Algorithm for tissue ischemia estimation based on electrical impedance spectroscopy.

The purpose of this paper is to present an algorithm developed for real-time estimation of skeletal muscle ischemia, based on parameters extracted from in vivo obtained electrical impedance spectra. A custom impedance spectrometer was used to acquire data sets: complex impedance spectra measured at 27 frequencies in the range of 100 Hz-1 MHz, and tissue pH. Twenty-nine in vivo animal studies on rabbit anterior tibialis muscle were performed to gather data on the behavior of tissue impedance during ischemia.

Microstructural properties of bone in rat vertebra after long-term clodronate treatment.

Bisphosphonates (BPs) are known to increase bone mineral density, but it is not known how this increase manifests at low hierarchic levels of the bone structure. The present study aimed to clarify the effects of the long-term use of clodronate on the microstructure and chemical composition of bone. The second lumbar vertebral body (L2) in growing rats, subjected to 32 weeks' treatment with clodronate at either a therapeutic dose of 2 mg/kg, or a high dose of 10 mg/kg, or physiological saline (control group), was studied by scanning electron microscopy for morphology, by backscattered electron image (BSE) for density, and by energy dispersive spectrometry for material analysis.

Supplemental systemic oxygen support using an intestinal intraluminal membrane oxygenator.

An intraluminal membrane oxygenator (IMO) prototype was surgically inserted in the ileum and evaluated as a method of supporting systemic oxygenation in an acutely hypoxemic porcine model. Animals were assigned randomly to the test (n = 12) or the control (n = 8) groups, which underwent identical protocols with the exception of the O2 flow in the IMO device, which was shut off in the control group. In each case, hypoxia was induced by a reduction in the inspired oxygen fraction (FiO2) to 0.

Selection of measurement frequencies for optimal extraction of tissue impedance model parameters.

The results are presented of a study performed to determine the measurement frequencies that provide optimal extraction of tissue impedance model parameters from in vivo measured electrical impedance spectra. Measurement frequency sets that are logarithmic and quasi-linear, and frequency sets that produce angularly equidistant points on the Nyquist loci are used to test the parametric fitting algorithm that calculates R0, R infinity, alpha and tau tissue parameters from complex impedance spectra. Simulated data, calculated in the presence of < or = 5% measurement noise, and in vivo experiments indicate that the quality of the fitted parameters depends upon the selection of measurement frequencies.

Effects of sample geometry and electrode configuration on measured electrical resistivity of skeletal muscle.

Over the past 40 years, researchers from a variety of scientific backgrounds have been using Rush's equations to analyze results of their electrophysiological studies. A lack of understanding of the constraints and the domain in which these equations are valid, often results in situations in which it is challenging to evaluate and compare results obtained by different investigators. In this paper, we reanalyzed the conditions for which Rush's equations were derived, and using mathematical modeling, computer simulation and in vitro measurements, we delineated areas of their appropriate application.

Real-time extraction of tissue impedance model parameters for electrical impedance spectrometer.

This paper presents a new algorithm for real-time extraction of tissue electrical impedance model parameters from in vivo electrical impedance spectroscopic measurements. This algorithm was developed as a part of a system for muscle tissue ischemia measurements using electrical impedance spectroscopy. An iterative least square fitting method, biased with a priori knowledge of the impedance model was developed.

In-vitro and in-vivo comparative analysis of four tissue pH monitoring systems.

The purpose of this investigation was to identify the type of pH-reference electrode combination that is the most suitable and reliable in clinical applications involving long-term postoperative monitoring of microvascular reconstructive transplants and diagnosis of compartment syndrome. Four types of pH-sensing devices were chosen for the study: a standard glass pH electrode, a polymer-based pH electrode, an ISFET pH sensor, and a fiberoptic pH sensor. Various combinations of electrodes were tested in vitro for typically four days.

Biochemical and morphological characterization of carbon tetrachloride-induced lung fibrosis in rats.

The short-term and long-term lung CCl4 injuries in rats were studied by i.p. CCl4 for 2 or 5 weeks, respectively, and the lung injury in the third progression group receiving i.

Conductance volumetric model of an eccentrically positioned catheter within a three-compartment ellipsoidal ventricle.

This paper presents a mathematical model of the electric field generated and resistance measured by a conductance catheter within a three-compartment ellipsoidal approximation of a cardiac ventricle. The model is based on a novel combination of analytical and numerical techniques. The numerical component of the model predicts displacement of the catheter along the central longitudinal ventricular axis, as well as eccentric positions off that axis.

Blood glucose measurement by multiple attenuated total reflection and infrared absorption spectroscopy.

The difficulty of measuring physiological concentrations of glucose in blood by conventional infrared absorption spectroscopy is due to the intrinsic high background absorption of water. This limitation can be largely overcome by the use of a CO2 laser as an infrared source in combination with a multiple attenuated total reflection (ATR) technique. To demonstrate the applicability of this technique, we compared in vitro measurements of glucose in blood obtained from an experimental infrared laser spectrometer with independent measurements made by a standard YSI 23A laboratory glucose analyzer.

Verifying copper toxicosis in Bedlington terriers by analytical electron microscopy of needle biopsies of liver.

Diagnosis of copper toxicosis in Bedlington terriers was performed by analytical electron microscopy of needle biopsy of the liver. The animals were four Bedlington terriers clinically suspected of hereditary copper toxicosis, and four healthy control animals of the same breed. Light microscopy of the livers of the diseased animals revealed dense bodies in the hepatocytes which stained histochemically for copper.

Carbon dioxide laser based multiple ATR technique for measuring glucose in aqueous solutions.

Conventional IR transmission methods are not suitable to measure accurately the concentration of biological molecules in aqueous solutions since the dominant water component has a high intrinsic absorption band over a wide range of the IR spectrum. This limitation can be largely overcome by the use of a laser as a light source. This paper describes the design of an experimental IR spectrometer based on a CO(2) laser and an ATR technique.

Location and identification of colloidal gold particles on the cell surface with a scanning electron microscope and energy dispersive analyzer.

The use of colloidal gold particles for locating cell surface components by scanning electron microscopy (SEM) has been restricted due to difficulties in the identification of these gold particles under SEM. It is shown here how the gold particles bound to cell surfaces can be located and identified under SEM using the secondary electron imaging (SEI) mode with an energy dispersive X-ray microanalyzer (EDS). This enables reliable identification of gold particles and good quality micrographs of the cells to be achieved at the same time.

Ovarian development of Corynosoma semerme (Acanthocephala) during experimental infections in rats.

The general structure and aspects of the development of the ovaries of the palaeacanthocephalan Corynosoma semerme were studied by transmission electron microscopy using worms varying in age from 18 to 90 h obtained from experimental primary infections in hydrocortisone-treated rats instead of seals, which serve as the natural definitive hosts. The observations can be interpreted to show that the immature ovaries become transformed relatively rapidly from cellular spheres to the more complex mature ovaries consisting of the supporting and oogonial syncytia and the germ-line cells. The supporting syncytium developed before the oogonial syncytium.

Possible forms for dwell-time histograms from single-channel current records.

Certain macromolecules embedded in the cell membranes of a variety of cells behave as gated ion-selective pores or channels. The length of time that a channel remains open or closed is not deterministic in nature and must be described in terms of relative probabilities. If channels act independently of each other and appropriate experimental conditions can be maintained, the behavior of a channel can be described by a homogeneous Markov process.

Quantitative x ray microanalysis of pulmonary mineral particles in a patient with pneumoconiosis and two primary lung tumours.

The right upper lung lobe of a 74 year old man was resected for a central tumour. Two primary cancers were found; a central small cell carcinoma and a peripheral squamous cell carcinoma. In addition, the peripheral lung tissue showed generalised peribronchiolar fibrosis extending from the non-respiratory bronchioles to the level of the alveolar ducts.