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At least 289 records · Page 16Linked to original sources
PubMed2004

Inhibition of glucocorticoid-induced cataracts in chick embryos by RU486: a model for studies on the role of glucocorticoids in development.

Cataract formation can be induced by glucocorticoid treatment of developing chick embryos. We show here that this response can be blocked very effectively by use of the antiglucocorticoid RU486. When dexamethasone (0.02 micromol/egg) was administered from day 13 to 16 chick embryos, their lenses (over 80%) became cataract (GC-induced cataract; stage IV-V) within 48 hrs. These GC-induced cataract formations were prevented by administration of RU486 (0.2 micromol/egg) on day 9. However, RU486 also inhibited hatching even though the embryos showed normal growth and appearance. In control embryos, more than 90% live chicks (39/42 chicks) were hatched on day 22. Chick embryos treated with RU486 on day 9 appeared to grow normally until 21, but could not hatch. When chick embryos were treated with RU486 (0.2 micromol/egg) on day 15, more than 80% live embryos (34/42 chicks) were hatched on day 23 with normal appearance, which was one day delay comparing to the control. These observations indicate that endogenous glucocorticoids are involved in the ability to hatch and that RU486 is able to block the actions of endogenous glucocorticoids. Thus, RU486 should be a very useful tool for studies on other biochemical and physiological aspects of chick embryo development that are under glucocorticoid control.

Animals↗
PubMed2006

Is estradiol mandatory for an adequate follicular and embryo development? A mouse model using aromatase inhibitor (anastrozole).

BACKGROUND: Although high levels of estradiol are found in the follicular fluid, little is known about its necessity for adequate follicular growth, oocyte maturation and embryo development. Arimidex (anastrozole) is a potent aromatase inhibitor capable to induce an in-vivo milieu deprived of estradiol. This study uses a mouse model applying Arimidex to create an in-vivo system lacking of estradiol, in order to explore whether this gonadal steroid hormone is mandatory for folliculogenesis followed by normal fertilization and embryo development. METHODS: Experiment 1: Immature C57 Black female mice, aged 3-4 weeks were superovulated by 5 IU PMSG given intraperitoneally. A study group (9 mice) was concomitantly injected with 0.1 mg of Arimidex intraperitoneally given the morning day before PMSG, the morning day of PMSG injection and the following two days. The control group (8 mice) was similarly injected with normal saline. Estradiol (E2) and progesterone (P) serum levels were tested 48 hours after PMSG and the ovaries of each mouse blindly examined by a pathologist to evaluate follicular development. Experiment 2: 48 h after PMSG superovulation, hCG (7.5 IU) was injected intraperitoneally, followed by mating. The study group was treated with Arimidex 0.1 mg intraperitoneally daily from a day prior to PMSG injection to the day of sacrifice. The control group was treated similarly by normal saline. Forty-two hours after mating blood was withdrawn for E2 and P levels followed by tubal dissection. Embryos of 2-4 cells were cultured in-vitro and the development to the morula, blastocyst and hatching blastocyst stages were examined 24, 42, and 48 h later. RESULTS: Experiment 1: A significant reduction of E2 levels was achieved in the Arimidex group in comparison to control group (126.3+/-104.8 and 1910+/-960 pmol/L, respectively; p < 0.0001). Nevertheless, the two groups did not differ by the mean number of follicles (27+/-9.5 and 30.4+/-13.0) or the distribution for antral (65% and 68.4%) and pre-antral (35% and 31.6%) follicles, respectively. Experiment 2: The reduction of estradiol during follicular phase did not hamper follicular development, in-vivo fertilization and in-vitro embryo development. Similar rates of embryo development to the morula stage (90.6% and 86%), blastocyst stage (86% and 89%) and hatching blastocyst (81% and 78%) were achieved in the Arimidex group and the control group, respectively. CONCLUSIONS: Adequate folliculogenesis is independent of estrogen but is conditioned on gonadotropin stimulation. Moreover, depletion of estradiol in the vicinity of the oocyte did not impair its developmental potential, including its fertilization and development into morulae, blastocysts and hatching blastocysts.

Anastrozole↗
PubMed1994

Glucose metabolism, triglyceride and glycogen levels, as well as eicosanoid production in isolated uterine strips and in embryos in a rat model of non-insulin-dependent diabetes mellitus during pregnancy.

Spontaneous contractile activity, glucose (Glu), glycogen (GLY), triglyceride (TG) metabolism and eicosanoid production, was evaluated in isolated uterine strips from control and non-insulin-dependent diabetic rats on day 10 of pregnancy. Metabolism of Glu, levels of GLY and TG and eicosanoid production were also studied in day 10 embryos obtained from both experimental groups. "In vitro" isometric developed tension (IDT), was similar at 0 hr in control and diabetic uterine preparations, but IDT was decreased after a 60 min incubation in the diabetic group. The frequency of contractions (FC) was similar at 0 hr and after 60 min incubation in both experimental groups. On the other hand, the production of 14CO2 from U14C-glucose was lower in isolated uteri and embryos obtained from diabetic rats than in controls. Initial TG levels were similar in uteri isolated from control and diabetic rats, and higher in embryos obtained from diabetic mothers than in controls. Levels of TG in uterine strips suspended in Glu or Glu-free medium did not differ at 0 hr or at 60 min either in controls or in diabetic rats. On the contrary GLY levels in uterine strips from diabetic animals were higher than in controls, whereas in embryos from diabetic mothers GLY levels were similar to controls. Levels of GLY in uterine strips from controls and diabetic animals decreased after 60 min incubation only in the absence of Glu in the incubation medium. Production of PGE2, PGE1, 6-keto-PGF1 alpha, PGF2 alpha, TXB2 and LTB4 was studied in uterine strips and embryos obtained from control and diabetic rats. No differences were found between control and diabetic uterine prostanoid production, but lower production of LTB4 was observed in diabetic uteri. However production of PGE2 and PGF2 alpha was greater in embryos obtained from diabetic mothers than in controls. In this study, we observed lower uterine metabolic alterations than in the pancreatectomized diabetic rat model studied previously, but important anomalies in the embryos obtained from non-insulin-dependent diabetic mother were found.

Animals↗
PubMedDate not supplied

Developmental stages in the rabbit embryo: guidelines to choose an appropriate experimental model.

Researchers involved in the field of congenital malformations are often forced to work on an animal model. Both accurate description of its normal development and comparative staging with human development will be mandatory. To complete the lacking medical literature, we herein provide such data for the rabbit model. Sampled rabbit embryos were staged using the Carnegie criteria, in order first to determine if they were consistent with the rabbit developmental pattern, and second to compare this pattern with the human one. Our results show a suitable comparison of rabbits and humans in early developmental stages, except for the neural growth.

Animals↗
PubMed1985

A model for avian lung ventilation, and the effect of accelerating stimulation in Japanese quail embryos.

A simple stages model is proposed for the interval between the start of lung ventilation and the start of clicking in Japanese quail embryos. The model is extended to describe the effect of accelerating stimuli and is fitted to data sets from three different experiments. We see that the model provides a useful synthesis of the variety of results, and furnishes a framework for the analysis of further experiments.

Animals↗
PubMed1994

Repression of ALA synthase by heme and zinc-mesoporphyrin in a chick embryo liver cell culture model of acute porphyria.

We characterize a liver cell culture model for acute hepatic porphyrias that recapitulates the biochemical features of the human syndrome. In chick embryo liver cells in primary culture exposed to glutethimide and 4,6-dioxoheptanoic acid, heme alone produced a transient dose-dependent decrease in delta-aminolevulinate synthase and a concomitant increase in heme oxygenase. The addition of low concentrations of zinc-mesoporphyrin (50-200 nM), an inhibitor of heme oxygenase, led to more prolonged decreases in activity of the synthase and to an additive effect with heme. These effects of zinc-mesoporphyrin were associated with prolonged inhibition of heme oxygenase. These results suggest that the treatment of choice of acute porphyric syndromes may be the combination of low doses of heme and zinc-mesoporphyrin or another similarly non-toxic inhibitor of heme oxygenase.

5-Aminolevulinate Synthetase↗
PubMed2006

Roadmap to embryo implantation: clues from mouse models.

Implantation involves an intricate discourse between the embryo and uterus and is a gateway to further embryonic development. Synchronizing embryonic development until the blastocyst stage with the uterine differentiation that takes place to produce the receptive state is crucial to successful implantation, and therefore to pregnancy outcome. Although implantation involves the interplay of numerous signalling molecules, the hierarchical instructions that coordinate the embryo-uterine dialogue are not well understood. This review highlights our knowledge about the molecular development of preimplantation and implantation and the future challenges of the field. A better understanding of periimplantation biology could alleviate female infertility and help to develop novel contraceptives.

Animals↗
PubMed2005

[Effects of jiantai liquid on the expression of estrogen/progesterone receptors in embryo implantation dysfunction mice endometrium].

OBJECTIVE: To explore the mechanism of Jiantai liquid on the endometrium development of embryo implantation dysfunction mice. METHOD: The model of embryo implantation dysfunction mice was induced by mifepristone and treated by Jiantai liquid. All animals were sacrificed on day 8 of pregnancy. Estradiol and progesterone concentrations in serum and endometrium tissue homogenates were measured by radioimmunoassay method, the endometial expressions of estrogen receptor (ER)and progesterone receptor (PR)assessed by immunohistochemical SP method. RESULT: There were no significantly differences in the estradiol and progesterone concentrations in serum and uterus tissue homogenates among three groups( P > 0.05). Absorbency and area rate of ER, PR in model group' s gland and stroma were higher than those in model group(P < 0.05), which was similar with the control group( P > 0.05). CONCLUSION: Jiantai liquid increase the implantation rate and improve the endometrial development by increasing the expressions of ER, PR in endometrium of embryo implantation dysfunction

Animals↗
PubMed1982

The role of urinary obstruction in the genesis of renal dysplasia. A model in the chick embryo.

Although obstruction of urinary drainage is the current pathogenetic mechanism believed responsible for renal dysplasia, the results of experimental studies have not uniformly substantiated this impression. To help resolve this issue, we evaluated the effect of obstruction of the urinary drainage of the embryonic kidney upon the later development of the kidney. We developed a model which allowed us to ligate the ureter surgically of the chick embryo before and after the appearance of nephrons. Initially, the normal morphologic features of renal development were studied in 22 embryos at various stages of incubation and in 94 metanephric rudiments cultivated as chorioallantoic membrane (CAM) grafts. Then, the morphologic features of renal development were studied in 151 metanephric rudiments subjected to surgical ligation of the primitive ureter and then cultivated as CAM grafts. The ligations were performed with 9-0 silk suture, aided by the operating microscope, and induced before and after the appearance of nephrons. Renal differentiation of the non-ligated rudiments cultivated as CAM grafts resembled that which appeared in situ. Renal differentiation of 87 per cent of nonligated rudiments which survived grafting displayed normal renal development and 13 per cent displayed mild hydronephrosis. Renal differentiation of 67 per cent of the ligated rudiments which survived grafting displayed hydronephrosis and 33 per cent displayed normal development. Dysplasia was never seen in any specimen. Obstruction of the ureter of the developing kidney caused only hydronephrosis in the chick model. It appears that renal dysplasia is not solely caused by simply mechanical obstruction to urinary drainage, even when the obstruction is imposed at early stages of renal development.

Animals↗
PubMed1986

Experience with the cryopreservation of human embryos using the mouse as a model to establish successful techniques.

Mouse embryos at the one-, two-, and eight-cell stages have been used to optimize the conditions for cryopreservation of human oocytes and embryos. For storage in glass vials using 1.5 M dimethyl sulfoxide (DMSO) as a cryoprotectant and slow cooling (approximately 0.3 degrees C/min), phosphate-buffered medium was superior to Hepes-buffered medium. Termination of slow cooling at -80 degrees C before transfer to liquid nitrogen with subsequent slow thawing (approximately 8 degrees C/min) resulted in more embryos surviving than when cooling terminated at -40 degrees C and rapid thawing (approximately 500 degrees C/min) was employed. Dilution of DMSO upon thawing with medium containing 0.5 M sucrose gave higher embryo survival rates than a stepwise (0.25 M decrements) dilution. Using these techniques, three pregnancies were established upon the transfer of 11 frozen-thawed embryos to seven patients. Rates of embryo survival using the simpler cryopreservation technique of ice-free vitrification in 0.25-ml straws have been disappointing.

Animals↗
PubMed1997

Inactivation of single genes within the virulence regulon of an M2 group A streptococcal isolate result in differences in virulence for chicken embryos and for mice.

An M2 streptococcal isolate and isogenic mutants in which either the emm or mrp gene was insertionally inactivated were tested for virulence using either a mouse model or a chicken embryo model. The results of the studies using the mouse model demonstrated that neither the emm nor mrp gene products had a significant effect on virulence when mice were challenged via the i.p. route. However, when the bacteria were injected into the skin the emm gene product was identified as a virulence factor. In parallel studies in the chicken embryo model the mrp gene product was found to be a major virulence factor, while a minor contribution to virulence could also be attributed to the emm gene product. The importance of these gene products to virulence was noted when the chicken embryo were injected either i.v or when the bacteria were placed on top of the chorioallantoic membrane. The direct comparison of a single wild type group A organism and its paired isogenic mutants in two animal models suggests that different combinations of bacterial factors are required to overcome host defense strategies associated with different animal species.

Animals↗
PubMed1999

Angiostatic activity of steroids in the chick embryo CAM and rabbit cornea models of neovascularization.

Ocular neovascular diseases represent a major cause of blindness in the world. Angiostatic steroids are a unique class of compounds which inhibit the formation of new blood vessels in various models, including ocular models of angiogenesis. In search of potent new anti-angiogenic agents for the treatment of ocular neovascular disease, a large group of steroids were evaluated for angiostatic activity in the chick embryo CAM model. Angiostatic activity was found among all steroid classes included in the study. There was a good correlation between the angiostatic efficacies of 15 diverse steroids tested in the chick CAM and in the rabbit LPS-induced corneal pocket models of neovascularization (r=0.76, p=0.01). These studies show that potent angiostatic steroids inhibit neovascularization in two different animal models, suggesting a common mechanism of action. Glucocorticoid therapy is sometimes associated with ocular side effects. Two of the most potent angiostatic steroids, AL-3789 and AL-4940, were evaluated for glucocorticoid-mediated antiinflammatory activity in the in vitro U937 cell model of LPS-induced IL-1 induction and found to be devoid of glucocorticoid activity. Angiostatic steroids which lack glucocorticoid activity should be attractive drug candidates for treating ocular neovascular disease.

Angiogenesis Inhibitors↗
PubMed1994

Assessment of ventricular relaxation in the developing chick embryo using a monoexponential model.

In this study, the ventricular pressure decline during isovolumic relaxation in early diastole was modeled by regressing pressure and pressure change vs. time to a monoexponential formula: P(t) = P infinity+P0e-t/tau, where P(t) is ventricular pressure at time t, P infinity is the pressure in the fully relaxed ventricle, P0 is the pressure at the end of ventricular ejection, and tau is the ventricular relaxation rate constant. Analysis was performed on 330 ventricular pressure waveforms from 22 chick embryos, stages 17, 23, and 26, during baseline and following cardiac cycle length perturbation. Three computational models were evaluated. Based on analysis of the confidence intervals of estimates of P infinity and analysis of residuals, a least-squares nonlinear regression of pressure vs. time, which allowed estimates of tau and P infinity, best approximated the pressure decline. Isovolumic pressure decline in the embryonic heart is well approximated by a monoexponential model if both P infinity and tau are estimated. Negative values of P infinity during early stages of cardiac morphogenesis support the idea that diastolic suction plays a role in ventricular filling in the developing heart.

Animals↗
PubMed2000

Differential sensitivity of mouse neural crest cells to ethanol-induced toxicity.

Neural crest cells (NCCs) have been identified as an important target population relative to ethanol-induced teratogenicity in both mouse and avian models. Additionally, whole embryo culture mouse models have shown strain-related differences in sensitivity to ethanol-induced damage following acute exposure during early NCC development. That differential sensitivity of NCCs may contribute to these strain differences has been unexplored. For this purpose, cultured NCCs from an inbred mouse strain (C57BL/6J; C57) that is more sensitive to ethanol-induced teratogenicity than an outbred strain (ICR) were compared. This study showed that the incidence of cell death was significantly higher for the C57 NCCs than those from the ICR strain at all ethanol concentrations tested, and as early as 12 hours after initial exposure to 100 mM ethanol. The lateral mobility of the membrane lipids was faster and the membrane GM1 content was lower in C57 cells than ICR cells both under control conditions and at all doses and times tested. Ethanol exposure resulted in significant increases in the membrane lipid lateral mobility, and decreases in the membrane GM1 content that occurred in a dose and time-dependent manner in the NCCs from both strains. A significant correlation was found between the GM1 content and lateral mobility of the membrane lipids, the lateral mobility of membrane lipids and cell viability, as well as the GM1 content and cell viability in the NCCs from both strains. These results suggest that different strain sensitivities to ethanol-induced teratogencity may lie, at least in part, in the interstrain differential response of the NCC population and that the vulnerability of the NCCs to ethanol-induced death may be related to their endogenous membrane GM1 content.

Animals↗
PubMedDate not supplied

The role of heat shock proteins in reproduction.

Heat shock proteins (HSP) were first identified in cells after exposure to elevated temperature. Subsequently HSP have been identified as a critical component of a very complex and highly conserved cellular defence mechanism to preserve cell survival under adverse environmental conditions. HSP are preferentially expressed in response to an array of insults, including hyperthermia, free oxygen radicals, heavy metals, ethanol, amino acid analogues, inflammation and infection. HSP interact with intracellular polypeptides and prevent their denaturation or incorrect assembly. In addition HSP are also involved in several processes essential for cellular function under physiological conditions. HSP production is enhanced during in-vitro embryo culture and they are among the first proteins produced during mammalian embryo growth. The spontaneous expression of HSP as an essential part of embryo development is well documented and the presence or absence of HSP influences various aspects of reproduction in many species. Finally, HSP are immunodominant antigens of numerous microbial pathogens, e.g. Chlamydia trachomatis, which have been recognized as the main cause of tubal infertility. Many couples with fertility problems have had a previous genital tract infection, have become sensitized to microbial HSP, and a prolonged and asymptomatic infection may trigger immunity to microbial HSP epitopes that are also expressed in man. Antibodies to both bacterial and human HSP are present at high titres in sera and hydrosalpinx fluid of many patients undergoing in-vitro fertilization (IVF). In a mouse in-vitro embryo culture model, these antibodies impaired the mouse embryo development at unique developmental stages. Recent studies indicate an association between a previous infection, immunity to HSP and reproductive failure.

Animals↗
PubMed1999

Heat shock protein expression during gametogenesis and embryogenesis.

When cells are subjected to various stress factors, they increase the production of a group of proteins called heat shock proteins (hsp). Heat shock proteins are highly conserved proteins present in organisms ranging from bacteria to man. Heat shock proteins enable cells to survive adverse environmental conditions by preventing protein denaturation. Thus the physiological and pathological potential of hsps is enormous and has been studied widely over the past two decades. The presence or absence of hsps influences almost every aspect of reproduction. They are among the first proteins produced during mammalian embryo development. In this report, the production of hsps in gametogenesis and early embryo development is described. It has been suggested that prolonged and asymptomatic infections trigger immunity to microbial hsp epitopes that are also expressed in man. This may be relevant for human reproduction, since many couples with fertility problems have had a previous genital tract infection. Antibodies to bacterial and human hsps are present at high titers in sera of many patients undergoing in vitro fertilization. In a mouse embryo culture model, these antibodies impaired the mouse embryo development at unique developmental stages. The gross morphology of these embryos resembled cells undergoing apoptosis. The TUNEL (terminal deoxynucleotidyl transferase-mediated X-dUTP nick end labeling) staining pattern, which is a common marker of apoptosis, revealed that embryos cultured in the presence of hsp antibodies stained TUNEL-positive more often than unexposed embryos. These data extend preexisting findings showing the detrimental effect of immune sensitization to hsps on embryo development.

Animals↗
PubMed2005

Pathways of vitamin A delivery to the embryo: insights from a new tunable model of embryonic vitamin A deficiency.

Circulating retinoids (vitamin A and its derivatives) are found predominantly as retinol bound to retinol-binding protein (RBP), which transports retinol from liver stores to target tissues, or as retinyl ester incorporated in lipoproteins of dietary origin. The transport of retinoids from maternal to fetal circulation is poorly understood, especially under conditions of inadequate dietary vitamin A intake. Here we present RBP-/- mice as a tunable model of embryonic vitamin A deficiency. This model has enabled us to analyze metabolic links between maternal nutrition and retinoid delivery to the fetus. Our data show that retinol-RBP is the primary contributor to fetal development, whereas retinyl ester are largely responsible for accumulation of fetal retinoid stores. Furthermore, these studies indicate the importance of embryonic RBP in distributing vitamin A to certain developing tissues under restrictive diets. We also show differences among developing tissues in their dependency on the embryonic retinol-RBP pathway. Finally, we demonstrate that accumulation of embryonic vitamin A stores does not depend on the expression of RBP in the fetal liver.

Animals↗