Adrenal cortex and stomach lesions associated with stress in wild male African green monkeys (Cercopithecus aethiops) in the post-capture period

The objective of this study was to look for early pathological changes in stress target organs, adrenal glands, and stomachs in captured wild African green monkeys (AGMs). Three wild-caught male AGMs and seven singly housed wild AGMs were euthanized on day 1 and day 45 post-capture, respectively, and compared with four wild males euthanized with a rifle as controls. Morphometric analyses of the adrenal cortices and the cortical zones were done using an image analyzer. By day 45, the confined animals were clinically healthy, but had lost 47% mean body weight despite ad libitum feeding. The width of zona fasciculata in the controls was significantly smaller compared with that of 45-day monkeys (P < 0.05). Numerous acidophilic, hyperplastic and hypertrophic cells were present in the zona fasciculata of the 1-day confined AGMs. In the 45-day monkeys, there was glandular hyperplasia in the zona glomerulosa and the acini were distended and vacuous; yellow, granular pigmentation was distributed in the zona fasciculata. Acute stomach lesions represented by petechiation were seen in one monkey on day 1. Deep, circular, mucosal erosions, one to five in number and measuring from 0.5 to 1 mm in diameter, were present in three monkeys on day 45 post-capture. There were no adrenal cortex or stomach lesions in the rifle-shot monkeys. In conclusion, pathological lesions in the adrenal glands, and stomachs of the wild AGMs and weight loss occurred within the initial 45-day period following capture and confinement.

Animal consciousness

Dr Miriam Rothschild had an owl who became so jealous when Rothschild's daughter was born, the bird would try to attack both her and the child. Animals can often appear to have emotions, to be highly intelligent, motivated and sentient but are they conscious?

The effect of dietary protein on the mineral status of vervet monkeys with special reference to the impact of milk solids on calcium excretion

This study assessed the impact of Westernised and traditional African diets on mineral metabolism in general and calcium status in particular in vervet monkeys. Twelve adult male vervet monkeys (Cercopithecus aethiops), with an average weight of 5+/-0.58 kg each, were divided into two groups of six individuals each and fed traditional diets containing largely maize + legumes (17.4%) or Westernised diets containing milk solids (17.2%) as the source of high crude protein for 8 weeks. Blood was taken at 2-week intervals, the animals were weighed, while urine and stool samples were collected over 24 hours. The monkeys on the milk solids diet had diarrhoea for 6 weeks post-dietary intervention, and produced significantly greater quantities (P<0.02) of stool. These animals also produced significantly more urine (P<0.02). There was no difference in the degree of calciuresis of the two groups, but the monkeys on maize + legume proteins absorbed significantly more calcium during weeks two and six (P<0.04). Furthermore, both groups of monkeys showed a significant decline in plasma calcium levels over the experimental period (P<0.001). The diets had no effect on phosphate levels in the plasma or urine. However, both groups of animals absorbed less phosphate (P<0.09). There was an increasing loss of urinary magnesium (P = 0.03) in both groups, with the milk solids group showing lower plasma levels of this element (P = 0.09). However, the milk solids group lost less magnesium through the stool (P<0.03). In addition, the animals on milk solids showed significant natriuresis (P<0.05), while plasma sodium levels in both groups declined over time (P<0.03). Both diets induced a state of urinary potassium loss (P = 0.0003) and decrease in plasma potassium (P<0.0002). Urinary pH and plasma urea were unaffected by the diets, but the monkeys on maize + legumes excreted significantly less (P<0.001) urinary urea. This study indicates that the milk solids diet compromised mineral homeostasis by interfering with gut and renal functioning, while the traditional African diet did not induce these effects.

Plasma and red blood cell total phospholipid fatty acid status of nonpregnant female Vervet monkeys (Cercopithecus aethiops) on a high carbohydrate maintenance diet

Nonhuman primates are of interest as models of human physiology to study the effect of multiple pregnancies on birth weight. Reference plasma and red blood cell (RBC) total phospholipids fatty acids were established in nonpregnant breeding female Vervet monkeys. Twenty-three clinically healthy nonpregnant Vervet monkeys (Cercopithecus aethiops), contained in a controlled closed environment and consuming a high carbohydrate diet (68 E%) that contained 20 E% fat and 12 E% protein were sampled for blood during a cross-sectional study. A low intake of omega3 fatty acids was reflected by a high omega6/omega3 ratio (66:1) of the diet. Inverse relations were seen between plasma and RBC total phospholipid fatty acids, 18:2omega6, 20:3omega6, and 20:4omega6, which suggested selective incorporation in membranes. Low levels of 20:5omega3 and 22:6omega3 of plasma and RBC total phospholipids render Vervet monkeys as ideal subjects to study the effect of omega3 fatty acid supplementation on pregnancy outcomes.

Activity-dependent regulation of cytochrome b gene expression in monkey visual cortex

The recent demonstration that certain mitochondrial subunits of cytochrome oxidase (CO) are regulated by neuronal activity has stimulated interest in the molecular processes that coordinate nuclear and mitochondrial gene expression following synaptic stimulation. We have studied the constitutive expression and activity-guided regulation of cytochrome b (cyt b), a gene that is encoded by mitochondrial DNA and that was cloned by subtractive hybridization from the lateral geniculate nucleus in the monkey. We have found cyt b mRNA expression in monkey striate cortex to be similar to that of CO activity with regard to the laminar profile and the presence of blobs in the supragranular layers. Layers 2/3, 4C, and 6 contained large numbers of stained cells, many of which were judged to be excitatory neurons, because they showed a Zif268-immunopositive nucleus. We have also found that removal of functional activity reduced cyt b mRNA content in area V1. Columns of reduced cyt b staining were visible after 3 days and were especially striking after 6 days of monocular deprivation. After 3 months of deprivation, the columns lost their contrast and became blurred. Our principal finding, that neuronal activity regulates cyt b levels, suggests that expression of a mitochondrial gene can be affected in a manner similar to that of several known nuclear genes. The differences in cyt b mRNA levels and CO activity after long-term deprivation suggests that some form of differential control is exerted on cyt b. Cyt b expression, therefore, may be used as a marker of altered mitochondrial transcription that is guided by the metabolic demands of active neurons.

The primate subthalamic nucleus. I. Functional properties in intact animals

1. The present study tests several key aspects of the current model of the intrinsic circuitry of the basal ganglia, in particular the degree to which basal ganglia-thalamocortical circuits are functionally segregated at the level of the subthalamic nucleus (STN). To this end the responses of STN cells to somatosensory examination (n = 301 cells), the polarity and latencies of neuronal responses to passive and active movements (n = 223 cells), responses to microstimulation (n = 1589 sites), and cross-correlation functions of pairs of neighboring neurons (n = 72 pairs) were studied in STNs of three African green monkeys. 2. The activity of 55% of cells examined in STN was briskly modulated in response to passive movements of individual contralateral body parts. Of these, 86% responded to passive joint rotation of muscle palpation, but in some cases (25% of responding cells) responses were also elicited by light touch. In 91% of the responding cells responses were elicited by manipulations around a single joint only. 3. The caudoventral sector in STN was largely devoid of cells with responses to somatosensory stimulation. Within the rostrodorsal zone a lateral region containing neurons that responded to arm movements and a more medial region with neurons responding to leg movement were found. Cells responding to orofacial movements were located more dorsally and rostrally. Neurons with similar responses to active and passive movements of the limbs tended to be clustered within "arm" and "leg" zones. 4. Of identified arm cells in STN (n = 80), 36% responded to the application of torque pulses to the elbow (43 responses overall). Forty-eight percent of these cells responded to both extension and flexion torques. Ninety-three percent of the responses were initial increases in discharge, which characteristically occurred earlier and were shorter than initial decreases. Fifty-three percent of the responses were biphasic or multiphasic. 5. During active step tracking movements 40% of STN arm cells (n = 53 cells) responded with significant changes in activity. Thirty-six percent of these cells showed responses with both extension and flexion movements. Of the responses, 90% were increases in discharge. Only 14% of all responses were biphasic or multiphasic. Responses tended to occur around the time of movement onset (average latency 2 ms after movement onset). 6. Microstimulation (bipolar pulses, 40 microA, 200-500 ms train duration, 400 Hz) of the core of STN itself did not appear to produce movement.4+ synchronized activity in only 11% of pairs.(ABSTRACT TRUNCATED AT 400 WORDS)

Tunica vaginalis sperm reservoir in a monkey model of vas deferens obstruction

Repeat microscopic epididymal sperm aspiration (MESA) is used to treat congenital absence of the vas deferens (CAVD). Use of alloplastic implants as reservoirs results in poor sperm motility and pregnancy rates. An autoplastic tunica vaginalis reservoir for epididymal sperm has been used in four patients, with one resultant pregnancy. We studied this technique in a monkey model. Eight reservoirs were created in four monkeys (Cercopithecus aethiops). The vas deferens was ligated close to the epididymis. A transverse incision was made in the caput epididymis, and sperm were aspirated for analysis. Cut margins of the epididymal duct were sutured open to the visceral layer of the tunica vaginalis. The defect in the parietal layer of the tunica vaginalis was repaired, and sterile Tyrode's solution was instilled in the potential space between the parietal and visceral layers. Initial epididymal sperm obtained at the creation of the sperm reservoir demonstrated adequate mean motility (60.5%, grade 1.5), morphology (82.8% normal), and viability by Eosin-Y exclusion (69.9%). At 4 weeks, no reservoirs were palpable. Percutaneous aspiration (25-gauge angiocatheter) yielded no fluid. Surgical exposure of the reservoirs demonstrated significant adhesions and scar formation between the parietal and visceral layers of the tunica vaginalis, obliterating the potential space. No sperm were detected in irrigant fluids at this time. In conclusion, adhesion and scar formation may prevent use of the tunica vaginalis reservoir as an alternative to repeat MESA in treatment of CAVD.

[Age-related changes in bone mineral density, mean width and area of the lumbar vertebrae in male African green monkeys (Cercopithecus aethiops)]

We were able to measure bone mineral density (BMD), mean bone width and the area of the lumbar vertebrae in male African green monkeys with a dual-energy X-ray absorptiometry (DPX-alpha, Lunar, USA). For analysis of spinal bone mass, mean width and area of the bone, we scanned lumbar vertebrae L3-L5 using a pediatric analysis program. We used restraining bed made of formed polystyrol to support the animal in a supine position. The precision of the measuring technique was calculated by averaging the coefficients of variance of the 5 scans obtained in 5 animals aged from 5 to 7 years. The precision values for BMD, bone width and area were 1.9%, 0.9% and 2.6%, respectively. Furthermore, age-related changes in bone measurements were demonstrated using laboratory-bred males (n = 45) and, additionally, wild-originated males (n = 7, estimated ages over 15 years old). The values of B M D, bone width and area at 6 months old were about 0.3 g/cm2, 1.2cm and 4.5 cm2 respectively. These values increased with aging to about 0.7 g/cm2, 1.5 cm and 11cm2 at 5 years old, respectively, and were judged to reach plateau. However, animals over 10 years old and wild-originated animals which had been kept over 10 years in our breeding colony showed rather smaller BMD and area values than the animals aged 5 to 10 years. The animals aged between 5 and 10 years seemed to have retained a peak bone mass in this primate species.

Estrogen induces synaptic plasticity in adult primate neurons

The number of axosomatic synapses, the length of the synaptic plates and the perimeter of the post synaptic neuronal perikarya were assessed on thin sections from the infundibular hypothalamic nucleus and from the ventrobasal thalamus of 3 adult ovariectomized African green monkeys that were treated with estradiol valerate and of 3 control animals that were injected with vehicle. Estradiol valerate treatment resulted in a 61% [corrected] decrease in the number of axosomatic synapses in the infundibular hypothalamic nucleus. The length of the synaptic plates and the perimeter of the postsynaptic cells were not affected by the hormonal treatment. The decrease in the number of axosomatic synaptic inputs in the infundibular hypothalamic nucleus was accompanied by a significant increase in the glial ensheathing of neuronal somas. No effect of the hormonal treatment was detected in the ventrobasal thalamus. The results indicate that estrogen may induce glial and synaptic plasticity in the hypothalamus of adult primates.

African green monkeys have sexually dimorphic and estrogen-sensitive hypothalamic neuronal membranes

Previous studies have shown sex differences in intramembrane particle content in the arcuate neurons of the rat hypothalamus. In this study, freeze-fracture replicas were prepared from the infundibular hypothalamus of adult African green monkeys (Cercopithecus aethiops) in order to determine whether primates also have sexual dimorphism in neuronal membranes. Intramembrane particles (IMP) were quantitatively assessed in the perikaryal plasma membranes of infundibular neurons. Four groups of monkeys were studied: intact males, intact females, ovariectomized females injected with 20 mg of estradiol valerate over 10 days and ovariectomized females injected with vehicle (castor oil). Membranes from females showed an increased numerical density of IMPs when compared to males. Ovariectomy of females did not affect IMP content, while estrogen administration resulted in a significant decrease in IMP numerical density to reach male values. These findings indicate a sex difference in neuronal membranes in the hypothalamus of monkeys and suggest that as in rodents, neuronal plasma membrane organization in higher primates may be modulated by gonadal steroids.

Effects of speed on forelimb joint angular displacement patterns in vervet monkeys (Cercopithecus aethiops)

Shoulder, elbow and wrist joint angular displacement patterns were analyzed for five vervet monkeys across increasing speed. Within symmetrical gaits, the peak positions of the pattern for each joint tended to decrease with increasing speed as did the yield angle of the elbow (more "yielding"). Across the walk(run)-gallop transition there were no notable changes in the displacement patterns, but there was a consistent decrease in the range of elbow movements and an increase in the yield angle. Across symmetrical gaits, there was also a tendency for some of the peak positions to decrease. These results are compared with those available for cats and dogs, and are interpreted relative to functional and neurological aspects of forelimb movements in primates.

Effects of size on vervet (Cercopithecus aethiops) gait parameters: a longitudinal approach

Changes in the values of certain locomotor parameters were analyzed over a range of speeds for five immature vervet monkeys sampled at 6 month intervals over approximately a 3 year period. Lateral and diagonal sequence walking gaits and transverse and rotary gallops were commonly used. The monkeys switched from walking to galloping at long cycle durations for their mass, although, as a group, their transition speeds were in agreement with data from other mammals. However, for individual monkeys, transition speed was not consistently dependent on body mass. Cycle and stance durations generally increased with increasing size at each speed for each animal, with the greatest increases occurring at slower speeds. Swing durations increased slightly with size. For any particular individual, speed was highly predictable from cycle (or stance) duration and body mass (or age). However, the multiple regression equations for each animal were significantly different from each other, suggesting that no single equation is satisfactory for all of the individuals within a species.

Effects of growth and speed on hindlimb joint angular displacement patterns in vervet monkeys (Cercopithecus aethiops)

Hip, knee, and ankle joint displacement patterns are compared across both age and speed for five immature vervet monkeys sampled approximately every 6 months over a 3 year period. The analysis indicated that, as a group, the animals displayed no consistent changes in joint patterns as they grew. However, individual animals showed consistent patterns. There were also no consistent effects of size across animals at the walk-gallop transition. This is contrary to McMahon's prediction (J. Appl. Physiol. 39:619-627, 1975) based upon his elastic-similarity model of animal scaling. With increasing speed, when symmetrical gaits were used, all of the animals tended to show a decrease in the relative positions of the hip, knee, and ankle maximum values. Furthermore, across the walk-gallop transition, the animals tended to show a decrease in the range of ankle and knee movements.

Prostaglandins mediate the ocular hypotensive action of the angiotensin converting enzyme inhibitor MK-422 (enalaprilat) in African green monkeys

MK-422 (enalaprilat) (0.0005-0.5%) significantly reduced intraocular pressure (IOP) in African Green monkeys. Studies utilizing unilateral instillation of MK-422 and its inactive R-isomer indicated a local site of action within the eye which is dependent upon inhibition of angiotensin converting enzyme, also known as kininase II. Tonography showed a small increase (21%) in conventional aqueous humor outflow facility which did not entirely account for the IOP lowering effect of MK-422. Pretreatment with indomethacin or pilocarpine specifically attenuated the ability of MK-422 to lower IOP suggesting that biosynthesis of prostaglandins and uveoscleral outflow pathways are important in mediating the ocular hypotension. The data indicate that MK-422 may lower IOP in monkeys by virtue of its ability to prevent the breakdown of bradykinin and thereby promote the formation of endogenous prostaglandins in the eye.

Early experience and cross-generational continuity of mother-infant contact in vervet monkeys

This report presents evidence that suggests that spontaneously-occurring variation in early mother-infant experience within the normal range can influence primate mothering behavior in the next generation. Longitudinal observations of vervet monkeys (Cercopithecus aethiops sabaeus) living in naturally composed captive social groups demonstrated that the average amount of contact that mothers maintained with their infants in the first six months of life could be predicted by the amount of mother-infant contact the females had experienced as infants. A female's early experience in infancy was a better predictor of adult mothering behavior than variables measuring social learning as a juvenile, shared circumstances, and average similarity between mothers and daughters.

Role of supraspinatus in the quadrupedal locomotion of vervets (Cercopithecus aethiops): implications for interpretation of humeral morphology

Various researchers have noted that terrestrial and arboreal monkeys often differ in the degree to which the greater tubercle of the humerus projects proximally beyond the profile of the humeral head. These differences have been associated with differing leverage requirements for supraspinatus during quadrupedal locomotion. Although Jolly (The Baboon in Medical Research, Vol. II., pp. 23-50, 1967) suggested that a projecting tubercle can be related to the ability of supraspinatus to control more exactly the passive humeral retraction that occurs during support phase of quadrupedalism, most workers emphasize a link between this bony trait and the need for powerful or rapid protraction of the forelimb during swing phase of terrestrial quadrupedalism. We report on an EMG analysis of supraspinatus function showing that the muscle does not act as a brachial protractor during quadrupedalism, even in the relatively cursorial vervet monkey. We suggest that differences in greater tubercle projection can be related to the degree of mobility of the shoulder, and that supraspinatus size is determined by the interaction of greater tubercle height, adaptive importance of brachial elevation, and body size.

Semen characteristics of vervet monkeys

Semen samples (91) from 47 vervet monkeys were collected by electroejaculation over a 2 year period. Seventy-eight of these were from 37 singly caged males of unknown fertility and 13 from 10 breeding males of known fertility. Mean values for semen characteristics of the singly caged males were: volume 0.45 ml, pH 7.8, concentration 184 x 10(6)/ml, forward progression rating 2.95 (scale 0-4), motility 55.4%, live 68% and abnormal morphology 3.5%. Mean values for semen characteristics for the breeding males were: volume 0.86 ml, pH 9.00, concentration 117.15 x 10(6)/ml, forward progression rating 3.00 (scale 0-4), motility 43.6%, live 53.3% and abnormal morphology 6%. Semen volumes in the singly caged males were lower than the volumes reported in other studies.

Laminar organization and contrast sensitivity of direction-selective cells in the striate cortex of the Old World monkey

The directional preference of neurons sampled from all layers of the striate cortex was determined using the responses to drifting grating stimuli of optimal spatial and temporal frequency. In addition, contrast sensitivity as a function of spatial frequency was measured and from the resulting spatial contrast sensitivity function the peak contrast sensitivity and optimal spatial frequency were obtained. The distribution of directionally selective cells showed a distinct laminar pattern. Upper layer 4 (4a, 4b, and 4c alpha) and layer 6 were the only cortical layers with neurons that showed a pronounced preference for the direction of stimulus motion. The directionally selective cells in these layers are among those with the highest contrast sensitivities but had optimal spatial frequencies that were confined to the low and middle range of the optimal spatial frequency distribution. These findings suggest that the directionally selective cells may fall into at least 2 distinct populations, which may be the first stages in the visual pathway that correspond to those channels, inferred from psychophysical experiments, that underlie the detection of movement.

Multimicroelectrode investigation of monkey striate cortex: spike train correlations in the infragranular layers

1. In the infragranular layers of the striate cortex of three monkeys, we studied tangential neuronal interactions by analyzing cross-correlograms calculated from spike trains recorded with 30 closely spaced microelectrodes. 2. There are two major types of correlogram structures--"narrow" peaks a few milliseconds wide, sometimes accompanied by small lateral troughs, and "broad" peaks approximately 30- to 100-ms wide. Isolated troughs are rare. Both types of structures are superimposed in the same correlograms; they are not due to shared optical stimulation. 3. In layer VI, narrow peaks are largest in a short lateral range of approximately 220 micron, and they depend on ocularity. In layer V, the lateral range is greater, and the dependency on ocularity is weak. 4. In addition, narrow peaks are largest at distances of 160 micron if the angles of preferred orientation are similar. In layer VI, however, at tangential distances of 300-400 micron, peaks are smaller, and troughs are found more often, for neuron pairs with parallel orientations compared with those with orthogonal orientations. From the agreement of this finding with a cooperative theory, we conclude that orientation selectivity is shaped by collective interactions. 5. Broad peaks always depend on ocularity, and the associated lateral interaction range exceeds the maximum of 1 mm investigated. Their size sharply decreases with receptive-field distance. 6. Average mutual delays of spikes of neuron pairs, manifest as lateral displacements of broad peaks, are interdependent; the delay between neurons 1 and 3 is the sum of that of neurons 1 and 2 and of neurons 2 and 3. This feature permits to rank the neurons on a "delay scale." 7. We conclude from 5 and 6 above that broad peaks partly result from intraretinal interactions whose effects are transmitted to the cortex via slow and fast pathways. 8. Lateral troughs adjacent to narrow peaks provide evidence that neurons at the "slow" end of the delay scale inhibit those at the "fast" end, and to a lesser extent, nondirectional neurons inhibit directional ones.

Neuronal synchrony in monkey striate cortex: interocular signal flow and dependency on spike rates

A hypercolumn of monkey striate cortex was studied with an array of 30 closely spaced microelectrodes. Prominent broad peaks appearing in spike train correlograms are considered here. These were not due to shared stimulation, were mostly 30 to 100 ms wide, and were presumably the consequence of intraretinal lateral interactions. The correlogram peak areas were found to be predictable from the products of the spike rates, to which they were proportional. One can conclude that the correlation occurs before the overall reduction of spike rates from retina to cortex takes place. Furthermore, when a neurone dominated by one eye was stimulated via that eye, the correlogram formed with a neurone dominated by the other eye showed a displaced peak, indicating that excitation traveled from the well-responding to the unresponsive neurone in about 10 ms. When a left-eye stimulus was delivered, the same pair of neurones had a correlogram with a reversed peak displacement. This effect was only observed in layers IVb and c, indicating that in these layers the paths from the two eyes to a given cell are of unequal length, whereas in other layers, cells receive input from both eyes via similar connections differing only in strength.

Absolute auditory thresholds in three Old World monkey species (Cercopithecus aethiops, C. neglectus, Macaca fuscata) and humans (Homo sapiens)

We investigated the absolute auditory sensitivities of three monkey species (Cercopithecus aethiops, C. neglectus, and Macaca fuscata) and humans (Homo sapiens). Results indicated that species-typical variation exists in these primates. Vervets, which have the smallest interaural distance of the species that we tested, exhibited the greatest high-frequency sensitivity. This result is consistent with Masterton, Heffner, and Ravizza's (1969) observations that head size and high-frequency acuity are inversely correlated in mammals. Vervets were also the most sensitive in the middle frequency range. Furthermore, we found that de Brazza's monkeys, though they produce a specialized, low-pitched boom call, did not show the enhanced low-frequency sensitivity that Brown and Waser (1984) showed for blue monkeys (C. mitis), a species with a similar sound. This discrepancy may be related to differences in the acoustics of the respective habitats of these animals or in the way their boom calls are used. The acuity of Japanese monkeys was found to closely resemble that of rhesus macaques (M. mulatta) that were tested in previous studies. Finally, humans tested in the same apparatus exhibited normative sensitivities. These subjects responded more readily to low frequencies than did the monkeys but rapidly became less sensitive in the high ranges.

Reproduction in the vervet monkey (Cercopithecus aethiops): endometrial oestrogen and progestin receptor dynamics during normal and prolonged menstrual cycles

Sixteen individually caged adult female vervet monkeys (Cercopithecus aethiops), whose reproductive parameters had been studied for 5 years, were hysterectomized/ovariectomized during three reproductive states; i.e. the late follicular (15.4 +/- 4.7 (S.D.) days) and luteal (27.8 +/- 4.7 days) phases of the normal cycle (20-50 days), and during prolonged intermenstrual intervals (PII; 99.0 +/- 2.5 days since the previous menses). These latter animals showed characteristics of both follicular and luteal phases; i.e. their ovaries contained both corpora lutea and large antral follicles and systemic oestradiol and progesterone concentrations were raised. Analysis of cytoplasmic oestrogen and progestin receptors (CER and CPR) revealed that endometrium during PII had CER levels of 0.58 +/- 0.07 pmol/mg protein, similar to those of the follicular phase (0.60 +/- 0.12); CPR levels (1.20 +/- 0.87) were not different from those of the luteal phase (1.05 +/- 0.45). The ratio of CPR to CER during the luteal phase was about tenfold higher than that of the follicular phase. Levels during PII were intermediate between the two phases. Under receptor-activating conditions, the DNA-binding components of the PII cytoplasmic fraction underwent over 40% loss while those present during both phases of the normal cycle doubled. The hormone-binding sites at all times remained intact indicating that the DNA and hormone-binding sites are distinct on both CER and CPR. Less than 50% interaction of CER/CPR with DNA-cellulose was obtained, indicating the presence of only limited quantities of cytoplasmic activating factors which may be a prerequisite for receptor binding to the genome. During PII, factors which deactivate DNA-binding sites may also have been induced. Extensive accumulation of nuclear oestrogen receptor was evident in PII endometrium with 80% being salt-resistant. This level is higher than that in the follicular and luteal phases (37 and 52% respectively). These data, suggesting a possible aberration of receptor activation in vitro and receptor processing in vivo, may be indicative of endometrial dysfunction during PII. This could lead to a delay in menstruation.