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Biomedical subjects

M Dorland

Publications and source records attributed to M Dorland.

14 recordsLinked to original sources
PubMed2000

In vitro culture of rat pre-antral follicles with emphasis on follicular interactions.

The present study was designed to determine whether rat pre-antral follicles can grow under in-vitro conditions. Emphasis is on whether follicular interaction is involved in in-vitro follicle culture, and furthermore its role in follicular development has been assessed. Pre-antral follicles were isolated mechanically from 10-day old rat ovaries. They were divided into small (50 microm < diameter < 100 microm) and large (120 microm < diameter < 200 microm) pre-antral follicles and cultured individually or in groups for 6 days in medium with or without fetal calf serum (FCS). Based on morphological criteria, large pre-antral follicles cultured in groups in serum-free medium had significantly higher survival rates than those cultured individually. In the presence of FCS, no significant difference was detected with respect to the survival. However, the large pre-antral follicles cultured in groups had a significantly greater increase in diameter than those cultured individually. Furthermore, follicles cultured in groups in FCS-containing medium exhibited significantly more follicular cell proliferation than those in serum-free medium, based on DNA measurement. The present culture system (with or without FCS) proved to be insufficient for small pre-antral follicles to stimulate growth comparable to that of large pre-antral follicles. The transmission electron microscopical (TEM) study revealed the ultrastructural differences between follicles cultured in FCS-containing and serum-free media. Taken together, the results suggest that interfollicular factors are involved in follicle development in vitro, which especially at the early folliculogenesis stage plays a positive role in terms of follicular growth as well as survival. The present culture model allows further investigation of factors that regulate early folliculogenesis.

Animals↗
PubMed1999

Antral follicle counts by transvaginal ultrasonography are related to age in women with proven natural fertility.

OBJECTIVE: To investigate the relation between reproductive age and ultrasound (US)-based follicle counts and the reproducibility of follicle counts in regularly cycling women with proven fertility. DESIGN: Prospective observational study. SETTING: Tertiary fertility center. PATIENT(S): Healthy female volunteers with proven fertility, recruited by advertisement in local newspapers. INTERVENTION(S): The number of antral follicles sized 2-10 mm and ovarian volume were estimated by transvaginal US in the early follicular phase of the menstrual cycle in 162 women. A subgroup of 81 women underwent transvaginal US at several times in three subsequent cycles. MAIN OUTCOME MEASURE(S): Antral follicle count and total ovarian volume. RESULT(S): Women aged 25-46 years (n = 162) were studied. The relation of age with the US indices was computed after natural log transformation. Antral follicle count showed the clearest correlation with age (R = -0.67). A biphasic linear model gave the best fit to the data. Before the age of 37 years, the antral follicle count showed a mean yearly decline of 4.8%, compared with 11.7% thereafter. The reproducibility of the antral follicle count in two subsequent cycles was moderate. CONCLUSION(S): The number of small antral follicles in both ovaries as measured by US is clearly related to reproductive age and could well reflect the size of the remaining primordial follicle pool.

Adult↗
PubMed1998

Developmental and endocrine aspects of normal ovarian aging.

Supplies of follicles are established during early fetal life and decrease exponentially thereafter by a process called atresia. Subfertility only starts at a mean age of about 30-31 years, when the remaining follicle reserve has become a fraction of its original number. Thereafter, a further decrease in both oocyte quantity and quality dictates the subsequent reproductive events including decrease of fertility, increased abortion rate, the end of fertility, the beginning of cycle irregularity and, when almost no follicles are left, the occurrence of menopause. The same remarkable variation of age at menopause almost certainly is also present for the preceding reproductive events. When quantity and quality of antral follicles drop below a critical threshold, there is a subsequent drop in inhibine B resulting in the selective FSH rise at a mean age of 37-38 years. This FSH rise explains the accelerated follicle depletion, the increased proportion of growing follicles reaching the selectable stage, the shortening of the follicular phase and the increased incidence of dizygotic twinning. The concurring decrease of oocyte quality is in line with the increased incidence of abortions and chromosomal aberrations after age 35.

Aging↗
PubMed1998

General ageing and ovarian ageing.

The age related decrease in female fertility is associated with a decrease in follicle numbers and oocyte quality. Meiotic division errors, mitochondrial DNA mutations and ageing itself have been suggested to play a part in the age associated reduction in oocyte quality. During the past decades several hypothesis have been proposed, trying to explain the underlying mechanisms. However, none of them is yet conclusive. This review will consider the main hypotheses regarding the age related reduction in oocyte quality. This will be reviewed together with recent results of studies analysing a possible relationship between ageing and ovarian ageing. On the basis of our own results and those presented in the literature, it is concluded that ovarian ageing may only be related to specific aspects of general ageing.

Aging↗
PubMed1998

Ovarian reserve tests in infertility practice and normal fertile women.

The decline in fecundity with the age of the woman is mainly attributed to the loss of follicles from the ovary and a decrease in oocyte quality. Evaluation of the aging status of the ovary in an individual woman has been hampered by a lack of knowledge with regard to the relative contribution of these two factors. Most if not all so called ovarian reserve tests (ORT) reflect indirectly the remaining follicle pool in the ovary. Direct a priori assessment of oocyte quality is not possible to date. In this section the predictive value of several ovarian reserve tests for the outcome of fertility treatment is listed and commented. In addition, the study of several of the ORTs in normal, fertile women is described. From the data presented dynamic testing of the ovarian function by the clomiphene citrate and GnRH agonist stimulation test, as well as static testing by the use of ultrasound based antral follicle counts seem to offer the highest clinical value. Studies performing direct comparison of these tests are needed, as well as analysis of the way these tests should direct decision making in infertility diagnosis and treatment.

Aging↗
PubMed1998

Age at menopause as a marker of reproductive ageing.

Ages of menopause and of the preceding reproductive events such as the beginning of subfertility and infertility, are likely to be dictated by the process of follicle depletion leading to loss of oocyte quantity and quality. To some extent this process is influenced by lifestyle factors like smoking, and possibly also by the use of oral contraceptives. Genetic factors and possibly also events during intrauterine life, probably play a more important role in the age-dependent decrease of female fertility.

Age Factors↗
PubMed1998

Fetal growth retardation as a cause of impaired ovarian development.

Low birthweight has been associated with diseases and disorders later in life. It has been suggested that this is caused by the impaired development of abdominal organs, especially in cases of growth retardation. Besides general malnutrition of the fetus, preferential bloodflow to the heart and brain may further deprive organs, such as liver, pancreas and kidney, of nutrients. As a result these organs may not develop properly. Anatomically, the ovary is situated close to the kidney and it is very likely that, similar to the kidney, ovarian development can be negatively affected by intra-uterine growth retardation. Placental insufficiency, which is an important cause of severe intra-uterine growth retardation, was used as a model to investigate this hypothesis. In the present study, the volume percentages of primordial follicles in the ovaries of four severely growth-retarded fetuses of different gestational ages are compared to those of four age-matched controls. It is found that these volume percentage in growth-retarded fetuses were significantly lower than those observed in the age-matched controls. It can be concluded that ovarian development is impaired in intra-uterine growth-retarded fetuses. These findings further suggest that, as a result of the premature loss of follicles, females with low birthweights may encounter fertility problems later in life.

Birth Weight↗
PubMed1997

Age at natural menopause in a population-based screening cohort: the role of menarche, fecundity, and lifestyle factors.

OBJECTIVE: To verify whether a population-based hypothesis (age at menarche and age at natural menopause have an inverse relationship) also applies at the level of the individual and to investigate what other factors predict age at natural menopause. DESIGN: Prospective cohort study (the Doorlopend Onderzoek Morbiditeit/Mortaliteit [DOM] project). SETTING: Prevention Breast Cancer Screening Centre, Utrecht, The Netherlands. PATIENT(S): A cohort of 3,756 Dutch women, born between 1911 and 1925, participating in a population-based breast cancer screening program, who experienced a natural menopause. Three samples of women were studied: a sample who did not use oral contraceptives (OCs) (n = 3,347), a sample of OC users (n = 409), and a combined sample of OC users and nonusers (n = 3,756). MAIN OUTCOME MEASURE(S): Age at menopause and menarche, fertility patterns, OC use, height, weight, smoking, and demographic variables. RESULT(S): No relation was found between age at menarche and age at natural menopause. The total percentage of variance in age at natural menopause explained by multiple regression including all factors was minimal, ranging from 1.3% to 9.7% in OC users. Linear regression analysis indicated a slight secular trend in age at menopause. CONCLUSION(S): Frisch's hypothesis could not be corroborated at the individual level. These results suggest that age at menarche and menopause should be treated as independent risk factors for breast cancer. Modification of age at menopause by lifestyle factors (except possibly for OC use) appears minimal.

Age Factors↗
PubMed1996

Age-dependent decrease in embryo implantation rate after in vitro fertilization.

OBJECTIVE: To investigate the relation between the implantation rate per embryo after replacement in IVF-ET in relation to female age. DESIGN: Retrospective study using linear and biphasic models in a multivariate analysis. SETTING: Academic tertiary care institution. INTERVENTION(S): In vitro fertilization-ET and determination of gestational sacs at 6 to 7 weeks of pregnancy buy ultrasound. MAIN OUTCOME MEASURE(S): Implantation rate as defined by the number of gestational sacs per embryo replaced. RESULT(S): Woman's age and embryo morphology were strongly related to the implantation rate, indication for IVF-ET and cycle rank number also were related significantly but less strongly. A linear model was built describing the decrease in implantation rate with age, resulting in a decrease of approximately 7%. A biphasic model was tested also and performed significantly better, resulting in a yearly decrease of > 20% after 37 years of age. CONCLUSION(S): The most important independent factors related to the ability of embryos to implant are female age and embryo morphology. The best way to describe the relation with female age is biphasic model with a discontinuity at approximately 37 years of age.

Aging↗
PubMed1993

Cytogenetic analysis of day-7 bovine embryos by cytophotometric DNA measurements.

A Feulgen staining procedure that stains the DNA of individual fixed nuclei stoichiometrically was used to analyse cytophotometrically the incidence of total ploidy and mixoploidy in 28 day-7 bovine embryos that had been fixed after collection ('non-cultured' embryos). The influence of culture on the incidence of chromosome abnormalities was further studied in another group of 24 embryos ('cultured' embryos) by culturing them for 24 h in Whittingham's medium. Of the total 52 embryos studied, two appeared to be entirely abnormal: one embryo was completely haploid, whereas the other embryo was completely triploid. Individual hyperdiploid nuclei and hypodiploid nuclei were frequently observed in the otherwise diploid embryos. As haploid polar bodies can still be present in morulae and blastocysts (to a maximum of three), only embryos with more than three hypodiploid nuclei were considered as abnormal. Of the 'non-cultured' embryos, 33.3% had one or more hyperdiploid nuclei, whereas 51.9% had more than three hypodiploid nuclei. In this latter group, 35.7% of the embryos also had hyperdiploid nuclei. The results also showed that day-7 bovine embryos that are completely haploid, completely triploid or mixoploid cannot be detected only by examining their morphology. It is concluded that the incidence of, especially, mixoploidy in embryos can be better studied by measuring the DNA content of the individual nuclei of an embryo rather than by analysing chromosomes, as in the latter method only dividing cells can be analysed. The presence of hyperdiploid and hypodiploid nuclei may indicate the frequent occurrence of mitotic segregation failures during mitosis in bovine embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗