The effect of pancreatic islet transplantation and insulin therapy on experimental diabetic autonomic neuropathy.

Rats with chronic streptozotocin (SZ) diabetes develop dilatation of the alimentary tract, loss of fecal consistency, and autonomic neuropathy involving unmyelinated axons of the extrinsic innervation of the small bowel. Diabetic autonomic neuropathy involving the ileal mesenteric nerves is characterized by modest to marked dilatation of axons by distinctive subcellular organelles identical to those described in experimental and clinical axonal dystrophies. Axonopathy is confined to the alimentary tract; examination of myelinated and unmyelinated axons of the sciatic (midthigh level) and distal somatic nerves of the tail of diabetic animals with prominent ileal axonopathy failed to demonstrate significant numbers of dystrophic axons. The prevention or reversal of diabetic autonomic neuropathy by a variety of experimental manipulations clearly indicates that the lesions we have demonstrated in chronically SZ-induced diabetic animals were produced by diabetes and were not the result of a direct neurotoxic effect of the diabetogenic agent streptozotocin. Animals did not develop axonopathy after simultaneous administration of SZ and nicotinamide, a procedure which prevents pancreatic beta-cell necrosis and induction of diabetes while exposing the nervous system to a possible neurotoxic agent. Selected animals that were given SZ, became diabetic, and subsequently received daily insulin therapy or pancreatic islet transplantation also did not develop axonopathy. Transplantation of pancreatic islets 6 mo after induction of diabetes, a time at which mesenteric axonopathy was well developed, quickly reestablished normoglycemia, and within 3 mo resulted in nearly complete resolution of the neuropathy. Mild chronic diabetes maintained for 5-6 mo failed to produce significant levels of axonopathy.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of aldose reductase inhibitor sorbinil on neuroaxonal dystrophy and levels of myo-inositol and sorbitol in sympathetic autonomic ganglia of streptozocin-induced diabetic rats.

Biochemical and ultrastructural effects of the aldose reductase inhibitor sorbinil were examined in two experimental rat models of chronic diabetic neuropathy: rats with streptozocin-induced diabetes (STZ-D) and rats fed a galactose-enriched diet. The frequency of neuroaxonal dystrophy in the superior mesenteric sympathetic ganglia of rats with untreated 8-mo STZ-D increased sevenfold compared with that in age-matched controls. Animals chronically maintained on a diet containing 50% galactose, however, did not develop neuroaxonal dystrophy in excess of that found in untreated age-matched control rats. Institution of sorbinil therapy at the time of induction of STZ-D decreased, but did not completely normalize, the frequency of neuroaxonal dystrophy without altering the severity of diabetes; this finding is based on measurements of plasma glucose, body weight, food consumption, 24-h urine volume, and levels of glycosylated hemoglobin. Sorbitol levels in the superior cervical sympathetic ganglia (SCG) of untreated 8-mo-diabetic animals increased three- to fourfold compared with levels in controls. The increase in sorbitol content of diabetic SCG was completely prevented by early institution of dietary sorbinil therapy. The myo-inositol content of 8-mo-diabetic SCG was modestly decreased compared with controls. Sorbinil administration improved but did not completely normalize diabetic SCG myo-inositol. The sorbitol content of the SCG, superior mesenteric and celiac sympathetic ganglia, and a major trunk of the superior mesenteric nerve of short-term (2.5-mo)-diabetic rats increased comparably, but only the diabetic SCG showed a decrease in myo-inositol.

Retrograde axonal transport of 125I-nerve growth factor in rat ileal mesenteric nerves. Effect of streptozocin diabetes.

The retrograde axonal transport of intravenously (i.v.) administered 125I-nerve growth factor (125I-NGF) was examined in mesenteric nerves innervating the small bowel of rats with streptozocin (STZ) diabetes using methods described in detail in the companion article. The accumulation of 125I-NGF distal to a ligature on the ileal mesenteric nerves of diabetic animals was 30-40% less than in control animals. The inhibition of accumulation of 125I-NGF in diabetic animals was greater at a ligature tied 2 h after i.v. administration than at a ligature tied after 14 h, which suggests that the diabetic animals may have a lag in initiation of NGF transport in the terminal axon or retardation of transport at some site along the axon. The 125I-NGF transport defect was observed as early as 3 days after the induction of diabetes, a time before the development of structural axonal lesions, and did not worsen at later times when dystrophic axonopathy is present. Both the ileal mesenteric nerves, which eventually develop dystrophic axonopathy in experimental diabetes, and the jejunal mesenteric nerves, which never develop comparable structural alterations, showed similar 125I-NGF transport deficits, suggesting that the existence of the transport abnormality does not predict the eventual development of dystrophic axonal lesions. Autoradiographic localization of 125I-NGF in the ileal mesenteric nerves of animals that had been diabetic for 11-13 mo demonstrated decreased amounts of 125I-NGF in transit in unligated paravascular nerve fascicles. There was, however, no evidence for focal retardation of transported 125I-NGF at the sites of dystrophic axonal lesions.

Effects of sorbinil, dietary myo-inositol supplementation, and insulin on resolution of neuroaxonal dystrophy in mesenteric nerves of streptozocin-induced diabetic rats.

Previous studies indicate that experimental diabetic autonomic neuropathy can be largely prevented by initiating therapy at the onset of diabetes. More clinically relevant, however, is the ability of therapy to reverse established neuropathy produced by long-standing diabetes. We have examined the effect of selected therapies on established neuroaxonal dystrophy (NAD) in ileal mesenteric nerves, a rat model of diabetic autonomic neuropathy. Groups of 3-mo-old rats were made diabetic with streptozocin (STZ-D) and allowed to survive untreated for 5 mo, at which time they were begun on sorbinil, dietary myo-inositol, and daily insulin therapies or left untreated for an additional 2 or 4 mo. Ultrastructural evidence of NAD was demonstrated in ileal mesenteric nerves of rats with untreated 5-mo STZ-D and increased with the duration of diabetes. No lesions were demonstrated in control rats of any age. myo-Inositol or sorbinil administration failed to alter the severity of diabetes as measured by its metabolic indices. Institution of sorbinil or insulin treatment at 5 mo of diabetes prevented the increase in, but did not normalize, NAD at 7 or 9 mo. Dietary myo-inositol failed to significantly reverse established NAD or prevent its initial development. Morphometric examination of ileal mesenteric nerves demonstrated a decrease in the number of axons comprising each diabetic Schwann cell unit, suggestive of chronic cycles of axonal degeneration and regeneration. This parameter, clearly abnormal by 5 mo of diabetes, was not normalized by 2 or 4 mo of insulin, sorbinil, or myo-inositol treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural appearance of intentionally frustrated axonal regeneration in rat sciatic nerve.

The ultrastructural appearance of axons regenerating after crush injury was examined in rat sciatic nerves in which proximodistal growth was interrupted (frustrated regeneration) by placement of a tight ligature 1 cm distal to the original crush injury, and in nerves lacking a distal tie (unimpeded regeneration). Examination of unimpeded regenerating axons four and seven days after injury showed minute axonal sprouts as well as scattered dilated (2-10 microns) axonal profiles containing large numbers of anastomosing tubulovesicular elements and vacuoles. These dilated profiles were consistent with the appearance of growth cones, the motile tips of regenerating axons, as described in various in vivo and in vitro systems. The ultrastructural appearance of regenerating axons accumulating proximal to a frustrating tie was a function of time after arrival at the ligature. At the earliest time examined (one week) large numbers of axonal profiles accumulated at the ligature which were qualitatively similar to growth cones seen in unimpeded regeneration, although slightly larger in diameter. With time, the uniform population of growth cones proximal to the frustrating ligature was replaced by dilated axons containing large numbers of neurofilaments, dense collections of heterogeneous membranous organelles, or delicate to coarse tubulovesicular elements admixed with a variety of subcellular organelles. Rare examples of axonal dystrophy were demonstrated after chronic frustration of regeneration; however, they represented only a small percentage (less than 1%) of frustrated axons. Frustrated regeneration was accompanied by scattered examples of demyelination/remyelination of large axons proximal to the ligature as well as transperineurial growth of axons as microfascicles to escape the site of ligation.

Ultrastructural and biochemical characterization of autonomic neuropathy in rats with chronic streptozotocin diabetes.

Alterations in the extrinsic innervation of the alimentary tract and in various sympathetic autonomic ganglia were examined using quantitative ultrastructural and biochemical methods in streptozotocin diabetic rats maintained without treatment for 9-15 months. Ileal mesenteric nerves of 13-15 month diabetics showed the characteristic alterations of neuroaxonal dystrophy qualitatively similar to changes seen in this system in animals which were diabetic for shorter durations. Dystrophic axonopathy was not accompanied by significant axonal loss or atrophy. Dystrophic axons, presumably involving presynaptic elements, also were increased in frequency in the superior mesenteric ganglia, but not in the superior cervical ganglia, of animals diabetic for various durations. In addition, the superior mesenteric ganglia of diabetic animals contained an increased number of postsynaptic dendritic processes which were dilated by unusual tubular profiles. These ganglionic alterations were not accompanied by changes in the activity of the presynaptic cholinergic marker enzyme, choline acetyltransferase. The activity of the noradrenergic marker enzyme, dopamine-beta-hydroxylase, was unaltered in diabetic superior mesenteric ganglia compared to controls, but showed a 30-40% decrease in diabetic superior cervical ganglia, in which site it was unaccompanied by neuronal loss, atrophy, or ultrastructural alterations.

Neuroaxonal dystrophy in the autonomic ganglia of aged rats.

Distinctive axonal abnormalities in selected sympathetic ganglia of male and female Sprague-Dawley and male Fischer 344 rats have been characterized as a function of increasing age. Dilated intraganglionic axons contained a variety of unusual subcellular organelles, including large numbers of compact or loosely aggregated tubulovesicular profiles, layered membranous loops, and collections of normal and degenerating organelles, identical to those described in clinical and experimental neuroaxonal dystrophy. Although occasional dystrophic axons were encountered free within the ganglionic neuropil, the majority were intimately associated with the surface of major dendrites or perikarya of principal sympathetic neurons and presumably represent terminal preganglionic axons. However, neither synaptic vesicles in dystrophic axons nor the association of dystrophic axons with post-synaptic densities were demonstrated. Dystrophic axons were infrequent within the prevertebral superior mesenteric and celiac ganglia before one year of age, but increased substantially in numbers thereafter. Similar findings expressed as lesions per mm2 were approximately tenfold less frequent in the paravertebral superior cervical ganglia of the same animals.

Dystrophic axonal swellings develop as a function of age and diabetes in human dorsal root ganglia.

Neuroaxonal dystrophy, characterized by swollen axon terminals and, to a lesser degree, enlarged initial segments of axons or perikaryal projections, develops in human dorsal root sensory ganglia as a function of aging and diabetes. Lesions are typically located within the satellite cell capsule and are intimately applied to sensory neuronal perikarya, which are compressed and distorted but are otherwise normal. Swollen axons contain large numbers of neurofilaments that are immunoreactive with antisera to highly phosphorylated neurofilament epitopes but fail to stain with antisera directed against hypophosphorylated neurofilament epitopes. Other dystrophic swellings contain collections of tubulovesicular profiles admixed with neurotransmitter granules. Neuroaxonal dystrophy involves subpopulations of intraganglionic axons and apparent terminals, notably those containing CGRP, while apparently sparing others, including noradrenergic sympathetic axons. Diabetic subjects develop lesions prematurely and in greater numbers than in aged subjects. Individual dystrophic axons in diabetics and aged human subjects are identical in their light microscopic, immunohistochemical and ultrastructural appearance, suggesting the possibility of shared pathogenetic mechanisms.

Effect of sorbitol dehydrogenase inhibition on experimental diabetic autonomic neuropathy.

The polyol pathway and its dependent biochemical pathways are thought to play a role in the pathogenesis of diabetic neuropathy. We have developed an animal model of diabetic autonomic neuropathy characterized by neuroaxonal dystrophy involving ileal mesenteric nerves and prevertebral sympathetic superior mesenteric ganglia (SMG) in chronic streptozocin-diabetic rats. Our previous studies have shown a salutary effect of aldose reductase inhibitors on experimental autonomic neuropathy, suggesting a role for the polyol pathway in its pathogenesis. In the current studies we have examined the effect of the sorbitol dehydrogenase inhibitor (SDI) CP-166,572, which interrupts the conversion of sorbitol to fructose (and reactions dependent on the second step of the polyol pathway) resulting in markedly increased levels of sorbitol in peripheral nerve. Fourteen weeks of treatment with CP-166,572 resulted in a dramatically increased frequency of neuroaxonal dystrophy in ileal mesenteric nerves and SMG. Although lesions developed prematurely and in greater numbers in SDI-treated diabetics than untreated diabetics did, their anatomic distribution and ultrastructural appearance were identical to that previously reported in long-term untreated diabetics. CP-166,572 treatment did not produce neuroaxonal dystrophy in control animals despite the fact that sciatic nerve sorbitol levels were markedly increased, reaching the same levels as untreated diabetic animals. Treatment of diabetic rats for 14 weeks with the aldose reductase inhibitor zopolrestat resulted in a significant decrease in the frequency of neuroaxonal dystrophy compared with untreated diabetics.

Inhibition of sorbitol dehydrogenase exacerbates autonomic neuropathy in rats with streptozotocin-induced diabetes.

We have developed an animal model of diabetic autonomic neuropathy that is characterized by neuroaxonal dystrophy (NAD) involving ileal mesenteric nerves and prevertebral sympathetic superior mesenteric ganglia (SMG) in chronic streptozotocin (STZ)-diabetic rats. Studies with the sorbitol dehydrogenase inhibitor SDI-158, which interrupts the conversion of sorbitol to fructose (and reactions dependent on the second step of the sorbitol pathway), have shown a dramatically increased frequency of NAD in ileal mesenteric nerves and SMG of SDI-treated versus untreated diabetics. Although lesions developed prematurely and in greater numbers in SDI-treated diabetics, their distinctive ultrastructural appearance was identical to that previously reported in long-term untreated diabetics. An SDI effect was first demonstrated in the SMG of rats that were diabetic for as little as 5 wk and was maintained for at least 7.5 months. As in untreated diabetic rats, rats treated with SDI i) showed involvement of lengthy ileal, but not shorter, jejunal mesenteric nerves; ii) demonstrated NAD in paravascular mesenteric nerves distributed to myenteric ganglia while sparing adjacent perivascular axons ramifying within the vascular adventitia; and, iii) failed to develop NAD in the superior cervical ganglia (SCG). After only 2 months of SDI-treatment, tyrosine hydroxylase immunolocalization demonstrated marked dilatation of postganglionic noradrenergic axons in paravascular ileal mesenteric nerves and within the gut wall versus those innervating extramural mesenteric vasculature. The effect of SDI on diabetic NAD in SMG was completely prevented by concomitant administration of the aldose reductase inhibitor Sorbinil. Treatment of diabetic rats with Sorbinil also prevented NAD in diabetic rats not treated with SDI. These findings indicate that sorbitol pathway-linked metabolic imbalances play a critical role in the development of NAD in this model of diabetic sympathetic autonomic neuropathy.

The effect of pancreatic islet transplantation and insulin therapy on neuroaxonal dystrophy in sympathetic autonomic ganglia of chronic streptozocin-diabetic rats.

The frequency of neuroaxonal dystrophy was determined in the superior mesenteric/celiac sympathetic ganglia in a streptozocin-treated rat model of diabetic autonomic neuropathy. Dystrophic axonopathy was increased 5- to 6-fold in 9-month untreated diabetics compared to age-matched controls. Pancreatic islet transplantation therapy or daily insulin administration prevented the development of dystrophic axonopathy. Transplantation of islets after 6 months of diabetes, a time at which dystrophic axonopathy is well developed, resulted in nearly complete resolution of the neuropathy within 3 months.

Axonal cytoskeletal pathology in aged and diabetic human sympathetic autonomic ganglia.

Prevertebral sympathetic ganglia develop markedly enlarged argyrophilic neurites as a function of age, gender and diabetes. Immunolocalization studies demonstrate their preferential labeling with antisera to highly phosphorylated 200 kDa neurofilament (NF-H) epitopes, NPY, peripherin and synapsin I, but not to hypophosphorylated NF-M and NF-H or MAP-2. The immunophenotype of dystrophic neurites in conjunction with the results of histochemical and ultrastructural studies are consistent with the terminal axonal and/or synaptic origin of neuritic dystrophy in the sympathetic ganglia of aged and diabetic human subjects.

Vacuolar neuritic dystrophy in aged mouse superior cervical sympathetic ganglia is strain-specific.

We have developed a model of autonomic nervous system aging using the mouse superior cervical sympathetic ganglion (SCG) which is characterized by the reproducible development of distinctive, markedly-enlarged neuritic swellings (vacuolar neuritic dystrophy, VND). These structures contained an admixture of lucent vacuoles and subcellular organelles, and involved both presynaptic and postsynaptic ganglionic elements. Quantitation of the frequency of VND was accomplished at the light microscopic level and validated by ultrastructural examination. VND lesions were 30-100-fold more frequent in the aged mouse paravertebral SCG than in the prevertebral celiac/superior mesenteric (C/SMG) sympathetic ganglia. Although VND was identified in all ages of mice examined, the number of lesions increased significantly with age. The frequency of VND was a function of the strain of mouse examined with a 40-fold difference in VND frequency between C57BL6 mice, the least involved strain, and the DBA/2J strain, which was most affected and began to develop significant numbers of lesions at an early age. As in our human studies of aging in the sympathetic nervous system, there was a prominent gender effect with males developing twofold greater numbers of VND lesions than females. Mice maintained on a significant calorie restricted diet for 30 months developed 70% fewer lesions than ad libitum-fed, age and sex matched controls. The aging mouse SCG, therefore, represents a robust animal model with reproducible, quantifiable and unambiguous neuropathology. Insights into pathogenetic mechanisms gained in the subsequent analysis of this relatively simple peripheral sympathetic nervous system model may contribute to the understanding of some of the most complex and significant problems involving higher brain function.

Effect of IGF-I and neurotrophin-3 on gracile neuroaxonal dystrophy in diabetic and aging rats.

Neuroaxonal dystrophy (NAD), a distinctive axonopathy characterized by dramatic swelling of preterminal axons and nerve terminals by the accumulation of a variety of subcellular organelles, develops in the central projections of sensory neurons to medullary gracile nuclei in aged animals and man, and in a number of diseases and experimental conditions. Although its pathogenesis is unknown, proposed mechanisms include abnormalities of axonal regeneration, collateral sprouting and synaptic plasticity which may reflect alteration in neurotrophic support. In the current study, we have demonstrated quantitatively that aging causes the expected marked increase in the frequency of gracile NAD; however, substantial numbers of dystrophic axons develop between 6 and 10 months of age, earlier than expected. Although diabetes has been reported to increase the frequency of NAD in the central processes of sensory neurons in the gracile fasciculus of genetically diabetic BB rats, we have found that 8-10 months of streptozotocin-induced diabetes results in fewer dystrophic axons in the gracile nucleus than in age-matched controls. Administration of neurotrophin-3 (NT-3) and insulin-like growth factor-I (IGF-I), which have been shown to affect synaptic plasticity (implicated in the pathogenesis of NAD), for the last two months before sacrifice did not affect the frequency of gracile NAD in controls or diabetics. The sensory terminals in the gracile nuclei provide a simple, well-characterized experimental system in which questions of pathogenesis and prevention of neuroaxonal dystrophy can be addressed.

Fine structure of ascosporogenesis in Nematospora coryli Peglion, a pathogenic yeast.

Observations with the electron microscope of the early stages of ascospore formation in Nematospora coryli Peglion reveal the following sequence of events. Partial dissociation of the nuclear membrane is followed by the appearance of unit membranes. Each unit membrane gives rise to two pairs of double membranes delimiting the ascospores from the epiplasm of the ascus. Enlarged mitochondria which have a granular matrix and limited cristae development are also regularly seen.

Acrylamide-induced sympathetic autonomic neuropathy resulting in pineal denervation.

The effect of acrylamide on the sympathetic innervation of the rat pineal gland was examined by using ultrastructural, immunohistological, biochemical, and physiological methods. Separation of sympathetic terminals from perivascular pineocyte processes was facilitated by administration of the false neurotransmitter 5-hydroxydopamine, which preferentially labeled sympathetic terminals, shortly before sacrifice. Administration of acrylamide (50 mg/kg/day, intraperitoneally) for 1 to 2 weeks resulted in the near-total loss of pineal parenchymal perivascular axons and axons intercalated between individual pineocytes. More proximal portions of these sympathetic axons located within the capsule of the pineal gland developed markedly enlarged swellings containing neurofilaments and tubulovesicular elements. The ultrastructural appearance of axons swollen by tubulovesicular elements resembled that of regenerating axons and axons whose regenerative progress had been frustrated. The activity of pineal dopamine-beta-hydroxylase, a noradrenergic marker enzyme confined to sympathetic axons and their terminals and absent in pineocytes, was determined in an attempt to develop a quantitative measure of the extent of sympathetic denervation. The loss of 50% of pineal dopamine-beta-hydroxylase activity underestimated the extent of parenchymal denervation due to the marked engorgement of remaining capsular sympathetic axons by immunoreactive dopamine-beta-hydroxylase. The daily rhythm of pineal serotonin N-acetyltransferase (NATase) activity, which is dependent on the circadian variation in the activity of pineal sympathetic axons, was decreased 90% by chronic acrylamide administration. Pineal NATase activity increased 25- to 50-fold in acrylamide intoxicated rats in which isoproterenol was used to stimulate pineocyte beta-adrenergic receptors directly, which is evidence against a nonspecific toxic effect of acrylamide on pineocytes. Administration of N,N'methylene-bis-acrylamide, a non-neurotoxic analog of acrylamide, was without effect on pineal ultrastructure or NATase activity.

Fine structure of presynaptic axonal terminals in sympathetic autonomic ganglia of aging and diabetic human subjects.

The neuropathologic changes that may underlie autonomic nervous system dysfunction in nondiabetic elderly human subjects or as a complication of diabetes have been systematically examined in sympathetic ganglia of a series of autopsied human subjects. As in animal models of aging and diabetes, enormously swollen terminal axons were found closely apposed to the perikarya of principal sympathetic neurons in prevertebral superior mesenteric sympathetic ganglia of aged and diabetic human subjects. Dystrophic axons consisted of two stereotyped forms: the first was composed of large numbers of misaligned aggregates of neurofilaments surrounded by variable numbers of small dense core vesicles; the second was characterized by large numbers of mitochondria, vacuoles, and dense and multivesicular bodies. The fine structural characteristics of neuroaxonal dystrophy, its predilection for prevertebral rather than paravertebral sympathetic ganglia, and the tendency for multiple dystrophic axons to cluster preferentially around selected neurons were identical in aged and diabetic human ganglia and were similar to changes seen in animal models of aging and diabetes. Neither diabetic nor aging ganglia demonstrated evidence of neuronal degeneration. Such structural changes may represent a degenerative influence of diabetes and aging on the normal remodeling of nerve terminals in autonomic ganglia, i.e., the continually ongoing process of turnover and replacement of axonal terminals. Similarity of lesions in human diabetes and aging suggests the possibility of pathogenetic mechanisms that are common to diabetes and the aging process. The substantial parallels between humans and animal models provide support for the validity of testing some proposed pathogenetic mechanisms directly in animal models.

Experimental diabetic autonomic neuropathy characterization in streptozotocin-diabetic Sprague-Dawley rats.

Rats with chronic streptozotocin-induced diabetes develop enlargement of the alimentary tract, loss of fecal consistency, and autonomic neuropathy involving the extrinsic innervation of the ileum. In this study we have continued the characterization of the unmyelinated axonopathy involving the ileal mesenteric nerves of outbred Sprague-Dawley rats diabetic for 1.5 to 10 months using ultrastructural methods. Axonopathy in the alimentary tract of chronically diabetic rats is characterized by modest to marked dilation of axons by distinctive subcellular organelles identical with those described in experimental and clinical axonal dystrophies. Lesions are infrequent 1.5 and 3 months after induction of diabetes, increasing rapidly in numbers thereafter. Axonal lesions are reproducibly encountered in the ileum, cecum, and rectum but not in the proximal jejunum of chronically diabetic rats. Sectioning of mesenteric nerves along their longitudinal axes demonstrates the focal and in some instances apparent terminal nature of the axonal dilation. Disappearance of dystrophic axons distal (peripheral) to mesenteric crush injury confirms the origin of the axons extrinsic to the gut wall. Only rare examples of dystrophic diabetic axonopathy were detected within the wall of the ileum, presumably representing involvement of terminal axonal segments within the intrinsic ganglia. Examination of the mesenteric nerves of 18- and 30-month-old control rats failed to demonstrate dystrophic axonopathy, providing evidence that diabetic axonopathy does not represent premature development of an aging change in mesenteric nerves. Examination of the autonomic innervation of various other tissues including spleen, bladder, vas deferens, and iris, as well as the phrenic, sciatic, vagus, and tail nerves of 4- to 12-month diabetic animals, failed to demonstrate reproducible axonopathy comparable to that involving the alimentary tract of the same animals. The paravascular fascicles of ileal mesenteric nerves of 6- to 7-month diabetic and age-matched control rats were examined by morphometric methods and failed to demonstrate significant loss of axons or an appreciable shift in mean fiber diameter.

Sympathetic neuronal destruction in macaque monkeys by guanethidine and guanacline.

To determine whether the peripheral sympathetic neurons of subhuman primates are destroyed by guanacline treatment, we treated Macaca fasicularis with 2 or 20 mg/kg of guanethidine, guanacline, or the saturated analog of guanacline (SAG) 5 times per week for 4 or 12 weeks. All monkeys given 20 mg/kg of guanethidine, guanacline, or SAG showed a marked loss of neurons in the ganglia of the peripheral sympathetic nervous system. Treatment of macaques with 2 mg/kg of the guanidinium compounds resulted in patches of small-cell infiltrate, slight neuronal loss, and degenerative alterations in the sympathetic ganglia. Neuronal alterations in sympathetic ganglia of all treated monkeys were accompanied by a prominent heterogeneous infiltrate of mononuclear cells arranged primarily in a perivascular distribution and extending into the ganglionic neuropil. Peripheral sensory ganglia were unaffected. These histological findings are similar to those described in the guanethidine-induced immune-mediated sympathectomy, which has been extensively studied in the rat.

Effect of diabetes and aging on human sympathetic autonomic ganglia.

Although autonomic dysfunction frequently complicates the clinical course of patients with diabetes, relatively little is known of its underlying neuropathology. Using experimental animal models as a guide, the prevertebral superior mesenteric (SMG) and paravertebral superior cervical (SCG) sympathetic ganglia have been examined in a series of adult autopsied diabetic and non-diabetic patients of various ages using histochemical, ultrastructural, morphometric, and immunohistochemical methods. Quantitative studies demonstrated that markedly swollen argyrophilic terminal axons (neuroaxonal dystrophy) containing large numbers of disorganized neurofilaments developed in the SMG but not SCG as a function of diabetes, increasing age, and gender (males were more severely affected than females). As in experimental animals, diabetic (types I and II) patients developed histologically identical lesions prematurely and in greater numbers than age-matched nondiabetic patients. Morphometric studies showed a small but statistically significant decrease in neuronal density in the SMG but not SCG of diabetic patients. The dimensions of individual sympathetic neurons were not significantly different in aging or diabetes. The pathological lesions identified in the SMG may contribute to the autonomic dysfunction so commonly observed in diabetic patients.