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PubMed1992

High sensitivity quantification of RNA from gels and autoradiograms with affordable optical scanning.

To increase sensitivity and to improve normalization of RNA levels in Northern blot analysis, a comparatively inexpensive optical scanner was utilized for digitizing photonegatives of ethidium bromide stained gels and autoradiograms. The optical scanner captures the image with a maximum resolution of 300 dots per inch by assigning one of 256 gray levels (8-bit) to each dot in the image. With the use of the public domain NIH Image program (requires a Macintosh II and an 8-bit video card), gel or autoradiogram bands in the digitized image are selected and their average gray scale density measured. We found that the digitized image of a photonegative of a TAE (Tris-acetate/EDTA) agarose gel, loaded incrementally with 50-1500 ng total RNA, produced a linear response over a 4-fold range down to 100 ng (R2 greater than 0.950). In utilizing "quantification" gels like this, RNA samples that are too dilute or too small for traditional spectrophotometric techniques can be normalized and loaded uniformly onto subsequent Northern gels. Results from autoradiogram scans demonstrate highly linear gray scale responses over a 4-fold range of total RNA (R2 greater than 0.950) that are reproducible with different blots and probe types (e.g., riboprobe, cDNA and oligonucleotide). In addition, we describe a normalization technique using a 30-mer oligonucleotide probe for rat 28S ribosomal RNA as a measure of total RNA loaded per gel lane. Altogether, this scanning, ribosomal RNA normalization system allows the measurement of relative changes between 20% and 400% using standard autoradiographic methods.

Actins↗
PubMed1975

[Computerized axial tomography of the skull - diagnostic possibilities and clinical results (author's transl)].

Computerized axial tomography is a new method of tissue examination with x-rays whereby a picture can be produced which is a representation of a slice of the skull. This is done by irradiating the skull from 180 or 225 incremental angles and measuring the absorption at each of these angles. Then with the aid of a computer a tomogram is produced which can be displayed on a screen. These tomograms are representations of a cross-section of the skull composed of 160 X 160 points showing the various intracranial structures with great detail. The present study demonstrates the diagnostic possibilities of the high definition matrix with reference to brain disorders in a large sample of patients for the first time. Some tumours are shown as areas of decreased absorption compared with normal brain tissue. Others, however, have been found to have higher absorption values. With glioblastomas very contrasting pictures are produced with coexistng areas of decreased, increased and similar values to brain tissue. The most important finding is the visualization of brain oedema which appears as a low density area. A grading system of brain oedemas is proposed. The brain oedema associated with tumours has been found to propagate mainly in the white matter producing finger-like shapes. Out of 209 intracranial tumours 203 were recognized in the plain scan, a further five after contrast enhancement. In patients who have suffered from a stroke the differentiation between haemorrhage and infarction is made simple due to the contrasting appearance between the two types of lesion. Location, size and propagation direction of a haematoma as well as rupture of a haemorrhage into the ventricular system can be defined exactly. With brain infarction the hypoxically damaged tissue is well delineated and readily attributable to a given vascular area. In head injuries, for the first time it is possible to differentiate brain contusion with oedema from intracerebral haematoma. Coup and contre-coup are demonstrated. All types of acute intracranial haematomas may be diagnosed easily. With chronic subdural haematomas the new method fails if the contents of the haematoma shows the same absorption values as brain tissue. Late sequelae of head trauma such as contusion defects and necrosis of tissue after oedema can be seen in the tomogram. With infantile hydrocephalus, subdural effusions and malformations of the brain, computerized axial tomography offers a complete diagnosis so that other invasive, neuroradiological investigations may be avoided. Orbital tumors are picked out with great clarity. The high definition matrix allows the demonstration of the optic nerve, the lense and the suspension of the eyeball. Without doubt in the coming years computerized axial tomography will play a dominant role in the diagnosis of brain disorders.

Absorption↗
PubMed1991

[Digital thoracic radiography--a comparison of digital and analog imaging techniques].

New analog and digital imaging techniques for the chest became available in recent years. In this study conventional film/screen radiography was compared with slit technique ('AMBER'), storage phosphor radiography and digital image intensifier radiography by phantom exposures and patient examinations. Because of its low spatial resolution, quality of digital image intensifier radiography was insufficient for chest imaging. The slit technique demonstrated the highest image quality, especially in the fields of the mediastinum and the thoracic wall. In comparison to conventional film/screen radiography, storage phosphor radiography had advantages in the mediastinal field. Digital techniques are connected to new possibilities of image post-processing, storage and transfer. For difficult conditions of exposure (emergency unit) over- or underexposed images can be avoided by these new digital techniques. The combination of slit- and storage phosphor-technique did not increase image quality.

Analog-Digital Conversion↗
PubMed1991

Radiation methods and means for testing radiodiagnostic equipment.

Discussed are the requirements for the methods and means of checking the electrical and radiation characteristics of radiodiagnostic equipment at three test levels, i.e. on release from the manufacturer, during the periodic test of the parameters and adjustment and repair in the clinic. Discussed are the description and construction of the simple and contact measuring devices for checking parameters at each level. The capabilities of the devices are compared to those of the series-produced analogs of various firms.

Analog-Digital Conversion↗
PubMed1991

Effects of digital low pass filtering on the parameters of nystagmus eye movements.

We examined how lowpass filtering has an influence on nystagmus parameters: durations, amplitudes, and mean velocities of its slow and fast phases. We experimented with two types of common linear digital filters by using both nonrecursive and recursive filters, and with two types of nonlinear digital filters by using so-called standard median and hybrid median filters. We concluded that 70 Hz as strict cutoff frequency is high enough not to cause errors in the nystagmus parameters when information content in nystagmus signals is filtered above that cutoff frequency with linear filters. Using nonlinear filters good window lengths of filtering are equal to or less than about nine samples for a sampling frequency of 400 Hz which we applied.

Analog-Digital Conversion↗
PubMed1991

A microcomputer system for assessment of peripheral blood flow. An example of nasal blood flow.

We have designed and implemented a microcomputer system for studying the effect of various mediator substances on the nasal blood flow. The system uses an IBM PC/AT microcomputer, which is connected with a Laser Doppler Flowmeter (LDF) and an iontophoretic drug application system. The LDF measures flux from the tissue that in the example is the inferior nasal turbinate. The flux is converted to digital form by an analog-digital converter of 12 bits. The program is implemented in the Pascal language. In the analysis, a flux level, amplitude, rise time and decay time of the pulse wave are determined. The effect of drugs on the flux can be studied by applying them iontophoretically. In the program the length and number of the drug application periods as well as the recording period are user-driven. In the nasal blood flow iontophoretically administered adrenaline reduced significantly the flux parameters and histamine canceled this effect. Tachyphylalaxis was a frequent observation in repeated measurements. The system can be used to evaluate the role of different transmitters in the etiology of chronic rhinitis.

Adult↗
PubMed1991

Fluorescent image cytometry: from qualitative to quantitative measurements.

Image analysis is being increasingly used in biology and medicine; however, in order to obtain truly quantitative data and thus avoid errors in interpretation, a certain number of precautions must be taken when the image is digitized, well before any attempt is made to analyse or interpret the data. This is particularly true for image microfluorometry. In this article we will examine an image analysis system for fluorescent images composed of a mercury lamp, a microscope, a high sensitivity video camera and an image analyser and evaluate the principal sources of random and non-random errors, various constraints, and their relative importance. A signal correction protocol is proposed to minimize non-random errors during digitalization. A few examples are given to illustrate its efficiency.

Analog-Digital Conversion↗
PubMed1991

Automated image-based cytometry with fluorescence-stained specimens.

The combination of digitized microscopy, algorithms for object recognition and fluorescent labeling is a promising approach for reliable, quick, automated and cost-effective screening of clinical specimens. We describe two conceptually different algorithms for detecting objects in fluorescence microscopic images. One, which is partially automated, compares a mask that represents a typical object with every position in the image; the other, which is fully automated, calculates threshold intensities to segment the image into regions of objects and background. Applications of the algorithms in conjunction with a prototype image-based cytometer are demonstrated for determining the DNA ploidy distribution of cultured human endometrial cells and determining the DNA ploidy distribution and the fraction of cells expressing the E6 antigen of human papilloma virus serotypes 16 and 18 in a PAP smear. The encouraging results from this study suggest that automated image-based cytometry utilizing fluorescent stains will be a valuable asset for clinical screening.

Algorithms↗
PubMedDate not supplied

Application of piezo film technology for the quantitative assessment of pruritus.

A method to quantitate scratching has been developed for assessing the efficacies of interventions purported to ameliorate pruritus. The technique employs a piezo film sensor attached to the finger and the supporting electronics to amplify, transmit, and process the signals generated by the piezo film. The piezo film is essentially a contact microphone on the fingernail of the scratching subject. The method is currently incorporated into clinical trials, and preliminary results are promising.

Analog-Digital Conversion↗
PubMed1991

Atrial and His-Purkinje conduction times during isoflurane anaesthesia in humans.

The effect of isoflurane 2.0 MAC on human atrioventricular conduction time was studied. A non-invasive recording system for the detection of His-Purkinje potentials based on signal averaging techniques was used. Recordings were made in 15 patients before and after induction with isoflurane. We were able to measure atrial (P-H) and His-Purkinje (HPS) conduction times in 11 patients. Mean (+/- SEM) P-H conduction time decreased from 101.8 +/- 5.3 to 89.3 +/- 3.3 ms (P less than 0.01). HPS conduction times did not change significantly. Heart rate increased significantly from 86.7 +/- 4.2 to 94.9 +/- 4.7 beats min-1 (P less than 0.05). Systolic blood pressure decreased from 117.3 +/- 4.6 to 94.1 +/- 4.7 mmHg (P less than 0.05). It is concluded that the effects of isoflurane on supraventricular conduction time in humans depend on interactions of several different mechanisms.

Adolescent↗
PubMed1991

[Bidimensional measurements of the dental arches using a digitizer].

This method is based on the photographic reproduction of plaster models of dental arches, having previously identified reference points at a canine, molar and inter-incisor level. Subsequent measurement, using a digitizer, of the distances between the above points allows a precise bidimensional measurement to be easily obtained. By selecting plaster models for the different stages of treatment, the method can also be used to monitor changes in the dimensions of the alveolodental arch induced by therapy, or the possible presence of long-term recidivation.

Analog-Digital Conversion↗
PubMed1991

Analysis of microtubule arms and bridges in mitotic and interphase amebae of Dictyostelium discoideum.

We have analyzed transparencies of electron micrographs from ultrathin longitudinal sections through mitotic spindles of undifferentiated amebae of Dictyostelium discoideum for the presence of arms on microtubules (MTs) and bridges between them. We used the technique of microdensitometer scanning and computer-based model matching by cross-correlation and autocorrelation. We also determined that spindle MTs are composed of 13 protofilaments. Although regularly arranged lateral appendages are not a universal feature of MTs in these cells, both cross-correlation and autocorrelation analysis revealed that bridges between a kinetochore MT and its neighbor, and between MTs in the zone of overlap of the central spindle were significantly arranged on a 12-dimer superlattice. In addition, the autocorrelation analysis indicated a slight match with the 12-dimer model for neighboring non-kinetochore MTs. Although electron micrographs revealed putative arms on cytoplasmic and astral MTs, as well as bridges between central spindle MTs outside the zone of overlap, their arrangement did not match any of the models tested. Bridges between non-kinetochore MTs in the half-spindles possibly serve to reinforce the spindle scaffold. Bridges between kinetochore MTs and their neighbors may contribute to the mechanical stability of kinetochore fibers or they may be involved in poleward movements of the chromosomes. In the zone of overlap of the central spindle, the occurrence of frequent and regularly spaced bridges is consistent with models predicting that a sliding mechanism operates between MTs of opposite polarity in this region of the spindle to produce its elongation.

Analog-Digital Conversion↗
PubMed1991

A pneumatic bladder array for measuring dynamic interface pressure between seated users and their wheelchairs.

An understanding of the dynamic pressure distribution changes that take place on the sitting surface of a wheelchair while one propels oneself on a level surface may influence the design of wheelchair seat cushions engineered to minimize pressure sores in wheelchair users. A pneumatic pressure transducer array and associated multiplexer were developed to permit measurement of dynamic interfacial pressure changes on the seated wheelchair user during short bursts of locomotion on a level surface. The system design, calibration and interface to an IBM PC computer are described. Each transducer element consists of a 0.7" thick x 1.25" diameter bladder innervated by a miniature piezoresistive pressure transducer. Fifty elements make up the array covering a 7.5" x 15" area. The 50 differential outputs were multiplexed with six 16 to one CMOS analog switches and one 4-channel differential CMOS analog switch. A Keithley 570 data acquisition system was utilized. Frequency response, effect of normal loading and effect of shear loading on a single transducer element are discussed.

Analog-Digital Conversion↗