Microdroplet In Vitro Fertilization Can Reduce the Number of Spermatozoa Necessary for Fertilizing Oocytes

Successful in vitro fertilization (IVF) in mice has been achieved using spermatozoa at concentrations specifically optimized for the experimental conditions, such as species and source of spermatozoa. Although IVF in mice is mostly performed using about 80–500 µl drops, it is expected that the number of spermatozoa used for insemination can be reduced by decreasing the size of the IVF drops. The present study was undertaken to examine the extent to which the number of spermatozoa used for IVF could be reduced by using small droplets (1 µl). We devised the experimental parameters using frozen–thawed spermatozoa from C57BL/6 mice in anticipation of broader applications to other mouse facilities. We found that as few as 5 spermatozoa per droplet could fertilize oocytes (1 or 3 oocytes per droplet), although the fertilization rates were low (13–15%). Practical fertilization rates (> 40%) could be achieved with frozen-thawed C57BL/6J spermatozoa, which are sensitive to cryopreservation, when 20 sperm per droplet were used to inseminate 3 oocytes. Even with spermatozoa from a very poor quality suspension (10% motility), about 25% of oocytes were fertilized. Our calculations indicate that the number of inseminated spermatozoa per oocyte can be reduced to 1/96–1/240 by this method. In two separate embryo transfer experiments, 60% and 47%, respectively, of embryos developed to term. Our microdroplet IVF method may be particularly advantageous when only a limited number of motile spermatozoa are available because of inadequate freezing-thawing or genetic reasons.     

Applicability of effective medium theory to wood density measurements using terahertz time-domain spectroscopy

The use of an effective medium theory is important when accurately measuring wood density using millimeter and terahertz wave techniques. To confirm the applicability of this theory to the evaluation of wood density, the relative permittivity and dielectric loss of oven-dry flat-sawn specimens of 11 different wood species were measured in a frequency range of 0.15–1.2 THz using a transmission measurement system for terahertz time-domain spectroscopy. A mixture model based on the effective medium theory well explained the density dependence of relative permittivity over the entire frequency range, while it did not fully explain that of dielectric loss, especially for higher frequencies. This indicates that wood scatters the terahertz wave with a wavelength close to the transverse sectional dimensions of the pores in wood in the same way as Mie scattering. It was found from the dielectric loss spectrum of wood substance that the frequency around 0.23 THz was preferable for the nondestructive evaluation of wood.     

Effect of pore conformation on dielectric anisotropy of oven-dry wood evaluated using terahertz time-domain spectroscopy and eigenvalue problems for two-dimensional photonic crystals

To clarify the effect of pore conformation on the dielectric anisotropy of wood, the relative permittivity along the longitudinal and tangential axes of flat-sawn oven-dry specimens of 12 different wood species was measured using terahertz time-domain transmission spectroscopy and compared with the values calculated using the eigenvalue problem for two-dimensional photonic crystals. The measured dielectric anisotropy, which is the ratio of the relative permittivity along longitudinal axis to that along the tangential axis, was well explained by the calculated value. It was concluded that the ratio of tangential to radial widths of wood pores affects the relative permittivity along the tangential axis, and that the dielectric anisotropy decreased with an increase in the ratio. This discussion can also be applied to the relative permittivity in frequencies below 0.15 THz. These findings show promise as a new method for evaluating the porous structure of wood.     

Purification and characterization of a corrinoid compound from Chlorella tablets as an algal health food

Vitamin B(12) content of an algal health food, Chlorella tablets (Chlorella sp.), was determined by both Lactobacillus leichmannii ATCC 7830 microbiological and intrinsic factor-chemiluminescence methods. The values of 200.9-211.6 microg/100 g dry weight determined by the chemiluminescence method were similar to the values (201.3-285.7 microg/100 g dry weight) determined by the microbiological method. A corrinoid compound was purified to homogeneity from the Chlorella tablets and characterized. The purified corrinoid compound was identified as vitamin B12, on the basis of silica gel 60 TLC, C18 reversed-phase HPLC, 1H NMR spectroscopy, and UV-Vis spectroscopy.     

Condensation of semiconductor microcavity exciton polaritons

A phase transition from a classical thermal mixed state to a quantum-mechanical pure state of exciton polaritons is observed in a GaAs multiple quantum-well microcavity from the decrease of the second-order coherence function. Supporting evidence is obtained from the observation of a nonlinear threshold behavior in the pump-intensity dependence of the emission, a polariton-like dispersion relation above threshold, and a decrease of the relaxation time into the lower polariton state. The condensation of microcavity exciton polaritons is confirmed.     

Characterization of corrinoid compounds from a Japanese black tea (Batabata-cha) fermented by bacteria

A Japanese fermented black tea (Batabata-cha) contained a considerable amount of vitamin B(12) (456 +/- 39 ng per 100 g dry tea leaves and 2.0 +/- 0.3 ng per 100 mL of tea drink). A corrinoid compound was partially purified and characterized from the tea leaves. The patterns of the purified compound by the silica gel 60 thin-layer chromatography and C18 reversed phased high-performance liquid chromatography were identical to those of authentic vitamin B(12). When 20 week old vitamin B(12) deficient rats, which excreted substantial amounts (about 250 mg/day) of methylmalonic acid in urine as an index of vitamin B(12) deficiency, were fed the tea drink (50 mL/day, 1 ng of vitamin B(12)) for 6 weeks, urinary methylmalonic acid excretion (169 +/- 29 mg/day) of the tea drink-supplemented 26 week old rats decreased significantly relative to that (250 +/- 32 mg/day) of the deficient rats. The results indicate that the vitamin B(12) found in the fermented black tea is bioavailable in mammals.     

Oxidative activation of O,S-dimethyl phosphoramidothiolate

O,S-Dimethyl phosphoramidothiolate, the insecticide methamidophos, is converted oxidatively into a potent anti-cholinesterase agent by the action of m-chloroperbenzoic acid. The active intermediate is not stable enough to be isolated. From some chemical evidence, the sulfoxide, i.e., dimethyl phosphoramidothiolate S-oxide, is most probably the active intermediate. A similar activation may occur by biological oxidation.