Placentation and hormonal maintenance of pregnancy in the impala (Aepyceros melampus).

INTRODUCTION: The impala is a widely distributed African ungulate. Detailed studies of the placenta and ovaries in impala undertaken in the 1970s did not address the endocrine functions of the placenta. METHODS: The uteri of 25 pregnant impala estimated to be between 49 and 113 days of the 190 day gestation were examined grossly, histologically and immunohistochemically. RESULTS: A single corpus luteum was present in either maternal ovary but the conceptus was always situated in the right uterine horn. The fetal membranes extended to the tips of both uterine horns. The amnion was in intimate contact with, but not fused to, the allantochorion. Placentation was typically ruminant with fetal macrocotyledons attached to the rows of maternal caruncles. The fetal villi were highly branched, especially in the centre of each placentome where the attenuated maternal epithelium lining the placental crypts was absent in some places. Both the corpus luteum and the uninucleate trophoblast cells of the interplacentomal allantochorion stained strongly for 3-ß hydroxysteroid dehydrogenase, and progestagen concentrations in allantoic and amniotic fluids increased significantly as gestation progressed, with a tendency to do likewise in maternal serum. Binucleate trophoblast cells stained positively for bovine placental lactogen, but neither the placenta nor the maternal corpus luteum showed evidence of oestrogen synthesis. DISCUSSION: Despite exhibiting the same basic type of placentation, both the gross and histological structure of the impala placenta, along with its immunohistochemical properties, demonstrates that great variation exists across ruminant placentas.

Ovarian and placental morphology and endocrine functions in the pregnant giraffe (Giraffa camelopardalis).

Gross, histological and immunocytochemical examinations carried out on maternal and fetal reproductive tissues from two pregnant giraffes at an estimated 8 and 13.5 months of gestation (term=15 months) revealed a typically ruminant macrocotyledonary placenta with binucleate trophoblast cells scattered sparsely in the placentome where they stained intensely with a prolactin antiserum. Binucleate cells were present in greater numbers in the intercotyledonary allantochorion where they did not stain for prolactin whereas the uninucleate trophoblast still did. A single large corpus luteum of pregnancy and several small luteinised follicles were present in the maternal ovaries while the fetal ovaries at 13.5 months gestation showed an assortment of enlarging antral follicles and partially and completely lutenised follicles, the granulosa and luteal cells of which stained positively for 3ß-hydroxysteroid dehydrogenase (3ß-HSD), 17,20 lyase, prolactin, progesterone receptor and androgen receptor, but negatively for aromatase. The uninucleate trophoblast of the placentome and intercotyledonary allantochorion, the epithelium of the maternal endometrial glands, the seminiferous epithelium in the fetal testis at 8 months of gestation and the zonae fasciculata and reticularis of the fetal adrenal at 13.5 months also stained positively for 3ß-HSD and negatively for aromatase. Endocrinologically, it appears that the giraffe placenta is more similar to that of the sheep than the cow with a placental lactogen as the likely driver of the considerable degree of luteinisation seen in both the maternal and the fetal ovaries.

Serial measurement of peripheral oestrogen and progesterone concentrations in oestrous mares to determine optimum mating time and diagnose ovulation.

Rapid enzyme-based immunoassays were used to measure concentrations of oestradiol-17 beta and progesterone in daily blood samples recovered throughout oestrus and for a few days after ovulation from 34 Thoroughbred and 8 pony-type maiden, barren and foaling mares. The first detectable fall in oestradiol-17 beta levels occurred in 88% of the mares within the interval -72 to 0 h with respect to ovulation and in 65% of mares within the interval of -48 to 0 h. The results indicated that serial daily hormone assays of this type could, in a high proportion of animals, predict a correct time for a single mating and diagnose the occurrence of ovulation in Thoroughbred mares at stud in the absence of the present management system which includes repeated veterinary examinations of the ovaries. However, the absolute need for serial daily sampling from all mares to produce interpretable hormone profiles, and the cost of this sampling and the hormone assays, make the method impractical at the present time.

Case report of the Prader-Willi syndrome.

A case of Prader-Willi Syndrome in a 12-year-old girl is described, together with the dental findings which exhibit extensive periodontal disease for her age, which has hitherto not been recorded in the literature.

The radiographic and surgical evaluation of meniscal dysfunction of the temporomandibular joint.

A retrospective study of 106 patients who underwent temporomandibular joint surgery for meniscal dysfunction was conducted. The patients were evaluated by tomography and arthrography of the temporomandibular joint and abnormalities of the hard and soft tissue structures were determined by these investigations and compared directly with the findings at surgical examination. Tomography had a high degree of correlation with bony pathology as did arthrography with meniscal displacement. The arthrogram also frequently revealed the presence of meniscal scarring associated with the head of condyle in long-standing cases, but gave an incidence of 3% false/positive findings of a perforation of the meniscus.

Observations and management of fractures of the proximal phalanx in young Thoroughbreds.

A retrospective study of 119 cases of fracture of the proximal phalanx is described. The short incomplete sagittal fracture (split pastern) was most common and carried a good prognosis for a return to racing following conservative treatment. Longer incomplete fractures also had a good prognosis but complete fractures, either through the lateral cortex of the proximal phalanx or through the bone into the proximal interphalangeal joint, required internal fixation. Careful assessment of these and comminuted fractures was essential before surgery was undertaken. Most comminuted fractures were treated with a view to the animal retiring to stud rather than racing again. Humane destruction was considered to be justifiable for such fractures in colts or geldings of no stud value or if the fracture was severely comminuted.

Induction of ovulation in anoestrous mares with a slow-release implant of a GnRH analogue (ICI 118 630).

A total of 18 experimental pony and 136 commercial maiden, barren and foaling Thoroughbred mares in seasonal or lactation-related anoestrus were injected subcutaneously with 1 or 2 slow-release D,L-lactide-glycolide co-polymer implants impregnated with 0.9 or 1.8 mg of the potent GnRH analogue, ICI 118 630, to give a daily release of, respectively, 30 or 60 micrograms analogue for 28 days; 32 of the Thoroughbred mares were also given a daily oral dose of 27.5 mg allyl trenbolone for 5 days after injection of the implant. Thirteen pony (76%) and 120 Thoroughbred (88%) mares ovulated 3-18 days after treatment with ICI 118 630 and the additional treatment with allyl trenbolone did not significantly reduce the considerable variation in the interval between treatment with GnRH analogue and ovulation. Of 100 Thoroughbred mares mated during the GnRH analogue-induced oestrus, (70%) conceived. The results of this trial demonstrated that low-dose, slow-release formulations of GnRH agonists have considerable potential as a practical method of hastening renewed ovarian cyclicity in anoestrous mares.

Use of ultrasound echography for early diagnosis of single and twin pregnancy in the mare.

In 1981 a trial was conducted on 6 Newmarket Thoroughbred stud farms into the use of real-time ultrasound echography (scanning) as an aid to the early diagnosis of pregnancy in the mare. The procedure was found to be practicable and interpretation of the findings was relatively straightforward. Pregnancy was positively diagnosed from as early as 14 days after ovulation and a number of twin pregnancies were recognized, some in which the conceptuses were situated in separate horns of the uterus but an almost equal number in which the conceptuses were together in the same horn. It was concluded that the technique of scanning will become an established part of stud-farm practice because it enables early identification of non-pregnancy and also of twin pregnancy before the critical stage of endometrial cup formation.

Clinical report of a paralytic syndrome affecting stallions, mares and foals on a thoroughbred studfarm.

An outbreak of ataxia and paralysis on a Thoroughbred studfarm is reported. The cause of the disease was attributed to equid herpesvirus (EHV1) infection which stemmed from a single 10-month abortion on the studfarm. Stallions, mares and foals were all affected but the most serious clinical signs occurred in the mares. there were 35 out of 39 mares, 2 out of 4 stallions and 5 out of 39 foals which exhibited signs of ataxia. Nine mares became recumbent and died or were euthanased. Treatment with betamethasone and antibiotics was given. The outbreak was contained to one area of the stud apart from secondary spread to 2 in-contact mares on different premises.

Preliminary studies on the use of an oral progestogen to induce oestrus and ovulation in seasonally anoestrous Thoroughbred mares.

Daily oral administration of 30 mg allyl trenbolone (Regumate) for 10 to 15 days to 61 barren, maiden and lactating Thoroughbred mares which were exhibiting either deep anoestrus, shallow anoestrus, prolonged spring oestrus or lactation anoestrus, resulted in 54 mares (88 per cent) showing oestrous behaviour within 8 days, and 51 mares (84 per cent) ovulating within 18 days, after the last dose of compound. Response rate was lowest in mares in deep anoestrus. Of the 38 Regumate-treated mares which were covered during the induced oestrus, 21 (55 per cent) conceived. The practical value of this form of progesterone withdrawal therapy as a method for hastening the onset of the breeding season in Thoroughbred mares is discussed.

An outbreak of contagious equine metritis in 1977 and its effect the following season.

An outbreak of contagious equine metritis occurred in Newmarket in 1977. This survey records the effect on fertility of 20 of the stallions which were infected. Swabbing of mares since then has detected 37 carrier mares harbouring the organism, most frequently in the clitoral area. This swabbing programme reduced the incidence of new cases in 1978 to 3 mares and 1 stallion.

Observations on thyroid hormones in the blood of thoroughbreds.

During an investigation of a group of clinically well thoroughbreds housed in the same stable, it was noted that seven of the 14 had no detectable thyroxine in the plasma (less than 5 nmol/litre). An investigation of thoroughbreds in this stable over a five month period suggested that the thyroids were functioning normally and that the thyroxine was excreted in the urine. Thyroxine binding studies on the blood of these horses suggested that the major part of the circulating thyroxine was bound to albumin. The thyroxine had been displaced resulting in an apparent absence of plasma thyroxine since the limit of detection for normal radioimmunoassay is 5 nmol/litre. It is concluded that the measurement of plasma thyroxine as an indication of thyroid function in the thoroughbred can prove unreliable.