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At least 145 records · Page 8Linked to original sources

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↗

PubMed1975

[The relationship between the development of the clinical picture of the disease and the rate of development of the intracranial focus (an experimental study)].

Experiments on 53 dogs with a slowly increasing limited brain cavity depicted some traits in the development of intracranial hypertension and in the clinical development of the disease with regard to the rate of intensification of the focus. The rate of an increasing focus exerts great influence on the correlation between the duration of the period of larvated (compensated) and manifest development of the pathological by volume process in the brain cavity. The author distinguishes 4 types in the development of the disease: chronic, subacute, acute and stroke-like conditioned by the degree of expressiveness in the compensatory mechanisms and factors leading to a breakdown of compensation.

Acute Disease↗

PubMed1976

Studies on the development of endocrine glands in fishes. V. Development of the thyroid gland in two species of teleosts.

In Channa punctatus the thyroid anlage is seen 40 h after hatching and is recognized as cells aggregating in the form of follicles with no colloid. During subsequent stages of development the thyroid follicles increase in number and in 5 days old larva an active division of cells and many follicles in the form of epithelial cords are seen. In 2 months old juvenile fish several thyroid follicles and lymphatic vessels are seen enclosed by connective tissue capsule. In Clarias batrachus the thyroid anlage is seen as a group of cells around tiny colloid droplets and is situated just below the bifuration of the 1st branchial artery. This stage is seen in 60 h old larva and is developed into thyroid follicles which is a long chain along the jugular vein and ventral aorta during latter stages of development. It is concluded that during early larval period of these fishes, the thyroid cells begin to trap iodine from the blood and synthesize it in the form of thyroid hormone which is stored as colloid and is also liberated in blood stream simultaneously. The compact nature of the thyroid gland in C. punctatus is because of development of connective sheath around follicles during early stages.

Animals↗

PubMed1991

A flourishing time for flower development. Workshop on Flower Development, sponsored by Fundación Juan March, Madrid, Spain, March 11-13, 1991.

Molecular genetics has recently erupted in the field of flower development, an area of research traditionally cultivated by plant physiologists. The isolation and molecular characterization of seven homeotic genes (four in Antirrhinum majus and three in Arabidopsis thaliana) that control both floral organogenesis and the transition from inflorescences to floral meristems is leading to major breakthroughs in the understanding of the mechanisms governing flower development. This has already had a great impact among plant physiologists, who are incorporating mutant analysis into studies of floral induction and flower development. We are still missing data about the nature of the pollen product of the S-locus in self-incompatibility systems, although current experimental approaches might provide this information in the near future. Gene technology appears to have a high potential in hybrid seed production through the construction of male sterile plants as well as of plants able to restore fertility. The study of genes regulating pigment formation in flowers continues to provide interesting data on gene expression in plants, in which phenomena such as co-suppression and methylation seem to play an important role. Altogether, one can predict that very exciting times are coming in the field of flower development.

Gene Expression Regulation↗

PubMed1990

A comparison between hepatocellular carcinoma-developing and non-carcinoma-developing patients with cirrhosis over a long follow-up period.

An attempt was made to identify possible risk factors for developing hepatocellular carcinoma by comparing 48 autopsy cases that developed hepatocellular carcinoma and 40 autopsy cases that did not develop hepatocellular carcinoma during a follow-up period of more than three years after the diagnosis of cirrhosis. Serum hepatitis B surface antigen positivity, Child's A grade and a family history of chronic liver disease and/or HBV carrier were significant independent risk factors for the progression to hepatocellular carcinoma (p less than 0.05, p less than 0.01, p less than 0.05, respectively). Hepatocellular carcinoma tended to develop in hepatitis B surface antigen-positive males with a history of excessive alcohol intake. These results suggest that more careful and frequent examinations with various imaging modalities are needed for early detection of hepatocellular carcinoma in cirrhotic patients with these risk factors.

Carcinoma, Hepatocellular↗

PubMed1989

[Development of mandibular movements associated with growth and development of stomatognathic system].

In order to clarify the development of mandibular movements associated with growth and development of the stomatognathic system, we compared the mandibular movements of children with normal occlusion at different Hellman's dental age between IIA and IIIB, during tooth tapping movements using the following 7 different kinds of frequency; ad lib.; 1 time/sec, 2 times/sec and 3 times/sec movements with reguration; 1 time/sec, 2 times/sec and 3 times/sec movements without reguration. Then, we determined the correlation between the results and the subjects' chronological age and obtained the following findings. 1) During 5 strokes between the 3rd and 7th strokes after the start of the tooth tapping movements, mandibular movements were not very diversified among 30 tooth tapping movements using the 7 different kinds of frequency, and the mean values were almost consistent. 2) In the 5 strokes between the 3rd and 7th strokes at all dental age, each determined item showed minimal dispersion during the 3 times/sec unregurated movements. 3) In the following items, changes related to age were noted during the 3 times/sec unregurated movements. (1) Cycle time decreased and became closer to the calculated value (333.33 msec), and maximum velocity in closing increased as age advanced. (2) Although there was no significant correlation with the subjects' chronological age, degree of mandibular opening, duration of opening phase, duration of closing phase, duration of occluding phase and velocity peak time in opening decreased, and maximum velocity in opening increased as age advanced. (3) Velocity peak time in closing was only slightly influenced by age. 4) These results indicate that mandibular movements develop in the course of growth and development of the stomatognathic system.

Humans↗

PubMed1985

Studies on the development of infant foods from plant protein sources. Part III. Preparation, processing and properties of various products developed.

Studies have been carried out on the development of a low-cost, high-quality infant food of low paste viscosity from rice, chickpea (Cicer arietinum) and cow's milk. In order to improve the overall quality of the product, chickpea was processed by different methods prior to its incorporation. A number of formulations was prepared by mixing 52% rice, 30% each, the processed chickpea sample, and 18% whole milk powder. These mixtures were processed by extrusion cooking or drum drying. In the case of the extrusion cooking method, from the nutritional and technological points of view, it was found advantageous to incorporate milk powder after cooking a mixture of rice and chickpea. The values of net protein ratio (NPR) of the products developed, whether processed by extrusion cooking or drum-drying methods, were statistically equal, and not significantly different from those of casein. Supplementing the product with methionine and threonine showed no effect in improving the NPR value, suggesting that these amino acids were not limiting. There were slight differences in the digestibilities of proteins in the products developed and all were lower than that of casein. Depending on the processing method, differences were observed in paste viscosities of the products. After partial hydrolysis of the products with pounds amylase, both the cold and hot paste viscosities were greatly reduced and were comparable with those of whole milk powder. From the results herein reported, it can be concluded that the drum-dried product prepared using rice:chickpea (carbonate presoaked):milk (52:30:18) is the best of all the products developed. Its amino acid composition compares favorably with that of the milk proteins.

Amino Acids↗

PubMed1984

The development of infections of the genitourinary tract in the wives of infertile males and the possible role of spermatozoa in the development of salpingitis.

Genitourinary tract infections developing in wives during marital life in 1,350 infertile couples were examined. Women married to men with a history of genital tract infection had a significantly higher incidence of vaginitis, urinary tract infection, salpingitis and genital herpes when compared with women whose husbands did not have genital tract infections before the marriage. Of the variables examined, the two factors that showed the most significant association with the tendency to develop salpingitis were the sperm count and the length of time the couple had been trying to achieve a pregnancy. The wives of azoospermic males did not have pelvic inflammatory disease develop but had the same incidence of infection of the lower part of the genital tract as the other studied groups. It is suggested that the bacterial flora of the seminal fluid can play a role in developing salpingitis in the female and that spermatozoa may be involved in delivering bacteria to the higher genital tract structures.

Adult↗

PubMed1982

Development of the optic nerve in Xenopus laevis. I. Early development and organization.

Development of the Xenopus laevis optic nerve was studied by light and electron microscopy from embryonic stage 26, before the retina has formed, to juveniles, 8 months postmetamorphic. Low-power EM photographs of sections through the retinal optic nerve (RON), middle optic nerve (MON) and chiasmatic optic nerve (CON) were prepared at different stages and the areas containing large axons (0.5 micron) were traced in optic nerve reconstructions. Ordering of fibre size along a dorsoventral axis was noted in the embryonic nerve, and this pattern persisted throughout development. Most large fibres, myelinated and unmyelinated, occupy an eccentric dorsocentral position in the MON while small axons are seen in a ventral peripheral crescent. In the CON, the dorsal one third to one half is occupied by large fibres while the ventral CON contains small fibres exclusively. If, as assumed, large axons are older than small axons (0.1-0.3 micron), then patterns of large and small axons along the nerve might reveal a chronotopic fibre ordering. Chronotopic ordering was confirmed by autoradiographic analysis of the distribution of old, labelled fibres and young, unlabelled newly arriving fibres in optic nerves between stage 51 and 57. The young-old labelling pattern corresponds to the small and large axon patterns respectively, in all sections of the optic nerve. Chronotopic ordering of fibres in the developing optic nerve can be explained, in part, by the dorsoventral asymmetric marginal growth of the developing retina and the phenomenon of fibre following as ganglion cell axons join near neighbour fascicles in the retina, converge at the optic disc and grow through the optic nerve.

Animals↗

PubMed1980

Criteria for development of animal models of diseases of the respiratory system: the comparative approach in respiratory disease model development.

Advances in the understanding of human respiratory disease can come from careful clinical studies of the diseases as they occur in man, but such studies are naturally limited in terms of experimental manipulation. In the last 2 decades, an increasingly complex plethora of experimental respiratory disease models has been developed and utilized by investigators, but relatively less attention has been paid to the naturally occurring pulmonary diseases of animals as potential models. This paper is aimed at presenting selected examples of spontaneous pulmonary disease in animals that may serve as exploitable models for human chronic bronchitis, bronchiectasis, emphysema, interstitial lung disease, hypersensitivity pneumonitis, hyaline membrane disease, and bronchial asthma. Chronic bronchitis in dogs is characterized by chronic cough, excessive mucus production, and chronic inflammatory changes in bronchial walls. The disease affects mainly smaller-breed dogs of middle age or older. Equine chronic bronchitis tends to be a small airway disease with marked goblet cell proliferation and excessive mucus production, which may be accompanied by alveolar emphysema. Many animals develop bronchiectasis or bronchiolitis obliterans secondary to chronic suppurative bronchopneumonia, but chronic respiratory disease (CRD) of rats may be the most useful model of bronchiectasis. Models for emphysema must include actual alveolar destruction and ideally should be accompanied by appropriate pathophysiologic decrements. Many animals occasionally develop emphysema, but the disease has not been well documented, except possibly in horses. The interstitial lung diseases of man represent a complicated and poorly understood group of entities and near-entities. The same is true for animals, although interstitial lung disease in animals is much less common than bronchopneumonia. Cattle seem prone to develop interstitial lesions. Proliferative interstitial pneumonia of cattle includes many morphologic similarities to the spectrum of human interstitial pneumonitides. Fibrosing alveolitis of cattle is a morphologic end point that may have its origins in different forms of interstitial injury. Hypersensitivity pneumonitis has been best detailed in cattle and in horses and is clinically, etiologically, immunologically, and morphologically similar to the disease in man. Hyaline membrane disease has been poorly documented in animals, with the possible exception of the neonatal respiratory distress syndromes of foals and piglets. Bronchial asthma is similarly not well established as a spontaneous disease in animals, although experimental models exist. Eosinophilic bronchiolitis of cattle may represent a useful asthma model but has been poorly detailed. In order to make them useful as models, more attention should be paid to detailing the clinical, morphologic, and etiologic aspects of these naturally occurring animal pulmonary diseases.

Animals↗