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At least 379 records · Page 21Linked to original sources
PubMed1988

A comparative study of the effects of aging on the responsiveness of the cholinergic receptor of the isolated ileum of mouse and rat.

The responsiveness of the cholinergic receptor (ChR) of the isolated ileum of mouse and rat was characterized by determining the ED50 of acetylcholine (ACh) and pA2 of mepenzolate (MPZ) in tissues from animals of different ages. The ages (in months) of mice were 3, 6 and 18 and; 3, 6, 12 and 24 for rats respectively. The responsiveness of ChR in mice and rats decreased with age. There was no difference in the pA2 between the preparations derived from mice and rats nor was it affected by age. The results of this investigation suggest that (1) changes in the peripheral ChR with age may have potential in the understanding of central aging process and (2) the use of age rather than the weight of animal may provide reproducible data in studies using isolated preparations.

Acetylcholine↗
PubMed1986

An optimized method for measuring cyclosporin A with 125I-labeled cyclosporin.

We evaluated the use of the new iodinated ligand for the in vitro measurement of cyclosporin A by radioimmunoassay (RIA). Substitution of the iodinated cyclosporin (125I-CyA) for the corresponding tritium-labeled analog (3H-CyA) considerably simplifies and accelerates the currently available RIA, and improves its precision. Analysis of the respective dose-response curves showed that the 50% B0 value was lower for the 125I-CyA assay than for the 3H-CyA assay (37 vs 77 micrograms/L). Use of whole-blood specimens minimized interferences from temperature and hematocrit. We conclude that the use of 125I-CyA in a commercially available RIA for whole-blood specimens is accessible to most laboratories and provides rapid, reproducible data for management of transplant patients.

Computers↗
PubMed1987

Cataractogenic risk factors.

It was the intention of this study to provide a review on cataractogenic risk factors which are already known from the early and recent literature. Additional causative or mutual causative factors have been derived from recent studies [Bloemendal et al., 1984; Hockwin et al., 1984; Rink and Hockwin, 1985b; Eckerskorn et al., 1986]. Under this view it seems necessary to classify the cataractogenic risk factors into 3 subgroups: (a) factors from which we definitely know their cataractogenic potential and their mode of action (e.g. diabetes); (b) factors from which we certainly know that they are closely related to cataractogenesis, without knowing the mechanism of action, and (c) factors that are only assumed to be involved in the development of cataractogenesis; however, neither origin nor mode of action has been explained (e.g. nicotine or alcohol intake). For further epidemiological research it would be important to introduce many of the known factors into the corresponding questionnaires. As we may assume that different risk factors with differing mechanisms of action are responsible for the variety of cataract types, it is a prerequisite for future studies to improve the cataract classification systems possibly by using the Scheimpflug camera method [Eckerskorn et al., 1986] which results in hard, reliable and highly reproducible data.

Adolescent↗
PubMedDate not supplied

[Concentration osmometer for determining the amount of water bound to the macromolecular substrate of blood substitutes].

Consideration is given to the technique and the device for detecting water amount linked to high-molecular compounds presenting the base for blood substitutes. The device is simple in use, outputs reproducible data comparable to the well known results (e.g. for polyglucine). It should be recommended for evaluating hemodynamic parameters of newly developed blood substitutes.

Blood Substitutes↗
PubMedDate not supplied

Interlaboratory comparison of analyses for heavy metals in clam tissue.

Results are reported for an interlaboratory study conducted to assess the reproducibility of analyses for lead, copper, cadmium, and zinc. The 10 participating laboratories analyzed 2 samples of freeze-dried clam tissue and 1 disguised sample of NBS Oyster Tissue. Interlaboratory variations were observed for all metals, although the methods yielded reproducible data for Cu and Zn with average interlaboratory coefficients of variation of 15 and 11%, respectively. The performance of methods used for Cd and, more so, for Pb was less than satisfactory. Cadmium levels in the 3 samples ranged from about 0.7 to 3.7 ppm with an average interlaboratory coefficient of variation (CV) of 24%. Lead levels in the 3 samples were about 0.5 ppm with an interlaboratory CV of 68%. Some laboratories' results were consistently high or low but data were insufficient to relate these trends to one particular variable. Results from this study were compared with 5 other studies reported in the literature since 1980. Coefficients of variation from all studies were comparable for samples with similar metal concentrations.

Animals↗
PubMed1985

Trypanosoma cruzi: isolation and characterization of two clones derived from neonatal mice.

The Tulahuen strain of Trypanosoma cruzi was cloned in 15 C3H/Anf neonatal mice. Ten of these 15 neonates became parasitemic before the 12th day and died before the 19th day after the inoculation of a single bloodstream trypomastigote. Two clones were selected and maintained, while the other isolates which did not grow in a liquid metacyclic stage culture (LMC) medium were eventually discarded. The kinetics of in vitro growth and transformation from epimastigote to metacyclic trypomastigote of these two clones were characterized in LMC medium at 27 degrees C. Infectivities for vertebrate cells in vitro were retained by these two clones during the period of cultivation. The tropism for brain, heart, lungs, esophagus, stomach, large intestine, liver, pancreas, spleen, lymph nodes, kidneys, bladder, and skeletal muscles was also examined in the mice. The communication describes the establishment and characterization of T. cruzi clones. The utilization of these cloned parasites should produce some advantages in generating reproducible data in investigations.

Animals↗
PubMed1986

Evoked sensory nerve action potentials: effect of different recording electrodes on distal latencies and amplitudes.

The evoked sensory nerve action potentials (ESAP) of the median nerve were studied in 20 subjects using an antidromic technique, recording the distal latency to onset and to peak, and peak to peak amplitude, using three different recording electrodes. The electrodes used were the TECA digital ring electrodes, AERO MED wire loop stretch and squeeze-type electrodes, and Neurodiagnostic finger clip electrodes. Because the Neurodiagnostic finger clip electrodes are wider than the others, they were placed at different points over the proximal and distal interphalangeal joints to evaluate any changes in the ESAP caused by different interelectrode distance. The values obtained for the distal latencies and amplitudes for each electrode were compared using the unpaired Student's t-test. There were no statistically significant differences found in the ESAP distal latencies to onset or peak using any of the electrodes or various placements. When comparing the amplitude responses, the only statistically significant difference was noted when the TECA digital ring electrodes were compared to a particular arrangement of the Neurodiagnostic finger clip electrodes (p less than 0.05). It was therefore concluded that any of these electrodes can be used to obtain reliable reproducible data for nerve conduction studies.

Adult↗
PubMed1974

Quantitative evaluation of the effectiveness of Connaught freeze-dried BCG vaccine in mice and in guineapigs.

Although the field trials carried out by the Medical Research Council of Great Britain demonstrated that BCG vaccination can confer a substantial degree of immunity against tuberculous infection, it does not follow that BCG substrains other than the one used for those trials will produce equally favourable results. In fact, there is increasing evidence that different BCG strains may differ widely in their protective potency. The experiments described here further confirm these differences. They also show how the determination of the minimum dose of a BCG vaccine capable of delaying the development of tuberculous infection in mice and in guinea-pigs can yield reproducible data that may help to characterize individual BCG strains.The main purpose of these experiments was to determine the protective potency of Connaught freeze-dried BCG vaccine, lot 140, and to compare it with that of three other BCG vaccines. Marked differences were found with respect to the minimum protective dose for mice or guinea-pigs and the degree of immunity and tuberculin allergy produced in guinea-pigs as shown by the dose-response relationships recorded over a wide dosage range. The results suggest that the Connaught vaccine equals or surpasses the other vaccines in effectiveness.Such tests require a reference BCG vaccine of high protective potency for both animals and man.

Animals↗
PubMed1979

High pressure liquid chromatographic determination of carbohydrates in food products: evaluation of method.

A high pressure liquid chromatographic (HPLC) method for determining 5 common carbohydrates in food products was evaluated. Reproducibility data were generated showing a relative standard deviation of 2.8%. Recovery studies on a variety of foods gave an average recovery of 98.8%. The HPLC data for 3 varieties of ready-to-eat cereals were compared with data from 4 independent laboratories using current AOAC chemical methods. The HPLC mean values differed from the chemical mean values by 3.2%.

Chromatography, High Pressure Liquid↗
PubMed1981

[Reactive SH-groups in clinical practice. Methodological notes].

Experimental investigations have been performed in order to point out the extrinsic factors influencing the results of -SH group determination. It has been observed that the anticoagulants normally used to obtain plasma samples, influence the serum -SH groups; in particular, heparin increases and citrate depresses the levels; the most reproducible data were obtained in serum samples. In addition it has been shown that the exposure to light for 6-8 hours lowered the serum -SH groups, whereas darkness prevented these changes. Serum-SH groups were not influenced by the administration of non steroidal anti-inflammatory agents, whereas D-Penicillamine and Tiopronin induced an increase of the -SH levels, ranging between 15-20%. The levels returned to the basal values within two hours from the drug intake. Following the methodological criteria here described it is possible to obtain a good information about the -SH group reserve, which free radicals generated in several diseases could consume. The practical usefulness of the serum -SH group determination in oxidative-peroxidative processes in discussed.

Adult↗
PubMed1983

Selachian tooth development: I. Histogenesis, morphogenesis, and anatomical features in Squalus acanthias.

We have determined the general features of epithelial-mesenchymal interactions during fetal and mature adult stages of odontogenesis in the selachian spiny dogfish, Squalus acanthias. The general features of odontogenesis included the formation of an extended dental lamina, bud, cap, bell, and crown stages as identified and described using serial sections from fetal as well as adult specimens and light microscopy. Fetal and adult lengths, the rostrum-caudal fin distance, were correlated with the number of tooth rows and columns present in each specimen. This positional information and terminology was extremely valuable in attempting to acquire reproducible data for analyses. Whereas a number of histologic features of fetal and adult odontogenesis were comparable to those described in Mammalia, we found a number of epithelial-mesenchymal interaction characteristics unique to elasmobranch tooth development, including the persistence of the dental lamina in the adult stages, the coupling of cervical inner enamel epithelia between sequential stages of tooth formation, and the patterns of odontogenesis in the adult dentition.

Animals↗
PubMed1982

Radioisotope dilution technique for determination of vitamin B12 in foods.

A radioisotope dilution (RID) method for the determination of vitamin B12 is presented. The method combines a standard extraction procedure (AOAC 43.108, 12th ed.) with a commercially available RID assay kit. The method was evaluated on a wide range of fortified and unfortified food products. Recovery studies on both groups yielded average recoveries of 98.1 and 95.8%, respectively. Reproducibility data generated from replicate analyses on both groups gave a relative standard deviation of 6.9% for the fortified group and 9.2% for the unfortified group. For the samples studied, the mean vitamin B12 content determined by the RID method was 8.01 micrograms/100 g vs a mean of 7.54 micrograms/100 g by the AOAC microbiological method; the correlation coefficient was r = 0.983.

Food Analysis↗
PubMed1981

Proliferation of glioma cells in serum-free defined medium.

The requirement for a serum supplement to basal culture medium to support the growth and viability of cells in vitro has been a major hindrance to reducing and thereby controlling experimental variables. The complexity and undefined nature of serum as well as the variability of serum lots make it difficult to reproduce data and to interpret results of experiments. This paper presents preliminary results obtained with C6 glioma cell cultures in which serum was replaced by growth factors and a hormone. A brief review of the use of serum-free defined medium for the culture of tumor cells and the potential uses of defined media that are cell-type specific are also presented.

Animals↗
PubMed1980

[Significance of echocardiography in monitoring blood circulation].

The ability to perform bedside examinations in acutely ill patients, the sensitivity of the technique and the accuracy of serial examinations have led to increasing use of echocardiography in the intensive care setting. In addition to diagnostic information, the procedure provides the clinician with objective reproducible data for noninvasive evaluation of follow-up and therapeutic action. It provides an important approach to the patient with cardiac enlargement and congestive heart failure. In the patient with chest pain it may detect a cause of ischemia other than coronary artery obstruction and in the presence of unquestionable coronary artery disease it provides information towards early recognition and follow-up of complications. In acute left-sided heart failure it helps in the delineation of conditions amenable to specific therapeutic interventions. Echocardiograpy may point to the origin of systemic emboli by detecting mitral and valvular vegetations in infectious endocarditis, mitral stenosis and in rare cases of atrial myxoma. It may accelerate decisions for invasive procedures.

Abdomen, Acute↗
PubMed1995

Closed- and open-state binding of 4-aminopyridine to the cloned human potassium channel Kv1.5.

The effect of 4-aminopyridine (4-AP) on membrane and gating currents of Kv1.5 channels was studied in a human cell line. The rank order of block was cell-attached > whole cell >> outside-out macropatches, which suggested that 4-AP blocked channels from the cytosolic face. Stimulation after exposure to 4-AP during rest resulted in a "supernormal" current immediately after the onset of depolarization, followed by open channel block during maintained depolarization. 4-AP remained trapped in closed channels, and unblock after drug washout required depolarization. At higher concentrations, 4-AP induced channel block by binding to closing or nonconducting channels. This effect could be reduced by hyperpolarization and higher pulsing rates. Block of Kv1.5 channels under steady-state conditions was correlated with a dose-dependent reduction in gating charge movement. The normalized voltage dependence of gating was shifted to more negative potentials by 4-AP. A model incorporating both open and closed channel binding of 4-AP reproduced data, including the "supernormal" current, by shifting the Po - V curve slightly to the left. The results show that 4-AP can both enhance and block Kv1.5 current and suggest that 4-AP can bind with different affinities to more than one site on Kv1.5 channels.

4-Aminopyridine↗
PubMed1994

Pulmonary function testing in the critically ill neonate, Part I: An overview.

Respiratory insufficiency, a frequent problem encountered by the critically ill neonate, has many etiologies. Pulmonary function testing can effectively diagnose, quantify, and qualify the dysfunction so as to better define a prognosis and guide appropriate therapy. Recent advances in computer-assisted technology and miniaturization of equipment now allow simple, reproducible, and rapid neonatal pulmonary function assessment at the bedside. The indications for, and benefits of, pulmonary function testing vary with gestation, age, and clinical condition of the infant. The overall description of the pulmonary function profile is discussed in this article. The general questions and approaches utilized for routine testing, the initial pulmonary function profile, and evaluation of the acutely ill infant and that of the convalescing preterm are addressed. The expertise of the intensive care nurse is invaluable in ensuring that safe, accurate, and reproducible data are obtained. The nurse can then use the data to alter the infant's care plan and to determine the necessity and timing for retesting. Specific information on methodology and examples of specific tests are given in related articles (Parts II, Vol. 13 No. 2 and III, Vol. 13 No. 4, respectively). A complete knowledge of pulmonary function assessment is important for any nurse caring for critically ill neonates.

Humans↗
PubMed1977

Semiautomated method for the fluorometric determination of total vitamin C in food products.

A simple method employing simultaneous extraction and oxidation has been developed for the semiautomated determination of ascorbic and dehydroascorbic acids in food products. Recovery studies were conducted on ready-to-eat breakfast cereals and both fresh and canned fruits and vegetables, with average recoveries of 101, 100, and 102%, respectively. Reproducibility data were generated showing a relative standard deviation of 3.5%. The automated method was compared with the manual AOAC fluorometric method and with indophenol titration; correlation coefficients were 0.9960 and 0.9926, respectively. The hydrolysis product of dehydroascorbic acid, 2,3-diketogulonic acid, a reported interference in this method, was prepared and shown not to form an interfering fluorescent derivative.

Ascorbic Acid↗
PubMed1993

Stereological estimates of volume-weighted mean glomerular volume in streptozotocin-diabetic rats.

BACKGROUND: The stereological estimate of mean glomerular volume is an objective and reproducible method of measuring glomerular size in terms of absolute volume. This method provides objective, unbiased, and reproducible data that may be used in the description of glomeruli. EXPERIMENTAL DESIGN: We have made a morphometric analysis of glomerular size in three cortical areas (superficial, midcortical, and juxtamedullary) in normal and diabetic animals, using the point-sampled intercepts method. The kidney weight and volume as well as the cortical and glomerular volume density were also calculated. Our study included 35 animals (5 control and 30 experimental). Fifteen experimental animals were treated with 50 mg/kg streptozotocin dissolved in citrate buffer at pH 4.5. The other 15 animals were sham injected with citrate buffer. In all cases the tissues were fixed in 10% formaldehyde and embedded in paraffin. Sections were cut at 4 microns and stained with periodic acid-Schiff and a systematic sampling was performed. RESULTS: In the control and experimental groups the juxtamedullary glomeruli was significantly larger than superficial and midcortical glomeruli. Mean values of the kidney weight and volume and the volume-weighted mean glomerular volume show a significant increase at 4, 20, and 50 days after streptozotocin-induced diabetes. CONCLUSIONS: The increase in the volume-weighted mean glomerular volume was similar in the three cortical areas, thus suggesting that the effect of diabetes on glomerular enlargement is similar in all cortical areas.

Animals↗