Activity and process stability of purified green pepper (Capsicum annuum) pectin methylesterase

Pectin methylesterase (PME) from green bell peppers (Capsicum annuum) was extracted and purified by affinity chromatography on a CNBr-Sepharose-PMEI column. A single protein peak with pectin methylesterase activity was observed. For the pepper PME, a biochemical characterization in terms of molar mass (MM), isoelectric points (pI), and kinetic parameters for activity and thermostability was performed. The optimum pH for PME activity at 22 degrees C was 7.5, and its optimum temperature at neutral pH was between 52.5 and 55.0 degrees C. The purified pepper PME required the presence of 0.13 M NaCl for optimum activity. Isothermal inactivation of purified pepper PME in 20 mM Tris buffer (pH 7.5) could be described by a fractional conversion model for lower temperatures (55-57 degrees C) and a biphasic model for higher temperatures (58-70 degrees C). The enzyme showed a stable behavior toward high-pressure/temperature treatments.     

Determination of hydrolyzable tannins (gallotannins and ellagitannins) after reaction with potassium iodate

A widely used method for analyzing hydrolyzable tannins afer reaction with KIO(3) has been modified to include a methanolysis step followed by oxidation with KIO(3). In the new method, hydrolyzable tannins (gallotannins and ellagitannins) are reacted at 85 degrees C for 20 h in methanol/sulfuric acid to quantitatively release methyl gallate. Dried plant samples can be methanolyzed under the same conditions to convert hydrolyzable tannins to methyl gallate. Oxidation of the methyl gallate by KIO(3) at pH 5.5, 30 degrees C, forms a chromophore with lambda(max) 525 nm, which is determined spectrophotometrically. The detection limit of the method is 1.5 microg of methyl gallate, and with plant samples, relative standard deviations of less than 3% were obtained.     

Correlations of stomatal conductance with hydraulic, chemical and environmental variables in five urban tree species

Recent findings suggest that stomatal conductance (g_s) may be as closely linked to plant chemical variables as to hydraulic variables. To test this in an urban field setting, we examined seasonal g_s in relation to a number of plant and environmental variables in five temperate, deciduous tree species. Stomatal conductance was generally more closely correlated with abscisic acid concentrations in xylem sap than with shoot water potential, shoot osmotic potential, pH of xylem sap or environmental variables. Seasonal g_s was mostly poorly correlated with shoot water potential and osmotic potential. Among environmental variables, PPFD accounted for most variability in g_s. We tested a model, developed previously in maize, that describes regulation of g_s by abscisic acid concentration of xylem sap with leaf water status acting to modify stomatal sensitivity to the abscisic acid signal. This model explained somewhat more variation in g_s than abscisic acid concentrations alone. Response surface models, especially those incorporating environmental variables, were most successful at explaining g_s. Our findings with urban trees are consistent with the theory of regulation of g_s by root-sourced abscisic acid.     

Diphenhydramine Intoxication in a Dog1

We report a case of diphenhydramine intoxication in a dog. A five month old intact male Labrador Retriever was presented after ingesting approximately 36 diphenhydramine tablets (50 mg/tablet; approximate ingested dose of 1800 mg or 67 mg/kg). Physical examination findings included severe ataxia, profound disorientation, severe continuous spastic muscle tremors, hyperthermia, tachycardia, tachypnea, and hyperesthesia. The dog was unresponsive to intravenous diazepam and phenobarbital, but rapidly responded to an intravenous bolus and subsequent continuous infusion of guaifenesin and supportive fluid therapy. The serum diphenhydramine level on admission was 537 ng/ml. The toxic level is not reported for dogs, but is considered>60 ng/ml in people. The dog was discharged 24 hours after admission with no apparent residual effects.     

Dens invaginatus of the mandibular first molars in a dog

A 6-year-old dog was presented for draining tracts associated with both mandibular first molar teeth. Radiographs of the affected teeth showed periapical bone lysis. Surgical tooth extractions were performed and the tooth segments were submitted for histopathologic examination. Microscopic evaluation of the teeth showed in folding of the enamel and dentin consistent with a diagnosis of dens invaginatus. Examination performed 13-months following the extraction procedures indicated uncomplicated healing at the extraction sites and no other visible evidence of endodontic disease.