Microscopy images as interactive tools in cell modeling and cell biology education

The advent of genomics, proteomics, and microarray technology has brought much excitement to science, both in teaching and in learning. The public is eager to know about the processes of life. In the present context of the explosive growth of scientific information, a major challenge of modern cell biology is to popularize basic concepts of structures and functions of living cells, to introduce people to the scientific method, to stimulate inquiry, and to analyze and synthesize concepts and paradigms. In this essay we present our experience in mixing science and education in Brazil. For two decades we have developed activities for the science education of teachers and undergraduate students, using microscopy images generated by our work as cell biologists. We describe open-air outreach education activities, games, cell modeling, and other practical and innovative activities presented in public squares and favelas. Especially in developing countries, science education is important, since it may lead to an improvement in quality of life while advancing understanding of traditional scientific ideas. We show that teaching and research can be mutually beneficial rather than competing pursuits in advancing these goals.     

Tumour-expressed CD43 (sialophorin) mediates tumourmesothelial cell adhesion

Mesothelial cell intercellular adhesion molecule-1 (ICAM-1) has recently been shown to play a role in tumour cell adherence to the peritoneum. However, solid tumours poorly express its most ubiquitous ligand, beta2 integrin. The aim of this study was to investigate the role of the beta2 integrin subunit and CD43, a known ligand for ICAM-1, in the development of peritoneal metastases. beta2 Integrin subunit and CD43 expression was assessed on a number of tumour cell lines. Adhesion of SW1222 and PSN-1 cells to human peritoneal mesothelial cells was investigated using a fluorometric assay incorporating an inhibitory antibody to beta2 integrin and CD43. beta2 Integrin expression was not inducible on these tumour cell lines, but Western blotting demonstrated CD43 expression in all the cancer cell lines examined and cell surface expression was confirmed by flow cytometry. The anti-CD43 antibody significantly reduced adhesion of PSN-1 and SW1222 cells to HPMC, however beta2 integrin inhibition did not reduce tumour cell adhesion. CD43 is expressed by a variety of carcinoma cell lines, and plays a role in tumour cell-peritoneal adhesion probably via interactions with its putative ligand ICAM-1.     

Ketogenic Diet Increases Glutathione Peroxidase Activity in Rat Hippocampus

Ketogenic diets have been used in the treatment of refractory childhood epilepsy for almost 80 years; however, we know little about the underlying biochemical basis of their action. In this study, we evaluate oxidative stress in different brain regions from Wistar rats fed a ketogenic diet. Cerebral cortex appears to have not been affected by this diet, and cerebellum presented a decrease in antioxidant capacity measured by a luminol oxidation assay without changes in antioxidant enzyme activities—glutathione peroxidase, catalase, and superoxide dismutase. In the hippocampus, however, we observed an increase in antioxidant activity accompanied by an increase of glutathione peroxidase (about 4 times) and no changes in lipoperoxidation levels. We suggest that the higher activity of this enzyme induced by ketogenic diet in hippocampus might contribute to protect this structure from neurodegenerative sequelae of convulsive disorders.     

A role of CXC chemokine ligand 12/stromal cell-derived factor-1/pre-B cell growth stimulating factor and its receptor CXCR4 in fetal and adult T cell development in vivo

The functions of a chemokine CXC chemokine ligand (CXCL) 12/stromal cell-derived factor-1/pre-B cell growth stimulating factor and its physiologic receptor CXCR4 in T cell development are controversial. In this study, we have genetically further characterized their roles in fetal and adult T cell development using mutant and chimeric mice. In CXCL12(-/-) or CXCR4(-/-) embryos on a C57BL/6 background, accumulation of T cell progenitors in the outer mesenchymal layer of the thymus anlage during initial colonization of the fetal thymus was comparable with that seen in wild-type embryos. However, the expansion of CD3(-)CD4(-)CD8(-) triple-negative T cell precursors at the CD44(-)CD25(+) and CD44(-)CD25(-) stages, and CD4(+)CD8(+) double-positive thymocytes was affected during embryogenesis in these mutants. In radiation chimeras competitively repopulated with CXCR4(-/-) fetal liver cells, the reduction in donor-derived thymocytes compared with wild-type chimeras was much more severe than the reduction in donor-derived myeloid lineage cells in bone marrow. Triple negative CD44(+)CD25(+) T cell precursors exhibited survival response to CXCL12 in the presence of stem cell factor as well as migratory response to CXCL12. Thus, it may be that CXCL12 and CXCR4 are involved in the expansion of T cell precursors in both fetal and adult thymus in vivo. Finally, enforced expression of bcl-2 did not rescue impaired T cell development in CXCR4(-/-) embryos or impaired reconstitution of CXCR4(-/-) thymocytes in competitively repopulated mice, suggesting that defects in T cell development caused by CXCR4 mutation are not caused by reduced expression of bcl-2.     

Production and characterization of a thermostable alpha-amylase from Nocardiopsis sp. endophyte of yam bean

Thermostable amylolytic enzymes have been currently investigated to improve industrial processes of starch degradation. Studies on production of alpha-amylase by Nocardiopsis sp., an endophytic actinomycete isolated from yam bean (Pachyrhizus erosus L. Urban), showed that higher enzyme levels were obtained at the end of the logarithmic growth phase after incubation for 72 h at pH 8.6. Maximum activity of alpha-amylase was obtained at pH 5.0 and 70 degrees C. The isolated enzyme exhibited thermostable properties as indicated by retention of 100% of residual activity at 70 degrees C, and 50% of residual activity at 90 degrees C for 10 min. Extracellular enzyme from Nocardiopsis sp. was purified by fractional precipitation with ammonium sulphate. After 60% saturation produced 1130 U mg-1 protein and yield was 28% with purification 2.7-fold. The enzyme produced by Nocardiopsis sp. has potential for industrial applications.     

Synthesis of a new 5'-O-triphosphate analog of 5-methyl 2'-O-deoxycytidine. Preliminary in vitro labelling for non-radioactive detection of DNA

We report the synthesis of the triphosphate of 5-methyl 4-N-[6-(p-bromobenzamido)hex-1-yl]-2'-O-deoxycytidine 3A. We also analyzed the formation of intramolecular H-bonds of 5-methyl 4-N-[n-[6-(p-bromobenzamido) caproyl amino]alk-1-yl]-2'-deoxycytidine compounds, and confirmed their presence by 1H-NMR studies. In vitro DNA labeling with modified nucleotides is preliminarily evaluated.     

Distribution of interstitial telomere-like repeats and their adjacent sequences in a dioecious plant, <Emphasis Type="Italic">Silene latifolia</Emphasis>

The dioecious plant Silene latifolia has large, heteromorphic X and Y sex chromosomes that are thought to be derived from rearrangements of autosomes. To reveal the origin of the sex chromosomes in S. latifolia, we isolated and characterized telomere-homologous sequences from intra-chromosomal regions (interstitial telomere-like repeats; ITRs) and ITR-adjacent sequences (IASs). Nine genomic DNA fragments with degenerate 84- to 175-bp ITRs were isolated from a genomic library and total genome of male plants. Comparing the nucleotide sequences, the IASs of the nine ITRs were classified into seven elements (IAS-a, IAS-b, IAS-c, IAS-d, IAS-e, IAS-f, and IAS-g) by sequence similarity. The ITRs were grouped into two classes (class-I and -II ITRs) according to the classification of IASs. The class-I ITRs were sub-grouped into three subclasses (subclasses-IA, -IB, and -IC ITRs) based on the arrangement of IAS elements. By contrast, the class-II ITR was located between two different IASs (IAS-f and IAS-g). Genomic Southern analyses showed that both the male and female genomes contained six (IAS-f) to 153 (IAS-d) copies of each IAS per haploid genome. Fluorescence in situ hybridization analyses showed that one IAS element, IAS-d, was distributed in the interstitial and proximal regions of the sex chromosomes of S. latifolia. The distribution of IAS-d is important evidence for past telomere-mediated chromosome rearrangements during the evolution of the sex chromosomes of S. latifolia.     

The anti-HIV pentameric pseudopeptide HB-19 binds the C-terminal end of nucleolin and prevents anchorage of virus particles in the plasma membrane of target cells

The multivalent pseudopeptide HB-19 that binds the cell-surface-expressed nucleolin is a potent inhibitor of human immunodeficiency virus (HIV) infection by blocking virus particle attachment and thus anchorage in the plasma membrane. We show that cross-linking of surface-bound HB-19A (like HB-19 but with a modified template) results in aggregation of HB-19A with surface nucleolin. Consistent with its specific action, HB-19A binding to different types of cells reaches saturation at concentrations that have been reported to result in inhibition of HIV infection. By using Chinese hamster ovary mutant cell lines, we confirm that the binding of HB-19A to surface nucleolin is independent of heparan and chondroitin sulfate proteoglycans. In vitro generated full-length nucleolin was found to bind HB-19A, whereas the N-terminal part containing the acidic amino acid stretches of nucleolin did not. The use of various deletion constructs of the C-terminal part of nucleolin then permitted the identification of the extreme C-terminal end of nucleolin, containing repeats of the amino acid motif, RGG, as the domain that binds HB-19A. Finally, a synthetic peptide corresponding to the last C-terminal 63 amino acids was able to inhibit HIV infection at the stage of HIV attachment to cells, thus suggesting that this domain could be functional in the HIV anchorage process.     

Fecundity of the Hypostomus affinis (Siluriformes,Loricariidae) in the Lajes Reservoir,Rio de Janeiro,Brazil

The armored catfish Hypostomus affinis is a widespread Loricariidae fish in the Lajes Reservoir (22 degrees 42'-22 degrees 50' S; 43 degrees 53'-44 degrees 05' W), the largest lentic environment in the Rio de Janeiro State, but little is known about their reproductive biology. One hundred and twenty five females, captured from January 1996 to December 1997, were used to assess ovarian development (29 were used to determine fecundity). The oocyte distribution by size-diameter classes revealed the occurrence of two modes suggesting an asynchronic development of the ovaries. The total fecundity ranged from 1235 to 4304, averaging 2374. An exponential relationship between fecundity and total length was determined, and a direct linear relationship was found between fecundity and total weight and gonad weight.