Laboratory Animal Science 49(2)

Special Topic Overview: Interpretation of phenotype in genetically engineered mice. Laboratory Animal Science 49(2), 137.
Abstract: Conclusion: There is little gene redundancy in mammals and knockout
phenotypes likely exist even if none are immediately apparent.
Discussion: Knockout mice are generated by the injection of genetically engineered or gene-targeted ES cells into a mouse blastocyst to generate a chimeric embryo, which in turn can pass the engineered gene to its offspring. If the germline of a chimeric mouse is colonized by cells derived from the ES cells, the chimera is termed a "germline" chimera. Gene targeting in ES cells uses the ES cells' DNA repair apparatus to bring about homologous recombination between an exogenous DNA fragment transfected into the ES cell and its homologous region in the genome. This recombination usually results in replacement of the endogenous region with the exogenous fragment, thereby altering the endogenous gene in a prespecified manner.
Variation of this procedure can alter genes to ablate functions or make more subtle mutations (e.g. introduce point mutations, remove specific splicing products, switch isoforms and humanize genes).
Note: because background-dependent phenotypic variability will likely be found for most knockout mice, it is useful to backcross a targeted allele onto several background strains. However, putting a targeted allele on a mixed strain background also provides useful information.
- generating homozygous mutant knockouts on a mixed background is faster
- mixed genetic background knockouts often have a wider range of phenotypes
In conclusion: there is little gene redundancy in mammals, there are knockout phenotypes even if none are immediately apparent, and investigating phenotypes in mixed genetic background colonies may not only reveal phenotypes, but may lead to better understanding of the molecular or cellular mechanism underlying the phenotypes and may lead to modifier gene discovery.
Questions: Questions:
1) T/F - ES cells have been produced from several species (hamsters, rat, rabbit, pig, bovine, zebrafish), but the knockout technology to date has only been successful in mice.
2) An established combination for successful germline transmission uses ES cells from -------- strain and injection of these cells into the blastocyst of --------- strain.
a- C57BL/6; 129
b- 129; C57BL/6
c- Swiss; C57BL/6
d- CD1: 129
Answers: Answers:
1) T
2) b

B-virus specific pathogen free breeding colonies of macaques (Macaca mulatta): retrospective study of seven years of testing. Laboratory Animal Science 49(2), 144.
Abstract: This is a review of the NIH B Virus Resource Laboratory database of B virus testing results from 6 colonies attempting to become B virus free over 7 years. They use a battery of four tests: a titration ELISA at the first level, which determines the titer; an SPF ELISA which is more sensitive but less specific; Western Blot; and finally a competition ELISA (which removes cross-reacting antibodies such as HSV1 and 2 before running) as the most specific.
They found that the probability of detecting a positive animal decreased from .116 to .005, probably the limit of the test, in 3 years. Comparing this with samples from non-SPF colonies, the probability of a positive averages .163-.318. These numbers should not be used as prevalences of B virus, but they do give some indication of the risk. She concludes that a testing and culling program can decrease the risk of B virus exposure.
An Appendix gives a 4-year plan for producing a B virus negative colony. In year 1 macaques are housed individually, and tested twice with 6 months between tests. Seropositives are culled. In year 2 they are tested two or three times. In the last half of year 2 the animals are placed into SPF groups. They are grouped as seronegative, indeterminant, or seropositive (culled). In year 3 the colony is closed, and seronegatives are tested once or twice. Those with indeterminant results are tested more often. If an animal tests positive all animals in the contact group are tested 2-3 times per year. Beginning in year 4 the SPF status is maintained and breeding can begin. Reports are submitted to the B virus testing laboratory showing the history of each animal's housing and contacts.
Questions: Questions
1. What is the Latin name for "B virus"?
2. What does the ELISA for B virus detect?
Answers: Answers
1. Herpesvirus simiae, or Cercopithecine herpesvirus type 1
2. Antibodies

Selection of the most efficacious of twenty-two inactivated sendai virus nasal vaccines by determination of the protection index in mice. Laboratory Animal Science 49(2), 149.
Abstract: Previously it was shown that several chemicals used to inactivate the Nagoya strain of Sendai virus offered complete protection from infection. This article is a follow-up on the dependency of immunogenicity of inactivated Sendai virus upon the modifier inactivant. Inactivation of the MN strain of virus took between 2-6 months. This is a more virulent form of Sendai virus than Nagoya.
Mice were given the vaccines intranasally three times at two-day intervals and challenged 7 days later. Infection was assessed by immunofluorescence and results were reported by protection index (PI). Twelve vaccines induced >/= 2.0 PI in the nasal mucosa. Serum hemagglutination inhibition (HI) titer was low for all vaccines, meaning serum from vaccinated mice did not prevent virus attachment to cells in vitro. A high PI showed no correlation with high serum HI titers. The conclusions of this article were that 6 of the 22 vaccines tested provided the strongest defense in the respiratory tract. In addition, in the authors^Ò opinion, modification of ribose OH of RNA had an advantage over other sites in the virion.
Questions: Questions:
1.What test can be used to assay the ability of serum to prevent viral absorption to cells?
2.T/F A low serum HI titer means animals are not protected from infection.
3.T/F Inactivation of a virus for vaccine purposes does not depend upon the method of inactivation.
Answers: Answers:
1. Hemagglutination inhibition test (HI)
2. False, for a variety of reasons.
3. False, as this article points out, there's quite a variation.

Cardiovascular pathology possibly associated with ketamine/sylazine anesthesia in Dutch Belted Rabbits. Laboratory Animal Science 49(2), 153.
Abstract: The authors had observed myocardial necrosis and fibrosis in a number of Dutch Belted rabbits that had been anesthetized with ketamine/xylazine multiple times for electroretinography and visual-evoked potential studies. Another previous observation of myocardial fibrosis in NZW rabbits anesthetized with combinations including detomidine (an alpha-2 agonist as is xylazine) suggested to them that the observed pathology could be the result of the anesthesia regimen. In this study an additional 35 animals were evaluated. Most of these animals were also being used in a separate ophthalmology study. Radiographic, electrocardiographic, echocardiographic, and pathologic examinations were performed. There were four groups of animals. Group A (n=9, 1 f, 8 m, mean age 21 mo.) had been anesthetized 8-10 times over a 12 mo. period. Group B (n=11, 9 f, 2 m, mean age 7 mo.) had been anesthetized once for a terminal study. Group D (n=5, 5 f, mean age 20 mo.) had been anesthetized 1-3 times for echocardiographic studies only. The vendor of the rabbits provided formalin fixed hearts from retired breeders that had never been anesthetized to serve as histological control Group C (n=10, 5 f, 5 m, mean age 30 mo.). Echocardiographic parameters did not differ markedly between groups. (Note that the n's listed in Table 1 are incorrect, not all animals were studied. See Methods section for correct number. Also the results section incorrectly refers to echo results on Group C, the fixed hearts. I hope that's a typo.) Only 7 Group A animals were evaluated radiographically. No abnormalities were noted. Electrocardiograms were obtained on the same seven animals. No abnormal rates or rhythms were seen. It was noted that one rabbit had indications of right ventricular hypertrophy based on wave shape but no values were given. Seven Group A animals were the presence of antibodies to canine coronavirus. All were negative.The primary observation in this paper was that a greater degree of myocardial fibrosis was seen in the Group A rabbits. Unfortunately the significance of this observation is questionable since these animals were being compared to others that were not matched for age, sex, nor husbandry. It was noted that myocarditis, myofiber degeneration and necrosis were seen principally in the animals that had been anesthetized only once. This interesting observation was not discussed further. Three Group A rabbits were evaluated for serum vitamin E concentrations. The value given was stated to be low but no reference range was given so it is not clear how low they were. Also since no samples were taken from any of the other groups it is impossible to speculate on its significance. At the end of this paper we know no more than when we started, that there is a possible association of heart pathology with multiple anesthetic events. On a positive note, if you have any interest in the use of rabbits as models of cardiopathology, the introduction, discussion, and references are well done and would be of value. Just skip all the stuff in between.
Questions: QUESTIONS: 1. Why did they look for antibodies to canine coronavirus?
2. Why did they look at Vit E levels?
Answers: ANSWERS:
1. They were looking for antibodies to the rabbit pleural effusion disease/infectious cardiomyopathy virus which cross reacts with the canine coronavirus antigen in the IFA test.
2. Diets low in Vit E can cause myocardial as well as skeletal muscle degeneration.

Animal models of spinal cord contusion injuries. Laboratory Animal Science 49(2), 161.
Abstract: This article describes the use of rats and cats for animal models of spinal cord injury (SCI). The yearly incidence of SPI is 28 to 50 injuries per million in people, thus a reliable and reproducible animal model is needed.
Cats provide a better model for intensive therapeutic regimens due to their larger size; rats are smaller and are less expensive to purchase and house. SCI in both animal species was induced by a contusion devise and also by spinal cord transection. The contusion devise dropped a specific weight from a predetermined height to the desired location on the spinal cord.
Animals were provided with appropriate post-operative care, monitored by behavioral tests, electrophysiologic tests, and histologic evaluation at the end of the study. There were three experimental groups for each species: moderate contusion, severe contusion, and transection. Within each experimental group, results were consistent, demonstrating the value of these methods of creating SCI.
Questions: Questions:
1. What are the advantages for using cats as a model for SCI?
2. What are the two tests used to test electrophysiology after SCI?
Answers: Answers:
1. Cats are larger in size, facilitating more intensive therapeutic regimens.
2. The electrophysiologic tests consisted of somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs).

Auditory brainstem responses in golden syrian hamsters (Mesocricetus auratus) affected with the Wh gene. Laboratory Animal Science 49(2), 173.
Abstract: This article describes hearing evaluation of the anophthalmic white (ATW) Golden Syrian hamster (Mesocricetus auratus) which is thought to be homologous to the human Waardenburg syndrome (WS) which is a condition that represents the most common form of inherited deafness in human infants. WS in humans is an autosomal dominant mutation that is characterized by sensorineural hearing loss (this is deafness due to lesions of the cochlea and/or acoustic nerve and/or central neural pathways), dystopic canthrom (this is a malposition of the angle at either end of the fissures between the eyelids), and pigmentary disturbances. The gene in the hamster identified with anophthalmic white is the Wh gene which is an autosomal semi-dominant gene. Morphologically, in homozygote hamsters, includes blindness, infertility, small adrenals, growth retardation, increased metabolism, increase food & water intake, white body color and deafness. Deafness has been reported due to degeneration of the tectorial membrane noted between 10-15 days of neonatal life. However, it is apparent there is little data on evaluation of the hearing loss associated with this gene in hamsters. To evaluate hearing in 20 hamsters this group used auditory brainstem responses (ABR). Instrumentation for evaluation uses a digitally generated electrical pulse to generate Gaussian-shaped (bell shaped) alternating broadband clicks. The hearing range in adult hamsters has been reported from 500-20,000 Hz with thresholds (defined as the lowest intensity level where peaks are noted) between 2,000-4,000 Hz. A normal hamster ABR is defined as 4 positive-going peaks (I, II, III, IV) at a specific time point after stimulus with Peak III being noted as the most robust. Comparisons were made between the ATW, Agouti, Cream, Black-eyed white (BEW) and White Bellied agouti (WBA) hamsters. An interesting factor is noted here with these groups in that there is an epistatic interaction of genes (Wh and e) on coat color and the Wh expression is enhanced by the cream e. The e gene is an autosomal mutation that prevents eumelanin and affects the coat color. Therefore, WBA hamsters used were noted as Wh/wh;E/e and the BEW hamsters were noted as Wh/wh;e/e. The Agouti and Cream hamsters were wh/wh;E/e and wh/wh;e/e respectively. The ABR threshold of the Agouti and Cream hamsters was approximately 50 decibel peak equivalent sound pressure level (dB pe SPL) and considered normal. The ABR threshold of the BEW and WBA hamsters was slightly higher at 75-80dB pe SPL. It is suspected that the BEW and WBA hamsters have higher thresholds and therefore variable degrees of hearing loss as a result of heterozygous expression of the Wh gene. The ABR waves of the ATW hamsters were not seen even at 100dB pe SPL indicating complete hearing loss as a homozygous expression of the Wh gene. However, there have been other genes related to hearing loss in mice discovered and include TECTA, MYO6A, MYO7A and MYO15. These genes have been found to encode for proteins associated with the inner ear cochlea such as actin and have not been ruled out as a condition that may have affected these hamsters.
Questions: 1. What is meant by an epistatic interaction of genes?
2. T or F: The reasons for deafness in the anophthalmic (ATW) hamsters is the same as seen in human infants with Waardenburg Syndrome (WS)?
Answers: 1. Epistatic in this situation means the interaction between genes at different loci resulting in one gene to be unexpressed or masked by superimposition of the other gene. In this particular example there is a change in hair coat as in the Agouti hamster (wh/wh;E/e) compared to the White Bellied Agouti/WBA (Wh/wh;E/e). Both animals are heterozygous at the E (creme) loci but are different Wh thereby resulting in different phenotypes.
2. False: In hamsters it is due to degeneration of the tectorial membrane. In humans it is due to a lack of neural crest derived cells resulting in aplasia of the posterior semicircular canal and poor development of the vestibule. Note that there have been no homozygous cases of WS reported.

In vivo properties of three human HER2/neu-expressing murine cell lines in immunocompetent mice. Laboratory Animal Science 49(2), 179.
Abstract: This journal article describes the development and biological properties of 3 murine tumor cell models which express the human HER2/neu proto-oncogene and are capable of growing in immunocompetent mice.
HER2/neu encodes for a receptor-like transmembrane glycoprotein. HER2/neu expression is markedly increased in some breast, colon, lung and ovarian cancers. Monoclonal antibodies targeting different aspects of the HER2/neu gene may be useful as therapeutic agents; however, their evaluation in animal models has been difficult because human tumors do not grow in immunocompetent mice.
In order to produce murine tumors that express HER2/neu, the authors transduced 3 murine derived tumor cell lines, CT26, MC38 and EL4, with cDNA encoding human HER2/neu. CT26 and MC38 are murine colon adenocarcinoma cell lines and EL4 is a murine lymphoma cell line.
The 3 transduced cell lines (CT26-HER2/neu, MC38-HER2/neu and EL4-HER2/neu) were transplanted into immunocompetent BALB/c or C57BL/6 mice by either subcutaneous or intravenous injection. Tumor growth rates, tumor phenotype, the ability to induce metastases, HER2/neu expression, antigen shedding and the anti-HER2/neu host response were analyzed. BALB/c and C57BL/6 mice transplanted with nontransduced CT26, MC38 and EL4 tumor cells served as comparison groups.
In vitro expression of HER2/neu in transduced murine tumor cells was confirmed by flow cytometry and immunohistochemistry. Subcutaneously transplanted transduced tumors showed the same time of tumor onset and growth rates when compared to their nontransduced like comparison groups. All 3 transduced tumors, as well as the 3 nontransduced tumors, exhibited the same malignant phenotype: extensive infiltration of the subcutaneous space and part of the muscular coat.
Intravenous transplantation of high doses of CT26-HER2/neu and MC38-HER2/neu or EL4-HER2/neu transduced cells resulted in death of all mice within 1 or 2 months, respectively, due to disseminated malignant disease. Intravenous transplantation of low doses of the same transduced cells resulted in some mice survival. Intravenous injection of CT26-HER2/neu cells resulted predominantly in infiltration of malignant cells into the lung parenchyma. Intravenous injection of MC38-HER2/neu cells resulted in metastasis to lungs, liver, brain, bone marrow and the subcutaneous space. Intravenous injection of EL4-HER2/neu cells resulted in metastasis to thymus, lymph node, kidney, liver, ovary, peritoneum, bone marrow and the subcutaneous space.
Flow cytometry and immunohistochemistry was used to confirm cell surface expression of HER2/neu in transduced tumors and cells in culture.
The production of murine anti-HER2/neu antibodies was assessed by ELISA and confirmed in all mice with tumors expressing human HER2/neu.
Tumor antigen shedding (ECD^HER2) has been described in patients with breast cancer. High levels of tumor antigen (> or = to 500 ng/ml) may interfere with therapy in humans. In this study, tumor antigen could not be detected by ELISA in culture supernatents or sera of mice transplanted with transduced tumors.
The authors concluded that the 3 murine models may be useful in the evaluation of cancer therapies that target HER2/neu.
Questions: Questions:
1. Subsets of which human cancers show increased expression of HER2/neu?
2. How was the MC38 colon adenocarcinoma induced in the C57BL/6 mouse?
Answers: Answers:
1. Subsets of human breast, colon, lung and ovarian cancers show markedly increased expression of HER2/neu.
2. The MC38 colon adenocarcinoma was induced in C57BL/6 mice by subcutaneous administration of dimethylhydrazine.

Rabbit intestinal xenograft model for human Encephalitozoon infections in mice. Laboratory Animal Science 49(2), 189.
Abstract: Microsporidia are primitive eukaryotic, intracellular, spore-forming protozoa that lack mitochondria, true golgi, and peroxisomes.
Human microsporidial infections have become more prevalent with the advent of HIV and AIDS. A major route of infection is speculated to be by oral injestion of spores which can lead to chronic debilitating diarrhea and possible systemic spread.
In order to further elucidate the pathogenesis of this disease the authors used a model in which fetal rabbit intestines were xenografted into the subcutaneous tissues of athymic and SCID mice.
Once the model was established the xenografted tissues were inoculated with either Encephalitozoon cuniculi, E. intestinalis, or E. hellem. All microsporidia established themselves as intracellular parasitophorous vacuoles in the xenograft enterocytes. Multi-systemic spread of infection was demonstrated for E. cuniculi and E. intestinalis. One of ten mice infected with E. hellem was found in the lungs. The pulmonary infection of E. hellem was speculated to be a result of inhalation of spores while grooming the inoculation site or alternatively, some of the spores may have made it through the system and excreted in the urine and feces without detectably infecting any organs where they could gain access to the pulmonary system through coprophagy. (In humans, E. hellem is speculated to be acquired by the respiratory route).
Other unique findings in this model system: first report of E. cuniculi infecting and causing inflamation in the salivary glands and first report of hepatic infection of E. intestinalis in a laboratory animal model.
This study demonstrates that the fetal rabbit intestinal xenograft model may be useful for studies of intestinal microsporidial infection and systemic infection in humans.
Histopathology and EM presented.
Questions: Questions:
1. With regards to pathogenesis, which organism doesnít belong with the others:
E. cuniculi
E. intestinalis
E. hellem
Enterocytozoon bieneusi
2. Characteristics of microsporidia include (more than one):
A. eukaryotic
B. intracellular
C. spore forming
D. protozoa
E. Gram +
3. How are microsporidia different than eukaryotic cells (3 Characteristics)?
4. Why were the mice and fetal rabbits used to produce the model described in this article?
Answers: Answers:
1. C. E. hellem - infection and dissemination is believed to be via the pulmonary system. (Enterocytozoon bieneusi is the most commonly diagnosed infection in humans, it also infects the intestinal tract and causes diarrhea in humans)
2. ABCDE (all of them)
3. Lack mitochondria, true golgi, and peroxisomes (They also produce spores and contain a sporoplast which plays a role in infection)
4. Mice: immunodeficient mice (SCID and nude) are readily available and will not reject the xenotransplant. Rabbits are the natural hosts for E. cuniculi. The intestines of fetal rabbits are sterile, therefore less risk of infection at surgical site and bacterial colonization will not interfer with microsporidial infection.
5. Encephalitozoonsis, Pasteurellosis, Toxoplasmosis, Psoroptiasis (P. cuniculi), Trauma
6. Brain: granulomatous encephalitis with perivascualar cuffing
Kidneys: granulomatous nephritis with plasmacytic interstitial infiltration

Rhesus monkey (Macaca mulatta) model of Helicobacter pylori: noninvasive detection and derivation of specific-pathogen-free monkeys. Laboratory Animal Science 49(2), 197.
Abstract: H. pylori is a microaerophillic, gram neg., spiral bacterium that infects the gastric mucus of half the world's human population. It is associated with peptic ulcer disease and gastric malignancy. This study evaluates the rhesus monkey model, the detection testing methods, and strategies to develop a H. pylori naïve colony. The rhesus is a good animal model for H. pylori because it is naturally infected and the infection resembles the human condition. There is a high prevalence of infection with H. pylori 1 yr. (65%), 2 yrs. (84%), 3 yrs. (96%) and 4 yrs. (100%). Therefore, to develop a SPF colony it is essential to remove the infants within 24 hrs. of birth. Serologic identification of H. Pylori using a rhesus-derived antigen antigen ELISA is more specific (94%) and sensitive (95%) than the human-derived ELISA (83% specific, 69% sensitive). There is also minor problem with spontaneous H. heilmannii infection causing antigenic cross-reactions. The [C] urea breath test is highly sensitive (96%) and specific (88%) for detection. Culture using a brucella agar is also very specific, but not very sensitive. Histology of gastric biopsies are very specific but not sensitive due to variability of biopsy location. A Warthin-Starry silver stain is used to identify gastritis and differentiate H. pylori from H. heilmanni infections.
Questions: Questions:
1. What diagnostic methods are good way to identify H. pylori infections in rhesus monkeys?
2. How can a SPF rhesus population negative for H. pylori be derived?
Answers: Answers:
1. The [C] urea breath test and rhesus derived ELISA methods are good methods to identify chronic H. pylori infections in rhesus monkeys.
2. Isolation of newborn monkeys and segregation of the naive population are methods used to develop a SPF rhesus population.

Power spectral analysis of heart rate variability for assessment of diurnal variation of autonomic nervous activity in miniature swine. Laboratory Animal Science 49(2), 202.
Abstract: Spectral analysis of heart rate variability can be used to provide information on underlying autonomic nervous system functions. The purpose of this study ws to establish characteristics of power spectral analysis of heart rate (HR) variability of autonomic nervous system functions in miniature swine.
Ten adult male miniature swine were allotted to two groups. Group 1: Three swine were inplanted with a vascular access port in the left carotid artery and left internal jugular vein. The following measurements were then taken: ECG using an apex-base lead; blood pressure using a catheter connected to a transducer and respiration waveform using a respiratory band wrapped around the last intercostal space, which stretches during inhalation. After a 30 minute acclimatization period, stable parameters were continously and simultaneously recorded for 30 minutes. Control recordings using IV administered saline were followed by blockade of autonomic nervous system functions using atropine, propranolol, and atropine and propanolol administered IV into the left jugular vein in that order at 24 hour intervals. Parameters were recorded from before injection of drugs to 30 minutes post-injection.
Group 2: Seven swine were instrumented with a jacket for 24 hour Holter ECG recordings using the apex-base lead.
All data underwent power spectral analysis. Two major spectral components, one at low frequency (LF) and one at high frequency (HF) in the power spectrum were defined, establishing that HR had a diurnal pattern. The LF and HF during the dark phase tended to be higher than the LF and HF during the light phase suggesting that parasympathetic nervous activity predominates during the dark phase in miniature swine. Autonomic nervous system blockade with atropine significantly increased HR and abolished the HF and LF areas; whereas, propanolol decreased HR, but had no significant effect on HF and LF powers (figure 2). Blockade with both atropine and propanolol significantly reduced LF and HF areas (not shown).
According to the Authors, these results indicate that HR variability in the HF and LF components are mediated by the parasympathetic system, but that the sympathetic system mediates only the LF component.
The Authors concluded that 1.) in miniature swine, parasympathetic nervous system activity may predominate in the dark phase and 2.) the characteristics of power spectra and diurnal variation of the autonomic nervous system in miniature swine are similar to those in humans. These findings are important because epidemiology studies have indicated a circadian pattern of adverse cardiac events, with incidence of myocardial infarction and sudden cardiac death peaking in the morning. Therefore, miniature swine may provide a useful model for biobehavioral an pharmocotoxicologic studies.
Questions: Questions:
1.) What is the function of the autonomic nervous system?
2.) Atropine is a
a. parasympathomimetic
b. parasympatholytic
3.) Which neurotransmitter does atropine prevent from binding to muscarinic receptors?
4.) What effect does propranolol have on the myocardium?
Answers: Answers:
1.) The autonomic nervous system reacts to maintain involuntary functions (i.e., respiration, heart rate, blood pressure, GIT functions, etc.)
2.) b
3.) acetylcholine
4.) propranolol is an antiarrhythmic drug

Corynebacterium bovis infection in immunocompetent Hirsute mice. Laboratory Animal Science 49(2), 209.
Abstract: Corynebacterium bovis infection of athymic nude mice has been shown to produce hyperkaratotic dermatitis (HD). The source of the C. bovis has not been found, however. Other mice are also susceptible to infection with C. bovis--in particular immunocometent hirsute hetrozygous (nu/+) mice have been shown to be carriers. In addition, CD-1 mice have been shown to be susceptible to infection with C. bovis when they were housed with C. bovis-infected nude mice. (Note: C. bovis is a common inhabitant of the bovine mamary gland, and contemporary research facilities rarely house nude mice with dairy cows.)
This study investigate the possibility that immunocompetent hirsute mice may be naturally infected with C. bovis, and thus a source of infection for nude mice. A number of hirsute mouse strains were chosen and examined by histopathology and skin culture. Hirsute mice fell into two groups: prior housing with healthy nude mice and nude mice with HD.

Results: 1. C. bovis was only detected on hirsute mice that were housed with nude mice affected with HD. Interestingly, several DBA/2 mice that became infected with D. bovis eliminated the infection within a month after being removed from the affected nude mice.
2. It is unlikely that immunocompetent hirsute mice are a reservior of C. bovis infection.
Questions: Questions:
1. What does hirsute mean?
2. What chromose is the nude mutation on in the mouse?
Answers: Answers:
1. hairy, shaggy
2. chromosome: 11

Influences of somatotropin on biomechanical properties of porcine skin. Laboratory Animal Science 49(2), 212.
Abstract: The purpose of this study was to evaluate the effects of somatostatin or growth hormone administration on tensile strength and deformation of skin in growing pigs. Hormone and gene therapy are being used more and more in medicine, agriculture, and horticulture to increase growth and productivity. Somatotropin has been used to enhance mild production in dairy cows, increase lean meat production in pigs, and treat children with impaired pituitary function. Published research in rodents suggest that somatotropin will enhance mechanical strength and healing of soft tissues and bone fractures (callus formation, but may hinder secondary healing). This increase in mechanical stress may be due to enhancement of collagen production for alterations in collagen cross linking.
Crossbred pigs (8) were treated daily with pituitary-derived porcine somatotropin (pST), and controls (8) were given buffer.
Skin thickness and tensile strength of specimens from the shoulder and rump of treated and control pigs were measured. Administration of pST results in 29% and 18% increases in skin thickness in the should and rump, respectively. In contrast, pST administration resulted in an average 28% reduction in tensile strength of skin. In these pigs, pST treatment was associated with an increase in soluble collagen, but pST had little effect on the concentration of total or insoluble collagen. The increase in skin thickness and the reduced tensile strength is supported by quantitative chemical and tensile analysis suggestive of the presence of material with less relative mechanical stability, eg., higher proportion of newly formed collagen molecules (soluble) with a relative reduction in mature intermolecular cross-lined collagen fibers (insoluble).
Questions: Questions:
1. Because porcine skin is considered to be an excellent model for human skin, patients receiving somatotropin treatment should be aware of that:
a. increase in the thickness of skin
b. decrease in the tensile strength of skin
c. no change in tensile strength of skin
d. a and b
e. a and c
2. This study suggests that there is a change in skin thickness and tensile strength after administration of somatotropin, or growth hormone. Which of the following is a correct statement based on the above article review? Because porcine skin is considered to be an excellent model for human skin, patients receiving somatotropin treatment should be aware of that:
a. Skin thickness increased due to an overall increase in soluble collagen. This increase in collagen resulted in a greater density of collagen and cross-linking and thus a greater tensile strength.
b. Skin thickness increased due to an overall increase in soluble collagen. This increase in collagen resulted in a greater density of collagen. But, tensile strength was reduced, possibly due to the fact that the soluble collagen had not formed mature covalent cross-links.
c. Skin thickness decreased due to an overall reduction in soluble collagen. This reduction in collagen resulted in a lower density of collagen, and thus a reduction in tensile strength in shoulder and rump skin.
Answers: Answers:
1. d
2. b

New technique for superselective arterial (chemo-) embolization of the rat liver. Laboratory Animal Science 49(2), 216.
Abstract: Transcatheter arterial embolization has been used to treat spinal cord angioma, arteriovenous fistula and to control bleeding in vascular tumors of soft tissue organs and bones. Substances used to induce embolization are categorized according to the localization of vessel occlusion and include central, peripheral and capillary.
Central occlusion: stainless steel coils, Gelfoam segments (not effective as an antitumor treatment due to collateral vessel formation) Peripheral occlusion: Ivalon or gelfoam powder or cubes Capillary occlusion: silicone, cyanoacrylate, alcohol and a prolamine solution - ETB (at this level, collateral formation does not form) The authors present a surgical method of local embolization of the liver in which ETB blended with chemotherapeutic agents is infused into the lobar artery. This method is referred to as chemoembolization. The technique described allows for the selective occlusion of an artery supplying a single lobe of the rat liver as chemotherapy of an experimentally induced tumor located in a single rat liver lobe. ETB is a highly viscous vegetable prolamine substance made by Ethicon. The technique was reported to be successfully based on histopathology but data was not supplied.
Questions: Questions:
1. Transcatheter embolization has been used to treat the following conditions
a. soft tissue tumors
b. spinal cord angiomas
c. arteriovenous fistulas
d. bone tumors
e. all of the above
2. The method in which an occlusive substance blended with a anticancer drug is infused into main arterial blood supply to a tumor is referred to as
Answers: Answers:
1. e
2. chemoembolization