Elasticity-induced force reversal between active spinning particles in dense passive media.

The self-organization of active particles is governed by their dynamic effective interactions. Such interactions are controlled by the medium in which such active agents reside. Here we study the interactions between active agents in a dense non-active medium. Our system consists of actuated, spinning, active particles embedded in a dense monolayer of passive, or non-active, particles. We demonstrate that the presence of the passive monolayer alters markedly the properties of the system and results in a reversal of the forces between active spinning particles from repulsive to attractive. The origin of such reversal is due to the coupling between the active stresses and elasticity of the system. This discovery provides a mechanism for the interaction between active agents in complex and structured media, opening up opportunities to tune the interaction range and directionality via the mechanical properties of the medium.

Sarcoidosis: social predictors of severity at presentation.

To determine relationships among social predictors and sarcoidosis severity at presentation, demographic characteristics, socioeconomic status, and barriers to care, A Case-Control Etiologic Study of Sarcoidosis (ACCESS) was set up. Patients self-reported themselves to be Black or White and were tissue-confirmed incident cases aged > or =l8-yrs-old (n=696) who had received uniform assessment procedures within one of 10 medical centres and were studied using standardised questionnaires and physical, radiographical, and pulmonary function tests. Severity was measured by objective disease indicators, subjective measures of dyspnoea and short form-36 subindices. The results of the study showed that lower income, the absence of private or Medicare health insurance, and other barriers to care were associated with sarcoidosis severity at presentation, as were race, sex, and age. Blacks were more likely to have severe disease by objective measures, while women were more likely than males to report subjective measures of severity. Older individuals were more likely to have severe disease by both measures. In conclusion, it was found that low income and other financial barriers to care are significantly associated with sarcoidosis severity at presentation even after adjusting for demographic characteristics of race, sex, and age.

Genetic variation in eastern North American and putatively introduced populations of Ceratocystis fimbriata f. platani.

The plant pathogenic fungus Ceratocystis fimbriata f. platani attacks Platanus species (London plane, oriental plane and American sycamore) and has killed tens of thousands of plantation trees and street trees in the eastern United States, southern Europe and Modesto, California. Nuclear and mitochondrial DNA fingerprints and alleles of eight polymorphic microsatellite markers of isolates of C. fimbriata from these regions delineated major differences in gene diversities. The 33 isolates from the eastern United States had a moderate degree of gene diversity, and unique genotypes were found at each of seven collection sites. Fingerprints of 27 isolates from 21 collection sites in southern Europe were identical with each other; microsatellite markers were monomorphic within the European population, except that three isolates differed at one locus each, due perhaps to recent mutations. The genetic variability of C. fimbriata f. platani in the eastern United States suggests that the fungus is indigenous to this region. The genetic homogeneity of the fungus in Europe suggests that this population has gone through a recent genetic bottleneck, perhaps from the introduction of a single genotype. This supports the hypothesis that the pathogen was introduced to Europe through Naples, Italy during World War II on infected crating material from the eastern United States. The Californian population may also have resulted from introduction of one or a few related genotypes because it, too, had a single nuclear and mitochondrial genotype and limited variation in microsatellite alleles.

Characterization and Distribution of Two Races of Phialophora gregata in the North-Central United States.

ABSTRACT Genetic variation and variation in aggressiveness in Phialophora gregata f. sp. sojae, the cause of brown stem rot of soybean, was characterized in a sample of 209 isolates from the north-central region. The isolates were collected from soybean plants without regard to symptoms from randomly selected soybean fields. Seven genotypes (A1, A2, A4, A5, A6, M1, and M2) were distinguished based on DNA fingerprinting with microsatellite probes (CAT)(5) and (CAC)(5), with only minor genetic variation within the A or M genotypes. Only the A1, A2, and M1 genotypes were represented by more than one isolate. The A genotypes dominated in the eastern Iowa, Illinois, and Ohio samples, whereas the M genotypes were dominant in samples from western Iowa, Minnesota, and Missouri. In growth chamber experiments, isolates segregated into two pathogenicity groups based on their aggressiveness toward soybean cvs. Kenwood and BSR101, which are relatively susceptible and resistant, respectively, to brown stem rot. In both root dip inoculation and inoculation by injecting spores into the stem near the ground line (stab inoculations), isolates of the A genotypes caused greater foliar symptoms and more vascular discoloration than isolates of the M genotypes on both cultivars of soybean. All isolates caused foliar symptoms in both cultivars and in three additional cultivars of soybean with resistance to brown stem rot. Greater differences between the A and M genotypes were seen in foliar symptoms than in the linear extent of xylem discoloration, and greater differences were seen in Kenwood than in BSR101. Inoculation of these genotypes into five cultivars of soybean with different resistance genes to brown stem rot showed a genotype x cultivar interaction. A similar distinction was found in an earlier study of the adzuki bean pathogen, P. gregata f. sp. adzukicola, and consistent with the nomenclature of that pathogen, the soybean pathogens are named the aggressive race (race A) and the mild race (race M) of P. gregata f. sp. sojae.

Species Delimitation and Host Specialization of Ceratocystis laricicola and C. polonica to Larch and Spruce.

Ceratocystis laricicola and C. polonica are fungal symbionts of bark beetle species of the genus Ips that attack species of Larix and Picea, respectively, across Eurasia. Earlier studies found that these fungal species were morphologically identical, had similar isozymes patterns, and had identical internal transcribed spacer (ITS) sequences of the rDNA operon. We analyzed 27 isolates from Europe, southwestern Siberia (Russia) and Japan, representing the known geographic ranges of the two species. Phylogenetic analysis of the DNA sequences of a portion of the MAT-2 idiomorph showed these species to be distinct, with the Japanese isolates of C. laricicola having a sequence slightly different (5 bp) from those of the Russian and European isolates of C. laricicola. Sexual compatibility tests showed full interfertility among isolates of C. polonica from Europe, Russia and Japan, but isolates of C. polonica were not fully interfertile with isolates of C. laricicola. A Russian and a European isolate of C. laricicola mated with each other but not with the Japanese isolates of C. laricicola. Mature L. sibirica and P. obovata were inoculated with isolates of C. laricicola and C. polonica from Europe, Russia, and Japan, and measurement of lesions in the inner bark/cambium region demonstrated strong host specialization. The data suggest that the two fungal species are very closely related and are distinguished primarily by their physiological specialization to the hosts of their bark beetle vectors.

The root rot fungus Armillaria mellea introduced into South Africa by early Dutch settlers.

Dead and dying oak (Quercus) and numerous other woody ornamental trees and shrubs showing signs and symptoms of Armillaria root rot were identified in the Company Gardens, Cape Town, South Africa, which were established in the mid-1600s by the Dutch East Indies Trading Company. Nineteen isolates from dying trees or from mushrooms were collected and analysed to identify and characterize the Armillaria sp. responsible for the disease. The AluI digestion of the amplified product of the first intergenic spacer region (IGS-1) of the rRNA operon of 19 isolates from the Company Gardens was identical to that of some of the European isolates of A. mellea s. s. The IGS-1 region and the internal transcribed spacers (ITS) were sequenced for some of the Cape Town isolates. Phylogenetic analyses placed the Cape Town isolates in the European clade of A. mellea, which is distinct from the Asian and North American clades of this species. Identification based on sexual compatibility was conducted using A. mellea tester strains in diploid-haploid pairings, which showed some compatibility between the Cape Town isolates and testers from Europe. Somatic compatibility tests (diploid-diploid pairings) and DNA fingerprinting with multilocus, microsatellite probes indicated that the Cape Town isolates were genetically identical and may have resulted from vegetative (clonal) spread from a single focus in the centre of the original Company Gardens (c. 1652). The colonized area is at least 345 m in diameter. Assuming a linear spread rate underground of 0.3 m/year to 1.6 m/year, the genet (clone) was estimated to be between 108 and 575 years old. These data suggest that A. mellea was introduced into Cape Town from Europe, perhaps on potted plants, such as grapes or citrus, planted in the Company Gardens more than 300 years ago.

Depression in sarcoidosis.

Sarcoidosis, a chronic, multisystem disease, impacts quality of life and may increase depression risk. No previous study has reported the depression prevalence among U.S. sarcoid patients. This cross-sectional study examined sociodemographic and disease morbidity factors associated with depression. Patients diagnosed for > or = 1 yr and treated at one of six centers were eligible (n = 176); 154 completed a questionnaire of demographics, treatment, access to medical care, and a short-form Center for Epidemiologic Studies- Depression Scale (CES-D). The primary outcome variable was a CES-D score of > or = 9, indicating clinical depression. The prevalence of depression was 60%. Gender, income, access to medical care, dyspnea on exertion, and number of systems involved were associated with depression. Female sex, decreased access to medical care, and increased dyspnea predicted depression (odds ratio [OR] = 3.33, 11.64, and 2.78, respectively) after adjusting for race, income, and steroid therapy. Despite tertiary care access, patients reported medical care limitation. Health care providers must be sensitive to multiple barriers faced by chronic sarcoid patients; acknowledging depression risk and improving access to medical care will promote better overall health among sarcoid patients. Future studies of sarcoidosis will need to address depression diagnosis and treatment.

Deletion of the MAT-2 mating-type gene during uni-directional mating-type switching in Ceratocystis.

Ceratocystis eucalypti is strictly heterothallic, with single ascospore strains representing one of two opposite mating types. Most other Ceratocystis species, including C. virescens, C. pinicola, and C. fimbriata, are homothallic. In the homothallic species, the MAT-2 strains are self-fertile, while MAT-1 strains are self-sterile and grow more slowly than MAT-2 strains. The current hypothesis is that self-fertility of MAT-2 strains is due to the deletion of the MAT-2 mating-type gene, resulting in the expression of the MAT-1 mating type. These mutant MAT-1 strains are able to cross with MAT-2 strains. Part of the MAT-2 mating-type gene in C. eucalypti, C. pinicola, and C. fimbriata was amplified using degenerate primers designed from the conserved MAT-2 HMG DNA-binding motif. The expected approximately 300-bp PCR products were cloned and sequenced. Specific primers were designed that amplified 210-bp fragments only in MAT-2 isolates of C. eucalypti, C. virescens, C. pinicola, and C. finbriata. These fragments were present in self-fertile field isolates and self-fertile progeny but were absent in the self-sterile (MAT-1) progeny from selfings of C. virescens, C. pinicola, and C. fimbriata, thus supporting the hypothesis that the MAT-2 mating-type gene is deleted during uni-directional mating-type switching. A Southern-blot analysis was performed to confirm the deletion of MAT-2 gene in self-sterile progeny. The DNA sequence data for the C. eucalypti MAT-2 mating-type gene was increased to 1371-bp using TAIL-PCR and uneven PCR, representing a portion of the complete MAT-2 gene DNA sequence.

Molecular Identification of Fungi Associated with Vascular Discoloration of Soybean in the North Central United States.

Brown stem rot is a common but poorly understood vascular wilt disease of soybean. In order to more clearly delimit the causal agent (Phialophora gregata) and distinguish it from other morphologically similar fungi from discolored soybean stems, fungi were isolated on a semi-selective medium from discolored and non-discolored soybean stems collected at random across Iowa, Illinois, Minnesota, Missouri, and Ohio. A total of 11 fungi were commonly isolated and characterized based on colony morphology and DNA sequences of the internal transcribed spacer region of the rDNA operon. Phomopsis longicolla was the most frequently isolated fungus, but it was isolated more commonly from lightly discolored or non-discolored stems than from discolored stems. Phialophora gregata was the next most frequently isolated fungus and was isolated more commonly from discolored stems and more commonly in 1996 than in 1995, which had a warm growing season and relatively little brown stem rot. In inoculation experiments, only P. gregata was capable of causing the vascular discoloration and leaf symptoms typical of brown stem rot; none of the seven isolates could be considered non-defoliating. Two other fungi, Plectosphaerella cucumerina and Gliocladium roseum, were similar in colony morphology to Phialophora gregata but were not pathogenic to soybean, and these may be the same species as those referred to by earlier workers as Acremonium spp. or the non-defoliating form of P. gregata.