Comparison of the metabolic and toxic effects of 2-chloropropionate and dichloroacetate

The metabolic and toxic effects of 2-chloropropionate and dichloroacetate, activators of the pyruvate dehydrogenase complex, were compared. In 4-hr fasted mice, the oral LD50 values for 2-chloropropionate and dichloroacetate were 15.4 +/- 0.1 and 32.1 +/- 1.1 mmol/kg, respectively. In suckling rats, both compounds effectively lowered blood lactate and glucose levels and increased blood ketone bodies. Although comparable effects were brought about by both compounds on other metabolites, dichloroacetate caused a greater increase in blood ketone bodies. In a prolonged oral toxicity study using male rats, both compounds decreased growth rate and food consumption and caused neurotoxic effects. Both compounds brought about hind limb weakness, slower nerve conduction velocities and decreased diameter of tibial nerves. 2-Chloropropionate treatment caused testicular abnormalities manifested by testicular maturation arrest and degeneration of germ cells. 2-Chloropropionate-treated rats had significantly lower plasma triacylglycerol levels than control or dichloroacetate-treated rats. In mature rats, total serum ketone bodies were increased by dichloroacetate but not significantly elevated by 2-chloropropionate. Although 2-chloropropionate may lack sufficient safety to warrant chronic use in humans, it is a useful research tool for studying the metabolic effects of activation of the pyruvate dehydrogenase complex. Since 2-chloropropionate is not converted to oxalate and is not as ketogenic as dichloroacetate, 2-chloropropionate may be useful clinically in situations requiring only short-term therapy.

Metabolism of phospholipids in peripheral nerve from rats with chronic streptozotocin-induced diabetes: increased turnover of phosphatidylinositol-4,5-bisphosphate

The effect of chronic streptozotocin-induced diabetes on phospholipid metabolism in rat sciatic nerve in vitro was investigated. In normal nerve incubated for 2 h in Krebs-Ringer-bicarbonate buffer containing [32P]orthophosphate, radioactivity was primarily incorporated into phosphatidylinositol-4,5-bisphosphate and phosphatidylcholine. Smaller amounts were present in phosphatidylinositol-4-phosphate, phosphatidylinositol, and phosphatidic acid. As compared to controls, phosphatidylinositol-4,5-bisphosphate in nerves from animals made diabetic 2, 10, and 20 weeks earlier accounted for 30-46% more of the isotope, expressed as a percentage, incorporated into all phospholipids. In contrast, the proportion of radioactivity in phosphatidylcholine decreased by 10-25%. When the results were expressed as the quantity of phosphorus incorporated into phospholipid, only phosphatidylinositol-4,5-bisphosphate displayed a change. The amount of isotope which entered this lipid increased 60% and 67% for 2- and 10-week diabetic animals, respectively. Increased phosphatidylinositol-4,5-bisphosphate labeling was observed when epineurial-free preparations were used or when the composition of the incubation medium was varied. Sciatic and caudal nerve conduction velocities were decreased after 10 and 20 weeks but were unchanged after 2 weeks. We conclude that an increase in the turnover of phosphatidylinositol-4,5-bisphosphate in sciatic nerve from streptozotocin-diabetic rats appears relatively early and persists throughout the course of the disease. This metabolic alteration may be related to a primary defect responsible for the accompanying deficient peripheral nerve function.

Effects of streptozotocin diabetes on the noradrenergic innervation of the rat heart: a longitudinal histofluorescence and neurochemical study

The effects of the age of induction and total duration of streptozotocin diabetes on the sympathetic noradrenergic innervation of the rat heart was examined with glyoxylic acid induced histofluorescence to demonstrate the distribution of noradrenergic fibers within the heart, and with high performance liquid chromatography with electrochemical detection to measure tissue levels of the neurotransmitter norepinephrine. Diabetes was induced in male Sprague-Dawley rats at 1, 2, and 4 months of age. Within each of these groups, diabetic rats survived for periods of 1, 2, and 4 months. Additional groups of diabetic rats survived to a chronological age of 8 months. Norepinephrine levels in the hearts of diabetic rats were increased over those of control rats in all groups at 1 month duration of diabetes. Ventricles were generally affected to a greater extent than atria. At 2 months duration of diabetes, ventricular levels remained elevated while atrial norepinephrine levels were at or below control levels. At 4 months duration of diabetes, and in all groups at 8 months of age, the norepinephrine levels were at or below control levels, except in the ventricles of rats induced at 4 months of age, which remained elevated. Histofluorescence studies demonstrated the presence of axon bundles and varicose noradrenergic profiles in the diabetic rat hearts, distributed in a pattern similar to that seen in controls. However, at 1 month duration of diabetes in all groups, the density of noradrenergic varicosities in diabetic rat hearts appeared increased with abundant branched profiles. These results are surprising, since studies on genetic models of diabetes have suggested decreased norepinephrine levels in the heart. The present study suggests that during the early phases of streptozotocin induced diabetes, noradrenergic nerves are still intact and may be susceptible to pharmacologic manipulation. The later fall of norepinephrine levels back to or below control levels may indicate actual neuronal damage, suggesting that early intervention may be necessary to protect these nerves from degeneration. This issue is potentially important in view of the reported toxic effects of high NE levels on the heart, and the high incidence of death from myocardial infarct in diabetic humans with autonomic neuropathy.

Excretion of urinary volatile metabolites in response to alloxan induced diabetes of short duration in rats

Alterations in urine volatile metabolites due to the induction of alloxan diabetes in the rat were examined by capillary gas chromatography and gas chromatography--mass spectrometry for the five days immediately following the onset of chronic hyperglycemia. Elevations of a number of metabolites were observed including several short chain ketones, acetophenone, 2-acetylfuran and indole. The value of urine volatile metabolic profiles as characteristic indicators of the diabetic condition is demonstrated through profiles obtained from a diabetic animal which spontaneously reverted to normal.

Ultrastructural axonal pathology in experimentally diabetic and aging control rats

Electron microscopic examination of tibial nerves from streptozotocin-diabetic, alloxan-diabetic and age-matched control rats was undertaken at two weeks and two, four, eight, and twelve months following the induction of diabetes. Many myelinated axons of both diabetic and control rats contained glycogen-like granules, axon-Schwann cell networks and fingerlike intrusions of myelin. These axonal changes were observed more frequently with advancing age and duration of diabetes, suggesting that they are related to aging or repeated injury. A larger proportion of diabetic axons than control axons were affected at early time periods, but by eight and twelve months the control axons were as frequently (or more frequently) involved as diabetic axons. Thus, experimental diabetes may confer upon peripheral myelinated axons an increased susceptability to aging or repeated injury. Specific morphologic abnormalities in peripheral myelinated axons associated uniquely with streptozotocin or alloxan diabetes in the rat were not noted.

Structural relationships between the endogenous volatile urinary metabolites of experimentally diabetic rats and certain neurotoxins (l)

High resolution glass capillary gas chromatography and GC/MS were utilized to examine qualitative and quantitative variations from normal of urinary volatile metabolites of long-term alloxan and streptozotocin diabetic rats. Volatile metabolites were structurally compared with known neurotoxins to examine any possible relationship between these metabolites and the development of the diabetic polyneuropathy.

Synthesis of myelin, particulate, and soluble protein subfractions of rat sciatic nerve during the early stage of Wallerian degeneration: a comparison of metabolic studies using double and single isotope methods and recovery

The recovery, electrophoretic composition and synthesis of the myelin, particulate protein and soluble protein subfractions of rat sciatic nerve were compared in normal, sham-operated, and degenerating rat sciatic nerve at one, three and five days after neurotomy. Both single and double isotope methods were used to measure changes in synthesis in vitro and double isotope methods were used in vivo. The wet weights of nerves undergoing Wallerian degeneration for 5 days increased by 40 percent compared to normal and sham-operated nerves. The recovery, specific radioactivity, and synthesis of the myelin was reduced. The effect on myelin protein synthesis was similar in vitro and in vivo. The myelin loss was relatively constant in amount (30-40 microgram) regardless of differences in nerve sizes of young and old rats, consequently the percentage of myelin loss was inversely proportional to nerve size. The recovery of particulate protein increased, its rate of synthesis remained unchanged, and accordingly the specific radioactivity was decreased. The recovery, specific radioactivity, and the rate of synthesis of the soluble protein fraction were all elevated. The protein composition of the three fractions, as analyzed qualitatively by polyacrylamide disc gel electrophoresis, remained essentially unchanged through five days of degeneration. With regard to comparisons of the single and double isotope methods, results shows that the latter are more ideally suited to measuring changes in synthesis during the non-steady state conditions that are characteristics of rapid degeneration.

Effects of surgically induced instability on rat knee articular cartilage

Degenerative lesions in the articular cartilage were present following transection of the anterior cruciate ligament in the rat. These lesions included surface disruptions, a reduction in matrix proteoglycans, and cellular changes and therefore were similar to lesions seen in dogs following transection of the anterior cruciate ligament as well as lesions seen in other mechanical derangement models. Lesions were more frequently encountered in animals that had been exercised on a treadmill. This suggests that the rat knee joint may be a useful small animal model in studying the effect of mechanical derangement on articular tissues.

Functional roles of monoaminergic pathways to sympathetic preganglionic neurons

Despite considerable progress in mapping the central monoaminergic pathways to sympathetic preganglionic neurons in the spinal cord, the respective functional roles of these pathways have not been resolved. Evidence for both excitation and inhibition has been advanced for each of the three monoamines, serotonin, norepinephrine, and epinephrine. Our previous studies on spinal sympathetic pathways to sympathetic preganglionic neurons support the prevailing opinion that serotonin pathways are inhibitory but did not satisfactorily resolve the functional role of the norepinephrine pathways. However, more recent studies showing that intraspinally evoked sympathetic discharges were rapidly and markedly enhanced by phosphodiesterase inhibitors and that this effect was prevented by clonidine have led to formulation of a coherent hypothesis which accommodates much of the conflicting evidence regarding norepinephrine. In addition, evidence for the role of the epinephrine pathways has been obtained by using a selective inhibitor of epinephrine synthesis. The results of these recent studies complement our previous results and suggest that the excitability of sympathetic preganglionic neurons is regulated by excitatory norepinephrine pathways and inhibitory epinephrine pathways that activate or suppress adenylate cyclase to control intraneuronal levels of cyclic AMP.

Glycogen accumulation in tibial nerves of experimentally diabetic and aging control rats

Tibial nerves of streptozotocin-diabetic, alloxan-diabetic, and age-matched control rats were examined at 2 weeks and 2, 4, 8, and 12 months following the induction of diabetes. Glycogen-like granules accumulated within perineurial and Schwann cells of only the diabetic animals. This accumulation may reflect a metabolic abnormality in these cells which could account for the reduced conduction velocities seen in the peripheral nerves of these same diabetic rats (Moore et al. 1980a). Glycogen-like granules were also present and increased with age in myelinated axons of both diabetic and control rats. Quantitative data suggest that axonal accumulation of glycogen-like granules is related to aging or injury related phenomena to which diabetic axons may be more susceptible.

Neonatal intracranial hemorrhage and maternal use of aspirin

A prospective study of 108 infants born at 34 weeks' gestation or earlier or weighing 1500 g or less was carried out to determine the incidence of intracranial hemorrhage and the multiple risk factors that may cause or aggravate this hemorrhage in premature infants. On day 2 post partum, mothers were questioned regarding maternal risk factors, including the use of either aspirin or acetaminophen during the last week of pregnancy. Between days 3 and 7 post partum, computed tomographic scanning was performed on the 108 infants. Of the total, 53 (49%) developed intracranial hemorrhage. The incidence of hemorrhage in the infants whose mothers had ingested aspirin was significantly greater (P less than .05) than that seen in infants whose mothers did not take either aspirin or acetaminophen (control group). The incidence of intracranial hemorrhage among infants whose mothers ingested acetaminophen was not significantly different from that of the control group. This study indicates that aspirin is associated with an increased incidence of intracranial hemorrhage in the authors' population. The use of aspirin in the last 3 months of pregnancy is highly questionable and probably inappropriate.

Effect of activated charcoal administration on acetylcysteine serum levels in humans

The effect of orally administered activated charcoal on the absorption of acetylcysteine in three men was studied. Each of the three volunteers was given 140 mg/kg acetylcysteine as a single oral dose. Blood samples were taken at 0, 0.5, 1, 1.5, 2, 4, 6, and 8 hours after acetylcysteine ingestion. Following a one-week washout period, each subject was given orally 50 g of Activated Charcoal, USP, 15 minutes before a 140-mg/kg acetylcysteine oral dose. Blood samples were taken. Acetylcysteine content in the plasma was determined with a high-pressure ion-exchange chromatography system using a gold-mercury electrochemical cell. No statistically significant differences were found between total areas under the curves, peak concentrations, or time of peak concentrations of acetylcysteine given with or without charcoal. Although acetylcysteine absorption was delayed in two patients, the differences were not significant. These data suggest that acetylcysteine absorption is not impaired by activated charcoal administration. This conflicts with previously published in vitro data; therefore, it is recommended that activated charcoal should not be administered concomitantly with acetylcysteine as a usual procedure until more data are available.

The effect of diabetes on leucine and fucose incorporation into PNS myelin proteins

Peripheral neuropathy is a common complication associated with diabetes mellitus. Segmental demyelination and other pathological changes frequently accompany loss of sensory amd motor nerve function. Morphological changes seen in diabetic nerve myelin may be a result of altered Schwann cell metabolism under hyperglycemic conditions. Using both alloxan and streptozotocin - induced diabetic rats of 2, 4 and 8 months duration of diabetes, metabolic changes in isolated sciatic nerve myelin were assessed using a double-label in vitro incubation system. Incorporation of 3H-fucose and 1-14C-leucine into myelin was determined per microgram protein. Specific activities of incorporated protein precursors were compared as a ratio of fucose to leucine. Using the Newman-Kuels test for multiple comparisons, statistically significant increases were found in the incorporation ratios of diabetic rats at 2 and 4 months of diabetes when tested against age-matched controls.

Repeatabilities of serum constituents in Holstein-Friesians affected by feeding, age, lactation, and pregnancy

Effects of feeding regimen (pasture and drylot), physiological stage (lactating pregnant, lactating nonpregnant, and dry), and age on metabolites in blood serum were measured in 100 Holstein Friesian cows over 18 mo. Calcium, cholesterol, uric acid, total protein, albumin, and alkaline phosphatase were affected by physiological stage, whereas feeding regimen affected creatinine. Inorganic phosphate, blood urea nitrogen, glucose, lactic dehydrogenase, and glutamic oxaloacetic transaminase were affected by the interaction of stage and regimen. Age of animal affected cholesterol, glucose, and lactic dehydrogenase. Variances among and within cows were not consistent across physiological stages providing different repeatabilities for each stage. For example, total protein was highly repeatable in the two lactating stages but only moderately repeatable in dry animals (.61, .73, .26). Alkaline phosphatase and creatinine had consistently high repeatabilities.

Acute carbamazepine toxicity resulting from overdose

Four patients with an acute overdose of carbamazepine were examined with serial blood level determinations. The clinical spectrum consisted of coma, respiratory depression, seizures, myoclonus, nystagmus, hyperreflexia, hyporeflexia, delayed gastric emptying with cyclic coma, ataxia, sinus tachycardia, and atrioventricular conduction delay. Carbamazepine elimination half-lives varied from 10 to 29 hours, and in one case carbamazepine-10,11-epoxide was measured and had a half-life of 24 hours.

Rates of protein synthesis and turnover in fetal life

Uniformly labeled [14C]lysine was infused at constant rate into the inferior vena cava of eight ovine fetuses with gestational ages ranging from 110 to 145 days. The infusion lasted 9 to 13 h and produced a steady-state specific activity of free lysine in the fetal plasma. In the steady state, approximately 9% of the infused radioactivity was excreted by the fetus as 14CO2, indicating fetal catabolism of lysine. At the end of the infusion, the fetal carcass was analyzed for its total content of labeled and unlabeled lysine. The rate of protein synthesis was calculated from the carcass-to-plasma lysine specific activity ratio. The fractional rate constant (Ks) for the unidirectional flux of lysine into fetal proteins was inversely related (r = -0.88) to fetal age: Ks = 0.584 - 0.0036 age (days). In each fetus, Ks was 2-4 times greater than the estimated fractional rate of fetal protein accretion (KG). The discrepancy between Ks and KG demonstrates that a large fraction of protein synthesis in the ovine fetus is devoted to protein turnover.

Age as a variable in acetaminophen overdose

More than 300 accidental ingestions of acetaminophen products in children 6 years of age and younger have been reported to the Rocky Mountain Poison Center, Denver, during September 1974 to September 1979. Few of these have resulted in toxic reactions, based on clinical examination of the children. This report documents 17 childhood ingestions of acetaminophen in which plasma levels of the substance were measured and liver function was evaluated. Thirteen of these cases occurred as a result of accidental ingestion by children 6 years of age or younger; five of these children had documented plasma levels that were in the toxic range of an adult nomogram and were treated with acetylcysteine. Only minor abnormalities in liver function were observed in the treated children, even when therapy was instituted as late as 20 hours after ingestion.