The effects of freeze drying and freeze drying additives on the prothrombin time and the international sensitivity index.
(17/944)
AIM: To determine whether freezing, freeze drying protective additives, or freeze drying of plasma samples from patients on coumarin treatment and from normal individuals affects prothrombin times or the international sensitivity index (ISI) calibration. METHODS: The effect of the addition of the protective additives singly and combined on the prothrombin time of coumarin samples and normal samples before and after freeze drying was observed using high and low ISI reference thromboplastins. ISI values were also determined. RESULTS: Freezing caused a prolongation of prothrombin time in the normal plasma samples with both reagents, which was significant with the low ISI human. Prolongation (non-significant) of the prothrombin time in coumarin plasma samples occurred with the human reagent only. Significant prolongation of normal prothrombin time by some of the protective additives before and after freeze drying was observed with both thromboplastins but to a greater extent with the human. Significant prolongation of prothrombin time in coumarin plasma samples was observed, but again was more marked with human thromboplastin. An approximate ISI was determined on the 20 coumarin samples. The only marked ISI change was with the WHO human thromboplastin after freeze drying of plasma, where a decrease from 0.95 to 0.90 was observed, corresponding to a marked prothrombin ratio increase. CONCLUSIONS: Freeze drying additives and the freeze drying procedure prolong normal and coumarin prothrombin times, with low ISI thromboplastin. Less marked prolongations occurred with a high ISI rabbit reagent, coumarin samples showing more significant prolongations. Marked ISI change in freeze dried plasma was only recorded with the low ISI ECAA human reagent. Frozen normal plasma samples cannot be used with confidence for ISI calibrations. (+info)
Engineering desiccation tolerance in Escherichia coli.
(18/944)
Recombinant sucrose-6-phosphate synthase (SpsA) was synthesized in Escherichia coli BL21DE3 by using the spsA gene of the cyanobacterium Synechocystis sp. strain PCC 6803. Transformants exhibited a 10,000-fold increase in survival compared to wild-type cells following either freeze-drying, air drying, or desiccation over phosphorus pentoxide. The phase transition temperatures and vibration frequencies (P==O stretch) in phospholipids suggested that sucrose maintained membrane fluidity during cell dehydration. (+info)
Field application to malaria studies of the passive haemagglutination (PHA) test with lyophilized cells.
(19/944)
Lyophilized cells for the passive (formerly indirect) haemagglutination test for malaria were tested in a small field trial. A comparison was made with results obtained with samples from the same persons by another method in another laboratory (Center for Disease Control, Atlanta, GA, USA). The use of lyophilized cells of standardized reactivity clearly adds to the simplicity and rapidity of the test, and justifies its recommendation for use in field studies. (+info)
Large-scale use of freeze-dried smallpox vaccine prepared in primary cultures of rabbit kidney cells.
(20/944)
A lyophilized smallpox vaccine made from infected monolayer cultures of primary rabbit kidney cells was used together with a calf lymph vaccine in a field trial in Lombok, Indonesia, in 1973. About 60 000 children below 15 years of age were vaccinated: some 50 000 with the tissue culture vaccine and about 10 000 with calf lymph vaccine. Similar results were obtained with both vaccines in primary vaccinees and in revaccinees as regards the take rate, pock reactions, and serious secondary reactions. (+info)
Scanning electron microscopy of the luminal epithelium of the mouse uterus.
(21/944)
Four methods of manipulating mouse uterine tissue during fixation, preparatory to examination of the luminal epithelium by scanning electron microscopy (S.E.M.), are described and the results assessed. The appearance of the epithelium varies according to the technique used, the choice of method depending on the type of information required from the S.E.M. study. Surface topography is preserved in a condition most closely resembling that of fresh tissue by opening the uterus and fixing the tissue flat. Critical examination of cellular and subcellular surface detail, however, depends on adequate spreading of the epithelial layer during fixation by distension of the uterine lumen under positive pressure. The method of tissue manipulation has a more profound effect on the appearance of the sample than any of the dehydration techniques which follow. For routine S.E.M. examinations at medium magnifications (smaller than X10,000), specimens which were air dried from alcohol, acetone or ether, or freeze dried, gave satisfactory results. Air drying from amyl acetate, and CO2 critical-point drying gave superior results at higher magnifications (greater than X10,000) with better preservation of individual microvilli. (+info)
Proficiency test specimens for water bacteriology.
(22/944)
A procedure for the preparation and distribution of simulated water specimens for coliform density testing is described. Lyophilization of Escherichia coli in a cooked meat-glucose supporting substrate provides stable samples which may be distributed to participants in a proficiency testing program. Logarithmic conversion of the data allows statistical evaluation of the results for inter- and intralaboratory variation. Comparisons between the most probable number and membrane filter techniques indicate no significant difference in the accuracy of these techniques, although the membrane filter technique is more precise. (+info)
Lyophilized 7 alpha-hydroxysteroid dehydrogenase: a stable enzyme preparation for routine bile acid analysis.
(23/944)
Preparations of 7 alpha-hydroxysteroid dehydrogenase (7 alpha-HSDH) from Escherichia coli strain 23 can be frozen and thawed without significant loss of activity. 7 alpha-HSDH may then be lyophilized into powder form, which is stable for more than 6 months (3% loss of activity). The lyophilized 7 alpha-HSDH preparation has the additional advantage over previously described preparations of a low and stable fluorescence background when applied to the fluorometric estimation of bile acids, especially in combination with thin-layer chromatography. Analysis of duodenal aspirates from 18 normal subjects gave bile acid ratios identical with those reported earlier and obtained by using gas-liquid chromatography. A significant difference in the glycine: taurine ratio between males and females was observed. (+info)
Anhydrobiotic engineering of gram-negative bacteria.
(24/944)
Anhydrobiotic engineering aims to improve desiccation tolerance in living organisms by adopting the strategies of anhydrobiosis. This was achieved for Escherichia coli and Pseudomonas putida by osmotic induction of intracellular trehalose synthesis and by drying from trehalose solutions, resulting in long-term viability in the dried state. (+info)