Cytoarchitecture of the Hippocampal Formation in the African Giant Rat (Cricetomys gambianus, Waterhouse).

The African Giant Rat, AGR is an indigenous nocturnal rodent noted for its unique olfactory and cognitive abilities. They have been deployed more recently in the detection of landmines and diagnosis of tuberculosis - two scourges that have had a tremendous negative impact on the African landscape. This olfactory-aided cognition has been linked to the hippocampus. While the anatomical infrastructure of the olfactory bulb of the AGR has been elucidated, little is known about the adaptive cytoarchitecture of the AGR hippocampal formation. This study describes the histological features, including subfields and stratifications of the AGR hippocampus using Nissl and Golgi stains. The basic cytoarchitecture of the AGR hippocampus observed in this study, with respect to stratification, subfields and cell types, is similar to those reported in the laboratory rats. Cell types identified in the AGR hippocampus include pyramidal cells, granule cells and mossy cells with mossy fibers and Schaffer collaterals also delineated. Hippocampal proper subfields CA1 to CA4 were identified. CA3 pyramidal neurons formed a well-defined cell layer starting in between the upper and lower ends of the dentate gyrus and had larger, more distinct pyramidal cells and higher cell layer thickness (240.0±6.0 µm) relative to subfields CA1 (87.0±2.0 µm) and CA2 (109.0±4.20 µm) with significant statistical differences at p<0.001. The detailed, delicate arrangement of various cell types and subfields, intricate wiring with synapses and laminar organization of the hippocampal formation noticed in the AGR strongly supports the canonical trisynaptic circuitry of the hippocampus. It will however be necessary to carry out densitometric studies and detailed neurochemical profiling of the AGR hippocampus to fully elucidate the functional leverage of this unique rodent. We, therefore, suggest the suitability of this rodent as a model for olfaction-linked memory studies.

Developmental horizons in the pre-natal development of the Greater cane rat (Thryonomys swinderianus).

The Greater cane rat (GCR, Thyronomys swinderianus) is a precocial rodent predominantly found within Africa. Economic and scientific interests have led to several research efforts towards the domestication and better understanding of the biology and development of this rodent. Despite these efforts, information on the pre-natal development of this rodent is currently lacking. This study characterises distinct developmental milestones including skin pigmentation, emergence and distributions of hairs, calvarium consistency, teeth eruption, development of appendages, sensory organs and external genitalia in the pre-natal GCR and assesses quantitative body parameters, that is body weight, body and crown-rump lengths across its entire gestation length (gestation days [GDs] 10-140). Using these external features, we provide baseline reference ontogenetic scales for GCR embryos and fetuses, employable for stage, age and sex estimation of the pre-natal GCR in future studies. We observed that the first evidence of an embryo was not seen before the end of the first trimester (GD50) and that the late second trimester (GD80-GD100) marks the transition from embryogenesis to fetogenesis in the GCR. As both events occur at a much later developmental time point when compared to precocial non-rodents including human, sheep and pig and slightly later when compared to other precocial rodents such as guinea pig, our data provide first indication that the pre-natal GCR development might be associated with a reproductive delay. Together, this study expands our knowledge of the development and biology of the GCR, which will improve reproductive and breeding management, and native species conservation of this hystricomorph mammal.

Peripheral axonopathy in sciatic nerve of adult Wistar rats following exposure to vanadium.

Depletion of myelin and neurobehavioural deficits are indications that vanadium crosses the blood-brain barrier and such neurotoxic effects of vanadium on the brain of Wistar rats have been elucidated. The effect however on the peripheral nerves, is yet to be reported. Thus, this work was designed to evaluate the axonal and myelin integrity of sciatic nerves in Wistar rats following exposure to vanadium. Ten male Wistar rats were exposed to 3 mg/kg body weight of sodium metavanadate for 7 days, subjected to rearing and forelimb grip behavioural tests, and sciatic nerves processed for histology (haematoxylin and eosin, cresyl violet, and luxol fast blue). Dystrophic axons with vesiculated myelin, thinned myelin sheath, and demyelinated axons were observed in the vanadium exposed rats, suggestive of axonopathy, classified as fourth-degree nerve injury. Lower behavioural scores were recorded for vanadium-dosed rats; thus, corroborating histological pictures observed of the sciatic nerves. Authors posit that vanadium crossed the "blood-nerve" barrier and caused the observed axonal pathologies and myelin depletion in the sciatic nerves of these rodents with resultant motor deficits. The present paper discusses possible motor deficits and the likely public health importance in regions with crude oil pollution and gas flaring rich in vanadium products.

Astrocyte morphology, heterogeneity, and density in the developing African giant rat (Cricetomys gambianus).

Astrocyte morphologies and heterogeneity were described in male African giant rats (AGR; Cricetomys gambianus, Waterhouse) across three age groups (five neonates, five juveniles, and five adults) using Silver impregnation method and immunohistochemistry against glial fibrillary acidic protein. Immunopositive cell signaling, cell size and population were least in neonates, followed by adults and juveniles, respectively. In neonates, astrocyte processes were mostly detected within the glia limitans of the mid and hind brain; their cell bodies measuring 32 ± 4.8 µm in diameter against 91 ± 5.4 µm and 75 ± 1.9 µm in juveniles and adults, respectively. Astrocyte heterogeneity in juvenile and adult groups revealed eight subtypes to include fibrous astrocytes chiefly in the corpus callosum and brain stem, protoplasmic astrocytes in the cortex and dentate gyrus (DG); radial glia were found along the olfactory bulb (OB) and subventricular zone (SVZ); velate astrocytes were mainly found in the cerebellum and hippocampus; marginal astrocytes close to the pia mater; Bergmann glia in the molecular layer of the cerebellum; perivascular and periventricular astrocytes in the cortex and third ventricle, respectively. Cell counts from twelve anatomical regions of the brain were significantly higher in juveniles than in adults (p ≤ 0.01) using unpaired student t-test in the cerebral cortex, pia, corpus callosum, rostral migratory stream, DG, and cerebellum. Highest astrocyte count was found in the DG, while the least count was in the brain stem and sub cortex. Astrocytes along the periventricular layer of the OB are believed to be part of the radial glia system that transport newly formed cells towards the hippocampus and play roles in neurogenesis migration and homeostasis in the AGR. Therefore, astrocyte heterogeneity was examined across age groups in the AGR to determine whether age influences astrocytes population in different regions of the AGR brain and discuss possible functional roles.

Macro-anatomical investigations of the skeletons of the African giant rat (Cricetomys gambianus Waterhouse 1840) II: Fore limb

In this study, 7 African giant rats (Cricetomysgambianus Waterhouse 1840) were used to investigate the bony fore limb. It was observed that the supraspinous fossa was larger than the infraspinous fossa. The slender, curved clavicles were about 2.53 cm long. The humerus was peculiar and the ridges and the tuberosities were well developed. There was a supracondylar foramen in the mediodistal region of the humerus in all the rats, while 3of the rats (42.9%) had a supratrochlear foramen. The radius and ulna were distinct but appeared fused in most of the African giant rats used in this study. In the carpal proximal row, radial carpal and intermediate carpal bones were fused to form the Os carpi intermedioradiale. The manus was complete, with five digits. There were two phalanges in the first digit and the other four digits were composed of three phalanges. On the palmar face of the man us there were radial and ulnar sessamoids (ossa sessamoidea palmaria) with an irregular surface. In conclusion, there were some prominent features in the forelimb bones of the African giant rat that typifies them asfast running, burrowing and shoveling rodents (AU)

No disponible

Macro-anatomical investigations of the skeletons of the African giant rat (Cricetomys gambianus Waterhouse): Pelvic limb

In this study, the hind limb bones of adult African giant rats (Cricetomys gambianus Waterhouse)were used to investigate their gross morphology. The ventrocaudal iliac spine was absent in the animals while the pelvic symphysis was fused. The average distance between the mid-acetabulum and the tuber coxae was41.00 mm, and the average distance between the mid-acetabulum and the ischial tuberosity (tuber ischiadicum) was 26.00 mm. The averagesagittal length and width of the for amenobturatum were 20.00 mm and 14.00 mm, respectively. Sexual differences were observed in the Os coxae. There were three trochanters on the femur while the fovea capitis was absent and replaced by an indistinct depression. The tibia and fibula were almost fused int he distal half before dividing distally to form the medial and lateral malleolus. The tibia has a distal depression not reported in literature. There were 8 tarsal bones and the pedis was complete with five digits (AU)

No disponible