Linear Dose-response Curve Research Articles

Propylene Glycol-Free Melphalan Induces Higher Remission Rates in Multiple Myeloma Patients Undergoing Autologous Transplantation

Abstract 4551 Background:In a recent phase IIa open-label, randomized, cross-over design study, we evaluated the pharmacokinetics of Propylene Glycol-Free Melphalan (PG-free Mel) HCL and Alkeran in multiple myeloma patients undergoing transplantation. In this study, we have shown through statistical tests of the geometric means of AUC that PG-free Mel was bioequivalent to Alkeran, and provided marginally higher blood drug levels. Hypothesis:Because this new formulation is associated with marginally higher blood drug levels and because melphalan is associated with a linear dose-response curve, we speculated that patients treated on study would have a better multiple myeloma response compared to matched controls. Goal:To assess day +100 multiple myeloma responses from the study patients (n=24) receiving PG-free Mel conditioning in combination with Alkeran. Responses were assessed based on International Uniform Response Criteria for Multiple Myeloma. Comparison was made to a matched cohort of patients who received conventional melphalan. Methods:We compared the study patient responses to matched controls (n=24) treated exclusively with Alkeran or generic melphalan conditioning within the same time frame in a case-control study design. The controls were matched to study population based on disease stage, age, and pre-transplant response. Results:The study population and the control cohort were well matched in terms of age, gender, disease stage, and pre-transplant response. However, the study population had more patients with high-risk cytogenetics (10 vs 3). Overall response (CR, VGPR, and PR) was higher in the study population (22 vs 19). While no patient on the study progressed within 100 days of transplant, 3 patients in the matched cohort progressed within 100 days. The median duration of follow up of surviving patients was 650 days in the study cohort and 409 days in the matched control cohort. Twenty three study patients and 22 patients in the matched control cohort were reported alive. On the other hand, 7 study patients and 8 patients in the matched cohort progressed during follow up. Conclusion:Compared to matched controls, PG-free Mel, as part of the melphalan conditioning regimen, resulted in higher remission rates and less disease progression at day 100 post autologous transplant for multiple myeloma. Disclosures:Off Label Use: Propylene glycol free melphalan for high-dose therapy and autologous transplant for multiple myeloma.

Isopentenyladenosine and cytokinin-like activity of different humic substances

Increasing attention has been devoted in the last few years to the mechanisms by which humic substances (HS) influence plant growth. Nevertheless, amongst the biologically active compounds that might be present in HS, only indoleacetic acid has been identified. An enzyme-linked immunosorbent assay (ELISA) was applied to detect the presence of isopentenyladenosine (IPA), a cytokinin, in two lignosulphonate-humates, leonardite humic acid and in a high molecular weight humic fraction extracted from earthworm faeces. The IPA concentration ranged from 34 to 145pmolmg−1 humic C and was estimated by using a linear dose–response curve between the carbon (C) concentration and percentage of binding of an anti-IPA monoclonal antibody. The cytokinin-like activity of HS was evaluated by weighing small radish (Raphanus sativus L.) cotyledon leaves and measuring chlorophyll and protein contents, the activities of ATP sulfurylase and O-acetylserine sulfhydrylase on maize plants. It is noteworthy that, amongst the four HS, those from earthworm faeces showed the highest amount of IPA and the strongest cytokinin-like activity in both plants. The presence of IPA confirmed that HS influence plant metabolism at different levels. Our results open new perspectives in the plant–HS relationship and shed new light on the active components of HS.

Contrasting Theories of Interaction in Epidemiology and Toxicology

Background: Epidemiologists and toxicologists face similar problems when assessing interactions between exposures, yet they approach the question very differently. The epidemiologic definition of “interaction” leads to the additivity of risk differences (RDA) as the fundamental criterion for causal inference about biological interactions. Toxicologists define “interaction” as departure from a model based on mode of action: concentration addition (CA; for similarly acting compounds) or independent action (IA; for compounds that act differently).Objectives: We compared and contrasted theoretical frameworks for interaction in the two fields.Methods: The same simple thought experiment has been used in both both epidemiology and toxicology to develop the definition of “noninteraction,” with nearly opposite interpretations. In epidemiology, the “sham combination” leads to a requirement that noninteractive dose–response curves be linear, whereas in toxicology, it results in the model of CA. We applied epidemiologic tools to mathematical models of concentration-additive combinations to evaluate their utility.Results: RDA is equivalent to CA only for linear dose–response curves. Simple models demonstrate that concentration-additive combinations can result in strong synergy or antagonism in the epidemiologic framework at even the lowest exposure levels. For combinations acting through nonsimilar pathways, RDA approximates IA at low effect levels.Conclusions: Epidemiologists have argued for a single logically consistent definition of interaction, but the toxicologic perspective would consider this approach less biologically informative than a comparison with CA or IA. We suggest methods for analysis of concentration-additive epidemiologic data. The two fields can learn a great deal about interaction from each other.

The Association of Cysteine with Obesity, Inflammatory Cytokines and Insulin Resistance in Hispanic Children and Adolescents

ContextPlasma total cysteine (tCys) independently relates to fat mass in adults. Dietary cyst(e)ine promotes adiposity and decreases glucose tolerance in some rodent models, but alleviates insulin resistance in others.ObjectiveTo investigate whether the association of tCys with body fat extends to children at particular risk of obesity, and whether tCys is associated with insulin resistance and obesity-associated inflammation.MethodsWe explored the cross-sectional relations of fasting plasma tCys and related metabolites with body composition measured by dual-energy X-ray absorptiometry in 984 Hispanic children and adolescents aged 4–19 years from the Viva La Familia Study. Linear and logistic regression and dose-response curves were used to evaluate relations of tCys with obesity, insulin resistance and inflammatory markers including interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), monocyte chemoattractant protein-1 (MCP-1) and C-reactive protein (CRP).ResultstCys, methionine and total homocysteine (tHcy) increased with age. Upper tCys quartile was independently associated with a 5-fold increased risk of obesity (95% CI 3.5–8.0, P<0.001), and 2-fold risk of insulin resistance (95% CI: 1.6-5.0, P<0.001; adjusted for body fat%). Within the overweight/obese subgroup, but not in normal-weight children, tCys accounted for 9% of the variability in body fat% (partial r = 0.30, P<0.001; adjusted for age and gender). tCys correlated positively with serum non-esterified fatty acids and leptin, partly independent of body fat, but was not associated with serum IL-6, TNF-α or MCP-1. A positive correlation with CRP disappeared after adjustment for BMI.ConclusiontCys is independently associated with obesity and insulin resistance in Hispanic children and adolescents, highlighting a previously underappreciated link between the sulfur amino acid metabolic pathway and obesity and cardiometabolic risk.

Equivalent doses for gynecological patients undergoing IMRT or RapidArc with kilovoltage cone beam CT

PurposeTo investigate in-field and peripheral kilovoltage cone beam CT (CBCT) doses in gynecological patients in comparison with IMRT or RapidArc scatter and linac leakage doses. Materials and methodsMonte Carlo codes BEAMnrc/DOSXYZnrc were used to simulate dose for daily use of kV CBCT in patients undergoing adjuvant pelvic radiotherapy for uterine or ovarian malignancies. Biological effectiveness was accounted for using a lineal energy based quality factor. Organ equivalent doses (OED) within the treatment field were modeled with linear-exponential, plateau and linear dose response curves. CBCT doses in peripheral regions were compared with IMRT and RapidArc scatter doses as well as linac leakage doses. ResultsCBCT doses in peripheral regions were on the order of linac leakage doses and one order of magnitude lower than IMRT or RapidArc scatter doses. OEDs increased slightly, leveled off or even decreased within the treatment field with the addition of CBCT doses according to different dose response models. ConclusionThe results of this study indicate that patients undergoing IMRT or RapidArc treatments with daily use of kV CBCT imaging are not subjected to additional risk due to CBCT imaging doses.

Simultaneous Detection and Semiquantification of DNA Damage in Normal and Apoptotic Cells

We developed a triple-labeling immunofluorescence technique that simultaneously identifies total DNA (DAPI), DNA damage (antibodies), and dead cells [terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells] and a method that semiquantifies DNA damage in paraffin-embedded tissues. Using this technique in combination with our analysis method, scientists can now simultaneously detect and compare the relative amounts of DNA damage of almost any kind (except single-strand and double-strand breaks), using indirect fluorescent antibody labeling, in both normal and dying cells of different tissues. Simultaneous labeling of DNA damage and dead or TUNEL-positive cells can reduce processing costs and analysis time, and can lead to discoveries concerning how cells die from different DNA damages. We used increasing doses of UV (290 to 400 nm) radiation to create DNA damage in the form of cyclobutane pyrimidine dimers and 6-4 photoproducts that kill some of the cells in 3-dimensional tissue-engineered skin and vaginal samples. We describe a protocol that reliably detects and semiquantifies DNA damage in both normal and apoptotic cells. We show this triple-labeling immunofluorescence technique and analysis method yields linear UV dose response curves for damage to DNA bases that allows semiquantification of cyclobutane pyrimidine dimers and calculation of its repair rate (T=1 and 24 h), whereas TUNEL allows quantification of the number of apoptotic cells. Scientists can now create beautiful fluorescent pictures that simultaneously detect DNA damage in both normal and apoptotic cells to assess and semiquantify the damage to understand better how different insults lead to the cell's demise.

Immunoliposome-PCR: a generic ultrasensitive quantitative antigen detection system

BackgroundThe accurate quantification of antigens at low concentrations over a wide dynamic range is needed for identifying biomarkers associated with disease and detecting protein interactions in high-throughput microarrays used in proteomics. Here we report the development of an ultrasensitive quantitative assay format called immunoliposome polymerase chain reaction (ILPCR) that fulfills these requirements. This method uses a liposome, with reporter DNA encapsulated inside and biotin-labeled polyethylene glycol (PEG) phospholipid conjugates incorporated into the outer surface of the liposome, as a detection reagent. The antigenic target is immobilized in the well of a microplate by a capture antibody and the liposome detection reagent is then coupled to a biotin-labeled second antibody through a NeutrAvidin bridge. The liposome is ruptured to release the reporter DNA, which serves as a surrogate to quantify the protein target using real-time PCR.ResultsA liposome detection reagent was prepared, which consisted of a population of liposomes ~120 nm in diameter with each liposome possessing ~800 accessible biotin receptors and ~220 encapsulated reporters. This liposome detection reagent was used in an assay to quantify the concentration of carcinoembryonic antigen (CEA) in human serum. This ILPCR assay exhibited a linear dose–response curve from 10-10 M to 10-16 M CEA. Within this range the assay coefficient of variance was <6 % for repeatability and <2 % for reproducibility. The assay detection limit was 13 fg/mL, which is 1,500-times more sensitive than current clinical assays for CEA. An ILPCR assay to quantify HIV-1 p24 core protein in buffer was also developed.ConclusionsThe ILPCR assay has several advantages over other immuno-PCR methods. The reporter DNA and biotin-labeled PEG phospholipids spontaneously incorporate into the liposomes as they form, simplifying preparation of the detection reagent. Encapsulation of the reporter inside the liposomes allows nonspecific DNA in the assay medium to be degraded with DNase I prior to quantification of the encapsulated reporter by PCR, which reduces false-positive results and improves quantitative accuracy. The ability to encapsulate multiple reporters per liposome also helps overcome the effect of polymerase inhibitors present in biological specimens. Finally, the biotin-labeled liposome detection reagent can be coupled through a NeutrAvidin bridge to a multitude of biotin-labeled probes, making ILPCR a highly generic assay system.

WE‐A‐BRB‐03: A Fiber Optic Dosimeter to Calibrate P‐32 Conformal Brachytherapy Sources

Purpose: Conformal brachytherapy plaques are used to irradiate the dura for paraspinal tumors. The plaques consist of Phosphorus‐32 chemically bonded to a flexible polymeric film. Radiochromic film has been successfully used to calibrate P‐32 plaques, but this method is time consuming due to the film characteristics. We investigate using a commercial fiber optic dosimetry system as a more efficient calibration method. Methods: A calibration curve for the radiochromic film was determined using an ADCL calibrated Strontium‐90 source, and this film is used to measure the dose rate of a P‐32 plaque. The Orbital Therapy system consists of a small cylindrical plastic scintillator coupled to a fiber optic cable. The dosimeter, controlled by a LabView‐based user interface, counts scintillation photons during a set time period and provides an immediate readout. Custom plastic phantoms hold the dosimeter probe in contact with a P‐32 plaque. The counts from the fiber optic dosimeter are plotted against the expected surface dose and modeled with a linear function to extract the dose deposited per count. Different measurement designs are considered to select a measurement time with accurate and reproducible results. Results: The fiber optic dosimeter is observed to have a linear dose response curve to both P‐32 and Sr‐90 sources. For a P‐32 plaque each count corresponds to 1.5 microGy, while for a Sr‐90 source each count corresponds to 1.16 microGy. We average 10 consecutive 6‐second measurements of the P‐32 plaque for a standard deviation of 0.1% and precision within 1%. Conclusions: The Orbital Therapy fiber optic dosimeter is acceptable for calibrating P‐32 conformal brachytherapy plaques. Initial calibration of the dosimeter requires a calibrated source of the same isotope, as the dose response depends on the beta energy spectrum. Once calibrated, the dosimeter is faster, simpler, and less error‐prone than using film for P‐32 plaque calibration.

A new immunoprecipitation-real time quantitative PCR assay for anti-Th/To and anti-U3RNP antibody detection in systemic sclerosis

IntroductionClassic anti-nucleolar antibodies anti-Th/To and U3 ribonucleoprotein (-U3RNP) can help in the diagnosis, prediction of organ involvement and prognosis in systemic sclerosis (SSc); however, no validated commercial assay is available. We aimed at establishing a novel quantitative real time PCR (qPCR) method to detect these antibodies.MethodsStandard immunoprecipitation (IP) was performed using K562 cell extract and RNA components were extracted. cDNA was reverse transcribed from RNA components and Th RNA and U3 RNA were detected by qPCR using custom primers. Cycle threshold (Ct) values were compared in a titration experiment to determine the assay efficacy. The new assay was evaluated by testing 22 anti-Th/To and 12 anti-U3RNP positive samples in addition to 88 controls, and the results were compared with IP as a gold standard.ResultsBy testing serial 1:8 dilutions of cell lysate as the substrate in the IP step, RNA extracted after IP, and its derived cDNA, linear dose response curves were noted for both anti-Th/To and -U3RNP. With every dilution, Ct values changed approximately three as expected, reflecting the eight-fold difference of cDNA. The Ct difference between positive and negative samples was 8 to 13, which was similar throughout the dilutions. In the specificity analysis, the Ct values of positive samples were clearly different from the negative groups and the results by qPCR had a near perfect correlation with IP.ConclusionsOur new method readily detects these two clinically important antibodies in SSc. Making tests for anti-Th/To and -U3RNP antibodies widely available to clinicians should be helpful in the diagnosis and follow-up of SSc patients.

Mutagenicity assessment of contaminated soil in the vicinity of industrial area

In the industrial area of Chinhat, Lucknow (India) wastewater coming from pesticide manufacturing and other industries is used to irrigate the agricultural crops. This practice has been polluting the soil and pollutants might reach the food chain. Gas chromatographic analysis revealed the presence of certain organochlorine pesticides in soil samples. Samples were extracted using different solvents, i.e., hexane, acetonitrile, methanol, chloroform, and acetone (all were HPLC-grade, SRL, India). Soil extracts were assayed for mutagenicity using Ames Salmonella/mammalian microsome test. Mutagenicity was observed in the test samples and TA98 was the most responsive strain for all the soil extracts (irrigated with wastewater) in terms of mutagenic index in the presence (+S9) and absence (-S9) of metabolic activation. In terms of slope (m) of linear dose-response curve for the most responsive strain TA98 exhibited highest sensitivity against the soil extracts in the presence and absence of S9 fraction. Hexane-extracted soil sample (wastewater) exhibited maximum mutagenicity in terms of net revertants per gram of soil in the presence and absence of S9 mix as compared to the other soil extracts. Groundwater-irrigated soil extracts displayed low level of mutagenicity as compared to wastewater-irrigated soil. The soil is accumulating a large number of pollutants due to wastewater irrigation and this practice of accumulation has an adverse impact on soil health.

An in vitro coupled transcription/translation reporter system for hepatitis C virus RNA-dependent RNA polymerase

Hepatitis C virus (HCV) NS5B, an RNA-dependent RNA polymerase (RdRp), is an attractive target for antiviral agents. The in vitro RNA synthesis system based on radioisotopic readout is commonly used for polymerase inhibitor screening; however, this system generates large amounts of radioactive waste and is not amenable to high-throughput applications. To overcome this limitation, we generated pFLuc-(−)UTRΔC-RLuc, a bicistronic reporter vector, which allows effective and sensitive distinction of RdRp activity by using a cell-free coupled transcription/translation system. This reporter construct comprises the firefly luciferase (FLuc) and the Renilla luciferase (RLuc) genes in reverse orientation flanked by the two negative strands of the HCV 5′- and 3′-untranslated regions in which FLuc and RLuc reporter proteins are regulated by bacteriophage T7 polymerase and NS5B polymerase, respectively. The increase in RLuc activity was proportional to the amount of active RdRp. This cell-free dual reporter system was further validated using specific RdRp inhibitors. Hence, linear dose–response curves between RLuc activity and specific inhibitors were obtained, as was faster drug screening through real-time measurement of chemiluminescence. Moreover, this reporter system is suitable for robust in vitro screening because of a statistically acceptable Z′ factor value of 0.79 under the antiviral screening condition in the 96-well format.

SU-E-T-76: Construction of a Cost-Effective and Versatile Optically Stimulated Luminescence Detector (OSLD) Reader for Research

Purposes: To build a cost-effective and versatile optically stimulated luminescence detector (OSLD) reader. Methods: An instrument was built to perform three integrated tasks including light detection, stimulation and instrument control. A photomultiplier tube (PMT) is used to detect the OSLDˈs luminescence. Four high-powered green light emitting diodes (LEDs) are used as stimulation sources. The PMT and LEDs are controlled using a data acquisition board (DAQ). A custom-made light-tight chamber made of aluminum integrates these components. A 24 V DC power supply powers an LED driver, which supplies a constant current to the LEDs. The PMT is powered using the same power supply and a voltage regulator. The DAQ is controlled by a computer connected via a USB cable running a program written in LabVIEW, which allows continuous wave (CW) and pulsed OSL measurements. Results: Preliminary results show that the standard deviation of the PMT counts is 1.2 times higher than that expected due to Poisson statistics. The initial intensity of the OSL signal from four Al2O3:C OSLDs exposed to 100 mGy were within 2%. A linear dose response curve was observed for Al2O3:C OSLDs exposed to doses between 100 mGy and 10 Gy. Conclusions: The OSLD reader presented good stability with reproducible results of the initial intensity of the OSL signal. The device is portable, more cost-effective and yet more versatile than the currently available commercial OSLD readers. Our OSLD reader may be used to perform OSL research in clinical dosimetry. The detailed design of our OSLD reader including technical drawings, circuitry and software are available upon request.

Dietary lysine requirement and efficiency of lysine utilization for growth of Atlantic cod

This study was conducted to evaluate the minimum dietary lysine requirement, the maintenance lysine requirement and the efficiency of lysine utilization for growth of Atlantic cod. Eight fish meal and wheat gluten-based diets, containing graded levels of crystalline l-lysine–HCl, were fed to quadruplicate groups of cod for 9 weeks. The diets contained 13.7 to 28.3 mg lysine kg −1 (protein-bound form). A fishmeal-based control diet (30.6 mg lysine kg −1) was also fed at ration levels of 33, 66 and 100%. Exponential models predicted that the minimum dietary lysine requirement required to reach 95% of maximum nitrogen gain was 23.8 g kg −1 DM (protein-bound form; 27.1 g kg −1 DM free-form lysine) and 95% of maximum lysine gain was 26.2 g kg −1 DM (protein-bound form; 29.9 g kg −1 DM free-form lysine). In cod fed diets containing lysine concentrations up to 89% of the requirement based on lysine gain, a linear relationship was found between digestible lysine intake and lysine gain (R 2 = 0.91); 85% of the digestible lysine intake over maintenance was deposited in the cod. Neither the linear dose–response curve, nor the linear relationship between digestible lysine intake of the control diet and lysine deposition in the cod, had Y-intercepts significantly different from zero and therefore, the maintenance lysine requirement of the cod could not be estimated.

Practical Risk Assessment and Management Issues Arising were we to Adopt Low-Dose Linearity for all Endpoints

The 2009 National Research Council report, Science and Decisions, proposes harmonizing dose-response approaches for cancer and non-cancer endpoints, and for non-cancer quantitative risk assessment, this would usually take the form of a low-dose linear no-threshold dose-response curve. The soundness of this recommendation has been questioned, but I focus on its consequences if adopted, many of them apparently unintended. If most endpoints for most agents are assumed to have non-zero low-dose risks, then the critical-effect concept, choosing the one endpoint on which to calculate acceptable doses, loses its basis. All regulatory decisions, since they entail substituting some exposures (and their attendant risks) for others, become risk-risk trade-off decisions, and equity questions are raised since risk transfer is inevitably involved. A valid basis for estimating low-dose linear components is not evident, and upper-bound approaches fail to be reliably public health-protective owing to the risk trade-off decisions that need to be faced.

A novel application of normoxic polymer gel dosimeters for near real-time dose measurement using cone-beam computed tomography

The aim of this study is to evaluate the feasibility of using cone-beam CT system as a near real-time measurement device in dose estimation with normoxic polymer gel dosimetry (MAG). Each vial was filled with MAG gel and irradiated with uniform doses of 0–10 Gy to generate dose response curves. After irradiation, a cone-beam CT was used to perform the 3D dose measurement. In this study, two groups of gel samples were irradiated and measured in two ways for comparison: near real-time measurement, in which the gel phantom was read right after the irradiation, and delayed measurement, in which the measurement was performed 30 min, 4 h and 1 day after the irradiation for the gel phantom to be exposed to oxygen. All groups were also performed with and without a full bowtie filter to estimate the influence of a full bowtie filter to dose response. The linear dose response curves with and without a full bowtie filter for the four different CT imaging times were within a range 0.044–0.049Δ N CT cGy −1 and 0.061–0.063Δ N CT cGy −1, respectively, with no significant difference at different imaging times. Nevertheless, dose response curves with the full bowtie filter were higher than those without, with p-value <0.05 for all the different imaging times tested. Normoxic polymer gel dosimetry combined with cone-beam CT provides a useful method for near real-time dose measurement.

SU‐GG‐T‐332: Dose to Contralateral Breast: A Comparison of Traditional Linac and Tomotherapy Techniques

Purpose: To characterize the dose and its distribution to the contralateral breast in patients undergoing whole‐breast radiotherapy using helical tomotherapy, and traditional linac with enhanced dynamic wedges or field‐in‐field techniques. Method and Materials: At the start of this IRB approved study, patients were selected and offered consent and enrollment. Dosimetry was performed using thermoluminescent dosimeters (TLDs) which were individually calibrated and tracked to generate a linear dose response curve for each. Positions for measurement were marked on the patient for reproducibility. The measurement positions were 5 cm superior, inferior, medial, and lateral to the breast center of the contralateral breast and 2 cm from center of sternum toward the contralateral breast. TLDs were placed in buildup caps to ensure buildup to electronic equilibrium. TLDs were placed daily for five consecutive treatments and then read 10 days after the last treatment. Calibration curves were applied to the TLD readings. Results: To date, three patients have been treated on Tomotherapy and five patients with traditional tangents. The contralateral breast doses, presented as a percentage of the prescription dose ± 1 standard deviation, are as follows: Tomotherapy; two cm from sternum 36 ± 8%, five cm medial 17 ± 6%, five cm superior 6 ± 1%, five cm lateral 6 ± 1%, five cm inferior 6 ± 1%. Traditional tangents; two cm from sternum 12 ± 5%, five cm medial 5 ± 2%, five cm superior 2 ± 1%, five cm lateral 2 ± 1%, five cm inferior 2 ± 1%. The average breast dose, calculated as the arithmetic mean of the doses five cm from the breast center, were 9 ± 6% for Tomotherapy and 3 ± 2% for traditional tangents. Conclusion: At our institution, helical tomotherapy produces doses in the contralateral breast that are approximately three times that of traditional tangents.

A UVB Wavelength Dependency for Local Suppression of Recall Immunity in Humans Demonstrates a Peak at 300 nm

UVB radiation is a potent environmental carcinogen that not only causes mutations in the skin but also profoundly suppresses skin immune responses. Although this UVB-induced suppression of antitumor immunity has a key role in skin cancer development, the wavelengths within UVB causing greatest in vivo immunosuppression in humans are as yet unknown. We have identified a wavelength dependency for immunosuppression in humans across the UVB spectrum. We established linear dose-response curves for UV-induced local suppression of recall contact hypersensitivity responses at four wavelengths between 289 and 322 nm and found peak immune suppressive effectiveness at 300 nm and no detectable suppression at 322 nm within a physiologically relevant dose range.

Mutagenicity of N-ethyl-N-nitrosourea, N-methyl-N-nitrosourea, methyl methanesulfonate and ethyl methanesulfonate in the developing Syrian hamster fetus

N-ethyl-N-nitrosourea (ENU) and N-methyl-N-nitrosourea (MNU) are well-known direct-acting transplacental mutagens and carcinogens. Methyl methanesulfonate (MMS) and ethyl methanesulfonate (EMS) are also direct-acting but more stable compounds and form a different proportion of the various methyl and ethyl DNA adducts. The transplacental mutagenicity and carcinogenicity of MMS and EMS have not been well characterized. We tested the mutagenicity to the developing Syrian hamster by these compounds under identical conditions and with a range of dose. Mutant fetal cells were selected for diphtheria toxin resistance. All four compounds were significantly mutagenic. MNU was the most active and MMS the least active of the compounds. ENU and MNU demonstrated linear dose–response curves, whereas that for EMS seemed to be supralinear over the range 0.125–0.5 mmol/kg. At its highest dose, EMS was comparable to ENU in mutagenicity. In view of a recent accidental exposure of pregnant women and others to EMS, further studies of this compound in animal models may be warranted.

Modeling dose-Response at Low dose: A Systems Biology Approach for Ionization Radiation

For ionization radiation (IR) induced cancer, a linear non-threshold (LNT) model at very low doses is the default used by a number of national and international organizations and in regulatory law. This default denies any positive benefit from any level of exposure. However, experimental observations and theoretical biology have found that both linear and J-shaped IR dose-response curves can exist at those very low doses. We develop low dose J-shaped dose-response, based on systems biology, and thus justify its use regarding exposure to IR. This approach incorporates detailed, molecular and cellular descriptions of biological/toxicological mechanisms to develop a dose-response model through a set of nonlinear, differential equations describing the signaling pathways and biochemical mechanisms of cell cycle checkpoint, apoptosis, and tumor incidence due to IR. This approach yields a J-shaped dose response curve while showing where LNT behaviors are likely to occur. The results confirm the hypothesis of the J-shaped dose response curve: the main reason is that, at low-doses of IR, cells stimulate protective systems through a longer cell arrest time per unit of IR dose. We suggest that the policy implications of this approach are an increasingly correct way to deal with precautionary measures in public health.

Analysis of human luteinizing hormone and human chorionic gonadotropin preparations of different origins by reversed-phase high-performance liquid chromatography

Specific reversed-phase high-performance liquid chromatography conditions are reported for the analysis of recombinant and native human luteinizing hormone (hLH) and human chorionic gonadotropin (hCG) preparations. Heterodimeric hLH, hCG and their α- and β-subunits migrated with significantly different retention times ( t R) in the following order of increasing hydrophobicity: α-hCG < α-hLH < hCG < hLH < β-hCG < β-hLH. Under these conditions, the main peak of three hCG preparations ran about 4% faster than the average t R (38.35 ± 0.42 min; RSD = 1.1%) of four hLH preparations. Four heterogeneous urinary products were also analyzed, hLH, hFSH and hCG peaks being identified. Quantitative analysis was validated for the homogeneous preparations and a highly linear dose–response curve ( r = 0.99998; p < 0.0001; n = 20) used to assess the accuracy, precision and sensitivity of the analysis. Quantification of the different gonadotropins in the heterogeneous preparations was also carried out, but with limitations in accuracy.