Comparison between Dual-Energy CT and Quantitative Susceptibility Mapping in Assessing Brain Iron Deposition in Parkinson Disease

BACKGROUND AND PURPOSE

Both dual-energy CT and quantitative susceptibility mapping can evaluate iron depositions in the brain. The purpose of this study was to compare these 2 techniques in evaluating brain iron depositions in Parkinson disease.

MATERIALS AND METHODS

Forty-one patients with Parkinson disease (Parkinson disease group) and 31 age- and sex-matched healthy controls (healthy control group) were included. All participants underwent brain dual-energy CT and quantitative susceptibility mapping. ROIs were set bilaterally in the globus pallidus, substantia nigra, red nucleus, caudate nucleus, and putamen. CT values and magnetic susceptibility values were obtained in each ROI. Differences in CT values and magnetic susceptibility values between the Parkinson disease and healthy control groups were compared, followed by analysis of receiver operating characteristic curves. Correlations between CT values and magnetic susceptibility values were then evaluated.

RESULTS

The CT values of the bilateral globus pallidus, substantia nigra, and red nucleus were higher in the Parkinson disease group (P < .05). The magnetic susceptibility values of the bilateral globus pallidus and substantia nigra were higher in the Parkinson disease group (P < .05). The CT value of the right globus pallidus in linear fusion images had the highest diagnostic performance (0.912). Magnetic susceptibility values of the bilateral globus pallidus in the Parkinson disease group were positively correlated with CT values at the level of 80 kV(peak), linear fusion images, and SN150 kV(p) (r = 0.466∼0.617; all, P < .05).

CONCLUSIONS

Both dual-energy CT and quantitative susceptibility mapping could assess excessive brain iron depositions in Parkinson disease, and we found a positive correlation between CT values and magnetic susceptibility values in the bilateral globus pallidus.

[Recurrence and influencing factors of diabetic foot ulcer in patients with type 2 diabetes mellitus]

Objective: To investigate the recurrence and influencing factors of diabetic foot ulcer in patients with type 2 diabetes mellitus. Methods: Totally 185 type 2 diabetes patients with new-onset of diabetic foot ulcers admitted to Fuyang People's Hospital of Anhui Province from January 2011 to December 2015 were enrolled in this study, including 120 males and 65 females, aged 40-79 years. All the patients were followed up for 3 years, and their clinical data were retrospectively analyzed by the case-control study. The Kaplan-Meier cumulative recurrence curve was drawn according to the 3-year cumulative recurrence rate of diabetic foot ulcers. The time to visit, toe involvement, and amputation of involved toes in patients with recurrent diabetic foot ulcer were counted at the initial onset and the recurrence of the ulcers, respectively, and the data were statistically analyzed with t test and chi-square test. According to the recurrence of diabetic foot ulcers, the patients were divided into foot ulcer recurrence group and foot ulcer non-recurrence group. The gender, age, course of diabetes mellitus, length of hospital stay, visit time, body mass index, glycosylated hemoglobin HbA1c, total bilirubin, albumin, creatinine, cholesterol, low density lipoprotein (LDL), high density lipoprotein (HDL), triglycerides, hemoglobin, white blood cell count, toe involvement, toe amputation, ankle-brachial index, diabetic retinopathy (DR), diabetic peripheral neuropathy (DPN), diabetic nephropathy (DN), history of hypertension, cardio-cerebrovascular disease, smoking, residence, solitary life, and walking disorder of patients between the two groups were compared, and the data were statistically analyzed with t test and chi-square test. Log-rank test was performed on the indexes with P<0.1 in comparison between two groups, and the indexes with statistically significant differences in Log-rank test were analyzed by multivariate Cox regression analysis to screen the influencing factors of recurrence of diabetic foot ulcer. Results: (1) The 3-year cumulative recurrence rate of diabetic foot ulcers in 185 patients with type 2 diabetes mellitus was 47.0% (87/185). (2) For 87 patients with diabetic foot ulcer recurrence, compared with that at the initial onset of the ulcers, the visit time was significantly shorter (t=10.593, P<0.01), the toe amputation rate was significantly increased (χ(2)=5.118, P<0.05), but there was no obvious change in toe involvement at the recurrence of the ulcers. (3) There were statistically significant differences in age, course of diabetes mellitus, length of hospital stay, body mass index, glycosylated hemoglobin HbA1c, total bilirubin, albumin, creatinine, cholesterol, LDL, HDL, hemoglobin, white blood cell count, gender, toe amputation, ankle-brachial index, DR, history of cardio-cerebrovascular disease, solitary life, and walking disorder of patients between foot ulcer recurrence group (87 patients) and foot ulcer non-recurrence group (98 patients) (t=5.123, 4.242, 5.324, -24.572, 6.102, -1.984, -9.747, 3.226, 3.076, 3.646, -4.683, -7.502, 8.095, χ(2)=5.621, 18.433, 4.546, 5.785, 9.655, 7.625, 7.886, P<0.05 or P<0.01), while the rest of the indexes of patients between the two groups were similar. Log-rank test showed that the two groups had statistically significant differences in age, course of diabetes mellitus, length of hospital stay, glycosylated hemoglobin HbA1c, total bilirubin, albumin, creatinine, ankle-brachial index, DPN, and walking disorder (χ(2)=210.046, 44.837, 34.107, 98.685, 66.532, 294.451, 260.554, 5.012, 6.818, 11.160, P<0.05 or P<0.01). Age, total bilirubin, albumin, DPN, and walking disorder were the influencing factors for the recurrence of diabetic foot ulcers in patients with type 2 diabetes mellitus (hazard ratio=1.024, 0.678, 0.849, 2.335, 4.099, 95% confidence interval=1.001-1.047, 0.558-0.823, 0.797-0.904, 1.280-4.258, 2.044-8.223, P<0.05 or P<0.01). Conclusions: The 3-year cumulative recurrence rate of diabetic foot ulcers in patients with type 2 diabetes mellitus is relatively high, with the influencing factors being age, total bilirubin, albumin, DPN, and walking disorder.

Advances in renal (patho)physiology using multiphoton microscopy

Multiphoton excitation fluorescence microscopy is a state-of-the-art confocal imaging technique ideal for deep optical sectioning of living tissues. It is capable of performing ultrasensitive, quantitative imaging of organ functions in health and disease with high spatial and temporal resolution which other imaging modalities cannot achieve. For more than a decade, multiphoton microscopy has been successfully used with various in vitro and in vivo experimental approaches to study many functions of different organs, including the kidney. This study focuses on recent advances in our knowledge of renal (patho)physiological processes made possible by the use of this imaging technology. Visualization of cellular variables like cytosolic calcium, pH, cell-to-cell communication and signal propagation, interstitial fluid flow in the juxtaglomerular apparatus (JGA), real-time imaging of tubuloglomerular feedback (TGF), and renin release mechanisms are reviewed. A brief summary is provided of kidney functions that can be measured by in vivo quantitative multiphoton imaging including glomerular filtration and permeability, concentration, dilution, and activity of the intrarenal renin-angiotensin system using this minimally invasive approach. New visual data challenge a number of existing paradigms in renal (patho)physiology. Also, quantitative imaging of kidney function with multiphoton microscopy has tremendous potential to eventually provide novel non-invasive diagnostic and therapeutic tools for future applications in clinical nephrology.

Cholesterol-3-beta, 5-alpha, 6-beta-triol induced genotoxicity through reactive oxygen species formation

The mutagenicity of oxysterols, cholesterol-3beta,5alpha,6beta-triol (alpha-Triol), 7-keto-cholesterol (7-Keto) and cholesterol-5alpha,6alpha-epoxide (alpha-Epox) were examined by the Ames method and chromosome aberration test in this study. Only alpha-Triol concentration-dependently caused an increase of bacterial revertants in the absence of metabolic activating enzymes (S9), but not 7-keto and alpha-Epox. The mutagenic effect of alpha-Triol was reduced by the addition of S9. On the other hand, although alpha-Triol significantly induced chromosome aberration in CHO-K1 cells with and without S9. However, the addition of S9 reduced the degree of abnormal structure chromosome compared to without S9 mix. Catalase and superoxide dismutase (SOD) inhibited alpha-Triol induced increase of revertants in Salmonella typhimurium and chromosome aberration frequency in CHO cells, suggesting that reactive oxygen species (ROS) might be involved in the genotoxic effect of alpha-Triol. Treatment with alpha-Triol increased the ROS production in CHO cells, which could be attenuated by catalase and SOD. Results in this study suggested, for the first time that alpha-Triol, causes genotoxic effect in an ROS-dependent manner.

Reactive oxygen species are crucial for hydroxychavicol toxicity toward KB epithelial cells

Betel quid (BQ) chewing shows a strong correlation to the incidence of oral submucous fibrosis (OSF), leukoplakia and oral cancer. BQ contains mainly areca nut, lime, Piper betle leaf (PBL) and the inflorescence of P. betle (IPB). Hydroxychavicol (4-allyl-catechol, HC), as a major phenolic compound in PBL and IPB, is shown to induce oxidative stress, glutathione (GSH) depletion and cell cycle deregulation. Using bivariate BrdU/PI flow cytometry, KB cells in DNA synthesis (S phase) are shown to be sensitive to the toxic effect of HC and show cell cycle arrest and apoptosis following exposure to 0.1 and 0.3 mM HC. HC-induced apoptosis and cell cycle arrest are associated with mitochondrial membrane potential (delta Psim) depolarization as revealed by a decrease in rhodamine fluorescence. N-acetyl-L-cysteine (1 mM), superoxide dismutase (100 U/ml) and catalase (1000 U/ml) were effective in prevention of HC-induced GSH depletion (as indicated by chloromethylfluorescein fluorescence), reactive oxygen species (ROS) production (by dichlorofluorescein fluorescence), cell cycle arrest and apoptosis. However, dimethylthiourea (2 mM), neocuproine (1 mM), 1,10-phenanthroline (200 microM) and desferrioxamine (0.5 mM) showed little effect on HC-induced cell changes. HC elevated the cellular and mitochondrial GSH levels at moderate concentrations (0.05-0.1 mM), whereas at a concentration of 0.3 mM, inhibitory effects were noted. These results indicate that HC consumption may be associated with BQ-chewing-related oral mucosal diseases via GSH depletion, ROS production, mitochondrial dysfunction, cell cycle disturbance and the induction of apoptosis. These events are related to the production of superoxide radicals and hydrogen peroxide.

Synthesis, antiplatelet and vasorelaxing effects of monooxygenated flavones and flavonoxypropanolamines

A series of flavones and flavonoxypropanolamines were synthesized and tested in-vitro for their ability to inhibit aggregation of washed rabbit platelets and human platelet-rich plasma (PRP), and for vasoconstriction of rat thoracic aorta. The various substituted positions of the hydroxyl group in flavone ring B and the various oxypropanolamine side chains substituted at position C-2' of flavone modified the antiplatelet effects. All the compounds tested in human PRP showed significant inhibition of secondary aggregation induced by adrenaline (epinephrine), suggesting that the antiplatelet effect of these compounds is mainly due to an inhibitory effect on thromboxane formation. Compounds 11 and 12 also had potent vasorelaxant effects in rat thoracic aorta. Phenylephrine- and high-K+-induced 45Ca2+ influx in aorta were both inhibited by the selected compound 11. This result indicates that the inhibitory effect of 11 on the contractile response caused by high-K+ medium and noradrenaline (norepinephrine) in rat thoracic aorta is mainly due to inhibition of Ca2+ influx through both voltage-dependent and receptor-operated Ca2+ channels.

Quantitation of Na+-K+-2Cl- cotransport splice variants in human tissues using kinetic polymerase chain reaction

A kinetic reverse transcription-polymerase chain reaction (RT-PCR)-based assay is described that can discriminate and quantitate differentially spliced mRNAs. This assay should be generally applicable for high-throughput quantitation of differentially spliced transcripts. The utility of this method was assessed for spliced transcripts encoded by the human Na+-K+-2Cl- cotransporter gene hNKCC1. Evidence is presented that the NKCC1 isoform of the human Na+-K+-2Cl- cotransporter is differentially spliced analogous to that recently described for the mouse Na+-K+-2Cl- cotransporter gene BSC2. The nucleotide sequences of the two human splice variants predict Na+-K+-2Cl- cotransporter proteins differing only in length. Stable transfectants expressing these human splice variants, designated NKCC1a or NKCC1b, were constructed. Both splice variants produce functional Na+-K+-2Cl- cotransporters in vivo. The abundance of NKCC1 mRNA and patterns of differential splicing in 10 different tissue types and three cell lines were quantitated using the kRT-PCR assay. The results showed that the total amount of NKCC1 mRNA varied by more than 30-fold in the human tissues and cell lines examined. The ratio of NKCC1a/NKCC1b varied nearly 70-fold among these same tissues and cell lines suggesting that differential splicing of the NKCC1 transcript may play a regulatory role in human tissues.

Triptolide and chemotherapy cooperate in tumor cell apoptosis. A role for the p53 pathway

Triptolide (PG490), a diterpene triepoxide, is a potent immunosuppressive agent extracted from the Chinese herb Tripterygium wilfordii. We have previously shown that triptolide blocks NF-kappaB activation and sensitizes tumor necrosis factor (TNF-alpha)-resistant tumor cell lines to TNF-alpha-induced apoptosis. We show here that triptolide enhances chemotherapy-induced apoptosis. In triptolide-treated cells, the expression of p53 increased but the transcriptional function of p53 was inhibited, and we observed a down-regulation of p21(waf1/cip1), a p53-responsive gene. The increase in levels of the p53 protein was mediated by enhanced translation of the p53 protein. Additionally, triptolide induced accumulation of cells in S phase and blocked doxorubicin-mediated accumulation of cells in G(2)/M and doxorubicin-mediated induction of p21. Our data suggest that triptolide, by blocking p21-mediated growth arrest, enhances apoptosis in tumor cells.

Effects of cartap on isolated mouse phrenic nerve diaphragm and its related mechanism

Cartap, a nereistoxin analogue pesticide, is reported to have no irritation to eyes in rabbits. However, we have demonstrated recently that cartap could actually cause acute death in rabbits via ocular exposure. Our preliminary study with isolated mouse phrenic nerve diaphragms has shown that instead of neuromuscular blockade, cartap caused muscular contracture. The objective of the study was to examine the effect of cartap on the neuromuscular junction in more detail and to investigate its possible underlying mechanism with isolated mouse phrenic nerve diaphragms and sarcoplasmic reticulum (SR) vesicles. Cartap or nereistoxin at various concentrations was added in the organ bath with isolated mouse phrenic nerve diaphragm and both nerve- and muscle-evoked twitches were recorded. Instead of blocking the neuromuscular transmission as nereistoxin did, cartap caused contracture in stimulated or quiescent isolated mouse phrenic nerve diaphragm. Both the cartap-induced muscular contracture force and the time interval to initiate the contracture were dose-dependent. The contracture induced by cartap was not affected by the pretreatment of the diaphragm with the acetylcholine receptor blocker alpha-bungarotoxin; the Na(+) channel blocker tetrodotoxin; or various Ca(2+) channel blockers, NiCl(2), verapamil, and nifedipine. On the contrary, the contracture was significantly inhibited when the diaphragm was pretreated with ryanodine or EGTA containing Ca(2+)-free Krebs solution or in combination. This suggested that both internal and extracellular Ca(2+) might participate in cartap-induced skeletal muscle contracture. Moreover, cartap inhibited the [(3)H]-ryanodine binding to the Ca(2+) release channel of SR in a dose-dependent manner. Additionally, cartap could induce a significant reduction in Ca(2+)-ATPase activity of SR vesicles at a relatively high dose. The results suggested that cartap might cause the influx of extracellular Ca(2+) and the release of internal Ca(2+), with subsequent induction of muscular contracture in the isolated mouse phrenic nerve diaphragm. Based on these findings, we propose that the acute death of rabbits following ocular exposure to cartap might have resulted from respiratory failure secondary to diaphragm contracture.

Induction of skeletal muscle contracture and calcium release from isolated sarcoplasmic reticulum vesicles by sanguinarine

The benzophenanthrine alkaloid, sanguinarine, was studied for its effects on isolated mouse phrenic-nerve diaphragm preparations. Sanguinarine induced direct, dose-dependent effects on muscle contractility. Sanguinarine-induced contracture was partially inhibited when the extracellular Ca(2+) was removed or when the diaphragm was pretreated with nifedipine. Depletion of sarcoplasmic reticulum (SR) internal calcium stores completely blocked the contracture. Sanguinarine induced Ca(2+) release from the actively loaded SR vesicles was blocked by ruthenium red and dithiothreitol (DTT), consistent with the ryanodine receptor (RyR) as the site of sanguinarine action. Sanguinarine altered [(3)H]-ryanodine binding to the RyR of isolated SR vesicles, potentiating [(3)H]-ryanodine binding at lower concentrations and inhibiting binding at higher concentrations. All of these effects were reversed by DTT, suggesting that sanguinarine-induced Ca(2+) release from SR occurs through oxidation of critical SH groups of the RyR SR calcium release channel.

Alterations in the properties and isoforms of sciatic nerve Na(+), K(+)-ATPase in methylcyclopentadienyl manganese tricarbonyl-treated mice

The in vivo effect of methylcyclopentadienyl manganese tricarbonyl (MMT), an organic manganese-containing compound, on the mouse motor nerve was studied. The motor nerve conduction velocity was markedly decreased in MMT-treated mice. The Na(+),K(+)-ATPase activity of sciatic nerve isolated from MMT-treated mice was decreased; however, the sciatic nerve Na(+),K(+)-ATPase activity was not affected by the in vitro treatment of MMT. Moreover, [(3)H]ouabain binding of sciatic nerve isolated from MMT-treated mice was decreased. Using Western blot analysis, the amount of Na(+),K(+)-ATPase catalytic alpha1 subunit polypeptide in sciatic nerve of MMT-treated mice was also decreased. These results indicate that a causal relationship may exist between reduced nerve Na(+),K(+)-ATPase activity and motor nerve conduction velocity in MMT-treated mice and that a measurable decrease in alpha1 catalytic subunit isoform of Na(+),K(+)-ATPase may be necessary for the development of peripheral neuropathy by MMT.

Transcript quantitation in total yeast cellular RNA using kinetic PCR

Kinetically monitored, reverse transcriptase-initiated PCR (kinetic RT-PCR, kRT-PCR) is a novel application of kinetic PCR for high throughput transcript quantitation in total cellular RNA. The assay offers the simplicity and flexibility of an enzyme assay with distinct advantages over DNA microarray hybridization and SAGE technologies for certain applications. The reproducibility, sensitivity and accuracy of the kRT-PCR were assessed for yeast transcripts previously quantitated by a variety of methods including SAGE analysis. Changes in transcript levels between different genetic or physiological cell states were reproducibly quantitated with an accuracy of +/-20%. The assay was sufficiently sensitive to quantitate yeast transcripts over a range of more than five orders of magnitude, including low abundance transcripts encoding cell cycle and transcriptional regulators.

Inhibition of agonist-induced vasocontraction and impairment of endothelium-dependent vasorelaxation by extract of motorcycle exhaust particles in vitro

The in vitro effects of motorcycle exhaust particulate extract (MEPE) on blood vessels were studied in thoracic aorta isolated from Wistar rat. The MEPE relaxed the phenylephrine-precontracted aorta with an EC50 value of 0.05 +/- 0.004 mg/ml. This relaxing effect of MEPE persisted in endothelium-denuded aorta, suggesting that the relaxation induced by MEPE is endothelium-independent. The phenylephrine-induced vasocontraction and inositol 1,4,5-triphosphate formation were inhibited concentration dependently in aorta pretreated with MEPE. However, the high-K+-induced vasocontraction and the Ca2+ sensitivity of the contractile proteins were not significantly affected by MEPE. In addition to the inhibitory effects on agonist-induced contraction, the vasorelaxing effects both of acetylcholine and of sodium nitroprusside were impaired by MEPE. The inhibitory effects of MEPE on acetylcholine and sodium nitroprusside, but not phenylephrine, were reversed by cotreatment with superoxide dismutase. These results showed that the MEPE, added in vitro, inhibited the phenylephrine-induced, but not depolarization-induced, vasocontraction of aorta. The MEPE also impaired the vasorelaxation induced by acetylcholine in a superoxide anion-dependent manner.

Cascades of mammalian caspase activation in the yeast Saccharomyces cerevisiae

Caspases (aspartate-specific cysteine proteases) play a critical role in the execution of the mammalian apoptotic program. To address the regulation of human caspase activation, we used the yeast Saccharomyces cerevisiae, which is devoid of endogenous caspases. The apical procaspases, -8beta and -10, were efficiently processed and activated in yeast. Although protease activity, per se, was insufficient to drive cell death, caspase-10 activity had little effect on cell viability, whereas expression of caspase-8beta was cytotoxic. This lethal phenotype was abrogated by co-expression of the pan-caspase inhibitor, baculovirus p35, and by mutation of the active site cysteine of procaspase-8beta. In contrast, autoactivation of the executioner caspase-3 and -6 zymogens was not detected. Procaspase-3 activation required co-expression of procaspase-8 or -10. Surprisingly, activation of procaspase-6 required proteolytic activities other than caspase-8, -10, or -3. Caspase-8beta or -10 activity was insufficient to catalyze the maturation of procaspase-6. Moreover, a constitutively active caspase-3, although cytotoxic in its own right, was unable to induce the processing of wild-type procaspase-6 and vice versa. These results distinguish sequential modes of activation for different caspases in vivo and establish a yeast model system to examine the regulation of caspase cascades. Moreover, the distinct terminal phenotypes induced by various caspases attest to differences in the cellular targets of these apoptotic proteases, which may be defined using this system.

Mediation of gamma-hexachlorocyclohexane-induced DNA fragmentation in HL-60 cells through intracellular Ca2+ release pathway

The cytotoxicity of gamma-hexachlorcyclohexane (gamma-HCC) was evaluated in HL-60 cells. Gamma-HCC dose-dependently induced cytotoxicity of HL-60 with an IC50 value of 60+/-5 microM. The gamma-HCC treated cells showed some characteristic changes of apoptosis, including blebbing of the membrane, condensation of the nuclear chromatin, vacuolation of cytoplasm and internucleosomal DNA fragmentation. Gamma-HCC induced DNA fragmentation of HL-60 cells in a dose-, time- and Ca2+-dependent manner. The DNA fragmentation induced was inhibited by intracellular Ca2+ chelator, calmodulin antagonist and Ca2+ sensitive endonuclease inhibitor. Gamma-HCC caused a steady increase in the cytosolic free Ca+ concentration due to release from intracellular stores. Neither the DNA fragmentation nor the increase of intracellular Ca2+ induced by gamma-HCC was inhibited by the removal of extracellular Ca2+. These data suggested that the cytotoxicity of gamma-HCC in HL-60 cells is mediated by the increase of intracellular Ca2+ concentration and the activation of Ca2+-dependent endonuclease, which triggers apoptosis in a Ca2+ and calmodulin-dependent manner.

Analysis of colorectal cancer by comparative genomic hybridization: evidence for induction of the metastatic phenotype by loss of tumor suppressor genes

Current models suggest that colon cancer initiation and progression are secondary to both the activation of oncogenes and the deletion of tumor suppressor genes. The role of each, however, is still poorly understood, particularly with regard to the induction of metastasis. We hypothesized that genetic differences exist between tumors that metastasize distantly and those that do not, and that oncogenes and tumor suppressor genes participate equally in this process. To address this hypothesis, human tumor specimens from localized [tumor-node-metastasis (TNM) stage I-III] and primary colon cancers (n = 10) were directly compared with metastatic (TNM stage IV) lesions (n = 10) using comparative genomic hybridization analysis. Although several alterations were shared equally between primary tumors and metastases (+7q, +19q, and +20q), two patterns of distinguishing alterations were observed: (a) alterations that were more extensive in liver metastases than in primary tumors (+8q, +13q, -4p, -8p, -15q, -17p, -18q, -21q, and -22q); and (b) alterations that were unique to metastatic lesions (-9q, -11q, and -17q). Overall, genetic losses were more common than gains, and, more importantly, the number of losses/tumor was significantly higher for metastases than for primary tumors (9.3 + 1.3 versus 4.1 + 0.7; P = 0.00062, Wilcoxon's rank-sum test). The distinct predominance of genetic losses in the metastatic lesions when compared with the primary localized tumors provides evidence that the metastatic phenotype is induced by the deletion of tumor suppressor genes and permits the construction of physical maps targeting regions where novel tumor suppressor genes are likely to exist.

Emodin-induced muscle contraction of mouse diaphragm and the involvement of Ca2+ influx and Ca2+ release from sarcoplasmic reticulum

1. The effects on skeletal muscle of emodin, an anthraquinone, were studied in the mouse isolated diaphragm and sarcoplasmic reticulum (SR) membrane vesicles. 2. Emodin dose-dependently caused muscle contracture, simultaneously depressing twitch amplitude. Neither tubocurarine nor tetrodotoxin blocked the contraction suggesting that it was caused myogenically. 3. The contraction induced by emodin persisted in a Ca2+ free medium with a slight reduction in the maximal force of contraction. The contraction induced by emodin in the Ca2+ free medium was completely blocked when the internal Ca2+ pool of the muscle was depleted by ryanodine. These data suggest that the contraction caused by emodin is due to the release of Ca2+ from the intracellular ryanodine-sensitive pool. 4. In contrast to the effect seen in the Ca2+ free medium, emodin induced a small but consisted contraction in the ryanodine-treated muscle in Krebs medium. The contraction was blocked in the presence of dithiothreitol and was partially blocked by nifedipine, suggesting that oxidation of a sulphhydryl group on the external site of dihydropyridine receptor is involved. 5. Emodin dose-dependently increased Ca2+ release from actively loaded SR vesicles and this effect was blocked by ruthenium red, a specific Ca2+ release channel blocker, and the thiol reducing agent, DTT, suggesting that emodin induced Ca2+ release through oxidation of the critical SH of the ryanodine receptor. 6. [3H]-ryanodine binding was dose-dependently potentiated by emodin in a biphasic manner. The degree of potentiation of ryanodine binding by emodin increased dose-dependently at concentrations up to 10 microM but decreased at higher concentrations of 10-100 microM. 7. These data suggest that muscle contraction induced by emodin is due to Ca2+ release from the SR of skeletal muscle, as a result of oxidation of the ryanodine receptor and influx of extracellular Ca2+ through voltage-dependent Ca2+ channels of the plasma membrane.

Studies on neuromuscular blockade by boldine in the mouse phrenic nerve-diaphragm

The effects of boldine [(S)-2,9-dihydroxyl-1,10-dimethoxy-aporphine], a major alkaloid in the leaves and bark of Boldo (Peumus boldus Mol.), on neuromuscular transmission were studied using a muscle phrenic-nerve diaphragm preparation. Boldine at concentrations lower than 200 microM preferentially inhibited, after an initial period of twitch augmentation, the nerve-evoked twitches of the mouse diaphragm and left the muscle-evoked twitches unaffected. The twitch inhibition could be restored by neostigmine or washout with Krebs solution. The twitches evoked indirectly and directly were both augmented initially, suggesting that the twitch augmentation induced by boldine was myogenic. Boldine inhibited the acetylcholine-induced contraction of denervated diaphragm dose-dependently with an IC50 value of 13.5 microM. At 50 microM, boldine specifically inhibited the amplitude of the miniature end plate potential. In addition, boldine was similar to d-tubocurarine in its action to reverse the neuromuscular blocking action of alpha-bungarotoxin. These results showed that the neuromuscular blockade by boldine on isolated mouse phrenic-nerve diaphragm might be due to its direct interaction with the postsynaptic nicotinic acetylcholine receptor.

Effects of boldine on mouse diaphragm and sarcoplasmic reticulum vesicles isolated from skeletal muscle

The effects of boldine [(S)-2,9-dihydroxy-1,10-dimethoxyaporphine], a major alkaloid in the leaves and bark of boldo (Peumus boldus Mol.), on skeletal muscle were studied using mouse diaphragm and isolated sarcoplasmic reticulum membrane vesicles. Boldine, at 10-200 microM, has little effect on the muscle-evoked twitches; however, the ryanodine-induced contracture was potentiated dose-dependently. At higher concentrations of 300 microM, boldine by itself induced muscle contracture of two phases, which were caused by the influx of extracellular Ca2+ and induction of Ca2+ release from the internal Ca2+ storage site, the sarcoplasmic reticulum, respectively. When tested with isolated sarcoplasmic reticulum membrane vesicles, boldine dose-dependently induced Ca2+ release from actively loaded sarcoplasmic reticulum vesicles isolated from skeletal muscle of rabbit or rat which was inhibited by ruthenium red, suggesting that the release was through the Ca2+ release channel, also known as the ryanodine receptor. Boldine also dose-dependently increased apparent [3H]-ryanodine binding with the EC50 value of 50 microM. In conclusion, we have shown that boldine could sensitize the ryanodine receptor and induce Ca2+ release from the internal Ca2+ storage site of skeletal muscle.

Litebamine N-homologues: preparation and anti-acetylcholinesterase activity

Litebamine N-homologues were easily prepared from laurolitsine, generally via three reaction steps (N-alkylation, solvolysis with 1 M NH4OAc under reflux, and the Mannich reaction) in more than 80% overall yield. Among the prepared compounds, N-propyl-, N-isobutyl-, and N-isopropylnorlitebamines exhibited moderate antiacetylcholinesterase activity (IC50 ca. 7.0 microM), while the corresponding N-metho salt of N-propylnorlitebamine showed potent activity (IC50 2.70 microM).

Comparative studies on the induction of muscle contracture in mouse diaphragm and Ca2+ release from sarcoplasmic reticulum vesicles by organotin compounds

Effects of organotins, including triethyltin and tributyltin, on skeletal muscle were studied with diaphragm and isolated sarcoplasmic reticulum membrane vesicles. Triethyltin induced muscle contracture in mouse diaphragm while tributyltin had comparatively less potency and efficacy in inducing the muscle contracture. The contracture induced by tributyltin was inhibited when the diaphragm was pretreated with low Ca2+ medium or caffeine while the contracture induced by triethyltin persisted in the Ca2+-free medium but was inhibited by pretreatment of caffeine. Pretreatment of dithiothreitol blocked the contracture induced by tributyltin but not that by triethyltin. Triethyltin dose-dependently induced Ca2+ release from sarcoplasmic reticulum vesicles and inhibited the Ca2+-ATPase activity. These results suggested that triethyltin induced contracture in mouse diaphragm was mainly by induction of Ca2+ release and inhibition of Ca2+ uptake of the internal Ca2+ storage site the sarcoplasmic reticulum, while the tributyltin induced contracture might be due to enhancement of extracellular Ca2+ influx which further induce the release of internal Ca2+ through the Ca2+-induced Ca2+ release mechanism.

Rat liver transcript profiling in normal and disease states using a kinetic polymerase chain reaction assay

Synthesis of a number of rat liver proteins, including albumin, fibrinogen, apolipoprotein AI, and transferrin, is elevated in the nephrotic syndrome (NS). Increased synthesis of these proteins is regulated at the transcriptional level and occurs in the context of increased mRNA encoding each protein. Changes in albumin, fibrinogen, apolipoprotein AI, and transferrin mRNA levels in total cellular RNA isolated from the livers of normal rats and rats with passive Heymann nephritis were measured using a kinetically monitored, reverse transcriptase-initiated PCR (kRT-PCR) assay. The kRT-PCR assay rapidly quantitated changes in rat liver mRNA levels with an accuracy comparable to that of more labor-intensive mRNA quantitation methods. The relative levels of beta-actin, apolipoprotein AI, fibrinogen, and albumin mRNAs were very similar in total cellular RNA isolated from rat liver versus H4C3 hepatocytes in culture, suggesting that the H4C3 hepatocyte is an appropriate model for studying expression of genes encoding proteins secreted by the liver. Taken together, the results demonstrate the feasibility of using the kRT-PCR assay for isolation and characterization of a soluble factor responsible for elevated synthesis of hepatocyte mRNAs associated with the nephrotic syndrome.

Mechanism of vasorelaxation of thoracic aorta caused by xanthone

The effect of xanthone on smooth muscle was studied in thoracic aorta isolated from rats. Xanthone relaxed the norepinephrine-induced contraction of rat thoracic aorta. This relaxing effect of xanthone persisted in endothelium-denuded aorta suggesting that the relaxation induced by xanthone is endothelium-independent. The norepinephrine and high-K+-induced vasoconstriction was inhibited dose dependently in aorta pretreated with xanthone with IC50 values of 60.26 +/- 8.43 and 82.9 +/- 13.21 microM, respectively. The inositol 1,4,5-trisphosphate formation induced by norepinephrine (3 microM) in rat aorta was not affected by xanthone (10-100 microM), suggesting that the vasorelaxant effect of xanthone was not exerted on the receptor. Xanthone concentration dependently inhibited the 45Ca2+ influx induced by either norepinephrine or high-K+, suggesting that xanthone might act as a blocker of both receptor-operated and voltage-dependent Ca2+ channels. Furthermore, xanthone caused an increase in the level of intracellular cyclic adenosine 3',5'-monophosphate (cAMP), but not cyclic guanosine 3',5'-monophosphate (cGMP) content. These data suggested that the mechanism of xanthone-induced vasorelaxation might involve the increase of intracellular cyclic adenosine 3',5'-monophosphate (cAMP) content and block of Ca2+ channels.

Modulation of cytochrome P-450-dependent monooxygenases, glutathione and glutathione S-transferase in rat liver by geniposide from Gardenia jasminoides

Geniposide is an iridoid glycoside extracted from the fruits of Gardenia jasminoides, which are used as a food colorant and as a traditional Chinese medicine for treatment of hepatic and inflammatory diseases. The effects of geniposide and G. jasminoides fruit crude extract on liver cytochrome P-450 (P-450)-dependent monooxygenases, glutathione and glutathione S-transferase were investigated using rats treated orally with the iridoid glycoside (0.1 g/kg body weight/day) or the fruit crude extract (2 g/kg/day) for 4 days. The treatments decreased serum urea nitrogen level but increased liver to body weight ratio, total hepatic glutathione content and hepatic cytosolic glutathione S-transferase activity. Treatments with geniposide and G. jasminoides decreased P-450 content, benzo[a]pyrene hydroxylation, 7-ethoxycoumarin O-deethylation, and erythromycin N-demethylation activities in liver microsomes without affecting aniline hydroxylation activity. The natural products had no effect on glutathione content and monooxygenase activities in kidney microsomes. Immunoblotting analyses of liver microsomal proteins using mouse monoclonal antibody 2-13-1 to rat P4503A1/2 revealed that geniposide and G. jasminoides crude extract decreased the intensity of a P4503A-immunorelated protein. Protein blots probed with mouse monoclonal antibody 1-12-3 to rat P4501A1 and rabbit polyclonal antibody against human P4502E1 showed that both treatments had little or no effect on P4501A and 2E proteins. The present findings demonstrate that geniposide from G. jasminoides has the ability to inhibit a P4503A monooxygenase and increase glutathione content in rat liver.

Suppression of microsomal cytochrome P450-dependent monooxygenases and mitochondrial oxidative phosphorylation by fullerenol, a polyhydroxylated fullerene C60

The acute toxicity of fullerenol-1 was determined using mice pretreated intraperitoneally (i.p.) with polyhydroxylated C60 derivatives. The LD50 value of fullerenol-1 was estimated to be 1.2 g/kg. Pretreatments with 0.5 and 1.0 g/kg fullerenol-1 decreased cytochromes P450 and b5 contents, and NADPH-cytochrome P450 reductase, benzo[a]pyrene hydroxylase, 7-ethoxycoumarin O-deethylase, aniline hydroxylase, and erythromycin N-demethylase activities in liver microsomes. Pretreatments with 0.01 and 0.1 g/kg fullerenol-1 had no effect on these monooxygenases. Additions of fullerenol-1 to mouse liver microsomes suppressed monooxygenases activities toward benzo[a]pyrene, 7-ethoxycoumarin, aniline, and erythromycin with IC50 values of 42, 94, 102 and 349 microM, respectively. Fullerenol-1 exhibited noncompetitive and mixed-type of inhibition in benzo[a]pyrene hydroxylation and 7-ethoxycoumarin O-deethylation, respectively. Additions of fullerenol-1 to rat liver mitochondria resulted in a dose-dependent inhibition of ADP-induced uncoupling and markedly inhibited mitochondrial Mg2+ -ATPase activity with an IC50 value of 7.1 microM. These results demonstrate that fullerenol-1 can suppress the levels of the microsomal enzymes in vivo and decrease the activities of P450-dependent monooxygenase and mitochondrial oxidative phosphorylation in vitro.

Polycyclic aromatic hydrocarbons-induced vasorelaxation through activation of nitric oxide synthase in endothelium of rat aorta

In the present study, the effect of polycyclic aromatic hydrocarbons (PAHs) on isolated rat aorta was investigated. Acenaphthylene and naphthalene dose-dependently relaxed the phenylephrine-induced contraction of rat aorta with 50% vasorelaxation at 40.8+/-19.83 and 118.75+/-9.83 microM, respectively. The vasorelaxation effect was diminished in the denuded (endothelium removed) aorta suggesting that the relaxation effect of PAHs was endothelium dependent. By comparing PAHs with different ring structures, we have found that acenaphthylene has the highest potency to induce vasorelaxation. Pretreatment with the nitric oxide synthase inhibitor, L-N(G)-nitroarginine methyl ester, and the guanylate cyclase inhibitor, methylene blue, prevents the vasorelaxation induced by PAHs. These results indicate that the vasorelaxation effect of PAHs is mediated by activation of nitric oxide synthase of endothelium.

Polycyclic aromatic hydrocarbons inhibit the activity of acetylcholinesterase purified from electric eel

Polycyclic aromatic hydrocarbons (PAHs) are formed during the incomplete combustion of fossil fuels, wood and municipal waste incineration, from internal combustion engines, and from various food cooking operations and are common environmental contaminants which have been detected in surface waters, sediments, soils, plants, and both rural and urban air. In this study, we have shown that, for the first time, in vitro addition of PAHs dose-dependently inhibited the activity of acetylcholinesterase purified from electric eel in a competitive manner. The PAHs containing 3 or higher aromatic rings showed the highest inhibitory effect with the IC50 values between 2 and 6 ppm. Among the PAHs tested, chrysene and pyrene exhibit the highest and lowest potency with IC50 values of 2. 40+/-0.04 and 5.22+/-0.38 ppm, respectively. PAHs with lower number of aromatic rings, such as naphthalene, acenaphthylene and fluorene, and oxygenated PAHs, such as anthraquinone and xanthone, showed no or slight inhibition of the acetylcholinesterase activity.

Emergency airway management

Maintenance of the airway is the most important and one of the most challenging functions that an emergency physician has to perform. This article is a review of the various techniques that can be used by both emergency and nonemergency physicians to secure the airway. It includes standard orotracheal intubation, nasotracheal intubation, fiberoptic intubation, and cricothyroidotomy. The medications used in these procedures and in rapid sequence intubation are discussed.

Induction of calcium release from isolated sarcoplasmic reticulum by triphenyltin

A direct peripheral myopathy has been found in organotin intoxication and suggested to be a significant factor in the development of muscle weakness following exposure. In this study, by using the isolated sarcoplasmic reticulum membrane vesicles, we have shown that triphenyltin dose-dependently induced Ca2+ release from the actively and passively loaded sarcoplasmic reticulum vesicles. Triphenyltin induced Ca2+ release in ruthenium red-sensitive and insensitive ways with EC50 values of 75 and 270 microM, respectively. The Ca2+-ATPase activity and Ca2+ uptake of sarcoplasmic reticulum were also inhibited by triphenyltin. Triphenyltin exerted dual effects on the apparent [3H]ryanodine binding. Triphenyltin (0.5-10 microM) dose-dependently potentiated the [3H]ryanodine binding; however, the [3H]ryanodine binding decreased as the concentration of triphenyltin increased. The dissociation of bound [3H]ryanodine was facilitated by triphenyltin. The present study suggested that the internal Ca2+ store of skeletal muscle could be depleted by triphenyltin through the inhibition of the Ca2+ uptake and the induction of Ca2+ release by acting on the Ca2+-ATPase and Ca2+ release channel, also known as the ryanodine receptor, of sarcoplasmic reticulum, respectively. These results could partly explain the development of muscle weakness in organotin intoxication; however, their relevance to the development of peripheral myopathy requires further examination.

Induction of calcium release from sarcoplasmic reticulum of skeletal muscle by xanthone and norathyriol

1. Effects of xanthone and its derivative, 1,3,6,7-tetrahydroxyxanthone (norathyriol), on Ca2+ release and ryanodine binding were studied in isolated sarcoplasmic reticulum (SR) vesicles from rabbit skeletal muscle. 2. Both xanthone and norathyriol dose-dependently induced Ca2+ release from the actively loaded SR vesicles which was blocked by ruthenium red, a specific Ca2+ release inhibitor, and Mg2+. 3. Xanthone and norathyriol also dose-dependently increased apparent [3H]-ryanodine binding. Norathyriol, but not xanthone, produced a synergistic effect on binding activation when added concurrently with caffeine. 4. In the presence of Mg2+, which inhibits ryanodine binding, both caffeine and norathyriol, but not xanthone, could restore the binding to the level observed in the absence of Mg2+. 5. Xanthone activated the Ca(2+)-ATPase activity of isolated SR vesicles dose-dependently reaching 70% activation at 300 microM. 6. When tested in mouse diaphragm, norathyriol potentiated the muscle contraction followed by twitch depression and contracture in either a Ca(2+) -free bathing solution or one containing 2.5 mM Ca2+. These norathyriol-induced effects on muscle were inhibited by pretreatment with ruthenium red or ryanodine. 7. These data suggest that xanthone and norathyriol can induce Ca2+ release from the SR of skeletal muscle through a direct interaction with the Ca2+ release channel, also known as the ryanodine receptor.

Modulation of microsomal cytochrome P450 by Scutellariae Radix and Gentianae scabrae Radix in rat liver

The present study has determined the effects of Scutellariae Radix (Huangqin) and Gentianae scabrae Radix (Longdan) on liver microsomal cytochrome P450 (P450)-dependent mono-oxygenases using rats pretreated with crude extracts of medicinal herbs. Scutellariae Radix resulted in a 53% decrease of pentoxyresorufin O-dealkylase activity in liver microsomes. In contrast, Gentianae scabrae Radix caused a 50% increase of benzo(a)pyrene hydroxylase activity. Immunoblotting analysis of liver microsomes revealed that Scutellariae Radix induced and suppressed the levels of P450 1A and 2B proteins, respectively. Scutellariae and Gentianae scabrae Radixes had no effects on microsomal aniline hydroxylase activity and P450 2E1 protein.

Binding sites for abundant nuclear factors modulate RNA polymerase I-dependent enhancer function in Saccharomyces cerevisiae

The 190-base pair (bp) rDNA enhancer within the intergenic spacer sequences of Saccharomyces cerevisiae rRNA cistrons activates synthesis of the 35S-rRNA precursor about 20-fold in vivo (Mestel,, R., Yip, M., Holland, J. P., Wang, E., Kang, J., and Holland, M. J. (1989) Mol. Cell. Biol. 9, 1243-1254). We now report identification and analysis of transcriptional activities mediated by three cis-acting sites within a 90-bp portion of the rDNA enhancer designated the modulator region. In vivo, these sequences mediated termination of transcription by RNA polymerase I and potentiated the activity of the rDNA enhancer element. Two trans-acting factors, REB1 and REB2, bind independently to sites within the modulator region (Morrow, B. E., Johnson, S. P., and Warner, J. R. (1989) J. Biol. Chem. 264, 9061-9068). We show that REB2 is identical to the ABF1 protien. Site-directed mutagenesis of REB1 and ABF1 binding sites demonstrated uncoupling of RNA polymerase I-dependent termination from transcriptional activation in vivo. We conclude that REB1 and ABF1 are required for RNA polymerase I-dependent termination and enhancer function, respectively, Since REB1 and ABF1 proteins also regulate expression of class II genes and other nuclear functions, our results suggest further similarities between RNA polymerase I and II regulatory mechanisms. Two rDNA enhancers flanking a rDNA minigene stimulated RNA polymerase I transcription in a "multiplicative" fashion. Deletion mapping analysis showed that similar cis-acting sequences were required for enhancer function when positioned upstream or downstream from a rDNA minigene.

Analysis of the yeast transcription factor TFIIA: distinct functional regions and a polymerase II-specific role in basal and activated transcription

To probe the structure and function of the Saccharomyces cerevisiae general transcription factor TFIIA, we have systematically mutagenized the genes encoding both subunits and analyzed the effects of the mutations both in vivo and in vitro. We found that the central nonconserved region of the large subunit is not essential for function and likely acts as a spacer between the conserved N- and C-terminal regions. Deletion mutagenesis of the large subunit defined a region which is required for TATA binding protein (TBP) interaction. Alanine scanning mutagenesis defined a cluster of four basic residues which are likely required for interaction with DNA in the TBP-DNA complex. Much of the conserved regions of both subunits is required for subunit association, suggesting that these conserved regions fold into compact domains which extensively interact. In vitro transcription performed with extracts from yeast strains with mutations in either the large or the small TFIIA subunit demonstrated that TFIIA stimulates both basal and activated polymerase II (Pol II) transcription. The TFIIA-depleted extracts have normal Pol I and Pol III transcription activity, showing that TFIIA is a Pol II-specific factor. In vivo depletion of TFIIA activity reduced transcription from four different Pol II promoters. Finally, alanine scanning mutagenesis of TFIIA's small subunit has identified at least one mutation which is defective in transcription but which is not defective in subunit association or binding to TBP or TBP-DNA complexes.

Effects of bipyridylium compounds on calcium release from triadic vesicles isolated from rabbit skeletal muscle

1. The effects of 1,1'-diheptyl-4,4'-bipyridinium dibromide (DHBP), a viologen for electrochromic memory display agent, on calcium release and ryanodine binding were studied with triad-rich sarcoplasmic reticulum (SR) vesicles isolated from rabbit skeletal muscle. 2. DHBP inhibited the calcium release induced by 2 mM caffeine and 2 micrograms ml-1 polylysine with an IC50 value of 5 micrograms ml-1 and 4 micrograms ml-1 respectively. 3. DHBP inhibited [3H]-ryanodine binding in a dose-dependent manner with an IC50 of 2.5 micrograms ml-1 and 90-100% inhibition at 20-30 micrograms ml-1. 4. Calcium uptake by SR was inhibited in the presence of caffeine and this inhibition was antagonized by concomitant addition of DHBP. 5. The effect of DHBP on muscle twitches was studied on the mouse diaphragm. Muscle twitches elicited by direct electrical muscle stimulation and contractions induced by either 10 mM caffeine or 1 microM ryanodine were blocked by pretreatment with DHBP. 6. Data from this study provided evidence that DHBP blocked the calcium release from SR by direct interaction with the calcium release channel, also known as the ryanodine receptor. A possible use of this agent as a specific inhibitor for calcium release and as a muscle relaxant was suggested.

Effects of signalling transduction modulators on the transformed phenotypes in v-H-ras-transformed NIH 3T3 cells

Several signalling transduction modulators were used to examine their effects on the morphological changes, foci formation in soft agar and cellular growth in v-H-ras-transformed NIH 3T3 cells. The results from this study showed that specific tyrosine kinase inhibitors (genistein and tyrphostin 23) and cyclic AMP-elevating agents (forskolin and 3-isobutyl-1-methyl-xanthine) could effectively induce differential flat phenotype of v-H-ras transformant at micromolar concentrations. At the same dose range, both signalling modulators also caused a significant suppression of anchorage-independent and cellular growth in the same transformant. By contrast, compound inhibitors such as protein kinase C (staurosporin and H-7), phospholipase A2 (aristolochic acid), phospholipase C (neomycin sulfate) and cyclooxygenase (indomethacin) all did not alter the cellular morphology or foci formation in soft agar, although PKC inhibitors exhibited a slight inhibition on the cellular growth. Based on these observations, we propose that the alterations of protein kinase A or tyrosine kinase-associated signal pathways is necessary and the original cause of the transformation event, but that increase of the activities of protein kinase C, phospholipase C, phospholipase A2 or cyclooxygenase probably is an indirect result of the v-H-ras-mediated transformation.

Sequence similarity between the long terminal repeat coding regions of mammary-tumorigenic BALB/cV and renal-tumorigenic C3H-K strains of mouse mammary tumor virus

The long terminal repeat (LTR) of mouse mammary tumor virus (MMTV) encodes a protein which functions as a superantigen. The BALB/cV strain differs from other exogenous MMTVs antigenically, biochemically, on the basis of restriction fragment analysis, and by the specificity of its superantigen for V beta 2+ T cells. In order to elucidate the origin of the BALB/cV virus and to better understand the interaction of its superantigen with the T cell receptor, we have determined the nucleotide sequence of the BALB/cV LTR open reading frame, including 93 bases downstream of the translation termination site. The encoded protein's C-terminal portion, thought to control superantigenic specificity, is identical to the C3H-K strain of MMTV, isolated from a rare kidney adenocarcinoma. The remainder of the coding sequence is highly related to many MMTV strains. Like other MMTV strains, the BALB/cV LTR maintains intact an 18 base pair sequence, located downstream of the translational termination site, which is lacking in the C3H-K LTR. Sequence comparison between the BALB/cV LTR and other MMTV strains indicates that the most likely origin for the BALB/cV open reading frame sequence is a recombination event involving the endogenous provirus mtv-6.

Muscle contracture and twitch depression induced by arsenite in the mouse phrenic nerve-diaphragm

The purpose of this investigation was to explore the possible mechanism of muscle contracture and twitch depression induced by arsenite in the mouse diaphragm. Arsenite-contracture was dependent on extracellular Ca2+; both EGTA and Ca(2+)-channel blockers (nifedipine and verapamil) inhibited arsenite-contracture. However, the activators caffeine and ryanodine and the inhibitor ruthenium red of the Ca2+ releasing channel of sarcoplasmic reticulum (SR) all exerted a profound inhibitory action on arsenite-contracture. Neither the Ca(2+)-release nor the Ca(2+)-ATPase activity of SR. were affected by 50 microM arsenite. These findings indicate a possibility that arsenite induced muscle contracture by enhancing Ca(2+)-entry which further induced Ca(2+)-release from SR. Moreover, the possible mechanism of twitch blockade induced by arsenite was studied by an electrophysiological technique. The frequency of miniature endplate potential (m.e.p.p.) was initially increased but eventually abolished by arsenite, while the amplitude of m.e.p.p. remained unaffected and that of endplate potential rapidly declined. It is considered that arsenite increased the spontaneous release of transmitter by enhancing Ca2+ entry into the nerve terminal and inhibited the evoked transmitter release possibly by acting at a certain site which governs transmitter release.

Schizophrenic delusions among Koreans, Korean-Chinese and Chinese: a transcultural study

In this transcultural study of schizophrenic delusions among Koreans, Korean-Chinese and Chinese, many delusions were shown to be different among the three groups in their frequency and content and the differences could be explained by sociocultural and political factors. Delusional themes sensitive to influence by sociocultural or political situations and changes seem to be 'family', 'love affairs', 'religious matters', 'economic matters', 'specific physical damage' and 'political themes.' Delusions about 'family', 'love affair', 'being raped', 'religious matters' and 'economic and business matters' were most frequent in Koreans. Delusions of 'blood-relatedness', 'longevity' and 'political themes' were most frequent in Korean-Chinese. Delusions of 'bloodsucking and brain or viscera extracted' and 'poison or being pricked by poisoned needle' were most prominent in Chinese.

A novel photoactivatable cross-linker for the functionally-directed region-specific fluorescent labeling of proteins

A cleavable cross-linking reagent, sulfosuccinimidyl-2(7-azido-4-methylcoumarin-3-acetamido)-ethyl-1,3'- dithiopropionate (SAED), was synthesized for the selective transfer of a coumarin fluorophore from a 'donor' protein to a position near the binding site of an interacting 'target' protein. SAED contains a terminal N-sulfosuccinimidyl ester for conjugation to the donor, a terminal photoactivatable azido-coumarin species for cross-linking with the interacting target, and a central disulfide spacer for the release of the labeled target after cleavage. To evaluate the effectiveness of this labeling reagent, soybean trypsin inhibitor (STI) was derivatized (approximately 0.5 mol/mol) with SAED and then photolyzed in the presence of trypsin. A single fluorescent cross-linked species (6-7 mol% of total STI) was observed by SDS/PAGE and, after reductive cleavage, was shown to be a 1:1 STI-trypsin complex. This complex was not detected without photolysis or with an inactivated cross-linker. Importantly, complex formation was inhibited by an excess of unmodified STI and prevented by substitution of a non-interacting protein for trypsin. Cleavage of the cross-linked complex revealed that the trypsin, but not the STI, was fluorescent; the uncomplexed trypsin fraction remained unlabeled. These results demonstrated the specificity of the labeling of trypsin by fluorescent-transfer cross-linking with SAED. An efficiency of about 15% for this cross-linking mediated labeling of trypsin was calculated. The short cross-linking span of SAED (less than or equal to 1.8 nm) strictly limited the labeling to the vicinity of the contact region of trypsin with STI. Thus, this novel cross-linker permits the region-specific targeting of a fluorophore near a functionally important binding site.

Characterization of "depolarization"-induced calcium release from sarcoplasmic reticulum in vitro with the use of membrane potential probe

In the triad, the complex of transverse (T) tubule and sarcoplasmic reticulum (SR) Ca2+ release is induced from SR by mediation of the T-tubule. We report here evidence that this Ca2+ release is produced by depolarization of the T-tubule moiety. Thus, we found that the amount of [14C]SCN- taken up by T-tubules and triads (but not that by SR) increased upon incubation with (K, Na) gluconate, Mg ATP, indicating that the T-tubule was polarized making the lumenal side (equivalent to the extracellular side of an intact muscle fiber) more positive. Upon mixing with choline chloride, the procedure to induce Ca2+ release, [14C]SCN- uptake decreased, indicating that the T-tubule became depolarized. Activation of the T-tubule polarization by Na+ and prevention of it by digoxin [inhibitor of the (Na+, K+) pump], respectively, led to activation and inhibition of choline chloride-induced SR Ca2+ release.

Conformational changes in the foot protein of the sarcoplasmic reticulum assessed by site-directed fluorescent labeling

Ca2+ release from sarcoplasmic reticulum during excitation--contraction coupling is likely to be mediated by conformational changes in the foot protein moiety of the triadic vesicles. As a preparative step toward the studies of dynamic conformational changes in the foot protein moiety, we have developed a new method that permits specific labeling of the foot protein moiety of the isolated membranes with a fluorophore. A novel fluorescent cleavable photoaffinity cross-linking reagent, sulfosuccinimidyl 3-((2-(7-azido-4-methylcoumarin-3-acetamido)ethyl)dithio)propionate (SAED), was conjugated with site-directing carriers, polylysine (Ca(2+)-release inducer) and neomycin (Ca(2+)-release blocker). The conjugates were allowed to bind to polylysine- and neomycin-binding sites of the heavy fraction of SR (HSR). After photolysis, the cross-linked reagent was cleaved by reduction and the fluorescently labeled HSR was separated from the carriers by centrifugation. These procedures led to specific incorporation of the methylcoumarin acetate (MCA) into the foot protein. Polylysine and neomycin bound to different sites of the foot protein, since neomycin, at release-blocking concentrations, did not interfere with polylysine binding. The fluorescence intensity of the foot protein labeled with the carrier, neomycin, showed biphasic changes as a function of ryanodine concentration (increasing up to 1 microM ryanodine and decreasing above it), while with the carrier polylysine, ryanodine induced no change in fluorescence intensity. In contrast, the fluorescence intensity of the foot protein labeled with each of the two carriers, neomycin and polylysine, showed almost identical calcium dependence (first increasing from 0.1 microM to about 3.0 microM calcium concentration, and then decreasing at higher calcium concentrations).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of anti-triadin antibody on Ca2+ release from sarcoplasmic reticulum

The monoclonal antibody, mAb GE 4.90, raised against triadin, a 95 kDa protein of sarcoplasmic reticulum (SR), inhibits the slow phase of Ca2+ release from SR following depolarization of the T-tubule moiety of the triad. The antibody has virtually no effect on the fast phase of depolarization-induced Ca2+ release nor on caffeine-induced Ca2+ release. Since the slow phase of depolarization-induced Ca2+ release is also inhibited by dihydropyridines (DHP), these results suggest that triadin may be involved in the functional coupling between the DHP receptor and the SR Ca2+ channel.

Direct effects of phorbol esters and diacylglycerols on the T-tubule Mg(2+)-ATPase

T-tubule membrane vesicles isolated from skeletal muscle contain a very active Mg(2+)-ATPase (EC 3.6.1.34) which is modulated by lectins and is located in the junctional region near the sarcoplasmic reticulum membranes (1). The effects of several prominent lipophilic agents upon the ATPase have led us to evaluate the action of diacylglycerols and phorbol esters upon the enzyme. The ATPase is inhibited by submicromolar levels of the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), and the diacylglycerol, 1-oleoyl-2-acetyl-sn-glycerol (sn-OAG), with K0.5s of 0.2 and 0.5 microM, respectively. Significantly, 4-alpha-phorbol 12,13-didecanoate (4-alpha-phorbol) the TPA analogue shown to be inactive toward protein kinase C (PKC), inhibited the ATPase with a K0.5 of 0.3 microM, and 1-stearoyl-2-arachidonyl-sn-glycerol, the preferred endogenous activator of PKC, was not inhibitory toward the ATPase. 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (a membrane permeant PKC inhibitor) and peptide 19-36 (the highly specific PKC pseudosubstrate inhibitor) were both without effect upon the ATPase and did not affect TPA inhibition. ATPase activity was not altered under phosphorylating conditions in experiments using exogenous rat brain PKC. ConA protected ATPase activity against inhibition by TPA, 4-alpha-phorbol, and sn-OAG. Additionally, phorbol-12,13-dibutyrate binding studies demonstrated that the ATPase was capable of significant phorbol binding with ConA protection. The data are consistent with a direct and specific effect of phorbol esters and diacylglycerols upon the ATPase, without any participation of PKC. We conclude that the transverse tubule (T-tubule) ATPase is an alternate receptor for diacylglycerol and TPA in skeletal muscle and that the mode of action of these agents upon the ATPase (inhibition) is opposite to their mode of action on PKC (activation). The data demonstrate that substantial care must be taken in ascribing either cellular or subcellular effects of phorbol esters and diacylglycerols exclusively to the activation of PKC and that alternate receptors may exist. Criteria are recommended for the demonstration of PKC-independent modulation by phorbols and diacylglycerols.

Intravesicular calcium transient during calcium release from sarcoplasmic reticulum

The time course of changes in the intravesicular Ca2+ concentration ([Ca2+]i) in terminal cisternal sarcoplasmic reticulum vesicles upon the induction of Ca2+ release was investigated by using tetramethylmurexide (TMX) as an intravesicular Ca2+ probe. Upon the addition of polylysine at the concentration that led to the maximum rate of Ca2+ release, [Ca2+]i decreased monotonically in parallel with Ca2+ release. Upon induction of Ca2+ release by lower concentrations of polylysine, [Ca2+]i first increased above the resting level, followed by a decrease well below it. The release triggers polylysine, and caffeine brought about dissociation of calcium that bound to a nonvesicular membrane segment consisting of the junctional face membrane and calsequestrin bound to it, as monitored with TMX. No Ca2+ dissociation from calsequestrin-free junctional face membranes or from the dissociated calsequestrin was produced by release triggers, but upon reassociation of the dissociated calsequestrin and the junctional face membrane, Ca2+ dissociation by triggers was restored. On the basis of these results, we propose that the release triggers elicit a signal in the junctional face membrane, presumably in the foot protein moiety, which is then transmitted to calsequestrin, leading to the dissociation of the bound calcium; and in SR vesicles, to the transient increase of [Ca2+]i, and subsequently release across the membrane.

Conformational change of the foot protein of sarcoplasmic reticulum as an initial event of calcium release

Heavy sarcoplasmic reticulum vesicles were labeled with the thiol-reacting fluorescent probe N-(7-dimethylamino-4-methyl-4-coumarinyl)maleimide (DACM), and the DACM-labeled foot protein moiety was purified. The fluorescence intensity of the DACM attached to the foot protein decreased by the addition of low (activating) concentrations of ryanodine, while it increased at higher (inhibitory) concentrations, suggesting that the lower fluorescence represents the active state of the foot protein, while the higher fluorescence, its inactive state. Under conditions that induce Ca2+ release from SR (Ca2+ jump, addition of Ca2+ release inducing reagents such as caffeine and polylysine), the fluorescence intensity of the protein-attached DACM decreased rapidly (e.g. k congruent to 70 s-1 under optimum conditions). The initial rate of Ca2+ release from the DACM-labeled SR showed a close correlation with the amplitude of the fluorescence change of the foot protein-attached DACM under variety of conditions; e.g. in the presence of Ca2+, polylysine, ATP, and ruthenium red, etc. The fluorescence change of the foot protein was much faster than Ca2+ release from SR under a variety of conditions of Ca2+ release. We propose that the binding of release triggering reagents to the foot protein induces a rapid conformational change, which in turn regulates Ca2+ release.

Effects of dihydropyridines on calcium release from the isolated membrane complex consisting of the transverse tubule and sarcoplasmic reticulum

We have investigated a) the effects of the dihydropyridines (DHPs) nifedipine and nimodipine on depolarization-induced (T-tubule-mediated) Ca2+ release in the vesicles consisting of the complex of the T-tubule and SR, and b) the binding of [3H]nimodipine to these vesicles. These DHPs inhibited the slow but not the fast phase of depolarization-induced release, both of which are mediated via the T-tubule. The DHPs have no effect on caffeine-induced release in which T-tubules are not involved. There are two classes of DHP binding sites: one, with high affinity and small capacity, and another, exhibiting low affinity and a much larger capacity. The inhibition paralleled the low affinity binding of DHP with no correlation with the high affinity binding. These results suggest that the low affinity DHP binding sites located probably in the DHP receptor, rather than the high affinity DHP binding site, are responsible for the inhibition of e-c coupling.