Synchronization of masseter activity patterns between the right and left sides during chewing in healthy young males.

Masseter activity patterns during chewing, which were quantitatively assessed using T50 values, were compared between the right and left sides of healthy young males. Surface electromyograms were recorded from both masseters, and each participant was asked to chew four different agar samples at his own pace across two separate sessions. The four agar samples, each possessing differing textural properties, consisted of two normal and two distinctive agar varieties. The Pearson's correlation coefficient was calculated for each pair of T50 values to evaluate the degree of synchronization of activity patterns between both masseters. A three-way analysis of variance revealed significant main effects of the 'participant' and 'experimental session' factors, but not of the 'test food'. The number of significant coefficients increased stepwise by increasing the number of chews per sequence. These results suggest the importance of the initial stages of chewing sequences in facilitating the synchronization of bilateral masseter activity patterns.

Sequential analysis of masseter activity patterns during chewing in healthy males.

The present study examined sequential changes in masseter activity patterns observed during chewing of four different agar samples in eight healthy young males. Two parameters, T(50) and D(50), were specifically used for evaluation of the activity patterns of individual bursts. Statistical significances were detected in regression coefficients (21.9% of 32 trials) and Spearman's rank correlation coefficients (28.1%) between the calculated T(50) values and chewing cycles, whereas no significant differences among the four agar samples were found. Three (I-III) types of activity patterns of masseter bursts during chewing sequences were classified by the D(50) values, which were derived from the T(50) values. The three types physiologically corresponded to incrementing (Type I), decrementing (Type III) and mixed discharge patterns (Type II). The classification of activity patterns suggested the usefulness of D(50) values in the sequential analysis of masseter activity patterns.

Changes in the amount of cytoplasmic inclusions in mouse oocytes during meiotic maturation in vivo and in vitro.

Background and aims: The changes in cytoplasmic inclusions during meiotic maturation have only been examined in porcine oocytes. In the present study, the amount and the number of cytoplasmic inclusions (glycogen granules, lipid droplets and fibrous structures) were examined in mouse oocytes in the process of in vivo and in vitro maturation. For those inclusions that changed in amount during maturation, we also examined their content in oocytes treated with olomoucine, an inhibitor of cyclin-dependent kinase, in order to clarify the relationship between nuclear maturation and changes in the inclusions. Methods: Nuclear maturation in the oocytes cultured for various periods and those collected from antral follicles and oviducts was examined after staining with aceto-orcein. For the demonstration of glycogen granules and lipid droplets, oocytes were stained with periodic acid-Schiff or Sudan IV. Fibrous structures in the oocytes were observed under an electron microscope. Results: The amount of glycogen granules, Sudanophilic lipid droplets and fibrous structures did not change in the oocytes matured in vivo and in vitro, whereas the number of the lipid droplets increased during maturation. In the oocytes treated with olomoucine, the resumption of nuclear maturation was inhibited, whereas the increase in the number of Sudanophilic lipid droplets was not inhibited. Conclusion: Present findings suggest that the increase in the number of Sudanophilic lipid droplets occurs in the cytoplasm of mouse oocytes during maturation, regardless of in vivo or in vitro maturation, and that such the change in the inclusion is not related to nuclear maturation. (Reprod Med Biol 2004; 3: 231-236).

Changes in the activities of hydroxysteroid dehydrogenases in mouse oocytes during meiotic maturation.

The activities of hydroxysteroid dehydrogenases (HSDs) were histochemically demonstrated in mouse oocytes in the process of maturation in vivo and in vitro, and the changes in steroid metabolism during meiotic maturation and also the relationship between nuclear maturation and changes in steroid metabolism in the cytoplasm were examined. In mouse oocytes 0 h after human chorionic gonadotrophin (hCG) injection, the activities of Delta(5)-3beta-HSD (with DHA, pregnenolone and 17alpha-hydroxypregnenolone as the substrates), 17beta-HSD (estradiol-17beta and testosterone) and 20beta-HSD (17alpha-hydroxyprogesterone and 20beta-hydroxyprogesterone) were observed in 87 to 97% of those, but that of 20alpha-HSD (20alpha-hydroxyprogesterone) was not. The percentages of oocytes showing the activities of Delta(5)-3beta-HSD, 17beta-HSD and 20beta-HSD did not change during maturation in vivo or in vitro. Oocytes with 20alpha-HSD activity appeared 4 h after the hCG injection or after culture for 4 h and the rates of those reached 92 and 100%, respectively, 14 h after the hCG injection or after culture for 14 h. In oocytes cultured for 8 h with olomoucine or 3-isobutyl-1-methylxanthine, nuclei were almost all in the germinal vesicle stage, and activity of 20alpha-HSD was observed in 84 and 89% of the treated oocytes, respectively. On the other hand, 81% of control oocytes showed 20alpha-HSD activity, with no significant difference from the rate for the olomoucine- or 3-isobutyl-1-methylxanthine-treated oocytes. The present findings suggested that the metabolic abilities of progesterone, 17alpha-hydroxyprogesterone, 17alpha,20beta-dihydroxyprogesterone, 20beta-hydroxyprogesterone, androgen and estradiol-17beta in the cytoplasm are constantly present in mouse oocytes in the process of maturation in vivo and in vitro. The results also suggested that the metabolic ability of 20alpha-hydroxyprogesterone in mouse oocytes increases during maturation, but the change in the metabolic ability of such a steroid is not related to nuclear maturation.