Ultrastructural Studies of Acrosomal Formation in the Testis of Male Greater Cane Rat (Thryonomys swinderianus)

Purpose:

In furthering the understanding of the process of spermatogenesis in the greater cane rat, this study describes the ultrastructural spermiogenic transformation and acrosomal formation in the testes of this hystricomorphic rodent that is currently undergoing domestication in parts of West Africa.

Materials and Methods:

Testicular samples were obtained from ten sexually mature cane rats that were perfused-fixed using Karnovsky's fixative (phosphate buffered 2% paraformaldehyde – 2.5% glutaraldehyde fixative at pH 7.4). The samples were processed for ultrastructural analysis and examined under the transmission electron microscope.

Results:

The testes of the cane rat showed uniqueness in its cellular associations and the ultrastructure of the spermatogenic cells especially in the formation of the acrosome. The spermatid differentiation and acrosomal formation occurred in 12 steps with the first three steps being the Golgi phase and the next three steps making up the cap phase. While the three steps that follow constitute the acrosomal phase, the last 3 steps make up the maturation phase. At the cap and acrosomal phases, the entire acrosomal system comprising the vesicle and granule covers the head of the spermatids with no clear indentation of the nuclear surface by the formed acrosome. Furthermore, elongated spermatids at the maturation phase contained abundance of nuclear vacuoles.

Conclusion:

This work has not only provided information that will further the understanding of spermatogenesis but also aid the understanding of acrosomal reaction in the reproduction of the greater cane rat.

Immunolocalization And Distribution Pattern of Estrogen (ERα and ERβ) and Progesterone (PR) Receptors along the Excurrent Duct of Male Greater Cane Rat (Thryonomys swinderianus)

The excurrent duct, which plays vital roles in the reproductive biology of all male mammals, shows some structural variations among different species. Some hormones such as testosterone, estrogen and progesterone, through their different receptors, have been known to be involved in the normal functioning of the excurrent duct. Here we evaluated the presence, localization and patterns of distribution of three hormone receptors, estrogen alpha (ERα), estrogen beta (ERβ) receptors and progesterone receptors (PR) along the excurrent duct of sexually matured male greater cane rats. Immunohistochemistry revealed presence of ERα in epididymal stroma but not epithelium, selective ERβ staining in narrow & apical cells as well as unique presence of PR in caudal epididymis, which to the best of our knowledge, is the first report on the cellular localization of progesterone receptor in the cauda epididymis. The result suggests the possible involvement of not only estrogen but also progesterone in the modulation of epididymal function in greater cane rat.

Influence of Tramadol on Anaesthetic Indices and Physiological Parameters of Epidural Lignocaine in West African Dwarf Sheep Undergoing Laparo-Ovariectomy

The influence of tramadol on the anaesthetic indices and physiological parameters of epidural injection of lignocaine was evaluated in West African Dwarf (WAD) sheep undergoing laparo-ovariectomy. Ten female sheep weighing (16.2 ± 1.3 kg) were randomly allocated into anaesthesia with epidural injection of lignocaine (4mg/kg) (LIG), or lignocaine (2mg/kg) and tramadol (2mg/kg) (LIG-TRA). Following anaesthesia, they were aseptically prepared and subjected to laparo-ovariectomy. Behavioural changes were noted as they occur, and onset of drug action (OAN) (time between epidural injection and loss of pedal reflex), duration of analgesia (DAN) (time between disappearance and reappearance of pedal reflex) were determined. Also, duration of recumbency (DRC) (time between loss of righting reflex and returns to sternal recumbency) and recovery time (RCT) (time between re-appearance of pedal reflex and when the animal was able to stand without ataxia) were determined. Rectal temperatures (RT), respiratory rates (RR) and heart rates (HR) were determined every ten minutes for two hours. Results were expressed as mean ± standard error of mean. Anaesthetic indices were compared with Student's t-test, while physiological parameters were compared with analysis of variance (ANOVA) for repeated measures. In this study, one sheep anaesthetized with LIG-TRA had bloat while none in sheep anaesthetized with LIG had bloat. The OAN was significantly (p < 0.05) shorter in LIG-TRA (1.4 ± 0.5 mins) than with LIG (4.4 ± 2.8 mins). Although DAN and DRC were longer in LIG-TRA (133 ± 19.5 mins, 192.6 ± 43.6 mins) than LIG (119.4 ± 52.5 mins; 166.2 ± 30.6 mins) respectively, values were not statistically significant (p = 0.863). In addition, RCT was longer in LIG-TRA (56.0 ± 48.6 mins) than LIG (34.0 ± 20.6 mins). The RT, RR and HR did not differ significantly (p > 0.05) between LIG-TRA and LIG, and as well as throughout the duration of study. It was therefore concluded that tramadol did not appear to improve the anaesthetic indices of epidural lignocaine injection in sheep but increased the duration of recumbency with the tendency to cause bloat.

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.

Anatomical and immunohistochemical characteristics of the prostate gland in the greater cane rat (Thryonomys swinderianus)

This study examined the morphology and immunohistochemical features of the prostate gland in 15 captive-reared male greater cane rat of known reproductive and medical history. Samples of the glands were taken after gross examination and routinely prepared for both histological and ultrastructural analysis. Immunohistochemistry was also carried out on paraffin-embedded sections of the glands using rabbit polyclonal antibodies against oestrogen receptors (ERα and ERβ) and mouse monoclonal antibody for the progesterone receptor (PR). The prostate, which constitutes 0.04% of the body weight, was a paired, lobulated, brownish gland having three left and four right lobes that partly cover the pelvic urethra. Based on the amount and arrangement of the secretory epithelial folding and relative to their distances to the urethra, two histological zones, the central and peripheral, were identified. However, the epithelium of both zones was lined by predominantly simple cuboidal cells with occasional basal cells. The main ultrastructural features of these cuboidal cells were the presence of several nuclear pores on the nucleus, moderately well-developed, short microvilli and bleb-like apical projections, as well as inter-cellular lacunae seen between these cells and the basal cells. The cuboidal epithelial cells also showed positive nuclear staining for ERα and ERβ but not for PR. It is however interesting that the ERα-positive staining was more at the epithelial cells, which is uncommon. These findings highlight the peculiarities in the structure and ultrastructure as well as the unique expression of the oestrogen receptors in the prostate gland of the greater cane rat.

The structure of the penis with the associated baculum in the male greater cane rat (Thryonomys swinderianus)

In this study, the structures of penises of eight sexually mature male greater cane rats were examined at both macroscopic and histological levels. Each animal was sacrificed after anaesthesia with ether and then dissected open with the penis exposed from its root. The penises were first grossly examined, measured, and then prepared for histological examination. From this study it was observed that the body size has no allometry with penile size, but the testicular weight correlated with Os penis length in the greater cane rat. Grossly, the penis which was whitish in colour, with a mean length of 5.46 ± 0.36 cm, has no obvious collum penis but a flexura that turns it caudo-ventral and separates the corpus and glans penis. There was the presence of cornified papillae covering parts of the corpus and glans penis as well as a blind sac sacculus urethralis under the urethra on the glans penis. Histologically, the corpora cavernosa penis were completely separated by a connective tissue septum which sent the trabeculae network into the cavernous tissues and replaced the caverns as it moves from corpus to glans penis. The Os penis formed through endochondral ossification after 42 months of age in this animal. Therefore, from a histological standpoint, the cane rat penis belongs to the intermediate type. In conclusion, these findings provide vital information on the penile anatomy of the greater cane rat, which will serve as a basis for comparing penile morphology among the suborder hystricomorpha and expand knowledge of the reproductive biology in this animal.

The immunohistochemical localization of desmin and smooth muscle actin in the ovary of the African giant rat (Cricetomys gambianus) during the oestrous cycle

The aim of this study was to describe the distribution of smooth muscle actin and desmin immunopositive cells in the ovary of the giant rat. In addition, the study describes the morphological changes in the ovary of this species during the oestrous cycle. Healthy secondary and tertiary follicles dominated the ovary during pro-oestrus and oestrus. The theca externa of the tertiary follicles was immunopositive for smooth muscle actin, but immunonegative for desmin. Oestrus was also characterized by the presence of corpora haemorrhagica, which had an outer layer of smooth muscle actin immunopositive cells. Differentiating corpora lutea were observed during metoestrus. A further notable feature of the ovary during metoestrus was the presence of numerous atretic secondary and tertiary follicles. In the later stages of atresia, the follicles were infiltrated by desmin and smooth muscle actin immunopositive cells. Dioestrus was characterized by the presence of non-regressing and regressing corpora lutea. Immunostaining for smooth muscle actin was demonstrated in the enclosing layer of the corpora lutea, as well as in the tunica media of blood vessels within the corpora lutea. The results of this study have shown that morphological changes in the ovary of the giant rat during the oestrus cycle are similar to those of laboratory rodents. Furthermore, the results of the immunohistochemical study indicate that the perifollicular distribution of desmin and smooth muscle actin cells changes during follicular development and atresia.

Morphometric and histopathological studies on the effects of some chromatographic fractions of Phyllanthus amarus and Euphorbia hirta on the male reproductive organs of rats

The aqueous crude extracts of P. amarus and E. hirta were administered to thirty eight-week old sexually mature male albino to determine the effects of these extracts on the male reproductive organs of these animals. The results from this study revealed that the aqueous crude extracts of P. amarus and E. hirta caused varying degrees of testicular degeneration as well as reduction in the mean seminiferous tubular diameter (STD) in the treated rats. It thus shows that the aqueous crude extracts of P. amarus and E. hirta have potentially deleterious effects on the testes and accessory organs of rats. Great caution should therefore be exercised in the use of these plants for medicinal purpose.