Topography of Purkinje Cells and Other Calbindin-Immunoreactive Cells Within Adult and Hatchling Turtle Cerebellum

Abstract

The turtle's cerebellum (Cb) is an unfoliated sheet, so the topography of its entire cortex can be easily studied physiologically by optical recordings. However, unlike the mammalian Cb, little is known about the topography of turtle Purkinje cells (PCs). Here, topography was examined using calbindin-D(28K) immunohistochemistry of adult and hatchling turtles (Trachemys scripta elegans, 2.5-15 cm carapace length). Each Cb was flattened between two Sylgard sheets and fixed in paraformaldehyde. Sections (52 microm thick) were cut parallel to the flattened cortex (tangential), resulting in calbindin-immunolabeled PCs being localized to three to six sections for each turtle. PC position and size were quantified using Neurolucida Image Analysis system. Although hatchling Cb were medial-laterally narrower (3.0 vs. 6.5 mm) and rostral-caudally shorter (2.5 vs. 5.5 mm) than adult Cb, both averaged near 15,000 PCs distributed uniformly. Hatchling PCs were smaller than adult PCs (178 vs. 551 microm(2)) and more densely packed (2,180 vs. 625 cells/mm(2)). Calbindin immunoreactivity also labeled non-PCs along the Cb's marginal rim and its caudal pole. Many of these were very small (22.9 microm(2)) ovoid-shaped cells clustered together, possibly proliferating external granule layer cells. Other labeled cells were larger and fusiform-shaped (12.6 x 33.4 microm) adjacent to inner granule cells along the marginal rim, suggestive of migrating cells. It is not known whether these are new neurons being generated within the adult and hatchling Cb and if they connect to efferent and afferent paths. Based on these anatomical findings, we suggest that unique physiological features may exist along the rim of the turtle Cb.

In Vivo Evidence That TRAF4 Is Required for Central Nervous System Myelin Homeostasis

“…Histological analysis using Cresyl violet staining showed several alterations, notably a less compact granular layer, a less cohesive Purkinje cell layer, and a Purkinje cell body with altered morphology (reduced cell size, condensed nuclei) in the absence of TRAF4 (a and b, and insets). Calbindin 28K (Calb28), a marker for Purkinje cells [44], immunostaining revealed obvious gaps in the Purkinje cell layer in the TRAF4-KO brain compared with WT (c and d), suggesting Purkinje cell degeneration in the absence of TRAF4. Accordingly, TRAF4-KO Purkinje cell nuclei presented altered ultrastructural features, namely condensed chromatin and blebbing of the nuclear membrane (e and f), as previously described in apoptotic cells [45].…”

A novel path for rapid transverse communication of vestibular signals in turtle cerebellum

“…observation). Its cortex also has relatively uniform cellular distribution (Ariel et al 2009) with its three-layered structure and neuronal morphologies that are typical of those found in mammalian cerebellum (Tolbert et al 2004). On the other hand, the rim of the turtle cerebellum has two distinct features.…”

“…Second, its very edge is in contact with the brainstem and vasculature. Along that Cb rim, there is evidence of a proliferating zone of small cells that may display unique morphologies as they migrate (Ariel et al 2009;Martin et al 2008). It is not known whether these features of neurogenesis have any relationship to the lateral localization of the optical responses to nVIII stimulation or to the cerebellar processing that occurs in vCb.…”

Topography and Response Timing of Intact Cerebellum Stained With Absorbance Voltage-Sensitive Dye

“…At those magnifications, each diode detects 0.06 and 0.024 mm 2 of Cb, respectively. Given 645 Purkinje cell bodies/mm 2 in turtle Cb (see Ariel et al 2005), each diode may image not only 39 and 15 somata, but also the dendritic trees of many more PCs.…”

“…It has specific advantages in that its flat, thin profile makes a natural slice for whole-tissue optical recordings using voltage-sensitive absorbance dyes. Its thickness and PC density are quite uniform, except for a narrow lateral region distal to the peduncle (see Ariel et al 2005). Climbing fiber input, from the IO, is readily stimulated (Ariel 2005;Straka and Dieringer 1992) near the obex where axons from the contralateral IO coalesce to form the dense bundle of olivocerebellar axons that travel together to the peduncle.…”