 4 days. Heating J2 in soil to sublethal temperatures (35 degrees C to 40 degrees C) decreased endospore attachment. Incubating P. penetrans endospores in soil at 30 degrees C to 70 degrees C for 5 hours a day over 10 days resulted in reductions of endospore attachment to nematodes as temperatures of incubation increased to 50 degrees C and higher.

Introduction of soluble proteins into the MHC class I pathway by conjugation to an HIV tat peptide

Protection against most intracellular pathogens requires T cells that recognize pathogen-derived peptides in association with MHC class I molecules on the surface of infected cells. However, because exogenous proteins do not ordinarily enter the cytosol and access the MHC class I-processing pathway, protein-based vaccines that induce class I-restricted CTL responses have proved difficult to design. We have addressed this problem by conjugating proteins, such as OVA, to a short cationic peptide derived from HIV-1 tat (residues 49-57). When APC were exposed in vitro to such protein conjugates, they processed and presented the peptides in association with MHC class I molecules and stimulated CD8+ Ag-specific T cells. Moreover, Ag-specific CTLs were generated in vivo by immunizing mice with histocompatible dendritic cells that had been exposed to protein-tat conjugates.

Introduction of soluble proteins into the MHC class I pathway by conjugation to an HIV tat peptide

Protection against most intracellular pathogens requires T cells that recognize pathogen-derived peptides in association with MHC class I molecules on the surface of infected cells. However, because exogenous proteins do not ordinarily enter the cytosol and access the MHC class I-processing pathway, protein-based vaccines that induce class I-restricted CTL responses have proved difficult to design. We have addressed this problem by conjugating proteins, such as OVA, to a short cationic peptide derived from HIV-1 tat (residues 49-57). When APC were exposed in vitro to such protein conjugates, they processed and presented the peptides in association with MHC class I molecules and stimulated CD8+ Ag-specific T cells. Moreover, Ag-specific CTLs were generated in vivo by immunizing mice with histocompatible dendritic cells that had been exposed to protein-tat conjugates.

Comparative studies of phase-cycling schemes for multiple pi-pulse sequences

Recently, a new phase cycling scheme was introduced by this laboratory for use in biological solid-state NMR experiments involving multiple pi-pulses with characteristics that suggested it may enhance the sensitivity of these kind of experiments (Y. Li and J. N. S. Evans, 1995, Chem. Phys. Lett. 241, 79 and Erratum, 1995, ibid. 246, 527; Y. Li and J. N. S. Evans, 1996, J. Magn. Reson. B 111, 296). The new sequence followed the supercycled concept proposed a decade ago for heteronuclear decoupling experiments. In this paper, more detailed experiments demonstrate that the claim of enhanced sensitivity was unfounded, and in fact the supercycle proposed differs little from the established XY-8 and XY-16 based supercycles.

Adaptation of soil solarization to the integrated management of soilborne pests of tomato under humid conditions

ABSTRACT Soil solarization was shown to be cost effective, compatible with other pest management tactics, readily integrated into standard production systems, and a valid alternative to preplant fumigation with methyl bromide under the tested conditions. Solarization using clear, photoselective, or gas-impermeable plastic was evaluated in combination with metham sodium, 1,3-dichloropropene + chloropicrin, methyl bromide + chloropicrin, pebulate, or cabbage residue. Strip solarization, applied to 20-cm-high, 0.9-m-wide beds, was conducted to achieve compatibility with standard production practices and resulted in soil temperatures 2 to 4 degrees C above those temperatures resulting when using conventional flatbed solarization. Soil temperatures were 1 to 2 degrees C higher at the edges of the raised beds, eliminating any border effects associated with solarization. Following a 40- to 55-day solarization period, the plastic was painted white and used as a production mulch for a subsequent tomato crop. The incidence of Southern blight and the density of Paratrichodorus minor and Criconemella spp. were lower (P < 0.05) in solarized plots. No differences (P < 0.05) in the incidence of Fusarium wilt and the density of nutsedge and Helicotylenchus spp. were observed between plots receiving solarization and plots fumigated with a mixture of methyl bromide + chloropicrin. The severity of root galling was lower (P < 0.05) when soil solarization was combined with 1,3-dichloropropene + chloropicrin (16.2 + 3.4 g/m(2)) and a gas-impermeable film. The incidence of bacterial wilt was not affected by soil treatments. Marketable yields in plots using various combinations of soil solarization and other tactics were similar (P < 0.05) to yields obtained in plots fumigated with methyl bromide + chloropicrin. The results were validated in several large scale field experiments conducted by commercial growers.

Suppression Mechanisms of Meloidogyne arenaria Race 1 by Pasteuria penetrans

The biological control of Meloidogyne arenaria on peanut (Arachis hypogaea) by Pasteuria penetrans was evaluated using a six x six factorial experiment in field microplots over 2 years. The main factors were six inoculum levels of second-stage juveniles (J2) of M. arenaria race 1 (0, 40, 200, 1,000, 5,000, and 25,000 J2/microplot, except that the highest level was 20,000 J2/microplot in 1995) and six infestation levels of P. penetrans as percentages of J2 with endospores attached (0, 20, 40, 60, 80, and 100%). The results were similar in 1994 and 1995. Numbers of eggs per root system, J2 per 100 cm(3) soil at harvest, root galls, and pod galls increased with increasing nematode inoculum levels and decreased with increasing P. penetrans infestation levels (P </= 0.05), except that there was no effect of P. penetrans infestation levels on J2 per 100 cm(3) soil in 1994 (P> 0.05). There were no statistical interaction effects between the inoculum levels of J2 and the infestation levels of P. penetrans (P > 0.05). When the infestation level was increased by 10%, the number of eggs per root system, root galls, and pod galls decreased 7.8% to 9.4%, 7.0% to 8.5%, and 8.0% to 8.7% in 1994 and 1995, respectively, whereas J2 per 100 cm(3) soil decreased 8.8% in 1995 (P </= 0.05). The initial infestation level of P. penetrans contributed 81% to 95% of the total suppression of pod galls, whereas the infection of J2 of the subsequent generations contributed only 5% to 19% suppression of pod galls. The major suppressive mechanism of M. arenaria race 1 by P. penetrans on peanut is the initial endospore infestation of J2 at planting.

Distance measurements in nucleic acids using windowless dipolar recoupling solid state NMR

A windowless, homonuclear dipolar recoupling pulse sequence (DRAWS) is described and a theoretical basis for describing its recoupling performance is developed using numerical techniques. It is demonstrated that DRAWS recouples weak dipolar interactions over a broad range of experimental and molecular conditions. We discuss two spectroscopic control experiments, which help to take into account effects due to insufficient proton decoupling, relaxation, and static dipolar couplings to nearby 13C spins at natural abundance. Finally DRAWS is used in combination with selective 13C labeling to measure 13C-13C distances in five doubly labeled DNA dodecamers, [d(CGCGAAT*T*CGCG)]2, which contain the binding site for the restriction enzyme EcoRI. The longest distance reported is 4.8 A. In most cases the distances agree well with those derived from X-ray crystallographic data, although small changes in hydration level can result in relatively large changes in internuclear distances.

Pathogenicity of Fungi to Eggs of Heterodera glycines

Twenty-one isolates of 18 fungal species were tested on water agar for their pathogenicity to eggs of Heterodera glycines. An egg-parasitic index (EPI) for each of these fungi was recorded on a scale from 0 to 10, and hatch of nematode eggs was determined after exposure to the fungi on water agar for 3 weeks at 24 C. The EPI for Verticillium chlamydosporium was 7.6, and the fungus reduced hatch 74%. Pyrenochaeta terrestris and two sterile fungi also showed a high EPI and reduced hatch 42-73%. Arthrobotrys dactyloides, Fusarium oxysporum, Paecilomyces lilacinus, Stagonospora heteroderae, Neocosmospora vasinfecta, Fusarium solani, and Exophiala pisciphila were moderately pathogenic to eggs (EPI was 2.0-4.5, and hatch was reduced 21-56%). Beauveria bassiana, Hirsutella rhossiliensis, Hirsutella thompsonii, Dictyochaeta heteroderae, Dictyochaeta coffeae, Gliocladium catenulatum, and Cladosporium sp. showed little parasitism of nematode eggs but reduced hatch. A negative correlation was observed between hatch and fungal parasitism of eggs. Fusarium oxysporum, H. rhossiliensis, P. lilacinus, S. heteroderae, V. chlamydosporium, and sterile fungus 1 also were tested in soil in a greenhouse test. After 3 months, the nematode densities were lower in soil treated with H. rhossiliensis and V. chlamydosporium than in untreated soil. The nematode population densities were correlated negatively with the EPI, but not with the percentage of cysts colonized by the fungi. Plant weights and heights generally increased in the soil treated with the fungi.

Suppression of Meloidogyne arenaria Race 1 by Soil Application of Endospores of Pasteuria penetrans

The potential of Pasteuria penetrans for suppressing Meloidogyne arenaria race 1 on peanut (Arachis hypogaea) was tested over a 2-year period in a field microplot experiment. Endospores of P. penetrans were mass-produced on M. arenaria race 1 infecting tomato plants. Endospores were inoculated in the first year only at rates of 0, 1,000, 3,000, 10,000, and 100,000 endospores/g of soil, respectively, into the top 20 cm of microplots that were previously infested with M. arenaria race 1. One peanut seedling was planted in each microplot. In the first year, root gall indices and pod galls per microplot were significantly reduced by 60% and 95% for 100,000 endospores/g of soil, and 20% and 65% for 10,000 endospores/g of soil, respectively. Final densities of second-stage juveniles (J2) in soil were not significantly different among the treatments. The number of endospores attached to J2 and percentage of J2 with attached endospores significantly increased with increasing endospore inoculation levels. Pasteuria penetrans significantly reduced the densities of J2 that overwintered. In the second year, root and pod gall indices, respectively, were significantly reduced by 81% and 90% for 100,000 endospores/g of soil, and by 61% and 82% of 10,000 endospores/g of soil. Pod yields were significantly increased by 94% for 100,000 and by 57% for 10,000 endospores/g of soil, respectively. The effect of P. penetrans on final densities of J2 in soil was not significant. Regression analyses verified the role of P. penetrans in the suppression of M. arenaria. The minimum number of endospores required for significantly suppressing M. arenaria race 1 on peanut was 10,000 endospores/g of soil.

Effects of soil treatments on the survival of soil microorganisms

In biological control studies of plant-parasitic nematodes in field soil improved methods are needed for reducing or eliminating specific soil inhabiting microorganisms. Microwave heating of soil decreases soilborne fungi and bacteria, but not Pasteuria spp. Bacterial and fungal colony forming units were reduced to nondetectable levels in microwaved heated field soft (650 watts) at 5.2% moisture when treated for 6 minutes and 4 minutes, respectively.

Reversal of experimental autoimmune encephalomyelitis by a soluble peptide variant of a myelin basic protein epitope: T cell receptor antagonism and reduction of interferon gamma and tumor necrosis factor alpha production

An immunodominant epitope of myelin basic protein (MBP), VHFFKNIVTPRTP (p87-99), is a major target of T cells in lesions of multiple sclerosis (MS) and in experimental allergic encephalomyelitis (EAE). T cells found in EAE lesions bear the same amino acids in the third complementary determining region of the T cell receptor (TCR) as those found in MS lesions. We analyzed the trimolecular interactions between MBP p87-99, class II major histocompatibility complex (MHC), and TCR, and designed soluble inhibitors for therapy. F, N, I, and V at positions 90, 92, 93, and 94 interact with MHC, whereas K, T, and P at positions 91, 95, and 96 interact with TCR. The peptides, p87-99[95T > A] and p87-99[96P > A] could compete more effectively with p87-99 for binding to MHC and could antagonize the in vitro response to T cells to p87-99 more effectively than p87-99[91K > A]. However, only p87-99[91K > A] prevented and reversed EAE, indicating that the extent of MHC or TCR competition does not predict success in treating EAE. To elucidate the mechanism of inhibition of EAE, draining lymph node cells from rats immunized with the native peptide alone or together with each of the three TCR antagonists were challenged in vitro with p87-99. Administration of p87-99[91K > A], but not p87-99 [95T > A] or p87-99[96P > A], reduced the production of tumor necrosis factor (TNF)- alpha and interferon (IFN) gamma. IFN-gamma and TNF-alpha are two cytokines that are critical in the pathogenesis of EAE and MS.

Interacting gray solitons

We present what is to our knowledge the first general theory for describing interacting well-separated gray spatial solitons, propagating in an arbitrary self-defocusing nonlinearity. It reveals why two dark solitons will in general repel, becoming less dark as they propagate. The results are illustrated with analytic expressions for the Kerr and the saturating nonlinearities.