SEARCH · Search PubMed
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.
A fluorochromatic cytotoxicity assay featuring direct use of whole blood and quantitative evaluation is described. Its application to tissue typing for H-2 antigens together with data indicating reproducibility specificity of the assay are presented. Procedures for visual and automated quantification are included.
A simple and highly sensitive analytical isoelectric focusing (IEF) technique using immunofixation with anti-C2 serum followed by silver staining has been developed in order to study simultaneously the structural polymorphism of both native C2 and C2 activation fragments (C2a MW 74,000 and C2b MW 34,000). Structural C2 polymorphism of C2*B and C2*C allotypes (but not of C2*A1) was found to be associated with the C2a fragment, whereas C2b appears to display no polymorphism. Commercially available IEF gels and C2 antisera gave reproducible allotyping data and make this technique of general use for densitometric analysis of native and activated C2. In vivo C2 activation was studied through C2a/native C2 area ratios obtained by computerized densitometry. Significantly lower ratios were observed in healthy individuals than in patients with systemic lupus erythematosus (SLE), reflecting an abnormally high classical pathway activation of complement in SLE. This methodology may be of value for immunogenetic and functional studies of other complement components.
The aim of this paper is to clarify the mechanism of gel electrophoresis of DNA under constant-field conditions. We have conducted a large number of experiments on double-stranded DNA varying in length between approximately 10 and approximately 50,000 base-pairs, in both agarose and polyacrylamide gels ranging from 0.5% to 12% concentration, and with electric field strengths ranging from 0.5 to 8 V/cm. We have made (logarithmic) plots of velocity against length of DNA for all of the various test conditions. At the left-hand side of these plots, all of the empirical curves have a unique, standard shape. When the curves are normalized so that their left-hand parts coincide, a second feature emerges in that, while for any given test the curve follows the "master curve" up to a certain point, it then "breaks away" and becomes horizontal. We describe these two patterns of behaviour as "regions 1 and 2", respectively. We find simple yet comprehensive empirical formulae that fit the observations in the two regions of behaviour: these express the velocity in terms of length of DNA, electric field strength and gel concentration. We then construct two separate theories for the two regions of behaviour. The first theory involves the statistics of motion of an object through a random array of gel obstacles, with the instantaneous speed depending on the number of obstacles with which the object is currently in contact. The second theory is based on the mechanical hypothesis (for which there is other, independent support) that the DNA moves through the gel by piling up against a barrier, which eventually breaks or deforms under the resulting force, thereby allowing the DNA to move on to the next barrier. The statistical theory is an adaptation of existing work, while the mechanical one is new. We also describe experiments on the migration of repeated-sequence, curved DNA with length up to 1500 base-pairs, and we discuss its behaviour in terms of our two theories. Our studies by electron microscopy are consistent with the view that this repeated-sequence DNA adopts a superhelical configuration. Finally, we show that a very wide range of observations may be understood clearly by means of our two theoretical schemes.
The volume of the lumbar sac measured in 4 subjects was found to be 15.5 ml. Exactly 15 ml of lumbar cerebrospinal fluid (L-CSF) was permitted to flow freely out during a lumbar puncture in 20 neurological patients and small samples of the L-CSF were collected in the beginning (sample 1), at the middle (sample 2), and at the end (sample 3) of this procedure either for 5-HIAA or HVA measurement. The concentrations of 5-HIAA and HVA increased in an exponential manner from sample 1 to sample 3. These results indicate that CSF in the lumbar sac is not a homogeneous fluid as is generally believed and that certain rules have to be followed in the sampling of the L-CSF to obtain reproducible biochemical data.
The transport of the amino acids, cystine and lysine, was studied in epithelial cell lines propagated from human kidney cortex. Cystine uptake data were reproducible in different cell lines and did not vary over several cell passages of an individual cell line. The transport of this disulfide amino acid was sodium-dependent with kinetic analysis showing one apparent Kt system of 0.09 mmol/L and Vmax of 0.054 mmol/L cell water/min. Studies of the kinetics of lysine transport, however, revealed two uptake systems with apparent high and low affinities with Kt of 0.14 mmol/L and 5 mmol/L and Vmax of 0.041 and 0.167 mmol/L cell water/min, respectively. Glutamate appeared to be the most potent inhibitor of cystine uptake by these cultured human renal cells and this interaction was competitive. Although cystine did not inhibit lysine uptake, arginine and ornithine were shown to be major inhibitors, thus providing evidence for the presence of a shared dibasic amino acid transport system.
Two frequency scanning ultrasonic spectrographs utilizing time-delay signal processing techniques have been developed. These permit measurement of time delays (and hence velocity changes) in a sample in the order of 10(-8) s. The present instruments allow such measurements to be made continuously over a frequency range of 1-10 MHz. These instruments have been used to monitor changes in velocity as a function of frequency during coagulation in purified human fibrinogen solution and human plasma. It was found that velocity dispersion occurred at discrete frequencies during the coagulation process. The frequency dependent data is reproducible, although this depends to some extent upon the samples used. The instruments which were calibrated using a fixed length of coaxial cable, exhibit a high degree of reproducibility.
The development of valid structure biodegradation relationships (SBRs) is restricted by the lack of reproducible published data and by the considered endpoint of degradation data. A classification scheme is required for comparative evaluation of degradation data obtained by different test methods. SBRs based on substructure indicators are available for application to most compounds, but the reliability is still uncertain. SBRs based on physico-chemical parameters are only available for a few classes of compounds based on specific test methods. A combination of several SBRs covering the various transformation pathways provides a promising tool for predicting biodegradability. Two models describing biodegradation are introduced.
Eighteen normal male subjects were recruited for a double-blind, placebo-controlled, randomized, two-period crossover study to determine the effects of a new, potent, highly selective, oral peptide leukotriene antagonist (ICI 204,219) on cutaneous vasculature. Skin testing for leukotriene D4 (LTD4) and histamine was performed at three different time intervals after receiving ICI 204,219 or placebo. The LTD4 threshold dose responses were recorded in duplicate to verify reproducibility. These data confirm known remarkable dose-response variation of cutaneous vascular reactions to LTD4 since some subjects reacted to a dose as low as 0.001 fmol. Twelve subjects (67%) demonstrated a more than one-half log increase in their threshold response after receiving ICI 204,219. Five of these 12 subjects (28%) had greater than 1 log-dose response after ICI 204,219. Two of these subjects (11.1%) had a 5 or 10 log increase in their threshold response after receiving ICI 204,219. Given the role of leukotrienes as potentially important mediators in immediate-type reactions, our results raise the possibility for additional investigation of the antagonistic effect of ICI 204,219 in nonallergic and allergic cutaneous diseases.
C57BL/6 inbred female mice preimmunized by serial injections of isogeneic male spleen cells were mated and the effects of the circulating anti H-Y antibodies on the fetal gonads and on their fertility were studied. Female mice receiving injections of saline formed one control group and those given female spleen cells a second control group. The experiment was carried out three times and since observations were similar and reproducible the data of all three sets were pooled. There was no significant change in the birth weights of newborns, total number of conceptions or sex ratio in the study group compared to either of the controls. There was no difference in the mean live birth rate between the study group and both the controls. Although the incidence of stillbirths in the study group was higher than that in both controls the difference was not statistically significant. In the study group there were no histopathological changes in the gonads from female pups compared to ovaries from the controls. In contrast, the gonads of male pups showed mild to severe structural disorganization in the study group, but not in the female spleen cell injected group. In spite of the morphological changes in the testes, the newborn male pups had a normal anogenital distance and testicular descent suggesting that Leydig cell function was normal.
The glucose content of the culture liquid during shift experiments and synchronized cultures of Saccharomyces cerevisiae H1022 (ATCC 32167) was monitored using a greatly improved and highly precise FIA. During shift-up experiments on the dilution rate, an overshoot of the glucose-concentration was observed. The amplitude of the overshoot showed a dependency on the duration of undisturbed cultivation before application of the shift. Mutarotational non-equilibrium was excluded as the cause of the observed overshoot. For the first time glucose measurements of oscillating cultures of Saccharomyces cerevisiae are demonstrated with high accuracy and reproducibility. The data strongly support the proposals by Münch et al. (1992a, b) that faint oscillations in glucose concentration are responsible for the persistence of the synchronization. Analytical subsystems prove to be a powerful tool for investigation of the dynamics of metabolic pathways of microbial organisms. Accurate glucose measurements at low concentrations point out the limits and allow refinements of commonly used models.
We have described a method for identifying component wave forms of evoked potentials by reference to a model of the dynamic behavior of neuronal systems. The method parsimoniously reproduces measured data and provides a means for utilizing a priori information from sets of experimental data to discriminate between experimental variables. The method appears successful in quantifying the physiologic variability in the amplitude, shape and latency of EP component wave forms.
Molecular sequences are experimentally derived data that can be expected to contain errors as a result of diverse phenomena such as biological variation, molecular cloning artifacts, imperfect sequence determination, and data handling during contig assembly. Errors will affect the reliability of database searches and sequence alignments, but their impact may be minimized by the use of analytical techniques that anticipate that the data will be imperfect.
The fundic mucosa of resting and acid-secreting rabbit stomachs were freeze-fractured and replicated to compare the intramembranous particles on the parietal cell tubulovesicles (rest) and canaliculus (secretion). The particles were counted and their shadow diameters were measured using an image analysis program. The tubulovesicles bore 9,726 +/- 400 particles per microns2 (mean +/- SD), having a mean diameter of 8.4 nm (n = 2,571). The canaliculus bore 8,369 +/- 430 particles per microns2, having a mean diameter of 7.7 nm (n = 3,259). The data were reproducible: three fractures of tubulovesicles and canaliculus gave essentially the same distributions of particle diameters. By contrast, the frequency distributions of tubulovesicle and of canaliculus particle diameters were significantly different (P less than 0.0005). Neither the opposite curvatures of tubulovesicle and canaliculus microvillus fractures nor subpopulations of tubulovesicles with different particle diameters, were the cause of the difference, since there was only one population of tubulovesicles. We therefore postulate that the diameters of intramembranous particles of tubulovesicles and canaliculus are different and suggest, as a working hypothesis, that the difference could be due to a conformational change of the major intramembranous protein, the (H+,K+)-ATPase.
Positron emission tomography (PET) has been used to measure changes in regional blood-brain barrier (BBB) permeability in patients with primary cerebral lymphoma undergoing radiotherapy and chemotherapy. The method employed is to measure the rate of wash-out of a radioactive tracer (68Ga-EDTA) from blood into brain tissue using time-sequence PET imaging. Preliminary studies carried out on patients with more common primary cerebral tumours show that time-activity data are reproducible to approximately 10%. Measurements made in 2 patients with primary cerebral lymphoma treated with initial chemotherapy showed significant changes in permeability in the region of the tumour. Within 5 weeks of the start of treatment, permeability values reached the levels of normal brain. No changes in BBB permeability in normal brain were seen immediately after radiotherapy.
A detailed description of the India ink injection technique for assessment of experimental burn wound depth is presented with emphasis upon special technical manipulations. Assessment of the burn depth is mandatory for the establishment of a burn wound model as well as to reproduce consistent data among different investigators.
A model of the hippocampal granule cells was created that closely approximated most of the measured intracellular responses from a neuron under a variety of stimulus conditions. This model suggests that: (1) A simple, four-conductance model can account for most of the intracellular behavior of these neurons. (2) The repolarization mechanism in granule cells may be different from that in squid axons. A weak potassium conductance may be present in hippocampal granule neurons, which simultaneously give rise to a small, passive depolarizing afterpotential. (3) The strength duration properties may assist in identifying the electronic and sodium channel properties with short stimulus pulse widths. (4) Repetitive firing responses are highly dependent on the cell's recent history of activation and the regulation of the slow potassium conductance and calcium dynamics. (5) The anodic break response is probably not a property of typical granule cells. Through thorough and precise comparison of experimental and model responses, computer simulations can help assembling channel information into verifiable models that accurately reproduce intracellular data.
Explore the source record for details and available documents.
The optimal number and placement of electrocardiographic (ECG) leads to detect myocardial ischemia induced by coronary balloon inflation was assessed by analyzing ST segment changes in the standard 12-lead ECG and Frank X, Y, Z leads at 90-s intervals during 34 consecutive coronary angioplasty procedures. Mean occlusion time during angioplasty was 218 +/- 65 s. Myocardial ischemia, defined as transient angina or ST segment deviation greater than or equal to 1 mm in at least one lead, occurred in 33 (97%) of the 34 procedures. The most sensitive single leads (V2 or V3) detected 17 (51%) of 33 ischemic episodes. The best dual-lead combinations (leads V2 and V5, leads a VF and V3 and leads V3 and Y) increased the sensitivity of 69% (23 of 33). The three-lead combination V2, V5, Y had the highest detecting power (78% [26 of 33]). The X, Y, Z leads by themselves had a sensitivity of only 60% (20 of 33). From this proposed orthogonal lead system (V2, V5, Y), which combines anteroposterior (V2), left to right (V5) and inferosuperior (Y) forces, the spatial ST vector magnitude was calculated and monitored during balloon inflations. A good correlation was observed between this ST vector magnitude and the sum of ST deviations on the standard ECG (r = 0.940, p less than 0.00001), and these data were reproducible over sequential balloon inflations. The results of the study suggest that this orthogonal lead system is of considerable value in the detection and quantification of acute myocardial ischemia and, in this respect, is more useful than the Frank orthogonal vector system.