The control by ventilation of airborne bacterial transfer between hospital patients, and its assessment by means of a particle tracer. I. An airborne-particle tracer for cross-infection studies

A simple and convenient particle tracer for studies of the effectiveness of isolation units and other places in limiting the airborne transfer of bacteria is described. Particles of potassium iodide 7-8 mum. diameter are generated by spraying from solution and collected on membrane filters. The particles can be identified by development with 0.1% acid palladium chloride solution, when dark brown spots approximately 100 mum. in diameter are produced.

The control by ventilation of airborne bacterial transfer between hospital patients, and its assessment by means of a particle tracer. 3. Studies with an airborne-particle tracer in an isolation ward for burned patients

Airborne-particle transfer has been studied in a burns unit using potassium iodide particles. The observed rates of transfer were in good agreement with the values predicted by a theoretical model.An estimate of the average transfer between rooms under conditions of normal activity and with correctly functioning ventilation showed that the isolation system was highly efficient, the proportion transferred being probably less than 1 in 10(5). However, the ventilation often did not function as designed and under these conditions the efficiency was reduced by a maximum of a factor of ten. These rates of transfer do not seem great enough to account for the high rate of cross-infection found in this unit.

Spot test for lipoxygenase activity

A qualitative iodometric test for lipoxygenase activity is described. The sensitive method is useful for rapidly screening large numbers of samples, as from a chromatography column or after enzyme inactivation treatment in food processing.

On the existence of lipid peroxides in rat tissue

1. The colorimetric micro-adaption of the iodometric method and the colorimetric thiocyanate method for the determination of lipoperoxides were compared. Similar results were obtained when methyl linoleate hydroperoxide was tested, but when lipid from rat liver, muscle, kindney and testes was examined, substantial amounts were found by the iodometric, but almost nothing by the thiocyanate method.

2. The main reason for the discrepancy between the methods seems to be that the iodometric micromethod also estimates substances other than true lipoperoxides. The presence of ubiquinone and vitamin A in the organ extracts was shown to interfere in this way in the method.

3. The yellow colour which develops when retinol and its esters are tested by the iodometric micromethod is due not to liberated iodine but to conversion products of retinol.

4. It is concluded that the occurrence of substantial amounts of lipoperoxides in vivo has so far been demonstarted only in the adipose tissue, and not in the parenchymatous organs of the rat.

A pigmented gelatin mass for vascular injection

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Flavin-photosensitized reactions of retinol and stilbene

1. Retinol and stilbene are both isomerized when they are illuminated anaerobically in the presence of flavins. 2. Triplet quenchers (e.g. oxygen, potassium iodide and paramagnetic ions) inhibit the reaction more efficiently than they quench flavin fluorescence. At 77 degrees C in a diethyl ether-isopentane-ethanol (5:5:2) glass retinol quenches flavin phosphorescence, but not its fluorescence. 3. For the stilbene reaction cis/trans photostationary-state mixtures are obtained with different flavins and these are linearly related to the phosphorescence transition energies of the flavins used. 4. The reaction involves the triplet state of flavin and a scheme for the reaction is suggested. 5. The dependence of the rate of reaction on substrate concentration is explicable in terms of this scheme. 6. The photobleaching of rhodopsin sensitized by flavin is also demonstrated.

Microspectrophotometry of newly synthesized starch in situ

Many of the cells in stem sections of several Commelinaceae species synthesized much new starch when incubated in buffered 1% glucose 1-phosphate solution. The starch appeared in the cytoplasm rather than in the plastids. Although the starch I2-KI color was uniform within any one cell, there was considerable variation from cell to cell, even in the same section. The colors with I2-KI ranged from blue, through purples to magenta and mahogany. Tests with α-amylase and with β-amylase showed the starch to be amylose. Microspectrophotometrically determined extinction curves, based on the new starch in situ, varied with the visualized color. As expected, starch which stained blue with I2-KI had an absorption maximum in the orange-red wavelengths above 600 mµ; increasingly red I2-KI colors were characterized by shifts of the absorption maximum further into the shorter wavelengths. The course of new starch digestion by α-amylase and by β-amylase was followed visually and with the microspectrophotometer. Similarities and differences between these spectral curves and those published for in vitro studies are pointed out. The difficulties met with in using the microspectrophotometric method are discussed.