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PubMed1975

Brain tissue transplanted to the anterior chamber of the eye: 3. Substitution of lacking central noradrenaline input by host iris sympathetic fibers in the isolated cerebral cortex developed in oculo.

Fetal parietal cerebral cortex was homologously transplanted to the anterior chambers of the eyes of adult rats. The transplants got vascularized, proliferated, as measured by in vivo stereoscopic inspections, and differentiated into brain tissue similar to cortex cerebri in situ and survived for long times, greater than 41/2 months. Fibers from the intact sympathetic adrenergic ground plexus of the iris were able to innervate the transplants in an organotypic way regarding fluorescence morphology, pattern of distribution of the nerve terminals and, to a certain extent, density of innervation, the only variable parameter being density of innervation. Thus, in unpretreated or MAO inhibited transplants only rather few to scattered terminals could be found, while after preincubation in 10(-5)M alpha-methyl-noradrenaline the number of visible terminals was normal or slightly less than normal, as compared to cortex cerebri in situ. When superior cervical ganglia (SCG) were transplanted together with fetal cortex tissue to sympathetically denervated eyes the ingrowth in the cortex tissue was similar to that after single cortex transplantation combined with 5 day old SCG, while a marked hyperinnervation was encountered when combined with adult SCG. It is concluded that the developing cortex cerebri, deprived of its normal CNS source of adrenergic nerves, is able to receive sympathetic adrenergic nerves from the iris in an organotypic way upon transplantation to the anterior chamber of the eye.

Animals↗
PubMed1992

Risk factors for the degradation of lung elastic fibers in the ventilated neonate. Implications for impaired lung development in bronchopulmonary dysplasia.

In order to evaluate the risk for proteolytic destruction of lung parenchymal elastic fibers in ventilated premature infants, the concentrations of elastase were determined in tracheal aspirates of 65 infants from whom we obtained a total of 327 sequential samples. Elastase was detected at least once in 39 of the 65 infants studied. Eleven of these infants were ventilated with greater than 60% oxygen for greater than 5 days. In 19 infants, the presence of elastase was associated with positive bacterial and/or viral cultures and/or elevated ratios (greater than 0.22) of immature neutrophils to total neutrophils. Elastase was not detected in the lung secretions of 26 infants ventilated with greater than 60% oxygen for less than 3 days, suggesting minimal risk for elastic fiber destruction in the intubated infant who neither has pneumonia nor requires prolonged hyperoxic ventilation. The risk for elastic fiber destruction was further evaluated by analyzing sequential urine and tracheal aspirate samples for the presence of an elastolytic degradation product of elastin (desmosine). The biochemical data indicated a potential risk for proteolytic destruction of elastic fibers in association with infection and/or prolonged hyperoxic exposure. In addition, autopsy specimens obtained from three of the infants revealed structurally abnormal lung parenchymal elastic fibers. Because elastic fibers are believed to provide the structural support for alveolar septal development, proteolytic degradation of these fibers may be a significant factor in the impaired lung development that occurs in infants with bronchopulmonary dysplasia.

Bronchopulmonary Dysplasia↗
PubMedDate not supplied

Gravimetric determination of amylase-treated neutral detergent fiber in feeds with refluxing in beakers or crucibles: collaborative study.

As an important constituent of animal feeds, fiber represents the portion of feeds that is bulky and difficult to digest. The neutral detergent fiber (NDF) method, developed over 30 years ago, is the method of choice for measuring total fiber in forages and other feeds. Several modifications that were made to improve its general applicability to all feeds and others developed in individual laboratories often resulted in variability among laboratories in measuring NDF. The amylase-treated NDF (aNDF) method, therefore, was developed as an accurate and precise method of measuring total insoluble fiber in feeds. A collaborative study was conducted to evaluate the repeatability and reproducibility of the aNDF method over the full range of animal feed materials. Twelve laboratories representing research, feed company, regulatory, and commercial feed testing laboratories analyzed 11 materials as blind duplicates. The materials represented feed matrixes, including animal products; high-protein, high-fat, and high-pectin feeds; oil seeds; grains; heated by-product feeds; and legume and grass hays and silages. Materials selected varied in chemical composition and contained 0-90% aNDF, 1-16% ash, 1-20% crude fat, 1-40% crude protein, and 0-50% starch. Correcting results for changes in blanks and reporting results as ash-free aNDF organic matter (aNDFom) improved the repeatability and reproducibility of results when aNDF was <25%. The within-laboratory repeatability standard deviation (Sr) for percentage aNDFom in feeds varied from 0.21 to 1.82 and among-laboratory reproducibility standard deviation (S(R)) varied from 0.37 to 2.24. The HORRAT was <2 for all materials except feed materials containing >10% fat. However, standard deviations of repeatability and reproducibility for feeds with >10% fat were similar to those of other materials. It is recommended that the aNDF method be accepted for Official First Action status.

Algorithms↗
PubMed1993

Asbestos fiber type in malignant mesothelioma: an analytical scanning electron microscopic study of 94 cases.

Although the association between asbestos exposure and malignant mesothelioma is indisputable, controversy continues regarding the relative contribution of the various types of asbestos fibers to the development of mesothelioma. We examined the types of asbestos fibers recovered from lung parenchyma in more than 90 cases of malignant mesothelioma from the United States, using an analytical scanning electron microscope. Almost half of the patients were former asbestos insulators or shipyard workers. The fibers were recovered from lung tissues obtained at autopsy or surgical resection by means of a sodium hypochlorite digestion procedure. Amosite asbestos was identified in 81% of the cases and accounted for 58% of all fibers 5 microns or greater in length. Tremolite/actinolite/anthophyllite were identified in 55% of the cases and accounted for 10% of all fiber types. Chrysotile was identified in 21% of the cases and accounted for 3% of fibers exceeding 5 microns in length. Crocidolite was found in 16% of the cases and accounted for 3% of fibers exceeding 5 microns in length. Nonasbestos mineral fibers (commonly found in the lungs of the general population) were observed in 71% of the cases and accounted for 25% of all fibers 5 microns or greater in length. The findings in this study are at odds with the assertion that crocidolite asbestos is responsible for most mesotheliomas in the United States.

Adult↗
PubMed1995

Actomyosin kinetics and in vitro motility of wild-type Drosophila actin and the effects of two mutations in the Act88F gene.

Two missense mutations of the flight muscle-specific actin gene of Drosophila melanogaster, Act88F, assemble into normally structured myofibrils but affect the flight ability of flies and the mechanical kinetics of isolated muscle fibers. We describe the isolation of actin from different homozygous Act88F strains, including wild-type, an Act88F null mutant (KM88), and two Act88F single point mutations (E316K and G368E), their biochemical interactions with rabbit myosin subfragment 1 (S1), and behavior with rabbit myosin and heavy meromyosin in in vitro motility assays. The rabbit and wild-type Drosophila actins have different association rate constants with S1 (2.64 and 1.77 microM-1 s-1, respectively) and in vitro motilities (2.51, 1.60 microns s-1) clearly demonstrating an isoform-specific difference. The G368E mutation shows a reduced affinity for rabbit S1 compared with the wild type (increasing from 0.11 to 0.17 microM) and a reduced velocity in vitro (reduced by 19%). The E316K mutant actin has no change in affinity for myosin S1 or in vitro motility with heavy meromyosin but does have a reduced in vitro motility (15%) with myosin. These results are discussed with respect to the recently published atomic models for the actomyosin structure and our findings that G368E fibers show a reduced rate constant for delayed tension development and increased fiber stiffness. We interpret these results as possibly caused either by effects on A1 myosin light chain binding or conformational changes within the subdomain 1 of actin, which contains the myosin binding site. E316K is discussed with respect to its likely position within the tropomyosin binding site of actin.

Actins↗
PubMed2006

An immunohistochemical study of the attachment mechanisms in different kinds of adhesive interfaces in teeth and alveolar bone of the rat.

BACKGROUND AND OBJECTIVE: This study was designed to examine the histological and immunohistochemical nature of different kinds of adhesive interfaces in the rat molar region under identical experimental conditions and to discuss the structural and functional similarities between these adhesive interfaces. MATERIAL AND METHODS: Four kinds of adhesive interfaces - an initial attachment layer for principal fibers on the developing alveolar bone surface, a reattachment layer for principal fibers on resorbed alveolar bone surface, cement lines on the alveolar bone surface unrelated to the principal fibers, and the cemento-dentinal junction - were examined in 25-d-old male Wistar rats. Routine histological staining, immunohistochemical staining for bone sialoprotein and osteopontin, and digestion tests with trypsin were conducted. RESULTS: The adhesive interfaces showed very similar histological and immunohistochemical features: they were intensely hematoxylin-stainable, deficient in collagen fibrils, and rich in bone sialoprotein and osteopontin. After trypsin treatment the four adhesive interfaces had lost immunoreactivity to bone sialoprotein and osteopontin, and the two adjacent tissue parts held together finally separated at the adhesive interfaces. CONCLUSION: The above findings suggest that (i) the different types of adhesive interfaces in the rat molar region have a common structure in that they are filled with highly accumulated bone sialoprotein and osteopontin and deficient in collagen fibrils; (ii) accumulated bone sialoprotein and osteopontin are closely associated with the adhesion at the interfaces; and (iii) the adhesive interfaces have a similar developmental process.

Adhesiveness↗
PubMed1997

Airway hyperresponsiveness in a rat model of chronic bronchitis: role of C fibers.

We evaluated the role of C fibers in the development of airway hyperresponsiveness in a rat model of chronic bronchitis. Neonatal rats were treated with capsaicin (50 mg/kg, subcutaneously), a procedure which results in permanent depletion of tachykinins from the lungs and airways as well as degeneration of C fibers. Control rats were treated with the vehicle used to dissolve capsaicin. Three months later, rats from both groups were exposed either to SO2 gas (250 ppm, 5 h/d, 5 d/wk for 4 wk) or to filtered air for the same period of time. One day after the last exposure, rats were anesthetized and instrumented for the measurement of pulmonary resistance (R(L)), dynamic compliance (Cdyn), and airway responsiveness to inhaled aerosolized methacholine. There was a small (30%) but significant increase in R(L) in neonatal capsaicin- but not vehicle-treated rats exposed to SO2. Chronic exposure to SO2 resulted in increased airway responsiveness in both groups of rats, but the effect was more pronounced in the neonatal capsaicin-treated animals in which the doses of methacholine required to double R(L) or decrease Cdyn by 50% decreased 6.3-fold and 4.6-fold, respectively, compared with only 2.2- and 1.3-fold decreases in vehicle-treated rats. Morphometric analysis of histologic sections of airways demonstrated that the average area of smooth muscle in the airway wall, normalized by the length of basement membrane, was significantly greater in SO2 compared with air-exposed capsaicin-treated rats, but not in vehicle-treated control rats (p < 0.012). The maximal tension generated by tracheal rings in response to cholinergic agonists was also significantly increased by SO2 exposure in neonatal capsaicin-treated, but not vehicle-treated rats (p < 0.002). These results support the hypothesis that rather than contributing to the pathophysiologic manifestations of bronchitis, C fibers limit the development of airway obstruction and airway hyperresponsiveness during induction of chronic bronchitis by SO2 exposure. The enhanced contractile responses of airways from the SO2-exposed neonatal capsaicin-treated rats may result from increased airway smooth muscle mass and contribute to the increased airway responsiveness observed in these animals.

Animals↗
PubMed1993

Oriented cell and fiber attachment systems in vivo.

This investigation was undertaken to evaluate whether an oriented cell and fiber attachment system would develop if demineralized dentin surfaces were approximated in vivo. The approximated surfaces consisted of the internal, parallel surfaces of dentin cylinders. The experimental group was demineralized on both the external and internal surfaces of the dentin cylinder with citric acid, pH 1.0, for 3 minutes, but only the external surface of the control dentin cylinder was demineralized. Specimens were implanted transcutaneously into the backs of rats with one end protruding through the surface of the skin. Three specimens in each group were available for analysis at 1 and 10 days after implantation. The groups were compared using histologic and histometric analysis and the following conclusions were made. There were marked differences in the initial cellular response between the groups, and demineralization with citric acid prior to implantation predisposed towards a greater cell attachment at 1 and 10 days. An oriented fiber attachment developed between the demineralized approximated surfaces by 10 days, but did not develop between nondemineralized approximated surfaces. The morphology of the fiber attachment system was structurally similar to a periodontal ligament, with inserting fibers perpendicular to the implant surface. The findings of this study suggest that spatial approximation of appropriate substrates facilitates development of cell and fiber orientation. Thus, to regenerate a functionally oriented attachment system in the clinical setting, it may be beneficial to provide substrates that are appropriately approximated.

Acid Etching, Dental↗
PubMed1993

Development of innervation of skeletal muscle fibers in man: relation to acetylcholine receptors.

The aim of this study was to establish the time scale of developmental changes in innervation of skeletal muscle fibers in man. Specimens of thigh and intercostal muscle from 19 embryos and 18 infants were examined with histological methods which enabled the discrimination between fetal (gamma) and adult (epsilon) types of acetylcholine receptors (AChRs). At 8 weeks of development, AChRs were distributed diffusely in the myotube membranes. Following onset of innervation in approximately the ninth week the length of the AChR positive area diminished and reached its shortest size at the sixteenth developmental week. At the sixteenth and eighteenth week some nerve terminals opposed the muscle membrane outside the AChR positive area. Decrease in the number of nerve terminals, strongly suggesting elimination of polyneuronal innervation, started in the sixteenth week and was completed in the twenty-fifth week. This fetal (gamma) type of AChR could no longer be demonstrated after the thirty-first week. The length of the end-plates as determined by the presence of AChRs increased again in the last week before birth and reached a plateau size by the end of the first year after birth. It is concluded that in man the transition from poly- to mononeuronal innervation takes place between the sixteenth and twenty-fifth weeks of development. The evidence available suggests that the retraction of nerve terminals is preceded by loss of AChRs from the muscle membrane facing the terminals. There is no relationship between retraction of nerve terminals and the switch from fetal to adult type of AChR. The size of the presynaptic apparatus changes little after the first year of life.

Child↗
PubMed1972

Development of a receptor on a foreign nerve fiber in a Pacinian corpuscle.

When the sensory fiber of a Pacinian corpuscle (in cat mesentery) is transected (at the inferior mesenteric nerve) transduction fails within 30 hours: the nerve ending produces no generator potentials in response to mechanical stimulation. Electrically elicited nerve impulse conduction continues for at least another 18 hours. A transducer mechanism develops on a regenerating nerve fiber when this fiber enters the denervated corpuscle. Such transducer development takes place on myelinated fibers from the inferior mesenteric nerve, which normally supplies corpuscles, as well as on myelinated hypogastric nerve fibers, which normally do not go to corpuscles, including fibers larger than the original corpuscle afferents.

Action Potentials↗
PubMed1960

Multinucleation of skeletal muscle in vitro.

Healthy, mature, spontaneously contracting muscle was cultivated from explants of 13-day chick embryos for periods up to 4 months in the multipurpose chamber (Rose, 1954) using cellophane-strip technique (Rose et al., 1958) with silicone gaskets, Eagle's medium including 10 per cent horse serum reinforced with 300 mg-per cent of glucose, and the teased type of explant. This method provided optically ideal conditions for the study of muscle fibers with oil immersion, phase contrast time-lapse cinematography at 1 frame per minute without apparent damage for periods as long as 10 days. In no case was mitosis, amitosis, or nuclear "budding" observed in the course of muscle development. Multinuclear muscle fibers have been shown with cine technique to result from both myoblast fusion and polar extension of preformed (explanted) muscle tissue. Myoblast fusion was the only demonstrable way of giving rise to multinucleation. Nuclear membrane "wrinkling" was shown to be merely a temporary distortion that occurred during nuclear migration and rotation. It is suggested that this phenomenon may be responsible for numerous reports of amitosis in the genesis of muscle fibers. The histological development of new straps resulted from an orderly sequence of events. Included in these were polar extension, nuclear migration, rotation, and fixation. Following these events there was increased mitochondrial activity, myofibril formation, and cross-banding. Spontaneous contractions were seen throughout the entire course of differentiation in vitro but became more regular and stronger in the later stages.

Animals↗
PubMed2004

Development of new dosimetry using extended DNA fibers.

We applied fluorescent microscopy to monitor the damage of DNA upon exposure to gamma radiation. Our developed dosimetry demonstrated that the number of breaks in DNA is proportional to the dose of the irradiation but is not dependent on dose rate of the irradiation and the GC content of DNA.

Journal Article↗
PubMed1979

A new grouping of intrafusal muscle fibers based on developmental studies of muscle spindles in the cat.

The development of muscle spindles was studied using the tenuissimus muscle of the cat. Observations show that the intrafusal muscle fibers develop as two separate groups: one group represented by a single nuclear bag fiber while the second group comprises the second nuclear bag fiber in association with all the nuclear chain fibers. This grouping is most pronounced in the fetus and is clearly seen in neonatal kittens (i.e., up to 2 weeks of age). As the intrafusal fibers begin to separate from each other, the groupings become less noticeable, although this basic pattern is often retained in the adult. The pattern of intrafusal fiber grouping is most noticeable in the equatorial regions of the spindle and least noticeable in the polar regions. This is not the grouping of fibers which would have been expected from a consideration of existing reports on muscle spindles. The implications for spindle form and function are considered.

Animals↗
PubMed2005

Thermal tuning of mechanically induced long-period fiber grating.

We have developed a wideband tunable optical filter that uses a long-period fiber grating (LPFG) in which both resonance wavelength and its signal attenuation can be adjusted. We create the grating mechanically by pressing a spring coil to an optical fiber. We achieve continuous fine tuning of wavelength and attenuation by varying the temperature of the LPFG. The adjustable ranges of the LPFG are more than 200 nm in resonance wavelength and more than 10 dB in signal attenuation.

Journal Article↗
PubMed1990

Calibers and microtubules of nerve fibers: differential effect of undernutrition in developing and adult rats.

Sural nerves of 9-week-old rats undernourished since birth, and of adult rats food-restricted for 27 and 48 days, were studied to explore the effect of severe undernutrition on the caliber and microtubules of axons in growing and non-growing animals. In 9-week-old undernourished rats, the number and caliber of myelinated fibers were normal while the cross-sectional area of non-medullated fibers was 29% smaller than controls. By contrast, in adult undernourished rats the cross-sectional area of myelinated fibers was affected sooner and to a greater extent (-28%) than that of non-medullated fibers (-23%). Regardless of age, in both controls and in undernourished rats non-medullated fibers of equal caliber had similar microtubular content. The same was found in 3-microns myelinated axons. These findings indicate that food restriction affects proportionately caliber and microtubules of axons. It is proposed that the anatomy of the axon is in a dynamic equilibrium and that microtubules participate in the specification of the axonal caliber.

Age Factors↗