Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Methods”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed1980

The determination of ammonium in Kjeldahl digests using the gas-sensing ammonia electrode. Comparison of the direct method with the known-addition method.

The efficacy of the ammonia electrode for analysis of the nitrogen content of a large series of Kjeldahl digests was investigated. By using this electrode, two methods for the measurement of ammonium concentrations were compared, the direct method and the known-addition method. When the direct method was used, a marked shift in the electrode potential occurred within a few hours, causing errors of 9-17% in the results. When the ammonium concentrations were calculated from the difference in electrode potential before and after addition of a known amount of an ammonium standard solution (known-addition method), it was possible to carry out reproducible measurements and the shift in the electrode potential did not influence the results. In two series of identical samples the coefficient of variation was respectively 1.45% and 0.80%.

Ammonia↗
PubMed1989

The vaginal contraceptive diaphragm and the condom--a reevaluation and comparison of two barrier methods with the rhythm method.

The use-effectiveness and continuation rates of two barrier methods of contraception, the diaphragm and condom, were studied during a two-year follow-up in a group of 85 and 98 women, respectively. All were highly motivated. Results were compared to a group of 64 women using the periodic abstinence or rhythm method, i.e. not using any contraceptive. The patients selected the method of contraception they preferred and were instructed in their proper use. Results showed good continuation rates in the groups using a diaphragm and the condom for 2 years, for a total follow-up of 5570 cycles. Pregnancy rate after 24 months of use, as calculated by Pearl's formula, was 2.48 for the diaphragm, 3.21 for the condom, and 5.19 in the rhythm group. No serious side effects or complications occurred in either group. The study demonstrated a fair acceptability and use-effectiveness for barrier contraceptive. We suggest that these harmless and complication-free methods may still be reasonable alternatives for the "modern" methods, the pill and the IUD.

Adolescent↗
PubMed1975

Catecholamines in urine; an evaluation of alumina-trihydroxyindole methods and a description of an improved method.

A critical assessment of the accuracy and practicability of five alumina-trihydroxyindole methods for the estimation of urinary catecholamines, including our proposed method, was undertaken. The recovery of noradrenaline added to urine obtained by these methods was quantitated against different types of standards, and varied from 22.9 per cent to 104.8 per cent. The major analytical problems (fluorescence suppression and loss of catecholamines during column chromatography) were evaluated and related to the recovery of the respective procedures. The improved method we developed is simple, rapid and reliable. The low fluorescence suppression and column losses of noradrenaline of this method, averaging 2.9 per cent and 5.3 per cent, respectively, resulted in a mean recovery of 92.0 per cent against an external standard. Both the chromatography step and fluorescence development are simple and short, and a batch of ten cases can be completed within 3 hours.

Aluminum↗
PubMed1988

Comparison between the photoelectric method and H2 clearance method for measuring cerebrocortical blood flow in cats.

The photoelectric method using carbon black as a nondiffusible tracer of blood was compared with the hydrogen clearance (H2) method in nine anesthetized cats. A photoelectric apparatus and H2 electrode were applied to a small region of the cerebral cortex (left ectosylvian gyrus) for simultaneous measurement of the regional CBF. The values of CBF(H2) and CBF(photoelectric) were 50.7 +/- 19.2 and 52.1 +/- 14.5 ml.100 g-1.min-1, respectively. CBF(H2) and CBF(photoelectric) were found to correlate well (r = 0.588, p less than 0.01) when changes in CBF were induced by CO2 inhalation, exsanguination, hyperventilation, and occlusion of the middle cerebral artery. The correlation between CBF(H2) and CBF(photoelectric) was much better in the case of intraindividual comparisons (r = 0.957, p less than 0.01). In addition to its merits in common with the H2 clearance method, such as handiness, low cost, and strict regionality, the photoelectric method displayed the following advantages: time-to-time measurements of CBF (less than 20 s), immediate display of the microcirculatory flow pattern, and simultaneous monitoring of cerebral blood volume. However, measurements from deep structures of the brain are better performed by the H2 method despite the disadvantage of the use of a potentially explosive gas.

Animals↗
PubMed1993

A numerical method for allocating microbial isolates to strain types when characterized by typing methods that are not 100% reproducible.

Many methods for typing microbial strains are not 100% reproducible. This can create problems when deciding whether different groups of isolates are really distinct or represent typing errors or variation of a single strain. Neither hierarchical clustering nor iterative partitioning methods are suited for analysing such data. A novel iterative partitioning method is described which allows for the uncertainty of the typing method in use. Before grouping strains, the maximum dimension of the groups is set based on a previous knowledge of the typing method's reproducibility. Isolates are only allocated to a group if they differ from that group's typical strain type by less than the number of reaction differences required to distinguish between two strains. In a series of Monte Carlo studies the accuracy of strain allocation was found to be very good, even when the two groups were situated close to each other.

Bacteria↗
PubMed1985

A comparison of reference method values for sodium, potassium and chloride with method-dependent assigned values.

The concentrations of sodium, potassium, and chloride in various control sera were determined by reference methods. The reference method values were compared with the corresponding method-dependent assigned values. Sodium: Measurements by flame photometry and ion selective electrodes differed on the whole by less than 1% from the reference method value; determinations by photometry differed, however, by -4.7%. Potassium: The mean bias was -1.2% with flame photometry and -0.4% with ion selective electrodes, whereas nephelometric procedures differed by -1.9 or -4.8%. Chloride: Satisfactory agreement was obtained with values given for ion selective electrodes (-0.3%), for some coulometric procedures (-0.7 and 0.4%), and photometric determinations using mercury rhodanide (-0.5 and +0.7%). Values for mercurimetric titration and for photometric determinations using mercury 2,4,6-tri-(2-pyridyl)-s-triazine differed by + 2.5 and + 1.8%. Proposals concerning the allowable deviation from reference method values are discussed.

Chlorides↗
PubMed1988

[The determination of oxalate in urine by enzymatic method using oxalate oxidase: comparison between enzymatic and gas-chromatographic methods].

Urinary oxalate is one of the most important constituents of urolithiasis, but the determination of oxalate in urine has not been performed as a routine laboratory examination. We tried to measure oxalate in urine by the enzymatic method with oxalate oxidase. The linearity of the standard curve and reproducibility of this method were confirmed. (Linearity: r = 0.996, S.D./mean: 0.5-3.6%, recovery rate: 99.5 +/- 3.3 (mean +/- S.D.)%) The correlation between this method and gas-chromatographic method was 0.926. The enzymatic method with oxalate oxidase can be utilized for determining the urinary oxalate as a routine laboratory examination.

Chromatography, Gas↗
PubMed1980

[Determination of proteins with the Coomassie brilliant blue G 250 method. IV. Use with cerebrospinal fluid proteins and comparative analysis with the biuret and Lowry methods].

The method of Bradford with Coomassie Brillant Blue G 250 for protein assay has been applyed to CSF in comparison with biuret and Lowry's methods. The results of Coomassie method closely agree with Lowry, and are similar to those of biuret. It is suggested to replace the previously used methods for CSF protein assay by the Bradford's method, because it keeps the sensitivity of Lowry and the simplicity of biuret. It adds too the advantage of requiring less time.

Cerebrospinal Fluid Proteins↗
PubMed1981

Preincubation of serum aspartate aminotransferase with pyridoxal 5'-phosphate in the SMAC: comparison with revised DuPont aca method and recommended IFCC method.

The method for continuous-flow assay of aspartate aminotransferase with the Technicon SMAC was modified to include preincubation of the serum enzyme with pyridoxal 5'-phosphate, to be consistent with the recommendations of IFCC and the Standards Committee of AACC. Preliminary estimates of the imprecision of the modified method on SMAC gave day-to-day standard deviations of 5.3 U/L at mean of 48 U/L (n = 66) and 6.2 U/L at 155 U/L (n = 61). Added bilirubin, sodium pyruvate, ascorbic acid, and endogenous lipids did not interfere. Comparison of results for 50 samples by this method with those by the manual IFCC method gave y = 1.1113x - 0.3 U/L, Sy/x = 4.4 U/L, and r = 0.997. Similar data are presented for the revised AST method for the DuPont aca discrete analyzer. Clinical data show that AST activities increase by as much as 200% when the serum is preincubated with pyridoxal 5'-phosphate.

Animals↗
PubMed1991

The AMeX method: a multipurpose tissue-processing and paraffin-embedding method. III. Extraction and purification of RNA and application to slot-blot hybridization analysis.

RNA was extracted from tissues processed by a new fixation and paraffin-embedding method (the AMeX method) and examined by Northern blot analysis and slot-blot analysis. The RNA extraction method for AMeX-processed tissue sections after the deparaffinization step was the same as that for fresh materials. The total amount of cellular RNA extracted from AMeX-processed mouse liver tissue was slightly less than that extracted from fresh tissue. In tissues of malignant lymphoma, the total amount of cellular RNA extracted from 25 sections each 20 microns thick was about 1.6-1.8 micrograms/mm2, regardless of the histological subtype and period of storage. The extracted RNA was moderately degraded, and usually could not be used for Northern blot hybridization analysis. The intensity of ethidium bromide staining and the hybridization signals of RNA extracted from AMeX-processed tissues were usually reduced in comparison with RNA from fresh material, but specific signals could be detected by slot-blot hybridization analysis. We have demonstrated previously that the AMeX method preserves high-molecular-weight DNA and various antigens. Since the present study showed that information on mRNA can be obtained from AMeX-processed tissue, the versatility and usefulness of this method were further proven.

Animals↗
PubMed1993

An ultrafiltration method for the removal of interfering agents and its application to the determination of free ammonia in solutions of oxystarch by the Berthelot reaction method.

Oxystarch was chosen as a model compound for studying biological ammonia-sequestering systems. Ammonia was determined by use of an ion-selective electrode, by L-glutamate dehydrogenase (L-GDH), and by two different Berthelot procedures, in the presence and absence of oxystarch. In the presence of total oxystarch the Berthelot method, particularly when low concentration reagents were used, detected significantly less (P < 0.10) free ammonia than either L-GDH or ion-selective electrode methods. A 0.5-kDa molecular weight cutoff sample ultrafiltration step was added prior to analysis by L-GDH and Berthelot procedures. To facilitate complete removal of oxystarch by the ultrafiltration step, oxystarch was dialyzed before use, yielding a high-molecular-weight fraction (> 1 kDa). Removal of high-molecular-weight oxystarch species and bound ammonia by ultrafiltration of samples prior to assay completely negated discrepancies between ammonia levels measured by L-GDH and both Berthelot methods. The correlation of the levels of measured ammonia, as determined by L-GDH and Berthelot methods, in mixtures with high-molecular-weight oxystarch was significantly improved by the addition of the sample ultrafiltration step. Improved correlation of results from such fundamentally different methods demonstrates the removal of interfering agents as well as the nonperturbatory nature of the improved procedure. The addition of such an ultrafiltration step may be applied to the determination of ammonia by the otherwise interference-prone Berthelot assay in mixtures with any interfering macromolecules, without the inconvenience or potential variabilities associated with distillation or diffusion procedures.

Ammonia↗
PubMed1995

Stereological methods based on point counting and unbiased counting frames for two-dimensional measurements in muscles: comparison with manual and image analysis methods.

Stereological methods, using the principle of point counting and unbiased counting frames, for the estimation of muscle area, total fibre area, number of muscle fibres and mean fibre area are described in detail. Their practical application is demonstrated on cross-sections of the rat soleus muscles. It is shown that the efficiency of these methods is high and their results are comparable with those achieved by the conventional manual and image analysis methods. The main advantages of two-dimensional stereological methods in muscle morphometry are pointed out: measurements are made directly on specimens under the microscope and in the simplest implementation do not require sophisticated and expensive technical equipment. Furthermore, unbiased results are obtained, no segmentation and edge effect problems arise and the quantity of work invested in stereological estimation is reasonable. Based upon the study of the efficiency of used stereological methods, a suitable test system for muscle morphometry is proposed.

Animals↗
PubMed1991

Comparison of the Ruthenium hexammine trichloride method to other methods of chemical fixation for preservation of avian physeal cartilage.

Several methods of chemical fixation of avian physeal cartilage were compared. The Ruthenium hexammine trichloride method was compared to isotonic glutaraldehyde and neutral buffered formalin for light microscopy and paraffin embedment, and to two osmium-ferrocyanide methods and a combination of 1% glutaraldehyde and 4% formaldehyde for electron microscopy. Only the Ruthenium hexammine trichloride method prevented the loss of matrix proteoglycans and shrinkage of chondrocytes. In undecalcified paraffin-embedded cartilage, preservation of matrix and cellular detail was excellent, but Ruthenium hexammine trichloride interfered with Haematoxylin and Eosin staining. Glutaraldehyde gave more intense eosinophilia than neutral buffered formalin. Ultrastructurally, the Ruthenium hexammine trichloride method was the most consistent and gave the best overall fixation. Matrix elements and cellular and nuclear membranes were well preserved. It did result in vacuolation of the cytoplasm and mitochondria, and it increased granularity of the cytoplasm, chromatin, and rough endoplasmic reticulum. Other fixatives produced minimal vacuolation and finer granularity, but preservation was less consistent, cell/matrix contrast was often excessive, and they caused shrinkage of all chondrocytes. Large dilatations of the rough endoplasmic reticulum that appear to be cytoplasmic inclusions by light microscopy are described for the first time in avian cartilage.

Animals↗
PubMed1994

The Lactational Amenorrhea Method (LAM): a postpartum introductory family planning method with policy and program implications.

It is well accepted that breastfeeding contributes significantly to child survival and child nutrition. Healthful child spacing is associated with improved birth outcomes and maternal recovery. On a population basis, breastfeeding may contribute more to birth spacing than all family planning use combined in many countries. However, while breastfeeding does provide a period of infertility, until recently, there was no reliable way for an individual woman to capitalize on this lactational infertility for her own efficacious child spacing. The Lactational Amenorrhea Method (LAM) is a new introductory family planning method that simultaneously promotes child spacing and breastfeeding, with its optimal nutrition and disease preventive benefits for the infant. LAM, as it is called, is based on the utilization of lactational infertility for protection from pregnancy and indicates the time for the introduction of a complementary family planning method. LAM is recommended for up to six months postpartum for women who are fully or nearly fully breastfeeding and amenorrheic, and relies on the maintenance of appropriate breastfeeding practices to prolong lactational infertility, with the concomitant delay in menses return. A recent clinical trial confirmed the theoretical 98% or higher effectiveness of the method and field trials are demonstrating its acceptability. Nonetheless, some demographers and family planning organizations continue to debate its value. The development, efficacy, and sequelae of the method are presented using data from several studies by the authors.

Amenorrhea↗
PubMed1995

Error analysis of table look-up method for cerebral blood flow measurement by 123I-IMP brain SPECT: comparison with conventional microsphere model method.

While N-isopropyl-p-[123I]iodoamphetamine (IMP) is commonly used as a flow tracer, significant clearance from the brain causes underestimation of CBF as compared with true CBF when conventional microsphere model analysis is applied. We previously reported a simple "table look-up" method for CBF measurement using IMP taking into account this clearance effect. The method is based on a two-compartment model, the K1 (corresponding to CBF) and k2 constants being obtained from a table from the ratio of the 1st SPECT (40 min) to the 2nd SPECT (180 min) counts. Arterial input data used were obtained by one point blood sampling 10 min after IMP infusion against the standard input function. In the present study, this approach was compared with conventional microsphere model analysis. For 30 subjects, the latter method entailed 8 min continuous arterial blood sampling after IMP infusion and the use of SPECT data at the end of this period, calibrated by a count ratio of 8 min/40 min planar images of whole brains. A good correlation was observed between the two methods (r = 0.88), but an overestimation of table look-up method CBF as compared with microsphere model CBF was observed contrary to theoretical predictions. Limitations in the estimation of SPECT data at 8 min, obtained with SPECT data at 40 min for calibration of the count ratio of 8 min/40 min whole brain planar images, might be responsible for this.

Amphetamines↗
PubMed1978

An assessment of the radial diffusion method for the measurement of pepsin in gastric secretion and its comparison with the haemoglobin substrate colorimetric method.

The radial diffusion method of pepsin assay has been compared with a modified Anson-Mirsky colorimetric method. Though claimed to measure accurately over a wide range, we found that the assay range of the radial diffusion method was only 10 to 100 mg/l; even with these narrow limits, it was inaccurate. In contrast, the colorimetric method was much more rapid, sensitive and could accurately measure a wide range of 0.5 to 500 mg/l. The colorimetric technique is therefore the superior method.

Diffusion↗
PubMed1987

An improved high performance liquid chromatographic method for determining urinary oxalate, making use of an ID-MS reference method.

With the aid of a newly developed isotope dilution mass spectrometric (ID-MS) measurement of urinary oxalate, an existing HPLC method for assaying this substance was investigated. Results obtained with this method were too high, apparently due to a systematic error. Subsequently, this method was improved by additional prepurification in three different ways: (a) precipitation with CaSO4 to Ca-oxalate, (b) adsorption (and subsequent desorption) to columns supplied with a commercial kit for urinary oxalate and (c) the enzymatic destruction of urinary oxalate present. This work demonstrates the successful use of a reference method in improving a newly developed analytical procedure and presents a reliable and reproducible HPLC method for determining urinary oxalate.

Chromatography, High Pressure Liquid↗
PubMed1994

A comparison of methods for phase II cancer clinical trials: advantages of the triangular test, a group sequential method.

In cancer, the purpose of Phase II studies is to determine whether the response rate p to a new treatment is greater than a prespecified value p0, defined as the largest response rate for which Phase III studies are not worthwhile. It concerns, for example, determining whether the response rate to a new drug is greater than 20%. The main problem is of a decision making nature, and amounts to the comparison of an observed percentage with a theoretical percentage. One way of resolving it is to perform a single statistical analysis after the inclusion of a predetermined number of patients N, but it is not always possible because of high values of N. Furthermore, this approach presents ethical problems when elements in favor of inefficacy or efficacy are available early in the trial. For these reasons, several authors have developed methods which allow to perform repeated analyses and possibly to reach an early conclusion of the study: two-stage, multistage, sequential and group sequential methods. This article considers the main decision making methods proposed in the literature for Phase II studies in oncology. The bibliographic study, which highlights the interest of using group sequential methods, and especially the Triangular Test, is confirmed by a comparative study of the statistical properties of the different methods.

Clinical Trials, Phase II as Topic↗