Occurrence Of Sensitization Research Articles

POTASSIUM NITRATE REDUCES SENSITIVITY DURING AND AFTER IN-OFFICE BLEACHING: A TRIPLE BLIND, RANDOMIZED CLINICAL TRIAL

This study aimed to assess the effect of using potassium nitrate in gel and dentifrice for reducing sensitivity during and after bleaching. Seventy-five patients were randomly divided into three groups according to treatment: Previous placebo gel + Colgate Total 12™ (PL + CT); Previous placebo gel + Sensodyne™ (PL + SD); Previous 5% potassium nitrate gel + Colgate Total 12™ (NT). Tooth sensitivity was registered in a verbal scale and a Visual Analogue Scale at the 40th minute, immediately after removing the bleaching gel, and 24 hours after each session. The descriptive analysis of color was performed and Cochran's Q test was applied for the comparative analysis of sensitivity. The Kruskal-Wallis test, Dunn's post-test, and Friedman's ANOVA were used for sensitivity intensity. The intergroup assessment showed that in PL + CT, the occurrence of sensitivity was significantly higher than in PL + SD and NT (p < 0.05). The assessment 24 hours after the second session showed that patients from PL + SD reported less sensitivity (40.0%) than NT (64.0%) and PL + CT (96.0%). As for color, all groups succeeded after 14 days. It can be concluded that the use of potassium nitrate in both presentations reduces tooth sensitivity.

Patch test results to the Spanish baseline patch test series according to age groups: A multicentric prospective study from 2019 to 2023.

Patch test results may be influenced by age-related factors. However, there is still discordant evidence between age and patch test results. We aim to evaluate the patch test results reflecting skin sensitisation, their relevance and association with clinical features by age group. Prospective multicentric study of all patients patch tested with the Spanish baseline series in participating centres. Age groups were pre-defined as children (0- to 11-years), adolescents (12- to 18-years), young adults (19- to 30-years), middle-aged adults (31- to 65-years) and older adults (≥66-years). Occurrence of sensitisation, relevance and clinical features were compared by age group. Factors associated with skin sensitisation were investigated with multivariate logistic regression. A total of 13 368 patients were patch-tested. Differences in positive patch test results and relevance by age were detected with the highest proportion in middle-aged adults. Age-related trend differences were found for nickel, potassium dichromate, caines, colophony, Myroxylon pereirae resin, 2-hydroxyethyl methacrylate and limonene hydroperoxide. The multivariate logistic analysis (adjusted for sex, atopic dermatitis, body location and occupational dermatitis) showed an association between the age group of 31-65 (OR: 1.41, 95% CI: 1.26-1.58) and above 66-years (OR: 1.15, 95% CI: 1.01-1.32) with a higher proportion of positive results, compared with young adults. Positive patch test results vary according to age, with the highest occurrence in middle-aged adults. Most haptens did not present age-related differences, reinforcing the use of baseline series regardless of age.

Effect of Post-Weld Heat Treatment on Microstructure and Hardness Evolution of Functionally Graded Materials Produced by Direct Energy Deposition

In this work, the effects of post weld heat treatment (PWHT) on the microstructure and mechanical properties of functionally gradient materials (FGM) was investigated. The FGM consisted of five different layers which were mixtures of austenitic stainless steel (type 316L) and ferritic steel (LAS). The ratio of type 316L and LAS powder in each deposition layer was 100:0, 75:25, 50:50, 25:75, and 0:100. FGM samples were successfully fabricated without cracks or delamination by a direct energy deposition process. The sensitization phenomenon of the FGM samples was investigated after PWHT. The PWHTs were conducted at 700<sup>o</sup>C, 900<sup>o</sup>C, and 1100<sup>o</sup>C for 4 hours and the samples were then air-cooled. After PWHT, the annealed specimens were observed by optical and scanning electron microscopy to analyze their microstructure. The occurrence of sensitization was found in the specimen annealed at 700<sup>o</sup>C. The contents of Cr and C increased substantially along grain boundaries. However, the sensitization did not occur in other samples annealed at 900<sup>o</sup>C and 1100<sup>o</sup>C. In the C and D layers of the 1100<sup>o</sup>C annealed sample, micro-hardness was measured to be very high due to the formation of bainitic ferrite and a lath martensite structure. In addition, a reduction of the austenite fraction was confirmed by Electron Back Scatter Diffraction.

Corrosion analysis of post-heat treatment and post-weld SS316 with electrokinetic reactivation and cyclic polarization method

Austenitic stainless steel 316 has very high mechanical properties and corrosion resistance. This type of steel is widely used both in the nuclear and non-nuclear industries. In the nuclear industry, SS316 is used as a cladding material for uranium fuel due to its good corrosion and mechanical properties, and also low neutron absorption cross-section. In the Center for Nuclear Fuel Technology (PTBBN BATAN), it is used as material for the container of nuclear waste that is to be stored on Temporary Storage Installation of Spent Fuel (KHIPSB3 BATAN). SS316 is used as material for can to contain high-activity solid waste from the testing activity in Radiometallurgy Installation (IRM BATAN). The lid of the container is sealed with the GTAW welding process in order to tightly contain the solid waste. The main problem with the heat treatment and welding process of austenitic stainless steel is the occurrence of sensitization in a temperature range of 500-800°C. Therefore fully electrochemical analysis of SS316 stainless steel in various mediums has been conducted. SS 316 specimen was heat-treated to simulate the heat generated by the welding process. Sensitization analysis was conducted with qualitative and quantitative methods by EIS and EPR, and pitting corrosion resistance was by cyclic polarization method. The solution used for EIS and cyclic polarization test was 0 − 3.5% concentration of NaCl, and for EPR test was a mixture of H2SO4 and KSCN. Material characterization before and after corrosion testing was microstructure examination. The result of the corrosion test showed that heat treatment on the temperature range of 500-800°C caused sensitization. The corrosion test curve result showed that a heat treatment temperature of 650°C for 1 hour had the highest activation current. The lowest Rp value for SS316 specimen post heat treatment in 675°C was 69.410 ohm. The welded SS316 specimen had a higher corrosion current than that of the unwelded specimen. The microstructure of the welded specimen showed that there was intergranular corrosion particularly in the HAZ region. The effect of NaCl concentration on the cyclic polarization test showed that the higher the NaCl concentration, the more easily the pitting corrosion. The indication of pitting corrosion occurrence was evaluated by considering the Epit and Erp values. The lower Epit value meant that pitting corrosion was more easily to occur.

Microstructure and property evolutions of a novel Super304H steel during high temperature creeping

ABSTRACTHigh-temperature creep tests of a novel Super304H steel under 650 °C/195 MPa were conducted and the evolutions of microstructure and property with creep time of the material were investigated by using optical microscope, scanning electron microscope, micro Vickers hardness tester and electrochemical workstation. The results show that M23C6 carbides precipitated along grain boundaries of austenite matrix in a chain distribution and then got coarsened with the increase of creep time. Creep cavities started to form near the surface when the steel was crept for 2500 h. Afterward creep cavities increased, developed, interconnected and finally formed micro cracks along grain boundaries till fracture at the time of 4578 h. The hardness of the steel increased dramatically at the early stage of creeping and reached a high level at 500 h, and then kept a stable state at the succedent stage till fracture. Intergranular corrosion susceptibility of the steel increased first and then declined gradually, indicating the occurrence of sensitization – desensitization process of the steel during creeping.

A novel in vitro analog expressing learning-induced cellular correlates in distinct neural circuits.

When presented with noxious stimuli, Aplysia exhibits concurrent sensitization of defensive responses, such as the tail-induced siphon withdrawal reflex (TSWR) and suppression of feeding. At the cellular level, sensitization of the TSWR is accompanied by an increase in the excitability of the tail sensory neurons (TSNs) that elicit the reflex, whereas feeding suppression is accompanied by decreased excitability of B51, a decision-making neuron in the feeding neural circuit. The goal of this study was to develop an in vitro analog coexpressing the above cellular correlates. We used a reduced preparation consisting of buccal, cerebral, and pleural-pedal ganglia, which contain the neural circuits controlling feeding and the TSWR, respectively. Sensitizing stimuli were delivered in vitro by electrical stimulation of afferent nerves. When trained with sensitizing stimuli, the in vitro analog expressed concomitant increased excitability in TSNs and decreased excitability in B51, which are consistent with the occurrence of sensitization and feeding suppression induced by in vivo training. This in vitro analog expressed both short-term (15 min) and long-term (24 h) excitability changes in TSNs and B51, depending on the amount of training administered. Finally, in vitro application of serotonin increased TSN excitability without altering B51 excitability, mirroring the in vivo application of the monoamine that induces sensitization, but not feeding suppression.

The amphetamine-associated context exerts a stronger motivational effect in low-anxiety rats than in high-anxiety rats

This study used the conditioned place preference test to explore the effects of subchronic amphetamine administration on drug-associated cues in rats with different emotional reactivity. We also examined the changes in markers of dopaminergic activity in brain regions in response to the amphetamine-paired context, after a withdrawal period preceded by subchronic amphetamine treatment. We used low-anxiety (LR) and high-anxiety (HR) rats, which are known to exhibit distinct levels of susceptibility to amphetamine. Compared to HR rats, LR rats spent significantly more time in the amphetamine-paired compartment after the withdrawal period preceded by subchronic amphetamine treatment. Compared to HR control rats, LR control rats showed higher expression of the D1 receptor in the nucleus accumbens core (NAC core) and basolateral amygdala and higher expression of the D2 receptor in the NAC core. After the amphetamine treatment and withdrawal period, the LR rats showed higher D1 receptor expression in the NAC core, an increased level of homovanilic acid (HVA) in the prefrontal cortex, the NAC and the central amygdala than HR rats, as well as lower D2 receptor expression in the NAC core and the amygdala than LR control rats.These results indicate that the differences in the activity of the dopaminergic mesolimbic system in the HR and LR rats are maintained and even enhanced after a multi-day break in the use of the drug, indicating the occurrence of sensitisation. These findings show that the innate reactivity of the limbic dopaminergic innervations, dependent on the level of emotional reactivity, may significantly and chronically modify the development and maintenance of sensitisation to amphetamine.

Failure Analysis of a Reactor in Ethylbenzene Unit

In this study, failure of the cone of a reactor in an ethylbenzene unit of a petrochemical complex has been investigated. The material of the cone was found to be ASME A240 Type 304H which was severely corroded at elevated temperature. The study of the microstructure of the material showed the occurrence of carburization which led to sensitization and resulted in corrosion of the material. The result of the microhardness testing and double-loop electrochemical polarization investigation proved the diffusion of carbon through the material and occurrence of sensitization.

Sensitization Of Aisi 409 Ferritic Stainless Steel During Low Heat Input Arc Welding

The occurrence of sensitization during continuous cooling after welding was investigated for titanium-stabilized AISI 409 ferritic stainless steel. Due to its relatively high titanium content, type 409 is generally believed to be resistant to sensitization during welding, requiring exposure to a temperature within the chromium carbide precipitation range after welding to induce knifeline attack. This investigation studied the effect of welding at low heat input levels (up to 1.25 kJ/mm) on the occurrence of sensitization and intergranular corrosion in this steel, and examined whether sensitization could be induced during continuous cooling after welding. It was shown that titanium stabilization does not prevent sensitization during low heat input welding in type 409. The high temperatures experienced by the high temperature heat-affected zone adjacent to the fusion line promote the partial dissolution of titanium carbides during the weld thermal cycle, and the high cooling rates associated with low heat input welding suppress re-precipitation during cooling through the high temperature portion of the cooling cycle. At lower temperatures chromium-rich M23C6 precipitates nucleate at the ferrite grain boundaries, resulting in sensitization.

Application of uncooled microbolometer detector arrays for recording radiation of the terahertz spectral range

The mechanism of occurrence of sensitivity of microbolometer detector arrays based on vanadium oxide to terahertz radiation are analyzed. Experimental data are given showing the possibility of increasing the sensitivity of microbolometer detectors in the terahertz range by using an additional thin metal absorbing layer applied on the microbolometer membrane. A polarization dependence of the sensitivity of microbolometers in the terahertz and far infrared spectral ranges is found. It is shown that the sensitivity of microbolometers in the terahertz range is due to the absorption of radiation in the narrow metal runs placed on the support legs of the microbolometers and playing the role of an ohmic contact between the heat-sensitive layer and the processing curcuit.

Mapping a dominant negative mutation for triforine sensitivity in lettuce and its use as a selectable marker for detecting hybrids

Some lettuce cultivars are highly sensitive to triforine, an inhibitor of sterol biosynthesis found in some commercial systemic fungicides. First symptoms of a sensitive reaction are usually observed within 24–48 h after treatment and include severe wilting, necrosis and rapid plant death. We mapped a single dominant gene (Tr) that confers sensitivity of lettuce to triforine to linkage group 1 of the integrated genetic map of lettuce. The occurrence of sensitivity is not uniform across horticultural types of lettuce. While over 80% of green-romaine lettuce cultivars tested were sensitive, most cultivars of all other lettuce types were insensitive to triforine. All accessions of wild Lactuca spp. were insensitive to triforine. Allelism tests using F1 and F2 progeny revealed that sensitive cultivars of all horticultural types likely carry the same Tr gene. The dominant allele for sensitivity found in cultivated lettuce probably had a monophyletic origin. The reaction to triforine can be used as a marker for detecting hybrids originating from a cross between phenotypically similar parents with different responses to triforine treatment. It also provides an indication of genotypes for which applications of triforine-containing fungicides are inappropriate.

The influence of stabilization with TITANIUM on the HEAT-AFFECTED ZONE SENSITIZATION of 11 to 12% chromium ferritic stainless steels under low heat input welding conditions

The occurrence of sensitization during continuous cooling after welding was investigated for two low chromium ferritic stainless steels: a non-stabilized steel conforming in composition to EN 1.4003, and a corresponding grade stabilized with titanium to increase its sensitization resistance. These steels transform partially to austenite in the high temperature heat-affected zone (HTHAZ) adjacent to the fusion line during cooling, with the austenite subsequently transforming to martensite below the Ms temperature. In the non-stabilized condition these alloys are known to sensitize during continuous cooling after welding at low heat inputs levels (below approximately 0.5 kJ/mm). The rapid cooling rates associated with low heat input welds suppress austenite nucleation in the HTHAZ, resulting in almost fully ferritic microstructures. Chromium-rich carbides precipitate at the continuous ferrite-ferrite grain boundaries, resulting in chromium depletion. Slower cooling rates promote the formation of more austenite in the HTHAZ during cooling. The austenite absorbs excess carbon, preventing supersaturation of the ferrite and inhibiting carbide precipitation. Titanium stabilization does not prevent sensitization during low heat input welding, and may even be detrimental. The high temperatures experienced by the HTHAZ promote the dissolution of titanium carbides, and the titanium is retained in solid solution due to fast cooling. At lower temperatures chromium-rich M23C6 precipitates nucleate at the ferrite-ferrite grain boundaries, resulting in sensitization. The titanium in solid solution acts as a strong ferrite-former, increasing the ferrite content in the HTHAZ. The non-stabilized 1.4003 steel contained considerably more grain boundary martensite in the HTHAZ after low heat input welding than the titanium-stabilized grade, despite having very similar Kaltenhauser ferrite factors. The presence of grain boundary martensite in the non-stabilized grade increased the resistance to sensitization under low heat input conditions.

Intergranular stress corrosion cracking of acoustic-filter hooks used in car

Some acoustic-filter hooks used in car fractured in service. The failure mechanism of the hooks is intergranular stress corrosion cracking. The necessary conditions (susceptible composition of the hook materials; presence of chloride in service environment; presence of residual tensile stress and occurrence of sensitization in the fracture region) caused intergranular stress corrosion mechanism. Non-qualified chemical composition of the hooks (much higher carbon content than the specified of AISI 304 stainless steel) is mainly responsible for the failure of the hooks, which is a key inherent factor.

THE EFFECT OF IRRADIATION ON ENAMEL MICRO-STRUCTURE CHANGES

Radiotherapy plays an important role in the management of head and neck carcinoma therapy. The radiation dose ranges from 40 – 70 Gy, depends on the severity and location of the malignancy. Many patients experience an increased dental caries or sensitivity occurrence following radiotherapy. The objective of this study is to analyze the enamel micro-structure changes after irradiation. Nine polished enamel slabs were prepared from impacted 3rd molars. The slabs were flushed in non-ionic distilled water and dried by using air spray and divided into 3 groups, the control, 20 Gy and 40 Gy irradiation group. Irradiations were performed from Co60 using Gammacell-220E, with duration variables to produce the irradiation doses of 20 and 40 Gy. Philips pW370-XRD was used to examine specimen microstructure changes after irradiation. 1-way ANOVA was used for statistics analysis. It was revealed that grain size after 40 Gy irradiation was 66.29±2.7 nm, and after 20 Gy was 51.64±15.8 whilst 43.95±11.1 nm for the control group. The micro-stain deviation of the 40 Gy group was 0.594±0.15 N/m, and 0.45±2.6 N/m for the 20 Gy group, and 0.378±0.27 N/m for control group. Statistic analysis showed significant grain size differences between 40 Gy compared to both 20 Gy and control groups, but not between 20 Gy compared to the control group. Similarly, there were micro-stain differences between 40 Gy compared to 20 Gy and control groups, but not between 20 Gy compared to control group. It was concluded that irradiation with 40 Gy caused elevation of the enamel microstrain and apaite grainsize. Elevation of the enamel microstrain could lead to enamel crack and gave hypersensitive sensation.

Relapse to drug and alcohol use: a matter of sensitization.

Repeated exposure of rats to cocaine, amphetamine, opiates, nicotine and alcohol causes a very long-lasting (months) increase in the behavioral effects of these addictive drugs and drug-associated environmental stimuli (sensitization). This hypersensitivity is associated with persistent changes in the reactivity of neurons of the motivational (mesocorticolim-bic) system in the brain. Using an animal model for relapse, recent studies in our laboratory show that relapse to drug-seeking behavior (following extinction of intravenous cocaine or heroin self-administration) depends on the occurrence of sensitization. Accordingly, sensitization and conditioning seem to be more important for the persistence of drug and alcohol addiction then the occurrence of withdrawal phenomena. Biochemical research on the molecular and cellular basis of behavioral sensitization and behavioral studies on readjustment of stimulus responsiveness in rats, is of great importance for the development of an adequate pharmacotherapy of addiction.

P-242 - Occurrence of sensitization to methamphetamine-induced disorganization of locomotor activity rhythm in rats

P-242 - Occurrence of sensitization to methamphetamine-induced disorganization of locomotor activity rhythm in rats

Sensitization of meningeal sensory neurons and the origin of headaches.

The headaches that accompany certain intracranial pathologies (such as meningitis, subarachnoid haemorrhage and tumour) have been considered to result from mechanical or chemical stimulation of pain-sensitive structures of the intracranial meninges. Although the recurrent headache of migraine is of unknown origin and is not accompanied by an identifiable pathology, it shares with intracranial headaches features that suggest an exaggerated intracranial mechanosensitivity (worsening of the pain by coughing, breath-holding or sudden head movement). One possible basis for such symptoms would be a sensitization of meningeal afferents to mechanical stimuli. Previous studies of neuronal responses to meningeal stimulation have focused primarily on cells in the central portion of the trigeminal pathway, and have not investigated the possible occurrence of sensitization. We have recorded the activity of primary afferent neurons in the rat trigeminal ganglion that innervate the dural venous sinuses. Chemical stimulation of their dural receptive fields with inflammatory mediators both directly excited the neurons and enhanced their mechanical sensitivity, such that they were strongly activated by mechanical stimuli that initially had evoked little or no response. These properties of meningeal afferents (chemosensitivity and sensitization) may contribute to the intracranial mechanical hypersensitivity that is characteristic of some types of clinically occurring headaches, and may also contribute to the throbbing pain of migraine.

Combined effects of strain and grain size on carbide precipitation and sensitization in 304 stainless steel

The dramatic effects of uniaxial strain on sensitization in austenitic stainless steels is now well documented. Many parameters influence the occurrence of sensitization and the degree of sensitization (DOS) is thus a function of microstructural characteristics (which of course includes the grain size) and chemical composition, including the carbon content (which is the most critical compositional element controlling sensitization). However, there have been no studies evaluating simultaneous effects of deformation (strain) and grain size on sensitization development. A study of two grain sizes and carbon content variations by Pascali, et al found that desensitization was delayed at the larger grain size (68 [mu]m) in comparison to the smaller grain size (17[mu]m), especially at aging temperatures near 600 C. In this study the authors present some preliminary results of the combined effect of grain size and uniaxial strain on sensitization (DOS) in 304 stainless steel.

Possible involvement of supersensitivity in cerebral β-adrenergic and dopaminergic receptors in the occurrence of sensitization to d-methamphetamine in mice

Behavioral sensitization of mice (male STD-ddy) to d-methamphetamine (MAP) and its correlation with the neurochemical alterations in cerebral catecholaminergic systems were investigated following the repeated administration of MAP (5 mg/kg, i.p. x 2/day, 5 days). MAP-pretreated mice showed an enhancement in MAP-stimulated locomotor activity following the readministration of MAP (0.625 mg/kg). The metabolic turnovers of cerebral norepinephrine (NE) and dopamine (DA) showed a significant decrease in these sensitized mice. The activities of tyrosine hydroxylase. DOPA decarboxylase, monoamine oxidase and catechol-O-methyltransferase, however, showed no change under the same experimental conditions. On the other hand, the repeated MAP pretreatment induced the enhancement of the specific bindings of [(3)H]dihydroalprenolol and [(3)H]spiperone to cerebral synaptic membrane, which resulted from the increase of B(max) values. Furthermore, pretreatments of mice with propranolol (10 mg/kg) and haloperidol (0.1 mg/kg) inhibited the development of behavioral sensitization to MAP. These results suggest that the supersensitivity in cerebral ?-adrenergic and dopaminergic receptors may be involved in behavioral sensitization to MAP.

Sensitivity to epoxy resins and triethylenetetramine

The present studies concerned 31 work sites in eight factories at which 422 persons were employed. In the course of seven years there were 126 cases of dermatitis, 99 of whom were patch-tested. Positive reactions to epoxy resin and/or to triethylenetetramine were found in 65.7% of the subjects. The aetiology of the other cases is discussed. Some of the patients who were positive to epoxy resin were tested with Bisphenol A and modified resins with blocked epoxy groups. The latency period of dermatitis and the localization were recorded, as well as the influence of the season and of certain working conditions on the occurrence of sensitization. Of the 80 patients who changed their occupation, there were relapses in 50 within one year. Relapses were more frequent in persons who continued to work with epoxy resins for more than three months after the appearance of dermatitis and in those simultaneously sensitive to allergens in the standard series.