PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Reproductive Period”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62Linked to original sources
PubMed2006

Males also have their time of the month! Cyclic disposal of old spermatophores, timed by the molt cycle, in a marine shrimp.

That sexually mature females go through hormonally regulated reproductive cycles is a well-established phenomenon in sexually reproducing organisms. Males, on the other hand, are commonly regarded as being continuously ready to mate. 'Programmed sperm degradation' on a periodic basis or an innate sperm 'expiry date' have never been shown. This manuscript describes a newly discovered molt-dependent mechanism by which old sperm is periodically removed from the reproductive system of male Litopenaeus vannamei shrimp. Firstly, it is shown that the spermatophores of males held in captivity become progressively melanized, a process that eventually renders them impotent. Then, by using melanin specks as a color marker, it is demonstrated that this phenomenon can be delayed and even reversed as long as the males remain sexually active. Lastly and most importantly, it is shown that male shrimp go through reproductive cycles that are strictly associated with their molt cycles, which, in turn, are hormonally regulated. Intact intermolt spermatophores disappeared about 12 h premolt, and a new pair of spermatophores appeared in the ampoules the day after the males had molted. This phenomenon was observed in an almost constant portion of males, both those in an all-male population and those in mixed male/female populations, even during the times that the females of those populations were not vitellogenically active. To the best of our knowledge, this is the first report of males of any animal species exhibiting endogenous reproductive cycles, as do females, and of the finding that spermatozoa have a predetermined expiry date, a feature that may possibly contribute to male fitness.

Animals↗
PubMed1992

Mammalian GnRH involvement in prostaglandin F2 alpha and sex steroid hormones testicular release in two amphibian species: the anuran water frog, Rana esculenta, and the urodele crested newt, Triturus carnifex.

The present work was carried out to study the in vitro effects of mammalian gonadotropin-releasing hormone (mGnRH) on Rana esculenta and Triturus carnifex testis production of prostaglandin F2 alpha (PGF2 alpha) and sex steroid hormones during the prereproduction, reproduction, and postreproduction periods. In R. esculenta, testicular PGF2 alpha release was lower during postreproduction, and mGnRH increased PGF2 alpha in prereproduction and reproduction. Androgens were higher during prereproduction, and mGnRH induced an androgens increase in prereproduction and reproduction. In T. carnifex testicular PGF2 alpha release was lower during reproduction, and mGnRH increased PGF2 alpha in prereproduction and reproduction. Androgens were higher in reproduction and lower in postreproduction, and mGnRH induced an androgens increase in reproduction. Estradiol-17 beta release was higher in postreproduction, and mGnRH induced an estradiol decrease in reproduction and an increase in postreproduction. These results seem to indicate the involvement of PGF2 alpha in the testicular reproductive activity, and a similar mGnRH mechanism of action, both in R. esculenta and in T. carnifex. In addition, taken together with previous studies, they seem to suggest that the relationship found between mGnRH and PGF2 alpha or sex steroids could be widespread in amphibians.

Androgens↗
PubMed1990

[Diseases and culling of Swiss dairy cows. 2. Culling and relation between diseases and milk production parameters].

During three years (1982 to 1984) data were collected concerning diseases and reasons for culling in 612 dairy farms with Brown Swiss, Simmental and Black and White cattle. The frequency of culling increases in all three breeds with increasing age, from 20% at the first lactation up to 33% from the 4th lactation on. The main reasons for disposal are insufficient production, reproductive problems or udder diseases. After treatment for reproductive problems, mastitis or acetonemia, the risk for culling within the same lactation period is increased. Reproductive problems (no heat symptoms, repeat breeder, ovarian cysts) and acetonemia increase with increasing milk production in all three breeds. In cows with high 100-day-performance they are also more frequent. The occurrence of acute mastitis shows no general trend with increasing milk production or with high 100-day-performance. No systematic relationship is found between reproductive disorders or acute mastitis and persistency of milk production. On the other hand, acetonemia is somewhat more frequent in cows showing higher persistency.

Age Factors↗
PubMed1985

A prospective multicentre study to develop universal immunochemical tests for predicting the fertile period in women. World Health Organisation Task Force on Methods for the Determination of the Fertile Period, Special Programme of Research, Development and Research Training in Human Reproduction.

Two immunochemical tests for predicting the fertile period have been adapted for application throughout the world. The estrone test involves the measurement of estrone-3-glucuronide (E1-3-G) in daily samples of early morning urine. The start of the fertile period is identified by a sustained rise in the concentration of E1-3-G (as determined by cumulative sum analysis); the end of potential fertility occurs 120 hours (5 days) after the peak level. Alternatively, the ratio of E1-3-G to pregnanediol-3 alpha-glucuronide (Pd-3 alpha-G) can be calculated and the fertile period identified between a defined rise in this index and the peak value plus 144 hours (6 days). One hundred thirty-one women from 10 countries provided samples from 557 menstrual cycles, and the results from 455 (82%) were accepted for statistical analysis. There were highly significant differences (P less than 0.0001) in the concentrations of the metabolites between centres, but the time intervals between both the rise and peak days and the day of the luteinizing hormone (LH) peak were less significantly different (P less than 0.05) for the estrone test and not significantly different for the ratio test. The fertile period was defined as the day of the LH peak -3 to the day of the LH peak +2. The estrone test successfully delineated this phase in 78% of menstrual cycles, and the ratio test, in 74%. The mean lengths of the derived fertile periods by both methods were 9.3 (SD 2.3) and 10.0 (SD 2.4) 24-hour periods (or days), respectively.

Adult↗
PubMed2005

Effects of bisphenol A given neonatally on reproductive functions of male rats.

Male Sprague-Dawley rats (Crj:CD (IGS) were treated neonatally with bisphenol A (BPA) to evaluate effects on reproductive parameters. Animals were given BPA subcutaneously in corn oil to dosages of 0.002-97 mg/kg body weight, or 0.9 mg/kg 17beta-estradiol (E2) once a day from postnatal day (PND) 0 to PND 9. Preputial separation, copulatory rate, fertility rate, sperm analysis, serum testosterone levels, and gene expression in the testis were assessed. Males in the E2 group showed a decrease in testis weight and alterations of estrogen-mediated gene expression in the testis on PND 10, and by PND 150 incomplete preputial separation, decreases in the copulatory rate, testicular and accessory organ weights and number of sperm. In contrast, males in all BPA groups showed normal reproductive parameters. These results indicate that in male rats, BPA given during the neonatal period neither affected reproductive function nor evoked estrogen-mediated gene responses in the testis.

Animals↗
PubMed1999

Long-term effect of neonatal monosodium glutamate (MSG) treatment on reproductive system of the female rat.

The study aimed at determining effects of monosodium glutamate (MSG), introduced in the perinatal period, on the reproductive system of sexually mature female rats. In days 2, 4, 6, 8, 10 the newborns received s.c. injections of MSG (4 mg/g body weight) or 2% NaCl solution. When the animals reached the age of 6, 12 or 18 months, their ovaries and uteri were isolated for histological and morphometric studies while in their sera estradiol level was estimated by the RIA technique. The perinatal injection of MSG was found to decrease relative weights of ovaries and uteri. In the ovaries increased numbers of primordial follicles and decreased numbers of graafian follicles were detected. Also the thickness of endometrium and of the epithelium, which lined the endometrium, were lowered in females, which received perinatal injections of MSG, as compared to the controls. Serum estradiol level in MSG injected females was lowered at the age of 12 and 18 months. In 12 and 18 month old females the alterations were accompanied by obesity and a decreased body length.

Age Factors↗
PubMed2004

[Condition of children after assisted reproduction in the Czech Republic in the period of 1995-1999].

INTRODUCTION AND PROBLEM: Since the introduction of in vitro fertilization (IVF) there has been continuing discussion on possible genetic defects and malformations in children in connection with the technique of assisted reproduction. These data have not been so far analyzed in the all-state scale of the Czech Republic and our contribution thereby contributes by present complex analysis of the data to the knowledge of this problem in this country. MATERIAL AND METHODS: The paper analyzes data of children from IVF Registry for the years 1995-1998 and compares the results obtained with those of children born after spontaneous pregnancy in the Czech Republic in the period of 1995-1999. The incidence of inborn defects in children born after IVF methods has been confronted with data from the VV Registry after spontaneous conception. It is a retrospective analysis of individual anonymous data. RESULTS: In the period of 1995-1998 there were 3,782 successful pregnancies after IVF, which ended by successful delivery of the children. In the period of 1995-1999, 367,735 children were born in the Czech Republic on the whole. In the total number of 3,782 successful pregnancies, 5,126 children were born, 5,108 being born alive and were stillborn. The frequency of children having been delivered with an inborn defect were 2.98% in the IVF children and 2.77% in other born children, the difference not being statistically significant. CONCLUSION: The analysis of our cohort of IVF children has not revealed increased rate of inborn defects in comparison with children born after spontaneously conception.

Congenital Abnormalities↗
PubMed2004

Assessment of changes in utero-ovarian arterial impedance during the peri-implantation period by Doppler sonography in women undergoing assisted reproduction.

OBJECTIVE: To investigate changes in utero-ovarian blood flow during the peri-implantation period and their significance in successful embryo implantation. METHODS: A prospective longitudinal study was conducted in 317 women undergoing in-vitro fertilization-embryo transfer (IVF-ET) treatment. All of them had at least one good-quality embryo for transfer on the second or third day after oocyte retrieval. Measurement of endometrial thickness and color flow imaging with pulsed waveform analysis of uterine and ovarian arteries were performed before ET and 5-6 days after ET. RESULTS: There were no significant differences in the age of patients, duration of infertility or number of embryos transferred between women who became pregnant (n = 91) and those who did not (n = 226). There was no difference in mean endometrial thickness between the two groups before ET, while a thicker endometrium was found in women who had conceived compared with those who had not 5-6 days after ET (P = 0.02). Mean uterine arterial resistance index (RI) and pulsatility index (PI) values were significantly lower in the pregnant than in the non-pregnant group before ET (P = 0.04 and P = 0.003, respectively), but no significant differences were found between the two groups 5-6 days after ET. In contrast, the mean ovarian arterial RI and PI values were similar between the two groups before ET, yet the pregnant group showed significantly lower RI and PI values compared with the non-pregnant group 5-6 days after ET (P = 0.002 and P = 0.01, respectively). A significantly higher peak systolic velocity (PSV) of intraovarian vessels was also noted in the pregnant group 5-6 days after ET. CONCLUSION: Different utero-ovarian blood flow changes during the peri-implantation period occur in conception and non-conception cycles in women following IVF. Doppler assessment of uterine arterial resistance can help to determine a time interval within the menstrual cycle that is of optimal endometrial status for embryo implantation in assisted conception programs. Delay in achieving adequate uterine perfusion during the temporal window of embryo implantation may have an impact on endometrial receptivity.

Adult↗
PubMed1993

[Effect of perinatal administration of monosodium glutamate (MSG) on the reproductive system of the male rat].

The study was aimed at investigating the effect of monosodium glutamate administered during the perinatal period on the reproductive system of sexually mature male rats. Monosodium glutamate (at a dose of 4 mg/g of body weight) or hypertonic saline was administered subcutaneously to newborn rats at 2--nd, 4-th, 6-th, 8-th and 10-th day of life. At the age of four months the rats were killed and histological and morphometric examinations of testes, epididymis, seminal vesicles and ventral prostate were carried out. Blood serum levels of LH, FSH, testosterone and 17-beta-estradiol were determined by radioimmunoassay. The administration of monosodium glutamate caused inhibition of growth, obesity and decrease in weight of pituitary glands and testes. Blood serum levels of and FSH as well as the height of epithelial cells of accessory sexual glands remained unchanged, whereas testosterone level was lowered.

Animals↗
PubMedDate not supplied

Aging, antiaging, ontogenesis and periods of age development.

An internally contradictory character of individual development may suggest a new periodization of the latter. Etagenesis is an age-associated development of an organism from the zygote to death. Ontogenesis is the period of realization of the genetic program of the organism's development under effects of exogenic factors, the period of growth and shaping of its main structure and functions, and the period of formation of its reproductive function. Mesogenesis is the period of the relatively stable state which is characterized by changing the balance between the processes of aging and antiaging, i.e. the vitauct. Gerontogenesis is the period during which destructive processes of aging prevail over antiaging processes. No strict borderlines between the above periods exist.

Aging↗
PubMed1995

The expression of interstitial collagenase in human endometrium is controlled by progesterone and by oestradiol and is related to menstruation.

Human endometrial tissue, sampled at different periods of the reproductive cycle, expressed interstitial collagenase mRNA, protein and activity only just before and during the menstrual period. This clear-cut correlation and the inhibition of collagenase expression by progesterone and oestradiol in tissue culture point to a pivotal role of this proteinase in the mechanism of menstrual tissue breakdown and bleeding.

Blotting, Northern↗
PubMedDate not supplied

Changes in reproductive organs of female rats treated with bisphenol A during the neonatal period.

The effects of neonatal administration of estrogenic agents on rat reproductive organs were examined. Either bisphenol A (BPA; 0.25, 1, or 4mg/pup) or 10 micro g 17beta-estradiol (E(2)) was given subcutaneously to Sprague-Dawley female rats during the neonatal period from post-natal day (PND) 0 to 9. Animals ovariectomized at 80 days were given subcutaneous injections of 1 micro g/kg E(2) for 3 days from PND 94 to 96. Clefts in the clitoris, early vaginal opening, irregular estrous cycles, a decrease in the area occupied by the corpora lutea (CL) in the ovary, and multiple cystic follicles in the ovary were found in the animals treated neonatally with 1mg BPA. Uterine fluid weight measured after E(2) treatment on PND 94-96 was less than controls. In addition to these abnormalities, unusual body weight gains, persistent vaginal cornification, and lack of CL were observed in females treated neonatally with 4mg BPA. The ovary weight on PND 80 and uterine fluid weight measured after E(2) treatment on PND 94-96 were less than controls for the 4mg BPA group. Neonatal treatment with 10 micro g E(2) induced similar abnormalities as found in the 4mg BPA group. These results show that BPA when given during the neonatal period caused changes in female reproductive organs.

Animals↗