Monoamine oxidase in developing chick retina

The developmental changes in monoamine oxidase (MAO) activities towards 5-hydroxytryptamine (5-HT) and beta-phenylethylamine (PEA) in chick retina were investigated. The whole pattern of the developmental changes in MAO activity towards 5-HT was similar to that towards PEA, even though the activity towards 5-HT was much lower than that towards PEA during the period from the 12th day of incubation to the 14th day after hatching. The MAO activities on the 12th day of incubation were low and increased remarkably until the 18th day of incubation. Then they remained unchanged until the 7th day after hatching; therefore, they decreased. The activities measured on the 14th day after hatching are on the same level as those of an adult. The multiplicity of MAO in the retinae of a chick on the 12th day of incubation and of an adult was also studied with specific inhibitors. The result showed that the major part of MAO in chick retina is type B enzyme; that type A MAO in the retina of an adult is, however, relatively higher than that in the retina of the embryo on the 12th day of incubation. It was found that an appreciable amount of MAO activity towards 5-HT in chick retina is due to type B MAO.     

Temporal pattern of plasminogen activator activity in the developing chick cerebellum

Plasminogen activators are considered to be involved in several developmental events. The present work aims at characterizing the developmental pattern of expression of plasminogen activators in the chick cerebellum. Soluble fractions derived by ultracentrifugation from Triton X-100 treated membrane fractions were used for determination of the enzyme activity with a radial fibrinolytic assay. By using specific inhibitors and different anti-plasminogen activators antibodies it is shown that only one type of the enzyme, the urokinase-type plasminogen activator, is expressed during the cerebellum ontogeny. Our results show the existence of a bimodal pattern of enzyme activity with two peaks that temporally coincide with the processes of massive neuronal migration, neurite outgrowth and synapse formation and plasticity. It is proposed that plasminogen activator could play a role in these developmental events and that its pattern of variability is developmentally regulated.     

Biogenesis and function of lipolysosomes in developing chick hepatocytes

Proliferation of lipolysosomes is one of the characteristic aspects of embryonic chick hepatocytes. Formation of lipolysosomes is observed in the well-developed trans-Golgi network, with the highest frequency occurring from 11 to 14 days of incubation. The lipolysosomes usually contain a small and electron-dense lipid inclusion; however, during development, they gradually enlarge with an accompanying reduction in the electron density of the inclusion. Lipolysosomes isolated from neonatal chick liver homogenates were mainly composed of esterified cholesterol and showed considerably high activity of lysosomal enzymes. Moreover, the lipolysosome fraction is clearly shown to be a function of intralysosomal lipolysis via acid lipase. This accumulation of esterified cholesterol within lipolysosomes might be attributed to an excessive uptake and conversion of plasma lipoproteins to lipolysosomes. This concept is supported by the appearance of an abundance of coated pits and both "early" and "late" endosomes. The major components of plasma lipoprotein are low density lipoprotein (LDL) and high density lipoprotein (HDL), the cholesterol-rich lipoproteins, whose cholesterol content increases during the last week of incubation when the lipolysosomes quickly enlarge. Plasma lipoprotein particles are produced in the yolk sac epithelium from yolk very low density lipoprotein (VLDL) and transferred via the vitelline circulation to the chick liver. After hatching, when the supply of nutrients from the yolk sac is terminated, lipolysosomes immediately decrease in size and number. The cholesterol and fatty acids released are useful as an energy source and lipid metabolism in general, especially after hatching. Food intake induces the use of and accelerates the disappearance of lipolysosomes. Instead of lipolysosomes, lipid droplets appear and increase in number and size with concomitant increases of triglyceride concentrations in the liver homogenates, suggesting that lipogenesis has begun in the chick hepatocyte.     

Widespread programmed cell death in early developing chick optic tectum

We demonstrate that widespread programmed cell death exists in proliferative regions of chicken optic tectum during early development using a sensitive fluorescent ISEL method (FISEL+) and antibody staining for an antigen in dying cells. Several developmental stages from embryonic day (E) 3 to E18 were examined. FISEL+-positive cells were rare before E7 and between E9 to E12. However, massive labeling was observed in the ventricular zone (VZ) between stages E7.5 and E8. At this time extensive cell migration is underway and many labeled cells were found not only in the VZ (premigratory cells) but also in the intermediate zone and tectal plate (migratory cells). Many labeled cells were also found in upper tectal laminae at late developmental stages (E15 and E18).     

The effect of hyperoxia on embryonic and organ mass in the developing chick embryo

OBJECTIVES: We investigated the sensitivity and specificity of exercise-induced T wave normalization (TWN) in infarct-related electrocardiographic leads (IRLs) for detection of residual viability in the infarct area. BACKGROUND: The meaning of exercise-induced TWN on IRLs is not yet well understood. Recent reports suggest that TWN during dobutamine echocardiography could indicate the presence of viable myocardium. METHODS: We evaluated 40 consecutive patients with a recent acute myocardial infarction and negative T waves in at least two IRLs. All patients underwent exercise testing; positron emission tomography (PET) with nitrogen-13 ammonia and fluorine-18 fluorodeoxyglucose; and coronary angiography. RESULTS: Twenty-four patients showed exercise-induced TWN: 18 at a work load < or =50 W (group la) and 6 at a work load > or =75 W (group 1b); 16 patients did not show TWN (group 2). On the PET study, viability in the infarct area was present in 17 patients (94%) from group la, in only 1 (16%) from group 1b and in 4 (25%) from group 2 (p < 0.0001). The sensitivity, specificity and diagnostic accuracy of exercise-induced TWN, in comparison with residual viability, were, respectively, 82%, 67%, 75% for TWN at every work load and 77%, 94%, 85% for TWN at a work load < or =50 W. Moreover, the sensitivity and diagnostic accuracy of TWN at the low work load were higher for anterior infarctions (87% and 88%, respectively). CONCLUSIONS: Exercise-induced TWN on IRLs at low work loads is a sensitive and specific index for the presence of residual viability in the infarct area. Sensitivity and diagnostic accuracy of this sign are higher for anterior infarctions.     

Analysis of elastin gene expression in the developing chick aorta using cloned elastin cDNA

A segment of chick elastin cDNA cloned in the plasmid pBR322 was sequenced by the method of Maxam and Gilbert ((1977) Proc. Natl. Acad. Sci. U. S. A. 74, 560-564) and the 192-base pair insert was found to be derived from the nontranslated region of the 3' end of the mRNA. The nick-translated cDNA was used to identify and to estimate the relative amounts of elastin mRNA in the developing chick embryo aorta by blot hybridization. A single species of 3.5 kilobases hybridized to the cDNA probe and this species increased greatly between day 7 and day 14 of embryonic development. This increase was paralleled by an increase in translatable aortic elastin mRNA and by the in vivo rate of elastin synthesis, demonstrating that the change in synthesis during development is largely controlled by the elastin mRNA content of the aorta.     

Proteins and glycoproteins of membranes from developing chick red cells

Membrane vesicles produced when chick erythroid cells are disrupted by nitrogen cavitation were isolated by centrifugation in a sucrose step gradient and purified on a linear sucrose gradient. Sodium dodecyl sulfate-polyacrylamide gel analysis of isolated membranes shows eight to ten proteins and four to five glycoproteins. Membranes must be prepared with protease inhibitors, otherwise an endogenous activity degrades high molecular weight polypeptide components. Red cells from several stages of development (5- and 17-day embryos and adult chickens) all appear to have the same major embrane proteins. However, primitive erythroid cells from 5-day embryos lack a Mr = 40,000 glycoprotein that is present in definitive erythrocytes from 17-day embryos and from adult chickens; erythrocytes from young chicks show a decrease in the amount of a glycoprotein of Mr = 50,000. Lactoperoxidase-catalyzed iodination of intact 5-day embryonic red cells detects three surface components which comigrate with the membrane glycoproteins on sodium dodecyl sulfate polyacrylamide gels.     

Pentobarbital modulatory effect on GABA binding sites in developing chick optic lobe

The care for elderly patients is traditionally a task of the general practitioner and will be of increasing importance in the future. Medical considerations focus on the patient's functional abilities which should play a primary role. These should, however, not neglect the patient's resources for the development of social and mental competence. Medical interventions so far will also need social indications evaluating their importance in the every day life context of the individual patient. Based on scientific knowledge of geriatrics and gerontology there should be a wide-spread introduction of standardized instruments into geriatric diagnostics and evaluation. Geriatric screening may be one example. This will support the development of a special geriatric quality management in general practice. There is a need for further development of ambulatory rehabilitation for the elderly. The general practitioner in this field will have to control the teamwork with rehabilitation-professionals and professionals from the social support services.     

A new source of cells contributing to the developing gastrointestinal tract demonstrated in chick embryos

BACKGROUND & AIMS: Smooth muscle cells in the walls of the gastrointestinal tract are thought to derive solely from mesoderm surrounding the primitive gut. A population of neuroepithelial cells has recently been shown to migrate from the ventral part of the neural tube in the region joined by the vagus nerve. We sought to determine if these cells contributed to the development of the stomach and intestine. METHODS: Cells of the ventral hindbrain of chick embryos were tagged by replication-deficient retroviral vectors containing the lacZ gene, providing a permanent label that is transmitted without dilution as the cells divide. Embryos were processed for detection of labeled cells. Specific markers were used to determine differentiation of progeny in the gastrointestinal tract. RESULTS: Cells labeled in the ventral neural tube migrate in association with the vagus nerve. Labeled cells are found in the intestine and stomach after time for further migration and differentiation. Using a specific marker, they were clearly identified as smooth muscle cells. CONCLUSIONS: Some of the smooth muscle cells of the gastrointestinal tract are derived from precursor cells that originate in the ventral part of the hindbrain neural tube. Their developmental importance and functional significance remain to be determined.     

Differential expression of PSA-NCAM and HNK-1 epitopes in the developing cardiac conduction system of the chick

Studies on a platelet-derived growth factor (PDGF) responsive osteosarcoma cell line, MG-63, were initiated to determine the effects of phosphatidylinositol (Ptdlns) 3-kinase inhibitors on serum-stimulated cell proliferation and PDGF-stimulated DNA replication, actin rearrangements, or Ptdlns 3-kinase activity. In a dose-dependent manner, the fungal metabolite wortmannin and a quercetin derivative, LY294002 (2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one), inhibited serum-stimulated MG-63 cell proliferation. The mitogenic effects of PDGF on MG-63 cells, as determined by incorporation of [3H]-thymidine, were also substantially inhibited in the presence of 0.10 microM wortmannin or 10 microM Ly294002. Furthermore, MG-63 cells stimulated by PDGF form distinct actin-rich, finger-like membrane projections which are completely inhibited by either 0.10 microM wortmannin or 10 microM LY294002. At these same concentrations, wortmannin and LY294002 were also effective at reducing levels of phosphatidylinositol 3-phosphate in PDGF-stimulated MG-63 cells. Treatment of these cells with increasing concentrations of wortmannin reduced the level of PDGF stimulated tyrosine phosphorylation of the PDGF receptor but did not significantly affect the amount of the Ptdlns 3-kinase regulatory subunit, p85, associated with the receptor. Additionally, pretreatment of cells with 0.250 microM wortmannin followed by stimulation with PDGF resulted in a slightly reduced level of receptor autokinase activity; however, similar treatment with 50 microM LY294002 did not affect the level of autokinase activity. These results demonstrate the effects of two different Ptdlns 3-kinase inhibitors on serum- and PDGF-stimulated MG-63 cell proliferation and PDGF-stimulated morphological changes and suggest a greater role for Ptdlns 3-kinase in these processes.     

Reduced levels of acetylcholine receptor expression in chick ciliary ganglion neurons developing in the absence of innervation

Chick ciliary ganglion neurons receive innervation from a single source, the accessory oculomotor nucleus (AON), and nicotinic ACh receptors (AChRs) mediate chemical synaptic transmission through the ganglion. Previous experiments examining the developmental expression of AChRs in embryonic chick ciliary ganglion neurons in situ have shown that AChR levels increase substantially in the neurons at the time of innervation. Prior to synapse formation, few AChRs are detected in the neurons. In the present experiments, the role of presynaptic inputs in inducing an increase in AChRs was established by examining AChR levels in ciliary ganglion neurons that have been deprived of innervation by surgical ablation of the AON prior to synapse formation. AChR levels were dramatically reduced in neurons of input-deprived ganglia as compared to control innervated neurons at all developmental stages examined from embryonic day (ED) 5 to ED 12 as determined by indirect immunocytochemical labeling of frozen ganglion sections with the anti-AChR monoclonal antibody mAb 35, and light microscopy. In contrast, neuronal somata of input-deprived and control ganglia had equivalent levels of immunolabeling for three other components, a transmembrane glycoprotein of synaptic vesicles, SV2, and two microtubule-associated proteins, MAP 1B and MAP 2, from ED 5 up to ED 10. The results demonstrate that presynaptic inputs specifically increase the levels of AChR expression in developing neurons. In addition, changes in the levels of immunolabeling for AChRs, SV2, MAP 1B, and MAP 2 in neuronal somata after ED 10 demonstrate that other major developmental events also influence the levels of these components in neurons. Declines in the intensity of AChR, SV2, MAP 1B, and MAP 2 immunolabeling within a subset of neuronal somata in both operated and control ganglia at ED 10 and 12 coincide with the period of neuronal cell death. Increases in AChR labeling in the rest of the neuronal population of input-deprived ganglia at ED 12 suggest that, in addition to innervation, synapse formation with the peripheral target tissue influences AChR levels in developing neurons in situ.     

Structural features of collapsin required for biological activity and distribution of binding sites in the developing chick

We have used Fc-chimeras of collapsin-1/Sema III to study the structure-function activity of this recently identified repulsive axonal guidance molecule and to map the distribution of its binding sites during chick development. Our results show that the biological activity of the collapsin-Fc in an in vitro collapse assay is independent of both the Ig-domain and the positive charged carboxy terminus. Collapsin binding sites were found on a number of neuronal fiber tracts, and in two instances (DRG tracts and the retinotectal projection) this expression is both highly dynamic and consistent with them playing a role in axonal growth and guidance. Collapsin-1 binding sites were also found on a number of nonneuronal structures that do not produce collapsin-1 mRNA. We postulate that these sites may act to localize or concentrate collapsin-1 released from growing axons and in this way allow for an autocrine axonal guidance mechanism to function during development.     

LHRH neurons migrate into the trigeminal nerve when the developing olfactory nerve fibers are physically interrupted in chick embryos

Multiple methods of tocolysis and fetal surveillance provide unprecedented ways to improve multifetal outcomes through meticulous antepartum care. Although few practitioners have much experience with these complicated pregnancies, knowledge is growing with the increasing incidence of multifetal pregnancy. A review of the current literature regarding antepartum surveillance provides the basis for a discussion of the techniques essential to quality nursing care during multifetal pregnancy. Guidelines are provided for nursing standards in documentation, terminology, and care during surveillance of multiple fetuses.     

Net transfer and incorporation of yolk n-3 fatty acids into developing chick embryos

The effect of egg yolk fatty acid composition on the uptake and utilization of essential n-6 and n-3 fatty acids by the developing chick embryo was studied. Eggs were enriched with n-9, n-3, or n-6 fatty acids by incorporating sunflower seed high in oleic acid (C18:1 n-9), flax seed rich in linolenic acid (C18:3 n-3), or sunflower seed high in linoleic acid (C18:2 n-6) into the laying hen diets. Fertile eggs were collected and incubated. The fatty acid composition of eggs and newly hatched chicks were compared. Feeding diets containing flax seed increased (P < .05) total n-3 fatty to 528.4 mg compared with 53.9 and 39.3 mg for eggs from hens fed diets with high oleic acid or regular sunflower seed, respectively. Levels of C18:2 n-6 and monounsaturated fatty acids were higher in eggs from hens fed diets containing regular or high oleic acid sunflower seeds. Dietary fat did not influence the total lipid content of the egg yolk or total lipids of chick tissues. The fatty acid composition of the hatched progeny was significantly altered by egg yolk lipids. However, the percentage incorporation of essential n-6 and n-3 fatty acids into the progeny increased when yolk sources of these fatty acids were low. The developing chick embryo appeared to preferentially take up docosahexaenoic acid and arachidonic acid from the yolk lipids. Evidence also suggests that conversion of C18:2 n-6 and C18:2 n-3 to longer chain n-3 or n-6 fatty acids occurs during the incubation period.