Biomedical subjects

L Cochon

Publications and source records attributed to L Cochon.

14 recordsLinked to original sources

PubMed2005

Changes in rat soleus muscle phenotype consecutive to a growth in hypergravity followed by normogravity.

It has been demonstrated that a long-term stay in hypergravity (HG: 2G) modified the phenotype and the contractile properties of rat soleus muscle. The ability of this muscle to contract was drastically reduced, which is a sign of anticipated aging. Consequently, our aim was to determine whether rats conceived, born, and reared in hypergravity showed adaptative capacities in normogravity (NG: 1G). This study was performed on rats divided into two series: the first was reared in HG until 100 days and was submitted to normogravity until 115 to 220 postnatal days (HG-NG rats); the second was made up of age paired groups reared in normogravity (NG rats). The contractile, morphological, and phenotypical properties of soleus muscle were studied. Our results showed that the NG rats were characterized by coexpressions of slow and fast myosin, respectively, 76.5 and 23.5% at 115 days. During their postnatal maturation, the fast isoform was gradually replaced by slow myosin. At 220 days, the relative proportions were respectively 91.05% and 8.95%. From 115 to 220 days, the HG-NG rats expressed 100% of slow myosin isoform and they presented a slower contractile behavior compared with their age-matched groups; at 115 days, the whole muscle contraction time was increased by 35%, and by 15%, at 220 days. Our study underlined the importance of gravity in the muscular development and suggested the existence of critical periods in muscle phenotype installation.

Animals↗

PubMed2004

Pituitary-ovarian function following the standard levonorgestrel emergency contraceptive dose or a single 0.75-mg dose given on the days preceding ovulation.

We assessed to what extent the standard dose of levonorgestrel (LNG), used for emergency contraception, or a single dose (half dose), given in the follicular phase, affects the ovulatory process during the ensuing 5-day period. Fifty-eight women were divided into three groups according to timing of treatment. Each woman contributed with three treatment cycles separated by resting cycles. All received placebo in one cycle, and standard or single dose in two other cycles, in a randomized order. The diameter of the dominant follicle determined the time of treatment. Each woman had the same diameter assigned for all her treatments. Diameters were grouped into 33 categories: 12-14, 15-17 or 18-20 mm. Follicular rupture failed to occur during the 5-day period in 44%, 50% and 36% of cycles with the standard, half dose and placebo, respectively. Ovulatory dysfunction, characterized by follicular rupture associated with absent, blunted or mistimed gonadotropin surge, occurred in 35%, 36% and 5% of standard, single dose or placebo cycles, respectively. In conclusion, LNG can disrupt the ovulatory process in 93% of cycles treated when the diameter of the dominant follicle is between 12 and 17 mm. It is highly probable that this mode of action fully accounts for the contraceptive efficacy as well as the failure rate of this method. The present data suggest that half the dose may be as effective as the standard dose.

Adolescent↗

PubMed2002

Nonmenstrual adverse events during use of implantable contraceptives for women: data from clinical trials.

Contraceptive methods, including implants, do not prevent common symptoms and adverse health events that most people experience. It is difficult, therefore, to decide whether or not the occurrence of symptoms or adverse events that are common can be attributed to use of a contraceptive method or to determine if a given method changes the likelihood of their occurrence. Based on the review of the literature, no apparent differences in the frequency of adverse events are evident between the six-implant or two-rod levonorgestrel systems and the single implant etonogestrel and nomegestrol acetate systems. The most frequent adverse events reported in clinical trials that are probably related to implant use are headaches and acne. Weight gain, dizziness, and mood changes are also frequently mentioned adverse events and are possibly steroid-related. Other possibly related adverse events, although much less frequently reported, are loss of libido, fatigue, hair loss, and other skin conditions. Persistent ovarian follicles that spontaneously disappear are a common event during use of progestin-only contraceptives, and providers should be aware of this condition to avoid unnecessary interventions. Overall, the vast experience reported in the clinical studies reviewed here show that all existing implantable contraceptives are equally safe. This can probably be attributed to the low-hormonal dose delivered by progestin-implant systems.

Abdominal Pain↗

PubMed2002

Effects of the Yuzpe regimen, given during the follicular phase, on ovarian function.

This study was conducted to assess to what extent the Yuzpe regimen, or half the dose, given in the follicular phase, prevents ovulation during the ensuing 5 days. Sixty women were divided into six groups. All groups received placebo in one cycle and drug in another, in a randomized order. Groups differed by the dose and size of the leading follicle at the time of treatment (12-14, 15-17, or 18-20 mm). Ovulation was absent during the ensuing 5 days in 13 of 20 participants (65%) and in 8 of 20 participants (40%) who received the full and the half dose, respectively, when follicles were 12-17 mm. No ovulation occurred, within the critical period, in 7 of 39 placebo cycles (18%). When follicles were 18-20 mm, treatment did not prevent ovulation. In most drug-treated cycles, plasma gonadotropin and sex steroid levels were significantly depressed within the 5-day period, even when follicular rupture occurred within that period. In conclusion, the Yuzpe regimen can suppress or postpone ovulation to an extent that exceeds the fertile life of spermatozoa. Lack of ovulation within the critical period and dysfunction of the ovulatory process probably account for the contraceptive effect of this method in most cases. The present data do not warrant the use of half the dose of the Yuzpe regimen.

Contraceptives, Postcoital↗

PubMed2000

Ovarian function during use of Nestorone(R) subdermal implants.

Nestorone(R) progestin (NES) is a potent 19-nor-progesterone derivative which is biologically inactive when administered orally; however, it is an excellent option for implant contraception. The objective of this study was to evaluate ovarian function during use of either one 4-cm or two 3-cm NES implants for 24 months. A total of 60 volunteers were enrolled in each dose group. Vaginal ultrasound (VUS) and blood sampling for determinations of estradiol (E(2)), progesterone (P) and NES serum levels were carried out twice a week for 6 consecutive weeks, beginning in months 1, 6, 12, 18, and 24 of implant use. Serum levels of NES declined with time, with a more pronounced decrease during the first 18 months of implant use; thereafter, NES levels remained stable until the end of the study at 24 months. Luteal activity was very infrequent during the first year of use (<3%) but increased during the second year, occurring in 27% and 35% of the sampling periods in the 1-implant group, and 2% and 16% of the sampling periods in the 2-implant group, at months 18 and 24 of use, respectively. No luteal activity was observed with NES levels above 80 pmol/L. Serum P levels in periods of luteal activity were significantly lower than those of controls. Persistent anovulatory follicles were the most common VUS finding and this was associated with E(2) levels that remained within the normal range (101-1500 pmol/L) in the majority of the sampling periods studied. Considering that a single implant offers advantage for insertion and removal, a new single NES implant is being developed with a slightly higher release rate, to reduce effectively the incidence of ovulation and provide a greater margin of safety beyond 2 years.

Adolescent↗

PubMed2000

Prevalence of enlarged ovarian follicles among users of levonorgestrel subdermal contraceptive implants (Norplant).

OBJECTIVE: The aim of this study was to determine the prevalence of enlarged follicles, as detected by a single clinical or ultrasonographic examination, among users of levonorgestrel subdermal contraceptive implants (Norplant implants). STUDY DESIGN: This was a cross-sectional study of 103 users of Norplant implants and 50 users of the TCu380A intrauterine contraceptive device, all of whom received reproductive health services from PROFAMILIA, Santo Domingo, Dominican Republic. Bimanual pelvic examination and vaginal ultrasonography were performed. Enlarged follicles (>25 mm) were followed up weekly. The chi(2) test was applied to these data. RESULTS: Enlarged follicles were detected by ultrasonography in 17. 5% of Norplant implants users and 4% of TCu380A intrauterine contraceptive device users, respectively (P <.04). There was no difference according to duration of use. The longest time to involution of the follicles was 4 weeks. Forty percent of the enlarged follicles detected by ultrasonography were also detected by bimanual pelvic examination. CONCLUSION: Enlarged follicles are a frequent finding among women who use Norplant implants, but they are less frequent than described in previous studies, which were based on serial ultrasonographic scans in selected groups of users. Physicians and users should be aware of the transient nature of these enlarged follicles, which do not require intervention.

Contraceptive Agents, Female↗

PubMed1999

Timing of onset of contraceptive effectiveness in Norplant implant users. II. Effect on the ovarian function in the first cycle of use.

The objective of this study was to time the onset of contraceptive effectiveness in Norplant implant users, when the capsules were inserted beyond the first 7 days of the cycle, based on the immediate effect on the ovarian activity. A total of 42 healthy women requesting Norplant implant contraception were enrolled at clinics in Santo Domingo, Dominican Republic, and in Baltimore, Maryland. Implants were inserted on days 8-13 of the menstrual cycle. Blood samples for estradiol (E2), progesterone (P), luteinizing hormone (LH) (in a subset of 12 women), and levonogestrel (LNG) assay, were taken at 0 h and at 6, 12, 24, 72, and 168 h postinsertion. Ovulation, as defined by P > 2.5 ng/mL, occurred in 40% of subjects. A short lasting, frequently blunted, LH peak occurred within 12 h postinsertion, in all these subjects. The remaining subjects had anovulatory cycles with two distinct E2 profiles: continuously increasing E2 levels to a high mean of 414.3 pg/mL (28%), or no sustained increase in E2 (32%). Most cycles (86%) in which Norplant was inserted with high E2 levels (> 175 pg/mL) were ovulatory, whereas none were ovulatory with low E2 (< 100 pg/mL) at insertion. Based on the endocrine effects of Norplant implant insertion in the midadvanced follicular phase, in which ovulation will either occur within 48 h of insertion or will be impaired, additional contraceptive protection is necessary only for 3 days.

Adolescent↗

PubMed1998

Sex hormone binding globulin and free levonorgestrel index in the first week after insertion of Norplant implants.

Levonorgestrel has an inhibitory effect on sex hormone binding globulin (SHBG). This decrease in SHBG leads to an increase in the free levonorgestrel index (FLI), which has a stronger biological effect. The interaction between serum levels of levonorgestrel and SHBG in long-term users of Norplant implants has been described. This study was designed to understand the same interaction immediately after the insertion of the implants, in a group of 16 women, sampled at 0 and 6 h and at 1, 3, and 7 days after Norplant implant insertion. Peak serum levonorgestrel levels were achieved at 24 h after insertion, remaining stable on day 3 and decreasing by > 10% by day 7. SHBG did not change during the first 24 h, but decreased by 19% and 60% on days 3 and 7, respectively. FLI more than doubled from day 1 to day 7 after insertion. The large decrease in SHBG and doubling of FLI is not followed by a similar reduction in levonorgestrel, which is hard to explain without an increase in the release rate of the steroid from the capsule.

Contraceptive Agents, Female↗

PubMed1998

Timing of onset of contraceptive effectiveness in Norplant implant users. Part I. Changes in cervical mucus.

OBJECTIVE: To provide scientific data regarding the changes in cervical mucus within the first hours to days after Norplant implant insertion and to estimate when the cervical mucus is hostile enough to suggest a contraceptive effect. DESIGN: Multicenter, clinical descriptive study. SETTING: Family planning clinics. PATIENT(S): Forty-two women who were between days 8 and 13 of their menstrual cycle and who had requested Norplant implants were admitted to the study. INTERVENTION(S): Cervical mucus and blood samples were obtained. MAIN OUTCOME MEASURE(S): Cervical mucus scores, sperm penetration distances, and serum levels of progesterone, estradiol, and levonorgestrel. RESULT(S): The median cervical mucus score observed at baseline was 6 ("fair"), indicating that the mucus was already somewhat hostile before insertion of the Norplant implants. The median scores declined to 5 at 12 and 24 hours and continued to decrease through day 7 to 2 ("poor"), a score that is judged as hostile to sperm penetration. Overall, 73% of all subjects had a poor cervical mucus score by 3 days after insertion; at 7 days after insertion, 90% exhibited poor mucus and none had a good score. There was a substantial drop in the overall median distance traveled by the vanguard sperm after 12 hours for each cervical mucus score grouping. The distance traveled decreased rapidly between 12 and 24 hours to < 0.5 cm in subjects with fair and poor mucus, and by day 3, 91% of the subjects exhibited poor sperm penetration. CONCLUSION(S): On the basis of our findings, deterioration of the quality of the cervical mucus and sperm penetration is evident by 24 hours after insertion, although not to a level that would suggest adequate protection until 72 hours after insertion. Therefore, we are confident in recommending that backup methods of contraception (e.g, condoms) need not be used for more than 3 days after insertion, even when the implants are inserted close to ovulation. These findings provide policy makers, clinic managers, and clinicians with important information about how they can improve client access to Norplant implants.

Adult↗

PubMed1996

Hormonal treatment for bleeding irregularities in Norplant implant users.

OBJECTIVE: Our purpose was to evaluate whether prolonged or irregular bleeding during Norplant implant use could be alleviated with the use of oral hormonal medication. STUDY DESIGN: One hundred fifty users of the Norplant levonorgestrel contraceptive implant with prolonged or frequent bleeding were enrolled in this prospective, randomized, comparative study and assigned to one of three treatment groups for 20 days: ethinyl estradiol 50 microg, an oral contraceptive (50 microg ethinyl estradiol and 250 microg levonogestrel), and placebo. Total days of bleeding during treatment and length of the bleeding-free interval were analyzed. RESULTS: Women treated with the levonorgestrel-ethinyl estradiol pill bled an average of 2.6 days during treatment compared with 5.4 and 12.3 days in the ethinyl estradiol and placebo groups, respectively. Differences between both hormonal groups and placebo were significant (p <0.00001); moreover, the combined pill was more effective than ethinyl estradiol along (p <0.0001). CONCLUSION: The combined pill proved to be an excellent palliative treatment and is a more practical approach because of availability at all clinic sites.

Adult↗

PubMed1996

Effect of preovulatory insertion of Norplant implants over luteinizing hormone secretion and follicular development.

OBJECTIVE: To determine whether the process of ovulation could be interrupted by the insertion of Norplant implants (Leiras Pharmaceuticals, Turku, Finland) in the advanced preovulatory phase. DESIGN: Prospective study. SETTING: The Department of Biomedical Research at the Family Planning Clinic of PROFAMILIA, Santo Domingo, Dominican Republic. PATIENTS: Healthy women of reproductive age, requesting Norplant implants contraception. Thirteen of 15 women volunteers who were admitted completed the study. INTERVENTIONS: Norplant implants were inserted when the dominant follicle reached a mean diameter of 16 mm, based on serial vaginal ultrasounds (US) beginning on day 10 of the cycle. Blood samples for determination of E2, P, LH, and levonorgestrel, were taken and vaginal US performed at 0, 4, 24, 48, and 72 hours after insertion. If follicle rupture had not occurred at 72 hours after insertion, blood sampling and US were done three times per week during 2 additional weeks. RESULTS: Follicle rupture occurred in 11 of 13 subjects within 72 hours after insertion, with the exception of 1 subject in whom rupture occurred between 72 and 192 hours. Two women already had an LH peak at the time of insertion. In 9 of the remaining 11 women, a shortlasting, blunted LH surge was observed at 4 hours postinsertion. In the remaining two women, who had the lowest E2 levels, ovulation was inhibited, and a persistent follicle developed without luteinization. CONCLUSIONS: The insertion of Norplant implants in the advanced follicular phase will not inhibit ovulation if sufficient E2 priming has occurred. On the contrary, the exogenous progestin may rapidly foster ovulation shortly after.

Drug Implants↗

PubMed1992

Free levonorgestrel index and its relationship with luteal activity during long-term use of Norplant implants.

Levonorgestrel serum levels and sex hormone binding globulin (SHBG) were measured in 82 women during different years of use of Norplant implants. The ratio between levonorgestrel and SHBG was calculated as an indicator of the free biologically active fraction of levonorgestrel (free levonorgestrel index, FLI). These parameters were then correlated with the presence of luteal activity, as determined by progesterone levels above 9.6 nmol/L, in a sampling run of 10 samples taken twice a week for five consecutive weeks. Levonorgestrel serum levels remained constant around 1.0 nmol/L during the five-year period. SHBG levels were below normal for the first 18 months of use, returning to normal levels during the last three years of use. The FLI in the first two years was significantly higher than that observed in the later years. The frequency of cycles with luteal activity was 12% during the first 2 years, increasing to 44% in the latter years, when FLI levels were lower. Our results suggest that the changes in SHBG and consequently in the free biologically active fraction of levonorgestrel may largely account for the differences in degree of ovarian suppression observed between the first two years of use of Norplant implants and the latter three, even in the absence of a significant variation in total levonorgestrel concentrations.

Drug Implants↗

PubMed1991

Ovulatory dysfunction during continuous administration of low-dose levonorgestrel by subdermal implants.

OBJECTIVE: To study the endocrinologic profile of regularly menstruating users of levonorgestrel subdermal implants. DESIGN: Observational, prospective, case-controlled comparative study. SETTING: The Family Planning Clinic of PROFAMILIA, in Santo Domingo, Dominican Republic. PATIENTS, PARTICIPANTS: Thirty one regularly cycling Norplant users and 12 nonhormonal contraceptors who volunteered to participate. INTERVENTIONS: Norplant contraceptive implants were inserted in 31 subjects between 13 and 77 months before this study. MAIN OUTCOME MEASURES: Follicle-stimulating hormone, luteinizing hormone, estradiol (E2), and progesterone (P) were serially assayed for one menstrual cycle. RESULTS: Almost half of the cycles among Norplant users were anovulatory; all the rest (55%) had some form of dysfunction: diminished gonadotropin surge, luteal phase insufficiency (low P levels and shortened luteal phase), and E2 profiles different from normal controls. CONCLUSIONS: Anovulation is clearly one of the main mechanisms of action of Norplant, but even in presumptive ovulatory cycles, the dysfunctions described possibly contribute to the high contraceptive effectiveness of Norplant.

Adult↗

PubMed1990

Ovarian endocrine function through five years of continuous treatment with NORPLANT subdermal contraceptive implants.

Ovarian endocrine function was assessed in 88 women using NORPLANT subdermal implants during different periods of use and in a control group of 15 women using non-hormonal contraception. Blood samples for estradiol (E2) and progesterone (P) assays were obtained twice a week for five consecutive weeks. Three distinct E2 patterns were observed: one was characterized by fluctuating levels within a normal range (20 to 400 pg/ml), a second pattern corresponded to continuous low E2 levels (below 75 pg/ml in the 10 samples) and the third was characterized by high broad estradiol peaks reaching over 400 pg/ml. The proportion of sampling runs characterized by normal fluctuating levels increased from 38% in the first two years of use to 80% during the fifth year of use. Low E2 profile was only observed during the first two years of use (27%) and in only 1 case at the beginning of the third year of use (5%). The percentage of cycles with high broad estradiol peaks remained between 20-40% without a clear tendency to change in either direction with duration of use. Thirty-three percent of the observed sampling runs had luteal activity (P above 3 ng/ml). The proportion of runs with luteal activity increased from 14% during the first two years of use to 40% during the third and fourth, and 60% during the fifth year of use. All control subjects had luteal activity. The mean highest progesterone level was lower in the NORPLANT runs (8.7 +/- 3.9 ng/ml) as compared to the controls (11.3 +/- 3.8 ng/ml). NORPLANT sampling runs with luteal activity had normal fluctuating E2 levels with only one exception. However, not all cycles with normal E2 levels showed luteal activity. On the other hand, all runs with low E2 levels or high broad E2 peaks were without luteal activity. In summary, women using continuous low-dose levonorgestrel contraception through NORPLANT subdermal implants, have a variable degree of ovarian activity as compared with the more complete depression of ovarian function observed among pill or injectables' users. Ovarian activity becomes closer to normal during the third through fifth year of use.

Contraceptive Agents, Female↗