A phase-shifting control for variable frequency multi-cells interleaved boost pre-regulator based on FPGA device

In this paper were investigated phase-shift control strategies applied to a four cells interleaved high input-power-factor pre-regulator boost rectifier, operating in critical conduction mode, using a non-dissipative commutation cells and frequency modulation. The digital control has been developed using a hardware description language (VHDL) and implemented using the XC2S200E-SpartanII-E/Xilinx FPGA, performing a true critical conduction operation mode for a generic number of interleaved cells. Experimental results are presented, in order to verify the feasibility and performance of the proposed digital control, through the use of a Xilinx FPGA device.

A COMPARATIVE-STUDY OF 4 DIFFERENT STAINING METHODS FOR ESTIMATION OF LIVE YEAST FORM CELLS OF PARACOCCIDIOIDES-BRASILIENSIS

A comparative study of four different staining methods for estimation of live yeast form cells of Paracoccidioides brasiliensis was carried out. The staining methods used were fluorescent staining, vital dye exclusion tests with erythrosin B and by Janus green and lactophenol cotton blue staining. Colony forming units (cfu) of the yeast form of eight P. brasiliensis isolates on brain heart infusion agar (BHIA) supplemented with 4% horse serum plus 5% P. brasiliensis cell extract (BHIA + HS + EXT) were examined for reliability of staining in determining the number of live fungal units in eight different isolates. Cfu on BHIA + HS + EXT plates showed an excellent plating efficiency over 96% in all isolates tested. The percentage of the live cells indicated by fluorescent staining (FL) or vital dye exclusion test with erythrosin B (EB) or Janus green (JG-1) was lower than that of cfu. By contrast, the percentage due to modified dye exclusion test with Janus green (JG-2) and that due to lactophenol cotton blue staining (LPCB) showed a close correration to that of cfu. Our results indicate that the modified dye exclusion test with Janus green and lactophenol cotton blue staining are useful for estimating cell viability of yeast form cells of P. brasiliensis.

Cytoplasmic protrusions from digestive cells of bees

Midgut cells from the honey bee, Apis mellifera, and the stingless bees Scaptotrigona postica and Melipona quadrifasciata anthidioides were examined ultrastructurally and histochemically. Several types of protrusions were evident in the apical surface of the midgut cells. Large apical protrusions formed by the whole apical surface of the cell, whose content had a homogeneous cytoplasmic matrix devoid of organelles and with a different electron density from the subjacent cytoplasm. These protrusions can be cast out to the midgut lumen. A second type of large apical protrusion was produced between the cell microvilli, presenting many ribosomes and polyribosomes. In addition to these large protrusions two other kinds of small ones were observed. One type crowned the cell apex forming small spheres with irregular contours near the cells, and increasing in size further away. The other type was characterized by the microvilli swelling with an electron-lucent content. The Gomori acid phosphatase reaction was positive at the cell apex, in the pinched off protrusions and in the microvilli. These results are discussed in relation to the possible role of cell protrusions in secretory mechanisms.

Ultrastructure of digestive cells in stingless bees of various ages (Hymenoptera, Apidae, Meliponinae)

The ultrastructure of digestive cells of newly emerged, nurse and forager worker bees is described. Newly emerged bees have the endoplasmic reticulum characteristically in whorls and stacks as well as in parallel arrays of smooth endoplasmic reticulum. Nurse bees have spherits, autophagic vacuoles, lysosomes and multivesicular bodies. Forager bees have many cells with disorganized cytoplasm containing vacuoles, lamellated bodies, lipid inclusions, microbodies and intranuclear crystalloid inclusions. The basal cell region stays essentially unchanged. The changes observed are discussed in relation to previous observations on other insect species.

Mast cells in the developing avian eye

Mast cells are present in the eye of Gallus domesticus, appearing in the anterior uvea in embryos at stage 39 HH (13th day). In hatching and adult birds, they are present in the sclera, uvea, pectinate Ligament, and conjunctiva. Mast cells are absent in the cornea, retina, and pecten oculi.Maturing mast cells in the anterior eye segment appear as round cells having eccentric nuclei and a few cytoplasmic metachromatic granules, whose fluorescence increases during development. Mature cells are more numerous in late development, and their cytoplasm is rich in metachromatic and intensely fluorescent granules. Ultrastructurally, maturing mast cells display progranules and a few electron dense and homogeneous granules on one side of the cell. Mast cells of adult birds possess homogeneous cytoplasmic granules, some of which display protuberances that penetrate hollows of adjoining granules. Heterogeneous granules exhibiting latticed and mottled patterns are also present. The existence of mast cells in the anterior eye segment indicates that these cells might perform a physiological role during development and in aqueous humor outflow. They might modulate exchanges between blood and aqueous humor through chemical mediators present in their granules. (C) 1996 Wiley-Liss, Inc.

Release of intermediate reactive hydrogen peroxide by macrophage cells activated by natural products

By determining the hydrogen peroxide (H2O2) released in cultures of peritoneal macrophage cells from Swiss mice, we evaluated the action of 27 vegetable compounds (pristimerin, tingenone, jatrophone, palustric acid, lupeol, cladrastin, ocoteine, boldine, tomatine, yohimbine, reserpine, escopoletin, esculine, plumericin, diosgenin, deoxyschizandrin, p-arbutin, mangiferin, and others) using a 2 mg/ml solution of each compound (100 mug/well). Macrophages are cells responsible for the development of the immunological response reaction, liberating more than one hundred compounds into the extracellular environment. Among these are the various cytokines and the intermediate compounds of nitrogen (NO) and oxygen (H2O2). This coordinated sequence of biochemical reactions is known as the oxidative burst. When we compared the results with those obtained with zymosan (an important stimulator of H2O2) we observed that the compounds showing the highest activity were substances 2 (tingenone), 16 (reserpine) and 20. Other substances such as compounds 1, 4, 5, 6, 8, 12, 13, 14, 15, 17, 19, 23, 24, 26, and 27 also showed a certain activity, but with less intensity than the aforementioned ones. Compounds 3, 7, 9, 10, 11, 18, 21, 22 and 25 presented no activity. These results suggest that natural products (mainly tingenone and reserpine and others) with different chemical structures are strong immunological modulators. However, further tests are needed to determine the 'oxidative burst' in future studies.

Growth and differentiation of bone marrow hematopoietic cells in mice bearing Ehrlich ascite tumor and treated with Dicyclopentadienildichiorotitanium (IV)

In this work we have:investigated the growth and differentiation of bone marrow stem cells in mice bearing Ehrlich ascites tumor-and treated with three dose-regimens of Dicyclopentadienyldichlorotitanium (IV) (DDCT). We also: studied the presence of colony stimulating factors In the serum of PDCT-treated animals as well-as the effects-of the drug on the survival of the tumor-bearing mice. The-results demonstrated that the myelosuppression developed in the tumor-bearing animals is prevented by the administration:of 1, 2 or 3 doses of 15 mg/kg DDCT. In the treatment with three doses, however, 23 % of the animals died. Moreover, DDCT treatment in normal animals resulted in increased numbers of CFU-GM. We observed the presence of stimulating factors in the serum of drug-treated animals which induced the growth and differentiation of bone marrow progenitor cells from normal animals in vitro. on the other hand, in vitro addition of the drug to these cultures had no effect. Thus, we conclude that the drug protects against the myelosuppression induced by the tumor and that this protection may be related to an indirect action of the drug. (C) 1998 International Society for Immunopharmacology. Published by Elsevier B.V. Ltd.

Radioprotection of beta-carotene evaluated on mouse somatic and germ cells

In the present paper, the protective effect of beta-carotene was evaluated after whole body exposure of mice to 2 Gy of X-rays. Splenocytes, reticulocytes, bone marrow cells and spermatids were evaluated for the frequency of micronuclei (MN) induced by X-rays. Mice were treated (gavage) with beta-carotene (10, 25 and 50 mg/kg b.w.) for 5 consecutive days and, 4 h after the last treatment, the animals were irradiated. The results obtained showed different frequencies of X-ray-induced-MN between different cell populations analysed and also different response of these cells to the beta-carotene treatment. The radioprotective effect of beta-carotene was observed in splenocytes, reticulocytes, and spermatids but not in bone marrow cells. No dose-response relationship for beta-carotene was detected. The time of sampling, the sensitivity of the cells as well as the antioxidant activity of beta-carotene are discussed as important factors for the radioprotective action of this provitamin.

Nanostructured organic layers via polymer demixing for interface-enhanced photovoltaic cells

Significant progress is being made in the photovoltaic energy conversion using organic semiconducting materials. One of the focuses of attention is the morphology of the donor-acceptor heterojunction at the nanometer scale, to ensure efficient charge generation and loss-free charge transport at the same time. Here, we present a method for the controlled, sequential design of a bilayer polymer cell architecture that consists of a large interface area with connecting paths to the respective electrodes for both materials. We used the surface-directed demixing of a donor conjugated/guest polymer blend during spin coating to produce a nanostructured interface, which was, after removal of the guest with a selective solvent, covered with an acceptor layer. With use of a donor poly(p-phenylenevinylene) derivative and the acceptor C-60 fullerene, this resulted in much-improved device performance, with external power efficiencies more than 3 times higher than those reported for that particular material combination so far.

INFLUENCE OF DIABETES-MELLITUS ON THE GLUTATHIONE REDOX SYSTEM OF HUMAN RED-BLOOD-CELLS

Several components of the erythrocyte-dependent glutathione redox system (reduced glutathione, GSH; oxidized glutathione, GSSG; glutathione peroxidase, GSH-Px; glutathione reductase, GSH-Red) were determined in patients with types I and II diabetes mellitus (DM). All groups studied were male subjects: G1, 20 young healthy individuals (aged 23.7 +/- 4.2 years); G2, 15 young insulin-treated type I DM patients; G3, 20 older insulin-treated type II DM patients; 04, 21 older oral hypoglycemic agent-treated type II DM patients; G5, 28 aged healthy individuals (aged 68.9 +/- 11.5 years). There were no differences between G1 and G2, G3 or G4 regarding erythrocyte GSH, GSSG, and GSH-Red (without FAD) levels. GSH-Px activity was significantly lower in G2 when compared to G1 (15.2 +/- 4.9 vs 20.6 +/- 6.6 IU/g Hb). The GSH-Red and GSH-Px activities and GSH levels were significantly higher in 03 (4.6 +/- 1.7 IU/g Hb, 20.2 +/- 8.7 IU/g Hb and 3.5 +/- 1.3-mu-M/g Hb) and G4 (5.0 +/- 2.2 IU/g Hb, 16.9 +/- 6.1 IU/g Hb and 5.0 +/- 2.3-mu-M/g Hb) when compared to G5 (3.4 +/- 0.9 IU/g Hb, 12.0 +/- 3.6 IU/g Hb and 2.3 +/- 0.9-mu-M/g Hb). The findings suggest that treatment of DM can stimulate the redox activity of red blood cells in aged subjects.

Catecholamine effects on human melanoma cells evoked by α1-adrenoceptors

The biological effects of catecholamines in mammalian pigment cells are poorly understood. Our previous results showed the presence of α1-adrenoceptors in SK-Mel 23 human melanoma cells. The aims of this work were to (1) characterize catecholamine effects on proliferation, tyrosinase activity and expression, (2) identify the α1- adrenoceptor subtypes, and (3) verify whether chronic norepinephrine (NE) treatment modified the types and/or pharmacological characteristics of adrenoceptors present in SK-Mel 23 human melanoma cells. Cells treated with the aradrenergic agonist, phenylephrine (PHE, 10-5 or 10-4 M), for 24-72 h, exhibited decreased cell proliferation and enhanced tyrosinase activity, but unaltered tyrosinase expression as compared with the control. The proliferation and tyrosinase activity responses were inhibited by the α1-adrenergic antagonist prazosin, suggesting they were evoked by α1-adrenoceptors. The presence of actinomycin D, a transcription inhibitor, did not diminish PHE-induced effects. RT-PCR assays, followed by cloning and sequencing, demonstrated the presence of α1A- and α1B-adrenoceptor subtypes. NE-treated cells (24 or 72 h) were used in competition assays, and showed no significant change in the competition curves of α1-adrenoceptors as compared with control curves. Other adrenoceptor subtypes were not identified in these cells, and NE pretreatment did not induce their expression. In conclusion, the activation of SK-Mel 23 human melanoma α1- radrenoceptors elicit biological effects, such as proliferation decrease and tyrosinase activity increase. Desensitization or expression of other adrenoceptor subtypes after chronic NE treatment were not observed.

Role of natural killer cells in antitumor resistance

Natural killer cells constitute a population of lymphocytes able to non-specifically destroy virus-infected and some kinds of tumor cells. Since this lytic activity was shown by non-immunized animals the phenomenon is denominated natural killer (NK) activity and contrasts with specific cytotoxicity performed by cytolytic T lymphocytes (CTLs) because it does not depends on MHC-restricted peptides recognition. In fact, the main feature of most functional receptors of NK cells (NKRs) is their ability to be inhibited by different kinds of class I MHC antigens. In the middle of the 1950's, Burnet & Thomas forged the concept of tumor immunosurveillance and NK cells can be considered one of the main figures in this phenomenon both for effector and regulatory functions. In the present review the early studies on the biology of NK cells were revisited and both their antitumor activity and dependence on the activation by cytokines are discussed.

The effect of CpG-ODN on antigen presenting cells of the foal

Background: Cytosine-phosphate-guanosine oligodeoxynucleotide (CpG-ODN) has been used successfully to induce immune responses against viral and intracellular organisms in mammals. The main objective of this study was to test the effect of CpG-ODN on antigen presenting cells of young foals. Methods: Peripheral blood monocytes of foals (n = 7) were isolated in the first day of life and monthly thereafter up to 3 months of life. Adult horse (n = 7) monocytes were isolated and tested once for comparison. Isolated monocytes were stimulated with IL-4 and GM-CSF (to obtain dendritic cells, DC) or not stimulated (to obtain macrophages). Macrophages and DCs were stimulated for 14-16 hours with either CpG-ODN, LPS or not stimulated. The stimulated and non-stimulated cells were tested for cell surface markers (CD86 and MHC class II) using flow cytometry, mRNA expression of cytokines (IL-12, IFNα, IL-10) and TLR-9 using real time quantitative RT-PCR, and for the activation of the transcription factor NF-κB p65 using a chemiluminescence assay. Results: The median fluorescence of the MHC class II molecule in non-stimulated foal macrophages and DCs at birth were 12.5 times and 11.2 times inferior, respectively, than adult horse cells (p = 0.009). That difference subsided at 3 months of life (p = 0.3). The expression of the CD86 co-stimulatory molecule was comparable in adult horse and foal macrophages and DCs, independent of treatment. CpG-ODN stimulation induced IL-12p40 (53 times) and IFNα (23 times) mRNA expression in CpG-ODN-treated adult horse DCs (p = 0.078), but not macrophages, in comparison to non-stimulated cells. In contrast, foal APCs did not respond to CpG-ODN stimulation with increased cytokine mRNA expression up to 3 months of age. TLR-9 mRNA expression and NF-kB activation (NF-kB p65) in foal DCs and macrophages were comparable (p > 0.05) to adult horse cells. Conclusion: CpG-ODN treatment did not induce specific maturation and cytokine expression in foal macrophages and DCs. Nevertheless, adult horse DCs, but not macrophages, increased their expression of IL-12 and IFNα cytokines upon CpG-ODN stimulation. Importantly, foals presented an age-dependent limitation in the expression of MHC class II in macrophages and DCs, independent of treatment. © 2007 Flaminio et al; licensee BioMed Central Ltd.