SummaryLignification of cell walls during plant development has been identified as the major factor limiting forage digestibility and concomitantly animal productivity. cDNA sequences encoding a key lignin biosynthetic enzyme, cinnamyl alcohol dehydrogenase (CAD), were cloned from the widely grown monocotyledonous forage species tall fescue ( Festuca arundinacea Schreb.). Recombinant tall fescue CAD expressed in E. coli exhibited the highest V max / K m values when coniferaldehyde and sinapaldehyde were used as substrates.Transgenic tall fescue plants carrying either sense or antisense CAD gene constructs were obtained by microprojectile bombardment of single genotype-derived embryogenic suspension cells. Severely reduced levels of mRNA transcripts and significantly reduced CAD enzymatic activities were found in two transgenic plants carrying sense and antisense CAD transgenes, respectively. These CAD down-regulated transgenic lines had significantly decreased lignin content and altered ratios of syringyl (S) to guaiacyl (G), G to p -hydroxyphenyl (H) and S to H units. No significant changes in cellulose, hemicellulose, neutral sugar composition, p -coumaric acid and ferulic acid levels were observed in the transgenic plants. Increases of in vitro dry matter digestibility of 7.2 -9.5% were achieved in the CAD down-regulated lines, thus providing a novel germplasm to be used for the development of grass cultivars with improved forage quality.

Dry matter digestibility is one of the most important characteristics of forage. The major constraint on ruminant digestion of forage cell walls is lignin. Sequences of cDNA encoding a key lignin biosynthetic enzyme, caffeic acid O-methyltransferase (COMT), was cloned from the widely grown monocot forage species tall fescue (Festuca arundinacea Schreb.). Enzymatic properties of recombinant COMT protein expressed in E. coli were determined using six substrates. The preferred substrates for tall fescue recombinant COMT were 5-hydroxyferulic acid and caffeoyl aldehyde. Transgenic tall fescue plants carrying either sense or antisense COMT gene constructs were obtained by microprojectile bombardment of single-genotype-derived embryogenic suspension cells. Consistent and closely related molecular and biochemical data demonstrated that two co-suppressed transgenic lines were down-regulated in their lignin biosynthesis. These COMT down-regulated transgenic tall fescue plants showed substantially reduced levels of transcripts, significantly reduced enzymatic activities, significantly decreased lignin content, apparently altered lignin composition and significantly increased (9.8-10.8%) digestibility.

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Eosinophilic esophagitis (EoE) is a chronic, immune-mediated inflammatory disease with incompletely understood pathogenesis. Though disease manifestations were initially ascribed to a delayed reaction to food allergens, emerging evidence suggests that modifiable host factors and environmental allergen exposure may also play critical roles in the pathogenesis and ongoing manifestations of EoE. As with other atopic diseases, lack of early-life exposure to microbial pathogens leads to an immune tolerance defect and reprograms the commensal gut microflora toward a type 2 T helper (Th2) phenotype; the esophageal microbiota, a rich environment consisting of diverse bacterial species, is greatly altered by inflammation. Although multiple early life microbiome-altering factors are associated with EoE development, no causative, direct relationships have been identified. Interestingly, large, cross-sectional analyses of several populations identify an inverse relationship between Helicobacter pylori presence and EoE, likely via virulence factors that downregulate Th2 inflammation, though causality has not been proven. In regard to environmental allergens, some studies support seasonal variation in EoE diagnosis and flares, and EoE can be generated after a large, identifiable aeroallergen exposure. Examples include mouse models of intranasal Aspergillus dosing and following initiation of oral immunotherapy to foods or environmental allergens. Conversely, treatment of allergic rhinoconjunctivitis may improve EoE symptoms, though data is limited to case reports and small series. Unfortunately, biologic therapies for atopic conditions have failed to improve EoE symptoms despite improvement in esophageal eosinophil count, though dupilumab shows promise in ongoing studies. Overall, this chapter shows that EoE pathogenesis is likely multifactorial, and the environment is a key component in our understanding of EoE.

Intervention in the home environment to reduce asthma triggers theoretically improves health outcomes for asthmatic children. Practical benefit from application of these interventions has proven difficult. This single-blind study tested the effectiveness of simple low-cost home interventions in improving health scores of children with asthma. Families with at least one asthmatic child were recruited. Initial health examination, health, and home assessments were conducted and targeted interventions were implemented. Interventions included dehumidification, air filtration, furnace servicing, and high-efficiency furnace filters. When present, gross fungal contamination was remediated. Asthma education was provided along with education in healthy home practices. Follow-up assessments were conducted after 6 months. Health surveys were completed at enrollment and follow-up. This study enrolled 219 children with asthma. Home inspections and interventions were conducted in 181 homes and 83 families completed all phases. Reduction in asthma and allergy-related health scores was shown in follow-up health surveys. Health improvements were significant for cough when heating, ventilation, and air conditioning (HVAC) service and dehumidification were used. Breathing problems were significantly improved for dehumidification, HVAC service, and room air cleaners. Total dust allergen load was reduced for the dehumidification group (p < 0.05). Mold spore counts were reduced one order of magnitude in 25% of the homes. Indoor spore counts adjusted for outdoor spore levels were reduced overall (p < 0.01). Simple low-cost interventions directed to producing cleaner indoor air coupled with healthy home education improve the indoor air quality and health in asthmatic children.

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