Diagnosis of sexual cycle by means of vaginal smear method in the chinchilla (Chinchilla lanigera)

An investigation was made as to whether the sexual cycle and pregnancy can be determined by means of vaginal smear in chinchillas. This study represents the first attempt to record changes which occur in the pattern of exfoliated cells in chinchilla's vaginal smear during anoestrus, proestrus, oestrus, metoestrus and pregnancy. Fifteen female chinchillas aged from 8 months to 3 years and bred through harem breeding method were used. The major change during proestrus was an increase in the proportion of superficial cells, with a corresponding decrease in other cells. Goblet cells were observed in the smears prepared by strong aspiration during this cycle. Neutrophils, small and large intermediates and parabasal cells were not found in the smear during oestrus and the smear consisted of superficial cells only. In the proportion of neutrophils, small and large intermediates and parabasal cells increased during metoestrus. In addition, metoestrum and foam cells were found in this cycle. In anoestrus; superficial and parabasal cells were present in small numbers. Also small and large intermediate cells as well as neutrophils were present. Traces of foam and metoestrum cells were found. During pregnancy, neutrophils generally of medium density were present, parabasal; small and large intermediate cells were present at low or medium density, and superficial cells were only present in trace amounts.     

Oestrous cycle of captive southern hairy-nosed wombats (Lasiorhinus latifrons) in South Australia, Australia

There is limited information available on the oestrous cycle of female southern hairy-nosed wombats (Lasiorhinus latifrons). This is mainly due to an extremely poor breeding success in captivity and the difficulty in routine recapturing of these cryptic, semi-fossorial animals in the wild. The aim of this study was to characterise the oestrous cycle of this species by monitoring peripheral plasma concentrations of progesterone and oestradiol, assessing changes in vaginal cytology, pouch condition and the urogenital sinus. Eight adult female wombats were monitored during the breeding season (July-December) over 2 years (2002-2003). Samples were collected up to three times a week. Vaginal smears contained several cell types, categorised by morphology, as either superficial epithelial cells or parabasal-intermediate cells. Leucocytes were also counted. Plasma progesterone profiles showed a mean oestrous cycle length of 36.33+/-0.67 days with a peak progesterone concentration of 139.53+/-10.62nmol/L. Levels of oestradiol peaked at a mean level of 467.33+/-44.32pmol/L on average 5 days before a rise in plasma progesterone values. The proportion of epithelial cells in vaginal smears varied throughout the cycle, with a high percentage of superficial epithelial cells observed during the follicular phase. During periods when progesterone concentrations were high, a greater percentage of parabasal-intermediate cells was observed. In conclusion, this study has characterised the oestrous cycle of the southern hairy-nosed wombat and confirmed that changes in vaginal smears together with pouch and urogenital sinus details could be used to determine signs of oestrus in this species.     

高原鼢鼠发情周期阴道细胞变化特征及血清促性腺激素含量动态

In order to determine the change characteristics of vaginal cells in the estrus cycle and the duration of the estrus cycle, vaginal smears and HE staining methods were used to observe and count the types, morphological changes, and proportions of vaginal cells in plateau zokor (Eospalax baileyi). The hormone secretion dynamics of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in the serum of plateau zokor in the estrus cycle were determined by ELISA. The results showed that the main vaginal cells of plateau zokor were leukocytes, nuclear epithelial cells, incompletely cornified epithelial cells, and complete cornified epithelial cells. The proportion of nuclear epithelial cells in the proestrus was significantly higher than that during the other three periods (48. 4 ±3. 09)% (n=12, P < 0. 05). The proportion of complete cornified epithelial cells in the oestrus was the highest and significantly higher than that in the other three periods (59. 73 ±7. 59)% (n=15, P < 0. 05). The proportion of leukocytes in the metestrus and dioestrum was significantly higher than that in the proestrus and oestrus (P < 0. 05). The expression level of LH was the highest in the metestrus (4. 709 5 ±1. 094 0) ng/mL (n=6, P < 0. 05), which showed an increasing trend in proestrus and oestrus, and a decreasing trend in the metestrus and dioestrum. There was no significant difference in the expression level of FSH among the four periods (P > 0. 05); the estrus cycle duration of plateau zokor was 16 to 19 d, the characteristics of vaginal cell types in different stages of the estrus cycle were obvious, and the relative number was statistically significant. The study provided a basis for vaginal smear identification in the estrous cycle and reproductive physiology study of plateau zokor.     

The use of cytological examination of vaginal smears (CEVS) in the selection of rabbits for superovulation

In the present study, we examined two factors associated with the reproduction of rabbit does, cytology of vaginal smears and color of vulva, as potential predictors of the success of superovulation treatment. Vulval color and vaginal smear cytology were assessed in 55 young New Zealand does. Superovulation was then induced by a single administration of eCG (20 IU/kg BW i.m.). Does were artificially inseminated 3 days later, followed by intravenous administration of hCG (120 IU per animal). Does were classified with regard to vulval color (white, rose, red, purple), and the predominant cell type in the vaginal smear (i.e. parabasal, intermediate, superficial, or anuclear). Furthermore, we categorized cells into two groups because we usually observed parabasal and intermediate cells (Group A), and superficial and anuclear cell (Group B) in the same smear. Does were humanely killed 19 h after administration of hCG and the total numbers of corpora lutea (CLs), oocytes, and zygotes (i.e. 1-cell embryos) were determined. The zygotes were assessed by morphological appearance and classified as normal or abnormal. The color of the vulva at the time of eCG treatment did not predict the success of superovulation in terms of the number of CLs, oocytes or zygotes. Does with predominantly superficial cells in vaginal smears yielded significantly fewer CLs and oocytes-zygotes (OZ) compared to does with predominantly parabasal, intermediate, or anuclear cells (P<0.05). Does with predominantly superficial cells in vaginal smears tended to yield fewer normal zygotes (nZ), but this reached significance only when compared to does with predominantly parabasal cells (P<0.05). Does in Group A yielded significantly more (P<0.05) CLs, OZ and nZ compared to does in Group B. Does with predominantly parabasal and intermediate cells in vaginal smears and rose color vulva tended to yield more OZ and nZ (P<0.05). These results suggest that the cytology of vaginal smears may help identify does with a significantly higher likelihood of yielding low numbers of CLs, oocytes, or nZ.     

Quality assurance of canine vaginal cytology: A preliminary study

Regulatory controls of quality assurance in veterinary laboratories are less common than in human reproduction laboratories and the intra- and inter-technician variation in the assessment of canine vaginal cytology has not been reported. This study was designed to determine whether variation in classification of vaginal epithelial cells and interpretation of vaginal cytology smears existed within and between technicians in a canine reproductive laboratory.Sixteen vaginal cytology smears representing different known stages of the oestrous cycle were examined twice by one experienced technician and three inexperienced technicians in a blinded random order study design. Seven assessments were made; counting and classifying one hundred vaginal epithelial cells into four morphological classifications and assessment of three cellular categories. Technicians also interpreted their results and reported the stage of the cycle they thought each slide represented. In addition, selected samples were sent to four external commercial laboratories for interpretation.For the experienced technician, intra-technician variation was low for the morphological classifications and cellular assessments (r = 0.69-0.95). There was more intra-technician variation between results from Examination One and Examination Two for the inexperienced technicians (r = 0.53-0.92 where correlations were found). When inexperienced technicians' results were compared to results from the experienced technician, the inter-technician variation was low; results were correlated for 17 of the 21 observations (four morphological classifications and three cellular assessments across the three technicians) (r = 0.38-0.87). When technician interpretations of stage of the oestrous cycle were compared to the known stage of the cycle for each smear, the experienced technician correctly interpreted 19 of the 32 smears, whilst the three inexperienced technicians correctly interpreted 14, 16, and 18 of the 32 smears. The interpretation of vaginal smears by external laboratories was varied and sometimes inconclusive; 50% of laboratories incorrectly identified metoestrus smears as proestrus and 25% of the laboratories incorrectly identified an oestrus smear as proestrus.The results of this study are highly important for clinicians undertaking canine reproductive assessments since they demonstrate the potential for variability of results. While the greatest precision was found when vaginal smears were examined by an experienced technician (who, on a daily basis, examines many smears), more variability in both the reporting of different cell types and interpretation of the smears was observed by inexperienced technicians and when samples were sent to external commercial laboratories. These findings suggest that suitable quality control programmes should be implemented for laboratories that are undertaking routine assessments of canine reproductive function.     

Cycles of mating behaviour, oestrogen and progesterone in the thick-tailed bushbaby (Galago crassicaudatus crassicaudatus) under laboratory conditions

Vaginal smears and blood samples were taken throughout the reproductive cycle of female Galago c. crassicaudatus. Blood plasma was assayed for oestradiol and progesterone, and vaginal smears were initially classified dioestrus or vaginal oestrus. During vaginal oestrus the females were tested daily for sexual receptivity by being placed with a male. Those days on which the male achieved intromission were reclassified as behavioural oestrus. During dioestrus the females were tested weekly with males. Female receptivity increased and then declined across a 6-day period of behavioural oestrus during the 44-day cycle. Fully cornified smears were characteristic of the period of maximal receptivity and oestradiol secretion. The luteal phase lasted 24 days with a plasma progesterone peak midway through dioestrus.     

小鼠发情周期卵泡发育动态及其对超数排卵的影响

该文探讨了小鼠发情周期中阴门状态、阴道脱落细胞类型变化规律、卵泡发育规律及其相互关系,并比较了发情周期不同阶段的超排效果。结果表明,采用阴门状态观察法和阴道脱落细胞涂片法,能有效判断小鼠发情周期阶段。卵巢组织切片观察结果表明,在发情周期不同阶段,小鼠的卵泡发育和黄体的生成与消退存在明显的规律性变化;小鼠发情周期中,其阴门状态、阴道脱落细胞种类及卵泡发育动态之间存在相关关系;发情周期不同阶段开始超排的小鼠,其配种见栓率和回收胚胎平均数均存在明显差异,发情前期显著优于发情后期与间情期(P<0.05),并高于发情期,但差异不显著(P>0.05),即阴门状态观察法与阴道脱落细胞涂片法均可用于小鼠发情周期阶段的判断,发情前期为最适宜的小鼠超排时期。     

Vaginal cytology in endocrinopathies

In order to evaluate the diagnostic significance of vaginal smears in endocrinopathies associated with menstrual disorders, the cytologic pattern of vaginal smears was examined in 703 patients who had a well-established diagnosis of the disorder's origin. The patients were classified into four groups according to their menstrual disorders: primary amenorrhea (159 patients), secondary amenorrhea (116 patients), primary oligomenorrhea (214 patients) and secondary oligomenorrhea (214 patients). Using the maturation index and the maturation value, three cytologic patterns of vaginal smears were distinguished: parabasal cell pattern, intermediate cell pattern and superficial cell pattern. The frequency with which the cytologic patterns occurred in the groups of patients and their subdivisions are presented. As a whole, the 703 patients showed 25.2% with a parabasal cell pattern, 58.3% with an intermediate cell pattern and 16.5% with a superficial cell pattern. Although the cytohormonal pattern of vaginal smears in endocrinopathies with associated menstrual disorders is not diagnostic of a specific endocrinopathy, the cellular patterns may prove helpful in suggesting a range of diagnoses or in excluding some possibilities.     

Effect of oestrogen on Pasteurella pneumotropica in rat vagina

The effects of ovarian hormones on the vaginal population of Pasteurella pneumotropica in rats were investigated. Specified-pathogen-free adult female Wistar-Imamichi rats with a 4 day oestrous cycle were inoculated with P. pneumotropica in the vagina. Cyclic changes in the vaginal population of P. pneumotropica were not observed in ovariectomized rats and the bacterial population was at a similar level to that at normal dioestrus. Administration of oestrogen to ovariectomized rats caused an increase in the numbers of P. pneumotropica and total bacteria in the vagina nearly equal to that at oestrus in intact rats. The numbers of these organisms in the vagina of ovariectomized rats treated with progesterone did not change and were similar to those of control ovariectomized rats treated with sesame oil. Vaginal smears of ovariectomized rats treated with oestrogen were characterized by abundant cornified non-nucleated epithelial cells with many adherent Gram-negative coccobacilli and were similar to smears from intact rats at oestrus. These findings suggest that the proliferation of P. pneumotropica at oestrus in rat vagina may be primarily due to the environment provided by the degeneration of vaginal epithelial cells promoted by oestrogen secretion from the ovaries.     

Characteristics of the oestrous cycle and influence of social factors in grey short-tailed opossums (Monodelphis domestica)

Characteristics of the oestrous cycle of grey short-tailed opossums were studied by vaginal smears. The period of oestrus was identified by a sudden proliferation of epithelial cells which lasted about 6 days (range 3-12 days), followed by a leucocytic infiltration. Oestrous cycle length showed a bimodal distribution of 14.4 days (5 cycles, range 11-17 days) and 32.3 days (10 cycles, range 28-39 days). Females housed with males showed more days of epithelial cell proliferation than did females housed alone, and oestrous periods tended to occur in synchrony, suggesting that social factors may influence the oestrous cycle in this species.     

Performing Vaginal Lavage,Crystal Violet Staining,and Vaginal Cytological Evaluation for Mouse Estrous Cycle Staging Identification

A rapid means of assessing reproductive status in rodents is useful not only in the study of reproductive dysfunction but is also required for the production of new mouse models of disease and investigations into the hormonal regulation of tissue degeneration (or regeneration) following pathological challenge. The murine reproductive (or estrous) cycle is divided into 4 stages: proestrus, estrus, metestrus, and diestrus. Defined fluctuations in circulating levels of the ovarian steroids 17-β-estradiol and progesterone, the gonadotropins luteinizing and follicle stimulating hormones, and the luteotropic hormone prolactin signal transition through these reproductive stages. Changes in cell typology within the murine vaginal canal reflect these underlying endocrine events. Daily assessment of the relative ratio of nucleated epithelial cells, cornified squamous epithelial cells, and leukocytes present in vaginal smears can be used to identify murine estrous stages. The degree of invasiveness, however, employed in collecting these samples can alter reproductive status and elicit an inflammatory response that can confound cytological assessment of smears. Here, we describe a simple, non-invasive protocol that can be used to determine the stage of the estrous cycle of a female mouse without altering her reproductive cycle. We detail how to differentiate between the four stages of the estrous cycle by collection and analysis of predominant cell typology in vaginal smears and we show how these changes can be interpreted with respect to endocrine status.     

First postpartum estrus and pregnancy in the female collared peccary (Tayassu tajacu) from the amazon

The onset of sexual cycle postpartum was described in the collared peccary (Tayassu tajacu). Serum progesterone and 17beta-estradiol profiles, vaginal smears and external genitalia were analyzed in 20 animals housed with their piglets during the first postpartum month. The appearance of external genitalia showed no variation in any of the females: a shallow, reddish vulva, and vaginal mucus were constant features throughout the study. Based on hormonal profiles and vaginal smear cell patterns, 16 (80%) of the 20 peccaries showed signs of estrus and were considered cycling. The remaining four females (20%) did no show signs of estrus confirmed by low levels of progesterone (0.9+/-0.4 ng/mL) during the first postpartum month. In the cycling peccaries, a serum 17beta-estradiol peak (53.4+/-8.1 pg/mL) was observed on Day 7+/-1 postpartum, along with a linear increase in progesterone concentration from 3 (4.3+/-2.6 ng/mL) to 11 (30.8+/-4.9 ng/mL) days after this estradiol peak. Proportions of the different cells of the vaginal epithelium also changed in these females: superficial plus intermediate cells amounted to 76% of the cell total between Days 6 and 9 postpartum, corresponding to the estradiol peak. Nine (56%) of the 16 cycling females mated, indicated by the presence of sperm cells in their vaginal smears, and 6 (67%) became pregnant, reaching term. Non-pregnant cycling females (n=10) showed a steady decrease in serum progesterone concentration from 11 to 23 days after the estradiol peak, when basal levels were attained and a new estradiol peak registered, indicating the resumption of cyclicity in these females. The time interval between the two estradiol peaks was 23.5+/-2.1 days in these females. In pregnant females, progesterone concentrations continued to rise to levels of 60 ng/mL (n=6) 23 days after mating. These findings indicate that the lactating collared peccary female can become cycling and fertile during the early postpartum period, and that a predominance of superficial plus intermediate vaginal cells can be taken as the first sign of estrus.     

食蟹猴阴道涂片的动态观察

目的　为食蟹猴实施人工授精和适时配种提供一种有效的测定排卵期的方法。方法　选择 4～ 6岁性成熟的雌性食蟹猴 30只 ,对其阴道涂片进行动态观察。结果与结论　食蟹猴阴道涂片中主要有角化上皮细胞、中层基底细胞、白细胞和细胞碎片等。分析结果说明 ,白细胞数各时期差异均具显著性 ;角化上皮细胞在月经前期和月经期没有差异 ,但其他各期差异具显著性 ;月经期和月经后期中层基底细胞数目变化差异不显著 ,但其他各期差异具显著性 ;月经前期和月经期的细胞碎片数目相似 ,但其他各期差异具显著性。各时期细胞成份变化规律是 ,角化上皮细胞从月经期到排卵期呈逐渐增加至最高 ,然后逐渐减少 ;而白细胞、中层基底细胞和细胞碎片则恰好相反。     

Artificial intelligence in automated classification of rat vaginal smear cells.

Microscopic examination of vaginal smears has been used routinely to determine the stage of the estrous cycle of female rats in reproductive research. The stage of the estrous cycle is based on relative counts of nucleated epithelial cells, cornified epithelial cells and leukocytes. The purpose of this project was to explore automation of vaginal smear analysis using image processing and artificial intelligence techniques. A fully connected back-propagation neural network was used to locate all potential objects in a digitized scene. A unique algorithm was then employed to center a subsequent sampling box to collect pixel intensity values from the red and green components of each image. A final neural network was used in the classification of cell type. Neural networks were used because of their ability to generalize among input patterns and to tolerate extraneous noise due to variations in staining artifacts and aberrant illumination of the microscope field. This preliminary cell diagnosing system not only provides the basis for the fully automated system but also provides a method by which many other cytologic image processing problems can be automated.     

Reproductive functional anatomy and oestrous cycle pattern of the female brush-tailed porcupine (Atherurus africanus,Gray 1842) from Gabon

In the present study, we examined certain features of the functional anatomy of the female genital tract of the wild brush-tailed porcupine (Atherurus africanus) to obtain data on the reproductive biology of this African forest rodent. Two consecutive experiments were performed. The aim of the first was to establish macroscopic and microscopic features of the genital organs, and to explore correlations between predominant ovarian structures and vaginal contents in 20 wild, mature females. In the second experiment, we inspected the external genitalia and vaginal smears of a further 10 females in captivity on a daily basis for 90 days. The uterus of the brush-tailed porcupine is bicornuate and composed of two separated uterine horns, a uterine body and cervix. The genital tract does not present a vaginal vestibule. Thus, there is no portion common to genital and urinary tracts. Females in the follicular phase of the oestrous cycle showed increased cornification of the vaginal epithelium and a high density of eosinophilic cells in vaginal smears. The vulva and vaginal opening were open, reddish and tumefacted. In luteal phase or in pregnancy, epithelial cornification and eosinophilic features were notably reduced and the vagina presented a pale, non-tumefacted vulva and a vaginal closure membrane. Females in captivity showed spontaneous cycles, a polyoestrous reproduction pattern and, based on features of the external genitalia and vaginal smears, their oestrous cycle length was 27.1+/-6.4 days (n=12).     

Relationships between ovarian morphology, vaginal cytology, serum progesterone, and urinary immunoreactive pregnanediol during the menstrual cycle of the cynomolgus monkey

Three different indices of ovulation and luteal activity were studied in eight regularly cycling cynomolgus monkeys. A significant relation between changes in serum progesterone and immunoreactive pregnanediol (I-PD) in urine was obtained. The occurrence of ovulation could be determined reliably from a change in the ratio of cornified to basal epithelial cells in vaginal smears, and luteal activity could be assessed reliably from daily measurements of urinary pregnanediol. The time of ovulation could be defined more precisely by daily I-PD radioimmunoassays than by the vaginal smear pattern. Measurements of I-PD also have the advantage of ease and noninvasiveness over serum progesterone determinations. More detailed information about changes in hormonal activities could not be obtained reproducibly from thorough examination of cell types in vaginal smears.     

Ultrastructure of the nonhuman primate vaginal mucosa: epithelial changes during the menstrual cycle and pregnancy

Ultrastructural changes in the vaginal epithelium of the rhesus monkey during the menstrual cycle and pregnancy were studied by scanning and transmission electron microscopy. During the menstrual cycle, the epithelium was keratinized but varied in thickness. Cells of the basal and parabasal layers were polyhedral in shape but as they differentiated they accumulated glycogen and filaments. Cells in the intermediate layers had keratohyaline and membrane-coating granules. Cells in the superficial layers had a thickened cell envelope, abundant keratin filaments, electron-dense intercellular material, and focal tight junctions. The epithelial surface had numerous microridges and numerous adherent bacteria; bacteria were rare on desquamating cells. The epithelium remained keratinized for about the first month of gestation, then underwent "mucification." The cells contained abundant granules and Golgi apparatus. Concomitant with this transformation, bacteria were no longer adherent to the epithelial surface and the surface cells had microvilli instead of microridges. The epithelial changes during pregnancy were roughly associated with the changing pattern of steroid hormone secretion during gestation.     

A comparative study of the estrogenic potential of two synthetic estrogens (mestranol and ethinylestradiol)

The purpose of this study was to establish the relative estrogenicity of ethinylestradiol and mestranol and to establish .05 and .1 mg of mestranol as standard reference preparations for the comparative study of other compounds. Patients were selected from a large group of primary amenorrhea, secondary amenorrhea, and postmenopausal women. All required hormonal replacement therapy. Patients with chromosomal abnormalities or those with diminished or abnormal response were excluded. Vaginal cytology was used as the main method for the assessment of the response. Before treatment all had either an atrophic pattern (Maturation Index = 50-50-0) or a hypertrophic pattern (MI=5-95-0) with a mean value of 10-87-3 for patients with primary amenorrhea and 18-79-3 in the other 2 groups. Patients with a proliferative intermediate cell pattern and postmenopausal women thought to have continuing endogenous estrogen activity were omitted. Ethinylestradiol or mestranol were given orally in doses of .025, .05, and .1 mg for a period of 10 days during which frequent vaginal smears were made. When cell patterns showed extremely marked cytolysis of the glycogen-containing intermediate cells and a low percentage of karyopyknotic superficial cells these patients were excluded. 40 women were finally included. The effects of estrogen on the vaginal epithelium in all 40 women after 10 days therapy were quite uniform. In those cases showing delayed regression of estrogenic effects 4 mg of chlormadinone acetate was given daily for 10 days. These patients then showed a reduction in the superficial cell percentage accompanied by a shift to the left in the maturation index such as 0-40-60 before to 0-95-5 after treatment. A few women had an insignificant reduction in the superficial cell percentages. Changes in the percentages of the intermediate type of cells were not significant. The regression was considered to be complete when the smear contained mainly small intermediate cells and parabasal cells with numerous leukocytes and some necrotic debris. Both estrogen preparations produced the same vaginal response at .05 mg doses. Tablets of .05 and .1 mg mestranol were chosen for further study. The increase in the superficial cell index to 30 (SD plus or minus 18.5) following treatment with .05 mg and the increase to 54.1 (SD plus or minus 26.7) following .1 mg have been adopted as standard vaginal responses. The term estrogenic effect used in vaginal cytology is taken to mean the local vaginal effect induced by estrogens.     

Proliferation of Pasteurella pneumotropica at oestrus in the vagina of rats

Using a colony of Wistar-Imamichi rats contaminated with P. pneumotropica, the vaginal microflora was qualitatively and quantitatively investigated by swabbing. P. pneumotropica was the most dominant organism in the majority of rats examined. The population of P. pneumotropica and indigenous bacteria increased significantly higher at oestrus than in other oestrous stages. By the vaginal flushing technique changes in the population of P. pneumotropica and total bacteria, and changes in vaginal cell type and bacterial counts adhering to vaginal epithelial cells were consecutively investigated. The populations of P. pneumotropica and total bacteria were maximal at oestrus. The increase was correlated with an increase in cornified non-nucleated cells, with large numbers of adherent Gram-negative coccobacilli. The findings indicate that the vagina is a suitable site for colonization by P. pneumotropica in adult female rats, and that proliferation of P. pneumotropica may be due to increased affinity of the organism for cornified non-nucleated cells.     

Determination of oestrous condition in female mice is dependent upon time of day

Mice were maintained in rooms with constant ambient conditions and a 12 h light:12 h dark daily light regimen with the lights on starting at 06:00 h. In Exp. I, detection of puberty, as measured by first vaginal oestrus, was recorded at significantly earlier ages when vaginal smears were taken at 04:00 or 08:00 h than at other times of the day. In Exp. II, adult females were detected as being in oestrus more frequently when vaginal smears were taken within 6 h before or after the onset of the light part of the cycle each day than at other times.