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PubMed2003

The effects of isolation rearing on open-field behavior in male rats depends on developmental stages.

The effects of the duration of isolation and age during isolation on open-field behavior in rats were examined. An inner wall divided the floor of the field into two areas, a peripheral alley and the center square, and the subjects' behavior in each area was measured. An increase in the tendency to avoid the center square was found in rats isolated during their juvenile stage, which disappeared if they were reared in pairs for a long period after isolation. On the other hand, subjects isolated during their postmaturity stage displayed an increased tendency to approach the center square whereas isolation during sexual maturity had no effect. The duration of isolation showed no consistent effect; rather, the effect depended on the age of the subjects during isolation. These findings suggest that isolation affects the open-field behavior of rats in various ways, depending on their age during isolation.

Aging↗
PubMed1980

EEG developmental stages.

Data in the literature show that in humans the fraction of the total electroencephalographic (EEG) energy that appears in the alpha frequencies rises from about zero at birth to about 70% in adults. This rise is shown to occur mainly in 5 stages, the ages of which correlate with those of stages of increase in brain weight. Supporting the correlation are data on gender dimorphism in humans in both brain weight and EEG development, as well as limited data on development in kittens, rats, mice, and guinea pigs.

Adolescent↗
PubMed1994

Developmental stages in experimental liver metastases: relation to invasiveness.

We have previously reported that an invasive morphotype can be evoked in a rat colon carcinoma by transplanting it into pre-induced subcutaneous granulation tissue. We have now studied the interaction of the same tumor with liver tissue, which is extremely poor in connective tissue in comparison with the subcutaneous site. Tumor cells were injected into the portal system and the resulting experimental liver metastases were examined by electron microscopy and immunohistochemistry. Early metastases consisted of well-differentiated acini, fully surrounded by connective tissue that was derived from the periportal stroma. In a later stage, this connective tissue was overgrown by tumor cells and, almost immediately, acinar differentiation was lost. Most metastases eventually reached the liver capsule, which reacted by forming a layer of granulation tissue. Only in this layer, we observed invasion by thin tumor cell strands, which were often intimately associated with fibroblasts or with blood capillaries. The tumor cells remained smooth and rounded during this process. After fully penetrating the granulation tissue, the tumor cell strands reached the liver surface, where they formed poorly structured papillary masses that were nearly devoid of stroma. Our observations indicate that, even in a relatively homogeneous organ like the liver, the tumor-host interaction is highly complex and dynamic. They also confirm the notion that granulation tissue stimulates tumor invasiveness. Finally, they show that tumor cells can actively invade host tissues without exhibiting a "fibroblastic" morphology.

Animals↗
PubMed1987

Microtubule-associated proteins present in different developmental stages of Drosophila melanogaster.

Microtubule-associated proteins (MAPs) have been isolated from different development stages of Drosophila melanogaster and characterized by their association to tubulin, but not to tubulin lacking its 4-kD carboxy terminal region (S-tubulin), and by their ability to promote tubulin polymerization. Following these criteria some peptides of Mr 255, 205, and 180 kD were identified as MAPs. By means of immunological analogy we have identified a peptide related to mammalian brain MAP known as tau factor.

Animals↗
PubMed1989

Cachectin/TNF kills or inhibits the differentiation of 3T3-L1 cells according to developmental stage.

The effects of cachectin/tumor necrosis factor (TNF) on growth and differentiation of 3T3-L1 cells were examined. This fibroblastic cell line can be induced to differentiate into a mature cell type having the biochemical and morphological characteristics of normal adipocytes. At various stages of growth and differentiation, 3T3-L1 cells were exposed to 2.5 x 10(-16) to 2.5 x 10(-8) M (4.2 fg/ml to 420 ng/ml = ca. 1.2 x 10(-14) to 1.2 x 10(-16) U/ml) recombinant human cachectin/TNF for 24 hr, after which cytotoxicity or differentiation was evaluated. During log-phase cell growth, cachectin/TNF had no significant effect on cell viability, and the preadipocytic cells were also resistant to the cytotoxic effect of cachectin/TNF at the contact-inhibited confluent stage. However, when cachectin/TNF was added to the cells during induced differentiation, only 20% of the cells survived. After differentiation into adipocytes, cells regained their resistance to cachectin/TNF-induced cytotoxicity. Cachectin/TNF also markedly affected the differentiation of 3T3-L1 cells into adipocytes. When cells in the confluent phase of growth were exposed to cachectin/TNF for 24 hr, their subsequent hormone-induced differentiation to adipocytes was inhibited. Like cachectin/TNF, IL-1 also induces suppression of lipoprotein lipase and enhances lipolysis in differentiated 3T3-L1 adipocytes; however, in contrast to cachectin/TNF, IL-1 had no effect on the viability or differentiation of pre-adipocyte 3T3-L1 cells. These results indicate that the cytotoxic action of cachectin/TNF varies in the same cell type depending on the stage of growth or differentiation. The results also imply that cachectin/TNF may play a normal role in controlling the differentiation of certain types of cells in vivo including adipocyte lineages.

Animals↗
PubMed1990

Precocious induction of tyrosine aminotransferase mRNA by hydrocortisone in cultured fetal rat hepatocytes at different developmental stages.

Tyrosine-aminotransferase (TAT) is encoded by a liver-specific gene known to be expressed perinatally. Fetal rat hepatocytes (gestation day 19) in primary cultures, in which TAT gene expression is normally undetectable, are induced by hydrocortisone to express TAT-mRNA in a dose-dependent manner (greater than 10(-7) M). In hepatocytes incubated with hydrocortisone, TAT-mRNA levels were marginal after 24 hours, reaching maximal levels at 48 hours. After a pre-incubation of hepatocytes for 24 hours in the absence of hydrocortisone followed by exposure to hydrocortisone (24-48 hours). TAT-mRNA levels were high. Hepatocytes derived from fetuses of gestation days 14 and 17 displayed comparable levels of TAT-mRNA in response to hydrocortisone. These results demonstrate that cultured hepatocytes of gestational stages as early as day 14, which initially do not respond to hydrocortisone by TAT gene induction, undergo a "maturation" process during the initial 24 hours following cultivation, resulting in the acquisition of precocious competence for TAT gene transcription in response to hydrocortisone. This suggests that one or more factor(s), required for hydrocortisone-inducible TAT gene transcription, and not available in fetal liver until birth (Gluecksohn-Waelsch: Cell, 18:225-237, 1979) appear in fetal hepatocytes upon cultivation during this "maturation" period, thus permitting precocious TAT gene expression in vitro.

Animals↗
PubMed2006

Localization, specific activity, and molecular forms of acetylcholinesterase in developmental stages of the cestode Mesocestoides corti.

The nervous system of flatworms is quite simple although there is increasing evidence indicating that it is chemically complex. Studies of the nervous system in these animals have only been performed in the larval stage or in the adult worms, which are easy to obtain in nature, while the description of the nervous system in developing stages of these organisms is missing. Mesocestoides corti is a parasitic platyhelminth whose larvae can be induced in vitro to develop to adult, sexually mature worms, opening the possibility of studying the nervous system of a flatworm in different stages of development. Here, we describe the presence, activity, location, and molecular forms of acetylcholinesterase (AChE) in different stages of development of M. corti, from the larvae to adult forms of this endoparasite, obtained in in vitro cultures after induction of the larval stage with trypsin. Our results point to AChE as a molecular marker of the nervous system in platyhelminthes. The change in molecular forms of this enzyme and the increase in its activity during development from larvae to adult worm may reflect the presence of a more complex nervous system, necessary to adjust and coordinate the movement of a much bigger structure. A relationship between the development of the reproductive apparatus in segmented and adult worms with a more complex nervous system in these stages is also apparent. Finally, our study opens the possibility of applying anti-AChE as more effective therapeutic strategies against cestode parasites.

Acetylcholinesterase↗
PubMed2006

Regulation of intracellular Ca2+ by P2Y1 receptors may depend on the developmental stage of cultured rat striatal neurons.

Mixed striatal cell cultures containing neurons and glial cells were grown either in neurobasal medium (NBM) or Dulbecco's modified Eagle's medium (DMEM). Whole-cell patch-clamp recordings indicated that, if at all, only a single, low amplitude spike was evoked shortly after starting the injection of a depolarizing current pulse into NBM neurons. In contrast, DMEM neurons fired series of high amplitude action potentials, without apparent spike frequency adaptation. The possible reason for the observed action potential failure in NBM neurons was a low density of Na+ channels per unit of membrane surface area. However, both in NBM and DMEM neurons, ATP did not induce inward current responses via P2X receptor-channels, although GABAA and N-methyl-D-aspartate (NMDA) receptor-channels could be activated by muscimol and NMDA, respectively. Ca2+ imaging experiments by means of the Fura-2 method were utilized to measure intracellular Ca2+ ([Ca2+]i) in neurons and glial cells. NBM, but not DMEM neurons responded to ATP with [Ca2+]i transients; glial cells grown in either culture medium were equally sensitive to ATP. ATP caused an increase of [Ca2+]i by a mechanism only partly dependent on external Ca2+; the residual ATP effect was blocked by cyclopiazonic acid (CPA) and was therefore due to the release of Ca2+ from its intracellular pools. The receptor involved was characterized by P2 receptor antagonists (PPADS, MRS 2179, AR-C69931MX) and was found to belong to the P2Y1 subtype. CPA caused an early [Ca2+]i response due to release from intracellular storage sites, followed by a late [Ca2+]i response due to the influx of this cation from the extracellular space, probably triggered by the opening of store-operated channels (SOCs) in the plasma membrane. It is concluded that in partial analogy with the effect of CPA, ATP releases [Ca2+]i via the Gq/phospholipase C/inositoltrisphosphate (IP3) pathway, thereby opening SOCs. It is hypothesized that this effect of ATP may have an important role for the proliferation and migration of striatal neuronal progenitors.

Adenosine Diphosphate↗
PubMed2003

Morphology, ultrastructure, and implied function of ciliated sensory structures on the developmental stages of Merizocotyle icopae (Monogenea: Monocotylidae).

Experimental infections were used to track the fate of the dorsal sensilla of Merizocotyle icopae (Monogenea: Monocotylidae) from nasal tissue of the shovelnose ray, Rhinobatos typus (Rhinobatidae). Scanning and transmission electron microscopy revealed that 3 types of uniciliate dorsal sensilla exist at different times in the development of the monogenean. Type 1 sensilla have little or no invagination where the cilium exits the distal end of the dendrite and possess a ring of epidermis surrounding the cilium distal to the invagination. Type 2 sensilla have a deep invagination where the cilium exits the dendrite. Type 3 sensilla can be distinguished from the other types by the shape of the dendrite. The larvae have predominantly Type 1 dorsal sensilla, most of which are lost approximately 24 h after infection and a few Type 2 sensilla, which are retained. Additional Type 2 sensilla (termed Adult Type 2 sensilla), which are slightly different morphologically from the Type 2 sensilla of the larvae, form in later stages of development. Numerous Type 3 sensilla are unique to the dorsal surface of adults. Loss of all Type 1 sensilla upon attachment to the host, R. typus, suggests that these may be chemo- or mechanoreceptors responsible for host location by the swimming infective larvae. Type 2 sensilla appear to be important in the larvae, juveniles, and adults whereas the modality mediated by Type 3 is specific to adults.

Animals↗
PubMed1977

An electron microscopic study of early developmental stages, myogenesis, oogenesis and cnidogenesis in the anthomedusa, Podocoryne carnea M. Sars.

This descriptive electron microscopic study of the blastogenetic medusa development of Podocoryne carnea focuses on the earliest stages of primordium formation, myogenesis, oogenesis and cnidogenesis. The events which take place at the cellular level prior to the formation of stage 1 (Frey, '68), which are characterized by ecto- and entodermal accumulations of undifferentiated I-cells and the beginning of transdifferentiation of epithelial cells, have been subdivided into four distinct stages (U1-U4). The genealogy of cells participating in medusa differentiation indicates that some cell types of the medusa are derived by transdifferentiation from the polyp's epithelial cells, while others originate by differentiation from I-cells. The myogenesis of the subumbrellar muscle cells resembles vertebrate myocardiac differentiation in many respects.

Animals↗
PubMed2002

Are Echiura derived from a segmented ancestor? Immunohistochemical analysis of the nervous system in developmental stages of Bonellia viridis.

Despite several unquestionably homologous characters with Annelida, the Echiura have generally been considered to form a distinct taxon due to apparent lack of segmentation: neither in the body cavity nor in any other structures of the adult animals have clear signs of a metameric organization been observed. However, it must be considered that this lack of segmentation could represent a secondary condition and that Echiura are derived from segmented ancestors. An immunohistochemical analysis visualized with confocal laser-scanning microscopy (cLSM) shows the development of serially repeated units in the nervous system of Bonellia viridis. This organization corresponds to the metameric ganglia typical of Annelida. Antibodies against the neurotransmitters serotonin (5-hydroxytryptamine) and FMRFamide label distinct subsets of neurons. Their perikarya are arranged in discrete repetitive units in the ventral nerve cord of different larval stages. Labeling of neurotubuli using antibodies against different tubulin isoforms provides additional support for the metameric character of the nervous system. Contrary to previous descriptions, the peripheral nerves extending from the ventral nerve cord into the body wall musculature are paired and are evenly distributed; their arrangement corresponds to that of the serotoninergic perikarya. Morphological and neurochemical differentiation of the nervous system clearly proceeds from anterior to posterior, indicating the occurrence of a posterior growth zone. The serial ganglionic organization of the nervous system of Articulata is generally regarded as having evolved in conjunction with repetitive muscular units, in particular with the formation of typical annelid segments. Therefore, these results are interpreted as an indication that Echiura are derived from segmented ancestors and thus support the systematic inclusion of the Echiura within the Annelida.

Animals↗
PubMed1988

Number of olfactory marker protein-containing receptor cells is influenced by developmental stage of the olfactory bulb.

In vitro studies on E15 rat embryos have shown that the number of receptor neurons containing olfactory marker protein (OMP) is markedly increased when olfactory mucosa (OM) is cultured in direct contact with the presumptive olfactory bulb (POB). This facilitatory influence is tissue-specific; that is, it is absent when the POB is substituted with other nervous or non-nervous tissues. In the present quantitative immunohistochemical study, we show that the enhancing influence of the POB is also a stage-specific phenomenon. The number of OMP-containing receptor cells is greatest when E15 OM is cultured with POB of the same age. If the POB was taken from a less mature (E13) or from a more mature (E17) embryo, the number of OMP-containing cells was greatly reduced.

Animals↗
PubMed2001

Detection of transgene in progeny at different developmental stages following testis-mediated gene transfer.

We recently reported that exogenous DNA injected into testis as a liposome complex can be transferred into the egg via sperm by natural mating and integrated in the genome (testis-mediated gene transfer: TMGT). Here, we studied the efficiency of each of the several liposomes in associating foreign DNA with sperm, the expression of an introduced gene in early embryos, and the presence of the DNA in fetuses and pups at different ages. The CMV/beta-actin/EGFP fusion gene, encapsulated with different liposomes, was injected into rat testis, and spermatozoa in the cauda epididymis were obtained 1, 4, and 14 days after injection. We tested each of the 8 liposomes, and found that only 2, DMRIE-C and SuperFect, led to the detection of foreign DNA on all of the days examined, with relatively higher ratios of rats having positive sperm. By means of TMGT using either of those two liposomes, more than 80% of morula-stage embryos expressed EGFP, as observed by fluorescence microscopy. Then we detected introduced DNA in the progeny by PCR and Southern dot blot, and found that the ratio of animals carrying the foreign DNA decreased as they developed, and that only a part of postpartum progeny were foreign-DNA-positive with high incidence of mosaicism. These results suggest that, although, the success rate is still limited, foreign DNA could be integrated into the genome of the progeny by TMGT at least under specific experimental conditions, the efficiency of which depends largely on the characteristics of the liposome. The results also suggest that TMGT could be applicable to fetal gene therapy as well as to the generation of transgenic animals.

Animals↗
PubMed1990

Interlitter variability and developmental stage of day 11 rat embryos produced by overnight and morning short-period breeding regimens.

Day 11 rat embryos produced by overnight and morning short-period breeding regimens were compared for differences in interlitter variability and stage of development. Female Sprague-Dawley rats were mated either overnight (5 PM-9 AM, n = 22) or for 3 hr in the morning (8-10 AM, n = 20), and the presence of a vaginal plug was determined (day 0). At 11 AM on day 11 of gestation, rats were killed and embryos were examined for crown-rump length, somite number, and general morphology; protein content was determined later. There were no differences in mean number of implantations, live embryos, and abnormalities between the two regimens. There were significant differences in mean crown-rump length, somite number, and protein content but not in the magnitude of their variances. The difference in mean somite number was 1.2 (23.7 vs. 24.9), which corresponds to a time difference in development of approximately 2 hr. The range of mean somite number in morning short-period breeding group was 3.2 (22.2-25.4), corresponding to approximately 5.3 hr. These results are inconsistent with the popularly held hypothesis that the timing of fertilization is the major cause of interlitter variability.

Animals↗
PubMed1992

Developmental stages of the CD (Sprague-Dawley) rat skeleton after maternal exposure to ethylene glycol.

Ethylene glycol (EG), a chemical which causes skeletal malformations in rats, was administered by gavage to sperm positive CD rats on gestational days (gd) 6 through 15 at doses of 0 or 2,500 mg/kg/day to assess its effects on the pre- and postnatal skeletal development. Dams and fetuses/pups were killed on gd 18, 20, postnatal day (pnd) 1, 4, 14, 21, or 63, and offspring were double-stained for examination of skeletal malformations and degree of ossification of rapidly developing skeletal districts. No difference in gestational day of delivery between controls and the EG-treated dams was seen. Fetal weights per litter were significantly decreased with EG treatment in both the gd 18 and 20 groups. Pup body weight on pnd 1 was significantly below controls; however, EG had no effect on pup body weight on pnd 4-63. The percentage of fetuses/pups with skeletal malformations per litter was significantly increased after EG exposure for all time points except at pnd 63, with a predominance of axial skeletal defects. The percentages of total ossification, of sternabrae ossified, and of vertebral centra ossified were significantly reduced in the EG groups on gd 20 and on pnd 1-21, but not on gd 18 or on pnd 63. When the ossification data were subjected to statistical analysis with fetal/pup weights as a covariate, the values for EG-exposed pups on gd 20 were not statistically significantly different from the control values. The reduced ossification values for EG-exposed pups on pnd 1-21 retained statistical significance even after covariate analysis. There was no effect of dose or body weight on ossification of fore- or hindlimb digits. In conclusion, the differences in incidence of skeletal alterations observed prenatally and through pnd 21 were not evident by pnd 63, suggesting that perinatal skeletal abnormalities may not always be permanent.

Animals↗
PubMed1998

Two-dimensional protein maps of xenopus eggs and embryos at different developmental stages.

Protein expression during the early development of Xenopus has been followed by 2D-polyacrylamide gel electrophoresis (PAGE). The analysis of two-dimensional maps of eggs and embryos at different stages of development has allowed the separation of more than 2000 spots. Identification of numerous polypeptides was obtained in four different ways: (1) immuno-blotting; (2) amino terminal sequence after blotting on to PVDF membranes; (3) comigration; and (4) assignment in comparison with proteins separated by 2D techniques on reference maps such as human liver, red blood cells, plasma and cerebrospinal fluid reported in the Swiss 2D-PAGE Data Base. The maps presented in this report are a step toward the study of the protein expression in Xenopus eggs and embryos and may be a powerful working tool since Xenopus embryos are popular models for the study of development.

Animals↗