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At least 523 records · Page 29Linked to original sources
PubMed2003

Protein quality control in the endoplasmic reticulum.

Protein folding and quality control in the endoplasmic reticulum (ER) are synchronized mechanisms ensuring that only properly folded proteins are integrated in the plasma membrane or secreted from the cell. These mechanisms act in close collaboration with the molecular machinery involved in retrograde-translocation and degradation of non-native proteins and with the ER-stress activated signalling systems. The common goal of these mechanisms is to prevent expression and secretion of misfolded proteins. Protein misfolding can be detrimental to the cell and contributes to the disease mechanism in several inherited disorders, e.g. cystic fibrosis, familial hypercholesterolemia and diabetes insipidus. This review outlines the molecular mechanisms in protein quality control occurring in the ER, signalling caused by ER stress, and finally ER associated protein degradation.

Animals↗
PubMed2000

Audit and internal quality control in immunohistochemistry.

AIMS: Although positive and negative controls are performed and checked in surgical pathology cases undergoing immunohistochemistry, internal quality control procedures for immunohistochemistry are not well described. This study, comprising a retrospective audit, aims to describe a method of internal quality control for immunohistochemistry. A scoring system that allows comparison between cases is described. METHODS: Two positive tissue controls for each month over a three year period (1996-1998) of the 10 antibodies used most frequently were evaluated. All test cases undergoing immunohistochemistry in the months of April in this three year period were also studied. When the test case was completely negative for a given antibody, the corresponding positive tissue control from that day was examined. A marking system was devised whereby each immunohistochemical slide was assessed out of a possible score of 8 to take account of staining intensity, uniformity, specificity, background, and counterstaining. Using this scoring system, cases were classified as showing optimal (7-8), borderline (5-6), or unacceptable (0-4) staining. RESULTS: Most positive tissue controls showed either optimal or borderline staining with the exception of neurone specific enolase (NSE), where most slides were unacceptable or borderline as a result of a combination of low intensity, poor specificity, and excessive background staining. All test cases showed either optimal or borderline staining with the exception of a single case stained for NSE, which was unacceptable. CONCLUSIONS: This retrospective audit shows that immunohistochemically stained slides can be assessed using this scoring system. With most antibodies, acceptable staining was achieved in most cases. However, there were problems with staining for NSE, which needs to be reviewed. Laboratories should use a system such as this to evaluate which antibodies regularly result in poor staining so that they can be excluded from panels. Routine evaluation of immunohistochemical staining should become part of everyday internal quality control procedures.

Humans↗
PubMed1995

Quality control of platelet concentrates by the Thrombostat 4000.

Quality control of platelet concentrates (PC) is an important prerequisite for good transfusion praxis. However, direct measurement of platelet function is complex, since available methods (e.g. aggregometry, serotonin release) are time consuming and require special equipment. Therefore a test system is needed, which is easy to handle, fast, and achieves reliable results. The present paper compares the results of conventional platelet function tests with those of a modified in-vitro bleeding test (IVBT) (Thrombostat 4000) in liquid-stored and cryopreserved PCs. A high correlation between aggregometry, serotonin release, GMP 140 expression upon stimulation, and IVBT was demonstrated. Therefore IVBT seems to be a good alternative to the conventional platelet function tests for quality control of PCs. In addition, a good correlation between the results of IVBT of patients' blood after PC transfusion and IVBT of patients blood before transfusion supplemented with platelets of the respective PC could be found. Therefore IVBT seems to be able to predict PC transfusion success. However, since these data were obtained in a small sample undergoing bone marrow transplantation, further studies are needed to verify this hypothesis.

Bleeding Time↗
PubMedDate not supplied

[Biological safety in dentistry: development of a useful method for quality control of sterilization].

534 autoclaves from Rosario dentist offices were controlled by a method developed in our laboratory, that consists in: a) a procedures instruction; b) a survey ; c) a colorimetric control; d) a biological control. By this method it is possible to detect the mistake in the autoclave function by only one step. The results showed that 86.90% of the autoclaves lacked thermometers, 76.60% lacked manual thermostats, 83.33% were automatic and 58.80% did not sterilize. It can be concluded the necessity of a periodic control by this method, the importance of a commercial quality control of the furnaces and the urgency of continuous education over biosafety concepts.

Argentina↗
PubMed1977

Use of equilibrated blood for internal blood-gas quality control.

We have used equilibrated human blood for blood-gas quality control since 1970. In blood equilibrated 24 h after shedding, gas tensions are stable for 4 to 6 h at 0 to 4 degrees C; each control specimen is analyzed several times during that period to resolve malfunctions, etc. Three-fourths of all errors in gas-tension measurement detected with equilibrated blood were detected with the highest-tension controls. Equilibrated blood controls signal about one error every 14 d on each instrument. For more complete quality control, we supplement analysis of equilibrated blood with other sorts of controls, comparing results obtained by assaying each patient's specimen on two instruments being our most effective adjunct. Such comparisons have identified erroneous assays in 3.9% of the specimens tested. The magnitude of interinstrument discrepancies (random errors) have ranged from 9 to 100% of the appropriate determinations. We use control data derived from equilibrated blood analysis for special management purposes (evaluating instruments, quantitating micro- vs. macro-sampling discrepancies, and decreasing instrument-repair costs).

Acidosis↗
PubMed2005

Quality control of SMBG in clinical practice.

We present results of quality control of self-monitored blood glucose (SMBG) performed in diabetes outpatient clinic. The tests included: inspection of glucose meter, blood glucose self-measurement by a patient, glucose measurement by point-of-care analyzer used in a clinic and with the laboratory method. In the study 158 glucose meters were controlled and compared with HemoCue glucose analyzer used in the clinic as the reference. 122 glucose meters readings were also compared with the reference laboratory method. Tested glucose meters included: Accutrend {18}, Glucotrend {59}, Precision QiD {39}, One Touch {26} and Glucocard II {16}. Reference glucose assays were performed using glucose oxidase method on Hitachi 911 analyzer. Glucose concentrations measured by the controlled glucose meters ranged from 36 to 425 mg/dL. The analytical bias of the glucose meters amounted from 2.48% to 8.27%. Correlation coefficient between results obtained by the tested glucose meters and HemoCue analyzer ranged from 0.957 to 0.980 and between glucose meters and laboratory method from 0.955 to 0.985. Passing-Bablok agreement test and Deming regression analysis indicated good concordance of results between all the tested glucose meters and HemoCue analyzer, whereas good agreement with the laboratory method was found for Accutrend, Glucotrend, Precision QiD and One Touch glucose meters. In conclusion, good analytical performance of the employed glucose meters and a bias less than 10% from the reference values were found. Results of this study show the possibility for routine, convenient for the patient quality control of SMBG in an outpatient clinic.

Blood Glucose Self-Monitoring↗
PubMed2000

Biological quality control for exercise testing.

BACKGROUND: A study was undertaken to evaluate the use of a biological quality control programme for a computer controlled, breath-by-breath exercise test system over a 2.5 year period. METHODS: One healthy volunteer performed a regular progressive treadmill test with breath-by-breath measurements of oxygen uptake (VO(2)), carbon dioxide output (VCO(2)), ventilation (VE), and the ECG heart rate (HR). Following a familiarisation period, five consecutive tests were performed and the measurements at peak exercise were averaged to give baseline values. All tests were compared with these values. RESULTS: A total of 35 tests were recorded. The within subject standard deviation for measurements at peak exercise were 52 ml/min for VO(2), 74 ml/min for VCO(2), 3.1 l/min for VE, and 3 beats/min for HR. The mean (SE) percentage variation in measurements at peak exercise compared with the baseline values was +0.37 (0.30)% for VO(2), -0.10 (0.39)% for VCO(2), -0.88 (0.52)% for VE, and +1.2 (0.26)% for HR. The variability present in measurements made during high and moderate intensity exercise (73% VO(2)peak) was not significantly different (p>0.05). During the study period the quality control detected a fault on the oxygen analyser which was not apparent from the automatic calibration. CONCLUSIONS: Regular quality control using a healthy volunteer allows all components of the breath-by-breath system to be checked simultaneously and in a manner which is consistent with its clinical use. This practice can highlight faults not detected by automatic calibration.

Calibration↗
PubMed1992

Computerization of general practices and quality control. Blood glucose regulation in type 2 diabetics investigated in the Registration Network family practices.

The extent to which computerized medical administration facilitates quality control was studied using as an example the quality of blood glucose regulation in diabetics supervised by general practitioners in 11 computerized practices. Systematic use of the general practice computer rapidly provided an unequivocal answer that 37% of such patients were not regulated in accordance with the guidelines for type 2 diabetes mellitus of the Dutch College of General Practitioners. The extra workload for the participating general practitioners was minimal. Automated recording of problem lists, as applied in the general practices belonging to the Registration Network, facilitates access to data on chronic diseases and risk factors for purposes of research, quality control and quality assessment.

Blood Glucose↗
PubMed2001

Molecular diagnosis of Y chromosome microdeletions in Europe: state-of-the-art and quality control.

The polymerase chain reaction (PCR) screening of microdeletions of the Y chromosome has become an important diagnostic step in the work-up of male infertility. However, there is no agreement about how this diagnosis should be performed. There are suggestions that the large variation in deletion frequency reported in the literature could be due to the various selection criteria of the patients analysed, although methodological aspects may play a role as well. As for other genetic diseases, molecular diagnosis of Y chromosome microdeletions should be controlled by adopting strict internal quality control measures and by participating in external quality assessment schemes. Such an external quality assessment project is presently being organized jointly by the European Academy of Andrology and the European Molecular Genetics Quality Network. Three preliminary trials have given a state-of-the-art picture of the diagnostic performance in various European laboratories, showing an overall rate of misdiagnosis of approximately 5% for both AZFb and AZFc regions, and providing data useful in the generation of guidelines for the molecular diagnosis of Y chromosome microdeletions.

Cytogenetic Analysis↗
PubMed1997

Processor quality control in laser imaging systems.

Sensitometric techniques for performing processor quality control in laser imaging systems are analyzed in this study. The sensitivity of conventional x-ray films using simulated screen-light sensitometry is compared with helium-neon (HeNe) laser film exposed with a simulated red-light sensitometer, a standalone (reference) laser sensitometer, an experimental (unstable) laser sensitometer, and laser printers. Infrared (IR) laser film exposed with an IR laser diode and a simulated IR sensitometer are also evaluated. It is demonstrated that laser-generated step tablets provide an easy and reliable method of performing laser film processor quality control.

Helium↗
PubMed1999

[Studies on pharmacognostic identification and quality control standards for hongqu].

OBJECTIVE: To develop effective methods for quality control of the traditional Chinese drug Hongqu. METHOD: TLC and microscopic identification were performed. HPLC was used to determine the content of lovastatin. RESULT: A lot of hyphae and spores in Hongqu were observed under microscope. The spot of lovastatin was found on the TLC chromatogram. The standard curve of lovastatin by HPLC was linera in the range of 5 micrograms/ml-100 micrograms/ml. The average recovery of lovastatin was 96.4%, RSD 3.68%, n = 5. CONCLUSION: The methods are simple, sensitive and accurate. These studies provide the scientific basis for quality evaluation and quality control of Hongqu.

Chromatography, High Pressure Liquid↗
PubMed2002

The transitional ER defines a boundary for quality control in the secretion of tsO45 VSV glycoprotein.

Quality control in the secretory pathway limits forward transport of newly synthesized cargo proteins to those that have acquired their fully folded conformation. To determine which organelles participate in this conformation-dependent sorting process, we analyzed the trafficking of the temperature-sensitive, thermo-reversible folding mutant of vesicular stomatitis virus glycoprotein (tsO45 G protein) in VERO cells. Using temperature blocks, the G protein could be localized to the ER (39.5 degrees C), to the vesiculo-tubular clusters (VTCs, 15 degrees C), and to the trans-Golgi network (TGN, 20 degrees C). To localize the G protein specifically to ER exit sites, we incubated cells at 10 degrees C. The exit sites contained Sec13p, a COPII component, and were devoid of calnexin and other ER chaperones. We found that if the G protein in the exit sites was misfolded by a temperature shift from 10 degrees C to 39.5 degrees C, it failed to enter the VTCs. Instead, it was returned to the reticular ER where it associated with calnexin. However, if the G protein was in the VTCs or beyond, its folding status no longer affected further transport. The observations indicate that quality control took place in the ER and in the ER transitional elements, but not in the VTCs or the Golgi complex. The results provide a way to discriminate biochemically between exit sites and VTCs, two related structures that are difficult to distinguish from each other.

Animals↗
PubMed1979

Intralaboratory quality control of hematology. Comparison of two systems.

Two systems for quality control have been compared, viz., the whole-blood control preparation method and the algorithm method using the geometric moving average XB and a new estimator Y. The system involving whole-blood controls has the advantage of simplicity of operation, but the economic cost of commercial preparations is often high. The algorith system has the advantage that results of all the test samples are used in the calculation; to some extent, this provides a buffer against random variation. The number of count-outs in a given channel is related to the precision of the channel, which in turn is a function of the number of determinations and calculations required for that result. An error of around 1% is introduced into the result each time a calculation is performed. A successful quality control scheme should contain elements of both control preparation and algorithm methods.

Erythrocyte Count↗
PubMed2000

Lessons from a multicentre study of the detectability of viral genomes based on a two-round quality control of GB virus C (GBV-C)/hepatitis G virus (HGV) polymerase chain reaction assay.

The aim of this study was to determine whether multicentre quality controls for the detectability of viral genomes could contribute to the improvement of diagnostic performance in the participating laboratories. The study was carried out during two successive rounds, during which 18 laboratories specialized in nucleic acid testing analyzed, through a polymerase chain reaction (PCR) assay, a common panel of GB virus C (GBV-C)/hepatitis G virus (HGV) RNA-positive and -negative samples. During the first round, the laboratories used either an 'in-house' PCR procedure or a partly standardized commercial test. After decoding the results of the first round, the procedures of the participating laboratories were compared in order to establish a consensus procedure deduced from those of the laboratories which provided the best results. During the second round, each participating laboratory could use the resulting consensus procedure, or its own procedure, or both. The results of this quality control study indicated that, whatever method used, even specialized and trained laboratories may give false-negative or false-positive results. The commercial assay did not guarantee a systematic high quality level of results. The striking heterogeneity of results observed among laboratories using the same commercial assay confirm that molecular biology methods need skilled technicians. The results of this quality control study suggest that full standardization of viral genome detection, including all steps of the procedure, is necessary and that the laboratories performing PCR should participate in repeated quality control studies, whatever technique is being used.

Flaviviridae↗