5/10/05 CSULB

Understanding Testicular and Apoptotic Activity in Testicular Regression in American Crows (Corvus brachyrhnchos)

By Luwanda k Jenkins

5/10/05 CSULB

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Testis

Hypothalamus

Pituitary

Photoperiod

FSH LH

GnRH

Testosterone

Reproduction in American Crows

- Testis function is controlled through the HPG axis

- Seasonal breeders

- The transition from breeding to non-breeding season is marked by a reduction in testicular activity

Hypothalamus

Pituitary

Photoperiod

FSH LH

GnRH

Testosterone

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

TestisTestis

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5/10/05 CSULB

- Non-breeding season is characterized by testicular regression and ultimately testicular function

- Breeding season is characterized by an increase in testes mass, seminiferous tubules, and spermatogenesis

How does testicular regression occur?

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Apoptosis

- Stimulated by extracellular and intracellular signals

- Characteristics . cell shrinkage . nuclei breakdown . DNA fragments . membrane asymmetry lost . phagocytosed

Necrosis - Cell swells and burst - Inflammatory response

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Hypothesis:

- American crows experience low levels of apoptosis as the breeding season begins and high levels of apoptosisduring the non-breeding season, which eventually tapersoff to a basal level.

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- Fas/FasL and Caspase 3 will both be present.

- Both Sertoli (to a lesser extent) and germ cells will be dying.

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Methods:

-Animals: a) Adult and juvenile male American Crows (n = 60) b) OCVCD and Predator Management

Tissue processing-

Morphology TUNEL Analysis Immunohistochemistry

- Statistical Analysis

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Testis Mass Appears to Increase During the Start of Breeding season

Paired Testis Mass In March

0

0.5

1

1.5

2

2.5

3

1 2 3 4

Weeks In March

Pair

ed

Testi

s M

ass (

g)

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Expected Results:

- Decrease in testis mass and mean tubule diameter in post-breeding season crows

Paired Testis Mass During Breeding and Non-Breeding Season

0

1

2

3

4

March April May June July August

Months (March-August)

Paire

d Te

stis

Mass

(g)

Mean Tubule Diameter During Breeding and Non-Breeding Season

050

100150200250300

March April May June July August

Months (March-August)

Sem

inife

rous

Tu

bule

Dia

met

er

(um

)

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- Increase in TUNEL labeling in post-breeding season crows

- Both Sertoli and germ cells stain TUNEL positive

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Conclusion-Testicular regression is caused by an increase in apoptosis

-Both Sertoli and Germ cells (spermatogonia and spermatocytes) undergo apoptosis

- FasL and Caspase 3 is localized to Sertoli cells

- Fas protein and Caspase 3 is localized to germ cells

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Significance - Little is know about American crow testicular physiology

- American crow population is on a steady incline

- American crows have a high susceptibility to the WNV

Goal: develop an avian contraceptive

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Acknowledgements:

- Howard Hughes Medical Institute

- Dr. Kelly Young (Research Mentor)

- Dr. Robert Cummings (OCVCD)

- Mr. Wally Ross (Predator Management)

- Coventry Dougherty and Chantelle Moffat-Blue (lab partners)

- Dr. Zed Mason (Instructor)