BRAF mutations are sufficient to promote nevi formation and cooperate with p53 in the genesis of melanoma

Melanoma is the most lethal form of skin cancer, and the incidence and mortality rates are rapidly rising. Epidemiologically, high numbers of nevi (moles) are associated with higher risk of melanoma . The majority of melanomas exhibit activating mutations in the serine/threonine kinase BRAF . BRAF mutations may be critical for the initiation of melanoma ; however, the direct role of BRAF in nevi and melanoma has not been tested in an animal model. To directly test the role of activated BRAF in nevus and melanoma development, we have generated transgenic zebrafish expressing the most common BRAF mutant form (V600E) under the control of the melanocyte mitfa promoter. Expression of mutant, but not wild-type, BRAF led to dramatic patches of ectopic melanocytes, which we have termed fish (f)-nevi. Remarkably, in p53-deficient fish, activated BRAF induced formation of melanocyte lesions that rapidly developed into invasive melanomas, which resembled human melanomas and could be serially transplanted. These data provide direct evidence that BRAF activation is sufficient for f-nevus formation, that BRAF activation is among the primary events in melanoma development, and that the p53 and BRAF pathways interact genetically to produce melanoma.     

Calcium depletion dissociates and activates heterodimeric notch receptors

Notch receptors participate in a highly conserved signaling pathway that regulates morphogenesis in multicellular animals. Maturation of Notch receptors requires the proteolytic cleavage of a single precursor polypeptide to produce a heterodimer composed of a ligand-binding extracellular domain (N(EC)) and a single-pass transmembrane signaling domain (N(TM)). Notch signaling has been correlated with additional ligand-induced proteolytic cleavages, as well as with nuclear translocation of the intracellular portion of N(TM) (N(ICD)). In the current work, we show that the N(EC) and N(TM) subunits of Drosophila Notch and human Notch1 (hN1) interact noncovalently. N(EC)-N(TM) interaction was disrupted by 0.1% sodium dodecyl sulfate or divalent cation chelators such as EDTA, and stabilized by millimolar Ca(2+). Deletion of the Ca(2+)-binding Lin12-Notch (LN) repeats from the N(EC) subunit resulted in spontaneous shedding of N(EC) into conditioned medium, implying that the LN repeats are important in maintaining the interaction of N(EC) and N(TM). The functional consequences of EDTA-induced N(EC) dissociation were studied by using hN1-expressing NIH 3T3 cells. Treatment of these cells for 10 to 15 min with 0.5 to 10 mM EDTA resulted in the rapid shedding of N(EC), the transient appearance of a polypeptide of the expected size of N(ICD), increased intranuclear anti-Notch1 staining, and the transient activation of an Notch-sensitive reporter gene. EDTA treatment of HeLa cells expressing endogenous Notch1 also stimulated reporter gene activity to a degree equivalent to that resulting from exposure of the cells to the ligand Delta1. These findings indicate that receptor activation can occur as a consequence of N(EC) dissociation, which relieves inhibition of the intrinsically active N(TM) subunit.     

Band 4.1-like proteins of the bovine lens. Effects of differentiation, distribution and extraction characteristics.

Bovine lens epithelium, cortex and nucleus were screened for the presence of red-cell-membrane band 4.1-like proteins by using an immunoblot method. Lens epithelial cells were found to contain proteins of Mr 78 000 and higher (approximately 150 000) that cross-reacted with anti-(protein 4.1) sera. Fibre cells of the superficial cortex were also found to contain these two proteins, as well as an additional protein of approx. 80 000 Mr. In contrast, deep layers of the cortex and the lens nucleus contained no detectable cross-reactive protein at these Mr values. Treatment of a crude membrane fraction prepared from superficial bovine cortices with a low-ionic-strength buffer resulted in release of the high-Mr band 4.1-like protein. The 80 000- and 78 000-Mr proteins remained with the membrane fraction in low-ionic-strength buffer, but were released into solution by high-ionic-strength-buffer treatment. We have also demonstrated that the human red-blood-cell membrane, like lens epithelial cells and fibre cells, also contains a high-Mr band 4.1-like protein that is released from membranes by low-ionic-strength-buffer treatment.     

Determinants of exclusive breastfeeding practice to infants aged less than six months in Offa district,Southern Ethiopia: a cross-sectional study

Background

World Health Organization (WHO) recommends timely initiation of breastfeeding after birth and only feeding breast milk to infants during the first 6 months of life. It was estimated that exclusive breastfeeding can reduce infant deaths by 13%. The practice of exclusive breastfeeding is suboptimal in many parts of Ethiopia to a varied extent. Factors associated with exclusive breastfeeding practice and the proportion of its practice was not well documented in Offa district. Therefore, this study was aimed to assess the determinants of exclusive breastfeeding in the first 6 months of life in Offa district, Southern Ethiopia.

Methods

A community-based cross-sectional study was carried out in 396 mothers of infants younger than 6 months using random sampling. Data were collected from mothers of the infants by trained interviewers. Exclusive breastfeeding was measured by the history of infant feeding in the prior 24 h. Pretested and structured questionnaires adopted from standard questionnaires and Ethiopia linkages modules were used. Multivariate logistic regression was used to identify factors significantly influencing exclusive breastfeeding practice.

Results

Based on findings of this study of 396 participants, the proportion of exclusive breastfeeding was 78.0% and awareness of exclusive breastfeeding and bottle feeding were 85.6 and 6.1% respectively. About 6% of infants were given prelacteal feeds. The number of infants fed cow milk was 12.9%, formula 7.8%, water 8.5%, fruits and semisolids 1.5%, over 24 h prior to the survey. The initiation of breastfeeding within one h (AOR 2.2; 95% CI 1.1, 4.27), attending formal education (AOR 4; 95% CI 2.20, 7.25), having an awareness on the benefits of exclusive breastfeeding (AOR 6; 95% CI 3.10, 11.70) and knowledge of colostrum feeding (AOR 2.1; 95% CI 1.11, 4.27) had a statistically significant association with exclusive breastfeeding in the study area.

Conclusions

The practice of exclusive breastfeeding as well as awareness was worthy in Offa district. Additionally the proportion of bottle feeding use was small. However, feeding other than breast milk was associated with the perception that breast milk alone was insufficient for their child. Strategies on promoting exclusive breastfeeding practice must focus on strengthening women’s education and awareness creation activities further.

     

Regulatory Mechanisms of Vitamin D<Subscript>3</Subscript> on Production of Nitric Oxide and Pro-inflammatory Cytokines in Microglial BV-2 Cells

Inhibition of pro-inflammatory functions of microglia has been considered a promising strategy to prevent pathogenic events in the central nervous system under neurodegenerative conditions. Here we examined potential inhibitory effects of nuclear receptor ligands on lipopolysaccharide (LPS)-induced inflammatory responses in microglial BV-2 cells. We demonstrate that a vitamin D receptor agonist 1,25-dihydroxyvitamin D₃ (VD3) and a retinoid X receptor agonist HX630 affect LPS-induced expression of pro-inflammatory factors. Specifically, both VD3 and HX630 inhibited expression of mRNAs encoding inducible nitric oxide synthase (iNOS) and IL-6, whereas expression of IL-1β mRNA was inhibited only by VD3. The inhibitory effect of VD3 and HX630 on expression of iNOS and IL-6 mRNAs was additive. Effect of VD3 and HX630 was also observed for inhibition of iNOS protein expression and nitric oxide production. Moreover, VD3 and HX630 inhibited LPS-induced activation of extracellular signal-regulated kinase (ERK) and nuclear translocation of nuclear factor κB (NF-κB). PD98059, an inhibitor of ERK kinase, attenuated LPS-induced nuclear translocation of NF-κB and induction of mRNAs for iNOS, IL-1β and IL-6. These results indicate that VD3 can inhibit production of several pro-inflammatory molecules from microglia, and that suppression of ERK activation is at least in part involved in the anti-inflammatory effect of VD3.     

Multi‐century tree‐ring precipitation record reveals increasing frequency of extreme dry events in the upper Blue Nile River catchment

Climate‐related environmental and humanitarian crisis are important challenges in the Great Horn of Africa (GHA). In the absence of long‐term past climate records in the region, tree‐rings are valuable climate proxies, reflecting past climate variations and complementing climate records prior to the instrumental era. We established annually resolved multi‐century tree‐ring chronology from Juniperus procera trees in northern Ethiopia, the longest series yet for the GHA. The chronology correlates significantly with wet‐season (r = .64, p < .01) and annual (r = .68, p < .01) regional rainfall. Reconstructed rainfall since A.D. 1811 revealed significant interannual variations between 2.2 and 3.8 year periodicity, with significant decadal and multidecadal variations during 1855–1900 and 1960–1990. The duration of negative and positive rainfall anomalies varied between 1–7 years and 1–8 years. Approximately 78.4% (95%) of reconstructed dry (extreme dry) and 85.4% (95%) of wet (extreme wet) events lasted for 1 year only and corresponded to historical records of famine and flooding, suggesting that future climate change studies should be both trend and extreme event focused. The average return periods for dry (extreme dry) and wet (extreme wet) events were 4.1 (8.8) years and 4.1 (9.5) years. Extreme‐dry conditions during the 19th century were concurrent with drought episodes in equatorial eastern Africa that occurred at the end of the Little Ice Age. El Niño and La Niña events matched with 38.5% and 50% of extreme‐dry and extreme‐wet events. Equivalent matches for positive and negative Indian Ocean Dipole events were weaker, reaching 23.1 and 25%, respectively. Spatial correlations revealed that reconstructed rainfall represents wet‐season rainfall variations over northern Ethiopia and large parts of the Sahel belt. The data presented are useful for backcasting climate and hydrological models and for developing regional strategic plans to manage scarce and contested water resources. Historical perspectives on long‐term regional rainfall variability improve the interpretation of recent climate trends.     

Notch signaling specifies megakaryocyte development from hematopoietic stem cells

In the hematopoietic system, Notch signaling specifies T cell lineage fate, in part through negative regulation of B cell and myeloid lineage development. However, we unexpectedly observed the development of megakaryocytes when using heterotypic cocultures of hematopoietic stem cells with OP9 cells expressing Delta-like1, but not with parental OP9 cells. This effect was abrogated by inhibition of Notch signaling either with gamma-secretase inhibitors or by expression of the dominant-negative Mastermind-like1. The importance of Notch signaling for megakaryopoietic development in vivo was confirmed by using mutant alleles that either activate or inhibit Notch signaling. These findings indicate that Notch is a positive regulator of megakaryopoiesis and plays a more complex role in cell-fate decisions among myeloid progenitors than previously appreciated.