Effects of odorants on pigment aggregation and cAMP in fish melanophores.

Odor perception within olfactory neuroepithelium and pigment translocation within melanophores both seem to rely on a cAMP-based second messenger system. From studies on cultured frog melanophores, Lerner et al. (Proc. Natl. Acad. Sci. USA 85:261-264, 1988) suggested that some aspect of odor perception may be mediated by a nonspecific mechanism whose signal is transduced by a cAMP-based second messenger system. In the present study, odorants (beta-ionone, benzylaldehyde, cineole, cinnamaldehyde, and octanol), which previously have been shown to stimulate formation of cAMP in the olfactory neuroepithelium, were investigated for possible pigment dispersing and cAMP-increasing effects. Pretreatment of fish melanophores with the adenylate cyclase activator forskolin (1 microM) resulted in an approximately 300% increase in cAMP and an almost complete blockage of noradrenaline-induced pigment aggregation. However, none of the tested odorants were able to increase the cAMP level and only cinnaldehyde and beta-ionone were found to have any pigment dispersing activity.

Local and non-local receptor signalling.

It is suggested that the physiological response caused by an excited membrane-bound receptor can be either local, i.e. localized close to the receptor site, or non-local, spreading over a large volume in the cell. A simple model is presented which shows how locality and non-locality are related to the intrinsic "efficacy" of the drug used in classical receptor theory. It is further demonstrated how the shape of the physiological response versus receptor occupancy is determined by the number of receptor sites which contribute to the physiological response at a given location in the cell.

Measurements of light transmission through single melanophores.

A photometrical method has been developed that allows assessment of subcellular pigment migration in melanophores of the fish cockoo wrasse (Labrus ossifagus L.) The pigment migration was studied with local light spot transmission measurements. Depending on where the light beam is placed on the melanophores it is possible to study events within an area of approximately 75 microns 2. Measuring pigment translocation in different parts of a melanophore gives new possibilities to study how cell membrane receptor-mediated signals are spread within a single cell, which will increase our understanding of how receptor activating drugs exert their cellular effect. The technique can be used in pharmacological and biophysical studies and in biosensors, pharmaceutical screens, environmental detectors, etc. The method clearly has the ability to study local and small changes in light transmission due to displacement of melanophore pigment granules. Since one melanophore on the tip of an optical fibre would be enough to obtain a measurable effect, the presented technique provides the basis for future development of biosensors small enough for in vivo applications, e.g., to monitor the catecholamine levels of circulating blood.

Mechanical pulse wave propagation in gel, normal and oedematous tissues.

The velocity, attenuation and frequency content of the mechanical pulse wave propagation in gels of various water contents, in normal tissues from various sites and in oedematous tissues from different patients were investigated. The properties of the propagated pulse wave depend on the water content of the gel and the viscoelastic properties of the tissues. From the dependence of the pulse wave propagation velocity on elasticity, viscosity and density, information may be obtained concerning the effects of oedema on the mechanical properties of tissue.

Impression technique for the assessment of oedema. Technical improvement and methodological evaluation of a new technique.

A new instrument for the assessment of oedema based on the impression method is described. The measurement parameters are defined and the errors corresponding to the electrical and mechanical stability of the instrument are measured. The overall accuracy is calculated theoretically for the translocated volume. The accuracy and reproducibility are evaluated on plastic foam. The clinical procedure to measure oedema with this instrument is described. We show that the accuracy of the translocated volume parameter is very dependent on the overall stability of the instrument and that this instrument has an overall relative error of less than 7.3 per cent for a representative measurement. Experimental measurements on plastic foam show that the measurement parameters could be reproduced with standard deviations of less than 6 per cent and that the standard deviations for translocated volume are within the calculated overall relative error. Measurements on four patients with chronic oedema in an extremity show significantly different results on locations where pitting could be recognised compared to the contralateral nonoedematous extremity.

Effects of sodium nitrite on ultraviolet light-induced relaxation and ultraviolet light-dependent activation of guanylate cyclase in bovine mesenteric arteries.

It was demonstrated that precontracted strips from different bovine mesenteric arteries showed variation in sensitivity to ultraviolet radiation (366 nm). Some strips relaxed when they were exposed to ultraviolet light, others showed no sensitivity at all and, finally, some showed contraction. However, all arteries relaxed when they were irradiated with UV-light in the presence of 10 microM NaNO2. Ultraviolet radiation (366 nm) increased the activity of guanylate cyclase in crude homogenate from bovine mesenteric arteries by about 20-fold in the presence of NaNO2, while UV-light in the absence of sodium nitrite had no effect on the guanylate cyclase activation. These results support the notion that nitrite may be essential for vascular smooth muscle relaxation by UV-light, possibly through the release of nitric oxide.

Fish scales as biosensors for catecholamines.

Certain fish scales contain specialized cells (chromatophores) with pigment granulas, which can be dispersed or aggregated in the cells. The degree of aggregation is determined by a transmitter substance, noradrenaline, released by the sympathetic nerve endings in the skin. Isolated scales from, for example, cuckoo wrasse (Labrus ossifagus) retain a large sensitivity to externally applied noradrenaline (or more generally catecholamines) for several weeks. The degree of aggregation in isolated scales can be measured objectively by simple photometric techniques. We demonstrate in this paper how fish scales can be used to monitor catecholamine levels in human blood plasma. A discussion of other potential biosensor applications of this intact biological receptor-effector system is also given.

Changes in skin potentials induced by skin compression.

Changes in skin potentials are known to occur upon stretching and compressing the skin. In this work the relationship between compressional force and changes was studied for forces up to 13.7 N. For a given force, a flatter compressing surface gave lower potential changes than a more curved surface. When temperature increased both changes in potential and current decreased.

Fluid translocation measurement. A method to study pneumatic compression treatment of postmastectomy lymphoedema.

Tissue fluid translocation under the action of deformation was measured to study the pneumatic compression treatment of postmastectomy lymphoedema of the arm. Analysis of the results provides statistically significant parameters for characterization of the oedema. Mobility of the fluid in pitting oedematous tissue was significantly greater than that of normal tissue and decreased after pneumatic compression treatment. Oedematous fluid at the distal sites of the arm showed a greater mobility than that of the proximal sites. Improvement in the oedema due to pneumatic compression treatment was found to be greater at the distal sites than at the proximal sites. In addition, oedema recurred between the treatments and repeated treatments produced the best results. Measurement of fluid translocation is useful in selecting and evaluating the effectiveness of lymphoedema treatment, as well as in determining the viscoelastic properties of the oedematous tissues.

Peripheral nerve as an osmometer: role of endoneurial capillaries in frog sciatic nerve.

The sciatic nerve of the frog was perfused in vivo with isotonic Ringer solution followed by Ringer made hypertonic by addition of sucrose or of NaCl. Nerve diameter and endoneurial hydrostatic pressure fell during hypertonic Ringer perfusion. Using a model that describes the elastic and osmotic properties of the nerve, sigma sLp, the product of the osmotic reflection coefficient at endoneurial capillaries for s equals sucrose or NaCl (which approximates 1), and of capillary hydraulic conductivity, was found to equal 73 X 10(-13) cm3 X s-1 X dyn-1. The nerve is elastic. It has a compliance K of 3.7 X 10(-5) cm2 X mmHg-1, corresponding to a modulus of elasticity E of the perineurium equal to 1.2 X 10(6) dyn X cm-2. The results indicate that the nerve behaves as an osmometer during vascular perfusion, due to the low permeability of endoneurial capillaries to small solutes such as NaCl and sucrose. A low capillary hydraulic conductivity limits bulk water flow between blood and nerve, and a low compliance limits nerve swelling and edema.

Myocardial oxygen pressure across the border zone during acute coronary artery occlusion in the pig heart.

An experimental model for studies of local myocardial ischemia is described. During coronary artery occlusion of various durations, from two to sixty minutes, tissue oxygen pressure (ptO2) was measured across the "border zone" i.e., the tissue between normal and ischemic myocardium. PtO2 was measured with a surface oxygen electrode with eight measuring points arranged in an array. In fourteen pigs a total of forty coronary artery occlusions were studied. During occlusion one single pattern of ptO2 values was found; the measurements from the first point, closest to the core of ischemia, dropped rapidly to zero while the second, third and fourth measuring points showed a stepwise slower decrease in ptO2. In four animals we found a spontaneous increase in ptO2 during coronary artery occlusion. Upon reopening of the occluded artery there was a rapid rise in ptO2 as well as an "overshoot". Our findings support the hypothesis of a narrow "border zone" with a small residual blood flow thus subjectable to treatment aiming at reduction in the size of the infarct.

Microcomputer-based system for registration of oxygen tension in peripheral muscle.

For registration of oxygen tension fields in peripheral muscle a microcomputer based system was designed on the M6800 microprocessor. The system was designed to record the signals from a multiwire oxygen electrode, MDO, which is a multiwire electrode for measuring oxygen on the surface of an organ. The system contained patient safety isolation unit built on optocopplers and the upper frequency limit was 0.64 Hz. Collected data were corrected for drift and temperature changes during the measurement by using pre- and after calibrations and a linear compensation technique. Measure drift of the electrodes were proved to be linear and thus the drift could be compensated for. The system was tested in an experiment on pig. To study the distribution of oxygen statistically mean, standard deviation, skewness and curtosis were calculated. To see changes or differences between histograms a Kolmogorv-Smirnov test was used.

Characterization of subcutaneous edema by mechanical impedance measurements.

The mechanical behavior of gels of various water content, normal and edematous tissues have been studied. Static deformations and vibrations at low frequencies were applied to an area of each of these structures. Softer structures, e.g., gel containing a high percentage of water and pitting edema, have lower mechanical impedance (MI), while harder structures, e.g., nonpitting edema have higher MI. A comparison of the static force measured at bilateral sites on normal subjects show lower differences in impedance than do similar comparisons made in subjects having unilateral edema. This difference is more pronounced with greater static compression. The differences in the MI between different structures are greater at the lower frequencies. At the lower frequencies up to around 30 Hz the ratio of the magnitude of MI of edematous skin and that of contralateral normal skin can indicate the degree of edema. The MI of edematous tissues depends on the type of edema and varies with its degree. Thus this study introduces a quantitative method for the diagnostic and therapeutic assessment of unilateral subcutaneous edema.

Locally applied 133Xenon for the measurement of regional cerebral blood flow (rCBF): an experimental study in the pig.

A method for measuring regional cerebral blood flow has been developed. On pig brain cortex a 1 cm2 size polyester film was placed, under which 0.6-1.3 mCi of 133Xenon in 2-4 microliter of saline was applied atraumatically. The wash-out process was registered with an external detector, and can be described as a sum of monoexponential functions. The first component of the curve, obtained by curve resolution, indicates blood flow in grey matter and the second slow component indicates blood flow in white matter. When total ischaemia was induced, there was no wash-out of the isotope. Freezing the brain after isotope application at different stages during the wash-out showed isotope in both grey and white matter. The isotope did not diffuse into the polyester film. This technique was also used in studies on the spinal medulla where white matter is outermost and grey innermost. The wash-out curve obtained consisted of only one monoexponential function; blood flow from grey matter was not present in the wash-out curve. For calculation of cerebral blood flow a modified two-compartment model was used. It is concluded that this method measures local cerebral blood flow in both grey and white matter. The method can be used clinically to measure the local cerebral blood flow during neurosurgical operations.

A multiwire surface oxygen pressure electrode for measurement across zones of normal and damaged tissue.

The standard MDO multiwire surface oxygen electrode was redesigned to enable measurements across transition zones between normal and, e.g., ischemic tissues. The eight measuring points were arranged in an array 2.2 mm long. This array multiwire electrode (AME) has been tested and showed the same electrochemical properties as the standard MDO electrode. The resolving power was tested and an individual measuring point was affected by a change in surrounding pO2 if it occurred within a distance of 20 microns. In experiments in the pig heart subjected to local ischemia it was found that both ischemic and normal tissue oxygen pressure were registered simultaneously by the AME.