Formation and early development of follicles in the polycystic ovary.

BACKGROUND: Polycystic ovary syndrome is the most common cause of anovulatory infertility. It has long-term health implications and is an important risk factor for type 2 diabetes. However, little is known about the cause of polycystic ovaries. We have used detailed morphological analysis to assess the hypothesis that there is an intrinsic ovarian abnormality that affects the earliest stages of follicular development. METHODS: We took small cortical biopsies during routine laparoscopy from 24 women with normal ovaries and regular cycles and from 32 women with polycystic ovaries, 16 of whom had regular, ovulatory cycles and 16 of whom had oligomenorrhoea. We used computerised image analysis to assess the density and developmental stage of small preantral follicles in serial sections of fixed tissue. FINDINGS: Median density of small preantral follicles, including those at primordial and primary stages, was six-fold greater in biopsies from polycystic ovaries in anovulatory women than in normal ovaries (p=0.009). In both ovulatory and anovulatory women with polycystic ovaries, we noted a significant increase in the percentage of early growing (primary) follicles and a reciprocal decrease in the proportion of primordial follicles compared with normal ovaries. INTERPRETATION: Our findings indicate that there are fundamental differences between polycystic and normal ovaries in early follicular development, suggesting an intrinsic ovarian abnormality. The increased density of small preantral follicles in polycystic ovaries could result from increased population of the fetal ovary by germ cells, or from decreased rate of loss of oocytes during late gestation, childhood, and puberty.

Dietary L-histidine regulates murine skin levels of trans-urocanic acid, an immune-regulating photoreceptor, with an unanticipated modulation: potential relevance to skin cancer.

Solar ultraviolet-B radiation (UVB; 290-320 nm) causes skin cancer and suppresses cell-mediated immunity, preventing the rejection of UV-induced tumors. One mechanism initiating UV suppression involves the trans to cis photoisomerization of urocanic acid (UCA), a histidine derivative found in the stratum corneum. The addition of L-histidine to nonpurified mouse diet has been shown to increase skin trans-UCA levels and sensitivity to UVB immune suppression. Specially formulated L-histidine diets (0.40-64 g/kg) fed to BALB/c mice that were monitored over a 19-wk period resulted in an unexpected modulation of skin trans-UCA. ANOVA revealed a group-time interaction, providing initial evidence that the skin levels of trans-UCA were modulating up and down in all groups except the control group (6.4 g/kg diet). We observed that both high (64 g/kg diet) and low (0.4 g/kg diet) levels of dietary L-histidine resulted in the increase of skin trans-UCA to levels significantly higher than those recorded in the control group. In mice fed these histidine levels, skin trans-UCA increased to between 2.9 and 3.6 nmol/mg skin (64 g/kg diet, over 5 wk; 0.4 g/kg diet, over 8 wk) and then decreased to approximately 1.69 nmol/mg skin, the base-line level (64 g/kg diet, over 11 wk; 0.4 g/kg diet, over 17 wk). The increase in trans-UCA levels in mice with low L-histidine intake may be the result of protein malnutrition, consistent with weight loss observed in those mice. The modulation of trans-UCA levels in skin by dietary L-histidine has not been previously described; its role in skin cancer development is under investigation.

The effects of UVA-I (340-400 nm), UVA-II (320-340 nm) and UVA-I+II on the photoisomerization of urocanic acid in vivo.

Ultraviolet B radiation (280-320 nm) can systemically suppress contact hypersensitivity (CHS), delayed type hypersensitivity (DTH) and tumor rejection responses in mice. Several models have been postulated for the initiation of this UVB-induced immune suppression and, although the complete mechanism is unclear, our early studies suggested that initiation is via the activation of a photoreceptor in the skin, identified as urocanic acid (UCA). Recent preliminary data from our laboratory and others indicated that UVA (320-400 nm)-emitting broad-band sunlamps can also isomerize UCA but may not lead to immune suppression, in contrast to UVB-emitting sunlamps, which cause both effects. Although the reason for this inconsistency is unknown, the emission spectra of UVA lamps contain differing amounts of UVB, UVA-I (340-400 nm) and UVA-II (320-340 nm) from those of UVB sources. In this study we determined a detailed dose-response for the isomerization of UCA in mouse skin using the UVA-I, UVA-II and UVA-I+II wavelength ranges. The dose-response curves obtained were put on an equal energy basis by quantum correction and the possibility of wavelength interaction for this effect investigated. A simple additive wavelength interaction between UVA-I, UVA-II, and UVA-I+II was observed for trans-UCA photoisomerization. This result indicates that the failure of UVA-I, UVA-II or UVA-I+II radiation to induce immune suppression of the CHS response in an animal model is not due to complex wavelength interactions and/or the presence of an in vivo endogenous photosensitizer of UCA isomerization. Other factors, such as downstream blocking by UVA of the cis-UCA generated signal, may be involved.

Dietary beta-carotene and ultraviolet-induced immunosuppression.

Ultraviolet (UV)-induced immunosuppression is a critical step in UV carcinogenesis, permitting tumour outgrowth. We investigated the effect of dietary beta-carotene on UV suppression of contact hypersensitivity (CHS) to trinitrochlorobenzene (TNCB) in BALB/c mice. Mice were fed for 10-16 weeks chow alone or supplemented with 1% beta-carotene or placebo as beadlets. Serum beta-carotene was detectable by high performance liquid chromatography (HPLC) analysis only in beta-carotene-fed mice (2.06 +/- 0.15 micrograms/ml). Serum retinol was 0.22-0.27 micrograms/ml in all three groups. Mice (n = 41/dietary group) were irradiated with 0, 4.5, 9 or 18 kJ/m2 of UVB and the CHS response was measured. Decreased CHS responses were observed in all UV-irradiated groups compared with unirradiated controls. UV dose-responses for suppression of CHS derived by first-order regression analyses of plots of percentage suppression of CHS as a function of log10UV dose showed significant slopes (P < 0.02) for all three dietary groups and similar residual variances between groups, P > 0.05. The UV dose for 50% suppression of CHS was 6.3 kJ/m2 for control, 6.4 kJ/m2 for placebo, and 5.5 kJ/m2 for beta-carotene-fed mice. No significant differences in slopes or elevations between UV dose-responses were observed, P > 0.05. Skin levels of the initiator of UV-induced immunosuppression, cis urocanic acid, were determined by HPLC in mice given 0 or 9 kJ/m2 of UV (n = 28/dietary group). No significant differences were observed between dietary groups (range 35.2-41.1 ng/mg skin, P > 0.15) We conclude feeding beta-carotene to BALB/c mice does not alter susceptibility to UV immune suppression, in contrast to human studies.