Dexamethasone inhibits the pyrogenic activity of prostaglandin F2 alpha, but not prostaglandin E2

The effect of dexamethasone on prostaglandin (PG) E2- and PGF2 alpha-induced fever was studied in rats. Intracerebroventricular injection of PGE2 and PGF2 alpha (500 ng) induced increases in body temperature (maximal temperature rises of 0.97 +/- 0.13 degrees C and 0.78 +/- 0.18 degrees C, respectively, vs. vehicle 0.12 +/- 0.09 degrees C) of unrestrained rats maintained within the thermoneutral zone. PGE2-induced fever peaked earlier and the defervescence was faster when compared to the response induced by PGF2 alpha. Subcutaneous pre-administration of dexamethasone (0.5 mg/kg) did not affect PGE2-induced fever (maximal temperature rise of 1.00 +/- 0.08 degrees C), but completely prevented the pyrogenic activity of PGF2 alpha (maximal temperature rise of 0.16 +/- 0.16 degrees C). Neither PGE2- nor PGF2 alpha-induced fever was significantly altered (maximal temperature rises of 0.90 +/- 0.11 degrees C and 0.64 +/- 0.14 degrees C, respectively) by intraperitoneal administration of indomethacin (2 mg/kg). These results demonstrate for the first time that glucocorticoids, in addition to inhibiting endotoxin- and cytokine-induced fever, can also modulate the pyrogenic activity of some prostaglandins, possibly via suppression of the synthesis of corticotropin-releasing factor, indicating that multiple mechanisms may be involved in the antipyretic activity of these steroids.     

Interleukin-1beta and the interleukin-1 receptor antagonist act in the striatum to modify excitotoxic brain damage in the rat

The cytokine interleukin-1 (IL-1) has been implicated in ischaemic, traumatic and excitotoxic brain damage. The results presented here reveal novel actions of IL-1 in the striatum which markedly exacerbate cortical neuronal damage elicited by local excitotoxins in the striatum or cortex. Intrastriatal infusion of IL-1 receptor antagonist, IL-1ra, markedly inhibited striatal neuronal damage caused by N-methyl-D-aspartate (NMDA) or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor activation in the rat. In contrast, intracortical infusion of IL-1ra failed to inhibit NMDA or AMPA receptor-induced damage in the cortex. Intrastriatal co-infusion of IL-1 with the NMDA or AMPA receptor agonist did not affect local striatal damage induced by activation of either glutamate receptor subtype, but caused extensive cortical damage when administered into the striatum with AMPA. This secondary damage was significantly reduced by pretreatment with the NMDA receptor antagonist (MK-801), which did not affect local (striatal) damage caused by AMPA. Infusion of IL-1beta into the striatum (but not the cortex) markedly enhanced cortical damage caused by infusion of an NMDA or AMPA receptor agonist into the cortex. These data reveal selective actions of IL-1 and IL-1ra in the striatum, which influence cortical neuronal loss and suggest that IL-1 selectively enhances damage caused by AMPA receptor activation.     

Transient field produced by a traveling-wave wire antenna

The electromagnetic fields of a transient traveling wave current on a straight wire segment are calculated directly in the time domain. Retarded potential theory is used to establish an impulse response valid in both far and near zones. A closed-form expression for the field due to a rectangular current pulse is obtained, and corresponding plots are given. Numerical results from this permit the investigation of the differences between near versus far zones and coated versus uncoated wires. Experimental findings for both coated and uncoated wires show good agreement with theory. A formula for far-zone radiation from an arbitrarily shaped wire is developed; results for a proposed directive antenna geometry are presented     

ICE CREAM - ITS PRESENT DAY MANUFACTURE AND SOME PROBLEMS

Ingredients used in ice cream, UK legislation, and mix processing and freezing are discussed. Problems caused by the increasing costs of some of the raw materials are mentioned and possible ways of offsetting these costs are suggested. The importance of adequate quality control, particularly microbiological, is stressed.     

Use of minimum phase signals to establish the time reference intransient radar target identification schemes

The minimum phase representation of the transient scattered field response of aircraft targets is used to establish the time origin of a measured signal in reference to a stored target library. This allows time-shift-sensitive schemes such as the E-pulse method and neural networks to be used effectively. An example in which the wavelet spectra of unknown and library target responses are correlated demonstrates the viability of the technique     

A Hallen-type integral equation for symmetric scattering from lossycircular disks

A rigorous technique is presented for calculating the current induced on a thin lossy disk by rotationally symmetric sources, and the resulting scattered field. A Hallen-type integral equation is developed for the current using the magnetic vector potential, and it is solved by the method of moments. It is shown that the diffraction lobes usually associated with radiation above a finite circular ground plane can be reduced dramatically by the addition of loss. Application to a quarter-wave monopole radiating above a finite circular perfectly conducting ground plane shows good agreement with experiment     

Determination of the natural modes for a rectangular plate[transient scattering]

A coupled surface integral equation formulation for determination of the natural frequencies of a rectangular plate is proposed. The method of moments solution to this formulation and the subsequent numerical results are presented. The natural frequencies predicted by the theory have been verified by an experiment. In comparison with the existing formulation of this problem, the present formulation predicts equally well for the first few dominant modes but better for the higher modes. Also, in the present formulation, no convergence problem has been encountered