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R L Brown

Publications and source records attributed to R L Brown.

At least 55 records · Page 3Linked to original sources
PubMed1998

The promoter of the plant defensin gene PDF1.2 from Arabidopsis is systemically activated by fungal pathogens and responds to methyl jasmonate but not to salicylic acid.

The plant defensin PDF1.2 has previously been shown to accumulate systemically via a salicylic acid-independent pathway in leaves of Arabidopsis upon challenge by fungal pathogens. To further investigate the signalling and transcriptional processes underlying plant defensin induction, a DNA fragment containing 1184 bp and 1232 bp upstream of the transcriptional and translational start sites, respectively, was cloned by inverse PCR. To test for promoter activity this DNA fragment was linked to the beta-glucuronidase (GUS)-encoding region of the UidA gene as a translational fusion and introduced into Arabidopsis ecotype C-24. Challenge of the transgenic plants with the fungal pathogens Alternaria brassicicola and Botrytis cinerea resulted in both local and systemic induction of the reporter gene. Wounding of the transgenic plants had no effect on GUS activity. Treatment of the transgenic plants with either jasmonates or the active oxygen generating compound paraquat strongly induced the reporter gene. In contrast, neither salicylate nor its functional analogues 2,6-dichloroisonicotinic acid and 1,2,3-benzothiodiazole-7-carbothioic acid S-methyl ester resulted in reporter gene induction. These results are consistent with the existence of a salicylic acid-independent signalling pathway, possibly involving jasmonates as regulators, that is triggered by pathogen challenge but not by wounding. The transgenic plants containing the PDF1.2-based promoter-reporter construct will provide useful tools for future genetic dissection of this novel systemic signalling pathway.

Acetates↗
PubMed1998

Training the trainers: substance abuse screening and intervention.

OBJECTIVE: Screening and brief intervention for substance abuse is effective yet underutilized by primary care physicians. This article reports on Project SAEFP (Substance Abuse Education for Family Physicians), which aimed to enhance the clinical and teaching skills and activities of U.S. family practice residency faculty. METHOD: Ten five-day workshops were designed and administered for 165 participants. Evaluation data included measures of participant satisfaction and pre-workshop and twelve-month post-workshop measures of the frequency of teaching, consulting, and clinical activities, and the attainment of self-identified teaching goals. RESULTS: The participants were very satisfied with the workshops. They improved significantly in the key outcome measures. CONCLUSIONS: Several workshops may have contributed to the apparent success of Project SAEFP. Attributes of the workshops which might have facilitated their success were their duration, funding, frequency of offering, collegial learning environment, opportunities for active learning, emotionally moving exposure to recovering individuals, focus on how to modify curriculum at participant residency programs, availability of family physician role models as faculty, and readily usable instructional materials. Planners of interventions for physician educators might profit from similar attention to these attributes.

Adult↗
PubMed1998

Protein profiles and antifungal activities of kernel extracts from corn genotypes resistant and susceptible to Aspergillus flavus.

Mechanisms of resistance to infection by the fungus Aspergillus flavus and accumulation of aflatoxin were studied in kernels of resistant (GT-MAS:gk, Mp420) and susceptible ( Pioneer 3154, Deltapine G-4666) corn genotypes. Proteins from kernel extracts of corn genotypes were analyzed by several methods of polyacrylamide gel electrophoresis. Consistent differences in protein profiles were detected among genotypes. Several proteins were unique to or present in greater concentration in resistant genotypes, whereas others were present only in susceptible genotypes. Extracts of resistant kernels showed markedly greater antifungal activity against A. flavus than did susceptible kernel extracts. Results from the present study suggest a role for kernel proteins in resistance to A. flavus infection and aflatoxin contamination in corn genotypes.

Aspergillus flavus↗
PubMed1997

Serum-free culture conditions for cells capable of producing long-term survival in lethally irradiated mice.

The goal of ex vivo culture is to expand and/or differentiate cells in culture such that they retain their functional characteristics when reinfused into a patient. The studies presented here analyzed the use of culture conditions devoid of serum to expand murine hematopoietic stem cells. Bone marrow cells from male B6D2F1/J mice were cultured for up to 28 days in serum-free medium in the absence or presence of stem cell factor (SCF), GM-CSF or a combination of the two factors. Cells cultured for up to 21 days were assessed for granulocyte-macrophage colony-forming cells (GM-CFC), spleen colony-forming units, and cells responsible for short-term and long-term hematopoietic repopulation in lethally irradiated mice. Compared to initial seeding levels, the presence of SCF and GM-CSF increased total cell numbers 90-fold and GM-CFC numbers 42-fold over a 21-28 day culture period. Although spleen colony-forming unit cells did not increase, they were maintained at initial seeding levels over a 21-day period in the presence of SCF and GM-CSF. In lethally irradiated mice, survival enhancement and hematologic reconstitution were optimum with cells cultured for only seven days: survival at six months was 100% with cells cultured in SCF plus GM-CSF or SCF alone, compared to 50% with cells cultured with only GM-CSF. Hybridization analysis of bone marrow, spleen and thymus DNA from irradiated mice transplanted with these cultured cells confirmed male donor cell-derived repopulation at 45 days and 180 days post-transplant. These studies illustrate that murine GM-CFC can be expanded and that long-term repopulating hematopoietic cells can, at the minimum, be maintained ex vivo in serum-free culture. The use of defined serum-free culture systems holds great promise for further evaluation of the mechanisms that control hematopoietic stem cell proliferation.

Animals↗
PubMed1997

Allergenicity of gourmet nut oils processed by different methods.

BACKGROUND: No information is available on allergenicity of tree nut oils, and information on peanut oils has been conflicting. Many of the nut oils now on the market undergo minimal processing and may contain residual antigen. OBJECTIVE: This study was carried out to determine whether several of the new "gourmet" tree nut oils, as well as peanut oils, contain residual proteins that could bind IgE from sera of patients with allergy. METHODS: Several brands of walnut, almond, hazelnut, pistachio, and macadamia nut oils were examined. Peanut oils, both unrefined oils (which have been shown to contain allergenic proteins) and refined oils (without previously demonstrable allergens), were also examined to confirm reproducibility of immunoreactivity as reported by other investigators. Oils were extracted with 0.2 mol/L ammonium bicarbonate, and protein concentrations in the aqueous extracts were measured. IgE binding was assayed by slot-blot and Western immunoblotting. Pooled sera from patients with a history of systemic reactions to various tree nuts or peanuts were used as appropriate. RESULTS: The oil extracts known to be from oils that had undergone less processing at lower temperatures tended to demonstrate qualitatively greater IgE binding and higher protein concentrations. CONCLUSIONS: Tree nut and peanut oils may pose a threat to patients with allergy, depending on the method of manufacture and processing.

Allergens↗
PubMed1997

Physicians' decisions to prescribe benzodiazepines for nervousness and insomnia.

OBJECTIVE: To assess the effects of particular clinical cues on decisions about prescribing benzodiazepines. DESIGN: A factorial survey based on social judgment theory. SETTING: A midwestern U.S. medical school. PARTICIPANTS: Physicians (n = 115) recruited from the staff by invitation and interview. MEASUREMENTS AND MAIN RESULTS: Physicians indicated their level of agreement with prescribing a benzodiazepine for 24 hypothetical cases of nervousness and insomnia. The cases stemmed from the same scenario but varied systematically with regard to psychiatric diagnosis, recent ability to work, and long-term social stability. A fourth cue, called "health status," covertly depicted the presence or absence of three common alcohol-related medical problems. One fourth of the physicians agreed with prescribing for 15 or more cases, and 15% disagreed for all of them. Agreement was cumulative and least common for major depression, more common for adjustment disorder, and most common for generalized anxiety. Agreement with prescribing for cases with alcohol-related medical problems was 14% less than that for cases without them. Over half the physicians agreed with prescribing for 4 or more of the 12 cases with alcohol-related medical problems. CONCLUSIONS: Prescribing decisions varied widely. Some physicians avoided benzodiazepines unnecessarily for some cases, while others agreed with prescribing for patients with a high probability of alcohol abuse. Blanket calls for more or less prescribing are overly simplistic; physicians should be able to recognize substance use disorders among anxious patients and make prescribing decisions based on relevant literature and clinical cues.

Adjustment Disorders↗
PubMed1997

In vivo comparison of two enteric-pouch power transformers for circulatory support.

A defunctionalized ileal pouch is thin-walled (1-2 mm), well perfused (blood flow, 0.3-1.0 ml/g/min), and tactile-insensitive. If fixed within the abdominal wall and provided with a miniature stoma for primary wire entry, the heat dissipating capacity and achievable geometries could facilitate small efficient intra- to extracorporeal power transformers with virtually complete magnetic flux containment. Two transformers (A, weighing 102 gm with dual ferrite cores, intraluminal primary and extraluminal secondary each with 10 turns on its own crescentic ferrite core, 90 kHz, coupling coefficient k = 0.90-0.96; and B, 68 gm, a single flexible torroidal magnetic metallic tape core with attached 11 turn primary and free 14 turn serosal secondary, 14.7 kHz, k = 0.99) met the electrical and anatomic requirements. Each was implanted (minilaparotomy, coil-pouch fixation within abdominal musculature) in 4 dogs for 14-21 days to test the operative feasibility, electrical function, warming, and flux containment. For canine testing, wires were tunneled to a chewing-inaccessible site. Neither tissue necrosis, infection, provokable interference from contiguous metal, nor coil displacement were observed; secretions were retained in Group A pouches only. The mean power transmissions for the transformers were A: 24.90 +/- 1.50 W and B: 24.92 +/- 0.89 W, after operation for 7 days or more. The mean efficiencies were A: 75.6 +/- 0.1% total DC/DC, 96.2% coils and B: 80.4 +/- 0.1% total DC/DC, 96.2% coils. The peak skin surface magnetic fluxes for transformers A and B, both trivial at 1.7 and 1.2 G, respectively, were similar. Warming was 0.62 +/- 0.30 degrees C in Group A and 0.73 +/- 0.19 degrees C in Group B. The probability values were p < 0.5 (NS) for DC/DC efficiency and p > 0.10 (NS), for A versus B in all other areas of comparison. Observations for both were encouraging. Transformer B, with less mass, lower frequency, higher efficiency, and intrinsic invulnerability to displacement, was selected for longer term evaluation.

Abdominal Muscles↗
PubMed1997

Plasmids and Aeromonas virulence.

Most putative virulence determinants of Aeromonas species are chromosomally encoded. However, several recent reports have indicated that some may be carried on or regulated by plasmids. Therefore, we examined the plasmid carriage rate of a total of 140 clinical and environmental Aeromonas isolates. Plasmid carriage was compared with the ability of an isolate to produce toxins and adhere to HEp-2 cells. Overall, plasmid incidence in Aeromonas species was low (23/140, 16%) and independent of the source of the isolate. Plasmids were, however, more common in environmental isolates of A. veronii biovar sobria than in clinical isolates of this species (P < 0.05). We could find no evidence to support the recent literature findings that plasmids may have a role in Aeromonas virulence.

Aeromonas↗
PubMed1997

Molecular genetic evidence for the involvement of a specific polygalacturonase, P2c, in the invasion and spread of Aspergillus flavus in cotton bolls.

Isolates of Aspergillus flavus can be differentiated based on production of the polygalacturonase P2c. One group of isolates produces P2c, whereas the other group does not. In general, the group that produces P2c causes more damage and spreads to a greater extent in cotton bolls than those isolates that do not produce P2c. To determine whether P2c contributes to disease, the expression of pecA, the gene previously determined to encode P2c, was genetically altered. Adding the pecA gene to a strain previously lacking the gene resulted in the ability to cause significantly more damage to the intercarpellary membrane and the ability spread to a greater extent within the adjacent locule compared to the abilities of a control transformant. Conversely, eliminating the expression of pecA by targeted disruption caused a significant reduction in aggressiveness compared to that of a nondisrupted control transformant. These results provide direct evidence that P2c contributes to the invasion and spread of A. flavus during infection of cotton bolls. However, other factors not evaluated in this study also contribute to aggressiveness.

Aspergillus flavus↗
PubMed1997

Growth of an Aspergillus flavus transformant expressing Escherichia coli beta-glucuronidase in maize kernels resistant to aflatoxin production.

Kernels of a maize inbred that demonstrated resistance to aflatoxin production in previous studies were inoculated with an Aspergillus flavus strain containing the Escherichia coli beta-D-glucuronidase reporter gene linked to a beta-tubulin gene promoter and assessed for both fungal growth and aflatoxin accumulation. Prior to inoculation, kernels were pin-wounded through the pericarp to the endosperm, pin-wounded in the embryo region, or left unwounded. After 7 days incubation with the fungus, beta-glucuronidase activity (fungal growth) in the kernels was quantified using a fluorogenic assay and aflatoxin B content of the same kernels was analyzed. Kernels of a susceptible inbred, similarly treated, served as controls. Results indicate a positive relationship between aflatoxin levels and the amount of fungal growth. However, resistant kernels wounded through the pericarp to the endosperm before inoculation supported an increase in aflatoxin B over levels observed in nonwounded kernels, without an increase in fungal growth. Wounding kernels of the resistant inbred through the embryo resulted in both the greatest fungal growth and the highest levels of aflatoxin B1 for this genotype. Maintenance of resistance to aflatoxin B1 in endosperm-wounded kernels may be due to the action of a mechanism which limits fungal access to the kernel embryo.

Aflatoxin B1↗
PubMed1997

A two-item screening test for alcohol and other drug problems.

BACKGROUND: Although nonmedical use of illicit and prescription drugs is not uncommon among American adults, the currently recommended screening tests for substance use disorders (SUDs) focus only on alcohol. This study reports on the criterion validity of a two-item conjoint screening (TICS) test for alcohol and other drug abuse or dependence for a primary care sample. METHODS: A random sample of 434 primary care patients aged 18 to 59 years responded to nine screening items, which emanated from a focus group process. The DSM-III-R criteria for SUDs, as operationalized by the Composite International Diagnostic Interview-Substance Abuse Module, served as the criterion standard. RESULTS: At least one positive response to the TICS ("In the last year, have you ever drank or used drugs more than you meant to?" and "Have you felt you wanted or needed to cut down on your drinking or drug use in the last year?") discriminated current SUDs with approximately 81% sensitivity and specificity. The TICS was particularly sensitive to polysubstance use disorders. Respondents with zero positive responses had a 7.4% chance of a current SUD; one positive response, 45.0%; and two positive responses, 75.0%. CONCLUSIONS: More than 80% of young and middle-aged patients with current alcohol or other drug problems may be recognized by the TICS, which is easily integrated into a clinical interview.

Adolescent↗
PubMed1996

Crystallization and preliminary X-ray diffraction studies of a cobalt-substituted derivative of the iron-dependent alcohol dehydrogenase from Zymomonas mobilis.

The iron-dependent alcohol dehydrogenase from Zymomonas mobilis has been crystallized in a form suitable for X-ray diffraction studies. The crystals grew in hanging drops by vapor diffusion, equilibrating with a solution comprising 25-27% methoxypolyethylene glycol 5000 and 1 mM Co(2+) in a 0.2 M succinic acid/potassium hydroxide buffer at pH 5.5-5.7 at 281 K. Crystals are tetragonal, P4(1)22 (or P4(3)22), with unit-cell dimensions a = b = 125.7, c = 248.1 A. Four molecules comprise the asymmetric unit, and a self-rotation function indicates twofold local symmetry perpendicular to the unique axis and 15 degrees from a crystallographic twofold axis. Diffraction data to 3.0 A have been collected.

Journal Article↗
PubMed1996

The simultaneous analysis of patient, physician and group practice influences on annual mammography performance.

The current study examined the relationship of several variables at the patient (n = 2780), physician (n = 166), and group practice (n = 45) levels for predicting receipt of annual mammography screening. Patient-level variables included constructs from the Triandis Model of Choice; physician-level variables included measures of barriers and receptivity to prevention, as well as demographic information. Hierarchical modeling demonstrated that variables at the patient and physician level reliably predict annual mammography screening, while frequency of screening did not vary across group practices after accounting for patient and physician variables. Patient-level predictors included social norms, perceived consequences and perceived barriers. The only physician-level predictor identified was annual mammography recommendation. These findings add to data which emphasize the importance of public education and social support in health maintenance activities.

Aged↗
PubMed1996

Covalent activation of retinal rod cGMP-gated channels reveals a functional heterogeneity in the ligand binding sites.

Ion channels gated by the binding of multiple ligands play a critical role in synaptic transmission and sensory transduction. It has been difficult to resolve the contribution of individual binding events to channel gating because ligands are continuously binding and unbinding at each site. In examining the allosteric mechanism of retinal rod cGMP-gated channels, we have circumvented this problem by making use of a cGMP derivative, 8-p-azidophenacylthio-cGMP (APT-cGMP), that can be covalently tethered to the binding sites in the presence of long-wavelength UV light. In excised membrane patches, a population of channels was isolated that contained covalently-attached ligands at all but one site. Activation of these channels by cGMP revealed a previously unknown heterogeneity in the ligand-binding sites. The dose-response relations were much shallower than predicted by single-site activation models, but were well described by models in which there are two populations of sites, in roughly equal proportion, that bind cGMP with apparent affinities that differ by a factor of 25. The two apparent affinities, incorporated into a four-site model of the channel, provided an accurate description of the patch's original dose-response relation. A comparison of results on native and expressed channels suggests that the heterogeneity in the native channel arises at least in part from the presence of two different cGMP-binding subunits.

Ambystoma↗
PubMed1996

Resistance to aflatoxin contamination in corn as influenced by relative humidity and kernel germination.

Kernels of corn population GT-MAS:gk, resistant to aflatoxin B1 production by Aspergillus flavus, and susceptible Pioneer hybrid 3154 were tested for aflatoxin when incubated under different relative humidities (RH). High aflatoxin levels were not detected in either genotype at RH < 91%. Resistance in GT-MAS:gk was consistent across all RH levels (91 to 100%) at which significant aflatoxin accumulation was detected. Aflatoxin levels in GT-MAS:gk averaged about 98% less than those in susceptible Pioneer 3154, which suggests that storage of this or other genotypes with similar resistance mechanisms may be possible under moisture conditions less exacting than are required with susceptible hybrids. Results for fungus growth and sporulation ratings on kernel surfaces were similar to those for aflatoxin levels. When kernels of both genotypes were preincubated 3 days at 100% RH prior to inoculation with A. flavus, germination percentages increased to very high levels compared to those of kernels that were not preincubated. In preincubated kernels aflatoxin levels remained consistently low in GT-MAS:gk but decreased markedly (61%) in Pioneer 3154. When eight susceptible hybrids were evaluated for aflatoxin accumulation in preincubated kernels, seven of these supported significantly lower toxin levels than kernels not subjected to preincubation. Average reduction across hybrids was 83%, and reductions within hybrids ranged from 68 to 96%. Preincubated kernels of one susceptible hybrid (Deltapine G-4666) supported aflatoxin levels comparable to those in resistant GT-MAS: gk. Data suggest that an inhibitor of aflatoxin biosynthesis may be induced during kernel germination. Possible mechanisms for embryo effects on resistance to aflatoxin accumulation are discussed.

Aflatoxins↗
PubMed1996

Substance abuse among patients with chronic back pain.

BACKGROUND: Little is known about substance use and substance use disorders among primary care patients with chronic back pain. This study compared groups of patients with and without chronic back pain for the prevalence of substance use and substance use disorders. It also assessed the temporal relationship between the onset of chronic back pain and that of substance use disorders. METHODS: Adult patients aged 18 to 59 years who made three or more visits for back pain to a family practice clinic were eligible for the pain group. The comparison group consisted of a random sample of patients of the same ages who made appointments with the same clinic. A validated diagnostic interview about substance use disorders and other issues related to substance use was administered. RESULTS: Ninety-two percent of the patients in the chronic pain group reported severe pain, high disability, and severe to moderate limitation of activity. Two thirds (67%) of this group reported having continuous pain, and 21% experienced at least one episode of pain daily. Forty-four percent said their pain continously interfered with their activities, and 31% reported daily disruption of activity. There was little difference, however, in the adjusted rates of lifetime and current substance use disorders between the chronic pain and comparison groups. Lifetime prevalence rates were 54% for the pain group and 52% for the comparison group; current prevalence rates were 23% for both the pain and comparison groups. Substance abuse preceded the onset of pain by as much as 20 years for 77% of patients with chronic pain who had current substance use disorders and 63% of those who had lifetime substance use disorders. CONCLUSIONS: Chronic back pain did not connote special risk for current substance use disorders.

Adolescent↗