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PubMed1984

Postnatal differentiation of rat optic nerve fibers: electron microscopic observations on the development of nodes of Ranvier and axoglial relations.

The postnatal differentiation of rat optic nerve fibres was examined by transmission electron microscopy. The results show that many early developing axons contain clusters of vesiculotubular profiles prior to myelination. At places vesicular elements appear to fuse with the axolemma, and, in addition, some axons exhibit deep axolemmal invaginations and axoplasmic lamellated bodies. It is suggested that these features might reflect axolemmal remodelling, possibly involving axoglial signalling and/or functional differentiation of the axolemma. The size distribution of unmyelinated optic nerve axons changes little during development. Ensheathment of larger axons commences 6 days postnatally. The subsequent formation of compact myelin sheaths is accompanied by an increase in axonal diameter. The early sheaths are a few microns long and separated by long bare axon segments. In optic nerves from 10-12-day-old rat pups, a few sheaths consisting of about five layers border primitive asymmetric nodes with a patchy axolemmal undercoating. Extensions from one of the terminating sheaths are often associated with undercoated patches of axolemma. Relatively differentiated nodes of Ranvier first appear 14-16 days after birth. The continued nodal maturation involves establishment of a regular nodal geometry, increasing distinctness of the axolemmal undercoating, and formation of perinodal astrocytic processes embedded in an extracellular node gap substance. The results are compared with available data on the conduction properties of rat optic nerve fibres during development.

Animals↗

PubMedDate not supplied

The significance of type 2C muscle fibers in Duchenne muscular dystrophy.

Undifferentiated type 2C fibers, which are dark on ATPase staining with both alkaline and acid preincubation, comprised on average 16.1% of the muscle fibers in 12 patients with Duchenne muscular dystrophy (DMD). Many of type 2C fibers had characteristics of regenerating fibers: basophilic cytoplasm, vesicular nuclei with occasional prominent nucleoli, high alkaline phosphatase and nonspecific esterase activity, and also high oxidative enzyme activity at the periphery of the fiber. A localized high acetylcholinesterase activity suggested the presence of a neuromuscular junction in some of the type 2C fibers. In serial sections, histochemical reactions characteristic of the type 2C fiber were present in segments of a single fiber, which in other parts was either a type 1 or a type 2 fiber. Since most of the opaque (hyaline, dark) fibers, which previously have been thought to be precursors of necrotic fibers, behaved as differentiated type 1 or type 2 fibers, the presence of type 2C fibers in DMD may not reflect "dedifferentiation" of fiber type, but rather indicate an active regenerating process. It remains unknown whether the type 2C fiber segments in DMD develop into fully differentiated functional fibers or remain as incompletely regenerated fibers.

Adenosine Triphosphatases↗

PubMed1994

Formation of focal adhesions by osteoblasts adhering to different substrata.

In this study, the adhesion of an osteoblast cell line to glass and titanium surfaces coated with different extracellular matrix components has been examined. On uncoated glass or titanium surfaces, osteoblasts attached but failed to spread. On these surfaces the cells did not develop focal adhesions or stress fibers. Precoating glass coverslips or titanium disks with fibronectin enhanced spreading and resulted in the rapid formation of focal adhesions and their associated stress fibers. Osteoblasts also spread and developed focal adhesions and stress fibers on glass or titanium coated with serum. In this situation the spreading was less rapid than that on fibronectin. Following incubation with serum, we demonstrated that the surfaces became coated with vitronectin. On the vitronectin-coated surfaces, it was shown that the osteoblast focal adhesions contained integrins of the beta 3 family. In contrast, osteoblasts adhering to fibronectin-coated surfaces accumulated beta 1 integrins within their focal adhesions. The enhanced formation of focal adhesions by osteoblasts plated on surfaces coated with extracellular matrix proteins suggests that precoating titanium and other implant materials with extracellular matrix proteins may improve osseointegration.

3T3 Cells↗

PubMed1991

Improved on-line thoracic duct drainage for lymphocytapheresis.

Lymphocytapheresis using thoracic duct drainage (TDD) is a recognized technique of extracorporeal immunomodulation for various autoimmune diseases such as rheumatoid arthritis (RA), and its clinical benefit has been reported and generally accepted. Lymphocytapheresis using TDD is very selective for removing lymphocytes (especially helper T-cells) but raises some problems such as hypoproteinemia due to the massive removal of lymph, and difficulties in repeated treatment. Along with the development of a new polyester fiber filter, we have developed a simple and effective method of lymphocytapheresis for wide adoption for these techniques. We performed lymphocytapheresis using TDD in patients with RA and previously reported its clinical efficacy indicated by the significantly lower number of peripheral lymphocytes and T4/T8 ratio. We present here our newly-developed on-line system designed to prevent hypoproteinemia. Furthermore we report on the advantages with a new subcutaneous vascular access device set up to manage the problems of repeated treatments. A small reservoir for keeping the thoracic duct open and returning lymph to the patient permitted sufficient lymph drainage and removal of lymphocytes and the clinical application of TDD is discussed.

Arthritis, Rheumatoid↗

PubMed1997

[Kindling induced mossy fiber sprouting has no functional significance in developing seizure discharges in rats].

It is reported that chronic electrical stimulation of perforant path (PP) produces mossy fiber sprouting in dentate granule cells and as a result new recurrent excitatory circuits are formed. It has been assumed that the circuits are responsible for the well-known lowering in the threshold required to generate seizure discharges by the electrical stimulation. The assumption was tested in the present investigation. Current source density analysis of the field potential in the dentate gyrus was carried out in control (n = 8) and kindled (n = 10) rats under pentobarbital anesthesia during seizure discharges. The field potential was produced by stimulating the PP and recorded simultaneously from 10 sites which were 50 microns apart from each other. The field potential consisted of a monosynaptic excitatory postsynaptic field current (EPSC) in the middle molecular layer followed by a population spike current (PSC). In the kindled rats, following the EPSC and PSC, a late sink appeared in the supragranular layer (SGL). The amplitude of the SGL late-sink showed a positive correlation with the density of Timm granules (r = 0.76). The latency difference between the onset of PSC and that of the SGL late-sink ranged from 0.5 to 1.5 ms. This suggested the possibility that the SGL late-sink is produced via the recurrent excitatory circuit newly formed by mossy fiber sprouting. The SGL late-sink, however, evoked no further firing in dentate granule cells. During 5 Hz PP stimulation for 10 s, the amplitude of SGL late-sink increased gradually at first, but later it decreased gradually and disappeared before seizure discharges produced. Accordingly, there was no evidence suggesting that the new recurrent excitatory circuit played any role in producing seizure discharges. During seizure discharges, the EPSC resembling the SGL late-sink appeared spontaneously only in the SGL and seemed to initiate repetitive synchronized-firing of granule cells in one of four kindled rats. The number of burst discharges and the duration of seizure discharges with the late sink, however, were not significantly different from those of seizure discharges without such a late skin. These results suggest that the newly formed recurrent circuit plays no essential role in decreasing the threshold required to generate seizure discharges or in developing them.

Action Potentials↗

PubMed2001

Role of cholinergic mossy fibers in vestibular nuclei in the development of vestibular compensation.

Several lines of evidence have suggested that acetylcholine is a possible neurotransmitter/neuromodulator involved in vestibular compensation. However, details of cholinergic effective sites during vestibular compensation remain unclear. In this study, we selectively damaged the rat vestibulo-floccular cholinergic mossy fibers using ethylcholine mustard aziridinium ion. In these animals, unilateral labyrinthectomy caused more severe vestibulo-ocular deficits, especially in the initial stage. These findings suggest that the vestibulo-floccular cholinergic mossy fibers serve to restore the balance between intervestibular nuclear activities in order to induce vestibular compensation in the initial stage.

Animals↗

PubMed1988

Adult human masseter muscle fibers express myosin isozymes characteristic of development.

Masseter muscle biopsies were obtained from nine patients undergoing orthognatic surgery or surgery for parotid tumors. A detailed enzyme-histochemical and immunocytochemical study of these muscles was performed using antibodies specific to the various isozymes of the myosin heavy chain (MHC) in order to identify the MHC isozymes that were present in the different fiber types. The contractile proteins in these same biopsies were analyzed by two-dimensional gel electrophoresis, native pyrophosphate gel electrophoresis, and by an immunopolypeptide mapping approach. These studies have shown that there is a very heterogeneous distribution of the myosin isozymes, with many fibers containing more than one myosin type. We also present evidence that in addition to adult fast and slow myosin, the human masseter muscle contains two proteins, neonatal MHC and embryonic myosin light chain, that are characteristic of developing muscle.

Electrophoresis↗

PubMed1988

Nodal myosin distribution in the bovine heart during prenatal development: an immunohistochemical study.

A novel type of cardiac myosin heavy chain, immunologically related to the myosin isoforms expressed during skeletal muscle development, has recently been described in sinoatrial and atrioventricular nodal fibers of the adult bovine heart (Gorza et al, J Cell Biol 1986; 102:1758-1766). The tissue-specific expression of this myosin type has been utilized in the present study to investigate the differentiation of nodal fibers during cardiac development. In 4-6-week-old bovine embryos, reactivity for nodal myosin was observed in a cluster of cardiac fibers in the sinus venosus wall, corresponding to the sinoatrial node primordium and in a number of fibers localized in the left atrial wall, especially in proximity to vascular orifices, possibly corresponding to the postulated left-sided sinoatrial node. In contrast, reactivity for nodal myosin was not detected in the atrioventricular node until 12 weeks of gestation. Before this stage, fibers reactive for nodal myosin were also seen scattered in the left atrial wall and interatrial septum, raising the possibility that atrioventricular nodal fibers may derive from the left-sided sinoatrial node. Reactivity for nodal myosin was never seen in normal atrial and ventricular myocardium, nor in the ventricular conduction tissue, indicating that nodal myosin does not represent a primordial myosin form, but is rather a specific marker of a distinct muscle cell lineage.

Animals↗

PubMedDate not supplied

A new approach to the bending properties of hair fibers.

A new test developed to characterize the bending properties of treated or virgin hair fibers is described. The device consists of a pendulum that bends a sample made up of 39 parallel hair fibers at each swinging stroke. Hair bending stiffness can be assessed by the number of strokes observed until the pendulum stops. The mechanical behavior of natural hair fibers is related to their geometric characteristics. The effects of various hair treatments can be assessed by this method.

Elasticity↗

PubMed1979

The relationship between the mobility of human teeth and their supracrestal fiber support.

A method to study the relationship between the mobility of human teeth and their supracrestal fiber support was developed. The results of this study would indicate that: (1) The supracrestal fibers do not contribute significantly to the support of a normal premolar tooth. (2) As a human premolar tooth develops moderate to severe loss of osseous support, the relative contribution of the supracrestal fibers to the support of the tooth increases significantly.

Adolescent↗

PubMed1993

Effects of prenatal undernutrition on developing rat diaphragm.

The effects of maternal nutritional deprivation (ND) on the proportions and cross-sectional areas (CSAs) of type I and II fibers in the developing rat diaphragm (Dia) were examined. In addition, the effects of ND on in vitro contractile and fatigue properties were also studied. Compared with in the control (CTL) group (from pups of well-nourished mothers), proportions of type II fibers were significantly lower in the ND group during the first 3 postnatal wk. However, this difference did not persist into adulthood. CSAs of type I and II fibers were larger in ND Dia than in CTL Dia during early postnatal development, but in adults type I and II fiber CSAs were larger in CTL than in ND Dia. Interstitial space comprised a smaller fraction of total muscle area in ND Dia throughout postnatal development and persisted in adults. Estimated fiber density (no. of fibers/CSA muscle) was lower in ND groups at all ages. In addition, the total number of fibers was significantly lower in ND Dia at all ages. Optimal muscle fiber length for peak twitch and maximum isometric force generation was shorter in ND Dia at all ages. At postnatal days 7 and 14, specific force (maximum tetanic force in N/cm2) of ND Dia was significantly lower than that of CTL Dia. At day 21, Dia specific force was comparable between the two groups but was significantly lower in adult ND compared with adult CTL Dia. Except for days 0 and 14, ND Dia was more fatigue resistant than CTL Dia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2004

Coordination of trigeminal axon navigation and patterning with tooth organ formation: epithelial-mesenchymal interactions, and epithelial Wnt4 and Tgfbeta1 regulate semaphorin 3a expression in the dental mesenchyme.

During development, trigeminal nerve fibers navigate and establish their axonal projections to the developing tooth in a highly spatiotemporally controlled manner. By analyzing Sema3a and its receptor Npn1 knockout mouse embryos, we found that Sema3a regulates dental trigeminal axon navigation and patterning, as well as the timing of the first mandibular molar innervation, and that the effects of Sema3a appear to be mediated by Npn1 present in the axons. By performing tissue recombinant experiments and analyzing the effects of signaling molecules, we found that early oral and dental epithelia, which instruct tooth formation, and epithelial Wnt4 induce Sema3a expression in the presumptive dental mesenchyme before the arrival of the first dental nerve fibers. Later, at the bud stage, epithelial Wnt4 and Tgfbeta1 regulate Sema3a expression in the dental mesenchyme. In addition, Wnt4 stimulates mesenchymal expression of Msx1 transcription factor, which is essential for tooth formation, and Tgfbeta1 proliferation of the dental mesenchymal cells. Thus, epithelial-mesenchymal interactions control Sema3a expression and may coordinate axon navigation and patterning with tooth formation. Moreover, our results suggest that the odontogenic epithelium possesses the instructive information to control the formation of tooth nerve supply.

Animals↗

PubMed1981

Lesion-induced sprouting of hippocampal mossy fiber collaterals to the fascia dentata in developing and adult rats.

A lesion-induced formation of an abnormal projection of hippocampal mossy fiber collaterals to the molecular layer of the fascia dentata was studied in rats. Both immature (1--30 days old) and adult rats were subjected to hippocampal and entorhinal lesions which alone or in combination removed one or more of the major afferents to the dentate molecular layer (commissural, associational, and perforant path). Some lesions in addition transected the main part of the mossy fibers en route from the dentate granule cells to the hippocampal pyramidal cells in regio inferior (CA3). The formation of aberrant mossy fiber terminals in fascia dentata (supragranular mossy fibers) was monitored by the histochemical Timm sulphide silver method, but the presence of aberrant terminals was also observed in the electron microscope. Abnormal amounts of supragranular mossy fiber terminals were found following entorhinal lesions of both immature and adult rats, but not following commissural lesions. Even larger amounts of aberrant terminals were, however, found in immature and adult rats subjected to lesions which removed most of the associational hippocampodentate projection by isolating columns of fascia dentata from major parts of the hilus (CA4). Pure transections of the fascia dentata perpendicular to its longitudinal septotemporal axis did not in itself cause aberrant supragranular terminals, although such lesions partially damaged the associational afferents. When the transections were combined with commissural lesions or entorhinal lesions or both, large amounts of supragranular terminals did, however, form at the denervated levels septal to the transection. After comparison of the amounts and distributions of the aberrant terminals found after the different lesions and in transplants of dentate tissue with different amounts of afferent input, we conclude that it is deafferentation of the dentate molecular layer, and not axotomy of the mossy fibers in the hilus of CA3 (pruning), that causes the aberrant growth of mossy fiber collaterals. Moreover, simultaneous removal of more than one afferent system seems to have a potentiating rather than a simple additive effect on the formation of supragranular mossy fibers.

Afferent Pathways↗

PubMed1974

Calcium binding and tension development in detergent-treated muscle fibers.

The nonionic detergent Brij 58 eliminates irreversibly the capability of the sarcoplasmic reticulum (SR) of skinned crayfish muscle fibers to sequester Ca and to release it under appropriate stimulation. In contrast to deoxycholate (DOC) which causes an irreversible diminution of tension as well, Brij 58 does not affect the contractile proteins. Comparison of the time-course of tension development before and after Brij treatment demonstrates that Ca is accessible to the contractile proteins more rapidly after the SR is destroyed but, nevertheless, much more slowly than is predicted for free diffusion of Ca in the myoplasm. Slowing apparently results because of the presence of ca 1 mmol/kg fiber of myoplasmic Ca-binding sites that remain after Ca uptake of the SR is eliminated. A theoretical model is presented which allows for the effects of binding sites and of an unstirred layer in the vicinity of the fiber on Ca diffusion into the myoplasm.

Animals↗

PubMed1991

Aggregation of myonuclei and the spread of slow-tonic myosin immunoreactivity in developing muscle spindles.

The pattern of regional expression of a slow-tonic myosin heavy chain (MHC) isoform was studied in developing rat soleus intrafusal muscle fibers. Binding of the slow-tonic antibody (ATO) began at the equator of prenatal intrafusal fibers where sensory nerve endings are located, and spread into the polar regions of nuclear bag2 and bag1 fibers but not nuclear chain fibers during ontogeny. The onset of the ATO reactivity coincided with the appearance of equatorial clusters of myonuclei (nuclear bag formations) in bag1 and bag2 fibers. Moreover, the intensity of the ATO reaction was strongest in the region of equatorial myonuclei and decreased with increasing distance from the equator of bag1 and bag2 fibers at all stages of prenatal and postnatal development. The polar expansion of ATO reactivity continued throughout the postnatal development of bag1 fibers, but ceased shortly after birth in bag2 fiber coincident with innervation by motor axons. Thus, afferents that innervate the equator might induce the slow-tonic MHC isoform in bag2 and bag1 fibers by regulating the myosin gene expression by equatorial myonuclei, and efferents or twitch contractile activity might inhibit the spread of the slow-tonic MHC isoform into the poles of bag2 but not bag1 fibers. Absence of ATO binding in chain fibers suggests that chain myotubes may not be as susceptible to the effect of afferents as are myotubes that develop into bag2 and bag1 fibers. The different patterns of slow-tonic MHC expression in the three types of intrafusal fiber may therefore result from the interaction of three elements: sensory neurons, motor neurons, and intrafusal myotubes.

Aging↗

PubMed1976

Tension development in skinned glycerinated rabbit psoas fiber segments irrigated with soluble myosin fragments.

Single glycerinated rabbit psoas muscle fibers were skinned by splitting them lengthwise. The fiber segments thus obtained were more easily accessible to solutes in the surrounding medium than the intact fibers. Using such segments, active tension could be fully abolished by adding N-ethylmaleimide under conditions which lead to inhibition of actin activation of the ATPase activity of myosin. Such muscles could, however, develop tension after irrigation with myosin or with the water-soluble active myosin fragments heavy meromyosin (HMM) or its subfragment 1 (HMM-S1). The induced tensions increased with increasing protein concentration in the irrigating solution. At any given protein concentration, the tension generated by myosin was larger than that produced by HMM which was, in turn, greater than that induced by HMM-S1 e.g. at 15 mg/ml protein the tensions produced by these three myosin moieties were 44.0, 14.0 and 2.8 g/cm2, respectively. The tension was found to be intimately associated with ATP splitting; thus, HMM and HMM-S1 which have been treated with reagents abolishing actin-activated ATPase failed to induce tension development. A contractile force may thus be generated through the interaction with actin of the water-soluble, enzymatically active, myosin subfragments involving the splitting of ATP.

Actins↗

PubMed1996

Normal development of tyrosine hydroxylase and serotonin immunoreactive fibers innervating anterior cingulate cortex and visual cortex in rabbits exposed prenatally to cocaine.

Anterior cingulate cortex develops abnormally in rabbits exposed to cocaine in utero but visual cortex is normal. The interactions of cocaine with the dopamine, norepinephrine and serotonin systems makes each a potential candidate for influencing these developmental effects. Here, we report no differences in the distribution and density of serotonin and tyrosine hydroxylase-immunoreactive fibers in the anterior cingulate cortex in postnatal rabbits exposed prenatally to cocaine or saline. Because the pattern and extent of cortical innervation by these systems appears normal, the data suggest that the effects of prenatal exposure to cocaine may involve changes in monoamine signaling distinct from morphological reorganization of the cortical afferents.

Animals↗

PubMed1990

Differential expression of the two delta-crystallin/argininosuccinate lyase genes in lens, heart, and brain of chicken embryos.

Chicken delta-crystallin/argininosuccinate lyase (ASL), a major enzyme-crystallin of the embryonic lens, is encoded by two similar, tandemly arranged genes (delta 1 and delta 2). We show here by the polymerase chain reaction (PCR) and in situ hybridization that although the amount of mRNA for each of the delta-crystallins increases in the lens epithelial and fiber cells during development of the embryonic chicken, the delta 1 mRNA accumulates preferentially in the fiber cells. The delta 1/delta 2 mRNA ratio actually decreased from 16.5 +/- 7 to 6.5 +/- 1 in the central epithelial cells while it increased from 20 +/- 10 to 95 +/- 5 in the fibers between 6 and 14 days of development. By contrast, the heart and brain of 4- to 8-day-old embryonic chickens showed 10(3) to 10(4) times less delta-crystallin mRNA per microgram of total RNA than the lens, with a delta 1/delta 2 mRNA ratio of only 0.20 to 0.30. The tissue-specific differences in the relative expression of the two delta-crystallin genes suggest that the delta 2 polypeptide is principally responsible for ASL activity and that the delta 1 polypeptide is specialized for lens transparency. The trace amounts of delta 1 mRNA in the heart and brain raise the possibility that the delta 1 polypeptide contributes to or modulates ASL activity of the native tetrameric protein. Transfection experiments in which we used the pSVOCAT plasmid demonstrated that both delta-crystallin genes contain an enhancer in their third intron. The promoter and enhancer of each delta-crystallin gene were functionally comparable in the pSVOCAT plasmid when tested in primary embryonic lens epithelial cells, suggesting that the differential expression of the two delta-crystallin genes in the lens requires additional cis-regulatory sequences, post-transcriptional mechanisms, or both.

Animals↗