Genetic Differentiation and Host Specificity Among Populations of Alternaria spp. Causing Brown Spot of Grapefruit and Tangerine x Grapefruit Hybrids in Florida

ABSTRACT Alternaria spp. were sampled from brown spot lesions in several geographically separated citrus groves and different grapefruit and tangerine x grapefruit hybrid cultivars in Florida and screened for variation at 16 putative random amplified polymorphic DNA loci. Populations of the pathogen on two hybrids, Minneola and Orlando, in five locations throughout Florida were moderately differentiated (Nei's coefficient of gene differentiation [G(ST)] = 0.12) among locations. The hypothesis that host-specialized forms of Alternaria spp. cause brown spot on different Citrus spp. and cultivars was tested by estimating genetic differentiation among isolates sampled from different hosts and by pathogenicity assays. Isolates sampled from grapefruit and the hybrid cv. Nova were genetically distinct from isolates sampled from other hybrid cultivars including Robinson, Sunburst, Minneola, Orlando, and Murcott. No differentiation could be detected among isolates sampled from this latter group of hybrids. Quantitative pathogenicity assays on leaves using spray inoculation revealed that 'Nova' isolates were not significantly more pathogenic on 'Nova' compared with isolates from 'Minneola' and 'Orlando'. Similarly, grapefruit isolates were not significantly more pathogenic on grapefruit compared with isolates from 'Minneola'. Isolates from all hosts had similar disease rankings on each inoculated cultivar, with 'Minneola' the most susceptible, followed in decreasing order of susceptibility by 'Orlando', 'Sunburst', 'Nova', and 'Duncan' grapefruit. Rough lemon was generally immune to all isolates tested; however, occasional brown spot lesions were observed on leaves of this host with isolates from grapefruit. No evidence was found to support the hypothesis that unique genotypes of the pathogen, which are more virulent on 'Sunburst' or grapefruit, have been introduced to Florida. Populations of Alternaria spp. causing brown spot of citrus on grapefruit and 'Nova' in Florida are genetically distinct from isolates on other cultivars, and we speculate that these populations are in the early stages of adaptation to and possible speciation on these hosts.

Attention-deficit hyperactivity disorder in children and youth: a quantitative systematic review of the efficacy of different management strategies

OBJECTIVE

To obtain estimates of the relative efficacy of 3 main treatment strategies for attention-deficit hyperactivity disorder (ADHD) in children and youth (age < 18 years).

DESIGN

quantitative systematic review of randomized trials.

SUBJECTS

999 patients with ADHD from 26 randomized trials.

INTERVENTIONS

medications alone, behavioural interventions alone, and a combination of these 2 modalities.

MAIN OUTCOME MEASURE

differences in scores between treatment groups on commonly used teacher- and parent-completed behaviour rating scales.

RESULTS

Medication-only therapy was efficacious in ADHD. Behavioural therapies used alone appeared not to be efficacious in ADHD. Combination therapy was more efficacious than placebo or no treatment for parent but not teacher ratings, not more efficacious than drug therapy alone, and more efficacious than behavioural treatments alone based on parent but not teacher ratings.

CONCLUSION

Though stimulant medications were found to be an effective treatment strategy for ADHD in children and youth, it proved difficult to assess the relative benefits of behavioural interventions alone and combined medication and behavioural therapy because of the paucity of treatment studies other than medication-only treatment studies and heterogeneity of various kinds that exist in relation to ADHD studies and treatments.

Expression of bcl-2 in enteric neurons in normal human bowel and Hirschsprung disease

OBJECTIVE

The bcl-2 protein has the functional role of blocking apoptosis, ie, programmed cell death. This protein is widely expressed in the developing central and peripheral nervous systems. The purpose of this study was to map bcl-2 expression in the human enteric nervous system, as this has not previously been done.

METHODS

Rectal specimens were obtained at autopsy of 13 fetuses at 13 to 31 weeks of gestation. Normal colon was also obtained from 5 children and 2 adults, and, in addition, ganglionic and aganglionic bowel resected in 11 patients with Hirschsprung disease was examined. Specimens were fixed in formalin, embedded in paraffin, and analyzed with immunohistochemical methods, using antibodies raised against bcl-2 and neuron-specific enolase (NSE).

RESULTS

The bcl-2 protein was expressed in myenteric and submucous ganglion cells in fetuses, children, and adults. Nerve fibers of the enteric plexuses that were bcl-2 immunoreactive were few compared with the number of NSE-immunoreactive nerve fibers. In aganglionic bowel no bcl-2-or NSE-immunoreactive ganglion cells were revealed. Results of NSE immunohistochemistry showed clearly stained hypertrophic nerve bundles, known to be of extrinsic origin, which were only weakly bcl-2 immunoreactive.

CONCLUSION

Expression of bcl-2 in enteric ganglion cells of the myenteric and submucous plexuses is displayed in the fetus and during childhood and is also retained in adult bowel. Immunohistochemical analysis of bcl-2 provides a good marker for identification of ganglion cells in Hirschsprung disease and may also be valuable for the diagnosis of disorders characterized by hypoganglionosis or hyperganglionosis.

Population Genetic Structure and Host Specificity of Alternaria spp. Causing Brown Spot of Minneola Tangelo and Rough Lemon in Florida

ABSTRACT Alternaria spp. were sampled from two rough lemon (RL) and two Minneola tangelo (MIN) groves in a limited geographic area in central Florida to test for host-specialized forms of the pathogen. Isolates of Alternaria spp. were scored for variation at 16 putative random amplified polymorphic DNA (RAPD) loci and for pathogenicity on both hosts. Subpopulations on each host were differentiated genetically and pathogenically, which was consistent with the hypothesis of host specialization. Highly significant genetic differentiation was detected among all four subpopulations (Nei's coefficient of gene differentiation [G(ST)] = 0.292, P = 0.000); most of the differentiation occurred between hosts (G(ST) = 0.278, P = 0.000). Phenograms of qualitative similarities among isolates within subpopulations revealed two or three distinct clusters of isolates within each subpopulation. The majority of isolates sampled from RL were pathogenic on RL and not on MIN, although a few RL isolates were able to induce disease on MIN, and 44% were nonpathogenic on either host. In contrast, isolates from MIN were pathogenic only on MIN, never on RL, and only 3% of the isolates were nonpathogenic. Overall, three genetically distinct clusters of isolates were detected on both hosts. One of the clusters (cluster A) sampled from RL was pathogenic on RL and not on MIN and consisted almost entirely of one RAPD genotype. This cluster also contained two isolates that were 93% similar to the majority genotype but were pathogenic on MIN and not RL. In isolates from MIN, two distinct clusters of isolates were found in one subpopulation (clusters B and C), and three distinct clusters were found in another subpopulation (clusters A, B, and C). Clusters A and B were found on both hosts, while cluster C was limited to MIN. Populations of Alternaria spp. sampled from RL and MIN showed a high degree of host specificity; however, the specificity obscured a high level of genetic variation within subpopulations.

Differential expression of inducible nitric oxide synthase in septic shock

During cardiopulmonary bypass (CPB), the septic patient has markedly decreased peripheral vascular resistance as a consequence of endotoxin release from microorganisms. This decrease in peripheral vascular resistance is the result of endotoxin-induced nitric oxide (NO) produced by inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS). iNOS and eNOS are responsible for the synthesis of NO because of various stimuli, including the bacterial endotoxin, lipopolysaccharide (LPS). We tested the hypothesis that a differential expression of iNOS among human endothelial cells and murine macrophage is dependent upon exposure to endotoxin and various pro-inflammatory cytokines. Using a human endothelial cell line, ECV-304 and murine macrophage cell line, RAW 264.7, we quantified the expression of iNOS with specific FITC-conjugated antibodies using fluorescence activated cell sorter (FACS) and NO production with a Bioxytech nitric oxide spectrophotometric assay. This in vitro septic model utilized LPS supported with species-specific interferon-gamma, interleukin-1 beta, and tumor necrosis factor-alpha. The cell type were stimulated for 8 hours with combinations of the cytokines mentioned. The FACS data demonstrated a significant stimulus-dependent increase in iNOS expression among the macrophage groups; however, the stimulated endothelial cells showed no significant change in iNOS expression. The nitric oxide production data demonstrated significant increases in NO production among macrophage stimulated groups; whereas, endothelial stimulated groups exhibit no significant change. We conclude that NO secreted during septic shock is the result of activated macrophage, not the endothelium. The clinical relevance is that the more severe the infectious process, the lower the PVR may be during CPB because of increased NO production from activated macrophage.

Safe biotechnology 9: values in risk assessment for the environmental application of microorganisms. The Safety in Biotechnology Working Party of the European Federation of Biotechnology

Risk assessment for the deliberate release of microorganisms into the environment is traditionally carried out on a case-by-case basis. In a similar approach to that used when assessing human pathogenicity, we propose an alternative approach by introducing risk classes to facilitate or complement this type of risk assessment. These consider several sets of scenarios that address the different values that need to be protected. Examples of this approach include risk-class definitions for soil fertility and biodiversity.

Induction of micronuclei in V79 cells by fractions of roofing asphalt fume condensate

More than 50,000 workers in the United States are exposed to roofing asphalt fumes that may pose genotoxic and potential carcinogenic hazards. The Type III roofing asphalt is most frequently used in roof-application. Results of our previous studies showed that fume condensates of Type III roofing asphalts induced micronuclei (MN) in vitro in cultured V79 cells and DNA adduct formation in vivo in rat lung cells. In this study, the genotoxicity of whole fume condensates (WFC) of Type III roofing asphalt and its five chemical fractions (A, B, C, D and E) was determined by the micronucleus assay using V79 cells. Linear regressions were determined for the dose response of MN frequencies and percent of binucleated and multinucleated cells (MTC) following the treatment. Results showed that the numbers of micronucleated cells in cultures treated with Type III roofing asphalt WFC and its fractions B, C, D and E were significantly higher than that in the control culture, and that the slopes of the linear regression line for fractions B and C were greater than those for the WFC and fractions D and E. A clear dose response of binucleated cells was also induced by the WFC and fractions B and C. These findings indicate that: (1) WFC and all fractions, except fraction A, induced MN formation in cultured V79 cells; (2) fractions B and C possess the highest genotoxic activity; (3) the roofing asphalt WFC contains chemicals or chemical classes that induce not only chromosomal aberrations but also binucleation in V79 cells.

Mathematical modelling of anisotropy in fibrous connective tissue

We present two modelling frameworks for studying dynamic anistropy in connective tissue, motivated by the problem of fibre alignment in wound healing. The first model is a system of partial differential equations operating on a macroscopic scale. We show that a model consisting of a single extracellular matrix material aligned by fibroblasts via flux and stress exhibits behaviour that is incompatible with experimental observations. We extend the model to two matrix types and show that the results of this extended model are robust and consistent with experiment. The second model represents cells as discrete objects in a continuum of ECM. We show that this model predicts patterns of alignment on macroscopic length scales that are lost in a continuum model of the cell population.

Accessory wandering spleen associated with short pancreas. A pediatric case report

We present an extremely rare case of a 5-year-old girl with short pancreas associated with three accessory spleens, one of which was a large wandering spleen. The diagnosis was established by US and CT. A large accessory wandering spleen is considered to be at risk of torsion and infarction as well as susceptible to abdominal trauma. The authors discuss the difficulty of establishing the diagnosis and underline the importance of US and CT as pre-operative diagnostic tools.

Interstitial cells of Cajal in the human fetal small bowel as shown by c-kit immunohistochemistry

BACKGROUND

Interstitial cells of Cajal (ICCs) express the tyrosine kinase receptor c-kit, which is required for their development and spontaneous pacemaker activity in the bowel. From murine models it has been proposed that ICCs do not develop until after birth, but more recent findings indicate that c-kit is expressed early in the embryonic period. The temporal development of ICCs in the human gut remains unknown.

AIM

To investigate ICCs in the human fetal small bowel using c-kit immunohistochemistry.

SUBJECTS

Small bowel specimens were obtained at post mortem examination of 16 fetuses and nine neonates, eight of whom were premature, born at gestational ages of 13 to 41 weeks, without gastrointestinal disorders.

METHODS

Immunohistochemical analysis was performed on material fixed in formalin and embedded in paraffin. The specimens were exposed to antibodies raised against c-kit (an ICC marker) and neurone specific enolase (a general neuronal marker). The ABC complex method was used to visualise binding of antibodies to the corresponding antigens.

RESULTS

c-kit immunoreactive cells were visualised from 13 weeks of gestation. The immunoreactivity was mainly localised in association with the myenteric plexus. From about 17-18 weeks of gestation, the ICCs formed a layer along the myenteric plexus, whereas this layer appeared to be disrupted at 13-16 weeks of gestation. CONCLUSIONS ICCs are c-kit immunoreactive at least from a gestational age of 13 weeks in the human fetal small intestine. From 17-18 weeks of gestation until birth, they form a continuous layer around the myenteric ganglia.

Spatially varying equilibria of mechanical models: application to dermal wound contraction

Mechanochemical models based on the Oster-Murray continuum framework have been applied to a variety of biological settings to obtain an understanding of the morphogenesis of living tissues. Wound-healing in mammalian skin is an important example, because a complex sequence of biochemical and biomechanical responses are orchestrated to close a wound by a combination of new tissue formation and wound contraction. Mechanical interactions between dermal fibroblastic cells and the collagen-rich extracellular matrix are crucial in the development of a contracted wound state. We and others have previously proposed mechanochemical models for wound repair to gain a greater understanding of both normal and abnormal healing. In the present work, the existence of spatially varying equilibria of these models is investigated by using a small-stain approximation and phase-plane techniques, with numerical simulations to confirm the analytical predictions. These results are sources of novel insight into the roles of key biological parameters in determining the mechanical properties of a contracted wound. These methods may also be relevant to other morphogenetic scenarios for which similar mechanochemical models have been proposed.

The effect of addition of calcipotriol ointment (50 micrograms/g) to acitretin therapy in psoriasis

Our purpose was to find out whether the addition of calcipotriol ointment (50 micrograms/g) to systemic treatment with acitretin produces additional therapeutic effects and thereby an acitretin-sparing effect, and further to investigate the safety and tolerability of this combination. A multicentre, randomized, double-blind placebo-controlled study was designed. Patients were randomized to receive calcipotriol or placebo. All patients were treated with a starting dose of 20 mg acitretin per day and doses were adjusted at 2-weekly intervals with increments of 10 mg per day up to a maximum of 70 mg per day. The dose requirement for acitretin, clinical signs and adverse events were recorded. Seventy-six patients were randomized to treatment with calcipotriol 50 micrograms/g ointment twice daily and 59 patients to treatment with the vehicle only twice daily. Clearance or marked improvement was achieved by 67% of the patients in the calcipotriol group and by 41% of the patients in the placebo group (P = 0.006). Calcipotriol treatment proved to have a statistically significant additional effect to acitretin on the Psoriasis Area and Severity Index, redness, thickness and scaliness as compared with placebo. Clearance or marked improvement was achieved with a statistically significantly lower cumulative dose of acitretin by the patients in the calcipotriol group as compared with the placebo group. The number of patients reporting adverse events was pronounced and largely related to acitretin. No significant differences were observed between the two treatment groups with respect to adverse events. Laboratory assessments were essentially normal. The addition of calcipotriol ointment to acitretin treatment contributes to the efficacy, reduces the cumulative dose of acitretin to reach marked improvement or clearance, and is well-tolerated and safe.

Developmental gene expression of sympathetic nervous system tumors reflects their histogenesis

Comparisons of the developing human sympathetic nervous system (SNS) to tumors presumed to derive from these cells may suggest tumor progenitors and predict tumor biologic behavior. Classic neuroblastoma (NB) and its more highly differentiated stroma-rich subtypes, extra-adrenal sympathetic paraganglioma, and pheochromocytoma were examined for the presence of the developmentally characterized gene products NSE, S-100, CD44, Bcl-2, HNK-1, PNMT, TrkA, IGF2, and tyrosine hydroxylase. The marker gene expression profiles of these tumors were compared with those similarly determined for a number of normal prenatal and postnatal human SNS cell types. Sympathetic paraganglioma, pheochromocytoma, and stroma-rich NB display marker expression profiles mimicking those of childhood sympathetic paraganglia, adrenal chromaffin cells, and sympathetic neurons, respectively. A selection of differentiating, extra-adrenal NB tumors with prognostically favorable features possess marker gene expression profiles paralleling that observed for fetal extra-adrenal sympathetic paraganglia/small intensely fluorescent cells. In contrast, undifferentiated, clinically aggressive NB tumors manifest characteristics mirroring that of embryonic/early fetal sympathetic neuroblasts of sympathetic ganglia and of the adrenal gland. These findings suggest that clinical features, such as primary tumor location and age at diagnosis, provide prognostic information for NB patients by virtue of the existence and biology of the presumed tumor progenitor cell type.

A mathematical model for the capillary endothelial cell-extracellular matrix interactions in wound-healing angiogenesis

Angiogenesis, the process by which new blood capillaries grow into a tissue from surrounding parent vessels, is a key event in dermal wound healing, malignant-tumour growth, and other pathologic conditions. In wound healing, new capillaries deliver vital metabolites such as amino acids and oxygen to the cells in the wound which are involved in a complex sequence of repair processes. The key cellular constituents of these new capillaries are endothelial cells: their interactions with soluble biochemical and insoluble extracellular matrix (ECM) proteins have been well documented recently, although the biological mechanisms underlying wound-healing angiogenesis are incompletely understood. Considerable recent research, including some continuum mathematical models, have focused on the interactions between endothelial cells and soluble regulators (such as growth factors). In this work, a similar modelling framework is used to investigate the roles of the insoluble ECM substrate, of which collagen is the predominant macromolecular protein. Our model consists of a partial differential equation for the endothelial-cell density (as a function of position and time) coupled to an ordinary differential equation for the ECM density. The ECM is assumed to regulate cell movement (both random and directed) and proliferation, whereas the cells synthesize and degrade the ECM. Analysis and numerical solutions of these equations highlights the roles of these processes in wound-healing angiogenesis. A nonstandard approximation analysis yields insight into the travelling-wave structure of the system. The model is extended to two spatial dimensions (parallel and perpendicular to the plane of the skin), for which numerical simulations are presented. The model predicts that ECM-mediated random motility and cell proliferation are key processes which drive angiogenesis and that the details of the functional dependence of these processes on the ECM density, together with the rate of ECM remodelling, determine the qualitative nature of the angiogenic response. These predictions are experimentally testable, and they may lead towards a greater understanding of the biological mechanisms involved in wound-healing angiogenesis.

Application of Karasek's demand/control model a Canadian occupational setting including shift workers during a period of reorganization and downsizing

PURPOSE

To apply Karasek's Job Content Model to an analysis of the relationships between job type and perceived stress and stress behaviors in a large company during a period of reorganization and downsizing.

DESIGN

Cross-sectional mail-out, mail-back survey.

SETTING

A large Canadian telephone/telecommunications company.

SUBJECTS

Stratified random sample (stratified by job category) of 2200 out of 13,000 employees with a response rate of 48.8%.

MEASURES

Responses to 25 of Karasek's core questions were utilized to define four job types: low-demand and high control = "relaxed"; high demand and high control = "active"; low demand and low control = "passive", and high demand and low control = "high strain." These job types were compared against self-reported stress levels, perceived general level of health, absenteeism, alcohol use, exercise level, and use of medications and drugs. Similar analyses were performed to assess the influence of shift work.

RESULTS

Employees with "passive" or "high strain" job types reported higher levels of stress (trend test p < .0001); poorer health (trend test P = .006); and higher levels of absenteeism (trend test p < .0001). More shift workers reported themselves in poor or fair health (chi-square p = .018) and reported high levels of stress at home (chi-square p = .002) than nonshift workers. The relationships between job type and levels of stress, health and absenteeism, however, held for nonshift workers as well.

CONCLUSIONS

Job types with high demand and low control were associated with increased stress, increased absenteeism, and poorer self-concept of health. The demand/control model of Karasek and Theorell was validated in this setting with respect to stress and some stress-associated attitudes and behaviors.

Spatial association of apoptosis-related gene expression and cellular death in clinical neuroblastoma

Several unique features of neuroblastoma (NB), including the capacity for spontaneous regression and maturation to benign pathology, suggest that genes that regulate cellular proliferation, survival and differentiation may be involved in directing clinical tumour aggressiveness. The in situ expression of Bcl-2, Rb, p21, p53 and Bax proteins, as well as the proliferation marker proliferating cell nuclear antigen (PCNA) were examined immunocytochemically in a selection of 38 stage- and outcome-identified NB tumours. Apoptotic cells were identified morphologically and by a DNA fragmentation labelling technique (TUNEL). Although the tumour cell density of Bcl-2, p53, Bax, PCNA and TUNEL positivity correlated with patient survival, a spatially organized expression pattern was further recognized in stroma-poor differentiating tumours. Immature tumour cells adjacent to thin fibrovascular stroma are proliferating, as evidenced by PCNA positivity, and often express Bcl-2. At increasing distance from this fibrovascular stroma, intermediately differentiated tumour cells express Rb, while with more advanced differentiation, proliferation ceases and Bcl-2 immunoreactivity is lost. The most differentiated tumour cells, which often express p53, and occasionally p21 and Bax, lie adjacent to TUNEL-positive, morphologically apoptotic cells. This spatial organization in favourable outcome NB tumours suggests that physiological regulation of differentiation and apoptosis may be involved in tumour regression.

A developmental model of neuroblastoma: differentiating stroma-poor tumors' progress along an extra-adrenal chromaffin lineage

The prognosis of children with neuroblastoma (NB) is dependent upon the patient's age at diagnosis, the location of the primary tumor, and histologic tumor cell differentiation. These characteristics, as well as the presumption that NB results from clonal expansion of primitive cells involved in sympathetic nervous system (SNS) development, predict that a model of tumorigenesis based upon normal fetal SNS histogenesis might indicate tumor progenitor status and define biologic and clinical behavior. Immunohistochemistry and in situ hybridization were used to examine a panel of marker gene products predicted or shown to be expressed during SNS development in the normal human fetal SNS from 8 to 24 weeks' gestational age. A similar analysis was performed in a selection of clinical NB tumors, and the results were compared. In a subset of differentiating, often extra-adrenal NB tumors in patients who frequently had a favorable outcome; advancing morphologic tumor cell differentiation spatially paralleled an advancing fetal extra-adrenal chromaffin marker gene expression phenotype (ie, increasing TrkA, TrkC, TH, IGF-2, and neuron-specific enolase expression but a lack of phenylethanolamine N-methyltransferase expression). In these tumors, expression of gene products associated with normal fetal sympathetic ganglionic differentiation (ie, Bcl-2, HNK-1, and neuropeptide Y) was lost with morphologic tumor cell differentiation. In contrast, undifferentiated tumors, the majority of which were high stage, adrenal in origin, and prognostically unfavorable, displayed marker expression characteristics mirroring that of an early fetal ganglionic lineage. Thus, we show that morphologic differentiation in stroma-poor NB tumors, long held as an important prognostic feature in tumor grading systems, often corresponds to an extra-adrenal chromaffin rather than a ganglion cell or adrenal medullary chromaffin phenotype. Understanding the biology of extra-adrenal chromaffin tissues may provide an explanation for the clinically less aggressive nature of differentiating NB tumors and suggest potential mechanisms for spontaneous regression and/or treatment response.

Alterations in neurotrophin and neurotrophin-receptor localization in Hirschsprung's disease

Interactions of the trk family of tyrosine kinase receptors with neurotrophins promote growth and differentiation of nervous-system cells during development. Disturbances in neurotrophic signalling could be involved in functional or aganglionic conditions of the intestine such as Hirschsprung's disease (HD). Intestinal resection specimens from 20 children with HD and from 10 normal age-matched controls were evaluated immunocytochemically for the presence of TrkA, TrkB, and TrkC protein, and the neurotrophin ligands brain-derived neurotrophic factor [BDNF] and neurotrophin-3 (NT-3). All three neurotrophin receptors are localized with cellular specificity to the enteric nervous system of normal and proximal ganglionic HD intestine; however, none was detected in the hypertrophic nerve fibers of aganglionic HD segments. Aganglionic HD intestine lacked intense and specific TrkC and BDNF enteric ganglionic immunoreactivity. NT-3, localized to enteric plexuses and basal lamina of ganglionic intestine, was not detected in ganglion cells located at the "transitional zone" of HD intestine. These data suggest that neurotrophic influences may be involved in enteric nervous-system cellular survival and differentiation in functional intestinal disorders such as HD.