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PubMed1990

Kindling in developing animals: expression of severe seizures and enhanced development of bilateral foci.

In adult rats, alternating stimulations between two limbic sites can result in one site kindling normally, while the other is retarded in an early non-generalized kindling stage. This phenomenon has been named kindling antagonism. In this report, we present data indicating that kindling antagonism does not occur in 16-day-old rats. Instead, 16-day-old rats receiving alternating stimulations in the amygdala and hippocampus develop progressively more severe seizures. Kindling with alternate stimulations is elicited at a much faster rate at the two foci compared to kindling from a single site, either the hippocampus or amygdala. All groups develop generalized seizures including seizure stages 6 and 7, consisting of wild jumping, running with vocalizations and tonus. These seizures appear after relatively few stimulations in the pup, in comparison to the adult. The results indicate that the immature brain is less able to suppress the generalization of seizures than the adult. The age-specific enhanced development of bilateral foci may be due to underdeveloped inhibitory systems and may underlie the propensity of the immature CNS to develop multifocal seizures.

Amygdala↗
PubMed1990

The postnatal development of the air-righting reaction in albino rats. Quantitative analysis of normal development and the effect of preventing neck-torso and torso-pelvis rotations.

The aim of this study was to describe the ontogenesis of the air-righting reaction (ARR) in rats. The first experiment was performed on 6 newborn albino rats of both sexes and followed the development of the ARR over postnatal days 1-21. The degree of rotation achieved after falling from different heights was quantified according to a rating scheme. It appeared that the air-righting reaction is effected by a spiral movement which spreads in a cranio-caudal direction. The reaction develops between postnatal day 8 and 18. On postnatal day 10 only a few animals are able to turn their heads, this being possible only from a falling height of 60 cm and corresponding to a falling time of 350 ms. A rapid development of the reaction was found between days 10 and 14. The second experiment on 8 rats involved the use of immobilization in order to isolate the mechanisms that trigger the ARR. The immobilization prevented neck-torso rotation, torso-pelvis rotation, and both rotations in different animals. Despite the disruption of important (afferent) feedback systems, the reaction developed within the same age period as in control rats. Thus, the Magnus "chain reflex hypothesis' as basis for the ARR is rejected in favor of a central motor program hypothesis.

Age Factors↗
PubMed1991

Comparison on collagen gene expression in the developing chick embryo tendon and heart. Tissue and development time-dependent action of dexamethasone.

Glucocorticoids modulate various cellular functions such as proliferation, energy metabolism and the synthesis of proteins. In the present study, the response of collagen genes to dexamethasone in different stages of chick embryo development was studied in tendon and heart using Northern blot analysis and specific cDNA probes. The changes in collagen gene expression were compared to alterations in two reference mRNAs: actin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The levels of specific mRNAs measured per ribosomal RNA in tendon and heart varied markedly during normal development. In tendon the relative levels of alpha 1(I), alpha 2(I) and alpha 1(III) collagen mRNAs were highest between days 14-16 when also the synthesis of matrix proteins is most active. In heart the levels of these mRNAs peaked at day 12. In addition, qualitative differences were observed in the expression of actin genes between tendon and heart. Dexamethasone in high dose decreased collagen mRNA levels in tendons, while in heart a stimulatory effect was noted. Dexamethasone also decreased GAPDH mRNA levels in tendons. The alterations in gene expression after dexamethasone treatment in tendon and heart did not correlate with the level of specific glucocorticoid receptors, which varied markedly during the development of chick embryos. The cDNA for pro alpha 1(I) collagen hybridized to two transcripts corresponding to 6.2 and 5.1 kb in tendon and heart. During normal development of chick embryos the ratio of 6.2/5.1 kb mRNAs decreased markedly in heart, but no such change was observed in tendons. Dexamethasone, however, decreased the ratio of 6.2/5.1 kb transcripts in tendons. There was a significant correlation between the ratio 6.2/5.1 kb transcripts and total alpha 1(I) mRNA both in tendon and heart, suggesting that the 6.2 kb transcript may be associated with the rate of synthesis of type I collagen.

Actins↗
PubMed1989

Oxidative influence on development and differentiation: an overview of a free radical theory of development.

Metabolic gradients exist in developing organisms and are believed to influence development. It has been postulated that the effects of these gradients on development result from differential oxygen supplies to tissues. Oxygen has been found to influence the course of development. Cells and tissues in various stages of differentiation exhibit discrete changes in their antioxidant defenses and in parameters of oxidation. Metabolically generated oxidants have been implicated as one factor that directs the initiation of certain developmental events. Also implicated as factors that modulate developmental processes are the cellular distribution of ions and the cytoskeleton both of which can be influenced by oxidants. The interaction of oxidants with ion balance and cytoskeleton is discussed.

Animals↗
PubMed1989

Submicroscopic localization of glycogen in mouse blastocysts developed in vivo and in blastocysts developed in vitro from two-cell embryos.

Ultrahistochemical method according to Thiéry (1967) was used to determine the occurrence and localization of glycogen in blastocysts developed in vivo and in blastocysts developed from 2-cell embryos of the mouse for 62 to 64 h in in vitro culture. The presence of glycogen was found in blastocysts of both experimental groups. Glycogen had a monoparticulate character, i.e. the form of beta-granules, localized above all in the ground cytoplasm of cells. Their size varied from 10 to 30 nm. In the blastocysts developed in the physiological uterine environment the glycogen content was relatively low, trophoblasts cells containing regularly a higher amount of glycogen particles than embryoblast cells. In the blastocysts developed in the culture medium in the presence of currently used energy sources the distribution and content of glycogen were clearly graded according to the cell types. Compared with the in vivo-blastocysts, an abnormally high amount of glycogen was observed in the cytoplasm of trophoblast cells, a medium amount in the prospective endoderm cells and the minimum amount in the prospective ectoderm cells. The authors are of the opinion that differences in the accumulation of glycogen and its occurrence in the individual cells are in connection with their position in the blastocyst and with their relation to the surrounding microenvironment. It can be judged from the findings of glycogen deposits inside autophagic vacuoles and multivesicular bodies as well as inside extracellular located sacs that simultaneously with glycogen accumulation there also proceeds its partial degradation in lysosomal structures of blastocyst cells.

Animals↗
PubMed1989

Normal and abnormal visual development in kittens: insights into the mechanisms that underlie visual perceptual development in humans.

For many years the mechanisms that underlie normal and abnormal development of visual perception in human infants have been explored in anatomical and physiological studies on two species of frontal-eyed mammals, namely, cats and, to a lesser extent, monkeys. The unstated assumption underlying the investigations on cats is that despite substantial differences in the organization of the visual pathways of cats and humans, as well as quantitative differences in their perceptual abilities, principles of development established in the former also apply to humans. This review examines the extent to which this assumption may be valid. Following a review of certain anatomical peculiarities of the cat visual system, several of the differences as well as the parallels between the perceptual abilities of cats and humans are summarized. The latter similarities, as well as the larger number of parallels between the two species that can be drawn during development, attest to the validity of the choice of the cat for study of the mechanisms that underlie human visual development.

Animals↗
PubMed1991

Expression of two members of the Wnt family during mouse development--restricted temporal and spatial patterns in the developing neural tube.

The Wnt gene family encodes a group of cysteine-rich proteins implicated in intercellular signaling during several stages of vertebrate development. This family includes Wnt-1 and Wnt-3, both discovered as activated oncogenes in mouse mammary tumors. Here we describe the molecular cloning of an additional member of the Wnt family, called Wnt-3A, and the spatial and temporal expression pattern of this gene as well as that of its close relative Wnt-3. The putative amino acid sequences of both proteins are almost 90% identical, but in situ hybridization to mouse embryo sections showed highly restricted patterns of expression of Wnt-3 and Wnt-3A, largely in separate areas in the developing nervous system. In the spinal cord Wnt-3 was expressed at low levels in the alar laminae and in the ventral horns, whereas Wnt-3A expression was confined to the roof plate. In the developing brain Wnt-3 was expressed broadly across the dorsal portion of the neural tube with a rostral boundary of expression at the diencephalon. In contrast, Wnt-3A was expressed in a narrow region very close to the midline; expression extended into the bifurcating telencephalon, in a highly localized fashion. Both Wnt-3 and Wnt-3A were expressed in the ectoderm, and Wnt-3A was also expressed in the periumbilical mesenchyme. Characteristic expression patterns of these two closely related genes suggest that Wnt-3 and Wnt-3A play distinct roles in cell-cell signaling during morphogenesis of the developing neural tube.

Amino Acid Sequence↗
PubMed1987

Development of enzymic zonation in liver parenchyma is related to development of acinar architecture.

The appearance of the distribution patterns of the NH3-metabolizing enzymes carbamoylphosphate synthetase, glutamate dehydrogenase, and glutamine synthetase in the developing liver of an altricial species (rat) was compared with that in the developing liver of a closely related, precocial species (spiny mouse). The comparison showed that the development of hepatic acinar architecture, rather than perinatal adaptation, is responsible for the development of periportal and pericentral compartments of gene expression. Conditions that confine the expression of specific enzymes to the pericentral compartment of the acinus originate before conditions that confine the expression of (other) specific enzymes to the periportal compartment. However, whether or not the site of gene expression is restricted to specific compartments within the liver acinus, the rate of expression of the gene involved can also be adaptively regulated. Therefore, different factors appear to control the site and the rate of gene expression within one tissue.

Aging↗
PubMed1992

Early heart development in the chick embryo: effects of isotretinoin on cell proliferation, alpha-actin synthesis, and development of contractions.

Isotretinoin is a potent retinoic acid used in the treatment of skin disorders. Though very effective, it is teratogenic if administered during pregnancy, and its teratogenic effect may be related to the normal activity of retinoids as signalling molecules in the embryo. Although its exact mechanism of action is unknown, it has been suggested that it causes its characteristic pattern of defects that includes heart defects, by inhibiting the migration of neural crest cells. However, other effects on cells are known. We studied early cardiac cell proliferation using incorporation of bromodeoxyuridine (BrdU) and detection with a monoclonal anti-BrdU. Proliferation in heart tissue of whole embryo cultures was inhibited in medium with 10(-6) M isotretinoin to 62% of the control level in myocardium. We studied its effects in culture on precardiac explant development in the absence of the neural crests. Culture of precardiac mesodermal-endodermal explants revealed that development of heart vesicles from the mesoderm was little affected, but the development of heartbeat was inhibited depending on dose in the 10(-5) to 10(-7) M range. The effect on development of contractions was augmented in the presence of serum; it could be duplicated by all-trans-retinoic acid, and it was reversible. Synthesis of the alpha-actin isotype, analyzed by isoelectric focusing, was found to be inhibited or delayed. The results suggest multiple effects of retinoids on growth, morphogenesis, and differentiation of early cardiac tissue, and are discussed in relation to the potential role of retinoids in early embryogenesis.

Actins↗
PubMed1967

Health, population, and economic development. International health programs have an important role in promoting economic development and population control.

Health as a basic human value is particularly important to people in the developing world. Rates of economic development lower than had been hoped for and ever more steeply rising population growth have precipitated a reaction against public health programs. Among economists, agriculturalists, and even health professionals the philosophy arose that one should "hold back" on using modern weapons against disease because they are "too effective." To satisfy the recognized popular demand, simple and relatively ineffective measures of curative medicine could be substituted. It was said that the emphasis should be, instead, on agriculture, community development, education, and industrialization and that family planning should be pushed as a separate program. Documentation presented here sharply challenges such a point of view. No segment of the total development process can be effective without the other sectors.

Demography↗
PubMed1979

Development and aging of cholinergic synapses. I. Endogenous levels of acetylcholine and choline in developing autonomic ganglia and iris of the chick.

Acetylcholine (ACh) and choline (Ch) levels were measured by means of a sensitive micromethod in developing irises, ciliary and sympathetic ganglia of the chick, starting at 5--7 days of incubation (DI) up to 1 year of age. The neurotransmitter is present in all three organs at relatively low levels (1--10 pmol) from 5 DI (iris) or 7 DI (ciliary and sympathetic ganglion). This is followed by a rapid and sustained 9-fold increase in all three tissues up to 14 DI. Thus, it appears that low levels of ACh may be sufficient for neurotransmission to occur in the primitive ciliary ganglion and iris. After hatching, total ACh levels continue to increase up to 1 year of age in the iris and ciliary ganglion and up to 3 months in the sympathetic ganglion. The increase may depend on either an increased functional demand for the neurotransmitter or an increased number of preganglionic terminals. In general Ch levels parallel closely the levels of ACh in each organ throughout development. It is concluded that ACh and Ch are present since the earliest detectable stages of development in the ganglia and iris, and their first increase seems to be correlated to the phase of innervation of the organs. The subsequent increase probably correlates to synaptogenesis. The close relationship between Ch and ACh levels indicates a regulatory role of Ch for ACh synthesis during neuronal development.

Acetylcholine↗
PubMedDate not supplied

Evaluation of education program developments: illustration of the research and development cycle.

The Research and Development (R and D) cycle is a program development model used to translate research findings into educational programs or products ready for use in the field. The R and D cycle is illustrated by describing its application to Effective Patient Teaching, a course on teaching skills for health professionals. Evaluation is a continuing part of program development. Evaluation methods need not follow a rigid formula; methods will generally change with the stages of program development and the evaluation purposes.

Educational Measurement↗
PubMed1982

Macrocyst development in Dictyostelium discoideum. I. Induction of synchronous development by giant cells and biochemical analysis.

In Dictyostelium discoideum, cytological and physiological studies on macrocyst formation revealed that this process consists of at least two steps: the production of giant cells, which are believed to be formed from the fusion of cells of two opposite mating types, and the subsequent induction of macrocyst development by the giant cells. The conditions that had been considered formerly to be required for macrocyst formation, such as darkness at the presence of two cells of complementary mating types in heterothallic strains, were actually required only for the production of the giant cells. Once giant cells are produced, the surrounding cells can aggregate and form macrocysts even in the light. Furthermore, it was demonstrated that giant cells can switch the developmental mode of the surrounding cells to macrocyst formation. That is, if a critical number of the isolated giant cells are introduced into a cell population of a single strain of NC4, which normally would produce only fruiting-bodies, macrocysts are formed instead. When in the presence of giant cells, the development of macrocysts may be initiated by starvation. Therefore, if all cells are made to starve simultaneously development begins and proceeds synchronously. Using this technique of synchronous development, the developmental kinetics of enzyme activities were assayed during macrocyst and fruiting-body formation. Considerable differences in the patterns of those enzyme activities were demonstrated between the two developmental modes of D. discoideum.

Acetylglucosaminidase↗
PubMed1975

Moral development and perceptual role-taking egocentrism: their development and interrelationship across the life-span.

Moral judgments and perceptual role taking egocentrism were assessed in seventy-two middle-class people whose age range encompassed a significant portion of the life span. Findings support the anticipated curvilinear relationship between moral development and age, and egocentrism and age. However, the close conceptual development and age, and egocentrism and age. However, the close conceptual relationship between moral development and egocentrism throughout life received only slight statistical support, which attained significance only in the fifteen- to nineteen-year-old age group. The existence of "self-involving" egocentrism was postulated to be an important determinant or moral development during adulthood.

Adolescent↗
PubMed1995

Human prenatal craniofacial development related to brain development under normal and pathologic conditions.

A survey is given of current knowledge of the interrelationship between facial, cranial and brain development in humans. First, normal facial, cranial (mandible, maxilla, palatine bone, cranial base, theca cranii, dentition), and brain development are described separately. Then, developmental interrelationships are illustrated under normal and pathologic conditions (cleft lip and palate, holoprosencephaly, anencephaly, amniotic band sequence). New observations are described in detail, and references are given to previously published articles. A close interconnection exists between the development of the face, the craniofacial skeleton, and the brain. This is illustrated by new observations in cleft palate fetuses and new theories about the etiology of holoprosencephaly and tooth agenesis. The survey focuses, moreover, on the importance of the face and the cranial base in endocrine development. Borderlines between face regions and cranial regions with different developmental origin are set up for future elucidation of the etiology behind syndromes involving the craniofacial regions.

Amniotic Band Syndrome↗
PubMed1991

Development of multipotential haemopoietic stem cells to neutrophils is associated with increased expression of receptors for granulocyte macrophage colony-stimulating factor: altered biological responses to GM-CSF during development.

Interleukin-3 (IL-3) dependent multipotent haemopoietic stem cells FDCP-Mix A4 (A4) were induced to differentiate and develop into mature neutrophils in response to Granulocyte Macrophage Colony Stimulating Factor (GM-CSF) plus granulocyte CSF (G-CSF). This resulted in an increase in cell number over seven days of culture, following which the cells lost the ability to undergo further proliferation. The effect of GM-CSF on these cells has been assessed at various stages of development. Clonogenic cells, able to respond to GM-CSF, were generated only at days 3, 4 post-induction. From day 5 onwards, mature post-mitotic neutrophils are produced and clonogenic cells are lost. Loss of proliferative potential, in response to GM-CSF, was confirmed using [3H]-thymidine incorporation. Receptors for GM-CSF, were also measured during development using [125I]-GM-CSF binding assays. Although the dissociation constant for GM-CSF binding sites did not vary considerably, the number of such sites increased dramatically from about 20 (day 0, when the cells have a primitive morphology) to about 1000 by day 6 (when the cells are predominantly mature neutrophils). GM-CSF-stimulated Na+/H+ antiport activation was also determined. Although few GM-CSF receptors are expressed at day 0, there is a significant response (63% of maximal) to GM-CSF in terms of intracellular alkalinisation: this response increased markedly until, by day 4 (700 GM-CSF binding sites/cell), there is a maximal activation of the antiport by GM-CSF. By day 7 (greater than 900 GM-CSF binding sites/cell), however, there is significant reduction in activation of the Na+/H+ antiport by GM-CSF. Nonetheless, increased viability of these mature cells is still seen in response to GM-CSF. These results suggest that not only does expression of GM-CSF receptors alter during development of multipotential cells to mature neutrophils, but that these receptors are coupled to different intracellular effector mechanisms as the cells progressively mature.

Cell Differentiation↗
PubMed1976

[Development of the neuronal structure of the hippocampus during pre- and post-natal ontogenesis in the albino rat. I. Neurohistological demonstration of the development of lung-axonal neurons in the CA3 and CA4 regions].

In this paper qualitative investigations by means of light microscopy (Golgi impregnation) considering the ontogenesis of efferent neurons of the CA3, CA4a, CA4b regions in the rat hippocampus are presented following the already described development of CA1 pyramids (MINKWITZ and HOLZ 1975). After the migration of neuroblasts the types of projective neurons can be distinguished in the mentioned regions at the end of the prenatal period. During the first postnatal time particularly the basal dendritic tree develops expressing more distinctly the typical forms of pyramids (CA3, CA4a) and the of the multipolare neurons of CA4b. No distinct qualitative jumps at the transition of the regions in contrast to the CA3--CA1 boundary can be observed. Temporal retardations in the appearance of postsynaptic structures (microdendrites, excrescenses, spines) at pyramidal neurons from CA4 to CA3 and CA1 are regarded as signs of earlier development of the phylogenetic older pool of cells. During the early postnatal developmental period (until stage P10) proceedings of the growth are predominant. Later on, during the late postnatal period, the maturation of the neurons takes place with a considerable multiplication of spines distributed in similar ways as known from other pyramids. At stage P20 neurons of all hippocampal regions cannot be distinguished from adult ones without using morphometric procedures. The development of parts of the intrahippocampal network including mossy fibre system and SCHAFFER collaterals is discussed with regard to in this way appearing boundaries between fascia dentata and regio inferior CA4, CA3) and regio superior (CA1). These fibre systems establish by their stepwise construction one of the basic elements to hippocampal functioning.

Age Factors↗