Vocal Parameters of Aerobic Instructors with and without Voice Problems

Aerobic instructors frequently experience vocal fatigue and are at risk for the development of vocal fold pathology. Six female aerobic instructors, three with self-reported voice problems and three without, served as subjects. Measures of vocal function (perturbation and EGG) were obtained before and after a 30-minute exercise session. Results showed that the group with self-reported voice problems had greater amounts of jitter, lower harmonic-to-noise ratios, and less periodicity in sustained vowels overall, but no significant differences in measures of perturbation and EGG were found before and immediately after instruction. Measures of vocal parameters showed that subjects with self-reported voice problems projected with relatively greater vocal intensity and phonated for a greater percentage of time across beginning, middle, and ending periods of aerobic instruction than subjects with no reported voice problems.     

Absolute Continuity for Unbounded Jacobi Matrices with Constant Row Sums

We investigate the spectral properties of a class of Jacobi matrices in which the subdiagonal entries are quadratics and the row sums are constants.     

Structural and Functional Changes in Catalase Induced by Near-UV Radiation

Part one of this study shows that exposure of purified beef liver catalase in buffered solutions to BL lamps that provide a mixture of 99% UVA and 1% UVB (to be labeled UV_A) alters its chemistry and enzymatic activity. Thus, its spectral absorbance lost detail, it aggregated and exhibited a lower isoelectric point and its enzymatic activity was substantially reduced. These photochemically induced changes were increased by irradiation in phosphate buffer or in physiological medium (minimal essential medium) containing riboflavin and tryptophan. Neither α-tocopherol nor de-feroxamine were protective against these UV_A-induced changes in pure catalase. We further investigated the effect of UV_A radiation on the activity of catalase in cultured lens epithelial cells and the protective effects of antioxidants. Cultured lens epithelial cells of rabbits and squirrels were exposed to near-UV radiation with representation in the UVA region of 99% and 1% UVB. Catalase assays were done on ho-mogenate supernatants of cells kept dark or UV exposed. In some instances, cells were cultured in medium containing a-tocopherol or deferoxamine prior to UV radiation. Comparisons were made between UV-exposed lens cell catalase activity when exposure was done with or without the antioxidants. The UV_A radiation was strongly inhibitory to both rabbit and squirrel lens epithelial cell catalase activities. The range of fluxes of near UV radiation was compatible with that which could reach the lens from the sunlit environment. Catalase inactivation was lessened in cells preincubated with a-tocopherol and deferoxamine. This suggests that both singlet oxygen and hydroxyl radical formation may be involved in near-UV damage to lens epithelial cell catalase. Such inhibition of catalase by near-UV would enhance H₂O₂ toxicity and stimulate SH oxidation so as to damage the lens.     

X-ray absorption spectroscopy of selenate reductase

The metal sites of selenate reductase from Thauera selenatis have been characterized by Mo, Se, and Fe K-edge X-ray absorption spectroscopy. The Mo site of the oxidized enzyme has 3 to 4 sulfur ligands at 2.33 A from two molybdopterin cofactors, one Mo=O group at 1.68 A and one Mo-O with an intermediate bond length of 1.81 A. The reduced enzyme has a des-oxo active site, again with about four Mo-S ligands (at 2.32 A) and possibly one oxygen ligand at 2.22 A. The enzyme was found to contain Se in a reduced form (probably organic) although the sequence does not indicate the presence of selenocysteine. The Se is coordinated to both a metal (probably Fe) and a lighter scatterer such as carbon.     

Modification of the<Emphasis Type="Italic"> Limulus</Emphasis> amebocyte lysate assay for the analysis of glucan in indoor environments

-1,3-d-Glucan is a biologically active component mainly from fungi that has been shown in several studies to be related to respiratory health outcomes from damp building exposures. Here, we report the development and application of a method for the analysis of the glucan extracted in 0.5 N NaOH solution making use of an available preparation of Limulus amebocyte lysate (LAL). The method yields reproducible -1,3-d-glucan measurements from samples of outdoor air, yeast cells, fungal spore preparations and ragweed pollen, and is more sensitive than competing measurements. The LAL-based measurement compared favourably to that based on size-exclusion chromatography using UV and refractive index detection. Growth conditions of the fungi did not materially change the concentrations of glucan in spores indicating that this is a stable property. Glucan content was proportional to spore surface area; however, some species contain higher relative spore glucan contents.     

Structural Investigations into the retro-Diels-Alder Reaction. Experimental and Theoretical Studies

The manifestations of the retro-Diels Alder reaction in the ground-state structures of a range of cyclopentadiene and cyclohexadiene cycloadducts 9-15 have been investigated by a combination of techniques. These include low-temperature X-ray crystallography, density functional calculations (B3LYP/6-31G(d,p)) on both the ground states and transition states, and the measurement of (13)C-(13)C coupling constants. We have found that the carbon-carbon bonds (labeled bonds a and b), which break in the rDA, are longer in the cycloadducts 9-15 than in their corresponding saturated analogues 9s-15s, which cannot undergo the rDA reaction. The degree of carbon-carbon bond lengthening appears to be related to the reactivity of the cycloadduct, thus the more reactive benzoquinone cycloadducts 5b and 13 have longer carbon-carbon bonds. Those cycloadducts 14 and 15 which are predicted to undergo asynchronous reactions show differing degrees of carbon-carbon bond lengthening, reflecting the differing degrees of bond breaking at the calculated transition states for the rDA.     

Determination of percentage of RoundUp Ready soya in soya flour using real-time polymerase chain reaction: interlaboratory study

An interlaboratory study was conducted to evaluate a method for determination of the percentage of RoundUp Ready (RR) soya in soya flour using Taqman technology. The method included DNA extraction from the test portion with cetyltrimethylammonium bromide buffer followed by chloroform extraction and Wizard resin cleanup steps. The DNA was then assayed with primer and probe sets specific for lectin as the endogenous control and the RR insert as the target. The percentage of RR soya in the soya fraction of the sample was calculated by using a matrix-matched standard curve. Ten samples of split-level blind duplicates were sent to 22 laboratories in 12 countries worldwide. Test portions contained 0, 0.5, 0.7,1.6, 2, and 3.9% (w/w) RR soya prepared gravimetrically from commercially available RR standard reference materials. Based on the results for test materials, the relative standard deviation for repeatability (RSDr) for the method ranged from 9.3 to 19.3% and, for reproducibility (RSDR), ranged from 20.3 to 33.7%.     

Underpotential deposition and anodic stripping voltammetry at mesoporous microelectrodes

Using the technique of liquid crystal templating a series of high surface area mesoporous platinum microelectrodes was fabricated. The underpotential deposition of metal ions at such electrodes was found to be similar to that at conventional platinum electrodes. The phenomena of underpotential deposition, in combination with the intrinsic properties of mesoporous microelectrodes (i.e. a high surface area and efficient mass transport) was exploited for the purpose of anodic stripping voltammetry. In particular the underpotential deposition of Ag(+), Pb(2+) and Cu(2+) ions was investigated and it was found that mesoporous microelectrodes were able to quantify the concentration of ions in solution down to the ppb range. The overall behaviour of the mesoporous electrodes was found to be superior to that of conventional microelectrodes and the effects of interference by surfactants were minimal.     

Liquid chromatographic/electrospray ionization mass spectrometric studies of proanthocyanidins in foods

The proanthocyanidins in three foods (pinto beans, plums and cinnamon) were studied with electrospray ionization (ESI) mass spectrometry (MS) in the negative mode following separation by normal-phase high-performance liquid chromatography. The MS/MS analysis demonstrated that the major ions derived from heterocyclic ring fission and retro-Diels-Alder reaction of flavan-3-ol provided information about the hydroxylation pattern and type of interflavan bond. The connection sequence of the oligomers was identified through diagnostic ions derived from quinone methide (QM) cleavage of the interflavan bond. Novel heterogeneous B-type proanthocyanidins containing (epi)afzelechin as subunits were identified in pinto beans. Proanthocyanidins with interestingly different A-type linkages were identified in plums and cinnamon. In efforts aimed at extending the identification capacity of ESI-MS to polymers, we found that the polymeric procyanidins fragmented readily instead of forming multiply charged ions in the negative ESI mode. Fragmentation patterns were proposed based on our data obtained by ESI-MS/MS and ESI time-of-flight MS.     

Comparison of crude extract from durio zibethinus M. (durian) leaf waste via ultrasound-assisted extraction and accelerated solvent extraction: antioxidant activity and cytotoxicity

Abstract

The objective of this study was to compare the antioxidant activity and cytotoxicity of Durio zibethinus M. (Durian) leaf extract from two extraction methods. Ultrasound-assisted extraction and Accelerated-solvent extraction were used to produce crude extract. The results revealed that UAE achieved 3× higher in total phenolic content in the leaf extract compared to ASE. DPPH radical scavenging activity was 4.6× higher in leaf extract from ASE. No significant differences reported in ferric reducing power, and total flavonoid content of the leaf extract between the two methods. Cytotoxicity via MTT assay demonstrated no significant differences in cell viability upon exposure to the leaf extract from both methods. This suggested that they were appropriate in producing Durio zibethinus M. leaf extract for end use application in food related product. Both ensured similar level of safety in Durio zibethinus M. leaf extract as a new potential ingredient for the food industry.