Mus musculus More laboratory mice are used in research every yyear than any other animal species. Relatively inexpensive to purchase and maintain. Efficient breeders
Mice are used in a wide variety of research programs: genetics cancer infectious disease studies
400 documented inbred strains of mice. The different varieties are: identified by a series of letters and numbers. Some of the more common strains include: BALB/c C3H C57BL/6 DBA
Hybrids Two strains may be bred together to produce a mixture of the genes of each strain. designated by combining the letters and numbers C57BL/6 X C3H = B6C3F1 F1 first generation of this cross. F2 second generation.
Outbred mice: breed individuals not closely related: to bring together distantly related members of a species in order to breed genetically varied offspring Outbred mouse stocks are also used in research, including: CF1 ICR Swiss Webster (SW)
the technique of introducing the genetic material (DNA) from one animal into the fertilized egg of a different animal. Used to study the function of the various genes.
Involves the removal or blocking of a gene from the animal (as opposed to addition or knock-in ). Knockout animals are used to study the diseases associated with defective genes. I.E: Sickle cell anemia and cystic fibrosis are two human diseases identified as being caused by a defect in a specific gene
Method of correcting defective genes which have been implicated in causing disease Research involving gene therapy uses Research involving gene therapy uses transgenic animals as models of these diseases.
A naturally-occurring genetic defect that resulted in: An animal with no hair A deficiency in its immune system The genetic mutation causes a deteriorated or absent thymus gland, resulting in an inhibited immune system due to a greatly reduced number of T cells Should be housed in Sterile conditions due to this condition The nude mouse, and other mice with genetic deficiencies, has become very valuable in the study of immune diseases and cancer.
most common: In the dorsum scruff method, the mouse's back skin is grasped (scruffed). Your thumb and 2nd, 3rd, and 4th fingers hold the scruff. If you require the head to be fully immobilized, your grasp can include the ears and skin over the top of the head. In this method, the mouse is held by a continuous length of a skin fold.
Second method is the tail wrap method,,you transfer the tail from your thumb and forefinger to the 4th and 5th fingers of the same hand. These fingers press into your palm the mouse's s tail, close to the animal's rump. Then, your thumb and forefinger grasp a scruff of skin at the neck of the mouse. In this method, the mouse is hld held by two points: the scruff and the base of the tail. To further immobilize the hindquarters, you may gently entrap one leg along with the tail beneath your 5th finger. It is important to provide back support to the mouse and avoid hyperextension of its back.
For manipulations in which more restraint is necessary, the animal may be caught by the base of the tail, then the loose skin at the back of the neck is grasped close to the head. This restraint t technique causes no discomfort to the mouse and protects the handler. Initially, the animal is placed on a surface it can grasp, such as a cage top, while one hand is used to grasp the base of the tail. See Figure (a) below. The other hand is used to grasp the scruff of the neck.
To hold the mouse with one hand, restrain the neck area with one hand, while grasping the tail between the fourth and fifth fingers of the same hand. See Figure (b). If the skin is grasped too far from the head, the mouse will be able to turn and bite the handler. The mouse must be held firmly but gently, so it will not have difficulty breathing. This manipulation results in restraint that frees the technician s dominant hand for other functions while securely restricting ti the animal s movement.
Very young mice (or pups) less than 10 days old should be picked up by: Cupping the hands around the whole body; Grasping the skin across the shoulder blades with forceps; or Picking up a group of pups together with a g p g p p p g small amount of nesting material
Body temperature: 35.8 to 37.4 C (96.6 to 99.7 F) Heart rate: 328 780 per minute (Heart rate is too rapid to be measured by observation alone, but can be measured by electronic recording devices.) Respiration rate: 90 220 per minute (Respiration rate is too rapid to be measured by observation alone, but can be measured by electronic recording devices.) Weight: Adult 25 to 40 grams; newborn 1.0 gram Water consumption: 4 7 ml, or 1.5 ml per 10 grams of body weight, per day Food consumption: 3-6 grams, or 1.5 grams per 10 grams of body weight, per day Feces: Is firm, rice-sized, and dark brown. Food and water consumption influence the amount of feces produced. Abnormal feces are soft and discolored. Urine: Mouse urine has a strong odor and is clear and yellow. Mice urinate small amounts frequently. Life span: 1 to 3 years
Note the difference in the anogenital difference between the female (left) and the male (right)
The anogenital distance (the distance between the anus and genital papilla) of most rodents, including mice, is greater in the male than in the female. Gender determination in newborns is best done by comparing several animals at a time. In most adult rodents, the testes of the adult male are readily observed between the tail and the penis.
Two mating systems are commonly used for breeding mice: Monogamous pairing Polygamous, or harem, breeding (Multiple females per male) Males may be left continuously with the females or separated prior to parturition.
Female mice come into estrus,, or heat, every four to five days and within 24 hours after parturition (delivering pups). Estrus is characterized by a willingness of the female to mate.
Females are poly estrous. Polyestrous means that multiple estrous cycles occur in a mating season. Inbred strains typically have smaller litters than outbred stocks. Breeding mice and other rodents usually build nests if appropriate bedding is available
Postpartum estrus is the estrus that occurs after parturition. Due to postpartum p estrus, female mice frequently deliver their next litter just at the time of weaning of the previous litter. Attention must be given to separating weanling animals promptly to avoid overcrowding
Newborn young are pink, hairless and helpless. At birth their eyelids are sealed and their external ears are not yet fully developed. Shortly after birth healthy newborn mice (and rats) develop a distinct white spot that is visible through their transparent skin on the left side of the abdomen.
This milk spot is actually the stomach full of milk, and is a good indication that they are healthy and nursing in a normal fashion.
Other breeding data: Sexual maturity: 40 to 60 days of age Estrous cycle: 4 5 days; y;postpartum p estrus Gestation: 19 21 days Litter size: 6 12 Cannibalism: If possible, newborn litters should not be disturbed for several days to prevent the possible destruction of the litter by the adults dl Weaning: 21 days, but may be longer for large litters and some strains, e.g., transgenics
Early signs of stress or disease in mice are: Lack of grooming g behavior A dull haircoat Decreased activity Hunched posture
Mice may be housed in: hanging wire-bottom cages The grid size of wire-bottom cages should be large enough for feces to drop through but small enough to provide the animals with good footing. ldb h b ll Solid-bottom shoebox cages, generally in groups of five.
Wire-bottom cages are inappropriate for breeding Wire bottom cages are inappropriate for breeding pairs because nesting material may fall through the wire, the pups cannot be kept warm, and the sensitive skin of the pups may be injured by the wire.
Incisor (front) teeth of mice grow continuously. Occasionally, however, due to dietary, genetic, or anatomical causes, these teeth may become overgrown and interfere with the animal s ability to eat. The excess growth can be ti trimmed carefully with scissors to temporarily correct the problem.
The common laboratory rat, Rattus norvegicus,, was developed from the wild brown Norway rat. Today, there are a number of inbred strains and outbred stocks, although h outbred rats are used more commonly in laboratories. Nutrition and behavioral studies often employ rats as animal models. As in mice, rats can develop naturally- occurring diseases such as diabetes and hypertension (high blood pressure), which makes them valuable in the study of the same diseases which occur in humans.
Three stocks of outbred laboratory rats are commonly used in research: Wistar Sprague Dawley Long Evans
Wistar (WI). This albino rat was developed at Wistar (WI). This albino rat was developed at the Wistar Institute in Philadelphia. It has a relatively wide head and long ears. The tail is usually shorter than the body.
Sprague-Dawley (SD). Originally produced by Sprague Dawley (SD). Originally produced by Sprague-Dawley Farms in Madison, Wisconsin, this albino rat is faster growing than the Wistar rat. It has a longer, narrower head, and its tail is about the same length as its body.
This rat is smaller than either the Wistar or the Sprague-Dawley. Its white body fur is usually intermingled with patches of black, and its head is usually black. Because of the black "hood," this animal is sometimes known as the hooded rat. (See photo) http://www.youtube.com/watch?v=2qy2uxbstvo
Figure 1 Figure 2 Inbred rat strains are also available commercially. The Fisher 344 (F344)(see figure 1) and Lewis (LEW)(see figure 2) strains are two that are commonly used in research
Rats, like mice, may be picked up by the tail. However, care must be taken to hold the tail at the base (close to the rat s body). If the tail is grasped near the distal end (the tip), the tail skin may pull off, resulting in serious injury. This method of manipulation is used primarily il for brief periods of handling, such as when the cage is being changed.
A safer method for both the rat and the handler is to grasp the whole body of the rat. Initially, the rat may be caught by the base of the tail. Then one hand is placed over the animal s back, with the thumb and forefinger gently but firmly pressing its forelegs toward its head. If more control is needed, the tail or hindquarters may be restrained with the other hand. The rat must not be grasped so tightly around the thorax that its breathing is restricted.
Commercial plastic restraint devices, similar to those used for mice, are also useful for some procedures. Rats respond positively to gentle handling and become more relaxed the more they are handled. d
Body temperature: 35.9 9 37.5 5 C(96.6 99.5 5 F) Heart rate: 250 to 600 per minute. The respiratory and heart rate depend on the strain of rat and the surrounding environment. As with most animals, the respiratory and heart rate increase if the rat is excited itd Respiration rate: 66 144 per minute Weight: Adult male, 300 500 grams; adult female, 200 400 grams; newborn, 5 grams Water consumption: 24 60 ml per day, or 10 12 ml per 100 grams body weight daily Food consumption: 15 30 g per day, or 5 6 g per 100 grams body weight daily Feces: The feces should be a firm, dark brown, elongated mass with rounded ends Urine: The urine of the rat should be clear and yellow Urine: The urine of the rat should be clear and yellow Life span: 2.5 3.5 years
As with most rodents, the anogenital distance is about twice as great in the male as in the female. In adult male rats the testes protrude prominently from beneath the tail. Rats may be bred in monogamous pairs or polygamous (harem) systems. Females are polyestrous and have a postpartum estrus. They come into heat and are receptive to males within 24 hours of parturition. The young, like mice, are born pink-skinned, hairless, and helpless.
Other breeding data: Sexual maturity: 65 110 days Estrous cycle: 4 5 days Gestation: 20 22 days Litter size: 7 11 Cannibalism: Usually the female rat does not cannibalize her young unless they are unhealthy Weaning: 21 days
Rats normally sit on all four limbs on the cage floor. An early sign of poor health is a rat that sits hunched over. Healthy rats keep themselves groomed and clean. Like most other laboratory rodents, rats are nocturnal creatures. Unlike male mice, group housed male rats rarely fight. Female rats are also usually docile in group housing situations.
The tears and saliva of rats contain a substance called porphyrin. This material appears red or reddish- brown in color, and sometimes can be seen around the eyes and on the end of the nose. It is especially noticeable on white animals. In older animals, all of the fur may appear reddish in color due to the animal licking itself while grooming. Excessive accumulation of porphyrin around the eyes, nose or on the front legs can be a sign of illness and should be reported to a supervisor.
Rats are much stronger than mice. They are capable of knocking off unsecured cage lids and escaping. To prevent this, the tops of all cages housing rats must be secured.
Rats may be housed in shoebox cages that contain a suitable direct contact bedding. Both single and group housing systems are used. Rats as well as most other rodents can also be housed in suspended d wire-bottom cages.
Rat shoebox cages should be changed once or twice a week depending on the number of animals housed in a cage. Shelving and cage racks should be sanitized at least once every two weeks, and drop pans must be cleaned at least twice weekly.
Like all rodents, the front (incisor) teeth of the rat grow continuously throughout life. The constant gnawing gthe rat does while eating hard pellets usually keeps the teeth worn down to a normal size.
Sometimes, however, the teeth may become overgrown and interfere with the animal s ability to eat. This is a common problem in rodents and rabbits and one that the technician must learn to recognize when it occurs. Sometimes the teeth th can be seen protruding from the mouth and other times the rat may just show signs of decreased food intake and loss of weight
Clipping off the extra length with scissors or Clipping off the extra length with scissors or small wire cutters cures the problem temporarily.
1)What advantage/s do shoebox cages offer in the husbandry of mice? a)the bedding in shoebox cages provides the mice with security. b)the bedding in shoebox cages provides the mice with warmth. c)the bedding in shoebox cages is beneficial for breeding. d) All of the above e) None of the above
2)What is the name for the behavior when a behaviorally dominant mouse chews fur off a more subordinate mouse. a)grooming b) Fighting c) Trimming d) Barbering e) None of the above
3) How often should solid-bottom rodent cages and accessories be washed? a)once a month b)when odors are detectable c) every day d)one to three times a week e) at least
4)The proper method for picking up a mouse is. a)grasp the tail near the base, using smooth-tipped forceps b) grasp the tail near the base, using your thumb and forefinger fi c)grasp the mouse by the skin on the back of the neck using a smooth-tipped tipped forceps d) All of the above
5)Which stock of rat is also known as the hooded rat? a)lewis b)fisher 344 c)long Evans d) Wistar
6)The front teeth of rats grow throughout their lives and are called. a)molars b) incisors c) bicuspids d) cuspids
7) True or False: The anogenital distance is twice as great in The anogenital distance is twice as great in females as in male rats
8) Scientific name for a laboratory mouse is: a) canis familares b)felis cattus c) mus musculus d) rattus norviegicus i
9) Some early signs of stress or disease in mice are: a)lack of grooming behavior b) A dull haircoat c)decreased activity d)hunched posture e) )All of the above
10) Nude mice should be housed in: a) Sterile Housing b) Barrier Housing c) Conventional Housing
11) Malocclusion is a condition defined as : a) rings on the tail b) dominance of another mouse c) over grown teeth d) none of the above
12) Scientific name for a laboratory rat is: a) sus scrofa domestica b) cavia porcellus c) mesocricetus auratus d) rattus norviegicus
13) What is the distinct white spot in newborn mice called? a) white pouch b) food c) milk spot
14) Outbred mice are: a) Two strains bred together to produce a mixture of the genes of each strain. b)breeding individuals id not closely l related c) introducing the genetic material (DNA) from one c) introducing the genetic material (DNA) from one animal into the fertilized egg of a different animal.
15) True or False: Rats are much stronger than mice