Hematogenous metastases of carcinoma to dorsal root ganglia

Summary Hematogenous metastases of carcinoma to dorsal root ganglia was found in 2 of approximately 500 consecutive autopsies in which a lumbar dorsal root ganglion was routinely examined microscopically. The primary tumors were poorly differentiated colonic adenocarcinoma and oat cell carcinoma of the lung, both with widespread hematogenous metastases which spared the central nervous system. No symptoms were detected clinically. In the same series of patients the sural nerve as well as the lumbar plexus were histologically sampled but no examples of distant endoneurial metastases were found. The vascular endothelium of dorsal root ganglia is fenestrated and, presumably as a consequence, provides no bloodganglion barrier. This microvascular difference may account for the susceptibility of the ganglia to metastases when compared to nerve trunks which possess unfenestrated endothelium and blood-nerve barrier.     

Exogenous silver in dorsal root ganglia,peripheral nerve,enteric ganglia,and adrenal medulla

Summary Following intraperitoneal (i.p.) or oral administration of silver salts, the anatomic distribution of silver in the peripheral nervous system (PNS) has been studied. The structures examined were dorsal root ganglia, peripheral nerve (N. ischiadicus), enteric ganglia, and adrenal medulla.Four days after an i.p. injection of silver lactate, silver deposits were found in these structures. The silver content remained stable during the observation period (45 days).The localization of silver deposits in the orally treated animals was independent of the administered silver salt (silver nitrate or silver lactate).The silver deposits in neurons and chromaffin cells were located in the cytoplasm. In all organs silver was present in large amounts in connective tissue membranes, macrophage-like cells, vascular basal laminae, and supporting cells. Satellite cells of the dorsal root ganglia were always heavily stained, white less stain was present in Schwann cells of the peripheral nerves.Intracellular deposits were invariably located in lysosomes, whereas extracellular grains were found in connective tissue fibers and basement membranes.     

Morphological effects of neuropathy-inducing organophosphorus compounds in primary dorsal root ganglia cell cultures

Chick embryo dorsal root ganglia (DRG) cultures were used to explore early pathological events associated with exposure to neuropathy-inducing organophosphorus (OP) compounds. This approach used an in vitro neuronal system from the species that provides the animal model for OP-induced delayed neuropathy (OPIDN). DRG were obtained from 9-day-old chick embryos, and grown for 14 days in minimal essential medium (MEM) supplemented with bovine and human placental sera and growth factors. Cultures were then exposed to 1 microM of the OP compounds phenyl saligenin phosphate (PSP) or mipafox, which readily elicit OPIDN in hens, paraoxon, which does not cause OPIDN, or the DMSO vehicle. The medium containing these toxicants was removed after 12 h, and cultures maintained for 4-7 days post-exposure. Morphometric analysis of neurites was performed by inverted microscopy, which demonstrated that neurites of cells treated with mipafox or PSP but not with paraoxon had decreased length-to-diameter ratios at day 4 post-exposure. Ultrastructural alterations of neurons treated with PSP and mipafox included dissolution of microtubules and neurofilaments and degrading mitochondria. Paraoxon-treated and DMSO control neuronal cell cultures did not show such evident ultrastructural changes. This study demonstrates that chick DRG show pathological changes following exposure to neuropathy-inducing OP compounds.     

Sulfite and base for the treatment of familial amyloidotic polyneuropathy: two additive approaches to stabilize the conformation of human amyloidogenic transthyretin

Recently, we presented evidence that sulfite protects transthyretin (TTR) from normal human individuals and heterozygotes with amyloidogenic TTR mutations against the decay of tetramers into monomers. In this paper we demonstrate a stabilizing effect of sulfite on TTR tetramers from a familial amyloidotic polyneuropathy (FAP) patient homozygous for the most-common amyloidogenic TTR-V30 M mutation. We compare the conformational stability of partially sulfonated TTR from a heterozygote for normal TTR and amyloidogenic TTR-V30 M with the stability of untreated TTR from a compound heterozygote for amyloidogenic TTR-V30 M and TTR-T119 M known to have only minor or no problems of FAP. Using a combination of polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS) gradient PAGE we demonstrate that TTR dimers containing amyloidogenic TTR mutations decay into monomers at pH<7.4. Increasing the pH by some 0.2 units within physiological ranges, i.e., pH 7.0–7.4, and sulfonation of TTR were observed to have additive inhibitory effects on the transition of dimers into monomers. We conclude that mild acidifying episodes in the interstitial volume of tissues at risk for amyloidosis could contribute to the development of FAP. Early and permanent efforts to counteract acidosis by treatment with base could possibly help to delay the onset of the disease. The intake of sulfite could support these efforts.Essential details of this paper were presented at the 5th International Symposium on Familial Amyloidotic Polyneuropathy and Other Transthyretin Related Disorders, 24–27 September 2002, Matsumoto, Japan.     

Reversible effects of hypoxia on neurons in mouse dorsal root ganglia in vitro

Mouse dorsal root ganglia (DRG) were isolated and maintained in a tissue chamber. Membrane potential of ‘A-type’ neurons was recorded with intracellular electrodes. When the supply of oxygen was reduced, cells depolarized by a few mV and then maintained a stable membrane potential or partially repolarized. During depolarization the action potential was reduced in amplitude and the hyperpolarizing afterpotential was depressed. Reoxygenation within 15–88 min was followed by a brief period of hyperpolarization and then complete recovery. In about 60% of the cells, invasion of the cell soma by impulses triggered by dorsal root (DR) stimulation failed during hypoxia while action potentials could still be evoked by stimulation of the peripheral nerve and by direct intracellular stimuli. Conduction from DR into the peripheral nerve stump was unchanged indicating that the blockade of DR-evoked impulse conduction occurred at the bifurcation of the axon. Results with paired pulse stimulation indicated that impulses passing the axon bifurcation leave a long lasting ( 25 ms) post-spike subnormal period. In DRG cells treated with tetraethylammonium (TEA) the calcium-mediated ‘shoulder’ of the action potential was curtailed during oxygen withdrawal. In contrast to CNS neurons, DRG cells did not show early hypoxic hyperpolarization, nor the delayed hypoxic spreading depression-like depolarization. The findings support the suggestion that the reversible depression of synaptic potentials in the CNS during the early phase of hypoxia is caused by a combination of conduction failure at axon branch points and curtailment of voltage calcium currents of presynaptic terminals, both effects resulting in reduced transmitter output.     

DNA breaks detected by in situ end-labelling in dorsal root ganglia of patients with AIDS

Distal sensory axonal polyneuropathy (DSP) is the most frequent HIV-associated peripheral neuropathy. DSPs tend to occur in full-blown AIDS and worsen as CD4 cell counts decrease in blood. To assess a possible role for apoptosis in the pathogenesis of the neuropathy, we used in situ end-labelling (ISEL) detecting DNA strand breaks in DRG neurons of 19 HIV-infected patients, of whom nine had axonal polyneuropathy, and 11 controls. Sensory neurons with ISEL-assessed DNA breaks were observed in 9/19 patients with AIDS, 0/3 patients with pre-AIDS, and 1/11 controls. The prevalence of DNA breaks in neurons was higher in AIDS patients than in controls ( P <0.05). Among AIDS patients, DNA breaks in neurons were more abundant in patients with peripheral neuropathy ( P <0.04). It is possible that DNA breaks of DRG neurons induce the axonopathy and consequently play a role in the pathogenesis of DSP. It cannot be excluded, however, that DNA breaks could represent the result rather than the cause of axonopathy. We suggest that ISEL may detect neurons that were primed to apoptosis before death in relation with the HIV infection, and undergo DNA fragmentation at time of death, rather than neurons that underwent pre-mortem both priming and triggering steps of the apoptotic process. This hypothesis could explain why most ISEL-positive neurons lack typical apoptotic morphology and why normal controls do not show ISEL positive cells.     

Development of inflammatory hypersensitivity and augmentation of sodium channels in rat dorsal root ganglia

The development of thermal allodynia in relationship to sodium channel augmentation in dorsal root ganglia (DRGs) was studied in albino rats. Paw withdrawal latencies were measured hourly following complete Freund's adjuvant (CFA) injections. Sodium channels were demonstrated with immunocytochemistry. Sustained minimum latencies were attained between 10 and 12 h post-injection. Sodium channel labeling began to increase at 23 h post-injection and reached maximum levels by 24 h. Thermal hypersensitivity is thus established 12 h before sodium channel augmentation can be demonstrated.     

The effects of lead on transient outward currents of acutely dissociated rat dorsal root ganglia

The effects of Pb2+ on transient outward currents (TOCs) were investigated on rat dorsal root ganglia (DRG) neurons at postnatal days of 15 approximately 21, using the conventional whole-cell patch-clamp technique. In media-sized (35 approximately 40 microm) neurons and in the presence of 50 mM TEA, TOCs that preliminarly included an A-current (IA) and a D-current (ID), were clearly present and dominant. Application of Pb2+ lengthened the initial delay of TOCs and increased the onset-peak time in a concentration-dependent manner. The amplitudes of initial outward current peak were reduced with increasing Pb2+ concentrations. The inhibitory effects of Pb2+ on TOCs were reversible with 80 approximately 90% of current reversed in 2 approximately 10 min at 1 approximately 400 microM Pb2+. For the normalized activation curves fitted by a single Boltzmann equation under each condition, there was a shift to more depolarized voltages with increasing concentrations of Pb2+. The V1/2 and the slope factor (k) increased from 12.76+/-1.49 mV and 15.31+/-1.66 mV (n=10) under control condition to 39.91+/-5.44 mV (n=10, P<0.01) and 21.39+/-3.13 mV (n=10, P<0.05) at 400 microM Pb2+, respectively, indicating that Pb2+ decreased the activation of TOCs. For the normalized steady-state inactivation curves, the V1/2 and the k increased from -92.31+/-2.72 and 8.59+/-1.36 mV (n=10) to -55.65+/-3.67 (n=10, P<0.01) and 23.02+/-2.98 mV (n=10, P<0.01) at 400 microM Pb2+, respectively. The curves were shifted to more depolarized voltages by Pb2+, indicating that channels were less likely to be inactivated at higher concentrations of Pb2+ at any given potential. The fast (tf) and slow (ts) decay time-constants were both significantly increased by increasing concentrations of Pb2+ (n=10, P<0.05), indicating that Pb2+ increased the decay time-course of TOCs. These effects were concentration-dependent and partly reversible following washing. Ca2+ modulated the TOCs gating and might share same binding site with Pb2+, for which Ca2+ had very low affinity. In summary, the results demonstrated that Pb2+ was a dose- and voltage-dependent, and reversible blocker of TOCs in rat DRG neurons. After Pb2+ application, normal sensory physiology of DRG neurons was affected, and these neurons might display aberrant firing properties that resulted in abnormal sensations. This variation caused by Pb2+ could underlie the toxical modulation of sensory input to the central nervous system.     

Potential treatment of transthyretin-type amyloidoses by sulfite

Familial amyloidotic polyneuropathy (FAP) and senile systemic amyloidosis (SSA) are characterized by systemic extracellular deposition of insoluble transthyretin (TTR) fibrils. While only normal TTR is found in fibrils from SSA patients who predominantly suffer from cardiomyopathy, autosomal dominant FAP preferentially affects peripheral nerves and heart and is associated with so-called amyloidogenic mutations of this protein, giving rise to TTR forms of decreased stability. Using isoelectric focusing in urea gradients we were able to demonstrate a stabilizing effect of sulfite on TTR monomers and tetramers, as well as an increase in the tetramer/monomer ratio. We demonstrate that this ratio, which is decreased in FAP patients, can be increased to beyond normal levels. We show that doses of sulfite which are tolerable in vivo produce a significant increase in the tetramer/monomer ratio and postulate that sulfite may be a potent drug for delaying the onset and progress of FAP and SSA. Received: July 20, 1999 / Accepted: July 26, 1999 · Published online: September 27, 1999     

Reversal by NGF of cytostatic drug-induced reduction of neurite outgrowth in rat dorsal root ganglia in vitro

Cytostatic drugs, like cisplatin, vincristine and taxol, when given to cancer patients may cause peripheral neuropathies. We were interested in the potential neuroprotective effects of neurotrophic factors against such neuropathies. To this aim we studied the effects of these cytostatic agents on sensory fibers located in the dorsal root ganglia (DRG) in vitro and studied whether nerve growth factor (NGF) could reverse the cytostatic induced morphological changes on intact DRG (1 DRG/well, n=10per dose). Neuritogenesis from DRG was measured with an image analysis system following exposure to different concentrations of cytostatic drugs in the presence of 3 ng NGF/ml and cytosine arabinoside (Ara-C, 10⁻⁶ M). Relative neurite outgrowth in intact DRG in culture was reduced dose-dependently, (a) by vincristine starting at a dose of 0.4 ng/ml for 2 days (−33% as compared to control; P < 0.001, Student's t-test); (b) by taxol 10 ng/ml (−60%; P< 0.001), and (c) by cisplatin 3 μg/ml (−47%, P < 0.001). Cisplatin also prevented the migration of satellite cells away from the intact DRG along the extending neurites into the well in contrast to control, vincristine, or taxol. To evaluate the neuroprotective potential of NGF in this in vitro cytostatic neuropathy model, we incubated intact DRG with cytostatic agents in combination with increasing amounts of NGF. Neurite outgrowth from DRG treated with vincristine (0.5 ng/ml) + NGF (3 ng/ml) for 2 days was significantly higher (+87%) than after treatment with vincristine + 1 ng NGF/ml (P < 0.001). Neutrite outgrowth from DRG treated with taxol (20 ng/ml) + NGF (3 ng/ml) for 2 days was significantly higher (+ 228%) than after taxol + 1 ng NGF/ml (P < 0.05). Neurotogenesis from DRG treated with cisplatin (2.5 μg/ml) + NGF (3 ng/ml) for 2 days was significantly increased (+105%) compared to treatment with cisplatin + 1 ng NGF/ml (P < 0.001). DRG thus appear to be a very suitable model for studying cytostatic drug-induced neuropathies in vitro and NGF has a clear neuroprotective effect on the vincristine-, taxol-, and cisplatin-induced neuropathies in this in vitro model.     

Cholinergic markers are expressed in developing and mature neurons of chick dorsal root ganglia

The presence of acetylcholinesterase has been reported in chick dorsal root ganglia at early developmental stages although acetylcholine is not known to play a role in these ganglia. Recently, we reported that during development the level of acetylcholinesterase increases continuously and the enzyme becomes gradually expressed in all sensory neurons. These observations prompted the study of the developmental pattern of expression of other cholinergic markers, such as choline acetyltransferase (ChAT) and the high affinity transport mechanism for choline. ChAT activity is barely detectable at early developmental stages (E7) and increases markedly thereafter, with an activity profile similar to that described for acetylcholinesterase. A similar increase in enzyme activity is also observed when ChAT is measured in dorsal root ganglia explants and in dissociated cells in culture. The study of ChAT activity in cultured cells shows an increase over a period of 3 days, thus ruling out the hypothesis that motor fibers, still associated to the ganglia, may represent a possible source of the enzyme. Immunostaining of whole ganglia or cultured cells shows that ChAT immunoreactivity is not restricted to a specific neuronal subpopulation but appears as a common marker of sensory neurons. High affinity choline uptake, blocked by hemicholinium, is present in sensory neurons cultured from E7 dorsal root ganglia. Observations on cultured neurons from later stages (E18) indicate that choline transport is not a transient property of sensory neurons. These observations show a similar pattern of expression of several cholinergic markers during development. Such a pattern is maintained at significant levels also in mature ganglia. © 1994 Wiley-Liss, Inc.     

Differential effects of HIV infected macrophages on dorsal root ganglia neurons and axons

Human immunodeficiency virus-associated distal-symmetric neuropathy (HIV-DSP) is the most common neurological complication of HIV infection. The pathophysiology of HIV-DSP is poorly understood and no treatment is available for this entity. The dorsal root ganglia (DRG) are the principal sites of neuronal damage and are associated with reactive mononuclear phagocytes as well as HIV-infected macrophages. To determine the role of HIV-infected macrophages in the pathogenesis of HIV-DSP, we developed a technique for culturing human DRG's. When the dissociated DRG neurons were exposed to supernatants from macrophages infected with CXCR4 or CCR5 tropic HIV-1 strains axonal retraction was observed without neuronal cell death but there was mitochondrial dysfunction in the neuronal cell body. Even though CXCR4 and CCR5 were expressed on the DRG neurons, the effects were independent of these receptors. Antioxidants rescued the neuronal cell body but not the axon from the toxic effects of the culture supernatants. Further, peripheral nerves of HIV-infected patients obtained at autopsy did not show evidence of increased oxidative stress. These observations suggest a differential effect on the axon and cell body. Different mechanisms of injury may be operative in these two structures.     

Alteration of neuronal cytoskeletal organization in dorsal root ganglia associated with pyridoxine neurotoxicity

Summary The pathogenesis of the sensory neurotoxicity arising from high doses of pyridoxine is obscure. Beagle dogs were fed 200 mg pyridoxine/kg per day and killed at 4, 10, 14 and 16 days. Dorsal root ganglia (DRG) and their processes were processed for electron microscopy and teased-fiber preparation following perfusion of anesthetized animals with heparinized saline and a fixative solution of 3% paraformaldehyde, 1% glutaraldehyde. Four days after initiation of treatment a striking accumulation of neurofilament (NF) in proximal unmyelinated axons of the DRG was observed. Domains of altered NF cytoskeleton consisting of well-demarcated zones of higher packing density and anomalous orientation were observed, mainly in the myelinated part of the DRG segment. In addition, aggregates of microtubules (MT) were noted. In the cyton the Golgi complexes were abundant and the Nissl bodies together with the NF appeared increased in numbers. At 10 days NF and MT aggregations were readily apparent in both perikarya and proximal cell processes. This phenomena was diminished in the 14-and 16-day-treated animals and retrogressive histological features appeared in the soma and in axons. Degeneration of NF with subsequent reduction in size of the axonal swellings and axonal breakdown with phagocytosis were prominent in central and peripheral processes of DRG. Cytons distended by NF were less prominent. Necrotizing changes, evidenced by disruption of the soma with the proliferation of satellite cells, were present. These results indicate that an early morphological correlate of pyridoxine neurotoxicity is the accumulation of NF with MT-NF dissociation in the unipolar process of the DRG in the absence of extensive vacuolization, and that the observed cytoskeletal disruption may be related to an increased rate of NF protein synthesis together with mechanical obstruction of transport phenomena.Supported by grant No. 7301600 of the Ottawa General Hospital Research Fund. Dr. Clapin is a Long-Term Fellow of the Ontario Mental Health Foundation; Dr. Dancea is a Research Fellow of the Ottawa General Hospital     

Transthyretin-type cerebral amyloid angiopathy in type I familial amyloid polyneuropathy

Summary To clarify the pathogenesis of cerebrovascular amyloid deposits, histological and immunocytochemical studies were performed on the central nervous system (CNS) in ten casès with type I familial amyloid polyneuropathy (FAP). They commonly suffered from peripheral somatic and autonomic nerve disorders without any CNS dysfunctions. However, all cases showed CNS amyloid deposits, mainly on the leptomeningeal vessels and pia-arachnoid membranes, with arteries and arterioles in the subarachnoidal space being the predominant site of cerebral amyloid accumulation. Using immunocytochemical staining methods with antibodies to amyloid -protein, human cystatin C and transthyretin (prealbumin), all of these amyloid deposits were specifically immunolabeled by the anti-human transthyretin antibody. However, there were no transthyretin-related amyloid deposits in the brain parenchyma. It is concluded that CNS transthyretin-immunoreactive amyloid deposition with cerebral amyloid angiopathy (CAA) is a common pathological finding in this disease. Moreover, the patients with type I FAP are known to have an amyloid protein precursor (a variant of transthyretin) in serum. This transthyretin type of CAA, therefore, seems to be an example of cerebrovascular amyloid deposits derived from a serum precursor.Supported by a grant-in-aid for Scientific Research from the Ministry of Education, Science and Culture and grants from the Intractable Disease Division, Ministry of Health and Welfare, Primary Amyloidois Research Committee, and Kanae Foundation of New Medicine, Japan     

Markers shared between dorsal root and enteric ganglia

Although the bowel is known to contain intrinsic primary afferent neurons with mucosal projections these cells have not been identified. The current study was undertaken to determine whether carbohydrate differentiation antigens or enzymatic markers common to primary sensory neurons could be found in enteric neurons. Subpopulations of sensory neurons of rat dorsal root ganglia (DRG) can be identified by the immunocytochemical detection of lactoseries and globoseries carbohydrate differentiation antigens with monoclonal antibodies (MAbs) and by the histochemical demonstration of carbonic anhydrase (CA)- or fluoride-resistant acid phosphatase (FRAP) activities; therefore, these markers, and their coincident expression with neuropeptides, were studied in neurons of the rat small intestine. Subsets of enteric neurons were demonstrated by a MAb (1B2/1B7) recognizing greater than 45%, and by a MAb (alpha-SSEA-1) recognizing less than 0.1%, of DRG neurons, as well as by CA, but not FRAP activity. 1B2/1B7+ neurons were found in both the submucosal (approximately 46% of neurons) and myenteric plexuses (approximately 2% of neurons). Submucosal 1B2/1B7+ neurons with mucosal projections also displayed vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY) but not substance P (SP) or calcitonin-gene-related peptide (CGRP) immunoreactivities. SSEA-1+ neurons were only found in the myenteric plexus, did not project to the mucosa (and thus are unlikely to be primary afferents), and were SOM+ or ENK+ but VIP- and NPY-. CA activity was intense in approximately 39% of the neurons of the submucosal plexus and in mucosal nerve fibers. Some (approximately 20%) of the submucosal CA neurons were also CGRP+, but VIP- and NPY-; therefore, MAb 1B2/1B7 and CA activity mark different nonoverlapping sets of submucosal neurons. Following the neonatal administration of capsaicin (50 mg/kg), 1B2/1B7 immunoreactivity was lost from all submucosal neurons; however, VIP immunoreactivity was not depleted from the cell bodies. Although it cannot yet be concluded that the MAb 1B2/1B7 or CA markers demonstrate the intrinsic sensory neurons of the gut, the presence in the bowel of both is consistent with the supposition that sensory neurons related to those of DRG are also found in the intestine. The functional and possible developmental significance of this relationship remains to be defined.     

Chronic pain induces nociceptive neurogenesis in dorsal root ganglia from Sox2-positive satellite cells

Chronic pain is one of the most prevalent chronic diseases in the world. The plastic changes of sensory neurons in dorsal root ganglia (DRG) have been extensively studied as the underlying periphery mechanism. Recent studies revealed that satellite cells, the major glial cells in DRG, also played important roles in the development/modulation of chronic pain. Whether DRG satellite glial cells generate new neurons as their counterparts in enteric nerve ganglia and carotid body do under pathological conditions remains poorly investigated. Here, we report that chronic pain induces proliferation and upregulation of progenitor markers in the sex-determining region Y-box 2 (Sox2)- and platelet-derived growth factor receptor alpha (PDGFRα)-positive satellite glial cells. BrdU incorporation assay revealed the generation of IB4- and CGRP-positive neurons, but not NF200-positive neurons in DRG ipsilateral to injury. Genetic fate tracings showed that PDGFRα-positive cells did not generate neurons, whereas Sox2-positive cells produced both IB4- and CGRP-positive neurons. Interestingly, glial fibrillary acidic protein-positive cells, a subpopulation of Sox2-positive satellites, only gave birth to IB4-positive neurons. Local persistent delivery of tetrodotoxin to the sciatic nerve trunk significantly reduced the pain-induced neurogenesis. Furthermore, patch-clamp studies demonstrated that these glia-derived new neurons could fire action potentials and respond to capsaicin. Taken together, our data demonstrated a chronic pain-induced nociceptive neurogenesis in DRG from Sox2-positive satellite cells, indicating a possible contribution of DRG neurogenesis to the pathology of chronic pain.     

Voltage-gated calcium currents in whole-cell patch-clamped bullfrog dorsal root ganglion cells: effects of cell size and intracellular solutions

Acutely dissociated bullfrog dorsal root ganglion (DRG) cells could be divided into two classes by measurement of cell capacitance. A bimodal distribution of cell capacitance was found and a value of 75 pF was used to divide frog DRG cells into ‘small’ and ‘large’ types. Two distinct voltage-activated Ca²⁺ currents were evoked in both classes of cells: a rapidly inactivating, low-voltage-activated current and a slowly-inactivating, high-voltage-activated current. When the recording pipette contained CsCl, greater peak inward current values and densities were seen in large cells compared to small cells. No significant differences were observed in the distribution of low-and high-voltage-activated currents in small and large cells. Replacement of pipette solutions containing CsCl with solutions containing equimolar concentrations of Cs glutamate,l-arginine Cl, orN-methyl-d-glucamine significantly increased both the reversal potential and the maximum amplitude of the Ca²⁺ currents in both small and large DRG cells. These increases indicate that internal substitutions with organic ions suppresses outward currents more effectively than does CsCl. In contrast to findings with CsCl, when organic ions were used in the pipette solution a significantly higher proportion of low-threshold Ca²⁺ channels was observed in small cells compared to large cells. These observations indicate that when organic solutions were used internally, significant differences in the proportion of low-threshold to high-threshold Ca²⁺ channels were observed in small and large cells. The composition of the internal solution is a critical variable when determining the type and amount of inward Ca²⁺ current in different types of neurons.     

Hereditary and acquired amyloid neuropathies

Amyloid neuropathies occur in a context of hereditary (FAP) or acquired amyloidosis. They present usually as severe and progressive polyneuropathy and carry a poor prognosis. Most FAP are associated with endoneurial deposits of variant transthyretin (TTR) with substitution of one aminoacid and are secondary to a point mutation of the TTR gene. Portugal is the main endemic area of TTR-FAP, secondary to point mutation of exon 2. However, around the world, 50 other TTR gene mutations have been recently reported, each one in few families. Genetic studies are useful for diagnosis of FAP in patients with a positive family history and for identification of the cause of seemingly sporadic cases. TTR gene analysis is also useful for genetic counselling including antenatal diagnosis in variants with early onset. Gelsolin-FAP are the second variety and present as a benign cranial and sensory polyneuropathy and affect essentially Finnish patients. Acquired amyloid neuropathy concerns only immunoglobulin light chain amyloidosis (AL) and are frequently associated with renal manifestations and monoclonal protein in serum or urine. Specific treatment of amyloid polyneuropathy varies with the variety of amyloidosis including liver transplantation in TTR-FAP, at the onset of the disease or chemotherapy for immunoglobulin light chain amyloidosis. Received: 8 March 2001 / Accepted: 12 March 2001