Biodeterioration of Mayan buildings at uxmal and tulum,Mexico

Uxmal and Tulum are two important Mayan sites in the Yucatan peninsula. The buildings are mainly composed of limestone and grey/black discoloration is seen on exposed walls and copious greenish biofilms on inner walls. The principal microorganisms detected on interior walls at both Uxmal and Tulum were cyanobacteria; heterotrophic bacteria and filamentous fungi were also present. A dark‐pigmented mitosporic fungus and Bacillus cereus, both isolated from Uxmal, were shown to be acidogenic in laboratory cultures. Cyanobacteria belonging to rock‐degrading genera Synechocystis and Gloeocapsa were identified at both sites. Surface analysis previously showed that calcium ions were present in the biofilms on buildings at Uxmal and Tulum, suggesting the deposition of biosolubilized stone. Apart from their potential to degrade the substrate, the coccoid cyanobacteria supply organic nutrients for bacteria and fungi, which can produce organic acids, further increasing stone degradation.     

Multimodal pressure-flow method to assess dynamics of cerebral autoregulation in stroke and hypertension

Background

This study evaluated the effects of stroke on regulation of cerebral blood flow in response to fluctuations in systemic blood pressure (BP). The autoregulatory dynamics are difficult to assess because of the nonstationarity and nonlinearity of the component signals.

Methods

We studied 15 normotensive, 20 hypertensive and 15 minor stroke subjects (48.0 ± 1.3 years). BP and blood flow velocities (BFV) from middle cerebral arteries (MCA) were measured during the Valsalva maneuver (VM) using transcranial Doppler ultrasound.

Results

A new technique, multimodal pressure-flow analysis (MMPF), was implemented to analyze these short, nonstationary signals. MMPF analysis decomposes complex BP and BFV signals into multiple empirical modes, representing their instantaneous frequency-amplitude modulation. The empirical mode corresponding to the VM BP profile was used to construct the continuous phase diagram and to identify the minimum and maximum values from the residual BP (BP_R) and BFV (BFV_R) signals. The BP-BFV phase shift was calculated as the difference between the phase corresponding to the BP_R and BFV_R minimum (maximum) values. BP-BFV phase shifts were significantly different between groups. In the normotensive group, the BFV_R minimum and maximum preceded the BP_R minimum and maximum, respectively, leading to large positive values of BP-BFV shifts.

Conclusion

In the stroke and hypertensive groups, the resulting BP-BFV phase shift was significantly smaller compared to the normotensive group. A standard autoregulation index did not differentiate the groups. The MMPF method enables evaluation of autoregulatory dynamics based on instantaneous BP-BFV phase analysis. Regulation of BP-BFV dynamics is altered with hypertension and after stroke, rendering blood flow dependent on blood pressure.

     

Modeling alpha-helical coiled-coil interactions: the axial and azimuthal alignment of 1B segments from vimentin intermediate filaments

Attempts at predicting the relative axial alignments of fibrous protein molecules in filamentous structures have relied upon representing the (multichain) molecular structure by a one-dimensional sequence of amino acids. Potential intermolecular ionic and apolar interactions were counted and determined as a function of the relative axial stagger between the molecules. No attempts were made to consider the azimuthal aspect of the interacting molecules and neither were apolar or ionic energy terms used. Surprisingly, this simple approach proved remarkably informative and yielded accurate predictions of the axial periods present. However, a more comprehensive analysis involving the energetics of aggregation taking due regard for the relative azimuths of the molecules as well as their separation should decrease the noise level in the calculations and reveal other pertinent information. Toward that end, we have modeled the interaction between two alpha-helical coiled-coil segments in intermediate filament molecules (1B segments from human vimentin). The relative axial alignment and polarity of the molecules is already known from detailed crosslinking studies and this provides a criterion against which the success (or otherwise) of the modeling can be judged. The results confirm that an antiparallel alignment of two 1B segments is preferred over any of the parallel options (as observed experimentally). The calculated axial alignment, however, is not identical to that observed from detailed crosslinking studies indicating that other parts of the molecule (probably the head and tail domains as well as other coiled-coil segments) have a crucial role in determining the precise mode of axial aggregation. The results also show that the apolar interactions seem to be significantly less important in the alignment process than the ionic ones. This is consistent with the observation of a well-defined period in the linear disposition of the charged (but not apolar) residues along the length of the outer surface of the vimentin molecule.     

Further characterization of the binding of human recombinant interleukin 2 to heparin and identification of putative binding sites

We have previously provided compelling evidence that human recombinant interleukin 2 (IL-2) binds to the sulfated polysaccharides heparin, highly sulfated heparan sulfate and fucoidan. Here we show that IL-2 binding is dependent on heparin chain length, but with fragments as small as 15-mers retaining binding activity. The addition of exogenous heparin has no effect on the in vitro biological activity of IL-2. In addition soluble IL-2 receptor alpha and beta polypeptides do not compete with heparin for the binding of IL-2. IL-2 bound by heparin is still recognized by two IL-2 specific monoclonal antibodies, 3H9 and H2- 8, whose epitopes lie in the amino terminal region. Murine IL-2 unlike its human counterpart fails to bind to heparin. Human IL-2 analogs with single amino acid substitutions at positions Lys43, Thr51, and Gln126 analogs no longer bind to heparin. By contrast the Arg38Ala analog retains heparin full heparin binding activity. These experimental findings together with molecular modeling studies suggest two putative heparin binding sites on human IL-2, one involving four basic residues, Lys48, Lys49, Lys54, and His55, and the other being a discontinuous site comprising Lys43, Lys64, Arg81, and Arg83. Neither of these two clusters is completely conserved in murine IL-2. Overall our data suggest that the binding of human IL-2 to heparin and heparan sulfate does not interfere with IL-2/IL-2 receptor interactions. Therefore, binding to glycosaminoglycan may be a mechanism for retaining the cytokine in an active form close to its site of secretion in the tissue, thus favoring a paracrine role for IL-2.      

Efflux pumps expression and its association with porin down-regulation and β-lactamase production among <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> causing bloodstream infections in Brazil

Background  

Multi-drug efflux pumps have been increasingly recognized as a major component of resistance in P. aeruginosa. We have investigated the expression level of efflux systems among clinical isolates of P. aeruginosa, regardless of their antimicrobial susceptibility profile.     

Aspidosperma (Apocynaceae) plant cytotoxicity and activity towards malaria parasites. Part II: experimental studies with Aspidosperma ramiflorum in vivo and in vitro

Several species of Aspidosperma plants are used to treat diseases in the tropics, including Aspidosperma ramiflorum, which acts against leishmaniasis, an activity that is experimentally confirmed. The species, known as guatambu-yellow, yellow peroba, coffee-peroba andmatiambu, grows in the Atlantic Forest of Brazil in the South to the Southeast regions. Through a guided biofractionation of A. ramiflorum extracts, the plant activity against Plasmodium falciparum was evaluated in vitro for toxicity towards human hepatoma G2 cells, normal monkey kidney cells and nonimmortalised human monocytes isolated from peripheral blood. Six of the seven extracts tested were active at low doses (half-maximal drug inhibitory concentration < 3.8 µg/mL); the aqueous extract was inactive. Overall, the plant extracts and the purified compounds displayed low toxicity in vitro. A nonsoluble extract fraction and one purified alkaloid isositsirikine (compound 5) displayed high selectivity indexes (SI) (= 56 and 113, respectively), whereas compounds 2 and 3 were toxic (SI < 10). The structure, activity and low toxicity of isositsirikine in vitro are described here for the first time in A. ramiflorum, but only the neutral and precipitate plant fractions were tested for activity, which caused up to 53% parasitaemia inhibition of Plasmodium berghei in mice with blood-induced malaria. This plant species is likely to be useful in the further development of an antimalarial drug, but its pharmacological evaluation is still required.     

A peptide that antagonizes TCR-mediated reactions with both syngeneic and allogeneic agonists: functional and structural aspects

We identify and consider some characteristics of a peptide antagonist for the Ag-specific receptor on 2C cells (the 2C TCR). The peptide, GNYSFYAL (called GNY), binds to H-2K(b), and a very high-resolution crystal structure of the GNY-K(b) complex at 1.35 A is described. Although the GNY peptide does not bind to L(d), the potency of GNY-K(b) as an antagonist is evident from its ability to specifically inhibit 2C TCR-mediated reactions to an allogenic agonist complex (QLSPFPFDL-L(d)), as well as to a syngeneic agonist complex (SIYRYYGL-K(b)). The crystal structure and the activities of alanine-substituted peptide variants point to the properties of the peptide P4 side chain and the conformation of the Tyr-P6 side chain as the structural determinants of GNYSFYAL antagonist activity.     

The Anabolic Androgenic Steroid Nandrolone Decanoate Disrupts Redox Homeostasis in Liver,Heart and Kidney of Male Wistar Rats

The abuse of anabolic androgenic steroids (AAS) may cause side effects in several tissues. Oxidative stress is linked to the pathophysiology of most of these alterations, being involved in fibrosis, cellular proliferation, tumorigenesis, amongst others. Thus, the aim of this study was to determine the impact of supraphysiological doses of nandrolone decanoate (DECA) on the redox balance of liver, heart and kidney. Wistar male rats were treated with intramuscular injections of vehicle or DECA (1 mg.100 g⁻¹ body weight) once a week for 8 weeks. The activity and mRNA levels of NADPH Oxidase (NOX), and the activity of catalase, glutathione peroxidase (GPx) and total superoxide dismutase (SOD), as well as the reduced thiol and carbonyl residue proteins, were measured in liver, heart and kidney. DECA treatment increased NOX activity in heart and liver, but NOX2 mRNA levels were only increased in heart. Liver catalase and SOD activities were decreased in the DECA-treated group, but only catalase activity was decreased in the kidney. No differences were detected in GPx activity. Thiol residues were decreased in the liver and kidney of treated animals in comparison to the control group, while carbonyl residues were increased in the kidney after the treatment. Taken together, our results show that chronically administered DECA is able to disrupt the cellular redox balance, leading to an oxidative stress state.