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When a confocal fluorescence microscope with a high-numerical-aperture oil-immersion objective is focused deep into an aqueous medium, aberrations result that degrade image quality. We have designed and fabricated a simple two-level binary phase mask that partially corrects these aberrations, improving axial resolution. We present the design and some confirming results.

The B9 assay is known to be a specific and sensitive assay for the estimation of interleukin-6 activity. This assay was found to be compromised by lipopolysaccharide in concentrations > or = 40 ng lipopolysaccharide per ml. The lipopolysaccharide stimulates proliferation of the B9 cell line in a dose-dependent manner both when measuring the proliferation by thymidine incorporation and when using the MTT assay. However the LPS dose-response curve is different compared to the dose-response curve for IL-6. A sample containing 100 ng LPS/ml but no IL-6 would be estimated erroneously to contain 12 pg IL-6. The interference of lipopolysaccharide is totally abolished by the addition of polymyxin B to the samples but the addition has no effect on the IL-6 induced proliferation.

The enhanced depth discrimination of a confocal scanning optical microscope is produced by a pinhole aperture placed in front of the detector to reject out-of-focus light. Strictly confocal behavior is impractical because an infinitesimally small aperture would collect very little light and would result in images with a poor signal-to-noise ratio (SNR), while a finite-sized partially confocal aperture provides a better SNR but reduced depth discrimination. Reconstruction algorithms, such as the expectationmaximization algorithm for maximum likelihood, can be applied to partially confocal images in order to achieve better resolution, but because they are sensitive to noise in the data, there is a practical trade-off involved. With a small aperture, fewer iterations of the reconstruction algorithm are necessary to achieve the desired resolution, but the low a priori SNR will result in a noisy reconstruction, at least when no regularization is used. With a larger aperture the a priori SNR is larger but the resolution is lower, and more iterations of the algorithm are necessary to reach the desired resolution; at some point the a posteriori SNR is lower than the a priori value. We present a theoretical analysis of the SNR-toresolution trade-off partially confocal imaging, and we present two studies that use the expectationmaximization algorithm as a postprocessor; these studies show that a for a given task there is an optimum aperture size, departures from which result in a lower a posteriori SNR.

A kinetic chromogenic Limulus amebocyte lysate assay for detection of lipopolysaccharide in the picogram range is described. The kinetic Limulus assay was used to detect lipopolysaccharide in a tissue culture media containing interfering low-molecular-weight substances. The interfering substances were removed by ultrafiltration. The recovery of lipopolysaccharide from the ultrafiltrated tissue culture media was 61.6 +/- 21.4%. The kinetic Limulus assay was compared with the traditional end-point chromogenic Limulus assay. The results in the two assays showed a good correlation. The detection limit was 1 pg/ml in the chromogenic assay and 0.25 pg/ml in the kinetic assay.

We inoculated partially hydrolysed protein feed of low pH and an intact protein feed of neutral pH with various pathogenic bacteria, and showed that the low pH feed restricted bacterial growth. To study this effect in a clinical setting, 20 malnourished in-patients were randomised prospectively to receive one or other of these feeds. Both formulae were given as a continuous feed via a nasogastric tube, 1,000 ml over 12 h twice daily, using routine hygienic measures. On two occasions significant contamination was demonstrated (Erwinia herbicola and Acinetobacter Iwoffi), both occurring in the intact protein diet. When the bacteria were isolated and transferred to the hydrolysed protein diet, their growth was inhibited. The contamination did not cause clinical complications. The study demonstrates inhibition of microbial growth in a partially hydrolysed protein formula of low pH. This effect may reduce the risk of contamination, and limit infectious complications.

Isolated human mononuclear cells exposed to either lipopolysaccharide or Staphylococcus aureus secreted interleukin-1 like material. The secretion was concentration dependent. The minimal detectable level in the test solution of lipopolysaccharide and Staphylococcus aureus was 200 pg/ml and 10(5) cells/ml respectively. The sensitivity and specificity of the Limulus Amebocyte Lysate test, the rabbit pyrogen test and the monocyte test are compared. The monocyte test is proposed as an alternative in-vitro test to the rabbit pyrogen test.

Significant improvement in the longitudinal (optical axis) resolution of a microscope has previously been obtained either by posterior digital processing of optical sections collected with a conventional microscope, or by collecting sections with a confocal scanning microscope. In this paper we report the feasibility of obtaining longitudinal resolution comparable to the lateral diffraction limit by posterior processing of confocal sections. A confocal through-focus image series was simulated numerically and restored by constrained iterative deconvolution and by maximum likelihood. Several typical imaging situations were simulated. The results support the possibility of achieving equal longitudinal and lateral resolution.

This introduction describes the motivation behind this 10 Sept. 1990 issue featuring 3-D microscopy and provides a brief overview of the issue.

The effect of the cytokine interleukin-1 beta on the secretion of oxytocin and vasopressin from electrically stimulated rat neurohypophysis was examined in vitro. The release of oxytocin and vasopressin was concentration-dependently increased by interleukin-1 beta in the concentration range from 4.4 pM to 440 pM. The effect of interleukin-1 beta on oxytocin secretion was less intense as compared to vasopressin. After 440 pM interleukin-1 beta the electrically evoked release of oxytocin was increased about 22% and had not reached its maximum. The vasopressin response was maximal after 44 pM interleukin-1 beta, the response being increased 43% compared to control. No trace of interleukin-1 beta was found in the posterior pituitary (less than 350 pmol/lobe, radioimmunoassay). The results indicate that interleukin-1 beta might be involved the regulation of oxytocin and vasopressin at the pituitary level.

Exposure of Bacillus subtilis spores to ethylene oxide (EO) showed correlation between the killing rate and the EO concentration, when the temperature was kept at 55 degrees C and the relative humidity at 100%. The co-efficient of dilution was calculated to be 0.9. The effect of EO on Escherichia coli endotoxin was investigated by the chromogenic Limulus Amebocyte Lysate (LAL) test. A solution of endotoxin was dried on glass tubes and exposed to 450 or 900 mg EO/l during 1-46 h under the same conditions as the spore inactivation. The LAL activity of the endotoxin was reduced to about 30%. The EO-treated endotoxin was tested in the rabbit pyrogen test. The summed temperature increase for three rabbits was 0.9 degrees C, while the same assay using untreated test pieces showed an increment of 3.7 degrees C. Administration of the same quantity of EO-treated and untreated endotoxin to the rabbits, as adjusted by the LAL-test, produced the same temperature increment. The addition of polymyxin B (PB) to an endotoxin solution reduced the LAL activity by 75%. Had the endotoxin been exposed to EO, thereby reducing the LAL activity by 70%, addition of PB further reduced the activity by 99%. The reaction of EO on the endotoxin reduced the LAL activity as well as the pyrogenic response and increased the affinity to PB.

We describe the concept and first implementation of an innovative new instrument for quantitative light microscopy. Currently, it provides selective imaging of optical path differences due to birefringence; with further development, it is also possible to selectively image several optical properties, including refractive path differences, optical rotation, and linear and circular dichroism, all with diffraction-limited resolution. An image consists of a 512 X 512 element array, with each pixel displaying one of 256 grey levels, linearly proportional to the specific optical property being observed. Additionally, conventional brightfield and polarized light microscopy are available, with the accompanying advantages of laser scanning and digital image processing. The microscope consists of three subsystems, representing three distinct technologies. The laser scanning subsystem moves a focused microspot across the specimen; the output of a photodetector is an electric signal corresponding to a scanned image. The image display subsystem digitizes this signal and displays it as an image on a video monitor. When used in conjunction with a phase modulation feedback loop, the image formed is of the specimen's birefringent retardation or other selected optical property. The digitized images are also available for computer enhancement.

Microbial contamination of total parenteral nutrition including fat emulsions in 1-3 litres plastic infusion bags (the i.v. bag) was studied during production in the pharmacy and administration both at home and in the hospital. Production contamination was investigated by dispensing test bags containing growth medium mixed with dextrose-salt solution. In this highly sensitive system, contamination was detected in less than 4% of cases. In-use contamination was estimated at the end of the infusion. The average contamination rate (+/- growth) in the five patients studied was 6.7% accompanied by considerable variation. Identification of the contaminants revealed that 85% of the contaminated bags contained staphylococci, indicating skin contamination. An investigation on the effect of the procedure used for attaching the infusion set on the contamination rate, was carried out with bags that contained sterile growth medium. This showed no contamination in 14 cases indicating the catheter as the most plausible source of contamination. It is concluded that both production in the community pharmacy and administration in the home are not associated with a higher microbial contamination than in central hospitals. It is, however, recommended that the microbial quality of the production process and the administration procedure are regularly monitored.

A method of image reconstruction from projections is described which processes the data in polar rather than rectangular coordinates and which does not require back projection. It is based on the decomposition of the object and its shadow (set of projections) into circular harmonics or radial modulators of angular Fourier components. The radial modulators of the object may be reconstructed from those of the shadow using a space-variant system which becomes space-invariant under a coordinate transformation. Experiments using digital and optical implementations are described.

Four juvenile rhesus monkeys responded to the coo-type vocalization of their respective mothers by increasing dramatically their own vocalization rate and their locomotor activities. The juveniles appeared quite disturbed when they heard their mothers voices and this disturbance was, with one exception, apparently specific to their own mothers.

The release of vasopressin from the isolated superfused rat neurohypophysis was measured. The electrically evoked release of vasopressin after phasic submaximal stimulation was increased on exposure to the cytokine, interleukin-1 beta (44 pM). The release returned to its control level when the peptide was withdrawn. The results indicates a permissive role of interleukin-1 beta in the release of vasopressin.

In the past, most optical data processing systems have been restricted to performing linear space-invariant operations. However, a wide class of interesting data processing operations require linear space-variant filtering. Three methods for performing linear space-variant processing of 1-D inputs are described. Experimental results obtained with all three systems are presented, and their relative advantages and disadvantages are discussed.