Biomedical subjects

Carlos Avendaño

Publications and source records attributed to Carlos Avendaño.

7 recordsLinked to original sources

PubMed2006

Effects of long-term sensory deprivation on asymmetric synapses in the whisker barrel field of the adult rat.

Whisker trimming deprives the cortical barrel field from the patterned sensory input that derives from active touch but leaves passive tactile signals unaltered. We have studied in the rat barrel field, by stereological procedures, the effects of a sustained period of unilateral deprivation by whisker clipping during adolescence and early adulthood on (1) the surface density (SV) of asymmetric synapses, as determined from measuring the presynaptic membrane specializations, and (2) the numerical density of asymmetric synaptic profiles (NA), classified according to their postsynaptic target and their apparent curvature. Compared to control rats, the procedure did not change the overall volume of the region, the volume fraction occupied by each cortical layer, or the volume fraction occupied by unmyelinated axons and boutons. However, the deprived barrel cortex displayed an increase in SV in layers I and II, and an increase in NA in layer I and in the cortex as a whole, mainly due to an increase in profiles with a convex shape. Layer IV was the least affected by the deprivation. These results point to a net increase, rather than a decrease, of excitatory synapses in the deprived cortex, which could result from a deprivation-induced decrease in the rate of normal synapse loss. This effect occurs specifically in superficial layers, more involved in intracortical and cortico-cortical, rather than thalamo-cortical, processing.

Animals↗

PubMed2005

Neuron numbers in the sensory trigeminal nuclei of the rat: A GABA- and glycine-immunocytochemical and stereological analysis.

The volume, total neuron number, and number of GABA- and glycine-expressing neurons in the sensory trigeminal nuclei of the adult rat were estimated by stereological methods. The mean volume is 1.38+/-0.13 mm3 (mean+/-SD) for the principal nucleus (Vp), 1.59+/-0.06 for the n. oralis (Vo), 2.63+/-0.34 for the n. interpolaris (Vip), and 3.73+/-0.11 for the n. caudalis (Vc). The total neuron numbers are 31,900+/-2,200 (Vp), 21,100+/-3,300 (Vo), 61,600+/-8,300 (Vip), and 159,100+/-25,300 (Vc). Immunoreactive (-ir) neurons were classified as strongly stained or weakly stained, depending on qualitative criteria, cross-checked by a densitometric analysis. GABA-ir cells are most abundant in Vc, in an increasing rostrocaudal gradient within the nucleus. Lower densities are found in Vip and Vp. The mean total number of strongly labeled GABA-ir neurons ranges between 1,800 in Vp to 7,800 in Vip and 22,900 in Vc, and varies notably between subjects. Glycine-ir neurons are more numerous and display more homogeneous densities in all nuclei. Strongly labeled Gly-ir cells predominate in all nuclei, their total number ranging between 9,400 in Vp to 24,300 in Vip and 34,200 in Vc. A substantial fraction of immunolabeled neurons in all nuclei coexpress GABA and glycine. In general, all neurons strongly immunoreactive for GABA are small, while weakly GABA-ir cells which coexpress Gly are larger. In Vc, one-third of all neurons are immunoreactive: 16.6% of them are single-labeled for GABA and 31.6% are single-labeled for glycine. The remaining 51.8% express GABA and glycine in different combinations, with those showing strong double labeling accounting for 22.6%.

Animals↗

PubMed2005

Striatal projections from the lateral and posterior thalamic complexes. An anterograde tracer study in the cat.

Striatal projections from the lateral intermediate (LI) and posterior (Po) thalamic complexes were studied with the anterograde tracers wheat germ agglutinin-horseradish peroxidase and Phaseolus vulgaris leucoagglutinin. Projections to the lateral part of the head and body of the caudate nucleus (CN) and to the putamen (Pu) were found to arise from the ventral parts of the caudal subdivision of the LI besides the well established sources in the intralaminar and ventral thalamic nuclei. No projections to the CN and only a few to the Pu were found to arise from the medial division of the Po. The presence of terminal and intercalated varicosities in the thalamostriatal fibers suggests that they form both terminal and en passant synapses. Thalamostriatal fibers from these thalamic sectors were unevenly distributed within the CN, with patches of either low-density innervation or with no projections at all interspersed within irregular, more densely innervated areas. The former coincided with the acetylcholinesterase-poor striosomes and the latter areas of dense projection with the extrastriosomal matrix.

Acetylcholinesterase↗

PubMed2005

The intraluminal thread model revisited: rat strain differences in local cerebral blood flow.

There are major differences in the outcome of focal cerebral ischemia between rat strains. This study aimed to investigate whether inter-strain differences exist in the local cerebral blood flow, changes produced by intraluminal middle cerebral artery occlusion (MCAO). Fifty-four male Long-Evans, Sprague-Dawley or Wistar rats were subjected to 60 minutes of transient MCAO, carried out with a silicone-coated 4-0 nylon monofilament. Local cerebral blood flow was monitored on the parietal cortex with laser-Doppler flowmetry. The decrease in local cerebral blood flow during the first 20 minutes of occlusion was significantly greater in Long-Evans (74.6 +/- 8.9%) than in Sprague-Dawley (50.7 +/- 26.8%) and Wistar (49.0 +/- 21.9%) rats. Strain differences in local cerebral blood flow reduction were maintained, or increased, throughout the occlusion period. These results show that the intraluminal model of MCAO produces a more pronounced, persistent and stable local cerebral blood flow reduction, with less interanimal variability, in Long-Evans than in Sprague-Dawley or Wistar rats.

Analysis of Variance↗

PubMed2004

The size of the whisker barrel field in adult rats: minimal nondirectional asymmetry and limited modifiability by chronic changes of the sensory input.

We have evaluated quantitatively the whisker barrel field (posteromedial barrel subfield, PMBSF) size in rats raised in standard cages and in rats chronically exposed to an enriched sensory environment. Some animals were subjected to either chronic trimming of the right whiskers, or permanent transection of the right infraorbital nerve. Coronal brain sections were Nissl-stained or reacted for cytochrome oxidase. All, except the IoN-transected rats, showed +/-5% variation in mean PMBSF thickness, with no consistent side bias. In the transected animals, however, the left PMBSF was a significant 3.1% shallower than the right. This denervation-dependent radial shrinkage was consistent with an 11% volume shrinkage of the deafferented PMBSF. The mean volume of the PMBSF ranged between 8.7 and 9.5 mm(3), with moderate interindividual variability (3.5% to 11%). No significant differences in PMBSF volume were found between groups in the right hemisphere, nor in the right vs. left ratios. However, the PMBSF volume was a significant 6.6% larger in the enriched animals without whisker trimming. The PMBSF volume correlated positively with neocortical volume, and with PMBSF cortex thickness, in rats exposed to enriched environment. These data show that: (1) there is a moderate interanimal and lateral variability in the PMBSF volume, with no side preference; (2) exposing young adult rats to an enriched environment induces a discrete but significant enlargement of the PMBSF; (3) the effects of whisker trimming on the contralateral PMBSF, if any, are lost in the interanimal and lateral variability; and (4) such changes reach significance, however, when studied in combination with exposure to an enriched environment.

Animals↗

PubMed2003

Quantitative stereological evaluation of the gracile and cuneate nuclei and their projection neurons in the rat.

Stereological methods were employed to estimate the volume and neuron numbers of the rat dorsal column nuclei (DCN). These methods were applied to Nissl-stained sections from control animals and cases that received injections of horseradish peroxidase in the thalamus, the cerebellum, or the spinal cord. Additional cases received combinations of fluorescent tracers in the same structures, to examine whether some of the retrogradely labeled neurons sent collaterals to different targets. The mean volume of the DCN is 0.81 mm(3) (range 0.65-1.10 mm(3)), of which 3%, 39%, and 59% correspond, respectively, to the nucleus of Bischoff (Bi), the gracile (Gr), and the cuneate (Cu) nuclei. Within Cu, the middle division (CuM) is the largest (42%), followed by the rostral (CuR; 36%) and caudal (CuC; 22%) divisions. The mean total number of neurons in the DCN is 16,000 (range 12,400-19,500), of which 2.4%, 34.0% and 63.6% correspond, respectively, to Bi, Gr, and Cu. Within Cu, CuM contains 48% of all neurons, and 27% correspond to CuR and 25% to CuC. Interanimal variability is moderate for the whole DCN and Cu but increases when individual nuclei are considered. About 80% of DCN neurons project to the thalamus, 3% to the spinal cord, and 7% to the cerebellum. Thalamic-projecting cells are more numerous in CuM and Gr (83%), and relatively less common in Bi and CuC (72-74%). Most of the DCN neurons projecting to the spinal cord appear in CuC and CuM. Two-thirds of the neurons projecting to the cerebellum are located in CuR, 20% in CuM, and 15% in Gr. A small fraction of neurons projects simultaneously to spinal cord and thalamus.

Animals↗

PubMed2002

Cochlear abnormalities in insulin-like growth factor-1 mouse mutants.

Insulin-like growth factor 1 (IGF-1) modulates inner ear cell proliferation, differentiation and survival in culture. Its function in human hearing was first evidenced by a report of a boy with a homozygous deletion of the Igf-1 gene, who showed severe sensorineural deafness [Woods et al., New Engl. J. Med. 335 (1996) 1363-1367]. To better understand the in vivo role of IGF-1 during inner ear differentiation and maturation, we studied the cochleae of Igf-1 gene knockout mice by performing morphometric stereological analyses, immunohistochemistry and electron microscopy on postnatal days 5 (P5), P8 and P20. At P20, but not at P5, the volumes of the cochlea and cochlear ganglion were significantly reduced in mutant mice, although the reduction was less severe than whole body dwarfism. A significant decrease in the number and average size of auditory neurons was also evident at P20. IGF-1-deficient cochlear neurons showed increased apoptosis, along with altered expression of neurofilament 200 kDa and vimentin. The eighth nerve, the cochlear ganglion and the fibers innervating the sensory cells of the organ of Corti of the P20 mouse mutants presented increased expression of vimentin, whereas the expression of neurofilament was decreased. In addition, the myelin sheath was severely affected in ganglion neurons. In conclusion, IGF-1 deficit in mice severely affects postnatal survival, differentiation and maturation of the cochlear ganglion cells.

Aging↗