Med. &Biol. Eng. & Comput., 1978, 16, 11-14

Intestinal-prostatic impedance measurements in bulls E d u a r d o V a l d e z O s c a r W i l d e

M a x E. V a l e n t i n u z z i A n t o n i o F. C a r l i n o

O s c a r E. C l a v i n

Laboratorio de Bioingenieria, Facultad de Ciencias Exaetas y Tecnotogia and Departamento de Produccion Animal, Facultad de Agronomia y Zootecnia, Universidad Nacional de Tucuman, Argentina

A b s t r a c t - - T h e average intestinal-prostatic impedance in unanaesthetised bulls at ejaculation was ex- perimentally evaluated by the application of known stimulating rectangular pulses (2 ms width, repetition rates between 25-35 pulses/s) and found, on average, to be of the order of 65. 9 ~ (s.d. = 9 ) over a total of 14 ejaculations in eleven animals. The corresponding mean eiaculatory stimulating current dose was 0 .507 mA/kg (s.d, =0-181). In al l cases, the total current for fu l l ejaculation was higher than 170 mA. An empirical relationship between biological im- pedance and applied current (124 data points) was also determined, showing, as expected, a decrease with increasing current and tending to a constant value in the order of 62 ~ (s.e.e, = 12) for la = 2 8 8 mA. This impedance (which is faced by the stimulating electrodes inserted in the rectum) can be very easily estimated by means of the well known impedance technique at higher frequencies. In these experiments and at 12 kHz, the average over 44 measurements was 59 .3 ~ (s.d. = 10.7) , a value very close to those given above and, therefore, useful in the design of adequate eleetroejaculators.

Keywords - -B io log i ca l impedance, Electroejaculation

1 Introduction

IN a report of the first legal death penalties inflicted by electrocution, it is found that the post-mortem examinations of the bodies indicated that some of the convicts had an ejaculation as a direct result of the shock (MACDONALD, 1892). This observation probably led to the idea of using electricity as a well controllable means to obtain semen samples from laboratory animals. Batelli, who, in 1899, had started the study of cardiac fibrillation-defibrillation (PREVOST and BATELLI, 1899a, b), can perhaps be considered as the first to try electroejaculation in experimental animals (BATELU, 1922). This author must have been well aware of the effects of electric discharges on mammals because of his previous studies which, incidentally, had been encouraged by the interest aroused at the turn of the century around the potential risks of d.c. and a.c. for domestic use (BERNSTEIN, 1973). In this context and interestingly enough, electroejaculation would ap- pear as a byproduct of the above-mentioned studies and, ever since Batelli's trial in 1922, the technique developed rapidly, being today an accepted industrial and research procedure (BALL, 1974).

Received 22nd April 1977

0140-0118/78/0694-0011 $1.50/0 �9 IFMBE: 1978

However, there are still aspects which deserve consideration, particularly when using a rectal bipolar probe. One of them is the estimation of the electrical impedance faced by the stimulating electrodes. The objective of this paper is to report values for that impedance in order to establish a range useful as a design parameter in the con- struction of more adequate electroejaculators.

2 Materials and methods

2.1 Animals

Eleven bulls (unanesthetised and without sedatives or tranquilisers) were employed in these experi- ments, ten of the Argentine-Creole race, and one of the Holland-Argentine race. The average weight was 517kg (s.d. = 112-7), ranging from 322 to 658 kg. Their ages ranged from 2�89 to 6 years, with an average of 4 years (s.d. = 1- 5).

2.2 Electrodes and stimulation

The stimulating electrodes were placed in a rectal polyvinyl compound (p.v.c.) probe which was described by BoTrtNO et aL (1968). Its diameter is 45 ram, with a total length of approximately 400mm. Each electrode ends in nine metallic terminals (electrically interconnected) arranged in

Medical & Biological Engineering & Comput ing January 1978 11

a flower-like fashion. The distance between centres is 90 mm and the diameter of each flower is 35 mm (Fig. 1). When introduced into the rectum, the

< 90 m m > t ',

eeo--+ | -~' �9 @ �9 35mm | @ �9 45mm | o|

EA Z(I EB

' T Z1 Z 2

Z B

I position of the probe was such that the electrode terminals EA and EB faced the ventral wall of the intestine. The flower-like configuration, as stated by BOTTINO et al. (1968), favours a better distribu- tion of the stimulating current. The probe has a pistol-like handle with a push button to deliver the electric discharges by a finger-tip pressure of the operator.

The stimulator was a t 2 V battery-operated experimental unit based on a multivibrator circuit, able to deliver rectangular pulses of variable amplitude (0-20 V over 75f~), duration (0" 5, 1 and 2 ms) and repetition rate (20-50 pulse/s).

2.3 Impedance

The impedance Z, to be measured depends on the pathway of the current and, in a simplified manner, it can be represented by the combination shown in Fig. I, in which ZL = superficial fluid and rectal mucosa (tending to bypass the signal), Z1 and Z2 = rectal wall and adipose tissue (in series), ZB = structures to be stimulated (ampullae, seminal vesicles, prostrate, other excitable tissues related to these structures). Anatomical details justifying this interpretation can be found elsewhere in the litera- ture (BOTTINO et al., 1968; SALISBURY and VANDEMARK, 1964).

The impedance Z. was measured by the following two methods:

(a) By measuring the applied rectangular voltage Va across the electrodes and the circulating current I , with an oscilloscope (Tektronix 561A) and calculating Z, as the ratio of the two pre- vious data. The current was obtained as the voltage drop over a series known resistor of 2 .5~ .

(b) By using an impedance meter of constant current (about 100/~A) at 12kHz (CLAWN and VALEr~TI~UZZL 1977), according to a well-known principle (GEDD~S et al., 1962).

2.4 Procedure After placing the selected animal in a chute and

inserting the probe, the amplitude of stimulation

Fig. 1 Rectal probe. (a) Lower side geometry arrange- ment of the electrodes. (b) Impedance faced by the electrodes EA and EB when the probe is inserted in the rectum

(applied in short bursts of a few seconds each) was gradually increased until f u l l ejaculation took place. Repetition rates of 25-35 pulse/s were used. This procedure is standard and well described in the literature (BALL, 1974; BOTTINO et aS., 1968; SALISBURY and VANDEMARK, 1964). For each applied voltage amplitude, the impedance Z, was calculated by the method (a) mentioned above, making a special note of the values Za(E) when ejaculation occurred. At the beginning and end of each series of stimulations, the intestinal-prostatic impedance faced by the electrodes was also determined

i@ �9

1 50 i [

~" Z e +_ see. = 256.39 .!- 12

cX d , ',�9 �9

t " ,

�9 �9 ... �9 �9

�9 . �9 �9 �9 " - e ..... @

O � 9 - - - q ro � 9 �9

+~ I I" s'o +6o ;oL 2;0 2;o

[ o ,mA

Fig, 2 Intestinal-prostatic impedance Z a as a [unction of the applied current I+, Z e was fitted by the least-squares method

12 Medical & Biological Engineering & Computing January 1978

by method (b). It was called Z,12 to indicate the measurement at 12 kHz.

3 Results A total of 124 stimulations were performed on

the eleven available bulls. Ten animals produced good ejaculations containing mobile spermatozoa (checked under the microscope); one animal (T231, 570kg) did not ejaculate, even with maxi- mum current of almost 300 mA. Only fluid drip- ping was obtained. A few animals ejaculated at more than one value of I,.

Fig. 2 shows a scattergram of Z, (expressed in ohms) as a function of I , (expressed in milliamps). As expected in any biological material, the impe- dance decreases as the applied current increases. The solid line corresponds to the function

Ze = k ( I , ) - ~ . . . . . . . . (1)

in which k = 256.39 was calculated with the least- squares criterion (see Appendix) from

k = [ E Z , ( I , ) ~ ] / [ E ( I , ) -~ ] . . . . . (2)

where (Z~, Is) are the pairs of experimental values with i = 1 to 124. The dotted lines correspond to the estimated impedance Ze plus and minus, respectively, one standard error of the estimate (s.e.e.). They encompass 84 data points, i.e. 68% of the population. Ejaculation always occurred at values of current higher than 170 mA (to the right of the vertical bars in Fig. 2).

The average impedance ~7,(E) + s.d. at ejaculatory current over a total of 14 ejaculations was (65-9_+ 9) [2. The corresponding average voltage and current were

(15.8 + 2.6) V and (240.7 + 36.6) mA,

respectively. Dividing each ejaculatory current by the body weight gave (0.507+0.181)mA/kg as the mean specific value, with a minimum of 0.292 and a maximum of 0.845 mA/kg.

The impedance Z.(288) at Ia = 288mA was (62+12)1"~, as obtained from the fitted curve (Fig. 2) This value gives an idea of how small the intestinal-prostatic impedance seen by the stimulator can be.

On the other hand, measurements made with the impedance meter at 12kHz produced an average impedance (2,12-+ s.d.) = (59.3 + 10.7) [2, over a total Of 44 values. The minimum was 38 [2 and the maximum was 80[2. Attention is called to the similarity between the numerical values of Z,(288) and 2,12.

4 Discussion

As expected, the average ejaculatory impedance Z.(E) was slightly higher than the average value at 12 kHz. The more direct impedance technique can easily and safely estimate the intestinal-prostatic

electric hindrance to the stimulating current. From the data given previously, it can be stated that an adequate bull electroejaculator should be able to deliver a t l e a s t 300 mA (rectangular pulses, 2 ms width, 25-35 pulse/s) over a 60 fl impedance. This corresponds to an amplitude of 18 V.

An interesting concept to consider is the 'current dose' needed to obtain a full ejaculation. The value reported here can be rounded off as 0.5 mA/kg. However, it must be recalled that, in all probability, there is not a linear relationship between I. ] W and body weight W , and animals heavier than 700 kg may require more than the predicted 350mA. Besides, some animals may not respond at one given moment merely because of time-dependent physio- logical differences. This is offered as a possible explanation for the failure of one of the bulls.

The values reported here were taken as the design parameters to construct two electroejaculators which have been in use for over a year at the Agronomy School of the Universidad Nacional de Tucumfin.

In conclusion: (a) The average intestinal-prostatic ejaculatory im-

pedance in bulls has been experimentally evaluated.

(b) This impedance can be easily determined by means of the well known impedance technique at higher frequencies.

(c) The impedance values proved to be useful in the design of adequate electroejaculators.

(d) The concept of ejaculatory stimulating current dose is introduced.

Appendix

Derivat ion o f eqn. 2

A number N of experimental pairs of data points (x. Yi) is to be fitted by the proposed relationship

y - k ( x ) - ~ . . . . . . . . . . (3)

according to the least-squares criterion; i.e.

F = E ( y i - - y ) Z _ minimum . . . . . . (4)

Replacing eqn. 3 for y in eqn. 4 and taking the derivative with respect to k yields

d F ] d k : --2Xyi(x~)- ~ +2kX(x~)- § (5)

which, when equated to zero and solved for k, gives

k - [Y, y i ( x O - § . . . . . . (6)

an expression fully coincident with eqn. 2 if y is replaced by Z and x is replaced by L

A c k n o w l e d g m e n t s - - T h e ten Argentine-Creole bulls were kindly supplied by the Instituto Nacional de Tecnologia Agropecuaria (INTA) at its Leales Station (Tucmfin, Argentina). The Holland-Argentine specimen was supplied by the Agronomy School of the Universidad Nacional de Tucumfin (UNT). The project was supported

Medical & Biological Engineering & Computing January 1978 13

with funds from the Secretar[a de Ciencia y T6cnica (UNT), Fundaci6n Banco Empresario de Tucumfin and Instituto Nacional de la Actividad Hipica (INAH).

References

BALL, L. (1974) Electroejaculation of bulls. Proc. Fifth Tech. Conf. Artif Insem. Reprod., Nat. Assoc. Animal Breeders, Feb. 14-16, pp. 95-100.

BATTELLI, F. (1922) Une m6thode pour obtenir l'emission compl6te du liquide de vesicules seminales chez le cobaye. Comptes Rendus Soe. Physique et d'Histoire nat. Geneve, 39, 73.

BERr~STEIN, T. (1973) A grand success. IEEE Spectrum, 10, 54-58.

BOTTINO, J. A., Dozo, M. F., CASTRO, H. R. and ADROVER, J. (1968) Nuevo equipo y nueva t6cnica operatoria aplicados en la electroeyaculaci6n. Gaceta Veterinaria 30, 3-13.

CLAVIN, O. E. and VALENTINUZZI, M. E. (1977) Impedan- cimetro biol6gico de muy alta linealidad. Report to the Consejo Nacional de Investigaciones Cientificas y T6cnicas of Argentina (CONICET), Lahoratorio de Bioingenieria, Instituto de Ingenieria El6ctrica, Universidad Nacional de Tucum~n, Tucum~n, Argentina.

GEDDES, L. A., HOFE, H. E., HICKMAN, O. M. and MOORE, A. G. (1962) The impedance pneumograph Aerospace Med. 33, 28-33.

MACDONALD, C. F. (1892) The infliction of the death penalty by means of electricity. Trans. Med. Soc. State New York, 400-427.

PREVOST, J. L. and BATELLI, F., (1899a) Death by electric currents (alternating currents). Comptes Rendus Acad. Sci. Paris D 128, 668-670.

PREVOST, J. L. and BATELLt, F. (1899b) Some effects of electric discharge on the hearts of mammals, ibid. 128, 1267-1268.

SALISBURY, G. W. and VANDEMARK, N. L. (1964) Physio- logy of Reproduction and the Artificial Insemination of Cattle. W. H. Freeman and Co.

Mesures d'imp6dance prostatique et intestinale chez les taureaux Sommaire--L'imp~dance prostatique et intestinale normale chez des taureaux non anesth6si~s, au moment

de l'6jaculation, fut 6valu6e apr6s exp6riences par l 'application de pulsations rectangulaires stimu- lantes reconnues (2 m de largeur, tt une cadence r6p6t6e de 25 fi 35 impulsions/seconde), et estim6e, en moyenne, de l 'ordre de 65 "9 ~ (SD= 9) sur un total de 14 6jaculations chez onze animaux. La dose moyenne correspondante de courant de stimulation 6jaculatoire 6tait de 0,507 mA/kg (SD = 0" 181). Dans tous les cas, le courant total pour 6jaculation complete 6tait sup6rieur fi 170 mA. Une relation empirique fut ailleurs 6tablie entre l 'imp6dance biologique et le courant appliqu6 (124 points de donn6es), indiquant, comme pr6vu, une diminution avec une augmentation de courant, et une tendance vers une valeur constante de l 'ordre de 62 ~ (s.e.e.=12) pour Io+288 mA. Cette imp6dance (obtenue par les 61ectrodes de stimulation introduites dans le rectum) peut 6tre tr~s facilement estim6e, grace tt une technique r6put6e d'imp6dance fi des fr6quences plus 61ev6es. Pour ces exp6riences, la moyenne de plus de 44 mesures tt 12 kHz 6tait de 59" 3 ~ (SD = 10-7), une valeur tr~s proche de celle donn6e ci-dessus, et par cons6quent utile pour la mise au point d'61ectro- 6jaculateurs ad6quats.

Messung des Darm-Prostata-Widerstands bei Bullen Zusammenfassung--Der durchschnittliche Darm-Prostata-Widerstand bei nicht an~isthesierten Bullen bei

Ejakulation wurde experimentell unter Anwendung b~kannter rechteckiger Stimulierungsimpulse (2ms breit, mit 25-35 Impulsen pro Sekunde) untersucht und durchschnittlich in der Gr6Benordnung von 65-9 ~ (s.d. = 9) bei 14 Ejakulationen an elf Tieren festgestellt. Die zugeh6rige durchschnittliche ejakulationsstimulierende Stromst~irke betrug 0 ' 507 mA/kg (s. d. = 0-181). In s~imtlichei~ F~illen lag die Gesamtstromst~irke ffir volle Ejakulation fiber 170 mA. Augerdem wurde eine empirische Be- ziehung zwis~hen biologischer Impedanz und angewandter Stromst~irke (124 Datenpunkte) herge- stellt, aus def wie zu erwarten hervorgeht, dab der Widerstand mit steigender Strom3t~irke sinkt und zu einem konstanten Wert um 62 f~ (s.e.e. + 12) bei einem Stromvon Io = 288 tendiert. Dieser Wider- stand (der den Stimulierungselektroden, die in das Rektum eingeffihrt werden, gegeniibersteht) lgl3t sich leicht mittels der bekannten Widerstandstechnik bei h6heren Frequenzen schtitzen. Bei diesen Versuchen und bei 12 kHz lag der Durchschnittswert ffir 44 Messungen bei 59.3 f~ (SD = 10.7), ein Wert, der nahe bei den oben angegebenen liegt, und der daher ftir den Entwurf brauch- barer Elektroejakulatoren yon Nutzen ist.

14 Medical & Biological Engineering & Computing January 1978