Letter: Electrical method of detecting optimum time to inseminate.

PIP: Recently translated studies of the electrical resistance of cervical mucus as a test for the optimum time of insemination of agricultural animals are reviewed. The technique involves the measurement of the electrical conductivity of the surface of the mucosa in the vaginal vestibule. Experiments with cows and sows have shown that pregnancy or fertilization rates are considerably higher when mucosal electrical resistance is low at the time of insemination than when resistance is high. It has also been demonstrated in sows that mucosal resistance is higher in pregnant than in nonpregnant animals. Further research into these results is recommended.^ieng

'Self-correcting' spherical bioelectrode.

Most of the widely used biopotential macroscopic and microscopic bioelectrodes do not enable proper measurements while in contact with 'problematic' tissues, such as myocardial and other muscular tissues, cortical and intracavital tissues. A quantitative spherical electrode was designed as an example in the family of bioelectrodes enabling application in moving or vibrating media. The electrode developed is insensitive to its contact area. Decreasing the contact area to 40% causes 25% increase in measured resistance only. The electrode shows excellent performance in alternating current conditions combined with well-defined direct current characteristics.

Electrical impedance monitoring of the wound-healing process.

The healing process was studied of five surgical wounds in sheep caused by the implantation of pacemaker electrodes in the vaginal or vulvar submucosa, while the electrodes were being used for impedometric measurements of the tissue surrounding them. Separate measurements of conductance (G) and capacitance (C) were carried out at frequencies ranging from 10 Hz to 100 kHz. The highest specific conductance at 100 kHz (mumho/cm) was observed on the 3rd postoperative day - 3095 +/- 172 SEM (n = 5), at which time the wound area was considerably swollen. Thereafter, the conductance gradually decreased and stabilized in 17-20 days at 2194 +/- 54 when the healing process was terminated. The decreasing impedance angle and tissue phase angle indicated that during the healing process cell volume decreased and cell density increased.

Impedometric properties of the vulvar and vaginal tissues of ewes during the oestrous cycle.

Tissue electrical conductance (G) and capacitance (C) were measured in vulvar and vaginal tissues of ewes by a spectroimpedographic method at frequencies from 10 Hz to 100 kHz. The calculated specific conductance (mumho/cm) at 100 kHz was 3082 +/- 20 (s.e.m.) in oestrus and 2153 +/- 16 in dioestrus (n = 8) (P < 0.001). The impedance angle and the tissue phase angle increased during oestrus, indicating that cell volume increased and cell density decreased in comparison with dioestrus. The ratio of conductivities at higher and lower frequencies showed that extracellular water content was maximal during oestrus and coincided with standing heat.