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PubMed1991

[The embryological development of the nerve fibers of the tooth. An analysis of their formation and development correlated with the different evolutionary stages of the dental structures].

In this review the research on the growth and development of nerve fibers in the dental pulp have been summarized. The first part present the distribution, type, morphology and way of impulse transmission as well as the role of the pulpal nerves. The second part present the growth of the nerve fibers in the dental structures. Through the analysis of all the research done on this subjects two important thighs can be deduced: the developing innervation correlates with the stage of the development of individual teeth rather than the chronological age of the animal, and the dental pulp compared to other structures is relatively late in maturing. This is why the axons don't penetrate into the dental papilla until crown formation commences. Then the probable role of the pulpal nerves in tooth growth (dentinogenesis) has been analysed, but this activity, even though unessential, is evident only in developing final phases and not in the early ones; this is why the axons are separated from the early growing tissues. Concluding, our review shows the variation in number, type and function of the pulpal nerves from their developing period to their complete formation until senescence.

Dental Pulp↗

PubMed1991

Effect of heroin in decomposing tissues on the development rate of Boettcherisca peregrina (Diptera, Sarcophagidae) and implications of this effect on estimation of postmortem intervals using arthropod development patterns.

Larvae of the flesh fly Boettcherisca peregrina (Robineau-Desvoidy) were reared on the tissues of rabbits to study the effects of heroin on the development rates of this species. The rabbits were given 6, 12, 18, and 24 mg of heroin by cardiac puncture. From Hours 18 to 96, larvae feeding on tissues containing heroin (as morphine) developed more rapidly than those feeding on tissues from the control. The time required for pupation was significantly greater for colonies fed on tissues from heroin-dosed rabbits than for the control colony. The differences observed in the rates of development were sufficient to alter postmortem interval estimates based on larval development by up to 29 h and estimates based on pupal development by 18 to 38 h.

Animals↗

PubMed1985

Dynamics of the control of body pattern in the development of Xenopus laevis. I. Timing and pattern in the development of dorsoanterior and posterior blastomere pairs, isolated at the 4-cell stage.

Xenopus embryos have been selected in which the second cleavage is occurring in a frontal plane, i.e. one tending to lie at right angles to the prospective plane of bilateral symmetry for the body pattern. Some of these have been used to deduce a map of the disposition of materials for the normal mesodermal pattern (the normal 'fate map') by injecting blastomeres to found fluorescently marked clones from 4- to 32-cell stages. Other such 4-cell embryos have been separated into two isolates across this second cleavage; in fate-map terms, prospective dorsoanterior and posterior isolates. These have been allowed to develop to control axial larval stages, with examination of the time schedule of their gastrulation movements in relation to cofertilized whole controls. The patterns of mesoderm produced have been examined and interpreted in the light of quantitative knowledge about the normal pattern, and our current understanding of the map. A meaningful fate map exists for the egg material even at this early, essentially acellular stage, and it differs appreciably from what might have been expected in view of that traditionally shown for early gastrula stages. The patterns developed in the isolates show that at least in many eggs, widespread information that positively specifies material as to its body position is available from at most 1 h after the events that give rise to bilateral symmetry upon fertilization. This information usually leads to a mosaic development of the appropriate mesodermal part-pattern in dorsoanterior isolates, and frequently allows development that approximates to this in the reciprocal posterior part. Regulation, i.e. the replacement of removed information to specify a development more complete than the normal contribution in isolates, is not observed. The results suggest a revision of former claims for regulative ability in at least this amphibian embryo. They also imply that systems for ascribing position value (positional information) to early embryonic tissue can be diverse in dynamics, even among embryos whose body plans are obviously homologous as are those of vertebrates.

Animals↗

PubMed1989

Life expectancy in less developed countries: socioeconomic development or public health?

Various studies have enquired into the influence of socioeconomic development or public health measures on life expectancies in less developed countries. Analysis of the effect of these two groups of factors upon life expectancy, using data for 95 less developed countries, indicates that mortality is primarily influenced by such socioeconomic development measures as urbanization, industrialization, and education, and secondarily by such public health measures as access to safe water, physicians, and adequate nutrition.

Africa↗

PubMed1988

The importance of regressive changes in the development of the nervous system: towards a neurobiological theory of child development.

In this paper we propose that theories of early personality development be revised to consider knowledge of neurodevelopment. Research findings are reviewed that have established the presence of regressive changes in the normal development of the brain. These regressive changes, consisting of neuronal death and process and synapse elimination, are theoretically linked to three precursors of personality: sex differences, temperamental traits and perceptual-motor coordination. Evidence supporting these hypotheses is provided from studies examining how the effects of genetic, environmental, and experiential factors on brain development may determine the development of these personality features.

Animals↗

PubMed1985

A comparative analysis of the development of the primary somatosensory cortex: interspecies similarities during barrel and laminar development.

The development of the barrels and layers II-V was examined in Nissl-stained preparations of the primary somatosensory cortex in six species--hamster, mouse, rat, gerbil, rabbit, and guinea pig--that have increasingly longer gestation periods. The barrels and layers II-V begin to differentiate postnatally during the first week postpartum in the hamster, mouse, rat and gerbil; perinatally in the rabbit; and approximately 4 weeks prenatally in the guinea pig. The structure of the barrels and layers II-V is similar at the onset of their differentiation in each species, even though there are interspecies differences in the mature structure of the barrels and layer V. The rate of the initial differentiation of the barrels and layers II-V is also similar in each species, even though there are considerable interspecies differences in the duration of the preceding period of development. In each species, layer V begins to differentiate first from the cortical plate and, within 1 or 2 days, contains sublayers that eventually disappear in the rabbit and guinea pig. About 3 days after the initial differentiation of layer V, layers II-IV begin to differentiate, seemingly simultaneously, causing the cortical plate to have a trilaminar appearance. Barrels are first evident just before the appearance of the trilaminar plate in hamsters; concomitant with the trilaminar plate in mice, rats, and guinea pigs; and just after the trilaminar plate in gerbils and rabbits. Septa appear 1 or 2 days after the barrels except in rabbits, which never have septa. Barrel maturation proceeds rapidly after the initial appearance in all species except the hamster, in which continued maturation seems to be delayed until the appearance of the trilaminar plate. The barrels in immature rats and rabbits become more prominent than they will eventually be in the adults. Our results indicate a close and rapid developmental affiliation between layers II-V, especially layers II-IV, that seems quite separate from the development of layers I and VI. However, barrel development and differentiation of layers II-IV seem to be closely, but independently initiated. Secondary remodeling occurs in layer V and the barrels of some species.

Animals↗

PubMed1990

Stimulation of myeloid colony development elaborated by colony forming cells--fibroblasts from rat developing ossicles.

Subcutaneous implantation of demineralized bone matrix in rats results in endochondral bone formation and bone-marrow development. The cascade of events leading to this process occurs following the accumulation of mesenchymal cells with colony forming cell fibroblasts (CFC-F) potential in the implanted area, a process which commences already 72 h post implantation. It is demonstrated herein that CFC-F from various stages of ossicle development (days, 3, 7, 10, 14 or 18) stimulate hemopoiesis to the same extent as judged by the number of granuloid-macrophage-progenitors (CFU-GM), developed as hemopoietic colonies, and by the ratio of granuloid to macrophagic colonies. High concentrations of CFC-F, however, tend to diminish the stimulatory capacity. Prostaglandin E, CFU-GM, CFC-F, ossicle, growth factors, microenvironment, hemopoiesis, development.

Animals↗

PubMed1991

A longitudinal study of the relationship between early language development and play development.

Temporal correspondences between the attainment of specific milestones in play and language were examined through a longitudinal study of four Japanese children (aged 0;7 to 0;11 at the beginning of the study). There were developmental correspondences between the onset of six language landmarks (the emergence of first words, naming words, vocabulary spurts, word-chains, nonproductive two-word utterances, productive two-word utterances) and the onset of subcategories of play. Language and play both reflected the development of underlying symbolic ability, and both developed in parallel manner at the single-word stage. After the emergence of word-chains, language and play developed interdependently. All the children proceeded through the same sequence of stages, but the rate of development was different depending on their environment.

Child, Preschool↗

PubMed1983

Development of the pre-school child: the validation of a psychomotor screen, and the influence of the home environment on psychomotor development.

The present study was designed to validate and standardize a short psychomotor screening test on Australian four-year-old-preschool children and to assess their home environment using Caldwell's HOME Inventory. The Adelaide Psychomotor Screen (APS) is a short, 10-15 minute screening test which uses 13 separate items to assess "General" development, "Gross Motor" development, "Social/Emotional Behaviour" and "Speech". In the area of "General" development, 12 children screened as "abnormal" and 54 children screened as "normal" were further assessed by a psychologist on the McCarthy Scales of Children's Abilities. There was a high correlation between the APS "General" scores and the McCarthy (General Cognitive Index) scores (r = 0.75, p less than 0.001 for the younger children, and r = 0,90, p less than 0.001 for the older children). Caldwell's HOME Inventory takes an hour to complete, and involves a visit by the assessor to each home. The correlation between the HOME total scores and the McCarthy (General Cognitive Index) scores was r = 0.06, p less than 0.001. It is suggested that the HOME Inventory may be more valuable as a predictor of a child's future development than an index of his present developmental status. It is suggested that nurses and teachers used the APS as a screening test of the individual child, and use the HOME inventory as an assessment of the home environment.

Analysis of Variance↗

PubMed1994

Facial growth and development in unilateral cleft lip and palate during the period of puberty: comparison of the development after periosteoplasty and after primary bone grafting.

X-ray cephalometry was used in studies of facial growth and development carried out in 32 males with complete unilateral cleft lip and palate. They underwent primary periosteoplasty and were examined at the ages of 10 and 15 years. The results were compared with the development of the face in a longitudinal study of 20 males with the same type of cleft who were operated with a primary bone graft. The series with periosteoplasty showed a more marked proclination of the upper dentoalveolar component with the restoration of a positive overjet, as compared to a persistent anterior crossbite in the males with bone grafts. The lower jaw showed a larger protrusion, while individuals with bone grafts were characterized at the ages of 10 and 15 years by a larger posterior rotation of the mandible. The growth of the maxilla did not differ between series. In both series, there was a marked reduction in the growth of maxillary depth and of upper lip height, while the highest growth rate showed parameters of nasal prominence. An increasing mandibular protrusion and maxillary retrusion resulted in an impairment of sagittal jaw relations and in the flattening of the face, both of which occurred in almost all patients. The rotation of the lower jaw was not correlated with either the convexity of the face, sagittal jaw relations, or an overjet. The independence of developmental changes of selected characteristics at their initial state documented the impossibility of predicting the development of the face on the basis of a single x-ray examination at a given stage of development. Fixed appliances promoted a more marked proclination of upper incisors and the alveolar process than removable appliances, but they exerted no direct action on the other facial parameters studied.

Adolescent↗

PubMed1986

L-thyroxine, cortisol, and diet affect the postnatal development of the facial part of the skull in developing rats.

In rats, the effects of L-thyroxine (T4; 0.2 micrograms/g body weight), hydrocortisone (HC; 5 micrograms/g body weight) and mastication on the postnatal development of the facial part of the skull were examined. Administration of T4 and/or HC to rats for 5 consecutive days from day 5 after birth induced a precocious increase in the ratio of the facial length to the head length. The effects of these hormones decreased with the progression of weaning, and after the 20th postnatal day, the hormones had no effects on the postnatal development of either (facial and head) part of the skull. Moreover, these hormones played an additive role in the growth of facial part. On the other hand, continuous suckling from birth to the 30th postnatal day caused a significant decrease in the ratio of the facial length to the head length. These results suggest that increases in the circulating levels of T4 and HC in suckling rats and mastication in the weaning period are involved in development of the postnatal development of the facial part of the skull.

Aging↗

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↗