Stimulation of nerve growth factor and substance P expression in the iris–trigeminal axis of diabetic rats—involvement of oxidative stress and effects of aldose reductase inhibition

In rats with streptozotocin-induced diabetes, we measured increased (by 61%; P<0.05) mRNA for nerve growth factor (NGF) in the iris together with increased (by 82%; P<0.05) mRNA for preprotachykinin (the substance P precursor) in the trigeminal ganglion, suggesting that increased NGF was driving increased substance P gene expression. In other diabetic rats, these changes were prevented by treatment with either an antioxidant (butylated hydroxytoluene; 1% by diet) or an aldose reductase inhibitor (ARI) (sorbinil; 25 mg/kg/day p.o.) and the sorbinil treatment was associated with significant inhibition of polyol pathway intermediates in both lens and sciatic nerve. This suggests that polyol pathway activity in the lens may translate to oxidative stress-driving stimulation of NGF gene expression in the iris. The change is selective for NGF, because expression of the analogous neurotrophin, neurotrophin-3 (NT-3), was unaltered in the same irises. These changes suggest that oxidative stress and/or inflammation can drive up NGF expression in diabetes—a mechanism that might participate in iritis.     

Triazolam-induced changes in alcoholic thought processes

 This study was designed to examine and contrast cognitive effects (explicit memory and access to semantic knowledge) of the benzodiazepine Halcion (triazolam) in ten normal volunteers and ten cognitively unimpaired detoxified alcoholics. The two groups were indistinguishable from one another under placebo conditions on all measures of cognitive functioning. Under Halcion test conditions (0.375 mg PO), both groups were about equally impaired in their recall of to-be-remembered information. However, alcoholics, were more likely to recall information that they were not asked to remember (intrusion errors) on all measures of explicit remembering. Alcoholics also generated relatively uncommon (low frequency) responses from semantic memory, rather than common, categorically related associations in response to stimuli such as types of vegetables, flowers, and fruit following the administration of Halcion, but were not different from normal volunteers in the types of responses generated under placebo conditions. These findings suggest that a drug challenge that simulates many of the effects of acute alcohol administration induces alcoholics to think and remember differently (qualitatively) from normal volunteers. Received: 7 July 1997 / Final version: 22 September 1997     

Gut contents: A significant contaminant of Mytilus edulis whole body metal concentrations

Ingested matter can have a significant effect on whole body metal concentration measurements in Mytilus edulis. Depuration of mussels in clean seawater for 36 h prior to dissection eliminates most of these contaminating gut contents. Depuration followed by metal analyses is the most direct method of determining mussel tissue metal bioburdens. After being transplanted into a plume of primary treated sewage effluent in Salem Harbor, Massachusetts for 32 days, Al, Cr, and Fe concentrations in depurated mussels were significantly lower than those determined for either non-depurated mussels or for depurated mussels to which fecal concentrations of Al, Cr, and Fe were added back in. Although mathematical methods developed by both Ouellette (1978) and Boehm et al. (1988) could be applied to non-depurated mussels in order to correct for errors associated with gut metal contamination, these indirect methods were not as reliable as depuration prior to analysis.     

Regulation of the acid-labile subunit of the insulin-like growth factor ternary complex in patients with insulin-dependent diabetes mellitus and severe burns

OBJECTIVE Little information is available regarding the regulation of serum acid-labile subunit (ALS) in human disease. We have studied alterations in serum ALS of the insulin-like growth factor (IGF) ternary complex in children with untreated insulin-dependent diabetes mellitus (IDDM) and subjects with severe burns before and after insulin therapy. In addition, we have investigated the effect of insulin plus GH on serum ALS in burn patients. DESIGN Serum samples were obtained from children with newly diagnosed and untreated IDDM before the initiation of insulin therapy and 1 month thereafter. Serum samples were also obtained from adult patients with severe burns who were on a continuous infusion of a carbohydrate-rich enteral diet via nasogastric and duodenal catheters under basal conditions, after a 1-week period of continuous insulin infusion, and after an additional week of insulin plus recombinant GH. PATIENTS Twenty children and adolescents with untreated IDDM, aged 1.2–16 years, and 6 young adult patients with severe burns aged 17–28 years were studied longitudinally. Control sera were obtained from age, sex and pubertal status matched subjects (for children with IDDM) and from fed healthy adults. MEASUREMENTS Serum insulin, GH, cortisol and IGF-I were measured by radioimmunoassay, and serum ALS levels were assessed by Western immunoblot before and after treatment periods. RESULTS Serum ALS levels were lower in untreated children with IDDM (69 ± 6% of control children). Insulin therapy significantly increased serum ALS (79 ± 5%, P<0.05) in these children. Patients with severe burns also had lower serum ALS levels (79 ± 10% of control adults). After one week of insulin therapy serum ALS levels increased to 90 ± 15% of control values (P<0.05). Addition of GH to insulin therapy for another week did not significantly further increase serum ALS levels (95 ± 27%). Serum IGF-I concentrations increased nearly 2.5-fold in diabetic subjects and fourfold in burn subjects at the end of the study periods. There were no proteolytic fragments of ALS in the sera studied. The deglycosylation pattern of ALS did not differ between diabetic and control sera. CONCLUSION Serum ALS levels were diminished in children with untreated IDDM and were partially restored after the initiation of insulin therapy. Serum ALS levels were also diminished in patients with severe burn injury and restored by insulin treatment. Addition of GH to insulin therapy did not significantly increase serum ALS levels over levels obtained during insulin therapy alone. These decreases in serum ALS were smaller than the decrease in serum IGF-I concentrations in both conditions, suggesting that IGF-I is the limiting factor for the ternary complex formation in the catabolic states. Insulin may regulate circulating ALS levels in catabolic states and helps to restore the IGF system.     

TNFα Inhibits Schwann Cell Proliferation, Connexin46 Expression, and Gap Junctional Communication

Schwann cell responses to nerve injury are stimulated, in part, by inflammatory cytokines. This study compares changes in the phenotype of cultured Schwann cells after exposure to the cytokine tumor necrosis factor (TNF)-α or the mitogen neu differentiation factor (NDF)-β. TNFα inhibited proliferation in a dose-dependent manner without altering Schwann cell survival. TNFα also reduced both gap junctional conductance and Lucifer yellow dye coupling between Schwann cells. Moreover, both P₀and glial fibrillary acidic protein (GFAP) immunoreactivity were reduced. By contrast, NDFβ initially had little effect on cell division although it reduced junctional coupling within 8 h. However, by 48 h, NDFβ stimulated proliferation with a concomitant increase in coupling. Dividing Schwann cells (BrdU⁺) were preferentially dye coupled compared to nondividing cells, indicating an association between proliferation and coupling. Moreover, cultured Schwann cells expressed connexin46 mRNA and protein, and changes in the levels of the protein correlated with the degree of proliferation and coupling. The data thus provide evidence for cytokine-induced modulation of Schwann cell antigenic phenotype, proliferation, and gap junction properties. These observations suggest that enhanced gap junctional communication among Schwann cells after nerve injury could help to coordinate cellular responses to the injury, and that TNFα may be a signal which terminates proliferation as well as junctional communication.     

Development of Activity Assays for High-Volume Evaluation of Human Immunodeficiency Virus (HIV) Protease Inhibitors in Rat Serum: Results with Ditekiren

We showed previously that a commercially available synthetic tetradecapeptide, Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Leu-Val-Tyr-Ser, produces authentic angiotensin I (Ang I) upon incubation with the HIV-1 protease (S. K. Sharma et al., Anal. Biochem. 198:363, 1991). Therefore, we developed an Ang-I based activity assay for HIV protease inhibitors based on the technology developed earlier (M. J. Ruwart et al., Pharm. Res. 7:407, 1990; S. K. Sharma et al., Anal. Biochem. 186:24, 1990) for tracking renin inhibitors in rat sera. Ditekiren was either extracted from sera with ethyl acetate or assayed after the interfering substances in sera were precipitated with acetonitrile. Purified recombinant HIV-1 protease was added to extracted rat serum and the enzymatic reaction was initiated in the presence of the tetradecapeptide substrate. The inhibition of Ang I production was measured by a commercially available RIA kit. The cleanup methodology also enabled a commercially available Proteinase Scintillation Proximity Assay (SPA, Amersham) to quantify ditekiren in rat serum through the addition of recombinant HIV-1 protease and cleavage of substrate from SPA beads. Results were confirmed by HPLC or by the renin assay for ditekiren, which inhibits both aspartyl proteases. These technologies should prove useful for assessing serum levels of HIV protease inhibitors in rat.     

PDGF AA as mediator in nicotine-dependent carcinogenesis

Effect of nicotine on PDGF AA and PDGF BB interaction with cervicalcancer SiHa cells was tested. [¹²⁵I]PDGF AA was internalizedby cells and accumulated in the cytoplasm and nucleus (chromatin).In the absence of nicotine, maximal accumulation of [¹²⁵I]PDGFAA inside the cells occurred after 1 day of incubation, whichwas followed by a progressive degradation of the growth factorduring the next 2, 3 and 5 days of cell exposure. In the presenceof 0.001 or 0.01% nicotine, accumulation of [¹²⁵I]PDGF AA wasslightly higher than in the absence of nicotine, and maximalaccumulation occurred after 2 days of incubation. In the presenceof 0.1% nicotine, maximal accumulation occurred after 5 daysof incubation and was 20 and 14 times higher in the cytoplasmand chromatin, respectively. Nicotine-postponed degradationand increased nuclear accumulation of PDGF AA resulted in activationof RNA synthesis and cell proliferation. PDGF BB, which wasnot internalized by cells did not respond to nicotine treatment.The proposed mechanism of nicotine-PDGF AA co-carcinogenesismay involve inhibition of growth factor degradation at the lysosomallevel and an increased chromatin accumulation of the non-degradedPDGF.     

Relative effect of surgery and radiotherapy on the internal jugular vein following functional neck dissection

We examined the internal jugular veins in three groups of patients who had undergone (1) a functional neck dissection and radiotherapy, (2) a functional neck dissection alone, or (3) radiotherapy alone, using a noninvasive color Doppler ultrasound scan. The internal jugular veins were ultrasonically bilaterally normal in 18% of patients who had undergone a functional neck dissection and radiotherapy, in 88% of patients who had undergone a functional neck dissection alone, and in 57% of patients who had undergone radiotherapy alone. The combination of a functional neck dissection and radiotherapy significantly affected the internal jugular vein when compared with a functional neck dissection alone.     

Dexmedetomidine Produces Similar Alterations in the Determinants of Left Ventricular Afterload in Conscious Dogs before and after the Development of Pacing-induced Cardiomyopathy

Background: The authors tested the hypothesis that intravenous dexmedetomidine produces alterations in left ventricular (LV) afterload that are deleterious to cardiac performance in conscious dogs with pacing-induced cardiomyopathy.

Methods: Dogs (n = 8) were fitted with instruments for long-term measurement of LV and aortic blood pressure, aortic blood flow, and subendocardial segment length and received dexmedetomidine (1.25, 2.5, and 5 [micro sign]g/kg) in a cumulative manner before and after 19 +/- 3 (mean +/- SEM) days of rapid LV pacing. LV afterload was measured with aortic input impedance [Zin ([Greek small letter omega]) and quantified with a three-element Windkessel model. Hemodynamics and Zin ([Greek small letter omega]) were assessed under control conditions and 5 and 60 min after administration of each dose.

Results: Dexmedetomidine caused early and late decreases in heart rate, the maximum rate of increase of LV pressure, mean aortic blood flow, and stroke volume in dogs before and after pacing. Dexmedetomidine caused similar early increases in total arterial resistance and decreases in total arterial compliance in dogs before and after pacing. Early dexmedetomidine-induced increases in resistance and decreases in compliance caused similar reductions in mean aortic blood flow in cardiomyopathic compared with healthy dogs. Resistance and compliance returned to control values, and characteristic aortic impedance decreased late after dexmedetomidine in healthy dogs. In contrast, resistance remained elevated late after dexmedetomidine in dogs with dilated cardiomyopathy.