Influence of host phylogeny and water physicochemistry on microbial assemblages of the fish skin microbiome.

The skin of fish contains a diverse microbiota that has symbiotic functions with the host, facilitating pathogen exclusion, immune system priming, and nutrient degradation. The composition of fish skin microbiomes varies across species and in response to a variety of stressors, however, there has been no systematic analysis across these studies to evaluate how these factors shape fish skin microbiomes. Here, we examined 1922 fish skin microbiomes from 36 studies that included 98 species and nine rearing conditions to investigate associations between fish skin microbiome, fish species, and water physiochemical factors. Proteobacteria, particularly the class Gammaproteobacteria, were present in all marine and freshwater fish skin microbiomes. Acinetobacter, Aeromonas, Ralstonia, Sphingomonas and Flavobacterium were the most abundant genera within freshwater fish skin microbiomes, and Alteromonas, Photobacterium, Pseudoalteromonas, Psychrobacter and Vibrio were the most abundant in saltwater fish. Our results show that different culturing (rearing) environments have a small but significant effect on the skin bacterial community compositions. Water temperature, pH, dissolved oxygen concentration, and salinity significantly correlated with differences in beta-diversity but not necessarily alpha-diversity. To improve study comparability on fish skin microbiomes, we provide recommendations for approaches to the analyses of sequencing data and improve study reproducibility.

Novel pelagiphage isolate Polarivirus skadi is a polar specialist that dominates SAR11-associated bacteriophage communities at high latitudes.

The SAR11 clade are the most abundant members of surface marine bacterioplankton and a critical component of global biogeochemical cycles. Similarly, pelagiphages that infect SAR11 are ubiquitous and highly abundant in the oceans. Pelagiphages are predicted to shape SAR11 community structures and increase carbon turnover throughout the oceans. Yet, ecological drivers of host and niche specificity of pelagiphage populations are poorly understood. Here we report the global distribution of a novel pelagiphage called "Polarivirus skadi", which is the sole representative of a novel genus. P. skadi was isolated from the Western English Channel using a cold-water ecotype of SAR11 as bait. P. skadi is closely related to the globally dominant pelagiphage HTVC010P. Along with other HTVC010P-type viruses, P. skadi belongs to a distinct viral family within the order Caudovirales, for which we propose the name Ubiqueviridae. Metagenomic read recruitment identified P. skadi as one of the most abundant pelagiphages on Earth. P. skadi is a polar specialist, replacing HTVC010P at high latitudes. Experimental evaluation of P. skadi host range against cold- and warm-water SAR11 ecotypes supported cold-water specialism. Relative abundance of P. skadi in marine metagenomes correlated negatively with temperature, and positively with nutrients, available oxygen, and chlorophyll concentrations. In contrast, relative abundance of HTVC010P correlated negatively with oxygen and positively with salinity, with no significant correlation to temperature. The majority of other pelagiphages were scarce in most marine provinces, with a few representatives constrained to discrete ecological niches. Our results suggest that pelagiphage populations persist within a global viral seed bank, with environmental parameters and host availability selecting for a few ecotypes that dominate ocean viromes.

Increased Expression of the Δ133p53ß Isoform Enhances Brain Metastasis.

The Δ133p53ß isoform is increased in many primary tumors and has many tumor-promoting properties that contribute to increased proliferation, migration and inflammation. Here we investigated whether Δ133p53ß contributed to some of the most aggressive tumors that had metastasized to the brain. Δ133p53ß mRNA expression was measured in lung, breast, melanoma, colorectal metastases and, where available, the matched primary tumor. The presence of Δ133p53ß expression was associated with the time for the primary tumor to metastasize and overall survival once the tumor was detected in the brain. Δ133p53ß was present in over 50% of lung, breast, melanoma and colorectal metastases to the brain. It was also increased in the brain metastases compared with the matched primary tumor. Brain metastases with Δ133p53ß expressed were associated with a reduced time for the primary tumor to metastasize to the brain compared with tumors with no Δ133p53ß expression. In-vitro-based analyses in Δ133p53ß-expressing cells showed increased cancer-promoting proteins on the cell surface and increased downstream p-AKT and p-MAPK signaling. Δ133p53ß-expressing cells also invaded more readily across a mock blood-brain barrier. Together these data suggested that Δ133p53ß contributes to brain metastases by making cells more likely to invade the brain.

Chemotherapy in Pregnancy: Assessing the Safety of Adriamycin Administration in Pregnancy Complicated by Breast Cancer.

Pregnancy-associated breast cancer is challenging to treat. Treatment with chemotherapeutic agents such as anthracyclines poses a risk of cardiotoxicity, despite being considered safe after the second trimester of pregnancy. Management requires multidisciplinary comanagement with cardio-obstetrics, cardiology-oncology, maternal-fetal medicine, and oncology.

Multi-Institutional Physician Assistant Student Perception of Simulated Emergency Room Cases.

INTRODUCTION: During clinical experiences, physician assistant (PA) students are required to participate in the management of multiple patients simultaneously. One method of preparing students for clinical experiences is through the use of simulation. Simulation allows development of decision-making and teamwork skills. 1,2 A previous study of nursing students in a multiple-patient simulation demonstrated improved student readiness to care for multiple patients. 2 The present study evaluated the effect of using simulation on PA student comfort with managing multiple patients in an emergency room setting. METHODS: Four PA programs participated in this quasi-experimental pretest-posttest design. Four simulation days were held, each with 4 standardized cases. Half of the students acted as standardized patients, while the remainder of the students managed patients in small groups. Surveys were administered before and after the emergency medicine course. Descriptive statistics and statistical analysis for significance were performed using Excel and SPSS. RESULTS: Posttest results indicated significant improvement in student confidence in emergency scenarios, ability to perform a focused medical history, ability to choose and interpret laboratory values, time management, prioritizing patients in a simulated environment, and selecting appropriate treatment. Students reported satisfaction with the experience, feedback, and debriefing. Participation in these simulations increased student interest in pursuing a position in emergency medicine upon graduation. DISCUSSION: In clinical rotations, PA students are expected to manage multiple patients with a variety of conditions. In this study, students were initially uncomfortable managing multiple patients. Student comfort increased after a simulation experience. Increased opportunities for students to select appropriate diagnostics and treatment may increase their overall comfort in management of patients during rotations.

Antimicrobial Resistance in Aquaculture Environments: Unravelling the Complexity and Connectivity of the Underlying Societal Drivers.

Food production environments in low- and middle-income countries (LMICs) are recognized as posing significant and increasing risks to antimicrobial resistance (AMR), one of the greatest threats to global public health and food security systems. In order to maximize and expedite action in mitigating AMR, the World Bank and AMR Global Leaders Group have recommended that AMR is integrated into wider sustainable development strategies. Thus, there is an urgent need for tools to support decision makers in unravelling the complex social and environmental factors driving AMR in LMIC food-producing environments and in demonstrating meaningful connectivity with other sustainable development issues. Here, we applied the Driver-Pressure-State-Impact-Response (DPSIR) conceptual framework to an aquaculture case study site in rural Bangladesh, through the analysis of distinct social, microbiological, and metagenomic data sets. We show how the DPSIR framework supports the integration of these diverse data sets, first to systematically characterize the complex network of societal drivers of AMR in these environments and second to delineate the connectivity between AMR and wider sustainable development issues. Our study illustrates the complexity and challenges of addressing AMR in rural aquaculture environments and supports efforts to implement global policy aimed at mitigating AMR in aquaculture and other rural LMIC food-producing environments.

High-Throughput, Quantitative Analysis of Peptide-Exchanged MHCI Complexes by Native Mass Spectrometry.

Immune monitoring in cancer immunotherapy involves screening CD8+ T-cell responses against neoantigens, the tumor-specific peptides presented by Major histocompatibility complex Class I (MHCI) on the cell surface. High-throughput immune monitoring requires methods to produce and characterize small quantities of thousands of MHCI-peptide complexes that may be tested for a patient's T-cell response. MHCI synthesis has been achieved using a photocleavable peptide that is exchanged by the neoantigen; however, assays that measure peptide exchange currently disassemble the complex prior to analysis─precluding direct molecular characterization. Here, we use native mass spectrometry (MS) to profile intact recombinant MHCI complexes and directly measure peptide exchange. Coupled with size-exclusion chromatography or capillary-zone electrophoresis, the assay identified all tested human leukocyte antigen (HLA)/peptide combinations in the nanomole to picomole range with minimal run time, reconciling the synthetic and analytical requirements of MHCI-peptide screening with the downstream T-cell assays. We further show that the assay can be "multiplexed" by measuring exchange of multiple peptides simultaneously and also enables calculation of Vc50, a measure of gas-phase stability. Additionally, MHCI complexes were fragmented by top-down sequencing, demonstrating that the intact complex, peptide sequence, and their binding affinity can be determined in a single analysis. This screening tool for MHCI-neoantigen complexes represents a step toward the application of state-of-the-art MS technology in translational settings. Not only is this assay already informing on the viability of immunotherapy in practice, the platform also holds promise to inspire novel MS readouts for increasingly complex biomolecules used in the diagnosis and treatment of disease.

Reduced Sexual Desire in Young Norwegian Women: A Mixed-Methods Study.

Sexuality has become an area of social competence in which individuals strive to be recognized as sexually competent performers. However, a large proportion of young women experience reduced sexual desire. In this study, both quantitative and qualitative methods were applied. Using data from a questionnaire, the aim of this study was to explore the prevalence of, and the factors associated with, lack of sexual interest and desire among young women in Norway. Further, with the help of in-depth interviews, we investigated how young women with reduced sexual desire experience living with their desire problems and what they experience as the cause of their problems. The sample in the quantitative study consisted of 505 Norwegian women between the ages of 18 and 29 years. ANOVA was employed to explore differences in scores on psychological factors and relational factors, as well as between participants who experienced a lack of sexual interest and desire, and those who did not. The results indicate a high prevalence of lack of sexual interest and desire among women (37.1%), while low appearance satisfaction and low relationship satisfaction were central predictors of lack of sexual interest and desire. The sample in the qualitative study consisted of ten Norwegian women with reduced sexual desire between the ages of 18 and 29 years. Through thematic analysis, four themes emerged as experiences of living with reduced sexual desire: (1) physical and mental health, (2) being a young woman in today's society, (3) relational factors, (4) negative experiences, personal expectations toward sexuality, and sexual trauma.

A Novel and Ubiquitous Marine Methylophage Provides Insights into Viral-Host Coevolution and Possible Host-Range Expansion in Streamlined Marine Heterotrophic Bacteria.

The methylotrophic OM43 clade are Gammaproteobacteria that comprise some of the smallest free-living cells known and have highly streamlined genomes. OM43 represents an important microbial link between marine primary production and remineralization of carbon back to the atmosphere. Bacteriophages shape microbial communities and are major drivers of mortality and global marine biogeochemistry. Recent cultivation efforts have brought the first viruses infecting members of the OM43 clade into culture. Here, we characterize a novel myophage infecting OM43 called Melnitz. Melnitz was isolated independently from water samples from a subtropical ocean gyre (Sargasso Sea) and temperate coastal (Western English Channel) systems. Metagenomic recruitment from global ocean viromes confirmed that Melnitz is globally ubiquitous, congruent with patterns of host abundance. Bacteria with streamlined genomes such as OM43 and the globally dominant SAR11 clade use riboswitches as an efficient method to regulate metabolism. Melnitz encodes a two-piece tmRNA (ssrA), controlled by a glutamine riboswitch, providing evidence that riboswitch use also occurs for regulation during phage infection of streamlined heterotrophs. Virally encoded tRNAs and ssrA found in Melnitz were phylogenetically more closely related to those found within the alphaproteobacterial SAR11 clade and their associated myophages than those within their gammaproteobacterial hosts. This suggests the possibility of an ancestral host transition event between SAR11 and OM43. Melnitz and a related myophage that infects SAR11 were unable to infect hosts of the SAR11 and OM43, respectively, suggesting host transition rather than a broadening of host range. IMPORTANCE Isolation and cultivation of viruses are the foundations on which the mechanistic understanding of virus-host interactions and parameterization of bioinformatic tools for viral ecology are based. This study isolated and characterized the first myophage known to infect the OM43 clade, expanding our knowledge of this understudied group of microbes. The nearly identical genomes of four strains of Melnitz isolated from different marine provinces and the global abundance estimations from metagenomic data suggest that this viral population is globally ubiquitous. Genome analysis revealed several unusual features in Melnitz and related genomes recovered from viromes, such as a curli operon and virally encoded tmRNA controlled by a glutamine riboswitch, neither of which are found in the host. Further phylogenetic analysis of shared genes indicates that this group of viruses infecting the gammaproteobacterial OM43 shares a recent common ancestor with viruses infecting the abundant alphaproteobacterial SAR11 clade. Host ranges are affected by compatible cell surface receptors, successful circumvention of superinfection exclusion systems, and the presence of required accessory proteins, which typically limits phages to singular narrow groups of closely related bacterial hosts. This study provides intriguing evidence that for streamlined heterotrophic bacteria, virus-host transitioning may not be necessarily restricted to phylogenetically related hosts but is a function of shared physical and biochemical properties of the cell.

Diagnostic and economic evaluation of a point-of-care test for respiratory syncytial virus.

Respiratory syncytial virus is a common cause of bronchiolitis. Historically, point-of-care tests have involved antigen detection technology with limited sensitivity. The aim of this study was to prospectively evaluate the diagnostic accuracy and model the economic impact of the Roche cobas® Liat® point-of-care influenza A/B and respiratory syncytial virus test. The "DEC-RSV" study was a multi-centre, prospective, observational study in children under 2 years presenting with viral respiratory symptoms. A nasopharyngeal aspirate sample was tested using the point-of-care test and standard laboratory-based procedures. The primary outcome was accuracy of respiratory syncytial virus detection. The cost implications of adopting a point-of-care test were modelled using study data. A total of 186 participants were recruited, with both tests performed on 177 samples. The point-of-care test was invalid for 16 samples (diagnostic yield 91%) leaving 161 available for primary analysis. After resolving discrepancies, the cobas® Liat® respiratory syncytial virus test had 100.00% (95% CI 96.07%-100.00%) sensitivity and 98.53% (95% CI 92.08%-99.96%) specificity. Median time to result was 0.6 h (interquartile range (IQR) 0.5-1) for point-of-care testing and 28.9 h (IQR 26.3-48.1) for standard laboratory testing. Estimated non-diagnostic cost savings for 1000 patients, based on isolation decision-making on point-of-care test result, were £57 010, which would increase to £94 847 when cohort nursing is used. In young children the cobas® Liat® point-of-care respiratory syncytial virus test has high diagnostic accuracy using nasopharyngeal aspirates (currently an off-licence sample type). Time to result is clinically important and was favourable compared to laboratory-based testing. The potential exists for cost savings when adopting the point-of-care test.

Human Papillomavirus E6/E7 Expression in Preeclampsia-Affected Placentae.

Whether HPV is causative of pregnancy complications is uncertain. E6 and E7 affect functions underling preeclampsia (PET) in cultured trophoblasts, but whether E6 and E7 is produced in the placenta is uncertain. Here, we investigated whether E6/E7 was expressed in the placentae from pregnancies with PET, other pregnancy complications (fetal growth restriction (FGR) and diabetes mellitus), and uncomplicated pregnancies. Placental tissues collected from two geographical locations were subjected to RNAscope analyses of high- and low- risk E6/E7, and individual HPV types identified using an HPV array. High-risk E6/E7 expression was increased in both PET cohorts, (81% and 86% of patients positive for high-risk HPV DNA compared to 13% of control patients). Various HPV types were identified. Although HPV 18 was the most frequent in all cohorts, the majority of individuals had multiple HPV types (55% of the PET compared to 25% of the control cohort). Further evidence that E6 and E7 is present early when placental pathology underlying preeclampsia is established, is provided with the finding of high-risk E6/E7 in the first-trimester placenta anchoring trophoblast. In conclusion, E6/E7 expression and multiple HPV types were frequent in placentae from preeclampsia-complicated pregnancies.

The Δ133p53ß isoform promotes an immunosuppressive environment leading to aggressive prostate cancer.

Prostate cancer is the second most common cancer in men, for which there are no reliable biomarkers or targeted therapies. Here we demonstrate that elevated levels of Δ133TP53ß isoform characterize prostate cancers with immune cell infiltration, particularly T cells and CD163+ macrophages. These cancers are associated with shorter progression-free survival, Gleason scores ≥ 7, and an immunosuppressive environment defined by a higher proportion of PD-1, PD-L1 and colony-stimulating factor 1 receptor (CSF1R) positive cells. Consistent with this, RNA-seq of tumours showed enrichment for pathways associated with immune signalling and cell migration. We further show a role for hypoxia and wild-type p53 in upregulating Δ133TP53 levels. Finally, AUC analysis showed that Δ133TP53ß expression level alone predicted aggressive disease with 88% accuracy. Our data identify Δ133TP53ß as a highly accurate prognostic factor for aggressive prostate cancer.

Self-reported Patient Motivations for Seeking Cosmetic Procedures.

Importance: Despite the growing popularity of cosmetic procedures, the sociocultural and quality-of-life factors that motivate patients to undergo such procedures are not well understood. Objective: To estimate the relative importance of factors that motivate patients to seek minimally invasive cosmetic procedures. Design, Setting, and Participants: This prospective, multicenter observational study was performed at 2 academic and 11 private dermatology practice sites that represented all US geographic regions. Adult patients presenting for cosmetic consultation or treatment from December 4, 2016, through August 9, 2017, were eligible for participation. Exposures: Participants completed a survey instrument based on a recently developed subjective framework of motivations and a demographic questionnaire. Main Outcomes and Measures: Primary outcomes were the self-reported most common motivations in each quality-of-life category. Secondary outcomes were other frequently reported motivations and those associated with specific procedures. Results: Of 529 eligible patients, 511 agreed to participate, were enrolled, and completed the survey. Typical respondents were female (440 [86.1%]), 45 years or older (286 [56.0%]), white (386 [75.5%]), and college educated (469 [91.8%]) and had previously received at least 2 cosmetic procedures (270 [52.8%]). Apart from motivations pertaining to aesthetic appearance, including the desire for beautiful skin and a youthful, attractive appearance, motives related to physical health, such as preventing worsening of condition or symptoms (253 of 475 [53.3%]), and psychosocial well-being, such as the desire to feel happier and more confident or improve total quality of life (314 of 467 [67.2%]), treat oneself or celebrate (284 of 463 [61.3%]), and look good professionally (261 of 476 [54.8%]) were commonly reported. Motivations related to cost and convenience were rated as less important (68 of 483 [14.1%]). Most motivations were internally generated, designed to please the patients and not others, with patients making the decision to undergo cosmetic procedures themselves and spouses seldom being influential. Patients younger than 45 years were more likely to undertake procedures to prevent aging (54 of 212 [25.5%] vs 42 of 286 [14.7%] among patients ≥45 years; P < .001). Patients seeking certain procedures, such as body contouring (19 of 22 [86.4%]), acne scar treatment (36 of 42 [85.7%]), and tattoo removal (8 of 11 [72.7%]), were more likely to report psychological and emotional motivations. Conclusions and Relevance: This initial prospective, multicenter study comprehensively assessed why patients seek minimally invasive cosmetic procedures. Common reasons included emotional, psychological, and practical motivations in addition to the desire to enhance physical appearance. Differences relative to patient age and procedures sought may need further exploration.

Process Improvement to Enhance Quality in a Large Volume Labor and Birth Unit.

BACKGROUND: The goal of the perinatal team at Mercy Hospital St. Louis is to provide a quality patient experience during labor and birth. After the move to a new labor and birth unit in 2013, the team recognized many of the routines and practices needed to be modified based on different demands. METHODS: The Lean process was used to plan and implement required changes. This technique was chosen because it is based on feedback from clinicians, teamwork, strategizing, and immediate evaluation and implementation of common sense solutions. Through rapid improvement events, presence of leaders in the work environment, and daily huddles, team member engagement and communication were enhanced. The process allowed for team members to offer ideas, test these ideas, and evaluate results, all within a rapid time frame. For 9 months, frontline clinicians met monthly for a weeklong rapid improvement event to create better experiences for childbearing women and those who provide their care, using Lean concepts. At the end of each week, an implementation plan and metrics were developed to help ensure sustainment. The issues that were the focus of these process improvements included on-time initiation of scheduled cases such as induction of labor and cesarean birth, timely and efficient assessment and triage disposition, postanesthesia care and immediate newborn care completed within approximately 2 hours, transfer from the labor unit to the mother baby unit, and emergency transfers to the main operating room and intensive care unit. RESULTS: On-time case initiation for labor induction and cesarean birth improved, length of stay in obstetric triage decreased, postanesthesia recovery care was reorganized to be completed within the expected 2-hour standard time frame, and emergency transfers to the main hospital operating room and intensive care units were standardized and enhanced for efficiency and safety. Participants were pleased with the process improvements and quality outcomes. CLINICAL IMPLICATIONS: Working together as a team using the Lean process, frontline clinicians identified areas that needed improvement, developed and implemented successful strategies that addressed each gap, and enhanced the quality and safety of care for a large volume perinatal service.

Liquid infused porous surfaces for mineral fouling mitigation.

Prevention of mineral fouling, known as scale, is a long-standing problem in a wide variety of industrial applications, such as oil production, water treatment, and many others. The build-up of inorganic scale such as calcium carbonate on surfaces and facilities is undesirable as it can result in safety risks and associated flow assurance issues. To date the overwhelming amount of research has mainly focused on chemical inhibition of scale bulk precipitation and little attention has been paid to deposition onto surfaces. The development of novel more environmentally-friendly strategies to control mineral fouling will most probably necessitate a multifunctional approach including surface engineering. In this study, we demonstrate that liquid infused porous surfaces provide an appealing strategy for surface modification to reduce mineral scale deposition. Microporous polypyrrole (PPy) coatings were fabricated onto stainless steel substrates by electrodeposition in potentiostatic mode. Subsequent infusion of low surface energy lubricants (fluorinated oil Fluorinert FC-70 and ionic liquid 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm)) into the porous coatings results in liquid-repellent slippery surfaces. To assess their ability to reduce surface scaling the coatings were subjected to a calcium carbonate scaling environment and the scale on the surface was quantified using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). PPy surfaces infused with BMIm (and Fluorinert to a lesser extent) exhibit remarkable antifouling properties with the calcium carbonate deposition reduced by 18 times in comparison to untreated stainless steel. These scaling tests suggest a correlation between the stability of the liquid infused surfaces in artificial brines and fouling reduction efficiency. The current work shows the great potential of such novel coatings for the management of mineral scale fouling.

Essential amino acids regulate both initiation and elongation of mRNA translation independent of insulin in MAC-T cells and bovine mammary tissue slices.

Current nutrient requirement models assume fixed efficiencies of absorbed amino acid (AA) conversion to milk protein. Regulation of mammary protein synthesis (PS) potentially violates this assumption by changing the relationship between AA supply and milk protein output. The objective of this study was to investigate the effects of essential AA (EAA) and insulin on cellular signaling and PS rates in bovine mammary cells. MAC-T cells were subjected to 0 or 100% of normal EAA concentrations in DMEM/F12 and 0 or 100 µg insulin/L in a 2 × 2 factorial arrangement of treatments. Lactogenic bovine mammary tissue slices (MTS) were subjected to the same treatments, except low-EAA was 5% of normal DMEM/F12 concentrations. In MAC-T cells, EAA increased phosphorylation of mammalian target of rapamycin (mTOR; Ser2448), ribosomal protein S6 kinase 1 (S6K1; Thr389), eIF4E binding protein 1 (4EBP1; Thr37/46), and insulin receptor substrate 1 (IRS1; Ser1101), and reduced phosphorylation of eukaryotic elongation factor 2 (eEF2; Thr56) and eukaryotic initiation factor (eIF) 2-α (Ser51). In the presence of insulin, phosphorylation of Akt (Ser473), mTOR, S6K1, 4EBP1, and IRS1 increased in MAC-T cells. In MTS, EAA had similar effects on phosphorylation of signaling proteins and increased mammary PS rates. Insulin did not affect MTS signaling, perhaps due to inadequate levels. Effects of EAA and insulin were independent and additive for mTOR signaling in MAC-T cells. EAA did not inhibit insulin stimulation of Akt phosphorylation. PS rates were strongly associated with phosphorylation of 4EBP1 and eEF2 in MTS. EAA availability affected translation initiation and elongation control points to more strongly regulate PS than insulin.

Cross-linking by protein oxidation in the rapidly setting gel-based glues of slugs.

The terrestrial slug Arion subfuscus secretes a glue that is a dilute gel with remarkable adhesive and cohesive strength. The function of this glue depends on metals, raising the possibility that metal-catalyzed oxidation plays a role. The extent and time course of protein oxidation was measured by immunoblotting to detect the resulting carbonyl groups. Several proteins, particularly one with a relative molecular mass (M(r)) of 165 x 10³, were heavily oxidized. Of the proteins known to distinguish the glue from non-adhesive mucus, only specific size variants were oxidized. The oxidation appears to occur within the first few seconds of secretion. Although carbonyls were detected by 2,4-dinitrophenylhydrazine (DNPH) in denatured proteins, they were not easily detected in the native state. The presence of reversible cross-links derived from carbonyls was tested for by treatment with sodium borohydride, which would reduce uncross-linked carbonyls to alcohols, but stabilize imine bonds formed by carbonyls and thus lead to less soluble complexes. Consistent with imine bond formation, sodium borohydride led to a 20-35% decrease in the amount of soluble protein with a M(r) of 40-165 (x 10³) without changing the carbonyl content per protein. In contrast, the nucleophile hydroxylamine, which would competitively disrupt imine bonds, increased protein solubility in the glue. Finally, the primary amine groups on a protein with a M(r) of 15 x 10³ were not accessible to acid anhydrides. The results suggest that cross-links between aldehydes and primary amines contribute to the cohesive strength of the glue.

Effects of Chitin and Chitosan on the Incidence and Severity of Fusarium Yellows of Celery.

The effects of chitin and chitosan on disease incidence and severity of Fusarium yellows of celery and on populations of Fusarium oxysporum were investigated between 1994 and 1996. Field experiments were conducted at two locations with a history of severe Fusarium yellows. Disease incidence and severity were significantly reduced by pre-plant chitin amendments to soil. Chitosan applied as a root dip alone did not reduce disease incidence but significantly (P < 0.05) reduced disease severity when used with a tolerant celery cultivar. Standard soil dilution methods were used to enumerate populations of soil microflora. Chitin increased bacterial and actinomycete populations in soil in 2 of the 3 years of study. The effects of potential biocontrol agents recovered from chitin-treated plots in 1995 were studied in 1996; enriching the transplant medium with isolates of bacteria and actinomycetes 4 weeks and 1 week prior to transplanting did not alter the established equilibrium in the field, and no biocontrol effect was observed. Chitin amendments to soil or chitosan treatment of transplants did not reduce soil populations of F. oxysporum. Whether these treatments affected the F. oxysporum f. sp. apii subpopulation within the F. oxysporum population could not be determined.