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PubMed1990

Improved sample and reagent pipetting with the MINILAB.

MINILAB is a small photometer designed for use in small labs and physicians' offices. The instrument is preprogrammed for the determination of several analytes either in whole blood, plasma or serum. Each method is provided as a kit containing disposable cuvettes and capillaries for sample or reagent addition. We examined the precision of the MINILAB using the cholesterol and bilirubin methods for serum, following the recommendations provided for each method, and found that the precisions were not acceptable (CV up to 16% for cholesterol and 43% for bilirubin). Suspecting that these variations were due to sample and reagent pipetting, we tried a simple modification using a Microcap for pipetting and were able to improve the precisions, resulting in CVs of 1.4% for cholesterol and 3.5% for bilirubin.

Bilirubin↗

PubMed1990

Precise, easy measurement of glass pipet tips for microinjection or electrophysiology.

We describe a simple procedure to measure precisely the tip diameter of glass micropipets. This procedure can improve the precision of microinjection and some electrophysiological measurements due to their extreme sensitivity to the pipet's exact geometric dimensions. The technique is nondestructive and readily carried out as a brief, extra step in these applications. Digital measurements of the threshold pressures for gas bubbling from (gas filled) pipets submerged in methanol were used to calculate the corresponding inner tip diameters using the LaPlace equation. Direct measurements of the inner tip diameters (from 0.2-5.0 mu) using scanning electron microscopy confirmed the validity of this indirect, simple procedure.

Electrophysiology↗

PubMedDate not supplied

[Evaluation of pipetting systems. II. Precision and accuracy of precision dispensers].

OBJECTIVE: To evaluate the precision and accuracy of the liquid dispensers being used in our institution. MATERIAL: A total of 15 dispensers (8 micro and 7 macro) of automatic, semiautomatic or manual types were evaluated. They had been in use from 0.5 to 7 years. METHODS: The volume dispensed was established by gravimetry using an analytical balance (Chio JP-160) and deionized distilled water as previously described. The microdispensers were evaluated using volumes of 20 and 100 microL, and the macrodispensers with 1 and 5 mL. Each dispenser was evaluated using 10 replicates: the mean and the CV (coefficient of variation) were calculated with the 10 replicates. The mean was transformed to per cent of the theoretical volume. Thus a 100% ratio of accuracy corresponds to a perfect accuracy. An important methodological aspect was that the 10 dispensing replicates were performed personally by the habitual user of the dispenser. RESULTS: The mean and CV are shown in table 2 for the microdispensers, and in table 3 for the macrodispenser. In the total 25 evaluation in tables 2 and 3 there were 8 instances in which precision was poor (CV above 3%) and also 8 cases of sizable inaccuracy (ratio outside of 100 +/- 5%). In 4 (2 micro and 2 macro) of these 8 inaccuracies, the error ranged from 10% to 22%. A minority was within the specifications of precision and accuracy claimed by the manufacturers of the dispensers with the exception of the manual microdispensers which were within specifications in most instances. We attribute the latter to the lack of a mechanical device in the manual dispensers. CONCLUSIONS: As in a previous evaluation of automatic micropipettes, we detected a high proportion of pipetting systems out of specifications in both precision and accuracy. The magnitude of error in the accuracy of 4 dispensers (10 to 22%) would be catastrophic in methods demanding good pipetting.

Calibration↗

PubMed1995

Glycosylphosphatidylinositol-alkaline phosphatase from calf intestine as substrate for glycosylphosphatidylinositol-specific phospholipases--microassay using hydrophobic chromatography in pipet tips.

An electrophoretically homogeneous glycosylphosphatidylinositol- alkaline phosphatase fraction from calf intestine, obtained by hydrophobic chromatography, was used as "enzyme-labeled" substrate for testing phospholipase activity. The reaction products were separated by (i) hydrophobic chromatography in pipet tips and (ii) Triton X-114 phase partitioning. The chromatographic method presented permits high test frequencies, does not need temperature-controlled sample handling, and is only slightly disturbed by detergents, organic solvents, and proteins. The method was used to characterize phosphatidylinositol- specific phospholipase C from Bacillus cereus and phospholipase D from calf serum. Measurement of substrate hydrolysis by phospholipases is apparently linear to enzyme concentration and time. Relative activity of both enzymes is maximum at pH 6.5, corresponding to the optimal pH range found with other glycosylphosphatidylinositol substrates and phosphatidylinositol-specific phospholipases of other sources. Maximum activity of phospholipase C was found at 0.03% Triton X-100, 0.01% Brij 35, and 0.2% n-octylglucoside. The activity is not affected by Ca(2+), NaHCO(3), o-phenanthroline, or EDTA, increasingly inhibited by MgCl(2), MnCl(2), and ZnCl(2), and slightly activated by Na+ and K+. Calf serum phospholipase D shows maximum activity at 0.05% Triton X-100, 0.02% Brij 35, and 0.4% n-octylglucoside. The apparent Km values for phospholipase C (12.25 micron) and phospholipase D (4.94 micron) found with glycosylphosphatidylinositol-alkaline phosphatase are compared with values published for other glycosylphosphatidylinositol substrates.

Alkaline Phosphatase↗

PubMed1987

A polisher for patch pipets.

The design and construction of a novel apparatus to fire polish patch-clamp recording pipets is described. The device positions the polishing filament in the field of view of the high-power polishing objective and uses the mechanical stage of the microscope to hold the electrode, eliminating the need for a micromanipulator to hold either the filament or electrode.

Electrodes↗

PubMed1995

Chromosomal aberrations induced in human whole blood cultures by pipetting cell pellets in the presence of AluI.

A physical method is described to permeabilize human peripheral lymphocytes in culture for the restriction endonuclease AluI. Blood cultures are incubated for 20 h, pelleted, strongly pipetted with different types of Pasteur pipettes in the presence of AluI and recovered for up to 54 h in the presence of 5-bromodeoxyuridine. Up to 20% of aberrant first posttreatment (M1) metaphases with chromosome-type aberrations are found. The method works with whole blood cultures and is therefore easy to perform.

Bromodeoxyuridine↗

PubMed1988

Pipetting errors in viral titrations: a useful approach.

A simple recursive formula, which yields an estimate for the statistical error resulting from pipetting errors accumulated throughout a dilution procedure, is described. Its influence on the variance of the end-point titre estimate is then inferred.

Biometry↗

PubMed1994

Acaricide susceptibility of immature Ixodes scapularis (Acari: Ixodidae) as determined by the disposable pipet method.

The disposable pipet method was used to establish baseline dose-mortality data for immature stages of Ixodes scapularis Say for carbaryl, esfenvalerate, cyfluthrin, and permethrin. Permethrin and cyfluthrin were most toxic to both nymphs and larvae, followed in order by esfenvalerate and carbaryl, based on LD50 and LD90 values. Larvae were substantially more susceptible than nymphs to each compound.

Animals↗

PubMed1998

Upper limb disorder due to manual pipetting.

This case report describes the occurrence of non-specific upper limb symptoms, in a 47-year-old female scientific officer, associated, with manual pipetting. The discussion considers the difficulty of risk assessment and reduction for this common procedure.

Arm↗

PubMed1971

Safe, convenient pipetting device.

A finger-mounted pipetting device which can be fabricated in the laboratory is described.

Equipment and Supplies↗

PubMed2002

[The PIPET or Patient Individual Plate Easy Test].

The fresh outbreak of allergies and especially that increasingly early for food or even for new pneumallergens (sensitization already in utero) pushes us to test increasingly various and many allergens in children. The insufficiency of compliance of certain children to allergic skin tests encouraged us to seek new diagnostic methods. In our office we developed a new method of diagnosis by multipuncture, individualized and easily adaptable to each child. It is about a fast and reproductible prick-test which avoids stains and smudges due to the application of drops directly on the skin. It makes it possible to initially place easily all the tests on a plate (PIPET or Patient Individual Plate Easy Test) then on the skin by a multipuncture method. The tests can even already be prepared in the days which precede, provided that the plates are put in the fridge, with the name of the patient and the allergens used, for memory. It is about a rigorous test, reliable and careful, easy to carry out even in the most difficult children.

Allergens↗

PubMed1950