SUMMARY : Young actively dividing cultures of Pseudomnaspyocyanea (aeruginosa) at 37" were killed when diluted into cold liquids which were without effect when used above 18". In general the simpler the composition of the diluent the more lethal it was ; distilled water was the most active. The cooling had to be rapid to be effective. Old cultures were only slightly sensitive to this effect. The killed organisms appeared normal when examined under the microscope. Under similar conditions Staphylococcus aureus was resistant t o cold shock.The killing effect of cold diluent on young Escherichia coli was shown by Sherman & Albus (1923) who suggested that the organisms passed through a phase of 'rejuvenation ' before multiplication. Hegarty & Weeks (1940) made an extensive investigation into the sensitivity of E. coli to cold shock and showed that low osmotic pressure and cold were both necessary in order to kill organisms exposed to these conditions. Overnight broth cultures became sensitive within 20 min. of their addition to a suitable medium, i.e. before the first bacterial division took place. The organisms showed maximum sensitivity during the log phase of growth. No other report of this phenomenon appeared until that of Meynell (1958) who showed, with E. coli, that the number of organisms which appeared to be killed by cold shock depended upon the medium on which they were subsequently plated. The importance of the composition of the diluent and the speed of cooling were also emphasized. Cultures which had suffered cold shock showed no decrease in numbers on direct counting and the bacteria looked normal microscopically. The present investigation stemmed from the observation that direct viable counts of young shaken cultures of Pseudomonas pyo yanea (aeruginosa) diverged from those expected from the turbidity of the cultures. This paper reports work on the sensitivity of P. pyo yanea to cold shock.
METHODS
A retrospective study has been made to assess the value of specific protein analysis in a routine laboratory. The use of cellulose acetate electrophoresis, immunoelectrophoresis, and single radial immunodiffusion has been discussed with reference to the source of the request for the investigation and the yield of abnormal results. A scheme for the investigation of abnormal proteins is presented with a discussion of the problem of diagnosing myeloma as distinct from identifying an abnormal protein. The occurrence of double-zones on Tri-Partigen plates (Hoechst Pharm.) may be an early indication of myeloma, but does occur in other conditions. Levels of immunoglobulins in the geriatric age group have been shown to be similar to that of non-geriatric adults. Specific protein analysis has been shown to be of limited value in rheumatoid arthritis.
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