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 The Syrian Hamster A. Scientific name Syrian hamster= Mesocricetus auratus, chromosome # 2N=44
 Chinese hamster= Cricetulus griseus, chromosome # 2N=22
 European hamster= Cricetulus Cricetulus, chromosome # 2N=22 
          History Unlike most other laboratory rodents. the origin of current research hamsters is precisely known. Dr. Aharoni of the Hebrew University in Jerusalem collected a litter of 8 in Syria in 1930. One male and 2 females survived and were bred in the laboratory. Quickly became an important model for the study of  human visceral leishmaniasis, caused by L. donovani. Hamsters were eventually shipped to the U.S. during  WWII. 
          Biology: See attached data sheetHighlights cheek pouches - highly distensible, extend posteriorly from the cheek to the scapulae, - thin walled, well vasculized, and markedly deficient in  lymphatic vessels. - used for food storage - immunologically privileged sites for research use Flank gland (Hip gland) - prominent in male, darkly  pigmented in adult male - composed of sebaceous gland, terminal hair and pigment cells - usually covered by haircoat - secrete pheromones, used to mark out territory and contribute to the stimuli determining mating behavior. Brown adipose tissue: - mainly located between the scapulae. - the main function is to heat the blood passing through it - important for hibernation Stomach Forestomach:function similar to the rumen, the site of some pregastric fermentation. 
        Adrenal gland: male is bigger than female Spleen: male is smaller than female (in contrast to mice) Harderian gland: present, like rat  Uterus: duplex, each uterine horn having a cervix  which communicates directly with the vagina Teeth - 2(I 1/1, C 0/0, P 0/0, M 3/3)=16 - molar:fixed roots - incisor: open-rooted Colon and kidney - very long colon and long renal  papilla, function in water conservation. - hamsters are desert animals and excrete very thick concentrated urine.  pancreas: diffuse, like rat  Reproduction Highlights Mating  female is more aggressive than male, the female is always introduced into the males cage to prevent territorial defensive aggressive behavior by the  female. 
        mature female ovulates every 4 days, usually around midnight to 1 A.M.after a period of heat. Hand mating should be performed on the 3rd evening after the appearance of post-ovulatory mucus plug. sequential monogamy mating: a series of 7 females  is rotated. group mating: 10 to 12 females with 3 to 5 males, careful of fighting. - monogamous pairmating:place a prepubertal female and male  together permanently.  Pregnancy confirmed by the absence of the post-ovulatory plug on days 5 and 9 after breeding. short gestation (16 days) (Chinese hamster: 21 days) pseudopregnancy may occur on nonsuccessful 
breeding. Maternity care neonate hamsters are very immature, and require nest.  cannibalism is common during the first pregnancy and the first week post-partum.  Do'nt bother mother and babies between 2 days  before and 10 days after birth. 
fostering is rarely successful. Post-partum estrus: female is reported to have post-partum estrus, but ovulation does not occur. Caging Conventional cages are most commonly used, either solid bottom or wire. Space requirement -19 square inches for adults over 100 gm in body weight. 
        Males may be housed together, but females will fight  if housed together after 2 months of age.  Hamster are escape artists- be sure lids are secure. Environment Hamsters are nocturnal. If environmental temperature falls below 480 F hamsters will hibernate, with a resulting decrease  in their basal metabolic rate, body temperature,  heart and respiration rate. 

       Nutrition  Hamsters have been maintained very well by feeding commercial rodent diets.  Eat about 12 g, drink 10 ml water per 100 g body weight daily.  Hamsters are also coprophagic, like Guinea pig and rabbit.  Handling Hamsters may be very aggressive, especially females.   Hamsters will often bite if startled or are not used to handling. May pick up animals by: Grasp over head and shoulders Grasping skin over the back Using containers to pick up and transport Leather gloves are handy to have around Laboratory Procedures  Injections Intravenous (IV) - femoral vein cephalic vein saphenous vein Intraperitoneal (IP) Subcutaneous (SQ) skin over neck Intramuscular (IM)- caudolateral thigh muscles  Blood collection tail tip orbital plexus  (anesthetize) cardiac puncture (anesthetize)  Pharmacology  Hamsters are very resistant to morphine; reduced 
response to histamine (anaphylactic shock); sensitive to corticorsteroid. Antibiotic toxicity like rodent and rabbits. Avoid  or limit the duration of penicillin, tetracycline, erythromycin, and lincomycin.  Important Characteristics Relating To MajorResearch UsesCheek pouches-thin membranes that can be completely everted and exteriorized for study: a. Vascular 
research- blood vessels in the cheek pouch are readily visualized after the pouches are everted. b. Tumor growth studies- the cheek pouch has no lymphatic drainage and is termed "immunologically  privileged." Thus, iso-, allo-, and xenogeneic tumors will grow on the cheek pouch. Tumors  implanted in the cheek pouch can be readily  observed.  Predictable, regular female reproductive cycle:  Reproductive physiology and endocrinology-the female  reproductive cycle and hormone fluctuations have  been closely studied. The short 4 day cycling time is useful. and metabolic regulation studies. b.  Hypothermia studies. Susceptibility to oncogenic viruses in neonatal  hamsters: Experimental infections with human adenoviruses, SV-40, polyomavirus, and others often result in viral-induced tumors. Consequently, many  viral oncogenesis studies are performed in hamsters.

     Susceptibility to infectious agents: hamsters have been used in studies of many bacterial infections. (salmonella, M. leprae, others). Also sensitive to  experimental-induced infection diseases such as leptospirosis, influenza and canine distemper. 
     Dental caries studies: hamsters have been used in  experiments in dental caries production. Diet # 2000 can establish Streptococcus mutant in hamster and  produce caries. Diabetes mellitus: Spontaneous diabetes mellitus in Chinese hamster.  hyperglyceridemia:cardiomyopathy: BIO 14.6 hamster Brief Summaries of Diseases  Lymphocytic Choriomeningitis Virus-LCM virus is an arenavirus with zoonotic potential. Human outbreaks associated with infected hamster are well known. In humans, LCM usually produces flu like symptoms. However, infections can be fatal. Nearly all neonates and about half of young adults develop  persistent viremia and systemic lesions. large amounts of virus are shed in the urine. Screening  tests are available. Infected colonies should be destroyed, The incidence of LCM in pet shop hamsters  is unknown. Proliferative Ileitis-Known commonly as "wet tail". One of the more common diseases of hamsters. Diarrhea is the primary clinicalsign. Mortality in  weanlings and young can be high. Mucosal hyperplasia and/or hemorrhagic necrosis of the ileum is common. The prevalence of the disease in hamster colonies is unknown because screening tests are not available.  There is no effective treatment, but tetracycline  therapy has been reported to reduce mortality associated with epizootic. The etiology is unknown, but Campylobactera fetus subspecies jejuni has been isolated from animals in a number of epizootic. 
               Experimental campylobacter infections have not  transmitted by feeding ground ileal tissue from affected hamsters, so an infectious etiology is strongly suspected. Lymphomas Due to a Viroid (non-encapsulated naked  DNA):A highly unusual horizontally transmitted  mammalian viroid causes epizootic of ;lymphomas.  50-90% of infected young develop lymphomas. Clinical signs include emaciation, lethargy, diarrhea, rectal and abdominal hemorrhages, and SQ lumps. Also seen  in infected animals are non-bacterial enteritis, intussusception, pyelonephritis, several hepatic lesions, and warts due to an enzootic  papillomavirus. No treatment, no diagnostic tests available. Prevalence unknown.  Antibiotic-Induced Diarrhea:A number of antibiotics (tetracycline, penicillin, erythromycin, vancomycin, clindamycin) may cause gram negative overgrowth in 
 the gut. Other antibiotica can lead to overgrowth of  gram positive clostridial difficile that elaborate toxins. High morbidity and mortality can occur due  to toxemia. 5). A age related diseases include amyloidosis, chronic nephropathy(high protein diets 
increase the severity), and polycystic disease.