Dermal blood flow after local challenges with allergen, histamine, bradykinin and compound 48/80

Malathion dermal permeability in relation to dermal load: Assessment by physiologically based pharmacokinetic modeling of in vivo human data

Estimates of dermal permeability (K_p), obtained by fitting an updated human PBPK model for malathion to previously reported data on excreted urinary metabolites after 29 volunteers were dermally exposed to measured values of [¹⁴C]malathion dermal load (L), were used to examine the empirical relationship between K_p and L. The PBPK model was adapted from previously reported human biokinetic and PBPK models for malathion, fit to previously reported urinary excretion data after oral [¹⁴C]malathion intake by volunteers, and then augmented to incorporate a standard K_p approach to modeling dermal-uptake kinetics. Good to excellent PBPK-model fits were obtained to all of 29 sets of cumulative urinary metabolite-excretion data (ave. [±1 SD] R² = 0.953 [±0.064]). Contrary to the assumption that K_p and L are independent typically applied for dermally administered liquids or solutions, the 29 PBPK-based estimates of K_p obtained for malathion exhibit a strong positive association with the 2/3rds power of L (log-log Pearson correlation = 0.925, p = ∼0). Possible explanations of this observation involving physico-chemical characteristics and/or in vivo cutaneous effects of malathion are discussed. The PBPK model presented, and our observation that K_p estimates obtained by fitting this model to human experimental urinary-excretion data correlate well with L^2/3, allow more realistic assessments of absorbed and metabolized dose during or after a variety of scenarios involving actual or potential dermal or multi-route malathion exposures, including for pesticide workers or farmers who apply malathion to crops.

Hyper-releasability of mast cells in family members of infants with sudden infant death syndrome and apparent life-threatening events

BACKGROUND

An allergic reaction with increased degranulation of mast cells has been suggested as a possible mechanism in sudden infant death syndrome (SIDS).

STUDY DESIGN

Mast cell releasability was assessed in 2 study groups: A, 22 subjects, 16 first-degree relatives of infants who had had an apparent life-threatening event (ALTE) and 6 infants after ALTE and B, 46 first-degree relatives of SIDS cases. These groups were compared with 71 members of an age-matched control group. In each subject the skin wheal and flare reactions were measured after an intradermal injection of 0.02 mL of each of the following substances dissolved in phenol-saline solution: histamine 0.0001 mg/mL, histamine 0.001 mg/mL, codeine 0.5 mg/mL, codeine 1 mg/mL, compound 48/80 0.05 mg/mL, compound 48/80 0. 1 mg/mL, and phenol-saline solution. The size of wheal and flare skin reaction was assessed by computerized planimetry after the shape of the cutaneous response was copied onto a paper.

RESULTS

The wheal and flare skin reaction to each of the substances was significantly larger in the 2 study groups compared with the control group (P <.05) except for the wheal reaction to compound 48/80 0.1 mg/mL, codeine 0.5 mg/mL, and histamine in both concentrations for group A and the wheal reaction to codeine 1 mg/mL and histamine in both concentrations for group B. All individuals with increased reaction belonged to 3 (50%) of 6 families with ALTE history and to 8 (73%) of 11 families with SIDS history.

CONCLUSIONS

Increased mast cell hyper-releasability and degranulation take place in family members of some SIDS and ALTE cases and in some infants with ALTE, supporting a possible role for an immunologic mechanism in the pathophysiology of these entities.

Time course of the inflammatory response to histamine and allergen skin prick test in guinea-pigs

Plasma exudation and vasodilatation are key microvascular features of acute inflammation. Exudation and vasodilatation responses in the weal area after skin prick testing with histamine are essentially completed within 30 min. There is evidence to suggest that vasodilatation lasts considerably longer after provocation with allergen, but there is no information on the duration of plasma exudation. The purpose of this study was to measure the time course of the microvascular inflammatory response in the skin after histamine and allergen provocation. Skin prick tests were performed with histamine, allergen (ovalbumin) or saline (control) on guinea-pigs which were shaved on their backs. Radioactive 113mIn was used to label transferrin as a plasma tracer. Radioactivity was recorded from the superficial part of the skin by external detection of conversion electrons from the decay of 113mIn. The increase in count rate, corresponding to tracer accumulation by vasodilatation and/or plasma exudation, was used as a measure of the microvascular inflammatory response to skin prick test. The microvascular response was studied immediately and up to 30 min after provocation. The largest response to histamine and allergen occurred immediately after provocation. The exudative response then gradually declined to be absent after 25-30 min. Skin prick test with saline resulted in a small response of shorter duration. We conclude that the microvascular reaction to histamine as well as allergen provocation in guinea-pig skin has a rapid onset and a duration of approximately 30 min.

Evaluation of skin blood flow by laser Doppler flowmetry

Laser Doppler flowmetry is an excellent noninvasive technique for the measurement of cutaneous microcirculation. The list of applications of laser Doppler flowmetry in dermatology is long. It can be applied to monitor inflammation caused by various drugs, chemicals, and allergens related to blood flow. To measure certain inflammatory reactions a combination of other bioengineering measurements is desirable. Flaps can be monitored, and burn depth measured by laser Doppler flowmetry. Through blood flow measurement, the pathophysiology of various skin diseases can be verified and certain treatments can be partially monitored. Although it is not as directly applicable to daily clinical practice, except in a few cases, laser Doppler flowmetry is a very useful technique in various kinds of dermatologic research.

The association of individual allergen reactivity with respiratory disease in a national sample: data from the second National Health and Nutrition Examination Survey, 1976-80 (NHANES II)

The independent association of individual allergen reactivity with respiratory disease was evaluated with use of the second National Health and Nutrition Examination Survey, a sample of the U.S. white civilian population, ages 6 to 24 years (n = 4295). Eight, 1:20 wt/vol, 50% glycerol, unstandardized extracts were administered by prick puncture. Allergen reactivity was reported as the percent with a mean erythema diameter 10.5 mm or greater at 20 minutes. Only the prevalence of asthma and allergic rhinitis increased with the increasing number of positive allergen skin tests. The independent association of individual allergen reactivity with respiratory disease was quantified with logistic models that included other allergen reactivity, age, sex, smoking, and region. Asthma was associated with reactivity to house dust (odds ratio, 2.9; 95% confidence interval [CI] 1.7 to 5) and Alternaria (odds ratio, 5.1; 95% CI: 2.9 to 8.9). Allergic rhinitis was associated with reactivity to ragweed (odds ratio, 2.3; 95% CI: 1.5 to 3.3); ryegrass (odds ratio, 2.8; 95% CI: 1.8 to 4.3); house dust (odds ratio, 2.5; 95% CI: 1.6 to 3.9); Alternaria (odds ratio, 2.3; 95% CI: 1.5 to 3.4). Asthma only (without allergic rhinitis) was associated with dust and Alternaria. Allergic rhinitis only (without asthma) was associated with ryegrass, ragweed, and house dust. When both asthma and allergic rhinitis were present, only house dust and Alternaria remained associated. These findings highlight the association of specific allergens with upper and lower respiratory diseases and the interactions among coexisting respiratory diseases.