Histamine and histamine intolerance.

Histamine intolerance results from a disequilibrium of accumulated histamine and the capacity for histamine degradation. Histamine is a biogenic amine that occurs to various degrees in many foods. In healthy persons, dietary histamine can be rapidly detoxified by amine oxidases, whereas persons with low amine oxidase activity are at risk of histamine toxicity. Diamine oxidase (DAO) is the main enzyme for the metabolism of ingested histamine. It has been proposed that DAO, when functioning as a secretory protein, may be responsible for scavenging extracellular histamine after mediator release. Conversely, histamine N-methyltransferase, the other important enzyme inactivating histamine, is a cytosolic protein that can convert histamine only in the intracellular space of cells. An impaired histamine degradation based on reduced DAO activity and the resulting histamine excess may cause numerous symptoms mimicking an allergic reaction. The ingestion of histamine-rich food or of alcohol or drugs that release histamine or block DAO may provoke diarrhea, headache, rhinoconjunctival symptoms, asthma, hypotension, arrhythmia, urticaria, pruritus, flushing, and other conditions in patients with histamine intolerance. Symptoms can be reduced by a histamine-free diet or be eliminated by antihistamines. However, because of the multifaceted nature of the symptoms, the existence of histamine intolerance has been underestimated, and further studies based on double-blind, placebo-controlled provocations are needed. In patients in whom the abovementioned symptoms are triggered by the corresponding substances and who have a negative diagnosis of allergy or internal disorders, histamine intolerance should be considered as an underlying pathomechanism.

In vivo monitoring of cutaneous edema using spectral imaging in the visible and near infrared.

Tissue inflammation is often accompanied by local interstitial fluid accumulation expressed as edema. Edema can be the manifestation of infection, lymphatic blockage, wound healing, or even cancer, and is typically graded visually. Here we demonstrate that the edema reaction can be objectively quantitated in vivo by the use of spectral imaging. To this end we applied the method on a histamine-induced cutaneous edema model. Apparent concentrations of oxy-hemoglobin, deoxy-hemoglobin, and water were calculated for each pixel of a spectral image stack. These values were used to construct concentration maps for each of these molecules as well as an intensity map of an optical tissue-scattering parameter. The oxy-hemoglobin and the tissue water maps are two-dimensional quantitative representations of the skin areas involved in erythema and edema, respectively. These maps demonstrated characteristics of the wheal-and-flare reaction and their gray-level intensities were dependent on the applied histamine dose. We conclude that spectral imaging can be a valuable noninvasive tool in the study of edema pathology and can be used to monitor the edema reaction in vivo or follow the efficacy of treatments in a clinical setting.

Anxiolytic-like effect of saiboku-to, an oriental herbal medicine, on histaminergics-induced anxiety in mice.

Effect of saiboku-to, an oriental herbal medicine, on anxiety in mice was investigated using a light/dark test. Anxiogenic- and anxiolytic-like effects were evaluated on the basis of shortened and prolonged time spent in the light zone of the test. Subacute administration (once a day for 7 days) of saiboku-to (0.5-2.0 g/kg, p.o.) induced anxiolytic-like effect. To assess the effect of saiboku-to on brain histaminergic system in a state of anxiety, Compound 48/80 (1.0 microg/2 microl, i.c.v.), a non-neuronal mast cell histamine releaser, or thioperamide (10.0 mg/kg, i.p.), a neuronal histamine releaser possessing the inhibitory effect of histamine H(3) autoreceptors, induced decrease in the time spent in the light zone by co-injection with cimetidine (10.0 microg/2 microl, i.c.v.), a H(2) inhibitor, suggesting anxiety-like effect. These histaminergics-induced experimental anxieties were inhibited by pre-treatment with subacute administration of saiboku-to, as well as single treatment with diazepam. The results suggest that saiboku-to exhibits anxiolytic-like effect closely related to histaminergic system in the brain.

The influence of respiratory sounds on breathlessness in children with asthma: a symptom-perception approach.

The discordance between the objective and subjective symptoms of asthma has major effects on proper medication and management. In 2 studies the influence of respiratory sounds in the process of symptom perception underlying breathlessness was investigated in children aged 7-17 years. In Experiment 1, asthmatic wheezing sounds were recorded in 16 children during histamine-induced airway obstruction. Breathlessness correlated significantly with rank order of amount of wheezing, but not with lung function. In Experiment 2, after standardized physical exercise, 45 asthmatic and 45 nonasthmatic children were randomly assigned to (a) false feedback of wheezing, (b) quiet respiratory sounds, or (c) no sound. Asthmatic children reported significantly more breathlessness in the 1st versus the 3rd condition. In conclusion, many asthmatic children were easily influenced by wheezing in their estimation of asthma severity, reflected in breathlessness.