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PubMed2000

Regulation of mouse lens fiber cell development and differentiation by the Maf gene.

Maf is a basic domain/leucine zipper domain protein originally identified as a proto-oncogene whose consensus target site in vitro, the T-MARE, is an extended version of an AP-1 site normally recognized by Fos and Jun. Maf and the closely related family members Neural retina leucine zipper (Nrl), L-Maf, and Krml1/MafB have been implicated in a wide variety of developmental and physiologic roles; however, mutations in vivo have been described only for Krml1/MafB, in which a loss-of-function causes abnormalities in hindbrain development due to failure to activate the Hoxa3 and Hoxb3 genes. We have used gene targeting to replace Maf coding sequences with those of lacZ, and have carried out a comprehensive analysis of embryonic expression and the homozygous mutant phenotype in the eye. Maf is expressed in the lens vesicle after invagination, and becomes highly upregulated in the equatorial zone, the site at which self-renewing anterior epithelial cells withdraw from the cell cycle and terminally differentiate into posterior fiber cells. Posterior lens cells in Maf(lacZ) mutant mice exhibit failure of elongation at embryonic day 11.5, do not express (&agr;)A- and all of the (beta)-crystallin genes, and display inappropriately high levels of DNA synthesis. This phenotype partially overlaps with those reported for gene targeting of Prox1 and Sox1; however, expression of these genes is grossly normal, as is expression of Eya1, Eya2, Pax6, and Sox2. Recombinant Maf protein binds to T-MARE sites in the (alpha)A-, (beta)B2-, and (beta)A4-crystallin promoters but fails to bind to a point mutation in the (alpha)A-crystallin promoter that has been shown previously to be required for promoter function. Our results indicate that Maf directly activates many if not all of the (beta)-crystallin genes, and suggest a model for coordinating cell cycle withdrawal with terminal differentiation.

Animals↗
PubMed1975

[Clinical, electron-microscopic, and histochemical investigations of conjunctivitis lignosa (author's transl)].

A case is briefly described in which a typical conjunctivitis lignosa appeared after the eye had suffered lime burns. In order to help clarify the morphological connection between mucopolysaccharide production and fiber development in the tumor tissue which occurred after the burn, samples were examined histologically, histochemically and with the use of the electron microscope. The tumor had a cartilage like consistency. Its structure could be devided into three regions. Region A is the pseudo-membrane. It has root like extensions which anchor it to the underlying tissue, and which morphologically appear partially homogeneous and partially fibrous. Blood cells and cell remnants are included in the tissue of the pseudomembrane. The histochemical examination of the pseudomembrane did not present a uniform picture. Along with small amounts of dermatan-sulfate and chondroitin-sulfate B the membrane probably contained a rather large amount of hyaluronic acid. The pseudomembrane borders on a granular tissue (Region B) which is distinguished by the wide metachromatic sheathes of the blood vessels found in it and the particularly large number of active fibroblasts along its edges. The silver impregnation method and the electron-microscopic examination showed that the vascular sheathes consist of bundles of reticular fibers which constitute a three-dimensional network. A similar sort of sheath was observed around the fibroblasts. Chondroitin-sulfate makes up the largest fraction of the mucopoly-saccharides near the fibers and appears particularly concentrated at the intersections of the fibers, although it is also diffusely distributed as well. Dermatan-sulfate (or heparan-sulfate) is found only in the mucopolysaccharide sheath of the fibers themselves. The deep region of the tumor (Region C) consists almost exclusively of blood vessels, their sprouts and the fibroblasts which, with their wide fibrous sheathes, almost fill the spaces between the blood vessels. The reticular fibers and their mucopolysaccharide sheathes have the same structure as that observed in Region B, The fact that the mucopolysaccharides did not appear in plaques but rather as bound primarily to the fibers is grounds for suggesting that a fiber development disorder, probably stemming from the pericytes and fibroblasts rich in ergastoplasm and fibrilles, could play the principle role in conjunctivitis lignosa. The cartilagen like consistency of the tumor could be a result of the arrangement of the fibers and their mucopolysaccharide sheathes. Brief remarks are included concerning the therapeutic consequences of the study.

Adult↗
PubMed1994

Functional properties and nodal spacing of myelinated fibers in developing rat mental and sural nerves.

While the postnatal length growth of the largest internodes in the rat sural nerve (SN) is proportional to nerve elongation, in the developing inferior alveolar nerve (IAN), early postnatal myelin sheath remodelling allows internodal lengthening to exceed the growth rate of the whole nerve. To assess the functional consequences of ongoing myelin sheath remodelling in a developing nerve, we examined the physiological properties of the mental nerve (MN), a cutaneous IAN branch and the SN during maturation. In addition, the nodal spacing and the microscopic anatomy of the nodes in the two nerves were studied. The youngest MNs and SNs (2 weeks) exhibited comparable sensitivities to K(+)-channel blockade with 4-aminopyridine (4-AP), although myelin sheath remodelling was more frequent in the MNs. Subsequently, myelin sheath remodelling ceased in both nerves but the MNs exhibited a greater sensitivity to 4-AP. Large fibers in adult MNs and SNs had a similar nodal anatomy but the former had shorter internodes. Thus, myelin sheath remodeling, per se, does not appear to be a determinant of 4-AP sensitivity in mammalian myelinated fibers. Rather, sensitivity to potassium channel blockade is more likely mediated at the internodal or molecular level.

4-Aminopyridine↗
PubMed1997

Expression of an L1-related cell adhesion molecule on developing CNS fiber tracts in zebrafish and its functional contribution to axon fasciculation.

E587 antigen, an L1-related cell adhesion molecule, is expressed by growing axons and has previously been shown to enhance axon growth and to mediate fasciculation of axons from newborn retinal ganglion cells in goldfish. In zebrafish, the monoclonal antibody E17 against E587 antigen stains all axons in the primary tracts and commissures from 17 h postfertilization (pf) onward and axons which are added subsequently to this scaffold. Moreover, Fab fragments of an E587 antiserum (E587 Fabs) injected into the ventricle of 30-h pf zebrafish embryos caused a marked defasciculation of distinct axon bundles in the posterior commissure, in hindbrain commissures, and in longitudinal tracts of the hindbrain, where they also caused increased crossings between fascicles. The regulated expression of E587 antigen by all developing axons and the effects caused by E587 Fabs show that E587 antigen contributes to the formation of tight and orderly fascicles in the developing CNS.

Animals↗
PubMed1975

[Demonstration of temporary multi-innervation of the cerebellar Purkinje cells by the ascending fibers during development in the rat].

The one-to-one relationship between cerebellar Purkinje cells and climbing fibres in the adult rats is the result of a regressive process affecting a multi-afferent pathway during the early post-natal period, as shown from the innervation by several independent climbing fibres of more than 50% of the Purkinje cells tested electrophysiologically on days 8 and 9.

Action Potentials↗
PubMed1990

Differential distribution of myosin isoforms among the myofibrils of individual developing muscle fibers.

Myosin was localized in situ in the posthatch chicken pectoralis using isoform-specific mAbs. The distribution among myofibrils was demonstrated by immunofluorescence and by immunogold EM. Fluorescein- or rhodamine-labeled antibody (12C5) specific for the head region (S1) of myosin was used as a marker to identify "embryonic" myosin. In longitudinal semithin frozen sections, a minority population of myofibrils stained intensely with 12C5. All other myofibrils in the same cell stained only weakly. Similarly, in Lowicryl-embedded ultrathin sections prepared for EM, a minority population reacted preferentially with gold-labeled 12C5. An antibody (5B4) specific for the rod portion of "neonatal" myosin reacted strongly with nearly all myofibrils, and this was evident by light and electron microscopy. A few of the fibrils that reacted strongly with 12C5 reacted weakly with 5B4. These observations demonstrate that an epitope reacting with 12C5 is more abundant in some myofibrils than in others within the same cell. Three categories of myofibrils can be identified by their relative proportions of embryonic and neonatal forms of myosin: in nearly all fibrils, a neonatal isoform predominates; in a minority population, embryonic and neonatal isoforms are both abundant; and in a few fibrils, an embryonic isoform predominates. It is concluded that there are distinct populations of myofibrils in which specific isoforms are segregated within an individual cell.

Aging↗
PubMed2004

Genetic mapping of EST-derived microsatellites from the diploid Gossypium arboreum in allotetraploid cotton.

To increase the numbers of microsatellites available for use in constructing a genetic map, and facilitate the use of functional genomics to elucidate fiber development and breeding in cotton, we sampled microsatellite sequences from expressed sequence tags (ESTs) transcribed during fiber elongation in the A-genome species Gossypium arboreum to evaluate their frequency of occurrence, level of polymorphism and distribution in the At and Dt subgenomes of tetraploid cotton. From among ESTs derived from G. arboreum fibers at 7-10 days post anthesis (dpa), 931 ESTs were found to contain simple sequence repeats (SSRs); 544 (58.4%) EST-SSR primer pairs were developed, and 468 (86%) amplified PCR products from allotetraploid cotton (G. hirsutumcv. TM-1 and G. barbadense cv. Hai7124). However, only 99 (18.2%) of these were found to be polymorphic and segregating in our interspecific BC1 mapping population [(TM-1xHai7124)xTM-1]. In these amplified and informative EST-SSRs, hexa- and tri-nucleotide repeat motifs were the most frequent, representing 40.1 and 30%, respectively, of the total. A total of 111 loci detected with these 99 EST-SSRs were integrated into our backbone map including 511 SSR loci. The distribution of the EST-SSRs appeared to be non-random, since 72 loci were anchored to the At and 37 to the Dt subgenome of allotetraploid cotton based on linkage tests. Interestingly, out of the 10 pairs of duplicate loci amplified, seven were mapped to the corresponding homologous linkage groups and/or chromosomes. BLASTX analysis revealed that 69 of the 99 ESTs showed significant similarities to known genes. Some genes important for fiber development, such as sucrose synthase, were mapped to corresponding chromosomes. These EST-SSRs provide structural and functional genomic information that will be useful for understanding cotton fiber development.

Base Sequence↗
PubMed1991

Relationship of primary and secondary myogenesis to fiber type development in embryonic chick muscle.

The formation of fast and slow myotubes was investigated in embryonic chick muscle during primary and secondary myogenesis by immunocytochemistry for myosin heavy chain and Ca2(+)-ATPase. When antibodies to fast or slow isoforms of these two molecules were used to visualize myotubes in the posterior iliotibialis and iliofibularis muscles, one of the isoforms was observed in all primary and secondary myotubes until very late in development. In the case of myosin, the fast antibody stained virtually all myotubes until after stage 40, when fast myosin expression was lost in the slow myotubes of the iliofibularis. In the case of Ca2(+)-ATPase, the slow antibody also stained all myotubes until after stage 40, when staining was lost in secondary myotubes and in the fast primary myotubes of the posterior iliotibialis and the fast region of the iliofibularis. In contrast, the antibodies against slow muscle myosin heavy chain and fast muscle Ca2(+)-ATPase stained mutually exclusive populations of myotubes at all developmental stages investigated. During primary myogenesis, fast Ca2(+)-ATPase staining was restricted to the primary myotubes of the posterior iliotibialis and the fast region of the iliofibularis, whereas slow myosin heavy chain staining was confined to all of the primary myotubes of the slow region of the iliofibularis. During secondary myogenesis, the fast Ca2(+)-ATPase antibody stained nearly all secondary myotubes, while primaries in the slow region of the iliofibularis remained negative. Thus, in the slow region of the iliofibularis muscle, these two antibodies could be used in combination to distinguish primary and secondary myotubes. EM analysis of staining with the fast Ca2(+)-ATPase antibody confirmed that it recognizes only secondary myotubes in this region. This study establishes that antibodies to slow myosin heavy chain and fast Ca2(+)-ATPase are suitable markers for selective labeling of primary and secondary myotubes in the iliofibularis; these markers are used in the following article to describe and quantify the effects that chronic blockade of neuromuscular activity or denervation has on these populations of myotubes.

Animals↗
PubMed1984

Development of fiber types in human fetal muscle. An immunocytochemical study.

Human fetal muscles have been studied using immunocytochemical methods with antibodies directed against different myosin isoforms. We show that fiber type differences can be detected as early as 15-16 weeks of gestation. At this time it would appear that both the heavy and light chains characteristic of slow myosin are found in some myotubes.

Adenosine Triphosphatases↗
PubMed1985

Exogenous monoamines affect the segregation of retinogeniculate fibers in developing rats.

The development of retinogeniculate projections was examined in rats which had norepinephrine levels altered by subcutaneous administration of 6-hydroxydopamine (6-OHDA) or exogenous norepinephrine (NE) during early postnatal life. NE, but not 6-OHDA, treatment resulted in an abnormal segregation of crossed and uncrossed axons at postnatal day 10, such that projections from the two eyes occupied extensively overlapping territory. This effect is at least partially reversible since in animals examined 30 days after cessation of NE treatment the retinogeniculate projections ultimately became segregated.

Animals↗
PubMed2002

Non-contact detection of laser-generated surface acoustic waves using fiber optic Sagnac interferometer.

A high powered Q-switched Nd:YAG laser was used to excite the surface waves, and an optical fiber sensor was used to detect the out-of-plane displacements due to the propagating waves. This sensor is based on the fiber optic Sagnac interferometer, which has the path-matched configuration and does not require active stabilization. Quadrature phase bias between two interfering laser beams in the Sagnac loop is applied by controlling the birefringence in an optical path using a fiber polarization controller. A stable quadrature phase bias can be confirmed by observing the interferometer output according to the change of phase bias. Additional signal processing is not needed for the detection of ultrasonic waves using the Sagnac interferometer. The performance of the fiber optic Sagnac interferometer was investigated, and laser-generated surface wave signals were detected using this fiber optic sensor. The developed fiber optic sensor configured in this study is very simple and is effective for non-contact detection of ultrasonic waves.

Journal Article↗
PubMed1999

Developments in fiber diffraction.

Improved specimen preparation methods, third generation synchrotron sources, new data processing algorithms and molecular dynamics refinement techniques are, together, allowing the high-resolution structure determination of larger and larger macromolecular complexes by fiber diffraction. New synchrotron sources are also making possible both time-resolved studies and studies of ordered fibers only a few microns in diameter.

Animals↗
PubMed1976

Lateral motion of fluorescently labeled acetylcholine receptors in membranes of developing muscle fibers.

We have made direct, quantitative measurements of the lateral motion and age-dependent distribution of acetylcholine receptors (AChR) on the surface of rat myotubes in primary culture. AChR were fluorescently marked with tetramethylrhodamine-labeled alpha-bungarotoxin and AChR lateral motion was measured by the fluoresence photobleaching recovery technique. We found two coexisting distinct classes of AChR: (i) mobile, uniformly distributed AChR that appear on all myotubes shortly after fusion from myoblasts; and (ii) immobile, dense, highly granular AChR in patches of 10-60 mum size that appear shortly after fusion and disappear after myotubes have become extensively interconnected. In addition, evidence of turnover of AChR labeled with tetramethylrhodamine-alpha-bungarotoxin is seen in the gradual internalization of surface fluorescence within 36 hr after labeling. The relevance of these results to an understanding of the membrane dynamics and localization of muscle AChR is discussed.

Age Factors↗