Impairment of cell division of Trypanosoma cruzi epimastigotes

The mechanisms that facilitate the adaptation of Trypanosoma cruzi to two distinct hosts, insect and vertebrate, are poorly understood, in part due to the limited ability to perform gene disruption studies by homologous recombination. This report describes a developmentally-defective phenotype that resulted from integration of a drug marker adjacent to the GAPDH gene in T. cruzi.

Heparan sulfate and cell division

Heparan sulfate is a component of vertebrate and invertebrate tissues which appears during the cytodifferentiation stage of embryonic development. Its structure varies according to the tissue and species of origin and is modified during neoplastic transformation. Several lines of experimental evidence suggest that heparan sulfate plays a role in cellular recognition, cellular adhesion and growth control. Heparan sulfate can participate in the process of cell division in two distinct ways, either as a positive or negative modulator of cellular proliferation, or as a response to a mitogenic stimulus.

Heparan sulfate and control of cell division: adhesion and proliferation of mutant CHO-745 cells lacking xylosyl transferase

We have examined the role of cell surface glycosaminoglycans in cell division: adhesion and proliferation of Chinese hamster ovary (CHO) cells. We used both wild-type (CHO-K1) cells and a mutant (CHO-745) which is deficient in the synthesis of proteoglycans due to lack of activity of xylosyl transferase. Using different amounts of wild-type and mutant cells, little adhesion was observed in the presence of laminin and type I collagen. However, when fibronectin or vitronectin was used as substrate, there was an enhancement in the adhesion of wild-type and mutant cells. Only CHO-K1 cells showed a time-dependent adhesion on type IV collagen. These results suggest that the two cell lines present different adhesive profiles. Several lines of experimental evidence suggest that heparan sulfate proteoglycans play a role in cell adhesion as positive modulators of cell proliferation and as key participants in the process of cell division. Proliferation and cell cycle assays clearly demonstrate that a decrease in the amount of glycosaminoglycans does not inhibit the proliferation of mutant CHO-745 cells when compared to the wild type CHO-K1, in agreement with the findings that both CHO-K1 and CHO-745 cells take 8 h to enter the S phase.

Decreased memory T-cell response and function in human immunodeficiency virus-infected patients with tegumentary leishmaniasis

The effects of human immunodeficiency virus (HIV) on the immune response in patients with cutaneous leishmaniasis have not yet been fully delineated. This study quantified and evaluated the function of memory T-cell subsets in response to soluble Leishmania antigens (SLA) from patients coinfected with HIV and Leishmania with tegumentary leishmaniasis (TL). Eight TL/HIV coinfected subjects and 10 HIV seronegative subjects with TL were evaluated. The proliferative response of CD4+and CD8+T-cells and naïve, central memory (CM) and effector memory (EM) CD4+T-cells in response to SLA were quantified using flow cytometry. The median cell division indices for CD4+and CD8+T-cells of coinfected patients in response to SLA were significantly lower than those in patients with Leishmania monoinfection (p < 0.05). The proportions of CM and EM CD4+T-cells in response to SLA were similar between the coinfected patients and patients with Leishmania monoinfection. However, the median CM and EM CD4+T-cell counts from coinfected patients were significantly lower (p < 0.05). The reduction in the lymphoproliferative response to Leishmaniaantigens coincides with the decrease in the absolute numbers of both EM and CM CD4+T-cells in response to Leishmania antigens in patients coinfected with HIV/Leishmania.

Differential regulation of vitamin D receptor expression in distinct leukemic cell lines upon phorbol ester-induced growth arrest

A close correlation between vitamin D receptor (VDR) abundance and cell proliferation rate has been shown in NIH-3T3 fibroblasts, MCF-7 breast cancer and in HL-60 myeloblastic cells. We have now determined if this association occurs in other leukemic cell lines, U937 and K562, and if VDR content is related to c-myc expression, which is also linked to cell growth state. Upon phorbol myristate acetate (PMA) treatment, cells from the three lineages (HL-60, U937 and K562) differentiated and expressed specific surface antigens. All cell lines analyzed were growth inhibited by PMA and the doubling time was increased, mainly due to an increased fraction of cells in the G0/G1 phase, as determined by flow cytometry measurements of incorporated bromodeoxyuridine and cell DNA content. C-myc mRNA expression was down-regulated and closely correlated to cell growth arrest. However, VDR expression in leukemic cell lines, as determined by immunofluorescence and Northern blot assays, was not consistently changed upon inhibition of cell proliferation since VDR levels were down-regulated only in HL-60 cells. Our data suggest that VDR expression cannot be explained simply as a reflection of the leukemic cell growth state.

Detection of Bartonella henselae DNA in clinical samples including peripheral blood of immune competent and immune compromised patients by three nested amplifications

Bacteria of the genus Bartonella are emerging pathogens detected in lymph node biopsies and aspirates probably caused by increased concentration of bacteria. Twenty-three samples of 18 patients with clinical, laboratory and/or epidemiological data suggesting bartonellosis were subjected to three nested amplifications targeting a fragment of the 60-kDa heat shock protein (HSP), the internal transcribed spacer 16S-23S rRNA (ITS) and the cell division (FtsZ) of Bartonella henselae, in order to improve detection in clinical samples. In the first amplification 01, 04 and 05 samples, were positive by HSP (4.3%), FtsZ (17.4%) and ITS (21.7%), respectively. After the second round six positive samples were identified by nested-HSP (26%), eight by nested-ITS (34.8%) and 18 by nested-FtsZ (78.2%), corresponding to 10 peripheral blood samples, five lymph node biopsies, two skin biopsies and one lymph node aspirate. The nested-FtsZ was more sensitive than nested-HSP and nested-ITS (p < 0.0001), enabling the detection of Bartonella henselae DNA in 15 of 18 patients (83.3%). In this study, three nested-PCR that should be specific for Bartonella henselae amplification were developed, but only the nested-FtsZ did not amplify DNA from Bartonella quintana. We conclude that nested amplifications increased detection of B. henselae DNA, and that the nested-FtsZ was the most sensitive and the only specific to B. henselae in different biological samples. As all samples detected by nested-HSP and nested-ITS, were also by nested-FtsZ, we infer that in our series infections were caused by Bartonella henselae. The high number of positive blood samples draws attention to the use of this biological material in the investigation of bartonellosis, regardless of the immune status of patients. This fact is important in the case of critically ill patients and young children to avoid more invasive procedures such as lymph nodes biopsies and aspirates.

Morphological evidence by scanning electron microscopy of excretion of metacyclic forms of Trypanosoma cruzi in vector's urine

Comparision by scanning electron microscopy (SEM) of Trypanosoma cruzi flagellates attached to the cuticle of the rectal gland of infected Dipetalogaster maxima nymphs, showed marked differences before amd after feeding. Before feeding numerous metacyclic trypomastigotes were observed among the abundant epimastigotes that formed the carpet of flagellates. On the other hand, in insects that were allowed to urinate for 24 hours after a meal, the metacyclics were scarce,indicating that they had been detached by the urine flow. An asymetric type of cell division, probably originating both an epi-and a trypomastigote, was occasionally observed. The occurrence of swellings at different levels of the flagella of epimastigotes suggests that secondary sites of attachment may be common.

Effect of sphingosine and phorbol-12-myristate-13-acetate on the growth and dimethylsulfoxide-induced differentiation in the insect trypanosomatid Herpetomonas samuelpessoai

We investigated the effect of two modulators of protein kinase C, sphingosine and phorbol-12-myristate-13-acetate (PMA), on the growth and dimethylsulfoxide (DMSO)-induced differentiation in Herpetomonas samuelpessoai. Sphingosine did not stimulate the transformation of undifferentiated-promastigotes in differentiated-paramastigotes. PMA alone or in association with DMSO increased the number of paramastigotes in comparison to control cells. DMSO inhibited the parasite growth (35%) and several unusual morphological features resembling aberrant cell division were observed. Sphingosine did not significantly reduce the growth in contrast to PMA. Collectively, our results demonstrated that the reduction of the proliferation translates in an increase of the differentiation rate in the insect trypanosomatid H. samuelpessoai.

Ki-67 is expressed in multiplying forms of Schistosoma mansoni, but not in snail host tissues

Ki-67 is a protein expressed in the nucleus of several species during cell-division, being absent during the GO resting phase of the cellular cycle. During attempts to disclose mitosis in the so-called " amebocyte-producing organ " in Biomphalaria glabrata infected with Schistosoma mansoni, the parasite multiplying forms appeared strongly marked for Ki-67, while the snail tissues were completely negative. These data are worth registering to complement general data on Ki-67, and to help future studies on the relationship of the parasite and of its intermediate host.

Chromatin regulation in schistosomes and histone modifying enzymes as drug targets

Only one drug is currently available for the treatment and control of schistosomiasis and the increasing risk of selecting strains of schistosome that are resistant to praziquantel means that the development of new drugs is urgent. With this objective we have chosen to target the enzymes modifying histones and in particular the histone acetyltransferases and histone deacetylases (HDAC). Inhibitors of HDACs (HDACi) are under intense study as potential anti-cancer drugs and act via the induction of cell cycle arrest and/or apoptosis. Schistosomes like other parasites can be considered as similar to tumours in that they maintain an intense metabolic activity and rate of cell division that is outside the control of the host. We have shown that HDACi can induce apoptosis and death of schistosomes maintained in culture and have set up a consortium (Schistosome Epigenetics: Targets, Regulation, New Drugs) funded by the European Commission with the aim of developing inhibitors specific for schistosome histone modifying enzymes as novel lead compounds for drug development.

Prokaryotic cells: structural organisation of the cytoskeleton and organelles

For many years, prokaryotic cells were distinguished from eukaryotic cells based on the simplicity of their cytoplasm, in which the presence of organelles and cytoskeletal structures had not been discovered. Based on current knowledge, this review describes the complex components of the prokaryotic cell cytoskeleton, including (i) tubulin homologues composed of FtsZ, BtuA, BtuB and several associated proteins, which play a fundamental role in cell division, (ii) actin-like homologues, such as MreB and Mb1, which are involved in controlling cell width and cell length, and (iii) intermediate filament homologues, including crescentin and CfpA, which localise on the concave side of a bacterium and along its inner curvature and associate with its membrane. Some prokaryotes exhibit specialised membrane-bound organelles in the cytoplasm, such as magnetosomes and acidocalcisomes, as well as protein complexes, such as carboxysomes. This review also examines recent data on the presence of nanotubes, which are structures that are well characterised in mammalian cells that allow direct contact and communication between cells.

EFFECTS OF THIDIAZURON (TDZ) ON FRUITING OF TEMPERATE TREE FRUITS

Thidiazuron (TDZ) is a phenylurea like citokinin on cell division fruit growth and fruit shape in some deciduous fruit trees. The effects of TDZ applied during flowering on apple cultivars 'Gala' and 'Fuji" were evaluated during seven growing seasons with annual applications on the same trees. The effects on pear and kiwi fruit trees were also evaluated. Every year, TDZ significantly increased fruit set and fruit weight on apple trees. The seven-year average of the fruit set from TDZ at 10 mg.L-1 was 112.7% while the control was only 51.3%. TDZ did not affect the number of clusters. The fruit weight increased 7.0% and 18.3% when the trees were sprayed with TDZ at 10 mg.L-1 and 5 mg.L-1, respectively. TDZ also increased fruit yield per tree by 28.7% and 41.8% for the 10 mg.L-1 and 5 mg.L-1 treatments, respectively. TDZ reduced the seed number per fruit and the calcium content in the flesh fruit, but increased the fruit firmness. The fruit set increased significantly on pear cultivar Packm's Triumph treated with TDZ, and reduced the seed numbers per fruit. TDZ applied at 12.5 mg.L-1 increased fruit weight by 47,4% on "Monty" kiwi.

Metilglioxal: uma toxina endógena?

Methylglyoxal is a very reactive α-oxoaldehyde putatively produced by glycolysis, cytochrome P450-catalyzed acetone oxidation and aminoacetone oxidation. Methylglyoxal has been pointed as a substrate for the glyoxalase system ultimately energy-yielding pyruvate, but methylglyoxal is also a toxicant involved in protein aggregation and DNA modification. Controversial hypothesis on methylglyoxal as an anticancer agent, an energy-yielding glycolysis intermediates, and as a regulator of cell division have also been proposed. Methylglyoxal research focuses now on unveiling its biological properties and on the discovery of drugs capable to inhibit its toxic effects, principally in diabetes.

Cyanoaggregatum brasiliense gen. et sp. nov., a new chroococcal Cyanobacteria from Southern Brazil

The paper proposed Cyanoaggregatum brasiliense, a new genus and species from the plankton of a subtropical brackish coastal lagoon from Rio Grande do Sul State, South Brazil. It differs from all other members of Chroococcales by its characteristic arrangement of cells in irregular groups distributed in a single, flat or slightly curved layer, on irregular rows, slightly distant from each other, forming a mosaic-like pattern slightly below the surface of the mucilaginous colonial envelope. The cell division in one plane perpendicular to the long axis and the lack of pseudo-filaments indicate its classification in the family Synechococcaceae, sub-family Aphanothecoideae. The general characteristics, the diagnostic criteria and the taxonomic position are discussed, and a comparison between Cyanoaggregatum and its most closely related genera is presented. Physical and chemical data on the studied lagoon and geographical distribution are presented.

Effects of caffeine on mitotic index in Drosophila prosaltans (Diptera)

The effect of two concentrations of caffeine (1500 mg/ml and 2500 mg/ml) on mitotic indices of Drosophila prosaltans was analyzed in larval brain cells. Although the differences detected between treated and control cells were not significant, the percentages obtained suggest a possible effect of caffeine in slowing the process of cell division