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At least 451 records · Page 25Linked to original sources
PubMed2005

Serum protein profiling by miniaturized solid-phase extraction and matrix-assisted laser desorption/ionization mass spectrometry.

Serum profiling by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) holds promise as a clinical tool for early diagnosis of cancer and other human diseases. Sample preparation is key to achieving reproducible and well-resolved signals in MALDI-MS; a prerequisite for translation of MALDI-MS based diagnostic methods to clinical applications. We have investigated a number of MALDI matrices and several miniaturized solid-phase extraction (SPE) methods for serum protein concentration and desalting with the aim of generating reproducible, high-quality protein profiles by MALDI-MS. We developed a simple protocol for serum profiling that combines a matrix mixture of 2,5-dihydroxybenzoic acid and alpha-cyano-4-hydroxycinnamic acid with miniaturized SPE and MALDI-MS. Functionalized membrane discs with hydrophobic, ion-exchange or chelating properties allowed reproducible MALDI mass spectra (m/z 1000-12,000) to be obtained from serum. In a proof-of-principle application, SPE with chelating material and MALDI-MS identified protein peaks in serum that had been previously reported for distinguishing a person diagnosed with breast cancer from a control. These preliminary results indicate that this simple SPE/MALDI-MS method for serum profiling provides a versatile and scalable platform for clinical proteomics.

Blood Proteins↗
PubMed1989

Capillary cloning of primary human tumor cells: assay miniaturization for drug efficacy testing.

The conventional double-layer agar method of cloning human tumor cells requires a substantial number of viable tumor cells and 14-21 days of culture. These prerequisites frequently limit its utility as an assay. In an attempt to circumvent these limitations and to reduce the amount of drug that is needed in the assay, we have further developed and miniaturized the assay in which human tumor cells are cloned in glass microcapillary tubes. Cultures consisted of 50 microliters containing 15,000 nucleated cells in 975 mm capillary tubes which were incubated for seven days. The results from 50 consecutive tumor biopsies resulted in cloning efficiencies, ranging from 0.007% to 1.0% with an overall successful cloning of 88% of all tumors tested and a good linear growth relationship and chemotherapy sensitivity. This miniaturized assay offers distinct advantages for drug efficacy testing including high cloning efficiencies, small tumor sample and drug requirements, quicker assay turnaround time and a general conservancy of reagents and incubator space.

Antineoplastic Agents↗
PubMed1988

Changes in miniature end-plate currents due to high potassium and calcium at the frog neuromuscular junction.

Elevation of extracellular potassium concentration ([K+]o) in cutaneous pectoris neuromuscular junction from 2 to 20 mM slowly increased the variability of the amplitudes of miniature end-plate currents (AMEPC-s), (coefficient of variation of AMEPC-s increased by 73%). Mean AMEPC-s, however, decreased but not markedly (by 14%). Comparable MEPC changes were observed when [K+] was raised in the presence of choline chloride (50 microM), arguing that MEPC changes were not primarily due to a lower and less uniform vesicular filling. Channel kinetics were not altered by high [K+]o, since the time constant of decay of miniature end-plate currents (TMEPC-s) did not change. Acetylcholine clearance from the synaptic cleft, however, appeared to be faster in high [K+]o since with cholinesterase blocked throughout, TMEPC-s were shortened. The changes of spontaneous quantal discharge induced by high [K+]o can be almost entirely explained by altered spatial distribution of vesicular release if, as recent reports suggest, at high [K+]o, exocytosis appears randomly not only at but also in between the active zones. However, relatively greater frequency of large MEPCs suggests that in high [K+]o some, and possibly all, quanta are filled above normal levels. High [Ca2+]o appears to counteract, although not always completely, all changes in spontaneous quantal secretion induced by high [K+]o. It is possible that high [Ca2+]o reverses the changes in the spatial distribution of vesicular release induced by high [K+]o. However, high [Ca2+]o also leads to other pre- and postsynaptic changes.

Action Potentials↗
PubMed1996

Non-retinal abnormalities associated with progressive retinal atrophy (PRA) in the miniature poodle.

Osmotic fragility was examined in red blood cells taken from miniature poodles with progressive retinal atrophy (PRA). In this study, the median osmotic fragility for erythrocytes (concentration of NaCl required for 50% haemolysis) was found to be significantly lower for clinically affected, compared to unaffected animals. These differences were maintained regardless of changes in erythrocyte incubation pH (7.0, 7.5). There was no difference in the slope parameter of erythrocyte osmotic fragility profiles for both sets of animals, indicating a similar variability of erythrocyte age. In groups of animals maintained with the same diet and fasted for 12 hr, and in groups of animals with no dietary constraints, total plasma cholesterol was significantly lower for affected, compared to unaffected animals. Red blood cell indices were also assessed; mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), red blood cell count (RBC) and blood haemoglobin concentration (Hb) were normal, while erythrocyte packed cell volume (PCV) was significantly reduced for affected, compared to unaffected. Data from this study suggest that the abnormal erythrocyte osmotic fragility of affected animals is unlikely to be a consequence of a higher erythrocyte surface area/volume ratio, higher plasma cholesterol concentration, or greater proportion of new to old erythrocytes, and that a general membrane defect might be associated with prcd in the miniature poodle.

Age Distribution↗
PubMed1995

Modelling endplate currents: dependence on quantum secretion probability and decay of miniature current.

Quantification of the time course and amplitude of endplate currents (EPC) was made with respect to dispersion of quanta secretion and to changes in the exponential decay of miniature endplate currents (tau mepc). The relationship between RPC amplitude and tau mepc follows a double-exponential curve with tau1 = 0.3 ms and tau2 = 6 ms. If the amplitude of fully synchronised EPC is taken as 100%, then the loss of EPC amplitude is already 42% with "physiological" parameters of dispersion (the half-rise and decay constant of distribution of secretion probability = 0.5 ms, taumepc = 1 ms). This loss is even more substantial if secretion is more dispersed or miniature endplate currents decay faster.

Acetylcholine↗
PubMed1992

Miniature excitatory postsynaptic potentials in embryonic motoneurons grown in slice cultures of spinal cord, dorsal root ganglia and skeletal muscle.

Miniature excitatory postsynaptic potentials (mEPSPs) were recorded in motoneurons grown in organotypic cocultures of embryonic rat spinal cord, dorsal root ganglia and muscle in the presence of TTX. The motoneurons were electrically compact with a mean electrotonic length of 0.6. Spontaneous EPSPs were found in most of these motoneurons. With TTX the large EPSPs disappeared, whereas in more than half of the experiments mEPSPs persisted with a range in size of 1 to 4 mV (mean: 2.1 mV), probably originating from the spontaneous release of single vesicles. The net inward charge transfer at the soma ranged from 0.12 to 0.34 pC. The mEPSPs were heterogeneous in size even within pools of potentials that were homogeneous in shape. They had similar shapes and amplitudes as the smallest spontaneous unitary EPSPs mediated by presynaptic impulses, suggesting that for the smallest afferents not more than one vesicle was released per afferent impulse. Both the miniature and the TTX-sensitive EPSPs were readily blocked by the glutamate antagonist DNQX.

Animals↗
PubMed1982

Rapid miniaturized chromatography for Tc-99m IDA agents: comparison with gel chromatography.

Miniaturized chromatography systems for determining free pertechnetate and hydrolyzed reduced 99mTc levels in commercial 99mTc-labeled iminodiacetate (IDA) hepatobiliary radiopharmaceuticals were evaluated and the results compared with gel chromatography column scanning (GCS). Commercial IDA agents were evaluated including 2,6-dimethyl IDA, p-isopropyl IDA, p-butyl IDA, and 2,6-diisopropyl IDA. Of all the chromatography systems evaluated, only Gelman ITLC-SA with 20% NaCl and Gelman ITLC-SG with distilled water correlated with GCS in evaluating free pertechnetate and hydrolyzed reduced 99mTc levels for all IDA radiopharmaceuticals. The miniaturized chromatography procedure, as outlined, is rapid, taking less than 4 min, and can easily be incorporated into the daily quality control program in any nuclear medicine facility.

Chromatography↗
PubMed1992

Towards continuous glucose monitoring: in vivo evaluation of a miniaturized glucose sensor implanted for several days in rat subcutaneous tissue.

A miniaturized amperometric, enzymatic, glucose sensor (outer diameter 0.45 mm) was evaluated after implantation in the subcutaneous tissue of normal rats. A simple experimental procedure was designed for the long-term assessment of the sensor's function which was performed by recording the current during an intraperitoneal glucose load. The sensor was calibrated by accounting for the increase in the current during the concomitant increase in plasma glucose concentration, determined in blood sampled at the tail vein. This made it possible to estimate the glucose concentration in subcutaneous tissue. During the glucose load, the change in subcutaneous glucose concentration followed that in blood with a lag time consistently shorter than 5 min. The estimations of subcutaneous glucose concentration during these tests were compared to the concomitant plasma glucose concentrations by using a grid analysis. Three days after implantation (n = 6 experiments), 79 estimations were considered accurate, except for five which were in the acceptable zone. Ten days after implantation (n = 5 experiments), 101 estimations were accurate, except for one value, which was still acceptable. The sensitivity was around 0.5 nA.mmol-1.l-1 on day 3 and day 10. A longitudinal study on seven sensors tested on different days demonstrated a relative stability of the sensor's sensitivity. Finally, histological examination of the zone around the implantation site revealed a fibrotic reaction containing neocapillaries, which could explain the fast response of the sensor to glucose observed in vivo, even on day 10. We conclude that this miniaturized glucose sensor, whose size makes it easily implanted, works for at least ten days after implantation into rat subcutaneous tissue.

Animals↗
PubMed1984

Developmental changes of myelin-related lipids in brain of miniature swine.

The biochemical development of whole brains from male and female miniature swine aged 2 weeks to 1 year was studied. The data were similar for both sexes. The brain-body weight ratio declined rapidly for the first 10-12 weeks after birth, then decreased at a slower rate up to 1 year. Total brain lipid weight and lipid phosphorus changed rapidly during the first 8-10 weeks of life, but thereafter changed very little. The glycolipid content rapidly increased during the first 12-14 weeks of life and then increased at a slower rate. Total brain cholesterol increased continuously over the time period studied, although the rate of increase appeared to decline with age. Monogalactosyl diacylglycerol concentration remained constant up to about 8 weeks of age, but then decreased continuously up to 1 year. The alkali-labile fatty acid composition of pig brain remained relatively constant except for increases in 18:1 and 22:6(n - 3) and a decrease in 16:0. The increase in percentage of 18:1 was most rapid during the first 10 weeks of age. These data suggest that the "growth spurt" or active myelination phase of miniature pig brain development ends at 8-10 weeks post partum.

Age Factors↗
PubMed1996

On the possible origin of giant or slow-rising miniature end-plate potentials at the neuromuscular junction.

Giant or slow-rising miniature end-plate potentials (GMEPPs) caused by vesicular release of acetylcholine (ACh) occur at any time in about 50% of mouse diaphragm neuro muscular junctions, but generally at frequencies less than 0.03 s-1. Their frequency is, unlike that of miniature end-plate potentials (MEPPs), not affected by nerve terminal depolarization. Unlike MEPPs and stimulus-evoked end-plate potentials, GMEPPs have a prolonged time-to-peak and show an increase in time-to-peak with amplitude. By using these differences in amplitude and time course, GMEPPs can be separated from MEPPs. In contrast to MEPPs, GMEPPs are not blocked by botulinum neurotoxin type A. GMEPPs have a greater temperature sensitivity than MEPPs, disappearing at temperatures below 15 degrees C. Long-term paralysis by botulinum toxin and certain drugs which inhibit protein kinase C or affect actin filament polymerization (cytochalasins) enhance the frequency of GMEPPs. End-plate current recordings show that similar postsynaptic ACh receptors are activated by MEPPs and GMEPPs. It is suggested that GMEPPs are not caused by mechanisms involved in regulated neurotransmitter release but are generated by constitutive secretion.

Acridine Orange↗
PubMed2003

Command control for functional electrical stimulation hand grasp systems using miniature accelerometers and gyroscopes.

Recent commercially available miniature sensors have the potential to improve the functions of functional electrical stimulation (FES) systems in terms of control, reliability and robustness. A new control approach using a miniature gyroscope and an accelerometer was studied. These sensors were used to detect the linear acceleration and angular velocity of residual voluntary movements on upper limbs and were small and easy to put on. Five healthy subjects and three cervical spinal cord injured subjects were recruited to evaluate this controller. Sensors were placed on four locations: the shoulder, upper arm, wrist and hand. A quick forward-and-backward movement was employed to produce a distinctive waveform that was different from general movements. A detection algorithm was developed to generate a command signal by identifying this distinctive waveform through the detection of peaks and valleys in the sensor's signals. This command signal was used to control different FES hand grasp patterns. With a specificity of 0.9, the sensors had a success rate of 85-100% on healthy subjects and 82-97% on spinal cord injured subjects. In terms of sensor placement, the gyroscope was better as a control source than the accelerometer for wrist and hand positions, but the reverse was true for the shoulder.

Adult↗
PubMed2001

Miniaturized fiber-in-tube solid-phase extraction as the sample preconcentration method for microcolumn liquid-phase separations.

Miniaturized fiber-in-tube solid-phase extraction (fiber-in-tube SPE) has been developed as a solventless sample preconcentration technique for microcolumn liquid-phase separation methods. Short capillaries packed with polymer filaments were employed as the extraction tube and the preconcentration power for phthalates in aqueous solutions was studied. On the basis of the successful on-line coupling of this preconcentration method with liquid chromatography (LC), a more miniaturized extraction cartridge, which is installed in the rotor of the micro-injector, has been developed. With a modified commercially available valve, on-line coupling of this sample preconcentration method to capillary electrochromatography (CEC) was also investigated.

Journal Article↗
PubMed2004

A miniaturized heterogeneous fluorescence immunoassay on gold-coated nano-titer plates.

A miniaturized heterogeneous fluorescence immunoassay utilizing radiationless energy transfer to gold surfaces for fluorescence quenching is described. The phase-separation fluorescence immunoassay (PSFIA), a competitive heterogeneous assay, is carried out in the nanowells of a gold-coated nano-titer plate (NTP). Small analytes such as atrazine and histamine can be detected in nanoliter volumes with low limits of detection, maintaining a high degree of parallelization and miniaturization. The assay is characterized and optimized with respect to gold-layer thickness, surface concentration of immobilized analyte derivative, and antibody concentration. Various immobilization strategies are discussed.

Fluorescence Resonance Energy Transfer↗
PubMed2004

Miniaturization in sample treatment for environmental analysis.

The increasing demand for faster, more cost-effective and environmentally friendly analytical methods is a major incentive to improve the classical procedures used for sample treatment in environmental analysis. In most classical procedures, the use of rapid and powerful instrumental techniques for the final separation and detection of the analytes contrasts with the time-consuming and usually manual methods used for sample preparation, which slows down the total analytical process. The efforts made in this field in the past ten years have led to the adaptation of existing methods and the development of new techniques to save time and chemicals, and improve overall performance. One route has been to develop at-line or on-line and, frequently, automated systems. In these approaches, miniaturization has been a key factor in designing integrated analytical systems to provide higher sample throughput and/or unattended operation. Selected examples of novel developments in the field of miniaturized sample preparation for environmental analysis are used to evaluate the merits of the various techniques on the basis of published data on real-life analyses of trace-level organic pollutants. Perspectives and trends are briefly discussed.

Journal Article↗
PubMed2006

A windowless flow cell-based miniaturized fluorescence detector for capillary flow systems.

A miniaturized fluorescence detector utilizing a three-dimensional windowless flow cell has been constructed and evaluated. The inlet and outlet liquid channels are collinear and are located in the same plane as the excitation paths, while the optical fiber used to collect the emission light is perpendicular to this plane. The straightforward arrangement of the flow path minimizes band dispersion and eliminates bubble formation or accumulation inside the cell. The use of high-brightness light-emitting diodes (LEDs) as the excitation source and a miniaturized metal package photomultiplier tube (PMT) results in a compact and sensitive fluorescence detector. The detection limit obtained from the system for fluorescein isothiocyanate (FITC) in flow injection mode is 2.6 nmol/L. The analysis of riboflavin and FITC by packed capillary liquid chromatography is demonstrated.

Journal Article↗
PubMed2006

Miniaturized platforms for the detection of single-nucleotide polymorphisms.

Conventional methods for detecting single-nucleotide polymorphisms (SNPs), the most common form of genetic variation in human beings, are mostly limited by their analysis time and throughputs. In contrast, advances in microfabrication technology have led to the development of miniaturized platforms that can potentially provide rapid high-throughput analysis at small sample volumes. This review highlights some of the recent developments in the miniaturization of SNP detection platforms, including microarray-based, bead-based microfluidic and microelectrophoresis-based platforms. Particular attention is paid to their ease of fabrication, analysis time, and level of throughput.

Electrophoresis↗
PubMed2002

The cryosurgical ablation of bone tissue by means of a new miniature cryoprobe -- evaluation of the probe and adaption of the method to in vitro human bone.

Until now, modern miniature cryoprobes have been used successfully for the local destruction of soft-tissue tumors without damaging adjacent healthy tissue. In this study, the methodology of cryoablation was applied to bone, and the freezing effect as well as the cooling capacity of the probe were examined. Freezing was performed by cooling one or two probes, with a diameter of 3.2 mm, to -180 degrees C with liquid nitrogen. The cooling capacity of the probes was determined under optic and thermic control in a homogenous reference gel (gelatin), followed by an in vitro measurement on human bone. The simultaneous use of 2 probes resulted in a synergistic effect which produced an almost spherical expansion of frozen area in the homogenous gelatin. In vitro freezing of human tibiae produced equivalent freezing temperatures, with one or two probes, in comparison to the homogenous gelatin. An adequate tissue cooling of bone matrix can be achieved through the use of one or more miniature cryoprobes so that after in vivo testing, the use of this probe could possibly become an alternative or supplement to the surgical resection of pathologic bone processes.

Bone Matrix↗
PubMed2002

Molecular analysis of the Drosophila miniature-dusky ( m-dy) gene complex: m-dy mRNAs encode transmembrane proteins with similarity to C. elegans cuticulin.

Mutations in the Drosophila miniature-dusky ( m-dy) gene complex were first reported by Morgan and Bridges about 90 years ago. m-dy mutants have abnormally small wings, a phenotype attributed to a cell-autonomous reduction in the size of the epidermal cells comprising the differentiated wing. Using a molecular genetic approach, we have characterized the m-dy chromosomal interval and identified a pair of adjacent transcription units corresponding to m and dy. A dy mutant known as dy (And) has a single base substitution within the protein-coding region that is predicted to result in an amber stop codon and premature translational termination. We show that dy mRNA is expressed at two discrete periods during the life cycle--one during embryonic development and early larval instars, the second during adult development, coincident with wing differentiation. In agreement with the phenotypic similarity of m and dy mutants, sequence comparisons reveal a similarity between the predicted MINIATURE and DUSKY proteins, and indicate that the m and dy genes are members of a larger Drosophila gene family. Both m and dy, as well as other members of this superfamily, are predicted to encode transmembrane proteins with similarity to C. elegans cuticle proteins known as cuticulins. We postulate that m, dy and other members of this protein superfamily function as structural components of the Drosophila cuticulin layer. Such a role for m and dy products in wing differentiation is sufficient to explain the morphological phenotypes associated with m-dy mutants.

Amino Acid Sequence↗