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At least 397 records · Page 22Linked to original sources
PubMed1975

Determination of body fluid compartments by electrical impedance measurements.

?The ratio of the LF and HF impedances appears to be an excellent and simple tool for investigation of liquid specimens, either of the total human body, taking into consideration global impedances, or of a particular organ, taking into consideration local impedances. We have sketched out in this communication a study of the global impedance ratio variations with age, but a large number of studies still remain to be undertaken in those cases of severe denutrition, as in all cases of metabolic illnesses. We can state that, in most cases, not only does the ratio decrease but that there is extreme difficulty in reestablishing normal values. Whatever action is undertaken, it seems that the intracellular liquid compartment remains insufficient with respect to that of the extracellular liquid compartment. It is as if the water will not enter in the cells or as if it were no longer retained within the cells. Finally, with this concept of impedance ratios of Zlf/Zhf a promising experimental method has been found which will, perhaps, enable better infestigations in a field which has often been left to one side.

Body Composition↗
PubMed1975

Investigation of electrical impedance variations of dog brain tissue during experimental metabolic disturbances.

Experiments were carried out on dogs using bielectrode probes having as adequate impedancemeter. The probe is introduced via a cranial opening into the grey matter. This gives the following: a low frequency reading which is related to the extra cellular fluid component; a high frequency reading which is related to the total overall liquids; and a proportionality ratio of these liquids in the explored volume. The impedance variations are functions of the nature and intessity of vascular disturbance. Variation of the low frequency impedance (5 kHz) is the most significant. The experimental prodedure consists of: 1) Abrupt and permanent circulatory arrest; 2) Circulatory reduction by haemorrhage followed by recovery (if necessary by means of blood transfusion); 3) Anoxia by CO inhalation, recovery affected by means of O2 inhalation; and 4) Hypoglycemic coma induced by intravenous injection of insulin. The changes in the biochemical state of the cerebral tissue give very large variations of the low frequency impedance. It is these variations which are to constitute the object of this communication.

Animals↗
PubMed1975

The neuron of the fast conducting system in hirudo medicinalis: identification and synaptic connections with primary afferent neurons.

A single neuron, located in the center of each segmental ganglion of H. medicinalis is antidromically activated by electrical stimulation of the ventral cord anteriorly and posteriorly to the ganglion, at the same threshold as the fast conducting system (FCS) and with a latency equal to the FCS conduction time. This neuron is activated trans-synaptically by tactile and photic stimulation of the skin and by stimulation of high-threshold fibres running along the cord. A spike evoked by intracellular stimulation of this neuron propagates along the FCS. Intracellular staining shows that this neuron sends two axonal branches in the anterior and posterior median connectives. Direct electrical stimulation of touch cells (T cells), as well as mechanical stimulation of the skin, lowers the threshold of and may eventually fire, the FCS neurons, not only at the level of the ganglion to which they belong, but also at the level of the neighbouring ganglia. This effect is mediated by bilateral pathwasy located in the lateral connectives. It is concluded that the FCS consists of a chain of single neurons, located in each ganglion and electrotonically coupled to each other. Touch cells project with excitatory synapses on the FCS neurons.

Animals↗
PubMed1999

[The determination of anions of very weak acids by incompletely suppressed conductometric detection].

A novel method, incompletely suppressed conductometric detection, has been developed for the determination of anions of very weak acids. The principle of the method is discussed. The advantages of the method over the suppressed and nonsupressed methods for the determination of anions of very weak acids are also discussed theoretically. Results showed that the detection limits of the method for arsenous acid and boric acid were lower than those of nonsuppressed conductometric method. Being compared with suppressed conductometric method, the sensitivity was improved greatly. For 250 mg/L boric acid, 261- and 1002-fold increases in peak height and peak area were obtained, respectively. Within the linear range of the detection, the linear correlation coefficients of the peak areas of two weak acids were 0.9991 and 0.9985, respectively.

Anions↗
PubMedDate not supplied

[Conductometric method of studying aggregations of the formed elements of the blood].

To study an aggregation of formed blood cells a setup is proposed in which use is made of the conductometric method of measuring the resistance of a fine-pore filter through which the blood passes. A specially devised sensor allows it also to study the process of the cells aggregation in the vascular system of test animals and to control the dispersion of formed cells in the apparatus of extracoporeal circulation. Among advantages offered by the method are the objective character of measurement, the possibility of investigating the whole blood and due consideration of the part played by hydrodynamic factors.

Animals↗
PubMed2004

Conductometric study of shear-dependent processes in red cell suspensions. I. Effect of red blood cell aggregate morphology on blood conductance.

The conductance and capacitance of flowing and quiescent red blood cell (RBC) suspensions were measured at a frequency of 0.2 MHz. The results demonstrate that the time-dependent changes in the conductance recorded during the aggregation process differ in nature for suspensions of short linear rouleaux, branched aggregates and RBC networks. It is shown that the conductance of RBC suspensions measured during the aggregation and disaggregation processes follows the morphological transformations of the RBC aggregates. Thus, this method enables characterization of the morphology of RBC aggregates formed in whole blood and in suspensions with physiological hematocrits both under flow conditions and in stasis. These results in combination with previous ones suggest that this technique can be used for studies of dynamic RBC aggregation and probably for diagnostic use.

Blood Sedimentation↗