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PubMed1991

Visual assessment of sporozoite and bloodmeal ELISA samples in malaria field studies.

The accuracy of visually assessing positivity for samples of field-collected Anopheles tested by enzyme-linked immunosorbent assays (ELISA) for Plasmodium falciparum sporozoites and human bloodmeals was determined during malaria field studies in Kenya. Six observers familiar with ELISAs evaluated 5,344 sporozoite ELISA samples and four observers evaluated 360 bloodmeal samples as either positive or negative based on the presence and strength of green-colored peroxidase reactions relative to controls on each microtiter plate. Interobserver agreement ranged from 97.9 to 99.8% for sporozoite samples and from 90.3 to 96.1% for bloodmeal samples. For both assays, the mean sensitivity and specificity of visual readings, compared with spectrophotometric readings, exceeded 98% when absorbance values were greater than or equal to 0.4 (on a scale of 0.0 to 2.0). Most incorrect visual readings occurred for samples with absorbance values between 0.2 and 0.4. The total percentage of samples classified correctly by visual examination ranged from 97.7 to 99.5% for the sporozoite ELISA and from 95.0 to 96.7% for the bloodmeal ELISA. Thus, there was minimal error associated with visually determining positive reactions for the ELISA assays used in malaria field studies.

Animals↗
PubMed1992

A new guide for positioning of maxillary posterior denture teeth.

There is no definitive method for the arrangement of artificial teeth in complete denture construction. A new method is introduced whereby the maxillary posterior teeth have been set in approximate positions mediolaterally similar to their natural predecessors. The procedure is based on a constant relationship derived from the natural dentition. Its clinical application proved to be suitable for the arrangement of artificial teeth for complete dentures with minimal errors.

Adult↗
PubMed1991

Studies on in vitro proteolytic sensitivity of peptides inhibiting herpes simplex virus ribonucleotide reductases lead to discovery of a stable and potent inhibitor.

The nonapeptide, HSV R2-(329-337), corresponding to the subunit 2 (R2) carboxyl terminus of herpes simplex virus (HSV) ribonucleotide reductases, specifically inhibits this enzyme activity. We report here that under standard reductase assay conditions, this peptide was rapidly degraded by proteases present in the partially purified enzyme extract. The main process of proteolysis involves the successive removal of Tyr329 and Ala330, which corresponds to an aminopeptidase activity. Determination of the proteolytic susceptibility of HSV R2-(329-337) analogs showed that natural modifications which are present in the homologous varicella zoster virus (VZV) nonapeptide decreased its susceptibility to protease action 1.5-fold. Nx-acetylation, a modification known to protect peptides against aminopeptidase attacks, greatly improved the proteolytic resistance of HSV and VZV nonapeptides. Moreover, Ac-VZV R2-(298-306) exhibited a 15-fold higher potency on reductase inhibition than HSV R2-(329-337). The degradation process of HSV R2-(329-337) was partially inhibited by amastatin, bestatin, and leupeptin whereas it was completely abolished by bacitracin, suggesting a combined action of more than one aminopeptidase activity. Moreover, bacitracin protected most of these nonapeptide analogs from proteolysis, although it was less effective in preventing HSV R2-(332-337) degradation. Our results indicate that it is possible to determine, in the presence of bacitracin, the relative inhibitory potencies of HSV R2-(329-337) analogs with minimal error due to proteolytic susceptibility. Moreover, HSV R2-(329-337) modifications that were found to protect the peptide against degradation might be useful to increase its efficacy in vivo.

Amino Acid Sequence↗
PubMed1976

The temporal and steady-state relationships between activation of the sodium conductance and movement of the gating particles in the squid giant axon.

1. Comparisons were made between the kinetics and steady-state properties of the sodium conductance changes and of the sodium gating currents, in the squid giant axon perfused with caesium fluoride and maintained at a high membrane holding potential. The conductance measurements were made with reduced external sodium and as much electrical compensation as possible, in order to minimize errors caused by the series resistance. 2. After an initial delay of 10-150 musec whose size was a function of the holding potential and pulse amplitude, the conductance rise on depolarization followed cube law kinetics. 3. Values of the time constant taum, as defined by Hodgkin & Huxley (1952b), were determined for membrane potentials ranging between -140 and +70 mV. They lay on a nearly symmetrical bell-shaped curve with maximum (at 6-3 degrees C) of just under 500 musec at -36 mV. 4. Values of the gating current time constant tau(V) were determined over the same potential range, and found to lie on a very similar bell-shaped curve. A computed least-squares best fit gave the maximum as 460 musec, also falling at about -36 mV. 5. The midpoint of the minfinity curve lay at -34 mV, and its slope at this point was 0-0139 mV-1. Another series of measurements on intact axons gave a midpotential of -25 mV. In the perfused axons the state of the membrane was better described by the constant field equation than by gNa. Recalculation of minfinity from PNa shifted the curve about 15 mV in a positive direction.

Animals↗
PubMedDate not supplied

Silicon diode detectors used in radiological physics measurements. Part II: Measurement of dosimetry data for high-energy photons.

Initial calibration of a linear accelerator requires physics instruments to measure accurately central axis depth-dose and off-axis data, both in and out of the beam. These data for an 8- MeV unit were first measured using film, a Farmer 0.6-cm3 ion chamber, a 0.3-cm3 ion chamber, and a 0.1-cm3 silicon diode. Both small probes and film gave a high response compared to the Farmer probe, which has a uniform energy response. Measurements with the diode interfaced to an X-Y recorder required only a fraction of the time required with the chambers, minimizing error due to change in machine output, and permitted resolution of isodose lines in the penumbra. However, corrections required at points in depth due to nonuniform energy response of the unshielded diode were laborious. Construction of a partially shielded diode which duplicates the response of the Farmer probe eliminated the necessity for corrections, permitting rapid accumulation of a wide range of depth-dose and off-axis data.

Elementary Particles↗
PubMed1977

Measurement of body temperature in neonatal mice.

A simple method is described for obtaining repeated measurements of body temperature in young mice with minimal error introduced through stress. Temperatures are measured by an external thermocouple attached to the thorax in the region of the heart. A sling around the animal's thorax provides insulation for the thermocouple from surrounding air and mild restraint of the animal during measurement. Comparison with temperatures obtained in other locations indicates that external thoracic temperature as described gives a reliable estimate of true body temperature in mice up to 21 days old. Typical results with normal mice aged 1 day to 6 wk postpartum are included, together with a brief discussion of the technique's applicability.

Age Factors↗
PubMed1991

Short-term effect of tidal pleural pressure swings on pulmonary blood flow during rest and exercise.

Because pleural pressure (Ppl) has important effects on venous return and left ventricular function, it is possible that the magnitude of respiratory fluctuations in Ppl importantly influences cardiac output (pulmonary blood flow, QL) during exercise. To examine this question, we increased (+15 cmH2O) and decreased (-11 cmH2O) the amplitude of fluctuations in Ppl by elastic loading and unloading, respectively, during steady-state exercise (50 W) and estimated the corresponding changes in QL from measurement of breath-by-breath alveolar O2 consumption [(Vo2)A] by a modification of the technique of Beaver et al. (J. Appl. Physiol. 51: 1662-1675, 1981). Load changes were applied for three breaths. Using oscilloscopic volume feedback, subjects maintained constant breathing pattern and end-expiratory volume during control and experimental breaths. This procedure minimized errors in computing (Vo2)A. Furthermore, because over the brief period of load change (especially the first 1 or 2 breaths) mixed venous and arterial O2 contents were not likely to have changed, changes in (Vo2)A reflected changes in QL according to the Fick principle. In six normal subjects, neither loading nor unloading had any effect on (Vo2)A in the first, second, or third breath (P greater than 0.5). Additional studies at rest produced equally negative results. We conclude that the magnitude of respiratory fluctuations in Ppl has no short-term effect on pulmonary blood flow at rest or during mild exercise.

Adult↗
PubMedDate not supplied

Context effects in a double-weak theory of speech perception.

The present study provides an elaboration of the "double-weak" theory of speech perception proposed by Nearey (1990, 1991). In this framework, the objects of speech perception (and production) are viewed as neither primarily auditory nor primarily gestural; rather, they are abstract, symbolic elements lawfully constrained to map onto relatively simple (but not entirely transparent) patterns in both domains. Speech cannot be understood unless both articulation and acoustics are considered: Many production strategies appear to be directed at achieving acoustically-oriented goals, yet most context effects in speech perception seem to be motivated by the consequences of gestural overlap. The double-weak framework suggests that speech perception and speech production are less-than-perfect inverses of each other. Despite long-term accommodation of each for the demands of the other, real-time production and perception may operate as autonomous subsystems. A family of perceptual models is discussed that provides varying degrees of approximation to "ideal solutions" (in the sense of minimizing error rate) to classifying production data exhibiting contextual interactions. Members of this family that provide substantial, yet incomplete, compensation for the consequences of gestural overlap appear to be adequate to account for the results of many speech perception experiments. Such partial perceptual compensation allows, in principle, for the kind of imperfect "error correction" discussed by Ohala (1981, 1990) in conjunction with hypo- and hypercorrection phenomena.

Female↗
PubMedDate not supplied

Capillary blood glucose monitoring.

The complications associated with inaccurate capillary blood glucose monitoring and poor control of diabetes are well known. This article explores the research identifying potential causes of inaccurate testing, examines ways of minimizing error and investigates quality control issues.

Bias↗
PubMed1992

Leg length discrepancy in total hip arthroplasty.

After conducting a thorough literature review, we realized that no consensus exists regarding the definition of a significant postoperative inequality. Whereas some investigators quantitate the disparity, accepting as much as 2.0 cm or in some cases less, others define a significant disparity as one that promotes adverse functional effects postoperatively. This lack of a consistent definition reflects the wide disparity of opinion regarding the problem of postoperative leg length inequalities in total hip surgery. Although the literature may lack consistency, it does reflect the collective experience of many surgeons and provides valuable insight when approaching the issue of limb lengths in reconstructive surgery of the hip. We offer the following suggestions: 1. Begin with a thorough history and physical examination. Question the patient as to whether he or she actually perceives a leg length inequality. 2. Be aware of apparent leg length discrepancies in patients with hip disease. The perceived limb shortening is usually the result of a fixed adduction contracture with little true shortening. 3. Develop a consistent approach of evaluation preoperatively, intraoperatively, and postoperatively. Employ reliable and convenient clinical measures and radiographic techniques. A method of intraoperative assessment is mandatory. 4. Redundancy in the system helps to minimize error. Good preoperative planning does not supplant the need for intraoperative assessment and vice versa. 5. Address the issue of offset in preoperative planning. Anticipate its misleading effects on intraoperative evaluation. 6. Mention potential inaccuracies regarding limb length reconstruction in total hip surgery as part of a routine preoperative evaluation. Patients' expectations should be high but temporized with realism.

Anthropometry↗
PubMed1992

Computer-aided forensic facial reconstruction.

The reconstruction of facial features on the human skull for identification purposes has, in the past, utilized either two-dimensional drafting or three-dimensional sculpting techniques. We have developed two- and three-dimensional computer-aided routines to minimize errors introduced by limits of artistic ability or by inconsistencies in the application of techniques. These routines allow generalized facial features to be manipulated to conform to the size and shape of a specific skull. Subtle alterations of the surface form, texture, and color, based on age, sex, and race, enhance the individuality of the generated facial form.

Adult↗
PubMed1991

Automated microdensitometric quantification of bone ingrowth into porous implants.

The aim of this study was to develop a technique of automated histometric quantification of bone ingrowth into porous implant bodies that minimizes errors of volume determination arising from the section thickness of histologic specimens. A theoretical and experimental deduction is provided for the calculation of implant and bone layer thicknesses from the grey levels of microradiographs made from thick-section specimens. The presented method allows rapid raising of large amounts of histometric data when a computer-aided video system is available. A histologic preparation of specimens that permits the spatial reconstruction of the examined implant volume and analysis of three-dimensional distribution of bone ingrowth is suggested.

Absorptiometry, Photon↗
PubMed1991

[Three-dimensional reconstructions in neuroanatomy].

Computer-aided 3D reconstructions of neurofunctional systems and structures are generated as a reference for neuroimaging (CT, MRI, PET). The clinical application of these 3D reconstructions requires a coordinate system and conditions resembling the intravital neuroanatomy as far as possible. In this paper the neuroanatomical Reference System (NeuRef) of the Department of Neuroanatomy of Hannover Medical School is presented. This consists of methods to record brain structures from serial sections with minimal error (less than 1 mm) and to display 3D brain models derived from such a data base. In addition, NeuRef is able to generate sections through, for instance, the visual and pyramidal system and to transfer these data onto a corresponding CT image. Therefore, this method can serve as a diagnostic aid in neuroradiology, in operation planning, and radiotherapy. It can also be used in PACS.

Brain↗
PubMed1991

What effect does glucose have on measured creatinine in the peritoneal equilibration test?

Very high glucose concentrations falsely elevate measured creatinine. An appropriate correction factor may be applied to obtain an accurate creatinine value; however, the glucose interference is of a low magnitude in most dialysate samples at a 4-hour dwell time. Clinical interpretation of the peritoneal equilibration test using uncorrected creatinine values to determine the dialysate-to-plasma ratio at 4 hours is associated with minimal error.

Colorimetry↗
PubMed1990

ARIC hemostasis study--II. Organizational plan and feasibility study.

In our previous paper, we reported the development of a blood collection and processing system (BCPS) suitable for the ARIC multicenter hemostasis study. As an additional step of preparation for the ARIC study, we incorporated this BCPS into an organizational plan to increase efficiency and minimize errors. We initially designed organizational trays for blood collection tubes and aliquot tubes and developed a coordinated step-by-step plan for the orderly processing of blood samples. Once the plan was considered workable, we carried out a pilot study to test the feasibility of this integrated organizational plan. Included in the pilot study were 95 healthy subjects randomly selected from 4 ARIC field centers, whose age and gender were comparable to those projected for the ARIC population. We determined the time lapse of filling the first tube as an index of blood flow. The overall mean time-lapse was 23 s (S.D. = 5). There was no significant difference among the field centers. We also determined the entire time lapse required for completing the sample processing. The total processing time was always less than 60 min. By performing the processing of samples in pairs, all the samples from two subjects could be completely processed in 70 min. This greatly increased the efficiency of field center operation. We evaluated the potential in vitro hemostasis activation by measuring plasma beta-thromboglobulin and platelet factor 4 levels. The geometric means of both proteins were comparable to our previously reported results. Fibrinogen, factor VII, factor VIII, von Willebrand factor, antithrombin III, protein C and activated partial thromboplastin time were analyzed.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteriosclerosis↗
PubMed1990

[Experimental criteria for interpretation of bacterial sensitivity to dioxidine determined by diffusion from the disks].

Antibacterial activity of dioxidine against aerobic and facultative anaerobic organisms under conditions of anaerobiosis i. e. conditions really observed for example in abscess cavities or necrotic tissues is 30 to 100 times as high as that under aerobic conditions. There is a relationship between sensitivity of bacteria to dioxidine under aerobic and anaerobic conditions which is expressed by the regression equation. Therefore, comparison of the MICs determined under anaerobic conditions with the growth inhibition zones formed by disks with the drug under aerobic conditions is possible. The MIC of dioxidine was determined under anaerobic conditions for 179 clinical strains of aerobic and facultative anaerobic bacteria and the growth inhibition zones of the same bacteria under aerobic conditions were evaluated with the use of disks containing 100, 75, 50, 25, 20, and 15 micrograms of the drug. The border line. MIC differentiating between resistant and sensitive strains was chosen to be equal to 4 micrograms/ml. Differentiation of the strains into sensitive and resistant ones by the values of the growth inhibition zones was performed with the method of error minimization described by C. Metzler and R. De Haan in 1974. Disks containing 25 micrograms of the drug allowed one to differentiate the strains under aerobic conditions into sensitive and resistant ones: the growth inhibition zones greater than 11 mm corresponded to the sensitive strains (the MIC smaller than 4 micrograms/ml) and the growth inhibition zones smaller than 11 mm corresponded to the resistant strains (the MIC greater than 4 micrograms/ml).

Anti-Bacterial Agents↗
PubMed1977

Quantitation of bovine immunoglobulins: comparison of single radial immunodiffusion, zinc sulfate turbidity, serum electrophoresis, and refractometer methods.

Laboratory methods designed to quantitate serum immunoglobulin were evaluated: single radial immunodiffusion, zinc sulfate turbidity, and serum electrophoresis. Estimation of immunoglobulin concentration in neonatle calves, using total protein measurements, was also evaluated. Single radial immunodiffusion proved useful for quantitation when either class or subclass information was needed. Zinc sulfate turbidity measurements gave accurate results for total immunoglobulin except when hemolysis was present in the sample. A correction factor for hemoglobin that will minimize errors resulting from hemolysis was presented. Serum electrophoresis was also found to be an accurate quantitation method. Large errors were encountered in attempting to estimate immunoglobulin on the basis of total protein.

Animals↗