Biomedical subjects

I Barajon

Publications and source records attributed to I Barajon.

14 recordsLinked to original sources

PubMed1997

Effects of warm ischemia on valve endothelium.

BACKGROUND: This study investigates the time-dependent resistance of the endothelium of porcine aortic and pulmonary valves to different periods of warm ischemia (WIT). METHODS: Twenty-five 9-month-old swine were divided after death into five groups of WIT (0, 6, 12, 24, and 36 hours). Aortic and pulmonary valves were removed and a total of 15 aortic and 15 pulmonary valve specimens were obtained for each WIT interval. Valves were then examined for (1) their viability rate by the trypan blue dye exclusion method at light microscopy (percent of viability compared with 0 hours of WIT); (2) ultrastructural signs of irreversible or reversible ischemic damage by transmission electron microscopy (cell disruption, dilation of endoplasmic reticulum, cytoplasmic edema, nuclear and mitochondrial changes); (3) endothelial function by pharmacologic evaluation of both the endothelial-releasing capacity of prostacyclin and the endothelial-dependent dynamic responses to relaxing (acetylcholine from 1 x 10(-10) mol/L to 1 x 10(-4) mol/L) in aortic and pulmonary valve segments precontracted with norepinephrine (1 x 10(-6) mol/L) and contracting (NG-monomethyl-L-arginine, 1 x 10(-4) mol/L) drugs. RESULTS: Our results showed an endothelial progressive time-dependent ischemic injury, which reached significance after 12 hours of exposure. Viability and functional data indicated that 6 hours of WIT only provoked slight endothelial damage (p > 0.05 respect to time 0 hours), with signs at transmission electron microscopy consistent with a reversible injury. At 12 hours of exposure, we observed a significant reduction (p < 0.05) with respect to time 0 of the viability rate of prostacyclin production and of the endothelium-dependent dynamic responses to acetylcholine and NG-monomethyl-L-arginine. These functional impairments, although significant, were not consistent, however, with a complete loss of viability. Transmission electron microscopic observations confirmed the appearance of signs of irreversible injury; nevertheless, some elements were found to be well preserved or presented reversible damage. After 24 hours of WIT, ultrastructural and functional data were consistent with a dramatic decrease compared with controls in endothelial viability and functions (p < 0.01). Finally, after 36 hours of WIT, there was a subtotal loss of viability, of functions (p < 0.001) and, at transmission electron microscopic observations, of the endothelial layer of the valves. CONCLUSIONS: Our data show that the endothelial cells are resistant to short periods of WIT (up to 6 hours), and suggest that these cells can endure longer exposures, up to 12 hours of warm ischemia. Periods of 24 and 36 hours of WIT provoke progressive irreversible damage.

Acetylcholine↗

PubMed1996

Neuropeptides and morphological changes in cisplatin-induced dorsal root ganglion neuronopathy.

Dorsal root ganglia (DRG) neuronopathy was induced in rats by chronic treatment (2 mg/kg twice a week for nine injections) with the antineoplastic drug cisplatin. Morphological alterations and changes in peptide [calcitonin gene-related peptide (CGRP), substance P, galanin (Gal), and somatostatin] concentration were studied in the DRG, the spinal cord, and the sciatic nerve. Peptide concentration was increased in DRG neurons, with CGRP and Gal showing the highest increase. Conversely, in the sciatic nerve there was a general decrease in peptide content. In DRG a reduction in the nuclear, cytoplasmic, and nucleolar areas of primary sensory neurons was evident and was accompanied by clear-cut aspects of nucleolar structural damage. In peripheral nerves only extensive morphometric determinations could evidence a reduction in nerve conduction velocities and impairment in pain detection and coordination. Some of the nerve fibers presented axonal and adaxonal accumulations, suggesting the presence of an axonopathy. These results confirm that DRG cells are the primary target of cisplatin-induced neurotoxicity. Milder alterations can be detected in peripheral nerves. The increase in peptide concentration in DRG is probably due to cisplatin-related damage to the axonal transport system rather than to an increased synthesis.

Animals↗

PubMed1996

Anatomical organization of the spinal paths to the soleus and gastrocnemius muscles of the rat hind limb.

The anatomical organization of the motoneuronal columns of the soleus and lateral gastrocnemius muscle and of the related premotor interneurons was studied in rats, using the retrograde transneuronal transport of WGA-HRP. Motoneurons of the gastrocnemius muscle have a well-developed dendritic arborization which spreads into the transverse plane of the spinal cord extending to the intermediate region of the grey matter, while dendrites of the soleus muscle motoneurons spread mainly in the rosto-caudal plane, where they remain inside the border of the motoneuronal column and form small dendritic bundles, suggesting a coupling of neuronal activity as is to be expected in the motoneurons of a tonically active postural muscle such as the soleus. Gastrocnemial premotor interneurons are located close to the motoneuronal column, while the soleus premotor interneurons are scattered all over the ventral horn and intermediate grey. The number of labelled premotor interneurons is greater when the WGA-HRP is injected into the soleus muscle. In both cases, the premotor interneurons could be classified as four different types on the basis of the shape and size of the neuronal somata. The differences in the anatomical organization of the spinal paths to the gastrocnemius and soleus muscles reflect the different tasks performed by these two synergic muscles in normal motor behaviour: fast phasic activity by the gastrocnemius muscle, slow tonic anti-gravity activity by the soleus muscle.

Animals↗

PubMed1995

A simple method for overcoming some problems when observing thick reflective biological samples with a confocal scanning laser microscope.

A simple device is described, which allows the range of depth of scanning to be reduced when observing thick reflecting biological samples with a confocal scanning laser microscope (CSLM). Thick histological sections of human skin and rat brain stem were mounted between two coverslips ('sandwich' style) and the optical tomography was performed from both sides by turning the 'sandwich' upside-down. The samples were impregnated using standard Golgi-Cox, 'rapid Golgi' or other silver methods. The ability to turn the 'sandwich' upside-down is particularly useful when the reflective structure inspected is deep inside the section, i.e., near the lower surface of the specimen, or when it is opaque to the laser beam or excessively reflective.

Animals↗

PubMed1995

An ultrastructural study of neuronal changes in dorsal root ganglia (DRG) of rats after chronic cisplatin administrations.

In humans, the main dose-limiting side-effect of cisplatin (CDDP) treatment is a peripheral sensory neuropathy secondary to dorsal root ganglion (DRG) neuron involvement. To investigate further for neuronal alterations responsible for CDDP neurotoxicity we undertook the present experimental ultrastructural study, based on observations of 3 different groups of rats (6 animals in each group). Group A rats were treated with 1 mg/kg weekly for 9 weeks; Group B with 2 mg/kg weekly for 9 weeks; and group C rats served as untreated controls. At the end of the experiment, rats were perfused with 3% glutaraldehyde and lumbar DRGs were prepared for electron microscopic observations. In CDDP-treated rats somatic, nuclear and, above all, nucleolar size was reduced. Ultrastructurally, the nucleolus was the most affected structure. Nucleolar alterations were quantified morphometrically. Less marked changes were seen in the nucleus and in the RER and Golgi apparatus of the cytoplasm. The number of lysosomes and lipofuscins was greatly increased in CDDP-treated rats. The ultrastructural alterations observed in CDDP rats suggest that CDDP may be neurotoxic due to a reduction in protein synthesis. This assumption would explain why cells such as neurons, which are non replicating, but which have a high rate of protein synthesis, may be the target of the neurotoxic action of CDDP. The lack of an efficient blood/nerve barrier in the DRG explains the involvement of this particular type of neuron.

Animals↗

PubMed1994

Sulphorhodamine-labelled cells in the neonatal rat spinal cord following chemically induced locomotor activity in vitro.

1. Sulphorhodamine 101, a fluorescent dye and newly identified activity marker, was used to localize potential spinal locomotor networks in the neonatal rat spinal cord. 2. Preparations of the spinal cord with one entire hindlimb attached or the spinal cord in isolation were kept in vitro. Spinal locomotor activity was maintained chemically with NMDA (5-7.5 microM), in combination with 5-HT (7.5-20 microM), for 4-4.5 h in the presence of 0.0001-0.0005% sulphorhodamine 101. Matched non-locomoting controls were exposed to the dye in the absence of transmitters for a comparable time. Transverse sections of the lumbar spinal cord (L1-L6) were screened for rhodamine emission using an epifluorescence microscope. 3. In hindlimb-attached locomoting preparations with intact dorsal roots, labelled cells were found on the leg side in the dorsal horn (mainly laminae II-IV), in the intermediate grey (lamina VI-VII) and around the central canal (lamina X). Dorsal rhizotomy was performed on the leg side, to prevent synaptic activity due to afferent inflow. This largely reduced the number of labelled cells in the dorsal horn and in the lateral part of the intermediate grey matter. A further reduction of labelling in these areas was seen after complete isolation of the cord or when compared to the legless side, with the majority of labelled cells persisting in a bilateral cluster close to the central canal and in the medial intermediate grey. Few labelled cells were observed in non-locomoting preparations. The intensity of motoneuronal labelling was variable.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Transmission in a locomotor-related group Ib pathway from hindlimb extensor muscles in the cat.

It has been previously shown that phasic stimulation of group I afferents from ankle and knee extensor muscles may entrain and/or reset the intrinsic locomotor rhythm; these afferents are thus acting on motoneurones through the spinal rhythm generators. It was also concluded that the major part of these effects originates from Golgi tendon organ Ib afferents. Transmission in this pathway to lumbar motoneurones has now been investigated during fictive locomotion in spinal cats injected with nialamide and L-DOPA, and in decerebrate cats with stimulation of the mesencephalic locomotor region. In spinal cats injected with nialamide and L-DOPA, it was possible to evoke long-latency, long-lasting reflexes upon stimulation of high threshold afferents before spontaneous fictive locomotion commenced. During that period, stimulation of ankle and knee extensor group I afferents evoked oligosynaptic excitation of extensor motoneurones, rather than the "classical" Ib inhibition. Furthermore, a premotoneuronal convergence (spatial facilitation) between this group I excitation and the crossed extensor reflex was established. During fictive locomotion, in both preparations, the transmissions in these groups I pathway was phasically modulated within the step cycle. During the flexor phase, the group I input cut the depolarised (active) phase in flexor motoneurones and evoked EPSPs in extensor motoneurones; during the extensor phase the group I input evoked smaller EPSPs in extensor motoneurones and had virtually no effect on flexor motoneurones. The above results suggest that the group I input from extensor muscles is transmitted through the spinal rhythm generator and more particularly, through the extensor "half-centre". The locomotor-related group I excitation had a central latency of 3.5-4.0 ms. The excitation from ankle extensors to ankle extensors remained after a spinal transection at the caudal part of L6 segment; the interneurones must therefore be located in the L7 and S1 spinal segments. Candidate interneurones for mediating these actions were recorded extracellularly in lamina VII of the 7th lumbar segment. Responses to different peripheral nerve stimulation (high threshold afferents and group I afferents bilaterally) were in concordance with the convergence studies in motoneurones. The interneurones were rhythmically active in the appropriate phases of the fictive locomotor cycle, as predicted by their response patterns. The synaptic input to, and the projection of these candidate interneurones must be fully identified before their possible role as components of the spinal locomotor network can be evaluated.

Animals↗

PubMed1992

Induction of fos expression by activity in the spinal rhythm generator for scratching.

Fos expression was evaluated immunohistochemically in L7-S1 spinal segments after inducing fictive scratching in paralysed, unanaesthetized, decerebrate cats. The activity was induced by cutaneous stimulation of the pinna on one side and recorded from peripheral nerves. A cumulative duration of scratching of 60 to 90 min was effective in inducing fos expression. Most Fos-positive neurones were found in the dorsolateral part of the ventral horn and in the intermediate region of the spinal cord on the scratching side. In sham-operated animals the finding of Fos-positive neurones in these areas was very rare.

Animals↗

PubMed1992

Morphometric study of the sensory neuron and peripheral nerve changes induced by chronic cisplatin (DDP) administration in rats.

We performed a morphological, morphometric and toxicological study on the spinal ganglia and peripheral nerves of the rat after chronic administration of cisplatin (cis-dichlorodiammineplatinum II; DDP) with two different schedules. Severe damage of the spinal ganglia neurons was demonstrated with predominant involvement of the nucleus and nucleolus associated with a decrease in the cell size. Morphological and morphometric changes also occurred in the sciatic and peroneal nerves with the features of axonopathy. All these changes were more marked in the group of rats which underwent the most intense DDP treatment and the tissue platinum concentrations were also higher in this group. This experimental model is the first available for chronic DDP administration in which concomitant spinal ganglia and peripheral nerve damage has been confirmed pathologically. Our study supports the hypothesis that DDP-induced peripheral nerve fiber degeneration may result from nuclear and nucleolar changes in the sensory ganglion cell perikaryon.

Animals↗

PubMed1991

Effects of repeated administration of low doses of cisplatin on the rat nervous system.

Cisplatin is a very effective antineoplastic drug. To date its major toxic dose-limiting effect is peripheral neuropathy. Whereas the clinical and neurophysiological features of cisplatin-induced neuropathy are fairly well known, its pathogenesis is still unclear. We treated a group of Wistar rats with low doses of cisplatin for 70 days in order to evaluate the light-microscopic and ultrastructural changes induced by chronic cisplatin administration in the spinal cord, spinal ganglia and peripheral nerves. Although the most striking pathological alterations were observed in the spinal ganglia neurons, initial axonal neuropathy was also demonstrated, whereas the spinal cord neurons were completely normal. Our findings further support the hypotheses that spinal ganglion neurons are the primary target of cisplatin peripheral neurotoxicity and that peripheral nerve damage is secondary to this neuronopathy.

Animals↗

PubMed1990

Different neuronal types in transneuronally WGA-HRP-labeled premotor interneurons of the rat spinal cord.

Interneurons presynaptic to motoneurons were labeled by retrograde transneuronal transport of WGA-HRP. The tracer was injected either into the quadriceps muscles or into the posterior biceps muscles, thus labeling interneurons presynaptic to the quadriceps motoneurons (QINs) or interneurons presynaptic to posterior biceps motoneurons (PBINs). Statistical cluster analysis of area, perimeter, equivalent diameter and form factor of the labeled interneurons permitted the identification of 4 different types of premotor interneurons in the lumbar enlargement of the rat. Type I are small elongated interneurons which prevail in PBINs. Type II are medium-sized ellipsoidal cells prevailing in the QINs. Type 3 are small ellipsoidal neurons, slightly more frequent in PBINs. Type 4 is the smallest group and it is composed of large multipolar neurons. A different distribution of the 4 morphological neuronal types was found between the population of the QINs and the PBINs and in the laminae of ventral horn for each group.

Afferent Pathways↗

PubMed1990

The organization of corticopontine fibres in man.

Patients with lesions located in the frontal and temporal lobes, in the parieto-temporo-occipital border zone, and in the anterior limb of the internal capsule, did not present ataxia or other cerebellar signs. On the other hand, patients with the ataxic hemiparesis (AH) syndrome had lesions located in the posterior limb of the internal capsule, in the corona radiata and in the central region of the cerebral cortex. These findings in man do not confirm the existence of large frontal (Arnold's bundle) and temporal (Türck's bundle) projections to the pontine nuclei and indicate that the main bulk of corticopontine fibres originates from the central region of the cerebral hemisphere and courses in the posterior limb of the internal capsule. In man, the anatomical organization of corticopontine fibres is therefore similar to that recently demonstrated in animals.

Cerebellar Ataxia↗

PubMed1989

Blood-nerve barrier of endoneural vessels in experimentally-induced hypothyroidism in rats.

Hypothyroidism may cause peripheral nerve damage, even if the pathophysiology of these changes is still unclear. It has been suggested by some that an increased vascular permeability is involved in hypothyroidism, while others have suggested a "compressive" mechanism caused by mucinous material deposited in the endoneurium. We have studied histologically the endoneurium and evaluated endoneural-vessel permeability in sciatic nerve by means of the leakage of horseradish peroxidase (HRP) in pharmacologically-induced hypothyroidism in rats. We did not find any substantial differences between the hypothyroid group of animals and the controls with respect to endoneural-vessel permeability. In particular, no macromolecular deposits were present in the extracellular space of the endoneurium in either the treated or the control rats. We therefore believe that a "vascular" hypothesis is unlikely for nerve involvement during hypothyroidism, nor was the "compressive" hypothesis supported by our histological findings.

Animals↗

PubMedDate not supplied

Cisplatin induces apoptosis in SH-SY5Y human neuroblastoma cell line.

BACKGROUND: Cisplatin (CDDP) is cytotoxic, inducing apoptosis in some tumoral cell lines in vitro. Since CDDP is an effective drug in vivo treatment of neuroblastoma, we tested this drug on the human neuroblastoma SH-SY5Y cell line. Materials and methods. The effect of CDDP on cultured SH-SY5Y cells was determined with trypan blue dye exclusion test, LDH activity and DNA electrophoresis. Cultures were observed by light and electron microscope. Flow cytometric analysis was also carried out. RESULTS: CDDP inhibits the growth of neuroblastoma cells and reduces cell viability. Cell death occurs by apoptosis, as evidenced by morphological criteria and typical DNA laddering. Flow cytometry demonstrates that CDDP-treated cells are arrested in the G2/M phase before entering programmed cell death. CONCLUSIONS: CDDP is thus effective on the human neuroblastoma SH-SY5Y cell line, inducing apoptosis.

Apoptosis↗