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PubMed1982

[The mechanism of the development of contact sensitivity and the methods of assessing allergenicity of contact sensitizers].

Recent reports on the mechanism of the development of contact sensitivity and on the method of assessing allergenicity both in vivo and in vitro are reviewed. Various cell types and two processes, afferent and efferent limbs, involved in the contact sensitivity are discussed. Conditions for applying contact sensitizers which induce specific unresponsiveness, desensitization and antigenic competition are also discussed. Diagnostic methods for identifying contact sensitizers in vivo, patch testing, and in vitro, migration inhibition test and blastoid transformation are reported. Moreover, methods of assessing the allergenicity of contact sensitizers are reported centering on the guinea pig maximization testing.

Animals↗
PubMed1998

Comparison of sex differences in guinea-pig maximization test for detection of skin-sensitizing potential using OECD recommended positive control sensitizers.

Both male and female guinea pigs are widely used in tests to detect the skin-sensitizing potential of new chemicals. The aim of the present study was to investigate the influence of the animal gender on sensitization rates, with the guinea-pig maximization test (GPMT) using OECD recommended positive control sensitizers, and the differences of the density of Langerhans cells in male and female guinea pigs. The sensitization rates of males and females challenged with HCA, MBT or benzocaine gave almost the same results. There were no statistical differences between the mean responses of males and females. These results were confirmed by rechallenge with the OECD recommended positive controls. Furthermore, the density of Langerhans cells in abdominal epidermis in males (1229 +/- 45 cells/mm2) was the same as that in females (1242 +/- 89 cells/mm2). These results indicate that there is no significant influence of guinea-pig gender in the assessment of skin-sensitizing potential using the GPMT.

Acrolein↗
PubMed2006

ATP sensitivity of the ATP-sensitive K+ channel in intact and permeabilized pancreatic beta-cells.

ATP-sensitive K(+) channels (K(ATP) channels) couple cell metabolism to electrical activity and thereby to physiological processes such as hormone secretion, muscle contraction, and neuronal activity. However, the mechanism by which metabolism regulates K(ATP) channel activity, and the channel sensitivity to inhibition by ATP in its native environment, remain controversial. Here, we used alpha-toxin to permeabilize single pancreatic beta-cells and measure K(ATP) channel ATP sensitivity. We show that the channel ATP sensitivity is approximately sevenfold lower in the permeabilized cell than in the inside-out patch and that this is caused by interaction of Mg-nucleotides with the nucleotide-binding domains of the SUR1 subunit of the channel. The ATP sensitivity observed in permeabilized cells accounts quantitatively for K(ATP) channel activity in intact cells. Thus, our results show that the principal metabolic regulators of K(ATP) channel activity are MgATP and MgADP.

ATP-Binding Cassette Transporters↗
PubMed2005

ATP and sulfonylurea sensitivity of mutant ATP-sensitive K+ channels in neonatal diabetes: implications for pharmacogenomic therapy.

The prediction that overactivity of the pancreatic ATP-sensitive K(+) channel (K(ATP) channel) underlies reduced insulin secretion and causes a diabetic phenotype in humans has recently been borne out by genetic studies implicating "activating" mutations in the Kir6.2 subunit of K(ATP) as causal in both permanent and transient neonatal diabetes. Here we characterize the channel properties of Kir6.2 mutations that underlie transient neonatal diabetes (I182V) or more severe forms of permanent neonatal diabetes (V59M, Q52R, and I296L). In all cases, the mutations result in a significant decrease in sensitivity to inhibitory ATP, which correlates with channel "overactivity" in intact cells. Mutations can be separated into those that directly affect ATP affinity (I182V) and those that stabilize the open conformation of the channel and indirectly reduce ATP sensitivity (V59M, Q52R, and I296L). With respect to the latter group, alterations in channel gating are also reflected in a functional "uncoupling" of sulfonylurea (SU) block: SU sensitivity of I182V is similar to that of wild-type mutants, but the SU sensitivity of all gating mutants is reduced, with the I296L mutant being resistant to block by tolbutamide (</=10 mmol/l). These results have important implications for the use of insulinotropic SU drugs as an alternative therapy to insulin injections.

Adenosine Triphosphate↗
PubMedDate not supplied

Rapid hyperthermic cell sensitivity test measured by RNA synthesis using contact-sensitive plates of confluent Balb/c 3T3 cell monolayers.

We have developed a hyperthermic sensitivity test for human neoplastic cells using contact-sensitive confluent monolayers of BALB/c 3T3 cells designated as 'contact-sensitive plates (CSP)', which almost completely inhibited the growth of normal cells without influencing the growth of the human neoplastic cells. On 'CSP', the relative [3H]uridine incorporation into RNA of the hyperthermic cultures showed an excellent correlation with the relative clonogenic efficiency of the treated cultures. Since 'CSP' allows for only contact-insensitive tumour cells to proliferate, our assay will predict the hyperthermic sensitivity of only the neoplastic cells. Moreover, even 2 x 10(3) cells derived from clinical tumour tissues can be assayed within only 3 days. This assay system is potentially used as a rapid in vitro hyperthermic sensitivity test for human carcinoma.

Animals↗
PubMedDate not supplied

Prediction and consistency of blood pressure salt-sensitivity as assessed by a rapid volume expansion and contraction protocol. Salt-Sensitivity Study Group of the Italian Society of Hypertension.

BACKGROUND: This multicenter trial in essential hypertensive patients (n=94) is aimed i) to evaluate the distribution of blood pressure salt-sensitivity by a rapid volume expansion/contraction protocol over three days; ii) to investigate the within-patient reproducibility and to identify predictors of the response to the test; iii) to compare this response with the response to dietary NaCl restriction. METHODS: The study design included: 1) screening for salt-sensitivity by the rapid test; 2) a controlled trial of dietary salt restriction; 3) repetition of the rapid test in a subgroup of patients. RESULTS: The mean BP response to the rapid test fitted a Gaussian curve. In multivariate regression analysis, controlling for the effect of potential confounders, the blood pressure increment during the intravenous saline infusion was the best independent predictor of the response to the test (r=0.713) with minor contributions by the 24-h urinary sodium excretion before the test and by baseline fasting serum insulin. These three variables together explained 61% of the overall variability of the response. The Spearman rank correlation coefficient between the BP response to the rapid test and the response to the dietary protocol was 0.21, p=0.05. Upon repetition of the rapid test, the correlation coefficient between the responses observed on the two occasions was 0.60 (n=19, p<0.01); there were no patients misclassified across the extreme tertiles of the distribution of salt-sensitivity. CONCLUSION: We conclude that the rapid test reproducibly identified patients in the upper and lower parts of the distribution of salt sensitivity. The analysis of possible predictors of the response to the test suggested that the evaluation of the blood pressure response to saline infusion, upon careful standardization of dietary NaCl intake, may represent an alternative to the completion of the whole test for the screening of the salt-sensitivity.

Adult↗
PubMed1976

Tolerance and contact sensitivity to DNFB in mice. VI. Inhibition of afferent sensitivity by suppressor T cells in adoptive tolerance.

Tolerance in contact sensitivity to DNFB can be adoptively transferred to normal mice with lymph node cells from tolerant donors. This tolerance is antigen specific and is mediated by T cells, i.e., "suppressor" T cells. Experiments were carried out to investigate the mechanism(s) by which the suppressor T cells induce tolerance to DNFB contact sensitivity. The suppressor cells were effective only if they were present during the early stages of the afferent limb of sensitization. As measured by DNA synthesis, cell proliferation in the draining lymph nodes of recipients of suppressor cells was found to be significantly less than in control animals indicating that the suppressor cells acted, at least in part, by limiting or inhibiting DNFB-induced cell proliferation. This inhibition was shown to be antigen specific since the DNFB suppressor cells did not inhibit cell proliferation induced by oxazolone, an unrelated contact sensitizer. The ability to DNFB tolerant cells to block afferent sensitization pathways differs from the mechanism of tolerance to picryl chloride, reported by others, where efferent pathways are blocked.

Animals↗
PubMed1975

Conjunctival sensitivity in pathological cases, with simultaneous measurement of corneal and lid margin sensitivity.

A total of 209 pathological eyes each had 17 localities tested for sensitivity (cornea, caruncle, upper and lower lid margins (centrally, medially and laterally), and corresponding localities on the palpebral conjunctiva, and upper and lower halves of the bulbar conjunctiva). Reduced conjunctival sensitivity is seen in pemphigoid (excluding the lid margin) in contact lens wearers, at sites of nerves transected during operation and in rare cases of infectious conjunctivitis. Isolated corneal hypaesthesia is seen in bacterial or fungal keratitis. In herpes, the hypaesthesia extends over the bulbar conjunctiva, in zoster, over wider areas (including the lid margin). The sensitivity is normal in keratoconjunctivitis sicca and chronic conjunctivitis. In neurological diseases the hyposensitivity could include the cornea, conjunctiva and lid margin. The conclusion is drawn that a study of the conjunctivo-corneal sensitivity can give differential diagnostic information, provided the normal sensitivity range is known. This has been set out in a Table in 10-year age groups.

Adult↗
PubMed2001

[Correlation between 5-fluorouracil (5-FU) sensitivity as measured by collagen gel droplet embedded culture drug sensitivity test (CD-DST) and expression of orotate phosphoribosyl transferase (OPRT), thymidylate synthase (TS), and dihydropyrimidine dehydrogenase (DPD) in colorectal cancer].

The levels of OPRT, DPD, and TS were determined in colorectal cancer tissue specimens, and 5-FU sensitivity was measured by CD-DST. The correlation between enzyme activity and 5-FU sensitivity was then studied. Six patients with colorectal carcinoma who had undergone surgical resection in our institution between May and August 2000 were studied. The CD-DST method was used to measure the sensitivity to 5-FU under three sets of conditions: 0.2 microgram/ml x 5 days (A), 1.0 microgram/ml x 1 day (B), and 10.0 micrograms/ml x 3 h (C). The coefficients of correlation of tumor sensitivity to 5-FU and OPRT activity were A: 0.8246, B: 0.7670, and C: 0.7856, and to DPD activity were A: 0.2525, B: 0.3928, and C: 0.4337, while the coefficients of correlation to TS enzyme levels were A: -0.5240, B: -0.4770, and C: -0.6131. These findings demonstrate a high degree of correlation between OPRT activity at the tumor site and tumor sensitivity to 5-FU under a variety of conditions, suggesting that OPRT activity can be a useful indicator in predicting the anti-tumor effectiveness of 5-FU for a specific tumor.

Aged↗
PubMed2001

The noradrenergic inhibition of an apamin-sensitive, small-conductance Ca2+-activated K+ channel in hypothalamic gamma-aminobutyric acid neurons: pharmacology, estrogen sensitivity, and relevance to the control of the reproductive axis.

The present study sought to determine whether small-conductance, Ca2+-activated K+ currents underlie the afterhyperpolarization (AHP) in neurons of the preoptic area (POA), a brain region important in controlling reproduction. We used an ovariectomized, female guinea pig model to test two hypotheses: 1) the current associated with the AHP (I(AHP)) regulates the firing rate of POA neurons and 2) amine neurotransmitters modulate it in a gonadal steroid-sensitive manner. Intracellular recordings followed by combined histofluorescence/in situ hybridization for glutamic acid decarboxylase, 65-kDa isomer, revealed that POA neurons, including gamma-aminobutyric acid (GABA)ergic neurons, exhibited an AHP and spike frequency adaptation. The corresponding I(AHP) was sensitive to antagonism by CdCl2 (200 microM), apamin (0.3-1 microM), and dequalinium (3 microM). The beta-adrenergic receptor agonist isoproterenol inhibited the I(AHP) in a dose-dependent, timolol-sensitive fashion. In addition, the alpha1-adrenergic receptor agonist methoxamine dose dependently inhibited the I(AHP) in a prazosin-sensitive manner and increased neuronal firing rate. Twenty-four-hour pretreatment with estradiol benzoate (EB; 25 microg, s.c.) markedly potentiated the inhibitory effect of methoxamine on the I(AHP), whereas that for isoproterenol was unaffected. Similarly, bath application of 17beta-estradiol (100 nM; 15-20 min) mimicked the effect of EB on the methoxamine-induced inhibition of the I(AHP). Thus, POA GABAergic neurons express an apamin-sensitive channel that mediates, at least in part, the I(AHP), and tempers the excitability of these cells. Furthermore, these studies demonstrate that estrogen enhances the alpha1-adrenergic receptor-mediated inhibition of this current.

Animals↗
PubMed1999

[Comparison of sensitivity of artesunate-sensitive and artesunate-resistant Plasmodium falciparum to chloroquine and amodiaquine].

AIM: To explore the in vitro sensitivity of artesunate-sensitive and -resistant Plasmodium falciparum to chloroquine and amodiaquine and to observe the effect of artesunate combined with chloroquine and artesunate combined with amodiaquine on artesunate-resistant P. falciparum. METHODS: The sensitivity of the artesunate-sensitive and -resistant P. falciparum to chloroquine and amodiaquine and their combination with artesunate was compared by using Rieckmann's in vitro micro-technique. RESULTS: The ID50 and ID95 values of chloroquine, amodiaquine and artesunete were 90.9, 50.9, 9.6 nmol/L and 320.0, 320.0, 40.0 nmol/L to the artesunate-sensitive P. falciparum respectively and were 112.0, 133.5, 85.1 nmol/L and 320.0, 320.0, 400.0 nmol/L to artesunate-resistant P. falciparum, respectively. When artesunate was combined with chloroquine, the ID50 values of the 2 drugs were 3.2 and 20.0 nmol/L to the artesunate-resistant P. falciparum. When artesunate was combined with amodiaquine, the ID95 values of the 2 drugs were 3.2 and 5.0 nmol/L to the artesunate-resistant P. falciparum, respectively. CONCLUSION: The artesunate-resistant P. falciparum has no cross resistance to chloroquine and amodiaquine, however, artesunate combined with chloroquine or amodiaquine exhibit an apparent synergistic effect in vitro.

Amodiaquine↗
PubMed1989

Dendritic cells and T cells transfer sensitization for delayed-type hypersensitivity after skin painting with contact sensitizer.

The cells involved in the development of delayed-type hypersensitivity (DTH) to the contact sensitizer fluorescein isothiocyanate (FITC) were examined. Cells used for transferring sensitization were obtained from donor mice up to 5 days following skin painting with FITC. Recipient mice were sensitized by footpad injections of dendritic cells (DC) obtained from donor lymph nodes up to 3 days following skin painting, when DC expressed high levels of antigen. DTH, assessed by ear swelling 24 hr following ear challenge with FITC, was detected when recipient mice were challenged 5 days after transfer of DC, but not when ear challenged immediately after transfer. Removal of donor DC using the cytotoxic antibody 33D1, plus complement, either from the DC-enriched population or from whole lymph node cells 24 hr after skin painting, abolished the capacity to transfer DTH. Purified T lymphocytes obtained from donor mice between Days 3 and 5 after skin painting, transferred DTH when recipients were ear challenged with FITC 5 days after footpad injections. DTH also occurred in mice ear challenged with antigen immediately after receiving footpad injections of either normal or irradiated T cells obtained from donors 4 days after skin painting. B cells and macrophages did not transfer sensitization for DTH throughout the time-course. Therefore an early stage in the immune response, where antigen-bearing DC initiated DTH, was distinguished from a later stage, where T cells transferred sensitization.

Adjuvants, Immunologic↗
PubMedDate not supplied

[Methiothepin-sensitive serotonin receptors are involved in postsynaptic mechanism of sensitization of Helix lucorum escape reaction].

Tetanic electric stimulation of Helix foot evokes sensitization of escape reaction. This behavioral sensitization and posttetanic potentiation (PTP) of acetylcholine-induced inward current (ACh-current) in command Helix neurons of escape behavior were similar. Antagonist of serotonin receptors methiothepin prevents the PTP of the ACh-current and behavioral sensitization. Serotonin disrupts the PTP of the ACh-current. It is suggested that the increase in cholinosensitivity of the command neurons with the involvement of methiothepin-sensitive serotonin receptors may be the cellular postsynaptic mechanism of behavioral sensitization of Helix escape reaction.

Acetylcholine↗
PubMed1990

Insulin sensitivity in newly detected hypertensive patients: influence of captopril and other antihypertensive agents on insulin sensitivity and related biological parameters.

In a recent study in which metabolic characteristics of newly detected obese and nonobese hypertensive subjects were compared with those of normotensive subjects, insulin sensitivity was decreased, fasting insulin values and insulin values after an intravenous glucose tolerance test (IVGTT) were increased, and fasting and IVGTT glucose values were increased in both hypertensive groups. Furthermore, adverse alterations in lipid profile variables were found in the hypertensive groups when compared with the normotensive group. The effects of various antihypertensive agents on these metabolic variables have been assessed in prospective trials. Treatment with the beta 1-selective blocking agents metoprolol and atenolol was associated with decreased insulin sensitivity and increased fasting values of insulin and glucose. There were also indications of a suppressive effect on insulin secretion during IVGTT, as well as an increase in serum triglycerides and a decrease in serum high-density lipoprotein cholesterol. Hydrochlorothiazide treatment was associated with a decrease in insulin sensitivity and an increase in blood glucose concentrations. In addition, hydrochlorothiazide increased total cholesterol, particularly the low-density lipoprotein fraction. The calcium channel blocker diltiazem did not appear to produce any negative metabolic effects. Treatment with the angiotensin converting enzyme inhibitor captopril resulted in increased insulin sensitivity with no adverse effects on lipids. All of the agents reduced blood pressure to a similar degree. These findings, and those of other studies, suggest that captopril and diltiazem offer advantages over the other agents with regard to effects on risk factors for coronary artery disease other than hypertension. Unlike diltiazem, captopril improves insulin sensitivity and this may prove to be important.

Antihypertensive Agents↗
PubMed1990

Repeated amphetamine and fencamfamine: sensitization and reciprocal cross-sensitization.

The repeated administration of amphetamine and related dopamine agonists results in an augmented or sensitized behavioral response to subsequent administration of these drugs. In addition to reflecting central nervous system plasticity, this altered response profile may also represent an animal model for stimulant-induced psychosis in humans. Therefore, considerable interest has been focused on determining the mechanisms underlying the sensitization process. One approach involves comparing and contrasting the effects of various stimulants possessing different molecular mechanisms of action. In this regard, some evidence suggests that fencamfamine and amphetamine interact with pharmacologically distinguishable dopamine pools. Therefore, we compared the behavioral response profiles to the repeated administration of behaviorally comparable doses of amphetamine and fencamfamine, and examined the pattern of cross-interaction between the two stimulants. Fencamfamine produced an amphetamine-like pattern of behavioral augmentation, and both drugs exhibited identical patterns of cross-sensitization. These results lend further support to the sensitization model of stimulant psychosis. Possible dopaminergic mechanisms underlying the sensitization are discussed.

Amphetamine↗
PubMed1988

[Specific and nonspecific tuberculin sensitivity in school children in East Germany. East German draft report of a multinational epidemiologic study of the prevalence of specific and nonspecific tuberculin sensitivity in Europe].

By means of dual-testing with tuberculin (2 TU PPD RT 23 and 2 TE PPD Dessau) and sensitin Scrophulaceum (5 TU PPD scroph.) evidence and degree of specific and non-specific tuberculin sensitivity in schoolchildren aged 7-14 years was examined under the conditions of preceding BCG-vaccination as newborns in the counties of Cottbus, Erfurt and Neubrandenburg. In a cohort of 2,792 children sensitivity to tuberculin was found in 5.98% considering positive reactions with greater than or equal to 6 mm induration and in 1.50% considering reactions with greater than or equal to 10 mm only. Reactions with induration of 6 mm and more comprehend remaining allergy caused by BCG while the limit greater than or equal to 10 mm seems to be suitable to define tuberculosis infection prevalence. Tuberculin sensitivity shows frequencies corresponding with the epidemiology of tuberculosis. Sensitivity to PPD scroph. increases from north to south with significant difference between the counties of Neubrandenburg and Erfurt. Nonspecific tuberculin sensitivity is partly prevalent in the counties of Cottbus and Erfurt.

Child↗
PubMed1979

The production of contact sensitivity by the injection into the footpads of recipients of the lymph node cells from mice 1 day after painting the skin with contact sensitizing agent: requirement for matching at the major histocompatibility complex between donor and recipient mice.

Donor mice were painted on the skin of the abdomen with the contact sensitizing agent, oxazolone. One day later 2-5 x 10(6) cells from the regional lymph nodes were injected into the footpads of recipient mice. Contact sensitivity was detected 6 days later by challenging the ears of the recipients and measuring the increase of thickness at 24 h. Good contact sensitivity was obtained when CBA cells were injected into CBA mice and BALB/c cells injected into BALB/c mice; the injection of BALB/c (H-2d) cells into CBA (H-2k) mice and vice versa failed to give rise to contact sensitivity. Hybrid F1 cells gave intermediate responses. The contact sensitivity caused by the injection of small numbers of lymph node cells into the footpad is interpreted as a mode of active immunization and the present results show that this only occurs when there is genetic matching at the major histocompatibility complex between the donor and the recipient mouse.

Animals↗
PubMed1983

Changes in phage-sensitivity of Shigella flexneri strains. II. The F-like character of Ms2-sensitive variants.

Variants sensitive to male specific phage Ms2 appeared among Ms2 non-sensitive Shigella flexneri cultures in the course of liquid medium passages. Sensitivity to Ms2 was lost on acridine orange treatment and was transferable into Ms2 non-sensitive variants. The Ms2 sensitive variants had fimbrial antigen. Electron microscopy showed that Ms2 phages were adsorbed on the F-like fimbriae of these variants. It was assumed that F-like plasmids determining F-like fimbrial antigen were carried by these variants.

Adsorption↗