Biology

Question 1

Describe historical GP erythrocytic indices and WBC counts compared to other lab rodents and SPF GP. What is a potential explanation?

Answer 1

Historically, low RBC count, hemoglobin, and packed cell volume compared to other rodents with high WBC. These erythrocytic indices lower than seen with young, SPF GPs today - May indicated underlying subclinical disease in historical animals causing a relative anemia and leukocytosis.

Question 2

What is the predominant WBC in circulation?

Answer 2

Lymphocytes.

Question 3

Describe neutrophils in GPs.

Answer 3

Heterophils, or pseudoeosinophils, with distinct eosinophilic granules in cytoplasm.

Question 4

Describe Foa-Kurloff cells.

Answer 4

Estradiol-dependent mononuclear leukocyte unique to GP. Found primarily in thymus and sinusoids of liver, spleen, and lung, with increased number in peripheral circulation during pregnancy. Large numbers also seen in placenta, may have a role in preventing the maternal rejection of fetal placenta during pregnancy.

Question 5

What do Foa-Kurloff cells possess?

Answer 5

Large mucopolysaccharide, intracytoplasmic inclusion body, which is metachromatic and PAS positive. Contains proteoglycans and hydrolytic enzymes, similar to small intracytoplasmic granules found in NK cells. Has NK cytotoxic activity in vitro and may be part of cancer resistance.

Question 6

Which species are relatively resistant to the effects of steroids?

Answer 6

GP, ferrets, and NHPs. Numbers of thymic and peripheral lymphocytes not reduced markedly by corticosteroid injection.

Question 6

Describe the thymus in the GP.

Answer 6

Located in the ventral cervical region and easy to remove surgically, but has accessory thymic islets in contiguous fascia. Has no afferent lymphatic vessels.

Question 7

What is the dental formula of the GP?

Answer 7

2 (I 1/1, C 0/0, PM 1/1, M 3/3). Diastema present between incisors and premolars.

Question 8

Describe GP teeth.

Answer 8

All open-rooted and grow continuously (hypsodontic). Incisors white, unlike yellow to orange coloration of other rodents. Upper incisors shorter than lower pair.

Question 9

What type of fermenters are GPs?

Answer 9

Monogastric, hind-gut

Question 10

Describe the GP stomach.

Answer 10

Stomach undivided, unlike other rodents, and lined entirely with glandular epithelium.

Question 11

What is emptying time of the stomach, cecum, and total transit time, including coprophagy?

Answer 11

Gastric - 2h
Cecum - 20h
Total with coprophagy - 60-70h

Question 12

Compare the coronary artery blood flow and myocardiocyte stiffness between the GP and rat.

Answer 12

GP has lower basal coronary blood flow, lower peak coronary blood flow, and intercoronary collateral blood flow is well-developed, thus it is difficult to produce a cardiac infarct by acute coronary artery occlusion. Myocardiocytes are less stiff in GPs than rats.

Question 13

What respiratory models is the GP used for?

Answer 13

Airway hyperresponsiveness and reactions that resemble asthma.

Question 14

What is the Preyer or pinna reflex? What can it be used for?

Answer 14

Involves cocking of the pinna in response to a sharp sound. Used in otologic studies as a measurement of hearing function.

Question 15

What are the advantages of using the GP ear in auditory research?

Answer 15

Large bullae, ease of surgical entry to middle and inner ear, and protrusion of cochlea and blood vessels into the cavity of the middle ear, which allows examination of the microcirculation of the inner ear.

Question 16

What behavior can inner ear malformations cause?

Answer 16

Waltzing

Question 17

What hormone is responsible for postnatal growth in vertebrates?

Answer 17

Pituitary growth hormone.

Question 18

What is the outcome of a hypophysectomy in GP? How does this differ from most species?

Answer 18

Does not result in altered growth in GP, unlike most other species.

Question 19

What agent is responsible for growth in the GP and how is it controlled?

Answer 19

Somatomedins insulin-like growth factor I and IGF-II responsible for growth. These are not under the control of growth-hormone. Hypophysectomy does not decrease the level of somatomedins. Unknown what regulates somatomedin expression in GP.