Oxygen affinity of hemoglobin and peripheral nerve degeneration in experimental diabetes

Peripheral neuropathy remains a major complication of diabetes. Numerous etiological theories of metabolic and/or vascular disturbances have been suggested including decreased endoneurial oxygen tension with presumed tissue hypoxia. Increases in the affinity of hemoglobin for oxygen (Hb-O2 affinity) may also produce tissue hypoxia and such Hb-O2 affinity changes have been implicated in the pathogenesis of diabetic microangiopathy. In order to test whether affinity hypoxia might contribute to the development of diabetic peripheral neuropathy, we have utilized a rat model of high and normal Hb-O2 affinity produced by backcrossing animals with increased and decreased levels of 2,3-diphosphoglycerate (DPG). Diabetes was induced in ten high and ten low DPG animals with a tail vein injection of 55 mg/kg streptozotocin (STZ). Five animals in each group were treated with 2.4 U protamine zinc insulin (PZI)/day while the remaining animals were untreated. All rats were killed after 30 days, sections of tibial and sural nerve were rapidly removed and processed for teased fiber analysis. A minimum of 125 axons were assessed per nerve for E degeneration (myelin ovoids) using the classification developed by Dyck et al. Untreated animals, regardless of DPG levels, demonstrated 0% neuropathy. In contrast, all insulin-treated animals showed degeneration (0.4-17%) that inversely correlated with the DPG level (r = -0.59, P less than 0.04). The results of this study suggest that the level of RBC DPG (and presumably the Hb-O2 affinity) with its attendant effect on tissue oxygen release may play a role in the development of peripheral neuropathy in STZ-induced diabetic rats treated with insulin.

Evidence that down-regulation of beta-cell glucose transporters in non-insulin-dependent diabetes may be the cause of diabetic hyperglycemia

Non-insulin-dependent diabetes mellitus (NIDDM) is attributed to a failure of pancreatic beta cells to maintain insulin secretion at a level sufficient to compensate for underlying insulin resistance. In the ZDF rat, a model of NIDDM that closely resembles the human syndrome, we have previously reported profound underexpression of GLUT-2, the high-Km facilitative glucose transporter expressed by beta cells of normal animals. Here we report that islets of diabetic rats exhibit a marked decrease in the volume of GLUT-2-positive beta cells and a reduction at the electron-microscopic level in the number of GLUT-2-immunoreactive sites per unit of beta-cell plasma membrane. The deficiency of GLUT-2 cannot be induced in normal beta cells by in vivo or in vitro exposure to high levels of glucose nor can it be prevented in beta cells of prediabetic ZDF rats by elimination of hyperglycemia. We conclude that this dearth of immunodetectable GLUT-2 in NIDDM is not secondary to hyperglycemia and therefore that it may well play a causal role in the development of hyperglycemia.

Characteristics of children presenting with chest pain to a pediatric emergency department

Chest pain among children is a common complaint in primary care practice. However, the demographic features and treatment of such patients are controversial. We distributed a questionnaire to 336 consecutive patients with a complaint of chest pain seen during 1 year at an urban pediatric emergency department. Such visits represented 0.6% of all emergency encounters; the male:female ratio was 1.0. Physical examination was done in 325 patients. Chest-wall pain was the most common diagnosis (in 28% of cases). Other causes included pulmonary (in 19%), minor traumatic (in 15%), idiopathic (in 12%) and psychogenic (in 5%); miscellaneous causes (in 21%) most often indicated pain referred from the upper respiratory tract and the abdomen. The most common physical finding was chest tenderness (in 41% of cases). Investigations included chest radiography (in 50% of cases), electrocardiography (in 18%) and determination of the hemoglobin concentration and of the leukocyte count (in 13%); the results were rarely positive. Only eight patients (2%) required admission to hospital, and there were no cases of myocardial ischemia. The findings suggest that health care costs may be reduced by more judicious use of investigations. We conclude that chest pain is an uncommon and usually benign complaint in the pediatric emergency department. Most causes are evident on careful physical examination.

Relationship of ATP turnover, polyphosphoinositide metabolism, and protein phosphorylation in sciatic nerve and derived peripheral myelin subfractions from normal and streptozotocin diabetic rats

Sciatic nerve from streptozotocin-induced diabetic rats has previously been shown to incorporate more 32P into phosphatidylinositol-4,5-bisphosphate (PIP2) and the principal myelin proteins than normal nerve. In the present study, labeling of ATP and PIP2 was compared. Using nerve segments, [gamma-32P]ATP specific activity reached a plateau after incubation for 4 h with [32P]orthophosphate, whereas the specific activity of [32P]PIP2 rose much more slowly and was still increasing after 8 h. The rate of disappearance of radioactivity from prelabeled ATP was biphasic, with 75% being lost within 30 min and the remainder declining much more slowly for several hours thereafter. In contrast, no decrease in prelabeled PIP2 radioactivity could be detected for up to 4 h. The kinetics of ATP metabolism were not appreciably different for normal and diabetic nerve. However, after incubation with [32P]orthophosphate for 2 h, the specific activity of PIP2 was 50-120% higher in diabetic nerve. This phenomenon, therefore, cannot be ascribed to altered specific activity of the ATP precursor pool. Greater labeling of PIP2 in 32P-labeled diabetic nerve was present in purified myelin isolated using a simple discontinuous sucrose density gradient, but not in a "nonmyelin" fraction. When nerve homogenate was fractionated on a more complex gradient, three myelin-enriched subfractions were obtained which were heterogeneous as judged by morphological appearance, protein profile, and lipid metabolic activity. The proportion of total lipid radioactivity accounted for by PIP2 was elevated in all the subfractions relative to the homogenate. As compared to myelin subfractions from normal nerve, an increased percentage of 32P in PIP2 was obtained only in the major myelin subfraction from diabetic nerve. The phosphorylation of P0 relative to the other myelin proteins was also enhanced in this subfraction in nerve from diabetic animals.

Alteration of phosphoinositide metabolism, protein phosphorylation, and carbohydrate levels in sciatic nerve from Wistar fatty diabetic rats

Sciatic nerve from the Wistar fatty diabetic (FD) rat, a prospective model for non-insulin-dependent diabetes mellitus, was investigated to determine the content of carbohydrates and to measure the incorporation of 32P into phosphoinositides and proteins. This strain has been shown to develop structural abnormalities in nerves and to exhibit reduced conduction velocity. Males became diabetic between the ages of 8 and 10 wk and were maintained together with lean sibling controls until the animals were either 22 or 44 wk old. Throughout this period, FD rats displayed moderate hyperglycemia. The carbohydrate profile of FD rat sciatic nerve exhibited modest increases in glucose, fructose, and sorbitol levels and significantly reduced myo-inositol concentrations, which were comparable at both ages. When nerves from 22-wk-old animals were incubated with [32P]orthophosphate and incorporation of radioactivity into phospholipids was measured, an increase in isotope uptake into phosphatidylinositol-4,5-bisphosphate and phosphatidylinositol-4-phosphate in the distal portions of tissue from the FD rat was observed. This effect was more pronounced in nerves from 44-wk-old rats. Phosphorylation of the major myelin protein P0 was 70% higher in the most distal portion of FD sciatic nerve from 22-wk-old animals. A comparable rise in phosphorylation of P0 as well as the large (P1) and small (Pr) myelin basic proteins occurred in nerves from 44-wk-old rats. In these animals, an approximately 50% decrease in the uptake of 32P into P0 and P1 in the most proximal region of FD nerve was also apparent.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypoglycemic neuropathy in experimental diabetes

Morphological and electrophysiological observations were made over 4 weeks on 5 groups of 8-week-old male Sprague-Dawley rats. These were comprised of controls, untreated diabetics, and diabetic animals in which sustained hypoglycemia, moderate hypoglycemia, or normoglycemia was induced by continuous subcutaneous insulin infusion (CSII) therapy. Teased fiber studies showed a marked increase in the number of myelinated fibers undergoing axonal degeneration and regeneration in the tibial nerve of severe hypoglycemic and also in moderate hypoglycemic animals but not in controls, untreated diabetic and normoglycemic groups. There was also a significant correlation between episodes of hypoglycemia (less than or equal to 2.0 mmol/l) and the prevalence of axonal degeneration and regeneration in CSII-treated diabetics. Motor nerve conduction velocity was significantly reduced in the moderate and severe hypoglycemic groups and also in untreated diabetic animals when compared with controls. However, it was significantly improved in the normoglycemic group over the untreated diabetic and severe hypoglycemic groups. In conclusion, this study has demonstrated that severe or even mild hypoglycemia produced a detrimental effect on peripheral nerve structure and function in experimental diabetes. Therefore, it may be desirable to avoid even asymptomatic hypoglycemia in the management of diabetes.

Plasma levels of dantrolene following oral administration in malignant hyperthermia-susceptible patients

Reports of the lack of protection following oral dantrolene prophylaxis have led some authors to recommend only intravenous administration of dantrolene for prophylaxis against malignant hyperthermia at induction of anesthesia. The authors determined whether a specific regimen of preoperative oral dantrolene would result in protective blood levels at induction of anesthesia, and in the postoperative period. Ten malignant hyperthermia-susceptible (MHS) patients were given a total dose of 5 mg.kg-1 of oral dantrolene in three or four divided doses, every 6 h, with the last dose 4 h preoperatively. Plasma dantrolene levels were determined by reverse phase high pressure liquid chromatography at induction of anesthesia and every 6 h thereafter for 48 h. All ten patients had plasma dantrolene levels over 2.8 micrograms.ml-1 at induction of anesthesia, for at least 6 h and, in three patients, up to 18 h after induction. Every patient had an uneventful perioperative course. Side effects (drowsiness, weakness) occurred in seven patients. An elimination half-life of 15.8 +/- 6.0 h was determined. In contrast to intravenous dantrolene, this specific oral dantrolene regimen resulted in protective plasma levels for 6-18 h after induction of anesthesia. These results were likely due to the relatively high bioavailability of oral dantrolene and, possibly, to continued absorption of dantrolene in the postoperative period.

Insect repellent, N,N-diethyl-m-toluamide, effect on ammonia metabolism

There appear to be at least three mechanisms for systemic reactions to diethyltoluamide. As with most substances, allergy is possible. The ingestion of large doses can produce seizures and coma by a direct action on the CNS. This occurs in experimental animals in which seizures and coma followed by death can be produced rapidly if sufficiently large doses are given. Finally, with smaller systemic doses as may occur with absorption during heavy topical use, there is also the possibility of a perturbation of ammonia metabolism. Diethyltoluamide may then pose a substantial hazard to individuals with defects in ammonia metabolism.

Ultrastructural observations on myelinated fibres in experimental diabetes: effect of the aldose reductase inhibitor ponalrestat given alone or in conjunction with insulin therapy

Six groups of rats were studied over a 12-week period: onset and end controls, untreated diabetics, ponalrestat-treated diabetics, insulin-treated diabetics, and diabetics treated with ponalrestat and insulin. The concentrations of glucose, sorbitol and fructose significantly increased and that of myo-inositol significantly decreased in the sciatic nerve of untreated diabetic animals. Ponalrestat administration completely normalized sorbitol levels and partially corrected fructose and myo-inositol concentrations without altering nerve glucose levels. The biochemical abnormalities were also corrected in both the insulin-treated and insulin and ponalrestat-treated diabetic animals. Myelinated fibre cross-sectional areas and axonal areas were significantly less in the tibial nerve of diabetic animals as compared with age-matched controls. Insulin treatment partially corrected the reduction in fibre and axonal area but teased fibre preparations showed an excess of axonal degeneration as compared with controls, untreated diabetics and ponalrestat-treated diabetics. Ponalrestat given alone or in conjunction with insulin therapy did not correct the reduction in fibre or axonal area and single isolated fibres from diabetic animals treated with ponalrestat and insulin showed a marked excess of axonal degeneration, probably related to hypoglycaemia. The study fails to reveal any significant beneficial effect of aldose reductase inhibition on the structural abnormalities in peripheral nerve in experimental diabetes.

Revised pharmacokinetic constants for use under Système International

Two additional kinetic constants are defined and their values given for a number of drugs. These constants can be used when dealing with plasma drug levels reported in Système International Units in order to maintain traditional kinetic calculations in estimating loading doses, infusion rates, and plasma levels from drug ingestions. The constants are termed VDSI and ClSI and are used in place of the traditional apparent volume of distribution and total plasma clearance. Constants for a number of drugs are given.

Enhancement of central transmission to sympathetic preganglionic neurons by phosphodiesterase inhibitors and its prevention by clonidine

The effects of 3 phosphodiesterase inhibitors, aminophylline, isobutylmethylxanthine (IBMX), and RO 20-1724, were tested on descending intraspinal and spinal reflex transmission to sympathetic preganglionic neurons in unanesthetized spinal cats. Sympathetic discharges, recorded from upper thoracic preganglionic white rami, were evoked by stimulation (0.1 Hz) of descending excitatory pathways in the cervical dorsolateral funiculus (intraspinal) or of adjacent intercostal nerves (spinal reflex). Each phosphodiesterase rapidly and markedly enhanced transmission through intraspinal pathways but only slowly and modestly enhanced transmission through spinal reflex pathways. Pretreatment with a methyltyrosine-reserpine combination, chlorpromazine, or prazosin markedly restricted the enhancement of intraspinal transmission by IBMX to levels typically produced on spinal reflex pathways. Clonidine markedly depressed transmission through both pathways and prevented enhancement by the phosphodiesterase inhibitors. Yohimbine or tolazoline antagonized the depressant effects of clonidine and restored the ability of the phosphodiesterase inhibitors to enhance transmission. Somatic spinal reflexes were not affected by the phosphodiesterase inhibitors. The results suggest that descending norepinephrine pathways to sympathetic preganglionic neurons activate adenylate cyclase to generate cyclic AMP which increases neuronal excitability, possibly by phosphorylating membrane proteins. Clonidine appears to depress neuronal excitability by inhibiting adenylate cyclase through activation of alpha 2-adrenergic receptors.

Insulin reverses enhanced incorporation of 32P into polyphosphoinositides in peripheral nerve of the streptozotocin diabetic rat

The ability of insulin treatment to reverse altered phosphoinositide metabolism in sciatic nerve from streptozotocin diabetic rats was studied. Diabetes was induced in rats by means of a single injection of streptozotocin. Enhanced incorporation of 32P into phosphatidylinositol-4,5-bisphosphate (PIP2) was detectable as early as 8 days following intravenous injection of streptozotocin and was maximal after 4 weeks. Hormone treatment was initiated at this time by daily injections of protamine zinc insulin followed by the implantation of long-acting insulin osmotic minipumps, and 4 weeks later sciatic nerves were removed and incubated in the presence of [32P]orthophosphate. The increased labeling of PIP2 was completely reversed by hormone administration. In contrast, insulin (0.1 and 1.0 mU/ml) added to the incubation medium failed to reverse the altered pattern of 32P incorporation into PIP2. The uptake of 32P into PIP2 was greater than 80% higher into the proximal than into the distal portion of normal sciatic nerve when these were incubated separately. This metabolic difference was abolished in diabetic rats, although the incorporation into both segments was still significantly higher than in controls. These results strengthen the association of altered nerve PIP2 metabolism with the diabetic state and are consistent with the concept that experimental diabetic neuropathy is a distal axonopathy.

Cleansing the blood. Hemodialysis, peritoneal dialysis, exchange transfusion, charcoal hemoperfusion, forced diuresis

ECDR can be a valuable adjunct to the therapy of pediatric poisonings. Careful consultation with a medical toxicologist and a nephrologist will be useful in reaching the decision as to which poisonings lend themselves to ECDR and which method is most appropriate for the specific case. Avoid advice that amounts to, "if you are not certain, dialyze." While the risks of many ECDR techniques are acceptable in major medical centers, it may not be good medicine to superimpose any morbidity from ECDR upon the poisoned patient when there can be little expectation of drug removal. It is wise to phrase your questions to consultants carefully. The question: "can this substance be dialyzed (hemoperfused, plasmaphoresed, etc.)?" is loaded and the answer frequently will be "yes!" The more proper questions are: "how much drug can be removed by ECDR, how long will the method take, how will this affect the present condition of the patient?" Clearly, a risk: benefit ratio must always be considered. There are lists of substances that "can" be removed by ECDR. It is more difficult to judge how much of the body burden is removed by such methods. Digoxin "can" be dialyzed, but it is not quantitatively removed from the body and there is no accepted benefit from ECDR in this instance. The volume of distribution is a useful guide to determine which substances may be removed quantitatively by ECDR. The exaggerated claims to increased plasma clearance of a hemoperfusion device may not be meaningful if the distribution space is large and plasma levels are correspondingly low. Finally, many of the advantages and disadvantages of ECDR are not likely to change markedly as a result of technology. We currently have very efficient machines for ECDR. It is the chemical characteristics of some toxic substances that limit the more global role of ECDR in poisoning. Serologic therapy, such as specific Fab antibody fragments for use in digoxin poisonings or the exciting work by Russell and colleagues using affinity chromatography to purify specific antibody fragments from horse serum, may be applicable to numerous intoxications. This approach, used in combination with ECDR or alone, will undoubtedly influence the future growth of clinical toxicology.

Malpractice liability of allied health professionals: developments in an area of critical concern

Malpractice litigation has become a serious concern of health professionals, as well as a contributor to escalating health-care costs. Allied health professionals have had their conduct called into question in a number of such suits, but so far these have received little scholarly attention. The developing body of allied health professions law is described and analyzed herein, with particular attention given to the issues of fact and law that are most frequently disputed. The need for legal development that includes sensitivity to the knowledge, abilities, and practices distinctive to the various health professions is stressed.

Consequences associated with nonnarcotic analgesics in the fetus and newborn

Nonnarcotic analgesics include well-known, widely used substances such as acetylsalicylic acid (ASA) and acetaminophen. ASA is a potent inhibitor of prostaglandin synthesis, and this mechanism is responsible for many potential toxicities in the fetus and newborn. These may include bleeding, altered renal function, and constriction of the ductus arteriosus in addition to analgesia. As such, ASA is frequently avoided during gestation and the immediate neonatal period. Acetaminophen is less well recognized as an agent with activity outside the central nervous system. It does not possess antiinflammatory activity like other substances that inhibit prostaglandins but has been shown to be an analgesic with potency comparable to ASA. This is believed to be by inhibition of brain prostaglandin synthetase. We have determined by using the chronically catheterized sheep fetus that acetaminophen has potent activity on the ductus arteriosus and produces a constriction, in therapeutic analgesic quantities, comparable to ASA. Thus, acetaminophen may be a potent inhibitor of prostaglandin function in the fetus.

Antipyretics and analgesics in children

Physicians must carefully consider the appropriate use of antipyretic drugs in children. Despite the ubiquitous presence of acetaminophen and acetylsalicylic acid in the home, there are many factors to weigh prior to their use. The following is a discussion of these factors: efficacy versus toxicity, known effects versus uncertain complications of drug therapy. Acetaminophen and acetylsalicylic acid have equivalent antipyretic effects. Acetysalicylic acid is clearly the better anti-inflammatory drug. Therapeutic misadventures with both drugs have resulted in childhood fatalities. Since these medications are not restricted to prescription order by a physician, instructions as to their safe and appropriate use should become part of 'normal child' counselling by physicians to all parents.

Renal clearance of gentamicin in cystic fibrosis

This study was designed to corroborate previous observations of low serum concentrations of aminoglycosides after usual doses in patients with cystic fibrosis and to investigate possible mechanisms for this change. We studied gentamicin clearance after single and multiple intravenously administered doses in 10 non-acutely ill patients with mild to moderate CF. The data could best be described by a two-compartment model for drug elimination. The mean 1-hour serum concentration, mean volume of distribution, and mean total plasma clearance of gentamicin were not different from those reported for patients without CF. The similarity of the plasma and the renal gentamicin clearances, supported by the observations that greater than 80% of administered drug was excreted in the urine by 4 hours and that negligible amounts were detected in sweat, saliva, or sputum, implies that the kidney is the major route of elimination in patients with mild CF. The correlation of increased plasma gentamicin clearance as NIH score decreases supports the hypothesis that aminoglycoside pharmacokinetics are changed as the severity of disease increases. For patients with mild CF, standard doses of gentamicin (60 mg/m2) will give safe and therapeutic concentrations.

Electron microscopic study of intramembranous changes in protein-extracted peripheral nervous system myelin

Sciatic nerves from young mice were incubated for 2-8 hours in 0.5% Triton X-100 in 0.5 M ammonium acetate, a solution which solubilizes the large and small basic proteins of the myelin sheath. As previously noted (Peterson and Gruener, 1978), myelin sheaths from treated nerves extensively split and unravelled along major dense lines. Small focal areas of compact myelin remained. In freeze-fracture replicas, areas of myelin with lamellar splitting contained few intramembranous particles, while membrane areas with greater than normal densities of particles were associated with the patches of compact myelin membrane. Fixation for as short a time as 15 minutes stabilized the myelin membrane enough to prevent the Triton X-100 effects, even when incubations were extended to 20 hours. Controls, both untreated and 0.5 M ammonium acetate-treated nerves, had predominantly compact myelin sheaths; their leaflets were covered with numerous intramembranous particles. The data suggest that Triton X-100 alters the compact structure of peripheral nervous system myelin. In areas where lamellae are split and separated, there is a loss of intramembranous particles. It appears that the loss of intramembranous particles is related to the removal of the basic proteins which are located in major dense line regions of compact myelin sheaths.

Degenerative neuropathy in insulin-treated diabetic rats

Peripheral neuropathic alterations associated with diabetes and its treatment with insulin were studied in alloxan-induced diabetic rats. Treatment regimens included daily injections of Protamine Zinc Insulin (PZ), daily injections of Ultralente Insulin and subcutaneously implanted osmotic minipump delivered insulin. Non-diabetic and untreated diabetic groups served as controls. Two separate but similar studies were run, one lasting 4 weeks and the other 8 weeks. Conduction velocities performed on both sensory and motor nerves revealed no statistically significant differences among groups. Anatomical analysis of teased fibers from tibial nerves showed a significant number of fibers with ovoids, consistent with Wallerian-type axonal degeneration, only in the treated diabetic groups. Degeneration was especially severe in the PZI-treated group. Metabolic studies were performed using incorporation of radioactive isotopes ([3H]fucose, [14C]leucine) into myelin proteins of sciatic nerves. The ratio of [3H]fucose/[14C]leucine for the PZI-treated group was significantly decreased when compared to the control groups in both the 4 and 8 week study whereas the minipump-treated group showed no statistically significant difference from the control group in either study. Similar decreases in this ratio have been seen in conditions of peripheral nerve degeneration. It is concluded that daily injections of PZI insulin result in significant nerve degeneration in the alloxan diabetic rat, while continuous levels of insulin delivered by osmotic minipumps result in less degeneration.

Altered metabolic incorporation of fucose and leucine into PNS myelin of 25-week-old diabetic (C57BL/Ks [db/db]) mice: effects of untreated diabetes on nerve metabolism

Sciatic nerves of 25-week-old genetically diabetic (C57BL/Ks [db/db]) mice and their litter-mate controls were removed, and their metabolic incorporation of [3H]fucose and [14C]leucine into myelin was studied in vitro. Untreated diabetic animals showed significant increases (p less than 0.05) in the fucose/leucine incorporation into myelin when compared to values found for their litter-mates. These results correlated well with previous experiments performed on alloxan or streptozotocin-diabetic rats and thus show the in vitro incubation procedure to be a good indicator of altered metabolic conditions in peripheral nerves due to diabetes mellitus. The resulting ratio increases seen in diabetic animals is at variance with the decrease in ratios found in animals undergoing typical Wallerian degeneration. These results suggest that different metabolic processes operate in untreated diabetics than in normals or in those undergoing other degenerative nerve processes.

Neuropathic changes associated with insulin treatment of diabetic rats: electron microscopic and morphometric analysis

Tibial nerves from control, untreated alloxan diabetic, and 4-week insulin treated alloxan diabetic rats were examined with light microscopy and computerized morphometric analysis of axons. Teased fiber preparations and electron microscopy were utilized to evaluate nerve degeneration. The insulin treatment regimens included daily injections of protamine zinc insulin (PZI), daily injections of ultralente insulin, and continuously delivered insulin through osmotic minipumps. Evaluation of axon:myelin ratios, teased fiber profiles, and electron microscopic cross sections of nerves demonstrated different degrees of neuropathic changes within the treated groups. The control group and untreated diabetic group showed little or no degeneration, while all insulin-treated groups showed evidence of Wallerian degeneration. Among these insulin treated groups, the PZI-treated group showed the greatest number of degenerating profiles while the minipump group showed the least. These data suggest that insulin treatment of alloxan diabetes results in axonal degeneration which closely resembles findings in human diabetic neuropathies. The substantially diminished number of degenerating axons seen in the osmotic minipump insulin-treated rats suggests that continuous delivery of insulin may decrease the neuropathic changes seen with single injection insulin therapy. Since virtually all insulin-dependent diabetic patients receive daily administration of insulin, the possibility that peripheral neuropathies may in part result from the insulin treatment requires more extensive investigation in a variety of animal models to separate the neuropathic effects of diabetes from the neuropathic effects of insulin therapy.

The composition of the medial articular nerve to the knee in the dog

Light and electron microscopy were used to characterise the medial articular nerve to the knee in the dog, in terms of the total number of myelinated axons, the frequencies of different diameters of myelinated axons, the number of unmyelinated axons, and the ratios of unmyelinated to myelinated axons. Approximately 70% of all myelinated axons were of less than 5 micron diameter and, with the exception of two of sixteen nerves examined by light microscopy, all distributions were unimodal. The distributions of the two nerves of other than unimodal distribution were each characterised by a second, small peak of axon diameters ranging between 9 and 14 microns. Unmyelinated axons counted in five nerves suggested that approximately 72% of all axons of a given nerve were unmyelinated, giving a ratio of about 2.5 unmyelinated to 1.0 myelinated axon.