A possible case of renal oxalate deposit reported in an African fruit bat (Epomops franqueti).

We report a possible spontaneous case of oxalate nephrosis in an African fruit bat (Epomops franqueti), incidentally observed in Ibadan, South-West Nigeria, in an anatomical and serological survey of the species. Wild caught bats underwent sedation, intracardial perfusion, necropsy and histopathology. All 15 wild-caught African fruit bats were apparently healthy. However, light microscopy revealed mild oligofocal tubulonephrosis with intraluminal deposition of polarizing crystals interpreted as subclinical oxalate nephrosis in one case. In summary, we suggest a dietary aetiology, based on seasonal availability of high ascorbic acid or oxalate containing fruits. However, exposure to anthropogenic contaminants cannot be completely ruled out.

Oligodendrocyte morphology in the developing brain of the African giant rat (Cricetomys gambianus, Waterhouse): Histology, immunohistochemistry and electron microscopy.

Oligodendrocyte and myelin-related studies have been pivotal in understanding disruption of central nervous system (CNS) myelin through injury, toxicological, pathological degeneration or genetic intervention. The African giant rat (AGR) has been postulated as an indigenous wild-type model within the African context. This work thus describes oligodendrocyte morphologies and myelin components of the developing African giant rat brain using histological, immunohistochemical and ultrastructural techniques. Five types, precursor-progenitor oligodendrocytes, pre-oligodendrocytes, immature oligodendrocytes, mature non-myelinating oligodendrocytes and mature myelinating oligodendrocytes, were identified. The first four types were observed in neonates while juvenile and adult AGR had predominantly mature myelinating oligodendrocytes with evidence of myelin sheath deposition. All cell types identified showed positive CNPase-positive immunosignalling across all age groups. This suggests CNPase as a suitable, sensitive and reliable biomarker for studying CNS neurodegenerative/demyelinating disorders in the AGR. This baseline study has given detailed insight into the morphology of oligodendrocytes and myelin in the AGR. It may be useful for anatomical studies and detection of alterations in neurocellular profile of oligodendrocytes and myelin in the AGR in real-life or in experimental models.

Morphological Characterization of the African Giant Rat (Cricetomys gambianus, Waterhouse) Brain Across Age Groups: Gross Features of Cortices.

This experiment was designed to investigate the morphological characterization of the brain cortices of African giant rats, AGR (Cricetomys gambianus, Waterhouse) across age groups as related to function. A total of 15 male AGR were used for this study comprising of 5 neonates, 5 juveniles and 5 adults. Brains were described as having typical rodent features; the falx cerebri, the dura modification of interest, was partly inserted between the lobes of the olfactory bulb and extended towards the corpus callosum. Gross parameters extrapolated include cerebral and cerebellar cortical dimensions using a oneway ANOVA (p≤0.05). Most values showed highest significant value bias for juveniles over adults and neonates.  The average brain weight was 5.60±0.06g, 4.64±0.17g and 0.62±0.08g; cortex volume: 2.84±0.04cm3, 3.16±0.10cm3 and 0.23±0.02cm3 and antero-posterior dimensions: 11.93±0.26mm, 14.54±0.22mm and 6.00±0.16mm for adult, juvenile and neonates respectively. There was however adult bias in the cerebellum weight (0.83±0.02g, 0.76±0.02g and 0.04±0.02g); vermis length (13.23±0.32mm, 11.27±0.014mm and 0.24±0.02mm) and the antero-posterior length values (8.79±0.19mm, 6.97±0.03mm and 0.29±0.01mm) for adults, juveniles and neonates AGR respectively. Cortical parameters were related as a function of the brain development and plasticity, while age was described to play functional roles in intelligence determination of the AGR. The result of this study will be useful as baseline information for post mortem studies, medical imaging and useful as diagnostic tool for future research work on the AGR brain.

Spinal Cord Studies in the African Giant Rat (Cricetomys gambianus, Waterhouse).

The African giant rat, AGR, is known for advantageous behavioural patterns among which are cognition and dexterous locomotion. This study investigated the morphological, morphometric and possible functional aspects of the AGR spinal cord (SC) anatomy. Ten adult (5 males and 5 females) AGR were used to determine the gross and histological features of the SC which were typically of rodent features. The mean SC weight and length given as 2.50±0.24g and 15.87±0.24cm respectively for the male and 2.32±0.16g and 15.40±0.61cm for the female showed no sexual dimorphism. A positive linear relationship between the tail length and SC weight were found in both sexes (r =0.81 males; r =0.95 females) suggesting significant contribution of the filum terminale to SC weight. Forty-three internal structures including nuclear aggregations and tracts were traced. Eight nuclear aggregations of neurons involved in nociception and limb coordination were observed to be prominent and larger than in laboratory rats. Same was noted for the dorsal, ventral and lateral funicular tracts which control the limbic system. This study provides morphometric baseline research information and delineates the functional aspects of the AGR SC anatomy. The information provided further strengthens the drive proposing the AGR as an indigenous research model for regional anaesthesia and locomotor disease.

The olfactory bulb structure of African giant rat (Cricetomys gambianus, Waterhouse 1840) I: cytoarchitecture.

The olfactory system typically consists of two parallel systems: the main olfactory system and the accessory olfactory system. The main olfactory bulb (MOB) acts as the initial processing site for volatile chemical stimuli and receives input from the olfactory receptor cells located in the olfactory epithelium. The African giant rat is reputed to have abilities to detect landmines and tuberculosis samples by sniffing. This study therefore is a preliminary study on the histological and immunohistochemical anatomy of the olfactory bulb of the African giant rat (Cricetomys gambianus, Waterhouse). Nissl and Klüver-Barrera histological staining of the olfactory bulb revealed a cytoarchitecture typical of most mammals with 6 cell layers, and 1-2-layered glomeruli measuring approximately 150 µm each in diameter. Immunohistochemical staining with glial fibrillary acidic protein (GFAP) and 2',3'-cyclic nucleotide 3-phosphodiesterase (CNPase) revealed cellular conformations relative to most mammals. GFAP immunohistochemistry also revealed cell bodies and processes within the periglomerular area which may potentiate signaling from the olfactory receptor cells, while CNPase largely showed soma and evidence of myelin sheath deposition, confirming myelination at different layers of the bulb. Neurogenesis was examined using the neurogenic markers doublecortin (DCX) and Ki-67. Migration of newly generated cells was observed in all layers of the MOB with DCX and in most layers with Ki-67. The anatomy of the olfactory bulb is described as relatively large in the African giant rat, having a neuroarchitecture similar to most rodents.

Some aspects of the neurocraniometry of the African giant rat (Cricetomys gambianus Waterhouse).

Sixteen African giant rats (Cricetomys gambianus Waterhouse), consisting of 8 male and 8 female rats, were used to determine neurocranial measurements of the skulls. The mean neurocranial volume was 5.06 + or - 0.05 mL, neurocranial length was 3.33 + or - 0.08 cm, and the neurocranial height and index were 1.39 + or - + or - 0.04 cm and 41.74%, respectively. The mean whole skull length and height were 6.32 + or - 0.06 cm and 2.98 + or - 0.05 cm, respectively. The skull without the mandible was 1.83 + or - 0.02 cm in height, and the skull index was 28.41 + or - 0.58. The height of the skull of the African giant was approximately half (47%) of the skull length. The mean height and width of the foramen magnum were 0.78 + or - + or - 0.01 cm and 0.96 + or - 0.02 cm, respectively, while the foramen index was below 100 at 81.46 + or - 1.42. Parameters for the whole skull height and foramen magnum width showed significant difference between both sexes at p < 0.05. The foramen magnum showed shape variations and there were multiple hypoglossal foramina in over 87% of the rats. This study, in conclusion, highlighted the possibility of the estimation of the brain density and the use of the African giant rat for cranial pressure experiments.