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At least 109 records · Page 6Linked to original sources
PubMed1994

Progestogen-only contraceptives during lactation: II. Infant development. World Health Organization, Task Force for Epidemiological Research on Reproductive Health; Special Programme of Research, Development, and Research Training in Human Reproduction.

Growth, development and health of infants whose mothers used progestogen-only contraceptives during lactation were examined in a prospective, non-randomized study that was carried out in seven centres in five countries (Egypt, Thailand, Kenya, Chile and Hungary). The results on development are reported here. Breastfeeding women requesting effective contraception were admitted to the study at six weeks postpartum. Infants of acceptors of progestogen-only methods (pill, DMPA, NET-EN or NORPLANT implants) and non-hormonal methods (IUD, barrier methods or sterilization) formed the study groups. The follow-up was at monthly intervals until the end of the first postpartum year. At each visit, the infant examination included, among other things, a set of developmental tests covering the following areas: gross motor, vision and fine motor, hearing, language and concept development, and self help and social skills. Participating in the study were 2466 mother-infant pairs. The comparisons between the study groups were carried out within centres using life table methods and Cox-model analysis having the time to first passing the test as the criterion. There were altogether 247 comparisons between the study groups. Thirty-two (13%) of these comparisons showed statistically significant differences: 20 differences showed that the infants in the progestogen-only groups passed the tests at an earlier age and 12 at a later age than infants in the non-hormonal groups. Since no consistent trends were observed across the centres, we conclude that in this study the progestogen-only contraceptives used during lactation did not adversely affect infant development.

Adolescent↗
PubMed1987

Development of species identification in ducklings. XIII: A comparison of malleable and critical periods of perceptual development.

The present experiments sought to determine the relationship of the malleable period--when the mallard duck embryo is most susceptible to alien forms of maternal auditory stimulation--to the critical period, when the embryo must hear its own vocalizations in order to respond normally to the species-typical maternal call after hatching. It was found that a preference for either a wood duck or a chicken maternal call could be induced in devocalized mallard duck embryos by exposing them to either alien call some time between day 24, 0600 to day 26, 0600 hrs. Further experiments showed the height of the malleable period to be between day 24, 1400 hrs and day 25, 0800 hrs of embryonic development. Since the embryonic critical period for maintenance of the species-typical maternal auditory preference spans day 24, 0800 hrs to day 26, 0800 hrs, the malleable period for the induction of a preference for species-atypical maternal stimulation falls inside the critical period. While it is often assumed that malleable and critical periods overlap, this is the first behavioral study to actually demonstrate the temporal relationship of the two periods. It would seem important to further examine malleable and critical periods of development in a broader array of developmental contexts and species to determine whether malleable periods for atypical or abnormal development and critical periods for species-typical or normal development always coincide.

Acoustic Stimulation↗
PubMed1981

Natural killing and antibody-dependent cellular cytotoxicity in specific-pathogen-free miniature swine and germ-free piglets. II. Ontogenic development development of NK and ADCC.

The ontogenic development of natural killing (NK) and antibody-dependent cellular cytotoxicity (ADCC) in germ-free and specific-pathogen-fee (SPF) miniature swine were compared. Activities of NK and ADCC were tested by a short-term (2.5 to 4 h) 51Cr-labelled human myeloid cell line K562 and TNP-conjugated human B-cell line SB as target cells for NK and ADCC, respectively. Animals obtained by aseptic hysterectomy 3-5 days prior to term showed ADCC activities similar to adult levels but lacked NK activity. Hysterectomy-derived piglets which were colostrum-deprived and maintained in germ-free isolators developed NK activity at 3-4 weeks of age. In comparison, naturally-farrowed, colostrum-fed piglets maintained in our SPF facility developed NK activity at 2-3 weeks of age. Thereafter, there was no significant difference in the levels of either NK or ADCC between germ-free and SPF animals. This suggests that microbial flora and environment do not affect the development of effector cells for ADCC but do play some role in the maturation of NK cells during ontogeny. The difference in ontogeny of NK an ADCC further support our previous suggestion that the effector cells for NK and ADCC in swine are distinct sub-populations.

Animals↗
PubMed1991

Distribution and expression of two interactive extracellular matrix proteins, cytotactin and cytotactin-binding proteoglycan, during development of Xenopus laevis. I. Embryonic development.

An immunohistochemical study of the localization of cytotactin and cytotactin-binding (CTB) proteoglycan throughout embryonic development of the anuran Xenopus laevis reveals that both appear in a restricted pattern related to specific morphogenetic events. CTB proteoglycan expression is first detected during gastrulation at the blastopore lip. Later, it is seen in the archenteron roof around groups of cells forming the notochord, somites and neural plate. Cytotactin first appears after neurulation, and is restricted to the intersomitic regions. Both molecules appear along the migratory pathways of neural crest cells in the trunk and tail. Later, cytotactin is present at sites where neural crest cells differentiate, around the aorta and in the smooth muscle coat of the gut; CTB proteoglycan is absent from these sites. In the head, cytotactin is initially restricted to the regions between cranial somites, while CTB proteoglycan is distributed throughout the cranial mesenchyme. The expression of both molecules is later associated with key events in chondrogenesis during the development of the skull. After chondrogenesis, CTB proteoglycan is distributed throughout the cartilage matrix, while cytotactin is restricted to a thin perichondrial deposit. Both molecules are expressed in developing brain. These findings are compared to studies of the chick embryo and although distinct anatomical differences exist between frog and chick, the expression of these molecules is associated with similar developmental processes in both species. These include mesoderm segmentation, neural crest cell migration and differentiation, cartilage development, and central nervous system histogenesis.

Animals↗
PubMed1988

Developing rod photoreceptors from normal and mutant Rd mouse retinas: altered fatty acid composition early in development of the mutant.

The phospholipid and fatty acid contents of developing rod photoreceptor cells were determined in dissociated photoreceptor cells obtained from normal mice and from rd mice exhibiting an inherited retinal degeneration. Photoreceptors were dissociated from retinas by mechanical agitation after mild protease treatment and characterized by light and electron microscopy. Phospholipid classes were isolated by thin-layer chromatography, and fatty acyl groups separated and quantitated by capillary gas-liquid chromatography. Developing photoreceptor cells of normal retinas accumulated all phospholipid classes, but in proportions which shifted with age. The mole % contents of phosphatidylcholine (PC) and phosphatidylinositol (PI) decreased with age, whereas phosphatidylethanolamine (PE) and phosphatidylserine (PS) increased. The content of the polyunsaturated fatty acid docosahexaenoate (22:6), expressed as nmol/microgram lipid phosphorus, increased rapidly during development, whereas arachidonate (20:4) content tended to decline. Mono-unsaturated fatty acid levels (palmitoleate, 16:1; oleate, 18:1) declined with age. Among saturated fatty acids, palmitate (16:0) decreased during normal development, whereas stearate (18:0) increased. The total mass of phospholipid/photoreceptor cell in the normal, adult mouse retina was estimated to be approximately 14 pg. The total phospholipid content and mole % distribution of individual phospholipid classes in immature rd photoreceptors were similar to values for normal cells. In contrast, significant changes in fatty acid composition were detected between immature rd cells and normal cells. Rd cells generally had higher levels of saturated (myristate, 14:0; palmitate, 16:0) and monounsaturated fatty acids (oleate, 18:1) and lower levels of polyunsaturated fatty acids (arachidonate, 20:4; docosahexaenoate, 22:6), suggesting that fatty acid metabolism is altered by expression of the rd gene and/or by the associated impairment of photoreceptor cell differentiation.

Animals↗
PubMed1975

[Light microscopic studies on the development of Theileria annulata (Dschunkowsky and Luhs, 1904) in Hyalomma anatolicum excavatum (Koch, 1844). I. The development in the gut of engorged nymphs (author's transl)].

A laboratory strain of H. a. excavatum was selected on high susceptibility for T. annulata through several generations. Giemsa-stained smears and wet smears of gut and gut content were studied. After engorgement of erythrocytic stages of T. annulata by the nymphs the following development was observed: 1. Erythrocytic merozoites developed to slender, spindleshaped "microgamonts" in the gut 24 to 96 hours after repletion (p. repl.). Spherical stages with a conspicuous spike developed at the same time and earlier. The "microgamonts" then form up to 4 nuclei and several flagella-like appendices. Filiform "microgametes" obviously develop from the "microgamonts". In addition, spherical stages, i.e. "macrogametes", occur. 2. Spherical "zygotes" with a vacuole-like center appear in the epithelial cells of the gut from day 5 p. repl. These "zygotes" increase steadily in size and then stain more intensely up to day 12 p. repl. 3. From day 12 p. repl. the spherical "Zygotes" change to elongate forms by a continuing process of folding. Finally, from day 13 p. repl., they extend to clubshaped kinetes. These kinetes move actively by gliding within the gut cells and from day 17 p. repl. in the haemolymph. It could not be decided yet whether these kinetes are oo- or sporokinetes.

Animals↗
PubMed1978

On the development of the cerebellum of the trout, Salmo gairdneri. V. Neuroglial cells and their development.

The neuroglia of the cerebellum of Salmo gairdneri Richardson, 1836, has been studied in mature and developing specimens with light and electron microscopy. The light microscopic observations were largely carried out on Golgi material. The cerebellum of the trout contains all of the neurologlial cell types described for the mammalian cerebellum, viz. ependymal cells, Golgi epithelial cells, velate protoplasmic astrocytes, smooth protoplasmic astrocytes and oligodendrocytes. In addition two types of glial elements, which combine characteristics of ependymal cells and of velate astrocytes, are found. These elements are designated as ependymoid astrocytes and astrocytoid ependymal cells. Smooth astrocytes and oligodendrocytes were observed only in later stages of development and possibly arise from the secondary matrix. The other glial cell types, as well as transitional forms between these types, are present in rather early stages, and show a similar ultrastructure. It is plausible that all these types develop from the glioblasts produced by the ventricular matrix layer. Many glial cells are radially oriented and keep in contact with the meningeal surface throughout development. The lattice formed by matrix cells in the earliest stages, and by glial cells and the axons of granule cells later on, plays a role in directing the migration of cells. Other functions of the glia, such as dividing the cerebellar cortex in synaptic compartments, are suggested. It may be concluded that the high degree of differentiation of the teleostean cerebellum is also reflected by the morphology of the neuroglia.

Animals↗
PubMed1988

Computer-assisted analysis of the developing Purkinje neuron. I. Effects of the age of the animal at the moment of explantation on the subsequent dendritic development in organotypic cultures.

Purkinje cell dendritic arborization were studied in intracellularly horseradish peroxidase-stained mature neurons grown during 30-40 days in organotypic cerebellar cultures from kittens of various ages. The effects of the age of the animal at the moment of explantation upon the subsequent dendritic and axonal development were studied in kitten cerebella of 1, 12 and 21 postnatal days old. These effects were investigated by computer-assisted methods. Qualitative data were found to be different in these 3 in vitro models explanted at 3 different ages except for the spine development which remained the same. Quantitative data, obtained from 15 measurable parameters, showed that the degree of dendritic development was higher for the Purkinje cells explanted at the latest postnatal age: the older the animal, the larger the dendritic tree in culture. A discrimination analysis permitted a recognition of the 3 differently aged populations (94% well classified cells) based on 3 selected variables, number of primary dendritic trunks, number of rows and dendritic field areas. These results lend further support to the major role played in the final dendritic arrangement by extrinsic (discriminant factors, their pre-existence in vivo being responsible for the subsequent degree of the in vitro development of the Purkinje cell dendritic arbor.

Aging↗
PubMed1983

Stimulation of ornithine decarboxylase by histamine or norepinephrine in brain regions of the developing rat: evidence for biogenic amines as trophic agents in neonatal brain development.

Ornithine decarboxylase (ODC) initiates the synthesis of polyamines which play key roles in regulation of cellular development. Intracisternal administration of histamine or norepinephrine to developing rats produced age-dependent stimulation of ODC in brain. In cerebral cortex and ponsmedulla, stimulation by norepinephrine was demonstrable at postnatal day 7 and maximum stimulation occurred at about day 9. In contrast, cerebellum showed no initial reactivity to norepinephrine but still developed a large peak of response capability by day 9. In all 3 regions, the response declined rapidly thereafter during the period of major synaptogenesis of noradrenergic pathways. With histamine, none of the regions displayed ODC reactivity at 7 days postnatally; stimulation appeared by day 9, peaked at about day 11 and then declined rapidly. Thus, the trophic effect of histamine or norepinephrine toward ODC activity is present or develops postnatally and appears to terminate with synaptogenesis and onset of neurotransmitter properties of the amines.

Age Factors↗
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↗
PubMedDate not supplied

Middle-ear development. V: Development of umbo sensitivity in the gerbil.

PURPOSE: The development of the umbo response in the gerbil was studied in order to further elucidate the contribution of the middle ear to the development of auditory function. MATERIALS AND METHODS: Laser interferometry was used to study the development of umbo velocity in Mongolian gerbils between 10 days after birth and maturity. RESULTS: Before 15 days after birth, immaturities in the middle ear prevented any reliable measures of middle-ear motion. However, between 15 and 20 days after birth, a 10 dB improvement in umbo velocity was noted in the low-frequency (0.5 to 2.0 kHz) region of the umbo response. This improvement in sensitivity was correlated to an increased admittance due to an expanding bulla volume. Interestingly, umbo velocity remained relatively constant in the mid- and high-frequency regions of the response curve between 15 and 42 days after birth. The umbo response in the adult gerbil was decidedly different when compared with the response at 42 days after birth. CONCLUSION: We speculate that a decrease in bulla volume along with increased ossicular mass contributed to the changes in the adult umbo response. When the maturation of the umbo response was compared with more central ontogenetic measures, it became apparent that structures more central to the middle ear continued to develop well past the time the middle ear was structurally and functionally mature.

Acoustic Stimulation↗
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↗