Progressive Deficit of Retrograde Axonal Transport Is Associated with the Pathogenesis of Di-n-Butyl Dichlorvos Axonopathy

The induction of central-peripheral distal axonopathy in hens singly dosed with some organophosphorus (OP) compounds, such as di-n-butyl-2,2-dichlorovinyl phosphate (DBDCVP), requires greater than 80% organophosphorylation and subsequent intramolecular rearrangement ("aging") of a protein [neuropathy target esterase (NTE)] in the axon. Suprathreshold biochemical reaction, 24 h after dosing with DBDCVP (0.75-1.00 mg/kg s.c.), is shown to be associated with progressive decrement of retrograde axonal transport in sensory and motor fibers. The maximum transport deficit (about 70% reduction) is reached 7 days after DBDCVP, prior to the appearance of axonal degeneration and the onset of clinical signs of neuropathy (day 10-11). By contrast, phenylmethylsulfonyl fluoride (30 mg/kg s.c.), an agent that prevents the development of OP neuropathy by inhibiting NTE without the "aging" reaction, had no effect on axon transport, nerve fiber integrity, or clinical status and, when administered prior to a neurotoxic dose of DBDCVP (1.00 mg/kg s.c.), prevented DBDCVP effects. Paraoxon (0.2 mg/kg s.c.) neither inhibited NTE nor caused deficits in retrograde transport or neuropathy. Taken in concert, these studies demonstrate that induced deficits in retrograde transport are associated with the pathogenesis of OP-induced nerve-fiber degeneration and the threshold-initiating mechanism thereof.     

Intramyocellular lipid accumulation and reduced whole body lipid oxidation in HIV lipodystrophy

Antiretroviral therapy in human immunodeficiency virus (HIV)-positive patients can induce a lipodystrophy syndrome of peripheral fat wasting and central adiposity, dyslipidemia, and insulin resistance. To test whether in this syndrome insulin resistance is associated with abnormal muscle handling of fatty acids, 12 HIV-1 patients (8 females/4 males, age = 26 +/- 2 yr, HIV duration = 8 +/- 1 yr, body mass index = 22.0 +/- 1.0 kg/m(2), on protease inhibitors and nucleoside analog RT inhibitors) and 12 healthy subjects were studied. HIV-1 patients had a total body fat content (assessed by dual-energy X-ray absorptiometry) similar to that of controls (22 +/- 1 vs. 23 +/- 2%; P = 0.56), with a topographic fat redistribution characterized by reduced fat content in the legs (18 +/- 2 vs. 32 +/- 3%; P < 0.01) and increased fat content in the trunk (25 +/- 2 vs. 19 +/- 2%; P = 0.03). In HIV-positive patients, insulin sensitivity (assessed by QUICKI) was markedly impaired (0.341 +/- 0.011 vs. 0.376 +/- 0.007; P = 0.012). HIV-positive patients also had increased total plasma cholesterol (216 +/- 20 vs. 174 +/- 9 mg/dl; P = 0.05) and triglyceride (298 +/- 96 vs. 87 +/- 11 mg/dl; P = 0.03) concentrations. Muscular triglyceride content assessed by means of (1)H NMR spectroscopy was higher in HIV patients in soleus [92 +/- 12 vs. 42 +/- 5 arbitrary units (AU); P < 0.01] and tibialis anterior (26 +/- 6 vs. 11 +/- 3 AU; P = 0.04) muscles; in a stepwise regression analysis, it was strongly associated with QUICKI (R(2) = 0.27; P < 0.0093). Even if the basal metabolic rate (assessed by indirect calorimetry) was comparable to that of normal subjects, postabsorptive lipid oxidation was significantly impaired (0.30 +/- 0.07 vs. 0.88 +/- 0.09 mg x kg(-1) x min(-1); P < 0.01). In conclusion, lipodystrophy in HIV-1 patients in antiretroviral treatment is associated with intramuscular fat accumulation, which may mediate the development of the insulin resistance syndrome.     

Insulin resistance,intramyocellular lipid content,and plasma adiponectin in patients with type 1 diabetes

Insulin resistance is a key pathogenic factor of type 2 diabetes (T2DM); in contrast, in type 1 diabetes (T1DM) it is considered a secondary alteration. Increased intramyocellular lipid (IMCL) content accumulation and reduced plasma adiponectin were suggested to be pathogenic events of insulin resistance in T2DM. This study was designed to assess whether IMCL content and plasma adiponectin were also associated with the severity of insulin resistance in T1DM. We studied 18 patients with T1DM, 7 older and overweight/obese patients with T2DM, and 15 nondiabetic, insulin-resistant offspring of T2DM parents (OFF) and 15 healthy individuals (NOR) as appropriate control groups matched for anthropometric features with T1DM patients by means of the euglycemic hyperinsulinemic clamp combined with the infusion of [6,6-2H2]glucose and 1H magnetic resonance spectroscopy of the calf muscles. T1DM and T2DM patients showed reduced insulin-stimulated glucose metabolic clearance rate (MCR: 5.1 +/- 0.6 and 3.2 +/- 0.8 ml x kg(-1) min(-1)) similar to OFF (5.3 +/- 0.4 ml x kg(-1) x min(-1)) compared with NOR (8.5 +/- 0.5 ml x kg(-1) min(-1), P < 0.001). Soleus IMCL content was increased in T1DM (112 +/- 15 AU), T2DM (108 +/- 10 AU) and OFF (82 +/- 13 AU) compared with NOR (52 +/- 7 AU, P < 0.05) and the result was inversely proportional to the MCR (R2 = 0.27, P < 0.001); an association between IMCL content and Hb A1c was found only in T1DM (R2 = 0.57, P < 0.001). Fasting plasma adiponectin was reduced in T2DM (7 +/- 1 microg/ml, P = 0.01) and OFF (11 +/- 1 microg/ml, P = 0.03) but not in T1DM (25 +/- 6 microg/ml), whose plasma level was increased with respect to both OFF (P = 0.03) and NOR (16 +/- 2 microg/ml, P = 0.05). In conclusion, in T1DM, T2DM, and OFF, IMCL content was associated with insulin resistance, demonstrating that IMCL accretion is a marker of insulin resistance common to both primary genetically determined and secondary metabolic (chronic hyperglycemia) alterations. The increased adiponectin levels in insulin-resistant patients with T1DM, in contrast to the reduced levels found in patients with T2DM and in OFF, demonstrated that the relationship of adiponectin to insulin resistance in humans is still unclear.     

Impairment of Retrograde Neuronal Transport in Oxaliplatin-Induced Neuropathy Demonstrated by Molecular Imaging

Background and Purpose

The purpose of our study was to utilize a molecular imaging technology based on the retrograde axonal transport mechanism (neurography), to determine if oxaliplatin-induced neurotoxicity affects retrograde axonal transport in an animal model.

Materials and Methods

Mice (n = 8/group) were injected with a cumulative dose of 30 mg/kg oxaliplatin (sufficient to induce neurotoxicity) or dextrose control injections. Intramuscular injections of Tetanus Toxin C-fragment (TTc) labeled with Alexa 790 fluorescent dye were done (15 ug/20 uL) in the left calf muscles, and in vivo fluorescent imaging performed (0–60 min) at baseline, and then weekly for 5 weeks, followed by 2-weekly imaging out to 9 weeks. Tissues were harvested for immunohistochemical analysis.

Results

With sham treatment, TTc transport causes fluorescent signal intensity over the thoracic spine to increase from 0 to 60 minutes after injection. On average, fluorescence signal increased 722%+/−117% (Mean+/−SD) from 0 to 60 minutes. Oxaliplatin treated animals had comparable transport at baseline (787%+/−140%), but transport rapidly decreased through the course of the study, falling to 363%+/−88%, 269%+/−96%, 191%+/−58%, 121%+/−39%, 75%+/−21% with each successive week and stabilizing around 57% (+/−15%) at 7 weeks. Statistically significant divergence occurred at approximately 3 weeks (p≤0.05, linear mixed-effects regression model). Quantitative immuno-fluorescence histology with a constant cutoff threshold showed reduced TTc in the spinal cord at 7 weeks for treated animals versus controls (5.2 Arbitrary Units +/−0.52 vs 7.1 AU +/−1.38, p<0.0004, T-test). There was no significant difference in neural cell mass between the two groups as shown with NeuN staining (10.2+/−1.21 vs 10.5 AU +/−1.53, p>0.56, T-test).

Conclusion

We show–for the first time to our knowledge–that neurographic in vivo molecular imaging can demonstrate imaging changes in a model of oxaliplatin-induced neuropathy. Impaired retrograde neural transport is suggested to be an important part of the pathophysiology of oxaliplatin-induced neuropathy.     

Acute effects of valsartan on insulin sensitivity in obese, non-hypertensive subjects with and without type 2 diabetes.

BACKGROUND: Two studies were designed to determine whether a single dose (80 mg) of the angiotensin II receptor blocker (ARB), valsartan, alters insulin sensitivity in obese, non-hypertensive subjects with and without Type 2 diabetes. METHODS: Insulin sensitivity (S(I)), glucose effectiveness (S(G)), and acute insulin response (AIR(0-10 min)) were measured by means of a 3-hour insulin-modified frequently sampled intravenous glucose tolerance test (FSIVGTT) before and after a single dose of valsartan. Study 1: obese, normotensive non-diabetic male subjects (n = 12), mean (SD) age 37.2 +/- 11.2 years, BMI 32.8 +/- 6.8 kg/m (2); Study 2: obese, normotensive Type 2 diabetic patients (n = 12), mean age 55.7 +/- 6.9 years, BMI 35.0 +/- 6.8 kg/m (2)/l. Both studies were randomised, double-blind, placebo-controlled, single-dose crossover group studies involving subjects in two study days, two weeks apart. After fasting samples were taken, a 300 mg/kg iv glucose bolus was injected at 0 min, and 0.05 U/kg iv insulin was given 20 min later. Blood samples for analysis of glucose and insulin were taken throughout the 3-hour study period. RESULTS: Study 1 (non-diabetic subjects) S(I) 2.81 vs. 2.63 x 10 (-4) min (-1) per microU/ml (p = 0.54), S(G) 0.020 vs. 0.020 min (-1) (p = 0.90), AIR(0-10) min 3305 vs. 3450 microU/min/ml (p = 0.71); Study 2 (patients with type 2 diabetes) S(I) 0.59 vs. 0.85 x 10 (-4) min (-1) per microU/ml (p = 0.15), S(G) 0.013 vs. 0.014 min (-1) (p = 0.71), AIR(0-10) min 65 vs. 119 microU/min/ml (p = 0.14), placebo vs. valsartan, respectively. CONCLUSION: In obese, non-hypertensive non-diabetic and Type 2 diabetic subjects a single dose of valsartan does not alter insulin sensitivity.     

Acrylamide impairs fast and slow axonal transport in rat optic system

Effects of single and repeated doses of acrylamide on fast and slow axonal transport of radio labeled proteins following the injection of L-[4,5-³H] leucine have been studied in the optic system of male Sprague-Dawley rats. A single dose of acrylamide (100 mg/kg) had no effect, but higher concentrations (200–300 mg/kg) altered the distribution of fast axonally transported materials in optic nerves and optic tracts. Repeated doses of acrylamide (30 mg/kg/day, 5 days per week for 4 weeks) produced degeneration of tibial nerves but spared optic nerves and optic tracts. Fast axonal transport rate in optic axons was reduced by 50% (reduced to 4 mm/h from 8 mm/h) in acrylamide treated animals. Acrylamide also slowed the velocity of slow axonal transport of labeled proteins in optic axons to 1.0 mm per day from 1.3 mm per day. Since acrylamide impaired the rate of both fast and slow axonal transport in the absence of overt morphological damage, it can be concluded that deficit in axonal transport is an important factor in the pathogenesis of axonal degeneration in acrylamide neuropathy.     

Hyperglycemia reduces coronary collateral blood flow through a nitric oxide-mediated mechanism

We tested the hypothesis that hyperglycemia alters retrograde coronary collateral blood flow by a nitric oxide-mediated mechanism in a canine Ameriod constrictor model of enhanced collateral development. Administration of 15% dextrose to increase blood glucose concentration to 400 or 600 mg/dl decreased retrograde blood flow through the left anterior descending coronary artery to 78 +/- 9 and 82 +/- 8% of baseline values, respectively. In contrast, saline or L-arginine (400 mg x kg(-1) x h(-1)) had no effect on retrograde flow. Coronary hypoperfusion and 1 h of reperfusion decreased retrograde blood flow similarly in saline- or L-arginine-treated dogs (76 +/- 11 and 89 +/- 4% of baseline, respectively), but these decreases were more pronounced in hyperglycemic dogs (47 +/- 10%). L-arginine prevented decreases in retrograde coronary collateral blood flow during hyperglycemia (100 +/- 5 and 95 +/- 6% of baseline at blood glucose concentrations of 400 and 600 mg/dl, respectively) and after coronary hypoperfusion and reperfusion (84 +/- 14%). The results suggest that hyperglycemia decreases retrograde coronary collateral blood flow by adversely affecting nitric oxide availability.     

In vitro and in vivo leishmanicidal activity of Dysoxylum binectariferum and its fractions against Leishmania donovani

The leishmanicidal effect of crude ethanolic extract of stem bark of Dysoxylum binectariferum and its fractions has been investigated against Leishmania donovani, the causative agent of visceral leishmaniasis. Ethanolic extract was lethal to promastigotes as well as amastigote forms in macrophage system at the concentration of 100 microg/ml. Chloroform fraction significantly inhibited promastigote multiplication and was also active against amastigotes in infected J774A.1 macrophages at 100 microg/ml. Hexane fraction was moderately active and the other fractions were inactive against both the forms. When tested in vivo in hamsters, ethanolic extract was toxic at 500 mg/kg whereas exhibited marginal activity (67.7+/-5.3%) at 250 mg/kg x 5, p.o. on day 7 post treatment (p.t.) which increases slightly (69+/-4.7) by day 30 p.t. Chloroform and n-hexane fractions exhibited 64.3+/-4% and 47.8+/-4.6% parasite inhibition at the dose of 100 mg/kg x 5 p.o., respectively. The pure compound, rohitukine, obtained from chloroform fraction showed weaker in vitro activity and was ineffective in infected hamsters. The lead potential of this plant need further investigations.     

Loss of material from the retrograde axonal transport system in frog sciatic nerve

Rapid axonal transport was studied in sciatic nerve preparations of the amphibian Xenopus laevis maintained in vitro at 23.0 +/- 0.2 degrees C. A pulse of [35S]methionine-labeled material was allowed to move in the anterograde direction until encountering a lesion, at which a portion of the pulse reversed directions and moved in the retrograde direction. By constricting the nerve during the course of the experiment, it was possible to prevent continuous return of label from the lesion, thus creating a retrogradely moving pulse that contained a defined quantity of radiolabel. Movement of both the anterograde and the retrograde pulse were monitored continuously for up to 24 h using a position-sensitive detector of ionizing radiation. The front and the back edge of the anterograde pulse were found to move at the rates of (mm/day) 179.9 +/- 3.9 (+/- SEM) and 149.9 +/- 5.9, respectively, and the front and the back edge of the retrograde pulse moved at the rates of 155.8 +/- 11.3 and 84.6 +/- 2.9, respectively. By comparison of the quantity of label lost to the stationary phase to the quantity of label calculated to have been present in the anterograde pulse, it was determined that 0.068 +/- 0.009 of the anterograde pulse is lost to each 3.18-mm region of nerve. Comparison of the quantity of label calculated to have been present in the retrograde pulse to that in the anterograde pulse revealed that 0.057 +/- 0.014 of the retrograde pulse is lost to each 3.18-mm region of nerve. It is concluded that protein originating in the cell body and which reverses its direction of transport at a lesion can be lost from the retrograde axonal transport system.     

Diabetes affects retrograde but not anterograde transport of sciatic nerve phosphofructokinase in Sprague-Dawley rats.

Phosphofructokinase activity was measured in the sciatic nerve of streptozotocin-induced diabetic and nondiabetic rats. Average steady-state phosphofructokinase activity was obtained from three consecutive segments of the mid-femoral region in the left sciatic nerve in both diabetic (4 and 24 weeks) and nondiabetic, age-matched animals. Over time, phosphofructokinase activity significantly decreased (p less than 0.05) with diabetes, with no effect demonstrated within similar age-groups. The accumulation of phosphofructokinase activity was accomplished by ligating the mid-femoral region of the right sciatic nerve for 24 h. Anterograde and retrograde axonal transport of phosphofructokinase was measured in the 3-mm segment proximal and distal to the ligature, respectively. There was a trend (p = 0.0627) towards a decline in net proximal accumulation (mean proximal minus mean background) with age. Net distal (mean distal minus mean background) activity declined by 80% (p less than 0.05) in the control group between 4 and 24 weeks of the diabetic state. However, diabetic animals did not experience the same age-related decline in retrograde transport. The findings suggest that diabetes affects the age-associated evolution of retrograde transport, presumably a reflection of the neuropathy occurring in the distal axon branches, without altering anterograde transport to any appreciable extent.     

Effect of regional hyperemia on myocardial uptake of 2-deoxy-2-[(18)F]fluoro-D-glucose

2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) may be used to predict glucose kinetics when the factor relating differences in transport and phosphorylation between compounds remains constant ("lumped constant"). It is not clear whether hyperemia alters that factor. In anesthetized swine, myocardial FDG uptake was estimated by positron emission tomography, during an intracoronary infusion of either adenosine, ATP, or bradykinin (40 microg x kg(-1) x min(-1), 40 microg x kg(-1) x min(-1), and 2 nmol x kg(-1) x min(-1), respectively; n = 6 for all groups). In controls during normal perfusion (n = 6), FDG uptake was 0.78 +/- 0.32 micromol x g(-1) x min(-1), whereas glucose uptake by Fick was 0.71 +/- 0.25 micromol x g(-1) x min(-1) (r = 0.73; P < 0.05). Adenosine increased blood flow from 1.29 +/- 0.43 to 4.80 +/- 2.19 ml x g(-1) x min(-1) (P < 0.05) and glucose uptake from 1.16 +/- 1.10 to 3.35 +/- 2.12 micromol x g(-1) x min(-1) (P < 0.05), whereas FDG uptake in the hyperemic region was lower than remote regions (0.46 +/- 0.29 and 0.95 +/- 0.55 micromol x g(-1) x min(-1), respectively; P < 0.05). In the ATP and bradykinin groups, blood flow increased four- and twofold, respectively, with no net change in glucose uptake. FDG uptake in the hyperemic region was also significantly lower than remote regions. For all animals, the ratio of blood flow in the hyperemic region relative to remote region was inversely proportional to the ratio of FDG uptake in the same regions (r(2)=0.73; P < 0.001). Because nitric oxide elaboration during hyperemia could potentially alter substrate preference and FDG kinetics, six additional swine were studied during maximal adenosine before and after intracoronary N(G)-monomethyl-L-arginine (1.5 mg/kg). Inhibition of nitric oxide had no effect on either regional myocardial substrate uptake or FDG accumulation. In conclusion, hyperemia decreased regional myocardial FDG uptake relative to normally perfused regions and this effect on the lumped constant was independent of nitric oxide.     

Cytogenetic effects of acrylamide in the bone marrow of mice

A single i.p. injection of 100 mg/kg acrylamide monomer elevated the frequency of chromosome aberrations and micronucleated polychromatic erythrocytes in the bone marrow of male ICR mice. A positive relationship between frequency of micronuclei and dose of acrylamide was obtained in the dose range of 2 x 25, 2 x 50 and 2 x 100 mg/kg.     

Study of acute pharmacologic effects of prolactin on calcium and water transport in the rat colon by an in vivo perfusion technique

We investigated the acute effect of intraperitoneally administered prolactin on calcium and water transport in colon of sexually mature female Wistar rats using an in vivo perfusion technique. Test solution containing (in mM) NaCl, 100; KCl, 4.7; MgSO4, 1.2; CaCl2, 20; D-glucose, 11; sodium ferrocyanide (Na4Fe(CN)6), an index of net water transport, 20; and 0.7 (microCi 45CaCl2 (1 Ci = 37 GBq) was perfused througth the 8-cm colonic loop for 60 min at perfusion rates of 0.5 or 1.0 mL x min(-1). Calcium and water transport was also studied under a no flow condition to stimulate the condition often found in the colon by in vivo ligated colonic loop for 30 min. Control results showed no correlation between calcium transport and water flux. Flow of luminal solution at 0.5 and 1.0 mL x min(-1) was found to reverse net calcium absorption from 0.04+/-0.01 nmol x g(-1) dry weight x h(-1) to net calcium secretion of 0.04+/-0.04 and 0.9+/-0.02 nmol x g(-1) dry weight x h(-1), respectively. Neither 0.4, 0.6, nor 1.0 mg x kg(-1) prolactin had any effect on calcium fluxes in the colon. On the other hand, at a perfusion rate of 1 mL x min(-1), 0.4 mg x kg(-1) prolactin significantly decreased net water absorption from 3.86+/-0.90 to 0.88+/-0.64 mL x g(-1) dry weight x h(-1) (P < 0.001), and the higher doses of 0.6 and 1.0 mg x kg(-1) prolactin reversed net water absorption to net water secretion of 2.20+/-0.63 and 2.33+/-0.89 mL x g(-1) dry weight x h(-1), respectively (P < 0.001). The stimulatory effect of prolactin on water transport was completely abolished by reducing the perfusion rate from 1.0 mL x min(-1) to zero. The stimulatory effect of prolactin on water secretion at perfusion rate of 1.0 mL x min(-1) was also abolished when luminal [Na+] was reduced from 180 to 80 mM. We concluded that, unlike in the small intestine, calcium fluxes in the colon are not related to water transport and did not respond at all to prolactin. Water transport, on the other hand, was reversed from net absorption to secretion by prolactin. We propose that this prolactin-induced water secretion is probably mediated by recycling of luminal sodium in the vicinity of tight junctions.     

Methylprednisolone increases plasma leptin levels in Graves' hyperthyroidism patients with active Graves' ophthalmopathy.

Whether leptin, a product of the ob gene, can be stimulated by glucocorticoid administration has been an issue of controversy. We investigated the effect of intravenous administration of methylprednisolone (500 mg/day x 3 days) on plasma levels of leptin in 16 patients (female/male = 11/5) with Graves' hyperthyroidism and active ophthalmopathy who received pulse therapy. Significant elevation of plasma leptin levels started at the eighth hour (13.9+/-1.8 ng/mL, p=0.042) and lasted until the 72nd hour (21.2+/-5.0 ng/mL, p=0.009), as compared with basal levels (8.8+/-1.2 ng/mL). When methylprednisolone was replaced with oral prednisolone (10 mg three times per day x 2 weeks), no difference in plasma leptin levels was noted compared with basal measurement. Under methylprednisolone administration, a significant suppression of tumor necrosis factor-alpha began at the 24th hour (8.1+/-1.3 pg/mL, p=0.004) and lasted until the 48th hour (8.1+/-1.0 pg/mL, p=0.008), as compared with basal measurement (12.5+/-1.5 pg/mL). Compared with basal levels (93+/-2 mg/dL), significant elevation in the plasma glucose level started at the third hour (135+/-10 mg/dL, p=0.000) and lasted until the 72nd hour (110+/-4 mg/dL, p=0.019). The timing of serum insulin elevation approximated that of plasma glucose (3 hours: 14+/-3 microU/mL, p=0.006) and lasted until the end of prednisolone administration (2 weeks: 12+/-2 microU/mL, p=0.044), when compared with basal levels (14+/-3 microU/mL). We concluded that the parental administration of pharmacological doses of methylprednisolone to patients with Graves' hyperthyroidism could acutely raise their plasma level of leptin.     

Prolactin directly enhanced Na+/K+- and Ca2+-ATPase activities in the duodenum of female rats

Prolactin has recently been shown to directly stimulate 2 components of the active duodenal calcium transport in female rats, i.e., solvent drag-induced and transcellular-active calcium transport. Since the basolateral Na(+)/K(+)- and Ca(2+)-ATPases, respectively, play important roles in these 2 transport mechanisms, the present study aimed to examine the direct actions of prolactin on the activities of both transporters in sexually mature female Wistar rats. The results showed that 200, 400, and 800 ng/mL prolactin produced a significant increase in the total ATPase activity of duodenal crude homogenate in a dose-dependent manner within 60 min (i.e., from a control value of 1.53 +/- 0.13 to 2.29 +/- 0.21 (p < 0.05), 2.68 +/- 0.19 (p < 0.01), and 3.92 +/- 0.33 (p < 0.001) micromol Pi x (mg protein)(-1) x min(-1), respectively). Activity of Na+/K+-ATPase was increased by 800 ng/mL prolactin from 0.17 +/- 0.03 to 1.18 +/- 0.29 micromol Pi x (mg protein)(-1) x min(-1) (p < 0.01). Prolactin at doses of 400 and 600 ng/mL also significantly increased the activities of Ca(2+)-ATPase in crude homogenate from a control value of 0.84 +/- 0.03 to 1.75 +/- 0.29 (p < 0.05), and 2.30 +/- 0.37 (p < 0.001) micromol Pi x (mg protein)(-1) x min(-1). When the crude homogenate was purified for the basolateral membrane, the Na(+)/K(+)-ATPase activities were elevated 10-fold. In the purified homogenate, 800 ng/mL prolactin increased Na(+)/K(+)-ATPase activity from 1.79 +/- 0.38 to 2.63 +/- 0.44 micromol Pi x (mg protein)(-1) x min(-1) (p < 0.05), and Ca(2+)-ATPase activity from 0.08 +/- 0.14 to 2.03 +/- 0.23 micromol Pi x (mg protein)(-1) x min-1 (p < 0.001). Because the apical calcium entry was the first important step for the transcellular active calcium transport, the brush border calcium uptake was also investigated in this study. We found that, 8 min after being directly exposed to 800 ng/mL prolactin, the brush border calcium uptake into the duodenal epithelial cells was increased from 0.31 +/- 0.02 to 0.80 +/- 0.28 nmol x (mg protein)(-1) (p < 0.05). It was concluded that prolactin directly and rapidly enhanced the brush border calcium uptake as well as the activities of the basolateral Na(+)/K(+)- and Ca(2+)-ATPases in the duodenal epithelium of female rats. These findings explained the mechanisms by which prolactin stimulated duodenal active calcium absorption.     

Effective Suppression of Acrylamide Neurotoxicity by Lithium in Mouse

The primary objective of this investigation was to assess the neuroprotective efficacy of lithium in an acrylamide (ACR)-induced neuropathy model in mice. In this study, Kunming male mice were administered ACR (25 mg/kg bw, i.p. once a day) with or without lithium (25 mg/kg bw, i.p. once a day) for 2 weeks. All ACR-administered mice exhibited severe symptoms of neuropathy. We found that treatment with lithium effectively alleviated behavioral deficits in animals elicited by acrylamide. Interestingly, the reduction of hippocampal neurogenesis resulting from ACR injection was promoted by administration of lithium. Further, lithium treatment significantly offset ACR-induced depletion in p-GSK-3β (Ser9) levels in hippocampus. Collectively our findings suggest the propensity of lithium to attenuate ACR-induced neuropathy. Further studies are necessary to understand the precise molecular mechanism by which the lithium attenuates neuropathy. Nevertheless, our data clearly demonstrate the beneficial effects of lithium on ACR-induced neuropathy in mice and suggest its possible therapeutic application as an adjuvant in the management of other forms of neuropathy in humans.     

Prophylactic effects of magnesium and vitamin E in rat spinal cord radiation damage: evaluation based on lipid peroxidation levels

This study investigated the neuroprotective effects of magnesium sulfate prophylaxis and vitamin E prophylaxis in a rat model of spinal cord radiation injury. Groups were subjected to different treatment conditions for 5 days prior to irradiation, and outcomes were evaluated on the basis of lipid peroxidation levels in cord tissue. Four groups of rats were investigated: no radiation/treatment (n = 4), intraperitoneal (i.p.) saline 1 ml/day (n = 6), i.p. vitamin E 100 mg/kg/day (n = 6), and i.p. magnesium sulfate 600 mg/kg/day (n = 6). The thoracic cord of each non-control rat was exposed to 20 Gy radiation in a LINAC system using 6 MV x-rays, and malondialdehyde (MDA) levels (reflecting lipid peroxidation level) were determined 24 hours post-irradiation. The MDA levels in thoracic cord segments from the control rats were used to determine baseline lipid peroxidation. The mean levels in the control, saline-only, vitamin E, and magnesium sulfate groups were 12.12 +/- 0.63, 27.0 +/- 2.81, 17.71 +/- 0.44, and 14.40 +/- 0.47 nmol/mg tissue, respectively. The MDA levels in the saline-only group were significantly higher than baseline, and the levels in the vitamin E group were significantly lower than those in the saline group (P < 0.05 for both). The levels in the magnesium sulfate group were dramatically lower than those in the saline group (P < 0.001). The results indicate that i.p. magnesium sulfate has a marked neuroprotective effect against radiation-induced oxidative stress in the rat spinal cord.     

STUDIES ON AXOPLASMIC TRANSPORT OF INDIVIDUAL PROTEINS: 1–ACETYLCHOLINESTERASE (AChE) IN ACRYLAMIDE NEUROPATHY

Abstract— The axoplasmic transport rate and distribution of acetylcholinesterase (AChe, EC 3.1.1.7) was studied in the sciatic nerves of normal rats and those with a neuropathy due to acrylamide, by measuring the accumulation of the enzyme proximal to single and double ligatures. The single ligature experiments showed that the apparent transport rate of AChE was decreased in acrylamide neuropathy. The double ligature experiments indicated that only 8.1% of AChE was mobile in normal rat sciatic nerve. The mobility of the enzyme in acrylamide-treated rat sciatic nerves was altered to 11.8%. The absolute transport rate of AChE in normal rat sciatic nerve was 567 mm/24 h, and in acrylamide neuropathy it was decreased to 287 mm/24 h.
The amount of AChE activity transported in normal rat sciatic nerve was 2.64 μmol/24 h. The rats with acrylamide neuropathy showed a decrease in the amount of AChE activity moving in the orthograde direction (2.03 μmol/24 h).
The colchicine-binding properties of tubulin protein from sciatic nerves of normal and acrylamide-treated rats were studied. In rats with acrylamide neuropathy, a marked decrease of 75% in tubulin-colchicine binding was observed.     

Regulation of endogenous glucose production after a mixed meal in type 2 diabetes

The extent and time course of suppression of endogenous glucose production (EGP) in type 2 diabetes after a mixed meal have been determined using a new tracer methodology. Groups of age-, sex-, and weight-matched normal controls (n = 8) and diet-controlled type 2 diabetic subjects (n = 8) were studied after ingesting a standard mixed meal (550 kcal; 67% carbohydrate, 19% fat, 14% protein). There was an early insulin increment in both groups such that, by 20 min, plasma insulin levels were 266 +/- 54 and 190 +/- 53 pmol/l, respectively. EGP was similar basally [2.55 +/- 0.12 mg x kg(-1) x min(-1) in control subjects vs. 2.92 +/- 0.16 mg x kg(-1) x min(-1) in the patients (P = 0.09)]. After glucose ingestion, EGP declined rapidly in both groups to approximately 50% of basal within 30 min of the meal. Despite the initial rapid decrease, the EGP was significantly greater in the diabetic group at 60 min (1.75 +/- 0.12 vs. 1.05 +/- 0.14 mg x kg(-1) x min(-1); P < 0.01) and did not reach nadir until 210 min (0.96 +/- 0.17 mg x kg(-1) x min(-1)). Between 60 and 240 min, EGP was 47% higher in the diabetic group (0.89 +/- 0.09 vs. 1.31 +/- 0.13 mg x kg(-1) x min(-1), P < 0.02). These data quantitate the initial rapid suppression of EGP after a mixed meal in type 2 diabetes and the contribution of continuing excess glucose production to subsequent hyperglycemia.