Biomedical subjects

X Navarro

Publications and source records attributed to X Navarro.

At least 19 recordsLinked to original sources

PubMed2000

Nerve guides seeded with autologous schwann cells improve nerve regeneration.

This study evaluates the ability of Schwann cells (SCs) transplanted into a nerve guide to improve regeneration and reinnervation after sciatic nerve resection and repair, leaving a 6-mm gap, in the mouse. SCs were isolated from predegenerated adult sciatic nerves and expanded in culture using a chemically defined medium. Syngeneic, isogeneic, and autologous SCs were suspended in Matrigel and seeded in resorbable, permeable poly(l-lactide-co-epsilon-caprolactone) guides at 150,000 cells/tube. Guides containing SCs were compared to guides filled with Matrigel alone and with peroneal nerve autografts. Functional reinnervation was assessed by noninvasive methods to determine recovery of sweating, nociceptive, sensory, and motor functions in the hindpaw during 4 months postoperation. Morphological analysis of the regenerated nerves was performed at the end of follow-up. The group with an autograft achieved faster and higher levels of reinnervation and higher number of regenerated myelinated fibers than groups repaired by tubulization. The immunogenicity of transplanted SCs influenced the outcome of nerve regeneration. Transplants of autologous SCs resulted in slightly lower levels of reinnervation than autografts, but higher recovery and number of regenerated fibers reaching the distal nerve than transplants of isologous and syngeneic SCs, although most of the differences were not statistically significant. Syngeneic SCs did not improve regeneration with respect to acellular guides. Prelabeled transplanted SCs were found to survive into the guide 1-3 months after implantation, to a larger number when they were autologous than syngeneic. Cellular prostheses composed of a resorbable guide seeded with autologous SCs appear as an alternative for repairing long gaps in injured nerves, approaching the success of autografts.

Action Potentials↗

PubMed1999

Early social isolation decreases the expression of calbindin D-28k in rat cerebellar Purkinje cells.

The main objective of this study was to analyze the effects of early social isolation on the expression of calbindin D-28k (CAD-28k) in cerebellar Purkinje cells. Sprague-Dawley rats were reared either in isolation (IC) or socially housed conditions (SC) from postnatal days 18-32. Half of the rats of each group were sacrificed at 32 days of age and the cerebella processed for immunocytochemical labeling against CAD-28k. The remaining IC animals were housed under standard conditions for re-socialization between postnatal days 32 and 62. The results indicate that Purkinje cells of rats reared under early isolation show a marked loss of CAD-28k immunoreactivity, and that this deficiency is recovered by later social interaction, although the thickness of the molecular layer remains reduced.

Animals↗

PubMed1999

Olfactory bulb ensheathing cells enhance peripheral nerve regeneration.

Sciatic nerve resection leaving a 15 mm gap could not be repaired by bridging the stumps with a silicone tube prefilled with a laminin gel. However, when purified olfactory ensheathing cells (EC) were added to the gel filling the tube, successful axonal regeneration was observed in 50% of rats. With 12 mm gaps, regeneration occurred in 79% of rats with transplanted EC compared with 60% of those receiving collagen gel alone. Therefore, ECs help repair severe peripheral nerve injuries, in addition to their ability to promote axonal regeneration within the central nervous system.

Action Potentials↗

PubMed1999

Physiological and immunohistochemical characterization of cisplatin-induced neuropathy in mice.

We investigated the neuropathic effects of cisplatin in two groups of mice treated with 5 or 10 mg/kg/week of cisplatin for 7 or 8 weeks. Peripheral nerve functions were evaluated by sweat imprints, and electrophysiological, rotarod, and nociceptive tests. Protein gene product 9.5 (PGP), calcitonin gene-related peptide (CGRP), and vasoactive intestinal peptide (VIP) were immunohistochemically localized in footpads. Tibial nerves were analyzed morphometrically. Functional deficits developed progressively with higher cumulative doses, more markedly in mice treated with high than in those with low doses. From cumulative doses of 10 mg/kg, significant declines in sensory nerve conduction velocity and sudomotor responses were found, whereas motor and nociceptive functions were involved later. There were no morphometrical changes in tibial nerves. A marked decrease of CGRP- and VIP-immunoreactive nerves occurred in samples from treated mice, whereas PGP-labeled profiles decreased mildly at late stages. Impairment of the content of neuropeptides with neurosecretor role was detectable earlier than functional abnormalities. Immunohistochemical analysis of skin biopsies offers a useful diagnostic tool for peripheral neuropathies.

Animals↗

PubMed1999

Ensheathing glia transplants promote dorsal root regeneration and spinal reflex restitution after multiple lumbar rhizotomy.

Previously, we have shown that transplants of olfactory bulb ensheathing cells promoted regeneration of transected dorsal roots into the spinal cord. In this study, we assessed the ability of regenerating axons to make functional connections in the cord. Dorsal roots L3 to L6 were sectioned close to their entrance into the spinal cord and reapposed after injecting a suspension of ensheathing cells into each dorsal root entry zone (Group G). Afferent regeneration into the cord and recovery of spinal reflexes were compared with animals that received no injection (Group S) or culture medium without cells (Group C). Electrophysiological tests, to measure nerve conduction and spinal reflexes (H response and withdrawal reflex) evoked by stimulation of afferents of the sciatic nerve, were performed. At 14 days after surgery, H response was found in only 1 of 7 rats of Group G, and withdrawal reflexes were absent from all animals. At 60 days, the H response reappeared in 7 of 10 rats of Group G, and 1 of 5 of each of Groups C and S. The withdrawal reflex recovered in 4 of 10 rats of Group G, but in none of Groups C and S. Immunohistochemical labeling for calcitonin gene-related peptide (CGRP) in rats of Group G showed immunoreactive fibers entering the dorsal horn from sectioned roots, although at lower density than in the contralateral side. In conclusion, transplanted ensheathing cells promoted central regeneration and functional reconnection of regenerating sensory afferents.

Animals↗

PubMed1999

Magnetically aligned collagen gel filling a collagen nerve guide improves peripheral nerve regeneration.

Bioresorbable collagen nerve guides filled with either magnetically aligned type I collagen gel or control collagen gel were implanted into 4- or 6-mm surgical gaps created in the sciatic nerve of mice and explanted 30 and 60 days postoperation (dpo) for histological and immunohistochemical evaluation. The hypothesis was that contact guidance of regenerating axons and/or invading nonneuronal cells to the longitudinally aligned collagen fibrils would improve nerve regeneration. The criterion for regeneration was observation of regenerating myelinated fibers distal to the nerve guide. Consistent with previous studies showing poor regeneration in 6-mm gaps at 60 dpo with entubulation repair, only one of six mice exhibited regeneration with control collagen gel. In contrast, four of four mice exhibited regeneration with magnetically aligned collagen gel, including the appearance of nerve fascicle formation. The numbers of myelinated fibers were less than the uninjured nerve in all groups, however, which may have been due to rapid resorption of the nerve guides. An attempt to increase the stability of the collagen gel, and thereby the directional information presented by the aligned collagen fibrils, by crosslinking the collagen with ribose before implantation proved detrimental for regeneration.

Animals↗

PubMed1999

Highly permeable polylactide-caprolactone nerve guides enhance peripheral nerve regeneration through long gaps.

We compared regeneration and functional reinnervation after sciatic nerve resection and tubulization repair with bioresorbable guides of poly(L-lactide-co-epsilon-caprolactone) (PLC) and permanent guides of polysulfone (POS) with different degrees of permeability, leaving a 6 mm gap in different groups of mice. Functional reinnervation was assessed to determine recovery of motor, sensory and sweating functions in the hindpaw during four months postoperation. Highly permeable PLC guides allowed for faster and higher levels of reinnervation for the four functions tested than impermeable or low-permeable PLC guides, while semipermeable 30 and 100 kDa POS tubes yielded very low levels of reinnervation. The regeneration success rate was higher with PLC than with POS tubes. Morphometrical analysis of cross-sectional nerves under light microscopy showed the highest number of regenerated myelinated fibers at mid tube and distal nerve in high-permeable PLC guides. Impermeable PLC guides allowed slightly worse levels of regeneration, while low-permeable PLC guides promoted neuroma and limited distal regeneration. The lowest number of regenerated fibers were found in POS tubes. In summary, highly permeable bioresorbable PLC guides offer a suitable alternative for repairing long gaps in injured nerves, approaching the success of autologous nerve grafts.

Absorbable Implants↗

PubMed1999

Morphometric and ultrastructural changes with ageing in mouse peripheral nerve.

Qualitative and quantitative information is reported on the morphological changes that occur in nerve fibres and nonneuronal cells of peripheral nerve during the lifetime of the mouse. Tibial nerves of mice aged 6-33 mo were studied. With ageing, collagen accumulates in the perineurium and lipid droplets in the perineurial cells. Macrophages and mast cells increase in number, and onion bulbs and collagen pockets are frequently present. Schwann cells associated with myelinated fibres (MF) slightly decrease in number in parallel with an increase of the internodal length from 6 to 12 mo, but increase in older nerves when demyelination and remyelination are common. The unmyelinated axon to myelinated fibre (UA/MF) ratio was about 2 until 12 mo, decreasing to 1.6 by 27 mo. In older mice, the loss of nerve fibres involves UA (50% loss of 27-33 mo cf. 6 mo) more markedly than MF (35%). In aged nerves wide incisures and infolded or outfolded myelin loops are frequent, resulting in an increased irregularity in the morphology of fibres along the internodes. In the mouse there is an adult time period, 12-20 mo, during which several features of degeneration progressively appear, and an ageing period from 20 mo upwards when the nerve suffers a general disorganisation and marked fibre loss.

Aging↗

PubMed1999

Prolongation of nerve and epidural anesthetic blockade by bupivacaine in a lipid emulsion.

UNLABELLED: We assessed the effect of a lipid emulsion of bupivacaine on prolonging peripheral nerve and epidural anesthetic blockade in the rat. The intensity and duration of motor and sensory blockade produced by a single injection of aqueous solution (BPV-as) and lipid emulsion (BPV-em) preparations of 0.5% bupivacaine were evaluated by electrophysiological methods. Both preparations induced complete, reversible motor and sensory blockade after injection. The latency time to the maximal blockade and the duration of anesthetic blockade were more prolonged for BPV-em than for BPV-as. The increase in duration of maximal blockade was 1.4 times for nerve and 1.3 times for epidural anesthesia. Histological evaluation of spinal roots and spinal cord sections did not show any abnormalities or differences between animals injected with BPV-as and those injected with BPV-em. Pharmacokinetic studies showed lower plasma peak concentration and a longer elimination half-life for BPV-em than for BPV-as. Thus, BPV-em prolongs the effects of local anesthetics, allows a similar degree of blockade, and reduces the systems toxic effects of anesthetics compared with BPV-as. IMPLICATIONS: We assessed a lipid emulsion containing bupivacaine for peripheral nerve and epidural anesthetic blockade in the rat. The emulsion allowed a complete blockade, while increasing the duration of the anesthetic effect (by 30%-40%), compared with the standard bupivacaine aqueous solution.

Anesthesia, Epidural↗

PubMed1998

Changes in cholinergic responses of sweat glands during denervation and reinnervation.

Functional sudomotor responses have been studied in sweat glands reinnervated after sciatic nerve crush and partially denervated by cisplatin intoxication in the mouse. The sudomotor function mediated by the sciatic nerve was evaluated by silicone imprints on the plantar surface of the hindpaws. Five days after nerve crush, completely denervated sweat glands became unresponsive to cholinergic stimulation with pilocarpine. During the following weeks, the number of reinnervated, reactive sweat glands increased progressively to reach a maximum of 89% of preoperative control counts by 40 days after nerve crush. At this time, the mean volume of sweat secreted per gland was normal, but reinnervated glands showed a secretory activity abnormally sustained over time after pilocarpine stimulation and, on the other hand, had an increased resistance to the inhibition of secretion induced by atropine. The effects of cisplatin administration on sudomotor function were investigated in two groups of mice, one treated with high doses of cisplatin (10 mg/kg/week for 4 weeks) and another treated with low doses of cisplatin (5 mg/kg/week for 8 weeks). Cisplatin intoxication produced abnormal sudomotor responses indicative of denervation from cumulative doses of 10 mg/kg. The first abnormality found was a partial resistance of sweat glands to atropine, followed by a decrease in the sweat output per gland and finally a decline in the number of sweat glands activated by pilocarpine. These abnormalities in the sudomotor responses were more pronounced in mice treated with a high dose than in those with a lower dose regime.

Animals↗

PubMed1998

Influence of collagen and laminin gels concentration on nerve regeneration after resection and tube repair.

In order to assess the usefulness of collagen and laminin gels prefilling nerve chambers to enhance nerve regeneration, we compared reinnervation of target organs after sciatic nerve resection leaving gaps of 4 or 6 mm followed by repair with silicone tubes in different groups of mice. Tubes were prefilled with saline solution, collagen gels, or laminin-containing gels at different concentrations. Functional reinnervation was assessed by noninvasive methods to quantitate recovery of sweating, nociceptive, sensory, and motor functions in the hindpaw repeatedly during 4-5 months postoperation. The increase in gap length between nerve stumps delayed the beginning and reduced the degree of functional recovery achieved. Reinnervation started earlier and achieved slightly higher levels with collagen gel diluted at 1.28 mg/ml than with more concentrated (1.92 and 2.56 mg/ml) collagen gels and with saline-prefilled tubes bridging a 4-mm gap. Recovery was also better with diluted (4 mg/ml) than with concentrated (12 mg/ml) laminin-containing gel, although lower than with collagen gels and saline. By prefilling silicone tubes bridging a 6-mm gap, a length considered limiting for regeneration in the mouse sciatic nerve, with diluted collagen or laminin gels, both matrices allowed for higher levels of recovery and for successful regeneration in a higher proportion of mice than saline solution. The laminin gel performed slightly better than the collagen gel.

Animals↗

PubMed1997

Immunohistochemical study of skin reinnervation by regenerative axons.

The time sequence of sensory and sudomotor nerve regeneration to the mouse footpad was studied between one and seven weeks after crush or section of the sciatic nerve. Protein gene product 9.5, vasoactive intestinal peptide, substance P, and calcitonin gene-related peptide were localized in thick sections by using indirect immunofluorescence techniques and imaged by confocal microscopy. Nerve regeneration was visually assessed in all nerves and quantified in sweat glands. After denervation, protein gene product 9.5 immunoreactivity remained as dim fluorescence within thick fibers of dermal nerve trunks, whereas thin nerve fibers to sweat glands and to epidermis disappeared. By 14 days postcrush and 35 days postsection, the first protein gene product 9.5 immunoreactive regenerating axons appeared in large nerve trunks, quickly extending to epidermis and sweat glands. Reinnervation of Meissner's corpuscles occurred nearly simultaneous with return of epidermal free nerve endings and sudomotor network. Calcitonin gene-related peptide, vasoactive intestinal peptide, and substance P immunoreactivity disappeared completely one week after denervation, then reappeared at 17-18 days postcrush and 35 days postsection. Fewer nerve fibers were immunoreactive to these peptides than to protein gene product 9.5. The overall density of reinnervation, although reduced, more closely resembled normal in the sweat glands and Meissner's corpuscles than in the epidermis. Reinnervation was more successful after crush than after nerve section. The time course for functional return of sweating paralleled the return of protein gene product 9.5 immunoreactivity, whereas appearance of vasoactive intestinal peptide was delayed by several days.

Animals↗

PubMed1997

Long-term effects of pancreatic transplantation on diabetic neuropathy.

Restoration of a long-lasting euglycemic state by a functioning pancreatic transplantation (PTx) is the most logical treatment for insulin-dependent diabetes mellitus and for amelioration of secondary complications, including neuropathy. We evaluated neurological function by clinical examination, nerve conduction studies, and autonomic function tests in 115 patients with a functioning PTx and in 92 control patients treated with insulin, at baseline and 1, 2, 3.5, 5, 7, and 10 years later. In control patients, neuropathy progressively worsened during follow-up. The clinical examination score and composite indices of abnormality of motor and sensory nerve conduction decreased significantly at all intervals tested. Autonomic function indices also decreased, but significantly only after 1 year. In patients who received a successful PTx the neuropathy improved. The motor and sensory nerve conduction indices increased significantly at all intervals after transplantation, whereas the clinical examination and autonomic tests improved only slightly. Patients who received either a PTx alone, a PTx after a kidney graft, or simultaneous pancreatic and kidney transplantations improved similarly over the follow-up. These results indicate that a functioning PTx halts the progression and improves the signs of diabetic polyneuropathy by restoration of a normoglycemic state.

Adult↗

PubMed1997

Comparison of immunohistochemical and functional reinnervation of skin and muscle after peripheral nerve injury.

In order to investigate the usefulness of immunohistochemical detection of regenerating axons as a correlate of functional recovery, reinnervation of mouse foot pads, hairy skin, and muscle were studied at several intervals along 3 months after sciatic nerve crush using immunohistochemical markers PGP 9.5 and CGRP. These histological results were compared with functional recovery of sweat glands (SGs), plantar muscles, and pain sensibility. One week after nerve injury all neural functions were abolished in the operated hindpaw of all mice, no CGRP-immunoreactive (-ir) fibers were seen in the samples studied, while PGP 9.5 immunofluorescence remained at dim levels within nerve trunks, but disappeared from terminal innervation. The first PGP 9.5- and CGRP-ir regenerating fibers were seen at 15-16 days postoperation (dpo) in dermal nerve trunks of dorsal hairy skin and some days later in dermal trunks of foot pads. Regenerating nerve fibers progressed along the periphery of the dermis reinnervating the different dermal appendages. At 25 dpo all target organs were reinnervated. The first SGs activated by pilocarpine reappeared by 16 dpo and increased in number to 88% of control counts. Nociceptive responses reappeared at 17 dpo and reached 100% of control values. The first PGP immunofluorescence in neuromuscular junctions was seen at 16 dpo, while the first muscle action potentials were recorded at 19 dpo, and the potentials amplitude increased to 66% of controls. Good correlations were found between morphological and functional results of reinnervation. However, the density and distribution of nerve profiles in the tissues studied did not reach normal levels, while neural functions conveyed by small fibers reached levels similar to controls.

Animals↗

PubMed1997

Autonomic dysfunction in patients with non-alcoholic chronic liver disease.

AIMS: To assess the presence of autonomic neuropathy in patients with non-alcoholic chronic liver disease and its relationships with the severity of liver damage. METHODS: Thirty non-alcoholic patients with chronic liver disease and 26 healthy control subjects were studied. The silicone imprint technique was used to quantify the number of functioning sweat glands in order to assess peripheral sympathetic dysfunction. Heart rate variations in response to deep breathing at 6 per minute (deltaR6), to a Valsalva maneuver, and with orthostatism (RRmax/RRmin) were determined to assess parasympathetic vagal function. RESULTS: Mean values for autonomic tests were significantly lower in the group of patients with non-alcoholic chronic liver disease than in the control subjects. The number of activated sweat glands in the foot was abnormal in 19 (63%) patients. Among vagal tests, Valsalva ratio was abnormal in 14 (46%) and deltaR6 in 11 (36%) patients with liver disease. Vagal neuropathy (two or more abnormal heart rate tests) was definite in nine patients (30%). CONCLUSIONS: A high prevalence of abnormalities in both sympathetic and parasympathetic function tests, with a poor relationship with liver function parameters, has been found in patients with non-alcoholic chronic liver disease.

Adult↗

PubMed1996

Electrophysiological evaluation of spinal reflexes during epidural anesthesia in an experimental model.

We assessed the effects of epidural anesthesia with bupivacaine in the rat by serial recordings of spinal reflexes. The H wave from plantar muscles after electrical stimulation of the sciatic nerve evaluates a large nerve fiber spinal reflex arch. The extensor reflex response recorded from quadriceps muscle after stimulation of the contralateral tibial nerve assesses a reflex arch with small fiber afferents. After epidural injection of 0.2 mL of bupivacaine (0.25%, 0.5%, and 1.0% solutions) at the L5-L6 vertebral space, nociceptive, H, and extensor reflex responses were abolished within 1-3 min. Duration of complete blockade lasted 20-80 min, increasing with the anesthetic concentration, and complete recovery occurred after an additional period of 30-40 min. The responses recovered to amplitudes similar to preanesthesia controls, indicating that there was no damage to the nervous system. This study shows that electrophysiological recording and quantitation of nerve reflex responses is a useful and accurate method to evaluate the efficacy of local anesthetic agents.

Anesthesia, Epidural↗

PubMed1996

Neuropathy and mortality in diabetes: influence of pancreas transplantation.

We collected information on patient status and cause of death for 545 insulin-dependent diabetic subjects who had cardiorespiratory reflex and nerve conduction tests performed to determine if presence and severity of autonomic and somatic neuropathy is associated with mortality and if a functioning pancreas transplantation (PTx) influences mortality. Follow-up was 12-138 months. Abnormal cardiorespiratory reflexes were present in 417 patients and there was abnormal nerve conduction in 392 patients. Mortality rates for patients with abnormal tests were higher (P < 0.0001) than for patients with normal tests. A total neuropathy score that included cardiorespiratory and nerve conduction test scores predicted survival better than separate scores. Patients with moderate neuropathy, but not those with severe neuropathy, who retained a functioning PTx, had longer survival times than patients whose PTx failed in the first 3 months. Considering only patients transplanted after 1985, those with moderate neuropathy who retained a functioning PTx had even longer survival times than nontransplanted patients.

Adult↗

PubMed1996

Influence of physical parameters of nerve chambers on peripheral nerve regeneration and reinnervation.

We compared reinnervation of target organs after sciatic nerve section leaving gaps of 2, 4, 6, or 8 mm or gaps repaired with silicone tubes in different groups of mice. Functional reinnervation was assessed by noninvasive methods to determine recovery of sweating, nociceptive, and muscular functions in the hindpaw repeatedly during 3 months postoperation. The increase of gap length between nerve stumps delayed the beginning and reduced the degree of functional recovery achieved either with or without repair. When lesions were left unrepaired, functional reinnervation was only noticeable with a 2-mm gap and practically absent with longer gaps. With tube repair, reinnervation started earlier and achieved higher values than in the corresponding unrepaired groups. Tubulization was most effective with 4-mm gaps and comparatively less with shorter and longer gaps. With 4-mm gaps, recovery was higher when the silicone tube had a cross-sectional area 2.5 times that of the sciatic nerve than with narrower or wider tubes and when the wall was the thinnest available. In all cases muscle reinnervation showed a lower progression than sweating and nociceptive recovery.

Action Potentials↗