Prostaglandin F2 alpha and E2 production into uterine lymph of pregnant and non-pregnant ewes.

Uterine lymphatic cannulation was performed in pregnant and non-pregnant ewes so that serial lymph samples could be analysed for prostaglandins (PGs) on day 12 to 18 after oestrus. The production of PGF2 alpha into uterine lymph showed peaks of > 1000 pg/h between days 14 and 18 of the oestrous cycle. Such peaks were either absent or much reduced (< 900 pg/h) over the same period in four pregnant animals. PGE2 production into uterine lymph remained low (< 510 pg/h) both in the four non-pregnant animals in the later part of the oestrous cycle and in three of four pregnant animals between days 14 to 18 post mating.

Detection of oestrous-related odour in ewe urine by rams.

The ability of rams to discriminate between urine odour of oestrous ewes and urine odours from ewes at other days of the oestrous cycle was determined using operant conditioning techniques. Rams could discriminate between the odour of urine of oestrous ewes and the odours of urine from ewes at day 6 to day 1 before oestrus and from ewes at day 4 to day 10 after oestrus. Rams did not discriminate between odours of urine samples from different ewes in oestrus, or between urine odour of oestrous ewes (day 0) and urine odours from ewes at day 1 to day 3 after oestrus. These results support the hypothesis that ewes in oestrus produce an odour in urine that is detectable by rams.

Failure to detect a putative oestrus-indicating pheromone in the urine or vaginal secretions of female sheep.

Extensive use of gas chromatographic analysis of the volatile and non-volatile components of sheep urine and sheep vulvovaginal secretions at different stages of the oestrous cycle has not succeeded in identifying the putative oestrus-indicating pheromone produced by the ewe. However the putative pheromone is probably not a low molecular weight alcohol, diol, phenol, amine, amide, aldehyde, ketone, fatty acid or steroid.

The nervous control of intraluminal pressure in the vomeronasal organ of the domestic ram.

In order to examine whether an aspiration mechanism exists in the vomeronasal organ (VNO) of the domestic ram, experiments were conducted in chloralose-anaesthetized animals using acute electromanometry and electrophysiological techniques. Stimulation of the ipsilateral cervical sympathetic nerve activated a mechanism producing a negative (with respect to atmospheric pressure) intraluminal pressure which drew fluid into the VNO from the nasopalatine canal. The mechanism was under alpha-adrenergic control and did not seem to involve the carotid blood supply. An ipsilateral increase in intraluminal pressure occurred following electrical excitation of the maxillary trigeminal innervation. Thus a mechanism was demonstrated in the ram for conveying odours to the putative olfactory receptors in the VNO.

The lymphatic drainage of the cranial part of the sheep's uterus and its possible functional significance.

The lymphatic drainage of the cranial part of the uterus is described. Some of the uterine lymphatic vessels are closely associated with the ovarian arterial supply. It is proposed that the uterine lymphatics form part of the local pathway for the transfer of uterine prostaglandin F2 alpha to the ovary for luteolysis.

Surgical separation of the uterus and ovaries with simultaneous cannulation of the uterine vein extends luteal function in sheep.

The insertion of a glass cannula into the uterine branch of the utero-ovarian vein, followed by disconnection of all other tissues between the uterus and the ovary containing the luteal tissue in non-pregnant sheep, was followed by a prolongation of luteal function. A pathway involving uterine venous blood alone is therefore insufficient to explain the transfer of PGF-2 alpha from the uterus to the ipsilateral ovary. We suggest that lymph is also involved.

Sequential changes in the concentration of prostaglandins and steroids in uterine lymph in sheep during the oestrous cycle.

Sequential samples of uterine lymph were collected from 9 conscious sheep at 4 or 5 h intervals. The mean PGF2 concentration in uterine lymph increased significantly on days 10 and 11 but then fell again, only to increase once more (P less than 0.001) for the 4 days prior to oestrus. PGE2 concentrations in uterine lymph showed no significant changes during the cycle. Lymphatic oestradiol-17 beta concentrations fluctuated throughout the cycle, with peak values considerably higher than those found in peripheral or uterine venous blood.

Calcium action potentials in unfertilized eggs of mice and hamsters.

Measurements of membrane potential and resistance have been made in zona-free eggs of mice and hamsters. The mean +/- S.D. values for membrane potential were -91 +/- 28 mV (mouse) and -97 +/- 29 mV (hamster) and for input resistance were 430 +/- 230 M omega (mouse) and 410 +/- 150 M omega (hamster) respectively. Large fluctuations (20 mV) of membrane potential occurred apparently at random and these were accompanied by changes of membrane resistance. Depolarizing current pulses passed through the recording micro-electrode evoked action potentials in eggs of both species. The threshold for excitation was about -50 mV, the maximum rate of rise of the action potential was about 3 V.s-1 and its peak value was about +13 mV. Action potentials could be evoked in eggs bathed in sodium-free solution or in normal solution containing tetrodotoxin (3 microM). The presence of cobalt (5-20 mM), lanthanum (1 mM) or verapamil (200-400 microM) in the bathing solution suppressed the action potential. Raising the extracellular calcium concentration from 4 to 40 mM increased the peak value of the action potential by 25 mV. It is concluded that the plasma membranes of mouse and hamster eggs have voltage-dependent calcium channels.

Calcium-evoked opening of potassium channels in hamster eggs.

Measurements of membrane potential and resistance have been made in zona-free hamster eggs. The resting potential lay in the range -9 to -100 mV and the input resistance fell in the range 14 to 440 M omega; high resting potentials were associated with large input resistances. Calcium injected ionophoretically into an egg from an intracellular micro-electrode caused a reduction of the membrane resistance. The estimated reversal potential for the calcium-evoked response was about -80 mV and its amplitude depended on the extracellular concentration of potassium but not on the chloride concentration. We conclude that membrane potassium channels open in response to a rise in the cytosolic concentration of calcium ions. Evidence is presented to suggest that micro-electrode recordings of the membrane potential and resistance of eggs suffer from an impalement leak artifact. The presence of the artifact lowers the resting potential and resistance of the cell so that intracellular calcium injection causes a hyperpolarization. We conclude that a hyperpolarizing response to calcium would be unlikely in the absence of an impalement artifact.

Prostaglandin F2 alpha and PGE2 in uterine lymph during the oestrous cycle in sheep.

The concentration of prostaglandin F2 alpha (PGF2 alpha) in uterine lymph remained low (less than 1 ng/ml) during the first two-thirds of the oestrous cycle in the non-pregnant sheep. However increased amounts of PGF2 alpha were present from day 12 onwards. The concentration of prostaglandin E2 in uterine lymph remained low (less than 0.43 ng/ml) throughout the cycle.

Uptake of chlorotetracycline into mouse eggs.

The fluorescent compound chlorotetracycline (CTC) enters the mouse egg by a mechanism controlled by the oolemma. The intracellular distribution of CTC is non-uniform and during the early stages of uptake fluorescent patches are observed at the egg's surface probably close to the oolemma. Lanthanum blocks the entry of CTC into the egg's cytoplasm and in this condition the CTC remains at the surface of the egg; the labelled site is not the zona pellucida and is likely to be the outer surface of the oolemma. The results of this study of CTC uptake support the idea that this compound labels divalent (or trivalent) cations in the neighbourhood of cell membranes.

Prostaglandin production by the progesterone-dominated sheep uterus.

Daily treatment of sheep with progesterone resulted in the accumulation of sterile fluid in the uterus. The fluid contained high concentrations of prostaglandin (PG) F2 alpha but low concentrations of PGE2 and 6-oxo-PGF1 alpha. Uterine venous plasma also contained high concentrations of PGF2 alpha and low concentrations of PGE2. PGF2 alpha was the major PG synthesised by the sheep endometrium, but appreciable quantities of PGE2 and 6-oxo-PGF1 alpha were also formed. The findings of this study suggest that biochemical mechanisms exist in the progesterone-dominated sheep uterus which specifically synthesise and secrete PGF2 alpha.

Additional pathway of transfer of uterine prostaglandin F-2 alpha to the ovary in sheep.

The concentration of prostaglandin (PG) F-2 alpha was measured in different uterine and ovarian blood vessels between Days 12 and 16 of the oestrous cycle in 14 normal ewes. Concentrations of PGF-2 alpha significantly higher than peripheral levels were found in the uterine vein (P < 0.002) and oviducal vein (P < 0.002). This suggests that an additional pathway for PGF-2 alpha transfer to the ovary exists via the venous drainage passing alongside the oviduct.

Biphasic follicular growth in the guinea-pig oestrous cycle.

Follicular growth in the normal oestrous cycle of the guinea-pig is biphasic. The first wave of follicular growth culminates on Days 10--11 while the second wave ends in ovulation.

Production of 6-oxo-prostaglandin F1 alpha, PGF2 alpha and PGE2 by sheep uterine tissue.

Incubation in vitro of sheep uterine tissue revealed that although both caruncular and non-carunuclar endometrium can synthesize appreciabel quantities of PGF2 alpha, PGE2 and 6-oxo-PGF2 alpha, the myometrium synthesizes predominantly 6-oxo-PGF1 alpha. Non-caruncular endometrium contained more 6-oxo-PGF1 alpha than either the myometrium or the caruncles, while myometrial tissue possessed less PGF2 alpha than either caruncular or non-caruncular endometrium.

Uterine prostaglandin F2 alpha & E2 production and content during the second half of the oestrous cycle of the sheep - possible local control of the uterus by the ovary.

The amount of prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E2 (PGE2) in the endometrial tissue of sheep and the ability of this tissue to synthesize these prostaglandins have been monitored daily during the latter part of 12 oestrous cycles in seven ewes. Plasma concentrations of PGF2 alpha and progesterne were measured simultaneously during ten of these cycles. No difference could be found between the content of or the synthesizing ability for PGF2 alpha or PGE2 of caruncular and non-caruncular endometrial tissue, although the myometrium contained and produced significantly less PGF2 alpha than either of these tissues. There was no relationship between PGF2 alpha content, secretion and synthesizing ability of endometrial tissue although changes in the uterine content of PGE2 and PGF2 alpha were directly related. Changes in the ability of the uterine endometrium to synthesize PGF2 alpha varied with the presence or absence of the neighbouring ovary. When the adjacent ovary was present there was a statistically significant increase in the ability of the endometrium to synthesize PGF2 alpha 3 and 2 days before the onset of oestrus. In the absence of the ovary this increase did not occur. The data suggests that the ovary has a local controlling influence over the ability of the endometrium to synthesize PGF2 alpha.