Apparent Dose-dependent Manner Research Articles

Association Between Physical Activity and Mortality Among Community-Dwelling Stroke Survivors.

To determine the relationship between physical activity (PA) and mortality in community-dwelling stroke survivors. The Canadian Community Health Survey was used to obtain self-reported PA across 4 survey years and was linked to administrative databases to obtain prior diagnosis of stroke and subsequent all-cause mortality. PA was measured as metabolic equivalents (METs) per week and meeting minimal PA guidelines was defined as 10 MET-h/wk. Cox proportional hazard regression models and restricted cubic splines were used to determine the relationship between PA and all-cause mortality in respondents with prior stroke and controls, adjusting for sociodemographic factors, comorbidities, and functional health status. The cohort included 895 respondents with prior stroke and 97,805 controls. Adhering to PA guidelines was associated with lower hazard of death for those with prior stroke (adjusted hazard ratio [aHR] 0.46, 95% confidence interval [CI] 0.29-0.73) and controls (aHR 0.69, 95% CI 0.62-0.76). There was a strong dose-response relationship in both groups, with a steep early slope and the vast majority of associated risk reduction occurring between 0 and 20 MET-h/wk. In the group of stroke respondents, PA was associated with greater risk reduction in those <75 years of age (aHR 0.21, 95% CI 0.10-0.43) compared to those ≥75 years of age (aHR 0.68, 95% CI 0.42-1.12). PA was associated with lower all-cause mortality in an apparent dose-dependent manner among those with prior stroke, particularly in younger stroke survivors. Our findings support efforts towards reducing barriers to PA and implementation of PA programs for stroke survivors in the community. This study provides Class III evidence that in community-dwelling survivors of stroke, adhering to physical activity guidelines was associated with lower hazard of death.

(-)-Epigallocatechin‑3‑gallate inhibition of Epstein‑Barr virus spontaneous lytic infection involves downregulation of latent membrane protein 1

The Epstein-Barr virus (EBV) lytic cycle contributes to the development of EBV-associated diseases. EBV-encoded latent membrane protein 1 (LMP1) is key to EBV lytic replication, and our previous work indicated that epigallocatechin-3-gallate (EGCG) inhibited constitutive EBV lytic infection through the suppression of LMP1-activated phosphoinositide 3-kinase/Akt and mitogen-activated protein kinase kinase/extracellular signal-related protein kinase 1/2 signaling. The present study demonstrated that LMP1 in CNE-LMP1 constructed cells significantly induced the expression of the EBV lytic proteins BZLF1 (P<0.001) and BMRF1 (P<0.05) compared with CNE1 cells. Following treatment with a specific DNAzyme that targets LMP1, significantly reduced protein expression levels of BZLF1 and BMRF1 in EBV-associated epithelial carcinoma CNE1-LMP1 cells (P<0.001 and P<0.01, respectively) and lymphoma B95.8 cells (both P<0.01) were observed. Furthermore, EGCG significantly inhibited the mRNA and protein expression levels of LMP1 (P<0.05) in an apparent dose-dependent manner in CNE1-LMP1 and B95.8 cells. Thus, the present findings indicated that the molecular mechanism underlying EGCG inhibition of EBV lytic infection involves downregulation of LMP1.

Effect of naringin on ammonium chloride-induced hyperammonemic rats: A dose-dependent study

Abstract Introduction In mammals, ammonia is primarily a toxin that affects the central nervous system, leading to liver damage and urea cycle disorder. Increased accumulation of ammonia results in a spectrum of effects on the central nervous system exerted through both excitatory and inhibitory neurotransmission. The aim of this investigation was to examine the protective effect of naringin on ammonium chloride (NH 4 Cl)-induced hyperammonemic rats. Materials and methods Male albino Wistar rats were induced with intraperitoneal injections of NH 4 Cl [100 mg/kg body weight (b.w.)] and were treated with different concentrations of naringin (40 mg/kg, 80 mg/kg, and 160 mg/kg of b.w.) 3 times/wk for 8 consecutive weeks. Results Hyperammonemic rats showed elevated levels of ammonia, uric acid, creatinine, and bilirubin, and a reduced level of plasma urea. Body weights of normal and experimental rats were also measured. Oral administration of naringin significantly decreased the levels of blood ammonia, uric acid, creatinine, and bilirubin, and drastically increased the level of plasma urea. Conclusion Among the three doses, 80 mg/kg b.w. of naringin exhibited a more efficient antihyperammonemic effect in NH 4 Cl-induced hyperammonemic rats. Therefore, this study proves the protective effect of naringin in NH 4 Cl-induced hyperammonemic rats in an apparent dose-dependent manner.

Preparation, Pharmacokinetic Profile, and Tissue Distribution Studies of a Liposome-Based Formulation of SN-38 Using an UPLC-MS/MS Method.

The application of 7-ethyl-10-hydroxycamptothecin (SN-38) in cancer treatment is limited by its low solubility. This study is to develop a liposome-entrapped formulation of SN-38 (LE-SN38) to solve the obstacle and to evaluate its pharmacokinetic profile in dogs and tissue distribution in mice. LE-SN38 which is more likely to be suitable for large-scale production was prepared by the carrier-deposition method. An UPLC-MS/MS method was used to determinate the concentration of SN-38 in this study. LE-SN38 was cleared rapidly from dog plasma within 1h, and the AUC0-∞ values of three dosages of LE-SN38 indicated an apparent dose-dependent manner. As for the distribution study, the peak of SN-38 levels in most tissues were detected within 10 min after LE-SN38 administration. In addition, concentration of SN-38 in most tissues except kidney and heart in LE-SN38 group was higher than that in irinotecan hydrochloride (CPT-11) group generally, whereas the administrated CPT-11 had 20 times dosage compared to LE-SN38. LE-SN38 was rapidly eliminated from dog plasma and manifested linear dynamics in dose range of 0.411-1.644mg/kg. The distribution behavior of SN-38 is altered in a liposome-based delivery system. At the same time, LE-SN38 has lower toxicity compared to CPT-11 in some degree.

The effects on steroidogenesis and histopathology of adult male Japanese quails (Coturnix coturnix japonica) testis following pre-pubertal exposure to di(n-butyl) phthalate (DBP)

In the present study, we have investigated the effects of 30-day dietary (pre-pubertal) exposure to different doses (0 (control), 1, 10, 50, 200 and 400mg/kg bodyweight/day) of di(n-butyl) phthalate (DBP) on Leydig cells of adult male Japanese quails by quantifying the transcript levels for P450 side-chain cleavage (p450scc), P450c17 (CYP17), and 3β- and 17β-hydroxysteroid dehydrogenase (hsd) using quantitative (real-time) polymerase chain reaction (qRT-PCR). In addition, the plasma testosterone levels were analysed using radioimmunoassay (RIA) and testis was examined for evidence of gross pathology and histopathology. Our data showed that pre-pubertal exposure to DBP produced alterations in testicular architecture as evident by poorly developed or mis-shaped testis, and altered spermatogenesis due to tubular degeneration and atrophy of seminiferous tubules especially in the high DBP dose (200 and 400mg/kg) treated groups. In addition, DBP altered several key enzymes involved in testicular steroidogenesis pathways in an apparent dose-dependent manner. For example, biphasic effects of DBP were observed for P450scc and 3β-hsd mRNA, that were generally increasing at low dose 10mg/kg, and thereafter, an apparent dose-dependent decrease between 50 and 400mg/kg. The steroidogenic acute regulatory (StAR) protein was at the lowest detectable limits and therefore not quantifiable. These effects did not parallel the non-significant changes observed for plasma testosterone levels. The present data is consistent with previous reports showing that DBP modulates Leydig cell steroidogenesis in several species, with a potential negative effect on reproduction in those avian species that are vulnerable to endocrine disrupting chemicals.

A trans-spliced telomerase RNA dictates telomere synthesis in Trypanosoma brucei

Telomerase is a ribonucleoprotein enzyme typically required for sustained cell proliferation. Although both telomerase activity and the telomerase catalytic protein component, TbTERT, have been identified in the eukaryotic pathogen Trypanosoma brucei, the RNA molecule that dictates telomere synthesis remains unknown. Here, we identify the RNA component of Trypanosoma brucei telomerase, TbTR, and provide phylogenetic and in vivo evidence for TbTR's native folding and activity. We show that TbTR is processed through trans-splicing, and is a capped transcript that interacts and copurifies with TbTERT in vivo. Deletion of TbTR caused progressive shortening of telomeres at a rate of 3-5 bp/population doubling (PD), which can be rescued by ectopic expression of a wild-type allele of TbTR in an apparent dose-dependent manner. Remarkably, introduction of mutations in the TbTR template domain resulted in corresponding mutant telomere sequences, demonstrating that telomere synthesis in T. brucei is dependent on TbTR. We also propose a secondary structure model for TbTR based on phylogenetic analysis and chemical probing experiments, thus defining TbTR domains that may have important functional implications in telomere synthesis. Identification and characterization of TbTR not only provide important insights into T. brucei telomere functions, which have been shown to play important roles in T. brucei pathogenesis, but also offer T. brucei as an attractive model system for studying telomerase biology in pathogenic protozoa and for comparative analysis of telomerase function with higher eukaryotes.

Mechanisms of Morphine Enhancement of Spontaneous Seizure Activity

High-dose opioid therapy can precipitate seizures; however, the mechanism of such a dangerous adverse effect remains poorly understood. The aim of our study was to determine whether the neuroexcitatory activity of high-dose morphine is mediated by selective stimulation of opioid receptors. Mice hippocampi were resected intact and bathed in low magnesium artificial cerebrospinal fluid to induce spontaneous seizure-like events recorded from CA1 neurons. Application of morphine had a biphasic effect on the recorded spontaneous seizure-like events. In a low concentration (10 microM), morphine depressed electrographic seizure activity. Higher morphine concentrations (30 and 100 microM) enhanced seizure activity in an apparent dose-dependent manner. Naloxone, a nonselective opiate antagonist blocked the proconvulsant action of morphine. Selective mu and kappa opiate receptor agonists and antagonists enhanced and suppressed the spontaneous seizure activity, respectively. On the contrary, delta opioid receptor ligands did not have an effect. The proseizure effect of morphine is mediated through selective stimulation of mu and kappa opiate receptors but not the activation of the delta receptor system. The observed dose-dependent mechanism of morphine neuroexcitation underscores careful adjustment and individualized opioid dosing in the clinical setting.

Diminished prolactin from chlordecone treatment in ovariectomized (NZB × NZW)F1 mice

In murine models of systemic lupus erythematosus (SLE), administration of either prolactin or estradiol (E2) increases autoimmunity, and there is evidence that elevated prolactin in response to E2 administration may contribute substantially to E2 effects. Hormonal influence on SLE can extend to environmental agents, as demonstrated by the ability of estrogenic organochlorine pesticides such as chlordecone to accelerate the development of lupus in female (NZB×NZW)F1 mice. In order to evaluate a potential role for prolactin in chlordecone effects on SLE, it was necessary to first determine whether treatment with chlordecone, like E2, results in elevated prolactin levels. Ovariectomized (NZB×NZW)F1 mice were treated for 5–6 weeks with chlordecone or E2 in doses shown previously to significantly shorten the time to onset of SLE. At the end of the treatment period, serum prolactin levels were increased 10- to 20-fold in E2-treated mice compared to untreated controls, but decreased in an apparent dose-dependent manner in mice treated with chlordecone. Prolactin receptor in purified splenic B and CD4 T cells from treated animals, assessed through measurement of mRNA using quantitative real-time PCR, was increased by E2 treatment but unchanged in response to chlordecone. These observations suggest that the role of prolactin in eliciting autoimmunity in E2-treated animals is absent in the case of chlordecone, and by implication, that chlordecone possesses other actions that can replace the contribution of prolactin to development of SLE.

Regulatory Behavior and Skin Temperature in Mid-Aged Male Rats on Three Different Isoflavone-Containing Diets

Soy isoflavones, the most abundant phytoestrogens, are known as endocrine modulators and appear to be an effective treatment in some women during perimenopause when symptoms such as hot flashes may be reduced. This study examined the effects of dietary soy isoflavones on regulatory behaviors such as body weight, food and water intake, and skin tail temperature by feeding male Long-Evans rats one of the three standard chows (Phyto-free, Phyto-200, and Phyto-600) containing approximately 10-15 ppm, 200 ppm, and 600 ppm of isoflavones, respectively. In an apparent dose-dependent manner, body weight was decreased as a function of increasing isoflavone levels in the diets. The average skin tail temperature of Phyto-600-fed rats (25.5 degrees C) was significantly lower than Phyto-free (27.5 degrees C) values by approximately 2 degrees C. The rats on the Phyto-200 diet (26.6 degrees C) displayed a temperature in between the Phyto-free and Phyto-600 values. Similar to the body weight results, skin tail temperature was decreased in an apparent dose-dependent manner as a function of increasing isoflavone concentrations in the diets. These results suggest that consumption of soy isoflavones alters regulatory behaviors (such as body weight and food and water intake) and skin temperature regulation that may help explain, in part, the beneficial effects of soy isoflavones on obesity and hot flashes in humans.

Effectiveness of Colesevelam Hydrochloride in Decreasing LDL Cholesterol in Patients With Primary Hypercholesterolemia: A 24-Week Randomized Controlled Trial

To evaluate the efficacy, tolerability, and safety of colesevelam hydrochloride, a new nonsystemic lipid-lowering agent. In this double-blind, placebo-controlled trial performed in 1998, 494 patients with primary hypercholesterolemia (low-density lipoprotein [LDL] cholesterol level > or = 130 mg/dL and < or = 220 mg/dL) were randomized to receive placebo or colesevelam (2.3 g/d, 3.0 g/d, 3.8 g/d, or 4.5 g/d) for 24 weeks. Fasting serum lipid profiles were measured to assess efficacy. Adverse events were monitored, and discontinuation rates and compliance rates were analyzed. The primary outcome measure was the mean absolute change of LDL cholesterol from baseline to the end of the 24-week treatment period. Colesevelam lowered mean LDL cholesterol levels 9% to 18% in a dose-dependent manner (P<.001), with a median LDL cholesterol reduction of 20% at 4.5 g/d. The reduction in LDL cholesterol levels was maximal after 2 weeks and sustained throughout the study. Mean total cholesterol levels decreased 4% to 10% (P<.001), while median high-density lipoprotein cholesterol levels increased 3% to 4% (P<.001). Median triglyceride levels increased by 5% to 10% in placebo and colesevelam treatment groups relative to baseline (P<.05), but none of these differences were significantly different from placebo. Mean apolipoprotein B levels decreased 6% to 12% in an apparent dose-dependent manner (P<.001). No significant differences occurred in adverse events or discontinuation rates between groups, and compliance rates were between 88% and 92% for all groups. Colesevelam was efficacious, decreasing mean LDL cholesterol levels by up to 18%, and well tolerated without serious adverse events.

Homer Proteins Regulate Coupling of Group I Metabotropic Glutamate Receptors to N-Type Calcium and M-Type Potassium Channels

Group I metabotropic glutamate receptors (mGluR1 and 5) couple to intracellular calcium pools by a family of proteins, termed Homer, that cross-link the receptor to inositol trisphosphate receptors. mGluRs also couple to membrane ion channels via G-proteins. The role of Homer proteins in channel modulation was investigated by expressing mGluRs and various forms of Homer in rat superior cervical ganglion (SCG) sympathetic neurons by intranuclear cDNA injection. Expression of cross-linking-capable forms of Homer (Homer 1b, 1c, 2, and 3, termed long forms) occluded group I mGluR-mediated N-type calcium and M-type potassium current modulation. This effect was specific for group I mGluRs. mGluR2 (group II)-mediated inhibition of N-channels was unaltered. Long forms of Homer decreased modulation of N- and M-type currents but did not selectively block distinct G-protein pathways. Short forms of Homer, which cannot self-multimerize (Homer 1a and a Homer 2 C-terminal deletion), did not alter mGluR-ion channel coupling. When coexpressed with long forms of Homer, short forms restored the mGluR1a-mediated calcium current modulation in an apparent dose-dependent manner. Homer 2b induced cell surface clusters of mGluR5 in SCG neurons. Conversely, a uniform distribution was observed when mGluR5 was expressed alone or with Homer short forms. These studies indicate that long and short forms of Homer compete for binding to mGluRs and regulate their coupling to ion channels. In vivo, the immediate early Homer 1a is anticipated to enhance ion channel modulation and to disrupt coupling to releasable intracellular calcium pools. Thus, Homer may regulate the magnitude and predominate signaling output of group I mGluRs.

Effects of cadmium on cell viability, trophoblastic development, and expression of low density lipoprotein receptor transcripts in cultured human placental cells

Previously, we have demonstrated that cadmium inhibits progesterone release in cultured human trophoblast cells. In the present study, we investigated potential mechanism(s) by which cadmium may elicit this effect. Cytotrophoblasts were obtained via enzymatic dispersion, purified by density gradient centrifugation, and cultured with increasing concentrations of cadmium. Cadmium-induced suppression of progesterone release seemed to be independent of cell death, as no significant decline in viability was observed with cadmium treatment. Further, immunocytochemical localization of cellular boundaries and nuclei indicated approximately 94% syncytial maturity was attained by both untreated and cadmium-treated cells, demonstrating that cadmium did not inhibit syncytial development. However, the abundance of LDL receptor (LDL-R) mRNA transcripts, as determined by competitive RT-PCR, was reduced ( P < 0.05) by cadmium exposure in an apparent dose-dependent manner. Thus, the LDL-R, by which cholesterol substrate is supplied to the syncytiotrophoblast, is one site at which cadmium may interfere with placental progesterone production.

Sweat testing for heroin, cocaine, and metabolites.

Although a variety of drugs have been detected in sweat, little information is available on the characteristics of drug excretion in sweat under controlled-dosing conditions. A series of clinical studies were designed to determine the identity, concentration, time course, dose dependency, and variability of drug and metabolite excretion in sweat following administration of single doses of cocaine and heroin to human subjects. Sweat was collected by means of a sweat patch that could be worn for a period of several days to several weeks at a time, resulting in accumulation of drug in the patch. Sweat patches were removed at specified times and frozen until analyzed by gas chromatography--mass spectrometry. Cocaine and heroin were the major analytes excreted in sweat following their administration. Smaller amounts of cocaine metabolites were also detected following cocaine administration. 6-Acetylmorphine appeared rapidly after heroin administration and continued to increase while heroin content decreased, suggesting that heroin was undergoing hydrolysis in the sweat patch. Cocaine appeared in sweat within 1-2 hours and peaked within 24 hours in an apparent dose-dependent manner. Analysis of duplicate adjacent patches from individual subjects who had been administered cocaine provided similar quantitative results, suggesting that intrasubject variability was relatively low, whereas intersubject variability was high. These observations regarding the excretion of cocaine and heroin analytes in sweat have important forensic implications to other fields such as hair analysis. Sweat excretion could be an important mechanism by which drugs enter hair. These data also suggest that the sweat patch could serve as a useful monitoring device in surveillance of individuals in treatment and probation programs.

Single intraluminal delivery of antisense cdc2 kinase and proliferating-cell nuclear antigen oligonucleotides results in chronic inhibition of neointimal hyperplasia.

To develop an effective strategy to prevent neointima formation after angioplasty injury, we have identified cell-cycle regulatory proteins as targets for inhibition by using antisense oligonucleotides (ODNs). We utilized an intraluminal molecular delivery method that employs the protein coat of a Sendai virus complexed with liposomes that enhances markedly the efficiency of ODNs uptake. First, we examined the effect of antisense cdc2 kinase and proliferating-cell nuclear antigen (PCNA) ODNs in vitro. Cotransfection of antisense cdc2 kinase and PCNA ODNs inhibited serum-stimulated vascular smooth muscle cell growth, whereas antisense cdc2 kinase ODNs alone or PCNA ODNs alone failed to show any inhibitory effect. Transfection of the combination of antisense cdc2 kinase and PCNA ODNs into balloon-injured arteries in vivo provided a marked decrease in cdc2 and PCNA mRNA expression as determined by reverse transcription-PCR, compared to sense controls. Antisense ODN treatment significantly inhibited the increase in DNA synthesis induced by balloon injury. Moreover, antisense ODN administration inhibited completely neointima formation at 2 weeks after angioplasty in an apparent dose-dependent manner. Moreover, the inhibitory effect of antisense ODN on neointima formation persisted up to 8 weeks after a single transfection. The present study documents that a single intraluminal molecular delivery of combined cdc2 kinase and PCNA antisense ODNs results in a sustained inhibition of neointima formation in the rat carotid balloon-injury model.

In vivo evaluation of the genotoxic potential of curacron in somatic cells of mice.

Cytogenetic effects produced in somatic cells by Curacron, a phosphoric acid ester insecticide, were assessed in mice by three criteria: chromosome aberrations, sister chromatid exchange (SCE), and micronucleus induction. Curacron significantly increased the frequency of all three in an apparent dose-dependent manner. Curacron also inhibited the mitotic activity. The increased number of micronuclei is comparable to the increase in chromosome aberrations; the latter were mainly breaks. The frequency of SCE was considerably less than the frequencies of micronuclei and chromosome aberrations.

Acute, 14-day repeated dosing, and 90-day subchronic toxicity studies of carbon tetrachloride in CD-1 mice

CD-1 mice received carbon tetrachloride daily by gavage for 14 or 90 consecutive days. Corn oil was the vehicle used. The 14-day study involved doses of 625, 1250, and 2500 mg/kg; the 90-day subchronic study involved doses of 12, 120, 540, and 1200 mg/kg. The 14-day study revealed a dose-dependent mortality and decreased body weight in males, whereas females demonstrated mortality only at the high dose. Other dose-dependent findings included decreased fibrinogen and lymphocytes; increased LDH, SGPT (ALT), and SGOT (AST); increased liver weights and ratios in both sexes; and decreased lung, thymus, and kidney weights in males only. There were no compound-related deaths in the 90-day study. There were no consistent compound-related effects on any of the hematological or urinary parameters evaluated. LDH, SGPT (ALT), SGOT (AST), ALP, cholesterol, and bilirubin were increased in an apparent dose-dependent manner while blood glucose levels decreased at all dosage levels. Liver, spleen, and thymus weights and ratios were increased at all dosage levels in both sexes. Histopathology revealed no kidney damage, but liver damage was observed at all doses in both sexes. A no-observable-adverse-effect level was not obtained in these studies.

Induction of Hypozincemia and Hepatic Metallothionein Synthesis in Hypersensitivity Reactions

SummaryRecent evidence indicates that hypersensitivity reactions, produced in rats by the administration of a protein antigen, alters plasma zinc and iron homeostasis by depressing concentrations of these trace minerals. Studies were performed to determine if altered zinc homeostasis involves, in part, enhanced hepatic metallothionein (MT) synthesis. MT, a high cysteine-containing cytoplasmic protein, possesses a high affinity for zinc and other heavy metals and has been implicated in zinc homeostasis.Antigen challenge (0.5 mg BSA) in rats previously sensitized with either 5 or 10 mg BSA produced a significant decrease in plasma zinc and iron concentrations within 7 hr in an apparent dose-dependent manner. Plasma zinc depression was accompanied by an increase in hepatic MT content as well as MT-associated total Zn and 65Zn used to pulse-label the metalloprotein. The depression in plasma zinc, but not iron, and the enhanced synthesis of MT was significantly reduced by prior treatment of rats with actinomyc...