DjPum, a homologue of Drosophila Pumilio, is essential to planarian stem cell maintenance

As stem cells are rare and difficult to study in vivo in adults, the use of classical models of regeneration to address fundamental aspects of the stem cell biology is emerging. Planarian regeneration, which is based upon totipotent stem cells present in the adult--the so-called neoblasts--provides a unique opportunity to study in vivo the molecular program that defines a stem cell. The choice of a stem cell to self-renew or differentiate involves regulatory molecules that also operate as translational repressors, such as members of PUF proteins. In this study, we identified a homologue of the Drosophila PUF gene Pumilio (DjPum) in the planarian Dugesia japonica, with an expression pattern preferentially restricted to neoblasts. Through RNA interference (RNAi), we demonstrate that gene silencing of DjPum dramatically reduces the number of neoblasts, thus supporting the intriguing hypothesis that stem cell maintenance may be an ancestral function of PUF proteins.     

Physiological significance of estrogens in men--breakthrough in endocrinology

Estradiol (E2) is traditionally recognised as the female sex hormone. It has been believed for 40 years, that E2 didn't exert any influence or caused impairment of the gonadal function in men. The main source of E2 in men is adipose tissue and the brain. E2 is also produced in adrenals, liver, mammary glands, hair and in male gonad. Daily production and the level of E2 in the blood in men are higher than those in postmenopausal women. At the end of the 80-ties we were first reporting that during sexual maturation E2 can be the important hormonal signal for the initiation of spermatogenesis. The traditional view about unimportant or inhibitory role of E2 in male physiology was finally refuted thanks to discovering estrogen receptors in males. In the 90-ties, transgenic mice with the lack of estrogen receptor (ER) or gene encoding enzyme aromatase, that enable the conversion of testosterone into E2, were also produced. Observations of men with inherited mutations of these genes, considerably extended our knowledge about E2 in men in stroma bones formation, inhibition of their growing, lipids metabolism and sexual maturation, the effects that were attributed to testosterone action until today. New data also points at important role of estrogens and ER in the function of the cardio-vascular system and in counteracting coronary disease in men.     

Fighting an enemy within: cytoplasmic inhibitors of bacterial cysteine proteases

The genes encoding secreted, broad-spectrum activity cysteine proteases of Staphylococcus spp. (staphopains) and Streptococcus pyogenes (streptopain, SpeB) are genetically linked to genes encoding cytoplasmic inhibitors. While staphopain inhibitors have lipocalin-like folds, streptopain is inhibited by a protein bearing the scaffold of the enzyme profragment. Bioinformatic analysis of other prokaryotic genomes has revealed that two more species may utilize this same genetic arrangement to control streptopain-like proteases with lipocalin-like inhibitors, while three other species may employ a C-terminally located domain that resembles the profragment. This apparently represents a novel system that bacteria use to control the intracellular activity of their proteases.     

Differences in virulence between isolates of feline Sporotrichosis

Sporotrichosis is a chronic subcutaneous mycosis caused by Sporothrix schenckii. This work aimed to evaluate the virulence of two different isolates of S. schenckii from cutaneous (CUT) and systemic (SYS) forms of feline sporotrichosis. A standard inoculum with 2 × 10³ yeast cells/ml was prepared from each of the isolates. The experimental infection was carried out with 0.1 ml of the inoculum from both isolates and then injected in the paw pads of Swiss albino mice of groups CUT and SYS. The clinical evolution of the disease and the diameter of the lesion at the inoculated sites were evaluated during nine weeks. Four necropsies were done to collect material from the lesions (p < 0.01). Group CUT demonstrated a more evident clinical evolution of the disease from week two to week five; large lesions in the paw pad on week four (p < 0.01); and a higher incidence of lesions in other parts of the body (p < 0.01) than group SYS (p < 0.01). S. schenckii was isolated from the inoculated site in groups SYS and CUT until days 30 and 45, respectively. Granulomas with yeast cells usually localized in the central area were observed in histopathology sections on days 15 and 30 post-inoculations. Those yeast cells decreased on day 45 being absent on day 62 when tissue repair initiated. The results showed that distinct clinical isolates of S. schenckii cause significant differences in the clinical evolution of sporotrichosis.     

Homing of hemopoietic precursor cells to the fetal rat thymus: intercellular contact-controlled cell migration and development of the thymic microenvironment

Colonization of rat thymic anlage by the first wave of hemopoietic precursor cells (HPc) was investigated by means of transmission electron microscopy and immunocytochemistry. HPc began migration into the thymic anlage between 13 and 13.5 gestation days (GD), terminated colonization at about GD 16, and migrated sequentially through the two compartments of the thymic anlage under the control of typical populations of stromal cells. First, HPc migrated through the external compartment of the perithymic mesenchyme, tightly interconnected with fibroblasts. The type of junctions between the cells indicated that the fibroblasts played a role in the control of HPc trafficking and in their entrance to the epithelial compartment. The second stage of colonization was initiated by the entrance of HPc to the epithelial compartment and their interaction with thymic epithelial cells (TECs). Based on morphological criteria, two populations of HPc were distinguished that colonized the anlage at various stages of its development. The predominant population with ultrastructural traits common to thymocytes “homed” into the epithelial type primordium. A small number of HPc, identified by protein S-100 expression and by Birbeck’s granules as precursors of dendritic cells, colonized lymphoepithelial anlage in which subsets of cortical and medullary TECs could be distinguished. Thymocyte migration and their reciprocal interactions with cortical TECs differed from the trafficking of dendritic cells toward the medulla. The results demonstrated the influence of maturing thymocytes on the development of cortical epithelial cells and the dynamic organization of the medullary microenvironment with direct involvement of dendritic cells. This study was supported by UMS grant 501-2-0003404.     

Clinical and pathological importance of vacA allele heterogeneity and cagA status in peptic ulcer disease in patients from North Brazil

We have examined the prevalence of gene cagA and vacA alleles in 129 patients, 69 with gastritis and 60 with peptic ulcer diseases from North Brazil and their relation with histopathological data. vacA and cagA genotype were determined by polymerase chain reaction. Hematoxylin-eosin staining was used for histological diagnosis. 96.6% of the patients were colonized by Helicobacter pylori strains harboring single vacA genotype (nont-mixed infection). Among them, 11.8% had subtype s1a, 67.8% had subtype s1b, and 17% subtype s2. In regard to the middle region analysis, m1 alleles were found in 75.4% and m2 in 21.2% of patients. The cagA gene was detected in 78% patients infected with H. pylori and was associated with the s1-m1 vacA genotype. The H. pylori strains, vacA s1b m1/cagA-positive, were associated with increased risk of peptic ulcer disease and higher amounts of lymphocytic and neutrophilic infiltrates and the presence of intestinal metaplasia. These findings show that cagA and vacA genotyping may have clinical relevance in Brazil.     

Effects of sex, age, body mass, and capturing method on hematologic values of brown bears in Croatia

Effects of various intrinsic and extrinsic factors on 17 hematologic values from 56 brown bears (Ursus arctos) sampled in Croatia from 1981 to 2005 were evaluated. Differences between female and male bears were detected for number of erythrocytes, sedimentation rate after 30 min, and number of leukocytes and segmented neutrophils. Significant differences between free-living vs. captive and snared vs. not snared bears were detected for the same three parameters: leukocytes, segmented neutrophils, and eosinophils. It was concluded that the physical exertion of bears snared by leg, rather than their free-living status, influenced differences of results among these groups. The obtained mean values are useful reference values for the species.     

Cloning and characterization of a region responsible for the maintenance of megaplasmid pTAV3 of Paracoccus versutus UW1

Using cointegrate formation, we constructed a basic replicon of the megaplasmid/mini-chromosome pTAV3 of Paracoccus versutus UW1. It is composed of two adjacent modules, responsible for plasmid replication (rep) and partitioning (par). Functional analysis of the par region identified a determinant of incompatibility (inc2), whose presence is crucial for proper partitioning (the partitioning site). Database searches revealed that the only known replicon with significant homology to that of pTAV3 is encoded by the chromosome cII of Rhodobacter sphaeroides 2.4.1. Incompatibility studies showed that closely related basic replicons are also encoded by megaplasmids (above 400 kb) harbored by four strains of P. pantotrophus. Basic replicons of the pTAV3-type are able to maintain large bacterial genomes, therefore they appear to be good candidates for the construction of vectors specific for Alphaproteobacteria.     

A comparison of staphostatin B with standard mechanism serine protease inhibitors

Staphostatins are the endogenous, highly specific inhibitors of staphopains, the major secreted cysteine proteases from Staphylococcus aureus. We have previously shown that staphostatins A and B are competitive, active site-directed inhibitors that span the active site clefts of their target proteases in the same orientation as substrates. We now report the crystal structure of staphostatin B in complex with wild-type staphopain B at 1.9 A resolution. In the complex structure, the catalytic residues are found in exactly the positions that would be expected for uncomplexed papain-type proteases. There is robust, continuous density for the staphostatin B binding loop and no indication for cleavage of the peptide bond that comes closest to the active site cysteine of staphopain B. The carbonyl carbon atom C of this peptide bond is 4.1 A away from the active site cysteine sulfur Sgamma atom. The carbonyl oxygen atom O of this peptide bond points away from the putative oxyanion hole and lies almost on a line from the Sgamma atom to the C atom. The arrangement is strikingly similar to the "ionmolecule" arrangement for the complex of papain-type enzymes with their substrates but differs significantly from the arrangement conventionally assumed for the Michaelis complex of papain-type enzymes with their substrates and also from the arrangement that is crystallographically observed for complexes of standard mechanism inhibitors and their target serine proteases.