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medullated nerve fiber [keywords]
- [New insights into the study of optic nerve diseases]. [English Abstract, Journal Article]
- Nihon Ganka Gakkai Zasshi 2013 Mar; 117(3):187-210; discussion 211.
Optical coherence tomography (OCT) provides a new dimenstion in ophthalmology because it allows evaluation of the pathology in vivo, and provides information to assist the management of macular disease and glaucoma. It is necessary to differentiate the diagnosis of glaucoma from diseases of the optic nerve and of the visual pathway. This study evaluates the usefulness of OCT in detecting disorders of the optic nerve and visual pathway. In addition, the pathogenesis of glaucomatous optic neuropathy (GON), the most common optic neuropathy, was investigated by focusing on the dynamics of aquaporin. I. Evaluation of optic nerve and visual pathway disorders by optical coherence tomography. The swinging flashlight test is an easy, sensitive, objective test to detect relative afferent pupillary defects (RAPD). The number of RAPD detected by the swinging flashlight test was closely correlated with the ratio of retinal nerve fiber layer thickness (RNFLT) between the two eyes of 20 cases of unilateral optic atrophy. OCT could assess the amount of RAPD that reflected an asymmetrical functional disturbance of the optic nerves, as a structural difference. The time courses of RNFLT and ganglion cell complex (GCC) changes' were observed immediately following the time of injury in 4 cases of traumatic optic neuropathy. OCT revealed that both the RNFLT and GCC decreased rapidly from 2 weeks after the injury until 20 weeks later. The RNFLT decreased significantly in the horizontal direction in comparison to the perpendicular direction in 34 eyes from the cases of optic chiasm syndrome. This means that OCT could quantitatively detect the band atrophy of the optic disc in optic chiasm syndrome. Measuring the RNFLT showed a thinning of RNFLT in the perpendicular direction in comparison to the horizontal direction in ipsilateral eyes and thinning in the horizontal direction in comparison to the perpendicular direction in the contralateral eyes in optic tract syndrome. Measuring the GCC showed a thinning of the GCC in the temporal hemifield to the central fovea of the ipsilateral eyes, and thinning of the GCC in the nasal hemifield of the contralateral eyes. This means that OCT could detect the structural changes of hourglass atrophy in the ipsilateral eye and band atrophy in the contralateral eye at the optic disc as well as the homonymous hemianopia in the visual field. OCT was useful in evaluating the optic nerve and visual pathway disorders, but there were also some limitations. The thinning area of RNFLT measured by OPTVue and Cirrus were in entirely opposite directions in cases of optic chasm syndrome. The reason was attributed to the better performance of RTVue in measuring a thin RNFLT on the nasal side of the optic disc in comparison to Cirrus. The specific characteristics of the instruments should be considered when the results of OCT are evaluated. II. Dynamics of aquaporin in the optic nerve Aquaporin (AQP) is a membrane protein that forms a water channel to facilitate water crossing the plasma membrane. AQP-4 was originally thought to be expressed in the optic nerve, but it is expressed only in the retrobulbar medullated region of the optic nerve and the expression of AQPs in the optic disc has not been detected. This study investigated the expressions of AQPs in the optic nerve in rat, monkey and human. The results demonstrate that only AQP-9 was expressed at the unmedullated pre-lamina cribrosa and lamina cribrosa regions, and both AQP-4 and AQP-9 were expressed at the medullated retrobulbar region. Astrocytes were observed to express AQP-9, because AQP-9 immunoreactivity was identical to that of glial fibrillary acidic protein. Elevated intraocular pressure substantially reduced AQP-9 expression in the optic nerve, whereas expression of AQP-4 was not changed in rat eyes. The same phenomena were also observed in the monkey eye with ocular hypertension as well as human eye with glaucoma. AQP-9 is an aquaglyceroporin that allows solutes such as lactate rather than water to cross the cell membrane. The astrocyte-to-neuron lactate shuttle hypothesis has been proposed, in which lactate transported from astrocytes is used by neurons as an energy substrate. Reduction of AQP-9 expression in the optic nerve head under elevated intraocular pressures might be closely related to the pathogenesis of GON.
- [Histological study on sciatic nerve repair at different angles in rats]. [English Abstract, Journal Article]
- Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi 2011 May; 25(5):587-90.
To discuss the effect of sciatic nerve repair at different angles on the neural regeneration in rats.Seventy-two male Sprague Dawley rats were randomly divided into groups A, B, C, and D with 18 rats in each group. The right sciatic nerve was transected at 30, 45, 60, and 90 degrees in groups A, B, C, and D, respectively, and then was repaired. The morphologic assessment of nerve regeneration was performed by gross observation, the wet weight recovery rate of gastrocnemius, histological and ultrastructural observations at 1, 2, and 3 months after operation.Three months later, the wet weight recovery rate of gastrocnemius, motor nerve conduction velocity and action potential of sciatic nerve, axonal diameter, medullary sheath thickness, and medullated nerve fiber counting in groups A and B were significantly better than those in groups C and D (P < 0.01); but no significant difference was found between group A and group B (P > 0.05), and between group C and group D (P > 0.05).End-to-end neurorrhaphy at 30-45 degrees can effectively promote the sciatic nerve regeneration in rats.
- Multiple endocrine neoplasia type 2: an overview. [Journal Article, Review]
- Genet Med 2011 Sep; 13(9):755-64.
Multiple endocrine neoplasia type 2 is historically composed of three clinical subtypes, all of which are associated with germline mutations in the RET proto-oncogene. Multiple endocrine neoplasia type 2A, familial medullary thyroid carcinoma, and multiple endocrine neoplasia type 2B are collectively associated with a 70-100% risk of medullary thyroid carcinoma by age 70 years. Pheochromocytomas are identified in 50% of individuals with multiple endocrine neoplasia type 2A and multiple endocrine neoplasia type 2B. Furthermore, those with multiple endocrine neoplasia type 2A have a 20-30% risk for primary hyperparathyroidism. Individuals with multiple endocrine neoplasia type 2B often have distinct physical features including mucosal neuromas of the lips and tongue, medullated corneal nerve fibers, ganglioneuromatosis of the gastrointestinal tract, distinctive facies with enlarged lips, and a "Marfanoid" body habitus. Clinical recognition and accurate diagnosis of individuals and families who are at risk of harboring a germline RET mutation is critical for the prevention and management of potentially life-threatening neoplasms. This overview summarizes the clinical description of multiple endocrine neoplasia type 2, diagnosis and testing strategies, management and surveillance, and differential diagnosis for other related syndromes.
- [Effect of tetramethylpyrazine added to vitrification solution on peripheral nerve allografts regeneration]. [English Abstract, Journal Article, Research Support, Non-U.S. Gov't]
- Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi 2009 Jul; 23(7):868-72.
To investigate the effect of tetramethylpyrazine (TMP) with a certain concentration added to vitrification solution on peripheral nerve allografts regeneration.Forty-eight healthy clean SD male rats were selected as donors, and 96 healthy clean Wistar male rats as recipients, all rats being 3 months old and weighing 200-250 g. The sciatic nerves segments of 15 mm were removed from the donors, then randomly divided into 4 groups according to vitrification solution containing TMP. No TMP was used in group A as the control group; 100 mg/L, 200 mg/L and 400 mg/L TMP were used in group B, group C and group D, respectively. Then them were cryo-preserved at -196 degrees C for 3 weeks. Nerve defect of 10 mm in length was made in the sciatic nerves of recipients. After rewarming, the allografts were transplanted to the corresponding rats. The gross appearance, the morphological and electrophysiological changes, the image analysis of axons and motor end-plate were detected at 4, 8, 12 and 16 weeks.All rates survived to the end of the experiment. The adhesion and edema of allografts in group A and group B were obvious 4 weeks after operation; then adhesion and edema was obvious in group A and were improved in the other groups 8 weeks after operation. Adhesion was observed in groups A and B; no adhesion was observed in groups C and D at 12 weeks. The number of regeneration nerve, the latent, the amplitude, the nerve conduction velocity, the medullary sheath/microm2, the medullary sheath density/microm2 and the image analysis of axons and motor end-plate in groups A and B were significantly lower than those in groups C and D (P < 0.01); and there were no significant differences between groups C and D (P > 0.05). The observation of transmission electron microscope showed that medullated nerve fibers and myelin sheath of groups C and D were thicker than groups A and B, layers of groups C and D were clear.The vitrification solution with 200 mg/L tetramethylpyrazine has protective effect on regeneration of peripheral nerve allografts.
- [An experimental study on outcome of ipsilateral C7 nerve root transfer to repair the root avulsion of the brachial plexus]. [English Abstract, Journal Article, Research Support, Non-U.S. Gov't]
- Zhonghua Wai Ke Za Zhi 2008 May 15; 46(10):763-7.
To experimentally compare the treatment outcome of the injured upper limb of the root avulsion of C5 and C6 of the brachial plexus repaired by ipsilateral C7 nerve root transfer and other three multiple nerve transfers.One hundred and twenty SD rats of simulated C5 and C6 root avulsion randomly divided into 4 groups, and 30 each underwent various combined nerve transfers. Group A: the ipsilateral C7 root transferred to the upper trunk of brachial plexus and the spinal accessory nerve to the suprascapular nerve; Group B: partial fascicles of the ulnar nerve transferred to the biceps branch (Oberlin's procedure), the spinal accessory to the suprascapular and branches to the triceps long head to the axillary nerve; Group C: the phrenic transferred to the musculocutaneous, cervical plexus motor branches to the lower trunk (axillary nerve) of brachial plexus and the spinal accessory nerve to the suprascapular nerve; Group D: the phrenic transferred to the musculocutaneous and the spinal accessory nerve to the suprascapular nerve. Neurotization outcomes were evaluated at 3, 6 and 12 weeks postoperatively by comparing changes of behavioral tests (Ochiai clinical scores, Barth Foot-fault test and Terzis grooming test), neurophysiological investigations and muscular histology.At 3 weeks after operation, no significant difference was found between Group A and other three control groups in the three behavioral evaluations. Neurophysiologic investigations of the axillary nerve showed that Group A was superior to the other three groups. Muscular histological outcome of the axillary nerve and deltoid muscle showed that Group A was superior to the Group C and D, while no significant difference was found between Group A and B. Except that the thruput of regenerating medullated musculocutaneous nerve fibers of Group A was superior to Group C, neurophysiological and histological outcome of the musculocutaneous nerve and biceps showed that no significant difference was found between Group A and other three groups. At 12 weeks postoperatively, nearly all the behavioral, neurophysiological and histological determination showed that Group A was superior to the other three groups.Ipsilateral C7 transfer to the upper trunk of brachial plexus combined with the spinal accessory nerve to the suprascapular nerve is found to be significantly effective on treatment of the root avulsion of C5 and C6 of the brachial plexus.
- Repair of brachial plexus lower trunk injury by transferring brachialis muscle branch of musculocutaneous nerve: anatomic feasibility and clinical trials. [Journal Article, Research Support, Non-U.S. Gov't]
- Chin Med J (Engl) 2008 Jan 20; 121(2):99-104.
There are few effective methods for treating injuries to the lower trunk of brachial plexus, and the curative effect is usually poor. The purpose of this study was to provide anatomic references for transferring the brachialis muscle branch of musculocutaneous nerve (BMBMCN) for selective neurotization of finger flexion in brachial plexus lower trunk injury, and to evaluate its clinical curative effects.Microanatomy and measurement were done on 50 limbs from 25 adult human cadavers to observe the origin, branch, type of the BMBMCN and median nerve, as well as their adjacent structures. Internal topographic features of the fascicular groups of the median nerve at the level of the BMBMCN were observed. In addition, the technique of BMBMCN transfer for selective neurotization of finger flexion of the median nerve was designed and tested in 6 fresh adult human cadavers. Acetylcholinesterase (AchE) staining of the BMBMCN and median nerve was done to observe the features of the nerve fibers. This technique was clinically tried to restore digital flexion in 6 cases of adult brachial plexus lower trunk injury. These cases were followed up for 3, 6, 9 and 12 months postoperatively. Recovery of function, grip strength, nerve electrophysiology and muscle power of the affected limbs were observed and measured.The brachialis muscle was totally innervated by the musculocutaneous nerve (MCN). Based on the Hunter's line, the level of the origin of the BMBMCN was (13.18 +/- 2.77) cm. AchE histochemical staining indicated that the BMBMCN were totally made up of medullated nerve fibers. At the level of the BMBMCN, the median nerve consistently collected into three fascicular groups as shown by microanatomy in combination with AchE stain. The posterior fascicular group was mainly composed of anterior interosseous nerves and branches to the palmaris longus. The technique was tested in six fresh cadavers successfully, except that stoma split occurred in one case. Five of the six cases recovered digital flexion 12 months after operation, and at the same time grip strength, muscle power, and nerve electrophysiology also recovered markedly.The technique of transferring the BMBMCN for selective neurotization of finger flexion is anatomically safe and effective, with satisfactory clinical outcomes.
- [Experimental study on brachial plexus injury induced by radiation in rats]. [English Abstract, Journal Article]
- Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi 2007 Sep; 21(9):953-6.
To explore the changes of morphology and ventricornual motor neurons in SD rats' ventral horn of spinal cord after radiated as the therapy protocol for breast cancer, to discover the rule of radiation-induced injury of brachial plexus, and also if there exits the reversible conversion in neurons.Twenty SD rats were selected. The left side of the rats was used as the radiation side, and the right side as the control side. The RIBPI animal models were established by divided-dose of radiation. Using 2 Gy/time and 5 times/week, a total administered dose reached 30 Gy after 3 weeks. The behaviour of the rats was observed after radiation. At 3, 5, 7 and 9 weeks after the last radiation (n = 4), the wet weights of biceps brachii muscle, upper-limb circumference and compound action potential were examined; the pathological changes of biceps brachii muscle, the morphological changes, counts of the motor neurons in ventral horn and axons of bilateral spinal cord were observed by HE staining, argentums staining and toluidine blue staining.The rats showed lameness and a "claw hand" 3 weeks after radiation. Compared with control side, the wet weights of biceps brachii muscle and upper-limb circumference were significantly reduced, meanwhile, the compound action potential significantly decreased, and its latent period was also significantly prolonged 3, 5, 7 and 9 weeks (P < 0.05). The histological observation: Musculocutaneous nerve showed decreased medullated fibers, heterogeneous ditribution and decreased density, thin myelin sheath, damaged nerve structure and collagen hyperplasia; biceps brachii muscle showed degeneration, fiber breakage and inflammatory cell infiltration; The account of motor neurons in ventral horn was significantly decreased in the radiation side with time extending, the sign of cell death, such as, the neurons crimple, and karyolysis were observed (P < 0.05).Large dose of X-ray can induced brachial plexus injury, and the lameness, a "claw hand", biceps brachii muscle atrophy and the compound action potential abnormality. The account of motor neurons in ventral horn was significantly decreased. The motor neurons showed oxonal degeneration and myelinec degeration.
- A direct contact between astrocyte and vitreous body is possible in the rabbit eye due to discontinuities in the basement membrane of the retinal inner limiting membrane. [Journal Article, Research Support, Non-U.S. Gov't]
- Braz J Med Biol Res 2003 Feb; 36(2):207-11.
Different from most mammalian species, the optic nerve of the rabbit eye is initially formed inside the retina where myelination of the axons of the ganglion cells starts and vascularization occurs. Astrocytes are confined to these regions. The aforementioned nerve fibers known as medullated nerve fibers form two bundles that may be identified with the naked eye. The blood vessels run on the inner surface of these nerve fiber bundles (epivascularization) and, accordingly, the accompanying astrocytes lie mostly facing the vitreous body from which they are separated only by the inner limiting membrane of the retina. The arrangement of the astrocytes around blood vessels leads to the formation of structures known as glial tufts. Fragments (N = 3) or whole pieces (N = 3) of the medullated nerve fiber region of three-month-old male rabbits (Orictolagus cuniculus) were fixed in glutaraldehyde followed by osmium tetroxide, and their thin sections were examined with a transmission electron microscope. Randomly located discontinuities (up to a few micrometers long) of the basement membrane of the inner limiting membrane of the retina were observed in the glial tufts. As a consequence, a direct contact between the astrocyte plasma membrane and vitreous elements was demonstrated, making possible functional interactions such as macromolecular exchanges between this glial cell type and the components of the vitreous body.
- A technique for estimating activity in whole nerve trunks applied to the cervical sympathetic trunk, in the rabbit. [Journal Article, Research Support, Non-U.S. Gov't]
- Neurosci Lett 1999 Dec 24; 277(2):95-8.
The changes in sympathetic outflow may be evaluated from the amplitude of the antidromic compound action potential (ACAP) according to the collision technique described by Douglas and Ritchie (Douglas, W.W. and Ritchie J.M., A technique for recording functional activity in specific groups of medullated and non-medullated fibers in whole nerve trunks. J. Physiol., 138(1957) 19-30). This technique was revised, taking into account the depressant action exerted by antidromic stimulation on sympathetic preganglionic neurones (SPNs). Cervical sympathetic nerve (CSN) of rabbits was used as experimental model. Stimulation frequencies of 0.2-0.5 Hz were found to be sufficiently low to avoid depressant actions on CSN spontaneous activity; they were employed to test the sensitivity of the technique during different experimental manoeuvres, such as changes in pulmonary-ventilation, baroreceptor unloading and arousal stimuli. In addition a procedure was devised to calibrate the ACAP amplitude: high frequency antidromic stimulation was used to induce a complete and transient inhibition of SPNs which allows to record the ACAP maximum amplitude. ACAPs recorded in various experimental conditions can then be expressed as percentage of this value.
- Mechanisms for activation of aortic baroreceptor C-fibres in rabbits and rats. [Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.]
- Acta Physiol Scand 1999 Jul; 166(3):167-74.
In an earlier study, we examined the pressure-response characteristics of rat aortic baroreceptors with C-fibre (non-medullated) afferents. Compared with aortic baroreceptor fibres with A-fibre (medullated) afferents, the C-fibres were activated at higher pressures and discharged more irregularly when stimulated with a steady level of pressure. Here we examine the relationship between discharge and the aortic diameter in these two types of afferents in rats and rabbits. An in vitro aortic arch/aortic nerve preparation was used to record single-fibre activity simultaneously with aortic arch pressure and diameter. Diameter was measured using a highly sensitive non-contact photoelectric device. Baroreceptor discharge was characterized by stimulating the nerve endings with either slow pressure ramps from subthreshold to 200-250 mmHg, at a rate of rise of 2 mmHg s-1, or pressure steps from subthreshold to suprathreshold levels, at amplitudes of 110-180 mmHg. In response to these inputs, C-fibres in rabbits (conduction velocities= 0.8-2.2 m s-1) behaved much like those in rats. The C-fibres had significantly higher pressure thresholds (95 +/- 3 mmHg vs. 53 +/- 2 mmHg; mean +/- SEM), lower threshold frequencies (2.4 +/- 0.5 vs. 27.7 +/- 1.8 spikes s-1), lower maximum discharge frequencies (22.7 +/- 2.3 vs. 65 +/- 5.8 spikes s-1) and more irregular discharge in response to a pressure step when compared with A-fibres (conduction velocities of 8-16 m s-1). When plotted against diameter, C-fibre ramp-evoked discharge increased gradually at first, and then rose steeply at increasingly higher ramp pressures where aortic diameter became relatively constant. In contrast, A-fibre discharge was linearly related to diameter over a wide range of pressure. These results suggest two interpretations: (1) The relation between stretch and C-fibre discharge is highly non-linear, with a marked increase in sensitivity at large diameters. (2) C-fibres are stimulated by changes in intramural stress rather than stretch.