Effects of proteins from culture medium on surface property of silanes- functionalized magnetic nanoparticles

Monodisperse magnetic nanoparticles (MNPs) were synthesized by thermal decomposition of iron-oleate and functionalized with silanes bearing various functional groups such as amino group (NH2), short-chain poly(ethylene glycol) (PEG), and carboxylic group (COOH). Then, silanes-functionalized magnetic nanoparticles (silanes-MNPs) were incubated in cell culture medium plus fetal calf serum to investigate the effects of proteins from culture medium on surface property of MNPs. Zeta potential measurements showed that although surface charges of silanes-MNPs were different, they exhibited negative charges at neutral pH and approximate isoelectric points after they were incubated in cell culture medium. The reason was that silanes-MNPs could easily adsorb proteins from culture medium via non-covalent binding, resulting in the formation of protein-silanes-MNPs conjugates. Moreover, silanes-MNPs with various functional groups had different adsorption capacity to proteins, as confirmed by Coomassie blue fast staining method. The in vitro cell experiments showed that protein-silanes-MNPs had higher cellular uptake by cancer cells than silanes-MNPs.

Stability of hydrophilic magnetic nanoparticles under biologically relevant conditions

Hydrophilic 2,3-dimercaptosuccinnic acid (HOOC-CH(SH)-CH(SH)-COOH, DMSA) coated monodisperse magnetic nanoparticles (Fe3O4) were dispersed in water, RPMI-1640 with 10% (v/v) fetal calf serum, RPMI-1640, PBS and MES, respectively, to investigate their stability under biologically relevant conditions. The Photon Correlation Spectroscopy (PCS) results showed that DMSA-Fe3O4 nanoparticles existed as aggregate under biological conditions. UV-vis, MRI and AFM results indicated that DMSA-Fe3O4 nanoparticles dispersed in RPMI-1640, PBS and MES presented poor stability, whereas those dispersed in RPMI-1640 with fetal calf serum exhibited excellent stability, which was due to their adsorption from fetal calf serum, as confirmed by zeta potential and IR results. Additionally, in vitro cell experiments showed that DMSA-Fe3O4 nanoparticles with adsorption from fetal calf serum had higher intracellular uptake than those without adsorption from serum, indicating that fetal calf serum could play a great role in intracellular uptake of nanoparticles.

Extractive spectrophotometric determination of TRODAT-1 hydrochloride in lyophilized kit

A simple, sensitive, and accurate spectrophotometric method has been developed for the assay of TRODAT-1 hydrochloride in lyophilized kit. The method is based on the formation of ion-pair association complex of TRODAT-1 with bromothymol blue (BTB) in disodium hydrogen phosphate/citric acid buffer of pH 4.0. The colored product was extracted with chloroform, and measured spectrophotometrically at 414 nm. Beer's law was obeyed in the range of 5-25 microg/ml with molar absorptivity of 2.75 x 10(4) l/mol/cm. Optimization of experimental conditions was described for the method. The proposed method has been successfully applied for the analysis of TRODAT-1 hydrochloride in lyophilized kit. No interference with pharmaceutical excipients was observed.

Effect of exercise intensity and hypoxia on skeletal muscle AMPK signaling and substrate metabolism in humans

We compared in human skeletal muscle the effect of absolute vs. relative exercise intensity on AMP-activated protein kinase (AMPK) signaling and substrate metabolism under normoxic and hypoxic conditions. Eight untrained males cycled for 30 min under hypoxic conditions (11.5% O(2), 111 +/- 12 W, 72 +/- 3% hypoxia Vo(2 peak); 72% Hypoxia) or under normoxic conditions (20.9% O(2)) matched to the same absolute (111 +/- 12 W, 51 +/- 1% normoxia Vo(2 peak); 51% Normoxia) or relative (to Vo(2 peak)) intensity (171 +/- 18 W, 73 +/- 1% normoxia Vo(2 peak); 73% Normoxia). Increases (P < 0.05) in AMPK activity, AMPKalpha Thr(172) phosphorylation, ACCbeta Ser(221) phosphorylation, free AMP content, and glucose clearance were more influenced by the absolute than by the relative exercise intensity, being greatest in 73% Normoxia with no difference between 51% Normoxia and 72% Hypoxia. In contrast to this, increases in muscle glycogen use, muscle lactate content, and plasma catecholamine concentration were more influenced by the relative than by the absolute exercise intensity, being similar in 72% Hypoxia and 73% Normoxia, with both trials higher than in 51% Normoxia. In conclusion, increases in muscle AMPK signaling, free AMP content, and glucose disposal during exercise are largely determined by the absolute exercise intensity, whereas increases in plasma catecholamine levels, muscle glycogen use, and muscle lactate levels are more closely associated with the relative exercise intensity.

99mTc-TRODAT-1 SPECT study in early Parkinson's disease and essential tremor

OBJECTIVE

The clinical differentiation between early Parkinson's disease (PD) and essential tremor (ET) could be difficult, therefore, the aim of this study was to investigate 99mTc-TRODAT-1 SPECT as an applicable tool in this field.

METHODS

99mTc-TRODAT-1 single photon emission computed tomography (SPECT) was performed in 10 healthy volunteers, 27 patients with idiopathic PD (Hoehn and Yahr 1-1.5) and 12 patients with ET. The ratio of striatal (99m)Tc-TRODAT-1 binding was calculated as the index of (striatum - occipital cortex)/occipital cortex.

RESULTS

Compared with the striatal 99mTc-TRODAT-1 uptake in the ET group (0.49 +/- 0.07) or healthy controls (0.54 +/- 0.18), there was a significant decrease in the bilateral striatums of early PD, with a greater reduction in the contralateral striatum (0.27 +/- 0.08) than ipsilateral one (0.36 +/- 0.10, P < 0.01). Its sensitivity and specificity of differentiating early PD from ET was 96.4% and 91.7% respectively.

CONCLUSION

99mTc-TRODAT-1 SPECT can detect the dysfunction of nigrostriatal system in patients with early PD and provided a feasible tool to help differentiate early PD from ET.

Attention to the hiding iodine deficiency in pregnant and lactating women after universal salt iodization: A multi-community study in China

BACKGROUND

Monitoring of iodine nutrition depends chiefly on the urinary iodine concentration in representative samples from the population. International groups have recommended school-age children as a convenient group for surveys, because of their accessibility and young age, but the relevance of this group to others, especially pregnant women, is not well established.

OBJECTIVE

The purpose was to compare different approaches to assessing iodine nutrition within communities, especially for pregnant and lactating women.

DESIGN

In an urban and a rural site from each of the 11 Chinese provinces, covering a wide geographic and socioeconomic range, we measured the iodine content of household salt and drinking water, the thyroid volume in school children, and the urinary iodine concentration in five population subsets; in some sites we also assessed iodine in breast milk and thyroid size in adult women.

RESULTS

The median urinary iodine concentrations for pregnant and lactating women were well below those of the schoolchildren from the same community in most study sites, the difference between medians, at overall level, being about 50 microg/l for the pregnant and 40 microg/l for the lactating, respectively. When ranked by median urinary iodine concentrations at overall level, the order of the groups was: all infants, schoolchildren, women of childbearing age, lactating women and pregnant women in both urban and rural sites. This relative distribution was constant among the study sites. From it, we derived a relationship to predict the median values for other groups, based on the data of schoolchildren. The median iodine content of salt was 30.9 ppm in urban sites and 31.3 ppm in rural sites, respectively, close to the nationally mandated 35 mg/kg. Water had low iodine content (3.7 microg/l) in both urban and rural sites except in a rural site from Tianjin. Ultrasonography showed that 6.5% of 1329 children in urban sites and 5.3% of 1431 children in rural sites had thyroid enlargement. Breast milk had a median iodine content of 135.9 microg/l in the urban and 157.5 microg/l in the rural. The goiter prevalence by palpation was low (2.0%) among all women examined (3367), but higher in pregnant women (2.7%) than in lactating women or other adult women.

CONCLUSIONS

An effective iodized salt program has brought iodine sufficiency to most of China, but pregnant women in some areas may still risk deficiency and need further supplements. We suggest other countries and international agencies pay more attention to pregnancy, where iodine deficiency has its worst consequences.

Intensified exercise training does not alter AMPK signaling in human skeletal muscle

The AMP-activated protein kinase (AMPK) cascade has been linked to many of the acute effects of exercise on skeletal muscle substrate metabolism, as well as to some of the chronic training-induced adaptations. We determined the effect of 3 wk of intensified training (HIT; 7 sessions of 8 x 5 min at 85% Vo2 peak) in skeletal muscle from well-trained athletes on AMPK responsiveness to exercise. Rates of whole body substrate oxidation were determined during a 90-min steady-state ride (SS) pre- and post-HIT. Muscle metabolites and AMPK signaling were determined from biopsies taken at rest and immediately after exercise during the first and seventh HIT sessions, performed at the same (absolute) pre-HIT work rate. HIT decreased rates of whole body carbohydrate oxidation (P < 0.05) and increased rates of fat oxidation (P < 0.05) during SS. Resting muscle glycogen and its utilization during intense exercise were unaffected by HIT. However, HIT induced a twofold decrease in muscle [lactate] (P < 0.05) and resulted in tighter metabolic regulation, i.e., attenuation of the decrease in the PCr/(PCr + Cr) ratio and of the increase in [AMPfree]/ATP. Resting activities of AMPKalpha1 and -alpha2 were similar post-HIT, with the magnitude of the rise in response to exercise similar pre- and post-HIT. AMPK phosphorylation at Thr172 on both the alpha1 and alpha2 subunits increased in response to exercise, with the magnitude of this rise being similar post-HIT. Acetyl-coenzyme A carboxylase-beta phosphorylation was similar at rest and, despite HIT-induced increases in whole body rates of fat oxidation, did not increase post-HIT. Our results indicate that, in well-trained individuals, short-term HIT improves metabolic control but does not blunt AMPK signaling in response to intense exercise.

AMP-activated protein kinase, super metabolic regulator

The AMP-activated protein kinase (AMPK) is a metabolic-stress-sensing protein kinase that regulates metabolism in response to energy demand and supply by directly phosphorylating rate-limiting enzymes in metabolic pathways as well as controlling gene expression.

Progressive increase in human skeletal muscle AMPKalpha2 activity and ACC phosphorylation during exercise

The effect of prolonged moderate-intensity exercise on human skeletal muscle AMP-activated protein kinase (AMPK)alpha1 and -alpha2 activity and acetyl-CoA carboxylase (ACCbeta) and neuronal nitric oxide synthase (nNOSmu) phosphorylation was investigated. Seven active healthy individuals cycled for 30 min at a workload requiring 62.8 +/- 1.3% of peak O(2) consumption (VO(2 peak)) with muscle biopsies obtained from the vastus lateralis at rest and at 5 and 30 min of exercise. AMPKalpha1 activity was not altered by exercise; however, AMPKalpha2 activity was significantly (P < 0.05) elevated after 5 min (approximately 2-fold), and further elevated (P < 0.05) after 30 min (approximately 3-fold) of exercise. ACCbeta phosphorylation was increased (P < 0.05) after 5 min (approximately 18-fold compared with rest) and increased (P < 0.05) further after 30 min of exercise (approximately 36-fold compared with rest). Increases in AMPKalpha2 activity were significantly correlated with both increases in ACCbeta phosphorylation and reductions in muscle glycogen content. Fat oxidation tended (P = 0.058) to increase progressively during exercise. Muscle creatine phosphate was lower (P < 0.05), and muscle creatine, calculated free AMP, and free AMP-to-ATP ratio were higher (P < 0.05) at both 5 and 30 min of exercise compared with those at rest. At 30 min of exercise, the values of these metabolites were not significantly different from those at 5 min of exercise. Phosphorylation of nNOSmu was variable, and despite the mean doubling with exercise, statistically significance was not achieved (P = 0.304). Western blots indicated that AMPKapproximately 2 was associated with both nNOSmu and ACCbeta consistent with them both being substrates of AMPKalpha2 in vivo. In conclusion, AMPKalpha2 activity and ACCbeta phosphorylation increase progressively during moderate exercise at approximately 60% of VO(2 peak) in humans, with these responses more closely coupled to muscle glycogen content than muscle AMP/ATP ratio.

In vitro evidence for homologous recombinational repair in resistance to melphalan

BACKGROUND

The generation of DNA interstrand cross-links is thought to be important in the cytotoxicity of nitrogen mustard alkylating agents, such as melphalan, which have antitumor activity. Cell lines with mutations in recombinational repair pathways are hypersensitive to nitrogen mustards. Thus, resistance to melphalan may require accelerated DNA repair by either recombinational repair mechanisms involving Rad51-related proteins (including x-ray repair cross-complementing proteins Xrcc2, Xrcc3, and Rad52) or by nonhomologous endjoining involving DNA-dependent protein kinase (DNA-PK) and Ku proteins. We investigated the role of DNA repair in melphalan resistance in epithelial tumor cell lines.

METHODS

Melphalan cytotoxicity was determined in 14 epithelial tumor cell lines by use of the sulforhodamine assay. Homologous recombinational repair involving Rad51-related proteins was investigated by determining the levels of Rad51, Rad52, and Xrcc3 proteins and the density of nuclear melphalan-induced Rad51 foci, which represent sites of homologous recombinational repair. Nonhomologous endjoining was investigated by determining the levels of Ku70 and Ku86 proteins and DNA-PK activity. Linear regression analysis was used to analyze correlations between the various protein levels, DNA-PK activity, or Rad51 foci formation and melphalan cytotoxicity. All statistical tests were two-sided.

RESULTS

Melphalan resistance was correlated with Xrcc3 levels (r =.587; P =.027) and the density of melphalan-induced Rad51 foci (r =.848; P =.008). We found no correlation between melphalan resistance and Rad51, Rad52, or Ku protein levels or DNA-PK activity.

CONCLUSION

Correlations of melphalan resistance in epithelial tumor cell lines with Xrcc3 protein levels and melphalan-induced Rad51 foci density suggest that homologous recombinational repair is involved in resistance to this nitrogen mustard.

Antitumor efficacy of SarCNU in a human glioma xenograft model expressing both MGMT and extraneuronal monoamine transporter

Treatment of malignant brain tumors with chloroethylnitrosoureas (CENUs) in addition to surgical resection and radiotherapy remains the foundation of glioma therapy. However, the clinical response to CENUs is at best modest. A novel analogue of nitrosoureas, 2-chloroethyl-3-sarcosinamide-1-nitrosourea (SarCNU), as compared to the standard CENU, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), has been demonstrated to have increased anticancer effects both in vitro and in vivo. Unfortunately, many human tumors have been known to be resistant to CENUs since they express DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT). In order to assess whether SarCNU has an effect on MGMT positive tumors, we evaluated its antitumor efficacy using an MGMT positive human glioma (SF-767) nude mouse xenograft model. Since SF-767 has high MGMT levels, BCNU treatment (20 mg/kg, Q4D x 3 i.p.) alone did not result in a satisfactory anticancer effect (p > 0.05). As expected, O6-benzylguanine (O6-BG) (100 mg/kg), which was given prior to BCNU treatment, by depleting MGMT activity, significantly enhanced BCNU antitumor efficacy (p < 0.001). Moreover, SarCNU treatment (167 mg/kg, Q4D x 3 i.p.) alone had a better antitumor effect than O6-BG plus BCNU treatment (F = 51.7, p = 0.0004). However, in this xenograft model, O6-BG did not significantly enhance the anticancer efficacy of SarCNU (F = 0.8, p = 0.411). The SF-767 human glioma xenograft is positive for extraneuronal monoamine transporter EMT (EMT) as determined by reverse-transcription polymerase chain reaction (RT-PCR). Our present results suggest that SarCNU is also effective for MGMT positive tumor if they exhibit EMT.

Reciprocal phosphorylation and regulation of endothelial nitric-oxide synthase in response to bradykinin stimulation

Endothelial nitric-oxide synthase (eNOS) is phosphorylated at Ser-1179 (bovine sequence) by Akt after growth factor or shear stress stimulation of endothelial cells, resulting in increased eNOS activity. Purified eNOS is also phosphorylated at Thr-497 by purified AMP-activated protein kinase, resulting in decreased eNOS activity. We investigated whether bradykinin (BK) stimulation of bovine aortic endothelial cells (BAECs) regulates eNOS through Akt activation and Ser-1179 or Thr-497 phosphorylation. Akt is transiently activated in BK-stimulated BAECs. Activation is blocked completely by wortmannin and LY294002, inhibitors of phosphatidylinositol 3-kinase, suggesting that Akt activation occurs downstream from phosphatidylinositol 3-kinase. BK stimulates a transient phosphorylation of eNOS at Ser-1179 that is correlated temporally with a transient dephosphorylation of eNOS at Thr-497. Phosphorylation at Ser-1179, but not dephosphorylation at Thr-497, is blocked by wortmannin and LY294002. BK also stimulates a transient nitric oxide (NO) release from BAECs with a time-course similar to Ser-1179 phosphorylation and Thr-497 dephosphorylation. NO release is not altered by wortmannin. BK-stimulated dephosphorylation of Thr-497 and NO release are blocked by the calcineurin inhibitor, cyclosporin A. These data suggest that BK activation of eNOS in BAECs primarily involves deinhibition of the enzyme through calcineurin-mediated dephosphorylation at Thr-497.

Both extraneuronal monoamine transporter and O(6)-methylguanine-DNA methyltransferase expression influence the antitumor efficacy of 2-chloroethyl-3-sarcosinamide- 1-nitrosourea in human tumor xenografts

We previously have found that 2-chloroethyl-3-sarcosinamide-1-nitrosourea (SarCNU) is a selective cytotoxin that enters cells via the extraneuronal transporter for monoamine transmitters (EMT). Both in vitro and in vivo studies demonstrated that SarCNU was more effective than BCNU against human gliomas. To clarify whether EMT expression correlates with antitumor efficacy of SarCNU, we determined human EMT (EMTh) and O(6)-methylguanine-DNA methyltransferase (MGMT) expression in nine human xenograft models using semiquantitative reverse-transcription polymerase chain reaction. These results were compared with the antitumor effects of SarCNU and the standard chloroethylnitrosourea antitumor agent 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). There was no significant correlation between EMTh expression and antitumor efficacy of SarCNU or BCNU. Also, there was no significant correlation between MGMT expression and SarCNU efficacy. However, a significant correlation was found between MGMT expression and BCNU antitumor efficacy. Interestingly, multiple regression analysis demonstrated a significant correlation between SarCNU efficacy and EMTh plus MGMT expression, whereas there was no correlation between BCNU efficacy and MGMT plus EMTh expression. Thus, the absence of a linear correlation between SarCNU efficacy and EMTh expression appears to be due, at least in part, to the presence of DNA repair, specifically, MGMT, in these xenograft models. These studies suggest that MGMT expression alone correlates with BCNU activity, whereas both EMTh and MGMT expression are important determinants of SarCNU activity against human tumor xenograft models. SarCNU is in clinical trials and these results may have important clinical implications.

Morphine tolerance and dependence in nociceptin/orphanin FQ transgenic knock-out mice

It has been hypothesized that morphine tolerance and dependence in mice following chronic exposure may reflect increased compensatory activity of antiopioid systems. The endogenous peptide nociceptin/orphanin FQ has been shown to have anti-opioid effects, for example antagonizing morphine analgesia. Moreover, chronic morphine administration increases synthesis of the peptide, and morphine tolerance and dependence can be attenuated or reversed by antagonists and agonists of the nociceptin/orphanin FQ receptor, respectively. The present study seeks to confirm a role for nociceptin/orphanin FQ in opioid tolerance and dependence by comparing morphine ED(50) values and naloxone-precipitated withdrawal jumping in mice homozygous (knock-out) and heterozygous for a null mutation of the Npnc1 gene encoding the nociceptin/orphanin FQ propeptide, and their wild type littermates, following chronic morphine exposure. Relative to morphine-naive control mice, significant rightward shifts in the morphine dose-response curve, resulting in increased morphine ED(50) values (approximately two to three-fold), was observed for all genotypes following three days of repeated systemic morphine injections. However, no differences between genotypes in the magnitude of tolerance were observed. In contrast, knock-out mice displayed significantly increased naloxone-precipitated withdrawal jumping relative to heterozygous and wild-type mice following implantation with a morphine pellet (25mg) for 72h. Use of nociception/orphaninFQ transgenic knock-out mice thus demonstrate the differential involvement of nociceptin/orphanin FQ in morphine tolerance and dependence.

A PARAFAC algorithm using penalty diagonalization error (PDE) for three-way data array resolution

A modified parallel factors analysis (PARAFAC) algorithm with the penalty diagnolization error (PDE) was developed. This algorithm can overcome the slow convergence problem of the traditional PARAFAC method and is insensitive to the number of components, i.e., it is much faster than PARAFAC and insensitive to overestimation of the dimensionality of the model. The characteristic performance was demonstrated by treating simulated and real excitation-emission fluorescence data for samples of naphthalene, 1-naphthol and 2-naphthol with satisfactory results.

Aminohexanoic hydroxamate is a potent inducer of the differentiation of mouse neuroblastoma cells

Deoxyhypusine synthase is the key enzyme for modifying a lysine residue to hypusine in the cellular protein eukaryotic initiation factor 5A (eIF-5A). Deletion of the deoxyhypusine synthase or the eIF-5A gene in yeast produces lethal phenotype. Inhibition of deoxyhypusine synthase by 1-guanidino-7-aminoheptane (GC7) suppresses tumor cell growth. Hypusine formation represents one of the most specific polyamine-dependent biochemical reactions. In view of the importance of polyamines in growth regulation and cancer biology, deoxyhypusine synthase has been considered to be a good target for chemotherapeutic drug design. Using GC7 as a prototype we have synthesized and tested three classes of diamine analogs, namely, guanidino-, pyrimidino-, and hydroxamate derivatives, as potential inhibitors for deoxyhypusine synthase. Our study shows that (i) among all the compounds tested, GC7 remained to be the most potent inhibitor for deoxyhypusine synthase; (ii) N,N'-bispyrimidino-1, 9-diaminononane, although a poor inhibitor of deoxyhypusine synthase, was a potent growth inhibitor; and (iii) one of the hydroxamate derivatives, 6-aminohexanoic hydroxamate (HC6), prominently induced the differentiation of mouse neuroblastoma cells at sub-millimolar concentrations. Interestingly, other hydroxamates with different chain length were not nearly as effective as HC6 in inducing neuroblastoma cell differentiation. The effect of HC6 was also unique in that it could induce neurite outgrowth and the expression of neuron-specific genes such as synapsin I and MAP-2 in neuroblastoma cells in the absence of other promoting agents such as cAMP. The effect of HC6 on neuroblastoma cell differentiation was comparable with, or better than that of N(6),O(2)'-dibutyryl cAMP (Bt(2)cAMP), a standard reagent commonly used for inducing the differentiation of mouse and human neuroblastoma cells in culture.

AMPK signaling in contracting human skeletal muscle: acetyl-CoA carboxylase and NO synthase phosphorylation

AMP-activated protein kinase (AMPK) is a metabolic stress-sensing protein kinase responsible for coordinating metabolism and energy demand. In rodents, exercise accelerates fatty acid metabolism, enhances glucose uptake, and stimulates nitric oxide (NO) production in skeletal muscle. AMPK phosphorylates and inhibits acetyl-coenzyme A (CoA) carboxylase (ACC) and enhances GLUT-4 translocation. It has been reported that human skeletal muscle malonyl-CoA levels do not change in response to exercise, suggesting that other mechanisms besides inhibition of ACC may be operating to accelerate fatty acid oxidation. Here, we show that a 30-s bicycle sprint exercise increases the activity of the human skeletal muscle AMPK-alpha1 and -alpha2 isoforms approximately two- to threefold and the phosphorylation of ACC at Ser(79) (AMPK phosphorylation site) approximately 8.5-fold. Under these conditions, there is also an approximately 5.5-fold increase in phosphorylation of neuronal NO synthase-mu (nNOSmu;) at Ser(1451). These observations support the concept that inhibition of ACC is an important component in stimulating fatty acid oxidation in response to exercise and that there is coordinated regulation of nNOSmu to protect the muscle from ischemia/metabolic stress.

The preclinical pharmacologic study of dopamine transporter imaging agent [99mTc]TRODAT-1

The purpose of this study was to investigate the pharmacologic characteristics of TRODAT-1 (2beta-((N,N'-bis(2-mercaptoethyl)ethylene diamino)methyl), 3beta-(4-chlorophenyl)tropane) labeled with [99mTc] as an imaging agent for dopamine transporter (DAT). Radiochemical purity of [99mTc]TRODAT-1 was over 90%. The partition coefficients in octanol and buffer were 2.12 and 2.19 at pH 7.0 and 7.4, respectively. Animal studies have been performed in rats, rabbits, and normal and hemi-Parkinsonian model monkeys. Biodistribution displayed moderate uptake in rat brain (0.28 %ID/organ at 2 min) and the striatal uptake was 0.193, 0.142, and 0.136 %ID/g at 2, 60, and 120 min, respectively. The ratios of striatal/cerebellar (ST/CB) uptake were 2.4, 4.45, and 2.45 %ID/g at 60, 120, and 240 min, respectively. The major radioactivity was excreted by the hepatobiliary system. Blood clearance kinetics was performed in rabbits, and the initial half-life of 1.18 min and late half-life of 367.8 min were obtained. Brain single photon emission computed tomography imaging studies in normal monkeys showed the ratios of ST/CB uptake were 1.56-2.0 %ID/g and indicated that both uptake and retention in the striatal area were associated with the DAT. The imaging of hemi-Parkinsonian model monkeys also displayed the expected selectivity, the highest uptake being observed in the basal ganglia area of the normal side. Thereby, it is suggested that [99mTc]TRODAT-1 is a safe and useful imaging agent for localization of the presynaptic DAT in the brain.

Extraneuronal monoamine transporter expression and DNA repair vis-à-vis 2-chloroethyl-3-sarcosinamide-1-nitrosourea cytotoxicity in human tumor cell lines

We previously found that 2-chloroethyl-3-sarcosin-amide-1-nitrosourea (SarCNU), a new chloroethylnitrosourea analogue presently in phase I clinical trials, is a selective cytotoxin that enters cells via the extraneuronal transporter for monoamine transmitters (EMT). In this study, we assessed whether EMT expression correlates with SarCNU cytotoxicity by determining EMT expression in 23 human tumor cell lines with reverse-transcription PCR. Western blot analysis was used to measure protein levels of the DNA repair genes, O6-methylguanine-DNA methyltransferase (MGMT), and excision repair cross-complementing rodent repair deficiency gene 2 (ERCC2). SarCNU cytotoxicity was determined by the sulforhodamine B colorimetric anti-cancer-drug screening assay and correlated with gene expression. Almost all of the cell lines screened were positive for EMT expression. However, seven cell lines (MGR-1, MGR-2, T98-G, SKI-1, SKNSH, 297, and GBM) expressed low levels of EMT. Although there was no linear correlation between SarCNU cytotoxicity and EMT expression, SarCNU cytotoxicity significantly correlated with ERCC2 protein levels, and MGMT-rich (Mer+) cell lines (MGMT protein level >0.1) were more resistant to SarCNU than MGMT-poor (Mer-) cell lines (MGMT protein level <0.1). Moreover, multiple regression analysis indicated that the best correlation with SarCNU cytotoxicity was attainable with EMT plus MGMT and ERCC2 expression. This study suggests that in human tumor cell lines both EMT and DNA repair factors, specifically, MGMT and ERCC2, are important determinants of SarCNU activity. Because EMT is expressed in a wide variety of human tumors, SarCNU should be a more widely effective alternative chemotherapeutic agent.

Enhanced antitumor activity of sarCNU in comparison to BCNU in an extraneuronal monoamine transporter positive human glioma xenograft model

A novel analogue of nitrosoureas, 2-chloroethyl-3-sarcosinamide-1-nitrosourea (SarCNU), has demonstrated increased anticancer effects in vitro and in vivo. Our previous work suggested that SarCNU enters cells via the extraneuronal monoamine transporter (EMT), that contributes to its enhanced cytotoxicity. In the present study, comparative activities of SarCNU and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) were evaluated in an EMT positive human glioma xenograft model. Athymic nude mice implanted subcutaneously or intracranially with human glioma SHG-44, a cell line that has been confirmed EMT positive by using reverse-transcription polymerase chain reaction (RT-PCR) assay, were treated with SarCNU at an optimal dose of 167 mg/kg, or BCNU at 20 mg/kg or 30 mg/kg, q4d x 3 intraperitoneally (i.p.). In 17 animals with subcutaneous tumor grafts treated with SarCNU, 9 animals became tumor free and 8 demonstrated tumor regression. While in the BCNU treated group, there were only 2 out of 10 mice in the 20 mg/kg group and 2 out of 7 in the 30 mg/kg group, which demonstrated some tumor regression. There were 4 drug related deaths in the BCNU (30 mg/kg) group, while there were no drug related deaths in the SarCNU group. In the intracranially implanted mice, the median survival time in the SarCNU group was more than 130 days, while in the BCNU treated group it was only 22 days which was similar to the control group (18 days). This is the first demonstration that SarCNU, in comparison to BCNU, has enhanced anticancer activity in an EMT positive human glioma xenograft model.

Relationship between O6-methylguanine-DNA methyltransferase levels and clinical response induced by chloroethylnitrosourea therapy in glioma patients

BACKGROUND

Adjuvant nitrosourea chemotherapy fails to prolong survival significantly as many tumors demonstrate resistance to these drugs. It has been documented in cell lines that O6-methylguanine DNA methyltransferase (MGMT) plays an important role in chloroethylnitrosourea (CENU) drug resistance.

METHODS

We evaluated MGMT expression in 22 glioma specimens by using an immunofluorescence assay and compared the results with clinical responses of the patients to CENU-based chemotherapy.

RESULTS

Eight tumor samples had no detectable MGMT, whereas other samples had from 9,989 to 982,401 molecules/nucleus. In one group (12 patients), the tumor decreased in size or was stable (effective group), whereas in the other group (10 patients), the tumor demonstrated continuous growth during chemotherapy (progressive group). The Mer- patients (MGMT < 60,000 molecules/nucleus) appeared to have more chance of stable disease or response to CENU therapy than the Mer+ patients (MGMT > 60,000 molecules/nucleus) (X2 = 4.791, p = 0.0286). In patients with glioblastomas multiforme (GBMs), the median time to progression (TTP) of Mer+ patient was shorter than that of Mer- patient (t = 2.04, p = 0.049). As a corollary, the MGMT levels were significantly higher in GBM tumors from the progressive group than those from the effective group (t = 2.26, p = 0.029). However, there was no significant correlation between MGMT levels and either the survival time (r = 0.04, p = 0.8595) or TTP (r = 0.107, p = 0.6444).

CONCLUSION

This study suggests that being MGMT positive is indicative of a more aggressive disease that progresses more rapidly with CENU therapy. However, MGMT negative tumors are not always sensitive to CENU agents, suggesting that other factors are also important.

Pharmacology study of the neutral myocardial imaging agent technetium-99m-N(NOEt)2

OBJECTIVE

The biological properties of a new neutral myocardial imaging agent 99mTcN(NOEt)2 were evaluated.

METHODS

Blood clearance in rabbits, biodistribution in rats, and initial myocardial imaging in dogs were performed.

RESULTS

Radiochemical purity of 99mTcN(NOEt)2 was more than 90% and stable for 6 h at room temperature. Blood disappearance was analyzed with a biexponential model and T1/2(alpha) = 2.53 min, T1/2(beta) = 330 min and CI = 378 ml/h were obtained. Biodistribution studies demonstrated that 99mTcN(NOEt)2 localized selectively in the rat myocardium. Cardiac uptakes were 4.69, 4.20, 3.95 and 3.43% ID/g at 5, 30, 60 and 90 min postinjection, respectively. The mean heart-to-lung activity ratios were 1.69, 2.40 and 2.55 at 10 min, 30 min and 60 min postinjection, respectively.

CONCLUSION

Technetium-99m-N(NOEt)2 exhibited favorable stability and biological properties. Further study in humans is required.

AMP-activated protein kinase phosphorylation of endothelial NO synthase

The AMP-activated protein kinase (AMPK) in rat skeletal and cardiac muscle is activated by vigorous exercise and ischaemic stress. Under these conditions AMPK phosphorylates and inhibits acetyl-coenzyme A carboxylase causing increased oxidation of fatty acids. Here we show that AMPK co-immunoprecipitates with cardiac endothelial NO synthase (eNOS) and phosphorylates Ser-1177 in the presence of Ca2+-calmodulin (CaM) to activate eNOS both in vitro and during ischaemia in rat hearts. In the absence of Ca2+-calmodulin, AMPK also phosphorylates eNOS at Thr-495 in the CaM-binding sequence, resulting in inhibition of eNOS activity but Thr-495 phosphorylation is unchanged during ischaemia. Phosphorylation of eNOS by the AMPK in endothelial cells and myocytes provides a further regulatory link between metabolic stress and cardiovascular function.

Dealing with energy demand: the AMP-activated protein kinase

The AMP-activated protein kinase (AMPK) is a member of a metabolite-sensing protein kinase family that is found in all eukaryotes. AMPK activity is regulated by vigorous exercise, nutrient starvation and ischemia/hypoxia, and modulates many aspects of mammalian cell metabolism. The AMPK yeast homolog, Snf1p, plays a major role in adaption to glucose deprivation. In mammals, AMPK also has diverse roles that extend from energy metabolism through to transcriptional control.

Green tea epigallocatechin gallate shows a pronounced growth inhibitory effect on cancerous cells but not on their normal counterparts

(-)-Epigallocatechin gallate (EGCG), a catechin polyphenol compound, represents the main ingredient of green tea extract. Although EGCG has been shown to be growth inhibitory in a number of tumor cell lines, it is not clear whether the effect is cancer-specific. In this study we compared the effect of EGCG on the growth of SV40 virally transformed WI38 human fibroblasts (WI38VA) with that of normal WI38 cells. The IC50 value of EGCG was estimated to be 120 and 10 microM for WI38 and WI38VA cells, respectively. Thus, EGCG at 40 microM completely inhibited the growth of WI38VA cells, but had little or no inhibitory effect on the growth of WI38 cells. Similar differential growth inhibition was also observed between a human colorectal cancer cell line (Caco-2), a breast cancer cell line (Hs578T) and their respective normal counterparts. EGCG at a concentration range of 40-200 microM induced a significant amount of apoptosis in WI38VA cultures, but not in WI38 cultures, as determined by terminal deoxynucleotidyl transferase assay. After exposure to EGCG at 200 microM for 8 h, more than 50% of WI38VA cells in a confluent culture became apoptotic. In contrast, less than 1% of WI38 cells displayed apoptotic labeling under the same condition. EGCG did not affect the serum-induced expression of c-fos and c-myc genes in normal WI38 cells. However, it significantly enhanced their expression in transformed W138VA cells. It is possible that differential modulation of certain genes, such as c-fos and c-myc, may cause differential effects of EGCG on the growth and death of cancer cells.

Tubular epithelial-myofibroblast transdifferentiation in progressive tubulointerstitial fibrosis in 5/6 nephrectomized rats

BACKGROUND

Tubulointerstitial fibrosis is the final common pathway to end-stage renal failure. The present study investigated the potential role of tubular epithelial cells (TEC) in progressive fibrosis in the rat remnant kidney model.

METHODS

Rats underwent 5/6 nephrectomy or a sham operation (control), and groups of six animals were killed at weeks 1, 3, 5, 9, 13, 17 and 21.

RESULTS

Immunohistochemistry staining and in situ hybridization at week 3 after nephrectomy demonstrated de novo expression of alpha-smooth muscle actin (alpha-SMA)--a marker of smooth muscle cells and myofibroblasts--by TEC that was invariably associated with disruption of the tubular basement membrane (TBM). This phenotypic evidence of tubular epithelial-myofibroblast transdifferentiation was supported by ultrastructural studies identifying the presence of characteristic actin microfilaments and dense bodies within TEC with a transformed morphology. In the late stage of this apparent tubular epithelial-myofibroblast transdifferentiation, TEC lost apical-basal polarity and tight junctions, became elongated, detached from the TBM, separated from neighboring cells and appeared to migrate into the peritubular interstitium through the damaged basement membrane. Indeed, focal peritubular accumulation of alpha-SMA+ myofibroblasts and local tubulointerstitial fibrosis was closely associated with alpha-SMA+ tubules, suggesting a tubular epithelial origin for some of these cells. Quantitative analysis found a significant correlation between the number of alpha-SMA+ TEC and the accumulation of interstitial alpha-SMA+ myofibroblasts and the severity of tubulointerstitial fibrosis (both P < 0.001).

CONCLUSIONS

This study provides phenotypic and morphological evidence to support the hypothesis that TEC are pro-fibrogenitor cells capable of tubular epithelial-myofibroblast transdifferentiation in progressive renal fibrosis. In addition, we postulate that disruption of the TBM, which facilitates epithelial cell contact with the interstitial matrix, promotes this process of transdifferentiation.

Green tea epigallocatechin gallate shows a pronounced growth inhibitory effect on cancerous cells but not on their normal counterparts

(-)-Epigallocatechin gallate (EGCG), a catechin polyphenol compound, represents the main ingredient of green tea extract. Although EGCG has been shown to be growth inhibitory in a number of tumor cell lines, it is not clear whether the effect is cancer-specific. In this study we compared the effect of EGCG on the growth of SV40 virally transformed WI38 human fibroblasts (WI38VA) with that of normal WI38 cells. The IC50 value of EGCG was estimated to be 120 and 10 microM for WI38 and WI38VA cells, respectively. Thus, EGCG at 40 microM completely inhibited the growth of WI38VA cells, but had little or no inhibitory effect on the growth of WI38 cells. Similar differential growth inhibition was also observed between a human colorectal cancer cell line (Caco-2), a breast cancer cell line (Hs578T) and their respective normal counterparts. EGCG at a concentration range of 40-200 microM induced a significant amount of apoptosis in WI38VA cultures, but not in WI38 cultures, as determined by terminal deoxynucleotidyl transferase assay. After exposure to EGCG at 200 microM for 8 h, more than 50% of WI38VA cells in a confluent culture became apoptotic. In contrast, less than 1% of WI38 cells displayed apoptotic labeling under the same condition. EGCG did not affect the serum-induced expression of c-fos and c-myc genes in normal WI38 cells. However, it significantly enhanced their expression in transformed W138VA cells. It is possible that differential modulation of certain genes, such as c-fos and c-myc, may cause differential effects of EGCG on the growth and death of cancer cells.

Clinical response of O(6)-methylguanine-DNA methyltransferase levels to 1,3-(2-chloroethyl)-1-nitrosourea chemotherapy in glioma patients

Adjuvant nitrosourea chemotherapy fails to prolong patient survival significantly as many tumors demonstrate resistance to these drugs. It has been documented in cell lines that O(6)-methylguanine-DNA methyltransferase (MGMT) plays an important role in chloroethylnitrosourea (CENU) drug resistance. The authors evaluated MGMT expression in 22 glioma specimens by using an immunofluorescence assay and compared the results with clinical response of the patients to CENU-based chemotherapy. The patients were treated with CENU after evidence of progressive disease following surgery and radiotherapy. Eight tumor samples had no detectable MGMT, whereas other samples had from 9989 to 982,401 molecules/nucleus. In one group (12 patients), the tumor decreased in size or was stable (effective group), whereas in the other group (10 patients), the tumor demonstrated continuous growth during chemotherapy (progressive group). The median time to progression (TTP) was 6.7 months with a median survival of 13 months. The Mer(-) patients (MGMT < 60,000 molecules/nucleus) appeared to have more chance of stable disease or response to CENU therapy than the Mer(+) patients (MGMT > 60,000 molecules/nucleus) (chi-square = 4.791, p = 0.0286). In patients with glioblastomas multiforme (GBMs), the TTP of Mer(+) patients was shorter than that of Mer(-) patients (t = 2.04, p = 0.049). As a corollary, the MGMT levels were significantly higher in GBM tumors from the progressive group than those from the effective group (t = -2.26, p = 0.029). The TTP and survival time in the effective GBM group were also longer than those in the progressive GBM group. However, there was no significant correlation between MGMT levels and either the survival time (r = 0.04, p = 0.8595) or TTP (r = 0.107, p = 0.6444). Results from this study suggested that MGMT positivity is indicative of more aggressive disease that progresses more rapidly when exposed to CENU therapy. However, MGMT-negative tumors are not always sensitive to CENU agents, suggesting that other factors may also be important.

Excision repair cross-complementing rodent repair deficiency gene 2 expression and chloroethylnitrosourea resistance in human glioma cell lines

OBJECTIVE

Nitrosoureas are the standard chemotherapeutic agents for malignant brain tumors. However, their anticancer effects are limited because many tumors are resistant to these agents. Nucleotide excision repair can repair bulky deoxyribonucleic acid adducts, including deoxyribonucleic acid damage induced by ultraviolet light and some chemotherapeutic agents, and may be implicated in nitrosoureas resistance. In this study, we compared excision repair cross-complementing rodent repair deficiency Gene 2 (ERCC2), an important component of the nucleotide excision repair system, with 1 ,3-bis-(2-chloroethyl)-1-nitrosourea or (2-chloroethyl)-3-sarcosinamide-1-nitrosourea resistance in human glioma cell lines.

METHODS

ERCC2 expression was evaluated by using established quantitative reverse-transcription polymerase chain reaction. 1,3-Bis-(2-chloroethyl)-1-nitrosourea and (2-chloroethyl)-3-sarcosinamide-1-nitrosourea cytotoxicity were determined by a modification of the sulforhodamine B colorimetric anticancer drug screening assay.

RESULTS

A significant correlation between ERCC2 expression and 1 ,3-bis-(2-chloroethyl)-1-nitrosourea or (2-chloroethyl)-3-sarcosinamide-1-nitrosourea cytotoxicity was determined (r=0.737, P=0.0226 and r=0.789, P=0.0113, respectively).

CONCLUSION

Our results suggest that nucleotide excision repair, specifically ERCC2, may play an important role in nitrosoureas drug resistance in human gliomas.

Ligand- and DNA-induced dissociation of RXR tetramers

Unliganded bacterially expressed RXR alpha lacking the N-terminal region AB (apo-RXR alpha delta AB) was found in solution as an apparent mixture of 165 kDa tetramers and 42 kDa monomers which could be quantitatively separated by gel filtration and non-denaturing gel electrophoresis. Under identical conditions both liganded (holo-) and apo-RAR alpha delta AB were present as single monomeric species. apo-RXR alpha delta AB tetramers, as well as dimers of the apo-RXR ligand binding domain (apo-LBD), dissociated readily into monomers when exposed to their cognate ligand 9-cis retinoic acid (9c-RA). The apo-RXR alpha delta AB tetramer bound only transiently to a cognate DR1 response element, and was converted into DR1-apo-RXR alpha delta AB homodimer complexes indistinguishable from those generated by cooperative DNA binding of apo-RXR alpha delta AB monomers. In the absence of DNA, the addition of 9c-RA greatly accelerated the formation of heterodimers with the apo-RAR alpha delta AB heterodimerization partner. No RXR alpha delta AB or RAR alpha delta AB homodimers could be observed in solution, but upon mixing of the two receptor monomers stable heterodimers could be isolated which bound to DR5 response elements in a highly cooperative manner. In these heterodimers, RXR alpha delta AB interacted with its cognate ligand as efficiently as in RXR alpha delta AB homodimers. The presence of ligand did not alter the stability of RXR alpha delta AB homodimer or RXR alpha delta AB-RAR alpha delta AB heterodimer complexes on DR1 and DR5 response elements, respectively. These in vitro data support a model in which RXR tetramers could serve as an inactive pool with the dual function of: (i) rapidly supplying large amounts of RXR heterodimerization partners upon 9c-RA generation; and (ii) allowing RXR homodimer formation on "accessible" cognate response elements in the absence of 9c-RA. These events may represent a ligand-dependent regulatory mechanism controlling the availability of the promiscuous RXR dimerization partner that is engaged in multiple nuclear receptor signalling pathways.

Towards a bacteriorhodopsin-silicon neuromorphic photosensor

We describe our efforts towards constructing a hybrid protein-silicon neuromorphic photosensor based on the photo-active protein bacteriohodopsin. This protein displays an differential photosensitivity similar to the response of the receptive field of an X-type retinal ganglion cell. Similar bacteriohodopsin photoelectrode arrays display inherent edge detection and motion enhancement. We discuss challenges associated with constructing and understanding the protein-silicon interface and possible chemical solutions for our experimental device.

Evidence for nucleotide excision repair as a modifying factor of O6-methylguanine-DNA methyltransferase-mediated innate chloroethylnitrosourea resistance in human tumor cell lines

We examined the O6-methylguanine-DNA methyltransferase (MGMT) protein as well as MGMT activity levels and the excision repair cross-complementing rodent repair deficiency gene, ERCC2 (XPD), protein levels in 14 human tumor cell lines not selected for chloroethylnitrosourea (CENU) resistance. These results were compared with 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) cytotoxicity and UV light sensitivity. MGMT protein correlated significantly with MGMT activity (r = 0.9497, p = 0.0001). There was no significant linear correlation between BCNU cytotoxicity and MGMT content as determined by both Western analysis (r = 0.139, p = 0. 6348) and activity assay (r = 0.131, p = 0.6515). However, MGMT-rich cell lines were found to be more resistant than MGMT-poor cell lines to BCNU (t = 2.2375, p = 0.0225) but not to UV (t = 1.1734, p = 0.1317). Furthermore, the most BCNU-sensitive cell lines were all MGMT-poor. UV sensitivity was significantly correlated to BCNU cytotoxicity (r = 0.858, p = 0.0001). Significant correlations were found between ERCC2 protein levels and BCNU cytotoxicity (r = 0.786, p = 0.0009) or UV sensitivity (r = 0.874, p = 0.0001). Our results confirm that MGMT plays an important role in CENU resistance, but not in UV resistance. The correlation of UV sensitivity with BCNU cytotoxicity suggests that nucleotide excision repair is an important modifying factor of MGMT-mediated innate CENU resistance in human tumor cell lines, especially in highly resistant cell lines. ERCC2 may be implicated in this process.

Acromegaly with normal basal growth hormone levels

BACKGROUND

The most common cause of acromegaly is excess of growth hormone (GH) secretion.

METHODS

We report a 42-year-old male patient, who had become acromegalic over the past 5 years. There were no visual changes or change in sexual function, no gynaecomastia or galactorrhoea. Both CT and MRI scans showed a large mass measuring 2.5 x 2.5 x 3.5 cm, originating from the sella turcica and extending into and totally filling up the sphenoid sinus with diffusely invasive features.

RESULTS

Basal serum GH level was within normal range, but insulin-like growth factor 1 (IGF-1) was elevated with slightly increased prolactin (PRL) and impaired GH secretory regulation as well. A pituitary adenoma was partially removed through transsphenoidal microsurgery. Pathology confirmed a mammo-somatotrophic adenoma but immunocytochemistry study of the tumour showed only positivity for PRL but not GH.

CONCLUSIONS

When acromegaly occurs without GH level elevation, one should pay attention that: 1) IGF-1 might be the cause of the clinical feature of acromegaly; 2) The tumour might undergo morphological transformation; and 3) Hyperinsulinemia or GH receptor antibody formation could also be the cause of the acromegalic appearance.

Marked elevation of hypusine formation activity on eukaryotic initiation factor 5A in v-HA-RAS transformed mouse NIH3T3 cells

Hypusine formation on the eukaryotic initiation factor 5A (eIF-5A) precursor is ubiquitously present in eukaryotic cells and archebacteria. In this reaction, deoxyhypusine synthase catalyzes the conversion of one unique lysine residue on eIF-5A to deoxyhypusine using spermidine as the substrate. Hydroxylation of the deoxyhypusine residue completes hypusine formation on eIF-5A. Hypusine formation activity can be measured by an in vitro labeling technique in polyamine-depleted cells. In addition, an in vitro cross-labeling assay can be employed to measure simultaneously the relative deoxyhypusine synthase activity and protein substrate amount. Using these approaches, together with Western blot analysis, we showed that hypusine formation activity is serum-responsive and significantly elevated in Ras oncogene transfected NIH3T3 cells as compared to NIH3T3 cells. The large difference, >30-fold, in hypusine formation activity between these two cells is mainly due to difference in the amount of newly synthesized eIF-5A precursor rather than deoxyhypusine synthase. The deoxyhypusine synthase activity is about three-fold higher in Ras-3T3 cells than in 3T3 cells, and remains constant throughout serum stimulation in both cells. Despite the significant difference in eIF-5A protein amounts, the eIF-5A mRNA levels in 3T3 cells and in Ras-3T3 cells are almost identical. Furthermore, unlike serum-dependent increase in eIF-5A precursor protein, the eIF-5A mRNA in both cells is constitutively expressed after serum stimulation, suggesting that eIF-5A gene is regulated at posttranscriptional/translational level during serum stimulation and cell transformation.

Dramatic attenuation of hypusine formation on eukaryotic initiation factor 5A during senescence of IMR-90 human diploid fibroblasts

Deoxyhypusine synthase catalyzes the conversion of lysine to deoxyhypusine residue on the eukaryotic initiation factor 5A (elF-5A) precursor using spermidine as the substrate. Subsequent hydroxylation of the deoxyhypusine residue completes hypusine formation on elF-5A. Hypusine formation is one of the most specific polyamine-dependent biochemical events in eukaryotic cells. Although changes in polyamine metabolism have been demonstrated in human diploid fibroblasts during senescence (Chen and Chang, 1986, J. Cell. Physiol., 128:27-32.), it is unclear whether or not polyamine-dependent hypusine formation itself is an age-dependent biochemical event. In the present study, hypusine-forming activity was measured by a radiolabeling assay in cells whose polyamines have been depleted by prior treatment of alpha-difluoromethyl ornithine (DFMO). In addition, an in vitro cross-labeling assay was developed for simultaneous measurement of the deoxyhypusine synthase activity and protein substrate (elF-5A precursor) amount. We showed that the hypusine-forming activity in low-passage presenescent IMR-90 cells [population doubling level (PDL) = 15-23, termed young cells] was prominently induced by serum whereas little or no hypusine-forming activity could be detected in late-passage senescent cells (PDL = 46-54, termed old cells). The striking difference in hypusine-forming activity between young and old cells was due to changes in both deoxyhypusine synthase activity and elF-5A precursor amount in IMR-90 cells during senescence. However, Northern blot analysis showed no significant difference in the elF-5A messenger RNA (mRNA) between young and old cells, suggesting that the age-dependent attenuation of elF-5A precursor protein may be regulated at either translational or post-translational level.

Quantitation of ERCC-2 gene expression in human tumor cell lines by reverse transcription-polymerase chain reaction in comparison to northern blot analysis

Excision repair cross-complementing rodent repair deficiency genes (ERCC) are human genes implicated in nucleotide excision repair. ERCC-2 has been implicated in the repair of DNA damaged by chemotherapeutic agents, and may thus play an important role in anticancer drug resistance. ERCC-2 gene expression is low in primary tumor samples rendering it difficult to quantitate. We have developed a semiquantitative method to measure ERCC-2 gene expression utilizing reverse transcription-polymerase chain reaction (RT-PCR). Total RNA extracted from established human tumor cell lines was reverse-transcribed to obtain cDNA. Serially diluted reference ERCC-2 DNA fragment was amplified by PCR to obtain a 617-bp fragment. A standard curve was then created using densitometry readings of the 617-bp bands on agarose gel. A fixed amount of sample cDNA from each cell line was amplified at the same time and the resultant PCR product was read by densitometer. Using the standard curve, ERCC-2 gene expression in a given amount of total RNA was quantitated and normalized to beta-actin expression. There was minimal variation in three repeated experiments with PCR amplification. ERCC-2 gene expression determined by this semiquantitative PCR was also correlated to ERCC-2 quantitation by Northern blot analysis, with a significant concordance (r = 0.912, P = 0.0002). We also successfully applied this sensitive method to quantify five clinical glioma samples.

Intracellular calcium ion responses to somatostatin in cells from human somatotroph adenomas

OBJECTIVE

Various GH secretory responses to long-acting somatostatin (SRIH) analogues have been observed during the treatment of acromegalic patients. The effects of SRIH on intracellular Ca2+ homeostasis in human somatotroph adenoma cells has not been examined in detail, and the underlying mechanisms therefore remain to be determined. Using isolated cells from human somatotroph adenomas, we have investigated the SRIH-induced intracellular Ca2+ responses at a single-cell level with computerized real time intracellular calcium ion (Ca2+i) imaging.

PATIENTS

Adenoma specimens were obtained from 4 male and 11 female acromagalic patients (mean age 56, range 26-72 years) undergoing transsphenoidal hypophysectomy.

METHODS

The identity of the biopsy material obtained was confirmed by Immunocytochemistry for hGH and in situ hybridization histochemistry using a 35S end-labelled hGH oligodeoxynucleotide probe and probes complementary to proopiomelanocortin and prolactin. Genomic DNA coding for somatostatin receptor (SSTR2) from each adenoma was PCR amplified and sequenced. Cells cultured from these adenoma were subject to computerized real time intracellular Ca2+i imaging at a single cell level.

RESULTS

In cells from 11 of the 15 adenomas, SRIH produced a reversible, dose-independent reduction in [Ca2+]i from the mean of 167 +/- 11 to 43 +/- 3 nM within 51 +/- 1.8 s, and blocked the growth hormone releasing hormone (GRH)-induced increase in [Ca2+]i as expected. In the same adenomas, withdrawal of SRIH after a 30 second exposure produced a small but significant increase in resting [Ca2+]i. Pretreatment with pertussis toxin abolished the SRIH-Induced inhibition of [Ca2+]i and prevented the SRIH-induced inhibition of the effect of GRH on [Ca2+]i. One of the remaining 4 adenomas was completely unresponsive to SRIH despite responding vigorously to other ligands and Immunostaining strongly for GH. Surprisingly, cells from 3 adenomas showed a paradoxical increase in [Ca2+]i in response to SRIH in some or, in one case, all of the cells examined. In all adenomas the sequence of SSTR2 corresponded to wild-type.

CONCLUSIONS

In the majority of cells derived from human somatotrophic adenomas, SRIH caused a reduction in baseline [Ca2+]i and inhibition of GRH-induced [Ca2+]i increase, as observed in somatotrophs of other species. In addition, SRIH was found either to induce a paradoxical increase in [Ca2+]i or to have no effect on [Ca2+]i in a small proportion of somatotroph adenomas examined. This finding corroborates the clinical observation that the response to SRIH analogues varies markedly between somatotroph adenoma patients. There was no evidence of SSTR2 mutations in any of the adenomas examined.

Effects of inhibitors of deoxyhypusine synthase on the differentiation of mouse neuroblastoma and erythroleukemia cells

Deoxyhpusine synthase catalyzes the conversion of lysine to deoxyhypusine residue on the eukaryotic initiation factor 5A (eIF-5A) precursor using spermidine as the substrate. Subsequent hydroxylation of the deoxyhypusine residue completes hypusine formation on eIF-5A. Polyamines (putrescine, spermidine, and spermine) have been implicated in tumor growth and differentiation. Because deoxyhypusine/hypusine formation is one of the most specific polyamine-dependent biochemical events, we decided to use N1-guanyl-1,7-diaminoheptane (GC7), a potent inhibitor for deoxyhypusine synthase, to assess the role of hypusine formation on tumor growth and differentiation. GC7 suppressed the growth of N2a mouse neuroblastoma cells and DS19 murine erythroleukemia cells at micromolar concentrations. However, within a narrow concentration range, GC7 could promote the differentiation of mouse neuroblastoma cells in the presence of suboptimal amount of dibutyryl cAMP. In contrast, GC7 blocked the differentiation of DS19 cells induced with hexamethylene bisacetamide. Polyamine depletion by difluoromethyl ornithine (DFMO) has previously been shown to promote differentiation of neuroblastoma cells but inhibits erythrodifferentiation. Since our studies demonstrated that GC7 mimics the action of DFMO on tumor differentiation, it is likely that the effect of DFMO on tumor differentiation is mediated by hypusine formation and that GC7 represents a more specific inhibitor that can alter the differentiation program in certain tumor cells.

Correlation of chloroethylnitrosourea resistance with ERCC-2 expression in human tumor cell lines as determined by quantitative competitive polymerase chain reaction

We have developed a method to quantitate ERCC-2 gene expression in tumor cell lines. A mutant ERCC-2 DNA fragment (1-bp mutation) is used as a competitive DNA template in a coamplification PCR reaction with cDNA obtained by reverse transcribing DNase-free total RNA from six human tumor cell lines. The PCR products are separated on agarose gel by virtue of their differential banding pattern upon restriction enzyme digestion. Densitometric readings of the PCR products from a negative film of the gel are used to establish a linear regression curve, which in turn is used to quantitate ERCC-2 levels. Beta-actin expression is similarly quantitated. Normalized ERCC-2 gene expression (either to beta-actin or to total RNA) correlates with cytotoxicity of 1,3-bis-(2-chloroethyl)-1-nitrosourea or (2-chloroethyl)-3-sarcosinamide-1-nitrosourea, suggesting that ERCC-2 may play an important role in drug resistance in these cell lines. This method is reliable and can be used to quantitate gene expression in clinical tumor specimens.

Molecular cloning and functional characterization of a rat pituitary G protein-coupled adenosine triphosphate (ATP) receptor

There is increasing evidence that pituitary ATP receptors may play a novel role in modulating pituitary function. This work reports the isolation and expression of a pituitary ATP receptor gene clone from a rat pituitary complementary DNA library. The isolated clone (rpP2U) has a 1125-bp coding sequence flanked by 483 bp of 5' - and 422 bp of 3'-untranslated sequences. The deduced 374-amino acid product shows structural features common to other G protein-coupled receptors, and when stably transfected into a glioma cell line lacking endogenous ATP receptors, is functionally characterized as a P2U purinoceptor. Specifically, the ATP-induced intracellular Ca2+ mobilization in the transfected cells was inhibited by suramin, 2-methylthio-ATP had a modest stimulatory effect on intracellular Ca2+ mobilization, and beta, gamma-methylene ATP and alpha, beta-methylene ATP had no effect. The cloned receptor exhibited the agonist potency and efficacy profile of ATP approximately equal to uridine triphosphate > ADP approximately equal to uridine diphosphate > GTP. Such characteristics very closely mimic the pharmacologically defined P2U purinoceptor of primary rat gonadotropes and mixed sheep pituitary cells, and Southern blot analysis further indicates that there is only one allele in rat genome for the P2U purinoceptor. These findings suggest that the P2U purinoceptor is the predominant G protein-linked ATP receptor found in the pituitary.

Regulation of p53 expression in HeLa cells

Incubation of Hela cells in the presence of insulin results in suppression of p53 expression. Treatment of cells with vanadate, an inhibitor of protein tyrosine phosphatase, likewise led to a dramatic reduction in the level of p53 transcript. On the other hand, significant induction of p53 message was demonstrated when Hela cells were exposed to genistein, a protein tyrosine kinase inhibitor. When cells were cultured in the presence of phosphotyrosine, there was a marked decrease in p53 expression. Neither phosphoserine nor phosphothreonine had an effect on p53 expression. Furthermore, simultaneous presence of both insulin and phosphotyrosine did not result in a greater suppression of the p53 message than when either of the agents was acting singly.

A counter current vascular network model of heat transfer in tissues

A fully conjugated blood vessel network model (FCBVNM) for calculating tissue temperatures has been developed, tested, and studied. This type of model represents a more fundamental approach to modeling temperatures in tissues than do the generally used approximate equations such as the Pennes'BHTE or effective thermal conductivity equations. As such, this type of model can be used to study many important questions at a more basic level. For example, in the particular hyperthermia application studied herein, a simple vessel network model predicts that the role of counter current veins is minimal and that their presence does not significantly affect the tissue temperature profiles: the arteries, however, removed a significant fraction of the power deposited in the tissue. These more fundamental models can also be used to check the validity of approximate equations. For example, using the present simple model, when the temperatures calculated by the FCBVNM are used for comparing predictions from two approximation equations (a simple effective thermal conductivity and a simple Pennes' bio-heat transfer equation formulation of the same problem) it is found that the Pennes' equation better approximates the FCBVNM temperatures than does the k(eff) model. These results also show that the "perfusion" value (W) in the Pennes' BHTE is not necessarily equal to the "true" tissue perfusion (P) as calculated from mass flow rate considerations, but can be greater than, equal to, or less than that value depending on (1) how many vessel levels are modeled by the BHTE, and (2) the "true" tissue perfusion magnitude. This study uses a simple, generic vessel network model to demonstrate the potential usefulness of such fully conjugated vessel network models, and the associated need for developing and applying more complicated and realistic vascular network models. As more realistic vascular models (vessel sizes, orientations, and flow rates) are developed, the predictions of the fully conjugated models should more closely model and approach the true tissue temperature distributions, thus making these fully conjugated models more accurate and valuable tools for studying tissue heat transfer processes.

Microencapsulation for cell implants into the central nervous system: the importance of alginate viscosity and related factors

We have developed microcapsules using sodium alginate and poly-L-lysine with optimal combinations of experimental parameters and also used different autoclave times to evaluate the impact of sterilization on the property of capsules. We found that an autoclave time of 20 min was sufficient for sterilization of the alginate, and the optimal concentration of the alginate of low and high viscosity was 1.75 and 1.25% respectively. The capsules made with those optimal parameters remained intact for 6 months in an environment resembling that of the brain. Our results suggest that it is important to optimally combine experimental parameters in order to obtain reliable microcapsules, which may be used for many secretory cell implantats into the central nervous system in vivo.

Effects of extracellular nucleotides in the pituitary: adenosine triphosphate receptor-mediated intracellular responses in gonadotrope-derived alpha T3-1 cells

We have recently identified gonadotropes as target cells for ATP action via ATP receptors of the P2U subtype. The present studies have used gonadotrope-derived alpha T3-1 cells to examine the possible signaling mechanisms subserving ATP action in gonadotropes. Addition of ATP produced a biphasic intracellular Ca2+ (Ca2+i) response: a transient spike followed by a small plateau. Removal of extracellular Ca2+ or depolarization with KCl abolished the plateau but had no effect on the spike. The plateau was also blocked by cadmium or nifedipine but not nickel. Pretreatment with GnRH or thapsigargin but not ryanodine inhibited the subsequent Ca2+i response to ATP. Pertussis toxin had no effect on ATP-induced Ca2+i response, whereas the phospholipase C inhibitor U73122 reduced the response. These observations suggest that the Ca2+i response is mediated by a pertussis toxin-insensitive and phospholipase C-coupled G-protein and reflects Ca2+ release from the GnRH- and thapsigargin-sensitive Ca2+ pool followed by Ca2+ influx through high voltage-gated Ca2+ channels. Activation of these ATP receptors had no apparent effects on the cAMP and cGMP signaling systems. Treatment with ATP-gamma S caused the translocation of protein kinase C (PKC) epsilon but not PKC zeta and PKC alpha to the particulate fraction. These data not only characterize the ATP receptor-mediated intracellular signaling in alpha T3-1 cells and render further evidence for a mediator role for nucleotides in gonadotrope function but also provide the first direct demonstration of PKC translocation by ATP receptors.

Evidence for a role of pituitary ATP receptors in the regulation of pituitary function

Despite a rapidly increasing acceptance for a role of ATP as an extracellular mediator in several biological systems, the present report shows that ATP may mediate physiological responses in pituitary cells. We have now been able to demonstrate a specific action of ATP receptors to mediate the release of luteinizing hormone from gonadotropes and have coupled them with further studies that clearly show that ATP can be exocytotically released from cultured rat pituitary cells. Both ATP and UTP (100 microM) caused a > 14-fold increase in the rate of luteinizing hormone release from superfused cells. Adenosine 5'-[alpha, beta-methylene]triphosphate and 5'-[beta,gamma-methylene triphosphate were ineffective, and 2-methylthio-ATP had only a modest stimulatory effect. Homologous and heterologous desensitization occurred with UTP and ATP, and these did not have additive effects. Thus, nucleotides can be effective stimulators of luteinizing hormone release through a single class of ATP receptor (P2U subtype). The calcium ionophore A23187 provoked release of a substantial amount of ATP from pituitary cells in a concentration- and Ca(2+)-dependent manner, which was desensitized by pretreatment with A23187. This implies a possible paracrine and/or autocrine mechanism by which nucleotides may exert their effects on pituitary cells. In conclusion, we have provided strong evidence for a novel role of extracellular nucleotides as mediators in pituitary--in particular, in gonadotrope--function.

Amplitude-modulated circular-harmonic filter for pattern recognition

An amplitude-modulated circular-harmonic filter is proposed for rotation-invariant pattern recognition. We investigate the filter characteristics by varying two design parameters, A(ρ) and B(ρ), and select optimum values to design an amplitude-modulated circular-harmonic filter. When compared with the phase-only circular-harmonic filter, the amplitude-modulated circular-harmonic filter is found to yield a sharper correlation peak, a better noise tolerance, and an improved correlation discrimination.

Nucleotides as extracellular signalling molecules

There is now wide acceptance that ATP and other nucleotides are ubiquitous extracellular chemical messengers. ATP and diadenosine polyphosphates can be released from synaptosomes. They act on a large and diverse family of P2 purinoceptors, four of which have been cloned. This receptor family can be divided into two distinct classes: ligand-gated ion channels for P2X receptors and G protein-coupled receptors for P2Y, P2U, P2T and P2D receptors. The P2Y, P2U and P2D receptors have a fairly wide tissue distribution, while the P2X receptor is mainly found in neurons and muscles and the P2T and P2Z receptors confined to platelets and immune cells, respectively. Inositol phosphate and calcium signalling appear to be the predominant mechanisms for transducing the G-protein linked P2 receptor signals. Multiple P2 receptors are expressed by neurons and glia in the CNS and also in neuroendocrine cells. ATP and other nucleotides may therefore have important roles not only as a neurotransmitter but also as a neuroendocrine regulatory messenger.

Dosimetric characteristics of a commercial multileaf collimator

The dosimetric characteristics of a multileaf collimator (MLC) retrofitted to a SL25 linear accelerator have been investigated. Central-axis depth dose, surface dose, penumbra, beam flatness and symmetry, field size factors, beam transmission through leaves and/or diaphragms, and leakage between the leaves were measured. Quantitative measurements of all beam parameters show good agreement with the design specifications of the manufacturer. No changes were observed in flatness, symmetry, penumbra, and penetration for both 6- and 25-MV photon beams when compared to the values for the standard collimator. No significant differences were observed in the penumbra as a function of leaf position. Transmission measurements in areas shielded by either X diaphragms or leaves plus diaphragms are less than 1% of dose within open field. The average leakage between leaves is about 2.5% for 6-MV and 3.5% for 25-MV photon beams. The peak value of the leakage at any point between leaves is less than 5%. The dosimetric features of shaped fields using the MLC are comparable to those of alloy shaped fields with the standard SL25 collimator.