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PubMed2006

Evaluation of 17 CE-marked HBsAg assays with respect to clinical sensitivity, analytical sensitivity, and hepatitis B virus mutant detection.

Seventeen HBsAg assays, in use in the European market (CE-marked), were assessed for their diagnostic sensitivity using 38 commercially available seroconversion panels, and for their analytical sensitivity with the HBsAg ad and ay standards of the Paul-Ehrlich-Institut (PEI). In addition, the ability to detect HBsAg mutants was investigated by means of 21 recombinant HBsAg mutant samples and 5 natural mutants. Analysis of seroconversion data revealed that there were marked differences in the sensitivity among the CE-marked HBsAg assays. Differences in the window period between the most and the least sensitive assays were up to 2 weeks. Analytical sensitivities of the investigated assays ranged from 0.009 to 0.05 PEI-U/ml for HBsAg ad standard (relating to approximately 0.018 to 0.100 IU/ml of the 2nd WHO HBsAg standard) and 0.012 to 0.11 PEI-U/ml for the ay standard. Clinical and analytical sensitivities were basically correlated. The capacity to detect mutant HBsAg forms was influenced by the assay format and the properties of the monoclonal antibodies used for coating of the solid phase or in the conjugate. While some assays detected all mutants others exhibited weaknesses especially in recognising HBsAg mutations affecting loop 2 of the HBsAg a-determinant. The results obtained with the recombinant mutants were largely confirmed by the investigation of clinical samples. The study gives a broad overview of the current state of the art of about 70% of the HBsAg assays currently available in Europe. The overall sensitivity has not been improved further since 1995 when the most sensitive assay was introduced into the market. In addition, detection of HBsAg mutants seems problematic with several assays. It is concluded that there is potential to improve clinical sensitivity and mutant recognition of HBsAg assays.

Antibodies, Monoclonal↗
PubMedDate not supplied

Symptoms and health status in individuals with multiple chemical sensitivities syndrome from four reported sensitizing exposures and a general population comparison group.

Self-reported information about health and mental health status and history on (a) three diverse samples of individuals who reported multiple chemical sensitivities syndrome (n = 60) and (b) one sample of the general population (n = 60) was collected by telephone interview. Subjects from the general population were selected randomly from the telephone directory and were matched for age, gender, and socioeconomic status with index subjects. Data on an additional 10 subjects with multiple chemical sensitivities syndrome were also available for comparison on many of the variables of interest. The four diverse groups of patients with multiple chemical sensitivities syndrome had very similar general and specific indices of illness and sensitivity to chemicals. Members of the general population reported mild sensitivity to chemicals, and even those with more sensitivity differed from the multiple chemical sensitivities syndrome groups with respect to number and types of symptoms reported, duration and frequency of response, and associated features. Multiple chemical sensitivities syndrome was associated consistently with only one psychiatric variable, elevated negative affect scores, which were correlated significantly with the presence of illness. Patients with multiple chemical sensitivities syndrome from the diverse samples had very similar characteristic features, despite whether they had or had not received treatment by clinical ecologists.

Adult↗
PubMed1991

The relationship between the anoxic sensitivity and the extent of sensitization by nitrous oxide.

Nitrous oxide reacts during irradiation to increase the yield of .OH, a radical many believe to be a major cause of lethality. Logically, one would expect N2O to be a radiation sensitizer. In some instances it is, while in others it is not. In some cases we can explain why N2O fails to sensitize; factors such as dose rate, cell concentration, buffer composition and ionic strength all influence when N2O will sensitize and, if it sensitizes, by what magnitude. Based on the results presented here with multiple strains of procaryotic and eucaryotic cells, we believe the anoxic sensitivity is another critical factor that governs whether N2O will sensitize. Our data, with data from the literature, show a relationship between the anoxic sensitivity and the N2O enhancement ratio. N2O does not sensitize in vitro unless the anoxic sensitivity (inactivation constant, k) is less than approximately 0.2 daGy-1.

Animals↗
PubMedDate not supplied

Application of sensitive mouse lymph node assay for detection of contact sensitization capacity of dyes.

A sensitive mouse lymph node assay (SLNA) is a test method for the detection of contact allergens. The sensitization potential of test chemicals is determined by assessing total lymph node activation response induced by application of the chemical. In this study, we examined whether the SLNA would have a sufficient competence for determination of sensitization capacity of coloured chemicals routinely. Prior to this study, we investigated application of an Alamar Blue dye (non-radioisotope reagent) as an alternative to [3H]thymidine for measurement of cell proliferation. However, the Alamar Blue assay is useful for determining cell number but is not applicable to detect lymph node cell proliferation activity for 24-h culture in the SLNA. The SLNA was applied to evaluate the sensitization capacity of 20 dyes. Most of the sensitizing dyes were correctly determined as a sensitizer. Some chemicals that were known as strong sensitizers showed strong lymph node responses. Comparing the results of the SLNA with data from guinea-pig tests, the same predictions of sensitization capacity were made in nine out of ten cases. The SLNA also detected 13 of the 17 chemicals that were identified to be contact allergens by the human patch test. These data showed that the evaluation of the SLNA was not influenced by the colour property of the test chemicals and that the SLNA was a sufficiently sensitive robust screen test for the identification of contact allergens.

Allergens↗
PubMed1996

Sensitization interval and administration method alter the effect of 15-deoxyspergualin on heart transplantation in sensitized recipient rats.

We evaluated the effect of 15-deoxyspergualin (DSG) on accelerated rejection. Brown Norway rats (BN) served as organ donors and Lewis rats (LEW) as recipients. In an accelerated rejection model, after a LEW rat was sensitized with BN skin, a BN heart was transplanted. Various intervals between sensitization and heart transplantation were examined. The heart allografts in sensitized recipients were rejected earlier than those in unmodified recipients regardless of the sensitization interval. DSG (2.5 mg/kg per day), given to the recipients during the sensitization phase, significantly prolonged graft survival compared with the untreated hosts when the sensitization interval was short. When the recipients were treated with DSG after heart transplantation, heart graft survival was significantly prolonged regardless of the sensitization interval. Flow cytometric analysis and complement-dependent cytotoxicity tests revealed that DSG suppressed antidonor antibody formation and the postoperative administration of DSG significantly decreased the proliferation of B cells when the sensitization interval was short and the proliferation of class II antigen-positive cells when the sensitization interval was long.

Animals↗
PubMed1994

Characterization of illudin S sensitivity in DNA repair-deficient Chinese hamster cells. Unusually high sensitivity of ERCC2 and ERCC3 DNA helicase-deficient mutants in comparison to other chemotherapeutic agents.

Illudins, novel natural products with a structure unrelated to any other known chemical, display potent in vitro and in vivo anti-cancer activity against even multi-drug resistant tumors, and are metabolically activated to an unstable intermediate that binds to DNA. The DNA damage produced by illudins, however, appears to differ from that of other known DNA damaging toxins. The sensitivity pattern of the various UV-sensitive cell lines differs from previously studied DNA cross-linking agents. Normally, the ERCC1- (excision repair cross complementing) and ERCC4-deficient cell lines are most sensitive to DNA cross-linking agents, with ERCC2-, ERCC3- and ERCC5-deficient cell lines having minimal sensitivity. With illudins the pattern is reversed, with ERCC2 and ERCC3 being the most sensitive. The sensitivity to illudins in complementation groups 1 through 3 is due to a deficiency of the ERCC1-3 gene products, as cellular drug accumulation studies revealed no differences in transport capacity or total drug accumulation. Also, a transgenic cell line in which ERCC2 activity was expressed through an expression vector regained its relative resistance to the illudins. The EM9 cell line, which displays sensitivity to monoadduct producing chemicals, was not sensitive. Thus, excision repair is involved in repair of illudin-induced damage and, unlike other anti-cancer agents, the involvement of ERCC2 and ERCC3 helicases is critical for repair to occur. The requirement for ERCC2 and ERCC3, combined with the finding that ERCC1 but not ERCC2 is upregulated in drug-resistant tumors, may explain the efficacy of illudins against drug-resistant tumors. The inhibition of DNA synthesis in cells within minutes after exposure to illudins at nanomolar concentrations may be related to the finding that the ERCC3 gene product is actually the p89 helicase component of the BTF2 (TFII) basic transcription factor and the high sensitivity of ERCC3-deficient cells to illudins.

Animals↗
PubMed1981

Mutagen sensitivities and mutator effects of MMS-sensitive mutants in Neurospora.

7 mus (mutagen-sensitive) mutants of Neurospora crassa, which are more sensitive to the toxic effects of MMS (methyl methanesulfonate) than wild-type, were investigated for cross-sensitivities to other mutagens and inhibitors. These mutants have recently been mapped in 5 new genes, mus-7 to mus-11, and mutant alleles from each gene were checked for their effects on mutation frequencies. It was found that mutants in 3 of these 5 genes showed radiation-induced mutation frequencies similar to wild-type. These included 2 alleles of the gene mus-10, which were cross-sensitive only to UV and were the only mutants that produced some viable ascospores in homozygous crosses. The mutant of the second gene, mus-8, was especially sensitive to UV and mitomycin C and produced slightly reduced frequencies of spontaneous mutation. In contrast, the mutant of the third gene, mus-7, was not UV-sensitive but showed some cross-sensitivity to X-rays; mus-7 was highly sensitive to MMS and also to histidine, which inhibits various repair-defective mutants at concentrations well below those that reduce wild-type growth. None of these mus resemble mutants previously found in Neurospora, nor do they conform clearly to mutant types identified in E. coli or yeast. On the other hand mutants in 2 further genes, mus-11, and especially 2 alleles of mus-9, are very similar to uvs-3 of Neurospora and generally resemble mutants that are considered to be defective in "error-prone" repair. They were UV- as well as X-ray-sensitive, and showed strong spontaneous mutator effects but almost no increase in recessive lethal frequencies in heterokaryons after UV-treatments.

Deoxyribonucleases↗
PubMed1982

Sensitivity of the blue-sensitive cones across the central retina.

We measured increment thresholds up to 5 degrees eccentricity using a 10' dia flash viewed against 10(4) td of 572-nm background. We found two distinct sensitivity profiles, one with flash wavelengths 410-470 nm and another with 520-580 nm. Spectral sensitivity plots indicate blue-sensitive cones and green-sensitive cones for the two profiles, respectively. Sensitivity of blue-sensitive cones is maximum at 1 degree eccentricity. Measurements at greater eccentricities are susceptible to adaptation to test field. The light-collecting area of blue-sensitive cones raised to a power follows the sensitivity profile of blue-sensitive cones.

Adult↗
PubMed1983

X-ray-sensitive mutants of Chinese hamster ovary cell line. Isolation and cross-sensitivity to other DNA-damaging agents.

A standard technique of microbial genetics, which involves the transfer of cells from single colonies by means of sterile toothpicks, has been adapted to somatic cell genetics. Its use has been demonstrated in the isolation of X-ray-sensitive mutants of CHO cells. 9000 colonies have been tested and 6 appreciably X-ray-sensitive mutants were isolated. (D10 values 5-10-fold of wild-type D10 value.) A further 6 mutants were obtained which showed a slight level of sensitivity (D10 values less than 2-fold of wild-type D10 value). The 6 more sensitive mutants were also sensitive to bleomycin, a chemotherapeutic agent inducing X-ray-like damage. Cross-sensitivity to UV-irradiation and treatment with the alkylating agents, MMS, EMS and MNNG, was investigated for these mutants. Some sensitivity to these other agents was observed, but in all cases it was less severe than the level of sensitivity to X-irradiation. Each mutant showed a different overall response to the spectrum of agents examined and these appear to represent new mutant phenotypes derived from cultured mammalian cell lines. One mutant strain, xrs-7, was cross-sensitive to all the DNA-damaging agents, but was proficient in the repair of single-strand breaks.

Animals↗
PubMed1988

Comparison of a radioisotopic incorporation method and the mouse ear swelling test (MEST) for contact sensitivity to weak sensitizers.

A radioisotopic incorporation assay utilizing [125I]iododeoxyuridine was compared to the standard mouse ear swelling test (MEST) for the strong sensitizers dinitrofluorobenzene and oxazolone, and for the three weak sensitizers ethylenediamine (EDA), glutaraldehyde, and nickel sulfate. Mice were sensitized epicutaneously on the abdomen for 4 consecutive days prior to challenging the left ear with the test agent and the right ear with the vehicle. A comparison of the mean difference between the test and the control ears showed that measuring reactivity 48 hr postchallenge on Day 7 is the most sensitive time period in the radioisotopic incorporation method. Both the isotopic and MEST assays gave positive results with the potent sensitizers, although the response detected by isotopic labeling of emigrating cells was up to 1000-fold greater than that determined by ear swelling measurements. No response was detected to the moderate to weak sensitizer EDA in either assay. Reactivity to glutaraldehyde was not detected by the radioisotopic assay but was minimally responsive and significant by the MEST. The opposite was true for nickel sulfate where minimal but significant reactivity was seen in the isotopic assay but not in the MEST. Although the radioisotopic assay had the advantages of being more quantitative and of having improved sensitivity, it was of no greater value than the MEST for detecting weak sensitizers. It was concluded that the mouse was not a suitable model for routinely detecting reactivity to weak sensitizers regardless of which of the two assays were used.

Animals↗
PubMed1995

Induction of cisplatinum sensitivity without alteration in radiation sensitivity by fractionated radiation treatment of a human laryngeal squamous cell carcinoma cell line.

PURPOSE: To determine if fractionated radiation treatment can alter cisplatinum sensitivity of a human laryngeal squamous carcinoma cell line. METHODS AND MATERIALS: Human squamous carcinoma cells, both previously untreated, as well as survivors of fractionated radiation therapy, were tested in vitro for their sensitivity to gamma radiation and cisplatinum. Fractionated gamma radiation was delivered in 14 or 10 daily fractions of 2 Gy. The cell line, cSCC-20, was derived from an untreated primary human laryngeal carcinoma. RESULTS: The human laryngeal squamous cell carcinoma cell line, cSCC-20, was demonstrated to have heterogeneous subpopulations with respect to cisplatinum sensitivity. No variation in radiation sensitivity was seen among subpopulations of varying cisplatinum sensitivity. The cells were relatively radioresistant (Do = 2.5 Gy). Fractionated radiation treatments of the parent cell line (14 fractions, 14 days, 2 Gy/fraction) or a cisplatinum sensitive subline (10 fractions, 12 days, 2 Gy/fraction) induced cisplatinum sensitivity (factor of 1.3 to 1.4) in the surviving cells. CONCLUSION: Fractionated radiation treatment of human squamous carcinoma cells in vitro induced sensitivity to cisplatinum without concomitant alteration in radiation sensitivity.

Carcinoma, Squamous Cell↗
PubMed1991

Cross-sensitivity of gamma-ray-sensitive hamster mutants to cross-linking agents.

A range of hamster cell mutants, which have been characterised as sensitive to ionising radiation, were examined for their cross-sensitivity to four DNA-DNA cross-linking agents and the protein-DNA cross-linking agent, camptothecin. The mutants represent 7 distinct complementation groups. Two complementation groups were identified as having a major sensitivity to cross-linking damage, more marked than their sensitivity to ionising radiation (irs1, irs1SF). These two mutants also show sensitivity to UV-irradiation. Two of the remaining complementation groups (xrs and XR-1) have a defect in rejoining DNA double-strand breaks, and these exhibit sensitivity to 3 of the 4 DNA-DNA cross-linking agents. The results with these mutants suggest an involvement of double-strand break rejoining in the repair of certain cross-link damage. Two mutants were also notably sensitive to the topoisomerase I inhibiting anticancer drug, camptothecin. One of these mutants was sensitive to the DNA cross-linking agents examined (irs1SF), but the other was not at all sensitive to this class of drug (EM9).

Animals↗
PubMed2006

Nullifying drug-induced sensitization: behavioral and electrophysiological evaluations of dopaminergic and serotonergic ligands in methamphetamine-sensitized rats.

Repeated exposure to methamphetamine produces a persistent enhancement of the acute motor effects of the drug, commonly referred to as behavioral sensitization. Behavioral sensitization involves monoaminergic projections to several forebrain nuclei. We recently revealed that the ventral pallidum (VP) may also be involved. In this study, we sought to establish if treatments with antagonists or partial agonists to monoaminergic receptors could "reverse" methamphetamine-induced behavioral and VP neuronal sensitization. Behavioral sensitization was obtained in rats with five once-daily s.c. injections of 2.5mg/kg methamphetamine, an effect that persisted for at least 60 days. After the development of sensitization, 15 once-daily treatments of mirtazapine (a 5-HT(2/3), alpha(2) and H(1) antagonist), SKF38393 (D(1) partial agonist) or SCH23390 (dopamine D(1) antagonist) nullified indices of motor sensitization as assessed by measuring the motoric response to an acute methamphetamine challenge 30 days after the fifth repeated methamphetamine treatment. VP neurons recorded in vivo from methamphetamine-sensitized rats at the 30-day withdrawal time also showed a robust downward shift in the excitatory responses observed to an acute i.v. methamphetamine challenge in non-sensitized rats. This decreased excitatory effect was reversed by mirtazapine, but not by other antagonists that were tested. These data suggest a potential therapeutic benefit for mirtazapine in the treatment of methamphetamine addiction, and point to a possible role for the VP in the sensitization process to methamphetamine.

Action Potentials↗
PubMed2003

Proposal for a risk assessment methodology for skin sensitization based on sensitization potency data.

In this paper, we propose a quantitative risk assessment methodology for skin sensitization aiming at the derivation of 'safe' exposure levels for sensitizing chemicals, used e.g., as ingredients in consumer products. Given the limited number of sensitizers tested in human sensitization tests, such as the human repeat-insult patch test (HRIPT) or the human maximization test (HMT), we used EC3 values from the local lymph node assay (LLNA) in mice because they provide the best quantitative measure of the skin sensitizing potency of a chemical. A comparison of LLNA EC3 values with HRIPT and HMT LOEL, and NOEL values was carried out and revealed that the EC3, expressed as area dose, can be used as a surrogate value for the human NOEL in risk assessment. The uncertainty/extrapolation factor approach was used to derive (a) an 'acceptable non-sensitizing area dose' (ANSAD) to protect non-allergic individuals against skin sensitization and (b) an 'acceptable non-eliciting area dose' (ANEAD) to protect allergic individuals against elicitation of allergic contact dermatitis. For ANSAD derivation, interspecies, intraspecies and time extrapolation factors are applied to the LLNA EC3. For ANEAD derivation, additional application of a variable sensitization-elicitation extrapolation factor is proposed. Values for extrapolation factors are derived and discussed, the proposed methodology is applied to the sensitizers methylchloroisothiazolinone/methylisothiazolinone, cinnamic aldehyde and nickel and results are compared to published risk assessments.

Allergens↗
PubMedDate not supplied

The effects of antibodies against proteins of the s100 group on neuron plasticity in sensitized and non-sensitized snails.

The effects of antibodies to a total fraction of s100 proteins and protein s100b on the activity of defensive behavior command neurons LP11 and RP11 were studied in common snails, using non-sensitized animals and animals which had acquired nociceptive sensitization. In non-sensitized snails, application of antibodies against s100 or s100b (0.1 mg/ml) induced membrane depolarization, increased membrane permeability, and suppressed slow excitatory postsynaptic potentials in the responses of neurons to sensory stimulation. Acquisition of sensitization in snails in the presence of antibodies to s100 or s100b (0.1 mg/ml) led to significantly less marked facilitation of synaptic transmission and smaller increases in neuron membrane excitability than in cells of control sensitized animals. The difference in synaptic facilitation in the neurons of control sensitized snails and neurons in sensitized snails given antibody was comparable with the magnitude of synaptic depression due to antibody in non-sensitized animals. At a dose of 0.01 mg/ml, antibody had no effect on these measures of neuron activity. It is suggested that s100 proteins, particularly s100b, are involved in the mechanisms regulating excitability, the membrane potential, and synaptic transmission in command neurons in untrained snails, as well as in the mechanism of plasticity of the electrogenic membranes of nerve cells during the acquisition of nociceptive sensitization.

Action Potentials↗
PubMed1997

Calcium sensitivity and agonist-induced calcium sensitization in small arteries of young and adult spontaneously hypertensive rats.

The sensitivity of the myofilaments to Ca2+ is increased during agonist-induced contraction of vascular smooth muscle. Given the important contribution of vascular tone to the elevation of peripheral resistance observed in genetic hypertension, we have investigated whether alterations in myofilament Ca2+ sensitivity occur in small arteries from spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto (WKY) controls during the developmental and established phases of hypertension. Segments of mesenteric, renal, and femoral artery with an average lumen diameter <300 microm from 5- or 20-week-old rats were mounted in a wire myograph. Morphological measurements were made and the vessels permeabilized with Staphylococcus aureus alpha-toxin. Dose-response curves to increasing concentrations of Ca2+ were obtained and the ability of 100 nmol/L endothelin-1 (ET-1) or 10 micromol/L norepinephrine (NE) in the presence of 10 micromol/L GTP to enhance tension in response to low Ca2+ (pCa6.7) was determined. Systolic, diastolic, and mean blood pressures were higher in SHR than in WKY at 5 and 20 weeks. The media thickness:lumen diameter ratio was increased in mesenteric and femoral arteries from SHR compared with WKY at 5 and 20 weeks. There was no difference in media thickness:lumen diameter ratio in renal arteries or between 5- and 20-week animals in any vascular bed. The pCa curves were not different in mesenteric, renal, or femoral arteries from hypertensive compared with normotensive rats or between age groups, except in femoral arteries at 20 weeks, which exhibited a greater sensitivity to Ca2+ in SHR. Tension developed in response to maximal Ca2+ (pCa5.0) was greater in permeabilized mesenteric arteries from SHR compared with WKY at 20 weeks of age only; media stress was again similar in both strains but increased in older animals compared with younger animals in mesenteric arteries from WKY. The submaximal contraction induced by pCa6.7 was greater in femoral and renal than mesenteric arteries. GTP (10 micromol/L) augmented the tension developed to pCa6.7 in mesenteric arteries at 5 and 20 weeks and in renal arteries at 20 weeks. Addition of 100 nmol/L ET-1 or 10 micromol/L NE in the continued presence of GTP markedly increased tension in mesenteric arteries at 5 and 20 weeks. In renal arteries, 10 micromol/L NE enhanced Ca2+ sensitivity in the presence of GTP in SHR at 5 and 20 weeks and WKY at 5 weeks. In femoral arteries, there was a tendency for ET-1 and NE to increase Ca2+ sensitivity, but this increase was significant in WKY at 20 weeks (ET-1) and SHR at 5 weeks (NE) only. We have demonstrated that the sensitivity of the myofilaments to Ca2+ and ET-1- or NE-induced Ca2+ sensitization is not different in permeabilized small mesenteric, renal, or femoral arteries from SHR compared with WKY controls. Only in SHR mesenteric arteries at 20 weeks of age was there evidence of increased active tension in response to maximal Ca2+, despite structural differences, consistent with increased muscle mass in femoral arteries from SHR. We conclude that it is unlikely that a ubiquitous abnormality of the sensitivity of the contractile apparatus to Ca2+ or agonist-induced Ca2+ sensitization in vascular smooth muscle underlies the elevated total peripheral resistance associated with hypertension.

Aging↗