my role today is to describe the XML transport 

systems or so called ectoplasmic flow 

and the role of these systems in the normal maintenance of motor 

neurons.

And then to review what's known about external 

transport in motor neuron pathology.

Now on the first side mm this is 

a highly schematic representation of 

a motor neuron 

and in general it can be divided into three 

parts a cell body,

an axon and the synaptic 

terminals.

Now,

you all know that the cell body and the synaptic 

terminals are the business ends of the 

motor neurone.

The cell body with its dendrites,

which are not shown here are the area where 

uh the interplay 

with uh segmental and super segmental 

influences occurs.

The motor nerve terminal is the 

site of transmission too.

Uh the effect er in this case muscle 

at the neuromuscular junction.

What's not showing on this diagram is a really proportion 

of sizes of these structures,

the axon intervening between the cell body and the motor 

terminal is actually 

uh in a human motor neurone 

several 100 times the volume of either 

the cell body or of course the terminals.

And yet one of the striking facts in neurobiology is that the 

axum is almost entirely incapable 

of synthesis of such essential substances as 

proteins.

Rather,

the Exxon depends on 

uh the continuous delivery to 

it of uh proteins 

synthesized in the nerve cell body and 

carried by external transport.

The cell body is consequently one of the most vigorous sites of 

protein synthesis in the body.

In fact,

we probably should regard a normal cell body as a 

protein.

Secretary sell engaged in the internal secretion of 

protein and lack of proteins into the 

axon and the means by which these substances are 

moved within the axon are the accidental transport system.

So,

I'm talking about transport.

We're talking about the cell 

body synthesis of external substances 

in their movement within the axon.

At the present time,

we recognize three external transport systems which are 

summarized on the slide.

Two are engaged in moving material away from the cell 

body.

Fast anterograde and slow anterograde 

transport,

and one retrograde transport moves 

material toward the cell body.

Well briefly describe these 

systems of external transport and then return to our 

diagram attic uh neuron and fill 

in some of the pieces.

Fast anterograde transport moves materials down the 

Accident with a rate of about 400 millimeters a day.

It's worth reflecting that in the human psychotic nerve.

That means it will take roughly three days for newly synthesized 

protein to reach the motor nerve,

ending this rapidly transported material 

is associated in transport with sacks 

of smooth and a plasmid particular.

Um As we discuss in a moment,

transmission related enzymes are among the 

rapidly transported constituents that is cold master 

race,

dopamine,

beta hydroxy Alice and other 

enzymes involved in synaptic transmission.

Yeah,

these rapidly transported materials are preferentially 

distributed to the synaptic terminal and 

probably served to renew the member list components of the 

terminals,

the synaptic vesicles and the axle M.

O.

And as we'll see,

the mechanism of fast transport is unknown,

but micro tubules appear to be involved.

Slow transport on the other hand,

Moves materials at a discreet rate of 1 - two 

a day.

With still transport.

The materials carried are much better characterized 

and consists primarily of the bulk of 

ectoplasm that is micro tubules and neural 

filaments uh Instead of being 

preferentially distributed to the terminals,

solar transported materials are quite generally distributed 

along the axon and their role is 

a presumably the renewal of 

these.

X surprise my constituents 

finally,

retrograde transport carries materials toward the 

cell body.

Uh And as we'll see,

these are both recycled materials delivered 

to the ending by fast transport and exogenous 

substances taken up in the synaptic cleft.

Uh We'll discuss in a moment recent 

results suggest that the rate of retrograde transport should be 

regarded as 250 millimeters per 

day.

Now,

the next slide,

the next slide will show these systems in the 

context of our schematic nirvana.

Yeah.

First,

with regard to fast transport 

i in studies using 

protein or glycoprotein precursors 

injected near the cell body.

E.

M.

On choreographic and biochemical studies have 

shown the presumptive 

uh victoria will 

uh synthesis and transport of these 

materials uh 

loosen injected near a motor neuron cell body for 

example,

is incorporated into proteins which 

will be rapidly transported 

uh in rough and a plasma 

particular um A 

complement of these Are conjugated.

two sugars in the golgi apparatus 

informed lack of proteins.

Both the non glock 

oscillated proteins and the glycoprotein.

Then inter fast transport for the most part as 

member list components of smooth and the plasma,

particularly other 

substances such as cold as to raise our probably 

within the smooth.

And applies in particular these 

sacks or long to bills of ectoplasmic 

particular.

Um then enter the transport 

process and it's we look at the next 

side,

we can see that a 

if we take this as a rat 

lumbar,

eventual horn and imagine 

that we have just injected treated,

losing through micro pipettes into this region 

15 minutes later,

essentially no radio activity can be found out 

along the nerve.

Uh the position of radio activity 

along the nerve indicated on the X axis by 

three hours.

However,

a discreet front of radio activity has moved 

out,

Reaching about 50 in 

terms of 24 hours,

that would be about 400 a day 

By six hours.

This materials reached about 100.

So,

at the rate of fast transport,

as we have indicated,

measured by The fastest moving front 

of newly synthesized protein is about 

400 a day,

there's a good deal of confirmatory evidence indicating that endogenous 

enzymes a similarly move at that rate.

Uh This rate probably applies not 

just to peripheral neurons but to the central nervous system as 

well.

Uh Now,

if we go back to the previous 

slide at the level of 

the motor nerve ending,

it seems most probable that these 

transported sacks and vesicles of smooth 

enterprise in particular um provide precursors 

for synaptic vesicles indicated 

here and in addition are capable 

of merging with the axon terminal 

itself to add new Excel Emma to 

the synaptic terminal 

and elegant E.

M.

Auto radiographic studies by drones have 

very firmly confirmed that idea 

now.

Uh if we turn to slow transport,

uh we can first of all say that if the same sorts of 

techniques are used,

protein precursor is injected near the cell body.

That uh the synthesis 

of solar transported materials appears to take place 

primarily on polly ribosomes.

And as we've indicated,

the primary substances synthesized are micro tube 

bills and narrow filaments.

Uh whether these uh inter 

transport as a solid uh continuous 

fibers,

protein or a soluble subunits is not yet 

defined.

I these materials,

as we said before,

are distributed generally along the axon.

So that is indicated on the next slide,

The amounts of radio activity one finds as one goes 

distantly decrease.

It's also worth emphasizing that the rate 

at 1-2 mm a day.

Presuming that that's applicable to the human means that 

in a human psychotic nerve,

we would be talking about roughly three years before 

uh a fresh bullets of newly 

synthesized slowly transported protein would reach 

uh motor nerve endings in the foot.

Oh and 

now,

if we turn to a retrograde transport 

again for a moment 

uh we're here depicting 

the into psychosis 

of uh 

membrane uh at the synaptic terminal 

uh forming again,

sacks or tubules which are very similar to 

the s er that has carried anterograde 

which then enter a retrograde 

transport.

Now,

uh the use of radio chemicals has 

been more difficult in 

establishing rates of transport and retrograde 

direction because unlike 

newly synthesized proteins in the cell body,

a very rapid entry of a 

front of material doesn't occur with 

retrograde transport.

If an IUD nated preformed protein is 

injected into muscle up,

take it slow and one simply sees a 

gradation of 

transported activity along the nerve.

We've recently used a technique 

for identifying the fastest 

moving components of retrograde transport and have taken advantage 

of the fact that cold,

among other things,

reversible e stops both fast and low 

grade and retrograde transport.

So,

by putting a cold cuff on rats,

psychotic nerves and injecting an isolated protein in this 

case I donated tetanus toxin into 

the hind foot muscles.

Uh We have allowed a substantial accumulation of 

radio activity to occur distal to the 

cold block.

Then the cold block is rapidly re warmed 

in the front of transported material 

continues to move retrograde up the axon by doing 

that dr Lloyd shield in our laboratory has 

a established both in 

vitro and in vivo,

A very predictable and constant transport rate of 

about 200 and 50 millimeters a day.

Uh 242,

mm A day.

So that in many ways this 

retrograde transport system can be looked on as the 

obverse of anterograde transport.

Uh We imagine rapidly transported membrane 

carried to the Exxon terminal inserted into Excel 

Emma and at some later time 

into psychosis producing 

new member nous packages which are 

returned by retrograde transport.

The one edition being that exogenous materials from the synaptic 

cleft are capable of being carried back to the cell body.

Now,

later phenomenon probably has uh 

considerable biologic and pathologic 

significance.

We've indicated that tetanus toxin can be carried 

retrograde and work with dr Donald 

Price.

Uh Uh huh.

Uh We think it's most likely at the present time that the 

route of entry of tetanus uh 

into um motor neurons and the pre 

synaptic region or tetanus acts 

in clinical tetanus is via retrograde 

transport.

Uh similarly uh nerve growth 

factor and botulinum toxin appear to be carried 

retrograde through the same sort of 

system.

And finally it's very likely that a number of viruses and pathologic 

significance including uh polio viruses 

can ascend retrograde into the nervous system.

So that retrograde transport might be looked on if you will as 

a back door to the central nervous system and 

possibly quite important means of 

entry of a 

ideological path genetic factors in disease.

So that to summarize what 

we've said,

we've talked about a a 

rapidly transported.

Uh we talked about rapid transport 

of members elements from cell body to terminal 

from terminal to sell body.

And we think of fast anterograde and retrograde transport 

as essentially providing a high speed shuttle system 

between uh sell body in synaptic terminal.

On the other hand,

still transport provides a means of renewing 

the enormous amount of X applies um between 

so we have 

briefly and obviously highly schematically summarized 

these elaborate systems which neurons have evolved for maintenance of their 

axons.

We want now to focus on what's known about 

the role of these transport systems 

in a path of 

biology or pathology of motor neurons.

We should begin by emphasizing that at the moment only 

one process in only one 

process is there a clear cut relationship between 

accidental pathology,

excellent generation and external transport.

And that situation is in acute watery and degeneration of 

the axon while randy generation.

We mean the prompt degeneration,

the breakdown and ultimate figure psychosis of the axon 

that occurs after.

For example,

cutting a nerve that occurs in the distance,

dump the excellent segments separated 

from continuity with the cell body.

And a variety of 

approaches have indicated 

that the most important factor in initiating this 

process of orange generation is the acute 

complete interruption of accidental transport.

Inferential evidence suggests that it's fast 

axonal transport.

This most important if one 

calculates the time to failure to fire.

Of a no 

muscular preparation with a 

very distal external section 

and then increasingly lengthens the 

proximal,

increasingly lengthens the distal stump 

and measures the time to failure to fire.

one finds that each additional 15 millimeters 

of distance dumped length 

provides physiologic 

activity,

the capacity to transmit across the 

neuromuscular junction for about one additional 

hour.

Uh Similarly,

the length of the distal stump affects 

the development of pathologic 

changes of orange generation in the 

Exxon.

Uh in that 15 mm/h correlates very 

closely to the rate of fast 

external transport.

If uh excellent transport is interrupted not by 

excellent section,

but by application of culture seen or been 

blasting along the course of the nerve or by a 

sustained cold block.

A similar polarity generation of the 

distance stump occurs.

Having said that we really have summarized all that is 

known firmly about the relationship between 

transport and excellent pathology.

I'd like to turn to one kind of chronic axillary 

generation which has attracted our interest in the interest of a 

number of laboratories 

recently.

And that's the process of external dying back.

Now dying back today,

at least should be taken to indicate 

a situation in which the axon 

degenerates in a distant a proximal 

fashion chronically.

That is if one 

imagines the if one imagines 

the axon making contact 

with the neuromuscular junction.

Uh normally one can say in Warren degeneration 

that the accident was sectioned in the distance trump rapidly 

disappears in dying back.

One can document a very slow,

gradual process of 

distal to proximal degeneration 

so that I uhh 

we're talking about a chronic degenerative process,

which is certainly applicable to a number of human peripheral 

neuropathy.

Now,

the hypothesis that has 

been raised regarding this 

can be summarized as follows.

If we say that an acute interruption of external transport 

produces acute degeneration of the distance dump of 

the axon.

Uh then can't we imagine that a chronic 

partial impairment uh in the 

amount of transported material received by the 

axon might lead to 

a chronic excellent regeneration 

decrease in transport could certainly occur either 

because of fear interference 

with cell body synthetic functions or 

because of abnormalities and transport per 

se.

And we would imagine that larger or 

longer axons might be preferentially vulnerable 

simply because they have more access to maintain that the endings of 

their axons would represent,

if you will,

the last field of of irrigation.

Uh this has 

led to a hypothesis 

uh that really goes back at least 100 years 

and was very clearly articulated by 

1895.

Actually enough with regard to amyotrophic lateral sclerosis.

And the hypothesis is simply that nerve cell body 

synthetic uh deficiencies 

lead to just like some only 

generation.

Mhm.

Well,

in our laboratory and as I indicated in other laboratories 

recently,

we've begun testing this hypothesis using 

experimental toxic neuropathy.

The disorder that we have 

investigated most is 

acrylamide intoxication in the rat.

We've also uh more recently been investigating 

intoxication with 25 hexane dyan 

in collaboration of dr peter spencer at Albert Einstein 

acrylamide induces a 

dying back neuropathy.

This animal was intoxicated for about eight weeks with a 

chrome ride in his feed.

Mhm.

And uh 

you can see that there is marked weakness 

of defeat particularly 

uh and uh a lesser 

degree of weakness uh is president although it's not obvious 

from the side.

Uh more approximately sensory 

loss is uh 

distant predominant as well so that these animals are not 

only weak distantly but they have impaired sensation and 

difficulty walking for that reason.

Now is this dyslexic degeneration the result 

of diminished delivery of 

transported constituents to nerve 

terminals?

Well,

to investigate that question,

we've used a preparation,

we first of all you standard inv evil rate 

measurements of the kind that we talked about a minute ago.

We've also used a preparation mhm.

In which the rat sciatic nerve,

the dorsal root ganglion endorsing route are 

removed from the animal and 

placed in a short term culture situation in vitro.

In this arrangement,

the dorsal root ganglia,

that is the cell bodies that lead to the psychotic 

nerve and to the dorsal root 

uh mm 

are placed in a isolated chamber 

separated from the media 

surrounding the nerve and the roots by 

silicon grease barriers,

precursors such as treated lucy and created few coast can 

then be added to the ganglion chamber 

and transport 

uh synthesis of 

proteins or black of proteins will occur here and 

some fraction of those newly synthesized proteins will enter 

fast transport both up the root and 

down the nerve to make sure that we don't lose 

transported materials.

We like it.

The roots and nerves H two 

A allow quantitative evaluation 

of the fraction of materials entering transport.

So this type of preparation allows measurements of 

treated lucy inc,

as well as the fraction of milly synthesized materials entering 

transport.

I should mention also that no transport material 

or very little enters the ventral root.

As one would expect.

Uhh Now using 

preparations from animals chronically 

intoxicated with acrylamide compared to controls.

On the next slide,

we find no difference in total treated lucy 

inc by the cell bodies or 

in the fraction of newly synthesized material entering 

fast transport either down the nerve or up the ventral roots 

between the control and the crow might intoxicated 

animals.

Similarly,

if preparations from normal animals are incubated with 

acrylamide uh In the incubation media,

we find no impairment of either protein 

synthesis or fast transport.

On the other hand,

measuring fast transport rates,

not the total amount that gets into the accident.

Fast transport rates we do find,

as indicated in the next slide,

some slowing a fast transport.

In this normal animal,

rapidly transported material has reached about 60 

within three hours after 

injection treated losing into the ventral horn.

In this acrylamide intoxicated animal,

uh about 60 millimeters has reached 

four hours after injection 

of translated,

losing.

So the calculated rate would be about 424 

mm a day here And about 

336 mm a day 

here.

The next slide shows mean 

values for normal and acrylamide treated 

animals.

Uh And there's a slight but 

significant difference between the chrome I treated animals.

Very similar results have been obtained using two five X.

And I own and other laboratories slowing a fast 

transport at least Some preliminary studies has been suggested to 

occur with Christine neuropathy method,

beetle ketone intoxication and try a little crystal phosphate 

intoxication.

Now does this slowing of transport lead to the dyslexic 

degeneration?

Yeah,

we currently feel that considerable caution is required in 

making that interpretation of the data for two 

reasons.

1,

with acrylamide at least the slowing of fast 

transport is found only after the 

initial process of excellent regeneration has 

begun.

If that were the responsible factor,

you would anticipate finding a slowing of fast 

transport occurring prior to the 

beginning of maximum degeneration.

Also,

we have examined the role of fast 

transport in another abnormality produced by 

acrylamide and that's the impaired capacity of 

axons to regenerate.

Following a crush acrylamide,

intoxicated nerves are not able 

to grow out uh and regenerate 

uh or to mature their axons as well as 

normal animals has been shown by uh morgan 

Hughes and by ochoa previously 

and uh I am already graphic and 

radiochemical studies of uh preparations 

from those animals very clearly indicates 

that that failure of outgrowth cannot be 

ascribed to a failure of delivery 

rapidly transported materials to the growing 

tips.

So at present we can say that a gross impairment in cell body 

protein synthesis is not requisite for the development of a 

dying back picture.

It seems most likely that the slowing of fast transport at 

least in the case of acrylamide.

Uh uh that the slowing of fast 

transport and the dislike some of the generation are both 

consequences of some as yet unknown 

mechanism of action of the toxin 

curly.

A major need at present is for a study 

of individual proteins separated.

Uh For example,

electro theoretically.

Now,

how applicable such Studies are two.

Human degenerative diseases 

is not clear.

We think that the experimental models of dying 

back are quite good models of human dying back 

neuropathy,

many toxic neuropathy and probably those that 

occur in some degenerative conditions.

Perhaps Friedrich's ataxia.

The difficulty is that one criteria of dying back 

that we previously mentioned,

the selective vulnerability of larger longer 

axons can be satisfied on 

clinical or pathologic grounds in human material.

With the second criteria,

the demonstration of distal to proximal 

degeneration of individual actions is very difficult to 

establish.

The question we might raise is whether Ailes 

is a disorder in which an 

element of dying back might occur.

Uh This question uh It 

seems to me deserves re evaluation by classic neuropathy 

logic techniques because our thinking about the 

disorder uh at this point 

would be colored by the extent to which it 

represented a dying back process 

in the extent to which an analogy to these other disorders could 

be made.

But I would add that it will be very difficult to 

establish the spatial temporal evolution of the 

pathology in a less using classic classic 

techniques.

And I'd like to mention the value of animal 

models for that kind of path a biologic study.

Uh At this point there have been 

no very good models of A.

L.

S.

Uh There have been 

occasional models of motor neurone disease 

which dr john andrews at U.

C.

L.

A.

Among others has uh studied pathologically 

very extensively.

We recently have been introduced to a model uncovered by dr 

linda cork who is now at Hopkins 

uh of motor neurone disease.

Uh A spinal 

muscular atrophy occurring in 

Brittany 

spaniels.

Uh These dogs,

at a few months of life develop 

primarily approximately weakness and have 

muscle pathology changes that are uh 

strikingly similar to the human spinal muscular 

atrophy changes.

Uh They of course show loss of anterior 

horn cells in the spinal cord.

Uh And I would add that in addition they show 

changes in accident pathology which suggests 

some dynamic accidental process is going 

on as well.

And this pathology includes these enormous 

external swellings in the spinal cord here,

seeing an electron micrografx.

Uh So that in this situation at least 

the process of motor neuron degeneration 

is accompanied by an axonal degeneration that we cannot 

ascribe simply to water and degeneration due to the death 

of the motor neuron.

And as we've indicated before,

uh it would be of interest to 

uh reevaluate um pathology 

in a minute traffic lateral sclerosis with regard to the question 

of whether a distal uh to proximal 

degeneration occurs at any rate,

were quite interested in studying with 

uh transport.

And I am already graphic techniques 

these models of motor neuron disease.

Mhm.