Water balance of Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) maintained by brief daily spells of elevated air humidity.

A facility was constructed to expose cultured Dermatophagoides pteronyssinus (Trouessart) to 24-h cycles of changing relative humidity; low humidity was interrupted every day by a period of high humidity. The temperature was kept at 16 degrees C, a common temperature on the ground floor of Dutch houses. Partially dehydrated mites were exposed to various humidity regimes in the absence of food and liquid water. Some mites gained weight when moist air was given for only 1.5 h every day. In the presence of food, egg production was recorded when moist air was given for at least 3 h daily, whereas the average relative humidity was quite low and less than the critical equilibrium humidity of D. pteronyssinus. Brief spells of elevated humidity allowed populations to survive much longer in a microclimate that was otherwise too dry, and may be decisive for survival during the winter months. We found that average relative humidity was misleading as an indicator of mite survival and growth conditions.

Happiness reigns in the drug marketplace.

AIDS: Drug companies have changed their tactics of marketing anti-HIV agents; they are advertising in magazines designed for the lay public, such as GQ, Esquire, and Details. Such campaigns give the impression of AIDS as a manageable disease with treatments that can be lived with. This information is very useful, but some may be hard for many people to evaluate. Increased awareness of the products is good, however, excessive brand name recognition may be a disadvantage--the choice of drugs should be made by active dialogue between the physician and the patient. On a slightly different note, The Health Connection has been warned against overplaying data on the French company Arkopharma's product SPV-30, an extract of the European boxwood tree. When the labeling for SPV-30 made claims that it changes CD4 and viral load values, the Food and Drug Administration (FDA) said that the activity changed SPV-30's status from a dietary supplement to a drug. The results from a French trial of SPV-30 are expected this summer.^ieng

[Ultrasound follow-up of experimental partial Achilles tendon rupture]. / Sonographische Verlaufskontrolle von experimentellen partiellen Achillessehnenverletzungen.

We performed surgically an experimental partial Achilles tendon dissection on 28 New Zealand white rabbits. The changes in the healing process were sonographically followed and documentated in short periods of time for 2 months. The sonographically detectable changes during the healing process underlie certain rules. The changes in sonography can be explained by the histopathology with respect to the theoretics of ultrasound physics. Hematomas and the fibrous scars can be followed closely with sonography. Sonography is a method of high value in the diagnosis of partial and complete tendon tears and with respect to certain limits in the follow-up of the healing process, too. Certain limits in the evaluation of tendon injuries and their follow-up by sonography remain.

Mattresses as a winter refuge for house-dust mite populations.

House-dust mites are a major source of allergens. Beds are often heavily infested. It is conceivable that, during the winter period in temperate climates, the ambient indoor air is too dry for their survival, but that mites can still survive in beds where the humidity is raised when the bed is occupied. To investigate whether house-dust mites can take advantage of daily episodes with elevated humidity to restore water balance, we exposed mites to spells of high humidity (90% relative humidity [RH]), lasting 0, 1.5, 3, 6, or 12 h, once every day, while the humidity was low (10% RH) during the rest of the time. Survival was markedly promoted when only 1.5 h of moist air per day was given. Three hours of moist air per day allowed the mites to reproduce. The same average humidity but at a constant level would have been lethal to the mites. Thus, average humidity can be misleading as an indicator of mite survival conditions. Measurements of relative humidity were made inside the foam core of a mattress and underneath the ticking. The rise of humidity occurring when the bed was occupied was often insufficient for the mites, because the temperature rose at the same time. At higher temperatures, mites required a higher relative humidity, abolishing the effect of the simultaneous rise in absolute humidity. Thus, it seems quite possible to regulate house-dust mite numbers also in beds by reducing the water content of the ambient air. The rules governing changes in temperature and humidity inside a bed may be simple enough to allow assessment of house-dust mite living conditions by measurements in the ambient air.

The control of house dust mites in rugs through wet cleaning.

Nine rugs from the bedrooms of seven private homes were cut into strips. Half of the strips were wet-cleaned according to a commercial procedure, and the others were kept as controls. Subsequently the cleaned and noncleaned strips were stitched together again and returned to their respective bedrooms. After 0, 1, and 3 months, parts of the strips were taken to the laboratory for tests. The tests were designed to measure the suitability of the rugs as a habitat for house dust mites. To do this, a number of house dust mites were introduced into fragments of the rugs, and the number of survivors and offspring after 4 weeks was determined. Immediately after cleaning, the habitat was markedly less suitable than before. After 1 month, the habitat suitability was partly but not totally recovered. After 3 months, no effect of cleaning could be discerned.