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Choice of electrode material is crucial to the development of high‐performance supercapacitors. Since surface properties are key to the performance of an electrode material for supercapacitors, surface chemical treatment of electrode materials is an interesting topic of research. ZnCo2O4 (ZCO) is a low‐cost binary transition metal oxide with high theoretical conductivity and charge storage capacity making it a good choice for supercapacitor electrode. Herein, we present a systematic investigation of the influence of four different surface modifier (3 surfactants, 1 mineralizer) on ZCO electrode directly grown on Ni foam to compare the relative influence on the performance of the modified ZCO electrode. Analyses of the modified ZCO electrodes revealed the formation of cubic spinel phase of ZCO with average particle size of ~30 nm. The sodium dodecyl sulfate (ZCO−S) modified electrode (ZCO−S) exhibited the best electrochemical performance with specific capacitance of 1988 F/g at 1 A/g and 87 % capacity retention after 7000 cycles at 10 A/g. Further, an all‐solid‐state asymmetric supercapacitor (ASC) was fabricated with ZCO−S on Ni foam and carbon nanotube combination which exhibited specific capacitance of 102 F/g at 1 A/g corresponding to power density of ~1599 W‐kg−1 establishing ZCO−S as a very good electrode material for supercapacitor. [ABSTRACT FROM AUTHOR]

Herein, the favorable influence of sandwich‐stacked Sn/SAC305/Sn multilayers on the micromechanical and electrical properties of the Cu‐Sn/SAC305/Sn‐Cu solder joints over Cu‐SAC305‐Cu joints is reported. Solder joint interface is characterized through X‐ray diffraction spectroscopy, scanning electron microscopy, transmission electron microscopy, scanning tunneling microscopy (STM), and nanoindentation studies. The use of Sn multilayers facilitates the formation of more homogeneously distributed intermetallic compounds (IMCs) with smaller crystallite sizes and higher dislocation densities at the joint interface. Nanoindentation test results manifest that the hardness, modulus, and resistance to plastic deformation of the joint interface for the samples prepared with Sn multilayer are 3.26 GPa, 123.3 GPa, and 1.5 × 109, respectively, much higher and improved than 0.32 GPa, 41.82 GPa, and 5.28 × 105 in turn, found for samples prepared without using Sn multilayers. STM results confirm a much better electron transfer capacity of the solder joint interface that consists of Sn multilayers compared with solder joints produced without incorporation of Sn multilayer. Wherein, Sn multilayer containing solder joint found less prone to be affected by the humid atmosphere compared with nonlayered solder joint, in which, the former is found to be 48% less sensitive toward humidity (85% Rh) than later. [ABSTRACT FROM AUTHOR]

Background: Super-resolution is an emerging method for enhancing MRI resolution; however, its impact on image quality is still unknown.Purpose: To evaluate MRI super-resolution using quantitative and qualitative metrics of cartilage morphometry, osteophyte detection, and global image blurring.Study Type: Retrospective.Population: In all, 176 MRI studies of subjects at varying stages of osteoarthritis.Field Strength/sequence: Original-resolution 3D double-echo steady-state (DESS) and DESS with 3× thicker slices retrospectively enhanced using super-resolution and tricubic interpolation (TCI) at 3T.Assessment: A quantitative comparison of femoral cartilage morphometry was performed for the original-resolution DESS, the super-resolution, and the TCI scans in 17 subjects. A reader study by three musculoskeletal radiologists assessed cartilage image quality, overall image sharpness, and osteophytes incidence in all three sets of scans. A referenceless blurring metric evaluated blurring in all three image dimensions for the three sets of scans.Statistical Tests: Mann-Whitney U-tests compared Dice coefficients (DC) of segmentation accuracy for the DESS, super-resolution, and TCI images, along with the image quality readings and blurring metrics. Sensitivity, specificity, and diagnostic odds ratio (DOR) with 95% confidence intervals compared osteophyte detection for the super-resolution and TCI images, with the original-resolution as a reference.Results: DC for the original-resolution (90.2 ± 1.7%) and super-resolution (89.6 ± 2.0%) were significantly higher (P < 0.001) than TCI (86.3 ± 5.6%). Segmentation overlap of super-resolution with the original-resolution (DC = 97.6 ± 0.7%) was significantly higher (P < 0.0001) than TCI overlap (DC = 95.0 ± 1.1%). Cartilage image quality for sharpness and contrast levels, and the through-plane quantitative blur factor for super-resolution images, was significantly (P < 0.001) better than TCI. Super-resolution osteophyte detection sensitivity of 80% (76-82%), specificity of 93% (92-94%), and DOR of 32 (22-46) was significantly higher (P < 0.001) than TCI sensitivity of 73% (69-76%), specificity of 90% (89-91%), and DOR of 17 (13-22).Data Conclusion: Super-resolution appears to consistently outperform naïve interpolation and may improve image quality without biasing quantitative biomarkers.Level Of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:768-779. [ABSTRACT FROM AUTHOR]

The present work deals with investigating and understanding the influence of filler‐matrix interfacial interaction on the fracture toughness of epoxy matrix filled with functionalized grapheme‐based fillers—graphene oxide (GO) and n‐butylamine functionalized graphene oxide (GO‐ButA), in fully cured, stoichiometric epoxy systems. A common epoxy resin was cured with two different curing agents (a polyetheramine based and an aliphatic amine based) to understand the significance of the curing agent and of the neat matrix properties on epoxy toughenability. Fractographic and dynamic mechanical analysis (DMA) indicate improved filler‐matrix interfacial interaction with a maximum of 11% increment in crosslink density with GO‐ButA as fillers. However, these stoichiometrically cured epoxy nanocomposites are seen to embrittle upon addition of nano‐fillers, irrespective of the type of filler or matrix as well as their manufacturer. A hypothesis on the possible cause of this embrittlement is presented based on the build‐up of internal stresses during cool down after cure and/or post cure which is believed to be mostly concentrated around the filler‐matrix interface within these nanocomposites. This work shows that apart from interfacial interactions, nanocomposite fracture toughness is also influenced by the cure reactions and matrix crosslinking, both of which are affected by the choice of curing agent. POLYM. COMPOS., 39:E2356–E2369, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Deficiencies of the human cystathionine β-synthase (CBS) enzyme are characterized by a plethora of vascular disorders and hyperhomocysteinemia. However, several clinical trials demonstrated that despite reduction in homocysteine levels, disease outcome remained unaffected, thus the mechanism of endothelial dysfunction is poorly defined. Here, we show that the loss of CBS function in endothelial cells (ECs) leads to a significant down-regulation of cellular hydrogen sulfide (H2S) by 50% and of glutathione (GSH) by 40%. Silencing CBS in ECs compromised phenotypic and signaling responses to the VEGF that were potentiated by decreased transcription of VEGF receptor (VEGFR)-2 and neuropilin (NRP)-1, the primary receptors regulating endothelial function. Transcriptional down-regulation of VEGFR-2 and NRP-1 was mediated by a lack in stability of the transcription factor specificity protein 1 (Sp1), which is a sulfhydration target of H2S at residues Cys68 and Cys755. Reinstating H2S but not GSH in CBS-silenced ECs restored Sp1 levels and its binding to the VEGFR-2 promoter and VEGFR-2, NRP-1 expression, VEGF-dependent proliferation, and migration phenotypes. Thus, our study emphasizes the importance of CBS-mediated protein S-sulfhydration in maintaining vascular health and function.--Saha, S., Chakraborty, P. K., Xiong, X., Dwivedi, S. K. D., Mustafi, S. B., Leigh, N. R., Ramchandran, R., Mukherjee, P., Bhattacharya, R. Cystathionine β-synthase regulates endothelial function via protein S-sulfhydration. [ABSTRACT FROM AUTHOR]

ABSTRACT Polyaniline (PANI) is one of the most common polymers known for its conducting properties. However, poor water solubility limits its applications. In this work, PANI has been functionalized with sulfonic acid groups to produce sulfonated PANI (SPANI) offering excellent solubility in water. To compensate for the decrease of electrical conductivity due to functionalization, SPANI was combined with reduced graphene oxide (RGO) to form SPANI/RGO composites with interesting optical, thermal, and electrical properties. The composites have been characterized using X-ray diffraction (XRD), field emission scanning electron microscopy, UV-vis absorption spectroscopy, Raman spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, cyclic voltammetry, and four probe electrical conductivity measurement. The SPANI/RGO composites show increased thermal stability, reduced optical band gap and improved electrochemical properties compared with the pure polymer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42766. [ABSTRACT FROM AUTHOR]

Adaptive video coding algorithms can encode a video stream dynamically on the basis of the amount of bandwidth available in a network. In this paper, a novel approach for adaptive video coding based on look-up tables has been proposed. On the basis of the network conditions, the proposed codec estimates quantization parameter (QP) and also the spatial resolution for a group of pictures from the look-up table. Then, QP for each frame is estimated on the basis of the motion content in each frame. More motion leads to more burden of bits while encoding the motion vectors. Also, quantization noise is less prominent in high-motioned frames than frames possessing low motion information because of the temporal masking phenomenon of the human eyes. So, the main trick of the proposed scheme is to assign higher QP to the frames having higher motion than those having less motion. This method also reduces the requirement of excess bits for encoding of motion vectors having higher motion content. Additionally, QP is adjusted on the basis of the buffer availability in order to avoid bit loss error. Experimental results show the efficacy of the proposed codec. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT A three-phase water-soluble nanocomposite of single wall carbon nanotube/silver nanoparticle hybrid fibers embedded in sulfonated polyaniline has been synthesized by a simple chemical solution mixing process. The nanocomposite has been characterized by high resolution electron microscopy, X-ray diffractometry, FTIR spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Optical and electrical characteristics of the nanocomposite have been determined by UV-vis absorption spectroscopy, photoluminescence spectroscopy, and four-probe electrical conductivity measurement. A surface plasmon absorption band obtained around 460 nm indicates the presence of silver nanoparticles in the composite. The optical band gap calculation for sulfonated polyaniline vis-a-vis the nanocomposite supported the conductivity measurement. Over 1300 times increase in DC electrical conductivity has been observed for the three-phase nanocomposite, with a filler loading of 20 wt %, at 306 K. This observation could be explained by Mott's variable range hopping model considering a three-dimensional conduction. Such a nanocomposite has immense potential for use as a cathode material in lithium-ion batteries and supercapacitors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41692. [ABSTRACT FROM AUTHOR]

This study aimed to determine the cellular alterations in the gill of Labeo rohita exposed to lethal temperature maxima ( LTMax) and lethal temperature minima ( LTMin) by means of transmission electron microscopy ( TEM). Acclimation of advanced fingerlings of L. rohita was carried out at 26°C for 30 days. Acclimated fish were subjected to a constant rate of increase or decrease in temperature (0.3°C/min) until the LTMax and LTMin values were reached. Dissected gills were processed for TEM, both at the end of acclimation period at ambient temperature (26°C) and at lethal temperatures. Results indicated that at ambient temperature, the gill tissues appeared normal. However, significant changes were observed at lethal temperatures. The gill tissues at lethal temperature maxima showed severely damaged lamellae, with more vacuolated space. At lethal temperature minima, gill tissues showed increased density of mitochondria. Our prima-facie report indicated that L. rohita exposed to lethal temperatures exhibited marked ultrastructural changes in the gills. [ABSTRACT FROM AUTHOR]

The multidrug resistance (MDR) P-glycoprotein ABCB1 plays a major role in MDR of malignant cells and is regulated by various transcription factors, including Wnt/β-catenin/TCF4. The transcription factor PITX2 (Pituitary homeobox-2) is essential for embryonic development. PITX2 operates by recruiting and interacting with β-catenin to increase the expression of growth-regulating genes, such as cyclin D1/2 and c-Myc. The importance of PITX2 in malignancy is not yet known. Here we demonstrate that in the renal cancer cell lines ACHN and A498, the level of ABCB1 expression and function correlate with nuclear PITX2 localization and PITX2-luciferase reporter gene activity (A498 > ACHN). In A498 cells, doxorubicin toxicity is augmented by the ABCB1 inhibitor, PSC833. PITX2 overexpression increases ABCB1 expression and cell survival in ACHN cells. Silencing of PITX2 by siRNA downregulates ABCB1 and induces a greater chemotherapeutic response to doxorubicin in A498 cells, as determined by MTT cell viability and clonogenic survival assays. Two PITX2 binding sequences were identified in the ABCB1 promoter sequence. PITX2 binding was confirmed by chromatin immunoprecipitation. β-Catenin is not required for PITX2 upregulation of ABCB1 because ABCB1 mRNA increased and doxorubicin toxicity decreased upon PITX2 overexpression in β-catenin−/− cells. The data show for the first time that ABCB1 is a target gene of PITX2 transcriptional activity, promoting MDR and cell survival of cancer cells. [ABSTRACT FROM AUTHOR]

Effect of electron beam (EB) pretreatment on tire components has been investigated. The technique proved to be incredibly useful for reducing curing time of thick rubber products in the press and enhancing or retaining the properties required by a tire. This unique technique can be use to incorporate mixed crosslink in rubber products. Investigations were performed both on experimental compounds and industrial compounds. Experimental compound study was limited to development of theoretical data, effect of particular ingredients on EB radiation curing, and evaluating optimum dose required for obtaining optimum properties and reduction in cure time. The same sequence of study was followed on the compounds of tire components obtained from a reputed tire manufacturer. Components of tire such as inner liner and tread were irradiated with optimum doses selected in line with the study conducted on the experimental and industrial compounds. These components were then used to build the green tire. Properties of compound and tire as a whole were checked and are reported in detail in the article. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

Varying compositions of styrene-butadiene rubber (SBR) and ethylene-propylene diene monomer (EPDM) 50:50 blend containing multiple walled carbon nanotube (MWNT) as nanoparticulate filler (0.5-5%) were prepared and their efficacy for radiation vulcanization was analyzed by gel-content, Charlesby-Pinner parameter, and crosslinking density measurements. Radiation sensitivity of the nanocomposites increased with increase in the MWNT fraction and radiation dose in the dose range studied. The elastic modulus, tensile strength increased with the radiation dose, while elongation at break exhibited downward trend. The extent of reinforcement as assessed using Kraus equation suggested high reinforcement of blend on MWNT addition. The reinforcing mechanism of nanocomposites was studied by various micromechanics models which predicted higher modulus than the experimentally observed results, indicating agglomeration in the nanocomposites. The thermal stability of the composites increased with increase in MWNT loading has been attributed to the antioxidancy induced by nanotubes and higher crosslinking extent of the nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The biochemical and stress responses of two Indian major carps, rohu Labeo rohita and mrigal Cirrhinus mrigala were studied after acclimating them to four preset temperatures (26, 31, 33 and 36° C) for 30 days. The blood glucose and liver glycogen levels showed an inverse trend in both the species and were significantly different in L. rohita at higher temperatures. The decrease in the liver glycogen level of C. mrigala, however, was not significant. Plasma cortisol levels increased significantly whereas the ascorbic acid content in the brain and kidney of both the species decreased significantly with increasing temperatures. Total lipid content in the liver of both the species decreased significantly with increasing acclimation temperatures. The phospholipid concentration decreased in L. rohita with increasing acclimation temperatures, and in C. mrigala the values decreased up to 33° C and increased at 36° C. In C. mrigala, the cholesterol level decreased up to 33° C and then increased at 36° C, but the absolute value was lower in comparison to L. rohita. The cholesterol levels, however, were not significantly different in L. rohita. Triglycerides and free fatty acids concentrations decreased significantly with increasing acclimation temperatures in both the species. The present study indicates species-specific metabolic responses of L. rohita and C. mrigala to thermal acclimation. [ABSTRACT FROM AUTHOR]

Chronic myelogenous leukemia (CML) is a myeloproliferative disease associated with a characteristic chromosomal translocation called the Philadelphia chromosome. This results in the expression of the Bcr-Abl fusion protein, a constitutively active protein tyrosine kinase. Although there are a few treatment options with Bcr-Abl kinase inhibitors, drug resistance is often encountered. One of the major obstacles in overcoming drug resistance in CML is the high endogenous levels of heat shock protein 70 (Hsp70). Resveratrol is a phytoalexin produced by several plants. We studied the chemotherapeutic effects and mode of action of resveratrol on K562 (CML) cells. Resveratrol induced apoptosis in K562 cells in a time-dependent manner. This was established by increased annexin V binding, corroborated with an enhanced caspase-3 activity and a rise in the sub-G0/G1 population. Resveratrol treatment also caused suppression of Hsp70 both in mRNA and protein levels. The downregulation of Hsp70 by resveratrol exposure was correlated with a diminished presence of heat shock factor 1 (HSF1) in the nucleus, and the downregulation of transcriptional activity of HSF1. High endogenous levels of Hsp70 have been found to be a deterrent for sensitivity to chemotherapy. We show here that resveratrol could considerably enhance the apoptosis induction in K562 cells by 17-allylamino-17-demethoxygeldanamycin, an anticancer agent that inhibits Hsp90 but augments Hsp70 levels. We conclude that resveratrol significantly downregulated Hsp70 levels through inhibition of HSF1 transcriptional activity and appreciably augmented the pro-apoptotic effects of 17-allylamino-17-demethoxygeldanamycin. ( Cancer Sci 2008; 99: 1109–1116) [ABSTRACT FROM AUTHOR]

In this study we describe the development of peptidomimetic analogs of the potent vasoactive intestinal peptide receptor binding inhibitor, Leu1 -Met2 -Tyr3 -Pro4 -Thr5 -Tyr6 -Leu7 -Lys8 -OH 1, by incorporating furanoid sugar amino acids (SAAs) 2-4 into the molecule. The furanoid SAAs 2-4 were used as dipeptide isosteres to replace Tyr3 -Pro4 or Pro4 -Thr5 in sequence 1. The resulting analogs 5- 9 were tested for their anti-cancer activities in vitro, following the standard MTT assay on a panel of human cancer cell lines. One of the potent analogs, 6a was tested in vivo for tumor regression on primary colon tumor xenografted nude mice. Our experimental results suggest that many of these analogs show either retention or enhancement of biological activity. [ABSTRACT FROM AUTHOR]

Abstract: The role of serotonin in prenatal and postnatal brain development is well documented in the animal literature. In earlier studies using positron emission tomography (PET) with the tracer alpha[11C]methyl-l-tryptophan (AMT), we reported global and focal abnormalities of serotonin synthesis in children with autism. In the present study, we measured brain serotonin synthesis in a large group of autistic children (n = 117) with AMT PET and related these neuroimaging data to handedness and language function. Cortical AMT uptake abnormalities were objectively derived from small homotopic cortical regions using a predefined cutoff asymmetry threshold (>2 S.D. of normal asymmetry). Autistic children demonstrated several patterns of abnormal cortical involvement, including right cortical, left cortical, and absence of abnormal asymmetry. Global brain values for serotonin synthesis capacity (unidirectional uptake rate constant, K-complex) values were plotted as a function of age. K-complex values of autistic children with asymmetry or no asymmetry in cortical AMT uptake followed different developmental patterns, compared to that of a control group of non-autistic children. The autism groups, defined by presence or absence and side of cortical asymmetry, differed on a measure of language as well as handedness. Autistic children with left cortical AMT decreases showed a higher prevalence of severe language impairment, whereas those with right cortical decreases showed a higher prevalence of left and mixed handedness. Global as well as focal abnormally asymmetric development in the serotonergic system could lead to miswiring of the neural circuits specifying hemispheric specialization. [Copyright &y& Elsevier]

Purpose: Reoperation after failed cortical resection can alleviate seizures in patients with intractable neocortical epilepsy, provided that previously nonresected epileptic regions are accurately defined and removed. Most imaging modalities have limited value in identifying such regions after a previous surgery. Positron emission tomography (PET) using α−[11C]methyl- l-tryptophan (AMT) can detect epileptogenic cortical areas as regions with increased tracer uptake. This study analyzed whether increased cortical AMT uptake can detect nonresected epileptic foci in patients with previously failed neocortical resection. Methods: Thirty-three young patients (age 3–26 years; mean age, 10.8 years) with intractable epilepsy of neocortical origin, and a previously failed cortical resection performed at various epilepsy centers, underwent further presurgical evaluation for reoperation. AMT-PET scans were performed 6 days to 7 years after the first surgery. Focal cortical areas with increased AMT uptake were objectively identified and correlated to ictal EEG data as well as clinical variables (age, postsurgical time, etiology). Results: Cortical increases of AMT uptake were detected on the side of the previous resections in 12 cases. In two patients scanned shortly (within a week) after surgery, diffuse hemispheric increases were observed, without any further localization value. In contrast, in 10 (43%) of 23 patients scanned >2 months but within 2.3 years after surgery, focal cortical increases occurred, concordant with seizure onset on ictal EEG. Age, etiology (lesional vs. cryptogenic), epileptiform EEG activity during PET, or time of the last seizure were not significantly related to the presence of increased AMT uptake. All patients with localizing AMT-PET, who underwent reoperation, became seizure free (n = 5) or showed considerable improvement of seizure frequency (n = 2). Conclusions: AMT-PET can identify nonresected epileptic cortex in patients with a previously failed neocortical epilepsy surgery and, with proper timing for the scan, can assist in planning reoperation. [ABSTRACT FROM AUTHOR]

Although experiments have previously been carried out to determine the optimum sowing time of sesame, very few attempts have been made to determine the effects of macro and micro climatic variation on yield. Thus a field experiment was conducted at the University Research Farm, Bidhan Chandra Krishi Viswavidyalaya, Kalyani, India on an Entisol (alluvial, sandy loam) in the summer seasons of 1996 and 1997 to assess the effects of macro and micro climatic variations on yield of sesame for various dates of sowing. The number of seeds per capsule of sesame was highest in the crop sown on 19 February, although up to the 18 April sowing there was no significant variation. There was no appreciable variation in thousand-seed weight with date of sowing. Crops sown on 19 February and 1 March produced statistically similar yields. The average reduction in yield of sesame was 78.5 and 213 %, respectively, for crops sown on 10 February and 28 April, compared with the crop sown on 19 February. The cultivar Rama produced higher yields than B-67 and Kanke-1. Ambient temperature above 30 °C up to 100 % flowering had a direct positive effect on sesame yield. Crop exposure to 60–70, 70–80 and 80 % relative humidity up to 100 % flowering had a direct negative effect. Temperature profile at 50 days after emergence (DAE), relative humidity at 60 DAE, and photosynthetically active radiation (PAR) at 30 and 40 DAE within the crop canopy had direct positive effects on yield. Regression models suggested that temperature profile and PAR within the crop canopy produced 72 and 35 % variation in yield, respectively. [ABSTRACT FROM AUTHOR]

Demonstrates the association of small guanosine triphosphate-binding protein Rab3A with melanosomes in pigment cells. Isolation of melanosome enriched fraction; Pathways of transferring melanin pigment outside of the cytosol of melanocytes; Information on intracellular vesicle trafficking.

An experiment was conducted during the summer seasons of 1993 and 1994 on sesame (Sesamum indicum L.) to study the effect of certain meteorological parameters on the capsule production efficiency of the main stem and branches of sesame cultivars at different sowing dates in alluvial (Entisol) soil of the tropical humid region in West Bengal, India. The highest capsule production by the main stem and the first, second and third primary branches in accrocentric order was observed for the crop sown on 19 February. The number of capsules on the main stem was reduced by 70.51 and 34.98 % when the crop was sown on 21 March and 28 April, respectively. The humidity profile at 50 days after emergence (DAE) and photosynthetically active radiation (PAR) at 70 DAE had direct positive effects on main stem capsule production. The variations of 38, 21 and 56 % in main stem contribution to capsule production might be explained by the temperature profile, relative humidity and PAR, respectively. Thecultivar Rama produced higher numbers of capsules in branches than Kanke-1 and B-67 at all times of sowing. [ABSTRACT FROM AUTHOR]

Analyzes the expression of genes for tyrosinase, tyrosinase-related protein 1, tyrosinase-related protein 2 and melanocortin-1 receptor using reverse transcription polymerase chain reaction. Result of the incubation of melanocyte-stimulating hormone/isobutylmethylxanthine; Correlation of the abundance and gel mobility pattern with changes in activity in hybrids and parental melanoma cells.

Recent advances in melanogenesis have focused on the role of dihydroxyindole-2-carboxylic acid [(HO)2IndCOOH]. For example, it has been shown that formation of (HO)2IndCOOH from depachrome is catalyzed by dopachrome tautomerase, that the melanogenic protein tyrosinase-related protein (TRP)-1 can oxidize (HO)2IndCOOH to its indole quinone, that (HO)2IndCOOH-melanins can be synthesized chemically, that mammalian melanins are naturally rich in (HO)2IndCOOH subunits, and that (HO)2IndCOOH is incorporated into melanins are naturally rich in (HO)2IndCOOH subunits, and that (HO)2IndCOOH is incorporated into melanins of melanomas in mice. The question thus emerges as to the mechanims(s) by which (HO)2IndCOOH and other precursors become incorporated into melanins in vivo. Accordingly, an activity was partially purified that catalyzed melanin formation with (HO)2IndCOOH as a substrate. Analyses of the (HO)2IndCOOH polymerization factor from Cloudman melanoma cells revealed the following: it was proteinaceous in that it was heat labile and destroyed by proteinase K; it was a glycoprotein in that it adhered to wheat germ agglutinin and was eluted with N-acetyl glucosamine; it was located predominantly in the melanosomal fraction of cell homogenates; the activity was reduced by exposure to the metal chelators EDTA and EGTA, but not by phenylthiourea, a tyrosinase inhibitor; activity was found with the mouse pmel 17/silver locus protein immunopurified from human melanoma cells, and was significantly reduced in extracts of mouse melanocytes cultured from silver (si/si) mice compare to extracts from Si/Si melanocytes. In summary, an activity has been identified in human to mouse melanoma cells that catalyzes the superoxide-dependent polymerization of (HO)2IndCOOH to melanin in vitro, and appears to be a function of the pmel 17/silver protein of the human pmel 17 gene and the mouse silver locus. [ABSTRACT FROM AUTHOR]

The inhibitory effect of arbutin, a naturally occurring β-D-glucopyranoside derivative of hydroquinone, on melanogenesis was studied biochemically by using human melano-cytes in culture. Cells were cultured in the presence of different concentrations of arbutin. The maximum concentration of arbutin that was not inhibitory to growth of the cells was 100 ug/ml. At that concentration, melanin synthesis was inhibited significantly by ∼20% after 5 days, compared with untreated cells. This phenotypic change was associated with the inhibition of tyrosinase and DHICA polymerase activities, and the degree of inhibition was dose dependent. No significant difference in DOPAchrome tautomerase (DT) activity was observed before or after arbutin treatment. Western blotting experiments revealed there were no changes in protein content or in molecular size of tyrosinase, TRP-1 or TRP-2, indicating that inhibition of tyrosinase activity by arbutin might be due to effects at the post-translational level. [ABSTRACT FROM AUTHOR]

Cultured mouse Cloudman melanoma cells, EMT6 breast carcinoma cells, and 3T3 fibroblasts all accumulated in the G2/M phase of the cell cycle when exposed to UVB radiation. The effects of UVB were maximal at 20-30 mJ/cm2 for all three cell lines, and could be observed by flow cytometry as early as 12 hr post irradiation. It has been known since the mid-1970s that MSH receptor binding activity is highest on Cloudman melanoma cells when they are in the G2/M phase of their cycle. Here we show that either UVB irradiation or synchronization of Cloudman cells with colchicine results in a stimulation of MSH binding within 24 hr following treatment, a time when both treatments have resulted in accumulation of cells in the G2/M phase of the cycle. Furthermore, the two treatments performed together on the melanoma cells stimulated MSH receptor activity to the same extent as either treatment performed separately, suggesting that each may be influencing MSH receptor activity solely through a G2/M accumulation of cells. Together, these results raise the possibility that an increase in the number of cells in the G2 phase of the cell cycle is a generalized cellular response to injury, such as UV irradiation. However, in the case of pigment cells this response includes a mechanism for increasing melanin formation, i.e., increased MSH receptor activity. Should this be the case, similar G2/M 'injury responses' of other cell types might be expected, consistent with their differentiated phenotypes. [ABSTRACT FROM AUTHOR]

When human skin is exposed to ultraviolet (UV) light, a highly complex cascade of events ensues that culminates, among other things, in increased skin melanin content. From analyses at the tissue and cellular level, it has been shown that following exposure to UV light there is an increase in the number of active melanocytes in the basal layer of the epidermis, and individual melanocytes are stimulated to produce more melanin. In addition, the rate of transfer of melanosomes from melanocytes to keratinocytes is apparently increased, although the role of UV light in this process remains to be demonstrated. Recent biochemical evidence is reviewed on factors that regulate these processes. A plausible explanation for the effects of UV on pigmentation is that there are mechanisms in the skin for the orderly, regulated reception of UV signals that are then transduced to initiate the cascade. The signals involve both melanocytes and keratinocytes, and avail-able evidence supports a model in which melanotropins and their receptors play a central role in the process. [ABSTRACT FROM AUTHOR]