Routine Laboratory Conditions Research Articles

Development of resistance to ofloxacin.

As a member of the 4-quinolone group of antibacterial agents, ofloxacin shares the almost unique feature of being exempt from plasmid-borne resistance in either Gram-negative or Gram-positive bacteria. In the light of this feature, the development of resistance mediated through chromosomal mutation has been carefully studied, particularly the processes of mutation which confer resistance to levels of ofloxacin approaching those obtained at the site of infection after oral administration. With Escherichia coli strain KL16 being used as a model system, the genetics of the development of resistance to ofloxacin at least 2 mg/L have been studied. In common with many in vitro studies of the development of resistance to the newer 4-quinolones, it has been observed that the mutation frequency was extremely low (in the range 1 X 10(-10) to 1 X 10(-12) with bacteria grown under routine laboratory conditions. The resultant organisms were very slow growing, temperature sensitive and apparently auxotrophic. The mutation(s) were, however, very unstable and the mutants readily reverted to ofloxacin sensitivity in the absence of selection with ofloxacin. Subsequent studies of spontaneous mutation under growth conditions more closely related to the in vivo situation in the lumen of the gut, with limitation of oxygen supply, showed that mutation frequencies were in the order of 1 X 10(-8). Mutants obtained under these conditions displayed the same phenotype as found previously and were equally unstable. Examination of the physiology of the ofloxacin-resistant mutants has shown that they display significant metabolic defects with regard to being able to cope with environmental fluctuations.(ABSTRACT TRUNCATED AT 250 WORDS)

PRENATAL DIAGNOSIS OF α 1-ANTITRYPSIN DEFICIENCY BY RESTRICTION FRAGMENT LENGTH POLYMORPHISMS, AND COMPARISON WITH OLIGONUCLEOTIDE PROBE ANALYSIS

Prenatal diagnosis of sixteen pregnancies at risk for α 1-antitrypsin (AAT) deficiency has been achieved by restriction fragment length polymorphism (RFLP) analysis and compared with diagnostic results using hybridisation of M and Z specific oligonucleotides. The results of both tests were in accord for all samples, although under routine laboratory conditions RFLP analysis was more reliable. Because RFLP analysis does not depend on the type of mutation it was possible, in the product of an MZ and SZ mating, to predict an MZ rather than an MS phenotype using the RFLP method. The strong linkage dysequilibrium between an AvaII RFLP and the Z allele increases its diagnostic usefulness. Even so it seems reasonable to use oligonucleotide analysis in families where no siblings are available for comparison. In all other situations RFLP analysis is as accurate and reliable as oligonucleotide analysis and is technically easier, making it the preferred means of diagnosis for informative kindreds.

The enzyme-linked immunosorbent assay (ELISA) for determination of IgG and IgM antibodies after infection with mumps virus

Under routine laboratory conditions ELISA was tested for suitability for serological demonstration of specific antibodies of the immunoglobulin classes G and M against mumps virus. Sera from patients with known clinical and virological data were used. The results of ELISA were compared with those of CFT. 45 paired sera were tested in ELISA IgG, 87 first sera in ELISA IgM. Both tests were highly sensitive, antibodies were detected earlier and with higher titers than with the CFT. The ELISA IgM is particularly suitable for early diagnosis of mumps infection with the first serum. In addition 23 paired sera from patients with acute parainfluenza virus infection were examined for cross-reacting antibodies. Low anti-mumps IgG antibody titers were found in some sera. These findings reduced the mumps specificity of the IgG test. In five serum samples from one patient--obtained before, during, and after an infection with mumps--the course of IgG and IgM antibodies could be demonstrated. Advantages and limitations of ELISA IgG and IgM are summarized.

The analysis of essential oils and extracts (oleoresins) from seasonings ‐ A critical review

A critical review of the analytical methods employed for the determination of the relevant components of seasonings is presented. Where the available methods were inadequate, new ones have been devised. Particular emphasis has been placed on those methods of analysis that provide a rapid and sufficiently accurate appraisal of seasoning extracts and essential oils from seasonings under routine control laboratory conditions. At the same time, the margin of error of these methods has been determined. The individual seasoning extracts were assessed according to the following criteria: (1) essential oil--cardamom, laurel leaves, cloves, origanum (marjoram), sage, and thyme; (2) essential oil and nonvolatile lipids--dillseed, coriander, caraway, mace, nutmeg, pimento (allspice), and celery seed; (3) essential oil and/or pungent ingredients--capsicum, ginger, and pepper; (4) essential oil and/or coloring matter--turmeric (curcuma) and paprika; (5) essential oil and other components--garlic, onion, and cinnamon.

New, advantageous approach to the direct radioimmunoassay of cortisol.

Radioimmunoassay of serum cortisol is simplified by a unique solution to the problem of eliminating competition between cortisol-binding globulin and cortisol immunoglobulin. Increasing incubation temperature tends to release cortisol from its carrier protein while favoring the immunoglobulin reaction. We applied this methodology, using reagents supplied as a commercial kit. Serum, 5 mul, is diluted with 125I-containing(hydroxymethyl)aminomethane buffer and incubated at 45 degrees C for 1 h, then aspirated. All standards are constituted in steroid-deprived serum. The clinical validity of the method is supported by comparisons with conventional methods during months of use under routine laboratory conditions. The simplified method also offers improved performance characteristics and, as described, if fully instrumented. The significance of this use of thermodynamic properties is discussed in terms of more general applicability.

Evaluation of the vitatron “AKES”. modification for optimal use in routine enzyme analysis

The Vitatron has been used as designed by the manufacturer under routine laboratory conditions (Broughton, P.M.G., Buttolph, M.A., Gowenlock, A.H., Neill, D.W. and Sleutelberg, R.G. (1969) J. Clin. Pathol. 22, 278). We assessed the possibilities of the AKES with regard to determination of the activities of three enzymes: alanine transaminase (AIT), aspartate transaminase (AsT) and lactate dehydrogenase (LDH) in serum. Precision, accuracy, carry over and sample-diluent contamination were evaluated. This resulted in recommendations for optimal use in terms of capacity and precision, which were supported by computations on a mathematical model for measuring results.

Imaging and measuring electron beam dose distributions using holographic interferometry

Holographic interferometry was used to image and measure ionizing radiation depth-dose and isodose distributions in transparent liquids. Both broad and narrowly collimated electron beams from accelerators (2–10 MeV) provided short irradiation times of 30 ns to 0.6 s. Holographic images and measurements of absorbed dose distributions were achieved in liquids of various densities and thermal properties and in water layers thinner than the electron range and with backings of materials of various densities and atomic numbers. The lowest detectable dose in some liquids was of the order of a few kRad. The precision limits of the measurement of dose were found to be ±4%. The procedure was simple and the holographic equipment stable and compact, thus allowing experimentation under routine laboratory conditions and limited space.

Effects of Feedback and Reinforcement on the Control of Human Systolic Blood Pressure

An automatic procedure providing information about human systolic blood pressure at each successive heartbeat under routine laboratory conditions is described. Twenty normal male subjects were given feedback of their own systolic pressure, half operantly reinforced for increasing and half reinforced for decreasing their pressure. Significant differences in pressure were obtained in a single session. The apparatus and results suggest a possible approach to the treatment of essential hypertension.

Determination of Sulfamethazine in Mixed Feeds Containing Procaine Penicillin

Abstract Sulfamethazine in combination with procaine penicillin is used as a medicament in swine feeds. Interference from procaine must be eliminated to determine sulfamethazine by the Bratton-Marshall color reaction. In the method, sulfamethazine is extracted with hot methanol, the protein is precipitated with zinc sulfate and filtered, and the azo dyes of sulfamethazine and procaine are formed by the Bratton-Marshall color reaction. The mixed dye solution is shaken with chloroform to separate the procaine dye, made alkaline, and reshaken. An aliquot of the aqueous phase which contains the sulfamethazine dye is removed, re-acidified, and measured at 540 mμ.i against a standard curve. Procaine penicillin added at 25 times the formulation level does not interfere. Swine feeds at sulfamethazine levels of 0.011 and 0.044% give average recoveries of 95 and 99%, respectively, with a coefficient of variation of less than 6% under routine laboratory conditions.

Phenolphthalein Monophosphate as a Substrate for Serum Alkaline Phosphatase

Abstract The procedure for serum alkaline phosphatase determination employing phenolphthalein monophosphate as substrate was evaluated under routine clinical laboratory conditions. A straight-line response to increasing serum concentration was observed, and the reaction was shown to be Mg++ dependent. The method proved to be extremely simple, and the results obtained correlated well with those given by a standard routine procedure involving determination of the liberated inorganic phosphate.

Precision of plasma urea and electrolytes estimated by the AutoAnalyzer

The precision of sodium, potassium, chloride, and bicarbonate analyses carried out by the AutoAnalyzer has been studied under routine laboratory conditions. From the results it is concluded that a further increase in precision is desirable.

Silver-silver chloride electrode as a nonpolarizable bioelectorde.

A thermal-electrolytic method for the preparation of Ag AgCl electrodes suitable for measurement of bioelectrical changes in the microvolt range is given in detail. A potential of 0.5 mv or less between electrode pairs is easily attained; and such electrodes will accurately measure emf generated by both steady and fluctuating phenomena down to ±5 μv under routine laboratory conditions. Studies in the variations in potential for pairs of electrodes from the time they are introduced into the circuit until they reach a stable state, as well as long-term drift are presented. These data are analyzed in terms of activation, ohmic, and concentration polarization effects. Submitted on July 19, 1962

TWO SPECIAL PURPOSE BALANCES

SummaryTwo special purpose balances are described.(i) For the rapid estimation of moisture in butter.(ii) For weighing out 5 g cream directly into a cream butyrometer.Experience under routine laboratory conditions has shown both instruments to be rapid and reliable.