A modified procedure for the detection of microbial producers of extracellular proteolytic enzymes

Summary A simple procedure for the detection of microbial producers of proteolytic enzymes using dyed gelatin microcarrier particles incorporated into appropriate nutrient agar is described. Extracellular proteinases produced by the tested microbial strains hydrolyzed the substrate and clear dyed zones around and under the colonies were formed.     

Differential effect of phosphatidylethanolamine depletion on raft proteins: Further evidence for diversity of rafts in Saccharomyces cerevisiae

A considerable amount of evidence supports the idea that lipid rafts are involved in many cellular processes, including protein sorting and trafficking. We show that, in this process, also a non-raft lipid, phosphatidylethanolamine (PE), has an indispensable function. The depletion of this phospholipid results in an accumulation of a typical raft-resident, the arginine transporter Can1p, in the membranes of Golgi, while the trafficking of another plasma membrane transporter, Pma1p, is interrupted at the level of the ER. Both these transporters associate with a Triton (TX-100) resistant membrane fraction before their intracellular transport is arrested in the respective organelles. The Can1p undelivered to the plasma membrane is fully active when reconstituted to a PE-containing vesicle system in vitro. We further demonstrate that, in addition to the TX-100 resistance at 4 °C, Can1p and Pma1pa exhibit different accessibility to nonyl glucoside (NG), which points to distinct intimate lipid surroundings of these two proteins. Also, at 20 °C, these two proteins are extracted by TX-100 differentially. The features above suggest that Pma1p and Can1p are associated with different compartments. This is independently supported by the observations made by confocal microscopy. In addition we show that PE is involved in the stability of Can1p-raft association.     

Structural basis of interactions between human glutamate carboxypeptidase II and its substrate analogs

Human glutamate carboxypeptidase II (GCPII) is involved in neuronal signal transduction and intestinal folate absorption by means of the hydrolysis of its two natural substrates, N-acetyl-aspartyl-glutamate and folyl-poly-γ-glutamates, respectively. During the past years, tremendous efforts have been made toward the structural analysis of GCPII. Crystal structures of GCPII in complex with various ligands have provided insight into the binding of these ligands, particularly to the S1′ site of the enzyme. In this article, we have extended structural characterization of GCPII to its S1 site by using dipeptide-based inhibitors that interact with both S1 and S1′ sites of the enzyme. To this end, we have determined crystal structures of human GCPII in complex with phosphapeptide analogs of folyl-γ-glutamate, aspartyl-glutamate, and γ-glutamyl-glutamate, refined at 1.50, 1.60, and 1.67 Å resolution, respectively. The S1 pocket of GCPII could be accurately defined and analyzed for the first time, and the data indicate the importance of Asn519, Arg463, Arg534, and Arg536 for recognition of the penultimate (i.e., P1) substrate residues. Direct interactions between the positively charged guanidinium groups of Arg534 and Arg536 and a P1 moiety of a substrate/inhibitor provide mechanistic explanation of GCPII preference for acidic dipeptides. Additionally, observed conformational flexibility of the Arg463 and Arg536 side chains likely regulates GCPII affinity toward different inhibitors and modulates GCPII substrate specificity. The biochemical experiments assessing the hydrolysis of several GCPII substrate derivatives modified at the P1 position, also included in this report, further complement and extend conclusions derived from the structural analysis. The data described here form an a solid foundation for the structurally aided design of novel low-molecular-weight GCPII inhibitors and imaging agents.     

Effects of Bradykinin Postconditioning on Endogenous Antioxidant Enzyme Activity After Transient Forebrain Ischemia in Rat

Bradykinin is considered an important mediator of the inflammatory response in both the peripheral and the central nervous system and it has attracted recent interest as a potential mediator of brain injury following stroke. Bradykinin is recognized to play an important role in ischemic brain. We investigated the effect of bradykinin postconditioning on ischemic damage after 8 min of ischemia (four-vessel occlusion) and 3 days of reperfusion. Bradykinin was administered after 2 days of reperfusion at a dose of 150 μg/kg (i.p.). Catalase (CAT) activity was significantly increased in all examined regions (cortex, hippocampus and striatum) 3 days after 8 min of ischemia, but postconditioning decreased this activity below the control values. The total activity of superoxide dismutase (SOD) 3 days after ischemia was at control level with or without postconditioning. However, the analysis of individual SODs separately revealed interesting differences; while the activity of CuZnSOD was significantly decreased 3 days after ischemia, the activity of MnSOD was significantly increased compared to control levels. In both cases, postconditioning returned SOD activity to control levels. These findings are interesting because MnSOD is a mitochondrial enzyme and its activity in the cytosol suggests that a possible mechanism of protection provided by postconditioning could include prevention of release of mitochondrial proteins to the cytoplasm, resulting in protection against the mitochondrial pathway of apoptosis. 8 min of ischemia alone caused the degeneration of 52.37% neurons in the hippocampal CA1 region 3 days later. Bradykinin used as postconditioning 2 days after the same interval of ischemia enabled the survival of more than 97% of CA1 neurons. This study demonstrated that bradykinin postconditioning induces protection against ischemic brain injury and promotes neuronal survival.     

The place and role of serologic methods in detecting Helicobacter pylori infection

The aim of the study was to determine the place and role of serologic methods in detecting Helicobacter pylori (H. pylori) infection, on the basis of estimated enzyme-linked immunosorbent assay (ELISA) and complement fixation test (CFT) sensitivity and specificity. A total of 549 patients were included in the study. ELISA and CFT as serologic methods were compared with invasive methods (rapid urease test--CLO test, culture, histology). The sensitivity of serologic methods was above 90%, and their specificity was around 80%. Study results confirmed the value, reliability and usefulness of serologic methods in the detection of H. pylori infection.     

Poly(L-lysine)-modified iron oxide nanoparticles for stem cell labeling

New surface-modified iron oxide nanoparticles were developed by precipitation of Fe(II) and Fe(III) salts with ammonium hydroxide and oxidation of the resulting magnetite with sodium hypochlorite, followed by the addition of poly( L-lysine) (PLL) solution. PLL of several molecular weights ranging from 146 ( L-lysine) to 579 000 was tested as a coating to boost the intracellular uptake of the nanoparticles. The nanoparticles were characterized by TEM, dynamic light scattering, FTIR, and ultrasonic spectrometry. TEM revealed that the particles were ca. 6 nm in diameter, while FTIR showed that their surfaces were well-coated with PLL. The interaction of PLL-modified iron oxide nanoparticles with DMEM culture medium was verified by UV-vis spectroscopy. Rat bone marrow stromal cells (rMSCs) and human mesenchymal stem cells (hMSC) were labeled with PLL-modified iron oxide nanoparticles or with Endorem (control). Optical microscopy and TEM confirmed the presence of PLL-modified iron oxide nanoparticles inside the cells. Cellular uptake was very high (more than 92%) for PLL-modified nanoparticles that were coated with PLL (molecular weight 388 00) at a concentration of 0.02 mg PLL per milliliter of colloid. The cellular uptake of PLL-modified iron oxide was facilitated by its interaction with the negatively charged cell surface and subsequent endosomolytic uptake. The relaxivity of rMSCs labeled with PLL-modified iron oxide and the amount of iron in the cells were determined. PLL-modified iron oxide-labeled rMSCs were imaged in vitro and in vivo after intracerebral grafting into the contralateral hemisphere of the adult rat brain. The implanted cells were visible on magnetic resonance (MR) images as a hypointense area at the injection site and in the lesion. In comparison with Endorem, nanoparticles modified with PLL of an optimum molecular weight demonstrated a higher efficiency of intracellular uptake by MSC cells.     

Post-conditioning exacerbates the MnSOD immune-reactivity after experimental cerebral global ischemia and reperfusion in the rat brain hippocampus

This study monitored the effects of sub-lethal ischemia (post-conditioning) applied after a previous ischemic attack by way of the MnSOD immune-reactivity examined in CA1 and dentate gyrus of the rat hippocampus. The experimental 10 min transient cerebral ischemia was followed by 2 days of reperfusion, the rats then underwent a second ischemia (4 or 6 min post-conditioning). MnSOD immune-reactivity was evaluated after 5 h, 1 and 2 days. Results obtained by computer microdensitometric image analysis indicated that 4 min of ischemic post-conditioning caused higher MnSOD immune-reactivity than 6 min. However, higher viability of CA1 neurons after stronger (6 min) post-conditioning when production of MnSOD is lower, as well as differences between MnSOD in CA1 and dentate gyrus indicates another mechanism switching pro-apoptotic destination of CA1 neurons to anti-apoptotic.     

Cytotoxic activity of proflavine diureas: synthesis, antitumor, evaluation and DNA binding properties of 1',1'-(acridin-3,6-diyl)-3',3'-dialkyldiureas

The synthesis of novel 1',1'-(acridin-3,6-diyl)-3',3'-dialkyldiureas was reported. Their biological activity to inhibit cell proliferation was assessed by a MTT assay on two cell lines, HeLa and HCT-116, at micromolar concentration. 1',1'-(Acridin-3,6-diyl)-3',3'-dihexyldiurea hydrochloride was active on a HCT-116 cell line with an IC(50) value of 3.1 microM. The interaction of these compounds with calf thymus DNA was investigated by a variety of spectroscopic techniques including UV-vis, fluorescence and CD spectroscopy. From spectrofluorimetric titrations, binding constants for the DNA-drug complexes were determined (K=0.9-4.2x10(5) M(-1)). Antiproliferative activity of synthesized derivatives might be related to their intercalation into DNA.