Biomedical subjects

X Navarro

Publications and source records attributed to X Navarro.

At least 19 recordsLinked to original sources

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↗

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↗

PubMed1995

The effect of aging on efferent nerve fibers regeneration in mice.

This study evaluates the influence of aging on nerve regeneration and reinnervation of target organs in mice aged 2, 6, 9, 12, 18 and 24 months. In animals of each age group the sciatic nerve was subjected to crush, section or section and suture. Reinnervation of plantar muscles and sweat glands (SG) was evaluated over three months after operation by functional methods. Reappearance of SG secretion and motor responses occurred slightly earlier in young than older mice. The degree of motor and sudomotor reinnervation, with respect to preoperative control values, was also significantly higher in young than old animals. The differences were more pronounced after 12 months of age. The degree of recovery progressively decreased with the severity of the lesion, differences being more marked in older mice. Neurorraphy improved recovery, comparatively more in older than in young mice. These results indicate that, after injuries of peripheral nerves, axonal regeneration and reinnervation are maintained throughout life, but tend to be more delayed and slightly less effective with aging.

Aging↗

PubMed1995

Peripheral nerve repair: role of agarose matrix density on functional recovery.

This study presents quantitative data on the functional reinnervation of sweat glands, muscle and skin in the mouse paw after resection of the sciatic nerve and repair by entubulation with silicone tubes prefilled with agarose gels of different concentrations. The rate and the degree of functional recovery of animals with chambers filled with 0.5% agarose gels were slightly higher than with 1% agarose, and significantly higher than with 2% agarose. All these three groups recovered significantly better than a fourth group with an unrepaired resection. We conclude that peripheral nerves can regenerate through agarose gels in vvio and reinnervate distal target organs, but the concentration and the density of the exogenous intratubular matrix are important factors in determining the success of nerve regeneration and reinnervation.

Animals↗

PubMed1995

Functional sudomotor responses to cholinergic agonists and antagonists in the mouse.

This study evaluates the functional activity of the mouse sweat glands in response to cholinergic agonists and antagonists using the silicone imprint technique. In intact mice the response to acetylcholine, methacholine and pilocarpine did not differ significantly from control saline injection, indicating that immobilization induces high levels of sweating, masking the effects of cholinergic stimulation. Plantar emotional sweating was completely abolished by local anesthesia at the ankle. Under these conditions, administration of acetylcholine only provoked detectable sweating when injected locally into the sole skin. Methacholine activated an increasing number of sweat glands in a dose-dependent manner between 0.5 and 10 mg/kg; the response was maximal after 5-10 min of administration and decreased subsequently. With pilocarpine the maximum number of reactive sweat glands was observed at a dose of 2.5 mg/kg. The response was stable for 45 min with doses 2.5 and 5 mg/kg, but decreased exponentially with higher doses. The subtype of sweat gland muscarinic receptor was characterized by determining the inhibitory effect of different cholinergic antagonists on pilocarpine response. Atropine and 4-DAMP were equally potent inhibitors, showing a dose-related effect from 0.05 mg/kg. Pirenzepine only showed inhibitory effects with doses 10-times higher, whereas gallamine and hexamethonium did not induce inhibition at any of the doses tested. These findings suggest that the mouse eccrine sweat gland muscarinic receptors are predominantly M3.

Animals↗

PubMed1995

Innervation of cutaneous structures in the mouse hind paw: a confocal microscopy immunohistochemical study.

The normal innervation of structures in mouse foot pads was investigated with immunohistochemistry and confocal microscopy. Nerves were visualized by incubating Zamboni fixed, thick, frozen sections with antibodies to protein gene product 9.5 (PGP 9.5), vasoactive intestinal peptide, substance P, calcitonin gene-related peptide, and protein zero. The antibodies were localized using cyanine 3.18 labeled anti-rabbit gamma globulin. PGP 9.5 immunolocalization showed dense nerve bundles at the base of the foot pad with branches to larger blood vessels, sweat glands and epidermis. Sweat gland tubules were surrounded by numerous sudomotor axons; single fibers accompanied the sweat duct toward the skin's surface. Nerve bundles containing myelinated and unmyelinated axons ran through and around the centrally located sweat gland cluster to end in free nerve endings and Meissner's-like corpuscles at the apex of the foot pad. Other bundles running parallel to the epidermis gave arcuate branches that supplied epidermis on the sides of the pads with a rich nerve network, principally with free nerve endings that often reached the most superficial cell layers of epidermis. Calcitonin gene-related peptide-immunoreactive (-ir) nerves were distributed to dermis and epidermis in lower density than PGP 9.5-ir fibers. Substance P-ir fibers were less numerous; most terminated as free endings in deeper layers of epidermis. Vasoactive intestinal peptide-ir nerves almost exclusively innervated sweat glands, ducts and blood vessels, but not epidermis. The mouse hind paw has potential to serve as a model system for investigations of functional and morphological changes that affect peripheral and autonomic nerves under diverse experimental conditions.

Animals↗

PubMed1995

Autonomic neuropathy in chronic alcoholism: evaluation of cardiovascular, pupillary and sympathetic skin responses.

Autonomic nerve function was evaluated in 30 alcoholics and 30 healthy subjects by means of cardiovascular function tests, pupil cycle time (PCT), and sympathetic skin responses (SSR). Nutritional status was assessed by anthropometric parameters. Autonomic cardiovascular dysfunction was classified as early involvement in 5 patients, definite in 8, severe in 6 and atypical in 3. PCT was abnormal in 17 alcoholics. The duration of PCT became progressively longer as the severity of cardiovascular involvement increased. SSR was absent in 4 alcoholics in the palm and in 16 in the sole. These findings indicate that sympathetic and parasympathetic mediated functions are abnormal in chronic alcoholics with a similar frequency, involving different sites of the autonomic nervous system under variable patterns. Significant correlations between nutritional status and autonomic neuropathy were found.

Adult↗

PubMed1995

Neuropathy profile of diabetic patients in a pancreas transplantation program.

We describe the results of extensive neurologic evaluation of 290 patients with insulin-dependent diabetes mellitus who came to our institution as potential recipients of a pancreas transplant. Large nerve fibers were evaluated by motor and sensory nerve conduction, small sensory fibers by thermal sensation thresholds, vagal and vasomotor functions by cardiovascular reflexes, and sympathetic sudomotor fibers by silicone imprints and evaporimetry. A scored anamnesis revealed symptoms of neuropathy in 86% of patients; 94% had an abnormal neurologic examination. The most frequently abnormal measurements of motor conduction were the amplitude of the extensor digitorum brevis muscle action potential to peroneal nerve stimulation and the conduction velocity of peroneal and tibial nerves in more than 80% of patients. Sensory nerve action potentials were abnormal in 76% and the distal latency of the sural nerve in 91%. Heart rate variability with deep breathing and during a Valsalva's maneuver was abnormal in 90% and 88%. Sudomotor function was reduced in 59% on the foot. Thermal sensitivity limen was above normal limits in 95% in the foot and 77% in the hand. Composite indexes of the degree of abnormality found for each type of function tested were correlated one with another, but were not predictive of results for any other test. The neuropathy of most patients was symmetric, involving to a similar degree motor, sensory, and autonomic nerves. Thus, diabetic neuropathy is very common and severe among patients who decide to be candidates for pancreas transplantation.

Adult↗

PubMed1994

Effects of dizocilpine on autotomy behavior after nerve section in mice.

The effects of acute administration of dizocilpine (MK-801) at different perioperative times on autotomy behavior after sciatic and saphenous nerve transection were studied in the mouse. Control mice developed a severe self-mutilating behavior starting 1-3 days postoperation and reaching a maximum by 11 days. Mice injected with a single dose of dizocilpine (0.4 mg/kg i.p.) before operation, the 1st or 3rd postoperative day autotomized significantly less than controls. An 1-wk treatment with the same dose once a day did not show further benefit. A single administration of dizocilpine the 5th day after surgery slightly halted further progression of autotomy. Dizocilpine did not have any deleterious effect on normal peripheral nerve function. These results suggest that NMDA receptor blockade prevents development of hyperalgesia and neuropathic pain after peripheral nerve injuries but only when it is administered before or during the first 3 days after injury.

Animals↗