Questions Asked

I. NORMAL MOTOR NEURONS

A. Isolated Motor Neurons

1. Why isolate spinal motor neurons?
2. How can one isolate highly purified adult motor neurons?
3. What criteria identify the isolated cells as motor neurons?
4. How intact are the isolated cell bodies?
5. How can one label newly synthesized proteins in isolated motor neuron cell bodies?
6. How can one measure RNA synthesis in isolated motor neuron cell bodies?
7. How can one measure the volume of an isolated cell body?

B. Normal Motor Neurons: Biochemical characterization

1. How much DNA does the nucleus of a motor neuron contain?
2. How much RNA do motor neuron cell bodies contain?
3. How much protein do motor neuron cell bodies contain?
4. What are the major protein constituents of motor neuron cell bodies?
5. How stable are motor neuron cell body proteins post mortem?
6. How different are the proteins in the motor neuron cell body and the ventral gray matter?
7. How different are the proteins in the motor neuron cell body and motor axon?
8. How different are the proteins in spinal motor and sensory axons?
9. What fraction of its protein content does the motor neuron cell body export each day?
10. How much new protein travels by fast transport to the motor axon each day?
11. How much acetylcholinesterase enters the motor axon each day?
12. How much choline acetyltransferase and acetylcholinesterase do lumbar motor neuron cell bodies contain?
13. What fraction of the total choline acetyltransferase and acetylcholinesterase activity in the ventral gray matter is found in motor neuron cell bodies and their proximal dendrites?
14. How early during development can choline acetyltransferase and acetylcholinesterase be detected in motor neurons?

C. Normal Motor Neuron Size: Morphological and Biochemical Relationships

1. Why focus upon motor neuron size?
2. How are nucleolar, nuclear and cell body size related in motor neurons?
3. Is the cytoskeleton responsible for maintaining these size relationships?
4. What are the mechanical properties of the cytoskeleton in motor neuron cell bodies?
5. What are the solubility properties of the cytoskeleton in motor neuron cell bodies?
6. What are the major proteins in the cell body cytoskeleton?
7. Does the cytoskeleton cage lipofuscin granules?
8. Do large motor neurons contain more nuclear DNA than small motor neurons?
9. Do large motor neurons synthesize more RNA than small motor neurons?
10. Do large motor neurons synthesize more protein than small motor neurons?
11. Does growth hormone play a role in motor neuron size?
12. Does growth hormone help to maintain motor neuron size in adult animals?

II. INJURED MOTOR NEURONS

A. Changes in RNA, DNA and Proteins After Axotomy

1. Do the axotomy-induced changes in specific proteins differ in the injured ventral root and spinal cord?
2. How do these proteins change within axotomized spinal motor neuron cell bodies?
3. How much does the total protein content of spinal motor neuron cell bodies increase after ventral root transection?
4. Is the increase in protein content a consequence of increased protein synthesis?
5. How much is total RNA synthesis in motor neurons altered after ventral root transection?
6. Does DNA synthesis occur in injured motor neuron cell bodies?

B. Motor Neuron Size After Injury: Morphological and Biochemical Relationships

1. What is the magnitude and time course of changes in nucleolar, nuclear and cell body size after axotomy?
2. Do large motor neurons undergo the same relative increases in nucleolar, nuclear and cell body size after axotomy as small motor neurons?
3. Are changes in the cytoskeleton after axotomy responsible for the conjugate enlargement of the nucleolus, nucleus and cell body?
4. Is protein added to the cell body cytoskeleton after axotomy?
5. Does an increase in total transcription in spinal motor neurons always lead to increased nucleolar, nuclear and cell body size and protein content?
6. Do changes in the cytoskeleton underlie increased nuclear eccentricity after axotomy?
7. Does damming up of axonal cytoskeleton cause increased nuclear eccentricity and chromatolysis after axotomy?
8. What signals the cell body that its axon has been injured?
9. Do motor neurons on the opposite side of the spinal cord from a unilateral ventral root injury respond to axotomy?

III. MOTOR NEURON DISEASE

A. Motor neurons in ALS

1. Are sensory nerves affected by ALS?
2. Are large motor neurons more vulnerable to ALS than small ones?
3. Can one identify “sick” motor neurons isolated from ALS spinal cord?
4. Are there significant differences in the protein composition of motor neuron cell bodies isolated from normal and ALS spinal cord?
5. Does the protein composition of spinal ventral gray matter from ALS and control patients differ significantly?

B. Skin changes in ALS

1. Can collagen breakdown products be used for early diagnosis of ALS?
2. Are there protein cross-link abnormalities in motor neurons in ALS?