THE RELATION OF NERVE FIBERS TO THE DEVELOPING ENAMEL ORGANS AND DENTAL PAPILLAE OF HUMAN FETUSES OF 7.5 TO 12 WEEKS OF MENSTRUAL AGE.
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Amelogenesis↗
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A histochemical study of development of muscle fiber type and size in normal and "double muscled" cattle.
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Aerobiosis↗
Changes in actomyosin ATP consumption rate in rat diaphragm muscle fibers during postnatal development.
Early postnatal development of rat diaphragm muscle (Dia(m)) is marked by dramatic transitions in myosin heavy chain (MHC) isoform expression. We hypothesized that the transition from the neonatal isoform of MHC (MHC(Neo)) to adult fast MHC isoform expression in Dia(m) fibers is accompanied by an increase in both the maximum velocity of the actomyosin ATPase reaction (V(max) ATPase) and the ATP consumption rate during maximum isometric activation (ATP(iso)). Rat Dia(m) fibers were evaluated at postnatal days 0, 14, and 28 and in adults (day 84). Across all ages, V(max) ATPase of fibers was significantly higher than ATP(iso). The reserve capacity for ATP consumption [1 - (ratio of ATP(iso) to V(max) ATP(ase))] was remarkably constant ( approximately 55-60%) across age groups, although at day 28 and in adults the reserve capacity for ATP consumption was slightly higher for fibers expressing MHC(Slow) compared with fast MHC isoforms. At day 28 and in adults, both V(max) ATPase and ATP(iso) were lower in fibers expressing MHC(Slow) followed in rank order by fibers expressing MHC(2A), MHC(2X), and MHC(2B). For fibers expressing MHC(Neo), V(max) ATPase, and ATP(iso) were comparable to values for adult fibers expressing MHC(Slow) but significantly lower than values for fibers expressing fast MHC isoforms. We conclude that postnatal transitions from MHC(Neo) to adult fast MHC isoform expression in Dia(m) fibers are associated with corresponding but disproportionate changes in V(max) ATPase and ATP(iso).
Actomyosin↗
Recommendations of the fat and fiber groups from the workshop on new developments on dietary fat and fiber in carcinogenesis (optimal types and amounts of fat or fiber).
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Dietary Fats↗
Hollow fiber bioreactor: new development for the study of contrast agent transport into hepatocytes by magnetic resonance imaging.
The aim of our study was to develop a magnetic resonance (MR)-compatible in vitro model containing freshly isolated rat hepatocytes to study the transport of hepatobiliary contrast agents (CA) by MR imaging (MRI). We set up a perfusion system including a perfusion circuit, a heating device, an oxygenator, and a hollow fiber bioreactor (HFB). The role of the porosity and surface of the hollow fiber (HF) as well as the perfusate flow rate applied on the diffusion of CAs and O2 was determined. Hepatocytes were isolated and injected in the extracapillary space of the HFB (4 x 10(7) cells/mL). The hepatocyte HFB was perfused with an extracellular CA, gadopentetate dimeglumine (Gd-DTPA), and gadobenate dimeglumine (Gd-BOPTA), which also enters into hepatocytes. The HFB was imaged in the MR room using a dynamic T1-weighed sequence. No adsorption of CAs was detected in the perfusion system without hepatocytes. The use of a membrane with a high porosity (0.5 microm) and surface (420 cm2), and a high flow rate perfusion (100 mL/min) resulted in a rapid filling of the HFB with CAs. The cellular viability of hepatocytes in the HFB was greater than 85% and the O2 consumption was maintained over the experimental period. The kinetics of MR signal intensity (SI) clearly showed the different behavior of Gd-BOPTA that enters into hepatocytes and Gd-DTPA that remains extracellular. Thus, these results show that our newly developed in vitro model is an interesting tool to investigate the transport kinetics of hepatobiliary CAs by measuring the MR SI over time.
Animals↗
The contactin-related protein FAR-2 defines purkinje cell clusters and labels subpopulations of climbing fibers in the developing cerebellum.
FAR-2 is a novel neural member of the Ig superfamily, which is related to F11/F3/contactin and axonin-1/TAG-1. This protein is expressed by subpopulations of Purkinje cells in the chicken cerebellum and FAR-2-positive clusters of these neurons alternate with FAR-2-negative clusters in both tangential dimensions of the cerebellar cortex. Furthermore, FAR-2 is also expressed by one type of Purkinje cell afferents, namely, the climbing fibers, and different subpopulations of these axons show distinct levels of FAR-2 expression. Homology modeling using axonin-1 as a template reveals that the four aminoterminal Ig domains of FAR-2 form a compact U-shaped structure, which is likely to contain functionally important ligand-binding sites. FAR-2 is binding to the Ig superfamily protein NgCAM/L1, but not to the related receptor NrCAM, and it is also interacting with the modular ECM protein tenascin-R. These results suggest that FAR-2 may contribute to the formation of somatotopic maps of cerebellar afferents during the development of the nervous system.
Amino Acid Sequence↗
The early outgrowth of catecholaminergic fibers and the development of the nucleus of the locus coeruleus in tissue culture of newborn mice in Leighton tubes.
A simple and reliable method of sampling explants from the nucleus of the Locus Coeruleus of newborn mice and their cultivation in Leighton tubes is described. This technique reliably provides cultures available for experiments lasting, at least, ten days. The cells of the nucleus of the Locus Coeruleus and newly formed norepinephrine-containing fibers are demonstrated by fluorescence histochemistry together with pharmacological tests. Their morphological characteristics before and after fixation and staining are described. Electron microscopy confirmed the healthy condition of these cultures.
Animals↗
Development of corticospinal tract fibers and their plasticity. II. Neonatal unilateral cortical damage and subsequent development of the corticospinal tract in mice.
In this study, the right cerebral cortices of mice on postnatal day 0 (P0) were cryocoagulated with dry ice. Subsequent development of the corticospinal tract (CST) was studied morphologically and quantitatively, and was compared with that in age-matched controls. When the pyramidal tract was traced anterogradely by injecting HRP into the sensorimotor area of the left cerebral cortex of adult operated mice, the right CST originating from the healthy left hemisphere showed remarkable hypertrophy. The number of axons in the CST at the C4-C6 level became maximum on P14 in the control mice and rapidly decreased thereafter. In the operated mice, the axonal number in the right CST also was maximal on P14 and then rapidly decreased. However, the decrease in axonal number after P21 was less in the operated mice than in the controls. Moreover, the number of axons showed a slight increase after P56. These results indicate that the physiological elimination of the parent axons and their collaterals is much lower in the operated mice than in the controls, and that the increase in axon collaterals from parent axons in the hypertrophic right CST persists a long time in the operated mice.
Animals↗
Myosin heavy chain expression in developing rat intrafusal muscle fibers.
The immunocytochemical expression of several isoforms of myosin heavy chains (MHC) was determined in developing intrafusal and extrafusal fibers of the soleus muscle of prenatal and postnatal rats. At the onset of spindle assembly, both bag2 intrafusal myotubes and primary extrafusal myotubes bound a slow-twitch MHC antibody, whereas the bag1 and chain myotubes expressed a fast-twitch MHC isoform identical to that expressed by secondary extrafusal myotubes. Subsequently, developing intrafusal fibers began to express unique myosin isoforms, and ceased to express some of the myosin isoforms present initially. The initial similarity in MHC composition of intrafusal and extrafusal fibers suggests that these two kinds of mammalian muscle cell originate from a common pool of bipotential myotubes. Differences in MHC expression by intrafusal and extrafusal fibers in adult muscles might result from the effect of sensory neurons on the developing intrafusal myotubes.
Aging↗
Relationship of the sarcoplasmic reticulum to fibril and triadic junction development in skeletal muscle fibers of fetal monkeys and humans.
Examinations of stages of fibril development in muscle fibers of seven Rhesus monkey and six human fetuses reveal SR tubules encircling the Z lines at all stages of fibril development. The encircling SR tubules are continuous with the SR network of tubules which is found surrounding fibrils at all stages of development observed. The SR tubules encircling the Z lines show connections (electron-opaque strands) with the Z lines. The developing triadic junction shows a progressive increase in complexity of structures within the junction. First, membranes of T and SR become apposed with no visible structure between them- Second, tenuous connections are found traversing the space between apposed membranes. Third, well developed bridges are seen traversing the space. And finally, an intermediate density midway between the apposed membranes and parallel to them is found in favorable sections. Junctions between T tubule membranes were also observed and the structures in these junctions are somewhat similar to those found in junctions between T and SR membranes. The change in orientation of triads from predominantly longitudinal to predominantly transverse is complete in the 18-week monkey fetus and incomplete in the latest stage (28-week) of fetal development observed in humans.
Animals↗
A changing pattern of brain-derived neurotrophic factor expression correlates with the rearrangement of fibers during cochlear development of rats and mice.
The reorganization of specific neuronal connections is a typical feature of the developing nervous system. It is assumed that the refinement of connections in sensory systems requires spontaneous activity before the onset of cochlear function and selective sensory experience during the ensuing period. The mechanism of refinement through sensory experience is currently postulated as being based on the selective reinforcement of active projections by neurotrophins. We studied a presumed role of neurotrophins for rearrangement of afferent and efferent fibers before the onset of sensory function in the precisely innervated auditory end organ, the cochlea. We observed a spatiotemporal change in the localization of brain-derived neurotrophic factor (BDNF) protein and mRNA, which correlated with the reorganization of fibers. Thus, BDNF decreased in target hair cells during fiber retraction and was subsequently upregulated in neurons, target hair cells, and adjacent supporting cells concomitant with the formation of new synaptic contacts. Analysis of the innervation pattern in BDNF gene-deleted mice by immunohistochemistry and confocal microscopy revealed a failure in the rearrangement of fibers and a BDNF dependency of distinct neuronal projections that reorganize in control animals. Our data suggest that, before the onset of auditory function, a spatiotemporal change in BDNF expression in sensory, epithelial, and neuronal cells may guide the initial steps of refinement of the innervation pattern.
Afferent Pathways↗
Interaction of major intrinsic protein (aquaporin-0) with fiber connexins in lens development.
We observed that chick lens-fiber gap-junction-forming proteins, connexin (Cx) 45.6 and Cx56, were associated with an unknown protein, which was then identified as major intrinsic protein (MIP), also known as aquaporin-0 (AQP0), the most abundant membrane protein in lens fibers. A 1063 bp cDNA of chick MIP(AQP0) was identified that encodes a 262 amino acid protein with a predicted molecular weight of 28.1 kDa. Dual immunofluorescence and confocal microscopy of sagittal and coronal sections of the lens tissues showed that MIP(AQP0) consistently localized with gap junction plaques formed by Cx45.6 and Cx56 during the early stages of embryonic chick lens development. Immunoprecipitation combined with immunoblotting analyses revealed that MIP(AQP0) was associated with Cx45.6 and Cx56 at these developmental stages. The specificity of this interaction was further confirmed with the silver staining of the protein components of immunoprecipitates. The pull-down analysis of lens lysates revealed that C-terminus of MIP(AQP0) probably interacted with these two fiber connexins. In late embryonic and adult lenses, however, uniform co-distribution of MIP(AQP0) and fiber connexins was largely disrupted, except for the area surrounding the actively differentiating bow regions, as was revealed by immunofluorescence and immunoprecipitation experiments. The interaction of MIP(AQP0) with lens fiber connexins in differentiating lens cells but not in mature lens fibers suggests a potential role for MIP(AQP0) in the facilitation of fiber connexins for the formation of gap junctions during lens development.
Amino Acid Sequence↗
Nitric oxide synthase expression reveals compartments of cerebellar granule cells and suggests a role for mossy fibers in their development.
The developmental expression and cellular distribution of nitric oxide synthase was investigated in the murine cerebellum and in cerebellar neurons developing under controlled in vitro conditions. Cerebellar granule cells expressed nitric oxide synthase only after migration to the internal granule cell layer. Initially, the nascent internal granule cell layer throughout the cerebellum stained uniformly for nitric oxide synthase, but during the second postnatal week, a pattern emerged consisting of clusters of heavily stained granule cells separated by areas of unstained granule cells. This pattern persisted into adulthood. There was a close temporal correlation between innervation of the granule cell layer by mossy fibers and the emergence of granule cell compartments as defined by levels of nitric oxide synthase expression. Granule cells in dissociated cultures derived from cerebellar anlagen prior to mossy fiber innervation also express nitric oxide synthase. The time-course of nitric oxide expression was independent of electrical activity of the neuronal network forming in vitro. However, suppression of spontaneous electrical activity resulted in enhanced nitric oxide synthase expression. These findings indicate that granule cell precursors are endowed with an intrinsic program which regulates nitric oxide synthase induction and which is executed independently of correct positional cues. The data also suggest that electrical activity of ingrowing mossy fibers down regulates nitric oxide synthase expression and plays an important role in the generation of granule cell compartments. These compartments may contribute to the functional organization of the cerebellar cortex.
Afferent Pathways↗
Development of a chemiluminescent optical fiber immunosensor to detect Streptococcus pneumoniae antipolysaccharide antibodies.
A chemiluminescent-based optical fiber immunosensor was developed for the detection of antipneumococcal antibodies. This was accomplished by developing a different chemical procedure utilizing 3-aminopropyl trimethoxysilane and cyanuric chloride to conjugate pneumococcal cell wall polysaccharides to the optical fiber tips, and by improving the sensitivity of the photodetection system. The lowest titer of antipneumococcal antibodies detected by the optical fiber was at a 1:819,200 dilution. The lowest corresponding value by standard enzyme-linked immunosorbent assay was at a 1:98,415 dilution. It was concluded that the optical immunosensor system is an accurate and sensitive method to detect antipneumococcal antibodies and may be an adequate tool to monitor antibodies in specimens such as saliva and urine.
Antibodies↗
Lung tissue mechanics and extracellular matrix remodeling in acute lung injury.
UNLABELLED: This study was undertaken to test whether there is structural remodeling of lung parenchyma that could lead to tissue mechanical changes at an early phase of varying degrees of acute lung injury (ALI). Tissue resistance (R), dynamic elastance (E), and hysteresivity (eta) were analyzed during sinusoidal oscillations of rat lung parenchymal strips 24 h after intraperitoneal injection of saline (C) or paraquat (P [10, 15, 25, and 30 mg/kg]). These strips were also stained in order to quantify the amount of collagen and of three types of elastic fibers (elaunin, oxytalan, and fully developed elastic fibers) in the alveolar septa. E augmented progressively from C to P25, but the data from the P25 and P30 groups were not different (p < 0.0001). R and eta increased from C to P10 and from P15 to P25 (p < 0.001). Collagen fiber content increased exponentially with the severity of the injury. Elaunin and fully developed elastic fibers remained unchanged in the five groups, while oxytalan fibers increased only in the P25 and P30 groups. In conclusion, the pronounced mechanical changes at the tissue level and fibroelastogenesis happened at an early phase of the disease and even in mildly abnormal lung parenchyma. KEYWORDS: elastance; collagen fibers; elastin; paraquat
Acute Disease↗
The fine structure of elastic fibers.
The fine structure of developing elastic fibers in bovine ligamentum nuchae and rat flexor digital tendon was examined. Elastic fibers were found to contain two distinct morphologic components in sections stained with uranyl acetate and lead. These components are 100 A fibrils and a central, almost amorphous nonstaining area. During development, the first identifiable elastic fibers are composed of aggregates of fine fibrils approximately 100 A in diameter. With advancing age, somewhat amorphous regions appear surrounded by these fibrils. These regions increase in prominence until in mature elastic fibers they are the predominant structure surrounded by a mantle of 100 A fibrils. Specific staining characteristics for each of the two components of the elastic fiber as well as for the collagen fibrils in these tissues can be demonstrated after staining with lead, uranyl acetate, or phosphotungstic acid. The 100 A fibrils stain with both uranyl acetate and lead, whereas the central regions of the elastic fibers stain only with phosphotungstic acid. Collagen fibrils stain with uranyl acetate or phosphotungstic acid, but not with lead. These staining reactions imply either a chemical or an organizational difference in these structures. The significance and possible nature of the two morphologic components of the elastic fiber remain to be elucidated.
Acetates↗
Effect of hypobaric hypoxia on fiber type composition of the soleus muscle in the developing rat.
The fiber type composition of the soleus muscle was investigated in male Sprague-Dawley rats exposed to hypobaric hypoxia of 460 mm Hg from 5 to 12 weeks of age. The muscle fibers were classified as fast-twitch oxidative (FO) and slow-twitch (S) on the basis of adenosine triphosphatase (ATPase) and succinate dehydrogenase (SDH) reactions. Intermediate fibers (INT) with intermediate ATPase and high SDH reaction intensities were also examined. A type shift of muscle fibers from FO to INT and S was found in the control group during development. After exposure to hypoxia, the hypoxia group had a significantly greater percentage of FO fibers than the age-matched control group. There was no significant change in the total number of fibers in the muscle during development and after exposure to hypoxia. These results indicate that the increased percentage of FO fibers found in the developing rat under hypoxic conditions is due to a hypoxia-induced inhibition of the type shift of muscle fibers from FO to S during development.
Animals↗
Schwann cell internuclear distances in developing rat unmyelinated nerve fibers.
The interrelation of Schwann cells in developing rat cervical sympathetic trunk was studied by measuring distances between consecutive Schwann cell nuclei in teased unmyelinated nerve fiber bundles (Remak fibers). From 300 to 400 inter-nuclear Schwann cell distances (INDs) were measured at ten days and 2, 4, 5, 6, 8, 12, and 16 weeks after birth. Median INDs increased from 54mum at ten days to reach adult values (90mum to 100mum) at 16 weeks of age. Mean axonal diameters measured in the contralateral cervical sympathetic trunk increased from 0.57mum to 0.69mum during the same period. Developmental changes in median INDs of Schwann cells correlated significantly with age but did not parallel increases in axonal diameter.
Aging↗