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At least 919 records · Page 51Linked to original sources

PubMed2003

Developing patterns of nitric oxide synthesizing neurons in the rat striatum: histochemical analysis.

The prenatal and postnatal development of NADPH-diaphorase (NADPH-d)/neuronal nitric oxide synthase (nNOS) positive neurons was studied in the striatum of rats. NADPH-d was demonstrated enzyme histochemically and nNOS immunohistochemically using a polyclonal antibody. NADPH-d neurons appeared in the ventrolateral part of the striatum on embryonic day 18 (E18). Thereafter, the number of NADPH-d neurons increased and began to distribute homogeneously in the striatum. The density of NADPH-d neurons became highest at postnatal day 5 (P5) and then decreased as the volume of the striatum continued to increase. The number of NADPH-d neurons reached its peak around 3-4 weeks after birth. The sizes of NADPH-d neurons were measured. The NADPH-d neurons grew larger until P14 (mean area 260 microm(2)) and became smaller thereafter (mean area 170 microm(2)). Patches of high NADPH-d activity and tyrosine hydroxylase (TH) immunoreactivity were also examined in the developing striatum. The distributions of NADPH-d patches overlapped with those of TH-immunoreactive patches by P10. The spatiotemporal appearance of nNOS and overlapping of nNOS patchy distribution with TH point to an important role of NO and to an interaction between nNOS and DA fibers during development of the striatum.

Aging↗

PubMed2006

Alexander disease-associated glial fibrillary acidic protein mutations in mice induce Rosenthal fiber formation and a white matter stress response.

Mutations in the gene for the astrocyte specific intermediate filament, glial fibrillary acidic protein (GFAP), cause the rare leukodystrophy Alexander disease (AxD). To study the pathology of this primary astrocyte defect, we have generated knock-in mice with missense mutations homologous to those found in humans. In this report, we show that mice with GFAP-R76H and -R236H mutations develop Rosenthal fibers, the hallmark protein aggregates observed in astrocytes in AxD, in the hippocampus, corpus callosum, olfactory bulbs, subpial, and periventricular regions. Astrocytes in these areas appear reactive and total GFAP expression is elevated. Although general white matter architecture and myelination appear normal, when crossed with an antioxidant response element reporter line, the mutant mice show a distinct pattern of reporter-gene induction that is especially prominent in the corpus callosum, and histochemical staining reveals accumulation of iron in the same region. The mutant mice have a normal lifespan and show no overt behavioral defects, but are more susceptible to kainate-induced seizures. Although these mice demonstrate increased GFAP expression by themselves, further elevation of GFAP via crosses to GFAP transgenic animals leads to a shift in GFAP solubility, an increased stress response, and ultimately death. The mice do not display the full spectrum of pathology observed in human infantile AxD, but may more closely resemble the adult form of the disease. These studies provide formal proof linking GFAP mutations with Rosenthal fibers and oxidative stress, and correlate gliosis and GFAP protein levels to the severity of the disease.

Alexander Disease↗

PubMed1992

Fibroblast contraction occurs on release of tension in attached collagen lattices: dependency on an organized actin cytoskeleton and serum.

The generation of tension in granulation tissue undergoing contraction is believed to be a cell-mediated event. In this study we used attached collagen lattices as a model system for studying the cellular mechanisms of tension generation by fibroblasts in an extracellular matrix. Fibroblasts in attached collagen lattices developed stress fibers, surface associated fibronectin fibrils, and a fibronexus-like transmembrane association interconnecting the two structural components. Release of the attached collagen lattice from its points of attachment resulted in a rapid, symmetrical contraction of the collagen lattice. Rapid contraction occurred within the first 10 minutes after release of the lattice from the substratum, with greater than 70% of the contraction occurring within the first 2 minutes. Rapid contraction resulted in a shortening of the elongate fibroblasts and compaction of the stress fibers with their subsequent disappearance from the cell. Cytochalasin D treatment prior to release disrupted the actin cytoskeleton and completely inhibited rapid contraction. The removal of serum prior to release inhibited rapid contraction, while the re-addition of serum restored rapid contraction. These results demonstrate that fibroblasts can develop tension in an attached collagen lattice and that upon release of tension the fibroblasts undergo contraction resulting in a rapid contraction of the collagen lattice. Fibroblast contraction is dependent upon an organized actin cytoskeleton and is promoted by the presence of serum.

Collagen↗

PubMed2006

Comparison of different chondrocytes for use in tissue engineering of cartilage model structures.

This study compares bovine chondrocytes harvested from four different animal locations--nasoseptal, articular, costal, and auricular--for tissue-engineered cartilage modeling. While the work serves as a preliminary investigation for fabricating a human ear model, the results are important to tissue- engineered cartilage in general. Chondrocytes were cultured and examined to determine relative cell proliferation rates, type II collagen and aggrecan gene expression, and extracellular matrix production. Respective chondrocytes were then seeded onto biodegradable poly(L-lactide-epsilon-caprolactone) disc-shaped scaffolds. Cell-copolymer constructs were cultured and subsequently implanted in the subcutaneous space of athymic mice for up to 20 weeks. Neocartilage development in harvested constructs was assessed by molecular and histological means. Cell culture followed over periods of up to 4 weeks showed chondrocyte proliferation from the tissue sources varied, as did levels of type II collagen and aggrecan gene expression. For both genes, highest expression was found for costal chondrocytes, followed by nasoseptal, articular, and auricular cells. Retrieval of 20-week discs from mice revealed changes in construct dimensions with different chondrocytes. Greatest disc diameter was found for scaffolds seeded with auricular chondrocytes, followed by those with costal, nasoseptal, and articular cells. Greatest disc thickness was measured for scaffolds containing costal chondrocytes, followed by those with nasoseptal, auricular, and articular cells. Retrieved copolymer alone was smallest in diameter and thickness. Only auricular scaffolds developed elastic fibers after 20 weeks of implantation. Type II collagen and aggrecan were detected with differing expression levels on quantitative RT-PCR of discs implanted for 20 weeks. These data demonstrate that bovine chondrocytes obtained from different cartilaginous sites in an animal may elicit distinct responses during their respective development of a tissue-engineered neocartilage. Thus, each chondrocyte type establishes or maintains its particular developmental characteristics, and this observation is critical in the design and elaboration of any tissue-engineered cartilage model.

Aggrecans↗

PubMed1980

A case report of basal cell adenoma showing elastic fiber (elastin-basement membrane complex) formation of the submandibular gland.

A biopsy case of basal cell adenoma of the submandibular gland was reported in a 15-year-old boy. The tumor was pigeon's egg-sized, spherical in shape and encapsulated by fibrous tissue, and its cut-surface was grayish white. Histologic feature of this neoplasm was a trabecular or tubular monomorphic adenoma with well-developed elastic fibers (elastin-basement membrane complex) in the interstitial tissue. Electron microscopy disclosed 4 kinds of tumor cells, that is, secreting cells, squamous cell-like cells with tonofibrils and tonofilaments, clear cells with a few filaments, and myoepithelial cells. The interstitium contained elastin, collagen fibrils and basement membrane-like substance. Possible production of elastic fibers by the myoepithelial cells of this adenoma was discussed.

Adenoma↗

PubMed1994

Pharmacological characterization of serotonin synthesis and uptake suggest a false transmitter role for serotonin in the pituitary intermediate lobe.

A subpopulation of nerve fibers in the rat pituitary intermediate lobe (IL) have been shown to exhibit colocalization of serotonin (5-HT-IR) and tyrosine hydroxylase immunoreactivities and they are sensitive to neurotoxins specific to catecholamine neurons. This study was set out to examine the uptake and synthesis mechanisms of serotonin in these fibers. We developed an in vitro technique in which the neurointermediate lobe explants were incubated (14 and 48 h) in the presence of various drugs and serotonin was subsequently visualized by immunohistochemistry. Control incubation in the presence of serotonin (10(-6) M) resulted in a rich plexus of 5-HT-IR fibers in both posterior and intermediate lobes. Fluoxetine and citalopram (10(-6) M and 10(-5) M), inhibitors of 5-HT transporter, did not affect 5-HT-IR in the IL fibers, unless they were used in concentrations high enough (10(-4) M and 10(-3) M) to block unspecifically a number of monoamine transporters. The same applied for desipramine (10(-5)-10(-7) M), an inhibitor of the noradrenaline transporter. However, cocaine (10(-5)-10(-6) M) blocked serotonin uptake into these terminals, suggesting that serotonin uptake occurs through a dopamine transporter. Incubation of the IL in presence of L-tryptophan (10(-4) M) did not result in 5-HT-IR in the IL fibers showing colocalization of 5-HT-IR and tyrosine hydroxylase, which suggests that these fibers do not synthesize serotonin. The present results suggest that serotonin is taken up into the IL terminals by a dopamine transporter and is not synthesized in them, at least in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2004

Analysis of five differentially expressed gene families in fast elongating cotton fiber.

Using the suppression subtractive hybridization method, we isolated five gene families, including proline-rich proteins (PRPs), arabinogalactan proteins (AGPs), expansins, tubulins and lipid transfer proteins (LTPs), from fast elongating cotton fiber cells. Expression profile analysis using cDNA array technology showed that most of these gene families were highly expressed during early cotton fiber developmental stages (0 C20 days post anthesis, DPA). Many transcripts accumulated over 50-fold in 10 DPA fiber cells than in 0 DPA samples. The entire gene family --AGP, together with 20 individual members in other 4 gene families, are reported in cotton for the first time. Accumulation of cell wall proteins, wall loosening enzymes, microtubules and lipid transfer protein may contribute directly to the elongation and development of fiber cells.

Amino Acid Sequence↗

PubMed1987

NGF effects on developing forebrain cholinergic neurons are regionally specific.

Nerve growth factor (NGF) has been shown to have an effect on neurons in the central nervous system (CNS). A number of observations suggest that NGF acts as a trophic factor for cholinergic neurons of the basal forebrain and the caudate-putamen. We sought to further characterize the CNS actions of NGF by examining its effect on choline acetyltransferase (ChAT) activity in the cell bodies and fibers of developing neurons of the septum and caudate-putamen. ChAT activity was increased after even a single NGF injection. Interestingly, the magnitude of the effect of multiple NGF injections suggested that repeated treatments may augment NGF actions on these neurons. The time-course of the response to NGF was followed after a single injection on postnatal day (PD) 2. NGF treatment produced long-lasting increases in ChAT activity in septum, hippocampus and caudate-putamen. The response in cell body regions (septum, caudate-putamen) was characterized by an initial lag period of approximately 24 hr, a rapid rise to maximum values, a plateau phase and a return to baseline. The response in hippocampus was delayed by 48 hr relative to that in septum, indicating that NGF actions on ChAT were first registered in septal cell bodies. Finally, developmental events were shown to have a regionally specific influence on the response of neurons to NGF. For though the septal response to a single NGF injection was undiminished well into the third postnatal week, little or no response was detected in caudate-putamen at that time. In highlighting the potency and regional specificity of NGF effects, these observations provide additional, support for the hypothesis that NGF is a trophic factor for CNS cholinergic neurons.

Animals↗

PubMed1987

Fiber types and fiber diameters in canine respiratory muscles.

In the present study, we measured fiber types and fiber diameters in canine respiratory muscles and examined regional variation within the diaphragm. Samples of eight diaphragm regions, internal intercostals, external intercostals, transversus abdominis, and triceps brachii were removed from eight adult mongrel dogs, frozen, and histochemically processed for standard fiber type and fiber diameter determinations. The respiratory muscles were composed of types I and IIa fibers; no IIb fibers were identified. Fiber composition differed between muscles (P less than 0.0001). Normal type I percent (+/- SE) were: diaphragm 46 +/- 2, external intercostal 85 +/- 6, internal intercostals 48 +/- 3, transversus abdominis 53 +/- 1, and triceps 33 +/- 7. The diaphragm also contained a type I subtype [6 +/- 1% (SE)] previously thought only to occur in developing muscle. Fiber composition varied between diaphragm regions (P less than 0.01). Most notably, left medial crus contained 64% type I fibers. Fiber size also varied systematically among muscles (P less than 0.025) and diaphragm regions (P less than 0.0005). External intercostal fiber diameter was largest (47-50 microns) and diaphragm was smallest (34 microns). Within diaphragm, crural fibers were larger than costal (P less than 0.05). We conclude that there are systematic differences in fiber composition and fiber diameter of the canine respiratory muscles.

Analysis of Variance↗

PubMed1994

Distribution of cytoskeletal proteins (neurofilaments, peripherin and MAP-tau) in the cochlea of the human fetus.

We report here an immunohistochemical study of the distribution of intermediate filaments (neurofilament, peripherin) and a microtubule-associated protein, tau, in the human fetal cochlea at 27 weeks of gestation. Neurofilament immunoreactivity (160 and 200 KDa) was localized in afferent and efferent fibers of the cochlear innervation and restricted to a few small spiral ganglion neurons. Peripherin immunoreactivity was specifically distributed in some small ganglion neurons and in their central and peripheral extensions, particularly in fibers reaching the lower part of the outer hair cells. Double immuno-labelling studies with these neurofilaments and peripherin antibodies show that only small neuron cell bodies were stained. Morpholometrical data indicate that immunostained neurons could be related to the Type II neuron population in the spiral ganglion. Tau protein was localized in intraganglionic spiral bundle fibers and in fibers that reach the lower part of hair cells. These observations suggest that neurofilament and peripherin antibodies stain a particular population of human spiral ganglion neurons with Type II characteristics. Moreover, the specificity of peripherin labelling in Type II cells and their processes suggest that peripherin could be used as a probe for the developmental study of this system in the human cochlea. On the other hand, tau antibody appeared as a marker for efferent fibers during development and could give information on the ontogenesis of efferent innervation.

Cochlea↗

PubMed2002

Towards tissue engineering of a composite aortic valve.

A tissue-engineered valve needs to incorporate the complex microstructure of the native aortic valve if it is to be as durable as existing bioprosthetic valves. Native aortic valve cusps contain large collagen fiber bundles surrounded by tubes of elastin, linked together by elastin sheets and struts. They also contain glycosaminoglycans (GAGs) that bind water and give the valve cusp a gelatinous consistency. Our approach to tissue engineering the aortic valve is to fabricate the cusp from the building blocks described above. We have developed collagen fiber bundles using the principle of directed collagen gel shrinkage, a GAG matrix by crosslinking high molecular weight hyaluronan with divinyl sulfone, and elastin sheets and tubes by culturing neonatal aortic fibroblasts on the appropriate substrates. To make collagen fiber bundles, cells are mixed with solubilized fibrillar collagen and cast into silicon rubber wells fitted with microporous holders to entrap the gel and hold it in place. As the cells interact with the collagen fibrils, they contract and compact the gel. Since the gel is constrained in the longitudinal direction, it can contract only laterally, forming well-aligned, strong (> 1 MPa) collagen fiber bundles. Elastin sheaths from naturally around the collagen fiber bundles and atop the hyaluronan gel when the neonatal aortic fibroblasts are cultured for more than 4 weeks. The individual building blocks of the aortic valve cusp, designed and fabricated according to patterns dictated by the microstructure of the native aortic valve, will be stacked together to make the final composite, tissue-engineered aortic valve cusp.

Absorbable Implants↗

PubMed1995

Development of spontaneous activity and mechanosensitivity in axotomized afferent nerve fibers during the first hours after nerve transection in rats.

1. Spontaneous activity and ectopic mechanical excitability of axotomized unmyelinated and myelinated fibers in the sural nerve were examined in anesthetized rats. The analysis was performed within 30 h after the nerve lesion using single-fiber recordings that were performed proximal to the severed nerve end. 2. Among all unmyelinated fibers tested (n = 865), 4-8% exhibited persistent spontaneous activity of low and irregular frequency. The percentage of spontaneously active C fibers did not change significantly during the first 30 h. Only 6 of 796 A fibers had spontaneous activity. 3. Mechanical stimulation of the cut nerve end excited 5-8% of all C fibers under investigation. No development with time could be detected in the frequency of mechanically excitable C fibers. In contrast, beginning 6 h after nerve transection, the number of mechanically excitable A fibers rose with time, reaching 27% after 22-30 h. 4. Among the A fibers (C fibers) that exhibited mechanical excitability or spontaneous activity, only 4% (25%) had both properties, whereas 96% (75%) were either mechanosensitive or spontaneously active. 5. With time after the nerve lesion, the mean discharge rate of all spontaneously discharging C fibers decreased significantly from 49 imp/min (0.5-9 h after nerve lesion) to 11 imp/min after 22-30 h. The mean discharge rate of C fibers exhibiting solely spontaneous activity and those C fibers that were additionally mechanosensitive did not differ significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMedDate not supplied

[Two-dimensional reconstruction of birefringence map of the skeletal muscle sarcomere in relaxed and rigor states studied by interference microscopy].

A new method of automatized quantitative interferometry of skeletal muscle fibers was developed for the investigation of birefringence. A device based on the Linnic microscope was constructed to obtain phase images, which are two-dimensional pictures of birefringence. For the first time, two-and-three-dimensional maps of both total birefringence and birefringence for individual sarcomeres in the central part of muscle fiber were visualized using large databases. It was shown that total birefringence of fibers at rest length in the rigor state was lower as compared with the relaxed. Birefringence values from individual sarcomere interferograms revealed also that normalized A-disk birefringence was lower in the rigor state. The results obtained could be explained by a decrease of thick filaments anisotropy, due to the moving away of myosin heads from the rod during transition into the rigor state.

Animals↗

PubMed2005

Dietary fiber as a versatile food component: an industrial perspective.

The continued emphasis on the importance of dietary fibers to the Western diet and the need for products with a lower calorific content is pressuring food companies to allocate more resources to the development of fiber-enriched products. The challenge to the industry is to accomplish this goal without sacrificing the organoleptic appeal of some of their core offerings. As future research details specific nutritional benefits of individual components of dietary fiber, food companies will need flexible alternatives in order to validate new 'functional' food claims and to respond rapidly to emerging trends in fiber-enriched products. These objectives will be achieved by understanding the physicochemical basis for the biotechnical functionality of fibers and by developing, and making available fibers which provide a broad spectrum of bioactive and texture modulating properties.

Cell Wall↗

PubMed1994

Effects of various laser types and beam transmission methods on female organ tissue in the pig: an in vitro study.

The purpose of this in vitro study was to investigate and compare effects of various laser types (CO2, Argon, Erbium:YAG, Erbium:YSGG, and Holmium:YAG) and laser beam transmission methods (optical lens and flexible fiber) on ovarian and uterine tissue of the pig. The Erbium laser radiation was transmitted through Zirconium fluoride fibers (ZrF4). To circumvent the low mechanical stability of these fibers, we developed a special microlens system, which refocuses the radiation and protects the distal end from damage. Tissue lesions were performed with 1 and 5 joule. Histologic analysis of acute Er:YAG laser lesions reveal precise cutting effects with a minimal thermal damage zone of 40 microns and a high damage resistance of the fiber microlens systems. The extent of thermal damage caused by the Erbium:YSGG and CO2 laser is about two times larger, whereas the Argon and Holmium laser tissue lesions show a damage of the surrounding tissue of 200-300 microns. This study suggests that for precise cutting and coagulation, Erbium and Holmium lasers transmitted via our modified fiber tip may render the use of these lasers possible in a wide range of laparoscopic surgery applications.

Animals↗

PubMed1981

Measurement of point velocity in the canine coronary artery by laser Doppler velocimeter with optical fiber.

A laser Doppler velocimeter with an optical fiber was developed to investigate point blood velocity in the arteries and was applied to the measurement of blood velocity in the canine coronary artery. Fundamental experiments revealed that the accuracy of this method was satisfactory, since an excellent linear relation was found between the known blood velocity and the Doppler shift frequency (r = 0.998). The fiber tip (0.1 mm diam.) was inserted into the proximal portion of the left circumflex coronary artery and was traversed across the vascular lumen to measure the point velocity at each sampling point. Detailed velocity profiles were than reconstructed sequentially in three dimensional coordinates, i.e., velocity, diameter and time. In general the velocity waveform showed a diastolic dominant pattern which is characteristic of coronary arterial flow. One peak in early systole and two peaks in early and in late diastole were commonly observed in the velocity waveform near the center-line of the vessel. The velocity profiles were flat in the axial region and declined abruptly near the vessel wall. These results indicate that the laser Doppler velocimetry with an optimal fiber proved to be an accurate and feasible method of evaluating the point velocity of coronary artery flow.

Animals↗

PubMed1985

Collagen fiber formation in repair tissue: development of strength and toughness.

Dermal repair tissue shows a progressive increase in collagen content which may be related to the wound tensile strength. Wound strength and extensibility are lower than those found in normal skin. In animals, wounds closed by metal clips are chosen as a model to study the proliferative and remodeling phases of healing from a mechanical and morphological point of view. During the proliferative phase the low wound strength is associated with formation of collagen fibers of small diameter, later, (days 28-45) an acute change appears corresponding to the remodeling phase, with increased collagen fiber diameters observed by scanning electron microscopy and light microscopy, and increased tensile strength and toughness. By 180 days, wound strength and collagen fiber morphology were close to that observed in the normal skin. These observations show a direct relationship between collagen fiber diameter and tensile strength. In addition, packing density of collagen fibrils (determined by the birefringence retardation per unit thickness under polarized light) was unchanged until day 90, although collagen fiber diameters increased during this time.

Animals↗

PubMed2003

Developmental segregation in the efferent projections to auditory hair cells in the gerbil.

The auditory receptor epithelium of mammals receives efferent innervation from neurons within and surrounding the superior olivary complex of the brainstem (Warr [1975] J. Comp. Neurol. 161:159-181). Disruption of this pathway during early postnatal life, when olivocochlear axons are forming their final connections with auditory hair cells and nerve fibers, can lead to profound and permanent hearing impairments (Walsh et al. [1998] J. Neurosci. 18:3859-3869). Identification of the possible causes for this deterioration in auditory function requires a better understanding of the normal developmental interactions that occur between efferent axons and their target cells within the cochlea. To provide such information, we labeled developing efferent fibers at a constant location within the gerbil cochlea by using the fluorescent carbocyanine dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindo-carbocyanine perchlorate (DiI). The terminal arbors of these neurons were then reconstructed by using digital confocal microscopy. By postnatal day (P) 2, the efferent arbors associated with inner hair cells (IHCs) and outer hair cells (OHCs) displayed distinctly different morphologies closely resembling those described for adult animals (Brown [1987] J. Comp. Neurol. 260:605-619). Unlike their mature counterparts, however, P2 efferent axons frequently branched to contact both types of auditory hair cells. Unexpectedly, between P4 and P6, both IHC and OHC efferent axons produced additional branches that crossed the tunnel of Corti to invade the OHC zone. By P8, all of these supernumerary connections were eliminated, yielding completely segregated efferent pathways to IHCs and OHCs.

Aging↗