Animal models of human disease for the 21st century. Laboratory Animal Science 48 (6): 562.
This review article, a prelude to the symposium of the same title, emphasizes the importance of selecting the appropriate animal model for the research question(s) being asked. The article goes on to outline the needs, regarding appropriate animal models of human disease, for the next century. The specific needs are: 1) national repositories for import, cryopreservation, and distribution of genetically-defined models; 2) improved bioinformatics resources; 3) models and their repositories other than rodents; and 4) National Stock Centers to supply well-characterized biomaterials to the biomedical research community. The author goes on to emphasize that as the Human Genome Project nears completion, researchers will turn their focus to the "proteome" (i.e., characterization of proteins expressed by genes) and the "physiome" (i.e., the physiology of expressed proteins).
No questions

The contribution of avian models to our understanding of atherosclerosis and their promise for the future. Laboratory Animal Science 48 (6): 565.
Avian models were some of the first animal models of atherosclerosis. The four major avian models are chickens, turkeys, Japanese quail and pigeons. Chickens develop atherosclerosis in the aorta naturally, and at an accelerated rate if fed a cholesterol-containing diet. They are naturally cholesterolemic. Since Marek's disease exacerbates their atherosclerosis, chickens have been used to study the role of viruses in the pathogenesis of atherosclerosis. Turkeys naturally develop atherosclerosis, hypertension and dissecting aortic aneurysms. Japanese quail develop diet-induced atherosclerosis and sometimes myocardial infarction. Cholesterol-containing diets accelerate the atherosclerotic lesions, which are very similar to human lesions. Japanese quail's advantages are their relatively small size (120 g) and rapidly developing atherosclerotic lesions with cholesterol feeding.
Pigeons have been the most used avian species. Certain breeds, most notably the White Carneau (WC) are susceptible to developing atherosclerosis. Other breeds, especially Show Racers (SR) are resistant. In pigeons, atherosclerosis develops first in the aorta at the celiac artery bifurcation. In contrast to humans, coronary artery atherosclerosis in pigeons develops primarily in the small intramyocardial arteries. The microscopic appearance of their lesions is very similar to humans. Myocardial infarction may occur in severely affected older pigeons. With cholesterol feeding, both WC and SR pigeons develop marked hypercholesterolemia. Since differences in atherosclerosis between WC and SR pigeons can't be explained by known risk factors or by differences in lipoprotein metabolism, it suggests that there are genetic factors that can influence susceptibility to atherosclerosis that may be mediated directly at the arterial wall level.
Questions:
1) In pigeons, where does atherosclerosis develop first? A: In the aorta at the celiac artery bifurcation
2) What pigeon breed is the most resistant to atherosclerosis? A: Show Racer
3) What is the special nature of naturally developing atherosclerosis in turkeys? A: Complicated by hypertension and dissecting aortic aneurysms
4) True/False: Based on observations in chickens, atherosclerosis may be at least partially viral-mediated. A: True

Nonhuman primate models of athersclerosis. Laboratory Animal Science 48 (6): 569.
This article focuses on the different species of nonhuman primates used in atherosclerosis research. The following are certain aspects of athersclerosis that have been studied; 1) hyper/hypo responsiveness to dietary cholesterol, 2) age susceptibility to diet-induced athersclerosis, 3) gender differences in diet-induced atherosclerosis, 4) effects of different types of dietary fats and housing on athrerogenisis, 5) progression of coronary artery atheroclerosis and remodeling, 6) regression of diet-induced atherosclerosis, 7) psychosocial influences of atherogenesis, 8) the effects of menopause and hormone replacement on atherosclerosis, and 9) a cardiovascular procedure called post angio-plasty restenosis.
New World monkeys are of limited value in atherosclerosis research because of complications associated with chronic renal disease. Squirrel monkeys fed atherogenic diets ultimately develop lipid accumulations in the glomeruli. Proteinuria follows with elevations in plasma low density lipoproteins (LDL's). Cotton-top marmosets have been used in lipoprotein studies. It has been found that males are more likely to develop coronary artery atherosclerois. Cotton-tops marmosets also develop renal lesions similar to those seen in squirrel monkeys. Cynomologus and rhesus macaques as well as other monkeys have proven to be beneficial in the study of atherosclerosis.
Hyper/hypo-responsiveness to dietary cholesterol:
This phenomenon has been studied in various monkey species. Large individual differences in the responses of total plasma cholesterol concentrations occur among animals fed the same cholesterol- containing diets. Cynomolgus monkeys are being studied in which progeny of hypo- and hyper-responders have been produced. It has been shown that progeny will become hyper-responsive in an average of 8 years. In contrast, the progeny of hypo-responders will remain like their parents for the rest of their lives.
Effect of age on susceptibility to diet-induced atherosclerosis:
Young animals are relatively resistant to atherosclerosis but become more susceptible as they mature. Cebus monkeys have been used in which an atherogenic diet was given to pre- (6 mo-3.5y years) and post-pubertal (5.5-8.5 years). Plasma lipid responses seemed quite comparable however, as the animals grew older it was apparent that the post-pubertal monkeys had increased coronary artery atherosclerosis. Cynomolgus monkeys have also been fed atherogenic diets and plasma cholesterol levels were higher in pre-pubertal vs. post-pubertal animals. Cynomolgus adults also had increased coronary artery athersoclerosis similar to older cebus monkeys.
Physcosocial influences on atherogenesis:
Male and female cynomolgus monkeys were involved in a study that involved living in stable and nonstable social environments. Males that were housed in stable environments with the same monkeys for several years had little coronary artery atherosclerosis. Males housed in unstable environments involving different cage mates over the course of the study had increased heart rate and blood pressures. The author suspects that because a hierarchy system is never fully established in unstable living conditions, exacerbation of atherosclerosis occurs. Males living in a stable environment regardless of their level on the heiarchy scale suffered little coronary artery atherosclerosis. In females, depending on the hiearchy status the degree of atherosclerosis is proportional. Females at the top of the hierarchy were less stressed as opposed to subordinates and experienced little atherosclerosis. The subordinates were involved in stressful competitive social strategies to move up the hierarchy. The effect of competitive stress on coronary artery atherosclerosis was profound in female subordinates.
Surgical menopause and hormone replacement:
Surgically-menopausal cynomolgus females were fed atherogenic diets as well hormone replacements of estradiol with or without progesterone. It was found that the absence of estrogen leads to constriction of the artery and estrogen replacement allows the coronary artery to regain its ability to dilate.
Progestin effects on estrogen replacement therapy:
Women who have a uterus must have progestin added to their estrogen therapy in order to protect them from endometrial cancer. Medroxyprogesterone (MPA) commonly called Provera is the most widely used progestin. It was found in cynomolgus females that if progestin is supplemented when estrogen is given cyclically or continuously, then cardioprotection is attenuated and coronary artery dilation occurs as well.
Post-angioplasty restenosis:
Cynomolgus females are being used as the surgical model and the author reportsthat successful remodeling of the coronary artery has occurred with this technique. The common iliac artery is the site for the angioplasty with one serving as the control. It has been found that the lumens get bigger despite the fact that the atherosclerotic plaques get bigger because of the remodeling that occurs in the arteries.
No questions

Mouse models of atherosclerosis. Laboratory Animal Science 48 (6): 573.
The mouse is an excellent model for experimental atherosclerosis research. There are three quantitative atherosclerosis assays in use to evaluate the various mouse models:
1. cross-sectional lesion area at the aortic root (freshly perfused and isolated hearts are fixed in formalin, embedded in gelatin, frozen, and cut into thin sections at anatomically defined sites in the aortic sinus and valve region. These sections are stained for lipids, and the lesion areas is measured microscopically.)
2. en face method (the whole descending aorta is opened longitudinally, removed, and stained for lipids. This shows that the lesions are not diffuse, but rather at specific sites of lesion predilection where the flow is turbulent.)
3. aortic cholesterol and cholesterol ester mass (used to determine the extent of lesion formation in the aorta by biochemical measurement of free and, particularly, esterified cholesterol mass in the aorta.)
The earliest mouse model of atherosclerosis is the diet-induced model which has been used effectively, but the lesions tend to be small and are limited to the early fatty-streak stage. This model is also criticized because of the toxicity and inflammatory responses due to the diet. Of the more recent genetically engineered models, the apoE-deficient model is the only one that develops extensive atherosclerotic lesions on a chow diet. It is also the model in which the lesions have been characterized most thoroughly. The lesions develop into fibrous plaques; however, there is no evidence that plaque rupture occurs in this model. The LDL receptor-deficient and the human B transgenic models have elevated LDL levels, but no lesions, or only very small lesions, form on the chow diet. However, robust lesions do form on the western-type diet with these two models.
Questions:
1. What is the modern theory of atherogenesis?
2. True or False, mice make very good atherosclerosis models because, as with humans, they carry most of their plasma cholesterol on low-density lipoprotein (LDL).
3. List 3 uses for mouse models of atherosclerosis.
4. What is the primary difference between the atherosclerosis lesion pathology of humans and the ApoE-deficient mouse?
Answers:
1. The "response to injury hypothesis" which states that atherosclerosis is an excessive fibroproliferative response to an insult upon the arterial wall.
2. False, unlike humans, normal (wild type) mice carry most of their cholesterol on high-density lipoprotein (HDL), which we know in humans is protective against atherosclersois.
3. a. the model is useful for the identification of atherosclerosis susceptibility-modifying genes
b. the model can be used to identify the role of various cell types in atherogenesis
c. the model can be used to characterize environmental and dietary effects and to test therapies that might block or reverse lesion progression
4. Plaque rupture is not observed in the mouse model.

A Ret transgenic mouse model of thyroid carcinogenesis. Laboratory Animal Science 48 (6): 580.
The model is a ret/PTC1 transgenic mouse model of thyroid carinogenesis originally developed at Ohio State University by Dr. Sissy Jhiang. This mouse serves as a model of human papillary thyroid carcinoma. TSH has a strong influence in stimulating carcinogenesis in rodents; its contribution to human disease progression or recurrence is questionable. Tumor growth may be rapid in pregnant woman due to the contributions of human chorionic gonadotropin. However, genetic events appear to primarily influence differentiation of the initiated follicular cell humans. In iodine-deficient areas of the world progression to carcinoma is preceded by a follicular adenoma. In iodine-sufficient areas there is no pre-malignant adenoma to carcinoma pathway, however, occult papillary carcinomas are present at a relatively high frequency in aged human patients. The progression of follicular adenoma to carcinoma has been associated with ras mutations early in the process. Ret mutations have been uniquely associated with papillary thyroid carcinomas and are thought to play an early role in the formation of papillary carcinoma, and possibly also in the progression of occult papillary thyroid carcinoma to overt papillary thyroid carcinoma. Trk and met oncogenes may also be involved in the genesis of papillary thyroid carcinoma. Ultimately, both follicular and papillary carcinoma may progress to anaplastic carcinoma, one of the most rapidly progressive malignancies in humans, with low one-year survival rates. This has been associated with a high prevalence of p53 tumor suppressor gene mutations. Papillary thyroid carcinoma is differentiated from follicular thyroid carcinoma by the presence of papillary architecture, local invasion, high rate of regional lymph node metastases, nuclear grooves, pseudo-inclusions and nuclear clearing ("Orphan Annie Eye nuclei"). Ret is a proto-oncogene, which results in loss of function of the tyrosine kinase activity, has been incriminated in a number of human disease syndromes. Mutations of this gene lead to inheritance of several different familial neoplastic diseases, including medullary thyroid carcinoma as well as two different types of multiple endocrine neoplasia. Ret also has a role in Hirschsprung's disease patients. The resulting colonic hypoganglionosis or colonic aganglionosis results from loss of function of the tyrosine kinase activity, highlighting the role of ret in the differentiation and migration pathways of neural crest-derived tissues. The combination of the ret tyrosine kinase with the H4 gene produces the PTC-1 oncogene. The goal of this study was to define the role of the PTC-1 oncogene in both the initiation and progression of thyroid carcinogenesis. In the high copy line, mice have severe hypothyroidism characterized by sever dwarfism, a marked decrease in serum T3 and T4, a reciprocal elevation in serum TSH, and pituitary thyrothroph hypertrophy and hyperplasia representing a compensatory response to the hypothyroidism. Males also suffered from a prolapsed penis at about 2-3 weeks of age and if left untreated died. All mice in this line developed bilateral thyroid carcinomas within the first month of life. This high-copy line required exogenous dietary thyroxine for maintenance. The high-copy line developed bilateral thyroid carcinomas within 1-3 months of age. Breeding of these animals suggests that somehow "gene dose" may play a role in the induction of hypothyroidism. Histologically, the low-copy line was similar to the high-copy line. When exogenous TSH is administered, it promoted growth and local progression of the thyroid carcinomas. In a transgenic model, ubiquitous transformation events may affect all cells. There exist intermediate histologic changes that don't fall conveniently into the nomenclature that would apply to spontaneous disease.
No questions

Session Summary and Perspective. Laboratory Animal Science 48 (6): 584.
This article summarizes and gives the author's perspectives on the Animal Models of Human Disease for the 21st Century Conference. Important highlights of the author's discussion was the fact that there are a large and growing body of tissue-specific elements present within the genome that allows researchers to answer a lot of their own hypotheses. The author also states that it is important for researcher to come up with useful and truly conditional promoters for the regulation of transgene action in the development of genetic models of cancer and other diseases. The mouse is well known as the most appropriate model for a number of reasons including genetics. There are other animal models that have been developed but are not in routine use like the mouse. The rat and pig can now be bred as transgenics. The author has done some work himself to develop knockout rat models as well.
The author has created transgenic rats by isolating the metaphase plate of an unfertilized egg microsurgically. When that is done, the metaphase plate resides in a small portion of the ooplasm. When isolated, this fragment attempts to create a new polar body that results in an enucleated rat embryo. The enucleated rat embryo can then be put next to a cell that can be genetically manipulated.
Transgenic mice have been used to create tumors spontaneously by the insertion of specific gene. The author gives the example of spontaneous tumors created by the HPV-16 genome in its entirety without heterologous promoters. These animals spontaneously developed carcinomas or lymphomas without any other intervention at about 1 year of age. The mice however did not develop any cervical lesions. Researchers determined that a localized phenotype could be acquired with physiological relevant intervention. In other words, the position of the intact HPV intact genome to develop into both carcinomas and /or lymphomas had nothing to do with the integration of the transgene (position-independent phenomenon).
Loss-of-function mutations can also be developed in transgenic mice by either traditional transgenic methods (microinjection/retroviruses) or by ES cell-derived animals (chimeras). Saturation mutagenesis in which a wide variety of genes that were unsuspected in causing disease are now being studied and utilized.
No questions

Animal Models of Human Microsporidial Infections. Laboratory Animal Science 48 (6): 589.
These are obligate intracellular protozoan parasites that affect all major animal phyla. They are oval shaped relatively small, and stain with Gram's, Giemsa, modified trichome, PAS, and some chemoluminescent agents. The organisms are eukaryotic but they have prokaryotic ribosomal RNA, and they lack mitochondria and a true Golgi apparatus. The organism sporulates in all cases and is thought to be the transmissible agent. Mature spores have thick, chitinous outer coats. Enterocytozoon bieneusi afflicts the small bowel and biliary tract of AIDS patients. Animal models are macaque monkeys and pigs.
Encephalitozoon intestinalis is also a parasite of AIDS patients producing disease of small intestine and biliary tract. The animal model is the rabbit intestinal xenograft placed subcutaneously in the back of athymic mice. Encephalitozoon hellem seems to be mainly a respiratory tract pathogen reported in AIDS patients. The animal is athymic nude mice.
Encephalitozoon cuniculi is reported less frequently in AIDS patients than other microspiridia. It is by far the most common spontaneously occuring microspiridian of animals and has as its model the immunologically compromised mouse.
General note: Staining characteristics can help differentiate Encephalitozoon from Toxoplasma.
No questions

Animal Models of Human Hepatitides. Laboratory Animal Science 48 (6): 593.
This article provides a brief overview of the various hepatitis viruses and the associated animal models. An outline of the hepatitis viruses follows:
Hepatitis A
Picornaviridae family
ssRNA
spread by fecal-oral transmission
only hepatitis virus to be grown in cell culture
chimpanzee, marmoset and owl monkey are animal models
Hepatitis B
Hepadnoviridae family
dsDNA
spread by parenteral exposure and sexual contact
effective vaccine developed in chimps
chimps and gibbons are animal models
Hepatitis C
Flaviviridae
ssRNA
chimps and marmosets are animal models
Hepatitis D
"Plant" satellite virus
ssRNA
incomplete virus that requires Hep B virus to infect an individual
chimp and woodchuck are animal models
Hepatitis E
Calciviridae family
ssRNA
spread by fecal-oral contamination
ass'd. with contamined water
more mortality than Hep A
chimp, marmoset, rhesus, cynos, swine and owl monkeys are animal models
Hepatitis F
not yet identified
AKA "hepatitis non-A-E"
causes infection post-transfusion
Hepatitis G
Flaviviridae
ssRNA
spread by transfusion
not currently known to be pathogenic
Also discussed was what constitutes reproducible susceptibility in animal model of human hepatitis. The following criteria were listed:
1. always infected when previously exposed
2. infected in any suitable laboratory
3. infection readily recognized using available techniques (serology, PCR, ALT, biopsy)
Questions:
1. Which hepatitis virus is incomplete?
a. A
b. B
c. C
d. D
2. Which hepatitis virus is spread by fecal-oral contamination?
a. A
b. B
c. D
d. F
3. Which hepatitis virus is not known to be pathogenic?
a. A
b. C
c. F
d. G
ANSWERS:
1. d
2. a
3. d

Animal Models of Helicobacter Infection. Laboratory Animal Science 48 (6): 596.
This article focuses on Helicobacter as the bacteria relates to naturally occurring infection as well as animal models of experimental infection with different species of Helicobacter.
Natural Infections with Helicobacter species A number of bacteria have been isolated from the mouse liver, which include H. hepaticus, H. billis, H. pullorum, and H. canis . This article focused on H. hepaticus . H. hepaticus was isolated a few years ago at MIT in a breeding colony in which a fraction of the animals developed an acute hepatitis, accompanied by focal necrosis and focal non-supportive inflammation in 1-6 month old mice. Older animals developed chronic hepatitis, characterized by hepatocytomegaly, cholangitis, bile ductular hyperplasia, and ovoid cell hyperplasia, increased cell proliferation, and cirrhosis. Tumors appeared in animals older than 12 months of age with initial preneoplastic hepatocellular foci, hepatocellular adenoma, and eventually carcinoma. In animals infected with H. hepaticus, subacute hepatitis is characterized by foci of inflammation. Cholangitis is also frequently present. Silver stains are used to demonstrate the bacteria in the bilary cunaliculi and liver parenchyma. This is an important feature of H. hepaticus in that it is an intraluminal organism and can not be observed in the hepatocyte themselves. All Helicobacter species are found in the lumen of the gut, but are unable to penetrate the gut wall. H. hepaticus can also be found in the intestines and cecum. Helicobacter sp. will cause an intense inflammatory reaction that the immune system of the colonized host can not clear. When H. hepaticus is found in the intestines, the animal may represent a good model for inflammatory bowel disease. H. hepaticus can be seen in homogenized hepatic biopsies where it appears among cellular debris. The structure of H. hepaticus can be analyzed by electron and transmission electron microscopy. The organism can be stained using monoclonal antibodies used to stain H. pylori. PCR can detect and demonstrate the presence of H. hepaticus in the cecum and in the feces. Therefore transmission of the bacteria is considered to be fecal-oral within mice colonies.
H. muridarium - This bacterium has been located in the ileum of rats and the colon of mice.
H. mustelae- - This bacteria occurs the in 99% of ferrets in this country. It has been demonstrated that H. mustelae colonizes the lumen of the gastric glands and causes an intense inflammatory response. A number of the animals end up developing gastric ulcers. Small animal veterinarians must keep in mind that a bacterial cause of gastric ulcers should include Helicobacter.
H. felis - This bacterium was initially isolated in cats.
H. heilmannii- This bacteria is found in carnivores (dogs/cats/pigs/monkeys/humans). It is observed in the lumen of gastric glands, in the acid-producing parietal cell area of the stomach. By transmission electron microscopy (TEM), H. heilmannii can be seen in the canaliculi of the parietal cells and in the cells themselves. Preservation of the microvilli can be seen as well by TEM. The organisms can also be observed free floating in the mucus of the stomach and near the surface of normal gastric cells. H. heilmannii appears to colonize the stomach for life but causes less inflammation.
H. acynonix- This organism is found in cheetahs that were initially investigated for GI bleeding and were found to have gastric ulcers. Histology and culture of gastric biopsies demonstrated the presence of H. felis, H. heilmannii, and the newly described, H. acynonix.
H. nemestrinae- This organism is found in pigtailed macaques (M. nemestrina).
H. pylori Felines and monkeys (M.mulatta and fasicularis) are the two species that were found to be naturally infected with this organism. In cats, their immune system allows for the study of different types of immune reactions. Histologically, lymphoid aggregates are present in the lamina propria of the gastric mucosa. Diffuse inflammation that characterizes H. pylori is not seen in monkeys. Macroscopic gastritis has been observed in monkeys during a videogastroduodenoscopy. This procedure demonstrated that some animals would develop gastritis at a certain time, whereas at other times, gastritis disappeared spontaneously. Macroscopic gastritis will spontaneously fluctuate, although microscopic gastritis appears to remain constant. Microscopic gastritis is characterized by destruction or damage of the superficial epithelial cells. As demonstrated in H&E, gram, and PAS stained slides, the apical mucus of the superficial epithelial cells is reduced or entirely lost. Gastric ulcers have been demonstrated in some monkeys naturally infected with H. pylori . TEM shows the majority of organisms free floating in mucus as well as some being attached to the epithelial cells through the formation of pedestals similar to those described in humans. Microvilli present on superficial epithelial cells are also destroyed.
Experimental Infections with Helicobacter sp.
Ferrets- Animals colonized by H. mustelae can be used to determine the effect of therapeutic immunization, of novel treatments, or of superinfection with different strains. These animals can also be used to study prophylactic vaccination of experimental colonization.
Mice- Mice can be experimentally colonized by H. felis, and H. heilmannii, but it is much more difficult to colonize them with H. pylori. H felis is in close association with the surface, but it doesn't attach to surface epithelial cells, which makes it different from H. pylori. The intense inflammation and persistence of colonization makes this animal a useful model. In order to ensure inoculation of H. pylori , investigators have inoculated several strains and then isolated H. pylori. Recently, Adrian Lee in Australia initiated similar experiments but was immediately successful in colonizing animals with a strain isolated from a patient with a duodenal ulcer (Sydney Strain). H. pylori is believed to be able to attach to epithelial cells of mice. Transgenic mice are being created in which adhesion molecules are present on superficial epithelial cells, thus allowing H. pylori to attach. When the genetic basis of attachment is determined it maybe possible to develop a cure to prevent colonization by preventing bacterial attachment.
Cats- These animals may be inoculated with H. pylori and develop a persistent colonization which makes this animal useful as a model to study H. pylori colonization.
Gnotobiotic Piglets- These animals have been inoculated with H. pylori and colonization was observed at almost 100%. The model was used to study the initial immune response and also as a pre-clinical model to evaluate therapies for H. pylori. The model is limited in its use because of rapid growth, defined flora, its unique immune system which is not of a normal pig, and difficulty in maintaining the animal in a barrier system.
Nonhuman Primates- These animals can be inoculated with H. pylori as well as other strains to understand the pathogenesis as well as to develop treatment regimens to combat this bacteria. Animals were inoculated with several strains isolated from humans with various diseases such as nonulcer dyspepsia, duodenal ulcer, or gastric ulcer. Amplified PCR DNA fingerprinting was used to differentiate the strains to determine which strains were successful in colonizing the animals.
No questions

Inherited neurodegenerative diseases and transgenic models. Laboratory Animal Science 48 (6): 604.
The author described the use of transgenic mice to define pathogenic mechanisms (i.e., the influence of specific gene products on the disease pathology) for Alzheimer's Disease (AD). The most prominent clinical symptoms of AD is memory loss with cognitive deficits, while pathological changes of the hippocampus and cerebral cortex include amyloid plaques (defining feature), neurofibrillary tangles and reactive gliosis. Three different gene products were discussed and how mutations in the associated genes influenced AD onset as defined by deposition of amyloid plaques.
1. The first gene, APP, encodes a protein that undergoes proteolytic processing to various pieces. One length of this protein is a small peptide that is called the "A beta peptide," which is the peptide (length is 42) deposited in the amyloid plaques. Mutations in the APP gene, near the locus for the A beta peptide, cause early onset of AD.
2. Mutation of the gene, Presenilin-1, and subsequent expression has the effect of altering the processing of APP. The altered processing leads to an increased of the 42 length peptide. As 2 times the normal amount of 42 length peptide is present relative to mice that have only the APP gene in them, or mice that have the APP gene and normal (wild-type) presenilin-1 protein, the effects are additive.
3.The gene, Presenilin-2, can also be mutated to lead to early-onset AD. It appears that there is cross-regulation of Presenilin-1 by Presenilin-2.
Questions:
1. The peptide __________ is deposited in amyloid plaques.
2. What 3 genes, through mutation, have been shown to be associated with AD?
3. What is the pathological hallmark of AD? Where are the lesions observed?
Questions:
1. Your major professor may be developing Alzheimer's disease if:
a. he forgets where his keys are.
b. he forgets what his keys are.
2. With all the clinical cases of Alzheimer's around, why would an animal model be needed?
Answers:
1. A beta 42 peptide
2. APP, presenilin-1, presenilin-2
3. amyloid plaques, hippocampus and cerebral cortex
Answers:
1. b. This is an example given by the author to differentiate simple forgetfullness from cognitive deficits.
2. Multiple answers are possible here: a few advanced by the author include
a. Looking at the evolution of pathology (most human cases seen are end-stage).
b. define pathogenic mechanisms - looking at specific gene products on the disease pathology.
c. test novel therapies; in humans you can basically test one compound at a time, in animal models you can test combinations of compounds and potentially toxic compounds.

Nonhuman Primates as Models for Aging and Alzheimer's Disease. Laboratory Animal Science 48 (6): 611.
NHP brain undergoes significant structural and biochemical changes that parallel many of the changes that have been noted in the aged human brain. These changes are likely the basis for the significant declines in cognitive function that have been observed in both aged monkey and aged human populations. Rhesus monkeys have a life span of 35-40 years, with all major geriatric diseases increasing in incidence over the age of 20 years.
The following is a brief summary of the article:
1. It appears that cortical neurons are not lost with advanced age in monkeys.
2. Subcortical neurons, however, appear to decrease in both size and number.
3. Significant morphological changes have been noted in dendrites, axons and synapses in the prefrontal and visual cortices and hippocampus.
4. Senile plaques are present in animals greater than 20 years of age, with incidence of plaques increasing with advancing age. There appears to be no correlation between density of plaques and cognitive impairments in aged monkeys.
5. The beta amyloid peptide of the plaques binds strongly to Apolipoprotein E which has been linked to Alzheimer's disease in people.
6. Biochemical alterations may occur with advanced age in monkeys, although these alterations may be specific for both brain region and neurotransmitter type.
No questions

Primate Models of Osteoporosis. Laboratory Animal Science 48 (6): 618.
This is a summary of a presentation on primates as a model of osteoporosis. The female cynomolgus macaque is the common model. They are ovariectomized to simulate menopause in women. Osteopenia in these animals has been documented via the use of dual-energy X-ray absorptiometery (DEXA). The process of constant bone remodeling involves osteoclasts removing bone, and osteoblasts laying down osteoid in its place. 10 days later, mineralization occurs. Tetracycline and other fluorochrome labels are incorporated at the mineralization front, thus allowing visualization of the procedure. A bone-specific alkaline phosphatase can also be used to track bone formation. To summarize, the model has several similarities to humans:
1. Reproductive physiology is similar to humans
2. Skeletal response of cynos to ovariectomy is similar to menopausal women
3. Bone-turnover processes are similar to human beings.
Several drugs have been evaluated for prevention or treatment of osteoporosis. Premarin (a formulation of conjugated equine estrogens) can prevent osteopenia that develops in ovariectomized animals. It prevents the rise in bone turnover caused by ovariectomy. Nandrolone decanoate (an anabolic steroid) causes an increase in body weight, but not an appropriate increase in bone mineral density. It does prevent the development of osteopenia. This agent causes an increase in soft tissue mass, but actually depresses protein synthesis in bone. Parathyroid hormone (PTH) was shown to increase bone mass, however the total porosity of cortical bone increased in treated animals.
Questions:
1. Name 3 ways of monitoring bone turnover.
2. Ovariectomized cynos are appropriate animal models of osteoporosis because:
a. reproductive physiology is similar to humans
b. bone turnover processes are similar to humans
c. ovariectomy produces skeletal reactions similar to menopausal women
d. all of the above
3. Name 3 agents tested as treatment options for osteoporosis.
Answers:
1. DEXA (dual-action x-ray absorptiometry), tetracycline bond labelling, bone-specific alkaline phosphatase levels
2. d
3. Premarin, nandrolone decanoate and parathyroid hormone (PTH)

Non-Primate Models of Osteoporosis. Laboratory Animal Science 48 (6): 623.
This article reviews non- primate models of osteoporosis. Please read companion article on p. 618 for more of a background on osteoporosis. Osteoporotic individuals have an imbalance between osteoclastic bone resorption and osteoblastic bone rebuilding. Animal models include rats, ferrets, dogs, minipigs, and sheep.
RAT: The ovariectomized rat is the most common estrogen deficiency model. The model is rapid, easy to obtain, reproducible, and shows age related changes. A disadvantage is that the rat does not remodel its cortical bone and growth plates never close completely in adulthood.
FERRET: This model exhibits estrogen deficiency bone loss, Haversian-based skeletal remodeling and age related bone loss.
CANINE: Does not show bone mass loss in response to estrogen deficiency
but is a very good model to study cortical remoldeling patterns.
MINIPIGS: Good as a osteoclastic-dependent model (as a model for the prevention of osteoporosis) and is more similar in physiology to humans.
SHEEP: The ovariectomized sheep is an osteoclastic model with increased turnover rates associated with ovariectomy. Aged animals are readily available for aging studies.
Questions: 1. TorF The rat is a good human model for osteoporosis because it remodels its cortical bone and closes its growth plates in adulthood.
Answers: 1. F
2. T

CNS Regulation of Energy Balance and Body Weight Insights from Rodent Models. Laboratory Animal Science 48 (6): 630.
1. The ob gene expresses a protein, leptin. Leptin is responisible for decreasing food intake and increasing energy expentiture and non-shivering thermogenesis. Leptin is found in brown fat (rodents) and white fat in humans.
2. A family of leptin receptors exist, three short forms and one long form. The short forms are found in the choroid plexus and blood vessels and thought to aid in the movement of this protien. The long form acts as a transmembrane receptor for movement into cells in the dorsal medial nucleus and arcuate nucleus as well as other sites. Neurons in the arcuate nucleus express the POMC gene, responsible for the production of alpha melanocyte stimulating hormone (MSH), ACTH and endorphins. Leptin targets the POMC neurons. There is a family of melanocortin (MC) receptors, some (MC-1) only found in the haircoat and others MC- 3, MC-4, found in the brain. The normal agonsit at these MC sites is alpha-MSH which inhibits food intake. Antagonism of MC-3 and MC-4 receptor binding to alpha-MSH leads to increased food intake. The Agouti yellow (Ay) mouse, overexpresses the agouti protein which binds to the MC receptors all over the body, preventing MSH-mediated melanin pigmentation of the hair coat and inhibiting the inhibitory effect of alpha-MSH on food uptake and energy expenditure, resulting the morbid obesity of the Ay mouse.
3. Neuropeptide "Y" (NPY), produced in the paraventricular nucleus, has an opposite activity of leptin. This nucleus has neurons that feed directly into the anterior and posterior pituitary; the dorsal vagal complex (induction of insulin secretion); the ventral lateral medulla (cardiac modulation); and intermediate columns (innervation of sympathetic chain) NPY and leptin demonstrate reciprocal serum levels in various models of starvation, cold stress, obesity and have very similar histochemical localization in the PVN and other brain sites, suggesting very similar(same?) receptors. It is fairly clear that leptin regulates fat deposition by regulation caloric intacke, energy production and heat generation through its interaction with NPY in the PVN.
4. Rodent brown fat and skeletal muscle can produce uncoupling proteins that act as hydrogen (proton) acceptors for transport extracellularly allowing fatty acid oxidation (heat production) without involving ATP/ADP cycling. Coupling between this non-shivering theromgenesis and leptin is not understood but many cytokines,tissue necrosis factor (TNF), lipopolysaccharide(LPS) and interleukins 1 and 6 are all potent stimulations of these proteins anad may be responsible for the cachexia of some chronic diseases, especially cancers.
7. This paper discusses in depth, three monogenic obesity mouse models with signaling interruption thought to occur as indicated below:
a. The ob/ob mouse....produces a faulty leptin
b. The Ay mouse...produces excessive agouti protein which interfers with binding of alpha-MSH, the production of leptin stimulation of POMC neurons.
c. The agouti-like peptide mouse...exageration of an endogenous antagonist (agouti-like peptide)of MC-4 receptors only.
8. There were two rat models mentioned,
a. The fa/fa rat has a missense mutation in the extracellular domain of the leptin receptor making it non-functional.
b. The Koletski rat has a stop codon in the extracellular domain of the leptin receptor gene leading to a faulty receptor as well.
Questions:
1. Parabiosis between an ob/ob mouse and a normal mouse should ________.
a. produce no effect on the obese mouse
b. increase the intensity and rapidity of fat accumulation in the ob/ob mouse
c. cause the normal mouse to become obese
d. decrease fat accumulation in the ob/ob so that it reverts phenotypically to the normal mouse
2. In the agouti-like peptide mouse model only the MC-4 receptors appear to be antagonized to the normal agonist alpha-MSH, the mouse _________.
a. should have pigment deposition in the haircoat
b. should not have pigment deposition in the haircoat
c. will be obese with yellow haircoat
d. will be non-obese with a black haircoat
Answers
1. (d) the ob/ob gets normal leptin from the normal mouse and can then regulate its fat deposition appropriately.
2. (a) The MC-1 receptor in the haircoat is still responsive to stimulation by alpha- MSH, producing melanin in the haircoat.