Allergen extracts directly mobilize and activate human eosinophils

Allergic diseases are characterized by the presence of eosinophils, which are recruited to the affected tissues by chemoattractants produced by T cells, mast cells and epithelium. Our objective was to evaluate if allergens can directly activate human eosinophils. The capacity of purified allergen extracts to elicit eosinophil chemotaxis, respiratory burst, degranulation and up-regulation of the adhesion molecule complement receptor 3 (CR3) was determined in eosinophils isolated from healthy blood donors. Eosinophils stimulated with an extract from house dust mite (HDM) released the granule protein major basic protein (MBP) and up-regulated the surface expression of CR3. Cat allergen extracts also induced the up-regulation of CR3, but not the release of MBP; instead cat, as well as birch and grass allergens, elicited the release of eosinophil peroxidase (EPO). In addition, grass pollen extract caused the secretion of MBP. None of the allergens stimulated eosinophilic cationic protein release, nor production of free oxygen radicals. Both HDM and birch extracts were chemotactic for eosinophils. These findings establish that common aeroallergens can directly activate eosinophils in vitro. We propose that eosinophil activation in vivo is not exclusively mediated by cytokines and chemokines of the allergic inflammatory reaction, but could partly be the result of direct interaction between allergens and eosinophils.     

Stromal cells direct local differentiation of regulatory dendritic cells

CD11c(hi) dendritic cells (DC) play an essential role during the initiation of cell-mediated immunity. Recently, CD11c(lo)CD45RB(hi) DC with regulatory properties have been described. However, the origins of regulatory DC are poorly understood. Here, we show that spleen-derived stromal cells promote selective development of CD11c(lo)CD45RB(+) IL-10-producing regulatory DC from lineage-negative c-kit(+) progenitor cells. These DC have the capacity to suppress T cell responses and induce IL-10-producing regulatory T cells in vitro and to induce antigen-specific tolerance in vivo. Furthermore, stromal cells from mice infected with Leishmania donovani more effectively supported differentiation of these highly potent regulatory DC. The ability of tissue stromal cells to direct the development of DC with a regulatory phenotype thus provides a new mechanism for local immune regulation.     

Measurement of global and regional left ventricular performance with isotope technique in coronary heart disease

In order to evaluate the left ventricular function in coronary artery disease, radionuclide measurements of global and regional ejection fraction (EF), regional wall motion and phase analyses of the left ventricular contraction were performed by equilibrium technique. One group of patients with angina pectoris and one group with myocardial infarction were compared with a control group. All the above-mentioned parameters significantly separated the infarction group from the reference group both at rest and during work, while the group of patients with angina pectoris showed disturbances mainly during work, such as impaired ability to increase global and regional ejection fraction and regional wall motion. Adding regional analysis and phase analysis to the global EF determination increases the possibility of studying the left ventricular function. However, this addition has a limited value in detecting impaired left ventricular function compared to the determination of just global EF in patients with angina pectoris and in patients with myocardial infarction.     

Hemodynamic effects of loud noise before and after central sympathetic nervous stimulation

The hemodynamic effects of loud noise after central alpha 2-adrenoceptor stimulation were studied in 13 patients with mild (WHO 1) essential hypertension. The patients were randomized (double-blind) to treatment with either placebo or guanfacine 1-2 mg for four weeks and then crossed over and treated for another four weeks. All patients were exposed to a loud broad-band noise (105 dBA for 30 min) and all were studied both on placebo and guanfacine. Guanfacine significantly reduced the resting blood pressure from 141/92 to 134/88 mmHg (p less than 0.01) as well as heart rate at rest from 63 to 58 beats/min (p less than 0.05). Noise stimulation caused a significant increase in blood pressure and resistance in the placebo-treated group, while cardiac output decreased significantly. Pretreatment for one month with the central alpha 2-adrenoceptor stimulating agent guanfacine did not block the noise-induced pressor response nor the increase in peripheral resistance. A significant decrease in stroke volume was observed and cardiac output also tended to decrease in this group. It could be concluded that loud noise is a potent pressor stimulus which causes vasoconstriction and that the blood pressure response during noise could not be blocked by the centrally acting antihypertensive agent guanfacine. Since noise causes vasoconstriction it also induces an increased tone in the small arteries and, if the noise stimulus is sufficiently strong and repeated for a long time, it might cause structural changes in the resistance vessels and permanent arterial hypertension in humans.     

Modulation of stretch-evoked reflexes in single motor units in human masseter muscle by experimental pain

The interaction between muscle pain and motor function of the jaw has been examined in recent years, but the nature of the modulation of the short-latency stretch reflex by pain is not fully understood. In this study, the reflex responses to stretch were measured in single low-threshold motor units that were kept discharging at a constant frequency, before, during and after the induction of experimental pain in one masseter muscle by controlled infusion of hypertonic saline. The probability of evoking a reflex response in individual motor units in the painful muscle at near-monosynaptic latency was reduced by a mean of about 20%. However, the overall reflex response in the surface electromyogram of both the ipsi- and contralateral masseter muscles was greater during pain. This was apparently a secondary response to the pain-induced increase in pre-stimulus activity in the motoneurone pools of both muscles, because increased motoneurone excitability may facilitate stretch reflexes. It is concluded that the most likely explanation for the reduced reflex response of low-threshold masseter motor units during experimental pain is a tonic reduction in the fusimotor drive to the masseter spindles.     

Electrodermal Responsivity in Young Hypotensive and Hypertensive Men

Electrodermal responses were recorded during the presentation of 16 moderately intense (1000 Hz, 90dB) tones in three groups of young men: borderline hypertensives (138/79 mmHg), normotensives (112/65 mmHg), and hypotensives (104/63 mmHg). Electrodermal response habituation was measured as a decline in response over trials, number of trials to a response criterion of three successive nonresponses, and number of inversions of response amplitude (larger responses following smaller responses) in the stimulus sequence. Habituation was fastest in hypotensives. Nonspecific electrodermal responses at rest and during tone presentations were most frequent in borderline hypertensives, least frequent in the hypotensive group, with the normotensive group falling in between. There were no significant differences in electrodermal level. The rapid habituation rate in hypotensives is discussed in terms of cursory information processing associated with impulsive behaviour. The higher nonspecific electrodermal activity in borderline hypertensives is interpreted to indicate increased sympathetic nervous system activity.     

Time-resolved X-ray diffraction studies of myosin head movements in live frog sartorius muscle during isometric and isotonic contractions

Summary Using the facilities at the Daresbury Synchrotron Radiation Source, meridional diffraction patterns of muscles at ca 8°C were recorded with a time resolution of 2 or 4 ms. In isometric contractions tetanic peak tension (P ₀) is reached in ca 400 ms. Under such conditions, following stimulation from rest, the timing of changes in the major reflections (the 38.2 nm troponin reflection, and the 21.5 and 14.34/14.58 nm myosin reflections) can be explained in terms of four types of time courses: K ₁, K ₂, K ₃ and K ₄. The onset of K ₁ occurs immediately after stimulation, but that of K ₂, K ₃ and K ₄ is delayed by a latent period of ca 16 ms. Relative to the end of their own latent periods the half-times for K ₁, K ₂, K ₃ and K ₄ are 14–16, 16, 32 and 52 ms, respectively. In half-times, K ₁, K ₂, K ₃ lead tension rise by 52, 36 and 20 ms, respectively. K ₄ parallels the time course of tension rise. From an analysis of the data we conclude that K ₁ reflects thin filament activation which involves the troponin system; K ₂ arises from an order-disorder transition during which the register between the filaments is lost; K ₃ is due to the formation of an acto-myosin complex which (at P ₀) causes 70% or more of the heads to diffract with actin-based periodicities; and K ₄ is caused by a change in the axial orientation of the myosin heads (relative to thin filament axis) which is estimated to be from 65–70° at rest to ca 90° at P ₀. Isotonic contraction experiments showed that during shortening under a load of ca 0.27 P ₀, at least 85% of the heads (relative to those forming an acto-myosin complex at P ₀) diffract with actin-based periodicities, whilst their axial orientation does not change from that at rest. During shortening under a negligible load, at most 5–10% of the heads (relative to those forming an acto-myosin complex at P ₀) diffract with actin-based periodicities, and their axial orientation also remains the same as that at rest. This suggests that in isometric contractions the change in axial orientation is not the cause of active tension production, but rather the result of it. Analysis of the data reveals that independent of load, the extent of asynchronous axial motions executed by most of the cycling heads is no more than 0.5–0.65 nm greater than at rest. To account for the diffraction data in terms of the conventional tilting head model one would have to suppose that a few of the heads, and/or a small part of their mass perform the much larger motions demanded by that model. Therefore we conclude either that the required information is not available in our patterns or that an alternative hypothesis for contraction has to be developed.     

The Use of Lysostaphin in in Vitro Assays of Phagocyte Function: Adherence to and Penetration into Granulocytes

The usefulness of lysostaphin for the removal of cell-adherent and extracellular bacteria in assays performed to measure the intracellular killing of Straphylococcus aureus by granulocytes was investigated. The results showed that the adherence of lysosiaphin to the granulocyte surface is effectuated by a temperature-independent process and that bound lysostaphin is still microbicidal. Lysosiaphin also penetrates into the granulocytes by a temperature dependent process and kills ingested S. aureus intracellularly. Therefore, despite reports to the contrary in the literature, lysosiaphin is not a reliable agent for the removal of only extracellular S. aureus and should no longer be used in assays to determine the rate of intracellular killing by granulocytes.