Clinical Problem Solving Exercise: Neuromuscular weakness in a baboon. Laboratory Animal Science 49(4), 349.
Abstract: This is a thoroughly worked up and detailed case report of a 7 year-old, female baboon, initially presenting with mild lameness of the left hindlimb and progressing to include lateral recumbancy, vocalizing, guarding behavior of abdomen and head, anorexia, and photophobia. Successful clinical management of this iatrogenic brain abcess relied on appropriate and aggressive antimicrobial therapy, numerous diagnostic test and consults with specialists, surgical drainage of brain abscess on two separate occasions (Staphylococcus aureus cultured in both instances), and intensive handfeeding.
Refer to Table 1 for an overview of the clinical course timeline and Figure 4 for an algorithm for the treatment of human patients with multiple brain abscesses used by the authors.
Summary:
- Normally the brain is resistant to bacterial and fungal infections due to abundant blood supply and blood-brain barrier (BBB)
- BBB is composed of endotheilal cells of the CNS joined by tight junctions without a fenestrated cytoplasm, supported by astrocytic foot processes forming a lipoprotein barrier.
- 5 areas determined to need improvement to decrease the chances of future iatrogenic brain abcessation:
1. Use sterile bone cement rather than acrylic cement
2. For substances not prepared as pharmaceutical-grade which need to be given as injectables, use only freshly prepared solutions which have been filtered with a 0.22-u filter prior to administration
3. Use steam or gas autoclaving for equipment rather than cold sterilization
4. Mandatory viewing of tapes on aseptic surgical techniques and adherence to those principles
5. Routine inspection and cleaning of wound margins at least once a week with a 3 to 10% solution of povidone iodine
- BBB and structure of the abscess itself influence the choice of antibiotics for the treatment of brain abscesses.
- Intact or normal BBB allow penetration of lipophilic material into CNS readily (hydrohilic material penetrate poorly)
- With meningial inflammation, tight junctions open up and allow hydrophilic material to enter CNS
- Chloramphenicol, metronidazole, the quinolones, trimethoprim-sulfmethoxizole and 3rd generation cephalosporins penetrate the BBB readily.
- Beta-lactam and aminoglycoside antibiotics, vancomycin and 1st generation cephalosporins have poor CNS penetration.
- Brain abcesses traditionally require 6 to 8 weeks of antimicrobial treatment.
Questions: Questions:
1. What are 4 rule outs for the hypertense, white, cystic lesions observed on MRI in this case ?
2. What are two most common pathogenic organisms that can be found in brain abscesses?
3. T/F. During the cerebritis phase of a brain abscess, such an abscess can be treated with antibiotic therapy alone.
4. T/F. Normal BBB allows hydrophilic substances to penetrate the CNS readily
Answers: Answers:
1. Brain abcesses, neoplasms, cerebral infarctions, resolving hematomas
2. Anaerobes and gram-positive aerobic cocci
3. True. This period is 1 to 9 days post-inoculation of organisms into the brain parenchyma and since they are not emcapsulated, antibiotic therapy is more likely to provide adequate therapy without surgical drainage.
4. F. Lipophilic material penetrate readily into the CNS

Neurons and mechanisms of neuronal death in neurodegenerative diseases: a brief review. Laboratory Animal Science 49(4), 358.
Abstract: This article summarizes basic information about the anatomy of the CNS, characterizes normal and degenerating neurons, and provides a basic overview of representative human neurodegenerative diseases. Diagrams of neuron anatomy, including a synaptic junction and a proposed general pathway of neuronal apoptosis are illustrated.
Specific neurodegenerative diseases that lead to loss of specific neuronal populations and neuronal processes are: Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, amyotrophic lateral sclerosis, and peripheral neuropathies. Loss of synapses is associated with Alzheimer's Disease. Atrophy and loss of dopaminergic neurons in the substantia nigra and basal ganglia results in Parkinson's Disease. GABA spiny neurons, located in basal ganglia, are affected in Huntington's Disease. Amyotrophic lateral sclerosis affects the upper motor neurons of the motor cortex of the brain and the lower motor neurons of the brainstem nuclei and spinal cord. Most peripheral neuropathies result in changes of the neuronal processes. PNS disorders can result from genetic alterations or from metabolic, infectious, inflammatory, or chemical insults. Studies of animal models of these human diseases have provided insights into the pathogenesis of these disorders, as well as led to effective therapies for treatment of these disorders.
Questions: QUESTIONS
1. Which are componenets of white matter in the CNS?
a. astrocytes d. oligodendrocytes
b. neurons e. all of the above
c. myelinated nerve fibers f. all of the above, except b
2. List some neurotransmitters.
3. Which are features of apoptotic cells?
a. cellular swelling e. condensation of nuclear chromatin
b. cell lysis f. DNA fragmentation
c. shrinkage of cell cytoplasm g. all of the above
d. plasma membrane blebbing h. c,d,e,f,
4. Which disease is characterized by being autosomal dominant with signs of emotional disturbances, chorea, and dementia?
a. Alzheimer's Disease d. Parkinson's Disease
b. Amyotrophic lateral sclerosis e. none of the above
c. Huntington's Disease
Answers: ANSWERS
1. f
2. glutamate, aspartate, glycine, acetylcholine, dopamine, epinephrine, norepinephrine, histamine, substance P, gamma-aminobutyric acid, etc
3. h
4. c

Experimental Models of Parkinson's Disease: Insight from Many Models. Laboratory Animal Science 49(4), 363.
Abstract: Idiopathic Parkinson's Disease (PD) is a common neurodegenerative disorder whose clinical features include bradykinesia, resting tremor, rigidity, and postural imbalance. PD leads to progressive dysfunction and destruction of the mesencephalic dopaminergic neurons responsible for producing and transporting dopamine, via the nigrostriatal tract, to the striatum. The principal feature of the disease is the loss of striatal dopamine. Levodopa (L-Dopa) is the gold standard of treatment. Pharmacologic agents, neurotoxins, and genectic models have been used as experimental models of PD. All models lead to the depletion of dopamine.

Experimental Models
Reserpine and alpha-methyl-p-tyrosine models
- systemic admininstration
- causes depletion of catecholamines in brain, lead to akinetic state in rabbit
- rodents induces hypokinetic state due to depletion of dopamine at nerve terminals
- model used to investigate therapeutic effects of compounds
6-OHDA model
- 6-hydroxydopamine (6-OHDA) has specific neurotoxic properties in catecholaminergic nervous system
- OHDA uses same catecholamine transport system as dopamine and norepinephrine
- intracerebral or intraventricular injection (doesn't cross blood-brain barrier)
- long term destruction of dopaminergic neurons
- mice, rats, cats, dogs, nonhuman primates (rat most common model)
- model doesn't mimic slow, progressive dopaminergic neuronal degeneration
MPTP model
- compound found in synthetic heroin
- IV injection
- selectively lesions nigrostriatal system and induces behavioral changes similar to human condition
- results in depletion of striatal dopamine and nigrostriatal cell death in mice, cats, dogs, sheep, nonhuman primates
- C57BL/6 mouse most sensitive and common model
- Nonhuman primate best model for human PD
- However, no progressive neuronal loss seen in nonhuman primate
Methamphetamine
- long-term depletion of striatal dopamine and serotonin
- dopamine depleted at level of dopaminergic terminals, not cell bodies
- exerts neutotoxic effects through dopamine receptor and transporter
Genetic models
- weaver mouse: autosomal recessive mutation in potassium channel leads to neuronal cell death in cerebellum and nigrostriatal system
- used for evaluating efficacy of intrastriatal grafting of fetal dopaminergic cells
- mutant circling (ci) rat: abnormal and drug-induced circling
- AS/AGU rat: natural mutant from Albino Swiss (AS) rat
- motor changes- staggering gait, hind limb rigidity, difficulty in movement initiation
- substantial loss of dopamine in extracellular fluid of striatum, suggesting defect of dopaminergic neuron function
All 3 excellent models for investigating nigrostriatal cell death and dopaminergic neuron function
Questions: STUDY QUESTIONS
1. When do clinical signs of PD develop?
2. What is the pathologic hallmark of PD?
3. What enzyme metabolizes Levodopa?
4. What advantage does the unilateral 6-OHDA model have?
5. What animal is resistant to MPTP?
Answers: Answers:
1. striatal dopamine is reduced 80%
2. Lewy bodies, intracytoplasmic neuronal inclusions found in the SNpc, locus ceruleus, nucleus basalis of Meynert
3. DOPA decarboxylase
4. intact and lesioned nigrostriatal systems can be compared by observing resulting motor behavior asymmetry
5. rat

Pregnancy toxemia in the European ferret (Mustela putorius furo). Laboratory Animal Science 49(4), 372.
Abstract: Pregnancy toxemia in ferrets is a metabolic disease caused by energy imbalance. Energy imbalance can be caused by excess energy demand or inadequate dietary intake. This energy imbalance results in abnormal fat
and carbohydrate metabolism. Pregnancy toxemia can lead to significant mortality in jills and kits affected. The main risk factors include primiparity, large litters, and environmental or dietary stress. Pregnancy toxemia in ferrets resembles the syndrome in ruminants, camelids, rodents, and mink, as well as feline idiopathic hepatic lipidosis and human acute fatty liver of pregnancy. Pregnancy toxemia in ferrets does not have the same etiology as human pregnancy toxemia a.k.a. pre-eclampsia/eclampsia.
This study consisted of 10 cases (2 found dead, 8 underwent varying treatment regimens including caesarian section, fluid administration and nutritional suppementation) of pregnancy toxemia diagnosed in ferrets housed in either an academic institution animal facility or a commercial ferret breeding facility. Normal control blood samples were collected from 6 anesthetized, healthy primiparous jills from the commercial source. Diagnosis of pregnancy toxemia was made based on the evaluation signalment , history , and physical examination. Diagnostics performed
included CBC, chemistry profile, urinalysis, and abdominal radiographs. Gross liver appearance was noted at necropsy or at time of surgery. Gross and histologic pathology was performed on jills that died.
All cases of pregnancy toxemia reported in this study occurred within the last 8 days of gestation. Hematologic and clinical chemistry findings included anemia, hypoproteinemia, azotemia, and increased liver enzymes. Definitive diagnosis was based on finding of hepatic lipidosis. Hepatic lipidosis could be seen grossly as pale or yellow livers. Successful treatment consisted of aggressive attempts to stabilize jills, then caesarian section to deliver kits. In some cases it was necessary to cross-foster kits.
Prevention is the best solution to this problem. To minimize the occurrence of pregnancy toxemia 1) use good husbandry practices, 2) avoid diet changes and stress, and c) maintain a high nutritional plane (>20% fat; > 35% crude protein). Carefully monitor jills for body condition and appetite as pregnancy adances.
Questions: Questions:
1. Pregnancy toxemia in ferrets is associated with:
a) age
b) litter size
c) diet
d) all of the above
2. The pre-eclampsia-eclampsia syndrome of humans, non-obese guinea pigs, hamsters, and Patas monkeys has the same etiopathogenesis as pregnancy toxemia in ferrets.
True or False
3. Definitive diagnosis of pregnancy toxemia in ferrets is based on :
a) presence of anemia
b) histopathologic finding of hepatic lipidosis
c) azotemia
d) ketonuria
Answers: Answers:
1. d
2. False
3. b

Humoral immunity and protection of mice challenged with homotypic or heterotypic parvovirus. Laboratory Animal Science 49(4), 380-.
Abstract: Two serotypes of autonomously replicating parvoviruses infect laboratory mice: minute virus or mice (MVM) and mouse parvovirus (MPV). The genome
coding regions for the non-structural proteins are nearly identical whereas the capsid coding sequences are quite different. This study was undertaken to
determine if humoral immunity to one of these viruses confirmed clinical immunity to the other. The designed study was composed of different experiments to test both maternal and laboratory acquired passive immunity. The studies demonstrated that maternal antibody to MVM is protective of MVM challenge and that MPV maternal antibody is protective for MPV, but that no immunity was yeilded in the cross challenge studies. Passive transfer studies again demonstrated that MVM antibody protected against MVM infection (and MPV to MPV); however, no protective immunity was established in the cross challenge studies. The studies demonstrated an apparent less than optimal sensitivity of the current in situ hybridization techniques for detecting MPV-1a DNA in target tissues. The authors also caution MPV infected mice develop low convalescent antibody titers. Antibody seems to protect against detectable acute MPV infection; however, it is not certain that antibody will protect from persisant infection. The results indicated that humeral immunity to one murine parvovirus does not protect against infection with the other. Therefore, capsid proteins rather than non-structural proteins may play a major role in eliciting protective immunity.
Questions: 1) Structural proteins are important in protective immunity. True or False
2) Mouse parvovirus maternal antibody protects against infection with minute virus of mice infection.True or False
Answers: 1) False
2) False

Antibody responses after Sendai virus infection and their role in upper and lower respiratory tract disease in rats. Laboratory Animal Science 49(4), 385.
Abstract: Sendai virus infection in rats is a good model for studying immunologic responses of the host throughout the entire respiratory tract after infection. Sendai virus disease involves all tissues of the respiratory tract, allowing for the study of local lymphoid tissue response and humoral immunity.
Forty-two LEW/NCr rats were inoculated intranasally with Sendai virus and euthanized at 0,2,3,5,8,10, and 14 days postinoculation. Serum was collected, samples of nasal wash and bronchoalveolar lavage specimens were collected, and lymph tissues were collected. Lymph nodes of the upper respiratory tract (URT) were the innitial and major sites of antibody production. Humoral immunity is involved in the clearance of virus and resolution of disease. Immunoglobulin G (IgG) was the major class produced, supporting previous findings that specific IgG responses are important in the recovery and protection from viral lung disease. In contrast, the URT was not protected from infection or disease when animals given virus-specific antiserum or specific IgG were challanged with Sendai virus.
The conclusions from this study are that circulating components of immunity have a major role in resistance and recovery in the lower respiratory tract, whereas local responses are involved to protect the
URT.
Questions: Questions:
1. Why is Sendai virus infection a useful model for studying respiratory tract immune responses?
2. What is the major immunoglobulin subtype response in viral lung disease?
Answers: Answers:
1. Sendai virus disease involves all tissues of the respiratory tract including nasl turbinates, trachea, and lungs.
2. IgG

Lymphocyte subsets in neonatal and juvenile cats: comparison of blood and lymphoid tissues. Laboratory Animal Science 49(4), 395.
Abstract: The objective was to compare lymphocyte subpopulations in blood and lymphoid tissues (thymus and lymph nodes) in normal kittens up to 3 months old. As FIV (feline immunodeficiency virus) in cats is used as an animal model of pediatric HIV infection (vertical transmission and age-related influence of disease pathogenesis).
Kittens(1-90 days old)were determined to be free of FIV via PCR analysis of FIV DNA in blood lysates. Blood and tissues were collected at 1 day, 23 days, 46 days and 90 days of age for determination of lymphocyte subpopulations using two-color flow cytometry. Kittens were born with a high CD4-to-CD8 ratio for all tissues examined with a gradual decrease (seen by 23 days of age) in the ratio over time due to an increase in CD8+ cells. While CD4+ cells also increase in number in the blood, CD8+ cells increase at a higher, disproportionate rate. In comparison, the CD4-to-CD8 ratio in children decreases due to a decreased number of CD4+ cells. Increases in CD8+ lymphocytes in the thymus preceded that in the blood and lymph nodes. Thymus involution (physiologic) in the cat begins between 6-8 months of age. Thymus growth in the kitten was maximal at 23 days of age and began to decrease afterward.
Questions: No questions.

Effect of access to a running wheel on behavior of C57BL/6J mice. Laboratory Animal Science 49(4), 401.
Abstract: The purpose of the study was to evaluate how and when mice run on a running wheel and how ad libitum access to the wheel affects their behavior, feed intake and weight gain. C57BL/6J mice were used and it was found that the mice had the highest running activity at the beginning of darkness. The most active mouse strains cover a distance of 5.5 Km/day whereas the least active strains only cover 1 Km/day. C57BL mice cover about 2-3 Km/day. Mice which had access to the wheel spent more time feeding on the cage floor than did control mice. Experimental mice, therefore, spent less time climbing than did control mice. Climbing is a regular component of activity in mice and similar to wheel running, climbing involves more pronounced circadian rhythm than do other active behaviors. In this study the circadian rhythm of wheel running was more pronounced than that of any other form of active behavior measured, indicating that wheel running provides efficient entrainment for the biological clock. Therefore, climbing on the cage lid had a similar circadian rhythm as wheel running and a high energy expenditure. Since experimental mice climbed less their weight gain and feed intake were similar to those of control mice. This study concludes that wheel running can substitute for other forms of energy
consuming behaviors and vice versa.
Questions: Questions:
1) The highest level of running activity occurred at what time of day?
a. morning
b. middle of the night
c. onset of darkness
d. afternoon
2) Since experimental mice climbed less than control mice their feed intake and weight gain was:
a. increased
b. the same
c. decreased
d. feed intake increased, weight gain decreased
e. feed intake decreased, weight gain increased
Answers: Answers
1) C
2) B

Complications of Ileal Cannulation in Cats. Laboratory Animal Science 49(4), 406.
Abstract: Ileal cannulation is a technique that allows one to sample the ileal contents (ie. for nutritional studies). Ileal cannulation is a proven method for collecting chyme in several species although complications have been reported. There are a limited number of reports of this procedure in cats so the authors set out to evaluate this procedure in this species.
Six cats were utilized (5 male, 1 female). A three-piece Delcron T-cannula was used consisting of a threaded stem, an intralumenal flange, and an external retaining plate. A laparotomy was performed, a purse string suture was placed in the antimesenteric margin of the terminal part of the ileum, and a 1.5cm incision was made within the purse-string suture. The T-piece of the cannula was placed into the ileum, the purse-string tightened, and a second purse-string was placed in the ileum around the cannula. An 8mm skin biopsy bunch was used to cut a hole through the right abdominal wall and the stem of the cannula was directed through this hole. The external retaining plate was screwed onto the cannula stem to secure the cannula and ileum against the abdominal wall. A plug was placed into the cannula to prevent intestinal content leakage. An Elizabethan collar was placed on the cats post-operatively.
Many complications occurred. Four of the six cats either died or were euthanized. Complications included cannula displacement (1 cat), cellulitis and subcutaneous abscessation (4 cats), and ileal leakage with skin irritation (3 cats). Similar complications have occurred with ileal cannulation in other species. Direct ileal sampling was unsuccessful. Collection of chyle required placing a balloon over the open cannula and 2-3 hours was required to collect a 0.5ml sample. The bacteria isolated from the abscesses were consistent with intestinal flora. The infections were treated with appropriate antibiotics. The abscesses would heal but then recur. In an attempt not to disrupt the normal intestinal flora the first 2 cats did not receive antibiotics before or during surgery. However, because these cats developed infections the remaining 4 cats received perioperative antibiotics.
As it turns out perioperative antibiotics was not sufficient to control the problem of long-term contamination. The skin around the cannulas was cleaned daily, but was usually covered with ileal contents. The proteolytic enzymes in the ileal chyme caused skin scalding and alopecia. After removal of the cannula the ileal contents drained directly from the stoma onto the skin necessitating constant cleaning. The ileal stoma as well as the skin were allowed to heal by second intention after cannula removal. Complete closure of the stoma required 2 to 3 weeks.
Percutaneous endoscopic gastrostomy (PEG) tubes have been widely used in dogs and cats with great success. The low incidence of leakage and complications associated with PEG tubes as compared to ileal cannulas may relate to differences in the placement procedure (a better seal may form between the stomach and abdominal walls with the PEG tube as compared to the ileal and abdominal walls with the ileal cannula), the differences in the lumenal contents (ie. less bacteria reside in the stomach as compared to the ileum), and the anatomy (the placement location of the PEG tube on the dorsolateral stomach wall means the tube is not constantly immersed in gastric secretions thus reducing the potential for leakage). Ileal cannulation in cats will require further studies. Such studies should allow for refinements in the surgical technique and/or cannula configuration.
Questions: Questions:
1. Ileal cannulation can be used to sample ileal chyme. Why can't such a sample be obtained via endoscopy?
2. Why is the ileal chyme so irritating to the skin?
3. Why did the authors choose to let the ileal stoma heal by second intention as opposed to direct suturing?
Answers: Answers:
1. Because the ileums distant location in the small intestine prohibits access via endoscopy.
2. Because of the presence of proteolytic enzymes.
3. Because the authors were concerned about re-invading the abdomen in the face of infection.

Effects of citrated whole blood transfusion in response to hemorrhage. Laboratory Animal Science 49(4), 411.
Abstract: Citrate containing products are routinely used for veterinary transfusion procedures. However, the non-coagulatant effects of citrate, such as the chelation of cations such as calcium and magnesium, have not been evaluated. The authors set out to identify and quantify some of these non-coagulant effects.
Hounds were anesthetized with sodium pentothal (induction) and isoflurane (maintenance). The femoral artery and vein were cannulated for blood withdrawl and re-transfusion. Arterial blood pressure was measure from a catheter advanced to the abdominal aorta. A left lateral thoracotomy was performed to introduce a micromanometer pressure transducer to measure left ventricular pressure and left ventricular positive pressure over time. An aortic balloon occluder was placed around the ascending aorta to allow partial aortic occlusions for contractility measurements. An ultrasonic transit-time flow probe was placed on the ascending aorta to measure cardiac output. The circumflex artery was dissected and a Doppler flow probe was positioned on it to measure coronary flow. A catheter was placed in the coronary sinus for cardiac effluent blood analysis. Three pairs of omnidirectional transceiver piezoelectric crystals were positioned across the left ventricular short and long axes in six small incisions for continuous left vetricular volume and regional gractional shortening measurements. This allowed left ventricular volume to be estimated from a simple ellipsoid model. Hemodynamic monitoring included ECG monitoring and systemic indices of systemic and myoardial perfusion, oxygen delivery, substrate consumption, and ventricular and aortic pressures. Metabolic measurements included analysis of systemic arterial and venous and coronary sinus blood for lactate and glucose concentrations; sodium, potassium, and ionized calcium concentrations, pH, PCO2, and PO2.
The dogs were allowed to stabilize for 60 minutes. Baseline measurements were taken. After that time, hemorrhage was induced by opening the femoral artery until MAP of 45mmHg was obtained. After hemorrhage, measurements and blood samples were collected again. The dogs were re-transfused using LRS, whole blood, and saline. Additional measurements and samples were collected at 20 min, 1h, and 2h. Dogs were euthanized at the termination of the experiment.
Calcium levels declined significantly during the hemorrhage period and did not fully recover by 2h post-resuscitation. Myocardial function, cardiac output, and MAP all declined during hemorrhage, but recovered during the initial resuscitation phase. Ca concentration appeared to be significantly related to total peripheral resistance and possibly myocardial lactate consumption and end-systolic elastance. It did not appear to be related to myocardial glucose, oxygen metabolism, sodium and potassium concentrations, or pH.
Traditional hemorrhagic shock models used heparin. These models are no longer considered appropriate for experimental use because of the protective value of heparin seen in hemorrhagic shock. Citrate is replacing the use of heparin, but its non-anticoagulant features (potentially protective) must also be assessed. Massive infusion of citrated blood has been documented to cause hypocalcemia that may be fatal, even in normal (non-hemorrhaged) animals. Monitoring ionized calcium concentration during clinical or experimental resuscitation is highly recommened. In the absence of an ionized calicum analyzer, clinicians and researchers need to monitor signs of citrate-induced hypocalcemia and treat suspected cases with calcium.
Questions: Questions:
1. What do (a) CPD and (b) ACD stand for? Of these two anticoagulants and heparin, which is preferred for long term storage of blood?
2. Where is citrate metabolized?
3. Which of the following have been associated with citrate-induced hypocalcemia?
(a) Depressed CO
(b) Depressed systemic vascular resistance
(c) Depressed MAP
(d) Depressed stroke volume
(e) Prolonged QT interval
(f) Alkalosis
(g) a, b, f
(h) b, c, d
(i) All of the above
4. True or False: If transfusing with citrated blood and evidence of cardiac compromise is seen, treatment with calcium may be indicated because of citrate induced hypocalcemia.
Answers: Answers:
1. (a) citrate-phosphate-dextrose combination; (b) acid-citrate-dextrose combination; CPD
2. In the liver, kidney, and skeletal muscle; it is also excreted unchanged by the kidney, providing rapid return to normal coagulation.
3. i. all of the above
4. True

Evaluation of the micronucleus test in peripheral blood erythrocytes by use of the splenectomized model. Laboratory Animal Science 49(4), 418.
Abstract: This paper describes the determination of which common laboratory animal species, with intact spleen or with spleen removed surgically, are likely to be a reliable model or sensitive indicator for the Micronucleus (MN) test, using peripheral blood erythrocytes. The MN test detects the effect of mutagenic agents on chromosomes by identification of acentric fragments and/or lost chromosomes that form micronuclei. The classic method for the study of MN is to count them in polychromatic erythrocytes (PCE) of bone marrow, 24 to 48 hours after administration of the agent to be tested. The number of PCE varies in mammalian species, with many mamals not containing any PCE in peripheral blood, while others have numbers that are very high or very low.
The study looked at mongrel dogs, hamsters, gerbils, Sprague Dawley rats, BALB/c mice and New Zealand White rabbits; each animal species was divided into 2 groups that were or were not splenectomized. Each of the groups per species received treatment consisting of colchicine and Arabinose-C given intraperitoneally daily for 4 days. These agents are aneuploidogenic and clastogenic, respectively, and have been routinely used as posivite-control compounds in the MN assay. Dogs in the study did not receive micronucleogenic inducers. Instead, they received an anti-parasite treatment, and vaccination against rabies, distemper, hepatitis, and leptospirosis before splenectmoy, as well as two injections of benzyl penicillin after splenectomy.
Results indicated that there was a tendency for MN erythrocytes (MNE) numbers to increase after treatment, and this increase was higher in splenectomized than nonsplenectomized animals. The differences between the groups were significant only in hamsters, mice and dogs.
In this study, the total MNE were counted without distinguishing between polychromatic and normochromatic cells. The helps to overcome the difficulty with different species having varying numbers of PCE present in peripheral blood.
The hamster's response to MNE inducers after splenectomy was 56%. Other advantages to using the hamster are its size, ease of management, and ease of splenectomy. In contrast, for the rabbit, an increase in MNE was not observed with splenectomy or with MNE induction, making clear that the spleen is not responsible for their removal in this species.
Questions: Questions:
1) What does the micronucleus test detect? Based on this study, which species may be a candidate for an appropriate animal model?
2) Name the genus and species for the animals used in this study.
3) What are two agents routinely used as positive-control compounds in MN testing?
Answers: Answers:
1) The micronucleus (MN) test detects the effect of mutagenic agents on chromosomes by identification of acentric fragments and/or lost chromosomes that form micronuclei. The spleen of some animals, including humans, is responsible for removal from the circulation of erythrocytes with MN. Thus the presence of micronucleated erythrocytes (MNE) can be considered a sign of splenic absence or dysfunction. From the data presented, hamsters may be a representative animal model for the MN test.
2) Mongrel dogs (Canis familiaris)
Hamsters (Mesocricetus auratus)
Gerbils (Meriones unguiculatus)
Sprague-Dawley rats (Rattus norvegicus)
BALB/c mice (Mus musculus)
NZW rabbits (Oryctolagus cuniculus)
3) Colchicine (aneuploidogenic)
Arabinose-C (clastogenic)

Experimentally induced infection of gerbils with cilia-associated respiratory bacillus. Laboratory Animal Science 49(4), 421.
Abstract: Cilia-associated respiratory (CAR) bacilli are gram negative, motile, nonspore-forming bacteria. This organism colonizes ciliary respiratory tract epithelium of wild rats, rabbits, cattle, goats, and swine. This study was conducted to determine whether gerbils could be infected with CAR bacillus, and if so, whether respiratory tract disease occurred in this species. Two week old gerbils were innoculated intranasally with a rat isolate of CAR bacillus. Twelve weeks following innoculation, gerbils were euthanized and nasal cavity, trachea, and lungs were collected for histopathologic examination. Clinical signs of respiratory tract disease were not observed in either control or experimental animals; however, histologic lesions of tracheitis and bronchitis were evident in experimental animals. Steiner silver stained sections of lung revealed bacteria with an identical pattern as that seen with CAR bacillus colonization in other rodents. Consequently, gerbils are susceptible to the particular rat isolate of CAR bacillus.
Questions: Questions
1. What agent is CAR bacillus often associated with?
2. T/F Can CAR bacillus, alone, cause respiratory tract disease?
3. Describe clinical signs of infection with CAR bacillus.
Answers: Answers
1. Mycoplasma pulmonis
2. True
3. Usually asymptomatic, but in severe cases can cause weight loss, rough hair coat, and respiratory signs of wheezing and rales.

a-Mannosidosis in a guinea pig. Laboratory Animal Science 49(4), 424.
Abstract: The lysosomal storage disease alpha-mannosidosis arrises due to a deficiency in alpha-mannosidase, with resulting intracellular accumulation of mannose-containing oligosaccharides. This is most often the result of an autosomal recessive mutation.
A litter of 4 guinea pigs showed a poor growth rate. 2 of them showed ataxia and head pressing.
No significant macroscopic findings. Histologically there was vacuolation of cells throughout the body: hippocampus, cerebellum, choroid plexus, gastrointestinal tract (myenteric plexus), alveolar septae, renal tubular epithelial cells, pancreatic acinar cells, splenic red pulp, Kupffer cells, thyroid follicular epithelial cells. These histologic changes were consistent with those of a storage disease. Liver alpha-mannosidase enzyme activity was lower than control.
To the author's knowledge, this is the first reported case of alpha-mannosidosis in a guinea pig.
Questions: No questions

Evaluation of FVB/N mice as recipients for transgenic embryos. Laboratory Animal Science 49(4), 427.
Abstract: The FVB/N inbred mouse is attractive for transgenic analysis due to its vigorous reproductive performance, large litters, and embryos with prominent pronuclei. However, the focus of this paper was to evaluate the utility of FVB/N pseudopregnant females as embryo transfer recipients of DNA-microinjected embryos.
The pseudopregnant mouse is created by mating the female mouse with a vasectomized or genetically sterile male. The uterus of a pseudopregnant mouse is primed to accept and maintain transferred embryos.
This study compared the success of FVB/N mice vs. ICR mice as embryo recipients. Fifteen different DNA constructs were used for the comparison. C57BL/6 x C3H F1 (B6C3) mice were superovulated and used as embryo donors.
The day after inducing pseudopregnancy, all females received 14 two-celled embryos via surgical implantation into the left oviduct. The ampullae were graded as follows: 1 = normal size, 2 = 2 times normal, 3 = 3 times normal, 4 = 4 times normal. Pregnancy determination was made by abdominal palpation 2 weeks after embryo transfer.
Of the 115 FVB/N plugged females, 51% became pregnant. Eighty percent (36 of 45) FVB/N mice with grade-4 ampulla were pregnant, and 44% (14 of 32), 27% (8 of 30), and 13% (1 of 8) mice with grades 3, 2, and 1, respectively, were pregnant. Of 126 ICR plugged females, 89 (71%) were pregnant. Seventy-four percent (40 of 54) of ICR mice with grade-4 ampulla were pregnant, and 72% (31 of 43), and 62% (13 of 21), 63% (5 of 8), with grades 3, 2, and 1, respectively, were pregnant.
The results of the study suggest the advantage of using ICR mice over FVB/N mice as recipients of transgenic embryos using routine microinjections. Furthermore, the results suggest that ampulla grading appears to be beneficial to increase the number of pregnancies when using FVB/N mice but does not appear to offer any advantages when using ICR mice.
Questions: No questions

Technique for continuous monitoring of salivary cortisol concentration in pigs. Laboratory Animal Science 49(4), 429.
Abstract: Advantages of measuring cortisol levels in saliva include, direct measurement of the free, biologically active fraction of glucocorticoid hormones is possible without further lab work, so concentrations are less affected by corticosteriod-binding protein than are plasma values. Flow rate does not interfere with salivary cortisol values and the change with systemic values is prompt. Saliva is easily handled, no surgical preparation of the animal is required.
Disadvantages of measuring cortisol levels in saliva include contamination with plasma proteins, conversion in the salivary glands by 11B-hydroxysteriod dehydrogenase of free cortisol to cortisone, and a greater variation of saliva corticosteroid concentrations than total plasma concentrations.
Pigs have a circadian rhythm of plasma and salivary cortisol concentrations where the highest values are observed in the morning. The investigators used a small sealed plastic cylinder (diagram in article) with 12 tiny 1-mm pores, covered by a dialysis membrane. This product had been developed to continuously collect saliva in humans and interstitial fluid from rats. The cylinder is coated with polymer B-cyclodextrin, which has high affinity for steriod hormones and maintains a continuous concentration gradient between saliva and free concnetrations of cortiocosteriods inside the device for up to 8 hrs.
The investigators compared this new device (Oral diffusion sink) with the traditional cotton bud technique in pigs that were group and individually housed and in animals that were transported. ODS proved to be a useful method for obtaining samples for continuous measurement of corticol during transport. However, there were correlation problems with the ODS method in the housed animals due to food and water interference.
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