The presence of endotoxin activity in cases of experimentally-induced heartwater in sheep.

The presence of endotoxin was examined in 5 sheep with experimentally-induced heartwater. Two peaks in endotoxin levels were recorded in 4 out of the 5 sheep during the acute stage of the disease. The 1st peak coincided with or occurred shortly after the febrile reaction (over 40 degrees C). The 2nd peak occurred 3-5 days after the 1st, and in 2 sheep this 2nd elevation in endotoxin levels was associated with severe clinical signs (rapid and laboured breathing, cyanosis and recumbency), and 1 of the 2 sheep died on the day of the 2nd elevation. Both endotoxin peaks were of short duration and levels had decreased in the 24-h follow-up samples.

Glucocorticoid receptors in murine erythroleukaemic cells.

Glucocorticoid receptors in murine erythroleukaemic cells were studied in relation to hexamethylene bisacetamide (HMBA) induced differentiation. Specific binding of dexamethasone was measured. A single class of saturable, high affinity binding sites was demonstrated in intact cells; with cell homogenates or fractions binding was low and could not be reliably quantified. Receptor binding in whole cell suspensions was lower in cells which had been treated with HMBA (36.5 +/- 8.2 pmol/g protein) than in untreated controls (87.9 +/- 23.6 pmol/g protein); dissociation constants were similar in treated (2.7 nM) and untreated cells (2.5 nM). Dexamethasone, hydrocortisone, corticosterone and progesterone competed with tritium-labelled dexamethasone for receptor binding sites; cortisone, deoxycorticosterone and oestradiol had little effect.

Lightwave fiber tap.

This paper describes a device which samples the optical signal in an optical fiber for use in source stabilization via feedback control. This device incorporates a beam splitter formed on the fiber ends to deflect a portion of the light traveling down the fiber into a P-I-N photodetector. Advantages of this device include low insertion loss, an output that is relatively independent of the modal distribution within the fiber, and is a rugged small package.

Material dispersion in optical fiber waveguides.

In weakly guiding dielectric (glass) fiber waveguides the factors governing the envelope delay distortion of optical signals can be separated conveniently into material and waveguide contributions. By making use of the fact that the normal dispersion of the index-of-refraction of glasses accurately fits a single oscillator Sellmeier equation, simple relations of general validity are obtained for the material contribution to the group delay and frequency dependence of the group delay in dielectric fiber waveguides. Using these results expressions are obtained for the material contribution to the information bandwidth of fiber optic waveguides excited by wideband sources (light emitting diodes) and narrow band sources (lasers). It is shown that in single mode guides the bandwidth limitation imposed by material dispersion is negligible, while in multimode guides the difference in group delay of higher order modes imposes the most severe bandwidth limitation.