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PubMed2005

Structure and function of HtrA family proteins, the key players in protein quality control.

High temperature requirement A (HtrA) and its homologues constitute the HtrA family proteins, a group of heat shock-induced serine proteases. Bacterial HtrA proteins perform crucial functions with regard to protein quality control in the periplasmic space, functioning as both molecular chaperones and proteases. In contrast to other bacterial quality control proteins, including ClpXP, ClpAP, and HslUV, HtrA proteins contain no regulatory components or ATP binding domains. Thus, they are commonly referred to as ATP-independent chaperone-proteases. Whereas the function of ATP-dependent chaperone-proteases is regulated by ATP hydrolysis, HtrA exhibits a PDZ domain and a temperature-dependent switch mechanism, which effects the change in its function from molecular chaperone to protease. This mechanism is also related to substrate recognition and the fine control of its function. Structural and biochemical analyses of the three HtrA proteins, DegP, DegQ, and DegS, have provided us with clues as to the functional regulation of HtrA proteins, as well as their roles in protein quality control at atomic scales. The objective of this brief review is to discuss some of the recent studies which have been conducted regarding the structure and function of these HtrA proteins, and to compare their roles in the context of protein quality control.

Amino Acid Sequence↗

PubMed1980

An external quality-control scheme for tricyclic antidepressants.

Some hospital clinical pharmacology departments operate quality-control schemes to monitor the efficiency of their own and outside pharmacological laboratories in analysing specimens, to maintain or improve quality of performance and to compare the reliability of different methods. The Department of St. Bartholomew's Hospital, London, has been operating a quality-control scheme in which the results from some 18 or more laboratories in analysing the mixed tricyclic-antidepressant content of spiked sera were compared for reliability, six methods being used in all. The measures employed were the overall standard deviation and coefficient of variation, a small coefficient of variation indicating a good quality of performance. Sera contained either amitriptyline and nortriptyline, or imipramine and desipramine. The coefficients of variation were considerably smaller than those reported previously and were greater for external than internal laboratories, while laboratories where tricyclic antidepressants are assayed routinely had a low variation. The skill and experience of the analyst are therefore important. Although there is room for improvement in the scheme, it has already provided valuable objective measures of performance and emphasized the need for a self-critical approach.

Amitriptyline↗

PubMed1995

Identification of Rhizobium spp. in peat-based inoculants by DNA hybridization and PCR and its application in inoculant quality control.

Procedures based on DNA hybridization and PCR were developed for quality control of Rhizobium inoculants. Inoculants for pea and goat's rue were produced by Elomestari Ltd., Juva, Finland, in sterile dry fine peat by the standard procedure used by the company. The inoculants contained Rhizobium galegae HAMBI 1174 and HAMBI 1207 and an R. leguminosarum biovar vicia strain, 16HSA, either solely or in combinations of two or three strains. DNA was isolated from 1-g samples of each peat inoculant and analyzed by nonradioactive DNA-DNA hybridization and by PCR. The hybridization probes were total DNAs from pure cultures of R. galegae HAMBI 1207 and R. leguminosarum biovar viciae 16HSA and a 264-bp strain-specific fragment from the genome of R. galegae HAMBI 1174. The total DNA probes distinguished inoculants containing R. galegae or R. leguminosarum, and the strain-specific probe distinguished inoculants containing R. galegae HAMBI 1174. The hybridization results for R. galegae were verified in a PCR experiment by amplifying an R. galegae species-specific fragment and an R. galegae HAMBI 1174 strain-specific fragment in the same reaction. When suitable probes and primers are available, the methods described here offer promising alternatives for the quality control of peat-based inoculants.

Base Sequence↗

PubMed1977

Regional quality control survey of blood-gas analysis.

We undertook an external quality control survey of blood-gas analysis in 16 laboratories at 13 hospitals. All samples were prepared in the laboratories under investigation by equilibration of blood or serum with gas mixtures of known composition. pH of serum was measured with no significant bias but with an SD of random error 0.026 pH units, which was almost twice the SD of the reference range (0.015). An acceptable random error (half SD of reference range) was not obtained in a longitudinal internal quality control suvey although there were acceptable results for buffer pH in both field and internal surveys. Blood PO2 was measured with no significant bias but with SD of random error 1.38 kPa which reduced to 0.72 kPa by excluding one egregious result. The latter value was just over half of the SD of the reference range (1.2 kPa). PCO2 of blood was also measured without significant bias but with a much smaller SD of random error of 0.28 kPa (by excluding one egregious result), which was again just over half the SD of the reference range (0.51 kPa). Measurements of blood PO2 and PCO2 seem generally acceptable in relation to their respective reference ranges but measurements of pH were unsatisfactory in both internal and external trials.

Blood Gas Analysis↗

PubMed1987

[What is dynamic optimization and how can it be used in quality control?].

By means of an interdisciplinary approach concerning quality problems of tablets an access to the method of dynamic optimization is described. It could be shown that one needs only one equation to understand the basic principles of the application of this method in quality monitoring. This understanding is promoted by graphic methods effectively. Furthermore it is demonstrated that the dynamic optimization can be useful for the organization of quality control when the result of the quality monitoring process depends on the sequence of various tests.

Chemistry, Pharmaceutical↗

PubMed2005

[Quality control in herbal supplements].

Quality and safety of food and herbal supplements are the result of a whole of different elements as good manufacturing practice and process control. The process control must be active and able to individuate and correct all possible hazards. The main and most utilized instrument is the hazard analysis critical control point (HACCP) system the correct application of which can guarantee the safety of the product. Herbal supplements need, in addition to standard quality control, a set of checks to assure the harmlessness and safety of the plants used.

Dietary Supplements↗

PubMed2005

[Indicators as the basis for quality-control in the midwifery practice].

A study on the quality of primary obstetric care in uncomplicated pregnancies carried out by means of a checklist revealed substandard factors in perinatal care in 71 out of 72 pregnancies. However there are many objections to the quality-control procedure. Some items on the original checklist had to be abandoned due to lack of evidence. In other items definitions and circumstances had not been properly considered and in some cases the patient's own wishes were responsible for a change in policy. The quality of the care delivered cannot be judged only by counting items on a checklist, but requires careful consideration of the situation and of the circumstances that led to the choices in perinatal care.

Female↗

PubMed2000

New regulatory framework for wastewater quality control in Mexico.

This paper analyses the new regulatory framework for wastewater quality control developed in Mexico. It provides a description of the Mexican government strategies for water pollution control. The discussion focuses on the policy instruments used, their evolution and the main difficulties encountered in their implementation. The new regulatory framework is discussed highlighting some of the economic implications of the reforms. The paper concludes that proper institutional development and monitoring are essential factors for the success of any policy instrument for wastewater quality control.

Developing Countries↗

PubMed1981

Alternative quality control parameters for Autobac susceptibility testing disks: use of agar diffusion zone size results.

Persistent concerns about limitation in the assessment of the quality control of Autobac 1 (Pfizer Diagnostics Division, Groton, Conn.) led us to investigate an alternative method for monitoring the performance of Autobac susceptibility testing disks. Current methodology for quality control of the system provides data which are interpreted at the high end of a numerical scale; e.g., the control strain of Escherichia coli consistently exhibits a light-scattering index value of 1.00 for all antibiotics tested. This type of end-of-scale criterion may not detect individual antibiotic disk aberrations of individual clinical isolate susceptibilities. Disk diffusion testing allows a semiquantitative, continuous-scale determination and will detect test performance variations, unless the control strain is highly resistant. During a 6-month period daily quality control procedures for 10 Autobac antibiotics tested against control strains of E. coli and Pseudomonas aeruginosa were monitored, utilizing both Autobac 1 recommendations and disk diffusion susceptibility (Kirby-Bauer) methodology. Readings were carried out by one of six technologists. Zone sizes were within a range of +/- 3 mm of a mean value of 99% of the tests with E. coli and within +/- 3 mm for 98% of the tests with Pseudomonas. Reproducibility was excellent. The high reproducibility may be due to the disk manufacturing process, which provides rigorous disk preparation and acceptability standards, to strict laboratory storage procedure, and to our own careful assessment of disk cartridges before their use for clinical susceptibility testing. We recommend that each new cartridge be tested in this manner and that a similar procedure be considered for other automated procedures in which disks are used.

Agar↗

PubMed1988

Mouse embryo quality control for toxicity determination in the Norfolk in vitro fertilization program.

Ongoing quality control is necessary as part of the maintenance and improvement of a successful human in vitro fertilization (IVF) program. Using a mouse quality-control culture system, several instrument preparation protocols were reevaluated to determine their efficiency in the control or elimination of potential toxicity. Dilute concentrations of urine and endometrial fluid were also tested. Medium rinsed through laparoscope and aspiration needles failed to support embryo development. This effect was reversed in needles that were pretreated with rinses of Dulbecco's phosphate-buffered saline. Endometrial fluid demonstrated no obvious toxic effect, but urine-exposed embryos arrested in the two-cell state. The importance of periodic evaluation of materials and their pretreatment before use in in vitro fertilization of human oocytes is essential to ensure control of potentially toxic substances.

Animals↗

PubMed1992

Quality control of food products purchased by the National School-Feeding Programme in Pernambuco, northeast Brazil, from 1985 to 1988.

The effectiveness of the Quality Control System (QCS) implemented by the Fundação de Assistência ao Escolar (FAE) for quality control of food products from different types and origins purchased by the National School-Feeding Programme (NSFP) in Pernambuco, Northeast Brazil, was evaluated. Physicochemical, microbiological, microscopical and organopetical analyses were performed in 4,860 food samples and the main causes of alterations were detected. Perishability was the characteristic used for distribution of food items into 3 main groups: A, B, and C. In accordance with 972 Quality Certificates between 1985 and 1988, 31.89 of the samples were rejected. The main reasons for rejection were innacuracies of net weight and drained weight and high moisture contents. Group B presented the smallest number of altered samples (27%); for Groups A and C these values were 33% and 44%, respectively. Our data lead to the conclusion that the QCS implemented by FAE is of paramount importance for an adequate quality control of foods provided to beneficiaries and for a good cost effectiveness of the school-feeding programme.

Brazil↗

PubMed2001

Quality control of the automatic processor.

An often ignored component of a radiology quality control program is daily sensitometric testing of automatic film processors. Sensitometric strip tests can reveal fluctuating chemical activity levels of developing solutions that can have a detrimental effect on developing films. By performing a daily sensitometric strip test before patient films are developed, time, cost, and patient radiation exposure are minimized, which reduces the number of retakes as a result of processing problems. Sensitometric strip tests also assist in quality control by making troubleshooting more specific.

Quality Control↗

PubMedDate not supplied

[Program of quality control in gynecologic cytology at the Adolfo Lutz Institute: strategies and critical analysis of results of its pilot implementation].

The Quality Control in the Gynecological Cytology Program, Instituto Adolfo Lutz, was designed to assure a high-standard of laboratory analysis for the Gynecological Cancer Detection and Prevention System in the São Paulo State Public Health Service. This study presents strategies for intra-laboratorial quality control as well as preliminary results on 32,018 cases. The methods applied for the selection of cases to be reviewed were based on clinical and cytological conditions that could mean higher risk of development of neoplasia and/or conditions that might induce difficulties of interpretation. The classification and analysis of the discrepancies found in this initial experience are the highlight points of this Program. Out of the 492 cases submitted to review, 45 had received underscored initial interpretation, although none of them fit international criteria for "false-negative". Overscores were found in 51 cases, with only three cases fitting the criteria for "false-positive". Based on this initial experience, the Quality Control Program will be applied to the other laboratories of the Public Health Service. This intra-laboratory model of control will be coupled with external supervision by Instituto Adolfo Lutz.

Adolescent↗

PubMed1987

Fluorescence intensity as a quality control parameter in clinical flow cytometry.

The fluorescence intensity (FI) and percentage of immunostained peripheral blood lymphocytes (PBLs) were tested as parameters for monitoring quality control of monoclonal antibodies (MoAbs) and the staining procedure. Several potential variables were addressed, including optimal dilutions of MoAbs, standardization of instrument functions with fluorescent microspheres, stability of day-to-day fluorescence detection with fluorescent fixed cells, and effects of separation method and storage conditions on FI and PBL antigens. Although some small (but statistically significant) changes were found in certain tests, in general the FI and percentages of MoAB-positive human PBLs provided information useful in a standardized flow cytometry quality control program. This type of standardization and quality control facilities early discovery of methodologic and reagent problems in the clinical laboratory, as well as the ability to routinely evaluate disease states associated with abnormal antigen density.

Adult↗

PubMed1980

Characterisation of the protein matrix of quality control sera by a high resolution two-dimensional electrophoresis technique.

A high resolution two-dimensional electrophoresis technique (Iso-Dalt) has been employed to characterise the protein components of freshly drawn human serum and various human- and animal-based quality control sera. This technique allows a direct comparison to be made between the protein components of different materials. Similarities have been demonstrated between the protein components (protein matrix) of freshly drawn human serum and human-, equine- and bovine-based control sera, though some differences existed between sera from these three sources, mainly in the acidic high molecular weight quadrant and the lipoprotein and haptoglobin regions. The Iso-Dalt technique also revealed differences in the protein matrices of the various human-based quality control sera tested. Differences attributable to manufacturing technique were also discernible by inspection of the two-dimensional maps of the protein matrices. Although characterisation and comparison of protein components of the matrix of serum is difficult, the Iso-Dalt technique has proved a valuable tool in this characterisation and the subsequent assessment of the similarity of quality control sera to human serum. This type of information is valuable when considering the suitability of human- or animal-based sera for use in internal and external quality control procedures.

Animals↗

PubMed1976

A regional quality control program in microbiology. II. Advantages of simulated clinical specimens.

A regional quality control program was established using simulated clinical specimens introduced into the routine workload of participating laboratories in such a way that they were not detected as quality control specimens. Comparison of performance between these specimens and lyophilized cultures showed that additional information was obtainable with the former. In particular, it was observed that common pathogens such as Escherichia coli are poorly identified in clinical material. The examination of urines was inferior to examination of other types of specimens. The implications of these findings for the practice of diagnostic bacteriology are discussed.

Canada↗

PubMed1980

Quality-control plan for intravenous admixture programs. I: Visual inspection of solutions and environmental testing.

Two components of a model quality-control plan for intravenous admixture services--a 100% visual inspection and an environmental testing program--were developed and evaluated in two hospitals. Visual inspections are recorded by technicians on two forms that detail the types of solution, container, and device defects that should be checked. One form covers stock solutions and supplies, and the other covers prepared solutions. The environmental testing program uses two forms to record performance and results of routine microbial monitoring. The detailed quality-control forms are presented. Procedures for handling defective items and contamination problems are discussed. Evaluation of the visual and environmental plans showed they provided a systematic, workable, and modest-cost method of assuring and documenting conditions in an i.v. admixture service. To assure competent preparation, use and distribution of high-quality i.v. solutions, both components of the quality-control system must be performed on a routine basis.

Drug Combinations↗

PubMed2003

[Quality control of radioligand assay for glutamic acid decarboxylase antibody].

OBJECTIVE: To supply the quality control for glutamic acid decarboxylase antibody (GAD-Ab) measurement using radioligand assay. METHODS: The quality control of GAD-Ab determined with radioligand assay in 83 batches was analyzed. RESULTS: The intra-assay coefficient of variation (CV) was 4.3% to approximately 8.3% and the inter-assay CV was 7.1% to approximately 10.8%. A ratio of signal to noise (S/N) with 15 or more was defined as a valid measurement. Of the 83 batches, 67 batches (80.7%) met with the standard and the other 16 (19.3%) were not qualified. When the results were analyzed according to the season, the failure rate in summer was significantly higher than that in winter (38.5% vs 4.8%, P < 0.05). In addition, the mean value of S/N in summer was significantly lower than that in winter ( 14.1 +/- 7. 3 vs. 21.5 +/- 5.2, P < 0.01). Among the failed batches, 68.8% (11/16) was caused by TBST buffer and 50% (8/16) due to the increased temperature of TBST buffer. Other causes for the failure included the invalidation of reagents for in vitro transcription and translation. CONCLUSION: TBST buffer and other influential factors of radioligand assay in determining GAD-Ab, should be controlled strictly to ensure a reliable and repeatable result.

Autoantibodies↗