Articles: biological-models.
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IEEE Trans Biomed Eng · Jan 1991
Epidural spinal cord stimulation: calculation of field potentials with special reference to dorsal column nerve fibers.
The effect of electrical stimulation with several electrode combinations on nerve fibers with different orientations in the spinal cord was investigated by computing the steady-state field potentials and activating functions. At first an infinite homogeneous model was used while secondly the spinal cord and its surrounding tissues were modeled as an inhomogeneous anisotropic volume conductor. ⋯ With anodal stimulation the opposite will occur. It was found that parameters substantially affecting the potential distribution in the dorsal columns are the conductivity of the white matter and the width and the conductivity of the csf layer.
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The investigation of wound healing is dependent on the use of various models. This paper reviews several methods used to study wound healing, particularly in regard to connective tissue metabolism. The usefulness and potential pitfalls of cell culture are discussed. ⋯ Histologic methods are available to evaluate the cellular and matrix details within the wound. Additionally, methods developed in molecular biology are becoming applicable to healing studies and a safe means of investigating collagen metabolism in humans by the use of a stable oxygen isotope is being developed. The study of fetal wound healing provides an excellent example of the utility of many of these methods in achieving an understanding of the biology of this remarkable scarless process.
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Ventilation systems that operate at high-frequency and deliver small volumes have the potential to provide adequate alveolar ventilation without excessive pulmonary pressures. One way of producing high-frequency ventilation is by use of jet bursts of an input gas through a cannula controlled by a solenoid valve. This high-frequency jet ventilation has yet to be quantitatively analysed for optimal clinical use. ⋯ Using a nitrogen washout analysis, we evaluated the operating lung volume, effective dead-space volume (Veds), and effective ventilation rate (Veff). We found that Veds is independent of the individual effects of jet cycle frequency, duty cycle, cannula diameter, and entrainment fraction. While Veds was not affected significantly by the shape of the airway, it did depend on the distance of the jet cannula tip to the ventilated bag (or alveolar region) and on the tidal volume.
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Methods Find Exp Clin Pharmacol · Nov 1990
A pharmacological model of cerebral ischemia. The effects of indomethacin on cerebral blood flow velocity, quantitative EEG and cognitive functions.
Indomethacin decreases cerebral blood flow. Such an effect in humans might offer the possibility to establish a human model of cerebral ischemia. In the present study the effects of a single oral dose of 100 mg indomethacin were studied in male subjects with quantitative electroencephalography, cerebral blood flow velocity and the memory comparison task as parameters. ⋯ Ninety minutes after indomethacin ingestion recordings of quantitative electroencephalography and blood flow velocity were repeated and a parallel version of the memory comparison task was performed. The blood flow velocity decreased to 60% of the initial value; quantitative electroencephalography showed a -0.3 Hz slowing of the alpha peak frequency (p less than 0.01) and a decrease in the relative power of the alpha band (p less than 0.10) without any change in the delta or theta band. The memory comparison task showed an increase of the slope index (p less than 0.05), indicating a deterioration of cognitive functioning.