WEBVTT 00:00.000 --> 00:30.000 position:50% align:top line:0% *This machine-generated transcript may have errors. If remediation or a manually-generated transcript is needed, please contact NLM Support at https://support.nlm.nih.gov.* 00:53.140 --> 00:55.770 my role today is to describe the XML transport 00:55.770 --> 00:58.360 systems or so called ectoplasmic flow 00:58.940 --> 01:01.810 and the role of these systems in the normal maintenance of motor 01:01.810 --> 01:02.500 neurons. 01:02.930 --> 01:05.630 And then to review what's known about external 01:05.630 --> 01:07.660 transport in motor neuron pathology. 01:08.740 --> 01:11.700 Now on the first side mm this is 01:11.700 --> 01:14.070 a highly schematic representation of 01:14.070 --> 01:15.850 a motor neuron 01:17.300 --> 01:19.680 and in general it can be divided into three 01:19.680 --> 01:21.460 parts a cell body, 01:22.040 --> 01:24.310 an axon and the synaptic 01:24.310 --> 01:25.060 terminals. 01:26.440 --> 01:26.910 Now, 01:26.920 --> 01:29.830 you all know that the cell body and the synaptic 01:29.830 --> 01:32.560 terminals are the business ends of the 01:33.040 --> 01:33.850 motor neurone. 01:34.240 --> 01:36.220 The cell body with its dendrites, 01:36.220 --> 01:38.220 which are not shown here are the area where 01:38.230 --> 01:40.850 uh the interplay 01:40.850 --> 01:43.660 with uh segmental and super segmental 01:43.660 --> 01:44.760 influences occurs. 01:45.140 --> 01:47.940 The motor nerve terminal is the 01:47.950 --> 01:50.060 site of transmission too. 01:50.440 --> 01:52.960 Uh the effect er in this case muscle 01:53.340 --> 01:54.560 at the neuromuscular junction. 01:56.140 --> 01:58.930 What's not showing on this diagram is a really proportion 01:58.940 --> 02:01.300 of sizes of these structures, 02:01.720 --> 02:04.300 the axon intervening between the cell body and the motor 02:04.300 --> 02:06.300 terminal is actually 02:06.310 --> 02:09.100 uh in a human motor neurone 02:09.100 --> 02:12.040 several 100 times the volume of either 02:12.040 --> 02:14.260 the cell body or of course the terminals. 02:15.140 --> 02:17.690 And yet one of the striking facts in neurobiology is that the 02:17.690 --> 02:20.450 axum is almost entirely incapable 02:20.460 --> 02:23.160 of synthesis of such essential substances as 02:23.160 --> 02:23.880 proteins. 02:25.240 --> 02:25.630 Rather, 02:25.630 --> 02:27.460 the Exxon depends on 02:27.940 --> 02:30.730 uh the continuous delivery to 02:30.730 --> 02:33.660 it of uh proteins 02:33.670 --> 02:36.450 synthesized in the nerve cell body and 02:36.450 --> 02:38.560 carried by external transport. 02:40.440 --> 02:43.390 The cell body is consequently one of the most vigorous sites of 02:43.390 --> 02:44.960 protein synthesis in the body. 02:45.800 --> 02:46.590 In fact, 02:46.590 --> 02:49.470 we probably should regard a normal cell body as a 02:49.470 --> 02:50.040 protein. 02:50.050 --> 02:52.900 Secretary sell engaged in the internal secretion of 02:52.900 --> 02:55.560 protein and lack of proteins into the 02:55.560 --> 02:58.420 axon and the means by which these substances are 02:58.420 --> 03:01.240 moved within the axon are the accidental transport system. 03:01.250 --> 03:01.430 So, 03:01.430 --> 03:02.650 I'm talking about transport. 03:03.040 --> 03:05.870 We're talking about the cell 03:05.870 --> 03:08.800 body synthesis of external substances 03:08.810 --> 03:10.560 in their movement within the axon. 03:12.540 --> 03:14.060 At the present time, 03:14.070 --> 03:16.870 we recognize three external transport systems which are 03:16.870 --> 03:18.360 summarized on the slide. 03:20.240 --> 03:23.070 Two are engaged in moving material away from the cell 03:23.070 --> 03:23.550 body. 03:23.940 --> 03:26.580 Fast anterograde and slow anterograde 03:26.590 --> 03:27.390 transport, 03:27.510 --> 03:30.210 and one retrograde transport moves 03:30.210 --> 03:31.760 material toward the cell body. 03:32.140 --> 03:34.940 Well briefly describe these 03:34.950 --> 03:37.810 systems of external transport and then return to our 03:37.810 --> 03:40.560 diagram attic uh neuron and fill 03:40.560 --> 03:41.790 in some of the pieces. 03:43.240 --> 03:45.910 Fast anterograde transport moves materials down the 03:45.910 --> 03:48.460 Accident with a rate of about 400 millimeters a day. 03:49.210 --> 03:52.110 It's worth reflecting that in the human psychotic nerve. 03:52.110 --> 03:55.070 That means it will take roughly three days for newly synthesized 03:55.070 --> 03:56.510 protein to reach the motor nerve, 03:56.510 --> 03:59.410 ending this rapidly transported material 03:59.420 --> 04:02.350 is associated in transport with sacks 04:02.350 --> 04:03.720 of smooth and a plasmid particular. 04:03.720 --> 04:05.160 Um As we discuss in a moment, 04:05.740 --> 04:08.610 transmission related enzymes are among the 04:08.610 --> 04:11.610 rapidly transported constituents that is cold master 04:11.610 --> 04:11.940 race, 04:11.940 --> 04:12.360 dopamine, 04:12.360 --> 04:15.080 beta hydroxy Alice and other 04:15.090 --> 04:17.650 enzymes involved in synaptic transmission. 04:18.140 --> 04:18.340 Yeah, 04:18.930 --> 04:21.280 these rapidly transported materials are preferentially 04:21.280 --> 04:24.120 distributed to the synaptic terminal and 04:24.120 --> 04:26.870 probably served to renew the member list components of the 04:26.870 --> 04:27.430 terminals, 04:27.430 --> 04:29.160 the synaptic vesicles and the axle M. 04:29.160 --> 04:29.360 O. 04:30.240 --> 04:30.940 And as we'll see, 04:30.940 --> 04:33.030 the mechanism of fast transport is unknown, 04:33.040 --> 04:35.250 but micro tubules appear to be involved. 04:35.940 --> 04:38.220 Slow transport on the other hand, 04:38.230 --> 04:41.050 Moves materials at a discreet rate of 1 - two 04:41.580 --> 04:42.150 a day. 04:42.810 --> 04:43.900 With still transport. 04:43.910 --> 04:46.570 The materials carried are much better characterized 04:46.580 --> 04:48.880 and consists primarily of the bulk of 04:48.890 --> 04:51.680 ectoplasm that is micro tubules and neural 04:51.680 --> 04:54.560 filaments uh Instead of being 04:54.560 --> 04:56.150 preferentially distributed to the terminals, 04:56.150 --> 04:58.840 solar transported materials are quite generally distributed 04:58.850 --> 05:01.720 along the axon and their role is 05:01.730 --> 05:04.620 a presumably the renewal of 05:04.620 --> 05:04.800 these. 05:04.800 --> 05:06.220 X surprise my constituents 05:06.640 --> 05:08.380 finally, 05:08.380 --> 05:11.250 retrograde transport carries materials toward the 05:11.250 --> 05:11.950 cell body. 05:12.740 --> 05:14.650 Uh And as we'll see, 05:14.650 --> 05:17.640 these are both recycled materials delivered 05:17.640 --> 05:20.100 to the ending by fast transport and exogenous 05:20.100 --> 05:22.360 substances taken up in the synaptic cleft. 05:23.640 --> 05:26.420 Uh We'll discuss in a moment recent 05:26.420 --> 05:29.260 results suggest that the rate of retrograde transport should be 05:29.260 --> 05:31.770 regarded as 250 millimeters per 05:31.770 --> 05:32.350 day. 05:33.840 --> 05:34.040 Now, 05:34.040 --> 05:34.990 the next slide, 05:35.040 --> 05:38.040 the next slide will show these systems in the 05:38.040 --> 05:40.140 context of our schematic nirvana. 05:41.440 --> 05:41.760 Yeah. 05:42.640 --> 05:42.990 First, 05:42.990 --> 05:44.460 with regard to fast transport 05:45.340 --> 05:47.950 i in studies using 05:47.960 --> 05:50.430 protein or glycoprotein precursors 05:50.740 --> 05:52.360 injected near the cell body. 05:52.840 --> 05:53.310 E. 05:53.310 --> 05:53.450 M. 05:53.450 --> 05:56.280 On choreographic and biochemical studies have 05:56.290 --> 05:58.740 shown the presumptive 05:58.750 --> 06:01.390 uh victoria will 06:01.400 --> 06:04.140 uh synthesis and transport of these 06:04.140 --> 06:06.660 materials uh 06:07.240 --> 06:10.150 loosen injected near a motor neuron cell body for 06:10.150 --> 06:10.710 example, 06:11.030 --> 06:13.860 is incorporated into proteins which 06:13.860 --> 06:15.300 will be rapidly transported 06:15.310 --> 06:18.080 uh in rough and a plasma 06:18.080 --> 06:20.830 particular um A 06:20.840 --> 06:23.570 complement of these Are conjugated. 06:23.570 --> 06:25.400 two sugars in the golgi apparatus 06:26.540 --> 06:28.360 informed lack of proteins. 06:28.940 --> 06:31.580 Both the non glock 06:31.580 --> 06:34.040 oscillated proteins and the glycoprotein. 06:34.540 --> 06:37.410 Then inter fast transport for the most part as 06:37.410 --> 06:39.500 member list components of smooth and the plasma, 06:39.500 --> 06:42.160 particularly other 06:42.170 --> 06:44.500 substances such as cold as to raise our probably 06:44.500 --> 06:46.590 within the smooth. 06:46.590 --> 06:49.110 And applies in particular these 06:49.110 --> 06:51.900 sacks or long to bills of ectoplasmic 06:51.900 --> 06:52.320 particular. 06:52.320 --> 06:54.660 Um then enter the transport 06:54.660 --> 06:57.370 process and it's we look at the next 06:57.370 --> 06:57.820 side, 06:57.830 --> 06:59.960 we can see that a 07:00.540 --> 07:03.060 if we take this as a rat 07:03.180 --> 07:03.800 lumbar, 07:03.800 --> 07:06.790 eventual horn and imagine 07:06.790 --> 07:09.580 that we have just injected treated, 07:09.580 --> 07:12.260 losing through micro pipettes into this region 07:12.940 --> 07:14.340 15 minutes later, 07:14.350 --> 07:17.090 essentially no radio activity can be found out 07:17.090 --> 07:18.150 along the nerve. 07:18.330 --> 07:21.090 Uh the position of radio activity 07:21.090 --> 07:24.090 along the nerve indicated on the X axis by 07:24.090 --> 07:24.690 three hours. 07:24.690 --> 07:25.270 However, 07:25.520 --> 07:28.250 a discreet front of radio activity has moved 07:28.250 --> 07:28.650 out, 07:29.240 --> 07:32.030 Reaching about 50 in 07:32.030 --> 07:34.210 terms of 24 hours, 07:34.210 --> 07:36.460 that would be about 400 a day 07:37.040 --> 07:37.870 By six hours. 07:37.870 --> 07:39.310 This materials reached about 100. 07:40.540 --> 07:40.740 So, 07:40.740 --> 07:42.050 at the rate of fast transport, 07:42.060 --> 07:43.440 as we have indicated, 07:43.690 --> 07:46.150 measured by The fastest moving front 07:46.160 --> 07:48.940 of newly synthesized protein is about 07:48.940 --> 07:50.320 400 a day, 07:50.610 --> 07:53.480 there's a good deal of confirmatory evidence indicating that endogenous 07:53.480 --> 07:55.750 enzymes a similarly move at that rate. 07:56.340 --> 07:59.090 Uh This rate probably applies not 07:59.100 --> 08:02.030 just to peripheral neurons but to the central nervous system as 08:02.030 --> 08:02.460 well. 08:02.840 --> 08:04.250 Uh Now, 08:04.250 --> 08:06.490 if we go back to the previous 08:06.490 --> 08:09.290 slide at the level of 08:09.290 --> 08:10.760 the motor nerve ending, 08:11.140 --> 08:13.510 it seems most probable that these 08:13.930 --> 08:16.810 transported sacks and vesicles of smooth 08:16.810 --> 08:19.360 enterprise in particular um provide precursors 08:19.360 --> 08:22.330 for synaptic vesicles indicated 08:22.330 --> 08:25.230 here and in addition are capable 08:25.230 --> 08:27.350 of merging with the axon terminal 08:27.740 --> 08:30.490 itself to add new Excel Emma to 08:30.490 --> 08:32.560 the synaptic terminal 08:33.640 --> 08:34.990 and elegant E. 08:34.990 --> 08:35.350 M. 08:35.940 --> 08:38.750 Auto radiographic studies by drones have 08:38.760 --> 08:41.460 very firmly confirmed that idea 08:42.520 --> 08:43.060 now. 08:44.540 --> 08:47.360 Uh if we turn to slow transport, 08:47.940 --> 08:50.560 uh we can first of all say that if the same sorts of 08:50.560 --> 08:51.810 techniques are used, 08:51.820 --> 08:54.230 protein precursor is injected near the cell body. 08:54.720 --> 08:57.260 That uh the synthesis 08:58.140 --> 09:01.000 of solar transported materials appears to take place 09:01.000 --> 09:03.150 primarily on polly ribosomes. 09:03.940 --> 09:05.070 And as we've indicated, 09:05.070 --> 09:07.950 the primary substances synthesized are micro tube 09:07.950 --> 09:09.370 bills and narrow filaments. 09:10.240 --> 09:12.720 Uh whether these uh inter 09:12.720 --> 09:15.610 transport as a solid uh continuous 09:15.610 --> 09:16.010 fibers, 09:16.010 --> 09:18.830 protein or a soluble subunits is not yet 09:18.840 --> 09:19.660 defined. 09:20.740 --> 09:23.070 I these materials, 09:23.080 --> 09:24.380 as we said before, 09:24.390 --> 09:26.640 are distributed generally along the axon. 09:26.860 --> 09:29.660 So that is indicated on the next slide, 09:30.040 --> 09:32.900 The amounts of radio activity one finds as one goes 09:32.900 --> 09:34.510 distantly decrease. 09:35.140 --> 09:37.930 It's also worth emphasizing that the rate 09:38.100 --> 09:39.910 at 1-2 mm a day. 09:39.920 --> 09:42.880 Presuming that that's applicable to the human means that 09:42.880 --> 09:44.460 in a human psychotic nerve, 09:44.470 --> 09:47.460 we would be talking about roughly three years before 09:47.570 --> 09:50.250 uh a fresh bullets of newly 09:50.250 --> 09:53.200 synthesized slowly transported protein would reach 09:53.210 --> 09:55.260 uh motor nerve endings in the foot. 09:56.840 --> 09:59.610 Oh and 09:59.610 --> 10:00.420 now, 10:00.430 --> 10:02.960 if we turn to a retrograde transport 10:03.440 --> 10:05.860 again for a moment 10:06.540 --> 10:09.130 uh we're here depicting 10:09.910 --> 10:12.260 the into psychosis 10:12.740 --> 10:15.340 of uh 10:15.350 --> 10:18.090 membrane uh at the synaptic terminal 10:18.100 --> 10:20.590 uh forming again, 10:20.600 --> 10:23.590 sacks or tubules which are very similar to 10:23.590 --> 10:25.860 the s er that has carried anterograde 10:26.540 --> 10:28.940 which then enter a retrograde 10:28.950 --> 10:29.750 transport. 10:31.040 --> 10:31.570 Now, 10:31.580 --> 10:34.320 uh the use of radio chemicals has 10:34.320 --> 10:35.960 been more difficult in 10:35.970 --> 10:38.960 establishing rates of transport and retrograde 10:38.960 --> 10:41.500 direction because unlike 10:41.510 --> 10:44.160 newly synthesized proteins in the cell body, 10:44.640 --> 10:47.580 a very rapid entry of a 10:47.580 --> 10:50.400 front of material doesn't occur with 10:50.410 --> 10:51.960 retrograde transport. 10:52.640 --> 10:55.390 If an IUD nated preformed protein is 10:55.390 --> 10:57.450 injected into muscle up, 10:57.450 --> 11:00.180 take it slow and one simply sees a 11:00.190 --> 11:02.690 gradation of 11:02.700 --> 11:05.060 transported activity along the nerve. 11:05.740 --> 11:08.150 We've recently used a technique 11:08.150 --> 11:11.030 for identifying the fastest 11:11.030 --> 11:13.970 moving components of retrograde transport and have taken advantage 11:13.970 --> 11:15.260 of the fact that cold, 11:15.410 --> 11:16.530 among other things, 11:16.600 --> 11:19.490 reversible e stops both fast and low 11:19.490 --> 11:21.250 grade and retrograde transport. 11:21.740 --> 11:22.020 So, 11:22.020 --> 11:23.520 by putting a cold cuff on rats, 11:23.520 --> 11:26.360 psychotic nerves and injecting an isolated protein in this 11:26.360 --> 11:29.130 case I donated tetanus toxin into 11:29.130 --> 11:30.450 the hind foot muscles. 11:30.840 --> 11:33.830 Uh We have allowed a substantial accumulation of 11:33.830 --> 11:36.490 radio activity to occur distal to the 11:36.500 --> 11:37.350 cold block. 11:38.040 --> 11:40.650 Then the cold block is rapidly re warmed 11:41.140 --> 11:43.860 in the front of transported material 11:44.340 --> 11:47.330 continues to move retrograde up the axon by doing 11:47.330 --> 11:49.760 that dr Lloyd shield in our laboratory has 11:49.770 --> 11:52.320 a established both in 11:52.320 --> 11:53.590 vitro and in vivo, 11:53.590 --> 11:56.470 A very predictable and constant transport rate of 11:56.470 --> 11:58.520 about 200 and 50 millimeters a day. 11:58.530 --> 12:00.400 Uh 242, 12:01.120 --> 12:02.220 mm A day. 12:02.310 --> 12:05.300 So that in many ways this 12:05.310 --> 12:08.070 retrograde transport system can be looked on as the 12:08.070 --> 12:09.960 obverse of anterograde transport. 12:10.440 --> 12:13.410 Uh We imagine rapidly transported membrane 12:13.410 --> 12:16.290 carried to the Exxon terminal inserted into Excel 12:16.290 --> 12:18.910 Emma and at some later time 12:19.340 --> 12:21.570 into psychosis producing 12:21.650 --> 12:24.390 new member nous packages which are 12:24.390 --> 12:26.050 returned by retrograde transport. 12:26.640 --> 12:29.510 The one edition being that exogenous materials from the synaptic 12:29.510 --> 12:32.150 cleft are capable of being carried back to the cell body. 12:33.440 --> 12:33.690 Now, 12:33.690 --> 12:36.180 later phenomenon probably has uh 12:36.190 --> 12:38.900 considerable biologic and pathologic 12:38.900 --> 12:39.610 significance. 12:39.910 --> 12:42.360 We've indicated that tetanus toxin can be carried 12:42.360 --> 12:45.060 retrograde and work with dr Donald 12:45.060 --> 12:45.600 Price. 12:45.610 --> 12:47.860 Uh Uh huh. 12:48.440 --> 12:51.420 Uh We think it's most likely at the present time that the 12:51.420 --> 12:54.130 route of entry of tetanus uh 12:54.140 --> 12:56.640 into um motor neurons and the pre 12:56.640 --> 12:58.850 synaptic region or tetanus acts 12:59.440 --> 13:02.210 in clinical tetanus is via retrograde 13:02.210 --> 13:02.860 transport. 13:03.640 --> 13:06.250 Uh similarly uh nerve growth 13:06.250 --> 13:08.910 factor and botulinum toxin appear to be carried 13:08.920 --> 13:11.350 retrograde through the same sort of 13:11.350 --> 13:11.930 system. 13:12.060 --> 13:14.970 And finally it's very likely that a number of viruses and pathologic 13:14.970 --> 13:17.950 significance including uh polio viruses 13:18.100 --> 13:20.960 can ascend retrograde into the nervous system. 13:21.340 --> 13:24.150 So that retrograde transport might be looked on if you will as 13:24.150 --> 13:27.150 a back door to the central nervous system and 13:27.150 --> 13:30.130 possibly quite important means of 13:30.130 --> 13:32.260 entry of a 13:32.840 --> 13:35.360 ideological path genetic factors in disease. 13:36.940 --> 13:39.870 So that to summarize what 13:39.870 --> 13:40.350 we've said, 13:40.350 --> 13:43.310 we've talked about a a 13:43.320 --> 13:45.260 rapidly transported. 13:45.270 --> 13:47.650 Uh we talked about rapid transport 13:48.040 --> 13:50.960 of members elements from cell body to terminal 13:50.970 --> 13:52.260 from terminal to sell body. 13:52.480 --> 13:55.360 And we think of fast anterograde and retrograde transport 13:55.570 --> 13:58.370 as essentially providing a high speed shuttle system 13:58.380 --> 14:01.010 between uh sell body in synaptic terminal. 14:01.440 --> 14:02.100 On the other hand, 14:02.100 --> 14:04.890 still transport provides a means of renewing 14:04.900 --> 14:07.460 the enormous amount of X applies um between 14:09.140 --> 14:11.510 so we have 14:11.600 --> 14:14.590 briefly and obviously highly schematically summarized 14:14.710 --> 14:17.570 these elaborate systems which neurons have evolved for maintenance of their 14:17.570 --> 14:18.260 axons. 14:18.640 --> 14:21.550 We want now to focus on what's known about 14:21.560 --> 14:23.560 the role of these transport systems 14:23.940 --> 14:26.450 in a path of 14:26.450 --> 14:28.750 biology or pathology of motor neurons. 14:30.540 --> 14:33.370 We should begin by emphasizing that at the moment only 14:33.370 --> 14:35.910 one process in only one 14:35.910 --> 14:38.760 process is there a clear cut relationship between 14:39.140 --> 14:40.670 accidental pathology, 14:40.680 --> 14:43.460 excellent generation and external transport. 14:43.940 --> 14:46.870 And that situation is in acute watery and degeneration of 14:46.870 --> 14:49.370 the axon while randy generation. 14:49.380 --> 14:52.260 We mean the prompt degeneration, 14:52.270 --> 14:55.010 the breakdown and ultimate figure psychosis of the axon 14:55.440 --> 14:57.370 that occurs after. 14:57.380 --> 14:58.150 For example, 14:58.160 --> 15:00.460 cutting a nerve that occurs in the distance, 15:00.460 --> 15:03.350 dump the excellent segments separated 15:03.360 --> 15:06.060 from continuity with the cell body. 15:06.940 --> 15:09.350 And a variety of 15:09.490 --> 15:11.560 approaches have indicated 15:12.010 --> 15:14.730 that the most important factor in initiating this 15:14.730 --> 15:17.500 process of orange generation is the acute 15:17.500 --> 15:19.950 complete interruption of accidental transport. 15:20.640 --> 15:23.320 Inferential evidence suggests that it's fast 15:23.320 --> 15:24.160 axonal transport. 15:24.160 --> 15:26.290 This most important if one 15:26.300 --> 15:29.260 calculates the time to failure to fire. 15:29.540 --> 15:32.200 Of a no 15:32.200 --> 15:35.110 muscular preparation with a 15:35.120 --> 15:37.650 very distal external section 15:38.600 --> 15:40.940 and then increasingly lengthens the 15:40.940 --> 15:41.710 proximal, 15:42.050 --> 15:44.860 increasingly lengthens the distal stump 15:45.340 --> 15:47.160 and measures the time to failure to fire. 15:48.240 --> 15:50.980 one finds that each additional 15 millimeters 15:50.990 --> 15:52.760 of distance dumped length 15:53.240 --> 15:55.520 provides physiologic 15:55.530 --> 15:56.450 activity, 15:56.840 --> 15:59.600 the capacity to transmit across the 15:59.600 --> 16:02.230 neuromuscular junction for about one additional 16:02.230 --> 16:02.750 hour. 16:03.740 --> 16:05.620 Uh Similarly, 16:05.630 --> 16:08.270 the length of the distal stump affects 16:08.270 --> 16:11.140 the development of pathologic 16:11.140 --> 16:13.880 changes of orange generation in the 16:13.890 --> 16:14.550 Exxon. 16:15.040 --> 16:17.660 Uh in that 15 mm/h correlates very 16:17.660 --> 16:20.350 closely to the rate of fast 16:20.350 --> 16:21.360 external transport. 16:23.240 --> 16:26.110 If uh excellent transport is interrupted not by 16:26.110 --> 16:27.110 excellent section, 16:27.300 --> 16:29.940 but by application of culture seen or been 16:29.940 --> 16:32.710 blasting along the course of the nerve or by a 16:32.710 --> 16:33.960 sustained cold block. 16:34.440 --> 16:37.280 A similar polarity generation of the 16:37.280 --> 16:38.660 distance stump occurs. 16:40.040 --> 16:42.600 Having said that we really have summarized all that is 16:42.600 --> 16:45.450 known firmly about the relationship between 16:45.450 --> 16:47.360 transport and excellent pathology. 16:48.000 --> 16:50.700 I'd like to turn to one kind of chronic axillary 16:50.700 --> 16:53.650 generation which has attracted our interest in the interest of a 16:53.650 --> 16:56.000 number of laboratories 16:56.000 --> 16:56.660 recently. 16:57.640 --> 16:59.860 And that's the process of external dying back. 17:00.840 --> 17:02.900 Now dying back today, 17:02.910 --> 17:05.700 at least should be taken to indicate 17:05.710 --> 17:07.910 a situation in which the axon 17:07.920 --> 17:10.810 degenerates in a distant a proximal 17:10.820 --> 17:12.550 fashion chronically. 17:13.110 --> 17:15.310 That is if one 17:15.320 --> 17:17.960 imagines the if one imagines 17:18.340 --> 17:21.140 the axon making contact 17:21.140 --> 17:22.770 with the neuromuscular junction. 17:23.240 --> 17:26.210 Uh normally one can say in Warren degeneration 17:26.210 --> 17:28.900 that the accident was sectioned in the distance trump rapidly 17:29.130 --> 17:31.360 disappears in dying back. 17:31.940 --> 17:34.420 One can document a very slow, 17:34.430 --> 17:37.260 gradual process of 17:37.270 --> 17:39.560 distal to proximal degeneration 17:40.240 --> 17:42.760 so that I uhh 17:43.240 --> 17:45.570 we're talking about a chronic degenerative process, 17:45.890 --> 17:48.660 which is certainly applicable to a number of human peripheral 17:48.660 --> 17:49.360 neuropathy. 17:50.640 --> 17:50.880 Now, 17:50.880 --> 17:53.530 the hypothesis that has 17:53.530 --> 17:55.950 been raised regarding this 17:56.340 --> 17:57.690 can be summarized as follows. 17:58.840 --> 18:01.550 If we say that an acute interruption of external transport 18:01.550 --> 18:04.510 produces acute degeneration of the distance dump of 18:04.510 --> 18:05.260 the axon. 18:06.040 --> 18:08.860 Uh then can't we imagine that a chronic 18:08.870 --> 18:11.550 partial impairment uh in the 18:11.550 --> 18:13.950 amount of transported material received by the 18:13.950 --> 18:16.150 axon might lead to 18:16.150 --> 18:18.960 a chronic excellent regeneration 18:20.140 --> 18:22.840 decrease in transport could certainly occur either 18:22.840 --> 18:25.080 because of fear interference 18:25.080 --> 18:27.890 with cell body synthetic functions or 18:27.890 --> 18:29.550 because of abnormalities and transport per 18:29.550 --> 18:31.170 se. 18:32.120 --> 18:35.040 And we would imagine that larger or 18:35.040 --> 18:38.010 longer axons might be preferentially vulnerable 18:38.170 --> 18:41.070 simply because they have more access to maintain that the endings of 18:41.070 --> 18:42.410 their axons would represent, 18:42.420 --> 18:42.820 if you will, 18:42.820 --> 18:44.670 the last field of of irrigation. 18:46.040 --> 18:48.520 Uh this has 18:48.520 --> 18:50.920 led to a hypothesis 18:51.340 --> 18:54.320 uh that really goes back at least 100 years 18:54.320 --> 18:56.640 and was very clearly articulated by 18:56.650 --> 18:58.360 1895. 18:58.370 --> 19:01.290 Actually enough with regard to amyotrophic lateral sclerosis. 19:01.740 --> 19:04.430 And the hypothesis is simply that nerve cell body 19:04.440 --> 19:07.120 synthetic uh deficiencies 19:07.130 --> 19:08.900 lead to just like some only 19:08.900 --> 19:11.160 generation. 19:12.440 --> 19:12.770 Mhm. 19:14.920 --> 19:15.410 Well, 19:15.490 --> 19:17.990 in our laboratory and as I indicated in other laboratories 19:18.000 --> 19:18.550 recently, 19:18.550 --> 19:20.940 we've begun testing this hypothesis using 19:20.940 --> 19:22.720 experimental toxic neuropathy. 19:23.210 --> 19:25.300 The disorder that we have 19:25.310 --> 19:27.690 investigated most is 19:27.700 --> 19:29.860 acrylamide intoxication in the rat. 19:30.340 --> 19:33.060 We've also uh more recently been investigating 19:33.360 --> 19:36.160 intoxication with 25 hexane dyan 19:36.470 --> 19:39.460 in collaboration of dr peter spencer at Albert Einstein 19:40.020 --> 19:42.720 acrylamide induces a 19:42.730 --> 19:44.460 dying back neuropathy. 19:45.240 --> 19:48.050 This animal was intoxicated for about eight weeks with a 19:48.050 --> 19:49.350 chrome ride in his feed. 19:49.840 --> 19:50.050 Mhm. 19:50.540 --> 19:52.350 And uh 19:53.540 --> 19:56.180 you can see that there is marked weakness 19:56.190 --> 19:58.760 of defeat particularly 19:59.340 --> 20:02.190 uh and uh a lesser 20:02.190 --> 20:05.110 degree of weakness uh is president although it's not obvious 20:05.110 --> 20:05.900 from the side. 20:05.910 --> 20:08.890 Uh more approximately sensory 20:08.890 --> 20:10.860 loss is uh 20:11.240 --> 20:14.130 distant predominant as well so that these animals are not 20:14.130 --> 20:17.080 only weak distantly but they have impaired sensation and 20:17.080 --> 20:18.950 difficulty walking for that reason. 20:20.110 --> 20:23.020 Now is this dyslexic degeneration the result 20:23.030 --> 20:25.830 of diminished delivery of 20:25.830 --> 20:28.480 transported constituents to nerve 20:28.480 --> 20:29.170 terminals? 20:29.930 --> 20:30.160 Well, 20:30.160 --> 20:31.320 to investigate that question, 20:31.320 --> 20:33.340 we've used a preparation, 20:33.610 --> 20:36.200 we first of all you standard inv evil rate 20:36.200 --> 20:38.860 measurements of the kind that we talked about a minute ago. 20:38.980 --> 20:41.170 We've also used a preparation mhm. 20:41.590 --> 20:43.400 In which the rat sciatic nerve, 20:43.410 --> 20:45.990 the dorsal root ganglion endorsing route are 20:45.990 --> 20:48.760 removed from the animal and 20:48.760 --> 20:51.610 placed in a short term culture situation in vitro. 20:52.540 --> 20:53.960 In this arrangement, 20:54.220 --> 20:56.150 the dorsal root ganglia, 20:56.160 --> 20:58.920 that is the cell bodies that lead to the psychotic 20:58.920 --> 21:00.670 nerve and to the dorsal root 21:01.040 --> 21:03.460 uh mm 21:03.940 --> 21:06.470 are placed in a isolated chamber 21:06.620 --> 21:08.860 separated from the media 21:08.870 --> 21:11.630 surrounding the nerve and the roots by 21:11.640 --> 21:12.960 silicon grease barriers, 21:13.740 --> 21:16.660 precursors such as treated lucy and created few coast can 21:16.660 --> 21:19.560 then be added to the ganglion chamber 21:20.040 --> 21:22.170 and transport 21:23.040 --> 21:25.750 uh synthesis of 21:25.760 --> 21:28.630 proteins or black of proteins will occur here and 21:28.630 --> 21:31.030 some fraction of those newly synthesized proteins will enter 21:31.040 --> 21:33.880 fast transport both up the root and 21:33.880 --> 21:36.800 down the nerve to make sure that we don't lose 21:36.810 --> 21:38.020 transported materials. 21:38.020 --> 21:38.670 We like it. 21:39.140 --> 21:41.950 The roots and nerves H two 21:42.190 --> 21:45.140 A allow quantitative evaluation 21:45.490 --> 21:47.770 of the fraction of materials entering transport. 21:48.140 --> 21:51.140 So this type of preparation allows measurements of 21:51.140 --> 21:52.720 treated lucy inc, 21:53.130 --> 21:55.740 as well as the fraction of milly synthesized materials entering 21:55.740 --> 21:56.450 transport. 21:57.640 --> 22:00.480 I should mention also that no transport material 22:00.490 --> 22:02.150 or very little enters the ventral root. 22:02.160 --> 22:03.160 As one would expect. 22:04.050 --> 22:06.730 Uhh Now using 22:06.730 --> 22:09.270 preparations from animals chronically 22:09.270 --> 22:11.960 intoxicated with acrylamide compared to controls. 22:12.640 --> 22:14.860 On the next slide, 22:15.740 --> 22:18.710 we find no difference in total treated lucy 22:18.710 --> 22:21.640 inc by the cell bodies or 22:21.650 --> 22:24.540 in the fraction of newly synthesized material entering 22:24.540 --> 22:27.500 fast transport either down the nerve or up the ventral roots 22:27.510 --> 22:29.950 between the control and the crow might intoxicated 22:29.950 --> 22:30.560 animals. 22:31.030 --> 22:31.720 Similarly, 22:32.340 --> 22:35.210 if preparations from normal animals are incubated with 22:35.210 --> 22:37.960 acrylamide uh In the incubation media, 22:38.050 --> 22:40.600 we find no impairment of either protein 22:40.600 --> 22:42.270 synthesis or fast transport. 22:43.640 --> 22:44.470 On the other hand, 22:44.480 --> 22:46.440 measuring fast transport rates, 22:46.680 --> 22:48.730 not the total amount that gets into the accident. 22:48.730 --> 22:51.110 Fast transport rates we do find, 22:51.120 --> 22:52.580 as indicated in the next slide, 22:52.590 --> 22:54.330 some slowing a fast transport. 22:54.730 --> 22:56.450 In this normal animal, 22:57.930 --> 23:00.370 rapidly transported material has reached about 60 23:01.040 --> 23:02.950 within three hours after 23:03.710 --> 23:06.170 injection treated losing into the ventral horn. 23:06.620 --> 23:09.170 In this acrylamide intoxicated animal, 23:09.540 --> 23:12.400 uh about 60 millimeters has reached 23:12.410 --> 23:15.200 four hours after injection 23:15.200 --> 23:15.970 of translated, 23:15.970 --> 23:16.560 losing. 23:16.940 --> 23:19.710 So the calculated rate would be about 424 23:19.710 --> 23:22.640 mm a day here And about 23:22.650 --> 23:25.050 336 mm a day 23:25.060 --> 23:25.660 here. 23:26.340 --> 23:28.970 The next slide shows mean 23:28.970 --> 23:31.790 values for normal and acrylamide treated 23:31.790 --> 23:32.460 animals. 23:32.940 --> 23:35.580 Uh And there's a slight but 23:35.590 --> 23:38.360 significant difference between the chrome I treated animals. 23:38.740 --> 23:41.300 Very similar results have been obtained using two five X. 23:41.300 --> 23:44.200 And I own and other laboratories slowing a fast 23:44.200 --> 23:47.080 transport at least Some preliminary studies has been suggested to 23:47.080 --> 23:49.800 occur with Christine neuropathy method, 23:49.800 --> 23:52.570 beetle ketone intoxication and try a little crystal phosphate 23:52.570 --> 23:53.350 intoxication. 23:54.650 --> 23:57.650 Now does this slowing of transport lead to the dyslexic 23:57.670 --> 23:58.460 degeneration? 23:59.240 --> 23:59.440 Yeah, 24:00.040 --> 24:02.810 we currently feel that considerable caution is required in 24:02.810 --> 24:05.630 making that interpretation of the data for two 24:05.630 --> 24:06.170 reasons. 24:06.180 --> 24:06.760 1, 24:07.340 --> 24:09.980 with acrylamide at least the slowing of fast 24:09.980 --> 24:12.610 transport is found only after the 24:12.610 --> 24:15.390 initial process of excellent regeneration has 24:15.390 --> 24:15.860 begun. 24:16.640 --> 24:18.630 If that were the responsible factor, 24:18.640 --> 24:21.100 you would anticipate finding a slowing of fast 24:21.100 --> 24:23.740 transport occurring prior to the 24:23.750 --> 24:25.360 beginning of maximum degeneration. 24:26.340 --> 24:27.070 Also, 24:27.080 --> 24:29.700 we have examined the role of fast 24:29.700 --> 24:32.610 transport in another abnormality produced by 24:32.610 --> 24:35.160 acrylamide and that's the impaired capacity of 24:35.160 --> 24:36.750 axons to regenerate. 24:36.750 --> 24:38.930 Following a crush acrylamide, 24:38.930 --> 24:41.430 intoxicated nerves are not able 24:41.430 --> 24:44.290 to grow out uh and regenerate 24:44.300 --> 24:47.230 uh or to mature their axons as well as 24:47.230 --> 24:50.030 normal animals has been shown by uh morgan 24:50.030 --> 24:52.360 Hughes and by ochoa previously 24:53.240 --> 24:55.780 and uh I am already graphic and 24:55.780 --> 24:58.750 radiochemical studies of uh preparations 24:58.760 --> 25:01.650 from those animals very clearly indicates 25:01.660 --> 25:04.140 that that failure of outgrowth cannot be 25:04.140 --> 25:07.130 ascribed to a failure of delivery 25:07.130 --> 25:10.060 rapidly transported materials to the growing 25:10.060 --> 25:10.680 tips. 25:12.140 --> 25:14.940 So at present we can say that a gross impairment in cell body 25:14.940 --> 25:17.840 protein synthesis is not requisite for the development of a 25:17.840 --> 25:18.950 dying back picture. 25:19.720 --> 25:22.550 It seems most likely that the slowing of fast transport at 25:22.550 --> 25:24.030 least in the case of acrylamide. 25:24.640 --> 25:27.510 Uh uh that the slowing of fast 25:27.510 --> 25:30.160 transport and the dislike some of the generation are both 25:30.160 --> 25:32.400 consequences of some as yet unknown 25:32.410 --> 25:35.170 mechanism of action of the toxin 25:36.040 --> 25:36.550 curly. 25:36.560 --> 25:39.320 A major need at present is for a study 25:39.320 --> 25:42.010 of individual proteins separated. 25:42.020 --> 25:43.790 Uh For example, 25:43.790 --> 25:44.670 electro theoretically. 25:47.140 --> 25:47.580 Now, 25:47.590 --> 25:49.950 how applicable such Studies are two. 25:49.960 --> 25:51.870 Human degenerative diseases 25:52.540 --> 25:53.770 is not clear. 25:54.140 --> 25:56.820 We think that the experimental models of dying 25:56.820 --> 25:59.730 back are quite good models of human dying back 25:59.740 --> 26:00.530 neuropathy, 26:00.870 --> 26:03.810 many toxic neuropathy and probably those that 26:03.810 --> 26:05.900 occur in some degenerative conditions. 26:05.910 --> 26:07.460 Perhaps Friedrich's ataxia. 26:08.240 --> 26:11.240 The difficulty is that one criteria of dying back 26:11.250 --> 26:12.750 that we previously mentioned, 26:13.100 --> 26:15.790 the selective vulnerability of larger longer 26:15.790 --> 26:18.750 axons can be satisfied on 26:18.750 --> 26:21.460 clinical or pathologic grounds in human material. 26:22.040 --> 26:23.620 With the second criteria, 26:23.630 --> 26:26.410 the demonstration of distal to proximal 26:26.410 --> 26:28.970 degeneration of individual actions is very difficult to 26:28.970 --> 26:31.020 establish. 26:31.940 --> 26:34.850 The question we might raise is whether Ailes 26:35.150 --> 26:37.820 is a disorder in which an 26:37.820 --> 26:39.560 element of dying back might occur. 26:40.240 --> 26:43.050 Uh This question uh It 26:43.050 --> 26:45.900 seems to me deserves re evaluation by classic neuropathy 26:45.900 --> 26:48.820 logic techniques because our thinking about the 26:48.820 --> 26:51.760 disorder uh at this point 26:52.140 --> 26:54.600 would be colored by the extent to which it 26:54.610 --> 26:57.390 represented a dying back process 26:57.670 --> 27:00.620 in the extent to which an analogy to these other disorders could 27:00.620 --> 27:01.260 be made. 27:01.840 --> 27:04.100 But I would add that it will be very difficult to 27:04.110 --> 27:06.650 establish the spatial temporal evolution of the 27:06.650 --> 27:09.330 pathology in a less using classic classic 27:09.340 --> 27:09.990 techniques. 27:10.690 --> 27:13.640 And I'd like to mention the value of animal 27:13.640 --> 27:16.560 models for that kind of path a biologic study. 27:17.040 --> 27:19.800 Uh At this point there have been 27:19.810 --> 27:21.210 no very good models of A. 27:21.210 --> 27:21.360 L. 27:21.360 --> 27:21.770 S. 27:22.240 --> 27:24.770 Uh There have been 27:24.780 --> 27:27.470 occasional models of motor neurone disease 27:27.820 --> 27:29.640 which dr john andrews at U. 27:29.640 --> 27:29.780 C. 27:29.780 --> 27:29.910 L. 27:29.910 --> 27:30.040 A. 27:30.040 --> 27:32.880 Among others has uh studied pathologically 27:32.880 --> 27:33.850 very extensively. 27:34.740 --> 27:37.710 We recently have been introduced to a model uncovered by dr 27:37.710 --> 27:39.860 linda cork who is now at Hopkins 27:40.340 --> 27:43.030 uh of motor neurone disease. 27:43.040 --> 27:45.940 Uh A spinal 27:45.940 --> 27:48.260 muscular atrophy occurring in 27:48.740 --> 27:49.550 Brittany 27:49.550 --> 27:51.770 spaniels. 27:52.440 --> 27:53.610 Uh These dogs, 27:53.620 --> 27:55.860 at a few months of life develop 27:55.960 --> 27:58.540 primarily approximately weakness and have 27:58.550 --> 28:01.500 muscle pathology changes that are uh 28:01.510 --> 28:04.100 strikingly similar to the human spinal muscular 28:04.100 --> 28:05.460 atrophy changes. 28:06.200 --> 28:09.000 Uh They of course show loss of anterior 28:09.000 --> 28:10.460 horn cells in the spinal cord. 28:10.940 --> 28:13.680 Uh And I would add that in addition they show 28:13.690 --> 28:16.510 changes in accident pathology which suggests 28:16.510 --> 28:19.500 some dynamic accidental process is going 28:19.500 --> 28:20.270 on as well. 28:20.640 --> 28:23.320 And this pathology includes these enormous 28:23.330 --> 28:25.420 external swellings in the spinal cord here, 28:25.420 --> 28:27.390 seeing an electron micrografx. 28:27.400 --> 28:30.100 Uh So that in this situation at least 28:30.330 --> 28:33.310 the process of motor neuron degeneration 28:33.320 --> 28:36.150 is accompanied by an axonal degeneration that we cannot 28:36.160 --> 28:39.150 ascribe simply to water and degeneration due to the death 28:39.150 --> 28:40.050 of the motor neuron. 28:41.200 --> 28:42.960 And as we've indicated before, 28:43.340 --> 28:45.820 uh it would be of interest to 28:45.830 --> 28:48.650 uh reevaluate um pathology 28:48.660 --> 28:51.610 in a minute traffic lateral sclerosis with regard to the question 28:51.610 --> 28:54.350 of whether a distal uh to proximal 28:54.740 --> 28:57.300 degeneration occurs at any rate, 28:57.390 --> 29:00.390 were quite interested in studying with 29:00.400 --> 29:02.750 uh transport. 29:02.750 --> 29:04.330 And I am already graphic techniques 29:05.510 --> 29:07.560 these models of motor neuron disease. 29:10.040 --> 29:10.360 Mhm.