The Cotton Rat in Biomedical Research. Laboratory Animal Science 47 (4): 337.
    The cotton rat is susceptible to many human pathogens, thus making it a valuable model in biomedical research. Of the seven species of cotton rats, two are most used: Sigmodon hispidus, and Sigmodon fulviventer. These animals are widely distributed in the wild from the southern US, north to Virginia, west to California, and south to Mexico, Central America, and northern south America. Cotton rats are members if the family Cricetidae, and are nestbuilding rodents living in burrows or dense clumps of vegetation.
    Some of the historical research uses of Cotton rats include polio virus, respiratory tract disease, gene therapy, and filariasis. Filariasis has been the most frequent use, for studying immunologic and nutritional factors, chemoprophylaxis, vector transmission, and for screening antifilarial drugs. Currently this animal is used as a model for viral respiratory tract diseases, particularly those caused by paramyxovirus, such as respiratory syncytial virus, parainfluenza 3, and measles virus. It can also be used to study human adenovirus, and many other human pathogens including viral, protozoal, and bacterial pathogens.
    The biology of the cotton rat is reviewed. The number of chromosomes varies among species from 22 to 52. The name Sigmodon refers to S-shaped enamel loops on the grinding surfaces of the cheek teeth. Anatomy is similar to other rodents. These animals may be nocturnal, but may also be diurnal, or crepuscular in activity. Social groups consist of males dominating females and adults dominating the young. Generally they live as solitary animals, forming groups for reproduction. Young can survive in the wild by 5 days of age.
    There are four life stages: 1-75 days Juvenile, 76-200 days Young adults, 201-300 days Adults, and 300 days on Old Adults. Captive-bred animals have an average lifespan of 23 months, max. 3 years.
    Breeding is seasonal in the wild, but not in the lab. They may be harem bred, or placed in monogamous pairs. Pairs should be established when the female has reached puberty, earlier pairing seems to delay puberty. The estrous cycle averages 9 days, there is a postpartum estrus, gestation is about 27 days, young are born haired and eat solid food by one week of age. Normally they are weaned at 3-5 weeks of age, but they can be weaned as young as 5-10 days.
Cotton rats can be housed in large polycarbonate rat cages. They should have locking lids, and bedding for nesting. Nutritional requirements are similar to those for rats. They are also best handled like rats; some people prefer to wear leather gloves. Avoid picking them up by the tail as the tail skin easily degloves.
    Anesthesia, blood sampling, and light cycles can be the same as for other rodents such as rats.
    Pathologic findings in the cotton rat: Fighting is the most common clinical "disease". To evaluate pathology a sampling of 18 adult cotton rats were necropsied and all major organs examined histologically. Notable findings included: Kidneys - nephropathy with tubular changes, mineralization, and interstitial fibrosis; Cardiac and skeletal muscle - degenerative cardiomyopathy on the majority of animals, with similar lesions in skeletal muscle; other tissues - mineralization in salivary glands in several of the animals, no evidence of neoplasia.
    A discussion of use of the cotton rat in adenoviral-mediated gene therapy is presented. One of the important features of this species is that it is semipermissive for human adenovirus replication, thus the cotton rat is a tool for toxicity studies of adenoviral vectors. A study of cardiac delivery of the vector is fully described in the article, with the conclusion that no significant toxicity was seen with a range of vector doses.
Questions:
1. Name the Family containing the Cotton Rat. What is a common laboratory animal in the same Family?
2. Cotton rats may be nocturnal, diurnal, or crepuscular. Define crepuscular.
3. List three research uses of the Cotton Rat.
Answers:
1 Family: Cricetidae Common animal: Hamster
2. Crepuscular: Pertaining to a twilight state of consciousness.
3. Studies of: Filariasis, respiratory tract disease, polio, gene therapy, adenoviral infections and vectors, rickettsial diseases, measles virus, Lyme disease, and others.

Evaluation of Hyperplastic Goiter in a Colony of Syrian Hamsters (Mesocricetus auratus). Laboratory Animal Science 47 (4): 346.
    Report of examination of adult and juvenile hamsters during routine health monitoring of a closed Syrian hamster (SG) colony. Because the prevelence of spontaneous hyperplastic goiter typically occurs in 6-7% of older hamsters, an investigation was performed to classify the goiter and evaluate the role of diet in the development and resolution of thyroid hyperplasia in affected animals.
    Eighteen, 8 week old, male Syrian hamsters were obtained from a closed performed to classify the goiter and evaluate the role of diet in the development and resolution of thyroid hyperplasia in affected animals.
Eighteen, 8 week old, male Syrian hamsters were obtained from a closed breeding colony in which goiter developed in juvenile and adult hamsters. Twenty, 8 week old, male Syrian hamsters were obtained from the Fredrick Cancer
Research & Development Center (FCRDC) to be used as controls during the feeding trials. Feeding trials were performed because the SG hamsters had been fed an autoclavable mouse breeder diet for the last 5 years which was autoclaved for 3 minutes at 270 F. T he manufacturer's recommendation was that the feed be autoclaved for 30 minutes at 270 F. It was then hypothesized that inadequate autoclaving of the diet may have failed to inactivate goitrogenic substances in the feed. A nonautoclavable rodent diet was used as the control diet. The first feeding trial was performed to test the ability of the mouse breeder diet to induce hyperplastic goiter in a control group of fifteen FCRDC hamsters. Five of the FCRDC hamsters were fed the control diet for 6 months. The second feeding trial
    The results of the first feed trial on the basis of densitometric analysis of thyroid gland nuclear scans from the FCRDC hamsters fed the mouse breeder diet were not significantly larger than those fed the control diet. Thus, the results of the feeding trial failed to document goitrogenic activity of the mouse breeder diet. In the second feeding trial, there was no change in goiter size of the affected SG hamsters fed the control diet . Therefore, the feeding trial failed to confirm the role of diet in maintaining a hyperplastic goiter in SG hamsters. Histologic examination of thyroid glands from SG hamsters were consistent with a diagnosis of follicular cell hyperplasia. Histologically, these glands had decreased follicular colloid and increased number of irregularly sized follicles lined by columnar cells, with apical nuclei and a clear basilar cytoplasmic zone. Histological examination of the thyroid glands of FCRDC hamsters fed the mouse breeder diet were of normal glandular architecture characteri
    It is suspected that a genetic factor was the cause of the hyperplastic goiter in SG hamsters. The SG hamsters were from a closed colony which had been maintained that way for 35 years. The restriction of the SG hamster genetic pool may have increased the chance for the expression of an altered gene or genes affecting the thyroid function.
Questions/Answers:
1. What is the rate of prevelence of spontaneous hyperplastic goiter in aged Syrian hamsters?
2. T/F It has been shown that diets not correctly autoclaved will cause hyperplastic goiter in Syrian hamsters.
3. Describe what one would observe upon histological examination of goitrous thyroid gland.
1. 6-7%
2. F-Genetic factors are suspected in which a gene alteration has occurred affecting thyroid function.
3. Decreased follicular colloid, increased number of irregularly sized follicles lined by columnar cells with apical nuclei and a clear basilar cytoplasmic zone.

Hemolytic Disease of the Newborn in Rabbits. Laboratory Animal Science 47 (4): 351.
This article describes a rabbit model for erythroblastosis fetalis of newborns. This occures in humans when fetal red cells that express foreign antigen gain access to maternal circulation. The resulting alloimmunization affects subsequent pregnancies and leads to fetal anemia and extra vascular fluid increase due to cadiac failure(hydrops fetalis).
Alloimmunized does were bred to bucks of compatible and incompatible blood types. Median fetal hemoglobin was lower in litters of incompatible breedings and hydrops was noted in 63% of the time using ultrasound(see picture). The model will be helpful in future work toward successful immuno-modulation of this disease.
Questions:T or F
1.One would see this condition in primipara individuals.
2.One would expect to see high reticulocyte counts.
Questions:
1. the gestation period for the rabbit is:
a. 27-30 days
b. 30-33 days
c. 40-42 days
d. 50-55 days
2. The red cell antigen primarily responsible for HDN in humans is the _________ antigen.
3. Fetal hemoglobin values in the rabbit are typically higher/lower than neonatal hemoglobin values.
Answers: 1. F 2. T
Answers:
1. b
2. rhesus or RhD
3. higher

Bacterial Lipopolysaccharides Induce Peripheral Nerve Disturbances in Rats That Mimic Human Immune-Mediated Polyneuropathies. Laboratory Animal Science 47 (4): 354.
This study showed that a single injection of Escherichia coli lipopolysaccharide (LPS) given either IV or IP induced peripheral nerve disturbances in male Australian albino Wistar rats. Lipopolysaccharides given systemically have been shown to induce neuropathologic sequelae in the central nervous system but rarely have been observed to induce peripheral neuropathies in laboratory animals. Gram negative bacterial infections and toxins have been implicated in the pathogenesis of peripheral neuropathies in humans such as Guillain-Barre syndrome (GBS) and critical illness polyneuropathy (CIP). The goal of these experiments were to better characterize animal models for immune mediated peripheral neuropathies such as GBS and CIP. The tail flick and hot plate tests were used to assess pain perception due to LPS administration. The tail flick test is a standard method for determining level of analgesia in rats. The clinical signs observed in the rats were gait abnormalities, proprioceptive loss and to a lesser extent hind limb weakness and sensory deficits. Signs were more severe in males vs. female Wistar rats and were observed in a number of genetically related rat strains (Australian albino Wistar, outbred Wistar and inbred Lewis rats but not Sprague Dawley or inbred Fischer 344 rats). Development and severity of these signs were dependent on LPS dose and not body weight. The tail flick and hot plate tests showed that clinical signs were not associated with LPS induced changes in pain perception or the occurrence of spontaneous pain. These data indicate that LPS induced transient peripheral nerve disturbances in rats are influenced by genetic, sex and dose related factors.
Questions:
1. Which of the following is not a clinical sign associated with LPS induced peripheral neuropathy?
A. Sensory deficits
B. Thoracic limb weakness
C. Gait abnormalities
D. Hind limb weakness
2. The severity of clinical signs were dependent on:
A. Body weight
B. LPS dose
C. Strain of rat
D. Only B & C
E. All of the above
Answers:
1. B
2. D

Effects of Immobilization Restraint on Syrian Golden Hamsters. Laboratory Animal Science 47 (4): 362.
Rodent nose-only inhalation toxicology systems comprise whole-body immobilization in plastic restraint tubes. This type of restraint can have a variety of effects on animals. In this study body weight, food and water consumption, core body temperature, and plasma cortisol and corticosterone concentrations were assessed in animals immobilized in nose-only inhalation tubes, and the results were compared with those from unrestrained cage-control animals. Nose-only exposure methods are commonly used in inhalation toxicology experiments to prevent inadvertent systemic exposure that could occur through grooming and ingestion of the test compound and are used when limited quantities of the test materials are available. The most important finding in these studies was the marked difference in body weight between restrained hamsters and unrestrained cage controls. This body weight loss in these studies is important to the intrepretation of toxicology test results, since change in body weight is a well-accepted indication of toxicity.
No questions

Continuous Total Intravenous Anesthesia, Using Propofol and Fentanyl in an Open-Thorax Rabbit Model: Evaluation of Cardiac Contractile Function and Biochemical Assessment. Laboratory Animal Science 47 (4): 367.
    New Zealand White rabbits with open thorax in a non srurvival study were anesthesied with a continuos intravenous anesthesia with proponol and fentanyl and its cardiovascular function remained stable. Several experiments setting require prolongated and stable anesthesia, which provides sufficient analgesia with out comproming cardiovascular function. Rabbits are more highly reponsive to perioperative stress and express high individual variability in sensitivity to anesthetics.
    Voltile anesthetica are frequently used but they cause circulatory and respiratory depression. IntermitenTbolus adminisration of anesthetic drugs induces variable dephts of anesthesia, therefore continous infusion is prefered because fuctuations in concentration of the anesthetic between the various body compartments are minimized, inducing a stable depth of anesthesia.
    New Zeland White Rabbits were induced by intramuscular (im) administration of ketamine hydrochloride and xylazine hydrochloride and continuos total intravenous anestesia wiyh propofol, fentanyl and the neuromuscular agent vecuronium bromide was maintained. The mean duration of the open-thorax long term experiment was between 6,5 hours. Oxygenation conditions, acid-base balance, biochemical and hemodynamic variables, and cardiac contractile function were assessed before and after sternotomy.
    Propofol, a short acting IV administrated hypnotic agent , induces rapid onset of anesthesia . Fentanyl witch is a 100 times more potent than morphine, maintains cardiovasular stability, and has been reported to do so even at higher dosages. Using induction by intramuscular (im) administration of ketamine hydrochloride and xylazine hydrochloride and continuos total intravenous anestesia wiyh propofol, fentanyl and the neuromuscular agent vecuronium bromide all the measurements remained stable. The stability of the hemodynamic and biochemical parametres makes this anesthetic protocol with predeterminated drug dosages suitable for acute, open thorax, long term expermental observations for physiologic and pharmacologic reserach in vagotomized rabbits in nonsurvival studies.
QUESTIONS:
1.- Why is continous infusion prefered to bolus injections?
2.- Anesthesics used in a continuos intavenous anesthesia:
a. Fentanyl
b. Propofol
c.- Propofol and fentanyl
ANSWERS
1.- Because bolus injections induce variable depths of anesthesia
2.- c

Humane and Practical Implications of Using Carbon Dioxide Mixed with Oxygen for Anesthesia or Euthanasia of Rats. Laboratory Animal Science 47 (4): 376.
This study was undertaken to determine whether CO2 can be used as a humane as well as practical agent for euthanasia or anesthesia of rats. CO2 gas has been used to stimulate pain receptors (nociceptors) in the nasal mucosa and thus seems contradictory that this agent is used to induce painless anesthesia and death. The practical aspect of using different mixtures of CO2 and O2 for anesthetizing and euthanizing rats were investigated. In addition the response of human volunteers was measured after breathing various concentrations of CO2. The results indicate that the concentrations that most rapidly induce anesthesia and death are most likely to cause appreciable pain and distress, and those that are least likely to cause pain and distress may be unacceptably inefficient. At the lower concentrations of CO2 which are unlikely to cause pain, is associated with a slow and highly variable induction of unconsciousness and death, a high incidence of disturbing adverse reactions (seizures, excess salivation/foaming, serosanguinous nasal discharge) and marked histologic changes in the lung tissue. CO2 may cause pain by specifically forming carbonic acid in a moist environment, which then excites small nerve fibers, and the fibers then detect sensations of pain. The mean threshold pain sensations in humans is similar to rats and ranges from 37-50% CO2, when comparing cerebral pain-related electrical potentials. CO2 concentrations of 25-30% can cause subcortical depression resulting in complete anesthesia. The mechanism by which CO2 induces theses changes in central nervous system function is unknown, but appears to be due principally to alterations in cellular pH, electrolytes, and/or amino acids. Death results from depression of respiratory centers coupled with cerebral vasodilation leading to circulatory insufficiency. The only variable that differed significantly in rats exposed to CO2 in precharged versus nonprecharged chambers was time to recumbency, which was significantly shorter for most concentrations in the precharged chamber. The results indicate that to use CO2 in a humane manner for anesthesia or euthanasia of rats, it is essential to avoid exposure of conscious animals to concentrations of CO2 >70%. It is also important to use nonprecharged chambers and low gas flow rates, which will allow a more gradual buildup of CO2 in the animals environment.
Questions:
1. Which statement(s) are false regarding CO2 and conclusions drawn from this paper?
a. CO2 can form carbonic acid in a moist environment
b. High concentrations of CO2 cause greater adverse effects, but less pain.
c. CO2 concentrations of 25-30% can cause subcortical depression resulting in complete anesthesia.
d. It is recommended to avoid exposure of conscious animals to concentrations of CO2 <70%.
e. b and d
2. Which are important characteristics of an agent or method to be used for euthanasia?
a. ability to induce death without causing pain, anxiety, or distress.
b. reliability and safety for humane personnel
c. ability to induce rapid unconsciousness and death
d. minimal emotional impact on human observers
e. minimal interference with postmortem tissue evaluations
f. ease of administration and low cost
g. all of the above
Answer:
1. e. b and d
2. g. all of the above

Evaluation of Five Agents/Methods for Anesthesia of Neonatal Rats. Laboratory Animal Science 47 (4): 386.
A two part (short-term anesthesia and long-term anesthesia (30m)) study was uyndertaken with the intention of identifyng agents or methods that can be used to provide humane, safe and efective anesthesia for neonatal rats. Times to loss of the rigting reflex, surgical anesthesia (loss of the pedal reflex and failure to respond to a skin incision),heart rate, respiratory rate and oxigen saturation and recovery from anesthesia were evaluated. Part 1: ketamine, pentobarbital and fentanyl-droperidol proved unsafe (>50% mortality) and / or ineffective. In contrast methoxyflurane and hypotermia were safe and effectiveIn part II it was posible to safely maintain at a surgical plane of anesthesia for 30m with either methoxyfluorane or hypotermia. Supplementation with pentobarbital offered no advantages but significantly prolonged time to recovery. Hypothermia was induced by use of two methods: the standard techique of immersion in ice water, and a refined technique in which pupus were placed in a protective latex sleeve prior to immersion in ice water. With the second one the pain associated with rapid chilling can be decreased without significantlly affecting time to anesthesia, time to recovery, or postoperative course.
QUESTIONS:
1.- The best anesthesic for neonatal rats in long-term aneshesia
2.-Differences between the standard and refined technique to induce hypoyhermia
ANSWERS:
1.- Methoxyfluorane and hypotermia ( with or without pentobarbital)
2.- Refined tecnique: pupus are placed a protective sleeve prior to immersion(less painful)

Effects of Anesthsia and Open-Thorax Surgery on Coronary Vascular Reserve in Swine. Laboratory Animal Science 47 (4): 396.
    Anesthesia significantly affects central & peripheral circulation control & alters cardiovascular fucntions such as systolic, diastolic pressures, vascular resistance & regional myocardial blood flow distribution. The object of this study was to determine the effects of anesthesia on coronary vascular reserve. The advantages of using pigs for this study: coronary artery distibution & anatomic features are similar to man, pre-existing collateral channels & anastomoses are almost non-existent & myocardial biochemical & metabolic characteristic in response to ischemic injury are similar to man.
    The coronary hyperemic response was examined in pigs under anesthesia & while conscious. Tygon catheters were placed in the descending aorta, transonic flow probes & hydraulic occluders were placed on the left cranial descendin &/or left circumflex coronary arteris. The cornary reactive hyperemic response is expressed as repayment of flow deficit & was induced by complete coronary artery occlusiong for 15 sec. There was no significant difference in repayment of flow deficit between the anesthetized & conscious pigs 5 days post-op. At 3 & 5 weeks post-op the reactive hyperemic flow & repayment of flow deficit were greater in conscious pigs than in anesthetized pigs. The results showed that anesthesia & recent surgery attenuates coronary vascular reserve. The major factor in the attenuation of coronary reserve appears to be recent surgical manipulation because repayment of flow deficit was still depressed in conscious pigs during the early phase of surgical recovery.
No questions

The Repeated Sampling Bone Chamber: A New Permanent Titanium Implant to Study Bone Grafts in the Goat. Laboratory Animal Science 47 (4): 401.
Mature goats (Capra hircus sana) were induced with pentobarbital, intubated, and maintained on halothane and oxygen. Titanium bone chambers were implanted in the proximal medial tibias of the goats. Chambers included an outer housing fixed with cortical screws, an inner chamber screwed into the outer housing, and a peg to stabilize the horizontal chamber created by proper positioning of the inner and outer housings. Comparison between chip grafts, structural grafts, and empty chambers revealed no significant difference. Marked interanimal variation was found in a second experiment, emphasizing the use of repeated sampling in the same goat to to lower the intersample variability and reduced the number of animals required.
QUESTIONS:
1. What is RSBC?
2. When the chamber is assembled, what prevents rotation of the inner cylinder in the outer housing and ensures a stable conduit for tissue and bone ingrowth?
3. Why are the chambers implanted on the medial side of the tibia of the goat?
4. In this bone chamber model, because of the positioning of the holes of the inner and outer chambers the placement of the new tissue growth was not influenced by:
a. intraspecies variation
b. inter species variation
c. titanium
d. mechanical loading
5. During resorption, what growth factor is released from the bone matrix?
6. What is TRAP?
7. (True or False) Bone ingrowth was scant, with no difference between the chip graft, the structural graft, and the empty chamber.
ANSWERS:
1. What is RSBC?
Repeated Sampling Bone Chamber
2. When the chamber is assembled, what prevents rotation of the inner cylinder in the outer housing and ensures a stable conduit for tissue and bone ingrowth?
A peg.
3. Why are the chambers implanted on the medial side of the tibia of the goat?
The approach to the medial tibia has few muscles, vessels, or nerves.
4. In this bone chamber model, because of the positioning of the holes of the inner and outer chambers the placement of the new tissue growth was not influenced by:
d. mechanical loading
5. During resorption, what growth factor is released from the bone matrix?
Bone Morphogenic Proteins
6. What is TRAP? tartrate-resistant acid phosphatase An enzyme histochemical analysis. On the surface of dead bone graft many TRAP-positive osteoclasts were found.
7. (True or False) Bone ingrowth was scant, with no difference between the chip graft, the structural graft, and the empty chamber. True

Automated Procedure for Estimation of Blood Cholinesterase Activities in Rabbits. Laboratory Animal Science 47 (4): 407.
Cholinesterases are a group of enzymes that are found in the heart, intestinal mucosa, brain, blood , and other tissues. Cholinesterases exist in two principal forms: acetylcholinesterase (AchE) or true Cholinesterase and pseudo-Cholinesterase. These two enzymes forms can be distinguished from one another by their substrate specificities, sensitivities to inhibitors and different pH optima. AchE hydrolyzes acetylcholine, whereas pseudo-Cholinesterase hydrolyzes simple esters. The term red blood cell Cholinesterase (RBC-ChE) is used interchangeably with AchE, whereas pseudo-Cholinesterase is synonymous with plasma Cholinesterase (P-ChE).
Cholinesterase inhibitors used as insecticides include organophosphates and carbamates. Inhibition of AchE in vivo can have adverse effects ranging form hypersalivation to respiratory paralysis.
The purpose of this study was to determine the precision and accuracy of a modification of the Ellman procedure using the Multistat III Plus Centrifugal Analyzer (MCA) for ChE estimation: establish baseline blood AchE and pseudo-Cholinesterase activities in untreated rabbits by use of the MCA procedure; and evaluate the dynamics of rabbit blood AchE and pseudo Cholinesterase inhibition, using the MCA method.
Baseline plasma Cholinesterase, red blood cell Cholinesterase and whole blood Cholinesterase was determined. Rabbits were then challenged with 0.3 LD 50 of diazinon (a Cholinesterase inhibitor) and blood samples were obtained at hourly, and daily intervals. Cholinesterase activity was then determined using the MCA. Plasma Cholinesterase activity decrease to 4% within 6 h, whereas red blood cell Cholinesterase activity decreased to 51%. By 10 days, plasma and red blood cell Cholinesterase activities had returned to 100 and 91% of pre-challenge activities.
The authors conclude that the MCA method is suitable for assay of Cholinesterase activity in blood samples from animals. The procedure is sufficiently sensitive to detect decreases of Cholinesterase activity in rabbits that have been exposed to ChE inhibitors. This procedure should be suitable for environmental monitoring.
Questions
1. List several clinical signs of organophosphate toxicity.
2. Name one application for the use of this procedure.
Answers
1. SLUD: salivation, lacrimation, urination and defecation.
2. Environmental monitoring of organophosphate and carbamate use.

Simple Method of Multipurpose Airway Access through Percutaneous Tracheostomy in Rabbits (Oroctolagus cuniculus). Laboratory Animal Science 47 (4): 411.
The authors wished to develop a relatively atraumatic technique for anesthetized rabbits which would permit sampling or access to the trachea/bronchi without obstructing respiration. Specifically, their technique involves percutaneous tracheal access via a needle cricothyroidotomy over the prepared site. This was followed by introduction of a 5-F introducer set (included guidewire, sideport and introducer) which was advanced into the trachea. A 4-F balloon thermodilution catheter was advanced through the 5-F introducerand wedged in a small bronchus, permitting isolation of a distal airway while still permitting animals to spontaneously ventilate. The technique was rapidly acquired by investigational team members with little associated moribundity/mortality.
Bonus questions (from Biology of Lab Rabbit, 2nd Ed, not from this article):
1. In the rabbit, which lung has higher flow?
2. How does the vasoconstriction response of the pulmonary artery differ in the rabbit compared with other mammals?
Answers:
1. The left lung - thus resistance is lower in this lung in proximal airways compared with right lung (imp for sampling/substance delivery).
2. Vasoconstriction is induced by either norepinephrine or acetylcholine in the rabbit, whereas vasoconstriction is only caused by norepinephrine in other species.

Use of Magnetic Cell sorting to Isolate Blood Neutrophils from Rats. Laboratory Animal Science 47 (4): 414.
Collecting neutrophils in sufficient numbers from rat blood can limit the usefulness of this species in studying neutrophil function. This study involved a method to increase the number of neutrophils that could be collected from rats drinking alcohol on a long-term basis. The authors noted that long term consumption of alcohol causes a neutropenia. To increase neutophil yield, a magnetic cell-sorting technique was developed. Rats were exsanguinated and neutrophils were isolated using either density gradient centrifugation or magnetic cell sorting. With magnetic cell sorting, leukocytes were labeled with biotinylated anti-rat granulocyte antibodies, followed by addition of streptavidin-conjugated superparamagnetic micorbeads. The labeled cell suspension was applied to a steel wool column suspended within a magnetic field. Unlabeled cells were washed through the column. Retained, labeld neutrophils were eluted after the column was removed from the magnetic field. Compared with density gradient centrifugation, magnetic cell sorting yielded two to five times higher neurtrophil numbers per rat with increased purity. Viability was comparable for neutrophils isolated by the two techniques. The authors conlcude that magnetic cell sortign is a rapid, gentle method for isolation of rat blood neutrophils and enhances the potential usefulness of rats in neutrophil-related research.
Questions:
1. This technique can be said to subscribe to the philosophy of "the 3 Rs". Who is best known for first describing this philosophy?
2. Rats on a high ethanol diet had (higher or lower) neutrophil numbers than those on conventional chow?
Answers:
1. Russell and Burch, 1959, "The Principles of Humane Experimental Technique"...REFINEMENT of animals studies, REDUCTION in the numbers of animals used, and REPLACEMENT of animals, where appropriate...
2. Lower

Dysuria in an Experimental Lamb. Laboratory Animal Science 47 (4): 419.
A 6-month old female lamb,, whose mother had been treated with 80mg/week of testosterone in an experimental protocol, developed dysuria. On examination and radiography she was found to have masculinized genitalia-attributed to the intrauterine exposure to testosterone-, elevated serum BUN and creatinine, and a suspected ruptured bladder. At exploratory laparotomy, however, the bladder was found to be intact although there was 1.3 liters of reddish yellow fluid in the peritoneal cavity. The fluid's urea nitrogen and creatinine were higher than serum values.
At necropsy, the uterus contained 2 liters of urine. There were two 4-mm diameter ducts in the uterine submucosa, one of which was patent with the urethra. These ducts were determined to be remnants of the mesonephric (Gartner's) ducts that may have persisted due to the in utero testosterone exposure. Gartner's ducts or nonfunctional mesonephric remnants are commonly found in the cow, sow and cat and rarely found in other species, but have not previously been associated with any clinical signs. In this case, the presence of the ducts coupled with urethral obstruction due to the abnormal external genitalia morphology led to the development of urometra.
Questions:
1. T/F: Gartner's ducts are remnants of the caudal aspect of the mesonephric ducts and usually open near the vaginovestibular junction in the adult. Answer: True
2. The Gartner's duct may be a functional accesssory gland in the female camel. Answer: True

Chronic Ulcerative Typhlocolitis in CBH-rnu/rnu (Athymic Nude) Rats. Laboratory Animal Science 47 (4): 423.
This paper reports a disease outbreak occurring in a rat colony. These athymic nude rats had been maintained without incident in a flexible film isolator for some years. The strain was hysterectomy-rederived into a SPF barrier. Four months later, it was noted that some rats were passing unformed feces. Further investigation led to a diagnosis of ulcerative typhlocolitis. Both sexes were equally affected. The age of first diagnosis ranged from 8 to 23 weeks. Feces were described as "pale yellow/brown pasty... often with a mucoid coating". Blood was not grossly visible but could be detected with an occult blood test. Except for loose colon contents few gross lesions were seen although in some there was thickening of the cecal or colon wall and enlargement and hyperemia of the ileocecal lymph node. Microscopic lesions were confined to the cecum, proximal and sometimes distal colon. Lesions included cuboidal metaplasia of surface enterocytes, depletion of goblet cell mucus, dilation/hyperplasia of crypts, crypt abscesses, extension of crypts into the submucosa, proprial inflammatory infiltration, proprial/submucosal fibrosis, and epithelial ulceration. Inflammatory infiltrates consisted primarily of neutrophils and macrophages with smaller numbers of lymphocytes. No microorganisms were seen in association with these lesions and bacterial cultures and smears did not reveal any recognized pathogenic bacteria and serological tests were also negative. It was suggested that these animals could serve as a model for inflammatory bowel disease.
NO QUESTIONS BUT FYI:
1. Some other well recognized chronic inflammatory conditions affecting the large bowel in a variety of animal species include: Dogs - histiocytic ulcerative colitis of Boxers, eosinophilic colitis; Cats - ulcerative colitis; Horses - granulomatous and eosinophilic typhlocolitis; primates - spontaneous colitis in cotton-top tamarins; mice - spontaneous heritable colitis in C3H/HeJBir mice; Rabbits - histiocytic enteritis; and humans - ulcerative colitis, Crohn's disease. Colitis has also been reported in nu/nu and scid/scid mice in association with Helicobacter hepaticus. Spontaneous cases of G.I. tract inflammation have also been noted in rats expressing the HLA-B27 and B-2 microglobulin genes; in IL-2 and IL-10 knockout mice; and in mice with T-cell receptor and class II MHC mutations.
2. rnu ( Many fonts make this look like M U, so note that it really is R N U.) is the Rowett nude gene first detected in a colony of hooded rats at the Rowett Research Institute in Scotland. There is another allelic mutation, rnu with a superscripted N ( the New Zealand nude), which also produces an athymic nude animal. The similarities and differences between these two strains is well described in the NRC book, Immunodeficient Rodents.

Identification of Impaired-Glucose-Tolerant Animals from a Wistar Inbred Rat Colony. Laboratory Animal Science 47 (4): 428.
The Wistar strain of rats was brought to the animal facilities of the National Institute of Nutrition in 1920 and has been maintained by strict brother x sister mating. Four inbred lines within the colony, denoted A, B, C,and D, have been identified and redesignated as WNIN. Recently, hyperglycemic animals were noticed on a sporadic basis and analyses of the lines was initiated.
Rats were challenged with an oral dose of glucose and blood glucose (BG) concentration was measured. Animals with impaired glucose tolerance (IGT) were identified. Oral glucose tolerance test (OGTT) was tested on 144 rats from these sublines. 35 animals had IGT, most of them from the C and D sublines, with a greater number of males older than 3 months affected.
Plasma insulin concentrations were measured in 20 clinically normal rats vs. 20 rats with moderate IGT at 5 months of age using insulin radioimmunoassay. At all time points (O, 1, and 2 hr) the plasma insulin concentrations between normal rats and IGT rats were significantly different.
The lipid profile of IGT rats was compared with that of clinically normal animals; serum triglyceride concentration, free fatty acid and cholesterol concentrations were measured i in six animals each, with corresponding normal controls. The triglyceride values in IGT rats were almost doubled over those of normal rats. There was a marginal increase in cholesterol concentration in IGT rats, however the difference was not significant. No difference in free fatty acid values was found. In addition, gross and microscopic features of the pancrease and kidney of IGT rats did not indicate structural abnormalities.
Glucose intolerance observed in WNIN rats is due to prolonged inbreeding, the abnormal genes becoming segregated and fixed at various levels among the sublines, in purely random fashion. These rats had normal fasting blood glucose concentrations and hyperglycemia that was seen only after glucose challenge. No glycosuria was observed. These findings support a diagnosis of IGT over that of diabetes. This IGT impairment is expressed in both sexes, with no difference in blood glucose values between males and femailes. However, males are more likely to develop the syndrome.
Results of the study indicate that estimation of serum triglyceride concentration can be used to distinguish rats with IGT from normal rats.
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