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PubMed1994

Epidermal growth factor enhances oocyte maturation in pigs.

Epidermal Growth Factor (EGF) has been reported to stimulate nuclear maturation in porcine oocytes (Sommer et al., 1992). The objective of this experiment was to test the effect of EGF alone or in combination with gonadotropins and follicular shell coculture, on cytoplasmic maturation of oocytes in vitro. A preliminary experiment tested the effective dose of EGF for stimulation of oocyte nuclear maturation in our culture system. Nuclear maturation rates (MII%) of 67.2 +/- 4.6, 81.1 +/- 8.6, and 80.7 +/- 5.1 for oocyte complexes cultured in the presence of 0.1, 1, and 10 ng/ml EGF, respectively, were significantly higher (P < 0.05) than for oocytes cultured in the absence of EGF (18.1 +/- 9.4%). In the main experiment a 2 x 2 x 2 factorial random complete block design was used to examine the effect of EGF (1.0 ng/ml) alone or in combination with gonadotropins and follicular shell coculture on cytoplasmic maturation. Cytoplasmic maturation was evaluated by the ability of oocytes to decondense sperm nuclei after sperm penetration. EGF alone did not stimulate cytoplasmic maturation in oocytes in vitro (P > 0.05). However, EGF showed a positive interaction (P < 0.05) with gonadotropin treatment on male pronuclear formation. We conclude that EGF alone can stimulate nuclear maturation in pig oocytes, and EGF can interact with gonadotropins to enhance cytoplasmic maturation. A high level of cytoplasmic maturation of in vitro matured pig oocytes could be achieved using a combination of EGF, gonadotropin, and follicular shell supplementation to the culture environment.

Animals↗
PubMed2006

Combined influence of early sexual maturation and central adiposity on subsequent stature. A four-year follow-up of 1,605 Norwegian boys and girls: the Young-HUNT study.

INTRODUCTION: Shorter adult stature has been attributed to early sexual maturation, as well as early adiposity, but it is not clear if these factors are interrelated. RESULTS AND DISCUSSION: A number of 1,605 Norwegian adolescents were followed from early (baseline) to late adolescence (follow-up). Maturational timing was assessed by self-reports of pubertal status (pubertal development scale, PDS) in boys and age at menarche (AAM) in girls. Height, weight and waist circumference were measured at baseline and at follow-up. Differences in height at follow-up and height gain related to the timing of sexual maturation and the level of central adiposity (i.e. high or low waist circumference) at baseline were estimated using general linear modelling. At follow-up, the median height was 180 cm in boys and 167 cm in girls. Early maturing boys and girls with relatively high central adiposity at baseline were, on average, 5.7 cm (P value<0.001) and 3.6 cm (P value<0.001) taller than early maturing boys and girls with low central adiposity. Differences in stature related to central adiposity were less pronounced for intermediate and late maturing boys and girls. The height was lowest in boys (176.6 cm) and girls (163.8 cm) who had matured early and had low central adiposity at baseline. Height gain during follow-up was independent of the level of central adiposity, but was closely related to the timing of sexual maturation. The association between the early timing of sexual maturation and subsequent height was modified by the level of central adiposity in early adolescence. CONCLUSION: The results suggest that early maturity combined with adiposity yields higher stature than early maturity and leanness.

Adiposity↗
PubMedDate not supplied

The importance of considering biological maturity when assessing physical fitness measures in girls and boys aged 10 to 16 years.

It is widely considered that biological maturity influences physical fitness test performance, children can be advantaged/disadvantaged in physical fitness tests by being more or less mature than counterparts of the same chronological age. The current study sought to investigate the effect sexual maturity had upon performance in physical fitness tests. A cross-sectional study involving 161 girls and 152 boys was carried out. Each subject was assessed for stature, mass, self-assessment of sexual maturity, vertical jump, hand grip strength and the 20 m shuttle run test, all procedures were standardized. Spearman's rank correlation coefficients were developed to assess the relationship between maturity and physical fitness measures. ANCOVA inferential statistics were performed to investigate if performance in physical fitness tests differed between children of different sexual maturity stages irrespective of mass and stature. Significance was set at p < 0.05. Stage of sexual maturity was significantly correlated with all physical fitness measures (boys: r=0.56 to 0.73; girls: r=0.24 to 0.46). ANCOVA revealed that when stature and mass were taken into account significant differences were evident between sexual maturity stages in boys but not girls. This suggests that increases in mass and stature are primarily responsible for variation in girls' physical performance throughout maturation, whereas in boys there are some qualitative differences in performance due to other factors. It was concluded that sexual maturity has a large influence on physical fitness measures in boys but less effect in girls. Rating of physical fitness, particularly for boys should take into account biological maturity.

Adolescent↗
PubMedDate not supplied

Skeletal maturity and body size of teenage Belgian track and field athletes.

Attained skeletal maturity (TW2 RUS method), skeletal maturity relative to chronological age, and body size of national-level Belgian track and field athletes 15 to 18 years of age were considered. Among the 47 male athletes, 29 (62%) were skeletally mature, while 15 (52%) of the 29 female athletes were skeletally mature. There appeared to be a predominance of skeletally mature individuals among male sprinters and jumpers, while a majority of female sprinters were not skeletally mature. Both skeletally mature and immature individuals were rather evenly represented in the other track and field categories, with the exception of female throwers, who were skeletally mature. Mean statures and weights of skeletally mature and immature 16-, 17-and 18-year-old male athletes did not differ significantly, though the skeletally mature tended to be heavier. In contrast, the skeletally mature female athletes, on the average, were taller and heavier than the skeletally immature, although the differences among the small groups were not statistically significant.

Adolescent↗
PubMed1998

Ovarian modulation of the oestradiol-induced LH surge in prepubertal and sexually mature gilts.

The role of ovarian secretions in modulating positive oestrogen feedback on LH release in late prepubertal and sexually mature gilts was studied. Gilts were either ovariectomized (OVX) at 230 days of age (sexually mature, OVX 230, control), ovariectomized at 160 days of age (pre-pubertal, OVX 160) or ovariectomized at 160 days of age and given either low, high or very high oestradiol substitution therapy (two or three Silastic implants, 5 or 8 cm in length) from 160 days to 230 days (OVX 160 + 2E5, OVX 160 + 2E8 and OVX 160 + 3E8, respectively). The LH surge responses to three i.m. injections of oestradiol benzoate given at intervals of 12 h (in total 10 micrograms oestradiol benzoate kg-1 bodyweight) were compared at 260 days. An additional group of sexually mature gilts was ovariectomized at 260 days (OVX 260) and challenged with oestradiol benzoate at 360 days. LH surges with peak LH concentrations below pretreatment values (resembling LH responses to oestradiol benzoate in immature gilts) were classified as immature, and those with peak LH concentrations above pretreatment values as mature. LH concentrations before treatment with oestradiol benzoate were reduced (P < 0.05) in OVX 160 + 2E8 and OVX 160 + 3E8 gilts compared with OVX 230 (control). When compared with the control group, the time to LH surge peak was longer in OVX 260 gilts, LH peak amplitude was reduced in the OVX 160 group and the area under the curve of the LH surge (ng LH ml-1 plasma (48 h)-1) was less in all other groups (P < 0.05). Classification of LH surges by mature:immature criteria indicated a high mature:immature ratio in OVX 230 gilts (6/1) and a low ratio in OVX 160 (1/7) and OVX 260 (1/6) gilts. The long-term effect of ovariectomy was partially overcome in the OVX 160 + 2E5 group (mature:immature = 3/3). However, previous exposure to supraphysiological concentrations of oestradiol (as in groups OVX 160 + 2E8 and OVX 160 + 3E8) resulted in a high percentage of animals (66% and 100%, respectively) that did not respond to the oestradiol benzoate challenge with an LH surge. Immediately before oestradiol benzoate administration (30 days after removal of implants) plasma oestradiol concentrations in these two groups were still high (P < 0.05) compared with all other groups. GnRH-induced (0.2 microgram kg-1 bodyweight) LH secretion, evaluated 10 days after treatment with oestradiol benzoate, was depressed (P < 0.05) in OVX 160 + 3E8 gilts, but not affected by age at ovariectomy. We suggest that continuous ovarian secretion is necessary for the final maturation of the LH surge mechanism in late prepubertal gilts and also for maintaining the full functionality of this mechanism in sexually mature gilts. The range over which ovarian oestrogens tune the final maturation of this process appears to be rather narrow; however, other ovarian factors may contribute to the final maturation. Furthermore, continued exposure to supraphysiological concentrations of oestradiol was found to be detrimental to the development of the LH surge mechanism.

Analysis of Variance↗
PubMed2002

National estimates of the timing of sexual maturation and racial differences among US children.

OBJECTIVE: To provide clinically meaningful, normative reference data that describe the timing of sexual maturity indicators among a national sample of US children and to determine the degree of racial/ethnic differences in these estimates for each maturity indicator. METHODS: Tanner staging assessment of sexual maturity indicators was recorded from 4263 non-Hispanic white, black, and Mexican American girls and boys aged 8.00 to 19.00 years as part of the Third National Health and Nutrition Examination Survey (NHANES III) conducted between 1988 and 1994. NHANES III followed a complex, stratified, multistage probability cluster design. SUDAAN was used to calculate the mean age and standard error for each maturity stage and the proportion of entry into a maturity stage and to incorporate the sampling weight and design effects of the NHANES III complex sampling design. Probit analysis and median age at entry into a maturity stage and its fiducial limits were calculated using SAS 8.2. RESULTS: Reference data for age at entry for maturity stages are presented in tabular and graphical format. Non-Hispanic black girls had an earlier sexual development for pubic hair and breast development either by median age at entry for a stage or for the mean age for a stage than Mexican American or non-Hispanic white girls. There were few to no significant differences between the Mexican American and non-Hispanic white girls. Non-Hispanic black boys also had earlier median and mean ages for sexual maturity stages than the non-Hispanic white and Mexican American boys. CONCLUSION: Non-Hispanic black girls and boys mature early, but US children completed their sexual development at approximately the same ages. The present reference data for the timing of sexual maturation are recommended for the interpretation of assessments of sexual maturity in US children.

Adolescent↗
PubMed2000

Excessive concentration of glucose during in vitro maturation impairs the developmental competence of bovine oocytes after in vitro fertilization: relevance to intracellular reactive oxygen species and glutathione contents.

The effect of glucose (0, 1.5, 5.6 or 20.0 mM) in synthetic oviduct fluid supplemented with 20 amino acids (SOFaa) on the developmental competence of bovine oocytes after in vitro fertilization was investigated. Intracellular reactive oxygen species (ROS) and the glutathione content of bovine oocytes matured in SOFaa containing 0-20.0 mM glucose were also examined. When oocytes were matured in SOFaa without glucose, the nuclear maturation rate was lower than that in oocytes matured in glucose-containing medium. The developmental competence to the blastocyst stage of oocytes matured in 1.5 mM glucose was higher than that of oocytes matured in 20.0 mM glucose. In addition, the intracellular ROS content of oocytes matured in 0, 1.5 or 5.6 mM glucose was lower than that of oocytes matured in 20.0 mM glucose. Furthermore, the intracellular glutathione content of oocytes matured in 0, 1.5 or 5.6 mM glucose was higher than that of oocytes matured in 20.0 mM glucose. These results show that excessive glucose in the medium for oocyte maturation impairs the development of bovine oocytes to the blastocyst stage, possibly due to the increase of ROS and the decrease in the intracellular glutathione content of bovine oocytes.

Amino Acids↗
PubMed2002

Screening for cervical disease in mature women: strategies for improvement.

BACKGROUND: Cervical carcinoma remains a significant health risk for the older woman. In the current study the yield of screening of mature women in an established, opportunistic screening program was examined. Strategies for improving screening in this age group were identified through examination of recent Pap test history of women with high grade squamous intra-epithelial lesions (HSIL). METHODS: From the population based registry of the Ontario Cervical Screening Program, the Pap test cytodiagnoses for almost 700,000 women screened during the first six months of 2000 were classified by age quintile. Screening yields for younger women (< 50 years of age) and mature women (>/= 50 years of age) were compared using the detection ratio (abnormalities per 1000 women tested). Any pap test results during the three years preceding a diagnosis of HSIL in mature women were identified (excluding any Pap test in the six months immediately prior to the HSIL cytodiagnosis) and classified into one of three categories: no prior test known, prior negative Pap test known, and prior abnormal Pap test known. RESULTS: Twenty four percent of all Pap tests in the six month period were from mature women. Approximately 11% of all cytodiagnoses of HSIL and carcinoma (HSIL+), and 13% of all low grade squamous intra-epithelial lesions (LSIL), HSIL, carcinoma, and atypical glandular cells of uncertain significance (AGUS); [LSIL+ and AGUS] cytodiagnoses, were from mature women. The yield of Pap testing in mature women (1.7 HSIL+ per 1000 women tested) was slightly more than 40% of that for younger women (4.2 HSIL+ per 1000 women tested). Mature women with HSIL were more likely to have had a history of no prior screening (61.1%) than younger women (49.5%). The majority (62.9%) of mature women with HSIL and a prior known Pap test had a prior registered abnormal Pap test. CONCLUSIONS: Pap testing of mature women yields a significant number of abnormalities, but is less efficient than Pap testing of younger women. Screening yield could be increased by recruiting mature women who are currently inadequately screened and by revising guidelines for cessation of screening. Proper followup of mature women with Pap test abnormalities would improve clinical outcome but could adversely affect the yield of Pap testing, since current inappropriate repeat testing of women would decrease.

Adolescent↗
PubMed1990

Effects of gonadotropins and granulosa cell secretions on the maturation and fertilization of rat oocytes in vitro.

Fully grown germinal vesicle-stage oocytes are induced to resume meiosis and acquire the capacity to undergo fertilization in response to a surge of gonadotropins. The present study examined possible direct and indirect roles of gonadotropins in the maturation and fertilization of rat oocytes by determining 1) the effect of exogenous administration of gonadotropins (priming) to immature rats prior to oocyte collection on the capacity of oocytes to undergo maturation and fertilization in vitro, 2) the effect of follicle-stimulating hormone (FSH) in the maturation media on the resumption of meiosis and subsequent capacity of oocytes to undergo fertilization, and 3) the capacity of oocytes to undergo maturation and fertilization following culture in preovulatory follicular fluid or in conditioned media obtained from gonadotropin-stimulated granulosa cell (GC) cultures. In the first experiment, oocytes from unprimed rats underwent spontaneous meiotic maturation in vitro and 17% underwent subsequent fertilization. Priming increased the proportion of oocytes undergoing fertilization. Maturation of oocytes in media supplemented with various concentrations of FSH or for various lengths of time (6-16 h) in medium with 500 ng FSH/ml indicated that FSH slowed the rate of meiotic maturation, but had no effect on the capacity of the oocytes to be fertilized. Oocytes obtained from primed animals and cultured in the presence of preovulatory follicular fluid were fertilized in proportions similar to those cultured in serum-containing medium. In the third experiment, medium conditioned by FSH-stimulated GC for 40 h slowed the rate of meiotic maturation; the addition of luteinizing hormone (LH) to the FSH-stimulated cells produced a medium in which the rate of oocyte maturation was not different from that of control oocytes (in medium from unstimulated cells). Medium conditioned by FSH- or LH-stimulated GC, but not fibroblasts, increased the proportions of oocytes undergoing fertilization following maturation in those media. FSH + LH stimulation of GC increased the fertilization of oocytes to proportions significantly higher than with either gonadotropin alone. These data suggest that GC respond to gonadotropin stimulation by providing a factor(s) that regulates the rate of oocyte maturation and promotes the capacity of oocytes to undergo fertilization.

Animals↗
PubMed1994

Surface alterations of the bovine oocyte and its investments during and after maturation and fertilization in vitro.

Surface characteristics of the bovine oocyte and its investments before, during, and after maturation, and fertilization in vitro were evaluated by scanning electron microscopy (SEM). Oocyte diameters were also measured during SEM analysis of the oocyte. The cumulus cells manifested a compact structure with minimal intercellular spaces among them in the immature oocytes. These became fully expanded with increased intercellular spaces after maturation in vitro, but contracted again after fertilization. The zona pellucida (ZP) showed a fibrous, open mesh-like structure in the maturing and matured oocytes. The size and number of meshes on the ZP decreased dramatically after fertilization. The vitelline surface of immature oocytes was characterized by distribution of tongue-shaped protrusions (TSPs) varying in density. After 10 and 22 hr of maturation incubation, oocyte surface microvilli (MV) increased to become the predominant surface structure, and TSPs decreased substantially. The vitelline surface of fertilized oocytes (at 6 and 20 hr) was similar to that of the matured oocytes, but unfertilized oocytes had less dense MV than did fertilized oocytes (at 20 hr). The diameter of the oocytes decreased from 99 to 80 microns during maturation and increased to 106 microns after insemination (P < 0.05). Membrane maturation was characterized by surface changes from a TSP-predominant pattern to a MV-predominant pattern. Thus, the bovine oocyte maturation process was found to involve the expansion of cumulus cells and the maturation of the ZP, which changes dramatically upon fertilization. Also, volumetric changes occurred in ooplasm processed for SEM following oocyte maturation and insemination.

Animals↗
PubMed1995

Mechanism of action of epidermal growth factor-induced porcine oocyte maturation.

EGF has been reported to promote oocyte maturation in several species, although the mechanism of action is not yet known. The present study is designed to determine the pathway used by EGF to enhance porcine oocyte maturation. Oocytes were aspirated from 2-5 mm follicles and cultured with various treatments in Medium-199 at 37 degrees C, 100% relative humidity, and 5% CO2 for 48 hr for the maturation study and 3 hr for intracellular cAMP measurement. Although treatment with 100 IU/ml hCG stimulated both intracellular cAMP formation and oocyte maturation, 10 ng/ml EGF stimulated oocyte maturation only. Dibutyryl cAMP (dbcAMP) inhibited oocyte maturation at 10(-5), 10(-4), and 10(-3) M concentration s in the control medium. However, in the presence of 10 ng/ml EGF, dbcAMP inhibited oocyte maturation only at a concentration of 10(-3) M. Increasing concentrations of EGF (i.e., 25 and 50 ng/ml) were ineffective in overcoming the inhibitory effect of dbcAMP at 10(-3) M. In contrast, EGF reversed the decreased maturation rate caused by transforming growth factor-beta. Phorbol myristate acetate (PMA), a tumor-promoting phorbol ester, enhanced the spontaneous maturation rate; 4 alpha-phorbol dideconoate, an inactive phorbol ester, did not show this effect. PMA- and EGF-stimulated porcine oocyte maturation is reversed by calphostin-C, a PKC inhibitor. In conclusion, EGF's promotional activity on porcine oocyte maturation is independent of the cAMP pathway and probably mediated by the PKC pathway.

Animals↗
PubMed1995

Effect of cysteamine on glutathione level and developmental capacity of bovine oocyte matured in vitro.

The present study was carried out to evaluate if the addition of cysteamine to the culture medium during in vitro maturation of bovine oocytes increased the glutathione (GSH) levels in the mature oocytes, and if these changes may promote an improvement on in vitro development to the blastocyst stage. Follicular oocytes from slaughterhouse ovaries were matured in TCM 199 supplemented with 10% (v/v) fetal calf serum, hormones, and O (control), 25, 50, or 100 muM of cysteamine for 24 hr. After in vitro maturation the oocytes were fertilized and cultured for 8 days. The percentage of embryos that developed to the blastocyst stage was significantly higher (P < 0.01) for oocytes matured in medium containing 100 muM of cysteamine than for those matured in control medium. Moreover, the intracellular GSH levels were increased (P < 0.05) in oocytes matured with 100 muM of cysteamine with respect to control. No differences were observed in maturation and cleavage rates, and in the mean cell numbers per blastocyst among treatments (P > 0.05). These results indicate that the addition of thiol compounds such as cysteamine to maturation medium increases the efficiency of in vitro blastocyst production from immature bovine oocytes. The higher levels of GSH in oocytes matured in the presence of cysteamine suggest that the beneficial effects of cysteamine on in vitro maturation and subsequent development after in vitro fertilization are mediated by GSH.

Animals↗
PubMed1979

Mammalian oocyte maturation: model systems and their physiological relevance.

Maturation of mammalian oocytes is studied mainly in two dissimilar in vitro models: isolated oocytes maturing spontaneously in culture, and hormone-induced maturation of follicle-enclosed oocytes. In this discussion the following aspects of maturation in vitro in the two aforementioned models were compared: timing of germinal vesicle breakdown (GVB), involvement of cyclic nucleotides, protein synthesis and divalent cations. A third approach to the study of oocyte maturation in vitro, namely oocyte co-culture with follicular constituents was adopted in order to test the role of follicular components in the control of the resumption of meiosis. Such studies demonstrated an inhibitory action of granulosa cells, granulosa cell-conditioned medium and of follicular fluid upon the spontaneous maturation of the co-cultured oocytes. Furthermore, addition of LH to co-cultures of oocytes and granulosa cells induced resumption of meiosis. Although oocytes obtained by spontaneous or by hormone-induced maturation cannot be distinguished morphologically, the developmental potential of oocytes matured spontaneously has been questioned, at least in some species. Furthermore, analysis of the kinetics of spontaneous maturation suggests that oocytes dislodged from their follicles escape physiologic mechanisms ensuring meiotic arrest and skip some of the regulatory steps involved in the normal hormonal triggering of maturation. Oocyte co-culture with granulosa cells offers a close approximation to physiological conditions in that meiotic maturation depends on hormonal stimulation, while the system permits the application of separate treatments to the oocyte-cumulus complex and granulosa cells. As in any in vitro system, critical evaluation is required to discriminate between artifacts inherent in the model and physiological processes.

Animals↗
PubMed2002

The relationship between dental and skeletal maturity.

OBJECT: The purpose of this investigation was to evaluate the relationships between dental and skeletal maturity, primarily whether it is possible to assess skeletal maturity by dental maturity without reference to hand-wrist radiographs. PATIENTS AND METHODS: Research was carried out with a representative sample of 422 children (276 girls, 146 boys) aged 91-168 months. The investigated materials included a pre-treatment left hand-wrist radiograph plus dental panoramic and periapical radiographs. RESULTS: Spearman rank-order correlation analysis showed that a rho value of 0.588 between skeletal maturity level and lower first premolars was the lowest, and a rho value of 0.800 between skeletal maturity level and body height the highest in girls. In boys, a rho value of 0.474 between skeletal maturity level and upper canine was the lowest, and a rho value of 0.761 between skeletal maturity level and body height the highest. CONCLUSION: The relationship between dental maturity and skeletal maturity is not sufficient for dental maturity to be used as a substitute for skeletal maturity.

Adolescent↗
PubMed2005

Maturity-associated variation in the body size and proportions of elite female gymnasts 14-17 years of age.

The aim of this study was to evaluate variations in the size and body proportions of elite female gymnasts associated with individual differences in maturity status. The subjects were 150 gymnasts, 14.0-17.9 years of age, who had participated in the 24th World Championship in Artistic Gymnastics, Rotterdam. Height, body mass, sitting height and biacromial and bicristal breadths were measured. Leg length was estimated as the height minus sitting height, and the ratio of sitting height to height was calculated. Information on menarcheal status was obtained by means of a questionnaire, and hand-wrist radiographs were taken to assess skeletal maturity status. For the purpose of data analysis the gymnasts were divided into three maturity groups within each single-year chronological age (CA) group from 14 to 17 years: pre-menarcheal (n=65); post-menarcheal but not skeletally mature (SA<16.0 years, n=37); post-menarcheal, skeletally mature (n=48). Differences among the groups were tested with analysis of variance and post hoc Tukey tests. The results showed that pre-menarcheal gymnasts are smaller in all dimensions compared to post-menarcheal gymnasts in all age groups but that the significance of differences varies. Post-menarcheal, skeletally mature gymnasts are heavier than pre-menarcheal gymnasts, but weight does not differ between gymnasts in the two post-menarcheal groups (with one exception, 16 years). Post-menarcheal, skeletally mature gymnasts have proportionally shorter legs than gymnasts in the other two maturity categories. Elite gymnasts of contrasting maturity status show similar trends in body size and proportions similar to those of non-athlete adolescent girls of contrasting maturity status. The results highlight the need to consider maturity-associated variation in the body dimensions of gymnasts before attributing their characteristics to the demands of regular training.

Adolescent↗
PubMed1988

Effects of temperature alterations on population and cellular activities in hippocampal slices from mature and immature rabbit.

Effects of temperature on population spike and cellular activities have been assessed in the CA1 region of hippocampal slices from mature and immature rabbit. In field potential recordings, population spike amplitude was maximal at near 30 degrees C for both mature and immature tissue, and fell off as temperature was either raised (to a maximum of 44 degrees C) or lowered (to a minimum of 20 degrees C). With cooling below 30 degrees C, population spikes decreased in amplitude and became broader; stimuli always elicited some response, and changes due to cooling were reversible. With increases in temperature, however, irreversible decrease and/or loss of population spikes occurred when tissue was warmed beyond 43 degrees C. Input-output curves established for mature and immature slices indicated that, at all temperatures, population spike amplitude grew more rapidly with small increases in stimulus intensity in immature slices as compared to mature slices. Intracellular recordings were made from CA1 pyramidal cells in mature and immature hippocampal slices. For both mature and immature tissues, moderate warming (to 40 degrees C) produced membrane hyperpolarizations in many cells, especially in the mature hippocampus. Increasing temperature beyond 40 degrees C led to marked depolarizations in a number of cells, a depolarization that was irreversible, particularly in mature neurons. Cooling generally produced a depolarizing shift in membrane potential and an accompanying increase in input resistance; these effects, however, were reversible. Temperature changes in both warming and cooling directions had effects on repetitive firing patterns in both mature and immature neurons. In particular, spike trains elicited by a constant current pulse at a given membrane potential became shorter. The effects of cooling on this cell parameter were reversible, but warming-induced changes were usually permanent. Irreversibility of the warming effects was more pronounced in cells from mature than from immature hippocampus. As reported previously, cooling produced marked spike broadening and changes in synaptic potentials in both mature and immature neurons. These studies confirm previously reported temperature sensitivities of neuronal properties in hippocampal slices. On the basis of these data, and reports from other laboratories, it is clear that relatively small changes in temperature can have rather dramatic effects on properties of single cells and cell populations. Such temperature sensitivity is critical in evaluating data obtained from in vitro slice preparations.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1984

Arachidonic acid, 12- and 15-hydroxyeicosatetraenoic acids, eicosapentaenoic acid, and phospholipase A2 induce starfish oocyte maturation.

In starfish oocyte maturation (meiosis reinitiation) is induced by the natural hormone 1-methyladenine (1-Me-Ade). This paper shows that arachidonic acid (AA) induces oocyte maturation at concentrations above 0.5 microM. This maturation shares many characteristics with 1-MeAde-induced maturation: same kinetics, same required contact time, same stimulations of protein phosphorylation and sodium influx. Although calcium facilitates the AA-induced but not the 1-MeAde-induced maturation, AA, like 1-MeAde, does not stimulate the uptake of calcium. Calcium does not facilitate the uptake of AA by oocytes. Out of 36 different fatty acids (saturated and unsaturated), only eicosatetraenoic (AA) and eicosapentaenoic acids were found to mimic 1-MeAde. Calcium-dependent phospholipases A2 from bee venom and Naja venom also induce maturation (0.1-1 unit/ml) when added externally to the oocytes. Phospholipase A2 inhibitors (quinacrine, bromophenacylbromide) block maturation; inhibition is reversed by increasing the 1-MeAde concentration and only occurs during the hormone-dependent period. AA is usually metabolized through oxidation by cyclooxygenase or lipoxygenase. Cyclooxygenase inhibitors (acetylsalicylic acid, indomethacin, tolazoline) do not block maturation; prostaglandins E2, D2, F2 alpha, I2, and thromboxane B2 do not induce meiosis reinitiation. On the other hand, lipoxygenase inhibitors (quercetin, butylated hydroxytoluene, and eicosatetraynoic acid) block 1-MeAde-induced maturation; although leukotrienes (A4, B4, C4, D4, E4) have no effects on oocytes, two other lipoxygenase products, 12- and 15-hydroxyeicosatetraenoic acids (and their corresponding hydroperoxy-) induce oocyte maturation (around 1 microM). The possible mode of action of the fatty acids inducing oocyte maturation is discussed.

Animals↗
PubMed1994

Effect of sheep and human follicular fluid on the maturation of sheep oocytes in vitro.

This study examines the effect of sheep and human follicular fluid on the in vitro maturation (IVM) of sheep follicular oocytes. Oocyte cumulus complexes recovered post mortem were matured for 24 to 26 h at 38.6 degrees C, 5% CO(2) in air, in TCM-199 bicarbonate medium supplemented with 20% fetal calf serum (FCS) and, where stated, with maturation hormones, including FSH (5.0 microg/ml), LH (5.0 microg/ml) and estradiol (1 microg/ml), or with sheep follicular fluid recovered from large (>5 mm) or small (2 to 5 mm) ovarian follicles post mortem, or with human periovular follicular fluid obtained during routine IVF procedures. The matured oocytes were then denuded, and their maturation stage and developmental capacity were assessed by in vitro fertilization (IVF) and culture (IVC). It was found that inclusion of sheep or human follicular fluid or hormone supplements in the IVM media more than doubled the number of oocytes completing maturation (FCS alone 33%, compared with 76.2% for maturation hormones, 84.2% for fluid from large and 69.6% for fluid from small sheep follicles and 82.6% for human follicular fluid), and significantly increased fertilization rates (FCS alone 51.6%, compared with 71.9% for maturation hormones, 78.4% for fluid from the large and 75.7% for fluid from small sheep follicles and 73.1% for human follicular fluid) without discernible adverse effects on the development of the cleaving embryos to the morula or blastocyst stage in culture. Omission of FCS and supplements from the IVM medium resulted in a marked reduction (56%) in the number of oocytes maturing. This reduction could be offset to a large part, but not completely, by inclusion of human follicular fluid or human follicular fluid plus LH (5 microg/ml) in the medium. The results of this study show that addition of sheep or human follicular fluid to maturation medium can enhance rather than inhibit the maturation and fertilizability of sheep follicular oocytes in vitro.

Journal Article↗