Correlating sequential homology of Mce1A, Mce2A, Mce3A and Mce4A with their possible functions in mammalian cell entry of Mycobacterium tuberculosis performing homology modeling

OBJECTIVE

The striking homology of the Mycobacterium tuberculosis mammalian cell entry operons (mce1, mce2, mce3 and mce4) with other mycobacterial species and the proposed role of the mammalian cell entry protein 1A (Mce1A) of M. tuberculosis to facilitate invasion of host cells have led us to look into the finer details of these proteins in order to better understand their structure-function relationship.

DESIGN

We performed sequential alignments and secondary structure predictions of Mce1A, Mce2A, Mce3A and Mce4A, and compared these results with results from homology modeling by fold prediction and threading.

RESULTS

Sequential alignments showed that Mce1A and Mce2A are highly homologous, close to 70%, while the other combinations gave only about 30% similarities. The major parts of the proteins aligned without gaps and there were striking similarities by secondary structure predictions indicating that the proteins would have similar folds and to be alpha/beta proteins like the previously reported Mce1A model based on Colicin N. Fold prediction showed that the best templates for Mce2A were substrate-binding domain of DnaK and slow processing precursor penicillin acylase from Escherichia coli while the alpha-domains of Mce3A and Mce4A could both be modeled using the cytoplasmic domain of serine chemotaxis receptor as template.

CONCLUSION

Although different templates had to be used to model the MceA proteins, functional information may be derived that is relevant for their overall function in M. tuberculosis. The beta-domain is probably involved in binding with the receptors on target cells while the alpha-domain is more likely to be involved in pore formation. As predicted from the folds, Mce3A and Mce4A model structures indicate a lipid bound conformation and therefore may be required in signaling events of the mammalian cell entry process.

Adsorption of arsenic(V) by activated carbon prepared from oat hulls

The efficiency of self-manufactured activated carbon (AC) produced from oat hulls in adsorbing arsenic(V) was tested in a batch reactor. The results indicated that the adsorptive capacity of AC was affected by initial pH value, with adsorption capacity decreasing from 3.09 to 1.57 mg As g(-1) AC when the initial pH values increased from 5 to 8. A modified linear driving force model conjugated with a Langmuir isotherm was created to describe the study's kinetics. The test results show that rapid adsorption and slow adsorption exist simultaneously when AC is used to remove arsenic(V).

Effective charges in the fp shell

Following the heavy-ion fusion-evaporation reaction 32S+24Mg at 95 MeV beam energy the lifetimes of analogue states in the T(z)=+/-1/2 A=51 mirror nuclei 51Fe and 51Mn have been measured using the Cologne plunger device coupled to the GASP gamma-ray spectrometer. The deduced B(E2;27/2(-)-->23/2(-)) values afford a unique opportunity to probe isoscalar and isovector polarization charges and to derive effective proton and neutron charges, epsilon(p) and epsilon(n), in the fp shell. A comparison between the experimental results and several different large-scale shell-model calculations yields epsilon(p) approximately 1.15e and epsilon(n) approximately 0.80e.

Mast cells at the host-pathogen interface: host-protection versus immune evasion in leishmaniasis

Infection of a susceptible host with Leishmania, a protozoan parasite, causes the disease leishmaniasis, which is characterized by neutrophil, eosinophil, macrophage, lymphocyte and mast cell infiltration into the infected tissue followed by parasite growth. Although the roles played by other cells in leishmaniasis are known, the role of mast cells remains to be ascertained. Here, we demonstrate that Leishmania regulates mast cell infiltration to the site of infection, mast cell production and mast cell function resulting in differential growth of the parasite in resistant (C57BL/6 or CBA/T6T6) and susceptible (BALB/c) macrophages. An interleukin-3-dependent augmentation in mast cell committed progenitors is observed in BALB/c but not in C57BL/6 mice during Leishmania infection. The mast cell supernatants inhibit IFN-gamma-dependent restriction of Leishmania growth in macrophages in BALB/c mice whereas the reverse phenomenon occurs in C57BL/6 mice. Our data reveals a different facet of host-pathogen interaction.

Right myocardial bridge on CT coronary angiography

Myocardial bridging is a condition where the coronary artery traverses through the myocardium. Although it is not an uncommon finding in left anterior descending coronary artery (LAD), recently we came across a very rare case of right coronary artery (RCA) traversing through the right myocardium on CT coronary angiography.

Relativistic effects in hydrogenlike atoms embedded in Debye plasmas

Spectra of hydrogenlike atoms embedded in a Debye plasma are investigated. The state energies and the transition rates are studied using a fully relativistic formalism based on the Dirac equation. The effect of the plasma is described by introducing an exponential screening to the nuclear Coulomb potential (the Debye screening). Systematic trends with respect to both the nuclear charge and the screening parameter are observed for all calculated quantities. The pattern of splittings of ns(1/2), np(1/2) and np(3/2) is modified in a specific way due to the combined relativity and plasma effect. The transition rates decrease with an increase of the Debye parameter as well as with an increase of Z.

Comparative antimutagenic and anticlastogenic effects of green tea and black tea: a review

Tea is the most popular beverage next to water, consumed by over two-thirds of the world's population. It is processed in different ways in different parts of the world to give green, black or oolong tea. Experimental studies have demonstrated the significant antimutagenic and anticlastogenic effects of both green and black tea and its polyphenols in multiple mutational assays. In the present review, we have attempted to evaluate and update the comparative antimutagenic and anticlastogenic effects of green tea, black tea and their polyphenols in different test systems, based on available literature. Existing reports have suggested that the protective effects of black tea is as good as green tea, however, more studies on black tea and its polyphenols are needed before a final conclusion can be made.

Isomer formation and other issues in the substitution reactions of oxorhenium(V) complexes of 2,2'-bipyridine and related ligands

Two new oxorhenium(V) compounds were prepared and characterized: MeReO(mtp)(Me(2)Bpy) and MeReO(mtp)(dppb), where mtpH(2) is 2-(mercaptomethyl)thiophenol, Me(2)Bpy is 4,4'-dimethyl-2,2'-bipyridine, and dppb is 1,2-(Ph(2)P)(2)C(6)H(4). The more stable geometric isomer of MeReO(mtp)X forms MeReO(mtp)Y (X, Y = PR(3), NC(5)H(4)R) in two steps, both of which show a first-order dependence on [Y], proceeding through the metastable geometric isomer MeReO(mtp)Y. When Y = PR(3), no MeReO(mtp)Y was detected at equilibrium; with NC(5)H(4)R, however, both isomers were detected. The values of K(PyPy) were 8.5-9.8, largely irrespective of R; for NC(5)H(5), DeltaH degrees = -4.47 +/- 0.29 kJ and DeltaS degrees = 3.9 +/- 1.0 J K(-1). For the more symmetric edt ligand, geometric isomers do not exist, but enantiomers do. The rate of racemization of MeReO(edt)(NC(5)H(4)R) was proportional to [Py]. Values of k(rac) for 16 compounds span the range 135-370 L mol(-1) s(-1) in C(6)H(6) at 25 degrees C (rho = -0.39 +/- 0.07). In toluene-d(8), k(rac) for 4-picoline has DeltaH = 28.9 +/- 0.4 kJ, DeltaS() = -103.6 +/- 0.9 J K(-1). A common mechanism applies to ligand substitution (mtp) and racemization (edt). MeReO(dithiolate)Py complexes react with Bpy, Me(2)Bpy, Phen, and Me(2)Phen to form six-coordinate chelates, with rate constants 0.024-0.74 L mol(-1) s(-1) at 25 degrees C, some 10(3) times smaller than with pyridines, no doubt owing to the bulk of the bidentates. Values of DeltaS are -86 to -138 J K(-1), reflecting substantial orientational barriers as well as the inherent contribution of the associative mechanism. The product is MeReO(mtp)(Me(2)Bpy). The formation of the metastable isomer is consistent with the mechanism assigned to the ligand substitution and racemization reactions. Such compounds, once formed, no longer participate in ligand substitution reactions at reasonable rates. The formation of the metastable isomer is consistent with the mechanism assigned to the ligand substitution and racemization reactions.

Oxidation of [Ru(NH3)5isn](BF4)2 by hyochlorous acid and chlorine in aqueous acidic media

UV-vis stopped-flow studies of the reaction of [Ru(NH3)5isn](2+) (isn = isonicotinamide) with excess HOCl at 25 degrees C demonstrate that it proceeds in two time-resolved steps. In the first step [Ru(NH3)5isn](3+) is produced with the rate law -d[Ru(II)]/dt = 2(aK(h)[H(+)] + b[H(+)][Cl(-)] + c[Cl(-)])[HOCl](tot)[Ru(II)]/(K(h) + [H(+)][Cl(-)]). Here, K(h) is 1.3 x 10(-3) M(2) and corresponds to the equilibrium hydrolysis of Cl2, a is (8.34 +/- 0.19) x 10(3) M(-2) s(-1) and represents the acid-assisted reduction of HOCl, b is (4.04 +/- 0.13) x 10(4) M(-1) s(-1) and represents the reduction of Cl2, and c is (6.25 +/- 0.59) x 10(2) s(-1) and represents the Cl(-)-assisted reduction of HOCl. In the second step [Ru(NH3)5isn](3+) undergoes further oxidation to a mixture of products with the rate law -d[Ru(III)]/dt = e[Ru(III)][HOCl]/[H(+)] where e is (1.18 +/- 0.01) x 10(-2) s(-1). This step is assigned a mechanism with Cl(+) transfer from HOCl to [Ru(III)(NH3)4(NH2)isn](2+) occurring in the rate-limiting step. These results underline the resistance of HOCl to act as a simple outer-sphere one-electron oxidant.

Circulating dopamine level, in lung carcinoma patients, inhibits proliferation and cytotoxicity of CD4+ and CD8+ T cells by D1 dopamine receptors: an in vitro analysis

Besides cardiovascular and renal functions, the role of dopamine in periphery as an endogenous regulator of immune functions is in the limelight. In human malignancy, depression of T cell functions is known. Interestingly, recent evidences indicate significant elevation of plasma dopamine in malignancy due to stress of the disease process. Therefore, this study evaluates whether this increased plasma dopamine exerts any influence on the proliferation and cytotoxicity of CD4+ and CD8+ T cells. Patients with lung carcinoma were selected for this study due to the high prevalence rate of this kind of cancer in developing countries and also due to strong positive biochemical and psychological criteria of stress in most of the patients. Results showed significant elevation of plasma dopamine (48.6 +/- 5.1 pg/ml) in lung cancer patients than normal controls (10.2 +/- 0.9 pg/ml). In vitro dopamine concentration, simulating the plasma concentration of the patients, significantly inhibited the proliferation and cytotoxicity of T cells of these patients and also of the normal volunteers, in presence of their respective serum. The mechanism has been attributed to be D1 class of dopamine receptor mediated elevation of intracellular cAMP in these cell populations. The results may be of significance in understanding the role of peripheral dopamine as an immunomodulator in human health and diseases.

Immunobiology of CD28 expression on human neutrophils. I. CD28 regulates neutrophil migration by modulating CXCR-1 expression

CD28, described as a T cell costimulatory molecule so far, is expressed on human peripheral blood neutrophils, as shown by cell surface staining and immunoprecipitation with anti-CD28 monoclonal antibody, and by reverse transcription PCR. The phorbol 12-myristate 13-acetate-augmented expression of CD28 on these cells can be blocked by actinomycin D, an RNA transcription inhibitor, and staurosporin, a protein kinase inhibitor. Cross-linking of CD28 results in an early increase in IL-8 receptor A (IL-8RA or CXCR-1) expression and a concurrent increase in IL-8-induced chemotaxis. The expression of CXCR-1 is down-regulated by receptor internalization 3 h after CD28 cross-linking with concurrent decrease in IL-8-induced chemotactic migration. Thus, our results demonstrate for the first time that CD28 is expressed on human peripheral blood neutrophils and that CD28 may play an important role in the regulation of IL-8RA expression and migration of neutrophils in response to IL-8.

Role of paucibacillary leprosy in the transmission of disease

The objective of this study was to establish that paucibacillary leprosy also carried increased risk of infection to the community. All members of 100 families with an index paucibacillary case were clinically, bacteriologically and immunologically examined. The "comparison" group was sampled from suspect register. Fifty-six cases occurred among 944 contacts of index paucibacillary cases; of these, four were multibacillary and 52 were paucibacillary. In the "comparison" group, two contacts out of 760 developed paucibacillary leprosy. This difference, between the two groups, was statistically significant. All the 56 cases in the index case families were under 20 years of age; and 50 of them were aged under 15 years. Male/female ratio was 2.1:1. Of the 56 cases, 28 shared the same bed with the index patient, 20 shared the same room and eight lived in the same house. Lepromin positivity rate was higher in "comparison" families (92.2%) than in index case families (74.6%), the difference being statistically significant (x = 6.09, P < 0.001). Contacts of index case families, therefore, were immunologically at higher risk than contacts of "comparison" families.

Physiological concentrations of dopamine inhibit the proliferation and cytotoxicity of human CD4+ and CD8+ T cells in vitro: a receptor-mediated mechanism

OBJECTIVE

Dopamine, a catecholamine neurotransmitter, influences growth and proliferation of lymphocytes. Pharmacological doses of dopamine have been shown to modulate T cell functions significantly, but no information is available on the effect of physiological concentrations of circulating dopamine on CD4+ and CD8+ T cell functions. This information may be of importance since significantly elevated plasma dopamine levels were observed in humans during uncoping stress, and suppression of T cell functions during stress is a well-known phenomenon. However, the mechanism inducing the suppression of T cell functions during stress is not yet clear. In the present investigation, we evaluated the effect of the dopamine level attained in the plasma of individuals with uncoping stress on the proliferation and cytotoxicity of CD4+ and CD8+ T cells in vitro.

METHODS

T cell subpopulations were separated by panning. The effect of dopamine on IL-2-induced cell proliferation in vitro was evaluated by [3H]thymidine incorporation and cytotoxicity by 51Cr release, receptors by radioligand binding, cAMP by an assay kit and apoptosis by DNA fragmentation.

RESULTS

At these elevated physiological concentrations, dopamine was found to inhibit significantly the proliferation and cytotoxicity of CD4+ and CD8+ T cells in vitro. This dopamine-mediated inhibition of proliferation was more marked on CD8+ T cells than on CD4+ T cells. The underlying mechanism was found to be D1 class of dopamine-receptor-mediated stimulation of intracellular cAMP.

CONCLUSION

Results may be of significance to understand the role of peripheral dopamine in human neuroimmune communication in terms of physiological homeostasis in health and disease.