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1

Early postweaning social isolation but not environmental enrichment modifies vermal Purkinje cell dendritic outgrowth in rats

100%
Pascual R., Bustamante C.
Acta Neurobiologiae Experimentalis
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2013
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tom 73
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nr 3
In the present study, we analyzed the effects of enriched, social and isolated experiences on vermal Purkinje cell of the rat, together with anxiety-like behavior in the elevated-plus maze. Sprague-Dawley male rats were randomly submitted to either enriched, social, or isolated environments during the early postweaning period (postnatal days 22-32) and were then behaviorally evaluated in the elevated-plus maze and euthanized for histological analysis. Vermal Purkinje cells (sub-lobules Via and VIb) were sampled, drawn under camera lucida and morphometrically assessed using the Sholl's concentric ring method. Data obtained indicate that environmental enrichment did not significantly modify the Purkinje cell dendritic branching. On the contrary, Purkinje cell of animals reared in social isolation exhibited a significant reduction in dendritic arborization, which was closely associated with anxiety-like behaviors. The data obtained indicate that, although environmental stimulation in normal animals does not produce significant changes in vermal Purkinje cell dendritic arborization, these cells are vulnerable to early stressful experiences, which is in close association with anxiety-like behaviors.
2

Effects of neonatal maternal deprivation and postweaning environmental complexity on dendritic morphology of prefrontal pyramidal neurons in the rat

100%
Pascual R., Zamora-Leon S. P.
Acta Neurobiologiae Experimentalis
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2007
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tom 67
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nr 4
It has been reported that periodic maternal separation in rats leads to a variety of endure behavioral, neurochemical and microstructural sequelae associated with the pathophysiology of anxiety disorders. Since it has been proposed that these changes might be permanent, we examined whether environmental complexity aid to recover the structural dendritic impairment induced by neonatal maternal deprivation in the medial prefrontal cortex of the rat. In addition, the anxiety-like behavior was assessed in the elevated plus-maze. Repeated maternal separation between postnatal days 6–21 (3 hours daily) significantly reduced the dendritic material in layer II/III pyramidal neurons and induced anxiety-like behaviors in the elevated plus maze. Furthermore, environmental stimulation (twice a day, 1 h each) during 12 consecutive days (postnatal days 23–35) failed to recover the neuronal and behavioral disorders induced by neonatal maternal separation. The results demonstrated that (i) neonatal maternal separation severely altered pyramidal dendritic outgrowth in close association with anxiety-like behavior assessed in the elevated plus maze, and (ii) postweaning environmental complexity was unable to recover neither the prefrontocortical neuronal impairment nor the novelty-induced anxiety-like behavior triggered by early maternal deprivation.
3

Structural neuroplasticity induced by melatonin in entorhinal neurons of rats exposed to toluene inhalation

100%
Pascual R., Bustamante C.
Acta Neurobiologiae Experimentalis
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2011
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tom 71
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nr 4
Several clinical studies have shown that abusing volatile solvents, mainly toluene, produces neurological, neuropathological and neuropsychiatry disorders. Symptoms of these disorders include loss in impulse control, distractibility and memory deficits, which are associated with mild brain atrophy. The entorhinal cortex is critically involved in mnemonic processes, and memory disorders are the major symptom detected in chronic solvent abusers. Therefore, in the present study, we evaluated (1) whether the entorhinal neuronal morphology was impaired by subchronic toluene exposure and (2) if melatonin protected the neuronal cytoarchitecture, as has been demonstrated in neocortical neurons. Consistent with our previous findings, the present study indicates that the entorhinal cell dendritic arborization was significantly reduced in toluene- exposed animals, and melatonin administration significantly rescued the reduced dendritic branching induced by toluene neurotoxicity.
4

Effects of postweaning social isolation and re-socialization on the expression of vasoactive intestinal peptide (VIP) and dendritic development in the medial prefrontal cortex of the rat

81%
Pascual R., Zamora-Leon P., Valero-Cabre A.
Acta Neurobiologiae Experimentalis
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2006
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tom 66
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nr 1
In the present study we evaluated the effects of early social isolation and re-socialization on dendritic development and the expression of the vasoactive intestinal peptide (VIP) in the medial prefrontal cortex (mPFC) of the rat. Sprague-Dawley male rats were reared either in isolation (IC) or social (SC) conditions from postnatal day 18 to 32. Rats were then behaviorally evaluated in the open field test, and approximately half of the animals were sacrificed. Their brains were processed either for immunocytochemical labeling against VIP or for the Golgi-Cox-Sholl staining. The remaining IC rats were re-socialized during 30 additional days. The results demonstrated that early social isolation impair neuronal dendritic arborization and increase the number of VIP-immunoreactive neurons. Furthermore, animals displayed hyperlocomotion in the open-field test. According to our structural, immunocytochemical and open-field data, the resocialization experience was unable to reverse neuronal and behavioral abnormalities.
5
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Hypsodonty and enamel microstructure in the Paleocene gondwanatherian mammal Sudamerica ameghinoi

81%
Koenigswald W., Goin F., Pascual R.
Acta Palaeontologica Polonica
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1999
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tom 44
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nr 3
263-300
Gondwanatherians were the earliest mammals to develop hypsodont cheek-teeth with thick cementum, already by the Late Cretaceous. Hypsodonty occurred independently in Gondwanatheria and Theria; however, very similar biomechanical strategies are observed. The hypsodont molariform cheek-teeth of the early Paleocene Sudamerica ameghinoi, the youngest member of the Gondwanatheria, are described. Sudamerica had in the lower jaw a continuously growing incisor and, separated by a large diastema, four cheek-teeth which cannot be homologized with premolars or molars, therefore they are regarded as molariforms. The analysis of one fragmentary mandible and 30 isolated molariforms led to the recognition of 8 different morphological categories among them, corresponding to four upper and four lower molariforms. The height of the teeth indicates a relatively high shape of the skull. The molariforms are characterized by transverse lophs; when only slightly worn, they show central enamel islets in the anterior/posterior caps and in the transverse valleys. When the first quarter of the tooth is worn down, these islets disappear and the synclines expand leaving only a narrow central longitudinal ridge. The enamel of the molariforms of Sudamerica is one-layered and formed by radial enamel; it resembles the enamel of Gondwanatherium. Compared to the enamel of the Gondwanatheria from Madagascar and India, the South American gondwanatherians are distinctly less derived. In turn, the incisor enamel is less derived in Sudamerica, although younger, than in Gondwanatherium; both show a combination of radial and tangential enamel. The evolution of hypsodonty in gondwanatherians during the Late Cretaceous and early Paleocene cannot be correlated with a grass diet, since grasses were not present during that time. Various lines of evidence including the dental morphology and the inferred habitat for Sudamerica ameghinoi, suggest semiaquatic and perhaps a burrowing way of life, similar to that of living beavers.
6

Single course of antenatal betamethasone produces delayed changes in morphology and calbindin-D28k expression in a rat’s cerebellar Purkinje cells

81%
Pascual R., Valencia M., Larrea S., Bustamante C.
Acta Neurobiologiae Experimentalis
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2014
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tom 74
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nr 4
In the current study, we analyzed the impact of antenatal betamethasone on macroscopic cerebellar development, Purkinje cell morphology and the expression of the neuroprotective protein calbindin-D28k. Pregnant rats (Sprague-Dawley) were randomly divided into two experimental groups: control (CONT) and betamethasone-treated (BET). At gestational day 20 (G20), BET dams were subcutaneously injected with a solution of 0.17 mg kg-1 of betamethasone, while CONT animals received a similar volume of saline. At postnatal days 22 (P22) and P52, BET and CONT offspring were behaviorally evaluated, and the cerebella were histologically and immunohistochemically processed. Animals that were prenatally treated with a single course of betamethasone exhibited long-lasting behavioral changes consistent with anxiety-like behavior in the open-field test, together with (1) reduced cerebellar weight and volume, (2) Purkinje cell dendritic atrophy, and (3) an overexpression of calbindin-D28k. The current results indicate that an experimental single course of betamethasone in pregnant rats produces long-lasting anxiety-like behaviors, together with macroscopic and microscopic cerebellar alterations.
7
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New data on the Paleocene monotreme Monotrematum sudamericanum, and the convergent evolution of triangulate molars

80%
Pascual R., Goin F. J., Balarino L., Udrizar Sauthier D. E.
Acta Palaeontologica Polonica
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2002
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tom 47
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nr 3
We describe an additional fragmentary upper molar and the first lower molar known of Monotrematum sudamericanum, the oldest Cenozoic (Paleocene) monotreme. Comparisons suggest that the monotreme evolution passed through a stage in which their molars were “pseudo−triangulate”, without a true trigonid, and that the monotreme pseudo−triangulate pattern did not arise through rotation of the primary molar cusps. Monotreme lower molars lack a talonid, and consequently there is no basin with facets produced by the wearing action of a “protocone”; a cristid obliqua connecting the “talonid“ to the “trigonid” is also absent. We hypothesize that acquisition of the molar pattern seen in Steropodon galmani (Early Cretaceous, Albian) followed a process similar to that already postulated for docodonts (Docodon in Laurasia, Reigitherium in the South American sector of Gondwana) and, probably, in the gondwanathere Ferugliotherium.
8
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First ? cimolodontan multituberculate mammal from South America

71%
Kielan-Jaworowska Z., Ortiz-Jaureguizar E., Vieytes C., Pascual R., Goin F. J.
Acta Palaeontologica Polonica
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2007
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tom 52
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nr 2
We describe a Cretaceous ?cimolodontan multituberculate p4 from South America, for which we erect the new genus and species Argentodites coloniensis. This new taxon is represented by an isolated ?left p4 from the Upper Cretaceous (?Campanian or Maastrichtian) La Colonia Formation of Patagonia (Fig. 1). It has a strongly convex anterior margin and prismatic enamel, which attest to its cimolodontan nature, while the previously known p4 (MACN−RN 975) from the Late Cretaceous Los Alamitos Formation is roughly rectangular, suggesting “plagiaulacidan” affinity. The presence of normal prismatic enamel in Argentodites suggests similarities to Ptilodontoidea. However, it differs from the Late Cretaceous and Paleocene Laurasian cimolodontans (including Ptilodontoidea) in having a long, straight posterior margin, a nearly straight dorsal margin, characteristic of some “Plagiaulacida”, and in having the lingual side close to the mirror image of the labial side, the character that poses difficulties in establishing whether it is a right or left tooth. Because of these differences we assign Argentodites to ?Cimolodonta, tentatively only, superfamily and family incertae sedis.
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