The Syrian Golden Hamster Estrous Cycle: Unique Characteristics, Visual Guide to Staging, and Comparison with the Rat

Role of animal models in biomedical research: a review

The animal model deals with the species other than the human, as it can imitate the disease progression, its’ diagnosis as well as a treatment similar to human. Discovery of a drug and/or component, equipment, their toxicological studies, dose, side effects are in vivo studied for future use in humans considering its’ ethical issues. Here lies the importance of the animal model for its enormous use in biomedical research. Animal models have many facets that mimic various disease conditions in humans like systemic autoimmune diseases, rheumatoid arthritis, epilepsy, Alzheimer’s disease, cardiovascular diseases, Atherosclerosis, diabetes, etc., and many more. Besides, the model has tremendous importance in drug development, development of medical devices, tissue engineering, wound healing, and bone and cartilage regeneration studies, as a model in vascular surgeries as well as the model for vertebral disc regeneration surgery. Though, all the models have some advantages as well as challenges, but, present review has emphasized the importance of various small and large animal models in pharmaceutical drug development, transgenic animal models, models for medical device developments, studies for various human diseases, bone and cartilage regeneration model, diabetic and burn wound model as well as surgical models like vascular surgeries and surgeries for intervertebral disc degeneration considering all the ethical issues of that specific animal model. Despite, the process of using the animal model has facilitated researchers to carry out the researches that would have been impossible to accomplish in human considering the ethical prohibitions.

Ultrasonographic and macroscopic study of pregnancy in golden hamster

Background

Hamster is widely used as an experimental model in the study of reproductive system. However, pregnancy diagnosis and aging always have been a challenge. ultrasonography have been used in diagnosis of pregnancy in some small laboratory animals, such as rabbits, rats, and mice. Current study describes use of trans-abdominal ultrasonography for pregnancy diagnosis and fetal age estimation in golden hamster. Furthermore, a macroscopic examination was performed to evaluate the embryonic vesicle diameter, crown-rump length, and fetal head diameter. Ten adult female golden hamsters were selected and maintained under controlled light conditions (14 h light/10 h darkness). The estrous cycle was synchronized using eCG and hCG. During estrous (18 h after hCG injection), the hamsters were naturally mated. After seven days of mating, the hamsters were examined daily for pregnancy diagnosis and aging with an ultrasound scanner equipped with an 8.5-MHZ linear probe. On each day of the experiment, at least one of the pregnant hamsters was euthanized and dissected for macroscopic fetal measurements using a digital caliper.

Results

The gestational sac and crown-rump length were identified and measured by ultrasonographicly on day 7 of pregnancy and head could be visible after day 10 of gestation. Statistical analysis revealed that the ultrasound estimation of gestational age was significantly correlated with the actual age of the fetus (r = 0.98; p < 0.05).

Conclusions

Real-time ultrasound can be used for the diagnosis of pregnancy and estimation of fetal age in golden hamster from day 7 of gestation.

Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits

Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.

Histomorphological and Histochemical Investigation of The Vagina of Adult Guinea Pigs (Cavia porcellus)

This study was carried out to identify the morphological, histological and histochemical features of the vagina of the adult guinea pig (Cavia porcellus). To perform such project, 14 adult guinea pigs at their diestrous period were bought from the local breeders directly. Animals were euthanized, dissected and subsequently specimens from the cranial, middle and caudal portions of the vagina were collected and fixed. Fixation was implemented by using 10% neutral buffered formalin and Bouin’s solution. Post routine processing such as dehydration, clearing, embedding and blocks preparation, tissue sections of 6 μm were prepared and stained by using hematoxylin-eosin, Masson’s Trichrome, Alcian blue and Periodic acid shiff stains. Gross findings revealed that the vagina in the adult guinea pigs was characteristically very long tube-like structure with wide diameter. The vagina entirely was running ventral to the colon and then under the rectum in the pelvic cavity. It was terminated caudally by the vaginal orifice independent to the urethral orifice of the urinary system. Microscopic findings revealed mucous columnar lining epithelium which was folded at the vaginal fornix decreased caudally toward the external vaginal orifice where the epithelium changed into stratified squamous epithelium not keratinized. Thin dense lamina propria was continuous with loose connective tissue of the submucosa. Thickness of tunica muscularis was decreased which was surrounded with thick adventitia. Histochemically, the non-ciliated mucous columnar cells present in the lining epithelium of the cranial and middle regions of the vagina were positively stained with AB (pH 2.5) and PAS stains. The reaction with AB (pH 2.5) was more intense compared to the staining with PAS so that it indicated that mucin was more acidic than neutral in nature. Characteristic conclusions include that the vagina opening was U-shaped not circular and closed by transparent closure during the diestrous period. Histologically, the vagina also lined with mucoid lining and only the orifice and adjacent area lined with stratified squamous epithelium. Moreover, current study recorded differences in both macroscopic and microscopic aspects of the vagina in the guinea pigs compared to other animal considered laboratory species.