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At least 253 records · Page 14Linked to original sources

PubMed1989

Needle bevel direction and headache after inadvertent dural puncture.

To study the effect of needle bevel direction on the incidence and severity of headache following inadvertent dural puncture occurring during the identification of the epidural space, the authors randomly assigned obstetric anesthesia residents to identify epidural space with the bevel of the epidural needle oriented either parallel or perpendicular to the longitudinal dural fibers. If dural puncture occurred, an observer unaware of the needle bevel direction, daily assessed the presence and severity of any subsequent headache. Of the 1,558 women who received epidural analgesia during this study, 41 women suffered dural puncture, 20 with the needle bevel oriented perpendicular to the longitudinal dural fibers and 21 with the needle bevel inserted parallel to the dural fibers (NS). Fourteen of 20 women in the group in which the needle bevel was perpendicular to dural fibers developed a moderate to severe headache, whereas only five of 21 in the group in which the needle bevel was parallel to dural fibers did so (P less than 0.005). Similarly, we administered a therapeutic blood patch to ten of 20 women in the perpendicular group but to only four of 21 in the parallel group (P less than 0.05). Thus, identifying the epidural space with the needle bevel oriented parallel to the longitudinal dural fibers limits the size of the subsequent dural tear and, therefore, lowers the incidence of headache should dural perforation occur.

Analgesia, Epidural↗

PubMed2003

Electrophysiological evidence of monosynaptic excitatory transmission between granule cells after seizure-induced mossy fiber sprouting.

Mossy fiber sprouting is a form of synaptic reorganization in the dentate gyrus that occurs in human temporal lobe epilepsy and animal models of epilepsy. The axons of dentate gyrus granule cells, called mossy fibers, develop collaterals that grow into an abnormal location, the inner third of the dentate gyrus molecular layer. Electron microscopy has shown that sprouted fibers from synapses on both spines and dendritic shafts in the inner molecular layer, which are likely to represent the dendrites of granule cells and inhibitory neurons. One of the controversies about this phenomenon is whether mossy fiber sprouting contributes to seizures by forming novel recurrent excitatory circuits among granule cells. To date, there is a great deal of indirect evidence that suggests this is the case, but there are also counterarguments. The purpose of this study was to determine whether functional monosynaptic connections exist between granule cells after mossy fiber sprouting. Using simultaneous recordings from granule cells, we obtained direct evidence that granule cells in epileptic rats have monosynaptic excitatory connections with other granule cells. Such connections were not obtained when age-matched, saline control rats were examined. The results suggest that indeed mossy fiber sprouting provides a substrate for monosynaptic recurrent excitation among granule cells in the dentate gyrus. Interestingly, the characteristics of the excitatory connections that were found indicate that the pathway is only weakly excitatory. These characteristics may contribute to the empirical observation that the sprouted dentate gyrus does not normally generate epileptiform discharges.

Animals↗

PubMed1994

Type III collagen is a major component of interodontoblastic fibers of the developing mouse molar root.

BACKGROUND: Recently, collagenous interodontoblastic fibers (IOF) were reported in some particular developmental stages and/or locations of the tooth. However, it remained unclear whether these fibers were identical to so-called von Korff fibers. METHODS: To clarify this issue, we examined the developing mouse molar by three-dimensional reconstruction of 8 confocal images within a 6 micron-thick section using laser scanning confocal microscopy, and confirmed our findings using immunoelectron microscopy. RESULTS: In the root pulp during circumpulpal dentin formation, the IOF stained weakly for type I collagen, but stained strongly for type III collagen by a double-staining technique. It could be clearly seen that many immunoreactive fibers ran spirally among the odontoblasts and entered the predentin. This distribution pattern of IOF was similar to that of the classical von Korff fibers. Furthermore, the existence of anti-type III reactive collagen fibrils between odontoblasts was confirmed, whereas IOF were not observed in the coronal pulp during circumpulpal dentin formation. CONCLUSIONS: This study presents for the first time, immunohistochemical observations which demonstrate the presence of IOF at least during root circumpulpal dentin formation and which reveal that type III collagen is a major component of IOF.

Animals↗

PubMed1994

The initial contraction of skinned muscle fibers on photorelease of ATP in the presence of ADP.

1) We photoreleased ATP in skinned muscle fibers from rat psoas, and examined the effects of ADP on the ATP-induced isometric transient. 2) On release of ATP, the muscle stiffness initially falls at any [Ca2+]. ADP slowed this stiffness decrease, suggesting competition between ADP and ATP. Even in the presence of ADP, the rate of stiffness decrease was proportional to the amount of released ATP, but was not affected by Ca2+, P(i), or the fiber tension. 3) In the absence of ADP, the Ca2+ sensitive contraction occurs only after the initial phase. However, in the presence of ADP, the fiber developed tension during the initial phase before the late contraction. The initial contraction was insensitive to Ca2+, resistant to P(i) and BDM, larger on releasing more ATP, but not markedly influenced by the fiber tension. 4) Our results seem to suggest that, in the physiological reaction cycle, the cross-bridges develop significant force immediately after the binding of ATP, before releasing P(i).

Adenosine Diphosphate↗

PubMed1996

A fiber composite laminate endodontic post and core.

The goals of endodontic post and core procedures are to provide maximum retention of the post and resistance to fracture of the roots. Presented is a recently developed fiber composite laminate (FCL) post and core technique which results in a bonded structure that is conservative, morphologic, retentive, versatile, esthetic, and helps resist root fracture. To ascertain the durability of FCL posts and cores, an in vitro pilot study with stress testing is included. The results of the study are compared to other post and core materials to show how well this technique approaches the ideal characteristics for endodontic post and cores.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1992

CGRP as a marker of the climbing fibers during the development of the cerebellum in the rat.

Olivary fibers express CGRP-LI until the nest phase of their development and never in the next postnatal steps, that is, the "capuchon" stage. Together with other results presented in this volume regarding the postnatal development of CGRP binding sites in the cerebellar cortex, these immunohistologic findings suggest a role for CGRP in reshaping connectivity and in synapse stabilization of cerebellar circuitry during postnatal development.

Aging↗

PubMed1983

Organization of actin cytoskeleton in normal and regenerating arterial endothelial cells.

The distribution of actin stress fibers in normal and regenerating (after endothelial denudation by means of a balloon catheter) rabbit aortic endothelial cells has been studied by means of immunofluorescence with human actin autoantibodies on en face endothelial cell preparations. Our results show that: (i) under normal conditions actin is accumulated as a network at the periphery of endothelial cells. Stress fibers are present only in endothelial cells located immediately below intercostal artery branches; (ii) stress fibers develop in endothelial cells early during regeneration and persist after the end of endothelial mitotic and motile activities; and (iii) the orientation of stress fibers within the cytoplasm follows the direction of blood flow, with the exception of stress fibers situated in cells at the edge of the wound, when endothelial cell progression toward the denuded area as well as mitotic activity have ceased. We conclude that stress fibers are an organelle present in endothelial cells in vivo and that they reorganize during endothelial cell adaptation to unfavorable or pathological situations.

Actins↗

PubMed1985

PC12 cells stimulate slow-myosin light chain 2 synthesis in chick breast muscle culture.

Skeletal muscle fibers developing in vitro synthesize predominantly fast-myosin light chains, with a small contribution (less than 10%) from slow-myosin light chain 2. Muscle fibers can be cocultured with a rat adrenal pheochromocytoma-derived nerve cell line (PC12) known to display properties similar to sympathetic neurons. PC12 cells cultured alone synthesize catecholamines and respond to nerve growth factor by synthesizing acetylcholine and extending neurite structures. They also synthesize significant amounts of acetylcholine in the presence of nonneuronal cell types, including muscle. When cocultures of skeletal muscle fibers and PC12 cells are established, the muscle cells respond with an increased level of slow light chain 2 synthesis. Myosin light chains were identified by two-dimensional gel electrophoresis and immunoblotting with an antiserum specific to slow light chain 2.

Animals↗

PubMed2002

Early enteral supply of lactobacillus and fiber versus selective bowel decontamination: a controlled trial in liver transplant recipients.

BACKGROUND: Early enteral nutrition with solutions containing prebiotics (fiber) and probiotics (Lactobacillus) is suggested to reduce bacterial translocation and minimize the incidence of infections after liver transplantation. METHODS: In a prospective, randomized placebo-controlled trial consisting of 95 patients, we compared the incidence of postoperative infections and other complications after liver transplantation among three different groups, all supplied with early enteral nutrition: (a) standard formula plus selective bowel decontamination (SBD), (b) fiber-containing formula plus living Lactobacillus plantarum 299, and (c) fiber-containing formula plus heat-killed L plantarum 299. RESULTS: The groups were comparable regarding preoperative American Society of Anesthesiologists classification, Child-Pugh classification of cirrhosis, operative data, and degree of immunosuppression. The patients who received living lactobacilli plus fiber developed significantly fewer bacterial infections (13%) than the patients with SBD (48%). The incidence of infections was 34% in the group with inactivated lactobacilli and fiber. Cholangitis and pneumonia were the leading infections and enterococci the most commonly isolated bacteria. In the living Lactobacillus group, the mean duration of antibiotic therapy, the mean total hospital stay, and the stay on the intensive care unit were also shorter than in the groups with inactivated lactobacilli and fiber as well as with SBD. However, these differences did not reach statistical significance. CONCLUSIONS: Early enteral nutrition with fiber-containing solutions and living L plantarum 299 was well tolerated. It decreases markedly the rate of postoperative infections both in comparison with inactivated L plantarum 299 and significantly with SBD and a standard enteral nutrition formula. As it is a cheap and feasible alternative to SBD, further studies should evaluate whether this ecoimmunonutrition should be already started while patients are on the waiting list for transplantation.

Anti-Bacterial Agents↗

PubMed1992

Studies on the presence and functional properties of afferent C-fibers in the cat's dental pulp.

The present investigation describes how intradental afferent C-fibers can be identified and characterized in the anaesthetized cat. Functional single fibers innervating the lower canine tooth were recorded from filaments split from the inferior alveolar nerve. Fibers responding to monopolar electrical stimulation of the tooth were classified as slowly and fast conducting according to their conduction velocity (c.v.). The axonal c.v. was determined for 31 slowly conducting fibers by electrical stimulation of the nerve. Sixty-eight percent of these proved to be C-fibers. The slowly conducting fibers had higher activation thresholds, smaller amplitudes and longer durations of the action potentials than the fast conducting fibers. Many of the fast but none of the slowly conducting fibers were repetitively activated by a single stimulus pulse. The highest frequency at which the fibers responded to every stimulus pulse was much lower for the slowly than for the fast conducting fibers. Most of the slowly conducting intradental fibers tested were activated by both hot and cold stimulation of the tooth, by pressure applied to the pulp chamber and by the application of KCl or bradykinin to the pulp. Eight C-fibers responded to mechanical stimulation of the pulp. For some fibers the response magnitude correlated with the stimulus intensity. Many slowly conducting intradental fibers developed an ongoing discharge after heat and pressure stimulation. The results indicate that there exists in the dental pulp of the cat afferent C-fibers that resemble polymodal C-nociceptors. They might be involved in the generation of the dull aching pain present in inflammatory conditions of the pulp. The activation of intradental C-fibers in pulpitis might result either from the elevated pressure and/or by sensitization of the C-fiber endings by inflammatory substances released.

Action Potentials↗

PubMed1992

Dynamic changes in the density of radial glial fibers of the developing murine cerebral wall: a quantitative immunohistological analysis.

The density of radial glial fibers in the developing murine cerebral wall decreases dramatically during the terminal week of gestation. The present analysis characterizes these variations of fiber density quantitatively. Radial glial fibers were stained with monoclonal antibody RC2. Fibers were counted in a standard area of 2,000 microns2, passing orthogonally to the fiber long axis. At E14, fiber density is maximum and relatively uniform throughout the full width of the cerebral wall. Subsequently, the overall glial fiber density decreases and fiber density gradients emerge in the transmural span of fibers. These radial fiber density gradients are marked by sharp declines at the level of the ventricular-subventricular zone and in the zone of transition between intermediate zone (IZ) and cortical plate. In the interval E14-P0, the decrease in densities of fibers crossing the IZ is commensurate with the predicted diluting effects of tissue expansion with growth. By contrast, the decrease in fiber densities in ascent across the cortical plate beyond E14 through E17 exceeds that predicted by growth. The observations suggest that a substantial population of radial glial fibers do not span the full ventricular zone to the cerebral surface. A major contingent appears to extend only as far as the external sagittal stratum/subplate through E16. Subsequently, at a time when supragranular cortical layers are being assembled, the full set of fibers appears to extend more uniformly through the cortical strata. The late surge of fibers would be appropriate to the intercalation of groupings of neurons of the supragranular layers.

Animals↗

PubMed1990

Development of unmyelinated fibers in peripheral nerve--an immunohistochemical and electronmicroscopic study.

The development of the unmyelinated fibers in the mouse sciatic nerve was studied with immunohistochemical and electronmicroscopic techniques. Glial fibrillary acidic protein (GFAP)-immunostaining showed fainty-positive cells in transverse sections on day 2. Staining intensity and numbers of stained cells increased with age and both reached the maximum around day 30. Immunoelectronmicroscopy for GFAP revealed that positive staining was confined to the cytoplasm of Schwann cells of the unmyelinated fibers. In contrast vimentin-immunoreactivity was detectable as early as day 0. Schwann cells of both myelinated and unmyelinated fibers were positive. Electronmicroscopic study showed that Schwann cell families contained both larger and smaller axons on day 0. By day 5 majority of the larger axons were separated from Schwann cell families, which then contained only smaller axons. Ensheathment of smaller axons by Schwann cell processes were completed around day 30. These results showed that GFAP was expressed in Schwann cells of the unmyelinated fibers along with the differentiation and maturation of the unmyelinated fibers.

Aging↗

PubMed1988

Development of hypothalamic neurons in intraventricular grafts: expression of specific transmitter phenotypes.

The anlages of the medial-basal hypothalamus (MBH), septopreoptic area (POA), Rathke's pouch, and the parietal cortex (CC) of rats (at 12.5, 14.5 and 16.5 days of gestation) were transplanted singly or in combination into the third ventricle of adult female rats, and the development of neurons in the grafts was investigated immunohistochemically with the use of antisera to tyrosine hydroxylase (TH), somatostatin (SRIH), ACTH, methionine enkephalin-Arg6-Gly7-Leu8 (Enk-8), rat corticotropin-releasing factor (rCRF), rat hypothalamic growth hormone-releasing factor (rhGRF), and luteinizing hormone-releasing hormone (LHRH). TH and all the peptides examined except LHRH were detected in distinct neurons in MBH grafts and in cografts of MBH plus Rathke's pouch from 12.5-day-old embryos. SRIH, rCRF, Enk-8, and TH were found in POA grafts from embryos of the same age. Although immunoreactive LHRH was first detected in neurons in POA grafts from 16.5-day-old embryos, it appeared in cografts of POA and MBH from 12.5-day-old embryos. The immunoreactive fibers developed in the grafts expressed the same characteristic behaviors as in intact brain; the fibers containing hormonal substances formed complexes with the vasculature like in the organum vasculosum laminae terminalis (OVLT) or in the median eminence, while the fibers containing neurotropic signals formed fiber networks surrounding other nerve cell bodies as if they synaptically associate. In CC grafts, the neurons contained TH, SRIH, rCRF, or Enk-8, and their axonal processes formed fiber networks. These findings suggest that all the hypothalamic neurons examined are committed by 12.5 days of gestation to develop maintaining transmitter phenotype and target recognition capacity.

Adrenocorticotropic Hormone↗

PubMed1981

Effect of dietary wheat bran and dehydrated citrus fiber on 3,2'-dimethyl-4-aminobiphenyl-induced intestinal carcinogenesis in F344 rats.

The effect of dietary wheat bran and dehydrated citrus fiber on 3,2'-dimethyl-4-aminobiphenyl (DMAB)-induced colon and small intestinal carcinogenesis was studied in male F344 rats. Weanling rats were fed semipurified diets containing 5% alphacel, 5% alphacel + 15% wheat bran or 5% alphacel + 15% citrus fiber. At 7 weeks of age, all animals, except vehicle-treated controls, received weekly s.c. injections of 50 mg DMAB/kg body weight for 20 weeks. The DMAB- or vehicle-treated groups were autopsied 20 weeks after the last injection of DMAB. The animals fed the wheat bran diet and treated with DMAB had a lower incidence (number of animals with tumors) and multiplicity (number of tumors/tumor-bearing animal) of colon and small intestinal tumors than did those fed the control diet and treated with DMAB. Animals fed the diet containing citrus fiber developed fewer small intestinal tumors (incidence and multiplicity) than did the rats fed the control diet; the number of adenocarcinomas was reduced in rats fed the citrus fiber diet. This study thus indicates that diets containing wheat bran and citrus fiber reduce the risk for DMAB-induced intestinal cancer and that the protection against colon cancer depends on the type of fiber.

Aminobiphenyl Compounds↗

PubMed1971

Physiological studies during formation and development of rat neuromuscular junctions in tissue culture.

Developing neuromuscular junctions in tissue cultures of rat embryo spinal cord and muscle were studied with intracellular recording. Excitatory junctional potentials (ejps) were found during nerve or spinal cord stimulation, and also arising spontaneously. The time-course of the potentials tended to be shorter in cultures older than 9 days in vitro than in more recently innervated cultures. Evidence of multiple innervation was found in many cells. In order to test the hypothesis that transmitter was released in integral multiples of a quantal amount and according to a Poisson distribution, mean quantum content was calculated from the coefficient of variation of ejp amplitudes, the percentage of zero responses, and the ratio of mean amplitude to mean of the smallest class of amplitudes. The three independent measures were in fair or good mutual agreement, implying that the mechanism of transmitter release in newly developed junctions is the same as in the adult. In newly formed junctions, ejps were subthreshold for action potential generation, but afterwards mean quantum content increased and action potentials were generated by single ejps. In fibers developing both with and without innervation, the entire muscle cell surface was as sensitive to acetylcholine as the adult end plate region. Innervation was related to cross-striation: every cross-striated fiber tested was found to be innervated, and denervation in vitro led to loss of distinct cross-striations.

Acetylcholine↗

PubMed1984

Functional properties of auditory-nerve fibers during postnatal development in the kitten.

The discharges of the auditory-nerve fibers were studied in kittens between 2-40 days of age. Up to the 10th postnatal day, fibers could be divided into two main categories: fibers with spontaneous activity (SA) that respond to sound and fibers without SA but with evoked responses. A third, smaller, category, fibers having neither SA nor evoked activity, was also present. The development of SA comprises two phases. The first, lasting from birth up to the third postnatal week, shows a relatively fast increase and the second, lasting up to adulthood, a slower increase. Typical tone burst responses can be recorded at the end of the first postnatal week. Thereafter reactivity steadily increases especially after the 10th postnatal day. In young animals, rate level function is characterized by a steep segment with a low dynamic range followed by a decrease in activity that lasts until the end of the second week. At this point adult-like functions may be observed, although maximal firing still increases for some weeks. Tuning curves and threshold sensitivity tend to develop inversely at corresponding frequencies. Fibers with low characteristic frequencies reach adult threshold before that of high frequency fibers and high frequency fibers reach adult tuning before low frequency fibers. A comparison of auditory-nerve fiber activity in kittens show that maturation of most functional characteristics lasts several weeks after birth and in some cases continues after the first postnatal month.

Action Potentials↗

PubMed2005

Functional characterization of Gossypium hirsutum profilin 1 gene (GhPFN1) in tobacco suspension cells. Characterization of in vivo functions of a cotton profilin gene.

Cotton fiber is an extremely long plant cell. Fiber elongation is a complex process and the genes that are crucial for elongation are largely unknown. We previously cloned a cDNA encoding an isoform of cotton profilin and found that the gene (designated GhPFN1) was preferentially expressed in cotton fibers. In the present study, we have further analyzed the expression pattern of GhPFN1 during fiber development and studied its cellular function using tobacco suspension cells as an experimental system. We report that expression of GhPFN1 is tightly associated with fast elongation of cotton fibers whose growth requires an intact actin cytoskeleton. Overexpression of GhPFN1 in the transgenic tobacco cells was correlated with the formation of elongated cells that contained thicker and longer microfilament cables. Quantitative analyses revealed a 2.5-3.6 fold increase in total profilin levels and a 1.6-2.6 fold increase in the F-actin levels in six independent transgenic lines. In addition to the effect on cell elongation, we also observed delayed cell cycle progression and a slightly lower mitotic index in the transgenic cells. Based on these data, we propose that GhPFN1 may play a critical role in the rapid elongation of cotton fibers by promoting actin polymerization.

Actin Cytoskeleton↗

PubMed1982

Development of new hollow fiber membrane macromolecular filters.

Newly developed hollow fiber membrane filters made of ethylene-vinyl-alcohol designated as EVAL 2A, EVAL 4A, and EVAL 5A, were tested in vitro and applied clinically. EVAL 2A had the lowest molecular weight cut-off (30% rejection rate for 10(4) dalton dextran and 90% rejection rate for 10(5) dalton dextran); sieving coefficients (SC) of 0.78 for albumin, 0.59 for IgG, and almost 0 for IgM indicate its usefulness for separation of IgG from albumin when the recirculation flow on the filter was introduced. EVAL 4A and 5A showed higher cut-off levels (25% rejection of 10(5) dalton dextran and 80% rejection rate for 2 X 10(6) dalton dextran); SCs for albumin IgG, and IgM were 0.89, 0.83, and 0.24, respectively, indicating their usefulness in the separation of MMs of molecular size greater than IgG. IgM type cold agglutinin antibody (CAA), IC, and RF were effectively removed by these filters from CAA induced hemolytic anemia or rheumatoid vasculitis patients. Using recirculating flow to prevent filter plugging, one EVAL unit was found to be sufficient to treat 2-3 L plasma. These filter properties demonstrate the possible clinical application of EVAL filters for selective MM removal, when specific MM removal is indicated for the treatment of specific diseases.

Aged↗