Monocarboxylate transporters (MCTs) in skeletal muscle and hypothalamus of less or more physically active mice exposed to aerobic training.

AIMS: The synthesis of monocarboxylate transporters (MCTs) can be stimulated by aerobic training, but few is known about this effect associated or not with non-voluntary daily activities. We examined the effect of eight weeks of aerobic training in MCTs on the skeletal muscle and hypothalamus of less or more physically active mice, which can be achieved by keeping them in two different housing models, a small cage (SC) and a large cage (LC). MAIN METHODS: Forty male C57BL/6J mice were divided into four groups. In each housing condition, mice were divided into untrained (N) and trained (T). For 8 weeks, the trained animals ran on a treadmill with an intensity equivalent to 80 % of the individual critical velocity (CV), considered aerobic capacity, 40 min/day, 5 times/week. Protein expression of MCTs was determined with fluorescence Western Blot. KEY FINDINGS: T groups had higher hypothalamic MCT2 than N groups (ANOVA, P = 0.032). Significant correlations were detected between hypothalamic MCT2 and CV. There was a difference between the SC and LC groups in relation to MCT4 in the hypothalamus (LC > SC, P = 0.044). Trained mice housed in LC (but not SC-T) exhibited a reduction in MCT4 muscle (P < 0.001). SIGNIFICANCE: Our findings indicate that aerobically trained mice increased the expression of MCT2 protein in the hypothalamus, which has been related to the uptake of lactate in neurons. Changes in energy metabolism in physically active mice (kept in LC) may be related to upregulation of hypothalamic MCT4, probably participating in the regulation of satiety.

Use of combination therapy with cisplatin and calcitriol in the treatment of Y-79 human retinoblastoma xenograft model.

BACKGROUND: Retinoblastoma is the most common primary malignant intraocular neoplasm of childhood. The poor outcomes of patients with metastatic retinoblastoma have encouraged the search for new therapies. In the current study, the efficacy of combination therapy with calcitriol and cisplatin in athymic mice with subcutaneous Y-79 human retinoblastoma tumours was assessed. METHODS: 60 athymic mice were subcutaneously injected with human Y79 retinoblastoma cells. Animals were randomised into four groups: group 1, 50 microg of cisplatin; group 2, 0.05 microg of calcitriol; group 3, 0.05 microg of calcitriol and 50 microg of cisplatin; group 4, control. The cisplatin was administered once a week, and the calcitriol was given five times a week. RESULTS: There was a significant inhibition of tumour growth in animals treated with the combination therapy of calcitriol and cisplatin as compared with controls and cisplatin alone (p = 0.0001 and p = 0.0041 respectively). In terms of toxicity, serum calcium levels were increased, but there was no mortality and minimal nephrotoxicity in any of the groups. CONCLUSION: The present study shows that cisplatin given in combination with calcitriol may be a viable multidrug therapy option in the treatment of high-risk retinoblastoma.

The identification and differential expression of calcium-binding proteins associated with ocular melanoma.

Calcium-binding proteins may endow tumor cells with properties related to their malignancy and metastatic phenotype. Chromatographic procedures and amino acid sequence analysis were used in this study to identify seven calcium-binding proteins, annexin VI, cap g, annexin V, calmodulin, S100A11, S100B and S100A6, associated with uveal melanoma, the primary ocular tumor of adults. This series of calcium-binding proteins was identified in both primary tumors and cell lines of uveal melanoma. Several of the proteins were shown by immunochemical methods to be differentially expressed between normal uveal melanocytes and malignant melanomas of the uvea. In addition, the expression of S100A6 may correlate with the malignant properties of the tumor.

E2F-mediated growth regulation requires transcription factor cooperation.

Previous studies have indicated that the presence of an E2F site is not sufficient for G1/S phase transcriptional regulation. For example, the E2F sites in the E2F1 promoter are necessary, but not sufficient, to mediate differential promoter activity in G0 and S phase. We have now utilized the E2F1 minimal promoter to test several hypotheses that could account for these observations. To test the hypothesis that G1/S phase regulation is achieved via E2F-mediated repression of a strong promoter, a variety of transactivation domains were brought to the E2F1 minimal promoter. Although many of these factors caused increased promoter activity, growth regulation was not observed, suggesting that a general repression model is incorrect. However, constructs having CCAAT or YY1 sites or certain GC boxes cloned upstream of the E2F1 minimal promoter displayed E2F site-dependent regulation. Further analysis of the promoter activity suggested that E2F requires cooperation with another factor to activate transcription in S phase. However, we found that the requirement for E2F to cooperate with additional factors to achieve growth regulation could be relieved by bringing the E2F1 activation domain to the promoter via a Gal4 DNA binding domain. Our results suggest a model that explains why some, but not all, promoters that contain E2F sites display growth regulation.

Topographical regulation of cone and rod opsin genes: parallel, position dependent levels of transcription.

RNase protection assays were used to follow rhodopsin and red cone opsin mRNA levels during bovine fetal development as a function of retinal position. Following induction, an equivalent radial gradient of rod and cone opsin mRNA is present in the fetal retina. This gradient is maintained in the adult retina even though no corresponding gradient in rod or cone cell density is present. Since the mRNA expression gradient does not progress radially, position dependent levels of photoreceptor-specific transcription is suggested.

Parallel regulation of fetal gene expression in different photoreceptor cell types.

Transcriptional induction for multiple bovine rod-specific photoreceptor genes has been shown to coincide with the first emergence of rod outer segments (two-thirds gestation) suggesting a coordinate regulation of these genes. Since cone visual transduction proteins are encoded for by distinct genes and mammalian cone cell genesis has been found to precede rod cell genesis it is important to determine when induction of photoreceptor-specific gene expression occurs in cone cells and how the timing of this event compares to that in rods. RNase protection assays specific for each cell type-specific gene were used to compare mRNA levels for bovine rod and blue cone gamma subunits of cGMP phosphodiesterase and rhodopsin and red cone opsin from before transcriptional induction (4 months gestation) to the adult. Both pairs of rod and cone visual transduction mRNAs exhibit indistinguishable transcriptional induction points at around 6 months of gestation. Before this time, transcripts of all four genes are present at low, but detectable levels. Thus, although rod and cone cells are distinct cell types and cone cells may be committed well before rod cells early in development, during the final trimester when elaboration of outer segments begins, there appears to be a coordinated regulation of both rod- and cone-specific visual transduction genes.