Characterization and imaging in optically scattering media by use of laser speckle and a variable-coherence source

We demonstrate the application of laser-speckle statistics formed by a variable-coherence source illuminating a scattering medium, for determining the scattering parameter mu;(s)>(?) of a diffusion model for the medium. Furthermore, we apply this technique to visualize laterally localized inhomogeneities embedded within a highly scattering sample.

Figural aftereffects in the perception of faces

We examined figural aftereffects in images of human faces, for which changes in configuration are highly discriminable. Observers either matched or rated faces before or after viewing distorted images of faces. Prior adaptation strongly biases face perception by causing the original face to appear distorted in a direction opposite to the adapting distortion. Aftereffects transferred across different faces and were similar for upright or inverted faces, but were weaker when the adapting and test faces had different orientations (e.g., adapt inverted and test upright). Thus the aftereffects depend on which images are distorted, and not simply on the type of distortion introduced. We further show that the aftereffects are asymmetric, for adapting to the original face has little effect on the perception of a distorted face. This asymmetry suggests that adaptation may play an important normalizing role in face perception. Our results suggest that in normal viewing, figural aftereffects may strongly influence form perception and could provide a novel method for probing properties of human face perception.

Menopausal symptom control and side-effects on continuous estrone sulfate and three doses of medroxyprogesterone acetate. Ogen/Provera Study Group

OBJECTIVES

To establish the optimum oral daily dose of micronized medroxyprogesterone acetate (MPA), given in combination with 1.25 mg of estrone sulfate for menopausal symptom control.

METHODS

This multicenter, randomized, double-blind study was conducted on 568 postmenopausal women who were randomized to take estrone sulfate 1.25 mg daily with 2.5, 5.0 or 10 mg of MPA daily for 2 years. The number of vasomotor symptoms and the severity of mood swings, lethargy, vaginal dryness and loss of libido as well as side-effects were recorded in a diary. Blood pressure and weight were recorded at each 3-month visit.

RESULTS

Vasomotor symptoms were reported by approximately 80% of subjects at month 1, 23% at month 3 but only 9% by month 24. Mood swings, lethargy and vaginal dryness improved rapidly in the initial 3 months of therapy. Decrease in libido had a slower response to therapy in all three treatment groups. Breast tenderness was the commonest side-effect with 22% of subjects complaining of this in the first 3 months of therapy, dropping to 13% by 6 months. Headache, depression, nausea, bloating and irritability showed a similar pattern of decline. There was no significant difference in the rate of decrease in menopausal symptoms or reported side-effects between the three treatment groups. There was a small but significant (p < 0.001) decrease in systolic and diastolic blood pressure over the study period.

CONCLUSIONS

All three treatment regimens provide adequate symptom control. Side-effects decreased markedly after the first 3 months, with no significant difference between the treatment groups.

Bleeding pattern and endometrial changes during continuous combined hormone replacement therapy. The Ogen/Provera Study Group

OBJECTIVE

To establish the optimum oral daily dose of micronized medroxyprogesterone acetate, given in combination with a fixed oral dose of estrone (E1) sulfate as hormone replacement therapy, that provides endometrial protection and induces cessation of vaginal bleeding.

METHODS

This multicenter, randomized, double-blind study was conducted for 2 years. Five hundred sixty-eight postmenopausal women were randomized to take E1 sulfate 1.25 mg daily and one of three doses of medroxyprogesterone acetate (2.5, 5, or 10 mg) daily. Any vaginal bleeding was recorded by patients in a daily diary, and endometrial biopsies were performed at entry into the study and at 3, 12, and 24 months.

RESULTS

Forty-two percent of all women reported some bleeding at month 3 of therapy. However, by month 6, 76.5, 80.1, and 80.9% of women were amenorrheic in the 2.5-, 5-, and 10-mg medroxyprogesterone acetate groups, respectively. Over time, the percentage of women with no bleeding increased in each group, and by 24 months 91.5, 89.9, and 94.3% were amenorrheic in the 2.5- and 10-mg medroxyprogesterone acetate groups, respectively. Approximately 10% of women continue to have some bleeding, regardless of the dose of medroxyprogesterone acetate. There were no statistically significant differences in the number of women with bleeding at any time point between the three groups. There were no cases of endometrial hyperplasia reported in the study population over the 2 years.

CONCLUSION

All three studied doses of medroxyprogesterone acetate, given in combination with 1.25 mg of E1 sulfate, provide adequate endometrial protection and render approximately 80% of women amenorrheic by 6 months of therapy.

The induction of uterine leiomyomas and mammary tumors in transgenic mice expressing polyomavirus (PyV) large T (LT) antigen is associated with the ability of PyV LT antigen to form specific complexes with retinoblastoma and CUTL1 family members

The inactivation of certain tumor suppressor genes is thought to play an important role in the genesis of a number of tumor types. For example, inactivation of the Retinoblastoma (Rb) tumor suppressor is frequently observed in a proportion of sporadic human breast cancers. While these studies suggest that inactivation of key tumor suppressor genes may play an important role in the induction of mammary cancers, direct evidence supporting this contention is lacking. Because polyomavirus (PyV) Large T (LT) antigen is known to associate with and inactivate certain members of the Rb family (p105Rb, p107, p130), we have derived transgenic mice which express PyV LT antigen in the mammary epithelium. As expected mammary epithelial-specific expression of PyV LT antigen resulted in the induction of mammary tumors which correlated with their capacity to associate with Rb family members. In addition to mammary carcinomas, female transgenic mice expressing the PyV LT transgene frequently develop uterine leiomyomas. Because loss of heterozygosity involving the human CUTL1 (Cut like 1) gene located at chromosomal position 7q22 has been recently implicated in sporadic human uterine leiomyomas, we tested the hypothesis that PyV LT antigen may also form specific complexes with CUTL1. The results of these analyses revealed that specific complexes of CUTL1 and PyV LT antigen could be detected in both leiomyomas and mammary tumors. Taken together, these observations suggest that PyV LT antigen may be involved in inducing these tumors by sequestering both CUTL1 and Rb growth regulatory proteins.

Requirement for both Shc and phosphatidylinositol 3' kinase signaling pathways in polyomavirus middle T-mediated mammary tumorigenesis

Transgenic mice expressing the polyomavirus (PyV) middle T antigen (MT) develop multifocal mammary tumors which frequently metastasize to the lung. The potent transforming activity of PyV MT is correlated with its capacity to activate and associate with a number of signaling molecules, including the Src family tyrosine kinases, the 85-kDa Src homology 2 subunit of the phosphatidylinositol 3' (PI-3') kinase, and the Shc adapter protein. To uncover the role of these signaling proteins in MT-mediated mammary tumorigenesis, we have generated transgenic mice that express mutant PyV MT antigens decoupled from either the Shc or the PI-3' kinase signaling pathway. In contrast to the rapid induction of metastatic mammary tumors observed in the strains expressing wild-type PyV MT, mammary epithelial cell-specific expression of either mutant PyV MT resulted in the induction of extensive mammary epithelial hyperplasias. The mammary epithelial hyperplasias expressing the mutant PyV MT defective in recruiting the PI-3' kinase were highly apoptotic, suggesting that recruitment of PI-3' kinase by MT affects cell survival. Whereas the initial phenotypes observed in both strains were global mammary epithelial hyperplasias, focal mammary tumors eventually arose in all female transgenic mice. Genetic and biochemical analyses of tumorigenesis in the transgenic strains expressing the PyV MT mutant lacking the Shc binding site revealed that a proportion of the metastatic tumors arising in these mice displayed evidence of reversion of the mutant Shc binding site. In contrast, no evidence of reversion of the PI-3' kinase binding site was noted in tumors derived from the strains expressing the PI-3' kinase binding site MT mutant. Tumor progression in both mutant strains was further correlated with upregulation of the epidermal growth factor receptor family members which are known to couple to the PI-3' kinase and Shc signaling pathways. Taken together, these observations suggest that PyV MT-mediated tumorigenesis requires activation of both Shc and PI-3' kinase, which appear to be required for stimulation of cell proliferation and survival signaling pathways, respectively.

Adaptation and the color statistics of natural images

Color perception depends profoundly on adaptation processes that adjust sensitivity in response to the prevailing pattern of stimulation. We examined how color sensitivity and appearance might be influenced by adaptation to the color distributions characteristic of natural images. Color distributions were measured for natural scenes by sampling an array of locations within each scene with a spectroradiometer, or by recording each scene with a digital camera successively through 31 interference filters. The images were used to reconstruct the L, M and S cone excitation at each spatial location, and the contrasts along three post-receptoral axes [L + M, L - M or S - (L + M)]. Individual scenes varied substantially in their mean chromaticity and luminance, in the principal color-luminance axes of their distributions, and in the range of contrasts in their distributions. Chromatic contrasts were biased along a relatively narrow range of bluish to yellowish-green angles, lying roughly between the S - (L + M) axis (which was more characteristic of scenes with lush vegetation and little sky) and a unique blue-yellow axis (which was more typical of arid scenes). For many scenes L - M and S - (L + M) signals were highly correlated, with weaker correlations between luminance and chromaticity. We use a two-stage model (von Kries scaling followed by decorrelation) to show how the appearance of colors may be altered by light adaptation to the mean of the distributions and by contrast adaptation to the contrast range and principal axes of the distributions; and we show that such adjustments are qualitatively consistent with empirical measurements of asymmetric color matches obtained after adaptation to successive random samples drawn from natural distributions of chromaticities and lightnesses. Such adaptation effects define the natural range of operating states of the visual system.

Contrast adaptation and the spatial structure of natural images

Natural images have a characteristic spatial structure, with amplitude spectra that decrease with frequency roughly as 1/f. We have examined how contrast (pattern-selective) adaptation to this structure influences the spatial sensitivity of the visual system. Contrast thresholds and suprathreshold contrast and frequency matches were measured after adaptation to random samples from an ensemble of images of outdoor scenes or of synthetic images formed by filtering the amplitude spectra of noise over a range of spectral slopes. Adaptation selectively reduced sensitivity at low-to-medium frequencies, biasing contrast sensitivity toward higher frequencies. The pattern of aftereffects was similar for different natural image ensembles but varied with large changes in the slope of the noise spectra. Our results suggest that adaptation to the spatial structure in natural scenes may exert strong and selective influences on perception that are important in characterizing the normal operating states of the visual system.

Motion minima for different directions in color space

We have used the minimum-motion stimulus of Cavanagh, MacLeod & Anstis [(1987) Journal of the Optical Society of America A, 4, 1428-1438] to examine how signals along different directions in color space interact in motion perception. Stimuli were pairs of counterphasing gratings combined 90 deg out of phase in both space and time and modulated along different color-luminance axes. The axis for one of the gratings was fixed, while the axis for the second was varied so as to null perceived motion in the stimulus. The motion nulls show that observers are sensitive to motion signals carried by each of the cardinal directions of color space [an achromatic axis and L-M and S-(L+M) chromatic axes], but that signals along different cardinal axes are not combined to yield a net direction of motion. Pairing an achromatic and chromatic grating resulted in a motion null regardless of the relative or overall contrast of the two gratings, while the null directions for intermediate axes shifted depending on contrast. This result points to the special status of the luminance and chromatic axes. However, our results do not reveal a special pair of axes within the equiluminant plane. When contrasts along the cardinal axes are scaled for equal multiples of their respective detection thresholds, the L-M and S chromatic contrasts contribute roughly equally to the perceived motion, but are many times weaker than luminance contrast. Moreover, sensitivity to luminance motion is little affected by the presence of chromatic contrast, whereas sensitivity to chromatic motion is strongly masked by either luminance or chromatic contrast. These asymmetric interactions suggest that the motion of the luminance and chromatic components is encoded in qualitatively different ways.

Synergistic interaction of the Neu proto-oncogene product and transforming growth factor alpha in the mammary epithelium of transgenic mice

Transgenic mice expressing either the neu proto-oncogene or transforming growth factor (TGF-alpha) in the mammary epithelium develop spontaneous focal mammary tumors that occur after a long latency. Since the epidermal growth factor receptor (EGFR) and Neu are capable of forming heterodimers that are responsive to EGFR ligands such as TGF-alpha, we examined whether coexpression of TGF-alpha and Neu in mammary epithelium could cooperate to accelerate the onset of mammary tumors. To test this hypothesis, we interbred separate transgenic strains harboring either a mouse mammary tumor virus/TGF-alpha or a mouse mammary tumor virus/neu transgene to generate bitransgenic mice that coexpress TGF-alpha and neu in the mammary epithelium. Female mice coexpressing TGF-alpha and neu developed multifocal mammary tumors which arose after a significantly shorter latency period than either parental strain alone. The development of these mammary tumors was correlated with the tyrosine phosphorylation of Neu and the recruitment of c-Src to the Neu complex. Immunoprecipitation and immunoblot analyses with EGFR- and Neu-specific antisera, however, failed to detect physical complexes of these two receptors. Taken together, these observations suggest that Neu and TGF-alpha cooperate in mammary tumorigenesis through a mechanism involving Neu and EGFR transactivation.

Contrast Adaptation and the Spatial Structure of Natural Images

Contrast (pattern-selective) adaptation influences perception by adjusting sensitivity to the prevailing pattern of stimulation. We asked how the state of adaptation might depend on the patterns of spatial contrast typical of the natural visual environment. In one set of experiments, we examined whether adaptation to the characteristic amplitude spectra of natural images (which tend to decrease with frequency as 1/f) induces characteristic changes in contrast sensitivity. Contrast thresholds and suprathreshold contrast matches were measured after adaptation to random samples from an ensemble of images of natural outdoor scenes, or synthetic images formed by filtering the amplitude spectra of noise over a range of slopes. Adaptation differentially reduced sensitivity at low to medium spatial frequencies, but losses were not strongly dependent on the slope of the adapting spectra. In a second set of experiments, we examined the figural aftereffects induced by adaptation to naturalistic stimuli, by adapting and testing with images of human faces, for which small configural changes are highly discriminable. Observers adapted to frontal-view images of faces that were distorted by local expansions or contractions about the centre, and then adjusted distortions in test images to try to select the original face. Adaptation strongly biased perception in a direction opposite to the adapting distortion, with strongest aftereffects when test and adapting stimuli were derived from the same face image. Our results suggest that adaptation to the stimuli encountered in the course of normal viewing may exert ubiquitous and selective influences that are important in characterising the normal operating state of the visual system.

Induction of mammary epithelial hyperplasias and mammary tumors in transgenic mice expressing a murine mammary tumor virus/activated c-src fusion gene

Activation of the c-Src tyrosine kinase has been implicated as an important step in the induction of mammary tumors in both mice and humans. To directly assess the effect of mammary gland-specific expression of activated c-Src, we established transgenic mice that carry a constitutively activated form of c-src under transcriptional control of the murine mammary tumor virus long terminal repeat. Female mice derived from several independent transgenic lines lactate poorly as a consequence of an impairment in normal mammary epithelial development. In addition to this lactation defect, female mice frequently develop mammary epithelial hyperplasias, which occasionally progress to frank neoplasias. Taken together, these observations suggest that expression of activated c-Src in the mammary epithelium of transgenic mice is not sufficient for induction of mammary tumors.

Colour constancy influenced by contrast adaptation

Visual sensitivity is controlled by at least two distinct types of adaptation: light adaptation adjusts sensitivity to the mean luminance and colour in the stimulus, and contrast adaptation adjusts sensitivity to the variations in luminance and colour. Light adaptation is thought to be important in maintaining the perceived colour of objects despite changes in illumination ('colour constancy'), compensating for the mean changes in the light reflected from scenes under different illuminants. But for naturalistic colour signals, we show here that changes in an illuminant can also alter colour contrasts in images (how colours are distributed around the mean) enough to alter the state of contrast adaptation. Thus perceived colour under different illuminants may also be noticeably influenced by contrast adaptation.

Continuous combined piperazine oestrone sulphate and medroxyprogesterone acetate hormone replacement therapy--a study of bleeding pattern, endometrial response, serum lipid and bone density changes

This pilot study was conducted to establish the optimum oral dosage of medroxyprogesterone acetate (Provera) given daily in combination with a fixed dose of piperazine oestrone sulphate (Ogen), as hormone replacement therapy. A group of 32 nonhysterectomized, symptomatic menopausal women were randomly allocated to receive piperazine oestrone sulphate 1.25 mg daily and medroxyprogesterone acetate 2.5 mg, 5 mg or 10 mg daily for a 2-year period. This was an open study and the patients were reviewed at 3-monthly intervals for 2 years. Vaginal bleeding was reported by 58% of patients after the first 3 months of treatment. There was a gradual decline in the reported incidence of bleeding over the following 6 months particularly by women in the 5 mg and 10 mg Provera group. Only 10% of patients were still recording slight bleeding in the 10 mg group at 12 months. By 24 months all the women in the 5 mg and 10 mg Provera groups had ceased bleeding. There were 2 patients in the 2.5 mg Provera group with persistent proliferative endometrium at 24 months. All the remaining patients had atrophic endometrium. There was no significant difference in serum lipid changes between the 3 groups, but there was an overall reduction in total cholesterol, triglycerides and low density lipoprotein cholesterol in all women. There was no significant difference in bone mineral density changes between the groups over the 2-year period. Endometrial protection with increased incidence of amenorrhoea, without significant adverse effects, was seen with the use of 5 mg and 10 mg of provera.

The influence of contrast adaptation on color appearance

Most models of color vision assume that signals from the three classes of cone receptor are recoded into only three independent post-receptoral channels: one that encodes luminance and two that encode color. Stimuli that are equated for their effects on two of the channels should be discriminable only to the remaining channel, and are thus assumed to isolate the responses of single channels. We used an asymmetric matching task to examine whether such models can account for changes in color appearance following adaptation to contrast--to temporal variations in luminance and chromaticity around a fixed mean luminance and chromaticity. The experiments extend to suprathreshold color appearance the threshold adaptation paradigm of Krauskopf, Williams and Heeley [(1982) Vision Research, 32, 1123-1131]. Adaptation changes the perceived color of chromatic test stimuli both by reducing their saturation (contrast) and by changing their hue (direction within the equiluminant plane). The saturation losses are largest for test stimuli that lie along the chromatic axis defining the adapting modulation, while the hue changes are rotations away from the adapting direction and toward an orthogonal direction within the S and L-M plane. Similar selective changes in both perceived color and perceived lightness occur following adaptation to stimuli that covary in luminance and chromaticity. The selectivity of the aftereffects for multiple directions within color-luminance space is inconsistent with sensitivity changes in only three independent channels. These aftereffects suggest instead that color appearance depends on channels that can be selectively tuned to any color-luminance direction, and that there are no directions that invariably isolate responses in only a single channel. We use the perceived color changes to examine the spectral sensitivities of the chromatic channels and to estimate the distribution of channels. We also examine how adaptation alters the contrast-response function, how it affects reaction times for luminance and chromatic contrast, the extent to which the aftereffects exhibit interocular transfer, and the way in which the perceived color changes differ from those induced by conventional light adaptation.

Mammary tumorigenesis and metastasis in transgenic mice

The transgenic mouse has emerged as an important model system to assess the transforming potential of oncogenes in the mammary epithelium. Mammary gland-specific expression of oncogenes in transgenic mice has resulted in the induction of a variety of phenotypes ranging from benign epithelial hyperplasias to metastatic mammary tumors. The induction of tumors in most of these transgenic models is a multi-step process where transgene expression, although required, is not sufficient for conversion of the primary mammary epithelial cell to the transformed phenotype. While the identity of many of these collaborating genetic events is obscure, several approaches have been applied with might shed light on their nature. In a few exceptional transgenic strains, tumor progression can occur very rapidly suggesting that, if additional genetic events are required, they occur very frequently. Recent genetic and biochemical characterization of these strains offers insight into the molecular mechanisms that may underlie the complex phenotypic features exhibited by these transgenic strains.

Mammary tumors expressing the neu proto-oncogene possess elevated c-Src tyrosine kinase activity

Amplification and overexpression of the neu (c-erbB2) proto-oncogene has been implicated in the pathogenesis of 20 to 30% of human breast cancers. Although the activation of Neu receptor tyrosine kinase appears to be a pivotal step during mammary tumorigenesis, the mechanism by which Neu signals cell proliferation is unclear. Molecules bearing a domain shared by the c-Src proto-oncogene (Src homology 2) are thought to be involved in signal transduction from activated receptor tyrosine kinases such as Neu. To test whether c-Src was implicated in Neu-mediated signal transduction, we measured the activity of the c-Src tyrosine kinase in tissue extracts from either mammary tumors or adjacent mammary epithelium derived from transgenic mice expressing a mouse mammary tumor virus promoter/enhancer/unactivated neu fusion gene. The Neu-induced mammary tumors possessed six- to eightfold-higher c-Src kinase activity than the adjacent epithelium. The increase in c-Src tyrosine kinase activity was not due to an increase in the levels of c-Src but rather was a result of the elevation of its specific activity. Moreover, activation of c-Src was correlated with its ability to complex tyrosine-phosphorylated Neu both in vitro and in vivo. Together, these observations suggest that activation of the c-Src tyrosine kinase during mammary tumorigenesis may occur through a direct interaction with activated Neu.

Contrast adaptation dissociates different measures of luminous efficiency

We compared how contrast adaptation influences three alternative measures of luminous efficiency. Subjects judged the lightness, the flicker, or the motion of chromatic sine-wave gratings. Adaptation to gratings with correlated luminance and chromatic contrast strongly biases lightness matches and moderately biases minimum-motion settings for gratings that are counterphased at 1 Hz, but it has little effect on motion or flicker settings for gratings that are counterphased at 15 Hz. These results suggest that different measures of equiluminance tap neural pathways that can have different spectral sensitivities. At low temporal frequencies both perceived lightness and minimum-motion settings appear to depend on channels that do not represent luminance and color independently.

Expression of the neu protooncogene in the mammary epithelium of transgenic mice induces metastatic disease

Overexpression and amplification of the neu (c-erbB2, ERBB2) protooncogene have been implicated in the development of aggressive human breast cancer. To directly assess the effect of mammary gland-specific expression of the neu protooncogene, transgenic mice carrying unactivated neu under the transcriptional control of the mouse mammary tumor virus promoter/enhancer were established. By contrast to the rapid tumor progression observed in several transgenic strains carrying the activated neu transgene, expression of unactivated neu in the mammary epithelium resulted in the development of focal mammary tumors after long latency. The majority of the mammary tumors analyzed expressed elevated levels of neu-encoded mRNA and protein. Overexpression of neu in the mammary tumors was also associated with elevated neu intrinsic tyrosine kinase activity and the de novo tyrosine phosphorylation of several cellular proteins. Interestingly, many of the tumor-bearing transgenic mice developed secondary metastatic tumors in the lung. These observations suggest that overexpression of the unactivated neu protein can induce metastatic disease after long latency.

Induction of abortion in early first trimester human pregnancy using epostane

The role of epostane (Sterling Winthrop, Guildford, UK), a competitive inhibitor of the 3 beta hydroxysteroid dehydrogenase enzyme system (3 beta-HSD), as an abortifacient agent in early human pregnancy has been studied in 54 women. All were less than 49 days from their last menstrual period. Thirty were treated with 200 mg of epostane every 8 h for 7 days and 24 were given 200 mg every 6 h for 7 days. This caused a sustained reduction in circulating progesterone concentrations, a smaller fall in 17 beta-oestradiol and no effect on serum cortisol. Abortion occurred in 21 women (70%) in the lower dosage group and in 20 women (87%) in the higher dosage group. Abortion was incomplete in 6 of these 41 women. A worsening of pregnancy nausea and vomiting was noted by 66% of women in the first group and 84% in the second. There was no delay in the resumption of normal menstruation following abortion. This study confirms the potential of epostane as an effective inhibitor of ovarian and placental steroidogenesis and as a potent abortifacient agent in early human pregnancy.

Obstetric high risk screening and prediction of neonatal morbidity

A retrospective study using an obstetric risk score protocol was applied to a stratified sequential sample of 843 singleton livebirths, occurring in the Royal Hospital for Women, Sydney, over a 12-month period (March, 1985-February, 1986). Data collection included 53 prenatal factors, 41 intrapartum factors and 37 neonatal factors. The study was comprised of 346 women admitted to the hospital birth centre and 497 women admitted to labour ward. In labour ward admitted women there was a significant association between high prenatal scores, high intrapartum scores and high neonatal morbidity scores. Women admitted to the birth centre were subjected to a screening procedure which resulted in low prenatal and relatively low intrapartum risk scores. However, neonatal morbidity scores were similar for both groups. The risk scoring protocol used in this study requires further revision to allow the adequate selection of low risk women delivering infants with a low risk of neonatal morbidity in a low risk obstetric setting.

Temporal properties of brightness and color induction

With a matching procedure, we studied the temporal properties of direct brightness (or lightness) and chromatic changes (produced by modulation of the region being matched) and induced brightness and chromatic changes (produced by modulation of the surround of the region being matched). The amount of direct brightness and color change was found to vary only slightly with temporal frequency over the 0.5-8 Hz range studied, whereas induced changes were found to occur only at low temporal frequencies, below about 2.5 Hz. With high temporal-frequency modulation of the surround, the induced patterns appeared to flicker but not to change in brightness or color. Despite the fact that chrominance and luminance temporal contrast sensitivity functions are very different, the temporal induction curves for color and brightness were very similar. However, brightness induction was found to increase approximately linearly with increasing surround modulation up to very high levels, whereas the amount of color induction was much less dependent on the modulation depth of the surround.

Myometrial activity in first trimester human pregnancy after Epostane therapy. Effect of intravenous oxytocin

The effect on myometrial activity of Epostane, a competitive inhibitor of the 3 beta-hydroxy steroid dehydrogenase enzyme system (3 beta-HSD) has been studied in 20 women awaiting termination of pregnancy. The women were randomly allocated by a double-blind procedure into two groups. In the Epostane-treated group there were significant falls in serum progesterone and oestradiol concentrations after 3 days of treatment. The placebo-treated group showed a small but significant decline in serum progesterone concentration. Insertion of an intrauterine balloon catheter for pressure measurements produced significantly greater uterine activity in the Epostane-treated group. The oxytocin response was variable and there was no significant difference between the two groups. A small rise in the peripheral plasma concentration of a prostaglandin F2 alpha metabolite (PGFM) was observed in the placebo group following oxytocin injection. There was a significant inverse correlation between post treatment progesterone values and uterine activity. Epostane appears to sensitize the myometrium to endogenous oxytocics and this probably results from progesterone 'withdrawal'. This effect may prove useful in potentiating the action of exogenous myometrial stimulants, such as prostaglandins, and may have a role in the termination of early pregnancy.

Interruption of first trimester human pregnancy following Epostane therapy. Effect of prostaglandin E2 pessaries

The effect of Epostane, a competitive inhibitor of the 3 beta hydroxy steroid dehydrogenase enzyme system in combination with prostaglandin E2 (PGE2) for induction of abortion in early first trimester pregnancy has been studied in a group of 20 women awaiting termination of pregnancy. The women were consecutively assigned to four treatment groups. The first group was treated with PGE2 alone, administered vaginally as a lipid based (Witepsol) pessary. The remaining three groups received Epostane at differing doses for 5 days, and were treated with PGE2 on the fourth day. Significant falls in serum progesterone and oestradiol occurred in the Epostane-treated patients. Abortion was induced in one of the five control patients and in three of 10 patients treated with low doses (300-400 mg) of Epostane. Intrauterine pressure monitoring showed an increased reactivity to PGE2 in the treated groups. At the highest dose (600 mg) of Epostane, serum progesterone and oestradiol showed the greatest decline to 8% and 21% of the pretreatment values, a prompt and sustained pressure response occurred to PGE2 and abortion was induced in all five patients. A critical degree of progesterone suppression appears to sensitize the myometrium to exogenous prostaglandin. This combined treatment is an effective method of early pregnancy termination and may have a role in the management of mid-trimester abortion.