Charge migration in DNA: ion-gated transport.

Electron hole (radical cation) migration in DNA, where the quantum transport of an injected charge is gated in a correlated manner by the thermal motions of the hydrated counterions, is described here. Classical molecular dynamics simulations in conjunction with large-scale first-principles electronic structure calculations reveal that different counterion configurations lead to formation of states characterized by varying spatial distributions and degrees of charge localization. Stochastic dynamic fluctuations between such ionic configurations can induce correlated changes in the spatial distribution of the hole, with concomitant transport along the DNA double helix. Comparative ultraviolet light-induced cleavage experiments on native B DNA oligomers and on ones modified to contain counterion (Na(+))-starved bridges between damage-susceptible hole-trapping sites called GG steps show in the latter a reduction in damage at the distal step. This reduction indicates a reduced mobility of the hole across the modified bridge as predicted theoretically.

Medically useful criteria for analytic performance of laboratory tests.

To establish medically useful guidelines for analytic precision of commonly used clinical laboratory procedures, the authors conducted a mail survey of physicians selected randomly from national lists of specialists. They were asked to review, briefly, outlined clinical problems and select the change in test results that would alter their diagnosis or treatment or prompt further assessment of the patient's condition. The responses were used to calculate goals for laboratory precision that are sufficient to meet the present requirements of the average physician. The medically useful limits were compared with existing performance of laboratories as reported in national proficiency surveys and regional quality control programs. Almost all the common laboratory procedures they studied are being assayed at a precision level adequate for the perceived needs. The authors suggest that, for the more common constituents, further progress in clinical laboratory testing will depend on factors other than the improvement of analytic precision.

You can draw blood from the "IV arm" below the intravenous needle if you put a tourniquet in between.

The authors performed a comparative study of the values of 18 serum constituents of blood specimens taken simultaneously from the arm into which an intravenous solution was flowing, using a site distal to the intravenous needle, and from the other arm. Subjects of the study were 15 patients at the Norwalk Hospital. Statistical analysis showed no clinically significant difference between the levels in the two arms except for elevation of glucose in the "iv arm" when the intravenous solution contained glucose.

The medical usefulness of Stat tests.

Although Stat tests are one of the most important features of clinical laboratory performance, the indexed literature is devoid of significant discussion of the subject. The authors, undertook a study by querying hospital laboratories about their current practices and received 38 useable answers dealing with the types of tests done on an urgent basis, the turn-around time for reports, the limitations on ordering, the use of special Stat laboratories and instruments, and decisions regarding priorities.

Performance of "kits" used for clinical chemical analysis of GOT (aspartate aminotransferase).

Forty-three kits for clinical chemical analysis of GOT (aspartate aminotransferase) were evaluated. The reference method was the kinetic method performed on the Abott ABA-100 Bichromatic Analyzer. Specific data are tabulated for each kit and include ease and speed of testing and performance data. Most kits failed to provide completely adequate labelling information. Reproducibility CV for the kits varied widely (4.20 to 21.26 for the normal pool and 1.57 to 20.51 for the high pool). Many kits gave significant numbers of false positive and false negative results on patient samples. There is a need for manufacturers to either derive their own normal ranges or to establish exact equivalency values with the method used to establish the normal values. No difference was demonstrated between performance by two skilled technologists. However, we did detect lot-to-lot variation and differences in performance between narrow bandpass and wide bandpass spectrophotometers.

Planning and instituting new tests in the clinical laboratory.

The laboratory director will eventually face the problem of introducing a new test method. A whole spectrum of decisions must be made depending on the degree of novelty and complexity of the new test. The statistical comparison studies discussed in this article are generally applicable for all tests reported in a quantitative manner.