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PubMed1997

Role of calcium and cross bridges in determining rate of force development in frog muscle fibers.

The influence of Ca2+ and force-generating cross bridges on the kinetics of force development was examined in skinned frog muscle fibers activated by photolytic release of Ca2+ from caged Ca2+ at 10 degrees C. Isometric force development was fit by a double exponential equation with rates of 44.4 s-1 (kc1) and 6.1 s-1 (kc2); kc1 was not significantly different from the rate of force development observed in intact fibers. Maximum activation by caged Ca2+ from preexisting submaximal force produced rates of contraction similar to those observed with maximum activation from zero force. Decreasing the Ca2+ level to an extent that resulted in 50% of maximum force development produced an approximately sevenfold decrease in kc1 and no change in kc2. Partial extraction of troponin C reduced kc1 only slightly (by 16%), whereas decreasing the number of force-generating cross bridges by vanadate did not decrease kc1. Neither treatment altered kc2. Thus the rate of force development increases dramatically with increases in Ca2+ level.

Acetates↗

PubMed2005

Theory of generation of new frequencies by mixing of solitons and dispersive waves in optical fibers.

We develop a theory of the generation of new spectral components in optical fibers pumped with a solitonic pulse and a weak continuous wave (cw). We derive the wave number matching conditions for the above process and present an analytical method of finding the amplitudes of the generated waves. We discuss related effects of the depletion of the cw pump and spectral recoil on the soliton. We also point out examples of the generation of supercontinuum spectra in fibers, where mixing between solitons and dispersive waves plays an important role.

Journal Article↗

PubMed1990

[Large-scale production of monoclonal antibodies using hollow fiber bioreactor].

Development of large-scale monoclonal antibody production using industrial scale hollow fiber bioreactor is described. Hybridoma cell lines H505AC and A306AA were cultivated in the hollow fiber perfusion bioreactor with a total fiber surface area of 7.2 m2 (6 x 1.2 m2) to produce anti-hepatitis B surface antigen (anti-HBsAg) monoclonal antibody IgM and anti-alpha-fetal protein (anti-AFP) monoclonal antibody IgG. The highest anti-HBsAg IgM productivity obtained during 49 days cultivation of H505AC was 0.135 g/day and the total accumulated IgM was 1.90 g. Results from the cultivation of A306AA in the hollow fiber module for 23 days showed the highest anti-AFP IgG productivity and the total accumulated IgG were 0.672 g/day and 7.21 g, respectively.

Animals↗

PubMed1993

Evidence for myoblast-extrinsic regulation of slow myosin heavy chain expression during muscle fiber formation in embryonic development.

Vertebrate muscles are composed of an array of diverse fast and slow fiber types with different contractile properties. Differences among fibers in fast and slow MyHC expression could be due to extrinsic factors that act on the differentiated myofibers. Alternatively, the mononucleate myoblasts that fuse to form multinucleated muscle fibers could differ intrinsically due to lineage. To distinguish between these possibilities, we determined whether the changes in proportion of slow fibers were attributable to inherent differences in myoblasts. The proportion of fibers expressing slow myosin heavy chain (MyHC) was found to change markedly with time during embryonic and fetal human limb development. During the first trimester, a maximum of 75% of fibers expressed slow MyHC. Thereafter, new fibers formed which did not express this MyHC, so that the proportion of fibers expressing slow MyHC dropped to approximately 3% of the total by midgestation. Several weeks later, a subset of the new fibers began to express slow MyHC and from week 30 of gestation through adulthood, approximately 50% of fibers were slow. However, each myoblast clone (n = 2,119) derived from muscle tissues at six stages of human development (weeks 7, 9, 16, and 22 of gestation, 2 mo after birth and adult) expressed slow MyHC upon differentiation. We conclude from these results that the control of slow MyHC expression in vivo during muscle fiber formation in embryonic development is largely extrinsic to the myoblast. By contrast, human myoblast clones from the same samples differed in their expression of embryonic and neonatal MyHCs, in agreement with studies in other species, and this difference was shown to be stably heritable. Even after 25 population doublings in tissue culture, embryonic stage myoblasts did not give rise to myoblasts capable of expressing MyHCs typical of neonatal stages, indicating that stage-specific differences are not under the control of a division dependent mechanism, or intrinsic "clock." Taken together, these results suggest that, unlike embryonic and neonatal MyHCs, the expression of slow MyHC in vivo at different developmental stages during gestation is not the result of commitment to a distinct myoblast lineage, but is largely determined by the environment.

Cell Differentiation↗

PubMedDate not supplied

Experimental evaluation of a newly developed ultrathin silicone layer coated hollow fiber oxygenator.

The authors developed a new membrane oxygenator that consists of microporous polypropylene hollow fibers coated with a 0.2 micron ultrathin silicone layer. Five venoarterial bypasses were conducted on mongrel dogs for 24 hr using these new oxygenators. The blood flow rate was maintained at 750 ml/min, and the V/Q ratio was maintained at 1:1. As a control, three venoarterial bypasses were conducted under the same conditions using an oxygenator with the same design but without the silicone coating. Eight to 16 hr after the initiation of bypass, severe plasma leakage occurred in all control experiments, so the bypasses were terminated. However, plasma leakage did not occur throughout the 24 hr of any of the experiments using the new oxygenator. The O2 transfer rate of the new oxygenators after 24 hr of perfusion was 59.7 +/- 6.6 ml/min/m2, and the plasma free hemoglobin level 8 hr after the initiation of bypass was 41.4 +/- 40.2 mg/dl, compared with 145.3 +/- 189.6 mg/dl in the control group. Scanning electron microscopic examination of the silicone coated fibers after 24 hr of bypass revealed a few scattered platelet adherents and no damage to the silicone coated surface. These results suggest that this new oxygenator has satisfactory gas transfer and good durability.

Animals↗

PubMed2000

Light and electron microscopic study of the initial attachment of principal fibers to the alveolar bone surface in rat molars.

This study was designed to observe the principal fibers and alveolar bone in various developmental stages in rat molars using light and transmission electron microscopy and to elucidate the mechanism of initial principal fiber attachment to the alveolar bone surface. Maxillary alveolar bone between the 2nd and 3rd molars of 20- and 25-day-old rats was used. A proteoglycan-rich, fiber-poor, and electron dense layer formed on the alveolar bone surface before the principal fiber organization. This layer was not seen before principal fibers had started to develop. Principal fibers first contacted and then became embedded in this layer. With further development, new bone deposited on this layer and around already attached principal fibers. These findings suggest that this electron dense, proteoglycan-rich layer may act as an adhesive factor to mediate the initial attachment of principal fibers to the alveolar bone surface.

Alveolar Process↗

PubMed2006

Refinement of innervation accuracy following initial targeting of peripheral gustatory fibers.

During development, axons of the chorda tympani nerve navigate to fungiform papillae where they penetrate the lingual epithelium, forming a neural bud. It is not known whether or not all chorda tympani axons initially innervate fungiform papillae correctly or if mistakes are made. Using a novel approach, we quantified the accuracy with which gustatory fibers successfully innervate fungiform papillae. Immediately following initial targeting (E14.5), innervation was found to be incredibly accurate: specifically, 94% of the fungiform papillae on the tongue are innervated. A mean of five papillae per tongue were uninnervated at E14.5, and the lingual tongue surface was innervated in 17 places that lack fungiform papillae. To determine if these initial errors in papillae innervation were later refined, innervation accuracy was quantified at E16.5 and E18.5. By E16.5 only two papillae per tongue remained uninnervated. Innervation to inappropriate regions was also removed, but not until later, between E16.5 and E18.5 of development. Therefore, even though gustatory fibers initially innervate fungiform papillae accurately, some errors in targeting do occur that are then refined during later embryonic periods. It is likely that trophic interactions between gustatory neurons and developing taste epithelium allow appropriate connections to be maintained and inappropriate ones to be eliminated.

Animals↗

PubMed1992

Formation of highly organized skeletal muscle fibers in vitro. Comparison with muscle development in vivo.

Two methods were developed in which long-term cultures of quail skeletal muscle were established so that all of the muscle fibers develop in a highly oriented manner. The muscle fibers became spontaneously and vigorously contractile and established strong connections with the extracellular matrix at their ends that closely duplicate the structure of the myotendinous junction. A continuous basal lamina was formed around each muscle fiber that contained type IV collagen, laminin and heparan sulfate proteoglycan. With one of the methods, an extensive extracellular matrix developed around each muscle fiber that was highly organized with the formation of a distinctive epimysium, perimysium and endomysium. Analysis of the cultures by both methods for different isoforms of myosin showed expression of an adult form of myosin by some of the muscle cells. The results therefore demonstrate that muscle development in the present culture systems proceeds extensively for several weeks. It will now be possible to investigate directly the structure of the connections between muscle fibers and the extracellular matrix.

Animals↗

PubMed1993

A method to obtain a well-defined fraction of respirable para-aramid fibers.

We developed a preparation method to obtain respirable-sized fractions of para-aramid fibers. The procedure, based on floatability, consists of stirring and subsequent settling of p-aramid pulp in distilled water. Two distinct phases are obtained, with small fibers in the upper part of the suspension, which represents about 33% of the total volume. Optimal results were obtained when 2.0 g pulp was stirred for 15 hr in 800 ml distilled water containing 0.125% ethanol and settled for 5 hr. The mass yield ranged between 0.4 and 0.6%, more than 90% of the particles had an aspect ratio > or = 3:1. The mean fiber length was about 6 microns, and the mean fiber diameter was about 0.4 microns as determined by transmission and scanning electron microscopy. The number of fibers obtained was 4 x 10(6) fibers/micrograms under our standard conditions.

Chemical Fractionation↗

PubMed2004

Development of Al2O3 fiber-reinforced Al2O3-based ceramics.

The purpose of this study was to use a tape casting technique to develop an Al2O3 fiber-reinforced Al2O3-based ceramic material (Al2O3-fiber/Al2O3 composite) into a new type of dental ceramic. The Al2O3-based ceramic used a matrix consisting of 60 wt% Al2O3 powder and 40 wt% SiO2-B2O3 powder. The prepreg sheets of Al2O3-fiber/Al2O3 composite (in which uniaxially aligned Al2O3 fibers were infiltrated with the Al2O3-based matrix) were fabricated continuously using tape casting technique with a doctor blade system. Multilayer preforms of Al2O3-fiber/Al2O3 composite sheets were then sintered at a maximum temperature of 1000 degrees C under an atmospheric pressure in a furnace. The results showed that the shrinkage and bending properties of Al2O3-fiber/Al2O3 composite exceeded those of unreinforced Al2O3--hence demonstrating the positive effects of fiber reinforcement. In conclusion, the tape casting technique has been utilized to successfully develop a new type of dental ceramic material.

Aluminum Oxide↗

PubMed2005

Development of neurons and fibers containing calcium binding proteins in the pallial amygdala of mouse, with special emphasis on those of the basolateral amygdalar complex.

We studied the development of neurons and fibers containing calbindin, calretinin, and parvalbumin in the mouse pallial amygdala, with special emphasis on those of the basolateral amygdalar complex. Numerous calbindin-immunoreactive (CB+) cells were observed in the incipient basolateral amygdalar complex and cortical amygdalar area from E13.5. At E16.5, CB+ cells became more abundant in the lateral and basolateral nuclei than in the basomedial nucleus, showing a pattern very similar to that of gamma-aminobutyric acid (GABA)ergic neurons. Many CB+ cells observed in the pallial amygdala appeared to originate in the anterior entopeduncular area/ganglionic eminences of the subpallium. The density of CB+ cells gradually increased in the pallial amygdala until the first postnatal week and appeared to decrease later, coinciding with the postnatal appearance of parvalbumin cells and raising the possibility of a partial phenotypic shift. Calretinin (CR) immunoreactivity could be observed in a few cells and fibers in the pallial amygdala at E14.5, and by E16.5 it became a good marker of the different nuclei of the basolateral amygdalar complex. Numerous CB+ and CR+ varicosities, part of which have an intrinsic origin, were observed in the basolateral amygdalar complex from E16.5, and some surrounded unstained perikarya and/or processes before birth, indicating an early formation of inhibitory networks. Each calcium binding protein showed a distinct spatiotemporal expression pattern of development in the mouse pallial amygdala. Any alteration in the development of neurons and fibers containing calcium binding proteins of the pallial amygdala may result in important disorders of emotional and social behavior.

Amygdala↗

PubMed1998

Phospholipase cbeta4 is specifically involved in climbing fiber synapse elimination in the developing cerebellum.

Elimination of excess climbing fiber (CF)-Purkinje cell synapses during cerebellar development involves a signaling pathway that includes type 1 metabotropic glutamate receptor, Galphaq, and the gamma isoform of protein kinase C. To identify phospholipase C (PLC) isoforms involved in this process, we generated mice deficient in PLCbeta4, one of two major isoforms expressed in Purkinje cells. PLCbeta4 mutant mice are viable but exhibit locomotor ataxia. Their cerebellar histology, parallel fiber synapse formation, and basic electrophysiology appear normal. However, developmental elimination of multiple CF innervation clearly is impaired in the rostral portion of the cerebellar vermis, in which PLCbeta4 mRNA is predominantly expressed. By contrast, CF synapse elimination is normal in the caudal cerebellum, in which low levels of PLCbeta4 mRNA but reciprocally high levels of PLCbeta3 mRNA are found. These results indicate that PLCbeta4 transduces signals that are required for CF synapse elimination in the rostral cerebellum.

Animals↗

PubMed1994

In vivo evaluation of chemical biopersistence of man-made mineral fibers.

Techniques developed at the Harwell Laboratory for the determination of the biopersistence of man-made mineral fibers (MMMF) in vivo are described. Results obtained with samples of glass fiber with a range of compositions, and with a sample of rockwool, are summarized. With glass fibers the rate of dissolution of fibers in vivo depends not only on their chemical composition, but also on their length. Certainly, for all fibers exceeding 10 microns in length, the longer the fiber the more rapidly it dissolves. This effect is attributed to differences in the microenvironments to which long and short fibers are exposed. Although this phenomenon appears to operate with all glass fibers, it may not apply to other types of MMMF that dissolve more readily in environments with low pH. Finally, the article examines the validity of the intratracheal method of administration for studying the biopersistence of MMMF in vivo and the use of the rat for this purpose.

Animals↗

PubMed2000

Repression of myosin isoforms in developing and denervated skeletal muscle fibers originates near motor endplates.

During development of chicken pectoralis muscle, a neonatal myosin heavy-chain isoform is supplanted progressively by an adult isoform. This expression is under neuronal control. In this study we test the hypothesis that developmental myosin transformations are initiated near the motor endplate of each muscle fiber, thereafter progressing toward the fiber ends. By using immunocytochemical methods, pectoralis muscle from chickens aged 1-115 days after hatching were labeled by antibody against neonatal isoform. Ellipse minor axis and mean optical density of labeled and/or unlabeled fiber profiles from each bird were measured by computer image analysis. Acetylcholinesterase (AChE) activity was demonstrated histochemically. Using serial cross sections, we show that smaller fiber profiles are the tapered ends of larger fiber profiles. The largest fiber profiles (central regions of the fibers) were the first to lose their neonatal myosin during development. Motor endplates were localized by AChE activity to the central regions of the fibers. The pectoralis of mature chickens was denervated for 3, 7, 15, or 21 days. After 2 weeks' denervation, neonatal myosin is first reexpressed in the fiber ends. Dev Dyn 2000;217:50-61.

Animals↗

PubMed1990

Retinal axon pathfinding in the optic chiasm: divergence of crossed and uncrossed fibers.

In the developing mammalian visual system, retinal fibers grow through the optic chiasm, where one population crosses to the opposite side of the brain and the other does not. Evidence from labeling growing retinal axons with the carbocyanine dye Dil in mouse embryos indicates that the two subpopulations diverge at a zone along the midline of the optic chiasm. At the border of this zone, crossed fibers grow directly across, whereas uncrossed fibers turn back, developing highly complex terminations with bifurcating and wide-ranging growth cones. When one eye is removed at early stages, uncrossed fibers from the remaining eye stall at the chiasm midline. These results suggest that crossed and uncrossed retinal fibers respond differently to cues along the midline of the chiasm and that the uncrossed fibers from one eye grow along crossed fibers from the other eye, both guidance mechanisms contributing to the establishment of the bilateral pattern of visual projections in mammalian brain.

Animals↗

PubMed1978

Characteristics of Ca2+- and Mg2+-induced tension development in chemically skinned smooth muscle fibers.

Chemically skinned fibers from guinea pig taenia caecum were prepared by saponin treatment to study the smooth muscle contractile system in a state as close to the living state as posible. The skinned fibers showed tension development with an increase of Ca2+ in the solution, the threshold tension occurring as 5 X 10(-7) M Ca2+. The maximal tension induced with 10(-4) M Ca2+ was as large and rapid as the potassium-induced contracture in the intact fibers. The slope of the pCa tension curve was less steep than that of skeletal muscle fibers and shifted in the direction of lower pCa with an increase of MgATP. The presence of greater than 1 mM Mg2+ was required for Ca2+-induced contraction in the skinned fibers as well as for the activation of ATPase and superprecipitation in smooth muscle myosin B. Mg2+ above 2 mM caused a slow tension development by itself in the absence of Ca2+. Such a Mg2+-induced tension showed a linear relation to concentrations up to 8 mM in the presence of MgATP. Increase of MgATP concentration revealed a monophasic response without inhibition of Ca2+-induced tension development, unlike the biphasic response in striated muscle. When MgATP was removed from the relaxing solution, the tension developed slowly and slightly, even though the Mg2+ concentrations was fixed at 2 mM. These results suggest a substantial difference in the mode of actin-myosin interaction between smooth and skeletal muscle.

Adenosine Triphosphatases↗

PubMed2004

Theory of the soliton self-frequency shift compensation by the resonant radiationin photonic crystal fibers.

We develop a theory of the soliton self-frequency shift compensation by the resonant radiation recently observed in photonic crystal fibers. Our approach is based on the calculation of the soliton plus radiation solution of the generalized nonlinear Schrödinger (GNLS) equation and on subsequent use of the adiabatic theory leading to a system of equations governing evolution of the soliton parameters in the presence of the Raman effect and radiation. Our theoretical results are found to be in good agreement with direct numerical modeling of the GNLS equation.

Journal Article↗

PubMed1985

Antibody against nerve growth factor-inducible large external (NILE) glycoprotein labels nerve fiber tracts in the developing rat nervous system.

The NILE (nerve growth factor-inducible large external) glycoprotein is a 230,000-dalton molecule found on the surface of PC12 cells. Immunologically cross-reactive glycoproteins in the molecular weight range of 215,000 to 230,000 have been found on many types of neurons in culture. Using immunohistochemical methods, we have shown that NILE-related glycoproteins are present in neuronal fiber tracts of the developing rat brain. Antibody against the NILE glycoprotein specifically labels processes that appear identical to those recognized by antibodies against the neurofilament triplet of proteins. These processes are clearly distinct from the radial glial fibers recognized by antibody against the intermediate filament protein vimentin. NILE glycoprotein is not distributed uniformly over the entire neuronal surface but is concentrated on neurites and is much less abundant on cell bodies. NILE-positive fiber tracts are first seen in the spinal cord and rhombencephalon on embryonic day 11 and over the next 2 days appear in the mesencephalon and diencephalon. Staining in the telencephalon is not seen until embryonic day 15. The appearance of NILE immunoreactivity in these various regions closely parallels the appearance of neurofilament polypeptides, suggesting that NILE-related glycoproteins are present during the early phases of fiber tract formation. This idea is supported by the finding that the NILE glycoprotein can be found postnatally in parts of the nervous-system such as the cerebellar cortex and olfactory bulb which undergo major histogenesis during the postnatal period. In the cerebellum the appearance of NILE immunoreactivity in the two major fiber zones, the molecular layer and the white matter, parallels the development of the fiber structure of these layers. These findings support tissue culture studies which suggest a role for the NILE glycoprotein in mediating nerve fiber fasciculation.

Animals↗