Peroxynitrite reaction products of 3',5'-di-O-acetyl-8-oxo-7, 8-dihydro-2'-deoxyguanosine

Of the DNA bases, peroxynitrite (ONOO-) is most reactive toward 2'-deoxyguanosine (dGuo), but even more reactive with 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodGuo), requiring a 1,000-fold excess of dGuo to provide 50% protection against the reaction with 8-oxodGuo. Therefore, it seems reasonable that 8-oxodGuo is a potentially important target in DNA and that the structures of the reaction products with ONOO- should be characterized. Using 3', 5'-di-O-Ac-8-oxodGuo as a model compound, the reaction products with ONOO- have been isolated and identified under simulated physiological reaction conditions (phosphate/bicarbonate buffer at pH 7.2). The major reaction product, II, is unstable and undergoes base-mediated hydrolysis to 2,5-diaminoimidazol-4-one, IIa, and 3-(3, 5-di-O-Ac-2-deoxy-beta-D-erythro-pentofuranosyl)-5-iminoimidazolidine -2,4-dione, IIb. The latter compound further hydrolyzes to 3-(3, 5-di-O-Ac-2-deoxy-beta-D-erythro-pentofuranosyl)oxaluric acid, IIc. Other products include 3-(3, 5-di-O-Ac-2-deoxy-beta-D-erythro-pentofuranosyl)-2,4,6-trioxo-[1,3, 5]triazinane-1-carboxamidine, I, which further hydrolyzes to 1-(3, 5-di-O-Ac-2-deoxy-beta-D-erythro-pentofuranosyl)cyanuric acid, Ia. 1-(3,5-di-O-Ac-2-deoxy-beta-D-erythro-pentofuranosyl)parabanic acid, III, is a minor product that also may contribute to formation of IIc. The major products formed in these reactions are biologically uncharacterized but are similar to modified DNA bases that have been shown to be both premutagenic and blocks to DNA polymerization.

INCIDENCE AND ETIOLOGY OF RESPIRATORY DISTRESS IN NEWBORN

Screening of 1986 consecutive live births was done for evidence of Respiratory Distress by administering Downe's scoring in a prospective study at level II nursery of a medical college. A detailed antenatal, natal and postnatal history along with detailed examination supported by relevant investigations was carried out to arrive at the etiological diagnosis of Respiratory Distress Syndrome (RDS).

RESULTS

48 newborns developed RDS during the observation period. The incidence of RDS was 2.42%. Out of these 40.4% were <1500g, 16.6% above 2500 g and the rest between 1500-2500 g. Preterm were thirty times more prone to develop RDS than full term neonates. There was no significant difference in incidence of RDS in male and female neonates. The commonest cause of RDS was hyaline membrane disease (HMD) 18.8% followed by transient tachyopnea of the newborn (TTNB) 14.5% and meconium aspiration syndrome (MAS) 12.5%. HMD was predominantly seen in the preterm in the gestational age of 29 to 32 weeks, TTNB was seen equally in term as well as preterm neonates, where as MAS was common in the term than in the preterm neonates.

Crystal structure of a murine glutathione S-transferase in complex with a glutathione conjugate of 4-hydroxynon-2-enal in one subunit and glutathione in the other: evidence of signaling across the dimer interface

mGSTA4-4, a murine glutathione S-transferase (GST) exhibiting high activity in conjugating the lipid peroxidation product 4-hydroxynon-2-enal (4-HNE) with glutathione (GSH), was crystallized in complex with the GSH conjugate of 4-HNE (GS-Hna). The structure has been solved at 2.6 A resolution, which reveals that the active site of one subunit of the dimeric enzyme binds GS-Hna, whereas the other binds GSH. A marked asymmetry between the two subunits is evident. Most noticeable are the differences in the conformation of arginine residues 69 and 15. In all GST structures published previously, the guanidino groups of R69 residues from both subunits stack at the dimer interface and are related by a (pseudo-) 2-fold axis. In the present structure of mGSTA4-4, however, the two R69 side chains point in opposite directions, although their guanidino groups remain in contact. In the subunit with bound GSH, R69 also interacts with R15, and the guanidino group of R15 points away from the active site, whereas in the subunit that binds GS-Hna, R15 pivots into the active site, which breaks its interaction with R69. According to our previous results [Nanduri et al. (1997) Arch. Biochem. Biophys. 335, 305-310], the availability of R15 in the active site assists the conjugation of 4-HNE with GSH. We propose a model for the catalytic mechanism of mGSTA4-4 in conjugating 4-HNE with GSH-i.e., the guanidino group of R15 is available in the active site of only one subunit at any given time and the stacked pair of R69 residues act as a switch that couples the concerted movement of the two R15 side chains. The alternate occupancy of 4-HNE in the two subunits has been confirmed by our kinetic analysis that shows the negative cooperativity of mGSTA4-4 for 4-HNE. Disruption of the signaling between the subunits by mutating the R69 residues released the negative cooperativity with 4-HNE.

Assessment of sodium status in large ruminants by measuring the sodium-to-potassium ratio in muzzle secretions

OBJECTIVE

To develop a simple diagnostic test to assess sodium status in large ruminants on the basis of the sodium-to-potassium ratio (Na:K) and to determine its relevance.

ANIMALS

7 buffalo heifers and 21 lactating, pregnant, and nonpregnant dairy cows and heifers.

PROCEDURE

Buffalo heifers were subjected in 2 experiments to variable dietary sodium intake or sodium depletion and changes in sodium and potassium concentrations; Na:K was simultaneously monitored in various body fluids to study its value for indicating sodium status. Validity of the muzzle secretion test was assessed.

RESULTS

Muzzle secretion and urinary Na:K and sodium concentration, but not serum electrolyte concentrations, reflected the sodium status of buffalo heifers in response to the widely variable intake of sodium (0.03 to 0.16% of dry matter [DM]). Progressive sodium depletion during an 11-day period, using saliva deprivation caused reciprocal changes in sodium and potassium concentrations in saliva and muzzle secretion, but not in urine. Decreasing urine sodium concentration was associated with decreasing urine potassium concentration. Saliva, urine, and muzzle secretion Na:K closely reflected the degree of sodium deficit.

CONCLUSIONS AND CLINICAL RELEVANCE

Buffaloes or dairy cows maintained on optimal sodium intake had muzzle secretion and urine Na:K > 0.30. Muzzle secretion or urine Na:K < 0.20 or < 0.10, respectively, was indicative of sodium deficiency. Analysis of muzzle secretion Na:K, and to a large extent urine Na:K, may be used as a convenient diagnostic tool to assess sodium status in large ruminants. It has accuracy similar to that of saliva Na:K.

Do Indo-Asians have smaller coronary arteries?

There is a widespread belief that coronary arteries are smaller in Indo-Asians. The aim of the present study was to compare the size of atheroma-free proximal and distal epicardial coronary arteries of Indo-Asians and Caucasians. We analysed normal coronary angiograms from 77 Caucasians and 39 Indo-Asians. The two groups were comparable for dominance of the coronary arteries. Indo-Asian patients had generally smaller coronary arteries, with a statistically significant difference in the mean diameters of the left main coronary artery, proximal, mid and left anterior descending, and proximal and distal right coronary artery segments. There was a non-significant trend towards smaller coronary artery segment diameters for the distal left anterior descending, proximal and distal circumflex, and obtuse marginal artery segments. However, after correction for body surface area, none of these differences in size were statistically significant. Thus, the smaller coronary arteries in Indo-Asian patients were explained by body size alone and were not due to ethnic origin per se. This finding nevertheless has important therapeutic implications, since smaller coronary arteries may give rise to technical difficulties during bypass graft and intervention procedures such as percutaneous transluminal coronary angioplasty, stents and atherectomy. On smaller arteries, atheroma may also give an impression of more severe disease than on larger diameter arteries.

Changes in renal function with percutaneous transluminal coronary angioplasty

There is concern about adverse effects on renal function in patients with prolonged cardiac intervention procedures, when contrast media is used. To investigate this further we studied changes in renal function in 104 patients (79 male, 25 female; mean age 59.2, SD 9.8) undergoing routine elective percutaneous transluminal coronary angioplasty (PTCA), where 28 (27%) patients had concomitant stent implantation. There was associated diabetes in 15 patients (14%) and previous hypertension in 44 (blood pressure >160/90 mmHg, 44%). None of the patients were known to have congestive heart failure at the time of procedure or chronic renal failure (defined as serum creatinine >200 pmol/l). There was no significant change in mean serum urea pre- and post-PTCA (mean change -0.04 mmol/l, paired t-test P=0.90). However, there was a small rise in serum creatinine pre- and post-PTCA of borderline significance (mean change +5.8 micromol/l, P=0.051). Of the whole cohort, 65 patients (63%) had a rise in mean serum creatinine, whilst 45 (43%) showed a rise in serum urea levels. This deterioration in renal function was related to a difference in the procedure duration, but there were no statistically significant differences in mean age or volume of contrast media (Iopamide 340) between patients with or without deterioration in renal function. Patients with a rise in serum creatinine had lower baseline (pre-PTCA) serum urea and serum creatinine levels. In patients undergoing stent implantation, there was a higher quantity of contrast media, screening time and procedure duration. There were no significant differences in age, pre-PTCA serum urea and creatinine levels, and mean change in serum urea or creatinine levels in patients with and without stent usage. Whilst severe renal dysfunction following PTCA is uncommon, we suggest that some caution is necessary during PTCA or other cardiac interventions where more complex or prolonged procedures necessitating large volumes of contrast media use.

Monoclonal antibody to the delta opioid receptor acts as an agonist in dual regulation of adenylate cyclase in NG108-15 cells

Monoclonal antibodies generated against multiple antigenic peptides of the N-terminal sequence (3LVPSARAELQSSPLV17) of the cloned delta opioid receptor immunoprecipitated a 58 kDa protein from CHAPS-solubilized NG108-15 membranes. The immunoprecipitates bound [3H]DPDPE--but not [3H]DAMGO--with a Kd of 6.4 nM and a Bmax of 75 pM. Western blot analysis revealed a distinct band of 58 kDa. The antibodies inhibited basal and PGE1-stimulated cAMP levels, and mimicked the effect of agonists manifest in a compensatory increase in cAMP formation. The antibody will be potentially useful in the analysis of functional epitopes on the delta opioid receptor.

Outcome of psychosis in people of African-Caribbean family origin. Population-based first-episode study

BACKGROUND

An increased incidence of psychotic disorders has repeatedly been reported among African-Caribbeans in the UK.

AIMS

To test whether the increased incidence of psychotic disorders in first- and second-generation African-Caribbeans in the UK could be caused by a relative excess of affective-related psychoses with good prognosis.

METHOD

Thirty-three patients of African-Caribbean family origin identified in a population-based study of first-episode psychoses were compared with the remaining cases. Three-year outcomes and patterns of course were compared.

RESULTS

There was a trend for better outcomes in African-Caribbean patients for symptoms and social disability, but patterns of course were similar (odds ratio = 0.9 (0.50 to 2.00)) [corrected]. Pattern of course improved after adjustment for confounding by gender, social class, age, diagnosis and duration of untreated illness (odds ratio = 0.59 (0.21 to 1.66)) [corrected]. Diagnostic profiles were similar, with no evidence of greater diagnostic instability in the African-Caribbean group.

CONCLUSION

Pattern of course of psychosis did not differ significantly by ethnic family background. An excess of good-prognosis affective psychoses is an unlikely explanation for increased rates of psychosis in African-Caribbeans.

Recognition specificity of monoclonal antibodies which protect mice against Salmonella typhimurium infection

We used enzyme-linked immunosorbent assay (ELISA), competitive inhibition ELISA, flow cytometry and western immunoblots to study the antigenic specificity of two monoclonal antibodies (mAbs) raised against the cell surface antigens of Salmonella typhimurium. These mAbs (SH6.11 and WB60.4) protect CAF1 (Ity(r)) mice against endotoxemia and mouse typhoid. We found that SH6.11 and WB60.4 recognize Salmonella serogroup B-specific lipopolysaccharide O4 and O5 factors, respectively. These mAbs did not bind to Salmonella serotypes that belong to serogroup A, D1, E4, G2, or R and did not cross-react with other enteric and nonenteric bacterial species.

Leaching behaviour of Cd, Cu, Pb and Zn in surface soils derived from dredged sediments

Leaching of heavy metals from land-disposed dredged sediment spoils is a potential environmental hazard. The leaching behavior of Cd, Cu, Pb and Zn in surface soils sampled from abandoned dredged sediment disposal sites was assessed. Using simple mass-balance calculations, the significance of the leaching test results with respect to metal migration into underlying clean soil was appraised. The potential leachability, defined as the amounts released at constant pH 4, decreased in the order (% of total contents): Zn (58%) approximately equal to Cd (49%)>Cu (5%) approximately equal to Pb (2%). The kinetics of metal release were determined in a cascade shaking test using de-mineralized water acidified to pH 4 (HNO(3)). Metal concentrations in the leachates were low and metal migration was, assuming uniform convective flow, predicted to be of no environmental concern. It is emphasized that any long-term prediction of metal migration is uncertain.

Anti-genotoxicity and glutathione S-transferase activity in mice pretreated with caffeinated and decaffeinated coffee

In vivo anti-genotoxic effects of caffeinated and decaffeinated instant coffee were compared in mice after pretreatment either by gavage for 10 consecutive days or in the drinking water for 2 weeks. Changes in hepatic sulfhydryl (-SH) content and glutathione S-transferase (GST) activity were evaluated in pretreated animals. Both caffeinated and decaffeinated instant coffee induced a moderate increase in -SH content and GST activity following pretreatment (with 70, 140 and 280 mg/kg body weight) by gavage for 10 days. This enhancement was not always dose dependent. The maximum effect on GST activity was observed at a dose of 140 mg/kg body weight/day. However, such an effect was not observed after administration of drinking water containing 2% caffeinated/decaffeinated instant coffee for 2 weeks. Results of the bone marrow micronucleus test for evaluating genotoxic effects revealed that both caffeinated and decaffeinated instant coffee (140 mg/kg body weight/day) could exert significant anti-genotoxic effects against ip injected benzo[a]pyrene (BP), cyclophosphamide (CPH), 7,12-dimethylbenz[a]anthracene (DMBA), mitomycin C (MMC) and procarbazine (PCB) in animals pretreated by gavage. Anti-genotoxic effects against BP, DMBA and urethane (URE) were evaluated in animals that received drinking water containing 2% caffeinated/decaffeinated instant coffee for 2 weeks. With the exception of the anti-genotoxic effect of decaffeinated coffee against DMBA, there was no significant change in genotoxicity after the above pretreatment. From this work, there is no evidence for any significant difference in the in vivo anti-genotoxicity of caffeinated and decaffeinated instant coffee.

Modulatory potential of clocimum oil on mouse skin papillomagenesis and the xenobiotic detoxication system

The present study was designed to elucidate the mechanistic inhibitory efficacy of clocimum (an eugenol rich variety of Ocimum gratissimum; Labiatae) oil on murine skin papillomagensis. Topical application of clocimum oil (50 microl/animal/day) during peri-initiation stage (1 week before and 2 weeks after initiation) of 7,12-dimethylbenz[a]anthracene (DMBA)-induced papillomagenesis and/or during the tumour promotion stage reduced (P < 0.05) the (i) tumour burden to 5.00, 4.41 and 4.50 (positive control value 5.27); (ii) cumulative number of papillomas to 85, 75 and 72 (positive control value : 95); and (iii) percent incidence of mice bearing papillomas to 94, 89 and 88, respectively (positive control value 94). Significant (P < 0.01) elevation in the hepatic levels of glutathione S-transferase (GST), sulfhydryl (-SH) and cytochrome b5 (Cyt. b5) was observed by the respective topical treatment of clocimum oil. Even in the skin tissue of the mouse, the topical treatment of clocimum oil enhanced (P < 0.05) the -SH content. The results suggest the modest chemopreventive potential of clocimum oil against the murine skin papillomagenesis, and such effects may be partly due to the modulated xenobiotic detoxication system enzymes.

Use of pulsed-field gel electrophoresis for molecular epidemiologic and population genetic studies of Mycobacterium tuberculosis

Pulsed-field gel electrophoresis (PFGE) is a powerful molecular biology technique which has provided important insights into the epidemiology and population biology of many pathogens. However, few studies have used PFGE for the molecular epidemiology of Mycobacterium tuberculosis. A laboratory protocol was developed to determine the typeability, stability, and reproducibility of PFGE typing of M. tuberculosis. Formal data-analytical techniques were used to assess the genetic diversity elucidated by PFGE analyses using four separate restriction enzymes and by IS6110 RFLP analyses, as well as to assess the concordance among these typing methods. One hundred epidemiologically characterized clinical isolates of M. tuberculosis were genotyped with four different PFGE enzymes (AseI, DraI, SpeI, and XbaI), as well as by RFLP analysis with IS6110. Identical patterns were found among 34 isolates known to be genetically related, suggesting that the PFGE protocol is robust and reproducible. Among 66 isolates representing population-sampled cases, heterozygosity and information content dependency estimates indicate that all five genotyping systems capture quantitatively similar levels of genetic diversity. Nevertheless, comparisons between PFGE analyses and IS6110 typing reveals that PFGE provided more discrimination among isolates with fewer than five copies of IS6110 and less clustering in isolates with five or more copies. The comparisons confirm the hypothesis that the resolution of IS6110 RFLP genotyping is dependent upon the number of IS6110 elements in the genome of isolates. The general concordance among the results obtained with four independent enzymes suggests that M. tuberculosis is a clonal organism. The availability of a robust genotyping technique largely independent of repetitive elements has implications for the molecular epidemiology of M. tuberculosis.

Inhibitory potential of Chlorella vulgaris (E-25) on mouse skin papillomagenesis and xenobiotic detoxication system

The present study assesses the modulatory potential of Chlorella vulgaris (E-25) on murine skin papillomagenesis, and the role of xenobiotic detoxication system in modulating the papillomagenesis pattern. Topical application of E-25 (500 mg/kg b.w./day) during peri-, post- or peri- and post-initiational stages of 7,12-dimethylbenz [a] anthracene (DMBA)-induced papillomagenesis, significantly modulated the a) tumor burden to 5.00, 4.33 and 3.94 (positive control value: 5.88 b) cumulative number of papillomas to 90, 78 and 67 (positive control value: 106); and c) percent incidence of mice bearing papillomas to 94, 90 and 89 respectively (positive control value: 100). E-25 treatment alone or during peri-, post- or peri- and post-initiational stages significantly elevated the sulfhydryl (-SH) and glutathlone S-transferase (GST) levels in the liver and skin tissues. However, the levels of microsomal cytochrome b5 (Cyt. b5) and cytochrome P-450 (Cyt. P-450) were not appreciably modulated by the topical treatment of E-25. The results suggest the chemopreventive potential of E-25 during peri-, post- or peri- and post-initiational stages of murine skin papillomagenesis. The possible significance of xenobiotic detoxication system in modulating the papillomagenesis pattern is discussed.

Evaluating the Health of the Nation Outcome Scales. Reliability and validity in a three-year follow-up of first-onset psychosis

BACKGROUND

The HoNOS has been developed as a routine measure of outcomes in mental health.

AIMS

To explore the validity and interrater reliability of HoNOS in a first-onset psychosis follow-up study.

METHOD

Between 1992 and 1994 we ascertained a cohort of all persons with first-onset psychosis. We re-assessed these people at 3 years (n = 166) with several outcome scales, including HoNOS. Patients' keyworkers also completed the HoNOS. We estimated concurrent validity by calculating correlations between HoNOS and other scales, and interrater reliability.

RESULTS

Researcher HoNOS correlated highly with other scales (0.46 < p < 0.86; P < 0.001). Keyworker HoNOS correlations were lower (0.41 < p < 0.51; P < 0.05), but still significant for all scores except the HoNOS-social subscale (0.12 < p < 0.28). Agreements between researcher and keyworker HoNOS were modest (0.47 < ICC < 0.85).

CONCLUSIONS

In this research cohort HoNOS correlates well with established outcome scales. Keyworker ratings show similar, but weaker, relationships; its use in routine settings may require further training for calibration of severity.

HIV-1 Gag shares a signature motif with annexin (Anx7), which is required for virus replication

Genetic and biochemical analyses of the Gag protein of HIV-1 indicate a crucial role for this protein in several functions related to viral replication, including viral assembly. It has been suggested that Gag may fulfill some of the functions by recruiting host cellular protein(s). In our effort to identify structural and functional homologies between Gag and cellular cytoskeletal and secretory proteins involved in transport, we observed that HIV-1 Gag contains a unique PGQM motif in the capsid region. This motif was initially noted in the regulatory domain of synexin the membrane fusion protein of Xenopus laevis. To evaluate the functional significance of the highly conserved PGQM motif, we introduced alanine (A) in place of individual residues of the PGQM and deleted the motif altogether in a Gag expression plasmid and in an HIV-1 proviral DNA. The proviral DNA containing mutations in the PGQM motif showed altered expression, assembly, and release of viral particles in comparison to parental (NL4-3) DNA. When tested in multiple- and single-round replication assays, the mutant viruses exhibited distinct replication phenotypes; the viruses containing the A for the G and Q residues failed to replicate, whereas A in place of the P and M residues did not inhibit viral replication. Deletion of the tetrapeptide also resulted in the inhibition of replication. These results suggest that the PGQM motif may play an important role in the infection process of HIV-1 by facilitating protein-protein interactions between viral and/or viral and cellular proteins.

Ethanol inhibits G-protein-mediated glucose uptake by C6 glioma cells

The mechanism of ethanol inhibition of glucose uptake was investigated using C6 glioma cells. Basal [3H]2-deoxy-D-glucose (2DG) uptake by C6 cells was inhibited by ethanol in a concentration-dependent manner. Fifty, 75 and 100 mM ethanol significantly inhibited basal 2DG uptake by 12, 20 and 23%, respectively (p < 0.05). Carbachol (an agonist acting via G protein-coupled receptors) stimulated the uptake by 26% (p < 0.05). In the presence of 100 mM ethanol, the ability of carbachol to stimulate 2DG uptake was abolished. In contrast, ethanol did not inhibit the ability of insulin to stimulate 2DG uptake. These results suggest that ethanol inhibits 2DG uptake by selectively interfering with G protein-mediated signal transduction pathway.

Nickel uptake by Pseudomonas aeruginosa: role of modifying factors

Pseudomonas aeruginosa cells growing in minimal medium were 40-fold more sensitive to Ni2+ than cells growing in enriched medium, suggesting a possible protective role of medium ingredients. Likewise, cells pre-grown in enriched medium showed a high Km (6.15 mM) and increased Ni2+ uptake (950 nmol mg-1 protein, 1h) over cells pre-sown in minimal medium (Km, 0.48 mM; 146 nmol mg-1 protein, 1 h). The overall pattern indicates that cells pre-grown in enriched medium were characterized by having lowered affinity towards Ni2+ than those with minimal medium background. The enhanced Ni2+ uptake by enriched medium-grown cells can be correlated with the improved metabolic state of the cells. Ni2+ uptake was optimum at neutrality (pH 7.0). A major Ni2+ transport system was competitively inhibited by Mg2+, Zn2+, Cd2+, or Co2+ (400 microM each). Noticeably, a minor Ni2+ transport pathway was still operative even in the higher concentration range of Mg2+ (4 mM and 40 mM). The stimulation of Ni2+ uptake monitored in the presence of different carbon sources (0.5% wt/vol, each) showed the sequence: glucose (1.6-fold) > phenol = gallic acid (1.5-fold). Succinate, in comparison, reduced Ni2+ uptake (0.5-fold) possibly because of its acting as a metal chelator as well. Sensitivity of Ni2+ transport towards methyl viologen, azide, 2-4 DNP, and DCCD suggested that transport was energy-linked.

Respiratory pressures in normal Indian subjects

Regression equations for the prediction of maximum inspiratory pressures (MIP) in North Indian adults are reported, based on observations in 120 females and 153 males. Age and sex were the only significant predictor variables. MIP was significantly related to vital capacity, FEV1 and peak flow rate. The MIP observed in the present study are similar to those reported earlier in Caucasians and Chinese. The lower lung volumes and flow rates in Indians are not explained by differences in MIP.

Aortic coarctation diagnosed after hypertension in pregnancy

Coarctation of the aorta is an unusual cause of hypertension in pregnancy because the disorder in adults is often unrecognized by obstetricians or general practitioners managing antenatal clinics. We report 3 women with adult coarctation of the aorta that was diagnosed in the hypertension clinic after hypertensive pregnancies where the diagnosis had been missed.

Role of microtubules in glucose uptake by C6 glioma cells

Drugs that influence tubulin function were used to investigate the role of microtubules in hexose uptake by C6 glioma cells. In C6 cells, colchicine and vinblastine (which inhibit tubulin polymerization) inhibited radioactive [3H]2-deoxy-D-glucose uptake by about 30%. Paclitaxel (which promotes tubulin polymerization) stimulated hexose uptake by about 25%. To further demonstrate that microtubules play a role in hexose uptake, C6 cells were transfected with GLUT1 cDNA and then challenged with 100 nM paclitaxel. In GLUT1-transfected cells paclitaxel stimulated 2-deoxy-D-glucose uptake by about 35%. To study the role of tubulin in agonist-stimulated hexose uptake, the effect of colchicine on carbachol-induced uptake was next examined. Hexose uptake was increased with carbachol in concentration-dependent manner which was abolished by pretreatment with colchicine. To examine the specificity of the inhibitory effect of colchicine on G protein-mediated signal transduction pathway, the influence of colchicine on insulin (which acts via tyrosine kinase pathway) stimulation of 2-deoxy-D-glucose uptake was investigated. Hexose uptake was increased by insulin in a concentration-dependent manner which was unaffected by pretreatment with colchicine. These results suggest that microtubules are involved in basal and carbachol-stimulated glucose uptake by C6 cells.