Computer analysis of organelle translocation in primary neuronal cultures and continuous cell lines.

Organelle translocation in a number of cell types in tissue culture as seen by high-resolution Zeiss-Nomarski differential interference contrast optics was filmed and analyzed by computer. Principal cell types studied included primary chick spinal cord, chick dorsal root ganglion, ratbrain, and various clones of continuous cell lines. Organelle translocations in all cell types studied exhibited frequent, large changes in velocity during any one translocation. The appearance of particles as seen with Nomarski optics was correlated with their fine structures in one dorsal root ganglion neurite by fixing the cell as it was being filmed and obtaining electron micrographs of the region filmed. This revealed the identity of several organelles as well as the presence of abundant neurotubules but no neurofilaments. Primary cell cultures exhibited more high-velocity organelle movements than continuous cell lines. The net progress of an organelle in a given direction was greater in primary neuronal cells than in fibroblasts or continuous cell lines. These findings are correlated with the literature on organelle translocation and axoplasmic transport.

Amount and speed of fast axonal transport in diabetes.

Abnormalities in axonal transport have been observed in human and experimental diabetes and may be related to the pathogenesis of diabetic neuropathy. Axonal transport has previously been evaluated by indirect methods. In this study, direct-measurement techniques were applied (with computer-enhanced video-recorded images) for the first time to evaluate intra-axonal organelle speed and frequency (the amount of organelle traffic) in both the anterograde fast component (AFC) and retrograde fast component (RFC) of axonal transport in diabetic nerve. Sciatic nerve and dorsal and ventral nerve roots were studied in the animal model of insulin-dependent diabetes (BB/Wistar rat) and sciatic nerve in the non-insulin-dependent (streptozocin-induced) model of diabetes (STZ-D rat). STZ-D rats were studied at 1 mo, and BB/Wistar rats were studied at 1 and 2 mo of diabetes duration. Statistically significant decreases in peripheral axon organelle speed were found only for RFC at 1 mo of diabetes in both the BB/Wistar (8.1%) and STZ-D (5.4%) rats. The difference was no longer significant in BB/Wistar rats at 2 mo of diabetes. This recovery suggests that the underlying abnormality is reversible. No differences were seen in AFC of any axons, and the only other difference seen was a 5.1% decrement in RFC at 2 mo in the ventral roots. No significant difference was observed in any group for organelle frequencies. Other factors should be considered to explain the decrease in materials transported in accumulation studies. The transient deficits in RFC speed observed remain of undetermined significance in the pathogenesis of diabetic neuropathy.

Calcium dependent modulation of fast axonal transport.

The highly differentiated structure of the neuron poses special problems for the intracellular movement of molecules throughout the cell. Molecular transport distances from the synthesizing neuron cell body along the axon (which has no substantial synthetic capabilities) to the axon terminal are very great. The transported substances, transport support structures, translocator motors, and control elements are currently the focus of intense research. Interruption of this flow of molecules could have disastrous effects upon the cell and ultimately the organism resulting in neuropathological conditions. Calcium plays a critical role in modulating fast-axonal transport (FAT) speeds. Before discussing the effect of calcium on FAT, we summarize our broad perspective on the role of axonal transport in neurologic disease.

Fast axonal transport is modulated by altering trans-axolemmal calcium flux.

Factors involved in fast axonal transport (motor proteins, microtubules, organelles, etc.) have been identified but the molecular mechanism controlling transport is unknown. We used video enhanced microscopy to directly evaluate the effect of calcium on fast axonal transport (FAxT). FAxT alterations included rapid speed decreases (within minutes) in Ca2+ free buffer and rapid speed increases (within seconds) when axons were treated with parathyroid hormone, BAY K 8644, or K+ depolarization. The speed increases were blocked by dihydropyridine Ca2+ channel antagonists. Ryanodine (20 microM), known to block calcium release from subcellular stores, caused a decrease in the rate of retrograde FAxT. Calcium ionophore A23187 (at 1 and 20 micrograms/ml) caused increases in FAxT, an effect also noted only in retrograde moving organelle traffic. Hyper- or hypo-tonic solutions produced no alterations making axoplasmic viscosity changes an unlikely explanation for the speed changes. Reproducible alteration of FAxT by manipulation of Ca2+ levels provides evidence that Ca2+ modulates fast axonal transport. Retrograde transport appears more sensitive to changes in Ca2+ and differential effects on antero- and retro-FAxT mechanisms suggest directional specificity for some of these signals which may be based upon the organelle size. Endogenous substances (e.g. PTH) that trigger axonal Ca2+ changes may rapidly modulate the rate of material delivery in axons. The results are discussed within the context of a Ca2+/calmodulin-dependent modification of the cytoskeletal matrix.

Hyperpathia and sensory level due to parietal lobe arteriovenous malformation.

A 30-year-old man experienced the sudden onset of prickly dysesthesia in the perineum followed by a "heavy" sensation in the left lower extremity. There was no headache. He had a hyperpathic response to pinprick and temperature testing below the T-6 dermatome on the left and a decrease of light touch below T-10, also on the left. A small ruptured arteriovenous malformation was found in the right parietal lobe, medially, well above the thalamus, and in the region of the postcentral gyrus. The case provides rare and precise clinicoanatomic correlation of the discrete somatotopic organization of the sensory cortex. Furthermore, it indicates that sensory disturbances, characterized by a segmental level of abnormal sensation suggestive of a spinal cord or medullary lesion and by hyperpathia suggestive of a spinal, medullary, or thalamic localization, can be caused by a suprathalamic parietal deficit.

Spinal subarachnoid hematomas: clue to a source of bleeding in traumatic lumbar puncture.

Although damage to the veins of Batson's epidural plexus is usually considered the origin of bleeding in traumatic lumbar puncture, a lesion of these veins would not explain the cases in which postmortem examination shows blood confined to the subdural and subarachnoid spaces. In two patients who had lumbar punctures a few days before death, there was subarachnoid hematoma of the cauda equina at autopsy. In one of these cases, the radicular vessels were shown to be the source of bleeding. Spinal subarachnoid and subdural hemorrhages after lumbar puncture may be due to laceration of radicular vessels by the spinal needle.

Fast axonal transport in amyotrophic lateral sclerosis: an intra-axonal organelle traffic analysis.

Fast transport of intra-axonal organelles was studied in motor nerve from amyotrophic lateral sclerosis (ALS) patients. Organelle traffic in ALS nerves demonstrated a significant increase in anterograde mean speed, while retrograde mean speed was decreased compared with that of controls. Retrograde traffic density (organelles per unit time) was also significantly decreased in the ALS specimens. Anterograde transport machinery is therefore intact and may be responding to the increased physiologic demand of larger motor units. Diminished retrograde speed and organelle traffic density are consistent with a defect in retrograde transport and could impair communication between axon terminals and perikarya.

Ischemic optic neuropathy: a complication of cardiopulmonary bypass surgery.

Ischemic optic neuropathy followed cardiopulmonary bypass surgery in the postoperative period in 7 of 7685 consecutive procedures. Th visual loss was unilateral in four patients and bilateral in three and there was little improvement. This ischemic infarction of the optic nerve disk was attributed to hypotension, hypothermia, and activation of certain complement factors by the bypass procedure.

Amyotrophic lateral sclerosis: effects of acute intravenous and chronic subcutaneous administration of thyrotropin-releasing hormone in controlled trials.

We performed double-blind crossover trials to assess the effects of thyrotropin-releasing hormone (TRH) on amyotrophic lateral sclerosis patients. For acute intravenous trials, 500 mg TRH or placebo with norepinephrine was given at 1-week intervals (16 patients). CSF TRH concentration increased, and clinical side effects appeared with TRH. For chronic studies, 25 mg TRH and a saline placebo were given subcutaneously every day for 3 months (25 patients). CSF TRH level increased 29-fold after a single TRH injection, and mild transient side effects occurred. Vital signs, respiratory function, semiquantitative and quantitative neurologic function, muscle strength by manual and dynamometer testing, and EMG were studied. With daily TRH, 10 patients noted subjective improvement without objective evidence, and 10 patients complained of worsening of the disease with objective decline after TRH was stopped. Statistical analysis, however, showed no beneficial effects from either acute or chronic TRH trials.

Anomalies of heart, spleen, kidneys, gut, and limbs may result from an overdistended neural tube: a hypothesis.

A hypothesis is advanced that many congenital anomalies of non-neural organs may be produced by damage to their mesodermal or entodermal anlagen caused by overdistention of the embryonic neural tube. Evidence to support the hypothesis derives from: (1) seldom appreciated but unequivocal embryologic facts about prechoroid plexus neural tube morphogenesis; (2) an understanding of the role of neural tube overdistention in the production of various dysraphic conditions; (3) the frequency of association of non-neural anomalies with dysraphic conditions; and 4) an analysis of the anatomic features of the organ anomalies associated with dysraphism. The practical utility of the hypothesis is that (1) it helps explain a seemingly widely divergent subset of phenomenology and (2) it is testable. At present, treatment of children with congenital anomalies is largely palliative. Prevention of these distressing defects in the future will only be realizable if the mechanisms of their genesis are more clearly understood.

Mechanism and frequency of brachial plexus injury in open-heart surgery: a prospective analysis.

A computer-assisted prospective analysis of 531 patients undergoing open-heart operations revealed that 26 patients (5%) sustained brachial plexus injury. In 22 of the 26 patients (85%), the lesion involved the lower trunk or C8-T1 nerve roots. Electromyograms confirmed the clinical impression in 13 patients. In 19 of the 26 patients (73%), the side on which the plexus lesion was found correlated with the side of internal jugular vein cannulation. Because of the anatomical proximity of the lower trunk to the internal jugular vein and the preponderance of lower trunk lesions, we postulate that traumatic cannulation may be a major mechanism of plexus injury. Thus, the resulting syndrome of pain, dysesthesias, and hand weakness may sometimes be preventable.

Neurons from fetal rat brain in a new cell culture system: a multidisciplinary analysis.

A new culture system for cells from the mammalian brain was developed by a modification of a previously established technique. This modification involved the use of fluorodeoxyuridine and adult horse serum. The cultures contained large, easily visualized neurons both isolated from other neurons and in networks of varying complexity. These cells were large enough to permit reliable intracellular electrophysiologic recording and were often sufficiently dispersed to allow examination of membrane responses to iontophoretically applied neurotransmitter candidates. Many responses characteristic of central neurons in situ were seen, including evoked and spontaneous action potentials, complex patterns of inhibitory and excitatory post-synaptic potentials, and neurotransmitter-induced membrane responses. These preparations were examined by phase contrast microscopy, by light microscopy after silver impregnation and by Nomarski interference optics. Total choline acetyltransferase (CAT) activity was little changed and specific activity was increased in the new culture system as compared with the earilier system. Conditions which gave the highest specific activity of CAT also provided the best cultures from the standpoint of electrophysiologic and morphologic analysis. This new approach will allow, in culture, detailed multidisciplinary analyses of individual neurons and small networks of neurons from the mammalian brain.

Treatable extramedullary cord compression. Meningioma as a cause of the Brown-Séquard syndrome.

The Brown-Séquard syndrome is infrequently reported. Though widely considered indicative of intramedullary spinal cord disease, in the absence of penetrating spinal cord trauma, the syndrome is frequently an early stage of extramedullary spinal cord compression, as an extensive analysis of diverse literatures reveals. We describe two cases resulting from compression of the spinal cord by a meningioma. While previous reviews emphasize that radicular or vertebral pain is a prominent feature of spinal cord compression by intradural tumors, our patients had no pain referable to tumor. Awareness that painless extramedullary spinal cord compression can produce the Brown-Séquard syndrome, early myelography, and surgical intervention are necessary to prevent progressive deficit. Even when encountered in a patient who has previously well-documented demyelinating disease, the syndrome should not be written off as a relatively untreatable intramedullary process.

Fast axonal transport alterations in amyotrophic lateral sclerosis (ALS) and in parathyroid hormone (PTH)-treated axons.

Video-enhanced contrast techniques have been used to study fast axonal transport of organelles in diseased and normal human axons. A broad perspective on the importance of axonal transport in the pathogenesis of human neurological disorders is presented and problems in dealing with human nerve summarized. Results from analysis of organelle traffic in axons from motor nerve in patients with amyotrophic lateral sclerosis (ALS) show: 1) higher mean speed of anterograde organelles, 2) lower mean speed of retrograde organelles, and 3) lower retrograde organelle traffic density. Hyperparathyroidism, another human clinical syndrome, can mimic ALS. The effect of parathyroid hormone (PTH) on axons in vitro is to increase the mean speed of both anterograde and retrograde organelle traffic. The dose response curve and time course of the PTH effect are delineated. Dihydropyridine calcium channel antagonists block the PTH effect, implicating extracellular calcium in the alteration of organelle traffic speed. The results are discussed in relation to neuronal function and the regulation of fast axonal transport.

Malignant lymphoma of the central nervous system: a case of primary spinal intramedullary involvement.

Primary involvement of the spinal cord in malignant lymphoma is rare. Clinical and pathologic features of a case of malignant lymphoma initially involving the spinal cord and subsequently one cerebral hemisphere are reported and the medical literature reviewed. If malignant lymphoma of the central nervous system is diagnosed by means of brain biopsy examination, radiotherapy of any coexisting intramedullary spinal cord lesion of undetermined cause should be considered.

Multifocal pontine lesions in cancer patients treated with chemotherapy and CNS radiotherapy.

Multifocal pontine lesions were found at postmortem examination in four patients with various types of malignancy. The patients had undergone extensive evaluation and treatment with multiple chemotherapy regimens as well as radiotherapy to the central nervous system. The histologic character and striking anatomic distribution of the pontine lesions are described and their possible pathogenesis discussed.

Thoracic root pain in diabetes: the spectrum of clinical and electromyographic findings.

Diabetic thoracic radiculopathy has been reported rarely. Fifteen new cases, seen in an equal number of patients over a 3-year period and confirmed by electromyographic findings, have been analyzed. All patients presented with severe abdominal or chest pain, which often was not radicular in character. The presence of dysesthesias and an abnormal sensory examination of the trunk aided diagnosis. The pain was frequently associated with marked weight loss but carried a good prognosis for recovery. Six additional patients with negative electromyographic examinations were considered to have the disorder. Diabetic thoracic radiculopathy produces a distinct syndrome and may be more common than is generally recognized.

Influence of translocation track on the motion of intra-axonally transported organelles in human nerve.

The mechanism by which organelles are transported bidirectionally in axoplasm is still unknown; however, evidence of a key role for microtubules in many nonmammalian models has been established. We have observed common or shared tracks within the axoplasm of human nerves along which multiple organelles of varying size and shape are bidirectionally transported. Organelles traveling anterogradely and retrogradely were visualized by video-enhanced differential interference contrast optics and analyzed with the aid of computer-image-processing techniques. Speeds of translocating organelles were determined at eight to 16 translocation points along a path or "track." Each translocation speed was plotted against its corresponding position on the track to develop a "speed/position diagram." Regardless of mean organelle speed or direction of motion, organelles sharing a common track exhibited similar patterns of "speeding up" and "slowing down" relative to position along the track. Speed position data for organelles translocating the local axonal region of a common track showed no unique patterns (not different from a uniform distribution, p less than 0.05). The unique speed/position patterns exhibited by common tracks were not necessarily related to the patterns of other tracks in the immediate vicinity (distance between tracks of less than 0.50 micron). These findings suggest that there are "common tracks" shared by organelles moving retrogradely and anterogradely; both the organelles and the "track" associated with its translocation play a role in the resultant motion of that organelle; the influence exerted by a common track on the motion of an organelle results in a pattern of speed changes related to position along the track.

Direct measurement of fast axonal organelle transport in the sciatic nerve of rats treated with acrylamide.

The effects of acrylamide on fast axonal transport have been measured primarily using the indirect methods of isotope or enzyme accumulation. We report the first direct evaluation of the effects of subchronic acrylamide dosing (150, 300, or 500 mg/kg total dose, i.e., 50 mg/kg, 2x/wk, for 1.5, 3, 5 wk, respectively) on the fast axonal transport motility machinery itself using video-enhanced differential interference contrast optics with digital image processing and computer analysis. Four principle observations were made: (1) Rapid anterograde transport was not affected at any dosage level within 1 wk after cessation of dosing. (2) A high cumulative dosage (500 mg/kg total) of acrylamide or bisacrylamide produced approximately 7-18% decrease in the rate of retrograde transport in both myelinated and unmyelinated axons. (3) Lower dosages of acrylamide (150 or 300 mg/kg total) produced an increase in retrograde transport rates in myelinated axons only. (4) During the "recovery" phase for the 500 mg/kg acrylamide animals (i.e., 3 or 5 wk after the last dosage of acrylamide) the rate of anterograde transport in the myelinated axons was decreased at 3 wk but not at 5 wk, and the rate of retrograde transport in the myelinated axons returned to control levels while the retrograde transport in the unmyelinated axons continued at abnormally slow speeds. The application of this new technique to evaluate the neurotoxic effects of acrylamide provides evidence of dynamic changes in the axonal transport motility machinery itself and differential effects on myelinated versus unmyelinated fibers.