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Biomedical subjects

A Kolin

Publications and source records attributed to A Kolin.

At least 55 records · Page 3Linked to original sources
PubMed1977

Induction angiometer. Electromagnetic magnification of microscopic vascular diameter variations in vivo.

It is possible to obtain continuous linear recordings of changes in vascular diameters on the basis of the electromagnetic induction principle. An extracorporeal coil energized by an alternating current generates an AC magnetic field and acts as a transformer primary. An intravascular loop of fine wire acts as transformer secondary. The EMF induced in the loop is proportional to the diameter of the vessel which confines the loop. Relative measurements do not require a calibration. Absolute measurements require radiographic determination of vessel diameter. Changes of less than 0.1% in vascular diameters can be easily recorded. Variations in pulsatile diameter changes as well as pharmacologically induced changes in mean diameter have been studied.

Blood Vessels↗
PubMed1976

Extracorporeal magnet perivascular electromagnetic flow meters.

The "interrupted resonance" circuit proved effective in combination with an extracorporeal magnet in permitting electromagnetic blood flow measurements to be made in branch arteries of dogs by application of perivascular cuffs equipped with pick-up electrodes contacting the vessel wall. A four-turn coil, acting as a transformer secondary measures the amplitude of the magnetic field component which is effective in inducing the flow signal and thus permits calibrations for arbitrary orientations of the perivascular cuff relative to the magnetic field of the extracorporeal magnet. Recordings of mean and phasic blood flow in dogs' arteries provide illustrations of effectiveness in pharmacological studies and exhibit the reliability of the non-occlusive zero-flow base line obtained by de-energizing the magnet.

Animals↗
PubMed1976

The external field intravascular electromagnetic flowmeter system as applied to standard arteriographic catheters and conscious humans.

New methodology, utilizing electromagnetic principles, has been developed for the measurement of regional vascular blood flow in intact animals and man. The flow sensor consists of a fine, insulated wire loop which has a small electrode on each side of the loop. This loop-probe, which is inserted like a guidewire through standard cardiac or angiographic catheters, springs open upon emerging from the catheter, and the electrodes are automatically applied to diametrically opposite sides of the inner vascular wall. This miniaturization of the flow sensor has been achieved by imposing the magnetic field which pervaces the artery from a coli located outside the body. As blood flows through the vessel across the magnetic field, the induced voltage across the blood column detected between the electrodes is proportional to the volume rate of blood flow. The loop-probe can be used simultaneously as an arterial diameter gauge. Means are described for achievement of a reliable, nonocclusive zero-flow baseline and flow calibration.

Angiography↗
PubMed1976

Cerebellar dysgenesis in rats by diaplacental effects of 7,12-dimethylbenz[a]anthracene.

7,12-Dimethylbenz[a]anthracene (DMBA) administered iv to pregnant Sparague-Dawley rats produced cerebellar malfunction in at least 10% of the offspring. The underlying morphologic basis of the cerebellar symptomatology was found in maldevelopment of cerebellar cortex, ranging from focal loss of granule and Purkinje's cell layers to extensive areas of cortical disorganization with losses of granule neurons. An interference with the proliferation of the granule cell-layer primordium was suggested as a mechanism of this cerebellar dysgenesis. After a 200-day observation, no tumors were found in the offspring of the DMBA-treated, pregnant rats.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1974

A constant-field interrupted resonance system for percutaneous electromagnetic measurement of blood flow.

A combination of deformable flow probes of negligible lateral dimensions with an electronic circuit capable of providing a prolonged plateau of dB/dt = 0 and of sampling the flow signal at the end of this interval permits electromagnetic measurement of blood flow with a reliable zero base line secured by switching off the magnet. An extracorporeal magnet provides the magnetic field. The flow transducer is introduced into the vascular system percutaneously through a standard angiographic catheter by conventional technique. The idea of the current generator can be described as "principle of interrupted resonance." The current wave form can be described as a sequence of disconnected bisected sine waves joined at the apices by horizontal current plateaus where di/dt is strictly zero.

Animals↗
PubMed1971

Determination of arterial blood flow by percutaneously introduced flow sensors in an external magnetic field. II. Implementation of the method in vivo.

Blood flow in a dog's aorta has been measured by percutaneous introduction of a flow sensor. Two types of flow probes have been used in conjunction with an external magnetic field: Loop-shaped probes used as rate of volume-flow meters and L-shaped probes as velometers. Methods of calibration and establishing the base line are discussed, and the performance of the apparatus is illustrated by records of blood flow in the thoracic and abdominal regions of the aorta.

Acetylcholine↗
PubMed1970

A new approach to electromagnetic blood flow determination by means of catheter in an external magnetic field.

Maximal reduction in transverse catheter dimension has been achieved for the purpose of creating an intravascular electromagnetic flow sensor capable of percutaneous introduction into the vascular system. The electrodes are mounted on a flexible frame which collapses as it passes through a small branch blood vessel and expands to span the diameter of the main vascular trunk when entering it. Unlike the catheter flow sensors developed previously, which are velometers, i.e., sensors of fluid velocity, the present one is capable of measuring the volume rate of flow in branch blood vessels as well as in the major sections of the vascular tree. The magnetic field is provided by a large air core electromagnet placed externally to the animal or patient. A special circuit utilizing two electrodes and three leads permits reduction of the unwanted quadrature signal to zero. A standard sine wave electromagnetic flow meter channel designed for use with conventional electromagnetic flow transducers is adequate for flow measurements as well as for power supply to the large magnet. Illustrations of the performance of the apparatus in vitro and in vivo are presented.

Animals↗
PubMed1970

An electromagnetic catheter blood flow meter of minimal lateral dimensions.

A method is described to reduce the lateral dimensions of an electromagnetic catheter blood flow meter to the maximum possible extent. To achieve this, the magnetic field is generated by a magnet placed outside the subject. Thus, only the electrodes and a minimal supporting structure have to be introduced into the blood vessel to pick up the electromotive force induced in the blood streaming at right angles to the magnetic field. To suppress induction of a transformer electromotive force in the electrode leads, the latter form a co-axial lead system of small gauge. One electrode is at the tip of the insulated external tube of this lead system (a gauge no. 28 hypodermic tube) and is insulated from it. The other electrode is a bare section of the external tube about 2 cm from its tip. The tube is bent at an angle of about 30 degrees just below the second electrode. Thus, this bent section places the two electrodes near two diametrically opposite wall sections of the blood vessels after insertion of the fine catheter via a hollow catheter through a branch blood vessel into the main vessel. The catheter is rotated until the plane containing the bent section is perpendicular to the magnetic field. The potential difference between the two electrodes measures the volume rate of flow through the blood vessel. This principle can be used to monitor the flow in the major blood vessels as well as in their branches. Catheter flow meters down to about 0.5 mm in external diameter have thus been made and much smaller ones can be made without excessive difficulty.

Blood Flow Velocity↗
PubMed1970

A new approach to isoelectric focusing and fractionation of proteins in a pH gradient.

This paper describes a new method of condensation (focusing) of extended volumes of mixtures of proteins (or other ampholytes) into an isoelectric spectrum of discrete zones located at points of a pH gradient corresponding to the pI value of the individual proteins. In contradistinction to the currently practiced isoelectric focusing in "natural" pH gradients which may require as much as 96 hours for completion, the present method yields clear-cut condensations marking the isoelectric pH within about five minutes and complete fractionation within about 15 minutes. No "Ampholines" or other special buffers are required and establishment of the pH gradient requires only about 10 seconds rather than days as is common in natural pH gradient focusing. The pH gradient is generated by utilization of the temperature dependence of pH. By establishing a temperature gradient between 0 degrees and 50 degrees C in an electrophoretic column, a stable pH gradient extending over 1 pH unit can be maintained in the absence as well as the presence of a current. The pH gradient can be easily controlled by variation of the temperature limits so that high resolving power can be achieved in shallow pH gradients. The pI of the focused fractions is determined by measurement (by a thermistor or resistance thermometer) of the local temperature within each of the isoelectric zones that determine the local pH. The individual zones can be pipetted out. The method is illustrated by simultaneous condensation and evacuation of hemoglobin in two pH gradients traversed by opposite currents and by separation of hemoglobins A and S in 16 minutes in a pH gradient where the current passes in the direction of increasing pH in Tris buffer solutions stabilized by a sucrose density gradient.

Electrophoresis↗
PubMed1970

Determination of arterial blood flow by percutaneously introduced flow sensors in an external magnetic field. I. The method.

A method for determining the rate of blood flow in arteries without surgical intervention is described. It is shown that a probe capable of securing such information about flow in a blood vessel can be introduced into the vascular tree by means of a needle puncture in the skin made by a no. 18-guage hypodermic needle. A snugly-fitting guide wire is passed through the needle, which is then withdrawn. A Teflon catheter is then passed over the wire and pushed through the skin and subcutaneous tissues into the superficial branch artery from which the wire guides it deep into the aorta to a desired location. The guide wire is then withdrawn and a suitable sensing device of wire-like structure can be passed through the catheter into the major arterial trunk and, if desired, into some of its branches. Two types of sensors are used, loop-shaped ones which are used as volume-flow meters, and L-shaped probes used as volume-flow meters when they fir the artery precisely and as velometers when they do not. The sensors are used in conjunction with an apparatus consisting of a flat coil mounted over the animal and a standard electromagnetic sinusoidal flow meter channel.

Animals↗