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The effects of viral induced fever and environmental hyperthermia on embryonic development in pregnant rabbits are described. Embryonic development was not disturbed following fever, but there were anomalies in development following hyperthermia. Possible explanations for the different effects of hyperthermia and fever are discussed.
Gonotrophic and embryonic development of Wohlfahrtia magnifica were studied on pupae and adults reared in the laboratory. Gonotrophic development in screwworm begins 8 days after pupation in yellow eye pharate adults. The adult female emerges with its oocytes at stage 3 and requires only 2 days for complete oogenesis and 5 days for complete embryogenesis. Mating occurs 2-5 days after adult emergence, starting the embryonic development. Each female produces an average of 76.8 active larvae which can produce a traumatic lesion in their hosts. When food sources were regularly supplied synchronization of gonotrophic stages can be observed. These stages together with the embryonic ones are described.
Propiconazole is a fungicide used in a variety of agricultural applications. Preliminary studies had suggested that embryos of the crustacean Daphnia magna are particularly susceptible to the toxicity of this chemical. The goals of the present study were to define endpoints of daphnid embryonic development that could be routinely used to assess the embryo toxicity of chemicals and to characterize definitively the embryo toxicity of propiconazole to daphnids. Daphnid embryonic development was characterized into six readily distinguishable stages based on the degree of tissue differentiation. Embryonic development could be monitored either in the brood chamber of the maternal organism or using embryos removed from the brood chamber and incubated ex vivo. Standard toxicity assessment revealed that propiconazole elicited no significant adverse effects on daphnid survival or fecundity during a 21-d exposure to concentrations as high as 0.25 mg/L. Exposure to 0.25 mg/L propiconazole, however, caused a significant incidence of developmental abnormalities and embryonic death. Abnormalities were consistent with developmental arrest at later stages of embryonic maturation. Propiconazole elicited a steep concentration-response curve with respect to embryo toxicity, with a 10% and a 90% incidence of embryo toxicity measured at 0.50 and 0.82 mg/L, respectively. Direct exposure of embryos to propiconazole resulted in toxicity, though the incidence and characteristics of developmental abnormalities were not consistent with that observed during chronic exposures. However, maternal exposure to propiconazole followed by transfer of early embryos to propiconazole-free media resulted in embryo toxicity consistent with that observed during chronic exposure. These results indicate that propiconazole interferes with the later stages of daphnid embryonic development, and that this toxicity is manifested largely via maternal exposure to the fungicide.
This study examined the potential adverse effects of a new camptothecin anticancer agent, CKD-602, on the fertility and early embryonic development of Sprague-Dawley rats. Ninety-six rats of each gender were divided into four groups: three treatment groups and a control group. CKD-602 was administered intravenously to male rats at 0, 4.7, 14, and 42 microg/kg from 63 days prior to mating until the end of the mating period, and to female rats from 14 days before mating until day 6 of gestation. All the males were sacrificed after the end of the 14-day mating period, while all the females were subjected to a caesarean section on day 15 of gestation. In the high dose group, a high incidence of hair loss was observed in both genders. A decrease in the level of food consumption, followed by a decrease in body weight gain was also observed in both genders. At the scheduled necropsy, the gross postmortem examinations revealed an increase in the incidence of thymic atrophy, paleness of the thoracic and abdominal organs in both genders and an increase in the serum testosterone concentration. In addition, there was a decrease in the thymus weight of the males and an increase in the liver, spleen, kidneys, lung, and heart weights of the females. There was an increase in the number of fetal deaths and post-implantation losses as well as a decrease in the litter size found at the caesarean section of the dams. No treatment-related effect on the histopathological findings, sexual cycle, pre-coital time, mating index, fertility index, pregnancy index, and sperm parameters was observed. There were no adverse effects on the general findings and reproductive performance of the parent animals and early embryonic development in the low and medium dose groups. Overall, the no-observed-adverse-effect levels (NOAELs) of CKD-602 are believed to be 14 microg/kg for both general toxicity and early embryonic development, and more than 42 microg/kg for the reproductive performance of the parent animals.
The present study aims to provide data about the time required for Cynopoecilus melanotaenia kept at different temperatures to complete embryonic development. This information can be valuable for optimizing laboratory culture and facilitating future use of this species as a test organism in toxicity tests. Temperature effects on hatching rate are presented as well as information related to embryonic development stages. Eggs were observed daily, from start to finish of embryonic development. Thirteen developmental stages were described. Eggs were kept at two constant temperatures (20 degrees C and 25 degrees C) and at a variable ambient temperature (16-25 degrees C-mean = 21 degrees C, sd = 1.95), to determine developmental rate (velocity) at each temperature. A shorter incubation period was necessary to complete development at 25 degrees +/- 1 degrees C. However, all embryos kept at this temperature hatched with morphological defects, which prevented their survival. No significant difference in developmental time period (p = 0.05) was observed at the 20 degrees C and 16 degrees-25 degrees C (mean = 21 degrees C, sd = 1.95) temperatures.
Findings on embryonal development of renal fascia are given. By the end of the second and during the third months of embryogenesis renal fascia and fascio-mesenchymal clefts as a base for the future adipocyte spaces of retroperitoneum connected with it form around kidneys due to successive rearrangements of mesenchyme.
It has always been assumed that during development the embryo and fetus depend only on glycolysis for energy generation and that they do not oxidize fatty acids. Recently, however, we found abundant expression and activity of fatty acid oxidation (FAO) enzymes in the human embryo and fetus. In a search for FAO gene expression during development we came across two embryonic differentiation genes: differentiation defective (dif-1) and congested-like trachea (colt) of Caenorhabditis elegans and Drosophila melanogaster, respectively. Earlier studies showed that expression of these two genes is essential during developmental stages with high energy requirements. Both dif-1 and colt encode proteins with sequence similarity to the mitochondrial carnitine acylcarnitine carrier (CACT), which suggests that the DIF-1 and COLT proteins might be functional orthologues of CACT. To investigate this, we expressed both dif-1 and colt in Saccharomyces cerevisiae. Our results show that DIF-1 and COLT can functionally complement a yeast CACT deletion strain and thus function as carnitine acylcarnitine transporters. This finding is well in line with the recent observation that embryos are capable of oxidizing fatty acids and furthermore implies that FAO is essential during early embryonic development when the energy demand is high.
This study was conducted to investigate the effects of nitric oxide (NO) on human sperm activity, human sperm-oocyte fusion and mouse embryonic development. Results showed that various concentrations of NO synthase blocker, N(omega)-nitro-L-arginine methyl ester, did not affect sperm cell motility at 0, 1, 2 or 4 hr, respectively. In contrast, sodium nitroprusside (SNP) significantly inhibited sperm cell motility and caused apoptosis. The adversely dose-dependent effect was only observed if SNP was freshly prepared. Adenosine triphosphate reversed the hazardous effect of SNP on sperm activity/viability. Hemoglobin neutralized the adverse effect of SNP. In hemi-zona sperm fusion test, the number of sperm bound to the zona in the presence of 10(-4) M SNP was significantly less than the control group. SNP at 10(-4) M caused all mouse embryonic development arrest. 46% and 56% of zygote reached the blastocyst stage with the treatment of 10(-6) M and 10(-8) M SNP, respectively, while the control reached 70%. NO adversely affected human sperm activity, human sperm-zona binding and embryonic development. It would appear that high concentration of NO may potentially decrease fertility.
Nitric oxide (NO) has emerged as an important intracellular and intercellular messenger, controlling many physiological processes and participating in the fertilization process via the autocrine and paracrine mechanisms. This study investigated whether nitric oxide synthase (NOS) inhibitior (L-NAME) and L-arginine could regulate in vitro fertilization and early embryonic development in mice. Mouse epididymal spermatozoa, oocytes, and embryos were incubated in mediums of variable conditions with and without L-NAME or L-arginine (0.5, 1, 5 and 10 mM). Fertilization rate and early embryonic development were significantly inhibited by treating sperms or oocytes with L-NAME (93. 8% vs 66.3%, 92.1% vs 60.3%), but not with L-arginine. In contrast, fertilization rate and early embryonic development were conspicuously reduced when L-NAME or L-arginine was added to the culture media for embryos. Early embryonic development was inhibited by microinjection of L-NAME into the fertilized embryos in a dose-dependent manner, but only by high concentrations of L-arginine. These results suggest that a moderate amount of NO production is essential for fertilization and early embryo development in mice.
Development is the result of complex events, including cascades of transcriptional programs and numerous molecular interactions. Traditionally, research focus has been given to the characterization of individual mutants, regulators, or interactions. With the availability of complete genome sequences and high-throughput (HT) experimental techniques, probing development on a system level has become feasible. Pioneering work initiated in invertebrate model systems such as Caenorhabditis elegans has provided first drafts of catalogs of essential components, transcriptional regulatory diagrams and molecular interaction networks underlying developmental processes. Integrating these drafts approximates a system-level picture of development and provides local models for protein/gene functions. Here we summarize the progress toward elucidating developmental processes on a system level, including the applications of genomic technologies and computational analyses. We discuss C. elegans embryonic development in case studies to illustrate how various HT approaches can be integrated and how biological insights can be gained from these approaches.
Lineally related multipotent neuroepithelial cells (NEP), neuronal restricted precursors (NRP), and glial restricted precursors (GRP) have been identified in the spinal cord. To determine the sequence of differentiation and identify lineage and stage-specific markers, we have examined the spatiotemporal expression of established glial markers during rodent embryonic development and within fetal cell culture. In this report, we show that proliferating stem cells in the developing neural tube do not express any glial markers at E10.5. By E11, however, glial precursors have begun to differentiate and at least two regions of the ventral neural tube containing glial precursor cells can be distinguished, an Nkx2.2/Neurogenin 3 (Ngn3) domain and a platelet-derived growth factor receptor alpha (PDGFRalpha)/Olig2/Sox10 domain. Radial glia, as identified by RC1 immunoreactivity, develop in concert with other glial precursors and can be distinguished by their morphology, spatial distribution, and antigen expression. Astrocytes as assessed by glial fibrillary acidic protein (GFAP) immunoreactivity are first detected at E16. A novel dorsal domain of CD44 immunoreactivity that can be distinguished from the more ventral glial precursor domains can be detected as early as E13.5.
Retinal pigment epithelial cells from chicks at various stages of development were examined by transmission electron microscopy to determine how the adult form of the zonula adhaerens, composed of subunits termed zonula adhaerens complexes, is acquired. During early stages of development, between embryonic day 4 and embryonic day 7, the intermembrane discs of zonula adhaerens complexes appear to be formed from material already present between the junctional membranes of the zonulae adhaerentes. In contrast, the cytoplasmic plaque material of the zonulae adhaerentes is difficult to detect before hatching; it is seen as a dense band along the junctional membranes at hatching and as individual subunits in register with the intermembrane discs in adult retinal pigment epithelial cells. After embryonic day 16, when the zonulae adhaerentes increase dramatically in size, single zonula adhaerens complexes are also present basal to the zonulae adhaerentes along the lateral cell membrane. This suggests that, during later stages of development, the junctions grow in size and/or turn over by the addition of pre-assembled zonula adhaerens complexes.
Ovigerous females of the estuarine crab Chasmagnathus granulatus were exposed to mercury (0.1mg/L) during the entire, early, or late embryonic development. A delay in the egg incubation period and some morphological abnormalities were detected in larvae hatched from exposed females. Particularly, hypopigmentation of body chromatophores was the abnormality that showed the highest incidence, this incidence being greater when ovigerous females were exposed to mercury either during the totality or just the first half of the egg incubation period. In contrast, the effect of mercury on the morphology and pigmentation of eyes was greater when the exposure comprised the totality or just the second half of the incubation period. These results correlate with the timing of both body pigment synthesis and eye formation during embryonic development. Although these abnormalities have been observed in the same species with other heavy metals, such as zinc and copper, the responsiveness during the early and late embryonic development was different with mercury.
It has been well established that eggs of insects, including those of the silkworm Bombyx mori, contain various ecdysteroids and the amounts of these ecdysteroids fluctuate during embryonic development. In order to know the function of egg ecdysteroids in embryonic development of B. mori, we examined the biological activities of various egg ecdysteroids by in vitro ligand-binding assay and bioassay using B. mori eggs. First, using the ecdysteroid receptor of B. mori (BmEcR-B1/BmUSP heterodimer) prepared by yeast and Escherichia coli expression systems, the interaction between the ecdysteroid receptor and various egg ecdysteroids of B. mori was analyzed. The relative binding affinities of egg ecdysteroids to the BmEcR-B1/BmUSP heterodimer decreased in the order of 20-hydroxyecdysone > 2-deoxy-20-hydroxyecdysone > 22-deoxy-20-hydroxyecdysone > ecdysone > 2-deoxyecdysone > ecdysone 22-phosphate. Next, several egg ecdysteroids of B. mori were injected into the prospective diapause eggs, which show a very low level of free ecdysteroids at the onset of embryonic diapause (gastrula stage). Approximately 7% of them (P < 0.002, chi(2)-test) developed beyond the gastrula stage without entering diapause by the injection of 20-hydroxyecdysone (25 ng/egg). In contrast, the injection of other ecdysteroids was not effective in inducing embryonic development. These results suggest that 20-hydroxyecdysone, via the ecdysteroid receptor, is responsible for the developmental difference between diapause and non-diapause in B. mori embryos. Furthermore, it was suggested that continuous supply of 20-hydroxyecdysone may be required to induce embryonic development.
Somatotrophs become a significant population by day 16 of chicken embryonic development. We have previously demonstrated that an earlier induction of GH cell differentiation is possible with the addition of day 16 embryonic serum to cultures of day 12 pituitary cells, an age when somatotrophs are rare. The present study was designed to identify the blood-borne signal(s) responsible for the serum activity, using reverse hemolytic plaque assays to identify individual GH-secreting cells. The activity was found to be a heat-stable, ether-soluble compound(s) that is bound or inhibited by a trypsin-sensitive protein. The extent of GH cell differentiation was greater (P < 0.05; n = 3) in response to the ether phases of heated day 16 (14.1 +/- 0.4% of all cells) and day 12 sera (9.3 +/- 0.4%) than with untreated serum from days 16 and 12 (6.1 +/- 0.4% and 0.82 +/- 0.4%, respectively). Furthermore, ether-extracted day 16 serum was more effective than ether-extracted day 12 serum, which was also different from basal (0.85 +/- 0.4%; P < 0.05). Based on this biochemical profile, the abilities of various steroids to stimulate differentiation were tested. Three steroids were found to stimulate somatotroph differentiation in vitro: 17beta-estradiol, corticosterone, and progesterone. However, the estradiol receptor antagonist, tamoxifen, while abolishing the effect of estradiol, had no effect on the induction of differentiation by day 16 serum. In contrast, RU486, a specific glucocorticoid receptor antagonist in chickens, blocked the stimulatory effects of corticosterone, progesterone, and day 16 serum on somatotroph differentiation. We next tested whether the active compound in day 16 embryonic serum was corticosterone, the predominant glucocorticoid in chickens. Incubation of day 16 serum with corticosterone antiserum, but not control antiserum, suppressed day 16 serum-induced GH cell differentiation. Therefore, we conclude that corticosterone is the blood-borne signal capable of stimulating somatotroph differentiation in vitro. The present findings together with previous reports indicate that somatotroph differentiation during embryonic development may result from an increase in circulating glucocorticoid concentrations.
Homocysteine affects the migration and differentiation of neural crest cells in vitro and can result in neural tube defects in vivo. Furthermore, homocysteine has been described as an important determinant in vascular disease in human adults. However, little is known about the effects of homocysteine on the development of embryonic vessels. In this study, we injected homocysteine (30 micromol/L) into the neural tube lumen of chick embryos at the time point of neural crest cell emigration, and analyzed the effects on the neural crest-derived pharyngeal arch arteries, like the brachiocephalic arteries, and the mesoderm-derived arteries, such as the dorsal aorta. By stage HH35, we observed detachment of the endothelium, decreased expression of the extracellular matrix proteins fibrillin-2, and fibronectin in the pharyngeal arch arteries, whereas the dorsal aorta was identical in homocysteine-neural tube-injected and control embryos. No effect of homocysteine on endothelin-1 mRNA expression was observed. By stage HH40, the brachiocephalic arteries of homocysteine-neural tube-injected embryos displayed a decreased lumen diameter, an increased intima- and media-thickness, and an increased number of actin layers compared with the brachiocephalic arteries in control embryos. We propose that homocysteine affects the neural crest-derived smooth muscle cells and their extracellular matrix proteins in the pharyngeal arch arteries, resulting in an abnormal smooth muscle to endothelial cell interaction, leading to endothelial cell detachment. We suggest that, as in adult life, increased homocysteine concentrations lead to vascular damage in the embryo. This prenatal damage might increase the susceptibility to develop vessel pathology later in life.
We have investigated the distribution of CD15 immunoreactivity (IR) in chick sensory neurons during the embryonic development. IR first appeared around embryonic day 6 (E6) preferentially in the lateroventral part of the dorsal root ganglion (drg). Here it was located in the cytoplasm of the ganglion cells. Starting at E11, CD15 positive cells have been detected also in the dorsomedial part of the drug. Towards the end of embryonic development, these immunoreactive (ir) cells were evenly distributed within the drg. Around E 16 nerve fibres could also be found, expressing the CD15 epitope. These fibres run both in centripetal and centrifugal direction, and could be followed throughout peripheral nerves. IR was confined to peripheral nerves of the skin, where after its subepidermal arborisation fine nerve terminals entered the basal stratum of the epidermis or the dermal bulbous part of feathers. Until hatching no staining in visceral structures was detected. Our results suggest that CD15 is restricted to a subset of drg neurons innervating somatosensory targets. A role for the CD15 epitope for myelination is discussed.
During the first 24 h of post-embryonic development in Xenopus laevis, a rapid change in the neural activity underlying swimming occurs in which the duration of ventral root discharge on each cycle increases from a single compound impulse to discrete bursts of activity. Moreover, this change in motor output progresses rostrocaudally, suggesting that it could result from the influence of a descending neural pathway upon the spinal rhythm-generating circuitry during early post-embryonic development. To begin to examine whether serotonergic neurons of brainstem raphe nuclei might have a role in this swimming development, we have studied the effects of 5-hydroxytryptamine (5HT) on fictive swimming in embryonic and larval animals. As previously demonstrated for other vertebrate locomotor rhythms, we find that bath-applied 5HT enhances the duration of motor activity on each cycle of larval fictive swimming. In addition, our results show that the sensitivity of the swimming rhythm to exogenous 5HT follows a strict rostrocaudal gradient. In young embryos (stages 32-36) 5HT does not affect the duration of ventral root impulses per cycle; by the time of hatching (stage 37/38), rostral but not caudal discharge is enhanced, and by stage 42 (24 h post-hatching) 5HT can increase motor burst durations along most of the length of the animal. These reversible changes induced by bath-applied 5HT closely resemble the normal rostrocaudal development of burst discharge during swimming in animals some 12 h older.(ABSTRACT TRUNCATED AT 250 WORDS)