Cry1 circadian phase in vitro: wrapped up with an E-box.

The circadian timing of gene expression is determined by transcriptional regulation through upstream response elements present throughout the genome. Central to this regulation are the actions of a core group of transcriptional activators and repressors, which act through, and are themselves regulated by, a small set of canonical circadian response elements. Among these, the E-box (CACGTG) is crucial for daytime transcriptional activity. The mammalian Period (Per1-3) and Cryptochrome (Cry1-2) genes are E-box-regulated genes, but in peripheral tissues peak Cry1 mRNA expression is delayed by several hours relative to that of Per. It has been proposed that this delay originates from interactions between the proximal E-box and retinoic acid-related orphan receptor response elements (RORE) present in the Cry1 promoter. By using real-time luciferase reporter assays in NIH3T3 cells the authors show here that a proximal 47-bp E-box containing region of the Cry1 promoter is both necessary and sufficient to drive circadian Cry1 transcription with an appropriate phase delay (around 4 h) relative to Per2. The results therefore suggest that, at least in this in vitro model of the clock, RORE are not necessary for the appropriate circadian regulation of Cry1 expression and rather suggest that sequences surrounding the proximal E-boxes confer gene-specific circadian phasing.

Genetic and molecular analysis of the central and peripheral circadian clockwork of mice.

A hierarchy of interacting, tissue-based clocks controls circadian physiology and behavior in mammals. Preeminent are the suprachiasmatic nuclei (SCN): central hypothalamic pacemakers synchronized to solar time via retinal afferents and in turn responsible for internal synchronization of other clocks present in major organ systems. The SCN and peripheral clocks share essentially the same cellular timing mechanism. This consists of autoregulatory transcriptional/posttranslational feedback loops in which the Period (Per) and Cryptochrome (Cry) "clock" genes are negatively regulated by their protein products. Here, we review recent studies directed at understanding the molecular and cellular bases to the mammalian clock. At the cellular level, we demonstrate the role of F-box protein Fbxl3 (characterized by the afterhours mutation) in directing the proteasomal degradation of Cry and thereby controlling negative feedback and circadian period of the molecular loops. Within SCN neural circuitry, we describe how neuropeptidergic signaling by VIP synchronizes and sustains the cellular clocks. At the hypothalamic level, signaling via a different SCN neuropeptide, prokineticin, is not required for pacemaking but is necessary for control of circadian behavior. Finally, we consider how metabolic pathways are coordinated in time, focusing on liver function and the role of glucocorticoid signals in driving the circadian transcriptome and proteome.

The role of selective visceral angiography in the management of pancreatic and periampullary cancer.

A prospective study was undertaken to evaluate selective visceral angiography (SVA) in the management of patients with pancreatic and periampullary cancer. Over a 30-month period 52 patients with potentially resectable pancreatic or periampullary cancer underwent SVA; 4 patients had obvious angiographic evidence of widely disseminated disease and were not subjected to laparotomy while 2 further patients were eventually considered too frail for resection. The remaining 46 patients (median age 58 years, range 37-73 years, males 26, females 20) had no evidence of disseminated disease on ultrasonography and/or CT scanning and had both SVA and surgery and form the basis of this study. Vascular anomalies were detected in 16/46 (35%) patients. Hepatic metastases were wrongly diagnosed by angiography in 7 out of 9 patients (77%). SVA correctly predicted resectability or irresectability in 28/46 patients (overall predictive value 61%). Of the 27 patients who proved to have irresectable disease at operation, 11 were correctly identified by SVA (sensitivity 41%). Of the 13 patients reported to have irresectable disease, 2 underwent resection (false-positive rate 15%). Of the 33 patients reported to have resectable disease, 16 were irresectable (false-negative rate 48%). Overall there was a poor relationship between resectability and the angiographic features. On the basis of these data, SVA cannot be considered a sufficiently accurate means of assessing resectability. Its use for this purpose in patients with pancreatic and periampullary cancer is not justified.

The significance of steroid metabolism in human cancer.

Epidemiological and clinical evidence suggests that steroid hormones are intimately involved in the natural history of many cancers, including those of the breast, endometrium and prostate. However, it has been difficult to demonstrate that progressive changes in tumour development are related to circulating levels of steroids. This may be because further metabolism of steroids occurs locally within the tumour and its adjacent host tissue. Using the breast as an example, data has been reviewed that such local metabolism may (a) markedly change the biological potency of steroid hormones and (b) be associated with the risk, presence, pathology, stage and hormone sensitivity of cancer. The implications of these findings are discussed including the need to identify factors which regulate steroid metabolism in peripheral tissue and tumours. In this way the potential to influence the microenvironment around and within tumour cells may be realized in favour of the patient.

Aromatase activity in adipose tissue from breast quadrants: a link with tumour site.

To determine the importance of local oestrogen biosynthesis within the breast, aromatase activity was measured in adipose tissue from the breast quadrants of 12 consecutive mastectomies from patients with breast cancer. Activity was detected in all samples (range 3.6-35.0 fmol oestrogen/mg protein/h) but varied considerably not only among different patients but also among the quadrants of individual breasts. The highest activity in a breast was always found in a quadrant that contained tumour, whereas quadrants with the lowest activity were never associated with the presence of tumour. These results provide evidence of a significant relation between breast adipose tissue and breast cancer. Whether such an association occurs because breast tumours are more likely to develop in areas with enhanced oestrogen biosynthesis or because they secrete into their local environment factors capable of stimulating oestrogen biosynthesis remains to be determined.

Aromatase activity in breast adipose tissue from women with benign and malignant breast diseases.

In order to determine the significance of local oestrogen biosynthesis within the breast, aromatase activity has been measured in adipose tissue from the breasts of women with either benign (n = 36) or malignant breast disease (n = 51). Particulate fractions from all samples possessed aromatase activity, but levels in adipose tissue adjacent to malignant tumours were significantly higher than those in tissue close to benign breast lesions (P less than 0.0001). Elevated aromatase activity in adipose tissue from breast cancer patients may be of importance in view of the central role played by oestrogen in the natural history of breast cancer.

Cystic myxomatous degeneration of the femoral vein.

We present a case of cystic myxomatous degeneration of the femoral vein. The features are similar to those found in the equivalent disease of arteries. It is suggested that it may occur in veins as an unusual and rare late sequel of venous thrombosis and recanalisation. A search of the literature has revealed only one previously reported case.