Metabolic clearance rate, production rate, and mammary uptake and metabolism of progesterone in cows.

Tracer kinetic techniques have been used to measure the production rate, metabolic clearance rate and mammary uptake of progesterone in six experiments on two Jersey cowsmthe cows were surgically prepared so that the carotid artery, jugular vein and mammary vein concentrations of progesterone, and udder blood flow, could be determined in conscious animals without anaesthesia or stress. The mean production rate of progesterone was 173 +/- 23-3 (S.ET) mug/min, with values ranging from 80 to 276 mug/min in pregnancy. The metabolic clearance rate was 22-5 +/- 2-0 1/min, or 0-21 +/- 0-025 1/min/kg metabolic body weight. The mammary uptake of progesterone was low, 3-1 +/- mug/min, and udder uptake accounted for about 3% of progesterone production rate. During [3H]A1progesterone infusion, radioactivity was transferred from blood to milk, probably by diffusion down a concentration gradient. Progesterone accounted for more than 88% of the ether-soluble radioactivity recovered from milk.     

An analysis of specific stimuli causing the release of prolactin and growth hormone at milking in the goat

Experiments to investigate the relative importance of the tactile, conditioned and possible metabolic components of the milking stimulus on the release of prolactin and growth hormone (GH) from the anterior pituitary of the goat are described. A comparison of the hormonal responses to milking the auto-transplanted mammary gland (i.e. denervated gland) with that obtained by milking the intact mammary gland of the same goat showed that the concentration of prolactin in the plasma increased only after milking the intact gland, whereas in two out of four goats an increase in plasma GH was detected several minutes after milking the transplanted gland. In the intact animal significantly more prolactin (P less than 0-01) was released in response to milking both teats for 6 min as compared with that released by milking only one teat for the same time. No significant difference (P less than 0-1) was found for GH. Similar quantities of prolactin and GH were released by goats milked when conscious or under anaesthesia. A comparison of the hormonal responses to teat stimulation in the same anaesthetized goats with and without the removal of milk from the mammary gland showed a significant reduction (P less than 0-001) in the quantity of prolactin and GH released in the absence of milk removal. The significance of these results is discussed.     

Metabolic clearance rate and production rate of oestradiol in conscious rabbits.

A continuous isotope infusion technique was used to measure the metabolic clearance rate (MCRB) and production rate (PRB) of oestradiol-17beta in a group of six non-pregnant conscious Chinchilla rabbits. The mean MCRB of oestradiol was 162 ml/min (0 X 079 1/min/weight0 X 75), and at equilibrium a significant proportion of the radioactivity in the circulation was present as oestrone (conversion ratio oestradiol to oestrone, 27 X 6%). The mean PRB of oestradiol was 4 X 3 ng/min, which is equivalent to about 5 mug/day. Some day-to-day variation was seen in the endogenous concentrations of oestradiol, oestrone and progesterone although in general the levels of the two oestrogens were less than 30-40 pg/ml, and progesterone levels were below 300 pg/ml apart from short peaks up to 600 pg/ml. These values were compared with previous measurements of the ovarian secretion rate of oestradiol measured directly in anaesthetized animals.     

Progesterone and 5 beta-pregnanediol production by isolated fetal placental binucleate cells from sheep and goats

Enzymic dispersion and density gradient separation were used for the isolation of enriched populations (60-90%) of cells from the corpus luteum, placenta and peripheral blood of pregnant sheep and goats. Analysis of the steroids produced from radioactive pregnenolone demonstrated that placental binucleate cells can produce progesterone and 5 beta-pregnanediol whereas white blood cells were relatively inactive. Thus, sheep binucleate cells converted pregnenolone predominantly to progesterone as did sheep luteal cells. However, goat binucleate cells produced 5 beta-pregnanediol as the major metabolite, which is consistent with its production in vivo during pregnancy. Production of progesterone (sheep) or 5 beta-pregnanediol (goat) by binucleate cells was shown to be proportional to the number and viability of the cells. In contrast with the binucleate cells there was no evidence that trophectodermal uninucleate cells play a significant role in placental progesterone or 5 beta-pregnanediol synthesis in either species.     

Increase in milk secretion and mammary blood flow by intra-arterial infusion of insulin-like growth factor-I into the mammary gland of the goat

The close-arterial infusion of free insulin-like growth factor-I (IGF-I; 1.1 nmol/min) for 6 h into the pudic artery supplying one mammary gland of lactating goats caused a 25 +/- 6% (mean +/- S.E.M., n = 6) increase in the rate of milk secretion of that gland. The increase in the rate of milk secretion in the adjacent noninfused gland (14 +/- 4%) was not significantly different from that observed during saline infusion (4 +/- 5%). Blood flow to the infused gland was increased from 378 +/- 26 ml/min 1 h before to 487 +/- 56 ml/min approximately 5 h after the start of the infusion of IGF-I, declining to 420 +/- 44 ml/min approximately 2 h after the end of the infusion. The total concentration of IGF-I (free and bound) in milk of the infused gland was significantly higher than that of the non-infused gland. The concentrations of IGF-I in carotid arterial plasma samples increased during IGF-I infusion from a mean value of 32 +/- 2 nmol/l before to a maximum of 49 +/- 3 nmol/l 5 h after the infusion commenced. Circulating concentrations of total IGF-I declined slowly after the infusion with an estimated half-life of 5 h. Infusion of saline alone did not alter mammary blood flow or the concentration of total IGF-I in milk or plasma. The results indicate that the infusion of free IGF-I into the mammary arterial supply enhances milk secretion and mammary blood flow in intact, conscious goats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Partial pharmacodynamic model for the circadian-episodic secretion of cortisol in man.

A pharmacodynamic model was developed to facilitate computer analysis of the circadian-episodic influx of cortisol into plasma from the adrenal gland. The model consists of a catenary system of a biorhythmic control, the adrenal gland, and a body compartment containing circulating cortisol. Computer nonlinear regression analysis was carried out on data consisting of plasma cortisol concentrations measured at 30-min intervals over 1 day in a group of normal children. Circadian rhythmic synthesis of cortisol by the adrenal gland was described by a sinusoidal function which provides the level (284 plus or minus 50 mugg/h/m2) and amplitude (245 plus or minus 50 mug/h/m2) of the synthesis rate and the period (24 hours) and acrophase (8.14 plus or minus 1.95 h) of the cycle. Cosinor analysis of the data confirmed a highly significant circadian rhythm in the daily synthesis rate of cortisol. Episodic secretion, described by an empirical switch function, is assumed to result from accumulation of small amounts of cortisol precursors in the adrenal gland and intermittent stimulation of cortisol release by ACTH. This was found to take place over 46.6 plus or minus 2.4% of a 24-h day. Circulating cortisol is contained in a single body compartment with an apparent volume of distribution (5.3 plus or minus 0.55 liters/m2) from which elimination occurs by first-order metabolic clearance. The biological half-life averaged 0.96 plus or minus 0.18 h. Upon least-square optimization of selected kinetic parameters, the circadian-episodic model increases the accountable variation (r2 x 100) to 89% in comparison with the 35% obtained by use of only a periodic function.     

Peripheral plasma concentrations of pregnenolone sulphate, pregnenolone, progesterone and 20 alpha-hydroxy-4-pregnen-3-one in ewes throughout the oestrous cycle

Pregnenolone sulphate, pregnenolone, progesterone and 20 alpha-hydroxy-4-pregnen-3-one concentrations in peripheral plasma of normal cyclic ewes were measured by radioimmunoassay. The concentrations of these steroids were correlated with that of progesterone. The concentrations of all the steroids measured in peripheral plasma varied in a cyclic manner and showed a significant (P less than 0.05) positive correlation with the concentration of progesterone. Peripheral plasma concentrations of these steroids in ovariectomized and ovariectomized, dexamethasone-treated ewes were also determined. The plasma concentration of progesterone in ovariectomized ewes was undetectable but the concentrations of pregnenolone sulphate, pregnenolone and 20 alpha-hydroxy-4-pregnen-3-one remained similar to those observed at oestrus. Administration of dexamethasone to ovariectomized ewes had no effect on pregnenolone sulphate or pregnenolone concentrations but 20 alpha-hydroxy-4-pregnen-3-one concentrations, which were already very low, decreased further. It is proposed that the ovary, probably the corpus luteum, secretes pregnenolone sulphate, pregnenolone and 20 alpha-hydroxy-4-pregnen-3-one; however, pregnenolone sulphate and 20 alpha-hydroxy-4-pregnen-3-one may also arise from the metabolism of circulating pregnenolone and progesterone.     

Uptake of 125-I-labelled human placental lactogen and human placental lactogen by the tissues of normal and lactating rats.

The rate of clearance from the circulation and uptake into tissues of radioactive label was studied after i.v. injection of 125-I-labelled human placental lactogen (HPL) into rats at various stages of pregnancy. The half-life was obtained for the disappearance of the trichloroacetic acid-precipitable material from the plasma. The half-life, t1/2(S), calculated over the first 5 min after injection of the hormone was 5.4 equals or minus 1.1 (S.D.) min, while a half-life, t1/2(L), of 27.9 equals or minus 2.3 min was obtained from the decay period of 15-35 min. In the non-pregnant and pregnant rat the highest ratio of the radioactivity in an organ to that in the blood was 12-14:1 in the kidney. That the kidney is mainly involved in the uptake of exogenous HPL is further confirmed by the application of the histochemical immunoperoxidase technique. Human placental lactogen was localized in the cells of the proximal tubules of the cortex and to a lesser extent in the tubular lumen and the tubules of the medulla region. UPTAKE OF HPL in vivo occurs in the mammary gland tissue of the post-partum rat and reaches a maximum uptake between 15 and 30 min after injection of the hormone. Furthermore, specific uptake of HPL was observed on the alveolar cell membranes after the incubation of paraffin-embedded sections of formalin-fixed mammary gland and subsequent treatment by the peroxidase-labelled antibody method. These findings support the work of others who have demonstrated the presence of specific membrane receptors in the mammary gland for hormones with prolactin-like activity.     

Immunological clearance of 75Se-labelled Trypanosoma brucei in goats

An experiment was conducted to determine, under different conditions, the capacity of young adult East African goats to eliminate intravenously inoculated [75Se]selenomethionine-labelled Trypanosoma brucei from the bloodstream. Over 80% of labelled trypanosomes, preincubated for 1 h in inactivated normal goat serum, were detectable in the circulation 1 h after inoculation into normal goats. By contrast, after incubation in serum from goats which had been immunised against the homologous trypanosome clone, parasites were largely removed from the bloodstream within 5 min after inoculation. When the goats were necropsied 1 h after the inoculation of radiolabelled trypanosomes, 50% of the injected activity was found in the liver and lungs, the contribution of each organ being dependent to some extent on whether the inoculum was via a mesenteric or the jugular vein. The same result was obtained when labelled parasites were incubated in normal goat serum, and then inoculated into immunised goats; thus, rapid blood clearance occurred, and high activity was detected in the lungs and liver. The results confirm those of previous studies in laboratory mice in which the removal of trypanosomes from the circulation of an immune animal was achieved primarily by uptake of opsonised trypanosomes by elements of the mononuclear phagocytic system.     

Oestrogen production by the goat mammary gland: transient aromatase activity during late pregnancy

Mammary tissue from goats had significantly higher aromatase activity at 148-149 days of pregnancy than earlier in pregnancy or during lactation. Aromatase activity was determined by production of 3H2O from [1 beta-3H]androstenedione that was inhibited by 4-hydroxyandrostenedione. The time of maximum aromatization was during peak mammary output of oestradiol-17 beta described previously in vivo in the same species. Aromatase activity in the mouse mammary gland was low and no peak was observed in late pregnancy. It is concluded that the oestrogens produced by the mammary gland in the late-pregnant goat are formed by aromatization of androgens.     

Renal conservation of ketone bodies during starvation.

Renal handling of acetoacetate and beta-hydroxybutyrate was studied in 12 obese subjects undergoing total starvation. Simultaneously, the acetoacetate, beta-hydroxybutyrate, and inulin clearance rates were measured, and acetoacetate and beta-hydroxybutyrate reabsorption rates were calculated. Renal clearance of blood acetoacetate and beta-hydroxybutyrate remained constant. In contrast, acetoacetate reabsorption rate increased significantly from 47 plus or minus 10 mumoles/min on day 3 to 106 plus or minus 15, 89 plus or minus 10, and 96 plus or minus 10 mumoles/min on days 10, 17, and 24, respectively. Similarly, beta-hydroxybutyrate reabsorption rate increased significantly from 154 plus or minus 27 mumoles/min on day 3 to 419 plus or minus 53, 399 plus or minus 25, and 436 plus or minus 53 mumoles/min on days 10, 17, and 24, respectively. Both acetoacetate and beta-hydroxybutyrate reabsorption rates increased linearly when plotted against their filtered loads. Thus, no tubular maximal transport rate exists for acetoacetate or beta-hydroxybutyrate during physiologic ketonemia. Conservation 450-500 mmoles of ketone bodies/day prevents large urinary losses of cations during prolonged starvation. Since ammonium becomes the major cation excreted during prolonged fasting, the increased renal reabsorption of ketone bodies minimizes body protein loss and aids in maintaining high circulating acetoacetate and beta-hydroxybutyrate concentrations.     

Hormone receptor levels and hormone, RNA and protein metabolism in the genital tract during the oestrous cycle of the ewe

The concentrations of soluble oestradiol and progesterone receptor proteins and several metabolic activities were measured in the genital tracts of ewes killed on Days 0 (oestrus), 2, 5, 10 or 14 of the oestrous cycle. In caruncular endometrium and in whole uterus the concentrations of oestradiol receptor (pmol steroid bound/mg tissue DNA) were highest at oestrus and declined steadily thereafter to minimal values at Day 14. The concentrations of progesterone receptor were highest on Days 0-5, then declined to low levels on Day 10-14. There was little metabolism of either [3H]oestradiol or [3H]progesterone in minces of whole uterus and with either steroid the pattern of metabolism did not change at any stage of the cycle. The in-vivo rates of synthesis of protein in caruncular endometrium and in isthmic oviduct were highest at or shortly after oestrus (Days 0-2), then declined to low levels on Days 10-14. RNA:DNA ratios in these two tissues were also greatest at oestrus and subsequently fell to minimal values by Day 14. The results are discussed in relation to ovarian secretion of oestradiol and progesterone during the oestrous cycle of the ewe.     

Production of parathyroid hormone-related protein by the mammary gland of the goat.

Parathyroid hormone-related protein (PTHRP) has been quantified by sensitive specific immunoassays in mammary venous blood and milk from 7 days before to 7 days after parturition in the goat. A significant venous-arterial concentration gradient in plasma PTHRP 1-86 concentrations was demonstrated across the mammary gland, indicating that PTHRP enters the maternal circulation and may have a role in calcium homoeostasis during lactation. Significant and sustained increases in mammary venous and milk PTHRP 1-86 concentrations were found from 1 day before parturition to 7 days afterwards, with peak concentrations of 1.57 +/- 0.58 pmol/l (plasma) and 8.69 +/- 2.95 nmol/l (milk) (mean +/- S.E.M.) occurring on day -1 and the day of parturition respectively. Estimates of the mammary output of PTHRP into plasma in four goats averaged 9% (range 1-25%) of that secreted into milk. Suppression of maternal prolactin concentrations by bromocriptine significantly reduced milk yield and the mammary venous PTHRP concentration, without affecting the concentration of PTHRP in milk. In conclusion, parturition in the goat is associated with a sustained increase in secretion of PTHRP into both plasma and milk; the former may be involved in maternal calcium homoeostasis, whereas the latter may have a role in the neonate.     

Implications of progesterone metabolism in MA-10 cells for accurate measurement of the rate of steroidogenesis.

In virtually all studies with MA-10 cells, progesterone RIAs have been used to measure steroid synthesis. To test whether progesterone is a stable end product, we investigated the metabolism of added tritiated progesterone and pregnenolone in MA-10 cells over a period of 3 h. Steroids were then extracted, separated by HPLC, and identified by GC/MS. We found that more than 70% of radiolabeled steroids were converted to at least five different metabolites. A major metabolite (40%) was 5 alpha-pregnan-3 alpha or 3 beta-ol-20one. Similar studies, using radiolabeled T, demonstrated conversion to dihydrotestosterone and two forms of 5 alpha-androstane-diols. These data indicate the presence of active 5 alpha-reductase and 3 alpha- and/or 3 beta-hydroxysteroid dehydrogenase activities in MA-10 cells. Because these results suggest that progesterone is an unstable end product, to gauge the level of active metabolism, we incubated cells in the presence of inhibitors of pregnenolone metabolism and assessed pregnenolone levels by RIA. We discovered that basal levels of steroidogenesis in MA-10 cells were considerably higher than previously estimated. Moreover, dibutyryl cAMP-stimulated steroid production was linear over more than 13 h, in contrast to previous findings that measured progesterone levels. Other consequences of inaccurate assessment of steroidogenic activity in MA-10 cells because of the application of the progesterone assay are discussed.     

Mammary gland lactose, plasma progesterone and lactogenesis in the marsupial Macropus eugenii

Mammary gland lactose concentrations in pregnant tammar wallabies remained low at 115 +/- 24 (S.E.M.) micrograms/g wet weight of tissue until immediately before parturition, then increased to 1274 +/- 262 micrograms/g after birth. Concentrations in non-pregnant cyclic animals were generally low (143 +/- 36 micrograms/g), but were raised in three animals around the time of oestrus. Removal of the corpus luteum on day 18 of pregnancy or the oestrous cycle caused an increase in lactose concentrations in both lutectomized and sham-operated animals. This occurred despite a significant lowering of peripheral plasma progesterone concentration in only the lutectomized group. Plasma cortisol concentrations were high in some of these animals, but showed no consistent relationships with the raised lactose concentrations. The increased peripartum lactose concentration normally coincides with a sharp fall in peripheral plasma progesterone concentration, but artificial maintenance of high progesterone levels had no effect on the increase of mammary gland lactose at parturition. Mammary gland lactose concentrations in tammar wallabies are therefore a useful indicator of biosynthetic activity and as an index of lactogenesis but the role, if any, of progesterone withdrawal in lactogenesis remains unclear.     

Premature regression of corpora lutea in pseudopregnant rabbits following the removal of polydimethylsiloxane capsules containing 17 beta-estradiol.

17-beta-Estradiol, which is luteotropic in rabbits, was administered during pseudopregnancy via polydimethylsiloxane (Silastic) implants to determine the effects on serum progesterone concentrations. Implants which released estradiol at a rate of approximately 2 mug/day were place beneath the skin the day after sterile mating and ovulation (day 0). Blood (3 ml) was obtained from the marginal ear vein on days 3, 6, 9, 10, 11 and 12. Serum estradiol levels, determined by radioimmunoassay, were 2- to 3-fold higher in estradiol-treated rabbits (11.7 plus or minus 1.2 pg/ml) than in untreated pseudopregnant controls (5.9 plus or minus 1.4 pg/ml). Weights of corpora lutea in treated and control rabbits were not different at the conclusion of the experiment on day 12. Serum progesterone concentrations, also determined by radioimmunoassay, were not significantly different between treated and control animals. However, when estradiol implants were removed from other rabbits on day 10, a rapid decline in serum progesterone occurred, from 14.0 plus or minus 2.4 to 2.6 plus or minus 0.8 ng/ml 24 h later. By comparison, serum progesterone concentrations in rabbits with estradiol implants left in place and in untreated rabbits on day 12 were similar (similar to 12 ng/ml). The premature decline in serum progesterone was accompanied by a decrease in the wet weight of corpora lutea. Other experiments revealed: 1) a precipitous fall in serum estradiol to basal values within 2 h after estradiol implants were removed, preceding the decline in serum progesterone by approximately 6 to 10 h; 2) reduced levels of estradiol in ovarian venous blood, but elevated levels of estradiol in peripheral arterial blood of rabbits with estradiol impants. The inability to elevated estradiol to increase serum progesterone or weights of corpora litea suggests that the luteotropic effect is maximal when estradiol is present at physiological concentrations. Following the continuous administration of estradiol, ovarian secretion of estradiol appears diminished and the corpora lutea become dependent upon the exogenous estradiol for luteotropic support. Although the ovaries continue to release measureable quantities of estradiol, this is inmeasurable quantities of estradiol, this is insufficient to prevent regression of corpora lutea when exogenous estradiol is rapidly withdrawn from the circulation.     

Left and right ventricular volumes in A-V block, and their changes induced by the infusion of isoproterenol.

In mongrel dogs (14.5 to 26.3 Kg) during complete heart block and right ventricular pacing, the cardiovascular dynamics were observed with the effect of isoproterenol infusion (8 mug/min intravenously). During complete heart block, cardiac output 2.01 plus or minus 0.17 L/min, heart rate 57.6 plus or minus 3. 5 beats/min, and stroke volume 35.5 plus or minus 2%. Left ventricular (LV) residual fraction was 54 plus or minus 2%. LV end-diastolic volume (EDV) IN WHich almost complete filling is performed due to the long filling period was 4.01 plus orminus 0.35 ml/Kg by thermodilution method. Right ventricular (RV) residual fraction and EDV were 39 plus or minus 3% and 3.01 ml/Kg, which were significantly smaller than the left. Infusion of isoproterenol increased cardiac output (2.67 plus or minus 0.21 L/min), heart rate (66.9 plus or minus 3.5 beats/min), and stroke volume (40.4 plus or minus 3.1 ml), but both ventricular residual fractions and EDV's didnot change significantly, although mean blood pressure decreased remarkably. During right ventricular pacing the effects of isoproterenol were essentially the same as in complete heart block except no change of heart rate and relatively improved cardiac functions. The plots of derived force-velocity relationship expressed in normalized mean circumferential shortening rate (MCSR) and peak ventricular force (F) showed that isoproterenol increased the velocity of shortening of muscle contraction significantly without significant change of F, while increase of heart rate didnot. It is concluded that isoproterenol affects the myocardium mainly throughits direct action and the improvement of contractile state via positive chronotropic effect (Bowditch's effect) is relatively small.     

Rate of thyroxine secretion by male and laying Japanese quail: identification of the radioactive thyroxine degradation component of the multiphasic 131-I curve.

Counting of radioactivity in Japanese quail in vivo showed a rapid loss of 131-I from the body 12-24 h after the i.v. injection of [131-I]thyroxine (T4), followed by a period of slow decrease in counting rates to 96 h. From comparison of these [131-I]T4 curves with curves for 131-iodide-injected birds and from counts on serum and other tissues in vitro it was concluded that, for Japanese quail, the T4 secretion rate should be calculated using serum samples taken during the first 12 h. Using this time period, the parameters measured were: T4 distribution space, laying hens 45-7 and mature cocks 26-7 and mature cocks 26-3 ml/100 g body weight; fractional degradation rate for T4, hens 5-73 and cocks 3-12/day; serum T4 concentration (Tetrasorb-125 method), hens 1-20 plus or minus 0-07 and cocks 1-34 plus or minus 0-05 (S.E.M.) mug/100 ml (n= 16); T4 secretion rate, hens 3-14 and cocks 1-10 mug/100 g/day.     

EFFECT OF ORAL THYROTROPHIN-RELEASING HORMONE ON SERUM THYROXINE IN GROWTH HORMONE DEFICIENT AND NORMAL CHILDREN

Oral administration of synthetic TRH in a dose of 80 mg/1-73 m-2 at 0 and 12 h to normal and constitutionally small children caused a significant increase of total serum thyroxine (T4) within 6-24 h. The mean maximal T4 increment was +3-7 plus or minus 1-1 and +3-8 plus or minus 1-2 mug/dl (mean plus or minus 1 SD) respectively in the two groups. Of seventeen euthyroid GH deficient children, fifteen showed a normal and two patients a slightly subnormal response. Of fifteen hypothyroid GH deficient children nine had a prompt and normal increase of serum T4 indicating primary TRH deficiency. Two had a delayed T4 response and four had no response, even after prolonged stimulation. The localization of the primary defect in these latter subjects with severe hypothyroidism can not be made by measuring T4 only, since the thyroid gland may become unresponsive to TSH after longstanding TSH deficiency. TSH measurements are necessary in these circumstances for a clear localization of the primary defect. One GH deficient patient with hypothalamic TRH deficiency was treated with high oral TRH doses for 7 months and showed no side effects.     

Effects of phentolamine on coronary blood flow in patients with recent myocardial infarction.

The myocardial clearance of rubidium may be obtained by praecordial counting after intravenous injection of Rb-minus 86 Cl. Eight patients with recent myocardial infarction had this determination performed before and after the infusion of 10 mg phentolamine at a rate of 0.3 mg/minute. The average predrug myocardial clearance of Rb was 89.3 plus or minus 29.9 ml/min per 100 g myocardium. After phentolamine, the average myocardial clearance rose to 117.3 plus or minus 33.3 ml/min per 100 g myocardium (P LESS THAN 0.01). An explanation for this findings is presented as well as its possible clinical applications.