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 &#177; 0.05 mL, neurocranial length was 3.33 &#177; 0.08 cm, and the neurocranial height and index were 1.39 &#177; &#177; 0.04 cm and 41.74%, respectively. The mean whole skull length and height were 6.32 &#177; 0.06 cm and 2.98 &#177; 0.05 cm, respectively. The skull without the mandible was 1.83 &#177; 0.02 cm in height, and the skull index was 28.41 &#177; 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 &#177; &#177; 0.01 cm and 0.96 &#177; 0.02 cm, respectively, while the foramen index was below 100 at 81.46 &#177; 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

Intestinal intussusception due to concurrent infections with Hymenolepis nana and Dentostomella translucida in an African giant rat (cricetomys gambianus). A case report

A rare case of intestinal intussusception due to multiple worm infections (Hymenolepis nana and Dentostomella translucida) was observed in an African giant rat (Cricetomys gambianus, Waterhouse, 1840). The condition was observed as an incidental finding before an experimental dissection of the animals in the Department of Veterinary Anatomy, University of Agriculture Abeokuta, Nigeria. The rat was anorexic and depressed with rough hair coat, and died before the commencement of the experiment. Grossly, the intussusception was 7 cm in length and 27 cm caudal to the stomach and 81cm to the ileo-caecal junction. The affected part of the small intestine was moderately distended with worms and the associated mesenteric blood vessels were engorged. Microscopically, worms (H. nana and D. translucida) were observed in the lumen of the intestine with severe cellular infiltration mostly eosinophils, neutrophils and macrophages. Eggs of both worms, at different stages of development and a focus of attachment of the worms were observed on the intestinal mucosa. The zoonotic implications of these worms were discussed especially H. nana. This report appears to be the first reported case of intestinal intussusception due to multiple helminth infections in an African giant rat. KEYWORDS: Hymenolepis nana, Dentostomella translucida, Intestinal intussusception, African giant rat

Processing rodent brain tissues: review of basic anatomical techniques for scientists with minimal knowledge of neuroanatomy

An understanding of brain structure, how to harvest rodent brain samples and the various histological procedures to follow is imperative in conducting researches in neuroscience especially for beginners. The general brain aversion bias and complexity of studying the brain, poses a real challenge in identifying and understanding its anatomy either grossly or microscopically. Therefore, this review attempts to provide a basic explanation for researchers with little knowledge of neuroanatomy but are interested in processing brain tissues ranging from opening the skull of the rodents, harvesting freshly perfused or unperfused brain, weighing of the brain and identifying various landmarks on the brainstem, cerebellum, and cerebrum. This review further provides a clue to the various anatomical landmarks in the brain and the functional role each structure identified in such landmarks play. Since most of the brain cytoarchitecture is viewed microscopically, knowing the appropriate staining techniques that clearly show the desired brain cell or region in question is important in determining various neuropathologies as well as in conducting various pilot studies on the brain. This review therefore provides a solid foundation for researchers who are not too familiar with the brain but need to conduct various studies on it.Keywords: brain, histological procedures, anatomical landmarks, staining techniques, cytoarchitecture, fixatio

An anatomical perspective: does the male greater cane rat (Thryonomys swinderianus) have a scrotum?

We evaluated the anatomy of the “scrotal” skin pouch in an attempt to answer the question of whether (or not) there exist true scrotum in the greater cane rat (Thryonomys swinderianus). The “scrotal” skin folds from ten (10) matured male cane rats were morphologically and morphometrically studied with samples routinely processed for histology. Grossly, the pouch has features like fine hair on thin skin and longitudinal raphae typical of scrotum in other species. The histoarchitecture of the “scrotal” skin in the cane rat follows the normal scrotal pattern and the arrangements of the cutaneous strata, hair follicles and glands were similar in animals with perineal staining and those without perineal stain. The cane rat scrotal skin, though different in conformation from the scrotum of other mammalian species, has all the properties of a true scrotum thereby establishing the presence of scrotum in the greater cane rat.Keywords: Scrotum, Greater cane rat, Skin Pouch, Perineal stainin

Cytoarchitecture of the hippocampal formation in the African giant rat (Cricetomys gambianus, Waterhouse)

Summary: 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&lt;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.Keywords: African giant rat, brain, cornu ammonis, dentate gyrus, hippocampus, histolog

A review of the anatomy of the reproductive organs of the female African giant rat (Cricetomys gambianus, Waterhouse)

This review discusses the state of knowledge of the anatomy of the female African giant rat (Cricetomys gambianus, Waterhouse) reproductive organs with the aim of highlighting various anatomical characterizations and discoveries that have accumulated in the past five decades. Four vaginal mid-smear stages and three intermediate smear stages: late diestrus/early pro-oestrus, late pro-oestrus/early oestrus and late metestrus/early diestrus were reported. The nodular ovaries lie close to irregular coils of the oviducts which lack a distinct border between the ampulla and isthmus. The uterus has two horns and two partially fused cervices, separated by a mid-sagittal septum. Two pairs each, of inguinal and thoracic mammary glands are described. Unique features of the histology include follicles at late proestrus/early diestrus and mid oestrus stages with variably shaped mitochondria, profiles of Golgi complexes and dense concentrations of ribosomes. The theca interna shared similar ultrastructure with the granulosa cells containing in addition, lipid droplets and smooth endoplasmic reticulum. The vaginal basal lamina is highly convoluted during proestrus and oestrus while the epithelium displayed short microvilli at mid proestrus, cornification at late proestrus/early estrus, and desquamation at mid oestrus. Cervical epithelium varied between stratified cuboidal and stratified columnar without glands. Intraepithelial lymphocytes were observed along the vaginal epithelium. The evaluated cyclic patterns of the serum concentrations of FSH, LH, prolactin, estrogen and progesterone showed that the varying histological and ultrastructural features of the ovary at different stages of the oestrous cycle were dependent on these sex hormones. It is therefore recommended that, further investigations should be conducted to formulate colony breeding strategies